2012春通信与网络试卷2012-4-9.doc

科目信息通讯与网络班级姓名学号时间4/2012燕山大学试卷 密 封 线 共 8 页 第 1 页 题号一二三四五总分分数Part one: Fill in the blank according to your analysis. (20 percent)1. The second layer in the OSI model has three main functions , and .2. In ARQ, only the unacknowledged frame is retransmitted.3. When data and acknowledgment are sent on the same frame, this is called .4. Data communication standards fall into two categories: , 5. The RS-422 standard specifies that digital 1 of data must be volts.6. sponsored an important standard for local area networks called project 802.7. X.25 use approach to packet switching, and use to multiplex packet.8. 10base-T Ethernet shows topology.9. The transmission rate of the multiplexed path is usually the sum of the transmission rate of the signal sources in synchronous TDM. 10. Networking devices are divided into two categories: and .11. The full name of ISO is .12. If the frequency of a sine wave is one Terahertz, its period is .13. address can ensure accurate delivery between two application programs.14. is the maximum bit rate a transmission medium can transfer.15. FDDI uses encoding method.燕山大学试卷 密 封 线 共 8 页 第 2 页 Part two: Choose the best answer to complete each of the following statement. （20 percent）1. The light signal is propagated along the inner core of fiber-optic cable by .A. refraction B. reflection C. incidence D. transmission2. QAM is examples of ? A. digital-to-digital B. digital-to-analog C. analog-to-analog D. analog-to-digital3. As the data packet moves from the lower to the upper layers, headers are . A. Added B. rearranged C. subtracted D. modified4. In token ring, where is the token when a data frame is in circulation? A. at the receiving station B. at the sending station C. circulating in the ring D. none of the above5. If the maximum is value of a PCM signal is 127 and the minimum value is -127, how many bits were used for encoding?A. 5 B. 6 C. 7 D. 86. Which device controls the order of delivery of slot values that are stored in RAM.A. a crossbar B. across-point C. a TSI D. a transceiver7. Encryption and decryption is the function of layer.A. transport B. session C. presentation D. application8. Which is not mode of communication in system using HDLC? A. NRM B. ASM C. ARM D. ABM9. In the layer, the data unit is called a PDU. A. LLC B. MAC C. network D. transport10. In transport layer, the window size is originally 16, if 10 bytes are acknowledged and the window size is increased to 32, how many bytes should the right wall move?A. 10 B. 26 C. 32 D. 42Please write the answer in the following table12345678910燕山大学试卷 密 封 线 共 8 页 第 3 页 Part three: Concepts ( you must answer in English). (10 percent)1. Give the concept Frequency Spectrum. (2 percent)2. Give the full name of CSMA/CD. (2 percent)3. Give the concept Protocol and its three key elements. (2 percent)4. Give the concept Bit rate and Baud rate. (2 percent)5. Give the concept Multiplexing. (2 percent)燕山大学试卷 密 封 线 共 8 页 第 4 页 Part four: Calculation. (20 percent)1. Given 8-bit sequence of data 10001001, and a divisor of . (5 percent)Find the CRC. (You must write the process of calculation.)2. Using 2-line traditional telephone line for full-duplex data transmission, what is the maximum bit rate by FSK encoding. Assume the frequency difference in each direction is 300Hz. (5 percent)燕山大学试卷 密 封 线 共 8 页 第 5 页 3. Find the medium bandwidth for an 8-PSK signal transmitting at 2000 bps. The transmission is in full-duplex. (5 percent)4. Five signal sources are multiplexing together using synchronous TDM. Each source produces 200 characters per second. Each frame requires one bit for synchronization. (1) Whats the frame rate? (2) Whats the bit rate on the path? (5 percent)燕山大学试卷 密 封 线 共 8 页 第 6 页 Part five: Graphics question. (30 percent)1. Please encode the data stream 01101010 with (1) NRZ-I; (2) RZ; (3) Differential Manchester ; (4) AMI. (5 percent) 2. Please draw the window on each frames line. (5 percent)燕山大学试卷 密 封 线 共 8 页 第 7 页 3. The figure shows an example of polling using HDLC. The mainframe wants to receive data, secondary device B sends data0 and data1 to the mainframe. Then the mainframe sends an ACK to device B, and it would not receive data any more. According to the description, fill in the blank fields and the type of every frame in the figure. (10 pe