1 Telecommunications 2 3 IP Telephony Equipment 4 5 Voice Gateway Transmission Requirements 6 7 SP-3-4826-RV2 (to become ANSI/TIA-912-B) 8 9 10 With corrections per ballot comments SP-3-4826-RV2 (to be published as ANSI/TIA-912-B) 1 TABLE OF CONTENTS 2 3 TABLE OF CONTENTS ..................................................................................................................... I 4 1 INTRODUCTION ......................................................................................................................... 1 5 6 1.1 1.2 General .................................................................................................................................. 1 Purpose.................................................................................................................................. 1 7 1.3 Categories of Performance Criteria ...................................................................................... 1 8 2 SCOPE ........................................................................................................................................... 2 9 10 2.1 2.2 Compliance Reference Point ................................................................................................ 2 Compliance Interpretation .................................................................................................... 2 11 2.3 Regulatory Issues .................................................................................................................. 2 12 3 NORMATIVE REFERENCES.................................................................................................... 3 13 4 DEFINITIONS, ABBREVIATIONS AND ACRONYMS......................................................... 4 14 4.1 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 4.2 Insertion Loss Definition ...................................................................................................... 4 4.3 Sound Pressure Level Definition .......................................................................................... 4 4.4 0 dBr Point Definition .......................................................................................................... 4 4.5 Loudness Rating Definitions ................................................................................................ 4 4.5.1 Loudness Rating ............................................................................................................ 4 4.5.2 Relationship between Loudness Ratings and Loss Plans .............................................. 5 4.5.3 Half-Channel Send and Receive Loudness Rating (SLRHC and RLRHC)...................... 8 4.6 Port Definitions ..................................................................................................................... 8 4.7 Port Descriptions .................................................................................................................. 8 4.7.1 ONS – On Premise Station ............................................................................................ 8 4.7.2 OPS – Off Premise Station ............................................................................................ 8 4.7.3 DGS – Digital Station.................................................................................................... 9 4.7.4 WAN – Wide Area Network ......................................................................................... 9 4.7.5 PAL – Packet Access Line ............................................................................................ 9 4.7.6 DAL – Digital Access Line ........................................................................................... 9 4.7.7 FXO – Foreign Exchange Office ................................................................................... 9 4.7.8 FXD – Foreign Exchange Digital .................................................................................. 9 4.7.9 ATT – Analog Tie Trunk .............................................................................................. 9 4.8 Abbreviations and Acronyms ............................................................................................. 11 34 5 Voice Gateway Definition .................................................................................................... 4 PREAMBLE ................................................................................................................................ 12 35 5.1 General ................................................................................................................................ 12 36 5.2 Reference Impedance .......................................................................................................... 12 37 6 LOSS AND LEVEL PLANS ...................................................................................................... 13 38 39 6.1 6.2 Introduction ......................................................................................................................... 13 Port-to-Port Loss Allocation ............................................................................................... 14 40 6.3 Digital Padding ................................................................................................................... 14 i SP-3-4826-UGRV2 (to be published as ANSI/TIA-912-B) 1 6.4 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 6.5 Full-Channel Loss and Level Plan Requirements ............................................................... 15 6.5.1 Insertion Loss Criteria for Voice Gateways ................................................................ 15 6.5.2 Port-to-Port Loss Table Interpretation ........................................................................ 15 6.5.3 Port-to-Port Loudness Ratings Table Interpretation ................................................... 15 6.5.4 Voice Gateway Loss Ranges ....................................................................................... 15 6.5.5 ANSI/TIA-968-A and ANSI/TIA-968-A-1 Requirements .......................................... 15 6.6 Half-Channel Loss and Level Plan ..................................................................................... 19 6.6.1 Overview ..................................................................................................................... 19 6.6.2 Concept ........................................................................................................................ 19 6.6.3 Principle of Operation ................................................................................................. 19 6.6.4 Applicability ................................................................................................................ 20 6.6.5 Recommended Loss Ranges ........................................................................................ 20 6.6.6 Packet Network Losses................................................................................................ 20 6.6.7 Half-Channel Loss Plan Table .................................................................................... 21 6.6.8 Network Stability......................................................................................................... 22 7 18 19 20 21 22 23 LOSS PARAMETERS ............................................................................................................... 23 7.1 Frequency Response ........................................................................................................... 23 7.1.1 Rejection of Power Line Interference ......................................................................... 23 7.2 Tracking Error and Overload Compression ........................................................................ 23 7.2.1 Tracking Error ............................................................................................................. 23 7.2.2 Overload Compression ................................................................................................ 26 8 24 25 26 Voice Gateway Loss Plan Assumptions ............................................................................. 14 ECHO CONTROL AND RETURN LOSS ............................................................................... 27 8.1 8.2 9 Hybrid Balance Requirements ............................................................................................ 27 Input Impedance Requirements .......................................................................................... 28 NOISE AND DISTORTION IMPAIRMENTS ........................................................................ 30 27 28 29 30 31 32 33 34 35 9.1 Idle-Channel Noise ............................................................................................................. 30 9.1.1 3 kHz Flat Noise .......................................................................................................... 30 9.1.2 C- Message Weighted Noise ....................................................................................... 30 9.2 Longitudinal Balance .......................................................................................................... 31 9.2.1 Longitudinal-to-Metallic Balance ............................................................................... 31 9.2.2 Metallic-to-Longitudinal (Transverse Balance) Balance ............................................ 32 9.3 Crosstalk ............................................................................................................................. 33 9.3.1 Requirement ................................................................................................................ 33 9.4 Quantization Distortion ...................................................................................................... 33 36 9.5 37 10 Single-Frequency Distortion ............................................................................................... 33 OTHER IMPAIRMENTS ....................................................................................................... 34 38 39 40 41 42 10.1 Intermodulation Distortion ................................................................................................. 34 10.2 Envelope Delay ................................................................................................................... 35 10.2.1 Definitions ................................................................................................................... 35 10.2.2 Relative Envelope Delay (RED) Requirements .......................................................... 35 10.3 Impulse Noise ..................................................................................................................... 37 43 10.4 Jitter .................................................................................................................................... 37 ii SP-3-4826-RV2 (to be published as ANSI/TIA-912-B) 1 10.5 Gain Hit............................................................................................................................... 37 2 10.6 Phase Hit ............................................................................................................................. 37 3 10.7 Dropout ............................................................................................................................... 37 4 10.8 Peak-to-Average Power Ratio ............................................................................................. 37 5 11 SIGNAL LEVELS.................................................................................................................... 38 6 ANNEX A (INFORMATIVE) - MEASUREMENT GUIDELINES ........................................ 39 7 A.1 Gain Ripples in the Measurement Path .............................................................................. 39 8 9 A.2 A.3 Transmission Level Translation ......................................................................................... 39 Dial-up Port for Trunk Testing ........................................................................................... 39 10 11 A.4 A.5 Digital Test Port Availability.............................................................................................. 39 Hybrid Balance ................................................................................................................... 40 12 A.6 Input Impedance .................................................................................................................. 40 13 14 A.7 A.8 Idle Channel Noise .............................................................................................................. 44 Longitudinal Balance .......................................................................................................... 45 15 16 17 18 19 A.8.1 Longitudinal to Metallic Balance ....................................................................................... 45 A.8.2 Metallic to Longitudinal (Transverse) Balance .................................................................. 45 A.8.2.1 Transverse Balance Test (Analog) .............................................................................. 46 A.8.2.2 Transverse Balance Test (Digital) ............................................................................... 49 A.9. Crosstalk Coupling Loss ..................................................................................................... 50 20 ANNEX B (INFORMATIVE) - TELEPHONY LOSS LEVEL PLANNING OVERVIEW . 52 21 B.1 22 23 B.2 Send and Receive Levels .................................................................................................... 52 B.2.1 Telephone Equipment Loudness Ratings ........................................................................... 53 24 25 26 27 28 B.2.2 B.2.3 B.2.4 B.3 B.4 Overall Loudness Ratings ................................................................................................... 53 Optimum Overall Loudness Ratings ................................................................................... 54 ATT Network Interface Loudness Ratings ......................................................................... 55 Port-to-Port Loss Allocation ............................................................................................... 55 DTMF Overload on Analog Trunks ................................................................................... 56 29 30 B.5 B.6 Open Loop Loss and Network Stability ............................................................................. 57 Reference Levels................................................................................................................. 57 31 B.6.1 Zero-Level Point ................................................................................................................. 57 32 B.6.2 0 dBm0 Definition .............................................................................................................. 57 33 34 B.6.3 Digital Milliwatt ................................................................................................................. 57 B.6.4 Transmission Level Translation ......................................................................................... 57 35 36 37 38 39 40 Introduction ......................................................................................................................... 52 ANNEX C C.1 C.2 C.3 (INFORMATIVE) - LOSS DEFINITIONS ............................................................ 59 Echo Return Loss (ERL)..................................................................................................... 59 Return Loss (RL) ................................................................................................................ 60 Transhybrid Loss (THL) ..................................................................................................... 60 ANNEX D (INFORMATIVE) - PAN-EUROPEAN LOSS AND LEVEL PLANS - ES 202 020 61 iii SP-3-4826-UGRV2 (to be published as ANSI/TIA-912-B) 1 D.1 The Pan-European Half-Channel Loss Plan ....................................................................... 61 2 3 4 D.1.1 Voice Gateway Connections ............................................................................................... 61 D.1.2 Interface Descriptions ......................................................................................................... 62 D.1.3 Voice Gateway Half-Channel Loss Plan ............................................................................ 62 5 D.2 The Pan-European Full-Channel Loss Plan ........................................................................ 64 6 7 ANNEX E (INFORMATIVE) - LOSS PLAN AND LOUDNESS RATING REFERENCES AND HIERARCHY 65 8 ANNEX F (INFORMATIVE) - IP TRANSMISSION IMPAIRMENTS................................ 66 9 F.1 Delay ................................................................................................................................... 