Teaching Points
In this article, you will learn:
- Wi-Fi Channel
- Signal to Noise Ratio (SNR)
- Orthogonal (non-overlapping) vs. non-orthogonal (overlapping) channel
- DFS
- 3 types of interferences
- Co-Channel Interference (CCI)
- Adjacent Channel Interference (ACI)
- Non-Wi-Fi Interference (NWI)
Chief Compaints
- “My Wi-Fi speed fluctuate depending on the time of day.”
- “My Wi-Fi speed suddenly became persistently slower.”
- “I get sudden disconnect.”
- “Sometimes I have to reboot router [a few times] before speed improves.”
Signs/Symptoms
One day, my 2.4 GHz connection working smoothly but another day it becomes persistently slower. Sometimes, one may experience specific time of the day Wi-Fi becomes slower despite wired connection is still working as usual.
Assessment/Diagnosis
Channel Congestion related to Interference
There are many reasons and causes why WiFi could be slow but potentially fixable cause is channel congestion related to inteference. Today, let’s take a look at channel interference and how you can fix it using proper channel selection.
Interference
Interference is un-related signal that degrades your Wi-Fi signal. Since these signal are not part of your desired signal, they may be seen as a noise. Wi-Fi performance speed/coverage depends on signal to noise ratio (SNR) rather than just based on the signal strength of your source AP so minimizing interference is extremely important.
Let’s use audio system analogy here. Interference is anything that degrades your audio due to external source. In a quiet room/environment, you can hear music at lower volume and listen to all intricacy of Hi-Res music. In a noisy environment, even if you max out the volume of a loud speaker, you may barely hear the music and certainly not a detail signature of the audio.
Throughout this article, we will use analogy of audiophile tenants living in a large apartment complex with speakers. The apartment unit has two tower. The North tower unit tenants occupy entire floor. This will be used to show single family, single floor setup. On the South tower, each floor has multiple tenants. This is one floor multiple family setup.
Think each floor level as individual channels in Wi-Fi. Each speaker unit in a room/unit analogous to an access point/router transmitting WiFi signal. So audible audio range of the each speaker unit is basically the Wi-Fi signal range.
The main purpose separating North and South tower design is show whether you have control to all of the speaker sounds you are hearing vs. ones you do not have control over i.e. neighbors.
There are 3 types of interference (ref).
- Co-Channel Interference (CCI)
- Adjacent Channel Interference (ACI)
- Non-Wi-Fi Interference (NWI)
Let’s take one at a time with analogy.