WiQoSM: An Integrated QoS-Aware Mobility and User Behavior Model for Wireless Data Networks

Modeling mobility and user behavior is of fundamental importance in testing the performance of protocols for wireless data networks. While several models have been proposed in the literature, none of them can at the same time capture important features such as geographical mobility, user generated traffic, and wireless technology at hand. When collectively considered, these three aspects determine the user-perceived QoS-level, which, in turn, might have an influence on mobility of those users (we call them QoSdriven users) who do not display constrained mobility patterns, but they can decide to move to less congested areas of the network in case their perceived QoS-level becomes unacceptable. In this paper, we introduce the WiQoSM model which collectively considers all the above mentioned aspects of wireless data networks. WiQoSM is composed of i) a user mobility model, ii) a user traffic model, iii) a wireless technology model, and iv) a QoS model. Components i), ii), and iii) provide input to the QoS model, which, in turn, can influence the mobility behavior of QoS-driven users. WiQoSM is very simple to use and configure, and can be used to generate user and traffic traces at the APs composing a wireless data network. Based on WiQoSM, we perform an extensive simulation-based analysis of network usage under different combinations of network parameters, which discloses interesting insights and shows that WiQoSM, despite its simplicity, is able to capture important properties observed in real-world network deployments

Wireless Sensor Networking in Challenging Environments

Recent years have witnessed growing interest in deploying wireless sensing applications in real-world environments. For example, home automation systems provide fine-grained metering and control of home appliances in residential settings. Similarly, assisted living applications employ wireless sensors to provide continuous health and wellness monitoring in homes. However, real deployments of Wireless Sensor Networks (WSNs) pose significant challenges due to their low-power radios and uncontrolled ambient environments. Our empirical study in over 15 real-world apartments shows that low-power WSNs based on the IEEE 802.15.4 standard are highly susceptible to external interference beyond user control, such as Wi-Fi access points, Bluetooth peripherals, cordless phones, and numerous other devices prevalent in residential environments that share the unlicensed 2.4 GHz ISM band with IEEE 802.15.4 radios. To address these real-world challenges, we developed two practical wireless network protocols including the Adaptive and Robust Channel Hopping (ARCH) protocol and the Adaptive Energy Detection Protocol (AEDP). ARCH enhances network reliability through opportunistically changing radio\u27s frequency to avoid interference and environmental noise and AEDP reduces false wakeups in noisy wireless environments by dynamically adjusting the wakeup threshold of low-power radios. Another major trend in WSNs is the convergence with smart phones. To deal with the dynamic wireless conditions and varying application requirements of mobile users, we developed the Self-Adapting MAC Layer (SAML) to support adaptive communication between smart phones and wireless sensors. SAML dynamically selects and switches Medium Access Control protocols to accommodate changes in ambient conditions and application requirements. Compared with the residential and personal wireless systems, industrial applications pose unique challenges due to their critical demands on reliability and real-time performance. We developed an experimental testbed by realizing key network mechanisms of industrial Wireless Sensor and Actuator Networks (WSANs) and conducted an empirical study that revealed the limitations and potential enhancements of those mechanisms. Our study shows that graph routing is more resilient to interference and its backup routes may be heavily used in noisy environments, which demonstrate the necessity of path diversity for reliable WSANs. Our study also suggests that combining channel diversity with retransmission may effectively reduce the burstiness of transmission failures and judicious allocation of multiple transmissions in a shared slot can effectively improve network capacity without significantly impacting reliability

