Background: Unconstrained Coding of a Wiener Process 2 Ο 2 ln 2 R β 1 D W ( R ) = distortion-rate function [Berger 1970] find coefficients in the KarhunenβLoΓ¨ve of W t Z T A k = f k ( t ) dW t k = 1 , 2 , . . . 0 encode the coefficients using a standard random coding principle [Shannon] requires integration with respect to Brownian path in practice, imprecise at any timescale π β β π’ this talk: incorporate sampling into model β β 0.3 β 0.2 β 0.1 0 0.1 0.2 6 /17
Background: Unconstrained Coding of a Wiener Process 2 Ο 2 ln 2 R β 1 D W ( R ) = distortion-rate function [Berger 1970] find coefficients in the KarhunenβLoΓ¨ve of W t Z T A k = f k ( t ) dW t k = 1 , 2 , . . . 0 encode the coefficients using a standard random coding principle [Shannon] requires integration with respect to Brownian path in practice, imprecise at any timescale π β β π’ this talk: incorporate sampling into model β β 0.3 β 0.2 β 0.1 0 0.1 0.2 6 /17
Combined Sampling and Coding W T Β― M β { 0 , 1 } b T R c W T c W T decoder encoder = T β 1 f s s 7 /17
Combined Sampling and Coding W T Β― M β { 0 , 1 } b T R c W T c W T decoder encoder = T β 1 f s s Z T β£ β 2 1 W t β c inf lim D ( f s , R ) W t dt = T ββ W T β M β c T Β― W T 0 7 /17
Combined Sampling and Coding W T Β― M β { 0 , 1 } b T R c W T c W T decoder encoder = T β 1 f s s Z T β£ β 2 = β 1 W t β c inf lim D ( f s , R ) W t dt = T ββ W T β M β c T Β― W T 0 7 /17
Combined Sampling and Coding W T Β― M β { 0 , 1 } b T R c W T c W T decoder encoder = T β 1 f s s Z T β£ β 2 = β 1 W t β c inf lim D ( f s , R ) W t dt = T ββ W T β M β c T Β― W T 0 (R = 1) MSE f s [smp/sec] 7 /17
Combined Sampling and Coding W T Β― M β { 0 , 1 } b T R c W T c W T decoder encoder = T β 1 f s s Z T β£ β 2 = β 1 W t β c inf lim D ( f s , R ) W t dt = T ββ W T β M β c T Β― W T 0 (R = 1) MSE D W ( R ) 2 Ο 2 ln 2 f s [smp/sec] 7 /17
Combined Sampling and Coding W T Β― M β { 0 , 1 } b T R c W T c W T decoder encoder = T β 1 f s s Z T β£ β 2 = β 1 W t β c inf lim D ( f s , R ) W t dt = T ββ W T β M β c T Β― W T 0 (R = 1) MSE mmse ( f s ) = (6 f s ) β 1 D W ( R ) 2 Ο 2 ln 2 f s [smp/sec] 7 /17
Combined Sampling and Coding W T Β― M β { 0 , 1 } b T R c W T c W T decoder encoder = T β 1 f s s Z T β£ β 2 = β 1 W t β c inf lim D ( f s , R ) W t dt = T ββ W T β M β c T Β― W T 0 (R = 1) MSE D ( f , R = ? ) s mmse ( f s ) = (6 f s ) β 1 D W ( R ) 2 Ο 2 ln 2 f s [smp/sec] 7 /17
Main Result: Minimal Distortion under Sampling and Coding Theorem [K., Goldsmith, Eldar, β16] Z 1 1 + 1 οΏ½ D ( f s , R ) = min W ( Ο ) , ΞΈ S f d Ο 6 f s f s 0 Z 1 R ΞΈ = f s log + β₯ β€ S f W ( Ο ) / ΞΈ d Ο 2 0 (2 sin( ΟΟ / 2)) 2 β 1 1 S f W ( Ο ) = 6 8 /17
Main Result: Minimal Distortion under Sampling and Coding Theorem [K., Goldsmith, Eldar, β16] Z 1 1 + 1 οΏ½ D ( f s , R ) = min W ( Ο ) , ΞΈ S f d Ο 6 f s f s 0 Z 1 R ΞΈ = f s log + β₯ β€ S f W ( Ο ) / ΞΈ d Ο 2 0 (2 sin( ΟΟ / 2)) 2 β 1 1 S f W ( Ο ) = 6 ΞΈ W ( Ο ) S f Ο 1 8 /17
