Since major manufacturers showcased the progress of 5G technology at the MWC exhibition in 2015, 5G has quickly become a key topic in the communication industry. Chip manufacturers, equipment manufacturers and operators have all stepped up their efforts to lay out their strategies, striving to seize the initiative in the wave of the next-generation communication technology. For ordinary consumers, the most intuitive perception of 5G is that its transmission rate far exceeds that of 4G. At the industry level, 5G, with its core features of high performance, low latency and high capacity, has opened the door to practical application in emerging fields such as driverless technology, VR/AR and the Internet of Things. Behind this series of advantages lies the collaborative support of five core technologies: millimeter-wave, small base stations, Massive MIMO, beamforming, and full-duplex.
4G LTE technology once reshaped the mobile Internet ecosystem, but its transmission capacity and connection scale have been difficult to meet the demands of new scenarios. 5G has achieved all-round breakthroughs in core performance: In terms of speed, the peak speed of 4G can only reach the 100-megabit level, and it often takes about 10 minutes to download a high-definition movie. The peak rate of 5G can reach tens of Gbps. In theory, a high-definition movie can be downloaded within one second, with a speed increase of over a hundred times. In terms of connection capacity, the device access volume of 4G base stations is limited. When facing the connection demands of a vast number of terminals in the Internet of Things era, network congestion is prone to occur. 5G can achieve a connection density of millions of devices per square kilometer, laying the foundation for large-scale deployment of the Internet of Things. In terms of latency performance, the communication latency of 4G is usually at the level of tens of milliseconds, which cannot meet the real-time requirements of scenarios such as driverless technology and telemedicine. The end-to-end latency of 5G can be reduced to the millisecond level, providing technical support for high real-time industry applications.
The performance leap of 5G is not the result of a single technology, but rather the coordinated efforts of five key technologies, achieving technological innovation from dimensions such as spectrum resources, base station architecture, and signal transmission.
In the 4G era, the problem of scarce spectrum resources has gradually become prominent. The limited spectrum bandwidth has severely restricted the improvement of transmission rates. 5G innovatively introduces millimeter-wave technology (in the 26.5 to 300GHz frequency band), achieving a rate breakthrough by expanding the spectrum bandwidth. Take the 28GHz frequency band as an example, its available spectrum bandwidth can reach 1GHz, and the single-channel bandwidth of the 60GHz frequency band is as high as 2GHz, far exceeding the spectrum bandwidth of 4G. However, millimeter waves also have obvious shortcomings. Their signal penetration is weak and attenuation is fast. They are easily blocked in the environment of high-rise buildings in cities. This defect needs to be compensated for by small base station technology.
The characteristics of millimeter waves determine that 5G can no longer rely on the large macro base station architecture of the 4G era. Therefore, small base stations have become a key supplement to the deployment of 5G networks. The millimeter-wave frequency band has a high frequency and short wavelength, and the corresponding antenna size can be significantly reduced, providing a hardware foundation for the dense deployment of small base stations. Operators can deploy a small base station within a range of about 250 meters, forming a dense base station network in the city. This can not only cover the communication terminals that are difficult for macro base stations to reach, but also solve the problems of millimeter-wave signal penetration and attenuation. Meanwhile, the volume and power consumption of small base stations are much smaller than those of macro base stations, and they have significant advantages in deployment costs and energy consumption control.
4G base stations are usually equipped with only a dozen antennas, and their signal transmission and reception capabilities are limited. 5G base stations introduce Massive MIMO technology, which can support hundreds of antennas to form large-scale antenna arrays. This technology innovatively introduces a spatial domain resource sharing model, enabling base stations to simultaneously send and receive signals to multiple users. It not only increases the capacity of mobile networks by tens of times but also achieves dual gains in spectral efficiency and energy efficiency. However, at present, Massive MIMO technology is still mostly at the laboratory and small-scale field test stage, and its large-scale commercialization still needs to break through technical bottlenecks.
Although the multi-antenna architecture of Massive MIMO enhances the signal transmission and reception capabilities, it also brings the problem of signal interference. Beamforming technology specifically addresses this challenge. It can precisely control the electromagnetic wave direction of each antenna through algorithms, concentrating the signal energy in a specific direction to form a narrow beam rather than transmitting in all directions. This technology not only extends the signal transmission distance and avoids signal interference among multiple antennas, but also enhances the spectral utilization rate. Meanwhile, it can calculate the optimal signal transmission path through algorithms, further compensating for the coverage defect of millimeter waves.
4G communication adopts Frequency Division duplex (FDD) or Time Division Duplex (TDD) modes. Uplink and downlink communication require different frequencies or different time periods of spectrum resources, and there is a ceiling to spectrum utilization. The full-duplex technology of 5G enables two-way communication between the transmitter and the receiver at the same frequency and time, greatly enhancing the efficiency of spectrum utilization. It is one of the key technologies for 5G to achieve high throughput and low latency. However, the implementation of full-duplex technology still faces three major challenges: First, it is necessary to develop small-sized, low-power, and low-cost wideband self-interference cancellation circuits; Second, it is necessary to complete multi-dimensional optimization of the physical layer and MAC layer. Thirdly, it is necessary to achieve dynamic switching between full-duplex and half-duplex and adaptation to the existing frame structure.
Although 5G has demonstrated far more advantages than 4G in terms of technology, its commercialization remains full of uncertainties. At present, most of the five core technologies are still in the laboratory testing or small-scale pilot stage. From technical verification to large-scale commercialization, a series of challenges such as cost control, equipment compatibility, and network optimization still need to be overcome. However, with the continuous iteration of communication technology, the technical bottlenecks of 5G will gradually be broken through. It will not only reshape consumers' mobile Internet experience, but also become the core communication foundation for the digital transformation of industries such as driverless technology, smart industry, and telemedicine, driving society into a brand-new era of intelligent interconnection.
