Cellular PC Cards Keep Mobile Workers Connected

It’s getting easier all the time to find a wireless connection for your computer connection. Drop by your local Starbucks and it’s likely that half the tables have a laptop sitting open on them. Similarly, business travelers have come to expect wireless connections in their hotel rooms and airport lounges.

It’s not uncommon now for corporations and colleges to have wireless networks covering their entire campus, and municipalities such as Philadelphia have considered setting up a free service encompassing the entire city.

But while restaurant chains are spending millions setting up connections for their customers, telephone companies have already spent $160 billion dollars building a network of 175,000 cellular sites spanning the entire country.

And, just as millions of people are using these towers to send text messages and photos from their cell phones, employees can also use them to send and receive data from their laptops. While the transfer speeds aren’t as fast as Wi-Fi (the type of wireless network specifically designed for computers rather than phones), they can do it right from their car or a customer’s office, rather than having to drive someplace where they can buy a latte.

What is necessary to make the connection is a cellular PC card to plug into a slot on the laptop and a contract with a cellular provider, often the same one you are using for your phone service.

Cellular Standards
There are three major families of standards for cellular data transmission – Cellular Digital Packet Data (CDPD), Global System for Mobile Communications (GSM) and Code Division Multiple Access (CDMA).

The names for these standards describe technical aspects that only an engineer needs to know. But each of these standards contains different service levels, which is something you will be interested in. These families are not compatible with each other, so you should make sure that you select the one that best suits your needs.

As a comparison on the speeds, a dial up Internet connection runs at 56 kilobits per second (56 kbps) and a DSL line runs from about 384 kbps up to 3 Megabits per second (3Mbps). In most cases your cellular PC connection will run somewhat faster than a dial up connection, but slower than DSL or cable.

Here’s how the three standards break down:

  • Cellular Digital Packet Data (CDPD) is a technology broadly used by emergency services as well as freight carriers to keep in touch with their drivers. It transmits data at 19.2 kbps, a much slower rate than either GSM or CDMA. The advantage is that it has broad coverage and a low cost. If you are not already using this technology for your cell phone, however, don’t bother starting. The main cellular providers are phasing out support of CDPD. If you don’t need higher transmission rates, and the service is available in your area, Cingular Interactive’s Mobitex service and Motient Corporation both offer CDPD in the nation’s 500 largest cities.
  • Global System for Mobile Communications (GSM) is widely used in Europe and many other parts of the world. Some U.S. carriers including AT&T Wireless (now merged with Cingular) also provide it in certain areas. GSM comes with four data transmission rates: the original at 9.6 kbps, General Packet Radio Service (GPRS) at 56 kbps, Enhanced Data GSM Environment (EDGE) at 384 kpbs and Universal Mobile Telecommunications Service (UMTS) at 2 Mbps. GSM also includes the ability to send text messages of up to 160 characters using the Short Messaging Service (SMS). While it would be great to be able to transmit data at 2Mbps, it’s not likely that you will be able to find that service. More likely you will only be able to utilize the slower EDGE or GPRS transmission rates for the next several years.
  • Code Division Multiple Access (CDMA) is the most common standard in the Americas, as well as in Israel, New Zealand, Korea, Japan, Taiwan and China. Its original standard came in at 14.4 kbps, but it is more common to find the 144 kbps service (called 1xRTT &#151 One Times Radio Transmission Technology) in the United States. The fastest CDMA standard, the 2Mbps 1xEV-DO (1x Evolution Data Only), is only available in the Washington, DC, Las Vegas, Nevada and San Diego, California metropolitan areas at this time.

The maximum speeds listed above are the not speeds you can expect to see out in the field. The actual speeds typically run at about half that rate, although some carriers also use a compression format that allows the data go get through faster.

An Easy Choice
A variety of cellular PC cards offer an array of different bandwidths, power management schemes and antenna styles. Some, such as the Nokia D 311 have the advantage of being able to access both cellular and Wi-Fi networks. But, when it comes right down to it, the choice is very simple. It is the service that matters, not the hardware, so the important choice you have to make is which service provider to use. Then you’ll use whatever card your cellular provider chooses to support.

Selecting a cellular data provider comes down to four main issues:

Coverage Area &#151 The primary consideration, above speed or price, is whether you can actually get a signal and log on in the areas you want. When studying a carrier’s coverage map, be sure that it is not the one for digital coverage, but for digital data transmission.

For example, AT&T Wireless has one map on its Web site showing coverage for its GSM America plan, and a second map showing where it provides GPRS and EDGE data services.

Standard &#151 This is the choice between GSM and CDMA. If you frequently travel to Europe and need cellular data access there, choose GSM. Otherwise, CDMA is generally the better option.

Speed &#151 How much speed you need depends on what you use the computer for. You won’t want to download a 100MB Computer Aided Design (CAD) file over anything less than a 2Mbps connection. If you only need it occasionally to check e-mail or send in a customer order, you may be perfectly happy with one of the slower connections.

Price &#151 The prices are generally based on a flat monthly rate for a certain number of Megabytes of data transmission, plus a per-unit charge for anything above that level. In addition you can choose from unlimited use plans ($79.95 per month per laptop from Verizon) as well as plans that let you share the service among several users.

In pricing such a plan, it is essential that you correctly estimate the amount of usage in order to obtain the best price. With AT&T, for example, one small-business-shared-data plan runs $10.99 for 1MB and $10 for each additional Megabyte, while another is $54.99 for 50 MB and $1 for each additional Megabyte. If you sign up for the first plan and wind up using 10MB in a single month, it will cost you over $100, far more than you would pay on the 50 MB plan.

So, if you do sign up for one of the low cost plans, make sure the employees know exactly what they can and cannot do over the connection, otherwise you may find yourself paying $40 for a single four minute song they decided to download. (A movie could cost you thousands.)

Until such time as Wi-Fi is truly available everywhere, adding cellular service for employee laptops can be a cost effective means of keeping mobile employees in touch with the home office. It’s not the method of choice for doing heavy research over the Internet or other jobs requiring a large amount of data transfer. But it is ideal for short, routine tasks.

Drew Robb is a Los Angeles-based freelancer specializing in technology and engineering. Originally from Scotland, he graduated with a degree in geology from Glasgow’s Strathclyde University. In recent years he has authored hundreds of articles as well as the book, Server Disk Management by CRC Press.

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