Preface

The blogger is about to start university. Given the strict internet environment (referring to the expensive and poor-performing campus network) and the weak, laggy signals when using mobile data, I decided to prepare a CPE device. However, CPEs on the market either use obscure, uncertified modules or have poor antenna design with subpar signals. Therefore, I plan to handcraft a CPE router. This article will teach you how to make your own CPE router.

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Hardware Requirements

• A hardware device that supports installing OpenWrt or derivative systems based on it
• A mobile communication module compatible with the above hardware device

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Attachments

• OpenWrt
• X-wrt
• physdiskwrite

Specialized Terminology Explanation in This Article

• ISP - Internet Service Provider, i.e., carrier

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1. Installing the System

1.1 Downloading the System Image

• The system required for this tutorial is OpenWrt. Click here to jump to the official download site. You can also use the third-party system specially optimized for domestic users - X-wrt. Click here to jump to its official download site.

1.2 Installing the System

• Boot into any Windows PE environment. Use the physdiskwrite program to write the image to the hard drive.

Usage

physdiskwrite.exe -u -d <diskNumber> <path\to\system.img>

diskNumber is the disk index. If you don't know it, you can omit this parameter, i.e., do not include the -d command.
path\to\system.img is the file path to the system image.
-u removes the default 2GB disk size limit.

After the writing is complete, remove the external storage medium and reboot directly.

Note: The default rootfs partition size is very small. If expansion is needed, please manually expand it using software like DiskGenius.

2. Deploying the Environment

2.1 Initializing the System

After the first boot, please connect to the target machine via an Ethernet cable. When the device has two or more RJ-45 ports, one of them will automatically be changed to a WAN port. At that point, please connect a monitor to observe the system logs. If it shows the NIC mode as forwarding mode when you plug in the cable, then this port is usable. If not, please try a different port.

• Log into the admin panel using the default credentials admin. Navigate to System --> Administration, go to the SSH Access sub-section, enable SSH, and allow password access.
• Go to the Router Password sub-section to change the router password.

2.2 Adding the Corresponding Interface

• Navigate to Network --> Interfaces, click Add new interface... at the bottom left.
• Enter any name, select ModemManager for Protocol, and click Create interface.
• In General Settings, find Modem device and select the modem device you have connected.

Note: If you cannot find your connected device, please double-check the connection. If you are using a MiniPCIe interface modem on an x86 device, please observe if there are two or more MiniPCIe interfaces on the device. If so, try switching interfaces. Some interfaces only support the mSATA protocol, not the PCIe protocol.

• Enter the corresponding ISP's APN in the APN field. Refer to the table below for details.

ISP	APN
CMCC China Mobile	cmnet
CTCC China Telecom	ctnet
CUCC China Unicom	uninet

• Please enter the APN corresponding to the type of SIM card you have inserted.
• Go to Firewall Settings and assign the firewall zone as WAN.
• After ensuring all settings are correct, click Save.

Note: Due to characteristics of different ISPs, some configurations in General Settings may vary. The blogger here uses a standard CMCC SIM card, and this configuration works. For other ISPs, if this configuration doesn't work, please look up the specific settings yourself.

• Click Save & Apply to submit the configuration.

2.3 Verifying the Configuration

• After submission, return to the router admin homepage and wait for the network to connect. If you can access the internet normally, it proves the configuration is active, and your CPE is successfully set up.

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Conclusion

• The internet experience of a CPE depends on your antenna quality and the performance of the communication module. If you find the internet experience unsatisfactory, consider replacing it with a high-gain antenna and a higher-performance communication module.
• I am not a professional technician. If there are any omissions or errors, please feel free to point them out. I will humbly accept your suggestions.