Study On Space-Time Coding OFDM Technology In IEEE 802.16e System

As an important part of future communication technology, wireless technology, especially mobile wireless technology is now becoming one of the hotspots in communications market. A broadband wireless technology based on IEEE 802.16, WiMAX (Worldwide Interoperability for Microwave Access) can provide high-rate data, audio and video services in both fixed and mobile environment and meets all the requirements of mobility, broadband and IP-based architecture. It is a very promising wireless access technology.Among a variety of key technologies in IEEE 802.16e system, space-time coding is an important technology. It introduces space and time correlation at the transmitter, so as to provide diversity gain and higher transmission rate through space diversity and space multiplexing, and can greatly improve the performance and efficiency of OFDM systems. The work of this thesis is mainly on the system construction and key algorithms of space-time coding system based on IEEE802.16e. Useful simulation results and conclusions are drawn through both theoretic analysis and algorithmic simulation.In chapter Ⅰ, the research background of this thesis is introduced. The architecture and key technologies of IEEE 802.16e standard as well as the principles and applications of MIMO-OFDM technology are investigated.In chapter Ⅱ, the development of space-time coding is firstly retrospected, and the typical space-time block code—Alamouti code and general STBC are investigated in detail. The modeling of space-time MIMO channel is then discussed, and the simulation methods of MIMO wireless channel and MIMO correlated channel are analyzed specifically.In chapter Ⅲ, the IEEE 802.16e standard is firstly introduced, and the specific parts related with space-time coding is investigated with emphasis. A standard-based space-time system is then constructed, and all the important algorithmic modules are described. The complete graph of the system is also provided.In chapter Ⅳ, channel estimation and space-time decoding algorithms applicable to the specific system are studied. Channel estimation of OFDM system is theoretically analyzed firstly, then the multi-antenna channel estimation methods in IEEE 802.16e system is further discussed, which including estimation in frequency-domain and time-frequency-domain. The space-time decoding algorithm of various transmit format is then investigated, and data demodulation and LLR calculation are also studied. Simulation results of different transmit format and coding-modulation mode are given and compared at the end of this chapter.Chapter Ⅴ is the extended research of this thesis. Although antenna selection is not defined by the standard, it is an important technology in multi-antenna system and can provide higher system capacity with lower hardware complexity. In this chapter, antenna selection is discussed in MIMO-OFDM systems, and optimum, sub-optimum and simplified sub-optimum antenna selection algorithms are proposed to achieve higher capacity.Finally, the work of this thesis is summarized and aspects for further improvement are indicated.