During the spring of 2020 the fifth generation of cell phone systems, 5G, was launched in Sweden where I happen to live. Cell phone operators promise higher speeds and generallt better cell phone service, but in the tech industry there are higher expectations. So what is it we're going to use 5G for?
Before we get to what people want to do with 5G it can be a good idea to think a bit about what it is. On a very general level, a cell phone system needs wireless communication, in the shape of signals to and from a larger or smaller number of cell phones (or smart watches, surfpads, etc.), and some type of core system or network that can pass on information to the ordinary phone network or internet. In between thes two parts are the base stations. For most of us, base stations are the most visible part of the system (with the exception, of course, of our own cell phone). Communication between base stations and cell phones uses electromagnetic waves, generally radio- or microwaves. A "generation" of cell phone systems are a kind of agreement or standard covering everything from which frequencies of electromagnetic radiation are used and how base stations are built to how information sent over the network should look in order to be recognized and correctly interpreted. It is not a matter of a single invention or technological advancment but of an entire package of changes that work together in different ways.
The purely technological change that has gotten the most attention when it comes to 5G is the plan to use higher frequencies for communication, which in itself can make it possible to transfer data at a higher rate, but 5G also opens the possibility to package the information that is to be sent in a more efficient way, restructure the core network and start using transmit and receive antennas with a larger number of antenna elements in the base stations. With more antenna elements it becomes easier both to transmit electromagnetic waves in a specific direction and to distinguish between signals received from different cell phones (it works a little like how you determine a direction using radar). The more efficiently signals from different cell phones can be distinguished, the larger the number of cell phones that can be handled by the same base station at the same time. Compared to earlier generations of cell phone systems, these changes are expected to allow information transfer at a higher rate, space for more concurrent users in high-traffic areas and smaller delays (or latency) in the information transfer.
If you use the 4G network in your everyday life with few or no problems you might ask if any of these improvements are actually necessary. The thing is, the cell phone operators and other actors building the 5G network are not just after catering to the needs of cell phone users today. On one hand, they seem convinced that the type of cell phone users that exist today - you and I on our cell phones, calling and surfing - will come to expect higher speeds and more reliable connections. Maybe we will also use more units per person, such as a cell phone plus a smartwatch with its own SIM card. This is something operators want to be prepared for in order not to lose customers. On the other hand, they are also optimistic about a different way of using the cell phone network in the future - namely, communications between machines.
Imagine that you are driving a car that is equipped with advanced technology to help you as a driver - maybe it is also self-driving in simple situations. Suddenly something changes in the environment - maybe the traffic slows to a standstill or there's a rainstorm that reduces visibility and makes the road slippery. In most cases you will notice these things when you get to them (though I guess Google maps might warn you about the traffic jam). If the cars themselves could send information to each other those who have reached the traffic jam or the rainstorm could automatically warn other cars in the vicinity. If they could receive data from the surrounding infrastructure - transmitters in road signs or something - the cars might receive even more useful information. Is the traffic jam due to construction, for instance, or has the speed limit been temporarily changed on a stretch of road? That kind of information could reach the car itself and appear on e.g. heads-up displays. For a (partially) self-driving car it would make it easier to adapt the driving to circumstances or warn the human driver that they will have to intervene. This would, however, require reliable and fast wireless communication with low latency between a large number of users (cars and infrastructure transmitters). These are some of the things promised by 5G technology, and it is hoped that 5G will improve this vehicle-to-vehicle and vehicle-to-infrastructure communication.
Another frequently mentioned application for 5G is in so-called smart cities, which among other things means having a large number of sensor deployed to collect data on everything from traffic flow to water leaks. The sensors are supposed to be able to communicate via the cell phone network to flag problems or deliver data. There are also people who want to use 5G to improve people's health, for example by using wearable sensors, and to take automation of factories further. This overview from IEEE gives a fairly good idea about what people hope to be able to accomplish (it's also two years old, but a quick search shows that similar ideas are still relevant - see here, here och here).
As is always the case with visions for the future, it is important to remember that no one knows exactly what future developments will look like. Some applications that people have high hopes for will probably turn out to be hard to realize or be less useful than previously thought, and at the same time other ideas will come to the front when people start to use the technology and see the possibilities.
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