Opportunistic Relaying Schemes for Amplify and Forward Bidirectional Relay Channels with Multi antenna Sources

We consider a two-way relay network where the Amplify-and-Forward (AF) protocol is adopted by all relays in this paper.The network consists of two multi-antenna source nodes and multiple distributed single-antenna relays.Two opportunistic relaying schemes are proposed to efficiently utilize the antennas of the source nodes and the relay nodes.In the first scheme,the best relay is selected out by a max-min-max criterion before transmitting.After that,at each source,only the antenna with the largest channel gain between itself and the best relay is activated to transmit and receive signals with full power.In the second scheme,assisted by the best relay which is selected by the typical max-min criterion,both source nodes use all their antennas to exchange data,and match filter beamforming techniques are employed at both source nodes.Further analyses show that all schemes can achieve the full diversity order,and the conclusions are not only mathematically demonstrated but numerically illustrated.System performance comparisons are carried out by numerical methods in terms of rate sum and outage probability,respectively.The beamforming assisted scheme can be found to be superior to the antenna selection scheme when accurate Channel State Information (CSI) is available at the transmitters.Otherwise,the latter is very suitable.

Impact of Maximum Transmit Power Limit on the First-Order and Second-Order Performance of Cognitive Opportunistic Relaying

Abstract： This paper focuses on the first-or- der and second-order performance of dual-hop underlay cognitive radio systems with oppor- tunistic relaying （UCR-OR） over indepen- dent and non-identically distributed （i.ni.d） Rayleigh fading channels. For the UCR-OR systems, the tolerable maximum interference power （TMIP） Q at primary users （PUs） and the allowable maximum transmission power limit （AMTP） P at secondary users （SUs） are considered, simultaneously. We first obtain the closed-form solutions to the first-order performance such as outage probability, ave- rage symbol error ratio （SER）, and ergodic capacity （EC）. Secondly, we investigate the second-order statistical performance, i.e., ave- rage outage rate （AOR） and average outage duration （AOD）. With the consideration that in practice implementation the receiver perfor- mance is primarily influenced by the signal- to-noise ratio （SNR） （not the signal envelope）, the second-order statistical performance is investigated based on the equivalent instan- taneous end-to-end SNR. Finally, we present the detailed performance comparison analysis of UCR-OR systems by defining a random variable ,μ=Pmax/Q. The results show that the effect of μ on the first-order and second-or- der performances is different greatly. For the first-order performance, the perlbrmance gap is negligible when the value of// is relatively large. However, for the second-order one, the gap is distinct.

TWO-WAY DENOISE-AND-FORWARD NETWORK CODING OPPORTUNISTIC RELAYING AIMING AT MINIMIZING EUCLIDEAN DISTANCE IN MULTI-ACCESS PHASE

To exploit the effect of modulation schemes on the best relay selection,a novel Jointing Modulation schemes max-min criterion(JM-max-min) is proposed firstly for Two-Way De-Noise-and-Forward(DNF) Opportunistic Relaying systems(TW-DNF-OR) by aiming at minimizing the Pairwise Error Probability(PEP) of Multi-Access(MA) phase which dominates the error per-formance of TW-DNF-OR due to the presence of MA interference.The proposed JM-max-min criterion integrates perfectly the minimum distances of constellations and the relay links gains.Then,with the proposed JM-max-min criterion,we analyze the Symbol Error Probabilities(SEPs) of MA phase and BroadCast(BC) phase by using the approximated mathematics analysis,and present the corresponding closed-form expressions to SEPs.The numerical analysis shows,for a given modulations combination at both sources,the TW-DNF-OR systems with the proposed JM-max-min criterion outperform the one with the conventional max-min criterion.

Saturation throughput analysis of the cooperative MAC with opportunistic Relaying for Ad Hoc Networks

In this paper, the system saturation throughput of the cooperative MAC with opportunistic relaying for ad hoc networks is evaluated by exploiting the proposed analytical model based on the Markov chain model of DCF. Both of the cooperative scheme and opportunistic relaying are considered into the analytical model. Simulations are also performed to validate the proposed analytical model. Simulation results show that the cooperative MAC with opportunistic relaying can significantly improve the system performance. Furthermore, we also reveal the impact of the opportunistic relaying on the performance from the MAC layer perspectives.

Enhancement of Multicast Security with Opportunistic Relaying Technique over κ-μ Shadowed Fading Channels

The effects of scatterers, fluctuation parameter and propagation clusters significantly affect the performance of κ-μ shadowed fading channel. On the other hand, opportunistic relaying is an efficient technique to improve the performance of fading channels reducing the effects of aforementioned parameters. Motivated by these issues, in this paper, a secure wireless multicasting scenario through κ-μ shadowed fading channel is considered in the presence of multiple eavesdroppers with opportunistic relaying. The main purpose of this paper is to ensure the security level in wireless multicasting compensating the loss of security due to the effects of power ratio between dominant and scattered waves, fluctuation parameter, and the number of propagation clusters, multicast users and eavesdroppers, by opportunistic relaying technique. The closed-form analytical expressions are derived for the probability of non-zero secrecy multicast capacity (PNSMC) and the secure outage probability for multicasting (SOPM) to understand the insight of the effects of above parameters. The results show that the loss of security in multicasting through κ-μ shadowed fading channel can be significantly enhanced using opportunistic relaying technique by compensating the effects of scatterers, fluctuation parameter, and the number of propagation clusters, multicast users and eavesdroppers.

