Performance Analysis for Two-Way Relaying Networks with and Without Relay Selection

In this paper, we consider a two-way relaying network where two users communicate with each other with the help of multiple relays. Specifically, we first investigate the performance of a all-relay participating network with the amplify-and-forward relaying protocol. Based on the moment generating function-based method, we derive some tight bounds for the outage probability and bit-error rate performance. For comparison purpose, we then present a performance analysis for the relay selection scheme. Finally, numerical results are provided to verify our analysis.     

Diversity Analysis of Relay Selection Schemes for Two-Way Wireless Relay Networks

One-way wireless relay networks have recently received a lot of attention due to their ability to provide spatial diversity in fading wireless environment. Moreover, performing single-relay selection is a very attractive method due to its cost effective implementation and superior performance. However, one-way relay networks with the half-duplex signalling suffer from a spectral efficiency loss. To overcome such a drawback, two-way wireless relay networks have been proposed and these are also the networks considered in this paper. The paper analyzes the diversity orders of various relay selection schemes, including the best-relay selection, best-worse-channel selection, and maximum-harmonic-mean selection. The analysis is done for the amplify-and-forward protocol and under the two-step and three-step transmission procedures. In particular, it is shown that full diversity orders of R and R + 1 can be achieved in a R-relay wireless network with the two-step and three-step procedures, respectively. Numerical and simulation results are provided to verify our analysis.     

A Cooperative Relay Selection for Two-Way Cooperative Relay Networks in Nakagami Channels

We investigate the performance of the best-worse relay selection strategy in a two way cooperative non-regenerative relay network, where the relay is selected to maximize the worst Signal to Noise Ratio (SNR) of two links. In contrast to existing work, we aim to provide a theoretical performance analysis for this scheme under the more practical Nakagami channel. Closed-form expression of the probability density function for the SNRs of both two links is derived, based on which the outage probability of the best-worse relay selection is obtained. It is shown that the best-worse relay selection scheme achieves full diversity gain. Furthermore, the asymptotic packet error ratio with SNR increasing is also analyzed through rigorous derivations. The accuracy of our derivation is validated by computer simulations.     

Relay Selection for Secure Cooperative Networks with Jamming

This paper deals with relay selection in cooperative networks with secrecy constraints. The proposed scheme enables an opportunistic selection of two relay nodes to increase security against eavesdroppers. The first relay operates as a conventional mode and assists a source to deliver its data to a destination via a decode-and-forward strategy. The second relay is used in order to create intentional interference at the eavesdropper nodes. The proposed selection technique jointly protects the primary destination against interference and eavesdropping and jams the reception of the eavesdropper. The new approach is analyzed for different complexity requirements based on instantaneous and average knowledge of the eavesdropper channels. In addition an investigation of an hybrid security scheme which switches between jamming and non-jamming protection is discussed in the paper. It is proven that an appropriate application of these two modes further improves security. The enhancements of the proposed selection techniques are demonstrated analytically and with simulation results.     

BER-Constrained Incremental Relaying with Relay Selection in Cooperative Wireless Networks

One of the main drawbacks of cooperative communication systems with half-duplex relaying is inefficient use of spectrum. Incremental relaying is an effective technique that overcomes this limitation, particularly in the high-SNR regime. In this paper, for a multi-relay cooperative network with arbitrary number of relay nodes, we propose a spectrally-efficient incremental relaying scheme that eliminates redundant relay transmissions such that an average end-to-end bit error rate (BER) constraint is satisfied. For detect-and-forward relaying, under the assumption of error propagation from the relays to the destination, we analyze the performance of the system in terms of the end-to-end BER, the average spectral efficiency and the outage probability for Rayleigh fading environment. The performance of the system depends on a single threshold employed by the relays and the destination. We optimize this threshold such that the average spectral efficiency of the system is maximized under an average end-to-end BER constraint. This optimization criterion results in a constant-BER, variable-spectral efficiency relaying scheme. The proposed scheme makes use of spectrum as efficiently as possible, while providing the required quality of service at the destination.     

Jointing Adaptive Modulation Relay Selection Protocols for Two-Way Opportunistic Relaying Systems with Amplify-and-Forward Policy

Two novel best-relay selection protocols, the jointing adaptive modulation max–min (AM-MM) protocol and the jointing adaptive modulation maximum harmonic mean (AM-MHM) protocol, are proposed for two-way opportunistic relaying systems with amplify-and-forward policy (TWOR-AF). By integrating the adaptive modulation with the conventional max–min (NonAM-MM) and maximum harmonic mean protocols, the effect of the modulation schemes used at both sources is exploited perfectly in the proposed AM-MM and AM-MHM protocols. The analytical expressions to the approximate upper bounds of overall average symbol error probability (SEP) for TWOR-AF systems with these different relay selection protocols are obtained through theoretic analysis. The numerical results demonstrate that the average SEP of TWOR-AF systems can be improved greatly when the proposed jointing adaptive modulation relay selection protocols are performed. Furthermore, in certain channel realizations, the adaptive modulation non-selection protocol outperforms the conventional NonAM-MM protocol in which the adaptive modulation is not integrated.     

