Energy harvesting assisted cognitive radio: random location-based transceivers scheme and performance analysis

We consider spectrum-sharing scenario where coexist two communication networks including primary network and secondary network using the same spectrum. While the primary network includes directional multi-transceivers, the secondary network consists of relaying-based transceiver forwarding signals by energy harvesting assisted relay node. In cognitive radio, signals transmitted from secondary network are sufficiently small so that all of primary network receivers have signal to noise ratio (SNR) greater than a given threshold. In contrast, the transmitted signals from primary network cause increasing noise which is difficult to demodulate at secondary network nodes and hence it leads to the peak power constraint. In this paper, we focus on the influence of random location of transceivers at primary network using decode-and-forward protocol. Specifically, we derive closed-form outage probability expression of the secondary network under random location of transceivers and peak power constraint of primary network. This investigation shows the relationship between the fraction of energy harvesting time \(\alpha \) of time switching-based relaying protocol on outage probability of secondary network and throughput. In addition, we analyse the influence of the number of primary network transceivers as well as primary network’s SNR threshold on secondary network. Furthermore, the trade-off between increasing energy harvesting and rate was investigated under the effect of energy conversion efficiency. The accuracy of the expressions is validated via Monte-Carlo simulations. Numerical results highlight the trade-offs associated with the various energy harvesting time allocations as a function of outage performance.     

Optimal cooperative strategy based on quantum bat for cognitive radio of energy harvesting

In order to reduce energy consumption and improve spectral efficiency of the cognitive relay wireless communication system in 5G network,an optimal cooperative transmission strategy of information and energy was designed for cognitive relay radio with wireless energy harvesting.For the proposed optimal cooperative strategy,the maximal throughput formula and outage probability of secondary user were deduced.In order to resolve the derived maximum throughput equation,a quantum bat algorithm which was based on the optimization mechanism of quantum computing and bat algorithm was designed to solve the deduced equation,and the optimal cooperative transmission scheme for information and energy could be obtained.Simulation results show that the proposed optimal cooperative strategy not only can meet the information transfer demand of primary user,but also can realize the energy self-supply of the secondary user system and improve the communication quality of the secondary user.The proposed optimal cooperative strategy has a better performance than the cooperative strategy of existing cognitive relay radio for different simulation scenarios.     

能量收集认知多跳中继网络中断性能分析及优化

针对能量收集认知无线网络中的多跳中继传输问题,该文构建了一种新的具有主网络干扰的功率信标(PB)辅助能量收集认知多跳中继网络模型,并提出单向传输方案。在干扰链路统计信道状态信息场景下,推导了次网络精确和渐近总中断概率闭合式。针对精确总中断概率表达式的复杂性和非凸性,采用自适应混沌粒子群优化(ACPSO)算法对次网络总中断性能进行优化。仿真结果表明,PB功率、干扰约束、次网络跳数、能量收集比率、主接收端数目和信道容量阈值等参数对中断性能影响显著,所提算法能快速和有效地对网络中断性能进行优化。     

Simultaneous wireless information and power transfer for relay assisted energy harvesting network

The simultaneous wireless information and power transfer in an energy harvesting system is investigated, where a relay is self-sustained by harvesting radio-frequency (RF) energy from the transmitter and multiple user devices are distributed according to a homogeneous Poisson point process. A joint time switching and power splitting protocol for relay-assisted transmission is proposed, in which each time slot is split into two stages. In the first stage, the relay utilizes a portion of received RF signal power for energy harvesting and the remaining power for information processing. In the second stage, information is delivered from the relay to its closest destination node with the harvested energy. The outage probability, network throughput and energy efficiency are derived and analyzed in closed form. On this basis, the optimal power splitting and time switching ratio which maximizes network throughput is obtained. Simulation results are also provided to validate our theoretical analysis.     

Cooperative relay to improve diversity in cognitive radio networks

Recent studies demonstrated that dynamic spectrum access can improve spectrum utilization significantly by allowing secondary unlicensed users to dynamically share the spectrum that is not used by the primary licensed users. Cognitive radio was proposed to promote the spectrum utilization by opportunistically exploiting the existence of spectrum ?holes.? Meanwhile, cooperative relay technology is regarded widely as a key technology for increasing transmission diversity gain in various types of wireless networks, including cognitive radio networks. In this article, we first give a brief overview of the envisioned applications of: cooperative relay technology to CRNs, cooperative transmission of primary traffic by secondary users, cooperative transmission between secondary nodes to improve spatial diversity, and cooperative relay between secondary nodes to improve spectrum diversity. As the latter is a new direction, in this article we focus on this scenario and investigate a simple wireless network, where a spectrum-rich node is selected as the relay node to improve the performance between the source and the destination. With the introduction of cooperative relay, many unique problems should be considered, especially the issue for relay selection and spectrum allocation. To demonstrate the feasibility and performance of cooperative relay for cognitive radio, a new MAC protocol was proposed and implemented in a universal software radio peripheral-based testbed. Experimental results show that the throughput of the whole system is greatly increased by exploiting the benefit of cooperative relay.     

