Method and system for scanning for a downstream channel in a communication network
View Patent ↗A predetermined current frequency is selected for a cable modem or embedded media terminal adapter to evaluate for presence of a CMTS signal. A determination is made whether the current frequency carries signal energy as opposed to just noise. If no signal energy is detected, the current frequency is changed by ½ of a channel width to a new frequency, which becomes the current frequency, and the determination is re-performed. If the determination of the current frequency indicates that signal energy is present, but not CMTS energy, then a new frequency indicates that selected that differs from the current frequency by 1 MHz. If the determination at the current frequency indicates that CMTS signal energy is present, but QAM lock cannot be achieved, then a new frequency is selected by changing from the current frequency by a full channel width.
1. A computer-implemented method for reducing frequency scanning time in one or more of a plurality of remote network devices connected to a central network device comprising:
receiving at a receiver a signal associated with a current downstream frequency;
determining the signal energy content of the current downstream frequency at an end user device;
identifying a signal associated with a new downstream frequency at the end user device the new downstream frequency differing from the current downstream frequency by a half channel width, and the new downstream frequency being identified based on the determination of signal energy content in the current downstream frequency is zero;
repeating the method at the end user device upon identifying a signal associated with a new downstream frequency;
in response to identifying energy in the signal at the current downstream frequency, attempting QAM lock on the signal at the current downstream frequency;
determining that the signal at the current downstream frequency is not that of a headend device responsive to attempting QAM lock;
if the signal at the current downstream frequency is not that of a headend device, identifying a new downstream frequency at the end user device, wherein the new downstream frequency at the end user device that differs from the current frequency by a full channel width; and wherein scanning is restarted with an offset of 250 kHz from the original scanning after scanning a predetermined spectrum of frequencies without achieving lock to a CMTS signal.
2. The method of claim 1 further wherein the current downstream frequency is the new downstream frequency of a previous iteration of the method.
3. The method of claim 1 wherein the new frequency received by the one or more of the plurality of remote network devices differs from the current frequency by 1 MHz if the determination of signal energy content indicates that the current downstream frequency carries signal energy to which the remote network device cannot achieve QAM lock.
4. The method of claim 1 wherein the channel width is 6 MHz.
5. The method of claim 1 wherein the channel width is 8 MHz.
6. The method in claim 1 wherein a given frequency is not checked if it was evaluated in a previous pass through the spectrum.
7. A computer implemented method, comprising:
selecting a new frequency to scan in an end user device;
tuning a receiver to the identified frequency;
measuring an energy level associated with the selected frequency at the end user device;
comparing the measured energy level associated with the identified frequency at the end user device to an expected energy level associated with a downstream channel;
attempting to lock onto the downstream channel at the end user device if the measured energy level associated with the selected frequency meets an expected energy level;
repeating the method if the measured energy level does not meet the expected energy level or if the attempt to lock onto the downstream channel is unsuccessful, wherein selecting a new frequency is a half-channel width from a previous frequency;
wherein if the attempt to lock onto the downstream channel at the identified frequency is successful, but the signal is not originated by a headend device, repeating the method by selecting a new frequency that is a full channel width from a previous frequency; and wherein scanning is restarted with an offset of 250 kHz from the original scanning after scanning a predetermined spectrum of frequencies without achieving lock to a CMTS signal.
8. The computer implemented method of claim 7 , further comprising:
selecting a cached frequency from a frequency cache at the end user device;
attempting to lock onto the selected cached frequency using the end user device;
repeating the selection of a cached frequency and attempt to lock onto the selected cached frequency until lock is successful or cached frequencies are exhausted.
9. The computer implemented method of claim 7 , wherein if the measured energy is below the expected energy level but there is energy at the selected frequency, the step of selecting a frequency to scan in the end user device comprises changing a previously selected frequency by 1 MHz.
10. The computer implemented method of claim 8 , wherein if the measured energy is below the expected energy level and there is no energy at the selected frequency, the step of selecting a frequency to scan in the end user device comprises changing a previously selected frequency by half a channel width.
11. The computer implemented method of claim 7 , further comprising:
determining if any more frequencies within a frequency spectrum are left to scan;
performing a second scanning of the spectrum of frequencies;
if no channels are found on the second scanning of the spectrum of frequencies, revert to legacy frequency scanning methods.