7144957
Modeling two-windows TCP behavior in differentiated services networks
Two important issues in assured services within differentiated services architecture are bandwidth guarantee and fair sharing of unsubscribed bandwidth among TCP flows with and without bandwidth reservations. Although the subscribed bandwidth can be guaranteed by increasing network capacity or deploying strict admission control mechanisms, the costs of such solutions are very high. The issue of fair sharing of excess bandwidth is also not well solved. To address those issues, a modified TCP, named two-windows TCP, has been proposed. The performance of the protocol is evaluated by simulations. But its effectiveness is not validated theoretically under general network conditions, which is important for understanding the benefits and costs of using the protocol. In this paper, an analytical model is developed for the purpose. The model characterizes throughput of individual two-windows TCP flow as a function of contract rate, round trip time, loss rates of In and Out packets. Extensive simulations validate the analytical model. It's shown two-windows TCP is effective not only on solving the issues of bandwidth guarantee and fair sharing of unsubscribed bandwidth, but also on increasing the utilization of bottleneck link bandwidth. Moreover, its performance is robust to network conditions, which is important for wide deployment over Internet.
9503765
Unequal-arm adaptive rood pattern search for fast block-matching motion estimation in the JVT/H.26L
The adaptive rood pattern search (ARPS) algorithm proposed by Nie and Ma (2002) has shown two to three times of search speed-up improvement over that of diamond search (DS) based on the MPEG-4 verification model encoding platform. In this paper, first we have shown that the distribution of motion vectors bears a rood shape. An improved ARPS algorithm, called ARPS-3 or unequal-arm ARPS, is then proposed and experimented on the JVT/H.26L JM encoding platform. Due to complex modes and multiframe prediction, a new normalized computational cost metrics is also proposed for objectively measuring the computational gain or search speed-up. Experimental results show that ARPS-3 has achieved superb performance on many accounts while maintaining fairly close rate-distortion performance compared with that of the full search. It also outperforms its predecessors, ARPS and ARPS-2 (or equal-arm ARPS).
9933284
A MCMC approach for Bayesian super-resolution image reconstruction
In this paper, we consider the super-resolution image reconstruction problem. We propose a Markov chain Monte Carlo (MCMC) approach to find the maximum a posterior probability (MAP) estimation of the unknown high-resolution image. Firstly, Gaussian Markov random field (GMRF) is exploited for modeling the prior probability distribution of the unknown high-resolution image. Then, a MCMC technique (in particular, the Gibbs sampler) is introduced to generate samples from the posterior probability distribution to compute the MAP estimation of the unknown high-resolution image, which is obtained as the mean of the samples. Moreover, we derive a bound on the convergence time of the proposed MCMC approach. Finally, the experimental results are presented to verify the superior performance of the proposed approach and the validity of the proposed bound.
2488876
Tri-state median filter for image denoising
In this work, a novel nonlinear filter, called tri-state median (TSM) filter, is proposed for preserving image details while effectively suppressing impulse noise. We incorporate the standard median (SM) filter and the center weighted median (CWM) filter into a noise detection framework to determine whether a pixel is corrupted, before applying filtering unconditionally. Extensive simulation results demonstrate that the proposed filter consistently outperforms other median filters by balancing the tradeoff between noise reduction and detail preservation.
35556766
Error concealment for image transmission by multiscale Markov random field modeling
Transmission of visual data over communication channels introduces serious fidelity problems. The paper proposes an efficient error concealment algorithm for the image transmitted as encoded bitstreams. The proposed method introduces a multiscale Markov random field (MMRF) to model the original image. The established MMRF model is consequently employed to interpolate the missing blocks in the observing data via maximum a posterior (MAP) estimation. Compared with the conventional spatial interpolation scheme, this algorithm offers significant improvements on both subjective and objective qualities of the recovered image.
14032639
Sliding-window packetization for unequal loss protection based multiple description coding
Unequal loss protection (ULP) for transmitting embedded bitstream over packet erasure networks has been extensively studied. However, most of the existing works focused on rate-distortion optimization of individual encoding unit, e.g., a group of pictures (GOP), which may lead to noticeable video quality variations due to varying channel conditions. In this paper, a novel sliding-window packetization scheme is proposed, which combat bursty packet loss through GOP interleaving. Two levels of rate allocation are introduced: intra-GOP rate allocation minimizes the distortion of individual GOP, and provides hybrid FEC/retransmission packet loss recovery; while inter-GOP rate allocation intends to reduce video quality fluctuations by adaptively allocating bandwidth according to video signal characteristics. Through this way, more consistent video quality can be achieved under various packet loss probability, as verified by our experimental results.
5064603
The ascending star subgraph decomposition of some star forests