1

CEN4500C: Wireless Experiments Background

Wireless Measurements: Shao-Cheng Wang ( shaochew@ufl.edu )

Encounter-based Networks: Sapon Tanachaiwiwat ( stanachai@gmail.com )

Instructor: Dr. Helmy9/13/2007

2

Part I: Wireless MeasurementsAgenda

• Introduction

• Wireless measurement fundamentals

• Tools

• Potential Topics

• Reference

3

How does a coverage map look like?

http://www.ittc.ku.edu/wlan/images.shtml

4

coverage maps (cont’d)

5

Wireless fundamentals: SNR v.s. Distance

6

Wireless fundamentals: SNR v.s. Performance

SNR v.s. Delivery ratio(emulator)

SNR v.s. Delivery ratio(real measurement)

SNR v.s. TCP Tput(real measurement)

7

Tools

• Site-surveyer: Netstumbler (www.netstumbler.com)– Signal (in –dbm), SNR– AP MAC, SSID

8

9

Tools (cont’d)

• HP iPAQ

10

Tools (cont’d)

• Bandwidth test– NDT @ UF: http://ndt.server.ufl.edu:7123/

• TCP uplink/dnlink speed

– Myspeed: http://myvoipspeed.visualware.com/ • UDP loss rate, jitter

11

Potential experiment topics• Coverage Map:

– Create a coverage map of your choice: • SNR (enhanced with levels, dbm #’s)• SNR variations (weather, day/night)• Performance map• Find holes, additions, tech heterogeneity (11a/b/g/e/n) etc.

(please coordinate between groups for the area of interest)

– Reason about your choice and the implications of practicability– Observations/Surprises?

• AP Hunting/Coverage/Handover– Locate APs in some specific areas/buildings– Create an AP-specific coverage map– AP-coverage/handover map for routes on campus– Observations and discussions about the AP planning (evaluation

of planning, tradeoffs, applications, etc.)

12

Reference• Simon Byers and Dave Kormann, “802.11b access point mapping,”

Communications of the ACM, May 2003.• Daniel Aguayo, John Bicket, Sanjit Biswas, Glenn Judd, Robert

Morris, “Link-level Measurements from an 802.11b Mesh Network,” SIGCOMM 2004, August 2004

• Hiroto Aidal, Yosuke Tamura2, Yoshito Tobe2, Hideyuki Tokudal, “Wireless Packet Scheduling with Signal-to-Noise Ratio Monitoring,” LCN 2000

13

Part II: Encounter-based Networks Agenda

• Introduction

• Examples of Encounter based networking

• Encounter-based worm interactions

• Experiment for our class

• Reference

14

Introduction• What is Encounter-based networking

– Discontinuous path (Intermittent connection)

– Store-and-forward (Bundles)– Similar to delay-and-disruption-tolerant-

networking• Large delay• Low data rate• High loss rate

– Networking relying on encounter or relationships between nodes (Social networking)

• Basic assumptions of each node– Persistent storage– Willing to participate– Limitation of Power– Short Radio Range

A B

CE

FD

15

Examples of encounter-based networks

• Military tactical networks• Disaster relief• ZebraNet• Interplanetary networks• Underwater acoustic networks• Rural village networks• Other?

16http://www.cs.rice.edu/~animesh/comp620/presentations/JFP04_D.pdf

17

Encounter-based worms

• Future direction on worm attacks!! (Cabir, ComWar)– Rely on encounter pattern/relationships between users.– Close to flooding, i.e. Epidemic routing.– Propagate via Bluetooth connection (10-meter range)

• Question: How can we alleviate this problem?– Traditional prevention at gateway such as firewall not effective

against fully distributed attacks– Disconnected networks No centralized update

• Inspired by War of the Worms : CodeGreen worms launched to terminate CodeRed worms

• Approach: Deploy automated generated predator worm to terminate prey worm worm interaction

18

Encounter-based worm interaction

PredatorPrey

Susceptible

Prey and predator’s infection rate rely only on encounter characteristics

19

Experiment• Goal: To answer the following questions

– Is the UF campus the good target for worm propagation, given that it propagate via Bluetooth?

– If so, what places are most vulnerable?

– If you want to stop the propagation with other worm, how can you do it effectively?

• Equipments: iPAQs, your laptops, your strategies• Software: Modified Bluechat, Netstumbler, AirSnort, etc.

• Bluetooth device discovery– Distribution of Bluetooth devices that you encounter during the day

• E.g. Type of devices such as cell phone or lap top, brand of such devices such as Nokia, Motorola, etc.

• Bluetooth game Design the strategies for– Largest of encounter rate per day– Largest number of unique devices– Largest number of stable devices– Different roles between teams e.g. Cops and Cons

• Bluetooth and WLAN relationships– Can you derive the correlation between them?

• Bluetooth worm interactions– To test the real worm propagation/ interaction with static/mobility– Parameters

• Type of worm: one or two• Static or Mobile (human mobility)• Topology (for static): line, star, random• With/Without the super node, i.e., super mobile node which is our

radio-controlled truck20

21

Reference• E. Anderson, K. Eustice, S. Markstrum, M. Hansen, P. L. Reiher , “Mobile

Contagion: Simulation of Infection and Defense” PADS 2005: 80-87• S. Capkun, J. P. Hubaux, and L. Buttyan "Mobility Helps Security in Ad Hoc

Networks" Fourth ACM Symposium on Mobile Networking and Computing (MobiHoc), June 2003

• F. Castaneda, E.C. Sezer, J. Xu, “WORM vs. WORM: preliminary study of an active counter-attack mechanism”, ACM workshop on Rapid malcode, 2004

• A. Chaintreau, P. Hui, J. Crowcroft, C. Diot, R. Gass and J. Scott, “Impact of Human Mobility on the Design of Opportunistic Forwarding Algorithms” IEEE INFOCOM, April 2006

• W. Hsu, A. Helmy, "On Nodal Encounter Patterns in Wireless LAN Traces", The 2nd IEEE Int.l Workshop on Wireless Network Measurement (WiNMee), April 2006

• S.Tanachaiwiwat, A. Helmy, "Encounter-based Worms: Analysis and Defense", IEEE Conference on Sensor and Ad Hoc Communications and Networks (SECON) 2006 Poster/Demo Session, VA, September 2006

• A. Vahdat and D. Becker. Epidemic routing for partially connected ad hoc networks. Technical Report CS-2000.