Radio Interface Engineering Rules
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Document issue:
Document status:
Date:
PE/DCL/DD/014283
02.02 / EN
Standard
28/Sept/2006
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Copyright© 2006 Nortel Networks, All Rights Reserved
Printed in France
NORTEL CONFIDENTIAL
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and shall protect same in whole or in part from disclosure and dissemination to third parties and use same for
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The content of this document is provided for information purposes only and is subject to modification. It does not
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This is the Way. This is Nortel, Nortel, the Nortel logo, and the Globemark are trademarks of Nortel Networks. All
other trademarks are the property of their owners.
Radio Interface Engineering Rules
PUBLICATION HISTORY
Issue 01.01/EN, Preliminary
11/Mar/2005
Creation of the document for the V15.1 release
28/Jun/2005
Issue 01.02/EN, Standard
Update of the document for the V15.1 CHR
Issue 01.03/EN Preliminary
21/Oct/2005
Update of the document for the V15.1.1 release
14/April/2006
Issue 02.01/EN Preliminary
Update of the document for the V16.0 release
28/Sept/2006
Issue 02.02/EN Standard
Update of the document for the V16.0 ChR
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CONTENTS
1
INTRODUCTION............................................................................................................................6
1.1.
OBJECT .................................................................................................................................6
1.2.
SCOPE OF DOCUMENT .......................................................................................................6
1.3.
AUDIENCE OF THIS DOCUMENT ........................................................................................6
1.4.
DELTA BETWEEN RELEASES .............................................................................................6
1.4.1
1.4.1.1
1.4.1.2
1.4.2
1.4.2.1
1.4.3
1.4.3.1
2.
3.
Delta between V15.0 and V15.1 .....................................................................................6
General information .................................................................................................................... 6
Evolutions between releases........................................................................................................ 6
Delta between V15.1 and V15.1.1 ..................................................................................7
Evolutions between releases........................................................................................................ 7
Delta between V15.1.1 and V16.0 ..................................................................................7
Evolutions between releases........................................................................................................ 7
RELATED DOCUMENTS ..............................................................................................................8
2.1.
APPLICABLE DOCUMENTS .................................................................................................8
2.2.
REFERENCE DOCUMENTS .................................................................................................8
RADIO INTERFACE ENGINEERING RULES ..............................................................................9
3.1.
GSM RADIO PROPAGATION AND FREQUENCY ASPECTS ...............................................................9
3.1.1
Frequency spacing..........................................................................................................9
3.1.1.1 Intra_cell ..................................................................................................................................... 9
3.1.1.2 Intra_site.................................................................................................................................... 10
3.1.1.3 Inter_site.................................................................................................................................... 10
3.1.2
Types of frequency hopping..........................................................................................11
3.1.2.1 MA, HSN, MAIO...................................................................................................................... 12
3.1.2.2 Case of 1:1 fractional re-use pattern.......................................................................................... 12
3.1.2.3 Case of 1:3 fractional re-use pattern.......................................................................................... 14
3.1.2.4 1:1 versus 1:3 ............................................................................................................................ 15
3.1.2.5 AD HOC solution...................................................................................................................... 15
3.1.3
Frequency Load ............................................................................................................17
3.1.4
Radio link budget ..........................................................................................................17
3.1.5
Interference measurement ............................................................................................17
3.1.6
Antenna constraints ......................................................................................................17
3.1.6.1 900/1800 cositing ...................................................................................................................... 17
3.1.6.2 Blocking .................................................................................................................................... 18
3.2.
RADIO INTERFACE DIMENSIONING .............................................................................................18
3.2.1
Traffic models................................................................................................................18
3.2.2
Dimensioning principles ................................................................................................18
3.2.2.1 Tch dimensioning...................................................................................................................... 18
3.2.2.2 SDCCH dimensioning............................................................................................................... 19
3.2.2.3 BCCH dimensioning ................................................................................................................. 21
3.2.2.4 CCCH dimensioning ................................................................................................................. 22
3.2.2.5 Adaptation of CCCH dimensioning to the paging flow ............................................................ 22
3.3.
TDMA CONFIGURATIONS AND PRIORITIES ..................................................................................26
3.3.1
3.3.2
3.3.3
3.3.4
Standard cell .................................................................................................................26
Extended ccch...............................................................................................................27
EXtended cell ................................................................................................................27
TDMA priorities .............................................................................................................28
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3.3.4.1 Standard cell.............................................................................................................................. 28
3.3.4.2 Extended cell............................................................................................................................. 29
3.4.
MONOZONE AND CONCENTRIC CONFIGURATION ........................................................................30
4.
GPRS RADIO INTERFACE ENGINEERING RULES .................................................................31
4.1.
RADIO RESOURCES
.................................................................................................................31
4.1.1
TDMA rules ...................................................................................................................31
4.1.2
PDCH rules ...................................................................................................................32
4.2.
CODING SCHEMES CS-1 AND CS-2 ............................................................................................35
4.2.1
Coding schemes description: ........................................................................................35
4.2.2
Rules .............................................................................................................................36
4.3.
GPRS CHANNELS’ DIMENSIONING ..............................................................................................37
4.3.1
4.3.2
4.3.2.1
4.3.2.2
5.
GPRS impact in the ccch load ......................................................................................37
GPRS channels’ rules ...................................................................................................39
PDCH dimensioning rules......................................................................................................... 39
Dynamic sharing rules............................................................................................................... 40
EDGE RADIO INTERFACE ENGINEERING RULES .................................................................42
5.1.
OBJECTIF ................................................................................................................................42
5.2.
EDGE, A FORWARD STEP........................................................................................................42
5.3.
EDGE DEPLOYMENT STRATEGY ..............................................................................................43
5.4.
MAINS ENGINEERING RULES .....................................................................................................44
5.4.1
EDGE TDMA rules ........................................................................................................44
5.5.
SPECIFIC DATA FEATURES .......................................................................................................44
5.5.1
Network assisted cell change impact on gprs/edge networks ......................................44
5.5.2
Packet Flow COntext impact on GPRS/EDGE networks..............................................45
5.6.
DATA THROUGHPUT ESTIMATION .............................................................................................45
5.6.1
Radio conditions (C/I and Eb/No) distributions on the cell............................................48
5.6.1.1 C/N distribution......................................................................................................................... 48
5.6.1.2 C/N at cell edge ......................................................................................................................... 49
5.6.1.2.1 C/N distribution estimation ................................................................................................ 50
5.6.1.3 C/I distribution .......................................................................................................................... 50
5.6.1.3.1 C/I at cell edge.................................................................................................................... 50
5.6.1.3.2 C/I distribution ................................................................................................................... 51
5.6.2
Mean Throughput per TS calculation............................................................................52
5.6.2.1 BLER distributions on the cell .................................................................................................. 52
5.6.2.2 Throughput distributions on the cell ......................................................................................... 54
5.6.2.3 Link adaptation.......................................................................................................................... 55
5.6.2.4 Mean throughput / TS ............................................................................................................... 56
5.6.3
Comments on data throughput calculations..................................................................58
5.6.3.1 C/(I+N) versus BLER estimation .............................................................................................. 58
5.6.3.2 Limitations ................................................................................................................................ 58
5.7.
EDGE PERFORMANCES ESTIMATIONS .....................................................................................58
5.7.1
Incremental Redundancy ..............................................................................................60
5.7.1.1 Incremental Redundancy Functionality..................................................................................... 60
5.7.1.1.1 Retransmission table in UL ................................................................................................ 60
5.7.1.1.2 Retransmission table in DL ................................................................................................ 61
5.7.1.2 Incremental redundancy performance improvement ................................................................. 61
5.7.1.3 MCS usage distribution............................................................................................................. 63
5.7.2
High Power Amplifier impact on Data performances ....................................................66
5.7.3
Frequency Reuse..........................................................................................................68
5.7.4
Important hypothesis and assumptions supposed........................................................73
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5.7.5
BLER study ...................................................................................................................74
5.8.
UL PERFORMANCE ANALYSIS ..................................................................................................76
5.8.1
Different mobile type performance impact ....................................................................77
5.9.
LAB TEST RESULTS .................................................................................................................78
5.9.1
UL Lab Results..............................................................................................................78
5.9.2
DL Lab Results..............................................................................................................79
5.9.3
Real Link Adaptation impact on mean data throughput................................................79
5.9.4
Applicative versus RLC/MAC throughput relationship ..................................................80
5.10. CONCLUSION ..........................................................................................................................81
6.
ABBREVIATIONS AND DEFINITIONS.......................................................................................82
6.1.
ABBREVIATIONS ......................................................................................................................82
6.2.
DEFINITIONS ...........................................................................................................................84
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Radio Interface Engineering Rules
1 INTRODUCTION
1.1.
OBJECT
This document is an inventory of all the engineering rules concerning the GSM/
GPRS/EDGE radio Interface. An engineering methodology to estimate EDGE
introduction and performances in case of EDGE deployment on existing GSM/ GPRS
network is also detailed in this document.
.
1.2.
SCOPE OF DOCUMENT
This document is applicable from V16.0 release.
1.3.
AUDIENCE OF THIS DOCUMENT
This document is intended primarily for customer network designers and applications
engineers involved in GSM networks engineering with Nortel GSM networks.
1.4.
DELTA BETWEEN RELEASES
1.4.1 DELTA BETWEEN V15.0 AND V15.1
1.4.1.1
GENERAL INFORMATION
This document is created in V15.1 release since the BSS Engineering Rules
document has been split in different elementary rules. Nevertheless the majority of the
rules and recommendations of this document where already applicable to V15.0. The
main evolutions are presented below.
1.4.1.2
EVOLUTIONS BETWEEN RELEASES
New rules introduced and rules modified due to V15.1 evolutions
•
Air_TDMA_005
•
Air_FH_006
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Rules modified or added due to lack of precisions or return from experience (but not
linked to V15.1 content)
ƒ
Air_CS_002
Rules suppressed
•
None
Other main changes in the document
•
This document allows to group together three documents which
are the Radio interface, GPRS Interface and the new EDGE radio
interface. The last one for the moment is not detailed with all
engineering rules associated. Only EDGE TDMA rules are added
now. The next step may be for V15.1 CHR will be to provide
thanks the EDGE engineering study the mains rules deduced.
1.4.2 DELTA BETWEEN V15.1 AND V15.1.1
1.4.2.1
EVOLUTIONS BETWEEN RELEASES
New rules introduced and rules modified due to V15.1.1 evolutions
•
None
Rules modified or added due to lack of precisions or return from experience
(but not linked to V15.1 content)
•
Air_PDCH_004
•
Air_TDMA_003
Rules suppressed
•
None
Other main changes in the document
•
Addition of a new chapter providing information about Air
capacity for paging.
1.4.3 DELTA BETWEEN V15.1.1 AND V16.0
1.4.3.1
EVOLUTIONS BETWEEN RELEASES
New rules introduced and rules modified due to V16.0 evolutions
•
Air_NACC_001
•
Air_NACC_002
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Rules modified or added due to lack of precisions or return from experience
(but not linked to V16.0 content)
•
Air_PDCH_004
•
Air_freq_001
•
Air_freq_002
•
Air_freq_003
•
Air_FH_001
•
Air_FH_002
•
Air_FH_003
•
Air_HSN_001
•
Air_HSN_002
Rules suppressed
•
None
Other main changes in the document
•
2.
2.1.
2.2.
None
RELATED DOCUMENTS
APPLICABLE DOCUMENTS
[A1]
PE/DCL/DD/014281 PCUSN Engineering Rules
[A2]
PE/DCL/DD/014284 Agprs Interface Engineering Rules
REFERENCE DOCUMENTS
[R1]
PE/DCL/DD/014280 BSC/TCU3000 Engineering Rules
[R2]
PE/DCL/DD/014286 A and Ater Interfaces Engineering Rules
[R3]
PE/DCL/DD/014285 Abis Engineering Rules
[R4]
PE/IRC/APP/008966 EDGE Engineering Guideline
[R5]
PR/BTS/DD/4091
EGPRS Handbook
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Radio Interface Engineering Rules
3.
RADIO INTERFACE ENGINEERING RULES
3.1.
GSM RADIO PROPAGATION AND FREQUENCY
ASPECTS
3.1.1 FREQUENCY SPACING
3.1.1.1
INTRA_CELL
Rule
Air_Freq_001 (O)
Nortel BTS is using hybrid couplers technology. Considering the UL
power control activated, Nortel recommends 400khz frequency spacing
between TRX on a same cell with or without frequency hopping, in order
to respect the following minimum ratios recommended in 05.05 to
guarantee voice quality
C/I>=-9dB for first adjacent channels( 200kHz), C/I>=-41dB for second
adjacent channels( 400KHz), C/I>=-49dB for third adjacent channels (
600KHz).
Justification:
The most constraining case is the following one.
A UE at 30m from the BTS, and another one at the cell edge.
Based on many measurement campaingn analysis the signal received at 30m from
the BTS is -40dBm, the minimum signal received at the cell edge is -102dBm.
The pathloss difference is 62dB, in that case the UE near the BTS can create high UL
interferences from the UE far from the BTS.
The UL power control allows at least a 24dB dynamic in the reduction of the UE output
power.
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The pathloss difference with the UL poWer control is 38dB.
400KHz frequency spacing allow sufficient isolation.
