Communications MCQ Set 1
1. ____ carries digitally encoded user data.
a) Traffic channels
b) Control channels
c) Signalling channels
d) Forward channels
Answer: a [Reason:] Traffic channels carry digitally encoded user speech or user data. It has identical functions and formats on both the forward and reverse links.
2. ______ carries signalling and synchronizing commands.
a) Traffic channels
b) Control channels
c) Signalling channels
d) Forward channels
Answer: b [Reason:] Control channels carry signalling and synchronizing commands between the base station and mobile station. Certain types of control channels are defined for just the forward or reverse link.
3. Which of the following is not a control channel of GSM?
Answer: d [Reason:] There are three main control channels in the GSM system. These are the broadcast channel (BCH), the common control channel (CCCH) and the dedicated control channel (DCCH). Each control channel consists of several logical channels.
4. Which of the following is the forward control channel that is used to broadcast information?
Answer: a [Reason:] The broadcast control channel (BCCH) is a forward channel that is used to broadcast information such as cell and network identity, and operating characteristics of the cell.
5. Which of the following channel does not come under CCCH?
Answer: c [Reason:] CCCH consists of three different channels. They are paging channel (PCH), which is a forward link channel, the random access channel (RACH) which is a reverse link channel, and the access grant channel (AGCH) which is a forward link channel.
6. Which of the following channel provides paging signals from base station to all mobiles in the cell?
Answer: d [Reason:] The PCH provides paging signals from the base station to all mobiles in the cell. It notifies a specific mobile of an incoming call which originates from the PSTN.
7. _____ is a reverse link channel used by a subscriber unit to acknowledge.
Answer: a [Reason:] The RACH (Random Access Channel) is a reverse link channel used by a subscriber unit to acknowledge a page from the PCH. It is also used by mobiles to originate a call.
8. Which of the following channel is used by base station to provide forward link communication to mobile?
Answer: b [Reason:] The AGCH (Access Grant Channel) is used by the base station to provide forward link communication to the mobile. It carries data which instructs the mobile to operate in a particular physical channel with particular dedicated control channel.
9. Which of the following burst is used to broadcast the frequency and time synchronization control messages?
a) FCCH and SCH
b) TCH and DCCH
c) RACH and TCH
d) FCCH and DCCH
Answer: a [Reason:] FCCH and SCH burst are used to broadcast the frequency and time synchronization control messages. They are used in TS0 of specific frames.
10. Which of the following burst is used to access service from any base station?
Answer: b [Reason:] Each user transmits a burst of data during the time slot assigned to it. The RACH burst is used by all mobiles to access service from any base station, and dummy burst is used as filter information for unused timeslots on forward link.
11. Group of superframes in GSM is called multiframe.
Answer: b [Reason:] Each of the normal speech frames are grouped into larger structures called multiframes. These multiframes are grouped into superframes and hyperframes.
Communications MCQ Set 2
1. What is the condition for handoff?
a) A mobile moves into a different cell while in conversation
b) A mobile remains in the same cell while in conversation
c) A mobile moves to different cell when idle
d) A mobile remains in the same cell and is idle
Answer: a [Reason:] Handoff occurs when a mobile moves into a different cell while a conversation is in progress. The MSC automatically transfers the call to a new channel belonging to the new base station.
2. Handoff does not require voice and control channel to be allocated to channels associated with the new base station. State whether True or False.
Answer: b [Reason:] Handoff operation involves identifying a new base station. It also requires that the voice and control signal be allocated to channels associated with the new base station.
3. The time over which a call can be maintained within a cell without handoff is called ______
a) Run time
b) Peak time
c) Dwell time
d) Cell time
Answer: c [Reason:] The time over which a call is maintained within a cell without handoff is called as dwell time. Dwell time vary depending on speed of user and type of radio coverage.
4. Dwell time does not depend on which of the following factor?
c) Distance between subscriber and base station
d) Mobile station
Answer: d [Reason:] Dwell time of a particular user is governed by a number of factors. They include propagation, interference, distance between the subscriber and the base station, and other time varying effects.
5. Which of the following is associated with the handoff in first generation analog cellular systems?
a) Locator receiver
c) Cell dragging
d) Breathing cell
Answer: a [Reason:] Locator receiver is a spare receiver in each base station. It is used to scan and determine signal strengths of mobile users which are in neighbouring cells.
6. MAHO stands for ______
a) MSC assisted handoff
b) Mobile assisted handoff
c) Machine assisted handoff
d) Man assisted handoff
Answer: b [Reason:] MAHO stands for mobile assisted handoff. In 2G systems, handoff decisions are mobile assisted. In MAHO, every mobile station measure the received power from surrounding base station and continuously reports the results to serving base station.
