ENERGY SEPARATION AND DEMODULATION OF CPM SIGNALS

Transcription

1 ENERGY SEPARATION AND DEMODULATION OF CPM SIGNALS Balu Sanhanam SPCOM Laboraory Deparmen of E.E.C.E. Universiy of New Meico Moivaion CPM has power/bandwidh efficiency and used in he wireless sysem infrasrucure. Maimum likelihood demodulaion has significan compleiy. Sub-opimal schemes : rade-off compleiy for opimaliy, e.g., polynomial phase modeling. Tradiional applicaions: speech analysis/synhesis, image eure analysis, FM-voice separaion.

2 Teager Teager-Kaiser Energy Operaor Kaiser Energy Operaor Coninuous ime: Discree ime: 1] [ 1] [ ] [ ] [ 2 + = n n n n ] [ 2 oo o = Energy Separaion Algorihm ESA Energy Separaion Algorihm ESA Monocomponen AM FM Signals: ESA IF/IA Esimaes: cos τ τ ω d a i = o i ω o a

3 Higher-order Energy Operaors Coninuous Signals: o Υ = k k 1 k Discree Signals: Υ = [ n] [ n+ k 2] [ n 1] [ n+ k 1] k Feaures of Energy Operaors Oupu of energy operaor for sinusoidal inpus is he normalized signal energy. For ime-varying sources, energy operaor oupu racks he energy of source. k=2: energy, k=3: energy-velociy, k=4: energyacceleraion. Possess simpliciy, efficiency, and ecellen ime resoluion.

4 Tradiional Energy Applicaions Speech processing: AM/FM analysis/synhesis, forman frequency/bandwidh racking, AM/FM vocoder. Image processing: Mulidimensional AM/FM models, image eure analysis, segmenaion. Biomedical applicaions: MEG spike deecion, vocal rac pahology diagnosis, ECG analysis. Communicaions: cochannel FM-voice separaion and demodulaion. CPM Signal Model 2ε = cos ωc + φ ; a + φ Tb cpm ο ; 2 φ a = πh a[ k] q ktb k= q pτ = dτ 2 ωi = ωc + πh a[ k] p k = kt b a[ k] { ± 1, ± 3, ± 5,..., ± M 1}

5 CPM Signal Model IF disconinuous bu has coninuous phase CP. Smaller specral side lobes due o CP propery. p recangular: REC-CPM, raised cosine: RAC-CPM, LPF Gaussian: GMSK, 1-REC-CPM CPFSK. Full response p: L =1 memoryless, parial response: L > 1 memory. Consan modulus wih FM modulaion inde : h Energy-based CPM Demodulaion Apply muliband filering and energy deecion o suppress noise. Apply energy demodulaion algorihm: ESA/EDM/PASED o esimae IF. Median filer IF esimaes o remove spikes and subrac carrier bias. Apply mached filering wih sign deecion on carrier unbiased IF esimae.

6 Performance Merics Binary CPM: BPSK-AWGN P ε = Q 2γ b, γ = 1 b 2E No b M-ARY CPM: M-ARY PAM P 2Μ 1 = Q Μ 2 2 ε 6log av 2ME M 1 No 1-REC-CPM: CPM: Effec of h

7 1-REC-CPM: CPM: Effec of h Small h: weak modulaions Increasing h increases srengh of signal modulaions MESA zero-error hreshold decreases as h increases. Large h: ESA narrowband approimaion fails. L=1 CPM: Effec of p Smoohness of phase rajecories relaed o coninuiy of p. Smoohness of phase resuls in smaller specral sidelobes. 1-REC-CPM has narrower mainlobe bu larger sidelobes. GMSK: rade-off ISI for specral compacness.

8 M=4, 1-REC1 REC-CPMCPM M=4, 1-REC1 REC-CPMCPM As M increases, bandwidh of signal increases. Larger bandwidh: causes ESA o incur more error. MESA filers: larger noise bandwidh. Narrowband approimaion fails afer a cerain sage.

9 Minimum Shif Keying MSK Special case of 1-REC-CPM CPFSK wih h=0.5. Orhogonal signaling scheme wih frequencies: f f 1 1 = c, f 2 = fc + 4Tb 4 1 T b Minimum frequency deviaion o mainain an orhogonal signal consellaion. Phase ransiions are eiher +πh and -πh Minimum Shif Keying MSK

10 Two-componen CPM Disinc componens: filering adequae for separaion. MESA: muliband filering and energy deecion. Small specral separaions: significan componen ineracion. For cochannel condiions, filering inadequae for componen separaion. Two-componen CPM: EDM Muliband version MEDM helps o an een wih noise. For small specral separaions, EDM energy equaions become singular. Filer design: rade-off noise suppression and signal disorion. Doppler shif manifess as carrier drif in he IF esimae and can be subraced off.

11 Conclusions CPM -- relaed forms: CPFSK,MSK,GMSK formulaed in he AM FM framework of energy approaches. Energy operaor based CPM demodulaion compuaionally simpler alernaive. Energy demodulaion based framework can accommodae a Doppler shif in daa. Paricularly suied for binary modulaion M=2.