• Enhanced fade depth model for extremely wideband channels

      Sipal, Vit; Allen, Ben; Edwards, David J. (AMSE, 2010-06)
    • Environment effects and system performance characterisation of GPS antennas for mobile terminals

      Ur-Rehman, Masood; Gao, Yue; Chen, Xiaodong; Parini, Clive G.; Ying, Zhinong (IET, 2009)
    • Ergodic capacity for the SIMO Nakagami- Channel

      Vagenas, Efstathios D.; Karadimas, Petros; Kotsopoulos, Stavros A.; University of Patras, Greece (Hindawi Publishing Corporation, 2009)
      This paper presents closed-form expressions for the ergodic channel capacity of SIMO (single-input and multiple output) wireless systems operating in a Nakagami- fading channel. As the performance of SIMO channel is closely related to the diversity combining techniques, we present closed-form expressions for the capacity of maximal ratio combining (MRC), equal gain combining (EGC), selection combining (SC), and switch and stay (SSC) diversity systems operating in Nakagami- fading channels. Also, the ergodic capacity of a SIMO system in a Nakagami- fading channel without any diversity technique is derived. The latter scenario is further investigated for a large amount of receive antennas. Finally, numerical results are presented for illustration.
    • Error statistics of optimal and sub-optimal space-time trellis codes: concatenation requirements

      Rassool, Bilal A.; Allen, Ben; Nakhai, Reza; Roberts, Roshano; Sweeney, Peter; King's College London (IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 2003-09)
      The bit error rate and frame error rate performance of space-time trellis codes are analysed. The analysis shows that for increasing number of states in the trellis codes, the FER performance improves; however, the BER performance does not always do so. By considering error event paths in trellises of different complexities, it is shown that this effect is owed to the increased recovery time from an erroneous decision needed by the trellis code of higher complexity. The results from this study also indicate certain design criteria when space-time trellis codes are concatenated with channel codes.
    • Estimating position and velocity of mobile terminals in a microcellular network using an adaptive linear regression setup

      Porretta, Marco; Nepa, Paolo; Manara, Giuliano; Giannetti, Filippo; Dohler, Mischa; Allen, Ben; Aghvami, A.Hamid; Pisa University; University of Bedfordshire (IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 2004-09)
      Mobility tracking yields efficient network resource management and enables very useful additional services, provided that accurate online estimations of both the location and the velocity of a mobile user are performed. We present a novel method for tracing a mobile user by subsequently estimating his/her position through a single base station positioning (SBSP) method designed for microcellular and third generation (3G) wireless communications systems. Raw data about user position are then smoothed through a linear regression setup which adaptively varies its inertia on the basis of the previous observations. This results in a tracking method which is able to estimate both the location and the velocity of a user with high accuracy, as proven by numerical results obtained in different microcellular scenarios.
    • Evaluation of IEEE 802.11b and Bluetooth coexistence in an office environment

      Zeng, Z.; Allen, Ben; Liu, Z.; Aghvami, A.Hamid; King's College London (IET, 2004)
      IEEE 802.11b and Bluetooth (BT) have been comprehensively used as the core technologies of WLAN and WPAN respectively. However, since they both operate in the 2.4 GHz ISM frequency band, mutual interference between them can be significant. We evaluate the impact of BT interference on 802.11b systems in an office environment by a set of experiments. We include the experimental results that evaluate the narrowband interference problem in IEEE 802.11b networks; and we specify the attenuation requirement of interference suppression technologies utilised by the IEEE 802.11b system.
    • Existing wireless network security mechanisms and their limitations for ad hoc networks

      Safdar, Ghazanfar Ali; McGrath, Clare; McLoone, Maire (IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 2006)
    • Experimental circular phased array for generating OAM radio beams

      Bai, Qiang; Tennant, Alan; Allen, Ben; University of Bedfordshire; University of Sheffield (IEEE, 2014-09)
      A circular phased array antenna that can generate orbital angular momentum (OAM) radio beams in the 10 GHz band is described. The antenna consists of eight inset-fed patch elements and a microstrip corporate feeding network. A full-wave electromagnetic simulator is used to aid the antenna design and theoretical simulations are confirmed by measurements
    • Experimental demonstration of a macroscopic cryptography technique