Main Result: Minimal Distortion under Sampling and Coding Theorem [K., Goldsmith, Eldar, β16] Z 1 1 + 1 οΏ½ D ( f s , R ) = min W ( Ο ) , ΞΈ S f d Ο 6 f s f s 0 Z 1 R ΞΈ = f s log + β₯ β€ S f W ( Ο ) / ΞΈ d Ο 2 0 (2 sin( ΟΟ / 2)) 2 β 1 1 S f W ( Ο ) = 6 asymptotic density of ΞΈ Karhunen Loeve eigenvalues of W ( Ο ) S f W t = E [ W t | Β― f W ] Ο 1 8 /17
Minimal Distortion under Sampling and Coding β proof steps in proof: Z T β£ β 2 1 W t β c D ( f s , R ) inf E W t dt show that: I. lim = β£ W T β T T ββ W T ; c 0 Β― I β€ RT II. compute solution to optimization problem 9 /17
Minimal Distortion under Sampling and Coding β proof steps in proof: Z T β£ β 2 1 W t β c D ( f s , R ) inf E W t dt show that: I. lim = β£ W T β T T ββ W T ; c 0 Β― I β€ RT II. compute solution to optimization problem Step I: 9 /17
Minimal Distortion under Sampling and Coding β proof steps in proof: Z T β£ β 2 1 W t β c D ( f s , R ) inf E W t dt show that: I. lim = β£ W T β T T ββ W T ; c 0 Β― I β€ RT II. compute solution to optimization problem Step I: d : R b T f s c Γ L 2 [0 , T ] β [0 , β ) " # Z T w T ) def w T , b 1 w t ) 2 | Β― W T = Β― d ( Β― w T ( W t β b E = T 0 9 /17
Minimal Distortion under Sampling and Coding β proof steps in proof: Z T β£ β 2 1 W t β c D ( f s , R ) inf E W t dt show that: I. lim = β£ W T β T T ββ W T ; c 0 Β― I β€ RT II. compute solution to optimization problem Step I: d : R b T f s c Γ L 2 [0 , T ] β [0 , β ) w T w T b Β― " # Z T w T ) def w T , b 1 w t ) 2 | Β― W T = Β― d ( Β― w T ( W t β b E = T 0 T 0 9 /17
Minimal Distortion under Sampling and Coding β proof steps in proof: Z T β£ β 2 1 W t β c D ( f s , R ) inf E W t dt show that: I. lim = β£ W T β T T ββ W T ; c 0 Β― I β€ RT II. compute solution to optimization problem Step I: d : R b T f s c Γ L 2 [0 , T ] β [0 , β ) w T w T b Β― " # Z T w T ) def w T , b 1 w t ) 2 | Β― W T = Β― d ( Β― w T ( W t β b E = T 0 T 0 9 /17
Minimal Distortion under Sampling and Coding β proof steps in proof: Z T β£ β 2 1 W t β c D ( f s , R ) inf E W t dt show that: I. lim = β£ W T β T T ββ W T ; c 0 Β― I β€ RT II. compute solution to optimization problem Step I: d : R b T f s c Γ L 2 [0 , T ] β [0 , β ) w T w T b Β― " # Z T w T ) def w T , b 1 w t ) 2 | Β― W T = Β― d ( Β― w T ( W t β b E = T 0 T 0 9 /17
Minimal Distortion under Sampling and Coding β proof steps in proof: Z T β£ β 2 1 W t β c D ( f s , R ) inf E W t dt show that: I. lim = β£ W T β T T ββ W T ; c 0 Β― I β€ RT II. compute solution to optimization problem Step I: d : R b T f s c Γ L 2 [0 , T ] β [0 , β ) w T w T b Β― " # Z T w T ) def w T , b 1 w t ) 2 | Β― W T = Β― d ( Β― w T ( W t β b E = T 0 Z T β£ β 2 T 0 W T ) = 1 W T , c E d ( Β― W t β c W t dt T 0 9 /17
Minimal Distortion under Sampling and Coding β proof steps in proof: Z T β£ β 2 1 W t β c D ( f s , R ) inf E W t dt show that: I. lim = β£ W T β T T ββ W T ; c 0 Β― I β€ RT II. compute solution to optimization problem Step I: d : R b T f s c Γ L 2 [0 , T ] β [0 , β ) w T w T b Β― " # Z T w T ) def w T , b 1 w t ) 2 | Β― W T = Β― d ( Β― w T ( W t β b E = T 0 Z T β£ β 2 T 0 W T ) = 1 W T , c E d ( Β― W t β c W t dt T 0 use standard random coding [Shannon] with respect to samples Β― W n under metric d (rather than squared error) 9 /17
