Skip to main content

ASK, FSK, and PSK

 

ASK or OFF ON Keying

Ask is a simple (less complex) Digital Modulation Scheme where we vary the modulation signal's amplitude or voltage by the message signal's amplitude or voltage. We select two levels (two different voltage levels) for transmitting modulated message signals for the exam. And for example, we mapped the signal as two-level "+5 Volt" (which is the upper level) and another level, "0 Volt," which is considered as the lower level. Whenever we need to transmit binary bit "1," then the transmitter transmits a signal of "+5 Volts," and when we need to send bit "0," then it transmits no power. But the receiver is intelligent enough to deflect whether you've sent binary bit "1" or "0" by deflecting with quipped filters that can distinguish strings of bits. It is possible by the switching capability of the filter with the particular period to determine each bit from a string of bits.  

 
 

Fig 1: Output of ASK, FSK, and PSK modulation using MATLAB for a data stream "1   1    0   0   1    0   1   0"

FSK

Like other modulation techniques, the message signal is modulated with the high-frequency carrier wave,e, and then two binary values are represented by two different frequencies. The two frequencies are near the carrier frequency. For example, 

We choose two carrier frequencies, f1 and f2, and f1 > f2. Then we modulate binary bit "1" with f1 and binary "0" with f2 frequency, which is a lower frequency than f1. Now, the modulated signal will look like that,

S1(t) = A cos 2πfc1t      for  binary 1   

And S2(t) = A cos 2πfc2t      for  binary 0

Here, fc1 is different from f1. As you know, when the signal goes thru the modulation process, the frequency of the modulated signal is different from the carrier signal by the message signal's frequency.


PSK

In PSK, here,e the carrier signal phase is with a modulated signal with the phase related to the last bit for binary "1," and binary "0" is sent with a signal with the same phase as the preceding one. For example, whenever we need to transmit binary "1", we change the signal's phase by 180 degree, but the phase remains the same when we transmit binary "0". PSK carrier is used as follows

s(t) = A cos (2πfct + π)    for binary 1

s(t) = A cos (2πfct)           for binary 0 


Which of the modulation techniques—ASK, FSK, or PSK—can achieve higher bit rates?

Among ASK, FSK, and PSK, PSK (Phase Shift Keying) can generally achieve higher bit rates.

Here's why:

PSK (Phase Shift Keying):

Phase Shift Keying, or PSK, uses various phase shifts to encode extra bits per symbol. For instance, QPSK (Quadrature Phase Shift Keying) doubles the data rate over binary PSK by representing two bits each signal.

The bit rate can be further increased by using higher-order PSK methods, such as 8-PSK and 16-PSK, which can encode even more bits per symbol.


FSK (Frequency Shift Keying):

Because FSK often requires a higher frequency separation to discriminate between different symbols, fewer bits can be broadcast in a given bandwidth, resulting in a lower bit rate than PSK.

Although there are higher-order FSK systems, PSK is more bandwidth-efficient than them.


ASK (Amplitude Shift Keying):

ASK's ability to successfully raise bit rates is limited by its lower bit rate efficiency and increased susceptibility to noise and interference.

Bit rates can be increased via higher-order ASK (such as QAM, which combines ASK and PSK), but pure ASK is typically less effective than PSK.

In conclusion, among these three modulation strategies, PSK has the potential to produce the highest bit rates, particularly when utilising higher-order modulation techniques.

People are good at skipping over material they already know!

View Related Topics to







Admin & Author: Salim

profile

  Website: www.salimwireless.com
  Interests: Signal Processing, Telecommunication, 5G Technology, Present & Future Wireless Technologies, Digital Signal Processing, Computer Networks, Millimeter Wave Band Channel, Web Development
  Seeking an opportunity in the Teaching or Electronics & Telecommunication domains.
  Possess M.Tech in Electronic Communication Systems.


Contact Us

Name

Email *

Message *

Popular Posts

BER vs SNR for M-ary QAM, M-ary PSK, QPSK, BPSK, ...

