OTFS methods of data channel characterization and uses thereof

• US 10,334,457 B2
• Filed: 01/04/2018
• Issued: 06/25/2019
• Est. Priority Date: 05/28/2010
• Status: Active Grant

• Current Assignee: Cohere Technologies Inc
• Original Assignee: Cohere Technologies Inc
• Inventors: Hadani, Ronny, Rakib, Shlomo Selim
• Primary Examiner(s): Elliott, IV, Benjamin H
• Application Number:
  US15/862,499
• Publication Number:
  US 20180242170A1
• Time in Patent Office: 537 Days
• CPC Class Codes: H04B 1/692 Hybrid techniques using combinations of two or more spread spectrum techniques
• CPC Class Codes: H04B 7/0626 Channel coefficients, e.g. channel state information [CSI]
• CPC Class Codes: H04B 7/10 Polarisation diversity; Directional diversity
• CPC Class Codes: H04L 25/0212 of impulse response
• CPC Class Codes: H04L 25/0226 sounding signals per se
• CPC Class Codes: H04L 27/366 Arrangements for compensating undesirable properties of the transmission path between the modulator and the demodulator
• CPC Class Codes: H04L 5/0007 the frequencies being orthogonal, e.g. OFDM(A), DMT
• CPC Class Codes: H04L 5/0048 Allocation of pilot signals, i.e. of signals known to the receiver
• CPC Class Codes: H04W 24/02 Arrangements for optimising operational condition

Abstract

Fiber, cable, and wireless data channels are typically impaired by reflectors and other imperfections, producing a channel state with echoes and frequency shifts in data waveforms. Here, methods of using OTFS pilot symbol waveform bursts to automatically produce a detailed 2D model of the channel state are presented. This 2D channel state can then be used to optimize data transmission. For wireless data channels, an even more detailed 2D model of channel state can be produced by using polarization and multiple antennas in the process. Once 2D channel states are known, the system turns imperfect data channels from a liability to an advantage by using channel imperfections to boost data transmission rates. The methods can be used to improve legacy data transmission modes in multiple types of media, and are particularly useful for producing new types of robust and high capacity wireless communications using non-legacy OTFS data transmission methods.

Claims

1. A method for determining a two-dimensional (2D) channel state of an impaired data channel connecting at least one transmitter and at least one receiver, the impaired data channel comprising at least one reflector, the at least one reflector comprising a reflector location, a reflector frequency shift and at least one coefficient of reflection, the method comprising:

receiving channel-convoluted OTFS pilot bursts using a 2D pilot OTFS time-frequency bin structure with bin sizes and bin-coordinate positions proportional to an OTFS time-frequency grid; and

determining the 2D channel state of the impaired data channel based on the channel-convoluted OTFS pilot bursts,

wherein the channel-convoluted OTFS pilot bursts comprise a combination of direct OTFS pilot bursts and replica OTFS pilot bursts,

wherein the direct OTFS pilot bursts comprise a plurality of OTFS pilot symbols P_pt,pf, wherein the plurality of OTFS pilot symbols are transmitted as OTFS pilot symbol waveform bursts P_pt,pf·

W_p(pt, pf) over a plurality of combinations of times pt and frequencies pf, where each of the times pt and the frequencies pf are unique pilot time-frequency coordinates chosen from the OTFS time-frequency grid,

wherein the OTFS pilot symbol waveform bursts P_pt,pf·

W_p(pt, pf) are mutually orthogonal waveform bursts derived from cyclically time and frequency shifted versions of a common OTFS pilot basis waveform W_p,

wherein the direct OTFS pilot bursts travel directly from the at least one transmitter to the at least one receiver, and

wherein the replica OTFS pilot bursts comprise direct OTFS pilot bursts that have reflected off the at least one reflector before reaching the at least one receiver, thereby producing direct OTFS waveform bursts that are further reflector time-delayed and reflector frequency-shifted at the at least one receiver.

2. The method of claim 1, wherein the at least one receiver comprises a receiver location and a receiver frequency shift, and wherein the channel-convoluted OTFS pilot bursts further comprises a transmitter frequency shifted direct OTFS pilot burst and a receiver frequency shifted direct OTFS pilot burst.

3. The method of claim 1, wherein the 2D channel state is at least partially determined by using at least one 2D impulse response to mathematically describe how the impaired data channel causes at least some of the OTFS pilot symbol waveform bursts P_t1,f1W_p(t1, f1) transmitted at a first time-frequency coordinate to be projected onto different OTFS pilot symbol waveform bursts P_t2,f2W_p(t2, f2) originally transmitted at a different time-frequency coordinate, and bins different from those nominally corresponding to said OTFS pilot symbol waveform bursts P_t1,f1W_p(t1, f1).

