This example shows the oqpsk modulator baseband and oqpsk demodulator baseband blocks connected with no channel or impairments distorting the signal between them. The qpsk demodulator baseband block demodulates a signal that was modulated using the quadrature phase shift keying method. Oqpsk modulator baseband oqpsk demodulator baseband. The oqpsk modulation is a psk modulation, using 2 bits per symbol and a delay of one bit in the in quadrature signal refer to optisystem component library, oqpsk pulse generator. May 09, 2004 hello i have made a program in matlab that can demodulate an oqpsk modulated signal with noise additive white gaussian noise. For oqpsk, the quadrature signal has a 12 symbol period offset 0.
So i thought it would be easier to make a matlabfile instead. Thanks for the interested reader the specification can be found here. The zip archive files are password protected as described in appendix a of the text. The matlab simulated scurve for the qpsk modulation, performed in absence of noise and with a rolloff factor. You may be better off if you jointly do modulation and filtering on your own in this order. Qpsk vs oqpsk vs pi4qpskdifference between qpsk,oqpsk,pi. Phaseshift keying psk is a digital modulation process which conveys data by changing modulating the phase of a constant frequency reference signal the carrier wave. Oqpsk modulation techniques has attracted considerable attention in research area 24. Singlerate processing with oqpsk demodulator block. Matlab simulink following the suggestions of the paper. Need help to write matlab code for oqpsk modulation. This example shows the oqpsk modulator baseband block configured for singlerate processing using integer or bit for the input type. Pdf quadrature phase shift keying and offset quadrature.
Psk uses a finite number of phases, each assigned a unique pattern of binary digits. Mani, journal2015 international conference on communications and signal processing iccsp. I know that qpsk signal points are at 0,90,180,270 oqpsk the bit period of quadrature component is shifted by one bit period pi4qpsk signal points are at 45,5,225,315. Simulink model for zigbee transceiver using oqpsk modulation. Differential phase shift keying dpsk and offset quadrature phase shift keying oqpsk schemes are chosen to be investigated is multi environment channels, where both systems are designed using matlab simulink and tested. I know that qpsk signal points are at 0,90,180,270 oqpsk the bit period of quadrature component is sh. Hello guys, i am looking for the basic modulation code of oqpsk modulation for matlab. Qam is a better modulation technique than 4 bit qpsk modulation technique. The ber for an oqpsk signal in awgn is identical to that of a qpsk signal. In this lab, you will observe the quadrature phase shift keying qpsk modulation and demodulation building simulink simulation.
After running the simulation you can visualize the results from the eye. Demodulate fskmodulated data simulink mathworks india. Qpsk vs oqpsk vs pi4qpskdifference between qpsk,oqpsk,pi4qpsk. Communications toolbox provides tools for modulating and demodulating digital baseband signals using either matlab or simulink. I am trying to analyze whats the major difference between these three variants of 4psk. Because the loglikelihood algorithm computes exponentials using finite precision arithmetic, the computation of exponentials with large or small numbers can yield positive or negative infinity. Sarumathi 1department of ece bannari amman institute of technology, india 2department of ece, bannari amman institute of technology, india 3department of ece, bannari amman institute of technology, india. The oqpsk modulation scheme requires oversampling of two or greater in order to delay or offset the quadrature channel by 90 degrees. The input is a baseband representation of the modulated signal. In multirate processing mode, the input and output signals have different port sample times. This tutorial video teaches about simulating phase shift keying psk in matlab simulink download the simulink model here. Modulation plays an important role in transmission of signals from transmitter to receiver in all communication systems and the performance of digital modulation.
Offset qpsk oqpsk is a modulation scheme in which the inphase and quadrature bits do not change at the same time. Quadrature phase shift keying oqpsk are two wellaccepted modulation techniques used in code division multiple access cdma system. The carrier is phaseshifted with an arbitrary constant between 0 and 2pi. Qpsk matlab code download free open source matlab toolbox. Shift keying oqpsk and differential quadrature phase shift keying dqpsk. Oqpsk modulatian and demodulation by using simulink file. Oqpsk, awgn, time delay, matlab, simulink, modulation, demodulation. Singlerate processing with oqpsk modulator block matlab. The mfsk demodulator baseband block demodulates a signal that was modulated using the mary frequency shift keying method.
We have discuss all blocks used in the qpsk simulink model as shown in fig 2. The modulation is accomplished by varying the sine and cosine inputs at a precise time. One way to communicate a message signal whose frequency spectrum does not fall within that fixed frequency range, or one that is otherwise unsuitable for the channel, is to alter a transmittable signal according to the information in your message signal. Oqpsk and pi4 qpsk are variants of the basic qpsk modulation schemes. I just want to plot the qpsk baseband spectrum from the output data of the qpsk simulink block. In singlerate processing mode, the input and output signals have the same port sample time. Singlerate processing with oqpsk demodulator block matlab.
The code of qpsk modulation and demodulation technique has been developed according to the theory. Communications toolbox provides modulators and demodulators for these phase modulation techniques. This example shows how to simulate a basic communication system in which the signal is first qpsk modulated and then subjected to orthogonal frequency division multiplexing. In most media for communication, only a fixed range of frequencies is available for transmission. Comparison of performance metrics for qpsk and oqpsk. Phase modulation is a linear baseband modulation technique in which the message modulates the phase of a constant amplitude signal. You can attach the plots to your email message, or turn them in at the beginning of the next class period after the due date. Were about to serve up a bytesize portion of the alphabet soup called digital modulation lots of letters for a bunch of ones and zeros. The function upsamples by a factor of 2, because oqpsk does not. Pdf phase shift keying modulation approaches are widely used in the.
