Adaptive Three-Stage Hybrid RIS for Energy-Efficient and High-Performance Wireless Networks

A high performance wireless network is essential for for the railway communication and control systems. Research on the fading characteristics in railway environment is of great importance for the design of the railway wireless network. In this paper, measurements are taken in railway terrain cuttings area using track side base stations of the GSM-R network. The fitted path loss model, shadow fading, and dynamaic range of the small scale fading are obtained and compared to the results of viaduct scenario. The propagation environment of the terrain cuttings turns out to be worse than the viaduct area. The path loss exponent is found to be 4.3. The shadow loss can be reasonably described by a log-normal distribution. It is also found that the bridges over the cuttings can cause extra loss of about 5 dB. The dynamaic range of the small scale fading is from 27 dB to 40 dB with a mean value of about 33 dB.

We address the issue of power-controlled shared channel access in future wireless networks supporting packetized data traffic, beyond the voice-oriented continuous traffic primarily supported by current-generation networks. First, some novel formulations of the power control problem are introduced, which become progressively more general by incorporating various relevant costs. The analysis of the models under simple, yet natural, assumptions yields certain ubiquitous structural properties of 'optimal' power control algorithms. Based on such structural properties, we design a new family of distributed and asynchronous PCMA algorithms and evaluate them experimentally by simulation. They are found to perform substantially better than a standard benchmark algorithm for power control. This is a first step towards the design of full PCMA protocols for autonomous channel access in high-performance wireless networks.

As the density of wireless networks continues to grow with more clients, more base stations, and more traffic, designing cost-effective wireless solutions with efficient resource usage and ease to manage is an increasing challenging task due to the overall system complexity. A number of vendors offer scalable and high-performance wireless networks but at a high cost and commonly as a single-vendor solution, limiting the ability to innovate after roll-out. Recent Software-Defined Networking (SDN) approaches propose new means for network virtualization and programmability advancing the way networks can be designed and operated, including user-defined features and customized behaviour even at run-time. However, means for rapid prototyping and experimental evaluation of SDN for wireless environments are not yet available. This paper introduces Mininet-WiFi as a tool to emulate wireless OpenFlow/SDN scenarios allowing high-fidelity experiments that replicate real networking environments. Mininet-WiFi augments the well-known Mininet emulator with virtual wireless stations and access points while keeping the original SDN capabilities and the lightweight virtualization software architecture. We elaborate on the potential applications of Mininet-Wifi and discuss the benefits and current limitations. Two use cases based on IEEE 802.11 demonstrate available functionality in our open source developments.

This paper presents an Equivalent-Figure-of-Merit (EFOM) for designing and evaluating a wireless system towards low power and high performance. Relevant factors like delay, minimum latency, overhead length of a package, package length, data rate, bit-error-rate (BER), pre-receiving time of the receiver, average duty cycle and electronics performance factor are synthesized within a unique model. Comparing to other FOMs like energy per bit E bit , this EFOM is able to rank the overall performance of a wireless network concerning the information not only power efficiency but also about communication quality (speed, BER, wake-up time, etc.), communication effectiveness and user's satisfaction. Applying this model to the system design, a 60 GHz self-demodulating receiver is designed and optimized, which obtains high-speed versatile performance in a low-traffic wireless network with better power efficiency comparing to other low-power wireless interface, e.g. Bluetooth and so on.

The object of the study is a compact heptagonal broadband antenna specially designed for use in the 5G millimeter band using Koch fractals to improve performance. As a result of the study, the most important problem of achieving higher gain, improving bandwidth and reducing interference at higher frequencies, which is necessary for the effective functioning of 5G networks, was solved. As a result, the maximum realized gain of 5 dB was obtained at a frequency of 27.58 GHz with an impressive bandwidth in the range from 26.5 to 40 GHz. The use of Koch fractal geometry and defective ground planes significantly improves impedance matching and expands bandwidth, which explains the excellent antenna performance compared to traditional designs. The features and distinguishing features of the results obtained, thanks to which they allowed solving the problem under study, are its compact dimensions (only 9 mm by 9 mm) and the ability to maintain VSWR at a level of less than 2 in the entire frequency spectrum. These features make the antenna particularly suitable for millimeter-band integration and flexible applications such as portable devices and wearable home appliances. The field of practical application of the results includes integration into portable and wearable devices, improving the performance and connectivity of Internet of Things applications. The conditions of practical use require compliance with 5G network standards and compatibility with millimeter-wave technologies. This characterizes the antenna as a significant achievement in antenna technology, demonstrating its potential for widespread adoption in next-generation wireless communication systems and paving the way for more reliable and high-performance wireless networks

