Category: Wireless & Mobile Communications Objective Questions

Wireless & Mobile Communications Multiple Choice Questions on “Traffic Routing in Wireless Networks”.

1. The type of traffic carried by a network determines the routing service.
a) True
b) False
Answer: a
Clarification: The type of traffic carried by a network determines the routing services. It also determines protocols, and call handling techniques which must be employed.

2. Connection oriented services are also called __________
a) Datagram services
b) Virtual circuit routing
c) Connectionless services
d) Routing service
Answer: b
Clarification: Connection oriented services are also called virtual circuit routing. In connection oriented routing, the communications path between the message source and destination is fixed for the entire duration of the message.

3. Connectionless services are also called __________
a) Datagram services
b) Virtual circuit routing
c) Connection oriented services
d) Routing service
Answer: a
Clarification: Connectionless services are also called datagram services. In a connectionless service, a call set up procedure is not required at the beginning of a call, and each message burst is treated independently by the network.

4. First generation cellular systems provide connectionless services for each voice user.
a) True
b) False
Answer: b
Clarification: First generation cellular systems provide connection oriented services for each voice user. Voice channels are dedicated for users at the serving base station.

5. Wireless data networks are not well supported by ___________
a) Datagram services
b) Circuit switching
c) Connectionless services
d) Routing service
Answer: b
Clarification: Wireless data networks are not supported by circuit switching. It is due to their short, bursty transmissions which are often followed by periods of inactivity. Circuit switching is best suited for dedicated voice only traffic.

6. Packet switching breaks each message into smaller units.
a) True
b) False
Answer: a
Clarification: Packet switching breaks each message into smaller units for transmission and recovery. When a message is broken into packets, a certain amount of control information is added to each packet to provide source and destination identification, as well as error recovery provisions.

7. Header specifies the ___________ of a new packet.
a) Ending
b) Middle part
c) Beginning
d) Data information
Answer: c
Clarification: The header specifies the beginning of a new packet. It contains the source address, packet sequence number, and other routing and billing information.

8. The control field contains the ________
a) CRC
b) User data
c) Address
d) ARQ
Answer: d
Clarification: The control field defines functions such as transfer of acknowledgments, automatic repeat requests (ARQs), and packet sequencing. The information field contains user data. And the final field is the frame check sequence field or the CRC (cyclic redundancy check).

9. Circuit switching provides greater efficiency in comparison to circuit switching.
a) True
b) False
Answer: b
Clarification: In contrast to circuit switching, packet switching provides excellent channel efficiency for bursty data transmission of short length. An advantage of packet switched data is that the channel is utilized only when sending or receiving bursts of information.

10. __________ was developed by CCITT to provide standard connectionless network access protocols for three layers of OSI model.
a) Packet switching
b) Datagram routing
c) X.25
d) CDPD
Answer: c
Clarification: X.25 was developed by CCITT (now ITU-T) to provide standard connectionless network access (packet switching) protocols for the three layers (layer 1, 2 and 3) of the open systems interconnection (OSI) model.

11. X.25 protocols specify particular data rates.
a) True
b) False
Answer: b
Clarification: The X.25 protocol does not specify particular data rates or how packet switched networks are implemented. Rather, X.25 provides a series of standard functions and formats which give structure to the design of the software.

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Wireless & Mobile Communications Multiple Choice Questions on “Paging System”.

1. Which of the following technology is mainly designed for indoor coverage?
a) Femtocell network
b) 3GPP
c) LTE
d) AMPS
Answer: a
Clarification: Femtocell Network is a small-size Macro cell network designed for better indoor coverage. It began attracting attention from both industry and academy in late 2007.

2. Coverage of Femtocell Network is much larger than a regular Macro cell Network.
a) True
b) False
Answer: b
Clarification: The “femto” means 10-15. Coverage of Femtocell Network is much smaller than a regular Macro cell Network that is why this name is given. Femtocell Network, installed by end users at home or in an office environment.

3. Which of the following is not a component of Femtocell network?
a) F-BS
b) Internet link
c) FGW
d) BSC
Answer: d
Clarification: Similar to UMTS Terrestrial Radio Access Network (UTRAN) architecture, the Femtocell Network consists of three components: Femtocell Base Stations (F-BS), Internet Link, and Femtocell Gateway (FGW).

