3 research outputs found
Transmit Signal and Bandwidth Optimization in Multiple-Antenna Relay Channels
Transmit signal and bandwidth optimization is considered in multiple-antenna
relay channels. Assuming all terminals have channel state information, the
cut-set capacity upper bound and decode-and-forward rate under full-duplex
relaying are evaluated by formulating them as convex optimization problems. For
half-duplex relays, bandwidth allocation and transmit signals are optimized
jointly. Moreover, achievable rates based on the compress-and-forward
transmission strategy are presented using rate-distortion and Wyner-Ziv
compression schemes. It is observed that when the relay is close to the source,
decode-and-forward is almost optimal, whereas compress-and-forward achieves
good performance when the relay is close to the destination.Comment: 16 pages, 10 figure
Multi-Antenna Cooperative Wireless Systems: A Diversity-Multiplexing Tradeoff Perspective
We consider a general multiple antenna network with multiple sources,
multiple destinations and multiple relays in terms of the
diversity-multiplexing tradeoff (DMT). We examine several subcases of this most
general problem taking into account the processing capability of the relays
(half-duplex or full-duplex), and the network geometry (clustered or
non-clustered). We first study the multiple antenna relay channel with a
full-duplex relay to understand the effect of increased degrees of freedom in
the direct link. We find DMT upper bounds and investigate the achievable
performance of decode-and-forward (DF), and compress-and-forward (CF)
protocols. Our results suggest that while DF is DMT optimal when all terminals
have one antenna each, it may not maintain its good performance when the
degrees of freedom in the direct link is increased, whereas CF continues to
perform optimally. We also study the multiple antenna relay channel with a
half-duplex relay. We show that the half-duplex DMT behavior can significantly
be different from the full-duplex case. We find that CF is DMT optimal for
half-duplex relaying as well, and is the first protocol known to achieve the
half-duplex relay DMT. We next study the multiple-access relay channel (MARC)
DMT. Finally, we investigate a system with a single source-destination pair and
multiple relays, each node with a single antenna, and show that even under the
idealistic assumption of full-duplex relays and a clustered network, this
virtual multi-input multi-output (MIMO) system can never fully mimic a real
MIMO DMT. For cooperative systems with multiple sources and multiple
destinations the same limitation remains to be in effect.Comment: version 1: 58 pages, 15 figures, Submitted to IEEE Transactions on
Information Theory, version 2: Final version, to appear IEEE IT, title
changed, extra figures adde
Diversity-Multiplexing Tradeoff in Half-Duplex Relay Systems
Abstract β We study the multiple antenna half-duplex relay channel from the diversity-multiplexing tradeoff (DMT) perspective. We find performance upper bounds and show that compress-and-forward (CF) protocol achieves the upper bound. We argue that although it is hard to find the exact DMT expressions for decode-and-forward (DF) type protocols, they would be suboptimal in the multiple antenna case. We also study the multiple-access relay channel (MARC), and evaluate how CF works in this system. Our results show that CF is a robust strategy, which performs well in different relay networks and multiple antenna scenarios. I