Organizations that want to upgrade their existing 802.11b infrastructures will need to maintain backward compatibility; few can justify trashing their 802.11b equipment in favor of new 802.11a products. One option is to overlay single-mode 802.11a access points on the current 11b wireless network, but that setup can be unwieldy and expensive. Dual-mode APs, on the other hand, are easier to manage and cost far less than doubling up 802.11a and 802.11b APs.
You can simplify new installations of any kind that require 11a/11b coverage--SOHO, enterprise or hot-spot settings--by using dual-mode APs.. For example, organizations that don't have WLANs (wireless LANs) may want to provide hot zones to cover conference rooms or cafeterias; a dual AP is ideal for this scenario. In addition, some of the devices tested add value by providing upgrade paths to 802.11g and beyond (see "802.11g Adds to the Mix").
Of course, there's a catch: The propagation characteristics are vastly different among radios, and, save for a few of the APs we tested, 802.11b coverage is far greater than that of 802.11a. In a dual-AP environment, proper design of 802.11b cells would leave large dead zones between 802.11a cells. This can be fixed by lowering the output power of the 802.11b radio, if the AP allows, so that the coverage areas are concentric, or by supplementing the patchy 802.11a network with single-mode 11a APs. Either way, this problem affects every dual-mode infrastructure and, while it will require time and money to solve, the cost for doing so is usually less than that of overlaying 11b and 11a devices.
Another big concern for wireless network administrators is security. Unfortunately, none of the APs we tested offers a groundbreaking solution.
By the Numbers
In a Q302 ReefEdge survey of 935 IT networking and security professionals:
1st Position of 'security' on list of concerns
3rd: Position of 'cost' on list of concerns
9th: Position of 'interoperability' on list of concerns
57: percent said they have a wireless LAN deployment
85: percent of the remaining 43 percent said they have plans to deploy a wireless LAN within the foreseeable future
Although WEP (Wired Equivalent Privacy) is a good basic security precaution because it's easy to implement and doesn't cause a performance hit, WEP's days are numbered. Most vendors promised that WEP's pending successor, WPA (Wi-Fi Protected Access, see an overview), will be supported through free firmware upgrades, but only Cisco provides a stand-in for the moribund WEP--TKIP (Temporal Key Integrity Protocol).