Fading Relay Channels: Performance Limits and Space–Time Signal Design

Abstract

Cooperative diversity is a transmission technique, where multiple terminals pool their resources to form a virtual antenna array that realizes spatial diversity gain in a distributed fashion. In this paper, we examine the basic building block of cooperative diversity systems, a simple fading relay channel where the source, destination, and relay terminals are each equipped with single antenna transceivers. We consider three different time-division multiple-access-based cooperative protocols that vary the degree of broadcasting and receive collision. The relay terminal operates in either the amplify-and-forward (AF) or decode-and-forward (DF) modes. For each protocol, we study the ergodic and outage capacity behavior (assuming Gaussian code books) under the AF and DF modes of relaying. We analyze the spatial diversity performance of the various protocols and find that full spatial diversity (second-order in this case) is achieved by certain protocols provided that appropriate power control is employed. Our analysis unifies previous results reported in the literature and establishes the superiority (both from a capacity, as well as a diversity point-of-view) of a new protocol proposed in this paper. The second part of the paper is devoted to (distributed) space-time code design for fading relay channels operating in the AF mode. We show that the corresponding code design criteria consist of the traditional rank and determinant criteria for the case of colocated antennas, as well as appropriate power control rules. Consequently space-time codes designed for the case of colocated multiantenna channels can be used to realize cooperative diversity provided that appropriate power control is employed.

Cooperative Wireless Networking Beyond Store-and-Forward

“…When the assisting relays work under the half-duplex constraint, different cooperative protocols are possible [20]. Every protocol exhibits different capacity properties, but the efficiency of the cooperative transmission also depends on the way resources are allocated to the source and relay terminals.…”

Partial Information Relaying with Per Antenna Superposition Coding

“…Especially, it is crucial in cellular environments to mitigate intercell interference for an increased rate and extended coverage at cell edge. In such efforts, various relaying protocols such as amplify-and-forward (AF), decode-and-forward (DF), compress-and-forward (CF) have been proposed [1], [2], [3], [4]. Those relaying schemes are mainly to exploit the multipath diversity for power gain (or increased rate) that results from combining direct and relayed signals.…”

Performance of Cooperative Time-Reversal Communication in a Mobile Wireless Environment

“…One approach to improving the capacity of the network is to employ cooperative communication techniques, in which multiple nodes in the network cooperate to transmit information to a desired receiver node. Recently, both cooperative relay strategies [1][2][3][4][5][6] and cooperative transmission strategies [7][8][9][10] have been extensively studied. In this paper, we consider a cooperative transmission strategy based on a technique called time-reversal communication (TRC), which can be regarded as generalization of beamforming.…”