Performance enhancements for single hop and multi-hop meshed high data rate wireless personal area networks

This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University.The High Data Rate (HDR) Wireless Personal Area Networks (WPANs) typically have a limited operating range and are intended to support demanding multi-media applications at high data rates. In order to extend the communication range, HDR WPANs can operate in a wireless mesh configuration (i.e. enable multiple WPAN clusters) to communicate in a multi-hop fashion. HDR WPANs face several research challenges and some of the open key issues are limited capacity, optimum resource allocation to requesting devices and maintaining Quality of Service (QoS) for real time multimedia flows. Although, there have been some scheduling algorithms proposed for HDR WPANs, the main objective is to maintain the QoS in most cases whereas efficient and fair utilization of network capacity is still largely open for research. This thesis mainly intends to resolve the issues related to capacity of HDR WPANs such as admission control, fair allocation of Channel Time Allocations (CTAs), improvement in capacity through transmission power control, and efficient utilization of time by each flow. A technique which re-orders the time slots to reduce queuing delay for meshed WPANs is also proposed and evaluated. The first contribution aims to improve peer-to-peer connectivity in case of two or more independent piconet devices by proposing an inter-PAN communication framework that is augmented by an admission control strategy to handle the cases when the superframe capacity is congested. The queued devices are prioritized by proposing a parameter called the Rejection Ratio. The second contribution consists of a resource allocation framework for meshed WPANs. The main objectives are to reduce the control traffic due to high volume of channel time reservation requests and introduce an element of fairness in the channel time allocated to requesting devices. The objectives are achieved by using traffic prediction techniques and an estimated backoff procedure to reduce control traffic, and define different policies based on offered traffic for fair allocation of channel time. The centralized scheme uses traffic prediction techniques to use the proposed concept of bulk reservations. Based on the bulk reservations and resource allocation policies, the overall overhead is reduced while an element of fairness is shown to be maintained for certain scenarios. In the third contribution, the concepts of Time Efficiency and CTA switching are introduced to improve communication efficiency and utilization of superframe capacity in meshed WPANs. Two metrics known as Switched Time Slot (STS) and Switched Time Slot with Re-ordering (STS-R) are proposed which aim to achieve the purpose. The final contribution proposes and evaluates a technique called CTA overlappnig to improve capacity in single hop and meshed WPANs using tramission power control. Extensive simulation studies are performed to analyze and to evaluate the proposed techniques. Simulation results demonstrate significant improvements in meshed WPANs performance in terms of capacity utilization, improvement in fairness index for CTA allocation by upto 62% in some cases, reduction in control traffic overhead by upto 70% and reduction in delay for real time flows by more than 10% in some cases

Performance enhancements for single hop and multi-hop meshed high data rate wireless personal area networks

The High Data Rate (HDR) Wireless Personal Area Networks (WPANs) typically have a limited operating range and are intended to support demanding multi-media applications at high data rates. In order to extend the communication range, HDR WPANs can operate in a wireless mesh configuration (i.e. enable multiple WPAN clusters) to communicate in a multi-hop fashion. HDR WPANs face several research challenges and some of the open key issues are limited capacity, optimum resource allocation to requesting devices and maintaining Quality of Service (QoS) for real time multimedia flows. Although, there have been some scheduling algorithms proposed for HDR WPANs, the main objective is to maintain the QoS in most cases whereas efficient and fair utilization of network capacity is still largely open for research. This thesis mainly intends to resolve the issues related to capacity of HDR WPANs such as admission control, fair allocation of Channel Time Allocations (CTAs), improvement in capacity through transmission power control, and efficient utilization of time by each flow. A technique which re-orders the time slots to reduce queuing delay for meshed WPANs is also proposed and evaluated. The first contribution aims to improve peer-to-peer connectivity in case of two or more independent piconet devices by proposing an inter-PAN communication framework that is augmented by an admission control strategy to handle the cases when the superframe capacity is congested. The queued devices are prioritized by proposing a parameter called the Rejection Ratio. The second contribution consists of a resource allocation framework for meshed WPANs. The main objectives are to reduce the control traffic due to high volume of channel time reservation requests and introduce an element of fairness in the channel time allocated to requesting devices. The objectives are achieved by using traffic prediction techniques and an estimated backoff procedure to reduce control traffic, and define different policies based on offered traffic for fair allocation of channel time. The centralized scheme uses traffic prediction techniques to use the proposed concept of bulk reservations. Based on the bulk reservations and resource allocation policies, the overall overhead is reduced while an element of fairness is shown to be maintained for certain scenarios. In the third contribution, the concepts of Time Efficiency and CTA switching are introduced to improve communication efficiency and utilization of superframe capacity in meshed WPANs. Two metrics known as Switched Time Slot (STS) and Switched Time Slot with Re-ordering (STS-R) are proposed which aim to achieve the purpose. The final contribution proposes and evaluates a technique called CTA overlappnig to improve capacity in single hop and meshed WPANs using tramission power control. Extensive simulation studies are performed to analyze and to evaluate the proposed techniques. Simulation results demonstrate significant improvements in meshed WPANs performance in terms of capacity utilization, improvement in fairness index for CTA allocation by upto 62% in some cases, reduction in control traffic overhead by upto 70% and reduction in delay for real time flows by more than 10% in some cases.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Radio Communications

