Communications MCQ Set 1
1. Small scale variations of a mobile radio signal are directly related to _______
a) Impulse response of mobile radio channel
b) Impulse response of base station
c) Frequency response of antenna
d) Frequency response of base station
Answer: a [Reason:] The small scale variations of a mobile radio signal can be directly related to the impulse response of mobile radio channel. he impulse response is a wideband channel characterization and contains all information necessary to simulate or analyze any type of radio transmission through the channel.
2. Impulse response is a narrowband characterization. State whether True or False.
Answer: b [Reason:] Impulse response is a wideband channel characterization. It contains all information necessary to simulate or analyse any type of radio transmission through the channel.
3. Mobile radio channel can be modelled as a ______ filter.
Answer: c [Reason:] Mobile radio channel may be modelled as a linear filter with a time varying impulse response. The time variation is due to receiver motion in space. The filtering nature is caused by summation of amplitudes and delays of multiple arriving waves at any instant of time.
4. Impulse response does not play any role in characterization of the channel. State whether True or False.
Answer: b [Reason:] Impulse response is a useful characterization of channel. It may be used to predict and compare the performance of different mobile communication systems and transmission bandwidth for a particular mobile channel condition.
5. Received signal can be expressed as ______ of transmitted signal with channel impulse response.
Answer: d [Reason:] The received signal y(t) can be expressed as a convolution of transmitted signal x(t) with impulse response of mobile radio channel. The variable t represents the time variations due to motion and the channel impulse multipath delay for fixed value of t.
6. Discretization of multipath delay axis of impulse response into equal time delay segments is called __________
a) Excess delay bins
b) Delay bins
c) Discrete bins
d) Digital bins
Answer: a [Reason:] It is useful to discretize the multipath delay axis of the impulse response into equal time delay segments called excess delay bins. The technique of quantizing the delay bins determines the time delay resolution of the channel model.
7. Small scale received power is ____ of average powers received in each multipath component.
Answer: d [Reason:] The average small received power is the sum of the average powers received in each multipath component. This is the case if transmitted signal is able to resolve the multipath.
8. The received power of a wideband signal fluctuates significantly when a receiver is moved about a local area. State whether True or False.
Answer: b [Reason:] Amplitude of individual multipath components does not fluctuate widely in local area. Therefore, the received power of a wideband signal does not fluctuate significantly when a receiver is moved about a local area.
9. Average power for a CW signal is _______ to average received power for a wideband signal in small scale region.
b) Two times
c) Four times
d) Ten times
Answer: a [Reason:] Average power for a CW signal is equivalent to average received power for a wideband signal in small scale region. This can occur when either the multipath phases are identically and independently distributed or when path amplitudes are uncorrelated.
10. The received local ensemble average power of wideband and narrowband signals are ________
c) Not dependent
Answer: b [Reason:] The received local ensemble average power of wideband and narrowband signals is equivalent. When the transmitted signal has bandwidth greater than bandwidth of channel, the received power varies very little. However, if transmitted signal has very narrow bandwidth, large fluctuation occurs at receiver.
Communications MCQ Set 2
1. Which of the following techniques do not help in expanding the capacity of cellular system?
d) Microcell zone concept
Answer: b [Reason:] 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.
b) Cell splitting
d) Micro cell zone concept
Answer: a [Reason:] 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.
c) Cell splitting
d) Micro cell zone technique
Answer: c [Reason:] 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
d) Micro cell zone concept
Answer: d [Reason:] 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
d) Micro cell zone concept
Answer: a [Reason:] 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
Answer: c [Reason:] 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
c) Micro cell technique
Answer: a [Reason:] 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.
d) Mobile stations
Answer: b [Reason:] 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. State whether True or False.
Answer: b [Reason:] 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?
c) Antenna downtilting
Answer: c [Reason:] Antenna downtilting deliberately focuses 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). State True or False.
Answer: a [Reason:] 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?
d) Micro cell zone concept
Answer: b [Reason:] 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 ____________
d) Repeater noise and interference
Answer: d [Reason:] 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 [Reason:] 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
Answer: c [Reason:] 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.
