1 | %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
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2 | % Using WARPLab (SISO configuration) to Transmit Bits Over a Wireless |
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3 | % Channel . |
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4 | %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
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5 | |
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6 | % This matlab srcipt generates a bitstream, modulates the bitstream using |
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7 | % DQPSK, transmits the modulated symbols over a wireless channel using |
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8 | % WARPLab, and demodulates the received signal to obtain the |
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9 | % transmitted bits. Bit error rate (BER) is computed by comparing the |
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10 | % transmitted bitstream with the bitstream recovered at the receiver |
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11 | |
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12 | % The specific steps implemented in this script are the following: |
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13 | |
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14 | % 0. Initialization, define paramters, create pulse shaping filter, and |
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15 | % create reference matrix for detection of preamble |
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16 | % 1. Generate a random bit stream and map it to symbols |
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17 | % 2. Modulate the symbols (map symbols to constellation points) and append |
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18 | % preamble symbols |
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19 | % 3. Upsample the modulated symbols with the appended preamble and filter |
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20 | % using a pulse shaping filter |
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21 | % 4. Upconvert from baseband to 5MHz to avoid radio DC attenuation |
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22 | % 5. Transmit the signal over a wireless channel using Warplab |
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23 | % 6. Downconvert from 5MHz to baseband |
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24 | % 7. Filter the received signal with a Matched Filter (matched to the pulse |
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25 | % shaping filter), detect preamble, and downsample output of Matched Filter |
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26 | % 8. Demodulate and recover the transmitted bitstream |
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27 | % 9. Compute the Bit Error Rate (BER) and close sockets |
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28 | |
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29 | % Part of this code was adapted from Matlab's commdoc_mod and commdoc_rrc |
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30 | % examples. |
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31 | |
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32 | %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
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33 | % 0. Initialization, define paramters, create pulse shaping filter, and |
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34 | % create reference matrix for detection of preamble |
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35 | %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
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36 | % Define basic parameters |
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37 | M = 4; % Size of signal constellation |
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38 | k = log2(M); % Number of bits per symbol |
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39 | nsamp = 8; % Oversampling rate or Number of samples per symbol |
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40 | |
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41 | % Define parameters related to the pulse shaping filter and create the |
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42 | % pulse shaping filter |
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43 | % This pulse shaping filter is a Squared Root Raised Cosine (SRRC) filter |
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44 | filtorder = 64; % Filter order |
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45 | delay = filtorder/(nsamp*2); % Group delay (# of input samples). Group |
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46 | % delay is the time between the input to the filter and the filter's peak |
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47 | % response counted in number of input samples. In number of output samples |
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48 | % the delay would be equal to 'delay*nsam'. |
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49 | rolloff = 0.3; % Rolloff factor of filter |
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50 | rrcfilter = rcosine(1,nsamp,'fir/sqrt',rolloff,delay); % Create SRRC filter |
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51 | |
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52 | % Plot the filter's impulse response in a stem plot |
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53 | figure; % Create new figure window. |
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54 | stem(rrcfilter); |
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55 | title('Raised Cosine Impulse Response'); |
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56 | xlabel('n (samples)'); ylabel('Amplitude'); |
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57 | |
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58 | % Define number of symbols to process, number of bits to process, and the |
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59 | % preamble. |
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60 | % The Warplab transmit buffer can store a maximum of 2^14 samples, the |
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61 | % number of samples per symbol is equal 'nsam', and the SRRC filter delay |
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62 | % in number of samples is equal to 'delay*nsam'. Consequently, the total |
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63 | % number of symbols to be transmitted must be less than |
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64 | % (2^14-200)/nsam-2*delay. We subtract extra 200 to account for jitter in |
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65 | % sync trigger. |
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66 | nsym = floor((2^14-200)/nsamp-2*delay); % Number or symbols to transmit |
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67 | preamble = [-1;-1;-1;1;-1;0;0;0;0;0;0;0;0]; % Preamble is a Barker sequence |
