How to add same Awgn noise to different wireless signals? Also how to add transmitter noise to the signal in Matlab?

Hello everyone,

I am working on the simple simulation of wireless signal for LR-WPAN devices of IEEE 802.15.4™ standard . I am using OQPSK modulation for this purpose.

So in my experiment I would like to have same noise for all transmitted signals, but function

out = awgn(in,snr)

every time creates a random white gaussian noise that I apply to the signal. I tried the following format

out = awgn(in,snr,signalpower,seed)

where I explicitly set seed to 0 ,

and here is the snippet of my code:

waveform1 = lrwpan.PHYGeneratorOQPSK(message1_2, spc, '2450 MHz')
waveform2 = lrwpan.PHYGeneratorOQPSK(message2_1, spc, '2450 MHz')
spc = 4; 
K = 2;      % information bits per symbol
%applying white gaussian noise to both signals
SNR = 10*log10(spc) + 10*log10(K);
received_at_node2 = awgn(waveform1, SNR, -20, 0);
received_at_node1 = awgn(waveform2, SNR, -20, 0);

This makes signals similar however they are not exactly the same. Is there any way to make awgn repeatable for all the signal it is added to?

Also I would like to consider noise caused by transmitter and add it to my signals. What is the best way to do it and what are optimal values for this type of noise?

p.s. both signals are identical except that source and destination address fields are different.

Thanks in advance.