KR20030031201A - Wavelength assignment in wavelength division multiplexed ring networks - Google Patents

Abstract

PURPOSE: A wavelength assignment method for a ring network utilizing wavelength division multiplexing (WDM) is provided to flexibly assign wavelengths for the complete connectivity in a wavelength division multiplexing ring network and to form an optical path using the shortest wavelength with minimum influence on an existing network when nodes are added in the network. CONSTITUTION: A wavelength assignment method is provided for a ring network which comprises nodes in a number of N and a pair of optical fibers connecting the nodes and which assigns a predetermined wavelength between two different nodes. The wavelength assignment method comprises forming the first optical path from nodes{n, n+1 ,n+(N+1)/2} to nodes{n+1, n+(N+1)/2, n}; selecting node a at section((n+2), (N+1)/2) and node b at section((n+1+(N+1)/2), N); and forming the second optical path from nodes{n, a, n+(N+1)/2, b} to nodes{a, n+(N+1)/2, b, n}. "N" represents an odd number. "n" is a unique identification factor of wavelength(Wn) assigned to a corresponding optical path. The three steps are repeated at section (1, (N-1)/2) depending on the variable "n". Nodes a and b are not selected together.

Description

Wavelength Allocation Method for Ring Network Using Wavelength Division Multiplexing {WAVELENGTH ASSIGNMENT IN WAVELENGTH DIVISION MULTIPLEXED RING NETWORKS}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to optical communication networks, and more particularly, to a method for allocating wavelengths in a wavelength division multiplexing ring communication network.

Conventional wavelength division multiplexing ring-type communication networks have a plurality of nodes and a forward optical fiber link in which the optical signals travel in a clockwise direction and a reverse optical fiber link in which the optical signals travel in a counterclockwise direction. When all nodes have complete connectivity in such a wavelength division multiplexing ring network, a method of constructing an optical path and assigning wavelengths using the least wavelengths has attracted attention. In addition, there is a need for a method of constructing an optical path between nodes using minimum wavelengths without changing the previous network configuration possible when any node is added to such a ring network.

1 is a diagram schematically showing a ring-shaped communication network composed of five nodes with full connectivity. As shown, in a fully connected communication network, one node necessarily has one optical path with other nodes. The ring-shaped communication network includes a pair of optical fiber links, that is, a forward optical fiber link in which the optical signal proceeds in a clockwise direction and a reverse optical fiber link in which the optical signal travels in a counterclockwise direction, and a plurality of optical links are formed in each of the optical fiber links using a wavelength multiplexing scheme. The channel of is multiplexed. In such a ring network it is problematic to achieve full connectivity with the lowest possible wavelengths. That is, a method of constructing an optical path using the minimum possible wavelengths and a method of assigning a wavelength to each optical path become a problem. In addition, a requirement for assigning wavelengths to each optical path in the ring communication network is that the same wavelengths should not be used when the optical paths share the same optical fiber link.

First, consider the lower limit of the number of wavelengths required to construct such a ring network. First, assume that the optical path between each node is through the shortest path. That is, in FIG. 1, the optical paths from node 1 to node 3 are configured along the clockwise direction and are not configured along the counterclockwise direction. This is reasonable because it is an efficient way to use the available resources. Under these assumptions, some facts can be examined. First, the maximum distance L _max between any two nodes is (N-1) / 2 when the number of nodes N is odd, and N / 2 when N is even. In this case, the distance represents the number of hops, that is, the number of nodes between the two arbitrary nodes, and the distance between two adjacent nodes is one.

When the number of nodes is even, consider how to construct the longest light paths. At this time, there is no fixed way to configure the shortest path. The optical path construction method in this case is as follows.

2 is a diagram for describing a wavelength allocation method in a ring-type communication network having four nodes according to the related art. If the number of nodes is 4, the maximum distance is 2, as shown, and node 1 and node 3 can form the optical path clockwise using the wavelength W ₁ and node 2 and node 4 use the same wavelength W ₁ . The optical path can be constructed clockwise.