4. Which of the following is not true for Femtocell base stations?
a) Short range
b) Low power
c) High cost
d) Wireless handsets
Answer: c
Clarification: Femtocell Base Stations (F-BSs) are short-range, low-cost, low-power indoor devices to provide service for wireless handsets. F-BS, which looks like WLAN Access Point (AP), is a small device with at least two wireless and internet interfaces.

5. Any existing wireless telecommunication standard cannot be used at F-BS wireless interface.
a) True
b) False
Answer: b
Clarification: Wireless interface provides wireless radio access to Femtocell MSs. Any existing wireless telecommunication standard, such as UMTS/ CDMA200/ WIMAX/ LTE/ EV-DO, can be used at the F-BS wireless interfaces.

6. ________ acts as a gateway between the Internet and communication network.
a) F-BS
b) Internet link
c) FGW
d) BSC
Answer: c
Clarification: Femtocell Gateway (FGW) is a service provider’s device that acts as a gateway between the Internet and the communication network. One side of FGW connects a large number of F-BSs via broadband Internet, and the other side of FGW is connected to the telephony core network.

7. Femtocell network has improved seamless coverage and enhanced capacity.
a) True
b) False
Answer: a
Clarification: Femtocell Network is a so-called “double-win” strategy that brings benefits to both cellular users and cellular providers. It provides improved seamless coverage and enhanced capacity for cellular users.

8. In _________ all cellular users belong to open subscribers group (OSG) and can access F-BS unconditionally.
a) Closed access mode
b) Open access mode
c) Hybrid Access mode
d) Zero access mode
Answer: b
Clarification: In open access mode, all cellular users belong to open subscribers group (OSG) and can access F-BS unconditionally. Several cellular service providers have plans to deploy F-BS for better service quality to cover public hole areas.

9. In _______ a closed subscribers group (CSG) is set by F-BS owner to allow only small portion of cellular users to be served in the Femtocell Network.
a) Closed access mode
b) Open access mode
c) Hybrid Access mode
d) Zero access mode
Answer: a
Clarification: In closed access mode, a closed subscribers group (CSG) is set by F-BS owner to allow only small portion of cellular users to be served in the Femtocell Network. For example, people can install F-BS in their house and only household members can access F-BS to attain better service.

10. Femtocell Network has the capability to help Macro cell Network achieve seamless coverage.
a) True
b) False
Answer: a
Clarification: Femtocell Network has the capability to help Macro cell Network achieve seamless coverage. It can attain higher network capacity by transmitting over an Internet link.

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Wireless & Mobile Communications Interview Questions and Answers for freshers on “Improving Coverage and Capacity in Cellular Systems”.

1. Which of the following techniques do not help in expanding the capacity of cellular system?
a) Sectoring
b) Scattering
c) Splitting
d) Microcell zone concept
Answer: b
Clarification: As the demand for wireless service increases, the number of channels assigned to a call eventually becomes insufficient to support the required number of user. Techniques such as cell splitting, sectoring and coverage zone approaches are used in practice to expand the capacity of cellular system.

2. ________ uses directional antennas to control interference.
a) Sectoring
b) Cell splitting
c) Repeaters
d) Micro cell zone concept
Answer: a
Clarification: Sectoring uses directional antenna to further control the interference and frequency reuse of channels. By decreasing the cell radius R and keeping the co-channel reuse ratio D/R unchanged, cell splitting increases the number of channels per unit area.

3. _______ allows an orderly growth of cellular system.
a) Sectoring
b) Scattering
c) Cell splitting
d) Micro cell zone technique
Answer: c
Clarification: Cell splitting allows an orderly growth of cellular system. By defining new cells which have a smaller radius than the original cells, capacity increases due to additional number of channels per unit area.

4. Which of the following technology distributes the coverage of the cell and extends the cell boundary to hard-to-reach places?
a) Cell splitting
b) Scattering
c) Sectoring
d) Micro cell zone concept
Answer: d
Clarification: Micro cell 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 increased number of handoffs when sectoring which results in an increase of load on switching.

