Open Fronthaul w.r.t. ORAN Alliance is referred as Lower Layer Split (LLS) having a goal to increase the flexibility and competition on the telecom market. Lower layer split refers to the split between the Radio Unit (RU) and the Distributed Unit (DU).
The O-RAN fronthaul interface can be transported on eCPRI. The eCPRI specification is designed to support 5G fronthaul requirements and offers several advantages e.g. eCPRI enables the efficient use of packet-based transport technologies and allows RAN payloads to be carried over Ethernet. The higher layers of the O-RU interface are implemented on top of eCPRI, with several different LLS Options (1 to 8) to split the functionality between the O-RU and the O-DU.
Split Option 7-2x is one of famous LLS split option adopted by by O-RAN fronthaul specifications. This functional splitting between Distributed Unit (O-DU) and Radio Unit (O-RU) divide the function of Phy Layer (Layer 1) named as High Phy resides in DU and Low Phy resides in RU. An overview of Split Option 7-2x is shown in below picture.
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