Abstract
In this paper, we consider a wireless powered cognitive relaying system with a secondary relay (SR) capable of harvesting wireless energy. Along with an access point (AP) continuously transmitting the primary data to a primary user (PU), a secondary source (SS) can transmit the secondary data to a secondary destination (SD) with the help of SR using the decode-and-forward (DF) protocol. SR can harvest energy from both SS and AP in both time and power domains using time-splitting and power-splitting techniques. The interference from primary data transmissions can help boost the amount of harvested energy at SR. The transmit power of SS is regulated by the interference threshold at PU and the allowable peak power. Despite the above two constraints, the transmit power of SR is further constrained by the amount of harvested energy. Once SR successfully decodes the data from SS, it will forward the data to SD using a constrained power. We analyze the approximate outage probabilities for both primary and secondary systems. Simulation results are provided to verify the effectiveness of our theoretical analysis and reveal the impacts of various parameters to the outage performance.
Highlights
Spectrum sharing between primary users (PUs) and secondary users (SUs) can promisingly alleviate the spectrum scarcity problem [1]
2.1 Cognitive radio network We consider a cognitive radio network as shown in Fig. 1, where access point (AP) continuously transmits the primary data to PU, and secondary relay (SR) cooperatively forwards the secondary data from secondary source (SS) to secondary destination (SD)
The two lines SS→SR→ SD and AP→ PU are assumed to be parallel with a vertical distance d0
Summary
Spectrum sharing between primary users (PUs) and secondary users (SUs) can promisingly alleviate the spectrum scarcity problem [1]. SUs may share the spectrum with PUs in separate time [2], disjoint bandwidth [3], and space domain [4], etc. Cooperative relaying can improve the communication robustness by achieving the space diversity, but it degrades the spectrum efficiency due to the half-duplex operation of relays, which can be tackled by using the non-orthogonal multiple access (NOMA) and network coding techniques [6]. Cooperative relaying in cognitive radio networks can improve coverage for SUs’ transmissions, and offer better reliability compared with the point-to-point link [7,8,9]. Duong et al studied the DF cognitive relaying (CR) with multiple primary transceivers, where the transmit powers
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