Transmission of compressed multimedia data over wireless channels using space-time OFDM with adaptive beamforming

The transmission of multimedia data over wireless channels poses significant constraints on the communication system bandwidth, energy, and latency. To overcome these bottlenecks to wireless multimedia communication, various channel coding and transmit diversity schemes have been proposed. In previous work, we have shown that space-time block-coding (STBC) with adaptive beamforming (STBC-OFDM-AB) is an effective technique for improving the error-rate performance and channel capacity of wireless multimedia systems utilizing OFDM. In this paper, we introduce a transmission system for multimedia communication employing STBC-OFDM with adaptive beamforming incorporating a perceptually-based image compression coder - which consists of a 2-D discrete wavelet transform (DWT), an adaptive quantizer (with thresholding) and variable-length entropy encoding. Initial simulation results based on the transmission of compressed images, showed that the performance improvement introduced by STBC-OFDM-AB can be readily observed, and compared to other transmission methods is better suited to wireless multimedia communication

Multimedia transmission over wireless space-time-frequency coded OFDM

The transmission of multimedia data over wireless systems generally require network devices designed with a high communication bandwidth, power, and processing resources. To deal with these bottlenecks commonly associated with multimedia transmission, various diversity coding schemes have been proposed. We have previously shown that wireless OFDM systems based on space-time block-coding with adaptive beamforming (STBC-OFDM-AB) are well suited to multimedia communication. Recent studies have shown further performance gains in systems utilizing space-time-frequency (STF) coding. In this paper, we introduce a transmission system which combines STF coding with adaptive beamforming (STF-OFDM-AB). Simulation results based on the transmission of compressed images showed that the performance improvements introduced by STF-OFDM-AB can be readily observed

An unequal modulation scheme for the transmission of compressed multimedia data over MIMO-OFDM systems

Modern video/image source coders employ data compression techniques which encode information that are not equally important. Transform based or subband coders, compress data into their respective low-frequency and high-frequency components. In wireless/mobile communication systems, data representing the low-frequency components are more sensitive to the time-varying nature of channel conditions and propagation environments. To deal with this problem, we propose an optimum transceiver structure for a combined source-modulation coded MIMO-OFDM system with adaptive eigen-beamforming. Using an unequal adaptive modulator, we maximize the channel-to-noise ratio (CNR) based on a lookup matrix-adaptive bit and power allocation (LM-ABPA) scheme to sort and allocate subcarriers with the highest SNR to the low-frequency components of the compressed data, and adjusting the signal constellation/modulation type respectively. In comparison to other transmission systems, simulation results based on the application of compressed images showed that the proposed unequal adaptive modulation scheme achieves significant performance gains under a constant data rate loa

