Experiences with network-based user agents for mobile applications

Wireless networks are characterized by simple end devices and limited bandwidth. One solution to address these and other limitations of the wireless mobile environment that has been widely pursued is the placement of proxies, or agents, inside the network to assist with application processing that would normally take place on end devices. These agents can additionally manipulate data to reduce bandwidth requirements and assist in providing services. The design and implementation of a user agent is heavily impacted by the application it supports. In this paper we present our experiences with user agents in two different types of applications: telephony-based Personal Communication Services (PCS) and two-way messaging. To provide low latency service, the PCS user agents are mobile so that they may be kept close to their end devices. The design of the PCS agents limits migration overhead to the transfer of approximately 100 bytes of information in about 150 milliseconds. To provide advanced messaging services, the messaging user agent supports flexible messages while limiting air interface bandwidth usage. The messaging agents reduce uplink bandwidth usage by approximately 35% when applied to a cellular PCS system, and reduce message payloads by 97%. This revised version was published online in June 2006 with corrections to the Cover Date.