Customer EDGERPL - Module4 (v3.0).ppt

1 © NOKIA EDGERPL Company Confidential

EDGE Optimization

Network Performance MeasurementsEDGE Capacity Optimization


EDGE Optimization - Content• EDGE Radio Network Optimization Structure• Network Performance Measurements

• Accessibility• Traffic measurement

• EDGE Capacity Optimization• Maximizing TSL capacity (data rate)• Maximizing PSW territory with proper utilization• Improvement of user perception – higher layers’ optimization


EDGE Radio Network Optimization Structure

1. Network Performance Measurements

2. (E)GPRS Coverage optimization• GSM network optimization for higher signal level

• Sensitivity threshold• City and rural environment• Outdoor, Indoor, Incar

3. (E)GPRS Frequency allocation optimization• GSM network optimization for better C/I

4. (E)GPRS Capacity optimization • PSW optimization for maximizing TSL PSW capacity• PSW optimization for maximizing PSW territory with proper utilization

5. Quality of End User• PSW optimization for maximizing user data rate in BSS

• End-to-End performance analysis and optimization• TCP/IP and application layer optimization

GSM Network Optimization


Network Performance Measurements

AccessibilityTraffic Measurements


Network Performance Measurements - Intro

Measurements are needed to get clear picture about network performance. The (E)GPRS measurements are separated to

• Accessibility• Traffic and Mobility

The traffic figures can be measured by:• Network Doctor• NetAct Reporter (ND Browser, KPI Reporter)• EOSFLEX• Inspector• Traffica• Drive tests – application tester, measurement tools• Interface analyis


Accessibility Measurements – Drive Tests

Num

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Num

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of S

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Num

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of F

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Num

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of U

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Suc

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Rat

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]

Avg

of D

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ion

[ms]

Min

of D

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ion

[ms]

Max

of D

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ion

[ms]

Attach 209 184 25 0 86.1 2654.3 1212.5 10315.8

PDP Context Act. 217 210 7 0 95.5 1293.5 90.6 15840.8

Attach & PDP Context Activation results (GPRS Benchmark – 32 operators worldwide from drive measurements)

• 86 % success rate for attach – not only network problems: (no roaming, no GPRS subscription, etc)• 95 % success rate for PDP context activation – gives better picture about network capacity and quality


Traffic Measurements – Network DoctorNetwork Doctor measurements

• EDGE Traffic (Erl.)• EGPRS Traffic in Erlang DL• EGPRS Traffic in Erlang UL

• EDGE Throughput (kbps)• Average Effective Throughput per used TSL UL• Average Effective Throughput per used TSL UL• Average Total Throughput per used TSL UL• Average Total Throughput per used TSL UL

• RLC Payload (KB) and Utilization (%)• Total RLC Payload Data• Territory Utilization

• EDAP• Usage• Availability• Rejection


(E)GPRS Traffic (Erlang)DL EGPRS Traffic [Erlangs] (trf_162)

Indicates the amount of resources EGPRS data consumes on average during the period

Actual DL data throughput (blocks) / nbr of blocks equivalent to 1 tsl full use in each BTS of area =

sum over msc1…6 (dl_rlc_blocks_in_ack_mode+retrans_rlc_data_blocks_dl+dl_rlc_blocks_in_unack_mode)+sum over msc7…9 of(dl_rlc_blocks_in_ack_mode+retrans_rlc_data_blocks_dl++ dl_rlc_blocks_in_unack_mode)/2-----------------------------------------------------------------------------------

sum(period_duration*60)*50; 50 blocks /sec /tsl

Counters from table(s): p_nbsc_coding_scheme

ND226


(E)GPRS Traffic (Erlang)UL EGPRS Traffic [Erlangs] (trf_161) Indicates the amount of resources EGPRS data consumes on average during the period

Actual UL data troughput (blocks) / nbr of blocks equivalent to 1 tsl full use in each BTS of area =

sum over MSC1…6 of(ul_rlc_blocks_in_ack_mode+retrans_rlc_data_blocks_ul+BAD_RLC_VALID_HDR_UL_ACK+bad_rlc_valid_hdr_ul_unack+ul_rlc_blocks_in_unack_mode)+sum over MSC7…9 of(ul_rlc_blocks_in_ack_mode+retrans_rlc_data_blocks_ul+BAD_RLC_VALID_HDR_UL_ACK+bad_rlc_valid_hdr_ul_unack+ul_rlc_blocks_in_unack_mode)/2-------------------------------------------------------------------------------------------sum(period_duration*60)*50; 50 blocks /sec /tsl


Note that Ignore_due_to_BSN and MAC_Control_block counters are not available, making this formula show smaller values

ND226


(E)GPRS Throughput (kbps)Average Effective DL Throughput per used TSL [kbps/TSL]. (trf_73f):

DL Throughput = DL payload data in (kilobits) / DL time for data transfer (sec)=

sum(a.RLC_data_blocks_DL_CS1*20+a.RLC_data_blocks_DL_CS2*30)*8 /1000 +(sum over MCS-1 (xx)*22+sum over MCS-2 (xx)*28+sum over MCS-3 (xx)*37+sum over MCS-4 (xx)*44+sum over MCS-5 (xx)*56+sum over MCS-6 (xx)*74+sum over MCS-7 (xx)*56+sum over MCS-8 (xx)*68+sum over MCS-9 (xx)*74)*8/1000-----------------------------------------------------------------------------------------------sum(a.rlc_data_blocks_dl_cs1 + a.rlc_data_blocks_dl_cs2+ a.rlc_mac_cntrl_blocks_dl – a.dummy_dl_mac_blocks_sent + a.RETRA_RLC_DATA_BLOCKS_DL_CS1 + a.RETRA_RLC_DATA_BLOCKS_DL_CS2) /50+sum over msc1…6 of (yy)/50+sum over msc7…9 of (yy)/2/50

Where: xx=b.dl_rlc_blocks_in_ack_mode+b.dl_rlc_blocks_in_unack_modeyy=b.dl_rlc_blocks_in_ack_mode+b.retrans_rlc_data_blocks_dl+b.dl_rlc_blocks_in_unack_modea=p_nbsc_packet_control_unit & b=p_nbsc_coding_scheme

ND226


(E)GPRS Throughput (kbps)Average Effective UL Throughput per used TSL[kbps/TSL]. (trf_72f):

UL Throughput = UL payload data in (kilobits) / UL time for data transfer (sec)=

sum(a.RLC_data_blocks_UL_CS1*20+a.RLC_data_blocks_UL_CS2*30)*8 /1000+ (sum over MCS-1 (xx)*22+sum over MCS-2 (xx)*28+sum over MCS-3 (xx)*37+sum over MCS-4 (xx)*44+sum over MCS-5 (xx)*56+sum over MCS-6 (xx)*74+sum over MCS-7 (xx)*56+sum over MCS-8 (xx)*68+sum over MCS-9 (xx)*74)*8/1000--------------------------------------------------------------------------------------------------------------sum(a.rlc_data_blocks_ul_cs1+ a.rlc_data_blocks_ul_cs2 + a.rlc_mac_cntrl_blocks_ul + a.BAD_FRAME_IND_UL_CS1 + a.BAD_FRAME_IND_UL_CS2+

a.BAD_FRAME_IND_UL_UNACK+a.IGNOR_RLC_DATA_BL_UL_DUE_BSN) /50 +sum over MSC1…6 of (yy)/50+ sum over MSC7…9 of (yy)/2 /50

Where:xx=b.ul_rlc_blocks_in_ack_mode+b.ul_rlc_blocks_in_unack_modeyy= b.ul_rlc_blocks_in_ack_mode+ b.retrans_rlc_data_blocks_ul+b.

bad_rlc_valid_hdr_ul_ack+b.bad_rlc_valid_hdr_ul_unack+ b.ul_rlc_blocks_in_unack_modea=p_nbsc_packet_control_unit & b=p_nbsc_coding_scheme

ND226


(E)GPRS Throughput (kbps)Average Total DL Throughput per TSL [kbps/RTSL]. (trf_90a).

It indicates the total data rate per used TSL. The figure is affected by the used Coding Scheme and Link Adaptation.

All GPRS DL data + all EGPRS DL data (kbits) / time used for DL data transfer (sec) =

sum(a.rlc_data_blocks_dl_cs1 *23 + a.rlc_data_blocks_dl_cs2 *33 + a.rlc_mac_cntrl_blocks_dl *23 + a.RETRA_RLC_DATA_BLOCKS_DL_CS1*23 + a.RETRA_RLC_DATA_BLOCKS_DL_CS2* 33)*8/1000 +(sum over MCS-1 (xx)*30+sum over MCS-2 (xx)*36+sum over MCS-3 (xx)*45+sum over MCS-4

(xx)*52+sum over MCS-5 (xx)*63+sum over MCS-6 (xx)*81+sum over MCS-7 (xx/2)*123+sum over MCS-8

(xx/2)*147+sum over MCS-9 (xx/2)*159)*8/1000-----------------------------------------------------------------------------------------------------------------------------------------

-----------sum(period_duration)*60* sum(a.rlc_data_blocks_dl_cs1 + a.rlc_data_blocks_dl_cs2 +

a.rlc_mac_cntrl_blocks_dl + a.RETRA_RLC_DATA_BLOCKS_DL_CS1 + a.RETRA_RLC_DATA_BLOCKS_DL_CS2)+sum over MSC1…6 of

(b.dl_rlc_blocks_in_ack_mode+b.retrans_rlc_data_blocks_dl+b.dl_rlc_blocks_in_unack_mode)+sum over msc7…9 of b.dl_rlc_blocks_in_ack_mode+b.retrans_rlc_data_blocks_dl+

b.dl_rlc_blocks_in_unack_mode)/2/sum(period_duration*60)*50

Where:xx= (b.dl_rlc_blocks_in_ack_mode+b.retrans_rlc_data_blocks_dl+b.dl_rlc_blocks_in_unack_mode)Counters from table(s): a=p_nbsc_packet_control_unit, b=p_nbsc_coding_scheme

ND226


(E)GPRS Throughput (kbps)Average Total UL Throughput per TSL [kbps/RTSL]. (trf_89a).

