RandomCast: An Energy-Efficient Communication Scheme for Mobile Ad Hoc Networks

In mobile ad hoc networks (MANETs), every node overhears every data transmission occurring in its vicinity and thus, consumes energy unnecessarily. However, since some MANET routing protocols such as dynamic source routing (DSR) collect route information via overhearing, they would suffer if they are used in combination with 802.11 PSM. Allowing no overhearing may critically deteriorate the performance of the underlying routing protocol, while unconditional overhearing may offset the advantage of using PSM. This paper proposes a new communication mechanism, called RandomCast, via which a sender can specify the desired level of overhearing, making a prudent balance between energy and routing performance. In addition, it reduces redundant rebroadcasts for a broadcast packet, and thus, saves more energy. Extensive simulation using NS-2 shows that RandomCast is highly energy-efficient compared to conventional 802.11 as well as 802.11 PSM-based schemes, in terms of total energy consumption, energy goodput, and energy balance

Performance Prediction and Tuning for Symmetric Coexistence of WiFi and ZigBee Networks

Due to the explosive deployment of WiFi and ZigBee wireless networks, 2.4GHz ISM bands (2.4GHz-2.5GHz) are becoming increasingly crowded, and the co-channel coexistence of these two networks is inevitable. For coexistence networks, people always want to predict their performance (e.g. throughput, energy consumption, etc.) before deployment, or even want to tune parameters to compensate unnecessary performance degradation (owing to the huge differences between these two MAC protocols) or to satisfy some performance requirements (e.g., priority, delay constraint, etc.) of them. However, predicting and tuning performance of coexisting WiFi and ZigBee networks has been a challenging task, primarily due to the lack of corresponding simulators and analytical models. In this dissertation, we addressed the aforementioned problems by presenting simulators and models for the coexistence of WiFi and ZigBee devices. Specifically, based on the energy efficiency and traffic pattern of three practical coexistence scenarios: disaster rescue site, smart hospital and home automation. We first of all classify them into three classes, which are non-sleeping devices with saturated traffic (SAT), non-sleeping devices with unsaturated traffic (UNSAT) and duty-cycling devices with unsaturated traffic (DC-UNSAT). Then a simulator and an analytical model are proposed for each class, where each simulator is verified by simple hardware based experiment. Next, we derive the expressions for performance metrics like throughput, delay etc., and predict them using both the proposed simulator and the model. Due to the higher accuracy of the simulator, the results from them are used as the ground truth to validate the accuracy of the model. Last, according to some common performance tuning requirements for each class, we formulate them into optimization problems and propose the corresponding solving methods. The results show that the proposed simulators have high accuracy in performance prediction, while the models, although are less accurate than the former, can be used in fast prediction. In particular, the models can also be easily used in optimization problems for performance tuning, and the results prove its high efficiency

The Effective Transmission and Processing of Mobile Multimedia

Ph.DDOCTOR OF PHILOSOPH

Utilizing ZigBee Technology for More Resource-efficient Wireless Networking

Wireless networks have been an essential part of communication in our daily life. Targeted at different applications, a variety of wireless networks have emerged. Due to constrained resources for wireless communications, challenges arise but are not fully addressed. Featured by low cost and low power, ZigBee technology has been developed for years. As the ZigBee technology becomes more and more mature, low-cost embedded ZigBee interfaces have been available off the shelf and their sizes are becoming smaller and smaller. It will not be surprising to see the ZigBee interface commonly embedded in mobile devices in the near future. Motivated by this trend, we propose to leverage the ZigBee technology to improve existing wireless networks. In this dissertation, we classify wireless networks into three categories (i.e., infrastructure-based, infrastructure-less and hybrid networks), and investigate each with a representative network. Practical schemes are designed with the major objective of improving resource efficiency for wireless networking through utilizing ZigBee technology. Extensive simulation and experiment results have demonstrated that network performance can be improved significantly in terms of energy efficiency, throughput, packet delivery delay, etc., by adopting our proposed schemes

MAC/PHY Co-Design of CSMA Wireless Networks Using Software Radios.

