Practices Of Liaoyuan Mobile To Optimize GSM Wireless Network

Into the 21st century, mobile communication businesses have been developing rapidly. While large-scale network construction is now underway, all operators focus more on the network's operation quality, service quality, and rationality of network structure and configuration. The issues about how the network can continue its scientific and reasonable development to meet the need for future sustainable business development and the need for promotion of new businesses have now been listed as key tasks on agenda of mobile operators aiming at network optimization. Six years of development passed since 1997 when construction of Liaoyuan Mobile GSM mobile network began, while network optimization is also aspired to now. The problem is that in some belts where mobile users are concentrated, all base stations'communities are configured with high-frequency devices, plus the different heights of antennae in base stations, resulting in severe co-channel or next-channel interference with base stations of higher antennae impacted more. So the issues about how to eliminate channel interference in urban areas, how to reasonably control the coverage of base stations, and how to raise actual call quality have been emphasized in the Liaoyuan Mobile's efforts for wireless network optimization. Set in this context and under the precondition of careful studies on principles of GSM system and wireless network optimization, this paper, through incorporating the GSM network engineering practices of Liaoyuan Mobile, has utilized theories into reality, and obtained good effects. - 1. Outline of GSM system GSM belongs to the second generation of mobile communication system, is a public communication system that is characterized by complete functions, advanced technologies, and complicated equipments. Main components can be divided into mobile station (MS), base station subsystem (shortly called BS), and network sub-system (NSS). BS is composed of base transceiver station (BTS) and base station center (BSC); NSS is composed of mobile switch center (MSC), operation and maintenance center (OMC), home location register (HLR), visitor location register (VLR), authentication center (AUC), equipment identification register (EIR), etc. 2. Study on methods for optimization of GSM wireless network Trough analyses of some key factors that can influence wireless quality, the problems have been solved from the aspects of software and hardware, and thus raising the quality of wireless network. 2.1 Analysis of key points involved in wireless network optimization The major tasks of wireless network optimization are to solve the problems of call drop and jam. Therefore, this chapter is mainly used to introduce the varieties of and reasons for call drop and jam as well as relevant system parameters: 2.1.1 Varieties of and reasons for voice call drop In GSM networks, voice call drop can be categorized into wireless network call drop, Abis interface call drop, A interface call drop, TC interface call drop, and call drops for other reasons. About over half of the voice call drops happen in wireless networks and reasons for this phenomenon are the following: (1) Radio-frequency call drop (2) Call drops in switchovers (3) Interference call drop (4) Abis call drop(5) A interface call drop, etc. 2.1.2 Key means to address the problem of call drop (1) Adjustment of the call drop-related parameters through data collection and analysis (2) Adjustment of antenna feeder that can influence call drop (3) Examination of the call drop-causing switchover through data collection and analysis, and adjustment of switchover relationships among communities. 2.1.3 Wireless network parameters that are related to call drop (1) CRH of the community (2) Cycle of locating (3) Power control parameters (4) Switchover parameters (5) Other parameters, for example, preference of BCCH carrier frequency and direct connection into super layer. 2.1.4 Varieties of wireless jam and the system parameters Wireless jam includes: jam caused by high traffic, jam caused by equipment failure, jam caused by unreasonable parameter setting, etc. The parameters that can influence wireless network jam include: (1) Emission power (2) accmin (3) Community priority parameters: Level and Levthr(4) Koffset (5) Irrationality of station site, etc. 2.2 Steps for GSM wireless network optimization2.2.1 Collection of optimization data For satisfactory wireless network optimization, the following basic data should be collected: 1. Materials about community database, such as: quantity of base stations, latitude and longitude of base stations, community structure for each base station, quantity of voice channels, BISC of base station, community No., CGI of community, No. of BCCH and TCH carrier frequency, mode of frequency hopping, definition of relationship between two adjacent communities, materials about switchover, materials about power control, materials about system information, etc. 2. Materials about antenna feeder, such as: type of antenna feeder, feeder loss, standing wave ratio, gain of antenna, antenna height, direction angle of antenna, pitching angle of antenna. 3. Traffic statistic data, such as: 24-hour traffic statistic data of a whole day, traffic statistic data at busy time 4. Data of drive test, such as: drive test of the whole network in key cities, key drive test zones determined according to STS statistic data and user complaints. 5. Warning information of base stations, such as: historical information, and current information 6. User complaints, such as: complaints about network quality, complaint about network coverage, etc. 2.2.2 Analysis of optimization data After optimization data have been collected, analysis should be conducted especially about the following basic materials: 1. Analysis of community database materials; 2. Confirmation of community database materials; 3. Examination about the consistency of community database materials; 4. Analysis of the community database materials and searching for omitted adjacent relationships 5. Analysis of traffic statistic materials; 6. Analysis of drive test materials; 7. Analysis of base station warning and user complaints, etc. 3. Detailed optimization and adjustmentThe third step for wireless network optimization is about the following detailed optimization and adjustment based on the above-mentioned optimization data and particular analysis of basic materials: (1). Parameter adjustment Parameter adjustment is a process of optimized setting and adjustment of various parameters. The current available wireless resources should be made the best use of to even the business amount and signaling amount of the whole network through the mode of sharing the business amount. (2). Frequency adjustment Frequency adjustment can decrease the level of interference of the whole network. Micro-adjustment should be conducted continuously of distribution of network frequency to reduce interference furthermore and to gain the optimal frequency plan. (3). Antenna adjustment Deep coverage of the communities can be achieved through adjustment of base station antenna's direction angle and downward angle, or through adoption of the current frequency-shifting direct station, etc. (4). Supplement of indoor coverage system Indoor coverage system necessitates indoor wiring and installation of antenna to lead the signal source's signals into the wiring system, to expand the base station's coverage range, and to fully utilize currently available wireless resources and to save investment. 