5. Which of the following increases the number of base stations in order to increase capacity?
a) Cell splitting
b) Sectoring
c) Repeaters
d) Micro cell zone concept
Answer: a
Clarification: Cell splitting increases the number of base stations in order to increase capacity. Whereas, sectoring and zone microcells rely on base station antenna placements to improve capacity by reducing co-channel interference.

6. Which of the following trunking inefficiencies?
a) Cell splitting
b) Micro cell zone technique
c) Sectoring
d) Repeaters
Answer: c
Clarification: Sectored cells experience trunking inefficiencies. Cell splitting and zone micro cell techniques do not suffer the trunking inefficiencies experienced by sectored cells. They enable the base station to oversee all handoff chores related to microcells, thus reducing the computational load at MSC.

7. The process of subdividing a congested cell into smaller cells is called _______
a) Cell splitting
b) Sectoring
c) Micro cell technique
d) Repeaters
Answer: a
Clarification: Cell splitting is the process of subdividing a congested cell into smaller cells. Each small cell has its own base station and a there is a corresponding reduction in antenna height and transmitter power.

8. Cell splitting increases the capacity of a cellular system since it increases the number of times ________ are reused.
a) Cells
b) Channels
c) Transmitters
d) Mobile stations
Answer: b
Clarification: Cell splitting increases the capacity of a cellular system since it increases the number of times channels are reused. But it has a limitation that handoffs are more frequent and channel assignments become more difficult.

9. Cell splitting do not maintain the minimum c-channel reuse ratio.
a) True
b) False
Answer: b
Clarification: Cell splitting allows a system to grow by replacing large cells with smaller cells. It does not upset the channel allocation scheme required to maintain the minimum co channel reuse ratio Q between co-channel cells.

10. Which of the following technique is used to limit radio coverage of newly formed microcells?
a) Sectoring
b) Splitting
c) Antenna downtilting
d) Scattering
Answer: c
Clarification: Antenna downtilting deliberately radiated energy from the base station toward the ground (rather than toward the horizon). It is often used to limit the radio coverage of newly formed microcells.

11. Sectoring increases SIR (Signal to Interference Ratio).
a) True
b) False
Answer: a
Clarification: Sectoring increases SIR so that cluster size may be reduced. SIR is improved using directional antenna. And then capacity improvement is achieved by reducing the number of cells in a cluster, thus increasing the frequency reuse.

12. Which of the following has range extension capability?
a) Sectoring
b) Repeaters
c) Scattering
d) Micro cell zone concept
Answer: b
Clarification: Wireless operator needs to provide dedicated coverage for hard-to-reach areas, such as within buildings, or in valleys or tunnels. Radio transmitters used to provide such range extension capabilities are called as repeaters. They are bidirectional in nature.

13. Repeaters has one drawback of reradiating ____________
a) Frequency
b) Channels
c) Power
d) Repeater noise and interference
Answer: d
Clarification: Upon receiving signals from a base station forward link, the repeater amplifies and reradiates the base station signals to the specific coverage region. Unfortunately, the received noise and interference is also reradiated by repeater on both the forward and reverse link.

14. Which of the following is not an advantage of micro cell zone technique?
a) Reduced co channel interference
b) Improved signal quality
c) Increase in capacity
d) Increasing number of base stations
Answer: d
Clarification: The advantage of the zone cell technique is that co-channel interference in the cellular system is reduced since a large central base station is replaced by several low powered transmitters on the edges of the cell. Thus, signal quality is reduced and it leads to an increase in capacity.

15. In a micro cell zone concept, when a mobile travels from one zone to another within the cell, it retains the same _________
a) Power level
b) Base station
c) Channel
d) Receiver
Answer: c
Clarification: As a mobile travels from one zone to another within the cell, it retains the same channel. Thus, unlike in sectoring, a handoff is not required at the MSC when the mobile travels between zones within the cell. The channels are re used in co channel cells in a normal fashion.

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Wireless & Mobile Communications Questions and Answers for Aptitude test on “Frequency Modulation Vs. Amplitude Modulation”.

