4G LTE router : converting USB to ETH - Page 1
Forum section: electronics / projects

author: bonelli
author_rank: Contributor
timestamp: June 24, 2025, 03:49:02 pm
content: Hello,I plan to use a 4G LTE cat 4~6 module (from quectel or something like that) to build a 4G router. The router will be connected to an Ethernet switch. Hi-speed 4G modules are generally USB 2 HS (device).I didn't find any solution to convert the USB interface from the router to gigabit ETH. Obviously, I need something fast, reliable and low-latency (4G LTE cat 4 is 150Mbps, cat 6 is 300Mbps, I'm trying to find a cat 6 module).Any ideas ?Thanks !

author: grumpydoc
author_rank: Super Contributor
timestamp: June 24, 2025, 06:51:50 pm
content: When you say "4G LTE cat 4~6 module" do you mean something intended to plug into an external USB port or something with a MiniPCIe/M.2 interface?

author: bonelli
author_rank: Contributor
timestamp: June 25, 2025, 07:56:08 am
content: Quote from: grumpydoc on June 24, 2025, 06:51:50 pmIn can be both. I will select PCIe or USB depending of what I will found to convert it to ETH.The converter could be (preferably) an IC chip, or a software bridge running on a linux MPU.

author: ftg
author_rank: Frequent Contributor
timestamp: June 25, 2025, 07:57:44 am
content: If the router has USB Host and whatever operating system it runs has drivers for it, isn't this a USB Ethernet adapter?If you are rolling your own, Microchip LAN7500https://www.microchip.com/en-us/product/LAN7500and LAN7850https://www.microchip.com/en-us/product/LAN7850have public documentation.I also took a quick look at Realtek and their current site only seems to list USB 3.0 based solutions like RTL8153B-VB-CGhttps://www.realtek.com/Product/Index?id=4078&cate_id=786&menu_id=1008but sourcing those and their documentation might be annoying.

author: grumpydoc
author_rank: Super Contributor
timestamp: June 25, 2025, 08:29:27 am
content: Quote from: bonelli on June 25, 2025, 07:56:08 amThere's not really an "IC Chip" unless you really are rolling your own in which case you need an SoC of some sortFor an external USB dongle start with an existing router which has a USB interface and which is capable of running OpenWRT, or look at a platform designed for building routers such as the Banana Pi R4 (and other Banana Pi boards).

author: fchk
author_rank: Frequent Contributor
timestamp: June 25, 2025, 08:34:53 am
content: Quote from: bonelli on June 24, 2025, 03:49:02 pmLook here:https://www.waveshare.com/product/iot-communication/long-range-wireless/4g-gsm-gprs/5g-m.2-to-gigabit-eth.htmI've used this with an RM500U-CNV. This module has both USB 3.1 and PCIe interfaces. In this case thie PCIe is configured as root port and connected to a RTL8125B. This makes the whole thing a standalone 5G-Ethernet router.Configuration is not easy. It took me two days to figure everything out.

author: grumpydoc
author_rank: Super Contributor
timestamp: June 25, 2025, 10:39:57 am
content: Is this for a product that you are developing, or for personal use?

author: bonelli
author_rank: Contributor
timestamp: June 25, 2025, 03:31:47 pm
content: @fchk, thanks for the link, this product looks quite perfect for me.Quote from: grumpydoc on June 25, 2025, 10:39:57 amFor personal use. My new home is located 2km from a city, in mountain area. Wired internet connections are problematic. By chance I'm overlooking the city and there is a 4G/5G base station very close to me (but I'm suspecting it is looking the city : I am behind it).Someone lent me a 5G router with integrated antennas that sometime works in 5G mode, but the connection is not reliable (too bad SNR). When switching to LTE, bit rate is obviously lowered but the connection is more stable.I'm trying to buy/build something with free connectors to use external directional antennas (eventually 2 antennas for MIMO) to put some gain on the RF path and target the good direction.

