Wireless 101

Before we dig into the wonders and fun of AirPort, let's get acquainted with the general cast of characters in the current wireless scene. This includes Bluetooth, which you've probably encountered, even if you weren't aware of it.

Bluetooth

Bluetooth is a wireless specification common in PDAs, cell phones, keyboards, mice, MP3 players, and computers. Bluetooth is intended as an IrDA (short for Infrared Data Association, a trade group that codifies the infrared standards) replacement for using wireless peripherals, rather than an AirPort competitor for creating wireless networks of computers.

Bluetooth operates over the same 2.4 gigahertz (GHz) radio band as AirPort; though they use different modulation schemes to communicate, there is a real, yet minor, possibility of interference. Bluetooth devices can communicate from up to 30 feet away, and the signal can be boosted to extend its range to 300 feet. Bluetooth version 1.1 communication speeds run from 720 kilobits per second (Kbit/s) to 1 megabit per second (Mbit/s). More recently, the Bluetooth 2.0+ Enhanced Data Rate (EDR) specification has emerged, which offers a transmission speed up to three times faster (up to 3 Mbit/s) when used with other Bluetooth 2.0–compliant devices, yet is backward-compatible with older Bluetooth 1.1 devices.

Each Bluetooth device has its own profile that determines its capabilities, limits, and functions. When a Bluetooth device is not connected to another device, it checks about once a second for other devices on 32 predefined frequencies. Whenever another device comes into range, the two devices negotiate and establish what is called a piconet. If more devices come into range, piconets can join together and form scatternets.

Mac OS X 10.2.1 or later includes Bluetooth software. Bluetooth 2.0 hardware is built into all current PowerBook G4 computers as a standard feature and can be integrated into iBook, iMac G5, eMac, Mac mini, and Power Mac G5 computers as a build-to-order option. All Macintosh desktop and portable models with built-in Universal Serial Bus (USB) and Mac OS X 10.2.1 or later can take advantage of Bluetooth technology using a third-party USB adapter.

Wi-Fi

Let's get through the technical jargon right away: The Institute of Electrical and Electronics Engineers (IEEE) 802.11 standard is called Wi-Fi (wireless fidelity) or wireless Ethernet. The standard was developed to provide the benefits of Ethernet (802.3) networks without wires. Since the release of the initial 802.11 standard, it has been enhanced to make it faster, more compatible, and more secure. The most popular implementation of this technology currently is 802.11b (which Apple simply calls AirPort), an 11 Mbit/s standard in use all over the world. To satisfy the demands for even faster communications, a new 802.11g standard (which Apple calls AirPort Extreme) has been released with a maximum speed of 54 Mbit/s.

Devices based on the 802.11b and 802.11g standards are compatible with one another, so older products can communicate with newer products but do so at their maximum 11 Mbit/s data rate.

Both 802.11b and 802.11g networks operate in the popular 2.4 GHz frequency band. This frequency of radio waves passes readily through solid objects such as walls but is somewhat subject to interference from devices such as microwave ovens and cordless phones. However, instead of breaking the connection entirely, interference generally causes the Wi-Fi devices to automatically fall back to slower, more reliable data rates.

Because Apple has adhered to industrywide standards, Macintosh computers equipped with AirPort or AirPort Extreme can be used on almost all Wi-Fi networks, and third-party Wi-Fi devices. The Wi-Fi networks and devices can usually be used with Macintosh computers but may require special drivers or different setup utilities. Another advantage of Apple's adherence to industrywide standards is that Windows PCs and laptops can easily join Wi-Fi networks created with the use of AirPort, AirPort Express, or AirPort Extreme base station hardware. For simplicity's sake, this lesson focuses on Apple-branded AirPort solutions. Almost all Macintosh computers introduced since mid-1999 are capable of using AirPort, provided they have the necessary hardware (an AirPort or AirPort Extreme Card or AirPort, AirPort Express, or AirPort Extreme Base Station) and software (included as part of the operating system).

Power over Ethernet (PoE)

This recent standard, known formally as IEEE 802.3af, allows low-power network devices to receive DC power directly through the Ethernet cable, eliminating the need to connect a separate power supply to the device. This feature makes it feasible and cost-effective to install low-power Ethernet network hardware (such as Wi-Fi base stations or web cams) in locations where there is no AC power outlet nearby, such as in a ceiling crawlspace.

Several vendors now sell Ethernet network hardware, such as hubs, switches, and patch panels, that support the PoE specification. When this hardware is installed in a network, each supported Ethernet port will superimpose DC power directly onto the Ethernet data wires. Other network products that also support the PoE standard can then be connected and also powered by this DC power using normal Ethernet cabling, accomplishing two tasks (power supply and data connection) with a single connection.