A Walsh-Hadamard coded spectral efficient full frequency diversity OFDM system

A full frequency diversity COFDM (FD-COFDM) scheme based on sub-channel multiplexing is proposed to improve the performance of COFDM without sacrificing spectral efficiency. Since the channel suffers the frequency selective fading, the received signal contains strong inter-symbol interference (ISI). To obtain the diversity- and code-gains, an iterative receiving algorithm is presented. By jointly using diversity combining, interference cancellation and soft decoding, the proposed iterative receiving algorithm properly decodes the information bits in the strong ISI environment. Consequently, all the subcarriers of FD-COFDM participate in diversity so that the system can achieve full frequency diversity in most practical channels. The new receiving algorithm is relatively simple compared to the maximum likelihood estimation algorithm, and is therefore a better alternative to balance the algorithm complexity and system performance.