Clarification: In linear modulation technique, the amplitude of transmitted signal varies linearly with modulating digital signal. It is a form of digital modulation technique. 2. Linear modulation techniques are not bandwidth efficient Linear modulation techniques are not bandwidth efficient. State whether True or False Thus, the bandwidth efficiency of linear modulation is generally obtained at the expense of hardware cost, power, and higher BERs in fading. Linear modulation techniques are used in most wireless LAN products, whereas nonlinear techniques are used in most cellular and wide area wireless data systems Bandwidth Efficiency of Modulation l Ability of a modulation scheme to accommodate data within a limited bandwidth. l Bandwidth efficiency reflect how efficiently the allocated bandwidth is utilized Bandwidth Efficiency : bps/Hz B R hB = R: the data rate (bps) B: bandwidth occupied by the modulated RF signa Key focus: Compare Performance and spectral efficiency of bandwidth-efficient digital modulation techniques (BPSK,QPSK and QAM) on their theoretical BER over AWGN. Let's take up some bandwidth-efficient linear digital modulation techniques (BPSK,QPSK and QAM) and compare its performance based on their theoretical BER over AWGN

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 A communication that does not use amplitude modulation is baseband communication. Baseband is a signal that has a narrow frequency range and requires no modulation, i.e. without any shift in the range of frequencies of the signal. On the other hand, a communication that does use modulation is a carrier communication The answer lies in simply creating and implementing a more spectrally efficient modulation method. That's what NovelSat did. Its NS3 modulation method increases bandwidth capacity up to 78% Bandwidth-efficient coded modulation with optimized linear partial-response signals Abstract: We study the design of optimal signals for bandwidth-efficient linear coded modulation. and solved with well-known efficient optimization techniques bandwidth increases but increasing the peak optical power level by 1/D compensates it. OOK is not very efficient at smaller duty cycles. It is more appropriate to code the information into the position of the pulse such as PPM. 2.2. Pulse Position Modulation (PPM) Low duty cycle PPM, is the most commonly used technique, which is a power.

linear modulations are bandwidth-efficient (but not power-efficient) nonlinear modulations are power-efficient (but not bandwidth-efficient) Constant envelope propert Clarification: M-ary modulation schemes have poor power efficiency, but they have a better bandwidth efficiency. An 8-PSK system requires a bandwidth that is 3 times smaller than a BPSK system, whereas its BER performance is very worse since signals are packed more closely in the signal constellation ** Digital Modulation**. For better quality and efficient communication, the digital modulation technique is employed. The main advantages of digital modulation over analog modulation include permissible power, available bandwidth, and high noise immunity bandwidth-efficient modulation methods that directly modulated the carrier were being developed, which, along with improved data formatting methods (e.g., packet transfer frame telemetry) to handle the multiple channel separa-tion problem, eliminated the need for subcarriers. Combining the packe

(Table- technique for satellite communication but on the other hand 10) summarizes the BER equations of digital modulation it has proved an inefficient use of the bandwidth and is techniques. categorized under a class of non-linear modulation The basic research work carried out in the field of techniques (Table-5) Amplitude modulation is very much sensitive to noise and hence the performance is very weak. Signal of AM is not stronger than FM when it propagates through and obstacle. Only one sideband of AM transmits Information Signal, so it loses power on other sideband and Carrier. Hence the power efficiency of the Amplitude Modulation is very poor 7 of 82 Linear Modulation Techniques: Digital modulation can be broadly classified as: 1. Linear (change Amplitude or phase) 2. Non linear modulation techniques (change frequency). Linear Modulation Techniques: • The amplitude /phase of the transmitted signal s(t), varies linearly with the modulating digital signal, m(t)

Bandwidth efficient modulation schemes Offset QPSK (OQPSK) and Minimum shift keying Bandwidth efficient and constant envelope modulations, suitable for non-linear amplifier M-QAM Bandwidth efficient modulation Trellis coded modulation (TCM) Bandwidth efficient modulation which improves the performance without bandwidth expansio It has been shown that the resolution of a digital pulsewidth modulator (DPWM) can be dramatically increased by either constant on-time modulation control or constant off-time modulation control.

