If you're a novice, you'll probably run into a few problems when installing wireless access points (APs) for the first time. To ensure a successful installation, follow the instructions the wireless LAN vendor provides in the box with the AP. Also, don't be reluctant to call on the vendor's technical support people if problems arise.
- Run the initial AP configuration: Generally, you must initially configure the AP via a PC or laptop connected through an RS-232 cable to the AP's console port. Do this before mounting the APs out of easy reach. Most console ports are ANSI-compatible, but you'll probably need your own nine-pin RS-232 cable; vendors normally don't include one.
- Set the Service Set Identifier: The SSID is a 32-character unique identifier that all packets traversing the wireless LAN need in their headers. The SSID acts as a password when radio cards in mobile nodes attempt to join the network. All access points and radio cards in the network must be set to the same SSID. You can choose any combination of characters, but it's a good idea to use meaningful names.
- Set the IP address: The IP address differentiates APs. You need it to gain remote access over the wired network to the AP's configuration screens via Telnet, Web browser, or SNMP. Be sure to record each AP's IP address.
- Perform preliminary tests: Before mounting the AP in its operational location, configure one or more radio cards in mobile nodes and make sure they're able to associate with the AP. Don't forget -- be sure all SSIDs are set the same!
- Mount the AP as high as possible: For example, in warehouses, install the APs on the highest beams.
Orient the antennas correctly: With most antenna propagation patterns, setting the antennas parallel to the ground concentrates the signal power right at the floor. A vertical antenna spreads the signal to a wider area.
When installing APs, especially when you're high above the ground, it's easy to get confused as to which way to orientate the antennas. I remember fixing wireless LAN connectivity problems that had plagued one company for weeks. The AP installation company mounted the APs in the correct location, but the wireless LAN didn't support roaming in areas where coverage was expected. The site survey looked OK; the problem was that some of the AP antennas were orientated parallel to the ground, sending power directly below, but not to other areas. After reorienting the antennas vertically, roaming was restored to the uncovered areas.
- Run tests: After installing all of the APs, you should run tests to ensure that there's adequate coverage and the APs are operating properly. You can use the AP's built-in tests; for example, carrier tests scan the frequency band and make recommendations on which channels to use to avoid interference.
Most APs come with default factory settings that are adequate for most situations, assuming your APs and radio cards are from the same vendor. If necessary, you can change the settings from a PC by accessing the individual APs by IP address using telnet or a browser. For example, you might want to activate optional encryption. For most optional features to work properly, you must activate them on all access points and radio cards.
Next time, we'll take a close look at what's on the horizon: orthogonal frequency division multiplexing (OFDM).