Wireless Communications for Pen-based Computing

Editor’s Note: The following is an overview of wireless communications by Bill Frezza, Director of Strategic Sales for Ericsson GE Mobile Data Inc. He can be contacted at 15 E. Midland Ave., Paramus, NJ 07652.

The three major classes of wireless data communications networks that merit close investigation by the pen computing industry are:

• Wireless Wide Area Networks (WANs) that offer connectivity everywhere in the continental US.
• Wireless Metropolitan Area Networks (MANs) that offer connectivity across most major metropolitan areas of interest.
• Wireless Local Area Networks (LANs) that offer connectivity within specific buildings or facilities.

Each approach is suited for a different application and environment since no single technology can meet all of the needs for wireless network computing. The one thing they have in common is that they’re all limited in geographic extent due to the fundamental nature of radio propagation, the architecture of the particular system, and the FCC regulations governing use of the spectrum, and the maturity and level of investment made in deploying the network infrastructure.

WANs

Today, real wireless WANs can only be supported with satellite-based technology. Qualcomm, American Mobile Satellite Corp. (AMSC), and the now defunct Geostar are examples of companies that offer such services. These systems provide continuous over-the-road, low speed two-way data messaging virtually anywhere in the U.S. Because of this, they are becoming increasingly popular in niche markets such as long-haul trucking. Due to the high cost of transmission, the limited aggregate capacity of the network, and the minimal data rate and throughput achievable on mobile two-way satellite links, it remains unclear what roll wireless WANs will play in the future of widely used personal products like pen-based computers.

LANs

At the other extreme lie wireless LANs. Wireless LANs provide connectivity and resource sharing of computers and peripherals over a very limited physical area. Typical installations can cover several contiguous offices, a floor within a building, an entire multi-story building or a factory floor. Larger systems of linked sub-networks can even be used to cover a campus.

Numerous technologies have been developed to provide wireless LAN capability including spread spectrum, in-building microwave, and even infrared. NCR, Motorola, Proxim, Photonics, and BICC Communications are examples of a few of the companies offering products based on these technologies. Wireless LANs often have enough bandwidth to support full Ethernet or Token-Ring speeds. (Radio spectrum can often be obtained more readily for these extremely short range systems. For example, under FCC Part 15 portions of the 900 MHz band are unlicensed altogether provided certain rules are followed.) Wireless LANs will be important to the future of pen-based computers for applications where the users don’t stray too far. Examples include inventory control in a warehouse setting, vehicle maintenance in a repair depot, and groupware sessions for executives in conference.

MANs

The bulk of the investment and engineering development activity in wireless data networking today is going into wireless MANs. These systems provide data communications services in the major cities and surrounding areas across the U.S. They are designed to support the out-of-office worker, whose productivity gains are becoming dependent on the ability to “keep in touch.” The aggregate capacity, data rate, throughput, and transmission costs of wireless MANs lie in between that of WANs and LANs.

Wireless MANs can be divided into two general categories based on FCC licensing — private and public. Since the 1930s, private land mobile radio networks have been used to provide wireless voice capability using technology specifically designed for the use of a single entity. Examples include electric and gas utilities and public safety agencies. These organizations needed to obtain and manage their own spectrum, procure and install radio based stations, and operate and maintain their own networks.

Wireless public networks became a real possibility in the 1980s with the advent of cellular telephone and specialized mobile radio (SMR) systems. Although these two services are currently regulated and designed quite differently, both eliminate the need for end users to operate their own radio systems. Public networks are the key to the future of wireless pen-based computers.

Wireless MAN network technology can also be divided into two different connectivity classes — circuit switched and packet switched. Circuit switched networks are designed to support voice traffic, although they can also support data via the addition of external voiceband modems. These networks generally charge by the minute for connect time. Packet switched networks generally charge for each successfully delivered packet. Both architectures have a significant role to play in supporting pen computers depending on the traffic model of the driving application. From a cost perspective, circuit switched networks (for example, cellular telephone) are often superior for supporting file transfer activity while packet switched networks are superior for supporting interactive messaging.

ARDIS and RAM are the Main MANs

There are currently only two companies which provide packet switched Wireless Metropolitan Area Networking across the U.S.— ARDIS and RAM Mobile Data. ARDIS is based on a private data networking technology developed by Motorola under contract to IBM. The original design objective of this network was to provide a proprietary solution designed to support IBM’s own field service technicians operating within particular cities. The system does not support seamless nationwide roaming. Beginning in 1990, IBM and Motorola formed the ARDIS joint venture to remarket the service as a public network. ARDIS currently holds FCC licenses for single channel operating across more than 323 MSAs (Metropolitan Statistical Areas) nationwide, allowing it to offer more widespread coverage, today, than any of its competitors. They have not yet announced plans to convert their network infrastructure to Motorola’s new public network architecture, System Y, which is the foundation of Motorola’s international efforts.

RAM Mobile Data, a pioneer in paging and cellular telephone operations, uses a more recently developed public data networking technology known as Mobitex. Mobitex network equipment is provided by Ericsson and is the foundation of its international effort in wireless MAN. Mobitex networks are currently operational in the U.S., Canada, and the U.K., Norway, Finland, Sweden, and are scheduled for operation in Australia. Most importantly, RAM currently holds FCC licenses for between 10 and 30 frequency channels in each of the top 50 MSAs across the U.S., allowing it to support significantly more traffic than any of its competition.

While the technical issues can be complex, one thing is clear: laptop, notebook, palmtop, and pen-computing companies that offer wireless connectivity with seamless nationwide roaming will have a distinct competitive advantage over those who do not. Marketers, business planners, hardware, and software engineers working in pen computing need to learn about these new wireless technologies and being formulating action plans now. These plans must take into account not only where the wireless communications business has been, but also where it is going.