In the last decades the restless evolution of information and communication technologies (ICT) brought to a deep transformation of our habits. The growth of the Internet and the advances in hardware and software implementations modified our way to communicate and to share information. In this book, an overview of the major issues faced today by researchers in the field of radio communications is given through 35 high quality chapters written by specialists working in universities and research centers all over the world. Various aspects will be deeply discussed: channel modeling, beamforming, multiple antennas, cooperative networks, opportunistic scheduling, advanced admission control, handover management, systems performance assessment, routing issues in mobility conditions, localization, web security. Advanced techniques for the radio resource management will be discussed both in single and multiple radio technologies; either in infrastructure, mesh or ad hoc networks

Nouvelle méthode d'estimation des différences de temps d'arrivée pour la localisation des objets connectés haut débit

The forthcoming vision of Internet of Things (IoT) and Internet of Everything (IoE) will immerse people in so-called Smart Environments involving a great number of sectors of applications such as smart habitat, smart-cities, environment monitoring, e-health… IoT and IoE tend to make everyday objects readable, recognizable, locatable, addressable and controllable via the widespread wireless deployment and the internet. Among these capabilities, localization and more extensively the ubiquitous positioning will play, in the next future, a key role to promote another emerging vision: a spatio-temporal Internet of Places (IoP), which would be able to structure and organize, by means of wireless energy aware approaches, the spatial content of Internet. It is well known that in wireless local and personal area networks, the spectrum congestion, the low energy efficiency communications and the insufficient exploitation of the spatial resources are among the factors that may slow down its development in terms of throughput and autonomy. To overcome these unavoidable restrictions, wireless localization technology, as the mechanism for discovering spatio-temporal relationship between connected objects, appears here also as one of the key solutions. This is because dedicated localization techniques in wireless communication can help in developing more extensively the exploitation of spatial resources and allow driving optimized routing for low energy multi-hop communication and spectrum decongestion for Green ICT (Information and Communication Technology). To propose optimized systems achieving both high data rate communication and precise localization, we define a well suited TDOA (Time Difference of Arrival) based method able to perform localization based on communication signals and data only. With this technique, unlike conventional TDOA estimations, it is possible to drastically decrease the complexity of required infrastructures by using either SIMO (Single Input Multiple Output), MISO (Multiple Input Single Output) or MIMO (Multiple Input Multiple Output) configurations in connected objects. This whole study is made within the framework of the IEEE 802.11ad standard and WiGig alliance specifications, however the proposed solutions are compatible with other standards and can be extended to other context aware applications requiring localization inputs such as robotics for example or smart shopping...La vision future de l'internet des objets (IdO) et Internet du Tout (OIE) plongera les personnes soi-disant environnements intelligents impliquant un grand nombre de secteurs d'applications telles que l'habitat intelligent, smart-villes, surveillance de l'environnement, l'e-santé ... IdO et l'OIE ont tendance à faire des objets du quotidien lisible, identifiable, localisable, adressable et contrôlable via le déploiement sans fil généralisée et l'Internet. Parmi ces capacités, la localisation et plus largement le positionnement omniprésente joueront, dans un proche avenir, un rôle clé pour promouvoir une autre vision émergente: un Internet spatio-temporelle des lieux (IoP), qui serait en mesure de structurer et d'organiser, par des moyens des approches sans fil d'énergie savez, le contenu spatial d'Internet. Il est bien connu que dans les réseaux locaux sans fil et personnelles, l'encombrement du spectre, les communications à faible efficacité énergétique et l'exploitation insuffisante des ressources spatiales sont parmi les facteurs qui peuvent ralentir son développement en termes de débit et de l'autonomie. Pour surmonter ces restrictions inévitables, la technologie de localisation sans