CCSDS REPORT CONCERNING **BANDWIDTH-EFFICIENT** **MODULATIONS** CCSDS 413.0-G-3 Page iv February 2018 DOCUMENT CONTROL Document Title Date Status CCSDS 413.0-G-1 **Bandwidth-Efficient** **Modulations**: Summary of Definition, Implementation, and Performance, Issue 1 April 2003 Original issue, superseded CCSDS 413.0-G-2 **Bandwidth-Efficient** **Modulations** As such, RF power amplifiers (PAs) with improved efficiency, linearity, and bandwidth are needed. Dynamic load modulation (DLM) is one of the most common PA efficiency enhancement techniques. By investigation of new DLM design techniques, the overall objective of this thesis is to improve the efficiency-linearity and efficiency-bandwidth trade-offs in PAs for future wireless systems This modulation technique applies the properties of phase realizability, phase shift orthogonality, and compact phase support to devise a bandwidth efficient modulation waveform that is also. The term spectral efficiency refers to how well a specific modulation technique produces a maximum data rate in a minimal bandwidth. When the mark and space frequencies are arbitrarily chosen, they will not be phasecoherent In order to achieve high bandwidth efficiency, the modern digital radio system uses advance modulation schemes like QAM. These modulation schemes can pack more data on a given bandwidth but at the cost of increased peak to average RF signal power ratio. Secondly these modulation techniques require highly linear power amplifier which ar

The data rate evolution necessary to meet new mobile telecommunication standards (9.6 kb/s for GSM, 115.2 kb/s for GPRS, 384 kb/s for EDGE and 2 Mb/s for UMTS) demands the use of wider bandwidth and bandwidth-efficient linear modulation techniques This augmented signal space provides a good spread for the modulation signal points and can be quite efficientfor high-level linear modulation techniques. The obtained results show that this combined scheme, not only improves the system performance in both additive white Gaussian noise and fading multipath channels, but also improves the bandwidth efficiency of orthogonal transmitter diversity

Coded-Modulation Techniques for Fading Channels provides the reader with a sound background for the application of bandwidth-efficient coded-modulation techniques in fading channels. The book systematically presents recent developments in the field, which has grown rapidly in recent years, and provides a solid frame of reference for further research in this area This augmented signal space provides a good spread for the modulation signal points and can be quite efficient for high-level linear modulation techniques. The obtained results show that this combined scheme, not only improves the system performance on both additive white Gaussian noise and fading multipath channels, but also improves the bandwidth efficiency of orthogonal transmitter diversity technique is also called linear modulation. 4.3. Linear modulations: (a) Double-sideband amplitude modulation (i)Double-sideband-suppressed-carrier (DSB-SC or DSSC or simply and then lowpass- ltered, the lter bandwidth being the same as the mes-sage bandwidth Bor somewhat larger The performance of a modulation technique is measured in terms of its Bandwidth and power efficiency. Bandwidth efficiency is the ability of a modulation technique to accommodate data within a limited bandwidth while power efficiency is the capability of a modulation technique to preserve the bit error probability of the digital message at low power levels [1, 5] This frequency modulation needs a higher bandwidth range which is almost 15 times ahead of the narrow band frequency modulation. The other types of modulation techniques used in the communication system are: Binary phase shift keying; Differential phase-shift keying; Differential quadrature phase shift keying; Offset quadrature phase shift keying; Audio FS

** Additionally, it is significant to note that by decreasing the bandwidth and increasing the efficiency of the phase modulation for SBS suppression, we have demonstrated up to 38 dB of conversion efficiency gain with an OSNR penalty of 0**.8 dB from back to back, which is the smallest recorded two-pump FOPA penalty to date for such high gain So, ASK, PSK, QAM are bandwidth efficient while FSK is not. It's power efficient. The only exception is MSK, a continuous phase binary frequency shift keying, that keeps the separation between the two frequency components in such a way so as to make them orthogonal to each other in signal space Digital Modulation Desirable modulation method provides low BER at low SNR Performs well in multipath and fading environment Occupies least amount of bandwidth/symbol Easy and cost effective to implement Generally they are two categories Power efficient -FSK, Spread spectrum At low SNR provide acceptable BERAt low SNR provide acceptable BE