1. Which is the process of encoding information from a message source in suitable manner for transmission?
a) Modulation
b) Demodulation
c) Encryption
d) Decryption
Answer: a
Clarification: Modulation is the process of encoding information from a message source in suitable manner for transmission. It translates the baseband message signal to a bandpass signal at frequencies that are very higher compared to the baseband frequency.

2. The bandpass signal is called the modulating signal.
a) True
b) False
Answer: b
Clarification: The bandpass signal is called the modulated signal and the baseband message signal is called the modulating signal. Modulation is done by varying the amplitude, phase or frequency of a high frequency carrier in accordance with the amplitude of the message signal.

3. AM signal have all information in ______ of the carrier.
a) Amplitude
b) Magnitude
c) Frequency
d) Power
Answer: a
Clarification: AM signals have all information in the amplitude of the carrier. Because, AM signal superimpose the exact relative amplitudes of the modulating signal onto the carrier.

4. In frequency modulation, the amplitude of modulated carrier signal is ______and its frequency is ______ by the modulating message signal.
a) Constant, constant
b) Varied, constant
c) Constant, varied
d) Varied, varied
Answer: c
Clarification: In frequency modulation (FM), the amplitude of modulated carrier signal is kept constant while its frequency is varied by the modulating message signal. FM is the most popular analog modulation technique used in mobile communication.

5. FM signals have all their information in ______ of the carrier.
a) Amplitude
b) Magnitude
c) Frequency
d) Power
Answer: c
Clarification: FM signal have all their information in the phase or frequency of the carrier. This provides a nonlinear and very rapid improvement in reception quality once a certain minimum received signal level, called FM threshold is achieved.

6. Amplitude modulation has ______ relationship between the quality of the received signal and the power of the received signal.
a) No
b) Non linear
c) Constant
d) Linear
Answer: d
Clarification: In amplitude modulation schemes, there is a linear relationship between the quality of the received signal and the power of the received signal. AM signals superimpose the exact relative amplitudes of the modulating signal onto the carrier.

7. FM has _______ noise immunity when compared to amplitude modulation.
a) Same
b) Less
c) No
d) Better
Answer: d
Clarification: FM offers many advantages over amplitude modulation which makes it a better choice for many mobile radio applications. Frequency modulation has better noise immunity when compared to amplitude modulation.

8. FM signals are _____ susceptible to atmospheric and impulse noise as compared to AM.
a) Largely
b) Less
c) Not
d) Better
Answer: b
Clarification: FM signals are represented as frequency variations rather than amplitude variations. Therefore, FM signals are less susceptible to atmospheric and impulse noise.

9. Burst noise affects FM systems.
a) True
b) False
Answer: b
Clarification: If the FM received signal is above the FM threshold, burst noise does not affect FM system performance as much as AM systems. It is due to the fact that message amplitude variations do not carry information in FM.

10. AM has a modulation index.
a) True
b) False
Answer: b
Clarification: Unlike AM, FM has a modulation index. Hence, bandwidth occupancy can be varied to obtain greater signal to noise performance. Thus, it is possible to tradeoff bandwidth occupancy for improved noise performance.

11. Which of the following is an advantage of AM systems in comparison to FM sysytems?
a) Occupy less bandwidth
b) Superior performance in fading
c) Better noise immunity
d) Not susceptible to impulse noise
Answer: a
Clarification: AM signals are able to occupy less bandwidth as compared to FM signals, since the transmission system is linear. Small scale fading causes rapid fluctuations in the received signal. Thus, FM offers superior qualitative performance in fading when compared to AM.

12. An FM signal is a ______ envelope signal.
a) Varied
b) Small
c) Large
d) Constant
Answer: d
Clarification: An FM signal is a constant envelope signal. It is due to the fact that the envelope of the carrier does not change with changes in the modulating signal. Hence, the transmitted power of an FM signal is constant regardless of the amplitude of the message signal.

13. FM uses class______ amplifiers and AM uses class ______ amplifiers.
a) C, C
b) A, C
c) C, A
d) AB, C
Answer: c
Clarification: The constant envelope of the transmitted signal allows efficient class C amplifiers. However in AM, it is critical to maintain linearity between the applied message and amplitude of transmitted signal. Therefore, class A or AB are used for AM systems.