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68 | % modulated with BPSK |
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69 | nsym_preamble = length(preamble); % number of symbols in preamble |
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70 | nsym_payload = nsym-nsym_preamble; |
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71 | nbits = floor(nsym_payload*k); % Number of bits to process |
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72 | |
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73 | % Create a reference matrix used for detection of the preamble in the |
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74 | % received signal. We will correlate the received signal with the reference |
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75 | % matrix |
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76 | preamble_upsamp = upsample(preamble,nsamp); % Upsample preamble |
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77 | length_preamble_upsamp = length(preamble_upsamp); |
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78 | corr_window = 300; % We expect to find the preamble within the first |
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79 | % 300 received samples |
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80 | reference_samples = zeros(corr_window,1); % Create reference vector. |
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81 | reference_samples(1:length_preamble_upsamp) = preamble_upsamp; |
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82 | % First samples of reference vector correspond to the |
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83 | % preamble upsampled |
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84 | reference_matrix = toeplitz(reference_samples,... |
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85 | circshift(reference_samples(corr_window:-1:1),1)); |
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86 | % Create reference matrix. The first column of the reference |
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87 | % matrix is equal to the reference_samples vector. The i-th column |
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88 | % of the reference matrix is equal to circular shift of the |
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89 | % reference samples vector, it is a shift down by i samples. |
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90 | |
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91 | |
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92 | %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
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93 | % 1. Generate a random bit stream and map it to symbols |
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94 | %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
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95 | |
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96 | % Create a random binary data stream as a column vector. |
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97 | x = randint(nbits,1); |
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98 | |
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99 | % Map bits in vector x into k-bit symbols |
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100 | xsym = bi2de(reshape(x,k,length(x)/k).','left-msb'); |
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101 | |
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102 | % Stem plot of bits and symbols |
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103 | % Plot first 40 bits in a stem plot. |
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104 | figure; |
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105 | subplot(2,1,1) |
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106 | stem(x(1:40),'filled'); |
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107 | title('Random Bits'); |
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108 | xlabel('Bit Index'); ylabel('Binary Value'); |
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109 | % Plot first 40/k symbols in a stem plot. |
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110 | subplot(2,1,2) |
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111 | stem(xsym(1:40/k),'filled'); |
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112 | title('Random Bits Mapped to Symbols'); |
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113 | xlabel('Symbol Index'); ylabel('Integer Value'); |
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114 | |
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115 | %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
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116 | % 2. Modulate the symbols (map symbols to constellation points) and append |
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117 | % preamble symbols |
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118 | %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
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119 | |
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120 | % Modulate using DQPSK |
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121 | ytx_mod = dpskmod(xsym,M); |
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122 | |
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123 | % Append preamble |
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124 | ytx_mod = [preamble;ytx_mod]; |
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125 | |
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126 | %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
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127 | % 3. Upsample the modulated symbols with the appended preamble and filter |
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128 | % using a pulse shaping filter |
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129 | %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
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130 | % Upsample and apply square root raised cosine filter. |
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131 | ytx_mod_filt = rcosflt(ytx_mod,1,nsamp,'filter',rrcfilter); |
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132 | |
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133 | % Stem Plot of modulated symbols before and after Squared Root Raised |
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134 | % Cosine (SRRC) filter |
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135 | % Plots first 30 symbols. |
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136 | % Plots I and Q in different windows |
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137 | figure; % Create new figure window. |
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138 | subplot(2,1,1) |
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139 | stem([1:nsamp:nsamp*30],real(ytx_mod(1:30))); |
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140 | hold |
