lecture17

lecture17 - E E455/ 591 Fr equency Shi ft Keyi ng (FSK) Fr...

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EE455/ 591 EE455/ 591 Frequency Shift Keying (FSK) Notions of Error Correction Coding Reading: Read Section 7.4 Reading: Read Section 7.4 Review: Summary of PSK and QAM Topics: Topics: 1. 1. Frequency Shift Keying 2. 2. Offset QPSK (OQPSK) Offset QPSK (OQPSK) 3. 3. Minimum Shift Keying (MSK) 4. 4. Repetition Coding, Basic Idea of Coding
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Review: Error Probabilities (with Carrier) M s π sin = 0 N E Q P s b - - = 0 2 ) 1 ( 6 ) 1 ( 2 N M E Q M M P av M MPSK MFSK M 2 QAM Error Event Probability (d free : min distance btw signals): MPAM/ M 2 I s 1 E s s 2 Q s 8 s 5 s 6 s 7 I s 1 s 4 s 16 s 12 s 2 s 3 s 5 ψ 1 ψ 2 ψ 3 s i (t)= E s ψ i (t), i=1,2,3 s 1 s 3 s 2 Q 2 ; 2 ) 2 / ( 2 1 0 2 0 2 2 / 2 2 N N d Q d Q dx e free free x d free = = = - σ
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Error Probability for M 2 -QAM Consider 4PAM: 4PAM (In-phase) + 4 PAM (Quadrature) =16-QAM Since I and Q are orthogonal, need consider only either I or Q channel For MPAM with for Average signal energy: Energy per bit: D free : Probability of error: Same error event for M 2 -QAM! I s 1 s 4 s 16 s 12 s 2 s 3 s 5 Q m g m A T E s = ) 1 2 ( M m A m - - = g avg E M E 3 1 2 - = M E E avg b 2 log = g E 2 - - = - = 0 2 0 ) 1 ( 6 ) 1 ( 2 2 ) 1 ( 2 N M E Q M M N E Q M M P av g M
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1. Frequency Shift Keying (FSK) = 0 N E Q P s b 2FSK Signal Space: Signal in time: Want phase continuous in time (no discontinuity and better spectral falloff) Error Event Probability: (Independent of # of frequencies!)
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lecture17 - E E455/ 591 Fr equency Shi ft Keyi ng (FSK) Fr...

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