QUADRATURE PHASE SHIFT KEYING (QPSK) TECHNIQUES AND
ITS BLOCK DIAGRAM:
Advantages of QPSK
Very good noise immunity
Effective utilization of available
Low error probability
Very high bit rate data
is Synchronous reception. Therefore coherent carrier is to be recovered from
the received signal s(t).
Compare binary PSK with
bit forms a symbol. Two bits form a symbol.
possible symbols. Four possible symbols.
bandwidth is twice of fb. Minimum bandwidth is equal to fb.
duration = Tb. Symbol duration = 2Tb.
9. What are the
advantages of M-ary signaling scheme?
signaling schemes transmit bits at a time.
requirement of M-ary signaling schemes is reduced.
The probability of
error in M-Ary FSK as the value of m increases:
the value of „M‟ increases, the Euclidean distance between the symbols reduces.
Hence the symbols come closer to each other. This increases the probability of
error in M-ary systems.
Correlative coding allows the signaling rate of 2B0 in the channel of bandwidth B0. This is made physically possible by allowing ISI in the transmitted signal in controlled manner. This ISI is known to the receiver. Hence effects of ISI are eliminated at the receiver. Correlative coding is implemented by duobinary signaling and modified duobinary signaling.