| Communications Toolbox | |
Construct least mean square (LMS) adaptive algorithm object
alg = lms(stepsize)
alg = lms(stepsize,leakagefactor)
The lms function creates an adaptive algorithm object that you can use with the lineareq function or dfe function to create an equalizer object. You can then use the equalizer object with the equalize function to equalize a signal. To learn more about the process for equalizing a signal, see Using Adaptive Equalizer Functions and Objects.
alg = lms(stepsize) constructs an adaptive algorithm object based on the least mean square (LMS) algorithm with a step size of stepsize.
alg = lms(stepsize,leakagefactor) sets the leakage factor of the LMS algorithm. leakagefactor must be between 0 and 1. A value of 1 corresponds to a conventional weight update algorithm, while a value of 0 corresponds to a memoryless update algorithm.
The table below describes the properties of the LMS adaptive algorithm object. To learn how to view or change the values of an adaptive algorithm object, see Accessing Properties of an Adaptive Algorithm.
| Property | Description |
|---|---|
| AlgType | Fixed value, 'LMS' |
| StepSize | LMS step size parameter, a nonnegative real number |
| LeakageFactor | LMS leakage factor, a real number between 0 and 1 |
For examples that use this function, see Equalizing Using a Training Sequence, Example: Equalizing Multiple Times, Varying the Mode, and Example: Adaptive Equalization Within a Loop.
Referring to the schematics presented in Overview of Adaptive Equalizer Classes, define w as the vector of all weights wi and define u as the vector of all inputs ui. Based on the current set of weights, w, this adaptive algorithm creates the new set of weights given by
(LeakageFactor) w + (StepSize) u*e
where the * operator denotes the complex conjugate.
signlms, normlms, varlms, rls, cma, lineareq, dfe, equalize, Equalizers
[1] Farhang-Boroujeny, B., Adaptive Filters: Theory and Applications, Chichester, England, Wiley, 1998.
[2] Haykin, Simon, Adaptive Filter Theory, Third Ed., Upper Saddle River, N.J., Prentice-Hall, 1996.
[3] Kurzweil, Jack, An Introduction to Digital Communications, New York, Wiley, 2000.
[4] Proakis, John G., Digital Communications, Fourth Ed., New York, McGraw-Hill, 2001.
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