3.1.1.2
INTRA_SITE
Rule
Air_Freq_002 (O)
The recommendations are the same than the ones of the Rule
Air_Freq_001.
The most constraining case is shown in the picture below, when two
mobiles are in the adjacent sectors overlap area, one mobile is far from
the BTS in communication with sector 1 and another mobile near the
BTS in communication with sector2.
In that case, the highest pathloss difference between the UE is in the
worst case the same than the one calculated previously, the
recommendation is 400KHz frequency spacing.
3.1.1.3
INTER_SITE
Rule
Air_Freq_003 (O)
For the inter site scenario, the most constraining case, is when 2
mobiles are in the overlap area between 2 cells (see the picture below).
Each mobile UL transmission is an interference for the other cell and
each cell DL signal is an interference for the mobile not in
communication with it.
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As the pathloss difference between a mobile and each cell is less than
the margin taken for the HO (less than 6dB), the C/I can be equal to -6dB.
200KHz frequency spacing are necessary to ensure this, as they
guarantee 18dB isolation
3.1.2 TYPES OF FREQUENCY HOPPING
According to the type of combiners used in the BTS, two main types of frequency
hopping mechanism can be used:
- Synthesized mode
It consists in changing the RF channel of each TDMA frame except the BCCH, within
each cell of the network. Each hopping TDMA frame uses a RF channel picked in a
given frequency group which size can be higher than the number of TRXs in the cell.
Rule
Air_FH_001 (O)
When the BTS is equipped with hybrid combiners (H2D, H4D) or
duplexers, only the synthesized frequency hopping mode can be used.
Rule
Air_FH_002 (O)
It is not recommended to include the BCCH frequency in the list of
hopping frequencies whatever the choice of frequency hopping type.
Rule
Air_FH_003 (O)
In a cell where GPRS/EDGE service is activated and frequency hopping
is used for GPRS/EDGE TDMA, the maximum number of hopping
frequencies in this cell should be as shown in the following table:
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BSS Release
Max. Number of
Frequencies (CA)
Max. Number of Hopping
Frequencies (MA)
V15.0 / V15.0.1
55
55-n
V15.1/V15.1.1
52
52-n
From V16.0
50
50-n
where n is the number of non-hopping frequencies in cell.
Justification:
In case of using a higher number of hopping frequencies, there is no sufficient place to
carry the complete GPRS mobile allocation bitmap in the corresponding field of the
SI13. This truncates some mandatory fields of the SI13 and has as consequence a
GPRS/EDGE service dysfunction.
3.1.2.1
MA, HSN, MAIO
The following rules apply in the case where only Nortel BTS are used. (means that
they are synchronized).
3.1.2.2
CASE OF 1:1 FRACTIONAL RE-USE PATTERN
Rule
Air_HSN_001 (M)
In case of 1:1 fractional re-use pattern,
The HSN must be the same for all the cells within a site.
To get full benefit of frequency hopping, a minimum of 6 different
frequencies shall be used in each cell.
Justification:
Not following this rule will lead to frequency collision.
From Nortel Experience, 6 frequencies lead to a good protection against fading
effects.
Rule
Air_MAIO_001 (M)
The choice of MAIO depends on the frequency load.
Nortel’s experience recommends:
If frequency loads <=16.6%, the MAIO are given according to step 2 rule
and considering the TRX per order (TRX1 of cell1, TRX1 of cell2, TRX2 of
cell1...)
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Example:
•
TRX1 of cell 1: MAIO 0
•
TRX1 of cell 2: MAIO 2
•
TRX1 of cell 3: MAIO 4
•
TRX2 of cell 1: MAIO 6
•
TRX2 of cell 2: MAIO 8
If frequency load >16.6%, the MAIO are given according to step 2 rule as
long as the frequency is available (i.e. it has not already been chosen for
a previous MAIO). Then, the MAIO are given according to step 1 rule
which leads to adjacent frequencies. Step 1 MAIO are given to the cells
which have the smallest overlap with neighbors or which have the
smallest traffic.
Example:
There is one site, 3 cells and 10 frequencies in the group.
Frequency load = 20% (2 hopping TRXs per cell).
MAIO for hopping TRX1 and TRX2 of each cell:
•
cell 1: 0 & 6
•
cell 2: 2 & 8
•
cell 3: 4 & 9
If HSN make us start by f3, the frequencies in grey cases will be chosen.
MAIO
8
9
0
1
2
3
4
5
6
7
Cell1
f1
f2
f3
f4
f5
f6
f7
f8
f9
f10
Cell2
f1
f2
f3
f4
f5
f6
f7
f8
f9
f10
Cell3
f1
f2
f3
f4
f5
f6
f7
f8
f9
f10
There are adjacent interference (f1,f2,f3).
Justification:
In case of freq. load <= 16.6%, there are no intra site collision (adjacent or co
channel). All frequencies inside the group are adjacent so the step 2 rule allows
maximizing the space between the frequencies and ensuring the non-adjacency of the
frequencies.
However in case of freq. load > 16.6%, there are intra site collision (adjacent). The
step 1 rule will create adjacent interference. It is not recommended to use 1:1
frequency reuse pattern if the frequency load is >20%.
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3.1.2.3
CASE OF 1:3 FRACTIONAL RE-USE PATTERN
Rule
Air_HSN_002 (O)
In case of 1:3 fractional re-use pattern,
The HSN must be the same for all the cells within a site.
To get full benefit of frequency hopping, a minimum of 6 different
frequencies shall be used in each cell.
Justification:
Not following this rule will lead to frequency collision.
From Nortel Experience, 6 frequencies lead to a good protection against fading
effects.
Rule
Air_MAIO_002 (O)
The choice of MAIO depends on the frequency load
In case of frequency load <= 50%,
The frequencies must be non continuous per group. The MAIO are given
by considering the cells by order, then the rule is step 2 within the cell,
shift of 1 for cell2 and cell 3 same as cell1.
Example:
MAIO
0
1
2
3
4
5
Cell1
f1
F4
f7
F10
f13
f16
Cell2
f2
f5
f8
f11
f14
f17
Cell3
f3
f6
f9
f12
f15
f18
cell1_TRX1: MAIO 0
cell1_TRX2: MAIO 2
cell1_TRX3: MAIO 4
cell2_TRX1: MAIO 1
cell2_TRX2: MAIO 3
cell2_TRX3: MAIO 5
cell3_TRX1: MAIO 0
cell3_TRX2: MAIO 2
cell3_TRX3: MAIO 4
If case of frequency load > 50%
The MAIO are given according to step 2 rule as long as the frequency is
available (i.e. it has not already been chosen for a previous MAIO). Then,
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the MAIO are given according to step 1 rule. Step 1 MAIO are given to the
cells which have the smallest overlap with neighbors or which have the
smallest traffic.
Justification:
This recommendation comes from Nortel’s experience.
3.1.2.4
1:1 VERSUS 1:3
Rule
Air_FH_005 (O)
If available hopping frequencies < 27 and the grid of cells is irregular
then the 1:1 fractional reuse pattern is more suitable.
If available hopping frequencies >= 27, then 1:1 and 1:3 fractional reuse
pattern are quite similar. But if the grid of cells is regular and the height
of antenna are regular then the 1:3 fractional reuse pattern is more
suitable.
Justification:
This recommendation comes from Nortel’s experience (radio simulation and field
experience).
1:1 fractional reuse pattern will be better if available hopping frequencies <= 27 and
irregular grid as it will be better in terms of FER and SQI.
If the grid is regular, the 1:3 frequency reuse pattern will not bring about co channel
interference as the 1:1 will do in same situation.
3.1.2.5
AD HOC SOLUTION
1:1 and 1:3 are not the only solution for frequency planning
Due to the network densification, the frequency planning becomes more and more
difficult.
1:1 or 1:3 solutions need too many frequencies to be efficient in high dense urban
environments like New York
In that case the best way is to use an Automatic Frequency Planning tool (AFP).
This tool find the best frequency plan based on the simulated interference matrix, and
some QOS and C/I targets values. With a great propagation model used in the RF
planning tool the AFP can provides a very precise frequency plan.
The principle is to calculate a cost based on the input targets, and the solution
proposes at the end of the computation is the one with the lower cost
Below an example of AFP settings
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The user of this kind of tool should have an experiment on frequency planning in order
to provide the best inputs.
AFP is best way to obtain a good frequency plan; many operators use it in order to be
more efficient.
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3.1.3 FREQUENCY LOAD
The fractional reuse pattern that can be used in a network depends on the frequency
load.
Rule
Air_FL_001 (O)
For choosing the fractional re-use pattern, Nortel recommends to follow
this table.
Fractional re-use pattern
FrequencyLoad max
FreqLoadSite max
1:1
20%
20%
1:3
50%
16%
Figure 3-2 Frequency load versus fractional reuse pattern
Justification:
The results in this table come from Nortel simulation and field experience.
3.1.4 RADIO LINK BUDGET
For the radio link budget, there are no specific Nortel Networks engineering rules.
Please refer to the BPUG to get the value of parameters necessary for the radio link
budget.
3.1.5 INTERFERENCE MEASUREMENT
Please refer to BPUG document.
3.1.6 ANTENNA CONSTRAINTS
3.1.6.1
900/1800 COSITING
For conservative electromagnetic compatibility purpose, some separations between
antennas are required for isolation.
Rule
Air_Ant_001 (O)
In case of a co-siting situation, Nortel experimentation is:
In terms of electromagnetic compatibility, a separation of 50 cm
(horizontal and vertical) is necessary between one GSM 900 (emission or
reception) antenna and any GSM 1800 antenna.
Justification:
Any separation of 50 cm (vertical or horizontal) between the GSM 900 and the GSM
1800 antenna makes sure that no interference between GSM 900 system and GSM
1800 system will be encountered.
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Rule
Air_Ant_002 (O)
In terms of space diversity, an horizontal separation by 1.6 to 3.2 m (3.20
to 6.4m) is required between the two GSM 1800 (900) antennas for
efficient diversity gain.
2.4 to 4 m vertical separation can also be used.
3.1.6.2
BLOCKING
Rule
Air_Ant_003 (HC)
For Nortel BTS products, Nortel guarantees:
In case of GSM 1800 transceiver in a GSM 900 receiver, the level of
blocking is -13 dBm for out band and in band emission
In case of GSM 900 transceiver in a GSM 1800 receiver, the level of
blocking is -35 dBm for out band and in band emission.
3.2.
RADIO INTERFACE DIMENSIONING
3.2.1 TRAFFIC MODELS
Nortel has some traffic models to help operators to dimension their networks.
Please refer to the BSC overview document.
3.2.2 DIMENSIONING PRINCIPLES
3.2.2.1
TCH DIMENSIONING
Rule
Air_TCH_001 (O)
For TCH blocking rate, Nortel recommends
TCH blocking rate = 2% in normal loaded network to 5% in very loaded
network for traffic and data on the radio interface, depending of the
traffic load of the network.
TCH number is computed with the Erlang Law. Hence we can deduce the number of
DRXs.
For Nortel BTS, one cabinet can have at most 12 DRX for S12000, 8 DRX for S8000,
4 DRX for S4000 BTS, and S2000 H/L and e-cell BTS have 2 DRX per cabinet.
The maximum configurations are DLU dependant. All the configurations allowed are
given in the BTS Engineering Rules documents.
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3.2.2.2
SDCCH DIMENSIONING
Rule
Air_SDCCH_001 (O)
For SDCCH blocking rate, Nortel recommends
SDCCH Blocking rate
Middle LAC
LAC border
Normal load
0.1%
0.2%
Very loaded
0.1%
0.2%
Figure 3-3 SDCCH blocking rate
Justification:
This recommendation comes from Nortel field experience
- Rules related to DCU2
Rule
Air_SDCCH_002 (M)
In case of BTS with DCU2:
The TRX cannot support more than 1 SDCCH TS (SDCCH/8, SDCCH/8 +
CBCH or BCCH combined) on the same TDMA.
Justification:
For reasons of DCU2 and MNU load.
Rule
Air_SDCCH_003 (M)
In case of BTS with DCU2
On the TDMA carrying the BCCH (combined or not), TS7 = TCH
Both consecutive logical channels (TS1, TS2) or (TS3, TS4) or (TS5,TS6)
or (TS7, TS0) must respect the following constraints:
•
(TSa,TSb) = SDCCH/8 and TCH with (a,b)=(1,2) or (2,1) or (3,4)
•
(TSa,TSb) = SDCCH/8 + CBCH and TCH with (a,b)=(0,7) or (1,2) or
(2,1) or (3,4)
•
(TSa,TSb) = 2 TCH for all (a, b)
Justification:
In order to balance the load, 1 BCCH and 1 SDCCH are not managed by the same
processor so are not on two consecutive TS.
Rules related to all types of TRX (DCU4, DRX, eDRX). The OMC-R check is
introduced in V14 release.
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Rule
Air_SDCCH_004 (HC)
A SDCCH TS is either a BCCH COMBINED (4 sub channels), a SDCCH/8
(8 sub channels), a CBCH SDCCH_4 (3 subchannels + 1 CBCH) or a
CBCH SDCCH_8 (7 subchannels + 1 CBCH)
For a regular cell:
The TRX cannot support more than 2 SDCCH TS on the same TDMA.
The 2 SDCCH TS must be carried respectively by an odd and an even TS.
