Mixed THz/FSO Relaying Systems: Statistical Analysis and Performance Evaluation

Wireless communications and power line communications (PLC) are essential components for smart grid communications. This paper analyses the performance of a dual-hop wireless-power line mixed communication setup employing a decode-and-forward relay in terms of analytical average bit error rate (BER), outage probability, and average channel capacity. The Nakagami-m distribution captures the wireless channel fading; whereas the PLC channel gain is characterized by the Log-normal distribution. The additive PLC channel noise is assumed to be Bernoulli-Gaussian distributed. Approximate closed-form expression of the average BER and exact closed-form expression of the outage probability are derived for the considered system. Further, we obtain an approximate closed-form expression of the capacity of the wireless-power line mixed system in terms of the Meijer-G function. It is observed that the system performance deteriorates as the impulsive noise index and the arrival probability of the impulsive component of the PLC additive noise increase.

Cascaded double fading channels: A case of [formula omitted] – [formula omitted] shadowing

In this paper, we analyze the average bit error rate (BER) and outage probability performances of a free-space optical (FSO) system. We used M-ary amplitude shift keying modulation (M-ary ASK) scheme. Lognormal atmospheric turbulence with the effect of pointing errors (PE) and, path loss is employed to model the FSO channel. However, to overcome the degradation in BER performance due to pointing errors, the single-input-multiple-output technique with maximal ratio combining diversity is used. For instance, the average BER for M=2 without using SIMO is 1.944×10−6 at 0 dBm transmitted power, while the average BER for M=2 with using SIMO technique with N=2 become 1.512×10−11 at 0 dBm. The asymptotic expression for average BER and the closed-form expression for outage probability are both driven and tested with and without SIMO.

Physical transceivers have hardware impairments that create distortions which degrade the performance of communication systems. The vast majority of technical contributions in the area of relaying neglect hardware impairments and, thus, assumes ideal hardware. Such approximations make sense in low-rate systems, but can lead to very misleading results when analyzing future high-rate systems. This paper quantifies the impact of hardware impairments on dual-hop relaying, for both amplify-and-forward and decode-and-forward protocols. The outage probability (OP) in these practical scenarios is a function of the effective end-to-end signal-to-noise-and-distortion ratio (SNDR). This paper derives new closed-form expressions for the exact and asymptotic OPs, accounting for hardware impairments at the source, relay, and destination. A similar analysis for the ergodic capacity is also pursued, resulting in new upper bounds. We assume that both hops are subject to independent but non-identically distributed Nakagami-m fading. This paper validates that the performance loss is small at low rates, but otherwise can be very substantial. In particular, it is proved that for high signal-to-noise ratio (SNR), the end-to-end SNDR converges to a deterministic constant, coined the SNDR ceiling, which is inversely proportional to the level of impairments. This stands in contrast to the ideal hardware case in which the end-to-end SNDR grows without bound in the high-SNR regime. Finally, we provide fundamental design guidelines for selecting hardware that satisfies the requirements of a practical relaying system.

The outage probability (OP) and average bit error rate (BER) of wireless digital systems in a Nakagami-m fading environment have been well analyzed in the literature. Most of the analysis considers static wireless terminals in which the received signal power follows a gamma distribution. However, many mobile and ad hoc networks are composed of mobile receiving nodes with random mobility patterns. In this paper, we consider 1-D, 2-D, and 3-D wireless network deployment topologies with the random waypoint (RWP) mobility model. In such systems, the received power does not follow the gamma distribution in the presence of Nakagami-m fading. We derive the probability density function (pdf) and the cumulative distribution function (cdf) of the received signal power for a mobile node. Consequently, the OP and the average BER of general modulation schemes are derived. Moreover, the effect of co-channel interference on the OP is investigated for interference-limited and interference-plus-noise systems. The analysis quantifies the effects of the mobility and propagation environments, which are characterized by the path-loss exponent and Nakagami-m parameter for the desired and interfering signals, on the performance of a mobile receiver.

