Tham khảo tài liệu 'communication systems engineering episode 3 part 4', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | MASSACHUSETTS INSTITUTE OF TECHNOLOGY Department of Aeronautics and Astronautics Comm. Sys. Engineering Problem Set No. 8 Date Issued April 17 Date Due April 29 Problem 1 Suppose a cyclic code with generator string 11001 is used to generate a CRC. A Suppose the data sequence is 110101 what should the CRC be B Suppose you receive the sequence 1001111 did any errors occur C Find the generator matrix for the 7 3 block code based on the above generator. note that a 7 3 code has 3 information bits and 4 check bits . D Using the generator matrix from above generate all 8 codewords for this code. What is the minimum distance of the code Problem 2 A For the diagram below suppose you are using the Go Back N protocol with N 3 and indicate in the space provided the sender s sequence numbers SN and the receivers request numbers RN . The first RN and SN are 0 and 0 as indicated in the diagram. X lost packet What modulo will you use to number the packets SN 0 RN 0 B Suppose now that you are using the SRP with window size 4. In the diagram below indicate the sender s sequence numbers SN and the receiver ACK numbers. The first packet has sequence number 0 and it is acknowledged by ACK-0. What modulo will you use to number the packets ACK-0 I I I I I I I Problem 3 You have to design a satellite transmission link where two nodes communicate through a satellite. The distance between the two nodes through the satellite is 60 000 miles. The packets and acknowledgments are 1000 bits long. The transmission rate is 100Kbs. The link is full duplex and you propose to use Go Back N retransmission. What window size would you recommend using Problem 4 In class I said that for go back N packets must be numbered modulo N 1. Can you give an example in which go back n fails if the packets are numbered modulo N use N 3
