South Korean operator SK Telecom is using 5G passive optical networking (5G-PON) in about 10 percent of its network. The operator said it has deployed the technology in 227 central office terminals and plans to expand it to 30 percent of its network in 2018. Cities covered by the deployment include Seoul, Busan, Daugu, Daejeon, and Gwangui.

In an email exchange with SDxCentral, an SK Telecom spokeswoman said that 5G-PON will be used as a fronthaul technology, which means it will carry mobile traffic from the base station baseband processing units (BBUs) to the remote radio heads on the tower. The spokeswoman said that 5G-PON can be used for 5G, LTE, and fiber. Because of its flexibility, SK Telecom is hopeful that the technology will be incorporated into the 5G standard by the 3GPP and ETSI.

According to Erik Keith, principal analyst for global telecom technology and software at GlobalData, SK Telecom’s announcement is another indication that operators can’t have true 5G without deploying fiber to the towers and remote radio heads.

SK Telecom said that 5G-PON uses coarse wavelength duplex multiplexing (CWDM) subchannel technology to provide physical layer transport connections. It is a flexible technology that can adapt different types of transport signals and data rates using existing fiber. It also supports different fronthaul LTE protocols. In the future, SK Telecom believes it will be used with software-defined radio access networks (SD-RAN) that will likely be a part of the 5G network.

SK Telecom also said that because 5G-PON uses optical networking it doesn’t require power to operate, eliminating the need for a power supply. It also doesn’t need bulky enclosures that are currently necessary for outdoor installations.

Because it doesn’t need power, SK Telecom said that it will be able to use 5G-PON to migrate its network to a more distributed architecture. Plus, it can also be used for a protected ring architecture, which means that even if one line gets disconnected, the transport ring will continue to operate.

The operator is currently working with vendors such as Solid, HFR, SunwaveTec, and Coweaver on its 5G-PON deployment.

The fronthaul part of the network seems to be the latest focus for innovation in wireless networks, but 5G-PON isn’t the only option. Dali Wireless has developed a patented fronthaul interface that uses software-defined networking (SDN) to act as an intelligent aggregator-router. Dali’s interface sits between the BBUs and the radio heads on the tower allowing multiple operators to connect to multiple BBUs to create a multipoint-to-multipoint network.