7. A handoff is initiated when the power received from the base station of a neighbouring cell falls behind the power received from the current base station by certain level. State whether True or False.
Answer: b [Reason:] MAHO measures the power received from the surrounding base station. And a handoff is initiated when the power received from the base station of a neighbouring cell begins to exceed the power received from current base station.
8. What is the condition for intersystem interference?
a) Mobile moves from one cell to another cell
b) Mobile remains in the same cell
c) Mobile moves from one cellular system to another cellular system
d) Mobile remains in the same cluster
Answer: c [Reason:] An intersystem handoff is initiated when a mobile moves from one cellular system to another during a course of a call. An MSC engages in an intersystem interference when a mobile becomes weak in a given cell and MSC cannot find another cell to which call can be transferred.
9. What is the disadvantage of guard channel?
a) Efficient utilization of spectrum
b) Cross talk
c) Near far effect
d) Reduce total carried traffic
Answer: d [Reason:] Guard channel is a concept for handling priority in handoff. Here, a fraction of the total available channels in a cell is reserved exclusively for handoff requests from ongoing calls. This method has the disadvantage of reducing the total carried traffic, as fewer channels are allocated to originating calls.
10. Which of the following priority handoff method decrease the probability of forced termination of a call due to lack of available channels?
b) Guard channel
c) Cell dragging
d) Near far effect
Answer: a [Reason:] Queuing of handoff requests is a method to decrease the probability of forced termination of a call due to lack of available channels. Queuing of handoff is possible due to the fact that there is a finite time interval between the time the received signal level drops below the handoff threshold and the time the call is terminated.
11. Umbrella cell approach is possible by using ______
a) Antenna of same heights
b) Antenna of different heights
c) Different voice channels
d) Different control channels
Answer: b [Reason:] Umbrella cell approach is possible by using different antenna heights and different power levels. By using this approach, it is possible to provide large and small cells which are co-located at a single location.
12. Cell dragging is a problem occur due to ______
a) Pedestrian users
b) Stationary users
c) High speed mobile systems
d) Base stations having same frequency
Answer: a [Reason:] Cell dragging is a practical handoff problem in microcell system. It results from pedestrian users that provide a very strong signal to the base station.
13. What was the typical handoff time in first generation analog cellular systems?
a) 1 second
b) 10 seconds
c) 1 minute
d) 10 milliseconds
Answer: b [Reason:] In first generation analog cellular system, the typical time to make a handoff once the signal level is below the threshold, is about 10 seconds. This requires the value for threshold to be 6 dB to 12 dB.
14. How much time it takes for handoff in digital cellular systems like GSM?
a) 1 second
b) 10 seconds
c) 1 minute
d) 10 milliseconds
Answer: a [Reason:] In digital cellular systems, the mobile assista with the handoff procedure by determining the best candidate. Once the decision is made, it typically requires 1 to 2 seconds for handoff.
15. Soft handoff is also known as _________
b) Hand over
c) Break before make
d) Make before break
Answer: d [Reason:] Soft handoff is one in which the channel in the source cell is retained and used for a while in parallel with the channel in the target cell. In this case, the connection with the receiver target is established before the connection to the source is broken, hence this handover is called make-before-break.
Communications MCQ Set 3
1. The variability of the environment is slower for a smaller range of T-R separation distances in indoor models. State whether True or False.
Answer: b [Reason:] The indoor radio channel differs from the traditional mobile radio channel. The distances covered are much smaller and variability of the environment is much greater for a much smaller range of T-R separation distances.
2. Propagation within building is not influenced by ______
a) Layout of the building
b) Construction materials
c) Building type
d) Trees outside the building
Answer: d [Reason:] It has been observed that propagation within buildings is strongly influenced by specific features. These features are layout of the building, the construction materials, and the building type.
3. Smaller propagation distances make it more difficult to insure far-field radiation for all receiver location and types of antenna. State whether True or False.
Answer: a [Reason:] Smaller propagation distances make it more difficult to insure far field radiation for all receiver location and types of antenna. The condition is very variable for smaller propagation distances.
4. What is hard partition?
a) Partition as part of the building
b) Partition that can be moved
c) Partition not touching ceiling
d) Partition between different floors
Answer: a [Reason:] Partitions that are formed as part of the building structure are called hard partitions. Partitions vary widely in their electrical and physical characteristics. Thus, it makes difficult in applying general models to specific indoor installation.
5. Partitions that can be moved are called _______
a) Soft partitions
b) Hard partitions
c) Disk partition
d) Dynamic partition
Answer: a [Reason:] Partitions that may be moved are called soft partitions. They do not span to the ceiling. Office buildings often have large open areas which are constructed by using moveable office partitions. Thus, space can be reconfigured easily.
