Non-identical Rayleigh Fading Channels Research Articles

Analyzing device-to-device communication performance with amplify-and-forward relaying amid co-channel interference

<p>Currently, the pressing issue of spectrum limitation, driven by the increasing demand for wireless communication services, has led to the challenge of co-channel interference (CCI) due to the reuse of frequencies in wireless networks. To address this, non-orthogonal multiple access (NOMA) has emerged as a solution. This report conducts a thorough evaluation of NOMA’s system performance over independent and non-identical Rayleigh fading channels in device-to-device (D2D) communications networks, where CCI is significant. The analysis includes examining the probability density function (PDF) and cumulative distribution function (CDF) of the upper SINR threshold. Communication channels are defined as independent and non-identical Rayleigh fading channels, and probability expressions are formulated to assess system failure likelihood for two users. Additionally, Monte-Carlo simulations are conducted to validate the proposed theoretical mathematical expressions.</p>

Security-Reliability Trade-Offs for Satellite-Terrestrial Relay Networks with a Friendly Jammer and Imperfect CSI

This paper proposes and analyzes the reliability and security trade-off for a satellite-terrestrial (SatTer) relay system. Herein, a satellite sends confidential information to multiple ground users (GUs) with the help of a relay base station (BS) in the presence of multiple eavesdroppers trying to wiretap the information. In particular, a friendly jammer is deployed near the relay BS to improve secure transmissions. Moreover, the non-identical Rayleigh fading channels and imperfect channel state information (CSI) are adopted for a general system model. Then, we consider both amplify-and-forward (AF) and decode-and-forward (DF) relaying strategies to give a full picture of the benefits of each method. In this context, we derive the closed-form expressions of the outage probability (OP) and intercept probability (IP) corresponding to AF- and DF-based relaying schemes, which is a high challenge and has not been investigated before. Then, Monte-Carlo simulations are conducted to evaluate the correctness of the mathematical analysis and the effectiveness of the proposed methods. Furthermore, the security and reliability trade-off of the SatTer system and the influences of various system parameters (e.g., satellite's transmit power, channel estimation errors, relay's transmit power, fading severity parameter, the average power of light-of-sight, and satellite's multi-path components) on the system performance are shown.

Performance evaluation of cognitive relay networks for end user mobile over mixed realistic channels

Cognitive relay network is a spectrum dynamic paradigm that exploits the unused portions of the licensed spectrum. This is based on merging both cooperative relaying techniques and cognitive radio network to achieve spectrum efficiency and enhance the overall system performance. In this paper, the presence of mobile users at the destination node is considered. Here, the end users can navigate at relatively fast vehicular velocities causing dynamic multipath fading and high Doppler shift. which can be fairly modelled using Nakagami- m $m\;$ fading channel (i.e. m < 1 $\;m < 1$ ). In a spectrum scarcity environment, a secondary user must deploy an optimal power allocation policy to get higher transmission rates while the overall interference affecting the primary user (PU) is kept below a certain threshold value. In particular, the outage probability (OP) performance is studied over the mixed Rayleigh and Nakagami-m fading channels for different scenarios and a tight closed-form expressions are derived for the system OP of underlay dual-hop cognitive relay networks with a single amplifiy-and-forward (AF) relay with and without the use of the direct link transmission and selection diversity at the destination with interference power constraints for the primary network over independent and non-identical (i.n.i.d) Rayleigh and Nakagami-m fading channels when m < 1 $m < 1$ based on the statistical characteristics of signal-to-noise ratio. Numerical results are presented to evaluate the impact of the fading parameter, m, the maximum aggregated intrusion constraint, and the locations of the primary users (PUs) on different channel scenarios at high vehicular speeds. Monte Carlo simulations are presented to verify and validate analytical results.

