STBC Based Pilot-Aided Channel Estimation Method for SFBC-OFDM Systems

In this paper, an iterative channel estimation algorithm with joint detection is proposed for Multiple Input Multiple Output (MIMO) systems combined with Orthogonal Frequency Division Multiplexing (OFDM) also known as MIMO-OFDM systems using Space Time Block Codes (STBC) and Space Frequency Block Codes (SFBC). The proposed algorithm is based on an iterative process where pilot subcarriers are used for channel estimation in the first time instant, and then in the second time instant, the estimated channel is used to decode the data symbol in the adjacent data subcarrier. Once data symbols are recovered, the system recursively performs a new channel estimation using the decoded data symbols as pilots. The iterative process is repeated until all MIMO-OFDM symbols are recovered. In addition, the proposed channel estimation technique is based on the maximum likelihood (ML) approach which offers linearity and simplicity of implementation. The method also reduces the processing time via the use of subcarrier grouping for transmitted data recovery. From this we further propose an STBC and SFBC alternating scheme for pilot and data subcarriers. In this scheme STBC and SFBC are used for pilot and data subcarriers respectively, or vice versa. In addition, the efficiency of the method is demonstrated through computer simulation using multiple transmit and receive antennas and different modulation schemes.