System and Method for Performing Ranging in a Cable Modem System
First Claim
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1. A cable modem, comprising:
- a receiver configured to receive a subsequent ranging response generated by a cable modem termination system after generating a first ranging response, the subsequent ranging response comprising a plurality of ranging parameters including an upstream communications parameter, a timing adjust parameter, a power level adjust parameter, a carrier frequency offset parameter, and a plurality of equalization parameters, the equalization parameters including a number of ranging response equalizer coefficients;
a pre-equalizer configured to;
determine a delay offset based, at least in part, on a location of a main tap and a specified main tap location, wherein the specified main tap location is included in the subsequent ranging response;
convolve current pre-equalizer coefficients with the ranging response equalizer coefficients to generate new pre-equalizer coefficients for the main tap and a number of non-main taps, wherein each one of the taps has a real part and an imaginary part, and wherein the pre-equalizer is further configured to adjust the imaginary part of the main tap to zero;
identify each non-main tap having a determined magnitude squared value below a specified threshold and to set the new pre-equalizer coefficients for the real part and the imaginary part of each identified non-main tap to zero; and
generate scaled coefficients using the new pre-equalizer coefficients for the main tap and non-main taps; and
a gain stage configured to adjust a transmit power of the cable modem in response to an equalizer coefficient gain change value, the equalizer coefficient gain change value being determined, at least in part, from a ratio of a current equalizer coefficient gain value and a new equalizer coefficient gain value.
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Abstract
The present invention provides a system and method for performing ranging operations in a cable modem system. In accordance with embodiments of the present invention, transmission times, transmission power levels, transmission carrier frequencies, and pre-equalization parameters are adjusted to provide for robust operation of the cable modem system. More particularly, iterative processing steps are used to provide coefficient ordering, scaling, and aligning between the multiple cable modems and the cable modem termination system present in a cable modem system.
24 Citations
20 Claims
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1. A cable modem, comprising:
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a receiver configured to receive a subsequent ranging response generated by a cable modem termination system after generating a first ranging response, the subsequent ranging response comprising a plurality of ranging parameters including an upstream communications parameter, a timing adjust parameter, a power level adjust parameter, a carrier frequency offset parameter, and a plurality of equalization parameters, the equalization parameters including a number of ranging response equalizer coefficients; a pre-equalizer configured to; determine a delay offset based, at least in part, on a location of a main tap and a specified main tap location, wherein the specified main tap location is included in the subsequent ranging response; convolve current pre-equalizer coefficients with the ranging response equalizer coefficients to generate new pre-equalizer coefficients for the main tap and a number of non-main taps, wherein each one of the taps has a real part and an imaginary part, and wherein the pre-equalizer is further configured to adjust the imaginary part of the main tap to zero; identify each non-main tap having a determined magnitude squared value below a specified threshold and to set the new pre-equalizer coefficients for the real part and the imaginary part of each identified non-main tap to zero; and generate scaled coefficients using the new pre-equalizer coefficients for the main tap and non-main taps; and a gain stage configured to adjust a transmit power of the cable modem in response to an equalizer coefficient gain change value, the equalizer coefficient gain change value being determined, at least in part, from a ratio of a current equalizer coefficient gain value and a new equalizer coefficient gain value. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A method, comprising:
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receiving by a cable modem a subsequent ranging response generated by a cable modem termination system after generating a first ranging response, the subsequent ranging response comprising a plurality of ranging parameters including an upstream communications parameter, a timing adjust parameter, a power level adjust parameter, a carrier frequency offset parameter, and a plurality of equalization parameters, the equalization parameters including a number of ranging response equalizer coefficients; determining a delay offset based, at least in part, on a location of a main tap and a specified main tap location, wherein the specified main tap location is included in the subsequent ranging response; convolving current pre-equalizer coefficients with the ranging response equalizer coefficients to generate new pre-equalizer coefficients for the main tap and a number of non-main taps, wherein each one of the taps has a real part and an imaginary part; adjusting the imaginary part of the main tap to zero; identifying each non-main tap having a determined magnitude squared value below a specified threshold and to set the new pre-equalizer coefficients for the real part and the imaginary part of each identified non-main tap to zero; generating scaled coefficients using the new pre-equalizer coefficients for the main tap and non-main taps; and adjusting a transmit power of the cable modem in response to an equalizer coefficient gain change value, the equalizer coefficient gain change value being determined, at least in part, from a ratio of a current equalizer coefficient gain value and a new equalizer coefficient gain value. - View Dependent Claims (12, 13, 14, 15, 16, 17, 18, 19, 20)
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Specification