Generalized Nakagami-m Fading Channels Research Articles

Performance Evaluation of Reconfigurable Intelligent Surface against Distributed Antenna System at the Cell Edge

In small spaces in which typical cell towers cannot be constructed, distributed antenna systems (DASs) are the preferable approach for increasing network coverage, as they are a superior solution for congested, high-volume areas. However, due to their high cost and complexity in backhaul routing, reconfigurable intelligent surfaces (RISs) are a promising solution to overcome the major drawbacks of DAS systems while improving network coverage. Thus, this work investigated a correlation of execution in an RIS-aided system cell framework and DAS-aided system cell framework where a simple and precise structure for the performance measurement of area spectral efficiency (ASE) and energy efficiency (EE) under realistic channel presumptions was introduced. The analysis started with the downlink ergodic capacity with regards to the RIS framework and DAS framework under a generalized Nakagami-m fading channel with the presence of path-loss attenuation and interference from co-channel base stations (BSs), and was simplified further by utilizing a moment-generating function (MGF)-based approach. From the computed expression, the effects of traffic activity, EE and ASE were derived and analyzed for both systems in the presence of co-channel interference. The results were then verified by comparing them with Monte Carlo simulations, and the findings show that the two outcomes generally match. Based on these, it is demonstrated that the ASE performance of the RIS-assisted system in various traffic activity conditions outperforms the DAS-aided system; however, in high signal-to-noise (SNR) regions with full traffic activity, the ASEs are highest for both systems; by only 0.005 bits/s/Hz/km2.

On the secrecy outage analysis of underlay cognitive radio systems with buffer‐aided relaying under Nakagami‐ m channels

In this work, the physical layer security performance of an underlay cognitive buffer-aided relay network over the general Nakagami-m fading channel model is addressed, where a primary source communicates with a destination via a decode-and-forward relay node in the presence of an eavesdropper and a secondary communication system. The relay is equipped with a finite-size storage equipment or buffer which can store the sequence of received data packets from source and forward it immediately or subsequently in an adequate time-slot. In this way, the buffer relay enables to adopt a link selection scheme in order to detect the best available link, (i.e. the one with higher secrecy rate) among the available data at source or at the relay buffer. The closed-form expression for the secrecy outage probability (SOP), which is a widely adopted performance metric in the considered scenario, is also derived. Numerical results confirm the accuracy of the derived closed-form analytic expression for SOP and indicates the interaction between secrecy performance and the Nakagami channel parameter m. In particular, it is shown that the SOP experiences a significant drop as the Nakagami channel parameter increases for a predefined target secrecy rate.

VFD-NOMA Under Imperfect SIC and Residual Inter-Relay Interference Over Generalized Nakagami-m Fading Channels

Full-duplex (FD) non-orthogonal multiple access (NOMA) communications is a promising technology to enhance spectral efficiency in future wireless access network. However, self-interference cancellation in FD is still a major challenge and thus concept of virtual full-duplex (VFD) relaying has evolved recently. In this letter, we investigate the impact of imperfect successive interference cancellation and residual inter-relay interference on a decode-and-forward relaying based VFD-NOMA. Framework for outage probability (OP), asymptotic OP, and ergodic rate expressions is developed for the considered system model over generalized Nakagami-m fading channels. Accuracy of the derived closed-form expressions is verified through rigorous Monte-Carlo simulations.

Multiuser Full-Duplex IoT Networks With Wireless-Powered Relaying: Performance Analysis and Energy Efficiency Optimization

This paper considers an Internet-of-Things (IoT) network where a multi-antenna access point (AP) and several single-antenna IoT devices (IoDs), operating under the full-duplex (FD) mode, communicate with each other bidirectionally through the help of a wireless-powered FD relay. In particular, the power splitting (PS) protocol is adopted at the amplify-and-forward (AF) relay to implement a simultaneous wireless information and power transfer (SWIPT) receiver. For such a multiuser FD-IoT network assisted by a wireless-powered two-way relay, we derive exact overall outage probability (OOP) expressions and tight closed-form expressions for the ergodic sum rate (ESR) under generalized Nakagami-m fading channels. Furthermore, aiming to maximize the energy efficiency (EE), we obtain optimal power allocation (OPA) under the total power and rate threshold constraints. Finally, extensive numerical and simulation results are presented to corroborate our analytical findings.

On Impact of Imperfect CSI Over Hexagonal QAM for TAS/MRC-MIMO Cooperative Relay Network

In this letter, we investigate the effect of imperfect channel state information (CSI) on quadrature amplitude modulation (QAM) schemes for a multi-input and multi-output (MIMO) variable gain non-regenerative cooperative network over the generalized Nakagami-m fading channel. Energy-efficient and standardized transmit antenna selection strategy is employed, to evaluate the system performance by considering the antenna link, which maximizes the received signal power. Framework for the upper-bound outage probability (OP), asymptotic OP and the average symbol error rate for hexagonal QAM, rectangular QAM, and 32-cross QAM are provided. Useful insights are drawn from comparative ASER analysis of various QAM schemes by considering the impact of both the fading parameter and the imperfect CSI for MIMO channels. Finally, the derived analytical results are validated through Monte-Carlo simulations.

