GSM wireless network optimization settings

The development of wireless networks drives social progress. What problems should we pay attention to when optimizing wireless networks? Here is a detailed introduction.

.

During the basic construction of the GSM network, the construction cycle is short and the network changes frequently. In addition to large-scale expansion, there are also many small scale expansion, adjustment and upgrade projects. It is often because many problems are left behind after the project is completed, and network optimization is required. GSM wireless network optimization involves two core aspects: data collection analysis and implementation of optimization and adjustment schemes.

Data collection in GSM wireless network optimization settings is the prerequisite and basis for network optimization.

It mainly includes the base station parameter table, OMC statistical data, road test data, CQT data, system alarm event records, and complaints reported by the Customer Complaint Center.

(1) Base Station Site parameter table

Base station parameter table mainly includes: station name, station number, LAC number, configuration, frequency point, latitude and longitude, antenna height, antenna gain, antenna half power angle (vertical and horizontal), azimuth, elevation, base station type, etc. Prepare a map indicating the station number, frequency point, BSIC, and azimuth (antenna direction), and record the current system version and supported special functions.

(2) Statistics on OMC-R

The OMC-R statistical data records various operation indicators of the wireless network, reflecting the actual running status of the network. We often use statistical items such as call_setup_success_rate, drop_call, handover_success_rate, and traffic-out ratio. We need to make statistics every day for these main indicators, usually in busy hours, one morning or one night, depends on the specific situation. Collects carrier statistics such as BER, IOI, path unbalance, RFLOSSESTCH, and CHANREQMSFAIL to facilitate the diagnosis of RF hardware faults. Generally, in a non-frequency-hopping system, if the BER is greater than 1.8, the call quality is considered to be poor. If the IOI is greater than 10, interference may be considered as internal or external, if the value is greater than 30, it may be a hardware fault. The path balance is generally between 100 and 120. If the range is exceeded, it is deemed that the hardware is faulty. Collect statistics on network congestion conditions, such as PCH congestion, AGCH congestion, TCH congestion, and SDCCH congestion, the statistical system also has no available resource length. If the drop-down rate of a cell is very high, the ratio of RFLOSS and HOLOSS should be further calculated to further locate the reasons for the high drop-down. This data is the basis for our next step, such as parameter adjustment.

(3) Road Test Record Data

Conduct on-site road test through road test equipment to problematic locations, you can record the data of the receiving level, receiving quality, occupied residential area and channel, Layer3 message, six strongest adjacent residential areas, and switchover near the test point. Analyze the problems found during the road test, such as non-conformity between the tested data and the theoretical design data; drop calls; poor call quality caused by non-signal strength; blocking; abnormal switching; low signal level; TA is too large; signal blind zone. Then, based on the analysis of the road test data, check and modify the neighbor relationship and switching parameters, adjust the antenna inclination and direction, find the interference source, analyze the Signaling connection process of the air interface, and find installation errors of the antenna feedback system.

(4) Fixed-Point CQT testing and user Complaint Data

The CQT test can objectively reflect the network conditions. The selection principle should be able to reflect the overall network conditions and should be conducted in as many locations as possible, which should cover various representative sites; at the same time, the key points are highlighted. Most tests are conducted in a centralized location, such as hotels, malls, and residential areas. More than 30 sites are selected. Customer complaints should be classified based on dropped calls, access difficulties, poor call quality, and abnormal prompts. Pay attention to the time and location of the complaint, and the phone numbers of both parties: caller, called Number. The above information is collected and analyzed to help us grasp the main contradictions of the network and improve work efficiency.

Optimization and adjustment scheme for GSM wireless network optimization settings

After detailed data collection, analysis, and research, it often involves the adjustment of the antenna system, the adjustment of the base station, the adjustment of the frequency planning, the adjustment of system parameters, the traffic balancing, and the implementation of some micro-cellular optimization solutions.

