Cooperative Diversity Networks Research Articles

Impact of Co-channel Interference on the Performance of Cooperative Diversity Systems over α–μ Fading Channels

This paper investigates the impact of the co-channel interference on the performance of cooperative diversity networks. Selection combination technique is applied to the paths from multiple relay branches with no link directly connects the source and destination nodes. In addition, we derive the statistical characteristics of the upper bound of the SINR under the α–μ fading channel model, which then were used to derived the outage (P_{out}) and error (P_b(e)) probabilities for the cooperative network.

Performance of relay‐based decode‐and‐forward cooperative diversity systems over Rayleigh fading channels with non‐identical interferers

Incremental relaying was initially presented so as to adjust for the shortages or limitations related to the usual cooperative methods, specifically, the fixed relaying methods in which the relay node assists the source node in transmitting the signals belonging to the destination independent of the channel status. Matter of fact, the adaptive relaying methods related to the cooperative diversity networks have attracted current researchers’ attention as of being capable of offering an efficient way in assigning the channel expedients when required. In this study, a two-hop decode-and-forward incremental relaying over Rayleigh fading channels is assessed taking into account the existence of multiple non-identical interferers close to the destination. Interestingly, investigating the non-identical interferers case instead of identical ones, like what are published in the literature, is extremely challenging as it refers to a more generalised case. Interestingly, the performance of the system is degraded due to co-channel interference. To this end, tight closed-form expressions of the bit error rate and outage probability are ultimately obtained. Analytical and simulation results are introduced to consolidate the assumptions considered.

A closed-form ergodic capacity expression for a generic cooperative diversity network in Rayleigh fading channels

In this paper, we derive a closed-form ergodic capacity expression for a generic cooperative diversity network (GCDN) in Rayleigh fading channels. We first derive a closed-form probability density function (pdf) of the instantaneous diversity-combined signal-to-noise ratio, and then a closed-form ergodic capacity expression for the GCDN by using the derived closed-form pdf. Through numerical analyses, we analyze the ergodic capacities according to the number of cooperative nodes (CNs), respective numbers of CN antennas, and respective channel qualities between a set of the CNs and a user terminal, and also characterize the resulting ergodic capacity behaviors.

Performance investigation of multi-relay cooperative diversity networks

In this paper, we consider a cooperative network consisting of an origin node, multiple intermediate nodes and a final node. The performance of conventional selection combining (SC) suffers degradation for the described network model. In this paper, we propose a new form of SC for multiple intermediate nodes with the use of full channel state information. An end-to-end symbol error probability is derived for the proposed SC scheme with M-ary phase shift keying modulation technique in the presence of flat Rayleigh fading channel. We use decode and forward protocol at the intermediate nodes. The origin to final node link and the intermediate to final node links are assumed to be independent and identically distributed. The results show that the proposed SC scheme performs better than the conventional SC scheme. The analytical results are validated through Monte-Carlo simulations.

NetCoDer: A Retransmission Mechanism for WSNs Based on Cooperative Relays and Network Coding.

Some of the most difficult problems to deal with when using Wireless Sensor Networks (WSNs) are related to the unreliable nature of communication channels. In this context, the use of cooperative diversity techniques and the application of network coding concepts may be promising solutions to improve the communication reliability. In this paper, we propose the NetCoDer scheme to address this problem. Its design is based on merging cooperative diversity techniques and network coding concepts. We evaluate the effectiveness of the NetCoDer scheme through both an experimental setup with real WSN nodes and a simulation assessment, comparing NetCoDer performance against state-of-the-art TDMA-based (Time Division Multiple Access) retransmission techniques: BlockACK, Master/Slave and Redundant TDMA. The obtained results highlight that the proposed NetCoDer scheme clearly improves the network performance when compared with other retransmission techniques.

