Research Of Cooperative Communication Technique Based On Space-Frequency Code

So far. wireless mobile communication has experienced rapid of development, to confront the decline of interference of the radio channel, various diversity technology was proposed, for example space diversity, frequency diversity. In addition, the development of communication become broadband is inevitable, in recent years the MIMO and OFDM technology has had a huge role on the development of communication technology. MIMO technology is forming multiple paths in the receiver by using multiple antenna, through digital signal processing technology and the signal of transmission paths combine, MIMO technology improve the quality of received signal. However, because of the mobile station volume, size, etc, it is not suitable to install multiple antenna systems, then, cooperative communication technology emerged. In wireless network, source node using the adjacent nodes around to send information to each other, forming virtual MIMO, so as to improve the signal quality.The space-time codes used in orthogonal frequency division multiplexing systems, can form of two transmission scheme, the one for the space-time coding, and the other one for space-frequency coding, this paper mainly based on space-frequency coding, studied the cooperative of broadband wireless communications properties.besides, the paper mainly analyses the performance under the fading channel cooperative systems, and simulated the system BER.Based on orthogonal frequency division multiplexing technique, we discusses its application in cooperative communication, including:(])In non-code communication among cooperative OFDM system, this paper give three OFDM forwarding cooperative approach, AF, DF and AF/DF mixed forwarding mode, and simulate its BER in the Doppler frequency channel.(2)Among the space-frequency coding, we analyses the directly used for OFDM space-time codes scheme, space-frequency coding and space-frequency coding scheme based on repeated, it is concluded that the space-frequency coding scheme based on repeated gets the extra diversity gain in multipath channel, performance obviously than the other two.(3)In distributed space-frequency codes, the paper gives two mode, frequency division and time division cooperation model, analyzes the performance of the system and simulates the system BER.