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ADVANTAGES OF QPSK
With fourphases, QPSK can encode two bits per symbol, to minimize the BER —
twice the rate of BPSK. Ana...
Transmitter and receiver have to be synchronized very often, eg. by using special
synchronization patterns before user dat...
BPSK:
ADVANTAGES:
The system is simplest and has more power efficiency.
DISADVANTAGES:
It has low bandwidth efficiency.

A...
DPSK has some advantages over BPSK, but at the same time it has some drawbacks.

ADVANTAGES OF DPSK:
1) DPSK does not need...
8.PSK

Power efficiency. System is
the simplest

Low bandwidth efficiency

Low speed communication

DRAWBACKS OF BPSK: AMB...
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Advantages of qpsk

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Advantages of qpsk

  1. 1. ADVANTAGES OF QPSK With fourphases, QPSK can encode two bits per symbol, to minimize the BER — twice the rate of BPSK. Analysis shows that this may be used either to double the data rate compared to a BPSK system while maintaining the bandwidth of the signal or to maintain the data-rate of BPSK but halve the bandwidth needed. As with BPSK, there are phase ambiguity problems at the receiver and differentially encoded QPSK is more normally used in practice. One of the advantages of qpsk is its use of Differential QPSK (DQPSK). Here the phase shift is not relative to a reference signal but relative to the phase of previous two bits. The receiver does not need the reference signal but only compares two signal to reconstruct data. The phase shift can always be relative to a reference signal. If this scheme is used, phases shift of 0 means that the signal is in phase with the reference signal. A QPSK signal will then exhibit a phase shift of 450 for the data II, 135° for 10, 225° for 00, and 3150 for 01, with all phase shifts being relative of the reference signal. This is one of the advantages of qpsk. DISADVANTAGES OF QPSK: Interchannelinterference is significantly large in QPSK. To avoid ICI QPSK requires filtering, can change amplitude and phase of QPSKwaveform. QPSK requires around 8 times its bandwidth to transmit the same power. The disadvantage of QPSK relative to BPSK is that it is more sensitive to phase variations.
  2. 2. Transmitter and receiver have to be synchronized very often, eg. by using special synchronization patterns before user data arrives or via a plot frequency as reference. ADVANTAGES OF ASK ASK is heavily effected by noise and interference and can be easily demodulated. FSK is insensitive to channel fluctuations and not easily effected by noise. Reduction in the amount of energy required to transmit informations. It has good bandwidth efficiency DISADVANTAGES OF ASK Easily influenced to noise interference - refer to unintentional voltage probably affected by heat or electromagnetic induction created by other source. It has low power efficiency.
  3. 3. BPSK: ADVANTAGES: The system is simplest and has more power efficiency. DISADVANTAGES: It has low bandwidth efficiency. APPLICATIONS: It is used in low speed communications.
  4. 4. DPSK has some advantages over BPSK, but at the same time it has some drawbacks. ADVANTAGES OF DPSK: 1) DPSK does not need carrier at its receiver. Hence the complicated circuitry for generation of local carrier is avoided. 2) The bandwidth requirement of DPSK is reduced compared to that of BPSK. DISADVANTAGES: 1) The probability of error or bit error rate of DPSK is higher than that of BPSK. 2) Since DPSK uses two successive bits for its reception, error in the first bit creates error in the second bit. Hence error propagation in DPSK is more. Whereas in PSK single bit can go in error since detection of each bit is independent. 3) Noise interference in DPSK is more. In DPSK, previous bit is used to detect next bit. Therefore if error is present in previous bit, detection of next bit can also go wrong. Thus error is created in bit also. Thus there is tendency of appearing errors in pairs in DPSK.
  5. 5. 8.PSK Power efficiency. System is the simplest Low bandwidth efficiency Low speed communication DRAWBACKS OF BPSK: AMBIGUITY IN OUTPUT SIGNAL:

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