Ad-hoc Networking

 

Ralph Morelli, Trishan de Lanerolle of Trinity College,  and their

students (Antonio Alcorn, UConn,  Christopher Fei and Prasanna

Gautam, Trinity,  and Qianqian Lin, Wesleyan)

presented POSIT (http://posit.hfoss.org/),  an Android-based search and rescue

tool that implements  a form of ad-hoc networking called Random Walk Gossip (RWG). 

This is work in conjunction with the Prof. Simin Nadjm-Tehrani, Mikael Asplund, and Gustav

Nykvist of the Real Time Systems Laboratory at Linkoping University in Sweden, where

RWG was developed (http://www.ida.liu.se/~rtslab/HFN/rwg/index.shtml). 

 

• The POSIT project is looking for users to test the system.
• RWG is based on rap sockets, not UDP.  It randomly propogate messages through a partitioned or intermittently connected network.
• Field tests demonstrate that phone-to-phone broadcast messages are transmitted  at up to  400 meters, assuming  line-of-sight.
• RWG is designed to minimize power usage and bandwidth requirements.
• Other possible application were discussed:
  • pH sensor data aggregation?
• Possible optimizations were discussed:
  • Simulators: optnet, ns2
  • Possibility of p2p using cell radio
  • Adjust power level to conserve battery
  • DD-WRT for example.
  • Optimize algorithms: instead of complete randomization, look at contact history. A person may migrate between 2 groups for a reason, or regularly, e.g. for work. ("stability metric")
  • Oscar's AODV algorithm: modified to transmit video, photos, etc. high-bandwidt and uses a stability metric based on how long 2 nodes are in touch, on average. Simulated in NS2.
• SMS
  • Robert Kirkpatrick reported that SMS: didn't go down in Aceh; latencies were high.  In practice, SMS is usually last to go down, first to come back.

  • Data encoding/structured SMS?

  • Air traffic control over SMS?
  • MMS: less reliable, but messages queue up, then are sent once network comes back up
• User experiences are important.
  • Must be independent of protocol/technology.

  • User Interface: Firefighters can't read POSIT screen on the job.

  • Pony express message delivery
  • See Project Guardian (http://www.netsquared.org/projects/guardian-secure-private-anonymous-telephone-built-google-android) for ideas on privacy and security for on Android.
• Design Issues/Suggestions

  • Use preferred system, then failover to SMS

  • Get text out if you can't send the pictures because of bandwidth

  •  In disaster area, get coverage by driving around

  • Get into an exercise.

    •  Don't try to test prototypes in a disaster zone; becomes a nuisance to relief efforts.

  • Try to attend Camp Roberts exercise (in CA in November) and the Google Hacathon.

  • Generic synchronization of data structures; server drives around and updates extended RSS feeds

• Observations from disaster/crisis scenarios.

  • In Afghanistan: cell towers are autonomous, fenced in, with generator, guarded, satellite up link.

  • In US, most critical infrastructure is in the hands of the private sector

  • In Mexico Zapatistas want internet;

  • Mexico has a  cell # database -- security issues.

  • Military capability to create WiFi corridor: drop long-range heavy duty military routers every mile.

  • Mexico 1988 computer voting fraud: system "crashed" at a crucial time during the election