Communications MCQ Set 3
1. Frequency domain coders divides the speech signal into _____
a) A set of frequency components
b) A set of different amplitudes
c) A set of time delays
d) A set of phase components
Answer: a [Reason:] In the class of frequency domain coders, the speech signal is divided into a set of frequency components. Each frequency component is quantized and encoded separately.
2. In frequency domain coding of speech, the number of bits used to encode each frequency component is constant.
Answer: b [Reason:] Frequency domain coders have an advantage that number of bits used to encode each frequency component can be dynamically varied. They can also be shared among different bands.
3. Quantization is a ________ process.
Answer: c [Reason:] Quantization is a non-linear process. It produces distortion products that are typically broad in spectrum.
4. Sub band coding codes the short time transform of a windowed signal.
Answer: b [Reason:] It is function of block transform coding. However, a sub band coder divides the speech signal into many smaller sub bands and encodes each sub band separately according to some perceptual criterion.
5. Which of the following is one of the most frequently used transform in speech coding?
a) Fourier transform
b) Wavelet transform
c) Shearlet transform
d) Discrete cosine transform
Answer: d [Reason:] DCT (discrete cosine transform) is one of the most attractive and frequently used transforms for speech coding. Fast algorithms developed for computing the DCT in a computationally efficient manner are used.
6. What does ATC stands for in speech coders?
a) Automatic transform code
b) Air traffic controller
c) Active thermal convection
d) Adaptive transform coding
Answer: d [Reason:] In speech coding, ATC stands for adaptive transform coding. It is form of frequency domain coder that encodes the speech at bit rates in the range of 9.6 kbps and 20 kbps.
7. Waveform coders and Vocoders are the types of _______
a) Speech coders
b) Modulation technique
c) Frequency translation methods
d) Channel allocation for transmission
Answer: a [Reason:] Speech coders can be classified into waveform coders and Vocoders. Waveform coders convert the analog signal into digital signal. Vocoders exploit the special properties of speech signal to reduce the bit rate.
8. The type of frequency domain coding that divides the speech signal into sub bands is _____
a) Waveform coding
c) Block transform coding
d) Sub-band coding
Answer: d [Reason:] Sub band coding (SBC) is a method where the speech signal is subdivided into several frequency bands and each band is digitally encoded separately. The audible frequency spectrum 20Hz-20 KHz is divided into frequency sub-bands using a bank of finite impulse response (FIR) filter and output of each filter is sampled and encoded.
9. Speech coders are categorized on the basis of _______
a) Signal compression techniques
b) Frequency of signal
c) Bandwidth of the signal
d) Phase of the signal
Answer: a [Reason:] Speech coders are categorised on the basis of signal compression techniques. Speech coding is an art of compressing and then encoding speech signals.
10. The speech coding technique that is dependent on the prior knowledge of the signal is ______
a) Waveform coders
c) Sub band coding
d) Block transform
Answer: b [Reason:] Vocoders are dependent on the prior knowledge of the signals. They capture the characteristic elements of audio signal and then uses this characteristic signal to affect other audio signals.
Communications MCQ Set 4
1. What is the name of the web browsing format language supported by 2.5G technology?
a) Wireless Application Protocol
b) Hypertext Markup Language
c) Extensible Markup Language
d) Hypertext Transfer Protocol
Answer: a [Reason:] 2.5G technology supports a new web browsing format language, which is called Wireless Application Protocol (WAP). It allows standard web pages to be viewed in a compressed format specifically designed for small, portable hand held wireless devices.
2. What is the name of the internet microbrowser technology used by NTT DoCoMo in Japan?
a) Wireless Application Protocol
d) Hypertext Markup Language
Answer: b [Reason:] I-mode is a wireless data service and Internet microbrowser technology introduced by NTT DoCoMo on its PDC network in 1998. It is currently used by other wireless services throughout the world.
3. 2.5G upgrade path for a particular wireless carrier does not match the original 2G technology choice made earlier by the same carrier. (True or False).
