Ubiquiti UniFi access point radio tweaking and performance tuning

Trying to tweak the radio setup of my Ubiquiti UniFi access points, I started reading a bit more about how to set the different frequencies. Below is a summary of my reading and a few do's and don'ts.

Do:

• Do start off with default settings of your access points, install iPerf and baseline your initial Wifi speed results
• Download a Wifi analyzer for your smartphone and walk around your house to see which channels are occupied where. Perform a site survey.
• Do regular performance checks if you update settings and compare against the default ones
• Do alternate between different channels in your house for the same Wifi network (e.g. floor 0 on 1, floor 1 on 6 and floor 2 on 11)
• Do stick with the standard 2.4 GHz channels (1, 6 and 11) and set the channel width to 20 Mhz only
• Do stick with the standard 5 GHz channels (36, 40 and 44) and set the channel width to 40 or 80 Mhz
• Do set the Tx power manually, but not too high, as you may be your own source of interference
• Do consider if you need 2.4 GHz for "speed intensive" devices as 2.4 GHz networks can be interefering with each other in high-density areas. I have a 2.4 GHz Wifi network for "non-speed intensive" devices and a 5 GHz Wifi network for "speed intensive" ones. Both have a different SSID, which allows separate VLAN tagging and will never end up in the situation where you're "stuck" on a 2.4 GHz network, while you need higher speeds.
• Do know that Bluetooth, cordless phone and microwaves also operate on the 2.4 GHz band and can thus cause interference

Don't:

• Don't expect speeds of Wifi to match speeds of wired connections
• Don't set the Tx power to high and expect better performance of your Wifi network if there's no reason to, as it can also work against you
• Don't randomly set the 2.4 or 5 GHz channels and channel width
• Don't use DFS (Dynamic Frequency Selection) for 5 GHz as this may interupt channel communication when interference with radar signals are detected
• Don't count on the fact that band-steering will work for all of your devices
• Don't enable the Guest feature on your UniFi, as it will limit speeds. You're better off creating a separate network and SSID for this

What I did change:

• Sticked with one WLAN group (can be Default one)
• Go to devices, click on each AP listed. Under Configuration > WLANs: Create 2 SSIDs with different names in this WLAN group, one on 2.4 GHz with one name and another name for the 5 GHz one.

• Under Configuration > Radios: Set the channel width for 2.4 GHz onto HT20 and for 5 GHz onto VHT40 or VHT80 for each access point. Choose different channels for each AP, or alternate the ones furthest away from each other.

• One thing to further investigate is the Zero-handoff functionality. Well actually, don't use it! As it is clearly recommended by Ubiquiti to just use Fast Roaming, which is available by default. More discussion here.

The wireless network modes for a Linksys Dual-Band router will vary depending on the frequency band(s) you choose to enable. In the 2.4 GHz frequency, the Wifi signal range is divided into channels each at 5 MHz interval. Adjacent channels overlap and will interfere with each other at 20 MHz block. Setting the channel width to 40 MHz network will allow you to use 2/3 of the entire Wifi band. Thus having a higher chance of overlapping and interfering with other wireless networks. Meanwhile, if you set the channel width to 20 MHz, the network will only overlap with the two channels before and after that frequency.
You won't get better speed by doing that change. You may get better signal, but there's a downside to it. Essentially, you will have a higher chance to have collisions with other wireless networks around you. This is because each of these automatically uses +/- 2 channels to the left and the right for HT20, and because neighbour APs can coordinate the spectrum use with your APs. So by selecting ch 1 you instruct your AP to operate on ch 2 and 3 as well, by selecting 6 you tell the AP to transmit and receive on channels 4 to 8, etc.
Dual-band routers essentially give you two access points with each having their own bandwidth in them. Usually one AP will be in the 2.4 GHz range and the other will be in the 5 GHz range. Within each spectrum, there are several Wifi modes that you can enable. The fastest will be Wireless N, with speeds of 300 Mbps. However, that 300 Mbps is shared between all devices connected to that AP.
For example, if you have 5 devices in the 5 GHz AP and one is using up 200 Mbps, then the other 4 devices on the 5 GHz AP will have 100 Mbps to work with. - Source: Linksys

It is important to note that 2.4 GHz and 5 GHz have different characteristics that must be taken into account when deploying dual-band APs (2.4 GHz and 5 GHz capable) access points. The 2.4 GHz signal can travel further and has better penetration capabilities than 5 GHz. Thus the radius of a coverage cell on 2.4 GHz is longer than on 5 GHz. This could lead to dead zones in 5 GHz coverage if only 2.4GHz coverage is measured in a site survey, and will likely require different power settings for each radio to equalize coverage cells. - Source: Cisco Meraki

The 802.11 standard defines 23 20MHz wide channels in the 5GHz spectrum. Each channel is spaced 20MHz apart and separated into three Unlicensed National Information Infrastructure (UNII) bands. Wireless devices specified as 802.11a/n/ac are capable of operating within these bands. In the United States, UNII-1 (5.150 to 5.250 GHz) containing channels 36, 40, 44, and 48 and UNII-3 (5.725-5.825) containing channels 149, 153, 157, 161 are permitted. UNII-2 (5.250-5.350 GHz and 5.470-5.725GHz) which contains channels 52, 56, 60, 64, 100, 104, 108, 112, 116, 120, 124, 128, 132, 136, and 140 are permitted in the United States, but shared with radar systems. Therefore, APs operating on UNII-2 channels are required to use Dynamic Frequency Selection (DFS) to avoid interfering with radar signals. If an AP detects a radar signal, it must immediately stop using that channel and randomly pick a new channel. In the United States, even without the use of the UNII-2 band, 5GHz is well suited for high density deployments due to its greater number of non-overlaping channels. Below is a diagram showing the U.S. 5GHz channel plan. - Source: Cisco Meraki

Is your location close to an area that may contain a weather RADAR?  If so, you may want to consider not using some DFS channels (116-132.)  When RADAR is detected in the area, APs will be forced to move to another channel.  This channel may already be in use by a neighboring access point, causing co-channel interference. Source: Extreme Networks

Other useful links:
UBNT
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