Wireless & Mobile Communications Multiple Choice Questions on “Paging System”.
1. _________ also known as impulse or zero-carrier radio technology.
a) Ultra wideband technology
b) Femtocell technology
c) Multicasting
d) Multiplexing
Answer: a
Clarification: Ultra-wideband (UWB) technology is also known as impulse or zero-carrier radio technology. It appears to be one of the most promising wireless radio communication technologies of recent time.
2. UWB operates across narrow bandwidth.
a) True
b) False
Answer: b
Clarification: Unlike conventional radio systems, which operate within a relatively narrow bandwidth, the UWB radio system operates across a wide range of the frequency spectrum by transmitting a series of extremely narrow (10–1000 per second) and low-power pulses.
3. The basic element in DSC–UWB technology is the monocycle wavelet.
a) True
b) False
Answer: b
Clarification: The basic element in TM–UWB technology is the monocycle wavelet. Typically, wavelet pulse widths are between 0.2 and 1.5 nanoseconds, corresponding to center frequencies between 600 MHz and 5 GHz.
4. In TM–UWB, the system uses a modulation technique called _______
a) Pulse width modulation
b) Pulse code modulation
c) Pulse position modulation
d) Pulse amplitude modulation
Answer: c
Clarification: In TM–UWB, the system uses a modulation technique called pulse position modulation. The TM–UWB transmitter emits ultra-short monocycle wavelets with tightly controlled pulse-to-pulse intervals, which are varied on a pulse-by-pulse basis in accordance with an information signal and a channel code.
5. DSC-UWB uses _________
a) Pulse width modulation
b) Pulse code modulation
c) Pulse position modulation
d) Direct sequence modulation
Answer: d
Clarification: In DSC-UWB, the signal is spread by direct sequence modulating a wavelet pulse trains at duty cycles approaching that of a sine wave carrier. The spectrum spreading, channelization, and modulation are provided by a PN (pseudo noise) sequence, and the chipping rate is maintained as some fraction of the carrier center frequency.
6. The coherent interaction of signals in UWB arriving by many paths causes ____________
a) Ricean fading
b) Nakagami fading
c) Rayleigh fading
d) Multicast fading
Answer: c
Clarification: The coherent interaction of signals arriving by many paths causes the Rayleigh or multipath fading in RF communications. Inside buildings, when continuous sine waves are transmitted wherein the channels exhibit multipath differential delays in the nanosecond range, the multipath fading occurs naturally.
7. UWB technology supports low bit rate and low speed.
a) True
b) False
Answer: b
Clarification: UWB technology is appropriate for the high-performance wireless home network, which mandates support for large bit rate (50 Mbps), high-speed, affordable connectivity between devices, and simultaneous data transmission from multiple devices, and full-motion video capability.
8. Which of the following is not true for UWB?
a) Large spectrum
b) Lower price
c) Pulse data
d) Large interference
Answer: d
Clarification: The combination of a larger spectrum, lower power, and pulsed data means that UWB causes less interference than narrowband radio designs while yielding low probability of detection and excellent multipath immunity.
9. UWB systems are very complex, since they use radio frequency/intermediate frequency conversion stages.
a) True
b) False
Answer: b
Clarification: UWB systems are much less complex, since they do not use any radio frequency/intermediate frequency (RF/IF) conversion stages, local oscillators, mixers, and other expensive surface acoustic wave (SAW) filters common to traditional radio technologies.
10. Which of the following is a drawback of UWB technology?
a) Not appropriate for WAN
b) Power limited
c) Small spectrum
d) Limited jitter requirements
Answer: d
Clarification: UWB devices are power limited because they must coexist on a noninterfering basis with other licensed and unlicensed users across several frequency bands. For UWB systems using PPM as their modulation technique, limited jitter requirements could be an issue.
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