Category: Wireless & Mobile Communications Objective Questions

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

1. _________ also known as impulse or zero-carrier radio technology.
a) Ultra wideband technology
b) Femtocell technology
c) Multicasting
d) Multiplexing
Answer: a
Clarification: Ultra-wideband (UWB) technology is also known as impulse or zero-carrier radio technology. It appears to be one of the most promising wireless radio communication technologies of recent time.

2. UWB operates across narrow bandwidth.
a) True
b) False
Answer: b
Clarification: Unlike conventional radio systems, which operate within a relatively narrow bandwidth, the UWB radio system operates across a wide range of the frequency spectrum by transmitting a series of extremely narrow (10–1000 per second) and low-power pulses.

3. The basic element in DSC–UWB technology is the monocycle wavelet.
a) True
b) False
Answer: b
Clarification: The basic element in TM–UWB technology is the monocycle wavelet. Typically, wavelet pulse widths are between 0.2 and 1.5 nanoseconds, corresponding to center frequencies between 600 MHz and 5 GHz.

4. In TM–UWB, the system uses a modulation technique called _______
a) Pulse width modulation
b) Pulse code modulation
c) Pulse position modulation
d) Pulse amplitude modulation
Answer: c
Clarification: In TM–UWB, the system uses a modulation technique called pulse position modulation. The TM–UWB transmitter emits ultra-short monocycle wavelets with tightly controlled pulse-to-pulse intervals, which are varied on a pulse-by-pulse basis in accordance with an information signal and a channel code.

5. DSC-UWB uses _________
a) Pulse width modulation
b) Pulse code modulation
c) Pulse position modulation
d) Direct sequence modulation
Answer: d
Clarification: In DSC-UWB, the signal is spread by direct sequence modulating a wavelet pulse trains at duty cycles approaching that of a sine wave carrier. The spectrum spreading, channelization, and modulation are provided by a PN (pseudo noise) sequence, and the chipping rate is maintained as some fraction of the carrier center frequency.

6. The coherent interaction of signals in UWB arriving by many paths causes ____________
a) Ricean fading
b) Nakagami fading
c) Rayleigh fading
d) Multicast fading
Answer: c
Clarification: The coherent interaction of signals arriving by many paths causes the Rayleigh or multipath fading in RF communications. Inside buildings, when continuous sine waves are transmitted wherein the channels exhibit multipath differential delays in the nanosecond range, the multipath fading occurs naturally.

7. UWB technology supports low bit rate and low speed.
a) True
b) False
Answer: b
Clarification: UWB technology is appropriate for the high-performance wireless home network, which mandates support for large bit rate (50 Mbps), high-speed, affordable connectivity between devices, and simultaneous data transmission from multiple devices, and full-motion video capability.

8. Which of the following is not true for UWB?
a) Large spectrum
b) Lower price
c) Pulse data
d) Large interference
Answer: d
Clarification: The combination of a larger spectrum, lower power, and pulsed data means that UWB causes less interference than narrowband radio designs while yielding low probability of detection and excellent multipath immunity.

9. UWB systems are very complex, since they use radio frequency/intermediate frequency conversion stages.
a) True
b) False
Answer: b
Clarification: UWB systems are much less complex, since they do not use any radio frequency/intermediate frequency (RF/IF) conversion stages, local oscillators, mixers, and other expensive surface acoustic wave (SAW) filters common to traditional radio technologies.

10. Which of the following is a drawback of UWB technology?
a) Not appropriate for WAN
b) Power limited
c) Small spectrum
d) Limited jitter requirements
Answer: d
Clarification: UWB devices are power limited because they must coexist on a noninterfering basis with other licensed and unlicensed users across several frequency bands. For UWB systems using PPM as their modulation technique, limited jitter requirements could be an issue.

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Wireless & Mobile Communications Multiple Choice Questions & Answers (MCQs) on “Paging System”.

1. Which of the following is not a standard used for paging system?
a) POCSAG
b) ERMES
c) IS-95
d) FLEX
Answer: c
Clarification: IS-95 is a standard used for cellular system which is based on code division multiple access (CDMA). POCSAG (Post Office Code Standard Advisory Group), ERMES (European Radio Messaging System) and FLEX are the protocols used in paging system.

2. Paging system uses which mode of transmission?
a) Full duplex
b) Simplex
c) Half Duplex
d) Duplex
Answer: b
Clarification: Simplex systems communicate in only one way. For the paging systems, messages received are not acknowledged and thus they use simplex mode of transmission.

