---
# System prepended metadata

title: Daily Note 23/07/2020
tags: [O-RAN, Daily Notes]

---

# Daily Note 23/07/2020
###### tags: `Daily Notes` , `O-RAN`
## Name : Christofel Rio Goenawan
## University : Bandung Institute of Technology (ITB)


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## Schedule:
1. Study detailed works of O- DU High.
2. Study works of O- DU Low Interfaces.

## Outcome : 
1. Explain detailed functionality of O- DU High.
2. Explain architecture of O- DU Low Interfaces.

## Further Plan : 
- Study more detailed about O-DU Interfaces.
- Study more detailed about AIO Installation in Kubernets
- Try to deploy Acumos AIO in NTUST server


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## Daily Log

### 1.Study detailed works of O- DU High. <mark>(9.00)</mark>
- In this meeting Writer presents the progress and latest result to Prof Ray, mentors and internee.

### 2.Study works of O- DUY Low Interfaces. <mark></mark>
- Study more detail explanation in [Documentation](https://wiki.o-ran-sc.org/display/ORANDU/O-DU+High) and other sources.




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## Report


### 1. Functionality od O- DU High

>In this note Writer use [Documentation](https://wiki.o-ran-sc.org/display/ORANDU/O-DU+High) and [Ferlinda's Note](https://hackmd.io/@ferlinda/S1iQ2--pL) as study sources.

#### O- DU L2 Functional Block
From documentation , The simple functionality scheme of O- DU High can be seen as below.

![](https://i.imgur.com/B9B3gRy.png)


#### Functionality

From scheme above , we can see there are 4 main functionality as below.

1. **F1 Control Panel Inreface Handling Modules (F1AP Handler)**

F1AP Handler consists of tasks related to **cell management, UE management and semi-static Air Interface Resource Management** at the **cell level**.

:::info
The tasks define in 3GPP TS 38.473
:::
 
F1AP Handler functionality consists of 4 major function as below.

- **Cell State Manager** 
  - Handles all the tasks related to the handling of cells at O-DU Cell Start, Cell Stop, etc.
  - Manages a Finite State Machine (FSM) for handling cell specific procedures.
- **UE State Manager**
  - Handles procedures related to UE like SRB packet transfer, UE Context Setup, Release procedure, UE Context Modification procedure.
  - Manages internal state machine for handling UE specific procedures and interacts with other layers (RLC/MAC/F1U) for UE level interactions and signaling.
- **F1AP Interface Manager**
  - Interacts with O-CU-CP (Control Unit) to control commmunication setup and exchanges F1AP messages over SCTP interface.
- **Resource Manager**
  - Performs tasks like Admission Control, Bearer Control, etc.
  - Takes care of managing all the air interface resources for a UE (physical level resource allocation: SR, CSI resorces), etc.

2. **F1 User Plane Interface Handling Modules ( F1- U )**

F1- U consists of tasks related to **Tunnel management, DL and UL Data and Downlink flow control**. The detailed function of F1-U can be seen as below.

![](https://i.imgur.com/mDqxzSi.png)


- **Data Plane application**
  - Handles DL Data packets received within 3GPP TS 29.281 defined NR RAN Container
  - Performs UL Data packet transmission for packets received from RLC and invokes eGTPU encapsulation/decapsulation functionality for eGTPU header processing.
- **eGTPU encaps/decaps**
    *  Performs eGTPU header decapsulation and processing in the DL and eGTPU  header encapsulation for the  UL packets at F1-U.
- **Downlink Flow Control**
    * Downlink Data Delivery Status generation with feedback received from RLC.


3. **RLC Protocol Modules**

These modules **handles processing related to SRB and DRB plane**. MAC layer indicates downlink data notification request for logical channel along with desired **RLC PDU size** and **uplink data** by sending RLC PDUs. RLC uses logical channel for data transfer, forms SDUs by reassembling and the received PDUs and transmits SDUs to upper Layer via F1 interface.  The ELC Protocol Modules simple functional diagram can be seen as below.

![](https://i.imgur.com/ROX3Dxi.png)

The modules consiste of 2 main function as below.

1. **UE and Bearer Context Management**
2. **RLC Mode Receiver and Transmitter (Rx, Tx)** 
    * TM mode
    * UM mode
    * AM mode

4. **MAC Protocol Modules**

MAC Protocol Modules consists of 9 main functionality as below.

- **UE and Bearer Context Management**
    * Stores semi-static information on air interface resources for UE.
    * Keeps QoS related information for scheduler.
- **HARQ Management**
    *  Performs DL and UL HARQ management by keeping track of HARQ feedback, HARQ timer and providing free HARQ processes information to the scheduler.
- **RACH Manager**
    * RACH (Preamble) resource management, CRNTI Assignment, and do Message-2,3,4 resource allocation and handling.
- **CCCH Manager**
    * Handles DL and UL CCCH message and corresponding HARQ.
- **Resource Assign**
    * PDCCH, PDSCH, PUCCH, and PUSCH Resource Assignment based on resource allocation schedule from scheduler.
- **MAC Encoder**
    * Creates MAC Transport block based on input from shceduler, interfaces with RLC to get RLC PDUs.
- **Demultiplexer**
    * Demultiplexing UL Transport block containing MAC CE and RLC PDUs and sends it to respective tasks.
- **CSI Manager**
    * Configuration of Channel State Information and informing CSI feedback drom UE to scheduler.
- **PHY-MAC Interface**
    * Receive and rransmit L1-L2 interface messages.

:::info
 **Next Writer will learn more detailed about L2 MAC Scheduler**
:::

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### 2.  O- DU Low Interfaces

> In this note Writer use [Documentation](https://www.o-ran.org/specification-access) and [Ferlinda's Note](https://hackmd.io/@ferlinda/BJ6dLz06U) as study sources.

####  L1 Interfaces

From Ferlinda's Notes , L1 Interface have 3 main interfaces to communicate with other network functions as below.

1. **Interface between L1 and Front Haul** : It adopts the WG4 specification for the CUS plane communication.1. Interface between L1 and Front Haul, it adopts the WG4 specification for the CUS plane communication.
2. **Interface between O-DU Low and O-DU High** : It adopts the FAPI interface according to the WG8 AAL specification.
3. **Interface between O-DU Low and accelerator** : DPDK BBDev was adopted as original contribution, it will follow the WG6 definition after the WG6 specification is finalized.

WG Reference to [General Architecture of O-RAN](https://hackmd.io/@ferlinda/HJAv7fOE8) can be seen as below.

![](https://i.imgur.com/ooDdg3U.png)


---



## Reference
1. https://wiki.o-ran-sc.org/display/ORANDU/O-DU+High
2. https://www.o-ran.org/specification-access
