As Open Radio Access Network (O-RAN) deployments grow in popularity, Cisco has been one of the pioneers in bringing open networking tenets to the RAN space over more than four years through the O-RAN Alliance. In 2018, Cisco spearheaded the multivendor Open vRAN ecosystem at Mobile World Congress. In 2019 we led the architectural design and network build for the world's first fully software-defined network, and in 2020 we were the first to collaborate with a communication service provider to make a fully packetized phone call over a fronthaul network.

By moving away from legacy proprietary implementations, O-RAN allows operators to deploy more efficient and competitive Radio Access Networks able to support 5G advanced services and beyond. With Cisco leading the recommendation for O-RAN fronthaul, the O-RAN Alliance recently defined the Open Fronthaul Gateway (O-FHGW) specification based on a fully disaggregated software model. This allows operators to deploy a common hardware platform across cell sites to converge their legacy Common Public Radio Interface (CPRI) and Enhanced CPRI (eCPRI) traffic onto an O-RAN specified packet transport network architecture. Open fronthaul gateway supports legacy CPRI to eCPRI conversion, where 4G radio can connect to an open fronthaul gateway over a legacy CPRI interface. Meanwhile between the fronthaul gateway and the Open Distributed Unit there will be an O-RAN defined open interface.

Benefits of O-FHGW:

• Simplifies D-RAN and C-RAN implementation of non-open interfaces or legacy interfaces over packet-based transport architecture. The close interaction of radio and routing functions allows for complete radio-aware transport.
• Reduces the transport bandwidth up to 10x for some interface interworking options and improves the resources at cell sites
• Allows for cost-optimized, converged deployment of 4G and 5G cell site radios over common transport infrastructure
• Allows operators to deploy common hardware across RAN sites

In February 2020, Cisco extended the NCS 540 portfolio with the innovative NCS 540 Fronthaul router  which was optimized for packet-based fronthaul. It enhanced many aspects of the NCS 540 related to 5G including timing, latency, bandwidth, programmability, and security. Support for open fronthaul gateway has now been added to the NCS 540 Fronthaul router.

The NCS 540 Fronthaul enables the transport of O-RAN 7.2x eCPRI, an option adopted by O-RAN fronthaul specifications, and legacy CPRI traffic between a remote radio head and a base-band unit over a converged packet network. It provides rich transport features including segment routing, hierarchical Quality of Service (QoS), and Ethernet Virtual Private Network pseudowire emulation to meet the stringent latency and jitter requirements of packet-based fronthaul. The NCS 540 Fronthaul also complies with the fronthaul requirements for latency, QoS, and timing defined by IEEE 802.1CM standards profiles A and B.

The NCS 540 Fronthaul adds new features such as CPRI to Radio over Ethernet (RoE) mapper, and Time Sensitive Networking (TSN) features to transport legacy network traffic. The platform supports various CPRI bit rates covering CPRI options 3 to 8. Many global operators have already deployed Cisco's CPRI to the RoE mapper-based packet fronthaul solution to convert CPRI streams to packets based on IEEE 1914.1 and 1914.3 standards. Cisco has patented numerous innovations in this area which are contributing to the standards. This helps facilitate the deployment of CPRI and RoE in the industry.

In terms of management, the NCS 540 Fronthaul has its own interface. It implements several Yet Another Next Generation (YANG) data models, including ones from IETF and OpenConfig. It also has Cisco-specific ones for CPRI and RoE. Using a NETCONF client and an automation tool, an operator can read the data models and check hardware-specific parameters such as temperature and link status, configurations like the RoE mapper type, or packet counters to monitor the network.

Cisco has teamed up with Xilinx and Keysight to demonstrate interoperability testing and integration of O-RAN 7.2x Open Radio Unit, Open Distributed Unit, and legacy CPRI radio traffic on a converged transport network with fully programmable Cisco NCS 540 Fronthaul routers using a CPRI to RoE mapper.

MWC Demo link:https://www.mwcbarcelona.com/exhibitors/products/innovating-the-future-of-open-ran-with-full-integration-of-fronthaul-networks-from-4g-to-5g-nr

This demonstration highlights the ability of the O-RAN compliant NCS 540 Fronthaul router to converge legacy CPRI and new O-RAN interfaces using Ethernet-based fronthaul standards and shows the test and validation methodologies involved.

To see some examples of 5G implementations, read about our work with NTT DOCOMO, Sprint, and Indosat Ooredoo. Also take a look at our recent blogs on building trust in your network, building profitable access networks, and the future of the cell site.