Patching Scheme Research Articles

Hybrid Patching for a Sequence of Differently Exposed Images With Moving Objects

It is very challenging to synthesize a high dynamic range (HDR) image from multiple differently exposed low dynamic range images when there are moving objects in the images. This is due to the fact that the moving objects will cause ghosting artifacts to appear in the synthesized HDR image. To prevent such artifacts, a patching algorithm is required to correct motion regions such that all the moving objects are synchronized in the differently exposed images. In this paper, a new optimization problem is formulated to correct the motion regions of the multiple differently exposed images by considering both spatial and temporal consistencies. The resultant scheme is a hybrid patching scheme composed of a correction method which is an intensity mapping function at pixel level, and a hole-filling method that uses block-level template matching. The proposed patching scheme is not only robust to large intensity changes in these input images, but also at regions that are over- or underexposed. Experimental results show that the proposed method is able to prevent ghosting artifacts from appearing in the final synthesized HDR image.

On-Demand Video Streaming Schemes Over Shared-WDM-PONs

A critical challenge for video-on-demand (VoD) services is to provide an entertainment service with minimum playback delay. A passive optical network (PON) that employs a high-speed optical fiber from an optical line terminal (OLT) to a number of optical network units (ONUs) can offer high bandwidth for multimedia applications (such as VoD services) in an access network. In this paper, we propose two novel video streaming techniques, called OLT broadcasting with ONU fast patching (BFP) and prediction-based OLT broadcasting and ONU fast patching (PBFP). The BFP scheme utilizes the ONU fast patching scheme at each ONU, and proposes a heuristic algorithm to find near optimum solutions of related optimization problem so that the worst-case playback delay (WPD) is minimized. The PBFP adds a prediction level for video popularity to the BFP scheme and uses a seamless channel transition technique to seamlessly change the number of channels allocated to videos. We study the efficiency of the proposed schemes when they are used in a shared wavelength division multiplexed passive optical network (Shared-WDM-PON) that adapts the broadcast nature of a GPON's downstream wavelength to WDM-PONs. Our simulation results indicate that the proposed schemes can improve both WPD and average playback delay performance parameters.

Doppler radar data assimilation with a local SVD-En3DVar method

An observation localization scheme is introduced into an ensemble-based three-dimensional variational (3DVar) assimilation method based on the singular value decomposition technique (SVD-En3DVar) to improve assimilation skill. A point-by-point analysis technique is adopted in which the weight of each observation decreases with increasing distance between the analysis point and the observation point. A set of numerical experiments, in which simulated Doppler radar data are assimilated into the Weather Research and Forecasting (WRF) model, is designed to test the scheme. The results are compared with those obtained using the original global and local patch schemes in SVD-En3DVar, neither of which includes this type of observation localization. The observation localization scheme not only eliminates spurious analysis increments in areas of missing data, but also avoids the discontinuous analysis fields that arise from the local patch scheme. The new scheme provides better analysis fields and a more reasonable short-range rainfall forecast than the original schemes. Additional forecast experiments that assimilate real data from 10 radars indicate that the short-term precipitation forecast skill can be improved by assimilating radar data and the observation localization scheme provides a better forecast than the other two schemes.

The Microcosmic Model of Worm Propagation

Each year, large amounts of money and labor are spent on patching the vulnerabilities in operating systems and various popular software to prevent exploitation by worms. Modeling the propagation process can help us to devise effective strategies against those worms’ spreading. This paper presents a microcosmic analysis of worm propagation procedures. Our proposed model is different from traditional methods and examines deep inside the propagation procedure among nodes in the network by concentrating on the propagation probability and time delay described by a complex matrix. Moreover, since the analysis gives a microcosmic insight into a worm's propagation, the proposed model can avoid errors that are usually concealed in the traditional macroscopic analytical models. The objectives of this paper are to address three practical aspects of preventing worm propagation: (i) where do we patch? (ii) how many nodes do we need to patch? (iii) when do we patch? We implement a series of experiments to evaluate the effects of each major component in our microcosmic model. Based on the results drawn from the experiments, for high-risk vulnerabilities, it is critical that networks reduce the number of vulnerable nodes to below 80%. We believe our microcosmic model can benefit the security industry by allowing them to save significant money in the deployment of their security patching schemes.

