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LTE1891 – eNB Power Saving – Micro DTX
RA4115 FL16 Feature Overview
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LTE1891 – eNB Power Saving – Micro DTX
Agenda
Feature Overview
Configuration and Testing
Test Results
Operational Hints and Guidelines
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Subject: Presentation Notes Date: 2/4/2016 5:30:52 AM
The LTE1891 – eNB Power Saving – Micro-DTX feature provides further energy saving of an eNB. It is
obtained by switching off the cell's Power Amplifier (PA) for the duration of unused Orthogonal FrequencyDivision Multiplexing (OFDM) symbols.
This power saving feature enables to save up to 40% of power in LTE cells with very low traffic or without
traffic.
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Feature Overview
LTE1891 – eNB Power Saving – Micro DTX
The LTE1891: eNodeB Power Saving – Micro-DTX feature introduces an option for further eNB
energy saving. The mechanism used for this purpose is based on the concept of unused OFDM
symbols as well as a scheduler's role in switching off the Power Amplifier (PA).
The DL scheduler monitors the OFDM symbol durations in a timespan of 40 ms (the PA must be
switched on or off), collects the data into a message covering these 40 ms, and sends it to the
radio frequency (RF) module.
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Feature Overview
LTE1891 – eNB Power Saving – Micro DTX
In the LTE1891 feature, the Micro-DTX functionality allows switching off the PA of the LTE cell,
for the duration of individual OFDM symbols, at times when the scheduler has determined that
there is no DL signal to be sent over the air.
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Each LTE DL transmission is built of a sequence of Transmission Time Intervals (TTIs), each lasting 1
millisecond (ms). These so-called subframes are divided into 14 OFDM symbol durations. Even if there is no
user-related data to transmit, a transmitter sends some reference signals in a well-defined OFDM symbol
space within a subframe.
In the LTE1891: eNodeB Power Saving – Micro-DTX feature, the Micro-DTX (discontinuous transmission)
functionality allows switching off the PA of the LTE cell, for the duration of individual OFDM symbols, at
times when the scheduler has determined that there is no DL signal to be sent over the air. As a result, the
power consumption of the eNB is limited.
This feature finds the unused OFDM symbols only at times of a very low DL load (no users connected or
only few of them). The LTE1891: eNodeB Power Saving – Micro-DTX feature works for setups with a single
system module (MAC) entity controlling one or more PA(s) which are serving no other cells.
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Feature Overview
LTE1891 – eNB Power Saving – Micro DTX
The Micro-DTX feature operates on three time scopes:
• OFDM symbol time scope with respect to PA on/off control,
• TTI scope to define when DL signal (DL-S) operates or not and when OFDM symbols are
muted,
• 40 ms duration scope with respect to pattern selection and its ability to follow the traffic
demand (the trend in DL load).
Regarding the composition of activated features and parameter settings, the eNB chooses one
of the following:
• Using the minimum ON power-muting pattern,
• Using ONE of the predefined standard-muting patterns,
• Applying NO power-muting whatsoever.
If any kind of muting is applied, then the LTE1891: eNodeB Power Saving – Micro-DTX feature
marks all OFDM symbol durations (table cells) as NEEDS PA ON that contain mandatory
transmission defined on the OFDM symbol level.
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The feature LTE1113 “eICIC” has introduced the concept of ABS muting patterns: they define time intervals
when a macro cell is not allowed to send certain types of DL data, so the macro cell is said to be "muted".
LTE1891 adds the term "power muting" which indicates that the RF power amplifier(s) of a cell are switched
OFF in a specified interval of time.
ABS muting patterns always cover 40 ms duration and have well-defined starting times. Power-muting
patterns cover the same length of time and use the same starting times even if eICIC is not activated in the
cell.
The eNB shall maintain a set of two power-muting patterns, which are tables that each cover 4 radio frames
(40 subframes), and contain 14 OFDM symbol positions for each subframe. The 560 elements of one such
table are the candidates for "power muting", i.e. for switching off the power amplifiers if eNB can determine
that no DL transmission is required in this duration.
The eNB shall use table "A" for the current time interval (of 40 ms duration), and table "B" to collect the
required data for the next following time interval. Once that eNB system time has reached the end of table
"A", eNB shall swap the tables so that table "B" becomes the new table "A" and defines the eNB behavior,
while the new table "B" shall be cleared and used to collect the data for the next following 40 ms timeframe.
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Feature Overview
LTE1891 – eNB Power Saving – Micro DTX
Subframe “Power Muting Pattern” for Micro-DTX:
• The minimumON pattern shall be used in situations of no load in the cell. Its application
requires the raRespWinSize and the raContResoT are set such that the maximum of 8
consecutive muted subframes still allow the reception of RACH response messages – which
are already fulfilled by consistency checks.