66 10 F.2 Packet Loss ......................................................................................................................... 66 11 F.3 Voice Gateways and Network Performance ....................................................................... 66 12 F.4 Voice Quality of Service..................................................................................................... 67 13 14 ANNEX G (INFORMATIVE) - BIBLIOGRAPHY .................................................................. 68 15 iv SP-3-4826-RV2 (to be published as ANSI/TIA-912-B) 1 2 FOREWORD 3 4 5 (This foreword is not part of this standard.) 6 7 8 9 This document is a TIA Telecommunications Standard produced by Subcommittee TR-41.4 of Committee TR-41. This standard was developed in accordance with TIA procedural guidelines, and represents the consensus position of the Subcommittee, which also served as the formulating group. This standard is based on ANSI/TIA-912-A. 10 11 12 The TR-41.4 IP Telephony Infrastructures Subcommittee acknowledges the contribution made by the following individuals in the development of this standard. 13 Name Roger Britt Richard Frank Richard Hatherill Dorothy Lockard Joachim Pomy Kirit Patel Tailey Tung Representing Nortel Dietrich Lockard Group Maxxeon Dietrich Lockard Group Avaya Cisco Systems Siemens ICN Previous Versions TIA-912-B Editor Editor 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 The European version of this joint work is the "Harmonized Pan-European/North-American approach to loss and level planning for voice gateways to IP based networks" standard. Within ETSI it has the number ETSI ES 202 020 V1.4.1. There are seven annexes in this standard. Suggestions for improvement of this standard are welcome. They should be sent to: Telecommunications Industry Association Engineering Department Suite 300 2500 Wilson Boulevard Arlington, VA 22201 ( http://www.tiaonline.org ) v SP-3-4826-RV2 (to be published as ANSI/TIA-912-B) 1 1 Introduction 2 1.1 General 3 4 5 6 7 8 Advances in digital voice communications over packet channels such as the Internet and Local Area Networks have made it necessary to create a transmission standard for IP (Internet Protocol) Telephony systems. The term coined for these IP Telephony systems is “Voice Gateway” (VG), which is the equivalent to the term PBX as used for traditional time-divisionmultiplexed (TDM) systems. PBX requirements are specified in ANSI/TIA-464-C and its addendum, ANSI/TIA-464-C-1. 9 1.2 Purpose 10 11 12 This standard establishes performance and technical criteria for interfacing and connecting with the various elements of public and private telecommunications networks. Compliance with these requirements should assure quality service. 13 14 15 This standard is intended to be coordinated with the public network loss plan according to the principles of ITU-T Recommendation G.101 and ANSI T1.508 and to fully comply with the regulatory requirements of ANSI/TIA-968-A and its addendum, ANSI/TIA-968-A-1. 16 17 Voice quality-of-service issues such as the impact of transmission delay, speech compression and packet loss are addressed in TIA/EIA/TSB32-A and TIA/TSB116-A. 18 19 20 This standard was also developed in conjunction with ETSI TC STQ, who generated an equivalent half-channel loss plan standard, ETSI ES 202 020, for VGs that is harmonized with this standard. 21 1.3 Categories of Performance Criteria 22 23 Four types of requirements are specified in this standard: Mandatory, Recommended, Permissive and Advisory: 24 25 Mandatory requirements are designated by the terms “shall” and “shall not”. These requirements are used to indicate conformity in which no deviation is permitted. 26 27 28 Recommended requirements are designated by the terms “should” and “should not”. These requirements generally relate to compatibility or performance advantages toward which future designs should strive. 29 30 Permissive requirements are designated by the terms “may” and “may not”. These requirements are used to indicate an action that is permitted within the limits of the standard. 31 32 33 34 35 36 37 Advisory requirements are designated by the term “desirable”. Advisory criteria represent product goals or are included in an effort to ensure universal product compatibility and may be used instead of a recommended requirement. If both a mandatory and an advisory level are specified for the same criterion, the advisory level represents a goal currently identifiable as having distinct compatibility or performance advantages toward which future designs should strive. 1 SP-3-4826-RV2 (to be published as ANSI/TIA-912-B) 1 2 Scope 2 3 4 This standard covers the transmission requirements and specifically the loss plan for VGs. For the purposes of this standard, a VG is considered to be a device that performs voice routing functions between: 5 Telephones; 6 Public and private networks; 7 Packet-based networks1. 8 VGs include, but are not limited to: 9 Packet-based Enterprise equipment that is functionally equivalent to a TDM-based PBX; 10 Residential Gateways; 11 Voice-over-ADSL Integrated Access Device (IAD); 12 Voice-over-Cable Multimedia Terminal Adaptor (MTA). 13 Telephones referred to in this standard are assumed to comply with the requirements specified in: 14 ANSI/TIA-470.110-C for analog telephones, or 15 ANSI/TIA-810-B for digital telephones. 16 2.1 Compliance Reference Point 17 18 The reference point for this standard is determined at the VG interface boundaries and is not to be construed as a constraint on the internal coding or switching techniques of the VG. 19 2.2 Compliance Interpretation 20 21 A VG complies with this standard when it conforms to the requirements applicable to the interfaces with which it is equipped. 22 2.3 Regulatory Issues 23 24 25 26 This standard is intended to be in conformity with ANSI/TIA-968-A and its addenda regarding network harm, but is not limited to the scope of this standard. In the event that the ANSI/TIA968-A and its addenda requirements are more stringent than those contained in this standard, the provisions of ANSI/TIA-968-A and its addenda apply. 1 For historical reasons, the terms “IP” and “IP-based networks” are used extensively in this standard in a generic fashion, but the more generic terms “packet” and “packet-based networks” are now more appropriate. While it is not practical to replace every instance of “IP” with “packet” in this standard, it is the intent of this standard that “IP” and “packet” have the same generic meaning. 2 SP-3-4826-RV2 (to be published as ANSI/TIA-912-B) 1 3 Normative References 2 3 4 5 6 The following standards and recommendations contain provisions, which are referenced in this document. At the time of publication, the editions indicated were valid. All standards are subject to revision, and parties to agreements based on this document are encouraged to investigate the possibility of applying the most recent editions of the standards indicated below. ANSI and TIA maintain registers of currently valid national standards published by them. 7 8 [1] ANSI T1.508 (2003), Loss Plan for Evolving Digital Networks. 9 [2] ANSI/TIA-464-C-2002, Requirements for PBX Switching Equipment. 10 [3] ANSI/TIA-464-C-1-2004, Requirements for PBX Switching Equipment – Addendum 1. 11 12 [4] ANSI/TIA-470.110-C-2004, Handset Acoustic Performance Requirements for Analog Telephones. 13 [5] ANSI/TIA-810-B-2006, Transmission Requirements for Narrowband Digital Telephones. 14 15 [6] ANSI/TIA-968-A-2002, Technical Requirements for Connection of Terminal Equipment to the Telephone Network. 16 17 [7] ANSI/TIA-968-A-1-2003, Technical Requirements for Connection of Terminal Equipment to the Telephone Network – Addendum 1. 18 [8] ITU-T Recommendation G.101 (11/03), The transmission plan. 19 20 [9] ITU-T Recommendation G.122 (03/93), Influence of National Systems on Stability and Talker Echo in International Connections. 21 22 [10] ITU-T Recommendation G.711 (11/88), Pulse Code Modulation (PCM) of Voice Frequencies. 23 24 [11] ETSI ES 202 020 V1.4.1 (2006), Harmonized Pan-European/North-American approach to loss and level plan for voice gateways to IP based networks. 3 SP-3-4826-RV2 (to be published as ANSI/TIA-912-B) 1 4 Definitions, Abbreviations and Acronyms 2 For the purposes of this standard, the following definitions, abbreviations and acronyms apply. 3 4.1 Voice Gateway Definition 4 5 6 A device which routes packetized voice from one end-point to another, and provides other voice related functions that a data gateway would not provide, e.g., voice coding and/or compression and echo cancellation. 7 8 9 10 Its function is analogous to a PBX in that it provides connectivity between customer premise voice terminals. It may provide interfaces to analog and digital (TDM and IP) voice terminals, and access to both public and private WANs and public and private switched telephone networks. 11 4.2 Insertion Loss Definition 12 13 14 The insertion loss of a VG connection is defined as the 1 kHz level difference between the power delivered from a source connected across an input port to the power delivered to a measuring instrument connected across an output port. 15 16 Both the signal source and the measurement instrument are assumed to have an impedance of 600 at 1 kHz. 17 The insertion loss values are expressed as an absolute loss in dB between interface ports. 18 4.3 Sound Pressure Level Definition 19 20 Sound pressure level is a value expressed as a ratio of the pressure of a sound to a reference pressure. The following sound level units are used in this standard: 21 22 23 dBPa: 24 25 26 dBSPL: The sound pressure level, in decibels of a sound is 20 times the logarithm to the base 10 of the ratio of the pressure of this sound to the reference pressure of 2 X 10-5 N/m2 (0 dBPa = 94 dBSPL). 27 4.4 0 dBr Point Definition 28 29 30 31 32 From this standard’s loss plan perspective, the 0 dBr point is any point in the digital network. The “r” refers to the term “relative”, but unlike some loss plans, the loss plan in this standard is absolute, not relative, so the concept of relative levels is not used. Note: more rigorous definitions of the 0 dBr point may be required for other applications, e.g., for use with the EModel. 33 4.5 Loudness Rating Definitions 34 4.5.1 Loudness Rating 35 36 37 38 Loudness ratings are a function of the acoustic/electrical conversion characteristics of the originating and terminating equipment (typically telephones). These ratings are determined by measuring the conversion characteristics over the telephony frequency band and by applying a weighting factor for each third octave band. 39 40 41 These loudness ratings are defined as the Send Loudness Rating (SLR) and Receive Loudness Rating (RLR), and the sum of these ratings (plus any circuit gain or loss) is defined as the Overall Loudness Rating (OLR). The sound pressure level, in decibels of a sound is 20 times the logarithm to the base 10 of the ratio of the pressure of this sound to the reference pressure of 1 Pascal (Pa). Note: 1 Pa = 1 N/m2. 4 SP-3-4826-RV2 (to be published as ANSI/TIA-912-B) 1 The following convention is used in this standard when referring to loudness ratings: 2 3 The Send Loudness Rating (SLR) and Receive Loudness Rating (RLR) are collectively referred to as the Loudness Rating (LR). 4 5 The loudness ratings are given in the order SLR and RLR, i.e., a digital telephone with an SLR of 8 dB and RLR of 2 dB would be designated as having an LR of 8 and 2. 6 4.5.2 Relationship between Loudness Ratings and Loss Plans 7 8 9 10 11 12 In order to understand the relationship between loudness ratings and loss plans, five basic fullchannel scenarios are illustrated in Figures 1 to 5. Although these scenarios are simple, they can easily be applied to more complicated scenarios because the digital network is lossless and many combinations of TDM or IP networks can be inserted into the diagrams at the half-channel 0 dBr point, without affecting the end-to-end loss plan because the loss plan should only be applied at the edge of the network. 13 14 15 16 17 18 19 20 21 Each diagram follows the same format. On the left and right hand edges are either analog or digital telephones. Figure 1 illustrates the simplest example, two digital sets connected to a Voice Gateway. Starting in the top left corner, the SLR of the digital set is 8 dB. It is highlighted in bold because the 8 dB is an important standards requirement in ANSI/TIA-810-B, as identified in the yellow tab. Moving towards the center 0 dBr point, the half-channel SLR, SLRHC, remains at 8 dB, because there is no loss in the digital path including the upper left Tx pad of the DGS port (as specified in this standard) in the VG. For loss planning purposes, the “Terminal” label extends to the edge of the VG to be consistent with analog sets, whose loudness ratings include the copper line. Note: The VG loss plan is specified in Clause 6. 22 23 24 25 26 27 28 RLR works in a similar manner, but it is evaluated from right-to-left towards the 0 dBr point. The set RLR is 2 dB, the loss plan, i.e., Rx pad in the upper right of the VG, is 0 dB, so the halfchannel RLR, RLRHC, just to the right of the 0 dBr point, is still 2 dB. The optimum OLR of 10 dB for this upper connection is shown in the green box on the right hand side. It is calculated by adding the upper SLRHC to the upper RLRHC, i.e., OLR = 8 + 2 = 10 dB. The bottom connection from the right digital set to the left digital set is evaluated the same way and in this case is symmetrical. 29 Figure 1 – Scenario 1: Digital Set-VG-Digital Set Terminal TIA-810-B SLR 8 dB 0 dB Digital 10 dB OLR Set 0 dB 2 dB RLR TIA-810-B 30 31 32 33 34 35 36 37 Digital Line Public/Private Network TIA-912-B TIA-912-B SLRHC RLRHC 8 dB 2 dB Tx pad Rx pad 0 dB 0 dB DGS VG DGS 0 dB 0 dB Rx pad Tx pad 2 dB 8 dB RLRHC SLRHC TIA-912-B TIA-912-B 0 dBr Terminal TIA-810-B RLR 2 dB 0 dB Digital Line Digital OLR 10 dB Set 0 dB 8 dB SLR TIA-810-B Figure 2 illustrates a basic analog set connection with two analog sets connected, both with 0 km loops, to the same Digital End Office (DEO). Analog sets may or may not have loop compensation (shortened to “loop comp” in the diagrams). This feature is only applicable to short DEO lines. A detailed explanation of loop compensation is documented in Annex E of ANSI/TIA-470.110-C. Since the telephone in Figure 2 does not have any loop compensation loss (0dB), the OLR is quite loud at 3 dB. However, some telephones do have loop compensation and these telephones will have better, i.e., quieter, OLRs. Theoretically, DEOs should be able to 5 SP-3-4826-RV2 (to be published as ANSI/TIA-912-B) 1 2 detect very short loops like this and apply extra electrical loss to compensate for the lack of copper loss. 3 4 5 6 7 8 9 10 The loudness ratings of analog sets are determined acoustically at the handset and electrically at a termination that is the equivalent of the line card of a DEO, In addition, the LRs are usually specified at several different line lengths, meaning that the terms SLR and RLR include the copper line. So Figure 2 introduces the terms SLRT and RLRT for the loudness ratings of the telephone without the copper line, where the subscript ‘T’ refers to a telephone without the copper line, e.g., a 0 dB line. The SLRT of 4 dB and RLRT of -7 dB are specified in ANSI/TIA470.110-C as the SLR and RLR (bold 4 dB and -7 dB, respectively) for the 0 dB line. In addition, Annex E of ANSI/TIA-470.110-C describes this in more detail. 