If the number of nodes is an even number but not a multiple of four, the two nodes are not considered, and the required number of wavelengths is one in addition to the number of wavelengths when the number of nodes is a multiple of four. Considering this, when constructing optical paths between nodes using the shortest path, the minimum wavelength W to be provided is (N ² -1) / 8 when the number of nodes N is odd, and the number of nodes N is even yet a N ^2/8 in the case where a multiple of 4, the node number N is an even number while the case is not a multiple of ^{4 (N 2 +4) / 8} .

However, the above formulas are given as the lower limit of the required wavelength since the constraint that the optical paths sharing the same optical fiber link should have different wavelengths is not considered when constructing the optical path.

There are many ways to express the configured light path between each node, but the effective method of expressing the configured light path proposed by Ellinas is as follows.

3 is a diagram for describing a wavelength allocation method in a ring communication network having five nodes according to the related art. As shown in Table 1, a case in which a light path from nodes {A, B, D} to nodes {B, D, A} is configured using a wavelength W ₂ is expressed as a matrix.

A B C D E W ₂ One 2 X 2 X

In Table 1, the number represents the distance of the corresponding optical path (the number of hops between two nodes). Therefore, the meaning of 1 in the second column means that the optical path is configured from node A to node B, and the meaning of 2 in the third column means that the optical path is configured from node B to node D. The meaning of X in the fourth column means that the optical path of the node C is not formed using the wavelength W ₂ . Using this method, the optical paths configured for each wavelength can be easily expressed. At this time, the conditions that the matrix representing the configured optical paths, i.e., the necessary conditions, are divided into the necessary conditions in the row and the necessary conditions in the column as follows.

Requirements in the command line

1.If there is a K at (i, j), there is only X between (i, j) and (i, (j + K) mod N). This condition implies that the same wavelength must not be used when sharing fiber links.

2. The sum of all values in a row is N. This condition means the maximum use of a given wavelength.

Requirements in heat

1. No column has the same value. Having the same value means that multiple light paths are configured between the two nodes. Therefore, to maintain the minimum number of wavelengths, it should have only one value.

2. A column must have all values from 1 to L _max . L _max means the maximum distance. This means that full connectivity must be satisfied. However, this condition is satisfied only when the number of nodes is odd, and when it is even, this condition may not be satisfied for some matrices. The optical path with the maximum distance may be constructed through the other fiber link and may not appear in one fiber link. However, this condition must be met when the node is odd.

Therefore, by using the above-mentioned requirements when expressed in a matrix, it is possible to verify whether or not the wavelength allocation is normally performed.

The conventional wavelength allocation method is described below by dividing into an even number of nodes, an odd number of nodes, and a case of expanding nodes.

I. Wavelength allocation method when odd number of nodes

The wavelength allocation method in the case where the number of nodes is odd is as follows using a matrix.

1. Create a matrix equal to W, the number of columns equal to the number of nodes N, and the number of rows equal to the lower limit of the number of wavelengths required when the number of nodes is N.

2. Assign the set {1, 2, ..., L _max } to the first column and X to the rest.

3. Cycle the set used above. For example, iterates over the set {1, 2, ..., L _max } to form the set {L _max , 1, ..., 2}.

4. Allocate a cycled set in the next column and X for the rest.

5. Repeat steps 3 and 4 until the matrix is complete.

The above-described method is applied to a ring-shaped communication network having a node number N of seven as follows. If N is 7, the number of wavelengths W is (7 ² -1) / 8 = 6, and the maximum distance L _max is (7-1) / 2 = 3. In this case, the completed matrix is shown in Table 2 below.

A B C D E F G W ₁ One 3 X X 3 X X W ₂ 2 X 2 X One 2 X W ₃ 3 X X One 2 X One W ₄ X One 3 X X 3 X W ₅ X 2 X 2 X One 2 W ₆ X X One 3 X X 3

The first column is assigned {1, 2, 3} and the second column is assigned {3, 2, 1}, but the reason why it was not assigned in the second and third rows is that the previously assigned values are This is because the wavelength is already used at 2 and 3.

II. Wavelength Allocation Method for Even Number of Nodes

In the case where the number of nodes is even, the above-described method cannot be used, and a method of extending the wavelength after assigning wavelengths to a communication network having (N-1) or odd numbered nodes is used. However, there are some differences between the case where the number of nodes is a multiple of four and the case where the number of nodes is not.

