Performance Analysis of Parallel Interference Cancellation in Multicarrier DS-CDMA Systems

Abstract

In this paper, we present and analyze the performance of a parallel interference cancellation (PIC) scheme for multicarrier (MC) direct-sequence code-division multiple-access (DS-CDMA) systems. At each cancellation stage in the proposed PIC scheme, on each subcarrier, a weighted sum of the soft outputs of the other users in the current stage is cancelled from the soft output of the desired user (rather than making hard bit decisions of the other users and regenerating and canceling the interfering signals) to form the input to the next stage. At the last stage, the interference cancelled outputs from all the subcarriers are maximal ratio combined (MRC) to form the decision statistic. The scheme has the advantage of not requiring the amplitude estimates of the other users. We derive analytical expressions for the bit error rate (BER) at different stages in the proposed PIC scheme on Rayleigh fading channels. Analytical results are found to agree well with the simulation results. The results show that the proposed PIC scheme offers better interference suppression capability than the conventional matched filter (MF) receiver. We also obtain bounds on the coded BER of the proposed PIC scheme for a convolutionally coded multicarrier DS-CDMA system where the PIC-MRC output feeds a soft decision Viterbi decoder.

Indexing terms:

• Parallel interference cancellation
• Multicarrier DS-CDMA
• Fading channels

Additional information

Notes on contributors

K R Shankar Kumar

KR Shankar Kumar completed his PhD degree in the Department of Electrical Communication Engineering, Indian Institute of Science, Bangalore, India. His thesis research topic is multicarrier DS-CDMA systems.

A Chockalingam

A Chockalingam received the BE (Honours) degree in Electronics and Communication Engineering from the PSG College of Technology, Coimbatore, India, in 1984, the MTech degree with specialization in satellite communications from the Indian Institute of Technology, Kharagpur, India, in 1985, and the PhD degree in Electrical Communication Engineering (ECE) from the Indian Institute of Science (IISc), Bangalore, India, in 1993. During 1986 to 1993, he worked with the Transmission R&D division of the Indian Telephone Industries Ltd., Bangalore. From December 1993 to May 1996, he was a Postdoctoral Fellow and an Assistant Project Scientist in the Department of Electrical and Computer Engineering, University of California, San Diego (UCSD). From May 1996 to December 1998, he served Qualcomm, Inc, San Diego, CA, as a Staff Engineer/Manager in the systems engineering group. In December 1998, he joined the faculty of the Department of ECE, MSc, Bangalore, India, where he is an Associate Professor, working in the area of wireless communications and networks. He was a visiting faculty to UCSD during summers of 1999–2002. He is a recipient of the Swarnajayanti Fellowship from the Department of Science and Technology, New Delhi, Government of India. He is an Associate Editor of the IEEE Transactions on Vehicular Technology.