> For the complete documentation index, see [llms.txt](https://how.router.works/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://how.router.works/mobile/protocol.md).

# Mobile Protocol

## Introduction

Mobile protocol refers to communication technology and networking standards it uses to connect to cellular networks and transport data. 

The default mobile modem protocol on OutdoorRouter is "**Mobile-Data**." It has integrated the below QMI and PPP protocol and automatically invokes the most adaptable protocols depending on the mobile networks.

<div align="left"><figure><img src="/files/CIrMomDSBZLhgFmb3y59" alt="" width="375"><figcaption></figcaption></figure></div>

### QMI Protocol

QMI, short for Qualcomm MSM Interface, is a fast proprietary modem protocol used in many mobile modems for managing data sessions and enabling better carrier interoperability.

Due to the difference in the modem chipsets, the different mobile modems might use different QMI proxies. For example, Sierra modems use the QMI\_WWAN proxy, and Quectel modems use the GobiNet proxy. These proxies are using the same QMI protocol and provide similar working performance.

The primary difference is that GobiNet uses kernel space, while qmi\_wwan uses user space. In qmi\_wwan, only one process can handle the control port at a given time, while the GobiNet proxy allows multiple processes to access the device concurrently.

### **PPP Protocol**

PPP, short for Point-to-Point, is a traditional data link layer communications protocol. PPP protocol has been widely used and is the most flexible for device interoperability.

Some mobile carriers might not support QMI protocol to connect to their mobile networks. So, we must change the mobile protocol from the default “QMI” protocol to the “4G-PPP” one.

## **Switch Protocol**

**Example - Switch from Mobile Data to PPP**

If your carrier does not support the default Mobile-Data or QMI protocols, follow these steps to change the modem's protocol to Cellular PPP.

1. After logging into the router, go to "***Network > Interface***". \
   Locate the "**Mobile**" interface and click the "***Edit***" button.
2. Select "***Cellular PPP***" in the **Protocol** dropdown.
3. Click the "***Switch Protocol***" button. Then, it jumps to the Mobile configuration page based on the PPP protocol.

<div align="left"><figure><img src="/files/b6LUeMJ2DU8JM84ytxQ7" alt="" width="375"><figcaption></figcaption></figure></div>

Under the "**General Setup**" tab, ensure the Modem device uses "**/dev/ttyUSB2**". \
Choose the "**Active SIM card**" where your SIM card is inserted, and go to the related SIM1/2 tab to configure the settings below.

* **Service Type**\
  Choose "UMTS/GRPS" on the dropdown menu. Choose "CDMA/EV-DO" for American models.
* Enter the APN parameters - APN address, username, and password.
* For Europe/UK, change the "**Dial Number**" to **\*99#** and use the default ***\*99\*\*1#*** otherwise.
* Then click the "Save & Apply" button to submit the changes.

<div align="left"><figure><img src="/files/1PP1WIvbhga0EY7XihWV" alt="" width="375"><figcaption></figcaption></figure></div>

This will reconfigure the modem to leverage the PPP protocol for maximum compatibility with the mobile carrier. The router will leverage PPP for authentication and IP assignment.