Hardware PLL & Clock Steering™

The Spatial-Temporal Misalignment Issue

In telemetry drive-testing, mapping cellular data requires absolute synchronicity between cellular signal strength packets and GPS coordinates. However, GPS updates (typically arriving on a 1Hz clock) and cellular modem updates (arriving asynchronously) run on completely separate system clocks.

When recording at high speeds, this timing offset results in "spatial jitter". At 120 km/h, a tiny 500ms desync translates to a spatial shift of 17 meters, misaligning cellular readings with their actual location. Furthermore, logging data asynchronously causes "coordinate clumping"—where multiple distinct cellular packets are tied to the exact same coordinate because a new GPS fix has not arrived.

Hardware-Locked Clock Steering

CellScout implements a software-based Phase-Locked Loop (PLL) and Clock Steering algorithm to eliminate spatial drift. When the application detects mobility (speed > 2 km/h), the logging clock suspends fixed temporal updates and steers itself to align directly with the physical GPS hardware receiver.

If the cellular logging thread is ready to write a packet but the GPS hardware is lagging, the logging loop goes to sleep (utilizing a precise thread-synchronized wait lock) for up to 350ms. The exact millisecond the GPS hardware receives a fresh satellite coordinate, the loop wakes up and executes an atomic log snapshot. This lock completely eliminates spatial jitter and coordinate clumping, producing perfectly linear, mathematically precise drive test logs.