The 5G base station using MassiveMIMO can not only increase network capacity by multiplexing more wireless signal streams, but also greatly improve network coverage by beamforming.
Beam shaping technology makes the signal energy more focused on the target terminal through the spatial distribution of line gain throughout the day, so as to compensate for the loss of space transmission after signal transmission, and greatly improve the network coverage.
Compared with 4G base stations, AAU, which supports large-scale array antenna technology, is the main reason for the significant increase in the cost of 5G base stations.
Antenna size is frequency dependent, 5G antenna or 64 channels are dominant
According to the principle of wireless communication, in order to ensure the highest efficiency of antenna transmitting and receiving conversion, the distance between antenna oscillators must be greater than half of the wavelength of wireless signal, and the wavelength of wireless signal is inversely proportional to the frequency of wireless signal (lambda = c/f, where C is the speed of light, f is the frequency of wireless signal). That is, the higher the frequency of signal, the higher the wavelength of signal. Small.
In the future, 5G band or 3.5GHz and 2.6GHz will be the main band in China. According to this band, the half wavelength is about 4.3cm/5.8cm.
According to the current 5G test, the current 64-channel Massive MIMO technology is the mainstream test choice of various equipment manufacturers.
Although the more channels, the higher the network performance, but considering the size/weight of antenna, antenna performance and cost factors, operators are also considering the low-cost Massive MIMO scheme - 16 channels.
In our opinion, if the cost of 64-channel antenna is not reduced to the acceptable range of operators in the early stage of 5G, it is possible that operators will give priority to 16-channel antenna scheme while meeting the deployment and capacity requirements.
The architecture of 5G base station has changed greatly, and the trend of antenna active is obvious.
The 4G macro base station consists of three parts: antenna, radio frequency unit RRU and baseband processing unit BBU deployed in the computer room.
The 5G network tends to adopt the new wireless access network architecture of AAU+CU+DU, as shown in the following figure.
The antenna and RF unit RRU will be combined into a ew unit AAU (Active Antenna Unit), AAU will include not only the RF function of RRU, but also the processing function of some physical layer.
In 5G era, the increasing number of antenna channels and the active antenna put forward higher requirements for antenna design. Miniaturization and lightweight are the foundation.
In the 4G era, the antenna configuration is basically 4T4R (FDD) or 8T8R (TDD). According to the current test situation, the 5G era may be dominated by 64T64R large-scale array antenna.
The number of channels has increased by 7-15 times, which means that the antenna demand for RF devices has increased by 7-15 times. At the same time, the passive part of the antenna will be combined with RRU as AAU, which puts forward higher design requirements for the size and weight of the antenna in 5G era.
In the era of 4G, the weight of passive antenna + RRU is about 24-34 kg. At present, the weight of 5GAAU in the test is about 45 kg, which increases by 32%-88% year on year. Therefore, in the trend of 5G antenna integration, miniaturization and lightweight become the foundation of antenna design.
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