Minimal Distortion under Sampling and Coding β Proof steps in proof: Z T β£ β 2 1 W t β c D ( f s , R ) inf E W t dt show that: I. lim = β£ W T β T T ββ W T ; c 0 Β― I β€ RT II. compute solution to optimization problem 10 /17
Minimal Distortion under Sampling and Coding β Proof steps in proof: Z T β£ β 2 1 W t β c D ( f s , R ) inf E W t dt show that: I. lim = β£ W T β T T ββ W T ; c 0 Β― I β€ RT II. compute solution to optimization problem Step II: 10 /17
Minimal Distortion under Sampling and Coding β Proof steps in proof: Z T β£ β 2 1 W t β c D ( f s , R ) inf E W t dt show that: I. lim = β£ W T β T T ββ W T ; c 0 Β― I β€ RT II. compute solution to optimization problem Step II: Z T β£ β 2 inf 1 mmse ( W T | Β― W T ) + W t β c f D ( f s , R ) = lim E W t dt T T ββ β£ W T β 0 W T ; c f I β€ RT 10 /17
Minimal Distortion under Sampling and Coding β Proof steps in proof: Z T β£ β 2 1 W t β c D ( f s , R ) inf E W t dt show that: I. lim = β£ W T β T T ββ W T ; c 0 Β― I β€ RT II. compute solution to optimization problem Step II: Z T β£ β 2 inf 1 mmse ( W T | Β― W T ) + W t β c f D ( f s , R ) = lim E W t dt T T ββ β£ W T β 0 W T ; c f I β€ RT f use KarhunenβLoΓ¨ve transform of to evaluate last minimization W t Z T h i W t f f k = 1 , 2 , . . . Ξ» k f k ( t ) = f k ( s ) E W s ds, 0 10 /17
Minimal Distortion under Sampling and Coding β Proof steps in proof: Z T β£ β 2 1 W t β c D ( f s , R ) inf E W t dt show that: I. lim = β£ W T β T T ββ W T ; c 0 Β― I β€ RT II. compute solution to optimization problem Step II: Z T β£ β 2 inf 1 mmse ( W T | Β― W T ) + W t β c f D ( f s , R ) = lim E W t dt T T ββ β£ W T β 0 W T ; c f I β€ RT f use KarhunenβLoΓ¨ve transform of to evaluate last minimization W t Z T h i W t f f k = 1 , 2 , . . . Ξ» k f k ( t ) = f k ( s ) E W s ds, 0 Ξ» 1 , . . . , Ξ» b T f s c f W T covariance Kernel of has rank . Can ``guessββ eigenvalues b Tf s c 10 /17
Minimal Distortion under Sampling and Coding β Proof steps in proof: Z T β£ β 2 1 W t β c D ( f s , R ) inf E W t dt show that: I. lim = β£ W T β T T ββ W T ; c 0 Β― I β€ RT II. compute solution to optimization problem Step II: Z T β£ β 2 inf 1 mmse ( W T | Β― W T ) + W t β c f D ( f s , R ) = lim E W t dt T T ββ β£ W T β 0 W T ; c f I β€ RT f use KarhunenβLoΓ¨ve transform of to evaluate last minimization W t Z T h i W t f f k = 1 , 2 , . . . Ξ» k f k ( t ) = f k ( s ) E W s ds, 0 Ξ» 1 , . . . , Ξ» b T f s c f W T covariance Kernel of has rank . Can ``guessββ eigenvalues b Tf s c (2 sin( ΟΟ / 2)) 2 β 1 1 S f W ( Ο ) = asymptotic KL eigenvalues distribution is 6 10 /17
Analysis 11 /17
Analysis (R = 1) MSE D W ( R ) 2 Ο 2 ln 2 mmse ( f s ) f s [smp/sec] 11 /17
Analysis (R = 1) MSE D ( f , R ) s D W ( R ) 2 Ο 2 ln 2 mmse ( f s ) f s [smp/sec] 11 /17
Analysis ( f s = 1) (R = 1) MSE MSE D ( f , R ) s mmse ( f s ) 1 D W ( R ) 2 6 f s Ο 2 ln 2 D W ( R ) mmse ( f s ) f s [smp/sec] R [bits/sec] 11 /17
Analysis ( f s = 1) (R = 1) MSE MSE D ( f s , R ) D ( f , R ) s mmse ( f s ) 1 D W ( R ) 2 6 f s Ο 2 ln 2 D W ( R ) mmse ( f s ) f s [smp/sec] R [bits/sec] 11 /17
