| In recent years, with the development of the mobile communication, the third generation mobile communication system cannot meet the video transmission and multimedia services that have the higher requirements for communication quality and transmission rate. Thus, people begin to focus on the technology of the fourth generation mobile communication (4G). In order to spread improve the wireless network capacity and improve the data transmission rate under the fading wireless environment, MIMO and OFDM technology have been continuously developed, both of them can be regarded as the core of the4G technology in the protocol standard. This paper mainly analyzes and researches the space-time coding algorithms used by the MIMO and OFDM technology.First of all, this paper introduces the MIMO system model and briefly explains the characteristics of several common wireless channel model and diversity technology, then discusses the channel capacity of MIMO system by means of theoretical derivation and simulation. Second, the paper analyzes three typical decoding algorithms in MIMO systems, and compares the advantages and disadvantages of the corresponding scene about those coding scheme. Third, we combine the OFDM with MIMO technology, and analyze MIMO-OFDM system model. In MIMO-OFDM system, we analyze the space-time coding and decoding scheme, for the deficiency of this scheme, we introduce the idea of quasi orthogonal, and then propose an improved coding algorithm, the simulation verifies the validity of this improved algorithm. Finally, we research the space-time frequency coding scheme, which can be used to overcome the multipath interference. In addition, we discuss the STFBC coding method, the key technology and specific implementation process of this scheme. According to the structure of the cascade code thoughts, we construct a kind of new coding method, SCSTFBC, The simulation proves that the new coding method is valid and can improve the system performance. |
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