What change enabled the range doubling from wifi protocols 802.11g to 802.11n?

Question

I've been recently struggling with bad wifi reception through concrete walls and couldn't help but notice that both the integrated wifi in my laptop (a/g/n) and my phone (a/b/g/n/ac) have far better reception than my old linksys wrt45gs router (a/b/g) despite it having its two standard (yet glorious) external antennas.

I assume the difference has to do with the fact that the router doesn't have wifi-N capability and hence suffers from the limited range of wifi-G: 38m against 70m (!!), according to the wikipedia page on IEEE 802.11. I found explanations about changes that enhanced speed, but none on why such a dramatic improvement of range happend, hence the question:

What change enabled the range doubling (38m vs 70m, indoors [1]) from wifi protocols 802.11g to 802.11n ?

Answer 1

It's primarily due to the standard adding support for multiple send/receive antennas.

There's a lot of math involved that I don't fully understand, but the gist of it is that by receiving the signal from multiple locations that are a known distance apart from each other (ie. two antennas built into a device that are 10mm apart), the receiving client can more or less use the differences between the signals to mathematically compensate for bits and pieces that would have been completely lost in a single antenna scenario.

Here's a good link that probably describes it better than I can.