Wireless World

THE INFORMATION SUPERHIGHWAY IS TAKING TO THE AIRWAYS AS A HOST OF WIRELESS TECHNOLOGIES MATURES.

By Ira Brodsky

The day is dawning when, through wireless communications, we will be able to access cyberspace from the beach or a remote village in central Africa. But more important, wireless technology will inspire a myriad of new applications. For example, we may soon interact with local businesses and transportation systems (virtually all of which will be tied into the Internet) via pocket-size personal communicators.

But is wireless communication ready for prime time? Clearly not, because wireless computing is still in its infancy. While several mobile data services already exist, many more are on the way. The mobile radio industry - which for decades exclusively catered to industrial users - has finally awakened to opportunities posed by the personal computer. Thus, within just the last few years portable computers have begun to sprout antennas

Today, with a litle extra effort, you can log on wirelessly to the Net from practically any major city in the United States. All you need is a cellular-ready modem and cellular telephone. There also are two nationwide mobile data networks that offer wireless access to Internet e-mail. And other wireless technologies can be employed to extend access to locations that are difficult to reach via wire, such as parks, boats, or rural sites.

Admittedly, most existing wireless services offer only limited coverage, do not perform as well as their wireline But development activity has reached a counterparts, and can be expensive to use. fever pitch and we will soon be able to enjoy the fruits resulting from competition in the wireless arena. Significant breakthroughs in coverage, performance, and cost are in the offing.

A good example of how untethered access can transform a familiar application into something entirely new is wireless electronic mail. In the wired realm, e-mail serves as a fast, convenient, and reliable substitute for the post office. In the wireless realm, e-mail becomes a two-way messaging medium, replacing the telephone company, Business travelers equipped with wireless e-mail can bypass pay phones, voice mail, and telephone tag, Instead of trying to reach people directly - which is almost impossible when on the road - wireless e-mail users are able to communicate with other people in time slices.

A number of companies operate gateways bridging the wired and wireless dimensions. RadioMail Corp., in Menlo Park, Calif., links paging and nationwide mobile data networks with the Internet, LAN-based e-mail systems, and the public telephone network. In addition, RadioMail offers wireless access to news and stock quotes, delivery of text messages sent via wireless terminals to fax machines anywhere in the world, and a 24-hour toll-free dispatch service for operator-assisted message entry (permitting anyone, not just e-mail users, to reach RadioMail subscribers). RadioMail offers unlimited messages for $89 per month.

RadioFax is a particularly compelling service. Its urgent-looking cover sheet - replete with RadioMail's lightning bolt logo - often ensures a message is hand-carried to the intended recipient, whether he or she is in a meeting, the company cafeteria, or a colleague's office. And as a recent RadioMail ad in major airline magazine suggests, RadioMail users can even send faxes from the back seats of taxis.

Similar services are being introduced by Data Transmission Services (DTS) of Woodbridge, New Jersey, whose software comes bundled with one of a family of wireless modems recently introduced by IBM (see "The Mobile Office," page 43). DTS uses a different pricing model than RadioMail, charging $9.95 per month for basic service plus an additional charge (roughly S.40 per kilobyte) for each message. The firm hopes its pay-as-you-go program will attract customers who aren't quite ready for the all-you-can-eat plan.

Campbell, Calif.-based DA Systems offers near-worldwide access to Internet e-mail through the Inmarsat mobile satellite network and its U.S. agent, Washington, D.C.-based Comsat. The company also has pioneered "smart mail" that can be automatically filtered and redirected for mobile users. According to DA Systems president Russell Briggs, journalists covering the war in Bosnia have been using the service to file stories from the field and receive messages when terrestrial phone lines go down.

But there's more to come from wireless systems than e-mail. As higher performance wireless networks are established, users will be able to access the full panoply of Internet services, including bandwidth-intensive resources like FTP and the World-Wide Web.

The reason wireless data has so far failed to attract millions of subscribers is that most service providers have not set sufficiently high goals. Wishing to believe that users would be satisfied with low throughput and high latency (because such networks are easier to contruct), much of the industry wasted the last few years trying to convince corporate users to rewrite their applications and downgrade their expectations. But the fish weren't biting.

The first nationwide mobile data services on the air were low-speed packet radio networks - ARDIS (Advanced Radio Data Information Service) and RAM Mobile Data. These networks provide what could be described as wireless telex service. Like the clunky telex terminals common in the day before ubiquitous fax machines, ARDIS and RAM Mobile Data services let users send and receive short messages. The major difference is that these packet radio networks have been, to their credit closely integrated with modern computer networks.

