Interference-Aided Energy Harvesting: Cognitive Relaying with Multiple Primary Transceivers (original) (raw)
Related papers
To appear in Proc. IEEE GLOBECOM 2015
We consider a spectrum sharing scenario, where a secondary network coexists with a primary network of multiple transceivers. The secondary network consists of an energy-constrained decode-and-forward secondary relay which assists the communication between a secondary transmitter and a destination in the presence of the interference from multiple primary transmitters. The secondary relay harvests energy from the received radio-frequency signals, which include the information signal from the secondary transmitter and the primary interference. The harvested energy is then used to decode the secondary information and forward it to the secondary destination. At the relay, we adopt a time switching policy due to its simplicity that switches between the energy harvesting and information decoding over time. Specifically, we derive a closed-form expression for the secondary outage probability under the primary outage constraint and the peak power constraint at both secondary transmitter and relay. In addition, we investigate the effect of the number of primary transceivers on the optimal energy harvesting duration that minimizes the secondary outage probability. By utilizing the primary interference as a useful energy source in the energy harvesting phase, the secondary network achieves a better outage performance.
Wireless Energy Harvesting in a Cognitive Relay Network
Wireless energy harvesting is regarded as a promising energy supply alternative for energy-constrained wireless networks. In this paper, a new wireless energy harvesting protocol is proposed for an underlay cognitive relay network with multiple primary user (PU) transceivers. In this protocol, the secondary nodes can harvest energy from the primary network (PN) while sharing the licensed spectrum of the PN. In order to assess the impact of different system parameters on the proposed network, we first derive an exact expression for the outage probability for the secondary network (SN) subject to three important power constraints: 1) the maximum transmit power at the secondary source (SS) and at the secondary relay (SR), 2) the peak interference power permitted at each PU receiver, and 3) the interference power from each PU transmitter to the SR and to the secondary destination (SD). To obtain practical design insights into the impact of different parameters on successful data transmission of the SN, we derive throughput expressions for both the delay-sensitive and the delay-tolerant transmission modes. We also derive asymptotic closed-form expressions for the outage probability and the delay-sensitive throughput and an asymptotic analytical expression for the delay-tolerant throughput as the number of PU transceivers goes to infinity. The results show that the outage probability improves when PU transmitters are located near SS and sufficiently far from SR and SD. Our results also show that when the number of PU transmitters is large, the detrimental effect of interference from PU transmitters outweighs the benefits of energy harvested from the PU transmitters.
Energy Harvesting Based Multihop Relaying in Cognitive Radio Network
Wireless Personal Communications, 2017
In this paper, a multihop cognitive radio network using a series of multiple decode and forward (DF) energy harvesting relays is proposed to enhance the spectrum utilization and lifetime of the network. A time switching based energy harvesting scheme is considered for the DF relays. An analytical expression has been derived for evaluating the transmission power of the secondary source and secondary relays (SR) as well as SNR at SRs and secondary destination. The corresponding transmission power and signal to noise ratio (SNR) profiles are also analyzed for several numbers of relays under various locations of the primary transmitter (PT). An expression for a critical number of relays, for which the performance of the network is worst, has also been derived. It is seen that upto a critical number of relays the SNR decreases. However the SNR again increases with further increase in number of relays. Further secondary outage probabilities have been compared for several locations of PT. Analytical results following our development are presented and validated by MATLAB based simulation.
In this paper, we propose an energy harvesting (EH)-based spectrum access model in cognitive radio (CR) network. In the proposed scheme, one of available secondary transmitters (STs) helps a primary transmitter (PT) forward primary signals to a primary receiver (PR). Via the cooperation, the selected ST finds opportunities to access licensed bands to transmit secondary signals to its intended secondary receiver (SR). Secondary users are assumed to be mobile, hence, optimization of energy consumption for these users is interested. The EH STs have to harvest energy from the PT's radio-frequency (RF) signals to serve the PT-PR communication as well as to transmit their signals. The proposed scheme employs incremental relaying technique in which the PR only requires the assistance from the STs when the transmission between PT and PR is not successful. Moreover , we also investigate impact of hardware impairments on performance of the primary and secondary networks. For performance evaluation, we derive exact and lower-bound expressions of outage probability (OP) over Rayleigh fading channel. Monte-Carlo simulations are performed to verify the theoretical results. The results present that the outage performance of both networks can be enhanced by increasing the number of the ST-SR pairs. In addition, the out-age performance of both primary and secondary networks is severely degraded with the increasing of hardware impairment level. It is also shown that fraction of time used for EH and positions of the secondary users significantly impact on the system performance.
On Information and Energy Cooperation in Energy Harvesting Cognitive Radio
To appear in Proc. of IEEE PIMRC 2015
This paper considers the cooperation between primary and secondary users at information and energy levels when both users are energy harvesting nodes. In particular, a secondary transmitter helps relaying the primary message, and in turn, gains the spectrum access as a reward. Also, the primary transmitter supplies energy to the secondary transmitter if the latter is energy-constrained, which facilitates an uninterrupted cooperation. We address this two-level cooperation over a finite horizon with the finite battery constraint at the secondary transmitter. While promising the rate-guaranteed service to both primary and secondary users, we aim to maximize the primary rate. We develop an iterative algorithm that obtains the optimal offline power policies for primary and secondary users. To acquire insights about the structure of the optimal solution, we examine specific scenarios. Furthermore, we investigate the effects of the secondary rate constraint and finite battery on the primary rate and the probability of cooperation. We show that the joint information and energy cooperation increases the chances of cooperation and achieves significant rate gains over only information cooperation.