Performance Analysis of Two-Way Hybrid Decode-and-Amplify Relaying Scheme with Relay Selection for Secondary Spectrum Access

In this paper, we propose and analyze the outage probability of a two-way hybrid decode-and-amplify relaying scheme with relay selection for secondary spectrum access. In this scheme, a secondary network is co-located and uses the same spectrum as the primary network. The primary network is comprised of two primary terminals that attempt to transmit signals to one another; the secondary network is comprised of M secondary transmitter-receiver pairs (ST-SR). One of the secondary transmitters chosen to cooperate with the primary network uses a hybrid decode-and-amplify forward technique in order to relay primary and secondary signals. We derive expressions for the outage probability of the primary network as well as the secondary network over a Rayleigh fading channel. Simulation results are presented to verify theoretical analyses and to compare the performance of the proposed protocol to that of a two-way direct transmission protocol.     

Outage Probability and Ergodic Capacity Analysis for Two-Way Relaying System with Different Relay Selection Protocols

The outage probability and ergodic capacity analysis for decode-and-forward two-way relaying system is investigated in this paper. First, the exact expressions (or bounds) of outage probability, ergodic capacity and average bidirectional ergodic capacity (ABEC) for max–min relay selection, random relay selection and direct transmission protocols are derived through theoretic analysis, and performance comparisons among different relay selection protocols are developed. Then a novel maximum average bidirectional mutual information (MABM) relay selection protocol is proposed and analyzed. Simulation results demonstrate that the derived analytical results fit well with Monte-Carlo simulations. The proposed MABM protocol can always achieve larger ABEC than other protocols while keeping low outage probability, and the MABM and max–min protocols in this paper can always achieve better performance than the max–min selection and max-sum selection in Krikidis (IEEE Trans Veh Technol 59(9):4620–4628, 2010). In addition, outage probability, ergodic capacity and ABEC performance of the proposed protocol become worse while distance becomes larger.     

Relay Selection in Two-Way Cooperative Systems

In this paper, we present a design of two-way communication system with relay selection in two-way cooperative system over cascaded Nakagami- \(m\) fading channels. In the proposed scheme, in which all terminals are in motion as mobiles or vehicles, two users first broadcast their information to relays. Then, a single relay with a minimum sum symbol error rate (SER) will be selected to broadcast the received signals back to the sources. In other words, in the selection process, we investigate a simple suboptimal min-max criterion for relay selection, where a single relay that minimizes the maximum SER of two source nodes will be selected. Specifically, we have derived expressions of cumulative distribution function and moment generating function of end-to-end signal-to-noise ratio. By using these expressions, we have analyzed the performance of considered system in terms of outage probability and SER expression. Numerical and simulation results show the validity of the proposed mathematical analysis and point out the confirmation of the analytical results.     

A New Relay and Jammer Selection Schemes for Secure One-Way Cooperative Networks

This paper presents different relay and jammer selection schemes for one-way cooperative networks to increase the security against malicious eavesdroppers. We consider a single source-destination cooperative network with multiple intermediate nodes and one or more eavesdroppers. The selection in the proposed schemes is made with the presence of direct links and the assumption that the broadcast phase is unsecured. The proposed schemes select three intermediate nodes. The first selected node operates in the conventional relay mode and assists the source to deliver its data to the corresponding destination via a Decode-and-Forward strategy. The second and third selected nodes are used in different communication phases as jammers to create intentional interference at the eavesdroppers’ nodes. Moreover, a hybrid scheme which switches between jamming and non-jamming modes is introduced in this paper. The proposed schemes are analyzed in terms of ergodic secrecy capacity and secrecy outage probability. Extensive analysis and a set of simulation results are presented to demonstrate the effectiveness of the different schemes presented in this work. The obtained results show that the proposed schemes with jamming outperform the conventional non-jamming schemes and the hybrid switching scheme further improves the secrecy capacity. The impact of changing both the eavesdroppers and the relays location on ergodic secrecy capacity and secrecy outage probability is also discussed. Finally, the impact of the presence of multiple eavesdroppers is studied in this paper.     

