• View and rate scalable multiview image coding with depth-image-based rendering

      Velisavljević, Vladan; Stankovic, Vladimir; Chakareski, Jacob; Cheung, Gene (IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 2011)
      In this paper, authors propose a flexible codec and an associated bit allocation strategy to address both of these scenarios. In particular, we first present an edge-adaptive wavelet multiview image codec capable of producing a scalable bitstream from which proper subsets can be extracted and decoded at different bit-rates. Given our scalable codec, we then propose a rate allocation algorithm that performs one of the following two actions. The algorithm will either incrementally increase the number of bits for encoding texture or depth maps of already encoded viewpoints, or it will introduce into the scalable representation new texture or depth maps of previously uncoded captured viewpoints. The incremental choice of either refining an existing view or introducing a new one is carried out one layer at a time, such that the associated rate-distortion tradeoff is locally optimized. By employing our novel bit allocation strategy the proposed coder outperforms the state-of-the-art H.264/SVC codec as well as the same wavelet-based coder when armed with a simple suboptimal bit allocation with the same rate allocated to each map, in all coding scenarios studied in our experiments. Furthermore, our coder can achieve an arbitrarily fine granularity o- - f encoding bit rates, while providing the additional functionality of view embedded encoding, unlike the other related coders that we examined.
    • View-popularity-driven joint source and channel coding of view and rate scalable multi-view video

      Chakareski, Jacob; Velisavljević, Vladan; Stankovic, Vladimir; University of Alabama; University of Bedfordshire; Strathclyde University (IEEE, 2015-02-11)
      We study the scenario of multicasting multi-view video content, recorded in the video plus depth format, to a collection of heterogeneous clients featuring Internet access links of diverse packet loss and transmission bandwidth values. We design a popularity-aware joint source-channel coding optimization framework that allocates source and channel coding rates to the captured content, such that the aggregate video quality of the reconstructed content across the client population is maximized, for the given packet loss and bandwidth characteristics of the clients and their view selection preferences. The source coding component of our framework features a procedure for generating a view and rate embedded bitstream that is optimally decodable at multiple data rates and accounts for the different popularity of diverse video perspectives of the scene of interest, among the clients. The channel coding component of our framework comprises an expanding-window rateless coding procedure that optimally allocates parity protection bits to the source encoded layers, in order to address packet loss across the unreliable client access links. We develop an optimization method that jointly computes the source and channel coding decisions of our framework, and also design a fast local-search-based solution that exhibits a negligible performance loss relative to the full optimization. We carry out comprehensive simulation experiments and demonstrate significant performance gains over competitive state-of-the-art methods (based on H.264/AVC and network coding, and H.264/SVC and our own channel coding procedure), across different scenario settings and parameter values.
    • The Weibull–lognormal fading channel: analysis, simulation, and validation

      Karadimas, Petros; Kotsopoulos, Stavros A.; University of Patras (IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 2009)
      In frequency-nonselective fading channels, the partial waves arriving at the mobile receiver cannot explicitly be of homogeneous nature due to nonuniform scattering caused by objects of specific reflective nature. Moreover, shadowing influences the received signal level by causing slow variations to its local mean. In this paper, we investigate a mixture stochastic process accounting for both inhomogeneous scattering and shadow fading by multiplying a Weibull process with a lognormal process. The first process models the possible scattering nonuniformities of the channel, whereas the second process accounts for the slow-term variations of the local mean due to shadowing. An exact solution for the composite probability density function (pdf) will be given, together with approximate solutions for the second-order statistics, i.e., the level crossing rate (LCR) and the average duration of fades (ADF). The approximate solutions come from the assumption of a slowly time-varying lognormal process compared with the Weibull process, the validity of which will be tested via an efficient deterministic simulation scheme that implements the analytical model on a digital computer. Finally, a curve fitting of the LCR to real-world data drawn from channel measurements will demonstrate the flexibility and usefulness of the proposed model.
    • Wideband channels

      Sipal, Vit; Edwards, David J.; Allen, Ben; University of Oxford; University of Bedfordshire (Wiley-Blackwell, 2012)
      This chapter contains sections titled:Large Scale Channel Properties, Impulse Response of UWB Channel,Frequency Selective Fading in UWB Channels,Multiple Antenna Techniques,Implications for LTE-A
    • Wildlife and environmental monitoring using RFID and WSN technology

      Dyo, Vladimir; Ellwood, Stephen A.; Macdonald, David W.; Markham, Andrew; Mascolo, Cecilia; Pásztor, Bence; Trigoni, Niki; Wohlers, Ricklef (ACM, 2009)
    • WILDSENSING: design and deployment of a sustainable sensor network for wildlife monitoring

