Day2 Abis Capacity Evaluation for Network Modernization With GEMINI

1 © Nokia Siemens Networks Abis capacity evaluation/ K.Majchrowicz/ April 2009For internal use

Network EngineeringJune, 2009

GEMINI Network Engineering InformationGSM/EDGE Migration Network Infrastructure

Abis capacity evaluation for network modernization with GEMINI

2 For internal use © Nokia Siemens Networks Presentation / Author / Date

GEMINI

Revision HistoryRevision History

Issue Number Date of Issue Reason for Update

0.1 18.03.2009 Draft version

0.2 03.04.2009 The next draft version after the internal NE review

0.3 21.04.2009 The next draft version after the review done by Carlo Masseroni (COO RA GERD SA NT GSM BWA SIT)

1.0 22.04.2009 Approved by Sebastian Lasek (COO RA GERD SA NE)

Author: Krystian Majchrowicz, COO RA GERD SA NE

Co-authors: Marcin Grygiel (COO RA MRD SA NE), Andrzej Maciolek, Sebastian Lasek (COO RA GERD SA NE)


• KPI Requirement Specification

https://sharenet-ims.inside.nokiasiemensnetworks.com/Open/396539675

• Performance measurement counters

https://sharenet-ims.inside.nokiasiemensnetworks.com/Open/396551275

ReferencesReferences



• Purpose, methodology and outputs

• Inputs

• Configuration analysis for class B* sites identification

• Performance analysis for class C* sites identification

• Abis capacity analysis for class D* sites identification

• Performance observation for class D sites if Abis capacity not extended

• Identification of class A* sites

• Summary

* Definition of sites class A, class B, class C and class D is presented on the next slide

Table of ContentsTable of Contents



• The goal of the following slides is to present the methodology to determine the number of PCM line extensions needed after migration to GEMINI

• Analysis must be performed site by site

• As the results of these analyses sites can be classified as:

Class A - > no need for PCM line extension after migration

Class B - > PCM line extension required after migration due to configuration (existing number of TRXs can not be configured on existing number of PCM lines

when migrating to GEMINI)

Class C - > performance of PS services already (before migration) degraded due to under dimensioned Abis; after migration problem will be even more severe

therefore PCM line extension required before migration

Class D - > PCM line extension might be required if after migration PS data performance degradation is not acceptable

PurposePurpose,, methodology methodology and outputs and outputs



• The following inputs are required for these analysis: Configuration:

- Number of TRXs per site

- Number of PCM lines/ Abis subTSLs per site

- Number and capacity of LAPD links per site

Traffic load *

- CS Traffic (Erl)

- PS data volume

PS Traffic characteristic *

- Throughput

- M(CS) distribution

Abis statistics *

- Number of unsuccessful Abis subchanel allocation due to insufficient Abis resources

- Abis pool distribution (number of Abis subTSLs used for PS traffic)

Other

- For the complete list of KPIs used in these analysis see slide #20* all statistics shall be analyzed hourly in the hours of significant CS and PS traffic

InputsInputs



• Configuration rules define the max number of TRX controlled by a single PCM• each channel from each TRX is mapped permanently (i.e. 2

PCM TSLs per TRX are needed)

• due to implementation of LAPD multiplexing in GEMINI existing LPDLM* objects are mapped to the corresponding LAPD objects (with the same capacity)

• EDAP is needed for EDGE calls in GEMINI to guarantee throughput

• up to 15** TRX per PCM is possible assuming no EDGE traffic and max 64kbit/s for LAPD (see figure on the right) or ”Abis Compressed” (if more LAPD needed)• 15 TRX => 30 TSL

• 1 LAPD => 1 TSL

* Here LPDLM means BSC DB object which represents LAPD pool (set of 16 kbps PCM sub-slots) which may carry both LPDLM (management) and LPDLR (TRX) type signalling

** this is valid in case of E1 line only (most of the cases) where the number of TSL on 1 PCM line is 32 (1 TSL used for synchronization purposes);in case of T1 (24 TSL) up to 11 TRXs on one PCM line is possible

