• Network performance optimization: a case study of enterprise network simulated in OPNET

      Shah, Munam Ali; Safdar, Ghazanfar Ali; Maple, Carsten; Sardar, Khurram (IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 2011)
    • A new twist on UWB pathloss modelling

      Dohler, Mischa; Allen, Ben; Armogida, A.; McGregor, S.; Ghavami, Mohammad; Aghvami, A.Hamid (IEEE, 2004-05)
      Ultra wideband (UWB) systems facilitate extremely high data rates over fairly short distances. Notwithstanding the short communication distances, a proper powerloss model is required to knowledgably model and adjust the transmission power of such systems. The extremely wide bandwidth prohibits narrowband pathloss models to be applied to the link budget calculation of UWB systems. The contribution of this paper is the derivation of a novel breakpoint within the vicinity of the transmitter, which is shown to influence the UWB link budget considerably.
    • A node discovery service for partially mobile sensor networks

      Dyo, Vladimir; Mascolo, Cecilia (ACM, 2007)
    • Novel authenticated key management framework for ad hoc network security

      McGrath, Clare; Safdar, Ghazanfar Ali; McLoone, Maire (IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 2006)
    • A novel birefrigent photonic crystal fiber surface plasmon resonance biosensor

      Otupiri, R.; Akowuah, Emmanuel K.; Haxha, Shyqyri; Ademgil, H.; AbdelMalek, Fathi; Aggoun, Amar; Kwame Nkrumah University of Science & Technology, Ghana; University of Bedfordshire (IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 2014)
      A numerical analysis of a novel birefringent photonic crystal fiber (PCF) biosensor constructed on the surface plasmon resonance (SPR) model is presented in this paper. This biosensor configuration utilizes circular air holes to introduce birefringence into the structure. This PCF biosensor model shows promise in the area of multiple detection using HEx11 and HEy11 modes to sense more than one analyte. A numerical study of the biosensor is performed in two interrogation modes: amplitude and wavelength. Sensor resolution values with spectral interrogation yielded 5 × 10-5 RIU (refractive index units) for HEx11 modes and 6 × 10-5 RIU for HEy11 modes, whereas 3 × 10-5 RIU for HEx11 modes and 4 × 10-5 RIU for HEy11 modes are demonstrated for the amplitude interrogation.
    • A novel common control channel security framework for cognitive radio networks

      Safdar, Ghazanfar Ali; O'Neill, M. (Inderscience, 2012)
      Cognitive radio technology makes use of the underutilised spectrum opportunistically without causing interference to the primary users. Cooperatively communicating cognitive radio devices use the common control channel of the cognitive radio medium access control to perform free channel announcements, channel selection and channel reservation before any actual data transmission. Common control channel security is vital in order to ensure security in the subsequent communication among the cognitive radio nodes. Additional to well-known security problems in wireless networks, cognitive radio networks introduce new classes of security threats and challenges, such as misbehaviours in spectrum sensing, licensed user emulation and attacks in the common control channel transactions. This paper presents a novel common control channel security framework (protocol) for cooperatively communicating cognitive radio networks. To the best of the authors knowledge, this is the first paper to address the security requirements of the common control channel. An implementation of the proposed security protocol is discussed illustrating how two cognitive radio nodes can authenticate each other prior to any confidential common control channel negotiations. The protocol is formally validated by GNY logic and a security analysis of the protocol illustrates that it meets the principal security requirements of authentication, confidentiality, integrity and non-repudiation.
    • A novel dynamic Q-learning-based scheduler technique for LTE-advanced technologies using neural networks

      Comşa, Ioan-Sorin; Zhang, Sijing; Aydin, Mehmet Emin; Kuonen, Pierre; Wagen, Jean–Frédéric; University of Bedfordshire (IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 2012)
      The tradeoff concept between system capacity and user fairness attracts a big interest in LTE-Advanced resource allocation strategies. By using static threshold values for throughput or fairness, regardless the network conditions, makes the scheduler to be inflexible when different tradeoff levels are required by the system. This paper proposes a novel dynamic neural Q-learning-based scheduling technique that achieves a flexible throughput-fairness tradeoff by offering optimal solutions according to the Channel Quality Indicator (CQI) for different classes of users. The Q-learning algorithm is used to adopt different policies of scheduling rules, at each Transmission Time Interval (TTI). The novel scheduling technique makes use of neural networks in order to estimate proper scheduling rules for different states which have not been explored yet. Simulation results indicate that the novel proposed method outperforms the existing scheduling techniques by maximizing the system throughput when different levels of fairness are required. Moreover, the system achieves a desired throughput-fairness tradeoff and an overall satisfaction for different classes of users.
    • A novel lifecycle model for Web-based application development in small and medium enterprises

