5G NR Split Comparison Option 2, 6 & 7.2

As per 3GPP ,TR 38.801 define various split options between CU & DU:

Option 2 (3C-like split)

• The function split in this option is similar as 3C architecture in DC. RRC, PDCP are in the central unit. RLC, MAC, physical layer and RF are in the distributed unit

Option 6 (MAC-PHY split)

• - Physical layer and RF are in the distributed unit. Upper layers are in the central unit.

Option 7 (intra PHY split)

• - Part of physical layer function and RF are in the distributed unit. Upper layers are in the central unit.

Below are pros & cons for Option 2, 6, & 7.2 :

Latency comparison:

Use Cases:

• The most popular deployment options among those currently planning disaggregated small cell deployments are known as Split 6 and 7.x, as well as dual-split architectures including Split 2.
• Outdoor campus, urban and private networks are favoring Split 7.2 O-RU-based solutions, while split 6 S-RU based solutions are favored for indoor enterprise installations. Option 2 is preferred for <40km distance & latency tolerant deployment.
• Option 7.2 is preferred for Macro indoor/outdoor, also it allow minimal change in the gNB-RU side due to the change in 3GPP specifications.

References:

. 3gpp TR 38.801

. CISCO whitepaper-Bringing it All Together in 5G

. DTU Library: A Survey of the Functional Splits Proposed for 5G Mobile Crosshaul Networks