Methods and systems for use of common mode rejection (CMR) for echo cancellation in uplink communications
Systems and methods are provided for use of common mode rejection (CMR) for echo cancellation in uplink communications. A node in a cable network configured for transmitting downstream (DS) signals and receiving upstream (US) signals, may include echo cancelling circuits configured for cancelling echo introduced by the DS signals and/or transmittal of the DS signals, onto US signals and/or US reception path, to facilitate full-duplex (FDX) communications of the DS signals and US signal. The echo cancelling circuits may be configured for operating in the analog domain. The echo cancelling circuits may include an echo cancelling combiner configured for combining two or more upstream signals non-coherently.
1. A system for use in a node of a cable network, the system comprising:
one or more transmission circuits configured for transmitting downstream (DS) signals in the cable network;
one or more reception circuits configured for receiving upstream (US) signals in the cable network;
one or more echo cancelling circuits configured for cancelling echo introduced by transmitting of downstream signals onto upstream reception path, wherein the one or more echo cancelling circuits comprise a feed-forward (FF) digital-to-analog convertor (DAC) circuit,
the FF DAC to output an analog signal to combine with a signal corresponding to an output of one or more echo cancelling combiner circuits; and
a variable resistor circuit coupled to the FF DAC, the variable resistor circuit configured to selectively adjust the analog signal before the analog signal is combined with the signal corresponding to the output of the one or more echo cancelling combiner circuits, wherein:
the one or more transmission circuits and the one or more reception circuits are configured for supporting full-duplex (FDX) communications via the cable network;
the one or more echo cancelling circuits are configured at least for mitigating direct leakage associated with the DS signals, that is introduced onto the US signals; and
the one or more echo cancelling circuits are configured for operating in the analog domain.
2. The system of claim 1 , wherein the one or more transmission circuits are configured to generate the downstream (DS) signals as data over coaxial service interface specification (DOCSIS) based signals.
3. The system of claim 1 , wherein the one or more reception circuits are configured to handle data over coaxial service interface specification (DOCSIS) based upstream (US) signals.
4. The system of claim 1 , wherein the one or more echo cancelling circuits comprise the echo cancelling combiner circuit that is configured for combining two or more upstream signals non-coherently.
5. The system of claim 4 , wherein the echo cancelling combiner circuit comprises a plurality of balanced to unbalanced (balun) combiner circuits.
6. The system of claim 5 , wherein the plurality of balun combiner circuits is arranged such as a plurality of inputs into the echo cancelling combiner circuit are combined via the plurality of balun combiner circuits in non-coherent manner.
7. The system of claim 5 , wherein each balun combiner circuit of the plurality of balun combiner circuits comprises a 2-to-1 combiner circuit.
8. The system of claim 5 , wherein:
the echo cancelling combiner circuit is configured to receive four inputs;
the plurality of balun combiner circuits comprises three 2-to-1 balun combiner circuits;
each of a pair of the three 2-to-1 balun combiner circuits is configured to receive two different one of the four inputs; and
a last of the three 2-to-1 balun combiner circuits is arranged to receive an output from each of the pair of the three 2-to-1 balun combiner circuits.
9. A system for use in a node of a cable network, to support full-duplex (FDX) communications via the cable network, the system comprising:
an echo cancelling combiner circuit that is configured for combining two or more upstream (US) signals non-coherently, wherein:
the echo cancelling combiner circuit is configured at least for mitigating direct leakage associated with downstream (DS) signals, that is introduced onto the US signals, the mitigating including selectively injecting a signal that has been conditioned by a variable resistor circuit; and
the echo cancelling combiner circuit is configured for operating in the analog domain.
10. The system of claim 9 , wherein the echo cancelling combiner circuit comprises a plurality of balanced to unbalanced (balun) combiner circuits.
11. The system of claim 10 , wherein the plurality of balun combiner circuits is arranged such as a plurality of inputs into the echo cancelling combiner circuit are combined via the plurality of balun combiner circuits in non-coherent manner.
12. The system of claim 10 , wherein each balun combiner circuit of the plurality of balun combiner circuits comprises a 2-to-1 combiner circuit.
13. The system of claim 12 , wherein:
the echo cancelling combiner circuit is configured to receive four inputs;
the plurality of balun combiner circuits comprises three 2-to-1 balun combiner circuits;
each of a pair of the three 2-to-1 balun combiner circuits is configured to receive two different one of the four inputs; and
a last of the three 2-to-1 balun combiner circuits is arranged to receive an output from each of the pair of the three 2-to-1 balun combiner circuits.