Efficiency of WLAN 802.11xx in the multi-hop topology

The article presents the research results of the performance of wireless multi-hop networks. The analysis of the decrease in performance of such networks depending on the number of hops was performed for three popular transmission techniques used in mesh networks: Hybrid Wireless Mesh Protocol (default routing protocol for 802.11s), Optimized Link State Routing Protocol and Wireless Distribution System. Based on the measurements results, mathematical models for the decreasing of network transmission parameters depending on the number of hops were developed

Performance analysis of wireless mesh networks for underground mines

Abstract: Underground mines are harsh environments that have unique challenges that limit wireless communication. To ensure the safety and efficiency of mining operations, communication systems play a vital role. Despite the major developments in communication technologies, underground mines are still challenging environments for wireless communication, however, the advent of wireless mesh networks offers a cutting-edge solution to the mining industry and understanding the performance of this technology is fundamental to its application in dynamic areas of underground mines. This research project aims at conducting a performance analysis of wireless mesh networks by developing a prototype system set up of wireless mesh transceivers to conduct a feasibility study of data transmission on the network in underground mines. The second aspect of this study investigates network parameters, such as latency, throughput, and signal-to-noise, as a function of increasing mesh nodes on the network and internode spacing of mesh nodes. By combining theoretical models with real-time performance of the mesh system, realistic conclusions and better recommendations can be given to mining companies with regards to deploying wireless mesh systems in their underground mines.M.Ing. (Electrical and Electronic Engineering Science

Underground Mining Monitoring and Communication Systems based on ZigBee and GIS

ZigBee as a wireless sensor network (WSN) was developed for underground mine monitoring and communication systems. The radio wave attenuations between ZigBee nodes were investigated to measure underground communication distances. Various sensor node arrangements of ZigBee topologies were evaluated. A system integration of a WSN-assisted GIS for underground mining monitoring and communication from a surface office was proposed. The controllable and uncontrollable parameters of underground environments were assessed to establish a reliable ZigBee network

Best effort QoS support routing in mobile ad hoc networks

In the past decades, mobile traffic generated by devices such as smartphones, iphones, laptops and mobile gateways has been growing rapidly. While traditional direct connection techniques evolve to provide better access to the Internet, a new type of wireless network, mobile ad hoc network (MANET), has emerged. A MANET differs from a direct connection network in the way that it is multi-hopping and self-organizing and thus able to operate without the help of prefixed infrastructures. However, challenges such dynamic topology, unreliable wireless links and resource constraints impede the wide applications of MANETs. Routing in a MANET is complex because it has to react efficiently to unfavourable conditions and support traditional IP services. In addition, Quality of Service (QoS) provision is required to support the rapid growth of video in mobile traffic. As a consequence, tremendous efforts have been devoted to the design of QoS routing in MANETs, leading to the emergence of a number of QoS support techniques. However, the application independent nature of QoS routing protocols results in the absence of a one-for-all solution for MANETs. Meanwhile, the relative importance of QoS metrics in real applications is not considered in many studies. A Best Effort QoS support (BEQoS) routing model which evaluates and ranks alternative routing protocols by considering the relative importance of multiple QoS metrics is proposed in this thesis. BEQoS has two algorithms, SAW-AHP and FPP for different scenarios. The former is suitable for cases where uncertainty factors such as standard deviation can be neglected while the latter considers uncertainty of the problems. SAW-AHP is a combination of Simple Additive Weighting and Analytic Hierarchical Process in which the decision maker or network operator is firstly required to assign his/her preference of metrics with a specific number according to given rules. The comparison matrices are composed accordingly, based on which the synthetic weights for alternatives are gained. The one with the highest weight is the optimal protocol among all alternatives. The reliability and efficiency of SAW-AHP are validated through simulations. An integrated architecture, using evaluation results of SAW-AHP is proposed which incorporates the ad hoc technology into the existing WLAN and therefore provides a solution for the last mile access problems. The protocol selection induced cost and gains are also discussed. The thesis concludes by describing the potential application area of the proposed method. Fuzzy SAW-AHP is extended to accommodate the vagueness of the decision maker and complexity of problems such as standard deviation in simulations. The fuzzy triangular numbers are used to substitute the crisp numbers in comparison matrices in traditional AHP. Fuzzy Preference Programming (FPP) is employed to obtain the crisp synthetic weight for alternatives based on which they are ranked. The reliability and efficiency of SAW-FPP are demonstrated by simulations

