Codes And Differential Space-time Codes. Group Space Performance Studies

Space Time Coding combining diversity, coding and modulation, can effectively resist multipath fading in the channel and improve the capability of the system, so it will probably become the key technology of the 3rd generation of mobile communication system. This article mainly focuses on the research of basic principle of Space Time Coding technique and its application in the mobile communication system, through the method of theory analysis and computer imitation. The content of this article is as follows.1) It introduces the basic principle of Space Time Coding, discusses the capacity of Multi-Input Multi-Output system and provides design criteria and code rate for quasi-static flat-fading channels.2) It reviews the origin and developing status of Space Time Coding, introduces some important kinds of Space Time Coding including Layered Space Time Coding, Space Time Trellis Code, Space Time Block Coding, Differential Space Time Block' Coding, and analyses their merits and defects respectively.3) It analyses and compares in detail the theories, features and performances of encoding and decoding. It also provides the scheme based on orthogonal design, discusses the decoding project of Quasi-Orthogonal Space time block coding and gives some examples and result figures. The decoding project based on orthogonal design, greatly reduces the complexity of decoding STBC to the linear operation, which is much easier than Space Time Trellis Code, however, the capacity lightly declines.4) It discusses the code and decoding principle of Differential Space Time Block Coding, and puts forward the design rules of coefficients vector set of DSTBC. On analyzing the simulation results and figures of and discussing the application of DSTBC in the static image transmission, itprovides a project for protecting vital information in the transmitting process. Results show that differential detection performs about 3 dB worse than coherent detection which knows the correct channel state information. In the meantime of paying costs in capacity, Differential Space Time Coding gets rid of the reliance upon the Channel state information and will probably have a bright future under a certain circumstance. As based on the orthogonal design, Differential Space Time Block Coding has less complexity and time delay in decoding. Simultaneously, through the protection of vital bits, Differential Space Time Block Coding provides better PSNR and transmitting quality when BER increases.