## Path connectivity based spectral defragmentation in flexible bandwidth networks |

Optics Express, Vol. 21, Issue 2, pp. 1353-1363 (2013)

http://dx.doi.org/10.1364/OE.21.001353

Acrobat PDF (1023 KB)

### Abstract

Optical networks with flexible bandwidth provisioning have become a very promising networking architecture. It enables efficient resource utilization and supports heterogeneous bandwidth demands. In this paper, two novel spectrum defragmentation approaches, i.e. Maximum Path Connectivity (MPC) algorithm and Path Connectivity Triggering (PCT) algorithm, are proposed based on the notion of Path Connectivity, which is defined to represent the maximum variation of node switching ability along the path in flexible bandwidth networks. A cost-performance-ratio based profitability model is given to denote the prons and cons of spectrum defragmentation. We compare these two proposed algorithms with non-defragmentation algorithm in terms of blocking probability. Then we analyze the differences of defragmentation profitability between MPC and PCT algorithms.

© 2013 OSA

## 1. Introduction

1. R.-J. Essiambre, G. Kramer, P. J. Winzer, G. J. Foschini, and B. Goebel, “Capacity limits of optical fiber networks,” J. Lightwave Technol. **28**(4), 662–701 (2010). [CrossRef]

2. M. Jinno, H. Takara, B. Kozicki, Y. Tsukishima, Y. Sone, and S. Matsuoka, “Spectrum-efficient and scalable elastic optical path network: architecture, benefits, and enabling technologies,” IEEE Commun. Mag. **47**(11), 66–73 (2009). [CrossRef]

10. Yu. Xiaosong, J. Zhang, Y. Zhao, T. Peng, Y. Bai, D. Wang, and X. Lin, “Spectrum compactness based defragmentation in flexible bandwidth optical networks,” in *Proceedings of Optical Fiber Communication Conference and Exposition and National Fiber Optic Engineers Conference* (OFC/NFOEC 2012), paper JTh2A.35.

10. Yu. Xiaosong, J. Zhang, Y. Zhao, T. Peng, Y. Bai, D. Wang, and X. Lin, “Spectrum compactness based defragmentation in flexible bandwidth optical networks,” in *Proceedings of Optical Fiber Communication Conference and Exposition and National Fiber Optic Engineers Conference* (OFC/NFOEC 2012), paper JTh2A.35.

10. Yu. Xiaosong, J. Zhang, Y. Zhao, T. Peng, Y. Bai, D. Wang, and X. Lin, “Spectrum compactness based defragmentation in flexible bandwidth optical networks,” in *Proceedings of Optical Fiber Communication Conference and Exposition and National Fiber Optic Engineers Conference* (OFC/NFOEC 2012), paper JTh2A.35.

## 2. Path connectivity in flexible bandwidth optical networks

### 2.1 Node Spectral-X Eigenvector of Spectrum Usage Matrix

*G*{

*V*,

*E*,

*S*} where

*V*denotes the set of bandwidth-variable switching nodes,

*E*represents the set of bi-directional fiber links between nodes in

*V*. Let |

*V*| =

*N*and |

*E*| =

*L*denote the numbers of network nodes and links respectively.

*S*denotes the set of FSs on each link, |

*S*| =

*F*. The link spectrum occupation is expressed using an

*F*bit array, in which each binary bit indicates the usage of the corresponding FS. The bit value 1 means a free slot while the bit value 0 corresponds to an occupied slot. The Spectrum Usage Matrix of node

*k*, which degree is

*i-*th FS usage among the node connecting links. In detail, there are

*i-*th FS are free. Among these links, there exist

*i-*th FS can be allocated.

