Electronic Design
CRAN connects a large number of distributed radio receivers to a centralized basebandunit BBU pool in the cloud providing highbandwidth and lowlatency communications Image courtesy of ThinkStock

C-RAN connects a large number of distributed radio receivers to a centralized baseband-unit (BBU) pool in the cloud, providing high-bandwidth and low-latency communications. (Image courtesy of ThinkStock).

Research Agreement Targets Fronthaul Interface for 5G Networks

The rapid growth of small cells and distributed antenna systems is pushing wireless vendors toward a more centralized baseband architecture. In an attempt to more efficiently navigate these networks, the China Mobile Research Institute and Xilinx have agreed to research a next-generation fronthaul interface (NGFI) targeting 5G wideband multi-antenna systems.

Cloud-RAN (C-RAN) is one of the main network architectures that will be addressed by the new fronthaul interface. This architecture connects a large number of distributed radio receivers to a centralized baseband-unit (BBU) pool, providing high-bandwidth and low-latency communications. Depending on the scale of the network, these receivers can be located at cellular base stations, small cells, or antenna systems. This centralized control plane serves to reduce signal interference and smooth out the frequent handoffs between cells, according to the CMRI. The role of a fronthaul interface is to control the flow of data between the baseband controller and these remote radio units (RRUs).

As envisioned by the research institute, the NGFI will shift some BBU processing functions to the distributed radio receivers. Several RRUs will be combined into systems or packets managed by radio access units, according to a white paper released earlier this year. The new interface transforms the overall network from a point-to-point connection into a many-to-many fronthaul network by using a packet exchange protocol. As a result, the NGFI has the potential to increase bandwidth through statistical multiplexing and enable 5G networks to scale with larger multi-antenna systems.

The NGFI is being developed as an alternative to the Common Public Radio Interface (CPRI), a rival fronthaul standard that opponents contend is not suited for a centralized baseband architecture. Most of the criticism is related to the high costs and high-bandwidth requirements involved in using the CPRI standard in 5G networks. As mobile data traffic grows, operators will have to install more fiber-optic cables to support the CPRI standard, thereby increasing the total cost of ownership.

In contrast, the research institute expects the NGFI to reduce equipment costs by shifting BBU processes to the remote radio units. This is especially important as an increasing number of wireless carriers move toward C-RAN networks. A recent report from SNS Research is predicting that C-RAN investments will account for nearly 35% of the wireless market by 2020.

The NGFI is still a work in progress. Companies affiliated with the CMRI, including Alcatel-Lucent and the Intel China Research Center, have admitted that many technical points still have to be resolved. As part of the research agreement, however, Xilinx is contributing a validated NGFI reference design on its Zynq system-on-a-chip (SoC) platform. That reference design, which will be compatible with other Zynq and Zynq Ultrascale+ MPSoC devices, will serve as a baseline framework for 5G wireless network research.

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