Relay Link Research Articles

A Method of Relay Node Selection for UAV Cluster Networks Based on Distance and Energy Constraints

Cooperative communication is a key technology to improve the stability of UAV swarm communication. To reduce the energy consumption in cooperative communication, this study proposes a method for selecting relay nodes based on distance and energy constraints. First, a two-stage communication model was designed to explain the signal forwarding communication process. Subsequently, cluster head nodes were filtered through a competition mechanism to be used for forwarding source signals. The minimum communication capacity of the link contained the distance parameter of the relay link. Lastly, under energy and distance constraints, the optimal solution of the minimum interrupt function for the cluster head was found, and was defined as the best relay node. The experimental results show that the two parameters of network coverage and residual energy of the improved method were higher than those of other mainstream algorithms. Furthermore, the actual UAV networking test results show that the proposed relay selection method had the most residual energy. It is concluded that the relay selection method proposed in this study has good practicality and advancement in UAV cluster communication.

Performance Analysis for DF Relay-Aided Visible Light Communication System With NOMA

Visible light communication (VLC) has been deemed to be one promising technique for the sixth-generation wireless communication network. However, due to the attenuation properties, the VLC ranges are usually limited. To unlock the advantage of multiple light-emitting diodes (LEDs) and extend the coverage of VLC systems, a relay-aided VLC system with non-orthogonal multiple access (NOMA) is proposed in this paper. Specifically, a decode-and-forward (DF) relay protocol is introduced to construct the relay-aided VLC system with NOMA. Moreover, the closed-form expression of the outage probability (OP) in the DF relay-aided VLC system with NOMA is derived to accurately characterize the theoretical performance of the system. Thereafter, the effects of the corresponding parameters on the OP are investigated. Simulation results verify the accuracy of the derived theoretical expression and illustrate that the DF relay-aided VLC system with NOMA can effectively improve system outage performance. Compared to the direct transmission NOMA VLC system without relay link, our scheme can obtain <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\text{15}\,\text{dB}$</tex-math></inline-formula> transmit signal-to-noise ratio gains in <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$10^{-3}$</tex-math></inline-formula> OP level. Last but not least, the optimal transmit semi-angle and deployment height of the relay can be determined for achieving the optimal system outage performance.

Biased Stackelberg game‐based UAV relay anti‐jamming communications: Exploiting trajectory optimization and transmission mode selection

Although unmanned aerial vehicle (UAV) relay can provide auxiliary communication due to its flexible mobility, it is vulnerable to jamming attacks. This paper considers the UAV relay anti-jamming communication issue under the threat of a malicious jammer with beam-forming jamming capability. To prevent the relay link from deteriorating, UAV trajectory adjustment and transmission mode switching between half-duplex and full-duplex are two available schemes, while they will incur the additional flying costs and continuous mode switching, respectively. To balance the trade-off between trajectory optimization and mode selection, this paper investigates the joint trajectory optimization and mode selection anti-jamming approach. First, an anti-jamming utility considering the cost-efficient and end-to-end capacity gains is designed. Second, to model the bounded rationality of both the UAV relay and the jammer due to the adversarial context, a biased Stackelberg game to analyse the competitive system interactions is proposed. Moreover, the existence of Stackelberg equilibrium (SE) in the problem is proved. Finally, a joint mode selection and trajectory optimization (JMSTO) algorithm based on the multi-armed bandit is proposed to obtain the SE. It is further demonstrated that the JMSTO algorithm has a logarithmic regret. The results show that our proposed JMSTO algorithm is superior to non-joint optimization methods.

Time‐switched energy harvesting amplify‐forward relay with direct link: Performance analysis

SummaryA dual‐hop time‐switched (TS) energy harvesting (EH) amplify forward (AF) relay system has been considered, which comprises three nodes: source (S), destination (D), and an energy harvesting relay (R), respectively. Besides the relay link, the proposed architecture has an additional direct link between the source and destination node. For this model, we derive the expressions for system outage probability and throughput. The proposed architecture shows significant performance increments in terms of system outage probability and throughput when compared with a traditional EH relay system having no direct link.

