The Performance Analysis Of STTC-OFDM System Over Frequency-Selective Fading Channels

With the integration of Internet and multimedia services in next generation wireless communications, the demand for wide-band high data rate communication services is growing. In the future broadband wireless communications, there will be two severe challenges to be faced, which are frequency selective fading channels and bandwidth efficiency. Owing to these two challenges, MIMO and OFDM are imposed on more attention. Being one of the core MIMO techniques, the space-time code technique takes a very important status in the MIMO-OFDM system.Multiple-input-multiple-output (MIMO), employing multiple antennas on both transmitter and receiver, can improve the system capacity and performance without expanding the bandwidth or increasing transmit power. Space-time code (STC) is the coding scheme based on transmit diversity that can improve MIMO performance.By combining coding techniques with modulation, Space time trellis codes (STTC) can reach the compromise of Encoding Complexity, performance and frequency efficiency, which is regarded as the optimum code. Orthogonal frequency division multiplexing (OFDM), transforming high rate data transmission into lower rate transmission with multiple orthogonal sub-carriers, can eliminate frequency selective fading.In the paper, firstly the multiple-input-multiple-output technology and the multiple carriers multiplexing technology are discussed. Also the characters of wireless channels are introduced.On this basis, the space-time trellis codes and Decoding Principle and flat fading channel coding guidelines are introduced.The theory of OFDM and the key technologies are described. Simulatings above are based on frequency flat channels, while this paper makes more emphasis on the performance of STBC-OFDM in frequency selective fading channels. Moreover, the COST 207 fading channels are selected as the model of the frequency selective fading channels. The performance results of STBC-OFDM in different COST 207 fading channels are given, which contain typical Rural Area (RA), Typical Urban (TU), Bad Urban (BU) and Hilly Terrain (HT). It is noted that aforementioned researches are performed in Gaussian white noise. However, the non-Gaussian noise in the realistic communication systems is prevalent. Therefore, the performance results of STTC-OFDM with the non-Gaussian noise.are also researched. Then the performance of STTC-OFDM with the non-Gaussian noise in the COST 207 fading channels is explored, and Middleton Class A is selected as the model of the non-Gaussian noise. At last, the performance results are given.