bladeGPS

Real-time, broadcast-ephemeris-driven GNSS signal-simulator framework for bladeRF, based on the GPS signal model from gps-sdr-sim. Production backends turn receiver position and motion into continuous SC16 I/Q for GPS L1 C/A, Galileo E1 OS, BeiDou B1I D1/D2, GLONASS L1OF, or a jointly allocated mixture of all four. The pipeline includes native time conversion, orbit and clock modeling, iterative transmit time, navigation-message construction, spreading codes, modulation, Doppler, channel allocation, hardware validation, and real-time TX.

Repository description: Real-time multi-GNSS baseband and bladeRF transmitter for GPS L1 C/A, Galileo E1, BeiDou B1I, and GLONASS L1OF, driven by broadcast RINEX navigation and static, recorded, keyboard, or controller receiver motion.

Suggested GitHub topics: bladerf, gnss, gps, galileo, beidou, glonass, sdr, signal-simulator, rinex, baseband, c, navigation.

This is research and lab software. Only transmit GPS-like RF signals inside a properly shielded test setup, with appropriate attenuation, and only where you are legally allowed to do so.

Features

• GPS L1 C/A PRN 1-37 baseband generation with up to 16 simulated channels.
• Galileo E1-B/E1-C CBOC, BeiDou B1I D1/D2 BPSK, and GLONASS L1OF FDMA generation.
• Mixed RINEX 3/4 navigation ingestion with constellation-specific orbit, clock, navigation-message, code, modulation, visibility, Doppler, and allocation paths.
• Static receiver mode using latitude, longitude, and height.
• Dynamic receiver mode from CSV ECEF user motion files.
• Dynamic receiver mode from geodetic latitude/longitude/height CSV files.
• Dynamic receiver mode from NMEA GGA streams.
• Optional keyboard-controlled interactive motion mode.
• Optional live SDL2 USB/Bluetooth game-controller receiver motion.
• Timestamp-aware 10 Hz interpolation of ECEF, geodetic, and NMEA motion.
• RINEX broadcast navigation file parsing.
• Direct POSIX streaming of plain, .gz, and legacy Unix-compressed .Z supported RINEX 2, 3, and 4 navigation files.
• Per-satellite ephemeris selection and seamless 30-second ephemeris refresh.
• Iterative signal transit-time and Earth-rotation (Sagnac) correction.
• GPS/GST/BDT/GLONASS-UTC conversion with historical leap-second handling.
• Per-satellite transmit-time navigation-symbol/overlay alignment.
• Satellite clock bias, relativistic correction, signal group delay, and clock-drift modeling.
• Automatic daily GPS broadcast ephemeris download with NOAA/NGS primary and BKG IGS fallback sources when -e is omitted.
• Capability-driven bladeRF 1.0/2.0 adaptation for center frequency, exact sample rate, analog bandwidth, and portable overall TX gain.
• Hardware range checks and configuration read-back before RF transmission.
• Analog-filter validation against the complete occupied signal span, including an offset carrier.
• Deterministic SC16 Q11 headroom normalization, peak/rail telemetry, and zero-padded final-buffer flushing.
• Signal registry and RF validation for GPS L1 C/A, Galileo E1, BeiDou B1I, and GLONASS L1OF.
• Real-time SC16 I/Q streaming to bladeRF.
• Optional XB200 setup for GPS-band transmit filtering/path selection.
• Graceful generator/TX error propagation and SIGINT/SIGTERM shutdown.
• A true mixed-open runtime that jointly allocates and renders GPS L1 C/A, Galileo E1, BeiDou B1I, and GLONASS L1OF from one mixed navigation file.
• Independent software BPSK acquisition/correlation loopback validation.
• Deterministic core tests for system time, leap seconds, transmit alignment, coordinates, PRN codes, navigation coding, RF continuity, motion, and selection.
• Portable Makefile that uses pkg-config libbladeRF when available, with the original adjacent bladeRF source-tree fallback.

Requirements

• C compiler with C99-compatible libc behavior.
• POSIX threads.
• libbladeRF headers and library.
• A bladeRF device supported by libbladeRF.
• pkg-config is recommended so the Makefile can discover libbladeRF automatically.
• curl is required for automatic ephemeris download. gzip is required for downloads and for direct .gz/legacy .Z navigation input on POSIX.
• SDL2 is optional; when found through pkg-config, -j live controller input is enabled.

On macOS with MacPorts, for example, the build can use libbladeRF from /opt/local through pkg-config. On Linux, install libbladeRF development files through your package manager or build them from Nuand's source tree.

