Recursive MMSE-based iterative channel estimation for OFDM-IDMA systems

Combination of IDMA with Orthogonal Frequency Division Multiplexing (OFDM) transmission technique to form OFDM-IDMA system has been considered as a better option to Multicarrier-CDMA (MC-CDMA) systems. However, as the case with other multiple access schemes-based communication systems, availability of accurate estimate of channel state information (CSI) at the receiver end of the system remains a crucial factor for optimum performance of the OFDM-IDMA systems. In this paper we propose a linear algorithm for the implementation of the iterative channel estimation schemes OFDM-IDMA systems. In the scheme, a recursive minimum mean square error (RMMSE) algorithm is employed for the iterative channel estimation. The achievable results associated with the proposed RMMSE-based iterative channel estimator are documented in comparison with results associated with iterative channel estimator employing Least Mean Square (LMS), Normalized Least Mean Square (NLMS), and Variable Step Size Normalized Least Mean Square (VSSNLMS) algorithms. From the simulation results, it is evident that the proposed RMMSE-based iterative channel estimator outperforms the estimator based on the adaptive algorithms.