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141 | stem(real(ytx_mod_filt(1+delay*nsamp:1+30*nsamp+delay*nsamp)),'r'); |
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142 | title('I Signal'); |
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143 | xlabel('n (sample)'); ylabel('Amplitude'); |
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144 | legend('Before SRRC Filter','After SRRC Filter'); |
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145 | subplot(2,1,2) |
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146 | stem([1:nsamp:nsamp*30],imag(ytx_mod(1:30))); |
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147 | hold |
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148 | stem(imag(ytx_mod_filt(1+delay*nsamp:1+30*nsamp+delay*nsamp)),'r'); |
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149 | title('Q Signal'); |
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150 | xlabel('n (sample)'); ylabel('Amplitude'); |
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151 | |
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152 | %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
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153 | % 4. Upconvert from baseband to 5MHz to avoid radio DC attenuation |
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154 | %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
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155 | time = [0:1:length(ytx_mod_filt)-1]/40e6; % Sampling Freq. is 40MHz |
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156 | ytx_mod_filt_up = ytx_mod_filt .* exp(sqrt(-1)*2*pi*5e6*time).'; |
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157 | |
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158 | %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
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159 | % 5. Transmit the signal over a wireless channel using Warplab |
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160 | %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
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161 | % Follow the steps for transmission and reception of data using Warplab. |
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162 | % These are the steps in the matlab script warplab_example_TxRx.m |
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163 | |
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164 | % In this example the vector to transmit is the 'ytx_mod_filt' vector. |
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165 | |
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166 | %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
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167 | % 5.0. Initializaton and definition of parameters |
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168 | %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
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169 | %Load some global definitions (packet types, etc.) |
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170 | warplab_defines |
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171 | |
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172 | % Create Socket handles and intialize nodes |
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173 | [socketHandles, packetNum] = warplab_initialize; |
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174 | |
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175 | % Separate the socket handles for easier access |
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176 | % The first socket handle is always the magic SYNC |
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177 | % The rest of the handles are the handles to the WARP nodes |
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178 | udp_Sync = socketHandles(1); |
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179 | udp_node1 = socketHandles(2); |
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180 | udp_node2 = socketHandles(3); |
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181 | |
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182 | % Define WARPLab parameters. |
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183 | % Note: For this experiment node 1 will be set as the transmitter and node |
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184 | % 2 will be set as the receiver (this is done later in the code), hence, |
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185 | % there is no need to define receive gains for node 1 and there is no |
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186 | % need to define transmitter gains for node 2. |
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187 | |
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188 | TxDelay = 100; % Number of noise samples per Rx capture. In [0:2^14] |
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189 | TxLength =length(ytx_mod_filt_up); % Length of transmission. In [0:2^14-1-TxDelay] |
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190 | CarrierChannel = 12; % Channel in the 2.4 GHz band. In [1:14] |
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191 | Node1_Radio2_TxGain_BB = 3; % Tx Baseband Gain. In [0:3] |
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192 | Node1_Radio2_TxGain_RF = 40; % Tx RF Gain. In [0:63] |
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193 | Node2_Radio2_RxGain_BB = 13; % Rx Baseband Gain. In [0:31] |
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194 | Node2_Radio2_RxGain_RF = 2; % Rx RF Gain. In [1:3] |
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195 | TxMode = 0; % Transmission mode. In [0:1] |
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196 | % 0: Single Transmission |
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197 | % 1: Continuous Transmission. Tx board will continue |
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198 | % transmitting the vector of samples until the user manually |
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199 | % disables the transmitter. |
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200 | Node2_MGC_AGC_Select = 0; % Set MGC_AGC_Select=1 to enable Automatic Gain Control (AGC). |
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201 | % Set MGC_AGC_Select=0 to enable Manual Gain Control (MGC). |
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202 | % By default, the nodes are set to MGC. |
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203 | |
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204 | % Download the WARPLab parameters to the WARP nodes. |
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205 | % The nodes store the TxDelay, TxLength, and TxMode parameters in |
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206 | % registers defined in the WARPLab sysgen model. The nodes set radio |
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207 | % related parameters CarrierChannel, TxGains, and RxGains, using the |
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208 | % radio controller functions. |