Distributed Antenna-and-Relay Selection Schemes for MIMO Cooperative Relay Network

Relay selection, antenna selection, and link selection are three potent means to enrich network capacity in MIMO relaying networks. To reduce feedback overhead, in this paper, three distributed antenna-and-relay selection schemes are proposed for AF multiple-relay network, which is equipped with multiple antennas at nodes. Closed-form formulations of system outage probability are derived for these schemes, as well as the lower bounds and upper bounds. Furthermore, the approximate expressions of outage probability at high SNR regime are also derived, showing that the proposed optimal strategy can achieve full diversity order. In addition, link selection scheme can improve spectral efficiency since it saves one time slot when direct link is selected.

Analysis of High-Frequency Atmospheric Windows for Terahertz Transmission Along Earth-Space Paths

The atmospheric absorption effect greatly increases the transmission loss of terahertz (THz) waves, which limits the transmission distance. In this article, with the support of sufficient antenna gain, a series of high-frequency THz transmission windows in the ground-satellite link are presented. First, the more ideal ground-based site is determined. Based on the path loss model and the layered transmission theory, the total path loss is obtained. Combined with signal transmit power, antenna gain, signal-to-noise ratio, and noise power, total usable bandwidths and transmission windows in the 0.2–15 THz corresponding to antenna gain from 0 to 100 dBi are given. By taking the high-altitude platform as a relay link, the usable transmission windows are also given. The first six transmission windows are identified as [0.4776–0.48645 THz], [0.4906–0.49975 THz], [0.6618–0.6811 THz], [12.1015–12.10355 THz], [12.10425–12.11285 THz], and [12.11505–12.14355 THz] bands against 100 dBi gain near 1 and 10 THz bands, respectively. Furthermore, the influence of ice clouds on the transmission characteristics is analyzed. The additional attenuation in the partial usable atmospheric window frequency range can reach 1.84 dB typical, which is directly related to the effective radius and shape of particles.

Impacts of relay and direct links at destinations in full-duplex non-orthogonal multiple access system

In this study, one of effective methods of multiple access, namely non-orthogonal multiple access (NOMA), is investigated. Such NOMA scheme can be worked with signal processing at downlink side. As such, the base station sends mixed signals of two signals to destinations. A near user could be a relay to forward the signal to the distant user by leveraging benefits of full-duplex mode which allows relay to transmit and receive signals in the same time. For simple analysis, the two-user approach and fixed power allocation factors are implemented. We also derive formulas of the outage probability of two users (near-user and far-user) to indicate fairness and emphasize the role of the near user as a relay. This considered NOMA system adopts transmission with Nakagami-m fading channel. As a further metric, throughput is considered under the impacts of key system parameters. The transmit signal-to-noise ratio (SNR) at the base station make influences the performance of two users significantly as observation indicated in our simulation results. These results are confirmed by matching Monte-Carlo with the theoretical simulations.

Impacts of relay and direct links at destinations in full-duplex non-orthogonal multiple access system

Impacts of relay and direct links at destinations in full-duplex non-orthogonal multiple access system

Collaborative multiple access and energy-efficient resource allocation in distributed maritime wireless networks

With the rapid increasing of maritime activities, maritime wireless networks (MWNs) with high reliability, high energy efficiency, and low delay are required. However, the centralized networking with fixed resource scheduling is not suitable for MWNs due to the special environment. In this paper, we introduce the collaborative relay communication in distributed MWNs to improve the link reliability, and propose an orthogonal time-frequency resource block reservation based multiple access (RRMA) scheme for both one-hop direct link and two-hop collaborative relay link to reduce the interference. To further improve the network performance, we formulate an energy efficiency (EE) maximization resource allocation problem and solve it by an iterative algorithm based on the Dinkelbach method. Finally, numerical results are provided to investigate the proposed RRMA scheme and resource allocation algorithm, showing that the low outage probability and transmission delay can be attained by the proposed RRMA scheme. Moreover, the proposed resource allocation algorithm is capable of achieving high EE in distributed MWNs.

