Key Technology Research For GEG Satellite Mobile Communication System Based On OFDM

OFDM has been a core transmission technology for terrestrial wireless and mobilecommunications. In next generation satellite mobile communications, adopting OFDMcan both improve the system resource utilization rate and be very conductive to theintegration of satellite and terrestrial wireless and mobile communications. For thesatellite mobile communication system, adopting GEO satellite with multi-beam andhigh gain antenna has a better perspective. Therefore GEO satellite mobilecommunication system based on OFDM has great research value, and it is expected tobe the development direction of future satellite mobile communication systems.This dissertation studies some key problems in GEO satellite mobilecommunication system based on OFDM. And the main contributions of the dissertationare as follows:1. An architechture of the OFDM based GEO satellite mobile communicationsystem is illustrated, in which the basic schemes for each on-board functional moduleare provided.2. A long term channel prediction method is proposed for the GEO satellite mobilechannel based on Markov process. This method takes full advantage of the fadingcharacteristics of satellite mobile channel. It utilizes the correlation of the channel statesand Markov state transfer probability to predict the future channel state and outputs thechannel prediction value in the long term future according to autoregression prediction.And it solves the problem that the existing channel prediction methods in wirelesssystem are limited to channel coherence time and can not make long term prediction.Using this method to make efficient prediction of the satellite mobile channel hasinstructive meaning to adaptive transmission of OFDM satellite mobile communicationsystem and OFDM subcarrier resource allocation.3. Based on cross-layer design, an on-board call admission control scheme basedon network utility and dynamic system resource is proposed for OFDM satellite mobilecommunication system. In the proposed scheme, firstly, the OFDM subcarriertransmission capability is updated according to satellite channel states in physical layerand the variation of physical layer system resources is fed back to call admission control layer. And the allocated service bandwidth is adjusted dynamically in call admissioncontrol process. Then service call admission control is made by maximizing the totalsystem network utility. This scheme has high system resource utilization rateperformance and good call blocking probility performance when system load is heavy.4. An on-board suitable PAPR reduction method is proposed for the inherentPAPR problem in OFDM system. This method makes optimization of OFDM signalPAPR reduction and downlink subcarrier allocation jointly. Subcarriers are allocatedadaptively to each user terminal and each service, in the mean time, OFDM signalPAPR can be reduced through adjusting the subcarriers location that each serviceoccupies. The method can reduce the PAPR efficiently. And it would not degrade theOFDM signal and need not transmit side information.