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Digital Communication I: Modulation and Coding Course-Lecture 3

Transforming the information source to a form compatible with a digital system. Sampling. Aliasing. Quantization Uniform and non-uniform. Baseband modulation. Binary pulse modulation. M-ary pulse modulation. M-PAM (M-ary Pulse amplitude modulation).Assuming real time transmission and equal energy per transmission data bit for binary-PAM and 4-ary PAM | Digital Communication I: Modulation and Coding Course Term 3 - 2008 Catharina Logothetis Lecture 3 Lecture 3 Last time we talked about: Transforming the information source to a form compatible with a digital system Sampling Aliasing Quantization Uniform and non-uniform Baseband modulation Binary pulse modulation M-ary pulse modulation M-PAM (M-ary Pulse amplitude modulation) Lecture 3 Formatting and transmission of baseband signal Information (data) rate: Symbol rate : For real time transmission: Sampling at rate (sampling time=Ts) Quantizing each sampled value to one of the L levels in quantizer. Encoding each q. value to bits (Data bit duration Tb=Ts/l) Encode Pulse modulate Sample Quantize Pulse waveforms (baseband signals) Bit stream (Data bits) Format Digital info. Textual info. Analog info. source Mapping every data bits to a symbol out of M symbols and transmitting a baseband waveform with duration T Lecture 3 Quantization example t Ts: sampling time x(nTs): sampled . | Digital Communication I: Modulation and Coding Course Term 3 - 2008 Catharina Logothetis Lecture 3 Lecture 3 Last time we talked about: Transforming the information source to a form compatible with a digital system Sampling Aliasing Quantization Uniform and non-uniform Baseband modulation Binary pulse modulation M-ary pulse modulation M-PAM (M-ary Pulse amplitude modulation) Lecture 3 Formatting and transmission of baseband signal Information (data) rate: Symbol rate : For real time transmission: Sampling at rate (sampling time=Ts) Quantizing each sampled value to one of the L levels in quantizer. Encoding each q. value to bits (Data bit duration Tb=Ts/l) Encode Pulse modulate Sample Quantize Pulse waveforms (baseband signals) Bit stream (Data bits) Format Digital info. Textual info. Analog info. source Mapping every data bits to a symbol out of M symbols and transmitting a baseband waveform with duration T Lecture 3 Quantization example t Ts: sampling time x(nTs): sampled values xq(nTs): quantized values boundaries Quant. levels 111 3.1867 110 2.2762 101 1.3657 100 0.4552 011 -0.4552 010 -1.3657 001 -2.2762 000 -3.1867 PCM codeword 110 110 111 110 100 010 011 100 100 011 PCM sequence amplitude x(t) Lecture 3 Example of M-ary PAM -B B T ‘01’ 3B T T -3B T ‘00’ ‘10’ ‘1’ A. T ‘0’ T -A. Assuming real time transmission and equal energy per transmission data bit for binary-PAM and 4-ary PAM: 4-ary: T=2Tb and Binary: T=Tb 4-ary PAM (rectangular pulse) Binary PAM (rectangular pulse) ‘11’ Lecture 3 Example of M-ary PAM 0 Tb 2Tb 3Tb 4Tb 5Tb 6Tb 0 Ts 2Ts 0 T 2T 3T 2.2762 V 1.3657 V 1 1 0 1 0 1 0 T 2T 3T 4T 5T 6T Rb=1/Tb=3/Ts R=1/T=1/Tb=3/Ts Rb=1/Tb=3/Ts R=1/T=1/2Tb=3/2Ts=1.5/Ts Lecture 3 Today we are going to talk about: Receiver structure Demodulation (and sampling) Detection First step for designing the receiver Matched filter receiver Correlator receiver Lecture 3 Demodulation and detection Major sources of errors: Thermal noise (AWGN) disturbs the signal in .