Performance Of Relay System Research Articles

Secure 5G Wireless Communications: A Joint Relay Selection and Wireless Power Transfer Approach

In this paper, we investigate the secrecy performance of an energy harvesting relay system, where a legitimate source communicates with a legitimate destination via the assistance of multiple trusted relays. In the considered system, the source and relays deploy the time-switching-based radio frequency energy harvesting technique to harvest energy from a multi-antenna beacon. Different antenna selection and relay selection schemes are applied to enhance the security of the system. Specifically, two relay selection schemes based on the partial and full knowledge of channel state information, i.e., optimal relay selection and partial relay selection, and two antenna selection schemes for harvesting energy at source and relays, i.e., maximizing energy harvesting channel for the source and maximizing energy harvesting channel for the selected relay, are proposed. The exact and asymptotic expressions of secrecy outage probability in these schemes are derived. We demonstrate that applying relay selection approaches in the considered energy harvesting system can enhance the security performance. In particular, optimal relay selection scheme outperforms partial relay selection scheme and achieves full secrecy diversity order, regardless of energy harvesting scenarios.

Performance evaluation of HDAF relaying systems for pilot and data symbol burst transmission over quasi‐static Rayleigh fading channels

SummaryThis paper analyzes averaged symbol error probabilities of burst transmission consisting of pilot and data symbols for hybrid adaptive decode‐or‐amplify‐forward (HDAF) relaying systems. Under the assumption of quasi‐static Rayleigh fading channels with independent and non‐identically distribution, we consider a channel estimation scheme based on pilot symbols and show how channel estimation error affects received signal‐to‐noise ratio (SNR) and symbol error probability (SEP). Firstly, all the possible detection error‐events are presented for all the relay nodes, and their probabilities are derived as forms related with data symbol burst transmission. For the given error event, we analyze the conditional SEP as an exact form and then, the averaged SEP (ASEP) is approximately derived as a closed‐form. The simulation results verify that our derived ASEP expression is accurate over all the regions of SNR. Utilizing the proposed expressions, we can evaluate ASEP performance of HDAF relay systems easily and fast. Copyright © 2015 John Wiley & Sons, Ltd.

Performance of OFDM AF relay system with subcarrier mapping in the presence of carrier frequency offsets

This article deals with the performance analysis of orthogonal frequency division multiplexing (OFDM) amplify-and-forward (AF) relay system with subcarrier mapping (SCM) in the presence of carrier frequency offset (CFO). Although SCM in an OFDM system has been investigated extensively, nevertheless, the bit error rate (BER) of the system with CFO is not yet available in the literature. This paper presents the BER analysis of a dual hop OFDM AF relay system with ordered subcarrier paring schemes, i.e., best-to-worst (BTW) SCM and best-to-best (BTB) SCM. Accurate close-form expressions are derived for end-to-end BER while considering a dual-hop fixed gain AF relaying system with CFO in Rayleigh fading channel. To provide more insights, their closed-form asymptotic expressions are then obtained. It is shown that the presence of CFO causes the BER of system maintain a fixed level even while signal-to noise ratio (SNR) is in high regime. The simulation results verify that the derived average BER expressions are accurate in Rayleigh fading channel.

Performance of Dual Hop Relay System in the Presence of a Correlated Interferer Through Nakagami Fading Channel

This paper provides a unified approach for accurate numerical evaluations of the bit error rate of dual hop amplify and forward system in the presence of interference. Existence of independent or correlated interferer in one or both hops is assumed. Nakagami fading channel with integer and non-integer fading depth `m' is assumed. Depicted results show that correlation has insignificant effect relative to independent situation when the interferer power is equal to that of the desired signal. It can give relative improvement if the interferer is weaker (?12 dB) than the desired signal. Results showing appreciable improvement on the employment of diversity at both of the relay and destination are also displayed.

Performance Analysis of Dual-Hop Fixed-Gain Relay Systems over Extended Generalized-K Fading Channels

In current cooperative communication systems, a relay terminal is very often used as intermediate node and may degrade or improve the overall system performance, depending on the power imbalance between the hops. In this paper, an approach to estimate the performance of dual-hop fixed-gain relay system when each hop is subjected to extended generalized-K fading is presented. New closed form expressions are derived for the cumulative distribution function, the outage probability, and the ergodic capacity. Moreover, the average symbol error probability for coherent and non-coherent modulation schemes is derived. The accuracy of analytic results is verified through computer simulations.

