Digital Modulation Techniques Quiz

Amplitude Shift Keying (ASK)

• ASK transmits digital data over optical fiber.
• Receivers and transmitters are simple and inexpensive.
• ASK uses less bandwidth than Frequency Shift Keying (FSK), making it more bandwidth efficient.
• ASK is susceptible to noise interference, which can lead to data loss.

Frequency Shift Keying (FSK)

• FSK modifies the frequency of an analog carrier signal to reflect binary data.
• A higher frequency represents a binary high input, while a lower frequency represents a binary low input.
• Amplitude and phase of the carrier signal remain constant.
• FSK is less prone to noise issues than ASK.
• FSK offers a higher signal-to-noise ratio.
• Transmitters and receivers are simple for low data rate applications.
• FSK uses more bandwidth than ASK, making it less bandwidth efficient.
• FSK has lower power efficiency.

Phase Shift Keying (PSK)

• PSK modifies the phase of an analog carrier signal to reflect binary data.
• Amplitude and frequency of the carrier signal remain constant.

Binary Phase Shift Keying (BPSK)

• Also known as 2-phase PSK or Phase Reversal Keying.
• The carrier sine wave undergoes two phase reversals (0° and 180°).
• BPSK is a Double Side Band Suppressed Carrier (DSBSC) modulation scheme.
• Uses a 180° phase shift difference between binary 1 and binary 0.
• Considered the most robust digital modulation technique for long-distance wireless communication.

Quadrature Phase Shift Keying (QPSK)

• The carrier sine wave undergoes four phase reversals (0°, 90°, 180°, and 270°).
• Can be further extended to use eight or sixteen phase values.
• Encodes two bits per symbol.
• Uses phase shifts of multiples of 90 degrees.
• Has double the data rate carrying capacity compared to BPSK.

Advantages of PSK

• More power efficient than ASK and FSK.
• Less prone to errors.
• Carries data more efficiently than FSK.

Disadvantages of PSK

• Lower bandwidth efficiency.
• Complex detection and recovery algorithms for binary data.
• Requires a non-coherent reference signal.

Client-Server Network

• A network architecture where a central server manages resources and services for connected clients.
• Clients request services and data from the server.
• The server provides resources and services to clients.
• Examples: Web browsing, email, file sharing.

Peer-to-Peer Network

• Each connected node (peer) acts as both a client and a server.
• Peers can directly share resources and communicate with each other.
• No central authority or server.
• Examples: BitTorrent, file sharing applications.

Quantization

• The process of converting a continuous analog signal into a discrete digital signal.
• The process involves dividing the signal range into a finite number of levels.
• Each level is assigned a specific digital value.

Delta Modulation

• A simplified digitalization technique compared to Pulse Code Modulation (PCM).
• Delta Modulation focuses on changes from the previous sample.
• Modulator: Creates a stream of bits representing small changes in the analog signal.
• Demodulator: Uses a staircase-like signal and delays to reconstruct the analog signal from the digital data.

Adaptive Delta Modulation

• Improves Delta Modulation by adapting the step size based on signal changes.
• Allows for more accurate representation of the original signal.
• Enhances the performance of Delta Modulation.