尔雅数字通信原理课后答案(学习通2023完整答案)
37 min read尔雅数字通信原理课后答案(学习通2023完整答案)
第4周测试
1、数字Data transferred in the Data Link Layer is 通信通完in the form
A、Physical
B、原理Transport
C、课后Network Network layer
D、答案MAC sublayer of the data link layer
2、学习Which one of the following networking terms is 整答not associated with the same OSI layer as the others?
A、Router
B、尔雅Packets
C、数字Tcp
D、通信通完IP
3、原理Which of the following functions is 课后not performed by TCP?
A、Flow control
B、答案Sequencing
C、学习Error checking
D、Subnetting
4、Bit synchronization is handled at which layer?
A、Data link
B、Transport
C、Session
D、Physical
5、Identify the order of the 5 step encapsulation? 1. Create the segment 2. Convert the Frame to bits 3. Create the packet 4. Create the frame 5. user creates the data
A、1,2,4,2,5
B、2,1,3,4,5,
C、5,1,3,4,2,
D、5,3,4,1,2,
6、Which layers of the OSI model are included in the lower layers？
A、Application, Session, Presentation
B、Physical, Transport, Data link, network
C、Data link, physical, Network
D、Session, Data link, Physical
7、IP is implemented at which OSI model layer?
A、Transport
B、Session
C、Data link
D、Network
8、Where is encapsulation used in the osi model?
A、All seven layers of the receiving station
B、At peer layers of the sending station and receiving station
C、Only at the Network layer
D、At the sending Station
9、What is the Protocol Data Unit (PDU) employed at the Data Link Layer?
A、Bits
B、Frames
C、Packets
D、Segments
10、Which of the following protocols are examples of TCP/IP network access layer protocols?
A、Ethernet
B、HTTP
C、UDP
D、TCP
11、Transport layer protocols that establish a connection with another node before they begin transmitting data are known as :
A、Connectionless protocols
B、Syn-oriented protocols
C、Connection-oriented protocols
D、Ask.oriented protocols
12、A network layer protocols that reports on the success or failure of data delivery is :
A、IP
B、TCP
C、ARP
D、ICMP
13、Encryption takes place at which layer?
A、Application
B、Presentation
C、Session
D、Transport
14、Which layer establishes, maintains, and terminates communications between applications located on different devices?
A、Application
B、Presentation
C、Session
D、Network
15、Which layer uses the Segments as a Protocol Data Unit (PDU)?
A、Network
B、Physical
C、Data link
D、Transport
16、Which OSI layer defines the standards for cabling and connection ?
A、Layer 1
B、Layer 2
C、Layer 3
D、Layer 4
17、Packets are found at which layer?
A、Data link
B、Transport
C、Network
D、Session
18、What are the OSI layers above and below the Session layer？
A、Application, presentation, session, transport, network, data link, physical
B、Session, presentation, data transport, MAC, network, physical
C、Physical, data link, network, transport, session, presentation, application
D、Presentation, application, session, network, transport, data link, physical
19、What are the OSI layer above and below the Session layer.
A、Application and Physical layer
B、Application and Session layer
C、Presentation and Transport layer
D、Transport and Physical layer
20、. In the Data link layer for the OSI model, error checking is accomplished by a:
A、Transport
B、Network
C、Session
D、Data link
21、Error detection and recovery takes place at which layer?
A、Transport
B、Presentation
C、Data link
D、Network
22、Which layer handles the formatting of application data so that it will be readable by the destination system?
A、Application
B、Presentation
C、Transport
D、network E. Data link
23、The network layer uses physical addresses to route data to destination hosts.
A、True
B、False
C、字数补丁
D、字数补丁
24、Which layer falls between the Presentation layer and the Transport Layer?
A、Application
B、Session
C、Physical
D、Network
Week 10
Exam
1、The _______ layer is responsible for delivering data units from one station to the next without errors.
A、physical
B、data link
C、trnsport
D、network
2、The _______ model shows how the network functions of a computer ought to be organized.
A、CCITT
B、ANSI
C、OSI
D、ISO
3、TCP/IP is a ______ hierarchical protocol suite developed _____ the OSI model.
A、five-layer; before
B、five-layer; after
C、six-layer; before
D、seven-layer; before
4、Which of the following is an application layer service?
