5G RAN optimization using the

O-RAN software community’s

RIC (RAN Intelligent Controller)

ONS Europe, Sep-23-2019

Thoralf Czichy, Near-RT RIC PTL (thoralf.czichy@nokia.com), https://wiki.o-ran-sc.org/display/RICP

1 © 2019 Nokia
Copyright Nokia 2019
Content

1. Near-RT RIC within the O-RAN alliance architecture

2. xApps
3. RICP – near-RT RIC platform as open-source project
4. E2 concepts
5. E2 messages
6. Message flow examples
7. RIC components

2 © 2019 Nokia
ORAN alliance architecture Sometimes called
RAN Policy Guidance ORAN software community architecture for
near-RT RIC (this slideset just uses ”RIC”)
Function
https://www.o-ran.org/

3 © 2019 Nokia
 What is RIC: architecture and key requirements

RAN Use cases

Inventory Telemetry
>> 1 s Orchestrator
RAN analytics
(non-RT)
EMS functions Intelligent Network Policy Enforcement
Policy Control Intelligence
latency Controller Handover Management

A1 O1 Resource Radio-Link Management

Assurance Advanced SON

RAN Intelligent Controller Load Balancing

Resource
>10ms Radio Connection RRM Mobility Slicing Control RAN Slicing
3rd party
latency Optimization optimization optimization optim.
Applications
(xApps) (xApps) (xApps) (xApps) - Possibly co-localized with CU
Container platform (Akraino REC) Near RT: 10-100ms - Managing hundreds of DU’s
- host 3rd Party apps
E2 future extension E2 - Empowered with AI/ML
Real- - near-RT capabilities
time CU-CP - Role in network slicing.
3GPP E1 CU-UP
Multi-RAT RRC SDAP - A1: intend based interface
PDCP-C PDCP-U (policy)
- E2: interface with base station
- O1: for O&M purpose (FM, PM,
NVFI Platform: virtualization & COTS platform CM)
3GPP F1
DU RLC/MAC/PHY-High
DU RRU PHY-Low/RF

ORAN NGF-I (Open FH)

4 © 2019 Nokia
Content

1. Near-RT RIC within the O-RAN alliance architecture

2. xApps
3. RICP – near-RT RIC platform as open-source project
4. E2 concepts
5. E2 messages
6. Message flow examples
7. RIC components

5 © 2019 Nokia
xApps

Example xApps (under O-RAN SC’s RICAPP project)

• Measurement campaign xApp - general and procedure-specific KPIs for ~18 EN-DC related messages, using gs-
lite stream processing tool
• Admission control xApp – uses E2 to play with EN-DC’s SgNBAdditionRequest to implement simple admission
control on gNB.
• kpimon xApp - collects information from O-CU and O-DU using the E2 interface and calculates KPIs based on this
information. Provides information to other xApps
• Proprietary closed-source xApps
• A good way to start getting involved

Generally in areas of
• (from ORAN) Quality of experience (QoE)
• (from ORAN) Traffic steering
• (from ORAN) Massive MIMO, e.g., for customized beam sets
• (from ORAN) RAN slicing
• …

6 © 2019 Nokia
Content

1. Near-RT RIC within the O-RAN alliance architecture

2. xApps
3. RICP – near-RT RIC platform as open-source project
4. E2 concepts
5. E2 messages
6. Message flow examples
7. RIC components

7 © 2019 Nokia
RICP - Near-RT RIC as a O-RAN SC (Software community) project

• RIC and the O-RAN alliance specifications (in the eight O-RAN working groups) are being
developed in parallel. The current RIC platform is build around an experimental E2AP
specification proposal that also includes the ASN.1 definitions
• RIC as project of the ORAN software community (https://o-ran-sc.org/) has formally
started in June 2019. Candidate seed code is under https://gerrit.o-ran-
sc.org/r/#/admin/projects/ (all under “ric-plt” and under some under “com”) and based
on code developed by Nokia and AT&T.
• First formal release will be O-RAN SC’s “Amber” (end of November 2019) with
requirements listed in “O-RAN SC Ver A SW Requirements 20190731a” in https://wiki.o-
ran-sc.org/display/RSAC/Contributions
• Source code is distributed under the Apache 2 license.
• Simulators are used for development. O-RAN-SC’s O-CU eventually also needs to
implement them.

