Abstract
Cognitive radio is a promising technology that uses radio spectrum opportunistically and efficiently. In this paper, we present the performance of ‘Always transmit’ strategy, which consists of allowing the cognitive source to transmit over all time slots and in any time slot. Thus, the cognitive source will be able to operate continuously whenever either the primary user is active or absent. The proposed strategy is projected into dual-hop communication systems with decode-and-forward and relay selection over independent but not necessarily identically distributed Nakagami-m fading channels. We derive the closed-form expressions of the outage probability, and we analyze the performance. Simulation results show that the strategy ‘Always transmit + Relay’ outperforms other conventional cognitive radio strategies and the use of relays enhances the performance in deep fading channel.
Highlights
Significant attention has been given to cognitive radio as a new technology that uses radio spectrum opportunistically and efficiently and which allows new applications to share currently allocated spectrum while the quality of service (QoS) at primary side is guaranteed.There are three approaches of cognitive radio used to access licensed or unlicensed band [1]: spectrum interweave, spectrum underlay, and spectrum overlay.a- Spectrum interweave: the secondary user (SU) uses the first part of time slot for ‘spectrum sensing’ to detect spectrum hole and make a secondary user decision Hs(i) at time slot, and beginning transmission in the second phase, only if the result of sensing in the first phase is Hs(i) = H0
In (M Ridouani, A Hayar, A Haqiq, Continuous-transmit in cognitive radio systems: perform sensing and transmission in parallel anytime. submitted to IEEE TWC ), we have shown that the use of as power constraint is recommended for transmission, because it allows preserving the QoS of primary system at each time while guaranteing an outage performance limit for the secondary of about 20% of maximum degradation, and due to fading and by using average transmit power constraint, the energy efficiency is improved
Motivated by cooperative communications and our results in [17,18], in this paper, we extend our strategy ‘AT’ (the cognitive source (CS) will be able to transmit over all time slots and in any time slot, it will be able to operate continuously whenever either the primary user is active or absent) into cognitive relay selection
Summary
Significant attention has been given to cognitive radio as a new technology that uses radio spectrum opportunistically and efficiently and which allows new applications to share currently allocated spectrum while the quality of service (QoS) at primary side is guaranteed. In our previous works [16], where we have introduced our new strategy of transmission ‘Always Transmit (AT): to enhance the cognitive sources of data transmission and to provide continuous transmit solution by using mixed strategies in cognitive radio context, which it performed via the combination of the underlay and interweave approaches depending on the activity of the primary system’ and have shown that it outperforms other conventional cognitive radio strategies for power transmission and interference management, in [17], where we have derived the closed form and analyzed the performance of outage probability over Rayleigh fading, and in [18], where we have studied the trade-off between spectrum sensing duration and the QoS at cognitive network while guaranteeing certain QoS at primary network controlled by the outage probability limit, over independent but not necessarily identically distributed Nakagami-m channels.
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