11 12 13 14 The DEO loss plan is specified in ANSI/T1.508-2003 and it is 0 dB in the send direction and 6 dB in the receive direction. So at the 0 dBr point, the SLRHC remains at 4 dB, but the RLRHC changes to -1 dB from RLR -7 dB, due the 6 dB Rx pad. The connection is symmetrical, so the OLR is 3 dB in both directions, i.e., OLR = 4-1 = 3 dB. 15 Figure 2 – Scenario 2: Analog Set-DEO-Analog Set (0 km) Terminal TIA-470.110-C SLR 4 dB Anx E SLRT 4 dB 0 dB 3 dB OLR Analog Loop Set Comp 0 dB -7 dB RLRT Anx E 0 dB 0 km PSTN Subscriber Line 0 dB -7 dB RLR TIA-470.110-C Public Network T1.508 T1.508 SLRHC RLRHC 4 dB -1 dB Tx pad Rx pad 0 dB 6 dB AAL DEO AAL 6 dB 0 dB Rx pad Tx pad -1 dB 4 dB RLRHC SLRHC T1.508 T1.508 0 dBr Terminal TIA-470.110-C RLR -7 dB 0 dB 0 km PSTN Subscriber Line 0 dB Anx E RLRT -7 dB 0 dB Loop Analog Comp Set OLR 3 dB 0 dB 4 dB SLR TIA-470.110-C 4 dB SLRT Anx E 16 17 18 19 20 Scenario 3 is similar to Scenario 2 except the loop in both directions is increased to the typical length of 2.7 km or in terms of loss, 4 dB. As shown in Figure 3, the SLRHC is the optimum 8 dB at the 0 dBr point, while the RLRHC of 3 dB is very close to the optimum 2 dB, based on the RLRT of -7 dB plus the copper loss of 4 dB (RLR of -3 dB) and the DEO Rx loss pad of 6 dB. 21 Figure 3 – Scenario 3: Analog Set-DEO-Analog Set (2.7 km) Terminal TIA-470.110-C SLR 8 dB Anx E SLRT 4 dB 0 dB 11 dB OLR Analog Loop Set Comp 0 dB -7 dB RLRT Anx E 22 23 24 25 26 4 dB 2.7 km PSTN Subscriber Line 4 dB -3 dB RLR TIA-470.110-C Public Network T1.508 T1.508 SLRHC RLRHC 8 dB 3 dB Tx pad Rx pad 0 dB 6 dB AAL DEO AAL 6 dB 0 dB Rx pad Tx pad 3 dB 8 dB RLRHC SLRHC T1.508 T1.508 0 dBr Terminal TIA-470.110-C RLR -3 dB 4 dB 2.7 km PSTN Subscriber Line 4 dB 8 dB SLR TIA-470.110-C Anx E RLRT -7 dB 0 dB Loop Analog Comp Set OLR 11 dB 0 dB 4 dB SLRT Anx E Scenario 4 in Figure 4 is similar to Scenario 2 except the DEO in Scenario 2 is replaced with a VG. In addition, there are a number of other changes: (a) the port designation at the line card changes from AAL for the DEO to ONS for the VG, (b) the loudness rating specification for the set changes to Annex E of ANSI/TIA-470.110-C because most VGs have different lines cards 6 SP-3-4826-RV2 (to be published as ANSI/TIA-912-B) 1 2 3 4 compared to DEOs, (c) the loss plan changes from 0 dB and 6 dB in ANSI/T1.508 to 0 dB and 12 dB in this standard. The end result is an improved loss plan with an OLR of 9 dB because the VG inserts 6 dB more loss in the Rx direction knowing that there is no copper loss between the set and the VG. 5 6 7 8 9 10 11 At this point, it is worth explaining a subtle detail about the full-channel loss plans presented in Clause 6.5. ONS to ONS connections, like Scenario 4, are specified with 12 dB of loss and are shown in Figure 4 as 12 dB of loss in the receive direction. This may not be the optimum way to partition the loss plan, but it is the only way that it can be specified in Table 1 and Table 2. An alternative partitioning of the 12 dB is shown in the half-channel loss plan, Table 6, with 3 dB in the send direction (Tx pad) and 9 dB in the receive direction (Rx pad). Scenario 5 will expand more on this point. Also see Table 5, the last paragraph of Clause 6.6.1 and Annex B.4. 12 Figure 4 – Scenario 4: Analog Set-VG-Analog Set Anx E SLRT 4 dB 10 dB OLR Terminal Public/Private Network TIA-470.110-C Anx E TIA-912-B TIA-912-B SLR SLRHC RLRHC 4 dB 7 dB 2 dB Tx pad Rx pad 0 dB 0 dB 3 dB 0 dB Analog Loop Set Comp 0 dB -7 dB RLRT Anx E Digital 0 km Line Line ONS VG DGS 0 dB 9 dB 0 dB Rx pad Tx pad -7 dB 2 dB 8 dB RLR RLRHC SLRHC TIA-470.110-C Anx E TIA-912-B TIA-912-B 0 dBr Terminal RLR 810-B RLR 2 dB 0 dB Digital Line Digital OLR 9 dB Set 0 dB 8 dB SLR SLR 810-B 13 14 15 16 17 18 19 20 21 22 The final example, Scenario 5, shown in Figure 5, is the required loss plan for most Residential Gateways, like MTAs and IADs. This is because this type of VG generally has an ONS port on one side and a digital port on the other. While the digital port in the example is connected to digital set via a DGS port, in practice the digital port would be a PAL port. The loss plan for PAL and DGS ports is identical, so Scenario 5 correctly illustrates the loudness ratings and loss plan for the “typical” situation. The objective of most loss plans to present SLRHC 8 dB and RLRHC 2 dB at the 0 dBr point. This is achieved in Scenario 5 within the limitations of the 3 dB loss steps used by this standard. Be aware that is acceptable to fine tune the Tx pad to 4 dB, but it is unnecessary because the tolerance on analog telephone loudness ratings is wide. 23 24 25 26 27 Note that if the 3 dB and 9 dB loss plan in Scenario 5 was applied to Scenario 4 the OLR results would be the same. However, the loss partitioning in Scenario 5 has the advantage that the 3 dB Tx pad replaces the missing copper line, which helps to produce the correct level to the DTMF receiver in the VG. Similarly in the receive direction, Scenario 5 emulates Scenario 3 with the 9 dB partitioned as 3 dB copper line plus 6 dB for the DEO Rx pad. 7 SP-3-4826-RV2 (to be published as ANSI/TIA-912-B) Figure 5 – Scenario 5: Analog Set-VG-Digital Set 1 Anx E SLRT 4 dB 10 dB OLR Analog Loop Set Comp 0 dB -7 dB RLRT Anx E 2 3 Terminal Public/Private Network TIA-470.110-C Anx E TIA-912-B TIA-912-B SLR SLRHC RLRHC 4 dB 7 dB 2 dB Tx pad Rx pad 0 dB 0 dB 3 dB 0 dB Digital 0 km Line Line ONS VG DGS 0 dB 9 dB 0 dB Rx pad Tx pad -7 dB 2 dB 8 dB RLR RLRHC SLRHC TIA-470.110-C Anx E TIA-912-B TIA-912-B 0 dBr Terminal RLR 810-B RLR 2 dB 0 dB Digital Line Digital OLR 9 dB Set 0 dB 8 dB SLR SLR 810-B 4 4.5.3 Half-Channel Send and Receive Loudness Rating (SLRHC and RLRHC) 5 6 7 The concept of 0 dBr can apply at any point in the digital connection path. A special case is the VG-to-packet network connection point, as this is the reference point for all packet transmission levels. The SLR at the 0 dBr point is defined as the SLRHC (Half-Channel SLR). 8 9 Similarly, for the packet network-to-VG connection point, the RLR at the 0 dBr point is defined as the RLRHC (Half-Channel RLR). 10 11 See Clause 6.6 for further information on the half-channel loss plan and Annex B for further information on loudness ratings. 12 4.6 Port Definitions 13 14 15 16 Figure 6 illustrates the connection types, and corresponding VG port definitions, for a typical VG application. There may be other applications not covered by this diagram, but sufficient information is provided for users to determine the applicable connection types for their particular application, and the corresponding port losses to be applied. 17 18 19 Users should be aware that the port definition might only apply to the VG end of the connection, as other entities could have a different port definition for the same connection. For example, the VG FXO connection is defined as an AAL (analog access line) by the digital end office (DEO). 20 21 22 23 Note: Connections such as DAL, FXO, FXD, and ATT are generically referred to as trunks. This term refers to connections between DEOs in the PSTN, and analogously is used to describe connections between DEOs, PBXs, and VGs. It should also be noted that from a DEO and T1.508 perspective, these VG trunks are called lines. 24 4.7 Port Descriptions 25 4.7.1 ONS – On Premise Station 26 27 28 29 30 An ONS interface is used for standard analog telephones, representative of 2500-type POTS telephones, located on the same premises as the VG, and is the direct equivalent of the PBX ONS connection. The termination is 600 ohms, the connection loss from the station to the VG is typically low and the DC feed is usually a constant current supply that simulates a long loop. The term FXS is sometimes used in place of ONS. 31 4.7.2 OPS – Off Premise Station 32 33 An OPS interface is used for standard analog telephones, representative of 2500-type POTS telephones, not located on the same premises as the VG, and is the direct equivalent of the PBX 8 SP-3-4826-RV2 (to be published as ANSI/TIA-912-B) 1 2 3 4 OPS connection. The termination is 600 ohms, the connection loss from the station to the VG is typically significant and the DC feed is usually the same as a DEO (48 volts). This port is also used for analog two-wire connections to remote VGs, PBXs and Key Systems, via a local DEO. The term FXS is sometimes used in place of OPS. 5 4.7.3 DGS – Digital Station 6 A DGS interface is used for all digital telephones conforming to ANSI/TIA-810-B. 7 Note: This includes digital telephones based on both TDM and packet transmission. 8 4.7.4 WAN – Wide Area Network 9 10 11 A WAN interface connects from Enterprise VGs to packet-based wide area networks. The transmission path within the WAN is entirely digital. The only distinction between a WAN port and a PAL port is that the PAL port supports less bandwidth. 12 13 14 Note: The term WAN is used in the same context as PSTN, in that it represents connections between geographically separated VGs. It should be noted that WAN and LAN are synonymous from a transmission perspective. 15 4.7.5 PAL – Packet Access Line 16 17 18 A PAL interface connects from MTA or IAD VGs to packet-based wide area networks. The transmission path within the PAL is entirely digital. The only distinction between a WAN port and a PAL port is that the PAL port supports less bandwidth. 19 4.7.6 DAL – Digital Access Line 20 21 22 23 A DAL interface connects to all TDM-based digital network connections and it is the direct equivalent of the PBX DAL interface. It should be noted that although the connection to the public switched network may be digital, there is no guarantee that the end-to-end connection will remain digital. 24 4.7.7 FXO – Foreign Exchange Office 25 26 An FXO interface is used for analog connections to a central office. It is equivalent to the PBX term AAL(A), or analog access line (analog). 27 4.7.8 FXD – Foreign Exchange Digital 28 29 30 31 An FXD interface is used for digital connection, via a channel bank, to an analog access line (AAL) of a DEO. It is equivalent to the PBX term AAL(D), or analog access line (digital). A loss equivalent to the typical analog connection loss has to be inserted at the VG, as the channel bank is located close to the DEO. 32 4.7.9 ATT – Analog Tie Trunk 33 34 35 36 An ATT interface is used for four-wire analog private network connections, typically via the public network. This port also applies to two-wire VG interfaces that use an external four-wire termination set (4WTS) to connect to the public network. PBX documents may either use the same term, ATT, or the older term, A/TT. 37 9 SP-3-4826-RV2 (to be published as ANSI/TIA-912-B) 1 Figure 6 – Voice Gateway Port Definitions and Connections 2 Packe t Conne ction Packet Facilities (DEO, IDLC, VG) TDM Conne ction Analog Conne ction PAL WAN PAL WAN Voice Gateway Packet Network Ports DEO PAL PAL WAN WAN DAL DAL DAL DAL DT DAL AAL FXO AAL CB FXD Public Switched Network Ports Voice Gateway Private Network Ports (Enterprise, MTA & IAD) Telephone Access Lines OPS OPS ONS DGS PBX DAL DAL ONS AAL(A) ATT ATT DGS 3 4 VG Port Designation Port Definition PBX Port Designation ONS DEO Port Designation AAL ONS Analog On Premise Station OPS Analog Off Premise Station - can be via an analog connection through a DEO OPS AAL DGS Digital Station (telephone) DGS DAL WAN Wide Area Network (packet connection) - WAN PAL Packet Access Line (packet connection) - PAL DAL Digital Access Line - digital connection to a DEO DAL DAL FXO Foreign Exchange Office - analog connection to a DEO AAL(A) AAL FXD Foreign Exchange Digital - digital connection to a DEO via a channel bank AAL(D) AAL ATT Analog Tie Trunk - private analog network connection to a gateway/PBX ATT ATT 10 SP-3-4826-RV2 (to be published as ANSI/TIA-912-B) 1 4.8 Abbreviations and Acronyms 2 Abbreviations and acronyms, other than in common usage, are defined below. 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 AAL AAL(A) AAL(D) A/D ADSL ATT A/TT BRL CB CO D/A DAL DEO DID DGS DMW DT FDM FXD FXO FXS IAD IP LAN LR MTA OLL OLR ONS OPS PAL PBX PCM PSTN RLR RLRHC SLR SLRHC SPL TDM VG WAN Analog Access Line (Analog Interface at DEO) Analog Access Line (Analog Interface at PBX) Analog Access Line (Digital Interface at PBX) Analog-to-Digital Asynchronous Digital Subscriber Loop Analog Tie Trunk (latest acronym format) Analog Tie Trunk (previous acronym format) Balance Return Loss Channel Bank Central Office Digital-to-Analog Digital Access Line Digital End Office Direct Inward Dialing Digital Station Digital Milliwatt Digital Trunk Frequency Division Multiplexing Foreign Exchange Digital Foreign Exchange Office Foreign Exchange Station (see ONS & OPS) Integrated Access Device Internet Protocol Local Area Network Loudness Rating Multimedia Terminal Adaptor Open Loop Loss Overall Loudness Rating On Premise Station Off Premise Station Packet Access Line Private Branch Exchange Pulse Code Modulation Public Switched Telephone Network Receive Loudness Rating Half-Channel Receive Loudness Rating Send Loudness Rating Half-Channel Send Loudness Rating Sound Pressure Level Time Division Multiplex Voice Gateway Wide Area Network 11 SP-3-4826-RV2 (to be published as ANSI/TIA-912-B) 1 5 Preamble 2 5.1 General 3 4 Digital interfaces in the United States and Canada use -law encoding/decoding as defined in ITU-T Recommendation G.711 (1988), ‘Pulse Code Modulation of Voice Frequencies’. 5 6 7 8 The transmission requirements contained in this standard are based on an industry-developed fixed loss and level plan. The requirements were developed with the objective of maintaining or improving the quality of service for connections within existing and evolving communication networks. 9 10 11 The requirements contained in this standard are based on current understanding of required performance and on the capabilities of present technology. As technology evolves, or as performance needs change, these requirements may become subject to change. 12 13 Note: For historical reasons the terms Stations, Sets, Telephones, and Terminals are used interchangeably in this standard. 14 5.2 Reference Impedance 15 16 Transmission requirements contained here apply with station and trunk interfaces terminated in a nominal impedance of 600 , unless otherwise specified. 17 18 All measurements should be made at an equipment access point connected to the equipment by no more than 15 meters of cable, unless otherwise specified. 12 SP-3-4826-RV2 (to be published as ANSI/TIA-912-B) 1 6 Loss and Level Plans 2 6.1 Introduction 3 4 5 6 7 8 9 10 While this standard may appear to be a stand-alone document, it is not. Annex E best illustrates how this standard fits into the hierarchy of transmission planning standards. ITU-T Recommendation G.101 is at the top of the hierarchy and it provides the high level objectives for this standard. It is the objective of this standard to comply with the fundamental principles of transmission planning given in Clause 5 of Rec. G.101. In particular principle 5, which recommends that the optimum end-to-end loudness be OLR = 10 dB, partitioned as SLR = 8 dB and RLR = 2 dB on digital connections for optimum dynamic range, is the key objective of this loss and level plan. 11 12 13 14 15 16 17 Another important objective for this loss plan is to economically minimize the effect of echo due to signal reflections that are caused by impedance mismatching at 2-to-4 wire conversions in the transmission path. In general, the insertion of loss in the transmission path reduces the impairment due to echo, but increases the impairment due to noise. Another consideration that must be taken into account is that insertion of too much loss will adversely affect customer satisfaction with the received listening level. Therefore, rather than increasing loss indefinitely on longer circuits, echo is controlled by the deployment of echo cancellers. 18 19 20 21 If digital telephones (i.e., conforming to ANSI/TIA-810-B) are used at each end of the connection, and if the entire end-to-end connection is over a digital based network, then the loss plan is very simple. The digital sets provide the desired overall loudness rating, hence the VG would not insert any loss or gain in the voice channel. 22 23 24 In practice, however, many VG connections will involve the public network in one form or another, either by connections to the public switched network or by connections to private networks over public network facilities (e.g., tie trunks). 25 26 27 28 29 30 In general, connections through the public network can be analog either in whole or in part and involve 2-to-4 wire conversions. The allocation of loss among the public network subsystems affects the noise at the telephone receiver, the echo heard by the talker and the listener, the probability of hearing other conversations, and the probability of causing interference on connections being used by other customers. Also signals at too high a level can cause intermodulation distortion in some older carrier systems. 31 32 33 34 35 This standard recommends a loss and level plan for VGs that specifies the amount of loss or gain to be inserted by the gateway when interfacing with the various elements of public and private telecommunications networks. It is intended to be coordinated with the public network loss plan according to the fundamental loss planning principles of ANSI T1.508 and it is intended to fully comply with ANSI/TIA-968-A and ANSI/TIA-968-A-1. 36 The loss and level plan consists of two parts: 37 38 39 40 41 42 43 A full-channel plan that defines the port-to-port losses for all connections types. This is similar to the PBX loss level plan as specified in ANSI/TIA-464-C and ANSI/TIA-464-C-1, and ensures satisfactory interworking with the existing TDM-based public and private networks A half-channel plan that defines the port-to-packet network and packet network-to-port losses. This plan is specific to IP/packet telephony and will facilitate the interworking of national and international IP/packet telephony networks. 13 SP-3-4826-RV2 (to be published as ANSI/TIA-912-B) 1 6.2 Port-to-Port Loss Allocation 2 3 4 The allocation of the port-to-port loss to the send and receive ports directly influences the available dynamic range of the PCM coding scheme. This may lead to substantial impacts on speech transmission quality as perceived by the user. 5 6 Care should be taken to ensure that excessive input gain or loss does not cause either PCM encoding overload, or a poor signal-to-noise ratio, at the 0 dBr point. 