{[ promptMessage ]}

Bookmark it

{[ promptMessage ]}

L39review - Review for final exam Layered architecture...

Info icon This preview shows pages 1–8. Sign up to view the full content.

View Full Document Right Arrow Icon
Review for final exam Layered architecture APPLICATION LAYER TRANSPORT LAYER NETWORK LAYER DATA LINK LAYER PHYSICAL LAYER
Image of page 1

Info icon This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
PHYSICAL LAYER Limitations to Data Communication rates. Fourier Transform (finite energy time signals) . Important properties: Linear system: Y(f) = X(f)H(f) Scale change: Modulation property:
Image of page 2
The Sampling Theorem : 1. Sampling a bandlimited (W) waveform - (Sampling rate at least 2W samples/sec.) Reconstruction from samples: 2. Sending pulses through a bandlimited communication channel: response H(f) . If H(f) = 0 for * f *$ W, up to a maximum 2W pulses per second (bauds) can be sent through the channel.
Image of page 3

Info icon This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
CHANNEL IMPAIRMENTS, LIMITATIONS Distortion, noise, attenuation, interference, limited bandwidth LINEAR DISTORTION: H(f) = A(f)e J è (f) Combat with equalizer filter E(f), so E(f)H(f) has ideal filter characte ristic. NONLINEAR DISTORTION: nonlinearity creates new difference frequencies, (intermodulation distortion). NOISE: Random disturbances, usually additive Thermal noise Burst-type noises
Image of page 4
THERMAL NOISE Proportional to absolute temperature and proportional to bandwidth SPECTRAL DENSITY CONCEPT: S(f) measures how power of a random noise or signal is distributed in frequency. Thermal noise has a constant spectral 0 density, N /2. Maximum data rate of a channel - Shannon formula - assume thermal noise. 0 The noise power in a band of H herz is N H . S is the signal power.
Image of page 5

Info icon This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
ATTENUATION is bad because: 1. Weakened signal reduces information capacity. 2. Attenuation greater at higher frequencies. In relaying a digital signal, it is better to regenerate it than to just amplify it.
Image of page 6
GUIDED TRANSMISSION MEDIA Twisted pair, Coaxial cable, Optical fiber Guided media attenuation - in dB per kilometer V is voltage, P is power.
Image of page 7

Info icon This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Image of page 8
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}