review of digital comm-akm 081110

8/2/2019 Review of Digital Comm-AKM 081110

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Review of Digital Modulation

Dr. A.K.MukhopadhyayDepartment of ECE, Dr. B.C.Roy Engg

College, Durgapur

AKM/DigCom/Mod/1

AKM lecture notes on


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AKM lecture notes onAKM/DigCom/Mod

Types of Signal Transmission


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fCfC

Modulation Basic Principles

Modulating

Signal m(t), at

baseband(fB)

Carrier (fC)

Modulation on carriers

amplitude, frequencyor phase

Modulated Signal

carrying theinformation of

m(t), bandpass (fC)

AKM/DigCom/Mod AKM lecture notes on

The modulating signal is represented as a time-sequence of symbolsor pulses. Each symbol has mfinite states and carries nbits of informationwhere n= log2m bits/symbol.

One symbol (has mstates voltage levels)

(represents n= log2mbits of information)

...

0 1 2 3 TModulator


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Digital Modulation Features

The input is discrete signal (pulses or symbols in time sequence)

Robust against channel impairmentsEasier multiplexing of voice, data, video informations

Digital error-control codes

Encryption of the transferred signals

More secure link

Modulating signal is a binary or M-ary data

The carrier is usually a sinusoidal wave.

Change in Amplitude (ASK), Frequency (FSK), Phase(PSK)and combination of more than one parameters

(Hybrid/Multilevel ). Ex. : QAM (Phase and Amplitude

change), M-ary



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Digital Modulation Benefits

Provides low bit-error rates at low SNRsPower efficiency

Performance in multipath and fading conditionsNoise immunity efficiency

Minimum RF channel bandwidthBandwidth efficiency

Easy and cost-effective implementationTradeoffs for selecting a digital modulation scheme depending

on particular system or application.



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Modulation: representation

Any modulated signal can be represented as

s(t) = A(t) cos [wct + f(t)]

s(t) = A(t) cos f(t) cos wct - A(t) sin f(t) sin wct

amplitude

in-phase quadrature

phase or frequency

Linear versus nonlinear modulation impact on spectral efficiency

Constant envelope versus non-constantenvelope

hardware implications with impact on power efficiency

Linear: Amplitude or phase

Non-linear: frequency: spectral broadening

(=> reliability: i.e. target BER at lower SNRs)


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Linear Modulation Techniques

s(t)=[Sang(t-nT)]cos wct-[S bng(t-nT)] sin wct(t), in-phase Q(t), quadrature

LINEAR MODULATIONS

CONVENTIONAL

4-PSK

(QPSK)

OFFSET

4-PSK

(OQPSK)

DIFFERENTIAL

4-PSK

(DQPSK, p/4-DQPSK)

M-ARY QUADRATURE

AMPLITUDEMOD.(M-QAM)

M-ARY PHASE

SHIFT KEYING(M-PSK)

M 4 M 4M=4(4-QAM = 4-PSK)

Square

Constellations

Circular

Constellations

n n


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Generic Digital ModulatorsASK

AM

FSKVCOV1 and V2

BPSKMixer-V and +V

M-ary

DSPSource: Tomasi Electronic Comm


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PAM Circuits

Modulation

DetectionPeak detection, AM

http://www.tpub.com/content/neets/14184/css/14184_175.htm
http://www.tpub.com/content/neets/14184/css/14184_175.htmhttp://www.tpub.com/content/neets/14184/css/14184_175.htm


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Binary

Amplitude Shift Keying



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Frequency Shift Keying



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Simple FSK Circuit

http://www.edn.com/contents/images/101101di.pdf

Transceivershttp://jap.hu/electronic/rf.html
http://www.edn.com/contents/images/101101di.pdfhttp://jap.hu/electronic/rf.htmlhttp://jap.hu/electronic/rf.htmlhttp://www.edn.com/contents/images/101101di.pdf


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Phase Shift Keying

Binary

QuadratureM-ary



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Comparison of Modulation Techniques



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Power and Bandwidth Efficiency

Power efficiencyrefers to the ability of the modulation technique

to retain the message fidelityeven at low power level. Normally,the signal power needs to be increased to improve fidelity.

