Signal Encoding Techniques
description
Transcript of Signal Encoding Techniques
![Page 1: Signal Encoding Techniques](https://reader036.fdocuments.in/reader036/viewer/2022062800/56814123550346895dacfa4c/html5/thumbnails/1.jpg)
SIGNAL ENCODING TECHNIQUESEngr. Mehran Mamonai
Department of Telecommunication
![Page 2: Signal Encoding Techniques](https://reader036.fdocuments.in/reader036/viewer/2022062800/56814123550346895dacfa4c/html5/thumbnails/2.jpg)
Encoding Techniques
• Digital data, digital signal– Equipment less complex and expensive than digital-to-analog modulation
equipment
• Analog data, digital signal– Permits use of modern digital transmission and switching equipment
• Digital data, analog signal– Some transmission media will only propagate analog signals E.g.,
unguided media
• Analog data, analog signal– Analog data in electrical form can be transmitted easily and cheaply
i.e. Done with voice transmission over voice-grade lines
![Page 3: Signal Encoding Techniques](https://reader036.fdocuments.in/reader036/viewer/2022062800/56814123550346895dacfa4c/html5/thumbnails/3.jpg)
Digital Data, Digital Signal
• Digital signal– Discrete, discontinuous voltage pulses– Each pulse is a signal element– Binary data encoded into signal elements
![Page 4: Signal Encoding Techniques](https://reader036.fdocuments.in/reader036/viewer/2022062800/56814123550346895dacfa4c/html5/thumbnails/4.jpg)
Terms (1)
• Unipolar– All signal elements have same sign
• Polar– One logic state represented by positive voltage the
other by negative voltage• Data rate– Rate of data transmission in bits per second
• Duration or length of a bit– Time taken for transmitter to emit the bit
![Page 5: Signal Encoding Techniques](https://reader036.fdocuments.in/reader036/viewer/2022062800/56814123550346895dacfa4c/html5/thumbnails/5.jpg)
Terms (2)
• Modulation rate– Rate at which the signal level changes– Measured in baud = signal elements per second
• Mark and Space– Binary 1 and Binary 0 respectively
![Page 6: Signal Encoding Techniques](https://reader036.fdocuments.in/reader036/viewer/2022062800/56814123550346895dacfa4c/html5/thumbnails/6.jpg)
Interpreting Signals• Need to know
– Timing of bits - when they start and end– Signal levels
• What determines how successful a receiver will be in interpreting an incoming signal?– Data rate
• An increase in data rate increases bit error rate– Signal to noise ratio
• An increase in SNR decreases bit error rate– Bandwidth
• An increase in bandwidth allows an increase in• data rate
![Page 7: Signal Encoding Techniques](https://reader036.fdocuments.in/reader036/viewer/2022062800/56814123550346895dacfa4c/html5/thumbnails/7.jpg)
Comparison of Encoding Schemes (1)
• Signal Spectrum– Lack of high frequencies reduces required bandwidth
– Spectral efficiency (also called bandwidth efficiency)– With no dc component, ac coupling via transformer Possible– Concentrate power in the middle of the bandwidth, Transfer
function of a channel is worse near band edges.
• Clocking– Synchronizing transmitter and receiver
– Ease of determining beginning and end of each bit position– External clock– Sync mechanism based on signal
![Page 8: Signal Encoding Techniques](https://reader036.fdocuments.in/reader036/viewer/2022062800/56814123550346895dacfa4c/html5/thumbnails/8.jpg)
Comparison of Encoding Schemes (2)
• Error detection– Can be built in to signal encoding
• Signal interference and noise immunity– Some codes are better than others
• Cost and complexity– The higher the signal rate to achieve a given data
rate, the greater the cost
![Page 9: Signal Encoding Techniques](https://reader036.fdocuments.in/reader036/viewer/2022062800/56814123550346895dacfa4c/html5/thumbnails/9.jpg)
Encoding Schemes
• Nonreturn to Zero-Level (NRZ-L)• Nonreturn to Zero Inverted (NRZI)• Bipolar -AMI• Pseudoternary• Manchester• Differential Manchester• B8ZS• HDB3
![Page 10: Signal Encoding Techniques](https://reader036.fdocuments.in/reader036/viewer/2022062800/56814123550346895dacfa4c/html5/thumbnails/10.jpg)
NonReturn to Zero-Level (NRZ-L)
