The xRAN Forum announced two new specifications today that are intended to make fronthaul more efficient and make it possible for operators to use interoperable radios from different vendors. The specs build on an earlier release the group announced in April.
The xRAN Forum Fronthaul Working Group, which is chaired by Verizon, developed the new specifications.
The first specification builds on that original spec released in April. According to Dr. Sachin Katti, a professor at Stanford University who heads up the xRAN Forum, the April specification was a big step toward interoperability but it had some gaps. Today’s release, which is called xRAN Fronthaul Control, User, and Synchronization (CUS) Plane Specification, allows for radios from different vendors to be interoperable and enables more complex functionality because it will support additional technologies such as Licensed Assisted Access (LAA) and narrowband IoT (NB-IoT). LAA is a technology that allows operators to combine both licensed and unlicensed spectrum to deliver 4G and 5G services. NB-IoT is a 3GPP-based IoT network technology that many U.S. operators are deploying in the guard band of their spectrum licenses. NB-IoT supports speeds of 100 kb/s or slower.
This CUS spec also adds compression to increase fronthaul bandwidth and supports critical items such as synchronization and timing.
The second spec provides for a management plane, or M-Plane. Katti said that this allows for the baseband unit and the radio unit to exchange information about things like configuration. He said this is necessary when using radios from different vendors because they need to know what each is capable of doing and exchange a set of parameters.
The M-Plane is based on open source configuration languages like NETCONF/YANG and can support both traditional and hybrid deployment models.
O-RAN and xRAN
And it appears that we may soon have some resolution to the ever-confusing alphabet soup of RANs. The xRAN Forum announced in February that it was merging with the C-RAN Alliance (which was formed by China Mobile to look into virtualizing the RAN). The two groups would form the O-RAN Alliance, which stands for open RAN.
That merger is still happening, Katti said. It’s just taking a big longer than expected.
First the O-RAN Alliance had to be formed and then the governance and bylaws have to be approved. In late June the O-RAN Alliance named its board of directors and appointed Andrew Fuetsch, president of AT&T Labs, as its chairperson. The O-RAN Alliance also said that Bharti Airtel, China Telecom, KT, Singtel, SK Telecom, Telefonica, and Telstra were approved as new members. Those members join AT&T, China Mobile, Deutsche Telekom, NTT DoCoMo, and Orange.
Although Verizon wasn’t on that list, a company spokeswoman told SDxCentral that it was committed to pursuing open RAN and was just waiting to see final governance documents for the O-RAN Alliance before joining. A Sprint spokeswoman said that it was also in the process of joining the O-RAN Alliance even though it was not included in the list of operators.
Katti said that he expects all the bylaws to be approved and the paperwork to be completed by September. He also said that he will remain involved in the O-RAN Alliance as its technical chair.
Look for more specification releases to occur later in the year as other working groups release new architecture interfaces.