*i-*th FS for all possible path bandwidth is defined as

*j*. The value of

*i-*th FS to the adjacent available FSs and

*i-*th FS. So for Node

*k*, a notion of Spectral-X Eigenvector is introduced to denote its switching ability for all FSs. In detail, the

*Node Spectral-X Eigenvector*of node

*k*is defined as follows:

*k*is 3, the connecting links to the Node is L1, L2, L3 and their spectrum occupation status is shown in the figure. The eigenvector

*r*can be got according to Eq. (2). Figure 1(c) shows the possible accommodation states for all FSs when every adjacent links are on a candidate route. The blue dotted ellipse in Fig. 1(d) is the possible accommodation states set including the 7-th FS. The average bandwidth of these accommodation states including the 7-th FS is calculated according to Eq. (3):

_{k}### 2.2 Path Connectivity in flexible bandwidth optical networks

*p*with

*m*nodes (

*m*-elements-size vector space (

*Path Spectral-X Eigenvector Space*. The mean vector of Path Spectral-X Eigenvectors in the Space expresses the center of them, which is calculated as follow:

*a*and node

*b*are the nodes whose Node Spectral-X eigenvectors are the farthest and nearest to the mean vector

*a*and node

*b*’s Node Spectral-X eigenvectors is defined as

*Path Connectivity*

*a*and

*b*are the nodes whose eigenvectors are the farthest and nearest to the mean vector respectively. That is to say, the switching uniformity of these two nodes is of the greatest difference among all nodes along the path. In this way, Path Connectivity shows the largest barrier for traffic to go through this path. Figure 2 is a conceptualized illustration of the notions in the proposed model. As shown, the blue thick line represents path

*p*, consisting of node

*V1, V2, V5*and

*V*6. Take

*V5*for example, based on the spectrum occupation situation of connected links, the Spectrum Usage Matrix of node

*V5*can be expressed, which is shown in the bottom left of Fig. 2. According to Eq. (2) and Eq. (3),

*V5*can be got by Eq. (4), which is represented as

*p*(say

*p*, which is represented as the intersection angle between these two eigenvectors in the cube.

## 3. Path connectivity based dynamic spectral defragmentation

### 3.1 Maximum Path Connectivity algorithm (MPC)

**Step 1:**For each blocked connection request, find a candidate pair of route and consecutive slots set whose disruptions to the existing paths are minimized. If there are multiple candidates, choose the one having the smallest slot index on the selected route.

**Step 2:**Find all existing paths that conflict with the pair of route and slots set selected in Step 1. For each conflicting path, generate all available alternatives, which can be expressed by pairs of candidate routes and candidate slots set. Define these alternatives as

**Step 3:**Before accommodating the conflicting traffic, calculate the Path Connectivity of all candidate routes

**Step 4:**For each blocked connection request, if all conflicting paths have alternative paths, relocate the conflicting paths and then accommodate the new traffic. Otherwise block the connection request.

### 3.2 Path Connectivity Triggering algorithm (PCT)

**Step 1:**After connections release or new connections establish, update the Path Connectivity of all

*M*online connections and calculate the Average Path Connectivity

**Step 2:**Rank the

*M*online connections in an ascending order based on its Path Connectivity. Define the connection sequence as

**Step 3:**According to the connection sequence

**Step 4:**After re-allocating the spectrum for all online connections, update the Path Connectivity of them and calculate the Average Path Connectivity

*K*reaches the pre-defined maximum value

## 4. Simulation results and discussions

13. Y.-K. Huang, E. Ip, M. Huang, B. Zhu, P. N. Ji, Y. Shao, D. W. Peckham, R. Lingle, Y. Aono, T. Tajima, and T. Wang, “10X456-Gb/s DP-16QAM transmission over 8X100 km of ULAF using coherent detection with a 30-GHz analog-to-digital converter,” in *Proceedings of OptoElectronics Communication Conference* (OECC 2010), paper PD3.

14. S. Gringeri, B. Basch, V. Shukla, R. Egorov, and T. J. Xia, “Flexible architectures for optical transport nodes and networks,” IEEE Commun. Mag. **48**(7), 40–50 (2010). [CrossRef]

## 5. Conclusions

## Acknowledgments

## References and links

1. | R.-J. Essiambre, G. Kramer, P. J. Winzer, G. J. Foschini, and B. Goebel, “Capacity limits of optical fiber networks,” J. Lightwave Technol. |

2. | M. Jinno, H. Takara, B. Kozicki, Y. Tsukishima, Y. Sone, and S. Matsuoka, “Spectrum-efficient and scalable elastic optical path network: architecture, benefits, and enabling technologies,” IEEE Commun. Mag. |