For an extended cell:
The TRX cannot support more than 1 SDCCH TS per TDMA
(This unique SDCCH TS must be on an even TS.)
Justification:
For load reason no more than 2 SDCCH TS are supported more on one TDMA. In
order to balance the load on the different processors, the 2 SDCCH are carried on an
even and an odd TS so there are not supported by the same processor.
- Rules related to DCU2 combined with DCU4
Rule
Air_SDCCH_005 (M)
In the case of DCU2/DCU4 cell configuration and for defense reasons,
the TRX must not support more than one SDCCH/8 on the same TDMA.
- General rules
Rule
Air_SDCCH_006 (HC)
The SDCCH/8 + CBCH position must be <= TS3
Justification:
REC 05.02 Multiplexing and multiple accesses on the radio path
Rule
Air_SDCCH_007 (O)
SDCCH channels are preferably placed on the hopping TDMA.
Justification:
It allows
To better appreciate in advance the power the MS should use once on TCH
To free space on the BCCH frame for cell tiering or packet data communications
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Rule
Air_SDCCH_008 (O)
It is recommended to spread evenly the SDCCH onto the various TDMA
available in a cell (in particular avoid mixing SDCCH and BCCH on the
same TDMA if enough TRX are available in the cell)
Justification:
This recommendation allows splitting the load on the processors.
In case of cell tiering or GPRS, this rule allows to reserve channels for traffic.
Rule
Air_SDCCH_009 (O)
SDCCH channels are preferably placed on the same TS numbers to allow
gathering of Immediate Assignment messages
3.2.2.3
BCCH DIMENSIONING
Rule
Air_BCCH_001 (M)
One BCCH is required per cell. The BCCH is supported by the TS0 of the
beacon frequency.
In the case of one TRX per cell, BCCH can be combined with one SDCCH/4
(4 SDCCH channels) in order to have 7 TCH instead of 6. This configuration can be
applied under certain conditions such as the LA size. Actually, if the size of the LA is
too large, a great amount of paging will be generated and the PCH (which is limited in
this configuration) will not be able to flow all the paging messages.
Note: A lot of parameters can be configured to optimize the BCCH dimensioning,
among them numberOfslotsSpreadTrans, numberOfBlockforAccessGrant..., please
refer to BPUG for more information.
Rule
Air_BCCH_002 (O)
It is mandatory that the radio TDMA carrying BCCH channel should have
highest priority. It is strongly recommended that the BCCH priority is set
to "0". This TDMA must be the one and only one TDMA with the highest
priority. Refer to the table “TDMA Priorities".
Note: This new rule is introduced to secure the BCCH.
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3.2.2.4
CCCH DIMENSIONING
The number of CCCH radio time slots is 1 per cell
In some cases (microcell, dualband) we may need more than 1 CCCH. From V12,
thanks to extended CCCH, it is possible to support multiple CCCH per TDMA
supporting the BCCH in order to support a higher signaling traffic.
Hence up to 4 TS (TS0, TS2, TS4, TS6) per TDMA on BCCH frequency may be use
to support a high cell traffic.
The addition of CCCH TS will depend on the traffic model, the LAC repartition and the
environment.
Rule
Agprs_CCCH_001 (O)
2 CCCH TS may be necessary in a single layer cell if the number of TRX
per cell is > 6 and the offered traffic per LAC is > 1200 Erl with 1 CCCH
TS.
2 CCCH TS may be necessary in a multi layer cell if the number of TRX
per cell is > 5 with 1 CCCH TS.
3.2.2.5
ADAPTATION OF CCCH DIMENSIONING TO THE PAGING FLOW
The paging capacity of the Air interface is linked to different radio parameters.
Paging messages are sent on Air interface in CCCH blocks on the PCH radio
channel (in Nortel implementation cs-paging and ps-paging are both sent on these
radio channels). The capacity of the CCCH blocks depends on the type of pagings
(IMSI or TMSI): one CCCH blocks supports either:
•
paging on IMSI
•
1 paging on IMSI and 2 paging on TMSI
•
4 paging on TMSI.
In a 51 TS multi-frame, the number of CCCH blocks depends on the BCCH
TDMA configuration:
TDMA BCCH type
Number of CCCH blocks in a multi-frame = nCCCH
BCCH combined
3
BCCCH not combined
9
Extended CCCH
18
Extended CCCH 2
27
Extended CCCH 3
36
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In a given multi-frame some CCCH blocks are used for paging and some are used for
immediate assignment messages.
The parameter noOfBlocksForAccessGrant allows to reserve some blocks for
immediate assignment messages. In that case the number of CCCH blocks for paging
in a multiframe is nCCCH - noOfBlocksForAccessGrant.
(Note that when the value noOfBlocksForAccessGrant is set to 0, blocks are
preempted when needed for the immediate assignment messages).
A given mobile will listen to CCCH blocks corresponding to its "paging group".The
paging group of a mobile is determined by its IMSI number and by the "number of
multi frames between paging". This number is given by the parameter
noOfMultiframeBetweenPaging.
It corresponds to the number of multi-frames used to recover the same paging group
for a given mobile. The number of different paging groups possible is the number of
possible
CCCH
blocks
available
for
paging
during
these
noOfMultiframeBetweenPaging multi-frames. The paging are distributed on these
possible paging groups according to the IMSI number of the called mobile (with the
use of a "modulo" on the IMSI value). The different pagings are thus distributed in:
(nCCCH -noOfBlocksForAccessGrant)*noOfMultiframeBetweenPaging
Thus when a paging arrives for a mobile, this one will be sent in the appropriate
paging group: the BTS will have to wait for this paging group before sending this
paging. Moreover if the BTS has already some paging to send in this paging group; it
will wait for a new corresponding paging group before sending this paging message.
With Nortel BSS, the BTS is able to perform by itself some paging repetitions. Thus in
the different paging groups, the BTS will sent either new paging or some paging
repetitions. Nevertheless, new paging messages are always handled in priority
compare to paging repetitions.
(By this way, if a number of n repetitions is wanted at BH, it is possible to specify a
value m > n for this number of requested BTS repetitions: this will allow during non
busy hours to try to perform the m retries while may be at BH the dimensioning is only
able to support n repetitions).
In summary, the Air interface paging capacity will depend on:
- The ratio of IMSI paging vs TMSI paging
- The TDMA BCCH type
- The value of the parameter noOfBlocksForAccessGrant
- The latency before being able to send a given paging in the appropriate paging
group
- The number of wanted repetitions at BTS.
The following tables provide some indications of the Air interface capacity for paging
depending on some typical parameters (paging are supposed to arrive here uniformly
shared between the different paging groups and the latency is modeled through a
Pollaczek-Khintchine formula in order to limit the delay to a maximum corresponding
to one noOfMultiframeBetweenPaging duration).
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A ratio of 10% vs 90% between IMSI paging and TMSI paging is considered here.
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3.3.
TDMA CONFIGURATIONS AND PRIORITIES
3.3.1 STANDARD CELL
Recommended TDMA are of different types.
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3.3.2 EXTENDED CCCH
3.3.3 EXTENDED CELL
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3.3.4 TDMA PRIORITIES
3.3.4.1
STANDARD CELL
The following values are adapted to Nortel standard call profile with about 50% AMR
HR penetration. As it corresponds to an average call profile over the network, these
values could be adapted regarding the specificities of particular parts of the network.
Moreover for more aggressive call profile the number of SDCCH resources need to be
adapted
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3.3.4.2
EXTENDED CELL
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3.4.
MONOZONE AND CONCENTRIC CONFIGURATION
In different cases, some transceivers remain disabled/dependency due to a bad
configuration at the OMC-R. To avoid such situations the following rules must be
followed:
Rule
Air_zone_001 (HC)
If the concentric cell attribute is set to "monozone", the OMC-R has to
check that there is no transceiver associated to a transceiverZone,
before setting the BTS unlocked.
Rule
Air_zone_002 (HC)
If the concentric cell attribute is set to "monozone", the OMC-R has to
check that the transceiver equipment class of all transceiverEquipments
is set to 1, before setting the BTS unlocked.
Rule
Air_zone_003 (HC)
If the concentric cell attribute is set to "concentric" and transceiver
equipment class is the same for all transceiverEquipments, the OMC-R
has to check that the number of transceiverEquipments of both zones is
equal or greater than the number of transceivers of the both zones,
before setting the BTS unlocked.
Rule
Air_zone_004 (HC)
If the concentric cell attribute is not set to "monozone" and there are two
classes of transceiverEquipments, for each transceiverZone, the OMC-R
has to check that the number of transceiverEquipments is equal or
greater than the number of transceivers, before setting the BTS
unlocked.
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4.
GPRS RADIO INTERFACE ENGINEERING
RULES
4.1.
RADIO RESOURCES
A cell supporting GPRS uses physical channels to handle GPRS traffic. Those
channels (PDCH) shared by the GPRS subscribers can be taken from the available
resources in the GSM cell (see 12.3.2). The GPRS timeslot can be configured over
any TDMA of the cell, it can be a new TDMA or an already existing TDMA used by
GSM. High data rates cannot be reached when no new TRXs are added.
The BSC dynamically allocates the resources between GSM and GPRS. The GPRS
multi-frame structure is different from GSM. It consists of 52 TDMA frames divided into
12 blocks (each of 4 frames), with 2 idle frames and 2 frames used for timing advance:
Figure 4-1 GPRS MULTI-FRAME STRUCTURE
4.1.1 TDMA RULES
Rule
Air_TDMA_001 (HC)
Several GPRS TDMA per cell can be supported starting from V14. GPRS
service can be supported on any TDMA on the cell. This TDMA can be in
the Outer Zone and the Inner Zone of a Dual Band Cell. We can have a
TDMA in the Inner and second one in the Outer Zone. If the inner zone
coverage is lower to the outer zone coverage, we recommend
configuring PDTCH only in the outer zone.
Note:
This feature is very helpful in case of a high load on a particular TDMA and a lack of
GPRS resources. The operator can use additional TDMAs in order to decrease the
load on existing GPRS resources and increase data bandwidth. Nortel simulations
have shown that for a cell of 8 GPRS dedicated PDTCHs, with 10 GPRS subscribers
(4+1 Multislot class) the mean throughput will be 38Kbps/user for FTP and
23Kbps/user for HTML and email applications. To keep this quality of service with an
increasing number of GPRS users, we must add more PDTCHs on a new TDMA.
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Rule
Air_TDMA_003 (HC)
The Frequency Hopping for the PDTCH channels can be applied only in
Outer Zone for a Dual Zone Cell. No frequency hopping on a PDTCH
channels is possible in the Inner zone.
In outer zone, only one hopping frequency law can be declared for the
TDMA with PDTCH configured.
Rule
Air_TDMA_004 (HC)
Up to 32 GPRS subs MS can be supported by TDMA frame with a
maximum of 32 TFI values.
Justification:
This limitation is a consequence of the Temporary Block Flow Identifier (TFI) coding.
One TFI differentiates 2 Temporary Block Flows (TBFs) which have a common PDCH
allocated, one in UL and one in DL. Since it is coded on 5 bits, there are only 32
different possible TFI values, which will allow (1 UL + 1 DL) × 32 TBFs. We have 32
TFI and we always allocate one in UL and one in DL for one MS (due to TBF Keep
Alive).
4.1.2 PDCH RULES
Rule
Air_PDCH_001 (HC)
Up to 8 PDCH can be allocated to one user with the “TS aggregation”
according to its multi-slot capability. Thus it has to be taken into account
for radio resource dimensioning when several users are in the same cell.
A percentage of MS activity has to be used (in call profile).
Note:
The MS multi-slot capability provides a more efficient use of the air interface
resources. The TS aggregation can be done dynamically. A higher bandwidth can be
offered to the end user according to its multi-slot capability (all multi-slot classes 1 to
29 are supported). This can be useful for the operator or the end user since it can
provide lower costs with higher bit rates.
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Rule
Air_PDCH_002 (HC)
Each radio PDTCH can allocated to up to 7 subscribers (not 8, due to
USF utilization).
One PDTCH can handle up to 16 MS at most. Due to the system
limitation (USF limitation in UL) a maximum of 7 simultaneous users are
allowed per PDCH on the UL.
Justification:
The Timing Advance Index is coded on 4 bits, which gives a total of 16 different TAI
per PDTCH. On the other hand, the Uplink Status Flag is coded on 3 bits (system
limitation), which allows a maximum of 8 values in the UL. As USF=0 is reserved; only
a maximum of 7 subscribers can share one TS on the UL. When USF=0 is used, none
of the MSs is allowed to transmit in the following UL Radio Block, so one of the MSs
that only has a DL TBF can acknowledge the DL data coming from the PCUSN when
the PCUSN polls it. This rule is related to rule Air_TDMA_004 (HC):
If all the MSs on TS1 takes this TS1 as control TS, we can have only 16 MS on that
TS1. If a 2+1 MS takes its control information (TAI) on TS2 and is sharing TS1 and
TS2 with other MSs, it won't be counted among the maximum of 16 MSs allowed on
TS1 since a MS takes only 1 TAI on one of the TSs it is using. So the number of MSs
allowed per TDMA varies between 16 and 32 (depending on the number of PDTCH
per TDMA). Taking into account the USF (per PDTCH), only 7 MSs can have UL+DL
transfers and 32-7=25 MSs can have only DL transfers.
