Apparatus and method for synchronization in a multiple-carrier communications system by observing a phase-frequency relationship of a plurality of pilot signals

1. A method for determining a loss of synchronization between a transmitter and a receiver:

receiving, at the receiver, a plurality of pilot signals having different frequencies from transmitter;

detecting a phase-frequency relationship of the plurality of pilot signals; and

determining loss of synchronization from the phase-frequency relationship;

wherein the phase-frequency relationship comprises a line defined by a relationship between a phase and a frequency of the plurality of pilot signals;

wherein determining comprises determining loss of synchronization based on a slope of the line; and

wherein determining further comprises determining loss of synchronization based on the number of times the slope exceeds a timing threshold.

2. A method in accordance with claim 1 , wherein determining further comprises:

determining loss of synchronization when the number of times exceeds an occurrence threshold within a time period.

3. A method of determining a loss of synchronization between a transmitter and a receiver:

receiving, at the receiver, a plurality of pilot signals transmitted at different frequencies from the transmitter;

determining a slope of a line defined by a phase-frequency relationship of the plurality of pilot signals, the phase-frequency relationship defined by a plurality of phase-frequency values wherein each of a plurality of phase values is uniquely associated with each of a plurality of frequency values;

counting a number of times the slope exceeds a timing threshold; and

determining loss of synchronization between the transmitter and the receiver when the number of times is greater than an occurrence threshold in a time period.

4. A method in accordance with claim 3 , wherein determining the slope comprises:

curve fitting the plurality of phase-frequency values using linear regression.

5. A method in accordance with claim 4 , further comprising:

adjusting the receiver to synchronize the receiver to the transmitter in response to the loss of synchronization.

6. A phase-frequency slope synchronization detector comprising:

a phase detector adapted to determine a phase value for each of a plurality of received pilot signals transmitted from a transmitter at different frequencies; and

a controller adapted to determine a loss of synchronization between the transmitter and the receiver based on a phase-frequency relationship of the plurality of pilot signals;

wherein the phase-frequency relationship comprises a line defined by a relationship between a phase and a frequency of the plurality of pilot signals;

wherein the controller is further adapted to determine loss of synchronization based on a slope of the line; and

wherein the controller is further adapted to determine loss of synchronization based on the number of times the slope exceeds a timing threshold.

7. A phase-frequency slope synchronization detector in accordance with claim 6 , wherein the controller is further adapted to determine loss of synchronization when the number of times exceeds an occurrence threshold within a time period.

8. A receiver for determining a loss of synchronization between the receiver and a transmitter comprising:

a demodulator adapted to demodulate a plurality of pilot signals transmitted at different frequencies from the transmitter; and

a phase-frequency synchronization detector adapted to:

determine a slope of a line defined by a phase-frequency relationship of the plurality of pilot signals, the phase-frequency relationship defined by a plurality of phase-frequency values wherein each of a plurality of phase values is uniquely associated with each of a plurality of frequency values;

count a number of times the slope exceeds a timing threshold; and

determine loss of synchronization between the transmitter and the receiver when the number of times is greater than an occurrence threshold in a time period.

9. A receiver in accordance with claim 8 , wherein the phase-frequency synchronization detector is further adapted to determine the slope by applying a curve fitting algorithm using linear regression to the plurality of phase-frequency values.

10. A receiver in accordance with claim 9 , wherein the controller is further adapted to adjust the demodulator to synchronize the receiver to the transmitter in response to the loss of synchronization.

11. A multiple-carrier wireless communication system comprising:

a transmitter adapted to transmit a plurality of pilot signals through a wireless communication channel, each of the pilot signals having a unique frequency; and

a receiver adapted to detect a loss of synchronization between the receiver and the transmitter based on a phase-frequency relationship of the pilot signals received at the receiver, the phase-frequency relationship comprising a line defined by a relationship between a phase and a frequency of the plurality of pilot signals;

wherein the receiver comprises the phase-frequency synchronization detector adapted to;

determine a slope of the line defined by a phase-frequency relationship of the plurality of pilot signals, the phase-frequency relationship defined by a plurality of phase-frequency values wherein each of a plurality of phase values is uniquely associated with each of a plurality of frequency values;

count a number of times the slope exceeds a timing threshold; and

determine loss of synchronization between the transmitter and the receiver when the number of times is greater than an occurrence threshold in a time period.