2024年6月3日发(作者：)
移动通信试题库.doc
名词解释
1．Explain the difference between hard and soft handoff.
Answers：The hard handoff is that when the signal strength
of a neighboring cell exceeds that of the current cell, plus a
threshold, the mobile station is instructed to switch to a new
frequency band that is within the allocation of the new cell.
The soft handoff is that a mobile station is temporarily
connected to more than one base station simultaneously. A
mobile unit may start out assigned to a single cell. If the unit
enters a region in which the transmissions from two base stations
are comparable, the mobile unit enters the soft handoff state
until which it is connected to the two base stations.
2．What are the cores techniques of WCDMA?
Answers: The WCDMA key techniques mostly consist of the
power control technique, PN code technique, RSKE, Soft Handoff,
and Speech coding.
3．What is attenuation?
4．What two functions are performed by an antenna?
5．What are the advantages of using CDMA for a cellular
network?
Answers:(1)Frequency diversity; (2) Multipath resistance; (3)
Privacy; (4) Gracefue degradation.
6. What are the key differences between first and second
generation cellular system? Answers: The key differences
between the two generations:
(1). Digital traffic channels; (2). Encryption; (3). Error
detection correction;
(4). Channel access.
7. What are the cores techniques of TD-SCDMA?
Answers:The cores techniques of TD-SCDMA are smart
antenna (intelligent antenna), joint examination technique,
SCDMA technique, software wireless technique, and dynamic
channel allocation technique
8. What is direct broadcast satellite (DBS)?
Answers: The satellite video signals are transmission directly
to the home user.
9. What is an isotropic antenna?
Answers: An isotropic antenna is a point in space that
radiates power in all direction equally.
10. What is CDMA?
Answers: CDMA is a multiplexing technique used with spread
spectrum
11. What is frequency hopping spread spectrum?
Answers: The signal is broadcast over a seemingly random
series of radio frequency, hopping from frequency to frequency
at fixed intervals
12．What are the primary causes of atmospheric attenuation
for satellite communications? Answers:The primary causes of
atmospheric attenuation are oxygen and water
13．What is a SIR?
Answers: This ratio is defined to be the ratio of the desired
average signal power at a receiver to the total average
interference power.
14．What are features of CDMA?
Answers:(1) High spectrum efficiency(2)Release from
frequency management (3)Low mobile station transmit power
(4)Soft-handover (5)Path Diversity (RAKE Fingers) (6)Security
(7)Anti-jamming capability
15．In general, physical models include three basic modes of
propagation.
Answers：（1）Free-space or link-of-signal transmission;（2）
Reflection；（3）Diffraction.
16．In time, as more customers use the the system, traffic
may build up so that there are not enough frequency bands
assigned to a cell to handle its calls. A number of approaches
have been used to cope with this situation, including the
following。
Answers: (1)Adding new channels；(2)Frequency borrowing；
(3)Cell splitting；
(4)Cell sectoring；(5)Microcells。
17．Explain the difference between open-loop and closed-
loop power control.
Answers: Open-loop power control depends solely on the
mobile unit, with no feedback from the BS.
Closed-loop power control adjusts signal strength in the
reverse channel based on some metric of performance in that
reverse channel.
18．Define channel capacity.
Answers: The maximum rate at which data can be
transmitted over a given communication path, or channel, under
given conditions is referred to the channel capacity.
填空题
1．Antenna characteristics are essentially the same whether
an antenna is sending
or receiving electromagnetic energy.
2．The basis for analog signaling is a continuous constant
frequency signal known as the carrier signal.
3．Nikola Tesla invented the wireless telegraph in 1893.
4．A transmission from earth station to satellite is referred
to as uplink in the satellite communication.
5．The essence of a cellular network is the use of multiple
low-power transmitters, on order
of 100W or less.
6．Third generation system generally call WCDMA or UMTS.
7．Adjacent cells are assigned different frequencies to avoid
interference or crosstalk.
as a function of, an electromagnetic signal can be
either analog or digital.
An analog signal is one in which the signal intensity varies in
a smooth fashion over time.
9．The data signaling rate, or just data rate, of a signal is the
rate, in bits per second, that data are transmitted.
10The TD-SCDMA is a multiple connect into include the
FCDMA/TDMA/CDMA
11．Nikola Tesla invented the wireless telegraph in 1893.
12．A digital signal is one in which the signal intensity
maintains a constant level for some period of time and then
changes to another constant level.
13. Reflection occurs when an electromagnetic signal
encounters a surface that is large relative to the wavelength of
the signal.
14．If the size of an obstacle is on the order of the
wavelength of the signal or
less scattering occurs.
