Patent ID: 6628737
Filing Date: 2003-09-30
Classification: H04L

Abstract:
A signal quality measurement method including the steps of:sending a test signature from sending end to a receiving end of a connection; storing a copy of said test signal at said receiving end; measuring the similarity between said stored copy of said test signal and the signal received at said receiving end; selecting a sequence of different synchronization patterns directly from said stored copy of said test signal; determining, from said received signal, a sequence of signal segments that best matches said synchronization pattern sequence, wherein said determining step is a trellis based procedure that finds the sequence of signal segments that has the greatest probability of matching said synchronization pattern sequence; synchronizing said received signal with said signal segment sequence, thereby synchronizing said received signal with said stored copy of said test signal; comparing each synchronization pattern to a set of partially overlapping segments of the signal received by said receiver to determine where in said received signal each synchronization pattern is most likely found, wherein said comparing step includes comparing, for each synchronization pattern and segment, a distance measure representing the similarity between synchronization pattern and segment to a threshold and further marking a segment as a possible synchronization position for the corresponding synchronization pattern if said distance measure fails below said threshold; including an individual threshold for each synchronization pattern; dynamically updating each threshold in accordance with a prevailing disturbance level; and selecting another sequence of synchronization patterns, in which each synchronization pattern has another length, if a prevailing disturbance level changes a predetermined amount.