7 See Annex B.3 for further information on port-to-port loss allocation. 8 6.3 Digital Padding 9 10 11 12 Digital padding refers to the technique of implementing port-to-port losses by changing the level of the digitally encoded voice. Digital padding should be avoided wherever possible, as it has the potential to increase quantization distortion. Losses involving analog ports should be implemented before encoding or after decoding. 13 6.4 Voice Gateway Loss Plan Assumptions 14 15 16 17 The port-to-port losses for VGs were developed based on the loss plans for public and private networks. The VG loss plan is intended to provide satisfactory grade-of-service (GoS) performance and compatibility with the public and private network loss plans. The following assumptions were the prime considerations: 18 19 (1) The transmission loss and level plan of the PSTN, which is primarily an all-digital network with some fixed loss as described in T1.508, forms a basis for the private network loss plan. 20 21 (2) Digital end offices insert 6 dB of loss, as described in T1.508, in the receive direction of analog access lines to ensure network stability, echo control and optimum end-to-end levels. 22 (3) Transmission facilities have losses compatible with the VG port-to-port losses. 23 (4) The ONS connection loss from the station to the VG is typically low (0 dB assumed). 24 (5) The OPS connection loss from the station to the VG is typically significant (4 dB assumed). 25 26 (6) FXD connections require a loss equivalent to a typical analog connection to be inserted at the VG, as the channel bank is located close to the DEO. 27 (7) Non-proprietary VG stations have the following loudness ratings: 28 Station SLR (dB) RLR (dB) Notes 29 OPS 8 -3 a, b) 30 ONS 4 -7 a, c) 31 DGS 8 2 a, d) 32 Notes: 33 34 35 a) The OPS (off premise station) LRs are representative of 2500-type POTS sets operating on 26 gauge/2.75 km loops with normal 48 volt battery feed and 600 ohm termination, as measured at a VG OPS port. See ANSI/TIA-470.110-C, Annex E for further details. 36 37 38 b) The ONS (on premise station) LRs are representative of 2500-typePOTS sets operating on very short loops with the typical current-limited battery feed and 600 ohm termination of VG ONS ports. See ANSI/TIA-470.110-C, Annex E for further details. 39 40 41 c) The DGS (digital station) loudness ratings are chosen to improve interoperability with the standard ITU LR levels for digital sets of SLR = 8 dB and RLR = 2 dB. See ANSI/TIA-810-B for further details. 14 SP-3-4826-RV2 (to be published as ANSI/TIA-912-B) 1 6.5 Full-Channel Loss and Level Plan Requirements 2 3 4 5 6 The intent of the full-channel loss plans specified in Table 1 and Table 2 shall be implemented in Voice Gateways. The associated level plans are provide in Table 3 and Table 4. Related regulatory information on allowable net amplification between ports is provided in Table 5. A half-channel loss plan for packet-based voice services is provided in Table 6 that gives some clarification of the intent of the full-channel loss plan. 7 6.5.1 Insertion Loss Criteria for Voice Gateways 8 9 10 11 12 Enterprise VGs normally have call-by-call adjustable loss plans that permit compliance with the full matrix of port-to-port connections, as specified by the loss plan in Table 1. MTA and IAD VGs usually have fixed loss plans. Table 2 is a fixed loss plan subset of Table 1 that is appropriate for MTA and IAD VGs. The VG interfaces depicted in the loss plan are defined in Figure 6, and described in Clause 4.6. 13 6.5.2 Port-to-Port Loss Table Interpretation 14 15 In Table 1 and Table 2, arrows at the row and column designators indicate the transmission direction in which the co-ordinate loss values are to be inserted. 16 17 18 For example Table 1, co-ordinate 1B indicates a nominal port-to-port loss of 9 dB from the ONS interface to the OPS interface, and co-ordinate 2A indicates a 9 dB loss in the other direction, from the OPS interface to the ONS interface. 19 Note: This is a loss plan, therefore negative values denote gain; e.g., -6 indicates 6 dB of gain. 20 6.5.3 Port-to-Port Loudness Ratings Table Interpretation 21 22 23 24 Table 3 and Table 4 are provided to show the relationship between OLR and SLR, Loss, and RLR. For example, for an ONS to OPS connection, the ONS SLR is 4 dB, the VG loss is 9 dB (from 1B in Table 1), and the OPS RLR is -3 dB. The overall loudness ratings is therefore 4 + 9 - 3 = 10 dB. See Annex B.2 for further information on loudness ratings. 25 6.5.4 Voice Gateway Loss Ranges 26 27 28 The port-to-port losses in Table 1 and Table 2 are the recommended nominal values. Although there are no mandatory loss ranges associated with these values, it is desirable that the average 1 kHz loss fall within 0.5 dB of the nominal loss values given in Table 1 and Table 2. 29 6.5.5 ANSI/TIA-968-A and ANSI/TIA-968-A-1 Requirements 30 31 32 33 34 35 36 ANSI/TIA-968-A-1, an addendum to ANSI/TIA-968-A, relaxes the encoded analog content signal power limitations, relative to ANSI/TIA-968-A. The result is less allowable net amplification between some ports, more allowable amplification between other ports and no change in the allowable net amplification between most ports. The revised allowable Net Amplification between ports requirements are specified in Table 4.6 of ANSI/TIA-968-A-1, which for convenience, is reproduced in this standard as Table 5. Note that the values in Table 5 are in terms of gain, while the values in Table 1 and Table 2 are in terms of loss. 37 38 39 40 The requirements in Table 1 and Table 2 are coordinated with Table 4.6 of ANSI/TIA-968-A-1, so that all the values specified in Table 1 and Table 2 have either the same loss or more loss than Table 4.6 of ANSI/TIA-968-A-1. This means that compliance with Table 1 and Table 2 of this standard guarantees compliance with Table 4.6 of ANSI/TIA-968-A-1. 41 42 43 44 45 46 The situation where the value of loss specified in Table 1 and Table 2 are identical to the value of loss specified in Table 4.6 of ANSI/TIA-968-A-1 is addressed in Note 4 of Table 4.6. Note 4 permits the values in Table 4.6 to be exceeded as long as the absolute signal power limitations for the port are not exceeded. This includes Clause 6.5.4 of this standard, which allows a tolerance of up to 0.5 dB of additional gain, relative to the nominal losses specified in Table 1 and Table 2. 47 15 SP-3-4826-RV2 (to be published as ANSI/TIA-912-B) 1 Table 1 – Enterprise Voice Gateway Loss Plan 2 1 2 3 4 5 6 7 8 A B C D E F G H ONS OPS DGS WAN DAL FXO FXD ATT 12 9 9 9 9 0 3 6 9 6 6 6 6 0 0 0 3 0 0 0 0 -62 -32 0 3 0 0 0 0 -62 -32 0 3 0 0 0 0 -62 -32 0 3 0 0 0 0 0 0 0 6 0 3 3 3 0 0 0 9 3 3 3 3 0 0 0 Loss1 (dB) ONS OPS DGS WAN DAL FXO FXD ATT 3 4 5 6 7 8 9 10 11 12 Note 1: Losses have been selected as multiples of 3 dB, assuming that this simplifies the implementation. Note 2: There is a potential risk of DTMF overload if an FXO analog trunk is connected to DGS, WAN or DAL and the VG is located less than 2 km from the DEO due to the gain added in the A/D direction. In these cases it is recommended that the FXD to DGS, WAN or DAL setting be used instead because the FXD setting introduces 3 dB less gain in one direction and 3 dB more loss in the other direction. See Annex B.4 ‘DTMF Overload on Analog Trunks’. 13 Table 2 – MTA/IAD Voice Gateway Loss Plan 1 2 3 4 14 15 16 17 18 Loss1 (dB) ONS DGS PAL DAL A B C D ONS DGS PAL DAL 12 9 9 9 3 0 0 0 3 0 0 0 3 0 0 0 Note 1: Losses have been selected as multiples of 3 dB, assuming that this simplifies the implementation. For the optimum OLR of 10 dB, the “to ONS” loss value is actually 13 dB. 16 SP-3-4826-RV2 (to be published as ANSI/TIA-912-B) 1 Table 3 – Enterprise Voice Gateway Loudness Ratings 2 ONS OPS DGS WAN DAL FXO1 FXD1 ATT2 (dB) SLR 4 8 8 8 8 17 14 15 RLR OLR OPS -3 DGS 2 WAN 2 DAL 2 9 10 10 10 10 10 10 14 10 11 11 11 11 14 11 12 9 10 10 10 10 13 13 17 9 10 10 10 10 13 13 17 9 10 10 10 10 13 13 17 13 14 14 14 14 23 20 21 13 11 14 14 14 20 17 18 14 12 12 12 12 18 15 16 ONS1 -7 FXO1 6 FXD1 3 ATT2 1 3 4 Note 1: The loudness ratings for the FXO and FXD ports include a nominal 6 dB DEO loss. 5 6 Note 2: The loudness ratings for the ATT port include a nominal 2 dB trunk loss, see Annex B.2.4, ‘ATT Network Interface Loudness Ratings’. 7 8 9 Table 4 – MTA/IAD Voice Gateway Loudness Ratings ONS DGS PAL DAL 1 (dB) SLR 4 8 8 8 RLR OLR ONS1 -7 DGS 2 PAL 2 DAL 2 9 10 10 10 9 10 10 10 9 10 10 10 9 10 10 10 10 11 17 SP-3-4826-RV2 (to be published as ANSI/TIA-912-B) 1 2 Table 5 – ANSI/TIA-968-A-1, Clause 4.5.2.5 - Allowable Net Amplification Between Ports To → From ↓ TIA-912-A Port Designations ATT N/A DAL DAL DGS ONS OPS FXO & FXD DAL Lossless Tie Trunk Port (2/4 wire) Sub-rate 1.544 Mbps Satellite Tie Trunk Port (4-wire) Sub-rate 1.544 Mbps Tandem Tie Trunk Port (4-wire) Integrated Services Trunk Ports Approved Digital TE On Premises Station Port with Approved TE Off Premises Station Port (2-wire) Analog Public Switched Network Ports (2-wire) Sub-rate 1.544 Mbps Digital PBXCO Trunk Ports (4-wire) Tie Trunk Type Ports Lossless (2/4 wire) Sub-rate 1.544 Mbps Satellite (4-wire) Sub-rate 1.544 Mbps Tandem (4-wire) Integrated Services Trunk Ports Off Premises Station Ports (2-wire) ATT N/A DAL DAL OPS 0 dB 2 dB 2 dB 2 dB 2 dB 3 dB 3 dB 3 dB 1 dB Analog Public Switched Network Ports (2-wire) Sub-rate 1.544 Mbps Digital PBX-CO Trunk Ports (4-wire) FXO & FXD DAL -2 dB 0 dB 0 dB 0 dB 0 dB -2 dB 0 dB 0 dB 0 dB 0 dB -2 dB 0 dB 0 dB 0 dB 0 dB 0 dB 0 dB -2 dB 0 dB 0 dB 0 dB 0 dB 0 dB 0 dB 2 dB 4 dB 4 dB 4 dB 4 dB 4 dB 4 dB 3 dB 3 dB 0 dB 3 4 Note 1: In this table, positive values denote gain and negative (-) denotes loss 5 6 7 Note 2: The ANIS/TIA-968-A-1 limits shown in Table 5 are only provided as a convenience to users of this standard. The user should consult the latest revision of the ANSI/TIA-968-A standard and/or addendums to ensure compliance. 8 18 SP-3-4826-RV2 (to be published as ANSI/TIA-912-B) 1 6.6 Half-Channel Loss and Level Plan 2 6.6.1 Overview 3 4 5 6 Developing a loss plan is generally a complex process, as the objective is to ensure a satisfactory overall loudness rating (OLR) for all connections types. To do this the loudness ratings of the end points (telephones), and the transmission loss between the end points, must be known for each connection type. 7 8 9 10 11 This is a trivial exercise in a purely packet telephony environment, if one assumes that the end points are digital telephones with an LR of 8 dB and 2 dB (in line with ITU-T Recommendations), and that no gains or losses are introduced in the digital transmission path. In this case the OLR for any digital telephone-to-telephone connection world-wide is the ITU-T Recommendation G.101 objective of 10 dB. 12 13 14 The complexity is introduced when the packet telephony network connects to analog telephones and trunks. In this case the LRs of the telephones and trunks vary, although a loss-less digital transmission path can be maintained. 15 16 17 A half-channel loss plan for national and international packet telephony networks can be implemented based on the premise that only the LRs vary, and that the packet network does not introduce any additional gain or loss. 18 19 20 21 Full-channel loss plans are still required for VGs, as VGs can also connect to existing analog and TDM based digital networks. These connections require losses to be defined on a port-to-port basis for technical and regulatory reasons. A half-channel loss plan can therefore be considered as a sub-set of a full-channel loss plan that is only applicable to packet network connections. 22 6.6.2 Concept 23 24 25 26 27 The basic concept in the half-channel loss plan is to adjust all send levels on a packet telephony network to the optimum SLRHC of 8 dB. Digital telephones provide the reference SLR of 8 dB by definition. This is not an original concept, as it is the basis of the European dBr reference system. The move to standardize the North American digital telephone LRs to the ITU-T recommended levels makes this practical for packet telephony networks. 28 29 The same basic concept could be applied to the current non-packet PSTN and private networks, but existing industry standards and may make it difficult to implement. 30 6.6.3 Principle of Operation 31 32 33 The originating entity will adjust the SLR of the sending port to 8 dB at the ingress to the packet network, i.e., the 0 dBr point. The SLR at the 0 dBr point is defined as the SLRHC (Half-Channel SLR). 34 35 36 The terminating entity will adjust the RLR of the receiving port to 2 dB at the egress from the packet network, i.e., the 0 dBr point, to achieve the optimum OLR of 10 dB at the receiving port. The RLR at the 0 dBr point is defined as the RLRHC (Half-Channel RLR). 37 38 39 Note: The internationally recognized optimum OLR is 10 dB. See ITU-T Rec. G.101. The advantage of this approach is that neither entity requires knowledge of the other, so loss planning becomes a local issue. 40 19 SP-3-4826-RV2 (to be published as ANSI/TIA-912-B) Applicability 1 6.6.4 2 3 This loss plan applies to all kind of packet-based voice services, irrespective whether they provide: 4 real time conversational telecommunication between human subjects, or 5 6 listening-only telecommunication from a machine interface (stored speech) to a human subject, or 7 speaking-only telecommunication from a human subject to a machine interface; 8 9 The half-channel loss plan only applies to connections routed via packet networks, other VG port-to-port connections are subject to the full-channel loss plan recommendations. 10 6.6.5 Recommended Loss Ranges 11 The transmit and receive losses in Table 6 are the recommended nominal values. 12 13 Although there are no mandatory loss ranges associated with these values, it is desirable that the average 1 kHz loss fall within 0.5 dB of the nominal loss values given in Table 6. 14 6.6.6 Packet Network Losses 15 16 17 It is critical for the operation of a half-channel loss plan that no gain or loss is inserted during transmission through the packet network. Any level changes due to transcoding for example, should be less than 1 dB. 18 19 Note: Transcoding refers to the conversion from one voice coding algorithm to another, e.g., G.726 to G.729. 20 20 SP-3-4826-RV2 (to be published as ANSI/TIA-912-B) 1 6.6.7 Half-Channel Loss Plan Table 2 3 Table 6 shows the North American VG half-channel loss plan, given in loudness ratings and respective loss. 4 Table 6 - Voice Gateway Half-Channel Loss Plan WAN/PAL 0 dBr Point (dB) ONS OPS DGS WAN PAL DAL FXO FXD ATT a b SLR Tx Loss1 3 0 0 0 0 0 -6 -3 0 4 8 8 8 8 8 17 14 15 c =(a + b) SLRHC d =(e + f) RLRHC 7 8 8 8 8 8 112 112 15 2 3 2 2 2 2 6 6 4 e f Rx Loss1 9 6 0 0 0 0 0 3 3 RLR g =(c + d) OLR3 -7 -3 2 2 2 2 6 3 1 9 11 10 10 10 10 17 17 19 h =(8 + d) Desirable OLR 10 11 10 10 10 10 14 14 12 5 6 7 Column a shows the SLR of the telephone and trunk between the acoustic interface and the connection point to the VG. 8 9 Column b shows the transmit loss required to achieve the required SLRHC at the 0 dBr point, except for the analog trunks which use the historical send loss. 10 Column c shows the resulting Half-Channel SLR (SLRHC) at the 0 dBr point (WAN/PAL). 11 Column d shows the resulting Half-Channel RLR (RLRHC) at the 0 dBr point (WAN/PAL).. 12 13 14 Column e shows the receive loss required to achieve the desirable OLR, based on the RLR shown in column f, and the optimum SLR of 8 dB, except for the analog trunks which use the historical receive loss. 15 16 Column f shows the RLR of the telephone and trunk between the acoustic interface and the connection point to the VG. 17 Column g shows the resulting OLR, based on the actual SLR. 18 Column h shows the desirable OLR, based on the optimum SLR of 8 dB. 19 Notes: 20 21 1. Losses have been selected as multiples of 3 dB, assuming that this simplifies the implementation. All numbers in Table 6 are in dB. 22 23 24 2. It is not possible to achieve the optimum SLRHC of 8 dB for connections from analog networks due to the potential for DTMF signaling overload. See Annex B.4 ‘DTMF Overload on Analog Trunks’. 25 26 3. The OLR values shown in the table are as perceived by the listener, i.e. this is shown as a one-way connection. 21 SP-3-4826-RV2 (to be published as ANSI/TIA-912-B) 1 6.6.8 Network Stability 2 3 There is a potential for instability in connections involving 2-to-4 wire conversions if the open loop gain of the 4-wire loop approaches 0 dB. 4 5 6 Additional losses are inserted in public and private analog and digital TDM-based networks to ensure they are unconditionally stable, and the resultant high OLRs are accepted for mixed 2wire and 4-wire networks. 