      Dyo, Vladimir; Yousef, Kharsim; Ellwood, Stephen A.; Macdonald, David W.; Markham, Andrew; Trigoni, Niki; Wohlers, Ricklef; Mascolo, Cecilia; Pásztor, Bence; Scellato, Salvatore (Association for Computing Machinery (ACM), 2012-09)
      The increasing adoption of wireless sensor network technology in a variety of applications, from agricultural to volcanic monitoring, has demonstrated their ability to gather data with unprecedented sensing capabilities and deliver it to a remote user. However, a key issue remains how to maintain these sensor network deployments over increasingly prolonged deployments. In this article, we present the challenges that were faced in maintaining continual operation of an automated wildlife monitoring system over a one-year period. This system analyzed the social colocation patterns of European badgers (Meles meles) residing in a dense woodland environment using a hybrid RFID-WSN approach. We describe the stages of the evolutionary development, from implementation, deployment, and testing, to various iterations of software optimization, followed by hardware enhancements, which in turn triggered the need for further software optimization. We highlight the main lessons learned: the need to factor in the maintenance costs while designing the system; to consider carefully software and hardware interactions; the importance of rapid prototyping for initial deployment (this was key to our success); and the need for continuous interaction with domain scientists which allows for unexpected optimizations.
    • Wireless channel performance with topological antenna diversity

      Allen, Ben; Karadimas, Petros; University of Bedfordshire (University of Bedfordshire, 2012)
      Topological Antenna Diversity is achieved through exploitation of the Orbital Angular Momentum (OAM) of the transmitted electromagnetic wave. Topological diversity has recently been proposed as a great potential of improving the spectral efficiency (capacity) of radio transmissions [1]. OAM accounts for the phase front of the transmitted wave by providing independent phase states, thus, additional modes of propagation (degrees of freedom) resulting in independent simultaneous wireless radio links. OAM transmission has only very recently been applied to radio transmissions at much lower frequencies [1], [2], [3], [4] and, as such, these experiments raise as many questions as answers. For example, what aspects are fundamentally new? How can we best exploit this fascinating technique for realistic wireless systems? What are the benefits of OAM transmissions compared to multiple input-multiple output (MIMO) systems in terms of both simplicity and performance improvement?
    • Wireless data encoding and decoding using OAM modes

      Tennant, Alan; Chatziantoniou, Eleftherios; Allen, Ben; Bai, Qiang; University of Bedfordshire; University of Sheffield (IET, 2014-01)
    • Wireless networks: what next for radiowave propagation research

      Allen, Ben; Malik, Wasim Q.; Edwards, David J.; University of Oxford (IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 2008)
      This paper chronicles the progress in wireless information transmission and reception, and discusses future trends in radiowave propagation research. Since the conception of wireless transmission, a number of pioneers have successfully understood and characterised the behaviour of narrowband, wideband and ultra-wideband signal transmission in a variety of environments and spectral regions. The physics of signal propagation mechanisms is now well understood and represented by deterministic and stochastic models. Frequency, spatial and polarisation properties of signal propagation have also been exploited. So are there any fundamental research problems left? The aim of this paper is to provoke discussion and debate so that the state-of-the-art of radiowave propagation is understood and further challenges are amassed.
    • Wireless quality-of-service for 60GHz streaming media

      Allen, Ben; Safdar, Ghazanfar Ali; University of Bedfordshire, UK (University of Bedfordshire, 2011)
      The primary aim of this PhD is firstly to understand Ultra-wideband technology (WiMedia), its applications, QoS requirements and then feed this knowledge into development of some novel secure QoS policies and architecture for the said technology before deploying them after analysis performed through modelling and simulations.
    • A wireless sensor network based structural health monitoring system for an airplane

      Notay, J.K.; Safdar, Ghazanfar Ali (IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 2011)
    • Wireless sensor positioning with ultrawideband fingerprinting

      Ultrawideband (UWB) systems offer high spatiotemporal resolution and are therefore well suited to sensor localization applications. In this paper, we consider the use of UWB signals for positioning and ranging based on fingerprinting using a channel impulse response database. We use indoor measurements to demonstrate the reduction in the location estimation ambiguity and false alarm probability with an increase in the channel bandwidth.
    • Works in progress

      Mossiere, Jacques; Curry, Edward; Beloued, Abdelkrim; Gilliot, Jean-Marie; Andre, Françoise; Segarra, Maria-Teresa; Dyo, Vladimir; Di Muro, Etienne Antoniutti; Jaeger, Michael A. (IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 2006)
    • Worst case bounds of a cluster-based MAC protocol for wireless sensor networks

      Aslam, Nauman; Phillips, William; Safdar, Ghazanfar Ali (IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 2012)
      Quality of service is becoming highly important in wireless sensor networks (WSNs) due to many emerging applications; hence the need to know the worst case bounds for traffic delay and backlog in such networks is valuable. Network calculus provides a methodology for determining the worst case bounds in packet scheduling using the concept of arrival and service curves. Using Network Calculus, this paper presents a mathematical model of a TDMA-based medium access control protocol, where a cluster based system is modeled and arrival/service curve is proposed. In addition, the model is also extended to allow finding the maximum delay and backlog bounds for applications with certain QoS requirements.