{ "cells": [ { "cell_type": "markdown", "metadata": {}, "source": [ "# Chapter 13 : Multiplexing and Multiple Access Techniques" ] }, { "cell_type": "markdown", "metadata": {}, "source": [ "## Example 1 : pg 437" ] }, { "cell_type": "code", "execution_count": 1, "metadata": { "collapsed": false }, "outputs": [ { "name": "stdout", "output_type": "stream", "text": [ "a)The number of signals are 250.0\n", "b)The number of signals are 125.0\n", "c)The number of signals are 6.0\n", "d)The number of signals are 71.0\n" ] } ], "source": [ " \n", "# page no 437\n", "# prob no 13_1\n", "#calculate the no. of signals in all cases\n", "from math import log\n", "#given\n", "freq_band=1.*10**6;\n", "# A)For SSBSC AM, the bandwidth is the same as the maximunm modulating freq.\n", "fmax=4.*10**3;\n", "#calculations and results\n", "B=fmax;\n", "no_of_signal=freq_band/B;\n", "print 'a)The number of signals are ',no_of_signal\n", "# B)For DSB AM, the bandwidth is twice the maximunm modulating freq.\n", "B=2*fmax;\n", "no_of_signal=freq_band/B;\n", "print 'b)The number of signals are ',no_of_signal\n", "# C)Using Carson's Rule to approximate the bandwidth\n", "f_max=15.*10**3; deviation=75.*10**3;\n", "B=2*(deviation + f_max);\n", "no_of_signal=freq_band/B;\n", "print 'c)The number of signals are ',round(no_of_signal)\n", "# D)Use Shannon-Hartley theorem to find the bandwidth\n", "C=56.*10**3;M=4.;#for QPSK\n", "B=C/(2*log(M) /log(2));\n", "no_of_signal=freq_band/B;\n", "print 'd)The number of signals are ',round(no_of_signal)" ] }, { "cell_type": "markdown", "metadata": {}, "source": [ "## Example 2 : pg 444" ] }, { "cell_type": "code", "execution_count": 2, "metadata": { "collapsed": false }, "outputs": [ { "name": "stdout", "output_type": "stream", "text": [ "The noise power at BW=30 kHz is -129.059 dBm\n", "The noise power at BW=10 MHz is -103.83 dBm\n", "The value of SNR for BW=30 kHz is 19.059 dB\n", "The value of SNR for BW=10 MHz is -6.17 dB\n" ] } ], "source": [ " \n", "# page no 444\n", "# prob no 13_2\n", "#calculate the value of SNR and noise power in both cases\n", "#Voice transmisssion occupies 30 kHz.Spread spectrum is used to increase BW to 10MHz\n", "from math import log10\n", "#given\n", "B1=30.*10**3;#BW is 30 kHz\n", "B2=10.*10**6;#BW is 10 MHz\n", "T=300.;#noise temp at i/p\n", "PN=-110.;#signal has total signal power of -110 dBm at receiver\n", "k=1.38*10**-23;#Boltzmann's const in J/K\n", "#calculations and results\n", "#Determination of noise power at B1=30kHz\n", "PN1=10*(log10(k*B1*T/10**-3));\n", "print 'The noise power at BW=30 kHz is',round(PN1,3),'dBm'\n", "#Determination of noise power at B2=10MHz\n", "PN2=10*(log10(k*B2*T/10**-3));\n", "print 'The noise power at BW=10 MHz is',round(PN2,3),'dBm'\n", "#Determination of SNR for 30kHz BW\n", "SNR1=PN-PN1;\n", "print 'The value of SNR for BW=30 kHz is',round(SNR1,3),'dB'\n", "#Determination of SNR for 10MHz BW\n", "SNR2=PN-PN2;\n", "print 'The value of SNR for BW=10 MHz is',round(SNR2,3),'dB'" ] }, { "cell_type": "markdown", "metadata": {}, "source": [ "## Example 3 : pg 445" ] }, { "cell_type": "code", "execution_count": 3, "metadata": { "collapsed": false }, "outputs": [ { "name": "stdout", "output_type": "stream", "text": [ "Time required for each freq 0.1 sec/hop\n" ] } ], "source": [ " \n", "# page no 445\n", "# prob no 13_3\n", "#calculate the time required\n", "#given\n", "no_of_freq_hops =100.; total_time_req=10.;\n", "#calculations\n", "time_for_each_freq = total_time_req / no_of_freq_hops;\n", "#results\n", "print 'Time required for each freq',time_for_each_freq,'sec/hop'" ] }, { "cell_type": "markdown", "metadata": {}, "source": [ "## Example 4 : pg 446" ] }, { "cell_type": "code", "execution_count": 4, "metadata": { "collapsed": false }, "outputs": [ { "name": "stdout", "output_type": "stream", "text": [ "The no of signal changes i.e. symbol rate is 80000.0 baud\n" ] } ], "source": [ " \n", "# page no 446\n", "# prob no 13_4\n", "#calculate the no. of signal changes\n", "from math import log\n", "#given\n", "bit_rate=16.*10**3;#in bps\n", "#chip_rate =10:1;\n", "no_of_chip=10.;\n", "#calculations\n", "total_bit_rate=no_of_chip*bit_rate;\n", "m=4;n=log(m)/log(2);\n", "symbol_rate = total_bit_rate/n;\n", "#results\n", "print 'The no of signal changes i.e. symbol rate is ',symbol_rate,'baud'" ] }, { "cell_type": "markdown", "metadata": {}, "source": [ "## Example 5 : pg 447" ] }, { "cell_type": "code", "execution_count": 5, "metadata": { "collapsed": false }, "outputs": [ { "name": "stdout", "output_type": "stream", "text": [ "The value of BW after spreading 10.0 MHz\n", "The value of processing gain 16.99 dB\n", "The value of SNR after spreading in dB 3.01 dB\n" ] } ], "source": [ " \n", "# page no 447\n", "# prob no 13_5\n", "#calculate the value of BW, SNR\n", "#signal with bandwidth Bbb=200 kHz & SNR=20 dB spred at chip rate 50:1\n", "from math import log10\n", "#given\n", "Bbb=200.*10**3;#Bandwidth\n", "Gp=50.;#chip rate\n", "SNR_in=20.;#SNR is 20 dB without spreading\n", "#calculations and results\n", "#Determination of BW after spreading\n", "Brf=Gp*Bbb;\n", "print 'The value of BW after spreading',Brf/10**6,'MHz'\n", "#Converting into dB \n", "Gp_dB=10*log10(Gp);\n", "print 'The value of processing gain',round(Gp_dB,3),'dB'\n", "#Determination of SNR after spreadng\n", "SNR_out=SNR_in-Gp_dB;\n", "print 'The value of SNR after spreading in dB',round(SNR_out,3),'dB'" ] } ], "metadata": { "kernelspec": { "display_name": "Python 2", "language": "python", "name": "python2" }, "language_info": { "codemirror_mode": { "name": "ipython", "version": 2 }, "file_extension": ".py", "mimetype": "text/x-python", "name": "python", "nbconvert_exporter": "python", "pygments_lexer": "ipython2", "version": "2.7.11" } }, "nbformat": 4, "nbformat_minor": 0 }