Weird behaviour in the nLMS code.

Started by Jack L. in comp.dsp13 years ago 15 replies

Dear group, I have a problem with my nLMS code written in C. When the Euclidean norm isn't applied to the code, i.e., it's an ordinary LMS...

Dear group, I have a problem with my nLMS code written in C. When the Euclidean norm isn't applied to the code, i.e., it's an ordinary LMS algorithm, the system destabilises. Once applied, however, the weight vectors (seem to) converge. I can't believe the system stabilises only when normalisation is applied; this would suggest the LMS never worked. o_O Also, if you look at the code below ...


Compare LMS NLMS

Started by Gie78 in comp.dsp13 years ago 1 reply

Hi I have some Problems with the NLMS. I have written a MATLAB skript to simulate the LMS and NLMS now I will compare these two...

Hi I have some Problems with the NLMS. I have written a MATLAB skript to simulate the LMS and NLMS now I will compare these two algorithms. Especially the convergence speed. Here I will compare the learning curves. Inputsignal: White noise (Matlab randn()) My major Problem is the choose of the different Parameters like step size and so on. The coefficient-update: w(n+1)=w(n)+mu(n)*e...


filtered - x - LMS

Started by Gie78 in comp.dsp13 years ago 4 replies

Hi, some days before I asked you something about the LMS and the NLMS. Now I am would take one step forward to the FXLMS. I have ...

Hi, some days before I asked you something about the LMS and the NLMS. Now I am would take one step forward to the FXLMS. I have achieved very good results in signal attenuation with the NLMS (about 200db for white and colored noise input signals),but with the fxlms the noise reduction ratio decreased to 3dB. I use a simple 1 sample delay as secondary path and the same for the estimate...


Unipolar signal + lms or nlms

Started by Vicki in comp.dsp12 years ago 8 replies
LMS

Hi All, I need abit of confirmation and explanation if you all please. I have a unipolar signal which is being prewhitened by being put through...

Hi All, I need abit of confirmation and explanation if you all please. I have a unipolar signal which is being prewhitened by being put through a NLMS filter (order 16 taps). It has been suggested that I add in a DC-tap. I'm not sure exactly what I'm supposed to do... Do I now have 17 taps, or still 16 taps with the first one being the DC-tap? (Considering the small numebr of taps, d...


Subband - Affine projection algorithm

Started by thomas in comp.dsp12 years ago 4 replies

Dear All, I am doing a project on Variable step size Affine Projection Algorithm with subbands. It would be very helpful if i get a Matlab...

Dear All, I am doing a project on Variable step size Affine Projection Algorithm with subbands. It would be very helpful if i get a Matlab code of filterbank application in any adaptive filtering algorithm (LMS,NLMS,RLS or APA). Awaiting an earliest reply. Thanks. Regards Thomas Joseph.


Variable step size LMS

Started by Richard_K in comp.dsp11 years ago 2 replies

Currently I am trying to design an equalizer based on variable step size (VSS) NLMS algorithm. The adaptation of the step size is based on...

Currently I am trying to design an equalizer based on variable step size (VSS) NLMS algorithm. The adaptation of the step size is based on the instataneous squared error. The number of taps is 55. My initial step size (which is also equivalent to max. step size allowable) is 0.6 and the minimum step size allowable is 0.35, with the "Alpha" = 0.97, "Gamma" = 0.0005. I compare it to the conventional...


Time constant for NLMS algorithm

Started by Richard_K in comp.dsp11 years ago 1 reply

It is given by "Adaptive Filter Theory" that the average time constant for LMS algorithm is 1/(2*Step Size*average of the eigenvalue). However,...

It is given by "Adaptive Filter Theory" that the average time constant for LMS algorithm is 1/(2*Step Size*average of the eigenvalue). However, the time constant for NLMS algorithm is not given. Can anyone please tell me the average time constant expression for NLMS algorithm? Many thanks.


NLMS on EFCOP 56311

Started by WP in comp.dsp10 years ago

Hello, I try to speed up convergence of the LMS algorithm on EFCOP 56311. Have anyone tried to implement NLMS? My first approach seems to be...

Hello, I try to speed up convergence of the LMS algorithm on EFCOP 56311. Have anyone tried to implement NLMS? My first approach seems to be unstable probably because of fixed point arithmetic division. Could anyone help me? Best regards Wojciech


Single carrier FDE

Started by Richard_K in comp.dsp10 years ago 1 reply

Hi, I wrote a MATLAB program for single carrier cyclic prefix (SC-CP) frequency domain equalizer (FDE)that is adapted by LMS algorithm. Based...

Hi, I wrote a MATLAB program for single carrier cyclic prefix (SC-CP) frequency domain equalizer (FDE)that is adapted by LMS algorithm. Based on the simulation results, it converges well. However, when the LMS algorithm is modified to NLMS algorithm, it couldn't converge. If given that x[n] is the column input vector to the FDE for the kth block, how should I normalize the step size? Is th...


Affine Projection Algorithm

Started by HardySpicer in comp.dsp8 years ago 9 replies
LMS

What is the advantage if any of the APA over LMS or NLMS? Hardy

What is the advantage if any of the APA over LMS or NLMS? Hardy


estimation

Started by mmoctar in comp.dsp9 years ago 1 reply

Dear all, My question is about estimation I found in many algorithms. x(n)=b*x(n)+(1-b)*x(n-1);-----> (DCT and DFT LMS, power...