Interferência intersimbólica, ruído e capacidade de canal em um sistema de comunicação através-da-terra

Dissertação (mestrado)—Universidade de Brasília, Faculdade de Tecnologia, Departamento de Engenharia Elétrica, 2017.O ambiente de trabalho em uma mina é frequentemente perigoso, especialmente em minas subterrâneas. Para reduzir a ocorrência e a gravidade de acidentes, vêm surgindo legislações que visam regulamentar o setor de mineração e com isso torná-lo mais seguro e eficiente. Uma das demandas é o emprego de um sistema de comunicação que possa ser usado em caso de acidente. Os sistemas de comunicação através-da-terra (TTE - through-theearth), normalmente baseados em indução magnética, têm sido propostos para esse uso. Além da questão da segurança, um sistema de comunicação através-da-terra pode ser usado cotidianamente na mina. Um sistema de comunicação eficiente melhora o fluxo de informação e aumenta a chance de sucesso em atingir os objetivos traçados. Neste trabalho, é analisada a camada física dos sistemas de comunicação através-daterra com o objetivo de, por meio de simulações, propor técnicas que melhorem o desempenho dos sistemas. É mostrado que o canal TTE é passa-faixas e seletivo em frequência, além de depender fortemente da condutividade do solo. Por ser passa-faixas, há uma frequência ótima ou de pico, onde normalmente é centralizada a banda do sinal transmitido de modo a reduzir a interferência intersimbólica. Devido à forte atenuação do canal TTE com o aumento da frequência, sinais na banda VLF (very low frequency) são normalmente utilizadas. Nesta banda, o ruído atmosférico é relevante e é mostrado como isso piora o desempenho do sistema. Apesar de ser natural usar modulação digital com o espectro do sinal centralizado na frequência ótima, é mostrado que um sistema em banda base é viável e, para altas taxas de símbolo, seu desempenho é superior ao sistema em banda passante. Finalmente, é investigado o uso de antenas ressonantes em sistemas de comunicação TTE, como elas afetam a resposta em frequência e, consequentemente, a capacidade do canal. Observa-se que a capacidade do sistema ressonante é superior ao sistema nãoressonante quando a potência disponível é baixa.The work environment in a mine is often dangerous, especially in underground mines. To reduce the occurrence and severity of accidents, legislation has been emerging to regulate the mining sector in order to make it safer and more efficient. One of the demands is the implementation of a communication system that can be used in case of an accident. Through- the-earth (TTE) communication systems, usually based on magnetic induction, have been suggested for use in this scenario. In addition to safety and emergency applications, a TTE communication system can be used in daily mining operations. An efficient communication system improves the flow of information and increases the chance of success in reaching the objectives outlined. In this paper, we analyze the physical layer of through-the-earth communication systems. Using simulations, we propose techniques to improve the system performance. It is shown that the TTE channel is bandpass and frequency selective. Moreover, the channel response is strongly dependent on the soil conductivity. Since it is bandpass, there is also an optimum or peak frequency, often chosen as the carrier frequency in order to reduce intersymbol interference. Due to strong attenuation imposed by the TTE channel in higher frequencies, signals in the very low frequency (VLF) band are normally used. In this band, the atmospheric noise is relevant and it is shown that it worsens system performance. Although it feels natural to use digital modulation with carrier frequency equal to the optimum frequency, it is shown that a baseband system is feasible and, for high symbol rates, its performance is superior to a bandpass system. Finally, the use of resonant antennas in TTE communication systems is investigated. The resonant antennas affect the channel frequency response and, consequently, the channel capacity. It is observed that the capacity of the resonant system is higher than the non-resonant system when the available power is low