In this work, as a congestion control, the selective celt discarding scheme with an adaptive type-I hybrid automatic repeat request (ARQ) protocol in a wireless ATM network over a Markovian channel is modelled by a fluid queue. In our model, the traffic source is composed of two mini ON-OFF sources of high and low priority cell generators as a layered coded variable bit rate (VBR) source. For cell discarding scheme, when the buffer content exceeds a threshold, the incoming low priority cells are discarded. With an adaptive type-I hybrid ARQ protocol, different error correcting capability is introduced according to each state of the radio channel for combating the fluctuation of channel error statistics. Performance is measured in terms of loss behavior of high and low priority cells, which consists of the controlled loss produced by cell discarding and the tail loss produced at the end of the buffer. Such loss performance of adaptive type-I hybrid ARQ protocol is compared to non-adaptive one according to the source and channel correlation, the threshold, the discarding rate and error correction capability

Mobile ad hoc Network is infrastructure less wireless network and decentralized way, and then for a large network number of nodes dynamically therefor the connection established between source node to destination node is really challenging. The challenge is interconnecting ad hoc network to the internet seems from the needs to inform ad hoc nodes about available gateways in an extremely challenging scenario while a making a minimum consumption of the source network resources. Then an efficient gateway discovery of an ad hoc network becomes one of the central factors to enable the economic consumption of hybrid ad hoc network in future mobile and wireless network. In mobile ad hoc network have multihop nature of MANET therefore several reachable gateways for mobile node at any period of time. If the mobile node receives gatways advertisement from more than one gateway. It has to determine which gateway to use for connecting to the net. Most existing protocol choose the gateway which is closer in terms of the number of physical hops. This paper has focused on design an efficient and adaptive subnetting hybrid gateway discovery mechanism on the basis of dynamic TTL value adjustment such that congestion and unnecessary overhead is reduced. Selecting the gateway on the basis of one and two parameters will increase the performance and throughput of the network. The main objective of adaptive gateway discovery to determine the optimal TTL value in terms of number of hops to determine the proactive area, nodes outside this area follow the reactive approach. Consequently, for achieving a good trade off between performanceand network operating expense.

The next generations of industrial control systems will require high-performance wireless networks (named WirelessHP) able to provide extremely low latency, ultrahigh reliability, and high data rates. The current strategy toward the realization of industrial wireless networks relies on adopting the bottom layers of general purpose wireless standards and customizing only the upper layers. In this paper, a new bottom-up approach is proposed through the realization of a WirelessHP physical layer specifically targeted at reducing the communication latency through the minimization of packet transmission time. Theoretical analysis shows that the proposed design allows a substantial reduction in packet transmission time, down to 1 $\mu$ s, with respect to the general purpose IEEE 802.11 physical layer. The design is validated by an experimental demonstrator, which shows that reliable communications up to 20 m range can be established with the proposed physical layer.

Considering the limited bandwidth of the wireless link, it is important that the error control mechanism in wireless networks be spectrally efficient. Towards this end, we develop a hybrid error control architecture which takes into account the use of hierarchical video coding. Additionally, the architecture also includes a module which estimates the packet error rate and round trip time observed by the receiver and adjusts the level of redundancy used based on the estimate. By choosing different options in the architecture, we get different error control schemes. In this paper, we investigate the performance of five different error control schemes, namely ARQ, pure FEC, hybrid FEC/ARQ, hybrid FEC/ARQ with priority-dependent redundancy, and adaptive hybrid FEC/ARQ with priority-dependent redundancy. We evaluate the performance of these schemes using MPEG-2 video traces. The results show that pure FEC offers the worst overall performance. The ARQ scheme offers the best performance under low bit error rate and short round trip time, while the priority-aware hybrid FEC/ARQ with or without FEC adaptation offers the best performance under other conditions.

Pull-based data delivery is unsuitable for wireless mobile computing due to the limited bandwidth of wireless networks. To address this problem, dissemination based (or push-based) techniques can be used to allow the mobile units to share the broadcast data. This approach is very effective for very popular data. But broadcasting unpopular data repeatedly would waste the precious bandwidth severely. Therefore, the most likely mode of retrieval in wireless mobile environments is going to be mixed, i.e., the popular data objects are broadcast and other (unpopular) objects are provided on demand. To make the mixed approach work seamlessly, we need to measure which data objects are popular. However, the measurement in a wireless broadcasting environment is difficult since in passive broadcasting, users do not communicate with the server to acknowledge the usefulness of the broadcast. In this paper, we investigate an adaptive hybrid approach, in which the popularity of the data objects is determined interactively and dynamically. This information allows us to broadcast only popular data, whereas less popular data is transmitted on-demand (unicast) to conserve network bandwidth. Also, we use a novel technique to determine the amount of bandwidth to be assigned for both broadcast and unicast, in an integrated way. Our simulation results indicate that our technique outperforms recent techniques by a significant margin.

