lab11 - data communication in matlab

7/30/2019 Lab11 - Data Communication in Matlab

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Simulation of data communication in Matlab-Simulink

Modulation is generally nonlinear process, which modifies selected parameter (-s) of carrier

signal according to modulation signal (-s). Can be divided in:

Continuous analogharmonic carrier, analog modulation (e.g. AM, FM, PM)

Continuous digitalharmonic carrier, digital modulation (e.g. ASK, FSK, PSK, QPSK)

Discretepulse carrier, analog or digital modulation (e.g. PWM, PCM, DPCM )

Complexmore carrier parameters are modified simultaneously (e.g. QAM, APSK )

The aim of the lab is to show the possibility of simulation of data communication in Matlab

and to evaluate sensitivity of basic modulation types to different channel noise. Use the

following modulation types:

PMphase modulation

DPCMdifferential pulse-coded modulation

QAMquadrature amplitude modulation, changes carrier amplitude and phase

simultaneously in specific number of states (16, 64, 256 ). More states provides higher data

rate but also higher sensitivity to channel noise.

1) Start Matlab and run Communications Toolbox/Blocksetlibrary using commlib commandfrom the Matlab command prompt.

2) Become acquainted with library block features:a)Comm Sourcessignal/noise sources

b)Comm Sinksdata presentation blocksc)Source Codingsignal compressors and expanders, quantitizersd)Channel Codingchannel coders and decoderse)Modulationdigital and analog modulationsf) Channelsdifferent channel modelsg)SynchronizationPLL (phase lock loop)h)Utilitysupporting blocksintegrators, VCO, detectors, counters, scramblers, shift

registers

3) Run the DSP Blockset (digital signal processing) library using dsplib command from theMatlab command prompt.

4) Become acquainted with library block features:a)DSP sourcesbasic signal sources, especially harmonic

b)DSP Sinkssignal presentation blocks, especially oscilloscope5) Try the simulations in DEMO blocks and record the result while changing the important

simulation parameters.


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6) Simulate harmonic signal transmission over DPCM (blocks Sine Wave from DSPSources, DPCM Encoder and Decoder, Mux, Scope). While setting block parameters use

decimal point, Matlab doesnt accept comma (see Figures 1 and 2).

a)Observe the distortion of the output signal in areas with different slope of the signal,explain the reason of thin phenomenon.

b)Simulate transmission over the noisy communication channel of your choice, recordresults.

7) Simulate harmonic signal transmission over phase modulation system (PMmodulator/demodulator baseband)

a)Observe the signal at particular channel points.b)Find the time delay between transmitted and received signal.c)Simulate transmission over the noisy communication channel of your choice and

evaluate quality of transmission.

8) Simulate transmission of random digital signal by means of QAM modulation (blocksRandom-Integer Generator, Rectangular QAM modulator Baseband, AWGN Channel,

Discrete-Time Eye and Scatter Diagrams, see parameters on page 2-77 of Comm.Blockset Manual)

a)Become acquainted with data presentation in form of constellation diagram.b)Observe the symbols position within the constellation diagram in dependence on

signal to noise ratio (SNR) and number of modulation states (M-ary number), evaluate

the results.


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Notes to the measurement:

Point 6:

Figure 1 DPCM simulation schema


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Figure 2. DPCM functional blocks settings

Recommended values:

Gaussian Noise Generator:

- Mean valuemean value of noise, range from -1 to 1- Variancerandom noise variance, range from 1 to 10- Initial seedinitial state, leave 0- Sample timesampling period, leave 0.01

Other noise generator can be used as well.


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Point 7:

Figure 3. Simulation schema of phase modulation


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Figure 4. Phase modulationfunctional blocks settings

Recommended values:

Uniform Noise Generator:

- Noise lower boundminimum noise level, range from -0.5 to -5- Noise upper boundmaximum noise level, range from 0.5 to 5- Initial seedinitial state, leave 0- Sample timesampling period, leave 0.01

Other noise generator can be used as well.


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Point 8:

Figure 5. Simulation schematics of QAM


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Figure 6. QAM

functional blocks settings

Recommended values:

Rectangular QAM modulator:

- M-ary numbernumber of modulation states, set 2, 4, 8, 16, 32, 64, 128, 256AWGN Chanel

- Modeuse SNR- SNRsignal to noise ratio, range from 0 to 100

Random Integer Generator

- M-ary numbernumber of modulation states, set the same value as for QAMmodulator

lab11 - data communication in matlab

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