author: grumpydoc
author_rank: Super Contributor
timestamp: June 25, 2025, 04:08:36 pm
content: A couple of years ago I would have recommended an PC Engines APU, these days the Banana Pi R4 or one of the other Banana Pi boards is a good starting point.Or one of the small Intel Celeron mini PC's which can be had off AliExpressHere's mine based on an APU 3d4, the Quectel EP06 and an Asia RF AW7915-NP1I'm curently putting a 5G box together though haven't quite settled on the best hardware combinationIf you have 5G but it's unstable it might work OK with external antennae - which you are planning anyway. 5G cards tend to be M.2 and USB3 or PCIe though. I have one working on the BPi R4 using a T99W175 modem.

author: grumpydoc
author_rank: Super Contributor
timestamp: June 25, 2025, 04:12:08 pm
content: Quote from: bonelli on June 25, 2025, 03:31:47 pmhttps://www.cellmapper.netMight give you more info about the towers close to you and what areas they serve. You can get the cell tower ID using various free apps on your phone (certainly Androis, not sure about iPhone).

author: grumpydoc
author_rank: Super Contributor
timestamp: June 25, 2025, 04:23:06 pm
content: Quote from: fchk on June 25, 2025, 08:34:53 amI once bought a similar 3G device - worked OK but I was cheesed off to realise it was running OpenWRT but they denied any request for the code. I now stick to more open systems where I can.The linked system is 5G and comes with relatively expensive modem options - there is no guarantee it will work with cheaper modems such as the T99E175 (though buying that is a bit of a quagmire, there are multiple versions some supported, some not).

author: fchk
author_rank: Frequent Contributor
timestamp: June 26, 2025, 03:56:10 am
content: Quote from: grumpydoc on June 25, 2025, 04:23:06 pmYes, indeed. Most M.2 modem cards can't use their PCIe port as Root Port. You really should buy a bundle together with a suitable modem.

author: fchk
author_rank: Frequent Contributor
timestamp: June 26, 2025, 04:51:06 am
content: This is the configuration required for the Waveshare box with the RM5500UCNV modem.Base config:AT+QCFG="pcie/mode",1AT+QCFG="usbnet",5AT+QCFG="nat",1Stop asking for SIM pin:AT+CLCK="SC",0,"<PIN>"Setup APN: (example for Telekom.de)AT+QICSGP=1,1,"internet.telekom","telekom","tm",3Enable Ethernet:AT+QCFG="ethernet",1AT+QCFG="eth_at",1RebootAT+CFUN=1,1Dial-in automaticallyAT+QNETDEVCTL=1,3,1

author: grumpydoc
author_rank: Super Contributor
timestamp: June 26, 2025, 07:17:10 am
content: If you bought this thing as a bundle why the <expletive deleted> do you need to mess about with AT commands to get it to work?Wouldn't touch that with a barge pole.

author: fchk
author_rank: Frequent Contributor
timestamp: June 26, 2025, 07:23:26 am
content: Quote from: grumpydoc on June 26, 2025, 07:17:10 amWell, the 5G modem card IS the complete router. It already does NAT, DNS, DHCP etc. on its own without any additional PC. The carrier board only contains the connectors, the LAN-Chip, and power supply.

author: grumpydoc
author_rank: Super Contributor
timestamp: June 26, 2025, 07:59:55 am
content: Oh I seeIt's a nice box to house an expensive 5G modem and that's about it.Quote from: fchk on June 26, 2025, 07:23:26 amYes, they do, in fact they often have Linux as their embedded OS but they are not typically configureable in any useful way. So you wind up with "something else" like an R Pi anyway to do all that stuff and present it to the user in a reasonable way, not AT commands.By the way, bonelli, what's the budget for this project?Also despite the fact it would be my personal, dragged kicking and screaming last choice - have you considered Starlink?Edit:Oh, right - I'll admit to piqued interest now.So this takes a 5G modem, slaps an RTL8125 onto it's PCIe bus so it is acting as a PCIe hub and the RTL8125 is just a peripheral.I mean, it's an incredibly neat ideaI just wouldn't buy one.I would buy a suitable platform with an M.2/MiniPCIe slot and a modem card.It's much more flexible and doesn't constrain you to a specific LTE/5G modem (though picking a combination which works is tricky whatever approach you take).At least it's (the Waveshare thing) cheap enough only $120 with the RM500U-CNV, but that's without tax and shipping as far as I can see.