Home > Quantization Error > Quantization Error In Digital Communication# Quantization Error In Digital Communication

## The essential property of a quantizer is that it has a countable set of possible output values that has fewer members than the set of possible input values.

However, in some quantizer designs, the **concepts of granular error and overload** error may not apply (e.g., for a quantizer with a limited range of input data or with a countably doi:10.1109/TIT.1984.1056920 ^ Toby Berger, "Optimum Quantizers and Permutation Codes", IEEE Transactions on Information Theory, Vol. The potential signal-to-quantization-noise power ratio therefore changes by 4, or 10 ⋅ log 10 ( 4 ) = 6.02 {\displaystyle \scriptstyle 10\cdot \log _{10}(4)\ =\ 6.02} At lower amplitudes the quantization error becomes dependent on the input signal, resulting in distortion. check my blog

doi:10.1109/MCOM.1977.1089500 ^ Rabbani, Majid; Joshi, **Rajan L.; Jones, Paul** W. (2009). "Section 1.2.3: Quantization, in Chapter 1: JPEG 2000 Core Coding System (Part 1)". Text is available under the Creative Commons Attribution-ShareAlike License; additional terms may apply. Assuming an FLC with M {\displaystyle M} levels, the Rate–Distortion minimization problem can be reduced to distortion minimization alone. Also see noise shaping.) For complex signals in high-resolution ADCs this is an accurate model. More hints

An ADC can be modeled as two processes: sampling and quantization. Privacy policy About Wikipedia Disclaimers Contact Wikipedia Developers Cookie statement Mobile view All Syllabus Home About Search Unit 1 Unit 2 Unit 3 Unit 4 Unit 5 Unit 6 Unit 7 Gray, "Entropy-Constrained Vector Quantization", IEEE Transactions on Acoustics, Speech, and Signal Processing, Vol. **p.107. **

- IT-51, No. 5, pp. 1739–1755, May 2005.
- However, it is common to assume that for many sources, the slope of a quantizer SQNR function can be approximated as 6dB/bit when operating at a sufficiently high bit rate.
- The system operates with an average signal power above the error threshold so that the effect of channel noise is made negligible and performance is there by limited essentially by Quantization
- For some applications, having a zero output signal representation or supporting low output entropy may be a necessity.
- CT-3, pp. 266–276, 1956.
- In Schelkens, Peter; Skodras, Athanassios; Ebrahimi, Touradj.
- Gray and David L.
- For a given supported number of possible output values, reducing the average granular distortion may involve increasing the average overload distortion, and vice versa.
- pp.22–24.
- It is known as dither.

It is common for the design of a quantizer to involve determining the proper balance between granular distortion and overload distortion. Entropy coding techniques can be applied to communicate the quantization indices from a source encoder that performs the classification stage to a decoder that performs the reconstruction stage. John Wiley & Sons. Analog-to-digital converter (ADC)[edit] Outside the realm of signal processing, this category may simply be called rounding or scalar quantization.

However, the same concepts actually apply in both use cases. Solutions that do not require multi-dimensional iterative optimization techniques have been published for only three probability distribution functions: the uniform,[18] exponential,[12] and Laplacian[12] distributions. In contrast, mid-tread quantizers do have a zero output level, and can reach arbitrarily low bit rates per sample for input distributions that are symmetric and taper off at higher magnitudes. http://www.allsyllabus.com/aj/note/ECE/Digital%20Communication/unit3/Quantization%20Process.php doi:10.1109/TCT.1956.1086334 ^ a b c Bernard Widrow, "Statistical analysis of amplitude quantized sampled data systems", Trans.

In this second setting, the amount of introduced distortion may be managed carefully by sophisticated techniques, and introducing some significant amount of distortion may be unavoidable. In general, a mid-riser or mid-tread **quantizer may** not actually be a uniform quantizer – i.e., the size of the quantizer's classification intervals may not all be the same, or the Quantization Error/Noise. For the mean-square error distortion criterion, it can be easily shown that the optimal set of reconstruction values { y k ∗ } k = 1 M {\displaystyle \{y_{k}^{*}\}_{k=1}^{M}} is given

p.60. ^ Okelloto, Tom (2001). With Δ = 1 {\displaystyle \Delta =1} or with Δ {\displaystyle \Delta } equal to any other integer value, this quantizer has real-valued inputs and integer-valued outputs, although this property is The noise is non-linear and signal-dependent. Lloyd, "Least Squares Quantization in PCM", IEEE Transactions on Information Theory, Vol.

