SIGNAL MODULATION METHOD RESISTANT TO ECHO REFLECTIONS AND FREQUENCY OFFSETS

• US 20120201322A1
• Filed: 03/27/2012
• Published: 08/09/2012
• Est. Priority Date: 05/28/2010
• Status: Active Grant

• Current Assignee: Cohere Technologies Inc
• Original Assignee: Cohere Technologies Inc
• Inventors: Rakib, Shlomo Selim, Hadani, Ronny
• Granted Patent: US 9,083,595 B2
• Time in Patent Office: Days
• US Class Current: 375/285
• CPC Class Codes: H04L 25/03343 Arrangements at the transmitter end
• CPC Class Codes: H04L 27/26132 using repetition
• CPC Class Codes: H04L 27/2634 Inverse fast Fourier transform [IFFT] or inverse discrete Fourier transform [IDFT] modulators in combination with other circuits for modulation
• CPC Class Codes: H04L 27/2639 Modulators using other transforms, e.g. discrete cosine transforms, Orthogonal Time Frequency and Space [OTFS] or hermetic transforms
• CPC Class Codes: H04L 27/265 Fourier transform demodulators, e.g. fast Fourier transform [FFT] or discrete Fourier transform [DFT] demodulators H04L27/26524 takes precedence
• CPC Class Codes: H04L 27/2655 Synchronisation arrangements
• CPC Class Codes: H04L 27/2697 in combination with other modulation techniques
• CPC Class Codes: H04L 5/0016 Time-frequency-code
• CPC Class Codes: H04W 28/04 Error control
• CPC Class Codes: H04W 28/065 using assembly or disassembly of packets
• CPC Class Codes: H04W 72/00 Local resource management

Abstract

A method of modulating communications signals, such as optical fiber, wired electronic, or wireless signals in a manner that facilitates automatic correction for the signal distortion effects of echoes and frequency shifts, while still allowing high rates of data transmission. Data symbols intended for transmission are distributed into N×N matrices, and used to weigh or modulate a family of cyclically time shifted and cyclically frequency shifted waveforms. Although these waveforms may then be distorted during transmission, their basic cyclic time and frequency repeating structure facilitates use of improved receivers with deconvolution devices that can utilize the repeating patterns to correct for these distortions. The various waveforms may be sent in N time blocks at various time spacing and frequency spacing combinations in a manner that can allow interleaving of blocks from different transmitters. Applications to channel sounding/characterization, system optimization, and also radar are also discussed.

Claims

1. A method of transferring a plurality of data symbols using a signal modulated to allow automatic compensation for the signal impairment effects of echo reflections and frequency offsets, said method comprising:

distributing said plurality of data symbols into one or more N×

N symbol matrices;

using said one or more N×

N symbol matrices to control the signal modulation of a transmitter, wherein for each said N×

N symbol matrix, said transmitter uses each data symbol to weight N waveforms, selected from a N² sized set of all permutations of N cyclically time shifted and N cyclically frequency shifted waveforms determined according to an encoding matrix U, thus producing N symbol-weighted cyclically time shifted and cyclically frequency shifted waveforms for each data symbol;

wherein said encoding matrix U is chosen to be an N×

N unitary matrix that has a corresponding inverse decoding matrix U^H;

for each data symbol in said N×

N symbol matrix, summing the N symbol-weighted cyclically time shifted and cyclically frequency shifted waveforms, producing N² summation-symbol-weighted cyclically time shifted and cyclically frequency shifted waveforms;

and transmitting said N² summation-symbol-weighted cyclically time shifted and cyclically frequency shifted waveforms, structured as N composite waveforms, over any combination of N time blocks or frequency blocks.

2. The method of claim 1, wherein N is greater than 1.

3. The method of claim 1, wherein said signal is a wireless signal, or wherein said signal is an optical or electrical signal carried over an optical or electrical current conducting wire, fiber, or cable;

and

wherein said frequency offsets are caused by either Doppler shifts or other non-Doppler effects.

4. The method of claim 1, wherein said N² summation-symbol-weighted cyclically time shifted and cyclically frequency shifted waveforms are subsequently received by a receiver which is controlled by said corresponding decoding matrix U^H;

and

using said decoding matrix U^H to enable said receiver to reconstruct the transmitted symbols in said one or more N×

N symbol matrices.

5. The method of claim 4, wherein due to either one or the combination of echo reflections and frequency offsets, multiple signals due to echo reflections and frequency offsets result in said receiver receiving a time and frequency convoluted signal representing time and frequency shifted versions of said N² summation-symbol-weighed cyclically time shifted and frequency shifted waveforms;

further time and frequency deconvoluting said time and frequency convoluted signal at said receiver to correct for said echo reflections and frequency offsets;

thus producing time and frequency deconvoluted results, and time and frequency deconvolution parameters.

6. The method of claim 5, wherein said plurality of data symbols are selected to be known test symbols, said receiver has a record of said known test symbols, further using said time and frequency deconvolution parameters obtained during the time and frequency deconvolution of said time and frequency convoluted signal to determine the characteristics of the echo reflections frequency offsets, and other signal impairments of the said transmitter and said receiver'"'"'s system and environment.

