@nyonyo 

Because of the nature of wi-fi media - it is a half duplex technology.

More details - https://wififorbeginners.com/2016/12/05/wi-fi-secrets-part-1%E2%80%8A-%E2%80%8Awired-is-faster-than-wireless-networking/

That means the theoretical bandwidth for N150 - 75mbps, for N300 - 150mbps.

Given the wireless interference, obstacles and the distance between devices it's usually even lower.

@nyonyo 

Let me clarify some details.

In my post I was talking about the real bandwidth between a wireless client and the router.

What you're talking about is the negotiated wireless connection speed between the wireless device and the router.

In wireless connection properties you'll be able to see 150mbps/300mbps (for N150/N300) in ideal case.

It depends on the device you're testing with, the distance between the device and the router, any obstacles, wireless interference around you, etc.

Here's a screenshot of negotiated wireless connection speed between a laptop and the router:

In my previous post I was explaining that the real bandwidth in this case will be no more than 390mbps.

@nyonyo 

Read through this FAQ.

Also you can check these stories:

Theoretical wireless rate and actual wireless rate

802.11 Wireless Rate Calculation

And you should be able to find your answers.