Radio_Link_Fault

#Radio_Link_Fault.
[Coverage problem caused by BTS expansion]

If the coverage of the BTS shrinks after expansion, in addition to making the previous checks, you are supposed to check the following items.

1)         Check if the combiner keeps the same before and after expansion
The loss of different combiners varies greatly Therefore, the combiner configuration deserves special attention during BTS expansion. If different combiners are a must, you should fully communicate with customers.

2)         Check if the antennas are rationally selected
Suitable antennas must be selected for project installation and network planning so that the best coverage can be achieved. It must be pointed out that you should use zero-point filling antenna or the electrical title antenna when the antenna height is great. In addition, omni antennas cannot be widely used for the large area coverage. In this case, the coverage problem can be solved by directional antennas.

3)         Check if the installation of the newly-added antennas are qualified
You should first check if the design of the antenna height, azimuth angle, and antenna tilt is qualified. Generally, the important coverage areas cannot be bared by tower. Meanwhile, the important coverage areas cannot be perpendicular to the diversity direction of the antenna. In this case, the antenna diversity effect can be excavated to the maximum. To reduce the coverage shadow caused by the tower, you should pay attention to the distance between the antenna and the tower. Moreover, the pole of the omni antenna and the RF part of the antenna cannot be overlapped.

4) Check the position of the BCCH transmitter antenna
Since the tower effect is present, the BCCH transmitter antenna must be installed at a side of the important coverage area. In this case, the coverage shadow can be avoided. To prevent the assignment failure caused by the inconsistence of the BCCH coverage and TCH coverage, you can use the concentric channel allocation algorithm. In addition, the important coverage area cannot be perpendicular to the diversity direction of the antenna.

5)         Check if the tilts and the azimuth angles of the directional dual transmitter antennas are consistent with each other
If the tilts and azimuth angles of the directional dual transmitter antennas are inconsistent, call drop, assignment failure, and handover failure will easily occur. In this case, the coverage area of the BTS will become small. In addition, since the tower effect is present, the BCCH transmitter antenna must be installed at a side of the important coverage area. In this case, the coverage shadow can be avoided. Moreover, the important coverage area cannot be perpendicular to the diversity direction of the antenna.

6)     Check the set-top output power of various TRXs if the scheme for the maximum coverage is used.
When the maximum coverage is pursued, the TRXs are required to be combined in various ways. In this case, the coverage distance of the BCCH will be longer than that of the TCH. As a result, the TCH assignment failure will be caused, so the concentric technology is needed.
The channel assignment failure caused by low transmit level in the inner circle and the channel congestion in the external circle can be avoided if the TA values of the inner circle and the external circle are correctly set and allocated to the inner circle and external circle according to the right priority.

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