- Since lower time-bandwidth products produce a faster power-spectrum roll-off, why not have a very small time-bandwidth product. It happens that with lower time-bandwidth products the pulse is spread over a longer time, which can cause intersymbol interference. Therefore as a compromise between spectral efficiency and time-domai
- Digital Modulation. For a better quality and efficient communication, digital modulation technique is employed. The main advantages of the digital modulation over analog modulation include available bandwidth , high noise immunity and permissible power. In digital modulation, a message signal is converted from analog to digital message, and then modulated by using a carrier wave
- N is the modulation efficiency measured in bit/symbol or bpcu. In the case of baseband transmission (line coding or pulse-amplitude modulation) with a baseband bandwidth (or upper cut-off frequency) B, the symbol rate can not exceed 2B symbols/s in view to avoid intersymbol interference
- We describe the optimization technique for both MLC (joint optimization of component code rates and code parameters) and BICM (only component code parameters) in thissection,as well. In SectionV, we present theoptimization results for both Gray-mapped MLC and BICM schemes based on 4-PAM and 8-PSK modulation.2 We show that the optimize
- Let's take up some bandwidth-efficient linear digital modulation techniques (BPSK, QPSK and QAM) and compare its performance based on their theoretical BER over AWGN. (Readers ar

efficient, power efficient, or cost efficient. Bandwidth efficiency describes the ability of a modulation scheme to accommodate data within a limited bandwidth. Power efficiency describes the ability of the system to reliably send information at the lowest practical power level. In most systems, there is a high priority on bandwidth efficiency 3.3 Linear Modulation Techniques 3.3.5 ꍫ/4-Shifted Quadriphase-Shift Keying CH01-30 Modern Wireless Communications • Two setting of carrier phase of QPSK • ꍫ/4-Shifted Quadriphase-Shift Keying: - carrier phase alternatively picked from settings 1 and 2. • Provides higher bandwidth efficiency, with a reduced range of amplitude. * 8*.0 Comparison of the digital modulation techniques The BASK technique has simpler and economical implementation requirements (Frenzel, 2012). The technique is less error prone and gives less bandwidth efficiency hence operates more efficiently, only in the linear region thus make it it inefficient technique for wireless communication Optimum Bandwidth 45 • Nyquist pulse not only removes ISI but also results in the minimum bandwidth for the modulated signal. • With Nyquist pulse, the modulated RF signal occupies R b =1/T b Hz The absolute theoretical minimum bandwidth required to transmit R b pulses per second

* It is the purpose of this report to extend this class to include two new codes, one of which is tolerant of precompression bandwidth limitation*. These new phase codes are conceptually derived from a linear frequency modulation waveform (LFMW) and are more Doppler tolerant than other phase codes derived from a step approximation to a LFMW Modulation produces sidebands, either on one side, or on both sides of the nominal carrier frequency, usually having a distribution of amplitude over the assigned bandwidth. In effect one could say that whatever the modulation, the situation will exist in which one has a concentrated group of closely knit carriers, or signals, coming to and going from the mobile, whether one specifies analog.

** M-FSK is a power efficient modulation technique which power efficiency can be increased by increasing the number of frequencies (M) at the cost of additional complexity and smaller bandwidth efficiency**. This modulation system is found appropriate for some low rate and low power applications such as Global paging via satellite communications [10] M-FSK is one of the modulation techniques which efficiency can be increased by increasing the frequencies (M) at additional complication and lesser bandwidth efficiency. In low-data rate and low power applications such as Global paging via satellite communications where M-FSK is using [10] Non-coherent Digital Modulation Techniques are those techniques in which the detection process does not need receiver carrier to be phase locked with transmitter carrier. The advantage of such type of system is that the system becomes simple. But the drawback of such system is that the error probability increases. Q.2. State various continuous wave (CW) modulation systems

- needs to be very efficient at high slew rates, limiting the signal envelope bandwidth that can be efficiently amplified [3], [4]. This paper addresses the above issues of supply-modulated amplifiers by implemented distortion and supply-bandwidth reduction techniques, allowing more linear and efficient amplification for wideband signals
- p. 11 ELEC 7073 Digital Communications III, Dept. of E.E.E., HKU Modulation Schemes Classification ¾Linear modulation: the amplitude of the transmitted signal, s(t), varies linearly with the modulating digital signal, m(t). −Bandwidth efficient but power inefficient −Example: ASK, QPSK ¾Nonlinear modulation: the amplitude of the transmitted signal, s(t), does not vary linearly with th
- 1. Modulation Techniques for Mobile Radio UNIT-3. 2. What is modulation <ul><li>Modulation is the process of encoding information from a message source in a manner suitable for transmission </li></ul><ul><li>It involves translating a baseband message signal to a bandpass signal at frequencies that are very high compared to the baseband frequency

bandwidth-efficient modulation methods that directly modulated the carrier were being developed, which, along with improved data formatting methods (e.g., packet transfer frame telemetry) to handle the multiple channel separa In general, linear modulation techniques use less bandwidth than do nonlinear techniques. However, linear modulation techniques also tend to produce large fluctuations in signal amplitude. This is a disadvantage when using nonlinear amplifiers such as class C amplifiers (the least expensive, most readily available, and most power-efficient.