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209 | % The TxDelay, TxLength, and TxMode parameters need to be known at the transmitter; |
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210 | % the receiver doesn't require knowledge of these parameters (the receiver |
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211 | % will always capture 2^14 samples). For this exercise node 1 will be set as |
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212 | % the transmitter (this is done later in the code). Since TxDelay, TxLength and |
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213 | % TxMode are only required at the transmitter we download the TxDelay, TxLength and |
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214 | % TxMode parameters only to the transmitter node (node 1). |
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215 | warplab_writeRegister(udp_node1,TX_DELAY,TxDelay); |
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216 | warplab_writeRegister(udp_node1,TX_LENGTH,TxLength); |
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217 | warplab_writeRegister(udp_node1,TX_MODE,TxMode); |
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218 | % The CarrierChannel parameter must be downloaded to all nodes |
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219 | warplab_setRadioParameter(udp_node1,CARRIER_CHANNEL,CarrierChannel); |
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220 | warplab_setRadioParameter(udp_node2,CARRIER_CHANNEL,CarrierChannel); |
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221 | % Node 1 will be set as the transmitter so download Tx gains to node 1. |
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222 | warplab_setRadioParameter(udp_node1,RADIO2_TXGAINS,(Node1_Radio2_TxGain_RF + Node1_Radio2_TxGain_BB*2^16)); |
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223 | % Node 2 will be set as the receiver so download Rx gains to node 2. |
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224 | warplab_setRadioParameter(udp_node2,RADIO2_RXGAINS,(Node2_Radio2_RxGain_BB + Node2_Radio2_RxGain_RF*2^16)); |
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225 | % Set MGC mode in node 2 (receiver) |
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226 | warplab_setAGCParameter(udp_node2,MGC_AGC_SEL, Node2_MGC_AGC_Select); |
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227 | |
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228 | %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
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229 | % 5.1. Generate a vector of samples to transmit and send the samples to the |
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230 | % WARP board (Sample Frequency is 40MHz) |
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231 | %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
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232 | % Prepare some data to be transmitted |
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233 | |
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234 | % Scale signal to transmit so that it spans [-1,1] range. We do this to |
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235 | % use the full range of the DAC at the tranmitter |
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236 | scale = 1 / max( [ max(real(ytx_mod_filt_up)) , max(imag(ytx_mod_filt_up)) ] ); |
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237 | ytx_mod_filt_up = scale*ytx_mod_filt_up; |
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238 | |
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239 | Node1_Radio2_TxData = ytx_mod_filt_up.'; % Create a signal to transmit. Signal must be a |
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240 | % row vector |
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241 | |
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242 | % Download the samples to be transmitted |
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243 | % Hints: |
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244 | % 1. The first argument of the 'warplab_writeSMRO' function identifies the |
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245 | % node to which samples will be downloaded to. In this exercise we will set |
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246 | % node 1 as the transmitter node, the id or handle to node 1 is 'udp_node1'. |
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247 | % 2. The second argument of the 'warplab_writeSMRO' function identifies the |
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248 | % transmit buffer where the samples will be written. A node programmed with |
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249 | % the warplab_mimo_2x2_v04.bit bitstream has 2 transmit buffers and a node |
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250 | % programmed with the warplab_mimo_4x4_v04.bit bitstream has 4 transmit |
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251 | % buffers. For this exercise we will transmit from radio 2, hence, samples |
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252 | % must be downloaded to radio 2 Tx buffer, the id for this buffer is |
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253 | % 'RADIO2_TXDATA'. |
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254 | % 3. The third argument of the 'warplab_writeSMWO' function is the |
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255 | % vector of samples to download, it must be a row vector. For this |
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256 | % exercise the 'Node1_Radio2_TxData' vector is the vector of samples to be |
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257 | % transmitted, hence, this is the vector that must be downloaded to radio 2 |
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258 | % Tx buffer. |
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259 | |
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260 | warplab_writeSMWO(udp_node1, RADIO2_TXDATA, Node1_Radio2_TxData); |
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261 | |
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262 | %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
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263 | % 5.2. Prepare WARP boards for transmission and reception and send trigger to |
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264 | % start transmission and reception (trigger is the SYNC packet) |
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265 | %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
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266 | % The following lines of code set node 1 as transmitter and node 2 as |
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267 | % receiver; transmission and capture are triggered by sending the SYNC |
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268 | % packet. |
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269 | |
