LimeSDR - could this be of use for Mode-S/ADS-B reception?


#1

Admin, please don’t hurt me to much if this is the wrong thing to do…

I’m not sure on the rules regarding posting a link, but I just saw this via a Ubuntu FB page post… It’s for a new SDR which is about to be manufactured…

Judging by what I read, all the processing for dump1090 etc could be run on the FPGA on this board, at what seems like incredibly high speeds…

Worth thinking about…

crowdsupply.com/lime-micro/limesdr


#2

Looks similar to the bladeRF.

The biggest stumbling block with running ADS-B decoding on the FPGA is, well, actually writing the decoder for it. (That said, nuand are in the process of releasing something for the bladeRF, and they’re both using a Cyclone IV)

(you’ll need to actually get one first - the funding numbers don’t look great at the moment)


#3

FlightAware is a plane tracking company and FlightAware’s ADS-B network will work with other receivers so definitely post about receivers that do ADSB and how they work.

The LimeSDR is made by lime microsystems using their next generation SDR chip. The 7002 specs are much better than the 6002.
Looks like lime is doing a fire sale on their older generation chips. The new chip 7002 chips are what the older 6002 chip were priced at.
digikey.com/product-search/e … 6,fff80545

The hardest part of using the LimeSDR for ADS-B is the FPGA decoding. You will also probably not find an open sourced version of the FPGA ADS-B decoder and I haven’t seen anyone announce an open sourced FPGA RTL. The new SBS trilby receiver also has an FPGA and they will definitely have an FPGA ADS-B decoder. They haven’t said anything about how open their ADS-B decoder is or how well it performs.
kinetic.co.uk/TrilbyAbout.php

We are mostly finding that arm Cpu are getting cheaper much faster than FPGA. If FPGA are cheaper this might change but I don’t see this happening in this decade. So boards like the limeSDR are going to be in a niche where performance and low power are the main driving factors instead of cost.


#4

I think that the mode S beast is probably the best value for money fpga unit at the moment.
It is about 200 euro plus a case and if you need, they can build it (240 total euro excluding VAT).
It only does adsb/mode a/c/s. You can add up to three antenna additional feeds.

I posted about another fpga unit was was suppose to be open sourced. It was about twice the price. It may be better if it has a later fpga unit.


#5

[quote=“david.baker”]FlightAware is a plane tracking company and FlightAware’s ADS-B network will work with other receivers so definitely post about receivers that do ADSB and how they work.

The LimeSDR is made by lime microsystems using their next generation SDR chip. The 7002 specs are much better than the 6002.
Looks like lime is doing a fire sale on their older generation chips. The new chip 7002 chips are what the older 6002 chip were priced at.
digikey.com/product-search/e … 6,fff80545

The hardest part of using the LimeSDR for ADS-B is the FPGA decoding. You will also probably not find an open sourced version of the FPGA ADS-B decoder and I haven’t seen anyone announce an open sourced FPGA RTL. The new SBS trilby receiver also has an FPGA and they will definitely have an FPGA ADS-B decoder. They haven’t said anything about how open their ADS-B decoder is or how well it performs.
kinetic.co.uk/TrilbyAbout.php

We are mostly finding that arm Cpu are getting cheaper much faster than FPGA. If FPGA are cheaper this might change but I don’t see this happening in this decade. So boards like the limeSDR are going to be in a niche where performance and low power are the main driving factors instead of cost.
[/quote]

Hi David,

Actually, funny you should mention no one open sourcing the VHDL to an ADS-B decoder… github.com/Nuand/bladeRF-adsb :stuck_out_tongue: . We announced this just last week. It is a piece of bladeRF specific IP, and cannot run on other devices for a variety of reasons.

The algorithm we implemented runs in realtime on the bladeRF’s FPGA but cannot run in realtime on a modern Intel i7 or even most GPGPUs. Essentially every new sample triggers about 7000 new arithmetic operations, at 40MSPS that is about 280 GMACs (Multiply and Accumulates) which would translate to 280GFlops. However the GFlops require some logic, meaning a GPGPU would suffer from pipeline stalls, causing the effective GMAC/GFLOP requirement to jump 10x.

And you are right, the hardest part is definitely the VHDL, and the validation of the whole system. We began this project at your and Karl’s behest last summer and finished it by November, it’s a pity we never heard back from you.


#6

Looks great. This is an open sourced ADSB FPGA decoder. I will install this on a bladeRF in the office and give a review.

The FlightAware bladeRF project was getting so far behind. FPGA decoder is a better solution in the long run but making a decoder that can compete is hard to do.

The max message rate possible will be around 2000messages/sec and software solutions will probably max out around 1000 messages/sec because of FRUIT. We are seeing about 600messages/sec in some locations but measuring FRUIT rate is more difficult to do. FPGA decoders will definitely be able to decode more FRUITS (messages that collide) much better than software solutions.

Here is another link of the discussion about Nuand’s ADSB FPGA decoder.
ads-b-flight-tracking-f21/high-performance-vhdl-ads-b-decoder-open-sourced-t37187.html


#7

david i know this is a really old thread - but now about 6 weeks before the lime mini will be (hopefully) delivered i wanted to ask whether you did the test/review of the bladerf with the nuand ads-b decoder? and did you hear that something similar is in the pipeline for lime mini? my concern is that the fpga is really fast - but all decoder-software can’t compete to dump1090-mutability/fa. this way most of the speed advantage of fpga could be lost. maybe you should motivate obj to port his code for fpga :smiley:


#8

Some news on this one?


#9

I have a mini LimeSDR.

The max message limits for one site are already getting fairly close with current hardware and software solutions. Dump1090 can support other receivers and I think there will be more receivers added over time.

Do you have a specific receiver you are looking for? Do you have a mini LimeSDR?


#10

Quilty :joy:
I was trying to do a adsb decoder in GNU radio but I got lost