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.