Category: Wireless & Mobile Communications Objective Questions

Wireless & Mobile Communications Multiple Choice Questions on “Linear Predictive Coders”.

1. Linear predictive coders belong to _______ domain class of vocoders.
a) Time
b) Frequency
c) Direct
d) Indirect
Answer: a
Clarification: Linear predictive vocoders belong to the time domain class of vocoders. This class of vocoders attempts to extract the significant features of the speech from the time waveform.

2. Linear predictive coders are computationally simple.
a) True
b) False
Answer: b
Clarification: Linear predictive coders are computationally intensive. But, they are the most popular among the class of low bit vocoders. With LPC, it is possible to transmit good quality voice at 4.8 kbps and poorer quality voice at even lower rates.

3. Linear predictive coding system models the vocal tract as __________ linear filter.
a) Pole and zero
b) All zero
c) All pole
d) No pole
Answer: c
Clarification: The linear predictive coding system models the vocal tract as an all pole linear filter. The excitation to this filter is either a pulse at the pitch frequency or random white noise depending on whether the speech segment is voiced or unvoiced.

4. Linear predictive vocoders use __________ to estimate present sample.
a) Weighted sum of past samples
b) Multiplication of past samples
c) One past sample
d) Do not use past samples
Answer: a
Clarification: The linear predictive coder uses a weighted sum of p past samples. Using this technique, the current sample can be written as linear sum of the immediately precoding samples.

5. Which of the following LPC uses code book?
a) Multiple excited LPC
b) Residual excited LPC
c) LPC Vocoders
d) Code excited LPC
Answer: d
Clarification: Code excited LPC uses code book. In this method, the coder and decoder have a predetermined code book of stochastic (zero mean white Gaussian) excitation signals.

6. How many past samples are used by linear predictive coders to estimate present sample?
a) 100-150
b) 10-15
c) 1
d) 1000-1100
Answer: b
Clarification: LPCs uses weighted sum of past p samples to estimate the present samples. The number of past samples used by linear predictive coders ranges from 10 to 15.

7. Which of the non-linear transform is generally used to improve the coding of reflection coefficient?
a) Long area ratio transform
b) Mutual information
c) Least square
d) Interpolation
Answer: a
Clarification: Long area ratio (LAR) transform is generally used to improve the coding of reflection coefficient. This non linear transformation reduces the sensitivity of reflection coefficients to quantization errors. LAR performs an inverse hyperbolic tangent mapping of reflection coefficients.

8. Which of the following LPC uses two sources at the receiver?
a) Multiple excited LPC
b) Residual excited LPC
c) LPC Vocoders
d) Code excited LPC
Answer: c
Clarification: LPC vocoder uses two sources at the receiver, one of white noise and the other with a series of pulses at the current pitch rate. The selection of either of these excitation methods is based on voiced/unvoiced decision made at the transmitter.

9. Which of the following LPC produces a buzzy twang in the synthesized speech?
a) Multiple excited LPC
b) Residual excited LPC
c) LPC Vocoders
d) Code excited LPC
Answer: c
Clarification: LPC vocoder requires that the transmitter extract pitch frequency information which is often very difficult. Moreover, the phase coherence between the harmonic components of the excitation pulse tends to produce a buzzy twang in the synthesized speech.

10. The problem of buzzy twang in synthesized speech is mitigated by multipulse excited LPC or code excited LPC.
a) True
b) False
Answer: a
Clarification: LPC vocoder produces buzzy twang in the synthesized speech due to phase coherence between the harmonic components of the excitation pulses. This problem is mitigated by multipulse excited or code excited LPC.

11. Multipulse excited LPC requires pitch detection.
a) True
b) False
Answer: b
Clarification: Multipulse excited LPC does not require pitch detection and the prediction residual is better approximated by several pulses per pitch period. This is the reason for better speech quality.

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Wireless & Mobile Communications Multiple Choice Questions on “United States Digital Cellular (IS-54 and IS-136)”.

1. The dual mode USDC/AMPS system was standardized as ____________
a) IS-54
b) IS-136
c) PSTN
d) GSM
Answer: a
Clarification: The dual mode USDC/AMPS system was standardized as Interim Standard 54 (IS 54). It was standardized by Electron Industries Association and Telecommunication Industry Association (EIA/TIA) in 1990. It was later upgraded to IS-136.

