TECHNIA- International Journal of Computing Science and Communication Technologies, VOL. 3, NO. I, July 2010. (ISSN 0974-3375)
`
`ANALOG & DIGITAL MODULATION
`TECHNIQUES: AN OVERVIEW
`
`D.K.Sharma 1, A. Mishra2 & Rajiv Saxena3
`
`1Ujjain Engineering College, Ujjain, MP
`2Madhav Institute of Technology & Science, Gwalior, MP
`3Jaypee Institute of Engineering & Technology, Guna, MP
`1 rlilip slumn(l 11 7l@!•ahoo.com; 1tftrJb/Jtq•mi,•·irrnllilrfl iwo.l'nm; 1r"jil• .. mrerm(itljiet.rl£', in,
`
`Abstract:
`A tremendous technological transformation during the last two
`decades has provided a potential growth in the area of digital
`communication and lot of newer applications and technologies
`are coming up everyday due to these reasons. Restricting
`overself to
`the domain of modulation techniques a brief
`overview over different analog and digital modulation
`techniques has been provided in this article through extensive
`literature survey in a tabular manner enabling to analyze and
`establish the superiority at a glance of a specific modulation
`technique for a particular application.
`
`1.0 INTRODUCTION:
`Living in the era of communication every thing
`may be video, audio or any information in the form of
`electrical signal is termed as data and there is an enormous
`requirement of data transfer between two or more point
`through the world wide web, every moment of the clock,
`which is a big threaten to the existing communication
`systems because of the problems like spectral congestion,
`severe adjacent & co-channel interference problems and
`noise corrupted data reception etc. This has resulted in
`serious need for the research work all around the world for
`the development of the communication systems which can
`handle the above said problems, where each aspect of the
`communication systems is dealt with the development of
`new
`encoding
`techniques, modulation
`techniques,
`possibilities for newer transmission channels and off course
`the demodulation and decoding techniques [I, 2].
`The design of a communication system is application
`oriented and is dependent on the type of the signal. The
`choice of digital communication technique over its analog
`counter part becomes more evident of the fact that it provide
`larger immunity to noise for even at the price of large
`bandwidth requirements, where as the requirement of video,
`Audio and data over the computer network or the mobile
`telephony network termed as the third generation (3G)
`mobile communication poses a serious problem for the
`bandwidth so The existing modulation techniques need to be
`modified for the purpose where it can handle both the
`situations of noise and bandwidth efficiency [3, 4].
`The major advantage of using digital modulation
`technique is that the use of digital signals reduces hardware,
`noise and
`interference problems as compared
`to
`the
`analogue signal where large number of waveforms will be
`required resulting in a larger bandwidth for the symbol to be
`transmitted [5].
`Over the past years various modulation techniques
`have been designed
`and extensively used for various
`applications but the modern communication system requires
`data transmission at a higher rate, larger bandwidth in order
`
`to have multimedia transmission, hence the existing modulation
`techniques are not able to provide a complete solution keeping
`this in the view the authors of this article have tried to draw a
`sketch within the existing modulation techniques to derive out
`exactly what modifications or the alterations in the present
`techniques may sort out the problem or there is still a need for
`designing a new modulation technique for the purpose of the
`present communication system requirements [6, 7].
`
`2.0 Classification of Modulation Techniques.
`Modulation is the process of varying some parameter of
`a periodic waveform in order to use that signal to convey a
`message. Normally a high-frequency sinusoidal waveform is
`used as carrier signal. For this purpose
`,if the variation in the
`parameter of the carrier is continuous in accordance to the input
`analog signal the modulation technique is termed as analog
`modulation scheme if the variation is discrete then it is termed as
`Digital Modulation Technique [8].
`
`1 .
`Table-!: Type of Modulation T t:Cilmques
`
`Sr.
`No Modulation
`Techniques
`Analog
`Modulation
`Techniques
`
`01
`
`02
`
`Digital
`Modulation
`Techniques
`
`Type
`
`Notation
`
`(i) Amplitude
`Modulation
`(ii) Frequency
`Modulation
`(iii) Phase
`Modulation
`(i) Amplitude
`Shift Keying
`(ii) Frequency
`. Shift Keying
`(iii)Phase Shift
`Keying
`
`A.M.
