• Data Compression by using bit stuffing with threshold criteria in run length encoding scheme

      Qureshi, Faisal Fayyaz; Asghar, Muhammad Nabeel; Hussain, Fiaz; Safdar, Ghazanfar Ali; Shah, Syed Stiwat (IADIS, 2012)
    • Data transmission

      Walker, Stuart D.; Hugues-Salas, Emilio; Razavi, Rouzbeh; Ajmal, Tahmina (Elsevier, 2008)
    • Deconstructing space-frequency correlated ultrawideband MIMO channels

      Hong, Xuemin; Wang, Cheng-Xiang; Thompson, John; Allen, Ben; Malik, Wasim Q.; Heriot-Watt University (IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 2008-09)
      Conventional correlation models fail to accurately represent the correlation properties of ultrawideband (UWB) multiple-input multiple-output (MIMO) channels. In our previous work, a framework for constructing correlated UWB MIMO channel models was proposed, where spatial correlation was introduced into both the multipath amplitude and time-of-arrival (ToA) in the channel impulse response. Based on this framework, in this paper we first present a simplified UWB MIMO channel model that represents a reasonable compromise between analytical tractability and model accuracy. We show that this model yields a structured space-frequency (SF) channel covariance matrix, making it suitable for theoretical system performance analysis. To illustrate the merit of this model, we apply it to evaluate the maximum diversity order in SF coded UWB MIMO systems. In contrast to previous work based on conventional wideband MIMO correlated channel models, we show that the maximum diversity order of a UWB MIMO system is not limited by the sum of the ranks of multipath amplitude correlation matrices.
    • Depth map compression for depth-image-based rendering

      Cheung, Gene; Ortega, Antonio; Kim, Woo-Shik; Velisavljević, Vladan; Kubota, Akira (SpringerLink, 2013)
      In this chapter, we discuss unique characteristics of depth maps, review recent depth map coding techniques, and describe how texture and depth map compression can be jointly optimized.
    • Descriptor choice for UWB antenna arrays

      Sipal, Vit; Edwards, David J.; Allen, Ben; University of Oxford (IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 2012-03)
      The use of multiple antennas is an attractive option for ultrawideband communication and positioning systems. Despite intensive research interest, the framework for analysing ultrawideband arrays is ambiguous. For OFDM based systems which use many narrowband subcarriers, the preferred choice is the use of the classical array description by means of the array factor. For impulse radio systems, array factors cannot be used and new beam pattern descriptors have been developed. In this paper we explore and quantify the transition between narrowband and ultrawideband systems. We define the upper bandwidth for which it is still acceptable to use the description by the means of classical array factors. This limit enables a rule of thumb decision on the selection of a suitable UWB MIMO strategy
    • Design and optimisation of compact RF energy harvesting device for smart applications

      Allen, Ben; Jazani, David; Dyo, Vladimir; Ajmal, Tahmina; Ivanov, Ivan; University of Bedfordshire (IEEE, 2014-01)
      An optimised design of a radio frequency energy harvesting antenna is presented. The antenna is based on a compact ferrite rod which, together with the electronics, can directly replace batteries in suitable applications. The antenna is optimised such that the energy available for the applications is maximised, while considering constraints such as the device geometry and the Q-factor. That the antenna can power a wireless sensor node is shown from the ambient medium wave transmissions.
    • Design and optimisation of integrated hybrid surface plasmon biosensor

      Gorman, T.; Haxha, Shyqyri; University of Bedfordshire; University of Greenwich (Elsevier, 2014)
      In this paper we present a novel idea for an integrated surface plasmon biosensor. The proposed hybrid sensor aims to couple the high sensitivity of the well known Kretchmann prism excitation design with the more robust integrated waveguide design. The sensor is modelled and simulated using a 2D Finite Element Method (FEM) in order to establish the devices sensitivity, resolution and signal-to-noise-ratio.
    • Design and performance evaluation of IAR: Interference-Aware Routing metric for Wireless Mesh Networks