Channel Estimation for OFDM Modulated Two-Way Relay Networks

In this work, we introduce the model of employing orthogonal-frequency-division multiplexing (OFDM) for transmission over time-dispersive channels in the two-way relay network (TWRN), where two source terminals exchange their information through a relay terminal using the amplify-and-forward (AF) relaying scheme. We propose a two-phase training protocol for the channel estimation, which is compatible with the two-phase data transmission scheme. In the first phase, the two source terminals send their individual training sequences concurrently to the relay, while in the second phase the relay amplifies the received training sequences and broadcasts them to both source terminals. We propose two different types of training methods as well as develop their corresponding channel estimation algorithms at each of the two source terminals. The first type of training is block based, for which we first estimate the cascaded source-relay-source channels, and then design algorithms to recover the individual channels between sources and relay. The second type of training is pilot-tone (PT) based, for which we propose to directly estimate the individual channels between sources and relay. Moreover, the identifiability issues on the nonambiguous estimate of the channels in both types of proposed training are carefully addressed. Finally, various numerical examples are presented to corroborate our analytical results.     

Secure Communication for RF Energy Harvesting NOMA Relaying Networks with Relay-User Selection Scheme and Optimization

Mobile Networks and Applications - In this paper, we study the physical layer security (PLS) of a radio frequency energy harvesting (RF EH) non-orthogonal multiple access (NOMA) relaying network...     

用于机会中继的一种最佳中继选择算法

通过使用具有最佳瞬时信道质量的单个中继进行协作分集,机会中继可以获得与更为复杂的空时编码协作通信相同的分集增益。但是,随着可选择中继节点数的增加,最佳中继选择的失败概率会明显上升。文章提出了一种新的实用最佳中继选择算法,要求源站向最佳中继发送选择确认消息,竞争中继则在冲突发生后进行退避。仿真结果表明,采用新算法可以将选择失败的概率降低2～3个数量级,而增加的开销尚不到2％。     

放大转发中继网络中的一种中继选择方案

提出了一种放大转发网络中的中继选择方案,假设目的节点配置多个天线,源节点和所有中继节点都配置单个天线,方案选择一组中继同时在相同的频带上放大转发接收到的源节点信息以最大化接收信噪比。与只择一个最优中继的方案相比,方案在保持满分集阶数的情况下获得了更高的中断容量和更优的误符号率性能。与只选择一个最优中继的方案相比,在0.000 01的误符号率水平上,少需要发射功率1.6 dB。     

Joint Spectrum Allocation and Relay Selection in Cellular Cognitive Radio Networks

Cognitive Radio Network (CRN) has been proposed in recent years to solve the spectrum scarcity problem by exploiting the existence of spectrum holes. One of the important issues in the cellular CRNs is how to efficiently allocate primary user (PU) spectrum inside a CRN cell without causing harmful interference to PUs. In this paper, we present a cross-layer framework which jointly considers spectrum allocation and relay selection with the objective of maximizing the minimum traffic demand of secondary users (SUs) in a CRN cell. Specifically, we consider (1) CRN tries to utilize PU spectrum even when the CRN cell is not completely outside the protection region of the PU cell, and (2) cooperative relay is used in cellular CRNs to improve the utilization of PU spectrum. We formulate this cross-layer design problem as a Mixed Integer Linear Programming (MILP) and propose a low complexity heuristic algorithm to solve it. Compared to a simple channel allocation scheme, the numerical results show a significant improvement by using our proposed method and the performance is close to the optimal solution. We further consider the spectrum allocation among several CRN cells with the objective of maximizing the overall minimum throughput of all cells while ensuring each individual cell’s minimum throughput requirement. A low complexity algorithm is proposed to achieve the objective with satisfactory performance.     

Joint Clustering Relay Selection and Beamforming in Cooperative Cognitive Radio Networks

This paper proposes a joint clustering relay selection and beamforming method for a more realistic cooperative cognitive radio network, in which a secondary network of multiple secondary links and a relay network coexist with a primary network of one primary link. We aim to improve performance of the system in terms of maximizing the received signal power of the secondary destinations, subject to the constraint of received interference plus noise power of the primary destination using the proposed method. Since different relays cooperate differently towards the signals at the secondary and primary destinations, the proposed method can improve the performance of the system and enables the relay network to simultaneously transmit signals of all secondary links toward the destinations by clustering the relays. Results of simulations confirm validity of the method and improve the system performance compared to the existing cooperative beamforming and Zero-Forcing beamforming, in which no relay selection strategy is used.     

Intelligent Physical Layer Secure Relay Selection for Wireless Cooperative Networks with Multiple Eavesdroppers

Wireless Personal Communications - The modern and emerging wireless communication technologies are benefiting from relaying techniques, which is already adopted in long term evolution (LTE) Release...