8.15 Noncoherent orthogonal Modulation(1) Noncoherent orthogonal modulation –If two signal is orthogonal and have the same energy during interval T, carrier phase shifted signal of these two signal is assumed that remain orthogonal and have the same energy, regardless of the unknown carrier phase

8.15 Noncoherent orthogonal Modulation(2) Fig 8.26(a) Fig 8.26(b)

8.16 Noncoherent binary FSK One freq. represent symbol 1 and the other represent 0 fig 8.29

8.17 Differential PSK(1) Noncoherent version of PSK Combining differential encoding of the input binary wave and phase shift keying Receiver is equipped with a storage capability, so that it can measure the relative phase difference between the waveforms received during two successive bit intervals

8.17 Differential PSK(2) Generation of DPSK –If the incoming binary symbol is 1, leave the symbol unchanged with respect to the previous bit –If the incoming binary symbol is 0, change the symbol with respect to the previous bit –table 8.3 –fig 8.30(a)

8.17 Differential PSK(3) Optimum receiver –Inner product of two end point decide whether two symbol is same or not –fig 8.30(b)

8.18 Comparison of binary and quaternary modulation schemes Table 8.4 and fig 8.32 –BER decrease monotonically with increasing value of E b /N 0 –for any value of E b /N 0, coherent binary PSK, QPSK, and MSK produce smaller BER –there’s 3dB difference between coherent binary PSK and coherent binary FSK, between DPSK and noncoherent binary FSK –at high value of, DPSK and noncoherent binary FSK perform almost as well as coherent binary PSK and conventional coherent binary FSK

8.19 M-ARY modulation tech.(1) Send one of M possible signal, M = 2 n These signals are generated by changing the amplitude, phase, or frequency of a carrier in M discrete step or combine different method of modulation into a hybrid form When the bandwidth of the channel is less than the required value, we may use M-ary signaling scheme so as to utilize the channel efficiency

8.19 M-ARY modulation tech.(2) M-ary PSK –fig 8.33a

8.19 M-ARY modulation tech.(3) M-ary QAM –Signal consist of two phase-quadrature carriers, each of which is modulated by a set of discrete amplitude. –Fig 8.34, 8.35

8.19 M-ARY modulation tech.(4) M-ary FSK –fig 8.36

8.19 M-ARY modulation tech.(4) Comparison of M-ary digital modulation tech. –Among the family of M-ary PSK signals, QPSK offers the best trade-off between power and band-width –M-ary PSK and M-ary QAM have similar spectral and bandwidth, however M>4, the distance between the message points of M-ary PSK is smaller than the distance between the message points of M- ary QAM, for a fixed peak transmitted power

8.20 Power spectra Power spectra(power spectrum density) –distribution of power in the freq. Domain power spectra of binary PSK and FSK signals –fig 8.38 power spectra of QPSK and MSK signals –fig 8.39 power spectra of M-ary signals –fig 8.41

8.21 Bandwidth efficiency(1) The primary objective of spectrally efficient modulation is to maximize the bandwidth efficiency ratio of data rate to channel bandwidth bandwidth efficiency of M-ary PSK signals

8.21 Bandwidth efficiency(2) –Null-to-null bandwidth with encompassing the main lobe of the power spectrum –table8.6 Bandwidth efficiency of M-ary FSK signals –table8.7

8.22 Synchronization(1) Two basic modes of synchronization –when coherent detection is used, knowledge of both the frequency and phase of the carrier is necessary. The estimation of carrier phase and frequency is called carrier recovery or carrier synchronization –receiver has to know the instants of the time at which the modulation can changes its state(has to know the starting and finishing time of the symbol). The estimation of these times is called clock recovery or symbol synchronization

8.22 Synchronization(2) Carrier synchronization –PLL –Costas loop Symbol synchronization