Multi-hop Communication System Research Articles

Deep Learning-Based Joint Beamforming Design for Multi-Hop Reconfigurable Intelligent Surface (RIS)-Aided Communication Systems

Reconfigurable intelligent surface (RIS) is one of the promising technologies for sixth generation communications due to its advantages including energy saving, high spectral efficiency, etc. However, the non-convex joint beamforming design is a challenge, especially in the multi-hop RIS-assisted communication system. This paper proposes a deep learning-based joint beamforming (DLBF) design, aiming to maximize the system data rate for multi-hop RIS-aided communication systems. The proposed DLBF design consists of the reflection matrices design of all RISs and the transmit beamforming design at the base station, which has a reduced computational complexity. Numerical results show that the proposed DLBF can achieve 1.8 bit/s/Hz sum rate gain compared to the conventional beamforming method for the two-user scenario, which can be enhanced by large-scale users. The sum rate performance can be improved by increasing the number of RISs due to the reflection gain, and corresponding results provide a guidance of the multi-hop number selection for further investigation.

Analyzing the Performance of TAS/MRC with Decode-and-Forward Relaying for Multihop Transmission over Fisher-Snedecor F Fading Channels

This study comprehensively assesses a decode-and-forward relaying system that employs Transmit Antenna Selection/Maximal Ratio Combining (TAS/MRC) for multi-hop communication across Fisher-Snedecor F fading channels. The study primarily focuses on the average symbol error rate (ASER) and outage probability (OP) while using cross QAM (XQAM) and rectangular quadrature amplitude modulation (RQAM). The proposed MIMO system effectively decreases the hardware complexity and cost of large antennas by implementing Transmit Antenna Selection (TAS) at the source and relay nodes and Maximum Ratio Combining (MRC) diversity at the destination and relays. Analytical formulations for OP (outage probability) and ASER (average symbol error rate) are derived using PDF (Probability Density Function)-based methods. Monte-Carlo simulations further validate these formulas. The investigation indicates that system performance is improved under conditions of lighter shadowing compared to moderate and extreme shadowing settings. Additionally, increasing the hop count amplifies the observed performance. Moreover, when the fading parameter increases, both the OP and ASER decrease. This study comprehensively examines the impact of many parameters, including m, p, L, R, and o, on the behaviour of the system under Fisher-Snedecor F fading. Based on the findings, the combination of shadowing and multipath fading significantly affects the system's performance, with both m and p significantly influencing this. When examining the Signal-to-Noise Ratio (SNR), a comparison between RQAM and XQAM demonstrates that XQAM is superior. The research uncovers crucial information for planning and executing the TAS/MRC-based MIMO multi-hop communication system. This technology possesses the capability to enhance the effectiveness of similar communication systems, as seen by the encouraging advancements in performance, especially in scenarios including signal attenuation.

Performance Analysis of Multi-Hop Hybrid FSO/mm Wave Communication System for Next-Generation Wireless Networks

Next-generation wireless networks are facing increasing demand for high data rates, low latency, and seamless connectivity. To address these challenges, a multi-hop hybrid communication system integrating Free Space Optics (FSO) and millimeter wave (mm Wave) technologies for backhaul communication is proposed. This system combines the advantages of FSO, such as high bandwidth and low latency, with the robustness and reliability of mm Wave technology. The multi-hop architecture enables the formation of a network of interconnected nodes, providing improved coverage and flexibility. Each node is equipped with FSO and mm Wave transceivers, allowing for seamless handovers and adaptive routing. For the proposed system, analytical formulas for outage probability (OP) and average bit error rate (ABER) are derived and validated using simulations. The Monte Carlo simulations provide evidence of enhanced performance in the proposed Multi-Hop Hybrid FSO/mm Wave (MHFM) system compared to the FSO system.

An Insight to the Outage Performance of Multi-Hop Mixed RF/FSO/UWOC System

In this paper, we investigate the outage performance of the three-hop mixed system integrating radio frequency (RF), free space optics (FSO), and under water optical communication (UWOC) system. The closed-form analytical expressions for the outage probability of the system are derived. In the considered system, the RF channel follows the Nakagami-m distribution, the FSO channel observes the Gamma-Gamma fading statistics, and the UWOC link experiences a mixture Exponential Generalized Gamma (EGG) fading distribution. To verify the derived analytical expressions, numerical simulations are also carried out, and we present the influence of the various link parameters such as path loss, atmospheric turbulence, pointing errors, angle-of-arrival fluctuations, water salinity, and scintillation on the performance of the decode and forward (DF) relayed multi-hop communication system.