4. Practices of Liaoyuan Mobile to optimize GSM wireless network 4.1 Objectives of wireless network optimization In the section above, Liaoyuan GSM wireless network has been introduced briefly. A series of measures through frequency adjustment, adjustment of base station parameters, analysis and adjustment of drive test, etc. have brought the Liaoyuan Mobile network to the optimal operations, and have achieved the optimal utilization rate. Additionally, this network optimization can make the author fully familiar with the network's expanding trend, providing effective data for reference in the following work of network expansion. Wireless coverage, parameter adjustment, and service performance are targeted and centered by optimization ofthis time. Moreover, based on the actual conditions of Liaoyuan GSM, careful observation of distribution of base stations and the surrounding environment has been carried out. Many optimization methods, including frequency plan adjustment, antenna adjustment, adjustment of adjacent relationships among different communities, adjustment of community parameters, etc. have been adopted to control the interference in urban areas effectively. Through the following adjustment and repeated verification, the objective of raising call quality and user familiarity has been fully achieved.. 4.2 Key points for wireless network optimization (1). Solving the problem of call drop Call drops in this network is mainly concentrated in the aspect of radio-frequency loss call drop. Switchover call drops are also enormous. Call drops are frequent. Therefore, we have focused our efforts in this optimization on call drop as the major target for analysis and solution. (2). Reducing the ratio of the worst communities Ratio of the worst communities, an index that can reflect the network operation situation and the current traffic distribution, is a key point in our optimization. Elimination of the worst communities relies on analysis and sum-up of detailed statistic data and relies on timely maintenance and adjustment. (3). Increasing and decreasing the switchover relationships Whether or not switchover can succeed not only is an important statistic index but also can reflect the network operation situation, as well as closely related to other indexes. Raising switchover quality and sensitivity can raise call quality, and reduce switchover call drop. Reduction of pingpong switchover through raising switchover quality can also mitigate the system and channel load and ultimately reduce the jam. 4.3 Practical steps of wireless network optimization and the following effects Firstly, aiming at the situation of many call drops due to overtime of wireless link, the wireless link's parameters in this network have been adjusted. Also the measures of frequency adjustment and supplement of adjacent relationships have been combined to address the problem of call drops. Additionally, for the communities of this network where high call drop rate exists, drive test and statistic analysis together have been incorporated together for detailed solutions. Theprevalent problem of call drops in all communities of this network has been addressed by track analysis of A interface signals, resulting in reduction of total amount of call drops. Thorough elimination of call-drop problem in the current network has been achieved through examination and revision of corresponding time meters on the exchange side. Also, targeting the problem of switchover call drop, the community parameters and switchover parameters have been examined. For call drops demonstrated by statistic data of switchover origins and by actual drive test data, we have conducted detailed adjustment of current network's frequency has been conducted, and the adjacent relationships have been revised and supplemented. Secondly, detailed analysis and sum-up of reasons of the worst communities and the worst communities having emerged each week have been conducted. Then the communities suffering from high call-drop rate and high jam rate have been classified, the relevant statistic indexes, traffic situation within one week have been summed up and compared to propose corresponding solutions. Thirdly, the adjacent relationships of the network that have been omitted for definition have been supplemented. Adjustment has been made for the community antennae that were too high in urban areas in order to prevent trans-community coverage. Meanwhile large-scale frequency adjustment has been conducted to reduce the quality-caused emergency switchover as much as possible. At the same time, the switchover parameters of the communities that have too many switchovers have been adjusted to boost the switchover quality greatly. 4.5 Effects of the optimization and comparison and analysis of network performances This network optimization has reached the expected objectives and raised all indexes greatly. Large part of this paper is used for detailed analysis and sum-up of comparison of the effects before and after optimization. Meanwhile, our own suggestions have also been proposed in this paper. These parts can provide particular reference by Liaoyuan Mobile for its future GSM wireless network optimization. 5. Sum-up This paper is mainly concerned with three aspects: study on GSM system principles, study on GSM wireless network optimization, and engineeringrealization of Liaoyuan Mobile's GSM wireless network optimization. The following conclusions can be obtained: (1). There are great guiding effects in the study of and in-depth analysis of GSM network theories on detailed optimization practices. (2). Engineering realization of GSM wireless network optimization has stimulating effect on theoretical analysis. (3). Engineering realization of Liaoyuan GSM wireless network optimization has led to reasonable and quick working steps and methods for wireless network optimization, paving the way for successful completion of the work for wireless network optimization.