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In-Vehicle Communication

In-Vehicle Communication. SAN Group RTS Regular Meeting Presentation December 2008. FLEXIBILITY. A simple example of a periodic message set (a low network load of nearly 35%) b r = 250 kbps C M = 125 x (4x10 -3 ) = 0.5 msec. N1. N2. N3. N4. N5. TDMA Round. 2.5. 0 msec.

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In-Vehicle Communication

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  1. In-Vehicle Communication SAN Group RTS Regular Meeting Presentation December 2008

  2. FLEXIBILITY • A simple example of a periodic message set (a low network load of nearly 35%) br = 250 kbps CM = 125 x (4x10-3) = 0.5 msec

  3. N1 N2 N3 N4 N5 TDMA Round 2.5 0 msec TTP/C Scheduling • The respective time-triggered schedule for the message set can be constructed as follows • TDMA rounds (here 1 TDMA round) form the cluster cycle that repeats itself t

  4. All M3 M2 M1 M2 M1 M2 M3 M4 M5 2.5 0.5 1.0 1.5 2.0 0 5.0 3.0 3.5 4.0 4.5 2.5 M1, M4 and M5 Rt (M2’’) = 2.5 Rt (M3’’) = 1 Rt (M2’’’) = 1.5 Rt (M1) = 0.5 Rt (M4) = 2 Rt (M5) = 2.5 0.5 N/w load = 35 % BU = 40 % M1 7.5 5.5 6.0 6.5 7.0 5.0 M2 M3 10.0 8.0 8.5 9.0 9.5 7.5 M1 M4 M5 12.5 10.5 11.0 11.5 12.0 10.0

  5. M3 M2 M2 M1 CAN Scheduling • Scheduling is based on FPNS • Unique priority for each message (lower id. means higher priority M1, M4 and M5 t (msec) …. M3 M1 M4 M5 M2 M1 M2 …. …. 9.5 10.0 10.5 11.0 11.5 12.0 12.5 0 5.0 5.5 6.0 6.5 8.0 8.5 9.0 Rt (M2’’) = 0.5 Rt (M3’’) = 0.5 Rt (M2’’’) = 0.5 Rt (M1) = 0.5 Rt (M4) = 1 Rt (M5) = 1.5 TT Results Rt (M2’’) = 2.5 Rt (M3’’) = 1 Rt (M2’’’) = 1.5 Rt (M1) = 0.5 Rt (M4) = 2 Rt (M5) = 2.5 N/w load = 35 % BU = 41 %

  6. A further example of a periodic message set (an average network load of nearly 50%) br = 250 kbps CM = 125 x (4x10-3) = 0.5 msec

  7. N1 (M1) N2 (M2) N3 (M3) N4 (M4) N5 (M5) N1 (M6) N2 (M7) N3 (M8) N4 (M9) N5 (M10) 2.5 0 5.0 t TTP/C Scheduling Cluster Cycle TDMA Round #1 TDMA Round #2

  8. All M1 M1 M2 M3 M4 M5 M6 M7 M8 M9 M10 0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 M1 5.0 5.5 6.0 6.5 7.0 7.5 8.0 8.5 9.0 9.5 10.0 M1 M3 M1 M1 M3 M2 M2 Node 1: M1, M6 Node 2: M2, M7 Node 3: M3, M8 Node 4: M4, M9 Node 5: M5, M10 M1, M4-7 M2 M3 Rt (M2’’) = 2.5 Rt (M3’’) = 1 Rt (M2’’’) = 1.5 Rt (M4’’) = 2 Rt (M5’’) = 2.5 Rt (M6’’) = 3 Rt (M7’’) = 1 Rt (M8’’) = 1,5 M1 M7 M4 M5 M6 M2 10.0 10.5 11.0 11.5 12.0 12.5 13.0 13.5 14.0 14.5 15.0 M2 M1, M4-7, M8 M1 M3 M2 15.0 15.5 16.0 16.5 17.0 17.5 18.0 18.5 19.0 19.5 20.0 M2, M3 N/w load = 50 % BU = 60 % M1 M8 M4 M5 M7 M6 M7 20.0 20.5 21.0 21.5 22.0 22.5 23.0 23.5 24.0 24.5 25.0 M2 M3 M1 25.0 25.5 26.0 26.5 27.0 27.5 28.0 28.5 29.0 29.5 30.0

  9. CAN Scheduling Rt (M2’’) = 0.5 Rt (M3’’) = 0.5 Rt (M2’’’) = 0.5 Rt (M4’’) = 1 Rt (M5’’) = 1.5 Rt (M6’’) = 2 Rt (M7’’) = 3 Rt (M8’’) = 3 TT Results Rt (M2’’) = 2.5 Rt (M3’’) = 1 Rt (M2’’’) = 1.5 Rt (M4’’) = 2 Rt (M5’’) = 2.5 Rt (M6’’) = 3 Rt (M7’’) = 1 Rt (M8’’) = 1,5 N/w load = 50 % BU = 63 %