Build

make

Run the non-RF core-model checks with:

make check

If libbladeRF is not discoverable through pkg-config, the Makefile falls back to the historical layout:

../bladeRF/host/libraries/libbladeRF/include
../bladeRF/host/build/output

You can also pass flags explicitly:

make BLADERF_CFLAGS="-I/path/to/libbladeRF/include" BLADERF_LIBS="-L/path/to/lib -lbladeRF"

Clean build products:

make clean

For a guided first run, hardware/filter explanation, motion examples, and troubleshooting, read USER_GUIDE.md.

Usage

List the known signal profiles before configuring a run:

./bladegps -L

The status column is authoritative. Non-GPS profiles use a supplied mixed RINEX 3/4 file or auto-download a daily mixed file when -e is omitted. Complete GLONASS GNAV generation requires a RINEX 4 FDMA record because legacy RINEX 3 records omit four status/timing fields; bladeGPS refuses to fabricate them.

Usage: bladegps [options]
Options:
  -e <nav_file>    RINEX navigation file (daily broadcast data auto-downloads if omitted)
  -u <user_motion> User motion file (dynamic mode)
  -p <llh_motion>  Geodetic CSV motion: time,latitude,longitude,height
  -g <nmea_gga>    NMEA GGA stream (dynamic mode)
  -l <location>    Lat,Lon,Hgt (static mode) e.g. 35.274,137.014,100
  -t <date,time>   Scenario start time YYYY/MM/DD,hh:mm:ss
  -d <duration>    Duration [sec] (max: 86400)
  -x <XB number>   Enable XB board, e.g. '-x 200' for XB200
  -S <signal>      Signal profile (gps-l1ca, galileo-e1, beidou-b1i, glonass-l1of, mixed-open)
  -L               List signal profiles and implementation status
  -D <device>      libbladeRF device identifier
  -f <Hz>          TX center frequency
  -r <samples/s>   TX sample rate (at least 1 MHz and divisible by 10)
  -b <Hz>          TX analog bandwidth
  -G <dB>          Portable overall TX gain (default: 27 dB)
  -a <dB>          Legacy bladeRF 1 TXVGA1 gain (requires -A)
  -A <dB>          Legacy bladeRF 1 TXVGA2 gain (requires -a)
  -M <degrees>     Satellite elevation mask (-90 to 90)
  -i               Interactive mode: North='w', South='s', East='d', West='a', Up='e', Down='q'
  -j <index>       Live SDL USB/Bluetooth controller (left stick NE, right stick vertical)

Static location example:

./bladegps -e brdc2940.18n -l 59.3293,18.0686,30 -d 60

Automatic ephemeris download example:

./bladegps -l 59.3293,18.0686,30 -d 60

When -e is omitted, GPS downloads daily RINEX 2 navigation from NOAA/NGS CORS and then BKG. Galileo, BeiDou, and GLONASS try BKG's daily BRDC00IGS, BRDC00WRD, and BRDM00DLR mixed-navigation products in order. The downloader uses the -t scenario date if provided, otherwise the current UTC date, saves the decompressed file in the working directory, and reuses it on later runs.

The downloader writes to temporary .tmp files first, verifies that both the compressed and decompressed files were created, then renames them into place. Failed downloads or decompression errors clean up partial output and print a manual -e <nav_file> fallback hint.

Galileo example using a mixed RINEX 3/4 navigation file:

./bladegps -S galileo-e1 -e BRDC00IGS_R_20262740000_01D_MN.rnx \
  -l 59.3293,18.0686,30 -d 60

Use -S beidou-b1i or -S glonass-l1of for those integrated backends. The selected center frequency, sample rate, and bandwidth default to the profile's safe values and can be overridden with -f, -r, and -b.

Simultaneous open-service example (wideband hardware and a mixed RINEX 3/4 file):

./bladegps -S mixed-open -e BRDC00IGS_R_20262740000_01D_MN.rnx \
  -l 59.3293,18.0686,30 -d 60

The default mixed plan is centered at 1582.3925 MHz with 50 Msps and a 48 MHz analog filter around a 47.1 MHz minimum waveform span. The allocator considers all four constellations together and keeps the 16 highest-elevation healthy signals that fit the realized device passband. Device range checks can reject this plan on hardware that cannot provide the required instantaneous bandwidth.

Hardware adaptation and RF filtering

bladeGPS queries frequency, sample-rate, analog-bandwidth, and gain ranges from the opened device instead of assuming bladeRF 1.0 limits. It sets and reads back every timing-critical value. Exact sample rate and center frequency are required because silent coercion would change code, symbol, and carrier timing. Analog bandwidth may be quantized by hardware, but the realized value is accepted only when read-back agrees with libbladeRF, contains the complete modulated signal, and is no wider than the complex sample rate. Waveform occupancy and requested filter bandwidth are separate profile properties, so guard margin is not incorrectly advertised as emitted spectrum.

