Spectrally-efficient relay selection with limited feedback

Abstract

Abstract-This paper addresses the multiplexing loss that occurs in relay networks due to causality of relays and the halfduplex constraint. We devise relay selection methods to recover the multiplexing loss in decode-and-forward (DF) relay networks, while requiring very little feedback (merely bits/relay). Two network topologies are studied: First the case is considered where a direct link is available between the source and destination, in addition to the relayed links. For this configuration, an incremental transmission scheme is proposed, and comprehensively analyzed, which uses limited feedback to improve both diversity as well as multiplexing gain. Then, the case without a direct link is considered, for which efficient non-orthogonal DF protocols are produced and analyzed. An interesting feature of the latter methods is unequal error protection capability via a family of embedded diversity-multiplexing (DMT) curves, which can be very useful for practical applications. Even considering this method's minimal DMT, a marked improvement over previous DF methods is observed, especially in high spectral efficiencies.

Efficient multiple relay selection for cooperative communication using alamouti-coded virtual transmit antenna systems

“…In the former case, the source and the cooperating relays will not receive any control based packets from the destination. Whereas for the latter case, the destination select relays based on the number of transmitted symbols (which in our case is two) to cooperate instead of just selecting a single relay [13]. Selecting two relays has multiple benefits, it not only increases the diversity gain but it can be robust for a time varying environment.…”

“…[16] and BER, to corroborate the impact of relay selection using the concept of virtual antenna array. By definition [13], a channel achieves a multiplexing gain r and a diversity gain d with rate R(ρ) and resulting outage P out (ρ) such that,…”

“…Alamouti scheme) [1], the optimal tradeoff curve [16] and a slight modification to the ITRS scheme [13]. ITRS is modified to consider the initial transmission (where the source transmits and the destination receives the message via the relay) with the source not being able to transmit during successive transmission slots.…”

“…So, we can define the upper bound or the optimal DMT by taking the minimum of (19),(20) and considering rate loss k+2 k r induced by the cooperative nature of the system [13]. The optimal DMT is,…”

Enhanced performance of heterogeneous networks through full-duplex relaying

“…Nevertheless, with half duplex (HD) radios the cooperation suffers a multiplexing loss, once the relay listen in a first slot (time/frequency) and then retransmits the message in a second slot. Several solutions have been proposed trying to overcome the problem of the HD constraint as in [17,18] and references therein. On the other hand, incremental cooperative protocols, such as incremental-DF (IDF), can overcome the spectral inefficiency of HD cooperation through the exploitation of a return channel between nodes [15,16,19].…”