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ABSTRACT: Multiple input multiple output (MIMO) relay networks are wireless communication systems comprising of multiple nodes, each of which is equipped with multiple antennas. Information theories have shown that using multiple nodes to simultaneously relay a message can improve the capacity of source-to-destination communications. In this paper, we propose new relaying schemes for MIMO relay networks. The major concept behind the proposed schemes is to transform each of the MIMO relay channels into an equivalent triangular channel with positive real diagonal entries. By doing so, the resultant MIMO relay channel can simultaneously offer both distributed array gain (diversity gain obtained among relay nodes) and intranode array gain (diversity gain realized by multiple antennas of individual relay node) while maintaining the maximum spatial multiplexing gain (number of parallel data pipes). Based on this concept, three relaying schemes are derived that perform QR decomposition and phase control. Numerical results confirm that at least one of the proposed schemes outperforms the amplify-and-forward and the zero-forcing relaying schemes under various conditions. Moreover, we show that ratios of noise power level at relay and destination node have a great impact on capacities.
IEEE Transactions on Communications 10/2007; · 1.68 Impact Factor
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ABSTRACT: Recent advances in information theory have shown that the use of multiple nodes to simultaneously relay messages can further improve the capacity of source-to-destination communication. This has spurred interest in relay networks as a promising coverage extension technique. Many papers have explored the half duplex approach. This approach however limits the capacity since two time slots are required to send each message from source to destination node. To achieve higher capacity, we introduce the "relay node division duplex (RNDD)" approach, in which multiple relay nodes are divided into two groups that alternatively receive and transmit messages: while one group is receiving messages from the source node, the other is transmitting messages to the destination node. A difficulty of applying RNDD is that when the interference between the two relay groups is severe, the capacity will be greatly degraded. Therefore, we also propose a relay scheme that cancels the interference between relay groups by generating replicas of the interference from previously received signals at the destination node. Numerical results confirm that our method outperforms the conventional schemes that use the half duplex approach
Personal, Indoor and Mobile Radio Communications, 2006 IEEE 17th International Symposium on; 10/2006
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ABSTRACT: A multiple-input multiple-output (MIMO) relay network is composed of source, relay, and destination nodes, each of which is equipped with multiple antennas. Network information theory has shown that the use of multiple relay nodes in source and destination (S-D) communication makes the capacity of the S-D system logarithmically increase with the number of relay nodes. In [13], we proposed a MIMO relay scheme for a relay network with single source and destination pair; each of the multiple relay nodes performs QR decomposition of backward and forward channels in conjunction with phase control (QR-P-QR). In this paper, we extend this scheme to the MIMO relay network with multiple source and destination pairs. For this aim, we use the group nulling approach to decompose the multiple S-D MIMO relay channel to parallel independent S-D MIMO relay channels, and apply the QR-P-QR scheme in each of the decomposed MIMO relay links. Numerical examples show that the proposed relay scheme offers higher capacity than the existing zero-forcing (ZF) relaying scheme
Communications, 2005 Asia-Pacific Conference on; 11/2005
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ABSTRACT: Multiple-input multiple-output (MIMO) wireless networks are wireless communication systems composed of multiple nodes, each of which is equipped with multiple antennas. As proven by earlier studies, point-to-point MIMO systems offer significant capacity through spatial multiplexing and diversity techniques. Furthermore, recent studies have shown that the capacity of MIMO wireless networks can be greatly improved by using multiple relay nodes to relay messages simultaneously from source to destination. This paper proposes a relaying scheme for MIMO wireless networks. Its major concepts are: 1) performing QR decomposition on backward and forward channels in conjunction with phase control at each relay node, and 2) conducting successive interference cancellation (SIC) at the destination node. Such operations enable the wireless network to obtain distributed array gain among multiple relay nodes and receive array gain while maintaining maximum spatial multiplexing gain. Numerical examples have shown that the proposed relaying scheme is superior to previously proposed ones in both ergodic and outage capacity perspective.
Communications, 2005. ICC 2005. 2005 IEEE International Conference on; 06/2005
