WCDMA CSSR Optimization Tips

In this paper I would like to share how to improve Call set up Success Rate in WCDMA system.

In WCDMA CSSR is split per services such as: CSSR CS(Voice services), CSSR PS(Data services), CSSR Video(Video services) but the idea is same when we would like to improve Call set up success rate.

Here are some tips how to improve CSSR in WCDMA:

- Make sure no Blocking resources: Code,Power,CE,IUB

As we know in 3G WCDMA there are some resources like Code,Power,CE(Channel Element) and IUB. You have to make sure no blocking resources first to improve your CSSR. If you found some blocking based on your counter then you have to optimize. Here are some suggestion step to optimize blocking resources:

1. Code Blocking Optimization step:

1st action step: Physical Audit (involving TP analysis) : Make sure no overlap/overshooting coverage

2nd Action: Modify DLHOCECODERESVSF to lower SF (e.g from SF32 to SF 64)

3rd Action: Reduce HSPDSCHMINCODENUM (e.g from 5 to 4)

4th Action: Reduce HSSCCHCODENUM (e.g from 4 to 3)

2. Power Blocking Optimization Step:

- UL- Power Blocking

1st Action: Physical Audit (involving TP analysis)

2nd Action: Increase ULTOTALEQUSERNUM (e.g from 160 to 180)

3rd Action: Turn-off NBMULCACALGOSELSWITCH (set to ALGORITHM_OFF)

- DL- Power Blocking/DL - Power High Util

1st action: Physical Audit (involving TP analysis)

2nd Action: Activate 40W, maintain existing PCPICH setting

Step activate 40W in Huawei System:

- Block board with script: BLK BRD:CN=1,SRN=4,SN=x;

- Remove Locell  for 2nd carrier in nodeb with script : RMV LOCELL:LOCELL=x;

- Add Locell on 2nd carrier with script: 

ADD LOCELL:LOCELL=x,STN=x,SECN=x,SECT=LOCAL_SECTOR,ULGROUPNO=0,DLGROUPNO=0,TTW=FALSE,CN1=1,SRN1=4,SN1=x,ANT1N=ANTB,ULFREQ=9638,DLFREQ=10588,MXPWR=460,HISPM=FALSE,RMTCM=FALSE,VAM=FALSE;

- Modify Power to 40 W for 1st carrier with script: MOD LOCELL:LOCELL=x,SECT=LOCAL_SECTOR,MXPWR=460;

- Unblock Board with script: UBL BRD:CN=1,SRN=4,SN=x;

- Modify MAXTXPOWER  in RNC level for F1 dan F2 with script: MOD UCELL:CELLID=x,MAXTXPOWER=460;

- Check site Up or not with script: DSP UCELL:DSPT=BYNODEB,NODEBNAME="x";

3rd Action: Modify DL CAC parameters set to higher value. Parameters involved : DLCONVAMRTHD, DLCONVNONAMRTHD, DLOTHERTHD, DLHOTHD, DLCELLTOTALTHD

3. CE Blocking Optimization Step:

1st action: Verify CE license and CE board capability. Commands involved : DSP LICENSE, DSP BBPTC(Huawei LMT)

2nd Action: Physical Audit (involving TP analysis)

3rd Action: CE license and/or board upgrade

4th action: Modify LDR threshold. Sets involved : UCELLLDM, UCELLLDR

4. IUB Blocking Optimization Step:

1st Action: Verify Iub BW setting in Node-B and in RNC. Sets involved : IPPATH, IPLOGICPORT

2nd Action: Physical Audit (involving TP analysis)

3rd Action: Iub BW upgrade

4th action: Modify FTI to reduce Active Factor. Sets involved : TRMFACTOR, ADJMAP, ADJNODE

- Make Sure no Hardware Issue:

Hardware issue or wrong installation can be impacted to low CSSR such as WRFU problem or bad connector installation. You have to make sure no such hardware problem to make your CSSR good.

- Make Sure no Overshooting Coverage

As stated on resources optimization, you need to make sure no overshooting or coverage overlap to make your CSSR is good and no handle unnecessary traffic and make nodeB handle traffic heavily.

- Activate EFD(Enhanced Fast Dormancy) Feature

When fast dormancy, enhanced fast dormancy, or standard fast dormancy is applied, the UE can request the RNC to release the PS signaling connection if no more PS data is being transmitted. Upon receiving such a request, the RNC can either release the signaling connection and put the UE into idle mode, or maintain the signaling connection and put the UE through Cell_FACH to CELL/URA_PCH state to reduce battery consumption. The descriptions about fast dormancy, enhanced fast dormancy, and standard fast dormancy are as follows:

- With fast dormancy, after receiving a Signaling Connection Release Indication (SCRI) message from a UE, the RNC releases the UE RRC connection regardless of whether the message contains the cause value "UE Requested PS Data session end."