Iterative Antenna Selection for Decode-and-Forward MIMO Relay Systems Under a Holistic Power Model

In this letter, we investigate the antenna selection in decode-and-forward (DF) MIMO relay systems where the circuit power consumption is considered. The main problem is that the optimal active relay antenna subsets can only be selected by exhaustive search. To reduce the complexity, three iterative properties on the capacity bounds are first derived in this letter, which lay the foundation for our proposed algorithm. This algorithm can improve the performance of DF MIMO relay systems by the maximization of the upper and lower bounds on the capacity. Simulation results will show that the proposed low complexity algorithm has nearly the same performance as that of exhaustive search. In addition, it has a remarkable performance gain over the conventional DF MIMO relay protocol.

Adaptive power allocation and outage performance of cognitive best relay cooperation systems with multiple primary transceiver pairs and direct path between cognitive source and destination

Based on decode-and-forward (DF) protocol, this work focuses on the adaptive power allocation and outage performance of underlay cognitive radio and opportunistic relaying (UCR-OR) systems with direct path between cognitive source and destination. The UCR-OR systems suffer from the interference of multiple primary user (PU) pairs. Under the outage constraint of PUs and the cognitive peak transmit power limit, we first obtain the adaptive power allocation schemes for secondary transmitters. Secondly, we obtain the exact closed-form expression to the outage probability of UCR-OR systems by using appropriate mathematical proof. Finally, to obtain a clear insight and to highlight the effect of system parameters on the performance of UCR-OR systems, the asymptotic closed-form expression of outage probability is achieved with the assumption of high cognitive transmit power. The presented simulations show that, due to the adaptive power allocation employed, the outage probability of UCR-OR systems is decreasing with PUs' transmit power Pp when Pp is less than a specific value P � . Only when the value of Pp is

Analysis of Wireless Relay System under Interference Environment by SNR Enhancement Method

This paper emphasizes the wireless relaying performance analysis in interference environment. We will analyze the main performance metrics such as outage and error probability of the communication system in interference environment, and will make some simulation to demonstrate the result of theory analysis. In relay transmission system, either two relaying or multiple relaying, its basic principles are based on the two relaying system. In this paper, the wireless relay system performance in the interference environment will be analyzed and simulated on the basis of previous studies.

Performance analysis of cognitive relay systems with spectrum-sharing interference under a primary outage probability constraint

This paper investigates the performance of an underlay cognitive relay system where secondary users (SUs) suffer from a primary outage probability constraint and spectrum-sharing interference imposed by a primary user (PU). In particular, we consider a secondary multi-relay network operating in the selection decode-and-forward (SDF) mode and propose a best-relay selection criterion which takes into account the spectrum-sharing constraint and interference. Based on these assumptions, the closed-form expression of the outage probability of secondary transmissions is derived. We find that a floor of the outage probability occurs in high signal-to-noise ratio (SNR) regions due to the joint effect of the constraint and the interference from the PU. In addition, we propose a generalized definition of the diversity gain for such systems and show that a full diversity order is achieved. Simulation results verify our theoretical solutions.

Performance Analysis of Full-Duplex Relaying Employing Fiber-Connected Distributed Antennas

Different from the previous studies on distributed-antenna (DA) systems (DASs) that mostly focused on the enhancement of downlink or uplink performance of cellular systems through cooperation of DAs, this paper proposes and investigates the performance of a novel fiber-connected DA relay system (DARS) that employs radio-over-fiber (RoF) techniques to interconnect a DAS to a central processor, which collectively form a relay node. Under the assumption that self-interference can be perfectly canceled in DARS, full-duplex (FD) operation is possible, by which some antennas receive from the source, whereas other antennas simultaneously transmit to the destination. The numbers of transmit and receive antennas can be controlled to achieve a balance between the transmissions of the source-relay (SR) and relay-destination (RD) links. Consequently, higher spectral efficiency can be achieved compared with half-duplex (HD) relaying systems. For Nakagami fading channels with no direct source-destination (SD) link, we show that DARS can obtain the optimal diversity-multiplexing tradeoff (DMT). Moreover, as the primary purpose of FD relaying is to increase the throughput, we also analyze the throughput performance of DARS. Numerical results show that the FD-DARS with a large number of antennas exhibits a much better throughput performance than HD relaying systems and in regions with high signal-to-noise ratios.