• Two different voltages for 0 and 1 bits• Voltage constant during bit interval– no transition I.e. no return to zero voltage
• e.g. Absence of voltage for zero, constant positive voltage for one
• More often, negative voltage for one value and positive for the other
• This is NRZ-L
![Page 11: Signal Encoding Techniques](https://reader036.fdocuments.in/reader036/viewer/2022062800/56814123550346895dacfa4c/html5/thumbnails/11.jpg)
NonReturn to Zero Inverted (NRZ-I)
• Nonreturn to zero inverted on ones• Constant voltage pulse for duration of bit• Data encoded as presence or absence of
signal transition at beginning of bit time• Transition (low to high or high to low)
denotes a binary 1• No transition denotes binary 0• An example of differential encoding
![Page 12: Signal Encoding Techniques](https://reader036.fdocuments.in/reader036/viewer/2022062800/56814123550346895dacfa4c/html5/thumbnails/12.jpg)
NRZ (L & I)
![Page 13: Signal Encoding Techniques](https://reader036.fdocuments.in/reader036/viewer/2022062800/56814123550346895dacfa4c/html5/thumbnails/13.jpg)
Differential Encoding
• Data represented by changes rather than levels
• More reliable detection of transition rather than level
• In complex transmission layouts it is easy to lose sense of polarity
![Page 14: Signal Encoding Techniques](https://reader036.fdocuments.in/reader036/viewer/2022062800/56814123550346895dacfa4c/html5/thumbnails/14.jpg)
NRZ pros and cons
• Pros– Easy to engineer– Make good use of bandwidth
• Cons– dc component– Lack of synchronization capability
• Used for magnetic recording• Not often used for signal transmission
![Page 15: Signal Encoding Techniques](https://reader036.fdocuments.in/reader036/viewer/2022062800/56814123550346895dacfa4c/html5/thumbnails/15.jpg)
Multilevel Binary• Use more than two levels• Bipolar-AMI– zero represented by no line signal– one represented by positive or negative pulse– one pulses alternate in polarity– No loss of sync if a long string of ones (zeros still a
problem)– No net dc component– Lower bandwidth– Easy error detection
![Page 16: Signal Encoding Techniques](https://reader036.fdocuments.in/reader036/viewer/2022062800/56814123550346895dacfa4c/html5/thumbnails/16.jpg)
Pseudoternary
• One represented by absence of line signal• Zero represented by alternating positive and
negative• No advantage or disadvantage over bipolar-
AMI
![Page 17: Signal Encoding Techniques](https://reader036.fdocuments.in/reader036/viewer/2022062800/56814123550346895dacfa4c/html5/thumbnails/17.jpg)
Bipolar-AMI and Pseudoternary
![Page 18: Signal Encoding Techniques](https://reader036.fdocuments.in/reader036/viewer/2022062800/56814123550346895dacfa4c/html5/thumbnails/18.jpg)
Trade Off for Multilevel Binary
• Not as efficient as NRZ– Each signal element only represents one bit– In a 3 level system could represent log23 = 1.58
bits– Receiver must distinguish between three levels
(+A, -A, 0)– Requires approx. 3dB more signal power for
same probability of bit error
![Page 19: Signal Encoding Techniques](https://reader036.fdocuments.in/reader036/viewer/2022062800/56814123550346895dacfa4c/html5/thumbnails/19.jpg)
Biphase• Manchester
– Transition in middle of each bit period– Transition serves as clock and data– Low to high represents one– High to low represents zero– Used by IEEE 802.3
• Differential Manchester– Midbit transition is clocking only– Transition at start of a bit period represents zero– No transition at start of a bit period represents one– Note: this is a differential encoding scheme– Used by IEEE 802.5
![Page 20: Signal Encoding Techniques](https://reader036.fdocuments.in/reader036/viewer/2022062800/56814123550346895dacfa4c/html5/thumbnails/20.jpg)
Manchester Encoding
![Page 21: Signal Encoding Techniques](https://reader036.fdocuments.in/reader036/viewer/2022062800/56814123550346895dacfa4c/html5/thumbnails/21.jpg)
Differential Manchester Encoding
![Page 22: Signal Encoding Techniques](https://reader036.fdocuments.in/reader036/viewer/2022062800/56814123550346895dacfa4c/html5/thumbnails/22.jpg)
Biphase Pros and Cons
• Con– At least one transition per bit time and possibly two– Maximum modulation rate is twice NRZ– Requires more bandwidth