Tradeoff between fidelity and signal powerPower efficiency describes how efficient this tradeoff is

made

Eb: signal energy per bit N0: noise power spectral density P: Error probability


Bandwidth efficiency refers to the ability of a modulation scheme to

accommodate data within a limited bandwidth. It indicates how

efficiently the allocated bandwidth is utilized

R: the data rate (bps) B: bandwidth occupied by the modulated RF signal


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Tradeoff Between Bandwidth Efficiency and Power Efficiency

Adding error control codes

Improves the power efficiency -Reduces the requires receivedpower for a particular bit error rateDecreases the bandwidth efficiency -Consumes more

bandwidth.

M-ary keying modulationIncreases the bandwidth efficiencyDecreases the power efficiency - More power is requires at the

receiver

M-FSK keying modulationIncrease the power efficiencyDecrease the bandwidth efficiency



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Shannons Upper Limit on Bandwidth

The fundamental upper limit on bandwidth efficiency may be

achieved using Shannons theorem (1948) that relates thechannel bandwidth with the maximum data rate that can be

transmitted over a noisychannel.

Shannons Theorem:

C: channel capacity (maximum data-rate) in bps,B: RF bandwidth S/N: signal-to-noise ratio


Example:SNR for a wireless channel is 30dB and RF bandwidth is 200kHz. Compute the

theoretical maximum data rate that can be transmitted over this channel.Solution:


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Condition ForError Free Communications as per

Shanons Formula

Required channel quality

for error free communications


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Bandwidth ExpressionsBandwidth depends on whether the signal is at baseband or at Passband. For

baseband, Bandwidth = (1/2)Rb(1 + ) (using a Nyquist LPF )For passband digital signal, Bandwidth = Rb(1 + ) (using Nyquist BPF)

NOTE: Symbol Rate that is key to bandwidth, not the Bit RateDifferent modulation schemes pack different no. of bits in a single symbol. BPSKhas 1

bit per symbol, QPSKhas 2 bits per symbol.


Occupied Bandwidth, B = Rs ( 1 + ) where Rs is the symbol rateand is the filter roll-off factor

Noise Bandwidth, BN, for a channel will not be affected by the roll-off factor of filter. Thus BN= Rs


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ExampleGIVEN:QPSK modulation, Bit rate 512 kbit/s, Filter roll-off, =0.3FIND: Occupied Bandwidth, B, and Noise Bandwidth, BN

SOLUTION:

Symbol Rate = Rs = (1/2) (512 103) = 256 103Occupied Bandwidth, B = Rs (1 + )=256 103 ( 1 + 0.3) = 332.8 KHz

Noise Bandwidth is, BN = Rs = 256 kHzSame Example with FEC: We use 1/2-rate FEC.

Symbol Rate, Rs = (1/2) (2) (512 103) = 512 103 symbols/s

Occupied Bandwidth, B = Rs ( 1 + ) = 665.6 kHz

2 bits per

symbolNumber of

bits/s

2 bits per

symbol 2-rateFEC

Number of

bits/s



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DetectionCoherent Detection

Local oscillatorSynchronizationRF carrier

Mixer, LPF; PLL

Incoherent Detection

No local oscillatorEnvelope detector; DiscriminatorDifferential PSK

ComparisonReceiver Circuits

S/NTiming


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Coherent and Non-coherent Detection

Coherent Detection (most PSK, some FSK):Exact replicas of the possible arriving signals are available at thereceiver.This means knowledge of the phase reference (phased-locked).Detection by cross-correlating the received signal with each one of

the replicas, and then making a decision based on comparisons withpre-selected thresholds.

Non-coherent Detection (some FSK, DPSK):Knowledge of the carriers wave phase not required.Less complexity.Inferior error performance.