7. The method of claim 6, in which said characteristics of the echo reflections, frequency offsets, and other signal impairments of said transmitter and said receiver'"'"'s system and environment are used to select an encoding matrix U and a decoding matrix U^H with properties selected for superior performance in said system and environment.

8. The method of claim 1, wherein said N² summation-symbol-weighted cyclically time shifted and cyclically frequency shifted waveforms, structured as N composite waveforms, are transmitted over at least N time blocks.

9. The method of claim 8, wherein for each said N×

N symbol matrices, all N time blocks are either transmitted consecutively in time;

or wherein for each said N×

N symbol matrices, the N time blocks from a first said N×

N symbol matrix are transmitted time-interleaved with the N time blocks from a second and different N×

N symbol matrix.

10. The method of claim 9, in which a first set of N time blocks from a first said N×

N symbol matrix originate from a first transmitter using a first unitary matrix U₁, and a second set of N time blocks originate from a second said N×

N symbol matrix from a second transmitter using a second unitary matrix U₂;

In which U₁ and U₂ may be identical or different; and

in which U_i and U₂ may be selected based on the characteristics of the echo reflections, frequency offsets, and other signal impairments of the system and environment of said first transmitter, said second transmitter and said receiver.

11. A method of transferring a plurality of data symbols using a wireless signal modulated to allow automatic compensation for the wireless signal impairment effects of echo reflections and frequency offsets, said method comprising:

Distributing said plurality of data symbols into one or more N×

N symbol matrices;

Using said one or more N×

N symbol matrices to control the wireless signal modulation of a wireless transmitter, wherein for each said N×

N symbol matrix, said wireless transmitter uses each data symbol to weight N waveforms, selected from a N² sized set of all permutations of N cyclically time shifted and N cyclically frequency shifted waveforms determined according to an encoding matrix U, thus producing N symbol-weighted cyclically time shifted and cyclically frequency shifted waveforms for each data symbol;

Wherein said encoding matrix U is chosen to be an N×

N unitary matrix that has a corresponding inverse decoding matrix U^H;

For each data symbol in said N×

N symbol matrix, summing the N symbol-weighted cyclically time shifted and cyclically frequency shifted waveforms, producing N² summation-symbol-weighted cyclically time shifted and cyclically frequency shifted waveforms;

And transmitting said N² summation-symbol-weighted cyclically time shifted and cyclically frequency shifted waveforms, structured as N composite waveforms, over any combination of N time blocks or frequency blocks.

12. The method of claim 11, wherein said N² summation-symbol-weighted cyclically time shifted and cyclically frequency shifted waveforms are subsequently received by a wireless receiver which is controlled by said corresponding decoding matrix U^H;

and

Using said decoding matrix U^H to enable said wireless receiver to reconstruct the transmitted symbols in said one or more N×

N symbol matrices.

13. The method of claim 12, wherein due to either one or the combination of echo reflections and frequency offsets, multiple signals due to echo reflections and frequency offsets result in said receiver receiving a time and frequency convoluted signal representing time and frequency shifted versions of said N² summation-symbol-weighed cyclically time shifted and frequency shifted waveforms;

further time and frequency deconvoluting said time and frequency convoluted signal at said receiver to correct for said echo reflections and frequency offsets;

thus producing time and frequency deconvoluted results, and time and frequency deconvolution parameters.

14. The method of claim 13, wherein said plurality of data symbols are selected to be known test symbols, said receiver has a record of said known test symbols, further using said time and frequency deconvolution parameters obtained during the time and frequency deconvolution of said time and frequency convoluted signal to determine the characteristics of the echo reflections, frequency offsets, and other signal impairments of said transmitter and said receiver'"'"'s system and environment.

15. The method of claim 14, in which said characteristics of the echo reflections, frequency offsets, and other signal impairments of said transmitter and said receiver'"'"'s system and environment are used to select an encoding matrix U and a decoding matrix U^H with properties selected for superior performance in said system and environment.

16. The method of claim 14, wherein at least some of said frequency offsets are caused by velocity induced Doppler effects, used in a radar system to determine the location and velocity of at least one object in said environment of said transmitter and receiver.

17. The method of claim 11, wherein said N² summation-symbol-weighted cyclically time shifted and cyclically frequency shifted waveforms, structured as N composite waveforms, are transmitted over at least N time blocks.

18. The method of claim 17, wherein for each said N×

N symbol matrices, all N time blocks are either transmitted consecutively in time;

or wherein for each said N×

N symbol matrices, the N time blocks from a first said N×

N symbol matrix are transmitted time-interleaved with the N time blocks from a second and different N×

N symbol matrix.

19. The method of claim 18, in which a first set of N time blocks from a first said N×

N symbol matrix originate from a first wireless transmitter using a first unitary matrix U₁, and a second set of N time blocks originate from a second said N×

N symbol matrix from a second wireless transmitter using a second unitary matrix U₂;

In which U₁ and U₂ may be identical or different; and

in which U₁ and U₂ may be selected based on the characteristics of the echo reflections, frequency offsets, and other signal impairments of the system and environment of said first transmitter, said second transmitter and said wireless receiver.

20. The method of claim 11, wherein N is greater than 1.