6. Losses between the floors of the building can be determined using ________
a) Internal dimensions
b) Material used to create antenna
c) External dimension
d) Line of sight path
Answer: c [Reason:] The losses between floors of a building are determined by external dimensions as well as materials of the building. It is also determined using type of construction used to create the floors and external surroundings.
7. Technique of drawing a single ray between the transmitter and receiver is called ______
a) Secondary ray tracing
b) Primary ray tracing
c) Line of sight
d) Straight line tracing
Answer: [Reason:] PAF (path attenuation factor) represents a specific obstruction encountered by a ray drawn between the transmitter and receiver in 3-D. This technique of drawing a single ray between transmitter and receiver is called primary ray tracing.
8. ________ is a process of converting plain text into cipher text.
Answer: c [Reason:] Encryption is the most effective way to achieve data security. It is the process of encoding a message in such a way that only authorized parties can access it. Encryption does not itself prevent interference, but denies the intelligible content to a would-be interceptor.
9. _______reduces the cell size to increase capacity.
a) Intelligent cell approach
b) Microcell approach
c) Top down approach
d) Bottom up approach
Answer: b [Reason:] The microcell zone concept is used in cellular systems to specifically increase the capacity and coverage in cellular systems. A handoff is not required at MSC when the mobile travels between zones within a cell or when a mobile travels from one zone to another within the cell.
10. _________ configuration describes a desktop in an office.
a) Mobile and wired
b) Fixed and wired
c) Fixed and wireless
d) Mobile and wireless
Answer: b [Reason:] Fixed and wired configuration describes a desktop in an office. The device use fixed networks for performance reasons. Neither weight nor power consumption of the devices allow for mobile usage.
Communications MCQ Set 4
1. ISDN stands for ________
a) Integrated Services Digital Network
b) Integrated Services Discrete Network
c) Integrated Services Digital Node
d) Integrated Services Discrete Node
Answer: a [Reason:] ISDN stands for integrated services digital network. It defines he dedicated signalling network that has been created to complement the PSTN for more flexible and efficient network access and signalling.
2. ISDN is based on the concept of _______
Answer: b [Reason:] ISDN is a complete network framework designed around the concept of common channel signalling. While telephone users throughout the world rely on the PSTN to carry conventional voice traffic, new end-user data and signalling services can be provided with a parallel, dedicated signalling network.
3. Signalling component that supports traffic between the end-user and network is called ________
a) Network signalling
b) Digital subscriber signalling
c) Access signalling
d) Subscriber system signalling
Answer: c [Reason:] Access signalling supports traffic between the end user and the network. It defines how end users obtain access to the PSTN and the ISDN for communication or services.
4. Access signalling is governed by the SS7 suite of protocols.
Answer: b [Reason:] The second signalling component of ISDN, network signalling is governed by the SS7 suite of protocols. For wireless communication systems, the SS7 protocols within ISDN are critical to providing backbone network connectivity between MSCs throughout the world.
5. Information bearing channels in ISDN are called ______
a) D channels
b) Data channels
c) B channels
d) Voice channels
Answer: c [Reason:] The ISDN interface is divided into three different types of channels. Information bearing channels called bearer channels (B channels) are used exclusively for end user traffic (voice, data and video).
6. ISDN provides integrated end user access to only packet switched networks.
Answer: b [Reason:] ISDN provides integrated end-user access to both circuit switched and packet switched networks with digital end-to-end connectivity.
7. PRI interface in ISDN serves small capacity terminals.
Answer: b [Reason:] ISDN end users may select between two different interfaces. The BRI (basic rate interface) is intended to serve small capacity terminals while the PRI (primary rate interface) is intended for large capacity terminals.
8. Which of the following is based on ATM technology?
Answer: d [Reason:] Emerging networking technique, broadband ISDN (B-ISDN) is based on asynchronous transfer mode (ATM) technology. It allows packet switching rates up to 2.4 Gbps and total switching capacities as high as 100 Gbps.
9. Which of the following is true for ATM?
a) Circuit switched
b) Multiple access technique
c) Multiplexing technique
d) Handle only voice users
Answer: c [Reason:] ATM is a packet switching and multiplexing technique which has been specifically designed to handle both voice users and packet data users in a single physical channel.
10. ATM supports unidirectional transfer of data.
Answer: b [Reason:] ATM supports bidirectional transfer of data packets of fixed length between two end points. It preserves the order of transmission.
11. The data unit of ATM is _____
Answer: a [Reason:] The data unit of ATM is cell. They are routed based on header information in each unit (called a label) that identifies the cell as belonging to a specific ATM virtual connection.
12. ATM cells have fixed length of _______
a) 48 bytes
b) 47 bytes
c) 5 bytes
d) 53 bytes
Answer: d [Reason:] ATM cells have a fixed length of 53 bytes. It consists of 48 bytes of data and 5 bytes of header information. Fixed length packets result in simple implementation of fast packet switches.
