EXPERT RESPONSE
Wi-Fi Alliance certification of 802.11n draft 2.0 products and IEEE ratification of the final standard are expected to foster a new generation of wireless LANs.
Enterprises that have dabbled in best-effort Wi-Fi for email and Web access may tap 802.11n to deploy bigger, more comprehensive wireless deployments to support broader business applications. Those making more extensive use of Wi-Fi today but feeling cramped by performance and operational issues may upgrade their networks to 802.11n to improve speed, capacity, and coverage.
Next generation WLAN products will take advantage of 802.11n features. But, like most standards, 802.11n is chock full of options. Which options are the most important? That really depends on your business and how you're trying to use wireless. But here are a few recommendations that could apply to many 802.11n deployments:
- All 802.11n APs have multiple transmit/receive antennas, but the number of antennas and how they are used varies. The more antennas that a device transmits through simultaneously, the higher its maximum data rate. If high-throughput applications like video are important to you, then look for more transmit antennas (e.g., 3x3 instead of 2x2 APs).
- Extra antennas can improve reliability by sending the same signal redundantly through multiple antennas. If multipath is a significant issue in your location, then look for APs that can use extra transmit antennas for space-time block coding (e.g., 3x2 instead of 2x2 APs).
- 802.11n APs can use 20 or 40 MHz wide channels in either the 2.4 or 5 GHz band. Most existing Wi-Fi clients use the three non-overlapping channels in the 2.4 GHz band. If you plan to use 802.11n only for new devices and new applications, then reduce competition and interference by purchasing new APs and clients that can use 5 GHz band and 40 MHz channels.
- 802.11n APs can operate in several modes, including a Mixed Mode for compatibility with 802.11a/b/g WLANs. If you plan to deploy 802.11n in the same area as older a/b/g WLANs, determine how well your new AP performs in Mixed Mode and whether it supports Phased Coexistence Operation (PCO).
- 802.11n MAC layer enhancements can make more efficient use of available bandwidth. For busy WLANs, choose APs that support 802.11n frame aggregation options that bundle more data in each frame to reduce overhead.
- 802.11n AP coverage is harder to predict and changes more frequently. 802.11n channel allocation is also more complex. Built-in RF management tools that can automatically adapt your WLAN to its surroundings are important, as are planning tools that understand your new AP's capabilities, where to place them, and how to best configure them.
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