End-to-End Optimum ML Detection for DF Cooperative Diversity Networks in the Presence of Interference

Unlike the existing detectors, which are developed for decode-and-forward (DF) networks in the ideal interference-free case, we consider a more practical scenario where arbitrary interference exists. We consider a DF cooperative network consisting of a source, multiple relays, a destination, and multiple interferers affecting both the relays and the destination. Each relay is equipped with multiple antennas and knows its local instantaneous channel state information (CSI). Assuming that the destination knows the instantaneous CSI of the source-relay, relay-destination, and source-destination channels, we develop, for the first time in the literature, the end-to-end optimum maximum-likelihood (ML) detectors in closed-form for DF systems employing either simultaneous or orthogonal transmissions in the presence of interference. Furthermore, theoretical analysis shows that the proposed detectors achieve full diversity gains in the presence of interference with finite interference-to-noise ratios. Numerical results demonstrate that the proposed optimum detectors substantially outperform the conventional schemes which simply ignore interference.

도청자가 존재하는 무선 협력 네트워크의 전달 단말 선택을 통한 보안 전송률 최대 전송기술 및 성능분석

도청자가 존재하는 무선 협력 네트워크의 전달 단말 선택을 통한 보안 전송률 최대 전송기술 및 성능분석

Performance analysis of decode and forward cooperative diversity networks with threshold scheme

Cooperative diversity technique is used for achieving high data rate and low BER with low transmit power. The paper proposes a new scheme for selection of first relay having SNR above a predefined threshold level in cooperative diversity network, based on geometric distribution. Closed form expression for outage probability is derived for independent and identically distributed channels with decode and forward protocol. Numerical results show that the proposed scheme not only minimizes resource requirements but also improves the overall outage probability over previously proposed schemes for cooperative diversity network.

The queuing delay analysis at relay node based on cooperative GBN-ARQ protocols

In this paper, a single relay cooperative diversity network model is proposed, analyzing queuing delay of the packets at relay node. Using dynamic radio link adaptation in wireless networks, based on the character of GBN-ARQ protocol and the queuing theory, the paper solves the problem that packets wait to transmit at relay, and presents a relay node to destination node queuing analysis model for GBN-ARQ protocol with fixed feedback delay. The paper establishes Markov model of packet transmission, and the delay statistics at relay node are figured out by using matrix geometric methods.

Quasi-Orthogonal Space-Frequency Coding in Non-Coherent Cooperative Broadband Networks

So far, complex valued orthogonal codes have been used differentially in cooperative broadband networks. These codes however achieve less than unitary code rate when utilized in cooperative networks with more than two relays. Therefore, the main challenge is how to construct unitary rate codes for non-coherent cooperative broadband networks with more than two relays while exploiting the achievable spatial and frequency diversity. In this paper, we extend full rate quasi-orthogonal codes to differential cooperative broadband networks where channel information is unavailable. From this, we propose a generalized differential distributed quasi-orthogonal space-frequency coding (DQSFC) protocol for cooperative broadband networks. Our proposed scheme is able to achieve full rate, and full spatial and frequency diversity in cooperative networks with any number of relays. Through pairwise error probability analysis we show that the diversity gain of our scheme can be improved by appropriate code construction and sub-carrier allocation. Based on this, we derive sufficient conditions for the proposed code structure at the source node and relay nodes to achieve full spatial and frequency diversity.

Performance Study and Optimization of Cooperative Diversity Networks with Co-Channel Interference

In this paper, we investigate the effect of co-channel interference on the performance of cooperative diversity networks with amplify-and-forward (AF) relaying. We consider both conventional and opportunistic relaying. First, we obtain a tight upper-bound for the equivalent signal-to-interference-plus-noise ratio (SINR) at the destination. Subsequently, the cumulative distribution function (CDF), probability density function (PDF) and moment generating function (MGF) of the effective SINR are determined based on the upper-bound. Expressions for the error probabilities in both conventional and opportunistic relaying are derived utilizing the statistical characterization of the effective SINR. We also derive an approximate PDF of the equivalent instantaneous SINR at the destination. This leads to a simple and general asymptotic error probability expression which facilitates better insight into the effect of different system parameters on the error probability. Furthermore, we investigate the problem of optimum resource allocation in the network aiming at improving performance in the presence of resource constraints. We present numerical results that illustrate the excellent match between the analytical results and the simulation results, and the performance enhancement resulting from the proposed optimal resource allocation.

