Parameter Setting Keep Voice Traffic in 3G Network Huawei

Keep Voice Traffic in 3G network is one of strategic optimization in Cellular network. The reasons why should keep traffic in 3G shall be: 2G network Congestion/Blocking issue,2G network problem(HW/issue,Interference) even 2G network will be dismantled.

Today I would like to share Parameter setting to keep voice traffic in 3G due to 2G network Capacity will be decreased caused 4G Network will be deployed and use 2G Bandwidth. 2G will be dismantled due to 4G Network will be implemented so voice traffic will be keep in 3G network and all parameter that previously sharing to 2G will be disabled.

Below are list parameter in 3G Huawei to keep voice traffic in 3G network:

1. Decrease value setting of  2D/2F: 

  INTERRATCSTHD2DECN0: ex:-14 to -20

  INTERRATCSTHD2FECN0: ex:-12 to -18

  INTERRATCSTHD2DRSCP ex:-100 to -105

  INTERRATCSTHD2FRSCP ex: -97 to - 102

2. Decrease value setting of QQUALMIN ex: -18 to -22

3. Decrease value setting of FDDQMIN ex: -14 to -20(SET GCELLCCUTRANSYS in 2G side)

4. Remove IRATCS in UCELLLDR :  CSInterRatShouldNotLDHO/CSInterRatShouldBeLDHO

5. Setting SBHO to OFF : CSSERVICEHOSWITCH=OFF (Command:UCELLHOCOMM)

Detail Parameter can be described as follow:

INTERRATCSTHD2DECN0:

Threshold of triggering inter-RAT measurement for CS services when measurement quantity is Ec/No. The threshold of triggering the inter-RAT measurement (the threshold of enabling the compressed mode) is a key parameter in the inter-RAT handover policy. The setting of this parameter affects the proportion of the UEs in compressed mode in a cell and the success rate of the hard handover. The setting of this parameter should consider two factors, moving speed of the UE and cell radius. When Ec/No is used as the measurement quantity for CS services, the UE reports event 2D when the measured Ec/No value is lower than this threshold. Then, the RNC sends the signaling to enable the compressed mode and start inter-RAT measurement. For the UE moving at a speed of 5 km/h, the recommended threshold is -17 dB; for the UE moving at a speed of 50 km/h, the recommended threshold is -14 dB; for the UE moving at a speed of 120 km/h, the recommended threshold is -12 dB. In actual networks, set this parameter to -14 dB because the UEs in a cell usually move at different speeds. The emulation result shows that the call drop rate remains low for the UEs moving at a speed of 120 km/h when this parameter is set to -14 dB. If the cell is a macro cell, it indicates that micro cells exist in this cell. To enable the micro cells to handle more traffic, the compressed mode start and stop thresholds should be set higher, that is, the thresholds for events 2D and 2F using CPICH RSCP are set higher. If the cell is a micro cell, the default value should be modified according to the link budgeting result. Event 2D and event 2F are used to enable and disable the compressed mode respectively. When the cell is located in the center of the frequency coverage or the inter-frequency measurement quantity uses both Ec/No and RSCP, then the Ec/No value is used as the criterion for events 2D and 2F. To enable the compressed mode earlier, increase the threshold of triggering event 2D; otherwise, decrease the threshold of triggering event 2D. To prevent the frequent enabling and disabling of the compressed mode, increase the difference between the thresholds of triggering event 2D and event 2F. Event 2D and event 2F are used to enable and disable the compressed mode respectively in inter-RAT measurement. The requirements on the signal quality and inter-RAT handover policies vary with the service type. Therefore, the thresholds of enabling and disabling inter-RAT measurement are distinguished by CS, PS, and signaling. To enable the compressed mode earlier, increase the threshold of triggering event 2D; otherwise, decrease the threshold of triggering event 2D. To prevent the frequent enabling and disabling of the compressed mode, increase the difference between the thresholds of triggering event 2D and event 2F.