(1) daily Feedback System Adjustment

The antenna feed system of the base station is a very important part. Its quality directly affects the quality of communication and the coverage of residential areas. We can change the coverage of the base station community by adjusting the antenna height, downtilt angle, direction, and other factors to reduce interference with the same and adjacent frequencies of other cells. You can also adjust the relative positions of antennas to avoid the mutual influence between antennas, so as to achieve greater isolation. In addition, antenna with high gain, good direction, high frequency bandwidth, and good mechanical performance is also very important. However, the antenna adjustment range must not be too large. The following inclination angle should not be greater than 10 °, and the horizontal direction should be too large to deviate from the engineering design without special consideration.

(2) Base Station commissioning

On the basis of data analysis and on-site testing, some base stations may need to be re-tested to eliminate the impact of hardware faults on network performance. If necessary, the faulty hardware should be replaced in a timely manner.

(3) frequency planning Adjustment

Indicators such as interference and drop-off rate are most closely related to frequency planning. A good frequency plan can minimize the overall interference level of the system. Due to the inevitable defects in the pre-allocated frequency scheme in the initial stage of the project, there are often some serious adjacent frequency phenomena. In addition to the actual environment and terrain changes, we must make minor adjustments, in daily work, we must modify and adjust the measurement to further reduce interference and obtain the optimal frequency scheme. Many frequency points that are considered unavailable during frequency planning are actually available, while the frequency points that can be used during planning are considered as follows, in reality, the terrain height, reflection, and other factors may cause serious interference. In addition, the terrain causes a lot of cross-region coverage, and the antennas of these stations are often unable to be reduced due to objective reasons, which must be solved by more careful frequency adjustment. In practice, after we adjust the frequency of some residential areas, the interference problem is significantly improved. However, this is a repetitive task that requires constant adjustments to achieve the best results.

Good frequency planning is the basis for achieving good switching performance, especially BCCH planning. If it is not done well, it will lead MS to spend more time decoding BSIC due to the poor quality, so that the switching will become slow, or the BSIC will not be able to be resolved. At the same time, BSIC planning is also very important. BSIC = NCC + BCC, where TSC = BCC, NCC and BCC are 0 ~ 7. The BSIC code in decimal format is 0 ~ 63. Generally, a BSIC code is assigned to a station, but different BSIC codes can be used for different cells in a station. With NCC unchanged, we only plan for BCC. If the two sites are the same as BCCH and BSIC, but the distance between them is not enough, in this case, MS cannot correctly distinguish them, MS may measure and report a specific residential area, but this residential area may not be the adjacent area of the current residential area at all, which will lead to switchover failure.

The definition of the neighboring relationship is also an object that needs to be considered. If the neighboring relationship is not set, a large number of dropped calls will obviously occur. If there are too many neighboring relations, the switching performance will be affected. Therefore, we need to analyze the statistics of the OMC-R, and then delete the neighboring relationships that have not been switched over for a long time. Through the actual measurement, we can increase the neighboring relationships that should be done but not done so as to get a concise and complete neighbor relationship.

(4) parameter adjustment

You can adjust the parameters reasonably to achieve great results. In a sense, the optimization of the GSM network is the process of optimizing the settings and adjustment of various parameters in the network. No matter which manufacturer's device, there are a large number of parameters to control the channel configuration of the residential area, the paging, access, location update, and other behavior of the mobile phone. These parameters have an important impact on the network performance, such as the coverage of the residential area, inter-cell switching, and traffic load distribution. We need to grasp the basic principle of parameter adjustment to make full use of existing wireless resources and share the business volume so that the entire network's business volume and traffic are as even as possible, to improve the average network service level. Note that everything has two sides. Parameter modification must be moderate. If the parameter is too small, it does not take effect. If the parameter is too large, it will have a negative impact. When some optimization results are obtained, other indicators will inevitably be sacrificed. Because the cellular network is a whole system, you must consider the impact of local Parameter Adjustment on other regions, especially adjacent regions, when making parameter adjustment. Otherwise, parameter adjustment will have a negative impact, back to our original intention.

Concluding remarks on GSM wireless network optimization settings

Network optimization is a long-term, recurring, continuous system engineering that requires us to constantly explore and accumulate experience in practice. Only by solving various network problems, optimizing network resource configuration, improving the network running environment, and improving the network running quality can the network run in the optimal state, it provides a powerful foundation for the development of mobile communication services.