Packet Re-Management-Based C-NOMA for URLLC: From the Perspective of Power Consumption

Cooperative non-orthogonal multiple access (C-NOMA) has been gradually discussed in the ultra-reliable and low-latency communication (URLLC) scenarios. The recent research indicates that when optimizing blocklength, selection combining the re-transmission packet cannot sufficiently exploit the potential of C-NOMA. To tackle this problem, we propose a packet re-management framework to transmit different packets through direct and relay links, therefore, propose an energy-efficient transmission scheme. By investigating power consumption of unequal-blocklength non-orthogonal multiple access with appropriate successive interference cancelation order, we jointly optimize blocklength, power, and re-managed packet size to minimize the power consumption, under URLLC requirements and the maximum power constraint. Simulation results verify that the proposed scheme can reduce power consumption.

Exact Outage Analysis for Non-regenerative Secure Cooperation Against Double-tap Eavesdropping

This paper presents the secrecy performance analysis of an amplify-and-forward relay-assisted cooperative communication system in the presence of a passive external eavesdropper. In contrast to existing works that assume high signal-to-noise ratio (SNR) approximations, we have investigated exact and secrecy outage probabilities. Furthermore, we consider a more challenging scenario where the source may not be reachable to the intended user directly. But the eavesdropper can tap both the source link and the relay link. First of all, the outage probability is analyzed at the intended user as well as the eavesdropper. Next, defining the secrecy rate for the amplify-and-forward (AF) relaying system, the expression of the secrecy outage probability (SOP) and the secrecy intercept probability (SIP) have been derived, respectively. Noticing the complexity involved in the integration of SOP and SIP expressions, the closed-form expressions have been derived for asymptotic cases. Finally, the exact and asymptotic analysis has been verified by performing Monte-Carlo simulations. It is observed that the relay position should be closer to the source compared to the eavesdropper to achieve improved SOP.

Correlation of Serum Leptin with Body Mass Index and Insulin Resistance in Polycystic Ovarian Syndrome in a Tertiary Care Centre of Southern Odisha, India

Introduction: Leptin is an adipocyte derived hormone encoded by ob gene which serves as a relay link between metabolic signals and brain that regulate the hypothalamic pituitary ovarian axis. Leptin is related with obesity which is a most important cause of Polycystic Ovarian Syndrome (PCOS) in women of reproductive age group. Aim: To evaluate leptin concentration and to analyse its correlation with Body Mass Index (BMI) and insulin resistance in PCOS. Materials and Methods: This case-control study was conducted from December 2018 to December 2019 at Department of Biochemistry in collaboration with Department of Obstetrics and Gynaecology, MKCG Medical College and Hospital, Berhampur, Odisha, India. A total of 60 PCOS subjects, aged between 15-30 years (30 obese PCOS and 30 lean PCOS) and 30 age matched, normal ovulatory healthy controls were included in the study. Parameters such as serum leptin, fasting plasma insulin, Homeostatic Model Assessment-Insulin Resistance (HOMA-IR), Fasting Plasma Glucose (PPG), Postprandial Plasma Glucose (PPPG) were estimated using commercial kits. One-way Analysis of Variance (ANOVA) test was used for data analysis and the Pearson’s correlation method was used to find the correlation between the parameters. Results: The mean age of women in all the three PCOS groups was found to be 22.4±3.13 years. The BMI of obese PCOS patients (31.9±4.7 kg/m2 ) and lean PCOS patients (21.4±2.2 kg/m2 ) were higher than that of healthy controls (20.7±1.8 kg/m2 ) which was statistically significant (p-value &lt;0.001). The serum leptin in obese PCOS were significantly higher (28.0±17.8 ng/mL) than lean PCOS (5.8±2.2 ng/mL) and fasting plasma insulin in lean PCOS were (10.9±2.4 µIU/mL) significantly lower than obese PCOS (30.2±14.8 µIU/mL). Mean serum leptin levels had significant positive correlation with BMI in lean and obese PCOS and insulin resistance in obese PCOS. Conclusion: In the present study, high leptin concentration was observed in PCOS patients and there was positive correlation of leptin with BMI in both lean and obese PCOS groups and leptin was positively correlated with insulin resistance in obese PCOS.

