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*[O-RAN]:Open Radio Access Network

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# <center><i class="fa fa-book"></i> Introduction to O-RAN </center>
:::
###### tags: `study` `O-RAN`

:::success
**🎯 Goals:**
- [x] - <a href="#Module-1-the-characteristic-of-O-RAN">To know the characteristic of O-RAN</a>
- [x] - <a href="#Module-2-the-overall-architecture-of-O-RAN">To know the overall architecture of O-RAN</a>
- [x] - <a href="#Module-3-the-difference-between-O-RAN-and-5G">To know the difference between O-RAN and 5G</a>
- [x] - <a href="#27-Service-Management-and-Orchestration-%EF%BC%88SMO%EF%BC%89">To know the service Management and Orchestration （SMO）</a>
- [x] - <a href="#Module-4-Summary">Summary</a>
:::
:::info
:bookmark: **Reference:**
- [O-RAN ALLIANCE](https://www.o-ran.org/)
- [O-RAN Architecture Description](https://www.o-ran.org/specifications)
- [Open RAN – Service Management and Orchestration (SMO)](https://www.techplayon.com/open-ran-service-management-and-orchestration-smo/)
:::
[toc]

# Module 1: the characteristic of O-RAN
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## 1.1 O-RAN (Open Radio Access Network) overview map
- 
<br><br>
## 1.2 O-RAN concept
<br>
- 

It is a concept based on interoperability and standardization of RAN elements including a unified interconnection standard for white-box hardware and open source software elements from different vendors.
> Chinese: 可針對不同供應商的白牌硬體和統一且相通的開源軟體所組成

## 1.3 O-RAN architecture overview

O-RAN architecture integrates a modular base station software stack on off-the-shelf hardware which allows baseband and radio unit ==components from discrete suppliers to operate seamlessly together.==
> Chinese: O-RAN 架構以模組化形式，允許來自各家供應商組合運行。

## 1.4 O-RAN application

O-RAN underscores streamlined 5G RAN performance objectives through the common attributes of efficiency, intelligence and versatility. Open RAN deployed at the network edge will benefit 5G applications such as autonomous vehicles and the IoT, support network slicing use cases effectively, and enable secure and efficient over-the-air firmware upgrades.
> Chinese: 通過效率、智慧和多功能共同性強調了簡化的 5G RAN 性能目標，速度快、更安全。

# Module 2: the overall architecture of O-RAN

## 2.1 Overall architecture diagram


## 2.2 RIC non-Real-Time
### 2.2.1 The range of non real-time control
&emsp;&emsp; **>= 1 Second**
### 2.2.2 introduce
perform operations including policy management and analytics
> Point: 管理、分析

## 2.3 RIC near Real-Time
### 2.3.1 The range of non real-time control
&emsp;&emsp; **>= 10ms < 1 Second**
### 2.3.2 introduce
perform ==time sensitive== functions such as load balancing, handover and interference detection
> Point: 負責需要即時處理的功能

The RIC near Real-Time layer to benefit from ==intelligently trained models and real time control functions distributed== by the RIC non-Real-Time layer.
## 2.4 O-CU (The open Central Unit)
- In the architecture described in the standard,
- generally speaking, one `gNB-CU-UP` , One `gNB-DU` can only be connected to one `gNB-CU-CP`,
- but with proper configuration and implementation, it can also be connected to multiple `gNB-CU-CPs`.
- The two are indirectly ==through the E1== interface.
### 2.4.1<font class="title"> O-CU-CP</font> (Control Plane)
&emsp; Mainly responsible for the <font class="highlight">RRC</font> in gNB and the part of the control plane in <font class="highlight">PDCP</font>
### 2.4.2<font class="title"> O-CU-UP </font>(User Plane)
&emsp; Responsible for the <font class="highlight">SDAP</font> in gNB and the part of the user plane in <font class="highlight">PDCP</font>
### 2.4.3 Advantages and disadvantages of CP-UP separation
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**Advantages:**
- Increase the flexibility of network operation and management.
- Increase the possibility of performance optimization of the placement of RAN side functions.
- Increase the possibility of supporting interoperability between different manufacturers.
> point: flexibility and possibility
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**Disadvantages:**
- With the increase of network complexity.
- The maintenance work may also increase.
- The delay in the transmission of some signaling may increase.
> point: Complexity and delay in the transmission.
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*[commercial off-the-shelf]:商用現成或商用現貨產品是將已有的軟體或硬體包裝
*[NIC]:網路介面控制器
## 2.5 O-DU (The open distributed unit)
&emsp; Contains baseband processing such as RLC, MAC and High-PHY.<br>
&emsp; It is a commercial off-the-shelf (COTS) edge servers that can function as **baseband processing** unit to handles high **PHY** layer, **MAC** and **RLC layer** with network function virtualization (NFV) or **Containers**.