A、All of these
B、File transfer and access
C、Mail service
D、Remote log-in
5、The_________ layer is responsible for the delivery of a message from one process to another.
A、physical
B、transport
C、network
D、none of these
6、Communication between a computer and a keyboard involves ______________ transmission.
A、simplex
B、half-duplex
C、full-duplex
D、automatic
7、_______ refers to the structure or format of the data, meaning the order in which they are presented.
A、All of these
B、Syntax
C、Semantics
D、Timing
8、The information to be communicated in a data communications system is the _______.
A、Medium
B、Protocol
C、Message
D、Transmission
9、________ is a collection of many separate networks.
A、A WAN
B、An internet
C、A LAN
D、None of these
10、In _______ transmission, the channel capacity is shared by both communicating devices at all times.
A、simplex
B、half-duplex
C、half-simplex
D、full-duplex
11、This was the first network.
A、CSNET
B、NSFNET
C、ARPANET
D、ANSNET
12、_______ describes the position of the waveform relative to time 0.
A、Amplitude
B、Frequency
C、Voltage
D、Phase
13、A(n)_________ signal is a composite analog signal with an infinite bandwidth.
A、either digital or analog
B、analog
C、neither digital nor analog
D、digital
14、A sine wave in the ______ domain can be represented by one single spike in the _____ domain.
A、phase; time
B、time; frequency
C、frequency; time
D、time; phase
15、As frequency increases, the period ________.
A、doubles
B、remains the same
C、increases
D、decreases
16、________ is a type of transmission impairment in which the signal loses strength due to the resistance of the transmission medium.
A、Distortion
B、Noise
C、Decibel
D、Attenuation
17、The _________ product defines the number of bits that can fill the link.
A、bandwidth-delay
B、bandwidth-period
C、frequency-amplitude
D、delay-amplitude
18、________ is a type of transmission impairment in which an outside source such as crosstalk corrupts a signal.
A、Distortion
B、Noise
C、Attenuation
D、Decibel
19、If the bandwidth of a signal is 5 KHz and the lowest frequency is 52 KHz, what is the highest frequency?
A、57 KHz
B、47 KHz
C、10 KHz
D、5 KHz
20、AM and FM are examples of ________ conversion.
A、analog-to-analog
B、digital-to-digital
C、analog-to-digital
D、digital-to-analog
21、_________ utilization is the use of available bandwidth to achieve specific goals.
A、Amplitude
B、Frequency
C、Bandwidth
D、None of these
22、The sharing of a medium and its link by two or more devices is called _______.
A、line discipline
B、encoding
C、multiplexing
D、modulation
23、_________ cable consists of an inner copper core and a second conducting outer sheath.
A、Fiber-optic
B、Coaxial
C、Shielded twisted-pair
D、Twisted-pair
24、he inner core of an optical fiber is _________ in composition.
A、bimetallic
B、glass or plastic
C、copper
D、liquid
25、Signals with a frequency above 30 MHz use _______propagation.
A、none of these
B、ground
C、sky
D、line-of-sight
26、A(n) _________ medium provides a physical conduit from one device to another.
A、None of these
B、unguided
C、guided
D、either unguided or guided
27、In fiber optics, the signal is _______ waves.
A、radio
B、light
C、infrared
D、very low-frequency
28、_________ media transport electromagnetic waves without the use of a physical conductor.
A、Unguided
B、Guided
C、Either Guided or Unguided
D、None of these
29、________ cable is used for voice and data communications.
A、Fiber-optic
B、Twisted-pair
C、Coaxial
D、None of these
30、__________ consists of a central conductor and a shield.
A、Twisted-pair
B、Coaxial
C、Fiber-optic
D、None of these
31、In _______ transmission, bits are transmitted over a single wire, one at a time.
A、synchronous serial
B、asynchronous serial
C、parallel
D、asynchronous serial and synchronous serial
32、What is the major factor that makes coaxial cable less susceptible to noise than twisted-pair cable?
A、insulating material
B、inner conductor
C、diameter of cable
D、outer conductor
33、________ are used for short-range communications such as those between a PC and a peripheral device.
A、Radio waves
B、Infrared waves
C、Microwaves
D、None of these
34、Radio waves are _________.
