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PTC Radio and System Architecture

PTC Radio and System Architecture. Date: 2011-07-14. Authors:. Abstract.

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PTC Radio and System Architecture

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  1. PTC Radio and System Architecture Date: 2011-07-14 Authors: Jia-Ru Li, Lilee Systems

  2. Abstract • Mandate : United States President George Bush signed the railway safety bill [1] into law on October 16, 2008 after the collision of a Metrolink passenger train and a Union Pacific freight train in Los Angeles, California, resulted in the deaths of 25 and injuries to more than 135. The bill mandates the implementation of Positive Train Control (PTC)[2]. • Equipment : PTC involves four components • Equipment deployed on the locomotive • Equipment deployed at trackside houses • Equipment deployed at the control center • A bi-directional wireless data link • Deadline : The United States Congress set a • deadline of Dec 31, 2015 for the implementation of PTC technology. • Estimated 20,000 locomotives and 100,000 miles of track would need to be equipped with PTC [7] Jia-Ru Li, Lilee Systems

  3. System Architecture Office segment Dispatch System Back office Server Communication segment Locomotive segment Wayside segment Jia-Ru Li, Lilee Systems

  4. System Architecture (4 Segments) • Central Traffic Segment: • Dispatching service, central monitoring, back office servers • Locomotive Segment: • On-board train control computer, braking curve, movement authority • Wayside Segment: • Track switches, railroad crossing, signals • Communication Segment: • Mission critical radio that requires a standards committee to select “best of the breed” technology and a common air interface • IEEE LMSC has track records in creating standards for millions of devices to interoperate. (Bluetooth, WIFI, WIMAX, etc) Jia-Ru Li, Lilee Systems

  5. Comm for Office/Locomotive/Wayside Back Office Server Temp Speed Restriction Network Mgmt Service Database Maintenance Dispatcher Metro Ether Router Office Field Loco-motive BS BS BS BS BS BS WS WS WS fiber Jia-Ru Li, Lilee Systems

  6. Real World Validation in Rain & Fog Mobile (3 watt) Base station Mobile (10 watt) 10 miles 10 miles 19.2 miles 19.2 miles Both uses 3 dbi Omni Antenna(5ft), cable 15 ft Jia-Ru Li, Lilee Systems

  7. PTC Radio Interface Requirement • Supports various modulation (ex: GMSK, QPSK ….) • Supports Forward Error Correction (FEC) • Supports different channel spacing, different carrier • Supports link layer fragmentation • Supports • QoS (11e) • Link Layer Security (11i) • Supports higher mobility speed than conventional WIFI • Supports 64 time slot/sec (optional to support 128 slots/sec) • Supports priority-based association (Hi/Lo contention slots) • Supports Asymmetric uplink/downlink speeds • Handover (Pre-auth) • Link measurement (11k) Jia-Ru Li, Lilee Systems

  8. PHY using GMSK Jia-Ru Li, Lilee Systems

  9. PHY using QPSK Jia-Ru Li, Lilee Systems

  10. Low MAC protocol (CSMA/TDMA hybrid) 1 second 16 slots 16 slots 16 slots 16 slots 16 9 13 5 16 2 9 6 13 5 10 2 9 14 6 13 3 10 2 7 14 6 11 3 4 10 15 7 1 14 11 3 8 12 4 15 7 1 1 5 11 16 8 12 4 15 8 12 5 16 9 13 2 6 10 14 3 7 1 11 4 15 8 12 data slot Beacon contention slot # show basestation ptc station_table station slot type tx/rx self cast CRC error time to expired (ms) ========================================================================================= beacon 00-00 0 T 1 1 0 never 01 01-01 3 T 1 0 0 47258 02 02-02 3 T 1 0 0 57852 …… 30 30-30 3 T 1 0 0 48584 brdcst 31-31 3 T 1 1 0 never Reg-Hi 32-32 3 R 1 0 0 never 01 33-33 3 R 1 0 0 41474 02 34-34 3 R 1 0 0 53135 …… 28 60-60 3 R 1 0 0 48179 29 61-61 3 R 1 0 0 56440 30 62-62 3 R 1 0 0 52599 Reg-Lo 63-63 3 R 1 0 0 never ========================================================================================= TransAir mode Jia-Ru Li, Lilee Systems

  11. High MAC protocol CRC-16 implementation • High MAC support • Beacon • Probe request/response • Association/Authentication • Hand off request/response • Action Frame • Support MIB & PICS • Station table • Based on Std 802.11-2007 Association State Machine Jia-Ru Li, Lilee Systems

