Carrier frequency synchronization for OFDM-IDMA systems

The recently proposed Orthogonal Frequency Division Multiplexing-Interleave Division Multiple Access (OFDM-IDMA) scheme has been at the forefront of wireless communication systems research due to its promising features which include high efficiency, flexibility and high data-rate wireless transmission. Earlier, major research on this new scheme had only focused on the perfect-condition scenarios, with the assumption that the system is free from synchronization errors. However, recent studies show that synchronization errors, especially the carrier frequency offsets, have significant impact on the OFDM-IDMA systems. This work therefore examines comprehensively, analyses and verifies the impact of synchronization errors on the performance of the OFDM-IDMA hybrid multicarrier scheme. Furthermore, simple but effective synchronization algorithms, namely; the linear minimum mean-squared error (MMSE) based algorithm, and the Kernel Least Mean Square (KLMS) algorithm as well as its normalized counterpart called the Normalized-KLMS are adopted and adequately exploited to combat the degrading impacts of synchronization errors on the OFDM-IDMA scheme. The linear minimum mean-squared error (MMSE) based algorithm, is a non-data aided method, which focuses on the mitigation of the inter-channel interference induced by the effect of synchronization errors on the system. The Kernel Least Mean Square (KLMS) algorithm, as well as its normalized counterpart, presents an efficient approach for estimation and effective correction methods to combat the effect of carrier frequency offset errors on the performance of the OFDM-IDMA system. The bit error rate (BER) performance of these algorithms is presented, compared, and analyzed. Also, the achievable performance of these synchronization algorithms in a Rayleigh multipath channel scenario with varying mobile speed is analyzed and documented.