The University of Kent is a public research university based in Kent, United Kingdom. It was founded in 1965 and is regarded as one of the UK's "plate glass universities". The University of Kent's main site is a rural campus just north of Canterbury situated within 300 acres of park land, which houses over 4,300 students. Wikipedia.
Zhu H.,University of Kent
IEEE Journal on Selected Areas in Communications | Year: 2011
The microcellular system and distributed antenna system (DAS) are two promising systems for future high data rate wireless communications, since both systems can reduce the radio transmission distance between the transmitter and the receiver. This paper aims to compare the average spectrum efficiency and the cell edge spectrum efficiency between the two cellular systems in the downlink transmission. In order to achieve high spectrum efficiency, frequency reuse and/or spatial diversity are exploited in these two systems. The performances between the two cellular systems are theoretically compared in a network topology with seven macrocells, each of which has seven hexagonal sectors (or microcells). Moreover, the approach of antenna unit selection in the DAS for spatial diversity is presented. Numerical results show that the average spectrum efficiency per sector and the cell edge spectrum efficiency in the microcellular system are better than those in the DAS without frequency reuse. However, when the frequency reuse is considered in the DAS, the DAS outperforms the microcellular system in both of the average and cell edge spectrum efficiencies. © 2011 IEEE. Source
Sim K.M.,University of Kent
IEEE Transactions on Services Computing | Year: 2012
Agent-based cloud computing is concerned with the design and development of software agents for bolstering cloud service discovery, service negotiation, and service composition. The significance of this work is introducing an agent-based paradigm for constructing software tools and testbeds for cloud resource management. The novel contributions of this work include: 1) developing Cloudle: an agent-based search engine for cloud service discovery, 2) showing that agent-based negotiation mechanisms can be effectively adopted for bolstering cloud service negotiation and cloud commerce, and 3) showing that agent-based cooperative problem-solving techniques can be effectively adopted for automating cloud service composition. Cloudle consists of 1) a service discovery agent that consults a cloud ontology for determining the similarities between providers' service specifications and consumers' service requirements, and 2) multiple cloud crawlers for building its database of services. Cloudle supports three types of reasoning: similarity reasoning, compatibility reasoning, and numerical reasoning. To support cloud commerce, this work devised a complex cloud negotiation mechanism that supports parallel negotiation activities in interrelated markets: a cloud service market between consumer agents and broker agents, and multiple cloud resource markets between broker agents and provider agents. Empirical results show that using the complex cloud negotiation mechanism, agents achieved high utilities and high success rates in negotiating for cloud resources. To automate cloud service composition, agents in this work adopt a focused selection contract net protocol (FSCNP) for dynamically selecting cloud services and use service capability tables (SCTs) to record the list of cloud agents and their services. Empirical results show that using FSCNP and SCTs, agents can successfully compose cloud services by autonomously selecting services. © 2008-2012 IEEE. Source
Zhu H.,University of Kent
IEEE Journal on Selected Areas in Communications | Year: 2012
In high speed train (HST) system, real-time multimedia entertainments are very important applications in which a data stream often contains packets with different quality of service requirements. For example, video stream encoded with scalability contains the base layer packets with high quality (HQ) bit error rate (BER) requirement and enhancement layers' packets with low quality (LQ) BER requirement. When a conventional allocation approach, which only considers one BER constraint for one data stream, is applied to orthogonal frequency division multiple access (OFDMA) systems, the BER constraint will be the strictest one among multiple requirements from different types of packets, which leads to inefficient allocation when each data stream has multiple BER requirements. This paper aims to develop novel resource allocation approach by considering multiple BER requirements for different types of packets in one data stream. In order to not only simplify the resource allocation, but also to compensate for the channel estimation error caused by Doppler shift in the HST environment, a proper number of contiguous subcarriers are grouped into chunks and spectrum is allocated chunk by chunk. Simulation results show that the developed resource allocation scheme outperforms the conventional scheme, particularly when the BER ratio of HQ packets to LQ packets is larger than one. Furthermore, in order to reduce the complexity of resource allocation further, an empirical allocation scheme is proposed to allocate better chunks to HQ packets. It is shown that the performance of the empirical allocation scheme is quite close to that of the optimal scheme. © 2012 IEEE. Source
University of Kent | Date: 2013-11-11
Real-time depth measurements in sensing in spectral domain interferometry and for en-face and cross section image production in optical coherence tomography can operate without any need to linearize the data to maximize the output signal and achieve the theoretical depth resolution. Novel interferometry is disclosed, where parameters of a master interferometer dictate the results in a slave interferometer. The master interferometer can be the same measuring interferometer used in two stages. The master interferometer parameters are at least optical path difference (OPD) or the speed of variation of the OPD in the master interferometer. Coherence gated data are produced from selected axial positions which can be from positive or negative optical path differences, in parallel, enabling generation of en-face (C-scan) OCT images simultaneously from several depths, free from mirror terms, and production of A-scans and B-scan OCT images using plural reflectivity values measured in parallel from different depths within A-scans.
University of Kent | Date: 2011-07-08
A spectral interferometry apparatus and method is provided to supply unambiguous profiles (A-scans free of mirror terms) of the reflectivity versus optical path difference and make difference between the positive and negative optical path difference or provide output in a selected interval of optical path differences. The apparatus comprises object optics that transfer a beam from an optical source to a target object (