Modulation Constellation Diagrams BER vs. SNR BER vs SNR for M-QAM, M-PSK, QPSk, BPSK, ... What is Bit Error Rate (BER)? The abbreviation BER stands for bit error rate, which indicates how many corrupted bits are received (after the demodulation process) compared to the total number of bits sent in a communication process. It is defined as,  In mathematics, BER = (number of bits received in error / total number of transmitted bits)  On the other hand, SNR refers to the signal-to-noise power ratio. For ease of calculation, we commonly convert it to dB or decibels.   What is Signal the signal-to-noise ratio (SNR)? SNR = signal power/noise power (SNR is a ratio of signal power to noise power) SNR (in dB) = 10*log(signal power / noise power) [base 10] For instance, the SNR for a given communication system is 3dB. So, SNR (in ratio) = 10^{SNR (in dB) / 10} = 2 Therefore, in this instance, the s...

MATLAB Code for Pulse Width Modulation (PWM) and Demodulation

   Pulse Width Modulation (PWM) MATLAB Script clc; clear all; close all; fs=30; %frequency of the sawtooth signal fm=3; %frequency of the message signal sampling_frequency = 10e3; a=0.5; % amplitide t=0:(1/sampling_frequency):1; %sampling rate of 10kHz sawtooth=2*a.*sawtooth(2*pi*fs*t); %generating a sawtooth wave subplot(4,1,1); plot(t,sawtooth); % plotting the sawtooth wave title('Comparator Wave'); msg=a.*sin(2*pi*fm*t); %generating message wave subplot(4,1,2); plot(t,msg); %plotting the sine message wave title('Message Signal'); for i=1:length(sawtooth) if (msg(i)>=sawtooth(i)) pwm(i)=1; %is message signal amplitude at i th sample is greater than %sawtooth wave amplitude at i th sample else pwm(i)=0; end end subplot(4,1,3); plot(t,pwm,'r'); title('PWM'); axis([0 1 0 1.1]); %to keep the pwm visible during plotting. %% Demodulation % Demodulation: Measure the pulse width to reconstruct the signal demodulated_signal = zeros(size(msg)); for i = 1:leng...

Theoretical and simulated BER vs. SNR for ASK, FSK, and PSK

  BER vs. SNR denotes how many bits in error are received in a communication process for a particular Signal-to-noise (SNR) ratio. In most cases, SNR is measured in decibel (dB). For a typical communication system, a signal is often affected by two types of noises 1. Additive White Gaussian Noise (AWGN) 2. Rayleigh Fading In the case of additive white Gaussian noise (AWGN), random magnitude is added to the transmitted signal. On the other hand, Rayleigh fading (due to multipath) attenuates the different frequency components of a signal differently. A good signal-to-noise ratio tries to mitigate the effect of noise.  Calculate BER for Binary ASK Modulation The theoretical BER for binary ASK (BASK) in an AWGN channel is given by: BER  = (1/2) * erfc(0.5 * sqrt(SNR_ask));   Enter SNR (dB): Calculate BER BER vs. SNR curves for ASK, FSK, and PSK Calculate BER for Binary FSK Modulation The theoretical BER for binary FSK (BFSK) in a...

Antenna Gain-Combining Methods - EGC, MRC, SC, and RMSGC

 There are different antenna gain-combining methods. They are as follows. 1. Equal gain combining (EGC) 2. Maximum ratio combining (MRC) 3. Selective combining (SC) 4. Root mean square gain combining (RMSGC) 1. Equal gain combining method We add the correlated data streams from different antennas in the equal gain combining method. Then we multiply the resultant data with (1/(number of antennas)) For example, for two antenna gain-combining  If the received symbols are y1 and y2, then  Equal combing gain, y_egc = 0.5 * (y1 + y2) 2. Maximum ratio combining method We multiply the individual data streams with weights in the maximum ratio combining method. More weightage is multiplied by those data streams with maximum {|h|^2}, where h denotes the channel impulse response. And less weightage is multiplied by those data streams with corresponding small value of  {|h|^2}.  Then we sum the data streams to improve SNR. In the case of Maximum Ratio Combining, if y1 an...