Configuration analysis Configuration analysis (1/3)(1/3)



• in BR line Measurement Reports (MR) are usuallynot sent (default setting for RADIOMR=OFF) and therefore 1x64kbit/s LAPD per site is typically enough

• with GEMINI MR are sent from BSxx to BSC3iin a certain configurable frequency (every nth report is sent )

• this increases requirements for LAPD capacity and in some cases more than 1 x 64kbit/s LAPD link might be needed

• in such a case in order to allocate 15 TRXs into 1 PCM line (assuming no EDGE) compressed Abis must be used (see figure on the right):

• additional LAPD can be configured on Abis subTSLs dedicated for BCCH and SDCCH RTSLs

• considering 5/5/5 configuration at least 2 RTSLs per cell are configured as signaling and can be used for LAPD without radio performance degradation (see figure on the right)

• In such a case 1x 64kbit/s + 3 x 32kbit/s can be assigned for LAPD without radio performance degradation

• When more bandwidth needed for LAPD then additional channels are also possible however they reduce radio capacity (since they must be created on PCM SUBTSL where RTSL carrying TCH are mapped);up to 11 LAPD objects per site are allowed in BSC3i DB




• Conclusions: • every site with 1 PCM line and # TRXs >15

is automatically classified as Class B site since it is not possible to configure this site in GEMINI without PCM line extension (16 TRXs and more requires # PCM line>1)

• every site with 1 PCM line, 15 TRXs and EDGE traffic>0 is automatically classified as Class B site since it is not possible to configure this site in GEMINI without PCM line extension (with 15 TRXs it is not possible to configure any EDAP and therefore EDGE will be not served on this site*)

* master channels are enough for MCS1 only


Class BAbis capacity evaluation for network modernizationwith GEMINI


• Performance before the migration shall be analyzed in terms of Abis blocking to identify existing sites with underdimensioned Abis

• On these sites after migration to GEMINI problem will become more severe

• These sites are classified as Class C -> PCM line extension required before migration

• For these analysis following KPIs are to be monitored:• Abis utilization – if high it means that there might be problem of underdimesioned Abis

• Abis loss rate (number of unsuccessful Abis subchannel seizures to all Abis subchannel seizure attempts ) – high loss rate means that many Abis seizures attempts were unsuccessful due to lack of Abis resources and clearly indicates that PCM must be extended

• TCH blocking due to no Abis resources

• TBF rejections due to no Abis resources

• Portion of successful TBF establishments with reduced number of PDCHs due to lack of Abis resources – high rate means that many TBFs were successfully established but the number of allocated PDCHs reduced (comparing to the optimal) due to not sufficient Abis resources

Performance analysis Performance analysis (1/3)(1/3)

Class C

Abis capacity evaluation for network modernizationwith GEMINI


• Abis utilization:

- ABISPSUP [3] Mean number of allocated Abis subchannels

- ABISPSUP [1] Mean number of defined Abis subchannels

• Abis loss rate (number of unsuccessful Abis subchanel seizures to all Abis subchanel seizures):

- ABISPSUP [7] Number of unsuccessful Abis subchannel seizure attempts (incoming

attempts to seize one or more Abis subchannels can not be served because

not enough suitable Abis subchannels are free)

- ABISPSUP [6] Number of successful Abis subchannel seizures

• TCH blocking due to no Abis resources:

- ATCHSMBS [3] Attempted TCH/F seizures meeting an Abis subchannel blocked state

- ATCHSMBS [4] Attempted TCH/H seizures meeting an Abis subchannel blocked state

- ATTCHSEI [1] Attempted TCH/F seizures

- ATTCHSEI [2] Attempted TCH/H seizures

]ABISPSUP[1

]ABISPSUP[3RATEUSAGEABIS __

Performance analysis – KPI definitions Performance analysis – KPI definitions (1/2)(1/2)

,7]ABISPSUP[6

]ABISPSUP[7RATELOSSABIS __

,2]ATTCHSEI[1

,4]ATCHSMBS[3ABISNORATEBLOCKTCH ____

Class C



• TBF rejections due to no Abis resources:

- REJPDASS[15] Number of Rejected PDCH Assignments due to no Abis subchannel available for a DL TBF for background* traffic class

- NUACATCL [6] Number of Attempted PDCH Assignments for DL TBF for background services

• Portion of successful TBF establishments with reduced number of PDCHs (non ideal) due to lack of Abis resources

- UNSPDCSE[10] Number of degraded DL PDCH seizures due to not enough Abis subchannels for background* services. "Degraded assignment" means that the number of assigned TSLs is

lower than the optimal one

- NUACATCL [6] Number of Attempted PDCH Assignments for DL TBF for background* services

* for counters which differentiate for traffic classes (background, interactive and streaming) subcounters dedicated for background are always pegged (no matter what traffic class is)as long as QoS is disabled (PFCSUP= DISABLED)

[6] NUACATCL

5]REJPDASS[1ABISNORATELOSSTBF ____

Performance analysis – KPI definitions Performance analysis – KPI definitions (2/2)(2/2)

[6] NUACATCL

0]UNSPDCSE[1ABISNORATEREDSUCESTTBF ______

Class C



• KPIs presented on the previous slides give the indication whether site (or cells on this site) suffers from Abis blocking

• It is recommended to use 15 min granularity for the counters used in these KPIs for more precise analysis (to observe peaks)

• Additionally other KPIs can be used to see the level of PS services performance degradation:• Throughput per TBF

• Resource Assignment rate

• Mean number of TBFs per PDCH – presents the level of multiplexing

• Mean number of PDCHs per TBF – presents multislot allocation

• These KPIs give the indication on overall performance without pointing to radioor Abis problems. Therefore additionally it makes sense to observe KPIs indicating radio resource related problem:• TBF establishment failure rate due to congestion (no radio resources)

• Portion of successful TBF establishments with reduced number of PDCHs due to no radio resources (RR) – high rate means that many TBFs were successfully established but the number of allocated PDCHs reduced (comparing to the optimal) due to not sufficient radio resources

Performance analysis – additional KPIs Performance analysis – additional KPIs (1/2)(1/2)

Class C



• Finally KPIs presenting the load situation are also needed to check if the analysed data is statistically reliable:

• TCH Traffic carried

• HR usage

• Number of TSLs used for CS

• PS data volume

• Number of active PDCHs

Performance analysis – additional KPIs Performance analysis – additional KPIs (2/2)(2/2)

Class C



• Throughput per TBF in DL (kBytes/sec)

- MUTLLC [15] - Weighted LLC GPRS Data Throughput in DL for background*

- MUTLLC [20] - Weighted LLC EDGE Data Throughput in DL for background*

- MUTLLC [75] - Weighted LLC GPRS Data Volume in DL for background*

- MUTLLC [80] - Weighted LLC EDGE Data Volume in DL for background*

• Resource Assignment rate in DL

- TBFRASSR[4] - DL TBF resource assignment rate for background* services; “Resource assignment rate” is the ratio of assigned number of

TSLs to ideal number of TSLs (ideal is the output of RRM algorithm and does not necessarily

corresponds to the maximum allowed by the class of mobile)

* for counters which differentiate for traffic classes (background, interactive and streaming) subcounters dedicated for background are always pegged (no matter what traffic class is)as long as QoS is disabled (PFCSUP= DISABLED)

MUTLLC[80]MUTLLC[75]

MUTLLC[80]*MUTLLC[20]MUTLLC[75]*MUTLLC[15]

DLTBFPERTHR ___

Additional KPIs – definitions Additional KPIs – definitions (1/5)(1/5)