Unmanned aerial vehicle communications for civil applications: a review

The use of drones, formally known as unmanned aerial vehicles (UAVs), has significantly increased across a variety of applications over the past few years. This is due to the rapid advancement towards the design and production of inexpensive and dependable UAVs and the growing request for the utilization of such platforms particularly in civil applications. With their intrinsic attributes such as high mobility, rapid deployment and flexible altitude, UAVs have the potential to be utilized in many wireless system applications. On the one hand, UAVs are able to operate as flying mobile terminals within wireless/cellular networks to support a variety of missions such as goods delivery, search and rescue, precision agriculture monitoring, and remote sensing. On the other hand, UAVs can be utilized as aerial base stations to increase wireless communication coverage, reliability, and the capacity of wireless systems without additional investment in wireless systems infrastructure. The aim of this article is to review the current applications of UAVs for civil and commercial purposes. The focus of this paper is on the challenges and communication requirements associated with UAV-based communication systems. This article initially classifies UAVs in terms of various parameters, some of which can impact UAVs’ communication performance. It then provides an overview of aerial networking and investigates UAVs routing protocols specifically, which are considered as one of the challenges in UAV communication. This article later investigates the use of UAV networks in a variety of civil applications and considers many challenges and communication demands of these applications. Subsequently, different types of simulation platforms are investigated from a communication and networking viewpoint. Finally, it identifies areas of future research

A software-defined survivability approach for wireless sensor networks in future internet of the things

This thesis was submitted for the award of Doctor of Philosophy and was awarded by Brunel University LondonThe Internet of the Things (IoT) is evolving rapidly, and its significant impacts are expected to affect many application domains. Challenges in areas that humans have been striving to understand, measure, or predict—such as wildlife, healthcare, or environmental hazards—are likely to be addressed by the time IoT emerges. The underlying elements of IoT are wireless sensor networks (WSNs), which consist of a large number of sensor nodes. In the IoT sphere, sensor nodes represent tangible objects—Things—that monitor changes, collect information, and eventually send it through the Internet to a recipient party. Inherently, however, a wireless sensor node relies on limited computational resources with a limited power source. These undesirable qualities result in a low level of dependability. This research explores the viability of applying the unfolding network programmability concepts to overcome survivability obstacles in WSNs and the IoT. In particular, it examines the viability of software-defined networking (SDN) in network lifetime maximisation, failure detection, and failure recovery problems in WSNs. Software-defined networking is a new network programmability concept that separates the traditionally-tied control and data planes. It offloads the route computations and management from network devices to a logically centralised controller. This separation directly leads to better allocation of computational resources for the network nodes and allows endless orchestration possibilities for the controller. This thesis proposes an SDN-based solution to increase the survivability and resilience of WSN environments. Following an approach that conforms with the centralised nature of SDN environments and considers the limited resources of the WSN. A routing algorithm based on A-star was developed for WSNs, then deployed within an SDN environment to maximise the network lifetime. Apart from finding the path with the lowest energy burden, the algorithm offloads most of the control traffic from sensor nodes to the controller. This algorithm resulted in improved resource utilisation among the nodes due to plane decoupling. Additionally, it increased the lifetime of the network by 22.6% compared to the widely explored LEACH protocol. This thesis also investigates different failure detection and recovery practices in the SDN architecture. The simulation results show that adopting bidirectional forwarding detection (BFD) with the asynchronous echo mode for WSN in an SDN environment reduces control traffic for failure detection to between 27% and 48%. The thesis also evaluates the performance of multiple recovery approaches when adopting the premises of SDN. The simulation results indicate that path protection, using group tables from the OpenFlow protocol, has a recovery time up to eight times shorter than the restoration time. The results of the study reveal that using protection as a failure recovery technique significantly reduces control traffic overhead