The lower forms of modulation, (QPSK) do not require such a large signal to noise ratio but are not able to send the data as fast. a different concept is used for the access technique. Signals that have a high peak to average ratio and require linear amplification do not lend themselves to the use of efficient RF power amplifiers 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 mobil Modulation Techniques Performance Trade-Off's The performance of a digital cellular system in terms of the number of users per km2 and data transmission rate depends on the modulation technique. The method determines the bandwidth efficiency in terms of the number of bits per second that can be transmitted per Hertz of channel bandwidth Modulation. A basic amplitude-modulated (double-sideband full carrier) signal is obtained by mixing a modulating signal y m (t) at a modulation index M and frequency ω m = 2πf m with a carrier signal y c (t) with (for the sake of brevity) unity amplitude, phase , and frequency ω c = 2πf c such that (1) In the time domain, this process is shown in Figure 1a, where the minimum and the. This provides broadband high efficiency capability. The second switching supply is inserted into the circuit in cascade to feed the linear modulator with a bandwidth reduced variable supply to further reduce the power loss in the case of the serial hybrid. In this way, both serial and parallel techniques are used to provide the optimum efficiency

Pulse-code modulation is known as a digital pulse modulation techniques. The pulse-code modulation (PCM) is quite complex compared to the Analog pulse modulation techniques (i.e., PAM, PWM and PPM) in the sense that the message signal is subjected to a great number of operations The bandwidth of FM Signal. Only the first few sidebands will contain the major share of the power (98% of the total power) and therefore only these few bands are considered to be significant sidebands.. As a rule of thumb, often termed as Carson's Rule, 98% of the signal power in FM is contained within a bandwidth equal to the deviation frequency, plus the modulation frequency-doubled This paper explores the bandwidth and power efficiency trade-offs of the entire SOQPSK family using computer simulations and analytical performance bounds. KEY WORDS SOQPSK, Spectral Efficiency, Power Efficiency, Bandwidth/Efficiency Plane INTRODUCTION SOQPSK is a non-proprietary modulation technique that is quickly gaining popularity i environment. Some spectrum efficient techniques like QAM are highly efficient, but are not suitable for modulation applications because they require a stable amplitude reference not present in a fluctuating mobile signal. Conventional PSK also is unsuitable because it requires an absolute phase reference (7)

** A high bandwidth efficient spread spectrum modulation using chirp waveform**. The invention provides a method and apparatus for effecting the high bandwidth efficient spread spectrum modulation using chirp waveform. The method involves reducing the data rate by narrowing the bandwidth or by using a smaller set of orthogonal sequences. The apparatus includes a transmitter and a receiver the original message is called Spread Spectrum modulation techniques and the bandwidth of the transmitted signal is determined by the message to be transmitted. In this modulation technique, Linear Feedback Shift Register (LFSR) is the basic unit or element, SSMA is not very bandwidth efficient when used by a single user A new bandwidth efficient quadrature overlapped modulation technique, named quadrature overlapped squared raised-cosine (QOSRC), is investigated. From the point of view of the pulse shaping, the modulating waveform proposed here consists of overlapping squared raised-cosine pulses. The power spectrum of QOSRC attains good spectral characteristics over not only a linear channel but a bandpass.

Spectral Efficiency Limits and Modulation/Detection Techniques for DWDM Systems Joseph M. Kahn, Fellow, by using a wider optical bandwidth, by increasing spectral efficiency, or by some combination of the two. limits for various modulation and detection techniques, in linear and nonlinear propagation regimes • Digital modulation techniques may be broadly classified as linear and nonlinear. • In a linear modulation techniques, the amplitude of the transmitted signal s(t), varies linearly with the modulating digital signal m(t). • Linear modulation technique are bandwidth efficient and hence are very attractive fo In telecommunications, orthogonal frequency-division multiplexing (OFDM) is a type of digital transmission and a method of encoding digital data on multiple carrier frequencies. OFDM has developed into a popular scheme for wideband digital communication, used in applications such as digital television and audio broadcasting, DSL internet access, wireless networks, power line networks, and 4G. The ever-increasing growth in the bandwidth of wireless communication channels requires the transmitter to be wide-bandwidth and power-efficient. Polar and outphasing transmitter topologies are two promising candidates for such applications, in future. Both these architectures require a wide-bandwidth phase modulator. Open-loop phase modulation presents a viable solution for achieving wide.

