LINK BUDGET

Energy vs Power:
The energy is the capacity to do work and the
energy expended per time is called power
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LINK BUDGET

Energy vs Power:
 The average power is the energy per unit time and
 The bit rate is the number of bits per unit time.
 The division removes the units of time leaving
Energy per bit (Eb)
Pavg = Energy per unit time = E/Tb
Where Tb is the unit time (Bit time)
Pavg / Rb = (E/Tb )/ (1/Tb)= Eb
To compute Eb, we divide the average signal
power by its bit rate
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LINK BUDGET

we can also write the above equation in an alternative
form with the amplitude-squared representing the Pavg:
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LINK BUDGET

Eb/N0 - a measure for digital links:
Eb/N0 or what we call Signal to Noise Ratio (SNR), is the
most
common
parameter
used
to
compare
communication systems even when they have differing
bit rates, modulations, and even media.
In the dominator of the SNR, the quantity N0 is
called the noise density.
 It is the total noise power in the frequency band of
the signal divided by the bandwidth of the signal.
 It is measured as Watts/Hz and is the noise power in
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one Hz of bandwidth.

LINK BUDGET

Eb/N0 - a measure for digital links:
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LINK BUDGET

Eb/N0 - a measure for digital links: Conclusion
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LINK BUDGET

C/N and C/N0- a measure for analog links:

For analog signals, we use a quantity called C/N0 in
the same way as Eb/N0, where C is the signal
power.

C and Eb are related by the bit rate. So you will
typically see C/N0 specified for the analog portions (or
the pass-band signals) of the link and Eb/N0 for the
digital (or the baseband) portions
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