1. doc.: IEEE 802.11-03/810r0 Submission October 2003 Scott Marston, Boeing Measuring IEEE 802.11 Performance in Airplanes Scott Marston Cabin Systems Tech Center Boeing Commercial Airplanes scott.e.marston@boeing.com

2. doc.: IEEE 802.11-03/810r0 Submission October 2003 Scott Marston, Boeing Outline What’s unique about WLAN in airplanes? Types of Airplane WLAN Applications –Open - passenger connectivity –Closed - crew, entertainment, system monitoring, etc. Problems with today’s measurements –Signal Strength, SNR, EVM, don’t correlate to throughput or stability –PER does correlate, but only after link has degraded Measurement Requests to 802.11k TG Measurement Access

3. doc.: IEEE 802.11-03/810r0 Submission October 2003 Scott Marston, Boeing What’s Unique About WLANs in Airplanes? The network moves among different regulatory domains while operating The airplane has its own regulatory requirements (EMI, potential failure modes, etc.) Very high potential client density –Multiple NICs in every passenger seat –Adjacent Channel Interference –Dynamic RF changes have correspondingly high impact Highly reflective physical environment Potential mix of “open” and “closed” systems No IT personnel on board to manage or troubleshoot network problems

4. doc.: IEEE 802.11-03/810r0 Submission October 2003 Scott Marston, Boeing Closed vs. Open Onboard WLAN Closed – Airline controls all radios –In Flight Entertainment data distribution to seat-mounted equipment –Crew Information Services to mobile crew terminals on board and on ramp –System Status / System Health Monitoring Open – Passengers carry on their own radios –Internet / Telephone Connectivity

5. doc.: IEEE 802.11-03/810r0 Submission October 2003 Scott Marston, Boeing Today’s Standard Measurements Dynamic Frequency Selection and Transient Power Control are good, in theory –Haven’t had the opportunity to test them yet Signal Strength (RSSI), Noise Level –No correlation with link performance –Not repeatable or linear in controlled conditions Error Vector Magnitude (EVM) –Only marginally better quality indicator than RSSI/noise Packet Error Rate –Does sometimes seem to correlate to link bit rate, but only after the link has degraded

6. doc.: IEEE 802.11-03/810r0 Submission October 2003 Scott Marston, Boeing Transmitter Power, Antenna Pattern/Orientation, Clear/Blocked Line-of-Sight, Absorbing/Reflecting Materials (e.g., Bodies in Seats), Co-Channel Interference, …all impact Signal to Noise (Interference) Ratio and Media Access Coordination Measured Airplane Performance 802.11a Performance in an Airplane Theoretical vs. Measured

7. doc.: IEEE 802.11-03/810r0 Submission October 2003 Scott Marston, Boeing RSSI Variation with NIC and Orientation -55 dBm -62 dBm -52 dBm -64 dBm -60 dBm -48 dBm -62 dBm -68 dBm Anechoic Chamber 3 meters distance Three Identical Client Cards OrientationNIC #30NIC #2NIC #16 1-60-50-55 2-68-60-58 3-54-47-55 4-65-60-68 5-62-53-65 6-48-45-50 7-62-60-65 8-64-63-70 12 dB variation under identical conditions

8. doc.: IEEE 802.11-03/810r0 Submission October 2003 Scott Marston, Boeing Single NIC – RSSI vs. Distance Orientation NIC #002 @ 3 m NIC #002 @ 6 m Delta, 3 m – 6 m 1-48-568 2-58-602 3-53-574 4-53-6613 5-53-52 6-47-569 7-52-6412 8-55-7419 Theoretically expect 6 dB power delta with twice the distance

9. doc.: IEEE 802.11-03/810r0 Submission October 2003 Scott Marston, Boeing 802.11b RSSI in a 747 RF Signal & Noise strength measured two ways: -Airmagnet site survey tool -Client software on individual laptops Airmagnet Signal Client Signal Client Noise Airmagnet Noise

10. doc.: IEEE 802.11-03/810r0 Submission October 2003 Scott Marston, Boeing High Client Density Implies Adjacent Channels in Close Proximity 802.11a Adjacent Channel Performance can be marginal…

11. doc.: IEEE 802.11-03/810r0 Submission October 2003 Scott Marston, Boeing Coverage Area vs. Interference Area Co-Channel Interference Boundary Co-Channel Interference Area Desired Coverage Area

12. doc.: IEEE 802.11-03/810r0 Submission October 2003 Scott Marston, Boeing Airplane Channel Fading 3640444852566064 Channel Fade of 10 dB or more is common in airplanes

13. doc.: IEEE 802.11-03/810r0 Submission October 2003 Scott Marston, Boeing EVM vs. Link Performance According to Vector Signal Analyzer, EVM for this burst was -14.056 dB, which corresponds to 18 Mb/sec link. But burst was transmitted and received successfully at 54 Mb/sec.

14. doc.: IEEE 802.11-03/810r0 Submission October 2003 Scott Marston, Boeing Measurement Wish List Network Regulatory Domain Awareness –Local Spectrum Usage Limits –Local Human Exposure Limits What would it take to add “Commercial Airplane” to the list of country codes? Adjacent Channel Interference Indication Meaningful Signal Strength (instantaneous and over time) Meaningful Signal Quality (instantaneous and over time) Why was current link rate selected? (e.g., 36 Mb vs. 54) Which diversity antenna was used to Transmit or Receive a given frame?

15. doc.: IEEE 802.11-03/810r0 Submission October 2003 Scott Marston, Boeing Measurement Wish List (cont’d) Ideally, there would be a way to tell clients that are not Associated in the Service Set to stay out of certain channels, and/or turn power down How about specifying some channel models, including a narrowbody and widebody airplane!

16. doc.: IEEE 802.11-03/810r0 Submission October 2003 Scott Marston, Boeing Measurement Access Most onboard network management is either completely local or completely remote: –Local: Maintenance personnel solve problems on ground between flights –Remote: NOC accesses airplane via satellite or gatelink Aviation Industry already working on network MIB access protocols (SNMP/RMON, etc.) through Airlines Electronic Engineering Committee (AEEC) ARINC standards –http://www.arinc.com/aeec/