Managing Wireless N
Many IT managers think that migrating to 802.11n is a simple proposition: Just install the new access points and off you go. While organizations can expect better performance from 802.11n, the new wireless equipment still must be managed properly. Here are some points to consider:
- Expect your business model to change. A robust 802.11n wireless network will encourage your users to abandon wired Ethernet. Be sure to adjust your business model so you charge enough money to cover the increased use of wireless.
- Be strategic about your use of wireless. For example, even though many printers can operate over wireless today, you may still want to run your networked printers and cameras over the wired network to free up wireless bandwidth for notebook users.
- Use the built-in features in wireless controllers to manage the spectrum. You’ll have to make a decision about how to manage multiple spectrums and protocols. Be aware that 802.11n can use both the 5-gigahertz frequency of 802.11a and the 2.4GHz frequency of 802.11b/g. Most high-end 802.11n APs support a, b, g and n at the same time. Wireless controllers can be great resources when it comes to automatically assigning channels and load balancing the spectrum.
- 802.11n increases capacity, but decreases fast with distance. While 802.11n does deliver five times the capacity, if you want 300 megabits-per-second rates you have to be in the vicinity of the AP. Reusing the cable plant from a previous wireless generation might not be enough to provide the desired coverage.
- Gigabit Ethernet switches that handle both data and power make sense, but there are advantages to midspan Power over Ethernet (PoE) devices. Gigabit Ethernet and 802.3at PoE are often required for full-featured 802.11n performance. While Gig-E is more expensive (twice the cost of Fast Ethernet), you may decide it is worth the extra money to buy a Gig-E switch that supports both data and power. However, midspan PoEs can last for more than one generation of switches, a move that can save money. Another advantage of midspans is that they are designed strictly to manage power. Many of the old midspans don’t support Gigabit Ethernet, so if you move to a Gig-E switch and want to continue using midspan PoEs, make sure your existing midspans can support Gig-E. After all, an AP loaded with two radios could generate net throughput exceeding 250Mbps.
- Enable channel bonding only on the 5GHz spectrum. With 802.11n, channel bonding lets IT managers take two 20 megahertz channels and bond them together, delivering increased throughput. In the 5GHz spectrum, 12 non-overlapping channels are available, while the 2.4GHz spectrum allows for only three non-overlapping channels. It just makes sense to enable channel bonding on the 5GHz spectrum because there’s more space in which to maneuver.
- Plan on moving to the improved security standard. Improvements in data throughput and power management also come with an upgraded security standard, Wi-Fi Protected Access 2 (WPA2). Reconfigure all your clients to support the new security standard.
- Remember that 802.11n APs use three antennas. If you plan to use 802.11n for point-to-point or outdoor coverage, keep in mind that the new APs require three antennas. Network managers used to drill holes to the outside and slip a wire through, placing one antenna at the end. You can still drill holes and run wires, but you have to make room for and enable the three cables.
Philippe Hanset is a network architect in the Office of Information Technology at the University of Tennessee in Knoxville, Tenn.