Performance analysis of SWIPT‐assisted adaptive NOMA/OMA system with hardware impairments and imperfect CSI

AbstractThis paper investigates the effect of hardware impairments (HIs) and imperfect channel state information (ICSI) on a SWIPT‐assisted adaptive nonorthogonal multiple access (NOMA)/orthogonal multiple access (OMA) system over independent and nonidentical Rayleigh fading channels. In the NOMA mode, the energy‐constrained near users act as a relay to improve the performance for the far users. The OMA transmission mode is adopted to avoid a complete outage when NOMA is infeasible. The best user selection scheme is considered to maximize the energy harvested and avoid error propagation. To characterize the performance of the proposed systems, closed‐form and asymptotic expressions of the outage probability for both near and far users are studied. Moreover, exact and approximate expressions of the ergodic rate for near and far users are investigated. Simulation results are provided to verify our theoretical analysis and confirm the superiority of the proposed NOMA/OMA scheme in comparison with the conventional NOMA and OMA protocol with/without HIs and ICSI.

Outage Performance Comparison of Dual-Hop Full Duplex Underlay Cognitive Relay Networks

This paper investigates the outage probability performance of the secondary user (SU) in an underlay dual-hop, decode and forward (DF), full duplex cognitive relay network (FDCRN). First, we develop analytical closed form expression for outage probability and throughput for a dual-hop DF FDCRN by making use of the direct link signal as a useful signal to improve the signal-to-noise ratio at the secondary destination. Next, we compare the outage and throughput performance of various FDCRN and half duplex cognitive relay network (HDCRN) protocols, namely, (1) dual-hop DF FDCRN with direct link treated as interference, (2) dual-hop DF FDCRN with direct link signal cancelled by employing recursive backward interference cancellation technique, and (3) dual-hop DF HDCRN that employs maximal ratio combining at SD. Closed form expressions for the outage probabilities experienced in the secondary network are derived by taking into account the residual self-interference at the full duplex relay node, in independent non-identical Rayleigh fading channels. The analysis considers the maximum transmit power constraint of the individual secondary nodes and the tolerable interference threshold power constraint of the primary destination as well. The results demonstrate that the outage performance of the SU gets improved significantly when the direct link is exploited at the secondary destination. Further, we evaluate the impact of relay location and the power allocation ratio among secondary source and relay on the outage probability. The analytical results are validated by extensive Monte-Carlo simulations.

Joint Impact of RF Hardware Impairments and Channel Estimation Errors in Spectrum Sharing Multiple-Relay Networks

In this paper, we investigate the performance of a spectrum sharing decode-and-forward multiple-relay network (SSDMN) with direct link under the joint impact of two practical and detrimental imperfections, called transceiver hardware impairments (HIs) and channel estimation errors (CEEs). Here, we consider the hardware distortions induced by all the non-ideal secondary nodes and residual interferences originating from imperfect channel estimations. By taking these imperfections into account, we derive an exact closed-form expression for the outage probability of the considered SSDMN employing selection cooperation over independent and non-identical Rayleigh fading channels. We identify three important ceiling effects invoked by HIs, namely relay cooperation ceiling (RCC), direct link ceiling (DLC), and overall system ceiling. Specifically, we highlight the impact of these prevailing effects on the system’s performance and provide some useful insights about the tolerable level of HIs while designing the practical systems for a given rate requirement. We also illustrate that a potential direct link and a relaying link can, respectively, partially compensate for the incurred performance losses due to RCC and DLC effects. Moreover, we investigate the asymptotic behavior of outage probability to highlight the impact of HIs and CEEs on the achievable diversity and coding gains.

Optimization of decode-and-forward multihop full duplex relay networks under residual-self-interference

This paper investigates various optimization schemes for improving the performance of multi-hop full duplex (FD) decode and forward (DF) based relay networks with recursive backward interference cancellation (RBIC). We provide analytical expression for the outage probability of multi-hop FDR network by taking into account the residual self interference (RSI) at the full duplex relay (FDR) nodes, in independent non-identical Rayleigh fading channels. We then investigate optimal power allocation (OPA), optimal relay location (ORL) and the joint optimization of transmit power and relay location that minimizes the outage probability. We prove the convexity of all the above problems and determine the OPA vector by using the geometric programming while the ORL vector is obtained by applying Karush–Kuhn–Tucker (KKT) conditions. To solve the joint optimization problem, we devise an iterative, fast converging algorithm based on sequential geometric programming. Extensive numerical and simulation results demonstrate that both OPA and ORL can improve the outage probability of FDR system; however joint optimization leads to superior performance as compared to OPA, ORL and un-optimized cases. Secondly we consider the end-to-end rate maximization problem with maximum power constraint at the nodes. Since the optimization problem is nonconvex, we devise an iterative algorithm based on sequential convex programming to find the OPA vector. Results establish that OPA can lead to very large increase in the end-to-end rate as compared to uniform power allocation.