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Coherent Detection

ASKFSKPSK

Source: Tomasi Electronic Comm


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Coherent Detection

Carrier RecoveryNo carrier pilotSquare loopCostas loop

RemodulatorReferencehttp://www.mwrf.com/Art

icles/Print.cfm?Ad=1&Articl

eID=9366
http://www.mwrf.com/Articles/Print.cfm?Ad=1&ArticleID=9366http://www.mwrf.com/Articles/Print.cfm?Ad=1&ArticleID=9366http://www.mwrf.com/Articles/Print.cfm?Ad=1&ArticleID=9366http://www.mwrf.com/Articles/Print.cfm?Ad=1&ArticleID=9366http://www.mwrf.com/Articles/Print.cfm?Ad=1&ArticleID=9366http://www.mwrf.com/Articles/Print.cfm?Ad=1&ArticleID=9366


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Design Trade-offs

Primary resources:Transmitted Power.Channel Bandwidth.

Design goals:Maximum data rate.

Minimum error probability.Minimum transmitted power.Minimum channel bandwidth.Robust against interfering signals.Minimum circuit complexity.



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Coherent Binary PSK (BPSK)

Two signals, one representing 0, the other 1.

Each of the two signals represents a single bit of information.Each signal persists for a single bit period (T) and then may be replaced by

either state.

Signal energy (ES) = Bit Energy (Eb), given by:

Therefore



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BPSK representation

Lets consider the unidimensional base (N=1) where:

Lets also rewrite the signal amplitudes as a function of their

energy:


Therefore, we can write the signals s1(t) and s2(t) in terms

of 1(t):

This can be graphically

represented by signal

space diagram as:


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BPSK Modulation

-A

+A


Noise consideration in BPSK Detection

Actual BPSK signal is received with noise

AWGN is a good approximation of noiseOther noise models are more complex

Constellation becomes a distribution because of noisevariations to signal


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Bit Error Rate (BER) for BPSK

BER is given by

Eb/No(dB) BER

0 0.082 0.044 0.0146 0.00278 2*10-410 4*10-610.543 10-6

Approximationvalid for Eb/Nogreater than ~4 dB

Note that these calculations are for synchronous detection


erfc(z)= complementary error function of z = 1-erf(z)=


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Non-Coherent Modulation: DPSK

Information in MPSK, MQAM carried in signal phase.Requires coherent demodulation: i.e. phase of the transmitted signal carrier 0 must

be matched to the phase of the receiver carrier More cost, susceptible to carrier phase drift.Harder to obtain in fading channels

Differential modulation: do not require phase reference.More general: modulation with memory: depends upon prior symbolstransmitted.Use previous symbol as the a phase reference for current symbol

Information bits encoded as the differential phase between current & previoussymbolLess sensitive to carrier phase drift (f-domain) ; more sensitive to doppler effects:decorrelation of signal phase in time-domain

Differential PSKSimplicity

TransmitterReceiver


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DPSK

A 0 bit is encoded by no change in phase, whereas a 1 bit is encoded as a phase change of.

If symbol over time [(k1)Ts, kTs) has phase (k 1) = eji, i= 0, ,

then to encode a 0 bit over [kTs, (k+ 1)Ts), the symbol would have

phase: (k) = ejiand

to encode a 1 bit the symbol would have

phase (k) = ej(i+).DQPSK: gray coding:


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Coherent Quaternary PSK (QPSK)Four signals are used to convey information. This leads to a constellation of:

when shown as a phasor with reference to the signal phase, q,Each of thetwo states represents a two-bit information.