A、None of these
B、unidirectional
C、omnidirectional
D、bidirectional
35、Transmission media are usually categorized as _______.
A、determinate or indeterminate
B、metallic or nonmetallic
C、fixed or unfixed
D、guided or unguided
36、When a beam of light travels through media of two different densities, if the angle of incidence is greater than the critical angle, _______ occurs.
A、refraction
B、criticism
C、reflection
D、incidence
37、A parabolic dish antenna is a(n) _________ antenna.
A、unidirectional
B、horn
C、omnidirectional
D、bidirectional
38、Which of the following is not a guided medium?
A、atmosphere
B、fiber-optic cable
C、coaxial cable
D、twisted-pair cable
39、_______ signals can have only a limited number of values.
A、either digital or analog
B、digital
C、analog
D、neither digital nor analog
40、For a ______ channel, the Nyquist bit rate formula defines the theoretical maximum bit rate.
A、noisy
B、bandpass
C、noiseless
D、low-pass
41、_________ can impair a signal.
A、Noise
B、Attenuation
C、Distortion
D、All of these
42、What is the bandwidth of a signal that ranges from 1 MHz to 4 MHz?
A、3 MHz
B、none of these
C、1 KHz
D、4 MHz
43、Given two sine waves A and B, if the frequency of A is twice that of B, then the period of B is ________ that of A.
A、twice
B、the same as
C、one-half
D、indeterminate from
44、________ is a type of transmission impairment in which the signal loses strength due to the different propagation speeds of each frequency that makes up the signal.
A、Attenuation
B、Distortion
C、Decibel
D、Noise
45、A periodic signal completes one cycle in 0.001 s. What is the frequency?
A、100 Hz
B、1 MHz
C、1 Hz
D、1 KHz
46、The ____ address uniquely defines a host on the Internet.
A、physical
B、IP
C、port
D、specific
47、The _______ is the physical path over which a message travels.
A、Protocol
B、Signal
C、Medium
D、All of these
48、A ________ is a set of rules that governs data communication.
A、None of these
B、protocol
C、standard
D、forum
49、In a ______ connection, two and only two devices are connected by a dedicated link.
A、multipoint and point-to-point
B、point-to-point
C、None of these
D、multipoint
50、In a ________ connection, three or more devices share a link.
A、None of these
B、point-to-point
C、point-to-point and multipoint
D、multipoint
51、Signals with a frequency between 2 MHz and 30 MHz use _______ propagation.
A、none of these
B、sky
C、line-of-sight
D、ground
52、In a fiber-optic cable, the signal is propagated along the inner core by _______.
A、refraction
B、reflection
C、modulation
D、None of these
53、________ cable can carry signals of higher frequency ranges than _______ cable.
A、Coaxial; fiber-optic
B、Twisted-pair; fiber-optic
C、Coaxial; twisted-pair
D、None of these
54、________ cables are composed of a glass or plastic inner core surrounded by cladding, all encased in an outside jacket.
A、Twisted-pair
B、Coaxial
C、None of these
D、Fiber-optic
55、_________ are used for cellular phone, satellite, and wireless LAN communications.
A、Infrared waves
B、Radio waves
C、None of these
D、Microwaves
56、Which of the following primarily uses guided media?
A、radio broadcasting
B、cellular telephone system
C、satellite communications
D、local telephone system
57、A signal is measured at two different points. The power is P1 at the first point and P2 at the second point. The dB is 0. This means ________.
A、P2 equals P1
B、P2 is zero
C、P2 is much larger than P1
D、P2 is much smaller than P1
58、Signals can be ________.
A、digital
B、analog
C、either digital or analog
D、neither digital nor analog
59、A sine wave is ________.
A、periodic and continuous
B、aperiodic and discrete
C、aperiodic and continuous
D、periodic and discrete
60、________is the rate of change with respect to time.