Achieving maximum bit rate in a cognitive radio network with physical layer network coding

In this paper, the power allocation problem in a relay‐assisted cognitive radio network (CRN) is considered where the secondary users exchange information in an interweave mode on the basis of physical layer network coding. In order to enhance the capacity of CRN, using multiple‐input multiple‐output and orthogonal frequency division multiplexing has become very popular in the literature. This paper goes one step further to improve the throughput of secondary users using physical layer network coding by drawing off the transmission time. The main goal is to maximize the capacity of CRN, while keeping the total interference imposed on the primary users under a certain threshold. An optimal solution to this power allocation problem with limited relay power constraint, due to the limited budget, is derived; however, because of the high complexity of this method, an efficient suboptimal solution is also proposed.     

Secrecy Performance of CCRN with an EHAF Relay under Source and Destination Jamming

In this paper, we investigate the secrecy performance of a cooperative cognitive radio network (CCRN) considering a single energy harvesting (EH) half‐duplex amplify and forward (AF) relay and an eavesdropper (EAV). Power is allocated to each node under cognitive constraints. Because of the absence of a direct wireless link, secondary source (SS) communicates with secondary destination (SD) in two time slots. The SD and the SS broadcast jamming signal to confuse the EAV in the first and in the second time slots, respectively. The relay harvests energy in the first time slot and amplifies and forwards the signal to SD in the second time slot. The EAV employs maximal ratio combining scheme to extract the information. We evaluate the performance in terms of secrecy outage probability (SOP) of the proposed CCRN. The approximate expression of SOP is obtained in integration form. Improvement in SOP is expected for the proposed CCRN because of the use of jamming signals. The secrecy performance of CCRN improves with increase in primary transmit power, peak transmit power of secondary nodes, channel mean power, and energy conversion efficiency but degrades with increase in threshold outage rate of primary receiver and threshold secrecy rate. A MATLAB‐based simulation framework has been developed to validate the analytical work.     

Maximum harvested energy policy in full‐duplex relaying networks with SWIPT

It is considered that energy scavenging is a promising way for source node transfer energy to powered constraint relay in cooperative networks with advantage of cost‐effective maintenance and flexible deployment, which so‐called simultaneous wireless information and power transfer. In this paper, relay selection for optimal wireless energy is investigated. In terms of time switching–based relaying, this paper considers the performance comparison of 3 proposed relay selection schemes, namely, (1) optimal relay selection scheme , (2) maximum harvested energy relay selection scheme , and (3) minimum self‐interference relay selection . In particular, the system performance is studied intensively with regard to outage probability and throughput over Rayleigh fading channels. We also achieve the integral form for accurate expressions and closed form for approximate expressions. Finally, these analytical expressions are proved exactness according to Monte Carlo simulation.     

Performance analysis of energy harvesting cognitive relay networks with primary interference

This paper investigates the outage performance of multihop energy harvesting cognitive relay network (EH-CRN), in which the secondary nodes are powered by dedicated power beacons based on the time splitting strategy. Assuming a multihop secondary network, we derive an analytical expression for the outage probability experienced by a secondary user by taking into account the effect of interference power from primary source. The developed outage probability model can be used to assess the impact of some key parameters on the reliability of the secondary user’s link in an EH-CRN. We then investigate the optimal location of the relay node in a one dimensional two-hop secondary network that minimizes the outage probability. Next, we study how the various system parameters such as energy harvesting efficiency, path loss exponent, harvest-to-transmit time duration ratio and transmit power from primary source affect the optimal relay location. The outage improvement achieved when the relay is placed at the optimum location is also investigated. Furthermore, the sensitivity of optimal relay location to the variations in position of the primary receiver is examined. Extensive simulation results are used to corroborate the analytical findings.     

Power splitting–based energy‐harvesting protocol for wireless‐powered communication networks with a bidirectional relay

In this paper, we apply the power splitting–based energy‐harvesting protocol to enhance the transmission between a wireless access point and a mobile user via a helping relay. The mobile user exploits the energy supplied by the access point and forwarded by the relay to transmit its own data back to the access point, again with the helping of the relay. Here, the effect of various system parameters, including power‐splitting factor and the power‐to‐noise ratio on the system performance, is rigorously studied, with closed‐form expressions for the outage probability and system throughput as the results. Furthermore, we figure out the optimal power‐splitting ratio at which the information throughput from the user to the AP is maximized, subject to the constraint on the transmitting power at the access point. All above analytical results are also supported by Monte Carlo simulation.     

