Mobile Adhoc Network Simulator: mobile AntNet

1
Mobile Ad-hoc Network Simulator mobile AntNet
R. Hekmat (CACTUS TermiNet - TU Delft/EWI/NAS)
and Radovan Milosevic (MSc student)

• Mobile Ad-hoc networks
• Mobile ad-hoc networks are self-organized
  networks. Communication in ad-hoc network does
  not require existence of a central base station
  or a fixed network infrastructure. Each node of
  an ad-hoc network is the destination of some
  information packets while at the same time it can
  function as relay station for other packets to
  their final destination. This multi-hop support
  in ad-hoc networks, which makes communication
  between nodes outside direct radio range of each
  other possible, is probably the most distinct
  difference between mobile ad-hoc networks and
  wireless LANs. A mobile ad-hoc network may be
  connected at the edges to the fixed, wired
  Internet. In this case, mobile ad-hoc networks
  expand the present Internet and wireless access
  to the Internet. Mobile ad-hoc networks have
  certain advantages above traditional
  communication networks. For example, ad-hoc
  networks could increase mobility and flexibility,
  as ad-hoc networks can be brought up and torn
  down in very short time. Additionally, ad-hoc
  networks could be more economical in some cases
  because they eliminate fixed infrastructure costs
  and could reduce power consumption at mobile
  nodes.
• Ad-hoc network simulator
• To study network performance metrics like
  throughput, delay and routing protocol overhead
  in wireless ad-hoc networks we have developed a
  software simulation tool. This tool has a
  graphical user interface that allows us to
  monitor changes in the nodes routing table and
  data output variations when the network topology
  and the input traffic rates change. The input
  parameters for the simulator include
• number of nodes in the network,
• size of the service area,
• speed of the nodes,
• capacity and transmission delay of radio link
  between nodes,
• input traffic statistics per node, and
• buffer capacity per node.
• Routing principles
• The routing protocol used in our simulator is a
  modified version of AntNet1. AntNet is an
  adaptive approach to routing in packet-switched
  communication networks that is inspired by the
  stigmergy model of communication observed in ant
  colonies.

In our simulator program each node produces on
regular intervals artificial ants that are sent
to randomly chosen destinations. When a
destination is reached, the ant travels back to
the source node following the same route in
opposite direction. Ants are handled with high
priority at nodes and do not experience the same
delay as data packets. However, based on the
queue size at each node, ants collect information
about the delay that a data packet would
experience using the same path. This information
is used to update two data structures in each
node the routing table and the local traffic
statistics. In a network of N
nodes, the routing table at each node contains
the probabilities to reach any of the possible
N-1 destination through each of the k neighbours
of that node. Local traffic statistics at each
node are the sample mean and the variance of the
trip time to all other destinations in the
network plus the best trip time to each
destination. This information, which is collected
and updated by ants, is used to refresh routing
tables continuously. Program output On the
graphical user interface of the simulator one can
follow changes in the network topology and its
direct effects on the throughput, delay and
capacity usage in the entire network. Therefore,
this simulator helps to get a realistic feeling
about the behavior of ad-hoc networks under
varying circumstances. The following figure
depicts some simulation results that show changes
in the throughput and the packet delay as a
function of the speed of the network nodes. These
results are found for a Poisson traffic arrival
rate with an average of 40 kbit/s data input per
node. Acknowledgement We express
our gratitude towards dr. drs. L.J.M. Rothkrantz
at TU Delft/EWI. Our ad-hoc network simulator is
built upon an AntNet software implementation by
his team for dynamic vehicle routing in fixed
networks.
Email r.hekmat_at_ewi.tudelft.nl 1 G. Di Caro and
M. Dorigo, AntNet Distributed Stigmergetic
Control for Communications Networks. Tech.Rep.
IRIDIA/98-01, 1998, Université Libre de
Bruxelles, Belgium.
September 2003