![]() ![]() ![]() ![]() There are three major classes of digital modulation techniques used for transmission of digitally represented data:Īll convey data by changing some aspect of a base signal, the carrier wave (usually a sinusoid), in response to a data signal. A trade-off is that it has more demodulation errors.įurther information: Very minimum shift keying Introduction there is no need for the demodulator to keep track of a reference wave. DPSK can be significantly simpler to implement than ordinary PSK, as it is a 'non-coherent' scheme, i.e. Because the symbols are encoded in the difference in phase between successive samples, this is called differential phase-shift keying (DPSK). Alternatively, the phase shift of each symbol sent can be measured with respect to the phase of the previous symbol sent. This requires the receiver to be able to compare the phase of the received signal to a reference signal – such a system is termed coherent (and referred to as CPSK).ĬPSK requires a complicated demodulator, because it must extract the reference wave from the received signal and keep track of it, to compare each sample to. 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. Each pattern of bits forms the symbol that is represented by the particular phase. Usually, each phase encodes an equal number of bits. PSK uses a finite number of phases, each assigned a unique pattern of binary digits. It is widely used for wireless LANs, RFID and Bluetooth communication.Īny digital modulation scheme uses a finite number of distinct signals to represent digital data. The modulation is accomplished by varying the sine and cosine inputs at a precise time. And to identify which modulation scheme gives best BER performance.Phase-shift keying ( PSK) is a digital modulation process which conveys data by changing (modulating) the phase of a constant frequency carrier wave. It is observed that the BER is minimum for AWGN. By implementing the different modulation techniques, the criterion is comparison of the variation of BER for different SNR. Additive White Noise Gaussian (AWGN), multipath Rayleigh fading and Rician fading are considered in the channel. The performances of these modulation techniques are evaluated when the system is subjected to a number of users as well as noise and interference in the channel. We will go for analysis of Quadrature phase shift key and 16-ary Quadrature Amplitude modulations which are being used in wideband code division multiple access system, so that the system can go for more suitable modulation technique to suit the channel quality, thus we can deliver the optimum and efficient data rate to mobile terminal. We will use MatLab 7.4 for simulation and evaluation of BER and SNR for W-CDMA system models. We can analysis the performance of these modulation techniques when the system is subjected to AWGN and multipath Rayleigh fading are consider in the channel. The transmission from base station to mobile or downlink transmission using M-ary Quadrature Amplitude modulation (QAM) and Quadrature phase shift keying (QPSK) modulation scheme are consider in W-CDMA system. ![]()
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