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270 | % Enable transmitter radio path in radio 2 in node 1 (enable radio 2 in |
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271 | % node 1 as transmitter) by sending the RADIO2_TXEN command to node 1 using |
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272 | % the 'warplab_sendCmd' function. |
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273 | % Hints: |
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274 | % 1. The first argument of the 'warplab_sendCmd' function identifies the |
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275 | % node to which the command will be sent to. The id or handle to node 1 is |
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276 | % 'udp_node1'. |
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277 | % 2. The second argument of the 'warplab_sendCmd' function identifies the |
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278 | % command that will be sent. |
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279 | % 3. The third argument of the 'warplab_sendCmd' command is a field that is |
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280 | % not used at the moment, it may be used in future versions of WARPLab to |
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281 | % keep track of packets. Use 'packetNum' as the third argument of the |
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282 | % 'warplab_sendCmd' command. |
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283 | warplab_sendCmd(udp_node1, RADIO2_TXEN, packetNum); |
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284 | |
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285 | % Enable transmission of node1's radio 2 Tx buffer (enable transmission |
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286 | % of samples stored in radio 2 Tx Buffer in node 1) by sending the |
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287 | % RADIO2TXBUFF_TXEN command to node 1 using the 'warplab_sendCmd' function. |
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288 | warplab_sendCmd(udp_node1, RADIO2TXBUFF_TXEN, packetNum); |
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289 | |
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290 | % Enable receiver radio path in radio 2 in node 2 (enable radio 2 in |
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291 | % node 2 as receiver) by sending the RADIO2_RXEN command to node 2 using |
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292 | % the 'warplab_sendCmd' function. |
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293 | % Hint: The id or handle to node 2 is 'udp_node2'. |
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294 | warplab_sendCmd(udp_node2, RADIO2_RXEN, packetNum); |
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295 | |
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296 | % Enable capture in node2's radio 2 Rx Buffer (enable radio 2 rx buffer in |
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297 | % node 2 for storage of samples) by sending the RADIO2RXBUFF_RXEN command to |
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298 | % node 2 using the 'warplab_sendCmd' function. |
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299 | warplab_sendCmd(udp_node2, RADIO2RXBUFF_RXEN, packetNum); |
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300 | |
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301 | % Prime transmitter state machine in node 1. Node 1 will be |
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302 | % waiting for the SYNC packet. Transmission from node 1 will be triggered |
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303 | % when node 1 receives the SYNC packet. |
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304 | warplab_sendCmd(udp_node1, TX_START, packetNum); |
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305 | |
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306 | % Prime receiver state machine in node 2. Node 2 will be waiting |
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307 | % for the SYNC packet. Capture at node 2 will be triggered when node 2 |
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308 | % receives the SYNC packet. |
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309 | warplab_sendCmd(udp_node2, RX_START, packetNum); |
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310 | |
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311 | % Send the SYNC packet |
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312 | warplab_sendSync(udp_Sync); |
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313 | |
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314 | %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
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315 | % 5.3. Read the received smaples from the Warp board |
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316 | %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
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317 | % Read the received samples from the WARP board using the |
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318 | % 'warplab_readSMRO' function. (Read extra 100 samples to account for |
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319 | % jitter in sync trigger) |
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320 | % Hints: |
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321 | % 1. The first argument of the 'warplab_readSMRO' function identifies the |
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322 | % node from which samples will be read. In this exercise we set node 2 as |
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323 | % the receiver node, the id or handle to node 2 is 'udp_node2'. |
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324 | % 2. The second argument of the 'warplab_readSMRO' function identifies the |
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325 | % receive buffer from which samples will be read. A node programmed with |
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326 | % the warplab_mimo_2x2_v04.bit bitstream has 2 receive buffers and a node |
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327 | % programmed with the warplab_mimo_4x4_v04.bit bitstream has 4 receive |
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328 | % buffers. For this exercise samples were captured in node 2 radio 2, |
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329 | % hence, samples must be read from radio 2 Rx buffer, the id for this |
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330 | % buffer is 'RADIO2_RXDATA'. |
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331 | % 3. The third argument of the 'warplab_readSMRO' function is the number of |
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332 | % samples to read; reading of samples always starts from address zero. |
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333 | % For this exercise set third argument of the 'warplab_readSMRO' |