All UL data GPRS+EGPRS (kilobits) / time used for UL data transfer (sec) =

sum(a.rlc_data_blocks_ul_cs1 *23 + a.rlc_data_blocks_ul_cs2 *33 +a.rlc_mac_cntrl_blocks_ul *23 + a.BAD_FRAME_IND_UL_CS1*23 +a.BAD_FRAME_IND_UL_UNACK*23 + a.BAD_FRAME_IND_UL_CS2* 33+

a.ignor_rlc_data_bl_ul_due_bsn_CS1_aprx*23+a.ignor_rlc_data_bl_ul_due_bsn_CS2_aprx *33..+ )*8/1000+8*(sum over MCS-1 (xx)*30+sum over MCS-2 (xx)*36+sum over MCS-3 (xx)*45+sum over MCS-4 (xx)*52+sum over MCS-5 (xx)*63+sum over MCS-6 (xx)*81+sum over MCS-7 (xx/2)*123+sum over MCS-8 (xx/2)*147+sum over MCS-9 (xx/2)*159)/1000----------------------------------------------------------------------------------------------------------------------sum(period_duration)*60*sum(a.rlc_data_blocks_ul_cs1 + a.rlc_data_blocks_ul_cs2 +

a.rlc_mac_cntrl_blocks_ul + a.bad_frame_ind_ul_cs1 + a.bad_frame_ind_ul_cs2 + a.bad_frame_ind_ul_unack+ a.ignor_rlc_data_bl_ul_due_bsn)

+sum over MSC1…6 of (b.ul_rlc_blocks_in_ack_mode+b.retrans_rlc_data_blocks_ul+b.bad_rlc_valid_hdr_ul_unack+b.ul_rlc_blocks_in_unack_mode)+sum over MSC7…9 of (b.ul_rlc_blocks_in_ack_mode+b.retrans_rlc_data_blocks_ul+b.bad_rlc_valid_hdr_ul_unack+b.ul_rlc_blocks_in_unack_mode)/2 / sum(period_duration*60)*50

Counters from table(s):a=p_nbsc_packet_control_unit and b= p_nbsc_coding_scheme

ND226


EGPRS Traffic (RLC Payload)Total EGPRS RLC Data [Kbytes]. (trf_167).

Indicates the total amount of data transmitted in MCS1..9 in UL and DL. MAC blocks and RLC header Bytes are excluded to get a closer value to what the user experiences.

(sum over MCS-1 (xx)* 22+sum over MCS-2 (xx)* 28+sum over MCS-3 (xx)* 37+sum over MCS-4 (xx)* 44+sum over MCS-5 (xx)* 56+sum over MCS-6 (xx)* 74+sum over MCS-7 (xx/2)*112+sum over MCS-8 (xx/2)*136+sum over MCS-9

(xx/2)*148)))+(sum over MCS-1 (yy)* 22+sum over MCS-2 (yy)* 28+sum over MCS-3 (yy)* 37+sum over MCS-4 (yy)* 44+sum over MCS-5 (yy)* 56+sum over MCS-6 (yy)* 74+sum over MCS-7 (yy/2)*112+sum over MCS-8 (yy/2)*136+sum over MCS-9

(yy/2)*148)) /1024

Where xx=(UL_RLC_BLOCKS_IN_ACK_MODE+UL_RLC_BLOCKS_IN_UNACK_MODE)yy= (DL_RLC_BLOCKS_IN_ACK_MODE + DL_RLC_BLOCKS_IN_UNACK_MODE)


ND226


EGPRS Territory UsageTCH Capacity Usage in EGPRS traffic [%]. (trf_160).

Capacity used by EGPRS traffic / total TCH normal capacity =

sum(max of (( sum over MCS-1 (xx)+sum over MCS-2 (xx)+sum over MCS-3 (xx)+ sum over MCS-4 (xx)+sum over MCS-5 (xx)+sum over MCS-6 (xx)+

sum over MCS-7 (xx/2)+ sum over MCS-8 (xx/2)+sum over MCS-9 (xx/2)),(sum over MCS-1 (yy)+sum over MCS-2 (yy)+ sum over MCS-3 (yy)+sum over MCS-4 (yy)+sum over MCS-5 (yy)+sum over MCS-6 (yy)+sum over MCS-7 (yy/2)+sum over MCS-8 (yy/2)+ sum over MCS-9 (yy/2))))/50

/ sum(period_duration*60)100* --------------------------------------------------------------------------------------------------------

sum(decode(trx_type,0,ave_avail_TCH_sum))/sum(decode(trx_type,0,ave_avail_TCH_den)) + sum(decode(trx_type,0,ave_GPRS_channels_sum))/sum(decode(trx_type,0,ave_GPRS_channels_den))

Where: xx=(UL_RLC_BLOCKS_IN_ACK_MODE+RETRANS_RLC_DATA_BLOCKS_UL+BAD_RLC_VALID_HDR_UL_ACK+BA

D_RLC_VALID_HDR_UL_UNACK+UL_RLC_BLOCKS_IN_UNACK_MODE)yy=(DL_RLC_BLOCKS_IN_ACK_MODE+RETRANS_RLC_DATA_BLOCKS_DL+DL_RLC_BLOCKS_IN_UNACK_MODE)

Counters from table(s): p_nbsc_coding_scheme & p_nbsc_res_avail

ND226


(E)GPRS UtilizationPS utilization ratio [%]. (trf_96b).

100*Data blocks transmitted # greater one chosen, DL or UL/ (available GPRS channel time in sec)* (nbr of blocks per sec)=

sum(max of ( rlc_data_blocks_ul_cs1 + rlc_data_blocks_ul_cs2 + rlc_mac_cntrl_blocks_ul + BAD_FRAME_IND_UL_CS1

+ BAD_FRAME_IND_UL_CS2 + BAD_FRAME_IND_UL_UNACK + IGNOR_RLC_DATA_BL_UL_DUE_BSN, +( sum over MCS-1 (xx)+ sum over MCS-2 (xx)+ sum over MCS-3 (xx)+ sum over MCS-4 (xx)+ sum over MCS-5 (xx)+ sum over MCS-6 (xx)+ sum over MCS-7 (xx/2)+ sum over MCS-8 (xx/2)+ sum over MCS-9 (xx/2)), rlc_data_blocks_dl_cs1 + rlc_data_blocks_dl_cs2+ rlc_mac_cntrl_blocks_dl + RETRA_RLC_DATA_BLOCKS_DL_CS1 + RETRA_RLC_DATA_BLOCKS_DL_CS2) +( sum over MCS-1 (yy)+ sum over MCS-2 (yy)+ sum over MCS-3 (yy)+ sum over MCS-4 (yy)+ sum over MCS-5 (yy)+ sum over MCS-6 (yy)+ sum over MCS-7 (yy/2)+ sum over MCS-8 (yy/2)+ sum over MCS-9 (yy/2) ))

100*--------------------------------------------------------------------------------------------------------------------------------------- %

sum(decode(trx_type,0,ave_GPRS_channels_sum))/sum(decode(trx_type,0,ave_GPRS_channels_den))

*sum(a.period_duration*60)*50

Where xx=c.(UL_RLC_BLOCKS_IN_ACK_MODE+RETRANS_RLC_DATA_BLOCKS_UL+BAD_RLC_VALID_HDR_UL_UNACK+UL_RLC_BLOCKS_IN_UNACK_MODE)yy=c.(DL_RLC_BLOCKS_IN_ACK_MODE + RETRANS_RLC_DATA_BLOCKS_DL + DL_RLC_BLOCKS_IN_UNACK_MODE)

Counters from table(s): a= p_nbsc_res_avail & b= p_nbsc_packet_control_unit & c= p_nbsc_coding_scheme

ND226


(E)GPRS TBF RetainabilityDL Drops (MS lost) per 10Kbytes. (tbf_28c).

Indicates the amount of TBF releases due to no response from the MS. It can indicate bad radio conditions when high amount in comparison with data volume.

sum(DL_TBF_rel_due_no_resp_MS)---------------------------------------------------------------------------------------------------------------sum(rlc_data_blocks_dl_cs1*20 + rlc_data_blocks_dl_cs2*30 ) + (sum over MCS-1 (yy)*

22+sum over MCS-2 (yy)* 28+sum over MCS-3 (yy)* 37+sum over MCS-4 (yy)* 44+sum over MCS-5 (yy)* 56+sum over MCS-6 (yy)* 74+sum over MCS-7 (yy/2)*112+sum over MCS-8 (yy/2)*136+sum over MCS-9 (yy/2)*148) / 10240

Where yy=(DL_RLC_BLOCKS_IN_ACK_MODE + DL_RLC_BLOCKS_IN_UNACK_MODE)Counters from table(s): p_nbsc_packet_control_unit & p_nbsc_coding_scheme

Note: same problems as described in UL.

ND226


(E)GPRS TBF RetainabilityUL Drops (MS lost) per 10Kbytes. (tbf_27c).

Indicates the amount of TBF releases due to no response from the MS. It can indicate bad radio conditions when high amount in comparison with data volume.

sum(UL_TBF_rel_due_no_resp_MS)---------------------------------------------------------------------------------------------------------------(sum(rlc_data_blocks_ul_cs1*20 + rlc_data_blocks_ul_cs2*30 ) + (sum over

MCS-1 (xx)* 22+ sum over MCS-2 (xx)* 28+ sum over MCS-3 (xx)* 37+ sum over MCS-4 (xx)*

44+ sum over MCS-5 (xx)* 56+ sum over MCS-6 (xx)* 74+ sum over MCS-7

(xx/2)*112+ sum over MCS-8 (xx/2)*136+ sum over MCS-9 (xx/2)*148))/ 10240

Where xx=(UL_RLC_BLOCKS_IN_ACK_MODE + UL_RLC_BLOCKS_IN_UNACK_MODE)Counters from table(s): p_nbsc_packet_control_unit & p_nbsc_coding_scheme

Note: Slow cell- reselection can increment the denominator. The KPI compares TBF with RLC blocks although they are quite independent

ND226


EDAP Availability• KPIs related to EDAP are focused on Availability, Usage of the resources

and Amount of requests that cannot be granted due to capacity limitation of the EGPRS Dynamic Abis Pool.

• All counters are from p_nbsc_dynamic_abis

• On EDAP Availability:

Average available of 16kbps PCM sub-TSLs in DAP

076000 TOTAL_PCM_SUBTSLS_IN_EDAP

When UL and DL Dynamic Abis resource allocation occurs. The counter is incremented by the size of the Dynamic Abis Pool.