Phaseshift keying psk is a digital modulation scheme that conveys data by changing, or modulating, the phase of a reference signal the carrier wave. Any digital modulation scheme uses a finite number of distinct signals to represent digital data. Phase shift keying modulation approaches are widely used in the communication industry. The oqpsk demodulator baseband block applies pulse shape filtering to the input waveform and demodulates it using the offset quadrature phase shift keying. A programmable carrier phase independent symbol timing. This oversampling is achieved through interpolation filtering implemented by pulse shaping. Dpsk system using simulink download scientific diagram. Oqpsk uses a maximum phase transition of 90 degrees.
Understanding the phasing method of single sideband modulation rick lyons. Oqpsk modulatian and demodulation by using simulink. Digital modulation technique plays an important role in transmission of signals from. However the output of this block are the symbol coordenates in the signal space and when i use spectrum scope i dont get the theorical spectrum for the qpsk the sinc function. To learn more about digital modulation, see digital modulation. Demodulation using oqpsk method simulink mathworks. This can be achieved by using a filter either after power amplification, or at the intermediate frequency if, or at baseband. Handling spectral inversion in baseband processing eric jacobsen. Jul 17, 2017 simulink model for zigbee transceiver using oqpsk modulation under fading channels. The theoretical description of qpsk modulation and demodulation are available in the book of communication system by simon haykin. Performance evaluation of rician fading channels using. Performance comparison between dpsk and oqpsk modulation approaches in. An interesting fourier transform 1f noise steve smith.
Oqpskmodulator object modulates the input signal using the offset quadrature phase shift keying oqpsk method and applies pulse shape filtering to the output waveform. Can anyone tell me how i do this in matlab simulink because i am totally lost. It uses zigbee technology for communication and works on 2. Performance comparison between dpsk and oqpsk modulation.
They are widely used based on their unique individual phase transition functionalities compare to one another. Simulink model for zigbee transceiver using oqpsk modulation under fading channels conference paper april 2015 with 7 reads how we measure reads. Modulation using oqpsk method simulink mathworks espana. Matlab simulink is used to develop the system level design and its. This file includes qpsk modulatian and demodulation simulink model. Oqpsk simulation using matlab matlab answers matlab. I have already written the code of qpsk but i cant understand the difference between this code and the oqpsk. The signal is then passed through an additive white gaussian noise channel prior to being demultiplexed and demodulated. Qpsk modulator qpsk demodulator a slight modification to this basic qpsk technique gives various other forms of modulation techniques such as dqpsk, oqpsk.
Dqpsk and oqpsk modulation schemes in simulink environment p. The oqpsk modulator baseband block modulates the input signal using the offset quadrature phase shift keying oqpsk method and applies pulse shape filtering to the waveform. All these are modulation schemes used in wireless digital communication systems. Modern day communication demands significant rf spectrum limiting as frequency is the most useful resource of today. Matlab code for qpsk modulation and demodulation file. These techniques are more efficient in different scenarios when compared to basic qpsk. They are configured for framebased processing with bit signal inputs. Performance comparison between dpsk and oqpsk modulation approaches in multi environments channels with matlab simulink models. When outputtype is llr, if the demodulation computation outputs inf or inf value, it is likely because the specified noise variance values are smaller than the signaltonoise ratio snr. This block accepts a scalar or column vector input signal.
Oqpsk modulation scheme with half sine pulse shaping and direct sequence spread spectrum dsss technique is designed, and its performance under rayleigh fading channel is analyzed. So if the same word is transmitted then the constellation point transmitted still rotates by pi4 each period. The discussion then moves to binary phase shift keying bpsk and shows how this simpler format is modeled using the generic quadrature modulation models. The oqpsk modulation is a psk modulation, using 2 bits per symbol and a delay of. Qpsk modulatian and demodulation by using simulink file. Cross talk and unity of signals generated from dpsk and oqpsk are examined using. Demodulation using oqpsk method matlab mathworks france.
Compensate for carrier frequency offset for pam, psk, or qam. Multirate processing with oqpsk modulator block matlab. The coarse frequency compensator block compensates for a carrier frequency offset for bpsk, qpsk, oqpsk, 8psk, pam, and qam modulation schemes. Dqpsk modulation are presented and implemented using matlab with simulink. The input and output for this block are discretetime signals. The oqpsk modulator baseband block modulates the input signal using the offset quadrature phase shift keying oqpsk method and applies pulse shape. Ber performance evaluation of different phase shift keying. This example shows how to implement a practical ieee 802. This example shows the oqpsk demodulator baseband block configured for multirate processing using integer or bit for the input type. Do i rearrange them back into their odd and even positions. I have been looking at the oqpsk block in simulink but i dont know how to use it correctly. Simulink model for zigbee transceiver using oqpsk modulation under fading channels. This practical receiver has decoded standardcompliant waveforms received from commercial zigbee radios enabling home automation in the 2. Then, the second stage will be the implementation of qpsk using usrp hardware.
This example shows the oqpsk demodulator baseband block configured for singlerate processing using integer or bit for the input type. Removed offset quadrature phase shift keying modulation. Demodulate qpskmodulated data simulink mathworks united. The oqpsk demodulator baseband block applies pulse shape filtering to the input waveform and demodulates it using the offset quadrature phase shift keying oqpsk method. They are widely used based on their unique individual. A similar approach is then taken for developing models for multiple phase shift keying mpsk, minimum shift keying msk, and frequency shift. The pulseshaping filters play an important role in digital transmission.
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