function gainControl(G_TX_target, G_PA_dB, Nd, mu)

% Constants
N=length(G_TX_target);	% number of points
Ts = 1.0				% sample period in sec.

atten_res_dB = 0.010;	% attenuator resolution

%mu = 0.1;				% Averaging of measurement
knoise = 0.04;			% measurement noise

f_theta = 0.001;    	% Hz Temperature drift frequency	
a_theta = 5;			% dB Temperature drift level dB

atten_dB=40;				% initial value: Controller atten_ output


state = zeros(1, Nd-1);	% filter state for delay

error = 0;
enabled = 1;
LATENCY = 3;
latency_count = LATENCY;

for i=1:N,
	G_TX = G_PA_dB(i) - atten_dB + knoise*randn();
	[G_TX_est, state] = filter([zeros(1,Nd-1) 1], 1, G_TX, state);
	error_last = error;
	error = G_TX_est - G_TX_target(i);
	derror = abs(error) - abs(error_last);
	atten_dB = atten_dB + mu*error;
	atten_dB = getAtten(atten_dB, atten_res_dB);

	if enabled == 0
		G_TX = -120;
	end
	error_v(i) = error;
	derror_v(i) = derror;
	gain_dB_v(i) = G_TX;
	atten_v(i) = atten_dB;
	
	if enabled == 1
		if derror > -0.1 && abs(error) > 3
			if latency_count == 0
				enabled = 0;
			else
				latency_count = latency_count - 1;
			end
		else
			latency_count = LATENCY;
		end
	end
	
end

subplot(4,1,1)
plot((0:N-1)*Ts, G_TX_target, (0:N-1)*Ts, G_PA_dB); grid; legend('G_{TX_target}', 'G_{PA}'); xlabel('t/s'); ylabel('dB')
subplot(4,1,2)
plot((0:N-1)*Ts, error_v, (0:N-1)*Ts, derror_v); grid; legend('error', 'derror'); xlabel('t/s'); ylabel('dB')
subplot(4,1,3)
plot((0:N-1)*Ts, gain_dB_v); grid; title('Gain_{TX}'); xlabel('t/s'); ylabel('dB')
subplot(4,1,4)
plot((0:N-1)*Ts, atten_v); grid; title('atten'); xlabel('t/s'); ylabel('dB')

function atten = getAtten(gain_dB, res_dB)
	atten = max(0, min(40, res_dB*fix(gain_dB/res_dB)));