Cooperative diversity with opportunistic relaying

Abstract

Abstract-In this paper, we present single-selectionopportunistic-relaying with decode-and-forward (DaF) and amplify-and-forward (AaF) protocols under an aggregate power constraint. We show that opportunistic DaF relaying is equivalent to the outage bound of the optimal DaF strategy using all potential relays. We further show that opportunistic AaF relaying is outage-optimal with single-relay selection and significantly outperforms an AaF strategy with multiple-relay (MR) transmissions, in the presence of limited channel knowledge. These findings reveal that cooperative diversity benefits (under an aggregate power constraint) are useful even when cooperative relays choose not to transmit but rather choose to cooperatively listen; they act as passive relays and give priority to the transmission of a single opportunistic relay.

Outage optimality of opportunistic amplify-and-forward relaying

“…Although cooperative relaying has focused on simultaneous and in-band transmissions from multiple relays (see, e.g., [3] and references therein), recent asymptotic analysis showed that carefully selected single-relay transmissions incur no performance loss compared to multiple-relay transmissions in terms of the diversity-multiplexing gain tradeoff for both decode-and-forward (DF) and amplify-and-forward (AF) relays [4]. Subsequent finite signal-to-noise ratio (SNR) analysis showed that under an aggregate power constraint, specific single-relay selection among DF relays is globally outageoptimal, i.e., minimizes the outage probability and outperforms techniques based on multiple DF-relay transmissions [5]. Moreover, the optimal rule for single-relay AF transmission was presented-i.e., the opportunistic relay selection that minimizes the outage probability among all single-relay selection rules in AF environments.…”

Security and quality of service (QoS) co-design in cooperative mobile ad hoc networks

“…In the first time slot, the source broadcasts the signal which could be heard by all relay nodes in its radio coverage and the destination; in the second time slot, if the signal received by the selected relay node could be decoded successfully, it would be forwarded to the destination; the destination then combines the received signal from the source and selected relay to recover the information sent from the source. The source selects the best relay before transmitting the data from the source to the destination [15]. There is no requirement on all intermediate relays to listen to the source's broadcasting except for the selected relay; thus, power or energy spent by unselected relays on listening to the channel and receiving the message sent by the source is saved.…”

Building blocks of cooperative relaying in wireless systems

“…One way to do this is via a contention window with random slot selection by relays. Another idea is to distribute relay reports as a function of their desired parameters, such as quality of links to the source and destination [11]. Although packet collision is unavoidable in such approaches, it can significantly be reduced with very reasonable complexity.…”