Profile	Minimum waveform span	Default sample rate	Default filter
gps-l1ca	2.2506 MHz	2.6 Msps	2.5 MHz
galileo-e1	24.552 MHz	36.828 Msps	28 MHz
beidou-b1i	4.5012 MHz	5 Msps	5 MHz
glonass-l1of	8.9992 MHz	12 Msps	10 MHz
mixed-open	47.1 MHz	50 Msps	48 MHz

The Galileo filter is wider than its reference bandwidth so satellite Doppler and device filter quantization do not sit on the acceptance boundary. The mixed sample rate is wider than its analog filter, preserving a digital Nyquist guard at both edges.

Use -G for model-independent overall TX gain. This is a relative gain setting, not calibrated RF power. -a and -A remain available together for bladeRF 1.0 systems that explicitly require the legacy txvga1 and txvga2 stages; they are rejected on devices without those named stages.

With -x 200, the XB200 uses the native L-band bypass path and automatic low-loss TX filter selection; attachment, path, and filter selection are read back and verified. The RX path is not modified. On bladeRF 2.0, libbladeRF chooses the AD9361 interpolation/FIR mode while configuring sample rate; forcing another FIR mode here would override that device adaptation.

bladeGPS is transmit-only. No ADC or RX channel participates in generation, so configuring an ADC would be unnecessary and could disturb a separate receiver. On TX, every submitted SC16 Q11 block is measured; the final report shows peak level and rail contact. A final partial scenario block is zero-padded to a full synchronous transfer so libbladeRF cannot retain and drop the scenario tail.

User motion CSV example:

./bladegps -e brdc2940.18n -u circle.csv -d 120

NMEA GGA example:

./bladegps -e brdc2940.18n -g track.nmea -d 120

Geodetic motion example:

./bladegps -e brdc2940.18n -p route-llh.csv -d 120

XB200 example:

./bladegps -e brdc2940.18n -l 35.274,137.014,100 -x 200 -d 60

Interactive movement example:

./bladegps -e brdc2940.18n -l 59.3293,18.0686,30 -i -d 120

In interactive mode, w/s/a/d move north/south/west/east and e/q move up/down.

Input files

• brdc*.??n, brdc*.??n.gz, and brdc*.??n.Z files are GPS RINEX 2 broadcast navigation files. Mixed RINEX 3/4 navigation may likewise be plain, .gz, or legacy .Z on POSIX. Compressed input is streamed through gzip without constructing a shell command.
• circle.csv, satellite.csv, and ss520-4.csv are sample motion/position data files.
• run_bladerfGPS.sh is a convenience script retained from the original project.

User motion CSV rows use:

time_seconds,ecef_x_m,ecef_y_m,ecef_z_m

Records are consumed at 10 Hz. All four CSV fields must be finite numbers; malformed records are rejected instead of silently shortening the scenario. NMEA input accepts valid GGA fixes and ignores no-fix records. Checksummed sentences are verified; timestamps are unwrapped across midnight. All recorded motion formats are linearly resampled to the simulator's 100 ms clock, so irregular input spacing no longer changes simulated speed.

Geodetic motion rows use decimal degrees and metres:

time_seconds,latitude_degrees,longitude_degrees,height_metres

Latitude is limited to -90..90 degrees and longitude to -180..180 degrees. Records are converted to ECEF before signal generation.

Live controller example:

./bladegps -S gps-l1ca -l 59.3293,18.0686,30 -j 0 -d 120

The left stick commands north/east velocity and the right-stick vertical axis commands up/down velocity. Dead-zone removal and diagonal normalization are applied. Disconnecting the controller stops generation with an error rather than freezing the last velocity.

Signal support

“Implemented” below means connected to the production CLI and covered by software tests. It does not mean certified ICD conformance or calibrated RF interoperability. See SUPPORT_MATRIX.md for layer-by-layer coverage, payload boundaries, input formats, hardware support, and validation.

Profile	Constellation	Nominal carrier	Status	Notes
gps-l1ca	GPS	1575.42 MHz	Implemented	C/A ranging code, LNAV, RINEX 2 GPS navigation, PRN 1-37
galileo-e1	Galileo	1575.42 MHz	Software implemented	E1-B/C codes, CBOC, mixed-RINEX orbit/clock, ICD modulo-30 I/NAV page-part timing, vertical dummy pages for unavailable optional words, geometry, allocation and RF synthesis
beidou-b1i	BeiDou	1561.098 MHz	Software implemented	PRN 1–63 codes, D1/D2 selection, ephemeris/clock/ionosphere pages, geometry, NH overlay, allocation and RF synthesis
glonass-l1of	GLONASS	1602 MHz base	Software implemented	L1OF code, FDMA slot carriers, state-vector propagation, live UTC(SU)+3 immediate/time strings, safe unavailable-almanac marking, relative/meander modulation and RF synthesis
mixed-open	GPS + Galileo + BeiDou + GLONASS	1582.3925 MHz plan center	Software implemented	One mixed RINEX input, constellation-native timing, shared health/elevation allocator, 16-channel continuous wideband mixer

Unknown or non-implemented profiles fail closed instead of silently producing a GPS waveform. Galileo, BeiDou, GLONASS, and mixed operation consume either a supplied or automatically downloaded mixed RINEX 3/4 navigation file. See MULTI_GNSS.md for the payload contract and SUPPORT_MATRIX.md for exact layer-level status.