A、Time
B、Frequency
C、Voltage
D、Amplitude
学习通数字通信原理
数字通信是一种信息传输方式，它使用数字信号来传输和处理信息。数字通信原理包括信号的调制、传输、解调和处理，其中最重要的部分是数字信号的调制和解调。
数字信号的调制是将原始信息转换为数字信号的过程。根据信号的频率特性和调制方式，数字信号的调制可以分为幅度调制（AM）、频率调制（FM）、相位调制（PM）和脉冲调制（PCM）等几种类型。
在数字通信中，调制的基本目的是将原始信号转换为一种能够在信道中传输的信号。数字信号可以通过数字方式传输或者通过模拟方式传输。
数字信号的解调是将数字信号转换为原始信息的过程。解调的方法通常与调制的方式相对应，例如，如果原始信号是用频率调制方式调制的，则数字信号也应该用频率解调的方法来解调。
在数字通信中，信道是指信号传输的媒介或介质。数字信号在传输过程中常常受到很多噪声和干扰的影响，这些影响会导致数字信号的错误。因此，数字通信系统通常需要采用一些纠错码或冗余编码技术来保证数据的正确性。
数字通信的应用十分广泛，例如在电话网络、电视广播、互联网和移动通信等领域都有广泛应用。数字通信的快速发展促进了现代通信技术的发展，使我们的生活和工作变得更加便捷和高效。
数字信号的调制
数字信号的调制是将原始信息转换为数字信号的过程。在数字通信中，最常用的调制方式是正交振幅调制（QAM）和相位移键（PSK）调制。
正交振幅调制（QAM）
正交振幅调制是利用两路正交的基带信号进行调制的一种调制方式。QAM调制的基本思想是将数字信号分成两路信号进行调制，然后通过合并两路信号来得到一个更高速率的数字信号。
在QAM调制中，需要将数字信号转换为两路基带信号，分别为I路和Q路信号。I路信号通常用于调制正弦波，Q路信号用于调制余弦波。通过改变I路和Q路信号的幅度和相位，可以得到不同的数字信号。
QAM调制的优点是可以在较小的带宽内传输更多的信息，因此在数字通信中得到广泛应用。
相位移键（PSK）调制
相位移键调制是利用数字信号的相位差异进行调制的一种调制方式。在PSK调制中，数字信号所对应的二进制码被转换为不同的相位角，然后用一定的载波进行调制。
PSK调制的优点是比较简单，易于实现，同时在数字通信中也得到了广泛的应用。
数字信号的解调
数字信号的解调是将数字信号转换为原始信息的过程。在数字通信中，数字信号的解调通常与调制的方式相对应。
正交振幅调制（QAM）解调
在QAM调制中，需要将接收到的数字信号分为I路和Q路信号，然后分别进行解调。解调的过程是将接收到的信号与正弦波和余弦波相乘，然后进行滤波，最终得到原始信息。
QAM解调的过程比较复杂，需要进行多次运算和滤波。但是由于QAM调制具有较好的性能，因此在数字通信中得到了广泛的应用。
相位移键（PSK）解调
在PSK调制中，接收到的数字信号与相应的载波进行乘法运算，然后进行滤波，最终得到原始信息。
PSK解调的过程比较简单，只需要进行一次运算和滤波即可。因此在数字通信中得到了广泛的应用。
数字通信的信道编码
数字通信中，信道编码是用于纠正信道中错误的一种技术。通常的信道编码技术包括前向纠错码（FEC）和自适应纠错码（ARQ）。
前向纠错码（FEC）
前向纠错码是一种错误检测和纠正技术。在数字通信中，FEC通常使用哈密尔顿码、CRC校验和卷积码等编码方式。当接收到的码字发生错误时，FEC会根据码字的编码方式自动进行错误检测和纠正。
自适应纠错码（ARQ）
自适应纠错码是一种动态调整错误检测和纠正方法的技术。当接收到的码字发生错误时，ARQ会向发送方发送一个重传请求，要求重新发送数据。ARQ技术可以通过调整重传次数和重传的码字数量来适应不同的信道条件。
总结
数字通信是一种使用数字信号进行信息传输的技术。数字通信的基本原理包括数字信号的调制、传输、解调和处理。在数字通信中，最常用的调制方式是正交振幅调制和相位移键调制。数字信号的解调通常与调制的方式相对应。数字通信中还使用了一些纠错码和冗余编码技术来保证数据的正确性。数字通信的应用十分广泛，可以在电话网络、电视广播、互联网和移动通信等领域得到广泛应用。