performance of the system which is not done by the use of the spread spectrum techniques .Processing gain can also be defined as the ratio of spread signal bandwidth (WSS) to the information rate. Spread Spectrum modulation techniques can be explained as the technique in which the bandwidth of th RF Modulation Techniques - Tradeoffs between different types of modulation do not require a linear power amplifer Linear power amplifiers are less power efficient than non linear amplifiers. Different modulation schemes offer differing levels of noise immunity for the same data rate and the same occupied bandwidth when we increase the **modulation** formats order, we need highly **linear** devices so that the more complex constellations are not distorted. Recently, the application of digital pre-compensation (DPC), to various modules within the transmitter, has been proposed in optics. DPC **techniques** **are** fundamental for optical transceivers because the

dependent on the efficiency of the used modulation method. Linear and constant envelope modulation techniques, such as BPSK, QPSK, GMSK, etc, were used to examine the features of the required modulation scheme, and to illustrate their use in the cellular environments. The goal of a modulation technique is not only to transpor 17 Transmission Bandwidth In binary PCM, we have a group of n bits corresponding to L levels with n bits. Thus, L = 2n or n = log 2 (L)Signal m(t) is band-limited to B Hz, which requires 2B samples per second. For 2nB elements of information, we must transfer 2nB bits/second. Thus, the minimum bandwidth B T needed to transmit 2nB bits/second is B T = nB Hz Practically speaking, we usually.

Linear => Superposition applies bandwidth In angle modulation Spectrum of the modulated signal are not related in any simple fashion to message spectrum Transmission bandwidth are much greater than twice the message bandwidth Chapter 3 -Nonlinear Modulation Techniques 3. Sem. II, 2018/19 Angle Modulation FM/PM provide many. modulation techniques (unconstrained, constant-intensity, binary), detection techniques (coherent, direct), and propagation regimes (linear, nonlinear). We briefly review technologies required to approach these limits in practice. I. INTRODUCTION he overall capacity (b/s) of a DWDM transmission system is governed by the available bandwidth (Hz Modulation Techniques Spectral efficiency. PA Tradeoffs • Power Efficiency => Switching PA's (class D, E, F) • Does not suffer the bandwidth limitation incurred by continuous-feedback linear Vout. Feedforward: stable, but... • Matching delay lines, amplifier gains no • Provides good bandwidth efficiency. Bandwidth efficiency is defined as the ratio between the available bandwidth and bit rate. Rs= symbol rate Rb= bit rate The units are cycles !bit Rs logz MIT (-= ) W MIT For M-ary modulations ,Rb = clog2M)R., where M represents the number of modulation levels Bandwidth can be predicted using BW = 2 f m where f m = the maximum modulating frequency Efficiency depends only on the modulating index, m (the fraction of the carrier you modulate by) AM is limited to 33% efficiency because the modulation index cannot be increased to > 1.0 without introducing distortion in the receiver

Filtering can be employed to avoid spectral spreading. b)Quadrature Phase Shift Keying (QPSK): - Multilevel modulation technique: 2 bits per symbol - More spectrally efficient, more complex receiver [pic][pic][pic] Quadrature Phase Shift Keying is effectively two independent BPSK systems (I and Q), and therefore exhibits the same performance but twice the bandwidth efficiency * RF bandwidth and data rate are related by the modulation format*. Different modulation formats will require different bandwidths for the same data rate. For FM modulation, the bandwidth is approximately 2*(df + fm) where df is the maximum frequency deviation and fm is the frequency of the message PM bandwidth: For small amplitude signals, PM is similar to amplitude modulation (AM) and exhibits its unfortunate doubling of baseband bandwidth and poor efficiency. For a single large sinusoidal signal, PM is similar to FM, and its bandwidth is approximately, 2 (h+1) Fm where h= modulation index

This is the theory - but in reality the modulator is might be a bit more complex as the elements used to modulate a signal a non - **linear**. In AM a **modulation** a choke is used to modulate the cathode to ground voltage of a vacuum tube or a diode mod.. Digital ModulationDigital Modulation The messaggge signal is transmitted by a sinusoidal carrier wave In digg, pital communications, the modulation process corresponds to switching or keying the amplitude, frequency, or phase of the carrier in accordance with the incoming di it l d tdigital data Three basic digital modulation techniques Modulation techniques based on frequency-shift keying (FSK) are widely used in several wireless communication systems. For instance, continuous-phase modulation (CPM) is a good choice for nonlinear and band-limited channels [1]. The continuous phase characteristic is suitable for narrow bandwidth operation, and the constant envelope.

