Title :
Improved Turbo Decoding and Interference Cancellation for DS-CDMA with Random Spreading
Author_Institution :
Dept. of Electron. Eng., American Univ. in Cairo, Cairo
Abstract :
Parallel interference cancellation (PIC) receivers for turbo-encoded direct-sequence code-division multiple-access (DS-CDMA) systems with random spreading are considered. The residual multiple-access interference (RMAI) that remains in each user´s signal after PIC is modeled as Gaussian with time- dependent variance conditioned on the user cross-correlations. An enhanced estimate of the conditional variance of the RMAI is used in the log-likelihood ratio (LLR) computation for the Turbo decoders of each user. Significant performance gains reaching 2 dB are demonstrated on the frequency non-selective Rayleigh fading channel over the conventional LLR which assumes that the RMAI is Gaussian with a fixed variance.
Keywords :
Rayleigh channels; code division multiple access; decoding; interference suppression; spread spectrum communication; turbo codes; DS-CDMA; Gaussian model; cross-correlations; direct-sequence code-division multiple-access systems; frequency non-selective Rayleigh fading channel; log-likelihood ratio computation; parallel interference cancellation receivers; random spreading; residual multiple-access interference; turbo decoding; Detectors; Fading; Frequency; Interference cancellation; Iterative decoding; Multiaccess communication; Multiple access interference; Performance gain; Rayleigh channels; Turbo codes;
Conference_Titel :
Vehicular Technology Conference, 2006. VTC-2006 Fall. 2006 IEEE 64th
Conference_Location :
Montreal, Que.
Print_ISBN :
1-4244-0062-7
Electronic_ISBN :
1-4244-0063-5
DOI :
10.1109/VTCF.2006.325
