Coverage problem troubleshooting

Troubleshooting Process of Coverage Problems: In case of coverage problems, the onsite engineers can do as follows to handle the problems: 1. Analyze the hardware configuration, parameter settings, traffic statistics, and alarms. 2. Check the BTS hardware, test the TRX power and the transmit power on top of the cabinet, and perform drive tests on site. 3. Communicate with the customer that makes the complaints and perform field tests.Then, most coverage problems can be solved. 4. Check the hardware configuration: Check whether capacity expansion is performed and whether the combination mode changes according to the TRX configuration provided by the customer. Checking the hardware configuration helps determine whether a TRX is faulty or whether the TRXs are sufficient, because the number of TRXs may be smaller than that before network replacement, which leads to congestion and traffic decrease. 5. Check the parameter settings: Check the PDCH configuration and settings of the parameters closely related to the coverage, such as Power Class (0), RACH Min.Access Level (≤1), RXLEV_ACCESS_MIN, and Cell Layer (same as the layer of the neighboring cell). In addition, check the configuration of the neighboring cell relations. Cells in the same BSC should be configured as bidirectional neighboring cells; cells between different BSCs should be configured as external neighboring cells. Note that the serving cell should be configured as the neighboring cell of other cells. 6. Check the alarms and traffic statistics: > The coverage-related alarms are generated mainly because the TRX is faulty. i) Hardware alarms: LAPD alarm, TRX configuration alarm, TRX processor running Alarm, radio link critical alarm, TRX power decrease alarm, TRX power amplifier shutdown alarm, TRX voltage abnormal alarm, TRX hardware alarm, TRX VSWR alarm, TRX board communication alarm, CDU level-1 VSWR alarm, and CDU level-2 VSWR alarm. ii) Clock alarms: clock reference abnormal alarm, frame or TS number alarm, TRX clock major alarm, phase-locked loop critical alarm, and TMU clock alarm. iii) Transmission alarms: LAPD OML fault alarm, E1 remote alarm, and E1 local alarm. The preceding alarms do not necessarily cause the coverage decrease; however, if alarms are generated and cleared frequently, the coverage seems to be poor and the signal seems to fluctuate for the customer. In problem identification, handle these alarms first. > The measurement counters are related to KPI Measurement per Cell, Incoming/Outgoing Internal/External Inter-Cell Handover Measurement per Cell, Measurement of Power Control Messages per Cell, Receive Quality Measurement per TRX, and Uplink-and-Downlink Balance Measurement per TRX. i) Compare the number of SDCCH requests and the number of TCH requests respectively before and after network replacement to check whether the number of SDCCH requests and the number of TCH requests during paging response are normal. ii) Check whether congestion occurs according to the congestion rate. If the congestion rate is high, access to the network becomes difficult, thus causing complaints. iii) Compare the traffic volume in busy hours before and after network replacement to check whether the traffic volume decreases. Traffic volume is an important indicator of the coverage. iv) Compare the number of incoming inter-cell handovers and the number of outgoing inter-cell handovers respectively before and after network replacement to check whether the cooperation with the neighboring BTS is normal. v) Check the average receive level and the average receive quality in the uplink and the downlink. 7. Compare the drive test data before and after network replacement: This method is effective to solve the coverage problem and can provide valid evidence for coverage decrease. If network replacement is performed by the customer, the drive test data before network replacement may be unavailable; therefore, identifying the coverage problem becomes more difficult. You can perform drive tests after network replacement and check the BTS to identify the problems such as reverse connection of the feeder, poor coverage of the antenna, and handover failure. In addition, you need to communicate with the customer that makes the complaints and perform field tests to obtain the firsthand data for future comparison. 8. Check the BTS antenna and feeder: With the drive test results, check the antenna and feeder connections. If the drive test results show that the antenna coverage is poor, use the SITEMASTER to test whether the VSWR is smaller than 1.5. If the VSWR is greater than 1.5, check whether water runs into the antenna connector or feeder connector and whether the surge protector is faulty. If there are complaints about poor coverage after network replacement but the drive test results show that the coverage is normal, the poor coverage in some areas may be concerned with the antenna, especially the omnidirectional antenna, of the main BCCH changes, or the tilt or azimuth angle of the antenna changes. If the TMA is installed, you need to check whether the TMA is activated and functional. 9. Test the transmit power on top of the cabinet: Ensure that the cables are securely connected. Then, check whether the transmit power on top of the cabinet is normal. If the transmit power is abnormal, use a power meter to check the power of the TRX and combiner. If the TRX power decreases or the combiner loss is too high, replace the faulty TRX or combiner. The receiver sensitivity can be tested by only the CMD57, which is unavailable on site. Therefore, you can replace the faulty TRX. 10. Find out other causes: insufficient coverage, interference, poor electromagnetic environment, MS fault, SIM fault, or mistaken complaints due to the surrounding environment of the antenna, building in the cell, vegetation in the cell, transmission model, and emergence of new hotspot areas.