One day, my friend asked me, "Why my mobile internet suddenly slow in speed?" He said, "I have bought the best data plan, and usually, the internet speed is great!"
Then I asked him, "How many signal bar are there on your phone?" He replied, "Full signal", and had already tried turning off/on cellular data, even rebooting his phone.
I tried to estimate the connection between the problem and my knowledge about wireless connections.
Here's my analysis check lists:
1. The issue only occurred in one day or specific time
2. Full signal
3. His mobile data plan is good
4. All troubleshooting efforts have been exhausted
From the four parameters above, I think he has a good understanding of how to check the internet connection.
At last minute, I remembered the time when the problem occurred and related it to the technical specification of mobile internet and wireless connection.
I also remembered him saying that the problem usually occurs on Sunday night, that there's a lot of nightlife near his house, with even more people coming to the area.
Then I connected it to the analogy of a single source electrical circuit, where the current would be split between several parallel resistors.
And I discovered the root cause of this problem, overloading the single source.
I explained it to him. He said it made perfect sense and said, "I understand what you mean".
Here's full explanation about the problem: Why Is My Internet Slow? Common Causes and How to Fix Them
Thank you