Towards next generation WLANs: exploiting coordination and cooperation

Wireless Local Area Networks (WLANs) operating in the industrial, scientific and medical (ISM) radio bands have gained great popularity and increasing usage over the past few years. The corresponding MAC/PHY specification, the IEEE 802.11 standard, has also evolved to adapt to such development. However, as the number of WLAN mobile users increases, and as their needs evolve in the face of new applications, there is an ongoing need for the further evolution of the IEEE 802.11 standard. In this thesis we propose several MAC/PHY layer protocols and schemes that will provide more system throughput, lower packet delivery delay and lessen the power consumption of mobile devices. Our work investigates three approaches that lead to improved WLAN performance: 1) cross-layer design of the PHY and MAC layers for larger system throughput, 2) exploring the use of implicit coordination among clients to increase the efficiency of random media access, and 3) improved packets dispatching by the access points (APs) to preserve the battery of mobile devices. Each proposed solution is supported by theoretical proofs and extensively studied by simulations or experiments on testbeds

On Reliable Transmission of Data over Simple Wireless Channels

Standard protocols for reliable data transmission over unreliable channels are based on various Automatic Repeat reQuest (ARQ) schemes, whereby the sending node receives feedback from the receiver and retransmits the missing data. We discuss this issue in the context of one-way data transmission over simple wireless channels characteristic of many sensing and monitoring applications. Using a specific project as an example, we demonstrate how the constraints of a low-cost embedded wireless system get in the way of a workable solution precluding the use of popular schemes based on windows and periodic acknowledgments. We also propose an efficient solution to the problem and demonstrate its advantage over the traditional protocols

Estabelecimento de redes de comunidades sobreponíveis

Doutoramento em Engenharia InformáticaUma das áreas de investigação em Telecomunicações de interesse crescente prende-se com os futuros sistemas de comunicações móveis de 4a geração e além destes. Nos últimos anos tem sido desenvolvido o conceito de redes comunitárias, no qual os utilizadores se agregam de acordo com interesses comuns. Estes conceitos têm sido explorados de uma forma horizontal em diferentes camadas da comunicação, desde as redes comunitárias de comunicação (Seattle Wireless ou Personal Telco, p.ex.) até às redes de interesses peer-to-peer. No entanto, estas redes são usualmente vistas como redes de overlay, ou simplesmente redes de associação livre. Na prática, a noção de uma rede auto-organizada, completamente orientada ao serviço/comunidade, integralmente suportada em termos de arquitetura, não existe. Assim este trabalho apresenta uma realização original nesta área de criação de redes comunitárias, com uma arquitetura subjacente orientada a serviço, e que suporta integralmente múltiplas redes comunitárias no mesmo dispositivo, com todas as características de segurança, confiança e disponibilização de serviço necessárias neste tipo de cenários (um nó pode pertencer simultaneamente a mais do que uma rede comunitária). Devido à sua importância para os sistemas de redes comunitárias, foi dado particular atenção a aspetos de gestão de recursos e controlo de acessos. Ambos realizados de uma forma descentralizada e considerando mecanismos dotados de grande escalabilidade. Para isso, é apresentada uma linguagem de políticas que suporta a criação de comunidades virtuais. Esta linguagem não é apenas utilizada para o mapeamento da estrutura social dos membros da comunidade, como para, gerir dispositivos, recursos e serviços detidos pelos membros, de uma forma controlada e distribuída.One of the research areas with increasing interest in the field of telecommunications, are the ones related to future telecommunication systems, both 4th generation and beyond. In parallel, during the last years, several concepts have been developed related to clustering of users according to their interested, in the form of community networks. Solutions proposed for these concepts tackle the challenges horizontally, for each layer of the communication stack, ranging from community based communication networks (e.g. Seattle Wireless, or Personal Telco), to interest networks based on peer-to-peer protocols. However, these networks are presented either as free joining, or overlay networks. In practice, the notion of a self-organized, service and community oriented network, with these principles embedded in its design principles, is yet to be developed. This work presents an novel instantiation of a solution in the area of community networks, with a underlying architecture which is fully service oriented, and envisions the support for multiple community networks in the same device. Considerations regarding security, trust and service availability for this type of environments are also taken. Due to the importance of resource management and access control, in the context of community driven communication networks, a special focus was given to the support of scalable and decentralized management and access control methods. For this purpose, it is presented a policy language which supports the creation and management of virtual communities. The language is not only used for mapping the social structure of the community members, but also to, following a distributed approach, manage devices, resources and services owned by each community member

