s1 - wasted due to collisions? Solution. Also, the fraction...

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Cmpen/EE 362 Assignment 1 Solution Spring 2011 Problems 1-4. Text, Chapter 1, problems 1,9, 14,15. In the 2003 edition, these are problems 1, 10, 16 and 17. Problem 1. St. Bernard carrying 3 tapes of 7 gigabytes each. Speed 18 km/hour . Alternative is a transmission line sending at a rate 150 megabits/second. Up to what distance would Bernie be faster? Solution. The total in bits that Bernie is carrying is 3*7*8*10 = 1.68*10 . At 150 megabits/second, 91 1 the time to transport this many bits is 1.68*10 ./150*10 = 1, 120 seconds or .31111 hours, in which 11 6 time Bernie would have traveled 18*.3111 = 5.6 kilometers. So if the distance is less than 5.6 kilometers , Bernie would have delivered at a higher rate. Problem 9. Time divided into slots, n hosts each attempt with probability p. What fraction will be
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Unformatted text preview: wasted due to collisions? Solution. Also, the fraction of time (1-p) no one sends is wasted. The successful fraction is np(1-p) . n n-1 Problem 14. In Fig. 1-19 a service is shown. Any other services? If so, where? If not, why not? Solution. If k-1 is not the lowest layer, layer k-2 can provide service to layer k-1. Similarly, layer k+1 might be providing service to layer k+2, if there is such a layer . Problem 15. If p is probability a frame will not be received successfully, what is the mean number of times sent per success? Problem 14. In Fig. 1-19 a service is shown. Any other services? If so, where? If not, why not? Solution. If n frames are sent, about n(1-p) will be successful. sent/successful = 1/(1-p) = mean number of frames per success....
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