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# System prepended metadata

title: '[09/02/2021] All About RAN and O-RAN (part 1)'

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# [09/02/2021] All About RAN and O-RAN (part 1)
### Salman's Notes :memo:
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### What is RAN? :calling: 
RAN stands for Radio Access Networks. As explained in the last note, Cellular Networks have to transmit data to and from a massive amount of users that may or may not be on the move. ==RAN is a part of the cellular network that connects these users to the network.== RAN has to ensure that these users have stable connections to the network by handling any interference, and makes sure every user gets the corrent QoS that is true for their billing.

### How does it work? :construction_worker:
A User Equipment (UE) such as a smartphone, tablet, or any other devices connecting to the cellular network ==first establishes a connection through the Base Station==. The Base Station also connect the UE to the other part of the Cellular Network that is the Mobile Core. The Mobile Core consists of two parts, that is the Control Plane and the User Plane. The Control Plane tracks the registration, authentication, and mobility of the user while the User Plane is the channel for the data that will be sent by the user. Data will be sent only when the UE has been fully connected to the network. ==To ensure a stable connection for the user, the Base Station must also transfer the user to another Base Station if neccessary==

### What does RAN look like? :eyes: 
While it is difficult to view RAN physically as it is comprised of many components, we can somewhat view it internally as abstract concepts based on its function.
![](https://i.imgur.com/M91bBC9.png)
*Figure 1. RAN processing pipeline, including both user and control plane components.*

Figure 1 shows the flow of connection and data from  the Mobile Core to the Base Station. 

- The PDCP or the Packet Data Convergence Protocol is responsible for making security and efficiency changes to the packet such as compressing and decompressing the IP headers and adding protections. It is also responsible for making some forwarding decisions during handovers to other Base Stations.

- The RRC stands for Radio Resource Control that is used to configure the policies that will be used by the other components, and lives the Control Plane of the Mobile Core.

- The RLC (Radio Link Control) has the function of segmenting and assembling packets before a packet is sent and after they are received, respectively.

- The Scheduler that was discussed in the [last note](https://hackmd.io/@msalmana/HkR2UF6l_) lives in the MAC, or the Media Access Control. Therefore the MAC needs to do multiplexing and scheduling of packets to ensure a fair and stable connection for all users.

- The PHY or the Physical Layer is the layer near the Base Layer does the coding and modulation of the packets before they are given to the Digital/Analog Converter and RF Front End so that they can be transmitted with the right waveform and frequency.


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continued in part 2!

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### References
Title: 5G Mobile Networks: A Systems Approach
Authors: Larry Peterson and Oguz Sunay
Source: https://github.com/SystemsApproach/5G
License: CC BY-NC-ND 4.0
Link: https://5g.systemsapproach.org/ran.html

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