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SHDSL In the Railway Environment

SHDSL

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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

SHDSL

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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

V.23 1200bit/s SCADA/Telemetry/HABD multidrop over trackside pilot cables or FTN

SHDSL

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The Requirements

Open Standard Technology (COTS)Rail Network Capacity

Industrial robustness & reliability High isolation and EMC requirements

SHDSL

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SHDSL A Way Forward

SHDSL

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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

What is SHDLS?

SHDSL

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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

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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

POTS Speech band

Frequency

Rest of the available spectrum unused

MHz

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SHDSL Spectrum use

SHDSL Spectrum

Frequency Mhz 2.5MHz

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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

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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

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The success is in the connection setup!

SHDSL

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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

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

Overview G.hs

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Negotiation G.994.1 (G.hs)

Overview G.hs

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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

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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)

SHDSL

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UTPRS-422/485Blue HoseProfibus- DPTelephone wire CW1128, CW1308, CW1198Pilot cables

ANY Twisted Pair cable

BARBED WIRE !!!!!!!!!!!!

Oldest test cable 105 years! @ 2 Mbit/sLongest tested transmission 58km @ 192Kbit/S

What types of cables can be used?

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DDW-120+/225&226

Km/Miles

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Topologies

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Twisted Copper PairUp to 15.3 Mbit/s

Transparent Ethernet> 10km

Twisted Copper PairUp to 15.3 Mbit/s

Transparent Ethernet>10km

On each cable segment

Topologies

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DDW-226

Support for legacy RS232 build in

Twisted Copper PairUp to 15.3 Mbit/s

Transparent Ethernet> 10km

Redundant Ring

Legacy Serial Port – DDW-226

Ring Topology

Transparent Ethernet> 10km

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Using SHDSL

DDW-225/6

Twisted Copper PairUp to 15.3 Mbit/s

Legacy Serial Port – DDW-226

L3 Routing Topology

Transparent Ethernet> 10km

FTN or FTNe L3 Routing protocol

L3 Redundant networkL3 Mesh Topology

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Using SHDSL

L2 Diverse Topology

FTN or FTNe

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Thank you for listening