Signal-to-noise ratio on cc2530

thanks llya ,

I came across this formula

Receiver Sensitivity = -174 +10logB + NF +SNR .................................(1)

              where ,

                          Receiver Sensitivity is -98dB (cc2530)

                          NF is noise Figure 

                          SNR is SNRout   range from 5dB - 6dB

                         B - noise Bandwidth 

in (1) i guess 174 is due to the factor of temperature . I what to know whether NF same as that of noise level which you are talking about 

I am new this  i am not sure, please let me know if i am doing  wrong 

and then all i have to do is RSSI - NF to get SNR is it ??? and what/how would i get noise bandwidth B ???

thanking you

Regards 

Darshan

Hi Darshan,

hope this help

1) noise power at the receiver output (in dBm, subject to T = 300 K) is Pn = Pnoise+NF=-174+10log10(B)+NF

where B is the signal bandwidth given in Hz (for the IEEE 802.15.4 2450 MHz PHY equals to 3.5 MHz), NF is the noise factor presented in the corresponding datasheet.

2) subject to calculations with dBms, SNR = RSSI - Pn

Regards,

Ilya

Hi Dinesh,

the Noise Figure (NF) value is defined in the corresponding datasheet  as a rule.

I don't know why, but I see no NF value in the CC2530 chip datasheets. However, the CC2592 datasheet states that its NF is 4.7 dB and that value results in 3 dB improvement compared the sensitivity of the CC2530. Thus, the NF of the CC2530 is about 7.7 dB.

Regarding the Noise Bandwidth, its exact value is equal to the bandwidth of the CC2530's input filter. I have no such information but I guess that the values from 1.1 MHz to 3.5 MHz can be taken for calculations.

Subject to the 2.4 GHz receiver link with O-QPSK/DSSS signals, the minimum SNR that guarantees the target error rate (PER=1%) is 3 dB.

Best regards,

Ilya

Dear Dinesh,

could you give more information about the issue? The outage probability itself is a huge topic...

Best regards,
Ilya

dear ilya,

i have calculated the SNR value from different RSSI value.[SNR=RSSI-Pn]. after that i have calculated the BER corresponding to different SNR value from the formula BER= 0.5*erfc{sqrt(SNRdB)}. then i just want to find the signal outage probability from SNR. i dont know about the outage probability. but i have seen a matlab code for outage probability from SNR but i dont know whether it is right or not?

snr_db= [-15:35]
nr_of_bits = 2^10;
iterations = 1000;
snr_linear = 10.^(snr_db/10);


BER = zeros(1,size(snr_db,2));

for iSNR =1:size(snr_db,2)

sigma=1/sqrt(snr_linear(iSNR));

for i=1:iterations
transmit_bit =round(rand(1,nr_of_bits))*2-1;
h = complex(randn(1,nr_of_bits),randn(1,nr_of_bits));
noise = 1/sqrt(2)*[randn(1,nr_of_bits)+1j*randn(1,nr_of_bits)]*sigma;
received_bits = h.*transmit_bit + noise;
estmtd_h = conj(h);
detected_bits = ((received_bits.*estmtd_h)>=0)*2-1;
nr_of_errors= sum(not(detected_bits == transmit_bit));
BER(iSNR) = BER(iSNR)+ nr_of_errors;
end
BER(iSNR) = BER(iSNR) ./iterations./nr_of_bits;
end

semilogy(snr_db,BER);

Dear Dinesh,

the Matlab script you presented deals with BER calculations only. To put into consideration the outage probability, the capacity metric needs to be considered.

To calculate the outage probability, I'd suggest two basic equations:
C(h ; SNR) = log(1+|h|^2*SNR) - the capacity (SNR is fixed, h is the realization of flat fading Gaussian channel)
pout(R, SNR) = Pr{R > C(h ; SNR)} - the outage probability (R is the target data rate in bits/s/Hz)


Best regards,
Ilya

Dear Dinesh,

the performance of any wireless communication system is strongly depended on the properties of propagation channel. There is a lot of corresponding channel models that are used for theoretical analysis. The Matlab script you provided is based on flat fading Gaussian channel model. In general, it works as the multiplication of transmitter's output signal by some complex random value h (having certain statistic) and the addition of AWGN (having certain power to get target SNR).

Considering such metric as the capacity, multiple runs of the model give a set of the capacity values (the equation I've provided before) for the same fixed SNR. That set can be used to study the statistical properties of the capacity, including outage probability.

It should be noted that the flat fading Gaussian channel model don't allow to get results for some fixed positions of a transmitter and a receiver.

Hope this helps,
Ilya