Air Apparent?

Wireless carriers dream of the day when the decision about whether to purchase a wireless phone in addition to a wireline phone will become a decision about whether to purchase a wireless phone instead of a wireline phone. So what are the factors that stop all but the bravest of people from making this decision today? Is it an issue of radio technology, or are there some back-office, network issues, as well?

The simplest method for wireline replacement is to use a radio link instead of a copper wire to connect between a standard wireline phone and the telephone switch. This concept, known as wireless local loop (WLL), doesn't enhance the services provided to a current wireline customer. Instead, it merely offers an alternative method of connection to the carrier. The difficulty with this approach is getting the cost of the wireless connection down to the cost of a copper loop. The farther a customer is from the switch site, the more likely that this savings will be achieved. As a result, WLL is a viable alternative in rural areas and underdeveloped countries.

WLL customers gain no additional services, and, worse, they may have trouble with data services. Most digital wireless-access methods are optimized for voice and use low bit rates, such as 8kb/s or even 4kb/s. By comparison, wireline networks use 32kb/s or 56kb/s. Lower rates reduce costs by allowing more people to share the same equipment. The sophisticated voice coders necessary to achieve this compression generally will seriously damage modem tones. Even if modems could be used over these links, they could achieve speeds higher than the voice-coder rate only if the WLL infrastructure recognized an attempted data transmission and allocated more bandwidth. The process of recognizing modem tones is error-prone and would increase the cost and complexity of the WLL interface.

CULTURE CLASH Another approach to wireline replacement is simply to use a standard wireless phone to take advantage of some of wireless' inherent advantages, such as mobility. The same phone can be used whether the customer is in his home, office or even out at the cottage or on the ski slopes.

Even so, there are potential problems with this approach. One is that high-speed Internet access isn't possible. That drawback would force people who otherwise would go wireless to keep their wireline connections.

Another limitation, one that's less well-known, is the lack of operator services. Today, it's not possible to make a collect call to a wireless phone, to bill a call to a third party or to call person-to-person. Although most people don't use these services often, for some, they can be important. Anybody with children, for example, would want them to be able to call home if they have access only to a payphone but don't have coins or a phone card.

Wireline carriers provide operator services through a network of databases and the use of billing-record standards that aren't currently accessible by wireless carriers. The databases, known as line-information databases (LIDBs), allow one carrier to determine whether a line controlled by another carrier is eligible to, for example, receive a collect call or for third-party billing. Once the call is over, a billing record is generated in the exchange-message-interface/exchange-message-record (EMI/EMR) format so that it can be exchanged with the carrier that's responsible for the billing. Wireline carriers periodically work with one another to reconcile their bills.

Wireless carriers are locked out of this process. They don't maintain LIDB systems, and they use the CIBER format for the exchange of billing records. Establishing LIDB systems would be a major investment for wireless carriers. Even if a LIDB interface were simply added to existing HLRs, this approach would require considerable software development and probably a need for hardware upgrades to at least memory and disks. Converting CIBER records to EMI/EMR and vice-versa would require a significant industry effort to determine the appropriate mapping and then develop gateways. Furthermore, wireline carriers would have to open up the settlement "pot" for operator-assisted calls to the wireline industry. Wireless carriers will have to push long and hard before they can make any progress, and right now they don't even see it as an issue.

SPLIT PERSONALITY A third approach to wireline replacement is intriguing but has yet to take the world by storm. TIA standards committee TR-45.1, responsible for analog cellular standards, has developed a system that allows a wireline phone connection to be enhanced with cordless and cellular capabilities. This system includes a base station that could be installed in a home to provide cordless-like coverage within the home but use low power on cellular frequencies instead of cordless frequencies. Operating like a cordless phone, it would provide unlimited free calling within the range of the base station.

The other major part of this system, defined in TIA/EIA IS-680, is a signaling protocol between the base station and the supporting wireless system that runs over the wireline phone connection. Whenever the modified cellular phone detects its home base station, it registers, and the base station then uses the phone line to tell the wireless system that the mobile is present. Any calls made to the mobile's number then are diverted to the home phone line. By the same token, when the mobile phone moves outside the coverage area of the home base station, it registers with the public base station with the strongest signal, and calls are delivered to it in the same way as for other wireless phones.

There's little question that wireless technologies will continually nibble away at the market share of wireline phones. Butsome substantial issues have not yet been seriously tackled. When wireless carriers start fighting for access to wireline networks and databases, you'll know that a new phase in the struggle for dominance has begun.

Here's a look at some wireless-local-loop (WLL) standards, their status and Web sites with more information.

* TIA/EIA-664-536. Analog Group III fax for CDMA WLL systems. Awaiting publication.

* PN-3964. Use of A-interface standards in WLL. Under development.

* TIA/EIA/IS-680. Residential "cordless" interface between wireless residential extension (home base station) and public switched telephone network.

* www.diva.com/wpwll.htm. White paper titled WLL Technology: Motivations and Alternatives.

* http://members.tripod.com/puneeth/basic/Waiting_for_Wireless_Local_Loop_--_Janua ry_1999.htm. Article title "Waiting for WLL."

* http://sss-mag.com/wll.html. Good links to WLL sites.

* www.webproforum.com/wll/index.html. WLL tutorial.

* www1e.mesh.ne.jp/CNPWORLD/english/product/newloop/phs_wll.html. Diagram of PHS-based WLL systems.

* http://sawhney.kellogg.nwu.edu/globalcomm/sld001.htm. Presentation on trends in global communications, including WLL.

* www.tiaonline.org. Source for purchasing TIA standards.

* www.cnp-wireless.com. General information on wireless standards.