`
`F.M.
`
`P.M.
`
`A.S.K.
`
`F.S.K.
`
`P.S.K.
`
`2.1 Analog Modulation Techniques:-
`There are basically three type of analog modulation
`schemes the amplitude modulation , the Frequency modulation
`and the phase modulation schemes which have in turn lot of
`class subclass or derivatives as listed in Table-2 [9, I 0]. In case
`of th~ Amplitude Modulation there are several derivatives and it
`is evident from the comparative table -3 that the Single Side
`Band Suppressed Carrier (SSS-SC) has smaller bandwidth and
`power
`requirements
`in contrast with Double Side Band
`Suppressed Carrier (DSB -SC) and Double Side Band Full
`Carrier (DSB -FC) and Single Side Band Full Carrier (SSB -FC)
`but for detection of this signal, we require sharp cutoff Low Pass
`Filter (LPF) which is not practically viable. Using the Vestigial
`Side Band (VSB) technique in place of (SSB - SC), we can
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`achieve a low pass filter with a gradual cut off but it requires
`more BW and power than SSB-SC and less then the DSB-
`SC and DSB-FC and hence ideally SSB-SC is proves to be
`better than other AM schemes but practically, VSB proves
`to be a much better candidate then the other amplitude
`modulation techniques [11, 12].
`The Amplitude modulated signals require nonlinear
`amplifiers which generate spurious out-of-band spectral
`components which are filtered out with a great difficulty.
`Frequency Modulation proves to be better in comparison to
`amplitude modulation and phase modulation,
`and the
`derivative of frequency modulation, narrow band FM
`(NBFM) is usually employed to overcome above mentioned
`problems in the communication system [13, 14].
`Table-3 provides representation, bandwidth requirement and
`power requirement properties of various analog modulation
`techniques. The great merit of FM over AM is that FM
`allows us to suppress the effects of noise at the expense of
`bandwidth. The major limitation of the analog modulation
`systems for communicating over long channels is that once
`noise has been introduced at any place along the channel,
`then it
`is carried out
`till
`the end. Because the analog
`modulation system ( AM, FM and
`PM ) are extremely
`sensitive to the noise present at the receiver end in contrast
`to this if a digital signal is modulated and transmitted the
`received signal is far less sensitive to receiver [15’ 16].
`
`2.2 Digital Modulation Techniques:-
`After the conversion of an Analog signal to digital
`by sampling different type of digital modulation schemes
`can be achieved by the variation of different parameter of
`the carrier signal for example the Amplitude variation gives
`BASK, Frequency variation gives BFSK and the phase
`variation gives BPSK. Also sometimes a combinational
`variation of this parameter is done to generate the hybrid
`modulation technique viz. a combinational variation of
`Amplitude and Phase Shift Keying (APSK). Many more
`digital modulation techniques are available and can also be
`designed depending upon the type of signal
`and the
`application [17].
`Thus a better digital modulation technique is to be
`thought over by the designer which has an ability of
`exploiting
`the
`available
`transmitted
`power
`and
`the
`bandwidth to its full extent [18, 19].
`In order to achieve a discrete signal it is essential to
`have the modulating signal of the form ofa NRZ rectangular
`pulse thus yielding the modulated parameter as a discrete
`signal switching or keying between two discrete values [20].
`However, ASK, FSK, and PSK with Nyquiste pulse shaping
`at
`the base band form the basic technique of digital
`modulation, but other methods are
`also possible with
`hybridization of two or more basic digital modulation
`schemes with or without pulse shaping [21, 23].
`
`3. Classification of Digital Modulation.
`be
`can
`These
`digital modulation techniques
`classified basically either on the basis of their detection
`characteristics or in terms of their bandwidth compaction
`characteristics [24]. Various types of digital modulation
`techniques are listed in Table-4 and few of them have been
`comprehensively emphasized here in details providing a
`comparative analysis.
