Iterative equalization using optimal multiuser detector and trellis-based channel decoder in coded CDMA systems improves the bit error rate (BER) performance dramatically. However, given large number of users employed in the system over multipath channels causing significant multiple-access interference (MAI) and intersymbol interference (ISI), the optimal multiuser detector is thus prohibitively complex. Therefore, the sub-optimal detectors such as low-complexity linear and non-linear equalizers have to be considered. In this paper, a novel low-complexity block decision feedback equalizer (DFE) is proposed for the synchronous CDMA system. Based on the conventional block DFE, the new method is developed by computing the reliable extrinsic log-likelihood ratio (LLR) using two consecutive received samples rather than one received sample in the literature. At each iteration, the estimated symbols by the equalizer is then saved as a priori information for next iteration. Simulation results demonstrate that the proposed low-complexity block DFE algorithm offers very good performance gain over the conventional block DFE.

Meeting Name

IEEE Global Telecommunications Conference, 2005. GLOBECOM'05


Electrical and Computer Engineering

Keywords and Phrases

BER; Bit Error Rate; Block Codes; Block Decision Feedback Equalizer; Channel Coding; Code Division Multiple Access; Decision Feedback Equalisers; Error Statistics; Extrinsic Log-Likelihood Ratio; Intersymbol Interference; Iterative Equalization; Multipath Channels; Multiple Access Interference; Multiuser Detector; Synchronous CDMA Systems; Trellis Codes; Trellis-Based Channel Decoder

Document Type

Article - Conference proceedings

Document Version

Final Version

File Type





© 2005 Institute of Electrical and Electronics Engineers (IEEE), All rights reserved.

Publication Date

01 Jan 2005