Relay-Aided D2D MIMO Scheme (RAS) for Achieving Energy Efficiency in Satellite-Air-Ground Integrated Networks (SAGIN) Schéma D2D MIMO assisté par relais (RAS) pour atteindre l’efficacité énergétique dans les réseaux intégrés satellite-air-sol (SAGIN)

Space-air-ground integrated network (SAGIN), as a three-tiered architecture that assimilates satellite systems, aerial, and terrestrial communication networks, has become an intensive research domain in the present era of communications. SAGIN-based communication models are developed to enhance the user’s quality of experience (QoE). Besides providing noteworthy benefits in various applications and services, SAGIN has unprecedented challenges because of its self-organized, unpredictable, and heterogeneous nature. Relaying equipment in SAGIN can be a very low-orbit satellite, a base station (BS), and an unmanned vehicle assisting a pair of mobile users’ communications. Thus, developing a robust device-to-device (D2D) direct and relaying communication model concerning channel distribution is crucial. Based on this concern, this article proposes a relay-aided D2D multiple–input and multiple–output (MIMO) scheme (RAS) for enhancing the optimal energy efficiency (EE) as a function of spectral efficiency (SE). The proposed model derives a relay-based amplify-and-forward (AF) MIMO multihop communication system for implementation. The proposed computations of optimal EE and SE for D2D MIMO show that the approximation provided by a random matrix approximation is constrained to a specific signal-to-noise ratio (SNR) range when the optimal SE and EE are derived using Gaussian quadrature and a hypergeometric function.

OCHSA: Designing Energy-Efficient Lifetime-Aware Leisure Degree Adaptive Routing Protocol with Optimal Cluster Head Selection for 5G Communication Network Disaster Management

As an underlayment to cellular 5G communication network, device-to-device (D2D) communications will not only boost capacity utilization and power efficiency but also provide public health and public safety services. One of the most important requirements for these businesses is to have alternate access to cellular networks in the event that they are partially or completely disrupted as a result of a natural disaster. Despite limited communication coverage and bandwidth scarcity, the 3rd Generation Partnership Project (3GPP) must have developed a new device-to-device (D2D) communication method fundamental enhanced mobile that can strengthen spectral efficiencies besides allowing direct communication of gadgets in close propinquity devoid of transitory by elevated-node B (eNB). Unfortunately, enabling data transmission on a cellular connection offers a challenge in terms of two-way radio source administration, because D2D associates recycle cellular users’ uplink radio resources, which might create interference to D2D user equipment’s (DUE) receiving channels. In this study, we concentrate on optimal cluster head selection using the binary flower pollination optimization algorithm by designing an energy-efficient lifetime-aware leisure degree adaptive routing protocol named OptCH_L-LDAR. This topology is constructed with a multi-hop obliging communication system, instructed on the way to wrap an extensive remoteness connecting source and destination. The proposed OptCH_L-LDAR is compared with three state-of-art methods such as binary flower pollination (BFP) algorithm, time division multiple access (TDMA), and data-driven technique (DDT). As a result, the proposed OptCH_L-LDAR achieves 96% of energy efficiency, 89% of lifetime, 97% of outage probability, and 98% of spectral efficiency.

HP-DF SSK Method for UAVs Communication in Cooperative Multi-Hop Rician Networks

This paper presents techniques that are expected to improve the bit error rate (BER) performance of Unmanned Aerial Vehicles (UAVs) communication systems. The decode-and-forward (DF)-based cooperative multi-hop Rician network using space shift keying (SSK) modulation is employed for this purpose. The SSK modulation and cooperative communication are merged and used together. This enhances the BER performance for multiple-input multiple-output (MIMO) channels, thus accentuating its significance as an important technique for consistently reliable communication methodology while, at the same time, eliminating wastage of energy. The new technique is named as high performance (HP) due to not only BER performance improvement but also increase of the diversity of the communication system. This new model is further used for multi-hop networks and the resulting BER characteristics are assessed for possible enhanced performance in Rician channels. The paper also showcases the generalized-n-hop BER equation for various multi-hop DF-based cooperative communication systems in diverse UAV models. The Monte Carlo simulations further confirm the theoretical results that already exist for transmit-receive antennas. This work also underlines the fact that the number of hops in a communication system has no bearing whatsoever on the BER performance diversity value.