Comparisons among ASK, PSK, and FSK | And the definitions of each

Modulation ASK, FSK & PSK Constellation MATLAB Simulink MATLAB Code Comparisons among ASK, PSK, and FSK    Comparisons among ASK, PSK, and FSK Comparison among ASK,  FSK, and PSK Performance Comparison: 1. Noise Sensitivity:    - ASK is the most sensitive to noise due to its reliance on amplitude variations.    - PSK is less sensitive to noise compared to ASK.    - FSK is relatively more robust against noise, making it suitable for noisy environments. 2. Bandwidth Efficiency:    - PSK is the most bandwidth-efficient, requiring less bandwidth than FSK for the same data rate.    - FSK requires wider bandwidth compared to PSK.    - ASK's bandwidth efficiency lies between FSK and PSK. Bandwidth Calculator for ASK, FSK, and PSK The baud rate represents the number of symbols transmitted per second Select Modulation Type: ASK...

Constellation Diagrams of ASK, PSK, and FSK

BASK (Binary ASK) Modulation: Transmits one of two signals: 0 or -√Eb, where Eb​ is the energy per bit. These signals represent binary 0 and 1.    BFSK (Binary FSK) Modulation: Transmits one of two signals: +√Eb​ ( On the y-axis, the phase shift of 90 degrees with respect to the x-axis, which is also termed phase offset ) or √Eb (on x-axis), where Eb​ is the energy per bit. These signals represent binary 0 and 1.  BPSK (Binary PSK) Modulation: Transmits one of two signals: +√Eb​ or -√Eb (they differ by 180 degree phase shift), where Eb​ is the energy per bit. These signals represent binary 0 and 1.  Key Points For Binary Amplitude Shift Keying (BASK), binary bit '0' can be represented as lower level voltage or no signal and bit '1' as higher level voltage.  For Binary Frequency Shift Keying (BFSK), you can map binary bit '0' to 'j' and bit '1' to '1'. So, signals are in phase.  A phase shift of 0 degrees could represent a binary '1...

MATLAB Code for Pulse Amplitude Modulation (PAM) and Demodulation

  Pulse Amplitude Modulation (PAM) & Demodulation MATLAB Script clc; clear all; close all; fm= 10; % frequency of the message signal fc= 100; % frequency of the carrier signal fs=1000*fm; % (=100KHz) sampling frequency (where 1000 is the upsampling factor) t=0:1/fs:1; % sampling rate of (1/fs = 100 kHz) m=1*cos(2*pi*fm*t); % Message signal with period 2*pi*fm (sinusoidal wave signal) c=0.5*square(2*pi*fc*t)+0.5; % square wave with period 2*pi*fc s=m.*c; % modulated signal (multiplication of element by element) subplot(4,1,1); plot(t,m); title('Message signal'); xlabel ('Time'); ylabel('Amplitude'); subplot(4,1,2); plot(t,c); title('Carrier signal'); xlabel('Time'); ylabel('Amplitude'); subplot(4,1,3); plot(t,s); title('Modulated signal'); xlabel('Time'); ylabel('Amplitude'); %demdulated d=s.*c; % At receiver, received signal is multiplied by carrier signal filter=fir1(200,fm/fs,'low'); % low-pass FIR fi...

What are Precoding and Combining Weights / Matrices in a MIMO Beamforming System

MIMO / Massive MIMO Beamforming Techniques Precoding and Combining Weights...   Figure:  configuration of single-user digital precoder for millimeter  Wave massive MIMO system Precoding and combining are two excellent ways to send and receive signals over a multi-antenna communication process, respectively (i.e., MIMO antenna communication ). The channel matrix is the basis of both the precoding and combining matrices. Precoding matrices are typically used on the transmitter side and combining matrixes on the receiving side. The two matrices allow us to generate multiple simultaneous data streams between the transmitter and receiver. The nature of the data streams is also orthogonal. That helps decrease or cancel (theoretically) interference between any two data streams. The channel matrix is first properly diagonalized. Diagonalization is the process of transforming any matrix into an equivalent diagon...