INTERRATCSTHD2FECN0:

Threshold of stopping inter-RAT measurement for CS services when measurement quantity is Ec/No. The threshold of stopping the inter-RAT measurement (the threshold of disabling the compressed mode) is a key parameter in the inter-RAT handover policy. The setting of this parameter affects the proportion of the UEs in compressed mode in a cell and the success rate of the hard handover. The setting of this parameter should consider two factors, moving speed of the UE and cell radius. When Ec/No is used as the measurement quantity for CS services, the UE reports event 2F when the measured Ec/No value is higher than the value of this parameter. Then, the RNC sends the signaling to disable the compressed mode and stop the inter-frequency measurement. If the cell is a macro cell, it indicates that micro cells exist in this cell. To enable the micro cells to handle more traffic, the compressed mode start and stop thresholds should be set higher, that is, the thresholds for events 2D and 2F using CPICH RSCP are set higher. If the cell is a micro cell, the default value should be modified according to the link budgeting result. Event 2D and event 2F are used to enable and disable the compressed mode respectively. When the cell is located in the center of the frequency coverage or the inter-frequency measurement quantity uses both Ec/No and RSCP, then the Ec/No value is used as the criterion for events 2D and 2F. To enable the compressed mode earlier, increase the threshold of triggering event 2D; otherwise, decrease the threshold of triggering event 2D. To prevent the frequent enabling and disabling of the compressed mode, increase the difference between the thresholds of triggering event 2D and event 2F.

INTERRATCSTHD2DRSCP:

Threshold of triggering inter-RAT measurement for CS services when measurement quantity is RSCP. When RSCP is used as the measurement quantity for CS services, the UE reports event 2D when the measured RSCP value is lower than this threshold. Then, the RNC sends the signaling to enable the compressed mode and start the inter-RAT measurement. To enable the compressed mode earlier, increase the threshold of triggering event 2D; otherwise, decrease the threshold of triggering event 2D. To prevent the frequent enabling and disabling of the compressed mode, increase the difference between the thresholds of triggering event 2D and event 2F. In most cases, users want to be maintained within a 3G network. Therefore, the start threshold of the inter-RAT measurement is set smaller than that of the inter-frequency measurement in order to trigger inter-frequency easily. In scenarios where inter-frequency neighboring cells are unavailable or where inter-frequency coverage is insufficient, the inter-RAT measurement start threshold should be set relatively larger in order to trigger inter-RAT measurement easily, thus reducing call drops.

INTERRATCSTHD2FRSCP:

Threshold of stopping inter-RAT measurement for CS services when measurement quantity is RSCP. When RSCP is used as the measurement quantity for CS services, the UE reports event 2F when the measured RSCP value is larger than this threshold. Then, the RNC sends the signaling to disable the compressed mode and stop the inter-RAT measurement.

QQUALMIN:

Minimum CPICH Ec/No for the neighboring cell on cell reselection. The neighboring cell can be involved in cell sorting for reselection only when its CPICH Ec/No is above this threshold. If this parameter is set to the same value as Qqualmin for the serving cell, Qqualmin is not contained in SIB11 or SIB12. In this case, the UE extracts the Qqualmin from SIB3. For details, see the 3GPP TS 25.331. According to the 3GPP TS 25.304, S criterion for cell reselection is defined as follows: Srxlev > 0 and Squal > 0 Here, Squal = Qqualmeas - Qqualmin Srxlev = Qrxlevmeas - Qrxlevmin - Pcompensation "Qqualmeas" refers to the measured CPICH Ec/No. "Qrxlevmeas" refers to the CPICH RSCP. "Qrxlevmin" refers to the minimum CPICH receive power in the current cell. Pcompensation = max(UE_TXPWR_MAX_RACH - P_MAX, 0) "UE_TXPWR_MAX_RACH", also named as "MaxAllowedULTxPower", refers to the maximum uplink transmit power when the UE accesses a cell. "P_MAX" refers to the maximum RF output power of the UE.

FDDQMIN:

This parameter specifies one of the parameters for FDD cell reselection. A FDD cell becomes a candidate cell if all the following conditions are met for five consecutive seconds: 1.Receive level of the FDD cell > Average receive level of the current serving cell + "FDD Q offset"; The FDD cell meets the following condition in the case of any neighboring 2G cell: Receive level of the FDD cell > Receive level of any neighboring 2G cell + "FDD Q offset"; 2. Ec/No of the FDD cell > "FDD Qmin" - "FDD Qmin Offset"; 3. Receive level of the FDD cell > "RSCP Threshold"; If multiple FDD cells meet the preceding conditions, the MS reselects the cell with the strongest receive level. See 3GPP TSs 45.008 and 25.304. The values of this parameter correspond to the following decibel values: 0: -20 dB, 1: -6 dB, 2: -18 dB, 3: -8 dB, 4: -16 dB, 5: -10 dB, 6: -14 dB, 7: -12 dB.

