Difficulty: Easy & Basic
Why can nearby cells reuse the same radio channel?
A Shared copper
B Optical filtering
C Higher battery voltage
D Spatial separation
Answer: D. Spatial separation. Sufficiently separated cells can reuse spectrum while controlling co-channel interference.
Signals from two cells using the same frequency cause what?
A Thermal expansion
B Quantization noise
C Co-channel interference
D Clock drift
Answer: C. Co-channel interference. Co-channel interference comes from transmitters sharing a channel.
What is a guard band between adjacent radio channels?
A Time slot
B Coding block
C Antenna port
D Unused frequency gap
Answer: D. Unused frequency gap. The gap helps limit adjacent-channel interference.
How does OFDM divide a high-rate data stream?
A Across batteries
B Across fibre cores
C Across routers
D Across subcarriers
Answer: D. Across subcarriers. OFDM distributes data over many orthogonal subcarriers.
Why can an OFDM symbol include a cyclic prefix?
A Reduce multipath interference
B Boost antenna gain
C Encrypt symbols
D Reduce carrier frequency
Answer: A. Reduce multipath interference. The prefix acts as a guard interval against delayed echoes.
In TDMA, users share a carrier by taking turns in what?
A Time slots
B Wavelengths
C Polarizations only
D Code lengths
Answer: A. Time slots. Time-division multiple access allocates distinct time slots.
In FDMA, users are separated by what resource?
A Time slots
B Frequency channels
C Packet checksums
D Antenna heights
Answer: B. Frequency channels. Frequency-division multiple access assigns different frequency bands.
In CDMA, users are distinguished using which property?
A Spreading codes
B Separate cables
C Guard heights
D Power supplies
Answer: A. Spreading codes. Code-division multiple access assigns code sequences to users.
What do forward error-correction bits add to a message?
A Antenna gain
B Carrier frequency
C Cell radius
D Redundancy
Answer: D. Redundancy. Redundant coded bits let a receiver correct some transmission errors.
A burst of errors is spread over several codewords by what technique?
A Beamforming
B Duplexing
C Interleaving
D Frequency reuse
Answer: C. Interleaving. Interleaving rearranges symbol order so a burst affects separated coded positions.
Antenna gain is commonly compared with an ideal reference radiator. Which unit is used?
A dBm
B dBHz
C dBi
D dBW/km
Answer: C. dBi. dBi expresses antenna gain relative to an isotropic radiator.
For best reception, what should match between transmitting and receiving antennas?
A Cable colour
B Polarization
C Packet size
D Battery voltage
Answer: B. Polarization. Polarization mismatch can reduce received signal strength.
Which antenna pattern radiates broadly around its vertical axis?
A End-fire only
B Null-only
C Omnidirectional
D Single-point
Answer: C. Omnidirectional. An omnidirectional antenna has broad azimuth coverage.
Which antenna type concentrates energy toward a selected direction?
A Omnidirectional
B Isotropic loss
C Unpolarized
D Directional
Answer: D. Directional. A directional antenna provides greater gain in chosen directions.
How does receive diversity improve a wireless link?
A Combines independent paths
B Repeats one cable
C Raises noise floor
D Widens every channel
Answer: A. Combines independent paths. Independent signal paths reduce the chance that all copies fade together.
What does spatial multiplexing in MIMO send over separate antenna paths?
A One wider guard band
B Parallel data streams
C Only duplicate packets
D A fixed pilot tone
Answer: B. Parallel data streams. MIMO can use multiple antennas to carry parallel streams.
Beamforming steers energy by adjusting what across antenna elements?
A Signal phase
B Battery chemistry
C Packet length
D Carrier licence
Answer: A. Signal phase. Relative phases shape the combined radiation pattern.
A moving receiver observes a frequency shift. Which effect explains it?
A Doppler shift
B Fresnel reflection
C Interleaving
D Polarization
Answer: A. Doppler shift. Relative motion between transmitter and receiver shifts the observed carrier frequency.
A large building blocks part of the direct path, causing slow signal variation. This is called what?
A Quantization
B Shadowing
C Clipping
D Phase coding
Answer: B. Shadowing. Shadowing is large-scale signal variation from obstacles.
In free space, increasing separation generally does what to received power?
A Increases it
B Keeps it exact
C Makes it digital
D Reduces it
Answer: D. Reduces it. Free-space path loss grows as transmitter and receiver separate.
At fixed range and equal antenna gains, a higher carrier frequency has what free-space path loss?
A Smaller loss
B No loss
C Greater loss
D Exactly zero
Answer: C. Greater loss. Friis path loss increases with frequency under these fixed conditions.
Which indicator reports received radio signal strength at a device?
A FEC
B QAM
C RSSI
D TDD
Answer: C. RSSI. Received signal strength indication estimates received power.
A home wireless router usually provides which local radio network?
A WLAN
B Satellite uplink
C Fibre splice
D Cell backhaul
Answer: A. WLAN. A wireless local area network connects nearby devices through an access point.
Which technology commonly links nearby devices in a personal-area network?
A Microwave backhaul
B Bluetooth
C GPS
D Satellite TV
Answer: B. Bluetooth. Bluetooth is used for short-range personal-area device connections.
Which wireless technology is designed for very close proximity exchanges?
A WiMAX
B NFC
C Satellite
D Longwave broadcast
Answer: B. NFC. Near-field communication operates over very short distances.