No / Wireless sensor networks are an emerging technology for low-cost, unattended monitoring of a wide range of environments. Their importance has been enforced by the recent delivery of the IEEE 802.15.4 standard for the physical and MAC layers and the forthcoming ZigBee standard for the network and application layers. The fast progress of research on energy efficiency, networking, data management and security in wireless sensor networks, and the need to compare with the solutions adopted in the standards motivates the need for a survey on this field.

The revolutionary advances in the wireless communication technologies are inspiring the researchers to envision the next generation wireless networking architectures, i.e., Next Generation Wireless Internet (NGWI), InterPlaNetary (IPN) Internet, and Wireless Sensor Networks (WSN). There exist significant technological challenges for the realization of these envisioned next generation network architectures. NGWI will be the convergence of the Internet and heterogeneous wireless architectures, which have diverse characteristics and hence pose different sets of research challenges, to achieve anywhere, anytime seamless service to the mobile users. Similarly, the unique characteristics and challenges posed by deep space communications call for novel networking protocols to realize the IPN Internet objective. Furthermore, in order to realize the potential gains of WSN, it is imperative that communication challenges imposed by resource constraints of sensor nodes must be efficiently addressed with novel solutions tailored to the WSN paradigm. The objective of this research is to develop new advanced transport protocols for reliable data transport and real-time multimedia delivery in the next generation heterogeneous wireless network architectures. More specifically, the analytical rate control (ARC) protocol for real-time multimedia delivery is first proposed for wired/wireless hybrid networks. Next, a new rate control scheme (RCS) is proposed to achieve high throughput performance and fairness for real-time multimedia traffic over the satellite links. The unified adaptive transport layer (ATL) suite and its protocols for both reliable data transport (TCP-ATL) and real-time multimedia delivery (RCP-ATL) are introduced for the NGWI. A new reliable transport protocol for data transport in the IPN Internet (TP-Planet) is then proposed to address the unique challenges of the IPN Internet backbone links. A new integrated tranmission protocol (ITP) is then proposed for reliable data transport over multihop IPN Internet paths. Finally, the event-to-sink reliable transport (ESRT) protocol is proposed to achieve reliable event transport with minimum energy expenditure in WSN.

International Telemetering Conference Proceedings / October 18-21, 2004 / Town & Country Resort, San Diego, California / The Electrocardiograph (EKG or ECG) measures electrical changes of tissue surrounding the heart to create a time-based representation of the physical operation of the heart. The purpose of this paper is to explore the future of ECG telemetry systems and how they are used in health care. The initial goal is to develop an inexpensive, efficient, and robust real-time ECG telemetry system. The future goal is to create a wireless network of miniature body sensors capable of measuring ECG data and other vital signs.

International Telemetering Conference Proceedings / October 20-23, 2003 / Riviera Hotel and Convention Center, Las Vegas, Nevada / Wireless interfaces are becoming ubiquitous in terrestrial applications ranging from local area networking in business and commercial environments to large scale factory automation and process control. The pressure to develop these wireless interfacing techniques has come from the need to reduce cabling, reduce installation costs, and make it easier to extend network infrastructures. Concerns about electromagnetic compatibility, safety, reliability, and security have lead to the development of techniques and protocols that enable such wireless interfaces to be operated in electromagnetically harsh environments, without generating unacceptable interference, and providing reliable, dependable and secure data communications. On the face of it, the use of wireless interfaces onboard spacecraft looks like a good way of reducing the spacecraft harness mass and bulk. However, recent work by the European Space Agency has shown that, while harness reduction will undoubtedly be one benefit of using wireless interfaces, they offer many other benefits that will be more significant in the near future. Amongst these are significant advantages during integration and testing, the ability to retrofit and upgrade facilities, and cable replacement in moving structures such as robotic arms. In this paper we briefly survey the benefits of wireless interface technologies for spacecraft onboard use, and identify the challenges involved in adapting them for flight use. We then look at the considerations that should be taken into account in establishing the financial case for developing wireless interface technologies for flight applications.

