TABLE OF CONTENTS Since the mid-1980s, the TIA has been developing the ANSI-41 standard for cellular intersystem operations. The standard was always intended to evolve with the growing demands of the wireless marketplace. Initially, only basic capabilities to provide mobility were addressed. These capabilities eventually became the building blocks that now allow wireless service providers to offer a rich set of services to subscribers. This chapter follows the evolutionary path of ANSI-41, which leads to the sophisticated mechanisms that support truly advanced wireless services.
In the beginning, there was Interim Standard-41, named simply because 41 was the next available number for a new TIA standard. In 1984, the development of the first version of a cellular internetworking standard had begun. IS-41-0 was eventually published in February 1988 and addressed the following basic wireless intersystem functions:
Basic intersystem handoff
Basic service qualification
Basic OA&M (circuit management)
Basic intersystem handoff included the core functions still used today. For example, handoff measurements, handoff forward, handoff back, and inter-MSC trunk release were all supported. Multiple inter-system handoffs were allowed as a propagation of the basic handoff-forward procedures.
Basic service qualification addressed the operations to validate a mobile subscriber. Validation was a function to address the financial accountability of a roaming subscriber. This validation could only be performed when the roaming subscriber was visiting a neighboring system connected by direct point-to-point signaling links to the subscriber s home system. These operations were specified to occur between a visited MSC and...