Analysis ( f s = 1) (R = 1) MSE MSE D ( f s , R ) D ( f , R ) s mmse ( f s ) 1 D W ( R ) 2 6 f s Ο 2 ln 2 D W ( R ) mmse ( f s ) f s [smp/sec] R [bits/sec] β β₯ 1 + log( 3 + 2) R low sampling rate β 1 . 45 2 f s ! β 1 1 6 + 2 + 3 2 β 2 R/f s D ( f s , R ) = f s 6 11 /17
Analysis ( f s = 1) (R = 1) MSE MSE D ( f s , R ) D ( f , R ) s mmse ( f s ) 1 D W ( R ) 2 6 f s Ο 2 ln 2 D W ( R ) mmse ( f s ) f s [smp/sec] R [bits/sec] β β₯ 1 + log( 3 + 2) R low sampling rate β 1 . 45 2 f s ! β 1 6 + 2 + 1 3 2 β 2 R/f s D ( f s , R ) = f s 6 β = 18 + 3 D ( f s = 1 , R = 2) 96 11 /17
Excess Distortion due to Sampling D ( f s , R ) Ο ( Β― Β― (bits per sample) R = R/f s R ) excess distortion ratio: = D W ( R ) 12 /17
Excess Distortion due to Sampling D ( f s , R ) Ο ( Β― Β― (bits per sample) R = R/f s R ) excess distortion ratio: = D W ( R ) excess distortion due to sampling is only a function of bits/smp 12 /17
Excess Distortion due to Sampling D ( f s , R ) Ο ( Β― Β― (bits per sample) R = R/f s R ) excess distortion ratio: = D W ( R ) excess distortion due to sampling is only a function of bits/smp ) Β― R ( Ο Β― R [bit/smp] 1 12 /17
Excess Distortion due to Sampling D ( f s , R ) Ο ( Β― Β― (bits per sample) R = R/f s R ) excess distortion ratio: = D W ( R ) excess distortion due to sampling is only a function of bits/smp ) Β― R ( Ο β 1 . 12 Β― R [bit/smp] 1 Β― R = 1 example : with 1 bit/smp can attain 1.12 of optimal distortion at the same bitrate 12 /17
Excess Distortion due to Sampling D ( f s , R ) Ο ( Β― Β― (bits per sample) R = R/f s R ) excess distortion ratio: = D W ( R ) excess distortion due to sampling is only a function of bits/smp ) Β― R ( Ο β 1 . 12 Β― R [bit/smp] 1 Β― R = 1 example : with 1 bit/smp can attain 1.12 of optimal distortion at the same bitrate Β― Ο β 1 must have to get R β 0 12 /17
Real Stationary Gaussian Processes encode sample bitrate R decode Β― X t b X n X t representation 13 /17
Real Stationary Gaussian Processes encode sample bitrate R decode Β― X t b X n X t representation S X ( f ) = F { E X t X 0 } ( f ) 13 /17
Real Stationary Gaussian Processes encode sample bitrate R decode Β― X t b X n X t representation S X ( f ) = F { E X t X 0 } ( f ) Theorem [K., Goldsmith, Eldar, β14] fs Z 2 mmse ( f s ) + D X ( f s , R ) min { S X ( f ) , ΞΈ } d f = β fs 2 fs R ΞΈ = 1 Z 2 log + [ S X ( f ) / ΞΈ ] d f 2 β fs 2 13 /17
Real Stationary Gaussian Processes encode sample bitrate R decode Β― X t b X n X t representation S X ( f ) = F { E X t X 0 } ( f ) Theorem [K., Goldsmith, Eldar, β14] fs Z 2 mmse ( f s ) + D X ( f s , R ) min { S X ( f ) , ΞΈ } d f = β fs 2 fs R ΞΈ = 1 Z 2 log + [ S X ( f ) / ΞΈ ] d f 2 β fs 2 S X ( f ) ΞΈ f s 13 /17
Real Stationary Gaussian Processes encode sample bitrate R decode Β― X t b X n X t representation S X ( f ) = F { E X t X 0 } ( f ) Theorem [K., Goldsmith, Eldar, β14] fs Z 2 mmse ( f s ) + D X ( f s , R ) min { S X ( f ) , ΞΈ } d f = β fs 2 fs R ΞΈ = 1 Z 2 log + [ S X ( f ) / ΞΈ ] d f 2 β fs 2 S X ( f ) distortion f Nyq ΞΈ D X ( R ) f s mmse ( f s ) f s 13 /17
