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Comparison of Coloured Section Ring with Classical SDH Ring
Architectures
Tivadar JAKAB (speaker)
Technical University of Budapest Department of Telecommunications
Laurent. BLAIN, Andre HAMEL, Alain SUTTER France Telecom CNET
(Coloured Section Ring Architecture is covered by a patent owned by France Telecom)
Objectives
• Introduction of Coloured Section Ring Architecture
• Networking Aspects of Coloured Section Ring Architecture
• New Levels of Optimisation in Network Dimensioning
• Comparison Case Studies to Evaluate Coloured Section Ring Architecture
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SDH Ring Networks
• SDH - transmission networks in the present and in the future
• well known advantages (flexible configura- tion, good support for management, world- wide standard, etc..)
• SDH self-healing ring architectures are effec- tive solutions for full protected transmission networks
Limitations of SDH Rings
• Difficult to upgrade
• Uniform node architecture can conflict with the different demand loads of nodes
• In most popular two-fibre bi-directional rings (PP, MSSP) in case of different demand
patterns the ring link capacity often limits the utilisation of the ADM capacity
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WDM based ring architectures
• Coloured Demand Ring
– point to point approach
– wavelengths are assigned to demands
– flexible node architecture - easy to upgrade
• Coloured Section RIng
– transparent ring approach
– wavelengths are assigned to ring links
– optimal node visiting order, minimize transit in nodes - good SDH ADM capacity utilisation
Coloured Section Rings
• Basic idea
– SDH-transparent ring architecture – Different wavelength to each ring link
– Transit routes realised via the electrical ADMs
• Protection:
– Duplicated optical interfaces on the both sides of the electrical ADMs
– Linear multiplex section protection
• Extra features:
– Logical ring structure can be different from the physical one
– Multiplied insertion of nodes into the same ring – Capacity for protection separated in wavelength
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Coloured Section Rings (cont.)
• Advantages:
– Increased ring capacity, full electrical ADM capacity for working connections
– Optimal logical order of the ring nodes, minimised transit traffic in the nodes
• Drawbacks:
– Extra optical interfaces (in ADMs for linear MSP)
– MSP provides incomplete protection (no protection against transit node failures), however mixed
application of MSP and PP can solve the problem – Multiplied number of spare parts (optical interfaces
with transmitters at selected wavelengths)
Coloured Section Rings (cont.)
• Typical applications
– metropolitan area interoffice networks
• Planning:
– planning goal - ring dimensioning
– new levels of optimisation (connection order of nodes, node multiplication in the same ring)
– non-linear sub-problem: optimal node order
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Node Architecture in Coloured
Section Ring
Routing in
Coloured Section Ring
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Protection in Coloured Section
Ring
Comparison Case Studies
• Different comparison aspects
– Comparison of ADM capacity utilisations
» theoretical lower bound of the number of needed SDH ADMs per node can be obtained with a simplified approach, the number of ADMs in different ring architecture compared on that basis
– Total cost for SDH ADMs in different ring architecture – Cost gap for OADMs of Coloured Section Rings
» difference between the cost of SDH and CS rings devided by hte number of active nodes in CS ring
– Optimal tributary capacity of SDH ADMs in Coloured Section Rings
• Relative cost comparison
– Comparison of two-fibre path protected (PP) and multiplex section shared protected (MSSP) classical SDH rings with Coloured Section rings
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Network cases
• Assumptions for WDM-based rings
– Number of available wavelengths: 8
– Limited span length, no extra amplification needed (metropolitan area)
• Real network clusters from French and Hungarian metropolitan area networks
• Demands in VC4 units
• Cluster sizes from 4 to 8 nodes
• Total demand for clusters from 35 to 75 VC4
Cost model
• Only installation cost
• Simplified network cost : only equipment cost (SDH ADMs) considered, fibre and
management costs not included
• Equipment costs of different ADM
configurations (with two or four optical
interfaces, with different tributary capacities, etc.) based on functional equipment models
• Different cost ratios between electrical and optical parts studied
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Analysis of Results
• Classical SDH ring results obtained with help of a planning tool ANOP
– developed by France Telecom CNET
– based on mixed programing and simulated anneling
• CS ring results obtained with help of integrated transmission planning tool PLANET
– developed by Dept. of Telecomm., TUB
– applied in planning activities of Hungarian Telecom Co.
