New Intersystem Operations

A yawn is the ultimate sign of acceptance for technological advances. Pulling a cellular phone out of a shirt pocket used to be enough to elicit "oohs!" and "aahs!" Today, in a restaurant at least, the strongest reaction likely will be a dirty look from someone whose peace and carrots have been interrupted. Your phone ringing in a meeting while out of town once got the reaction of "How does your phone do that with such a little antenna?" at least from people who understood the difficulty in achieving that trick. Now every savvy consumer demands intersystem call delivery to roamers. What use is a phone if it cannot be used out of town?

The industry standard behind the magic of intersystem operations, including call delivery to roamers, is (except for GSM systems) TIA/EIA-41, which previously was called IS-41. IS-41 Revision A and Revision B, the earliest incarnations, only provided the bread-and-butter features of call delivery, roamer validation and control over a small number of roamer privileges such as the ability to make long-distance calls while roaming. Basic call-processing features such as forwarding, 3-way calling and call waiting also were supported.

IS-41 Revision C (and the similar ANSI equivalent, TIA/EIA-41 Revision D) provided some of the first WIN capabilities. A review of this version's features might lead you to believe that the standard had reached the pinnacle of complexity, but such a reaction would be premature. The fertile imaginations of engineers and marketers are far from exhausted and will be reflected when TIA/EIA-41 Revision E is published at the end of 1999 or early in 2000.

You can predict most of the TIA/EIA Revision E content because a number of modular add-on standards already have been published, or soon will be. The remainder of the modifications and additions to the standard mainly will be due to errors and ambiguities.

GOVERNMENT MANDATES One of the major influences on TIA/EIA-41 Rev. E will be U.S. government mandates for enhanced emergency services and number portability. The third government mandate, lawfully authorized electronic surveillance (CALEA), will have no effect on intersystem operations because intersystem signaling links are not secure enough to send information about wiretaps.

Emergency service enhancements are best known for the Dick Tracy technology necessary to track the location of a mobile dialing 911 to within about 400 feet. However, other issues are equally important in J-STD-034. They are the ability to identify the calling mobile; return a call to it for further information; to allow the deaf and hard of hearing to make calls using text-telephony devices connected to wireless phones; and improvements in the likelihood of getting a 911 call through in unfavorable conditions.

Number portability requires a new TIA/EIA-41 message to permit wireless systems to query industry databases containing re-routing information on phone numbers that have been moved from one carrier to another. Another important requirement in the wireless number portability standard IS-756 Revision A is for the MIN to be changed to identify the new carrier while the mobile's phone number stays the same.

MARKETING FEATURES New technological capabilities in wireless systems are important in the battle between TDMA and CDMA carriers for the hearts, minds and wallets of consumers. TDMA carriers have put a lot of effort behind providing virtual private wireless systems. This allows a phone to display the name of the private system instead of the carrier actually providing the service and assists the development of special billing arrangements. These private systems can be extended across multiple wireless systems and are supported by add-on standard IS-730.

A service that most likely will be attractive to consumers is calling name presentation because it is easy to use and provides information that many people would like to see.

CDMA standards were the first to offer data speeds above 9600b/s through air interface modifications and in the circuit-switched data standard IS-737. When TDMA standards were able to up the ante to about 28.8kb/s by combining all three time slots into one data call, CDMA carriers claimed speeds of 64kb/s. Now, if only the customers for circuit-switched data would line up for service.

NETWORK ENHANCEMENTS Some network enhancements are relatively invisible to consumers. Consequently, they will not bring in new revenue, but they may be able to reduce costs or enable future features for which consumers might pay.

Over-the-air activation reduces the cost of acquiring new subscribers. Instead of using dealers, with their hefty commissions, many carriers would like to sell more phones through discount outlets, using their spectrum to program the phones remotely. TIA interim standards IS-725 and IS-725 Revision A provide these capabilities for both TDMA and CDMA phones. Not only does the phone have to be programmed, but so do network databases such as the HLR and the authentication center. Because sensitive information is being transmitted over the publicly accessible airwaves, some of the data has to be encrypted.

There is even standard IS-778 designed to improve network support for authentication and reduce the likelihood that clever cloners can climb over network barriers. The standard defines methods to put a spotlight on intruders, as well as a way of interrogating them to determine whether they are friend or foe.

The WIN is a suite of TIA/EIA-4 message enhancements designed to distribute intelligence away from traditional network elements such as the HLR and MSC and toward service control points and service nodes. If the designers of this standard, IS-771, have done their homework, it should reduce the cost of implementing new features and diminish the time to market.

CELLULAR-PCS INTEROPERABILITY Interoperability between cellular and PCS frequency bands is increasingly important because even the largest carriers have to scramble to put a nationwide virtual network together using whatever frequencies they can either buy or, through roaming agreements, rent. Intersystem operations, even intersystem handoff, can be performed across frequency boundaries according to the specifications in TSB-76. These grand leaps across the spectrum are intended to be invisible to owners of phones with these capabilities.

Network enhancements also are being included to increase the maximum size of TIA/EIA-41 messages. Consumers are unlikely to notice this unless they are byte-counters. This capability could allow some features that require large amounts of data. The addition of IMSI to TIA/EIA-41 messages in IS-751 eventually will make international roaming easier and will enhance interoperability between TIA/EIA-41 and GSM networks, allowing more features to cross technology boundaries.

So what's the next step? Enough new capabilities are in the pipeline to ensure that there will be a Revision F. Probably a few of you currently are dreaming up new capabilities that will require intersystem protocol enhancements to work for roamers or that will require distributed logic to work even within the home network.