Adaptive relaying scheme for cognitive radio networks

Abstract

Cognitive radio (CR) systems allow unlicensed secondary users to transmit on the licensed frequency bands without degrading the licensed primary transmissions. Combining CR with other emerging transmission techniques, such as user cooperation may have many benefits on both the primary and secondary transmissions. In this study, the authors propose and investigate an adaptive relay-based cooperation scheme for CR networks that improves the secondary outage performance, while respecting a primary outage probability threshold. The proposed adaptive scheme considers one multi-antenna relay node that, by selecting the antenna(s) to use, can assist either the primary, the secondary or both transmissions simultaneously. Expressions of the conditional primary outage probability for Rayleigh fading channels are derived and used to investigate the associated power allocation problem. Simulation results show that both primary and secondary outage probabilities of the proposed scheme are significantly improved and outperform non-cooperative and cooperative schemes given in the literature.

Improving spectrum access using a beam‐forming relay scheme for cognitive radio transmissions

“…In our scheme, RE assists the primary transmission while ST sends x s using a controlled transmit power at the second sub-slot. x p is decoded by following a similar approach as in (9)- (11). † RE successfully decodes x p : In this case, RE applies a N × 1 weight vector w (DF) p to x p and forwards the product to PR at the second sub-slot.…”

“…We show that the secondary outage performance is improved at the expense of a substantial increase on the transmit power of the relay node. This scheme has been extended to the case of a multi-antenna relay with antenna selection in [11]. We also proposed an adaptive cooperative scheme in [12] where one relay node can assist primary transmissions, secondary transmissions or both transmissions simultaneously.…”

“…Even though some work has focused on exploiting user cooperation for CRNs, to the best of our knowledge not much work has been reported in investigating multi-antenna relaying for both primary and secondary transmissions [10][11][12][13][14][15][16][17]. Moreover, most work considering pre-coding at the multi-antenna CR nodes assume that the secondary nodes have perfect knowledge of the interference channel (ST-PR) and perfect knowledge of the primary channel (PT-PR) [17,18], which oversimplifies the system.…”

On the outage performance of decode-and-forward based relay ordering in cognitive wireless sensor networks

“…because it has been considered as a key technology for solving spectrum utilization and congestion issues [1] [2]. It is a well-known fact that most of the licensed spectrum remains unused in practice at different times.…”