Signal processing techniques for mobile multimedia systems

Recent trends in wireless communication systems show a significant demand for the delivery of multimedia services and applications over mobile networks - mobile multimedia - like video telephony, multimedia messaging, mobile gaming, interactive and streaming video, etc. However, despite the ongoing development of key communication technologies that support these applications, the communication resources and bandwidth available to wireless/mobile radio systems are often severely limited. It is well known, that these bottlenecks are inherently due to the processing capabilities of mobile transmission systems, and the time-varying nature of wireless channel conditions and propagation environments. Therefore, new ways of processing and transmitting multimedia data over mobile radio channels have become essential which is the principal focus of this thesis. In this work, the performance and suitability of various signal processing techniques and transmission strategies in the application of multimedia data over wireless/mobile radio links are investigated. The proposed transmission systems for multimedia communication employ different data encoding schemes which include source coding in the wavelet domain, transmit diversity coding (space-time coding), and adaptive antenna beamforming (eigenbeamforming). By integrating these techniques into a robust communication system, the quality (SNR, etc) of multimedia signals received on mobile devices is maximised while mitigating the fast fading and multi-path effects of mobile channels. To support the transmission of high data-rate multimedia applications, a well known multi-carrier transmission technology known as Orthogonal Frequency Division Multiplexing (OFDM) has been implemented. As shown in this study, this results in significant performance gains when combined with other signal-processing techniques such as spa ce-time block coding (STBC). To optimise signal transmission, a novel unequal adaptive modulation scheme for the communication of multimedia data over MIMO-OFDM systems has been proposed. In this system, discrete wavelet transform/subband coding is used to compress data into their respective low-frequency and high-frequency components. Unlike traditional methods, however, data representing the low-frequency data are processed and modulated separately as they are more sensitive to the distortion effects of mobile radio channels. To make use of a desirable subchannel state, such that the quality (SNR) of the multimedia data recovered at the receiver is optimized, we employ a lookup matrix-adaptive bit and power allocation (LM-ABPA) algorithm. Apart from improving the spectral efficiency of OFDM, the modified LM-ABPA scheme, sorts and allocates subcarriers with the highest SNR to low-frequency data and the remaining to the least important data. To maintain a target system SNR, the LM-ABPA loading scheme assigns appropriate signal constella tion sizes and transmit power levels (modulation type) across all subcarriers and is adapted to the varying channel conditions such that the average system error-rate (SER/BER) is minimised. When configured for a constant data-rate load, simulation results show significant performance gains over non-adaptive systems. In addition to the above studies, the simulation framework developed in this work is applied to investigate the performance of other signal processing techniques for multimedia communication such as blind channel equalization, and to examine the effectiveness of a secure communication system based on a logistic chaotic generator (LCG) for chaos shift-keying (CSK)

Tetrafurcation of the subscapular artery. Anatomical and clinical implications

Anatomic variations of axillary artery branches are commonly encountered during radiological investigation and surgical operations. Their existence can confuse interpretation of radiological results and lead to undesired complications during surgery. In this report authors describe a rare case of a subscapular arterial trunk that gave origin to thoracodorsal, circumflex scapular, posterior humeral circumflex, and lateral thoracic artery. Such a variation might cause undesired sequelae during trauma management and a variety of common flap harvesting operations including latissimus dorsi, scapular and parascapular flaps. Furthermore it presents embryological interest as it gives insight to embryologic development of axillary area

The conceptual design of SeamFrame

This project deliverable provides the underlying architecture of a concept for linking models and databases and it provides the design of SeamFrame, delivering its architecture to provide an integration framework for models and simulation algorithms, supported by procedures for data handling and spatial representation, quality control, output visualization and documentatio

Affine and toric hyperplane arrangements

We extend the Billera-Ehrenborg-Readdy map between the intersection lattice and face lattice of a central hyperplane arrangement to affine and toric hyperplane arrangements. For arrangements on the torus, we also generalize Zaslavsky's fundamental results on the number of regions.Comment: 32 pages, 4 figure

Lyashko-Looijenga morphisms and submaximal factorisations of a Coxeter element

When W is a finite reflection group, the noncrossing partition lattice NCP_W of type W is a rich combinatorial object, extending the notion of noncrossing partitions of an n-gon. A formula (for which the only known proofs are case-by-case) expresses the number of multichains of a given length in NCP_W as a generalised Fuss-Catalan number, depending on the invariant degrees of W. We describe how to understand some specifications of this formula in a case-free way, using an interpretation of the chains of NCP_W as fibers of a Lyashko-Looijenga covering (LL), constructed from the geometry of the discriminant hypersurface of W. We study algebraically the map LL, describing the factorisations of its discriminant and its Jacobian. As byproducts, we generalise a formula stated by K. Saito for real reflection groups, and we deduce new enumeration formulas for certain factorisations of a Coxeter element of W.Comment: 18 pages. Version 2 : corrected typos and improved presentation. Version 3 : corrected typos, added illustrated example. To appear in Journal of Algebraic Combinatoric

CD4-Transgenic Zebrafish Reveal Tissue-Resident Th2- and Regulatory T Cell-like Populations and Diverse Mononuclear Phagocytes.

