ECEN5533 Modern Commo Theory Dr. George Scheets Lesson #30 28 March 2016 n Problems: 6.1 – 6.3 n Exam #2: Monday, 4 April n Design #2 due Friday, 8 April

ECEN5533 Modern Commo Theory Dr. George Scheets Lesson #31 30 March 2016 n Problems: Old Exam #2 n Exam #2: Monday, 4 April n Design #2 due Friday, 8 April

ECEN5533 Modern Commo Theory Dr. George Scheets Lesson #32 1 April 2016 n Exam #2 next time n Design #2 due Friday, 8 April

BER for Coherent M-PSK n Not near Shannon Limit? u Room for improvement n Typically requires reduction in C = Information bps W = Bandwidth n ASK, PSK, QAM? u Parity Bits u Lower M in M-ary Image Source: Bernard Sklar's Digital Communcations

BER for Coherent Orthogonal M-FSK n Can Approach Limit u Increasing M u Requires additional tones Image Source: Bernard Sklar's Digital Communcations

Communication System Source Data, Digitized audio or video. Outputs bits. Channel Coder Adds extra FEC bits. Channel Attenuates, distorts, & adds noise to symbols. Modulator Converts bits to a symbol suitable for channel. Symbol Detector Examines received symbol & outputs 1 (binary) or more (M-Ary) bits. Channel Decoder Examines blocks of bits. If possible, corrects or detects bit errors. Outputs estimate of source bit stream.

Communication System Source Data, Digitized audio or video. Outputs bits. Channel Coder Adds extra FEC bits. Channel Attenuates, distorts, & adds noise to symbols. Modulator Converts bits to a symbol suitable for channel. Symbol Detector Examines received symbol & outputs 1 (binary) or more (M-Ary) bits. Channel Decoder Examines blocks of bits. If possible, corrects or detects bit errors. Outputs estimate of source bit stream.

Channel Coder n FEC codes used in power-limited environments u Cell Phones u Deep Space Probes u Compact Disk u Fiber Optic Networks n FEC codes work best for random errors n Errors frequently occur in bursts n Interleaving used to make bursty errors appear random

Communication System Source Data, Digitized audio or video. Outputs bits. Channel Coder Adds extra FEC bits. Channel Attenuates, distorts, & adds noise to symbols. Modulator Converts bits to a symbol suitable for channel. Symbol Detector Examines received symbol & outputs 1 (binary) or more (M-Ary) bits. Channel Decoder Examines blocks of bits. If possible, corrects or detects bit errors. Outputs estimate of source bit stream.

Modulation n Copper Cable u Electrical pulses frequently used n Fiber Cable u Electrical pulses converted to optical pulses n RF Systems u Sinusoid symbols used u Center frequency impacts antenna size n Binary versus M-Ary (excluding M-FSK) u M-Ary packs more bits in the bandwidth u M-Ary more susceptible to decoding errors u M-Ary used when bandwidth is tight & SNR decent

Communication System Source Data, Digitized audio or video. Outputs bits. Channel Coder Adds extra FEC bits. Channel Attenuates, distorts, & adds noise to symbols. Modulator Converts bits to a symbol suitable for channel. Symbol Detector Examines received symbol & outputs 1 (binary) or more (M-Ary) bits. Channel Decoder Examines blocks of bits. If possible, corrects or detects bit errors. Outputs estimate of source bit stream.

Communication System Source Data, Digitized audio or video. Outputs bits. Channel Coder Adds extra FEC bits. Channel Attenuates, distorts, & adds noise to symbols. Modulator Converts bits to a symbol suitable for channel. Symbol Detector Examines received symbol & outputs 1 (binary) or more (M-Ary) bits. Channel Decoder Examines blocks of bits. If possible, corrects or detects bit errors. Outputs estimate of source bit stream.

Symbol Detector Symbol Detector n Extremes: u Single Sample Not affected by increase in bit rate if SNR same u Infinite Sample (Matched Filter Detector) P(BE) gets worse as bit time decreases As T  0, P(BE) MFD  P(BE) SSD n INPUT: Binary ASK, PSK, FSK, or Pulse M-Ary Pulse (PAM) or 4-PSK (a.k.a. QPSK) or QAM (combo of ASK & PSK) n OUTPUT: Baseband bits (square pulses)

Communication System Source Data, Digitized audio or video. Outputs bits. Channel Coder Adds extra FEC bits. Channel Attenuates, distorts, & adds noise to symbols. Modulator Converts bits to a symbol suitable for channel. Symbol Detector Examines received symbol & outputs 1 (binary) or more (M-Ary) bits. Channel Decoder Examines blocks of bits. If possible, corrects or detects bit errors. Outputs estimate of source bit stream.

Syndrome n "A complex of symptoms indicating the existence of an undesirable condition or quality." American Heritage Dictionary n Medical Conditions u Cough u Fever u Knife sticking out of side of the head u etc.

Linear Block Codes n Parity Bits add redundancy Move Legal Words to Higher Dimension n Transmitter can use G to generate Code words from Data words u c = d G n Receiver can use H to generate Syndrome from received Code words n Syndrome provides clues as to underlying error