Link Stability and Node Energy Conscious Local Route-Repair Scheme for Mobile Ad Hoc Networks

Problem statement: A mobile ad hoc network is a self-configuring network of mobile nodes connected by wireless links. As the nodes are free to move randomly, topology of the network may change rapidly and unpredictably. As a result, intermediat e nodes in the communication routes tend to lose connection with each other during the communication process. In order to repair a broken link, an end- to- end (from source to destination) route discovery is typically performed to establish a new route for communication. The mechanism results in huge communication overhead and long delay in completion of the communication. So, it is rational to locally re pair a link, as much as possible, than to discover a whole new route. Approach: In the present article, we proposed a Link Stabili ty and Node Energy Conscious (LSNEC) local route repair scheme for mobile ad hoc networks. In case of breakage of a link from node na to another node nb in between a communication session, LSNEC instructs na to broadcast a ROUTE- REPAIR message within its radio-range specifying nb or any successor of nb in the broken route, as a desirable destination. If any node residing within the radio-range of na has an already established single/multi-hop path to any one of those destinati ons mentioned in the ROUTE-REPAIR message, it sends a REPAIR-ACK message back to na. Attributes of REPAIR-ACK include the identificati on number (s) of the destination (s) as well as identificatio n numbers, geographical positions (in terms of lati tude and longitude), radio-ranges and residual energies of n odes present in the associated path to that destina tion along with the intuitively computed stability of li nks between the consecutive nodes. The stability is computed depending upon relative velocities of the involved nodes, distance between them and the histo ry of survival of the link. The optimal path is chosen depending upon the residual energy of nodes, stabi lity of links and number of hops in that path. Results: In simulations we compared the LSNEC embedded versions of the protocols Ad hoc On-demand Distance Vector routing (AODV) and Associatively Based Routing (ABR) with their ordinary versions as well as PATCH and Quick Local Repair scheme (to be referred to as QLR subsequently in this study) embe dded versions. Both PATCH and QLR are well- known local repairing schemes for ad hoc networks. It is found that, LSNEC-AODV dramatically saves 57% control overhead compared to ordinary AODV, 32.7% compared to PATCH-AODV and 36.3% compared to QLR-AODV. Similarly, LSNEC-ABR saves 29.3% control overhead than ordinary ABR, 10.7% than PATCH-ABR and 12.8% than QLR-ABR. Accordingly decrease the power consumption of network nodes and delay in recovery. Conclusion: The simulation results emphatically illustrated th e performance benefit of our proposed scheme LSNEC compared to the other state-of-the-art local route- repair schemes, in respect of control overhead, ove rall energy consumption of the network, data packet delivery ratio and route recovery delay. LSNEC has its application wherever an ad hoc network is used. Please note that ad hoc networks are extremely usef ul in military and other tactical applications such as emergency rescue, exploration missions and other sc enarios w here cellular infrastructure is unavailab le.

On guaranteed VoD services in next generation optical access networks

Video on demand (VoD) is one of the most important services for many network operators that deploy and operate optical access networks. It is crucial to design next generation optical access networks that can guarantee a high quality VoD service. In this paper, we address this challenging issue and focus on the worst-case playback delay (WPD), which cannot be guaranteed by Internet-based video streaming, and has not been well addressed previously in optical access networks. Specifically, we first propose an integrated Gigabit Passive Optical Network (GPON) and Wavelength Division Multiplexing PON (WDM PON) architecture. With the proposed architecture, an optical line terminal (OLT) can broadcast popular videos through GPON and deliver other videos through WDM-PON, while the optical network units (ONUs) can conduct patching for their end users. We then elaborate on two minimum-WPD schemes. In the first one, we assume that the video broadcast schedule is fixed at the OLT and develop an optimal patching scheme at each ONU such that the WPD is minimized. In the second one, we consider coordinated OLT broadcast scheduling and ONU patching. A heuristic algorithm which can achieve near-optimal WPD is proposed for coordinated OLT broadcast scheduling and ONU patching. Simulation results confirm the superiority of the proposed schemes over the existing ones in terms of both worstcase and average delay performance.