• Pros– Synchronization on mid bit transition (self clocking)– No dc component– Error detection
• Absence of expected transition
![Page 23: Signal Encoding Techniques](https://reader036.fdocuments.in/reader036/viewer/2022062800/56814123550346895dacfa4c/html5/thumbnails/23.jpg)
Modulation Rate
![Page 24: Signal Encoding Techniques](https://reader036.fdocuments.in/reader036/viewer/2022062800/56814123550346895dacfa4c/html5/thumbnails/24.jpg)
Scrambling
• Use scrambling to replace sequences that would produce constant voltage
• Filling sequence – Must produce enough transitions to sync– Must be recognized by receiver and replace with original– Same length as original
• No dc component• No long sequences of zero level line signal• No reduction in data rate• Error detection capability
![Page 25: Signal Encoding Techniques](https://reader036.fdocuments.in/reader036/viewer/2022062800/56814123550346895dacfa4c/html5/thumbnails/25.jpg)
B8ZS• Bipolar With 8 Zeros Substitution• Based on bipolar-AMI• If octet of all zeros and last voltage pulse
preceding was positive encode as 000+-0-+• If octet of all zeros and last voltage pulse
preceding was negative encode as 000-+0+-• Causes two violations of AMI code• Unlikely to occur as a result of noise• Receiver detects and interprets as octet of all
zeros
![Page 26: Signal Encoding Techniques](https://reader036.fdocuments.in/reader036/viewer/2022062800/56814123550346895dacfa4c/html5/thumbnails/26.jpg)
HDB3
• High Density Bipolar 3 Zeros• Based on bipolar-AMI• String of four zeros replaced with one or two
pulses
![Page 27: Signal Encoding Techniques](https://reader036.fdocuments.in/reader036/viewer/2022062800/56814123550346895dacfa4c/html5/thumbnails/27.jpg)
B8ZS and HDB3
![Page 28: Signal Encoding Techniques](https://reader036.fdocuments.in/reader036/viewer/2022062800/56814123550346895dacfa4c/html5/thumbnails/28.jpg)
Digital Data, Analog Signal
• Public telephone system– 300Hz to 3400Hz– Use modem (modulator-demodulator)
• Amplitude shift keying (ASK)– Amplitude difference of carrier frequency
• Frequency shift keying (FSK)– Frequency difference near carrier frequency
• Phase shift keying (PK)– Phase of carrier signal shifted
![Page 29: Signal Encoding Techniques](https://reader036.fdocuments.in/reader036/viewer/2022062800/56814123550346895dacfa4c/html5/thumbnails/29.jpg)
Modulation Techniques
![Page 30: Signal Encoding Techniques](https://reader036.fdocuments.in/reader036/viewer/2022062800/56814123550346895dacfa4c/html5/thumbnails/30.jpg)
• One binary digit represented by presence of carrier, at constant amplitude
• Other binary digit represented by absence of carrier
where the carrier signal is Acos(2πfct)
Amplitude Shift Keying
![Page 31: Signal Encoding Techniques](https://reader036.fdocuments.in/reader036/viewer/2022062800/56814123550346895dacfa4c/html5/thumbnails/31.jpg)
Amplitude Shift Keying• Values represented by different amplitudes of carrier• Usually, Amplitude is one
– i.e. presence and absence of carrier is used• Inefficient modulation technique since it is much more
susceptible to noise– Atmospheric and impulse noises tend to cause rapid
fluctuations in amplitude• Linear modulation technique
– Good spectral efficiency– Low power efficiency
• Up to 1200bps on voice grade lines• Used for carrying digital data over optical fiber
![Page 32: Signal Encoding Techniques](https://reader036.fdocuments.in/reader036/viewer/2022062800/56814123550346895dacfa4c/html5/thumbnails/32.jpg)
Amplitude Shift Keying
![Page 33: Signal Encoding Techniques](https://reader036.fdocuments.in/reader036/viewer/2022062800/56814123550346895dacfa4c/html5/thumbnails/33.jpg)
• Two binary digits represented by two different frequencies near the carrier frequency
• where f1 and f2 are offset from carrier frequency fc by equal but opposite amounts
Frequency Shift Keying
![Page 34: Signal Encoding Techniques](https://reader036.fdocuments.in/reader036/viewer/2022062800/56814123550346895dacfa4c/html5/thumbnails/34.jpg)
Frequency Shift Keying