Although the packet radio companies talk about speeds ranging from 4.8 Kbs to 19.2 Kbps, users almost never see throughput that high. The networks assemble each user's data in packets containing origin and destination addresses, error checking and correction data, and other supervisory data. Over ARDIS and RAM networks, 40% to 60% of the raw data rate is consumed by protocol overhead. Therefore, 2.4 Kbps to 9.6 Kbps is the maximum instantaneous throughput users can expect.

But there's more bad news. These networks hoped to make their money by forcing large groups of users to share a single radio channel. Average throughput, therefore, also depends on the number of users active on channel at any given time. With even modest channel contention, throughput can quickly plummet to less than 1,200 bps.

There certainly are legitimate uses for low-speed, two-way wireless messaging, and the paging industry is pursuing this market. Indeed, two-way wireless for low-speed, two-way wireless messaging is a powerful enhancement to conventional paging, and a few paging operators are promoting the integration of paging with personal digital assistants (PDAS), palmtops, and notebook computers.

Let's take a closer look at the major two-way wireless messaging services. The ARDIS network was custom designed and built for IBM's National Service Division in the early 1980s by Motorola. In 1990, IBM and Motorola formed a joint venture to offer two-way wireless data service in more than 400 metropolitan areas across the United States. Motorola bought out IBM's share in 1994.

The network was optimized to deliver excellent in-building coverage - a key requirement in IBM's field service applications. This was accomplished by using single-channel overlapping radio cells that increase the probability of reaching indoor service technicians from outdoor base stations. But there are drawbacks to this scheme: Users must carry relatively high-power radio modems to reach base stations up to 20 miles away, and overlapping coverage means base-station transmissions must be staggered to prevent interference, which reduces the network's overall traffic capacity.

ARDIS consists of more than 1,300 base stations across the United States, most of which operate at 4.8 Kbps. They are being upgraded gradually to the newer RD-LAP protocol that runs at 19.2 Kbps. The firm provides service primarily to corporate customers such as NCR, Otis Elevator, and Pitney Bowes. ARDIS service pricing is a flat monthly rate plus per-packet charges (roughly $.50 per kilobyte). Radio modems for ARDIS are available from Motorola (the stand-alone InfoTAC modems) and IBM (Type 2 PCMCIA card plus external transceiver) for about $1,000 each.

The bottom line: ARDIS offers wireless access to Internet e-mail through RadioMail Corp. This network is not designed to support highly interactive applications or file transfers greater than 10 Kbps. Until recently, ARDIS did litle to attract a wider audience, but Motorola hopes the recent introduction of the Envoy (Magic Cap-based) and Marco (Newton OS-based) personal communicators will corect this (see "Making Waves," pg. 52).

RAM operates a nationwide through RadioMail and mobile data network based on the MobiTex standard developed in Sweden during the mid-198Os.The firm has built a U.S. MobiTex network with more than 800 base stations, concentrating coverage in places frequented by business travelers airports, major hotels, and convention centers.

Unlike the ARDIS network, MobiTex was designed to support multiple channels per base station. Therefore, MobiText offers somewhat better throughput (the radio channels run at 8 Kbps) and greater total capacity. Radio modems that operate over RAM's network are available from Ericsson (the stand-alone portable Mobidem), IBM (a Type 3 PCMCIA card), Motorola, and Intel.

RAM Mobile Data has done yeoman's work in cultivating horizontal business applications for mobile data. The firm has formed strategic alliances with companies such as AT&T EasyLink, Lotus Development Corp., and WordPerfect Corp. In 1994, the company enjoyed its first growth spurt - increasing from 5,000 to 27,000 subscribers. RAM Mobile Data also has installed several gateways, one of which provides conversion between MobiTex's arcane MASC packet radio protocol and TCP/P. RAM's pricing consists of a flat monthly fee plus per packet charges (roughly $0.25 per kilobyte).

The bottom line: RAM Mobile Data offers wireless Internet e-mail Data Transmission Services, Inc. Although somewhat more robust than RAM's performance is ARDIS's, the firm discourages file transfers in excess of 20 KB. Expect RAM Mobile Data to continue to play a pioneering role in two-way wireless messaging.

Perhaps the paging industry will have better luck convincing people to use lowspeed packet radio networks. After all, two-way messaging represents a major enhancement for customers accustomed to one-way paging.

