Cellular intersystem handoff: Creating transparent boundaries

Cellular systems are configured in such a way that a mobile subscriber who originates a call at any geographical point in the system will receive high quality, uninterrupted service while moving to any other geographical point within the system. However, with cellular systems operating in many cities in the U.S. and Canada, a new situation has arisen. Cellular service areas, which were once isolated, are now either adjacent to or overlapping other service areas. The need to provide high quality, uninterrrupted service while moving between cellular service areas has been under discussion for some time. An intersystem protocol for this application must not only satisfy the need of multivendor communications, but also take into account the diversity in cellular market sizes and applications. This paper approaches the issue of intersystem communications from two perspectives: 1. The services expected by a subscriber traveling between two systems are analyzed, and solutions to potential problems are discussed. 2. The characteristics of a protocol to provide these services are defined, and a protocol structure to accommodate these requirements is proposed.