Abstract
We investigate the performance of turbo interference cancellation receivers in the space time block coded (STBC) direct-sequence code division multiple access (DS-CDMA) system. Depending on the concatenation scheme used, we divide these receivers into the partitioned approach (PA) and the iterative approach (IA) receivers. The performance of both the PA and IA receivers is evaluated in Rayleigh fading channels for the uplink scenario. Numerical results show that the MMSE front-end turbo space-time iterative approach receiver (IA) effectively combats the mixture of MAI and intersymbol interference (ISI). To further investigate the possible achievable data rates in the turbo interference cancellation receivers, we introduce the puncturing of the turbo code through the use of rate compatible punctured turbo codes (RCPTCs). Simulation results suggest that combining interference cancellation, turbo decoding, STBC, and RCPTC can significantly improve the achievable data rates for a synchronous DS-CDMA system for the uplink in Rayleigh flat fading channels.
Highlights
The presence of multiple access interference (MAI) in CDMA systems has led many researchers to investigate ways of exploiting the MAI to improve the system performance
The objective of this paper is to investigate the performance of a synchronous turbo coded direct-sequence code division multiple access (DS-CDMA) system that employs an minimum mean squared error (MMSE) front-end turbo space-time multiuser detector at reception propagating through a Rayleigh fading channel
Depending on the concatenation scheme used, we divide these into MMSE front-end partitioned approach and MMSE front-end iterative approach receivers, thereafter referred to as PA and IA receivers, respectively. We further study these receivers in conjunction with rate compatible punctured turbo codes (RCPTC) in turbo spacetime coded MIMO-CDMA systems and investigate possible ways of achieving higher data rates in DS-CDMA uplink
Summary
The presence of multiple access interference (MAI) in CDMA systems has led many researchers to investigate ways of exploiting the MAI to improve the system performance. The optimum multiuser detector (MUD) proposed in [1] that consists of the maximum-likelihood sequence estimator (MLSE) based on the Viterbi decoding algorithm has shown huge improvements over the conventional correlation receiver. As the number of users increases so does its computational complexity. The demand for higher system capacity and higher data rates has led researchers to the investigation of MIMO wireless systems [4]. When many users are in the system, strong MAI will occur. In this case, diversity processing alone cannot improve the system performance
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