In this paper, the error performance analysis is performed for the decode-and-forward (DF) based dual hop mixed radio frequency-free space optical (RF-FSO) communication system with a direct RF link. The direct link between the source-destination (S-D) and the link between source-relay (S-R) are Nakagami-m distributed asymmetric radio frequency (RF) links and the R-D link is a free space optical (FSO) link characterized by the path loss, Gamma-Gamma distributed turbulence, and pointing errors. Selection combining diversity scheme is used to evaluate the performance of this dual branch cooperative system. For the considered system, novel closed-form mathematical expressions of cumulative distribution function and probability density function of instantaneous signal-to-noise ratio are derived. Using these, new mathematical expressions are obtained for the outage probability and the average bit error rate (BER) for various modulation techniques. The effects of fading, turbulence, and pointing errors are observed on the outage probability and the BER of the considered system. These performance metrics are also compared with those of a DF based dual hop mixed RF-FSO system without direct link. The improvement in the performance is observed due to the diversity introduced by addition of RF link.

In this paper, a mixture Gamma shadowed (MGS) model is proposed as a unified composite distribution via representing the shadowing impact by an inverse Nakagami- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$m$</tex-math></inline-formula> . The exact expression and the asymptotic behaviour at high average signal-to-noise ratio (SNR) regime of the fundamental statistics of a MGS distribution are derived first. These statistics are then applied to analyze the performance of the wireless communication systems over double shadowed <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\kappa$</tex-math></inline-formula> - <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\mu$</tex-math></inline-formula> fading channels. In particular, the outage probability (OP), average bit error probability (ABEP), average channel capacity (ACC), effective capacity (EC) and average area under the receiver operating characteristics curve (AUC) of energy detection (ED) are provided. The numerical and simulation results as well as a comparison with previous exact works are presented to verify the validation of our analysis.

The channel capacity and probability of outage results for optimum power and rate adaptation (OPRA) and truncated channel inversion with fixed rate (TIFR) schemes over correlated diversity branch obtained so far in literature are applicable only for m ? 1. This paper derived closed-form expressions for the average channel capacity and probability of outage of dual-branch maximal ratio combining (MRC) over correlated Nakagami-0.5 (m < 1) fading channels. This channel capacity and probability of outage are evaluated under OPRA and TIFR schemes. Since, the capacity and probability of outage expressions of dual-branch MRC under OPRA and TIFR schemes contain an infinite series; bounds on the errors resulting from truncating the infinite series have been derived for both average channel capacity and probability of outage. The corresponding expressions for Nakagami-0.5 fading are called expressions under worst fading condition with severe fading. Finally, numerical results are presented, which are then compared to the capacity and probability of outage results that previously published for OPRA and TIFR schemes. It has been observed that OPRA provides improved average channel capacity and probability of outage, as compared to TIFR under worst case of fading. It is also observed that probability of outage under TIFR scheme is not improved adequately than the probability of outage under OPRA even as employing diversity.

ABSTRACTIn this paper, we study key performance measures of dual-branch switch-and-stay combining (SSC) system operating in fading environment. Specifically, analytical expressions for the kth order moment, average signal-to-noise ratio, amount of fading and outage probability are obtained for an SSC system operating over fading channels. Expressions of the average bit error rate (BER) for coherent detection and non-coherent detection were also derived with SSC for various modulation schemes. The BER expressions for the coherent detection case were derived using the moment generating function-based approach. Some of the final expressions are presented in the form of infinite series. Therefore, those series are truncated and upper bounds are derived for truncation errors. Expressions to determine the optimum adaptive switching thresholds are also presented. Corresponding results for Nakagami-q and Nakagami-m fading are derived in this paper as special cases. Numerical results are provided to demonstrate the applications of the new results.

Performance analysis of RIS-assisted V2V communication under multipath interference

The performance of multihop detect‐and‐forward relaying system is analyzed over fluctuating two‐ray fading channels for 28 GHz millimeter wave communications. Exact closed‐form expressions for outage probability and average symbol error rate of various modulation schemes over nonidentically distributed fluctuating two‐ray fading channels have been obtained. The derived expressions are given in terms of the Lauricella hypergeometric functions and . Moreover, the derived expressions also accommodate several others reported results in the literature for two‐wave diffuse power, Rician, Rician shadowed, Nakagami‐m, and Hoyt fading channels. Asymptotic outage probability and average symbol error rate expressions are also derived, which provide useful insights on the factors governing the performance of the considered system. The numerical results have been verified with Monte‐Carlo simulation results.

