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Mitcsenkov Attila (BME TMIT, High Speed Networks Laboratory) 21 October 2014
Computer aided network planning and techno-economic
assessment of next generation optical access networks
Complex network planning methodology and framework
Image: Sumitomo Electric Lightwave
• Optical fiber “approaches” the customers:
- FTTC FTTB FTTH
• A.) Point-to-point Dedicated optical fiber to all customers
• B.) Point-multipoint systems Shared optical “feeder network”
- Active (e.g. Active Ethernet)
- Passive (PON)
Next Generation Access (NGA) networks
• „History”: ABON, BPON
• Currently deployed: - EPON (USA & Asia) / GPON (EU)
• Recent „upgrade”: - NGPON-1 10G EPON / 10G GPON
• Near future: - NGPON-2 TWDM PON, 40G
• Future development: - WDM PON (“virtual point-to-point”)
- Colorless vs. Tunable: no clear winner yet…
Passive Optical Networks (PON)
• Next Generation Access networks
- Short / near term demand: 100 Mb/s – 1 Gb/s per customer
- The common phrase: optical access is a “must”
• „FTTH boom”:
- Global Industry Analysts Inc.: 183.9 million FTTH/B subscriptions worldwide by 2015
- Deutche Telekom “will invest almost 30 billion euros over the next three years in order to ensure “the future of telecommunications.” (2012 – FTTC VDSL, Fiber & LTE)
- …
• What does it cost?
• Who will pay for it?
• Does it make sense?
Network design – The Motivation
• Economic aspects:
- Cost estimation
- Return of Investment, Cash Flow, … Business Case Analysis
- “What do engineers now about business…””
• Technical aspects:
- Quality parameters (bandwidth, delay, reliability, …)
- Support network planning: what and where to deploy?
- “Never let the marketing guys decide…”
• Decision support:
- Lowest cost vs. future proof technologies (e.g. VDSL vs. WDM PON)
- Best fitting solutions for each service area
The “crystal ball” : Techno-economic analysis
• Some fundamental questions:
- What is the cost of deploying a GPON network in XY area?
- And what about Active Ethernet, VDSL or Point-to-Point?
- Which one is the best?
- (what does “best” mean?)
The beginning Once upon a time…
?
?
?
• How to estimate the costs?
• Who will trust our estimation?
• Why exactly *** € / $? Why not less/more?
• We did a research of the literature (not to reinvent the wheel…)
- Rules of thumb: average cost per customer (but we didn’t have data for Hungary…)
- Geometric models to estimate the physical infrastructure (but our areas were not that regular / homogeneous…)
„Think, think, think…”
Geometric models 1. Triangle Model
E
A
B
C
D
R
F
F
FF
F
F
F F
F F
F
FP1
FP2
végpont
Kábel típus #1
Kábel típus #5
Kábel típus #4
Kábel típus #3
Kábel típus #2
α
AB BC R / 3 cos( / 2)
2CD CE R / 6 1 8 sin ( / 2)
DF R 0,132 0,336 n
Analytic calculations
Geometric models 2. Simplified Street Length model
Analytic calculations
n houses in a row
l = distance
between two houses
The central office
at the center
This serves n2
customers
2I n (n 1) l (n 1) l (n 1) l
n 1
i 1
F 4 l min i,n i n i
N: buildings in each street
L: distance between neighboring buildings
CO – Central Office in the geometric median, serving n2 customers
• How to estimate the costs?
• Who will trust our estimation?
• Why exactly *** € / $? Why not less/more?
• We did a research of the literature (not to reinvent the wheel…)
• Investigate the map
- “How big” network?
- How complicated “field”?
- How to adapt the geometric models?
- Knowing the network, we could answer all questions…
Think, think, think…”
• High level network design
- Network connections, system design, location of equipment, …
• Detailed and accurate information about the necessary physical infrastructure
- Network equipment
- Cable plant
- Optical fiber needs
• Provide “Bill of Material”
• Techno-economic analysis:
- Reliable preliminary cost estimation
- Comparison of technologies
Solution: Strategic design
• Design “guesswork” :
- Human creativity
- Time consuming
- N-1 unnecessary designs!
• Computer aided network design:
- Time and cost savings
- Repetitious calculations with variable parameters
- Highly complex
- Data availability
- Computing capacity
How to provide the “strategic design”?
• Geographic Information System (GIS) data and digital maps
• Increased computational capacity
• Modern algorithms
Map based, automatic design of access networks
• The technical preconditions were not met earlier (calling for the use of geometric models)
Opportunities that made the computer able to deliver
Challenges, model, cost function and constraints
Network planning as an optimization problem
What do we expect? What is a “good” network design?
What do we expect? What is a “good” network design?
Which one is the “better” PON network? Why?
• How to translate the problem to mathematics?
