5G is being deployed, let’s go back to what differentiates it from previous generations of telecommunications.
Messages can be transmitted using electromagnetic waves. For example, a cell phone exchanges messages with a radio station most often located at the top of a pylon or on a roof. For this, waves of different frequencies are used; lower ones propagate farther, higher ones require smaller antennas; even higher ones are used very little at the moment.
The first cellular networks were analog. They went digital with 2G, which also introduced SMS. With the new millennium, 3G has brought mobile telephony into the Internet world. With much higher speeds along with the explosion of smartphones, 4G has brought good definition video.
Every 10 years or so, a new standard and a new generation of cellular telephones arrive which transform uses; recently it was 5G.
Since the arrival of 2G, we have witnessed an exponential increase in data transported by the network, and a massive increase in the number of connected objects (telephone, television, remote monitoring, connected cars, etc.). This is enabled by scientific and technological advances which have improved the “pipes” through which data circulates. In fact, uses absorb everything that technology offers. It should be noted that the essential part of this connectivity comes from the optical fiber, which we will not discuss.
Cellular telephone technologies have provided efficient and affordable solutions for global communications service coverage, connecting remote locations, rural areas, road or rail transport routes. In this, they participate in reducing the territorial digital divide.
5G is causing real disruption. We would like to point to a scientific breakthrough at its base, but in fact it is based on a whole range of innovations. The world of the cellular telephone is a world of standards: it works because the operators agree, in a framework called 3GPP, on standards which will allow, for example, a packet of bits to pass. from your phone in the heart of New York, to a friend’s computer in her office in Rio. This requires bringing together a whole package of scientific and technical advances before launching a new standard. 5G is therefore more like a multi-blade knife, where each blade is either a techno coming from 4G, but improved, or a new techno that came out of the labs in the last ten years.
The functionalities of 5G
5G will allow technical improvements mainly in four directions: throughput, latency, density and virtualization.
A very visible aspect in cellular communications is the amount of information exchanged in a unit of time: the throughput. If the bitrate is too low, I can’t watch a movie, or I only do it with very poor quality. With 5G, you can expect “peak throughput” to be up to 10 times that of 4G, almost that of ordinary fiber optics. In fact, speeds will especially increase with new frequencies that mobile telephony will colonize with 5G, which are high frequencies between 1GHz and 6 GHz and even higher frequencies called “millimeter” above 6 GHz.
But let’s not dream: in the cell phone, we share frequencies between the different operators, and for each operator with the people around us: the neighbor who watches a rugby match, the neighbor who spends her evening on a network video game , etc. So what are our users going to observe? We will see the situation improve in very dense areas where cellular networks are already saturated or would be in the short term without 5G. We won’t really see a change in the low-density areas already covered by 4G, perhaps faster video downloads.
The second direction of improvement is latency, that is to say the time for a round trip between the phone and the application server, which is now counted in tens of milliseconds. With 5G, we will measure latency in milliseconds. To watch a movie, it doesn’t matter. But for a video game, for augmented reality, to perform a surgical operation remotely, it can make the difference between possible and impossible. The goal is for the whole system to offer much greater responsiveness together with a strong guarantee of message transmission.
The third dimension is density. We are talking about machine-to-machine communications and services requiring a massive number of low-energy, low-speed objects (the Internet of Things). One of the objectives is to be able to manage a million objects per square kilometer. In this dimension, 5G is in competition with so-called 0G techniques such as Sigfox and Lora. Traditionally, for the communication of objects, we distinguished between cheap, low-end objects, which used 0G, and objects more demanding in 4G. 5G claims to be able to cover the entire range with the same standard.
Be careful, all this will not happen overnight. 5G is coming in stages, because new radio components have to be installed everywhere, but also because, in order for it to function at its best, the software of the “network cores” will have to be transformed.
Energy efficiency has been a goal since the early days of 5G design. A break with previous generations is announced. We are aiming for a division by at least ten of the energy cost of the gigabyte transported. As we will see, this does not prevent legitimate fears about the effect of this technology on the environment.
For computer security, the subject is mixed: it is taken into account more than for 4G, which improves things. On the other hand, the surface of the possible attacks explodes as we will see it, in particular because of the extension of the software aspects of the networks, opening the door to other possibilities of attack. In fact, security control moves from hardware to software. In addition, this leads to real-time monitoring to detect attacks and be ready to remedy them. The increasingly massive use of artificial intelligence is complicating the task: on the one hand, because network software based on this technology will behave more difficult to predict, and on the other hand, because the attackers themselves will be able to press the AI. Conversely, attack detection systems may also include AI.
