Three dimensional model based coding methods are proposed as next generation image coding methods. These new representations need 3D reconstruction techniques. This paper presents a method that extracts the surfaces of static objects that occlude other objects from a spatiotemporal image captured with straight-line camera motion. We propose the concept of occlusion types and show that the occlusion types are restricted to only eight patterns. Furthermore, we show occlusion type pairs contain information that confirms the existence of surfaces. Occlusion information gives strong cues for segmentation and representation. The method can estimate not only the 3D positions of edge points but also the surfaces bounded by the edge points. We show that combinations of occlusion types contain information that can confirm surface existence. The method was tested successfully on real images by reconstructing flat and curved surfaces. Videos can be hierarchically structured with the method. The method makes various applications possible, such as object selective image communication and object selective video editing.

To reduce the computational complexity due to the long tap structure of filters used for subband coding, a new structure of filter banks is proposed. Applying the concept of hierarchical coding to the perfect reconstruction condition in a one-dimensional analysis/synthesis system, which is represented as a matrix operation in z-transform domain, our approach realizes perfect reconstruction with short length FIR filters and reduction of the number of filters by half compared with the conventional approaches. Moreover, it is expanded to two-dimensional case, where both a separable structure and a non-separable one are considered.

Havihg modified and extended the routing algorithm used in our previously proposed Bidirectional Shuffle Ring Network (BSRN), we here provide some adaptive routing algorithms that can relieve the congestion caused by bottlenecks when nonuniform traffic exists. As to preserve the transmission order of cells associated with a message which may otherwise arrive at the destination out of sequence if they are forwarded along different routing paths, two control schemes are also devised. The BSRN proves to be highly reliable and robust since countermeasures against node or link failure can also easily be realized.

Content delivery network improves end-user performance by replicating Web contents on a group of geographically distributed sites interconnected over the Internet. However, with the development whereby content distribution systems can manage dynamically changing files, an important issue to be resolved is consistency management, which means the cached replicas on different sites must be updated if the originals change. In this paper, based on the analytical formulation of object freshness, web access distribution and network topology, we derive a novel algorithm as follows: (1) For a given content which has been changed on its original server, only a limited number of its replicas instead of all replicas are updated. (2) After a replica has been selected for update, the latest version will be sent from an algorithm-decided site instead of from its original server. Simulation results verify that the proposed algorithm provides better consistency management than conventional methods with the reduced the old hit ratio and network traffic.

The IEEE802.11e is a standard developed by a Task Group E of the IEEE802.11 working group and defines a MAC protocol, which provides EDCA (enhanced distributed channel access) and HCCA (HCF controlled channel access) to support differentiation service over WLAN (wireless LAN). In IEEE802.11e WLAN, real-time application such as VoIP (Voice over IP) can have more chances to access the WM (wireless medium) than non real-time application. In addition to QoS support in WLAN, power consumption is a critical issue when WLAN is used in handheld devices. For power saving in the use of real-time applications like VoIP under EDCA, U-APSD (Unscheduled Automatic Power Save Delivery) was proposed in [2] and [4]. In fact, it can save power consumption and works well when it is used for bi-directional voice connections generated at constant bit rate. However, when it is used for real-time applications like ON-OFF traffic, buffering delay at AP (access point) increases. To reduce the buffering delay, this paper proposes two mechanisms. Simulation results show that they can alleviate buffering delay generated at AP.

3D model-based coding methods that need 3D reconstruction techniques are proposed for next-generation image coding methods. A method is presented that reconstructs 3D shapes of dynamic objects from image sequences captured using two cameras, thus avoiding the stereo correspondence problem. A coaxial camera system consisting of one moving and one static camera was developed. The optical axes of both cameras are precisely adjusted and have the same orientation using an optical system with true and half mirrors. The moving camera is moved along a straight horizontal line. This method can reconstruct 3D shapes of static objects as well as dynamic objects using motion vectors calculated from the moving camera images and revised using the static camera image. The method was tested successfully on real images by reconstructing a moving human shape.