fil, comme le mécanisme pour découvrir relation spatio-temporelle entre les objets connectés, apparaît ici aussi comme une des solutions clés. Ce est parce que les techniques de localisation dédiés à la communication sans fil peuvent aider à développer plus largement l'exploitation des ressources spatiales et de permettre la conduite routage optimisé pour une faible énergie communication multi-hop et la décongestion du spectre pour Green ICT (Information et Communication Technology). Pour proposer des systèmes optimisés atteindre à la fois la communication des taux de données élevés et la localisation précise, nous définissons un TDOA bien adapté (Time Difference of Arrival) méthode basée en mesure d'effectuer la localisation basée sur des signaux de communication et de données seulement. Avec cette technique, contrairement estimations TDOA classiques, il est possible de diminuer considérablement la complexité des infrastructures nécessaires en utilisant des configurations SIMO (Single Input Multiple Output), MISO (Multiple Input Single Output) ou MIMO (Multiple Input Multiple Output) dans les objets connectés . Toute cette étude est faite dans le cadre de l'IEEE 802.11ad spécifications de l'alliance standard et WiGig, mais les solutions proposées sont compatibles avec d'autres normes et peuvent être étendues à d'autres applications de contexte courant nécessitant entrées de localisation tels que la robotique par exemple ou de shopping intelligent..

Contributions to Improve Cognitive Strategies with Respect to Wireless Coexistence

Cognitive radio (CR) can identify temporarily available opportunities in a shared radio environment to improve spectral efficiency and coexistence behavior of radio systems. It operates as a secondary user (SU) and accommodates itself in detected opportunities with an intention to avoid harmful collisions with coexisting primary user (PU) systems. Such opportunistic operation of a CR system requires efficient situational awareness and reliable decision making for radio resource allocation. Situational awareness includes sensing the environment followed by a hypothesis testing for detection of available opportunities in the coexisting environment. This process is often known as spectral hole detection. Situational knowledge can be further enriched by forecasting the primary activities in the radio environment using predictive modeling based approaches. Improved knowledge about the coexisting environment essentially means better decision making for secondary resource allocation. This dissertation identifies limitations of existing predictive modeling and spectral hole detection based resource allocation strategies and suggest improvements. Firstly, accurate and efficient estimation of statistical parameters of the radio environment is identified as a fundamental challenge to realize predictive modeling based cognitive approaches. Lots of useful training data which are essential to learn the system parameters are not available either because of environmental effects such as noise, interference and fading or because of limited system resources particularly sensor bandwidth. While handling environmental effects to improve signal reception in radio systems has already gained much attention, this dissertation addresses the problem of data losses caused by limited sensor bandwidth as it is totally ignored so far and presents bandwidth independent parameter estimation methods. Where, bandwidth independent means achieving the same level of estimation accuracy for any sensor bandwidth. Secondly, this dissertation argues that the existing hole detection strategies are dumb because they provide very little information about the coexisting environment. Decision making for resource allocation based on this dumb hole detection approach cannot optimally exploit the opportunities available in the coexisting environment. As a solution, an intelligent hole detection scheme is proposed which suggests classifying the primary systems and using the documented knowledge of identified radio technologies to fully understand their coexistence behavior. Finally, this dissertation presents a neuro-fuzzy signal classifier (NFSC) that uses bandwidth, operating frequency, pulse shape, hopping behavior and time behavior of signals as distinct features in order to xii identify the PU signals in coexisting environments. This classifier provides the foundation for bandwidth independent parameter estimation and intelligent hole detection. MATLAB/Simulink based simulations are used to support the arguments throughout in this dissertation. A proof-of-concept demonstrator using microcontroller and hardware defined radio (HDR) based transceiver is also presented at the end.</p

