Routing and Wavelength Assignment in Wavelength-Convertible Waveband-Switched Networks

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Routing and Wavelength Assignment in
Wavelength-Convertible Waveband-Switched Networks
Routing and Wavelength Assignment in
Wavelength-Convertible Waveband-Switched Networks

• Fang-Sheng Lin
• Ching-Fang Hsu
• Te-Lung Liu

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Outline

• Introduction
• Related Work
• Reconfigurable MG-OXC architecture
• Waveband Assignment with Path-Graph (WAPG)
  algorithm
• The Proposed Scheme
• Problem Definition
• Least-Configuration with Bounded Conversion
  (LCBC) algorithm
• Performance Evaluation
• Conclusions

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Introduction (1/5)

• Owning to the development of DWDM systems, the
  number of wavelengths gets larger and larger.
• Traditional OXCs which switch traffic only at
  wavelength granularity will need a great deal of
  wavelength ports.
• higher complexity
• difficulty associated with controlling and
  management of such large OXCs

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Introduction (2/5)

• The main idea of Waveband Switching (WBS) is to
  aggregate a set of wavelengths into a band and
  switch the band using a single port whenever
  possible.

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Introduction (3/5)

• The wavelength continuity constraint on
  lightpath establishment existing in wavelength
  routed networks also apply to WBS networks.
• One possible way to relax the wavelength
  continuity constraint is to use wavelength
  converters at the switching node.

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Introduction (4/5)

• It is more practical and cost-effective to share
  a set of limited range wavelength converters at
  each node.

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Introduction (5/5)

• Focused on sub-path grouping strategy, we
  proposed a new heuristic algorithm to solve the
  dynamic RWA problem of wavelength-convertible WBS
  networks efficiently.

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Related Work (1/4) - Reconfigurable MG-OXC

• The Multi-granular Optical Cross-Connect (MG-OXC)
  architecture with wavelength conversion bank 1

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Related Work (2/4) - Reconfigurable MG-OXC

• There is a unique issue related to using
  wavelength converters
• In WBS networks, an instantiation of wavelength
  conversion requires all wavelengths in a waveband
  to be de-multiplexed and results in extra ports
  consumption.
• Hence, inefficient banding and employment of
  wavelength converters may cause more blocking of
  future requests due to the limitation of the OXC
  ports.

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Related Work (3/4) - WAPG algorithm

• The authors in 1 proposed a heuristic algorithm
  called Waveband Assignment with Path-Graph (WAPG)
  to address the effect on the blocking performance
  and efficient usage of wavelength converters in
  WBS networks.

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Related Work (4/4) - WAPG algorithm

• WAPG
• Find out a wavelength-continuous path similar
  First-Fit algorithm first.
• If no wavelength-continuous path can be found,
  find a non-wavelength-continuous path using
  minimum number of converters.
• However, it may cause undesired port usage.

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The Proposed Scheme (1/5) - Problem definition

• The network topology
• G(V, E)
• Each fiber link has W wavelengths, which are
  partitioned into B uniform wavebands.
• According to the index continuity, a fixed number
  K of wavelengths are chosen to be grouped into a
  band

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The Proposed Scheme (2/5) - Problem definition

• For the wavelength-convertible WBS networks, the
  major objectives of dynamic RWA problem include
• to minimize the configuration (switching) cost,
  i.e., the total number of ports used,
• to utilize wavelength conversion in a most
  efficient manner, and
• to achieve a magnificent network performance at
  the same time.

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The Proposed Scheme (3/5) - Least-Configuration
with Bounded Conversion

• We proposed a new heuristic algorithm, called
  Least-Configuration with Bounded Conversion
  (LCBC), based on
• the fixed routing algorithm,
• the layered graph approach, and
• a well-designed cost function

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The Proposed Scheme (4/5) - Least-Configuration
with Bounded Conversion
.
An illustration of layered graph modeling
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The Proposed Scheme (5/5) - Least-Configuration
with Bounded Conversion

• The proposed cost function

Wavelength conversion degree
The weight factor
The extra port consumption at node v while ? is
the input channel and ?' is the output channel
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Link capacity
?
0, no wavelength conversion performed
1, wavelength conversion occurred
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Performance Evaluation (1/4)

• USAnet
• 46 nodes and 76 links.
• Every node is assumed to be a MG-OXC.
• Adopting the share-per-node architecture
• 25 wavelengths converters per node

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Performance Evaluation (2/4)

• Traffic pattern
• A Poisson process with mean ?
• Exponentially distributed connection duration
  time whose mean is 1 time unit
• All existing connections can not be rearranged.

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Performance Evaluation (3/4)
93.8
3.8
ß vs. blocking probability (W80, K10)
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Performance Evaluation (4/4)
Blocking probability vs. arrival rate (W80,
K10, ß0.75)
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Conclusions (1/2)

• In this paper, we proposed a heuristic algorithm,
  named LCBC, to solve the problem of dynamic RWA
  in wavelength-convertible WBS networks.
• Adopting fixed routing as the routing selection
  algorithm, we transform the wavelength selection
  problem into an equivalent shortest-path problem
  in an auxiliary graph.
• Moreover, we proposed a cost function to
  calculate an appropriate weight to each edge,
  such that limited resource, including BTW/WTB
  ports and wavelength converters, could be
  utilized more efficiently.

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Conclusions (2/2)

• To investigate the efficiency, we developed the
  simulation to observe the performance of LCBC and
  that of WAPG with various ß, and conversion
  degree.
• LCBC can achieve much significant blocking
  performance gain.

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Thank you!