Research On Space-Time Coding Technology In MIMO-OFDM Systems

With the development of economy, advancement of society and improvement of people's of living standard, new wireless communication systems are expected to provide higher transmission rate, offer better quality and support faster moving terminals. The most effect way to meet such requirements is the MIMO technology, which deploys multiple antennas at the transmitter and the receiver. Recent research has shown that much larger channel capacity is feasible in MIMO systems than in the SISO systems. On the other hand, in the orthogonal frequency division multiplexing (OFDM) systems, the combination of MIMO space-time coding and frequency diversity technique can effectively confront frequency-selective multi-path fading, therefore robust data transmission in broadband channel is realized.This dissertation investigates several issues related to this hot research topic. To begin with, this paper investigates the information theory foundation of the popular MIMO system. The theoretical deduction of the channel capacity of the MIMO systems using multiple transmitting antennas and multiple receiving antennas from the view of information theory. It concludes that using the MIMO system can reach much higher channel capacity than the traditional SISO system.Second, this paper describes the diversity and the space-time coding design criteria in detail, and based on which, three main space-time coding techniques are studied, focused on vertical layered space-time codes (V-BLAST) decoding algorithm, and makes detailed comparison between the theoretical analysis and simulation results.At last, in order to improve the performance of space-time coding in the frequency selective fading channel, the space-time coding technique and orthogonal frequency multiplexing (OFDM) technique (STC-OFDM) are combined together A STBC-OFDM system is presented, and the SNR performance in the receiving end of the system is analyzed theoretically. And based on the analysis of the layered space-time coding and space-time coding in the OFDM system, a new coding and decoding system called STBC+OFDM is presented. This coding scheme considers the compromise of diversity and rate, and its decoding is simple, only a receiving antenna is needed in the receiving end to realize decoding and greatly reduces the complexity of the receiver. Finally, the fixed-point simulation confirmed the effectiveness of the scheme.