Several leading paging carriers plan to offer two-way services in the not-toodistant future. The simplest of these is acknowledgment paging, in which pagers use a response channel to confirm the receipt of pages. Plano, Texas-based PageNet plans to offer callers the ability to send digitized voice messages to subscribers equipped with pocket answering machines. And Jackson, Mississippi-based Mobile Telecommunication Technologies Corp. (MTEL) plans to offer two-way text messaging.

MTEL Owns the SkyTel nationwide paging service, a pioneer in one-way wireless e-mail. MTEL has established a new subsidiary called Destineer Corp. to provide two-way paging. Destineer hopes to engender a new generation of small, low power, mobile data devices and to extend two-way messaging services to PDAs, palmtops, and notebook computers.

Two-way services require a new paging network architecture. Conventional paging networks achieve broad coverage and ood building penetratíon through the use of simulcasting technology-that is, transmitting each message simultaneously from all of their base stations. The drawback to simulcasting is that it wastes capacity and limits throughput. By upgrading to a two-way architecture, paging networks can simulcast a wake-up message and quickly locate the intended recipient. Messages may then be directed exclusively to the closest transmitter. This approach enables paging carriers to send longer messages while continuing to serve a large population of users.

To accomplish this goal, paging carriers need to add receive sites to their infrastructure. Because mobile subscribers carry small battery-powered devices, the receive sites must be closer to the subscribers, and therefore they must be several times more numerous than the transmit sites.

Destineer will use a single 50 KHZ-wide channel in the 930 MHz band acquired in the Narrowband PCS auction in late 1994. The channel will run half-duplex: the base stations will transmit at 2.4 Kbps, while the subscriber devices will respond at 9.6 Kbps. Despite the relative high-speed outbound channcl, Destineer will be strictly a store-and-forward service. The company claims it will begin commercial operation sometime in the second half of 1995, with coverage in the top 300 U.S. markets by the end of the year.

Bottom line: Destineer is positioned to be the foremost nationwide messaging service, with wireless access to Internet email just one of many services. Destineer should stimulate widespread integration of wireless messaging and portable computers. Hardware is expected from companies such as Motorola (its Tango two way pager lets users respond by selecting preprogrammed messages) and Santa Clara, California-based Wireless Access (expected to introduce a two-way pager in PCMCIA card fomat). Destineer has said it would price its services within the reach of consumers and casual business users.

Many people feel the cellular telephone industry with its massive infrastructure, huge financial resources, and widespread acceptance (more than 24 million subscribers)is best qualified to serve wireless data markets. Cellular telephone service encompasses all of urban and much of rural America. Cellular carriers can leverage existing licenses, cell sites, antennas, and dedicated phone lines to provide mobile data services.

Circuit switched cellular technology enables data to be sent over circuit-switched (as opposed to packet-switched) cellular voice channels using dial-up modems. The key advantage of this approach is that it employs familiar dialup modem technology and communications software. Therefore, users who currently access the Net via wireline dial-up modems can expect similar (but perhaps somewhat slower) service via circuit switched cellular dial-up services.

The use of dial-up modems over today's cellular networks does present challenges. Most cell phones do not come equipped with RJ-11 modular phone jacks for hooking up modems or fax machines. Special adapters are available from companies such as Telular (Buffalo Grove, Ill.) and Motorola, but this means users must run a cable from the modem to the adapter, then from the adapter to the cell phone. Newer cellular modems may directly connect to handheld cell phones,

In either case, there is no standard cellular connector, and users must be careful to order the correct modem and acble for their brand and model of cell phone.

Cellular voice channel throw a number of obstacles in the way of dial-up data. In fact, some experts argue that cellular modems never will deliver satisfactory performance. We should not forget, however, that the same thing was once said about wireline dial-up modems.

Still, we must recognize that the cellular voice channel poses a rather adverse environment for dial-up modem use. Interruptions are common and signals can fluctuate wildly. The channel is briefly interrupted whenever a cell hand-off occurs, and contrary to what you might think, hand-offs can occur even when users are stationary, such as when the network decides to redistribute the traffic load among neighboring cells. Cellular modems also must be outfitted with special protocols that can handle more frequent data errors. Some modems are even optimized for the slight differences between cellular and landline voice channels.