Токоограничение в системе электропривода постоянного тока с модальным управлением и переменной структурой

Разработан и исследован эффективный метод ограничения тока в замкнутой системе электропривода постоянного тока с модальным управлением при различных режимах работы электродвигателя. В качестве объекта управления принят двигатель постоянного тока (ДПТ) независимого возбуждения с питанием от тиристорного преобразователя. Для решения поставленной задачи использованы методы теории автоматического управления. Исследован метод ограничения тока якорной цепи ДПТ в замкнутой системе с модальным управлением и переменной структурой. Произведен синтез коэффициентов модального регулятора тока и скорости вращения якоря ДПТ. Проведено моделирование переходных процессов пуска, торможения, реверсирования и стопорения ДПТ. Дана оценка качества процесса управления путем анализа переходных процессов замкнутой системы электропривода в среде моделирования динамических систем MatLab. Приведены рекомендации по выбору параметров релейных звеньев для обеспечения эффективного токоограничения. Выполнена проверка работоспособности системы электропривода при вариации параметров двигателя. В целом предложенный метод токоограничения успешно справляется со своей задачей, однако чувствителен к настройкам релейных элементов.

Performance Metrics for Bluetooth Scatternet Scheduling Using Relays

Abstract: While various ad hoc mobile wireless networks are already accessible, Bluetooth is one of the most up-to-date. A single-hop connection known as piconet is a simple Bluetooth communication architecture, allowing for just eight functioning electronic equipment, seven of which are operational slaves under a single master. A common hub called a relay links a huge network named Scatternet to a number of piconets. The efficacy of Scatternet design is clearly intrinsically connected to the effectiveness of relay nodes. Because every relay has several piconet transactions to process and manage, a reduction in the number of switches might lead to poor performance instead. The major aim of this research is to examine performance characteristics which impact interplay since the role of the base station is to multiple piconet transitions. In this study, we evaluate and respond to the technical issues that must be optimally solved the Scatternet data flow based on the relay node. Keywords: Bluetooth, Piconet, Scatternet, Relay Node

Misbehavior Detection and Optimal Threshold Analysis in DF Cooperative Relay Networks

In this letter, a detect-before-decode (DbD) method for relay misbehavior detection in a wireless decode-and-forward (DF) cooperative network is proposed. Since this method makes no use of the decoding results, the detection errors caused by erroneously decoding are eliminated. A unified sufficient statistic for relay misbehavior detection, which is applicable to all link outage conditions, is constructed. Furthermore, the closed-form expression of the optimal threshold which minimizes the source-to-destination outage probability is derived. Numerical simulations show that the proposed method outperforms the long-term relay link observing method in terms of false alarm and miss detection rates. It has the same false alarm and miss detection rates as the physical integrity check (PIC) method with lower computational complexity. The outage probability performance is also improved when transmit power is low.

On Deep Learning Assisted Self-Interference Estimation in a Full-Duplex Relay Link

On Deep Learning Assisted Self-Interference Estimation in a Full-Duplex Relay Link

ACTS: An Ant Colony Based Transmission Scheduling Approach for Cloud Network Collaboration Environment

