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Cellular Networking Perspectives

David Crowe’s Cellular Business Magazine Articles

September 1996 Issue

TIA TR-45: AMPS, Alive and Kickin’

The AMPS cellular standardization committee, TIA (Telecommunications Industry Association) TR-45, once described by the New York Times as “an obscure group of telecommunications experts,” does not deserve its obscurity. It has laboured successfully, for the most part, for over ten years to bring wireless standards from supporting only standalone analog systems to networked dual-mode systems, retaining compatibility at (almost) every step.

The success of AMPS cellular is directly related to the reliance on standards. There would not be over 30 million wireless phones in the US if the industry had not started with just one air interface standard. Not only that, but without the IS-41 standard for automatic roaming, the most lucrative segment of the market would have tired of cellular long ago. The biggest question mark on PCS is whether the competition between incompatible standards will stall its success. Will the greater technological competition in PCS provide greater customer choice or greater confusion? Will PCS justify deregulation of the telecommunications industry or provide a case study for why government should get involved to ensure rational competition?

TR-45, as a standards committee, has to stay away from such political issues and focus purely on technical issues. It does this through its five subcommittees that perform the actual standardization work. Member companies are manufacturers, carriers and other companies, who send employees to work cooperatively with their competition, at no charge to the TIA. The TIA does not participate in the technical work, being responsible solely for the open and fair conduct of standardization activities.

TR-45.1 develops analog cellular and PCS standards (most notably EIA/TIA-553 for analog cellular phones).

TR-45.3 develops TDMA digital cellular and PCS standards (IS-54 representing the first generation and IS-136 the second).

TR-45.4 develops standards for the interface between mobile switching centers (MSC) and base stations (BS).

TR-45.5 develops CDMA digital cellular and PCS standards (IS-95).

What about TR-45.2? I didn’t forget it, but its role is much wider and harder to define than the other TR-45.X subcommittees. It is basically responsible for everything that is left over; the network ‘glue’ standards, the most well known of which is the TIA IS-41 standard for automatic roaming (soon to be elevated to full ANSI status as TIA/EIA-689). TR-45.2 is divided into working groups, each with a different area of responsibility:

• The TR-45.2 plenary is not a working group (handling administrative and coordination issues), but has two ad hoc groups reporting directly to it. One group is developing wireless 9-1-1 standards for all types of cellular and PCS systems. The other is developing a standard to allow compliance with the US CALEA law, that requires telecom carriers to provide the ability to transparently intercept call setup and voice information from their subscribers when they receive a legitimate request from a law enforcement agency. Both of these groups are working in cooperation with the TR-46 standards committee (which has responsibility for non-AMPS-based PCS standards).
   
  TR-45.2 WG (Working Group) I is responsible for user level definition of features and capabilities, which are defined in the IS-53 standard.
   
• TR-45.2 WG II is responsible for the network level definition of features and capabilities, basically the definition of signaling message flows between elements of the wireless network (e.g. the IS-41 RegistrationNotification message that flows from an MSC to a Home Location Register (HLR) whenever a roamer registers in a new system). This work ends up in the IS-41 standard (sections 1 through 4).
   
  Working Group II also has a number of task groups to look at specific issues that will be included in IS-41 Revision D: PCS/Cellular interoperability, Data & Fax, TDMA Digital Control Channel Support, Advanced CDMA Feature Support and the Wireless Intelligent Network (WIN).
   
• TR-45.2 WG III takes over where WG II leaves off, by defining (to the last bit) the encoding of all IS-41 messages. This also ends up in IS-41 (sections 5 and 6).
   
• TR-45.2 WG IV is responsible for standards for call detail recording. This has resulted in the development of the IS-124 standard for semi-realtime transfer of call detail and billing records. This information is not only used for billing, but also for some fraud detection applications. In the future, the information may be used for several other applications, such as customer care, marketing research and traffic analysis.
   
• TR-45.2 WG V has been laid off, due to a reorganization.
   
• TR-45.2 WG VI is responsible for international applications of AMPS standards. This is a tricky area, because the TIA is only ANSI (American National Standards Institute) accredited, and international standards are outside its jurisdiction. However, the TIA has published TSB-29, which contains suggestions for the implementation of systems to facilitate international roaming. As the TIA begins to work more closely with the ITU (International Telecommunications Union), true international standards may be developed. Aside from developing TSB-29, Working Group VI also assists with the internationalization of other standards.
   
• TR-45.2 WG VII is responsible for interfaces to other telecommunications networks, most notably the PSTN (the Public Switched Telephone Network). It has developed the IS-52 dialing plan standard and the IS-93 PSTN interconnection standard. While these carry little weight today, compared to similar Bellcore recommendations, it is likely that, as telecom reform continues, more carriers will look for standards and away from proprietary Bellcore documents to provide interconnection.

You may be overwhelmed at this description of AMPS standardization efforts. That is simply because there is such a large need. Due to the increasingly competitive environment of telecommunications, there are probably more standards being developed than are minimally required. However, this slightly ‘wild west’ approach does allow standards to promote innovation and not ossification. I have experienced over 10 years on the bucking bronco of cellular and, with several fresh horses in the ring, I doubt that the ride will get any smoother or less exciting!