Device-to-Device Based Cooperative Relaying for 5G Network:A Comparative Review

Due to the proliferation of mobile internet access, the cellu-lar traffic is envisaged to experience a 1000-fold growth inthe second decade of the 21 st century. To meet such a hugetraffic demand, the Fifth Generation(5G) network have toadopt new techniques to substantially increase spectral effi-ciency and reliability. At the base station side, available re-sources(power supply, equipment size, processing capability,etc.) are far more sufficient than that of the terminal side,which imposes a high challenge on the uplink transmission.The concept of cooperative communications opens a possibili-ty of using multiple terminals to cooperatively achieve spa-tial diversity that is typically obtained by means of multipleantennas in the base station. The application of Device-to-Device(D2D) communications in the 3GPP LTE system fur-ther pushes the collaboration of terminals from the theory tothe practice. The utilization of D2D-based cooperative relay-ing is promising in the era of 5G. In this paper, we compara-tively study several cooperative multi-relay schemes, includ-ing the proposed opportunistic space-time coding, in thepresence of imperfect channel state information. The numeri-cal results reveal that the proposed scheme is the best coop-erative solution until now from the perspective of multiplex-ing-diversity tradeoff.

Outage analysis of opportunistic relay and beamforming in DF relay networks over Nakagami-m fading channels

In this paper, the outage performance of opportunistic relay （OR） and equal gain transmissionbeamfomaing （EGT-BF） are studied in decode-and-ibrward （DF） relay networks over Nakagami-m fading channels, assuming multiple relays are available in the networks. We derive the moment generation function （MGF） of the received signal-to-noise ratio （SNR） at the destination, then obtain the exact closedform solution of OR and the approximate closed form expression of EGT-BF in terms of outage probability respectively through numerical inversion of Laplace transform. Simulation results are given to verify the correctness of theoretical analysis. We also compare the outage performance of OR and EGT-BF with oth- er transmission strategies and find that when decoding results of relays are available at the destination, OR achieves high performance and is the optimal scheme to achieve the tradeoff between performance and overheads. When relay decoding information is unachievable, the performance of OR degrades significant- ly, and the EGT-BF is a more preferred scheme.

Enhancing Security in Multicellular Multicast Channels Reducing Interference Power with the Best Relay Selection

The capacity of wireless networks is fundamentally limited by interference. A few research has focused on the study of the simultaneous effect of interference and correlation, and less attention has been paid to the topic of canceling simultaneous effect of interference and correlation until recently. This paper considers a secure wireless multicasting scenario through multicellular networks over spatially correlated Nakagami-m fading channel in the presence of multiple eavesdroppers. Authors are interested to protect the desired signals from eavesdropping considering the impact of perfect channel estimation (PCE) with interference and correlation. The protection of eavesdropping is also made strong reducing the simultaneous impact of interference and correlation on the secrecy multicast capacity employing opportunistic relaying technique. In terms of the signal-to-interference plus noise ratio (SINR), fading parameter, correlation coefficient, the number of multicast users and eavesdroppers and the number of antennas at the multicast users and eavesdroppers, the closed-form analytical expressions are derived for the probability of non-zero secrecy multicast capacity and the secure outage probability for multicasting to understand the insight of the effects of aforementioned parameters. The results show that the simultaneous effects of correlation and interference at the multicast users degrade security in multicasting. Moreover, the security in multicasting degrades with the intensity of fading and the number of multicast users, eavesdroppers and antennas at the eavesdroppers. The effects of these parameters on the security in multicasting can be significantly reduced by using opportunistic relaying technique with PCE. Finally, the analytical results are verified via Monte-Carlo simulation to justify the validity of derived closed-form analytical expressions.

Performance analysis of opportunistic amplify-and-forward two-way relaying in two-wave with diffuse power fading channels

This paper considers cooperative amplify-and-forwards （AF） two-way relay networks （TWRNs） with opportunistic relay selection （ORS） in two-wave with diffuse power （TWDP） fading channels. To investigate the system performance, we first derive an easy-to-computer approximated expression for the exact outage probability to reduce computational cost. Furthermore, we presented compact expressions for the asymptotic outage probability and asymptotic symbol error rate, which characterizes two factors goveming the network performance at high signal-to-noise ratio （SNR） in terms of diversity order and coding gain. Additionally, based on the asymptotic outage probability, we determine the optimal power allocation solution between the relay and the sources to minimize the overall outage probability under the assumption that both the sources have identical transmit power. The correctness of the analysis is validated through Monte Carlo simulations. Our derived results can be applied to general operating scenarios with distinct TWDP fading parameters which encompass Rayleigh and Rician fading as special cases and arbitrary number of relays.