Could Someone Give me Advice on Configuring LimeSDR Mini for a Reliable 4G LTE Downlink?

General Discussion
1

Hello there, :wave:

I am working on setting up a LimeSDR Mini to experiment with receiving and analyzing 4G LTE signals. I have been following the basics from online documentation; but I am running into some challenges with both signal acquisition and configuration consistency.

LimeSDR Mini connected to a USB 3.0 port, LimeSuite, SDRangel, and gqrx for testing
A pair of wideband antennas, tuned for LTE frequencies 700–2600 MHz range

My primary goal is to capture a reliable downlink signal on a nearby LTE band e.g., Band 3 at 1800 MHz; visualize the spectrum, and confirm decoding or signal integrity.

Even after setting the correct frequency and gain, the signal seems very faint; and I often cannot get consistent spectrum visualization. Are there specific LimeSuite settings for RX gain; LNA; and TIA that you recommend for LTE? :thinking:

I have noticed some drift or inconsistencies in tuning. I am unsure whether this is related to calibration settings or the temperature of the device. Is there a particular way to ensure the LimeSDR stays tuned reliably over time?

Also, I have gone through this post; https://discourse.myriadrf.org/t/how-can-i-make-a-lte-4g-base-station-bacisly-with-limesdr-mini-cybersecurity which definitely helped me out a lot.

Are there any tools or scripts you suggest for isolating specific LTE channels or decoding them efficiently with SDRangel or other software? :thinking:

Thanks in advance for your help and assistance. :innocent:

2

Any settings made in Lime Suite will be lost when you exit this and then start another application, since it will reset the SDR. Lime Suite GUI is really an engineering tool and not for general use; gains should be set appropriately via an end user application.

There shouldn’t be too much frequency drift with temperature, but for cellular applications you may benefit from using an external frequency reference, e.g. a GPSDO. Else an SDR such as LimeSDR XTRX which has one integrated. With higher sample rates the board may heat up in use, and in such cases fan cooling may help with the noise figure.

I’m not aware that you can decode LTE channels with amateur radio / general purpose applications such as SDRangel. It’s not entirely clear to me what you are looking to achieve, but srsRAN 4G has examples for things like cell search and UE PDSCH decode:

https://docs.srsran.com/projects/4g/en/latest/usermanuals/source/1_setup.html#examples

You can use the stock version of srsRAN 4G with LimeSDR hardware via SoapySDR, or alternatively there is a fork with native Lime Suite API integration and we have found this to give better performance. For setup details, see:

https://librecellular.org/user/software

I’ve not tried out the aforementioned examples in our fork, since this is normally used to run up an eNodeB, but I can’t see why they shouldn’t work.