BPSK

[NonameNoface]

Hello All , A newbie getting started with LabView . I am not even sure if I am posting in the right forum . But here is something i want to start doing . I am trying to implement a BPSK system in Labview . The first thing I am looking to do is generate a sequence of 1's and -1's after which generate noise (possibly AWGN) and then convolve the data sequence with noise and eventually with the convolved output , try to obtain the data back . I'll be glad if someone can let me know how I can go about getting started. Any help would be appreciated . Regards NonameNoface

[hoffiz]

Hi,

Are you planning on generating this signal with any particular hardware or you just wanted to simulate the modulation in Software? We have some examples in the Modulation Toolkit for BPSK. Please take a look at this DevZone Article: Modulation Toolkit Shipping Examples.  Something that would for sure help you since you are getting started with LabVIEW are going to be these resources: Getting Started with LabVIEW, Getting Started with LabVIEW Virtual Instruments and How Can I Learn LabVIEW?, the first four classes are free.

Regards

[NonameNoface]

Hi Jamie , I am not particularly using any hardware to generate the signals . Instead using the software to generate the signals . I do have the modulation kit already for the QPSK model . So what i have done so far is , used that QPSK model , removed the quadrature components and I am trying to get that to interface with my speedy 33 . First I would like the software part of it to work before i can try anything with the speedy 33 , since I am not sure how i might go about interfacing it with the speedy 33 . The problem that i currently seem to face is , in the receiver part of the BPSK system , I need to be able to detect the phase of the signal after a convolution between the analog input and the carrier . Ideally , i would expect to use the integral function and then determine if the output is a positive or a negative value .if positive , that would mean a binary 1 , if negative a binary 0 . But since i am using it with a speedy 33 . I don't seem to have that option of using a integral function , which is where i want some help with . I am attaching the file of what i wnat I have done so far , if that might give you a idea of what I doing .. Thank you for your help Regards NonameNoface Message Edited by NonameNoface on 03-19-2008 08:12 PM

Message Edited by NonameNoface on 03-19-2008 08:13 PM

[hoffiz]

Hi,

With the modulation toolkit we do have an example that will do a one shot TX and RX is called: “MT PSK Transceiver (One Shot).vi” another example that might be useful will be MT PSK Transceiver (with FFT Spectrum).vi. Both of these examples you only need to change the M-PSK field to two and the simulated modulation and demodulation for BPSK will be done for you. In the second example additive white Gaussian noise is been added to the message.

Now; from the code you attached I can see you are not using the “Modulation Toolkit” in your code and even though I’m missing some VIs I can tell you are actually receiving a BPSK modulated signal as an array of doubles. Now my suggestion will be since phase by itself does not mean anything if it is not referenced is to generate a signal of the same frequency to be use as a reference.  One way to do it will be like they are in this picture: “Electronic Design”.  Other mathematical schemes for determining the “phase change” can be use but it will really be up to you to implement them in LabVIEW. I have done some DSP programming in other TI boards not related to NI and if I recall correctly all the math came from the Z domain.

I hope it helps

[NonameNoface]

Jamie , thanks for the reply ... now i am not sure if I do atcually have the modulation kit . But i am trying the demo version . where am i likely (the directory) to find the modualtion tool kit ? . thank you regards Mano

[NonameNoface]

adding to the last post .... where am i likely (the directory) to find the " MT PSK Transceiver " modulation tool kit after the demo version opens up? . thank you regards Mano

[NonameNoface]

Hi , Yes , i have found the MT PSK Transceiever ( One shot ) system . But when i try to execute it , it comes up with the error saying " Does not support the current Target Type " . Does that mean that the Speedy - 33 does not support this modulation model . Or if you could let me know what could possibly be the reason please .. thank you . Regards Mano ..

[hoffiz]

Hi,

From the error message you got and what I have been able to find in the DSP Module Help it seems that those VIs are not supported by the device. "When you select a VI under a DSP target in the Project Explorer window, the Controls and Functions palettes change to show VIs and functions that the DSP target can support." I’m trying to confirm this information with R&D, but most likely you will have to code your own BPSK scheme and use the “Modulation Toolkit” to compare the results. I'll get back to you with a complete answer.

[NonameNoface]

Hi Jamie , I had the same feeling that I would have to do my own codes . But , for example , if i would want to use a integral function which is available in a normal functions palette , but not under the speedy 33 target type , is it possible that i could import the integral function(or any missing function for that matter ) into the functions palette of the speedy 33 ? . thank you Mano ..

[hoffiz]

Hi Mano,

I have seen knowledge bases where other functions from the “math menu” on the functions palette are used, for example: How Can I Be Successful with Arrays in the LabVIEW DSP Module?  The function use in the knowledge base is included in the palette, but if a function is not included in the function palette then it is not supported.

Another useful resource would be this knowledge base: Which Numeric Data Types are supported by the LabVIEW DSP Module for Speedy33, DSK6711, or DSK6713?

Since the integration function is not included you might be able to do it yourself using loops.  Numerical integration. If you have question regarding how to do the numerical integration you can post in a LabVIEW discussion forum.