The Application Of DBF In OFDM System

With the development of mobile communication, wideband wireless commun- ication technology is attentioned. Due to the high capability of anti-interference and anti-multipath fading of OFDM(Orthogonal Frequency Division Multiplexing) technology, it has been recognized as the core technology in next generation wireless communication systems. Although the OFDM technology can overcome the ISI ,the wireless channel is a multi-user channel , there are multipath fading, delay spread, frequency expansion and other issues. The traditional methods of solving this problem include modulation and demodulation, channel coding, equalization, diversity, interlacing techniques. Smart antennas have brought about a new thought as the solution to all these problems, which is regarded as the Last Frontier of wireless mobile technology, DBF is an important research domain of smart antennas. When there is interference or strong interference even, DBF can suppress the interference, reduce the error rate of communication system, enlarge the system capacity. Therefore, DBF can achieve high-speed and reliable data transmission, which is applied to OFDM system. This dissertation develops the DBF, which is based on DOA(direction of arrival) ,with application to OFDM system. This dissertation investigates a module of four signals , two of which are OFDM signals of 16-QAM modulated, others are the multi-path components. Due to the correlation of the signal and its multi-path component, we use the spatial smoothing algorithm to , and then use the MUSIC algorithm. At last ,we use the MVDR algorithm to receive the signals. The simulation results show that DBF based on DOA can receive OFDM signals at the receiver as well as its multi-path components, which provides the foundation and guarantee for signal detection of the OFDM system.