Research On Key Techniques In Broadband Wireless Communications

The future broadband wireless communication is expected to provide high spectral efficiency, high-rate, and high-reliability transmission. MIMO (multi input multi output), OFDM (orthogonal frequency division multiplexing) and LDPC (low-density parity-check) codes, developing as three key technologies in broadband wireless communication, are pain more and more attention by experts in this field and a lot of explorative and heuristic research have been carried out.In this paper, we introduced briefly the development history, application and some key technologies of broadband wireless communication, discussed several high-speed FFT algorithms suitable for OFDM modulation. After comparison and analysis, a new scheme suitable for OFDM is proposed for the design and FPGA implementation of multi-mode FFT processor, which is of high speed and low complexity. Combining OFDM with space-time code, performance of STBC (Space-Time Block Code) and STTC (Space-Time Trellis Code) in OFDM systems are analyzed and compared in detail, simulations are also done in channels with different parameters. Aiming at the requirement of reliably providing very high data rate transmission for broadband wireless communication, a LDPC coded MIMO-OFDM system model is established. Combining MIMO-OFDM soft-decision detection with LDPC code logarithm likelihood ratio decoding, a joint iterative detection and decoding algorithm with low complexity and high performance is presented, at the same time, simulation results show that the algorithm can improve system performance substantially.