Cognitive amplify‐and‐forward relay networks with beamforming under primary user power constraint over Nakagami‐m fading channels

In this paper, we analyze the performance of cognitive amplify‐and‐forward (AF) relay networks with beamforming under the peak interference power constraint of the primary user (PU). We focus on the scenario that beamforming is applied at the multi‐antenna secondary transmitter and receiver. Also, the secondary relay network operates in channel state information‐assisted AF mode, and the signals undergo independent Nakagami‐m fading. In particular, closed‐form expressions for the outage probability and symbol error rate (SER) of the considered network over Nakagami‐m fading are presented. More importantly, asymptotic closed‐form expressions for the outage probability and SER are derived. These tractable closed‐form expressions for the network performance readily enable us to evaluate and examine the impact of network parameters on the system performance. Specifically, the impact of the number of antennas, the fading severity parameters, the channel mean powers, and the peak interference power is addressed. The asymptotic analysis manifests that the peak interference power constraint imposed on the secondary relay network has no effect on the diversity gain. However, the coding gain is affected by the fading parameters of the links from the primary receiver to the secondary relay network. Copyright © 2012 John Wiley & Sons, Ltd.     

非理想SIC下SWIPT-CR-NOMA网络中断性能分析

针对采用无线携能通信的多中继底层协作认知非正交多址接入网络,提出一种两阶段中继选择策略。认知中继执行功率划分的无线携能通信协议为次级用户提供解码转发服务,其能量开销源于所采集到的能量。考虑了实际的非正交多址接入网络中,中继节点与次级用户均无法完全消除多址干扰,即无法实现理想连续干扰消除。在干扰阈值约束下,推导了非理想连续干扰消除下两次级用户端中断概率的精确表达式,并通过蒙特卡洛仿真验证其正确性。此外,定量分析了各系统相关参数（最大发射功率、干扰阈值、功率分配系数等）的选取对次级用户中断性能的具体影响。结果表明,在相同的系统参数设置下,所提方案次级用户中断性能远优于现有部分中继选择方案。      

两阶段中继选择策略下SWIPT-CR-NOMA网络的中断性能分析

针对采用无线携能传输(SWIPT)的多中继协作底层认知NOMA网络,提出一种基于NOMA和串行干扰消除协议的两阶段中继选择策略(TSRS).在保护主用户的干扰温度限约束下,次级网络源节点和最优中继均以固定功率分配生成多用户叠加信号向下一跳链路发送,最优中继采用功率分割方案采集能量,只利用从第一跳链路采集到的能量提供解码...     

Performance analysis of MIMO cognitive amplify‐and‐forward relay networks with orthogonal space–time block codes

In this paper, we study the performance of multiple‐input multiple‐output cognitive amplify‐and‐forward relay networks using orthogonal space–time block coding over independent Nakagami‐m fading. It is assumed that both the direct transmission and the relaying transmission from the secondary transmitter to the secondary receiver are applicable. In order to process the received signals from these links, selection combining is adopted at the secondary receiver. To evaluate the system performance, an expression for the outage probability valid for an arbitrary number of transceiver antennas is presented. We also derive a tight approximation for the symbol error rate to quantify the error probability. In addition, the asymptotic performance in the high signal‐to‐noise ratio regime is investigated to render insights into the diversity behavior of the considered networks. To reveal the effect of network parameters on the system performance in terms of outage probability and symbol error rate, selected numerical results are presented. In particular, these results show that the performance of the system is enhanced when increasing the number of antennas at the transceivers of the secondary network. However, increasing the number of antennas at the primary receiver leads to a degradation in the secondary system performance. Copyright © 2014 John Wiley & Sons, Ltd.     

射频能量采集非可信中继网络中物理层安全传输

射频能量采集技术为能量受限无线通信系统提供了一种有效的能量供给方式.假设能量受限中继节点具有射频能量采集能力,本文设计了中继非可信情况下的物理层安全传输方案,配置多天线的源节点采用发送天线选择策略来增强中继节点的能量采集性能,目的节点发送人工干扰来抑制非可信中继对保密信息的窃听.在瑞利块衰落信道条件下研究了所提方案的物理层安全性能,推导了系统安全中断概率、连接中断概率和安全吞吐量的闭式表达式.计算机仿真验证了理论推导的正确性,揭示了各系统参数对物理层安全性能的影响关系.     

