Networking Group S. Yin
Internet Draft Sh.G. Huang
Intended status: Informational BUPT
Expires: November 2020 S. Zhou
X.K. Meng
R. Ma
BUPT
May 23, 2020

Optimization of RWA Problem through OSNR
draft-yin-rwa-osnr-05

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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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