PNT-00-009
Telecommunications Industry Association
(TIA)
Newport Beach, CA, 23 March 2000
PN-4643 G.pnt AD HOC COMMITTEE CONTRIBUTION
Technical Committee TR-30 Meetings
SOURCE:
Editor G.pnt
CONTRIBUTOR:
Name:
John Magill
Phone: +44 1666 510105
E-mail: johnmagill@probecom.co.uk
TITLE:
PN-4643 G.pnt: Draft text for G.pnt
PROJECT:
PN-4643 G.pnt
DISTRIBUTION:
Members of TR-30.1 PN-4643 G.pnt Ad Hoc and meeting attendees
Editors Note:
The following text is based on the agreements reached on G.pnt to date as given in Q.4/15
document FI-U12R1. In particular:

Section 5 encompasses the agreements on the system reference model given in section 5 of
FI-U12R1, and material from ;

Section 6 defines the agreed PSD mask including the clarifications of FI-064;

Section 7 defines the G.pnt frame format and is based on the text in FI-098.
* Contact:
John Magill
Lucent Technologies
Tel:
+44 1666 510105
Fax: +44 1666 510149
Email: johnmagill@probecom.co.uk
-2-
Summary
This Recommendation specifies the characteristics of devices designed for the transmission of data over
home phoneline networks. These devices are intended to be compatible with existing telephony devices
on the home phoneline. Additionally the specification provides for spectrum notching for compatibility
with Amateur Radio services.
This Recommendation defines:

the system reference model for these devices;

the required PSD mask;

the line signal frame format;
Table of Contents
1
SCOPE ................................................................................................................................... 3
2
REFERENCES ...................................................................................................................... 3
3
DEFINITIONS ...................................................................................................................... 4
4
ABBREVIATIONS ............................................................................................................... 4
5
SYSTEM REFERENCE MODEL FOR PHONELINE NETWORKING
TRANSCEIVERS ......................................................................................................................... 4
6
POWER SPECTRAL DENSITY ........................................................................................ 7
6.1 G.PNT PEAK-TO-AVERAGE RATIO ASSUMPTIONS................................................................. 8
7
G.PNT FRAMING ................................................................................................................ 9
7.1 PREAMBLE ......................................................................................................................... 10
7.2 FRAME TYPE (FT) .............................................................................................................. 11
7.3 END OF FRAME DELIMITER (EOF) ..................................................................................... 11
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-31
Scope
This Recommendation specifies the basic characteristics of devices designed for the transmission of data
over home phoneline networks.
These devices are intended to be compatible with other devices sharing the home phoneline network,
e.g.:

PSTN telephony services;

voiceband data services e.g. V.90;

ISDN Basic Rate services;

G.992.x ADSL services.
Additionally the specification provides for spectrum notching for compatibility with Amateur radio
services.
This Recommendation defines:
2

the system reference model for home phoneline tranceivers;

the required Power Spectral Density (PSD) mask;

the line signal frame format;