ND280


EDAP Usage

• On EDAP Usage:

Average usage of DL Dynamic Abis Pool [%] (dap_1). Average amount of EDAP resources used for DL data transfer during the period.

Sum(AVERAGE_DL_EDAP_USAGE_SUM) -----------------------------------------------

Sum(AVERAGE_EDAP_USAGE_DEN)

Peak usage of DL Dynamic Abis Pool [%]. Peak usage of 16 kbit/s PCM subTSLs in the downlink direction.

076004 PEAK_DL_EDAP_USAGE

ND280


EDAP Usage

• On EDAP Usage:

Average usage of UL Dynamic Abis Pool [%] (dap_2). Average amount of EDAP resources used for UL data transfer during the period.

Sum(AVERAGE_UL_EDAP_USAGE_SUM)------------------------------------------------


Peak usage of UL Dynamic Abis Pool[%]. Peak usage of 16 kbit/s PCM subTSLs in the uplink direction.

076005 PEAK_UL_EDAP_USAGE

ND280


EDAP RejectionNumber of UL TBFs without EDAP resources. Number of cases where scheduled UL TBF cannot be serviced due to lack of EDAP resources

076006 UL_TBFS_WITHOUT_EDAP_RES

Number of DL TBFs without EDAP resources. Number of cases where scheduled DL TBF that requires EDAP channels cannot use any EDAP channel

076007 DL_TBFS_WITHOUT_EDAP_RES

Number of cases where required EDAP channels cannot be granted to DL TBF. Updated always (on every scheduling round) when EDAP resources for TBF cannot be granted

076008 DL_TBFS_WITH_INADEQ_EDAP_RES

ND280

Lack of EDAP resources:

1.EDAP slot shortage. EDAP size does not meet capacity needs.

2.Blocking. EDAP 16kb slots can be blocked by channel test mode, 64 kb DSP conn. guard mode or TRX 16kb guard period.

3.Lack of free PCU DSP channels

On TBF requests:


Traffic Measurements – Drive Tests

High C/I

Average C/I

Low C/I

FTP Download Results

Download time 47s

Application Throughput 87 Kbit/s

Data Throughput 90 Kbit/s

Overhead 3 %


Download time 175s

Application Throughput 24 Kbit/s

Data Throughput 26,1 Kbit/s

Overhead 12 %


Download time 74s

Application Throughput 55.2 Kbit/s

Data Throughput 57 Kbit/s

Overhead 3 %

MET report


Traffic Measurements – ConclusionsAre the network figures below acceptable?

• Attach, PDP context and RAU success rate• Ratio of total and effective throughput• Retainability• Territory usage and utilization• EDAP performance• Available PCU capacity• Drive test results with cell-reselection


EDGE Capacity Optimization

Accessibility improvementMaximizing TSL Capacity (data rate)

Maximizing PSW territory with Proper Network Utilization

Improvement of user perception (higher layers)


Signalling Load and Capacity Requirements

Random AccessAccess Grant

Paging Channel

Existing GSMLoad

GPRS Attach/Detach

PDP ContentActivation

Paging

Routing AreaUpdate

Cell Update

GPRS DataTransfer

(Application)

Available capacity on signalling channels•TRXSIG•PBCCH


Accessibility – One / Two Phase AccessGPRS: one-phase access is possible, but only 1 TSL can be allocated to the TBF. Timeslot reconfiguration would be needed for multi slot allocation. EGPRS: two-phase access is mandatory

Using PBCCH improves the following aspects:• GPRS: one-phase access is possible. Network can allocate more than one

TSL to the UL TBF• EGPRS: one-phase access is possible only if “EGPRS Packet Channel

Request” (EPChR) is supported by the network. If EPChR is not supported, then EGPRS is forced to use two-phase access even if working in the PCCCH.

Gain• GPRS: bringing PBCCH into use makes an improvement in GPRS performance. This

gain is obtained from the transmission side due to timeslot allocation. In CCCH case only one TSL is assigned, while in PBCCH case we have two. This explains the increasing importance of the gain as the ping packet size becomes bigger

• EGPRS: In this case, two timeslots are assigned in both situations. Therefore, there is no transmission gain and all the improvement is due to the use of one-phase access. The results show no clear gain associated with the use of PBCCH in this particular case. This could be due to effects of the changing radio conditions that we get in the driving test. A stationary case could help solve the issue, but it was not possible to perform it due to time constraints


Accessibility – One / Two Phase Access

Route A, One phase access Ping RTT & Success RatesPBCCH-channel in use, Average C/I was 11.8 dB

0500

1 0001 5002 0002 5003 0003 500

Ping 32B Ping 256B Ping 1448BPing Payload Size (bytes)

RTT

(ms)

EdgeGprs

94% 96%96%

96%

87% 88%

Route A, Two phase access Ping RTT & Success RatesPBCCH-channel not in use, Average C/I was 11.8 dB

0500

1 0001 5002 0002 5003 0003 5004 000

Ping 32B Ping 256B Ping 1448BPing Payload Size (bytes)

RTT

(ms)

EdgeGprs

96%99%

98%98%

92%81%


Accessibility - TBF Release DelayIf there is not any RLC block received, the TBF will not be released immediately, but it can be kept alive for a given time period. There are two modifiable parameters related to Delayed TBF feature among PRFILE parameters:

• DL_TBF_RELEASE_DELAY (0,1-5sec, def 1s) This parameter is used to adjust the delay in downlink TBF release. An appropriate delay time increases the system performance, since the possibly following uplink TBF can be established faster, and frequent releases and re-establishments of downlink TBF can be avoided.

• UL_TBF_RELEASE_DELAY (0,1-3sec, def 0,5s) This parameter is used to adjust the delay in uplink TBF release. An appropriate delay time increases the system performance, since the possibly following downlink TBF can be established faster.

(in S9 till S10.5 CD4.0 it is hardcoded)This feature can improve the performance of interactive services like Vodafone Live.


PSW Optimization for Maximizing TSL Capacity

IntroductionRetransmission

MCSs and Link AdaptationIncremental Redundancy

MultiplexingEDAP, PCU


PSW Optimization for Maximizing TSL Capacity Introduction

The following events have impact on the PSW TSL capacity:

GSM Network• Low signal level – sensitivity threshold• Low C/I

BSS PSW Network• Retransmission

• MCSs and Link Adaptation• Incremental Redundancy

• Multiplexing• EDAP • PCU

GSM Network Optimization


RLC RetransmissionsRLC Retransmission (MS - PCU)

The TSL data rate can be improved by reduced retransmission ratio

• Proprietary Ack/Nack process with polling• Bad quality

• Retransmission of bad blocks (lost/corrupted)• Used to calculate the BLER• Link Adaptation and Incremental Redundancy

are used for minimazing the effect of bad quality

SGSN

Gb

BSC PCU

BTS


EGPRS RLC statsDL/UL ACK EGPRS Block Error Ratio [%] (rlc_21), (rlc_20). Indicates BLER for DL/UL data transmission for each MCS.

Sum over MCS-n (RETRANS_RLC_DATA_BLOCKS_DL)

100*--------------------------------------------------------- Sum over MCS-n (DL_RLC_BLOCKS_IN_ACK_MODE + RETRANS_RLC_DATA_BLOCKS_DL)where n can be from 1 to 9Counters from table(s):p_nbsc_coding_scheme

Sum over MCS-n (RETRANS_RLC_DATA_BLOCKS_UL)

100*-------------------------------------------------------- Sum over MCS-n (UL_RLC_BLOCKS_IN_ACK_MODE + RETRANS_RLC_DATA_BLOCKS_UL)

where n can be from 1 to 9.Counters from table(s):p_nbsc_coding_scheme

ND 275


(E)GPRS BLERUL ACK EGPRS Block Error Ratio [%] (rlc_18) Ratio of retransmitted UL blocks to all blocks sent in EGPRS coding schemes.

sum over MCS1 to 9 (RETRANS_RLC_DATA_BLOCKS_UL) 100 * ------------------------------------------------------------------------------------------- Sum over MCS1 to 9 (UL_RLC_BLOCKS_IN_ACK_MODE +

RETRANS_RLC_DATA_BLOCKS_UL)

Counters from table(s): p_nbsc_coding_scheme DL ACK EGPRS Block Error Ratio [%] (rlc_19) Ratio of retransmitted DL blocks to all blocks sent in EGPRS coding schemes.

Sum over MCS1 to 9 (RETRANS_RLC_DATA_BLOCKS_DL) 100 * ---------------------------------------------------------------------------------------------- Sum over MCS1 to 9 (DL_RLC_BLOCKS_IN_ACK_MODE

+RETRANS_RLC_DATA_BLOCKS_DL)


ND 226


MCS and Link Adaptation

Link Adaptation introductionMCS (CS) measurements

Parameters and its impact on network performanceLink Algorithm Response Time


Link Adaptation• The task of the LA algorithm is to select the optimal MCS for each

radio condition to maximize channel throughput and reduce retransmission

• To maintain good throughput the goal for the LA algorithm is to adapt to situations where signal strength compared to interference level is changing within time

• LA adapts to path loss and shadowing but not fast fading This corresponds to the "ideal LA" curves in link level simulations

• Incremental Redundancy (IR) is better suited to compensate for fast fading

• EGPRS LA is implemented in the Packet Control Unit (PCU)• In GSM Specification, there is full support for Bit Error Probability

(BEP) based Link Adaptation (LA) algorithm


LA- MS reported BEP interpretation3GPP TS 05.08 establishes following mapping tables:

Range of Expected MEAN_BEP

log10(actual BEP) intervalMEAN_BEP_0 > -0.60 MEAN_BEP_0/1/2 80%

MEAN_BEP_1 -0.64 -- -0.60 MEAN_BEP_1/0/2/3 80%

MEAN_BEP_2 -0.68 -- -0.64 MEAN_BEP_2/0/1/3/4 80%

MEAN_BEP_3 -0.72 -- -0.68 MEAN_BEP_3/1/2/4/5 80%

MEAN_BEP_4 -0.76 -- -0.72 MEAN_BEP_4/2/3/5/6 80%

MEAN_BEP_5 -0.80 -- -0.76 MEAN_BEP_5/3/4/6/7 80%

MEAN_BEP_6 -0.84 -- -0.80 MEAN_BEP_6/4/5/7/8 80%

MEAN_BEP_7 -0.88 -- -0.84 MEAN_BEP_7/5/6/8/9 80%MEAN_BEP_8 -0.92 -- -0.88 MEAN_BEP_8/6/7/9/1

070%

MEAN_BEP Probability that the expected MEAN_BEP is

reported shall not be lower than:

MS reported Mean_BEP and Var_BEP from

Nethawk traces

Mean_BEP VAR_BEPRange of Log10 (actual BEP) CV_BEP

Assigned MEAN_BEP

Assigned CV_BEP

E:.002 <BEP<.005 0 <VAR< .5 -2,30 0,5 MEAN_BEP_22 CV_BEP_6E:.002 <BEP<.005 .5<VAR<1.0 -2,30 1 MEAN_BEP_22 CV_BEP_4E:.001 <BEP<.002 .5<VAR<1.0 -2,70 1 MEAN_BEP_25 CV_BEP_4E:.001 <BEP<.002 .5<VAR<1.0 -2,70 1 MEAN_BEP_25 CV_BEP_4E:.001 <BEP<.002 .5<VAR<1.0 -2,70 1 MEAN_BEP_25 CV_BEP_4E:.002 <BEP<.005 0 <VAR< .5 -2,30 0,5 MEAN_BEP_22 CV_BEP_6E:.002 <BEP<.005 .5<VAR<1.0 -2,30 1 MEAN_BEP_22 CV_BEP_4E:.005 <BEP<.010 .5<VAR<1.0 -2,00 1 MEAN_BEP_21 CV_BEP_4E:.002 <BEP<.005 0 <VAR< .5 -2,30 0,5 MEAN_BEP_22 CV_BEP_6E:.005 <BEP<.010 0 <VAR< .5 -2,00 0,5 MEAN_BEP_21 CV_BEP_6E:.010 <BEP<.021 0 <VAR< .5 -1,68 0,5 MEAN_BEP_18 CV_BEP_6

CV_BEP 0 2.00 > std(BEP)/mean(BEP) > 1.75CV_BEP 1 1.75 > std(BEP)/mean(BEP) > 1.50

CV_BEP 2 1.50 > std(BEP)/mean(BEP) > 1.25






Select MCS for

next RLC

Block


Coding scheme (S10.5)

UL RLC DATA BLOCKS

Measurement Coding Scheme (S10 opt) is related to feature BSS10083 EGPRS (EDGE).

Bad headerC79008-c79006

Bad, valid header c79006 Bad header C79005

BAD_RLC_BAD_HDR_UL_UNACK

Bad,valid header c79004 BAD_RLC_VALID_HDR_UL_UNACK

Retransm.c79008 RETRANS_RLC_DATA_BLOCKS_UL

retransm. C79009 RETRANS_RLC_DATA_BLOCKS_DL

Valid c79000 DL_RLC_BLOCKS_IN_ACK_MODE

UNACK c79001 DL_RLC_BLOCKS_IN_UNACK_MODEACK

ACK

Valid c79002UL_RLC_BLOCKS_IN_ACK_MODE

UNACK

Valid c79003 UL_RLC_BLOCKS_IN_UNACK_MODE

Initial MCS is controlled by the operator. ( Parameters: Initial MCS for ACK mode and Initial MCS for UNACK mode)For ACK the LA algoritm optimises channel thruput For NACK BLER tried to be kept under a limit (parameter: Max BLER in unack mode)

DL RLC DATA BLOCKS

In this casethe MCS isnot known.

In this case theMCS is not known (reported as MCS0).

Bad headerC79007

Note: In case of MCS7-9 there are 2 RLC data blocks in a radio block. Ref. 03.64 chapter 6.5.5.1.2

Object level:BTS/MCS 0 MCS-11 MCS-22 MCS-33 MCS-44 MCS-55 MCS-66 MCS-77 MCS-88 MCS-99 MCS-5-7 10 MCS-6-9

EGPRS IncrementalRedundancy modes(not in S10?)

In DL packet transfer the PCU selects the MCS for each DL radio block within a TBF.

In the UL the PCU commands the MS to use a certain MCS in the PACKET UPLINKASSIGNMENT messageand can change the MCS in the PACKET UPLINKACK/NACK or PACKET TIMESLOT RECONFIGURE message.

Picture: coding_scheme_measAuthor: J.Neva 10/2001PMWG approval.: 1.0 2.10.2001

radio block block data blocks bit Abissize payload in a radio rate tsls(bytes) (bytes) block (kbps) needed

30 22 1 8.8 136 28 1 11.2 245 37 1 14.8 252 44 1 17.6 263 56 1 22.4 281 74 1 29.6 3

123 56 2 44.8 4147 68 2 54.9 5159 74 2 59.2 5

IGNOR_RLC_DATA_BL_UL_DUE_BSN c72072

Problem: common counter for GPRS and EGPRS

RLC dummy MAC for delayed TBF (MCS1 always)- no counter yet S11.5?

DL RLC MAC control blocks S11.5?

UL RLC MAC control blocks S11.5?

http://wwwdoc.ntc.nokia.com/draft/s10/en/REFERENCES/DN0163592/dn0163592-11-1.htm

http://nea.ntc.nokia.com/cgi-bin/cgiwrap/neva/counters?79006











EGPRS MCSsDL RLC Data MCS-n [kbytes] (trf_141)Amount of data transmitted in DL at the indicated MCS. For each MCS:

sum over MCS-n (xx) * nn / 1024 Where:xx =DL_RLC_BLOCKS_IN_ACK_MODE +RETRANS_RLC_DATA_BLOCKS_DL +DL_RLC_BLOCKS_IN_UNACK_MODEwhere n can be from 1 to 9 where nn is multiplier for each Coding Schemenn for each MCS:

» MCS-1 22» MCS-2 28» MCS-3 37» MCS-4 44» MCS-5 56» MCS-6 74» MCS-7 56» MCS-8 68» MCS-9 74 Counters from

table(s):p_nbsc_coding_scheme

ND 275


EGPRS MCSsUL RLC Data MCS-n [Kbytes] (trf_140)Indicates the amount of UL data transmitted at the indicated MCS. For each MCS following expression can be applied:

sum over MCS-n (xx) *nn / 1024

Where:xx =UL_RLC_BLOCKS_IN_ACK_MODE + RETRANS_RLC_DATA_BLOCKS_UL +BAD_RLC_VALID_HDR_UL_UNACK + UL_RLC_BLOCKS_IN_UNACK_MODEwhere n can be from 1 to 9

where nn is multiplier for eachCoding Scheme,nn for each MCS:

» MCS-1 22» MCS-2 28» MCS-3 37» MCS-4 44» MCS-5 56» MCS-6 74» MCS-7 56» MCS-8 68» MCS-9 74 Counters from

table(s):p_nbsc_coding_scheme

ND 275


Link Adaptation Parameters

Initial MCS for acknowledged mode MCA

Parameter Name Abbreviation

Initial MCS used at the beginning of a TBF for acknowledged mode

Description

1 .. 9, step 1

Range and Step

Initial MCS for unacknowledged mode MCU Initial MCS used at the beginning of a TBF for unacknowledged mode 1 .. 9, step 1

Maximum BLER in acknowledged mode BLA Maximum block error rate of first transmission in acknowledged mode

10 .. 100%, step 1

Maximum BLER in unacknowledged mode BLU

Maximum block error rate of first transmission in unacknowledged

mode10 .. 100%, step

1

mean BEP offset GMSK MBG

Adjust the MCS and modulation preferences. This is the offset added to reported GMSK mean BEP values before BEP table lookups. The value applies to both uplink and downlink

directions

-31 .. 31, step 1

mean BEP offset 8PSK MBP

Adjust the MCS and modulation preferences. This is the offset added to reported 8PSK mean BEP values before BEP table lookups. The value applies to both uplink and downlink

directions

-31 .. 31, step 1

ELAEGPRS Link Adaptation Enabled Enables EGPRS Link Adaptation for Ack mode or Ack and Unack mode 0,1,2, default 2


Link Adaptation - Initial MCSInitial MCS for acknowledged/ Unacknowledged mode (MCA/MCU)

LA uses always the same MCS at the beginning of the TBF using the parameter MCA and MCU depending on the RLC mode, e.g Acknowledge or Un-acknowledge. The Optimal MCS depends on the radio conditions and the type of traffic

Studies have been done to determine the optimal value for this parameter. Some of the conclusions reached are listed here:

• With FTP traffic model, MCS-9 is the best initial coding scheme to be used with IR

• With WWW traffic model, MCS-7 is the best initial coding scheme to be used with IR

• The initial coding scheme cannot be configured based on the service, so the more conservative value for the initial coding scheme is normally chosen as default (i.e. MCS-7)


Link Adaptation - Initial MCS

EGPRS; 2-slot mobiles; FTP model

0

10

20

30

40

50

60

70

80

90

Thro

ughp

ut [k

bit/s

]

Trh (LA) 81,9 77,2 60,1 53,0 43,7 36,9

Thr (noLa) 77,7 76,7 56,4 52,8 41,1 36,0

Realistic IR Memory No IR Realistic IR

Memory No IR Realistic IR Memory No IR

MC

S-9

MC

S-9

MC

S-7

MC

S-7

MC

S-7

MC

S-9

MC

S-9

MC

S-9

MC

S-9

MC

S-9

MC

S-9

MC

S-9

low load medium load high load

Effect of Initial MCS on FTP:



Results for MCA=5, 7 and 9 respectively.Different MCA cause the TBF to be established at the operator defined value, but the optimum MCS is reached rapidly.

Nethawk data averaged to smooth graphs.



LA Performance MCA=1

0

10

20

30

40

50

60

0 5 10 15 20 25 30

C/I (dB)

Thro

ughp

ut (K

bits

/s)

MCA=1 BLA=90MCA=1 BLA=50MCA=1 BLA=30MCA=1 BLA=10

FTP DL 1Mb 2TSL

Very stable behavior in low C/I

but poor performance when

C/I is high

No big differences for different BLA

values.