2. USDC is also known as ___________
a) SADC
b) NADC
c) PADC
d) N-AMPS
Answer: b
Clarification: USDC is also known as North American Digital Cellular (NADC). It has been installed in North America in the countries like Canada and Mexico.

3. USDC was designed to share different frequencies as compared to AMPS.
a) True
b) False
Answer: b
Clarification: The USDC system was designed to share the same frequencies, frequency reuse plan, and base stations as AMPS, so that base stations and subscriber units could be equipped with both AMPS and USDC channels within the same piece of equipment.

4. Because of the compatibility with AMPS, USDC is also known as ___________
a) SADC
b) PADC
c) D-AMPS
d) K-AMPS
Answer: c
Clarification: USDC (United States Digital Cellular System) maintains compatibility with AMPS in a number of ways. Therefore, USDC is also known as D-AMPS (digital AMPS).

5. USDC forward and reverse control channels use exactly the same signalling techniques as AMPS.
a) True
b) False
Answer: a
Clarification: To maintain compatibility with AMPS phones, USDC forward and reverse control channels use exactly the same signalling techniques as AMPS. USDC voice channels use 4-ary π/4 DQPSK modulation with a channel rate of 48.6 kbps.

6. USDC has ___________ as many control channels as AMPS.
a) Same
b) Three times
c) Twice
d) Four times
Answer: c
Clarification: USDC has twice as many control channels as AMPS. In addition to the forty two primary AMPS control channels, USDC specifies forty two additional control channels called the secondary control channels.

7. Which of the following data channels of USDC carries the user information?
a) DTC
b) CVDCC
c) SACCH
d) FACCH
Answer: a
Clarification: DTC (data traffic channel) is the most important data channel as far as the end user is concerned. It carries user information (i.e. speech or user data).

8. Which of the following channel is similar in functionality to the SAT used in AMPS?
a) DTC
b) CDVCC
c) SACCH
d) FACCH
Answer: b
Clarification: CDVCC (Code Digital Verification Color Code) is a 12 bit message sent in every time slot and is similar in functionality to the SAT used in AMPS. The CDVCC is an 8 bit number ranging between 1 and 255, which is protected with four additional channel coding bits from a shortened Hamming code.

9. Which of the following channel in USDC provides a signalling channel?
a) DTC
b) CVDCC
c) SACCH
d) FACCH
Answer: c
Clarification: The SACCH (slow associated control channel) is sent in every time slot and provides a signalling channel in parallel with the digital speech. The SACCH carries various control and supervisory messages between the subscriber unit and the base station.

10. Which of the following channel in USDC is used to send important control or specialized traffic data between the base station and mobile units?
a) DTC
b) CVDCC
c) SACCH
d) FACCH
Answer: d
Clarification: FACCH (fast associated control channel) is used to send important control or specialized traffic data between the base station and mobile units. The FACCH data, when transmitted, takes the place of user information data within a frame.

11. Which of the following speech coder is used in USDC?
a) Vector Sum Excited Linear Predictive coder
b) Formant Vocoder
c) Multipulse Excited Linear Predictive coder
d) Residual Excited Linear Predictive coder
Answer: a
Clarification: The USDC speech coder is called the Vector Sum Excited Linear Predictive coder (VSELP). This belongs to the class of Code Excited Linear Predictive coders (CELP) or Stochastically Excited Linear Predictive coders.

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Wireless & Mobile Communications Multiple Choice Questions & Answers (MCQs) on “Multiple Input Multiple Output (MIMO)”.

1. MIMO stands for _______
a) Many input many output
b) Multiple input multiple output
c) Major input minor output
d) Minor input minor output
Answer: b
Clarification: MIMO stands for Multiple Input and Multiple Output. It refers to the technology where there are multiple antennas at the base station and multiple antennas at the mobile device.

2. In MIMO, which factor has the greatest influence on data rates?
a) The size of antenna
b) The height of the antenna
c) The number of transmit antennas
d) The area of receive antennas
Answer: c
Clarification: By increasing the number of receiving and transmitting antennas, it is possible to linearly increase the throughput of the channel with every pair of antennas added to the system.

3. MIMO was initially developed in the year __________
a) 1980
b) 1990
c) 1980
d) 1975
Answer: b
Clarification: Since the initial development in the year 1990, MIMO Wireless Communications have become integral part of the most forthcoming commercial and next generation wireless data communication systems.

