A sphere decoding method applied to a MIMO channel is provided. The method includes generating, using a biometric reference template revocation engine, a biometric reference template revocation message and loading the biometric reference template revocation engine onto a secure portable device for generating on demand of the individual the biometric reference template revocation message. The playback system can provides first and second output waveforms, based on the first and second input waveforms in the memory, respectively, to form composite patterns of stimulation or waveforms. In addition, the information is enhanced by quality assurance at each step in this process to ensure the high quality of the resulting data. The anchor path delay is compared to each respective RT delay to determine a respective unanchored delay variation.