Wireless LAN Client Devices

The term “client devices” will, for purposes of this discussion, cover several wireless LAN devices that an access point recognizes as a client on a network. These devices include:

PCMCIA & Compact Flash Cards
Ethernet & Serial Converters
USB Adapters
PCI & ISA Adapters

Wireless LAN clients are end-user nodes such as desktop, laptop, or PDA computers that need wireless connectivity into the wireless network infrastructure. The wireless LAN client devices listed above provide connectivity for wireless LAN clients. It is important to understand that manufacturers only make radio cards in two physical formats, and those are PCMCIA and Compact Flash (CF). All radio cards are built (by the manufacturers) into these card formats and then connected to adapters such as PCI, ISA, USB, etc.

PCMCIA & Compact Flash Cards
The most common component on any wireless network is the PCMCIA card. More commonly known as “PC cards”, these devices are used in notebook (laptop) computers and PDAs. The PC card is the component that provides the connection between a client device and the network. The PC card serves as a modular radio in access points, bridges, workgroup bridges, USB adapters, PCI & ISA adapters, and even print servers. The following figure shows an example of a PCMCIA card.
Antennas on PC cards vary with each manufacturer. You might notice that several
manufacturers use the same antenna while others use radically different models. Some
are small and flat such as the one shown in the above figure, while others are detachable and connected to the PC card via a short cable. Some PC cards are shipped with multiple antennas and even accessories for mounting detachable antennas to the laptop or desktop case with Velcro.

Wireless Ethernet & Serial Converters
Ethernet and serial converters are used with any device having Ethernet or legacy 9-pin
serial ports for the purpose of converting those network connections into wireless LAN
connections. When you use a wireless Ethernet converter, you are externally connecting
a wireless LAN radio to that device with a category 5 (Cat5) cable. A common use of
wireless Ethernet converters is connection of an Ethernet-based print server to a wireless network.

Serial devices are considered legacy devices and are rarely used with personal computers. Serial converters are typically used on old equipment that uses legacy serial for network connectivity such as terminals, telemetry equipment, and serial printers. Many times manufacturers will sell a client device that includes both a serial and Ethernet converter in the same enclosure.

These Ethernet and serial converter devices do not normally include the PC card radio.
Instead, the PC card must be purchased separately and installed in the PCMCIA slot in
the converter enclosure. Ethernet converters in particular allow administrators to convert a large number of wired nodes to wireless in a short period of time.

Configuration of Ethernet and serial converters varies. In most cases, console access is provided via a 9-pin legacy serial port. The above figure shows an example of an Ethernet and serial converter.


USB Adapters
USB clients are becoming very popular due to their simple connectivity. USB client
devices support plug–n-play, and require no additional power other than what is delivered through the USB port on the computer. Some USB clients utilize modular, easily removable radio cards and others have a fixed internal card that cannot be removed without opening the case. When purchasing a USB client device, be sure you understand whether or not the USB adapter includes the PC card radio. In cases of a USB adapter that requires a PC card, it is recommended, although not always required, that you use the same vendor’s equipment for both the adapter and the PC card. Figure 4.14 shows an example of a USB client.


PCI & ISA Adapters

Wireless PCI and ISA are installed inside a desktop or server computer. Wireless PCI
devices are plug–n–play compatible, but may also only come as an “empty” PCI card and
require a PC card to be inserted into the PCMCIA slot once the PCI card is installed into the computer. Wireless ISA cards will likely not be plug-n-play compatible and will require manual configuration both via a software utility and in the operating system. Since the operating system cannot configure ISA devices that aren’t plug-n-play compatible, the administrator must make sure the adapter’s setting and those of the operating system match. Manufacturers typically have separate drivers for the PCI or ISA adapters and the PC card that will be inserted into each. As with USB adapters, it is recommended that you use the same vendor’s equipment for the PCI/ISA adapters and the PC card. The above figure shows an example of a PCI adapter with a PC card inserted.