matlab实现16QAM调制

以下是一个MATLAB实现的16QAM调制的示例代码：

clear all; clc;
nsymbol = 100000; % 符号数
M = 16; % 调制阶数
graycode = [0 1 3 2 4 5 7 6 12 13 15 14 8 9 11 10]; % 格雷码映射表

EsN0 = 5:20; % 信噪比范围
snr1 = 10.^(EsN0/10);
msg = randi([0, M-1], 1, nsymbol); % 随机生成调制信息
msg1 = graycode(msg + 1); % 根据格雷码映射表将信息映射为16QAM调制符号
msgmod = qammod(msg1, M); % 进行16QAM调制
scatterplot(msgmod); % 绘制星座图

spow = norm(msgmod).^2 / nsymbol; % 计算调制信号的功率

for i = 1:length(EsN0)
    sigma = sqrt(spow / (2 * snr1(i))); % 计算高斯噪声的标准差
    rx = msgmod + sigma * (randn(1, length(msgmod)) + 1i * randn(1, length(msgmod))); % 添加高斯噪声
    y = qamdemod(rx, M); % 进行16QAM解调
    decmsg = graycode(y + 1); % 根据格雷码映射表将解调结果映射回原始信息
    [err1, ber(i)] = biterr(msg, decmsg, log2(M)); % 计算误比特率和误码率
    [err2, ser(i)] = symerr(msg, decmsg);
end

p4 = 2 * (1 - 1 / sqrt(M)) * qfunc(sqrt(3 * snr1 / (M - 1))); % 计算理论误比特率
ser1 = 1 - (1 - p4).^2;
ber1 = 1 / log2(M) * ser1;

figure()
semilogy(EsN0, ber, 'o', EsN0, ser, '*', EsN0, ser1, EsN0, ber1, '-');
title('16QAM-AWGN')
xlabel('Es/N0');
ylabel('SER AND BER');
legend('BER simulation', 'SER simulation', 'SER theory', 'BER theory');

这段代码实现了通过16QAM调制生成随机消息，并在AWGN信道下进行了模拟。它包括了计算误码率和误比特率，并与理论值进行比较的过程。最后，绘制了误码率和误比特率性能曲线。<span class="em">1</span><span class="em">2</span><span class="em">3</span>
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