Viavi Solutions Inc.

Jds Uniphase Corporation

Ching-Chang Liao

Jim Walsh

Daniel Keith Chappell

Adam D Gray

Richard Earl Jones, Jr

The invention relates to a method and apparatus for evaluating a network and for predicting network performance for a higher order modulation by analyzing network signals modulated using a lower order modulation format. A margin index may be generated for the current or projected modulation formats based on displacement vectors for received symbols to indicate a margin remaining before a codeword error occurs to alert the network operator of potential performance issues before actual codeword errors occur.

Predictive network testing

Apparatus and method are provided for obtaining an upstream signal spectrum as it was during a time of transmission of a received upstream data packet. The apparatus includes an analog-to-digital converter (ADC), a packet detector coupled to ADC, and a spectrum calculation unit coupled to the ADC and the packet detector. In operation, the spectrum calculation unit computes a spectrum of the digitized upstream signal as it was between the start and end times of the first packet. As a result, the obtained spectrum is representative of a condition of the transmission path during transmission of the upstream data packet.

Cable network spectral measurement during upstream packet transmission

A method and an apparatus for identifying an origin of captured DOCSIS upstream bursts are disclosed. Upstream bursts are captured without knowing their allocated time slots in advance. Information from an upstream channel descriptor is used to generate RF waveforms of upstream burst preambles, which are then correlated to the captured upstream waveforms to determine the type of captured upstream bursts without having to decode the latter. Once the type of the captured upstream bursts is determined, information from the upstream channel descriptor is further used to demodulate and decode the upstream burst, so that CPE MAC addresses can be extracted. From the extracted CPE MAC addresses, the origin of the captured upstream bursts can be identified. The identification of origins of captured upstream bursts assists in locating faults in the cable network.

Identifying an origin of a DOCSIS upstream burst

In order to measure the performance of a DOCSIS upstream channel as well as to locate impairments, a special test signal is transmitted in a time slot of the upstream channel by a test instrument positioned anywhere within the CATV plant. A second test instrument, located at the termination point of the upstream plant, then detects, recovers, and processes the test signal in order to complete the measurement. The typical methods used to detect and recover bursted signals within a DOCSIS upstream channel use precise timing information transmitted in a corresponding DOCSIS downstream channel. Unfortunately, the downstream channel and thus the precise timing information are not always available to the secondary test instrument. The present invention also describes an apparatus and method for detecting a bursted test signal without the use of the DOCSIS upstream channel timing.

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Fishers, IN, United States of America

Ching-Chang Liao