In 2006, ZTE proposed the first BBU+RRU distributed base station architecture and applied it to the TD-SCDMA network of China Mobile Qingdao. At the time, it was a revolution in wireless base station architecture. Now, the BBU+RRU distributed base station has become mainstream. It has the following advantages:

- A series of RRUs enables indoor and outdoor coverage in different scenarios.
- RRUs are small and light and can be installed flexibly. This speeds up network deployment.
- RRUs can be installed close to the antenna site. This reduces feeder loss and increases site coverage.
- The BBU has a subrack structure that leaves no footprint.
- Baseband can be shared for flexible traffic scheduling.

 With these advantages, BBU and RRU are playing an increasingly important role in 2G, 3G and 4G network deployment. A state-of-the-art RRU is an important factor when an operator chooses an equipment supplier.

According to a report published by the GSA in November 2013, the number of commercial LTE networks worldwide totaled 222 in 2013, and the number of operators that had invested in LTE worldwide in 2013 was approaching 400. Operators are facing the difficulty of coexisting network standards and frequencies. To expand their existing networks or build new ones, an operator has to find extra room on an antenna site in order to install base stations or RRUs. Renting new sites for antennas is costly; therefore, operators seek to make full use of the limited site space they already have. Drawing on its rich experience with optical remote distributed base stations, ZTE has launched an ultra broadband RRU (UBR) that enables operators to use only one RRU instead of the traditional two (which operate on two frequency bands). This saves TCO.

Ultra Broadband By using a new type of amplifier and an advanced digital pre-distortion (DPD) architecture and algorithm, UBR is capable of single-channel, ultra-broadband transmission. UBR also uses advanced ultra-broadband DPD architecture and algorithms to provide industry-leading transmission bandwidth of 365 MHz. A traditional RRU can only work on a single frequency band with the general bandwidth of 30–40 MHz. Therefore, six conventional RRUs are needed to cover the six major frequency bands
Source: site chinois