Subspace-based estimation method of uplink FIR channel in MC-CDMA system without cyclic prefix over frequency-selective fading channel

The multipath nature of the wireless channel can be described as a finite impulse response (FIR) filter, which easily results in hostile intersymbol interference (ISI). Usually, multicarrier code-division multiple access (MC-CDMA) systems combat the hostile ISI with the aid of the cyclic prefix (CP). Nevertheless, the elimination of ISI in MC-CDMA systems is at the cost of reduction in spectral efficiency. To recover spectral efficiency, it is meaningful to investigate MC-CDMA systems without CP. This paper explores the estimation of the uplink FIR channel in the MC-CDMA system without CP. We interpret the MC-CDMA system without CP as an equivalent time-domain ISI-corrupted direct sequence (DS-) CDMA system. Based on subspace techniques, an uplink FIR channel estimation scheme is derived for the MC-CDMA system without CP. Simulations demonstrate the validity and the performance of the proposed uplink FIR channel estimation scheme.