On outage minimization in RF energy harvesting relay assisted bidirectional communication

This paper explores an end-to-end outage probability experienced in a bidirectional relay assisted communication where the relay is assumed to be equipped with an RF energy harvesting circuit. First, the closed-form expression for the outage of the system is derived. This is followed by the formulation of an unconstrained optimization problem to achieve minimum outage probability with respect to the relay placement and consequent time allocation for energy harvesting. The system model is further extended in an underlay cognitive radio framework to study the impact of a primary user outage constraint on the end-to-end outage performance of the two-way communications. The accuracy of analytical results is validated through simulation results. The impact of various system parameters like relay position, time allocation factor, target rate of transmission on the outage probability is also observed. In addition, it is also shown that spectral efficiency of the communication system using hybrid power-time switching relaying protocol is much superior to similar one-way and two-way relay assisted communication system with power splitting relaying protocol.

     

Performance analysis of two-way relay cooperation underlay cognitive radio networks based on WIPT

The two-way relay cooperation for underlay cognitive radio networks based on WIPT was presented,where secondary system adopted the two-way relay cooperative transmission.First,the relay adopted a power splitting protocol to harvest energy and to decode information transmitted by secondary users,then the relay forwarded information to two secondary users by using the harvested energy.Subsequently the exact expression of the outage probability,the ergodic capacity and energy efficiency of the secondary user system were derived.Finally,numerical simulation discusses the impact on the system performance with regard to secondary transmission power.The results reveal that the two-way relay cooperation effectively reduces the outage probability of data transmission.The capacity and energy efficiency of the system reaches optimal level when the power allocation coefficient is 0.5.     

Energy efficient bidirectional relay network with spatial modulation

S patial modulation is a potential candidate for 5G wireless communication systems that provides high spectral efficiency with high reliability and low complexity. Spatial modulation conveys information in the index of transmitting antenna along with conventional modulation scheme. Also, energy efficiency communication plays a vital role in 5G wireless communication. In this article, energy efficiency and spectral efficiency are focused on a bidirectional relay network. In the proposed bidirectional relay network, the energy consumption burden at the relay node is reduced by placing a power splitter that coordinates the energy harvesting and information processing at the relay node. Spatial modulation is employed at all nodes to reduce the effect of interchannel interference and synchronization problem in the receiver. The combined effect of spatial modulation in all nodes and energy harvest at the relay node are analyzed in the bidirectional relay network. The end‐to‐end outage probability expression for the bidirectional relay network is derived in terms of power splitting factor at relay node. Analytical simulation results have been verified by Monte‐Carlo simulations. The overall performance of the proposed system is compared with an existing literature and found that the proposed system is having better spectral efficiency and energy harvesting.     

Wireless information and power transfer using single and multiple path relays

A relay‐based wireless communication model can relay information along with the power bidirectionally using the amplify‐and‐forward scheme. This paper studies such model extensively. Three information and power relaying protocols, that is, time‐based switching relaying, power‐based splitting relaying, and hybrid time switching‐based and power splitting‐based relaying (HTPSR) are used to carry forward bidirectional information and power transfer. First, a solo relay model is studied, for which, we derived a throughput expression for end‐to‐end information transfer, and this is done for all the three relaying protocols. The paper indicates that the system throughput depends upon the time switching and the power splitting ratio. Further, to make the system more reliable and robust, multiple relays are used in the path. Various relay selection schemes are used for path selection in each transmission, thereby yielding different throughput performances. The results show that an optimal throughput is obtained for a given relay location at an optimal set of values of splitting and switching ratio. Moreover, the HTPSR outperforms both the power splitting and time switching protocol in system throughput performance for a single as well as a multiple‐relay model. Whereas, in relay selection schemes, the best SNR selection scheme outperforms in all the schemes used. The simulated results confirm that the system throughput is an active function of relay placement.     

Performance analysis of nonorthogonal multiple access‐based underlay cognitive relay network

This paper considers cooperative non‐orthogonal multiple access (NOMA) scheme in an underlay cognitive radio (CR) network. A single‐cell downlink cooperative NOMA system has been considered for the secondary network, consisting of a base station (BS) and two secondary users, ie, a far user and a near user. The BS employs NOMA signaling to send messages for the two secondary users where the near user is enabled to act as a half‐duplex decode‐and‐forward (DF) relay for the far user. We derive exact expressions for the outage probability experienced by both the users and the outage probability of the secondary system assuming the links to experience independent, nonidentically distributed Rayleigh fading. Further, we analyze the ergodic rates of both the users and the ergodic sum rate of the secondary network. The maximum transmit power constraint of the secondary nodes and the tolerable interference power constraint at the primary receiver are considered for the analysis. Further, the interference caused by the primary transmitter (PT) on the secondary network is also considered for the analysis. The performance of the proposed CR NOMA network has been observed to be significantly better than a CR network that uses conventional orthogonal multiple access (OMA) scheme. The analytical results are validated by extensive simulation studies.