UCELLLDR: 

Remove: CSInterRatShouldNotLDHO/CSInterRatShouldBeLDHO

DL LDR first action-10th/UL LDR first action-8 action:

NOACT: No load reshuffling action is taken. INTERFREQLDHO: The inter-frequency load handover is performed. BERATERED: Channels are reconfigured for the BE service. QOSRENEGO: The renegotiation on the QoS of the uncontrollable real-time service is performed. CSINTERRATSHOULDBELDHO: The inter-RAT SHOULDBE load handover of the CS domain is performed. PSINTERRATSHOULDBELDHO: The inter-RAT SHOULDBE load handover of the PS domain is performed. AMRRATERED (AMR service rate decreasing): The setting of the TFC subset and the negotiation of the service rate can be performed for the AMR voice service. MBMSDECPOWER (MBMS power limiting): The MBMS service is configured with the minimum power. CODEADJ (code tree reshuffling): The fragments of the downlink code tree are arranged. PSINTERRATSHOULDNOTBELDHO: The inter-RAT SHOULDNOTBE load handover of the PS domain is performed. PSINTERRATSHOULDNOTLDHO: The inter-RAT SHOULDNOTBE load handover of the PS domain is performed. The LDR takes the actions in the preset sequence and judges whether each action is successful. If an action is unsuccessful, the LDR turns to the next action. If an action is successful, a parameter is set to NOACT, or all the preceding actions are taken, the downlink LDR is finished, and the system waits for the next triggering of the LDR. Because each action is performed by its algorithm module, the LDR algorithm only selects users and delivers control messages, the execution result of each action can be obtained after a delay, and the LDR algorithm cannot wait for a long time, so the LDR can only judge whether the actions succeed by whether candidate users are found. The inter-frequency load handover has no impact on the QoS of users and can balance the cell load, so the inter-frequency load handover usually serves as the first action. The BE service rate reduction is effective only when the DCCC algorithm is enabled.

Step each command script are as follow:

1. UINTERRATHOCOV(RNC Parameter)

Script:

SET UINTERRATHOCOV:INTERRATCSTHD2DECN0=-20,INTERRATCSTHD2FECN0=-18,INTERRATCSTHD2DRSCP=-105,INTERRATCSTHD2FRSCP=-102;

Fallback:

SET UINTERRATHOCOV:INTERRATCSTHD2DECN0=-14,INTERRATCSTHD2FECN0=-12,INTERRATCSTHD2DRSCP=-100,INTERRATCSTHD2FRSCP=-97;

2. UCELLINTERRATHOCOV(Cells Parameter)

Script:

MOD UCELLINTERRATHOCOV:CELLID=30289,INTERRATCSTHD2DECN0=-20,INTERRATCSTHD2FECN0=-18,INTERRATCSTHD2DRSCP=-105,INTERRATCSTHD2FRSCP=-102;

Fallback:

MOD UCELLINTERRATHOCOV:CELLID=30289,INTERRATCSTHD2DECN0=-10,INTERRATCSTHD2FECN0=-8,INTERRATCSTHD2DRSCP=-90,INTERRATCSTHD2FRSCP=-87;

3. a.UCELLLDR(DL)

Script:

MOD UCELLLDR:CELLID=30639,DLLDRTHIRDACTION=PSInterRatShouldNotLDHO,DLLDRFOURTHACTION=InterFreqLDHO,DLLDRFIFTHACTION=NoAct;

Fallback:

MOD UCELLLDR:CELLID=30639,DLLDRTHIRDACTION=CSInterRatShouldNotLDHO,DLLDRFOURTHACTION=PSInterRatShouldNotLDHO,DLLDRFIFTHACTION=InterFreqLDHO;

3.b.UCELLLDR(UL)

Script:

MOD UCELLLDR:CELLID=30639,ULLDRSECONDACTION=PSInterRatShouldNotLDHO,ULLDRTHIRDACTION=InterFreqLDHO,ULLDRFOURTHACTION=NoAct

Fallback:

MOD UCELLLDR:CELLID=30639,ULLDRSECONDACTION=CSInterRatShouldNotLDHO,ULLDRTHIRDACTION=PSInterRatShouldNotLDHO,ULLDRFOURTHACTION=InterFreqLDHO;

4. UCELLHOCOMM

Script:

MOD UCELLHOCOMM: CellId=39251, CSSERVICEHOSWITCH=OFF;

Fallback:

MOD UCELLHOCOMM: CellId=39251, CSSERVICEHOSWITCH=ON;

Above parameter mentioned are valid only for Huawei Network because we are in Huawei project.

