KR20010058118A - Method for the planning of WDM path and SDH path considering the SDH demand in WDM mesh network - Google Patents

Abstract

PURPOSE: A WDM path and SDH path setting method considering SDH demand in WDM mesh network is provided to reduce costs of equipment by proposing algorithm to calculate at once WDM path setting problem and wavelength allocation problem. CONSTITUTION: Inputting the demand of each commodity of physical network which is required for data setting WDM(wavelength division multiplexing) path and SDH(synchronous digital hierarchy) path(A1). A path minimizing cost of WDM path is calculated if each data is input(A2). A path minimizing cost of SDH path is calculated after setting a number of WDM path gotten from previous process(A3). A sum up cost of path which is calculated separately is calculated and output(A4).

Description

{Method for the planning of WDM path and SDH path considering the SDH demand in WDM mesh network} considering synchronous digital hierarchy (SDH) demand in WDM mesh networks

The present invention relates to a WDM path and a SDH path setting method in consideration of the demand for synchronous digital hierarchy (SDH) in a wavelength division multiplexing (hereinafter referred to as WDM) mesh network, and more particularly, to a WDM mesh network. The present invention relates to a method for reducing the cost of equipment required for introducing WDM equipment by minimizing the cost of setting up the WDM path and the setting up of the SDH path in consideration of the SDH demand.

In general, mesh networks have many differences from rings.

In contrast to a specially shaped network structure with only two possible paths, the mesh network is a general network structure in which the number of possible paths increases exponentially with the number of nodes. Therefore, in case of a ring, routing can be performed using only an Add Drop Multiplexer (ADM) device, but a cross-connector (hereinafter referred to as XC) is used as a basic transmission node device in a mesh network. Routing is done.

As such, in the case of the mesh network, the number of possible paths becomes so large that dealing with the problem of WDM routing and wavelength allocation at once becomes a very complicated form. Therefore, most of the researches have been proposed to solve the WDM routing and wavelength assignment problems by dividing the WDM routing and wavelength assignment problems.

According to the present invention as described above, the present invention proposes an algorithm for calculating the WDM path setting problem and the wavelength allocation problem at once, thereby solving the problem of the WDM path setting and the SDH path setting in consideration of the SDH demand in the WDM mesh network. By minimizing the cost, it aims to implement a method of reducing the cost of equipment required for the introduction of WDM equipment.

1 is a flowchart illustrating a WDM path and an SDH path setting process considering SDH demands according to the present invention.

FIG. 2 is a flowchart illustrating a process of calculating the WDM path of FIG. 1.

WDM path and SDH path setting method considering the SDH demand in the WDM mesh network of the present invention for achieving the above object, the data to set the wavelength division multiplexing (WDM) path and SDH path A first process of inputting a demand amount for each item of a physical network;

A second step of calculating a path for minimizing the cost of the WDM path when each data is input;

A third step of setting the number of WDM paths obtained in the second step by the capacity constraint of each link, and then calculating a path for minimizing the SDH path cost;

And a fourth process of calculating and outputting the total cost of each of the calculated routes.

The above objects, features, and advantages will become more apparent from the following detailed description taken in conjunction with the accompanying drawings, which first describes some theoretical matters for the method to be implemented in the present invention.

In the present invention, the hydraulic model is established through the following settings.

1) It has two tiers between the WDM fast path and the SDH slow path.

At this time, the levels of the SDH path considered above are 52 Mbps, 155 Mbps, and the like, and the wavelength division multiplexing of these by several tens of units becomes the transmission level of the WDM high speed path.

2) Up to g SDH paths per system can fit in one WDM path.

If the SDH demand is 155 Mbps and the WDM can have 16 wavelengths, then one WDM path can pass g = 16 SDH paths.

3) Electrical level XC is possible at all nodes.

4) Simplify the model and algorithm by setting only the WDM path using 1 hop of physical link.

5) Demand is given as an integer number of minimum units of SDH demand for each node pair.

6) The main objective is to minimize the number of WDM wavelengths.

Cost factors that can be considered in the design of the mesh network include the number of WDM paths used above, the number of WDM wavelengths, the minimum cost of the SDH path (minimizing the number of traffic miles or hops), the XC cost of the SDH path, and the WDM path XC. There is a cost.

However, in the present invention, since the WDM point-to-point XC is set and only WDM paths using 1 hop physical link are considered, the number of WDM paths and the number of WDM wavelengths are the same. do.

The minimum cost factor of the SDH path is to optimize secondarily after minimizing the number of wavelengths, that is, after minimizing the number of WDM paths, and the present invention does not consider the XC cost and the WDM path XC cost of the SDH path. Do not.

When the above setting is completed, the following mathematical modeling is attempted.

The WDM path is set up to reflect the physical topology, and the SDH path is set up as the base topology.

Once the WDM path is determined, the topology interprets the SDH path as the underlying topology for routing. This reflects the hierarchy of SDH / WDM transport networks that are layered in the order of physical layer, WDM layer, and SDH layer. In terms of mathematical model, it determines which layer extracts the role of decision variables and constraints.

Specifically, the number of WDM paths used on each link serves as a capacity constraint of the topology in which the SDH paths are routed. The SDH path is therefore limited by the portology and path capacity of the WDM path.

Given SDH demand and obtaining link capacity, it becomes a network synthesis problem to determine topology and link capacity for demand in traditional network optimization field, and if WDM path is determined and link capacity is defined, link defined in network optimization field It can be interpreted as a multi-commodity network min cost flow problem that finds the optimal routing of each demand for capacity. We attempt to model decomposition to ensure that these two problem structures are used properly.

Referring to FIG. 1, the approach in the present invention is summarized with reference to FIG. 1. In the first step (A1), a demand amount for each item of a physical network, which is data for establishing a WDM path and an SDH path, is input.