Scalable wireless sensor networks for dynamic communication environments: simulation and modelling

This thesis explores the deployment of Wireless Sensor Networks (WSNs) on localised maritime events. In particular, it will focus on the deployment of a WSN at sea and estimating what challenges derive from the environment and how they affect communication. This research addresses these challenges through simulation and modelling of communication and environment, evaluating the implications of hardware selection and custom algorithm development. The first part of this thesis consists of the analysis of aspects related to the Medium Access Control layer of the network stack in large-scale networks. These details are commonly hidden from upper layers, thus resulting in misconceptions of real deployment characteristics. Results show that simple solutions have greater advantages when the number of nodes within a cluster increases. The second part considers routing techniques, with focus on energy management and packet delivery. It is shown that, under certain conditions, relaying data can increase energy savings, while at the same time allows a more even distribution of its usage between nodes. The third part describes the development of a custom-made network simulator. It starts by considering realistic radio, channel and interference models to allow a trustworthy simulation of the deployment environment. The MAC and Routing techniques developed thus far are adapted to the simulator in a cross-layer manner. The fourth part consists of adapting the WSN behaviour to the variable weather and topology found in the chosen application scenario. By analysing the algorithms presented in this work, it is possible to find and use the best alternative under any set of environmental conditions. This mechanism, the environment-aware engine, uses both network and sensing data to optimise performance through a set of rules that involve message delivery and distance between origin and cluster hea

Trustworthy Wireless Personal Area Networks

In the Internet of Things (IoT), everyday objects are equipped with the ability to compute and communicate. These smart things have invaded the lives of everyday people, being constantly carried or worn on our bodies, and entering into our homes, our healthcare, and beyond. This has given rise to wireless networks of smart, connected, always-on, personal things that are constantly around us, and have unfettered access to our most personal data as well as all of the other devices that we own and encounter throughout our day. It should, therefore, come as no surprise that our personal devices and data are frequent targets of ever-present threats. Securing these devices and networks, however, is challenging. In this dissertation, we outline three critical problems in the context of Wireless Personal Area Networks (WPANs) and present our solutions to these problems. First, I present our Trusted I/O solution (BASTION-SGX) for protecting sensitive user data transferred between wirelessly connected (Bluetooth) devices. This work shows how in-transit data can be protected from privileged threats, such as a compromised OS, on commodity systems. I present insights into the Bluetooth architecture, Intel’s Software Guard Extensions (SGX), and how a Trusted I/O solution can be engineered on commodity devices equipped with SGX. Second, I present our work on AMULET and how we successfully built a wearable health hub that can run multiple health applications, provide strong security properties, and operate on a single charge for weeks or even months at a time. I present the design and evaluation of our highly efficient event-driven programming model, the design of our low-power operating system, and developer tools for profiling ultra-low-power applications at compile time. Third, I present a new approach (VIA) that helps devices at the center of WPANs (e.g., smartphones) to verify the authenticity of interactions with other devices. This work builds on past work in anomaly detection techniques and shows how these techniques can be applied to Bluetooth network traffic. Specifically, we show how to create normality models based on fine- and course-grained insights from network traffic, which can be used to verify the authenticity of future interactions