Answer: b [Reason:] As 2.5G is the upgradation of 2G technology, 2.5G upgradation path must match the original 2G technology. For example, 2.5G upgrade solution designed for GSM must dovetail with original GSM interface so that change of hardware is not required.
4. Which of the following is not a TDMA standard of 2.5G network?
Answer: d [Reason:] GSM (Global System for Mobile) is a TDMA standard for 2G network. HSCSD (High Speed Circuit Switched Data), GPRS (General Packet Radio Service) and EDGE (Enhanced Data rates for GSM Evolution) are TDMA standards of 2.5G technology.
5. Which of the following is a 2.5G CDMA standard?
Answer: c [Reason:] IS-95B (Interim Standard 95B) is code division multiple access standard for 2.5G. It is an upgradation of IS- 95 which is a second generation standard of CDMA.
6. HSCSD supports which 2G standard?
c) GSM and IS-136
Answer: a [Reason:] High Speed Circuit Switched Data (HSCDC) supports the Global system for Mobile (GSM) standard. It only requires a software upgrade at the base station.
7. How does HSCSD differs from the GSM to obtain higher speed data rate?
a) By allowing single user to use one specific time slot
b) By allowing single user to use consecutive user time slots
c) By using 8-PSK modulation technique
d) By allowing multiple users to use individual time slot
Answer: b [Reason:] HSCSD allows individual data users to use consecutive time slots in order to obtain higher speed data access on the GSM network. In case of GSM, it limits each user to use only one specific time slot.
8. GPRS and EDGE supports which 2G standard?
a) GSM only
b) IS-136 only
c) GSM and IS-136 both
Answer: c [Reason:] GPRS (General Packet Radio Service) network provides a packet network on dedicated GSM or IS-136 radio channels. EDGE (Enhanced Data rates for GSM Evolution) is also developed keeping in desire both GSM and IS-136 operators.
9. How is HSCSD different from GPRS?
b) Multiple Access Scheme
c) Modulation technique
d) Switching Technique
Answer: d [Reason:] GPRS is a packet based network. HSCSD dedicates circuit switched channels to specific users whereas GPRS supports many more users, but in a bursty manner.
10. What changes GPRS need to acquire while upgrading itself from GSM?
a) A whole new base station
b) New transceiver at base station
c) New channel cards
d) New packet overlay including routers and gateways
Answer: d [Reason:] GPRS requires a GSM operator to install new routers and Internet gateways at the base station along with new software upgrade. New base station RF hardware is not required.
11. Which new modulation technique is used by EDGE?
b) 8- PSK
Answer: b [Reason:] EDGE uses a new digital modulation format, 8- PSK (Octal Phase Shift Keying). It is used in addition to GSM’s standard GMSK (Gaussian Minimum Shift Keying) modulation.
12. Various air interface formats used by EDGE are also known as ______
a) Modulation and coding schemes
b) Coding schemes
c) Modulating air interface
d) Air interface coding schemes
Answer: a [Reason:] EDGE allows nine different air interface formats known as multiple modulation and coding schemes (MCS). Each MCS state may use either GMSK or 8- PSK modulation for network access, depending upon the instantaneous demands of the network and the operating conditions.
13. EDGE is sometimes also referred as _______
Answer: c [Reason:] EDGE is sometimes also referred as Enhanced GPRS (EGPRS). It is an enhancement of a GSM network in which EDGE is introduced on top of the General Packet Radio Service (GPRS). It is used to transfer data in a packet switched mode on various time slots.
14. What is one disadvantage of EDGE in comparison to HSCSD and GPRS?
a) Low data rates
b) Small coverage range
c) Low speed
d) No advancement
Answer: b [Reason:] Because of the higher data rates and relaxed error control covering in many of the selectable air interface formats, the coverage range is smaller in EDGE than in HSCSD or GPRS.
Communications MCQ Set 5
1. Which of the following has no backward compatibility with 3G Cdma2000?
Answer: b [Reason:] 3G Cdma2000 is based on the original IS-95 and IS-95A CDMA standards, as well as the 2.5G IS-95B air interface. While upgrading, Cdma2000 maintains backward compatibility with existing IS-95, IS-95A and IS-95B equipments. Thus, Cdma2000 allow wireless carriers to introduce a family of new high data rate Internet access capabilities within existing systems.