3. The information sent by paging system is known as a ___________
a) Note
b) Line
c) Message
d) Page
Answer: d
Clarification: Page is concise information sent by a paging system to the subscribers of entire service area.

4. Which type of message cannot be sent with the help of paging system?
a) Alphanumeric message
b) Video message
c) Voice message
d) Numeric message
Answer: b
Clarification: The message sent by a paging system can be numeric, alphanumeric or voice depending upon the type of service.

5. What is a paging access number?
a) An e mail id
b) A username
c) A toll free telephone number
d) A registration number
Answer: c
Clarification: Paging access number is a telephone number which is used to send the information to the subscriber.

6. Which type of transmission technique is employed by paging system?
a) Simulcasting
b) Multicasting
c) Unicasting
d) Hybrid
Answer: a
Clarification: Simulcast is a reliable technique used by paging system by transmitting the same paging signal from multiple paging transmitters at approximately equal times.

7. Which of the following is not the property of paging system?
a) Asymmetric communication
b) Light weight
c) High cost
d) Wide area coverage
Answer: c
Clarification: One of the main reasons for the increased users of paging system was its less cost. But as the prices of cellular system declined, the users of paging system also decreased.

8. Which of the following properties describes the transmitters and receivers in paging system?
a) High complexity and high power transmitter, high complexity and high power receivers
b) Low complexity and low power transmitter, low complexity and low power receivers
c) Low complexity and low power transmitter, high complexity and high power receivers
d) High complexity and high power transmitter, low complexity and low power receivers
Answer: d
Clarification: High power of transmitters helps paging signal to easily penetrate the building and low power receivers allow long usage time and light weight batteries.

9. What is a pager in the paging system?
a) A transmitter
b) A receiver
c) A transceiver
d) An equalizer
Answer: b
Clarification: A pager is a wireless device which receives the page, i.e. numeric, alphanumeric or voice message sent by the transmitter.

10. Who introduced the paging system for the first time?
a) Al Gross
b) Teri Pall
c) Alexander Graham Bell
d) Martin Cooper
Answer: a
Clarification: AL Gross introduced the first paging system during world war in 1949.

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Wireless & Mobile Communications Multiple Choice Questions on “Free Space Propagation Model”.

1. The mechanism behind electromagnetic wave propagation cannot be attributed to ___________
a) Reflection
b) Diffraction
c) Scattering
d) Sectoring
Answer: d
Clarification: The mechanisms behind electromagnetic wave propagation are diverse. They can be greatly attributed to reflection, diffraction and scattering. Due to multiple reflections from various objects, the electromagnetic waves travel along different paths of varying lengths.

2. The propagation model that estimates radio coverage of a transmitter is called ___________
a) Large scale propagation model
b) Small scale propagation model
c) Fading model
d) Okumura model
Answer: a
Clarification: Large scale propagation model are useful in estimating the radio coverage area of a transmitter. They can predict the mean signal strength for an arbitrary transmitter-receiver (T-R) separation distance. They characterize signal strength over large T-R separation distances.

3. Propagation model that characterize rapid fluctuation is called _________
a) Hata model
b) Fading model
c) Large scale propagation model
d) Okumura model
Answer: b
Clarification: Fading models characterize the rapid fluctuations of the received signal strength over very short travel distance (a few wavelengths) or shot time durations (on the order of seconds).

4. Small scale propagation model is also known as _________
a) Fading model
b) Micro scale propagation model
c) Okumura model
d) Hata model
Answer: a
Clarification: Small scale propagation model is also called fading model. Fading model characterize the rapid fluctuations of the received signal strength over very short distance of a few wavelengths or short time duration. The propagation models are used to estimate the performance of wireless channels.

5. Free space propagation model is to predict ______
a) Received signal strength
b) Transmitted power
c) Gain of transmitter
d) Gain of receiver
Answer: a
Clarification: Free space propagation model predicts the received signal strength when there is an unobstructed line of sight path between transmitter and receiver. It assumes the ideal propagation condition that the environment is empty between the transmitter and receiver.

6. Which of the following do not undergo free space propagation?
a) Satellite communication system
b) Microwave line of sight radio links
c) Wireless line of sight radio links
d) Wired telephone systems
Answer: d
Clarification: EM signals when traveling through wireless channels experience fading effects due to various effects. But in some cases the transmission is with no obstruction and direct line of sight such as in satellite communication, microwave and wireless line of sight radio links.