Hope can use full for you who want to know deep about keeping voice traffic in 3G instead of 2G network for voice quality improvement.

You might also Need to know:

- VQI Optimization Improvement by turn off Speech codec 5.9, 7.4 and 4.75 Kbps in Huawei 2G Network

- VQI(Voice Quality Index) and Drop Call rate improvement in 2G Huawei by Setting more Full Rate and redimension channel

- 2G Theory and Concept

- Common question about RF Optimization

- TCH Block Rate Optimization Tips in Huawei GSM

- 2G Voice Quality Improvement by TRX Layering priority in Huawei GSM

- TBF Drop Improvement tips in Huawei GSM

- GPRS Packet Data Access Success Rate(PDASR) Improvement in Huawei GSM

- Call Drop Rate improvement by Parameter change in 3G UMTS/WCDMA Huawei Network

- Trial Power Control in GSM Huawei for Quality Improvement

- Power Control activation for Electricity Saving in Huawei GSM

- Handover Meaning in GSM and How to Optimize Handover Success Rate (HOSR) for GSM KPI Improvement

- WCDMA CSSR Optimization Tips

- CSSR Optimization for GSM and WCDMA

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

VQI Optimization Improvement by turn off Speech codec 5.9, 7.4 and 4.75 Kbps in Huawei 2G Network

In this chapter I would like to share about VQI(Voice Quality Index) improvement in Huawei 2G Network by setting off Several speech codec.Turn off speech codec is a better way to improve Voice Quality Index(VQI) in 2G network and Your KPI will improve significantly. As I share before, we can also improve VQI by setting more Full rate and re-dimension channel. Setting more Full rate and re-dimension channel to be More TCHFR also working but you will get more result and significant improvement on VQI by turn off several lower codec 5.9, 7.4 and 4.75 Kbps. Here is the result of VQI after turn off codec 5.9, 7.4 and 4.75 kbps in Huawei 2G network.

From the above Graph we can see the result of  VQI 3.5 improved significantly after turn off speech codec 5.9,7.4 and 4.75 Kbps. Now you can trial and implement also in your Network to get same result for the optimization improvement.Detail technical step and parameter change can be shown as below list.

Script Parameter change for above change request:
SET GCELLCCAMR:IDTYPE=BYID,CELLID=XXX,,ACTCDSETF=4_75KBIT/S-0&5_15KBIT/S-0&5_90KBIT/S-0&6_70KBIT/S-0&7_40KBIT/S-0&7_95KBIT/S-0&10_2KBIT/S-0&12_2KBIT/S-1;

Conclusion to improve Voice Quality index(VQI) in Huawei 2G Network:
1. Increase Full rate and re-dimension channel, result==>Little bit VQI improvement
2. Turn off codec 5.9,7.4 and 4.75 Kbps, result==>Significant VQI Improvement

You might also Need to know:
- VQI(Voice Quality Index) and Drop Call rate improvement in 2G Huawei by Setting more Full Rate and redimension channel
- 2G Theory and Concept
- Common question about RF Optimization
- TCH Block Rate Optimization Tips in Huawei GSM
- 2G Voice Quality Improvement by TRX Layering priority in Huawei GSM
- TBF Drop Improvement tips in Huawei GSM
- GPRS Packet Data Access Success Rate(PDASR) Improvement in Huawei GSM
- Call Drop Rate improvement by Parameter change in 3G UMTS/WCDMA Huawei Network
- Trial Power Control in GSM Huawei for Quality Improvement
- Power Control activation for Electricity Saving in Huawei GSM
- Handover Meaning in GSM and How to Optimize Handover Success Rate (HOSR) for GSM KPI Improvement
- WCDMA CSSR Optimization Tips
- CSSR Optimization for GSM and WCDMA
- Drop Call Rate Optimization, How to identify and finding root cause for Optimization solution on GSM and UMTS Network

2G Theory and Concept

This chapter is part of previous post about Common question about RF Optimization.In This post I would like  to share about 2G theory and concept that I ask to RF Guys that promoted to become RF Optimization Engineer. May be this post also use full for you especially for RF Engineer who will promoted also to become Optimization guy or just for your reference to improve your knowledge about basic RF Optimization. Here are the question that I made for RF Team and also the Best Answer I got from the Winner.

