Method and apparatus for maintaining synchronization in a communication system

An apparatus in a communication system, the apparatus comprising:

• a receiver configured to receive a plurality of signals from a central entity;
• a clock generation element configured to
• generate a symbol clock based on timing information included in a first signal received by the receiver and
• generate a maintained symbol clock comprising maintaining the symbol clock upon a loss of reception of the first signal;
• an offset determination element configured to determine a symbol clock offset between the first signal and a second signal received by the receiver using the maintained symbol clock;
• and
• an upstream timing element configured to adjust the maintained symbol clock based on the symbol clock offset to generate an adjusted symbol clock.

A method for maintaining synchronization in a communication system wherein a central entity transmits a signal containing timing information to one or more remote devices, the one or more remote devices using the timing information for scheduling transmissions, the method comprising:

• receiving a first signal from the central entity;
• generating a symbol clock based on timing information included in the first signal;
• upon a loss of reception of the first signal, maintaining the symbol clock to generate a maintained symbol clock;
• receiving a second signal from the central entity;
• determining a symbol clock offset between the first signal and the second signal using the maintained symbol clock;
• wherein determining the symbol clock offset using the maintained symbol clock comprises:
• identifying a first symbol clock offset that obtains a valid puncture alignment for Trellis Coded Modulation (TCM) decoding of first encoded data in the second signal;
• identifying a second symbol clock offset that obtains a valid frame alignment for Reed-Solomon decoding of second encoded data in the second signal;
• and
• combining the first symbol clock offset and the second symbol clock offset to generate a combined symbol clock offset;
• and
• adjusting the maintained symbol clock based on the combined symbol clock offset to generate an adjusted symbol clock.

A method for maintaining synchronization in a communication system wherein a central entity transmits a signal containing timing information to one or more remote devices, the one or more remote devices using the timing information for scheduling transmissions, the method comprising:

• receiving a first signal from the central entity;
• generating a symbol clock based on timing information included in the first signal;
• receiving calibration information from the central entity relating to a difference in forward error correction (FEC) alignment between the first and second signals;
• upon a loss of reception of the first signal, maintaining the symbol clock to generate a maintained symbol clock;
• receiving a second signal from the central entity;
• determining a symbol clock offset between the first signal and the second signal using the maintained symbol clock,
• wherein determining the symbol clock offset includes accounting for the difference in FEC alignment between the first and second signals;
• and
• adjusting the maintained symbol clock based on the symbol clock offset to generate an adjusted symbol clock.

A method for maintaining synchronization in a communication system wherein a central entity transmits a signal containing timing information to one or more remote devices, the one or more remote devices using the timing information for scheduling transmissions, the method comprising:

• receiving a first signal transmitted from the central entity;
• generating a symbol clock based on timing information included in the first signal;
• storing calibration information relating to a timing difference between the first signal and a second signal transmitted from the central entity;
• upon a loss of reception of the first signal, maintaining the symbol clock;
• accessing the calibration information;
• determining a symbol clock offset between the first signal and the second signal based on the calibration information;
• and
• adjusting the symbol clock based on the symbol clock offset.

An apparatus in a communication system, the apparatus comprising:

• a receiver configured to receive a signal from a central entity;
• a clock generation element configured to generate a symbol clock based on timing information included in a first signal and to maintain the symbol clock upon a loss of reception of the first signal;
• an offset determination element configured to determine a symbol clock offset between the first signal and a second signal using the maintained symbol clock,
• wherein the offset determination element identifies a first symbol clock offset that obtains a valid puncture alignment for Trellis Coded Modulation (TCM) decoding of first encoded data in the second signal, identifies a second symbol clock offset that obtains a valid frame alignment for Reed-Solomon decoding of second encoded data in the second signal, and combines the first symbol clock offset and the second symbol clock offset to generate a combined symbol clock offset;
• and
• an upstream timing element configured to adjust the maintained symbol clock based on the symbol clock offset to generate an adjusted symbol clock.

An apparatus in a communication system, the apparatus comprising:

• a receiver configured to receive a signal from a central entity,
• wherein the receiver receives calibration information from the central entity relating to a difference in forward error correction (FEC) alignment between the first signal and the second signal prior to receiving the second signal;
• a clock generation element configured to generate a symbol clock based on timing information included in a first signal and to maintain the symbol clock upon a loss of reception of the first signal;
• an offset determination element configured to determine a symbol clock offset between the first signal and a second signal using the maintained symbol clock,
• wherein the symbol clock offset determination includes accounting for the difference in FEC alignment between the first signal and the second signal;
• and
• an upstream timing element configured to adjust the maintained symbol clock based on the symbol clock offset to generate an adjusted symbol clock.

An apparatus in a communication system, the apparatus comprising:

• means for receiving a first signal transmitted from a central entity;
• means for generating a symbol clock based on timing information included in the first signal;
• means for storing calibration information relating to a timing difference between the first signal and a second signal transmitted from the central entity;
• means for maintaining the symbol clock upon a loss of reception of the first signal;
• means for accessing the calibration information;
• means for determining a symbol clock offset between the first signal and the second signal based on the calibration information;
• and
• means for adjusting the symbol clock based on the symbol clock offset.

A communication system, comprising:

• a central entity comprising
• a first transmitter configured to transmit a first downstream signal, wherein the first downstream signal contains timing information based on a first central symbol clock, and
• a second transmitter configured to transmit a second downstream signal, wherein the second downstream signal contains timing information based on a second central symbol clock;
• and
• a remote device comprising
• a receiver configured to receive the first downstream signal;
• a clock generation element configured to
• generate a remote symbol clock based on the first downstream signal, and
• maintain the remote symbol clock upon a loss of reception of the first downstream signal to generate a maintained remote symbol clock;
• and
• an offset determination element configured to determine a remote symbol clock offset between the first downstream signal and the second downstream signal using the maintained remote symbol clock.

A method for maintaining synchronization in a communications system, comprising:

• transmitting a first downstream signal from a central entity to one or more remote devices, wherein the first downstream signal includes timing information based on a first central symbol clock;
• receiving a first downstream signal;
• generating a remote symbol clock based on timing information included in the first downstream signal;
• upon a loss of reception of the first downstream signal, maintaining the remote symbol clock;
• transmitting a second downstream signal from the central entity to one or more remote devices, wherein the second downstream signal includes timing information based on a second symbol clock;
• receiving a second downstream signal;
• determining a symbol clock offset between the first downstream signal and the second downstream signal using the maintained remote symbol clock;
• and
• adjusting the maintained symbol clock based on the symbol clock offset to generate an adjusted symbol clock.