One obvious drawback to cellular-enabled modems is that similar modems usually are required at the other end of the link. This is bad news for those who want mobile access to any BBS, online service, or Internet service provider. Fortunately, a number of cellular carriers have installed modem pools in their switching offices to circumvent this problem. The mobile user establishes an over-the-air link to a cellular-enabled modem at the switching office, and the modem is connected back-to-back with a standard computer modem. Through a two-step dialing script, the mobile Iser can access any landline modem while enjoying the benefits of special cellular protocols (see figure below).

Cellular modems are available from a growing list of vendors including Microcom (Norwood, Mass.), Megahertz (Salt Lake City, Utah), AT&T Paradyne (Largo, Fa.), Sierra Wireless (Vancouver, B.C), and IBM. For corporate users, consistent nationwide service can be obtained through MCI's XstreamAir service, which and AT&T Paradyne's ETC protocols from anywhere in the United States.

Users can expect further improvements in cellular modem technology. Air Communications (Sunnyvale, Calif.) has developed a handheld cell phone with an integrated data/fax modem that can connect at speeds up to 14.4 Kbps. Mission Viejo, Calif.-based Celeritas Technologies Users can expect further improvehas discovered relatively simple methods for reshaping cellular voice channels to enhance modem performance. Cellular carriers also are taking steps to ensure reliable high-speed modem performance over their networks.

Bottom line: Circuit-switched cellular technology enables Internet access that is essentially the same as that of wireline dial-up modems. When investing in modems, users can feel secure that cellular voice networks are going to be around long time. Airtime service charges are generally the same as for voice about - $.40 per minute when in your home city, about cellular is also the only widely $.80 per minute when roaming in other towns - so it behooves users to operate at the highest possible data rate. Dial-up cellular is alsothe only widely available wireless service that can consistently handle large file transfers. While dial-up modems can be adapted to work via cellular voice channels, a big chunk of the cellular industry felt it would be wiser to create a service specifically designcd for data applications. Thus, Cellular Digital Packet Data (CDPD) was bom in 1992.

CDPD borrows cellular voice channels that are temporarily idle to provide a packet radio service (running at 19.2 Kbps) that appears to be qualitatively more robust than the ARDIS and RAM Mobile Data networks. CDPD is defined by an industry-developed specification that is closely based on existing standards, particularly TCP/IP. Not surprising, CDPD supports real-time interactive access to the Internet.

But CDPD has gotten off to a rough start. There is no doubt that the cellular industry underestimated the mobile-data learning curve. McCaw Cellular was particularly boastful about its CDPD plans, but did not introduce commercial service until April of this year - more than a year late. Part of the reason is that CDPD infrastructure equipment and subscriber devices have been late in arriving. There also has been some dissent in the CDPD ranks. For example, US West has withdrawn from CDPD development activities.

But what else is new? The CDPD folks now seem to be back on track and it is obvious that some carriers (such as McCaw Cellular) are investing heavily in the technology. But perhaps CDPD's prospects received their biggest boost with the introduction of portable radio modems that can operate over CDPD, circuit switched cellular, and wireline circuits. A hybrid spec also has been proposed that would allow applications to seamlessly switch between CDPD and circuit switched cellular - a capability that could blow ARDIS and RAM Mobile Data out of the water. In other words, cellular carriers could offer transaction, interactive, and file transfer services based on a single hardware and software platform. This would also take the heat off CDPD for being late, because circuit switched cellular service is already available nationwide and could be used in the interim for all three types of applications.

As of Febuary 1, 1995, commercial and pre-commercial CDPD service was available in 19 metropolitan areas. Radio modems are available from Sierra Wireless, PCSI (San Diego, Calif.), Cincinnati, Ohio), IBM, and Motorola. According to the CDPD Forum, infrastructure gear has been installed in more than 700 cell cites across the country.

Because it is closely based on TCP/IP and uses a somewhat more robust packet-radio protocol, CDPD is well-suited to Internet applications like Telnet and FTF. It also will be easier for corporate users to get their applications running on CDPD - which is certain to help stimilate growth. For those who demand access to the Internet anytime and anywhere, Sierra Wireless's nifty PocketPlus 210 supports CDPD, circuit switched cellular, and wireline operation in one small package. The only drawback to tri-mode operation is that (for now) you need to subscribe to both cellular voice and CDPD services.

A couple of entrepreneurial outfits are introducing high-performance wireless networks. While neither pretends it will offer nationwide coverage anytime soon, they are not to be dismissed. Los Gatos, Calif. based Metricom has crafted a compelling solution for campus environments. And Palo Alto, California-based Tetherless Access Ltd. has set its sights on supplying high-speed wireless TCP/IP networking technology for service providers in both the United States and abroad.