1. What do you know about interference?

Interference definition from Wikipedia:"interference is a phenomenon in which two waves superpose to form a resultant wave of greater, lower, or the same amplitude. Interference usually refers to the interaction of waves that are correlated or coherent with each other, either because they come from the same source or because they have the same or nearly the same frequency"

Good Answer from RF Team: 
Interference is RF Condition when Primary signal(Carrier) disrupted by other Signal that have same frequency or gap +-1 value of Primary frequency. There are 2 type of  Channel interference:  Co-channel interference and Adjacent Interference.
- Co-channel Interference  is interference caused by the use of the same frequency by a cell carrier and also another cell and its antenna facing each other. Example : Cell A with frequency 642 facing cell B with same frequency 642 too.

- Adjacent Interference is interference when Primary cell interfered by other cells with have frequency value gap +-1 from Primary cell. Example: Cell A with frequency 642 interfered by Cell  B with frequency 641 or Frequency C with frequency 643

2. How to improve Voice Quality in 2G?
There area many ways to improve voice quality such as: Clearing frequency interference, Hardware problem solving, transmission problem clearance, TRX Layering Priority and Increase Full rate setting. Buat Answer from RF Team is to the point--->>Increase Full rate Setting(Reduce Half rate) by setting TCHBISYTHRESHOLD and AMRTCHHPRIORLOAD for cells with low TCH Utilization.Of course this is correct answer because we are in Huawei Project :D. Increase Full rate also great impact to reduce drop call rate and improve VQI(Voice Quality Index) in 2G Huawei network

3.What is different between Cell selection/reselection and Handover?
Good Answer from RF team:
- Cell selection is The condition when UE camp on a Cell during start up from Switch Off
- Cell reselection : The condition when UE re-camp to other cell from a cell in Idle Mode because of UE moving
- Handover: The condition when serving cell change from a cell to other cells during connected mode because of UE moving.

4. What do you know about CRO?
Good answer from RF team:
CRO: Cell reselect Offset 
Coefficient that functioned to make a cell aggressive serving(dominant) or not dominant. When PT=0,Increasing this value will make serving cells aggressive(increasing traffic).When PT=31,increasing this value will make serving not dominant

5. In order to increase TCH traffic(erl),PT setting to zero(PT=0).What is the setting of CRO? Increase or decrease?
Correct answer: Increase value of CRO(cell reselect offset)

6. Please explain how to do traffic sharing in 2G?
Good answer from RF Team:
- Audit neighbor cells and do physical tuning.
- Make Faster/Easier Handover to neighbor cells for cells with high traffic to the lowest traffic. Ex: decrease value of: HOM(Handover margin),etc
-Make difficult handover from other cells to the highest traffic cells(ex: Increase HOM)
-Idle Setting parameter: Increase value of CRO for low traffic cells(PT=0)

7. What do you know about Power Control in GSM?
Good Answer from RF Team:
Power control is used to save power consume of MS/BTS. Power in MS/BTS will decrease in certain threshold when signal is considered as a Good and increase when considered as a bad.Power control is also used to reduce frequency interference.

8.There are 1 TRX in a cell in Hoping mode that not used power control but use Full power.Which one of TRX?

Correct Answer: TRX BCCH(TRX:0)

9. What is the benefit of Handover?
Good Answer from RF Team: Handover keep a call connected while user moving and continuing conversation between user.Handover also reduce interference and avoid cells overload.

10. What do you know about PBGTMARGIN?
PBGTMARGIN( Power Budget Margin) is Handover margin parameter in adjacent level that used to make faster or delay of handover to keep good mobility.

11. If you found TCH Blocking, what are your action to optimize TCH Blocking rate?
Good Answer from RF Team:
 - Check for channel allocation, check SDCCH utilization, if found low SDCCH Utilization(<<60%) then need to convert SDCCH to TCHFR
- Check hardware problem(get measurement TCH availability from statistic), if found degraded the need to escalate hardware problem to Field maintenance Team
- Check Timing advance, if found High TA need to do physical Tuning(down tilt)
- Check Neighbor relation, make sure doesn't missing any relation that causing handover problem and impact to congest on a cell.
- Check Half Rate Parameter (TCHBUSYTHRESHOLD/AMRTCHHPRIORLOAD ex. in Huawei), adjust HR setting if needed--->reduce value of TCHBUSYTHRESHOLD/AMRTCHHPRIORLOAD.

