InformationWeek

November 6, 2000

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Wireless Data
The Road To A Wireless Future

Wireless data technology has a migration path for every network

By Peter Rysavy, reprinted from Network Computing

More on wireless:

sidebar:The Battle For Cellular Supremacy

Companies Turn To Outsourcing For Wireless Services (10/30/00)

THE NEW WIRELESS ENTERPRISE (9/18/00)

Network Computing: The Road to a Wireless Future (10/30/00)

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or each of the past five years, industry pundits have been convinced it would be the year of wireless data in the wide area environment. And every year they cited a different reason: support for Internet protocols; phones with microbrowsers; support from industry giants such as Microsoft and IBM; and new platforms such as handheld computers. This year's reasons include the Wireless Application Protocol (WAP) and the forthcoming General Packet Radio Service (GPRS). Meanwhile, the latest buzz is about third-generation cellular and data throughputs of 2 Mbps just over the horizon.

Network managers face a difficult situation. More of the people they support are demanding wireless access to the company network. These people have experienced the advantages of wireless networks for voice communication. Now they want those advantages for data communication, especially as massive promotional efforts by major operators have significantly increased awareness of these services.

Meanwhile, millions of palm-sized devices are just begging to have wireless connections for applications such as E-mail and schedule synchronization. Wireless networking promises both greater work productivity and increased flexibility.

But today's solutions often involve specialized gateways, middleware, and reformatting of content. The higher data rates promised by future cellular networks are tantalizing because, for the first time, it might be possible to use E-mail, groupware, database access, and virtual private networks as they are used over dial-up or digital subscriber line types of connections.

By next year, cellular operators will offer IP packet-data services with rates as high as 144 Kbps, though 56 Kbps will be more typical of downlink speeds. This is a big step up compared with today's services, which are limited to about 9.6 Kbps. However, the industry is fragmented, with multiple wireless technologies deployed, each with its own data strategy.

There are huge market forces at play that will determine how and when next-generation wireless data services will arrive. Unfortunately, these forces are not all in alignment. One force driving the broad deployment of new data services is the success of wireless voice, leading the industry to view data as a vast new source of potential revenue. Data is also now an integral part of next-generation cellular systems, not just an afterthought. Complementary industry developments, including new handheld platforms and new delivery methods such as WAP, also help.

Other forces are acting in opposition, however. Because of the limited success of wide area systems so far and the unproven business case--not to mention an unclear perception of what customers really want from wireless data--network operators and vendors are proceeding tentatively. Also, Internet access speeds via wired line (DSL, cable modem, and so on) are being pumped up to a rate at which wireless will continue to be slower than wired lines for at least the next several years. Finally, the industry is still grappling with multiple wireless standards, leading to confusion and fragmentation.

Today's services have several notable attributes. First, they're slow. They weren't slow when they were first designed in the early 1990s, but today's typical rates of 9.6 Kbps to 14.4 Kbps simply don't stand up to the demands of rich Web pages and heavy-duty productivity applications such as Microsoft Exchange and Lotus Notes. Second, they generally rely on circuit-switched connections. With data as an afterthought for digital cellular systems, a dial-up model for data is easier to deploy than a packet-switched architecture. But dial-up means connection delays, an inability to push data to mobile users, and having to pay for connect times even when sessions are idle.

Today, cellular network operators emphasize mobile phones with microbrowsers, which is understandable given the limitations of today's networks. You don't need much bandwidth to fill up a six-line display of 12 characters. This kind of platform is useful for some tasks, such as help-desk functions, remote pricing information, and telephone databases, but it constitutes only a small subset of the information that an IT manager might want to make available to mobile workers.

GPRS Chart Nevertheless, today's wireless networks can be quite productive--as long as only small amounts of data are involved. In many instances, customers need to use wireless middleware systems that account for the limitations of today's wireless networks. Internet portals are also now targeting this industry by developing mobile content that can be accessed by microbrowser-equipped cell phones, giving users access to their E-mail; calendar; travel, entertainment, and restaurant information; sports results; package tracking; horoscopes; and so on. Despite these new consumer-oriented services, wireless networks today are used mostly for messaging applications or in vertical markets. But things are about to change.