      Waharte, Sonia; Ishibashi, Brent; Boutaba, Raouf; Meddour, Djamal-Eddine (SpringerLink, 2009-10)
    • Design of a 10Gbps optical burst mode DPSK receiver for data and clock recovery

      Ajmal, Tahmina; Quinlan, Terence; Razavi, Rouzbeh; Hugues-Salas, Emilio; Walker, Stuart D. (IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 2008)
      The paper presents a 10 Gbps DPSK burst mode receiver with zero latency clock synchronization. Concatenated phaseshift and resonator techniques maintain an NRZ data clock component over >1024 bit guard intervals.
    • Design of a compact RF energy harvester for wireless sensor networks

      Ajmal, Tahmina; Jazani, David; Allen, Ben; University of Bedfordshire (IET, 2012-06)
      We present a method for powering electronic devices from ambient Radio Frequency (RF) signals. Our proposed design of RF energy harvester is made of a compact ferrite rod antenna together with the electronics necessary for converting the received signal into a form that can directly replace batteries. We show that our device can, in principal, power a wireless sensor node from ambient medium wave transmissions so long as the node is within 120 km of a 150kW transmitter.
    • Design of a ferrite rod antenna for harvesting energy from medium wave broadcast signals

      Dyo, Vladimir; Allen, Ben; Jazani, David; Ivanov, Ivan; Ajmal, Tahmina; University of Bedfordshire (Institution of Engineering and Technology, 2014)
      Radio frequency (RF) energy harvesting is an emerging technology that has the potential to eliminate the need for batteries and reduce maintenance costs of sensing applications. The antenna is one of the critical components that determines its performance and while antenna design has been well researched for the purpose of communication, the design for RF energy harvesting applications has not been widely addressed. The authors present an optimised design for such an antenna for harvesting energy from medium wave broadcast transmissions. They derive and use a model for computing the optimal antenna configuration given application requirements on output voltage and power, material costs and physical dimensions. Design requirements for powering autonomous smart meters have been considered. The proposed approach was used to obtain the antenna configuration that is able to deliver 1 mW of power to 1 kΩ load at a distance of up to 9 km, sufficient to replace batteries on low-power sensing applications. Measurements using a prototype device have been used to verify the authors simulations.
    • Digital down-conversion and up-conversion: theory and implementation

      Zhang, Yue; Tang, Taiwen; Loo, Kok-Keong; Allen, Ben; Li, Daoliang (Cambridge University Press, 2011)
      Digital conversion is a fundamental part of many digital radio systems, which include upconversion of the discrete baseband signal stream into a high-resolution radio signal at the transmitter, and down-conversion of a high-resolution radio signal back into a baseband signal at the receiver. In this chapter, we cover the basics of digital conversion (analog to digital and digital to analog), the functionality of digital up-converter and digital down-converter in relation to conversion between intermediate frequency and baseband with the emphasis on the implementation of the DDC and DUC for standard wireless communication systems.
    • Directional wavelet transforms and frames

      Velisavljević, Vladan; Dragotti, Pier Luigi; Vetterli, Martin (IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 2002)
      The application of the wavelet transform in image processing is most frequently based on a separable transform. Lines and columns in an image are treated independently and the basis functions are simply products of corresponding one-dimensional functions. Such a method keeps simplicity in design and computation. A new two-dimensional approach is proposed, which retains the simplicity of separable processing, but allows more directionalities. The method can be applied in many areas like denoising, nonlinear approximation and compression. The results on nonlinear approximation and denoising show interesting gains compared to the standard two-dimensional analysis.
    • Directionlets: anisotropic multidirectional representation with separable filtering

      Velisavljević, Vladan; Beferull-Lozano, Baltasar; Vetterli, Martin; Dragotti, Pier Luigi (IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 2006-07)
    • Discrete directional wavelet bases and frames: analysis and applications

