In order to meet the increasing demand for bandwidth, China Unicom has proposed to promote the continuous sinking of large-capacity DWDM and gradually move towards the edge of the network. From the backbone layer to the metro area to the edge access, a large-capacity basic network based on DWDM is required to carry the upper-layer service network. In the future, services will be controlled and centralized dispatched mainly through DCs. The requirements for cloudification of services will be superimposed, which will place higher requirements on the bearer network. The basic requirements of 5G for transmission bearers include large bandwidth, low latency, high-precision time synchronization, network slicing, network intelligence, and low cost.China Unicom divides the metropolitan area network into a core aggregation layer and an access layer. The access layer can be subdivided into two layers: the integrated service access layer and the end service access layer. It should be noted that the two layers of the metropolitan area network do not completely correspond to the fronthaul, middlehaul, and backhaul of the 5G network
The core convergence layer will adopt the routing exchange technology and simplify the structure. The core layer adopts the 2-core structure, and the convergence layer can adopt the port structure with the goal of 100g. The core convergence layer should also consider the integration with IP man and communication cloud network. The access layer mainly adopts ipran, which is upgraded from the current Ge access ring rate to 10GE. Hot spots and high traffic areas can be bundled with 2 * 10g, which can be upgraded to 25 / 50g networking in the future. The access ring consists of 4-8 nodes.
Because of the large number of 5g base stations, the forward transmission cost sensitivity is high. The front transmission is mainly optical fiber direct drive, and WDM equipment can be used when the optical fiber is insufficient. 5g forward protocol is mainly 25gecpri, including 25gbidi (single fiber bidirectional, 10-15km, applicable to c-ran), 25gduplex (dual fiber bidirectional, 300m, FP / FB laser, applicable to d-ran) and 25g tunable DWDM interface (pab-wdm equipment meeting g.698.4 standard / front g.metro). In addition, in the core convergence layer, the 100g port of man is large and cost sensitive. China Unicom proposes to develop an optimized low-cost man coherent 100g optical module for man applications in the industry.
China Unicom also proposes to decouple and open the optical transmission system and modularize the equipment to promote innovation and reduce costs. Through decoupling and opening, it can avoid being locked by equipment manufacturers, open the industrial chain and reduce the construction cost. Each functional segment can be independently developed and upgraded, accelerate innovation, introduce new technologies faster, and reduce costs. Users can customize the network to realize quick business distribution. Simplify operation and reduce network operation cost. Modularization of wavelength division equipment is beneficial to the unit bandwidth of wavelength division equipment, with obvious advantages.