Testing an upstream path of a cable network
View Patent ↗An apparatus and method for testing an upstream path of a cable network are disclosed. The upstream path is tested by capturing and analyzing upstream data packets generated by a specific terminal device. A test instrument is connected at a node of the cable network. The test instrument establishes a communication session with the headend, informing the headend of an identifier of the device that will generate the test upstream data packet. The test upstream data packet is captured and analyzed at the headend, so that the results of the analysis can be communicated back to the test instrument. To speed up the packet capturing and filtering process, the upstream data packets can be pre-filtered based on packet duration and/or arrival time.
1. A method of testing an upstream path of a cable network, the method comprising:
receiving a request to demodulate and obtain signal quality information of an upstream data packet generated by a first terminal device connected to a cable network;
receiving the upstream data packet generated by the first terminal device;
demodulating the received upstream data packet, wherein demodulating the upstream data packet comprises demodulating upstream data packets determined to have a packet length of a first length, and not demodulating upstream packets determined to have a packet length other than the first length;
receiving the at least one upstream pre-equalization coefficient used by the first terminal device to generate the upstream data packet;
determining signal quality information pertaining to the upstream data packet;
correcting, using the at least one upstream pre-equalization coefficient, the determined signal quality information to account for pre-equalization of the upstream data packet, wherein the signal quality information includes measured frequency response information pertaining to the received and demodulated upstream data packet; and
communicating the corrected signal quality information to a test instrument.
2. The method of claim 1 , further comprising:
displaying the corrected signal quality information on a display of the test instrument.
3. The method of claim 1 , wherein the first terminal device is identified by a MAC address.
4. The method of claim 1 , wherein the at least one pre-equalization coefficient is obtained from a terminal devices database including records of terminal devices connected to the cable network.
5. The method of claim 1 , wherein the first terminal device is a test instrument, wherein the receiving of the request comprises receiving the request from the test instrument, and wherein the method further comprising generating the upstream data packet by the test instrument.
6. The method of claim 1 , wherein the corrected signal quality information includes at least one of modulation error ratio (MER), in-band frequency response, in-band group delay, micro-reflections, impulse noise, number of captured symbols in the upstream data packet, number of erroneously detected symbols in the upstream data packet, a constellation map, and RF power level.
7. The method of claim 1 , wherein the signal quality information comprises signal QAM quality information.
8. An apparatus for testing an upstream path of a cable network, the apparatus comprising:
a test instrument coupled to a node of the cable network, wherein the test instrument sends a test request to a headend of the cable network to demodulate and determine signal quality information of an upstream data packet generated by a first terminal device connected to the cable network, and
a test module disposed at the headend, the test module including:
a communication circuit to receive the test request and the upstream data packet;
a demodulator coupled to the communication circuit, to demodulate the upstream data packet generated by the first terminal device, wherein to demodulate the upstream data packet, the test module demodulates upstream data packets determined to have a packet length of a first length, and does not demodulate upstream packets determined to have a packet length other than the first length; and
a processor coupled to the demodulator and the communication circuit, the processor to:
determine the signal quality information pertaining to the demodulated upstream data packet, and
correct, using at least one upstream pre-equalization coefficient, the determined signal quality information to account for pre-equalization of the upstream data packet, wherein the signal quality information includes measured frequency response information pertaining to the received and demodulated upstream data packet,
wherein the communication circuit is to communicate the determined signal quality information back to the test instrument.
9. The apparatus of claim 8 , wherein the test module is coupled to a database of terminal devices to obtain the at least one pre-equalization coefficient.
10. The apparatus of claim 8 ,
wherein the test instrument comprises a display to display the determined signal quality information.
11. The apparatus of claim 8 , wherein the test instrument communicates with the test module via a dedicated Data Over Cable Service Interface Specification (DOCSIS) connection.
12. The apparatus of claim 8 , wherein the test instrument is to obtain signal quadrature amplitude modulation (QAM) quality information of the upstream data packet generated by a first terminal device connected to the cable network, wherein the signal QAM quality information is part of the signal quality information of the upstream data packet received and corrected by the processor.