Physical Validation
of 6G ISAC Limits
Real-world validation of Integrated Sensing and Communication fundamental limits using COTS acoustic hardware — proving that theoretical EFIM designs are highly sensitive to real-world physics.
What is 6G ISAC?
Integrated Sensing and Communication is a core component of future 6G networks
The Core Conflict
Communication signals must be highly unpredictable to maximize data transfer rates. Radar signals must be highly predictable to accurately measure distance and delay.
This fundamental conflict establishes the Capacity-Distortion trade-off — the central challenge that ISAC systems must navigate.
Why Acoustic?
Sound waves share key mathematical properties with RF waves — propagation, reflection, Doppler shift, and multipath fading. This makes acoustics an ideal low-cost, observable analog for 6G research.
- Full transparency — every signal can be heard and recorded
- Low cost — laptop mic + Bluetooth speaker only
- No spectrum licensing or RF shielding needed
Key Results
Physical validation of fundamental 6G ISAC limits using real-world acoustic experiments
Sub-centimeter ranging accuracy at 1.0m under ideal conditions
Accurate velocity tracking via FFT frequency shift analysis
Strict digital signal processing limit from pulse duration window
Catastrophic range ambiguity without proper waveform design
Radar Calibration — 10-Trial Results
Doppler Velocity Tracking
Velocity calculated using Doppler equation: v = (shift x v_sound) / (2 x f_0). System transmits continuous 10 kHz tone and analyzes FFT frequency shift.
System Architecture
Hardware and signal processing pipeline for the acoustic ISAC testbed
Hardware → Signal Processing → Validation
Speed of Sound — Thermodynamic Calibration
Arduino MPU6050 actively measures ambient temperature instead of using the standard 343 m/s assumption
ISAC Evolution
Three evolutionary stages of ISAC waveform design — from catastrophic failure to optimal joint performance
Up/down chirps encode binary data bits directly. Data bits cause severe range ambiguity — the radar completely fails to identify the target echo.
Separate dedicated radar chirp (2-6 kHz) + data chirps (8-12 kHz). Sensing accuracy restored, but effective data capacity is heavily sacrificed due to the extra radar chirp overhead.
Full payload used as matched filter. EFIM data subtraction mathematically suppresses communication noise, enabling simultaneous maximum data throughput and precise radar sensing.
The 8.74 m DSP Boundary
At 6 meters with a 0.05 s pulse, the round-trip distance is ~12 meters. The target echo falls completely below the environmental noise floor. The EFIM filter's 0.05 s window equals exactly 8.74 meters of travel — when it finds only static, the algorithm generates a false peak at the array boundary.
This perfectly demonstrates the strict range-energy constraint of ISAC waveforms and highlights the deep necessity of physical hardware validation over pure software simulation.
Scripts Overview
Complete Python codebase for the acoustic ISAC testbed
Standalone FMCW acoustic radar for distance measurement using chirp cross-correlation. The baseline pure sensing experiment.
Doppler velocity measurement via FFT frequency shift analysis on a continuous 10 kHz tone. Validates motion sensing.
Core ISAC validation — transmits combined radar + communication signal and extracts both using EFIM-inspired data subtraction.
Runs all 3 ISAC stages in a single trial and produces side-by-side comparison showing naive failure to EFIM success.
Phase sweep calibration to discover the destructive interference null pattern of the laptop acoustic channel.
Auto-calibrating stealth system: discovers null angle then demonstrates BPSK with and without null steering.
Quick stealth demonstration using pre-discovered null angle (MAGIC_PHASE = 7.2°) for self-interference cancellation.
Quick Start
Research Team
CT216 Group 14 — Dhirubhai Ambani University, Gandhinagar, Gujarat, India
Contact
202401151@dau.ac.in