Fast relay selection algorithm based on symbol error probability

This letter presents a study on statistical and symbol error performance analysis of the two-hop orthogonal frequency division multiplexing (OFDM) relay link with amplify-and-forward (AF) protocol and subcarrier mapping (SCM) scheme. Closed-form expressions for probability density function (PDF) and symbol error probability (SEP) of the signal-to-noise ratio (SNR) for the kth mapped subcarrier pair link (k-MSPL) are provided. Our asymptotic SEP analysis reveals that the traditional SCM which can maximize the capacity can not improve the average SEP for uncoded OFDM system, however the average SEP can be decreased significantly by dropping several worst links.

Cooperative communication is regarded as a key technology in wireless networks, including cognitive radio networks (CRNs), which increases the diversity order of the signal to combat the unfavorable effects of the fading channels, by allowing distributed terminals to collaborate through sophisticated signal processing. Underlay CRNs have strict interference constraints towards the secondary users (SUs) active in the frequency band of the primary users (PUs), which limits their transmit power and their coverage area. Relay selection offers a potential solution to the challenges faced by underlay networks, by selecting either single best relay or a subset of potential relay set under different design requirements and assumptions. The best relay selection schemes proposed in the literature for amplify-and-forward (AF) based underlay cognitive relay networks have been very well studied in terms of outage probability (OP) and bit error rate (BER), which is deficient in multiple relay selection schemes. The novelty of this work is to study the outage behavior of multiple relay selection in the underlay CRN and derive the closed-form expressions for the OP and BER through cumulative distribution function (CDF) of the SNR received at the destination. The effectiveness of relay subset selection is shown through simulation results.

This paper investigates the maximal ratio combining (MRC) performance of an amplify and forward (AF) relay system in Nakagami-m fading environments. The study considers a general scenario with distinct m fading parameters for the following three links, source to relay link, and source to destination link and relay to destination link. We derive new closed form expressions for the statistics of important performance metrics, including the moment generating function, outage probability, higher order moments of equivalent signal to noise ratio (SNR), ergodic capacity, and average symbol error probability (SEP) of common modulation types. In particular, we focus on analytical SEP expressions in the context of an additive white generalized Gaussian noise (AWGGN). As an active area of research, generalized noise receives much attention for its flexible model. However, analytical performance of modulation scheme in generalized noise type has not been found in open literature for AF relaying with MRC despite its practical usefulness. Without the help of analytical solutions, the SEP in generalized noise can only be obtained by a large number of repeated simulation experiments. Therefore, we present the general SEP expression by using special Fox’s H function. Simulation results verify the accuracy of our theoretical analysis and show that the diversity order of MRC criterion linearly depends upon Nakagami parameters of three links.

A relay selection algorithm is proposed to improve the system performance based on statistical channel state information(CSI) in amplify-and-forward(AF) cooperative networks. An exact and upper bound ergodic capacity formulation were derived for AF relay selection network. Theoretical analysis and simulation results validate the Tightness and feasibility of upper bound ergodic capacity.

Cooperative communication in wireless relay systems can improve the physical layer security, and the relay selection has great impacts on the security performances. In this paper the relay selection in Amplify-and-Forward (AF) cooperative networks is investigated. The system model constitutes of a source, an eavesdropper, a destination, and a number of intermediate nodes with secrecy constraints. The proposed optimal selection (OS) algorithm is based on the instantaneous channel state information (CSI) of two hops, jointly protects the target destination against eavesdropping and interference. To simplify the complexity of OS, the suboptimal selection (SS) algorithm is also presented, which is based on the instantaneous of the first hop and the statistical CSI of the second hop respectively. The secrecy capacity and secrecy outage probability of these two relay selection algorithms are analyzed. Simulation results of OS and SS validate our theoretical analysis and show enhancement in the secrecy rate over the direct transmission.

In this paper, we propose a set of joint transmit diversity selection (TDS) and relay selection (RS) algorithms based on discrete iterative stochastic optimization for the uplink of cooperative multiple-input-multiple-output (MIMO) systems. Decode-and-forward (DF) and amplify-and-forward (AF) multirelay systems with linear minimum mean square error (MSE), successive interference cancelation, and adaptive reception are considered. The problems of TDS and RS are expressed as MSE and mutual information (MI) joint discrete optimization problems and solved using iterative discrete stochastic algorithms. Such an approach circumvents the need for exhaustive searching and results in a range of procedures with low complexity and increased speed of convergence that can track the optimal selection over an estimated channel. The proposed schemes are analyzed in terms of their complexity, convergence, and diversity benefits and are shown to be both stable and computationally efficient. Their performance is then evaluated via MSE, MI, and bit error rate comparisons and shown to outperform conventional cooperative transmission and, in the majority of scenarios, match that of the optimal exhaustive solution.