Facilitating Internet of Things on the Edge

The evolution of electronics and wireless technologies has entered a new era, the Internet of Things (IoT). Presently, IoT technologies influence the global market, bringing benefits in many areas, including healthcare, manufacturing, transportation, and entertainment. Modern IoT devices serve as a thin client with data processing performed in a remote computing node, such as a cloud server or a mobile edge compute unit. These computing units own significant resources that allow prompt data processing. The user experience for such an approach relies drastically on the availability and quality of the internet connection. In this case, if the internet connection is unavailable, the resulting operations of IoT applications can be completely disrupted. It is worth noting that emerging IoT applications are even more throughput demanding and latency-sensitive which makes communication networks a practical bottleneck for the service provisioning. This thesis aims to eliminate the limitations of wireless access, via the improvement of connectivity and throughput between the devices on the edge, as well as their network identification, which is fundamentally important for IoT service management. The introduction begins with a discussion on the emerging IoT applications and their demands. Subsequent chapters introduce scenarios of interest, describe the proposed solutions and provide selected performance evaluation results. Specifically, we start with research on the use of degraded memory chips for network identification of IoT devices as an alternative to conventional methods, such as IMEI; these methods are not vulnerable to tampering and cloning. Further, we introduce our contributions for improving connectivity and throughput among IoT devices on the edge in a case where the mobile network infrastructure is limited or totally unavailable. Finally, we conclude the introduction with a summary of the results achieved

The dynamics and strategic analysis of wireless communications technology in the healthcare industry

Thesis (S.M.)--Massachusetts Institute of Technology, Sloan School of Management, 2006.Includes bibliographical references (leaves 98-99).The healthcare industry like other industry is on the cross roads as a result of rising demand for healthcare delivery and service, the industry is facing declining revenues and increasing cost. As a result, one of the industry's strategic arsenal to avert the continual declines in revenue and increases operating cost is to effectively use modern technology in form of wireless computing and communications technology to change the paradigm shift to improve outcomes of clinical services, enhance physician and nurse productivity and work flow efficiency, reduce supply chain cost, improve revenue collection and practice profitability. This report presents the dynamic and strategic analysis of wireless communications technology in the healthcare industry, by first evaluating the wireless technologies, industry standards and regulations, applicable standards for the healthcare information systems and innovative healthcare technologies.(cont.) Based on an in-depth technical analysis of the wireless technology, I analyzed the market and industry by applying frameworks including Porter's 5 forces and The Delta model and system dynamics models presented to illustrate contributing factors affecting new technology adoption in the healthcare industry and a holistic view of a healthcare IT system architecture. Lastly, I analyzed emerging wireless technologies including WiMAX, UltraWide -Band and RFID, and reviewed market opportunities in the healthcare industry through 2011.by John K. Eyemaro.S.M

A Comprehensive Survey on Moving Networks

The unprecedented increase in the demand for mobile data, fuelled by new emerging applications such as HD video streaming and heightened online activities has caused massive strain on the existing cellular networks. As a solution, the 5G technology has been introduced to improve network performance through various innovative features such as mmWave spectrum and HetNets. In essence, HetNets include several small cells underlaid within macro-cell to serve densely populated regions. Recently, a mobile layer of HetNet has been under consideration by the researchers and is often referred to as moving networks. Moving networks comprise of mobile cells that are primarily introduced to improve QoS for commuting users inside public transport because the QoS is deteriorated due to vehicular penetration losses. Furthermore, the users inside fast moving public transport also exert excessive load on the core network due to large group handovers. To this end, mobile cells will play a crucial role in reducing overall handover count and will help in alleviating these problems by decoupling in-vehicle users from the core network. To date, remarkable research results have been achieved by the research community in addressing challenges linked to moving networks. However, to the best of our knowledge, a discussion on moving networks in a holistic way is missing in the current literature. To fill the gap, in this paper, we comprehensively survey moving networks. We cover the technological aspects and their applications in the futuristic applications. We also discuss the use-cases and value additions that moving networks may bring to future cellular architecture and identify the challenges associated with them. Based on the identified challenges we discuss the future research directions.Comment: This survey has been submitted to IEEE Communications Surveys & Tutorial

