awgn noise

[sindhu kadirvel]

how can i add awgn to channel using optisystem?

[Damian Marek]

In Optisystem there is a component called the White Light Source in the /Transmitters Library/Optical Sources/ folder, it would be straight forward to use that with a power combiner or coupler to add the noise.

[sindhu kadirvel]

Hi Damian,

Thanks a lot for ur kind reply..can u pls send me a sample paper or example
using optisystem where they add awgn noise in optical wireless channel..It will be so much helpful for me..Thanks in advance.

Regards,
Sindhu

[Damian Marek]

I made a very simple example that is attached. You will see that the output is distorted by the addition of the white light noise.

[sindhu kadirvel]

Hi Damian,
U have already shared me a file on adding awgn noise.I cannot able to open that file facing problem.Can u please share me the screenshot.

[Damian Marek]

Sure no problem. The red line is the signal, blue line noise+signal and green line is the noise.

[sindhu kadirvel]

Thans a lot so much for ur reply damian.Its working now..I have an other doubt now.I want to model the channel for indoor visible light communication.Fso with parameters chosen distance can be used or owc chosen with frequency and distance can be used??i need air as the transmission medium…Which is more suitable?

[Damian Marek]

The FSO component is used to model terrestrial applications, so it is your best choice.

[sindhu kadirvel]

Hi Damian,

Thanks.I tried modelling using FSO .i dont know why my optical power is incerasing after passing through FSO component.Can you please take a look at the file attached and tell me the suggestions where i am going wrong.Pls help me on this.

Thanks,
Sindhu.K

[Damian Marek]

Hi Sindhu,

The geometrical loss model that the FSO component uses is not well suited for this application (short distance). Over 1 m with a 2 mrad beam divergence, there will not be significant geometrical loss, especially if the receiver aperture is 4 times larger than the transmitter.

I would just uncheck the Geometrical Loss box in the FSO component.

Regards

[sindhu kadirvel]

Hi Damian,

I modeled VLC system using white led of wavelength 450 nm and fso channel and added awgn noise.In the receiver side i used
gaussian filter optical filter to filter the noise.In OSA im not getting proper spectrum wn i tried to filter for 450 nm and 1 mhz bandwidth
data rate i have used is 20 kbps only.Where can i find the detailed description about optical filters and bandwidth?I dont knw where i am goin wrong?

[Damian Marek]

Please attach your project file, it might be a sampling rate issue.

[sindhu kadirvel]

Hi damian please take a look of it

[Damian Marek]

Hi Sindhu,

You only had one or two parameters off from a good simulation! The main issue here was the White Light Source, which was not centered at the correct frequency and the power was much too high (~36W) for the input signal. To fix it I set the center frequency of the white light to 450 nm, which is where your signal band is centered and I unchecked the PSD option and set the average power to 1 mW.

The technical background on the White Light source has more info on the PSD option, but basically when it is checked the power output will be the Power multiplied by the Sample rate. The background information can be found from the Help button on the component properties.

Regards

[sindhu kadirvel]

Hi Damian,

I got few doubts again
1.i need to use white LED as input source ahould i use LED or white light source available in optisystem.
Coz they used phosphorescent LEDs for transmisssion in VLC
2.i need to add awgn noise from fluorescent lamp of frequency 50 Hz and 36W
so i have used white light source.in the file which u have sent u have changed the wavelength to 450 nm.
Please help me out with my doubts.

[Damian Marek]

1) If you are driving the LED with an electrical source I would use the LED model. Otherwise the White light Source is fine.

2) Is 50 Hz the frequency of the driving electrical signal? Is 36 W the total power over the frequency range (if so what range) or is it the power spectral density?

Regards

[sindhu kadirvel]

Hi Damian,
50Hz is the powerline frequency of the fluorescent lamp used in indoor environment.
I need to model the channel as awgn channel.This ambient light noise will cause shot noise at the rx and i also need to include thermal noise.
Should i need to include white noise source in channel addition to LED and again in need to include photodiode diode parameters for shotnoise and thermal noise.If so how the optical filtering can be done here.How should i realise the channel here.
Please kindly help on this regards Damian.

[Damian Marek]

Yes, I would include both because the shot noise depends upon the intensity of the input signal. Generally the rule of thumb is to use a Bessel filter with a cutoff frequency of 0.75 * Bit rate. But you could optimize this for your system by trying different values.

[sindhu kadirvel]

May i please know how to remove the file submitted by me .osd file in public forum and have privacy for the files submitted only to optiwave members.

[Damian Marek]

You seemed to have removed the files yourself? Please let me know if you are having any trouble!

As an aside, users who have maintenance and are covered by support can email support@optiwave.com directly for confidential technical support.

[shamsudheen p]

Hi Damian,
I am working on the same visible light communiation as that of sindhu kathirvel. I want to input the data (eihter image or audio) which is fed to LED for modulation purpose. I came to know about using matlab component in optisystem. could you help me to solve this problem?

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