]TBFRASSR[4 SSIG_RATERESOURCE_A

Class C



• Number of TBFs per PDCH

- NTBFPDC[4] Mean Number of DL TBFs Allocated per PDCH

• Number of PDCHs per DL TBF

- NTBFPDC [4] - Mean Number of DL TBFs Allocated per PDCH

- NALLPDCH [6] - Mean number of used PDCH in downlink

- NACTTBF [13] - Mean Number of Active DL TBFs per Cell

]NACTTBF[13

[6] NALLPDCH * NTBFPDC[4] TBFPDCHs_PER_

NTBFPDC[4] CHTBF_PER_PD

Class CAdditional KPIs – definitions Additional KPIs – definitions (2/5)(2/5)



• TBF rejections due to no radio resources:

- REJPDASS [21] Number of Rejected PDCH Assignments due to no radio resources available for a DL TBF for background services

- NUACATCL [6] Number of Attempted PDCH Assignments for DL TBF

• Portion of successful TBF establishments with reduced number of PDCHs (non ideal) due to not enough radio resources

- UNSPDCSE[14] Number of degraded DL PDCH seizures due to not enough radio resources "Degraded assignment" means that the number of assigned

TSLs is lower than the optimal one- NUACATCL [6] Number of Attempted PDCH Assignments for DL TBF

[6] NUACATCL

1]REJPDASS[2RRNORATELOSSTBF ____

[6] NUACATCL

4]UNSPDCSE[1RRNORATEREDSUCESTTBF ______




• TCH traffic carried

- MEBUSTCH [1,2] - Mean number of busy TCH/F [1] and TCH/H [2]

• HR usage

• Number of TSLs used for CS*

* KPI only valid in case Enhanced Pairing is enabled (EPA=TRUE); otherwise KPI shall be skipped

,2]MEBUSTCH[1 ARR_DRTCH_TRAF_C

,2]MEBUSTCH[1

]MEBUSTCH[2 HR_USAGE

2

]MEBUSTCH[2]MEBUSTCH[1 LsCS_BUSY_TS




• PS data volume in kBytes

- MUTLLC [75] - Weighted LLC GPRS Data Volume in DL for background

- MUTLLC [80] - Weighted LLC EDGE Data Volume in DL for background

• Number of active PDCHs

- NALLPDCH[6] - Mean number of used DL PDCH. "Used" means that at least one TBF is allocated on the PDCH.

80]MUTLLC[75, PS_DATA

]NALLPDCH[6 PDCHs




Class CKPI definitions KPI definitions - summary - summary


back to slide #4


• Presented KPIs were defined and used in following AnatomN report

• Enclosed report can be reused in AnatomN for the other projects

• Based on this report sites suffering from underdimensioned Abiscan be identified if:

• Abis utilization (ABIS_USAGE_RATE) and Abis loss rate (ABIS_LOSS_RATE) are high

• Additionally blocking occurs due to not sufficient Abis resources observed by:– high TCH blocking due to no Abis resources in the cells served by this site (TCH_BLOCK_RATE_NO_ABIS)

– high TBF rejections due to no Abis resources in the cells served by this site (TBF_LOSS_RATE_NO_ABIS)

– high portion of successful TBF establishments with reduced number of PDCHs due to lack of Abis resources (TBF_EST_SUC_RED_RATE_DL_NO_ABIS)

– low Resource Assignment rate (RESOURCE_ASSIGN_RATE) – ideal number of PDCHsis not assigned to TBF due to insufficient Abis or radio resources

• PS or CS load (PS_DATA or TCH_TRAF_CARR_DR) is high enoughto guarantee statistical significance level of the analyzed data


Compressed (zipped) Folder

Class C



• In the following pictures KPI results for two exemplary sites are presented:

• BTSM 64.12 (2/2/2) – site with no Abis capacity problem– Abis utilization (ABIS_USAGE_RATE) is relatively low, there are no attempts to seize Abis channel which ends up unsuccessfully due to lack of Abis resources

(ABIS_LOSS_RATE =0)

– there is no TCH or TBF blocking due to not sufficient Abis resources (TCH_BLOCK_RATE_NO_ABIS and TBF_LOSS_RATE_NO_ABIS = 0)

– no TBF establishments with reduced number of PDCHs caused by not enough Abis resources TBF_EST_SUC_RED_RATE_DL_NO_ABIS = 0)