• At times of very low load in the cell, either the standard20 or the standard40 muting pattern
shall be used. The standard40 pattern shall be selected if siWindowLen is set to 40 and actDrx
is set to falso. Otherwise, the standard20 pattern shall be used.
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The bits in a power-muting pattern indicate:
0 = power-saving; the power-amp is OFF and OFDM symbol or subframe is muted
1 = DL transmission; "need power-amp ON", OFDM symbol or subframe is not muted.
(Note that eICIC muting patterns use the opposite convention, so for eICIC, 1 = ABS and 0 = nonABS)
Each message with a power-muting pattern also contains a time stamp which indicates to the RF unit the
time-span (starting radio frame number, unambiguous to an interval of at least 2 minutes) for which the
muting pattern is valid.
A "full-power" muting pattern has all bits set to 1. Sending no pattern at all has the same result as sending
the full-power pattern, since the RF modules will perform no muting if no message is received with a valid
pattern.
raRespWinSize = Random Access Response Window Size parameter defines the window size for the
random access response in TTIs.
raContResoT = The maximum content resolution timer parameter defines the maximum amount of time
allowed for contention resolution.
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Feature Overview
LTE1891 – eNB Power Saving – Micro DTX
The overall SIB Scheduling concept is as follows:
• MIB is transmitted at a fixed cycle (every 4 frames starting from SFN 0),
• SIB1 is also transmitted at the fixed cycle (every 8 frames starting from SFN 0),
• All other SIBs are being transmitted at the cycles specified by SIB scheduling information
elements in SIB1.
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According to 3GPP 36.331, section 5.2.1.2, the MIB scheduling is as follows:
The MIB uses a fixed schedule with a periodicity of 40 ms and repetitions made within 40 ms. The first
transmission of the MIB is scheduled in subframe #0 of radio frames for which the SFN mod 4 = 0, and
repetitions are scheduled in subframe #0 of all other radio frames.
In order to make sure the SIBs are received by the UE, an SI-window is defined to enable multiple
transmissions of the SI message within the window. The length of the SI-window can be set to 1, 2, 5 10, 15,
20 or 40 ms. Within an SI-window, only one SI message can be sent, and may be repeated multiple times.
When a UE tries to acquire an SI message, it listens from the starting of the SI-window until the SI message
is received.
Reference:
http://www.sharetechnote.com/html/BasicProcedure_LTE_SIB_Scheduling.html
http://lteuniversity.com/get_trained/expert_opinion1/b/hongyanlei/archive/2010/09/21/lte-systeminformation-part-3.aspx
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Feature Overview
LTE1891 – eNB Power Saving – Micro DTX
The Power Saving Mode is applied in the following scenarios:
• A cell without any RRC-connected UE (maximum saving) or a cell with a maximum of five UEs,
RRC-connected and with a low traffic volume (reduced savings),
• One or more micro-DTX-capable power amplifiers are connected,
• The cell bandwidth is five MHz or higher,
• siWindowLen is 20 ms or 40 ms.
The Power Saving Mode can be applied to OFDM symbols not using:
• Common reference symbols (CRS),
• Positioning reference symbols (PRS),
• Downlink synchronization (PSS, SSS) channel information,
• Downlink control channel information (PCFICH, PHICH, PDCCH),
• PBCH (MIB) and SIB >=2,
• Downlink non-UE specific information on PDSCH (SIB).
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Micro-DTX uses subframe patterns to define which TTIs are allowed for DL scheduling. The patterns are
chosen in such a way that they cause a minimal impact on other, timing-sensitive, functions. In macro cells,
they also allow straightforward cooperation with eICIC features. An O&M parameter controls the level of DL
resource usage at which the transition is made between a reduced power saving and provision of full
capacity.
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Feature Overview
Feature Interdependencies
The following features must be deactivated before activating LTE1891:
• LTE1382: Cell Resource Groups
• LTE1117: LTE MBMS
• LTE435: RF Sharing WCDMA-LTE
• LTE447: SW Support for RF Sharing GSM-LTE
• LTE1895: LTE-GSM and LTE-WCDMA RF Sharing for Dual Band Configurations
• LTE471: LTE Dual Carrier Operation within One RF Band
• LTE2019: Advanced Dual Carrier Operation within Same RF Unit
• LTE1829: Inter-eNB RF Sharing
• LTE2079: LTE-GSM RF Sharing with Full FBBC Support
• LTE2080: WCDMA-GSM RF Sharing with Full FBBC Support
• LTE819: DL Inter-cell Interference Generation
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The eNodeB Power Saving – Micro-DTX feature relies on a fast interface between the MAC and an element
that controls the PA(s) associated with a cell. This interface is represented by an open-base-stationarchitecture initiative (OBSAI). In the future, new RF HW is planned to perform micro-DTX without
transmitting the muting messages to the PA. The maximum permitted cable length when using OBSAI is
determined by the maximum permitted singlepath delay of 80 μs. It allows an approximately 16 km cable
length.