II-1. Wavelength allocation method when the number of nodes is even and multiple of four

1. Construct a matrix representing wavelength assignments for (N-1) nodes.

2. Consider adding a node to any column, and expand it by adding a column at that location.

3. In the newly added column, find the first number on the left for each row.

3-1. If this value is not L _max , increase it by 1, and write X in the newly added column.

3-2. If this value is L _max , decrease this value by q and write (q + 1) in the newly added column. Where q is the number of Xs from the newly added column until the first number is encountered.

3-3. (N / 4) rows are added and the wavelength is used to form the optical path having the maximum distance.

When the above-described method is applied to a communication network having a node number N of 8, the matrix shown in Table 3 below can be obtained. At this time, node E is added between node D and node F. FIG.

A B C D E F G H W ₁ One 3 → 3 X X One 3 X X W ₂ 2 X 2 → 3 X X One 2 X W ₃ 3 X X 1 → 2 X 2 X One W ₄ X One 3 → 2 X 2 X 3 X W ₅ X 2 X 2 → 3 X X One 2 W ₆ X X One 3 → 1 3 X X 3 W ₇ 4 X X X 4 X X X W ₈ X X 4 X X X 4 X

In the first row of <Table 3>, the number of first meetings on the left side of the column E is 3, so that the number cannot be increased. Has a value of 1. This method also applies to the second to sixth rows. Since N is 8, the number of newly added wavelengths is also 2. Then, the optical path having the maximum distance is selected and configured. Here, the wavelength W ₇ configures the optical paths of the node A-> node E, the node E-> node A, and the wavelength W ₈ comprises the optical paths of the node C-> node G, the node G-> node C. The optical paths between nodes B and F and nodes D and H are constructed using wavelengths W ₇ and W ₈ of the other optical fiber link.

II-2. Wavelength allocation method when the number of nodes is even and not a multiple of 4.

1. The method is the same as in the case of multiples of 4, except for assigning the wavelength for the optical path of maximum distance to the added wavelength.

2. When allocating the optical path of the maximum distance, use the added wavelength to bind 4 nodes and use one wavelength, and use the other wavelength for the remaining two nodes. At this time, the corresponding wavelength remains unused in the other optical fiber link.

If the above-described method is applied to a communication network having a node number N of 6, a matrix shown in Table 4 below can be obtained. At this time, node D is added between node C and node E. FIG.

A B C D E F W ₁ One 2 → 2 X One 2 X W ₂ 2 X 1 → 2 X One One W ₃ X One 2 → 1 2 X 2 W ₄ 3 X X 3 X X W ₅ X X 3 X X 3

Since the number of nodes is six, four nodes are considered to be one group, and the remaining two nodes are considered to be another group. In Table 4, nodes A, B, D, and E are considered as one group, and nodes C and F are considered as the remaining group. The wavelength W ₄ constitutes an optical path of A → D, D → A, and an optical path of E → B, B → E through the other optical fiber. Then, W ₅ is used to form an optical path of C → F, F → C, and the wavelength W ₅ of the other optical fiber link is not used.

As described above, the conventional method of allocating wavelengths by Elinas provides only a simple but fixed method. Of course, if you swap rows in a matrix, or freeze nodes and cycle through columns, you see that the transformed form appears, but you cannot escape the restricted form.

III. Wavelength Allocation Method When Expanding Nodes

Once a wavelength is allocated according to the method described above to have complete connectivity in a ring network having an arbitrary number of nodes, and when any node is added at an arbitrary position, the minimum network wavelength is minimized while minimizing the change of the existing network. Create a network with numbers and full connectivity.

If the number of nodes extends from odd to even, the method described above can be followed. From the results shown in Table 3, it can be seen that the minimum number of wavelengths can be used even when the node is expanded. Before node expansion, wavelength W ₁ was used to construct the optical path from node B to node F, but after node expansion, it changed to node B → node E, node E → node F, so node B and node in the existing network A change in F is required. However, at wavelength W ₂ , the optical path from node C to node F remains unchanged even after node expansion. Therefore, it can be seen that if a node is expanded using the above method, the node needs to be changed at wavelengths W ₁ , W ₄ , and W ₆ . In the case where the number of nodes is extended from even to odd, the wavelength allocation method using the matrix is as follows.

