OTFS methods of data channel characterization and uses thereof

Patent metadata

Field	Value
Publication number	US-9668148-B2
Application number	US-201514805407-A
Country	US
Kind code	B2
Filing date	Jul 21, 2015
Priority date	May 28, 2010
Publication date	May 30, 2017
Grant date	May 30, 2017

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.

First claim

The invention claimed is:

1. An automated method of acquiring a 2D channel state of an impaired data channel connecting at least one transmitter and at least one receiver,
said impaired data channel comprising at least one reflector, each said at least one reflector comprising a reflector location, reflector frequency shift, and at least one reflector coefficients of reflection;
each said at least one transmitter comprising a transmitter location and transmitter frequency shift;
each said at least one receiver comprising a receiver location and receiver frequency shift;
wherein said 2D channel state comprises information pertaining to relative locations, frequency shifts, and reflector coefficients of reflection of said at least one transmitters, receivers, and reflectors;
said method comprising:
using said at least one transmitter and at least one processor to transmit direct OTFS pilot bursts, said direct OTFS pilot bursts comprising a plurality of OTFS pilot symbols P pt,pf 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 said pt and pf are unique pilot time-frequency coordinates chosen from a two dimensional pilot OTFS time-frequency grid, and all said OTFS pilot symbol waveform bursts P pt,pf ·W p (pt, pf) are mutually orthogonal waveform bursts derived from time and frequency shifted versions of a same OTFS pilot basis waveform W p ;
said receiver configured to receive at least said pilot bursts according to at least a two dimensional pilot OTFS time-frequency bin structure with bin sizes and bin-coordinate positions proportional to said OTFS time-frequency grid;
wherein upon propagation through said impaired data channel, said direct OTFS pilot bursts then travel over at least one path, said at least one path comprising at least one of:
a: direct OTFS pilot bursts traveling directly from said at least one transmitter to said at least one receiver; and
b: replica OTFS pilot bursts comprising direct OTFS pilot bursts that have reflected off of said at least one reflector before reaching said at least one receiver, thereby producing direct OTFS waveform bursts that are further reflector time-delayed and reflector frequency-shifted at said at least one receiver;
wherein at said at least one receiver, a resulting combination of any said transmitter frequency shifted and receiver frequency shifted direct OTFS pilot bursts and any said replica OTFS pilot bursts produces channel-convoluted OTFS pilot bursts;
at said at least one receiver, using said bin structure to receive said channel-convoluted OTFS pilot bursts and using at least one processor to determine said 2D channel state of said impaired data channel connecting said at least one transmitter and said at least one receiver.

2. The method of claim 1 , wherein prior to transmission, said plurality of OTFS pilot symbols P pt,pf , and two dimensional pilot OTFS time-frequency grid and bin structure are chosen so that if, after transmission by said at least one transmitter, said impaired data channel subsequently causes at least some of said OTFS pilot symbol waveform bursts P t1,f1 ·W p (t1, f1) originally transmitted at a first time-frequency coordinate to be projected onto different OTFS pilot symbol waveform bursts P t2,f2 ·Wp(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,f1 ·W p (t1, f1), at least some of said projections will be detectable and quantifiable by said at least one receiver.

3. The method of claim 2 , wherein said plurality of OTFS pilot symbols P pt,pf transmitted as OTFS pilot symbol waveform bursts P pt,pf ·W 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,pf ·W p (pt, pf) with sufficient power to be detectable by said at least one receiver; and any of:
1: at least some of said plurality of OTFS pilot symbols are null pilot symbols intended to create empty pt and pf unique pilot time-frequency coordinates chosen from said two dimensional pilot OTFS time-frequency grid, where no waveform burst is transmitted; or
2: at least some of said plurality of OTFS pilot symbols are background pilot symbols intended to create a uniform background of pt and pf unique pilot time-frequency coordinates chosen from said two dimensional pilot OTFS time-frequency grid to enable projections of channel-convoluted non-null OTFS pilot bursts onto said uniform background to be detectable and quantifiable by said at least one receiver.

4. The method of claim 1 , wherein said 2D channel state is at least partially determined by using at least one 2D impulse response to mathematically describe how said impaired data channel causes at least some of said OTFS pilot symbol waveform bursts P t1,f1 ·W p (t1, f1) transmitted at a first time-frequency coordinate to be projected onto different OTFS pilot symbol waveform bursts P t2,f2 ·Wp(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,f1 ·W p (t1, f1).

5. The method of claim 4 , further using a plurality of said 2D impulse responses from a plurality of said bins to at least partially describe said 2D channel state as at least one 2D transform comprising at least one of a 2D Z-transform or other 2D transform.

6. The method of claim 1 , wherein said 2D channel state comprises a matrix or other mathematical transform for said impaired data channel, describing how all signals transmitted by said transmitter are coupled with all signals from said transmitter that are received by said receiver.

7. The method of claim 1 , wherein said plurality of OTFS pilot symbols P pt,pf are known by said at least one receiver, and wherein said plurality of OTFS pilot symbols are 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 said bins have time-frequency resolutions that are equal to or more precise than time-frequency resolutions of said grid.

8. The method of claim 1 , further transmitting a plurality of data symbols through said impaired data channel by using said at least one transmitter and at least one processor to also transmit at least some of said plurality of data symbols as direct data bursts comprising a plurality of data carrying waveform bursts, and to transmit said direct data bursts along with said direct OTFS pilot bursts to said at least one receiver;
wherein said direct data bursts also are reflected off of said at least one reflector, thereby producing replica data bursts comprising time-delayed and reflector frequency-shifted direct data bursts at said at least one receiver, and wherein at said at least one receiver, a resulting combination of any said transmitter frequency shifted and receiver frequency shifted direct data bursts, and replica data bursts, produce channel-convoluted data bursts;
using said 2D channel state and at least one processor to further perform at least one of:
a) precoding at least some of said direct data bursts at said at least one transmitter to pre-compensate for said impaired data channel; and
b) deconvoluting at least some of said channel-convoluted data bursts at said at least one receiver, thereby deriving at least an approximation of said plurality of data symbols.

9. The

Assignees

• Cohere Tech Inc

Inventors

• Hadani Ronny
• Rakib Shlomo Selim

Classifications

• H04W72/54

  based on quality criteria · CPC title

• H04L5/0048

  Allocation of pilot signals, i.e. of signals known to the receiver (allocation of control signalling H04L5/0053; use of control signalling H04L5/0091) · CPC title

• H04L27/2639

  Modulators using other transforms, e.g. discrete cosine transforms, Orthogonal Time Frequency and Space [OTFS] or hermetic transforms · CPC title

• H04B7/10

  Polarisation diversity; Directional diversity · CPC title

• H04W72/08

  Electricity · mapped topic