L1 Troubleshooting Guide

Index:1- Low TRX TCH Assign Efficiency .2- UL & DL path imbalance.3- 2G PS Traffic Loss.4- suffers High SDCCH Congestion.5- Carrier Configuration Error.6- Immediate Assignment SR.7- High TCH Cong. Rate.8- Low UL TBF EST. SR.9- low TCH Usability.10- Zero GPRS traffic

11- low TCH EFF HO.12- high BER.13- Zero TCH Traffic Volume.14- TDM Link Between TDM Switching Board and Service Board Faulty -Board Unavailable.15- Monitoring Device Maintenance Link Failure.

1- Low TRX TCH Assign Efficiency

1- Check the Configuration with the FM in the site.2- Swap the RF board for the faulty TRXs with another board which serves TRXs didn’t suffer from this counter.3- Check the connectors and jumpers for any damaged or loosing component and check the VSWR with the Site Master.4- Swap the Sector feeders with another sector which didn’t suffer from this problem.5- if you couldn’t experience any problems in the above steps. Then, you have a problem with the antenna.Note: After each step of the above, we need at least 2 hours to check the effect of the taken action from the FM side on the graph of the counter “Hut_TCH-Eff-R”.

2- UL & DL Path imbalance

1- Check the Configuration with the FM in the site.2- Swap the RF board for the faulty TRXs with another board which serves TRXs didn’t suffer from this counter.3- Check the connectors and jumpers for any damaged or loosing component and check the VSWR with the Site Master.4- Swap the Sector feeders with another sector which didn’t suffer from this problem.5- if you couldn’t experience any problems in the above steps. Then, you have a problem with the antenna.Note: After each step of the above, we need at least 2 hours to check the effect of the taken action from the FM side on the graph of the counter “Percentage 1+2 & Percentage 10+11”.

3-2G PS Traffic Loss

Hint : PS traffic loss is not a KPI it can be considered a Network health check

First of all we should check our node(BSC) for the below1-check HW BRD (FG2a) , ports and alarm log2- check current alarms & log for (PTPBVC – NSE fault – NSVL local and Remot –cell ps service faulty – cell out of service)3- Check local & remote NSVL status by (DSP NSVL )4- check for an action or immediate can affect PS CELLS5- check for 2G sites migrated to another area OR 3G sites Rehomed to your area6-check the counter : ZL9506:Total Bytes of LLC PDUs Sent per BSC for 2 weeks and compare 7- check with core team for BSC PS traffic behavior

4 -SDCCH CongestionHint : SDCCH is the main channel of call setup scenario & it is responsible for access users to get traffic channel so it is a main KPI, kindly follw up the below steps to find Reasons & solution

SDCCH congestion Rate = (Failed SDCCH seizures/SDCCH Seizure requests)*100

1-First of all check this congestion immediately by “ monitor channel status for most affected cells” & check if SDCCH is sufficient for traffic channel (No of TRX)

2-Check the cell is supporting Dynamic SDCCH configuration by “LST GCELLBASICPARA” & search for “SDCCH Dynamic Allocation Allowed” it must be yes

3-Check for NB sites is down or cells problem4-Check for TCH congestion or an event nearest to the area

5-Finally SDCCH congestion = all available SDCCH resources are busy & SDCCH Blocking = fail attempts to get SDCCH resources

 

5- Carrier Configuration Error.

Reason solution

If "Specific Problem" is "ARFCN and TRX Type Mismatch" Check the consistency between the Freq and the TRX type.

If "Specific Problem" is "Incorrect Signaling Channel Configuration" Check the signaling channel configuration./ lst GTRXCH

If "Specific Problem" is "Co-Cell Configuration Error" Not configured in our network

If "Specific Problem" is "Carrier Configuration Error-Configuration"Check the TRX configuration. Power ,send receive mode, RXU BRD parmeter

If "Specific Problem" is "Carrier Configuration Error-RAN Sharing" Not configured in our network

If "Specific Problem" is "Carrier Configuration Error-ARFCN" Check the ARFCN configuration of the carrier.

If "Specific Problem" is "Carrier Configuration Error-Bandwidth" Not configured in our network

If "Specific Problem" is "Carrier Configuration Error-Frequency"Check the frequency spacing configuration of the carrier. RF issue

If "Specific Problem" is "Carrier Configuration Error-Excessive Power"Check the power configuration. & check carrier distribution on the RFU BRD

If "Specific Problem" is "Carrier Configuration Error-UMTS Conflict" Check the common configuration for GSM and UMTS modes.

