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Channel Capacity calculation

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great55

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Hi Friends,
Pls culd any one give me some clue or idea in calculating the capacity of a channel using QPSK and 16QAM as the modulation means , given the system bandwidth and Eb/No ?? From


C=Wlog2( 1 + (R*Eb)/(N0*W) ) = Wlog2(1 + SNR ).
My thinking is that if C gives me my capacity then what wuld be R ( bit rate ) which really is also my capacity.

Any help ???
 

To understand Capacity (C),first you must know INFORMATION.

Capacity of a channel is the maximum information that can be sent via a channel. Its unit is :bit or nat or ...

If the channel gaussian, the capacity is calculated based on the formulation that you have written. if the bandwidth is in Hertz, then the unit of the capacity formula is (bit per second). in this sense, the other name for capacity is BIT RATE.

Summary: the unit of capacity is:bit.
For gaussian channel with the above formula, the capacity is interpreted based on the number of bits per second that can be send via the channel with the (bps) unit.

You can have a look at:
https://en.wikipedia.org/wiki/Channel_capacity
 

The given formula will calculate the capacity of a Gaussian channel, discarding any specific modulation. If you use any modulation scheme like PSK, Q-AM or something, the capacity of the specific system will be "constrained capacity" and it will be smaller than the real capacity. Of course, we consider non-fading channels. Capacity calculations in fading environments will be slightly different. The paper may be useful.
 

What I know is
C=Wlog2(1 + SNR ) is an upper limit.
it has nothing to do with the modulation scheme.
And your Rate can only be at most equal to C (i.e. R=C)
 

The real capacity is C=W log_2 (1 + SNR) but when a specific modulation scheme is used, the actual capacity will be degraded and this will be YOUR information rate not channel's. Because you limit the information source, and this limits the capacity. "Capacity of the channel" and "capacity of the system" are two different things.
 

Channel capacity in wireless commnication is calculated by the number of users per cell.

by increasing the size of the cell the capacity will decrease

by decreasing the size of the cell the capacity will increase
 

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