`
`3.1 Binary Amplitude Shift Keying [BASK]
`the
`The BASK is obtained by the alteration of
`amplitude of the carrier wave [1, 11]. It is a coherent modulation
`technique hence the concept of the co-relation between the
`signal, number of basis functions, the I and Q components and
`the symbol shaping are not applicable here. It has very poor
`bandwidth efficiency. The basic merit of this technique is its
`simple implementations but is highly prone to noise and the
`performance is well established only in the linear region which
`does not make it a viable digital modulation technique for
`wireless or mobile application in the present scenario. The
`combination with PSK [20] yields derivatives like QAM and M-
`Ary ASK, which have much important application with
`improved parameters.
`
`3.2 Binary Frequency Shift Keying [BFSK]
`When two different frequencies are used to represent
`two different symbols, then the modulation technique is termed
`as BFSK.BFSK can be a wideband or a narrow band digital
`modulation technique depending upon the separation between
`the two carrier frequencies, though cost effective and provides
`simple
`implementations but
`is not
`a bandwidth efficient
`technique and is normally ruled out because of the receiver
`design complexities [1-3, 12].
`
`3.3 Binary Phase Shift Keying [BPSK]
`When the phase of the carrier wave is altered with
`reference of the modulating signal then the resultant modulation
`scheme is termed as Phase Shift Keying. The digital modulation
`technique can be said to be the simplest
`form of phase
`modulation and is known as binary because the carrier phase
`represents only two phase states [13]. It is normally used for high
`speed data transfer application, provides a 3dB power advantage
`over the BASK modulation technique and is robust and simple in
`implementation but proves to be an inefficient user of the
`provided bandwidth and is normally termed as a non-linear
`modulation scheme.
`It provides small error rates than any other
`systems. The modulation techniques provide a number of
`derivatives [20].
`
`3.4 Differential Phase Shift Keying [DPSK]
`For the perfect detection of a phase modulated signal, it
`become evident that
`the receiver needs a coherent reference
`signal but if differential encoding and phase shift keying are
`incorporated together
`at
`the
`transmitter
`then the
`digital
`modulation technique evolved is termed as Differential Phase
`Shift Keying [1, 14]. For the transmission of a symbol 1, the
`phase is unchanged whereas for transmission of symbol 0, the
`phase of the signal is advanced by 1800 . The track of the phase
`change information which becomes essential in determining the
`relative phase change between the symbols transmitted. The
`whole process is based on the assumption that the change of
`phase is very slow to an extent that it can be considered to be
`almost constant over two bit intervals (7).
`
`3.5 Quadrature Phase Shift Keying (QPSK)
`Another extension of the PSK digital modulation technique
`is the division of the phase of the carrier signal designed by
`allotting four equally spaced values for the phase angle [1-3] as
`1t/4, 3Tt/4, 57t/4, and 77t/4, thus providing a major advantage over
`BPSK by having the information capacity double to it,
`i.e. the
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`QPSK has four message points in the constellation diagram
`and so it becomes a highly bandwidth efficient digital
`modulation technique. But the exact phase retrieval becomes
`a
`very
`important
`factor
`for
`the
`receiver
`design
`considerations,
`failing which can give rise to erroneous
`detection of the signal. This factor increases the receiver
`design complexities. To compensate for these problems,
`normally the idea of pulse shaping the carrier modulated
`signal
`is employed with the Root Raised Cosine Pulse
`shaping for achieving better performances which in turn
`provides a demerits that the constant envelope property of
`the signal
`is lost but then there is a lost but there is a
`remarkable improvement
`in the ISI performance of this
`digital modulation technique [15-18].
`
`3.6 Minimum Shift Keying [MSK]
`Minimum Shift Keying (MSK) is a modified form of
`continuous phase FSK. Here,
`in this case,
`the spacing
`between the two carrier frequencies is equal to half of the bit
`rate which is the minimum spacing that allows the two
`frequencies states to be orthogonal [1-3].
`An MSK signal can e said to be derived from either an
`Offset Quadrature Phase Shift Keying (OQPSK) signal by
`replacing a square pulse by ‘/2 cosinusoidal pulse or
`alternatively from an FSK signal. The information capacity
`of an MSK signal is equal to that of QPSK signal but due to
`the 1/2 cosine pulse shaping the bandwidth requirement is
`lesser than that required by QPSK.
`It achieved smooth
`phase transitions thus providing a constant envelope.