学习通数字通信原理
数字通信是一种信息传输方式，它使用数字信号来传输和处理信息。数字通信原理包括信号的调制、传输、解调和处理，其中最重要的部分是数字信号的调制和解调。
数字信号的调制是将原始信息转换为数字信号的过程。根据信号的频率特性和调制方式，数字信号的调制可以分为幅度调制（AM）、频率调制（FM）、相位调制（PM）和脉冲调制（PCM）等几种类型。
在数字通信中，调制的基本目的是将原始信号转换为一种能够在信道中传输的信号。数字信号可以通过数字方式传输或者通过模拟方式传输。
数字信号的解调是将数字信号转换为原始信息的过程。解调的方法通常与调制的方式相对应，例如，如果原始信号是用频率调制方式调制的，则数字信号也应该用频率解调的方法来解调。
在数字通信中，信道是指信号传输的媒介或介质。数字信号在传输过程中常常受到很多噪声和干扰的影响，这些影响会导致数字信号的错误。因此，数字通信系统通常需要采用一些纠错码或冗余编码技术来保证数据的正确性。
数字通信的应用十分广泛，例如在电话网络、电视广播、互联网和移动通信等领域都有广泛应用。数字通信的快速发展促进了现代通信技术的发展，使我们的生活和工作变得更加便捷和高效。
数字信号的调制
数字信号的调制是将原始信息转换为数字信号的过程。在数字通信中，最常用的调制方式是正交振幅调制（QAM）和相位移键（PSK）调制。
正交振幅调制（QAM）
正交振幅调制是利用两路正交的基带信号进行调制的一种调制方式。QAM调制的基本思想是将数字信号分成两路信号进行调制，然后通过合并两路信号来得到一个更高速率的数字信号。
在QAM调制中，需要将数字信号转换为两路基带信号，分别为I路和Q路信号。I路信号通常用于调制正弦波，Q路信号用于调制余弦波。通过改变I路和Q路信号的幅度和相位，可以得到不同的数字信号。
QAM调制的优点是可以在较小的带宽内传输更多的信息，因此在数字通信中得到广泛应用。
相位移键（PSK）调制
相位移键调制是利用数字信号的相位差异进行调制的一种调制方式。在PSK调制中，数字信号所对应的二进制码被转换为不同的相位角，然后用一定的载波进行调制。
PSK调制的优点是比较简单，易于实现，同时在数字通信中也得到了广泛的应用。
数字信号的解调
数字信号的解调是将数字信号转换为原始信息的过程。在数字通信中，数字信号的解调通常与调制的方式相对应。
正交振幅调制（QAM）解调
在QAM调制中，需要将接收到的数字信号分为I路和Q路信号，然后分别进行解调。解调的过程是将接收到的信号与正弦波和余弦波相乘，然后进行滤波，最终得到原始信息。
QAM解调的过程比较复杂，需要进行多次运算和滤波。但是由于QAM调制具有较好的性能，因此在数字通信中得到了广泛的应用。
相位移键（PSK）解调
在PSK调制中，接收到的数字信号与相应的载波进行乘法运算，然后进行滤波，最终得到原始信息。
PSK解调的过程比较简单，只需要进行一次运算和滤波即可。因此在数字通信中得到了广泛的应用。
数字通信的信道编码
数字通信中，信道编码是用于纠正信道中错误的一种技术。通常的信道编码技术包括前向纠错码（FEC）和自适应纠错码（ARQ）。
前向纠错码（FEC）
前向纠错码是一种错误检测和纠正技术。在数字通信中，FEC通常使用哈密尔顿码、CRC校验和卷积码等编码方式。当接收到的码字发生错误时，FEC会根据码字的编码方式自动进行错误检测和纠正。
自适应纠错码（ARQ）
自适应纠错码是一种动态调整错误检测和纠正方法的技术。当接收到的码字发生错误时，ARQ会向发送方发送一个重传请求，要求重新发送数据。ARQ技术可以通过调整重传次数和重传的码字数量来适应不同的信道条件。
总结
数字通信是一种使用数字信号进行信息传输的技术。数字通信的基本原理包括数字信号的调制、传输、解调和处理。在数字通信中，最常用的调制方式是正交振幅调制和相位移键调制。数字信号的解调通常与调制的方式相对应。数字通信中还使用了一些纠错码和冗余编码技术来保证数据的正确性。数字通信的应用十分广泛，可以在电话网络、电视广播、互联网和移动通信等领域得到广泛应用。
