filter

[desham]

My criteria is how it can handle the noise.what % of noise it can handle.Do i need any other filter to remove the noise effectively.

I need to calculate the %, can u suggest me i dont have any idea on it

[johnsold]

The reason your number of samples changes as you change frequency is the way the Simulate Signal Express VI is set up.  Under Timing both Automatic number of samples and Integer number of cycles are checked.  That combination will force the number of samples to change as you change frequency.

How do you define the "% of noise?" I have worked with filters and signal processing for many years and have never encountered that terminology.  Whether a filter is the best way to reduce noise depends very strongly on the system bandwidth and the nature of the signal(s) and noise.  You have not really described either.

Please define your system and tell us what you are trying to do. What is the source of the signals? What is the source or nature of the noise? What do you want to do with the signal after it is processed?

Lynn

[egraham]

Desham,

I'm not completely clear on what it is you're trying to do, but run the attached VI and see if this is what you're looking for. All it's doing is calculating the percent error based on what we know the signal should be compared to the filtered signal. Depending on what you're trying to do, there are so many ways to go about it.

The producer/consumer design doesn't have to be there, but if you end up acquiring real data rather than simulating data, it splits the tasks up between multiple processors.

Eric

[desham]

I want to  transmit the signal with cryptography algorithms and at the receiver i am filtering the signal (for securely receiving data  without any noise).i have to retransmit the signal if any samples drop .

When you pass samples through a filter, a certain number of the output samples will not be correct because the filter didn't block all the noise.  Wouldn't a percentage of effectivity be the number of bad samples divided by the total number of samples?

[egraham]

OK... so what is a bad sample? What is your criteria for judging whether or not a sample is bad?

[desham]

i dont know exactly what to do. 

we can filter the noise, From the filtering how to get the bad samples.... last 2 to 3 days  i am working on this.

My prof. said to work it out. But it is out of my reach. He told to find how much percentage my filter can handle the noise(efficiency).

Is there any way to find out efficiency. Please let me know

[egraham]

You can Google digital filter efficiency and several links come up that suggest this is something that has been studied before.

http://www.maik.ru/abstract/optelins/9/optelins0272_abstract.pdf

I would suggest before you continue tinkering with LabVIEW you should try to determine what the definition of efficiency is for your assignment. In analog filters efficiency might be related to power consumption. In the case of computer processing it could be related to how much it requires of the processor. I'm surprised your instructor hasn't given you any direction or you don't have any text book you can reference for ideas. It seems like some more reasearch is in order before spending any more time with LV.

[johnsold]

After looking at the VI you posted, I am thoroughly confused.

You create a simulated sine wave with noise.  You convert this to a digital waveform and then flatten the result to a string.  You hash the string and concatenate a key to the hashed string.  The key is not used in the hash process.

The vertical line on the BD apparently represents transmitting the data.

On the receiving side the original flattened string in hashed again and then concatenated with a different string. rsa encryption.vi and rsa decryption.vi use different algorithms and produce different results.  So of course the result is never equal to the transmitted string.  You unflatten the original flattened string, convert the digital waveform to an analog waveform and filter it.

The you repeat everything except the signal generation in the second case.

Please keep the size of your diagrams to one screen.  Yours can be reduced to that by just cleaning up the diagrams (provided you have a fairly large screen.

Presumably you are trying to simulate some kind of communication system.  Your simulation does not resemble any kind of communication system I have evert seen.  Filtering is usually applied to the analog signal before it is digitized.  The received signal is always analog, even if it represents a digital waveform.  After the signal is digitized, error correction is handled by error correcting codes, which may resemble the encryption process, although they have very different purposes.  Your encryption/decryption does nothing meaningful from a data security perspective because the keys are not used in the process.  I would expect the hash function to have a key input.

Lynn

[desham]

if noise is increased in the sine wave what will be the effect on transmissions, retransmissions and throughput of the signal

[johnsold]

The way you put your VI together, not much.

1. Try connecting the output of the DWDT Analog to Digital.vi directly to the DDWDT Digital to Analog.vi and the output to a graph.  You should get back what you put in except for quantization errors.  Quantization errors should be on the order of 2^-16 or one part in 65536.  However, the input is about 25 peak to peak and the output is 2 peak to peak and no longer remotely sinusoidal.

2. Why? Read the detailed help for the A/D converter.  You did not specify the full scale range and the default value clips your signal.  Increasing the noise will have a negligible effect.

3. The nature of the signal and the noise have absolutely nothing to do with transmission, retransmission, and throughput in the resend2.vi.  Transmission in that VI is lossless, noiseless, and zero delay.  In other words a perfect channel.  A typical data transmission model puts loss, noise, distortion, dispersion, and delay between the transmitter and the receiver.  You have a wire.

4. Then you do everything twice.  Notice that Filtered Signals 3 and 4 are very similar.  After the clipping in the first digitization, everything reproduces pretty well.

5. What is the purpose of the hash and rsa VIs? You only seem to check to see if hashing the same signal twice and concatenating it with different keys will give identical results, which of course it will not.

Lynn