`It has
`lower out of band power and can be said to be more
`spectrally efficient
`than the QPSK modulation technique
`[19-25].
`The major demerits which this digital modulation
`scheme suffer s is that it is in the class of linear modulation.
`The spectrum is not enough compact to realize [27] data rate
`approximating RF channel bandwidth. Table-2 [26, 27]
`summarizes representation and different properties of this
`technique.
`
`3.7 Gaussian Minimum Shift Keying [GMSK]
`An MSK signal
`is generated by applying a half
`sinusoidal pulse in place of a square pulse.
`If a Gaussian
`pulse shape is used instead then the resultant digital
`modulation technique is an improved version of the MSK
`digital modulation technique in the sense of bandwidth and
`spectral
`efficiency and
`is
`termed as GMSK digital
`modulation technique (Gaussian Minimum Shift Keying).
`Moreover,
`the major advantage in this technique is the
`sufficiently lower side lobe levels and the narrower main
`lobe as compared to a QPSK and MSK pulse [18].
`GMSK can be viewed as either a frequency or
`phase modulation scheme, although the rate of change of
`phase is limited by the Gaussian response but he phase
`carrier can still advance or retard up to 90° over the course
`of the bit period. The severity in pulse shaping lies on the
`bandwidth time product (BT) because of the reason that the
`achieved phase change over a bit period may fall short by
`7t/2 which will have a severe impact on bit error rate [28] but
`it still provides improved bandwidth efficiency over MSK.
`The bandwidth of a GMSK system is defined by
`the relationship between the premodulation filter bandwidth
`B and the bit period TB. Thus the decision of value of BT
`
`and data rate is crucial in the sense that there has to be a trade of
`between the BER and out of band interference [29, 30] as the
`narrow filter will
`result
`in provocation of
`Inter Symbol
`Interference (ISI) which on the other hand will reduce the signal
`power enormously [30].
`The generation of a GMSK signal can be done by any
`one of the two methods as in the case of MSK signals,
`the
`Frequency Shift Keying modulation method. Only difference
`which comes in here than the generation of MSK signal is that
`the pulse shaping by halfroot raised cosine pulse is replaced by a
`Gaussian pulse shape.
`
`3.8 Orthogonal Frequency Division Multiplexing (OFDM):-
`The OFDM is a modulation scheme having multicarrier
`transmission techniques here the available spectrum is divided
`into many carriers each one being modulated at a low rate data
`stream. The spacing between the carriers is closer and the
`carriers are orthogonal to one another preventing interferences
`between the closely spaced carriers hence OFDM can be thought
`of as a combination of modulation and multiplexing techniques,
`each carrier in a OFDM signal has very narrow bandwidth so the
`resulting symbol rate is low which means that the signal has high
`tolerance to multipath delay spread reducing the possibility of
`inter symbol
`interferences (ISI) which is the requirement for
`today’s communication systems.
`The higher is the transmission rate, the large will be the
`bandwidth of the signal
`as compared with the coherence
`bandwidth of the propagation channel, at this stage the different
`spectral components present
`in the signal will experience
`different fading characteristics,
`this frequency selective fading
`has to be characterized using appropriate techniques in order to
`achieve acceptable error rate at the detection or output in order to
`achieve characterization in frequency selective fading the basic
`approach is to partition the signal into frequency bands, each one
`of which is narrow as compared to the coherence bandwidth of
`the channel and subsequently each of this signal component is
`then modulated onto a different sub carrier and the signal
`components are sent parallel over the channel. Hence, each
`signal component will now experience non- frequency-selective
`fading because now the high rate serial data sequence is
`converted into a number of lower rate parallel sequences and
`then each of them is modulated onto a sub carrier, the effective
`method to achieve
`this
`is orthogonal
`frequency division
`multiplexing (OFDM). The modulation parameters dependent on
`the data rate used shall be set according to (Table-12) Rate
`Dependant Parameter.
`
`4.0 Comparison
`The BASK technique is simpler and economic in
`implementation and is less prone to errors but provides less
`bandwidth efficiency and operates efficiency in the linear region
`only, which does not make it an efficient
`technique for the
`wireless communication systems. On the other hand, he BFSK
`technique is
`still
`less prone to errors and the bandwidth
`requirement is the same as that of BASK (Table-4) but is not a
`bandwidth efficient technique. The error performance parameter
`is better
`to BASK (Table-9,10).