Energy Detection in Multihop Cooperative Diversity Networks: An Analytical Study

This work presents a study of detection performance of energy detector in relay-based multihop cooperative diversity networks operating over independent Rayleigh fading channels. In particular, upper bound average detection probability expressions are obtained for three scenarios: (i) multihop cooperative relay communication; (ii) multi-hop cooperative relay communication with direct link and maximum ratio combiner (MRC) at destination; and (iii) multi-hop cooperative relay communication with direct link and selection combiner (SC) at destination. Classical method of performance evaluation based on probability density function (PDF) of received signal-to-noise ratio (SNR) is used. Furthermore, an alternative series form representation of generalized Marcum- Q function is employed in order to simplify the ensuing mathematical derivations. Because the obtained detection probability expressions are in the form of infinite summation series, their respective truncation error bounds are also derived. In the end, analyses are validated with the help of simulations and several observations regarding the impact of different parameters on detector's performance are outlined.

Relay Selection of Cooperative Diversity Networks With Interference-Limited Destination

We study relay selection in both decode-and-forward (DF)-based and amplify-and-forward (AF)-based cooperative diversity networks consisting of a source, multiple relays, and a destination in the presence of multiple interferers, where each terminal has a single antenna and operates in half-duplex mode. In the network, it is assumed that the multiple interferers locate near the destination and far away from relays; thus, only the destination receives interfering signals, which is referred to as the interference-limited destination. Specifically, we first propose relay selection to maximize the mutual information on cooperative networks with the interference-limited destination. Then, for relay selection of DF-based networks, we derive the exact outage probability. Finally, for relay selection of AF-based networks, we derive the exact outage probability in integral form and its closed-form lower bound.

Performance of Incremental AF Relaying Cooperative Networks with the nth Best Relay over Rayleigh Fading Channels

Cooperative diversity networks have recently been proposed as a promising technology to improve performance over fading channels. In this paper, we consider incremental amplify-and-forward (AF) cooperative diversity networks which employ the N th best relay when the best relay is unavailable due to issues such as scheduling or load balancing. The end-to-end performance is analyzed over independent and identical (i.i.d.) and nonidentical (i.n.d.) Rayleigh fading channels. Closed form expressions for the bit error rate and channel capacity are derived, and results are presented to illustrate the performance. According to the analysis, The incremental AF strategy can reduce BER greatly when comparing to the conventional direct communication without cooperative, although it can not get the capacity of conventional direct communication, which is with the power as the total power of soure and N th best relay node in AF cooperative network. The incremental AF strategy with N th best relay can improve the capacity in high SNR region comparing to the complete cooperative with N th best relay when BER can be accepted by setting different threshold for SNR of the direct link between source node S and destination node D . The incremental N th best relay cooperative protocol can be useful when considering improving the error rate and bandwidth efficiency at the same time comparing to the conventional direct system and complete cooperative

BER analysis and power allocation for cooperative diversity networks with distributed Alamouti code

In this paper, we consider the distributed Alamouti code for a cooperative diversity network consisting of a source, a non-regenerative relay, and a destination. While in the first time phase, the source radiates signals to both relay and destination; in the second time phase, the source and the relay cooperatively send signals to the destination by using an Alamouti code. Considering the amplify-and-forward protocol and independent Rayleigh fading, we first derive the exact average bit error rate performance in a single integral expression so that the system performance can be numerically evaluated. Then, based on a new approximation method of the Marcum Q-function, we also give a tight upper bound for the system performance with a summation of a number of series components. We demonstrate through simulation that, in various operation scenarios with different channel quality and types of modulation, the results of the exact bit error rate expression accurately matches the simulation results, and the bound is tighter and more robust than existing approximation methods. Finally, we show that the analytic work also provides a method for the optimal allocation of power between the source and the relay in the second time phase. Copyright © 2013 John Wiley & Sons, Ltd.