Performance of Multihop Relaying System in Cognitive Radio Networks

This paper introduces multihop relay system where the benefits of spatial diversity are achieved from the concurrent reception of signals that have been transmitted by multiple terminals. Amplify and forward cooperative relays will be used in this system. It will be obvious that multihop system can effectively mitigate the performance deterioration caused by fading, without imposing delay or bandwidth expansion. The channel models are compared through the simulations to prove that multihop system is better than single hop system where it gives low symbol error rate and therefore the performance will be improved. Maximum Ratio Combining will be used. Analysis of different hops system will be made. Different modulations will be applied. From simulation results it will be obvious that symbol error rate will be reduced when using multihop than single hop.

Outage Performance of Opportunistic Relaying Systems with Limited Feedback

Outage Performance of Opportunistic Relaying Systems with Limited Feedback

On the Performance of Cellular Two-Way Relay Systems with Analog Network Coding and Multiuser Diversity

We consider a cellular two-way relaying system in which a multi-antenna base station (BS) communicates bidirectionally with one of several single-antenna mobile stations (MSs) via a single-antenna relay using analog network coding. We employ MS selection coupled with beamforming at the BS so as to maximize the end-to-end signal-to-noise ratios. In the considered system, the target rates at the sources can generally be different owing to the asymmetric traffic flow in opposite directions. With such a general setup, we perform an overall system outage probability analysis over Rayleigh fading channels. For more insights, we derive a closed-form asymptotic expression for overall outage probability and an upper bound expression for ergodic sum-rate of the system. Based on these expressions, we show that the system achieves a performance gain, and a diversity order of minimum of the number of BS antennas and the number of MSs. Moreover, we address the problem of optimization of relay location in order to minimize the overall system outage under asymmetric traffic conditions. Finally, we provide numerical and simulation results to corroborate the theoretical analysis and the advantages offered by the proposed scheme.

Performance Analysis on Two-Way Relay System with Co-Channel Interference

In this paper, we investigate the performance of two-way relay system with co-channel interference in a Rayleigh fading environment. Due to the mathematical intractability of original expression of signal-to-interference and noise ratio (SINR) induced by the bi-directional forwarding, a couple of effective bounds are derived for important performance metrics such as outage probability and average bit error rate of modulation, with application of diverse physical layer network coding (PNC) schemes of two time slot (2TS) and three time slot (3TS). Some asymptotic solutions are also proposed to intuitively exhibit the trends of performance in high SINR regime. We demonstrate that the performance bounds have practical meaning corresponding to different forwarding capability of the relay. Numeric simulations validate our analysis by showing that the theoretic bounds match well with simulation results. Additionally, the effect of distance between relay and sources is discussed in our interference scenario, as well as the impact of relay's power allocation factor in 3TS PNC scheme.

Performance analysis of multi-antenna relay communication systems with MRC

The performance of multi-antenna relay communication systems is investigated in this letter. The source broadcasts the signal to all the relays and the destination. Decode-and-forward scheme is adopted at the relays, and the destination employs maximum ratio combining (MRC) technique to maximize the received signal-to-noise ratio. Closed-form expressions of outage probability are derived in the MRC case and minimum routes MRC case. An adaptive grouping algorithm of relay antennas is also presented under the constraint of total antenna number. Simulation results show that the analytical curves agree with the simulated ones very well, and the performance of the proposed grouping algorithm is very close to the upper bound mentioned in other papers. Copyright © 2012 John Wiley & Sons, Ltd.