4. MIMO is a smart antenna technology.
a) True
b) False
Answer: a
Clarification: MIMO is one of several forms of smart antenna technology, the others being MISO (multiple input, single output) and SIMO (single input, multiple output). It is an antenna technology for wireless communications in which multiple antennas are used at both the source and the destination.

5. MIMO technology makes advantage of a natural radio wave phenomenon called _________
a) Reflection
b) Multipath
c) Refraction
d) Diffraction
Answer: b
Clarification: MIMO technology makes use of multipath phenomenon to maximize transmission by receiving bounced signals from obstructions. Multipath is a phenomenon in wave propagation.

6. Which of the following technology does not use MIMO?
a) 4G
b) Wifi
c) WiMax
d) AMPS
Answer: d
Clarification: MIMO is used in mobile radio telephone standards such as recent 3GPP and 3GPP2. In 3GPP, High-Speed Packet Access plus (HSPA+) and Long Term Evolution (LTE) standards take MIMO into account. Moreover, MIMO is also used in Wifi and WiMax.

7. MIMO means both transmitter and receiver have multiple antennas.
a) True
b) False
Answer: a
Clarification: MIMO provides a way of utilising the multiple signal paths that exist between a transmitter and receiver to significantly improve the data throughput available on a given channel with its defined bandwidth. It uses multiple antennas at the transmitter and receiver along with some complex digital signal processing.

8. _______ is a technique of transmit diversity used in UMTSS third-generation cellular systems.
a) STTD
b) SM
c) Collaborative Uplink MIMO
d) MU-MIMO
Answer: a
Clarification: Space Time Transmit Diversity (STTD) is a technique of transmit diversity used in UMTSS third-generation cellular systems. Space Time Transmit Diversity is optional in the UTRANN air interface, but compulsory for user equipment.

9. _______ is a transmission method used in MIMO wireless communications to transmit encoded data signals independently.
a) STTD
b) SM
c) Collaborative Uplink MIMO
d) MU-MIMO
Answer: b
Clarification: Spatial multiplexing is a transmission method used in MIMO wireless communications to transmit encoded data signals independently and separately (so-called streams) from each of the multiple transmit antennas.

10. _______ is an additional open-loop MIMO technique considered by the WiMAX vendors.
a) STTD
b) SM
c) Collaborative Uplink MIMO
d) MU-MIMO
Answer: c
Clarification: Collaborative MIMO is an open-loop MIMO technique considered by the WiMAX vendors to surge the spectral efficiency and capacity of the uplink communications path. It is compared with the regular spatial multiplexing, wherein data streams are transmitted multiplying from multiple antennas on the same device.

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Wireless & Mobile Communications Multiple Choice Questions on “Third Generation (3G) Wireless Networks”.

1. Which of the following is not a characteristic of 3G network?
a) Communication over VoIP
b) Unparalleled network capacity
c) Multi-megabit Internet access
d) LTE based network
Answer: d
Clarification: Multi-megabit Internet access, communication using Voice over internet Protocol (VoIP), voice activated calls, unparalleled network capacity are some of the characteristics of 3G network. 3G systems promise unparalleled wireless access which is not possible in 2G systems. LTE (Long term Evolution) is a standard of 4G systems.

2. What is the term used by ITU for a set of global standards of 3G systems?
a) IMT 2000
b) GSM
c) CDMA
d) EDGE
Answer: a
Clarification: International Telecommunications Union (ITU) used the term IMT-2000 in 1998. It is used for a set of global standards for third generation (3G) mobile telecoms services and equipment.

3. Which of the following leads to evolution of 3G networks in CDMA systems?
a) IS-95
b) IS-95B
c) CdmaOne
d) Cdma2000
Answer: d
Clarification: 3G evolution of CDMA system leads to cdma2000. It is based on the fundamentals of IS-95 and IS-95B. IS-95 is a 2G standard for CDMA systems. IS-95B is a CDMA system for 2.5G networks.

4. Which of the following leads to the 3G evolution of GSM, IS-136 and PDC systems?
a) W-CDMA
b) GPRS
c) EDGE
d) HSCSD
Answer: a
Clarification: The 3G evolution for GSM, IS-136 and PDC systems leads to W-CDMA (Wideband CDMA). It is based on the network fundamentals of GSM, as well as merged versions of GSM and IS-136 through EDGE. GPRS, EDGE and HSCSD are 2.5G networks.

