This document provides an overview of Open RAN terminology including virtualization, disaggregation, and decomposition. It explains the evolution from traditional integrated RAN architectures to disaggregated architectures with open interfaces. The key aspects covered are horizontal openness through open interfaces, vertical openness through virtualization and compute disaggregation, and the decomposition of RAN functions into distributed units and centralized units. References for further reading on Open RAN, O-RAN, and RAN disaggregation are also provided.

1. Beginners:
Open RAN Terminology
Virtualization, Disaggregation & Decomposition
@3g4gUK

2. Mobile Towers in Real Life
BBU + RU
Picture Source: National Instruments

3. Traditional Approach with ‘tight integration’
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RRU RRU
Dedicated Hardware
with SPP
Software
BBU
Proprietary or closed interfaces

4. Open RAN: Horizontal Openness (Open Interfaces)
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RRU RRU
Dedicated Hardware
with SPP
Software
BBU
Open Interfaces
Radio Hardware Disaggregation

5. 4G Evolved Packet System (EPS)
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MME/S-GW MME/S-GW
EPC
E-UTRAN
S1-U
X2
X2- U
eNB eNB
eNB
eNB
Open interfaces implies Open X2

6. Disaggregation: Vertical Openness (Virtualization)
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RRU RRU
COTS Hardware
with GPP
Software
vBBU
Open Interfaces
Compute Disaggregation

7. Evolution from Traditional to Virtualized to Containerized Deployment
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Picture Source: Kubernetes
VNF
CNF
PNF

8. Traditional Approach with ‘tight integration’
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RRU RRU
Dedicated Hardware
with SPP
Software
BBU
Proprietary or closed interfaces
2G, 3G & 4G

9. Decomposed Architecture with ‘tight integration’
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RRU RRU
Dedicated Hardware
with SPP
Software
DU
Proprietary or closed interfaces
Dedicated Hardware
with SPP
Software
CU
• RAN functional Split Architecture
• Used for 5G

10. Open RAN: Horizontal Openness (Open Interfaces)
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RRU RRU
Dedicated Hardware
with SPP
Software
DU
Open Interfaces
Dedicated Hardware
with SPP
Software
CU
Radio Hardware Disaggregation

11. Non-Standalone (NSA) NR, LTE assisted, EPC connected
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MME/S-GW MME/S-GW
EPC
E-UTRAN
S1-U
X2
X2- U
eNB eNB
en-gNB
en-gNB
Based on:
3GPP TS 37.340 V15.4.0 (2018-12)
Figure 4.1.2-1:EN-DC Overall Architecture

12. Next Generation Radio Access Network (NG-RAN)
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AMF/UPF AMF/UPF
5GC
NG-RAN
NG
Xn
Xn
ng-eNB ng-eNB
gNB
gNB
Based on:
3GPP TS 38.300 V15.4.0 (2018-12)
Figure 4.1-1: Overall Architecture

13. Disaggregation: Vertical Openness (Virtualization)
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RRU RRU
COTS Hardware
with GPP
Software
vDU
Open Interfaces
COTS Hardware
with GPP
Software
vCU
Compute Disaggregation

14. ©3G4G

15. Disaggregation
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Source: Red Hat

16. Disaggregation
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Source: Red Hat

17. O-RAN Architecture with CU & DU
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Source: Parallel Wireless

18. RAN Disaggregation by Prof. Sachin Katti, VMware
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4 levels of
disaggregation
taking place in the
RAN
1. Radio Hardware
2. Compute
3. Management
Plane
4. Control Plane (RIC)

19. ©3G4G
Source: Fierce Wireless, 5G Blitz Week, Spring 2021 - video

20. References & Further Reading
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• 3G4G: Open RAN, OpenRAN and O-RAN (link)
• Parallel Wireless: Whitepaper, Cloud-Native Applications 101 (link)
• The 3G4G Blog: 5G RAN Functional Splits (link)
• The 3G4G Blog: Open RAN Explanation, Videos, White papers and
Other Resources (link)
• Parallel Wireless: Introduction to O-RAN Philosophy (link)
• Sachin Katti: Virtualizing and Opening up the Telco Network (link)
• Tweet: Prof. Sachin Katti explains 4 levels of disaggregation taking place
in the RAN (link)
• The Mobile Network: How Nokia views the open and virtual RAN (link)
• RedHat Blog: Open RAN and O-RAN in Brief (link)

21. Thank You
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