4. The method of claim 3, further comprising:

using the at least one 2D impulse responses to at least partially describe the 2D channel state as at least one 2D transform comprising at least one of a 2D Z-transform or other 2D transform.

5. The method of claim 1, wherein the 2D channel state comprises a matrix or other mathematical transform describing how signals transmitted by the at least one transmitter are coupled with signals from the at least one transmitter that are received by the at least one receiver.

6. The method of claim 1, wherein the plurality of OTFS pilot symbols P_pt,pf is known by the at least one receiver, wherein the plurality of OTFS pilot symbols is further chosen to be any of:

one- or two-dimensional m-sequences comprising binary maximal-length shift register sequences, delta values P_i,j surrounded by regions of P_pt,pf zero values, one- or two-dimensional Barker codes, Costas arrays, Walsh matrixes, or other plurality of pilot symbols selected to facilitate acquiring said 2D channel state, and wherein the 2D pilot OTFS time-frequency bin structure comprises time-frequency resolutions that are equal to or more precise than time-frequency resolutions of the OTFS time-frequency grid.

7. The method of claim 1, wherein the impaired data channel is an optical fiber data channel comprising at least one optical fiber, an electrically conducting wire data channel comprising at least one metallic electrical conductor, or a data channel comprising a fluid.

8. The method of claim 1, wherein the plurality of OTFS pilot symbols P_pt,pf, the OTFS time-frequency grid and the 2D pilot OTFS time-frequency bin structure are chosen so that if the impaired data channel causes at least some of the OTFS pilot symbol waveform bursts P_t1,f1W_p(t1, f1) originally transmitted at a first time-frequency coordinate to be projected onto different OTFS pilot symbol waveform bursts P_t2,f2W_p(t2, f2) originally transmitted at a different time-frequency coordinate, and bins different from those nominally corresponding to said OTFS pilot symbol waveform bursts P_t1,f1W_p(t1, f1), at least some of the projections are detected and quantified by the at least one receiver.

9. The method of claim 8, wherein the plurality of OTFS pilot symbols P_pt,pf transmitted as OTFS pilot symbol waveform bursts P_pt,pfW_p(pt, pf) comprise at least one non-null OTFS pilot symbol P_pt,pf transmitted as an OTFS pilot symbol waveform burst P_pt,pfW_p(pt, pf) with sufficient power to be detectable by the at least one receiver;

and any of;

1;

at least some of the plurality of OTFS pilot symbols are null pilot symbols intended to create empty pt and pf unique pilot time-frequency coordinates chosen from the OTFS time-frequency grid, where no waveform burst is transmitted;

or

2;

at least some of the plurality of OTFS pilot symbols are background pilot symbols that create a uniform background of pt and pf unique pilot time-frequency coordinates chosen from the OTFS time-frequency grid, such that projections of channel-convoluted non-null OTFS pilot bursts onto the uniform background are detected and quantified by the at least one receiver.

10. An apparatus for determining a two-dimensional (2D) channel state of an impaired data channel connecting at least one transmitter and at least one receiver, the impaired data channel comprising at least one reflector, the at least one reflector comprising a reflector location, a reflector frequency shift and at least one coefficient of reflection, the apparatus comprising:

a processor; and

a memory comprising processor executable code, the processor executable code when executed by the processor causes the processor to implement;

receiving channel-convoluted OTFS pilot bursts using a 2D pilot OTFS time-frequency bin structure with bin sizes and bin-coordinate positions proportional to an OTFS time-frequency grid; and

determining the 2D channel state of the impaired data channel based on the channel-convoluted OTFS pilot bursts,

wherein the channel-convoluted OTFS pilot bursts comprise a combination of direct OTFS pilot bursts and replica OTFS pilot bursts,

wherein the direct OTFS pilot bursts comprise a plurality of OTFS pilot symbols P_pt,pf,

wherein the plurality of OTFS pilot symbols are transmitted as OTFS pilot symbol waveform bursts P_pt,pf·

W_p(pt, pf) over a plurality of combinations of times pt and frequencies pf, where each of the times pt and the frequencies pf are unique pilot time-frequency coordinates chosen from the OTFS time-frequency grid,

wherein the OTFS pilot symbol waveform bursts P_pt,pf·

W_p(pt, pf) are mutually orthogonal waveform bursts derived from cyclically time and frequency shifted versions of a common OTFS pilot basis waveform W_p,

wherein the direct OTFS pilot bursts travel directly from the at least one transmitter to the at least one receiver, and

wherein the replica OTFS pilot bursts comprise direct OTFS pilot bursts that have reflected off the at least one reflector before reaching the at least one receiver, thereby producing direct OTFS waveform bursts that are further reflector time-delayed and reflector frequency-shifted at the at least one receiver.

