5G Communication Operator Network Solution
Solution Introduction
5G moves part of the physical layer of the original BBU (Baseband Unit) in the 4G era to the AAU (Active Antenna Unit). In addition, the interface has also been changed from the original 100Gbit/s CPRI to 25Gbit/s. And the non-real-time functions of the BBU are being moved up to the CU (centralized unit) to prepare for cloud-based networks. This way, the DU (Distribution Unit) is the only part of the BBU. In other words, the 5G access network has evolved from the two-layer architecture of BBU and RRU to the three-layer architecture of CU, DU and AAU. This not only ensures high bandwidth and low latency of the network, but also facilitates flexible scheduling, network protection and management control.
For 5G fronthaul, there are now three basic options: fiber direct connection, passive WDM and active WDM/OTN.
The transmission distance of the fronthaul CPRI and eCPRI interfaces is generally controlled within 10km, so point-to-point optical fiber direct connection can be used between the BBU/DU and each AAU port.
This optical fiber direct connection solution is simple and easy to implement, and can meet the requirements of fronthaul carrying. But the biggest problem is that fiber optic resources take up a lot of resources. In the 5G era, with the rapid increase in 5G fronthaul bandwidth, the number of base stations, and the number of carrier frequencies, the optical fiber direct drive solution cannot be ignored. This solution is characterized by relatively low deployment costs, but is limited by terminal optical fiber resources. Suitable for scenarios with abundant optical fiber resources and small centralized BBU/DU.
Passive WDM connections can multiplex multiple wavelengths and transmit on a pair or a single fiber to connect multiple AAUs to a DU to save fiber. Passive multiplexers/demultiplexers can be deployed together with AAUs to handle single-station services, or they can be deployed at optical cross-connect sites to aggregate multi-station services.
Active WDM/OTN/SPN connections require the deployment of OTN equipment (such as WDM Mux/Demux, OADM, EDFA, OEO, etc.) between the AAU site and the DU computer room. It also utilizes WDM technology to provide multiple AAU to DU connections through a pair of optical fibers or a single fiber. Usually, 10G/25G gray optical modules with shorter transmission distances are used to connect AAU/DU to WDM/OTN/SPN. The connection between WDM/OTN/SPN network devices can be achieved through 10G/25G/50G/100G dual-fiber or single-fiber bidirectional optical fiber transceivers.
Solution Advantage
5G operates on a variety of frequency bands, including sub-6 GHz and millimeter wave frequencies. Fronthaul solutions must support these different frequency bands to ensure compatibility with different 5G deployments.
The fronthaul solution must provide a mechanism to accurately synchronize elements across the network, ensuring accurate time and phase synchronization. In 5G networks, this is critical for critical applications such as beamforming and advanced features such as coordinated multipoint (CoMP) transmission.
Fronthaul solutions should provide cost-effective deployment and maintenance options to help network operators manage their investments while delivering the benefits of 5G technology.