How to maintain good CDMA network

At present, the technical aspects of the CDMA network are mainly related to the quality of the handset, the call off line, the connection rate, the network coverage and the interconnection of other network mobile users. How to solve these problems of users is a very important factor in the development of Unicom CDMA. For CDMA networks, the high drop rate, low communication quality and low connection rate are mainly due to the following reasons: pilot-frequency pollution, interference, possible RF deviation of base station, covering problem

The CDMA channel is divided into two kinds of logical channels, the reverse channel is composed of the access channel and the reverse service channel, and the Forward channel is composed of pilot channel, synchronous channel, paging channel and several service channels. The forward channel configuration is not fixed, but the pilot channel must have. The pilot channel is continuously transmitted in the CDMA forward channel, which is used to synchronize and switch all the mobile stations in the base station coverage area. The base station uses the time deviation of pilot sequence to identify each forward CDMA channel. The reuse planning of adjacent cells is equivalent to the time offset planning of pilot PN sequence. That is, one of the 512 bias values (0-511) can be used to distinguish the pilot channel of the neighboring cell. When the pilot PN Sequence bias index of two adjacent base stations is only 1 o'clock, the phase interval of the pilot sequence is only 64 bits, in this case, when one of the base station's emission time error is large, it will be confused with the delay signal of another base station, then the so-called "pilot-frequency pollution" is produced.

If there are two neighbourhoods adjacent to C1 and C2, while mobile phones work in C2, when there is a large error in the time tolerance of the pilot channel of C1, due to the delay, the C1 pilot signal may be mistaken for a delay path of the C2 pilot channel, if the C1 pilot signal is strong enough, First, the switch can not detect the C1 signal, two possible C1 signal to the C2 formation of interference, both can lead to drop words.

Therefore, when it is suspected that pilot contamination may exist, the first possibility is that there is not enough protection in pilot planning, and the other may be that the time tolerance of pilot channel of some base stations has a large deviation. For the latter, a transmitter tester can be used to test the potential base station. (Computer science)

The user complained to the warning and network management reports that there is a problem with the call, and has ruled out base station and base station day feeder fault may be. That is, the need for interference detection and measurement.

* Measurements may be carried out at the base station antenna location;

* The measurement may be the same frequency, the so-called same frequency is the interference and the base station transmit signal same frequency, the measurement needs to interrupt the base station launch;

* Up/down frequency point interference may need to be measured;

* The interference signal intensity may be disorderly fluctuation, may use the Spectrum Analyzer maximum value to maintain the function, determines the maximum interference intensity;

* Non-common frequency signal may also cause interference, measurement can increase the frequency sweep width, observation of non-common frequency interference spectrum.

The typical measurement method of jamming signal is to use the Spectrum Analyzer to determine the frequency, bandwidth and intensity of the jamming signal, to estimate the source of the jamming by comparing the known communication system and broadcast system and the frequency and bandwidth of the known signals such as TV car, and to find the direction and position of the jamming source by directional antenna

The same frequency measurement needs to interrupt the base station business, so that the mobile phone in the base station coverage area will no longer communicate with the base station and shut down the base station launch. It is best to use the receiving antenna of the base station for the uplink interference measurement and connect the MT8212A directly to the receiving antenna port. If the business cannot be interrupted, it should be close to the base station uplink to receive the antenna near, or use receive backup antenna. The downlink interference measurement can be carried out in the coverage area of the base station. You can use directional or indefinite antennas. It may take a long time to measure the interference of a base station that cannot interrupt the business. Measure interference in the business silent clearance.

The best way to locate the radio frequency deviation of the base station is to use the base station transmitter tester to test the RF indexes such as power, frequency, modulation and code domain of the transmitter of the CDMA base station in detail.

For the coverage problem, the road test equipment is tested first, and when the problem is suspected, the transmitting power of the base station and the power of its Code field should be tested to locate the problem.

The CDMA network maintenance scheme of the company is as follows: 1. The achk-8609-001 of the base station transmitter integrated test system.

* All Chinese operating interface, easy to operate.

* Support the current all the world's digital mobile communication base station transmitter test requirements and wlan:cdma2000, IS-95, 1X ev-do, PHS, GSM, W-CDMA and so on. Multi-function, high precision and fast test speed, automatic search channel and frequency, support Gp-ib and rs232c control port, real special integrated transmitter tester: High-performance spectrum Analyzer, high-precision power meter and vector signal signal (modulation) analyzer, stability, reliability and repeatability, automatic report generation, The human factor is small, can satisfy the user special request, saves the investment. The test items are:

* Modulation analysis: Carrier frequency, frequency stability, vector error, phase error (effective value, peak), amplitude error.

* Code Domain Analysis function: Code domain power, code domain error, peak Code field error, time tolerance, phase tolerance and so on.

*RF Power, TPC and OBW (bandwidth consumption, proximity (carrier) stray, stray, i/q demodulation analysis, etc.

2. Cell Master mt8212a Day feeder analyzer; Spectrum analyzer; Power meter; T1/E1 tester.