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# System prepended metadata

title: <center><i class="fa fa-edit"></i>ALOHA Model </center>
tags: [Internship]

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# <center><i class="fa fa-edit"></i>ALOHA Model </center>
###### tags: `Internship`
:::info
**Goal:**
To gain a basic understanding of the components behind network technologies. Focus on vocabulary and systems overview.

**Resources:**
[DVB-RCS2 overview (Skinnemoen et al, 2017)](https://drive.google.com/file/d/1U9QFFTNPAvdSXlJMj0xZxlmB-WVMFJaO/view?usp=sharing)
[ALOHA Random Access Protocol (Tutorials Point)](https://www.youtube.com/watch?v=g32GA0YR26U)
:::

## ALOHA Random Access Protocol
Developed in 1970, ALOHA was the first random access protocol. It was designed for radio LAN, but has also been used for shared medium.

However, when applied to shared medium, it encounters the problem of collision. If multiple stations send frames at the same time, their signals collide and disrupt transmission. The times of collision are referred to as "vulnerable time."

There are two main types of ALOHA: pure ALOHA and slotted ALOHA.
### Pure ALOHA
![](https://i.imgur.com/NTvSNay.png)

Pure ALOHA allows frames to be transmitted at any time. As such, frames tend to be disrupted in fragments and the collision duration tends to span several frames.

### Slotted ALOHA
![](https://i.imgur.com/pt4kaGt.png)

Slotted ALOHA only allows stations to transmit frames in certain slots. When collisions occur, they would disrupt the entirety of certain frames and leave others wholly intact.