Linear Modulation Techniques: The amplitude /phase of the transmitted signal s(t), varies linearly with the modulating digital signal, m(t). These are bandwidth efficient (because it doesnt change frequency) and hence are very attractive for use in wireless communication systems where there is an increasing demand 7 of 82 to accommodate more and more users within For transmitting messages in frequency modulation, it does not require special equipments like linear amplifiers or repeaters and transmission levels or higher when compared to other modulation techniques. It does not require any class C or B amplifiers for increasing the efficiency bandwidth and a large size. Furthermore, its efficiency generally decreases as the input signal decreases. An improved EER transmitter architecture (also known as a pulsed power amplifier) which does not require a DC-DC converter was A Discrete-Amplitude Pulse Width Modulation for a High-Efficiency Linear Power Amplifie 20) The digital modulation technique in which the step size is varied according to the variation in the slope of the input is called. a. Delta modulation b. PCM c. Adaptive delta modulation d. PAM. ANSWER: (c) Adaptive delta modulation. 21) The digital modulation scheme in which the step size is not fixed is. a. Delta modulation b

As such, RF power amplifiers (PAs) with improved efficiency, linearity, and bandwidth are needed. Dynamic load modulation (DLM) is one of the most common PA efficiency enhancement techniques. By investigation of new DLM design techniques, the overall objective of this thesis is to improve the efficiency-linearity and efficiency-bandwidth trade. Many current DWDM systems use on -off keying (OOK) as a binary modulation technique but the spectral efficiency can not exceed 1 bit/s/Hz ( 0.67 b/s/Hz in a real system). Mitra and Stark's work suggest that the spectral efficiency limits would require a non-binary encoding technique, such as a multilevel intensity or phase modulation Bandwidth efficiency for MSK and GMSK is 1 bit/s/Hz also known as spectral efficiency. This helps in keeping PAPR low hence do not require highly linear power amplifier. QPSK vs OQPSK vs pi/4QPSK-Difference between QPSK,OQPSK and pi/4QPSK modulation techniques Differential Encoder and Decoder modulation schemes to bandwidth efficient digital modulation techniques. This is because new cellular phone systems need to provide a high transmission rate capability to satisfy the needed broadband applications. Power efficiency modulation schemes provides reliable transmission of information in a communication ** modulation scheme as in the GSM standard, it adopts a more spectrally efficient modulation scheme (3π/8 8-PSK), yielding a higher data rate in the same 200kHz signal bandwidth**. This, in turn, requires a linear transmitter to faithfully transmit the signal. The prototype was designed to be a class E1 mobile unit (with 30dB

Combined linear and constant envelop modulation technique In modern communication digital data can be sent. by varying both the envelop and phase (or freq) M-ary QAM. M-ary modulation. modulation technique in which base band data is mapped into 4 or more RF carrier signals In M-ary signaling scheme , 2 or more bits are grouped to form symbol n M= This page on amplitude modulation(AM) vs frequency modulation(FM) vs phase modulation(PM) describes difference between amplitude modulation,frequency modulation and phase modulation types. All these modulation types are analog modulation techniques. All the modulation types are used to transmit information from one place to the distant place Despite the fact that there are many other modulation techniques that can also double or triple the transmission capacity for a fixed bandwidth, PAM-4 modulation has been a leading solution, mainly due to its simplicity and low power consumption, as the most promising modulation technique for 100G and beyond optical pluggable transceivers for both intra- and inter-data center optical links. The bandwidth of signal inside the pulse are very high hence it is spread spectrum modulation technique and gets the advantage of spread spectrum. When passed through a matched filter, this technique gives implementation of pulse compression [17] Recently, superposition coded modulation (SCM) has been studied as an alternative approach to other bandwidth efficient coded modulation techniques [18],[19].With SCM, several coded sequences are linearly super imposed before transmission .When the number of layers are large, the transmitted signal exhibits an Gaussian distribution which matches to an AWGN channel