Sistema cooperativo cognitivocom compartilhamento espectral usando retransmissão incremental híbrida

Abstract

Cognitive radio and cooperative communication are considered two key technologies for the future of wireless communication systems. Cooperative communication over the last few decades has received considerable attention and is now a well - established technique for improving the performance of wireless systems by providing enormous performance gains obtained without the need for multiple antennas implemented at the terminals. On the other hand, the wireless community sees the need to use wireless resources more eficiently. Within this framework, cognitive radio emerged as a promising technique to alleviate the problem of spectrum scarcity and under utilization by allowing unlicensed users to access portions of spectrum initially allocated to a licensed user. Motivated by the promising gains acquired through the use of cooperative communication and the concept of cognitive spectrum sharing, a joint study of these two promising technologies is of extreme relevance to the next generations of wireless networks. In this work, the outage behavior for a cognitive cooperative system with spectral sharing and incremental hybrid retransmission in the relay node is investigated. This system is formed by a secondary network composed by three secondary nodes: the source, the relay and the destination; and a primary user. The cooperation occurs for ransmission between secondary users, in which a incremental hybrid relay protocol is used by the relay. In this scenario, relay relaying occurs only in case of need, either using the Amplify-and-Forward protocol (AF) or using the Decode - and - Forward protocol (DF), from the evaluation of source - destination channel and source - relay - destination channel. We adopt an underlay approach in the secondary communication, in which the transmission is governed by the reception interference of the primary user. The analytic and closed-form expression for the probability of outage is derived. The analytical results are corroborated by the Monte Carlo simulations, validating the theoretical expression developed and relevant discussions are provided.