Performance analysis of multi-hop underwater wireless optical communication system with space-time block codes considering the impact of beam spread function

The average bit error rate (ABER) performance of the decode-and-forward-based multiple-input multiple-output (MIMO) multi-hop underwater wireless optical communication (UWOC) systems has been investigated over the composite exponential-generalized gamma (EGG) fading channel with space-time block coding (STBC). The impacts of absorption, scattering, and the misalignment caused by spatial spreading in the sea, which are modeled by the beam spread function, as well as the turbulence-induced fading are all taken into account in this work. With the help of the moment generating function, Meijer’s-G function, and Gauss–Laguerre quadrature numerical methods, the approximate closed-form expressions of ABER for the UWOC system with binary phase shift keying are mathematically derived. Furthermore, numerical analyses are provided to investigate the effects of various hops, temperature gradients, air bubbles levels, STBC schemes, and turbulence severity on the performance of the multi-hop MIMO UWOC system. In addition, Reed–Solomon (RS) codes are adopted to improve the UWOC system performance. Results reveal that the ABER performance of this multi-hop UWOC system would degrade as the temperature gradients, hop numbers, and bubble levels (BLs) increases, which could be improved considerably by employing the STBC scheme. The ABER performance over the composite EGG distribution is mainly limited by the environmental parameters, whereas the fading can be significantly improved by RS codes. The ABERs of EGG distribution are compared with exponential-gamma and exponential-lognormal distributions in oceanic turbulence under different temperature gradients and BLs, respectively. These analytical results are also verified by Monte Carlo simulations. This work is beneficial for the design of UWOC system.

Design of Multihop Communication Systems Under Hardware Manufacturing Defects and Self Interference

Most studies on multi-hop communication systems are actually based on the assumption that hardware parts are built with high quality transmit/receive radio frequency chains, which are expensive and power-hungry. In practice, low cost hardware components are employed, which are prone to hardware manufacturing defects (e.g., phase noise, nonlinear power amplifier, inphase/quadrature imbalance, nonlinear low noise amplifier and analog to digital converter impairments). This paper focuses on the design of the transmitter, relay stations (RSs) and receiver for multi-hop communication systems under hardware defects. This paper analyzes the hardware defects and their impacts on the performance of multi-hop communication system. In addition, the impact of self-interference at the RSs is considered. The effect of hardware defects is modeled using distortion noises. A closed-form expression for the signal to noise and distortion ratios (SNDRs) is mathematically derived, then the performance metrics (i.e., SNDR, outage probability (OP) and ergodic capacity) are calculated, accounting for hardware defects. In addition, exact form expression of the average bit error probability is derived. To facilitate comparison, performance metrics of the proposed multi-hop relaying system and ideal system are illustrated. We also propose a linear minimum mean square error (LMMSE) and self-interference cancellation technique to mitigate the hardware defects. The results reveal that hardware defects can degrade the system performance. In addition, SNDR ceiling is inversely proportional to the summation of the square of hardware defect lev el. Also, the proposed mitigation technique can enhance the system performance.

Ergodic Capacity Evaluation of Multi-Hop Decode-and-Forward MIMO-OFDM Relaying Network

Spatial diversity plays a significant role in wireless communication systems, including the Fourth Generation (4G) and Fifth Generation (5G) systems, and it is expected to be a fundamental part of the future wireless communication systems as well. The Multiple-Input Multiple-Output (MIMO) technology, which is included in the IEEE 802.16j standard, still holds the most crucial position in the 4G spectrum as it promises to improve the throughput, capacity, spectral, and energy efficiency of wireless communication systems in the 2020s. This makes MIMO a viable technology for delay constrained medical and health care facilities. This paper presents an approximate closed-form expression of the ergodic capacity for the Decode-and-Forward (DF) protocol MIMO-Orthogonal Frequency Division Multiplexing (OFDM) relaying network. Although MIMO-OFDM is highly valuable for modern high-speed wireless communication systems, especially in the medical sciences, its performance degrades in multi-hop relay networks. Therefore, in this paper, an approximate closed-form expression is derived for an end-to-end ergodic capacity of multi-hop DF MIMO-OFDM wireless communication system has been presented. Monte-Carlo simulations are conducted to verify the performance of the presented analysis regarding the capacity (bits/s/Hz) for different SNR-dB values for single, 2 × 2, 4 × 4, and multi-hop DF MIMO-OFDM systems. The presented results provide useful insights for the research on the end-to-end ergodic capacity evaluation.

