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2024080705陈俊杰 #11

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189 changes: 64 additions & 125 deletions src/demodulation.py
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Original file line number Diff line number Diff line change
Expand Up @@ -5,150 +5,94 @@

import numpy as np


def bpsk_demodulate(symbols):
"""
BPSK解调

任务要求：
- 输入：接收到的复数符号序列（可能带噪声）
- 输出：恢复的比特序列
- 判决准则：
实部 > 0 → 比特 0
实部 ≤ 0 → 比特 1

参数:
symbols: 接收到的复数符号数组

返回:
bits: 恢复的比特数组

提示：
- BPSK符号主要在实轴上
- 只需要判断实部的正负即可
- 噪声会使符号偏离理想位置，但判决准则仍然有效

示例：
>>> symbols = np.array([0.9+0.1j, -1.1-0.05j, 0.85+0.2j])
>>> bits = bpsk_demodulate(symbols)
>>> print(bits)
[0 1 0]
"""

# TODO: 实现BPSK解调
# 提示：使用np.real()获取实部，然后判断正负

raise NotImplementedError("请实现BPSK解调函数")
"""BPSK解调"""
# 实部 > 0 → 比特 0；实部 ≤ 0 → 比特 1
return (np.real(symbols) <= 0).astype(int)


def qpsk_demodulate(symbols):
"""
QPSK解调

任务要求：
- 输入：接收到的复数符号序列
- 输出：恢复的比特序列（长度是符号数的2倍）
- 使用最小欧氏距离判决

参数:
symbols: 接收到的复数符号数组

返回:
bits: 恢复的比特数组

提示：
- QPSK有4个参考星座点（理想位置）
- 对每个接收符号，计算它到4个参考点的距离
- 选择距离最小的那个点，输出对应的比特对
- 参考点（格雷码）：
(1+1j)/√2 → 00
(-1+1j)/√2 → 01
(-1-1j)/√2 → 11
(1-1j)/√2 → 10

示例：
>>> symbols = np.array([0.6+0.6j, -0.7+0.8j])
>>> bits = qpsk_demodulate(symbols)
>>> print(bits) # 应该是 [0, 0, 0, 1]
"""

# 定义QPSK参考星座点（格雷码）
"""QPSK解调"""
constellation = {
0: (1 + 1j) / np.sqrt(2), # 00
1: (-1 + 1j) / np.sqrt(2), # 01
3: (-1 - 1j) / np.sqrt(2), # 11
2: (1 - 1j) / np.sqrt(2) # 10
(0, 0): (1 + 1j) / np.sqrt(2),
(0, 1): (-1 + 1j) / np.sqrt(2),
(1, 1): (-1 - 1j) / np.sqrt(2),
(1, 0): (1 - 1j) / np.sqrt(2)
}

# TODO: 实现QPSK解调
# 提示步骤：
# 1. 对每个接收符号，计算到4个参考点的欧氏距离
# 2. 找到距离最小的参考点
# 3. 将参考点的索引转换为2个比特

raise NotImplementedError("请实现QPSK解调函数")

bits = np.zeros(len(symbols) * 2, dtype=int)
points = list(constellation.values())
keys = list(constellation.keys())

for i, sym in enumerate(symbols):
# 计算欧氏距离
dists = [np.abs(sym - p) for p in points]
best_idx = np.argmin(dists)
b0, b1 = keys[best_idx]

bits[2*i] = b0
bits[2*i+1] = b1

return bits


def qam16_demodulate(symbols):
"""
16-QAM解调

任务要求：
- 输入：接收到的复数符号序列
- 输出：恢复的比特序列（长度是符号数的4倍）
- 使用最小欧氏距离判决

参数:
symbols: 接收到的复数符号数组

返回:
bits: 恢复的比特数组

提示：
- 16-QAM有16个参考星座点
- 可以分别对I路和Q路进行判决，简化计算
- I/Q分量的判决（格雷码）：
> 2/√10 → 00
0 ~ 2/√10 → 01
-2/√10 ~ 0 → 11
< -2/√10 → 10
"""

# TODO: 实现16-QAM解调
# 提示：可以采用两种方法
# 方法1：遍历16个参考点，找最小距离（简单但慢）
# 方法2：分别判决I路和Q路（快速且实用）

raise NotImplementedError("请实现16-QAM解调函数")
"""16-QAM解调"""
bits = np.zeros(len(symbols) * 4, dtype=int)

for i, sym in enumerate(symbols):
# 还原归一化以便于判断边界
sym_unnorm = sym * np.sqrt(10)
I = np.real(sym_unnorm)
Q = np.imag(sym_unnorm)

# 判决 I 路
if I > 2:
b0, b1 = 0, 0
elif I > 0:
b0, b1 = 0, 1
elif I > -2:
b0, b1 = 1, 1
else:
b0, b1 = 1, 0

# 判决 Q 路
if Q > 2:
b2, b3 = 0, 0
elif Q > 0:
b2, b3 = 0, 1
elif Q > -2:
b2, b3 = 1, 1
else:
b2, b3 = 1, 0

bits[4*i:4*i+4] = [b0, b1, b2, b3]

return bits


def test_demodulation():
"""
测试解调函数
需要先完成调制函数才能运行
"""
"""测试解调函数"""
from modulation import bpsk_modulate, qpsk_modulate, qam16_modulate
from utils import add_awgn, calculate_ber

print("=" * 50)
print("解调测试")
print("=" * 50)

# 测试BPSK
print("\n1. 测试BPSK解调...")
try:
bits_tx = np.random.randint(0, 2, 100)
symbols = bpsk_modulate(bits_tx)
symbols_rx = add_awgn(symbols, snr_db=10) # 添加10dB噪声
symbols_rx = add_awgn(symbols, snr_db=10)
bits_rx = bpsk_demodulate(symbols_rx)
ber = calculate_ber(bits_tx, bits_rx)
print(f" BER = {ber:.4f} (SNR=10dB)")
print(" ✅ BPSK解调测试通过")
except NotImplementedError:
print(" ⏸️ BPSK解调尚未实现")
except Exception as e:
print(f" ❌ BPSK解调测试失败: {e}")

# 测试QPSK
print("\n2. 测试QPSK解调...")
try:
Expand All @@ -159,28 +103,23 @@ def test_demodulation():
ber = calculate_ber(bits_tx, bits_rx)
print(f" BER = {ber:.4f} (SNR=10dB)")
print(" ✅ QPSK解调测试通过")
except NotImplementedError:
print(" ⏸️ QPSK解调尚未实现")
except Exception as e:
print(f" ❌ QPSK解调测试失败: {e}")

# 测试16-QAM
print("\n3. 测试16-QAM解调...")
try:
bits_tx = np.random.randint(0, 2, 100)
symbols = qam16_modulate(bits_tx)
symbols_rx = add_awgn(symbols, snr_db=15) # QAM需要更高SNR
symbols_rx = add_awgn(symbols, snr_db=15)
bits_rx = qam16_demodulate(symbols_rx)
ber = calculate_ber(bits_tx, bits_rx)
print(f" BER = {ber:.4f} (SNR=15dB)")
print(" ✅ 16-QAM解调测试通过")
except NotImplementedError:
print(" ⏸️ 16-QAM解调尚未实现")
except Exception as e:
print(f" ❌ 16-QAM解调测试失败: {e}")

print("\n" + "=" * 50)

print("\n" + "=" * 50)

if __name__ == "__main__":
test_demodulation()
test_demodulation()
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