Frequency offset detection method and apparatus

A frequency offset detection method comprising:

• calibrating a frequency offset of a clock signal output by a local crystal oscillator of a network element device;
• and
• performing frequency offset detection on a tracked reference clock signal by using the calibrated clock signal output by the local crystal oscillator,
• wherein the calibrating the frequency offset of the clock signal output by the local crystal oscillator of the network element device comprises:
• calculating an internal calibration value INNER_CAL according to n fifth count values N5k on n fifth counters and a third reference value N0, wherein N5k denotes a count value obtained by the kth fifth counter by counting rising edges of the clock signal output by the local crystal oscillator, N0 denotes a count value obtained, when the kth reference clock signal has no frequency offset and the clock signal output by the local crystal oscillator has no frequency offset, by the kth fifth counter by counting the rising edges of the clock signal output by the local crystal oscillator, and
• N
• 0
• =
• A
• ′
• ×
• f
• 0
• ′
• f
• k
• ,
• wherein A′ is a second preset count value, A′ is determined according to required precision of calibration performed on the frequency offset of the clock signal output by the local crystal oscillator, f0′ denotes a frequency existing when the clock signal output by the local crystal oscillator has no frequency offset, and fk denotes a frequency existing when the kth reference clock signal has no frequency offset;
• and n reference clock signals are clock signals extracted from received service signals by the local crystal oscillator, n is an integer greater than 2, and k is an integer greater than or equal to 1 and less than or equal to n;
• and
• performing, according to INNER_CAL, internal calibration on the frequency offset of the clock signal output by the local crystal oscillator.

A frequency offset detection apparatus comprising:

• a processor;
• and
• a non-transitory computer readable medium having a plurality of processor-executable instructions that, when executed by the processor, cause the processor to perform operations comprising:
• calibrating a frequency offset of a clock signal output by a local crystal oscillator of a network element device;
• and
• performing frequency offset detection on a tracked reference clock signal by using the calibrated clock signal output by the local crystal oscillator,
• wherein the processor is configured with processor-executable instructions to perform operations such that calibrating the frequency offset of the clock signal output by the local crystal oscillator of the network element device comprises:
• calculating an external calibration value EXT_CAL according to a first count value X on a first counter and a first reference value X0, wherein X denotes a count value obtained, when a reference clock signal input to the local crystal oscillator through an external clock interface has no frequency offset, by the first counter by counting rising edges of the clock signal output by the local crystal oscillator, X0 denotes a count value obtained, when the clock signal output by the local crystal oscillator has no frequency offset and the reference clock signal input to the local crystal oscillator through the external clock interface has no frequency offset, by the first counter by counting the rising edges of the clock signal output by the local crystal oscillator, and
• X
• 0
• =
• A
• ×
• f
• 0
• f
• ,
• wherein A is a first preset count value, A is determined according to required precision of calibration performed on the frequency offset of the clock signal output by the local crystal oscillator, f0 denotes a frequency existing when the clock signal output by the local crystal oscillator has no frequency offset, and f denotes a frequency existing when the reference clock signal input to the local crystal oscillator through the external clock interface has no frequency offset;
• and
• performing, according to EXT_CAL, external calibration on the frequency offset of the clock signal output by the local crystal oscillator.

A frequency offset detection apparatus comprising:

• a processor;
• and
• a non-transitory computer readable medium having a plurality of processor-executable instructions that, when executed by the processor, cause the processor to perform operations comprising:
• calibrating a frequency offset of a clock signal output by a local crystal oscillator of a network element device;
• and
• performing frequency offset detection on a tracked reference clock signal by using the calibrated clock signal output by the local crystal oscillator,
• wherein the processor is configured with processor-executable instructions to perform operations such that calibrating the frequency offset of the clock signal output by the local crystal oscillator of the network element device comprises:
• calculating an internal calibration value INNER_CAL according to n fifth count values N5k on n fifth counters and a third reference value N0, wherein N5k denotes a count value obtained by the kth fifth counter by counting rising edges of the clock signal output by the local crystal oscillator, N0 denotes a count value obtained, when the kth reference clock signal has no frequency offset and the clock signal output by the local crystal oscillator has no frequency offset, by the kth fifth counter by counting the rising edges of the clock signal output by the local crystal oscillator, and
• N
• 0
• =
• A
• ′
• ×
• f
• 0
• ′
• f
• k
• ,
• wherein A′ is a second preset count value, A′ is determined according to required precision of calibration performed on the frequency offset of the clock signal output by the local crystal oscillator, f0′ denotes a frequency existing when the clock signal output by the local crystal oscillator has no frequency offset, and fk denotes a frequency existing when the kth reference clock signal has no frequency offset;
• and n reference clock signals are clock signals extracted from received service signals by the local crystal oscillator, n is an integer greater than 2, and k is an integer greater than or equal to 1 and less than or equal to n;
• and
• performing, according to INNER_CAL, internal calibration on the frequency offset of the clock signal output by the local crystal oscillator.