Generate PSK signal without out of memory error

[SunJab]

Hi all,

I want to generate a PSK modulated signal with message bits length much larger like over IM bits atleast. I have to first generate the message bits, diffrentially encode them and modulate them at the end. But when I give larger length of bits to the input of PSK modulation vi, it gives me an out of momory error.

What I am doing to get rid of this out of memory error is... I generate 128k message bits using MT generate bits vi, Encode them and modulate them using MT PSK modulate vi and write the modulated signal data repeatedly in the binary file using binary file write vi that I placed within a for loop with loop count of 20 so that I writes modulated signal data for (20*128k= 2.56M encoded bits). But doing so introduces phase discontinuity.

Can anyone suggest a better way of generating PSK signal with message bits atleast 1M and without the out of momory error?

Any kind of help would be highly appretiated.

Best regards

[muks]

Not sure but will this help?

[Dan_K]

Hello Sandee,

The problem here is that when attempting to modulate a large number of bits in a single shot is that you are using the number of bits * samples per symbol * 24 bytes of memory just in creating the message and the modulated signal. In your case if you are using 16 samples per symbol this would require 384 MB of memory for a 1-shot operation of a 1M-bit message.

Luckily this problem has been taken into consideration within the Modulation toolkit (MT). If you take the MT PSK Transmitter VI example that is installed with modulation toolkit you can make some small modifications to implement your desired functionality.

By placing the code within a for loop and wiring the first call VI to the reset inputs of the MT VIs you can reset the VIs on the first iteration of the loop and be able to use the previous iteration states for further iterations. Also, to prevent losing samples due to filter delay you need to make sure to flush the buffers (an input to the MT Modulate PSK VI) on the last iteration.

Let me know how this goes in your specific application.