Simulation - II 10/12/08

(Due at the beginning of class on 10/19/08)


CS G254 Wireless Networks

This assignment will be graded out of 50 points.


You could use glomosim OR qualnet to finish this simulation assignment.

1.      Medium access control.

The goal of this work is to study the performance of IEEE 802.11 MAC protocol under highly-loaded network and lightly-loaded network, respectively. Please set up the simulation scenario as follows,

  • This is a network consisting of a base station (server) and multiple static nodes (clients).
  • All nodes are within transmission range of each other. In other words, no hidden or exposed terminal problems in this network.
  • Constant-Bit-Rate is chosen as upper layer application.
  • Each client node starts sending data from second 0, and transmission interval is 4ms. The packet size is 512 bytes. Assume that each node has an infinite number of packets to send.
  • The simulation time is 5 seconds.
  • The propagation model is FREE-SPACE model.
  • UNIFORM node placement.
  • Set your simulation terrain to be 500m*500m.
  • TX-POWER 20dBm
    RX-THRESHOLD -81.0dBm
  • If you use Qualnet, please set the MAC protocol as "MAC802.11".


Change the number of client nodes from 1 to 6, in steps of 1. Observe how the network performance changes in terms of the total throughput of base station and end-to-end delay averaged over all client nodes.

system throughput is defined as the total number of packets received by the base station.


a)      Brief description of your simulation procedure. Clearly describe how you define your app.conf. [3]

b)      Plot the node placement for a network consisting of 6 nodes. [1]

c)      Plot number of clients vs. system throughput. [4]

d)      Plot number of clients vs. end-to-end delay averaged over all nodes (Glomo.stat contains throughtput and end-to-end delay for individual nodes. You could write a very short shell script to calculate the system throughput and end-to-end delay.) [4]

e)      Analysis of your plots to discuss the benefits or disadvantages of 802.11. [3]


2.      Study of network capacity in grid network.

In this task, we are going to study the impact of space reuse and route lengths in grid network. Set up the network scenario as follows

        Edit nodes.input to define a grid network consisting of 4, 9 or 16 nodes. The distance between two adjacent nodes is 100m. (you need to do simulation for
    all 3 scenarios)

        Static routing is applied. ROUTES.IN could be downloaded from here.
    glomosim   qualnet

        Set simulation time to 10 minutes.

        Use 802.11 as MAC protocol.

        Define CBR application as follow:
CBR src dest 0 1500 2S 0 0

        Set up other parameters the same as in task2.


In your simulation, study the three grid topologies illustrated in the above figure.

Each node randomly chooses its destination among all other nodes in the grid network at the beginning of simulation, and keeps sending packets to this node through the whole simulation. The upper layer
CBR packets are routed to its randomly determined destination node by static routing scheme. It's acceptable that more than 1 node chooses the same destination node.


At the end of the simulation, calculate system throughput and end-to-end delay averaged over all nodes.

System throughput is defined as the total number of packets that have been successfully transmitted to destinations in the whole network
average End-to-End delay is defined as the end-to-end delay averaged across all nodes.


a)      Plot average system throughput vs. size of grid. [6]

b)      Plot average end-to-end delay vs. size of grid. [6]

c)      According to your simulation result, analyze how the network performance changes as the grid network expands. [3]


3.      Capacity of wireless networks

a.       State the main assumptions in the Gupta-Kumar model. Prove an upper bound on the per-connection bandwidth and show that it vanishes as the number of users increase. What is the practical implication of this result? [6]

b.      What are the assumptions underlying the Grossglauser-Tse mobility model? Give a heuristic argument that explains why the per-connection bandwidth does not vanish. [4]


4.      Geometry of cells.

a.       Prove that the only regular polygons with n sides that tessellate the plane are the triangle (n=3), square (n=4) and hexagon (n=6). Why is the hexagon the shape of choice for cell networks? [4]

b.      What is the channel reuse factor? Prove that the channel reuse factor can only take values of the form i2 +j2 + ij, for nonnegative integers i, j. [6]