QPSK MODULATION AND DEMODULATION MATLAB CODE PDF

Qpsk Matlab Code Search form Phase-shift 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. PSK uses a finite number of phases, each assigned a unique pattern of binary digits. Usually, each phase encodes an equal number of bits. Each pattern of bits forms the symbol that is represented by the particular phase. The demodulator, which is designed specifically for the symbol-set used by the modulator, determines the phase of the received signal and maps it back to the symbol it represents, thus recovering the original data.

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After oversampling and pulse shaping, it is intuitively clear that the signal on the I-arm and Q-arm are BPSK signals with symbol duration.

The signal on the in-phase arm is then multiplied by and the signal on the quadrature arm is multiplied by. QPSK modulated signal is obtained by adding the signal from both in-phase and quadrature arms. Note: The oversampling rate for the simulation is chosen as , where is the given carrier frequency and is the sampling frequency satisfying Nyquist sampling theorem with respect to the carrier frequency.

This configuration gives integral number of carrier cycles for one symbol duration. In this implementation, the I-channel and Q-channel signals are individually demodulated in the same way as that of BPSK demodulation. After demodulation, the I-channel bits and Q-channel sequences are combined into a single sequence.

The simulation involves, generating random message bits, modulating them using QPSK modulation, addition of AWGN channel noise corresponding to the given signal-to-noise ratio and demodulating the noisy signal using a coherent QPSK receiver. The waveforms at the various stages of the modulator are shown in the Figure 4.

Figure 4: Simulated QPSK waveforms at the transmitter side The performance simulation for the QPSK transmitter-receiver combination was also coded in the code given above and the resulting bit-error rate performance curve will be same as that of conventional BPSK.

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BPSK Modulation And Demodulation- Complete Matlab Code With Explanation

After oversampling and pulse shaping, it is intuitively clear that the signal on the I-arm and Q-arm are BPSK signals with symbol duration. The signal on the in-phase arm is then multiplied by and the signal on the quadrature arm is multiplied by. QPSK modulated signal is obtained by adding the signal from both in-phase and quadrature arms. Note: The oversampling rate for the simulation is chosen as , where is the given carrier frequency and is the sampling frequency satisfying Nyquist sampling theorem with respect to the carrier frequency. This configuration gives integral number of carrier cycles for one symbol duration. In this implementation, the I-channel and Q-channel signals are individually demodulated in the same way as that of BPSK demodulation.

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DecisionMethod Demodulation decision method Specify the decision method the object uses as Hard decision Log-likelihood ratio Approximate log-likelihood ratio. The default is Hard decision. When you set the BitOutput property to false, the object always performs hard decision demodulation. This property applies when you set the BitOutput property to true. VarianceSource Source of noise variance Specify the source of the noise variance as one of Property Input port.

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Qpsk Matlab Code

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