Networking Group                                                  S. Yin
Internet Draft                                               Sh.G. Huang
Intended status: Informational                                      BUPT
Expires: November 2022                                           S. Zhou
                                                               X.K. Meng
                                                                   R. Ma
                                                                    BUPT
                                                            May 12, 2022


                 Optimization of RWA Problem through OSNR
                           draft-yin-rwa-osnr-10


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   Legal Provisions and are provided without warranty as described in
   the Simplified BSD License.

Abstract

   This documentary provides a kind of routing optimization method. In
   the basic of RWA solution method, both the output power of the route
   and the OSNR value of the optical signal noise ratio are considered.
   The selected optimal route has a lower bit error rate and the whole
   communication network performance is improved.



Table of Contents


   1. Introduction ................................................ 2
      1.1. Terminology ............................................ 3
   2. Conventions used in document                          ................................. 3
   3. Overview              ....................................... 4
      3.1. RWA Problem ............................................ 4
   4. Calculation formula ......................................... 4
   5. Optimization of RWA problem through OSNR .................... 5
   6. Formal Syntax ............................................... 6
   7. Security Considerations                   .................................. 6
   8. IANA Considerations ......................................... 6
   9. Conclusions ................................................. 7
   10. References ................................................. 7
      10.1. Normative References                            ............................. 7
      10.2. Informative References                                ......................... 7
   11. Acknowledgments ............................................ 7

1. Introduction

   RWA is one of the core issues in the optimization of network
   performance. Currently, due to a variety of physical and technical
   constraints, optical network cannot provide all the required physical
   properties, thus the study and solution of the problem plays a vital
   role to optimize the network and improve the utilization rate of
   cyber source.

   The Routing and Wavelength Assignment (RWA) is one of the key
   problems of the optimization of network performance. At present, the
   RWA problem is usually solved by being decomposed into the routing
   sub problem and wavelength assignment problems.




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   However, in the existing solutions of RWA, the allocation of routing
   and wavelength only considers the network performance such as network
   throughput, required wavelength, optical fiber number and optical
   path blocking rate, while the output power and the Optical Signal
   Noise Ratio (OSNR) index after establishing optical path are not
   considered.

   In the long distance transmission of the optical transport network
   (OTN), the output power and optical signal-to-noise ratio (OSNR) of
   optical path will seriously affect the BER of communication system,
   so that the routing based on RWA algorithm is not the best, which
   impacts the overall network performance of communication system.

   So this method has taken a comprehensive consideration of the channel
   output power POUT and the OSNR performance in the existing RWA
   solution, in order to achieve the optimizing routing.

1.1. Terminology

   RWA: Routing and Wavelength Assignment.

   Wavelength Conversion: The process of converting an information
   bearing optical signal centered at a given wavelength to one with
   "equivalent" content centered at a different wavelength. Wavelength
   conversion can be implemented via an optical-electronic-optical (OEO)
   process or via a strictly optical process.

   OTN: Optical Transport Networks.

   OSNR: Optical Signal Noise Ratio

   OLA: Optical Line Amplifier

   ASE: Amplifier spontaneous emission noise



2. Conventions used in this document

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in RFC 2119 [RFC2119].







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3. Overview

   In dynamic optical transport network, research on the resource
   optimization and constraint-based routing problem mainly includes the
   following aspects:

   (1)path selection and wavelength assignment problem in optical layer.

   (2)Constraint-based routing problem under dynamic business in Multi-
   layer network.

   (3)resource optimization problem under dynamic business in the multi-
   layer network.

3.1. RWA Problem

   Optical layer path selection and wavelength assignment problem, which
   is called RWA (Routing and Wavelength Assignment, routing and
   wavelength assignment) problem, is mainly caused by the require of
   consistency and constraints of wavelength in the optical fiber link.

   Optical layer routing based on Dijkstra algorithm is usually started
   with the different parameters which are chosen refer to the least
   costly path. Common optical path selection algorithms contain mainly
   fixed routing algorithm, fixed alternate routing algorithm, adaptive
   routing algorithm and adaptive shortest alternate routing algorithm.

   Wavelength assignment algorithm is usually based on heuristic
   algorithms, aiming to obtain the minimum blocking rate under a
   certain number of wavelengths. There are several common wavelength
   assignment algorithms such as randomly assigned wavelength method,
   first-fit, the minimum application method, the most widely used
   method and the lightest load method. The core problem of dynamic
   business constraints routing issue is how to combine electrical and
   optical layers to find proper routes.



4. Calculation formula

   There are three important formula in this documentary.

   (1) Output power formula

       P_out=P_in+SUM[Gi-Li];0<i<=n




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   where P_out is the route output power, P_in is the fiber input power
   of the corresponding optical path sending end, Gi is the gain of the
   i-th optical amplifier in the corresponding route, Li is the loss of
   the i-th optical amplifier section in the corresponding route, n is
   the total number of optical amplifiers in the corresponding route.
   Power is in dBm and gain or loss is in dB.

   (2) ASE formula

   P_asei=NF+G+10*lg(h*v*B0)

   where P_asei is ASE power of the i-th OA, NF is noise figure of the
   i-th OA, in dB. h is Planck constant, v is the frequency of light,
   and B0 is the reference light bandwidth .

