Design And Realization Of GSM Downlink Broadcast Channel Demodulation

With its long-term development history in China, GSM mobile communicationsystem has become the most widely used communication system in the present days. The3G communication system has been used in business. However, due to the restrictions of3Gs cost and technology, operators still have to pay much for the maintenance andoptimization of GSM in the next few years. Building repeaters is the best solution toenhance network coverage in actual construction. In recent years, with the traditionalanalog repeater being replaced by digital repeater, a large number of GSM digital repeatershave been used in GSM network. The GSM digital repeater has achieved the goal ofnetwork coverage with a small capacity, but it makes adverse impact on GSM network aswell.Based on the above background, this paper brings broadcast channel demodulationmodule into traditional GRRU (GSM digital remote radio unit) system. The system isexpected to make the frequency-hopping synchronized with base station by abstractingfrequency-hopping information of GSM cell from demodulating GSM downlink broadcastchannel. This will help to improve GRRU work performance and reduce its adverse impacton GSM network.In this paper, Chapter1includes the development status of GSM communicationsystem, the significance and background of the research project, and a summary of theorganizational structure of the present research. Chapter2details the GSM communicationsystem with the theoretical knowledge of baseband. Chapter3discusses the technique ofGMSK modulation and the synchronization algorithm in system, and simulates GMSKmodulation and synchronization algorithm by MATLAB. Chapter4introduces the GSMbroadcast channel demodulation system in detail and focuses on the implementation ofGMSK demodulation and channel decoding module. In Chapter5, each module's logicfunction is implemented by FPGA and debugged on the digital signal processing platformbased on software radio. The research ends up with a summary of the thesis and deficiencies of previous work which gives directions for future work.