• Threshold optimization for energy detection-based spectrum sensing over hyper-Rayleigh fading channels

      Chatziantoniou, Eleftherios; Allen, Ben; Velisavljević, Vladan; University of Bedfordshire (IEEE, 2015-06)
    • Tuning of plasmonic nanoparticle and surface enhanced wavelength shifting of a nanosystem sensing using 3-D-FDTD method

      Bouali, A.; Haxha, Shyqyri; AbdelMalek, Fathi; Dridi, M.; Bouchriha, Habib; Carthage University; University of Bedfordshire (IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 2014)
      In this paper, we have used in-house the 3-D finite-difference time-domain method to analyze a novel design of metallic nanoparticles based on a sensing nanosystem. The proposed structure is composed of two gold-nanocylinders of finite height with varying radii separated by a nanogap. We have demonstrated that tunable plasmonic nanoparticles can be controlled by varying the size of the interparticles separation distance. By engineering the nanogaps, it is shown that a strong enhancement of the electric field is achieved. Our simulations show a pronounced wavelength shift for small nanogaps. In addition, the influence of the refractive index of the surrounding medium is presented.
    • Twenty years of ultrawideband: opportunities and challenges

      Sipal, Vit; Allen, Ben; Edwards, David J.; Honary, Bahram; University of Oxford; University of Bedfordshire; Lancaster University (IET, 2012-07)
      It has been 20 years since the word ultrawideband (UWB) has first been used in the open literature. In these 20 years, ideas have been transformed into real products. Yet, some might object that UWB has not yet lived upto the promises of gigabit wireless. This review shows that despite some drawbacks, UWB is not only needed because of the spectrum gridlock but it can still deliver its promises, including gigabit wireless. To do so, the gap between the potential, which is achievable, and the current performance must be closed. Thus, this review identifies some main issues of UWB (range, bit error rate performance, data rate, chip complexity and issues associated by strong narrowband interference). It shows that their reasons are well understood and addressed by erudite research, which includes low complexity chip design, alternative modulation schemes, multiple antenna systems, UWB radio-over-fibre, higher band UWB and interferer detection and suppression techniques. A specific feature of this review is the cross-layer approach. The latest findings from different system layers, for example, wave propagation, are linked to the system performance or complexity.
    • Ultra Wideband Systems and MIMO

      Sipal, Vit; Allen, Ben; Edwards, David J.; Malik, Wasim Q.; University of Bedfordshire (CRC Press, 2014-06)
    • Ultra wideband wireless sensor networks

      Allen, Ben (IEE, 2004-07)
      This paper explores the potential of UWB technology for wireless sensor networks. It will consider such aspects as power consumption, data rate, communication range, modulation, and coding schemes compared to similar technologies such as Zigbee and the potential impact of UWB capabilities and limitations on higher level protocol design.
    • Ultra wideband: applications, technology and future perspectives

      Allen, Ben; Brown, Anthony; Schwieger, Katja; Zimmermann, Ernesto; Malik, Wasim Q.; Edwards, David J.; Ouvry, Laurent; Oppermann, Ian (INTERNATIONAL WORKSHOP ON CONVERGENT TECHNOLOGIES (IWCT), 2005-06)
      Ultra Wide Band (UWB) wireless communications offers a radically different approach to wireless communication compared to conventional narrow band systems. Global interest in the technology is huge. This paper reports on the state of the art of UWB wireless technology and highlights key application areas, technological challenges, higher layer protocol issues, spectrum operating zones and future drivers. The majority of the discussion focuses on the state of the art of UWB technology as it is today and in the near future.
    • Ultra-wideband system design, signals and coding

      Allen, Ben; Edwards, David J.; Honary, Bahram (IET, 2012-07)
      Ultra-wideband wireless technology has held much promise as a means of delivering very high speed data over short ranges; delivering a plethora of data from dense wireless sensor networks; and exploited signals for location information, amongst a number of other applications. It has provided stimulation for new spectrum regulation and standards; innovative coding and, modulation schemes; a new approach to protocols; new insights into the radio channel and antenna behaviour
    • Ultra-wideband: antennas and propagation for communications, radar and imaging

