Abstract: Systems, methods, and apparatuses are presented for resolving any interference, noise, and/or collisions caused by two or more ingestible event markers (IEMs) transmitting simultaneously or concurrently. Methods include techniques from the perspective of the IEM for randomly varying signal transmission characteristics in order to avoid collisions with other concurrently transmitting IEMs. Methods also include techniques from the perspective of a receiver for receiving multiple transmission signals from multiple IEMs and for resolving any interference or signal collisions.

Abstract: Noise in a speech-plus-noise input signal is suppressed by splitting the input signal into spectral channels and decreasing the gain in the each channel which has a low signal-to-noise ratio (SNR). A voice operated switch (VOX) acts to detect noise-only input to gate a background noise (input signal) estimator and also to gate a residual noise (output signal) estimator. The gain in each of the channels is controlled by the current value (a posteriori) input signal SNR estimate, modified by the prior value (a priori) input signal SNR estimate, and smoothed as a function of the residual (output noise signal) estimate.