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Wi-Fi Hardware - Practices

This first chapter from the book Linux Unwired by Roger Weeks et al. introduces radio waves, antennas, connections without wires, Bluetooth, cellular data and infrared. (O'Reilly Media, ISBN: 0596005830, 2004.)

TABLE OF CONTENTS:
  1. Introduction to Wireless
  2. Radio Wave Behavior
  3. Connections Without Wires
  4. Operating Modes
  5. Wi-Fi Hardware
  6. Antennas
  7. Bluetooth, Cellular Data and Infrared
By: O'Reilly Media
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August 09, 2004

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As discussed previously, to make a Wi-Fi network, you need a minimum of two radios, whether you operate in Ad-Hoc or Infrastructure Mode. For PC hardware, there are three physical types of radio interface cards available: PC Card, PCI, and MiniPCI.

Of the three, the PC Card is by far the most common, because notebook PCs are widely deployed, and most have at least one card slot; notebook users are the most common users of 802.11 networks.

MiniPCI cards are the up-and-coming form factor. Many notebook manufacturers have built MiniPCI cards into their motherboards, which enables you to install network cards without using a PC Card slot.

At one time, PCI cards were not as common as the other types of radios, but they are staging a comeback with new offerings from Linksys and D-Link. Many manufacturers, such as Linksys and D-Link, produce some PCI cards now, which actually consist of a MiniPCI or PCMCIA card on a larger PCI card.

There is a fourth option for a growing number of notebook and PDA users: built-in Wi-Fi. Intel is marketing their Centrino chipset that integrates an 802.11b radio on the motherboard, and most notebook manufacturers offer Centrino notebooks. Similarly, other CPU manufacturers such as Via will be integrating wireless into their chipsets. Finally, there are a number of notebook and PDA models that feature built-in radios. Sony, for example, sells a Vaio notebook with an Orinoco radio built in and also sells the Clie handheld PDAs with optional Wi-Fi.

As of this writing, more and more dual-and tri-mode cards are available. These cards allow you to access 802.11a/b/g networks with a single radio. The maker of a radio chipset decides the level of support—as of this writing, support for these cards is still in flux under Linux. We’ll cover this in more detail in the next chapter.

Wireless access points are also available now in dual-and tri-mode. There is a wide range of access points on the market, which range from units geared specifically for home users with built-in firewalls, 4-port switches, and web-based configuration to models aimed at the corporate market with support for authentication protocols such as RADIUS and LDAP, the ability to run via Power Over Ethernet (POE), and connectors for external antennas.

Another category of access point is the “hotspot in a box.” With the rising popularity of Wi-Fi hotspots in cafes, hotels, and airports, many manufacturers have developed access points that are an all-in-one solution. These boxes provide the radio and Ethernet of a normal access point, but also have some form of authentication and payment system, which range from a web-based login to a printed coupon that the store clerk delivers to the customer.  

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