2.2G and 2.5G CDMA operators may selectively introduce 3G capabilities at each cell without changing entire base stations and reallocate spectrums. (True or False)
Answer: a [Reason:] Cdma2000 does not require change in entire base station or additional RF equipment. All the changes are made in software or in baseband hardware.
3. Which of the following the first 3G CDMA air interface?
c) Cdma2000 1xRTT
Answer: c [Reason:] Cdma2000 1xRTT is the first 3G air interface. Here, RTT stands for Radio Transmission Technology and 1x indicates that the bandwidth is one times that of the original CdmaOne channel. It is modulated on a single carrier.
4. Within ITU IMT-2000 body, Cdma2000 1xRTT is also known as ____
a) Cdma2000 1xEV-DO
b) Cdma2000 1xEV-DV
Answer: d [Reason:] Cdma2000 1xRTT is also known as G3G-MC-CDMA-1X. The initials MC stand for multicarrier. RTT stand for Radio Transmission Technology, a language suggested by IMT-2000 body. Usually, MC and RTT are omitted for convenience.
5. How many users are supported by Cdma2000 1X in comparison to 2G CDMA standard?
c) Six times
d) Ten times
Answer: b [Reason:] Cdma2000 support up to twice as many users as the 2G CDMA standard. It also provides the two times the standby time for longer lasting battery life.
6. Cdma2000 works in TDD mode only. State whether True or False.
Answer: b [Reason:] Cdma2000 works in both FDD and TDD mode. Cdma2000 developed for wide area cellular coverage uses FDD. And TDD is used by Cdma2000 for indoor cordless type applications.
7. Which of the following is not a characteristic of Cdma2000?
a) Adaptable baseband signalling rates
b) Adaptable baseband chipping rates
c) Multicarrier technologies
Answer: d [Reason:] Cdma2000 does not use OFDMA technique. OFDMA is used by 4G networks. Cdma2000 uses rapidly adaptable baseband signalling rates and chipping rates for each user. It also provides multi-level keying within same framework.
8. Cdma2000 1xEV was developed by ____
b) AT&T Laboratories
Answer: c [Reason:] Cdma2000 is an evolutionary advancement for CDMA. It was developed by Qualcomm Inc. It is a proprietary high data rate (HDR) packet standard that can be overlaid upon existing IS-95, IS-95B and Cdma2000 networks.
9. How is bandwidth increased in Cdma2000?
a) Clubbing adjacent radio channels
b) Changing the hardware of base stations
c) Change of spectrum
d) Change of RF equipment
Answer: a [Reason:] The increase in the bandwidth is achieved through clubbing the adjacent radio channels of CdmaOne and using multicarrier technologies. For example, Cdma2000 3xRTT uses these technologies by combining three adjacent 1.25 MHz bandwidth of CdmaOne channels.
10. What are the two options provided by Cdma2000 1xEV?
a) Cdma2000 1xRTT. Cdma2000 3xRTT
b) Cdma2000 1xEV-DO, Cdma2000 1xEV-DV
c) Cdma2000 1xEV-DT, Cdma2000 1xEV-DO
d) Cdma2000 1xRTT, Cdma2000 1xEV-DV
Answer: b [Reason:] Cdma2000 1xEV is an evolutionary upgrade for Cdma2000. It provides two options, for accessing only data (Cdma2000 1xEV-DO) and for both data & voice (Cdma2000 1xEV-DV).
11. Which of the following is not backward compatible with Cdma2000?
a) Cdma2000 1xRTT
b) Cdma2000 3xRTT
c) Cdma2000 1xEV-DO
d) Cdma2000 1xEV-DT
Answer: c [Reason:] Cdma2000 1xEV-DO option provides data rates of about 2.4 Mbps and supports data traffic only. No voice communication is supported. It relaxes the minimum latency requirement. But this mode is not backward compatible with Cdma2000.