– based on heuristics and graph algorithms
• Comparison of ADM capacity utilisations (PP, MSSP and Coloured Section Rings)
– theoretical optimum can be achieved with coloured section ring architecture in all studied cases
Analysis of Results (cont.)
• Total cost for SDH ADMs
– if the relative cost of the optical part of the SDH ADM less then 1/2 the WDM-based CS rings are with
comparable costs
• Cost gap for OADMs in WDM-based CS rings
– at least 15-25% of the SDH ADM cost is available for OADMs (OADM built up from passive elements, so 5% of the SDH ADM cost seems to be enough)
• Optimal tributary capacity of SDH ADMs in Coloured Section Rings
– higher tributary capacities (24 or 32 STM1s) optimal for smaller clusters (up to 6 nodes) with large total demand because of the lower transit traffic in nodes
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Utilisation of ADM Capacities in Different SH Rings
0 10 20 30 40 50 60 70 80 90 100
1 2 3 4 5 6 7 8 9 10 11 12
Network Cases
Efficiency of Installed ADM Capacity Utilisation [%]
PP Ring [16]
MSSP Ring [16]
CS Ring [16]
Network Cost Comparison (Cost option 1:1)
0 2 4 6 8 10 12 14 16 18 20
Total ADM Cost
PP Ring [16]
MSSP Ring [16]
CS WDM Ring [16]
Basic SDH ADM relative cost components:
two optical terminations: 0.5, electrical part with 16 STM-1s tributary capacity: 0.5
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Network Cost Comparison (Cost option 1:2)
0 2 4 6 8 10 12 14 16 18 20
1 2 3 4 5 6 7 8 9 10 11 12
Network Cases
Total ADM Cost
PP Ring [16]
MSSP Ring [16]
CS Ring [16]
Basic SDH ADM relative cost components:
two optical terminations: 0.33, electrical part with 16 STM-1s tributary capacity: 0.66
Network Cost Comparison (Cost option 1:3)
0 2 4 6 8 10 12 14 16 18 20
Total ADM Cost
PP Ring [16]
MSSP Ring [16]
CS WDM Ring [16]
Basic SDH ADM relative cost components:
two optical terminations: 0.25, electrical part with 16 STM-1s tributary capacity: 0.75
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Network Cost Comparison (Cost option 1:4)
0 2 4 6 8 10 12 14 16 18 20
1 2 3 4 5 6 7 8 9 10 11 12
Network Cases
Total ADM Cost
PP Ring [16]
MSSP Ring [16]
CS WDM Ring [16]
Basic SDH ADM relative cost components:
two optical terminations: 0.2, electrical part with 16 STM-1s tributary capacity: 0.8
Cost Gap for OADMs by Node (Cost option 1:1)
-0.40 -0.30 -0.20 -0.10 0.00 0.10 0.20 0.30 0.40 0.50
1 2 3 4 5 6 7 8 9 10 11 12
Cost Gap for One Additional OADM
Trib.: 16 STM-s1 Trib.: 24 STM-s1 Trib.: 32 STM-s1 (Basic SDH ADM relative cost components:
two optical terminations: 0.5, electrical part with 16 STM-1s tributary capacity: 0.5)
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Cost Gap for OADMs by Node (Cost option 1:2)
-0.30 -0.20 -0.10 0.00 0.10 0.20 0.30 0.40 0.50 0.60
1 2 3 4 5 6 7 8 9 10 11 12
Network Cases
Cost Gap for One Additional OADM
Trib.: 16 STM-s1 Trib.: 24 STM-s1 Trib.: 32 STM-s1 (Basic SDH ADM relative cost components:
two optical terminations: 0.33, electrical part with 16 STM-1s tributary capacity: 0.66)
Cost Gap for OADMs by Node (Cost option 1:3)
-0.30 -0.20 -0.10 0.00 0.10 0.20 0.30 0.40 0.50 0.60 0.70
1 2 3 4 5 6 7 8 9 10 11 12
