Static Power Allocation in Two-Hop MIMO Amplify-and-Forward Relay Systems

In this paper, we propose a static power allocation algorithm for a two-hop multi-input-multi-output (MIMO) amplify-and-forward (AF) relay system in which the interim channel state information over the first and the second hops is unavailable. Based on the path losses over the first and the second hops, this algorithm performs static power allocation between the source and relay nodes to maximize the equivalent received SNR of the system. We further investigate the optimal location of the relay node when the conventional fixed and the proposed optimal static power allocation schemes are applied. Our comparison between direct transmission and relay-based two-hop transmission indicates that whether the latter outperforms the former depends on a tradeoff between the received SNR gain and the multiplexing loss in the relay-based two-hop transmission scheme.

I. Introduction

Relay-based cooperative communication has become a hot topic in wireless communication. A typical single-user relay-based cooperative communication system consists of a source node (SN), one or more relay nodes (RN's), and a destination node (DN). As a repeater, the RN relays the signal from the SN to the DN after appropriate processing. It has been demonstrated that relay techniques can increase the communication coverage, decrease the overall transmit power, and enhance the capacity or reliability of the communication links [1] [2] [3].