7 8 9 10 11 The use of this approach for a half-channel plan would result in unacceptable OLRs for some connection types. Fortunately, the requirement for unconditional stability is not required in packet-based networks as a digital 4-wire loop will only oscillate when the hybrids at both ends of the loop are un-terminated, and under these conditions the 4-wire loop would not be connected to any analog loops that could be affected by digital loop oscillation. 12 Notes: 13 14 15 1. Oscillation in a 4-wire loop has shown to cause harm to analog frequency division multiplexing (FDM) transmission systems by affecting the FDM equipment's signal level management. There is no potential for such harm in purely digital systems. 16 2. See Annex B.5 for further information on open loop loss and network stability. 17 6.6.8.1 Stability Loss 18 19 20 21 22 23 24 ITU-T Recommendation G.122 specifies the minimum stability loss for national systems required to prevent instability on international calls. The stability loss of each national system represents one half of the open loop loss (OLL) of the 4-wire loops required to establish an international connection. This is equivalent to the VG loss on either side of a packet network connection. A stability loss of 6 dB at all frequencies between 200 and 3600 Hz will ensure that the G.122 requirements are met. However, stability losses of between 6 dB and 0 dB will formally comply with the present requirements of G.122. 25 26 This need not be a requirement for purely packet-based connections for the reasons discussed above. 27 22 SP-3-4826-RV2 (to be published as ANSI/TIA-912-B) 1 7 Loss Parameters 2 7.1 Frequency Response 3 4 5 6 The frequency response recommendations for the A/D and D/A conversions are shown in numerical form in Table 7, and graphically in Figure 7 & Figure 8 and Figure 9 & Figure 10, respectively. These figures are illustrative only. Measurement results must be normalized to 0 dB at 1004 Hz. 7 Table 7 - Frequency Response Recommendations Analog to Digital Digital to Analog Loss (dB) Loss (dB) Frequency (Hz) Min Max Min Max 200 0 3 0 2 300 -0.25 0.5 -0.25 0.5 3000 -0.25 0.5 -0.25 0.5 3200 -0.25 0.75 -0.25 0.75 3400 0 1.5 0 1.5 3400 to 4000 -14x+14 - -14x+14 - 4000 to 4600 -18x+14 - -14x+14 - 4600 to 12000 32 - 28 - 8 Where: x sin 4000 F / 1200 9 10 Note: Positive numbers indicate higher loss and negative numbers indicate lower loss than the reference loss at 1004 Hz. 11 7.1.1 Rejection of Power Line Interference 12 Rejection of power line interference should be greater than 20 dB at 60 Hz in the A/D direction. 13 7.2 Tracking Error and Overload Compression 14 7.2.1 Tracking Error 15 The tracking error for A/D and D/A conversions should not exceed the limits shown in Table 8. 16 17 The tracking error for all port-to-port connections should not exceed the limits shown in Figure 11. 18 Table 8 - Voice Gateway Tracking Error Limits Input Signal Tracking Error (dB) Level Range (dBm) Maximum Average 0 to -37 ±0.25 ±0.125 -37 to -50 ±0.5 ±0.25 19 23 SP-3-4826-RV2 (to be published as ANSI/TIA-912-B) 1 Figure 7 - Voice Gateway Frequency Response - Analog to Digital -5 Unacceptable Region Loss (dB) relative 0 dB @ 1004 Hz m. 0 Acceptable Region 0 dB, 1004 Hz 5 Unacceptable Region 10 15 20 25 30 35 100 200 3400 1000 Frequency (Hz) 10000 A/D 2 3 4 Figure 8 - VG Frequency Response - Analog to Digital - In -1 to +4 dB Region Only -1 Loss (dB) relative to 0 dB @ 1004 Hz m. Unacceptable Region 0 Acceptable Region 1 0 dB, 1004 Hz Unacceptable Region 2 3 4 100 200 1000 Frequency (Hz) 5 6 24 3400 10000 A/D SP-3-4826-RV2 (to be published as ANSI/TIA-912-B) 1 Figure 9 - Voice Gateway Frequency Response - Digital to Analog -5 Unacceptable Region Loss (dB) relative 0 dB @ 1004 Hz m. 0 Acceptable Region 0 dB, 1004 Hz 5 Unacceptable Region 10 15 20 25 30 35 100 200 3400 1000 Frequency (Hz) 10000 D/A 2 3 4 Figure 10 - VG Frequency Response - Digital to Analog - In -1 to +4 dB Region Only -1 Loss (dB) relative to 0 dB @ 1004 Hz m. Unacceptable Region 0 Acceptable Region 1 0 dB, 1004 Hz Unacceptable Region 2 3 4 100 200 1000 Frequency (Hz) 5 6 25 3400 10000 D/A SP-3-4826-RV2 (to be published as ANSI/TIA-912-B) 1 2 7.2.2 Overload Compression 3 4 For all port-to-port connections, the compression of a 1004 Hz input signal relative to a 1004 Hz, 0 dBm input signal should not exceed the values shown in Figure 11. 5 6 7 Note: Care should be taken to ensure that port-to-port losses are not implemented in a manner that causes PCM encoding overload. See Annex B.3 for further information on port-to-port loss allocation. 8 9 Figure 11 - Tracking Error and Overload Compression 10 11 26 SP-3-4826-RV2 (to be published as ANSI/TIA-912-B) 1 8 Echo Control and Return Loss 2 3 4 Echo in transmission systems is due to reflections from impedance mismatches, and the most common source of impedance mismatches in telephone networks is in the 2-to-4 wire converter or hybrid. The echo return loss is defined for two directions: 5 4-wire to 4-wire, which is a function of the hybrid balance; 6 2-wire, which is a function of the 2-wire input impedance. 7 Active echo control using echo cancellers or suppressers is beyond the scope of this section. 8 8.1 Hybrid Balance Requirements 9 10 11 12 For each interface, the line or trunk side 2-wire analog port should be terminated with the appropriate reference impedance (see 8.1.1.1). The reference impedances should consist of passive elements. The hybrid balance, when measured as described in Annex A.5, should exceed the values in Table 9 on 95 percent of the interfaces. 13 Note: Two-wire analog trunks include FXO, DID, and ATT ports. 14 15 16 17 Table 9 - Voice Gateway Minimum Hybrid Balance Recommendations Frequency Band Hybrid Balance 200 to 500 Hz Equal to or greater than the values located on a straight line intersecting 17 dB at 200 Hz and 22 dB at 500 Hz. 500 Hz to 2.5 kHz 22 dB 2.4 kHz to 3.4 kHz Equal to or greater than the values located on a straight line intersecting 22 dB at 2.5 kHz and 17 dB at 3.4 kHz. Note: All points are plotted on a log/linear scale with the impedance values in dB on the linear axis and the frequency in Hz on the logarithmic axis. 18 19 8.1.1.1 Hybrid Balance Reference Impedances 20 8.1.1.1.1 21 22 23 A reference impedance of 600 is recommended for ONS ports. This network has been selected to match the distribution of telephone set impedances expected in the VG on-premises environment. 24 8.1.1.1.2 25 26 A reference impedance of 600 is recommended for OPS and two-wire trunk ports that connect to facilities with line treatment2. 27 8.1.1.1.3 28 29 The reference impedance shown in Figure 12 is recommended for OPS and two-wire trunk ports that connect to facilities without line treatment. This impedance has been found to provide the ONS Ports OPS and Two-Wire Analog Trunk Ports With Line Treatment OPS and Two-Wire Analog Trunk Ports Without Line Treatment 2 As used in this context, the term "line treatment" means any equipment (e.g., an impedance compensator, a repeater, or a range extender) that presents a nominal impedance of 600 at the interface connecting to the port. 27 SP-3-4826-RV2 (to be published as ANSI/TIA-912-B) 1 2 best single compromise to the distribution of OPS line and 2-wire trunk impedances expected in the North American telephone network. 3 4 Figure 12 - OPS/2-Wire Trunk Reference Impedance 1000 350 0.21 F 5 6 7 8.2 Input Impedance Requirements 8 9 10 11 12 13 14 Requirements are given only for paths through the switch for which the connecting port interface (the interface on the other side of the switch) is 4-wire. In this way, the measured results are independent of any feedback resulting from imperfect balance of the far-end hybrids on 2-wire interfaces. While such imperfect balance does influence the 2-wire interface input impedance and the loss of the switch when it connects two 2-wire lines, the effects on in-service performance are controlled by having separate requirements for hybrid balance (Clause 8.1) and insertion loss (Clause 6). 15 16 17 18 The requirements for the input impedance are given in terms of a reference impedance (Z R) and minimum return loss. The return loss is defined in Annex C where the input impedance is denoted by ZI and reference impedance by ZR. The return loss is a function of frequency, and increases without limit as the input impedance approaches the reference impedance. 19 20 21 For each 2-wire and 4-wire analog port, the input impedance (Input Z) in terms of return loss (single frequency return loss and echo return loss) should exceed the values in Table 10 or Table 11 on 95 percent of the interfaces, when measured as described in Annex A.6. 22 8.2.1.1 Input Impedance Reference Impedances 23 8.2.1.1.1 24 25 26 ONS ports should meet the minimum input impedance requirement when using a reference impedance consisting of either 600 or a complex reference impedance as described in 8.2.1.1.4. 27 8.2.1.1.2 28 29 30 OPS ports should meet the minimum input impedance requirement with a reference impedance of 600 and may, optionally, also meet the input impedance requirement with a complex reference impedance as described in 8.2.1.1.4. 31 8.2.1.1.3 32 33 Two-wire analog trunks ports should meet the minimum input impedance requirement with a reference impedance of 600 . 34 Note: Two-wire analog trunks include FXO, DID, and ATT ports. ONS Ports OPS Ports Two-Wire Analog Trunk Ports 35 28 SP-3-4826-RV2 (to be published as ANSI/TIA-912-B) 1 2 8.2.1.1.4 Complex Reference Impedances 3 4 5 This option allows flexibility in the design of line input impedance for specific applications or terminations. The recommended reference impedance for measuring the return loss of lines designed with a complex input impedance network is either: 6 The network shown in Figure 12, 7 8 A network consisting of a 275 resistor in series with a parallel circuit of a 780 resistor and 0.15 µF capacitor, or 9 A network consisting of a 600 resistance in series with a 2.16 µF capacitor. 10 11 Table 10 - Voice Gateway Return Loss Recommendations for 600 ZR Return Loss Frequency Band Minimum Desirable 200 to 500 Hz Equal to or greater than the values located on a straight line intersecting 14 dB at 200 Hz and 22 dB at 500 Hz. Equal to or greater than the values located on a straight line intersecting 14 dB at 200 Hz and 26 dB at 500 Hz. 500 Hz to 2.5 kHz 22 dB 26 dB 2.4 kHz to 3.4 kHz Equal to or greater than the values located on a straight line intersecting 22 dB at 2.5 kHz and 14 dB at 3.4 kHz. Equal to or greater than the values located on a straight line intersecting 26 dB at 2.5 kHz and 14 dB at 3.4 kHz. 12 13 Table 11 - Voice Gateway Return Loss Recommendations for Complex ZR Return Loss Frequency Band Minimum Desirable 200 to 500 Hz Equal to or greater than the values located on a straight line intersecting 14 dB at 200 Hz and 22 dB at 500 Hz. - 500 Hz to 2.5 kHz 22 dB - 2.4 kHz to 3.4 kHz Equal to or greater than the values located on a straight line intersecting 22 dB at 2.5 kHz and 14 dB at 3.4 kHz. - 14 15 16 Note: All points are plotted on a log/linear scale with the impedance values in dB on the linear axis and the frequency in Hz on the logarithmic axis. 29 SP-3-4826-RV2 (to be published as ANSI/TIA-912-B) 1 9 Noise and Distortion Impairments 2 9.1 Idle-Channel Noise 3 4 Idle-channel noise is the short-term, average, absolute noise power measured with a flat or Cmessage weighting in the absence of signal. 5 6 Compliance with the idle-channel noise requirements should be determined as described in Annex A.7. 7 9.1.1 3 kHz Flat Noise 8 9 (1) The 3 kHz flat weighted noise should not exceed 35 dBrn on 50 percent of the connections. 10 11 (2) The 3 kHz flat weighted noise should not exceed 39 dBrn on 95 percent of the connections. 12 13 14 For interface transmission levels other than 0 dB, the 3 kHz flat weighted noise requirement should be shifted by a value that corresponds to the difference between the transmission level at that interface and 0 dB. 15 9.1.2 C- Message Weighted Noise 16 17 18 The maximum (95 percent) C-message weighted absolute noise power at an interface should not exceed the values given in Table 12. It is desirable that the mean C-message weighted absolute noise power also comply with the values shown in the table. 19 20 21 For interface transmission levels other than 0 dB, the C-message weighted noise requirement should be shifted by a value that corresponds to the difference between the transmission level at that interface and 0 dB. 22 Table 12 - Voice Gateway C-Message Weighted Noise Requirements C-Message Weighted Noise (dBrnC) in the Absence of Signal Connection Type Mean (Desirable) 95% (Maximum) Analog-to-analog 16 20 Analog-to-digital 15 19 Digital-to-analog 9 13 23 24 30 SP-3-4826-RV2 (to be published as ANSI/TIA-912-B) 1 9.2 Longitudinal Balance 2 3 The VG interfaces that are subject to longitudinal balance requirements include loop/ground start DEO/FXO trunks, reverse battery (DID) trunks, OPS lines, and digital service trunks. 4 9.2.1 5 (1) 6 The longitudinal-to-metallic balance is defined as: Longitudinal-to-Metallic Balance Definition. 7 Longitudinal Balance (dB) = 20 log|Vs / Vm|. 8 9 where Vs is the disturbing longitudinal rms voltage, and Vm the resulting metallic rms voltage of the same frequency. 10 11 The longitudinal-to-metallic balance recommendations only apply to analog ports. A low conversion of longitudinal into metallic noise is required to limit noise on the talking circuit. 12 (2) 13 14 15 The longitudinal-to-metallic balance of analog ports, when measured as described in Annex A.8.1, should meet or exceed the criteria of Table 13. It is desirable that the average balance be within the region labeled "desirable" in Figure 13. 16 Table 13 - Voice Gateway Longitudinal-to-Metallic Balance Requirements Recommendations. Frequency (Hz) Minimum Balance (dB) Average Balance (dB) 200 58 63 500 58 63 1 kHz 58 63 3 kHz 53 58 17 18 Figure 13 - Longitudinal Balance Limits 90 (60,80) 80 Des irable Reg ion (200,77.4) (600,70) 70 (1000,68.1) Accep tab le Regio n Balance (dB) (200,58) 60 Unacceptable Regio n 50 500 Frequ en cy (Hz) 50 19 31 (3000,58.7) (1000,58) (3000,53) (4000,54) 5000 SP-3-4826-RV2 (to be published as ANSI/TIA-912-B) 1 9.2.2 Metallic-to-Longitudinal (Transverse Balance) Balance 2 9.2.2.1 Definition 3 The transverse balance is defined as: 4 Transverse Balance (dB) = 20 log |Vm / Vs| 5 6 where Vs is the longitudinal rms voltage produced across a longitudinal termination Z1, and Vm is the metallic rms voltage across the tip-and-ring interface terminals of the VG. 7 8 9 Transverse balance (metallic-to-longitudinal balance) is specified in ANSI/TIA-968-A to ensure that a metallic signal is not converted into a longitudinal signal that could cause excessive noise in other pairs of a multi-pair cable. 10 9.2.2.2 Requirements. 11 12 13 The VG should meet the minimum transverse balance requirements as given in Table 14 for analog interfaces and Table 15 for digital service interfaces, when measured as described in Annex A.8.2. 14 (1) 15 16 The criteria given in Table 14 should be met for all possible combinations of through transmission paths between analog DEO trunk and station line interfaces of the VG. 17 Table 14 - Transverse Balance Requirements for Analog Interfaces Analog Interfaces Interface State Frequency Range Minimum Balance (dB) 200 Hz to 1 kHz 60 1 kHz to 4 kHz 40 Off-hook 200 Hz to 4 kHz 40 DEO Trunk-Ground Start Off-hook 200 Hz to 4 kHz 40 Reverse Battery (DID) Off-hook 200 Hz to 4 kHz 40 OPS Line Off-hook 200 Hz to 4 kHz 40 DEO Trunk-Loop Start On-hook 18 19 20 (2) Digital Interfaces Table 15 - Transverse Balance Requirements for Digital Interfaces Interface 1.544 Mbps Digital Trunk Frequency Range 15 kHz to 1.544 MHz 21 22 32 Minimum Balance (dB) 36 SP-3-4826-RV2 (to be published as ANSI/TIA-912-B) 1 2 9.3 Crosstalk 3 9.3.1 Requirement 4 5 The crosstalk coupling loss for every port-to-port connection, over the 200 to 3400 Hz frequency band, should comply with the following criteria: 6 7 8 (1) The crosstalk coupling loss between any established connection through the VG and at least 95 percent of all other through connections should be at least 75 dB, and it is desirable that this loss be at least 80 dB. 9 10 (2) The crosstalk coupling loss between any established connection through the VG and any other through connection should be at least 70 dB. 11 12 Compliance with the crosstalk coupling loss recommendations should be determined as described in Annex A.9. 13 9.4 Quantization Distortion 14 15 16 Ninety-five percent or more of all A/D and D/A connections should comply with the recommendations in Table 16, where the input signal is a 1004 Hz sinewave and the output distortion is measured using C-message weighting. 