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"# Chapter 13 : Multiplexing and Multiple Access Techniques"
]
},
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"metadata": {},
"source": [
"## Example 1 : pg 437"
]
},
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"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)"
]
},
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"metadata": {},
"source": [
"## Example 2 : pg 444"
]
},
{
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"execution_count": 2,
"metadata": {
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"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'"
]
},
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"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'"
]
},
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"cell_type": "markdown",
"metadata": {},
"source": [
"## Example 4 : pg 446"
]
},
{
"cell_type": "code",
"execution_count": 4,
"metadata": {
"collapsed": false
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"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'"
]
},
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"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'"
]
}
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