In the past decade, billions of devices and smartphones as terminals have been connected and managed by the wireless networks. Multimedia traffics in high performance wireless network utilities work on QoS-base multiple access protocols, specifically in 5G wireless networks or Industry 4.0. These protocols can enhance utility and effectiveness by increasing throughput, reducing delay, and lessening the loss ratio while the terminals communicate with other terminals in the wireless networks. In this paper, we will present a novel multiple-access protocol in the wireless network and evaluate and analyze the performances of multimedia traffic on the wireless network. Furthermore, administrators or IT regulators can use the protocol as an opportunity to create healthier network environments, which will definitely encourage continuing investment in wireless network and next-generation technology.

The wireless mesh network (WMN) is one of the most promising wireless technologies to achieve high network capacity at a reasonable cost. In WMNs using contention-based medium access method, there may be a lot of collisions and retransmissions in the nearby mesh point collocated with a mesh portal (MPP) due to the concentration of traffic. To reduce the contention around the MPP, an efficient medium access control (MAC) should be designed. In this paper, we propose an adaptive hybrid MAC (AHMAC) scheme which selectively uses point coordination function (PCF) and distributed coordination function (DCF) to effectively carry traffic concentrated on an MPP. For performance evaluation, we considered a mesh network consisting of IEEE 802.11s devices with single- or multi-interface environments. Simulation results showed that an AHMAC can accommodate around 60% more users in single- and multi-interface environments compared with conventional DCF.

Wireless networks have a key role in operational deployment, mobility, the flexibility of network organization and the variety of possible applications, in many cases being the only economically justified solution. Based on the above, for the deployment of wireless networks, the correct theoretical design of the wireless network is an important issue: the required number of devices, their characteristics, placement, energy characteristics of channels, distribution routes and coverage areas, etc. Correct theoretical analysis will ensure error-free construction of the network for the successful implementation of the tasks and will not lead to the need to attract additional material costs. One of the key tasks of wireless communication construction is a reliable assessment of the energy characteristics of a wireless communication channel. Modern global manufacturers of telecommunications equipment build both backbone equipment and equipment to cover WLAN (wireless local area networks) areas, based on IEEE 802.11 standards. One of the most modern standards of the IEEE 802.11 group is the IEEE 802.11ac standard, which is characterized by several improved technical characteristics compared to its predecessor IEEE 802.11n and older versions. That is why the task of evaluating the performance of modern wireless communication equipment based on IEEE 802.11ac standards and analyzing the evaluation of the energy characteristics of the communication channel to predict the parameters and performance characteristics of a point-to-point, point-to-multipoint or other wireless transmission systems within a certain wireless communication network. The following results of solving this problem are presented in this paper: – theoretical evaluation of the energy characteristics of the wireless communication channel. – laboratory studies of wireless communication equipment of the 802.11ac standard based on simulating a communication line using attenuators. – verification of the results of laboratory studies in field conditions based on the model for assessing the quality of communication in a wireless channel created based on the 802.11ac standard.

As wireless networks are increasingly deployed in the enterprise and other environments and such trends are expected to intensify with the emergence of high performance wireless networks, an important and emerging area of research is the dependability of wireless networks. Although, the dependability problem also arises in wireline counterparts, user mobility, location and link dependence, and fault propagation make dependability a challenging task in wireless networks. The main contribution of this paper is to propose a multilevel, fault-tolerant design for the emerging wireless networks. Extensive simulation results show that increased user mobility can be compensated by deploying multi-level redundancy and the performance of wireless link is not critical in the overall availability as long as the link availability stays above a certain threshold. One major contribution of our work is to demonstrate that optimal dependability performance can only be achieved by fault-tolerance at network level.

Industrial applications aimed at real-time control and monitoring of cyber-physical systems pose significant challenges to the underlying communication networks in terms of determinism, low latency, and high reliability. The migration of these networks from wired to wireless could bring several benefits in terms of cost reduction and simplification of design, but currently available wireless techniques cannot cope with the stringent requirements of the most critical applications. In this paper, we consider the problem of designing a high-performance wireless network for industrial control, targeting at Gbps data rates and 10- ${\mu }$ s-level cycle time. To this aim, we start from analyzing the required performance and deployment scenarios, then we take a look at the most advanced standards and emerging trends that may be applicable. Building on this investigation, we outline the main directions for the development of a wireless high-performance system.