7. The free space model predicts that received signal decays as a function of _________
a) Gain of transmitter antenna
b) T-R separation
c) Power of transmitter antenna
d) Effective aperture of the antenna
Answer: b
Clarification: As with most large scale radio wave propagation models, the free space model predicts that received signal decays as a function of the T-R separation distance raised to some power. Often it is given as a function of negative square root of the distance.

8. Relation between gain and effective aperture is given by ______
a) G=(4πA_e)/λ²
b) G=(4π λ²)/A_e
c) G=4πA_e
d) G=A_e/λ²
Answer: a
Clarification: The gain of the antenna is proportional to effective aperture area. Therefore, antennas with large effective apertures are high gain antennas and have small angular beam widths. Most of their power is radiated in a narrow beam in one direction, and little in other directions.

9. Relation between wavelength and carrier frequency is _________
a) λ=c/f
b) λ=c*f
c) λ=f/c
d) λ=1/f
Answer: a
Clarification: Wavelength is inversely proportional to carrier frequency. For electromagnetic radiation in free space, wavelength is a ratio of speed of light (c) and carrier frequency (f). Speed of light is 3*10⁸ m/s. The unit for wavelength is meters.

10. Which of the following antenna radiates power with unit gain uniformly in all directions?
a) Directional antenna
b) Dipole antenna
c) Isotropic antenna
d) Loop antenna
Answer: c
Clarification: Isotropic antenna radiates the power with unit gain uniformly in all directions. It is an ideal antenna. From practical point of view, there is no actual isotropic antenna. But, an isotropic antenna is often used as a reference antenna for the antenna gain.

11. EIRP is abbreviated as __________
a) Effective isotropic radiated power
b) Effective isotropic radio power
c) Effective and immediate radiated power
d) Effective and immediate ratio of power
Answer: a
Clarification: EIRP stands for Effective Isotropic Radiated Power. It is the amount of power that a theoretical isotropic antenna would emit to produce the peak power density observed in the direction of maximum antenna gain. EIRP also takes into account the losses in transmission line and connectors and includes the gain of the antenna.

12. Path loss in free space model is defined as difference of ________
a) Effective transmitted power and gain
b) Effective received power and distance between T-R
c) Gain and received power
d) Effective transmitter power and receiver power
Answer: d
Clarification: I Path loss is defined as difference of effective transmitter power and receiver power. Free-space path loss is the loss in signal strength of an electromagnetic wave that would result from a line-of-sight path through free space, with no obstacles nearby to cause reflection or diffraction.

13. Far field region is also known as _________
a) Near field region
b) Fraunhofer region
c) Erlang region
d) Fresnel region
Answer: b
Clarification: The far field is the region far from the antenna. In this region, the radiation pattern does not change shape with distance. Also, this region is dominated by radiated fields, with the E- and H-fields orthogonal to each other and the direction of propagation as with plane waves.

14. Fraunhofer distance is given by _____
a) 2D2/λ
b) 2D/λ
c) D/λ
d) 2D/λ2
Answer: a
Clarification: Fraunhofer distance, also known as far field distance is inversely proportional to wavelength. It depends on the largest physical dimension of the antennal (D). This distance basically denotes the boundary between far field and near field region.

15. Which of the following is called an ideal antenna?
a) Dipole antenna
b) Directional antenna
c) Isotropic antenna
d) Loop antenna
Answer: c
Clarification: Isotropic antenna is an ideal antenna that directs the power uniformly in all directions. It is a theoretical point source of electromagnetic. It is practically not possible. It is mainly used as a hypothetical antenna to measure the gain.

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

1. Carrier signal in modulation technique is _______ signal.
a) High frequency
b) Low frequency
c) High amplitude
d) Low amplitude
Answer: a
Clarification: Carrier signal in modulation technique is a high frequency signal. In amplitude modulation, the amplitude of a high frequency carrier signal is varied in accordance to the instantaneous amplitude of the modulating signal.

2. Modulation index of an AM signal is ratio of __________ to the _______
a) Peak carrier amplitude, Peak message signal amplitude
b) Peak message signal amplitude, Peak carrier amplitude
c) Carrier signal frequency, Message signal frequency
d) Message signal frequency, Carrier signal frequency
Answer: b
Clarification: The modulation index k of an AM signal is defined as the ratio of the peak message signal amplitude to the peak carrier amplitude. The modulation index is often expressed as a percentage. It is also called percentage modulation.