Cost Gap for One Additional OADM
Trib.: 16 STM-1s Trib.: 24 STM-1s Trib.: 32 STM-1s (ADM Relative Cost Components: Optical terminations: 0.25, Electrical part: 0.75)
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Cost Gap for OADMs by Node (Cost option 1:4)
-0.20 -0.10 0.00 0.10 0.20 0.30 0.40 0.50 0.60 0.70
1 2 3 4 5 6 7 8 9 10 11 12
Network Cases
Cost Gap for One Additional OADM
Trib.: 16 STM-s1 Trib.: 24 STM-s1 Trib.: 32 STM-s1 (Basic SDH ADM relative cost components:
two optical terminations: 0.2, electrical part with 16 STM-1s tributary capacity: 0.8)
Cost Gap for OADMs by Node (ADM trib. cap.: 16 STM-1 )
-0.40 -0.30 -0.20 -0.10 0.00 0.10 0.20 0.30 0.40 0.50 0.60
1 2 3 4 5 6 7 8 9 10 11 12
Relative Cost Gap for One Additional OADM
Rel. opt. cost: 0.5 Rel. opt. cost: 0.33 Rel. opt. cost: 0.25 Rel. opt. cost: 0.2
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Cost Gap for OADMs by Node (ADM trib. cap.: 24 STM-1 )
-0.40 -0.20 0.00 0.20 0.40 0.60 0.80
1 2 3 4 5 6 7 8 9 10 11 12
Network Cases
Relative Cost Gap for One Additional OADM
Rel. opt. cost: 0.5 Rel. opt. cost: 0.33 Rel. opt. cost: 0.25 Rel. opt. cost: 0.2
Cost Gap for OADMs by Node (ADM trib. cap.: 32 STM-1 )
-0.20 0.00 0.20 0.40 0.60 0.80
1 2 3 4 5 6 7 8 9 10 11 12
Relative Cost Gap for One Additional OADM
Rel. opt. cost: 0.5 Rel. opt. cost: 0.33 Rel. opt. cost: 0.25 Rel. opt. cost: 0.2
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Optimal Tributary Capacities for Coloured Section Rings
0 2 4 6 8 10 12
1 2 3 4 5 6 7 8 9 10 11 12
Network Cases
Total Number of SDH ADMs
Trib.: 16 STM-1s Trib.: 24 STM-1s Trib.: 32 STM-1s
Efficiency of ADM Capacity Utilisation in CS WDM Rings Realized with Different ADMs
0 10 20 30 40 50 60 70 80 90 100
1 2 3 4 5 6 7 8 9 10 11 12
Efficiency of the Utilisation of Installed ADM Capacities [%]
Trib. :16 STM-1s Trib.: 24 STM-1s Trib.: 32 STM-1s (100% = Installed ADM capacity is equal to the theoretical minimum ADM capacity)
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Conclusions
• Coloured Section Rings provide the best SDH ADM capacity utilisation from the studied
architecture
• Competitive cost of Coloured Section rings strongly depends on the cost of optical line interfaces
• If the relative cost of the optical part of the SDH ADM not higher than the 1/2 of the total cost the Coloured Section Rings are with
comparable costs of classical SDH rings
Conclusions (cont.)
• Coloured Section rings built up of standard SDH equipment and passive optical
components (except optical amplifiers, if needed)
• protection solutions based on well known
linear multiplex section protection techniques
• Coloured Section Ring architecture provides a cost effective solution for self-healing high speed network applications in the near future
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Node Architecture in Coloured
Demand Ring
Coloured Demand Ring
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Network Cost Comparison (Cost option 1:3)
0 5 10 15 20 25
1 2 3 4 5 6 7 8 9 10 11 12
Network Cases
Total ADM Cost
PP Ring [16]
MSSP Ring [16]
CS WDM Ring [16]
CS WDM Ring [24]
CS WDM Ring [32]
CD WDM Ring