17 Table 16 - Voice Gateway Quantization Distortion Requirements Input Signal Level (dBm) Input/Output Level Ratio (dB) 0 to -30 35 -40 29 -45 25 18 19 9.5 Single-Frequency Distortion 20 21 Ninety-five percent or more of all A/D and D/A connections in each connection category should comply with the following distortion limit: 22 23 24 For input signals at a constant 0 dBm level and any single frequency in the range of 0 to 12 kHz, the corresponding output signal power level at any other single frequency should not exceed -28 dBm.3 3 The -28 dBm limit is dependent upon the characteristics of the transmit and receive filters of the Voice Gateway. In the 0 to 3400 Hz frequency range, the limit value is influenced by the characteristics of the receive filter; in the 3.4 to 4.6 kHz range the limit value is dependent upon both transmit and receive filters; and in the 4.6 to 12 kHz range, the limit value is dependent upon the characteristics of the transmit filter and should be -32 dBm. 33 SP-3-4826-RV2 (to be published as ANSI/TIA-912-B) 1 10 Other Impairments 2 3 4 5 The following requirements apply to VGs intended to pass voiceband data. The following requirements are given, in addition to the voice requirements, to verify that the VG will function in a manner that will not be seen as an impairment to the performance of voiceband data modems. 6 10.1 Intermodulation Distortion 7 8 9 Intermodulation or harmonic distortion is caused by nonlinearities present in the electric-toelectric transfer function of the VG. This form of distortion is of primary concern to the transmission of data. 10 11 12 Intermodulation distortion is measured using the four-tone method that employs two pairs of equal-level tones transmitted at a total, composite power level of -13 dBm. One pair consists of the frequencies 857 and 863 Hz; the second pair uses the frequencies 1372 and 1388 Hz. 13 14 15 16 17 Intermodulation distortion is measured as the second- and third-order products resulting from the application of the four tones. The second- and third-order products are denoted as R2 and R3, respectively. R2 is the average power level in the 503-to-537 Hz and 2223-to-2257 Hz frequency bands, expressed in dB below the received power level. R3 is the total power level in the 1877to-1923 Hz frequency band, expressed in dB below the received power level. 18 19 20 21 At input port signal power levels other than 0 dBm, the four-tone signal power levels should be shifted by a value that corresponds to the difference between the signal level at the interface and 0 dBm. Since the R2 and R3 products are expressed in dB below the received signal level, their values are not affected by non-zero reference signal levels. 22 23 The intermodulation distortion limits on 95 percent or more of all connections should meet or exceed the values given in Table 17. 24 Table 17 - Intermodulation Distortion Limits for Voice Gateways Distortion Limits (dB below received level) R2 R3 46 dB 56 dB 25 26 34 SP-3-4826-RV2 (to be published as ANSI/TIA-912-B) 1 10.2 Envelope Delay 2 10.2.1 Definitions 3 4 5 6 7 Envelope Delay (ED) of a system is the propagation time through the system of a low-frequency sinusoidal envelope of an amplitude modulated sinusoidal carrier. If the frequency range of interest is denoted by R4, the carrier frequency is varied throughout R to obtain the ED as a function of frequency. The carrier is 50 percent amplitude-modulated with a sinusoidal signal of frequency 83.3 Hz. 8 9 Relative Envelope Delay (RED) is the difference between the ED at a given frequency f and the global minimum ED within the range R. 10 10.2.2 Relative Envelope Delay (RED) Requirements 11 (1) 12 On 95 percent of the connections of this type Station Interface-to-Trunk Interface and Trunk Interface-to-Trunk Interface 13 14 in the frequency range from 800 through 2700 Hz, the RED curve should lie below curve A in Figure 14; 15 16 it is desirable that in the frequency range from 500 through 3000 Hz, the RED curve lie below curve B in Figure 14. 17 (2) 18 19 20 21 22 The requirements for this connection allow twice the RED of those in 10.2.2(1). More precisely, let A' be a curve obtained by multiplying by 2 each ordinate of the curve A in Figure 14 and let B' be a curve obtained by multiplying by 2 each ordinate of the curve B in Figure 14. Then the RED requirements for connections of this type are obtained from those in 10.2.2(1) by substituting A' for A and B' for B. 4 Station Interface-to-Station Interface A general symbol R is used here because the frequency range of interest may change with application. For example, for mandatory requirements of this section R = [800 Hz, 2700 Hz], while for objective requirements R = [500 Hz, 3000 Hz]. 35 SP-3-4826-RV2 (to be published as ANSI/TIA-912-B) 1 Figure 14 - Relative Envelope Delay vs. Frequency 2 3 36 SP-3-4826-RV2 (to be published as ANSI/TIA-912-B) 1 10.3 Impulse Noise 2 3 The following impulse noise limits should be met under fully loaded busy-hour VG traffic conditions. 4 5 6 (1) On 95 percent or more of all connections through each connection category, the impulse noise level should not exceed zero counts above 55 dBrnC over a measurement interval of five minutes. 7 8 (2) It is desirable that the impulse noise level does not exceed zero counts above 47 dBrnC over a measurement interval of five minutes. 9 10.4 Jitter 10 11 Jitter on a port-to-port connection should not exceed 2 degrees within the 4-to-300 Hz frequency band. 12 10.5 Gain Hit 13 14 15 16 There should be no more than one gain hit per hour at a threshold level of 3 dB. If there is more than one hit in a period of 1 hour, the subsequent hour should have zero hits. A gain hit is an incidental modulation resulting in a rapid positive or negative shift of signal gain lasting for a period of at least 4 ms. 17 10.6 Phase Hit 18 19 20 21 There should be no more than one phase hit per hour exceeding a threshold of 20 degrees. If there is more than one phase hit in a period of 1 hour, the subsequent hour should have zero hits. A phase hit is an incidental modulation resulting in a rapid positive or negative shift of signal phase lasting for a period of at least 4 ms. 22 10.7 Dropout 23 24 25 There should be no more than one dropout per hour exceeding a threshold of 6 dB. If there is more than one dropout in a period of 1 hour, the subsequent hour should have zero dropouts. A dropout is a negative gain hit lasting a period of at least 10 ms. 26 10.8 Peak-to-Average Power Ratio 27 28 The VG should pass a signal, analog port-to-analog port, with a peak-to-average power ratio (P/AR) of 95. 29 30 P/AR = 100 x ((2Ep/EFWA)-1), where Ep is the normalized peak and EFWA is the normalized full rectified average of the envelope. 37 SP-3-4826-RV2 (to be published as ANSI/TIA-912-B) 1 11 Signal Levels 2 3 The VG should comply with ANSI/TIA-968-A and/or ANSI/TIA-968-A-1, Clause 4.5, for the following signal level limitations: 4 5 6 7 8 9 10 (1) In-band Signal Power Limits (a) Internal Signal Sources Not Intended for Network Control Signaling (b) Internal Signal Sources Intended Primarily for Network Control Signaling (c) Through Transmission (d) Idle State Circuit Stability for Tie Trunks (e) Metallic Signal Power at Frequencies in the range 3995 to 4005 Hz (f) Longitudinal Voltage in the 100- to 4000 Hz Frequency Range. 11 12 13 14 15 (2) Out-of-Band Signal Voltage Limits (a) Metallic Voltage (b) Longitudinal Voltage. 16 17 18 19 20 21 22 23 The above listed signal limitations should apply to: (1) (2) (3) (4) (5) (6) Analog Trunk interfaces (ground start, loop start, DID) OPS Lines Analog Tie Trunks Digital Trunk interface (ground start, loop start, DID, ISDN Basic Rate and Primary Rate) with encoded analog contents Digital OPS Lines with encoded analog contents Digital Tie Trunk interface with encoded analog contents. 38 SP-3-4826-RV2 (to be published as ANSI/TIA-912-B) 1 Annex A (informative) - Measurement Guidelines 2 This annex is informative only and is not part of this standard. 3 A.1 Gain Ripples in the Measurement Path 4 5 6 7 8 In any digital VG, connections from a 2-wire analog port to a 2-wire analog port will constitute a closed-loop feedback system. The feedback signal will cause ripples in the net through-gain response of a 2-wire to 2-wire connection. If care is not exercised, the ripple effect will influence measurement accuracy. The following two techniques for avoiding ripple influence on measurements are suggested: 9 10 11 12 (1) Perform test measurements on a 2-wire to 4-wire basis. This approach eliminates the feedback signal. Where appropriate, the requirements contained in these sections have been divided into transmit and receive portions to facilitate this approach. It will be necessary to employ a digital test meter and designated digital test sequences for these types of measurements. 13 14 Alternatively, a half-channel test, in which the two directions of transmission are terminated within the switching fabric, may be used (see Clause 8). 15 16 17 18 19 (2) Maintain a high-quality impedance match at each 2-wire to 4-wire interface to minimize the feedback signal. This approach requires use of a test impedance that closely matches the hybrid balance impedance. To satisfactorily reduce the ripple caused by the feedback signal, a hybrid balance of 25 dB (or greater) should be maintained at each 2-wire to 4-wire interface in the test connection. 20 A.2 Transmission Level Translation 21 22 Each the requirement in this section has been written with respect to the 0 dBr point in the switch. A 0 dBm0 signal at this point will decode to 0 dBm, or 1 mW in 600 . 23 24 25 In many cases, the interface level will be different from the 0 dBr point due to the losses introduced to meet the loss plan. In these cases (unless otherwise stated) the appropriate interface loss should be included when determining compliance with the requirements. 26 27 See Annex B.6 for further information on 0 dBr points, the definition of 0 dBm0, and transmission level translation. 28 29 30 31 32 33 34 35 36 37 A.3 Dial-up Port for Trunk Testing To avoid the gain variations that can occur among different terminations, it is recommended that a special dial-up port be designated for trunk testing. However, it should be recognized that even when using a single termination to test all trunks, consideration for gain tracking variation in the dial-up port must be included. The gain tracking variation will occur because different trunk losses will cause different signal levels at the dial-up port. The tracking variation will be limited by the tracking error requirements at the various interfaces (see Clause 7.2) A.4 Digital Test Port Availability For circuit and line-up purposes, the VG should have provisions for a test port, or equivalent, that enables 0 dBr point testing at a digital interface. 38 39 SP-3-4826-RV2 (to be published as ANSI/TIA-912-B) A.5 Hybrid Balance 1 2 3 The measurement technique described in this section is applicable to line or trunk units that connect to 2-wire analog interfaces. 4 5 Examples of test arrangements for testing for compliance with hybrid balance requirements are shown in Figure A1 (full-channel method) and Figure A2 (half-channel method). 6 7 When using the full-channel method (Figure A1), the impedance of the signal generator, ZG, and the signal detector, ZO, should match the impedance of the 4-wire port. 8 9 When using the digital half-channel method (Figure A2), the detector and generator should be equivalent digital instruments. 10 11 12 13 An analog half-channel method may also be used (similar to Figure A2). The tests can be made via a line or trunk unit access point, or a path can be set up between the line or trunk unit and a 4wire interface. If test access is from an analog interface, the generator impedance (ZG) and the detector impedance (ZO) should match the interface impedance. 14 15 16 Note: A Return Loss Measuring Set (RLMS), conforming to ANSI/IEEE Standard 743 is recommended as the signal generator and detector shown in Figure A1 (or an equivalent digital instrument for Figure A2). 17 The steps for measuring the hybrid balance are: 18 19 1. Measure the 2-to-4 wire and 4-to-2 wire loss through the hybrid at 1004 Hz, with the 2-wire port terminated in the appropriate reference impedance. 20 21 22 2. Measure the 4-wire to 4-wire loss (echo return loss) through the hybrid at frequencies over the range of 200 to 3400 Hz, with the 2-wire port terminated in the appropriate reference impedance. 23 24 3. Subtract the sum of the losses determined in Step 1 from the values measured in Step 2 to determine the hybrid balance over the specified frequency range. 25 A.6 26 27 Examples of test arrangements for testing compliance with the input impedance requirements are shown in Figures A3 through A6. 28 The steps for measuring the input impedance are: 29 30 1. Terminate the 4-wire analog ports not under test in impedances (ZT) that match the interface impedances. 31 32 2. Terminate the return loss measuring set with the reference impedance (ZR) for the port under test, as defined in 8.2.1. 33 34 35 3. Measure the single frequency return loss (SFRL) and echo return loss (ERL) over the range 200 to 3400 Hz to determine compliance with the return loss requirements in Table 10 (600 ZR) or Table 11 (Complex ZR). See Annex C for the SFRL and ERL definitions. Input Impedance 36 37 40 SP-3-4826-RV2 (to be published as ANSI/TIA-912-B) Signal Generator 4-Wire Analog Port ZG 2-Wire Port Under Test Transmit Path Through Voice Gateway Return Loss Measuring Set ZO ZR Reference Impedance Receive Signal Detector 1 2 3 4 Figure A1 - Equipment Connections for Testing the Hybrid Balance of a 2-Wire Analog Port Using the Full-Channel Method 5 4-Wire Digital Access Port Digital Signal Generator 2-Wire Port Under Test Transmit Path Through Voice Gateway Half Channel Adaptor Digital Signal Detector 6 7 8 9 ZR Receive Figure A2 - Equipment Connections for Testing the Hybrid Balance of a 2-Wire Analog Port Using the Digital Half-Channel Method 41 Reference Impedance SP-3-4826-RV2 (to be published as ANSI/TIA-912-B) 1 4-Wire Analog Port 2-Wire Port Under Test Reference Impedance ZR Transmit ZT Terminating Impedance Receive ZT Terminating Impedance Path Through Voice Gateway Return Loss Measuring Set 2 3 4 5 Figure A3 - Equipment Connections for Testing a 2-Wire Analog Port Input Impedance Using the Full-Channel Method 6 7 2-Wire Port Under Test Reference Impedance ZR Partial Path Through Voice Gateway Return Loss Measuring Set Half Channel Adaptor 8 9 10 11 Figure A4 - Equipment Connections for Testing a 2-Wire Analog Port Input Impedance Using the Digital Half-Channel Method 12 42 SP-3-4826-RV2 (to be published as ANSI/TIA-912-B) 1 4-Wire Analog Port Under Test Reference Impedance ZR 4-Wire Analog Port Return Loss Measuring Set Transmit ZT Terminating Impedance Receive ZT Terminating Impedance Path Through Voice Gateway Terminating Impedance ZT Receive or Transmit 2 3 4 5 Figure A5 - Equipment Connections for Testing a 4-Wire Analog Port Input Impedance Using the Full-Channel Method 6 7 4-Wire Analog Port Under Test Reference Impedance ZR Return Loss Measuring Set Partial Path Through Voice Gateway Terminating Impedance ZT Half Channel Adaptor Receive or Transmit 8 9 10 11 Figure A6 - Equipment Connections for Testing a 4-Wire Analog Port Input Impedance Using the Digital Half-Channel Method 12 43 SP-3-4826-RV2 (to be published as ANSI/TIA-912-B) 1 A.7 Idle Channel Noise 2 3 Idle-channel noise should be measured with a 3A type noise measuring set or equivalent, with flat or C-message weighting. 4 5 6 When testing a connection, all analog interfaces, except the one(s) being tested, should be terminated with appropriate impedances, and all digital input ports, other than the one(s) being tested, should be supplied with a digital equivalent of zero V. 7 8 9 10 11 Compliance with the 13 dBrnC noise requirement for D/A units should be tested by feeding 19 dBrnC of noise in digital form to the D/A unit input. This can be accomplished as shown in Figure A7. With the switch in position 1, the noise generator output should be varied until the D/A test set shows 19 dBrnC. With the switch in position 2, the noise measuring set indicator should not exceed 20 dBrnC. Digital Connection Nois e Generator 2 A/D Converter D/A Unit 1 D/A Tes t Set 12 13 Figure A7 - Idle-Channel Noise Test Arrangement 14 44 Nois e Meas uring Set SP-3-4826-RV2 (to be published as ANSI/TIA-912-B) 1 A.8 Longitudinal Balance 2 A.8.1 Longitudinal to Metallic Balance 3 4 5 6 The test procedure is detailed in Annex C of ANSI/TIA-470.210-C. It is recommended that a frequency selective voltmeter is used. These tests should be conducted for only the off-hook state of the VG. A.8.2 Metallic to Longitudinal (Transverse) Balance 7 8 9 The test procedure is outlined in the ANSI/TIA-968-A and TIA/EIA/TSB31-B, the Part 68 Rationale and Measurement Guidelines. Test circuits that satisfies the stated conditions are shown in Figure A8 (Analog), and Figure A9 (Digital). 10 11 12 13 A metallic voltage should be applied from a balanced source with a metallic impedance Z 0 at suitable points over the frequency range f1 to f2, and set so that Vm equals E volts when a termination of Z0 is substituted for the VG. The Z0 termination should then be replaced by the VG and the longitudinal voltage Vs measured. 