– high Resource Assignment rate (RESOURCE_ASSIGN_RATE) – ideal number of PDCHs is assigned to TBF very often since Abis resources are enough

• BTSM 64.13 (5/4/6/6) – site classified as Class C site (Abis extension required before migration)– very high Abis utilization (ABIS_USAGE_RATE=0.99) and therefore high Abis loss rate ABIS_LOSS_RATE =0.45)

– this is reflected in high TCH and TBF blocking due to no Abis resources (TCH_BLOCK_RATE_NO_ABIS and TBF_LOSS_RATE_NO_ABIS) as well as in high portion of TBFs established with reduced number of PDCHs due to lack of Abis resources (TBF_EST_SUC_RED_RATE_DL_NO_ABIS)

(at the same time reduced assignment rate due to no radio resources (TBF_EST_SUC_RED_RATE_DL_NO_RR) is low and no TBF are rejected due to no RR (TBF_LOSS_RATE_NO_RR))

– relatively low Resource Assignment rate (RESOURCE_ASSIGN_RATE) - it is caused by Abis since there is no radio congestion: no TBF blocking due to RR at all and relatively low portion of TBF established with reduced number of PDCHs due to lack of RR)

• BTSM 64.13 has higher TBF multiplexing (TBFs_PER_PDCH) than BTS 64.12 and lower multislot allocation (PDCHs_PER_TBF) caused by not enough Abis -> this has consequences in lower throughput (THR_PER_TBF)

• Traffic (PS_DATA or TCH_TRAF_CARR_DR) is high enough -> statistical significance


Abis capacity evaluation for network modernization with GEMINI Class C


• The last step is to identify these sites which currently do not suffer from Abis blocking but after migration performance of PS services is expected to be degraded due to insufficient Abis resources -> Class D

• For this reason max EDAP size after migration must be estimated and compared against number of Abis subchannels currently used for PS traffic

• For 1PCM line per site:Max EDAP* = 4 x (31 – LAPD size – 2 x Number of TRX per site)

- if parameter ABISCH in the object LPDLM is composed of 2 fields only (e.g. ABISCH=3-2) then:

LAPD size = number of LPDLM objects associated** with BTSM

- if parameter ABISCH in the object LPDLM is composed of 3 fields (e.g. ABISCH=3-2-1) then:

LAPD size = roundup (number of LPDLM objects associated** with BTSM /4)

• In case of 1PCM line for more than 1 site (multidrop configuration) for each site connected via this PCM EDAP size is calculated separately:- Max EDAP * for site A = 4* (Abis pool size for site A – 2 x Number of TRX in site A)

Abis pool size for site A = rounddown (number of SUBTSLB objects associated*** with BTSM corresponding to site A) /4)

- Max EDAP * for site B= 4* (Abis pool size for site B – 2 x Number of TRX in site B)

Abis pool size for site B = rounddown (number of SUBTSLB objects associated*** with BTSM corresponding to site B) /4)

* For the purpose of this analysis (in order to compare maximum possible EDAP size against number of Abis subchannels currently used for PS traffic presented on the next slides) EDAP size is given in the number of Abis subchannels (16kbit/s) even though in practice it is defined in the number of Abis TSLs (64kbit/s)

** BTSM is associated with LPDLM via ASSLAPD parameter on SUBTSLB object

*** BTSM is associated with SUBTSLB via ASSLAPD parameter on SUBTSLB object (BTSM:n can use these SUBTSLBthat contain the same BTSM:n in the ASSLAPD parameter)

Class DAbis capacity analysis Abis capacity analysis

(1/3)(1/3)



• Calculation example:

BTSM 64.24 with 1PCM line for the whole site with 1x64kbit/s LAPD and 12 TRXs (4/4/4)

Max EDAP = 4*(31 – 1 – 2 x 12) = 24

• This maximum theoretical EDAP size is compared against the currently used number of concatenated Abis subchannels