The second step (A2) calculates a path that minimizes the cost of the WDM path by using an algorithm (PTP-MWC) that calculates a network synthesis problem that determines the link capacity mentioned above.

The third step (A3) calculates a path that minimizes the cost of the SDH path using an algorithm (PTP-MRC) that minimizes the SDH path cost by setting the number of WDM paths obtained as the capacity constraint of each link.

By dividing the problem into two approaches, the primary goal is to reduce the number of wavelengths, reduce the wavelength, and then adjust the routing within the range that satisfies the wavelength, thereby further reducing the routing cost of the SDH path. .

The final step (A4) calculates and outputs the total cost of each of the calculated routes.

Meanwhile, the algorithm for calculating each of the minimum cost paths mentioned above is as follows.

First, the algorithm for calculating WDM paths (PTP-MWC) is a form of Network Synthesis Problem in the field of traditional network flow optimization, with each link capacity given as a variable. It is a matter of determining routing for each demand so that capacity can be minimized.

However, since the link capacity variable (the number of WDM paths used) is an integer, a solution different from that of a general real variable network analysis problem is required. In other words, it is a large integer programming problem with a large number of variables and a large number of constraints, and an integer condition is added.

Substituting this large water purification problem directly into a package that solves the water purification problem such as 'CPLEX' is not only time-consuming but also often solved by memory problems. Therefore, it is necessary to develop a new solution for analyzing the structure of the model and calculating it. The basic idea of this solution is to use a column generation method with path formulation.

This method has the disadvantage of solving the problem several times while continuously generating heat. However, since the problem is solved using only the necessary heat, the size of the problem can be reduced and a powerful linear programming method is called LP. There is an advantage in that relaxation can be obtained.

When the path is formulated, the number of variables increases exponentially, but the number of constraints is very small. Therefore, LP mitigation that ignores the integer condition of this problem can be solved by introducing heat generation technique and generating and solving only necessary heat.

However, since the above problem is an integer programming problem imposed with integer condition, it is possible that the optimal solution cannot be obtained by heat generation alone. In this case, we propose a method of branching with the optimal solution obtained through the heat generation technique for the LP relaxation problem, that is, the branch and price method. .

Here, when applying the heat generation technique, the problem of determining the optimality is to find the shortest path for each commodity. Therefore, the shortest path problem is solved for each item. It can be determined. The initial possible solution is to find a single random path for each item. Then we can apply the heat generation technique with only those paths.

The above items are summarized as follows with reference to FIG.

First, one path for each item is obtained using the shortest path algorithm currently used, and a linear planning problem is generated using the obtained initial possible solutions (B1).

If the cost of each link is solved at 1 / M, the optimal solution of the initial LP is obtained.

Subsequently, an optimal solution for the generated linear plan is obtained, the optimal solution is determined, and if it is not optimal, a newly obtained path is generated as a new column of the given LP problem and repeated (B2).

On the other hand, if the result of the determination is an optimal solution, branch to the non-integer solution using the branch limit method in the solution, and if the search for such a branch node is the end, it is terminated, and if it is not the last it is repeated from the step B2 (B3).

On the other hand, when describing the algorithm for calculating the SDH path (PTP-MRC), its model is in the form of an Integer Multi-Commodity Problem, Lagrang is a solution for calculating this integer multi-item problem There are a Lagrangian relaxation method and a heat generation method through path formulation. Among them, in the present invention, a branch evaluation method is applied using the path formulation method, and in particular, the value output from the WDM path calculation. Calculate using

At this time, since the Lagrangian relaxation method and the heat generation method through the path formulation are already known, a detailed description thereof will be omitted.

As a result of the computerized experiment of mesh network, inter-regional relay network, inter-regional network of USA, USA network, etc. using the algorithm of the present invention as described above, the algorithm of the present invention finds the optimal solution in terms of solution quality or A solution with a difference of about 2 was obtained, and the calculation time was much better than the direct solution using the integer programming method.

In particular, the direct solution using the integer programming method cannot solve the solution when the network size increases, whereas the algorithm can find an effective solution even if the network size increases.

As described in detail above, the present invention has the advantage of reducing the cost of equipment when introducing WDM equipment by minimizing the cost of setting up the WDM path and the setting up of the SDH path in consideration of the SDH demand in the WDM mesh network.

In addition, preferred embodiments of the present invention are disclosed for the purpose of illustration, those skilled in the art will be able to various modifications, changes, additions, etc. within the spirit and scope of the present invention, such modifications and modifications belong to the following claims You will have to look.

Claims (2)

A first step of inputting a demand amount of each item of a physical network, which is data to set a wavelength division multiplexing (WDM) path and an SDH path; A second step of calculating a path for minimizing the cost of the WDM path when each of the data is input; A third step of setting the number of WDM paths obtained in the second step by the capacity constraint of each link, and then calculating a path for minimizing the SDH path cost; And a fourth process of calculating and outputting the sum of the calculated paths, wherein the WDM path and the SDH path setting method are considered in consideration of the SDH demand in the WDM mesh network. The method of claim 1, Computing a path for minimizing the cost of the WDM path of the second step, using the shortest path algorithm to obtain one path for each input item, and using the obtained initial solution to generate a linear planning problem A first step; A second step of obtaining an optimal solution for the generated linear plan, determining whether it is optimal, and then repeatedly generating a newly calculated path as a new column of a given linear plan problem if it is not optimal; If the result of the determination is an optimal solution, the solution is branched to a non-integer solution using the branch limit method, and if the search for such a branch node is the last, the third step is repeated. WDM path and SDH path setup method considering the SDH demand in the WDM mesh network characterized in that the.