1

CEN6930: Wireless Experiments Background

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

Instructor: Dr. Helmy

2

Part I: Wireless MeasurementsAgenda

• Introduction

• Wireless measurement fundamentals

• Tools/Procedures

• 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 (cont’d)

• HP iPAQ: WiFiFoFum

8

Tools

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

9

Indoor measurements Outdoor measurements

Wireless coverage experiments

Indoor measurements

Outdoor measurements

Logistics• Exp: starts this week (?)• Form groups: 4~5 ppl• Equipment checkout: CSE401

– Bring your ID– 11am~6pm, no overnight checkout

• Preparations– Materials

• link: http://www.cise.ufl.edu/~sw0/cen6930/

– Software

• Wififofum: pocket pc wifi scannerhttp://www.aspecto-software.com/rw/applications/wififofum/

• Knsgem: convert wifi scanner output to google earth kml• Google earth

15

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.)

16

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