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01-30-2014, 04:59 PM
[Connection problems of antenna and feeder, combiner and splitter, and CDU]
If various connectors of the antenna and feeder system are not connected according to requirement, the performance of the antenna and feeder system will be affected. In this case, the coverage area of the BTS will also be affected.
- Water penetration occurs at the various connectors of the antenna and feeder system.
If water has penetrated into the connector and feeder, the standing wave ratio will increase. In this case, the coverage area will be affected.
- Various connectors are not tightened.
If the connectors for set-top jumpers, for the cables from TRX boards to combiner and splitter, and for various RF cables are not tightened, both the reception performance and the transmit performance of the system will decrease. In this case, the coverage area and the conversation quality will be affected.
- The transmitter antenna and the receiver antenna are inversely connected due to inconsistent configuration of the set-top jumper and data.
- The connection between the jumper and feeder is not tight, which results in high loss and standing wave ratio. In this case, the coverage will be affected and interference will be caused.

[Tower amplifier problem]
- Water penetration will increase the loss, deteriorate the standing wave ratio, and decrease the receiver sensitivity.
- The damage of the LNA (it is in the tower amplifier) will decrease the gain or even decrease the gain to a negative value.
- The input end and the output end of the tower amplifier are inversely connected. In this case, the tower amplifier will be short-circuited. If the short circuit lasts for a long time, the front module will be damaged.

[BTS front module problem]
- Isolator problem
- Duplexer and other filter damage
- Standing wave ratio error alarm
- LNA (low noise amplifier) damage
- Low TRX or amplifier output power

[Parameter configuration problem]
The parameters affecting coverage are listed below:
- TRX power class
- Tower amplifier attenuation coefficient
- MS maximum transmit power control power
- MS minimum Rxlev
- RACH minimum access threshold

III. Coverage Cases
Case 1: Use down tilt Omni antenna to improve coverage
[Problem description]
In a suburban area, the Omni antenna with a gain of 11dBi is used for the BTS. This coverage distance can reach 9km in plain environment. However, the coverage in the area near the BTS is poor. The Rxlev in the small town 800-1400m away from the BTS is about -90dBm.
[Problem analysis and solution]
On-site survey shows that the antenna height is too great. The height of the tower on which the antenna is installed 50m. Moreover, the tower is established on a small mountain, so the town is 120m below the antenna. The first judgment is that the phenomenon of "shadow under tower" has been caused.
Further analysis of the collected data finds that Omni antenna is used for the BTS. The antenna gain is 11dBi, and the vertical half power angel is 7 degrees. If the valid antenna height is 120m,