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Every network is different, but following a few simple guidelines will help optimise 802.11n networks to achieve maximum performance and resiliency. Ben Wilson of Xirrus looks at what it takes to successfully install and operate resilient, high performance Wi-Fi networks.


and have more configuration options than legacy 802.11abg networks. There are five key parameters to help optimise the


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performance and resiliency of 802.11n networks: Site surveys: Executing an on site site survey with actual products prior to deploying Wi-Fi equipment is important because it lets the network administrator know exactly where equipment needs to be placed – removes the guess work and identifies exactly what product, cable pulls, and switch ports are needed. It is also important to note the following: 802.11n networks use multiple input multiple output (‘MIMO’) to increase throughput and network performance, but can be affected by walls and other objects. Because of MIMO, 802.11n RF propagation can be significantly different than traditional 802.802.11abg networks. A site survey should be completed to test the RF characteristics of the environment prior to deployment. Operating 802.11n in the 5GHz band is a key


requirement to fully realising the benefits of 802.11n due to the additional channels and cleaner spectrum. When doing site surveys, it is important to study both the 5GHz and 2.4Ghz bands, as 802.11n can operate in both, and both should be used to support a wide range of client devices. -72dBm is recommended to ensure that multiple radios


are available at a sufficient RSSI level. It is important to survey for at least two radios at all locations, ensuring that at least one 2.4GHz and one 5GHz are visible, though two 5GHz radios would be better. Device placement: Use multi-radios Wi-Fi arrays so


that large numbers of users do not have to share a single radio. Set the cell size so that a minimal number of users are at the fringe of the cell. Don’t assume a lower network device count when designing 802.11n networks. Creating large cells is not recommended for an 802.11n design when high performance is desired. Security: With any wireless network, a key concern is


security. Using WPA2/AES encryption is recommended for 802.11n deployments – anything less is a compromise on security and performance. Also, legacy 802.11abg monitoring tools may not catch all of the threats for a 802.11n network, so if the network is migrated to 802.11n, the monitoring tools needs to be migrated as well. Wired switch network: In many networks, legacy access points are plugged into 10/100 Ethernet ports, which


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hile it may sound obvious to most, proper planning is crucial to deploying an 802.11n network, as these networks are more often used as the primary network connection


makes sense when using 802.11abg devices. However, this creates issues with 802.11n due to the increase in bandwidth and throughout. 802.11n Wi-Fi arrays should be plugged into Gigabit Ethernet switch ports to take full advantage of the throughput improvement of 802.11n. It is possible to minimise the traffic load from 802.11n networks at the core by processing as much traffic as possible at the edge, as well as ensuring the core is capable of seeing an increase in data traffic. Power: Most wireless networking devices are powered


through Ethernet cables using Power over Ethernet (PoE), and so it will be wise to use power injectors that are able to take full advantage of 802.11n performance and functionality, as well as being prepared for future 802.11n technology advances. 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’s


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. In high density, high performance user environments,


such as universities or hospitals, using non-bonded 20MHz channels may improve overall performance. 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.


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