Metricom has developed a wireless metropolitan area network called Ricochet that has turned more than a few heads, including that of Microsoft cofounder Paul Allen, who has invested more than $36 million in the company. Employing a radio technology pioneered for military applications - frequency hopping spread spectrum - Metricom offers a solution that is at once high-performance and low cost. (Believe it or not, the first patent for this technique was obtained in 1941 by Hollywood starlet Hedy Lamarr and her friend, symphony composer George Antheil.) Metricom emplys a unique mesh architecture that facilitates and simplifies network expansion. The network consists of poletop radios. each of which communicates with its neighbors as well as portable subscriber units. Each poletop radio is programmed with its precise geographical coordinates (derived from the GPS satellite network) upon installation, and acquires the identities and locations of neighboring units upon power up.

What does all of this mean? Ricochet is a self-routing network; packets hop from poletop to poletop until they reach their destination, usually a wireline access point.

The network runs at a raw data rate of 100 Kbps, delivering throughput up to 35 Kbps to end users. Networks may be deployed quickly because they operate in an unlicensed service from 902 MHz to 928 MHz. To make things more interesting, Metricom has broken the mold and is offering low flat-rate monthly pricing ($19.95) with unlimited usage.

Ricochet performs on a par with the fastest dial-up modems and is an excellent choice for untethered, campus-wide access to the Internet. So far, Metricom has networks running in the south San Francisco Bay Area as well as a couple of other cities. The firm is taking a guerrilla-warfare approach to deployment, teaming up with universities and large corporations.

Tetherless Access Ltd. (TAL) is focusing on high-speed wireless data service for fixed locations. Using radios developed by Sunnyvale, Calif.-based Cylink, TAL hopes its technology will find use among Internet service providers and major end-user organizations, both at home and abroad.

In developing countries, TAL can help users quickly deploy data links runnning at speeds up to 160 Kbps. Often the telephone infrastructure either doesn't exist or the waiting time for high-speed data lines is measured in years. According to TAL vice president of marketing Pete Farmer, banking, retailing, and manufacturing operations in these countries are eager to automate but they need better access to high-speed data lines.

In the United States, TAL can bring high-speed data to hard-to-reach locations, such as the mostly Hispanic rural community of Center, Colo., where TAL has teamed up with Dave Hughes of Old Colorado City Communications. Like Metricom, TAL Uses radios that are exempt from FCC licensing hassles.

TAL offers the wireless equivalent of a private 56 Kbps digital phone line - outperforming the fastest dial-up modems. TAL Îs a potential solution for organizations that wish to connect multiple users per site to the Internet, usually via a local area network. But like Metricom, TAL first must forge strategic alliances with local service providers and large organizations.

Ever wonder what Seattle-based tycoons Bill Gates and Craig McCaw would discuss if they got together? Now we know, because the emperors of software and cellular technology are teaming up to revolutionize spaceship Earth's telecommunications facilities.

A satellite network dubbed Teledesic would upgrade the entire planet's telecommunications infrastructure in one fell swoop. Even at several times its estimated $9 billion cost, Teledesic would be a bargain, providing service at data rates up to 2 Mbps virtually everywhere. Although the project is still under study, the dynamic duo hope Teledesic will become operational by the year 2001.

Most of the industry's experts howled when they received word of this one. Some even worry that Teledesic's 840 satellites would clutter the sky. But as Teledesic's president Russell Daggatt explains, a fleet of 840 satellites in low-earth orbit is roughly equivalent to a similar number of Volkswagens scattered over the Earth's roadways - hardly cause for a global traffic jam.

The obstacles to Teledesic are primarily political rather than technological. Many countries are suspicious of U.S.-conceived low-earth orbit satellite networks. As a result, low-earth orbit satellite hopefuls such as Teledesic and Iridium (a worldwide cellular telephone network that is Motorola's brainchild) are being forced to enlist partners abroad.

Bottom line: Teledesic won't be a factor until early in the next millennium. It will help extend the reach of the Internet, but probably will serve large corporations, governments, and universities first. But have no doubt, the day is surely coming when everyone-regardless of location - will be able to purchase bandwidth on demand. Then we will really see what cyberspace can do.

Ira Brodsky ([email protected]) is president of Datacomm Research Company, a consulting firm in Wilmette, Ill., and author of Wireless: The Revolution in Personal Telecommunications (Artech House).