A computer‐based testing system to evaluate protective relays as a tool in power system protection education

AbstractTeaching power system relaying is a fundamental issue in a power system high‐level course. However, for an effective instruction of this topic an experience with real equipments can be considered as fundamental. To achieve this purpose, in this paper a new approach for the practical learning of power system relaying is presented. This consists of a computer‐based testing system of relay‐operating characteristic. Different relay types and developed specific software are also an important piece of the laboratory practice. Using this system it is possible to understand the performance and limitations of different protective relay systems and to test a real relay disoperation. The benefit of using this system is not available through traditional lectures and textbooks. © 2009 Wiley Periodicals, Inc. Comput Appl Eng Educ 20: 19–28, 2012

Performance Analysis of Full Duplex on-regenerative Relay

In this letter, non-regenerative Amplify-and-Forward (AF) relay systems based on half and full duplex schemes are investigated and their performance is analyzed and compared in terms of outage probability. Although the AF relay systems have been widely investigated in many previous literatures, most of them adopted a half duplex scheme due to hardware limitation and mathematical tractability. To the best of our knowledge, this letter is the first study to investigate the performance of the full duplex AF relay system considering practical hardware limitations. In full duplex AF relay systems, it is important to secure the isolation between transmit and receive antennas. Our numerical and simulation results show that there exists a threshold point of the isolation gain that the full duplex relay system outperforms the half duplex relay system.

Orthogonal Space–Time Block Codes With CSI-Assisted Amplify-and-Forward Relaying in Correlated Nakagami-$m$ Fading Channels

In this paper, the performance of multiple-input multiple-output (MIMO) dual-hop amplify-and-forward (AF) relay systems using orthogonal space–time block codes (OSTBCs) over arbitrarily correlated Nakagami- <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$m$</tex></formula> fading channels is analyzed. In particular, closed-form expressions for the end-to-end outage probability (OP) and the symbol error probability (SEP) with arbitrary number of transceiver antennas and general correlation matrices are derived. Their mathematically tractable forms readily enable us to evaluate the performance of MIMO AF relay systems that utilize OSTBCs. For sufficiently high signal-to-noise ratios (SNRs), asymptotically tight approximations for the OP and SEP are also attained, which reveal insights into the effects of fading parameters and antenna correlation on the system's performance. Furthermore, we prove that the correlation has no impact on the achievable diversity gain, which is equal to the minimum of the sum of fading parameters between the two hops. Selected numerically evaluated results are presented, showing an excellent agreement between the proposed analysis and equivalent Monte Carlo simulations.

Water Supply Performance and Fire Suppression during the World Trade Center Disaster

This paper describes the New York City water supply performance and suppression of fire during the World Trade Center (WTC) disaster. The water losses sustained by damaged water distribution pipelines are discussed and their impacts on emergency response and telecommunications and transportation infrastructure are noted. The results of hydraulic network analyses are presented to quantify the performance of hose and engine relay systems from fireboats to the WTC site. The results of an analytical study of firefighting relay systems are summarized to provide guidance on the most effective selection of hose size, number of hose lines, and engines for future use of fireboats for landside fire protection. The fire department response to the WTC disaster is compared with similar response to the 1989 Loma Prieta earthquake. Drawing on lessons from both events, recommendations are made for improved emergency planning and services.

Multimode Antenna Selection for MIMO Amplify-and-Forward Relay Systems

Obtaining the most from multiple-antenna relay systems requires algorithms that configure the source and relay adaptively to instantaneous channel conditions. In this paper, we define an antenna selection mode of operation as the number of selected transmit antennas at the source (which is equal to the number of data substreams), the substream-to-antenna mapping at the source, the number of selected transmit antennas at the relay, and the substream-to-antenna mapping at the relay. We develop dualmode and multimode antenna selection algorithms to choose the mode that is most likely to deliver the lowest vector symbol error rate assuming the overall data rate is fixed. The effective condition numbers of both the two-hop channel and the relay channel are derived to give intuition on how the spatial characteristics of the constituent channels affect mode selection and to derive low complexity algorithms. Link-level simulations show that our proposed algorithms usually select the best mode, thus improving the diversity performance of spatial multiplexing relay systems and providing array gains over the existing single-stream relay transmission strategies. The two-hop multimode algorithms are shown by system-level simulations to improve the reliability of transmission and extend spatial multiplexing capability to cell-edge users in a multi-cell network.