Comparative throughput study of energy harvesting CR network with adaptive hybrid relay

In this paper, we have analyzed the throughput performance of spectrum sharing cognitive relay network incorporated with energy harvesting source and relay in presence of non-identical Rayleigh fading channel. In our model, multiple primary users are considered and their interference signal is used by source and relays to harvest energy. The relays follow Adaptive Hybrid (AHR) Protocol to forward source signal to destination. We use time switching relaying scheme to harvest secondary source as well as secondary relay. Throughput performance of the network is compared considering (a) delay-sensitive and (b) delay-tolerant transmission modes. It is observed that AHR protocol outperforms AF and DF protocols in both transmission modes. The effect of increasing the primary network operating power on system throughput is shown as a function of $$\alpha$$ . The impact of number of relays and number of primary users on secondary throughput performance is also studied. A comparison for various combinations of number of relays and number of primary users is also shown.

Cooperative spectrum sharing with multi-antenna based adaptive hybrid relay in presence of multiple primary users

Performance analysis of cooperative spectrum sharing network using multi-antenna based Adaptive Hybrid Relay (AHR) scheme in presence of multiple primary users under non-identical Rayleigh fading channel has been studied in this paper. An Adaptive Hybrid Relay equipped with multiple antennas at the input employs selection combining (SC) on the signals received from secondary user source (S) via multiple receiving antennas at the input and forwards the received signal to secondary user destination (D). The outage probability has been evaluated at the secondary destination where best relay selection (BRS) scheme is used. The comparison between outage performances of cooperative spectrum sharing for Amplify-and-Forward (AF), Decode-and-Forward (DF) and Adaptive Hybrid Relay (AHR) scheme is also presented. The effects of number of relay antennas (L), number of relays (K) and number of primary users (M) on the system performance have also been studied. It is seen that the outage performance improves considerably with increase in number of primary users (PUs). It is also observed that increase in number of primary users compensate the negative impact of high channel rate (R). A trade-off between number of relay and number of antenna at each relay is also shown.

Capacity and Fairness of Quality-Based Channel State Feedback Scheme for Wireless Multicast Systems in Non-Identical Fading Channels

In multi-group multicast systems with greedy scheduling and quality-based channel state information feedback (QCF), a novel scheme to determine group-specific QCF thresholds is proposed for non-identical Rayleigh fading channels. Unlike the conventional schemes using a single common QCF threshold, the proposed scheme using group-specific QCF thresholds provides a trade-off between system capacity and fairness. Hence, it can enhance the fairness for multicast groups at the cost of system capacity. We analyze the capacity, fairness, and feedback overhead of the multi-group multicast systems with greedy scheduling and group-specific QCF to validate the effectiveness of the proposed scheme.

Performance Improvement of Two-Hop Relay System Using Polarization Diversity

With growing demands for mobile data, providing reliable communication with high quality of service has become a critical issue. Wireless relaying has been recognized as an effective solution to enhance system coverage, data rate, reliability and energy efficiency by introducing additional network node-relay. However, complex wireless channel characteristics, such as fading, path loss, noise and interference limits the performance of such systems in a manner that it is dominated by the worst channel. That is why additional techniques are necessary to be implemented in order to improve the characteristics of this bottleneck link, and performance of relay system as whole. Multi-antenna relaying has emerged as a promising technique to overcome bottleneck effect in relay system and provide performance enhancements, but the small size of network nodes limits their use at wireless terminals. In this paper we propose the implementation of polarization diversity, where one compact dual-polarized antenna is used instead of two adequately separated antennas. Maximal ratio combining of diversity signals in amplify-and-forward relaying systems applying variable gain is analysed. Mixed Rayleigh/Ricean fading environment is assumed, while two diversity signals are described as two correlated and non-identical Rayleigh fading channels. Novel analytical model for determining the performance of the analysed relay system expressed through the system’s outage and bit error rate is derived. Excellent match between Monte-Carlo simulations and numerical results confirms the validity of the proposed analytical model. Furthermore, the presented results illustrate the effect of various channels parameters on the system performance, such as Ricean K factor, average signal to noise ratios, diversity signals’ correlation and cross-polar discrimination. For a given performance requirements, the proposed solution can significantly improve relay system performance.