Constant Modulus =>


we use the following ortho-normal basis:

This gives, (after some trigonometricmanipulations), the constellation

representation or Signal space diagram

of coherent QPSK


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QPSK Implementation

Note that the QPSK

signal can be seen tobe two BPSK signalsin phase quadrature



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QPSK Detection

Resources for DetectionMini Circuitshttp://www.minicircuits.com/pages/app_notes.htmlIntel

http://www.intel.com/netcomms/technologies/wimax/303788.pdf


Bit Error Rate (BER) for QPSKThe BER is the probability of choosing the wrong signal (symbol) stateBecause the signal is Gray coded the BER for QPSK is that for BPSK:BER (after a lot of derivation) is given by:

Approximationvalid for Eb/Nogreater than ~4 dBNote that Eb is here, not Es!
http://www.minicircuits.com/pages/app_notes.htmlhttp://www.minicircuits.com/pages/app_notes.htmlhttp://www.intel.com/netcomms/technologies/wimax/303788.pdfhttp://www.intel.com/netcomms/technologies/wimax/303788.pdfhttp://www.intel.com/netcomms/technologies/wimax/303788.pdfhttp://www.intel.com/netcomms/technologies/wimax/303788.pdfhttp://www.minicircuits.com/pages/app_notes.htmlhttp://www.minicircuits.com/pages/app_notes.html


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QPSK Waveform


d li d d l i ( )


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Ak x

cos(2pfct)

Yi(t) =Akcos(2pfct)

Bk x

sin(2pfct)

Yq(t) = Bksin(2pfct)

+ Y(t)

Yi(t) and Yq(t) both occupy the bandpass channel QAM sends 2 pulses/Hz

Quadrature Amplitude Modulation (QAM)

QAM uses two-dimensional signalingAkmodulates in-phase cos(2pfct)

Bkmodulates quadrature phase cos(2pfct+ p/4) = sin(2pfct)Transmit sum of inphase & quadrature phase components

Transmitted

Signal


QAM D d l i


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QAM Demodulation

Y(t) x

2cos(2 fct)2cos2(2 fct)+2Bk cos(2 fct)sin(2 fct)

= Ak{1 + cos(4 fct)}+Bk{0 + sin(4 fct)}

Lowpassfilter(smoother)

Ak

2Bksin2(2 fct)+2Ak cos(2 fct)sin(2 fct)

= Bk{1 - cos(4 fct)}+Ak{0 + sin(4 fct)}

x

2sin(2 fct)

BkLowpassfilter(smoother)

smoothed to zero

smoothed to zero


Si l C ll i P


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Signal Constellation PatternsEach pair (Ak, Bk) defines a point in the plane

Signal constellation is a set of signaling points

4 possible points per Tsec.

2 bits / pulse

Ak

Bk


4 bits / pulse

Ak

Bk(A, A)

(A,-A)(-A,-A)

(-A,A)


Ak

Bk


Ak

Bk


Point selected by amplitude & phase

Akcos(2pfct)+Bksin(2pfct)= Ak2+Bk2cos(2pfct+tan-1(Bk/Ak))


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QAM Constellations

Euclidean Distance

Constellation Displayhttp://www.lecroy.com/tm/library

/LABs/PDF/LAB303B.pdf

http://www.lecroy.com/tm/library/LABs/PDF/LAB303B.pdfhttp://www.lecroy.com/tm/library/LABs/PDF/LAB303B.pdfhttp://www.lecroy.com/tm/library/LABs/PDF/LAB303B.pdfhttp://www.lecroy.com/tm/library/LABs/PDF/LAB303B.pdf


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M-PSK and M-QAM

M-PSK (Circular Constellations)

16-PSK

an

bn4-PSK

M-QAM (Square Constellations)

16-QAM

4-PSK

an

bn

Tradeoffs

Higher-order modulations (M large) are more spectrallyefficientbut less power efficient (i.e. BER higher).

M-QAM is more spectrally efficient than M-PSK butalso more sensitive to system nonlinearities.

