Method and system for efficiently using a mobile unit for switching between communications systems

A method for operating a mobile unit that supports multiple communication systems in order to efficiently switch between the multiple communication systems, the method comprising:

• utilizing a footprint database to aid the mobile unit in switching from a source communication system to a target communication system, the footprint database comprising a plurality of system lists, the system lists including a plurality of cell entries linking each cell of a particular system to at least one cell in another system, wherein each of the cell entries is identified by a cell frequency and a color code, and includes a list of neighbors;
• identifying a current cell by a current cell frequency and a current cell color code;
• and
• identifying possible target cells through attempting an initial acquisition on target cells on a current cell list of neighbors.

A method for operating a mobile unit that supports multiple communication systems to efficiently switch between the multiple communication systems, the method comprising:

• creating a footprint database relating the coverage of the multiple communication systems, performed by creating a plurality of system lists, the system lists including a plurality of cell entries linking cells of a particular system to cells in other systems, wherein each of said cell entries is identified by a cell frequency and a color code;
• dynamically updating the footprint database;
• and
• utilizing the footprint database to aid the mobile unit in switching from a source communication system to a target communication system.