3. | O. Rival and A. Morea, “Cost-efficiency of mixed 10-40-100Gb/s networks and elastic optical networks,” in |

4. | A. N. Patel, P. N. Ji, J. P. Jue, and Ting Wang, “Routing, wavelength assignment, and spectrum allocation in transparent flexible optical WDM (FWDM) networks,” in |

5. | T. Takagi, H. Hasegawa, K. Sato, Y. Sone, A. Hirano, and M. Jinno, “Disruption minimized spectrum defragmentation in elastic optical path networks that adopt distance adaptive modulation,” in |

6. | K. Wen, Y. Yin, D. J. Geisler, S. Chang, and S. J. B. Yoo, “Dynamic on-demand lightpath provisioning using spectral defragmentation in flexible bandwidth networks,” in Proceedings of European Conference on Optical Communication (ECOC 2011), paper Mo.2.K.4. |

7. | A. N. Patel, P. N. Ji, J. P. Jue, and Ting Wang, “Defragmentation of transparent flexible optical WDM (FWDM) networks,” in |

8. | N. Amaya, M. Irfan, G. Zervas, K. Banias, M. Garrich, I. Henning, D. Simeonidou, Y. R. Zhou, A. Lord, K. Smith, V. J. F. Rancano, S. Liu, P. Petropoulos, and D. J. Richardson, “Gridless optical networking field trial: flexible spectrum switching, defragmentation and transport of 10G/40G/100G/555G over 620-km field fiber,” in |

9. | F. Cugini, M. Secondini, N. Sambo, G. Bottari, G. Bruno, P. Iovanna, and P. Castoldi, “Push-pull technique for defragmentation in flexible optical networks,” in |

10. | Yu. Xiaosong, J. Zhang, Y. Zhao, T. Peng, Y. Bai, D. Wang, and X. Lin, “Spectrum compactness based defragmentation in flexible bandwidth optical networks,” in |

11. | Y. wang, J. Zhang, Y. Zhao, J. Zhang, J. Zhao, X. Wang, and W. Gu, “Dynamic spectral defragmentation based on path connectivity in flexible bandwidth networks,” in |

12. | Y. Sone, A. Hirano, A. Kadohata, M. Jinno, and O. Ishida, “Routing and spectrum assignment algorithm maximizes spectrum utilization in optical networks,” in |

13. | Y.-K. Huang, E. Ip, M. Huang, B. Zhu, P. N. Ji, Y. Shao, D. W. Peckham, R. Lingle, Y. Aono, T. Tajima, and T. Wang, “10X456-Gb/s DP-16QAM transmission over 8X100 km of ULAF using coherent detection with a 30-GHz analog-to-digital converter,” in |

14. | S. Gringeri, B. Basch, V. Shukla, R. Egorov, and T. J. Xia, “Flexible architectures for optical transport nodes and networks,” IEEE Commun. Mag. |

**OCIS Codes**

(060.4250) Fiber optics and optical communications : Networks

(060.4510) Fiber optics and optical communications : Optical communications

**ToC Category:**

Backbone and Core Networks

**History**

Original Manuscript: October 1, 2012

Revised Manuscript: November 13, 2012

Manuscript Accepted: November 21, 2012

Published: January 14, 2013

**Virtual Issues**

European Conference on Optical Communication 2012 (2012) *Optics Express*

**Citation**

Ying Wang, Jie Zhang, Yongli Zhao, Jiawei Zhang, Jie Zhao, Xinbo Wang, and Wanyi Gu, "Path connectivity based spectral defragmentation in flexible bandwidth networks," Opt. Express **21**, 1353-1363 (2013)

