USRP Channel Sounder

A configurable real-time channel sounder for USRP devices, with TX/RX runtime in sounder/ and analysis tools in post_processing/.

Repository Layout

• sounder/: runtime TX/RX code.
• config/: example configuration files.
• figures/: README preview and example output images.
• post_processing/: analysis scripts and notebooks.
• requirements.txt: runtime Python dependencies.
• post_processing/requirements.txt: analysis dependencies.

Prerequisites

• Linux machine with USRP hardware.
• UHD driver
• Python 3.10+ recommended.
• Build tools for Cython compilation (the RX module is ChsRX.pyx).

Setup

Option 1: Native install

sudo apt-get update -y
sudo apt-get install -y libuhd-dev uhd-host python3-dev build-essential
uhd_images_downloader

python3 -m pip install -r requirements.txt

Option 2: Docker

sudo docker build --network=host -t ch-sounder .
sudo docker run -dit --network=host --privileged -v /dev:/dev --name sounder ch-sounder
sudo docker exec -it sounder bash

Running the Sounder

Run from the sounder/ directory:

cd sounder
python3 main.py -c ../config/tx_config.yaml

For RX mode:

cd sounder
python3 main.py -c ../config/rx_config.yaml

Optional flag:

python3 main.py -c ../config/rx_config.yaml --plot

Dry Run (No USRP Required)

Generate a waveform preview plot (time domain, spectrogram, cross-correlation, configuration readout) directly from a YAML config:

cd sounder
python3 dry_run_waveform.py -c ../config/tx_config.yaml -o ../plots/tx_dry_run.png

Optional: save generated complex samples:

python3 dry_run_waveform.py -c ../config/tx_config.yaml --save-npy ../plots/tx_dry_run.npy

Example outputs from the bundled A2G-500m campaign configs (config/a2g_500m/):

Variant	Dry-run preview
Baseline 56 MHz, ZC-401 x 8
High-resolution 100 MHz, ZC-401 x 8
Long-sequence 56 MHz, ZC-1021 x 4

The "Configuration" panel reports range resolution, unambiguous delay, and processing gain; the cross-correlation panel reports peak-to-sidelobe ratio (PSLR) of the matched filter response.

Configuration Guide

Both config/tx_config.yaml and config/rx_config.yaml use the same schema.

Key fields:

• MODE: TX or RX.
• PERIOD: burst scheduling rate (bursts per second).
• WAVEFORM: ZC, PN, or CHIRP.
• USRP: radio settings (SERIAL, SAMPLE_RATE, CENTER_FREQ, GAIN, clock/PPS refs).
• RECV_OPTS: RX duration, power/path-loss options, output type (npz/mat).
• WAV_OPTS: per-waveform parameters. For OFDM: N_FFT, CP_LEN, SUBCARRIERS, N_PILOTS, DC_GUARD_BINS, EDGE_GUARD_BINS, SEED, NORMALIZE_PEAK, TARGET_PEAK.
• GPS: optional USB GPS receiver (serial device, e.g. /dev/ttyACM0) for location/time metadata.

Output

RX captures are written under:

• measurements/YYYY-MM-DD_HH_MM/

Each directory includes:

• config.yaml: config snapshot.
• received_<timestamp>.npz or received_<timestamp>.mat: measurement files.

Post-processing

Install analysis dependencies:

pip install -r post_processing/requirements.txt

Use notebooks in post_processing/:

• PostProcess.ipynb
• RX_review.ipynb
• SigMF_conv.ipynb
• SigMF_demo.ipynb
• Antenna.ipynb

Hardware Notes

• USRP B210 / B205mini: max usable bandwidth is 56 MHz over USB 3.0; the highres_100mhz campaign variant requires an X310-class radio.
• Synchronization: with 10 MHz + 1PPS (GPSDO or signal-generator) on TX and RX, ppm-level oscillator drift translates to sub-Hz frequency offset at 3.4 GHz, which is well below the inter-burst interval. Therefore, no runtime CFO correction is needed in the sounder.
• DAC headroom: each generated burst is rescaled so its peak magnitude equals WAV_OPTS.TX_PEAK (default 0.85, ~1.4 dB back-off). Without this, the unit-modulus ZC portion would sit at 0 dBFS for the entire sequence and any fixed-point rounding or analog ringing could clip the DAC.

Dataset

Air-to-Ground Dryad dataset:

• https://datadryad.org/dataset/doi:10.5061/dryad.7h44j105p

Citation

@inproceedings{gurses2024air,
  author    = {A. G{\"u}rses and M. L. Sichitiu},
  title     = {Air-to-Ground Channel Modeling for UAVs in Rural Areas},
  booktitle = {2024 IEEE 100th Vehicular Technology Conference (VTC2024-Fall)},
  year      = {2024},
  pages     = {1--6},
  address   = {Washington, DC, USA},
  doi       = {10.1109/VTC2024-Fall63153.2024.10757825},
  publisher = {IEEE}
}

Troubleshooting

• If ChsRX import fails, ensure python3-dev, build-essential, cython, and numpy are installed.
• If external/GPS lock never completes, verify clock/PPS cabling and matching CLK_REF/PPS_REF settings.
• Use logs/out.log for runtime diagnostics.