Multiantenna Multisource Multirelay Spectrum Sharing Networks: Buffer-Aware Direct Link Activation for Higher Reliability and Lower Overhead

Cooperative relaying can be implemented in spectrum sharing networks to extend the range of reliable communication. In this paper, we incorporate multiple-antenna technology and buffer-aided relaying to guarantee a highly reliable connectivity for the secondary network with several source nodes. The multi-antenna configuration for the sources and destination nodes suggests that there are several potential source-to- destination channels which can be auspicious for the network in two ways. First: to balance up the buffer states. Second: to expand the link selection opportunity at each time step. Motivated by this rationale, we propose a buffer-aware communication protocol to incorporate the direct transmissions along the relaying links without incurring excess overhead for circulation of channel-state-information (CSI). Considering Nakagami-m fading, we derive closed-form expressions for the end-to-end (ete) outage probability and average packet delay of the secondary network under the proposed protocol. Through Monte-Carlo simulations, we investigate the influential network parameters and evaluate the proposed technique in comparison to two benchmark schemes, one with buffer-based link-prioritization and one without prioritization. Findings demonstrate that the proposed protocol outperforms both benchmarks in terms of outage probability and ete delay, especially as the number of nodes scales up. However, the superior performance comes at the cost of more CSI circulation. Furthermore, it is shown that if the global CSI cannot be collected accurately, then the dependency of the link selection on the global CSI should be relaxed to mitigate the performance loss. The theoretical and Monte-Carlo results coincide in several simulation examples, verifying the presented theoretical analysis.