High-order PSK signaling (HOPS) techniques for low-power spread spectrum communications
A signal receiver for receiving a HOPS-based communications signal includes a seed calculator configured to produce a series of seed vectors generated from a corresponding series of sets of key values. A sequence generator provides a series of internally generated sequences using the series of seed vectors. A fallthrough correlator produces a series of correlation values by correlating samples of a received signal and samples of the internally generated sequences. The spreading sequences are used by a transmitter to generate a transmit signal subsequently received as the received signal. A peak detector is configured to generate a trigger signal upon determining that at least one of the correlation values exceeds a threshold value. At least one of a plurality of demodulator chains is selected in response to the trigger signal and used to demodulate the received signal in order to recover data values carried by the received signal.
1. A signal receiver, comprising:
a seed calculator configured to produce a series of seed vectors generated from a corresponding series of sets of key values;
a sequence generator for providing a series of internally generated sequences using the series of seed vectors;
a fallthrough correlator configured to produce a series of correlation values by correlating samples of a received signal and samples of the internally generated sequences, the internally generated sequences corresponding to spreading sequences created using ones of the seed vectors wherein the spreading sequences are used by a transmitter to generate a transmit signal subsequently received by the signal receiver as the received signal;
a peak detector configured to generate a trigger signal upon determining that at least one of the correlation values exceeds a threshold value; and
a plurality of demodulator chains wherein at least one of the plurality of demodulator chains is selected in response to the trigger signal and used to demodulate the received signal in order to recover data values carried by the received signal.
2. The signal receiver of claim 1 wherein the seed calculator is implemented as a residue calculator configured to calculate, in response to the series of sets of key values, a series of residue vectors corresponding to the series of seed vectors wherein each of the key values is defined with respect to a residue number system (RNS).
3. The signal receiver of claim 2 wherein each of the residue vectors includes an integer number of index values and wherein the RNS is based upon an integer number of prime values, and wherein the integer number is larger than 1.
4. The signal receiver of claim 3 wherein the residue calculator is further configured to generate each of the integer number of index values for one of the residue vectors by separately reducing, modulo by a corresponding one of the integer number of prime values, a sum of the key values within a corresponding one of the sets of key values.
5. The signal receiver of claim 2 wherein each of the sets of key values includes a time-based counter value respectively corresponding to one of a plurality of time epochs, the residue calculator being configured to generate one of the sets of key values during each of the plurality of time epochs.
6. The signal receiver of claim 2 wherein the fallthrough correlator is further configured to use a magnitude of a peak value to estimate a power level of the received signal.
7. The signal receiver of claim 6 wherein the sequence generator is configured to dynamically vary a length of the internally generated sequences based on the estimate of the power level of the received signal.
8. The signal receiver of claim 2 wherein the received signal includes a series of signal bursts and wherein the fallthrough correlator is further configured to use a series of correlation values to determine at least one of frequency offsets and precision timing of ones of the signal bursts.
9. The signal receiver of claim 1 wherein the fallthrough correlator includes a plurality of complex multipliers, each of the plurality of complex multipliers being implemented with a reduced precision relative to a precision of the samples of the received signal.
10. The signal receiver of claim 9 wherein each the plurality of complex multipliers is implemented including one or more sign-selected adder trees.
11. The signal receiver of claim 1 wherein the transmitter is configured to transmit the transmit signal as a series of burst-mode communications messages and wherein a center frequency of each successive one of the burst-mode communications messages is selected pseudorandomly.
12. A method of signal reception, the method comprising:
calculating a series of seed vectors using a corresponding series of sets of key values;
generating a series of internally generated sequences using the series of seed vectors;
correlating samples of a received signal and samples of the internally generated sequences in order to produce a series of correlation values, the internally generated sequences corresponding to spreading sequences created using ones of the seed vectors wherein the spreading sequences are used by a transmitter to generate a transmit signal subsequently received as the received signal;
generating a trigger signal upon determining that at least one of the correlation values exceeds a threshold value;
selecting one of a plurality of demodulator chains in response to the trigger signal; and
demodulating the received signal using the one of the plurality of demodulator chains in order to recover data values carried by the received signal.
13. The method of claim 12 wherein the calculating includes calculating a series of residue vectors generated from the corresponding series of sets of key values wherein each of the key values is defined with respect to a residue number system (RNS) and wherein the series of residue vectors corresponds to the series of seed vectors.
14. The method of claim 13 wherein each of the residue vectors includes an integer number of index values and wherein the RNS is based upon an integer number of prime values, wherein the integer number is larger than 1.
15. The method of claim 14 further including generating each of the integer number of index values for one of the residue vectors by separately reducing, modulo by a corresponding one of the integer number of prime values, a sum of the key values within the corresponding one of the sets of key values.
16. The method of claim 13 wherein each of the sets of key values includes a time-based counter value respectively corresponding to one of a plurality of time epochs, the method further including generating ones of the sets of key values during each of the plurality of time epochs.
17. The method of claim 12 wherein the transmitter is configured to transmit the transmit signal as a series of burst-mode communications messages and wherein a center frequency of each successive one of the burst-mode communications messages is selected pseudorandomly.