Abstract
A power allocation strategy is proposed for single-antenna overlay cognitive radio networks, in which the secondary user helps transmit the signal of the primary user while concurrently conveying its own signal by means of a superposition coding technique. The study commences by deriving analytical expressions for the bit error rates (BERs) of the primary and secondary users. A power allocation strategy is then proposed for minimizing the total power consumption of the two users while simultaneously satisfying their respective BER constraints. The analytical BER formulas are not convex, and hence the optimization process presents a significant challenge. Accordingly, two more tractable BER approximations for the primary and secondary users are proposed to transfer the non-convex problem into a convex one. The simulation results confirm the effectiveness of the proposed power allocation strategy under various channel environments.
Highlights
Cognitive radio (CR) transceiver design has received significant attention in recent years due to the ability it provides to make more efficient use of the spectrum resources [1,2,3]
5 Conclusions This paper has considered the problem of optimizing the power allocation strategy in cooperative spectrum-sharing cognitive CR systems
Given the use of a superposition coding (SC) scheme at TB, analytical expressions have been derived for the corresponding Bit error rate (BER) at RA and RB
Summary
Cognitive radio (CR) transceiver design has received significant attention in recent years due to the ability it provides to make more efficient use of the spectrum resources [1,2,3]. The overlay CR model is designed to overcome the poor error performance at RB by enabling TB to help UA relay its signal while concurrently transmitting its own signal This assistive function can be realized using either some form of cooperative relaying technique or a superposition coding (SC) scheme [5, 14–17]. Due to the signal transmission protocol used in the considered overlay CR network, the error performances of UA and UB are inherently affected by both the transmitted powers of TA and TB and the power allocation factor used in the SC scheme. To evaluate the respective effects of these factors on the error performance, this study commences by analyzing the BERs of UA and UB, where the BER is expressed as a function of the transmitted powers of UA and UB and the power allocation ratio applied in the SC scheme.
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