Rule
Air_PDCH_003 (HC)
With TS Partitioning, operators will be able to handle more users per
PDCH, which leads to more users per cell at more variable data rates.
This feature is therefore best suited when many users share more than
one PDCH in one cell to avoid very low throughputs.
Justification:
TS partitioning feature allows finer granularity which gives more efficiency by
multiplexing one PDCH between several users (up to 7) sharing the same TS. When
several users share oneTS, data throughput available per user diminishes. A new MS
can access to the resource as soon as it receives the UL assignment from the PCUSN
(see figure 12.2).
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Figure 4-2 TS PARTITIONING BENEFITS
Rule
Air_PDCH_004 (HC)
If NMO1 feature is activated, it’s recommended to set the parameter
minNbrGprsTs different from 0.
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4.2.
CODING SCHEMES CS-1 AND CS-2
4.2.1 CODING SCHEMES DESCRIPTION:
In good radio conditions CS-2 provides a higher throughput than CS-1. CS-1 is used
to transfer the signaling while CS-2 allows a more efficient air-interface throughput for
data transfer.
Figure 4-3 SIMULATION RESULTS GIVING THE RLC/MAC THROUGHPUT (PER CS) VS BLER
CS-1 has the same coding as SDCCH, giving a payload rate of 9.05 Kbps and a
maximum data throughput of 8Kbps at the RLC/MAC layer.
CS-2 is a punctured version of CS-1; the payload rate is 13.4Kbps and the maximum
data throughput (at the RLC/MAC layer) allowed by this coding scheme is 12 Kbps per
TS. (For more details about coding scheme see "Access Network Parameters’ User
Guide").
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4.2.2 RULES
Rule
Air_CS_001 (O)
CS-1 and CS-2 are selected on a GPRS TDMA basis depending on the
operator’s radio engineering. It is recommended to use CS-2 rather than
CS-1 in order to offer better results for data transfer. Signaling must be
conveyed using CS-1.
Justification:
Simulation results achieved by Nortel show that it would be better to configure CS-2 in
most cases. Measurement results confirm that in a typical GSM cell, with a BLER
below 10%, CS-2 has often better throughput compared to CS-1 (see 12.2.1).
Rule
Air_CS_002 (O)
No impact will occur on the Abis interface with the first GPRS
introduction. The same mapping for GPRS is adopted as for GSM TSs on
the Abis interface. Thus no changes will occur regarding the Abis
dimensioning and architecture.
For more details on the Abis mapping, see the document “Abis Interface
Engineering Rules”.
Justification:
The first release of GPRS will only use CS-1 and CS-2, GPRS radio resources will
then use 16K TS like GSM TSs since CS-1 bit rate is 9.05 Kbps and CS-2 bit rate is
13.4Kbps. The separation between GSM and GPRS TSs will be done at the BSC
level.
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4.3.
GPRS CHANNELS’ DIMENSIONING
4.3.1 GPRS IMPACT IN THE CCCH LOAD
Rule
Air_DimCCCH_001 (O)
GPRS introduction in a GSM network has a low impact on CCCH. GSM
traffic has the most important impact on CCCH capacity.
Existing CCCH can cope with a traffic level compatible with what is
foreseen at the starting of a GPRS network. Therefore it doesn’t generate
changes in CCCH (RACH, AGCH, and PCH) dimensioning. The
introduction of GPRS in the first steps (low penetration rate) doesn’t
show major impact on the CCCH capacity.
Justification:
Considering the following hypothesis:
-One Routing Area = one Location Area (all PS and CS paging messages sent to the
same cells of the LAC),
-Using the Nortel standard GPRS call profile,
-Location Area of 80000 users and 11 paging message/cell/s,
-With 5%, 10 and 25% of GPRS penetration rate,
-In order to offer a minimum GPRS throughput (for 25% Class B GPRS MS
penetration), only fixed PDCH are considered. If the GPRS class B MS penetration
rate is less than 25% the data throughput will be higher. With a total UL_TBF_CCCH =
16.10 /subscriber/BH (16.1 channel request and 16.1 Immediate_Assignment)
And a total DL_TBF_CCCH = 13.15 /subscriber/BH (DL immediate assignment
messages)
NB: The results focus only on the GPRS impact over CCCH capacity.
With these hypotheses, 1 CCCH per cell is enough with a standard GSM call profile.
For the same conditions, with a heavier GSM traffic (short call GSM call profile) and
21.3 paging message/cell/s, the signaling traffic can exceed the CCCH capacity for 15
and 16 TRX configurations.
This means that a future traffic increase will need more CCCH capacity. So it would be
safer to add a new CCCH channel in this case. This shows the direct impact of GSM
traffic on the signaling traffic.
The number of GPRS paging messages is negligible comparing to GSM.
Additionally, “TBF pre-establishment” and “TBF keep alive” decrease the number of
TBF establishments, thus their activation will induce a significant decrease in CCCH
traffic load for GPRS.
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The following table shows a comparison between standard GSM call profile and Short
call GSM call profile with GPRS class B penetration rate from 5 to 25% with respect to
the CCCH capacity.
These recommendations are drawn with Nortel's GPRS call profile. Since the results
can vary a lot with the call profile and network inputs (LAC size, Number of users per
LAC…), specific studies must be done to give conclusions for operators. Additionally,
the number of users per LAC has an impact on the CCCH capacity. If the number of
users increases in the LAC, we will reach faster the CCCH capacity limit.
Rule
Air_DimCCCH_002 (O)
For the evolution of the GPRS services, an increase will be experienced
in the data traffic (call profile change). This will induce more signaling. In
these cases the use of extended CCCH is recommended to cope with the
additional signaling load.
The CCCH load depends on the following parameters:
•
GPRS call profile
•
GSM call profile
Extended CCCH is available starting from V12.4c. The CCCH can be spread over
up to four time slots per BTS (TS0, 2, 4 and 6) instead of using only one (TS0).
Extended CCCH will allow the BTS to handle larger volumes of traffic and thus to
improve the call set-up time.
Drawbacks
The use of new CCCH TS when needed (extended CCCH) has to be done carefully
regarding the overall dimensioning process since adding new CCCH TS decreases
the number of available traffic TCHs in the cell. Thus more resources need to be
added and this will impact the cell configuration.
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4.3.2 GPRS CHANNELS’ RULES
The traditional Erlang-B law is commonly used for circuit switched networks for radio
resource dimensioning. This law is no longer valid for GPRS since it’s a packet
queuing system with resource sharing. The major challenge is to find a traffic model
representing a subscriber and its behavior. Both voice traffic and data traffic have to
be considered to find the necessary resources for GPRS service.
4.3.2.1
PDCH DIMENSIONING RULES
Rule
Air_DimPDCH_001 (O)
Dimensioning has to use throughput at the application layer. The
throughput is a vital part of the service offered to the end user.
Dimensioning the air interface is an underlying issue since the radio
interface is the weakest link of the chain.
The effective
parameters:
•
throughput
of
a
subscriber
depends
on
several
Radio conditions (BLER)
•
Coding scheme
•
MS Multi-slot capability
•
Number of GPRS subscribers per cell
•
Number of active subscribers
•
GSM/GPRS TS dynamic sharing
•
GPRS busy hour
•
GSM busy hour
•
Call profile
We look forward to finding the number of PDCHs needed per cell to offer
the requested service. This result must be in keeping with the rules
listed above (see 12..1 “Radio Resources”).
Dimensioning methodology
First we derive the bit rate per PDCH using BLER and CS-2 as inputs for the
simulator:
Then we derive the needed bit rate service to offer on the Busy Hour (BH). We use the
data volume generated (using the call profile) by the active users on the BH:
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The mean bit rate to offer can be fixed by the operator, in this case there is no
need to compute it.
•
At this stage we compute the number of needed PDCHs: Number of
needed PDCH= [(Number of active users)*(mean bit rate at BH)]/
(%TS_Oc × bit rate/PDCH) Where %TS_Oc is the TS occupancy rate.
The features’ improvements (TBF establishment improvements, TS
partitioning, USF) help increasing this coefficient towards higher
efficiency of the radio resources. This will diminish the needed number
of PDCHs.
Although the radio dimensioning is a very important step in the GPRS
deployment, the operator might dimension its network with a 2 (or 3) year
traffic forecast. This will diminish the “re-dimensioning” effects since the first
GPRS introduction period is only an intermediary step towards a more stable
network.
4.3.2.2
DYNAMIC SHARING RULES
Rules
Rule
Air_DynSh_001 (O)
GPRS service capacity is directly related to the number of radio
resources (PDTCH) that GPRS is allowed to use. The “TS dynamic
sharing” feature is necessary to lower the GPRS impact on GSM,
particularly when the operator chooses to use shared TS. The operator
has the choice in a pool of 3 types of resources: (GSM dedicated TCHs;
Shared TCH-PDTCHs; dedicated PDTCHs).
Dynamic sharing between GSM and GPRS increases the radio interface
efficiency by sharing radio resources between circuit and packet
services. This efficiency has to be taken into account for GPRS radio
resource dimensioning to find the needed number of PDTCH to handle
the packet data traffic.
Justification:
The air interface efficiency in GSM goes up to 70% with a 2% blocking rate. Nortel’s
simulations of this feature show an efficiency increase up to 20% due to the
introduction of this feature.
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As a consequence of this rule, we can state that this feature allows the GPRS
introduction with a low impact on the cell configuration and network architecture. If the
operator doesn’t configure any fixed GPRS radio TS, no blocking rate increase is
experienced due to this feature.
Drawbacks
Fixed GPRS PDTCHs will decrease the cell capacity unless additional TDMA is
configured, which may require new network planning and configuration during GPRS
deployment. Additionally, TS dynamic sharing will have a direct impact on the BSC’s
CPU load. At each allocation or release of a GPRS radio TS; the BSC has to perform
2 switching connections, which will increase the load.
Fixed and Shared TS separation
The number of fixed and shared GPRS TS in a GSM network has to be specified per
cell using:
•
GSM blocking rate allowed (Degree of GSM priority over GPRS),
•
Number of existing TRX,
•
Measured cell load (Erlang, circuit GSM)
•
GPRS traffic estimation,
•
MS and network capabilities.
Once the number of needed PDTCHs is derived (see Rule Air_DimPDCH_001 (O)),
we must find an optimised set of TSs (GSM dedicated TCHs;
Shared TCHPDCHs; dedicated PDCHs) on the TDMA supporting GPRS. Shared
TCH-PDCHs number has to be chosen regarding the GSM TCHs blocking rate at the
voice BH. The measured cell load will give us the usage efficiency rate of the radio
resources. Thus blocking and efficiency rates have to be constantly monitored.
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5.
EDGE RADIO INTERFACE ENGINEERING
RULES
5.1.
OBJECTIF
The aim of this part is to detail Nortel Networks’ engineering methodology to estimate
EDGE performances if EDGE would be deployed on existing GSM network.
Incremental redundancy impacts on capacity estimations as well as frequency reuse
are also analyzed. Advantages of new powerful PA impact on DL performances are
explained. Even if DL performances are mainly studied, different type of UL mobiles
available on the market are also commented.
Test carried on platform and live network experience feedbacks from Engineering Test
Plan are also detailed. Finally, comparison between GPRS and EDGE in term of user
capacity is studied for an hypothetic FTP connection and specific allocator.
There is an evident inaccuracy in the estimation capacity performances but the
tendencies obtained give a good overview of expected performances.
5.2.
EDGE, A FORWARD STEP
GSM is a constantly evolving technology, and the next major milestone is Enhanced
Data Rates for GSM Evolution (EDGE). Data application requirement implies the
evolution of radio access techniques to satisfy user’s demand. 3G CDMA systems
offers data application possibility (main difference in term of application between 2.5G
and 3G is video conference capability) but the high cost to deploy them and early
deployment makes us consider the possibility to upgrade existing infrastructure to
adapt GSM networks and compete against new 3G generation system or complement
its coverage. GPRS was the first step; EDGE the step forward. EDGE improves GPRS
throughput performances by 3 times and allows dealing with 5 times more users.
Engineering methodology has changed between voice and data. For speech, end user
quality is equivalent to air interference quality. For data, excellent user quality is
assumed but it is less related to air interference quality, which could be bad. Although
air interface quality fixes throughput, one user can use several radio channels as time
slots are aggregated, allowing achieving higher throughputs. Therefore, data
throughput is the QoS parameter for data services since perfect reception is assumed.
No engineering change between GPRS and EDGE is applied.
Higher data throughput than GPRS is achieved thanks to new modulation usage,
which allows reaching higher data rates. Whereas GSM and GPRS use a Gaussian
Minimum Shift Keying (GMSK) modulation scheme, EDGE uses both GMSK and a
modulation called Eight Phase Shift Keying (8-PSK). 8-PSK can communicate three
bits of information in each radio symbol whereas GMSK can offer only one bit. The
higher the MCS, the higher the user data rate (these data rates are at RLC/MAC
level), since there are fewer bits of protection and less puncturing. It also means that
the highest MCSs will only be used in good radio conditions whereas in bad radio
conditions, the lowest MCSs will be used.
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Complementary to radio modulation, EDGE takes benefit from other improvements
such as: more performing link adaptation, incremental redundancy or advanced
RLC/MAC protocol. By adapting the coding schemes to the radio channel conditions
dynamically, it is possible to optimise communication performances and throughput.