12. How Many MCS used in EDGE ?
Correct Answer: 9 MCS

2G Daily OSS and Optimization Analysis 
To be Continued

You might also Need to know:
- TCH Block Rate Optimization Tips in Huawei GSM
- 2G Voice Quality improvement by TRX Layering Priority
- TBF Drop Improvement tips in Huawei GSM
- GPRS Packet Data Access Rate(PDASR) Improvement in Huawei GSM
- Common question about RF Optimization
- VQI(Voice Quality Index) and Drop Call rate improvement in 2G Huawei by Setting more Full Rate and redimension channel 












 

VQI(Voice Quality Index) and Drop Call rate improvement in 2G Huawei by Setting more Full Rate and redimension channel

VQI(Voice Quality Index) is Statistic KPI that indicate quality of voice services in GSM network, mostly identical with SQI(Speech Quality Index) in drive test performances. This KPI is also important to improve  and great influences to Drop call rate improvement.Good VQI means good voice quality and thus improving drop call rate performances in our network.There are some method  and step to improve voice quality, The common method is by setting more Full rate(decrease Half Rate services). As we know Full rate is better than Half rate if TRX resources is sufficient(doesn't limited). Half rate usually get more influenced by interference while Full rate is better and good perform as anti interference that's why Full rate services better than Half rate regarding quality improvement of voice services in GSM. Beside setting more full rate, we can also do re-dimension channel by change SDCCH or PDTCH into TCHFR. Please note that we only change for cells with low SDCCH or PDCH Utilization, don't change cells with high SDCCH or PDTCH utilization because will impact to blocking on SDCCH and PDTCH and also Packet Data Access Success Rate(PDASR). I have experiences the method of VQI improvement in 2G Huawei Network in My Country(Indonesia) which is located in Central Java area for Hutchison project. The method is listed as below action:
1. Setting more Full rate--->Increase value of TCHBUSYTHRESHOLD and TCHH AMRPRIORLOAD for cells with low TCH Utilization
2. Channel re-dimension----->Change SDCCH and PDTCH to TCHFR for cells with low SDCCH or PDTCH Utilization

Below are snap shoot Parameter change request(PCR) that we submitted in Netwatcher for your references and guidance about the action:
1. Setting more Full rate
Below picture shows parameter changing of TCHBUSYTHRESHOLD and AMRTCHHPRIORLOAD to get more Full rate Service for VQI Improvement

2. Channel re-dimension
Below picture shows Parameter changing of CHTYPE from SDCCH and PDTCH to TCHFR for VQI Improvement. This CR is only needed to change when SDCCH or PDTCH utilization are low(<<70%)

Those above method can be implemented to improve VQI and Drop Call rate for your GSM Network especially Huawei 2G Network. Below are the result after Parameter implemented in our Network Hutchison Central Java Indonesia.

From the above chart show that VQI was improved after parameter implemented: Increase Full rate allocation and redimensioning channel.
Ok, today sharing is enough for optimization tips about VQI and drop call rate improvement in 2G Huawei Network. hope can help you better in Network optimization knowledge and improve your KPI in your network.Thanks.

You might also Need to know:
- TCH Block Rate Optimization Tips in Huawei GSM
- 2G Voice Quality improvement by TRX Layering Priority
- TBF Drop Improvement tips in Huawei GSM
- GPRS Packet Data Access Rate(PDASR) Improvement in Huawei GSM
- Common question about RF Optimization

Common question about RF Optimization

Hi RF engineer,

This month I was assigned by Manager to make some question for RF Team related Job position upgrade from RF to Optimization Engineer. Here I would like to share some question test that I made for RF Team  just for your reference to expand your Optimization knowledge.

2G DT Analysis Part:
1. When you perform drive test in the field then you found dropped Call suddenly. What are the root cause possibility of dropped call and how to solve it?