### 2.5.1 O-DU Requirements and Characteristics:
- The O-DU shall connect to multiple O-RUs in the southbound interface (Fronthaul)
- The O-DU shall allow resource pooling for **Virtual Baseband** functions of high PHY layer, MAC and RLC, synchronization, OAM, Ethernet, as well as ==F1 interface== function
- O-DU shall support Linux operating system such as Ubuntu or similar
- O-DU shall support containerization with Docker, K8s or similar
- The O-DU shall be designed for both **outdoor and indoor** scenarios
### 2.5.2 O-DU Hardware Architecture:
- **Synchronization and Transport:** GPS/PTP (IEEE 1588) modules can be synchronization, ==GPS is an option== due to limit the hardware cost and complex design.
Transport NIC cards are deployed for southbound fronthaul connectivity between O-DU and O-RU and northbound mid-haul connectivity between O-DU and O-RU.
> (NIC) network interface controller: 網路介面控制器
>> network interface card: 網路卡
>> LAN adapter: 區域網路接收器
- **CPU Core and Memory:** These CPU cores and memory are made shared with the help of NFVI software.
- **FPGA** shall be used to process the FEC function with CPU cores to process the high physical, MAC, and RLC layer.

## 2.6 O-RU (The open radio unit)
*[Fiber]:光纖網路
*[Ethernet]:乙太網路
It is to convert radio signals sent to and from the antenna to a digital signal that can be transmitted over ==the fronthaul== to Distributed Unit (DU).
- Synchronization and Fronthaul Transport:
The fronthaul connectivity between O-RU and O-DU is eCPRI can be established using Fiber or Ethernet
- Lower PHY Layer Baseband Processing:
The lower PHY layer processing can be implemented by using ==FPGAs or ASICs==.
- RF Front End (RF FE):
- Power Amplifiers (PA)
- Low Noise Amplifiers (LNA)
- Digital Analog Converters (DAC)
- Analog Digital Converters (ADC)
- Digital Front End (DFE):
- Digital Up Converter (DUC)
- Digital Down Converter (DDC)
- Digital Pre-Distortion (DPD)
- Crest Factor Reduction (CFR)
- 

## 2.7 Service Management and Orchestration （SMO）

- A design environment for rapid application development
- A common data collection platform for management of RAN data as well as mediation for O1, O2 and A1 interfaces
- Support for licensing, access control and AI/ML lifecycle management, together with legacy north-bound interfaces
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- SMO framework can be used for RAN Optimization with the **help of Non-RT RIC** and **rApps**.
- The Non-RT RIC enables the intelligent RAN **optimization** in non-real-time by providing policy-based guidance using data analytics and **AI/ML** models.
:::
### 2.7.1 R1
- R1 interface to allow portability and lifecycle management of rApps.
- The interface enables **Open APIs** to be integrated in the SMO framework.
- It is a <u>**collection of services**</u> including service **registration** and discovery services, **authentication** and **authorization** services, **AI/ML** workflow services, and **A1, O1 and O2** related services.
### 2.7.2 A1
- A1 interface is used for **policy guidance**.
- Such as getting User-Equipment to change frequency.
### 2.7.3 O1
- For managing the operation and maintenance (**OAM**) of multi-vendor Open RAN functions.
### 2.7.4 O2
- **O-Cloud** infrastructure resource **management**
- It is used to support cloud infrastructure management and deployment operations
### 2.7.5 OFH M-Plane
- **As an alternative to O1** interface to supporting multi-vendor O-RU integrations.
- Open FrontHaul M-plane Including:
- startup installation
- software management
- configuration management
- performance management
- fault management
- file management.

# Module 3: the difference between O-RAN and 5G

## 3.1 Disaggregation
Disaggregation is essential for 5G deployment and evolution, enabling mobile operators to open the RAN network and leverage multi-vendor solutions.
>Point: 拆解5G架構並且白牌化

## 3.2 Diversity
Operators will be empowered to utilize best-of-breed components based on their individual network use case profile. This opens opportunities to reduce development cycles by developing different parts of the network separately while harnessing more innovation horsepower collectively.
>Point: 多元廠商，創新碰撞多樣性

# Module 4: Summary

## 4.1 O-RAN Benefits

Operational efficiencies have been realized through past RAN innovations such as cloud RAN (cRAN). By enabling an open, multi-vendor RAN ecosystem, combined with a more elastic and flexible RAN architecture that is already taking shape through virtualization
>Point: 開源原本的RAN技術，透過虛擬化形成的更具彈性和靈活性的 RAN 架構結合

- **Moving away from the vendor-specific**
not only enables more flexibility for operators, it also minimizes the “secret sauce” that leaves them reliant on a single vendor for all aspects of RAN implementation and optimization.
- **Low cost and easy integration**
Competition and proliferation resulting from of new entrants can potentially drive down O-RAN equipment costs. The inter-carrier, interoperability aspects of Open RAN can also be used to increase efficiencies for existing LTE networks as they continue to incorporate the virtualization and disaggregation that are prerequisite 5G RAN deployment.
>point: 降低 O-RAN 設備成本、整合作為 5G RAN 部署先決條件的虛擬化和分解。
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>**O-RU (radio unit)**: `開放式無線電單元`
**O-DU (distributed unit)**: `開放式分佈式單元`
**Near-RT RIC (Near-real-time RAN Intelligent Controller)**: `近即時網路智能控制`
**O-CU-CP (Unit – Control Plane)**: `O-RAN Central Unit – Control Plane`
**O-CU-UP (User Plane)**: `O-RAN Central Unit – User Plane`