3. If the peak message signal amplitude is half the peak amplitude of the carrier signal, the signal is _____ modulated.
a) 100%
b) 2%
c) 50%
d) 70%
Answer: c
Clarification: The modulation is also expressed in percentage. It is also called percentage modulation. The signal is said to be 50% modulated if the peak message signal amplitude is half the peak amplitude of the carrier signal.

4. A percentage of modulation greater than ___________ will distort the message signal.
a) 10%
b) 25%
c) 50%
d) 100%
Answer: d
Clarification: A percentage of modulation greater than 100% will distort the message signal if detected by an envelope detector. In this case the lower excursion of the signal will drive the carrier amplitude below zero, making it negative (and hence changing its phase).

5. The RF bandwidth of AM is ____________ the maximum frequency contained in the modulating message signal.
a) Equal
b) Two times
c) Four times
d) Ten times
Answer: b
Clarification: The RF bandwidth of an AM signal is equal to B_AM=2f_m. It is double the maximum frequency contained in the modulating message signal. AM spectrum consists of an impulse at the carrier frequency and two sidebands which replicate the message spectrum.

6. Single sideband AM systems occupy same bandwidth as of conventional AM systems.
a) True
b) False
Answer: b
Clarification: Single sideband (SSB) AM systems transmit only one of the sidebands (either upper or lower) about the carrier. Hence, they occupy only half the bandwidth of conventional AM systems.

7. How is the performance of SSB AM systems in fading channels?
a) Poor
b) Best
c) Good
d) Average
Answer: a
Clarification: SSB systems have the advantage of being very bandwidth efficient. But their performance in fading channels is very poor. For proper detection, the frequency of the oscillator at the product detector mixer in the receiver must be same as that of the incoming carrier frequency.

8. Which of the following is a disadvantage of tone-in-band SSB system?
a) High bandwidth
b) Bad adjacent channel protection
c) Effects of multipath
d) Generation and reception of signal is complicated
Answer: d
Clarification: Tone-in-band SSB systems has the advantage of maintaining the low bandwidth property of the SSB signals, while at the same time providing good adjacent channel protection. The tone in band system employs feedforward automatic gain and frequency control to mitigate the effects of multipath induced fading.

9. FFSR in AM systems stands for ________
a) Feedforward signal regeneration
b) Feedbackward signal regeneration
c) Feedbackward system restoration
d) Feedforward system restoration
Answer: a
Clarification: FFSR stands for Feedforward signal regeneration. If the pilot tone and the information bearing signal undergo correlated fading, it is possible at the receiver to counteract the effects of fading through signal processing based on tracking of pilot tone. This process is called FFSR.

10. AM demodulation technique can be divided into _____ and _____ demodulation.
a) Direct, indirect
b) Slope detector, zero crossing
c) Coherent, noncoherent
d) Quadrature detection, coherent detection
Answer: c
Clarification: AM demodulation techniques may be broadly divide into two main categories. They are called coherent and noncoherent demodulation. They are differentiated by the knowledge of transmitted carrier frequency and phase at the receiver.

11. Non coherent detection requires the knowledge of transmitted carrier frequency and phase at the receiver.
a) True
b) False
Answer: b
Clarification: Non coherent detection does require the knowledge of phase information. However, coherent detection requires knowledge of the transmitted carrier frequency and phase at the receiver.

12. A product detector in AM systems is also called ___________
a) Envelope detector
b) Differentiator
c) Integrator
d) Phase detector
Answer: d
Clarification: A product detector is also called a phase detector. It forms a coherent demodulator for AM signals. It is a down converter circuit which converts the input bandpass signal to a baseband signal.

13. AM system use only product detector for demodulation. They never use envelope detectors.
a) True
b) False
Answer: b
Clarification: AM systems can use either product detector or envelope detector for demodulation. As a rule, envelope detectors are useful when input signal power is at least 10dB greater than noise power, whereas product detectors are able to process the AM signals with input signal to noise ratios well below 0 dB.

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Wireless & Mobile Communications Multiple Choice Questions on “Characteristics of Speech Signals”.

1. The higher the bit rate, the more speech channels can be compressed within a given bandwidth.
a) True
b) False
Answer: b
Clarification: The lower the bit rate at which the coder can deliver toll quality speech, the more speech channels can be compressed within a given bandwidth. Thus, manufacturers are continuously in search of speech coders that provide toll quality speech at lower bit rates.

2. Which of the following are two types of speech coders?
a) Waveform coders and source coders
b) Active coders and passive coders
c) Direst coders and indirect coders
d) Time and frequency coders
Answer: a
Clarification: Speech coders can be categorised into waveform coders and source coders. Waveform coders can further be categorised into time domain and frequency domain. Source coders can be classified into linear predictive coders and vocoders.