In this paper, we investigate the transmission probabilities in three cases (depending only on the legitimate receiver, depending only the eavesdropper, and depending on both legitimate receiver and eavesdropper) in quantum key distribution (QKD) systems over free-space optical links. To be more realistic, we consider a generalized pointing error scenario, where the azimuth and elevation pointing error angles caused by stochastic jitters and vibrations in the legitimate receiver platform are independently distributed according to a non-identical normal distribution. Taking these assumptions into account, we derive approximate expressions of transmission probabilities by using the Gaussian quadrature method. To simplify the expressions and get some physical insights, some asymptotic analysis on the transmission probabilities is presented based on asymptotic expression for the generalized Marcum Q-function when the telescope gain at the legitimate receiver approaches to infinity. Moreover, from the asymptotic expression for the generalized Marcum Q-function, the asymptotic outage probability over Beckmann fading channels (a general channel model including Rayleigh, Rice, and Hoyt fading channels) can be also easily derived when the average signal-to-noise ratio is sufficiently large, which shows the diversity order and array gain.

In this paper, switch-and-stay combining (SSC) is considered in two-way relay systems with amplify-and-forward (AF) relays, among which one is activated to assist the information exchange between two sources. We assume that the two-way relay system operates in the analog network coding (ANC) protocol where the communication can only be achieved through the active relay without the direct link. The outage probability and the average bit error rate (BER) for Rayleigh fading channels are studied. In particular, we derive closed-form lower bounds for the outage probability and the average BER, which is tight for different fading conditions. Moreover, we present asymptotic analysis for both the outage probability and the average BER at high signal-to-noise ratio (SNR) region. It is shown that SSC can achieve the full diversity order in two-way relay systems with proper switching thresholds. Numerical and simulation results are also provided to verify the theoretical study.

This paper studies an Internet-of-Things (IoT) network employing a reconfigurable intelligent surface (RIS) over generalized fading channels. Inspired by the promising potential of RIS-based transmission, we investigate a RIS-enabled IoT network with the source node employing a RIS-based access point. The system is modelled with reference to a receiver-transmitter pair and the Fisher-Snedecor F model is adopted to analyse the composite fading and shadowing channel. Closed-form expressions are derived for the system with regards to the average capacity, average bit error rate (BER) and outage probability. Monte-Carlo simulations are provided throughout to validate the results. The results investigated and reported in this study extend early results reported in the emerging literature on RIS-enabled technologies and provides a framework for the evaluation of a basic RIS-enabled IoT network over the most common multipath fading channels. The results indicate the clear benefit of employing a RIS-enabled access point, as well as the versatility of the derived expressions in analysing the effects of fading and shadowing on the network. The results further demonstrate that for a RIS-enabled IoT network, there is the need to balance between the cost and benefit of increasing the RIS cells against other parameters such as increasing transmit power, especially at low SNR and/or high to moderate fading/shadowing severity.

SummaryIn this paper, we analyze the performance of maximum‐ratio combining (MRC) receivers for single‐input multiple‐output (SIMO) non‐orthogonal multiple access (NOMA) system. We explore the aforesaid system performance in presence of impairments like imperfect channel state information (CSI) and successive interference cancellation (SIC) errors. In general, receive diversity provides diversity gain and helps to maintain quality of service (QoS), while the NOMA system achieves higher spectral efficiency compared to orthogonal multiple access (OMA). Power‐domain NOMA system transmits superimposed‐coded signal, which utilize SIC detection method at the receiving users. Here, we derive the closed‐form expression of the average bit error rate (BER) for the MRC‐based NOMA system. We also analyze the performance of the system in high signal‐to‐noise ratio (SNR) regime through derived asymptotic expression. Furthermore, the outage probability, diversity order, and sum rate comparison between NOMA and OMA system are also presented. Simulation results also validate the derived theoretical expressions and confirm the diversity gain achieved for the considered system.