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Title: Locating the Problem of High RSSI Value of the CDMA450 ID: SE0000369967

Update Time: 2009-01-14 10:12:42

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Author: c60028130

Product Family: Antenna Feeder Product: Antenna & Feeder

Fault Type: Others

Keywords: CDMA450 RSSI connector quality

Digest: Phenomenon Description:

In a CDMA450 network in country s, the main and diversity RSSI values are high, and the base station uses the S5/5/5 configuration. The main and diversity RSSI values in sector 1 and sector 2 of BTS No.45 constantly remain at an abnormal value of -80 dBm.

Alarm Information: None

Cause Analysis:

According to the analysis, the reasons for the constantly high RSSI value are as follows: 1. The jumper connector is improperly made or connected. 2. The feeder connector is improperly made or connected. 3. The antenna has quality problem, such as, the passive intermodulation (PIM) is too strong. 4. There is interference causing high main and diversity RSSI values. 5. Metal objects or other building resides in the near-field and in front of the antenna. 6. The RF module is faulty. 7. The RF cable connector inside the cabinet is loosen.

Handling Process:

1. Before going to the site, check whether the problem still exists by querying with the maintenance console. 2. After arriving at the site, test the RSSI value of sector 1 and 2 of the base station. The RSSI values are still -80 dBm. 3. When the base station works in a normal state, connect an LMT to the base station, and flap the conjunction between the jumper connector and the feeder connector. Find that the RSSI varies ±10 dB. 4. Use a bare hand to screw the jumper connector. Find that the jumper connector is securely connected. Thus, suspect that the self-made jumper is faulty. 5. Replace the self-made jumper with the fix-length jumper, and test the RSSI value. Find that the RSSI value ranges between -101 dBm and -102 dBm. Flap the conjunction between the jumper connector and the feeder connector and find that the RSSI value is constant. 6. Check the removed four jumpers. Find that the external conductor is cut roughly and a large amount of copper scraps reside in the connector. Clearly, The self-made connector does not comply with specifications. 7. Remake the four jumper connectors, and connect them to the top of the cabinet. Then, test the RSSI. The RSSI value constantly ranges from -98 to -99dBm. Flap the connector, and the RSSI value is constant. 8. After adjusting the base station, observe the RSSI for a week and find that the RSSI value constantly resides at around -98 dBm, which is improved by 15 dBm compared with -80 dBm and meets the RSSI requirements (small than -90 dBm) for the S5/5/5 configuration.

Suggestions and Summary:

1. In the CDMA450 system, using the fix-length jumper in stead of the self-made jumper. This can reduce the quality problems caused by improper making of connectors. 2. During the acceptance of the CDMA450 system, besides checking the VSWR, sample the self-made connectors and make sure that these connectors are made in compliance with the specifications, and avoid the problem of high RSSI values caused by reduced number of carriers and increasing power. 3. Flap the conjunction between connectors and observe whether the RSSI changes obviously to find the engineering quality problem of the antenna system.

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