- With enhanced fast dormancy, UEs send SCRI messages that do not contain the cause value "UE

Requested PS Data session end" to the RNC. After receiving such an SCRI message, the RNC moves

the UE through Cell_FACH to CELL/URA_PCH state.

- Standard fast dormancy is applicable to fast dormancy UEs that comply with 3GPP Release 8 (R8 for short). With standard fast dormancy, UEs send SCRI messages that contain the cause value "UE

Requested PS Data session end" to the RNC. After receiving such an SCRI message, the RNC moves

the UE through Cell_FACH to CELL/URA_PCH state. Standard fast dormancy is valid only when theRNC has enabled the timer T323 in system information block type 1 (SIB1). You can refer to the document on your vendor to activate EFD feature.

- Adjust CPICH Power Setting

You can adjust CPICH Power setting to reduce coverage and improve your CSSR Ex: Change PCPICHPOWER from 330 to 300.

- Adjust Parameter QQUQALMIN

You can adjust QQUALMIN to improve CSSR and avoid congestion on blocking resources especially during event with potential to increasing traffic. Example: Change Qqualmin from -18 to -15 to avoid congestion.

You might also Need to know:
- How to Optimize Handover Success Rate in GSM Network
- CSSR Optimization for GSM
- Drop Call Rate Optimization in GSM and UMTS
- Power Control activation for Electricity Saving in Huawei GSM

CSSR Optimization for GSM and WCDMA

CSSR stands for Call Set up Success Rate  that is one of important KPI(Key Performances Indicator) in Optimization both GSM and UMTS/WCDMA. For the beginning we have to know that KPI in WCDMA including CSSR are separated based on each Services such as : CSSR CS( for Voice services), CSSR PS(for PS/Data Services), CSSR Video(for Video Services),CSSR HSDPA(For HSDPA Services), CSSR HSUPA(for HSUPA Services). In GSM there is only one type CSSR(Voice Services), For Data services usually called as PDASR(Packet data Access Success Rate) or TBF Establishment Success Rate.There are some tips how to optimizes CSSR in GSM and WCDMA.
1. GSM CSSR Optimization tips 
-Make Sure no Hardware issue
Hardware checking is always the first step to check all KPI because you will have no impact about your action if common problem like Hardware or Installation has occurred in your network. Defect GRFU/CU(TRX Module) or Combiner will make CSSR degraded below 95%. Swap module to other sector to identify the problem and replace bad module.Also make sure no problem with Power or Transmission. Check for TCH availability and active alarm to make sure no hardware issue.
-Make Sure no SD Blocking
Lack of SDCCH can make degradation in CSSR because SD Blocking included in CSSR Formula, make sure no SD Blocking found in your cells. If found then you have to add SD channel based on Erlang Calculation. If you lazy to calculate, just add 1 channel first :D ,then increase 1 channel again if still found Blocking on SDCCH.
-Make Sure no Frequency Interference
Frequency Interference can make high SD drop in your cells.SD drop also included in CSSR Formula,check for SD drop first if found then you need to clear the cells by re-tune/change BCCH Frequency. Interference problem also will impact to other KPI like drop call rate, Handover, etc
-Make Sure no Overshooting
Overshooting also will make your CSSR getting low and under threshold because to much attempt at the edge of Coverage with low RX Level. You have to make sure no overshooting occurred to make good CSSR. If found then you need to adjust your coverage by add Tilting value(Down Tilt)
-Tuning Parameter
You need to change parameter smoothly if all main problem have cleared. Try to change wisely related access parameter such as : RXLEVAMI/RXLEVACCMIN/AccMin(Different name between Vendor),RACHBT,T200,MAXRETR,etc.Make sure no extreme setting to avoid bad user perception :D.
-TRX Layering
Shifting traffic from bad TRX  to Good TRX can improve your KPI included CSSR. Try to set Good TRX as high priority  and bad TRX as lowest priority to improve your CSSR. TRX BCCH usually has better Quality to set as highest priority because Full Power(No Power Control).

2. WCDMA CSSR Optimization Tips
Continued here

You might also Need to know:
- How to Optimize Handover Success Rate in GSM Network
- Drop Call Rate Optimization in GSM and UMTS
- Power Control activation for Electricity Saving in Huawei GSM

Drop Call Rate Optimization, How to identify and finding root cause for Optimization solution on GSM and UMTS Network

