Cost Optimization Methods in the Design of Next Generation Networks

1
Cost Optimization Methods in the Design of Next
Generation Networks

• Halldor Matthias Sigurdsson, Danish Technical
  University
• Saemundur E. Thorsteinsson, Iceland Telecom
• Thomas K. Stidsen, Danish Technical University

????? ??927468
2
Outline

• INTRODUCTION
• PSTN (Public Switched Telephone Network)
• NGN (Next-Generation Network)
• MIGRATION PLAN
• THE TOTAL COST OF OWNERSHIP)
• MATHEMATICAL MODELING
• IMPLEMENTING THE MODEL
• OPTIMIZING THE MODEL
• CONCLUSION

3
PSTNIceland Telecoms PSTN

• LEs Local exchanges
• TEs Transit exchanges
• RSS remote subscriber
• stage
• Users are connected with a pair of copper wires
  (local loop) to the closest RSS.
• 10 LEs PSTN that all connect to twoTEs

4
PSTN-connectivity and topology map for circuit
switched network

• LTLs local trunk lines
• connect RSSs to LEs
• TTLstransit trunk lines
• connect LEs to TEs

5
NGN-principle parts(1)

• Telephony Sever(TSs)
• handle call and service control in the new
  system.
• In the migration plan, the two current TEs will
  be upgraded to TSs.
• Media Gateway(MGWs)
• core switches in the new IP or ATM backbone
  network.
• In the migration plan, an optimal number of LEs
  will be upgraded to MGWs.
• Access Ramps(ARs)
• termination points of the local loop.
• provide customers with both narrowband and
  broadband connectivity.
• In the first step of the migration plan, the
  current 210 RSSs will be kept unchanged.

6
NGN-principle parts(2)

• Connectivity Network
• a backbone IP or ATM network between MGWs.
• built on leased slots between
• nodes in the existing SDH fiber network.
• In the migration plan,
• MGWs can be located wherever there is an SDH
  node.
• will be connected to the TSs with SDH slots of
  the required bandwidth.

7
Migration Plan

• Base on upgrading existing
• TEs to TSs
• LEs to MGWs
• connect them all using an ATM or IP connectivity
  network.
• The Problem
• find the position and number of MGWs that
  minimize the TCO of the NGN network.

8
The Total Cost of Ownership (1)

• cost factors
• Leased line cost ,Depreciation ,Interest, Housing
  and internal services
• By simulating these five cost factors in a
  mathematical model for both the current and
  future networks.
• Minimizing
• exists an optimal number and position of MGWs

9
The Total Cost of Ownership (2)

• Reason Of Minimizing
• Step 1
• If the position of MGWs for each number of MGWs
  is
• optimized, a function of minimum total leased
  line cost relative to the number of MGWs can be
  found.

10
The Total Cost of Ownership (3)

• Reason Of Minimizing
• Step 2
• As the number of MGWs increases, these cost
  factors start increasing more rapidly than is
  saved in local leased
• line cost.
• At that point, the total cost is at a minimum.

11
MATHEMATICAL MODELING

• bandwidth requirements
• can be estimated based on empirical data and a
  statistical multiplexing factor.
• Distance matrix
• represents the shortest distance between any two
  nodes in the network
• can be populated using available operations
  research solutions of the shortest path problem,
• TCO( total cost of ownership)
• The TCO becomes the objective function in the
  optimization
• can be expressed as total leased line cost plus
  the sum over other cost
• components.

12
IMPLEMENTING THE MODEL

• Spreadsheet program
• Availability ,flexibility, and ease of use gives
  them strong appeal.
• an easy-to-use graphical user interface
• can get the estimated total cost of ownership
  for the future NGN
• examine the financial effect of combining
  structural changes with the migration.

13
OPTIMIZING THE MODEL

• Requires a third party solver addin.
• By combining intuition and heuristics,
• accurate approximations to the global optimum
  can be reached.
• GAMS (General Algebraic Modeling System)
• Ensure a global optimum
• The optimization produces
• a network structure with the lowest possible
  total cost of ownership.
• the model can also indicate how deviations from
  the optimum affect cost.

14
CONCLUSION

• 19 percent reduction in TCO can be achieved by
  changing the structure to three MGWs instead of
  upgrading all 10 LEs in the current
  circuit-switched configuration.
• The feasibility of NGN can be assessed by
  comparing the cost of NGN migration to that of
  maintaining the current circuitswitched network.