Maximum Channel Speed

Question 1

Nyquist Theorem

ideal channel, max. channel speed (max. data rate)

Answer 1

v = 2xHxlog2(N)

H - frequency bandwidth
N - number of levels used to encode data

Question 2

Shannon Theorem

more realistic channel, affected by noise

Answer 2

v = 2xlog2(1+S/N)

S/N - signal per noise ratio, expressed usually as 10xlog10(S/N) (understood as attenuation)

Question 3

Synchronous Time Division Multiplexing

Answer 3

• total achievable data rate of the medium&raquo_space; data rate of the signal
• multiple signals carried on a single path by interleaving in time portions of each (slots)
• interleaving may be at bit or at blocks
• time-slots preassigned to sources and are fixed i.e. synchronous
• time-slots do not have to be equally distributed among sources, depending on their own data rate

Question 4

Frequency Division Multiplexing

Answer 4

• total allocated bandwidth&raquo_space; required by a single signal
• no. of signals carried simultaneously, each signal modulated onto different carrier frequency which are separated for avoiding signals bandwidths to overlap
• input signals - analog/digital - converted to analog, multiplexed onto an analog composite signal

Question 5

Wavelength Division Multiplexing

Answer 5

• multiple beams of light at different frequencies - transmitted on the same optical fiber
• dense wavelength multiplexing - DWDM - use of more channels, more closely spaced than ordinary WDM