AFMPB: An adaptive fast multipole Poisson–Boltzmann solver for calculating electrostatics in biomolecular systems

A Fortran program package is introduced for rapid evaluation of the electrostatic potentials and forces in biomolecular systems modeled by the linearized Poisson–Boltzmann equation. The numerical solver utilizes a well-conditioned boundary integral equation (BIE) formulation, a node–patch discretization scheme, a Krylov subspace iterative solver package with reverse communication protocols, and an adaptive new version of fast multipole method in which the exponential expansions are used to diagonalize the multipole-to-local translations. The program and its full description, as well as several closely related libraries and utility tools are available at http://lsec.cc.ac.cn/~lubz/afmpb.html and a mirror site at http://mccammon.ucsd.edu/. This paper is a brief summary of the program: the algorithms, the implementation and the usage. Program summary Program title: AFMPB: Adaptive fast multipole Poisson–Boltzmann solver Catalogue identifier: AEGB_v1_0 Program summary URL: http://cpc.cs.qub.ac.uk/summaries/AEGB_v1_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: GPL 2.0 No. of lines in distributed program, including test data, etc.: 453 649 No. of bytes in distributed program, including test data, etc.: 8 764 754 Distribution format: tar.gz Programming language: Fortran Computer: Any Operating system: Any RAM: Depends on the size of the discretized biomolecular system Classification: 3 External routines: Pre- and post-processing tools are required for generating the boundary elements and for visualization. Users can use MSMS ( http://www.scripps.edu/~sanner/html/msms_home.html) for pre-processing, and VMD ( http://www.ks.uiuc.edu/Research/vmd/) for visualization. Sub-programs included: An iterative Krylov subspace solvers package from SPARSKIT by Yousef Saad ( http://www-users.cs.umn.edu/~saad/software/SPARSKIT/sparskit.html), and the fast multipole methods subroutines from FMMSuite ( http://www.fastmultipole.org/). Nature of problem: Numerical solution of the linearized Poisson–Boltzmann equation that describes electrostatic interactions of molecular systems in ionic solutions. Solution method: A novel node–patch scheme is used to discretize the well-conditioned boundary integral equation formulation of the linearized Poisson–Boltzmann equation. Various Krylov subspace solvers can be subsequently applied to solve the resulting linear system, with a bounded number of iterations independent of the number of discretized unknowns. The matrix–vector multiplication at each iteration is accelerated by the adaptive new versions of fast multipole methods. The AFMPB solver requires other stand-alone pre-processing tools for boundary mesh generation, post-processing tools for data analysis and visualization, and can be conveniently coupled with different time stepping methods for dynamics simulation. Restrictions: Only three or six significant digits options are provided in this version. Unusual features: Most of the codes are in Fortran77 style. Memory allocation functions from Fortran90 and above are used in a few subroutines. Additional comments: The current version of the codes is designed and written for single core/processor desktop machines. Check http://lsec.cc.ac.cn/~lubz/afmpb.html and http://mccammon.ucsd.edu/ for updates and changes. Running time: The running time varies with the number of discretized elements ( N) in the system and their distributions. In most cases, it scales linearly as a function of N.

Optimal server bandwidth for mobile video on demand

Multimedia services such as video-on-demand or Internet protocol television in mobile environments have established themselves in our daily lives, yet the obtained quality of service still leads to many open issues. One of them consists in minimizing the server bandwidth, and we recently proposed a novel patching scheme for transporting true video-on-demand called Hierarchical Patching, which minimizes the server bandwidth. In this paper, we present a new concept called Low Start, consisting of encoding the first part of a movie with a lower bitrate than the rest. In Hierarchical Patching, video parts at the beginning have a much higher probability to be transmitted than parts at the end. By using Low Start, we show that the overall server bandwidth can be drastically reduced. We furthermore investigate the impact of Low Start on the subjective quality of service as perceived by human observers, and show that, for mobile video, the optimal strategy is to encode a very short start time with a bandwidth as low as possible.

