Title: Network code assisted HARQ scheme in multi-user systems with cooperative relays

Authors: Chun Cheung, Roger S. Cheng

Addresses: Signal Processing and Communication Laboratory, Department of Electronic and Computer Engineering, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong. ' Signal Processing and Communication Laboratory, Department of Electronic and Computer Engineering, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong

Abstract: A network code assisted HARQ system considering uplink (UL) transmission with multiple mobile stations (MSs) cooperating with a relay-station (RS) is proposed. The RS is assumed to successfully monitor and decode the packets transmitted from the MSs to the base station (BS). The BS partitions the incorrectly decoded packets into groups based on their MS-to-BS channel conditions and feedbacks this partition to the RS. The RS employs a network-coded HARQ scheme within each group for subsequent retransmissions. We proposed a dynamic and adaptive partitioning method based on the BS channel state information and the corresponding HARQ retransmission schemes. Also, we derived a low-complexity joint demodulation and decoding structure. Simulations showed that our scheme improves the system throughput by 15% when compared with the relay assisted chase-combining HARQ system. We also explored suitable ranges of diversity orders for the RS-to-BS and MS-to-BS channels that provide significant system throughput improvements with practical implementation cost.

Keywords: cooperative relay; network code; hybrid ARQ; HARQ retransmission; multi-user; iterative decoding; uplink transmission; multiple mobile stations; relay stations; dynamic partitioning; adaptive partitioning; simulation; demodulation.

DOI: 10.1504/IJCNDS.2011.040557

International Journal of Communication Networks and Distributed Systems, 2011 Vol.6 No.4, pp.343 - 356

Published online: 05 Jun 2011 *

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