Currently, the vast majority of mobile application users have no wireless communications capabilities. Obviously, many of these are laptop users who may dial into a RAS unit from a hotel room while on the road. Additionally, a rapidly growing number of workers are equipped with Palm/Windows CE PDAs, RIM Blackberry pagers, and WAP phones from companies such as Nokia, Motorola, and Ericsson. Given a requirement to build a solution that meets all of these users' information-access needs, what's a poor developer to do? The first step is to pinpoint the platforms that will need to be supported. For a corporate developer, this is probably a fairly simple task. Best case scenario: Management dictates which devices are allowed. Worst case scenario: A quick poll of enterprise users reveals a mix of the most common operating platforms. For developers building commercial apps, the task boils down to an economic decision: Choose based on target geographic area and on other demographic info.
When speaking of wireless, it's also important to specify whether you're talking about short range, local area network (LAN), metropolitan area network (MAN), or wide area network (WAN). The most promising short-range wireless solution is Bluetootha specification that permits low-bandwidth wireless connections between disparate devices at a distance of up to 100 meters. Local-area wireless networks (known as wireless LANs) have been common for a while and are even available as a standard feature in products from Apple, Compaq, and Dell. Metropolitan area networks are growing in popularity and offer relatively high bandwidths using technologies such as MMDS and LMDS. Wide area networks are obviously of most interest to the application developer because they allow mobile users to roam anywhere and still use your application.
If you make the decision that you want a true wide-area wireless solution (requiring wireless communications back to one or more servers), you'll choose from a variety of options. In Europe, the prevailing standard for wireless communications is GSM (more info at http://www.gsmworld.com/). GSM phones support SIM card add-ons for security, mobile commerce, and even Java. When connected to another mobile device, a user can expect roughly 9.6 Kbps access, which is acceptable for simple text transfer and retrieval. SMS (Short Message Service) and WAP are also very popular in European countries, for a variety of reasons. In Japan, a number of communications technologies are used. The biggest success story to come out of the Japanese wireless world is that of NTT DoCoMo's i-Mode service (see http://www.eurotechnology.com/imode/faq.html for more information).
Unfortunately, in the United States, a hodgepodge of technologies and options awaits. Currently, the digital cellular networks are split, technology-wise, between GSM, TDMA, and CDMA. A path has been defined by the ITU that paves the way for all of these technologies to merge into a unified system known as 3G (for third-generation wireless). 3G systems offer the hope of global roaming and broadband wireless access, but it's becoming clear that this won't be widespread in the U.S. for at least five years. More common, from an application development point of view, is to use a data-only communications technology such as CDPD or Mobitex (more information and coverage maps available at http://www.wirelessdata.org/). Wireless data accounts can be set up with most major carriers, including AT&T, Cingular, and Verizon. These typically deliver bandwidth anywhere from 2.4 Kbps up to 14.4 Kbps. For applications that require very little bandwidth and that primarily transfer messages in short burst sequences, services such as Cellemetry, Aeris.net, and Motorola's REFLEX architecture work great.