In the past decade, CSMA-based protocols have spawned numerous network standards (e.g., the WiFi family), and played a key role in improving the ubiquity of wireless networks. However, the rapid evolution of CSMA brings unprecedented challenges, especially the coexistence of different network architectures and communications devices. Meanwhile, many intrinsic limitations of CSMA have been the main obstacle to the performance of its derivatives, such as ZigBee, WiFi, and mesh networks. Most of these problems are observed to root in the abstract interface of the CSMA MAC and PHY layers --- the MAC simply abstracts the advancement of PHY technologies as a change of data rate. Hence, the benefits of new PHY technologies are either not fully exploited, or they even may harm the performance of existing network protocols due to poor interoperability. In this dissertation, we show that a joint design of the MAC/PHY layers can achieve a substantially higher level of capacity, interoperability and energy efficiency than the weakly coupled MAC/PHY design in the current CSMA wireless networks. In the proposed MAC/PHY co-design, the PHY layer exposes more states and capabilities to the MAC, and the MAC performs intelligent adaptation to and control over the PHY layer. We leverage the reconfigurability of software radios to design smart signal processing algorithms that meet the challenge of making PHY capabilities usable by the MAC layer. With the approach of MAC/PHY co-design, we have revisited the primitive operations of CSMA (collision avoidance, carrier signaling, carrier sensing, spectrum access and transmitter cooperation), and overcome its limitations in relay and broadcast applications, coexistence of heterogeneous networks, energy efficiency, coexistence of different spectrum widths, and scalability for MIMO networks. We have validated the feasibility and performance of our design using extensive analysis, simulation and testbed implementation.PHDComputer Science & EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/95944/1/xyzhang_1.pd

Providing efficient services for smartphone applications

Mobile applications are becoming an indispensable part of people\u27s lives, as they allow access to a broad range of services when users are on the go. We present our efforts towards enabling efficient mobile applications in smartphones. Our goal is to improve efficiency of the underlying services, which provide essential functionality to smartphone applications. In particular, we are interested in three fundamental services in smartphones: wireless communication service, power management service, and location reporting service.;For the wireless communication service, we focus on improving spectrum utilization efficiency for cognitive radio communications. We propose ETCH, a set of channel hopping based MAC layer protocols for communication rendezvous in cognitive radio communications. ETCH can fully utilize spectrum diversity in communication rendezvous by allowing all the rendezvous channels to be utilized at the same time.;For the power management service, we improve its efficiency from three different angles. The first angle is to reduce energy consumption of WiFi communications. We propose HoWiES, a system-for WiFi energy saving by utilizing low-power ZigBee radio. The second angle is to reduce energy consumption of web based smartphone applications. We propose CacheKeeper, which is a system-wide web caching service to eliminate unnecessary energy consumption caused by imperfect web caching in many smartphone applications. The third angle is from the perspective of smartphone CPUs. We found that existing CPU power models are ill-suited for modern multicore smartphone CPUs. We present a new approach of CPU power modeling for smartphones. This approach takes CPU idle power states into consideration, and can significantly improve power estimation accuracy and stability for multicore smartphones.;For the location reporting service, we aim to design an efficient location proof solution for mobile location based applications. We propose VProof, a lightweight and privacy-preserving location proof scheme that allows users to construct location proofs by simply extracting unforgeable information from the received packets

Multimedia

The nowadays ubiquitous and effortless digital data capture and processing capabilities offered by the majority of devices, lead to an unprecedented penetration of multimedia content in our everyday life. To make the most of this phenomenon, the rapidly increasing volume and usage of digitised content requires constant re-evaluation and adaptation of multimedia methodologies, in order to meet the relentless change of requirements from both the user and system perspectives. Advances in Multimedia provides readers with an overview of the ever-growing field of multimedia by bringing together various research studies and surveys from different subfields that point out such important aspects. Some of the main topics that this book deals with include: multimedia management in peer-to-peer structures & wireless networks, security characteristics in multimedia, semantic gap bridging for multimedia content and novel multimedia applications

Energy Technology and Management

The civilization of present age is predominantly dependent on energy resources and their utilization. Almost every human activity in today's life needs one or other form of energy. As world's energy resources are not unlimited, it is extremely important to use energy efficiently. Both energy related technological issues and policy and planning paradigms are highly needed to effectively exploit and utilize energy resources. This book covers topics, ranging from technology to policy, relevant to efficient energy utilization. Those academic and practitioners who have background knowledge of energy issues can take benefit from this book

Telecommunications Networks

This book guides readers through the basics of rapidly emerging networks to more advanced concepts and future expectations of Telecommunications Networks. It identifies and examines the most pressing research issues in Telecommunications and it contains chapters written by leading researchers, academics and industry professionals. Telecommunications Networks - Current Status and Future Trends covers surveys of recent publications that investigate key areas of interest such as: IMS, eTOM, 3G/4G, optimization problems, modeling, simulation, quality of service, etc. This book, that is suitable for both PhD and master students, is organized into six sections: New Generation Networks, Quality of Services, Sensor Networks, Telecommunications, Traffic Engineering and Routing