Mobile Voice Over IP (MVOIP): An Application-level Protocol

Current Voice over Internet Protocol (VOIP) protocols require participating hosts to have fixed IP addresses for the duration of a VOIP call. When using a wireless-enabled host, such as a tablet computer on an 802.11 wireless network, it is possible for a participant in a VOIP call to roam around the network, moving from one subnet to another and needing to change IP addresses. This address change creates the need for mobility support in VOIP applications. We present the design of Mobile Voice over IP (MVOIP), an application-level protocol that enables such mobility in a VOIP application based on the ITU H.323 protocol stack. An MVOIP application uses hints from the surrounding network to determine that it has switched subnets. It then initiates a hand-off procedure that comprises pausing its current calls, obtaining a valid IP address for the current subnet, and reconnecting to the remote party with whom it was in a call. Testing the system shows that on a Windows 2000 platform there is a perceivable delay in the hand-off process, most of which is spent in the Windows API for obtaining DHCP addresses. Despite this bottleneck, MVOIP works well on a wireless network

Mobile Voice Over IP (MVOIP): An Application-level Protocol for Call Hand-off in Real Time Applications

This paper presents Mobile Voice Over IP, an application-level protocol to support terminal mobility in real-time applications such as voice over IP, on a wireless local area network. We describe our MVOIP implementation based on the ITU-T H.323 protocol stack, present experimental results on call hand-off latency, and discuss various implementation issues, including the task of quickly and accurately determining when call hand-off is necessary. We also discuss how 0IP relates to other proposed mobility support schemes, and how it can be generalized to provide application-level mobility support in a wide range of real and non real-time applications

Agent-Based Environment for Linking Simulations (ABELS)

On behalf of

Abstract Mobile Voice Over IP (MVOIP): An Application-level Protocol

Current Voice over Internet Protocol (VOIP) protocols require participating hosts to have fixed IP addresses for the duration of a VOIP call. When using a wireless-enabled host, such as a tablet computer on an 802.11 wireless network, it is possible for a participant in a VOIP call to roam around the network, moving from one subnet to another and needing to change IP addresses. This address change creates the need for mobility support in VOIP applications. We present the design of Mobile Voice over IP (MVOIP), an application-level protocol that enables such mobility in a VOIP application based on the ITU H.323 protocol stack. An MVOIP application uses hints from the surrounding network to determine that it has switched subnets. It then initiates a hand-off procedure that comprises pausing its current calls, obtaining a valid IP address for the current subnet, and reconnecting to the remote party with whom it was in a call. Testing the system shows that on a Windows 2000 platform there is a perceivable delay in the hand-off process, most of which is spent in the Windows API for obtaining DHCP addresses. Despite this bottleneck, MVOIP works well on a wireless network

DD* Lite: Efficient incremental search with state dominance

This paper presents DD * Lite, an efficient incremental search algorithm for problems that can capitalize on state dominance. Dominance relationships between nodes are used to prune graphs in search algorithms. Thus, exploiting state dominance relationships can considerably speed up search problems in large state spaces, such as mobile robot path planning considering uncertainty, time, or energy constraints. Incremental search techniques are useful when changes can occur in the search graph, such as when re-planning paths for mobile robots in partially known environments. While algorithms such as D * and D * Lite are very efficient incremental search algorithms, they cannot be applied as formulated to search problems in which state dominance is used to prune the graph. DD * Lite extends D * Lite to seamlessly support reasoning about state dominance. It maintains the algorithmic simplicity and incremental search capability of D * Lite, while resulting in orders of magnitude increase in search efficiency in large state spaces with dominance. We illustrate the efficiency of DD * Lite with simulation results from applying the algorithm to a path planning problem with time and energy constraints. We also prove that DD * Lite is sound, complete, optimal, and efficient. Keywords: Search, Dominance, Path-plannin