White space is the part of the radio spectrum which has been designated to sit empty between different channels of used space. The intent of leaving empty space in the radio spectrum is to ensure that signals do not interfere with each other. Recently government agencies around the world have been opening the white space up to tech companies to use. This is possible because technology is sophisticated enough that different devices can delineate between the different signals.
In India Microsoft is trying to put that white space to use by connecting users to the web with the empty space. Implementing this plan would require special equipment on the end of the consumer, but Microsoft said they are prepared to give any devices or antenna need to people who want to connect. Putting the white space to use is a common focus of tech companies and has gained the attention of Google and Facebook as well. In the long term it makes sense for these web and software companies to spend the money now in order to connect with potential customers down the road.
Further reading: India, Microsoft, White Space