1. Expand new columns where nodes are added, and expand rows by the number of wavelengths that should increase as the number of nodes expands.

2. For existing wavelengths, treat them in the same way as they used for existing wavelengths when extending from even to odd.

3. For each new wavelength, if there is an unassigned value from 1 to L _max for each node, assign the number; otherwise, assign X.

When the above-described method is applied to a communication network in which the number of nodes N is extended from 6 to 7, the matrix shown in Table 5 can be obtained. At this time, node D is added between node C and node E. FIG.

A B C D E F G W ₁ One One 2 → 3 X X 2 X W ₂ 2 X 1 → 2 X One One One W ₃ X 2 → 3 X X 2 X 2 W ₄ 3 → 3 X X One 3 X X W ₅ X X 3 → 1 3 X X 3 W ₆ X 2 X 2 X 3 X

As shown in Table 5, when the number of nodes N is 7, the lower limit value of the wavelength is 6, so that one row is added. In the wavelength W ₁ , the first meeting number is 2 when it goes to the left, so it is changed to 3, and in W ₅ , since the first meeting number is 3, it cannot be 4 (since L _max is 3). Since the number of Xs found until the encounter is 2, the value is reduced to 1 and 3 is written in the new column. In the extended wavelength W ₆ , 1, 2, and 3 values must be present in each row (to satisfy full connectivity), and the number is assigned to a position without a number, and X is assigned to a position without a number. . Through this process, the matrix is completed, and it can be seen that the changes in wavelengths W ₄ and W ₅ require a change to the existing communication network.

As described above, the wavelength allocation method in the conventional wavelength division multiplexing ring-type communication network has the advantage that it is possible to systematically and simply obtain the optical path between each node and the wavelength assigned to each optical path using a matrix, but it is fixed. There is a problem in that there is a lack of flexibility in the communication network configuration because it provides only a wavelength allocation method of the form.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned conventional problems, and an object of the present invention is to provide a more flexible method for allocating wavelengths to have complete connectivity in a wavelength division multiplexed ring network. .

In addition, an object of the present invention is to provide a wavelength allocation method that can configure the optical path using a minimum wavelength when the node is added in the already established ring-type communication network and minimizes the impact on the existing communication network.

In order to solve the above problems, according to the present invention, there is provided a wavelength division multiplexing scheme in which N nodes and a pair of optical fibers connecting the N nodes are sequentially connected, and a predetermined wavelength is allocated between the two different nodes. The wavelength allocation method of the ring communication network used is,

First lightpath constituting a first lightpath leading from nodes {n, n + 1, n + (N + 1) / 2} to nodes {n + 1, n + (N + 1) / 2, n} Configuration process;

Node selection process for selecting node a in interval of ((n + 2), (N + 1) / 2) and node b in interval of ((n + 1 + (N + 1) / 2), N) and;

A second light path constituting a second light path from nodes {n, a, n + (N + 1) / 2, b} to nodes {a, n + (N + 1) / 2, b, n} Including the configuration process,

N is an odd number, n is a unique identification factor of the wavelength W _n assigned to the corresponding optical path, and the first optical path configuration process, node selection process, and second optical path configuration process are performed using n as a variable [ 1, (N-1) / 2] is repeated a plurality of times, a and b are not selected in duplicate during the iteration process.

In addition, according to the present invention, a wavelength allocation of a ring-shaped communication network using a wavelength division multiplexing system comprising N nodes and a pair of optical fibers connecting the N nodes in turn and a predetermined wavelength is allocated between the two different nodes is performed. Way,

A node selection process of selecting node a in a section of [(N / 2), (n + 1)] and node b in a section of [N, (n + 1 + N / 2)];

A process of constructing a light path constituting a light path from nodes {n, a, n + N / 2, b} to nodes {a, n + N / 2, b, n},

N is an even number, n is a unique identification factor of the wavelength W _n assigned to the corresponding optical path, and the node selection process and the optical path construction process are performed using n as a variable [1, (N-1) / 2] Repeated a plurality of times in the interval, the a and b are not selected in duplicate in the repeating process.