Changing MCS more or less

frequently does not make a big difference since

the starting point is MCS1


Link Adaptation - Initial MCSLA Performance MCA=7

0

10

20

30

40

50

60

70

80

90

0 5 10 15 20 25 30

C/I (dB)

Thro

ughp

ut (K

bits

/s)


Much better performance for

high C/I, but lower throughputs for

low C/I

BLA=50 provides a very good

performance for high C/I. BLA=90 is

never optimal

Big differences for different BLA values.

FTP DL 1Mb 2TSL


Link Adaptation - Initial MCSLA Performance MCA=9

0

10

20

30

40

50

60

70

80

90

0 5 10 15 20 25 30

C/I (dB)

Thro

ughp

ut (K

bits

/s)


Better throughputs overall, but very

unstable in low C/I conditions

No big differences between different

values of BLA

FTP DL 1Mb 2TSL


Link Adaptation - Maximum BLERMaximum BLER in acknowledged/ unacknowledged mode (BLA/BLU).• Operator definable Maximum BLER for Ack and Unack Mode, BLA

and BLU, set the upper limit for the acceptable BLER when Link Adaptation algorithm selects the optimum MCS.

• When BLA is set to 90% the 3rd Step of the LA algorithm, in which BEP tables are mapped to BLER for each MCS, is very less restrictive.


Link Adaptation - Maximum BLER

LA performance BLA = 90%

0

20

4060

80

100

0 10 20 30

C/I (dB)

Thro

ughp

ut (k

bit/s

)

MCA1MCA7MCA9

NTN Results


Link Adaptation - Maximum BLER

LA performance BLA = 50%

0

20

4060

80

100

0 10 20 30

C/I (dB)

Thro

ughp

ut (k

bit/s

)

MCA1MCA7MCA9

NTN Results


Link Adaptation - Mean BEP Offset for GMSK/8PSK

Mean BEP offset GMSK/8PSK (MBG/MBP):• The offset is added to Mean_BEP values reported by the MS before

mapping into the LookUp tables.

Mean_BEP (LookUp) = Mean_BEP ( MS) + Mean BEP offset 8PSK

• Positive MBP/MBG will simulate worse BEP than actual radio conditions impose, therefore more robust MCS, lower MCS, will be generated by LA procedure. E.g average used MCS in the network will be lower.

• And vice versa, by setting MBP/MBG to negative values we simulate better radio conditions that existing, and therefore LA will produce less robust, or higher, MCS.


Mean_BEP_offset_GSMK & Mean_BEP_offset_8PSK

FTP ThroughputMBG = 0, different MBP

020406080

100

MBP = -20MCS4

MBP = -10MCS4

MBP = 0MCS7

MBP = 10MCS9

MBP = 20MCS9

kbit/

s

C/I adjusted so MCS7 is chosen by the LA algorithm (C/I = 15 dB, MCA = 9)

NTN Results


Mean_BEP_offset_GSMK & Mean_BEP_offset_8PSK

C/I adjusted so MCS7 is chosen by the LA algorithm (C/I = 15 dB, MCA = 9)

Setting MBP to –31 forces the modulation to be GMSK

FTP Throughput(MBP = -31, different MBG)

05

101520253035

MBG = -31 MCS1 MBG = -23 MCS2 MBG = -20 MCS4

kbit/

s

NTN Results


BEP Filtering PeriodAnother mean of optimizing the performance of EDGE is by the filtering length of the quality control measurements.

Bit error probability filter averaging period (BEP)With this parameter you define the bit error probability filter averaging period for EGPRS channel quality measurements.

Range:1,2,3,4,5,7,10,12,15,20,25, Default:10

• A rather shorter filtering period would suit better fast MS, and a longer period for slower MS.

• Although it is a POC parameter it has effect on EDGE LA procedure.


Incremental Redundancy

Incremental Redundancy introductionIncremental Redundancy parameters


Incremental Redundancy - Introduction• A re-segment bit is included within each

PACKET UPLINK ACK/NACK, PACKET UPLINK ASSIGNMENT and PACKET TIMESLOT RECONFIGURE messages in the DL.

• The re-segment bit is used to set the ARQ mode to type I or type II (incremental redundancy) for uplink TBFs. For retransmissions.

• Setting the re-segment bit to ‘1’ (type I ARQ) requires the mobile station to use an MCS within the same family as the initial transmission and the payload may be split.

• For retransmissions, setting the resegment bit to ‘0’ (type II ARQ) requires the mobile station shall use an MCS within the same family as the initial transmission without splitting the payload even if the network has commanded it to use MCS‑1, MCS‑2 or MCS‑3 for subsequent RLC blocks.

NOTE: This bit is particularly useful for networks with uplink IR capability since it allows combining on retransmissions.


Schemeusedfor

initialtransmi

ssion

Scheme to use for retransmissions after switching to a different MCS

MCS-9Commanded

MCS-8Commanded

MCS-7Commanded

MCS-6-9

Commanded

MCS-6Commanded

MCS-5-7

Commanded

MCS-5Commanded

MCS-4Commanded

MCS-3Commanded

MCS-2Commanded

MCS-1Commanded

MCS-9 MCS-9 MCS-6 MCS-6 MCS-6 MCS-6 MCS-3 MCS-3 MCS-3 MCS-3 MCS-3 MCS-3MCS-8 MCS-8 MCS-8 MCS-6

(pad)MCS-6(pad)

MCS-6(pad)

MCS-3(pad)

MCS-3(pad)

MCS-3(pad)

MCS-3(pad)

MCS-3pad)

MCS-3(pad)

MCS-7 MCS-7 MCS-7 MCS-7 MCS-5 MCS-5 MCS-5 MCS-5 MCS-2 MCS-2 MCS-2 MCS-2MCS-6 MCS-9 MCS-6 MCS-6 MCS-9 MCS-6 MCS-3 MCS-3 MCS-3 MCS-3 MCS-3 MCS-3MCS-5 MCS-7 MCS-7 MCS-7 MCS-5 MCS-5 MCS-7 MCS-5 MCS-2 MCS-2 MCS-2 MCS-2MCS-4 MCS-4 MCS-4 MCS-4 MCS-4 MCS-4 MCS-4 MCS-4 MCS-4 MCS-1 MCS-1 MCS-1MCS-3 MCS-3 MCS-3 MCS-3 MCS-3 MCS-3 MCS-3 MCS-3 MCS-3 MCS-3 MCS-3 MCS-3MCS-2 MCS-2 MCS-2 MCS-2 MCS-2 MCS-2 MCS-2 MCS-2 MCS-2 MCS-2 MCS-2 MCS-2MCS-1 MCS-1 MCS-1 MCS-1 MCS-1 MCS-1 MCS-1 MCS-1 MCS-1 MCS-1 MCS-1 MCS-1

Schemeusedfor

Initialtransmi

ssion

Scheme to use for retransmissions after switching to a different MCS

MCS-9Commanded

MCS-8Commanded

MCS-7Commanded

MCS-6-9

Commanded

MCS-6Commanded

MCS-5-7

Commanded

MCS-5Commanded

MCS-4Commanded

MCS-3Commanded

MCS-2Commanded

MCS-1Commanded

MCS-9 MCS-9 MCS-6 MCS-6 MCS-6 MCS-6 MCS-6 MCS-6 MCS-6 MCS-6 MCS-6 MCS-6MCS-8 MCS-8 MCS-8 MCS-6

(pad)MCS-6(pad)

MCS-6(pad)

MCS-6(pad)

MCS-6(pad)

MCS-6(pad)

MCS-6(pad)

MCS-6(pad)

MCS-6(pad)

MCS-7 MCS-7 MCS-7 MCS-7 MCS-5 MCS-5 MCS-5 MCS-5 MCS-5 MCS-5 MCS-5 MCS-5MCS-6 MCS-9 MCS-6 MCS-6 MCS-9 MCS-6 MCS-6 MCS-6 MCS-6 MCS-6 MCS-6 MCS-6MCS-5 MCS-7 MCS-7 MCS-7 MCS-5 MCS-5 MCS-7 MCS-5 MCS-5 MCS-5 MCS-5 MCS-5MCS-4 MCS-4 MCS-4 MCS-4 MCS-4 MCS-4 MCS-4 MCS-4 MCS-4 MCS-4 MCS-4 MCS-4MCS-3 MCS-3 MCS-3 MCS-3 MCS-3 MCS-3 MCS-3 MCS-3 MCS-3 MCS-3 MCS-3 MCS-3MCS-2 MCS-2 MCS-2 MCS-2 MCS-2 MCS-2 MCS-2 MCS-2 MCS-2 MCS-2 MCS-2 MCS-2MCS-1 MCS-1 MCS-1 MCS-1 MCS-1 MCS-1 MCS-1 MCS-1 MCS-1 MCS-1 MCS-1 MCS-1

Re-segment bit to "1" -> re-segmentation active

Re-segment bit to "0" -> re-segmentation non active046: 0063 EGPRS RE-SEGMENTATION.

Not modifiable parameter!

ETSI 04.60

ARQ Type II(Incremental Redundancy)

ARQ Type I(No Incremental Redundancy)

LA and Retransmissions on UL


Multiplexing

IntroductionTBF reallocation causes

Multiplexing measurementsMultiplexing parameters


Multiplexing - Introduction• Channel Allocation Algorithm tends to separate EDGE TBFs and

GPRS TBFs on different RTSL to avoid multiplexing, if only one PS Territory exists in the cell or there is high load.

• Synchronisation (every 18th Radio Block)• UL GPRS USF on DL EGPRS TBF• TSL sharing - GPRS/EGPRS TBFs’ multiplexing on a TSL

• The algorithm checks the need for re-allocation every TBF_LOAD_GUARD_THRSHLD, in order to separate sessions.

Best effort traffic - FTP traffic model

0

0.2

0.4

0.6

0.8

1

1.2

0 20 40 60 80 100

(E)GPRS Channel Utilisation (%)

Rate

Red

uctio

n (%

)

Reuse 2/6

Reuse 3/9

Reuse 4/12

Best effort traffic - FTP traffic model

0

0.2

0.4

0.6

0.8

1

1.2

0 20 40 60 80 100

(E)GPRS Channel Utilisation (%)

Rate

Red

uctio

n (%

)

Reuse 2/6

Reuse 3/9

Reuse 4/12

Rate reduction is due to the multiplexing of more than one user per TSL


Multiplexing - TBF Re-Allocation CausesExample of TBF re-allocation when GPRS/EGPRS mux, :GTBF1 weight=1,0ETBF1 weight=0,25GTBF2 weight=1,0Mux Penalty=2,5

BTS Ch.Load:GTBF1 Ch Load:

BTS Ch Load= sum ( TBF weights + penalties) for each RTSLGTBF1 Ch Load= sum(TBF weights + penalties) for each RTSL=

1,0+0,25+2,5=3,75

Average BTS Ch.Load = sum (TBF weights + penalties) / RTSL in PSW= (1,0+1,0+1,25+ 1,25+1,25)/5=1,15

For GTBF1: Average BTS Ch. Load=1,15 < Average TBF Ch Load=3,75 ???