If "Specific Problem" is "Dual RRU Power Sharing Configuration Error-Bandwidth" Not configured in our network

If "Specific Problem" is "RAN Sharing Carrier Configuration Error-Excessive Power" Not configured in our network

6- Immediate Assignment SR.

Hint: Immediate Assignment = call setup =accesses to SDCCH Immediate Assignment is the process of sending SDCCH request message till receiving SDCCH established message, so the failure in this KPI indicates that there are a problem in the SDCCH resources

1-check the N top cells for HW problem that can affect the SDCCH resources2-check for SDCCH congestion & take needed action as SDCCH congestion guide2-check if there are abnormal LU Req by checking the NB cells3-check the quality of UM interface by checking the ICM & check for path imbalance , VSWR4- check the quality of abis interface 5-Rst Cell

Finally Immediate Assignment SR = (call setup indications / channel Req)*100

7- High TCH Cong. Rate

1-Check if there was down E1 on the site or if there were any RF WH alarms.2-check the neighbor of the congested cells may be any neighbor site was down or had down cells.

8- Low UL TBF EST. SR

1-Check if there was down E1 on the site or if there were any RF WH alarms.2- Check congestion live on the site by viewing monitor channel status.3- if none of the above Reset the site and wait for 15 min to see the effect.

9- low TCH Usability.& Availability &high Non Radio Drops.

Available TCHs*{100}/Configured TCHs

1-Check if there were any blocked TRXs on the cell.2-check if there were any HW alarms (VSWR, HW critical alarm ….etc.)

10- Zero GPRS traffic

1- check if PTPBVC configured to the cell or not.2- and check if PTPBVC configured successfully.3-Remove any dummy Freq. in this cell.

11- low TCH EFF HO.

1- Check the NBRs relation in Configuration.2- Check NBR cells if suffer from alarms.3- Check Interference in cell.4- Check BER & HW problem.5- check this counter to help you in problem detection (NO of incoming BSC HO failure (NO Abis resources)) >>>refer to E1 problem6- Check this counter to help you in problem detection in site itself or NBR :• Incoming External inter cell HO request.• Successful Incoming External inter cell HO request.• Failed Incoming External inter cell HO request• Success rate Incoming External inter cell HO request• outgoing External inter cell HO request.• Successful outgoing External inter cell HO request.• Failed outgoing External inter cell HO request• Success rate outgoing External inter cell HO request

12- High BER (Bit Error Rate).1- Really, the BER alarm can’t be handled from our side. This alarm is handled by the TX team and the FM.2- For any BER ticket, forward the ticket to the TX team and provide them with the E1 data which suffers from the high BER (Subrack/ Slot/ Port on the BSC).3- we can monitor the BER by 3 different methods:

• Instantaneous monitoring: WEB LMT=> Monitor=> BERS Monitoring (SRN/SN/PN on the BSC).

• M2000=> Performance=> G-Abis measurement=> TRAU Link measurement (BER per Cell).

• M2000=> Performance=> Measurements related to port=> E1T1 Port Bit Error Measurement (BER Per BSC port).

4- Note: the last two methods are counters which can display the BER for a certain period.

13- Zero TCH Traffic Volume

1-check if there were Requests or it’s user behavior.2-check site HW alarms specially the VSWR Alarm2- make VSWR Test to the BTS and determine which antenna port has the VSWR.3-try to swap the BCCH channel to the free VSWR port4-open WO to FM to handle this alarms.

14- TDM Link Between TDM Switching Board and Service Board Faulty -Board Unavailable.1- When These two alarms appeared with each others, this means that the board that supports the TDM switching among subracks (TNUa) is faulty.2- As the TNUa board is working in active/standby mode, if the Active board became fauly. Then, the service will be switched over the standby one.3- handling alarms on such board takes place in the outage window (2-6 AM) as No services affected.4- Ask the FM to Reset the board and wait for about 5 minutes.5- if the board is still unavailable after H/W reset, Ask the FM to Replace the board with a New one. 6- if the first alarm appeared only but the board is working normally. Then, No need to Reset or replace the board, Just check the inter sub-rack connections among the TNUa boards with the FM (Full mesh topology).

15- Monitoring Device Maintenance Link Failure

1- Check the configuration from our side, ensure that each two boards have the same type on the same MON port have different communication address.2- Check the configuration with the FM in the site , ensure that it is the same as that configured from your side.3- Check that the PMU dip switches adjusted properly to represent the communication address configured from your side.4- if no problems experienced in the above steps. Then, the problem will be due to H/W, either boards (FMU, PMU, UPEU,….) or cables.