This is done by link adaptation: through radio measurements, the network chooses the
best MCS and adapts it. Estimated best MCS is used in each position of the cell. All
values presented in this document assumes ideal link adaptation algorithm.
Moreover, another feature is only available for EDGE: this is incremental redundancy,
IR, which is the possibility to retransmit a data block using a different puncturing
method and also recombining with received erroneous packets. By this way,
probability to receive a correct block is increased.
The RLC/MAC layer has been significantly improved in EDGE development. For
handsets supporting multiple TS, performance limitations in GPRS due to the limited
size of the acknowledge window is not reproduced in EDGE, i.e. in GPRS RLC
window size is 64, i.e. the transmitter cannot transmit block N+64 if block N has not
been correctly acknowledged by the receiver. In EDGE, windows size has been
extended to 1024 blocks, avoiding loss of incorrect blocks because of too bad radio
conditions.
Thus, thanks to all these improvements, EDGE offers better performances than
GPRS.
5.3.
EDGE DEPLOYMENT STRATEGY
There are two methodologies to design a data network:
•
First one is based on the deployment on current / existing network
characterized by a C/(I+N) distribution. User throughput will be distributed in
the cell according to the existent network air-interface quality.
•
Second one consists in implementing a new network for data or changing
existing cell planning, frequency planning or network densification, in order to
guarantee a given throughput or a given QoS to subscribers.
Several performance parameters are significant for an EDGE network design. Main
three parameters are mentioned in this document: mean data throughput per TS
overall cell, guaranteed data throughput, i.e. maximum data throughput at cell edge
with cell edge reliability and MCS usage distribution.
First two throughput metrics depend on the number of erroneous blocks that need to
be retransmitted on air interface. BLER, i.e. Block Error Rate, distribution, which is
different according to the MCS, depends on several parameters: BTS type (macro,
micro cell); MS performances, frequency band; environment and mobiles’ speed (TU3,
TU50…), features of signal processing (diversity, frequency hopping, incremental
redundancy…) and also on the radio condition of the cell, which is related to cell
planning and the frequency plan. MCS usage distribution determines which and where
each MCS is used and it has a big impact on backhaul dimensioning.
This document is focused on the performances of an EDGE networks deployed over
an existing GSM network. GSM networks typical values of coverage and frequency
plan are considered.
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5.4.
MAINS ENGINEERING RULES
5.4.1 EDGE TDMA RULES
Rule
Air_TDMA_005 (O)
Several EDGE TDMAs per cell can be supported starting from V15.1.
GPRS/EDGE service can be supported on any TDMA of a given cell, with
multiple GPRS/EDGE TDMAs in a same cell. Those TDMAs can be both
in the Outer Zone and the Inner Zone of a Dual Band Cell. In case the
inner zone coverage is smaller than that of the outer zone coverage, we
recommend configuring PDTCH only in the outer zone. Besides, in case
where the operator wants to support EDGE MS which do not support the
frequency band of the Inner zone (ex: Roamers), then Nortel
recommends not to configure any PDTCH in the Inner Zone.
5.5.
SPECIFIC DATA FEATURES
5.5.1 NETWORK ASSISTED CELL CHANGE IMPACT ON
GPRS/EDGE NETWORKS
This feature allows for the rel'4 MS an assistance during the cell re-selection during
the on-going TBF. The NACC feature is limited only to the intra-BSC cell re-selection
for the moment. For MS without NACC, the MS abruptly aborts the on-going TBF
without indicating it to the network. With MS supporting NACC, the MS dialogues with
the PCU in order to keep the initial TBF established for a maximum of 960ms during
the cell reselection. This avoids having a loss of service during re-selection by
performing a smooth transition between the TBF.
For the NACC usage it's necessary to respect the following rules:
Rule
Air_NACC_001 (M)
In a given BSC area, the (ARFCN, BSIC) shall be unique
Note: A notification is raised by PCU when this situation occurs in a cell
Rule
Air_NACC_002 (M)
The neighbor cells of a BSC shall not have the same (ARFCN, BSIC) than
any of the cell of that BSC Area.
Note: This configuration shall be ensured by the customer and cannot be detected by
the BSS (for example, with 2 BSCs configured on 2 different OMC-R, or in the
boundary with another BSS vendor, or in boundary with another country).
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5.5.2 PACKET FLOW CONTEXT IMPACT ON GPRS/EDGE
NETWORKS
This feature allows offering a support to Rel99 QoS management inside GPRS/EDGE
network. The PFC feature helps in supporting applications requiring a big bandwidth
with a good QoE to end users.
In order to ensure a significant success of admission control for RealTime MS, BSS
resources have to be allocated in coherence with the operator objectives.
According to theses PFC targets, the following recommendations present the principle
of resources dimensioning for the PDTCH and Jokers in the concerned cells for Air
interface. The Agprs interface document present the dimensioning principles for
dynamic Agprs resources and constraints.
PDTCH and Jokers dimensioning in the cell for Abis and Air interfaces:
N _ rtpfc _ pdtch ≤
N * GBR
pfcTsGuaranteedBitRateDl * ( 1 − pfcMinNrtBandwidthPerTs )
Npdtch >= N_rtpfc_pdtch
Njokers >= N_rtpfc_pdtch * pfcMinNumberOfJokersforTsGuaranteedBitRate
NDS0jokers = Njokers/4
If a significant bandwidth for the non PFC mobiles is reserved by the operator, then
the PDTCH and Jokers may of course be set to values higher than the one presented
here.
5.6.
DATA THROUGHPUT ESTIMATION
Mean data throughput offered by EDGE on a given cell depends on BLER distribution
on this cell. BLER distribution depends on radio conditions. Estimations between
BLER and radio conditions have been obtained through software signal processing
simulator at air-interference layer, where transmitter, receiver, interference and
multipath channel are modelled [R1].
Following global methodology is implemented to calculate EDGE mean throughput
offered per TS on a given scenario:
•
Implemented frequency plan on network determines C/I at cell edge. C/I
distribution on cell is obtained applying typical propagation model.
•
Cell size, once the environment is characterized, determines Eb/No at cell
edge. Eb/No distribution on cell is obtained applying typical propagation
model.
•
Thermal noise and interference are independent but with combined effects,
thus C/(N+I) is considered. BLER distributions on cell is deduced for each
MCS, from BLER=f[C/(I+N)].
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•
Throughput distribution on cell is deduced from these BLER distributions for
each MCS. User throughput at RLC/MAC layer is roughly estimated by the
following simplified formula:
Effective Throughput=MaxThroughput_MCS*(1-BLER) (1)
•
Finally, throughput is estimated integrating data throughput over coverage
area.
Calculations at cell edge determine guaranteed data throughput with certain reliability
since worst radio conditions are found.
BLER distribution over cell defines MCS distribution usage if perfect link adaptation is
considered, i.e. best data throughput is considered at each position over all MCS
available. Figure 1 gives an overview of the methodology:
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Voice cell range
Frequency plan
Eb/No distribution on
the cell
C/I distribution on the
cell
C/(N+I)
distribution on the
cell
R&D simulations:
BLER = f (C/(N+I))
BLER distributions on
the cell for each MCS
Throughput distributions on
the cell for each MCS
Mean throughput / TS
on the cell
Figure 5-1: Throughput calculation methodology scheme
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Note that this methodology is applicable to either DL or UL. Following steps are
detailed in the next sections:
- Calculations of C/I and Eb/No distributions on cell
- Calculations of throughput distributions on cell
- Calculations of mean throughput per TS on cell
5.6.1 RADIO CONDITIONS (C/I AND EB/NO) DISTRIBUTIONS
ON THE CELL
Let be a cell of range R. Cell is divided in concentric cells of radius ri, so that 0 ≤ ri ≤ R,
in order to determine Eb/No and C/I distributions on this cell (figure 2).
r6
r7
r8
r9
r10=R
r5
r4
r3
r2
ro
r1
R
Figure 5-2: Cell partitioning (schematic representation)
5.6.1.1
C/N DISTRIBUTION
The C/N distribution on the cell depends on voice pathloss. From this pathloss, C/N at
cell edge can be deduced and then Eb/No distribution.
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5.6.1.2
C/N AT CELL EDGE
The cell radius R corresponds to a given voice pathloss.
MS and BS sensitivities are deduced from this pathloss using the following formulas:
MS sensitivity calculation:
PathLoss _Voice = BS _TxPower − DL _ Losses − MS _ Sensitivity (2)
BS sensitivity calculation:
PathLoss _Voice = MS _TxPower −UL _ Losses − BS _ Sensitivit y (3)
Note: DL_Losses and UL_Losses correspond to all losses introduced in the
transmission – reception chain, in particular cable losses, BS antenna gain, slant
losses and penetration factor. Note that no body losses are included in these factors
since for data, handset is assumed to be separated enough from the body.
Then, MS and BS Eb/No at cell edge can be calculated using formula below:
Where:
- NF stands for noise factor. NF is 3 dB for BS and 8 dB for MS.
Being:
M = number of bits per symbol:
M = 1 for GMSK modulated signal (MCS-1 to MCS-4)
M = 3 for 8-PSK modulated signal (MCS-5 to MCS-9)
As M is different according to the modulation, Eb/No at cell edge is also different. 3
bits per symbol are transmitted in 8-PSK while 1 bit per symbol is being transmitted in
GMSK modulation. In other words, there are two Eb/No distributions: One for GMSK
MCS and another for 8-PSK MCS. The difference between the two distributions is
10*log(3) factor.
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5.6.1.2.1 C/N DISTRIBUTION ESTIMATION
A simplified propagation model is used to calculate C/N distribution over the cell
depending on each ri, i.e. UE cell position:
where:
•
5.6.1.3
α is propagation coefficient. Following values are used:
o
3.522 in dense urban, urban and suburban environments
o
3.441 in rural environment
•
R is cell radius
•
r is expressed in km
C/I DISTRIBUTION
C/I distribution on the cell depends on implemented frequency plan and radio
conditions. From this frequency plan, C/I at cell edge can be deduced and then C/I
distribution. It is very difficult to simulate C/I distribution as radio conditions vary
quickly.
5.6.1.3.1 C/I AT CELL EDGE
C/I at cell edge depend on frequency plan implemented on the network. Nortel
Networks experience and simulations have shown that 4*12 for non-hopping
frequency plan allow ensuring a minimum C/I of 12dB with 95% of reliability. So, the
C/I at cell edge is assumed equal to 12 dB.
Note: of course, if the frequency reuse pattern is higher, the C/I at cell edge is greater.
Following figure shows the C/I cdf depending on frequency plan.
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Comparatif entre les différent motifs
100
90
80
60
50
40
% P(C/I >= X)
70
30
20
10
0
0
2
4
6
8
10
12
14
16
18
20
22
24
26
28
30
X : Seuil de C/I (dB)
Figure 5-3 C/I Cdf depending on frequency reuse pattern
5.6.1.3.2 C/I DISTRIBUTION
Following formula is used to calculate C/I distribution over the cell depending on UE
position, i.e.
where:
- α is the propagation coefficient. Following values are used:
o
3.522 in dense urban, urban and suburban environments
o
3.441 in rural environment
- R is cell radius
- r is expressed in km
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Plan opérationnel
Motif 1-1
Motif 1-3
Motif 2-6
Motif 3-9
Motif 4-12
Motif 7-21
Radio Interface Engineering Rules
5.6.2 MEAN THROUGHPUT PER TS CALCULATION
5.6.2.1
BLER DISTRIBUTIONS ON THE CELL
BLER distributions are deduced using the R&D curves [R5]. These curves are actually
the results of simulations, giving performances for each MCS in term of BLER uplink
versus C/I or Eb/No according to:
o
Environment
o
Frequency
o
Activated features,
redundancy…
e.g.
diversity,
frequency
reuse,
incremental
For instance, hereafter are two simulations of BLER versus Eb/No (figure 4) and C/I
(figure 5) in following scenarios: TU50 propagation profile; 1800 MHz; no FH, no
diversity and no incremental redundancy:
Figure 5-4: BLER = f (Eb/No) in TU50, no FH, no IR, no Diversity and at 1800 MHz
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Figure 5-5: BLER = f (C/I) in TU50, no FH, no IR, no Diversity and at 1800 MHz
These curves show clearly that BLER performances for a given radio condition (C/I or
C/N) are not the same according to MCS considered. It means that BLER distribution
needs to be calculated for each MCS.
Thermal noise and interference noise effects are combined, thus, both are added to
calculate C/(N+I). R&D simulations are done for C/I, Eb/No and/or C/N. If both curves
are superposed for the same environment, C/(I+N) is expected to be found between
them. Thus for BLER distribution, mean values between BLER found with Eb/No
curves and BLER found with C/I curves is considered.
Methodology to calculate BLER distribution on the cell for one MCS is the following:
o
Consider each couple {C/I; C/N}i calculated previously for each ri
o
C/(I+N) is estimated following expression:
o Deduce from the R&D
simulations (BLER versus C/(I+N) in C/I curves and BLER versus C/(I+N) in
Eb/No curves for each considered MCS) TWO BLER values {BLERC/I;
BLEREb/No}i associated to C/(N+I)
o
In order to estimate BLER depending on C(I+N) and to take into account noise
characterization (either coverage or interference limited environment)
{BLERC/I; BLEREb/No}I are weighted following a baricenter weighting
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Note: Nortel Networks simulations are based on eDRX Nortel Networks
performances. Standard GSM 45.005 specifies MS performances in term of sensitivity
and C/I only at one BLER value (10% or 30% according to the MCS), if these figures
are compared with R&D Nortel Networks simulations, 4 dB degradation are found,
either for sensitivity or interferences figures.
