Channel Sounding Techniques

• US 20170207931A1
• Filed: 01/18/2017
• Published: 07/20/2017
• Est. Priority Date: 01/19/2016
• Status: Active Grant

• Current Assignee: National Instruments Corporation (Emerson Electric Company)
• Original Assignee: National Instruments Corporation (Emerson Electric Company)
• Inventors: Gul, Malik Muhammad Usman, Aziz, Ahsan, McCoy, James Wesley
• Granted Patent: US 10,708,086 B2
• Time in Patent Office: Days
• CPC Class Codes: H04J 13/0059 CAZAC [constant-amplitude and zero auto-correlation]
• CPC Class Codes: H04L 25/022 of frequency response
• CPC Class Codes: H04L 25/0224 using sounding signals
• CPC Class Codes: H04L 25/03159 operating in the frequency domain H04L25/03165, H04L25/03178 take precedence
• CPC Class Codes: H04W 56/001 Synchronization between nodes

Abstract

Techniques are disclosed relating to channel sounding. In some embodiments a transmitter transmits a periodic CAZAC sequence beginning at a point in time that corresponds to a timing signal (e.g., a pulse-per-second signal). In some embodiments, a receiver waits to begin processing received sequences for a time interval corresponding to the length of the CAZAC sequence, where the time interval begins at the same time as the timing signal. This may avoid a need for timing synchronization prior to processing, reduce processing and latency in receiver implementations, and may allow determination of a TOA as well as a channel impulse response estimate by correlating a received cyclically-shifted CAZAC sequence with a local version of the transmitted CAZAC sequence.

Claims

1. A method, comprising:

a channel sounding transmitter transmitting a repeated Constant Amplitude Zero Autocorrelation (CAZAC) sequence over a wireless channel in response to a first timing signal;

a channel sounding receiver receiving a circularly-shifted CAZAC sequence over the wireless channel in response to the transmission, wherein the circularly-shifted CAZAC sequence is processed beginning at a point in time corresponding to the length of the CAZAC sequence after a second timing signal that is synchronized with the first timing signal; and

processing the received circularly-shifted CAZAC sequence to generate a time of arrival (TOA) and a channel impulse response (CIR) estimate for the wireless channel.

2. The method of claim 1, wherein the processing includes correlating the circularly-shifted CAZAC sequence with a local version of the transmitted CAZAC sequence.

3. The method of claim 1, wherein the processing is performed without performing synchronization based on the received CAZAC sequence.

4. The method of claim 1, wherein the processing is performed without auto-correlating the received CAZAC sequence with itself.

5. The method of claim 1, wherein the processing includes averaging multiple circularly-shifted CAZAC sequences prior to performing a fast Fourier transform (FFT) and correlating the average of the circularly-shifted CAZAC sequences with a local version of the CAZAC sequence.

6. The method of claim 5, wherein the averaging is performed by a programmable hardware element and the correlating is performed by a processor.

7. The method of claim 1, wherein the channel sounding transmitter and channel sounding receiver are coupled to the same clock and the first timing signal and the second timing signal are the same signal.

8. The method of claim 1, further comprising:

synchronizing clocks on the transmitter and receiver;

wherein the first timing signal and the second timing signal occur at substantially the same time based on the synchronization.

9. The method of claim 1, wherein the first and second timing signals are pulse-per-second (PPS) signals.

10. A system, comprising:

one or more processing elements configured to;

receive a circularly-shifted Constant Amplitude Zero Autocorrelation (CAZAC) sequence from a wireless channel beginning at a point in time corresponding to the length of the CAZAC sequence after a timing signal, wherein the timing signal that is synchronized with a transmitter of the CAZAC sequence and used by the transmitter to initiate transmission of the sequence, and wherein the CAZAC sequence is transmitted in a repeated manner by the transmitter; and

process the received circularly-shifted CAZAC sequence to generate a time of arrival (TOA) and a channel impulse response (CIR) of the wireless channel.

11. The system of claim 10, further comprising:

the transmitter, wherein the transmitter is configured to transmit the CAZAC sequence based on the timing signal.

12. The system of claim 11, wherein the transmitter and a receiver that includes the one or more processing elements are physically coupled during the transmission and reception.

13. The system of claim 10, wherein the one or more processing elements are configured to process the received circularly-shifted CAZAC sequence without performing synchronization based on the received CAZAC sequence.

14. The system of claim 10, wherein the one or more processing elements are configured to process the received circularly-shifted CAZAC sequence without auto-correlating the received CAZAC sequence with itself

15. The system of claim 10, wherein the one or more processing elements are further configured to:

generate an average of multiple circularly-shifted CAZAC sequences; and

correlate the average with a local version of the CAZAC sequence.

16. The system of claim 15, wherein the one or more processing elements are further configured to:

perform a frequency transform on the average prior to the correlation.

17. The system of claim 15, wherein the one or more processing elements include a programmable hardware element configured to generate the average and a processor configured to process the average.

18. The system of claim 10, wherein the timing signal is a pulse-per-second (PPS) signal and wherein the TOA and the CIR of the wireless channel are useable in creating a model of the wireless channel.

19. The system of claim 10, wherein the timing signal is synchronized between the transmitter and receiver prior to transmission of the CAZAC sequence and wherein the receiver and transmitter are not physically coupled during the transmission of the CAZAC sequence.

20. A non-transitory computer readable storage medium having stored thereon design information that specifies a design of at least a portion of a hardware circuit in a format recognized by a computing system configured to use the design information to implement the circuit according to the design, including:

one or more processing elements configured to;

receive a circularly-shifted Constant Amplitude Zero Autocorrelation (CAZAC) sequence from a wireless channel beginning at a point in time corresponding to the length of the CAZAC sequence after a timing signal, wherein the timing signal that is synchronized with a transmitter of the CAZAC sequence and used by the transmitter to initiate transmission of the sequence, and wherein the CAZAC sequence is transmitted in a repeated manner by the transmitter; and

process the received circularly-shifted CAZAC sequence to generate a time of arrival (TOA) and a channel impulse response (CIR) of the wireless channel.