Aptitude [Sasken Placement]: Sample Questions 33 - 34 of 35
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Question 33
Explanation
- Phase shift keying (PSK) is a digital modulation scheme that conveys data by changing, or modulating, the phase of a reference singnal (the carrier wave) . Various types of PSK are, BPSK (Binary Phase Shift Keying) , QPSK (Quadrature Phase Shift Keying) , OQPSK (Offset Quadrature Phase Shift Keying) , / 4 QPSK (Π/ 4 - Quadrature Phase Shift Keying) and DPSK (Differential Phase Shift Keying) .
- In PSK or BPSK we use only one single type of phase shift for a bit transition, whereas in QPSK we use four types of phase shift for a bit transition.
Question 34
Explanation
Error control is the process of detecting and correcting both the bit level and packet level errors.
Error Detection
Error detection is the process of detecting the error during the transmission between the sender and the receiver.
Error Correction
This type of error control allows a receiver to reconstruct the original information when it has been corrupted during transmission.