CD4+ T cells are at the nexus of the innate and adaptive arms of the immune system. However, little is known about the evolutionary history of CD4+ T cells, and it is unclear whether their differentiation into specialized subsets is conserved in early vertebrates. In this study, we have created transgenic zebrafish with vibrantly labeled CD4+ cells allowing us to scrutinize the development and specialization of teleost CD4+ leukocytes in vivo. We provide further evidence that CD4+ macrophages have an ancient origin and had already emerged in bony fish. We demonstrate the utility of this zebrafish resource for interrogating the complex behavior of immune cells at cellular resolution by the imaging of intimate contacts between teleost CD4+ T cells and mononuclear phagocytes. Most importantly, we reveal the conserved subspecialization of teleost CD4+ T cells in vivo. We demonstrate that the ancient and specialized tissues of the gills contain a resident population of il-4/13b-expressing Th2-like cells, which do not coexpress il-4/13a Additionally, we identify a contrasting population of regulatory T cell-like cells resident in the zebrafish gut mucosa, in marked similarity to that found in the intestine of mammals. Finally, we show that, as in mammals, zebrafish CD4+ T cells will infiltrate melanoma tumors and obtain a phenotype consistent with a type 2 immune microenvironment. We anticipate that this unique resource will prove invaluable for future investigation of T cell function in biomedical research, the development of vaccination and health management in aquaculture, and for further research into the evolution of adaptive immunity.European Research Council (Grant IDs: ERC-2011-StG-282059 (PROMINENT), 677501 (ZF_Blood)), Biotechnology and Biological Sciences Research Council (Grant ID: BB/L007401/1), Dowager Countess Eleanor Peel Trust (Grant ID: TH-PRCL.FID2228), Medical Research Council, Department for International Development (Career Development Award Fellowship MR/J009156/1), Medical Research Foundation (Grant ID: R/140419), Cancer Research UK (Grant ID: C45041/A14953), Wellcome Trust and Medical Research Council to the Wellcome Trust–Medical Research Council Cambridge Stem Cell Institute (core support grant)This is the final version of the article. It first appeared from The American Association of Immunologists via https://doi.org/10.4049/​jimmunol.160095

Direct imaging of changes in aerosol particle viscosity upon hydration and chemical aging

Organic aerosol particles (OA) play major roles in atmospheric chemistry, climate, and public health. Aerosol particle viscosity is highly important since it can determine the ability of chemical species such as oxidants, organics or water to diffuse into the particle bulk. Recent measurements indicate that OA may be present in highly viscous states, however, diffusion rates of small molecules such as water are not limited by these high viscosities. Direct observational evidence of kinetic barriers caused by high viscosity and low diffusivity in aerosol particles were not available until recently; and techniques that are able to dynamically quantify and track viscosity changes during atmospherically relevant processes are still unavailable for atmospheric aerosols. Here we report quantitative, real-time, online observations of microscopic viscosity changes in aerosol particles of atmospherically relevant composition, using fluorescence lifetime imaging (FLIM) of viscosity. We show that microviscosity in ozonated oleic acid droplets and secondary organic aerosol (SOA) particles formed by ozonolysis of myrcene increases substantially with decreasing humidity and atmospheric oxidative aging processes. Furthermore, we found unexpected heterogeneities of microviscosity inside individual aerosol particles. The results of this study enhance our understanding of organic aerosol processes on microscopic scales and may have important implications for the modeling of atmospheric aerosol growth, composition and interactions with trace gases and clouds.Engineering and Physical Sciences Research Council (Career Acceleration Fellowship (Grant ID: EP/I003983/1), Prize studentship), Natural Environment Research Council (Studentship NE/J500070/1), European Research Council (Grant ID: 279405), Max Planck Society, European Union project PEGASOS (Grant ID: 265148