Furthermore, according to the present invention, the number of nodes is expanded in a ring-shaped communication network of a wavelength division multiplexing system having a pair of optical fibers connecting N nodes and the N nodes, respectively, and a predetermined wavelength is allocated between the two different nodes. When we do wavelength allocation method,

Expressing the optical path configuration and wavelength assignment before the node expansion in a matrix;

Adding a column corresponding to node expansion to the matrix;

Proceeding to the left for each row about the added column and finding that the first value is the maximum distance;

Select one of the rows whose first value is the maximum distance, increment it by 1, assign X to that row in the added column, change the value by calculating the distance from that node to the added node, if any Assigning this value to the corresponding row of the added column by calculating a distance from the added column to the node where the next value appears;

Proceeding to the left for each row about the added column, increasing the value by 1 for the first value not being the maximum distance, and assigning X to the corresponding row of the added column;

Adding rows by the number of added wavelengths, and completing a matrix for each added row,

The value used in the matrix represents a distance between nodes, and the X value does not constitute an optical path of the node.

1 is a schematic diagram of a ring network consisting of five nodes with full connectivity;

2 is a view for explaining a wavelength allocation method in a ring-type communication network having four nodes according to the prior art;

3 is a view for explaining a wavelength allocation method in a ring-type communication network having five nodes according to the prior art;

4A to 4C are diagrams for explaining a method of configuring three optical paths with one wavelength in a ring-shaped communication network of wavelength division multiplex according to the present invention;

5A and 5B are diagrams for explaining a method of configuring four optical paths with one wavelength in a ring-shaped communication network of wavelength division multiplexing according to the present invention;

6A to 9 are diagrams for describing a wavelength allocation method when the number of nodes is odd according to a preferred embodiment of the present invention;

10 and 13 are diagrams for explaining a wavelength allocation method when the number of nodes according to another embodiment of the present invention is even.

Hereinafter, with reference to the accompanying drawings will be described an embodiment of the present invention; In describing the present invention, detailed descriptions of related well-known functions and configurations are omitted in order not to obscure the subject matter of the present invention.

The wavelength division multiplexing wavelength allocation method according to the present invention is carried out using the following basic principles.

Basic principles

1. Use each wavelength to form as even an optical path as possible.

2. Each wavelength must be allocated once completely throughout the fiber link. This condition is to increase the use efficiency of the wavelength.

As shown in the existing wavelength allocation method, the minimum number of wavelengths required for allocating one optical path between nodes in a wavelength division multiplexed ring network is given as follows. And when the number of nodes is N, the total number of optical paths to be configured is N (N-1). In addition, when the minimum number of wavelengths W to be provided is the number of nodes N is an odd number (N ² -1) / 8 and, in the case where the number of nodes N is an even number while a multiple of 4 N ^2/8, and the number of nodes N (N ² +4) / 8 if even and not a multiple of 4.

Hereinafter, the wavelength allocation method according to the present invention will be described below by dividing into an odd number of nodes, an even number of nodes, and a case of expanding a node.

I. Wavelength allocation method when odd number of nodes

In this case, the number of optical paths to be provided through each optical fiber link is N (N-1) / 2. In addition, assuming that the optical paths are configured as uniformly as possible for each wavelength, three optical paths are configured for each of (N-1) / 2 wavelengths, and the remaining (N-1) (N-3) / 8 wavelengths are used. Each consists of four paths. In this case, the total number of wavelengths is (N-1) / 2 + (N-1) (N-3) / 8 = (N ² -1) / 8, and the total number of optical paths is 3 (N-1) The condition required as / 2 + 4 (N-1) (N-3) / 8 = N (N-1) / 2 can be satisfied.

Ⅰ-1. How to configure three light paths with one wavelength

At this time, only the clockwise optical fiber link is considered, and the counterclockwise optical fiber link can be easily inferred by the method described below.

1. Select three nodes {n, n + 1, n + (N + 1) / 2}.

2. Nodes {n + at nodes {n, n + 1, n + (N + 1) / 2} increasing by 1 in interval [1, (N-1) / 2] with n as a variable The process of constructing the optical path leading to 1, n + (N + 1) / 2, n} is repeated.