As for the scientific and technical innovations on which 5G is based, they can be grouped into two classes: radios and software.
Software technical innovations
Traditionally, telecom networks rely on dedicated machines: different levels of routers, firewalls, etc. The idea is to transport this to software architectures like those of web platforms. We are therefore talking about convergence between computer systems and communication systems. Aside from the purely electronic radio components, as soon as we go digital, we place ourselves on a network of generic machines (calculation, storage, connection) capable of performing all the different functions in software. For example, rather than installing a physical router which manages the routing of messages for a virtual network, we will deploy a virtual router on a generic computer of the network, which we can configure as needed.
Today, services are located in data centers that are sometimes very far from their users. This cloud computing induces transport costs for the messages and introduces an incompressible latency even if the communications are hyper-fast. The idea is to install small data centers in the network closer to the uses. For applications such as machine control or augmented reality, this saves valuable time for event detection and control.
A current limitation of cellular technology is the inability to guarantee quality of service. Network slicing makes it possible to virtually reserve a band of frequencies for a particular service, or more precisely to offer a certain guarantee of service. In certain configurations or for certain uses with specific requirements, the service is in a monopoly position and therefore does not have to be shared with other services. When we remotely control a precision machine tool, we want, for example, to guarantee a maximum delay of a few milliseconds between the command exerted by the pilot and its reception by the machine. To do this, we cannot compete with other services. In millimeter waves, for example, the network concerned may be of small area.
Radio technical innovations
With “massive MIMO” (multiple input, multiple output), each antenna consists of a large number of small antennas. Each small antenna of the station focuses the waves towards a user that it follows. More precisely, waves emitted by different elements of the antenna combine intelligently to achieve the ray that targets a particular user. This avoids the very wide watering of the environment that conventional antennas do. It is a more complex techno, but which will allow energy savings once well mastered. And you can use several remote antennas for the same communication, further improving focusing.
The use of higher frequencies makes it possible to increase the frequencies that can be used for communications and especially to arrive in bands where the availability of frequencies is important. The simultaneous use of different technologies and frequencies. For example, you can already make phone calls from your home using a cell phone or wifi (voice over Internet). Your phone has to choose and switching between them is complicated and very slow these days. Future generations of telephones will facilitate such simultaneous use of several technologies and frequencies in order to improve services, for example by avoiding falling into a “hole” when switching from one to the other.
TDD (Time Division Duplexing) mode
We share the same frequencies with a time distribution of the rising (from the phone to the station) and down (from the station to the phone) phases. This makes it possible not to choose a priori a sharing of frequencies between upstream and downstream traffic. The best use of frequencies is a key part of using cellular networks, as it is a scarce resource to be shared among all users.
The “small cells”
Techno makes it possible to use very high bands (for example, 26 GHz) which are available in very large quantities. But the messages propagate there much less far, a few hundred meters at most. We are therefore going to use very small antennas (cells) on lampposts, bus shelters, etc. It is a technology for downtown areas and busy places like stadiums or festivals.
This allows terminals to communicate directly with each other without going through the operator’s system. We can continue to communicate even when the network is saturated or when it malfunctions, for example in the event of a natural disaster or computer attack.
The idea is to be able to make better use of frequencies, by slipping temporarily when possible into unused frequencies.
When it comes to cognitive radio and end-to-end communications, while these two aspects are part of the 5G vision, they don’t seem really ripe yet at this point.
And tomorrow, 6G
If it is already not easy to say what will be the 5G being deployed, it becomes downright surreal to describe a technology still in research laboratories, 6G: we are not futurists! We will therefore content ourselves with presenting the main features. Technically, while aiming for even more speed, 6G aims for the “finest”: smaller antennas (small cells), and smaller data centers (edge). We will be permanently connected to the cellular network and to the same standards, even when it is by satellite. The network must put itself at our service, we “humans”, probably more and more immersed in a world of robots (which individually we do not necessarily want, but that is another subject); we are talking about virtual and augmented reality (which start), holography for remote meetings. And 6G should also be able to track objects moving at high speed or in complicated environments.
In fact, 6G will allow the fulfillment of the promises of 5G by making possible the communications between a massive number of machines of all kinds (perhaps millions per km square). If 5G has already been designed with energy sobriety as a goal, 6G will go even further in this direction.
Of course, artificial intelligence will be all over the place, if only because communication systems and their security have become too complex for the mere humans that we are. 6G will solve all the problems of cellular networks, it will be capable of everything. You do not see where this is leading us. Well, neither do we. This is why it is essential to follow all this closely, because we will have perhaps essential societal choices to make on subjects such as the level of robotization of our lives, safety or the environment.