Analysis of Call Drop

According to the definition of call drop measurement point, call drop is usually caused by the following:

Equipment problem. That is, call drop due to the equipment defects, such as UE , NodeB, RNC,CN;

RF problem. that is, call drop due to coverage problem or unsuitable radio layer parameters.

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Equipment Problem:

Call drop arising from equipment problem

Hardware problem

Transmission problem

Antenna and feeder fault

Other causes

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Analysis of Causes of Radio Link Failure

Analyze the causes of the failure of radio links.

The causes can be:

Interference

? Internal interference, external interference and the equipment interference

Poor coverage

? Coverage hole, dead zone, isolated island, uplink/downlink unbalance

parameter setting not proper

? radio link timeout counter, handover, power control etc.

Radio Link Fault - Coverage

Coverage:

Coverage over shooting

Coverage hole

Signal fading

Incomplete definition of adjacent cells
unbalance of uplink/downlink

Radio Link Fault - Interference

Interference:

Strong downlink interference (CPICH RSCP is not low, but Ec/Io is low)

Strong uplink interference. On the basis of the RSSI scanning result or analysis of the SIB7, there is uplink interference.

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Handover Problem:

Handover is too late

1)The soft handover threshold is too high or the time-to-trigger setting is too big.

2) The soft handover area is too small.

 Ping Pong Handover

In the handover area, because of the signal fluctuation, the UE will continually handover between source cell and target cell. For intra-frequency hard handover, since there are intra-frequency interferences, call drops are likely to occur; for inter-frequency handover, since the compressed mode measurement is required, ping pong handover will bring serious influence on the communication quality.

Good analysis.

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useful document, thanks