THE MAGAZINE FOR COMPUTER APPLICATIONS
Circuit Cellar Online offers articles illustrating creative solutions
and unique applications through complete projects, practical
tutorials, and useful design techniques.

ROAMING ABOUT

Wireless Connectivity for Mobile PCs
by Vinit Nijhawan

Start ý Local-Area Wireless ý Mobile Computer Technology ý Applications ý Sources and PDF

MOBILE COMPUTER TECHNOLOGY

There have been dramatic hardware and software advances in the mobile computer industry. General purpose use of hand-held or PDA computers is widespread with three dominant mobile operating systems. The Palm OS from Palm Computing (spin-off from 3COM), Windows CE from Microsoft, and Epoc32 from Psion have close to 100% marketshare. The Palm OS dominates the consumer market, Windows CE is the leader in industrial applications, and Epoc32 has a share of the European market. Many portable and vehicle-mount Windows CE computers are available for the industrial market, like the PC/Piranha from Kinetic Computer (see Photo 1).

Photo 1ýThe PC/Piranha wireless vehicle computer utilizes the industry-standard Windows CE operating system from Microsoft. The PC/Piranha is a multi-function computer designed for in-cab use with GPS, SAE J1708 engine interface, touchscreen, and wireless connectivity built in.

In creating a mobile application, network architects and software developers have to deal with the idiosyncrasies of the wireless link, namely low yet expensive bandwidth and variable delays. Variable delays are caused by a lack of 100% coverage and motion. Developers can create their own wireless IP software or use third-party wireless middleware software. The advantages of middleware software is that it is device and network independent. Thus, applications can be ported to various mobile terminals and operated over many networks without major changes.

There are many wireless middleware software and service providers with many new companies being formed. The old-time players are Nettech Systems, Sybase, and Dynamic Mobile Data. These companies have targeted vertical industries, such as field service and dispatch, using dedicated mobile terminals. New players are targeting horizontal applications using general-purpose mobile terminals like PDAs and cell phones. These companies are AvantGo, Aether Systems, ProxiWeb, and Everypath.com.

There has been an explosion of interest in connecting mobile devices to the Internet. Many analysts are convinced that Internet connectivity is the killer app for mobile data. Technically, it is difficult because of wireless network bandwidth (TCP/IP, the protocol used on the Internet, is chatty), and the small screens used in mobile terminals. (HTML is the coding language used for most Internet content and is generally designed for high-resolution CRT screens.)

There are solutions emerging for wireless interconnectivity, including the middleware services previously described. An emerging standard called Wireless Applications Protocol (WAP) uses a subset of another Internet coding scheme called XML to deliver web content to cell phones. WAP and its predecessors have been in development for more than three years, and WAP-enabled phones are becoming increasingly popular.

Unfortunately, the services for these phones have been slow to develop, primarily because standard HTML pages do not translate well to WAP. As a result, most WAP services and content must be developed from scratch. In spite of this, WAP content providers are proliferating and emerging, as are middleware software providers who are building smart filters that allow any HTML page to be displayed on a WAP-enabled phone.

PREVIOUS • NEXT