5. What is 3GPP?
a) Project based on W-CDMA
b) Project based on cdma2000
c) Project based on 2G standards
d) Project based on 2.5G standards
Answer: a
Clarification: 3GPP is a 3G Partnership Project for Wideband CDMA standards based on backward compatibility with GSM and IS-136. The project was established in December 1998. Its initial scope was to make a globally applicable third generation mobile phone system.

6. What is 3GPP2?
a) Project based on W-CDMA
b) Project based on cdma2000
c) Project based on 2G standards
d) Project based on 2.5G standards
Answer: b
Clarification: 3GPP2 is a 3G Partnership Project for Cdma2000 standards based on backward compatibility with earlier CdmaOne 2G CDMA technology. It was initiated by IMT-2000 to cover high speed, broadband and Internet Protocol (IP) based mobile systems. It mainly on North American and Asian regions.

7. Which of the following is not a standard of 3G?
a) UMTS
b) Cdma2000
c) TD-SCDMA
d) LTE
Answer: d
Clarification: UMTS (Universal Mobile Telecommunication System), TD-SCDMA (Time Division Synchronous Code Division Multiple Access), Cdma2000 are the standards defined for 3G networks. LTE (Long Term Evolution) is a 4G standard for high speed wireless communication.

8. Which of the following 3G standard is used in Japan?
a) Cdma2000
b) TD-SCDMA
c) UMTS
d) UTRA
Answer: c
Clarification: Japan uses UMTS (W-CDMA) standard for its 3G network. The standards used are UMTS 800, UMTS 900, UMTS 1500, UMTS 1700 and UMTS 2100. They are standardized by ARIB (Association of Radio industries and Business).

9. What does the number 2000 in IMT-2000 signifies?
a) Year
b) Number of subscribers per cell
c) Number of cells
d) Area (Km)
Answer: a
Clarification: The International Telecommunication Union (ITU) defined the third generation (3G) of mobile telephony standards, IMT-2000 to facilitate growth, increase bandwidth, and support more diverse applications. The number 2000 in IMT-2000 indicates the start of the system (year 2000) and the spectrum used (around 2000 MHz).

10. Which of the following is not an application of third generation network?
a) Global Positioning System (GPS)
b) Video conferencing
c) Mobile TV
d) Downloading rate upto 1 Gbps
Answer: d
Clarification: 3G applications include GPS (Global Positioning System), MMS (Multimedia Messaging System), video conferencing, location based services, video on demand, wireless voice telephony and high data rates with peak downloading rate of 100 Mbps. For 4G networks, the peak downloading rate is 1 Gbps.

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Wireless & Mobile Communications Multiple Choice Questions on “Outdoor Propagation Models”.

1. Which of the following is not an outdoor propagation model?
a) Longley-Rice model
b) Ericson Multiple Breakpoint Model
c) Hata model
d) Okumura model
Answer: b
Clarification: Ericson multiple breakpoint model is an indoor propagation model. Longley-Rice, Hata and Okumura model are outdoor propagation models. Most of these models are based on a systematic interpretation of measurement data obtained in the service area.

2. Longley –Rice model is applicable to _________
a) Point to point communication
b) All to all communication
c) Point to multipoint communication
d) Multipoint microwave distribution sstem
Answer: a
Clarification: The Longley-Rice model is applicable to point-to-point communication systems in the frequency range from 40 MHz to 100 GHz. They are applicable for different kinds of terrain. Terrain profile may vary from a simple curved Earth profile to a highly mountainous profile.

3. Longley-Rice prediction model is also referred as _________
a) Okumura model
b) Hata model
c) ITS irregular terrain model
d) Bertoni model
Answer: c
Clarification: The Longley Rice prediction model is also referred to as ITS irregular terrain model. The model is based on electromagnetic theory and on statistical analyses of both terrain features and radio measurements. It predicts the median attenuation of a radio signal as a function of distance and the variability of the signal in time and in space.

