Design and Experimental Validation of a Synchronized Multi-Rate Wireless Sensor Network for Multimodal Physiological and Biomechanical Data Acquisition

Reliable multimodal measurement requires coordinated acquisition of physiological and biomechanical signals operating at different sampling rates. A six-node wireless architecture was developed to support seven data streams: three surface electromyography (sEMG) signals (2 kHz each), photoplethysmography (PPG, 400 Hz configured), inertial measurements (416 Hz configured), and independent pinch- and grip-force streams (nominal 80-SPS HX711 mode; measured at 85.1 and 85.9 samples/s, respectively). An ESP32-S3 gateway uses a single ESP-NOW network for sensor-data delivery and continuous per-node clock compensation while preserving raw measurements, sample-level timing metadata, and end-to-end integrity diagnostics. Across three independent 30-min full-system recordings, pooled packet delivery and sample continuity were 99.987% and 99.988%, respectively. External common-input validation between two independent sEMG nodes yielded a drift-compensated timing mean absolute error of 0.0754 ms across 897 accepted events. A separate six-node GPIO reference-pulse test yielded a node-clock alignment mean absolute error of 0.3123 ms across 5319 matched events with 99.49% of events below 1 ms. Network-load and indoor distance tests further characterized communication robustness. These results demonstrate the feasibility and reliability of a unified wireless architecture that integrates heterogeneous multi-rate sensing, continuous clock-drift compensation, preservation of original sensor measurements, and comprehensive data-integrity monitoring for synchronized physiological and biomechanical data acquisition.