Good Answer

• Root Cause of Dropped Call:

1. Hardware Faulty
2. Frequency Interference(Co-channel or Adjacent)
3. Neighbor relation problem(missing Neighbor)
4. Low Signal Strength
5. Failed during HO process

• Drop call solution 

1. Hardware Troubleshooting
2. Clearing Frequency Interference
3. Fix Missing Neighbor
4. Antenna Tuning(Physical Optimization)
5. Change Parameter(HO Parameter, RLT,Timer,etc)

2. When you analyze log file you found too many handover failure. What is the root cause of handover failure and what is your action to solve handover failure?

Good Answer

• Root Cause and solution to solve handover failure:

1. TRX module faulty on target cells----> Need to fix TRX Module
2. Missing neighbor---> Fix neighbor relation
3. Congestion on target cells----> Upgrade TRX or HR threshold setting on target cell or Change HO parameter threshold to target cell
4. Frequency interference between source and target cells---->Change Frequency 
5. Far distance between cells----> Antenna tilt optimization or Propose new site to improve coverage

3. When perform Monthly drive test you found too much bad quality(RxQual>>5).  What is the root cause and solution to improve bad quality?

Good Answer

• Root Cause and solution to improve Bad Quality:

1. Interference problem(Co-channel/adjacent/external)----> Fix Interference problem by change frequency(BCCH/TCH) and find out source of external interference then report to Frequency Department regulation(DEPKOMINFO in Indonesia).
2. Hardware problem such as Bad TRX module, Combiner or Crossfeeder/installation problem------>> Fix hardware problem by troubleshooting proposal to FLM Team
3. Bad Level and low signal strength----> Change Antenna Tilt or propose new site to improve coverage

4. When you are positioned as Optimization Engineer, there are complain about Can't make a call. What is the root cause of Can't make outgoing call and what is the solution?

Good Answer

• Root Cause and solution of complain Can't make outgoing call

1. LAC CI didn't yet registered on Core side----->Check and register LAC CI on Core.
2. SDCCH Blocking on the cell-------->Add SD channel
3. Hardware problem(ex: TRX Module faulty or Combiner problem)------> Fix hardware problem
4. Low Coverage--------> Change Antenna tilt or propose new site to improve coverage.

5. What is the different of RXLevel, RXQual and SQI?

Good Answer

• RXLevel: Receive signal level by MS in dBm, where athe lowest value mean the lowest Level, the greatest value means the greatest level
• RXQual: Receive quality of signal by MS from the BTS which have rage from 0-7. The lowest value mean the best quality, the highest value mean the lowest Quality.
• SQI: Speech Quality index, Quality of Speech during dedicated call which range from -20 to 30. The highest value mean the best Quality of speech, The lowest value mean the bad one

6. During perform drive test you found low throughput. What is root cause of low throughput?

Good Answer
The root cause of low throughput:

• Interference problem(bad C/I)---> Clear frequency interference
• High Traffic------> Traffic sharing or change antenna tilt configuration
• Transmission capacity limitation---------> Upgrade Transmission(increase ABIS Capacity)
• Resource blocking(TRX Capacity issue)-------->Upgrade TRX

7. What is mean and root cause of Low signal strength? give some solution
Good Answer
Low signal strength mean low of the received signal level  by MS
Root cause and Solution:

• Hardware Faulty-------> Fix hardware issue
• Cell down-------->Fix cell down and make it up
• Output power problem---> Check setting of TRX Power and fix it.
• Antenna direction problem------->Change Antenna direction
• Over tilt of Antenna configuration-------> Change Antenna tilt(Up tilt)
• Missing neighbor relation-------> Fix missing neighbor
• Site location-----> Adjust Antenna tilt or propose new site to improve Coverage thus improve signal strength.

8. What is the trigger of  Handover?
Good Answer
Trigger of Handover: Level, Quality, Power Budget , Timing Advance.

9. What is the root cause and solution of Call block?
Good Answer
The root cause and solution of Call Block:

• SDCCH Blocking-----> Add SD channel
• TCH Blocking--------> Setting HR threshold, Upgrade TRX,Channel redimensioning
• Hardware faulty-------> Fix hardware issue
• High Traffic and congestion---->Review setting of HR threshold, Upgrade TRX or Traffic sharing
• Low RX Level--------> Improve Coverage by change antenna tilt or propose new site

2G Theory and Concept

You might also Need to know:
- TCH Block Rate Optimization Tips in Huawei GSM
- 2G Voice Quality improvement by TRX Layering Priority
- TBF Drop Improvement tips in Huawei GSM
- GPRS Packet Data Access Rate(PDASR) Improvement in Huawei GSM