Abstract
In this paper, a new full-duplex (FD) relaying scheme for a cooperative cognitive underlay network is proposed. The secondary network is composed of one secondary transmitter, one full-duplex secondary relay, and one secondary destination. The relay employs the selective-decode-and-forward (SDF) protocol. The secondary destination jointly decodes the signals from the secondary transmitter and the FD secondary relay so that the direct link can be seen as useful information rather than interference. The analysis includes the effect of the interference from the primary transmitter and the self-interference at the relay. Under equal power allocation strategy, closed-form expressions for the outage probability are derived for the proposed FD cooperative cognitive scheme, and the feasibility of FD relaying under cognitive constraints is shown. Our results also reveal that the proposed full-duplex joint-decoding (FDJD) cognitive network considerably outperforms the known full-duplex dual-hop (FDDH) scheme. Moreover, we propose an optimal power allocation (OPA) scheme. On the basis of the signal-to-interference-plus noise of the secondary network, the OPA strategy can choose between two modes of operation, cooperation between source and relay or source transmission only. Our results show that the FDJD scheme under the proposed OPA policy presents the best performance among all schemes investigated in this paper.
Highlights
With the objective of obtaining a more efficient utilization of the radio spectrum, in a cognitive radio network, the unlicensed users may communicate using frequencies of the licensed spectrum [1,2,3,4]
The optimal power allocation (OPA) strategy can choose between two modes of operation: (i) cooperation between source and relay or (ii) source transmission only
The secondary destination jointly decodes the signals from the secondary transmitter and the relay—which differs from other works proposed in the literature where the direct link is seen as interference rather than useful information
Summary
With the objective of obtaining a more efficient utilization of the radio spectrum, in a cognitive radio network, the unlicensed users ( referred to as secondary users) may communicate using frequencies of the licensed spectrum [1,2,3,4]. In [29], after matched filtering, the interference from the primary network is assumed to be seen as an additional Gaussian noise at the secondary one Based on such assumption, [29] carried out a closed-form outage analysis for a FD dual-hop (FDDH) relaying scheme, in which the selfinterference at the relay was taken into account and the direct link was seen as interference by the secondary destination. In [30], in a non-cognitive radio scenario, the authors evaluate the outage probability of a cooperative network, where the signal of the direct link is exploited at the secondary destination and the relay employs the selectivedecode-and-forward (SDF) protocol. In [32], we evaluated the performance of the scheme proposed in [30] assuming a cooperative cognitive network operating in a spectrum sharing scenario with a FD relay subject to self-interference. 1.2.1 Notations and functions Mathematical expectation is denoted by E [·]; Pr[ ·] stands for probability; fW (·) and FW (·) represent the probability density function (PDF) and cumulative distribution function (CDF) of a given random variable (RV) W, respectively
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