Overview

In this chapter, we discuss the ANSI-41 mobile telecommunications network functions related to call processing. These functions are divided into the following categories: ^[1]

• Call origination functions

• Call termination functions

• Feature control functions

We describe each of the call processing functions defined in ANSI-41 and provide examples of how the ANSI-41 mobile application part (MAP) operations (e.g., LocationRequest) are used to accomplish call processing tasks. We summarize this information at the end of the chapter. Of course, our descriptions are not intended to be a complete definition of how each of the ANSI-41 call processing functions works for that, we defer to the standard.

Note that we use the ANSI-41 convention for operation component acronyms; that is, the Invoke component acronym is in all-capital letters (e.g., LOCREQ), while the Return Result component acronym is in all-lowercase letters (e.g., locreq). Refer to the ANSI-41 standard for the descriptions of the individual ANSI-41 operations and parameters. Also, consult the Glossary for a description of general terms (e.g., serving system) not explicitly defined in this chapter.

Throughout this chapter we consider the serving system as a single entity encompassing the mobile switching center (MSC) and visitor location register (VLR) functional entities. This simplifies the descriptions of the ANSI-41 call processing functions and also is representative of a large percentage of the ANSI-41 implementations currently in service. However, keep in mind that the potential for separation of the MSC and VLR exists and is fully defined in ANSI-41.