For throughput calculation in DL, Nortel Networks prefers to use its own eDRX
performance figures without diversity; but considering a margin so that the
performances given by simulations are coherent with those given by the standard at
the BLER of standards (i.e. 10% or 30%).
UE signal processing algorithms implemented in the UE equipment should not be less
performing in the UE than in simulations considered. Thus, 0 dB C/I margins are
taken in the calculations in downlink.
Sensibility performances are different between UE and BS because of hardware
equipment performances. As it has been said, 4 dB degradation is found between
standard 05.05 and R&D signal processing simulations. Thus, 4 dB is the worst
conditions. On the other hand, it can be expected, UE performances will be better than
standard, UE suppliers will leave a margins to guarantee the standard. Therefore, 3
dB margin is proposed in C/N simulations in downlink.
Implementation margins could be also considered independently from those margins
to adapt eDRX performances to UE. In Uplink, 1 dB margin is proposed by default
in uplink.
5.6.2.2
THROUGHPUT DISTRIBUTIONS ON THE CELL
Having BLER distributions on the cell for each MCS, i.e. BLER value for each ri
between 0 and R, throughput distributions can be easily determined. Following
formula is used to calculate effective throughput per TS according to the BLER.
where MaxThroughput are according to MCS:
h
e
r
Table1: Maximum Throughput per TS according to the MCS
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Note: these throughput values are at RLC/MAC level.
5.6.2.3
LINK ADAPTATION
Link Adaptation (LA) allows changing MCS used in the transmission of RLC data
blocks according to radio conditions. To maximize data throughput, EDGE network
should choose in each point of the cell MCS, which maximizes throughput: this
algorithm is called Link Adaptation.
LA algorithm inside PCU selects the MCS for RLC data blocks based on the LQM
received from MS via PDAN for DL TBF, or received from BTS in-band for UL TBF.
The Link Quality Measurements (LQM) Report is made of 4 parameters:
o
MEAN-BEP [8-PSK / GMSK]
o
CV-BEP [8-PSK / GMSK]
stands for “Mean Bit Error Probability”
stands for “Coefficient of Variation of BEP”
LA algorithm relies on the use of MEAN_BEP and CV_BEP to derive the MCS number
that provides the maximum throughput. Only the measurements (MEAN-BEP / CVBEP) corresponding to the modulation really used for transmission are meaningful.
These MEAN_BEP and CV_BEP are estimated form a training sequence, thus, the
higher the MEAN_BEP the higher MCS is used
MEAN_BEP and CV_BEP are computed by the mobile and the BTS respectively for
DL and UL direction. They are filtered before being sent to the PCU as part of the
LQM report. The reported values are not the actual values, but integers, which can
take values from 0 to 31 for MEAN_BEP and from 0 to 7 for CV_BEP.
Performances which are presented in this document assume an ideal link adaptation,
only one throughput value (throughputi) is kept for each ri of the cell (0 ≤ ri ≤ R):
this throughput value is the best one among 9 throughputs offered by the different
MCS.
This means that only one throughput distribution results from link adaptation. MCS
usage on the cell is deduced from this throughput distribution (see figure 5-6)
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Figure 5-6: MCS distribution / usage on the cell (schematic representation)
Mean Throughput / TS
5.6.2.4
MEAN THROUGHPUT / TS
Having throughput value per TS for each ri of the cell, mean throughput per TS is
estimated by integration on coverage area (see figure 6).
Following formula is used:
where:
•
SurfaceTotale is coverage area, i.e.
•
Si is surface of the crown of range δ, centred on ri (actually δ= ri)
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Note that So and SR have different expressions since their range is /2:
Figure 5-7.- Mean data throughput integration
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5.6.3 COMMENTS ON DATA THROUGHPUT CALCULATIONS
5.6.3.1
C/(I+N) VERSUS BLER ESTIMATION
Since no R&D simulations have been done in C/(I+N), values are estimated form C/I
and C/N curves as explained in chapter 5.5.2.1.
5.6.3.2
LIMITATIONS
Several hypotheses are considered to simplify calculations: regular distributed omnicell; uniform traffic distribution; MS performances are deduced from eDRX
performances; perfect propagation model without fading effects; no antenna diagram
is considered; instantaneous perfect link adaptation…
5.7.
EDGE PERFORMANCES ESTIMATIONS
In this chapter, EDGE performance capacities are estimated. Impact on capacity of
incremental redundancy and frequency reuse are studied.
EDGE performance estimation depends critically on hypothesis and input parameters.
Thus, no estimation performance value has any sense if hypothesis associated are
not clearly specified. In this chapter, EDGE performance values are given in order to
show an idea on capacity performances but case-by-case capacity study should be
done to for each network separately. Maximum cell ranges are considered, thus
performances improve critically if inter-site distance is reduced.
For performance estimations calculated in this document, following default network
characteristics are considered:
•
4x12 frequency plan is considered by default estimating 12 dB C/I at cell
edge.
•
A cell size of 2.29 km at 900 MHz in TU3 and 6.95 km in TU50 is considered
using a default link budget considering a S222 BS configuration available.
Tables 2-6 detail link budget default parameters:
User Equipment Performances
Maximum UE Tx Power (dBm) / MEAN
UE Tx antenna gain (dBi)
UE Rx noise figure (dB)
UE Rx sensitivity (dBm)
Table 2: User Equipment performances
BS Performances
Maximum BS Tx power (dBm) / MEAN
BS Tx/Rx antenna gain (dBi)
BS Rx noise figure (dB)
BS Rx sensitivity (dBm)
33
0
8
-104
44.8
18
3
-114
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Slant losses (dB)
1.5
BS Rx cable & connector losses (dB)
3
Site antenna heigh (m)
30
Table 3: Base Station performances and characteristics
Configuration
Coupler Loss (dB)
Table 4: Coupler Losses
S222
1.4
S444
4.7
Margins
Area Reliability desired
Shadowing Margin
Building penetration factor (dB)
Body loss (dB)
Table 5: Link Budget Margins
TU3
TU50
Selected
environment
correction factor
0
-12
(dB)
Table 6: Selected environment correction
S888
7.8
90%
3.4
15
3
RU130/RA250
-22
Thus, taking into account all these input values, 5.7 dB C/N is found in UL at cell edge
for GMSK MCS and 11.1 dB C/N in DL.
C/I at cell
DL C/No at
UL C/No at
Environment
edge
cell edge
cell edge
Urban
TU3
12dB
11.1 dB
5.7 dB
Suburban
TU50
12dB
11.1 dB
5.7 dB
Table 7: C/I and C/N hypothesis considered for EDGE performances estimations in
different environments
Polarisation diversity gain is considered in UL calculations and no diversity is
considered in downlink.
ePa output power is considered the same for GMSK and 8-PSK modulation. 11%
mean downlink capacity per TS is lost if 3 dB output power loss is found for 8-PSK
modulation.
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Mean data throughput has been maximized independently from transmission impact.
There is a trade-off to be analysed between data throughput and backhaul
dimensioning. Backhaul dimensioning has an important impact on average throughput
because operator may want to sacrifice a little bit of radio throughput to get significant
gains on backhaul and equipment. As a typical example, if MCS 3, 6 and 8 are not
used in a typical urban environment, 33% on backhaul equipment is saved (which
translates into additional PCUSN and BSC savings because of connectivity needs) at
the expense of only 3.5 % mean throughput degradation.
5.7.1 INCREMENTAL REDUNDANCY
5.7.1.1
INCREMENTAL REDUNDANCY FUNCTIONALITY
In data systems, either packets are found correctly received or packets are requested
to be retransmitted. While in GPRS, wrong received packets were discarded, EDGE
allows to reuse old wrong received packet to combine them with fresh new packets to
increase probability of receive correctly a packet.
Incremental redundancy is highly related to retransmission. In order to allow this
recombination gain between packet, certain constraints should be respected in term of
MCS retransmission.
The MCSs are divided into different families A, B and C. Each family has a different
basic unit of payload. Different code rates within a family are achieved by transmitting
a different number of payload units within one Radio Block.
The following table lists the different coding schemes:
When a retransmission is needed, a MCS belonging to the same family as the original
block must be selected. If the LA-CommandedMCS does not belong to that family,
another MCS has to be chosen. The bloc may be segmented in two half-blocks if
needed, in order to be sent with MCS 2 or 3 from any 8-PSK MCS. (Re-segmentation
activated in DL and UL in Nortel implementation)
5.7.1.1.1 RETRANSMISSION TABLE IN UL
The following table synthesizes the situation for UL retransmission. This table is
normative (see [3GPP TS 04.60]).
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Figure 5-8: UL retransmission table
Note: In one particular case, the MCS selected for retransmission may be higher than
the MCS selected by the link adaptation algorithm. If the original block was transmitted
with family A and MCS 2 is commanded according to LA, MCS3 will be used.
5.7.1.1.2 RETRANSMISSION TABLE IN DL
The following table synthesizes the situation for DL retransmission. This table is not
normative. Nortel optimized the table to take advantage of Incremental Redundancy
(IR) on mobile side: the retransmission may be sent in higher MCS than the LA
commanded MCS in order to maximize incremental redundancy feature. (see bold
MCS where higher MCS are proposed)
5.7.1.2
INCREMENTAL REDUNDANCY PERFORMANCE IMPROVEMENT
Two different environments are analysed and compared: TU3 and TU50. Impact of IR
is underlined. Frequency reuse is considered, UL IR is available from V16.0.
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Tables 8 show mean data throughput per timeslot estimations and maximum data
throughput per timeslot at cell edge. Incremental redundancy gain is also deduced.
Mean Data Throughput
Max Data Throughput at cell edge
TU3 UL 900MHz IFH
UL no IR
22 kbps
9.2 kbps
UL IR
23.8 kbps
10.5 kbps
Gain IR
8.20%
14.10%
Table 8.1: Mean data throughput and maximum data throughput at cell edge in UL
TU3 in 900MHz without and with IR
Mean Data Throughput
Max Data Throughput at cell edge
TU3 DL 900MHz IFH
UL no IR
21.5 kbps
8.2 kbps
UL IR
22.1 kbps
9.7 kbps
Gain IR
2.80%
18.30%
Table 8.2: Mean data throughput and maximum data throughput at cell edge in DL
TU3 in 900MHz without and with IR
Mean Data Throughput
Max Data Throughput at cell edge
TU50 UL 900MHz IFH
UL no IR
22.6 kbps
10.3 kbps
UL IR
23.4 kbps
11 kbps
Gain IR
3.40%
6.40%
Table 8.3: Mean data throughput and maximum data throughput at cell edge in UL
TU50 in 900MHz without and with IR
Mean Data Throughput
Max Data Throughput at cell edge
TU50 DL 900MHz IFH
UL no IR
21.5 kbps
8.4 kbps
UL IR
21.5 kbps
9 kbps
Gain IR
2.90%
7.10%
Table 8.4: Mean data throughput and maximum data throughput at cell edge in DL
TU50 in 900MHz without and with IR
Note: For calculations of the throughput in DL, Nortel Networks eDRX performances
without diversity have been considered. No engineering margin in eDRX C/I
performances without diversity is taken since no difference should be found between
eDRX and UE signal processing implementation. 3dB engineering margin is taken in
Eb/No eDRX performances since eDRX performances are expected to be better than
UE, although UE performances are expected to be better than standards. For UL data
throughput calculations, 1dB implementation margin is considered.
Main conclusions on mean data throughput per TS for an ideal frequency hopping
network are:
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5.7.1.3
•
Around 22-23 kbps /TS are achieved in UL while 20-22 kbps / TS are
expected in DL.
•
As shown in tables 8, IR brings a gain around 8% in the mean data
throughput. Anyway, where IR becomes really interesting is in worst
conditions, i.e. at cell edge and in downlink where more retransmissions and
recombination are needed. Up to 60% increase of guaranteed capacity at cell
edge is obtained thanks to incremental redundancy.
•
Users’ speed degrades throughput performances. Higher MCS are affected
the most, thus performances of mean data throughput are decreased. Around
5% loss is found between a user moving at 3km/h and a 50 km/h under same
radio conditions.
MCS USAGE DISTRIBUTION
Table 12 and 14 show MCS used depending on UE-BS distance and maximum data
throughput at this cell position. Moreover, mean data throughput and guaranteed data
throughput are also shown for UL TU3 1800 no FH with IR and DL TU50 1800 no FH
without IR respectively
Table 13 and 15 shows MCS usage distribution for the same environment.