In this thesis, we analyze the performance of heterogeneous wireless communication systems that are composed of Optical Wireless Communication (OWC) and Radio Frequency (RF) systems. OWC systems further include long range outdoor Free Space Optical (FSO) systems and short range indoor Visible Light Communication (VLC) systems. Hybrid FSO/RF systems have emerged as a promising solution for high data rate wireless transmissions. Various transmission schemes including switch-over and soft-switching had been presented for hybrid FSO/RF systems. To overcome the drawbacks of existing schemes, we present a new transmission strategy for hybrid FSO/RF systems exploring an adaptive combining technology. This new strategy shows an improved outage performance. Typically, when the transmitter and the receiver are provided with channel state information, the transmission schemes can be adaptively designed allowing the channel to be used more efficiently. We present two new joint adaptive transmission schemes for hybrid FSO/RF systems. The first one is joint adaptive modulation and adaptive combining scheme which improves the spectral efficiency of hybrid FSO/RF systems. The other one is joint power adaptation and adaptive combining scheme which improves the throughput and the outage performance of hybrid FSO/RF systems. We accurately evaluate the performance of both schemes. FSO technology can be used effectively in multiuser scenarios to support Point-to-Multi-Point (P2MP) networks. In P2MP networks, FSO links are used for data transmission from a central location to multiple users. In this thesis, we present a new P2MP network based on hybrid FSO/RF transmission system. A common backup RF link is used by the central station for data transmission to any user in case of the failure of its corresponding FSO link. Based on a Markov Chain formulation, we study the performance of the resulting system. P2MP Hybrid FSO/RF network achieves considerable performance improvement over the P2MP FSO-only network. In VLC, Light Emitting Diode (LED) is used for the purpose of simultaneous illumination and data communication at high data rate. However, the light originating from a LED source is naturally confined to a small area and is susceptible to blockages. Hybrid VLC/RF systems have been emerged as a promising solution to provide enhanced communication coverage. We introduce a new dual-hop VLC/RF system with energy harvesting relay to extend the coverage of indoor wireless system based on VLC. The second-hop RF transmission uses the harvested energy over the first-hop VLC transmission. In this thesis, we propose two different approaches for energy harvesting at the relay terminal. In the first approach, the relay harvests light energy from different artificial light sources and sunlight entering the room. In this approach, we propose a novel statistical model for the harvested electrical power and analyze the probability of data packet loss. In the second approach, the relay harvests energy from the VLC link by extracting the direct current component of the received optical signal. In this approach, we investigate the optimal design of the hybrid VLC/RF system in terms of data rate maximization. In both cases, we present extensive numerical examples to define important design guide lines for VLC/RF systems. / Graduate

Optical wireless communications (OWC) has the potential to become a remedy for the shortage of the radio frequency (RF) spectrum. Especially in indoor environments, OWC could enable wireless home networking systems which offload data traffic from existing RF systems. In OWC, data is transmitted by modulating the intensity of light sources, typically incoherent light emitting diodes (LEDs). Thus, OWC systems employ intensity modulation (IM) and direct detection (DD) of the optical carrier. Since off-the-shelf LEDs have a limited modulation capability, the transmission bandwidth of practical OWC systems is restricted. Consequently, the available bandwidth has to be used efficiently. In this thesis, spectrally efficient optical wireless transmission techniques are evaluated. Firstly, multiple transmitter-receiver techniques are investigated. These multiple-input-multiple-output (MIMO) techniques provide high spectral efficiency, and therefore high data rates. Specifically, the MIMO techniques repetition coding (RC), spatial multiplexing (SMP) and spatial modulation (SM) are analysed for indoor OWC. The performance of these techniques is evaluated analytically and by means of computer simulations. It is shown that inducing power imbalance between the multiple optical transmitters can substantially improve the performance of optical MIMO techniques as the power imbalance improves the differentiability of the multiple channels. In addition, it is found that link blockage and the utilisation of transmitters having different optical wavelengths enhance channel differentiability as well. These methods enable the utilisation of optical MIMO techniques under conditions which typically disallow the application of MIMO schemes due to little differences between the multiple links. Secondly, a novel optical wireless transmitter concept is developed. This concept uses discrete power level stepping to generate intensity modulated optical signals, such as orthogonal frequency division multiplexing (OFDM) waveforms. The transmitter consists of several on-off-switchable LED groups which are individually controlled to emit scaled optical intensities. As a result, the digital-to-analogue conversion of the signals to be sent is done in the optical domain. This method enables the implementation of low-complex and power-efficient optical transmitter front-ends – the major shortcoming of conventional optical OFDM transmitters. Thirdly, a novel approach for wireless data transmission within an aircraft cabin is presented. The data is transferred by 2-dimensional visual code sequences. These sequences are displayed on the in-flight entertainment (IFE) screen and are captured by the built-in camera of a user device which acts as receiver. Transmission experiments within an aircraft cabin mock-up demonstrate the functionality of the implemented system under realistic conditions, such as ambient illumination and geometric configuration. Altogether, this thesis has analysed the potential of spectrally efficient optical wireless transmission techniques. It is shown that OWC systems can greatly benefit from these techniques.

