A lot of the wireless companies' 5G experimentation is taking place in super-high frequencies -- as high as 73,000 MHz. Today's cell phone networks broadcast signal in a range of 700 MHz to 3,500 MHz.

The advantage of high-frequency signals is that they're capable of providing significantly faster data speeds. The disadvantage is that they travel much shorter distances and they can't easily penetrate walls. That means thousands -- perhaps even millions -- of mini cell towers, or "small cells" would need to be placed on top of every lamp post, every building, inside every home and potentially every room.

That presents a host of problems. How can cell phone companies possibly process all that data? There are companies, such as Google's recently acquired Alpental, that are working on those "backhaul" issues. But they're not so close to a solution, according to Akshay Sharma, wireless infrastructure analyst at Gartner.

That's why 5G might complement 4G, rather than outright replace it. In buildings and in crowded areas, 5G might provide a speed boost. But when you're driving down the highway, 4G could be your only option -- at least for a while. (from CNN)