## Forums

## IEEE802.11a Matlab Simulation

Hi, I would like to simulate IEEE802.11a WLAN over a Rayleigh multipath channel using Matlab and I'm dealing with the...

Hi, I would like to simulate IEEE802.11a WLAN over a Rayleigh multipath channel using Matlab and I'm dealing with the function "h=rayleighchan(ts,fd,tau,pdb). I'm really confusing about the sample time(ts) which on I have to use 50ns as the bandwidth=20MHz or I should choose the time of OFDM symbol which is equal to 4us according to the IEEE standards. Do you have any idea? Thank you in...

## Entropy before and after Huffmann coding vs. channel capacity

inDear all, please help me to interpret some strange(?) behaviour of Huffmann coding and entropy. Let me explain it at an example: Consider a...

Dear all, please help me to interpret some strange(?) behaviour of Huffmann coding and entropy. Let me explain it at an example: Consider a source emitting four symbols x1-x4 with probabilities P(x1)=1/3, P(x2)=1/3, P(x3)=1/6, P(x4)=1/6. Calculating the entropy with H=sum(P(xi)*log2(P(xi)) gives us: H=1.918 Bit/symbol. So far so good. We perform Huffmann-Coding, arranging the symbols in the...

## Reed-Solomon FEC necessary to have the same characteristic for symbols and words?

inHi there, I have implemented an almost "universal" (read: compatible with most other decoders output) Reed-Solomon codec. I feel like I have a...

Hi there, I have implemented an almost "universal" (read: compatible with most other decoders output) Reed-Solomon codec. I feel like I have a good intuitive grasp on the whole codec, except for one thing: I just can't understand why we are tied to the same characteristic at both the symbol level and at the word level. Let me explain: if for example you choose to work on GF(2^8), this means ...

## hamming window overlap #2

inContinuing an old post regarding Hamming window overlaps: http://www.dsprelated.com/showthread/comp.dsp/105321-1.php The first answer...

Continuing an old post regarding Hamming window overlaps: http://www.dsprelated.com/showthread/comp.dsp/105321-1.php The first answer gives: "a 50% overlap would give a sum of 1.08". If I wish to reconstruct the input signal perfectly (so the amplitudes are exactly the same), then can I merely subtract the extra ~".08" from all the samples? --------------------------------------- Post...

## Find periodicity of a signal

inHello All I have two signals and I want to know which signal is more periodic than other. My approach: 1. Make both signals zero mean. 2....

Hello All I have two signals and I want to know which signal is more periodic than other. My approach: 1. Make both signals zero mean. 2. Take FFT of both signals. 3. Take sum of squared values of the output FFT within a band of 0.8 Hz to 2.6 Hz If the sum of first signal is high then the signal 1 is more periodic. This approach works but only 90% time. I need the success rate to be ...

## How to plot S-Curve for TED ?

inhi all , I simulated OQpsk modulated data which has 4 samples per symbol (base band). I also simulated the squaring and differentiating...

hi all , I simulated OQpsk modulated data which has 4 samples per symbol (base band). I also simulated the squaring and differentiating based Timing error detector .Now i want to know how well is it performing for that i want to simulate and draw the s -curve. can anyone suggest me a best method to plot s-curve! thanks in advance...

## kelly lochbaum closed mouth

Trying to implement kelly lochbaum for vocal tract I have a problem to represent closed mouth: 0 area gives a k=1, (total reflection of...

Trying to implement kelly lochbaum for vocal tract I have a problem to represent closed mouth: 0 area gives a k=1, (total reflection of presure wave seems ok to me) but 1+k=2 means pressure is not 0 in last tube section just after this junction. What am i misunderstanding? Thanks for your attention victor bombi --------------------------------------- Posted through http://www.DSPRelated.c...

## Round-half-even or Round-toward-nearest

inI just finished the reading of An introduction to different rounding algorithms, http://www.eetimes.com/document.asp?doc_id=1274485. I...

I just finished the reading of An introduction to different rounding algorithms, http://www.eetimes.com/document.asp?doc_id=1274485. I must admit I never pay much attention on the trick of the quantization. The approach of Round-toward-nearest is always used in my design. Did anyone have practical experiences to show the DSP filter performance improved or degraded by using Round-half-even ins...

## detecting an echo in DTMF tone in echo canceler

inI am facing some issue with my echo cancellation module. I am having a correlator and an adaptive filter modules. My correlator will detect...

I am facing some issue with my echo cancellation module. I am having a correlator and an adaptive filter modules. My correlator will detect presence of echo in the DTMF tones and will activate the adaptive filter. The adaptive filter will remove the echo present in the DTMF tones. Activation of adaptive filter is done only if the correlation is above a certain threshold. My issue is t...

## Need a reference for a very simple filter

inHello. I've developed a software that uses STFT with a very simple filter. What the software does is draw a graph of the frequencies as the...

Hello. I've developed a software that uses STFT with a very simple filter. What the software does is draw a graph of the frequencies as the y axis and of time as the x axis. The filter is used to determined which points in the graph will be painted. The filter is extremely simple, it linear, time in-variant, and simply paints only points (f,t) for which their magnitude is in a predefined...