11. The apparatus of claim 10, wherein the code further causes the processor to further implement:

receiving a plurality of channel-convoluted data bursts through the impaired data channel, wherein the plurality of channel-convoluted data bursts corresponds to a plurality of data symbols transmitted by the at least one transmitter; and

deconvoluting at least some of the plurality of channel-convoluted data bursts to derive an approximation of the plurality of data symbols,

wherein the plurality of channel-convoluted data bursts comprise a combination of direct data bursts and replica data bursts, and

wherein the replica data bursts comprise direct data bursts that have reflected off the at least one reflector before reaching the at least one receiver, thereby producing direct data bursts that are further reflector time-delayed and reflector frequency-shifted at the at least one receiver.

12. The apparatus of claim 11, wherein the plurality of data symbols is transmitted by any of TDMA, GSM, FDMA, OFDM, CDMA, OTFS wireless waveform bursts, or other types of wireless waveform bursts.

13. The apparatus of claim 12, wherein the deconvoluting is performed by using at least one 1D projection of the 2D channel state along any of a time axis, frequency axis, or time-frequency axis.

14. The apparatus of claim 10, wherein the impaired data channel is an optical fiber data channel comprising at least one optical fiber, an electrically conducting wire data channel comprising at least one metallic electrical conductor, or a data channel comprising a fluid.

15. The apparatus of claim 10, wherein the at least one receiver comprises a receiver location and a receiver frequency shift, and wherein the channel-convoluted OTFS pilot bursts further comprises a transmitter frequency shifted direct OTFS pilot burst and a receiver frequency shifted direct OTFS pilot burst.

16. The apparatus of claim 15, wherein the impaired data channel is a wireless data channel, wherein the at least one receiver is a wireless receiver, wherein the at least one reflector is a wireless reflector further comprising a reflector velocity, wherein the reflector frequency shift is at least partially determined by a reflector Doppler shift that varies according to the reflector velocity, and wherein the at least one coefficient of reflection is a reflector coefficient of wireless reflection,

wherein the at least one receiver further comprises a receiver velocity, and wherein the receiver frequency shift is at least partially determined by a receiver Doppler shift that varies according to the receiver velocity,

wherein the direct OTFS pilot bursts comprise a plurality of wireless OTFS pilot symbol waveform bursts, and

wherein, the 2D channel state comprises information pertaining to relative locations, velocities, velocity induced frequency shifts caused by the transmitter Doppler shift, the receiver Doppler shift, the reflector Doppler shift, and the at least one coefficient of reflection of the at least one transmitter, receiver, and reflector.

17. The apparatus of claim 16, wherein the direct OTFS pilot bursts are received at the at least one receiver as polarized direct OTFS pilot bursts comprising polarized wireless OTFS pilot symbol waveform bursts according to at least one polarization direction,

where the wireless reflector is a polarization altering wireless reflector that alters a polarization direction of its reflected wireless OTFS waveform bursts according to a first reflector polarization operator, thereby producing replica polarized OTFS pilot bursts that comprise polarization shifted time-delayed and reflector Doppler-shifted replicas of the polarized direct OTFS pilot bursts, and

wherein the code further causes the processor to further implement:

detecting a direction of polarization of the channel-convoluted polarized OTFS pilot bursts; and

using the direction of polarization of the channel-convoluted polarized OTFS pilot bursts to further determine the 2D channel state of the impaired data channel.

18. The apparatus of claim 10, wherein the 2D channel state is at least partially determined by using at least one 2D impulse response to mathematically describe how the impaired data channel causes at least some of the OTFS pilot symbol waveform bursts P_t1,f1W_p(t1, f1) transmitted at a first time-frequency coordinate to be projected onto different OTFS pilot symbol waveform bursts P_t2,f2W_p(t2, f2) originally transmitted at a different time-frequency coordinate, and bins different from those nominally corresponding to said OTFS pilot symbol waveform bursts P_t1,f1W_p(t1, f1).

19. The apparatus of claim 18, wherein the code further causes the processor to further implement:

using the at least one 2D impulse responses to at least partially describe the 2D channel state as at least one 2D transform comprising at least one of a 2D Z-transform or other 2D transform.