The Road Wirer
It wasn’t such a very long time ago that a passing reference to “wireless technology” generally meant cellular or satellite telephone (voice) service. Now “wireless” can evoke a host of complex and mind-numbing questions about equipment and services. I find it especially interesting that many of the cellular companies have changed their corporate names in such a manner to include or to add the word “wireless.” (Bell South Cellular is now Bell South Wireless, AT&T Wireless, etc.)
In broad terms, the world of wireless can be divided, (at least for now, it will probably change next week...) into six classifications of service: Cellular, Fixed Wireless, PCS, Internet Telephony, Global Satellite and Advanced Messaging and Paging.
Some background definitions of the six classisfications follow and then I will start our look at Cellular systems.
- Cellular includes both Analog voice systems using the simple Circuit Switched Cellular (CSC) and the networks that have been built by overlaying the existing cell tower locations to create new platforms that can accomodate data transfer like Cellular Digital Packet Data, (CDPD) or Time Division Multiple Access (TDMA).
- Fixed Wireless Systems that use narrow band radio transmission and a series of localized antenaes to reach wireless receivers/transceivers in certain local environments. These can be be as small as a warehouse or as large as a geographical region like San Franciso, in the case of the Ricochet system or Ardis in the east. Some wireless providers are also using existing fiber optic and TV coaxial cable to provide limited wireless service to some residential neighborhoods.
- Personal Communication Services, (PCS) using a variety of networks to provide e-mail, internet access and packaged content and telecommunication services to hand-held devices like Palm Tops.
- Internet Telephony providing both voice, data and fax services using Internet protocols (IP).
- Satellite service for both data and voice and
- Paging and advanced message delivery systems
Cellular: As of this date, nearly all urban and semi-rural areas within the continental USA have basic analog voice cellular service. It is, however still easy to find pockets of no-service in large sections of the back country in the western states. Like for instance, parked on the side of the road in Death Valley or Yosemite National Parks. Better go for a hike instead.
But, if you were lucky enough to have a cellular signal this is what happens: Basic analog cellular systems divides up a geographical area into small sections called cells. A cellular tower or cell site is built within each cell site. A cell site’s coverage area is generally 1 mile to 20 miles in diameter. A central computer in the cellular provider’s office monitors the weakness/strength of the radio signals coming from a cellular phone and can switch the signal from tower to tower as needed. The computer also switches the telephone call into the public telephone system. The Bell South Wireless website has a good explanation of this procedure at www.bscc.com. (Look at the wireless technology section.)
So the good news is that you have a good signal and are on a “one-rate” low cost national access plan. The bad news is that the cell tower your cellular phone is able to reach is not owned by the company under which you have the “one-rate” plan and so you are going to be lucky enough to pay “roam” charges of $1.00 to $3.00 per minute and the top speed you can reasonably expect to achieve is 9.6kbps. Pretty slow for surfing the web.
To meet the challenge of being able to be wireless and still send data at more reasonable speeds a number of telecommunication providers have begun to build new electronic platforms on top of existing cell tower locations. CDPD is supported by AT&T and several other national carriers. To access this network, one needs a special modem, (about $1000) and a CDPD service agreement (at around $65/mo). Through-put on this system, (when everything is working) is about 11.2kbps which is comparable to the performance seen with a 14.4 kbps modem on a public telephone landline. Sierra Wireless produces a product known as the Air Card, which is comprised of two Type II PCMCIA cards that allows access to both the switched circuit network and the CDPD networks.
Just to keep things interesting, there are a number of systems that use protocols that are not compatible with anything else. The GSM, (Global System for Mobile Communications) is used in Asia and Europe and has been introduced in the northeast. 3-G technology, (third generation cellular- broadband) is being hyped as capable of 28.8kbps level speeds. A claim that I find hard to believe...
The single biggest obstacle to purchasing a piece of equipment that can deliver true wireless capability at a reasonable speed and cost is still the lack of a consistent and reliable network. Although the Wireless providers are reluctant to use terms like roaming, they do have built-in fees for the transmission of data streams that use towers they they do not control. In this regard, I am very interested in a “new” type of wireless backbone that GTE Wireless will unveil in March. Known as the WIN-4 network, it may provide the first glimpse of a network that will provide digital/analog service to road adventurers.
And so the search goes on....
February 8, 1999