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Semisoft Handover Gain Analysis Over OFDM-Based Broadband Systems
Hyungkeuk Lee,Hyukmin Son,Sanghoon Lee IEEE 2009 IEEE Transactions on Vehicular Technology VT Vol.58 No.3
<P>Various approaches to analyze handover have been developed to guarantee the quality of service of multimedia services over mobile communication networks. However, no framework for multicarrier-based broadband systems, e.g., multicarrier code-division multiple access and orthogonal frequency-division multiple access, is available based on the perspective of link capacity. This paper presents a handover technique referred to as semisoft-handover-utilizing macroscopic diversity, which permits both hard and soft handover advantages for services over multicarrier-based broadband networks to be retained. Theoretical analysis is then performed to measure the handover gain over the forward link in terms of an outage probability. Simulation data verify that semisoft handover outperforms other traditional handover techniques, in particular for high-data-rate services.</P>
Visually Weighted Compressive Sensing: Measurement and Reconstruction
Hyungkeuk Lee,Heeseok Oh,Sanghoon Lee,Bovik, A. C. IEEE 2013 IEEE TRANSACTIONS ON IMAGE PROCESSING - Vol.22 No.4
<P>Compressive sensing (CS) makes it possible to more naturally create compact representations of data with respect to a desired data rate. Through wavelet decomposition, smooth and piecewise smooth signals can be represented as sparse and compressible coefficients. These coefficients can then be effectively compressed via the CS. Since a wavelet transform divides image information into layered blockwise wavelet coefficients over spatial and frequency domains, visual improvement can be attained by an appropriate perceptually weighted CS scheme. We introduce such a method in this paper and compare it with the conventional CS. The resulting visual CS model is shown to deliver improved visual reconstructions.</P>
A Cross-Layer Approach for Maximizing Visual Entropy Using Closed-Loop Downlink MIMO
Lee, Hyungkeuk,Jeon, Sungho,Lee, Sanghoon Hindawi Publishing Corporation 2008 EURASIP journal on advances in signal processing Vol.2008 No.1
<P>We propose an adaptive video transmission scheme to achieve unequal error protection in a closed loop multiple input multiple output (MIMO) system for wavelet-based video coding. In this scheme, visual entropy is employed as a video quality metric in agreement with the human visual system (HVS), and the associated visual weight is used to obtain a set of optimal powers in the MIMO system for maximizing the visual quality of the reconstructed video. For ease of cross-layer optimization, the video sequence is divided into several streams, and the visual importance of each stream is quantified using the visual weight. Moreover, an adaptive load balance control, named equal termination scheduling (ETS), is proposed to improve the throughput of visually important data with higher priority. An optimal solution for power allocation is derived as a closed form using a Lagrangian relaxation method. In the simulation results, a highly improved visual quality is demonstrated in the reconstructed video via the cross-layer approach by means of visual entropy.</P>
Cross-Layer Optimization for Downlink Wavelet Video Transmission
Hyungkeuk Lee,Sanghoon Lee,Bovik, Alan Conrad IEEE 2011 IEEE transactions on multimedia Vol.13 No.4
<P>Cross-layer optimization for efficient multimedia communications is an important emerging issue towards providing better quality-of-service (QoS) over capacity-limited wireless channels. This paper presents a cross-layer optimization approach that operates between the application and physical layers to achieve high fidelity downlink video transmission by optimizing with respect to a quality criterion termed “visual entropy” using Lagrangian relaxation. By utilizing the natural layered structure of wavelet coding, an optimal level of power allocation is determined, which permits the throughput of visual entropy to be maximized over a multi-cell environment. A theoretical approach to optimization using the Shannon capacity and the Karush-Kuhn-Tucker (KKT) conditions is explored when coupling the application with the physical layers. Simulations show that the throughput gain for cross-layer optimization by visual entropy is increased by nearly 80% at the cell boundary as compared with peak signal-to-noise ratio (PSNR).</P>