Distance (km)
0.00
0.11
0.23
0.34
0.46
0.57
0.69
0.80
0.92
1.03
1.14
1.26
1.37
1.49
1.60
1.72
1.83
1.95
2.06
2.17
2.29
Throughput / TS
MCS usage
(kbps)
(%)
59.2
MCS-9
59.2
59.2
59.1
58.4
56.2
52.0
46.4
40.4
35.3
MCS-8
30.4
26.3
MCS-7
23.2
20.5
18.2
16.1
14.3
12.8
11.9
MCS-4
11.1
10.5
MCS-3
Mean Throughput/TS (kbps):
Mean Throughput
/ TS calculation
0.0
0.3
0.6
0.9
1.2
1.4
1.6
1.6
1.6
1.6
1.5
1.4
1.4
1.3
1.3
1.2
1.1
1.1
1.1
1.1
0.5
23.8
Table 12: MCS usage distribution and data throughput depending on cell position in
UL TU3 900MHz IFH with IR
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MCS-1
MCS-2
MCS-3
MCS-4
MCS-5
MCS-6
MCS-7
MCS-8
MCS-9
% Users
0.0
0.0
4.9
18.5
0.0
0.0
49.0
9.5
18.1
% Users
Cumulative
100.0
100.0
100.0
95.1
76.6
76.6
76.6
27.6
18.1
Mean BLER
Mean BLER
when used
0.0
0.0
29.4
34.8
0.0
0.0
59.5
39.9
14.1
43.4
BLER at cell
edge
16.1
21.0
29.4
41.3
62.9
72.3
79.1
90.3
94.3
Table 13: MSC usage distribution in UL TU3 900MHz IFH with IR
Figure:
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Distance (km)
0.00
0.35
0.70
1.04
1.39
1.74
2.09
2.43
2.78
3.13
3.48
3.82
4.17
4.52
4.87
5.22
5.56
5.91
6.26
6.61
6.95
Throughput / TS
MCS usage
(kbps)
(%)
59.2
MCS-9
59.2
59.2
58.7
56.6
52.2
46.1
MCS-8
41.1
MCS-7
36.3
30.4
25.7
MCS-6
23.1
20.4
17.4
15.5
MCS-5
13.5
11.9
10.2
9.6
MCS-2
9.1
8.4
Mean Throughput/TS (kbps):
Mean Throughput /
TS calculation
0.0
0.3
0.6
0.9
1.1
1.3
1.4
1.4
1.5
1.4
1.3
1.3
1.2
1.1
1.1
1.0
1.0
0.9
0.9
0.9
0.4
20.9
Table 14: MCS usage distribution and data throughput depending on cell position in
DL TU50 900MHz IFH without IR
MCS-1
MCS-2
MCS-3
MCS-4
MCS-5
MCS-6
MCS-7
MCS-8
MCS-9
% Users
0.0
23.4
0.0
0.0
31.0
23.0
12.0
3.0
7.6
% Users
Cumulative
100.0
100.0
76.6
76.6
76.6
45.6
22.6
10.6
7.6
Mean BLER
Mean BLER
when used
0.0
18.4
0.0
0.0
43.6
27.9
20.8
15.3
5.2
27.6
BLER at cell
edge
11.3
25.1
59.4
87.3
69.8
81.1
96.9
99.3
100.0
Table 15: MSC usage distribution in DL TU50 900MHz IFH without IR
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Figure:
Main conclusions of MCS usage distribution in non-hopping frequency reuse patterns
can be stated as follows:
•
MCS 9 is used in a small cell coverage area near the BS.
•
MCS 6, MCS 7 and MCS 8 are mainly used over the cell.
•
MCS usage distribution shows 8-PSK MCS are mainly used all over the cell but
GMSK MCS are necessary to prevent worst punctual cases at cell edge, mainly in
downlink.
Frequency reuse degrades MCS data performances and it modifies critically MCS
usage distribution as it is detailed in the next chapter (same simulations without
frequency hopping have shown that MSC9 is much more used than with frequency
hopping)
5.7.2 HIGH POWER AMPLIFIER IMPACT ON DATA
PERFORMANCES
Nortel Networks proposes to increase power amplifier capabilities. ePA which allows
to transmit at 30W. For GMSK and 8-PSK can be replaced by a HePA (High ePA)
which is able to transmit at 60W. For GMSK and 45 W. for 8-PSK modulation.
Different advantages justify HePA deployment:
•
Increase on coverage or area reliability.
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•
Compensate coupling losses when higher configurations should be deployed.
•
Increase on data performances in coverage limited environments.
For the sake of quantifying HePA gain and MCPA, following environment is proposed:
TU3 dense urban environment with 510 meters cell range (maximum coverage once
link budget is defined) at 1800 MHz. 12 dB C/I are supposed at cell edge. H2D
coupling loss. Same example is calculated considering H4D and 420 meters cell
radius. Table xxx presents comparison between ePA, HePA and MCPA impact on
data throughput:
MCS usage distribution is also modified since radio coverage conditions are improved.
As shown in table xxx, higher MCS codecs are further used:
It should be underlined, that conditions proposed are significantly coverage limited. If
intercell distance would be reduced for any network design reason, e.g. capacity cell
splitting, HePA and MCPA gain will be reduced significantly.
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Besides, same coverage conditions have been considered, i.e. 510 m and 420m.
Therefore, all power gain has been translated in a performance gain instead of a
coverage improvement. Deploying a HePA can change link balance limitations, e.g.
typically for H2D coupling loss. For an ePA, downlink link budget is found to be the
most constraining link while when HePA is deployed, UL limitations are found (HePA
does not impact uplink link budget). This raises the question if it is worth to deploy a
TMA to improve UL constrains. Customers’ requirements should be taken into account
in order to answer that question. Deployment of a TMA is useful if higher coverage
gain is required or if UL performance becomes limiting factor. Moreover, TMA
deployment would degrade slightly DL performances since small DL loss in output
power should be considered. Therefore, no TMA addition is recommended when
HePA is deployed if it is not justified for UL performance improvement requirements.
5.7.3 FREQUENCY REUSE
Frequency reuse brings frequency and interferer diversity in the process of reception;
since changing the RF carrier while hopping allows to average the effects of strong
fading and allows spreading interferences across the network.
Frequency reuse is particularly efficient for slow moving mobiles and for a sufficient
number of hopping frequencies. It allows reducing the number of frequencies per TRX
and, thus, the capacity is increased since more TRX can be deployed in the same
frequency band.
Frequency load is crucial parameter in a network with frequency reuse. It is simply the
ratio between number of hopping TRXs in a cell and number of hopping frequencies.
Thus, it represents the time fraction for a given frequency being used in the network.
In order to determine impact of frequency reuse in EDGE MCS, frequency reuse gain
of each MCS is compared with speech’s gain.
Figure 5-9 shows sensitivity versus BLER performances for TU3, 900 MHz, no
diversity no frequency hopping. In order to guarantee 10% BLER, -107.3 dB sensitivity
is found. 4 dB gains on sensitivity is found due to frequency hopping as it is shown in
figure 5-10, where –111.3 dB is found to achieve 10% BLER.
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Figure 5-9- BLER versus sensitivity for speech in TU3 without frequency hopping
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Figure 5-10- BLER versus sensitivity for speech in TU3 with frequency hopping
Frequency reuse does not provide same benefits for data than for voice. If BLER
gains (for data) versus FER gains (for speech) are considered: spreading the errors
does not necessarily bring any improvement, as packets have to be received errorfree (used error correction algorithms must be able to correct all errors). In fact, FH
introduces errors in the bits flow which are difficult to correct if the signal correction
process is very poor. The more demanding on radio quality the protocol is, the less
benefits are given by frequency reuse.
Therefore, impact of frequency reuse for each MCS has to be calculated. Table 16
shows impact for TU3, 900 MHz, and no diversity for different MCS. Frequency reuse
impact on EDGE MCS is estimated in [R1]:
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As it has been test in the field, 16% frequency load brings same quality for speech,
considering DTX and power control inactivated, than a non-hopping frequency plan
network [R4]. Therefore, depending on frequency load deployed in the network,
different performances are found. Assuming that 4 dB gain brings same quality than
16% frequency load for speech, and knowing the impact of frequency hopping on
each MCS, frequency load required to achieve same performances as 4*12 frequency
plan can be calculated for each MCS using a linear approximation following equation
15.
Different frequency load for each MCS is required to achieve same performances as
non-hopping frequency plan network are shown in table 17:
Table 17.- FL for each MCS to obtain same performances as non-hopping frequency
plan
Even if frequency reuse gain depends on considered BLER, in Annex 2, it is shown
how using 10% BLER value is a good approximation for all MCS.
If frequency load in a network correspond to table 17 MCS FL, MCS performances of
this MCS are the same that no frequency hopping network. If FL is lower, frequency
hopping brings a gain in the performances of the MCS but if it is bigger degradation
has to be considered. Equation (16) estimates the gain or degradation depending on
frequency load implemented and MCS studied.
Degradation values are applied to C/(I+N). Same values are applied independently
from the environment.
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Table 18-20 show capacity increase thanks to frequency reuse. Dense Urban, TU3,
1800 MHz, no IR, downlink with diversity, 510 m. cell size study has been analysed.
Study compares capacity available for different frequency band, e.g. 5MHz, 7.5 MHz
and 10 MHz, considering same QoS in each scenario for users, i.e. same data
throughput. Capacity is then calculated as mean data throughput times the number of
TS available divided by the number of TS required to obtain the same QoS as nonhopping frequency reuse pattern network.
Downlink cases are mainly analysed in the document since asymmetrical traffic
expectations make downlink limited system.
As can be expected, frequency hopping degrades mean data throughput per timeslot.
But, frequency hopping associated with fractional reuse pattern allows increasing the
number of timeslots per site. Using a typical 16% frequency load allows increasing
37% capacity with regard to non-frequency hopping dimensioning if 10 MHz is
available. Capacity gain is critically dependant on frequency band available and
frequency load deployed in the network as it is shown in tables 18-20.
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5.7.4 IMPORTANT HYPOTHESIS AND ASSUMPTIONS
SUPPOSED
•
dB UE noise figure and 8 dB BS noise figure are considered
•
Engineering margins are left to adapt BS eDRX performances to UE
performance estimations.
•
For the simplicity of the analysis, no call profile is considered and number of
either EDGE or speech TS are fixed.
•
Moreover, voice and data busy hours are considered the same (worst case)
•
Perfect link adaptation is considered independently from BLER estimated,
thus no stability problem is considered in the backhaul even if BLER grow to
more than 50% BLER.
•
Results are purely radio capacity, thus no delay on protocols, neither
connection times nor release times are considered.
•
For mean data throughput calculations, users are supposed to request
maximum available data throughput.
•
Real distribution of BCCH and SDCCH are considered depending on base
station configuration.
•
Uniform user distribution is considered.
•
Maximum inter-site distance is considered following Nortel Networks default
link budgets.
•
Frequency reuse plans are considered always in 1:1 with 16% frequency load
independently from EDGE TS load.
•
70% channel occupancy is considered for both, speech and EDGE data TS.
Reference value of FL of 16% is estimated.
•
4*12 BCCH frequency plan is always considered, which corresponds to 12 dB
C/I with 95% reliability. 12 dB C/I are found considering full power TX by the
BS. Thus, worst case it is considered. There will be more interference
because of data but C/I should not be lower than 12 dB.
•
ePA usage with same output power for GMSK and 8-PSK modulation is
considered.
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5.7.5 BLER STUDY
Another study, which could be done with EDGE Radio Performance Excel tool is to
estimate mean BLER over the cell and expected BLER at cell edge.
For all presented exercise in this document, no limitations, in term of BLER, have
been taken into account. To calculate different MCS data throughput simple formula
was considered:
EffectiveThroughput=MaxThroughput_MCS*(1-BLER) (21)
Link adaptation was supposed to choose MCS, which optimizes maximum data
throughput independently from BLER estimated for each MCS. Thanks to RLC/MAC
layer improvement from GPRS, maximum EDGE BLER could be higher than 10%
BLER which is found in GPRS as limiting point. 100% maximum BLER is proposed
(even if it is unthinkable for good network stability) to calculate maximum radio data
throughput. Further studies will help to determine this value.
High BLER values are considered for 8-PSK modulations. 8-PSK data throughput
performances compared with GMSK modulations makes 8-PSK MCS suitable to be
chosen for ideal link adaptation algorithm than GMSK. For the sake of giving a simple
example, MCS5 working at 50 % BLER effective data throughput equals 11.2 kbps is
suitable for ideal link adaptation than MCS2 working at 2% BLER which represents
10.976 kbps effective data throughput ! Therefore, all mean BLERs given in this
chapter could be limited with a low loss in mean data throughput.
Following table shows mean BLER for an environment TU3; UL; 1800 MHz; IR where
8-PSK modulations are recommended to maximize data throughput. A MCS usage
distribution is shown as well as mean BLER per MCS and overall means BLER over
the cell:
For example, MCS 7 is used through 27% of the cell area with a mean BLER of
52.4%. Over the whole cell, meaning BLER of chosen MCS to maximize data
throughput is 30.7% BLER.
