RRU, or remote radio frequency unit, is one of the two cores of modern base stations (BBU and RRU), also known as the source of all evil radiation.
With the development of wireless network, a base station should support 2G, 3G, 4G and other systems, but also take into account more than 900M, 1800M, 2100M frequency band. There are even 4G dedicated frequency bands such as 700M and 2600M.
Considering that a base station usually has three sectors, 15 RRUs of various frequency bands will be attached to the iron tower, and then connected to three multi-port antennas, a total of 18 devices, resulting in a crowded tower.
Internationally, many operators charge for tower rental based on the number of devices attached to the tower, so how to reduce the number of devices attached to the tower under the premise of the same frequency band and capacity has become a strong demand.
In addition, in the later stage of the development of 4G network, in order to support stronger MIMO and diversity reception capability, RRU needs to support more and more antenna ports, from two ports, to four ports and even eight ports, the requirements for antennas are increasingly high, and the connection is also increasingly complex.
It was natural to think that since the RRU needs to be installed in close proximity to the antenna and must be connected with the RF wire, why not combine the pair into one module?
This WAY, NOT ONLY IS THERE LESS EQUIPMENT ON THE TOWER, THE JUMPER between the RRU AND the ANTENNA IS no LONGER NEEDED, AND there is NO FEEDER LOSS!
In this context, the RRU and Antenna are fused together, which is called Active Antenna Unit (AAU).
Active, because the device with the antenna needs power to send out the signal, after all, the RRU is installed inside. The traditional antenna does not need power supply, also called passive antenna.
With the advent of 5G era, in order to support ultra-high download speed, ordinary MIMO in 4G era is upgraded to Massive MIMO (Massive MIMO). RRU needs to support 64 channels of transmission and be connected to an antenna array containing 192 antenna elements.
So both RRU and antenna have to support 64 ports and connect them with 64 jumpers. Where does this fit? It's a little crazy, but it's a combination of the two.
In this way, AAU began to sprout in the 4G era, and became standard in 5G. RRU has become increasingly marginalized in the 5G era.
