S. Mandayam/ ECOMMS/ECE Dept./Rowan University Electrical Communications Systems ECE Spring 2008 Shreekanth Mandayam ECE Department Rowan University Lecture 12a April 15, 2008

S. Mandayam/ ECOMMS/ECE Dept./Rowan University Plan TDM Standards T1 (DS-1) Line North American TDMA Hierarchy Line Encoding Digital Bandpass Communications Why digital modulation? Digital Modulation: Introduction (ASK, FSK, PSK) Binary Phase Shift Keying (BPSK) Quadrature Phase Shift Keying (QPSK) M-ary PSK and M-ary QAM

S. Mandayam/ ECOMMS/ECE Dept./Rowan University ECOMMS: Topics

S. Mandayam/ ECOMMS/ECE Dept./Rowan University Digital Communications Transceiver Anti- aliasing Filter Data Encryption Encoder Source Encoder Error Control Encoder Channel/ Line Encoder Modulator MUX Audio Amp Source Decoder Data Encryption Decoder Error Control Decoder Equalization / Decision Circuits Demod- ulator DEMUX Reconstruction/ DAC ADC CODEC MODEM Analog o/p Multiple access channel Analog i/p Sampling Quantization

S. Mandayam/ ECOMMS/ECE Dept./Rowan University Time Division Multiplexing Message 1 Message 2 Message N Quantize & Encode Channel Message 1 Message 2 Message N Decode LPF

S. Mandayam/ ECOMMS/ECE Dept./Rowan University T1-Line TDM Format F Channel Channel Channel Frame = (24 Channels + F) = 125  s 193 bits Frame Sync Bit Even Frames: Odd Frames: Every Sixth Frame LSB (8th bit) is a Signaling bit Bipolar R-Z Line Encoding

S. Mandayam/ ECOMMS/ECE Dept./Rowan University North American TDMA Hierarchy 1 st M U X kbps 1 VF DS DS Mbps 4032 VF 5 th M U X 1 6 DS Mbps 672 VF 4 th M U X 1 7 DS Mbps 96 VF 3 rd M U X 1 4 DS Mbps 24 VF 2 nd M U X DS Mbps 8064 VF Figure 3-40, p. 207 in Couch Table 3-8, p. 208 in Couch Table 3-9, p. 209 in Couch

S. Mandayam/ ECOMMS/ECE Dept./Rowan University Digital Communications Transceiver Anti- aliasing Filter Data Encryption Encoder Source Encoder Error Control Encoder Channel/ Line Encoder Modulator MUX Audio Amp Source Decoder Data Encryption Decoder Error Control Decoder Equalization / Decision Circuits Demod- ulator DEMUX Reconstruction/ DAC ADC CODEC MODEM Analog o/p Multiple access channel Analog i/p Sampling Quantization

S. Mandayam/ ECOMMS/ECE Dept./Rowan University Line Encoding Couch, p. 157 Couch, p. 162

S. Mandayam/ ECOMMS/ECE Dept./Rowan University ECOMMS: Topics

S. Mandayam/ ECOMMS/ECE Dept./Rowan University Digital Communications Transceiver Anti- aliasing Filter Data Encryption Encoder Source Encoder Error Control Encoder Channel/ Line Encoder Modulator MUX Audio Amp Source Decoder Data Encryption Decoder Error Control Decoder Equalization / Decision Circuits Demod- ulator DEMUX Reconstruction/ DAC ADC CODEC MODEM Analog o/p Multiple access channel Analog i/p Sampling Quantization

S. Mandayam/ ECOMMS/ECE Dept./Rowan University Digital Bandpass Communications Why digital modulation? Reproduced from:

S. Mandayam/ ECOMMS/ECE Dept./Rowan University Industry Trends Reproduced from:

S. Mandayam/ ECOMMS/ECE Dept./Rowan University Applications Reproduced from:

S. Mandayam/ ECOMMS/ECE Dept./Rowan University Digital Modulation Carrier signal: A c cos (2  f c t +  ) Modulation: m(t) Modulated signal:A c (t) cos (2  f c (t) t +  (t)) Vary Vary Vary amplitude frequency phase Variations are discrete!!!!!  m(t); discrete

S. Mandayam/ ECOMMS/ECE Dept./Rowan University Recall: Dig Comm Principle ……… 1 0 Analog message Digital code Digital message Sinusoidal carrier modulate AM FM PM AM & PM 1 0

S. Mandayam/ ECOMMS/ECE Dept./Rowan University Signal Vector Representation Phase Magnitude S 0 degrees I Q I-Q Plane s(t) = A c (t) cos (2  f c t +  (t)) fixed!!!

S. Mandayam/ ECOMMS/ECE Dept./Rowan University Signal Changes: Representation in the IQ Plane S1S1 S2S2 I Q Magnitude Change S1S1 S2S2 I Q Phase Change S1S1 S2S2 I Q Magnitude & Phase Change Frequency Change ??? I-Q Diagrams or Constellations

S. Mandayam/ ECOMMS/ECE Dept./Rowan University Binary Phase Shift Keying (BPSK) I Q 10 IQ Diagram t  (t) 0 radians  radians s(t) = A c cos(2  f c t +  (t))

S. Mandayam/ ECOMMS/ECE Dept./Rowan University Quadrature Phase Shift Keying (QPSK) I Q 11 IQ Diagram s(t) = A c cos(2  f c t +  (t)) t  (t)     

S. Mandayam/ ECOMMS/ECE Dept./Rowan University M-ary Phase Shift Keying (M-ary PSK) I Q Octophase I-Q Constellation

S. Mandayam/ ECOMMS/ECE Dept./Rowan University M-ary Quadrature Amplitude Modulation (M-ary-QAM) I Q 16 QAM I-Q Constellation

S. Mandayam/ ECOMMS/ECE Dept./Rowan UniversitySummary