Time-switching Relaying Protocol Research Articles

An efficient time-switching relaying protocol for multiuser cognitive radio relay networks with SWIPT

In this paper, we propose a new time-switching relaying (TSR) protocol for multi-destination dual-hop underlay cognitive radio relay networks with simultaneous wireless information and power transfer (SWIPT) technique. The proposed protocol maintains the same receiver complexity of the conventional TSR protocol with the ability for implementing both of them using the same hardware. We study the performance of the proposed TSR protocol and compare it with the conventional TSR and power-splitting relaying (PSR) protocols. Unified analytical expression is derived for the outage probability, in addition to studying the performance at high signal-to-noise ratio (SNR) values where unified approximate and simple expressions for the outage probability are provided. The results show that the proposed TSR protocol outperforms the conventional TSR protocol in terms of outage probability. Also, findings illustrate that applying the SWIPT technique in multi-destination underlay cognitive relay networks results in a unity diversity order. In contrast to conventional relaying networks, results show that the best location for the relay node in SWIPT relay networks is either near the source or the destinations, but not in between.

A Novel Time-Switching Relaying Protocol for Multi-user Relay Networks with SWIPT

In this paper, we propose a new time-switching relaying (TSR) protocol for dual-hop relay networks with simultaneous wireless information and power transfer (SWIPT) technique. The proposed protocol maintains the same receiver complexity of the conventional TSR protocol with the ability for implementing them using the same hardware. We study the performance of the proposed TSR protocol and compare it with the conventional TSR and power-splitting relaying protocols. Unified analytical expressions are derived for the outage probability, achievable throughput, and the ergodic channel capacity, in addition to studying the performance at high signal-to-noise ratio values where a unified approximate expression for the outage probability and expressions for the diversity order and coding gain are provided. The results show that the proposed TSR protocol outperforms the conventional TSR protocol in terms of outage probability and throughput. Also, findings illustrate that applying the SWIPT technique in multi-destination relay networks results in a unity diversity order. In contrast to conventional relaying networks, results show that the best location for the relay node in SWIPT relay networks is either near the source or the destinations but not in between.

Outage analysis in two‐way communication with RF energy harvesting relay and co‐channel interference

AbstractThe study of relays with the scope of energy harvesting (EH) looks interesting as a means of enabling sustainable, wireless communication without the need to recharge or replace the battery driving the relays. However, the reliability of such communication systems becomes an important design challenge when such relays scavenge energy from the information bearing radio‐frequency signals received from the source, using the technique of simultaneous wireless information and power transfer (SWIPT). To this aim, this work studies bidirectional communication in a decode‐and‐forward (DF) relay–assisted cooperative wireless network in the presence of co‐channel interference (CCI). In order to quantify the reliability of the bidirectional communication systems, a closed‐form expression for the outage probability of the system is derived for both power splitting (PS) and time switching (TS) modes of operation of the relay. Simulation results are used to validate the accuracy of our analytical results and illustrate the dependence of the outage probability on various system parameters, like PS factor, TS factor and distance of the relay from both of the users. The results of performance comparison between PS relaying (PSR) and TS relaying (TSR) schemes are also presented. Besides, simulation results are also used to illustrate the spectral efficiency and the energy efficiency of the proposed system. The results show that, in terms of both spectral efficiency and energy efficiency, the two‐way communication system in the presence of moderate CCI power, performs better than the similar system without CCI. Additionally, it is also found that PSR is superior to TSR protocol in terms of peak energy efficiency.

Throughput analysis of cognitive wireless acoustic sensor networks with energy harvesting

We consider a wireless acoustic sensor network, where an energy-constrained acoustic node as relay initially harvests energy through the received radio frequency signal from the primary transmitter, and then, it forwards the primary acoustic signal together with its own message by using the harvested energy. Considering that a preset fixed transmission power is used for relaying, a continuous time energy harvesting scheme is adopted. We further consider two wireless information and energy transmission protocols, namely, time-switching relaying (TSR) protocol and power-splitting relaying (PSR) protocol in this system. For both protocols, we derive exact expressions of the throughput efficiency for both primary and secondary systems. Moreover, we address optimal power allocation strategy for both protocols under the performance criteria, and prove that the optimization problem with TSR can be solved by analyzing the monotonicity of optimization function and non-convex optimization problem with PSR can be converted into a convex problem. Two corresponding optimal algorithms are proposed to solve optimization problems. Numerical results reveal that the proposed protocols not only facilitate both the primary and secondary signals transmission but also outperform the existing fixed time duration energy harvesting scheme in terms of achievable rate. Furthermore, the PSR protocol can achieve higher secondary transmission rate than the TSR protocol in lower relaying transmission power.

