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<div class="title">BPSK modulation over an AWGN channel </div>  </div>
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<div class="textblock"><p>As a first example we will generate a sequence of 500000 random bits {0,1} and BPSK modulate these. Thereafter the BPSK signals will be transmitted over an AWGN channel with a signal-to-noise ratio <img class="formulaInl" alt="$E_b/N_0 = 0$" src="form_304.png"/> dB. The received signal is then decoded and the number of bit errors are calculated.</p>
<div class="fragment"><div class="line"><span class="preprocessor">#include &lt;<a class="code" href="itcomm_8h.html">itpp/itcomm.h</a>&gt;</span></div><div class="line"></div><div class="line"><span class="keyword">using namespace </span><a class="code" href="namespaceitpp.html">itpp</a>;</div><div class="line"></div><div class="line"><span class="comment">//These lines are needed for use of cout and endl</span></div><div class="line"><span class="keyword">using</span> std::cout;</div><div class="line"><span class="keyword">using</span> std::endl;</div><div class="line"></div><div class="line"><span class="keywordtype">int</span> main()</div><div class="line">{</div><div class="line">  <span class="comment">//Scalars</span></div><div class="line">  <span class="keywordtype">int</span> N;</div><div class="line">  <span class="keywordtype">double</span> N0;</div><div class="line"></div><div class="line">  <span class="comment">//Vectors</span></div><div class="line">  bvec bits, dec_bits;</div><div class="line">  vec symbols, rec;</div><div class="line"></div><div class="line">  <span class="comment">//Classes</span></div><div class="line">  <a class="code" href="classitpp_1_1BPSK.html">BPSK</a> bpsk;  <span class="comment">//The BPSK modulator/debodulator class</span></div><div class="line">  <a class="code" href="classitpp_1_1BERC.html">BERC</a> berc;  <span class="comment">//The Bit Error Rate Counter class</span></div><div class="line"></div><div class="line">  <span class="comment">//Init</span></div><div class="line">  N = 500000; <span class="comment">//The number of bits to simulate</span></div><div class="line">  N0 = 1;     <span class="comment">//0 dB SNR</span></div><div class="line"></div><div class="line">  <span class="comment">//Randomize the random number generator</span></div><div class="line">  <a class="code" href="group__randgen.html#ga001a62b1a1e3092d3bc60f71c95208cd">RNG_randomize</a>();</div><div class="line"></div><div class="line">  <span class="comment">//Generate the bits:</span></div><div class="line">  bits = <a class="code" href="group__randgen.html#ga5aa06887cf1fd3301b040987924068f0">randb</a>(N);</div><div class="line"></div><div class="line">  <span class="comment">//Do the BPSK modulation</span></div><div class="line">  bpsk.<a class="code" href="classitpp_1_1BPSK.html#a06cade730cc0156fca656082ac393277">modulate_bits</a>(bits, symbols);</div><div class="line"></div><div class="line">  <span class="comment">//Add the AWGN</span></div><div class="line">  rec = symbols + <a class="code" href="group__miscfunc.html#gaf559d29ca56ad3396a4284964b01a9b0">sqrt</a>(N0 / 2) * <a class="code" href="group__randgen.html#ga9ecf5af23567f51abc9af737fdbd872a">randn</a>(N);</div><div class="line"></div><div class="line">  <span class="comment">//Decode the received bits</span></div><div class="line">  bpsk.<a class="code" href="classitpp_1_1BPSK.html#a6a18384c68a902097511e336059e8099">demodulate_bits</a>(rec, dec_bits);</div><div class="line"></div><div class="line">  <span class="comment">//Count the number of errors</span></div><div class="line">  berc.<a class="code" href="classitpp_1_1BERC.html#a539b0c989badff3027d97e4693fc9cd7">count</a>(bits, dec_bits);</div><div class="line"></div><div class="line">  <span class="comment">//Print the results</span></div><div class="line">  cout &lt;&lt; <span class="stringliteral">&quot;There were &quot;</span> &lt;&lt; berc.<a class="code" href="classitpp_1_1BERC.html#a3ff000a38f8ab0e9a6a34329b51ca5ca">get_errors</a>() &lt;&lt; <span class="stringliteral">&quot; received bits in error.&quot;</span> &lt;&lt; endl;</div><div class="line">  cout &lt;&lt; <span class="stringliteral">&quot;There were &quot;</span> &lt;&lt; berc.<a class="code" href="classitpp_1_1BERC.html#a00504734327637cc923d5326a8ace54f">get_corrects</a>() &lt;&lt; <span class="stringliteral">&quot; correctly received bits.&quot;</span> &lt;&lt; endl;</div><div class="line">  cout &lt;&lt; <span class="stringliteral">&quot;The error probability was &quot;</span> &lt;&lt; berc.<a class="code" href="classitpp_1_1BERC.html#a4c66254b338ac55bfce1008fff5ce6db">get_errorrate</a>() &lt;&lt; endl;</div><div class="line">  cout &lt;&lt; <span class="stringliteral">&quot;The theoretical error probability is &quot;</span> &lt;&lt; 0.5*<a class="code" href="group__errorfunc.html#gaddd7604b61e53771a01d0a784e7c7a8a">erfc</a>(1.0) &lt;&lt; endl;</div><div class="line"></div><div class="line">  <span class="comment">//Exit program:</span></div><div class="line">  <span class="keywordflow">return</span> 0;</div><div class="line"></div><div class="line">}</div></div><!-- fragment --><p>When you run this program, the output will look something like this:</p>
<div class="fragment"><div class="line">There were 39224 received bits in error.</div><div class="line">There were 460776 correctly received bits.</div><div class="line">The error probability was 0.078448</div><div class="line">The theoretical error probability is 0.0786496</div></div><!-- fragment --> </div></div><!-- contents -->
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