A Near-Optimum Multiuser Receiver for STBC MC-CDMA Systems Based on Minimum Conditional BER Criterion and Genetic Algori
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Research Article A Near-Optimum Multiuser Receiver for STBC MC-CDMA Systems Based on Minimum Conditional BER Criterion and Genetic Algorithm-Assisted Channel Estimation Leandro D’Orazio,1 Claudio Sacchi,2 Massimo Donelli,2 J´erˆome Louveaux (EURASIP Member),3 and Luc Vandendorpe3 1
Centro Ricerche FIAT (CRF), Trento Branch, Via della Stazione 27, 38123 Trento, Italy Engineering and Computer Science Department (DISI), University of Trento, Via Sommarive 14, 38123 Trento, Italy 3 Laboratoire de T´el´ecommunications et T´el´ed´etection, Universit´e Catholique de Louvain, Place du Levant 2, 1348 Louvain-la-Neuve, Belgium 2 Information
Correspondence should be addressed to Claudio Sacchi, [email protected] Received 1 December 2010; Accepted 7 March 2011 Academic Editor: Alexey Vinel Copyright © 2011 Leandro D’Orazio et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. The implementation of efficient baseband receivers characterized by affordable computational load is a crucial point in the development of transmission systems exploiting diversity in different domains. This would be a crucial point in the future development of 4G systems, where space, time, and frequency diversity will be combined together in order to increase system throughput. In this framework, a linear multiuser detector for MC-CDMA systems with Alamouti’s Space-Time Block Coding (STBC), which is inspired by the concept of Minimum Conditional Bit Error Rate (MCBER), is proposed. The MCBER combiner has been implemented in adaptive way by using Least-Mean-Square (LMS) optimization. The estimation of Channel State Information (CSI), necessary to make practically feasible the MCBER detection, is aided by a Genetic Algorithm (GA). The obtained receiver scheme is near-optimal, as both LMS-based MCBER and GA-assisted channel estimation perform closely to optimum in fulfilling their respective tasks. Simulation results evidenced that the proposed receiver always outperforms state-ofthe-art receiver schemes based on EGC and MMSE criterion exploiting the same degree of channel knowledge.
1. Introduction Future mobile communications standards will be required to provide high performance in terms of data rate, capacity, and quality of service. For this reason, the efficient exploitation of diversity in different domains (time, space, frequency) will be an issue. Multicarrier modulations [1] and Multiple-Input Multiple-Output (MIMO) space-time coding [2] are among the enabling technologies of future diversity-based highcapacity wireless communications. As claimed by Ahmadi in [3], next-generation mobile WiMAX technology will be based on Orthogonal Frequency Division Multiple Access (OFDMA), supported by Time-Division Duplexing (TDD) or Frequency-Division Duplexing (FDD), and advanced multiantenna systems, exploiting novel space-time coding
schemes. OFDM and OFDMA apparently dominate the panorama of
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