This simulation exercise explores the impact of MAC overhead and multiple hops on achievable data throughput in a wireless network.
We'll separately analyse the impact of MAC overhead using single hop topology and impact of multiple hops on the attainable throughput.
Fig 1: The simulation set-up comprises two nodes S and D in direct range of each other. S acts as a CBR source, with D being the sink. Fig 2: The simulation set-up comprises a linear chain of nodes S-I1-I2...Im-D, where consecutive nodes are placed at a distance of 200m from each other. S acts as a CBR source, with D being the sink. We shall assume a data-rate of 11.0 Mbps, and vary the length of the chain.Part (a): Impact of MAC Overhead 1. Get the tcl script from here. 2. A script "single-hop.tcl" is provided. This script takes as a command-line argument the transmission rate (in bps). Script usage is : ns single-hop.tcl -drate {data-rate} 3. You are required to run simulations for data rate values 1.0e6, 2.0e6, 5.5e6 and 11.0e6. 4. Determine the achieved data throughput (in Mbps) for each. Plot a graph of (throughput/data-rate) vs. data-rate. (To calculate throughput, you need to calculate [num of received packets/num of sent packets]. Go through the sections 16.1.6 and 16.1.7 of the ns2 manual for understanding and using trace files. For this particular assignment, use the commands 'grep "^s" {trace file name} | wc -l' and 'grep "^r" {trace file name} | wc -l' to get the number of sent and received packets respectively.) 5. How does (throughput/data-rate) vary with changing datarate? Explain briefly the trends you observe, as well as any reasons for those trends. Part (b): Impact of multiple intervening hops between Source and Destination 1. Get the tcl script from here. 2. A script "multi-hop.tcl" is provided. This script takes as a command-line argument the total no. of nodes i.e. if you provide "k" as the argument, you shall have (k-1) hops between S and D. Script usage is : ns multi-hop.tcl -nn {numnodes} 3. Run simulations for k=2, 3, 4, 5, 6. 4. Plot the achieved end-to-end CBR throughput vs. the number of hops. 5. Explain briefly the trends you observe, as well as any reason for those trends.