O h M d l i S h


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Other Modulation SchemesOffset QPSK (OQPSK)

One of the bit streams delayed by Tb/2

Same BER performance as QPSKMinimum Shift Keying (MSK)

QPSK - also constant envelope, continuous phase FSK

minimum bandwidth, sidelobes large

1/2-cycle sine symbol rather than rectangular

Same BER performance as QPSK

can be implemented using I-Q receiverGaussian MSK (GMSK)

-- Reduces sidelobes of MSK using a pre-modulation filter

Used by RAM Mobile Data, GSM, CDPD, and HIPERLAN


http://www.emc.york.ac.uk/reports/linkpcp/appD.pdfhttp://ocw.mit.edu/NR/rdonlyres/Electrical-Engineering-and-Computer-Science/6-976High-Speed-Communication-Circuits-and-SystemsSpring2003/D5DCBE3A-60CD-48A6-977E-78BD8CBEF42E/0/proj2.pdfhttp://www.ictp.trieste.it/~radionet/2001_school/lectures/fitton/digital_mod.pdfhttp://www.plextek.com/papers/schmsv6.pdf
http://ocw.mit.edu/NR/rdonlyres/Electrical-Engineering-and-Computer-Science/6-976High-Speed-Communication-Circuits-and-SystemsSpring2003/D5DCBE3A-60CD-48A6-977E-78BD8CBEF42E/0/proj2.pdfhttp://ocw.mit.edu/NR/rdonlyres/Electrical-Engineering-and-Computer-Science/6-976High-Speed-Communication-Circuits-and-SystemsSpring2003/D5DCBE3A-60CD-48A6-977E-78BD8CBEF42E/0/proj2.pdfhttp://ocw.mit.edu/NR/rdonlyres/Electrical-Engineering-and-Computer-Science/6-976High-Speed-Communication-Circuits-and-SystemsSpring2003/D5DCBE3A-60CD-48A6-977E-78BD8CBEF42E/0/proj2.pdfhttp://ocw.mit.edu/NR/rdonlyres/Electrical-Engineering-and-Computer-Science/6-976High-Speed-Communication-Circuits-and-SystemsSpring2003/D5DCBE3A-60CD-48A6-977E-78BD8CBEF42E/0/proj2.pdfhttp://www.ictp.trieste.it/~radionet/2001_school/lectures/fitton/digital_mod.pdfhttp://www.ictp.trieste.it/~radionet/2001_school/lectures/fitton/digital_mod.pdfhttp://www.plextek.com/papers/schmsv6.pdfhttp://www.ictp.trieste.it/~radionet/2001_school/lectures/fitton/digital_mod.pdfhttp://www.plextek.com/papers/schmsv6.pdfhttp://www.plextek.com/papers/schmsv6.pdfhttp://www.ictp.trieste.it/~radionet/2001_school/lectures/fitton/digital_mod.pdfhttp://ocw.mit.edu/NR/rdonlyres/Electrical-Engineering-and-Computer-Science/6-976High-Speed-Communication-Circuits-and-SystemsSpring2003/D5DCBE3A-60CD-48A6-977E-78BD8CBEF42E/0/proj2.pdfhttp://ocw.mit.edu/NR/rdonlyres/Electrical-Engineering-and-Computer-Science/6-976High-Speed-Communication-Circuits-and-SystemsSpring2003/D5DCBE3A-60CD-48A6-977E-78BD8CBEF42E/0/proj2.pdfhttp://ocw.mit.edu/NR/rdonlyres/Electrical-Engineering-and-Computer-Science/6-976High-Speed-Communication-Circuits-and-SystemsSpring2003/D5DCBE3A-60CD-48A6-977E-78BD8CBEF42E/0/proj2.pdfhttp://ocw.mit.edu/NR/rdonlyres/Electrical-Engineering-and-Computer-Science/6-976High-Speed-Communication-Circuits-and-SystemsSpring2003/D5DCBE3A-60CD-48A6-977E-78BD8CBEF42E/0/proj2.pdfhttp://ocw.mit.edu/NR/rdonlyres/Electrical-Engineering-and-Computer-Science