- Modeling
- Cost function
- Constraints
• What is an optimal, or at least good topology?
- Economic aspects: what costs to consider?
• Complexity
- NP-hard (@see Travelling Salesman Problem)
- Large scale problem instances (10.000+ households)
Challenges
e 2
e3
e1 e4co
coKözpont (Central
Office, CO)
Elosztóhálózati
összeköttetés
Törzshálózati
összeköttetés
Gráfpont
Végpont
Elosztópont
Megengedett
elosztópont hely
Nem használt
hálózati szakasz
e 2
e3
e1 e4
Gráfél
Gráfpont
e 2
e3
e1 e4co
coKözpont (Central
Office, CO)
Gráfpont
Végpont
Megengedett
elosztóponti hely
Lehetséges
hálózati
összeköttetés
CO
Törzshálózat Elosztóhálózat
Központ
(Central
Office, CO)
Végpont/
előfizető
Elosztópont
Törzshálózat
Elosztóhálózat
Előfizetői
csoport
{i}
Modeling – translate it to the computer! Point-to-multipoint networks
• Flexible, accurate, parametric
• Contains all necessary data – and nothing else!
- Potential network links
- Distances
- Customer data
- Equipment locations
Network graph model
Goal: minimize costs
CAPEX Deployment cost
OPEX Operation,
Maintenance
Topology-dependent costs
(e.g. cable plant)
Topology-independent costs
(e.g. user modems)
Cable plant
- Two levels: deployment + fiber costs
- Stepwise: discrete increments
- Existing infrastructure (!)
Network equipment
- Central Office
- Distribution Units
- Customers
Relation between these:
- More distribution units less cable/fiber infrastructure
- Two extremities: point-to-point network (1 distribution units / ∞ distribution units)
Cost function „All inclusive”
C0
C0+n·Cv
Kábelhálózat
költsége
#szálszám
Építési
költségek
Telepítési
költésg
Szálköltség
} Kábelhálózat
létrehozása
• Constraint set:
- Distance limitations
- Complete access network reach
- Feeder network reach
- Distribution network reach
- Differential distance
- Capacity of distribution units
Physical and technical constraints
Központ
Végpont
Elosztópont
(Pl.. ETH Switch)
Törzshálózat
Elosztóhálózat
Előfizetői
csoport
{i}
{i}
L feedm
ax
L feedmax
Törzshálózat
hatósugara
Ldist max
Törzshálózat
hatósugara
Elosztóhálózat
hatósugara Ldist max
Elosztóhálózat
hatósugara
How to solve?
The challenge is given…
• Fundamentals of optimization: “No Free Lunch” Theorem
» Specialized algorithms needed
- Follow the designers’ way of thinking
- Identify technology specific constraints and costs
1. Subproblems and decomposition 2. Specialization
• Costs:
- Cable plant dominates
- Splitter costs: low
• Network reach: 20 km not decisive
• Primary goal: optimal clustering
• Solution:
- Maximize shared cable segments
- Clustering on the Shortest Path Tree
- Typically tree topologies…
Passive Optical Networks (GPON)
Központ
Végpont
Splitter
Törzshálózat
Elosztóhálózat
Előfizetői
csoport
{i}
{i}
Lm
ax
Lmax
Hálózat
hatósugara
GPON
10GPON
(WDM-PON)
Branch Contracting Algorithm
• Costs: - Distribution Unit: high CAPEX + OPEX
- Cable plant: high costs…
• Network reach: 20+3 km (not sharp)
• Main goal: - Minimize distribution units / groups
- Optimal clustering:
- No overlapping
- Nearby distribution unit
• Solution: - Iterative “bottom-up” clustering
- Increase group size if possible
- Avoid overlapping
Active Optical Networks (AETH)
Központ
Végpont
Elosztópont
(Pl.. ETH Switch)
Törzshálózat
Elosztóhálózat
Előfizetői
csoport
{i}
{i}
L feedm
ax
L feedmax
Törzshálózat
hatósugara
Ldist max
Törzshálózat
hatósugara
Elosztóhálózat
hatósugara Ldist max
Elosztóhálózat
hatósugara
Active
Ethernet
• Costs: - DSLAM: high CAPEX + OPEX
- Copper: almost for free
• Constraints: - Decisive: 300/800 m copper reach
• Goal: - Minimize DSLAMs, respect reach
constraints
• Solution: - Greedy algorithm
- Prioritize critical customer nodes
- Top-down clustering
Hybrid copper + fiber (VDSL)
Központ
Végpont
Elosztópont
(DSLAM)
Törzshálózat
(optika)
Elosztóhálózat
(réz)
Előfizetői
csoport
{i}
{i}L feed
max
L feedmax
Törzshálózat
hatósugara
Ldist m
ax
Optikai törzshálózat
hatósugara
Rézhálózat
hatósugara
Ldist max Elosztóhálózat
(réz)