Outage Analysis of Partial Relay Selection Schemes with Feedback Delay and Channel Estimation Errors in Nonidentical Rayleigh Fading Channels

This paper investigates the impact of the channel estimation error and outdated channel state information (CSI) on the outage performances of partial relay selection (PRS) and efficient partial relay selection (EPRS). Considering imperfect channel estimation and outdated CSI with decode-and-forward (DF) relaying strategy, closed-form expressions for exact outage probabilities and asymptotic outage probabilities for PRS and EPRS are provided assuming independent and nonidentically distributed Rayleigh fading channels. Numerical investigations verify the analytical expression for outage probability and show how much performance is degraded by the channel estimation errors and the feedback delay that causes the outdated CSI.

Performance Analysis of Opportunistic Scheduling in Dual-Hop Multiuser Underlay Cognitive Network in the Presence of Cochannel Interference

In this paper, the performance of a dual-hop multiuser underlay cognitive network is thoroughly investigated by using a decode-and-forward (DF) protocol at the relay node and employing opportunistic scheduling at the destination users. A practical scenario where cochannel interference signals are present in the system is considered for the investigation. Considering that transmissions are performed over nonidentical Rayleigh fading channels, first, the exact signal-to-interference-plus-noise ratio (SINR) of the network is formulated. Then, the exact equivalent cumulative distribution function (cdf) and the outage probability of the system SINR are derived. An efficient tight approximation is proposed for the per-hop cdfs, and based on this, the closed-form expressions for the error probability and the ergodic capacity are derived. Furthermore, an asymptotic expression for the cdf of the instantaneous SINR is derived, and a simple and general asymptotic expression for the error probability is presented and discussed. Moreover, adaptive power allocation under the total-transmit-power constraint is studied to minimize the asymptotic average error probability. As expected, the results show that optimum power allocation improves the system performance compared with uniform power allocation. Finally, the theoretical analysis is validated by presenting various numerical results and Monte Carlo simulations.

Influence of Channel Information Imperfection on Outage Probability of Cooperative Cognitive Networks with Partial Relay Selection

Influence of channel information imperfection on outage probability of cooperative cognitive networks with partial relay selection over independent and non-identical Rayleigh fading channels and under peak transmit power constraint and interference power constraint is thoroughly analyzed in this paper. To eliminate time-consuming simulations, we propose both exact and asymptotic outage probability expressions in closed-form, which facilitate in quickly evaluating this influence in key operation parameters and acquiring useful insights into performance limits. For comparison, we also derive similar expressions for two benchmark communications schemes in cognitive radio networks, namely direct transmission and dual-hop communications with partial relay selection. Various results show considerable system performance deterioration and performance saturation owing to channel information imperfection, and superiority of cooperative communications to direct transmission and dual-hop communications.

Outage Probability of Cognitive Selective DF Relay Networks with Multiple Primary Nodes and Heterogenous Non-Identical Constraints

Outage probability analysis of cognitive selective DF relay networks with selection combining technique taking into account all the following issues is important: multiple SU relays, multiple PUs, non-identical independent Rayleigh fading channels, non-identical interference power limits of PUs, non-identical maximum transmission power limits of SUs, and non-identical noise powers in signals. However, no existing works solve this task exactly. In this paper, to overcome the complexity in analyzing such non-identical-parameter networks directly, we conduct the analysis in two steps indirectly. In the first step, we obtain outage probability expressions of identical-parameter networks. Then in the second step, we propose a method for transforming a non-identical-parameter network into a new identical-parameter network, meanwhile guaranteeing that the distributions of end-to-end signal to noise ratio of the two networks before and after the transformation are identical. Thus the outage probability of the identical-parameter network can be regarded as outage probability of the corresponding non-identical-parameter network. Numerical simulations validate our analysis results and confirm the feasibility of the two-step indirect analysis approach.