/6-976High-Speed-Communication-Circuits-and-SystemsSpring2003/D5DCBE3A-60CD-48A6-977E-78BD8CBEF42E/0/proj2.pdfhttp://ocw.mit.edu/NR/rdonlyres/Electrical-Engineering-and-Computer-Science/6-976High-Speed-Communication-Circuits-and-SystemsSpring2003/D5DCBE3A-60CD-48A6-977E-78BD8CBEF42E/0/proj2.pdfhttp://ocw.mit.edu/NR/rdonlyres/Electrical-Engineering-and-Computer-Science/6-976High-Speed-Communication-Circuits-and-SystemsSpring2003/D5DCBE3A-60CD-48A6-977E-78BD8CBEF42E/0/proj2.pdfhttp://ocw.mit.edu/NR/rdonlyres/Electrical-Engineering-and-Computer-Science/6-976High-Speed-Communication-Circuits-and-SystemsSpring2003/D5DCBE3A-60CD-48A6-977E-78BD8CBEF42E/0/proj2.pdfhttp://ocw.mit.edu/NR/rdonlyres/Electrical-Engineering-and-Computer-Science/6-976High-Speed-Communication-Circuits-and-SystemsSpring2003/D5DCBE3A-60CD-48A6-977E-78BD8CBEF42E/0/proj2.pdfhttp://ocw.mit.edu/NR/rdonlyres/Electrical-Engineering-and-Computer-Science/6-976High-Speed-Communication-Circuits-and-SystemsSpring2003/D5DCBE3A-60CD-48A6-977E-78BD8CBEF42E/0/proj2.pdfhttp://ocw.mit.edu/NR/rdonlyres/Electrical-Engineering-and-Computer-Science/6-976High-Speed-Communication-Circuits-and-SystemsSpring2003/D5DCBE3A-60CD-48A6-977E-78BD8CBEF42E/0/proj2.pdfhttp://ocw.mit.edu/NR/rdonlyres/Electrical-Engineering-and-Computer-Science/6-976High-Speed-Communication-Circuits-and-SystemsSpring2003/D5DCBE3A-60CD-48A6-977E-78BD8CBEF42E/0/proj2.pdfhttp://ocw.mit.edu/NR/rdonlyres/Electrical-Engineering-and-Computer-Science/6-976High-Speed-Communication-Circuits-and-SystemsSpring2003/D5DCBE3A-60CD-48A6-977E-78BD8CBEF42E/0/proj2.pdfhttp://ocw.mit.edu/NR/rdonlyres/Electrical-Engineering-and-Computer-Science/6-976High-Speed-Communication-Circuits-and-SystemsSpring2003/D5DCBE3A-60CD-48A6-977E-78BD8CBEF42E/0/proj2.pdfhttp://ocw.mit.edu/NR/rdonlyres/Electrical-Engineering-and-Computer-Science/6-976High-Speed-Communication-Circuits-and-SystemsSpring2003/D5DCBE3A-60CD-48A6-977E-78BD8CBEF42E/0/proj2.pdfhttp://ocw.mit.edu/NR/rdonlyres/Electrical-Engineering-and-Computer-Science/6-976High-Speed-Communication-Circuits-and-SystemsSpring2003/D5DCBE3A-60CD-48A6-977E-78BD8CBEF42E/0/proj2.pdfhttp://ocw.mit.edu/NR/rdonlyres/Electrical-Engineering-and-Computer-Science/6-976High-Speed-Communication-Circuits-and-SystemsSpring2003/D5DCBE3A-60CD-48A6-977E-78BD8CBEF42E/0/proj2.pdfhttp://ocw.mit.edu/NR/rdonlyres/Electrical-Engineering-and-Computer-Science/6-976High-Speed-Communication-Circuits-and-SystemsSpring2003/D5DCBE3A-60CD-48A6-977E-78BD8CBEF42E/0/proj2.pdfhttp://ocw.mit.edu/NR/rdonlyres/Electrical-Engineering-and-Computer-Science/6-976High-Speed-Communication-Circuits-and-SystemsSpring2003/D5DCBE3A-60CD-48A6-977E-78BD8CBEF42E/0/proj2.pdfhttp://ocw.mit.edu/NR/rdonlyres/Electrical-Engineering-and-Computer-Science/6-976High-Speed-Communication-Circuits-and-SystemsSpring2003/D5DCBE3A-60CD-48A6-977E-78BD8CBEF42E/0/proj2.pdfhttp://ocw.mit