Efficient Video-on-Demand Streaming for Broadband Access Networks

We introduce three important factors for efficient video-on-demand (VoD) streaming strategy in broadband access networks such as a passive optical network (PON): an efficient streaming scheme for bandwidth savings, optimal use of deployed network bandwidth, and proactive use of user storage facilities. To achieve these goals, we propose efficient algorithms such as video adaptive streaming (VAST), video greedy adaptive streaming (VGAST), and video greedy adaptive streaming with proactive buffering (VGAST-PB). The VAST and VGAST algorithms use a patching scheme to save on network bandwidth for video streaming and increase the efficiency by adaptively changing the speed of patch streams and the patching window based on the time of the day and video popularity. VGAST-PB further improves the efficiency of VGAST by proactively buffering the popular videos. The proposed algorithms can be applied in fiber-to-the-x broadband access networks. To analyze the algorithms, we consider a typical 2.488 Gbps gigabit PON network providing VoD service to 512 households. We use a daily video request model and a video popularity model to determine the adaptive streaming speed and dynamic patching window. Numerical results show that, when the available network bandwidth is reduced below the required level due to background traffic, the efficient algorithms can con-siderably reduce the average user waiting time and the number of waiting requests.

The linearly scaling 3D fragment method for large scale electronic structure calculations

The linearly scaling three-dimensional fragment (LS3DF) method is an O(N) ab initio electronic structure method for large-scale nano material simulations. It is a divide-and-conquer approach with a novel patching scheme that effectively cancels out the artificial boundary effects, which exist in all divide-and-conquer schemes. This method has made ab initio simulations of thousand-atom nanosystems feasible in a couple of hours, while retaining essentially the same accuracy as the direct calculation methods. The LS3DF method won the 2008 ACM Gordon Bell Prize for algorithm innovation. Our code has reached 442 Tflop/s running on 147,456 processors on the Cray XT5 (Jaguar) at OLCF, and has been run on 163,840 processors on the Blue Gene/P (Intrepid) at ALCF, and has been applied to a system containing 36,000 atoms. In this paper, we will present the recent parallel performance results of this code, and will apply the method to asymmetric CdSe/CdS core/shell nanorods, which have potential applications in electronic devices and solar cells.

Multicast video-on-demand service in an enterprise network with client-assisted patching

Multicast Video-on-Demand (VoD) systems are scalable and cheap-to-operate. In such systems, a single stream is shared by a batch of common user requests. In this research, we propose multicast communication technique in an Enterprise Network where multimedia data are stored in distributed servers. We consider a novel patching scheme called Client-Assisted Patching where clients' buffer of a multicast group can be used to patch the missing portion of the clients who will request the same movie shortly. This scheme significantly reduces the server load without requiring larger client cache space than conventional patching schemes. Clients can join an existing multicast session without waiting for the next available server stream which reduces service latency. Moreover, the system is more scalable and cost effective than similar existing systems. Our simulation experiment confirms all these claims.

Segmented patching broadcasting protocol for video data

In adaptive segment-based patching scheme, the video is divided into fixed number of segments, which are transmitted over the server channels. For efficient transmission of the video segments, the server channels are classified into two types – regular and patching channels. A regular channel generally transmits fixed number of segments and a patching channel helps transmitting those segments that cannot be provided by any regular channel to the users. The number of segments transmitted by the first regular channel is decided by the number of regular channels that are allocated to the video by the video server. Other regular channels transmit pre-specified number of segments. This scheme estimates the bandwidth of the patching channels based on the requests received at the video server in terms of fixed time intervals, called time slots. The bandwidth estimation in this scheme is less accurate because for multiple requests received in a time slot more than one patching channels are used. Second, the probability distribution considered in this scheme does not satisfy the basic rule, i.e., the sum of all probabilities is not 1. In this paper, we address these issues and propose a new protocol named as Segmented Patching Broadcasting Protocol for Video Data. The average server bandwidth allocated to the patching channels is much less as compared to the adaptive segment-based patching scheme because only one patching channel is sufficient for any number of requests received in a time slot.