Outage Performance Analysis of Relay Selection Schemes in Wireless Energy Harvesting Cooperative Networks over Non-Identical Rayleigh Fading Channels

In this paper, we study relay selection in decode-and-forward wireless energy harvesting cooperative networks. In contrast to conventional cooperative networks, the relays harvest energy from the source’s radio-frequency radiation and then use that energy to forward the source information. Considering power splitting receiver architecture used at relays to harvest energy, we are concerned with the performance of two popular relay selection schemes, namely, partial relay selection (PRS) scheme and optimal relay selection (ORS) scheme. In particular, we analyze the system performance in terms of outage probability (OP) over independent and non-identical (i.n.i.d.) Rayleigh fading channels. We derive the closed-form approximations for the system outage probabilities of both schemes and validate the analysis by the Monte-Carlo simulation. The numerical results provide comprehensive performance comparison between the PRS and ORS schemes and reveal the effect of wireless energy harvesting on the outage performances of both schemes. Additionally, we also show the advantages and drawbacks of the wireless energy harvesting cooperative networks and compare to the conventional cooperative networks.

On the performance of cooperative cognitive networks with proactive relay selection

This paper provides a general outage analysis framework for cooperative cognitive networks with proactive relay selection over non-identical Rayleigh fading channels and under both maximum transmit power and interference power constraints. We firstly propose an exact closed-form outage probability expression, which is then exploited for determining the diversity order and coding gain for proactive relay selection scenarios as well as deriving system performance limits at either large maximum transmit power or large maximum interference power. The derived performance metrics bring several insights into system performance behavior without the need of time-consuming Monte-Carlo simulations. Various results confirm the validity of the proposed derivations and show that cooperative cognitive networks with proactive relay selection incur performance saturation and their performance depends considerably on the number of involved relays. In addition, cooperative cognitive networks are significantly better than dual-hop counterparts without any cost of system resources.

Outage analysis in cooperative cognitive networks with opportunistic relay selection under imperfect channel information

This paper proposes exact and limit outage probability expressions for thoroughly evaluating the performance of cooperative cognitive networks with opportunistic relay selection under imperfect channel information, independent and non-identical (i.n.i.) Rayleigh fading channels, maximum transmit power constraint, and interference power constraint. The proposed derivations can be straightforwardly extended to corresponding analysis in dual-hop cognitive networks with opportunistic relay selection to investigate how much performance gain can be achieved from using the direct channel between the source and the destination in relaying communications. Numerous results illustrate significant outage performance degradation and performance saturation due to channel information imperfection but the degradation and saturation level can be remedied by increasing the number of relays. Also, the channel direct brings a considerable performance improvement without any additional expense of system resources such as power and bandwidth. Moreover, channel information imperfection can cause interference power at primary users to exceed a pre-defined level, deteriorating the quality of service of primary users.

Effect of mutual interference and channel estimation error on outage performance of reactive relay selection in unlicensed systems

This study addresses the effects of channel estimation error and mutual interference between licensed and unlicensed systems on outage performance of reactive relay selection in unlicensed systems over independent non-identical (i.n.i) Rayleigh fading channels and under both the maximum transmit power constraint and primary outage constraint. Toward this end, power allocation for unlicensed users is first recommended to satisfy both constraints and account for channel estimation error and mutual interference. Then, we derive an exact closed-form outage probability representation for unlicensed systems to quickly evaluate this effect in key operation parameters. Various results corroborate the derived expressions and provide useful insights into system performance.

Bit error probability of decode‐and‐forward relaying with efficient partial relay selection in non‐identical Rayleigh fading channels

Efficient partial relay selection (EPRS) is an advanced technique to improve the performance of partial relay selection (PRS) at the cost of a small additional feedback overhead. However, EPRS has the worst performance but lower feedback overhead when compared with best relay selection. In this study, the authors present a bit error probability (BEP) analysis of EPRS in decode-and-forward relaying systems over independent and non-identical Rayleigh fading channels, where the direct link between the source and the destination is available. In particular, they provide an exact and closed-form expression of the BEP of M-ary square quadrature amplitude modulation for EPRS. The BEP analysis is verified through simulations. The numerical results show that EPRS significantly outperforms PRS for a large gap between the average channel powers for the first and the second hops except when all the average channel powers for the first hop are smaller than those for the second hop.