We describe a compression method for three-dimensional animation sequences that has notable advantages over existing techniques. We first aggregate the frame data by similarity and reorganize them into clusters, which results in the sequence split into several motion fragments of varying lengths. To minimize the number of clusters and obtain optimal clustering, we perform frame alignment, which eliminates the "global" rigid transformation from each frame data and use only "pose" when evaluating the similarity between frames. We then apply principal component analysis for each cluster, from which we get coordinates of corresponding frames in a reduced dimension. Because similar frames are considered, the number of coefficients required for each frame becomes smaller; thus, we obtain better dimension reduction for a given reconstruction error. Further, we perform intracluster compression based on linear coding. Because every motion fragment presents similar frames, conventional linear predictive coding can be replaced by key frame-based linear coding to achieve minimal reconstruction error. Results show that our method can obtain a high compression ratio, with a limited reconstruction error.
Multipath TCP (MPTCP) is a promising transport protocol that allows a multihomed device to simultaneously use multiple network interfaces to send application data over multiple paths.However, although applying MPTCP to data delivery introduces many and attractive benefits, the MPTCP is vulnerable to network attacks. When a path within the MPTCP connection suffers from some types of attacks (eg, a denial-of-service attack) and becomes underperforming, it will undoubtedly cause transmission interruption in the stable paths and thus degrade the application-level performance. Unfortunately, the MPTCP path management mechanism is very simple and cannot timely prevent the usage of underperforming paths in multipath transmission.In this paper, we introduce a new "potentially underperforming" (PU) concept to MPTCP and propose a novel PU-aware path usage management mechanism ((PU) 2 M 2 ) for MPTCP aiming to (1) detect and declare an underperforming path and prevent the usage of underperforming paths in multipath transmission, (2) provide a finite-state-machine model to change per-path's state accordingly and effectively manage multiple paths for data transmission, and (3) alleviate the packet reordering problem and make MPTCP avoid throughput performance degradation during network underperforming. We demonstrate the benefits of applying (PU) 2 M 2 to MPTCP. KEYWORDS multipath TCP, network attacks, path management, secure multipathing services 1 INTRODUCTION Recently, wireless access technologies such as IEEE 802.11 WiFi standards and 3G/4G cellular networks have undergone a period of dramatic development. These significant technological achievements provide a mobile user with ubiquitous Internet connectivity. 1,2 In the meantime, boosted by the technological innovation and newest progress of wireless access technologies, modern mobile devices (ie, Personal Digital Assistants and Smart phones) are equipped with multinetwork interfaces and enabled heterogeneous multiaccess capabilities (eg, the Apple iOS-based iPhone and iPad products enable "multipath transfer" feature, which combines WiFi and cellular interfaces to optimize network connection 3,4 ). Such smart multihomed devices can increase their goodput performance and quality of service (QoS) by making use of multiple paths concurrently in a heterogeneous network condition, supported by the Multipath TCP (MPTCP). 5The MPTCP is a TCP extension that enables a multihomed device to exploit multiple network interfaces for simultaneously scheduling the application data over multiple independent end-to-end available paths. 6 Figure 1 illustrates how a MPTCP-based terminal uses 2 different paths (A and B) simultaneously to communicate with an MPTCP-based application server. Such multipath transmission and bandwidth aggregation features is beneficial to system for goodput improvement, robustness enhancement, and other attractive benefits. Moreover, MPTCP preserves the regular socket APIs that are utilized by today's Internet applications. The multihomed devices can establish C...
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