System and method for establishing and/or maintaining a data session across packet data networks

A communication system selection algorithm (SSA) implemented by a mobile station chooses between available systems to select a system to serve the mobile station. During initialization, the SSA causes the mobile station to scan the environment and compare available communication systems to determine the best system to provide service. After an initial system is chosen, the SSA causes the mobile station to continuously, or at discrete time intervals, scan the environment for available systems, thus allowing for a seamless switch to an available system whenever a handoff is desired. The SSA chooses the best available system based on measurements of each available system and applying preference rules defined by a service provider and/or user of the mobile station.