      Huang, Wei; Li, Ru; Maple, Carsten; Yang, Hong-Ji; Foskett, David; Cleaver, Vince (Springer, 2010)
      Software engineering's lifecycle models have proven to be very important for traditional software development. However, can these models be applied to the development of Web-based applications as well? In recent years, Web-based applications have become more and more complicated and a lot of efforts have been placed on introducing new technologies such as J2EE, PhP, and .NET, etc., which have been universally accepted as the development technologies for Web-based applications. However, there is no universally accepted process model for the development of Web-based applications. Moreover, shaping the process model for small medium-sized enterprises (SMEs), which have limited resources, has been relatively neglected. Based on our previous work, this paper presents an expanded lifecycle process model for the development of Web-based applications in SMEs. It consists of three sets of processes, i.e., requirement processes, development processes, and evolution processes. Particularly, the post-delivery evolution processes are important to SMEs to develop and maintain quality web applications with limited resources and time.
    • Novel method for improving the capacity of optical MIMO system using MGDM

      Baklouti, F.; Dayoub, I.; Haxha, Shyqyri; Attia, R.; Aggoun, Amar; University of Bedfordshire (2014)
      In current local area networks, multimode fibers (MMFs), primarily graded index (GI) MMFs, are the main types of fibers employed for data communications. Due to their enormous bandwidth, it is considered that they are the main channel medium that can offer broadband multiservices using optical multiplexing techniques. Amongst these, mode group diversity multiplexing (MGDM) has been proposed as a way to integrate various services over an MMF network by exciting different groups of modes that can be used as independent and parallel communication channels. In this paper, we study optical multiple-input–multiple-output (O-MIMO) systems using MGDM techniques while also optimizing the launching conditions of light at the fiber inputs and the spot size, radial offset, angular offset, wavelength, and the radii of the segment areas of the detectors. We propose a new approach based on the optimization of launching and detection conditions in order to increase the capacity of an O-MIMO link using the MGDM technique. We propose a (3 $times$ 3) O-MIMO system, where our simulation results show significant improvement in GI MMFs' capacity compared with existing O-MIMO systems.
    • A novel powerloss model for short range UWB transmissions

      Dohler, Mischa; Allen, Ben; Armogida, A.; McGregor, S.; Ghavami, Mohammad; Aghvami, A.Hamid; King's College, London (IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 2004-05)
      Narrowband pathloss models are not applicable to the link budget calculation of ultra wideband (UWB) systems. In this paper, a rigorous analysis reveals the powerloss behavior of short-range UWB systems when operating in a cluttered environment. The contribution of this paper is the derivation of a power law model that exhibits a novel breakpoint within the vicinity of the transmitter, which is shown to influence the UWB link budget by up to 5 dB.
    • A novel single base station location technique for microcellular wireless networks: description and validation by a deterministic propagation model

      Porretta, Marco; Nepa, Paolo; Manara, Giuliano; Giannetti, Filippo; Dohler, Mischa; Allen, Ben; Aghvami, A.Hamid (IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 2004-09)
      Positioning algorithms in cellular networks has become increasingly important as a means of supporting emerging services that require a sufficiently precise estimation of the position of the mobile terminal (MT) associated with a given base station (BS). Currently, even the most sophisticated positioning algorithms require at least three BSs to achieve satisfactory precision. This paper presents a novel algorithm that makes use of a single-BS antenna array to locate MTs in cellular networks. A triangulation technique is utilized and supported by some minimal information about the environment in the BS neighborhood. This algorithm is shown to perform well when operating in a microcellular environment with perfect channel-parameter estimation. The effect of finite resolution of the input parameters is also investigated. The performance is analyzed for a universal mobile telecommunications system microcellular scenario through a three-dimensional deterministic channel model. Finally, the performance of the proposed positioning technique is compared to the well-known location method based on the time-of-arrival measurements at three different BSs.
    • Novel UWB pulse shaping using prolate spheroidal wave functions

      Dilmaghani, Reza S.; Ghavami, Mohammad; Allen, Ben; Aghvami, A.Hamid (IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 2003-09)
      In this paper novel prolate spheroidal wave functions are proposed as pulse shapes for use in impulse radio (ultra-wideband) communications. These classes of functions yields orthogonal pulses and have a constant pulse width regardless of the pulse order. This is an important property since it eliminates inter-symbol interference. An M-ary communications system is considered that employs these pulses, and the generation of these pulses using the eigenfunction form of a self-adjoint operator is proposed. It is also shown that these pulses are suitable for use in pulse position modulation (PPM) ultra wideband (UWB) communication systems.
    • On dependent bit allocation for multiview image coding with depth-image-based rendering