In traditional cloud computing research, it is often considered that the network resources between edge devices and cloud platform are sufficient, and the symmetry between the upward link from edge devices to the cloud platform and the downward link from cloud platform to edge devices is definite. However, in many application scenarios, the network resources between edge devices and cloud platform might be limited, and the link symmetry may not be guaranteed. To solve this problem, network relay nodes are introduced to realize the data transmission between edge devices and the cloud platform. The environment in which network relay nodes that can cooperate with the cloud platform is called cloud network collaborative environment (CNCE). In CNCE, how to optimize data transmission from edge devices to cloud platform through relay nodes has become one of the most important research topics. In this paper, we focus on the following two influencing factors that previous studies ignored: (1) the multi-link and multi-constraint transmission process; and (2) the timely resource state of the relay node. Taking these factors into consideration, we design a novel data transmission scheduling algorithm, called ant colony based transmission scheduling approach (ACTS). First, we propose a multi-link optimization mechanism to optimize the constraint limits. This mechanism divides the transmission into two links called the downlink relay link and uplink relay link. For the downlink relay link, we use the store-and-forward method for the optimization. For the uplink relay link, we use the min–min method for the optimization. We use the ant colony algorithm for the overall optimization of the two links. Finally, we improve the pheromone update rule of the ant colony algorithm to avoid the algorithm from falling into a local optimum. Extensive experiments demonstrate that our proposed approach has better results in transmission efficiency than other advanced algorithms.

Multipath Deadline-Aware Transport Proxy for Space Network

Space travel is becoming more accessible due to the low-cost spaceflight. One way to maintain the communication between the space station and the ground station is to use several relay satellites. However, those relay links suffer from high loss rate, limited bandwidth, and long round trip time (RTT). Meanwhile applications running over these links, such as real-time communication, usually have deadline requirements for their data transfer. Recently, QUIC version 1 is released as RFC9000 (by Iyengar and Thomson in 2021), which provides great opportunity to improve transport services. Based on QUIC, we develop multipath deadline-aware transport proxy (MPDTP) to provide the deadline-aware transmission service for those applications. To avoid the loss caused by congestion control of each application, the proxy aggregates the data transmission of applications and transmits them along multiple paths. MPDTP uses deadline-aware scheduling and adaptive redundancy to deal with the link fluctuation and packet loss. Based on our implementation experience, we give some guidance on how to standardize MPDTP.

Adaptive Irregular Constellations for Full-Duplex Relaying With Residual Self-Interference

We propose the use of adaptive optimized irregular constellation to enhance the performance of full duplex (FD) wireless radio systems which suffer from residual self-interference (RSI). Specifically, an error performance expression which takes into account the RSI level and signal-to-noise ratio is first derived for a single FD relay link. During the search for optimal constellation for a given parameter set, there are no predefined assumptions on symbol point locations. The optimization framework yields adaptive irregular constellations depending on RSI levels and power budget values. It is shown that the proposed adaptive transmission along with optimized irregular constellations achieves better error performance than the conventional <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> -QAM constellations and other <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> -ary improper Gaussian signaling (IGS) constellations.

Analysis of high-frequency atmospheric windows for terahertz communication between the ground and the satellite

The large path loss limits the transmission distance of terahertz wireless communication in the atmosphere. To realize long-range transmission of terahertz waves between the ground and the satellite, the first and key step is to find low attenuation atmospheric transparent windows. In this paper, based on the characteristics of atmospheric distribution in China, atmospheric model (am) is used to compute and compare atmospheric absorption attenuation of terahertz waves in two representative cities, and obtain the most ideal ground-based site suitable for terahertz communication between the ground and the satellite in China. Subsequently, by means of real atmospheric data and layered transmission theory, the total path loss of terahertz communication between the ground and the satellite is calculated. Combined with the signal transmit power, antenna gain, Signal-to-Noise Ratio (SNR), noise power and the corresponding path loss threshold, the total usable bandwidth and atmospheric windows in the 10−15 THz frequency band are given. Moreover, by taking the High Altitude Platform as the terahertz communication relay link between the ground and the satellite, the usable atmospheric windows in the 1−15 THz frequency band with antenna gain of 0−100 dBi are given, which provide theoretical and numerical reference for the establishment of ground-satellite communication links and the selection of ground-based sites and communication frequency bands in China.