Beamforming in Dual-Hop Fixed Gain Relaying Systems

The performance of beamforming in dual-hop cooperative networks with fixed-gain relays is investigated. These kinds of relays offer low complexity and ease of deployment when compared with variable-gain relays. In our analysis, the source and destination nodes are equipped with multiple antennas, whereas the relay is assumed to be a single-antenna device. Closed-form expressions for the outage probability (OP), probability density function (PDF), moment generating function (MGF), and generalized moments of the end-to-end signal-to- noise ratio (SNR) are obtained. It is shown that when the same antenna configurations are considered at the source and destination sides, the power imbalance between the hops may be either beneficial or detrimental for the overall system performance. In addition, depending on whether the average SNR of the second hop is equal, lower, or higher than that of the first hop, an increase of the number of antennas may not necessarily result in a substantial improvement in performance.