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SHDSL In the Railway Environment

SHDSL In the Railway Environment. History Lesson Analogue Leased lines. Dedicated lines between sites Lines are costly to maintain (BT will drop this service eventually) Bandwidth 33600 bps maximum, usually 9600bps Typically Master Slave relationship.

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SHDSL In the Railway Environment

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  1. SHDSL In the Railway Environment

  2. History Lesson Analogue Leased lines • Dedicated lines between sites • Lines are costly to maintain (BT will drop this service eventually) • Bandwidth 33600 bps maximum, usually 9600bps • Typically Master Slave relationship

  3. V.23 1200bit/s SCADA/Telemetry/HABD multidrop over trackside pilot cables or FTN Effective data rate; 1200/ number of outstation less pre / post amble time and inter- message gaps approx 50% e.g. 1200 / 10 =120 bps per unit 120bps less 50% = 60 Bits/s! RS-232 V.23

  4. The Requirements Open Standard Technology (COTS) Rail Network Capacity Industrial robustness & reliability High isolation and EMC requirements

  5. SHDSL A Way Forward

  6. What is SHDLS? • SHDSL stands for Symmetric High-Bitrate Digital Subscriber Loop • G.SHDSL was standardised in 2001 • Conforms ITU G.991.2 • Bi-directional data rates of 192kbit/s to 15.3Mbit/s over a single twisted pair • Upcoming ”Pair bonding” can be used to increase this data rate and provide link resilience

  7. Internationel Standards Why standard? Get away from proprietary solutions Increasing Interoperability  Joint development towards the same goal World-Wide COT’s equipment supply Focus on "spectral compatibility" Many different technologies have to coexist The introduction of new technology should not affect (s) the old New technologies must be designed to minimize the impact on future technologies

  8. Historical development POTS (Plain Old Telephone System) Limited to 4 kHz FTN(3.4kHz) Analogue Modem 300-33600 bps DSL Developed in the '80s Designed  to use all the available cable bandwidth In the Beginning Rest of the available spectrum unused Frequency MHz POTS Speech band

  9. SHDSL Spectrum use 2.5MHz Frequency Mhz SHDSL Spectrum

  10. SHDSL performance in the rail environment Performance Advanced modulation techniques “Spectral shaping” FEC (Forward Error Correction) provides robust transmission Error Rate 1000 times better than older Analogue modem, Unicode modulation schemes Error rates of 10^-7

  11. SHDSL in the rail environment Line Protection • TBU (Transient Blocking Unit) • Over Current / Voltage • Indirect Lightning Strikes • Power Induction • Short Circuits • Isolation to other interfaces

  12. The success is in the connection setup!

  13. Negotiation G.994.1 (G.hs) -> Data Mode Purpose:The units will arrive at the best possible link based on current cable-to-noise levels and the configured settings.G. Hs -> (Line Probing) -> G.hs -> Training -> Data Mode

  14. Negotiation Protocol G.994.1 (G.hs) -> Overview G.hs

  15. Negotiation G.994.1 (G.hs) Overview G.hs

  16. Negotiation G.994.1 (G.hs) What are they talking about: Max / Min Data Rate Training parameters Max / Average Latency Framing parameters Line Probe Sync Word Vendor ID Power Backoff Non-standardized information

  17. Choice of line speed Two Choices to set connection speed Fix Rate i.e. Lock unit to line speed Auto Rate (the DSL chip negotiation) DDW-225/226: fully automaticDDW-120 +: fully automatic (192-5696 kbps), semi-automatic (> 5696 Kbps)

  18. What types of cables can be used? UTP RS-422/485 Blue Hose Profibus- DP Telephone wire CW1128, CW1308, CW1198 Pilot cables ANY Twisted Pair cable BARBED WIRE !!!!!!!!!!!! Oldest test cable 105 years! @ 2 Mbit/s Longest tested transmission 58km @ 192Kbit/S

  19. DDW-120+/225&226 Km/Miles

  20. Topologies

  21. Topologies Twisted Copper Pair Up to 15.3 Mbit/s Transparent Ethernet > 10km Twisted Copper Pair Up to 15.3 Mbit/s Transparent Ethernet >10km On each cable segment

  22. Ring Topology • DDW-226 • Support for legacy RS232 build in Legacy Serial Port – DDW-226 Twisted Copper Pair Up to 15.3 Mbit/s Transparent Ethernet > 10km Transparent Ethernet > 10km Redundant Ring

  23. L3 Routing Topology Using SHDSL L3 Redundant network L3 Mesh Topology DDW-225/6 Legacy Serial Port – DDW-226 Twisted Copper Pair Up to 15.3 Mbit/s Transparent Ethernet > 10km FTN or FTNe L3 Routing protocol

  24. L2 Diverse Topology Using SHDSL FTN or FTNe

  25. Thank you for listening

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