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In an environment where GMSK is used, mean BLER is critically decreased. Following
table stands for TU50 UL 1800 MHz, no IR, 12dB C/I and 1.56 km cell range for a
S444 maximum BS configuration:
MCS-1
MCS-2
MCS-3
MCS-4
MCS-5
MCS-6
MCS-7
MCS-8
MCS-9
% Users
0.0
0.0
4.9
18.5
0.0
0.0
49.0
9.5
18.1
% Users
Cumulative
100.0
100.0
100.0
95.1
76.6
76.6
76.6
27.6
18.1
Mean BLER
Mean BLER
when used
0.0
0.0
29.4
34.8
0.0
0.0
59.5
39.9
14.1
43.4
BLER at cell
edge
16.1
21.0
29.4
41.3
62.9
72.3
79.1
90.3
94.3
Table 13: MSC usage distribution in UL TU3 900MHz IFH with IR
MCS-1
MCS-2
MCS-3
MCS-4
MCS-5
MCS-6
MCS-7
MCS-8
MCS-9
% Users
0.0
23.4
0.0
0.0
31.0
23.0
12.0
3.0
7.6
% Users
Cumulative
100.0
100.0
76.6
76.6
76.6
45.6
22.6
10.6
7.6
Mean BLER
Mean BLER
when used
0.0
18.4
0.0
0.0
43.6
27.9
20.8
15.3
5.2
27.6
BLER at cell
edge
11.3
25.1
59.4
87.3
69.8
81.1
96.9
99.3
100.0
Table 15: MSC usage distribution in DL TU50 900MHz IFH without IR
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Main conclusions in BLER study:
5.8.
•
Ideal link adaptation chooses MCS independently from associated BLER to
optimise data throughput. A further simulation study should be done to
estimate, which is the maximum BLER allowed in EDGE system to keep
stability.
•
Incremental redundancy reduces BLER at cell edge. BLER from MCS 2 does
not overcome 20% BLER without frequency hopping in any environment.
•
Frequency hopping degrades critically BLER performances. The validity of all
results presented in this document depends on stability because of high
BLERs.
UL PERFORMANCE ANALYSIS
EDGE UL performances are affected by the fact that it presents the advantage to have
diversity available but on the other hand, IR will not be available until V16 release.
Different types of mobiles are found in the market. 5 different GMSK mobiles are
possible. Power Class 4 mobiles for 900 MHz (33 dBm output GMSK power) are
widely expected while Power Class 1 mobile for 1800 MHz (30 dBm output GMSK
power) are supposed.
In term of 8-PSK modulation mobile performance, table xxx shows difference of power
performances depending on type of mobile and power class. E2 mobiles are widely
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expected to be found on the market. E2 Power Class mobiles have a different output
power between GSMK and 8-PSK modulation. 6 dB less 8-PSK modulation power are
found with regard to common 33dBm for GMSK modulation and 4 dB less power are
expected.
5.8.1 DIFFERENT MOBILE TYPE PERFORMANCE IMPACT
As explained in last chapter, different types of mobiles are found in the market,
presenting different radio performances in terms of 8-PSK modulation output power.
The less 8-PSK output power is available; less performing in terms of data throughput
is expected.
In order to quantify radio throughput degradation following environment is proposed:
1800 MHz, 510 meters cell range, H2D configuration, no FH available, no IR, 12 dB
C/I at cell edge (some coverage and interference propagation model as DL is
deduced)
Degradation depends critically on environment defined. If interference UL limited
environment is studied, mean data throughput degradation could be neglected.
E2 class mobiles usage affects also MCS usage distribution. The better power
capabilities, higher MCS could be used. Usage of E2 and E3 mobiles provoke
massive usage of GMSK modulation in UL.
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5.9.
LAB TEST RESULTS
Several tests simulating different radio condition environments have been carried in
platform as well as different mobile performances have been tested.
CAUTION: Measured performances in lab are applicative throughput while radio
RLC/MAC is shown in the rest of the document. This makes that comparison between
both figures should be done carefully. Chapter 9.4 shows a comparison between
measured and simulated performances with all hypotheses detailed supposed in order
to compare both performances.
5.9.1 UL LAB RESULTS
The goal of the test was to get for each EDGE coding schemes (MCS) and for the
default LA table, the graphic representation of the averaged end-to-end throughput
that can be obtained for different C/I values in uplink direction (FTP-PUT). TU3 radio
environment is simulated. During the whole test, the “C” value is fixed to -65 dBm,
while the “I” value while GMSK co-channel interference generated by an interferer tool
transmitting are produced at a constant level of -70 dBm, is modified through an
attenuator.
10 transfer iterations are executed for C/I value. Each throughput point of the curve is
the averaged result over the 10 iterations.
Motorola T725 (3+1) mobile handset was used. Diversity is available.
UL Applicative data throughput test results are shown in figure below:
Throughput in Degraded Radio Conditions C/I - FTP Put
50
s8k 1900MHz with Duplexer Diversity enabled.
No Hopping
Cochannel GMSK interference
TU3 Environment
MS Class 4 : 3+1
For LA, transfers with dropped IP frames due to
CRC are kept. For MCS curves, they are removed.
45
40
35
Throughput (kbps)
MCS9
MCS8
30
MCS7
MCS6
25
MCS5
MCS3
20
MCS2
LA Curve
15
10
5
0
0
10
20
30
40
50
C/I at BTS (dB)
Figure- UL applicative throughput test results
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5.9.2 DL LAB RESULTS
The goal of the test was to get for each EDGE coding schemes (MCS) and for the
default LA table, the graphic representation of the averaged end-to-end throughput
that can be obtained for different C/I values in downlink direction (FTP-GET). This is
done in a TU3 radio environment. During the whole test, the “C” value is fixed to -65
dBm, while the “I” value while GMSK co-channel interference generated by an
interferer tool transmitting are produced at a constant level of -70 dBm, is modified
through an attenuator. BROADCOM GC82 (4+1) card was used.
10 transfer iterations are executed for C/I value. Each throughput point of the curve is
the averaged result over the 10 iterations.
DL Applicative data throughput test results are shown in figure below:
Throughput in Degraded Radio Conditions C/I - FTP Get
s8k 1900MHz with Duplexer (bsTxPwrMax=41)
No Hopping
Cochannel GMSK interference
TU3 Environment
MS Class 8 : 4+1
For LA, transfers with dropped IP frames due to
CRC are kept. For MCS curves, they are removed.
200
Throughput (kbps)
150
MCS9
MCS8
MCS7
MCS6
MCS5
100
MCS3
MCS2
LA Curve
50
0
0
10
20
30
40
50
C/I at Ms (dB)
Figure .- DL applicative throughput test results
5.9.3 REAL LINK ADAPTATION IMPACT ON MEAN DATA
THROUGHPUT
Real UL and DL link adaptation measured curves using default adaptation table set
(see figure xxx and figure xxx) show impact of real link adaptation with regard to the
optimum LA curves, which would correspond to the choice of the MCS which would
maximize data throughput.
Applying engineering methodology detailed in chapter 6, and using UL and DL curve
performance obtained through lab measurements, (only C/I versus throughput is
considered), following mean data throughput performances are obtained:
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From 3% to 6% degradation is found due to real link adaptation algorithms with regard
to ideal link adaptation.
DL link adaptation looks like to be more performant than UL. This better functionality
could be attributed to incremental redundancy link adaptation aggressiveness. MCS
used are normally higher than link adaptation requests when are retransmitted in order
to take profit of IR functionality. This allows recovering some throughput compared to
ideal MCS par MCS optimized link adaptation.
UL incremental redundancy is still not implemented in the product and it is expected in
V16.
5.9.4 APPLICATIVE VERSUS RLC/MAC THROUGHPUT
RELATIONSHIP
Not deterministic link between applicative and RLC/MAC throughput can be found.
Several reasons are listed below:
- Different MCS are used during a communications, having each MCS a different
header payload.
- Throughput is critically related to application:
•
TCP throughput is related to network TCP/IP parameters
•
Depends on packet size (e.g. impact of slow starting affects applicative
throughput)
- UL and DL radio conditions are difficult to link and their relationship affects other link
performances:
•
Acknowledgements should be correctly received
- BLER impact on IP level cannot be evaluated linearly:
•
Low BLER: retransmissions at RLC/MAC level, which reduce applicative
throughput. No IP packet loss occurs; thus, lineal relationship could be used.
•
High BLER: retransmissions at RLC/MAC level, which reduce applicative
throughput and also IP packet loss occurs which no lineal relationship can be
done.
Some test on perfect radio conditions were carried on platform, i.e. BLER=0% for all
codecs. Different tests using a single codec were done. Big files of 8Mb were
transferred in order to avoid slow starting effect. Table xxx shows radio throughput
compared with TCP applicative layer results per codec.
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DL MCS
(kbps)
MCS-2
MCS-3
MCS-5
MCS-6
MCS-7
MCS-8
MCS-9
Average
4 TS
TCP Applicative Radio versus
MCS Max
MCS Max layer to Radio
Applicative
Throughput
Throughput Performances Throughput
41,43
11,2
44,8
8,13%
54,57
14,8
59,2
8,48%
82,19
22,4
89,6
9,02%
108,58
29,6
118,4
9,04%
162,39
44,8
179,2
10,35%
195,17
54,4
217,6
11,49%
210,61
59,2
236,8
12,44%
Table xxx.- Radio RLC/MAC versus TCP Applicative throughput comparison
As it is shown in table xxx, difference between radio and TCP applicative throughput is
dependent on MCS and it can be quantified between 8-12% in perfect radio
conditions.
5.10. CONCLUSION
Nortel Networks EDGE engineering data throughput performances estimation
methodology has been detailed. Different feature impacts on performances have been
analysed. Following conclusions are found for an only EDGE traffic networks scenario:
•
Incremental redundancy brings 15% mean data throughput/TS increase. Its
main advantage is reached in worst conditions, i.e. on cell edge where
guaranteed data throughput is increased up to more than 50% data
throughput.
•
Frequency hopping has shown to increase capacity more than 30%
depending on frequency band available and frequency load deployed.
Performances are critically dependent on scenario, frequency band available, EDGE
penetration, EDGE TS allocation strategy, reference taken for comparison... Thus, all
estimated performances are for the sake of giving examples and correspond to a
typical environment but case-by-case study should be reconsidered using each
customer network characteristics. Performance calculation inaccuracy concerns most
of results presented but not the tendencies obtained.
It has been detailed how EDGE TS allocation strategy depends on EDGE penetration
and frequency band available.
•
When best data throughputs and low data capacity are expected, PDTCH on
BCCH is best approach
•
When data capacity is required, it is worth to sacrifice a little bit of peak data
throughput to have a gain on data capacity by setting the PDTCH on a
hopping layer.
Finally, GPRS versus EDGE offered traffic load is compared to underline the
advantage on traffic load when bigger data throughput par TS is available. Data
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throughput does not only improve the transmission time but increases the number of
user which could be processed in the network if comparison is done at the same QoS
with GPRS.
6.
ABBREVIATIONS AND DEFINITIONS
6.1.
ABBREVIATIONS
A
ETSI generic name for BSS-NSS i/f
Abis
ETSI generic name for BTS-BSC i/f
Agprs
NORTEL specific name for BSC-PCU i/f
BCCH
Broadcast control channel
BH
Busy hour
BLER
Block error rate
BSC
BSS Base station subsystem
BTS
BSSGP BSS GPRS protocol
BVC
CCCH Common control channel
CS
CS-paging Circuit Switched-paging
CCU
Channel codec unit
DL
Downlink
FN
Frame number
Gb
ETSI generic name for PCU-SGSN i/f
GGSN
Gateway GPRS support node
Gi
ETSI generic name for GGSN-PDN i/f
GMM
GPRS mobility management
Gn
ETSI generic name for SGSN-GGSN i/f
GPRS
General packet radio service
GSL
GPRS signaling link
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I/F
Interface
IP
Internet protocol
LA
Location area
LAC
Location area code
LAI
Location area identity
LAPD
Link access protocol on D channel
LLC
Logical link control
MAC
Medium access control
MCS
Modulation and Coding Scheme
MO
Mobile originated
MS
Mobile station
MT
Mobile terminated
NS
Network service
NSAPI
Network service access point identifier
NSS
Network and switching subsystem
NTS
Number of TS assigned to the UL TBF
O&M
Operation and maintenance
OAM
Operation administration maintenance
OML
OAM link
PACCH
Packet associated control channel
PAREJ
Packet access reject
PBCCH
Packet broadcast control channel
PCA
Packet control acknowledgement
PCCCH
Packet common control channel
PCM
Pulse coded modulation
PCU
Packet control unit
PCUSN
Packet control unit support node
PCUSA
Packet control unit system application
PDAN
Packet DL Ack/Nack
PDAS
Packet DL assignment
PDCH
Packet data channel
PDN
Packet data network
PDP
Packet data protocol
PDTCH
Packet data traffic channel
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6.2.
PDU
Packet Data Unit
PRR
Packet resource request
PS-paging
Packet Switched-paging
PSTN
Public switched telephone network
QoS
Quality of service
RA
Rural Area (type of radio environment)
RA
Routing area
RAC
Routing area code
RAI
Routing area identifier
RACH
Random access channel
RLC
Radio link control
RRM
Radio Resource Management
RSL
Radio signaling link
SAPI
Service access point identifier
SGSN
Serving GPRS support node
SSN
Starting sequence number
TA
Timing advance
TBF
Temporary block flow
TCP
Transmission control protocol
TDMA
Time division multiple access
TFI
Temporary flow identity
TLLI
Temporary logical link identifier
TRX
BTS transceiver entity
TS
Timeslot
UL
Uplink
USF
UL state flag
DEFINITIONS
For the rules presented in the document, (O) means the rule is optional, (M) means
the rule is mandatory, (HC) means the rule is hard-coded.
Z END OF DOCUMENT Y
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