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334 | % function equal to 'TxLength+CaptOffset+100' (Read extra 100 samples to |
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335 | % account for jitter in sync trigger) |
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336 | [Node2_Radio2_RawRxData] = warplab_readSMRO(udp_node2, RADIO2_RXDATA, TxLength+TxDelay+100); |
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337 | |
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338 | % Process the received samples to obtain meaningful data |
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339 | [Node2_Radio2_RxData,Node2_Radio2_RxOTR] = warplab_processRawRxData(Node2_Radio2_RawRxData); |
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340 | |
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341 | %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
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342 | % 5.4. Reset and disable the boards |
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343 | %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
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344 | % Set radio 2 Tx buffer in node 1 back to Tx disabled mode |
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345 | warplab_sendCmd(udp_node1, RADIO2TXBUFF_TXDIS, packetNum); |
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346 | |
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347 | % Disable the transmitter radio |
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348 | warplab_sendCmd(udp_node1, RADIO2_TXDIS, packetNum); |
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349 | |
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350 | % Set radio 2 Rx buffer in node 2 back to Rx disabled mode |
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351 | warplab_sendCmd(udp_node2, RADIO2RXBUFF_RXDIS, packetNum); |
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352 | |
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353 | % Disable the receiver radio |
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354 | warplab_sendCmd(udp_node2, RADIO2_RXDIS, packetNum); |
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355 | %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
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356 | % 5.5. Plot the transmitted and received data |
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357 | %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
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358 | figure; |
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359 | subplot(2,2,1); |
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360 | plot(real(Node1_Radio2_TxData)); |
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361 | title('Tx Node 1 Radio 2 I'); |
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362 | xlabel('n (samples)'); ylabel('Amplitude'); |
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363 | axis([0 2^14 -1 1]); % Set axis ranges. |
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364 | subplot(2,2,2); |
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365 | plot(imag(Node1_Radio2_TxData)); |
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366 | title('Tx Node 1 Radio 2 Q'); |
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367 | xlabel('n (samples)'); ylabel('Amplitude'); |
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368 | axis([0 2^14 -1 1]); % Set axis ranges. |
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369 | subplot(2,2,3); |
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370 | plot(real(Node2_Radio2_RxData)); |
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371 | title('Rx Node 2 Radio 2 I'); |
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372 | xlabel('n (samples)'); ylabel('Amplitude'); |
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373 | axis([0 2^14 -1 1]); % Set axis ranges. |
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374 | subplot(2,2,4); |
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375 | plot(imag(Node2_Radio2_RxData)); |
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376 | title('Rx Node 2 Radio 2 Q'); |
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377 | xlabel('n (samples)'); ylabel('Amplitude'); |
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378 | axis([0 2^14 -1 1]); % Set axis ranges. |
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379 | |
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380 | %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
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381 | % 6. Downconvert from 5MHz to baseband |
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382 | %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
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383 | time = [0:1:length(Node2_Radio2_RxData)-1]/40e6; % Sampling Freq. is 40MHz |
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384 | yrx_bb = Node2_Radio2_RxData .* exp(-sqrt(-1)*2*pi*5e6*time); |
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385 | |
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386 | %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
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387 | % 7. Filter the received signal with a Matched Filter (matched to the pulse |
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388 | % shaping filter), detect preamble, and downsample output of Matched Filter |
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389 | %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
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390 | % Store received samples as a column vector |
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391 | yrx_bb = yrx_bb.'; |
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392 | |
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393 | % Matched filter: Filter received signal using the SRRC filter |
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394 | yrx_bb_mf = rcosflt(yrx_bb,1,nsamp,'Fs/filter',rrcfilter); |
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395 | |
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396 | % Correlate with the reference matrix to find preamble sequence |
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397 | correlation = abs( (yrx_bb_mf(1:corr_window).') * reference_matrix ); |
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398 | preamble_start = find(correlation == max(correlation)); % Start of preamble |
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399 | first_sample_index = preamble_start+length_preamble_upsamp; % Start of |
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400 | % first symbol after preamble |
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401 | |
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402 | % Downsample output of Matched Filter |
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403 | yrx_bb_mf_ds = yrx_bb_mf(first_sample_index:end); |
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404 | yrx_bb_mf_ds = downsample(yrx_bb_mf_ds,nsamp); |