15. For a data of R , the duration of a bit is R
T 1=seconds and the duration of a signal element is LT T S
=seconds. If C T is greater then or to S T , the spreading
modulation is referred to as
slow-frequency-hop spread spectrum; otherwise it is known
as fast-frequency-hop spread
spectrum.
16．A transmission from satellite station to earth is referred
to as downlink in the satellite
communication.
17．The cells sufficiently distant from each other can use the
same frequency band
18．Code division multiple access is a spread spectrum
based technique for multiplexing.
19．The objective of the third generation of wireless
communication is to provide fairly high speed
wireless communications to support multimedia, data, and
video in addition to voice.
20．Power control technique is core in the CDMA .
21．One purpose of the data-layer is to perform error
correction or detection.
22．The channel provides the physical means for
transporting the signal produced by the
transmitter and delivering it to the receiver .
24．The key physical resource is the radio spectrum in
wireless system.
24．A digital signal is one in which the signal intensity
maintains a constant level for some
period of time and then changes to another constant level.
25．The frequency is the rate at which the signal repeats.
26．An antenna that transmits equally in all directions called
the isotropic radiatio .
27．Noise can be defined as unwanted electrical signals
interference with the desired
signal.
28．The basic idea with cellular system is to reuse channel in
different cell, increasing the
capacity
29．During the period from 1895 to 1901 , Guglielmo
Marconi developed an apparatus for
transmitting radio waves over longer distances.
30．An electromagnetic signal can be either analog or digital.
An analog signal
is one in which the signal intensity varies in a smooth fashion
over time.
31．The spectrum of a signal is the range of frequencies that
it contains.
1.32．The same frequency assignments cannot be made in
adjacent cell because of inter-channel interference.
33．Handoff may be network initiated.
34．That each user occupies a cyclically repeating time slot
in the TDMA system. 35．All users in a CDMA, use the same
carrier frequency and may transmit simultaneously. 36．Self-
jamming is a problem in CDMA system.
37．The GSM key technique consist of eight parts
38. Reflection occurs when an electromagnetic signal
encounters a surface that is large relative to the wavelength of
the signal.
判断题
1. Thermal noise can be eliminated. ( N )
2. The time-selective channels are time-invariant channels.
( N )
3. A high SNR will mean a high-quality signal. ( Y )
4. Free-space propagation, in which the received power
decreases as the square of the distance from the transmitter. ( Y )
5. Fast fading is the rapid variation of signal levels when the
user terminal moves short distances. ( Y )
6. Traffic channels are used to exchange information. ( N )
7. Multiple access schemes are used to allow many mobile
users to share simultaneously a finite amount of radio spectrum.
( Y )
sequence multiple access is also called code division
multiple access (CDMA). ( Y )
9. The most popular second generation standards include
three TDMA standards and one CDMA standard. ( Y )
10. The NS controls handoff between cell in different BSSs,
authenticates users and validates their accounts, and includes
functions for enabling worldwide roaming of mobile users. ( Y )
11. Thermal noise cannot be eliminated. ( Y )
12. Frequency-Selective Channels is time-invariant channels.
( N )
13. The greater the bandwidth, the higher the information-
carrying capacity. . ( Y )
tion, wherein, for the plane-Earth model, the
received power decreases as the fourth power of distance. ( Y )
fading arises from the fact that most of the large
reflectors and diffracting objects along
the transmission path are distant from the terminal. ( Y )
l channels are used to exchange information. ( Y )
17. That each user occupies a cyclically repeating time slot in
the FDMA system. ( N )
users of a CDMA system share the same time-slot.
( N )
19. Like TDMA or FDMA, CDMA has a soft capacity limit.. ( N )
20. The NS controls handoff between cell in different BSSs,
authenticates users and validates their accounts, and includes
functions for enabling worldwide roaming of mobile users. ( Y )
选择题
For each sentence there are four choices. Choose the ONE
answer that best completes the sentence.
1. A general sine wave can be represented by three
parameters, they are ( A ).
A. peak amplitude, frequency, and phase;
B. speed, frequency, and phase;
C. peak amplitude, speed, and phase;
D. peak amplitude, frequency, and speed.
2．Transmission media can be classified as ( C ).
A. guided;
B. unguided;
C. guided and unguided;
D. wired and wireless.
3．Fading effects in a mobile environment can be classified
as either ( A ).
A. fast or slow;
B. fast and slow;
C. fast;
D. slow.
4．( D ) is the procedure for changing the assignment of a
mobile unit from one BS to another as the mobile unit moves
from one cell to another.
A. Transmission;
B. change;
C. divert;
D. Handoff;
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