hatósugara
DSL
• Costs:
- Cable plant costly
- Especially the deployment costs (with scarce networks)
• Goal:
- Minimize trenching / digging
• Solution:
- Steiner-tree problem
- Distance Network Heuristics (DNH):
- Graph-transformations + minimal cost spanning tree
Point-to-point optical networks
Központ
Végpont
Hozzűférési
hálózat
Lm
ax
Lmax
Hálózat
hatósugara
Pont-pont
optika
Computer aided optical access network design in practice
AccessPlan Framework
• Economic analysis
- Cost estimation (CAPEX)
- Business Case Analysis
- Compare technologies, decision support
• Geographic + Infrastructure Data
- Handling digital maps
- Existing infrastructure
AccessPlan Framework Modular setup
• Build network model
- Graph, nodes and edges
- Cost data
- Technical parameters and constraints
• Topology optimization
- Clustering, group formulation
- Distribution Unit placement
- Connection establishment
AccessPlan input data
Strategic network design
System design
Location of network
equipment
Bill of Material
(cable plant, equipment)
• Detailed input for further analysis and comparison
• Technical:
- Performance analysis
- Possible and guaranteed service levels
- Reliability, identification (protection) of critical nodes
• Economic:
- Cost estimation
- Business Case Analysis
• Does everything provided by the geometric models, but more accurate, detailed and reliable…
AccessPlan Results
Let’s see an example…
Case study
AccessPlan: select area
Example: Sashegy (Budapest)
Sashegy, Budapest Districts 11/12
Area of a Central Office 5 km2 / 4500 customers
• Inhomogeneous area
- Family, mid-size and large block houses
- Nature reserve area
- Cemetery
• Existing infrastructure
- Partly re-usable substructures
- Existing copper network
• Different cabling technologies – makes a cost difference
- Aerial cables and poles
- Existing substructures
- New trenching
Parameters of the case study
• 82 km street system
- 60 km existing infrastructure
- 2 km aerial network
- 20 km new trenching
• Graph model:
- 8000 nodes
- 8500 edges
• Map, street system & infrastructure
Phase #1: Process input data
• Customer database
• Demand points:
- 4239 households in
- 1079 buildings
• Graph model:
- 10 300 nodes
- 10 424 edges
Phase #1: Process input data
AccessPlan: planning rules and cost data
After a few minutes…
• Topology
• System design
• Location of network equipment
Phase #2: Topology design
• Technical & physical constraints
• Cost database (cost function)
Phase #3: Transform back onto the map
• Topology information, network characteristics
- System design
- Location of network equipment
- Fiber, cable and equipment needs
• Business Case Analysis
- CAPEX, OPEX, Cash Flow, Payback, etc.
• Techno-economic analysis, comparison
- GPON, 10GPON, Active Ethernet, VDSL, Point-to-point fiber, …
• Any custom reports and analytics
- Based on detailed topology information
- Upon request of the network operator
Phase #4: Reports and analyses
AccessPlan: plans and results
AccessPlan: analyses
0
0,5
1
1,5
2
2,5
3
3,5
P2P GPON AETH VDSL
CAPEX M EUR
Techno-economic analysis 1/4 Reports: CAPEX estimation
Techno-economic analysis 2/4 Reports: Cash Flow
GPO
N
Pont-
pont
Eth
ern
et
Éves Cash Flow
Éves Cash Flow
Akkumulált Cash Flow
Akkumulált Cash Flow
0
100
200
300
400
500
600
700
800
5 000 800 300
EU
R /
há
zta
rtá
s
Háztartás / km2
VDSL: 25 Mb/s vs. 50 Mb/s
VDSL25 VDSL50
0
100
200
300
400
500
600
700
800
900
1 000
5 000 800 300
EU
R /
há
zta
rtá
s
Háztartás / km2
GPON: 50 Mb/s vs. 100 Mb/s
GPON50 GPON100
Techno-economic analysis 3/4 Reports: CAPEX vs. bandwidth
Techno-economic analysis 4/4 Reports: cost per bit
0 Ft
200 Ft
400 Ft
600 Ft
800 Ft
1 000 Ft
1 200 Ft
1 400 Ft
P2P FTTH P2P FTTB 10GPONFTTH
10GPONFTTB
WDMPONFTTH
WDMPONFTTB
Ft / bit/sec
Agglomeráció 1 021 Ft 1 035 Ft 587 Ft 548 Ft 243 Ft 244 Ft
Kertváros 925 Ft 1 088 Ft 644 Ft 617 Ft 236 Ft 295 Ft
Belváros 1 039 Ft 1 260 Ft 788 Ft 717 Ft 270 Ft 347 Ft
1 Mb/s sávszélesség ára (Ft / Mb/s)
