【信号处理】Python实现BPSK、QPSK、8PSK、8QAM、16QAM、64QAM的调制和解调

傷城~ 2022-08-28 10:45 640阅读 0赞

### 目录 ###

*  1 引言
 *  2 实现
 *   *  2.1 调制
     *  2.2 解调
 *  3 完整编码和解码的例子

# 1 引言 #

本文不涉及原理讲解，只提供实现方法。需要借助Commpy开源包去实现通信中的各种处理。

*  源码下载地址[Commpy源码下载][Commpy]
 *  [Commpy官方文档][Commpy 1]

安装方法

方法一
    pip install scikit-commpy
    方法二
    git clone https://github.com/veeresht/CommPy.git
    cd CommPy
    python setup.py install

# 2 实现 #

## 2.1 调制 ##

import commpy as cpy
    bits = np.random.binomial(n=1,p=0.5,size=(128))
    Modulation_type ="BPSK"
    if Modulation_type=="BPSK":
    	bpsk = cpy.PSKModem(2)
      symbol = bpsk.modulate(bits)
      return symbol
    elif Modulation_type=="QPSK":
    	qpsk = cpy.PSKModem(4)
      symbol = qpsk.modulate(bits)
      return symbol
    elif Modulation_type=="8PSK":
    	psk8 = cpy.PSKModem(8)
      symbol = psk8.modulate(bits)
      return symbol
    elif Modulation_type=="8QAM":
    	qam8 = cpy.QAMModem(8)
      symbol = qam8.modulate(bits)
      return symbol
    elif Modulation_type=="16QAM":
    	qam16 = cpy.QAMModem(16)
      symbol = qam16.modulate(bits)
      return symbol
    elif Modulation_type=="64QAM":
    	qam64 = cpy.QAMModem(64)
      symbol = qam64.modulate(bits)
      return symbol

## 2.2 解调 ##

# 和调制一样，需要先定义调制方法的类，再去调用解调的函数。
    import commpy as cpy
    bits = np.random.binomial(n=1,p=0.5,size=(128))
    # Modem : QPSK
    modem = mod.QAMModem(4)
    signal = modem.modulate(bits)
    modem.demodulate(signal, 'hard')

# 3 完整编码和解码的例子 #

来源[Commpy 例子][Commpy 2]

# Authors: CommPy contributors
    # License: BSD 3-Clause
    
    from __future__ import division, print_function  # Python 2 compatibility
    
    import math
    
    import matplotlib.pyplot as plt
    import numpy as np
    
    import commpy.channelcoding.convcode as cc
    import commpy.channels as chan
    import commpy.links as lk
    import commpy.modulation as mod
    import commpy.utilities as util
    
    # =============================================================================
    # Convolutional Code 1: G(D) = [1+D^2, 1+D+D^2]
    # Standard code with rate 1/2
    # =============================================================================
    
    # Number of delay elements in the convolutional encoder
    memory = np.array(2, ndmin=1)
    
    # Generator matrix
    g_matrix = np.array((0o5, 0o7), ndmin=2)
    
    # Create trellis data structure
    trellis1 = cc.Trellis(memory, g_matrix)
    
    # =============================================================================
    # Convolutional Code 1: G(D) = [1+D^2, 1+D^2+D^3]
    # Standard code with rate 1/2
    # =============================================================================
    
    # Number of delay elements in the convolutional encoder
    memory = np.array(3, ndmin=1)
    
    # Generator matrix (1+D^2+D^3 <-> 13 or 0o15)
    g_matrix = np.array((0o5, 0o15), ndmin=2)
    
    # Create trellis data structure
    trellis2 = cc.Trellis(memory, g_matrix)
    
    # =============================================================================
    # Convolutional Code 2: G(D) = [[1, 0, 0], [0, 1, 1+D]]; F(D) = [[D, D], [1+D, 1]]
    # RSC with rate 2/3
    # =============================================================================
    
