Abstract
In this paper, the impact of co-channel interference (CCI) on the performance of an underlay cognitive radio network over Nakagami- ${m}$ fading channels is thoroughly presented and analysed. More precisely, a decode-and-forward relay protocol for a cognitive cooperative network is considered. In this study, the impact of both the primary transmitter interference and CCI on the secondary system performance are considered. First, an exact expression for the equivalent signal-to-interference-plus-noise ratio of the secondary system is obtained. Then, the corresponding exact and asymptotic cumulative distribution functions are derived. From this, the exact outage performance for the secondary network is investigated. Furthermore, the equivalent probability density function is obtained and discussed. In addition, approximate expressions for the average error probability and the system ergodic capacity performances are derived. From the results, it can be inferred that the presence of the CCI and primary network interference severely degrades the system performance. Moreover, a higher value of the shape parameter of the desired fading channel gives better performance and diversity gain. In addition, despite the impact of interferences, the secondary network performance gives better results in comparison to the Rayleigh fading channels scenario.
Highlights
A N UNDERLAY cognitive radio (CR) scheme [2] is one of the paradigms that has been proposed to realise a cognitive radio network
The following network parameter values are used: the co-channel interference (CCI) powers are IR = 2 dB, ID = 3 dB, the primary interference powers are IPR = 3 dB, IPD = 4 dB, and LR = 2, LD = 4, Ps = Pr = 15 dB, the considered power for the primary transmitter is at the secondary receiver node, bearing in mind that the power of the secondary transmitter attenuates with the distance and it is decreased when it reaches the secondary receiver node
This shows that having more channel paths provides more diversity; as a result, the diversity gain of the network increases leading to an enhancement of the system performance
Summary
A N UNDERLAY cognitive radio (CR) scheme [2] is one of the paradigms that has been proposed to realise a cognitive radio network. This is the key protection factor of the primary user’s quality of service (QoS). The phenomenon of a co-channel interference is important to consider in the spectrum sharing network such as underlay cognitive radio [5]. This is due to the coexistence of different kinds of users in the same frequency spectrum, in addition to the interference that might come from outside sources in the neighbouring cells that are working on the similar frequency. Rician and Nakagami distributions demonstrate almost the same behaviour when approaching their mean values [7]
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