Unmanned aerial vehicles (UAVs) for wireless communication and networks : potentials and design challenges

Unmanned aerial vehicles (UAVs) are mostly considered by the military for surveillance and reconnaissance operations, and by hobbyists for aerial photography. However, in recent years, the UAV operations have been extended for civilian and commercial purposes due to their agile and cost-effective deployment. UAVs appear to be more prolific platforms to enable wireless communication due to their better line-of-sight (LOS) channel conditions as compared with the fixed base stations (BSs) in terrestrial communication which suffer from severe path loss, shadowing, and multipath fading in more challenging propagation environments. In UAV-enabled wireless communications, the UAV can either act as a complementary aerial BS to provide on-demand communication or as an aerial user equipment (UE) which is operated by the existing cellular network. Several challenges exist in the design of UAV communications which include but not limited to channel modeling, optimal deployment, interference generation, performance analysis, limited on-board battery lifetime, trajectory optimization, and unavailability of regulations and standards which are specific for UAV communication and networking. This thesis particularly investigates some important design challenges for safe and reliable functionalities of UAV for wireless communication and networking. UAV communication has its own distinctive channel characteristics compared to the widely used cellular or satellite systems. However, several challenges exist in UAV channel modeling. For example, the propagation characteristics of UAV channels are under explored for spatial and temporal variations in non-stationary channels. Therefore, first and foremost, this thesis provides an extensive review of the measurement methods proposed for UAV channel modeling and discusses channel modeling efforts for air-to-ground and air-to-air channels. Furthermore, knowledge-gaps are identified to realize accurate UAV channel models. The efficient deployment strategy is imperative to compensate the adverse impact of interference on the coverage area performance of multiple UAVs. As a result, this thesis proposes an optimal deployment strategy for multiple UAVs in presence of downlink co-channel interference in the worst-case scenario. In particular, this work presents coordinated multi-UAV strategy in two schemes. In the first scheme, symmetric placement of UAVs is assumed at a common optimal altitude and transmit power. In the second scheme, asymmetric deployment of UAVs with different altitudes and transmit powers is assumed. The impact of various system parameters, such as signal-to interference-plus-noise ratio (SINR) threshold, separation distance between UAVs, and the number of UAVs and their formations are carefully studied to achieve the maximum coverage area inside and to reduce the unnecessary coverage expansion outside the target area. Fundamental analysis is required to obtain the optimal trade-off between the design parameters and performance metrics of any communication systems. This thesis particularly considers two emerging scenarios for evaluating performance of UAV communication systems. In the first scenario, the uplink UAV communication system is considered where the ground user follows the random waypoint (RWP) model for user mobility, the small-scale channel fading follows the Nakagami-m model, and the uplink interference is modeled by Gamma approximation. Specifically, the closed-form expressions for the probability density function (PDF), the cumulative distribution function (CDF), the outage probability, and the average bit error rate (BER) of the considered UAV system are derived as performance metrics. In the second scenario, the downlink hybrid caching system is considered where UAVs and ground small-cell BSs (SBSs) are distributed according to two independent homogeneous Poisson point processes (PPPs), and downlink interference is modeled by the Laplace transforms. Specifically, the analytical expressions of the successful content delivery probability and energy efficiency of the considered network are derived as performance metrics. In both scenarios, results are presented to demonstrate the interplay between the communication performance and the design parameters