Before smartphones, there was little interest in mobile wireless broadband. Mobile operators only had to carry voice signals and a low data rate of 8-10 kilobits per second was more than enough for that. So from 1G to 3G, operators focused instead on improving their economics, by increasing how many calls can be made within a particular cell with the same amount of spectrum. Then in the mid-2000s came the smartphone, which turned wireless broadband into a real customer demand. Which meant drastically raising data transfer rates. But how are operators going to do that without buying vast sums of bandwidth? Or pumping huge amounts of power into the signal? What the industry devised and adopted was deviously clever. In this video, the story of Multiple-Input, Multiple-Output or MIMO.