http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-21-2-1353

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### References

- R.-J. Essiambre, G. Kramer, P. J. Winzer, G. J. Foschini, and B. Goebel, “Capacity limits of optical fiber networks,” J. Lightwave Technol.28(4), 662–701 (2010). [CrossRef]
- M. Jinno, H. Takara, B. Kozicki, Y. Tsukishima, Y. Sone, and S. Matsuoka, “Spectrum-efficient and scalable elastic optical path network: architecture, benefits, and enabling technologies,” IEEE Commun. Mag.47(11), 66–73 (2009). [CrossRef]
- O. Rival and A. Morea, “Cost-efficiency of mixed 10-40-100Gb/s networks and elastic optical networks,” in Proceedings of Optical Fiber Communication Conference and Exposition and National Fiber Optic Engineers Conference (OFC/NFOEC 2011), paper OTuI4.
- A. N. Patel, P. N. Ji, J. P. Jue, and Ting Wang, “Routing, wavelength assignment, and spectrum allocation in transparent flexible optical WDM (FWDM) networks,” in Proceedings of Photonics in Switching (PS 2010), paper PDPWG1.
- T. Takagi, H. Hasegawa, K. Sato, Y. Sone, A. Hirano, and M. Jinno, “Disruption minimized spectrum defragmentation in elastic optical path networks that adopt distance adaptive modulation,” in Proceedings of European Conference on Optical Communication (ECOC 2011), paper Mo.2.K.3.
- K. Wen, Y. Yin, D. J. Geisler, S. Chang, and S. J. B. Yoo, “Dynamic on-demand lightpath provisioning using spectral defragmentation in flexible bandwidth networks,” in Proceedings of European Conference on Optical Communication (ECOC 2011), paper Mo.2.K.4.
- A. N. Patel, P. N. Ji, J. P. Jue, and Ting Wang, “Defragmentation of transparent flexible optical WDM (FWDM) networks,” in Proceedings of Optical Fiber Communication Conference and Exposition and National Fiber Optic Engineers Conference (OFC/NFOEC 2011), paper OTuI8.
- N. Amaya, M. Irfan, G. Zervas, K. Banias, M. Garrich, I. Henning, D. Simeonidou, Y. R. Zhou, A. Lord, K. Smith, V. J. F. Rancano, S. Liu, P. Petropoulos, and D. J. Richardson, “Gridless optical networking field trial: flexible spectrum switching, defragmentation and transport of 10G/40G/100G/555G over 620-km field fiber,” in Proceedings of European Conference on Optical Communication (ECOC 2011), PDP paper Th.13.K.1.
- F. Cugini, M. Secondini, N. Sambo, G. Bottari, G. Bruno, P. Iovanna, and P. Castoldi, “Push-pull technique for defragmentation in flexible optical networks,” in Proceedings of Optical Fiber Communication Conference and Exposition and National Fiber Optic Engineers Conference (OFC/NFOEC2012), paper JTh2A.40.
- Yu. Xiaosong, J. Zhang, Y. Zhao, T. Peng, Y. Bai, D. Wang, and X. Lin, “Spectrum compactness based defragmentation in flexible bandwidth optical networks,” in Proceedings of Optical Fiber Communication Conference and Exposition and National Fiber Optic Engineers Conference (OFC/NFOEC 2012), paper JTh2A.35.
- Y. wang, J. Zhang, Y. Zhao, J. Zhang, J. Zhao, X. Wang, and W. Gu, “Dynamic spectral defragmentation based on path connectivity in flexible bandwidth networks,” in Proceedings of European Conference on Optical Communication (ECOC 2012), paper P5.10.
- Y. Sone, A. Hirano, A. Kadohata, M. Jinno, and O. Ishida, “Routing and spectrum assignment algorithm maximizes spectrum utilization in optical networks,” in Proceedings of European Conference on Optical Communication (ECOC 2011), paper Mo.1.K.3.
- Y.-K. Huang, E. Ip, M. Huang, B. Zhu, P. N. Ji, Y. Shao, D. W. Peckham, R. Lingle, Y. Aono, T. Tajima, and T. Wang, “10X456-Gb/s DP-16QAM transmission over 8X100 km of ULAF using coherent detection with a 30-GHz analog-to-digital converter,” in Proceedings of OptoElectronics Communication Conference (OECC 2010), paper PD3.
- S. Gringeri, B. Basch, V. Shukla, R. Egorov, and T. J. Xia, “Flexible architectures for optical transport nodes and networks,” IEEE Commun. Mag.48(7), 40–50 (2010). [CrossRef]

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