3. Waveform coders has _______ complexity and achieves _______ economy in transmission bit rate.
a) Maximum, moderate
b) Maximum, high
c) Minimal, moderate
d) Minimal, high
Answer: c
Clarification: Waveform coders have minimal complexity. This class of coders achieves only moderate economy in transmission bit rate. They are designed to be source independent and hence code equally well a variety of signals.

4. Vocoders has _______ complexity and achieves _______ economy in transmission bit rate.
a) Maximum, moderate
b) Maximum, high
c) Minimal, moderate
d) Minimal, high
Answer: b
Clarification: Vocoders achieve very high economy in transmission bit rate. They are in general more complex. They are based on using a priori knowledge about the signal to be coded, and for this reason, they are signal specific.

5. Which of the following is not a property that is utilized in coder design?
a) Non zero autocorrelation between successive speech signals
b) Non flat nature of speech signal
c) Quasiperiodicity of voiced speech signals
d) Uniform probability distribution of speech amplitude
Answer: d
Clarification: Speech waveforms have a number of useful properties that can be exploited when designing efficient coders. They are non uniform probability distribution of speech amplitude, non-zero autocorrelation between successive speech samples, the nonflat nature of the speech spectra and quasiperiodicity of voiced speech signals.

6. Speech waveforms are _______
a) Bandlimited
b) Bandpass
c) High pass
d) Infinite bandwidth
Answer: a
Clarification: The most basic property of speech waveforms that are exploited by all speech coders is that they are bandlimited. A finite bandwidth means that it can be time-discretized at a finite rate and reconstructed complexity from its samples.

7. Which of the following is not a property of pdf of speech signals?
a) Non uniformity
b) Very high probability of non-zero amplitudes
c) Significant probability of very high amplitudes
d) Increasing function of amplitudes between these extremes
Answer: d
Clarification: There is a non-uniform probability distribution of speech amplitude. The pdf of a speech signal is in general characterized by a very high probability of non-zero amplitudes, a significant probability of very high amplitudes, and a monotonically decreasing function of amplitudes between these extremes.

8. Auto correlation function measures______ between samples of a speech signal as a function of _______
a) Similarity, frequency
b) Dissimilarity, time
c) Similarity, time
d) Dissimilarity, frequency
Answer: c
Clarification: The autocorrelation function (ACF) gives a quantitative measure of the closeness or similarity between samples of a speech signal as a function of their time separation. In every sample of speech, there is a large component that is easily predicted from the values of the previous samples.

9. Power spectral density of speech is flat.
a) True
b) False
Answer: b
Clarification: There is a nonflat characteristic in power spectral density of speech. It makes it possible to obtain significant compression by coding speech in the frequency domain.

10. Spectral flatness measure is the ratio of ______ and _____
a) Variance, Geometric mean
b) Geometric Mean, Variance
c) Arithmetic mean, geometric mean
d) Geometric mean, arithmetic mean
Answer: c
Clarification: Spectral flatness measure is defined as ratio of arithmetic to geometric mean of the samples of the PSD taken at uniform intervals in frequency. Spectral flatness measure is a qualitative measure of the theoretical maximum coding gain that can be obtained by exploiting the nonflat characteristics of speech spectra.

11. Low frequency signals contribute very little to the total speech signals.
a) True
b) False
Answer: b
Clarification: Lon term averaged PSD’s of speech show that high frequency signals contribute very little to the total speech energy. However, high frequency components are insignificant in energy, they are very important carriers of speech information.

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Wireless & Mobile Communications Multiple Choice Questions on “Integrated Services Digital Network (ISDN)”.

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
Clarification: ISDN stands for integrated services digital network. It defines the 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 __________
a) SS7
b) CCS
c) ARDIS
d) CDPD
Answer: b
Clarification: 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
Clarification: 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.
a) True
b) False
Answer: b
Clarification: 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
Clarification: 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.
a) True
b) False
Answer: b
Clarification: 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.
a) True
b) False
Answer: b
Clarification: 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?
a) SS7
b) CCS
c) ARDIS
d) B-ISDN
Answer: d
Clarification: 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
Clarification: 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.
a) True
b) False
Answer: b
Clarification: 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 ___________
a) Cell
b) Atom
c) Molecule
d) Packet
Answer: a
Clarification: 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
Clarification: 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.

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