14 The frequency ranges and terminations for each service are defined in Table A1. 15 The conditions for performing these measurements on the VG are: 16 17 18 (a) All values of dc loop current that the interface under test is capable of drawing when connected to the ANSI/TIA-968-A loop simulator circuit for DEO trunk interfaces, or the ANSI/TIA-968-A line simulator circuit for OPS and DID interfaces. 19 (b) All reasonable conditions of application of earth ground to the VG under test. 20 21 (c) All DEO trunk or OPS interfaces not under test, terminated in their appropriate networks or in some cases grounded (see (h), below). 22 23 (d) All other than DEO and OPS interfaces terminated in circuits appropriate to those interfaces. 24 (e) Both on-hook and off-hook states applicable to the interface under test. 25 26 (f) Impedances of the balance test circuit should be (Z0) metallic and (Z1) longitudinal, as defined in Table A1. 27 (g) Termination of all interfaces not being measured should be follows: 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 DEO trunk OPS, off-hook OPS, on-hook (h) (i) (ii) (i) (i) (ii) Figure A10 Figure A11 (unterminated). For station line interfaces designed to isolate longitudinal currents introduced through fully-protected premises wiring or through non-registered equipment, or both, either of the T or R conductors of all ONS station interfaces should be grounded, and the T or R conductors should be both: Terminated in an impedance that will reflect correct impedance to the network port to which it is connected for through transmission (see Figure A12). Unterminated. For station line interfaces not designed to isolate longitudinal currents introduced through unprotected premises wiring, the T&R conductors of all ONS station interfaces should be both: Terminated in a metallic resistance of 600 and a longitudinal resistance of 150 (see Figure A11). Unterminated. 45 SP-3-4826-RV2 (to be published as ANSI/TIA-912-B) 1 Table A1 - Termination and Frequency Ranges Analog voiceband 1.544 Mbps digital Longitudinal Termination (Z1) 500 90 Metallic Impedance (Z0) 600 100 Lower Frequency (f1) 200 Hz 10 kHz Upper Frequency (f2) 4 kHz 1.544 MHz 0.775 V 0.316 V Metallic Voltage for Test (E) 2 3 A.8.2.1 Transverse Balance Test (Analog) 4 Tip T1 Vs Oscillator Off-Hook Station Termination (Figs. A9 & A10 ) C3 C1 FCC Loop Simulator Circuit Rs Vm Voice Gateway Under Test C2 Off-Hook Trunk Termination (Fig. A11 ) C4 Ring Ground Plane Oscillator T1 C1, C2 C3, C4 Rs Audio oscillator with a source impedance of 600 WECo 111C or 119E, or ADC 118F, or equivalent 8 F, 400V dc, matched to within 0.1% 100 to 500 pF trimmer capacitor 500 Voice gateway ground 5 6 Figure A8 - Transverse Balance Test Circuit (Analog) 7 46 SP-3-4826-RV2 (to be published as ANSI/TIA-912-B) Tip R2 R1 R1 R2, R3 300 300 Voice gateway ground R3 1 2 Ring Figure A9 - Off-Hook Termination for OPS or Unprotected ONS Interfaces 3 4 Tip 600 Voice gateway ground Ring 5 6 7 Figure A10 - Off-Hook Termination for Station Interfaces with Longitudinal Current Isolation 8 9 Tip R2 R1 R4 R1 R2, R3 R4 R3 10 11 300 300 350 Voice gateway ground Ring Figure A11 - Off-Hook Termination for DEO Interfaces 12 13 14 47 SP-3-4826-RV2 (to be published as ANSI/TIA-912-B) 1 Notes: 2 1. Vm should not be measured at the same time that Vs is measured. 3 4 5 2. Use trimmer capacitors C3 and C4 to balance the test circuit to 20 dB greater balance than the equipment standard for all frequencies specified, with a 600 resistor substituted for the VG. 6 7 3. R1 of the off-hook terminations should be adjusted to obtain a balance of 60 dB from 200 Hz to 1 kHz and 40 dB from 1 kHz to 4 kHz. 8 9 4. Exposed conductive surfaces on the exterior of the VG should be connected to the ground plane. 10 11 5. Use the ANSI/TIA-968-A loop simulator for DEO trunks with resistor R1 of the simulator disconnected. 12 13 6. Use the ANSI/TIA-968-A line simulator for OPS lines and DID trunks with resistor R1 of the simulator disconnected. 14 15 7. Use the off-hook termination shown in Figure A10 for station interfaces with longitudinal current isolation as described in Clause A.8.2 (h). 16 17 48 SP-3-4826-RV2 (to be published as ANSI/TIA-912-B) 1 A.8.2.2 Transverse Balance Test (Digital) 2 T1 Spectrum Analyzer Spectrum Analyzer Vs Vm S3 RL Tip S1 C2 Tracking Generator Voice Gateway Under Test S2 C1 RCal Ring C2 Ground Plane Tracking Generator T1 C1 C2 RL RCal Tracking generator with a source impedance of 100 1:1 100 wide-band transformer 20 pF differential capacitor 3 pF composition RF capacitor 90 non-inductive precision resistor non-inductive precision resistor Voice gateway ground 3 4 Figure A12 - Transverse Balance Test Circuit (Digital) 5 Notes: 6 7 8 1. Capacitor C1 should be a dual-stator, air-variable RF capacitor that maintains a constant capacitance between stators, while providing a variable capacitance from either stator to ground. 9 10 2. Capacitor C2 may be placed on either line of the test set (as shown), to obtain proper balancing of the bridge. 11 49 SP-3-4826-RV2 (to be published as ANSI/TIA-912-B) A.9. Crosstalk Coupling Loss 1 2 3 4 A test arrangement for measuring crosstalk coupling loss is shown in Figure A13. It may be desirable when making crosstalk measurements that a 10 dBrnC level of noise exist at the input interface of the disturbed connection. 5 Test Procedure 6 7 8 (1) Vary resistors R1 through R4 (referring to Figure A13) to obtain the full loop current ranges specified for the VG interfaces under test, as measured by the 0-200 mA dc meters. 9 10 11 (2) Calibrate the 600 oscillator at 1004 Hz to a level of 0 dBm into a separate 600 resistor. Then, reconnect the oscillator, without changing its level, into the test circuit as shown in Figure A13. 12 (3) Take readings on both wave analyzers in the disturbed connections: 13 14 (a) Select the higher power reading and subtract it from the calibrated level of the oscillator. The result is value A. 15 (b) Interchange the oscillator and load resistor R5 and repeat (a). The result is value B. 16 17 (c) Interchange the disturbing and disturbed connections and repeat (a) and (b). The results are values C and D. 18 19 (d) Select the lowest power value of A, B, C, and D. This is the value of crosstalk coupling loss for that pair of connections. 20 (4) Repeat (3) for all frequencies over the range 200 to 3400 Hz. 21 (5) Repeat (4) for all loop current values according to (1). 22 (6) Repeat (5) for all pairs of connections of the VG. 50 SP-3-4826-RV2 (to be published as ANSI/TIA-912-B) Tip T1 Disturbing Connection Tip T2 mA Oscillator (600 ) mA R1 C1 Voice Gateway Under Test Ring C2 R5 R2 Ring Ground Plane Tip T3 Disturbed Connection Tip T4 mA WA R6 mA R3 C3 Voice Gateway Under Test Ring C4 R4 Ring Ground Plane Oscillator WA mA T1 to T4 R1 to R4 R5 to R7 C1 to C4 Audio oscillator with a source impedance of 600 Audio wave analyzer 0 to 200 mA ammeter WECo 111C or 119E, or ADC 118F, or equivalent (Zin = Zout) 2 kadjustable 600 10 F, 400V dc 1 2 Figure A13 - Crosstalk Coupling Loss Test Circuit 51 R7 WA SP-3-4826-RV2 (to be published as ANSI/TIA-912-B) 1 Annex B (informative) - Telephony Loss Level Planning Overview 2 This annex is informative only and is not part of this standard. 3 B.1 Introduction 4 5 Telephony loss planning is concerned with the end-to-end loss between the sender and receiver over a telephony network. 6 7 8 It is called a loss plan, as the primary purpose is to approximate the free air loss between a talker and listener in a normal conversation. A secondary purpose is to control echo due to impedance mismatches in connections with long delays. 9 10 11 The loss plan is also related to the optimization of signal levels in equipment involved in the endto-end connection, and to the provisions of ANSI/TIA-968-A regarding the prevention of network harm. 12 B.2 Send and Receive Levels 13 14 15 16 17 18 19 The objective of a telephone connection is to simulate a 1 meter free air path between two talkers. This simulation involves several objective and subjective factors that are not present in the 1 meter air path. These include monaural listening, narrowband frequency response, the preferred listening level and others. For any telephone connection, the optimum OLR to achieve the preferred listening level is 10 dB. In a digital connection, the network loss is zero; therefore, the required loudness ratings are adjusted in the send and receive sections of the digital telephone set. 20 21 22 The send and receive levels of a telephone relate the conversion of acoustic pressure to electrical power and vice versa. The acoustic pressure units are in dBPa (Pascals), and the electrical power units are in dB mW. 23 24 Pressure is measured in Newtons per square meter (Pascals), and the relationship between dBSPL and dBPa is shown Table B1. 25 Table B1 – Acoustic Levels 26 dBSPL dBPa Parameter 94 0 Acoustic Pressure referred to One Pascal 89.3 -4.7 Average speech level at the MRP 0 -94 Lower limit of human hearing 27 28 52 SP-3-4826-RV2 (to be published as ANSI/TIA-912-B) B.2.1 Telephone Equipment Loudness Ratings 1 2 3 4 The loudness ratings of a telephone are the unit-less acoustic-to-electrical-to-acoustic conversion factors as shown in Figure B.1. As the acoustic and electrical units are both relative levels in dBs, the conversion factors are also in dBs. 5 dBm dBPa Send Loudness Rating (SLR) dBm Electrical Loss (dB) dBPa Receive Loudness Rating (RLR) Overall Loudness Rating (OLR) 6 7 Figure B1 - Terminal Loudness Ratings 8 9 The loudness ratings of the three telephone ports defined in this standard are shown in Table B2. 10 11 Table B2 - Telephone Loudness Ratings Telephone Port SLR (dB) RLR (dB) Notes OPS 8 -3 1 ONS 4 -7 2 DGS 8 2 3 12 13 Notes: 14 15 16 17 18 1. The OPS loudness ratings are representative of 2500-type analog telephones operating on 26 gauge/2.75 km loops with normal 48 volt battery feed and 600 ohm termination, as measured at a VG OPS port. See ANSI/TIA-470.110-C, Annex E for further details. OPS loudness ratings are assumed to be the same as DEO AAL loudness ratings that have 900 ohm terminations, but it depends on the characteristics of the telephone. 19 20 21 2. The ONS loudness ratings are representative of 2500-type analog telephones operating on very short loops with the typical current-limited battery feed and 600 ohm termination of VG ONS ports. See ANSI/TIA-470.110-C, Annex E for further details. 22 23 3. The DGS loudness ratings of SLR = 8 dB and RLR = 2 dB conform to the requirements specified in ANSI/TIA-810-B. 24 25 26 27 B.2.2 Overall Loudness Ratings The Overall Loudness Rating (OLR) of a connection is the sum of the sending terminal SLR, any system or network loss, and the receiving terminal RLR. This is illustrated in Figure B2 for setto-set calls within a VG. 28 29 53 SP-3-4826-RV2 (to be published as ANSI/TIA-912-B) Digital Set Voice Gateway Digital Set 0 dB Loss SLR 8 dB RLR 2 dB OLR 10 dB ONS Set Voice Gateway ONS Set 12 dB Loss SLR 4 dB OLR 9 dB 1 2 3 4 5 6 7 RLR -7 dB Figure B2 - Telephone-to-Telephone Overall Loudness Ratings B.2.3 Optimum Overall Loudness Ratings Figure B3 shows a plot of OLR versus R-Value using the E-Model (ITU-T Recommendation G.107). The majority of the OLR values in Table 2 are at or above an R-Value of 90, which puts them in the ‘very satisfied’ category. See TIA/EIA/TSB32-A for information on use of the EModel. All other parameters at default values according to ITU-T Recommendation G.107 (03/2003) 100 95 R-Value 90 85 80 0 2 4 6 8 10 12 14 16 OLR (dB) 8 9 Figure B3 - E-Model Optimum Overall Loudness Rating 10 54 18 20 SP-3-4826-RV2 (to be published as ANSI/TIA-912-B) 1 2 3 4 5 6 7 B.2.4 ATT Network Interface Loudness Ratings In Table 3, the network interface loudness ratings for the ATT port are derived from the combination of analog POTS set loudness ratings and nominal network losses. The 0 dBr reference point cannot be used in this case because the tie trunk is analog, but a reference point can still be established as shown in Figure B4, at the ATT analog network interface point. Note that the ATT network interface loudness ratings include a nominal 2 dB trunk loss in both directions. SLR 8 dB RLR 1 dB 11 dB -1 dB -7 dB RLR OLR = 12 dB Digital Set 3 dB 2 dB 6 dB VG ATT Port Analog Tie Trunk VG ATT Port 0 dB 2 dB 9 dB Analog POTS set OLR = 17 dB RLR 2 dB 2 dB 15 dB SLR 13 dB 4 dB SLR Reference Point 8 9 Figure B4 - ATT Network Interface Loudness Ratings 10 11 B.3 Port-to-Port Loss Allocation 12 13 14 It should be noted, that the actual allocation of the port-to-port loss to send and receive direction directly influences the available dynamic range of the PCM coding scheme and the noise level. This may lead to substantial impacts on speech transmission quality as perceived by the user. 15 16 Care should be taken to ensure that excessive input gain or loss does not cause either overload, or a poor signal-to-noise ratio, at the 0 dBr point. 17 Example: 18 The ONS to OPS loss is specified as 9 dB. 19 20 21 This could be implemented (in an extreme case) as an ONS input loss of -9 dB (9 dB gain), and an OPS output loss of 18 dB. The overall loss would be 9 dB, but the effective SLR at the 0 dBr point would be -5 dB ([ONS SLR = 4] + [Tx loss = -9] = -5 dB). 22 23 24 25 26 27 28 SLR 8 dB = -19 dBm0 for an average talker. ONS SLR 4 dB plus 9 dB of gain means the average talker power would be -6 dBm0. A loud talker/loud set might add another 9 dB raising the power to +3 dBm0, which is the codec overload level point, where clipping occurs. Voice peaks are about 12 dB higher than the average level, so the average talker would have peaks at +6 dBm0, 3 dB above the clipping point and the loud talker would be always be clipping. Obviously, adding 9 dB of transmit gain followed by 18 dB of attenuation is the wrong strategy for this connection. The correct approach is 3 dB of transmit loss, followed by 6 dB of receive-side loss. 55 SP-3-4826-RV2 (to be published as ANSI/TIA-912-B) 1 B.4 DTMF Overload on Analog Trunks 2 3 4 5 There is a potential for codec overload on the analog trunk interface when using the FXO to WAN setting, and in-band DTMF signaling is used for voice mail access, credit card verification, etc. This is only likely to happen in the situation where both the subscriber doing the signaling and the VG are close to the central office. 6 7 8 9 10 11 12 13 Given that some subscribers are going to be located close to the central office, the decision on when to introduce additional loss in the VG analog trunk interface has to be based on the distance of the VG from the central office. The generally excepted definition of a short loop is 2 km or less (less than approximately 3 dB loss), and therefore the recommendation is that an additional 3 dB of loss be inserted in the analog trunk interface for short loops when making FXO-to-WAN connections. The simplest way to do this is to use the FXD/WAN setting. This will also have the added advantage of reducing the OLR of the connection to a more comfortable level. 14 15 16 17 18 19 20 Figure B5 illustrates the subscriber to VG losses, and the resultant DTMF level at the analog trunk interface, for both long and short loops. It is assumed that the analog set is transmitting DTMF signals at the maximum level of 0 dBm, rather than the nominal level of -2 dBm and that the DEO is still using the old loss plan with the A/D pad = 0 dB and the D/A pad = 0 dB (the lowest loss option). If the new DEO loss plan in T1.508 (2003), with A/D pad = 0 dB and the D/A pad = 6 dB, was used then this DTMF overload issue would be eliminated. However, this would require that VG installer know which version of T1.508 the DEO used. Analog Set Connected via an Analog Trunk (Long Loop) DTMF Level 0 dBm Loss -0.5 dBm -0.5 dBm -3.0 dBm 3.0 dBm 0.5 dB 0 dB 2.5 dB -6 dB PSTN Subscriber Line 2500 Analog Set Analog Trunk FXO to DEO 0.35 km WAN Voice Gateway 2 km Analog Set Connected via an Analog Trunk (Short Loop) DTMF Level 0 dBm Loss -0.5 dBm -0.5 dBm -1.0 dBm 2.0 dBm 0.5 dB 0 dB 0.5 dB -3 dB PSTN Subscriber Line 2500 Analog Set Analog Trunk 0.35 km 21 22 FXD to DEO WAN 0.35 km Figure B5 - DTMF Levels for Long and Short Loop Analog Trunks 23 24 56 Voice Gateway SP-3-4826-RV2 (to be published as ANSI/TIA-912-B) 1 2 3 4 B.5 Open Loop Loss and Network Stability Annex A6 of TIA/EIA/TSB32-A provides an overview of 4-wire loop stability or ‘Singing’. The fundamental principle is that a 4-wire loop will oscillate if the sum of all losses and gains around the loop at one single frequency is equal to or less than 0 dB. 5 6 B.6 Reference Levels 7 B.6.1 Zero-Level Point 8 9 10 11 The zero-level point (ZLP) generally represents the digital (PCM) switching point in a VG. A 0 dBm0 signal at this point will decode to 0 dBm, or 1 mW in 600 The “B” revision of this standard replaced the term “zero-level point” with the term “0 dBr point”. B.6.2 0 dBm0 Definition 12 13 14 The 0 dBm0 level corresponds to the digital milliwatt (DMW) and is defined as the absolute power level at a digital reference point of the same signal that would be measured as the absolute power level, in dBm, if the reference point was analog. 