“Fly-By-Wireless”

Chris DimoulisCS 441

Fall 2013

Aircraft Systems (Current)Benefits of Wireless SystemCharacteristics and ObstaclesProposed Solutions

Cables and Pulleys Direct connection from flight controls to

control surface Hydraulic

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

View and manipulate flight and engine data\

Old Systems Pressure systems for altitude and airspeed 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: $14MB787: $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+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 canfill 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]

ECMA-368 can provide adequate data rate, contention free, and security properties

Needs predictable real-time behavior 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.