A Novel Cooperative Relaying Network Scheme with Inter-Relay Data Exchange

Salma Ait FARES  Fumiyuki ADACHI  Eisuke KUDOH  

Publication
IEICE TRANSACTIONS on Communications   Vol.E92-B   No.5   pp.1786-1795
Publication Date: 2009/05/01
Online ISSN: 1745-1345
Print ISSN: 0916-8516
Type of Manuscript: Special Section PAPER (Special Section on Radio Access Techniques for 3G Evolution)
Category: 
Keyword: 
cooperative relay network,  transmit beamforming,  MRC,  adaptive antenna array,  optimal relay locations,  

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Summary: 
In this paper, we propose a novel scheme of cooperative relaying network based on data exchange between relays before forwarding their received data to destination. This inter-relay data exchange step is done during an additional middle-slot in order to enhance the transmit signals from relays to the destination under low transmit power condition. To reduce the propagation errors between relays as well as the required transmit power during this data exchange, only the relay possessing the highest SNR is engaged into exchanging data by forwarding its received signal to the other relays. As for the remaining non-selected relays, i.e. with low SNR, the transmitted signal is estimated by using both signals received separately at different time slots (i.e., 1st and 2nd slot) from source and the 'best' selected relay, respectively, emulating virtual antenna array where appropriate weights for the antenna array are developed. In addition, we investigate distributed transmit beamforming and maximum ratio combining at the relays and the destination, respectively, to combine coherently the received signals. At the relay optimal location and for low SNR condition, the proposed method has significant better outage behavior and average throughput than conventional methods using one or two time slots for transmission.