|Analysis of Web Content Delivered to a Mobile Computing Environment Page 2 of 9|
|Written by Anthony Perreault|
Background of Wireless Technology
The basis of wireless technology is radio communication. Whether it be your home wireless network, the wireless local area network at your work or college, or the network of cellular towers that allow continuous communication across the United States, at heart they all share similar technology of radio frequency (RF) communication. This section will briefly explore how wireless communication—from your Bluetooth headset to the wireless mobile computing device—operates.
In the United States the governing body for public and private broadcast communication is the Federal Communications Commission (FCC). Besides monitoring content that is broadcast over the airwaves, the FCC is responsible for the allocation of radio frequencies used in private and public transmissions. The FCC licenses portions of the radio spectrum for use to companies such as Verizon, Sprint, AT&T, T-Mobile and other cellular telephone providers. Other areas of the radio spectrum are licensed out to radio stations and broadcast television. Selected frequencies of the radio spectrum are reserved for police, ambulance, and other emergency use. Still other frequency ranges are reserved for the military, air traffic control, and scientific use, primarily radio astronomy.
The FCC has set aside radio frequencies that the public can access, through the use of low-power radio transmitters and receivers, without the need of a license. In this realm lie the wireless personal area network (WPAN) and the wireless local area network (WLAN). Because the range of the radio transmissions is limited to usually under a hundred meters, the FCC does not require a license. This open area of the radio spectrum has led to an explosion of wireless devices such as Bluetooth headsets, keyboards and computer mice. And wireless Internet access points, more commonly known as Wi-Fi hot spots, have resulted in the ability to access the Internet through your Wi-Fi enabled laptop or mobile computing device.
Wireless Networks: Bluetooth, WPAN, WLAN, and WWAN
Perhaps the best known and used wireless network, beyond the cellular telephone, is the home-based wireless network that connects computers and printers to a wireless router, which itself is linked to the Internet through a high-speed connection such as cable, DSL, or satellite. This home network allows computers in different rooms to communicate with each other to transfer files, such as audio or streaming video downloaded from the Internet. It also allows various computers with disparate operating systems to share resources, such as the Internet connector or a printer, without the need for physical cables or reconfiguration of software.
Home networks, or WPAN (Wireless Personal Area Networks), come in two types: Bluetooth and IEEE 802.11 (Mallick 48). What makes Bluetooth technology both convenient and useful is that it is very much plug-and-play. Bluetooth devices will automatically configure themselves, according to Franklin and Layton, creating localized networks called piconets that can be shared by up to eight Bluetooth-enabled devices.
The Institute of Electrical and Electronic Engineers (IEEE) designates specifications for electronic devices and unlicensed communication protocols (Mallick 52). One such set of communication specifications is IEEE 802.11, more commonly known as Wi-Fi and by Apple users as Airport and Airport Extreme. This specification is used in both the home and office environments to create WLANs—wireless local area networks. The 802.11 specification is broken down into subsets with an alphabetic suffix; this suffix represents when this particular subset was first proposed (Mallick 57). Many laptop computers now come standard with both Wi-Fi (802.11) cards as well as Bluetooth for devices such as wireless keyboards and mice.
The 802.11 specification subset that has seen the largest commercial penetration is 802.11b, or as it is more commonly known, Wi-Fi (Mallick 57). With its extended range and data transmission, 802.11b is useful in the office environment or college campus.
The WWAN—wireless wide area network—is the realm of cellular telephony. This cell—or area of coverage—of a tower is determined by network protocol, signal power, and obstructions that may block the signal; cell coverage is anywhere from 1 to 40 kilometers in range (Mallick 66). In populated areas where there are more calls to handle, microcells are established that can handle this increased volume of data (Mallick 67). When on a cell phone and moving between cells, the process of transferring the signal between cells is called a handoff or a handover; missed handoffs result in what is known as a dropped call and, depending on the network protocol used, the connection might have to be re-established by the user of the phone (Mallick 67).
