10 Tips and Tricks for a High-Performance WLAN Video Transcription:
Hi there SecurEdge fans. Welcome to another edition of our Whiteboard Wednesday. This week we’re going to chat about wireless network design, specifically highlighting ten tips and tricks you should use to design and configure a high-performance wireless LAN (WLAN).
The first tip we would like to share with you is to design for 5 GHz as primary coverage. The 5 GHz band provides 8 times the capacity of 2.4 GHz and is the least congested of the radio bands with up to 25 channels to use. 2.4 GHz should only be considered as secondary for devices that lack 5GHz capability since it is limited to just 3 channels to use.
Another tip we would suggest is defining your coverage goals. Coverage that is too aggressive can lead to co-channel and even adjacent channel interference or contention, too conservative of coverage and the result can be poor client performance due to inadequate signal strength and RF deficiencies in areas. A signal strength of -67dB is the current standard to target in support of low power mobile devices like phones and tablets.
We would also recommend Placing APs Where Users are Located. In-room placement is best for client performance, avoid hallways, if at all possible, unless it is required for voice roaming or location tracking. The idea is to get the APs closest to where the devices are being used.
Another tip we would recommend is to Tailor Coverage to the facility. Utilize RF obstructions like walls, doors, stairwells, elevator shafts to attenuate the signal between APs to minimize channel re-use. Consider using proper antennas and orientation for optimal signal propagation. Don’t fall victim to thinking that omni-directional antennas are the solution for all situations.
We would recommend Fine Tuning your AP Power Levels. On-site signal measurements of RF propagation through construction materials should be gathered and used to tune the system. Consider your AP density and channel re-use requirements. Adjust the power levels for link symmetry with devices that are in use and always design to include the lowest power device like a mobile phone or tablet.
We would also recommend Disabling 2.4 GHz Radios if Necessary. Disabling some of the 2.4GHz AP radios can prevent co-channel interference and still provide some additional bandwidth to the WLAN.
Another tip we would suggest is to Design and Validate with Representative Client Devices. What I mean by that is spot-check the WLAN with actual client devices to ensure the design matches your actual client performance, alternatively, measure with a standard RF site survey adapter and compensate the signal based on actual client device characteristics. Ensure that devices are running same firmware and/or drivers. The same device but with different firmware or drivers can result in differences of signal levels of 15dB or 20dB.
Another tip or trick that we want to make you aware of is that Higher AP Density Requires Smaller Channel Widths. Use 20 MHz instead of 40 MHz in areas where AP density is high. This reduces co-channel and adjacent channel interference and shared channel capacity between clients. It also reduces client contention and improves network stability. Never use 80 or 160MHz channel widths unless APs are extremely RF isolated and/or the AP count is 4 or less. Beware that many manufacturers ship their products with these bonded channels settings as the default when in fact they should rarely ever be used.
Another recommended tip or trick is to Disable lower data rates to improve network performance. Removing the legacy data rates of 1-11Mbps from the WLAN is helpful. These data rates are only used in support of legacy 802.11b clients which for the most part are no longer in use. Leaving these data rates enabled can negatively impact network performance. Disabling these data rates reduces overhead on the WLAN and forces clients to connect to APs closer in proximity to themselves. By connecting to closer APs “sticky client” issues are avoided which is where client devices choose to connect to APs that are too far away to support symmetrical TX\RX operations. Perform this for both the 2.4 & 5GHz radios.
Minimizing the Number of SSIDs is a tip or trick that we use in the field always. Network overhead increases with each SSID that is broadcast. We recommend no more than 4 SSIDs in a given RF domain. Make sure your WLAN solution supports multiple authentication methods for an SSID so that you can collapse your SSIDs based on mutual supported authentication mechanisms. In some situations, the overhead from all the SSID’s being broadcast consumes so much of the airtime that the remaining bandwidth is too little to support client operations.
Finally, we would recommend Enabling DFS Channels in 5GHz Spectrum. If your WLAN isn’t near any airports, military radar installations or Doppler weather radar (TWDR) sites you can use the 5GHz DFS channels 52 through 144 for indoor installations. This can provide up to 13 additional channels for use. Keep in mind that more RF channels is equal to more bandwidth. Also, avoid channel 144 from this range unless you have a very dense AP deployment, or you can verify that all your devices support this channel. Devices that do not support channel 144 still do exist and using this channel essentially disables their access to Wi-Fi.
Ok, That’s all I have for this week’s Whiteboard Wednesday on Wireless Design. I hope you are able to make use of these tips and tricks and thanks for watching. If you have any questions or comments please leave them below for us in our comments section.