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405 | |
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406 | % Slice symbols of interest (nsym_payload symbols were transmitted so if |
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407 | % yrx_bb_mf_ds has more than nsym_payload elements the extra elements of the |
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408 | % yrx_bb_mf_ds vector are due to the extra samples read from the Rx buffer |
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409 | % and the extra samples added by the delay of the filters) |
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410 | yrx_bb_mf_ds = yrx_bb_mf_ds(1:nsym_payload); |
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411 | |
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412 | % Stem Plot of signal before Matched Filter, after Matched Filter, and |
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413 | % after downsampling |
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414 | % Plots first 30 symbols. |
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415 | % Plots real and imaginary parts in different windows |
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416 | figure; % Create new figure window. |
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417 | subplot(2,1,1) |
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418 | stem(real(yrx_bb(first_sample_index-(1+delay*nsamp):first_sample_index-(1+delay*nsamp)+30*nsamp)),'b'); |
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419 | hold |
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420 | stem(real(yrx_bb_mf(first_sample_index:first_sample_index+30*nsamp)),'r'); |
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421 | stem([1:nsamp:nsamp*30],real(yrx_bb_mf_ds(1:30)),'k'); |
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422 | title('I Symbols'); |
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423 | xlabel('n (sample)'); ylabel('Amplitude'); |
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424 | legend('Before Matched Filter','After Matched Filter','After Downsample'); |
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425 | subplot(2,1,2) |
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426 | stem(imag(yrx_bb(first_sample_index-(1+delay*nsamp):first_sample_index-(1+delay*nsamp)+30*nsamp)),'b'); |
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427 | hold |
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428 | stem(imag(yrx_bb_mf(first_sample_index:first_sample_index+30*nsamp)),'r'); |
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429 | stem([1:nsamp:nsamp*30],imag(yrx_bb_mf_ds(1:30)),'k'); |
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430 | title('Q Symbols'); |
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431 | xlabel('n (sample)'); ylabel('Amplitude'); |
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432 | |
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433 | % Scatter Plot of received and transmitted constellation points |
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434 | h = scatterplot(yrx_bb_mf_ds(1:end),1,0,'g.'); |
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435 | hold on; |
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436 | scatterplot(ytx_mod(nsym_preamble+1:end),1,0,'k*',h); |
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437 | title('Constellations'); |
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438 | legend('Received','Transmitted'); |
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439 | axis([-2 2 -2 2]); % Set axis ranges. |
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440 | hold off; |
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441 | |
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442 | %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
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443 | % 8. Demodulate and recover the transmitted bitstream |
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444 | %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
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445 | |
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446 | % Demodulate signal using DQPSK |
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447 | zsym = dpskdemod(yrx_bb_mf_ds,M); |
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448 | |
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449 | % Map Symbols to Bits |
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450 | z = de2bi(zsym,'left-msb'); % Convert integers to bits. |
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451 | % Convert z from a matrix to a vector. |
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452 | z = reshape(z.',prod(size(z)),1); |
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453 | |
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454 | % Plot first 80 transmitted bits and first 80 received bits in a stem plot |
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455 | figure; |
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456 | subplot(2,1,1) |
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457 | stem(x(1:80),'filled'); |
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458 | title('Transmitted Bits'); |
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459 | xlabel('Bit Index'); ylabel('Binary Value'); |
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460 | subplot(2,1,2) |
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461 | stem(z(1:80),'filled'); |
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462 | title('Received Bits'); |
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463 | xlabel('Bit Index'); ylabel('Binary Value'); |
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464 | |
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465 | %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
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466 | % 9. Compute the Bit Error Rate (BER) and close sockets |
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467 | %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
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468 | % Compare x and z to obtain the number of errors and the bit error rate |
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469 | [number_of_errors,bit_error_rate] = biterr(x(3:length(z)),z(3:length(z))) |
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470 | % We start comparing at three because the first two bits are are always |
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471 | % lost in DQPSK. We compare until minlen because z may be shorter |
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472 | % than x due to the jitter of the synch pulse. |
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473 | |
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474 | % Close sockets |
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475 | pnet('closeall'); |
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476 | |
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