M ary psk modulation

M- Ary PSK Modulation Technique , make it easier to understand this type of modulation technique which is usually used in communication system

1. M- ary PSK Modulation What is the M- ary PSK Modulation? M- ary Phase Shift Keying - or MPSK - is a modulation where data bits select one of M phase shifted versions of the carrier to transmit the data. Thus, the M possible waveforms all have the same amplitude and frequency but different phases. The signal constellations consist of M equally spaced points on a circle. Note: M = 2 n where n is integr No. 1,2,3,……

2. BPSK Vs. MPSK

3. An M- ary phase-shift keying ( M -PSK) signal can be defined by: for i = 0, 1, ..., M - 1. Here, A is a constant, fc is the carrier frequency, q ' is the initial phase angle, and T is the symbol duration . So By sub. In s(t) Equation we get: The signal has a power P = /2 , so that A = √2 P . Thus equation can be written as:   where E = PT is the energy of s ( t ) contained in a symbol duration for i = 0, 1, ..., M - 1. For convenience, the arbitrary phase angle q ' is taken to be zero.

4. A possible mapping table for M -PSK coherent demodulation.

5. If we take: as the orthonormal basis functions, the applicable signal constellation diagrams of the M -PSK and 4-PSK signals are shown in Figure. All signal points lie on a circle of radius signal constellation of m- ary PSK modulation

6. signal constellation of m- ary PSK modulation

7. How to get Probability of Error For M-PSK? probability of error for M-PSK modulation technique calculated by: From the previous signal constellation we noticed that: So the probability of error will given by:  

8. P erformance of Error For Mpsk The performance of symbol error probability for different values of M

9. Detection of MPSK

10. Conclusion The performance of a modulation scheme is often measured in terms of its power and bandwidth efficiencies. Power efficiency: – Problem : in order to increase noise immunity, it is necessary to increase the signal power. The amount by which the signal power should be increased to maintain a certain BER depends on the modulation scheme. – Power efficiency describes the ability to preserve the fidelity of a digital message at low power levels. – The power efficiency expresses the "signal energy over the noise energy " ratio ( Eb /No ) required at the receiver to guaranty a certain BER.

11. • Bandwidth efficiency: – Problem : increasing the data rate implies decreasing the pulse width of the digital symbol, which increases the bandwidth of the signal . – Bandwidth efficiency describes how efficiently the allocated bandwidth is used – Defined as the ratio of the throughput data rate per Hertz (bps/ Hz) – Fundamental upper bound: C/B = log2(1+S/N) where C is the channel capacity (bps), B the bandwidth (Hz) and S/N the signal-to-noise ratio. Conclusion

12. C onclusion There are some Factors that influence the choice of Digital Modulation: • Very often there is a trade-off: – adding error control coding reduces the bandwidth efficiency (redundancy is transmitted too) but increases the power efficiency (there remain fewer errors ). – M- ary schemes increase the bandwidth efficiency but require higher transmission power to keep the same BER - Other factors are important – cost and the complexity of the receiver – for wireless networks, the robustness under various types of channel impairments such as Rayleigh fading and multipath dispersion is important