User Agent Migration Policies in Multimedia Wireless Networks

Multimedia wireless networks often employ network based user agents as proxies for mobile users. In this paper, we consider a fundamental question in the design of these networks: should the user agents migrate and if so, what are good user agent migration policies? We first introduce a general framework for malysing user agent migration policies. We then highlight , through analysis and simulation, the numerous parameters and tradeoffs that dictate the design oj migration policies. Finally, we identify two simple threshold-based policies that deliver very good perfor-irnance over a wide range of system parameters and ~configurations. IKeywords: Wireless Networks :1 Introduction Multimedia wireless networks are characterized by ~ig~ficmtdifferences in communication and processing speeds between the wireless endpoints and fixed servers. In these networks, there is often a need to introduce an intermediary server through which the wireless endpoint communicates with the fixed network. The intermediary server, which resides in the fixed network, has access to high bandwidth links and large computational resources. These resources can be utilized by moving selected functionality from the mobile terminal to this intermediary server. When this intermediary server represents a particular mobile user, and performs actions on behalf of that mobile user, it is termed a ” user agent “. The need for such an agent inside the fixed network, acting on be-lhalf of a mobile user, has been proposed by several researchers [1, 3, 7]. Although agents themselves have received considerable attention, the issue of user agent mobility has ~eceived less attention to date. In many applications, this issue hw been resolved somewhat in an ad-hoc manner, based on the environment in which the application operates. For example, user agents in [3] are placed at a fixed well known location (such as the mobile user’s home workstation) since the application operates s in a campus area environment. Similarly, there is the concept of a home agent in the Mobile IP proposal [6]. On the other hand, user agents in [7] are migrated along with the mobile user since the application operates over a wide-area environment. When the user agents are fixed, appropriate initial placement of agents can help in balancing the computational load placed on the network servers by the user agents. For example, load balancing can be achieved by distributing the user agents evenly among all the network servers and keeping them fixed. However, such an approach could result in large distances separating …