Outage-Optimal Power and Time Allocation for Rate-Aware Two-Way Relaying With a Decode-and-Forward Protocol

We consider a two-way relaying network, where two communicating nodes exchange their data with the help of a decode-and-forward (DF) relay. For the network, optimization of power allocation (PA) and time allocation (TA) is explored to minimize the system outage probability in supporting asymmetric data rates. We tackle the joint optimization of PA and TA with full channel state information (CSI) by dividing the problem into two convex optimization problems, which find the optimal PA in a closed form for a given TA and then find the optimal TA with the binary search method. To lower the complexity of the joint optimization, we devise suboptimal schemes, i.e., one selecting the TA value adaptively from two predetermined TA values and the other employing a single fixed TA value. We analyze the outage probabilities and asymptotic behaviors of the proposed PA-TA schemes in generalized Nakagami-m fading channels. The results show that PA optimization improves the performance for both symmetric and asymmetric rate transmissions, but TA optimization improves the performance only for the asymmetric rate transmission. In addition, the suboptimal schemes get close to the optimal scheme in the outage performance when two relay channels are asymmetric with unequal fading parameters and an asymmetric relay position.

Fading severity effects on collaborative sensing for opportunistic spectrum access

This paper investigates the performance of collaborative sensing of opportunistic spectrum access in a Nakagami fading channel with non-integer fading parameters. This technique provides an opportunity for secondary users to utilize the unused spectrum bands by primary users (licensees). In particular, we looked at the scenario when the channel between primary and secondary users is a generalized Nakagami-m fading channel. Numerical evaluation of the probability of misdetection in Nakagami fading channel with real value fading parameters is presented. Soft decision combining techniques were considered, namely square law and maximum selection combining. The performance analysis was extended to hard decision combining techniques. The obtained results showed how the spectrum utilization improved significantly when combining techniques are applied. In addition, the results revealed how soft decision combining techniques outperformed hard ones.

Comprehensive Error Analysis of Multi-Antenna Decode-and-Forward Relay in Fading Channels

A comprehensive analytical framework of dual-hop fixed decode-and-forward cooperative networks with multi-antenna relay and distributed spatial diversity is developed over generalized Nakagami-m fading channels. The effect of Rician fading for the relay-destination link has been of special interest. The multi-antenna relay employs selection combining (SC) and the destination adopts distributed SC. Analytical expressions for the cumulative distribution function (CDF) of the end-to-end signal-to-noise ratio (SNR) are derived and used to evaluate the bit error probability (BEP) for coherent and non-coherent binary modulation schemes in a unified manner. Numerical and simulation results are presented to illustrate the impact of the Rician K-factor and Nakagami-m parameter on the end-to-end performance.

A General Upper Bound to Evaluate Packet Error Rate over Quasi-Static Fading Channels

We propose a new analytical approach to evaluate the average packet error rate (PER) of a conventional packet transmission system over a quasi static fading channel, by presenting an integral inequality lemma. The basic idea of the approach is that, given the PER for the AWGN channel as a function of signal-to-noise ratio (SNR), the average PER over Rayleigh fading channel can be generally upper bounded by a quite simple inequality, i.e.,1 - exp(-w <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">o</sub> /γ̅), for both coded and uncoded schemes, where w <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">o</sub> , defined by an integral expression, corresponds exactly to the inversion of coding gain; and this bound is tight in the high SNR region or for long packet systems. We further apply the integral inequality to extend our research to more general Nakagami-m fading channel.

On the relay position selection for the diamond network over Nakagami‐m fading channels

AbstractThe diamond relay channel, or diamond relay network, is a kind of efficient cooperative network in which the source node cooperates with two neighbors. In this paper, we study the impact on the performance of such a network caused by the relays' position for a general Nakagami‐m fading channel, which extends the previous work for a special Rayleigh fading case. In particular, the symmetric scenario for the two relays is investigated but the channel conditions of the two source‐relay‐destination links may have great difference due to the different values of m for the four Nakagami‐m fading channels. We study how to select the position of the two relays and give clear restrictions of their positions based on the requirement of the throughout improvement and network stability. Finally, we show how to find the optimal position to achieve the largest throughput improvement. The numerical results confirm our analysis and the interesting illustrations show much insight on the cooperative neighbor selections. Copyright © 2010 John Wiley &amp; Sons, Ltd.