4. The extra term for additional attenuation due to urban clutter near the receiving antenna is called __________
a) Power factor
b) Urban gain
c) Clutter factor
d) Urban factor
Answer: d
Clarification: The urban factor (UF) is derived by comparing the predictions by the original Longley –Rice model with those obtained by Okumura. It deals with radio propagation in urban areas and is relevant to mobile radio.

5. Longley Rice model’s merit is to provide corrections due to environmental factors.
a) True
b) False
Answer: b
Clarification: One shortcoming of the Longley –Rice model is that it does not provide a way of determining corrections due to environmental factors. It does not consider correction factors to account for the effects of buildings and foliage. Multipath is also not considered.

6. Which method is used by Edwards and Durkin algorithm to calculate the loss associated with diffraction edges?
a) Epstein and Peterson method
b) Interpolation method
c) Knife edge diffraction method
d) Fresnel- Kirchoff method
Answer: a
Clarification: The Edwards and Durkin algorithm uses Epstein and Peterson method to calculate the loss associated with two diffraction edges. It is the sum of two attenuations. First is loss at second diffraction edge caused by first diffraction edge. And second is the loss at receiver caused by second diffraction edge.

7. Durkin’s model can read digital elevation map.
a) True
b) False
Answer: a
Clarification: Durkin’s model is very attractive because it can read in a digital elevation map and perform a site specific propagation computation on the elevation data. It can produce a signal strength contour that is reported to be good within a few dB.

8. Which of the most widely used model for signal prediction in urban areas?
a) Ericsson Multiple Breakpoint Model
b) Log distance path loss model
c) Okumura model
d) Attenuation factor model
Answer: c
Clarification: Okumura’s model is one of the most widely used models for signal prediction in urban areas. This model is applicable for frequencies in the range 150 MHz to 1920 MHz (Extrapolated upto 3000 MHz).

9. Okumura model is applicable for distances of _________
a) 1 m to 10 m
b) 1 km to 100 km
c) 100 km to 1000 km
d) 10 km to 10000 km
Answer: b
Clarification: Okumura’s model is applicable for distances of 1 km to 100 km. It can be used for base station antenna heights ranging from 30 m to 1000 m. Okumura developed a set of curves giving the median attenuation relative to free space in an urban area.

10. Okumura model is considered to be complex in predicting path loss.
a) True
b) False
Answer: b
Clarification: Okumura’s model is considered to be among the simplest and best in terms of accuracy in path loss prediction for mature cellular and land mobile radio system. It is very practical and has become a standard for system planning in modern land mobile system in Japan.

11. Which of the following is the major disadvantage of the Okumura model?
a) Complex
b) Inaccurate
c) Not practical
d) Slow response to rapid change in terrain
Answer: d
Clarification: The major disadvantage with the model is its slow response to rapid changes in terrain. Therefore the model is fairly good in urban and suburban areas, but not as good in rural areas. Common standard deviations between predicted and measured path loss values are 10 dB to 14 dB.

12. The Hata model is empirical formulation of which model?
a) Okumura model
b) Longley- Rice model
c) Durkin’s model
d) Walfisch and Bertoni model
Answer: a
Clarification: The Hata model is an empirical formulation of the graphical path loss data provided by Okumura. It is valid from 150 MHz to 1500 MHz. Hata presented the urban area propagation loss as a standard formulation. It supplied correct Equations for application to other situations.

13. Hata model is well suited for _________
a) Personal communication system
b) Large cell mobile radio system
c) Small cell mobile radio system
d) Every mobile radio system
Answer: b
Clarification: Hata model is well suited for large cell mobile radio systems. But it is not well suited for personal communication system (PCS) which have cells on the order of 1 km radius. Hata model does not have any path specific corrections which are available in Okumura model.

14. Which of the following considers the impact of rooftops and building?
a) Okumura model
b) Hata model
c) Walfisch and Bertoni model
d) Longley- Rice model
Answer: c
Clarification: The impact of rooftops and building height is considered by Walfisch and Bertoni model. It uses diffraction to predict average signal strength at street level. It considers path loss to be a product of three factors.

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Wireless & Mobile Communications Multiple Choice Questions on “Constant Envelope Modulation”.

1. In non-linear modulation, the amplitude of the carrier varies with the variation of modulating signal.
a) True
b) False
Answer: b
Clarification: In non-linear modulation, the amplitude of the carrier is constant regardless of the variation in the modulating signal. Many practical mobile radio communication systems use these types of nonlinear modulation methods.