.edu/NR/rdonlyres/Electrical-Engineering-and-Computer-Science/6-976High-Speed-Communication-Circuits-and-SystemsSpring2003/D5DCBE3A-60CD-48A6-977E-78BD8CBEF42E/0/proj2.pdfhttp://ocw.mit.edu/NR/rdonlyres/Electrical-Engineering-and-Computer-Science/6-976High-Speed-Communication-Circuits-and-SystemsSpring2003/D5DCBE3A-60CD-48A6-977E-78BD8CBEF42E/0/proj2.pdfhttp://ocw.mit.edu/NR/rdonlyres/Electrical-Engineering-and-Computer-Science/6-976High-Speed-Communication-Circuits-and-SystemsSpring2003/D5DCBE3A-60CD-48A6-977E-78BD8CBEF42E/0/proj2.pdfhttp://ocw.mit.edu/NR/rdonlyres/Electrical-Engineering-and-Computer-Science/6-976High-Speed-Communication-Circuits-and-SystemsSpring2003/D5DCBE3A-60CD-48A6-977E-78BD8CBEF42E/0/proj2.pdfhttp://ocw.mit.edu/NR/rdonlyres/Electrical-Engineering-and-Computer-Science/6-976High-Speed-Communication-Circuits-and-SystemsSpring2003/D5DCBE3A-60CD-48A6-977E-78BD8CBEF42E/0/proj2.pdfhttp://ocw.mit.edu/NR/rdonlyres/Electrical-Engineering-and-Computer-Science/6-976High-Speed-Communication-Circuits-and-SystemsSpring2003/D5DCBE3A-60CD-48A6-977E-78BD8CBEF42E/0/proj2.pdfhttp://ocw.mit.edu/NR/rdonlyres/Electrical-Engineering-and-Computer-Science/6-976High-Speed-Communication-Circuits-and-SystemsSpring2003/D5DCBE3A-60CD-48A6-977E-78BD8CBEF42E/0/proj2.pdfhttp://ocw.mit.edu/NR/rdonlyres/Electrical-Engineering-and-Computer-Science/6-976High-Speed-Communication-Circuits-and-SystemsSpring2003/D5DCBE3A-60CD-48A6-977E-78BD8CBEF42E/0/proj2.pdfhttp://ocw.mit.edu/NR/rdonlyres/Electrical-Engineering-and-Computer-Science/6-976High-Speed-Communication-Circuits-and-SystemsSpring2003/D5DCBE3A-60CD-48A6-977E-78BD8CBEF42E/0/proj2.pdfhttp://www.emc.york.ac.uk/reports/linkpcp/appD.pdf


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Minimum Shift Keying (MSK) spectra

AKM lecture notes on Modulation


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System Performance

Eye DiagramSuperposition of sampled pulses

Eye OpeningContrast between 0 and 1http://www.complextoreal.com/chapters/eye.pdf
http://www.complextoreal.com/chapters/eye.pdfhttp://www.complextoreal.com/chapters/eye.pdf


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Summary of Digital Communications Parameters

M = modulation size. Bw= Bandwidth in Hertz = Roll-off factor (from 0 to 1)

Gc = Coding Gain (convert from dB to linear) Ov= Channel Overhead (0 to1)Bits per Symbol: Symbol Rate [symbol/second]

Gross Bit Rate [bps]:

Net Data Rate [bps]:

Required Eb/No (using coding gain):

Required C/N:

Required Signal Strength [Watts]:

Where ,k = Boltzman constant = 1.38e-23 J/HzTS = System Noise TemperatureT0 = ambient temperature (usually 290 K)F = System Noise figure in linear scale (not in dB)

AKM lecture notes on ModulationAKM/DigCom/Mod


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review of digital comm-akm 081110

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