Real Stationary Gaussian Processes encode sample bitrate R decode Β― X t b X n X t representation S X ( f ) = F { E X t X 0 } ( f ) Theorem [K., Goldsmith, Eldar, β14] fs Z 2 mmse ( f s ) + D X ( f s , R ) min { S X ( f ) , ΞΈ } d f = β fs 2 fs R ΞΈ = 1 Z 2 log + [ S X ( f ) / ΞΈ ] d f 2 β fs 2 S X ( f ) distortion f Nyq D f R ( f X , R ) s ΞΈ D X ( R ) f s mmse ( f s ) f s 13 /17
Classification of Gaussian Processes 14 /17
Classification of Gaussian Processes ) β 0 for zero distortion must have R β β D W ( R ) 14 /17
Classification of Gaussian Processes ) β 0 for zero distortion must have R β β D W ( R ) β D ( f s , R ) f s ( R ) R β β as how to set so that β 1 D W ( R ) 14 /17
Classification of Gaussian Processes ) β 0 for zero distortion must have R β β D W ( R ) β D ( f s , R ) f s ( R ) R β β as how to set so that β 1 D W ( R ) Wiener process R/f s β 0 14 /17
Classification of Gaussian Processes ) β 0 for zero distortion must have R β β D W ( R ) β D ( f s , R ) f s ( R ) R β β as how to set so that β 1 D W ( R ) Wiener process R/f s β 0 ( ) S f X bandlimited Gaussian processes ΞΈ R/f s β β f s 14 /17
Classification of Gaussian Processes ) β 0 for zero distortion must have R β β D W ( R ) β D ( f s , R ) f s ( R ) R β β as how to set so that β 1 D W ( R ) Wiener process R/f s β 0 ( ) S f X bandlimited Gaussian processes ΞΈ R/f s β β f s S ( ) f X Gauss-Markov (OrnsteinβUhlenbeck) process R/f s β 1 / ln 2 ΞΈ f s 14 /17
Classification of Gaussian Processes β D ( f s , R ) f s ( R ) R β β as how to set so that β 1 D W ( R ) 15 /17
Classification of Gaussian Processes β D ( f s , R ) f s ( R ) R β β as how to set so that β 1 D W ( R ) S ( ) f X R/f s β β Class 1: ΞΈ processes with rapidly decreasing spectrum f s 15 /17
Classification of Gaussian Processes β D ( f s , R ) f s ( R ) R β β as how to set so that β 1 D W ( R ) S ( ) f X R/f s β β Class 1: ΞΈ processes with rapidly decreasing spectrum f s ( ) S f X R/f s < β Class 2: processes with slowly decreasing spectrum ΞΈ f s 15 /17
Classification of Gaussian Processes β D ( f s , R ) f s ( R ) R β β as how to set so that β 1 D W ( R ) S ( ) f X R/f s β β Class 1: ΞΈ processes with rapidly decreasing spectrum f s challenge in encoding: high-resolution quantization ( ) S f X R/f s < β Class 2: processes with slowly decreasing spectrum ΞΈ f s 15 /17
Classification of Gaussian Processes β D ( f s , R ) f s ( R ) R β β as how to set so that β 1 D W ( R ) S ( ) f X R/f s β β Class 1: ΞΈ processes with rapidly decreasing spectrum f s challenge in encoding: high-resolution quantization ( ) S f X R/f s < β Class 2: processes with slowly decreasing spectrum ΞΈ f s challenge in encoding: adapting to high innovation rate 15 /17
Classification of Gaussian Processes β D ( f s , R ) f s ( R ) R β β as how to set so that β 1 D W ( R ) S ( ) f X R/f s β β Class 1: ΞΈ processes with rapidly decreasing spectrum f s challenge in encoding: high-resolution quantization ( ) S f X R/f s < β Class 2: processes with slowly decreasing spectrum ΞΈ f s challenge in encoding: adapting to high innovation rate Z f s 1 log + S X ( f ) lim S X ( f s ) d f < β f s ββ f s β f s 15 /17