  12. Link Level Fragmentation 1500 byte = 13 fragment takes 27s for round trip 56 byte = 1 fragment takes 500 ms for round trip 1500 bytes (or bigger) IP/TCP Session Payload crc # ping -s 1500 10.3.10.1 PING 10.3.10.1 (10.3.10.1) 1500(1528) bytes of data. 1508 bytes from 10.3.10.1: seq=0 ttl=255 time=26728 ms 1508 bytes from 10.3.10.1: seq=1 ttl=255 time=26152 ms 1508 bytes from 10.3.10.1: seq=2 ttl=255 time=26024 ms 1508 bytes from 10.3.10.1: seq=3 ttl=255 time=26772 ms 1508 bytes from 10.3.10.1: seq=4 ttl=255 time=26966 ms 1508 bytes from 10.3.10.1: seq=5 ttl=255 time=26724 ms 1508 bytes from 10.3.10.1: seq=6 ttl=255 time=26952 ms 1508 bytes from 10.3.10.1: seq=7 ttl=255 time=26956 ms 1508 bytes from 10.3.10.1: seq=8 ttl=255 time=26238 ms 1508 bytes from 10.3.10.1: seq=9 ttl=255 time=26384 ms 1508 bytes from 10.3.10.1: seq=10 ttl=255 time=26466 ms # ping –s 56 10.3.10.1 PING 10.3.10.1 (10.3.10.1) 56(84) bytes of data. 64 bytes from 10.3.10.1: seq=0 ttl=255 time=420 ms 64 bytes from 10.3.10.1: seq=1 ttl=255 time=435 ms 64 bytes from 10.3.10.1: seq=2 ttl=255 time=492 ms 64 bytes from 10.3.10.1: seq=3 ttl=255 time=539 ms 64 bytes from 10.3.10.1: seq=4 ttl=255 time=535 ms 64 bytes from 10.3.10.1: seq=5 ttl=255 time=404 ms 64 bytes from 10.3.10.1: seq=6 ttl=255 time=494 ms 64 bytes from 10.3.10.1: seq=7 ttl=255 time=496 ms 64 bytes from 10.3.10.1: seq=8 ttl=255 time=516 ms 64 bytes from 10.3.10.1: seq=9 ttl=255 time=528 ms 64 bytes from 10.3.10.1: seq=10 ttl=255 time=542 ms Jia-Ru Li, Lilee Systems

  13. Standards based Security – 802.1x (11i) Jia-Ru Li, Lilee Systems

  14. Standardization Drives Volume • History tells us the 2nd hump comes from standardization • It helps the customer to gain confidence in a given technology and willing to invest engineering resources • Standardization helps other industries to adopt the same technology and drive more usage cases • It usually happens 2-3 years after initial usage Jia-Ru Li, Lilee Systems

  15. ERTMS (European Rail Traffic Management System)http://en.wikipedia.org/wiki/European_Rail_Traffic_Management_System • The two main components of ERTMS • ETCS (European Train Control System) - a standard for on-board train control( http://en.wikipedia.org/wiki/European_Train_Control_System) •  GSM-R – GSM standard modified for railway operations • Specification • Modulation is GMSK . FDD duplex • TDMA frames with a period of 4.615 ms. Each TDMA frame is divided in 8 time-slots (577 µs each), carrying 148 bits • Frequency Band • In Europe — 876 MHz — 880 MHz: data transmission (uplink) — 921 MHz — 925 MHz: data reception (downlink) • In China: a 4 MHz of the E-GSM band (900 MHz-GSM) • In Australia, it is being implemented using 1800MHz band Jia-Ru Li, Lilee Systems

  16. Radio Interoperability Requirement[6] • Interoperability is achieved through an open, peer reviewed process • IEEE selects best of breed technology with cost maturity in mind • IEEE provides long term spec maintenance & administration • Interoperable mechanisms • By single vendor – Limited competition. High risk and high cost • By closed industry consortium – Not enough radio experts or researchers • By open Industry consortium (eg. ERTMS[4]) – allow peer reviews • By standards body(eg. IEEE) – allow diff industry to share spec (rail & sensor) • By national body(ANSI, ITU) – allow countries to adopt as national standard • Ultimate Goal: Interchangeability – allows end users to select different vendors’ products based on the same industry standards. • Interchangeability supports free market response Jia-Ru Li, Lilee Systems

  17. Why IEEE and LMSC? • Rail related standards AREMA/AAR/ITC[5] (similar to ETCS) Radio related standard  IEEE (similar to GSM-R) • Reuse mature technology from IEEE LMSC WGs • Association, Beacon, Information Element, interface MIB • Authentication, security (802.1x, 802.11i), 4-way handshake • PICS (Protocol Implementation Conformance Statement proforma) • Small modification to low MAC and PHY • CSMA+TDMA hybrid • BPSK/QPSK with GMSK for backward compatibility • Full duplex or half duplex • TDD (similar to WIFI) • Meets different FCC subpart rules Jia-Ru Li, Lilee Systems

  18. Relationship with existing TG/WG • S1G: Study Group Sub 1 GHz Operation • Study to determine if PTC requirement is already included in S1G • If not, add PTC requirement into PAR and 5C • TGaf : TV White Spaces • meet the legal requirements for channel access and coexistence in the TV White Space • TGae:  Prioritize 802.11 management frames  • Defines mechanisms for sending the PTC management frame using existing mechanisms for medium access • Decide if new SG/Adhoc group should be established to facilitate the Congressional mandate (RSIA’08) Jia-Ru Li, Lilee Systems

  19. Straw Poll #1 • Do you think 0WNG should invite various industry experts in railroad and others (eg. sensor) to provide more information about requirements? • Agree: • Disagree: • Abstain: Jia-Ru Li, Lilee Systems

  20. Straw Poll #2 • Assuming the results of Straw Poll #1 are affirmative, do you agree that the IEEE 802.11 WG should form a study group to pursue this task? • Agree: • Disagree: • Abstain: Jia-Ru Li, Lilee Systems

  21. References • RSIA’08 - Summary of the Rail Safety Improvement Act of 2008 http://www.fra.dot.gov/downloads/RSIA%20Overview%20031009.pdf • PTC - Positive train control http://en.wikipedia.org/wiki/Positive_train_control • ACSES - Advanced Civil Speed Enforcement System http://en.wikipedia.org/wiki/ACSES • ERTMS - European Rail Traffic Management system http://en.wikipedia.org/wiki/European_Rail_Traffic_Management_System • ITC Draft Standards http://aar-x.arinc.net • Interoperable Positive Train Control http://www.billpetit.com/Papers/2009%20AREMA%20Conf/Petit_2009_AREMA_ICBS_Paper_V2.pdf • Signal and Train Control http://www.fra.dot.gov/downloads/research/PTC_Technical.pdf Jia-Ru Li, Lilee Systems

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