Performance optimisation of RF energy harvesting relay-based interweave/underlay cognitive radio network

ABSTRACTThis paper investigates the performance of energy harvesting (EH) relay-based interweave/underlay cognitive radio network. The relay employs amplify and forward (AF) technique along with time-switching relaying protocol (TSR) for EH. Based on sensing accuracy, we derive an expression for optimisation of charging duration TSR parameter and sensing duration for maximising throughput of interweave cognitive radio (CR). Based on sensing efficiency, throughput and outage probability for underlay CR is analysed considering the interference temperature constraints and optimal power distribution parameter at secondary user (SU) terminals. Variations in the sum-rate and detection probability are considered in terms of cumulative distribution functions (CDF) of the terminal Signal to Noise Ratios (SNRs). We prove that erogodic sum-rate is maximised in underlay CR case, when interference power distribution parameter is half across the SU terminals. The optimised values of switching-time ratios have been derived analytically for both interweave and underlay CR. The results thus obtained are compared by taking symmetrical and asymmetric channels between SU terminals. Analytical results are validated through Monte-Carlo simulations to confirm the accuracy of the derived expressions.

Impact of residual transmit RF impairments on energy harvesting relay selection systems

ABSTRACTIn this paper, we study the impact of residual transmit radio-frequency impairments (RTRIs) on a dual-hop energy-harvesting system in which a source and a destination both having multiple antennas communicate to each other with the help of single-antenna amplify-and-forward (AF) relays. The source and destination employ maximum ratio transmission (MRT) and maximal ratio combining (MRC), respectively, to exploit the benefits of using multiple antennas. To simplify the system complexity, we propose two partial relay selection (PRS) schemes (RSSs) that maximise the combined channel gains of the first hop (PRS-1 scheme) and the second hop (PRS-2 scheme), respectively. Both time-switching relaying (TSR) and power-splitting relaying (PSR) protocols are examined. In order to evaluate the system performance, the analytical expressions for outage probability and ergodic capacity are derived, and then the throughput expressions for delay-limited and delay-tolerant transmission modes are formulated. The analytical results are validated by Monte Carlo simulations. Our results show that: (1) The impact of RTRI can be significantly reduced by increasing the number of antennas and relays. (2) The PRS-1 scheme outperforms the PRS-2 scheme. (3) In the delay-limited mode, the TSR protocol performs better than the PSR protocol at high impairment levels, whereas in the delay-tolerant mode, the throughput of the PSR protocol is superior to that of the TSR protocol.

Maximum Transmission Rate of PSR/TSR Protocols in Wireless Energy Harvesting DF-Based Relay Networks

In this paper, we consider the power splitting relaying (PSR) and time switching relaying (TSR) protocols for decode-and-forward (DF)-based relay networks consisting of a source, a relay, and a destination. For the networks, the relay is assumed to have a rechargeable battery with a certain amount of remaining energy for energy harvesting through the received signal transmitted from the source. Specifically, for the PSR protocol with and without the direct-path, we present the outage probability expression with a given power splitting coefficient, and we obtain the optimum power splitting coefficient to maximize the transmission rate and derive its transmission rate and outage probability, where the optimum coefficient depends on channel conditions and remaining energy. For the TSR protocol with and without the direct-path, we present the outage probability expression with a given time switching coefficient, and we obtain the optimum time switching coefficient to maximize the transmission rate and derive its transmission rate, where the optimum coefficient also depends on channel conditions and remaining energy.

Wireless information and power transfer in two-way relaying network with non-coherent differential modulation

In this paper, we consider a denoise-and-forward (DNF) two-way relay network (TWRN) with non-coherent differential binary phase-shift keying modulation, where a battery-free relay node harvests energy from the received radio frequency (RF) signals and uses the harvested energy to help the source nodes for information exchange. Based on the power splitting (PS) and time switching (TS) receiver architectures, power splitting relaying (PSR) and time switching relaying (TSR) protocols at relay are studied. In order to investigate the effect of power allocations on two source nodes, power splitting coefficient and time switching factor at relay on performance, the two proposed protocols are analyzed and the bit error rate (BER) expressions of end-to-end system are derived. Based on these expressions, the optimal power of sources, the power splitting ratio and the time switching factor are obtained via the numerical search method. The simulation and numerical results provide practical insights into the effect of various system parameters, such as the power splitting coefficient, the time switching factor, sources to relay distances, the noise power, and the energy harvesting efficiency on the performance of this TWRN. In addition, the results show that the PSR protocol outperforms the TSR protocol in terms of throughput under various network geometries.