Multi-hop DF relayed FSO links with various modulation formats emulated by a dual-hop scheme for strong turbulence conditions

In this work, we try to minimize the mathematical complexity in analyzing outage and error performance by emulating multi-hop terrestrial FSO communication system as a single dual-hop scheme. More specifically, we approximate the topology of such a system and we estimate analytically its performance, by taking into account various modulation formats for strong and saturated atmospheric turbulence conditions. The theoretical study of the FSO system performance is performed using either the negative exponential or the K distribution models, while the well-known modulation formats on-off keying (OOK), pulse amplitude modulation (PAM) and pulse position modulation (PPM), have been employed. Thus, closed form mathematical expressions for outage probability and average BER estimation are derived and their outcomes can easily be used for the design of modern optical wireless links. Finally, using the obtained mathematical forms, the corresponding numerical results are presented using realistic FSO parameter values.

On the performance of DF-based multi-hop system over α − κ − μ and α − κ − μ-extreme fading channels

Several emerging application scenarios for the multi-hop wireless networking have been introduced in 5G and beyond networks, to provide ultra-low latency and much higher data rate to the end users. In this work, an integrated performance evaluation of a decode-and-forward (DF) multi-hop wireless communication system is undertaken over the non-linear generalized α−κ−μ and α−κ−μ-Extreme fading models. Novel closed-form expressions for the amount of fading (AoF), channel capacity under various adaptive transmission techniques are derived. Additionally, decoding error probability for short packet communication is derived and analyzed. The provided expressions are very useful in designing the channel/link quality for practical multi-hop communication networks. The effects of the fading parameters and the number of hops on the system performance are demonstrated. The correctness of the proposed solutions has been corroborated by comparing them with Monte Carlo simulation results.

ABER performance investigation of LDPC-coded multi-hop parallel underwater wireless optical communication system: publisher's note.

This publisher's note corrects several equations and a sentence in Appl. Opt.59, 1353 (2020)APOPAI0003-693510.1364/AO.59.001353.

ABER performance investigation of LDPC-coded multi-hop parallel underwater wireless optical communication system.

The average bit error rate (ABER) performance of a low-density parity-check (LDPC)-coded multi-hop parallel underwater wireless optical communication (UWOC) system is investigated with the combined effects of absorption, scattering, the misalignment characterized by the beam spread function, and the ocean turbulence-induced fading modeled by log-normal distribution. With the max-min criterion as the best path selection scheme, the cumulative distribution function for identically and independently distributed and non-identically and independently distributed links are derived, respectively. Then, the analytical ABER expressions of binary phase shift keying and multiple phase shift keying subcarrier intensity modulation schemes are deduced with the help of the Gauss-Laguerre quadrature rule, and they are also confirmed by Monte Carlo simulation. In addition, LDPC codes are applied in the simulation to improve the system performance. The results show that the combined degrading effects are mainly limited by the link length, especially under the coastal ocean condition. And the multi-hop parallel transmission demonstrates good ABER performance and can expand the communication range in ocean. Furthermore, LDPC codes can significantly improve the ABER performance of the UWOC system, and the coding gain is strongly affected by channel conditions and the corresponding parameters of LDPC codes. This work is beneficial for the UWOC system design.

Minimax Optimization for Recipe Management in High-Mixed Semiconductor Lithography Process

This article addresses the application of minimax optimization in the control design of complex dynamic systems of the semiconductor manufacturing. We highlight the main challenge in the control system of high-mixed wafer fabrication during the photolithography process called overlay control. In the semiconductor photolithography process, the sophisticated and high-mixed setting is generated by multiple recipe adjustments for the single scanner device. The high complexity will be moderated if there is a communication interface among the process variables. We design a communication protocol for the high-mixed photolithography process for overlay control. The proposed system is designed on the basis of the recipe management system for a distinct batches of recipes. The focal point of switching recipes performs as a communication hop, where aligning recipes together make a multihop communication system for recipe management. The proposed multihop communication system is optimized by the minimax decision rule to select the best parameter setting for each recipe and boost the overlay compensation.

