Research On Channel Coding Technology Based On Spatial Diversity

With the rapid development of modem communication technology and computer technology, new communication and information cases are springing every day, at the same time, the requirement of communication quality and data rate are also enhanced continuously. The conventional channel coding adds the redundancy in the time domain to enhance the reliability of received data or correction errors. In recent years, with the development of distributed networks and multi-antennas technology, many channel coding technologies which add redundancy in the time and spatial domain appear, we call those channel coding technology in time-spatial domain or channel coding technology based on spatial diversity.Starting with the analysis of character of wireless channel, we summarize the history and actuality of channel coding in time domain, channel coding in time-spatial domain. After the introduction of several typical channel coding technologies in time domain using in modern wireless communication system, we focus on the channel coding in time-spatial. We classify the channel coding in time-spatial domain into two cases: single antenna system and multi antenna system.In the single antenna system case, we mainly analyze the distributed cooperative communication systems. At first, we take the channel coding in time-spatial domain based on user cooperation as example and introduce the conceptions and process methods in multi devices cooperative systems. Then we introduce the channel coding technology in time-spatial domain based on base station cooperation and analyze the effect of BS cooperation on cell coverage. Also, we simulate the effect on region partition of cell when we use MRC and cooperative coding separately, and we can see that cooperative coding can enhance the cell coverage greatly. We propose a distributed Turbo coding (DTC) structure based BS cooperation after the analysis above. DTC system send the bits after coding to a spatial interleaver, and then transmit them through three BS separately to the user, then the spatial diversity gain is obtained and the channel resources allocation can be realized in three cells region. The simulation indicated that DTC structure has some advantage in resource allocation success probability and BER performance compared with the traditional coding structure, and it's a good tradeoff between resource allocation success probability and BER performance.In the multi antenna system case, at first, we introduce the three branches of space-time coding in MIMO system: STBC, STTC and BLAST/HLST. Then we explain the main detection algorithms of V-BLAST. To solve the disadvantage of traditional detection algorithm of V-BLAST, we proposed a new two-stage iterative successive detection (TISD) algorithm. TISD has better detection performance compared traditional detection algorithm. Because the error propagation is the bottle-neck of successive detection performance, we proposed the window TISD (Win-TISD) algorithm based on TISD. The Win-TISD avoids the error propagation and can obtain excellent detection performance compared with TISD and others algorithms. At last, consider that the error probability descends with the iteration, we also proposed a Win-TISD with variable window length, in which, we reduce the window length in the first some iterations to avoid error propagation, and add window length in the last iterations to enhance the diversity gain.