15 16 17 The absolute power in dBm is defined as 10 log (power in mW/1 mW). When the test impedance is 600 resistive, dBm can be referred to a voltage of 775 mV, which results in a reference active power of 1 mW. 18 0 dBm0 corresponds to an overload level of approximately 3 dBm in the A/D conversion. 19 B.6.3 Digital Milliwatt 20 21 The digital reference level is the Digital Milliwatt (DMW) as defined in ITU-T Recommendation G.711, Tables 5 (A-law) and 6 (-law). 22 23 A 1 kHz signal at a nominal value of 0 dBm0 will be present at the output of a perfect codec if the periodic PCM code sequence specified in Table 5 or 6 is present at the input of the decoder. 24 25 26 The use of an exact 1 kHz signal can cause problems with some transmission and measuring equipment, so digital periodic sequences representing reference frequencies of 1004 Hz (IEEE) or 1020 Hz (ITU) are generally used instead. 27 These reference signals can be at either -10 dBm0 or 0 dBm0 +/- 0.03 dB. 28 B.6.4 Transmission Level Translation 29 30 31 The requirements in this standard that are affected by signal level are specified with respect to the 0 dBr point. The gain or loss from the port interface to the 0 dBr point has to be taken into account when making measurements. 32 33 In the case of input ports, the input level should be increased or decreased by the amount equivalent to the loss or gain from the interface to the 0 dBr point. 34 35 In the case of output ports, the output measurement should have an amount equivalent to the loss or gain from the 0 dBr point to the Interface, added or deleted. 36 37 38 Note: This amount is not the same as the loss specified in Table 1 and Table 2, as these loss requirements are for port-to-port connections, and the port-to-0 dBr-to-port losses and gains are defined by the VG manufacturer. 39 40 It is generally easier to set up the test connection as an analog-port to digital-port connection, although this is not a requirement. 41 42 43 57 SP-3-4826-RV2 (to be published as ANSI/TIA-912-B) 1 Example: 2 Output Interface – Idle-Channel Noise 3 4 Requirement: The 3-kHz flat weighted noise should not exceed 35 dBrn on 50 percent of the connections. 5 6 7 8 Given the case of a DAL to OPS port, and assuming the manufacturer has implement the 6 dB loss in the OPS interface, then the maximum allowable noise level would be adjusted by 6 dB, as shown below: 9 10 11 12 13 0 dBr Point OPS Interface Noise Measuring Set 0 dBm0 6 dB Loss 29 dBrn max. 14 58 SP-3-4826-RV2 (to be published as ANSI/TIA-912-B) 1 Annex C 2 This annex is informative only and is not part of this standard 3 4 5 6 C.1 Echo Return Loss (ERL) Echo return loss (ERL) is a weighted average of the return loss values over the frequency range 400 to 3400 Hz. Frequency multiples of 8 kHz must be avoided; the table below shows one convention for avoiding multiples. ERL is calculated as follows: RL( f i ) N 10 W( f i )10 ERL 10log10 i 1 N dB W( f i ) i1 7 8 (informative) - Loss Definitions where RL f i Return loss or transhybrid loss, in dB, at frequency f i , 9 10 W f i Weighting factor at frequency f i (see the following table ). Frequency fi (Hz) ERL Weights W(fi) 402 0.0631 602 0.6761 803 1.0000 1004 1.0000 1205 1.0000 1405 1.0000 1606 0.9550 1807 0.7586 2008 0.4467 2208 0.1995 2409 0.0813 2610 0.0324 2811 0.0129 3011 0.0051 3212 0.0021 3413 0.0009 59 SP-3-4826-RV2 (to be published as ANSI/TIA-912-B) 1 2 3 4 C.2 Return Loss (RL) Return loss (RL) at an impedance discontinuity in a transmission path is the ratio (in dB) of the power level of an incident signal to the power level of the resulting reflected signal. The general expression for return loss is: 5 ZI + ZR RL = 20 Log ZI - ZR 6 7 8 dB where ZI and ZR are the input and reference impedances respectively. 9 10 Single-frequency return loss (SFRL) is the lowest value of non-weighted return loss occurring in the frequency range 200 to 3200 Hz. 11 12 Single-frequency transhybrid loss (SFTHL) is the lowest value of loss, from the input pair to the output pair of the same 4-wire interface, occurring in the frequency range 200 to 3200 Hz. 13 14 15 C.3 Transhybrid Loss (THL) Transhybrid loss (THL) is the loss from the input pair to the output pair of the same 4-wire interface. 60 SP-3-4826-RV2 (to be published as ANSI/TIA-912-B) 1 Annex D (informative) - Pan-European Loss and Level Plans - ES 202 020 2 D.1 3 D.1.1 Voice Gateway Connections 4 5 6 7 The Pan-European Half-Channel Loss Plan Figure D.1 illustrates the connection types for a typical Pan-European VG application. There may be other applications not covered by this diagram, but sufficient information is provided for users to determine the applicable connection types for their particular application, and the corresponding interface losses to be applied. 8 Packet Connection Packet Facilities TDM Connection Analog Connection WAN WAN IP Network Ports MD Digital Public Exchange K2 KD Public Switched Network Ports Private Network Ports Voice Gateway Telephone Ports MD M2 M4 L22 LD L21 LD 9 10 Figure D.1 - Pan-European Voice Gateway Connections 11 61 Voice Gateway PBX SP-3-4826-RV2 (to be published as ANSI/TIA-912-B) 1 D.1.2 Interface Descriptions 2 Telephone Interfaces 3 L2 – 2-wire Analogue 4 5 6 7 The L2 interface provides for the connection of 2-wire analogue extension lines and will carry signals such as speech, voice-band analogue data and DTMF signals, etc. In addition, the interface L2 provides for ordinary functions such as direct current (DC) feeding, DC signalling, ringing, etc. 8 9 10 Note: The L2 interface is subdivided into short lines and long lines for transmission planning purposes. These are designated L21 and L22 respectively, and are equivalent to the North American ONS and OPS ports. 11 LD – Digital 12 13 The LD interface is a digital extension interface used to connect terminals which are also intended to be connected directly to digital interfaces of the public switched network. 14 Public Network Interfaces 15 K2 – 2-wire Analogue 16 17 The K2 interface provides for the connection of 2-wire analogue subscriber lines between a VG and a public exchange. 18 KD – Digital 19 The KD interface provides for the connection of a digital access to the public switched network. 20 Private Network Interfaces 21 M2 – 2-wire Analogue 22 23 The M2 interface provides for the connection to 2-wire analogue circuits (e.g. leased lines) between a VG and a PBX. 24 M4 – 4-wire Analogue 25 26 The M4 interface provides for the connection to 4-wire analogue circuits (e.g. leased lines) between a VG and a PBX. 27 28 Note: The M4 interface is used as the generic private network analogue interface for loss planning purposes. The required losses for the M4 and M2 interfaces are the same. 29 MD – Digital 30 The MD interface provides for connection to a system specific (digital) inter-VG circuit. 31 32 Note: The MD interface shares the KD designation for loss planning purposes (they are both digital connection with zero loss). 33 Packet Network Interfaces 34 WAN – Wide Area Network 35 A WAN interface connects from VGs to packet-based wide area networks. 36 37 38 Note: The term WAN is used in the same context as the public switched network, in that it represents connections between geographically separated VGs. It should be noted that WAN and LAN are synonymous from a transmission perspective. 39 40 41 D.1.3 Voice Gateway Half-Channel Loss Plan Table D.1 shows the VG half-channel loss plan for the Pan-European region, given in equivalent loudness ratings and respective loss. 62 SP-3-4826-RV2 (to be published as ANSI/TIA-912-B) 1 Table D.1: Voice Gateway Half-Channel Loss Plan 2 WAN 0 dBr Point (dB) L21 L22 LD WAN KD K2 M4 a b SLR Tx Loss 5 23 0 0 0 -6 -2 3 6 8 8 8 16 10 c =(a + b) SLRHC d =(e + f) RLRHC 8 8 8 8 8 101 8 2 2 2 2 2 4 2 e f Rx Loss 10 7 0 0 0 -1 -2 RLR g =(c + d) OLR2 -8 -5 2 2 2 5 4 10 10 10 10 10 14 10 h =(8 + d) Desirable OLR2 10 10 10 10 10 12 10 3 4 5 Column a shows the SLR of the telephone and trunk between the acoustic interface and the connection point to the VG. 6 Column b shows the VG transmit loss required to achieve the required SLRHC at the 0 dBr point. 7 Column c shows the resulting Half-Channel SLR (SLRHC) at the 0 dBr point (WAN). 8 Column d shows the resulting Half-Channel RLR (RLRHC) at the 0 dBr point (WAN). 9 10 Column e shows the VG receive loss required to achieve the desirable OLR, based on the RLR shown in column f, and the optimum SLR of 8 dB. 11 12 Column f shows the RLR of the telephone and trunk between the acoustic interface and the connection point to the VG. 13 Column g shows the resulting OLR, based on the actual SLR. 14 Column h shows the desirable OLR, based on the optimum SLR of 8 dB. 15 16 Note 1: It is not possible to achieve the optimum SLRHC of 8 db for connections from analogue networks due to the potential for loop instability. 17 18 Note 2: The OLR values shown in the table are as perceived by the listener, i.e., this is shown as a one-way connection. 19 20 21 22 Note 3: Although this Standard does not apply to Local Exchanges, in some situations, the same product may be capable of being either a VG or a Local Exchange. Loss plan designers should be aware of the subtle difference between the two loss plans: The L2 Tx loss at a Local Exchange is 0 dB, rather that the 2 dB for an L22 Tx loss at an Enterprise Voice Gateway. 23 24 63 SP-3-4826-RV2 (to be published as ANSI/TIA-912-B) 1 D.2 The Pan-European Full-Channel Loss Plan 2 Full-Channel Loss Plan Interpretation 3 4 5 Table D.2 shows the interface-to-interface loss in the Pan-European full-channel loss plan. Arrows at the row and column designators indicate the transmission direction in which the coordinate loss values are to be inserted. 6 7 8 For example, co-ordinate 1 B indicates a nominal interface-to-interface loss of 12 dB from the L21 interface to the L22 interface, and co-ordinate 2A indicates a 12 dB loss in the other direction, from the L22 interface to the L21 interface. 9 Note: This is a loss plan, therefore negative values denote gain; e.g., -6 indicates 6 dB gain. 10 Table D.2: Voice Gateway Full-Channel Loss Plan (Pan-European) A B C D E F G L21 L22 LD WAN KD/MD K2 M4 Loss (dB) 1 L21 15 12 5 5 5 4 3 2 L22 12 9 2 2 2 1 0 3 LD 10 7 0 0 0 -1 -2 4 WAN 10 7 0 0 0 -1 -2 5 KD/MD 10 7 0 0 0 -1 -2 6 K2 4 1 -6 -6 -6 -7 -8 7 M4 8 5 -2 -2 -2 -3 -4 11 12 Note: The interface-to-interface losses are the sum of the transmit and receive half-channel losses defined in Table D.1. 13 Full-Channel Loudness Ratings Table Interpretation 14 15 16 17 Table D.3 is provided to show the relationship between OLR, SLR, RLR and interface-tointerface loss. For example, for an L21 to L22 connection, the L21 SLR is 3 dB, the VG loss is 12 dB (from 1B in Table B.1), and the L22 RLR is -5 dB. The overall loudness ratings is therefore 3 + 12 - 5 = 10 dB. 18 Table D.3: Voice Gateway Full-Channel Loudness Ratings (Pan-European) L21 L22 LD WAN KD/MS K2 M4 RLR -8 -5 2 2 2 5 4 SLR OLR L21 3 10 10 10 10 10 12 10 L22 6 10 10 10 10 10 12 10 LD 8 10 10 10 10 10 12 10 WAN 8 10 10 10 10 10 12 10 KD/MS 8 10 10 10 10 10 12 10 K2 16 12 12 12 12 12 14 12 M4 10 10 10 10 10 10 12 10 64 SP-3-4826-RV2 (to be published as ANSI/TIA-912-B) 1 Annex E (informative) - Loss Plan and Loudness Rating References and Hierarchy G.101 SLR 8 dB1 RLR 2 dB OLR 10 dB Digital Analog TIA-810-B SLR 8 dB RLR 2 dB TIA-470.110-C SLR 8 dB RLR -3 dB @ 2.7 km T1.508 Loss A/D 0 dB Loss D/A 6 dB TIA-912-B Loss A/D 0 dB Loss D/A 6 dB TIA-464-C TIA-464-C-1 Loss A/D 0 dB Loss D/A 6 dB T1.508 Loss D/D 0 dB Loss D/D 0 dB SLR = SLRset + Loss A/D = 8 + 0 = 8 dB RLR = RLRset + Loss D/A = -3 + 6 = 3 dB OLR = SLR + Loss A/D + Loss D/D + Loss D/A + RLR = 8 + 0 + 0 + 6 - 3 = 11 dB 2 3 TIA-920 SLR 8 dB RLR 2 dB TIA-912-B Loss D/D 0 dB Loss D/D 0 dB TIA-464-C TIA-464-C-1 Loss D/D 0 dB Loss D/D 0 dB SLR = SLRset + Loss D/D = 8 + 0 = 8 dB RLR = RLRset + Loss D/D = 2 + 0 = 2 dB OLR = SLR + Loss D/D + RLR = 8 + 0 + 2 = 10 dB Where: SLR and RLR are at the 0 dBr point. Note 1: According to ITU-T Recommendation G.100.1, Clause 6.3, SLR > 2 dB gives reasonable protection against objectionable speech clipping. Figure E.1 – Hierarchical Relationship between Loudness Rating and Loss Plan Standards 65 SP-3-4826-RV2 (to be published as ANSI/TIA-912-B) 1 Annex F 2 3 4 5 The effects of impairments introduced by IP networks are described in TIA/TSB-116-A, Voice Quality Recommendations for IP Telephony. The effects of impairments are evaluated using the E-model, which includes the effects of both the terminal equipment (end points) and the transmission network. 6 7 IP networks impact two of the impairment parameters; end-to-end delay and packet loss. Unfortunately both these have significant effects on speech quality. 8 9 A VG is also likely to perform TDM/IP conversions, and will need to employ echo cancellers if there are any 2-to-4 wire converters on the TDM side of the conversion. F.1 Delay 10 11 (informative) - IP Transmission Impairments End-to-end delay is a combination of the: 12 The sending end point encoding and packetizing delay, 13 The network processing and propagation delay, 14 The receiving end point jitter buffer, depacketizing, and decoding delay. 15 16 17 There is an interaction between the network delay and the receiving end point delay, in that the end point has to compensate for network delay variances via a jitter buffer, and increased variances lead to longer average delay in the end point. 18 Note: Other processes such as transcoding or encryption will also add delay. 19 20 21 22 23 F.2 Packet Loss Packets can be lost either in the network, or can be discarded by the end point because they are too late (delayed beyond the range of the jitter buffer). In this case there is an interaction between network delay variances and packet loss in the end point. F.3 Voice Gateways and Network Performance 24 25 The purpose of standards for voice transmission is to ensure that voice quality is achieved by adherence to the standards. 26 27 In a PBX standard, the TDM transmission and switching is a dedicated resource within the PBX framework, and under normal conditions has little or no impact on voice quality. 28 29 30 31 In a VG standard, transmission and switching is via IP networks, which can introduce impairments as noted above, and may also be shared by other entities beyond the control of the VG. Ensuring good voice quality will therefore require the use of managed networks and other techniques, which is beyond the scope of this standard. 32 66 SP-3-4826-RV2 (to be published as ANSI/TIA-912-B) 1 F.4 Voice Quality of Service 2 3 4 There are a number of standards groups addressing the issue of voice quality of service (QoS). Users of this standard should ensure they are familiar with the work of these groups, as the methods and techniques for managing voice QoS are constantly evolving. 5 Some of the major groups involved in IP telephony voice QoS are listed below: 6 TIA Telecommunications Industry Association 7 www.tiaonline.org 8 TR-41 User Premises Telecommunications Requirements 9 10 ATIS Alliance for Telecommunications Industry Solutions 11 http://www.atis.org/ 12 PRSSC Performance, Reliability, and Security Standards Committee 13 14 IETF Internet Engineering Task Force 15 www.ietf.org 16 MPLS Multiprotocol Label Switching 17 DIFFSERV Differentiated Services 18 19 20 ITU-T International Telecommunication Union - Telecommunication Standardization Sector 21 www.itu.int/ITU-T 22 ITU-T SG 12 End-to-end transmission performance of networks and terminals 23 24 ETSI European Telecommunications Standards Institute 25 www.etsi.org 26 27 TISPAN Telecommunications and Internet converged Services and Protocols for Advanced Networking 28 STQ Speech Processing, Transmission and Quality Aspects 29 67 SP-3-4826-RV2 (to be published as ANSI/TIA-912-B) 1 Annex G (informative) - Bibliography 2 3 4 [G1] ANSI/TIA-470.210-C Requirements. (April 2004), Resistance and Impedance Performance 5 [G2] TIA/EIA/TSB31-B (February 1998), Part 68 Rationale and Measurement Guidelines. 6 7 [G3] TIA/EIA/TSB32-A (December 1998), Overall Transmission Plan Aspects for Telephony in a Private Network. 8 [G4] TIA/TSB-116-A (March 2006), Voice Quality Recommendations for IP Telephony. 9 10 [G5] IEEE 743-1995, Standard Methods and Equipment for Measuring the Transmission Characteristics of Analog Voice Frequency Circuits. 11 12 [G6] ITU-T Recommendation G.100.1 (11/01), The use of the decibel and of relative levels in speechband telecommunications. 13 14 [G7] ITU-T Recommendation G.107 (03/05) and Amendment 1 (06/06), The E-Model, A Computational Model for use in Transmission Planning. 15 16 68 1 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17