      Cheung, Gene; Velisavljević, Vladan; Ortega, Antonio (IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 2011-11)
    • On space–frequency correlation of UWB MIMO channels

      Hong, Xuemin; Wang, Cheng-Xiang; Thompson, John; Allen, Ben; Malik, Wasim Q.; Ge, Xiaohu (IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 2010-11)
    • On statistical characterization of EESM effective SNR over frequency selective channels

      Hui Song; Kwan, R.; Jie Zhang; University of Bedfordshire (IEEE, 2009-08)
      A novel expression of the moment generating function (MGF) of the exponential effective SNR mapping (EESM) signal-to-noise ratio (SNR) over two correlated but not necessarily identically distributed Nakagami-m fading channels is presented. Based on the MGF, a novel expression for the average effective SNR is also presented. Numerical evaluation of these expressions shows that the proposed approach can be a useful and efficient analytical tool in analyzing the characteristics of EESM over correlated Nakagami-m fading channels.
    • On the analysis of switched-beam antennas for the W-CDMA downlink

      Allen, Ben; Beach, Mark (IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 2004-05)
      Smart antennas are widely recognized as an enabling technology for addressing the demand of future wireless network capacity when employed in place of traditional fixed-coverage sector antennas. Furthermore, switched-beam antenna systems offer a robust implementation against multipath propagation effects and reduced complexity that is inherent with fully adaptive implementations. This paper introduces a simple closed-form expression for evaluating the capacity increase of W-CDMA cellular networks employing switched-beam antennas. The expression incorporates the effect of practical antenna patterns and the impact of multipath scattering on code orthogonality, as well as that of pilot signal power. The results show that a reduction in downlink interference of approximately 6 dB can be achieved by installing an eight-beam antenna system in a 120° sector configuration when representative values of these parameters are taken into account.
    • On the complexity of routing in wireless multihop network

      Waharte, Sonia; Golynski, Alexander; Boutaba, Raouf; University of Bedfordshire; Google Inc.; University of Waterloo (IEEE, 2012-08)
      Wireless backbone networks represent an attractive alternative to wired networks in situations where cost, speed of deployment, and flexibility in network design are important. In typical configurations, users connect to wireless routers of the backbone network, which then redirect the traffic to one of the existing network gateways. To improve the network performance, wireless backbone routers redirect their traffic to the network gateways so as to maximize amount of traffic that can be sup- ported by the network. In this paper, we prove that this problem is NP-hard as a result of the wireless interference that is created between geographically close transmission links. We consequently design and investigate the performance of interference-aware algorithms suitable for multi-channel environments against more traditional routing approaches. We evaluate their performance in simulated environments based on data taken from existing networks, and show that interference-based heuristics exhibit advantageous performance in non-uniform deployment.
    • On the range of Wimedia OFDM UWB wireless

      Sipal, Vit; Edwards, David J.; Allen, Ben; University of Oxford (IEEE, 2012-09)
      We show a significant discrepancy between the range estimates and the actual performance of an ultrawideband wireless system based on the Wimedia standard. We also show this discrepancy to be linked to the combination of frequency selectivity of the ultrawideband channel and the low dynamic range available to ultrawideband receiver. We propose an alternative means of range estimation combining the statistics of frequency selective fading and the path-loss and we show that this algorithm provides significantly more accurate estimation.
    • On the scatterers' mobility and second order statistics of narrowband fixed outdoor wireless channels

      Karadimas, Petros; Vagenas, Efstathios D.; Kotsopoulos, Stavros A. (IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 2010)
      In this paper, we study the temporal behavior of narrowband fixed outdoor wireless channels by modeling the impact of scatterers' mobility on the second order statistics of such channels. We show that the Nakagami-m, gamma, Weibull and lognormal probability density functions (PDFs) can adequately approximate the scatterers' mobility at outdoor environments by comparing the theoretically derived autocorrelation functions (ACFs) with measured ACFs. These theoretical ACFs arise after considering several candidate PDFs for the impact of scatterers mobility. We select that PDF whose ACF provides the best fitting to measurements. The modeling of scatterers' mobility lead us to present analytical expressions for the level crossing rate (LCR) and average fade duration (AFD) together with an exact expression for the power spectral density (PSD).
    • On-body bluetooth link budget: effects of surrounding objects and role of surface waves

      Ur-Rehman, Masood; Gao, Yue; Chen, Xiaodong; Parini, Clive G.; Ying, Zhinong; Bolin, Thomas; Zweers, J. W. (IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 2008)