• Since EDAP considers only slave channels (1 master channel is always available for PS traffic) its size (calculated in the number of 16kbit/s subchannels) should only be compared with the number of subchannels 2x16kbit/s ..5x16kbit/s (subchannel 1x16kbit/s excluded)

• KPI definition:

Mean number of Abis subchannels used for PS traffic (single Abis subchannel for PS excluded) :

- ABISPSUP [3] Mean number of allocated Abis subchannels

- ABISPDIS [3] Concatenated Abis subchannels (2 x 16 Kbps) usage rate




This KPI is to be compared against EDAP size and therefore it gives the number of Abis subchannels used for PS traffic. Number of Abis subchannels is multiplied by the probability that the subchannel serves PS traffic. For CS1 and MCS1 EDAP is not needed (1 Abis subchannel is enough). Therefore for the purpose of the comparison against EDAP size the number of Abis subchannels used to serve CS1 or MCS1 is excluded (ABISPDIS[2] - Abis subchannels 1 x 16 Kbps usage rate)

Class D

100

3..6] ABISPDIS[* ]ABISPSUP[3PSFORSUBTSLABIS ___

Abis capacity analysis Abis capacity analysis (2/3)(2/3)



• BTSM 64.24 (after migration) on one existing PCM line can have max EDAP size of 24 subchannels (5 Abis TSLs)

• Currently it uses up to 85 subchannels• Conclusion:

Extra PCM line for the site under analysis must be added on otherwise after migration performance of PS services might be limited by Abis due to EDAP implementation(no Abis resources sharing between CS and PS traffic) Performance degradation can be observed in terms of:- lower (M)CS distribution – usage of high coding schemes (e.g.. MCS9) will be reduced and usage of low coding schemes (e.g.. MCS1-4) will increase- lower throughput

Class D

max EDAP =24 subTSLs

Abis capacity analysis Abis capacity analysis (3/3)(3/3)



• If for sites classified as Class D sites number of PCM lines is not expanded performance after migration must be observed and compared against performance before migration

• Performance of CS services (expressed as TCH blocking) might improve (in scenario when the busy hour occurs at the same time on all cells of the site) because with GEMINI there is no TCH blocking due to Abis (since there is no overbooking in Dynamic Abis). This can be measured in terms of TCH blocking rate:

– Formula before GEMINI:

– ATCHSMBS [1] Attempted TCH/F seizures meeting a TCH blocked state

– ATCHSMBS [2] Attempted TCH/H seizures meeting a TCH blocked state

– ATCHSMBS [3] Attempted TCH/F seizures meeting an Abis subchannel blocked state

– ATCHSMBS [4] Attempted TCH/H seizures meeting an Abis subchannel blocked state

– ATTCHSEI [1] Attempted TCH/F seizures

– ATTCHSEI [2] Attempted TCH/H seizures

– Formula in GEMINI:

TCH raw blocking (blck_1a) =

– Counters from table: p_nbsc_traffic

– tch_req_rej_lack (001011) - number of requests for TCHs that are rejected because there are no radio resources available. This counter is also updated when a request for TCH is rejected because of a mismatch between the types of the requested channel and the A interface circuit.Updated when the RRM has no TCHs available for either call or HO attempt requests, or the RRM changes the A interface circuit pool before the TCH allocation.

– tch_rej_due_req_ch_a_if_crc (001122)- number of requests for TCHs that are rejected because of a mismatch between the types of the requested channel and the A interface circuit, whether queuing occurred or not. Counter 001011 is updated along with this counter.

– tch_request (001010) - total number of requests for a TCH (successful and unsuccessful).

Performance observations (1/Performance observations (1/55))

Class D

,2]ATTCHSEI[1

..4]ATCHSMBS[1*100__ RATEBLOCKTCH




• TBF blocking rate might improve after migration to GEMINI because with Dynamic Abis master channels are always available, while in BR due to common pool for CS and PS shared between cells of the same site, it can happen that TBF is rejected since there is no Abis resources (PDT) at all. For this reason TBF blocking in GEMINI means TBF rejection due to no radio resources only. In BR TBF blocking is defined as the unsuccessful TBF establishment attempt caused by no radio or no Abis resources.