      Dragotti, Pier Luigi; Velisavljević, Vladan; Vetterli, Martin; Beferull-Lozano, Baltasar (SPIE, 2003)
      The application of the wavelet transform in image processing is most frequently based on a separable construction. Lines and columns in an image are treated independently and the basis functions are simply products of the corresponding one dimensional functions. Such method keeps simplicity in design and computation, but is not capable of capturing properly all the properties of an image. In this paper, a new truly separable discrete multi-directional transform is proposed with a subsampling method based on lattice theory. Alternatively, the subsampling can be omitted and this leads to a multi-directional frame. This transform can be applied in many areas like denoising, non-linear approximation and compression. The results on non-linear approximation and denoising show interesting gains compared to the standard two-dimensional analysis.
    • Discrete directional wavelet bases for image compression

      Dragotti, Pier Luigi; Velisavljević, Vladan; Vetterli, Martin; Beferull-Lozano, Baltasar (SPIE, 2003)
      The application of the wavelet transform in image processing is most frequently based on a separable construction. Lines and columns in an image are treated independently and the basis functions are simply products of the corresponding one dimensional functions. Such method keeps simplicity in design and computation, but is not capable of capturing properly all the properties of an image. In this paper, a new truly separable discrete multi-directional transform is proposed with a subsampling method based on lattice theory. Alternatively, the subsampling can be omitted and this leads to a multi-directional frame. This transform can be applied in many areas like denoising, non-linear approximation and compression. The results on non-linear approximation and denoising show very interesting gains compared to the standard two-dimensional analysis.
    • Discrete multidirectional wavelet bases

      Velisavljević, Vladan; Beferull-Lozano, Baltasar; Vetterli, Martin; Dragotti, Pier Luigi (IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 2003)
      The application of the wavelet transform in image processing is most frequently based on a separable construction. While simple, such an approach is not capable of capturing properly all 2D properties in images. In this paper, a new truly separable multidirectional transform is proposed with a subsampling method based on lattice theory. Applications are possible in many areas of image processing. Some promising improvements are achieved in nonlinear approximation and denoising of images.
    • Disparity map compression for depth-image-based rendering

      Cheung, Gene; Ortega, Antonio; Kim, Woo-Shik; Velisavljević, Vladan; Kubota, Akira; National Institute of Informatics, Japan; University of Southern California; Texas Instruments; University of Bedfordshire; Chuo University (Springer, 2012-03)
    • Diversity analysis of multi-antenna UWB impulse radio systems with correlated propagation channels

      Liu, Junsheng; Ghavami, Mohammad; Chu, Xiaoli; Allen, Ben; Malik, Wasim Q.; King's College, London (IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 2007-03)
      Providing diversity is one of the two possible objectives (the other one is providing multiplexing) of a multi-input multi-output (MIMO) system. For ultra wideband (UWB) impulse radio systems using rake receivers, there are already richly inherent multipath diversities. However, there may be UWB applications making use of more than one UWB transmit antenna and/or receive antenna, which leads to UWB MIMO systems. The difference between the diversity analyse of a UWB MIMO system from that of a narrow band system lies in the different choice of propagation channel model for the branches linking each transmit antenna and receive antenna. Similar to the narrow band system, the existence of the correlation between the branches can severely degrade the diversity performance, and complicate the performance analyse. In this paper, the wideband propagation channel for the UWB MIMO system, with pre-defined correlation model for the branches, is broken down into several uncorrelated elementary narrow-band propagation channels with equivalent diversity performance. Based on this, a novel method for evaluating the diversity performance of a MIMO UWB impulse radio system is presented.
    • Down-link beamforming effects on the code orthogonality in UTRA-FDD systems

      Hunukumbure, Mythri; Beach, Mark; Allen, Ben; University of Bristol (IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 2002-09)
      A novel approach in quantifying code orthogonality factor for UTRA-FDD systems is extended in this paper to include the impact of down-link beamforming. The effects of fixed beamforming on code orthogonality is analysed through the aid of real channel data taken from urban cellular environments. The results show a significant overall improvement in code orthogonality with beamforming, especially in the case of an urban large cell.