• Most common form is binary FSK (BFSK)• Less susceptible to error than ASK• Up to 1200bps on voice grade lines• Used for high-frequency (3 to 30 MHz) radio
transmission• Can be used at higher frequency on LANs using
co-axial• Amplitude of the carrier wave is constant– Power-efficient
![Page 35: Signal Encoding Techniques](https://reader036.fdocuments.in/reader036/viewer/2022062800/56814123550346895dacfa4c/html5/thumbnails/35.jpg)
Binary Frequency Shift Keying
![Page 36: Signal Encoding Techniques](https://reader036.fdocuments.in/reader036/viewer/2022062800/56814123550346895dacfa4c/html5/thumbnails/36.jpg)
FSK on Voice Grade Line
![Page 37: Signal Encoding Techniques](https://reader036.fdocuments.in/reader036/viewer/2022062800/56814123550346895dacfa4c/html5/thumbnails/37.jpg)
Multiple FSK
• More than two frequencies used• More bandwidth efficient• More prone to error• Each signalling element represents more than
one bit
![Page 38: Signal Encoding Techniques](https://reader036.fdocuments.in/reader036/viewer/2022062800/56814123550346895dacfa4c/html5/thumbnails/38.jpg)
Multiple Frequency-Shift Keying (MFSK)
![Page 39: Signal Encoding Techniques](https://reader036.fdocuments.in/reader036/viewer/2022062800/56814123550346895dacfa4c/html5/thumbnails/39.jpg)
Binary Phase-Shift Keying (BPSK)
• Linear modulation technique
![Page 40: Signal Encoding Techniques](https://reader036.fdocuments.in/reader036/viewer/2022062800/56814123550346895dacfa4c/html5/thumbnails/40.jpg)
Phase Shift Keying (PSK)
• Phase of carrier signal is shifted to represent data
• Binary PSK– Two phases represent two binary digits
• Differential PSK– Phase shifted relative to previous transmission rather
than some reference signal• Binary 0 – signal burst of same phase as previous signal burst• Binary 1 – signal burst of opposite phase to previous signal burst
![Page 41: Signal Encoding Techniques](https://reader036.fdocuments.in/reader036/viewer/2022062800/56814123550346895dacfa4c/html5/thumbnails/41.jpg)
Binary Phase-Shift Keying (BPSK)
![Page 42: Signal Encoding Techniques](https://reader036.fdocuments.in/reader036/viewer/2022062800/56814123550346895dacfa4c/html5/thumbnails/42.jpg)
Differential PSK
![Page 43: Signal Encoding Techniques](https://reader036.fdocuments.in/reader036/viewer/2022062800/56814123550346895dacfa4c/html5/thumbnails/43.jpg)
Four-level PSK (QPSK)
![Page 44: Signal Encoding Techniques](https://reader036.fdocuments.in/reader036/viewer/2022062800/56814123550346895dacfa4c/html5/thumbnails/44.jpg)
Quadrature PSK• More efficient use by each signal element
representing more than one bit– e.g. shifts of /2 (90o)– Each element represents two bits– Can use 8 phase angles and have more than one
amplitude– 9600bps modem use 12 angles , four of which have
two amplitudes• Offset QPSK (orthogonal QPSK)– Delay in Q stream
![Page 45: Signal Encoding Techniques](https://reader036.fdocuments.in/reader036/viewer/2022062800/56814123550346895dacfa4c/html5/thumbnails/45.jpg)
QPSK and OQPSK Modulators
![Page 46: Signal Encoding Techniques](https://reader036.fdocuments.in/reader036/viewer/2022062800/56814123550346895dacfa4c/html5/thumbnails/46.jpg)
Examples of QPSF and OQPSK Waveforms
![Page 47: Signal Encoding Techniques](https://reader036.fdocuments.in/reader036/viewer/2022062800/56814123550346895dacfa4c/html5/thumbnails/47.jpg)
Performance of Digital to Analog Modulation Schemes• Bandwidth
– ASK and PSK bandwidth directly related to bit rate– FSK bandwidth related to data rate for lower frequencies, but
to offset of modulated frequency from carrier at high frequencies
– Bandwidth of modulated signal (BT)– ASK, PSK BT =(1+r)R– FSK BT= 2DF+(1+r)R
– R = bit rate– 0 < r < 1; related to how signal is filtered– DF = f2-fc=fc-f1
– In the presence of noise, bit error rate of PSK and QPSK are about 3dB superior to ASK and FSK
![Page 48: Signal Encoding Techniques](https://reader036.fdocuments.in/reader036/viewer/2022062800/56814123550346895dacfa4c/html5/thumbnails/48.jpg)
Performance of Digital to Analog Modulation Schemes• Bandwidth of modulated signal (BT)
• MPSK
• MFSK
– L = number of bits encoded per signal element– M = number of different signal elements
