Browsing by Author "Ormondroyd, Prof R. F."

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    Image processing and agent-based framework for the geolocation of emitters
    (2010-11-04) Mikhalev, A.; Ormondroyd, Prof R. F.
    The research presented in this thesis is about a task of geolocation of radio frequency emitters. In this research the problem of geolocation of non-collaborative emitter was addressed. This thesis presents the novel algorithm for the RF emitter geolocation based on the image process technique known as Hough Transform. The comparison of this algorithm with traditional approaches to geolocation showed a number of benefits, like robustness, accuracy and advanced fusion capability. The application of the Hough Transform to data fusion allowed to use the modern concepts of agentbased fusion and cluster level fusion, thus moving the solution of the problem of the geolocation to upper level of fusion hierarchy. The work on Hough Transform lead to a comparison of the Bayesian and non-Bayesian approaches in solving the task of geolocation. Exploitation of the comparison lead to the derivation of a generalized estimator. This estimator highlighted a number of mathematical functions which can be exploited for geolocation and data fusion. These functions has been tested for the purpose of data fusion in geolocation and it was found that Hough Transform is a useful alternative approach for the data fusion for geolocation of RF emitter.
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    A Novel training-based MIMO channel estimation scheme for layered space-time systems in frequency selective wireless channels
    (2009-07-14T12:52:42Z) Siyau, M. F.; Ormondroyd, Prof R. F.; Nobles, P.
    New development in wireless technology using multiple antennas with appropriate space-time processing has recently become the new frontier of wireless communication systems due to the potential for providing very high spectral efficiency and enormous capacity improvement over the conventional wireless radio communications. The technical advances in using the multiple-input multiple-output (MIMO) wireless links present a promising breakthrough in resolving the bottleneck of current capacity limitation for future intensive wireless networks. The MIMO wireless systems utilize multiple antennas at both side of the transmitter and the receiver for enormous gains in spectral efficiency as well as system capacity in terms of higher data throughput by exploiting the multipath diversity in a rich scattering environment. A number of MIMO systems have been proposed to permit very high transmission rate, far exceeding the conventional communication technique. In particular, the Bell Laboratories layered space-time (BLAST) architecture has been presented that uses concept of spatial diversity and successive interference cancellation technique to improve the quality of signal reception over the flat-fading or the frequency selective fading channel. However, in order to achieve the quoted capacity gains in MIMO systems, the channeli nformation in terms of the multiple channeli mpulse responses(C IRs) and their fading coefficients must be known or estimated, which requires the design of a suitable channele stimator.T hus far, existing MIMO channele stimations chemesh aveb eenm ostly limited to the flat-fading case or cater specifically for coded space-time systems such as space-timeb lock code systems.I n this thesis,t he work is to considert he existing MIMO channel estimation techniques (used in the flat fading condition) and extend them to cater for a more realistic time-varying, frequency selective fading channel. The focus of this thesis has been the design and development of suitable training-based MIMO channel estimation scheme as well as the formulation of a new pilot code to enable effective estimation for the frequency selective channel. The novel channel estimator is also incorporatedi nto the BLAST architecturet o allow the practical assessmenotf using nonidealized channel to be studied and analysed for the performance of the MIMO systems. The driver for this work has been the recognition of the importance of channel knowledge for all the MIMO system to be used in practical application.
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    Optimisation of wireless communication system by exploitation of channel diversity
    (2009-01-23T16:06:05Z) Iqbal, K.; Ormondroyd, Prof R. F.
    Communication systems are susceptible to degradation in performance because of interference received through their side lobes. The interference may be deliberate electronic counter measure (ECM), Accidental RF Interference (RFI) or natural noise. The growth of interference communication systems have given rise to different algorithms, Adaptive array techniques offer a possible solution to this problem of interference received through side lobes because of their automatic null steering in both spatial and frequency domains. Key requirement for space-time architecture is to use robust adaptive algorithms to ensure reliable operation of the smart antenna. Space division multiple access (SDMA) involves the use of adaptive nulling to allow two or more users (mobiles) in the same cell to share same frequency and time slot. One beam is formed for each user with nulls in the direction of other users. Different approaches have been used to identify the interferer from desired user. Thus a basic model for determining the angle of arrival of incoming signals, an appropriate antenna beam forming and adaptive algorithms are used for array processing. There is an insatiable demand for capacity in wireless data networks and cellular radio communication systems. However the RF environment that these systems operate in is harsh and severely limits the capacity of traditional digital wireless networks. With normal wireless systems this limits the data rate in cellular radio environments to approximately 200 kbps whereas much higher data rates in excess of 25Mbps are required. A common wireless channel problem is that of frequency selective multi-path fading. To combat this problem, new types of wireless interface are being developed which utilise space, time and frequency diversity to provide increasing resilience to the channel imperfections. At any instant in time, the channel conditions may be such that one or more of these diversity methods may offer a superior performance to the other diversity methods. The overall aim of the research is to develop new systems that use a novel combination of smart antenna MIMO techniques and an advanced communication system based on advanced system configuration that could be exploited by IEEE 802.20 user specification approach for broadband wireless networking. The new system combines the Multi-input Multi-output communication system with frequency diversity in the form of an OFDM modulator. The benefits of each approach are examined under similar channel conditions and results presented.