Classification of Gaussian Processes β D ( f s , R ) f s ( R ) R β β as how to set so that β 1 D W ( R ) S ( ) f X R/f s β β Class 1: ΞΈ processes with rapidly decreasing spectrum f s challenge in encoding: high-resolution quantization Z f s 1 log + S X ( f ) lim f = β S X ( f s ) d f s f s ββ β f s ( ) S f X R/f s < β Class 2: processes with slowly decreasing spectrum ΞΈ f s challenge in encoding: adapting to high innovation rate Z f s 1 log + S X ( f ) lim S X ( f s ) d f < β f s ββ f s β f s 15 /17
Summary 16 /17
Summary encoding a realization of the Wiener process involves sampling and quantization (encoding) 16 /17
Summary encoding a realization of the Wiener process involves sampling and quantization (encoding) closed-form expression for distortion at any sampling rate and bitrate: 1 bit per sample attains 1.12 times the optimal distortion at the same bitrate 16 /17
Summary encoding a realization of the Wiener process involves sampling and quantization (encoding) closed-form expression for distortion at any sampling rate and bitrate: 1 bit per sample attains 1.12 times the optimal distortion at the same bitrate sampling rate must increase faster than bitrate in order to get D ( f s , R ) /D W ( R ) β 1 16 /17
Summary encoding a realization of the Wiener process involves sampling and quantization (encoding) closed-form expression for distortion at any sampling rate and bitrate: 1 bit per sample attains 1.12 times the optimal distortion at the same bitrate sampling rate must increase faster than bitrate in order to get D ( f s , R ) /D W ( R ) β 1 a new way to classify spectrum of continuous-time signals: D X ( f s ( R ) , R ) /D X ( R ) β 1 R/f s β β Class 1: (bandlimited, rapidly decreasing PSD) (Wiener, Gauss-Markov,β¦) R/f s < β Class 2: 16 /17
The End! A. Kipnis, A. J. Goldsmith and Y. C. Eldar, βRate-distortion function of sampled Wiener processesβ, on Arxiv A. Kipnis, A. J. Goldsmith, Y. C. Eldar, T. Weissman, βDistortion-rate function of sub-Nyquist sampled Gaussian sourcesβ, IEEE Trans. Info. Th. Distortion 4 sin 2 ( ΟΟ / 2) β 1 1 6 D W ( R ) 2 R β 1 Ο 2 ln 2 mmse ( f s ) ΞΈ Ο 1 f s [smp/sec] 17 /17
Classification of Gaussian Processes 18 /17
Classification of Gaussian Processes ) β 0 for zero distortion must have R β β D W ( R ) 18 /17
Classification of Gaussian Processes ) β 0 for zero distortion must have R β β D W ( R ) β D ( f s , R ) f s ( R ) how to set so that β 1 D W ( R ) 18 /17
Classification of Gaussian Processes ) β 0 for zero distortion must have R β β D W ( R ) β D ( f s , R ) f s ( R ) how to set so that β 1 D W ( R ) Wiener process: R/f s β 0 18 /17
Classification of Gaussian Processes ) β 0 for zero distortion must have R β β D W ( R ) β D ( f s , R ) f s ( R ) how to set so that β 1 D W ( R ) Wiener process: R/f s β 0 ( ) S f X bandlimited Gaussian processes [K., Goldsmith, Eldar, Weissman β13]: ΞΈ R/f s β β f s 18 /17
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