5.6.3 MPSK Unfortunately,the LO has phase ambiguities and DPSK is often employed for solution. DPSK Sym Abs-mapping:Relative mapping:A0 MPSK Instead of absolute phase-mapping 0 0 0 (Carrier-phs) 1 π/2 π72 of info sym,PSK with differential 2 π π 1,2.,ML-- phase-mapping is called DPSK. 3 3m/2 3π/2 0 The signals:s()=gr()cos 00 =Amg(I)cos2πf1 -cos4 Min- 2 %0-28,0cos2 Dist The basis: %0=是,0sm20 Prob of err is computed by, r( →⑧T-0 1=T Two sync demod.that requires: c0s21 The local cos/sin are coherent with the carriers in recv sig. r→⑧8，T-0 The sampler/integrator is synchronous with the symbols in sin2ft recv sig. UESTC-Digital transmission through the AWGN channel Prof李晓峰 5