      Ajmal, Tahmina; Lepley, Jason J.; Walker, Stuart D. (IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 2006)
      Physical layer cryptography offers the unique possibility of certifiably secure data transmission between remote locations. We present here for the first time, to our knowledge, the experimental results of a secure full Poincare occupancy polarization encrypted data transmission system. The scheme uses an approach to macroscopic physical layer cryptography based on combining a multilevel polarisation modulation cipher with a differential phase shift keying data transmission technique. Depolarized noise is added to the encrypted data so as to hide both the data and key from a potential eavesdropper. Experimental results prove the effectiveness of the technique over amplified optical transmission links. The technique hence opens up new avenues for long distance secure data transmission over fibre links
    • Exploration and analysis of fade depth scaling

      Sipal, Vit; Allen, Ben; Edwards, David J. (IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 2010-11)
      This paper presents a study of fade depth scaling properties of extremely wideband wireless links. The behaviour effects robustness of communication system and needs to be considered in system design as it influences the required link budget fade margin. This paper introduces a new simplified model of fade depth scaling as a function of bandwidth. It is based on higher number of measurements compared to preceding works. As a result, thorough exploration of fade depth dependency on frequency and distance has been conducted. The results provide more insight into the issue of fade depth scaling, which can be used in the design of wideband wireless communication systems.
    • Exploration of Nakagami fading in ultra-wideband wireless channels

      Sipal, Vit; Allen, Ben; Edwards, David J. (IET, 2011-04-14)
    • Fade depth scaling with channel bandwidth

      Malik, Wasim Q.; Allen, Ben; Edwards, David J. (IET, 2007-11)
      The dependence of small-scale fading on bandwidth is quantified experimentally in the 3.1–10.6 GHz band for indoor channels. The fade depth converges to 4 dB at 1 GHz bandwidth, with little reduction for further increase in bandwidth. A simple yet accurate empirical fade depth model is developed, enabling convenient evaluation of the link budget for a channel with given bandwidth.
    • A fibre optic tiltmeter [for volcano monitoring]

      Ur-Rehman, Masood; Ahmed, W.; Ajmal, Tahmina (IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 1996)
      A simple, rugged and highly sensitive fibre optic tiltmeter has been designed and its prototype model tested. The sensor intensity modulates the light with the change in the level of Hg surface with tilt. Hence, producing a detector output proportional to the tilt angle. The most important attribute of the tiltmeter is its ability to measure tilts of the order of microradians with a high degree of precision, hence making it an important tool for geophysical monitoring. Besides, the dielectric construction and inherent compatibility with fibre optic telemetry make the sensor suitable for monitoring the conditions of hostile and remote sites of volcanoes. The prototype model has been developed using rugged and easy to handle plastic fibres and the results obtained were satisfactory with a sensitivity of approximately 1.0 mV/μrad
    • Fountain coding in ad hoc wireless networks

      Allen, Ben; Dyo, Vladimir; University of Bedfordshire, UK (University of Bedfordshire, 2011)
      The aim of this PhD is to investigate innovative means of achieving real-time communications over an ad hoc wireless network by using Fountain coding, and more specifically as a novel means of message routing.
    • Frequency band sharing in CDMA-based micro/macro-cellular systems

      Ghorashi, S.A.; Said, F.; Dohler, Mischa; Allen, Ben; Aghvami, A.Hamid; King's College London (IEEE, 2005-09)
      A novel approach is proposed and analysed in this paper, where the micro-cell utilises the same frequency band as the macro-cell to transmit non-real time data. The main idea is that, whenever the macro-cell interference falls below a given threshold, the micro-cell schedules data with a transmission rate dependent on the micro-cell signal strength and the macro-cell interference level. We prove analytically that utilizing the hence created micro-cell transmission scheme non-real time data can be transmitted at micro-cells. We also derive the average duration and the frequency of transmit event for non-real time data transmission at micro-cells, all of which is verified by means of a dynamic CDMA system level simulator.
    • Frequency selectivity in confined environments

      Sipal, Vit; Gelabert, Javier; Stevens, Christopher; Allen, Ben; Edwards, David J.; University of Oxford (IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 2011-04)
      This paper explores the wireless channel propagation properties in confined environments from the resonator perspective. The relationship between the performance of a communication system and the combination of the environment's size, system frequency, and system bandwidth are analysed. The conclusions of the analysis are supported by simulation and measurement results. The impact of frequency selectivity on communication systems is discussed and approaches to alleviate this issue are evaluated.
    • Frequency-selective fading of ultrawideband wireless channels in confined environments

      Sipal, Vit; Gelabert, Javier; Allen, Ben; Stevens, Christopher; Edwards, David J. (2011-08)
    • A generalized analysis of three-dimensional anisotropic scattering in mobile wireless channels-part I: theory

      Karadimas, Petros; Zhang, Jie (IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 2011)