Cellular carriers expected wireless Internet access to be the next big thing, but while they were waiting for consumers to jump on the bandwagon, a sleepy technology that had been around for years took them by surprise. Short Messaging Service, or SMS, has become wildly popular in Europe and Asia, where more advanced digital networks made SMS available long before its debut in North America. Now, SMS is catching on here as a relatively low cost and easy to use solution for on-the-go connectivity.

What is SMS?
Short Messaging Service, otherwise known as text messaging, mobile messaging, or alphanumeric paging is a digital cellular network feature. It lets you send short text and numeric messages to and from digital cell phones, cell phones and e-mail addresses, as well as cell phones and public SMS messaging gateways on the Internet.

SMS is convenient and cost effective for a number of reasons. When you compare it with the cost of airtime for voice calls or wireless web access, SMS is a real bargain. Messages can be received while making voice calls, and there are no busy signals to contend with. Plus, if you should you find yourself in a situation where talking on a cell phone is inappropriate, SMS is silent and discreet. Messages generated by SMS are immediately delivered directly to your phone. There is no need to call an access number, as is the case with voice-mail. Also, most carriers offer SMS alerts (information packets, such as stock quotes, sports scores, and news) that can be delivered to your phone at regularly scheduled intervals.

Currently, there are approximately 16 billion SMS messages sent globally each month, with the majority of that traffic occurring in Western Europe and Asia. In North America most major cellular providers offer either one-way or two-way SMS to their subscribers. With one-way service, you can receive messages; while with two-way service, you can both receive and send messages.

What is the difference between SMS, Instant Messaging Service (IMS), and e-mail?
E-mail is by far the most popular messaging service currently in use in North America. Although both e-mail and SMS are "store and forward" systems that utilize a gateway to pass messages from senders to recipients, the most obvious difference between the two are the length and complexity of the messages. SMS messages are limited to between 80 to 500 characters depending on the service provider. A typical SMS message weighs in at about 120 characters.

While e-mail lets you attach files, imbed images, and make use of HTML, SMS messages are limited to text and numeral display. However, there are a few exceptions. The Nextel SMS service lets you automatically make calls from phone numbers appearing in the message text - -much like a hypertext link in an e-mail. Also, on European GSM cellular networks, SMS messages delivered to Nokia phones may have distinct ring tones or graphics attached.

On the other hand, Instant Messaging Service (IMS), made popular by AOL Instant Messenger, allows you to have virtual real-time text conversations (or chat) with people who are simultaneously connected to the Internet. SMS messages are immediate, but not simultaneous. SMS messages are sent to and processed by a Short Message Service Center, which then delivers the message to the intended recipient''s cell phone. If a message is sent to a phone that is turned off, the service center will store it and try to redeliver it for a period of 3 to 7 days, depending on the service provider.

Which companies offer SMS, and how much does it cost?
Today, most major cellular providers-- Nextel, Cingular, Verizon, Sprint PCS, AT&T Wireless, VoiceStream, and US Cellular--offer some form of SMS. Features and costs vary widely from carrier to carrier, so it is best to check the FAQ pages about mobile messaging, or SMS, at your service provider''s web site.

Keep in mind that messages can only be sent from your phone or pager to other phones or pagers within your network. You can send messages across networks if you use a public SMS messaging gateway, send from an e-mail account, or send from a PC equipped with text messaging software.

Some questions you should consider when comparing carriers include:

• How long are messages held by the carrier for delivery when your phone is offline?
• How many messages can be stored in the inbox?
• Is one-way messaging (receive), or two-way messaging (send and receive) available in your service area, and while roaming?
• Which features are provided through your carrier''s public SMS gateway?
• Are SMS alerts (news, sports scores, etc.) available?

In general, companies offer messaging free of charge as part of select service plans, for a per message fee, or for a monthly fee, which includes a set number of messages. If you purchase a plan that has a per message fee, incoming messages will cost less than outbound messages, and are only a few cents. If you cannot get free SMS with the service plan you''ve chosen, and plan to send or receive many messages, a monthly plan is generally more cost effective than a per message plan.

Which devices are compatible with SMS?
The most common devices used with SMS are digital cell phones equipped with one-way receive SMS capability. A number of digital pagers also have this feature. If you own an analog cell phone, or one that is several years old, chances are it will not be compatible with SMS. Check with your cellular carrier to be certain.

Newer model cell phones from a number of companies like Nokia and Motorola are equipped with two-way messaging. A number of advanced pagers sporting tiny QWERTY keyboards are also equipped with two-way SMS. If you are purchasing an SMS-equipped phone or pager, check with the service providers to see which models are compatible with the various networks.

Also, look for a phone that has predictive text input, or Tegic T9 software. Predictive text input makes typing long messages with a typical 12-button phone keypad significantly easier. Rather than having to punch a key multiple times to select the appropriate letter -- for instance punching the #2 key once for A, twice for B, and three times for C -- you can simply spell out a word. The software will guess the word you are trying to spell and fill in the blanks, therefore reducing the overall number of key punches.

The increasingly popular pagers from Research in Motion (RIM) that work with BlackBerry service use a messaging system different from SMS. BlackBerry operates on packet-switched networks, and therefore works more like a PC-based e-mail system than phone-based SMS. Messages can be longer, and can run through a single established e-mail account, such as your office e-mail address. However, Cingular offers Interactive Messaging PLUS, which is SMS-based, and compatible with the RIM 950 and 957 pagers.

Currently wireless service providers catering to the handheld market do not offer SMS. Like the BlackBerry service, these providers depend on networks that use a different system than SMS. Messages to and from hand helds work in conjunction with standard e-mail, but images are often stripped out.

How do you send and receive messages?
Once you have subscribed to SMS through your service provider, receiving messages is easy. Most phones will display an incoming message alert graphic on the screen. Depending on the device, you may also set a tone to sound when incoming messages arrive. Once a message is received, you can use the scroll keys on your phone or pager to view the message text. Options to store, reply, or forward each message will be available at that time.

It is also easy to send a message. The exact procedure varies from device to device, but it usually involves entering the recipient''s phone number or e-mail address, and then composing the message with the phone keypad. You may have the option to send the message instantly or store it for later delivery.

How do you use public gateways to send messages?
Cellular service providers who offer SMS also offer public SMS gateways, which allow you to compose and send messages from the service provider''s web site. A number of independently operated message gateways also exist on the Internet. Some gateways have more features than others. A few let you compose messages to more than one recipient, create group lists, manage messages, and send pre-set or customized replies.

By using a public gateway you can send a message to a device on another network, and friends or business associates without SMS-equipped phones or pagers can send messages to you. If you don''t have access to your e-mail account, or an SMS-equipped phone, a public gateway (available from any computer with Internet access) is a convenient way keep in contact.

Unfortunately, the one drawback to using public gateways is file security. Unlike Web transmissions that occur as secure transactions, any third party could monitor the cell phone number and message contents when a message is sent through a public gateway. Messages sent from phone to phone through Short Message Service Centers are more secure, but the possibility exists that these transmissions could also be monitored.