At this point, we have seen some of the fundamental advantages that millimeter wave is poised to offer us from a technological perspective. Those are the advantages that make 5G millimeter wave deployments not just technologically or economically viable, but also commercially lucrative because they can open the doors to many other applications and services that we may not even have thought of before. That brings us to get some detailed understanding of some of the practical scenarios in which we can see millimeter wave networks. We have several examples coming up, but all those examples can be broadly classified, into two umbrellas, outdoor over here, and indoor deployments. Now, outdoor deployments is something that can intuitively make sense to us because most of the base stations that we see around us today are deployed outdoors, either on roofs of buildings or in an open field, etc. A cellular signal existing outdoors is a second nature to us by this point in time. But one might ask, what about the users who are located indoors? The rationale behind that question might be one small point we saw earlier about building penetration loss in that millimeter wave signal can lose maybe 90 percent or even more of its energy, when trying to penetrate through one or more walls of a building that may be made of bricks, plasters, etc. If a millimeter wave signal ends up losing 90 percent or more of its energy when going from outside of a building to inside can we really bank on millimeter wave to provide equivalent performance and all those improvements for indoor users as well? Well, the answer to that question is with some modifications, yes, we indeed can. That is where indoor deployments make their appearance. Now you might ask what are indoor deployments? Well, indoor deployments are where your base station along with the users, also exists at the same indoor facility where those users are going to use the network. But hold on a second. You might ask, how am I going to fit that humongous cell phone tower inside of a building or inside of a concert arena? Well, you don't have to fit the whole structure. There are two types of cells, as we had seen in module 2. There are macro cells that provide a citywide coverage, and then there are small cells that provide a coverage to smaller areas. Small cells, by definition, have only a subset of capabilities as macro cells and as such, they are significantly smaller in their size, their power requirements, as well as their footprints. When people think of indoor deployments, we are by default thinking about small cell deployments. Imagine a movie theater or an office building, a football stadium, concert arena, where your otherwise default option would be to bank on outdoor coverage, coming in with some bare bones, through port, and a latency offering. But with the advent of small cells, you can have a dedicated millimeter wave network inside your venue be it football stadium, enterprise building, etc. Just like you have cell phone towers outside of buildings currently, imagine you have miniature base stations known as small cells residing inside the buildings or inside those football stadiums or concert arena. Because those signals don't have to encounter building propagation loss anymore, virtually all the advantages that outdoor deployments had, the indoor users can leverage pretty much all the advantages using such small cell based indoor deployments. Such possibility of indoor deployments opens the doors to many other scenarios where cellular connectivity would otherwise be difficult or sometimes even unthinkable. But with the advent of small cells and indoor deployments, it is possible to provide an equivalent degree of performance, not just outdoors, but indoors as well which is anyways, where many users spend their time anyways. Now that we have understood the basic difference between outdoor and indoor deployments, let's try to look at some of the real life examples under both categories, wherein millimeter-wave could provide us some unique and promising benefits.