2. In constant envelope family of modulation, class C amplifiers introduces degradation in spectrum occupancy.
a) True
b) False
Answer: b
Clarification: The constant envelope family of modulation has an advantage of satisfying various conditions. In this, power efficient Class C amplifiers can be used without introducing degradation in the spectrum occupancy of the transmitted signal.

3. Constant envelope modulation techniques occupy ______ bandwidth than linear modulation schemes.
a) Larger
b) Smaller
c) Same
d) Twice
Answer: a
Clarification: Constant envelope modulation technique occupies a larger bandwidth than linear modulation technique. It is one of the disadvantage of constant envelope modulation. It is not well suited where bandwidth efficiency is more important than power efficiency.

4. In BFSK __________ of constant amplitude carrier signal is switched between two values.
a) Phase
b) Angle
c) Frequency
d) Amplitude
Answer: c
Clarification: In BFSK, the frequency of a constant amplitude carrier signal is switched between two values according to the two possible message states. These states are called high and low tunes, which corresponds to binary 1 or 0.

5. MSK stands for ________
a) Maximum shift keying
b) Minimum shift keying
c) Minimum space keying
d) Maximum space keying
Answer: b
Clarification: MSK stands for minimum shift keying. It is a special type of continuous phase shift keying. It is form of digital modulation technique that was developed in 1950s.

6. What is the modulation index of MSK?
a) 0.1
b) 1
c) 0.5
d) 0
Answer: c
Clarification: Minimum shift keying is a special type of CPFSK. Its peak frequency deviation is equal to ¼ the bit rate. In other words, MSK is continuous phase FSK with a modulation index of 0.5.

7. The modulation index of an FSK signal is similar to modulation index of ________
a) Amplitude modulation
b) Phase modulation
c) QPSK
d) Frequency modulation
Answer: d
Clarification: The modulation index of an FSK signal is similar to FM modulation index. It is defined by (2∆F)/Rb. Here ∆F is the peak RF frequency and Rb is the bit rate.

8. The name minimum phase shift keying implies minimum _________
a) Frequency separation
b) Amplitude separation
c) Phase change
d) Amplitude deviation
Answer: a
Clarification: The name minimum phase shift keying implies minimum frequency separation, i.e. the bandwidth that allows orthogonal detection. A modulation index of 0.5 corresponds to the minimum frequency spacing that allows two FSK signals to be coherently orthogonal.

9. MSK is sometimes also referred as _________
a) Slow FSK
b) Fast FSK
c) Slow PSK
d) Fast PSK
Answer: b
Clarification: Minimum shift keying is sometimes also referred as fast FSK. It is so called because frequency spacing used is only half as much as that used in conventional noncoherent frequency shift keying.

10. Which of the following is not a property of MSK?
a) Variable envelope
b) Spectral efficiency
c) Good BER performance
d) Self synchronizing capability
Answer: a
Clarification: MSK has a constant envelope. It is a spectrally efficient scheme. It possesses properties such as constant envelope, spectral efficiency, good BER performance and self-synchronizing capability.

11. MSK is a special form of OQPSK.
a) True
b) False
Answer: a
Clarification: Yes, MSK can be thought of as a special form of offset quadrature phase shift keying. The condition is that baseband rectangular pulses are replaced with half sinusoidal pulses.

12. GMSK is a ________ of MSK.
a) Integral
b) Opposite
c) Derivative
d) Similar
Answer: c
Clarification: Gaussian minimum phase shift keying is a simple binary modulation scheme. It is viewed as a derivative of MSK. GMSK considerably reduces the sidelobe levels in the transmitted spectrum.

13. Which of the following holds true for GMSK?
a) Minimum ISI
b) Minimum error rate
c) Good spectral efficiency
d) Variable envelope property
Answer: c
Clarification: GMSK sacrifices the irreducible error rate caused by partial response signalling in exchange for extremely good spectral efficiency and constant envelope properties. And the premodulation Gaussian filtering introduces ISI in the transmitted signal.

14. MSK has complex demodulation and synchronization circuits.
a) True
b) False
Answer: b
Clarification: MSK has simple demodulation and synchronization circuits. It has various other advantages like continuous phase property makes it highly desirable for highly reactive loads. Due to these advantages, MSK is a popular modulation scheme for mobile radio communication.

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