Subject: Re: [GSoC 2026] Self-proposed idea: BeiDou B1C Signal Simulator OOT Module
Hello Sir, The constellation simulator direction makes much more sense. If the output can actually give a software receiver enough to compute a real PVT fix, that's something genuinely useful for researchers, students, anyone. So here's how I'm thinking about the expanded scope now - multi-constellation , with Doppler shifts and time-of-flight delays that match what a receiver at a given location and time would actually see - Generate proper navigation messages so a receiver can extract ephemeris and compute a position fix - Validate everything using GNSS-SDR as a software receiver feed the generated I/Q straight in and check if it produces a valid PVT solution. No hardware needed. One thing I'm unsure about: is it better to do BeiDou B1C really well and completely, or to cover B1C + GPS L1C + Galileo E1 at a slightly shallower level? Since all three share 1575.42 MHz I can see the appeal of multi-constellation.Would love your take on this. I'll start working on a proper week-by-week draft and share it here soon for feedback. Best, Devanshi. On Thu, Mar 19, 2026 at 12:50 AM Daniel Estévez <[email protected]> wrote: > Hi Devanshi, > > Thanks for sharing this idea. Here is some quick feedback. > > You don't say explicitly, but my understanding from what you wrote is > that your idea is to generate a single B1C signal with nominal chip rate > and no Doppler. This does not seem enough work even for a small (90 > hour) project, specially if you are already strongly familiar with GNSS > signal generation and the B1C signal. Such kind of simulator is of > fairly limited use, since it only allows to test that a receiver is > capable of acquiring and tracking a single signal in these conditions. > It is more common to have constellation simulators, which are capable of > simulating signals from multiple satellites whose times of flight and > Dopplers are consistent with the signals that a receiver in a given > location would see. A constellation simulator, if well planned out, > might be reasonable for a GSoC project (probably more on the larger side > of the project size spectrum). Constellation simulators can be used to > obtain a PVT solution with a receiver, and test it in reasonably > realistic conditions. > > You should detail in your proposal how you plan to test this. It is fine > that the tool itself generates baseband IQ and does not require any > hardware, but you will need to test somehow that the signals you are > generating are correct. Ideally you would use a hardware receiver and an > SDR to transmit your baseband IQ, but this requires you to already have > this hardware. If you don't have the required hardware, using a software > receiver is a good alternative, but you will need to identify such a > software receiver that allows you to check all you generate. > > Another way in which you could increase the scope of your proposal and > make it more attractive is by including open service signals from other > constellations (GPS, Galileo, etc.), all of which have ICDs which are > publicly accessible. > > Best, > Daniel. > > On 18/03/2026 19:22, Devanshi B wrote: > > Hi GNU Radio community, > > > > I am Devanshi , a GSoC 2026 applicant interested in proposing a self- > > directed project. > > > > I have strong familiarity with GNSS signal generation concepts and the > > BeiDou B1C ICD specification, with hands-on experience . > > > > Proposed idea: A GNU Radio OOT module tentatively gr-beidou > > implementing a BeiDou B1C software signal simulator. The module would > cover: > > > > - B1C PRN code generation (data and pilot components, per ICD) > > - BOC modulation > > - Basic CNAV-1 navigation message framing > > - Baseband I/Q output usable for receiver testing and simulation > > > > The implementation would be built entirely from the public BeiDou B1C > > ICD with no hardware dependency making it useful for receiver testing, > > education, and research. I plan to model the module structure after gr- > > satellites, which sets a great precedent for clean, well-documented > > signal-level OOT modules. > > > > This fills a genuine gap no open-source GNU Radio B1C signal generator > > currently exists. > > > > if any mentor would be interested in supervising this, or if there is a > > better framing that fits current GNU Radio priorities. > > > > Cyberspectrum is the best spectrum. > >