Detection for an AF Cooperative Diversity Network in the Presence of Interference

We consider an amplify-and-forward (AF) cooperative diversity network consisting of one source, multiple relays, one destination, and multiple interferers. It is assumed that only partial channel information of the interferers is known at the system. For this scenario, we derive an optimum/suboptimum detection rule. Furthermore, we propose an optimum relay power allocation scheme to maximize the instantaneous signal-to-interference-plus-noise-ratio (SINR). An exact and closed-form instantaneous BER expression is also presented. Numerical results demonstrate that the proposed scheme considerably outperforms the existing schemes.

Regenerative Cooperative Diversity Networks With Co-channel Interference: Performance Analysis and Optimal Energy Allocation

A study of the effects of co-channel interference on a multirelay system with decode-and-forward (DF) protocol is presented. Orthogonal relaying is considered, and all relays that correctly decode the message in the broadcasting phase participate in the adaptive relaying phase. First, the effective signal-to-interference-plus-noise ratio (SINR) at the receiver is derived. Then, considering outage as the performance metric, we obtain exact closed-form expression for the outage probability. Simple and general asymptotic expressions for the outage probability, which explicitly show the coding and the diversity gains, are also derived and discussed. Furthermore, we present optimal energy-allocation schemes for minimizing outage under different resource constraints. Monte Carlo simulations are further provided to confirm the analytical results and illustrate the outage performance for different interference conditions and optimization schemes.

On the cumulative distribution function of the sum and harmonic mean of two α−μ random variables with applications

The sum and harmonic mean of random variables (RVs) appear frequently in performance evaluation studies of wireless communications systems. In particular, the sum appears in the performance evaluation of maximal ratio combining (MRC) and equal gain combining (EGC) diversity receivers whereas the harmonic mean is encountered in performance evaluation studies of cooperative diversity networks with non-regenerative relays. In this study, the authors propose highly accurate finite-series approximations for the cumulative distribution function (CDF) of the sum and harmonic mean of two α−μ distributed RVs. The proposed approximations do not require neither a look-up table nor solving complicated transcendental equations, as is typically the case in the literature. The results reveal that the proposed approximations are very accurate over the typical range of interest when compared with the exact CDFs computed using numerical integration methods.

Impact of Imperfect Channel Estimation and Co-Channel Interference on Regenerative Cooperative Networks

In this work, we analyze the performance of decode-and-forward cooperative diversity networks with imperfect channel estimation and co-channel interference. Orthogonal relaying is considered and all relays that correctly decode the source message in the broadcasting phase participate in the relaying phase. First, the output signal-to-interference-plus-noise ratio (SINR) at the destination is derived. Then, considering error and outage as the performance metrics, we obtain exact closed-form expressions for the error and outage probabilities. Simple and general asymptotic expression for the error probability, which explicitly shows the coding and the diversity gains, is also derived and discussed.

Outage Probability Analysis of Cooperative Diversity Networks Over Weibull and Weibull-Lognormal Channels

This paper presents the analysis of outage probability for a cooperative diversity wireless network using amplify-and-forward relays over independent non-identical distributed Weibull and Weibull-lognormal fading channels for single as well as multiple relays. To reach that end, a closed-from expression for the moment-generating function of the total signal-to-noise-ratio (SNR) at the destination is derived in terms of the tabulated Meijer's G-function. Since it is hard to determine the exact probability distribution function of the SNR, a tight lower bound approximation is proposed. Simulation results are presented that show that the outage probability lower bound tends to be tight at high SNR values thus verifying the analytical results. The results also show the potential gain of relaying on the outage probability.