Not only is there a tremendous amount of new wireless technology in development, but a good chunk of it is about to be deployed. The best way to get a clear picture is to examine the data strategies for the three principal digital cellular technologies. In the United States, the two dominant cellular technologies are TIA/EIA-136, which is a time-division multiple access (TDMA) technology; and IS-95, a code-division multiple access (CDMA) technology. TDMA, the oldest U.S. digital technology, divides radio channels into three time slots, with each user receiving a distinct slot. This method lets three users communicate on each radio channel without interference. CDMA, a newer U.S. digital technology, uses spread-spectrum technology, in which many users share the same radio channel simultaneously but are distinguished by unique pseudo-random codes.

The largest TDMA carriers are AT&T Wireless Services and SBC Communications Inc., while the largest CDMA carriers are Sprint PCS and Verizon. Global System for Mobile Communications (GSM) technology is a distant third in the United States, but it dominates worldwide. In the United States, the dominant GSM carrier is VoiceStream Wireless Corp. AT&T Wireless Services, Sprint PCS, and VoiceStream all offer nationwide coverage.

Developed in Europe, GSM is the most mature cellular technology worldwide. Analog systems in neighboring European countries were not compatible, increasing the motivation for a consistent digital cellular standard there. In the United States, TIA/EIA-136 was the first digital technology deployed, but upstart Qualcomm introduced its CDMA technology as an alternative, and the cellular world hasn't been the same since. In fact, all new third-generation systems are now based on CDMA, though as luck and intellectual-property disputes would have it, there are multiple incompatible flavors of CDMA (see chart below).

The highest level of excitement is about third-generation--or 3G--cellular, called International Mobile Telephone 2000 (IMT-2000), an international standardization effort orchestrated by the International Telecommunications Union, under the United Nations. IMT-2000's original goal was one worldwide cellular standard, but its outcome was different. IMT-2000 mandates mobile data rates of 144 Kbps, outdoor pedestrian rates of 384 Kbps, and indoor rates of 2 Mbps.

Each of the three cellular technologies has a 3G plan. But before 3G becomes available, some operators are already beginning to deploy data services that people have dubbed 2.5G. With 3G networks years away from broad deployment but 2.5G networks about to roll out, IT managers should seriously evaluate 2.5G services.

GSM has deployed data service longer than any other cellular network. Millions of users, mostly in Europe, are taking advantage of circuit-switched data service at rates as fast as 14.4 Kbps. The first new higher-speed alternative is a service called High Speed Circuit Switched Data, which combines as many as four time slots in each radio channel's eight time slots for download speeds as fast as 56 Kbps. Upload speeds remain at 14 Kbps. The devices most likely to use HSCSD are PC Card modems. This service is about to be available from operators such as Orange in the United Kingdom, SingTel in Singapore, and Sonera in Finland, but most operators are not pursuing HSCSD and instead are placing their bets on GPRS, a 2.5G technology.

GPRS is an IP-based packet-data system. Packet technology means the channel is used only for the time needed to send a packet of data, and it then becomes available for other users, much like Ethernet. Packet capability is win-win for everybody. Network operators like it because packet technology supports more users than circuit-switched technology. Users like it because packet technology enables sustained virtual connections to services, eliminates long dial-up delays, and allows information such as E-mail to be pushed to users. GPRS has a maximum theoretical rate of greater than 160 Kbps, but service and device implementations will limit speeds to between 28 Kbps and 56 Kbps on downloads and to 14 Kbps on uploads.

As shown in the chart on page 129, there are two key infrastructure elements that underlie GPRS service. The Serving GPRS Support Node (SGSN) keeps track of mobile nodes. It tunnels packets to and from the Gateway GPRS Support Node (GGSN), which connects the GPRS network to other networks, such as the Internet. An operator might have multiple serving nodes, perhaps one per city, but needs only one gateway node for each interconnecting network.