Low Pass Interpolation in multiple access systems

This work investigates the performance of Low Pass Interpolation/ Pilot Symbol Assist Modulation for mobile reception in OFDMA and MC-CDMA systems. The interpolation is used to track the channel state, normalize the signal received by each sub-carrier with its associated transfer factor and subsequently mitigate the effect of frequency selective fading channel. As the data symbols spread by code sequence, more resistance and reliability have been gained, as compared to OFDMA performance where the same number of users are multiplexed to be transmitted over the channel. The simulated error rates prove that the bit error rate of MC-CDMA system falls more rapidly as we increase the transmitted signal power compared to the OFDMA system. Further, simulation-based results show a reasonable gain in the performance by tracking channel state more precisely and improve the performance of Low Pass Interpolation at the expense of higher complexity and longer processing time, through the use of feedback to aid in determining the frequency domain equalization and merge block type and comb type channel estimation to get an efficient mechanism. However, the error rates depicted that MC-CDMA scheme is infirm with the presence of the channel path delay even with new frequency domain channel equalization.