As a special type of mobile ad hoc networks (MANETs), vehicular ad hoc networks (VANETs) are expected to support vehicle to vehicle communication and vehicle to infrastructure communication. The conventional relay selection scheme proposed for MANETs may perform poorly in VANETs due to the unique characteristics of VANETs, including highly dynamic network topology, unstable link status and multiple types of services with various QoS requirements. In the paper, a relay vehicle selection algorithm is proposed for a VANET with multiple source vehicles (SVs) and relay vehicles (RVs). Stressing the cooperation and competitive relationship among SVs and RVs in relay selection, a cooperative Game model is formulated. To achieve the maximization of joint payoff functions of all the SVs and RVs, modified Kuhn-Munkres algorithm is applied and the optimal relay vehicle selection is obtained. Numerical results demonstrate that compared with previous scheme, the proposed scheme offers better performance in terms of throughput, successful transmission rate and transmission delay.

Performance analysis of a dual-hop semi-blind amplify-and-forward (AF) relay system in mixed Nakagami-m and Rician fading channels, is proposed. We derived the closed-form expression for the cumulative distribution function (CDF) of the equivalent end-to-end signal to noise ratio (SNR), based on which the exact outage probability and symbol error probability (SEP) are investigated. The theoretical analysis is validated by Monte Carlo simulation results.

This paper considers the performance analysis of constructive interference (CI) precoding technique in multi-user multiple-input single-output (MU-MISO) systems with a finite constellation phase-shift keying (PSK) input alphabet. Firstly, analytical expressions for the moment generating function (MGF) and the average of the received signal-to-noise-ratio (SNR) are derived. Then, based on the derived MGF expression the average symbol error probability (SEP) for the CI precoder with PSK signaling is calculated. In this regard, new exact and very accurate asymptotic approximation for the average SEP are provided. Building on the new performance analysis, different power allocation schemes are considered to enhance the achieved SEP. In the first scheme, power allocation based on minimizing the sum symbol error probabilities (Min-Sum) is studied, while in the second scheme the power allocation based on minimizing the maximum SEP (Min-Max) is investigated. Furthermore, new analytical expressions of the throughput and power efficiency of the CI precoding in MU-MISO systems are also derived. The numerical results in this work demonstrate that, the CI precoding outperforms the conventional interference suppression precoding techniques with an up to 20 dB gain in the transmit SNR in terms of SEP, and up to 15 dB gain in the transmit SNR in terms of the throughput. In addition, the SEP-based power allocation schemes provide additional up to 13 dB gains in the transmit SNR compared to the conventional equal power allocation scheme.

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.

In this paper, we study the performance of mixed free space optical (FSO)-radio frequency (RF) multi-user relay network with aperture selection and opportunistic user scheduling in the presence of Poisson field interference. The considered system includes multiple optical sources (apertures), one amplify-andforward (AF) relay, and multiple users. The source is connected with the relay node through FSO links and the relay is connected with the users through RF links with a Poisson field interference at the users. The FSO-RF channels are assumed to follow Málaga-M/shadowed κ-μ fading models with pointing errors on the FSO links. Exact closed-form expressions are derived for the outage probability and average symbol error probability (SEP). Moreover, the system performance is studied at the high signal-to-noise ratio (SNR) regime, where an approximate expression for the system outage probability is derived, in addition to deriving the system diversity order and coding gain. Then, the optimum source and relay transmission powers and relay position are determined to minimize the system asymptotic outage probability. The Monte-Carlo simulations are provided to validate the achieved exact and asymptotic results.

On the performance of roadside unit-assisted energy harvesting full-duplex amplify-and-forward vehicle-to-vehicle relay systems

Full-duplex amplify-and-forward relay system with direct link: Performance analysis and optimization

In this paper, we derive the Symbol Error Probability (SEP) of Round Robin (RRS), Centralized (CRS) and Distributed Relay Selection (DRS) techniques for Free Space Optical communications. RRS consists to randomly select a node as relay with equal probability. It does not consider the SNR value for relay selection. In CRS, the SNRs of different relays are sent to a Central Node (CN) for detecting the relay with highest SNR. The CN selects the best relay with largest SNR. We propose a new DRS where each relay is allowed to transmit only when its SNR is higher than a given threshold T. The threshold T is optimized with the Gradient algorithm to guarantee the lowest SEP. The suggested DRS with optimal threshold allows close performance to CRS and better performance than RRS. DRS is less complex than CRS since no signalization is needed.

This paper is devoted to an investigation of an exact average symbol error probability (SEP) for amplify and forward (AF) relaying in independent Nakagami‐m fading environments with a nonnegative integer plus one‐half m, which covers many actual scenarios, such as one‐side Gaussian distribution (m = 0.5). Using moment generating function approach, the closed‐form SEP is expressed in the form of Lauricella multivariate hypergeometric function. Four modulation modes are considered: rectangular quadrature amplitude modulation (QAM), M‐ary phase shift keying (MPSK), M‐ary differential phase shift keying (MDPSK), and π/4 differential quaternary phase shift keying (DQPSK). The result is very simple and general for a nonnegative integer plus one‐half m, which covers the same range as integer m. The tightness of theoretical analysis is confirmed by computer simulation results.