Some key technologies of 5G communication

5G has high performance, low latency and high capacity characteristics according to 3GPP definition, and these advantages are mainly embodied in millimeter wave, small base station, massive MIMO, Full-duplex and beamforming technology.

Among them, massive MIMO and beamforming are closely related.

1, millimeter wave

There are generally two ways to increase the transmission rate of wireless transmission, one is to increase the spectrum utilization and the other is to increase the bandwidth of the spectrum. 5G using millimeter wave (26.5~300ghz) is the second method to promote the rate, in the 28GHz band as an example, its available spectrum bandwidth to 1GHz, and 60GHz band for each channel the available signal bandwidth is 2GHz. Millimeter wave the biggest disadvantage is poor penetration, attenuation, so the millimeter wave band 5G communication in high-rise environment transmission is not easy, and small base station will solve this problem.

2. Small Base Station

The millimeter wave frequency is very high, the wavelength is very short, this means that its antenna size can be very small, this is the basis of the deployment of small base station. The future 5G mobile communications will no longer rely on the large base station of the fabric architecture, a large number of small base stations will become a new trend, it can cover the large base station could not touch the peripheral communication. Because of the large reduction in volume, we can set up around 250 meters to deploy a small base station. In this way, operators can deploy thousands of small base stations in each city to form dense networks, where each base station can receive signals from other base stations and send data to users in any location. The small base station not only in the scale is far smaller than the big base station, the power consumption also greatly shrinks.

3, massive MIMO

In addition to the millimeter wave broadcast, the 5G base station will also have more than the current cellular network base station more antennas, that is, massive MIMO technology. See Bowen http://blog.csdn.net/oqqhutu12345678/article/details/73968552 existing 4G base station only has more than 10 antennas, but 5G base station can support hundreds of antennas, these antennas can pass massive MIMO technology forms a large array of antenna arrays. This means that the base station can send and receive signals from more users at the same time, thereby increasing the capacity of the mobile network by dozens of times times or greater.  MIMO (multiple-input multiple-output) means multiple input and multiple outputs, which are actually applied to some 4G base stations. But so far, massive MIMO has been tested only in laboratories and in several field tests. Ove Edfors, a professor at Lund University, has pointed out that "massive MIMO opens up a new direction for wireless communication--when the traditional system uses time domain or frequency domain to realize resource sharing between different users, massive MIMO introduces the spatial domain, The approach is to use a large number of antennas in the base station and to synchronize with it, so that the spectrum of efficiency and energy efficiency can be achieved dozens of times times gain. ”

4. Beam forming

Massive MIMO is the key technology for 5G to realize commercial, but multiple antennas are bound to bring more interference, and beamforming is the key to solve this problem. Massive MIMO's main challenge is to reduce interference, but it is precisely because massive MIMO technology each antenna array integrated more antennas, if the effective control of these antennas, so that the space emitted by each of the electromagnetic waves to offset or enhance each other, you can form a very narrow beam, rather than the full launch , the limited energy is concentrated in a specific direction for transmission, not only the transmission distance farther, but also avoids the signal interference, this kind of wireless signal (electromagnetic wave) in a particular direction of the transmission of technology is called beam forming (beamforming). The advantage of this technology is not only that it can improve spectrum utilization, through which we can send more information from multiple antennas at the same time; in large antenna base stations, we can even calculate the best path of signal transmission through signal processing algorithm, and finally move the location of the terminal. Therefore, the beam forming can solve the problem of millimeter wave signal being blocked by obstacle and long distance attenuation.

5, full duplex technology

Full-duplex technology refers to the equipment of the transmitter and receiver occupy the same frequency resources at the same time work, so that both ends of the communication can use the same frequency at the same time, breaking through the existing Frequency division duplex (FDD) and the time Division Duplex (TDD) mode, this is the communication node to achieve two-way communication is one of the key, It is also the key technology required for 5G for high throughput and low latency . Simultaneously receiving and sending on the same channel, which undoubtedly greatly improves the spectral efficiency. But 5G also faces a challenge to use this disruptive technology, according to the information published before the mobile communications, there are three major challenges: (1) circuit board design, self-interference cancellation circuit to meet the broadband (greater than 100MHZ) and MIMO (more than 32 days) of the conditions, and the requirements of small size, Low power consumption and cost cannot be too high. (2) Optimization design problems of physical layer and MAC layer, such as coding, modulation, synchronization, detection, interception, collision avoidance, ACK, etc., especially for the physical layer optimization of MIMO. (3) Optimization of the control surface for dynamic switching between Full-duplex and Half-duplex, and the optimization of existing frame structure and control signaling.