– REJPDASS[15] Number of Rejected PDCH Assignments due to no Abis subchannel available for a DL TBF for background* traffic class

– REJPDASS [21] Number of Rejected PDCH Assignments due to no radio resources available for a DL TBF for background services

– NUACATCL [6] Number of Attempted PDCH Assignments for DL TBF


Downlink multislot allocation blocking (tbf_16b) =

– Counters from table: p_nbsc_packet_control_unit

– NO_RADIO_RES_AVA_DL_TBF (072080 ) - no radio resources are available for a downlink TBF. Updated when a new downlink TBF is requested but the PCU has no radio resources available for it or when the reallocation of the existing downlink TBF fails because of a lack of radio resources.

– REQ_1_TSL_DL (072039) - the number of requests for one TSL in downlink TBF allocation. Updated when one TSL is requested for a particular TBF in downlink TBF allocation or in DL TBF reallocation, when one DL TSL is requested

– …

– REQ_12_TSL_DL (072039) - the number of requests for 12 TSL in DL TBF allocation.Updated when one TSL is requested for a particular TBF in DL TBF allocation or in DL TBF reallocation.

[6] NUACATCL

5,21]REJPDASS[1*100____ ABISNORATELOSSTBF

Performance observations (Performance observations (22//55))

Class D

_DL)REQ_12_TSL..DLREQ_2_TSL_ TSL_DLsum(REQ_1_

) _DL_TBFIO_RES_AVAsum(NO_RAD

*100


• Performance of PS services might be limited due to EDAP implementation and therefore following KPIs are to be observed:• EDGE DL Throughput – it is expected that for class D sites if no Abis

capacity enhancement – throughput will decrease (EDGE considered only since GPRS functionality in GEMINI is limited – no CS3 and CS4)

• DL MCS distribution – as presented on the graphs below it is expected that the usage of high MCS (e.g. MCS 6-9) will be reduced and usage of low MCS (e.g. MCS1) will increases

Class DPerformance observations (Performance observations (33//55))


MCS distribution for cell A before migration

MCS distribution for cell A after migration to GEMINI


• EDGE DL Throughput:


▪ MUTLLC [20] - Weighted LLC EDGE Data Throughput in DL for background in kbytes/s


Volume weighted LLC throughput (llc_3a)= [kbit/s]

▪ Counters from table: p_nbsc_packet_control_unit

▪ AVG_VOL_WGHT_LLC_TROUGHPUT_NUM (072109 ) - The numerator for downlink Volume Weighted (VW) LLC throughput in EDGE mode, for MSs which are capable of four or more TSLs in downlink allocation. Longer data bursts are weighted more than short bursts. The counter contains the sum of the throughputs weighted by the volume of each LLC transmission burst within the TBF. An LLC transmission burst is a transmission period between two transmission breaks. The unit of the counter is 100 bytes^2/10 ms.

▪ AVG_VOL_WGHT_LLC_TROUGHPUT_DEN (072110 ) The denominator for Volume Weighted (VW) LLC throughput in EDGE mode, for MSs which are capable of four or more TSLs in downlink allocation. The counter contains all the bytes transmitted within TBFs

Class D

[kbit/s]MUTLLC[20]* 8DLTBFPERTHR ___




• MCS distribution– Formula before GEMINI:

where c=1 for MCS1

c=2 for MCS2

..

c=9 for MCS9

▪ NTRAPDU [18..26] - Number of transmitted DL PDUs with MCS-1 ... MCS-9

▪ NRETPDU [18..26] - Number of retransmitted DL PDUs with MCS-1 ... MCS-9

▪ Remark: in DL directions the retransmission is included in NTRAPDU[14 .. 26]. Since formula to be used in GEMINI does not include retransmission, retransmitted PDUs (counted by NRETPDU) are excluded here


▪ Counters from table: p_nbsc_coding_scheme

▪ DL_RLC_BLOCKS_IN_ACK_MODE (079000) - number of DL RLC data blocks sent to an EGPRS MS in acknowledged mode for the first time. Retransmitted blocks are not included.