Drop call rate is Main KPI that very important in RF Optimization. Drop Call  indicate how connection between Handset and Network become discontinue and causing bad experiences on user experiences because the call is release suddenly. In this paper I will share everything I know related drop call rate both on GSM and UMTS Network. Based on my experience the root cause of Drop Call Rate can be listed as follow:
- Hardware Problem.
This problem is very critical related to all KPI including Drop Call rate. If the problem is coming from hardware, percentage of drop call rate would be very high(usually more than 1 %) and you have to replace bad module with good module. For example in GSM Network you have to check and make sure TRX module such as GRFU/CU or Combiner/Duamco working properly. To make sure the problem was coming from hardware or bad module, you can identify by trying Swap module first. For example: if the problem high drop call rate is occurred in sector-1, you can swap TRX Module sector-1 to sector-2 and Combiner from sector-1 to sector-3. If the problem move to other sector then indicate the problem is coming from that module. For example in the above case if the problem move to sector-2, so the problem is TRX Module(GRFU/CU) or if the problem move to sector-3 then the problem should be Combiner/Duamco. In UMTS Network also same, if the problem is coming from hardware then you have to identify what module the problem is. You can identify the problem by swap WRFU Module. If the problem high drop call happened in one site/NodeB, you can try swap GTMU(Transmission module). Beside defect module the problem can be occurred due to wrong or bad installation such as Semirigid connection, Cross feeder problem or etc(especially for new site)
- Frequency Interference. 
Frequency interference is include in problem that can impact to high drop call rate because the Noise(Interference Signal) is very high and affecting to Carrier( primary Signal) and also affect to bad vice quality. To overcome the problem in GSM network you have to re-tune/ change Frequency that suspected Interference especially on BCCH Frequency for RF Hoping cells. As we know in GSM there area 2 type of Frequency Interference that called Co-Channel Interference(Same Frequency) and Adjacent Interference( Difference 1 Frequency  channel). Sample for Co-channel Frequency : Frequency Cell A=  Cell B = 670 with close location of cell each other. Sample for Adjacent Interference : Frequency Cell A=670 and Cell B=671 or 669 and the position of cells is close each of other. The solution in GSM network for interference is retune or change Frequency for one of the cells to avoid interference. in UMTS network the frequency interference also can occurred and indicated by bad Ec/No(Quality).Different with GSM, to overcome Interference in UMTS network is commonly solved by Change Antenna Tilt or reduce CPICH Power to avoid Coverage overlap. The other solution to reduce Drop call rate in UMTS Network is by making fast IRAT handover to GSM Network. In Huawei implement by Changing Parameter IRAT Handover 2D/2F.
- Overshooting Cells
Overshooting cell can be the one that causing high drop call rate in the network.To overcome this issue you have to change tilt configuration of Antenna, for example change Mechanical Tilt  from 0 to 2. Overshoot is common problem for both GSM and UMTS that causing drop call due to bad RX level in the edge of Coverage or bad RSCP and Ec/No in UMTS Network. The solution is same for both GSM and UMTS that is change Antenna configuration tilt/Down tilt.
- Missing neighbor.
Missing neighbor also will causing High drop call rate in your network. You have to check and make sure relation of the cells is complete and  no missing neighbor. The solution is same for both GSM and UMTS, you have to make sure no missing neighbor to avoid high drop call rate.
- Wrong Parameter Configuration
Wrong parameter configuration will causing high drop call rate in your network. Make sure to check all parameter and configure accordingly.In GSM there is parameter related drop call rate KPI such as : RLT(Radio Link Timeout), You can set by increase RLT to reduce drop call but will affect to Customer Experiences because release call is too long even when radio environment is poor and conditionally should be released. The other solution to reduce drop call related parameter is by adjust HO Parameter to make fast handover to a good cells in surrounding closest cells such as adjust PBGT, RXLEVMIN to target Cells. Making fast HO to a good cells can be implemented on both GSM and UMTS Network. You have to find out parameter related Radio Link and HO parameter in your vendor you are working for because the Parameter name would be different but in same Idea That is Radio Link Time out and Handover Parameter.
- Power or Transmission Problem
Power problem can make high drop call rate in the network. You have to make sure no power problem by check the alarm and Cell Availability.If the problem occurred you need to follow up the problem to Field Maintenance Team to fix it.
Transmission problem also can make drop call rate very high and affecting to your KPI. You need to check alarm related transmission and make sure also cell availability is stable. If you found transmission problem the you have to follow up the problem to Transmission Team to check and fix it.
- Contour Problem(Hilly/Rural Contour)
Bad contour can be the one that causing high drop call rate especially if your network in Hilly or Rural area. Check and identify your cells by drive test to make sure the problem is causing by contour or check the coverage by Simulation. If the problem is bad contour then you have to  adjust tilt of the cell or re-azimuth make sure coverage continuous.
- Discontinuous Coverage
If your coverage discontinue due to lack of site then you need to propose new site to your operator. Discontinue coverage also can occurred due to wrong antenna configuration such as over tilt. You need to check tilt configuration of the antenna and make sure no over tilt that causing coverage become discontinue.

Thanks for visiting my blog and hope can help your network problem related Drop Call Rate Optimization on GSM and UMTS Network

You might also Need to know:
- How to Optimize Handover Success Rate in GSM Network
- CSSR Optimization for GSM and WCDMA
- Power Control activation for Electricity Saving in Huawei GSM
- Handover Optimization Improvement step in GSM