WWANs have evolved over the course of the years. While the history of how the cellular networks came about and the evolution of the network protocols are beyond the scope of this article, it should be recognized that in the United States there exists two basic networks, 2G (second generation) and 3G (third generation). Virtually all cellular telephones on the market in the US today operate as 2G devices with basic data services such as email and instant messaging. In populated areas 3G networks provide increased data bandwidth. This increased bandwidth allows the mobile user to have an “always-on” data connection to the Internet through their cell phone; examples of these cell phones are Apple’s iPhone or the newest generation of the RIM Blackberry.
Wireless Application Protocol (WAP) and Wireless Markup Language (WML)
Wireless Application Protocol (WAP) is the method by which wireless information is delivered and presented to mobile phones and other wireless devices. WAP uses Wireless Markup Language (WML), which is a subset of Extensible Markup Language (XML), to format the content delivered to the microbrowser that resides as an application on the mobile phone. Most low-end mobile phones use WAP and WML to send and receive text messages (SMS—Short Message Service), emails, and very basic Internet service (Mallick 117).
WAP is similar to Hypertext Transmission Protocol (HTTP) in that WAP, like HTTP, is the method by which the information and the formatting instructions—WML for WAP, HTML/XHTML for HTTP—are carried. The technical communicator should know is that WAP is another method by which content is delivered to the low-end mobile phones and how to code for this environment.
WML is part of the wireless application environment and is based off XML (Mallick 311). WML is based on a deck and card metaphor; a WML page is a deck that is created from a series of cards. When the deck is accessed by the microbrowser, all cards for the deck are downloaded to the phone where all the interaction takes place with no further need to access the content provider until a new deck is requested (Mallick 313; Moll 44). Because many of the low-end mobile phone screens are around 150 x 150 pixels, the amount of information that can appear on them is limited to around five lines with around 12 characters per line (Mallick 312). With such a limited display, the information presented has to be exactly what the user is looking for and navigation has to be as easy as possible. Interaction with the WML deck and cards is through the keypad of the phone; options should be as few as possible and use the least amount of keystrokes. The microbrowsers also have minimal navigational commands such as Submit, Back, Link, and More (Mallick 312).
Because WML is based on XML, the rules for XML formatting must be followed. Part of this formatting includes using the WAPForum Document Type Definition (DTD) in the WML code to identify the document as a WAP / WML document type (Mallick 312). Likewise, the following XML rules need to be followed when coding for WML (Mallick 313):
It is beyond the scope of this paper to provide details on how to design and code for WML and XML. There are many exceptional books on the subject of XML and w3schools.com provides excellent online introductions and tutorials to WAP, WML, and XML.
HTML / XHTML / HTML-MP / XHTML Basic
The last several generations of smart phones and mobile computing devices have browsers that are capable of interpreting Hypertext Markup Language (HTML), Extensible Hypertext Markup Language (XHTML), and Extensible Hypertext Markup Language-Mobile Profile (XHTML-MP) (Mallick 316-23).
HTML is the markup language that formats content for web pages. It is a loose standard in that tags do not have to be closed in order for the browser to interpret the formatting commands, and that tags also are not case sensitive; it is fairly common to see tags such as
without a closing tag or tags with different cases such as
XHTML combines elements of XML with HTML. As such, XHMTL code is far stricter in how it is formatted than HTML, which leads to better coding practices. XHTML documents have to conform to XML syntax rules (Mallick 321):
One of the advantages of using XHTML is the support for cascading style sheets (CSS) to control document appearance.
XHTML-MP is a subset of XHTML Basic that is recognized by W3C that is designed for mobile browsers. XHTML Basic is, according to W3C’s website, a “document type [that] includes the minimal set of modules required to be an XHTML Host Language document type…It is designed for Web clients that do not support the full set of XHTML features; for example, Web clients such as mobile phones, PDAs, pagers, and settop boxes.” XHTML Basic can be thought of as the minimal amount of modules that is needed to make and support XHTML documents for desktop and laptop browsers, as well as being modular in design so that additional modules, such as the Mobile Profile, can be added to target specific browsers. Note that XHTML Basic is designed from the start to be used by mobile phones and PDAs without any additional modules; the inclusion of the Mobile Profile module increases the functionality of the mobile browser (Mallick 323).