Research On Downlink Of Wide-Band Ground- Air Communication System Based On MIMO-OFDM

As the development of wide-band ground-air communication, higher communication rate, much better quality of service and higher spectral efficiency is requested. Simultaneously, the fixed-rate data transmission has been far from satisfying the modern complex business requirements. Variable-rate communication, which can meet the requirement of high-rate multi-media communication, is becoming a hotspot. After my selective study of ground-air channel’s features and the basic principle of MIMO and OFDM, a novel ground-air system scheme for multi-users’ variable-rate communication is proposed; then the space-time and space-frequency block code(STBC and SFBC) used in the scheme is farther discussed. And finally the scheme’s performance under ground-air channel is given. The main work and contributions are described as follows:1. The features of ground-air channel are discussed. Then the channel’s time-domain implementation is derived.2. A novel ground-air system scheme based on MIMO and OFDM is proposed, of which the argumentation about functions of each component is made and the parameters is given.3. Two methods combining OFDM with MIMO — STBC-OFDM and SFBC-OFDM are proposed; And their signal-to-noise performance under time delay with channel side information(CSI) is simulated. It induces that STBC-OFDM is better than SFBC-OFDM when there is a large time delay or few subcarriers for change in the gain between two coded subcarriers is big.4. Because it is hard to acquire the accurate channel side information, a differential space-time block code without CSI is applied in the system scheme. Then the performance of DSTBC and DSFBC combined with OFDM under ground-air channel is obtained. It appears that each has its strong point, so choice should be made by the feature of the paratical channel.