Dear all, My question is about estimation I found in many algorithms. x(n)=b*x(n)+(1-b)*x(n-1);-----> (DCT and DFT LMS, power normalized-NLMS) and sometimes its: x(n)=b1*x(n)+(1-b1)*x(n-1) if x(n)> x(n-1); x(n)=b2*x(n)+(1-b2)*x(n-1); I'm working in echo cancellation... I want to know how derive it and the effects on my x(n) signal... References are welcome... thank you


DCT-lms

Started by mmoctar in comp.dsp9 years ago

Hi all, Is there a best way for eigenvalue estimation in speech case for DCT-lms? I test my algorithm with power normalization as proposed by...

Hi all, Is there a best way for eigenvalue estimation in speech case for DCT-lms? I test my algorithm with power normalization as proposed by Farhang, Ali H Sayed and Haykin, my convergence still under the NLMS one and when I increase the number of taps(500 taps) it become difficult to converge. Is DCT-lms useful for AEC. thank you in advance


design of adptive DFE

Started by cpshah99 in comp.dsp8 years ago 32 replies
LMS

Hi All If you have to design a symbol spaced adaptive DFE using LMS or NLMS algorithm in real time, how will you select the number of...

Hi All If you have to design a symbol spaced adaptive DFE using LMS or NLMS algorithm in real time, how will you select the number of feedforward taps, feedback taps and step sizes. But the conditions are: The length of training sequence is 511 symbols and you can use any kind of channel coding (LDPC, Turbo etc..). Assume synchronization is achieved. And you can only use single element TX...


wav file

Started by mmoctar in comp.dsp8 years ago 5 replies

Hi all, I'm working on acoustic echo cancellation, my question is; When I test an algorithm like LMS or NLMS should I change the scale of...

Hi all, I'm working on acoustic echo cancellation, my question is; When I test an algorithm like LMS or NLMS should I change the scale of my wave signal? As pcm file are Q15 between 1 and -1, do I need to multiply my signal by 2^15 for test under matlab. Like input=2^15*wavread('input.wav'). My question is relative to the fact that signal level have an impact on algorithm performances. tha...


Convergence of adaptive DFE

Started by cpshah99 in comp.dsp8 years ago 3 replies
LMS

Hi All I am trying to demodulate real time data using adaptive DFE. The channel is highly time varying and the multipath spread is approx....

Hi All I am trying to demodulate real time data using adaptive DFE. The channel is highly time varying and the multipath spread is approx. 50 - 100 symbols at the data rate of 4ksps. I have 1000 symbols long training sequence. The problem is that adaptive DFE is not able to converge. The algorithms that I am using is LMS and NLMS. I have been palying with filter lengths and step sizes. I ...


RF interference cancellation using NLMS

Started by pacman101 in comp.dsp7 years ago 5 replies

Hello, I'm currently trying noise cancellation for RF applications. I have a known interfering source that I am trying to cancel out so that I...

Hello, I'm currently trying noise cancellation for RF applications. I have a known interfering source that I am trying to cancel out so that I can have a better representation of the signal I am interested in. I implemented the Normalized LMS in Gnuradio. Unfortunately the performance is never consistent. About 10% of the time the algorithm works very well showing excellent cancellation....


A que on LMS vs NLSM

Started by cpshah99 in comp.dsp7 years ago 2 replies

Hi All It is known from the books that NLMS is better than LMS when the dynamic range of the input signal to the equalizer is large. But...

Hi All It is known from the books that NLMS is better than LMS when the dynamic range of the input signal to the equalizer is large. But if we use an AGC before the equalizer and then use LMS to adapt the taps, what would be the performance compared to NLMS? Best Regards Chintan


Colored Noise in Noise cancellation

Started by pacman101 in comp.dsp7 years ago 6 replies

Hello, I can't seem to find references on the performance of noise cancellation algorithms namely LMS, RLS, NLMS, etc when it comes to...

Hello, I can't seem to find references on the performance of noise cancellation algorithms namely LMS, RLS, NLMS, etc when it comes to suppressing colored noise. I have read somewhere that these algorithms do not perform very well when the noise spectrum isn't flat but I can't seem to find a reference to that claim. Can somebody explain this behavior to me and why? Is this even true?...


nlms algorithm

Started by abhi5491 in comp.dsp2 years ago 3 replies

can any one tell me which type of nlms code is this? It is in book " C Algorithms for Real-Time DSP by Paul Embree" /* function...

can any one tell me which type of nlms code is this? It is in book " C Algorithms for Real-Time DSP by Paul Embree" /* function lms(x,d,b,l,mu,alpha) Implements NLMS Algorithm b(k+1)=b(k)+2*mu*e*x(k)/((l+1)*sig) x = input data d = desired signal b[0:l] = Adaptive coefficients of lth order fir filter l = order of filter (> 1) mu = Convergence parameter (0.0 to 1.0)


Question about SMI and RLS

Started by Jeff in comp.dsp14 years ago 6 replies
LMS

Hi, Due to the unsatisfactory convergence of LMS under ill-condition of covariance matrix, the least square based algorithms are more favorable...

Hi, Due to the unsatisfactory convergence of LMS under ill-condition of covariance matrix, the least square based algorithms are more favorable in adaptive antennas. The experiment research on adaptive antennas is not very much, because of the high cost I think. Even though, there is some research using SMI, RLS and QR-RLS algorithms. As we know, the computation of SMI is proportional with M...