Performance of multicarrier complementary-coded CDMA under frequency-selective Nakagami-m fading channels

Abstract

Multicarrier complementary-coded code division Multiple Access (MC CC-CDMA) is becoming an attractive multiple access technique for high data rate transmission in future wireless communication systems. MC CC-CDMA systems transmitting over frequency-selective channels suffer from multiple access interference (MAI) owing to non-ideal correlation properties of complementary codes (CC). MC CC-CDMA with equalization has recently gained much attention for its ability to offer an excellent performance than traditional systems in frequency-selective fading channels. In this paper, the authors present an analytical study and investigation of MC CC-CDMA downlink system using different combining schemes. The use of parallel interference cancellation (PIC) under frequency-selective Nakagami-m fading channels is also analyzed. A comparison among different combining schemes is provided to show the impact of PIC with minimum mean square error combining (MMSEC) and maximal ratio combining (MRC) on the performance of MC CC-CDMA system. The analytical and simulation results show that the combination of general combining schemes with PIC provides an efficient solution to suppress MAI in downlink MC CC-CDMA system than conventional MC-CDMA systems using Walsh codes under frequency-selective channels.

Successive interference cancellation in asynchronous CC-CDMA systems under Rician fading channels

“…Suboptimum interference cancellation techniques which employ successive interference cancellation (SIC), parallel interference cancellation (PIC) [10], zero forcing (ZF) detectors, and minimum-mean-square error (MMSE) detectors [11] were analyzed to reduce the computational complexity incurred in BS receivers. PIC was studied for downlink CC-CDMA systems operating under frequencyselective Rayleigh fading channels [12] and Nakagami-m fading channels [13]. Pre-equalization schemes were also studied for downlink CC-CDMA systems to overcome MAI and increase diversity gain with zero-forcing compared to MMSE combining [14].…”

Suitable Spreading Sequences for Asynchronous MC-CDMA Systems

“…there is a timing misalignment among users, such as the uplink channel of cellular mobile systems. To mitigate MAI, several techniques were proposed recently [1], [5], [6]. However, these techniques only add to the complexity of MC-CDMA systems.…”

“…However, these techniques only add to the complexity of MC-CDMA systems. In contrast, MAI interference could be eliminated through the design of a set of sequences with impulsive auto-correlation function (ACF) and zero cross-correlation functions (CCF) [6], [8]. Unfortunately, such ideal sequences are impossible to construct [8].…”