Blind frequency offset estimation and intercarrier interference cancelation for FD-MC-CDMA systems in aerial vehicle communication

FD-MC-CDMA is an attractive candidate for next generation high speed aerial vehicle communication for its high spectrum efficiency and excellent BER performance. Similar to other multi-carrier transmission technologies, FD-MC-CDMA suffers significant performance degradation resulting from intercarrier interference (ICI) in high mobility environments. Particularly, because of the ICI is observed from all other subcarriers, the benefit of decomposing subcarriers into non-contiguous sets diminishes. In this paper, we propose a parallel processing based blind frequency offset estimation and ICI cancelation method for FD-MC-CDMA system to significantly improve the BER performance in high mobility environment. Specifically, by exploiting frequency offset quantization, the proposed scheme takes advantage of the orthogonality of the ICI matrix and offers excellent ICI cancelation and significant BER improvement. Moreover, the proposed scheme does not lower the transmission rate or reduce the network capacity. It is important to note that the proposed ICI cancelation scheme maintains the low complexity of optimum multi-user detection (MUD) receiver and achieves the ICI cancelation and excellent BER performance at linearly growing cost. Simulation results in AWGN channel and multi-path fading channel confirm the performance of the proposed scheme in the presence of frequency offset and in mobile channel.

I. Introduction

Multi-carrier CDMA (MC-CDMA) is a strong candidate for next generation wireless communication due to its high spectral efficiency, large system capacity, high flexibility in data rate and easy implementation using the fast Fourier transform (FFT) device without increasing the transmitter and receiver complexities [1]. Particularly, frequency division multi-carrier CDMA (FD-MC-CDMA) [2] [3] [4] has become an attractive solution for high speed aerial vehicle communication because of its low complexity multi-user detection (MUD) gain and superb BER performance. However, like other multi-carrier transmission technologies such as OFDM, FD-MC-CDMA system also suffers from intercarrier interference (ICI) caused to Doppler shift in high mobility environment. With this frequency offset, the orthogonality among the subcarriers is lost, ICI is generated and BER performance degrades sig-nificantly. Compared to other multi-carrier transmission tech-nologies, FD-MC-CDMA is hit the hardest since the superb performance of FD-MC-CDMA relies on the non-contiguous decomposition of the subcarrier sets and the corresponding low complexity MUD receiver. However, in a mobile environment with ICI, the FD-MC-CDMA receiver can no longer ignore the users on other subcarrier sets, leading to larger performance loss than other multi-carrier transmission technologies.