Making The Call With Two-Way Paging By Peter Rysavy   The wireless data market is poised for dramatic growth. Although the number of subscribers still is relatively low, carriers are offering networks with excellent coverage, lower prices and more options for mobile workers to access the Internet and corporate systems such as Lotus Development Corp.'s Notes. The wireless WANs that have been deployed include cellular-based systems, such as analog, digital and cellular digital packet data (CDPD), and data-only networks, such as ARDIS and RAM Mobile Data (see "Digital Cellular: On the Road to PCS," February 15, 1996, and "Wireless Data Made to Order," March 15, 1996). But now there is a new player: two-way paging. Two-way paging offers some significant capabilities with distinct advantages. In this article, we will explore how two-way paging works, discuss the types of applications supported and consider its limitations. We also will discuss the results of our testing with SkyTel's network to determine whether its promises live up to reality. SkyTel is the only national provider with two-way service, but other paging companies are considering two-way service. What is two-way paging? Quite simply, it is alphanumeric paging that lets the pager send messages, either to respond to messages it receives or to originate messages. How might you use this service? You're a network manager with a network-diagnostic program that pages you when it detects a problem, such as the file server running out of disk space. Using your pager, you could return a message indicating whether you can respond to the emergency. You could send a message indicating which backup server to engage. You could respond with predefined messages such as "on my way," "will arrive in 15 minutes" or "send number to call," for example. If your reply indicated you could not respond, the diagnostic program c ould then page somebody else. Sizing Them Up The pagers will come in various shapes and sizes. Some will look almost like today's al phanumeric pagers. Others, such as Motorola's forthcoming PageWriter will add small keyboards and larger displays. Some will be PC Card devices that will operate in a notebook computer or handheld PC. SkyTel's unit, called SkyWriter, looks almost identical to today's one-way alphanumeric pagers. What type of messages will two-way paging support? That remains to be seen, but because of the limited bandwidth, it probably won't be practical to send messages larger than 500 characters. With SkyTel's current pricing of about 25 cents per 80-character message, you will want to limit how much information you send. Message delivery times are on the order of tens of seconds to minutes (in contrast, message delivery times for wireless data networks typically are less than five seconds). Even with these limitations, there should be many ways for users to take advantage of t he service. You should expect a few specific applications for two-way pagers. One would be a reliable paging model where the pager simply acknowledges that it received the page. Another would be menu response, where a message sent to the pager would contain a list of reply messages; you scroll through these and select a response. (With SkyTel's service you can send up to 10 reply messages, each of which can be up to 15 characters.) Another application is general messaging, where you initiate messages from the pager. With SkyTel's SkyWriter, you compose messages by moving a cursor over a displayed alphabet, selecting one letter at a time. This works fine for short messages (20 characters or so). Additionally, computer connectivity with the SkyWriter is accomplished via a serial cable and through the use of a connectivity package available from SkyTel. In the future, pagers will be available in a PC Card format, making it easy to use the keyboard on a notebook or personal digital assistant (PDA) to compo se messages.

Updated January 10, 1997