Abstract

We introduce an overlay cooperative cognitive radio scheme, in which the secondary network transmits only during the retransmissions of the primary network. The secondary network makes use of multiple relays in order to increase its performance compared to a non-cooperative scenario. Moreover, the secondary operates without harming the performance of the primary network. Different cooperative protocols are employed and associated with hybrid automatic repeat request mechanisms. Our results show that the incremental decode-and-forward technique allows the secondary network to achieve the highest throughput among the considered methods, at the cost of a very small degradation in the performance of the primary network.

Highlights

  • Cognitive radio was introduced by Mitola and Maguire [1] to designate adaptive and intelligent communication devices, which can learn about its surroundings

  • The secondary users are allowed to transmit simultaneously to the primary users whereas the interference they cause is below a given threshold [5,6,7]

  • Note that in this case, the only difference is that the maximum throughput in the secondary network is Rs, since the selected relay only cooperates if requested by Ds, so that it is possible to deliver a message in a single time slot if the secondary direct link is not in outage

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Summary

Introduction

Cognitive radio was introduced by Mitola and Maguire [1] to designate adaptive and intelligent communication devices, which can learn about its surroundings. An outage occurs in the primary network when the accumulated mutual information after at most two transmissions is less than the attempted rate Rp. in order to define the overall outage probability of the primary network, we first define Un, the event that no relay was able to correctly decode both the messages from Tp and Ts, so that if the secondary link is active, it operates in a non-cooperative mode. The term (C) in Eq (6) is the probability that an outage occurred in the primary link after two transmissions, given that Ds failed to decode the message from Tp. In order to analytically evaluate the outage probability in the primary link after a retransmission, it is important to note that the mutual information Ip, seen at the primary destination Dp after two transmissions from the primary depends on the behavior of the secondary network. In which we used Bayes’ theorem and the fact that Ip,2 ≥ Ip,

Secondary throughput
Primary without secondary
Findings
Conclusions
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