YES! Then GTBF1 is re-allocated to RTSL 3 & 4!

GTBF1 GTBF1ETBF1 ETBF1 ETBF1

GTBF2 GTBF2 GTBF23 4 5 6 7

1.0 1.0 1.25 1.25 1.253.75 3.75


MultiplexingGMSK RLC Data Share[%] (rlc_41). Share of MCS1..4 out of all RLC data transmitted in EGPRS. The MCS used can be downgraded due to LA as well as MS synchronisation and GPRS/EGPRS mux when DL EGPRS TBF co-exists with UL GPRS TBF.

( sum over MCS-1 (xx)* 22+sum over MCS-2 (xx)* 28+sum over MCS-3 (xx)* 37+sum over MCS-4 (xx)* 44)

100* -------------------------------------------------------------------------------------------------------------------------------------

(sum over MCS-1 (xx)* 22+sum over MCS-2 (xx)* 28+sum over MCS-3 (xx)* 37+sum over MCS-4 (xx)* 44+sum over MCS-5 (xx)* 56+sum over MCS-6 (xx)* 74+sum over MCS-7 (xx/2)*112+sum over MCS-8 (xx/2)*136+sum over MCS-9 (xx/2)*148)

Where:xx =UL_RLC_BLOCKS_IN_ACK_MODE +RETRANS_RLC_DATA_BLOCKS_UL +BAD_RLC_VALID_HDR_UL_UNACK +UL_RLC_BLOCKS_IN_UNACK_MODE +DL_RLC_BLOCKS_IN_ACK_MODE +RETRANS_RLC_DATA_BLOCKS_DL +DL_RLC_BLOCKS_IN_UNACK_MODE Counters from table(s): p_nbsc_coding_scheme

ND226


MultiplexingGMSK RLC Data Block Share[%] (rlc_39). Uses the RLC Data block to calculate share of GMSK blocks used during the EGPRS data transfer.

Sum over MCS 1..4 (UL_RLC_BLOCKS_IN_ACK_MODE + RETRANS_RLC_DATA_BLOCKS_UL +BAD_RLC_VALID_HDR_UL_UNACK +UL_RLC_BLOCKS_IN_UNACK_MODE +DL_RLC_BLOCKS_IN_ACK_MODE +RETRANS_RLC_DATA_BLOCKS_DL +DL_RLC_BLOCKS_IN_UNACK_MODE)

100*--------------------------------------------------------------------------------------Sum over MCS 1..9 (UL_RLC_BLOCKS_IN_ACK_MODE + RETRANS_RLC_DATA_BLOCKS_UL +BAD_RLC_VALID_HDR_UL_UNACK +UL_RLC_BLOCKS_IN_UNACK_MODE +DL_RLC_BLOCKS_IN_ACK_MODE +RETRANS_RLC_DATA_BLOCKS_DL +DL_RLC_BLOCKS_IN_UNACK_MODE)


ND226


Multiplexing - Parameters• There are limitations on the amount of TBF that can be allocated

to a RTSL, and those are Operator definable, via BSC Level parameters:

Parameter Name Abbreviation

Description Range and Default

Maximum Number of DL TBF MNDL maximum number of TBFs that a radio time slot can have in average, in a GPRS territory, in the

downlink direction.

1..9, default:9

Maximum Number of UL TBF MNUL maximum number of TBFs that a radio time slot can have in average, in a GPRS territory, in the

uplink direction.

1..7, default:7


Multiplexing - EGPRS/GPRS

(EDGE and GPRS users)

0

1

2

3

4

5

6

7

8

9

10

GPRS DL EDGE DL GPRS UL EDGE DL GPRS DL EDGE DL GPRS UL EDGE DLSession UL/DL

User

Ave

rage

DL

Thro

ughp

ut (k

Bps)

Trial 1 Trial 2 Trial 3 Average

Sequential

Simultaneous

SequentialSimultaneous

EDGE DL is affected by the GMSK scheduling due to GPRS UL

In DL throughput degradation is due to RTSL sharing.


Multiplexing - EGPRS/GPRS Different EGPRS/GPRS multiplexing cases. (Amount of RTSLs in use)


EGPRS Dynamic Abis Pool (EDAP)

EDAP countersEDAP measurements

EDAP monitoring


EGPRS Dynamic Abis Pool - CountersDynamic Abis needed because the data rates per tls vary between 8.8-59.2kbps. Allows to dimension to average data rates instead of peak rates.

Reporting needs:- find out pools where the pool capacity is not adequate (moving cells between pools)- see which cells are in pool

Object level: BSC/ EDAP

Measurement dataPCM subtslsc76000

without EDAP

ULc76006

DLc76007

Usage %

DL UL

Avec76001/c76003

Peakc76004

Avec76002/c76003

Peakc76005

DL, with inadeq. EDAPc76008

Dynamic Abis pool for data-static tsl for signalling and voice-dynamic for EDGE TRXs

TBFs

BSC BTS1 BTS2 BTS3

dynamic

static

max20TRX/DAP

BCF

http://nea.ntc.nokia.com/cgi-bin/cgiwrap/neva/counter_list_bsc.pl?counter_id=76000











EGPRS Dynamic Abis Pool - PIs• KPIs related to EDAP are focused on Availability, Usage of the resources

and Amount of requests that cannot be granted due to capacity limitation of the EGPRS Dynamic Abis Pool.

• All counters are from p_nbsc_dynamic_abis

• On EDAP Availability:

Average available of 16kbps PCM sub-TSLs in DAP

076000 TOTAL_PCM_SUBTSLS_IN_EDAP

When UL and DL Dynamic Abis resource allocation occurs. The counter is incremented by the size of the Dynamic Abis Pool.

ND280


EGPRS Dynamic Abis Pool - PIsOn EDAP Usage:

Average usage of DL Dynamic Abis Pool [%] (dap_1). Average amount of EDAP resources used for DL data transfer during the period.

Sum(AVERAGE_DL_EDAP_USAGE_SUM) -----------------------------------------------


Peak usage of DL Dynamic Abis Pool[%]. Peak usage of 16 kbit/s PCM subTSLs in the downlink direction.

076004 PEAK_DL_EDAP_USAGE

ND280


EGPRS Dynamic Abis Pool - PIsOn EDAP Usage:

Average usage of UL Dynamic Abis Pool [%] (dap_2). Average amount of EDAP resources used for UL data transfer during the period.

Sum(AVERAGE_UL_EDAP_USAGE_SUM)

------------------------------------------------


Peak usage of UL Dynamic Abis Pool[%]. Peak usage of 16 kbit/s PCM subTSLs in the uplink direction.

076005 PEAK_UL_EDAP_USAGE

ND280


EGPRS Dynamic Abis Pool - PIs

Number of UL TBFs without EDAP resources. Number of cases where scheduled UL TBF cannot be serviced due to lack of EDAP resources

076006 UL_TBFS_WITHOUT_EDAP_RES

Number of DL TBFs without EDAP resources. Number of cases where scheduled DL TBF that requires EDAP channels cannot use any EDAP channel

076007 DL_TBFS_WITHOUT_EDAP_RES

Number of cases where required EDAP channels cannot be granted to DL TBF. Updated always (on every scheduling round) when EDAP resources for TBF cannot be granted

076008 DL_TBFS_WITH_INADEQ_EDAP_RES

Lack of EDAP resources:

1.EDAP slot shortage. EDAP size does not meet capacity needs.

2.Blocking. EDAP 16kb slots can be blocked by channel test mode, 64 kb DSP conn. guard mode or TRX 16kb guard period.

3.Lack of free PCU DSP channels

On TBF requests:ND280


Dynamic A-Bis Counters - ExampleDynamic A-Bis Counters

0

20

40

60

80

100

120

Average usage (%) of DL Dynamic Abis Pool C76004 -Peak usage (%) of DL Dynamic Abis PoolAverage usage (%) of UL Dynamic Abis Pool C76005 -Peak usage (%) of UL Dynamic Abis Pool



0

20000

40000

60000

80000

100000

120000

140000

160000

180000

C76008 -Number of cases where the required EDAP channel cannot be granted to DL TBF



0

2000

4000

6000

8000

10000

12000

14000

16000

C76006 -Number of UL TBFs without EDAP resourcesC76007 -Number of DL TBFs without EDAP resources


EDAP Monitoring The following actions may have to be considered if the Dynamic Abis counters indicate problems in Dynamic Abis usage:

• Increasing EDAP size• Decreasing the number of EDGE TRXs and/or EGPRS channels attached to

EDAP• Sharing the load between PCUs (moving an EDAP(s) and/or (E)GPRS

channels from one PCU to another) decreasing the initial CS/MCS for TBFs, in DL and/or UL direction

Alarms: 3068 EGPRS DYNAMIC ABIS POOL FAILURE• If the BSC cannot connect one DAP circuit to EDAP because of connection

failure, the BSC sets the alarm 3068 and then attaches all successfully connected DAP circuits to EDAP.

• The BSC sets the alarm 3068 if an EDAP configuration update or an EDAP modification to PCU fails.

• PCU capacity (for example, PCU DSP resource load for on-going EGPRS calls using EDAP resources) may start limiting the EGPRS and GPRS RR procedures. It is possible that new (E)GPRS TCHs cannot be added to the PCU.

• If the BSC cannot attach DAP circuits to EDAP, the BSC sets the alarm 3068.


PCU Performance Analysis


PCU Performance Dimensioning and Analysis

• EDGE Optimization requires the analysis of PCU dimensioning and Cell allocation in order to:

• Avoid PCU overload due to EDGE traffic increase.• Minimize Impact of Cell Re-selection.• Allocate enough EDAP resources per PCU.