![Page 49: Signal Encoding Techniques](https://reader036.fdocuments.in/reader036/viewer/2022062800/56814123550346895dacfa4c/html5/thumbnails/49.jpg)
Multilevel PSK
• Using multiple phase angles with each angle having more than one amplitude, multiple signals elements can be achieved
• D = modulation rate, baud• R = data rate, bps• M = number of different signal elements = 2L• L = number of bits per signal element
![Page 50: Signal Encoding Techniques](https://reader036.fdocuments.in/reader036/viewer/2022062800/56814123550346895dacfa4c/html5/thumbnails/50.jpg)
Quadrature Amplitude Modulation (QAM)• QAM is a combination of ASK and PSK• Two different signals sent simultaneously on
the same carrier frequency
![Page 51: Signal Encoding Techniques](https://reader036.fdocuments.in/reader036/viewer/2022062800/56814123550346895dacfa4c/html5/thumbnails/51.jpg)
Quadrature Amplitude Modulation (QAM)• QAM used on asymmetric digital subscriber line
(ADSL) and some wireless• Logical extension of QPSK• Send two different signals simultaneously on
same carrier frequency– Use two copies of carrier, one shifted 90°
– Each carrier is ASK modulated– Two independent signals over same medium– Demodulate and combine for original binary output
![Page 52: Signal Encoding Techniques](https://reader036.fdocuments.in/reader036/viewer/2022062800/56814123550346895dacfa4c/html5/thumbnails/52.jpg)
QAM Modulator
![Page 53: Signal Encoding Techniques](https://reader036.fdocuments.in/reader036/viewer/2022062800/56814123550346895dacfa4c/html5/thumbnails/53.jpg)
QAM Levels• Two level ASK– Each of two streams in one of two states– Four state system– Essentially QPSK
• Four level ASK– Combined stream in one of 16 states
• 64 and 256 state systems have been implemented
• Improved data rate for given bandwidth– Increased potential error rate
![Page 54: Signal Encoding Techniques](https://reader036.fdocuments.in/reader036/viewer/2022062800/56814123550346895dacfa4c/html5/thumbnails/54.jpg)
Analog Data, Digital Signal
• Digitization– Conversion of analog data into digital signal
• Once analog data have been converted to digital signals, the digital data:– Digital data can then be transmitted using NRZ-L– Digital data can then be transmitted using code
other than NRZ-L– Analog to digital conversion done using a codec
![Page 55: Signal Encoding Techniques](https://reader036.fdocuments.in/reader036/viewer/2022062800/56814123550346895dacfa4c/html5/thumbnails/55.jpg)
Digitizing Analog Data
![Page 56: Signal Encoding Techniques](https://reader036.fdocuments.in/reader036/viewer/2022062800/56814123550346895dacfa4c/html5/thumbnails/56.jpg)
Digital Coding Schemes
• Pulse code modulation (PCM)
• Delta modulation (DM)
![Page 57: Signal Encoding Techniques](https://reader036.fdocuments.in/reader036/viewer/2022062800/56814123550346895dacfa4c/html5/thumbnails/57.jpg)
Pulse Code Modulation(PCM) (1)• Based on the sampling theorem• Each analog sample is assigned a binary code
– Analog samples are referred to as pulse amplitude modulation (PAM) samples
• The digital signal consists of block of n bits, where each n-bit number is the amplitude of a PCM pulse
• E.g.: 4 bit system gives 16 levels• Quantized
– Quantizing error or noise– Approximations mean it is impossible to recover original
exactly– Leads to quantizing noise
![Page 58: Signal Encoding Techniques](https://reader036.fdocuments.in/reader036/viewer/2022062800/56814123550346895dacfa4c/html5/thumbnails/58.jpg)
Pulse Code Modulation(PCM) (2)• 8 bit sample gives 256 levels• If a signal is sampled at regular intervals at a rate
higher than twice the highest signal frequency, the samples contain all the information of the original signal– (Proof - Stallings appendix 4A)
• Voice data limited to below 4000Hz• Require 8000 sample per second• 8000 samples per second of 8 bits each gives
64kbps• Quality comparable with analog transmission
![Page 59: Signal Encoding Techniques](https://reader036.fdocuments.in/reader036/viewer/2022062800/56814123550346895dacfa4c/html5/thumbnails/59.jpg)
PCM Example
