### :school: TEEP 2024_RT LAB_ORAN DPDK

#### :book: Milestone 3: Understanding and Learning Basic Knowledge about O-RAN

:::success
List the essential information of this chapter.
1. know O-RAN module how the functions.
2. O-RAN Architecture
3. Protocol stack
4. Call flow
:::

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### 1. know O-RAN module how the functions.


In the O-RAN architecture, the radio side includes Near-RT RIC, O-CU-CP, O-CU-UP, O-DU, and O-RU. The management side includes Service Management and Orchestration Framework that contains a Non-RT-RIC function.

Components Definition:
For the purposes of the present document, the terms and definitions given in 3GPP TR 21.905 and the following apply. A term defined in the present document takes precedence over the definition of the same term, if any, in 3GPP TR 21.905.

* **near-RT RIC**: O-RAN near-real-time RAN Intelligent Controller: a logical function that enables near-real-time control and optimization of O-RAN elements and resources via fine-grained data collection and actions over E2 interface.
* **non-RT RIC**: O-RAN non-real-time RAN Intelligent Controller: a logical function that enables non-real-time control and optimization of RAN elements and resources, AI/ML workflow including model training and updates, and policy-based guidance of applications/features in near-RT RIC.
* **NMS**: A Network Management System
* **O-CU**: O-RAN Central Unit: a logical node hosting RRC, SDAP and PDCP protocols
* **O-CU-CP**: O-RAN Central Unit – Control Plane: a logical node hosting the RRC and the control plane part of the PDCP protocol
* **O-CU-UP**: O-RAN Central Unit – User Plane: a logical node hosting the user plane part of the PDCP protocol and the SDAP protocol
* **O-DU**: O-RAN Distributed Unit: a logical node hosting RLC/MAC/High-PHY layers based on a lower layer functional split.
* **O-RU**: O-RAN Radio Unit: a logical node hosting Low-PHY layer and RF processing based on a lower layer functional split. This is similar to 3GPP’s “TRP” or “RRH” but more specific in including the Low-PHY layer (FFT/iFFT, PRACH extraction).
* **O1**: Interface between management entities in Service Management and Orchestration Framework and O-RAN managed elements, for operation and management, by which FCAPS management, Software management, File management shall be achieved.
* **O1***: Interface between Service Management and Orchestration Framework and Infrastructure Management Framework supporting O-RAN virtual network functions.
* **xAPP**: Independent software plug-in to the Near-RT RIC platform to provide functional extensibility to the RAN by third parties.

### 2. O-RAN Architecture
i will explained this diagram from top to bottom.

#### O-CU (Centralized Unit)
O-CU can also be referred to as L3. On the O-CU side, there is 2 scheme:
1. User Plane
any 2 element that use in User Plane, there are:
1.1 SDAP
1.2 PDCP

2. Control Plane
any 2 element that use in Control Plane, there are:
1.1 RRC
1.2 PDCP

#### O-DU (Distributed Unit)
O-DU can also be referred to as L2. On the O-DU side, there are 2 element:
1. RLC

2. MAC

Note: O-DU with 3 elements (there is an additional high PHY) is an example of the many configurations (Functional split options) that exist. in this example I will explain that the O-RAN architecture scheme uses the functional split option 7

#### O-RU (Radio Unit)
O-RU can also be referred to as L1. O-RU usually separated into 2 element, high PHY and low PHY.
1. High PHY (H-phy):
* Main Functions: High PHY focuses on the high physical layer in the network architecture, which involves high-level signal processing and high-level functionality.
* Specific Tasks: Complex signal processing, modulation, and other high-level features.
* Implementation: Can be implemented using more advanced and powerful hardware.

2. Low PHY (L-phy):
* Main Functions: Low PHY, on the other hand, focuses on the low physical layer, which is involved in more basic and more fundamental tasks in signal processing.
* Specialized Tasks: Tasks such as analog-digital signal conversion, basic modulation, and other physical tasks.
* Implementation: Usually implemented using simpler and more efficient hardware.

### 3. Protocol stack

**RRC (Radio Resource Control):**
* Main Function: Responsible for the management and control of radio resources between user devices (UE - User Equipment) and base stations (gNB - gNodeB).
* Role: Handles initialization and connection establishment procedures, and manages the allocation and management of radio resources.

**PDCP (Packet Data Convergence Protocol):**
* Main Function: Responsible for managing the transmission and reception of packet data, and providing compression and decompression functions.
* Role: Handles data transmission protocols at the IP layer and provides data-related security.

**RLC (Radio Link Control):**
* Main Function: Manages data transmission and reception at the radio link layer, providing reliable delivery services.
* High RLC: Focuses on high-level functionality, such as retransmission, block rebuilding, and flow control.
* Low RLC: Responsible for low-level functions such as merging and splitting of data blocks.

**MAC (Medium Access Control):**
* Main Function: Responsible for managing access to radio channels and allocation of radio resources.
* High MAC: Focus on high-level tasks such as resource allocation, QoS (Quality of Service) control, and spectrum allocation control.
* Low MAC: Responsible for low-level tasks such as access control and HARQ (Hybrid Automatic Repeat reQuest) control.

**PHY (Physical Layer):**
* Main Function: Handles the transmission and reception of physical signals over radio channels.
* High PHY: Focus on high-level signal processing, complex modulation, and other high-level physical functions.
* Low PHY: Responsible for low-level physical tasks such as basic modulation and analog-digital signal conversion.
### 4. Call flow