6 votes 6 votes In P-persistent CSMA network there are 5 systems in a slot. The probability of station not transmitting the data is 0.6. Only two stations should transmit the data to avoid collision. What is the probability that channel is collision free? My answer is 0.6825 and answer given is 0.34 - 0.35. I solved this as P (no collision) = either 2 stations are transmitting or 1 station or none. Computer Networks computer-networks csma-cd + – Vikrant Singh asked Jan 29, 2015 • edited Jan 29, 2015 by Vikrant Singh Vikrant Singh 4.5k views answer comment Share Follow See all 0 reply Please log in or register to add a comment.
Best answer 7 votes 7 votes Favorable case here is no station is transmitting, exactly one is transmitting or exactly 2 is transmitting. $P = {}^5C_0 \times {0.6}^5 + {}^5C_1 \times {0.6}^4{0.4} + {}^5C_2 \times {0.6}^3{0.4}^2 \\= 0.68256.$ Arjun answered Aug 20, 2016 • selected Apr 8, 2017 by Kapil Arjun comment Share Follow See all 3 Comments See all 3 3 Comments reply Nishi Agarwal commented Oct 5, 2019 reply Follow Share Is this ans correct or 0.365 if we will take on 5C2 case??? Can u clarify? 1 votes 1 votes palashbehra5 commented Jan 11, 2022 reply Follow Share Why would there be any collision in the case of only one station transmitting? Makes perfect sense to include 5C0 and 5C1. 0 votes 0 votes mahendrapatel commented Jan 15, 2023 reply Follow Share Sir,jab only 2 stations should send frame likha hua hai,to ham 0,1 station ki probability kyu le???? 0 votes 0 votes Please log in or register to add a comment.
10 votes 10 votes In question ask only two stations transmit. So, we consider two stations only. probability =5C2(0.42)(0.63)=0.3456 hareesh answered Feb 1, 2015 hareesh comment Share Follow See 1 comment See all 1 1 comment reply Aboveallplayer commented Aug 20, 2016 reply Follow Share but of only one statuon transmit then also it will be collisoin free. why we are not considering that case? 2 votes 2 votes Please log in or register to add a comment.