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Sep 11, 2025
By CEO
10 Min Read

How to Make an SMS Broadcaster Using USRP SDR or LimeSDR

Sending broadcast SMS is a core feature of GSM networks. Telecom operators use it for alerts, cell information, and emergency notifications. With modern Software Defined Radios (SDR) like LimeSDR or USRP, researchers and hobbyists can experiment with building a lab-scale SMS broadcaster to better understand GSM technology.

What You Need

Hardware

SDR Device:

A host computer (Ubuntu Linux recommended)

Software

OpenBTS or OsmoBTS + OsmoBSC + OsmoMSC (open-source GSM stack)
Asterisk (for SMS routing, optional)
GNU Radio (signal processing)
YateBTS (alternative to OpenBTS, simpler setup)

Step 1: Setting Up the Environment

1. Install Dependencies

sudo apt update
sudo apt install build-essential cmake libuhd-dev uhd-host \
    libboost-all-dev libsqlite3-dev asterisk libusb-1.0-0-dev

2. Install SDR Drivers

For LimeSDR:

sudo add-apt-repository -y ppa:myriadrf/drivers
sudo apt update
sudo apt install limesuite limesuite-udev limesuite-images

For USRP:

sudo apt install uhd-host uhd_images_downloader

Step 2: Setting Up the GSM Stack

Option A: Using Osmocom

Osmocom stack is more modular and production-like.

osmo-bts-trx

Handles BTS logic

osmo-bsc

Base Station Controller

osmo-msc
osmo-stp
osmo-hlr

Simplified all-in-one setup

Start BTS:

osmo-trx-lms  # For LimeSDR
osmo-trx-uhd  # For USRP

Then:

osmo-bts-trx -c osmo-bts-trx.cfg
osmo-bsc -c osmo-bsc.cfg

Step 3: Broadcasting an SMS

Once the BTS is running, you can send Cell Broadcast SMS (CBS):

With Osmocom:

osmo-msc -c osmo-msc.cfg

Then inject a broadcast message:

telnet localhost 4254
> subscriber msisdn {msisdn} sms sender {msisdn} send "SMS"

Step 4: Testing

Insert a SIM card

Check if the broadcast message arrives

Practical Applications (in a Legal Setup)

Research GSM layer 3 messaging

Study SMS delivery mechanisms

Learn about Cell Broadcast Service

(used for disaster alerts, weather updates, etc.)

Educational demos in telecom labs

Demo

Conclusion

Using LimeSDR or USRP, you can build a small-scale GSM SMS broadcaster for research. Open-source stacks like OpenBTS and Osmocom give full control over the GSM protocol, enabling you to study how operators manage SMS broadcasts.

Important: Never transmit outside licensed spectrum without authorization. Keep your experiments legal, safe, and in a controlled environment.

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