Abstract
This paper studies sum rate maximization of a cognitive radio network, where a full-duplex relay (FDR) is considered to assist data transmission. An FDR equipped with multiple transmit/receive antennas is introduced to harvest energy from the radio frequency signal of the primary system to reuse the energy for its own data transmission. By exploiting the time-switching relaying protocol, we first formulate an optimization problem for the sum rate of primary and secondary receivers and then propose a low-complexity algorithm to find the optimal solution. Numerical results verify the effectiveness of the proposed technique for wireless information and power transfer in cognitive radio systems.
Highlights
In-band full-duplex (FD) radio has recently attracted much attention to improve the capacity of wireless communication systems
To evaluate the proposed algorithm (Algorithm 1), we consider three other schemes: (i) SR and PR directly receive the signals from secondary transmitter (ST) and primary transmitter (PT), respectively, in which the harvesting time α for ST is optimized (Opt.α w/oFDR); (ii) data transmission using the same beamforming and detection as the proposed method is performed with α fixed to 0.5; (iii) we plot the performance of a baseline scheme using a half-duplex relay (HDR)
We can observe that the proposed method provides the best performance, due to the fact that the power is efficiently utilized by a cooperation between the harvesting time and beamforming at the FD relay (FDR)
Summary
In-band full-duplex (FD) radio has recently attracted much attention to improve the capacity of wireless communication systems. To further enhance the performance for SWIPT-based CRN systems, the authors in [24] developed a model, where an FD-enabled access point simultaneously charges the battery of ST and receives the signals from PT in the first phase, and in the second phase, the ST transmits/forwards the messages to secondary/primary receivers (SR/PR). The proposed model brings some advantages: (i) inherited from the property of relaying, the FDR utilizes distances geometrically near receivers for improving the system performance; (ii) FDR is able to exploit the benefit of the multiple-antenna technique to harvest energy and transmit data efficiently; (iii) the proposed model is suitable for CRNs, in that the CRNs can sense the appearances of PT’s signals in one block transmission to recycle the energy from PT’s signal, instead of requesting the new energy beam from PT. X ∼ CN ( a, σ2 ) indicates that the random variable x follows the complex normal distribution with mean a and variance σ2
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