Hardware

Go-anywhere Internet access with digital cellular services: Is it for real?

Is wireless Internet connectivity in your future? Is it in your present? Is it really? See what Bryan Pfaffenberger has to say about the state of go-anywhere access.


The answer is a resounding “maybe.” Just imagine: Your notebook computer has an antenna-equipped PC card, which enables you to access the Internet anywhere, any time, and what’s more, you’ll get download speeds that are more like those you’d associate with ISDN than with a 56-Kbps modem. It’s coming, we’re told. Is it here?

As attorneys like to say, “It depends.” In some metropolitan areas, the use of digital cellular telephone services for data transmission is exploding; one survey found that data transfers accounted for more than 60 percent of system traffic. But let’s get real. According to most of the verbiage you'll read on this subject, the arrival of Internet-ready digital cellular telephony is being held back by two major factors: competition between two major and incompatible protocols (TDMA and CDMA) and the high cost of upgrading existing analog systems to one of the new, digital protocols.

Understanding cellular telephony
World War II proved the usefulness of the walkie-talkie, a wireless communications service that enables mobile, two-way communication. (A wireless communications medium uses radio or infrared signals.) But a walkie-talkie signal weakens and finally disappears when you get out of range of the transmitting unit. In 1971, AT&T discovered a way to solve this problem: build a network of automatic repeating transmitters (called a cell site), each of which would broadcast a signal throughout a limited geographic area, called a cell. As a caller moves from one area to another, a new cell site automatically steps in to keep the signal strength strong. All cell sites are connected to a Mobile Telephone Switching Office (MTSO), which in turn is connected to the standard PSTN telephone system.

Originally (and still predominantly) an analog system, cellular telephone service was introduced commercially in 1983. The original cellular telephony protocol, Advanced Mobile Phone Services (AMPS), defines the basic features of analog cellular service, including its 800-MHz transmission frequency. In 1985, only 90,000 subscribers made use of the new service. By late 2000, despite long-standing complaints about the poor quality of AMPS-based services, the number had grown to 102 million; since 1995, the subscriber base has been growing by an estimated 20 to 30 percent per year. These are numbers you’d associate with Internet growth. Can the cellular phone system deliver universal, wireless Internet service?

Although it's possible to purchase a computer modem that's compatible with today's analog cellular services, performance ranges from poor to abysmal. Limited to 9600 bps in theory, actual performance is usually much worse, due to noise and interference—in many cases, you're lucky to get 1200 bps, which puts you back into the mid- to late-1980s, modem-wise. Universal wireless Internet access isn't going to happen with analog technologies, and it might not happen anytime soon with digital cellular technologies, either, as you'll learn in this article.

Introducing digital cellular services
Analog cellular services are rapidly giving way to digital cellular services. In general, digital cellular services are far superior. They offer cleaner sound, less interference, more features, and longer battery life. As you've probably heard, however, there are several competing standards for digital telephone service in the United States, and this fact has served to delay the development of digital cellular services.

The older of the digital telephony standards, Time Division Multiple Access (TDMA), enables multiple users to connect on one of a limited number of frequencies by parceling out tiny slices of time to each user. Here's the idea: Imagine that four college roommates are having trouble sharing a single phone line, so they agree that Michaela uses the phone from 7-7:30, Kyung from 7:30-8, Allison from 8-8:30, and Maria from 8:30-9. With TDMA, though, the time slices are so tiny that all four people could be using the same digital phone frequency at what seems like the same time. Among the carriers that use TDMA are AT&T Wireless and Nextel. In addition, TDMA is the basis of a narrowband version of the standard, called GSM, which is widely implemented in Europe and Asia.

The newer of the digital telephony standards, Code Division Multiple Access (CDMA), uses a coding algorithm that spreads a given transmission across a spectrum of frequencies. Many users can broadcast at the same time using CDMA. To capture an individual message out of the cacophony, the receiving station detects the message's code and uses it to decipher the message. If you're having trouble grasping how CDMA works, here's another roommate example. Suppose Michaela, Kyung, Allison, and Maria have friends over, but the four all start talking at once. That's no problem, though, because they've invited friends from their own countries: for example, Michaela is speaking Italian to Federico, who has no trouble separating what Michaela is saying from Korean (Kyung), English (Allison), and Spanish (Maria). Because CDMA can cram more users into the available frequency space, most new digital cellular systems (and most of the proposals for new digital cellular technologies) are based on CDMA. Service providers that use CDMA in the United States include Sprint PCS and Verizon Wireless.

