Wireless Communication MCQ || Wireless Communication Questions and Answers

Answer.3. 300 Hz

Explanation

• Antenna diversity, also known as space diversity or spatial diversity, is any one of several wireless diversity schemes that use two or more antennas to improve the quality and reliability of a wireless link.
• Antenna diversity is a technique that can be used to improve radio communication and maximize the chance of a packet getting through at a given time and in a given position between a receiver and transmitter in a non-static environment.
• There is various antenna diversity types such as space diversity, frequency diversity, time diversity, polarization diversity, pattern diversity, directional diversity, transmit-receive diversity.

Answer.4. Constraint length

Explanation

• A convolutional code is a type of error-correcting code. For generating a convolutional code, the information is passed sequentially through a linear finite-state shift register.
• An (n, k, L) convolutional code can be implemented with a k-input, n-output linear sequential circuit with input memory L.
• The constraint length is defined as K = n(L + 1).
• The code rate R = k/ n.
• The parameter N is called the constraint length and indicates the number of input data bits that the current output is dependent upon. The constraint length determines how powerful and complex the code is.

Answer.2. 1990

Explanation

Multiple-Input Multiple-Output (MIMO) is a wireless technology that uses multiple transmitters and receivers to transfer more data at the same time. MIMO was initially developed in  1990.

MIMO communication sends the same data as several signals simultaneously through multiple antennas, while still utilizing a single radio channel. This is a form of antenna diversity, which uses multiple antennas to improve the signal quality and strength of an RF link.

Answer.3. Multiple input Multiple Output (MIMO)

Explanation

Smart antennas (also known as adaptive array antennas, digital antenna arrays, multiple antennas, and, recently, MIMO) are antenna arrays with smart signal processing algorithms used to identify spatial signal signatures such as the direction of arrival (DO of the signal and use them to calculate beamforming vectors which are used to track and locate the antenna beam on the mobile/target.

Smart antennas should not be confused with reconfigurable antennas, which have similar capabilities but are single element antennas and not antenna arrays. It is an antenna technology for wireless communications in which multiple antennas are used at both the source and the destination.

Answer.2. Non-linearity

Explanation

• In software programming, a block code is used to convert software code or an algorithm into any particular form so that errors, if any, in the code can be minimized. Block code can also be applied in the domains of telecommunications, information theory, and coding theory.
• Block codes are linear, systematic, and cyclic in nature.
• The codewords in a linear block code are blocks of symbols that are encoded using more symbols than the original value to be sent. A linear code of length n transmits blocks containing n symbols.

Answer.4. Simulcasting

Explanation

Simulcast (simultaneous broadcasting) means multiple base stations transmitting the same voice (or dat signal on the same frequency at the same time. This means that every frequency pair – probably your existing channels – can each provide greatly extended coverage across a very wide area.

Simulcast paging allows for a paging message to be sent from multiple base stations to all receiver units in a multiple coverage areas simultaneously, compensating for coverage overlap and delay.

Answer.1. Time diversity

Explanation

Time diversity is obtained by re-transmitting the same signal at a separate interval of time. The re-transmission interval should be less than the coherence time. Time Diversity also does not require any increase in transmission power.

Space Diversity: Replica of the same signal is transmitted through the different antennas. Space should be between adjacent antennas so that channel gain will be independent of the signal path.

Space diversity may give a path that avoids shadowing and also decrease the large-scale fading. Space diversity offers a different path without an increase in transmitter power or bandwidth.

Space diversity reception methods can be classified into four categories. They are selection diversity, feedback diversity, maximal ratio combining, and equal gain diversity.

Answer.3. Limited coverage area

Explanation

A cordless telephone or portable telephone is a telephone which has a portable handset but which one can use like landline phone communication; such telephones operate using radio-frequency transmission rather than a physical insulated wire or a direct connection to a telephone line. Most cordless phones offer about the same range. That’s because they all use DECT technology to send out a signal from the base to the handset. As a result, you can expect up to 50 meters range for indoor usage, and up to 300 meters outdoors.

Cordless telephone systems are wireless, but they have a disadvantage of limited coverage area with a cell size of approx. 300 m. Being digital, they have very less chance of eavesdropping.

Answer.4. Simple structure

Explanation

A lattice phase equalizer or lattice filter is an example of an all-pass filter. That is, the attenuation of the filter is constant at all frequencies but the relative phase between input and output varies with frequency.

The structure of a lattice equalizer is more complicated than a linear transversal equalizer. But, numerical stability and faster convergence are two advantages of lattice equalizer. Also, its unique structure allows dynamic assignment of the most effective length of lattice equalizer.

Answer.4. FCC and RCC

Explanation

In radio communication, a control channel is a central channel that controls other constituent radios by handling data streams. FCC (Forward Control Channel) and RCC (Reverse Control Channel) are control channels responsible for initiating mobile calls.

The Forward Control Channel is a downlink analog AMPS (Advanced Mobile Phone Service) channel. It is used to support paging, broadcast, and access messages to the mobile. Contrastingly, a reverse channel refers to the frequencies used by cellular telephones to communicate with a telephone tower.