Intending to contribute to constructing better multimedia network systems, we propose a new concept of image database system of which form of storage is featuring exponential or graceful oblivion and abrupt recollection like the human memory property. By virtue of this property of database storages that is realized by employing hierarchical or pyramidal image coding, the database memory and transmission costs can be significantly reduced. In this paper we will describe the details of the concept, the results of theoretical analysis based on a simplified model which reveals the effectiveness of the proposed system, the structure of an experimental prototype system and the result of an experimental image retrieval service carried out by implementing it over ATM high speed channels.

With the advance of high-speed network technologies, availability and popularity of streaming media contents over the Internet has grown rapidly in recent years. Because of their distinct statistical properties and user viewing patterns, traditional delivery and caching schemes for normal web objects such as HTML files or images can not be efficiently applied to streaming media such as audio and video. In this paper, we therefore propose an integrated caching scheme for streaming media with segment-based caching and hierarchically distributed proxies. Firstly, each stream is divided into segments and their caching algorithms are considered to determine how to distribute the segments into different level proxies efficiently. Secondly, by introducing two kinds of segment priorities, segment replacing algorithms are proposed to determine which stream and which segments should be replaced when the cache is full. Finally, a Web-friendly caching scheme is proposed to integrate the streaming caching with the conventional caching of normal web objects. Performance of the proposed algorithms is verified by carrying out simulations.

Ad hoc networks have recently become a hot topic. In ad hoc networks, battery power is an important resource, since most terminals are battery powered. Terminals consume extra energy when their network interfaces are in the idle state or when they overhear packets not destined for them. They should, therefore, switch off their radio when they do not have to send or receive packets. IEEE802.11 features a power saving mechanism (PSM) in Distributed Coordination Function(DCF). In PSM for DCF, nodes must stay awake for a fixed time, called ATIM window (Ad-Hoc Traffic Indication Map window). If nodes do not have data to send or receive, they enter the doze state except for during ATIM window. However, ad hoc networks with PSM have longer end-to-end delays to deliver packets and suffer lower throughput than the standard IEEE802.11. To solve this problem, this paper proposes a protocol that reduces delay and achieves high throughput and energy efficiency. Simulation results show that our proposal outperforms other PSMs in terms of throughput, end-to-end delay and energy efficiency.

The efficient distribution of stored information has become a major concern in the Internet. Since the web workload characteristics show that more than 60% of network traffic is caused by image documents, how to efficiently distribute image documents from servers to end clients is an important issue. Proxy cache is an efficient solution to reduce network traffic. And it has been shown that an image caching method (Graceful Caching) based on hierarchical coding format performs better than conventional caching schemes in recent years. However, as the capacity of the cache is limited, how to efficiently allocate the cache memory to achieve a minimum expected delay time is still a problem to be resolved. This paper presents an integrated caching algorithm to deal with the above problem for image databases, web browsers, proxies and other similar applications in the Internet. By analyzing the web request distribution of the Graceful Caching, both replacing and pre-fetching algorithms are proposed. We also show that our proposal can be carried out based on information readily available in the proxy server; it flexibly adapts its parameters to the hit rates and access pattern of users' requesting documents in the Graceful Caching. Finally we verify the performance of this algorithm by simulations.

CDN (Content Delivery Networks) improves end-user performance by replicating web contents on a group of geographically distributed servers. However, repeatedly keeping the entire replica of the original objects into many content servers consumes too much server resource. This problem becomes more serious for the large-sized objects such as streaming media, e.g. high quality video. In this paper, we therefore propose an efficient replication method for layered video streams in CDN, which can reduce user response delays and storage costs simultaneously. Based on an analytical formulation of the cooperative replication of layers and segments of each video stream, we derive a replication algorithm which solves next three problems quantitatively. (1) How many servers should be selected to replicate a given video stream? (2) For a single video stream, how many layers and segments should be stored in a given server? (3) After selecting a group of servers for each video stream, how do we allocate the replication priority (i.e. order) to each server? Simulation results verify that the proposed algorithm efficiently resolves the above problems and provides much better performance than conventional methods.