`It requires matched filer
`detection and because of this, the receiver design complexities
`increase and so it
`is seldom used for wireless or mobile
`application.
`The BPSK modulation technique is still better than the
`above mentioned two modulation techniques.
`It is a coherent
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`modulation technique and can be used for high speed data
`transfer application and has a basic advantage of double
`information capacity (Table-7) over BASK and BFSK.
`Simple implementation and robustness makes it a useful
`technique for satellite communication but on the other hand
`it has proved an inefficient use of the bandwidth and is
`categorized
`under
`a
`class of non-linear modulation
`techniques (Table-5). The error performance is better and is
`optimized to achieve minimum possible error rate (Table-6,
`7).
`The detection of phase shift (Table-8) makes the
`receiver design complex, so the technique is not of interest
`for the wireless or mobile communication applications.
`The DPSK technique provides information capacity
`to BPSK and is considered to be more viable
`similar
`technique than BPSK and is a non coherent orthogonal
`modulation (Table-4, 5). But the receiver complexities are
`more than BPSK because memory is required in the system
`to keep the track of relative phase difference.
`The most widely used technique is the QPSK modulation
`technique which has an information capacity double to
`BPSK (Table-4) over the same bandwidth and requires
`coherent detection, so it can be considered to be highly BW
`efficient. Since the modulation envelope is also constant
`hence it
`is
`said to be spectrally efficient modulation
`technique also. Thus it provides major advantages over
`BPSK and has also overcome the major drawbacks of the
`BPSK.
`the detection of exact
`In detection of a QPSK signal,
`phase shit becomes an important criterion which on the
`other hand increases receiver design complexities as well.
`The improvement further in this modulation technique can
`be achieved by pulse shaping the modulated carrier. The
`pulse shaping by ‘/z co-sinusoidal pulse shaping provides a
`better performance modulation technique,
`the Minimum
`Shift Keying (MSK), which can also be viewed as
`comprising of two CPFSK signals. This has a major
`advantage that the out of band power is significantly lower
`than QPSK (Table-7) and the 99% of total power of MSK is
`1.2 TB thus spectrally efficient and constant envelopes.
`It
`has proved to be a better modulation technique than QPSK
`in the sense that the signal coherence and deviation ratio are
`largely unaffected by variation in input rates (Table 11).
`But
`the basic demerit
`(Table 7) of MSK modulation
`technique is that the spectrum is not enough compact for the
`realization of higher data rates. The GMSK modulation
`technique is a variation of MSK where the co-sinusoidal
`pulse shaping of the modulated carrier is replaced by the
`Gaussian pulse shaping. This improves the envelope and
`the spectral efficiency (Table 6, 7). A BT = 0.3 GMSK has
`been more popular than its other variants as it is optimized
`for the better bandwidth and error performances at
`this
`value. The major disadvantage shown by this modulation
`technique is its high susceptibility to ISI at higher data rates
`due to the narrow symbol shape (Table 7). The technique is
`highly used in GSM mobile communication.
`The average probability of bit error at the output of a
`demodulator and decoder is the performance measure of the
`demodulator decoder combination. To be more precise the
`probability of error is a function of code characteristics,
`waveforms,
`the transmitted power, characteristics of the
`transmission channel and the demodulation and decoder
`combination. Hence the reconstructed signal at the receiving
`
`end is an close approximation of the transmitted signal and the
`difference or some function of the difference in the original and
`the reconstructed signal. This marks a measure of performance in
`terms of distortion in a digital communication system. (Table-
`10)
`summarizes
`the BER equations of digital modulation
`techniques.
`in the field of
`The basic research work carried out
`communication lead to the development of new modulation
`techniques, coding techniques, error rate performances analysis
`but
`the ever increasing demand of the faster communication
`system with large bandwidth requirements has again generated a
`new hunger towards the development of newer techniques, so
`many modulation techniques like BPSK, DPSK, MSK, GMSK,
`M-ary QAM have been developed. The major consideration with
`any modulation technique developed is
`that
`its detection
`performance should show a better bit
`error
`rate
`(BER)
`performance, several methods have been devised for the exact or
`improved BER performances of the modulation techniques.