The difference between the original signal and the reconstructed signal is the quantization error and, in this simple quantization scheme, is a deterministic function of the input signal. http://caribtechsxm.com/quantization-error/quantization-error-quantization-noise.php Moreover, the technique can be further **generalized in a straightforward** way to also include an entropy constraint for vector data.[23] Uniform quantization and the 6 dB/bit approximation[edit] The Lloyd–Max quantizer is Adapted from Franz, David (2004). John Wiley & Sons.

Mid – tread type: Quantization levels – odd number. The input and output sets involved in quantization can be defined in a rather general way. Mean squared error is also called the quantization noise power. http://caribtechsxm.com/quantization-error/quantization-error-and-quantization-step-size.php Examples of fields where this limitation applies include electronics (due to electrons), optics (due to photons), biology (due to DNA), physics (due to Planck limits) and chemistry (due to molecules).

For a given supported number of possible output values, reducing the average granular distortion may involve increasing the average overload distortion, and vice versa. Sullivan, "Efficient Scalar Quantization of Exponential and Laplacian Random Variables", IEEE Transactions on Information Theory, Vol. M.

In such cases, using a mid-tread uniform quantizer may be appropriate while using a mid-riser one would not be. For example, for N {\displaystyle N} =8 bits, M {\displaystyle M} =256 levels and SQNR = 8*6 = 48dB; and for N {\displaystyle N} =16 bits, M {\displaystyle M} =65536 and ISBN978-0-470-72147-6. ^ Taubman, David S.; Marcellin, Michael W. (2002). "Chapter 3: Quantization". The calculations above, however, assume a completely filled input channel.

Gray, Vector Quantization and Signal Compression, Springer, ISBN 978-0-7923-9181-4, 1991. ^ Hodgson, Jay (2010). Sampling converts a voltage signal (function of time) into a discrete-time signal (sequence of real numbers). The Quantization error, Q is a random variable and will have its sample values bounded by [-(Δ/2) < q < (Δ/2)]. More about the author The JPEG 2000 Suite.

Oliver, J. At asymptotically high bit rates, the 6dB/bit approximation is supported for many source pdfs by rigorous theoretical analysis.[4][5][7][8] Moreover, the structure of the optimal scalar quantizer (in the rate–distortion sense) approaches The analysis of quantization involves studying the amount of data (typically measured in digits or bits or bit rate) that is used to represent the output of the quantizer, and studying The terminology is based on what happens in the region around the value 0, and uses the analogy of viewing the input-output function of the quantizer as a stairway.

Ind., Vol. 79, pp. 555–568, Jan. 1961. ^ Daniel Marco and David L. Within the extreme limits of the supported range, the amount of spacing between the selectable output values of a quantizer is referred to as its granularity, and the error introduced by Lloyd, "Least Squares Quantization in PCM", IEEE Transactions on Information Theory, Vol. AIEE Pt.

Rounding and truncation are typical examples of quantization processes. Solving the unconstrained problem is equivalent to finding a point on the convex hull of the family of solutions to an equivalent constrained formulation of the problem. The difference between the blue and red signals in the upper graph is the quantization error, which is "added" to the quantized signal and is the source of noise. the problem that the sampled value of signal falls outside the total amplitude range of Quantizer, 8σx is less than 10-4.

The book inserts equal importance to the theory and application aspect of the subject whereby the authors selected a wide class of problems.The Salient features of the book are:1. Lloyd's Method I algorithm, originally described in 1957, can be generalized in a straightforward way for application to vector data. Mid-Rise type Quantizer 2. doi:10.1109/JRPROC.1948.231941 ^ Seymour Stein and J.

This two-stage decomposition applies equally well to vector as well as scalar quantizers. Common word-lengths are 8-bit (256 levels), 16-bit (65,536 levels), 32-bit (4.3billion levels), and so on, though any number of quantization levels is possible (not just powers of two). The noise is non-linear and signal-dependent. IT-28, pp. 129–137, No. 2, March 1982 doi:10.1109/TIT.1982.1056489 (work documented in a manuscript circulated for comments at Bell Laboratories with a department log date of 31 July 1957 and also presented

SAMS. Non- Uniform Quantizer 0 Ts 2Ts 3Ts Time Analog Signal Discrete Samples ( Quantized ) In Uniform type, the quantization levels are uniformly spaced, whereas in nonuniform type the spacing between