|My fiber 40Mbps broadband was giving me 38Mbps wifi. But suddenly its dropped to 27Mbps.|
Are you talking about internal or external connectivity here? I suspect external which would mean you performed a bandwidth test online. Is this correct? If not, how then are you checking your bandwidth? If you are using an online bandwidth tester, are you testing during peak, or non-peak hours?
If during peak usage hours, consider that your bandwidth test can, and will be affected by total amount of traffic on the server you're testing on as well as traffic between the server and you. Do bandwidth test during peak hours and you're likely to get a lower reading than if you did it during off-peak hours.
Also, keep in mind that wireless never performs as well as wired network connections. This is due to wireless' inherent susceptibility to lag and latency. Overall, one can expect (on average) to achieve about 85% of their rated bandwidth. The other 15% gets used up in overhead. So to me, 38 Mbps is unusually high for a 40 Mbps rated link.
In my estimation, a 27 Mbps wireless connection is about what I'd expect on a 40 Mbps link. If you consider overhead, a wired connection should be getting (again, on average) about 34 Mbps and I would expect wireless to be significantly less than that.
It matters not how straight the gate,
How charged with punishments the scroll,
I am the master of my fate;
I am the captain of my soul.