Performance analysis for multi-hop UOWC system over mixture Exponential–Gamma with two IM-DD fading channels

This paper provides the end-to-end performance of a multi-hop underwater optical wireless communication (UOWC) system using channel-state-information assisted (CSI) or fixed-gain amplify-and-forward (AF) relays, in which the intensity modulation-direct detection (IM-DD) is taken into account for detection. Particularly, not only the IM-DD input-independent but also the IM-DD cost-dependent additive white Gaussian noise (AWGN) channel is considered in such system analyses. In order to focus on multi-hop performance improvement and simplify calculation, the pointing error is not considered in this paper. In our study, the channel irradiance fluctuations are characterized by the mixture Exponential–Gamma (EG) distribution. With Fox H-function, exact analytical expressions for the probability density function (PDF) and the cumulative distribution function (CDF) are derived, respectively. Based on these formulas, with different hop numbers N, the outage probability (OP) and the average bit-error rate (ABER) of various modulation schemes are presented. Furthermore, numerical analyses are provided and to further investigate the effects of the turbulence severity on the performance of multi-hop UOWC system. And simulation results verifies the accuracy of the obtained analytical and asymptotic expressions. The obtained results indicate that the overall system performance enhances with an increase of the number of hops.

Ratio of Products of Fluctuating Two-Ray Variates

This letter provides a statistical analysis for the ratio of the products of fluctuating two-ray (FTR) random variables (RVs), in which exact expressions for the probability density function (PDF), cumulative distribution function (CDF), generalized moment generating function (MGF), which coincides with the $n$ -th moment by setting $s=0$ , the amount of fading, and channel quality estimation index, are derived. To show the usefulness of the derived expressions, we study the performance of multihop wireless communication systems subject to multiple interferers. The outage probability is examined, based on which an asymptotic analysis is carried out. Monte Carlo simulations are presented to corroborate the proposed analysis.

Network coded multicast for multi-hop D2D communication systems

ABSTRACTIn this paper, we consider the wireless communication systems where multi-hop Device-to-Device (D2D) networks can coexist with the conventional cellular networks by sharing the downlink resource of cellular users (CUs). A multicast data flow is distributed over the multi-hop D2D networks where network coding (NC) can be employed at the intermediate nodes. To maximize the utility of the multicast flow, we formulate a joint optimization problem for the systems while guaranteeing the quality-of-service (QoS) for regular CUs. We propose a subgradient algorithm to solve the optimization problem by decomposing it into three sub-problems: multicast rate control, NC subgraph selection, and downlink resource reusing. In particular, we develop a greedy algorithm to deal with the downlink resource reusing sub-problem for it is NP hard. Numerical and simulation results prove the superior performance of the proposed techniques compared with the conventional routing scheme.

Adaptive Optimization of Multi-Hop Communication Protocol for Linear Wireless Monitoring Networks on High-Speed Railways

The multi-hop communication protocol can balance the energy consumption of sensors to extend the service lifetime in high-speed railways (HSRs). However, the communication via multiple hops will increase the data transmission latency. Most previous studies have focused on optimizing either the sensor network lifetime or the data transmission latency but have not considered both. This paper presents an adaptive multi-objective optimization model for multi-hop communication systems. This model explicitly addresses the trade-off between the lifetime and the latency associated with the use of network-level wireless condition monitoring systems for ensuring the railway operational safety. Numerical examples with various operational scenarios are developed to demonstrate the superiority and practicality of the proposed approach. Compared with the three previously applied protocols, the proposed approach can achieve longer sensor network lifetime, shorter data latency, and greater system utility (accounting for both lifetime and latency). This paper provides the technical support for the development of stable and reliable wireless monitoring management systems for HSR safety.

PARATUCK semi-blind receivers for relaying multi-hop MIMO systems

In this paper, two receivers are proposed for a multiple-input multiple-output (MIMO) relaying multi-hop communication system using a Khatri-Rao space-time (KRST) coding at the source and amplify-and-forward (AF) relays. It is shown that the third-order tensor of signals received at the destination satisfies a PARATUCK-(K+1) tensor model, where K is the number of relays. After formulating the system model, the expressions of the Cramér-Rao bound (CRB) for the communication channels are derived for the particular case of a two-hop system, i.e., K=1. The presented tensorial modeling enables a joint semi-blind estimation of the transmitted symbols and the channels. The first proposed estimation algorithm is a non-iterative technique based on a rearrangement of the Kronecker product, while the second proposed receiver is based on the alternating least squares (ALS) algorithm. The uniqueness of the tensor decomposition and the identifiability conditions of the proposed algorithms are discussed. The performance of these receivers is evaluated by means of Monte Carlo simulations.