8 © 2019 Nokia
Content

1. Near-RT RIC within the O-RAN alliance architecture

2. xApps
3. RICP – near-RT RIC platform as open-source project
4. E2 concepts
5. E2 messages
6. Message flow examples
7. RIC components

9 © 2019 Nokia
E2 concepts adapted from O-RAN WG3 E2GAP (General Aspects and Principles)

• RAN Function definition. Defines the RAN Function Name and describes the E2 services that the specific RAN Function is currently
configured to present over the E2 interface. Typical functions are X2AP, F1AP, E1AP, S1AP, NGAP interfaces and RAN internal functions like UE,
cell, node management.
• More detailed E2SM (E2 Service Model) specifications define the function-specific protocols that are implemented on top of the E2 specification.
• In some of RICAPP’s xApps, we use an experimental E2 service model ”E2SM for X2AP” for some of the xApps being developed.
• For example, while the E2AP specification proposal defines the concept of event triggers, it is the E2SM for X2AP that defines the specific gNB/eNB-side
triggers in the X2AP function based on matching X2AP message type, or X2AP IE.
• RIC Event Trigger approach. Describes the approach to be used in RIC Subscription messages to set RIC Event Trigger Definition in the RAN
Function. For example, the X2 interface RAN Function may support event triggers for a specific X2 interface (i.e. connected to a specific LTE
eNB), for a given interface direction, interface Message type and one or more specific values in one or more nominated IEs (Information
Elements).
• RIC Action Definition approach. Describes the approach to be used in subsequent RIC Subscription messages to set required sequence of
RIC Action in the RAN Function. For example, the X2 interface RAN Function may support INDICATION messages of complete interface
message for Report and Insert RIC Services and a particular mechanism to configure one or more POLICY services.
• RIC Indication header and message approach. Describes the approach to be used by RAN when composing Indication messages for RIC
Report and Insert services. For example, the X2 interface RAN Function uses X2AP based ASN.1 encoding of either whole messages or
selected Information Elements
• RIC Control header and message approach. Describes the approach to be used by RIC when composing Control messages. For example, the
X2 interface RAN Function could use X2AP based ASN.1 encoding of whole messages.
• RAN Function Policies. Describes the set of policies that the RAN Function is configured to support and the corresponding parameters that
may be used to configure the policy using RIC Policy services

10 © 2019 Nokia
Many-to-many relationships, but only zero or one RIC per RAN node

The E2 manager is the one that initiates

E2 connections with the RAN nodes. It is
often referred to as xApp ”zero” – even if
it is actually part of the RIC platform. RAN
configuration information learned from
the RAN during connection establishment
(and later RAN Configuration Update
procedures) is stored by the RIC E2
manager.

The RAN (gNB/eNB) shall be able to

function independently of the RIC and
shall maintain normal RAN functionality
when and if the E2 interface and/or RIC
fails. To this end the E2 interface is
functionally an optional interface.

11 © 2019 Nokia
Content

1. Near-RT RIC within the O-RAN alliance architecture

2. xApps
3. RICP – near-RT RIC platform as open-source project
4. E2 concepts
5. E2 messages
6. Message flow examples
7. RIC components

12 © 2019 Nokia
 Indication-Report Control

Policy Indication-Insert

13 © 2019 Nokia
Content

1. Near-RT RIC within the O-RAN alliance architecture

2. xApps
3. RICP – near-RT RIC platform as open-source project
4. E2 concepts
5. E2 messages
6. Message flow examples
7. RIC components

14 © 2019 Nokia
Expected gNB side of E2 implementation
Example E2 indication report
gNB CU
For example: SgNB Addition Request
E2 Agent
E2 Connection Management • Event filter:
E2 • Triggers on matching events
RIC E2AP
ASN.1 Subscriptions
• Call flow (Report case):
INDICATION CONTROL
• Event filter always forwards message to event
handler
filter miss • If filter matches, event filter forwards to E2
E2 functional procedures
report if filter allows indication handler which then sends it to RIC
as Report-Indication
• xApp(s) in RIC perform analysis
Local policy

filter

eNB Event handler

X2
CP-X2 (UE and Cell functions) in gNB

15 © 2019 Nokia
Incoming E2 INDICATION – general flow

RIC

xApp
RMR library

2. E2 INDICATION

RMR library
1. E2 INDICATION
E2 Termination gNB

16 © 2019 Nokia
Expected gNB side of E2 implementation
Example E2 policy
gNB CU
E2 Agent For example, SgNB Addition Request
E2 Connection Management • Event filter:
E2
RIC E2AP
ASN.1 Subscriptions • Triggers on matching events

