Non-invasive digital communications test system

摘要

Method and apparatus for non-invasively testing performance of a digital communication system. The test system finds particular application in digital broadcast systems where interruption of regular service for test purposes is impracticable. In one embodiment oriented to digital television cable broadcast systems, unwanted reflections due to loose connectors and other causes may be localized within a subscriber's home. The test system takes advantage of information typically generated by digital receivers to correct for communication channel imperfections. Examples of such information include current filter parameters computed for use in an internal adaptive equalizer, internal loop parameters, and the difference between the signal received and a reconstruction of that signal from the symbols estimated by the receiver.