Methods and apparatus for generating synchronization/pilot sequences for embedding in wireless signals

1. A method for generating a set of synchronization/pilot sequences, the method comprising the steps of:

generating a candidate synchronization/pilot sequence using initial conditions;

repeating the generating step a first number of iterations using different initial conditions for each iteration to generate a plurality of candidate synchronization/pilot sequences;

performing a plurality of correlations among the candidate synchronization/pilot sequences to generate a plurality of correlation values;

determining a plurality of permutations of the candidate synchronization/pilot sequences, wherein each permutation of the plurality of permutations includes a different set of multiple candidate synchronization/pilot sequences, and wherein each permutation includes a number, D, of candidate synchronization/pilot sequences; and

identifying a selected permutation from the plurality of permutations based on the correlations among the candidate synchronization/pilot sequences in the selected permutation, wherein the selected permutation corresponds to the set of synchronization/pilot sequences being generated.

2. A method for generating a set of synchronization/pilot sequences, the method comprising the steps of:

generating a candidate synchronization/pilot sequence using initial conditions by

generating a constant modulus phase sequence having the initial conditions corresponding to a random phase,

applying a power profile to the constant modulus phase sequence to produce a power-adjusted phase sequence,

performing a time-domain transformation of the power-adjusted phase sequence to produce a time-domain sequence,

setting amplitudes of the time-domain sequence to unity while maintaining phases of the time-domain sequence to produce an amplitude-adjusted time-domain sequence,

performing a frequency-domain transformation of the amplitude-adjusted time-domain sequence to produce a modified frequency-domain sequence,

applying the power profile to the modified frequency-domain sequence while maintaining phases of the modified frequency-domain sequence to produce a power-adjusted frequency-domain sequence, and

repeating, at least an additional time for the power-adjusted frequency-domain sequence, the steps of performing the time-domain transformation, setting the amplitudes, performing the frequency-domain transformation, and applying the power profile to produce the pilot sequence;

repeating the generating step a first number of iterations using different initial conditions for each iteration to generate a plurality of candidate synchronization/pilot sequences;

performing a plurality of correlations among the candidate synchronization/pilot sequences to generate a plurality of correlation values;

determining a plurality of permutations of the candidate synchronization/pilot sequences, wherein each permutation of the plurality of permutations includes a different set of candidate synchronization/pilot sequences, and wherein each permutation includes a number, D, of candidate synchronization/pilot sequences; and

identifying a selected permutation from the plurality of permutations, wherein the selected permutation corresponds to the set of synchronization/pilot sequences being generated.

3. The method of claim 1 , wherein performing the plurality of correlations comprises the steps of:

performing a plurality of cross-correlations among the candidate synchronization/pilot sequences to generate a plurality of maximum cross-correlation values;

performing a plurality of auto-correlations among the candidate synchronization/pilot sequences to generate a plurality of secondary maximum auto-correlation values; and

including the maximum cross-correlation values and the secondary maximum auto-correlation values in the plurality of correlation values.

4. A method for generating a set of synchronization/pilot sequences, the method comprising the steps of:

generating a candidate synchronization/pilot sequence using initial conditions;

repeating the generating step a first number of iterations using different initial conditions for each iteration to generate a plurality of candidate synchronization/pilot sequences;

performing a plurality of correlations among the candidate synchronization/pilot sequences to generate a plurality of correlation values, wherein performing the plurality of correlations comprises performing P 2 cross-correlations, and P auto-correlations, where P is a number of candidate synchronization/pilot sequences being correlated;

determining a plurality of permutations of the candidate synchronization/pilot sequences, wherein each permutation of the plurality of permutations includes a different set of candidate synchronization/pilot sequences, and wherein each permutation includes a number, D, of candidate synchronization/pilot sequences; and

identifying a selected permutation from the plurality of permutations, wherein the selected permutation corresponds to the set of synchronization/pilot sequences being generated.

5. The method of claim 1 , further comprising

eliminating, from the candidate synchronization/pilot sequences, any candidate synchronization/pilot sequences that do not meet a peak-to-average power ratio selection criteria.

6. The method of claim 5 , wherein the step of eliminating uses a peak-to-average power ratio threshold value as the peak-to-average power ratio selection criteria, and comprises eliminating, from the candidate synchronization/pilot sequences, any candidate synchronization/pilot sequence that exceeds the peak-to-average power ratio threshold.

7. The method of claim 6 , wherein the peak-to-average power ratio threshold is a threshold value in a range between 0 decibels and 2.0 decibels.

8. The method of claim 1 , wherein the step of identifying the selected permutation comprises selecting the selected permutation from the plurality of permutations that corresponds to a maximum cross correlation threshold or a maximum secondary peak of an auto-correlation.

9. The method of claim 1 , further comprising the steps of:

combining each synchronization/pilot sequence of the set of synchronization/pilot sequences with phase shifted input data to produce a plurality of combined signals;

determining peak-to-average power ratios for at least some of the combined signals;

identifying a selected combined signal based on the peak-to-average power ratios; and

transmitting the selected combined signal over a wireless communication channel.

