MIMO Relay Network with Precoding

We study the achievable rate in a MIMO, dual-hop, relay network where source and relay nodes may precode their input signals before transmission. Although an iterative expression for optimal precoders in this scenario is available in the literature, the corresponding achievable rate cannot be obtained analytically. We therefore propose approximate expressions for the precoding matrices and present semianalytical derivations of the achievable rate, which represent a significant progress toward closed-form expressions of this important metric. Beside being mathematically tractable, our expressions for the precoders provide data rates that are very close to the optimum and outperform existing approximate schemes. We apply our expressions to the analysis of the tradeoffs existing between achievable rate and nodes power consumption.