Evolution of a telecommunications network from ring to mesh structure

• US 7,260,059 B2
• Filed: 06/28/2002
• Issued: 08/21/2007
• Est. Priority Date: 06/28/2001
• Status: Expired due to Fees

• Current Assignee: Telecommunications Research Laboratories
• Original Assignee: Telecommunications Research Laboratories
• Inventors: Grover, Wayne D., Leung, Kwun Kit, Clouqueur, Matthieu Arnold Henri
• Primary Examiner(s): Pham; Chi
• Assistant Examiner(s): TRAN, PHUC H
• Application Number:
  US10/187,314
• Publication Number:
  US 20030016623A1
• Time in Patent Office: 1,880 Days
• Field of Search: 370254-258
• US Class Current: 370/222
• CPC Class Codes: H04J 14/0227 Operation, administration, maintenance or provisioning [OAMP] of WDM networks, e.g. media access, routing or wavelength allocation
• CPC Class Codes: H04J 14/0241 Wavelength allocation for communications one-to-one, e.g. unicasting wavelengths
• CPC Class Codes: H04J 14/0283 WDM ring architectures
• CPC Class Codes: H04J 14/0284 WDM mesh architectures
• CPC Class Codes: H04J 14/0286 WDM hierarchical architectures
• CPC Class Codes: H04J 14/0287 Protection in WDM systems
• CPC Class Codes: H04J 14/0291 Shared protection at the optical multiplex section (1:1, n:m)
• CPC Class Codes: H04L 12/437 Ring fault isolation or reconfiguration for SDH/SONET ring networks H04J3/085
• CPC Class Codes: H04L 12/46 Interconnection of networks
• CPC Class Codes: H04L 69/40 for recovering from a failure of a protocol instance or entity, e.g. service redundancy protocols, protocol state redundancy or protocol service redirection management of faults, events, alarms or notifications in data switching networks H04L41/06
• CPC Class Codes: H04Q 11/0062 Network aspects
• CPC Class Codes: H04Q 2011/0081 Fault tolerance; Redundancy; Recovery; Reconfigurability
• CPC Class Codes: H04Q 2011/0086 Network resource allocation, dimensioning or optimisation
• CPC Class Codes: H04Q 2011/009 Topology aspects

Abstract

Ongoing growth in transport demand is served while deferring or eliminating expenditure for additional capacity by reclaiming the protection capacity and inefficiently used working capacity in existing multi-ring network. Reclamation is through re-design of the routing and restoration in the network using mesh principles within the pre-existing ring capacities. The installed working and protection capacity of existing rings is viewed as a sunk investment, an existing resource, to be “mined” and incorporated into a mesh-operated network that serves both existing and ongoing growth. A complete double or even tripling of demand could be supported with little or no additional capacity investment through the period of ring-to mesh conversion by ring-mining. An existing ring set may be converted to a target architecture of “p-cycles” instead of a span-restorable mesh, through placement of straddling span interface units to convert ring ADMs to p-cycle nodal elements.

Claims

1. A method of providing protection for a telecommunications network against failure of a span or node in the telecommunications network, in which the telecommunications network initially has protection organized in rings of connected protection links, the method comprising the steps of:

selecting ring nodes for conversion from ring node to mesh node according to a strategy that increases and optimizes demand served by the telecommunications network, wherein the strategy takes into account the cost of conversion of the selected nodes from ring node to mesh node;

breaking connections between protection links at the selected ring nodes; and

connecting the protection links into a mesh network of links of spare capacity, thereby converting each of the selected ring nodes from a ring node to a mesh node.

2. The method of claim 1 in which the mesh network is configured into cycles of connected links of spare capacity in readiness for span failure.

3. The method of claim 2 further comprising the step of adding a straddling span interface at the node for re-routing failed working channels onto the broken connection links upon failure of the working channels.

4. The method of claim 1 in which connecting the protection links into a mesh network comprises accessing an extra traffic feature of an add-drop multiplexer at a node and connecting the extra traffic feature to a mesh cross-connect at the node.

5. The method of claim 1 further comprising the step of adding capacity on a span of the telecommunications network to increase the demand served by the telecommunications network.

6. The method of claim 1 further comprising the step of re-using selected ones of plural add-drop multiplexers within the ring.

7. The method of claim 1 further comprising the step of abandoning selected segments of ring capacity in the telecommunications network.

8. The method of claim 1 in which the strategy uses an integer programming formulation to minimize an objective function that sums the cost for adding new capacity modules and the cost of converting or re-using ADMs.

9. The method of claim 8 in which the objective function is minimized according to a set of constraints selected from the group consisting of:

a) the demand served is a multiple of the original demand;

b) there is enough working capacity in the network to support the routing of all the demands;

c) the sum of restoration flows for each single span cut is equal to the working capacity to be restored;

d) there is enough spare capacity on each span to support all the restoration flows that cross the span in every span failure case;

e) the sum of mesh working and spare capacity on each span does not exceed the amount of available capacity on that span;

f) the capacity from a ring is not reclaimed on a span that is not covered by that ring; and

g) any ADM is converted (if at a degree 3+site) or re-used (if at a degree 2 site) if the capacity of the ring it belongs to is reclaimed on one of its two adjacent spans.

10. The method of claim 9 in which the objective function is minimized according to each one of constraints a) through g).