• PCU dimensioning in BSC:• At least 1 PCU for BSC serving GPRS• PCU supports 256 Abis TCHs, 128 cells and 64 BTSs• PCU Data processing is 2 Mbps. Taking into consideration

that the PCU can handle a max of 31 PCM TSL on the Gb interface.

• Gb 64 Kbps Dimensioning in BSC:• At least 1 x 64 Kbps per active PCU.• Dimensioning should be based on estimated GPRS traffic in

Busy Hour plus the Overhead.


PCU PerformanceIt is possible to monitor PCU overload by following GPRS traffic

counters:• Counter 002063, PEAK GPRS CHANNELS

• Measures the peak number of radio time slots (Abis channels) in GPRS use within a measurement period for a BTS. The total number of GPRS channels in a PCU is the sum of counter 002063 values of all the BTSs served by the PCU

• Counter 073000, UL DL RLC MAC BLOCKS• Measures the total number of radio blocks carrying an

uplink/downlink RLC/MAC block within a measurement period in a TRX. Sum of active UL/DL channels in TRX = 073000/(measurement period(min.)*60sec*50block/second)

• The total number of active channels in a PCU is the sum of counter 073000 values of all the TRXs served by the PCU


PCU PerformanceAlarms:• 3164 PCU PROCESSOR OVERLOAD

• The processor load of the PCU is limited by limiting GPRS traffic by adjusting the scheduling rate:

The lower the scheduling rate is, the more idle blocks are sent instead of RLC data blocks. Lowering the scheduling rate lowers the processor load at the expense of data throughput.

• The solution to overcome the overloaded situation is to decrease the number of GPRS channels allocated to the PCU.


BSS PSW Optimization for Maximizing PSW Territory with Proper Network

UtilizationMultislot usage limitations

Cell-reselectionSegmentation (MultiBCF-CBCCH)

Hopping


Multislot UsageThe target is to maximize the PSW territory with proper utilization.

The following items can reduce the multislot usage:TSL unavailability• Timeslots unavailable for any traffic on normal TRXs. (ND226 - uav_13)CSW Traffic• Average CS traffic on normal TRXs. (ND266 – trf_97)

• This KPI includes all types of CS traffic (single TCH, HSCSD) on normal TRXs

• HSCSD/(E)GPRS interworking• Territory downgradeFree Timeslots• Free timeslots for CSW downgrade• Free timeslots for CSW upgrade


ADDIT.GPRS CH USEDach_1

AVG. AVAILABLE CS CAPACITYava_15 (S9)

AVG.AVAIL. DEFAULT GPRS CAPACITYava_16 - ach_1 (S9)

AVG. AVAIL. DEDICATED GPRS CHsava_17 (S9)

PEAK DEDICATED GPRS CHANNELS/c2066(S9)

PEAK GPRS CHANNELS/c2063(S9)

The following are the operator configurable parameters for territory management: GPRSenabled (BTS-level) GPRSenabledTRX (TRX-level) DedicatedGPRScapacity (BTS-level) DefaultGPRScapacity (BTS-level) PreferBCCHfreqGPRS (BTS-level) TerritoryUpdateGuardTimeGPRS (BSC-level)

GENA

GTRXCDED

CDEFBFG

GTUGT

UNAVAILABLE TCHc2040

AVG. BUSY TCH = CS traffictrf_12b

AVG. TSL USED FOR UL GPRS trf_78b

AVG. TSL USED FOR DL GPRS trf_79bFree capacity

PS resources

Availability ava_1d

The main principle is that GPRS (PS) uses the capacity that remains from the CS traffic.Territories consist of consecutive timeslots.

• Circuit Switched traffic has priority• In each cell Circuit Switched & Packet Switched territories are defined• Territories consist of consecutive timeslots

TRX 1

TRX 2

CCCH TS TS TS TS TS TS TS

TS TS TS TS TS TS TSTS

DedicatedGPRS

Capacity

CircuitSwitchedTerritory

PacketSwitchedTerritory

Territory border movesDy n a m ic a l ly based onCircuit Switched traffic load

DefaultGPRS

Capacity

AdditionalGPRS

CapacityCDED

CDEF

Given as % over dual TCH tsls ofGPRS enabled TRXs. Rounded downwards.

CS resources

PS trafficCS traffic

correlation to the nbr of PCUs

correlation to the voice call blocking

Territory Downgrade - Measurements


Territory Downgrade - MeasurementsThe territory downgrade heavily depends on the size of dedicated and default territory.• Territory downgrade due to CSW traffic rise

• Downgrade request below Default territory because of rising CSW (c1179)

• Territory downgrade due to less PSW traffic• Downgrade request back to the Default territory when there is no

need for additional channels anymore (c1181)

• Territory upgrade request rejection beyond default territory• Upgrade request beyond Default territory for additional resources,

which can be rejected because of (c1174):1. PCU and EDAP capacity limitation (256 Abis TSL per PCU)2. High CSW load3. No (E)GPRS capable resorce left (No (E)GPRS enable TRX or the maximum

(E)GPRS capacity reached)0 1 2 3 4 5 6 7

Default territory

1174

1181

1180

1179

0 1 2 3 4 5 6 7

Default territory

1174

1181

1180

1179


Free TimeslotsWhen a downgrade or upgrade procedure is requested the following parameters can reduce or increase the border between CSW and PSW territories:

0..10s, default:4With this parameter you define a period following a GPRS upgrade during which the probability for a GPRS

downgrade in a BTS should be no more than 5%. Based on the given time and the size of a BTS (number

of TRXs) the BSC defines a margin of idle TSLs that is required as a condition for starting a GPRS territory upgrade in the BTS. A GPRS upgrade may be done if

the number of free TSLs in a BTS is at least equal to the defined margin still after the upgrade.

CSUFree TSL for CS upgrade

0..100%, default:95The parameter gives a target probability of TCH availability for CS services in a BTS with GPRS territory. Based on the given probability and the size of a BTS

(number of TRXs) the BSC defines a margin of idle TCHsthat it tries to maintain free for the incoming CS TCH requests in the BTS. If the number of idle TCHs in the

circuit switched territory of a BTS decreases below the defined margin a GPRS territory downgrade is started.

CSDFree TSL for CS downgrade

Range and DefaultDescriptionAbbreviationParameter Name

0..10s, default:4With this parameter you define a period following a GPRS upgrade during which the probability for a GPRS

downgrade in a BTS should be no more than 5%. Based on the given time and the size of a BTS (number

of TRXs) the BSC defines a margin of idle TSLs that is required as a condition for starting a GPRS territory upgrade in the BTS. A GPRS upgrade may be done if

the number of free TSLs in a BTS is at least equal to the defined margin still after the upgrade.

CSUFree TSL for CS upgrade

0..100%, default:95The parameter gives a target probability of TCH availability for CS services in a BTS with GPRS territory. Based on the given probability and the size of a BTS

(number of TRXs) the BSC defines a margin of idle TCHsthat it tries to maintain free for the incoming CS TCH requests in the BTS. If the number of idle TCHs in the

circuit switched territory of a BTS decreases below the defined margin a GPRS territory downgrade is started.

CSDFree TSL for CS downgrade

Range and DefaultDescriptionAbbreviationParameter Name


Cell Re-selection - FlushA gradual introduction of EDGE capable TRXs is foreseen, which means that some BTSs will have EDGE TRXs and some others will not Target is to minimize the effect of flush and extend the EGPRS service area

Experiences • Tests performed in Field show that effective coverage of an EDGE

site can be extended by making use of the C32 parameter. This feature allows operators to extend their EDGE coverage in the initial phases of the EDGE network roll-out when few sites are supporting EDGE

• When GREO parameter was set to –16 dB it was possible to extend the Edge cell packet coverage about 150 meters

• Accordingly when the GREO parameter was 8 dB the cell reselection from GPRS to EDGE happened about 50 meters before


Cell Reselection- Measurements

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16

18

20

1 2 3 4

Sample number

Tim

e (s

)

Tx Gap (EdToEd)

Time to Inm.Assign (EdToEd)

Cell re-selection EDGE to EDGE in different BSC with different RA and LA.

Cell re-selection EDGE to EDGE cell in the same site. No RAU and no LAU needed.

0

2

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8

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1 2 3 4

Sample number

Tim

e (s

)

Tx Gap (EdToEd)

Time to Inm.Assign (EdToEd)


Cell Re-selection Parameters

Parameter Name Abbreviation Description Range and DefaultGPRS RxLev Acess Min GRXP Minimum power level an MS has to receive

before it is allowed to access the cell-110dBm..-47dBm, def –105dBm

GPRS MS Pwr Max CCH GTXP1 Maximum transmission power level a mobile station can use when accessing a packet

control channel in the cell for GSM 900/800 bands.

3..43dBm, def 33dBm

GPRS Cell Reselect Hys GHYS Additional hysteresis applied in READY state for selecting a cell in the same routing area.

0..14dB,step2, def 4dB

RA Reselect Hys RRH Additional hysteresis applied in both STANDBY and READY states for selecting a cell in a

different routing area.

0..14dB,step2, def 4dB

C31 Hys CHYS Flag which indicates if set to Y that the GPRS_CELL_RESELECT_HYSTERESIS shall be

applied to the C31 GPRS cell reselection criterion

Y/N, def N

C32 Qual QUAL Flag indicating an exception rule for GPRS_RESELECT_OFFSET. If the parameter

C32_QUAL is set to Y, positive GPRS_RESELECT_OFFSET values shall only be applied to the neighbor cell with the highest

received level average value.

Y/N, def N

SEG Level Parameters related to Cell reselection:



Parameter Name Abbreviation Description Range and DefaultRandom Access Retry RAR Mobile station should try to access another cell

if available in the event of an abnormal release with cell reselection.

Y/N, def N

Reselection Time RES Time, in seconds, that a mobile station which has performed an abnormal release with cell

reselection from this cell is not allowed to reselect this cell if another cell is available. If the parameter has the value "not allowed", it

means the same as setting the random access retry value to N.

5,10,15,20,30,60,120,300s, N, Def 5s

Priority Class PRC HCS (hierarchical cell structures) priority for the cells. 0 is the lowest and 7 is the highest

priority.

0…7, def 0.

HCS Threshold HCS Signal strength threshold for applying HCS in GPRS and LSA reselection.

