1. Heterogeneous WiFi Transfer Characteristics
Kevin Sinha and Rigoberto Núñez
ECE 4605
Final Presentation
Thursday, December 7, 2006

2. Introduction
Context: Wireless networks are everywhere and are still increasing in number, it is important to distinguish the quality of available connections
Motivation: To see if we are meeting the need for higher throughput rates, stronger security, and better quality of service
Problem Statement: How do the throughputs of b/g/n wireless technologies measure up in real-world environments?

3. Background Research Differences between b/g/n
802.11g with MIMO
Ideal Range
(indoor)
~150 feet
~100 feet
~160 feet
Up to 3x g
(300 ft.)
Ideal Throughput
11 Mbit/s
54 Mbit/s
540 Mbit/s
Up to 8x g (432 Mbit/s)

4. Background Research Test Equipment and Environments
2 laptops
Linksys router (b/g), Linksys SRX router (MIMO – “n”)
Netgear card (b), Linksys card (g), Linksys SRX card (MIMO – “n”)
350 watt DC to AC inverter
Software: DU Meter, Bandwidth Monitor Pro, WatchWAN (didn’t work)
Environments
Outdoor: ex. Wal-mart? Office Depot?
Indoor: ex. Interior of parking lot?

5. Work Performed
Background work – collecting WiFi networking data and equipment
Original tests:
Indoor vs. Outdoor
2-floor
Elevator
New tests:
Vehicle Mobility
TCP vs. UDP
Times of the day (Centergy Building)

6. New or Revised Slide
Vehicle Mobility
Goal: To see how throughput was affected when data was transferred wirelessly between two vehicles in motion
2 cars in the Office Depot parking lot
Tested in 4 sets for each of b/g/n – 10 miles/hour following, 25 miles/hour following, 15 miles/hour opposite direction, and 75 miles/hour on I-75
5 loops each parking lot set
Parking area photo and diagram

9. Vehicle Mobility – 10 miles/hour
802.11g
802.11n

10. Vehicle Mobility – 25 miles/hour
802.11g
802.11n

11. Vehicle Mobility – Opposite
802.11g
802.11n

12. Vehicle Mobility – 70 miles/hour
New or Revised Slide
Vehicle Mobility – 70 miles/hour
We decided to go ahead and tackle one of our “future work” goals by taking our vehicle mobility testing to the highways of Atlanta
Chose three paths along I-75 that were approximately equal in length (about 4.5 miles)
Maintained an average speed of 70 miles/hour
Because the tests were performed in an environment where we had minor control, we did them twice each and picked the “better” data to discuss
Maps for our paths are shown on the next slide – arrows indicate direction of motion, and green/red dots indicate the points where we started/stopped data collection

13. Vehicle Mobility – 70 miles/hour
New or Revised Slide
Vehicle Mobility – 70 miles/hour
802.11n
802.11b, g

14. Vehicle Mobility – 70 miles/hour
New or Revised Slide
Vehicle Mobility – 70 miles/hour
802.11b
802.11g
802.11n

15. Vehicle Mobility – 70 miles/hour Results Discussion
New or Revised Slide
Traffic varied from a line-of-site connection between our two vehicles to 2-3 cars in between our vehicles, which resulted in a good representation of the real environment
Traffic influence on the data can be seen at the low points, where interference in the signal caused dips and/or drops
Interestingly, b and g averages were better at 70 miles/hour than our 10 and 25 miles/hour tests – this is probably due to environment in which our 70 mile/hour test the cars were always “aligned” (one behind the other), whereas in our 10 and 25 tests, the cars had significantly less harmonious motion (sharp turns, driving at angles, etc.). However, the MIMO test averages decreased in performance from b->g->n, which may reflect their design differences (use of multiple antennas)

16. Vehicle Mobility – Overall
New or Revised Slide

17. New or Revised Slide
TCP vs. UDP
Goal: To see how throughput differed when transferring a file directly (via TCP) versus viewing it in a streaming format (UDP)
UDP tests were performed using VideoLan VLC media player and monitored using Wireshark to ensure UDP connection
Indoor tests were redone to ensure absolute similarity in the test environment (only other network in the area was GTwireless at a 30% connection-availability)
Maintained constant 25ft distance
Used 500mb Video File – Taxi Driver DVD-Rip (Legal)

18. New or Revised Slide
TCP vs. UDP - Results

19. Times of the Day Centergy Building
Goal: To see how concentration of networks and business-day network activity affects throughput
Tested in an area of extremely concentrated WiFi network activity (5th floor hallway)
3 times of the day: approximately 10:30AM, 3:30PM, and 7:30PM
Monitored all other networks, and performed throughput measurements on both Channel 1 and Channel 6
Maintained 25ft distance for all testing

20. Times of the Day 10:30am Results

21. Times of the Day 3:30pm Results

22. Times of the Day 7:30pm Results

23. Times of the Day Overall Results

24. Summary and Conclusions
New or Revised Slide
Summary and Conclusions
Conclusions
Many results consistently followed theoretical limitation-estimates, but a couple of interesting anomalies
Mobility testing: Vehicle distance has more influence than speed
Time of Day testing: N fluctuates noticeably more than B/G, which performed similarly
At high-speeds (highway testing), the interference of traffic played a large role in the ability to transmit
Lessons Learned
Ideal test locations with good line-of-sight, limited traffic, and few network connections are difficult to find
Unexpected environmental factors: equipment failing, rough weather (rain)
Future Work
Multiple users, Additional interference testing

25. Questions?