In this study, the authors consider the communication scenario where two sources communicate with the help of a single relay, modelled as a half-duplex butterfly network. Closed-form expressions of the outage probabil...
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In this study, the authors consider the communication scenario where two sources communicate with the help of a single relay, modelled as a half-duplex butterfly network. Closed-form expressions of the outage probabilities are derived in the high signal-to-noise ratio (SNR) regime for the orthogonal amplify-and-forward and non-orthogonal amplify-and-forward protocols. Then the expressions are approximated to enable power allocation. Closed-form power allocation schemes are proposed for each protocol, where only statistical channel knowledge is required. It is shown that the authors analyses match well with simulation results and the approximated versions are very close to the simulation results. The proposed power allocation schemes achieve a large SNR gain over the equal-power strategies and approach the optimal power allocation schemes.
In this study, the optimal power allocation (OPA) problem is studied for the two-way relay channel employing the analogue network coding protocol with the asymmetric traffic requirements in a cognitive radio network. ...
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In this study, the optimal power allocation (OPA) problem is studied for the two-way relay channel employing the analogue network coding protocol with the asymmetric traffic requirements in a cognitive radio network. The OPA scheme is proposed by maximising the sum-rate of the success delivery bit from the secondary user (SU) perspective subject to the sum-power constraint and the interference power threshold (IPT) constraints to the primary user (PU). In particular, for the purpose of accomplishing the power allocation more realistically, the interference to each other between the PU and the SU and the relay is taken into consideration and by solving the optimisation problem composed for each case, the closed form expressions of each node power are obtained. All the simulation results have demonstrated that the system with the proposed scheme outperforms the equal power allocation (EPA) scheme irrespective of the IPT. When the IPT constraint is introduced, the sum-rate of the success delivery bit of the SU communication converges to a certain level with the increasing total power. Meanwhile, the proposed strategy is superior to the conventional EPA scheme for any relay location, which is more remarkable when the relay is located on either end node regardless of the traffic symmetry or the asymmetry.
Opportunistic relay selection (RS) is an efficient method to obtain diversity gain in analoguenetworkcoding (ANC) protocol with multiple relays. However, in networks with mobile relays, the channel state information...
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Opportunistic relay selection (RS) is an efficient method to obtain diversity gain in analoguenetworkcoding (ANC) protocol with multiple relays. However, in networks with mobile relays, the channel state information (CSI) used in the RS procedure becomes outdated because of the time-varying nature of fading channels, which severely deteriorates the system performance. In this study, the authors study the RS strategy which aims to optimise the outage performance of the ANC protocol with multiple mobile relays. RS schemes for two different cases are designed, that is, (i) the scheme with only the outdated CSI during the RS procedure, and (ii) the scheme with both the outdated CSI and the statistical knowledge of channels during the RS procedure. The closed-form expressions of the outage probabilities as well as the asymptotic expressions are analytically derived for the proposed schemes, and moreover, the achievable diversities are analysed based on the asymptotic expressions. Simulation results are presented to evaluate the performances while validate the theoretical analyses for the proposed schemes.
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