14. AM exhibits capture effect characteristics.
a) True
b) False
Answer: b
Clarification: AM systems do not exhibit capture effect characteristics because all the interferers are received at once and must be discriminated after the modulation process. FM exhibits this characteristic. Capture effect is a direct result of rapid non-linear improvement in received quality for an increase in receives power.

15. Which of the following is a drawback of FM systems?
a) Burst noise
b) Susceptible to atmospheric noise
c) Wider frequency band
d) Poor performance in fading
Answer: c
Clarification: FM systems have many advantages over AM systems. They also have certain disadvantages. FM systems require a wider frequency band in transmitting media in order to obtain the advantages of reduced noise and capture effect. It is generally several times as large as that needed for AM.

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Wireless & Mobile Communications Multiple Choice Questions on “Convolutional Codes”.

1. Block codes can achieve a larger coding gain than convolution coding.
a) True
b) False
Answer: b
Clarification: Convolution code can achieve a larger coding gain that can be achieved using a block coding with the same complexity. Their mapping is highly structured, enabling a decoding method considerably different from block codes.

2. Which of the following indicates the number of input bits that the current output is dependent upon?
a) Constraint length
b) Code length
c) Search window
d) Information rate
Answer: a
Clarification: Constraint length determines the number of input data bits that the current output is dependent upon. The constraint length determines how powerful and complex the code is.

3. Which of the following is not a way to represent convolution code?
a) State diagram
b) Trellis diagram
c) Tree diagram
d) Linear matrix
Answer: d
Clarification: Linear matrix is not a way to represent convolution code. Various ways of representing convolution codes are generator matrix, generator polynomial, logic tables, state diagram, tree diagram and trellis diagram.

4. Which of the following is not an algorithm for decoding convolution codes?
a) Viterbi algorithm
b) Stack algorithm
c) Fano’s sequential coding
d) Ant colony optimization
Answer: d
Clarification: There are a number of techniques for decoding convolution codes. The most important of these methods is Viterbi algorithm. Other decoding algorithms for convolutional codes are Fano’s sequential coding, stack algorithm and feedback coding.

5. Viterbi algorithm performs ____________ decoding of convolutional codes.
a) Maximum likelihood
b) Maximum a posteriori
c) Minimum square
d) Minimum mean square
Answer: a
Clarification: Viterbi algorithm performs maximum likelihood decoding of convolutional codes. The algorithm was first developed by A.J. Viterbi. It is one of the most important algorithm used for decoding convolutional codes.

6. Fano’s algorithm searches all the paths of trellis diagram at same time to find the most probable path.
a) True
b) False
Answer: b
Clarification: Fano’s algorithm searches for the most probable path through the trellis diagram by examining one path at a time. The error rate performance of Fano’s algorithm is comparable to Viterbi’s algorithm.

7. Which of the following is not an advantage of Fano’s algorithm in comparison to Viterbi’s algorithm?
a) Less storage
b) Large constraint length
c) Error rate
d) Small delays
Answer: d
Clarification: In comparison to Viterbi decoding, sequential decoding has a significantly larger delay. In advantage over Viterbi decoding is that it requires less storage, and thus codes with larger constraint lengths can be employed.

8. In comparison to stack algorithm, Fano’s algorithm is simpler.
a) True
b) False
Answer: b
Clarification: In comparison to Fano’s algorithm, the stack algorithm is computationally simpler since there is no retracting over the same path. But stack algorithm requires more storage than Fano’s algorithm.

9. Which of the following is not an error correction and detection code?
a) Block code
b) Convolutional codes
c) Passive codes
d) Turbo codes
Answer: c
Clarification: There are three basic types of error correction and detection codes. They are block codes, convolutional codes and turbo codes. A channel coder operates on digital message data by encoding the source information into a code sequence.

10. Which decoding method involves the evaluation by means of Fano’s algorithm?
a) Maximum Likelihood Decoding
b) Sequential Decoding
c) Maximum a priori
d) Minimum mean square
Answer: b
Clarification: Fano’s algorithm involves sequential decoding. It searches for the most probable path through the trellis by examining one path at a time.

