PSK bandwidth efficiency

[pdcom]

psk bandwidth

why PSK is bandwidth efficient.

As we see by using QPSK we are inreasing bit rate and also the bandwidth is also increasing.

kindly explain!

 

[Bhanumurthy]

bpsk bandwidth efficiency

Hi,
Bandwidth efficiency is defined as Bitrate/Bandwidth.The Bandwidth efficiency 'ρ'
of M-ary PSK signals is given by
ρ = Rb/B = log M(to the base 2)/2.
Hence,
for M= 2 4 8 16 32 64
ρ= 0.5 1 1.5 2 2.5 3
Hence, as the number of states, M, is increased, the bandwidth efficiency of M-ary PSK signals is improved at the expense of error performance.

And, i want to correct u in one aspect.Please remember that as M increases, the BW reduces.Hence, if BPSK(M=2) BW is 'fb' Hz ,say, then the BW of QPSK(M=4) will be 'fb/2' and the BW of 8-PSK will be 'fb/3' and so on.
Hope u got my answer.
Regards
Bhanumurthy.

 

[neouser]

I do not think the rite explanation was given above :
the bandwidth efficiency (Theoretical) of a M-ary PSK is
Data-Rate(bps) / Bandwidth (Hz)

For BPSK, 1 Hz signal (just one symbol) can carry 1 Bit
QPSK, 1 Hz signal (just one symbol) can carry 2 Bits

Thus for the same bandwidth we get twice the data rate in QPSK.

See below Table for others :

BPSK - 1bit/second/Hz
QPSK - 2bit/second/Hz
8PSK - 3bit/second/Hz