AdHoc Wireless Commands

1
Ad-Hoc Wireless Commands

• //Bring up the wireless interface
• ifconfig ath0 up
• //Scan for Wireless access points (Must be in
  Managed Mode)
• iwlist ath0 scan
• //Set static ip address on wireless interface
• ifconfig ath0 192.168.1.x
• //Setup essid name and broadcast in Ad-Hoc mode
• iwconfig ath0 mode Ad-Hoc essid CS496
• //Switch back to Managed mode
• iwconfig atho mode managed
• //connect to another Ad-Hoc Node (ip addr is
  static)
• iwconfig ath0 essid CS496

2
Commands we could try

• //Set bitrate on wirless interface to 54MB
• iwconfig ath0 rate 54M
• // try iperf with UDP at 54Mbps. (in bits per
  second)
• iperf -c server addr -u -b 56623104
• //try iperf in bidirectional test at the same
  time
• iperf -c server addr -d -L 496
• //try iperf in bidirectional test individually
• iperf -c server addr -r -L 496

3
Experiment 10/09/2005

• Estimated distance is approx. 1600ft.
• Location Green Lot to Purple Lot in Southwest.
• Conditions Light Rain
• Machines Powered by cars.

4
Configuring etc/init.d/interfaces

• auto ath0
• iface ath0 inet static
• address 192.168.1.x
• netmask 255.255.255.0
• wireless_mode Ad-Hoc
• wireless_essid CS496

5
Initial Test Results

• Yagi to Yagi
• Before setting the rate to 54M ('ifconfig ath0
  rate 54M)
•   Link Quality 19/94 Signal -73dBm Noise -95dBm
• 0.0-10.0 sec  7.48 MBytes  6.26 Mbits/sec
• After
• Link Quality 30/94 Signal -65dBm Noise -95dBm
•  0.0-10.0 sec  31.3 MBytes  26.2 Mbits/sec
• Parabolic to Parabolic
• Before setting the rate to 54M ('ifconfig ath0
  rate 54M)
• Link Quality 40/94 Signal -55dBm Noise -95dBm
•  0.0-10.0 sec  7.55 MBytes  6.33 Mbits/sec
• 0.0-10.0 sec  26.6 MBytes  22.3 Mbits/sec
  (After direction adjustment)
• After
• Link Quality 55/94 Signal -40dBm Noise -95dBm
•  0.0-10.0 sec  32.3 MBytes  27.1 Mbits/sec

6
Things to try

• Establish Test plan
• Further distance
• How do we make a multihop network?
• Plausible

7
Calculating path loss

• L 20 log(d) 20 log(f) 36.6
• (where Lloss in db, ddistance in miles, ffreq
  in Mhz)

8
Ad Hoc On-Demand Distance Vector Routing

• The Ad hoc On Demand Distance Vector (AODV)
  routing algorithm is a routing protocol designed
  for ad hoc mobile networks. AODV is capable of
  both unicast and multicast routing. It is an on
  demand algorithm, meaning that it builds routes
  between nodes only as desired by source nodes. It
  maintains these routes as long as they are needed
  by the sources. Additionally, AODV forms trees
  which connect multicast group members. The trees
  are composed of the group members and the nodes
  needed to connect the members. AODV uses sequence
  numbers to ensure the freshness of routes. It is
  loop-free, self-starting, and scales to large
  numbers of mobile nodes.

9

• Node 1 wants to send to Node 3 but they are not
  direct neighbors
• Node 2 has a route to Node 3
• Each node keeps a table of its neighbors and
  keeps the table updated with HELLO messages
  broadcast at regular intervals.
• Graphics courtesy of NIST

10

• RREQ Routing request message
• RREP Routing reply

11
Kernel AODV

• http//w3.antd.nist.gov/wctg/aodv_kernel/index.htm
  l
• NIST implementation of AODV, source code freely
  available.
• Trouble is it only works with kernel 2.4 and runs
  in kernel space

12
AODV a better implementation

• http//core.it.uu.se/AdHoc/AodvUUImpl
• Compiles against kernel 2.6
• Runs as User space daemon
• Liscenced to GPL
• But we Need kernel source for 2.6.11 in order to
  compile!!!

13
Some interesting links

• Revisiting MAC Design for an 802.11based Mesh
  Network
• http//www.cse.iitk.ac.in/users/braman/papers/2p.p
  df
• HostAP
• http//hostap.epitest.fi/
• Opportunities and Challenges for Mesh Networks
  Using Directional Antennas
• http//www.cs.ucdavis.edu/prasant/WIMESH/p13.pdf
• A Topology Control Approach to Using Directional
  Antennas in Wireless Mesh Networks
• http//www.cs.sunysb.edu/hgupta/ps/directional.p
  df