Cause analysis and solution of high drop rate in XXX GSM network

(1) When the mobile phone is moving, it enters the blind area of wireless coverage, and the handover request fails, and the call is dropped.

(2) "Far-end island effect" produces dropped calls. Due to the high antenna (or other reasons) and large cell coverage, the frequency reuse distance is shortened or the cell coverage is overlapped, resulting in the interference of the same frequency and adjacent frequencies, resulting in dropped calls.

(3)FHU is in FLT, resulting in disconnection. The FHU unit in BTS is a frequency hopping unit connecting FU and CU. If it becomes, it will seriously affect the normal connection of the call, and the connection between CU and FU is not smooth or wrong, resulting in the disconnection.

(4) The voltage standing wave from the combiner to the antenna is relatively large, resulting in dropped calls. Because the voltage standing wave ratio (VSWR) of the combiner connected to the antenna through antenna feeder is large, the transceiver performance of BTS is degraded, which makes the signal quality received by mobile phone in the cell worse, and finally leads to dropped call.

(5) The actual transmitting direction of the antenna deviates from the direction defined by the data, which changes the wireless coverage. When the signal is extremely weak or even blind, the mobile phone will be disconnected when it enters the community.

(6) Unsuccessful handover leads to dropped calls. Due to handover parameters, such as uplink level handover threshold (L-RXLEV-ULH), uplink quality handover threshold (L-RXQUAL-ULH), downlink level handover threshold (LRXLEV-DLH), downlink quality handover threshold (L-RXQUAL-DLH) and handover power control parameters (U-RXLEV-DLP, URXLL

(7) Incorrect setting of allowed network color code (allowed by NCC) parameter leads to dropped call. The allowed network color code parameters define the NCC code set of the cell to be measured by the mobile station, which provides a feasible target cell for cell phone handover. If the data definition is wrong, it will lead to unsuccessful handover and cell reselection, resulting in dropped calls.

2 1. What are the common methods to solve dropped calls?

Answer:

(1) Check whether the parameter setting of NCC PERMITTED is correct and whether all cells are included, and make corrections and modifications according to the actual situation. Mobile communication, home of communication engineers, communication talents, job hunting, network optimization, communication engineering, business travel accommodation, blacklist of communication enterprises; R-Q6]2o*s0t#R'x9A

(2) According to the traffic analysis results and handover test of 0MC-R, check whether the dropped call is caused by unsuccessful handover. If yes, check parameters such as HO-MAGIN, L-RXLEV-DLH through 0MC-R to see whether these data are set and whether the setting is reasonable, and adjust the switching parameters according to the actual network operation, and then conduct field dialing test until it is the best.

(3) If the handover control parameters are checked correctly, the test results of wireless field strength can be analyzed to see whether there is a blind area of network coverage. For cells with blind spots, the antenna height and wireless pitch angle can be adjusted to avoid covering blind spots. In places with dense high-rise buildings, the minimum allowable access level (rx lev-AC-access-MIN) of a community can be appropriately lowered, so as to relatively increase its coverage and reduce blind areas, but this will lead to a negative impact on the decline of call quality.

(4) In areas where heavy telephone traffic really causes dropped calls, as well as commercial centers and high-rise buildings where users are concentrated, the communication environment of the community can be improved by adding microcells, thus reducing the dropped call rate and improving the operation quality of the network. Mobile communication, home of communication engineers, communication talents, job hunting, network optimization, communication engineering, business travel accommodation, blacklist of communication enterprises.

(5) Check the frequency planning of the network through OMC-R to confirm whether there is co-frequency interference and whether the cell frequency reuse distance is within the allowable range. If not, we should make corresponding adjustments. The frequency of Nanmen Station of our company was modified due to the fault handling problem, which led to the frequency reuse with another station, Beijing Road Station (the two stations are far away), and the same frequency point caused serious dropped calls, so the mobile phone could not occupy the channel of a major commercial street between the two stations. After field test, it was found that the same frequency interference was caused by frequency reuse overlap, and the modified frequency point returned to normal.

(6) Check whether the BTS has FHU fault by using 0MC-R or LMT. If an FHU is in FLT state, the FHU unit is disabled if the initialization is unsuccessful. If both FHU are in FLT state, the STSE board should be replaced if the initialization is unsuccessful.

(7) Detect the standing wave ratio from the combiner to the antenna with the on-site master instrument. If the VSWR is greater than the normal value 1.5, it needs to be checked and repaired from the feeder to the dead line; If the VSWR is less than 1.5, the transmission part is normal.

(8) If there is a blind spot in a community with low business volume due to high-rise buildings and water, call reestablishment (re) can be set up, so that when a cell phone is dropped due to the blind spot, the call can be resumed through call reestablishment to reduce the dropped call rate. However, because the other party will hang up before the renovation is completed, wasting network resources, it is generally not used in communities with large traffic.