`The main objective of a communication system
`designer is to transmit message as speedily as possible, with least
`probability of error. Fast communication is possible by:
`(i)
`reducing the time of each massage; but this, in turn, increase the
`bandwidth and (ii)
`simultaneous
`transmission of
`several
`messages over a single physical channel. This process is known
`as multiplexing. So OFDM can be a good candidate over other
`digital modulation schemes.
`
`5.0 Conclusions:
`
`An analysis of the digital modulation technique carried
`in this article reveals
`that
`the selection of a digital
`out
`modulation technique is
`solely dependent on the type of
`application.
`This is because of the fact
`that some of the
`technique provide lesser complexities in the design of the
`modulation and demodulation system and prove economic like
`the BASK, BFSK, BPSK and DPSK techniques and can be
`visualized for the systems which really does not require high
`amount of precisions or when economy is the major aspect and
`the BER performances can be tolerated.
`On the other hand when the system designer has a sole
`consideration for the techniques like BASK, BFSK, BPSK and
`DPSK doesn’t under the region of consideration and the system
`designer has to think in terms of better modulation techniques
`like the QPSK, MSK and GMSK, where GMSK has proved its
`performance over
`the other
`two in the
`area of mobile
`communication because of the spectral efficiency. But
`the
`search for a better modulation technique doesn’t end here as the
`criterion for higher data rate communication is taking the lead in
`almost every area of communication and thus the ISI and BER
`realization become very important and crucial aspect for any
`future digital modulation technique.
`Taking the above facts into consideration, the design of
`a digital communication system is very trivial and is very much
`applications oriented, as one application may require higher
`precision in data reception where as the other may compromise
`on this aspect but may be rigid on the aspect of the available
`bandwidth or power,
`thus the parameters like the modulation
`bandwidth, power, channel noise and the bit error rate become
`very important parameters in the designing of digital/wireless
`communication system.
`
`Reference:
`
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`27.
`
`28.
`
`29.
`
`30
`
`Sr
`No
`
`2
`
`4
`
`
`
`
`F. Amoroso and JA Kivett, ‘Simplified MSK signaling technique’, IEEE
`transaction on communications, vol. COM-25, pp 433-441. 1977.
`K. Murota and K Hirade,
`‘GMSK Modulation for Digital mobile
`Telephony’, IEEE transactions on communications, vol. COM-29, no 7,
`1044-1050, 1981.
`MA Wickert and WS Sward, ‘Limiter Discriminaor — Detected GMSK
`with FM and GMSK interference
`in
`land mobile channel’,
`IEEE
`transactions on communications, vol. COM-47, pp. 1963-1700, 1999.
`in
`M.A. Mendlovitz, ‘Reduction of adjacent channel
`interference effect
`GMSK communication Links’, MILCOM proceedings, IEEE transactions,
`vol. 1, pp 685-690 (Oct-7-10), 2002
`
`Table-2: Classification ofAnalo - Mildululllm ‘l‘echnit tlL’S
`
`
`
`
`
`TYPE
`
`Linear
`
`Linear
`
`Linear
`
`REPRESENT
`ATION
`AM
`DSB-SC
`
`AM
`DSB-FC
`
`AM
`SSB-SC
`
`SSB-FC
`AM
`
`S Haykin, Digital Communication, John Wiley & Sons, Inc , Replika
`Press Pvt Ltd, N. Delhi, India, 2000-2001
`A.B. Carlson, P.B. Crilly, J.C. Rutledge, Communication Systems,
`McGraw-I-lill, Singapore, International Edition, 2002, (4lh Ed).
`K S. Shanmugam, Digital & Analog Communication, John Wiley &
`Sons, Inc , Replika Press Pvt. Ltd , N Delhi, India, 2000.
`HP. LATHI, Modem Digital and Analog Communication Systems,
`Oxford University Press, New Delhi, India, (3"1 Ed.).
