Use of SS7 in D-AMPS-based PCS: orthodoxy vs. heterodoxy

the Advanced Mobile Phone System (AMPS), is among the key technologies for providing personal communications services (PCS). PCS will ultimately enable communication with a person anytime, anyplace, and in any form. Its key features have been described in recent publications [1–3]. D-AMPS has been specified by the Electronic Industry Association (EIA) in cooperation with the Telecommunication Industry Association (TIA). A simplified version of its reference model is depicted in Fig. 1. The functional entities shown in the figure can be implemented in a variety of physical configurations because more than one entity can be located in a node. When not collocated, these entities communicate via well-defined and standardized interfaces. Um, B, C, D, E, M, and N are the interfaces standardized so far. Signaling at these interfaces, except the air interface (Um), is based on Signaling System No. 7 (SS7). SS7 is a general-purpose common channel signaling (CCS) system specified by the International Telecommunication Union — Telecommunications Standardization Sector (ITUT) and adapted to North American needs by the American National Standards Institute (ANSI). It is made of a network services part (NSP) and user parts (UPs). The NSP can be further broken into the message transfer part (MTP) and the signaling connection control part (SCCP). Examples of UPs are the integrated service digital network (ISDN) user part (ISUP) and the mobile application part (MAP); for an overview see [4]. The use of SS7 in D-AMPS-based PCS goes beyond signaling, although signaling remains the sole purpose assigned to SS7 in its specifications. Besides its orthodox use for signaling, SS7 is used for the operation, administration, maintenance, and provisioning (OAM&P) of the D-AMPS-based PCS network and also for an alphanumeric messaging service known as short message service (SMS). This article contrasts the orthodox and heterodox uses of SS7 in D-AMPS-based PCS. It also makes a plea for a gradual return to orthodoxy with the use of SS7 confined to signaling. Our plea is motivated by the fact that currently deployed SS7 networks may not have enough capacity to spare for heterodox use. Furthermore, we argue that it does not make economic sense to add capacity to SS7 networks for meeting heterodox requirements. Viable alternatives to the current D Use of SS7 in D-AMPS-Based PCS: Orthodoxy vs. Heterodoxy