Patching-based broadcasting scheme for video services

In two-level patching scheme [D. Guan, Y. Songyu, A two-level patching scheme for video-on-demand delivery, IEEE Transactions on Broadcasting 50(1) (2004) 11–15], the video duration is divided into periods and the periods are divided into time-windows. The first request in a period initiates a zero-level channel and the first request in a period, which is the first end of a time-window, initiates a one-level channel. The other requests in a time-window initiate their own two-level channels. In a time-window, the size of the consumed video has been estimated. This scheme suffers from two problems. (i) The consumed video data transmitted by a two-level channel in a time-window has been taken half of its size, which is less accurate. It is because, since both ends of the video data provided by a two-level channel are random, and in that case, it should be one third of the time-window size, not the half. (ii) The probability of zero requests has been taken non-zero, which is also less accurate because, using bandwidth for no-request, the bandwidth is wasted. The probability of zero requests should be zero as there must be at least one request to view the video, if bandwidth is used, so that the bandwidth can be utilized. In this paper, we propose the patching based broadcasting scheme for video services in which both the issues are addressed, making the scheme more versatile. In this scheme, the users are provided immediate services using different level channels.

Hierarchical video patching with optimal server bandwidth

Video patching is a way for transporting true video-on-demand, that is, instantaneous without any delay, from a video server to several clients. Instead of sending a unique stream to each newly arriving client, clients share as many multicast transmissions as possible, and are serviced only those parts of the video that they have missed. We present a novel video patching scheme using hierarchies of patches. Our scheme minimizes the bandwidth needed by the video server, and may result in the fact that clients receive several streams in parallel. We show analytically that for Poisson arrival our algorithm achieves the optimal possible server bandwidth for all schemes where clients share multicast transmissions. We also show, how our approach can be combined with batching. This combination requires less server bandwidth than all fixed start point periodic broadcast algorithms.

Robust video-on-demand streaming in peer-to-peer environments

This paper presents a new video-on-demand streaming technique in peer-to-peer (P2P) environments. While a number of P2P live video streaming techniques have been proposed in the past, we argue that the two types of video streaming, live and on-demand, have some subtle differences. Most notably, a P2P video-on-demand streaming technique has to handle the asynchronous arrival of peers efficiently, and provide robust recovery under the rather frequent peers’ failure. Our answer to the challenge is an application multicast tree, called P2VoD (Peer-To-peer for Video-On-Demand streaming). P2VoD proposes a number of ideas, including a caching scheme, a generation concept, and a distributed directory service. Through analytical analysis, we show that P2VoD is sound and efficient. We also compare P2VoD against a recently proposed P2Cast system by Guo et al. [Y. Guo, K. Suh, J.F. Kurose, D.F. Towsley, P2cast: peer-to-peer patching scheme for vod service., in: WWW, 2003, pp. 301–309] using both analytical analysis and simulation. The result shows that P2VoD performs better than P2Cast in a number of important performance metrics.

Piecewise Patching for Time-shifted TV Over HFC Networks

In video-on-demand (VOD) systems, a number of sophisticated architectures have been proposed to provide instantaneous services through the use of multicast technology. Most of the architectures focus on minimizing bandwidth requirements under the assumption that clients play from beginning to end, but this assumption is not suitable for time-shifted TV. Moreover, they have been proposed on an IP network, and failed to make full use of the broadcasting property of hybrid fiber coaxial (HFC) network. In this paper, we propose a novel delivery scheme, named as piecewise patching (PP), to tackle these problems. The piecewise patching scheme provides the video data for the users in a piecewise mode instead of a whole patching stream which includes all missing data. The former user can utilize the data from the later users' patching stream whose playback time is in advance of the former user's patching stream. In the proposed scheme, each client receives the data simultaneously from arbitrary channels which broadcast the same content. Simulation results show that the proposed scheme improves the performance of time-shift TV service significantly in terms of total server bandwidth requirement.

Adaptive segment-based patching scheme for video streaming delivery system

In on-demand video streaming system, periodic broadcast technique scheme has been shown to be very effective for serving a popular video in reducing the demand on server bandwidth. On the contrary, reactive server transmission approach is more suitable for the video that is not popular enough. However, the level of demand on a video may change by time. In this paper, we propose a segment-based patching scheme which allocates adaptively transmission resources according to the varying client request rate. Our technique smoothly adjusts itself to cope with the changing workloads. The scheme tries to dynamically search the optimal number of channels assigned to the video by the newly updated request rate so as to minimize the bandwidth requirement. We also show how to seamlessly perform the transition of changing the number of channels with the guarantee that the clients viewing this video will not experience any disruption. Simulation results indicate that the scheme adapts very well to the changing client request rate and improves the system performance significantly in terms of the total server bandwidth requirement.

