ECEN 5032 Data Networks Physical Layer: Communication Theory Peter - - PowerPoint PPT Presentation

ECEN 5032 Data Networks

Physical Layer: Communication Theory

Peter Mathys

mathys@colorado.edu

University of Colorado, Boulder

Data Networks, Communication Theory, c

• 1996–2005, P

. Mathys – p.1/4

Communication System

Data Networks, Communication Theory, c

• 1996–2005, P

. Mathys – p.2/4

Communication System Blocks

Source can be analog (e.g., voice, music) or digital (e.g., computer data, WAV file). Source Coding compresses source signal by removing redundancy (e.g., WAV

• MP3, JPEG,

MPEG). May also include A/D conversion. Secrecy Coding transforms compressed source signal using secret key. Only recipient with key can recover source signal. Channel Coding adds redundancy with the goal of detecting and/or correcting transmission errors. Modulator changes input signal into a form suitable for transmission over channel. E.g., Digital

• analog,

and/or baseband to bandpass.

Data Networks, Communication Theory, c

• 1996–2005, P

. Mathys – p.3/4

Communication System Blocks

Channel is characterized by passband with bandwidth

• , input power limitation, and noise
• SNR

(signal-to-noise ratio), fading. Fading is change of signal strength, caused by intersection of several radio waves from the same source arriving along different propagation paths.

Data Networks, Communication Theory, c

• 1996–2005, P

. Mathys – p.4/4