Why do we need a new generation of mobile network? That is the question we will answer in this video. We will take four service examples and analyze which part is the most important for quality of service. First, let's imagine someone wants to download a film on a high definition screen. The film involves five gigabyte file, or four times ten to the tenth power bits. How does that work? Very simply put. A request is sent by the terminal to the server, and then the film is transferred as a series of packets. All of the packets together make up the file. If each packet is received 100 milliseconds after it is sent because it crosses the network, the total time to load is, first of all, 200 milliseconds, the time for the request and the first return packet arrive, which make 0.2 seconds. Next, at 10 megabits per second, we'll have a total duration of 4,000 seconds plus 0.2 seconds at the beginning, totaling 1.1 hours. At one gigabits per second, the duration is 40.2 seconds. As our case, we see that the time that the first packet takes to cross the network is negligible compared to the total transfer time. What counts is quality of service, which comes down to speed. The rate perceived by the user can be defined as the number of bits correctly received by the receiver in a given time frame in average reception conditions. What does that look like in 4G? It typically means 10 megabits per second. That means my film will take over an hour to download. That's too slow. Let's take another example. The factory of the future with an automated production line. In that scenario, we could imagine that the computer that controls the robots would regularly send small packets. For example, a 56 byte control packet would be sent every two milliseconds. So that's 56 times 8 divided by 2 kilobits per second, or a rate of 224 kilobits per second. We don't need a very high bit rate. On the other hand, we clearly don't want a packet to take 100 milliseconds to arrive. Each would arrive much later than the robots reply, which wouldn't be a reply in that case. What really matters is latency. That means the length of time between the source sending a small packet and the receiver receiving it. 100 milliseconds is not possible, even if we had 100 gigabits per second. The goal is to have one milliseconds of latency. What do we get with 4G? A latency of at least 10 milliseconds. Third example, so-called intelligent transport systems, more precisely connected vehicles. More and more vehicles are communicating either with other vehicles or with an infrastructure. For example, support service can be provided, if there is a blind intersection. An ambulance arrives and the driver needs to be alerted that there is a risk of collision so he or she can break on time. The system should be reliable. What counts is that the information sent by the vehicle is correctly received by the surrounding vehicles. So reliability can be defined as the probability of correctly transmitting a few bits within a given timeframe. The goal, for example, is for 32 bytes packet to be sent in less than three milliseconds, in 99.999 percent of cases. What do we get with 4G? Typically, in 50 milliseconds, we have a delivery probability of 99.9 percent when we have network coverage. So 4G is not adequate. Another example with smart objects. For example, connected mailbox. As soon as the mail worker has put the package or later in the mailbox, a short message is sent to the owner of the mailbox. The owner receives one, two, or three messages per day at most. A message can be sent in 10 seconds or even in a minute. It's not a problem. It's not a question of data bit rate or of latency. On the other hand, we expect to see a huge increase in the number of connected objects with connected clothing. For example, connected homes, connected container, or sustainable agriculture with sensors that help farmers add up the amount of fertilizer required. We expect to see a huge number of smart objects in the future. What is important is the number of devices per surface unit, so per square kilometer. The aim is to be able to handle one million smart objects per square kilometer. What do we get with 4G? 4G is able to handle around 100,000 possible connected objects per square kilometer. We can see from these four examples, that the different services do not have the same constraints in terms of performance. The important constraint might be the speed perceived by the user for downloading files. I mean the data bit rate or latency in industrial communications or reliability in vehicle communication or for connected objects, that connection density. Obviously, several criteria might be involved in a certain service. For example, latency and reliability. We have seen that 4G was not able to meet all user needs, so the question is, is it possible to have a system that meets all of these needs? That's what we will see in the next video.
