Patent ID: 8856850

Claim:
A method of tagging signals for leakage detection and leakage measurement, the signals being transmitted in cable television networks, the cable television networks jointly comprising a frequency spectrum that comprises a plurality of cable television channels and a guard band, and a plurality of subnetworks including a first subnetwork, a second subnetwork, and a third subnetwork, the method comprising: 1) placing in the guard band a first narrowband tagging signal, a second narrowband tagging signal, and a third narrowband tagging signal, each having an amplitude, wherein the first narrowband tagging signal, the second narrowband tagging signal, and the third narrowband tagging signal have the same amplitude and have different center frequencies with respect to one another; and creating tagging information for the first narrowband tagging signal, the second narrowband tagging signal, and the third narrowband tagging signal by amplitude-modulating the first narrowband tagging signal, the second narrowband tagging signal, and the third narrowband tagging signal with a modulation depth of less than 30% and a modulation frequency of between 1 Hz and 50 Hz; 2) obtaining a spectral signature of signals transmitted in the second subnetwork by reducing the amplitude of the second narrowband tagging signal in the second subnetwork to be lower than the amplitude of the first narrowband tagging signal in the second subnetwork and to be lower than the amplitude of the third narrowband tagging signal in the second subnetwork; and 3) obtaining a spectral signature of signals transmitted in the third subnetwork by reducing the amplitude of the third narrowband tagging signal in the third subnetwork to be lower than the amplitude of the first narrowband tagging signal in the third subnetwork and to be lower than the amplitude of the second narrowband tagging signal in the third subnetwork.