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Fronthaul is defined as the fiber-based connection in RAN infrastructure between the Baseband Unit (BBU) and Remote Radio Unit (RRU). Fronthaul originated with LTE networks when operators first moved their radios closer to the antennas. This new link was established to supplement to the backhaul connection between the BBU and central network core.
With the rapid development of 3G, 4G wireless communication systems and FTTx, the consumption of optical fiber resources in access network becomes more and more serious. 5G intensive networking and deep coverage need to consume more access fiber resources. The lack of access fiber resources has attracted more and more attention from major operators at home and abroad. In order to save 5G optical fiber resources, Sintai Communication aims at 4G C-RAN and 5G fronthaul transmission, providing the best fronthaul bearing solution and a full range of optical forward access devices.
In the wireless fronthaul transmission, the BBU and the RRU adopt the passive wavelength division bearer mode. Based on the WDM technology, the backbone fiber can realize the remoteness of multiple base stations by only one core, which can greatly save fiber resources. It’s applicable to areas where fiber resources are tight or BBUs are deployed in a centralized way .
Sintai has also proposed the semi-active WDM solution for 5G fronthaul transmission. It is similar to passive WDM, network management monitoring and optical layer protection functions are added on the basis of maintaining end-to-end low passive WDM cost. DU side equipment is active with optical layer protection and automatic switching. Power failure of equipment only affects network management but does not affect service. No power for remote system with the ability of outdoor deployment. Passive mux/demux can be deployed together with AAU to handle single-station service, or can be deployed at optical intersection site to converge multi-station service
5G network consists of the access network(AN), bearer network, and Core Network(CN). The access network is generally a radio access network (RAN), which is mainly composed of communication base stations. Unlike 4G technology, 5G is not made up of BBU(Base Band Unit)、RRU(Remote Radio Unit）or antenna; instead, it is reconfigured as the following three functional entities: CU (Centralized Unit, Distribute Unit), DU (Distribute Unit, Distribute Unit), and AAU(Active Antenna Unit, Distributed Unit). The original 4G RRU and antenna are combined into AAU, and the BBU is separated into CU and DU. The DU is embedded in the AAU, and one CU can be connected to multiple DUs.
The concept of WDM(meaning Wavelength Division Multiplexing) is to use multiple light sources operating at different wavelengths to transmit a few independent information streams simultaneously over the same optical fiber.
A primary difference between fronthaul and backhaul is the part of the network the technology is deployed on. Backhaul links the mobile network to the wired network, while fronthaul describes the network architecture that connects the remote cell sites to the BBU.
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