………
References
The following ITU-T Recommendations, and other references contain provisions which, through
reference in this text, constitute provisions of this Recommendation. At the time of publication, the
editions indicated were valid. All Recommendations and other references are subject to revision; all users
of this Recommendation are therefore encouraged to investigate the possibility of applying the most
recent edition of the Recommendations and other references listed below. A list of the currently valid
ITU-T Recommendations is regularly published.
ITU-T Recommendation G.9921 - 1999 – Asymmetrical Digital Subscriber Line (ADSL) Transceivers
ITU-T Recommendation G.992.2 - 1999 – Splitterless Asymmetric Digital Subscriber Line (ADSL)
Transceivers
ITU-T Recommendation J.112 – Transmission systems for interactive cable television services
ITU-T Recommendation V.90 – A digital modem and analogue modem pair for use on the Public
Switched Telephone Network (PSTN) at data signalling rates of up to 56 000 bit/s downstream and up to
33 600 bit/s upstream
IEEE 802.3 – title tba
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-43
Definitions
This Recommendation defines the following terms:
tba
4
Abbreviations
ADSL
Asymmetrical digital subscriber line
CP
Customer Premises
DF
Data Frame
DSL
Digital subscriber line
EOF
End of frame delimiter
FT
Frame Type
IF
Isolation Filter
IFG
Inter-frame gap
ISDN
Integrated Services Digital Network
MAC
Media Access Control
NI
Network interface
NID
Network interface device
PHY
Physical Layer
PSD
Power spectral density
PSTN
Public switched telephone network
RFI
Radio Frequency Interference
5
System Reference Model for Phoneline Networking Transceivers
The G.pnt Recommendation defines base level physical layer (PHY) and media access control (MAC)
functionality between the phoneline interface and a host interface as shown in Figure 1. The primary
interface is the wire-side electrical and logical interface (W1) between a G.pnt station and the phone
wire.
106751604
-5HOST-SIDE
INTERFACES
OPTIONAL
MAC
G.pnt STATION
PHY
W1
PHONEWIRE
Figure 1 – Basic Reference Model
An alternative more functional oriented view of the same picture is shown in Figure 2 below:
Link Layer Protocols
Bus
MAC
PHY
•
•
•
•
Link Setup
Link Integrity
Error Control
•
Optional PHY-MAC Interface
•
•
CSMA/CD
Collision Resolution
•
•
•
•
Syncrhonization
Timing
Modulation
Figure 2 – Functional View of Reference Model
The G.pnt system implements a shared medium single-segment network. All stations on a segment are
logically connected to the same shared channel on the phoneline.
Multiple G.pnt network segments and other network links can be connected through ISO network Layer 2
(L2 or Data Link) or Layer 3 (L3 or IP) relays.
106751604
-6G.pnt STATIONS
S0
S1
...
SN
OTHER G.pnt
SEGMENTS
L3 ROUTER
"GATEWAY"
L2 BRIDGE
OTHER TYPE NETWORK
SEGMENTS
G.pnt SEGMENT
WIDE
AREA
V.90
ISDN
G.992.1 or .2
J.112 CABLE
OTHER...
Figure 3 – Wide area network interworking
In Figure 3, a Layer 3 router/gateway is shown which interconnects a wide-area network link to the inpremise G.pnt network. Such a wide-area link might be provided via subscriber line (modem e.g.V.90,
Basic Rate ISDN, ADSL i.e. G.992.1 or G.992.2), cable (J.112) or wireless link. Also shown is a L2
bridge which interconnects the first G.pnt network with, e.g., other G.pnt network segments or IEEE
802.3 (10BASE-T, 100BASE-T) networks.
A
OUTSIDE
SUBSCRIBER
LOOP
B
C
NID
*IF
*Optional Isolation Filter
E
F
G
Figure 4 – Network topologies
Home phoneline transceivers should be designed to work over "as is" customer premise wiring. The
topologies anticipated are random combinations of star, tree and multi-point bus wiring e.g. as shown in
Figure 4.
106751604
-7Within a topology, each wiring run may have one or more modular connectors at wall plates, and variable
length extension wires (shown as a double line in Figure 4) run from the wall plates to the attached POTS
or G.pnt device. In this example, stations A and B are on one bus; station C is on a second bus, which is
un-terminated at the end; station E is at the end of a direct run from the Network Interface Device (NID);
and stations F and G share a single wall plate via a two outlet adapter. Many other topologies are
possible. An optional Isolation Filter (IF) may be placed between the NID and the customer premise
wiring.
6
Power Spectral Density
The G.pnt PSD mask is given in Figure 5. A G.pnt transceiver shall be constrained by the upper bound as
depicted in Figure 5 with a measurement made across a 100 load across Tip and Ring at the transmitter.
This mask applies to all payload encoding schemes employed by G.pnt transceivers. Note that all
segments in the mask are straight lines on a semilog plot.
Maximum-length frames and minimum inter-frame gaps (IFGs) are assumed. Since most of the frame
data can be expected to be randomized by a data scrambler, these assumptions allow the burst
transmissions to be treated as a single continuous data stream for the purpose of defining the PSD mask.
106751604
-8Figure 5: G.pnt PSD Mask
Frequency (MHz)
PSD Limit (dBm/Hz)
0.015 < f <= 1.7
-140
1.7 < f <= 3.5
-140 + (f – 1.7)*50.0/1.8
3.5 < f <= 4.0
-90 + (f – 3.5)*17.0
4.0 < f < 7.0
-71.5
7.0 <= f <= 7.3
-81.5
7.3 < f < 10.0
-71.5
10.0 <= f < 13.0
-81.5 – (f –10.0)*43.5/3.0
13.0 <= f < 25.0
-125
25.0 <= f < 30.0
-140
The 10 dB notches at 4.0, 7.0 and 10.0 MHz are designed to reduce RFI egress in the radio amateur
bands.
The resolution bandwidth used to make this measurement shall be 10 kHz for frequencies between 2.0
and 30.0 MHz and 3 kHz for frequencies between 0.015 and 2.0 MHz. An averaging window of 213
seconds shall be used, and 1500-octet frames separated by an IFG duration of silence shall be assumed.
A total of 50 kHz of possibly non-contiguous bands may exceed the limit line under 2.0 MHz, with no
sub-band greater than 20 dB above the limit line. A total of 100 kHz of possibly non-contiguous bands
may exceed the limit line between 13.0 and 30.0 MHz, with no sub-band greater than 20 dB above the
limit line.
6.1
G.pnt Peak-to-Average Ratio Assumptions
To meet national conducted emissions regulations, the transmitted power averaged over a short window
must be constrained. In addition, the desire to avoid audible interference in telephones leads to limits on
peak transmitted power. Therefore, a viable constellation scaling is one that sets the outer points to
approximately the same amplitude and allows the average power to decrease with increasing
constellation size.
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-9-
The following assumptions are made:

the peak-to-average ratio at the wire interface of a transmitting device is less than 9.5 dB for the
choice of constellation that yields the highest average transmitted power;

the ratio of the maximum value of the average power over a 2-sec sliding window to the average
power is less than 2.7 dB for the same constellation choice.
7
G.pnt Framing
The G.pnt frame format is given in Figure 6. This consists of a preamble and frame type (FT) field, G.pnt
header and payload, and a trailer (EOF). Each of the fields, except the G.pnt header and payload, is a
fixed sequence for each G.pnt transmission. A minimum silence gap, referred to as the inter-frame gap
(IFG), follows every frame. The G.pnt header, payload, and IFG are for further study.
16
Bytes
PREAMBLE
32.0
sec
1
Byte
1
Byte
Frame
Type
G.pnt Header and Payload
EOF
InterFrame
2.0
sec
2.0
sec
Gap
Figure 6. Basic Frame Format
Figure 7 indicates that preamble, FT, and EOF generation is logically distinct from the G.pnt header and
payload generation. This allows different framing, modulation, and synchronization methods for the
G.pnt header and payload (as indicated by the information in the Frame Type field).
106751604
- 10 -
G.pnt header and
payload transmitter
G.pnt MAC
+
G.pnt preamble, FT,
and EOF transmitter
Figure 7. Basic Structure of a G.pnt Transmitter
7.1
Preamble
The preamble is a fixed sequence known by every burst receiver using the same band on the wire. It is
proposed to use the bit sequence 0xFC483084, repeated 4 times, with bits transmitted most significant
octet first, least significant bit first and mapped according to Figure 8.
Figure 8. Preamble Symbol Map
The symbol values are shown with bits ordered such that the right-most bit is the first bit received from
the preamble generator.
The resulting length-64 sequence of 4-point symbols is interspersed with zero-valued symbols to produce
a length-128 sequence that is transmitted using quadrature amplitude modulation with a symbol interval
of 0.25 µsec, a carrier frequency of 7.0 MHz. Transmit filtering sufficient to meet the PSD mask defined
in §6 is applied.
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- 11 7.2
Frame Type (FT)
The frame type (FT) field is an 8-bit field that is set to a known value by the transmitter. It is encoded
into 4 symbols according to the diagram in the previous section, then interspersed with 4 zeros, and it is
quadrature amplitude modulated with a carrier frequency of 7.0 MHz. The receiver decodes this field and
discards the frame if it is not a known value.
The Frame Type is intended to provide flexibility for defining other frame formats and modulators in
future versions of the recommendation. Initially, a known value of 1 is proposed.
7.3
End of Frame Delimiter (EOF)
The end-of-frame delimiter (EOF) is the first eight symbols of the length-128 preamble, quadrature
amplitude modulated with a carrier frequency of 7.0 MHz and an initial phase of 2*pi*tau*7.0+phi,
where tau is the offset from the last symbol of the FT field in microseconds and phi is the initial phase of
the modulator (at the start of the burst).
106751604