Feature Overview
HW Requirements
The following RF modules support micro-DTX:
FHED, FHFB, FRAA, FRBE, FRBF, FRBG, FRCC, FRCG, FRGA, FRGB, FRGU,
FRGY, FRHC (at least version A102), FRHF (at least version A102), FRHG, FRMC,
FRME, FRMF, FRNC, FRPA, FRPB, FXED, FXEE, FRSA, FRGX, FRDC, and FXEF.
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Management Data
New Performance Measurement Counters and New BTS faults
• New Counters
Counter ID
Counter name
Measurement
M8010C93
Suppressed OFDM symbols with micro DTX ratio in RF
module
LTE Power and Quality DL
Fault ID
Fault name
Reported Alarm
109710 / 4304
Too Long Fiber for mDTX activation
7655 (CELL NOTIFICATION)
109975 / 4308
Micro DTX configuration failure
7655 (CELL NOTIFICATION)
• New BTS faults
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Management Data
New Parameters introduced by LTE1891
• New Parameters
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Parameter Name
Abbreviated Name
Managed Object
Activate eNode B power saving – Micro-DTX
actMicroDtx
LNCEL
Micro-DTX aggressiveness
mdtxAggressiveness
LNCEL
Number of non-muted PDCCH symbols if cell is empty
mdtxPdcchSymb
LNCEL
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Configuration and Testing
Activation of the LTE1891 feature
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Parameter name:
Activate eNode B power saving - Micro DTX
Parameter short name:
actMicroDtx
Short description:
This parameter activates the feature 'eNode B power
saving - Micro DTX'.
Full description:
It is possible to reduce power consumption by having
the power amplifiers associated with a cell shut down
during OFDM symbol
times that are not used for any
DL transmission.
Managed object class: LNCEL
Managed object full name: LTE BTS Cell
Range:
Type: Boolean
Default value: false
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Configuration and Testing
Micro-DTX aggressiveness (mandatory parameter)
The “aggressiveness” parameter controls the decision whether using a standard muting pattern
or applying no muting.
 If the estimated PRB usage in the upcoming pattern period exceeds the value of
mdtxAggressiveness, no muting will be applied in the upcoming period (Default = 0.4).
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Range:
Type:
Decimal
Default value:
0.4
Minimum value:
0.1
Maximum value:
0.6
Step:
0.05
Conversion between value in SCF file and value shown in UI:
Value in UI = Value in SCF file * 1 / 20 + 0
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Configuration and Testing
Number of non-muted PDCCH symbols if cell is empty (mandatory)
This parameter temporarily overrides the maxNrSymPdcch value for muted subframes, when the
eNB is in the mdtxMinimumState and cell has at least 10 MHz bandwidth (Default = 3).
Small values might lead to reduced PRACH performance.
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Range:
Type:
Decimal
Default value:
3
Minimum value:
1
Maximum value:
3
Subject: Presentation Notes Date: 2/4/2016 5:30:55 AM
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Configuration and Testing
SI window length
This parameter SI Window Length defines the common System Information scheduling window
for all SIs.
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Consistency Check:  ERROR:
Parameter actMicroDtx (Activate eNode B power saving - Micro DTX) value true needs to be equal to false
because parameter siWindowLen (SI window length) in object LNCEL does not match the regular expression
20ms|40ms.
Configuration and Testing
Test setup
• Equipment:
- One eNB with an FSMF system module and a Radio Module supporting mDTX (e.g. FXEE),
- (optional) UE establishing a call on the eNB (to observe power behavior),
- Clamp Multimeter / Powermeter with USB and / or Bluetooth interface to a PC.
• Configuration:
- Enable the feature with the parameter actMicroDtx = ‘true’,
- Set the other parameters (mdtxAggressiveness, mdtxPdcchSymb, siWindowLen) accordingly,
- Observe the power behavior over time.
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Configuration and Testing
Test execution
• Observe the eNB power behavior using the following settings:
- Cell blocked,
- Cell unblocked,
- Micro-DTX activated / deactivated,
- Change the number of non-muted PDCCH symbols,
- No UE connected,
- Connect a UE and produce traffic with iperf / jperf,
- Let the UE go idle.
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Test Results
Results from MBB R&D Ulm
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Testresult from R&D Ulm:
FRGY RRH
RF Output power = 60 Watt
Number of non-muted PDCCH symbols if cell is empty = 1
No UE connected
Micro-DTX aggressiveness = 0.1
SW-Load: FL16_ENB_0000_000200_000000
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