How is frequency up-conversion performed ?
It is performed in a mixer using a signal from the local
oscillator (heterodyne) with frequency fh.
What a superheterodyne receiver do ?
It converts the EM field to an RF signal at the carrier frequency fc and then to an intermediate frequency (IF) f0.
How is frequency down-conversion performed ?
It is performed in a mixer using a signal from the local oscillator (heterodyne) with frequency fh.
Cite wave propagation types.
Ground (surface) waves.
Sky waves.
Direct waves.
What is a transmission half-duplex ?
A system enables communication in both directions, but only one direction at a particular time (not simultaneously).
What is a full-duplex transmission ?
A system allows simultaneous communication in both directions.
What is circuit switching ?
It establishes a dedicated communications channel (circuit) through the network for two nodes before they may communicate. The circuit guarantees the full bandwidth of the channel and remains connected for the entire duration of the communication session.
What is packet switching ?
It splits the data to be transmitted into small units, called packets. Packets are labelled with destination and may be routed independently
through the network via different paths. Packet switching shares available
bandwidth between multiple communication sessions.
What is a simplex transmission ?
The communication can be performed only in one direction.
Wireless channels suffer from:
A. Multipath
B. No noise
C. Perfect stability
D. Full isolation
Answer: A
ISI is caused by:
A. Multipath
B. Encryption
C. Sampling
D. Ethernet
Answer: A
Fading refers to:
A. Rapid signal strength changes
B. Quantization
C. Optical dispersion
D. Image blur
Answer: A
Doppler shift is due to:
A. Movement
B. Quantization
C. Modulation
D. Sampling
Answer: A
Equalizers reduce:
A. ISI
B. Colors
C. Noise
D. Compression
Answer: A
Pilots are used for:
A. Channel estimation
B. Encryption
C. Video coding
D. Storage
Answer: A
Multipath causes:
A. ISI
B. Encryption
C. Quantization
D. Sampling
Answer: A
Wireless channels are:
A. Time-varying
B. Always stable
C. Noise-free
D. Perfect
Answer: A
Diversity reduces:
A. Fading
B. Sampling
C. Quantization
D. Video blur
Answer: A
Coherence time measures:
A. How fast channel changes
B. Bitrate
C. Compression
D. Power
Answer: A
