Simulation Research On Performance Of Space-Time Block Coding Based On OFDM And Beamforming

MIMO is considered as one of the key techniques of the next mobile communication systems and it can not only improve the capacity and spectral efficiency of communication systems effectively without expanding the bandwidth or increasing transmit power, but also improve the reliability of systems. And OFDM is one of the key techniques of 4G because of its higher spectrum efficiency and capability to combat frequency selecting fading. It is easy to combine OFDM with many other techniques such as STC, diversity, smart antenna and so on. And combining the MIMO and OFDM together, as MIMO-OFDM systems, is imposed on more attention.Space-time code scheme is one of the key techniques of MIMO systems and it has been one of the hotspots in communication field. It can make full use of the multi-path in the wireless communication systems so as to combat multi-path fading. But space-time code design is complicated in frequency selecting fading condition. It is a good way to combine STC with OFDM to solve this problem. Otherwise, various interference and multi-path fading exist in practical wireless communication systems at the same time. And the interference can be mitigated with beam-forming. Therefore, it is very useful to study the STC based on OFDM systems and beam-forming.This paper studies the STBC technique based on OFDM systems and beam-forming particularly. This dissertation firstly summarizes research status of correlate techniques both domestic and overseas, and then introduces three main space-time code schemes with emphasis on space-time block code scheme. After introducing several typical beam-forming rule and algorithm, the system model of combining STBC with beam-forming is founded and simulated. At last, the STBC-OFDM systems is particularly analyzed and simulated. The simulation results confirm that in contrast with OFDM, the STBC-OFDM improves BER performance whether in flat fading condition or frequency selecting fading condition. It is also be confirmed by simulation that different modulation schemes such as BPSK and QPSK in STBC-OFDM result in different BER performance. Therefore, for improving system performance the modulation scheme in STBC-OFDM should be changed according to the channel environment when the adaptive modulation scheme is considered.