N,-110..-40dBm, step2, def N

SEG Level Parameters related to Cell reselection:



Parameter Name Abbreviation Description Range and DefaultGPRS Temporary Offset GTEO Negative offset of the C32 reselection criterion

for the duration of the GPRS penalty time (GPET) after the MS has placed the cell on the list of the strongest carriers. It is used by the mobile station as part of its calculation of C32

for the cell reselection process.

0..70dB, step 10dBDef 0dB

GPRS Penalty Time GPET Duration for which the GPRS temporary offset (GTEO) applies.

10..320s, step 10sDef 10s

GPRS Reselect Offset GREO Offset of the C32 reselection criterion for a adjacent cell.

-52,-48dB, … 48dBDef 0dB

GPRS Cell Barred GBAR Combine the cell barred (BAR) and cell bar qualify (QUA) parameters and indicate the

status for cell reselection.

0/1 def 0.

ADJ Level Parameters related to Cell reselection:


Flush – Cell-(re)selection

Data rate (kbit/s)

Percentage of locations (throughout all the network) where EGPRS MS throughput

is greater than X

64 30%

32 95%

16 100%

Data rate

(kbit/s)

Percentage of locations

(throughout all the network) where

EGPRS MS throughput

is greater than X

64 72%

32 98%

16 100%

Data rate (kbit/s)

Percentage of locations

(throughout all the network) where

EGPRS MS throughput

is greater than X

64 92%

32 99%

16 100%

•15% Load•25% EGPRS MSs penetration•1/4 of the BTS are EDGE capable

NC0 Enhanced NC0: C31/C32 NCCR


problems in cell reselection C1/C2 C31/32Good cell coverage planning Good cell coverage planning

Shorter GPRS neighbour listC31/32 brings more control over cell reselectionUse the GPRS cell reselection hysterisis parameters

2. Acquiring the (P)SI is slow Reserve many blocks for PBCCH( PSI)

Use NMO1 for combined RA/LA updatePACKET PSI STATUS message makes the cell update faster

4.RADIO STATUS triggers during cell reselection

There is an in bulit solution in S10.5 There is an in bulit solution in S10.5

In S9 make the PCU allocation manually if necessary

In S10.5 PCU allocation algorithm takes care of it.

In S10.5 PCU allocation algorithm takes care of it.

5.Most of the cell reselections are inter-

PCU

3.Cell update is slow

Use NMO1 for combined RA/LA update

1. Too frequent cell reselections

Use cellreselecthysterisis cautiously

Cell-Reselection Conclusions


MultiBCF and Common BCCH - Segmentation

Single vs. Separated Territories• Nokia Resource Allocation Algorithm tries to separate GPRS TBFs

and EGPRS TBF into different RTSL, however deployment strategy is critical:

• Separate EGPRS and GPRS territories:• Better usage of resources• Very unlikely that timeslots will be shared between GPRS and EGPRS

=> Good quality for EGPRS & (perhaps) heavy GPRS congestion• Need for dedicated timeslots in both GPRS and EGPRS territory =>

Not realistic if PS traffic is low• Single territory for EGPRS and GPRS ( multiplexing )

• Less dedicated timeslots• Higher risk of EGPRS timeslot sharing• The “penalty” method is used to avoid timeslot sharing between GPRS

and EGPRS (impact on applications not yet tested)


GPRS - EGPRS Segmentation • There can be separate GPRS and EGPRS territory in the segment. If

there is no capacity in EGPRS territory a EGPRS MS can be allocated a TSL in GPRS territory but the TBF is a GPRS TBF not a EGPRS TBF.

• If there is only EGPRS territory available in a cell, also all GPRS TBFs will be allocated in it.

Following combinations are possible within one segment

• on GPRS territory (=BTS with GPRS TRXs)a)GPRS MS - GPRS TBF. ave tbfs per tsl counter updatedb)EGPRS MS - GPRS TBF. ave tbfs per tsl counter updated (reason: cell

doesn't support EGPRS, or all capacity used)

• on EGPRS territory (=BTS with EGPRS TRXs)c) GPRS MS - GPRS TBF. Ave tbfs per tsl counter updated.d)EGPRS MS - EGPRS TBF. Both Ave EGPRS tbf and ave tbfs per tsl updated


GPRS - EGPRS SegmentationBoth EGPRS and GPRS territory can be on same segment, but one BTS may have only EGPRS capable or non-capable TRXs. Because measurements are collected per BTS, we can distinguish all other combinations except the amount of tbfs per tsl on GPRS territory between EGPRS and GPRS capable MS (a and b).

1) Assume we have only GPRS territory and EGPRS TBFs come there as GPRS TBFs. ->only c72099..c72104 triggered

2) Assume that the GPRS territory is full and some GPRS TBFs get to EGPRS territory. ->only c72099..c72104 triggered

3) Signalling TBFs ->only 72099..72104 triggered

c72107..c72110 are updated only when EGPRS TBF created on EGPRS territory.


GPRS and EGPRS in a SEGMENT• Parameters involved in the procedure:

Parameter Name Abbreviation Description Range and Default

BTSLoadInSeg LSEG Load limit for a BTS. Is used in controlling the load distribution

between BTSs in a segment

0..100%, def 70%

NonBCCHLayerOffset NBL Predefined offset margin used when evaluating the signal level of the non

BCCH layer

-40..+40dBm, def 0dB

DirectAccess DIRE Signal level compared to non BCCH layer offset. When the value of this parameter is higher than the value of the parameter non BCCH layer

offset the direct GPRS access to non BCCH layer BTS is applied

-40..+40dBm, def 0dB

RxLevAccessMin RXP Minimum power level an MS has to receive before it is allowed to access

the cell.

-110dBm..-47dBm,Def –105dBm

RxLevMinCell SL Minimum signal level of an adjacent cell, when a handover is allowed to

one of them.

-110dBm..-47dBm,Def –100dBm


NBL Offset ParameterNBL offset measurement result with assimetric tilting on 900 MHz and 1800 MHz


Direct Access Parameter (DIRE)An example: EGPRS TBF drops from EDGE to GPRS probably solved by changing DIRE parameter

DIRE > NBL

DIRE = 0 dBm


EGPRS on BCCH vs. FH TRXs

BCCH and Hopping Throughput Comparison- DL

0

2

4

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12

14

9 8 7 6 5 4 3 2 1

MCS

Thro

ughp

ut (K

B/s

)

BCCH- Average DL Throughput HoppingAverage DL Throughput

BCCH and Hopping Throughput Comparison- UL

0

1

2

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7

9 8 7 6 5 4 3 2 1

MCS

Thro

ughp

ut (K

B/s

)BCCH- Average UL Throughput HoppingAverage UL Throughput

Field Testing show that expected throughputs for each MCS are achieved with both implementation:


LLC, SNDCP, TCP/IP and Application Layer Optimization for Maximizing

User Data Rate Throughput at Application Layer


EDGE Protocol Stack

LLCSNDCP

LLCSNDCP

L1/RF L1/RFUmMS BTS

FRNS

BSSGP

FRNS

BSSGP

Gb SGSN

GTPUDPIP

L1L2

GTPUDPIP

L1L2

Gn GGSN

RLC/MAC RLC/MAC

DAbis DAbisAbis BSC / PCU

IP

L1

L2

WWW/FTPServer

Gi

TCP

HTTPor FTP

L1

L2

IPTCP

HTTPor FTP


LLC & SNDCP LayerLLC (Logical Link Control) Layer• ACK/UN-ACK MODE (ACK recommended for TCP Header

Compression)• LLC Retransmission timer (default 10s) – applied if ACK MODE • Maximum number of retransmissions (default 3)• Maximum number of outstanding I frames (default 8) • Ciphering Mode in Use (ON/OFF)

SNDCP (Sub Network Dependent Convergence Protocol) Layer:• Data Compression (ON/OFF) (of V42bis Users)

• Good for text, inefficient for graphics and ciphered text• TCP Header Compression (ON/OFF)

• Possible problem in bad radio condition – compressed header if corrupted cannot be decompressed and the consecutive headers as well. If applied, than LLC ACK MODE is recommended


TCP Layer - Performance BottlenecksDefault parameter settings in Opearting Systems are optimized for LAN environment

• TCP slow start mechanism• Small TCP window size• Spurious timeouts and retransmissions due to variable bit rate,

variable delay and poor error recovery• Packet loss on poor links• Packet loss due to congestion• Link outage due to temporary loss of radio coverage• Delays caused by cell reselections• Slow TBF resource allocation in uplink or downlink• Blocking by higher priority traffic


TCP Optimization• Reduce slow start inefficiencies

• Increase initial TCP widow size• Ensure TCP window size is large enough in order to fully utilize the

network resources• Minimize packet loss• Quickly recover from packet loss

• TCP protocol enhancements – depends on capabilities on both ends

• Avoid delay spikes which might cause spurious timeouts• Try to reduce variance in delay.

• Avoid spurious retransmissions• Accurate RTT and RTO estimation


TCP/IP Optimization Settings• Maximum Transmission unit 1500 bytes (MSS=1460bytes)

• MTU = MSS + TCPHeader + IPHeader• Optimum balance between throughput, header payload ratio

and fragmentation• Receiver Window Size (RWIN)

• Should reflects BDP=RTT*Throughput• too short -> delay spikes, too high -> PCU buffers flood

• Congestion Window (CWIND)• Max number of packets sent without ACK, optimum 5

• Retransmission Interval Timer (RTO)• Too low -> too retransmissions, too long -> delay in data

recovery• RTO = RTT + 4*stdev_RTT


Annex - Traffic Measurements

Data amounts in radio blocks using different Modulation and Coding Schemes

MCSRadio block size [bytes]

Number of RLC data blocks in radio block

RLC data block payload

Total payload [bytes]

MCS-1 30 1 22 22

MCS-2 36 1 28 28

MCS-3 45 1 37 37

MCS-4 52 1 44 44

MCS-5 63 1 56 56

MCS-6 81 1 74 74

MCS-7 123 2 56 112

MCS-8 147 2 68 136

MCS-9 159 2 74 148

Note: In case of MCS7..9 each radio block contains 2 RLC blocks.

Customer EDGERPL - Module4 (v3.0).ppt

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Transcript of Customer EDGERPL - Module4 (v3.0).ppt