Wireless PANs

As we continue to distribute intelligence into smaller and smaller devices and everyday accessories, the area domain of the network is reduced, until it rests upon our very selves, in the form of PANs. Many approaches to PAN are under investigation and development, including the use of our own human energy fields to create a low-power network to provide connectivity between the badge-based computers, smart wearables, and implants that are on or in the person.

A wireless PAN is a network that serves a single person or a small workgroup. Limited distance, limited throughput, low volume, and peripheral sharing are characteristics of PANs. Today, PANs are generally used to transfer data between a laptop or PDA, or a desktop machine or server, to a printer. They also provide support for virtual docking stations, peripheral sharing, and ad hoc infrared links. Future applications will grow to embrace wearables and will rely on human energy fields to power badge-based computers. At the moment, wireless PANs largely use infrared links, but that will change as intelligence begins to migrate onto and into the human.

The main PAN standards today, as discussed in the following sections, include Infrared Data Association (IrDA), Bluetooth, and HomeRF. Technologies such as Bluetooth and HomeRF are expected to be deployed in dual-mode smart phones that we'll be able to use to download e-mail and Web data while on the road and then exchange that data with a laptop or desktop machine in the office.

IrDA

The IrDA standard is sometimes referred to as point-and-squirt because it allows you to point your notebook at a printer and squirt the document via the air, rather than requiring a cable. IrDA operates at 115.2Kbps but is moving toward 4Mbps, 10Mbps, and 20Mbps rates. Low cost, low power, and high noise immunity are characteristics of IrDA, which is standard on many notebooks and printers.

Bluetooth

Of great interest at the moment is a standard called Bluetooth, which was the joint effort of 3Com, Ericsson, IBM, Intel, Lucent, Microsoft, Motorola, Nokia, and Toshiba. It involves a very low-cost chip, ideally at US$5. (That's not to say it's there already. We're still probably more in the US$10 to US$20 range, but the idea is to get it down to about US$5 a chip and embed it in everything around you.) Bluetooth would give each device a short-range wireless capability. It operates over a 100-foot (30-meter) coverage area, so it's a technology that would allow personal digital assistants, laptops, cell phones, and any intelligent appliance embedded with such a chip to communicate and be linked wirelessly. We're looking at supporting 1Mbps by using FHSS in the 2.4GHz band. One synchronous channel can be configured either asymmetrically or symmetrically. With asymmetric arrangements, you get 721Kbps downstream and 57.6Kbps upstream; with symmetrical arrangements, you get 432.6Kbps in each direction. Bluetooth also offers up to three asynchronous channels, at 64Kbps each.

Bluetooth standards include authentication, encryption, forward error correction, and automatic request for retransmission. More than 2,000 manufacturers have joined the movement. Bluetooth is an important standard, particularly to the realm of pervasive computing, and, again, this emphasizes the inevitable requirement for a wireless home area network (HAN) between your other options that you'll need for high-speed entertainment and computing networks. (Chapter 15 "The Broadband Home and HANs," discusses HANs.)

HomeRF

The HomeRF standard was developed by the HomeRF Working Group, which was founded in 1998 by Compaq, IBM, Hewlett Packard, and others. It uses Shared Wireless Access Protocol (SWAP) and provides an open standard for short-range transmission of digital voice and data between mobile devices. It transmits in the 2.4GHz band and uses a frequency hopping technique. Up to 127 devices can be addressed within a range of 150 feet (46 meters), and HomeRF supports a data rate of 1Mbps to 2Mbps.

For more learning resources, quizzes, and discussion forums on concepts related to this chapter, see www.telecomessentials.com/learningcenter.