QoS Scheduling in IEEE 802.16 Broadband Wireless Access Networks

With the exploding increase of mobile users and the release of new wireless applications, the high bandwidth requirement has been taking as a main concern for the design and development of the wireless techniques. There is no doubt that broadband wireless access with the support of heterogeneous kinds of applications is the trend in the next generation wireless networks. As a promising broadband wireless access standard, IEEE 802.16 has attracted extensive attentions from both industry and academia due to its high data rate and the inherent media access control (MAC) mechanism, which takes the service differentiation and quality of service (QoS) provisioning into account. To achieve service differentiation and QoS satisfaction for heterogenous applications is a very complicated issue. It refers to many fields, such as connection admission control (CAC), congestion control, routing algorithm, MAC protocol, and scheduling scheme. Among these fields, packet scheduling plays one of the most important roles in fulfilling service differentiation and QoS provisioning. It decides the order of packet transmissions, and provides mechanisms for the resource allocation and multiplexing at the packet level to ensure that different types of applications meet their service requirements and the network maintains a high resource utilization. In this thesis, we focus on the packet scheduling for difficult types of services in IEEE 802.16 networks, where unicast and mulitcast scheduling are investigated. For unicast scheduling, two types of services are considered: non-real-time polling service (nrtPS) and best effort (BE) service. We propose a flexible and efficient resource allocation and scheduling framework for nrtPS applications to achieve a tradeoff between the delivery delay and resource utilization, where automatic repeat request (ARQ) mechanisms and the adaptive modulation and coding (AMC) technique are jointly considered. For BE service, considering the heterogeneity of subscriber stations (SSs) in IEEE 802.16 networks, we propose the weighted proportional fairness scheduling scheme to achieve the flexible scheduling and resource allocation among SSs based on their traffic demands/patterns. For multicast scheduling, a cooperative multicast scheduling is proposed to achieve high throughput and reliable transmission. By using the two-phase transmission model to exploit the spatial diversity gain in the multicast scenario, the proposed scheduling scheme can significantly improve the throughput not only for all multicast groups, but also for each group member. Analytical models are developed to investigate the performance of the proposed schemes in terms of some important performance measurements, such as throughput, resource utilization, and service probability. Extensive simulations are conducted to illustrate the efficient of the proposed schemes and the accuracy of the analytical models. The research work should provide meaningful guidelines for the system design and the selection of operational parameters, such as the number of TV channels supported by the network, the achieved video quality of each SS in the network, and the setting of weights for SSs under different BE traffic demands

Supporting Internet Access and Quality of Service in Distributed Wireless Ad Hoc Networks

In this era of wireless hysteria, with continuous technological advances in wireless communication and new wireless technologies becoming standardized at a fast rate, we can expect an increased interest for wireless networks, such as ad hoc and mesh networks. These networks operate in a distributed manner, independent of any centralized device. In order to realize the practical benefits of ad hoc networks, two challenges (among others) need to be considered: distributed QoS guarantees and multi-hop Internet access. In this thesis we present conceivable solutions to both of these problems. An autonomous, stand-alone ad hoc network is useful in many cases, such as search and rescue operations and meetings where participants wish to quickly share information. However, an ad hoc network connected to the Internet is even more desirable. This is because Internet plays an important role in the daily life of many people by offering a broad range of services. In this thesis we present AODV+, which is our solution to achieve this network interconnection between a wireless ad hoc network and the wired Internet. Providing QoS in distributed wireless networks is another challenging, but yet important, task mainly because there is no central device controlling the medium access. In this thesis we propose EDCA with Resource Reservation (EDCA/RR), which is a fully distributed MAC scheme that provides QoS guarantees by allowing applications with strict QoS requirements to reserve transmission time for contention-free medium access. Our scheme is compatible with existing standards and provides both parameterized and prioritized QoS. In addition, we present the Distributed Deterministic Channel Access (DDCA) scheme, which is a multi-hop extension of EDCA/RR and can be used in wireless mesh networks. Finally, we have complemented our simulation studies with real-world ad hoc and mesh network experiments. With the experience from these experiments, we obtained a clear insight into the limitations of wireless channels. We could conclude that a wise design of the network architecture that limits the number of consecutive wireless hops may result in a wireless mesh network that is able to satisfy users’ needs. Moreover, by using QoS mechanisms like EDCA/RR or DDCA we are able to provide different priorities to traffic flows and reserve resources for the most time-critical applications