    # Number of delay elements in the convolutional encoder
    memory = np.array((1, 1))
    
    # Generator matrix & feedback matrix
    g_matrix = np.array(((1, 0, 0), (0, 1, 3)))
    feedback = np.array(((2, 2), (3, 1)))
    
    # Create trellis data structure
    trellis3 = cc.Trellis(memory, g_matrix, feedback, 'rsc')
    
    # =============================================================================
    # Basic example using homemade counting and hard decoding
    # =============================================================================
    
    # Traceback depth of the decoder
    tb_depth = None  # Default value is 5 times the number or memories
    
    for trellis in (trellis1, trellis2, trellis3):
        for i in range(10):
            # Generate random message bits to be encoded
            message_bits = np.random.randint(0, 2, 1000)
    
            # Encode message bits
            coded_bits = cc.conv_encode(message_bits, trellis)
    
            # Introduce bit errors (channel)
            coded_bits[np.random.randint(0, 1000)] = 0
            coded_bits[np.random.randint(0, 1000)] = 0
            coded_bits[np.random.randint(0, 1000)] = 1
            coded_bits[np.random.randint(0, 1000)] = 1
    
            # Decode the received bits
            decoded_bits = cc.viterbi_decode(coded_bits.astype(float), trellis, tb_depth)
    
            num_bit_errors = util.hamming_dist(message_bits, decoded_bits[:len(message_bits)])
    
            if num_bit_errors != 0:
                print(num_bit_errors, "Bit Errors found!")
            elif i == 9:
                print("No Bit Errors :)")
    
    # ==================================================================================================
    # Complete example using Commpy features and compare hard and soft demodulation. Example with code 1
    # ==================================================================================================
    
    # Modem : QPSK
    modem = mod.QAMModem(4)
    
    # AWGN channel
    channels = chan.SISOFlatChannel(None, (1 + 0j, 0j))
    
    # SNR range to test
    SNRs = np.arange(0, 6) + 10 * math.log10(modem.num_bits_symbol)
    
    
    # Modulation function
    def modulate(bits):
        return modem.modulate(cc.conv_encode(bits, trellis1, 'cont'))
    
    
    # Receiver function (no process required as there are no fading)
    def receiver_hard(y, h, constellation, noise_var):
        return modem.demodulate(y, 'hard')
    
    
    # Receiver function (no process required as there are no fading)
    def receiver_soft(y, h, constellation, noise_var):
        return modem.demodulate(y, 'soft', noise_var)
    
    
    # Decoder function
    def decoder_hard(msg):
        return cc.viterbi_decode(msg, trellis1)
    
    
    # Decoder function
    def decoder_soft(msg):
        return cc.viterbi_decode(msg, trellis1, decoding_type='soft')
    
    
    # Build model from parameters
    code_rate = trellis1.k / trellis1.n
    model_hard = lk.LinkModel(modulate, channels, receiver_hard,
                              modem.num_bits_symbol, modem.constellation, modem.Es,
                              decoder_hard, code_rate)
    model_soft = lk.LinkModel(modulate, channels, receiver_soft,
                              modem.num_bits_symbol, modem.constellation, modem.Es,
                              decoder_soft, code_rate)
    
    # Test
    BERs_hard = model_hard.link_performance(SNRs, 10000, 600, 5000, code_rate)
    BERs_soft = model_soft.link_performance(SNRs, 10000, 600, 5000, code_rate)
    plt.semilogy(SNRs, BERs_hard, 'o-', SNRs, BERs_soft, 'o-')
    plt.grid()
    plt.xlabel('Signal to Noise Ration (dB)')
    plt.ylabel('Bit Error Rate')
    plt.legend(('Hard demodulation', 'Soft demodulation'))
    plt.show()

[Commpy]: https://github.com/veeresht/CommPy/tree/15eef391a30097cb2801222817179cd56bc8baa4
[Commpy 1]: https://commpy.readthedocs.io/en/latest/index.html
[Commpy 2]: https://github.com/veeresht/CommPy/blob/15eef391a30097cb2801222817179cd56bc8baa4/commpy/examples/conv_encode_decode.py