Smart Antennas Technology Based On OFDM Systems

With SDMA technology, smart antennas can double the expansion of communication capacity and maximize the use of spectrum resources, but also can effectively overcome the delay spread, multipath fading and other adverse effects. OFDM technology is a unique multi-carrier technology with high spectrum efficiency and good anti-multipath interference. The combination of smart antennas and OFDM can greatly improve the system performance. Smart antennas and OFDM technology have been the key technologies of next generation mobile communication.The paper mainly researches digital beamforming technology in the OFDM system with smart antennas. At first, two basic beamforming frameworks of smart antennas-OFDM systems are introduced in this paper, as time domain beamforming and frequency domain beamforming. Then, several improved algorithms are introduced in this paper, including the improved optimum beamforming algorithm based on time domain beamforming, subcarrier clustering based on frequency domain beamforming and hybrid-FFT based on the combination of time domain beamforming and frequency domain beamforming. At last, the paper presents a new pre-FFT beamforming algorithm based on frequency-domain adaptive equalization. The new algorithm cascades an adaptive equalization after the FFT module, in order to equalize every subcarrier in frequency domain. Equalization technique can compensate the channel distortion, effectively reducing the BER. Simulation results show that the new algorithm has low complexity, good effects of anti-multipath and better performance.