5G, you will be able to make phone calls

Yes, the title is correct. 5G will enable phone calls.

I believe many 5G users will be confused when seeing the title. I have used my 5G mobile phone for many years. If 5G cannot make calls, have I made calls in vain for the past few years?

But if I tell you that 5G is actually just going to support voice calls, would you be surprised? In fact, all your past calls were made on the 4G network without you even noticing.

As for why we have to adopt this approach, we have to start with the evolution history of mobile communications.

When mobile communications were first invented, they were used exclusively for making phone calls. In the 1G era, analog communications simply convert the fluctuations of human voices into fluctuations of electric current, which are then converted into fluctuations of electromagnetic waves, and then restored to human voices.

After listening to my description, you can also feel that analog communication is not reliable. The way of information transmission is simple and crude, with large loss and low transmission rate. Moreover, even if 1G can only support voice calls, due to the limitations of analog communication, it can basically only guarantee that voice can be heard. It is a pure luxury to want to hear the phone clearly.

With the upgrading of mobile communication technology, the 2G era has arrived. Compared with 1G, the most fundamental change of 2G is the adoption of digital communication technology for the first time. The voice of people talking is no longer simply transmitted directly through the fluctuation of electric current, but is first converted into a bit sequence such as 01010101 that can be processed by the chip, and then transmitted through electromagnetic waves through a series of operations.

The advantage of this is that digital information can be processed using various advanced digital technologies: such as compression, encoding, encryption, etc. Therefore, under the same frequency resources, the quality of voice calls can be greatly improved.

Moreover, starting from 2G, mobile communications can transmit simple data services. Although from today's perspective, the network speed of dozens or hundreds of Kbps is definitely a turtle speed.

In order to transform the data network, 2G added a set of core network equipment adapted to data services on the basis of the original voice core network (the core switching network of mobile communications). The original voice core network used CS (Circuit Switch), which means that an exclusive circuit needs to be established in advance for data exchange before communication.

The technology used in the newly built data core network is called PS (Packet Switch). The so-called packet switching is similar to our access to the Internet. There is no need to establish a connection in advance before communication. Instead, the data of different users are divided into packets, and the transmission resources are shared and transmitted on demand.

Therefore, the core network responsible for the voice part is generally called the CS domain, and the core network responsible for the data part is called the PS domain.

Mobile communication technology continued to develop and entered the 3G era. The emergence of iPhone 3G and its epoch-making product APP Store made 3G network the starting point of the mobile Internet era. However, 3G technology was not adapted to its application scenarios: on the one hand, the mobile Internet exploded and various mobile APPs emerged in an endless stream; on the other hand, the design stage of 3G did not anticipate that data services would become the main scenario for mobile phone use so quickly. It still used the PS and CS architecture that was exactly the same as 2G and was not very suitable for high-speed Internet access.

As a result, 3G undoubtedly became a short-lived communication standard. Mobile communication technology quickly entered the 4G era, and with the goal of high-speed mobile Internet access, it made drastic changes to the mobile network architecture.

In order to adapt to the transmission of data services, the 4G network directly cancelled the CS domain and the core network was completely PS domain-based, greatly improving the mobile phone Internet access speed.

However, this brings a problem: the PS domain can only transmit data packets, but cannot realize voice calls. Although voice calls are becoming less and less important to mobile phone users, if a mobile network cannot support voice calls, it is equivalent to losing its most fundamental soul function. Therefore, in order to solve this problem, the clever mobile communication experts used a transitional method to help 4G networks realize voice functions: CSFB.

The so-called CSFB is the abbreviation of CS Fallback. The CS here refers to the circuit switched CS, and Fallback means fallback.

That is to say, under the 4G network, if the mobile phone wants to make a call, it needs to fall back from the 4G network to the CS domain. The CS domain here is of course not the 4G one (4G has cancelled the CS domain), but 3G or 2G.

Although CSFB solves the problem of whether or not it can be used, it still has major drawbacks: first, since it has to fall back, you cannot make calls directly on 4G, which will inevitably increase the call connection time and cause poor user perception; second, in the 4G era, the voice quality still remains at the level of 2G or 3G, which is unacceptable.

Therefore, in order to realize independent voice calls in 4G, mobile communication experts have designed a control system for 4G that can make voice calls, like data Internet access, transmit voice data directly in the PS domain in the form of IP packets. This system is called IMS (IP Multimedia Subsystem).

Under the control of IMS, not only voice data can be transmitted directly through the PS core network in the form of IP packets, but video data can also be transmitted through the PS core network in the form of IP packets, adding a form of video calls.

This method of carrying voice and video directly through the 4G core network is called VoLTE (Voice over LTE, LTE is the abbreviation of 4G) to distinguish it from CSFB.

You may ask, when I use WeChat to send and receive audio and video, isn't it also transmitted directly through the 4G PS core network via WeChat packets? Why do we have to set up an IMS?

You are right. WeChat voice and video calls can indeed be made directly without going through IMS. However, WeChat voice and video do not have any quality assurance and use the same QoS (Quality of Service) as ordinary mobile phone Internet access.

Although users can tolerate WeChat voice problems, they generally cannot tolerate the situation where mobile phone calls are stuck or they simply cannot make calls. Therefore, the existence of IMS allows mobile phone calls and videos to be managed with higher QoS, achieving high-quality calls.

Therefore, VoLTE not only has a short connection time (compared to CSFB) but also has high quality (compared to WeChat), making it the best choice for making calls.

When it comes to 5G, the network architecture basically continues the framework of 4G, so from a hardware perspective, it actually supports direct voice calls (IMS was built simultaneously). However, due to the imperfect 5G coverage in the early stages of 5G, there was no risk of directly promoting 5G voice calls, and instead voice calls were allowed to fall back to the well-covered 4G network.

This type of call is called EPS FB, where EPS is the abbreviation of 4G network and FB still means Fall Back.

However, as 5G construction enters its mature stage and coverage continuity is achieved, 5G will finally enter the independent voice era like 4G. This voice call mode in 5G is called VoNR (Voice over NR, NR is the abbreviation of 5G network).

Although it doesn't sound like anything special, after all, for users, it's just a phone call. It doesn't matter whether it's EPS FB, CSFB, VoLTE, VoNR or WeChat call.

But VoNR is indeed different this time. Through the upgrade and transformation of 5G's IMS and combined with the characteristics of 5G's large bandwidth, VoNR can not only achieve the highest quality voice and video calls in the voice call interface, but also can even realize real-time Chinese-English translation, voice-to-text and other functions during the call. In addition, it can also provide special functions such as screen sharing and remote collaboration. It is equivalent to providing rich interactive capabilities in the original call interface and opening up capabilities to external companies.

Although the development of 5G networks has been widely criticized for the lack of compatible applications, the emergence of VoNR has undoubtedly increased the hope for the diversified development of 5G services.

After all, if we only focus on the increased network speed of 5G to develop related innovative applications, it is indeed easy to fall into misunderstandings. Even the clearest video will ultimately be restricted by the resolution of the human eye, and even the coolest VR will require complex peripherals to implement. Letting 5G return to the essence of mobile communications and exploring how to use 5G's more convenient services to facilitate everyone's life seems to be the only way to truly allow every ordinary person to feel the changes that 5G has brought to social life.