Orthogonal chirp modulation in multipath environments

• US 7,110,432 B2
• Filed: 01/14/2002
• Issued: 09/19/2006
• Est. Priority Date: 01/14/2002
• Status: Active Grant

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: Hooton, Thomas R.
• Primary Examiner(s): Burd, Kevin
• Assistant Examiner(s): Aghdam, Freshteh N
• Application Number:
  US10/047,325
• Publication Number:
  US 20030133496A1
• Time in Patent Office: 1,709 Days
• Field of Search: 375/139, 375/150, 375/152, 375/302, 375/322, 385/37, 385/39
• US Class Current: 375/139
• CPC Class Codes: H04B 1/69 Spread spectrum techniques
• CPC Class Codes: H04B 2001/6912 using chirp

Abstract

Methods and systems for communication systems are disclosed. Chirp signals generated according to a chirp rate and carrier frequency are used for communication. The chirp rate can be determined by solving integrals or by simulation of transmission parameters. A chirp signal is transmitted from a base station and delayed versions of the chirp signals are created. The delayed versions are generated by the chirp signal reflecting off of reflectors. A receiving station receives an incoming signal. The incoming signal includes the LOS signal plus delayed versions, noise and/or interference. Unwanted signals, either LOS or delayed versions, noise and/or interference are removed from the incoming signal to obtain the desired chirp signal. Using the chirp rate, the chirp signal is converted to a corresponding digital signal.

Claims

1. A communication system comprising:

a base station operative to generate a chirp signal according to a chirp rate selected to reduce bandwidth usage and to reduce transmission errors, the base station being operative to transmit the chirp signal, the chirp signal being substantially orthogonal to delayed versions of the transmitted chirp signal; and

a receiving station operative to receive an incoming signal, the incoming signal including the chirp signal.

2. The system of claim 1, the chirp signal being a relatively narrowband signal.

3. The system of claim 2, the incoming signal further comprising noise, multipath, and other signals and the receiving station removing the noise, multipath, and other signals from the incoming signal to obtain the chirp signal.

4. The system of claim 3, the base station further comprising a transmitter chirp generator to convert base station data to a digital chirp signal and a digital to analog converter to the digital chirp signal to the chirp signal.

5. The system of claim 4, the receiving station further comprising:

an analog to digital converter to convert the incoming signal into a received digital signal; and

a receiver matched filter matched according to the transmitter chirp generator, to remove unwanted signals from the received digital signal utilizing the chirp rate and to demodulate the chirp signal to obtain the base station data.

6. The system of claim 1, the chirp rate being dynamically modifiable.

7. The system of claim 1, the chirp rate being dynamically modifiable according to transmission errors and bandwidth usage.

8. A communication system comprising:

means for creating a chirp signal such that delayed versions of the chirp signal are substantially orthogonal to the chirp signal;

means for transmitting the chirp signal;

means for receiving an incoming signal comprising the chirp signal; and

means for removing unwanted signals from the incoming signal to obtain the chirp signal.

9. A receiver matched filter system comprising:

a matched filter operative to receive an input signal and to demodulate the input signal according to a stored signal template to obtain a digital data signal, the input signal including a chirp signal, the chirp signal being relatively narrowband and substantially orthogonal to delayed versions of the chirp signal in the input signal; and

a signal template generator operative to determine the signal template and to provide the signal template to the matched filter, the signal template including signal template parameters associated with the chirp signal.

10. The system of claim 9, the signal template parameters comprising a chirp rate, a modulation type, a carrier frequency and a baud time, the system further comprising:

a controller operative to detect transmission errors in the digital data signal and to modify the chirp rate, the modulation type, the baud time, and the carrier frequency based on the transmission errors.

11. The system of claim 10, the controller being further operative to track bandwidth usage and to modify at least one of the chirp rate, the modulation type, the baud time, and the carrier frequency based on the bandwidth usage.

12. The system of claim 11, the controller being further operative to generate feedback data based on the transmission errors and the bandwidth usage and to provide the feedback data to a base station.

13. A transceiver device comprising:

a transmitter chirp filter comprising;

a chirp rate determiner operative to determine a first chirp rate; and

a signal converter operative to convert an input signal to a first chirp signal according to the first chirp rate and a first carrier frequency; and

a receiver chirp filter comprising;

a receive filter operative to receive an input signal and to demodulate the input signal according to a second carrier frequency and a second chirp rate to obtain an analog signal, the input signal including a second chirp signal, the second chirp signal being relatively narrowband and substantially orthogonal to delayed versions of the second chirp signal; and

a chirp rate component operative to determine the second chirp rate and provide the second chirp rate to the receive filter.

14. The transceiver device of claim 13, the first chirp rate and the first chirp signal being substantially equal to the second chirp rate and the second chirp signal.

15. The transceiver device of claim 13, the first chirp rate and the second chirp rate selected to reduce transmission errors and bandwidth usage.

16. A method of operating a communications system comprising:

determining at least one of a chirp rate, baud time, carrier frequency, and modulation;

generating a digital chirp signal according to the at least one of chirp rate, baud time, carrier frequency, and modulation; and

transmitting the digital chirp signal, the transmitted chirp signal being substantially orthogonal to delayed versions of the transmitted chirp signal.

17. A method of operating a communications system comprising:

determining at least one of a chirp rate, baud time, carrier frequency, and modulation;

generating a digital chirp signal according to the at least one of chirp rate, baud time, carrier frequency, and modulation; and

transmitting the digital chirp signal, the transmitted chirp signal being substantially orthogonal to delayed versions of the transmitted chirp signal,

wherein determining the chirp rate comprises;

selecting transmission parameters based on a desired implementation, the transmission parameters including the carrier frequency, sampling rate, available bandwidth, minimum path delay, and baud rate;

selecting an estimated chirp rate based on the transmission parameters;

simulating transmission of a simulated chirp signal based on the transmission parameters to obtain a simulation result;

on the simulation result being acceptable, providing the estimated chirp rate as the chirp rate; and

on the simulation result being unacceptable, modifying the estimated chirp rate.

18. The method of claim 17, further comprising converting the digital chirp signal to an analog chirp signal and transmitting the analog chirp signal.

19. The method of claim 18, further comprising:

receiving an incoming signal, the incoming signal including the digital chirp signal;

removing noise from the incoming signal;

downconverting the incoming signal; and

performing an analog to digital conversion on the incoming signal.

20. The method of claim 19, further comprising:

removing multipath signals, noise, and unwanted signals from the incoming signal; and

demodulating the incoming signal to obtain digital data.

21. A method of simulating a chirp signal comprising:

determining transmission parameters for a desired implementation, the transmission parameters including an estimated chirp rate and a differential path delay;

generating a desired signal from the transmission parameters such that delayed versions of the desired signal are substantially orthogonal to the desired signal;

generating at least one delayed signal from the desired signal, where the at least delayed signal is a delayed version of the desired signal; and

generating a nearly worst case delayed signal from the desired signal, where the nearly worst case delayed signal is a nearly worst case delayed version of the desired signal;

simulating transmission and reception of the desired signal, the at least one delayed signal and the nearly worst case delayed signal; and

determining acceptability of the estimated chirp rate.

22. The method of claim 21, further comprising:

on the estimated chirp rate being not acceptable, modifying the transmission parameters and re-performing the transmission simulation.

23. The method of claim 21, the transmission parameters further including carrier frequency and baud time.

24. The method of claim 21, the acceptability determined by computing a matched filter output.

25. The method of claim 21, the nearly worst case signal being generated about 180 degrees out of phase from the desired signal.