Patent ID: 7773711

Claim:
A method of assessing the quality of data signals which are transmitted from a transmitter location to at least one data receiving location, said method including the steps of: identifying a known signal data sequence; inserting said known signal data sequence into the transmitted signal: and wherein a broadcast data receiver at said at least one receiving location includes detection means to detect whether the known signal data sequence is present or not in the signal received at the receiving location, the method further including the steps of; using a sequence detector which operates on the received samples to generate approximations of the known data signal sequence at a default symbol rate; using a correlator to generate a correlation between the known marker symbol values and the symbol approximations; and setting a threshold above which a correlation is determined to represent a match of correlated signals and provides symbol retiming information, where the modulation error ratio is calculated using the received retimed sample marker data sequence and the ideal representation of the mark or symbol sequence when the threshold is attained, to provide an indication of signal quality and integrity for the data transmission path between the transmitting and receiving locations; such that when the broadcast data receiver is unable to lock to a data signal, the modulation scheme required to allow said lock may be determined without changing the applied modulation scheme, by characterizing the quality of the known signal data sequence detected.