4A to 4C are diagrams for explaining a method of configuring three optical paths with one wavelength in a ring-shaped communication network of wavelength division multiplex according to the present invention. The ring network has N nodes, and FIG. 4A shows nodes {1, 2, (N + 3) / 2} selected, and FIG. 4B shows nodes {2, 3, (N + 5) /. 2} is selected, FIG. 4C shows a case where nodes {(N-1) / 2, (N + 1) / 2, N} are selected. Referring to FIG. 4A, a light path from nodes {1, 2, (N + 3) / 2} to nodes {2, (N + 3) / 2, 1} using wavelength W ₁ is configured. Referring to 4b, a light path from nodes {2, 3, (N + 5) / 2} to nodes {3, (N + 5) / 2, 2} using wavelength W ₂ is constructed, and FIG. 4C. Let us look at nodes {(N-1) / 2, (N + 1) / 2, N} using wavelength W _{(N-1) / 2} A light path leading to N-1) / 2} is constructed.

I-2. How to configure four light paths with one wavelength

1. Select nodes {n, n + (N + 1) / 2} as reference nodes. The following steps 2 and 3 are repeated with n being the variable and increasing by 1 in the interval [1, (N-1) / 2].

2. Any node a in the interval ((n + 2), (N + 1) / 2) and any node b in the interval of ((n + 1 + (N + 1) / 2), N) Select. At this time, the nodes {n, n + 1, n + (N + 1) / 2} cannot be selected. Scenes from nodes {n, a, n + (N + 1) / 2, b} to nodes {a, n + (N + 1) / 2, b, n} between 4 selected nodes including the reference node Construct a furnace.

3. In the interval [(n + 2), (N + 1) / 2], select any node a 'not selected in the above process, and select [(n + 1 + (N + 1) / 2), In the interval of N], select any node b 'not selected in the above process and select nodes {a', n + (N +) at nodes {n, a ', n + (N + 1) / 2, b'}. 1) / 2, b ', n}. This process is repeated until all nodes are selected.

5A and 5B are diagrams for explaining a method of configuring four optical paths with one wavelength in a ring-shaped communication network of wavelength division multiplex according to the present invention. As shown in FIG. 5A, when the reference node is set to nodes {1, (N + 3) / 2}, any one node in the interval [3, (N + 1) / 2] and [ One node can be selected in the interval (N + 5) / 2, N]. When node 4 and node (N-1) are selected, nodes {4, (N) at nodes {1, 4, (N + 3) / 2, (N-1)} as shown in FIG. 5A. Four light paths are constructed, leading to +3) / 2, (N-1), 1}. If the reference node is set to nodes {(N-3) / 2, (N-1)}, there is only one case of node (N + 1) / 2 and node N that can be selected, respectively. In this case, nodes {(N + 1) / 2, (N) at nodes {(N-3) / 2, (N + 1), (N-1), N} as shown in FIG. 5B -1), N, (N-3) / 2} to constitute four optical paths.

If the reference node is set to nodes {1, (N + 3) / 2}, any one node in the interval [3, (N + 1) / 2] and [(N + 5) / 2, N Since any node in the interval can be selected, the number of optical paths constructed in this case is 4 (N-3) / 2. If the reference node is set to nodes {2, (N + 5) / 2}, any one node in the interval [4, (N + 1) / 2] and [(N + 7) / 2, N] Since any one node in the interval can be selected, the number of optical paths constructed in this case is 4 (N-5) / 2. The total number of optical paths thus constructed is 4 ((N-3) / 2 + (N-5) / 2 + ... + 1) = (N-1) (N-3) / 2 As described above, (N-1) (N-3) / 2 optical paths can be configured at (N-1) (N-3) / 8 wavelengths.

In the above-described wavelength allocation method, different types of wavelength allocation methods appear according to a method of selecting two arbitrary nodes for a reference node. This will be described with reference to the following examples.

Example 1

6A to 9 are diagrams for describing a wavelength allocation method when the number of nodes is odd according to a preferred embodiment of the present invention.