INDICATION CONTROL
• Call flow (Policy case):
• Event trigger forwards message to Local
Policy
Filter miss
E2 functional procedures • Local policy applies rules and either
POLICY with accept proceeds with original/modified message or
POLICY with reject replies with SgNB Addition Reject

Local policy
• Event handler processes the message as
before

filter

eNB Event handler

X2
CP-X2 (UE and Cell functions) in gNB

17 © 2019 Nokia
E2 SETUP

RIC

Redis RAN RNIB

6. E2Manager saves the node data in

RNIB

E2 Manager

REST
1. /nodeb/endc-setup (gNB)

5. E2 SETUP RESPONSE via RMR 2. E2 SETUP REQUEST via RMR

3. SCTP connect

E2 Termination 4. E2 SETUP REQUEST (ASN.1)

gNB
5. E2 SETUP RESPONSE (ASN.1)

18 © 2019 Nokia
xApp E2 Subscription

RIC
RAN config RNIB

2. Fetch NB list

1. E2 Subscription Request REST API 4. Update RMR routes with the new REST API
xApp Subscription ”xApp – subscription” information
Routing
6. E2 Subscription Ack
Manager Manager
RIC xApp FWK RMR library RMR library

3. Send E2 Subscription Request to all NBs 5. Update RMR

routes with the
new ”xApp –
subscription”
information

RMR library gNB

E2 Termination

eNB

19 © 2019 Nokia
Content

1. Near-RT RIC within the O-RAN alliance architecture

2. xApps
3. RICP – near-RT RIC platform as open-source project
4. E2 concepts
5. E2 messages
6. Message flow examples
7. RIC components

20 © 2019 Nokia
 Image repo Helm charts
xApps
RIC platform
Adm Ctrl xApp Measurement
xApp and Config campaign xApp VES Agent /

REST
Manager RIC xApp framework RIC xApp framework
VESPA

O1 A1 xApp Prometheus

REST
kpimon RIC demo xApp

API Gateway (Kong)

REST Mediator (report/control)
RIC xApp framework RIC xApp framework
Routing Manager Logging &
REST OpenTracing
A1 xApp1 xApp2

REST
Subscription (Resource
REST

Manager RIC xApp framework RIC xApp framework Manager)

E2 Manager Redis RAN RNIB Redis xApp DBs E2 Termination E2

REST

(e.g., cell data) (e.g., UE RNIB)

RMR library (over NNG) ASN.1 Prometheus exporters Trace&log Redis SDL + R-NIB API

RIC xApp Framework

21 © 2019 Nokia
Abbreviations
SON Self organizing networks
RRH Remote Radio Head = RU Radio Unit
RNIB Radio network information base ( in RIC)
EPC Evolved packet core (LTE core)
gNB (next) generation node B 5G’s base station. Further split into CU (centralized unit) – CU-CP, CU-UP, DU (distributed unit) and RU (e.g. via eCPRI)
eNB Evolved node B = LTE’s base station
MME Mobility management entity
SGW Serving gateway
S1-c EPC’s eNB-to-MME control plane traffic
S1-u EPC’s eNB-to-SGW user plane traffic
5G NSA Non-standalone option 3 ”EN DC” (eNB dual connectivity with various submodes for S1-u termination) and suboptions
5G SA 5G standalone achitecture
NR New radio interface (5G)
NG-RAN (RAN) Next generation radio (5G)
5GC 5G core
PDCP Packet data convergence protocol (in 5G gNB split architecture typically the lowest layer still on CU)
SDAP Service Data Adaptation Protocol (new in 5G)
ONAP Open network automation platform
MANO Management and orchestration
NMS Network management system
VESPA VNF event stream Prometheus Adapter
QoE Quality of experience

23 © 2019 Nokia