  10. A further example of a periodic message set (a high network load of nearly 85%) br = 250 kbps CM = 125 x (4x10-3) = 0.5 msec

  11. N1 (M1) N2 (M2) N3 (M3) N4 (M4) N5 (M5) N1 (M6) N2 (M7) N3 (M8) N4 (M9) N5 (M10) 2.5 0 5.0 t TTP/C Scheduling Cluster Cycle TDMA Round #1 TDMA Round #2

  12. All M1-6 M1 M2 M3 M4 M5 M6 M7 M8 M9 M10 0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 M1 M2 M3 M4 M5 M6 5.0 5.5 6.0 6.5 7.0 7.5 8.0 8.5 9.0 9.5 10.0 M7 M1-6 M7 M8 M1-6, M7, M9-10 M8 M1-6 Node 1: M1, M6 Node 2: M2, M7 Node 3: M3, M8 Node 4: M4, M9 Node 5: M5, M10 M1-6, M9-10 Rt (M2’’) = 1 Rt (M3’’) = 1.5 Rt (M4’’’) = 2 Rt (M5’’) = 2.5 Rt (M6’’) = 3 Rt (M7’’) = 2.5 Rt (M8’’) = 1 Rt (M9’’) = 4.5 Rt (M10’’) = 5 Rt (M7’’’) = 1.5 Rt (M8’’’) = 3 Rt (M9’’’) = 4.5 Rt (M10’’’) = 5 Rt (M74) = 4.5 Rt (M84) = 5 M7 M8 M1 M2 M3 M4 M5 M6 M7 M9 M10 10.0 10.5 11.0 11.5 12.0 12.5 13.0 13.5 14.0 14.5 15.0 M7 M1-6, M9-10 M1 M2 M3 M4 M5 M7 M6 M8 15.0 15.5 16.0 16.5 17.0 17.5 18.0 18.5 19.0 19.5 20.0 M7, M8 M1 M3 M4 M5 M2 M6 M9 M10 20.0 20.5 21.0 21.5 22.0 22.5 23.0 23.5 24.0 24.5 25.0 N/w load = 85 % BU = 88 % M2 M3 M1 M4 M5 M6 M7 M8 25.0 25.5 26.0 26.5 27.0 27.5 28.0 28.5 29.0 29.5 30.0

  13. CAN Scheduling TT Results Rt (M9’’) = 4.5 Rt (M10’’) = 5 Rt (M9’’’) = 4.5 Rt (M10’’’) = 5 Rt (M74) = 4.5 Rt (M84) = 5 Rt(M9’’) = 4 Rt (M10’’) = 4.5 Rt (M9’’’) = 3.5 Rt(M10’’’) = 4 Rt (M74) = 0.5 Rt (M84) = 1 N/w load = 85 % BU = 91 %

  14. DEPENDABILITY • dependability = predictability + reliability • Predictable: Time-triggered manner, Predefined communication schedule • Reliability: fault confinement and fault tolerance (a fault does not reveal an error in the system)

  15. DEPENDABILITY • Let us suppose that retransmissions occur for M1 (2), M2 (3), and M5 (2) as a result of some fault (faulty message) starting from the time 5 msec on the high load CAN network, • Error recovery time ~ 17-31 bits • Result in messages M6 and M7 miss their deadlines • CRC, retransmission and error counter • Very difficult to solve the problem • “Babbling idiot” fault • The node has to diagnose itself

  16. For the TT network, • Retransmission is not allowed • No deadline miss for other messages • Because of predictability, easy to define and solve the problem • Replicated communication channels and nodes • CRC • Error handling strategy (fail silence and restart after a self test) • Fault confinement mechanisms: • Bus guardian • Membership functions • Clique avoidance algorithm • Error Containment (control and data errors) • CNI acts as control error containment boundaries • For data errors, High Error Detection Coverage Mode (HEDC) provides two mechanisms, • end-to-end CRC calculation by application task (two CRC calculations) • Time redundant execution of application tasks at the sender

  17. COMPOSABILITY • For TT network • Communication not depending on host controller and application software in it since • System integration does not change temporal behavior • Thus composable w.r.t. temporal properties • For CAN network • Temporal behavior is dependent on host controller

  18. EXTENSIBILITY • For the TT network, difficult to add new nodes and messages • Construction of new schedule (TDMA rounds that form cluster cycle) • Construction of Message Descriptor List (MEDL) • For CAN network it is an easy process, • Update for message priorities

  19. In-vehicle Systems’ Requirements* * T. Nolte, “Share-driven scheduling of embedded networks”, Doctoral dissertation No. 26, Mälardalen University, Sweden, 2006.

  20. INITIAL RESEARCH QUESTIONS • Integration, coherence and interoperability of different in-vehicle networks in a car • What makes FlexRay as a strongest candidate for in-vehicle networks instead of CAN? • Schedule construction • Fault tolerance • Performance analysis and comparison • Any possible improvement • Reservation based approaches for event-triggered traffic of hybrid communication networks

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