Throughput and Outage Probability of Wireless Energy Harvesting Based Cognitive DF Relaying Network
Materials Today: Proceedings, 2017
This paper evaluates the throughput performance and outage probability of a secondary user (SU) in a decode-and-forward (DF) relaying network based on wireless energy harvesting under cognitive radio constraint. The energy constrained relay node first harvests energy through radio-frequency (RF) signals from the source node. Next, the relay node uses the harvested energy to forward the decoded source information to the destination node. The power transmitted by source and relay node is constrained by the tolerable interference threshold of the primary unit receiver. The source node transfers energy and information to the relay node through power splitting-based relaying (PSR). In PSR, the relay splits the received power for energy harvesting and information processing. The interference caused by a primary unit transmitter at the SU relay and destination nodes is also considered. Considering wireless energy harvesting constraint at the relay node, we analyse the achievable throughput and outage performance of a cognitive DF relaying network. We study the impact of different system parameters such as power splitting ratio, primary transmitter power and tolerable interference threshold of PU receiver on the throughput and outage performance of SU.
IEEE Journal on Selected Areas in Communications, 2016
Energy efficiency has become an encouragement, and more than this, a requisite for the design of next-generation wireless communications standards. In current work, a dual-hop cognitive (secondary) relaying system is considered, incorporating multiple amplify-and-forward relays, a rather cost-effective solution. First, the secondary relays sense the wireless channel, scanning for a primary network activity, and then convey their reports to a secondary base station (SBS). Afterwards, the SBS, based on these reports and its own estimation, decides cooperatively the presence of primary transmission or not. In the former scenario, all the secondary nodes start to harvest energy from the transmission of primary node(s). In the latter scenario, the system initiates secondary communication via a best relay selection policy. Performance evaluation of this system is thoroughly investigated, by assuming realistic channel conditions, i.e., non-identical link-distances, Rayleigh fading, and outdated channel estimation. The detection and outage probabilities as well as the average harvested energy are derived as new closed-form expressions. In addition, an energy efficiency optimization problem is analytically formulated and solved, while a necessary condition in terms of power consumption minimization for each secondary each node is presented. From a green communications standpoint, it turns out that energy harvesting greatly enhances the resources of secondary nodes, especially when primary activity is densely present.
2016 IEEE International Conference on Communications (ICC), 2016
A dual-hop cognitive (secondary) relaying system incorporating collaborative spectrum sensing to opportunistically switch between data transmission and energy harvesting is introduced. The secondary relays, first scan the wireless channel for a primary network activity, and then convey their reports to a secondary base station (SBS). Afterwards, the SBS, based on these reports and its own estimation, decides cooperatively the presence of primary transmission or not. In the former scenario, all secondary relays start to harvest energy from the transmission of one or more primary nodes. In the latter scenario, the system initiates secondary communication via a best relay selection policy. The performance of the proposed scheme is thoroughly investigated by assuming realistic channel conditions, i.e., non-identical link-distances and outdated channel estimation, while its overall energy consumption is evaluated, indicating the efficiency of the switching approach.
Cooperative spectrum sharing-based relaying protocols with wireless energy harvesting cognitive user
IET Communications
The theory of Simultaneous Wireless Information and Power Transfer (SWIPT) in energy-constrained wireless sensor networks has attracted considerable attention from the research community due to its promising features in increasing the lifetime of devices in addition to mitigating the environment hazards caused by using conventional cell batteries. On the other hand, the advancements in the areas of cooperative spectrum sharing protocols have enabled efficient use of spectrum band between primary and secondary users. Owing to this fact, in this paper, we consider an energy-constrained secondary user which harvests energy from the primary signal and forwards this latter with the guarantee of spectrum access. Two key protocols are proposed, namely time-splitting cooperative spectrum sharing (TS-CSS) and power-sharing cooperative spectrum sharing (PS-CSS), based on time splitting and power sharing at the relay, respectively. Assuming a Nakagami-m fading model, exact closedform expressions for the outage probabilities of the primary and secondary users are derived in decode-forward (DF) and amplifyforward (AF) relaying modes. From the obtained results, it is shown that the secondary user can carry its own transmission without any adverse impact on the performance of the primary user and that the PS-CSS protocol outperforms the TS-PSS protocol in terms of outage probability over a wide range of signal-to-noise ratio (SNR). Furthermore, the effect of various system parameters, such as splitting ratio, distance between nodes and harvesting efficiency, on the system outage performance on employing the proposed protocols is investigated and several insights are drawn.
Optimal time sharing in underlay cognitive radio systems with RF energy harvesting
2015 IEEE International Conference on Communications (ICC), 2015
Due to the fundamental tradeoffs, achieving spectrum efficiency and energy efficiency are two contending design challenges for the future wireless networks. However, applying radio-frequency (RF) energy harvesting (EH) in a cognitive radio system could potentially circumvent this tradeoff, resulting in a secondary system with limitless power supply and meaningful achievable information rates. This paper proposes an online solution for the optimal time allocation (time sharing) between the EH phase and the information transmission (IT) phase in an underlay cognitive radio system, which harvests the RF energy originating from the primary system. The proposed online solution maximizes the average achievable rate of the cognitive radio system, subject to the ε-percentile protection criteria for the primary system. The optimal time sharing achieves significant gains compared to equal time allocation between the EH and IT phases.