The provisioning of the seamless handovers for real-time services in-between UMTS/ WLAN loose-interworking by the network-layer technologies has been studied. Issues are how to execute such a vertical handover in a fast and efficient manner as well as how to achieve it in a viable way. To resolve such issues, a novel scheme called 'designated crossover point' (DCP) within the existing IP end-to-end Quality of Servce (QoS) architecture has been proposed. The DCP is an agent at the edge router in the customer's premise to join the old RSVP signalling path and new RSVP signalling path. With the DCP in place, the vertical handover can be greatly accelerated. Besides, by enabling the DCP to handover to the edge router in the customer's network currently visited by the mobile, lower charging cost can be achieved. Finally, there is no modification required for the devices in the provider's network and thus the viability is much improved. It is then end up with a topology for resource management in IP backbone for UMTS/WLAN loose-interworking to support the idea of DCP. To determine when to perform the rerouting to remove the possible derouting caused by DCPs, use of an adaptive rule has been suggested. Simulation results show in general that the adaptive rule is effective.

Proxy partial caching, e.g. segment-based proxy caching or proxy prefix caching, partitions the object into nonoverlapping pieces. The proxy cache then treats each piece as an individual file when performing caching and replacing. Upon receipt of request to the object, the proxy cache delivers the cached portion to the client immediately to mask the start-up delay. However, two architectural challenges are confronted when implementing this technique in the web proxy software, e.g., Squid cache. The first challenge is related to caching video streams. Although not until recently, HTTP is recognized as an efficient method to support interactive video, many fundamental issues are still required to be solved. To this end, we propose an approach of segment-based video streams retrieval and caching via HTTP byte-range requests to further mask the possible startup delay, enhance the interactive function "pause", and simplify the web proxy cache design. Proxy partial caching introduces the second architectural challenge called dirty-initial-segments problem, i.e. cached portion in the proxy cache is inconsistent with the original in the server. If this happens, the cached portion already delivered to the client cannot be concatenated with the latter portion from the server. To relieve this problem, we propose a novel algorithm called validating upon partial replacement, which synchronizes the operations of proactive consistency validation, partition and replacement performed upon an object. We show that our proposed algorithm bears the merit of controllable chance to disturb users, easily embedding into the existing web proxy cache software with minimum modification, and improving the cache performance.Keywords-Web proxy cache, partial caching, cache consistency, cache replacement algorithm, video on demand.

Abstract-We propose a scheme called Type-Aware Error Control (TAEC) to provide robust interactive video services over timevarying wireless channels. Basically, TAEC explores the temporal dependence of video frames by pushing out the lower impact frames. In doing so, queuing delay is controlled and the important frame is retransmitted multiple times. We consider the application of the nonstationary stochastic control to further improve the wireless system throughput by exploring the multiuser diversity gain. The techniques involved in our proposed solution consist of constructing a Markov model, reducing the number of parameters estimated, and avoiding the state explosion problem. The provisioning of immediate bandwidth guarantee is another feature of TAEC, i.e., when exploring the multiuser diversity gain, the users share their reserved bandwidth only if the perceived video qualities are acceptable. As shown in the simulation, TAEC improves the perceived video quality in terms of luminance PSNR when compared to other schemes.

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