Method for presence detection inside a vehicle of a passenger using a Smart Personal Communication Device (SPCD), in particular a smartphone, by which at least one passenger-related first sensor signal (SS-1) of the Smart Personal Communication Device (SPCD) is compared with at least one vehicle-related second sensor signal (SS-2) of the vehicle, in particular of a Vehicular Gateway in the vehicle, such that a simple "YES"-Statement (Y-S) or NO"-Statement (N-S) regarding the presence of the passenger in the vehicle is made, characterized in that ( a) in a Signal Pre-Processing Step (SPPS) the first and second sensor signals (SS-1, SS-2) are independently pre-processed each by executing at least a Re-Sampling and a Magnitude Calculation to induce signal-specific magnitude values (MV-1, MV-2), which in particular are pre-processed additionally each by executing a Clipping Detection being executed preferably between the Re-Sampling and the Magnitude Calculation, ( b) in a Vehicle Identification Step the signal-specific magnitude values (MV-1, MV-2) are compared by applying a "Cross-Correlation Function " such that the signal-specific magnitude values (MV-1, MV-2) are executed in the order of "Overlapping in Time Domain", "Windowed Cross-Correlation" and Metrification to induce due to the Metrification at least one metrification-based identification value (IDV, IDV-1, IDV-2, IDV-3) and the at least one metrification-based identification value (IDV, IDV-1, IDV-2, IDV-3) is compared each with an overall threshold value such that, if one of the at least one metrification-based identification value (IDV, IDV-1, IDV-2, IDV-3) is below or below and equal to the threshold value, the "NO"-statement (N-S) regarding the presence of the passenger in the vehicle is made otherwise the "YES"-statement (Y-S) regarding the presence of the passenger in the vehicle is made, whereby in particular correspondingly an output quantity is provided, which is preferably a Boolean value. ( a) in a Signal Pre-Processing Step (SPPS) the first and second sensor signals (SS-1, SS-2) are independently pre-processed each by executing at least a Re-Sampling and a Magnitude Calculation to induce signal-specific magnitude values (MV-1, MV-2), which in particular are pre-processed additionally each by executing a Clipping Detection being executed preferably between the Re-Sampling and the Magnitude Calculation, ( b) in a Vehicle Identification Step the signal-specific magnitude values (MV-1, MV-2) are compared by applying a "Cross-Correlation Function " such that the signal-specific magnitude values (MV-1, MV-2) are executed in the order of "Overlapping in Time Domain", "Windowed Cross-Correlation" and Metrification to induce due to the Metrification at least one metrification-based identification value (IDV, IDV-1, IDV-2, IDV-3) and the at least one metrification-based identification value (IDV, IDV-1, IDV-2, IDV-3) is compared each with an overall threshold value such that, if one of the at least one metrification-based identification value (IDV, IDV-1, IDV-2, IDV-3) is below or below and equal to the threshold value, the "NO"-statement (N-S) regarding the presence of the passenger in the vehicle is made otherwise the "YES"-statement (Y-S) regarding the presence of the passenger in the vehicle is made, whereby in particular correspondingly an output quantity is provided, which is preferably a Boolean value. the signal-specific magnitude values (MV-1, MV-2) are compared by applying a "Cross-Correlation Function " such that the signal-specific magnitude values (MV-1, MV-2) are executed in the order of "Overlapping in Time Domain", "Windowed Cross-Correlation" and Metrification to induce due to the Metrification at least one metrification-based identification value (IDV, IDV-1, IDV-2, IDV-3) and the at least one metrification-based identification value (IDV, IDV-1, IDV-2, IDV-3) is compared each with an overall threshold value such that, if one of the at least one metrification-based identification value (IDV, IDV-1, IDV-2, IDV-3) is below or below and equal to the threshold value, the "NO"-statement (N-S) regarding the presence of the passenger in the vehicle is made otherwise the "YES"-statement (Y-S) regarding the presence of the passenger in the vehicle is made, whereby in particular correspondingly an output quantity is provided, which is preferably a Boolean value.