   (3)OSNR formula

   OSNR=P_in-sum[P_asek-sum[Lm]+sum[Gi]];0<m<=k,0<i<=k+1

   where P_in is the fiber input power of the corresponding optical path
   sending end, P_asek is ASE power of the i-th OA, Lm is the loss of
   the m-th optical amplifier section in the corresponding route, Gi is
   the gain of the i-th optical amplifier in the corresponding route. k
   is the total number of optical amplifiers in the corresponding route.
   OSNR is in dB.



5. Optimization of RWA problem through OSNR

   Through routing algorithm and wavelength assignment algorithm, we
   calculate the K feasible routing of a specific business wavelength. K
   feasible routing pathes are arranged according to preset priority,
   among them, the ith routing is recorded as Ri , i=1,2,3 We choose
   the first reachable optical path and calculate the output power and
   OSNR value of the first path, and do the following operations
   according to whether the two indicators have reached the threshold .

   Firstly, calculate the output power according to the formula of the
   optical path and compare with the optical fiber output power
   threshold standard. If the output power does not meet the threshold
   requirement which determines by the average output power of the
   corresponding fiber, it means that the receiving terminal has not
   detected the signal, so the OSNR value will not be calculated.
   Therefore, in order to meet the requirement of output power, it is
   necessary to choose a new path with larger Optical amplifier gain to
   recalculate.


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   Secondly, if the output power meets the threshold requirement, the
   OSNR value of the optical path is calculated. Moreover, if the OSNR
   value meets the OSNR threshold requirement at the same time, then the
   optical path is established successfully. If the OSNR value does not
   meet the threshold requirement, then the routing needs to be
   reselected by the following ways.

   (1)Choose the optical path routing which has less relay. One OLA
   increase in the light path will amplify the signal and noise at the
   same time, and the ASE noise brings by OLA will be superimposed in
   the signal. Therefore, the value of OSNR will be reduced after the
   signal is released by OLA. As a result, under the premise of meeting
   the power requirements of the receiving terminal, we choose less
   optical path and increase the corresponding OSNR value to achieve the
   threshold requirement.

   (2) If the number of relays in the optical path is the least, then
   the suboptimal path is adopted, in which is to choose a light path
   with a large number of OLA and smaller gain G.



6. Formal Syntax

   The following syntax specification uses the augmented Backus-Naur
   Form (BNF) as described in RFC-2234 [RFC2234].

7. Security Considerations

   This model is very similar with a security standpoint of the
   information that can be currently conveyed via GMPLS routing
   protocols. This kind of information includes network topology, link
   state and current utilization, as well as the capabilities of
   switches and routers within the network, which is owing to that the
   information should be protected from disclosure to unintended
   recipients. In addition, the intentional modification of this
   information can significantly affect network operations, particularly
   due to the large capacity of the optical infrastructure has been
   controlled.

8. IANA Considerations

   This informational document does not make any requests for IANA
   action.





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9. Conclusions

   This document discussed an information model for RWA computation in
   OTN and presented the method has taken a comprehensive consideration
   of the channel output power POUT and the OSNR performance in the
   existing RWA solution, in order to achieve the optimizing routing.

10. References

10.1. Normative References

   [1]  Bradner, S., "Key words for use in RFCs to Indicate Requirement
         Levels", BCP 14, RFC 2119, March 1997.

   [2]  Crocker, D. and Overell, P.(Editors), "Augmented BNF for Syntax
         Specifications: ABNF", RFC 2234, Internet Mail Consortium and
         Demon Internet Ltd., November 1997.

   [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
             Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC2234] Crocker, D. and Overell, P.(Editors), "Augmented BNF for
             Syntax Specifications: ABNF", RFC 2234, Internet Mail
             Consortium and Demon Internet Ltd., November 1997.

10.2. Informative References

   [3]  Faber, T., Touch, J. and W. Yue, "The TIME-WAIT state in TCP
         and Its Effect on Busy Servers", Proc. Infocom 1999 pp. 1573-
         1583.

   [Fab1999] Faber, T., Touch, J. and W. Yue, "The TIME-WAIT state in
             TCP and Its Effect on Busy Servers", Proc. Infocom 1999 pp.
             1573-1583.

11. Acknowledgments

   This document is supported in part by the National Natural Science
   Foundation of China (Nos.61601054, 61331008, 61701039 and 61571058),
   the National Science Foundation for Outstanding Youth Scholars of
   China (No.61622102) and Youth research and innovation program of
   BUPT(2017RC14).







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Authors' Addresses

   Shan Yin
   BUPT
   No.10, Xitucheng Road,Haidian District
   Beijing 100876
   P.R.China
   Phone: +8613488795778
   Email: yinshan@bupt.edu.cn


   Shanguo Huang
   BUPT
   No.10, Xitucheng Road,Haidian District
   Beijing 100876
   P.R.China
   Phone: +8613693578265
   Email: shghuang@bupt.edu.cn


   Shuang Zhou
   BUPT
   No.10, Xitucheng Road,Haidian District
   Beijing 100876
   P.R.China
   Phone: +8618101053965
   Email: zs_yolanda@163.com


   Xiangkai Meng
   BUPT
   No.10, Xitucheng Road,Haidian District
   Beijing 100876
   P.R.China
   Phone: +8618810320812
   Email: 18810320812@163.com


   Rong Ma
   BUPT
   No.10, Xitucheng Road,Haidian District
   Beijing 100876
   P.R.China
   Phone: +8613361181853
   Email: 190449115@qq.com




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