Radio bearer capacity and planning for ETCS · PDF fileRadio bearer capacity and planning for...

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ALSTOM HÖRMANN FUNKWERK KÖLLEDA KAPSCH MARCONI MOBILE ACCESS NORTEL NETWORKS SAGEMSIEMENS INFORMATION & COMMUNICATION SIEMENS TRANSPORTATION SYSTEMS 1

Radio bearer capacity and planning for ETCS

Solutions for BSS redundancy

Eric SAUTHIERLaurent POUTAS

10th December 2003

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AgendaAgenda

IntroductionØ Targets of BSS redundancy

Single coverage architecturesØ Definition, Pros & Cons

Double coverage architecturesØ Definition, Pros & Cons

Capacity aspectsØ Theoretical capacities vs. terrain realities

Border issuesØ Illustration through Basel city

Conclusion

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IntroductionIntroductionTarget of BSS redundancyTarget of BSS redundancy

• The very purpose of GSM-R is to ensure safe and reliable communicationsfor railways environment

è ETCS level 2/3 maximum non-availability times:

• The RF interface is a key point for reliability aspects:– Open interface exposed to external perturbations– Lots of on-field equipments prone to disturbances (BTS, transmissions; antennas)– Accomodating small spectrum allocations (4 MHz for standard GSM-R)

è Redundancy is aimed at improving system overall availability

ETCS 2/3

Other voice/data services

4 hours per 10 years (i.e. 99.995 % availability)

8 hours per year (i.e. 99.91 % availability)

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Single coverage architecturesSingle coverage architecturesLow overlap sitesLow overlap sites

• Single layer, normal cell overlapPROS

– Low cost– Easier to parameter– Most efficient spectrum use for capacity– Fewer sites acquisition

CONS– Loss of service if a BTS is down

BSC A MSC A

Safety first!If the ETCS service isdown, trains will stop

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Single coverage architecturesSingle coverage architecturesHigh overlap sitesHigh overlap sites

• Single layer, high cell overlap (if a cell is missing, service is still ensured)PROS

– BTS redundancy– Medium cost

CONS– No redundancy in case of any BSS element failure, except for a single BTS– Some impact on QoS (high number of HO)– Less efficient spectrum usage (large cell overlap)– Numerous site acquisitions– Medium parameter settings complexity (definition & maintenance)

BSC A MSC A

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Double coverage architecturesDouble coverage architecturesCo-located sitesCo-located sites

• Dual layers, co-located BTSPROS

– Full system redundancy available– Low number of site acquisition (if site/mast sharing)

CONS– Higher cost– Parameter settings more complex– Loss of service if a physical site is blown

BSC B MSC B

BSC A MSC A

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Double coverage architecturesDouble coverage architecturesInterleaved sitesInterleaved sites

• Dual layers, interleaved BTSPROS

– Full system redundancy available– Service is still ensured if a site is blown

CONS– Higher cost– Less efficient spectrum usage (multi-server effect)– Parameter settings more difficult– Lots of site acquisition

BSC BMSC B

BSC A MSC A

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Capacity AspectsCapacity Aspects

Theoretical capacities– Planning in ideal conditions:

• single straight track,• flat & homogenous terrain

– The ratio of available frequencies to the distance remains the sameè Only minor capacity differences among the different architectures.

Real world– Complex topology– Crossings, nodes negative impact over C/I– Obstacles, Tunnels

• Need to manage mobility (High speed, HO, ..) highly depends on C/I

è Although practically achievable values are lower,the flexibility of GSM-R redundant architectures allowsto offer good capacity even with strong terrain constraints

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ETCS solution in a difficult case:ETCS solution in a difficult case:Spectrum sharing in BaselSpectrum sharing in Basel

Case studyImplementation of ETCS facing terrain constraints

Basel, Switzerland gathers difficulties:– Complex spectrum sharing at border– Unfavourable topology: 3 countries, many tracks

Rhein

Railways

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DFF973DDSUI972

SUISUISUI971DDSUI970DDF969

SUISUISUI968DDSUI967DDF966

SUISUISUI965DFF964DDF963

SUISUISUI962SUIFF961DFF960

SUISUISUI959SUIFF958SUISUISUI957SUIFF956

D-SUIF-D-SUIF-SUIARFCH

European spectrum sharingagreement (1999)

• 9 channels for F-SUI bordersituation

• Only 6 channels for F-D-SUIborder situation !

• 9 channels for D-SUI bordersituation

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Frequency reuse policy

• 9 channels to use for F-SUI and D-SUI situation

– Redundant architecture on trackspossible

– Redundant architecture for clusterplanning not possible

• Only 6 channels to use forF-D-SUI situation !

– Redundant architecture on tracks onlypossible under ideal conditions

– No complete cluster 7 planningpossible

13

45

6

2

13

45

6

2

1/25

67

8

3/49

1/25

67

8

3/49

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• Frequency planning of this high traffic area with only 6 possible channels !

D-SUIF-D-SUIF-SUI

69

9

Solution: Cross border agreement between the three operatorsè common planning of Basel area (F/D/SUI)

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Meeting ETCS challenges with GSMRMeeting ETCS challenges with GSMRReliability and capacityReliability and capacity

• GSMR meets ERTMS reliability targets thanks to redundancysolutions available at each BSS level (TRX, BTS, BSC, MSC,transmissions).

• Flexible redundant coverage solutions: they can be mixed to tightlymeet terrain constraints and customer requirements.

• Very good integration of GSMR track coverage with tunnel and indoorcoverage solutions.

• GSM-R has a high spectrum efficiency in traffic hot spots thanks tothe reuse of public GSM experience.

• One active TRX per site solutions available to fit ERTMS over tightspectrum allocations.

• GSM-R redundancy solutions offer the best answer toERTMS requirements, meeting expectations in a wide rangeof operational situations.

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Meeting ETCS challenges with GSMRMeeting ETCS challenges with GSMRConclusionConclusion

GSM-R flexible architectures can fulfil ETCS needs,from a low cost, single coverage solution to a higher cost, fullyredundant solution guaranteeing ETCS service.

CapacityReliability

Cost

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