Cellular Networks MCQ || Cellular Networks Questions and Answers

Answer.1. IEEE 802.11

Explanation

• IEEE 802.11 is used in most home and office networks to allow laptops, printers, smartphones, and other devices to communicate with each other and access the Internet without connecting wires.
•  IEEE 802.11 is a set of media access control and physical layer specification for implementing WLAN computer communication.

Answer.2. Bandwidth efficiency

Explanation

• Bandwidth efficiency can be defined as the effective and useful use of every Hertz of frequency available for communication. In radio communication, bandwidth efficiency is essential as the available spectrum for communication is very limited.
• Bandwidth efficiency reflects how efficiently the allocated bandwidth is utilized. It is defined as the ratio of throughput data rate per Hertz in a given bandwidth. It describes the ability of a modulation scheme to accommodate data within a limited bandwidth.

Answer.1. GFSK

Explanation

Bluetooth technology uses a special binary frequency-shift keying modulation scheme called Gaussian Frequency Shift Keying (GFSK). This form of modulation is spectrally efficient and also enables the use of efficient radio power amplifiers, thereby saving on battery life.

Answer.3. Hexagon

Explanation

• Hexagonal cell shape is perfect over square or triangular cell shapes in cellular architecture because it cover an entire area without overlapping i.e. they can cover the entire geographical region without any gaps. Each cell has its own base station with transmitter power and antenna height.
• The hexagonal cell shape is conceptual and is a simplistic model of the radio coverage for each base station, but it has been universally adopted since the hexagon permits easy and manageable analysis of a cellular system.

Answer.4. Product detector

Explanation

• A product detector is a type of demodulator used for AM and SSB signals. Rather than converting the envelope of the signal into the decoded waveform like an envelope detector, the product detector takes the product of the modulated signal and a local oscillator, hence the name.
• Techniques such as slope detection, zero-crossing detection, phase-locked discrimination, and quadrature detection are used to demodulate FM.

Answer.2. Locator receiver

Explanation

• An analog cellular system refers to a first-generation (1G) cellular network that transmits voice communication using a form of analog modulation. It consists of three elements: a mobile telephone, cell sites, and mobile switching centers.
• The Locator receiver is a spare receiver in each base station. It is used to scan and determine signal strengths of mobile users who are in neighboring cells.

Answer.2. Angle of arrival

Explanation

• Angle of arrival (Ao is the direction of propagation of a radio-frequency wave incident on an antenna array.
• Three principle shape factors are angular spread, angular constriction, and azimuthal direction of maximum fading. They are exactly related to the average rate at which a received signal fades.
• Angular Spread:-  The shape factor angular spread is a measure of how multipath concentrates about a single azimuthal direction.
• Angular Constriction:- The shape factor angular constriction is a measure of how multipath concentrates about two azimuthal directions.
• Azimuthal Direction of Maximum Fading:- A third shape factor, which may be thought of as an orientation parameter, is the azimuthal direction of maximum fading.

Answer.4. Near-far effect

Explanation

• The situation where the received power difference between two CDMA users is so great that discrimination of the low power user is impossible even with low cross-correlation between the codes. If the power of each user within a cell is not controlled such that they do not appear equal at the base station receiver then the near-far problem occurs.
• One of the main problems with adjacent channel interference is the near-far effect. It occurs when a mobile close to a base station transmits on a channel close to one being used by a weak mobile.

Answer.2. Level crossing rate (LCR)

Explanation

• The terms slow and fast fading refer to the rate at which the magnitude and phase change imposed by the channel on the signal changes.
• The level crossing rate (LCR) and average fade duration of a Rayleigh fading signal are important statistics. They are useful for designing error control codes and diversity schemes to be used in mobile communication.
• The level crossing rate (LCR), how often the envelope crosses a certain threshold, and the average fade duration (AF, how long the envelope stays below a given threshold, are two important second-order statistics of multipath fading channels

Answer.3. Microcell zone concept

Explanation

• The increased number of handoffs required when sectoring is employed results in an increased load on the switching and control link elements of the mobile system.
• In the microcell concept for seven cell reuse scheme, each of the three (or possibly more) zone sites are connected to a single base station and share the same radio equipment. The zones are connected by coaxial cable, fiberoptic cable, or microwave link to the base station.
• Multiple zones and a single base station make up a cell. As a mobile travels within the cell, it is served by the zone with the strongest signal. This approach is superior to sectoring since antennas are placed at the outer edges of the cell, and any base station channel may be assigned to any zone by the base station.
• The Microcell zone concept distributes the coverage of the cell and extends the cell boundary to hard-to-reach places. It is the solution for the problem of an increased number of handoffs when sectoring which results in an increase of load on switching.