10. The method of claim 9 , wherein identifying the selected combined signal comprises the step of:

identifying the selected combined signal as the combined signal of the plurality of combined signals that has a lowest peak-to-average power ratio of the peak-to-average power ratios.

11. The method of claim 9 , further comprising the steps of:

receiving a received combined signal from the wireless communication channel, wherein the received combined signal represents a channel-affected version of the selected combined signal;

determining estimated channel errors within the received combined signal based on the set of synchronization/pilot sequences; and

applying corrections to the received combined signal, based on the estimated channel errors, to produce output data.

12. A method for generating a wireless signal in which a synchronization/pilot sequence is embedded, the method comprising the steps of:

combining each synchronization/pilot sequence of a set of synchronization/pilot sequences with phase shifted input data to produce a plurality of combined signals, wherein the set of synchronization/pilot sequences includes synchronization/pilot sequences generated by generating a plurality of candidate synchronization/pilot sequences, wherein each candidate synchronization/pilot sequence of the plurality is generated using a different random phase, performing a plurality of correlations among the candidate synchronization/pilot sequences to generate a plurality of correlation values, determining a plurality of permutations of the candidate synchronization/pilot sequences, wherein each permutation of the plurality of permutations includes a different set of multiple candidate synchronization/pilot sequences, and wherein each permutation includes a number, D, of candidate synchronization/pilot sequences, and identifying a selected permutation from the plurality of permutations based on the correlations among the candidate synchronization/pilot sequences in the selected permutation, wherein the selected permutation corresponds to the set of synchronization/pilot sequences being generated;

determining peak-to-average power ratios for at least some of the combined signals;

identifying a selected combined signal based on the peak-to-average power ratios; and

transmitting the selected combined signal over a wireless communication channel.

13. The method of claim 12 , wherein identifying the selected combined signal comprises the step of:

identifying the selected combined signal as the combined signal of the plurality of combined signals that has a lowest peak-to-average power ratio of the peak-to-average power ratios.

14. The method of claim 12 , further comprising the steps of:

receiving a received combined signal from the wireless communication channel, wherein the received combined signal represents a channel-affected version of the selected combined signal;

determining estimated channel errors within the received combined signal based on the set of synchronization/pilot sequences; and

applying corrections to the received combined signal, based on the estimated channel errors, to produce output data.

15. A system comprising:

a transmitter adapted to generate and transmit a wireless signal in which a synchronization/pilot sequence is embedded by

combining each synchronization/pilot sequence of a set of synchronization/pilot sequences with phase shifted input data to produce a plurality of combined signals, wherein the set of synchronization/pilot sequences includes synchronization/pilot sequences generated by generating a plurality of candidate synchronization/pilot sequences, wherein each candidate synchronization/pilot sequence of the plurality is generated using a different random phase, performing a plurality of correlations among the candidate synchronization/pilot sequences to generate a plurality of correlation values, determining a plurality of permutations of the candidate synchronization/pilot sequences, wherein each permutation of the plurality of permutations includes a different set of multiple candidate synchronization/pilot sequences, and wherein each permutation includes a number, D, of candidate synchronization/pilot sequences, and identifying a selected permutation from the plurality of permutations based on the correlations among the candidate synchronization/pilot sequences in the selected permutation, wherein the selected permutation corresponds to the set of synchronization/pilot sequences being generated,

determining peak-to-average power ratios for at least some of the combined signals,

identifying a selected combined signal based on the peak-to-average power ratios, and

transmitting the selected combined signal over a wireless communication channel.

16. The system of claim 15 , wherein the transmitter is a wireless communication device selected from a group that includes a cellular telephone, a radio, an unmanned autonomous vehicle, a one-way pager, a two-way pager, a personal data assistant, a computer, a base station, a wireless transmitter, and a wireless transceiver.

17. The system of claim 15 , wherein the transmitter is further adapted to identify the selected combined signal by identifying the selected combined signal as the combined signal of the plurality of combined signals that has a lowest peak-to-average power ratio of the peak-to-average power ratios.

18. The system of claim 15 , further comprising:

a receiver adapted to receive a received combined signal from the wireless communication channel, wherein the received combined signal represents a channel-affected version of the selected combined signal, determine estimated channel errors within the received combined signal based on the set of synchronization/pilot sequences, and apply corrections to the received combined signal, based on the estimated channel errors, to produce output data.

19. The system of claim 18 , wherein the receiver is a wireless communication device selected from a group that includes a cellular telephone, a radio, an unmanned autonomous vehicle, a one-way pager, a two-way pager, a personal data assistant, a computer, a base station, a wireless transmitter, and a wireless transceiver.

20. The system of claim 15 , wherein the system is a multi-carrier communication system selected from a group that includes a multi-carrier based, ultra-wideband system, an orthogonal frequency division multiplexing multiple access system, a multi-carrier code division multiple access system, a digital video broadcasting system, a WiMax system, a long range broadband wireless system, a wireless local area network system, and an 802.11a system.