Noise margin measurement and error probability prediction
AssigneeHewlett-Packard Company
InventorsThomas M. Crawford, Alastair S. Reynolds, Ivan R. Young
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Abstract
This invention relates to method and apparatus for measuring noise margins in digital transmission systems. The method requires the introduction of a variable pulse into a sequence of pulses which represents normal traffic, varying a parameter of the pulse, detecting the pulse, and accumulating information concerning the variations to determine probability distribution of the deviations produced by measuring the variations relative to a standard. The apparatus includes means for introducing the variable pulse into a sequence of pulses and for observing and recording detection of the variable pulse in each sequence to compile a probability distribution of the aforementioned deviations.
Claims37
A method of measuring noise margins in a digital transmission system comprising a receiver, the method comprising the steps of:
- (a) providing a pulse of a specified state and at least one parameter of which can be varied, within a sequence of pulses, which sequence is repeatable and is generated to be representative of normal traffic along a given transmission path of the system;
- (b) varying the value of said at least one parameter of said pulse until said pulse when varied is such that it can be detected by a detector circuit of the system;
- (c) detecting said pulse when varied, prior to any error correction thereof by an in-built error correction means of the system;
- (d) repeating steps (a), (b) and (c) by providing said pulse at a different predetermined and repeatable position in said sequence, for each repetition, and detecting change of state of said pulse at each position;
- and
- (e) accumulating the value of the variations of said at least one parameter as deviations from a selected reference value for each pulse position to determine the probability distribution of said deviations.
Apparatus for use in measuring noise margins in a digital transmission system comprising a receiver, the apparatus comprising:
- (a) pulse sequence providing means, having an output, for providing a sequence of pulses which is substantially repeatable and is generated to be representative of normal traffic to the receiver of the system;
- (b) variable-pulse providing means, having an output connected to the output of the pulse sequence providing means, for providing a variable pulse to be inserted at a predetermined position in said sequence of pulses;
- (c) variable-pulse moving means, coupled with the variable-pulse providing means, for moving the variable pulse from one position to another within said sequence of pulses;
- (d) value varying means, coupled with the variable pulse providing means, for varying the value of at least one parameter of said variable pulse;
- (e) output examining means, coupled with the output of a detector of the system, for examining the output from the detector to which said sequence, including said variable pulse, has been fed;
- (f) state determining means, coupled with the output from the detector, for determining which state of a number of possible output states of said variable pulse is indicated by the value of said output of said detector;
- (g) value monitoring means, coupled with the output from the detector, for monitoring the value of said at least one parameter while examining said output from said detector;
- and
- (h) accumulator means, coupled with the value monitoring means, and with the state determining means, for accumulating values of deviations of said at least one parameter from a selected reference value for each pulse position to determine the probability distribution of said deviations.
Dependencies are inferred from the claim text.