# Cognitive Radio Questions and Answers – Next Generation Wireless Network – Position Awareness – 1

This set of Cognitive Radio Multiple Choice Questions & Answers (MCQs) focuses on “Next Generation Wireless Network – Position Awareness – 1”.

1. Which among the following statements is false about a very high frequency omnidirectional range (VOR)?
a) VOR is a radio navigation system for aircrafts
b) The frequency range of VOR is 108.00 to 117.95 MHz
c) VOR is intolerant of diffraction
d) VOR signals show more accuracy than nondirectional radio beacon

Explanation: Very high frequency omnidirectional range is a radio navigation system incorporated in aircrafts to stay on route with the help of radio signals transmitted by a network of ground radio beacons. A prominent feature of VOR is that the bearing from the station to the aircraft is unaffected by wind and orientation of the aircraft.

2. Which among the following is used to determine the position of an aircraft using very high frequency omnidirectional range (VOR)?
a) Round trip time of a radial from a single VOR station
b) Intersection of radials from a single VOR station in different directions
c) Intersection of radials from a single VOR station with a delay between the signals
d) Intersection of radials from two different VOR stations

Explanation: Line of position in very high frequency omnidirectional range is called the radial. The line of position consists of a highly directional signal sent by the VOR ground station using a phased antenna array and a reference signal in phase with the directional antenna. The intersection of radials from two different VOR stations is used to determine the position of an aircraft.

3. What is the accuracy range offered by very high frequency omnidirectional range?
a) 50 m
b) 60 m
c) 80 m
d) 90 m

Explanation: Very high frequency omnidirectional range is a short-range radio navigation system. The signals are kept in the line of sight between the transmitter and receiver. It offers an accuracy of 90 m.

4. Which among the following techniques is employed in long range navigation (LORAN)?
a) Round trip time of a radio pulse
b) Time difference between two radio pulses
c) Phase difference between two continuous signals
d) Phase difference between the transmitter and the receiver

Explanation: Long range navigation is a hyperbolic radio navigation system operating at low frequencies. The hyperbolic navigation system in LORAN uses the time difference between radio pulses to locate the object of interest. An electronic clock was employed to generate trigger signals that maintain a fixed delay such as 1 ms between the transmitters.

5. What is the parameter which differentiates LORAN – B from LORAN – A?
a) Method of extraction of timing
b) Number of receivers
c) Number of transmitters
d) Determination of station location

Explanation: LORAN – B employed phase comparison variation and hence used a different method of timing extraction compared to LORAN A. The disadvantage of LORAN B is that its pulse length was about 40 microseconds and the technique exhibited phase distortion.
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6. Which among the following techniques were employed for the identification of pairs in LORAN stations?
a) Modulation technique
b) Encoding scheme
c) Phase comparison between signals
d) Pulse repetition frequency

Explanation: LORAN stations are composed of a master station and two slave stations. Each pair typically broadcasted over the following frequencies of 1.75, 1.8, 1.85, or 1.9 MHz. However, the location of stations is such that it allowed a particular station to pick up signals from at least three stations. Thus to detect to pairs of signals, pulse repetition frequency comparison is employed.

7. Which among the following is essential for geo-location using IP address?
a) Database of registration lifetime of IP packets
b) Database of IP addresses
c) Database of routing path
d) Database of port address

Explanation: Geo-location software translates an IP address into a geo-location and provides the name of a country, city, or zip code. The software exploits the IP address of the sender included in the IP packet. There are a number of geo-location databases that offer different levels of accuracy.

8. Which among the following are sources for constructing an IP database?
a) Network routing information
b) Data mining
c) Regional Internet registry
d) Data scrubbing

Explanation: The primary source of the IP address database is the regional internet registries that assign the IP addresses to organizations within their service area. Network routing information extracted at the endpoint of an IP address, data mining, and data provided by Internet Service Providers are useful for constructing the IP database.

9. Which among the following is an application of geo-location software?
a) Regional licensing
b) Firewall
d) Diagnostic tools

Explanation: Internet services such are live streaming sporting events, or online streaming of television shows and music might be permitted to broadcast only over certain licensed territories. Geolocation is applied to avoid license violations. Fraud detection, Geomarketing, and gaming are other regions of interest.

10. Very High Frequency Omnidirectional Range begins with transmission of frequency modulated signal.
a) True
b) False

Explanation: Very High Frequency Omnidirectional Range begins with transmission of amplitude modulated signal with a constant frequency. The transmitted signal passes through a set of antenna in a circle introducing frequency modulated Doppler onto the received signal. The relative phase angle between amplitude modulated signal and frequency modulated signal is employed to find the location of the source.

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