Iterated SISO MUD for synchronous uncoded CDMA systems over AWGN channel: performance evaluation in overloaded condition

Ferry P. Wathan, Reza Hoshyar, Rahim Tafazolli
2007 2007 International Symposium on Communications and Information Technologies  
The performance of various iterated soft-input softoutput (SISO) multiuser detection (MUD) techniques is evaluated and compared for the case of overloaded condition for symbolsynchronous uncoded Code-Division Multiple Access (CDMA) systems over Additive White Gaussian Noise (AWGN) channel. We show that, via computer simulation, while the Bit-Error Rate (BER) performance of the serial version of the Symbol-Level iterated (SLi) SISO MUD technique is inferior to its parallel counterpart, its
more » ... gence rate is the faster between the two. Yet, the Chip-Level iterated (CLi) SISO MUD performs the best. Moreover, the Max-Log-MAP version of the CLi SISO MUD complementing the recently proposed Low-Density Signature (LDS) structure is introduced and compared to its Log-MAP version. The sensitivity of the various CLi SISO MUD techniques to the existence of the short-cycles in the underlying factor graph of the LDS structure is also analyzed. Our simulations confirm that the Max-Log-MAP version performs better compared to its more complex Log-MAP version in higher system loading condition. We also show that a performance close to single-user bound can be achieved at higher Signal-to-Noise Ratio (SNR) regime for system loading of up to 250%. 1 The scalability is one of the more important aspects in wireless communication in order to obtain a reliable and flexible system without having to compromise the signalling overhead each time a connection is terminated. 397 1-4244-0977-2/07/$25.00 c 2007 IEEE Authorized licensed use limited to: University of Surrey. Downloaded on April 15,2010 at 15:18:33 UTC from IEEE Xplore. Restrictions apply.
doi:10.1109/iscit.2007.4392052 fatcat:sotnmnh5vzh3vcutmpjff5qjpq