![Page 60: Signal Encoding Techniques](https://reader036.fdocuments.in/reader036/viewer/2022062800/56814123550346895dacfa4c/html5/thumbnails/60.jpg)
PCM Block Diagram
![Page 61: Signal Encoding Techniques](https://reader036.fdocuments.in/reader036/viewer/2022062800/56814123550346895dacfa4c/html5/thumbnails/61.jpg)
Delta Modulation
• Analog input is approximated by a staircase function– Move up or down one level () at each sample
interval
• The bit stream approximates derivative of analog signal (rather than amplitude)– 1 is generated if function goes up– 0 otherwise
![Page 62: Signal Encoding Techniques](https://reader036.fdocuments.in/reader036/viewer/2022062800/56814123550346895dacfa4c/html5/thumbnails/62.jpg)
Delta Modulation - example
![Page 63: Signal Encoding Techniques](https://reader036.fdocuments.in/reader036/viewer/2022062800/56814123550346895dacfa4c/html5/thumbnails/63.jpg)
Delta Modulation
• Two important parameters– Size of step assigned to each binary digit (δ)– Sampling rate
• Accuracy improved by increasing sampling rate– However, this increases the data rate
• Advantage of DM over PCM is the simplicity of its implementation
![Page 64: Signal Encoding Techniques](https://reader036.fdocuments.in/reader036/viewer/2022062800/56814123550346895dacfa4c/html5/thumbnails/64.jpg)
Delta Modulation - Operation
![Page 65: Signal Encoding Techniques](https://reader036.fdocuments.in/reader036/viewer/2022062800/56814123550346895dacfa4c/html5/thumbnails/65.jpg)
Delta Modulation - Performance
• Good voice reproduction – PCM - 128 levels (7 bit)– Voice bandwidth 4khz– Should be 8000 x 7 = 56kbps for PCM
• Data compression can improve on this– e.g. Interframe coding techniques for video
![Page 66: Signal Encoding Techniques](https://reader036.fdocuments.in/reader036/viewer/2022062800/56814123550346895dacfa4c/html5/thumbnails/66.jpg)
Analog Data, Analog Signals
• Why modulate analog signals?– Higher frequency can give more efficient
transmission– Permits frequency division multiplexing ( will be
discussed in chapter 8)• Types of modulation– Amplitude Modulation– Angel Modulation
– Frequency Modulation– Phase Modulation
![Page 67: Signal Encoding Techniques](https://reader036.fdocuments.in/reader036/viewer/2022062800/56814123550346895dacfa4c/html5/thumbnails/67.jpg)
Amplitude Modulation
• cos2πfct = carrier
• x(t) = input signal• na = modulation index (< 1)– Ratio of amplitude of input signal to carrier
• Double sideband transmitted carrier (DSBTC)
![Page 68: Signal Encoding Techniques](https://reader036.fdocuments.in/reader036/viewer/2022062800/56814123550346895dacfa4c/html5/thumbnails/68.jpg)
Amplitude Modulation
![Page 69: Signal Encoding Techniques](https://reader036.fdocuments.in/reader036/viewer/2022062800/56814123550346895dacfa4c/html5/thumbnails/69.jpg)
Spectrum of AM
![Page 70: Signal Encoding Techniques](https://reader036.fdocuments.in/reader036/viewer/2022062800/56814123550346895dacfa4c/html5/thumbnails/70.jpg)
AM Power
• Transmitted power
• Pt = total transmitted power in s(t)
• Pc = transmitted power in carrier
![Page 71: Signal Encoding Techniques](https://reader036.fdocuments.in/reader036/viewer/2022062800/56814123550346895dacfa4c/html5/thumbnails/71.jpg)
Single Sideband (SSB)
• Variant of AM is single sideband (SSB)– Sends only one sideband– Eliminates other sideband and carrier
• Advantages– Only half the bandwidth is required– Less power is required
• Disadvantages– Poor performance in fading channels
![Page 72: Signal Encoding Techniques](https://reader036.fdocuments.in/reader036/viewer/2022062800/56814123550346895dacfa4c/html5/thumbnails/72.jpg)
Angle Modulation
• Frequency modulation– Derivative of the phase is proportional to
modulating signal
• Phase modulation– Phase is proportional to modulating signal
![Page 73: Signal Encoding Techniques](https://reader036.fdocuments.in/reader036/viewer/2022062800/56814123550346895dacfa4c/html5/thumbnails/73.jpg)
Analog Modulation
![Page 74: Signal Encoding Techniques](https://reader036.fdocuments.in/reader036/viewer/2022062800/56814123550346895dacfa4c/html5/thumbnails/74.jpg)
Required Reading
• Stallings chapter 5