▪ DL_RLC_BLOCKS_IN_UNACK_MODE (079001) - number of DL RLC data blocks in unacknowledged mode sent to an EGPRS MS. In unacknowledged mode there are no retransmissions on RLC level. The PCU does not know how many of these blocks get correctly through to the MS.

▪ Remark: Formula rlc_57 for MCS distribution in GEMINI can not be used as it considers ack mode onlywhile formula before GEMINI considers also unack mode

Class D

CK_MODE)CKS_IN_UNADL_RLC_BLO K_MODEOCKS_IN_AC(DL_RLC_BL 9 -1 MCS over Sum

CK_MODE)CKS_IN_UNADL_RLC_BLO K_MODEOCKS_IN_AC(DL_RLC_BL n -MCS over Sum

][___ nMCSDLOFRATIO

8..26]NRETPDU[..26]NTRAPDU[18

17]NRETPDU[c17]NTRAPDU[c

1][__

cDLDISTRMCS




• Class A site is a site where there is:• number of TRXs on site <=15 -> site is not classified as Class B

• currently no Abis blocking -> site is not classified as Class C

• theoretical max EDAP size is greater than or equal to the mean numberof used concatenated Abis subTSLs -> site is not classified as Class D

• Number of Class A sites can be calculated according to the formula:

Number of Class A sites = number of all sites - number of Class B sites - number of Class C sites - number of Class D sites

Identification of Class A sites Identification of Class A sites (1/2) (1/2)

Class A




• Example of site in Class A: BTSM 64.12 (2/2/2):• 6 TRXs -> number of TRX on site <=15 -> site is not classified as Class B

• Moderate Abis utilization (ABIS_USAGE_RATE =45%)

• ABIS_LOSS_RATE =0 (no unsuccessful Abis subchanel seizures due to no Abis resources)

• no TCH blocking due to no Abis resources (TCH_BLOCK_RATE_NO_ABIS =0)

• no TBF rejections due to no Abis resources TBF_LOSS_RATE_NO_ABIS = 0)

• no TBF establishments with reduced number of PDCHs due to lack of Abis resources (TBF_EST_SUC_RED_RATE_DL_NO_ABIS = 0)

• high Resource Assignment rate (RESOURCE_ASSIGN_RATE)

• Moderate Abis utilization is reflected in the moderate HR penetration (HR_USAGE): in BR if percentage of busy Abis resources is above predefined threshold HR starts to be allocated due to Abis shortage

Class A

• Max theoretical EDAP = 4*(31-1-2*6) =72 ; however in practice (due to EDAP limitation in GEMINI to 12) => max EDAP = 48

• BTSM 64.12 after migration can have max EDAP size of 48 subchannels (12 Abis TSLs)

• Currently it uses up to 59 subchannels

• EDAP size will be high enough to keep up the current performance

Identification of Class A sites Identification of Class A sites (2/2)(2/2)

theoretcial EDAP =72 subTSLs

currently no Abis blocking ->site is not classified as Class C

site is not classified as ClassD

EDAP =48 subTSLs


• Presented slides aims to propose the methodology to identify possible needs for PCM line extensions after migration to GEMINI

• By following this methodology it is possible to estimate quantity requirements for PCM line extension and approximate extra cost related to this

• All defined KPIs are valid if Packet Flow Context is disabled (almost 100% of all cases); if PFC is active (PFCSUP= ENABLED) then formula must be enhanced to include also subcounters for streaming and interactive traffic class

• Since PS traffic volume is usually much higher in DL than in UL therefore all PS related KPIs are defined for downlink;

if PS traffic volume is higher in UL then all KPIs must be modified to replace DL related subcounters with UL related

• Since migration to GEMINI is possible from both BR9.0 and BR10.0 all KPIs defined in this slide set (dedicated for BR line) are valid for BR9.0 and BR10.0

SummarySummary


Documents

Day2 Abis Capacity Evaluation for Network Modernization With GEMINI