4G changes the way we live, while 5G will transform our society. A 5G network is an integrated network oriented to multiple application scenarios. “Internet of Everything” in the 5G era will bring revolutionary network experience and completely new business application models compared with 4G, bringing infinite possibilities for operators’ future service expansion. Compared with previous mobile communication systems, 5G needs to meet the challenges of more diversified scenarios and extreme performance. The application scenarios of 5G technologies can be classified to three categories: enhanced Mobile Broadband (eMBB), massive machine-type communications (mMTC) and ultra Reliable & Low Latency Communication (uRLLC). They pose higher requirements for bandwidth, latency, flexible connection, reliability and SDN capability of transport networks.
In the recently released 5G – Deployment and Commercial Considerations, Ovum clearly states, “Due to the low-latency requirement and different deployment scenarios, 5G transport needs to address a different mix of connections for fronthaul, midhaul, and backhaul.” “Key new technologies include Flex Ethernet (FlexE), segment routing, time-sensitive networking, and SDN.” Besides, the Ovum analyst believes the transport network must support time synchronization, network slicing, large-bandwidth interfaces and efficient hybrid transport of CPRI/eCPRI. These key technologies can meet the requirements of 5G in terms of connection capability, bandwidth capacity, differentiated latency features, synchronization precision and resource orchestration on demand.
ZTE, as a leader in 5G transport network solutions, began to actively trace and promote the compilation of standards and specifications related to 5G transport, tackle 5G key technologies, and carry out related equipment development and testing work in 2015. Through constant technological accumulation and innovation, ZTE provides a flexible, expandable, and unified 5G Flexhaul solution oriented towards 5G fronthaul, midhaul and backhaul.
ZTE 5G Flexhaul Solution
By deeply integrating IP, FlexE and optical architecture, ZTE’s 5G Flexhaul solution provides flexible ultra-large pipe transport capability for 5G fronthaul, midhaul and backhaul services. FlexE over DWDM expands network capacity by biding bandwidths of multiple wavelengths and links, substantially improving flexible bandwidth expandability and reducing early-stage network construction costs. Segment routing technology together with intelligent traffic engineering of SDN is used to cope with the demand for ubiquitous flexible connection brought by cloudification of 5G core networks and base stations, and meet the requirement for Mesh networking brought by down-shifting of L3 to base stations. 5G Flexhaul performs unified planning, scheduling, maintenance and management by SDN controllers. It supports slicing of the forwarding plane, control plane and management plane. In cooperation with slices of wireless and core networks, it provides end-to-end (E2E) 5G slicing solutions to meet the multi-scenario and multi-tenant requirements of 5G vertical industry applications.
As a technological leader in the industry, ZTE has been continuously reinforcing its leading position in key technologies of 5G transport. Based on deep understanding of communication networks and profound technology accumulation, ZTE has carried out a series of technology extension and perfection work based on existing FlexE technology standards. Besides providing large-bandwidth extension technologies, ZTE also proposes a series of revolutionary technologies based on FlexE. Using original FlexE Tunnel technology, ZTE extends the OAM and ultra-fast protection switchover technology based on traditional FlexE (Flexible Ethernet) timeslot cross-connection to form an end-to-end, ultra-low-latency and physically isolated FlexE Tunnel solution, extending FlexE from a point-to-point interface technology to an end-to-end networking technology. It is another important milestone of 5G Flexhaul solution, providing important technological support for 5G transport and bringing revolutionary transformation to Ethernet transport technology.
Less than 0.5us single-hop ultra-low-latency forwarding
Traditional packet devices employ hop-by-hop forwarding policy for service packets. Each node in the network needs to perform MAC layer and MPLS layer resolution for data packets. The resolution wastes much time, so the single-device forwarding latency is up to dozens of µs.
FlexE technology implements service flow forwarding based on physical layer using timeslot cross-connection technology. The user packets do not need resolution at intermediate network nodes and so the service flow forwarding is completed almost in real time. The minimum single-hop forwarding latency can be less than 0.5us, laying a good foundation for ultra-low-latency service transport.
End-to-end service isolation
FlexE can implement not only large-bandwidth expansion but also precise division of high-rate interfaces, enabling transmission of different low-rate services in different timeslots and physical isolation between them. The sub-channel features of FlexE and timeslot cross-connection features at the physical layer enable the users to build cross-NE E2E rigid FlexE Tunnels on the transport network to form strict physical layer service isolation as the intermediate network nodes do not need to resolve service packets. FlexE implements flexible sub-channel isolation for different types of services and provides the best forwarding plane support for 5G transport network slicing.
Service protection switchover within 1ms
FlexE Tunnel provides FlexE channel layer protection function, highly improving the reliability of service transport in FlexE Tunnel. When a customer service cannot be transported smoothly in one Tunnel, it can be switched to the standby Tunnel within 1ms, so that the whole network can reach the industrial-grade reliability of 99.9999%.
Besides, the innovative 3A (Advanced clock source, Accurate time stamp and Agile algorithm) clock synchronization technology of ZTE 5G Flexhaul solution employs common view clock source, physical layer time stamp, high-precision phase-locked loop and automatic difference control technologies to provide ultra-high-precision synchronization. The single-node synchronization precision can be higher than 2ns, meeting the requirements of new air interfaces of 5G base stations, inter-site cooperation and base station location services.
At the ITU-T SG15 plenary session held in Geneva, Switzerland in June 2017, Chinese enterprises including China Mobile, ZTE and China Academy of Information and Communications Technology (CAICT) submitted a large number of 5G transport-related proposals to actively promote the research on 5G transport standards. Participating experts considered transport networks supporting 5G requirements a very important new subject, and formally passed the initiation of Transport network support of IMT-2020/5G (TRGS-TN5G) technical report and the research plan of 5G transport standards at the summary meeting on June 30. It marks an important step of ITU-T in the research on 5G transport standards and a great contribution of Chinese enterprises to promote related research. ZTE’s proposal FlexE layer network model is the first in the industry that proposes the FlexE-based layer network model architecture, laying a foundation for the research on FlexE-based 5G transport standards.
In August 2017, ZTE in cooperation with Telefonica successfully completed the phase-1 5G transport test at the Future Network Lab in Madrid Spain, perfectly verifying the excellent performance of 5G Flexhaul solution in CPRI/eCPRI unified transport, ultra-low latency and fast switchover.
In September 2017, ZTE successfully passed the phase-1 test of 5G transport SPN (Slicing Packet Network) prototype experiment of China mobile, demonstrating that ZTE’s 5G Flexhaul solution can provide strong support for SPN technology solution, which lays a solid foundation for accelerating 5G commercialization.
The renowned consulting company GlobalData speaks highly of ZTE 5G Flexhaul, holding that it furthers its stake in the 5G market by providing fronthaul, midhaul and backhaul integrated transport capability and flexible deployment on demand capability for 5G.
ZTE has been dedicated to leading 5G innovations by putting 5G development as the core strategy. ZTE’s 5G Flexhaul solution has fully covered the key 5G transport technologies proposed in the Ovum report. At the same time, ZTE has carried out 5G R&D and cooperation with a number of high-end operators including China Mobile, Japan SoftBank, Orange, Telefonica, Telstra and Italy WindTre. As the 5G is pending, ZTE will definitely follow the trend and provide the most competitive 5G transport solutions.
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