`N Sarkar, elements of Digital Communication Systems, Oxford
`University Press, New Delhi, India, 203 (Ist Ed)
`HP HSU, Analog and digital Communication, Schaum’s outline
`Series, McGraw-I-Iill, USA, CA, 1976
`T Aulin and WC. Sundberg,
`“Continuous Phase Modulation — Part
`I
`: Full Response Signaling”,
`IEEE transactions on communications
`(Legacy, pre-l988), vol COM-29, no.3, pp 196-209, 1981.
`AN. Rydbeck and C E. Sundberg,
`“Continuous Phase Modulation —
`Part
`II:
`Full Response Signaling",
`IEEE transactions
`on
`communications (Legacy, pre-1988), vol Com-29, no 3, pp 210-225,
`1981.
`'Communications Efficiency of Certain digital Modulation
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`
`10
`
`11.
`
`12
`
`13.
`
`14
`
`15
`
`16
`
`17
`
`18
`
`19
`
`20
`
`21
`
`22
`
`23
`
`24.
`
`25
`
`26
`
`MODULATION
`TECHNIQUES
`Amplitude Modulation
`Double-Sideband
`Su ressed Carrier
`Amplitude Modulation
`Double-Sideband With Full
`Carrier
`
`
`Amplitude Modulation
`Single-Sideband Suppressed
`Carrier
`Amplitude Modulation
` < SB "-
`Single-Sideband With Full
`Carrier
`
`Amplitude Modulation
`
`
`Vestigial-Sideband
`
`
`
`Narrow-Band Frequency
`Modulation
`
`
`Wide-Band Frequency
`
`Modulation
`
`BANDWI
`
`
`DTH
`ANALOG
`
`
`(B. W.)
`MODULATION
`
`
`
`
`AM-DSB-FC
`
`
`
`AM-DSB-SC
`
`
`
`83.33%
`AM-SSB-SC
`1/4 Pc
`
`
`
`
`>SSB-SC
`Greater than
`AM-VSB
`
`
`
`
`
`SSB-SC
`
`
`NBFM
`Same as
`Same as
`
`
`DSB-SC DSB-SC
`
`
`More than
`
`WBFM
`NBFM
`
`
`Pc = carrier
`
`
`
`
`power
`a)": _
`
`
`modulating
`modulatio
`modulati
`
`
`
`
`frequency
`n index in
`on in PM
`
`FM
`
`Table—4: Classification & Performance Analysis ofDigital Modulation
`Tcthm ties 1-7
`
`
`Rt.- m-srculuiion
`
`
`
`Modulation
`
`
`555
`
`REMBRANDT EXHIBIT 221 7
`
`REMBRANDT EXHIBIT 2217
`
`

`

`TECHNIA — International Journal of Computing Science and Communication Technologies, VOL. 3, NO 1, July 2010 (ISSN 0974-3375)
`
`bits
`
`Binary
`Modulation
`Scheme
`
`'
`
`.
`
`Per
`Sub-
`carrier
`
`Amplitude
`2R5
`
`Shift Ke in
`coherent
`
`Frequency
`Shifi Kcvin_
`Binary Phase
`Shitt Keying
`Differential
`Phase Shift
`
`Where“
`
`Coherent
`N n
`°
`coherent
`
`2R3
`
`2R5
`
`2R3
`
`
`
`
`
`
`
`M-ary QAM
`
`Coherent
`
`Coherent
`
`2 Rb /N
`2 Rb /N
`
`Quadrature
`Modulation
`Scheme
`
`
`Quadrature
`Phase Shift
`Coherent
`2R5
`0]
`
`
`KeyingMinimum
`
`Phase Shift
`Coherent
`Less than
`
`
`Keving
`QPSKWhere
`
`
`M-ray
`:
`Modulation
`
`
`Scheme
`2N ’ N
`
`M-ary Phase
`
`Shifi Kevin ,
`M-ary PSK
`Quadrature
`Amplitude
`Shifi
`Table-12: Numerical Values for the OFDM [Multicarrier Modulation Schemes]
`Modulation
`Parameters
`M-ary
`
`
`5"
`PARAMETERS
`VALUE
`M-ary FSK
`03
`Frequency
`Coherent M 2 Rb /N
`
`
`
`
`
`11%-
`Shifi K