      Allen, Ben; Dohler, Mischa; Okon, Ernest; Malik, Wasim Q.; Brown, Anthony; Edwards, David J. (Wiley-Blackwell, 2006-10)
      This book provides up-to-date material on fundamental design concepts and principles for UWB antennas and arrays. In addition, the propagation of UWB radiation is addressed and gives a better understanding of the nature of propagation of UWB waves including interference, coexistence, diversity and MIMO (multiple-input, multiple output - transmission of the same information by multiple transmitters and multiple receivers) and propagation through biological materials. Existing and proposed applications of UWB technology is also looked at.
    • Ultrawideband as an industrial wireless solution

      Hancke, Gerhard P.; Allen, Ben (IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 2006-10)
      Ultrawideband wireless technology transmits data at very high rates over a wide frequency spectrum, at low power, making it suitable for the industrial environment. We discuss the benefits and challenges of using wireless communication in the industrial environment, and we explain why UWB is a suitable wireless solution for addressing these challenges. We also consider some unresolved system-level and operational issues for incorporating UWB technology in industrial environments
    • Ultra‐wideband spatial channel characteristics

      Malik, Wasim Q.; Liu, Junsheng; Allen, Ben; Edwards, David J. (Wiley, 2007)
      The Shannon capacity of a wireless channel varies logarithmically with SNR and linearly with bandwidth. The latter is especially of interest for UWB systems, which yield very high information rates as a direct consequence. As both the signal bandwidth and the transmit power, and consequently SNR, of UWB systems are controlled by regulations, increasing the capacity beyond a certain limit is not possible in the conventional manner.
    • UMTS spatio-temporal propagation trial results

      Allen, Ben; Webber, Julian; Karlsson, Peter; Beach, Mark (IEE, 2001-04)
      The demand for novel signal processing architectures in mobile communication systems has never been greater. This is driven by the increasing demand for multimedia services and the inevitable rollout of 3G cellular systems such as Universal Mobile Telecommunications System (UMTS). Two techniques that are currently being considered to meet this demand are: multi-user detectors (MUDs) and smart antennas. In order to assess the performance of these techniques, the characteristics of the environments is of prime importance. This paper reports on a spatio-temporal measurement system that has been used to measure the multi-dimensional channel characteristics. The trials data can be used to assess the performance of MUDs and smart antennas for UMTS. The system has been used to characterise a number of representative environments, namely: urban, rural, indoor and outdoor-indoor. The channel data allows an appraisal of UMTS Terrestrial Radio Access (UTRA) Frequency Division Duplex (FDD) and Time Division Duplex (TDD) wireless communications systems incorporating novel signal processing techniques. Thus, the relative merits of each can be determined
    • User positioning technique for microcellular wireless networks

      Porretta, Marco; Nepa, Paolo; Manara, Giuliano; Giannetti, Filippo; Dohler, Mischa; Allen, Ben; Aghvami, A.Hamid (IET, 2003-05)
      A novel algorithm that makes use of a single base station to locate mobile terminals in cellular networks, by resorting to a triangulation technique supported by minimal information about the environment in the base station neighbourhood, is presented. The algorithm is shown to perform well when operating in a microcellular environment and perfect channel estimation is assumed.
    • User-action-driven view and rate scalable multiview video coding

      Chakareski, Jacob; Velisavljević, Vladan; Stankovic, Vladimir (IEEE, 2013-09)
      We derive an optimization framework for joint view and rate scalable coding of multi-view video content represented in the texture plus depth format. The optimization enables the sender to select the subset of coded views and their encoding rates such that the aggregate distortion over a continuum of synthesized views is minimized. We construct the view and rate embedded bitstream such that it delivers optimal performance simultaneously over a discrete set of transmission rates. In conjunction, we develop a user interaction model that characterizes the view selection actions of the client as a Markov chain over a discrete state-space. We exploit the model within the context of our optimization to compute user-action-driven coding strategies that aim at enhancing the client's performance in terms of latency and video quality. Our optimization outperforms the state-of-the-art H.264 SVC codec as well as a multi-view wavelet-based coder equipped with a uniform rate allocation strategy, across all scenarios studied in our experiments. Equally important, we can achieve an arbitrarily fine granularity of encoding bit rates, while providing a novel functionality of view embedded encoding, unlike the other encoding methods that we examined. Finally, we observe that the interactivity-aware coding delivers superior performance over conventional allocation techniques that do not anticipate the client's view selection actions in their operation.
    • 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?