11. In Viterbi’s algorithm, the selected paths are regarded as __________
a) Survivors
b) Defenders
c) Destroyers
d) Carriers
Answer: a
Clarification: In Viterbi’s algorithm, the selected paths are regarded as survivors. The path thus defined is unique and corresponds to the decoded output.

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Wireless & Mobile Communications Multiple Choice Questions on “Wireless Data Services”.

1. US cellular standard CDPD stands for _________
a) Cellular Digital Packet Data
b) Cellular Digital Packet Data
c) Cellular Digital Pocket Data
d) Cellular Discrete Pocket Data
Answer: a
Clarification: US cellular standard CDPD stands for Cellular Digital Packet Data. In 1993, US cellular industry developed CDPD to coexist with the conventional voice only cellular system.

2. CDPD is data service for third generation US cellular systems.
a) True
b) False
Answer: b
Clarification: CDPD is a data service for first and second generation US cellular systems and uses a full 30 kHz AMPS channel on a shared basis. CDPD provides mobile packet data connectivity to existing data networks.

3. Which of the following is true for CDPD?
a) Expensive to install
b) Uses different infrastructure
c) Complex
d) Inexpensive to install
Answer: d
Clarification: CDPD directly overlays with existing cellular infrastructure and uses existing base station equipment, making it simple and inexpensive to install. CDPD does not use the MSC, but rather has its own traffic routing capabilities.

4. CDPD channel is _________
a) Simplex
b) Complex
c) Duplex
d) Expensive
Answer: c
Clarification: Each CDPD channel is duplex in nature. The forward channel serves as a beacon and transmits data from the PSTN side of the network, while the reverse channel links all mobile users to the CDPD network and serves as the access channel for each subscriber.

5. CDPD transmissions are carried out using ________ blocks.
a) Fixed length
b) Variable length
c) Long
d) Short
Answer: a
Clarification: CDPD transmissions are carried out using fixed length blocks. User data is protected using a Reed-Solomon (63, 47) block code with 6 bit symbols.

6. MDLP is _________
a) Layer protocol used in CDPD
b) Layer protocol used in GSM
c) Layer protocol used in ARDIS
d) Layer protocol used in CDMA
Answer: a
Clarification: MDLP (Mobile data link protocol) is a lower layer protocol of CDPD. It is used to convey information between data link layer entities (layer 2 devices) across the CDPD air interface.

7. The layer protocol, RRMP stands for _________
a) Radio Resource Management Protocol
b) Radio Resource Mobile Protocol
c) Radio Rate Management Protocol
d) Radio Rate Mobile Protocol
Answer: a
Clarification: The radio resource management protocol (RRMP) is a higher, layer 3 protocol used to manage the radio channel resources of the CDPD system and enables an M-ES to find and utilize a duplex radio channel without interfering with standard voice services.

8. ARDIS is a public network service.
a) True
b) False
Answer: b
Clarification: ARDIS (Advanced Radio Data Information Systems) is a private network service provided by Motorola and IBM. It is based on MDC 4800 and RD-LAP protocols developed at Motorola.

9. RMD is a _______ and ________ data service.
a) Private, two way
b) Public, one way
c) Public, two way
d) Private, one way
Answer: c
Clarification: RAM Mobile Data (RMD) is a public, two way data service based upon the Mobitex protocol developed by Ericsson. RAM provides street level coverage for short and long messages for users moving in an urban environment.

10. The MSC provides subscriber access to the PSTN via the _______
a) Signalling transfer points
b) Service management system
c) Database service management system
d) Switching end points
Answer: d
Clarification: The MSC provides subscriber access to the PSTN via the switching end points (SEPs). The SEP implements a stored program control switching system known as the service control point (SCP).

11. ________ controls the switching of messages between nodes in the CCS network.
a) Signalling transfer points
b) Service management system
c) Database service management system
d) Switching end points
Answer: a
Clarification: The signalling transfer point (STP) controls the switching of messages between nodes in the CCS network. For higher reliability of transmission, SEPs are required to be connected to the SS7 network via at least two STPs.

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