| A good mobile network is the most important basis on network operation for mobile operators. The network quality of service, capacity and network covers all determines the income of the operators and operating efficiency. In the second generation of digital mobile cellular system, air interface is affecting the quality of network coverage and the most important part of, Air interface is the most important interface of mobile communication system. Network capacity, network coverage and service quality is closely related to air interface.Air interface is wireless interface between mobile network terminal equipment and base stations, according to different usage environment, the influences of various factors, there are many unstable factors, Air interface protocols and signaling message relative cable structure is more complicated. So for mobile network monitoring is the key of the network monitoring of air interface, only the realization of dynamic monitoring, analysis of network failure will be more accurate. This is also evaluating of the network planning, network and network optimization areas of concern.The current GSM network monitoring method is more mature Abis interface, A interface and PRI interface such as cable interface measurement. In China, air interface monitoring study is less. Mobile communication network belongs to high-tech industry and develops in a high speed. Mobile communication network update quickly, the traditional hardware design is subject to the mobile communication network of air interface monitoring system hardware is not easy to change. And poor generality shortcomings. Therefore, this system adopts the Software defined Radio technology. In the general-purpose computer and general software defined radio platform, GSM air interface monitoring system was designed and implemented.In China, the main research focus in the GSM special receiving chip as the core, or demodulation decoding algorithm simulation. Abroad study using the software defined Radio technology in mobile communication network project began in an analysis of the air interface started five years ago, the Airprobe open source of GSM system air interface monitoring project. The project of using open source GNU Radio software defined Radio platform and general peripherals software defined Radio platform USRP1. It receives and analyzes the GSM base station broadcast channel and common control channel successfully.ilistener system is in the air interface monitoring system on the basis of open source Airprobe system, through the reconstruction of Airprobe open source, reproduction, and the GSM network air interface monitoring system application background of learning and accumulation, gradually found the light of the defects in the Airprobe system to improve and upgrade, and conducted research and system design.This topic has the specific research results are as follows:(1) In the Airprobe system, signal receiving and data processing as the same program. Program code is too long, code implementation also not use multithreading technology is optimized. Partial spin-off ilistener system program into four parts:the signal receiving module, data communication module, signaling parsing module and control center module. On the realization of the code, the use of the multithreaded programming technology, make full use of general computer multi-core processor resources.(2) The signal receiving module hardware part. Through the further study of the GSM network air interface part of the agreement. The software defined radio technology is applied in the existing GSM network air interface system research. And on the existing GSM air interface analysis system Airprobe, based on software defined radio technology carried on the thorough analysis. Airprobe system mainly solves the broadcast channel receives the analysis, lack of dedicated control channel analysis, lack of adopting analyze frequency hopping communication GSM network. Existing Airprobe system due to adopting the design of the single channel receiver. Therefore is not suitable for hopping communication and the analysis of the air interface uplink channel, to this, this paper studies the principle of the multi-channel receiver, design of multi-channel receiver.The signal receiving module software part based on the research of the GSM protocol, the GSM protocol in the abrupt pulse sequence of frame structure, the GSM network system structure and the dedicated control channel mapping in the physical channel. The realization of the code for signal receiving module, make ilistener system can real-time analysis of the air interface.(3) In order to improve the working efficiency of the monitoring system to dedicated control channel, the network structure and network programming in the computer network, is adopted in the system data communication module, joined the data communication module, receiving parts and analysis of the system can connect through the network, improve the flexibility of system deployment. Network communication is what Airprobe system does not have function.(4) The study of channel allocation in the GSM protocol part principle, signaling parsing module is designed. Signal analysis module based on GSM dedicated control channel and channel allocation process, the data communication module to receive part of the processing. The final output of air interface signaling data to an XML file, realized the uplink channel and frequency hopping communication environment air interface dedicated control channel signaling real monitoring.(5) By studying the SSH protocol in the remote control computer control, the design of the control center module. Through the control center module, ilistener system user can easy to use, and remote control ilistener system within the local area network. In the signal receiving part joined the scanning function of community. Airprobe system also lack of this part. |
