Nokia Bell Labs demonstrated that a commercial next-generation passive optical network (NG-PON) can transport ultra-low latency common public radio interface (CPRI) streams using a standard single fiber running between the baseband unit (BBU) and a cell site’s remote radio head (RRH). The demonstration supported the latency requirements for the fronthaul of commercial radio equipment, showing that existing fiber networks can be used to cost-effectively transport mobile traffic, which will help accelerate 5G networks. In a release, Nokia said the demonstration is a “world first” and a significant industry breakthrough in supporting mobile fronthaul and latency sensitive services.

Fronthaul is an essential element of the centralized radio access network (C-RAN) architecture in mobile networks, where the processing power is centralized and moved away from the cell sites. This helps reduce cost and power consumption and facilitates cell cooperation that enhances mobile network capacity and coverage. In a C-RAN architecture, the CPRI and some of the next generation fronthaul interfaces require ultra-low latency transport — often in the sub-millisecond range — to meet the timing and synchronization requirements of 4G and 5G networks.

Nokia Bell Labs validated that the use of next generation PON technology — XGS-PON, where X = 10, G = gigabit, S-PON = symmetrical passive optical network — satisfies these strict timing constraints and delivers the needed capacity, while reducing the cost of mobile cell site transport. XGS-PON runs on existing gigabit PON (GPON) fiber access networks that are used for fiber to the home (FTTH) or fiber to the building (FTTB), which will help operators quickly and cost-effectively get the transport coverage required for densifying cell sites.

Peter Vetter, head of access research at Nokia Bell Labs, said, “This is an important milestone in the industry and in the advancement of 5G, showing for the first time how a PON network can effectively be used to support very high capacity, low latency applications. It demonstrates the flexibility of PON to support traditional CPRI and evolving mobile specifications, such as fronthaul over simpler native Ethernets, and validates the readiness of PON for the 5G era.”

Federico Guillén, president of Nokia's fixed networks business group, said, “I’ve often said that the world is going wireless but wireless is going fixed. This Bell Labs demonstration is another example, successfully showing how fixed access technologies can be used to support mobile deployments. Mobile environments that may have traditionally relied on dedicated transport networks to connect cell sites to their core networks can now use existing fiber access networks as an alternative. The massive scale, capacity and coverage of fiber access networks make them a perfect match to support 5G.”