RAN Intelligence Controller (RIC): An Introduction

Mobile Telecommunications Networks are getting complex. Mobile Network Operators are faced with many challenges like Network Economics, need for being Agile and Innovative and at the same time provide best-in-class service to its subscribers. OpenRAN Solution has been one of the disruptive concept trying to disrupt the traditional RAN solution market by equipping Operators with capabilities they need in order to address the challenges they face. Networks are getting complex and there is a need for Self-Optimizing & Self-decision-making networks.

Software Defined Networking (SDN) concept has been now widely adopted for communications networks given the benefits it provides. As per Wikipedia definition of SDN:

“Software-defined networking (SDN) technology is an approach to network management that enables dynamic, programmatically efficient network configuration to improve network performance and monitoring, making it more like cloud computing than traditional network management. SDN is meant to address the static architecture of traditional networks. SDN attempts to centralize network intelligence in one network component by disassociating the forwarding process of network packets (data plane) from the routing process (control plane). The control plane consists of one or more controllers, which are considered the brain of the SDN network where the whole intelligence is incorporated.”

SDN Architecture (Source: ONF)

ORAN-Alliance is further enhancing SDN capability of the RAN solution by introduction of RAN Intelligence Controller (RIC). RIC and CU-CP/CU-UP Split introduce Control and Data plane separation.

Source: ORAN-Alliance

CU-CP/CU-UP split is first level of Control & Data plane separation. RIC extends the control & data plane separation. RIC takes the intelligence out of the RAN nodes like CU & DU and makes them available as xApp/rApp applications. xApp/rApp are the applications on Near-RT RIC and Non-RT Application frameworks. Apps use standard interfaces like E2/O1 to talk to the Data plane nodes like CU/DU. RIC Frameworks expose Open APIs that can be used by xApp/rApp for their functioning. Thus RIC framework and xApp/rApp are decoupled and standardized.

xApp/rApp Applications provide the flexibility and programmability of the RAN. xApp/rApp make use of concepts like AI/ML, Policy guidance and Enrichment info based analysis and analytics to execute and realize the business needs of the Operator. These Applications could be built by RAN vendor, 3rd Party or Operators themselves.

There are two types of RICs, Near-Real Time RIC and Non-Real Time RIC. ORAN provides a three different Control loops for decision making.

• O-DU Scheduler control loop

• Near-RT RIC control loop

• Non-RT RIC control loop

Source: ORAN-Alliance

Depending on use case needs either of the control loops can be used. Control loops are defined based on the controlling entity. Control loops run in parallel of each other.

Typical execution time for use cases:

• Non-RT RIC Control loop — is 1 second or more.

• Near-RT RIC Control loop — is between 10 ms to 1 second.

• O-DU scheduler loop — is below 10 ms.

rApps control the Non-RT RIC Control loop. Due to Non-Real time nature they are called Non-Realtime RIC Apps. xApps control the Near-RT RIC Control loop. Due to Near-Real time nature they are called Near-Realtime RIC Apps.

RIC solution can either augment traditional SON or repackage SON use cases to provide a flexible, standards based, interoperable, multi-vendor, programmable solution for RAN optimization.

ORAN-Alliance has listed several use cases to be covered by RIC based Network optimization and managements. Just to name a few are:

• Traffic Steering.

• QOS/QOE Optimization.

• Energy saving.

• Slice SLA assurance.

• Others.

This RIC xApp/rApp use case list is going to grow over time as time progresses. RIC is going to be a valuable and important component of the RAN solution which will provide flexible, standards based, interoperable, multi-vendor, programmable solution for network optimization and management. This will thus help in Networks to become Self-optimizing and Self-decision making.