대규모 VOD 시스템을 위한 효율적인 P2P 기반의 프록시 패칭 기법

대규모 VOD 시스템에서는 동시에 다수의 클라이언트 요청에 따른 서버 저장장치 및 네트워크 대역폭 병목현상이 발생하며, 이를 해소하기 위한 효율적인 서버 대역폭 감소 기법이 필요하다. 패칭 기법은 멀티캐스트를 활용한 대표적인 VOD 시스템의 병목현상 해결 기법 중의 하나이다. 본 논문은 기존 패칭 기법의 성능 향상을 위하여 프리픽스 캐싱과 P2P 프록시를 결합한 새로운 P2P 프록시 패칭 기법을 제안한다. 제안된 기법에서 각각의 클라이언트는 자신이 받고 있는 스트림을 동일한 비디오를 요청한 다른 클라이언트들에게 멀티캐스트 함으로써 다른 클라이언트를 위한 프록시 역할을 수행한다. P2P 프록시와 프리픽스 캐싱의 사용으로 인하여 패칭 윈도우 크기를 벗어나는 사용자 요청들은 새로운 정규 채널을 생성하는 대신 이전의 패칭 그룹에 속한 다른 클라이언트로부터 정규 스트림을 전송받음으로써 서버로 집중되는 부하를 줄일 수 있다. 시뮬레이션을 통하여 프리픽스 크기와 요청 간격에 따른 서버의 대역폭 요구량을 측정한 결과에서 제안된 기법이 기존의 패칭 방법보다 서버의 평균 대역폭 요구량을 전체적으로 약 <TEX>$33\%$</TEX> 감소시킬 수 있음을 보인다. The main bottleneck for large scale VOD systems is bandwidth of storage or network I/O due to the large number of client requests simultaneously, and then efficient techniques are required to solve the bottleneck problem of the VOD system. Patching is one of the most efficient techniques to overcome the bottleneck of the VOD system through the use of multicast scheme. In this paper, we propose a new patching scheme, called P2P proxy patching, for improving the typical patching technique by jointly using the prefix caching and P2P proxy. In our proposed scheme, each client plays a role in a proxy to multicast a regular stream to other clients that request the same video stream. Due to the use of the P2P proxy and the prefix caching, the client requests that ive out of the patching window range can receive the regular stream from other clients in the previous patching group without allocating the new regular channels from the VOD server to the clients. In the performance study, we show that our patching scheme can reduce the server bandwidth requirement about <TEX>$33\%$</TEX> less than that of the existing patching technique with respect to prefix size and request interval.

Best-Effort Patching for Multicast True VoD Service

A multicast Video-on-Demand (VoD) system allows clients to share a server stream by batching their requests, and hence, improves channel utilization. However, it is very difficult to equip such a VoD system with full support for interactive VCR functions which are important to a growing number of Internet applications. In order to eliminate service (admission) latency, patching was proposed to enable an existing multicast session to dynamically add new clients, and requests can be served without delay if patching channels are available. A true VoD (TVoD) service should support not only zero-delay client admission but also continuous VCR-like interactivity. However, the conventional patching is only suitable for admission control. We propose a new patching scheme, called Best-Effort Patching (BEP), that offers a TVoD service in terms of both request admission and VCR interactivity. Moreover, by using a novel dynamic merging algorithm, BEP significantly improves the efficiency of TVoD interactivity, especially for popular videos. We also model and evaluate the efficiency of the dynamic merging algorithm. It is shown that BEP outperforms the conventional TVoD interaction protocols.

A Two-Level Patching Scheme for Video-on-Demand Delivery

Although patching has shown to be a simple and efficient technique for immediate media on-demand delivery, there is still much scope for further improvement compared with the lower bound of the server network-I/O bandwidth requirement. In this paper, a new technique of two-level patching scheme is proposed for the first time, in which patching channels are rearranged through merging and further patching. Simulation results show that the proposed two-level patching scheme outperforms the conventional patching technique by a significant margin. It even performs better than the dynamic skyscraper algorithm over a wide range of client request rates. Furthermore, it is reasonably competitive with hierarchical multicast stream merging (HMSM) at low to modest client request rates. Most importantly, the implementation complexity of our algorithm is much lower than the skyscraper and HMSM.