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Re: [Discuss-gnuradio] BER calculation using digital_bert_tx.py and digi


From: Hitesh Kasera
Subject: Re: [Discuss-gnuradio] BER calculation using digital_bert_tx.py and digital_bert_rx.py
Date: Fri, 16 Oct 2015 23:53:26 +0530

Hi..

I found the mistake which i was doing in digital_bert_tx.py file.
i was always transmitting 1 but after scrambling when we do packing then according to this statement
self._pack = blocks.unpacked_to_packed_bb(self._mod.bits_per_symbol(), gr.GR_MSB_FIRST) in qpsk modulation in place of 1 it will take 2 bits 0 and 1 so in receiver there will be two bits in place of only 1 thats why the error is >10%.
i tried to correct it by replacing self._mod.bits_per_symbol() to a constant 1 both in qpsk and bpsk and calculated BER for both. For bpsk i used bit rate 250kbits/second and for qpsk i used 500kbits/second. By setting these data rates i am getting same SNR for Both but not same BER. Do i need to change any other parameter for qpsk? if any one has any idea about it please tell me.

Best Regards,
Hitesh
      

On Tue, Oct 13, 2015 at 12:13 AM, Hitesh Kasera <address@hidden> wrote:
Hi everyone,
I am trying to calculate BER for bpsk and qpsk using digital_bert_tx.py and digital_bert_rx.py. i want to compare BER of qpsk and bpsk. At same SNR around 20db i am getting constant .16 BER for qpsk and for bpsk it is 1e-12. when i change the SNR using gain of Transmitter and Receiving end there is no change in BER for qpsk, for bpsk its changes. I am not able to understand why with qpsk its not working. if anyone has any idea or anyone who has calculated BER previously please help me.

Best Regards,
Hitesh


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