You'll also run across the term Personal Communication Service (PCS), which can be implemented with TDMA or CDMA. In the United States, PCS refers collectively to a group of related digital cellular telephone service technologies, including voice mail, global roaming, e-mail, Web access, and pager-style messaging, that operate at a frequency of 1900 MHz. PCS services appear to provide the Internet-anywhere service that everyone seems to want. Can PCS provide the roaming Internet access that so many people are asking for? If you read the full-page ads for PCS services in today's newspapers, you might think so.

My phone is a Web browser (Not!)
You can get digital cellular phones right now that implement the Short Messaging Service (SMS), an updated version of pager technology that enables digital cellular phones to send and receive e-mail and to access the Web. But these services won't please most Internet users. Because SMS is a text-only technology, you can access only those Web sites that have created special pages conforming to the Wireless Application Protocol (WAP), a standard for displaying relatively sparse amounts of text-based information on PCS devices. Although more than 40 million WAP-enabled devices are currently in use by consumers, very few of them actually use WAP to access the Internet—and those who do aren't happy with the results. One study found that 70 percent of WAP users had a negative impression of the service. Still, WAP's usability will improve as more Web sites develop and deploy effective WAP versions of their content. For example, WellMed.com offers WAP access to its database of drug interactions; the site could be a lifesaver if you get sick while you're traveling and need to find out whether a prescribed drug conflicts with one you're already taking. Another point in WAP's favor: There's every reason to expect a convergence between personal digital assistants (PDAs), such as the Palm, and digital cellular phones. Why keep your to-do list, calendar, appointments, and addresses in a separate box? With an Internet-enabled PDA/phone, you can take advantage of synergies that just aren't there with separate devices, such as transparent and automatic network-based synchronization with your desktop system. That's the philosophy behind the Ericsson R380s, and you're sure to see more signs of convergence in the months to come.

For experienced Internet users, the real payoff won't come until you equip your notebook with a digital cellular modem capable of working with your digital cellular phone. Such a connection frees you from the text-only restrictions of WAP and enables full Internet access. But even then, you won't get the bandwidth you've been dreaming about. When connected via a cellular modem, you can expect a maximum data transfer rate of 19.2Kbps, which is a lot slower than a 28.8-Kbps modem. Interference problems may cause the actual data transfer rate to drop to 9600Kbps—about what you'd experience with AMPS, under ideal conditions. Is this progress?

On the horizon: Packet-switched cellular Internet services
Why can't you get good Internet access via digital cellular services? High-bandwidth wireless service isn't going to happen if you've got to upload and download by means of a constant, switched connection to a cellular tower. There simply isn't enough bandwidth for all those phones out there.

There's another way, though. Unlike voice transmissions, data transmissions tend to be "bursty." For example, your connection may transmit very little data for a while and then, after you click a hyperlink, there's a lot of activity. For bursty transmissions, circuit-switched networks are a very inefficient choice; they require keeping a connection open even when little or no data is being transmitted. Bursty data is much more efficiently transferred by means of packet-switching networks. In a packet-switching network, which is inherently much more efficient than a circuit-switched network, messages are broken up into units of fixed size, each of which is labeled with its destination address. The packets are flung out onto the network; devices called routers make sure that they're sent along the correct path to their destination.

Compared to circuit-switched Internet access, a packet-switching wireless service is a whole different ball game—it's like the difference between connecting to AOL via a dial-up modem connection and plugging into a 100-Mbps Ethernet. Like an invisible, ubiquitous Ethernet, a digital cellular Internet network is an "always-on" technology; you're billed only for the actual amount of data that's sent and received. Phones equipped with packet-switching Internet capabilities will still be able to place circuit-switched calls, of course.

Packet-switched cellular Internet services will require new standards and new technologies, including roaming services and security, and they're only now beginning to appear. For example, a new digital wireless standard called General Packet Radio Service (GPRS) will enable digital PCS devices to connect to the Internet at speeds of up to 170Kbps, and that's better than ISDN. On the horizon are Third Generation (3G) wireless data systems, which will deliver ubiquitous Internet connectivity at speeds of 384Kbps and higher—up to a projected 2Mbps—but don't expect such services to become widely available until 2005 or later.

So, what's the future look like? Take stock of the various devices you're using. Chances are you've got a PDA, a notebook computer, a desktop computer, and a cellular phone. If you make heavy use of a PDA, you might be quite happy with a combined CDA/digital PCS phone, such as that spiffy (and pricey) Ericsson mentioned earlier. If you need to access the graphical Web, you'll be looking for a service that implements GPRS or some other packet-switched Internet standard, but don't expect to see these services until later this year in leading markets, and much later than that in peripheral markets. Three or four years down the road, you'll start seeing some really attractive options, but be forewarned: They'll be very expensive, at least at first. There's every indication, though, that within five to seven years, you'll be able to get reasonably fast, secure, and reliable Internet access just about anywhere you can use a cellular phone.

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