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48 Cards in this Set
- Front
- Back
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________ is the process of converting digital data to a digital signal.
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Line coding
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PCM is an example of _______ conversion.
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analog-to-digital
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The Nyquist theorem specifies the minimum sampling rate to be_______.
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twice the highest frequency of a signal
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The first step in PCM is ________.
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sampling
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Which of the following quantization level results in a more faithful reproduction of the signal?
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32
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If the frequency spectrum of a signal has a bandwidth of 300 Hz with the highest frequency at 600 Hz, what should be the sampling rate, according to the Nyquist theorem?
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1200 samples/s
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In _________ transmission, we send bits one after another without start or stop bits or gaps. It is the responsibility of the receiver to group the bits.
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synchronous
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The ________ rate defines the number of data elements sent in 1s; the ______ rate is the number of signal elements sent in 1s.
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data; signal
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The minimum bandwidth of Manchester and differential Manchester is ____ that of NRZ.
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twice
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In Manchester and differential Manchester encoding, the transition at the middle of the bit is used for __________.
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synchronization
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In _______encoding, we use three levels: positive, zero, and negative.
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bipolar
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________ is normally referred to as mB/nB coding; it replaces each m-bit group with an n-bit group.
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Block coding
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________ provides synchronization without increasing the number of bits.
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Scrambling
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_______ encoding has a transition at the middle of each bit.
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RZ
Manchester Differential Manchester (all of the above) |
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_______ provides redundancy to ensure synchronization and inherent error detection.
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Block coding
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Block coding can help in _______ at the receiver.
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Synchronization
and Error detection |
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In _______ transmission, a start bit and a stop bit frame a character byte.
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asynchronous serial
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In _______ transmission, bits are transmitted simultaneously, each across its own wire.
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Parallel
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In asynchronous transmission, the gap time between bytes is _______.
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variable
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______ substitutes eight consecutive zeros with 000VB0VB.
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B8ZS
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Which encoding method uses alternating positive and negative values for 1s?
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AMI
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In _______ transmission, bits are transmitted over a single wire, one at a time.
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asynchronous serial
and synchronous serial |
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Which of the following encoding methods does not provide for synchronization?
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NRZ-L
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_________ media transport electromagnetic waves without the use of a physical conductor.
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Unguided
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________ are used for short-range communications such as those between a PC and a peripheral device.
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Infrared waves
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_____ cable can carry signals of higher frequency ranges than _____ cable.
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Coaxial; twisted-pair
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A parabolic dish antenna is a(n) _______ antenna.
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unidirectional
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In a fiber-optic cable, the signal is propagated along the inner core by _______.
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reflection
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Radio waves are _________.
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omnidirectional
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Signals with a frequency above 30 MHz use _______propagation.
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line-of-sight
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Transmission media lie below the _______ layer.
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physical
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What is the major factor that makes coaxial cable less susceptible to noise than twisted-pair cable?
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outer conductor
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What is the time between samples for a voice channel using PCM? Give the answer in microseconds.
Hint: Use the Nyquist sampling theorem on a 4 KHz voice channel |
125 microseconds
4 KHZ nyquist sampling = 8 KHz 8 khz = 8000 samples/sec 1/8000 = 125 microseconds |
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___________ multiplexing is commonly used for multiplexing digitized voice streams and data streams.
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Synchronous time division
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________ can be achieved by using multiplexing; ______ can be achieved by using spreading.
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Efficiency; privacy and antijamming
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Which multiplexing technique transmits digital signals?
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TDM
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_______ is designed to be used in wireless applications in which stations must be able to share the medium without interception by an eavesdropper and without being subject to jamming from a malicious intruder.
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Spread spectrum
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In ________ TDM, each input connection has an allotment in the output even if it is not sending data.
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synchronous
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In a multiplexed system, __ lines share the bandwidth of ____ link.
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n; 1
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In synchronous TDM, for n signal sources of the same data rate, each frame contains _______ slots.
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n
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The ___________ accepts the multiplexed data stream, separates the data according to channel, and delivers data to the appropriate output lines.
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demultiplexer
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The __________ multiplexing is the most heavily used. A familiar example is broadcast and cable television.
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frequency division
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The _______ technique uses M different carrier frequencies that are modulated by the source signal. At one moment, the sign modulates one carrier frequency; at the next moment, the signal modulates another carrier frequency.
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FHSS
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The ______ technique expands the bandwidth of a signal by replacing each data bit with n bits.
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DSSS
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The transmitted data in synchronous TDM are organized into _________ .
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frames
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Which multiplexing technique involves signals composed of light beams?
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WDM
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Which multiplexing technique transmits analog signals?
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FDM
and WDM |
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With __________ , multiplexing time slots are not preassigned to particular data sources. Rather, user data are buffered and transmitted as rapidly as possible using available time slots.
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statistical time division
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