Communications MCQ Set 5
1. Which of the following is not a source of interference?
a) Base station in different cluster
b) Another mobile in same cell
c) A call in progress in neighbouring cell
d) Any BS operating on same frequency
Answer: a [Reason:] Interference is a major limiting factor in the performance of cellular radio systems. Sources of interference includes another mobile in the same cell, a call in progress in neighbouring cell, other base stations operating in the same frequency band, or any non-cellular system which inadvertently leaks energy into the cellular frequency band.
2. Interference on voice channels causes _______
a) Blocked calls
b) Cross talk
d) Missed calls
Answer: b [Reason:] Interference on voice channels causes crass talk. Here, the subscriber hears interference in the background due to an undesired transmission.
3. Interference in control channel leads to ________
a) Cross talk
c) Blocked calls
d) Voice traffic
Answer: c [Reason:] On control channels, interference leads to missed and blocked calls. This happens due to errors in the digital signalling.
4. Interference is more severe in rural areas. State whether True or False.
Answer: b [Reason:] Interference is more severe in rural areas. It happens due to the greater RF noise floor and the large number of base stations and mobiles.
5. What are co-channel cells?
a) Cells having different base stations
b) Cells using different frequency
c) Cells using adjacent frequency
d) Cells using same frequency
Answer: d [Reason:] Due to frequency reuse concept, there are several cells that use the same set of frequencies. These cells are called co-channel cells. And the interference between these cells is called co-channel interference.
6. Co-channel interference is a function of ______
a) Radius of cell
b) Transmitted power
c) Received power
d) Frequency of mobile user
Answer: a [Reason:] This is the case when the size of each cell is approximately the same and the base stations transmit the same power. Co-channel interference ratio is independent of the transmitted power and becomes a function of the radius of the cell ® and the distance between centers of the nearest co channel cell (D).
7. Co-channel reuse ratio is define by ______
Answer: b [Reason:] Co-channel reuse ratio is defined by Q=D/R. By increasing the ratio of D/R, the spatial separation between co-channel cells relative to the coverage distance of a cell is increased. Thus, interference I reduced from improved isolation of RF energy from the co-channel cells.
8. Co-channel ratio in terms of cluster size is defined as ______
Answer: a [Reason:] Co-channel reuse is defined using Q=√(3N). A small value of Q provides larger capacity since the cluster size N is small. However, a large value of Q improves the transmission quality, due to smaller level of co-channel interference.
9. What is the cluster size for CDMA?
Answer: c [Reason:] CDMA systems have a cluster size of N=1.Therefore, frequency reuse is not as difficult as for TDMA or first generation cellular systems.
10. What is breathing cell effect?
a) Fixed coverage region
b) Dynamic and time varying coverage region
c) Large coverage region
d) Very small coverage region
Answer: b [Reason:] Breathing cell is a concept used by CDMA systems. They had a dynamic, time varying coverage region which varies depending on the instantaneous number of users on the CDMA radio channel.
11. Adjacent channel interference occurs due to _______
a) Power transmitted by Base station
c) Same frequency of mobile users
d) Imperfect receiver filters
Answer: d [Reason:] Interference resulting from signals which are adjacent in frequency to the desired signal is called adjacent channel interference. It results from imperfect receiver filters which allow nearby frequencies to leak into the passband.
12. Which of the following problem occur due to adjacent channel interference?
a) Blocked calls
b) Cross talk
c) Near-far effect
d) Missed calls
Answer: c [Reason:] 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.
13 In near-far effect, a nearby transmitter captures the __________
a) Receiver of the subscriber
b) Transmitter of the subscriber
c) Nearby MSC
d) Neighbouring base station
Answer: a [Reason:] Near-far effect occurs if an adjacent channel user is transmitting in very close range to a subscriber’s receiver while the receiver attempts to receive a base station on the desired channel. In this effect, a nearby transmitter captures the receiver of the subscriber.
14. Adjacent channel interference can be minimized through _______
a) Changing frequency of base stations
b) Careful filtering and channel assignments
c) Increasing number of base stations
d) Increasing number of control channels
Answer: b [Reason:] Adjacent channel assignment can be minimized through careful filtering and channel assignments. Each cell is given only a fraction of the available channels, a cell need not be assigned channels which are all adjacent in frequency.
15. In dynamic channel assignment, any channel which is being used in one cell can be reassigned simultaneously to another cell in the system at a reasonable distance. State whether True or False.
Answer: a [Reason:] Dynamic channel assignment (DCA) is one well known solution to the micro cellular channel assignment problem. The dynamic nature of the strategy permits adaptation to spatial and traffic variations while the distribution of control reduces the required computational load.