error on piecewise 'First argument must be a condition.'

I want to calculate SNR as below, but error message 'First argument must be a condition.'displayed. I think first argument is condition so I can't understand why my expression is bad. please tell me what is the problem of my code.

%% parameter
syms TOP
Fp=48;
Nch=103;
Rch=0.064;     
delta=0.0875;  
B=9;
h = 6.62e-34;   
F = 10^0.5;
c=299792458;   
lamda=1577.5e-9; 
G = 10^0.95;
NS=133;                             
gammaS=1.3;     
betaS=21.7;     
alfaS=0.023;
%% calculation
ASES = NS*h*c/lamda*F*(Rch*1e+12)*(G-1);
etaS = NS*4*gammaS^2/(27*pi*betaS*alfaS*(Rch)^2)*asinh(pi^2*betaS/(4*alfaS)*(Rch)^2*Nch^(2*Rch/delta));
popt=(ASES/(2*etaS))^(1/3);
NLIS = etaS*(0.001*(TOP/Nch))^3;
SNR1 = (0.001*(TOP/Nch))/(ASES+NLIS)*0.5;
SNR2=popt/(1.5*ASES)*0.5;
pch =(0.001*(TOP/Nch));
SNR = piecewise(pch<popt,SNR1,0,SNR2);
T = Fp*2*Rch/delta*B*log2(1+SNR)

Answer 1

[KALYAN ACHARJYA]

As per the syntax definition of the piecewise funtion

piecewise(condition, value, condition, value....)

In the above code

SNR = piecewise(pch<popt,SNR1,0,SNR2);
%.............................^ is that condition

Here modification

piecewise(condition, value, otherwise)
SNR = piecewise(pch<popt,SNR1,SNR2);

Pls check as per requirements.

[柊介 小山内]

thank you. I can resolve problem!