Routing and Bandwidth Assignment for Flexible Grid Wavelength Switched Optical Networks

• US 20140341572A1
• Filed: 09/30/2011
• Published: 11/20/2014
• Est. Priority Date: 08/23/2011
• Status: Active Grant

• Current Assignee: Telefonaktiebolaget LM Ericsson
• Original Assignee: Telefonaktiebolaget LM Ericsson
• Inventors: Sambo, Nicola, Bottari, Giulio, Castoldi, Piero, Cugini, Filippo, Iovanna, Paola
• Granted Patent: US 9,338,529 B2
• Time in Patent Office: Days
• US Class Current: 398/48
• CPC Class Codes: H04J 14/0224 Irregular wavelength spacing, e.g. to accommodate interference to all wavelengths
• 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 14/0257 Wavelength assignment algorithms
• CPC Class Codes: H04J 14/026 using WDM channels of different transmission rates
• CPC Class Codes: H04J 14/0267 Optical signaling or routing
• CPC Class Codes: H04J 14/0269 using tables for routing
• CPC Class Codes: H04J 14/0271 Impairment aware routing
• CPC Class Codes: H04Q 11/0062 Network aspects
• CPC Class Codes: H04Q 2011/0086 Network resource allocation, dimensioning or optimisation

Abstract

Routing and bandwidth assignment of new paths of different bandwidths, occupying different numbers of adjacent frequency slots in a wavelength switched optical network, involves selecting a route, and assigning a set of adjacent frequency slots. The assignment can place wider bandwidth ones of the new paths at an opposite end of a spectrum of the available frequency slots, to an end where narrower bandwidth ones are placed. A size of sets of available adjacent slots remaining after the assignment is likely to be increased, compared to a conventional first fit assignment. A wider subsequent new path can sometimes be accommodated along all or some of the route and thus the blocking probability can be lowered. The selecting of which of the possible routes to use can be made dependent on which has more sets of available adjacent frequency slots, or which has a wider gap between occupied slots.

Claims

1. A method of routing and bandwidth assignment of new paths in a wavelength switched optical network, the network being arranged to carry paths of different bandwidths, occupying different numbers of adjacent frequency slots, the method having the steps of:

selecting a route for each of the new paths; and

assigning a set of adjacent frequency slots to each respective new path,

wherein for selected routes having more than one available set of sufficient adjacent frequency slots for their respective new paths, the assignment is made so as to place wider bandwidth ones of the new paths at an end of a spectrum of the available frequency slots, opposite to an end of the spectrum of the available frequency slots where narrower bandwidth ones of the new paths are placed.

2. The method of claim 1, wherein the network is able to carry paths using different modulation formats, and the slot assignment is made dependent on the modulation format chosen for the respective new path.

3. The method of claim 1, the network having a path computation element and a database of slot availabilities, and the step of assigning the slots being carried out by the path computation element by accessing the database of slot availabilities.

4. The method of claim 1, wherein only the paths having the widest bandwidth of the path sizes are assigned to the opposite end of the spectrum.

5. The method of claim 1, the step of selecting the route being made according to which of the possible routes having a larger number of different sets of available adjacent frequency slots.

6. The method of claim 1, the step of selecting the route being made based on a first modulation format, and if no route is possible for a given new path using the first modulation format, the step of selecting the route comprises trying again using a second, less efficient modulation format in terms of needing to occupy more adjacent frequency slots.

7. The method of claim 1, the routing and frequency slot assignment being carried out dynamically in real time for requests for new paths while the network is in operation.

8. An apparatus for routing and bandwidth assignment of new paths in a wavelength switched optical network, the network being arranged to carry paths of different bandwidths, occupying different numbers of adjacent frequency slots, the apparatus having:

a selection part arranged to select a route for each of the new paths, and assign a set of adjacent frequency slots to each respective new path, wherein for selected routes having more than one available set of sufficient adjacent frequency slots for their respective new paths, the assignment is made so as to place wider bandwidth ones of the new paths at an end of a spectrum of the available frequency slots, opposite to an end of the spectrum of available frequency slots where narrower bandwidth ones of the new paths are placed.

9. A method of routing and bandwidth assignment of new paths in a wavelength switched optical network, the network being arranged to carry paths of different bandwidths, occupying different numbers of adjacent frequency slots, the method having the steps of:

selecting a route for each of the new paths; and

assigning a set of adjacent frequency slots to each respective new path,

wherein the step of selecting the route comprises the steps of determining which routes are possible in terms of having sufficient available adjacent frequency slots with sufficient optical transmission quality for the respective new path, and selecting which of the possible routes to use according to their sets of available adjacent frequency slots.

10. The method of claim 9, the step of selecting the route being made based on a first modulation format, and if no route is possible for a given new path using the first modulation format, the step of selecting the route comprises trying again using a second, less efficient modulation format in terms of needing to occupy more adjacent frequency slots.

11. The method of claim 9, the routing and frequency slot assignment being carried out dynamically in real time for requests for new paths while the network is in operation.

12. The method of claim 9, the step of determining of which routes are possible having the steps of determining a distance for each route, and determining whether there is sufficient reach of an optical signal, according to a modulation format being used, for the distance involved.

13. The method of claim 9, the step of selecting which of the possible routes to use according to their sets of available adjacent frequency slots comprising a step of selecting according to which has a larger total number of different sets.

14. The method of claim 9, the step of selecting which of the possible routes to use according to their sets of available adjacent frequency slots comprising a step of selecting according to which has a wider gap between occupied slots.

15. The method of claim 12, the determining of which routes are possible having the step of, where there is not sufficient reach, determining if optical regeneration is available along the route, and determining if the route is possible with any available optical regeneration.

16. The method of claim 10, the modulation formats comprising at least 4-QAM, 16-QAM, and 64-QAM, using a single carrier.

17. The method of claim 10, the modulation formats comprising at least orthogonal frequency division multiplexed.

18. An apparatus for routing and bandwidth assignment of new paths in a wavelength switched optical network, the network being arranged to carry paths of different bandwidths, occupying different numbers of adjacent frequency slots, the apparatus having:

a selection part for selecting a route for each of the new paths, and for assigning a set of adjacent frequency slots to each respective new path, the selection part being arranged to determine which routes are possible in terms of having sufficient available adjacent frequency slots with sufficient optical transmission quality for the respective new path, and to select which of the possible routes to use according to their sets of available adjacent frequency slots.

19. A computer readable medium having instructions which when executed by a computer, cause the computer to carry out a method of routing and bandwidth assignment of new paths in a wavelength switched optical network, the network being arranged to carry paths of different bandwidths, occupying different numbers of adjacent frequency slots, the method comprising:

selecting a route for each of the new paths; and

assigning a set of adjacent frequency slots to each respective new path,

wherein for selected routes having more than one available set of sufficient adjacent frequency slots for their respective new paths, the assignment is made so as to place wider bandwidth ones of the new paths at an end of a spectrum of the available frequency slots, opposite to an end of the spectrum of the available frequency slots where narrower bandwidth ones of the new paths are placed.

20. A computer readable medium having instructions which when executed by a computer, cause the computer to carry out a method of routing and bandwidth assignment of new paths in a wavelength switched optical network, the network being arranged to carry paths of different bandwidths, occupying different numbers of adjacent frequency slots, the method comprising:

selecting a route for each of the new paths; and

assigning a set of adjacent frequency slots to each respective new path,

wherein the step of selecting the route comprises the steps of determining which routes are possible in terms of having sufficient available adjacent frequency slots with sufficient optical transmission quality for the respective new path, and selecting which of the possible routes to use according to their sets of available adjacent frequency slots.