Lessons Learnt From 802.11n Wi-Fi Deployments

RF Design

Probably the most obvious reason for an 802.11n network is the increase in network performance.  An 802.11n network will always perform higher than an 802.11abg network; however, there are some design decisions to take into consideration.

802.11n is the first Wi-Fi standard that is able to operate in both the 2.4GHz and the 5GHz bands, but 5GHz has many advantages over 2.4GHz, including less congestion, more available channels, and higher throughput.  Making the move to 5GHz is easy as nearly all enterprise laptops support 5GHz.

Be sure to purchase laptops that allow the radio frequency to be selected in software rather than fixed at a certain frequency.  Further, when moving to 802.11n, don’t expect to support more users per radio, as the goal of deploying 802.11n should be to get more bandwidth per user.  Because wireless is a shared medium, total performance of a radio will drop as more users are added.

Another significant feature of 802.11n is channel bonding, which takes two 20MHz channels and combines them together, forming a single 40MHz channel – effectively doubling the bandwidth.  Use of bonding effectively cuts the number of available channels to use in half, and so is most practically implemented in the 5GHz band where many more channels are available.  In the 2.4GHz band, with only three non-overlapping channels available, bonding is only possible on one pair of channels.  (Due to this channel limitation and the interaction with legacy Wi-Fi clients, bonding is not recommended in the 2.4GHz band.)

In high-density, high performance user environments, such as universities or hospitals, using non-bonded 20MHz channels may improve overall performance.  We have found that some clients may not operate properly with bonded channels and as a result the network should be designed to handle these clients by turning bonding off on certain radios, or even entirely.

Final Thoughts

To achieve a high performance network capable of replacing wired switches, a multi-radio, 5GHz 802.11n Wi-Fi network will provide the best results. The overall network must be appropriately designed, from the supporting wired network, to wireless device placement, to the RF design.  Stations should be capable of operating at 5GHz to take full advantage of 802.11n functionality and achieve maximum performance.

With a properly designed 802.11n Wi-Fi network, IT managers now have the ability to deploy wireless networks that can replace their wired networks. Existing wired network budgets can be reallocated to wireless equipment that, with proper design, will deliver similar end-user experience but with all the flexibility and mobility benefits wireless brings.

Ben Wilson is UK Country Manager for Xirrus