“Fly-By-Wireless”
Chris Dimoulis
CS 441
Fall 2013

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Aircraft Systems (Current)
Benefits of Wireless System
Characteristics and Obstacles
Proposed Solutions

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Cables and Pulleys
 Direct connection from flight controls to control surface
Hydraulic
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 Direct manipulation of hydraulic actuators in flight controls
Fly-By-Wire
 Avionics Full Duplex Switched Ethernet (AFDX) used to send data from controls to actuators

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View and manipulate flight and engine data\
Old Systems
 Pressure systems for altitude and airspeed
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 Mechanical linkages for engine data (tachometer and manifold pressure)
New Systems
 Full Authority Digital Engine Control (FADEC)
 Automatically controls engine parameters, sends data to pilots through AFDX

 Cost from Weight Reduction
 Cable costs: A320: $14M B787: $50M [1]
 A380: 300 miles (500 km) of wire [2]
 Weight reduction means better fuel efficiency and increased space for revenue weight

 Improved Safety and Less Maintenance
 Less Wire degradation
 U.S. Navy: 78 aircraft made non-mission capable due to wiring, 1000 aborts from wiring faults [2]
 Wired interconnects and potential fires
▪ B 747 tank explosion due to arcing between fuel sensor wiring [3]

 Real-Time and Deterministic [1]
 Aircraft Network must behave in a predictable way
 Current system provides 100Mbps
 Latencies must be bounded and deadline constraints respected

 Reliability and Availability
 Probability of failure needs to be 10 -9 per flight hour [1]
 Fault Detection
 Long lifetime: Avionics system lifetime can be 20
– 30 years [1]

 Security [1]
 Data confidentiality to prevent passive eavesdropping
 Data integrity to guarantee data is not altered in transit
 Prevent unauthorized access to network

 Electromagnetic Compatibility [1]
 Deployment is in a harsh physical environment
 Large temperature and humidity changes along with vibrations
 Intense radio frequency noise

Table reproduced from [1]

 802.11n
+ Adequate Data rate
+ Uses Point Coordination Function for contention free mode
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+ Reliability: Automatic Retransmission ReQuest
(ARQ )
Not adapted for multicast [1]
High possibility of interference from common devices [1]

 ECMA-368 High Rate Ultra WideBand
+ Adequate Data rate and ranges
+ Distributed Reservation Protocol
 TDMA (Contention free)
+ More secure from “man-in-middle” than 802.11

 Begin with a hybrid system
 Full Duplex Ethernet Switch to connect clusters
Image reproduced from [1]

 MAC Protocol Proposals
 Need predictable behavior under real-time constraints
▪ Synchronization protocol for TDMA
 Reliability Mechanism for sending/receiving data
▪ Probability of failure to be 10 -9 per flight hour

 Synchronization Protocol
 IEEE1588 Wired network synchronization have been implemented within few nanoseconds precision
 IEEE1558 has reached less than 200 nanosecond precision for wireless network synchronization, however too many messages
 Proposed enhanced IEEE1588

 Synchronization Protocol
 Master/Slave/Passive node
 If slave node fails passive node can fill in
Image reproduced from [1]

 Reliability Mechanism
 Need adequate acknowledgement and retransmission mechanism
 Communication is multicast
▪ Multiple ACKs colliding?
▪ Overhead from sender needing to receive all ACKs

 Reliability Mechanism
 Designated “leader” of cluster
 ACK from leader, NACK from rest
 If sender hears NACK or nothing (due to
ACK/NACK collision) then it will retransmit
Image reproduced from [1]

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ECMA-368 can provide adequate data rate, contention free, and security properties
Needs predictable real-time behavior
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 Enhanced IEEE1588 synchronization
Reliable data reception
 Cluster leaders with ACK/NACK messages

[1] D. Dang, A. Mifdaoui,and T. Gayraund, “Fly-By-Wireless for Next
Generation Aircraft: Challenges and Potential solutions.” (In Press: 2012)
In: Wireless days conference, 21-23 Nov 2012, Dublin, Ireland
[2] R. K. Yedavalli, R. K. Belapurkar, “Application of Wireless Sensor
Networks to Aircraft Control and Health Management.” Journal of control
Theory & Applications. February 2011; 9(1):28.
[3] M. Panitz, D. Hope, W. Crowther, et al. “The opportunities and challenges associated with wireless interconnects in aircraft.” Proceedings Of The
Institution Of Mechanical Engineers -- Part G -- Journal Of Aerospace
Engineering (Sage Publications, Ltd.) [serial online]. April 2010;224(4):459.