The work described in this thesis is concerned with self-localisation (automated estimation of sensor locations) and source-localisation (location of a target) using Wireless Sensor Networks (WSNs). The motivation for the research in this thesis is the on-line localisation of marmots from their alarm calls. The application requires accurate 3D self-localisation (within a small percentage of sensor spacing) as well as timely operation. Further challenges are added by the high data-rate involved: sensor nodes acquire data at a rate that is greater than the available network bandwidth. This data cannot be streamed over a multi-hop network, implying a need for data reduction through in-network event detection and local data compression or filtering techniques. The research approach adopted in this thesis combined simulation, emulation and real-life experimentation. Real-life deployment and experimentation highlighted problems that could not be predicted in controlled experiments or simulation. Emulation used data gathered from controlled, real-life experimentation to simulate proposed system refinements; this was sufficient to provide a proof-of-concept validation for some of the concepts developed. Simulation allowed the understanding of underlying theoretical behaviour without involving the complex environmental effects caused by real-life experimentation. This thesis details contributions in two distinct aspects of localisation: acoustic ranging and end-toend deployable acoustic source localisation systems. With regard to acoustic ranging and 3D localisation, two WSN platforms were evaluated: one commercially available, but heavily constrained (Mica2) and one custom-built for accurate localisation (Embedded Networked Sensing Box (ENSBox)). A new proof of concept platform for acoustic sensing (based on the Gumstix single-board computer) was developed by the author (including the implementation of a ranging mechanism), based on experiences with the platforms above. Furthermore, the literature was found to lack a specific procedure for evaluation and comparison of self-localisation algorithms from theoretical conception to real-life testing. Therefore, an evaluation cycle for self-localisation algorithms that encompassed simulation, emulation and real-life deployment was developed. With respect to source localisation, a hardware and software platform named VoxNet was designed and implemented.

International Telemetering Conference Proceedings / October 21, 2002 / Town & Country Hotel and Conference Center, San Diego, California / Commercial wireless protocol use (e.g. Wireless Access Protocol, Bluetooth, etc.) is becoming widespread as the demand to access computing devices in remote locations grows. Although not widely prevalent today, wireless access of post processed telemetry data will become a common activity. Essential to the use of such a capability is the security of the wireless links involved in the data transfer. Each wireless protocol has an associated security paradigm. Some protocols have stronger security schemes than others and this should influence protocol selection for particular telemetry data transfer applications.

The world's demand for energy is an ongoing challenge, which has yet to be overcome. The efforts to find clean energy alternatives to fossil fuels have been hampered by the lack of investment in technology and research. Among these clean energy alternatives are ocean waves and wind. Wind power is generated through the use of wind generators that harness the wind's kinetic energy; it has gained worldwide popularity as a large-scale energy source, but only provides less than one percent of global energy consumption. Due to infrastructure limitations on installations of wind turbines at locations where high winds exist, wind energy faces critical challenges difficult to overcome to continue improving electricity generation. Ocean wave energy on the other hand seems like a promising adjunction to wind energy. Ocean energy comes in a variety of forms such as marine currents, tidal currents, geothermal vents and waves. Most of today's research however is based on wave energy. It has been estimated that approximately 257 Terawatt hour per year (TWh/year) could be extracted from ocean waves alone. This amount of energy could be enough to meet the U.S. energy demands of 28 TWh/year. Technologies such as point absorbers, attenuators and overtopping devices are examples of wave energy converters. Point absorbers use a floating structure with components that move relative to each other due to the wave action. The relative motion is used to drive electromechanical or hydraulic energy converters. The total energy throughput of a single point absorber however, does not justify for the great engineering cost and effort by researchers. Thus the need to explore other alternatives of wave conversion that result in no extra-added cost but yet increases throughput. Our research focuses on exploring a novel method to maximize wave energy conversion of an array-based point absorber wave farm. Unlike previous research, our method incorporates a predictive control algorithm to aid the wave farm with the prediction of dynamics and optimal control trajectory over a finite time and space horizon of ocean waves. By using a predictive control algorithm, wave energy conversion throughput can be increased as opposed to a system without. This algorithm requires that the wave characteristics of the incoming wave be provided in advance for appropriate processing. This thesis focuses on designing an efficient and reliable wireless communications system capable of delivering wave information such as speed, height and direction to each point absorber in the network for further processing by the predictive control algorithm. This process takes place in the presence of harsh environmental conditions where the random shape of waves and moving surface can further affect the communication channel. In this work we focus on the physical layer where the transmission of bits over the wireless medium takes place. Specifically we are interested in reducing the bit error rate with a unique relaying protocol to increase packet transmission reliability. We make use of cooperative diversity and existing protocols to achieve our goal of merit and improve end-to-end system performance. / Graduation date: 2012

The recent advances in mobile computing and distributed multimedia systems allow mobile hosts (clients) to access wireless multimedia Data at anywhere and at anytime. In accessing multimedia information on the distributed multimedia servers from wireless personal communication service systems, a channel assignment problem and synchronization problems should be solved efficiently. Recent demand for mobile telephone service have been growing rapidly while the electro-magnetic spectrum of frequencies allocated for this purpose remain limited. Any solution to the channel assignment problem is subject to this limitation, as well as the interference constraint between adjacent channels in the spectrum. Channel allocation schemes provide a flexible and efficient access to bandwidth in wireless and mobile communication systems. In this dissertation, both an efficient distributed algorithm for dynamic channel allocation based upon mutual exclusion model, and an efficient distributed synchronization algorithm using Quasi-sink for wireless and mobile multimedia systems to ensure and facilitate mobile client access to multimedia objects are proposed. Algorithm's performance with several channel systems using different types of call arrival patterns is determined analytically. A set of simulation experiments to evaluate the performance of our scheme using message complexity and buffer usage at each frame arrival time.