The source tree contains tested signal primitives for all 63 BeiDou B1I ranging-code assignments, the GLONASS L1OF ranging code and FDMA carrier slots, all 50 official Galileo E1-B and E1-C primary codes, and Galileo CBOC shaping.

The typed RINEX 3/4 loader, GPS LNAV adapter, Galileo/BeiDou Keplerian propagation, BeiDou GEO transform, GLONASS state-vector propagation, navigation scheduling, modulation, joint channel allocation, and FIFO producer are connected to mixed-open RF output. Software loopback validates independent BPSK acquisition; physical hardware and receiver certification remain environment-dependent.

Implementation notes

• The simulator generates 0.1 second blocks at the selected sample rate for bladeRF SC16 transmission; GPS defaults to 2.6 Msps.
• The requested duration emits the complete number of 100 ms blocks.
• The newest healthy in-fit broadcast record already in force is selected independently per constellation/PRN; unhealthy or arbitrary future records cannot mask usable data.
• Record age is compared in continuous GPS time after native GPS/GST/BDT/UTC conversion.
• Navigation data and overlay phases use iterative per-satellite transmit time rather than receiver time.
• Primary-code, navigation-symbol, and secondary/NH overlay clocks share the same per-satellite Doppler scale, preserving component alignment in motion.
• Standalone GPS L1 C/A and mixed-open use the same constellation-neutral scheduler, allocator, continuous-phase renderer, SC16 normalization, and FIFO.
• Non-GPS 30-second navigation cycles are regenerated at every cycle boundary; Galileo GST TOW and BeiDou BDT SOW therefore advance instead of repeating a cached frame.
• Mixed RINEX files are counted and allocated dynamically; there is no fixed 4096-record truncation ceiling.
• BeiDou Klobuchar coefficients are read from RINEX 3 BDSA/BDSB headers or RINEX 4 ION C ... D1D2 records and range-checked at their ICD scales.
• Ephemeris handovers rebuild LNAV data while preserving range-rate continuity.
• FIFO access between the GNSS producer and TX thread is protected with the legacy-named gps.lock mutex.
• Generation completion wakes both FIFO condition variables so shutdown and initialization failures do not deadlock waiting threads.
• Command-line path arguments are bounded to the internal MAX_CHAR buffers.
• Malformed NMEA GGA lines are skipped instead of crashing the parser.
• If -e is omitted, GPS tries NOAA/NGS and BKG RINEX 2 data; non-GPS profiles try three BKG mixed-RINEX daily products.
• Auto-downloaded ephemeris cache files are ignored by git so local runs do not dirty the repository.
• The full module map, data flow, threading model, FIFO behavior, downloader lifecycle, and extension points are documented in ARCHITECTURE.md.

Project documentation

• ARCHITECTURE.md - maintainer architecture, runtime flow, modules, and extension points.
• USER_GUIDE.md - installation, safe first run, RF/filter planning, every input mode, hardware behavior, shutdown, troubleshooting, and conducted acceptance testing.
• GPS_L1_CA_COVERAGE.md - implemented L1 C/A coverage, wired gaps, and non-certified areas.
• MULTI_GNSS.md - constellation architecture, current capability matrix, and acceptance gates.
• SUPPORT_MATRIX.md - detailed per-service, input, timing, hardware, motion, and validation support matrix.
• CLI_REFERENCE.md - every option, accepted range, default, interaction, RF-plan equation, exit behavior, and example.
• DATA_FORMATS.md - RINEX, compression, motion, NMEA, typed navigation-record, and generated-sample formats.
• API_REFERENCE.md - exported C types/functions, units, parameters, return values, validation, and internal helper map.
• CHANGELOG.md - release history.
• LICENSE - MIT license.

Release history

See CHANGELOG.md.

Safety

This software can generate RF signals in protected satellite navigation bands. Never connect a bladeRF running this program to an antenna in an unshielded environment unless you have explicit legal authority. For receiver testing, use a shielded enclosure, direct cable injection, attenuation, and isolation appropriate for your equipment.

License

Copyright (c) 2015 Takuji Ebinuma.

Distributed under the MIT License. See LICENSE.