请写出完成BPSK和QPSK调制在AWGN信道下的SNR-BER误码率性能评估的matlab代码

以下是BPSK和QPSK调制在AWGN信道下的SNR-BER误码率性能评估的MATLAB代码：

clear all;
close all;

% Modulation type
mod_type = 'BPSK'; % 'BPSK' or 'QPSK'

% Channel parameters
SNR_dB = 0:1:15; % SNR in dB
SNR = 10.^(SNR_dB/10); % SNR in linear scale
nbits = 1e5; % number of bits
nerr = zeros(size(SNR)); % number of errors
nframes = 10; % number of frames

% Modulation
if strcmp(mod_type,'BPSK')
  bits = randi([0 1],1,nbits); % generate random bits
  x = 2*bits - 1; % BPSK modulation
else
  bits = randi([0 1],1,2*nbits); % generate random bits
  x = 1/sqrt(2)*(2*bits(1:2:end)-1 + 1i*(2*bits(2:2:end)-1)); % QPSK modulation
end

% AWGN channel
for i=1:length(SNR)
    for j=1:nframes
        % Add noise
        n = sqrt(1/2/SNR(i))*(randn(size(x))+1i*randn(size(x))); 
        
        % Received signal
        y = x + n;
        
        % Demodulation
        if strcmp(mod_type,'BPSK')
            bits_hat = y>0;
        else
            bits_hat = zeros(1,2*nbits);
            bits_hat(1:2:end) = real(y)>0;
            bits_hat(2:2:end) = imag(y)>0;
        end
        
        % Count errors
        nerr(i) = nerr(i) + sum(bits~=bits_hat);
    end
end

% BER calculation
BER = nerr/nbits/nframes;

% Plot results
figure;
semilogy(SNR_dB,BER,'o-');
grid on;
xlabel('SNR (dB)');
ylabel('BER');
if strcmp(mod_type,'BPSK')
    title('BPSK modulation in AWGN channel');
else
    title('QPSK modulation in AWGN channel');
end