From：Zhaoqing Xiangjiasheng Technology Co., Ltd Release time：2020-11-17
RRU, the remote radio unit, from 3G to 4G, is composed of BBU+RRU+antenna mode. And AAU is an upgrade of RRU, an advanced device version of RRU, which is currently used by 5G base stations.
The reason why AAU appeared in 5G is actually because 5G introduced the technology of Massive MIMO.
Massive MIMO: Massive multiple input and multiple output.
In fact, this is also the mainstream of the current 5G era, and its purpose is to provide ultra-high download speeds. 4G, RRU supports 4T4R downlink and supports up to 4 data signals transmission, and 4 uplink antennas receive one signal at the same time to enhance uplink coverage.
The 5G Massive MIMO AAU generally uses 192 antenna elements to support 64 channels of transmitting and receiving signals, which is 16 times more powerful than RRU. The lower 12 lines stably support 24 channels of data transmission and the uplink simultaneously receives 12 channels of signal data. The advantage is too obvious!
However, it is not difficult to see that 5G and 4G both use the same carrier bandwidth and sub-carrier spacing. With the support of Massive MIMO, the downlink throughput of the cell can be increased by 5 times!
The characteristics of Massive MIMO are obvious. There are many radio frequency channels, the antenna array is large in scale, the complexity is increased, and the coupling between modules is closer.
Therefore, in the Sub6G frequency band in the 5G era, AAU supporting Massive MIMO has become the absolute mainstream.
5G is first deployed in urban hotspots. These places are usually densely covered with tall buildings. Not only does it need to cover the ground, but the vertical coverage of tall buildings is also very important.
Massive MIMO AAU's large-scale antenna array not only supports multi-stream transmission in the horizontal plane, but also flexibly distributes the beams on the vertical plane, greatly enhancing the coverage of tall buildings.
Since there are many transmitting channels, a very narrow beam can be formed, and the ability of space division multiplexing is stronger, sharing the same frequency and time resources to multiple users. The industry can support up to 24 downlink data streams to be sent at the same time. Compared with 4G 4x4 MIMO (4 streams), the cell capacity is improved by 5 times.
The substantial increase in speed is exactly the full meaning of the eMBB service in the initial stage of 5G deployment, allowing users to intuitively feel the invigoration brought by 5G.
It was AAU that carried the banner of 5G.