6A to 6C are diagrams for describing a method of configuring three optical paths for each wavelength in a ring-shaped communication network of a wavelength division multiplex method having a node number of seven. FIG. 6A illustrates a case where nodes {1, 2, 5} are selected, FIG. 6B illustrates a case where nodes {2, 3, 6} are selected, and FIG. 6C illustrates a case where nodes {3, 4, 7} are selected. Referring to FIG. 6a by using a wavelength W ₁ and the optical path leading to the node from the nodes {1,2, 5}, {2, 5, 1} configurations, the node to Referring to FIG. 6b using a wavelength W ₂ { 2, 3, 6} is configured to the optical path leading to the nodes {3, 6, 2}, Figure 6c, using the wavelength W ₃ nodes {3, 4, 7} at nodes {3, 4, 7} , A light path leading to 3} is constructed.

7A to 8B are diagrams for describing a method of configuring four optical paths for each wavelength in the ring communication network shown in FIG. 6. In FIG. 7A to FIG. 8B, the reference node is set to nodes {1, 5}, in FIG. 7A, additionally select nodes {3, 7}, and in FIG. 7B, nodes {4, 6} are further selected. In addition, nodes {3, 6} are additionally selected in FIG. 8A, and nodes {4, 7} are additionally selected in FIG. 8B.

In the case of FIG. 7A, four light paths are formed from nodes {1, 3, 5, 7} to nodes {3, 5, 7, 1}. In the case of FIG. 7B, four light paths are configured from nodes {1, 4, 5, 6} to nodes {4, 5, 6, 1}. In the case of FIG. 8A, four light paths are configured leading from nodes {1, 3, 5, 6} to nodes {3, 5, 6, 1}. In the case of FIG. 8B, four light paths are configured from nodes {1, 4, 5, 7} to nodes {4, 5, 7, 1}.

In FIG. 9, the reference node is set to nodes {2, 6} and further selects nodes {4, 7}. In the case of FIG. 9, four light paths are formed from nodes {2, 4, 6, 7} to nodes {4, 6, 7, 2}.

Table 6 below shows the optical path construction method corresponding to FIGS. 6, 7A, 7B, and 9 using a matrix, and Table 7 below illustrates FIGS. 8B and the optical path construction method corresponding to the case of FIG. 9 are displayed by using a matrix.

One 2 3 4 5 6 7 W ₁ One 3 X X 3 X X W ₂ X One 3 X X 3 X W ₃ X X One 3 X X 3 W ₄ 2 X 2 X 2 X One W ₅ 3 X X One One 2 X W ₆ X 2 X 2 X One 2

One 2 3 4 5 6 7 W ₁ One 3 X X 3 X X W ₂ X One 3 X X 3 X W ₃ X X One 3 X X 3 W ₄ 2 X 2 X One 2 X W ₅ 3 X X One 2 X One W ₆ X 2 X 2 X One 2

II. Wavelength Allocation Method for Even Number of Nodes

First consider the wavelength allocation method for the optical paths with the largest distance. If the number of nodes is 4, the maximum distance is 2, as in the case of FIG. 2, wherein nodes 1 and 3 can configure an optical path using the wavelength W ₁ in a clockwise direction, and nodes 2 and 4 are counterclockwise. using the same wavelength W ₁ can form an optical path. Thus, one wavelength is required for two pairs of nodes spaced apart at maximum distance. If it is even and not a multiple of 4, then the number of wavelengths for the nodes excluding one pair of nodes is (n-2) / 4, and another wavelength is needed for one pair of nodes not considered further Do. If we assign wavelengths in this way, the number of wavelengths W _longest needed for the optical path with the maximum distance is N / 4 if it is a multiple of 4, and (N-2) / 4 + 1 is not do.

If it is a multiple of 4, the optical path with the maximum distance is assigned and the number of remaining wavelengths is N ² / 8-N / 4 = N (N-2) / 8, and the number of optical paths to be constructed using these ( The number of optical paths in one optical fiber link) is N (N-1) / 2-N / 2 = N (N-2) / 2. Also, in case of even number, not even multiple of 4, assign the optical path with maximum distance and the number of remaining wavelengths is (N ₂ +4) / 8- (N-2) / 4-1 = N (N-2) / 8, and the total number of optical paths to be constructed using these is N (N-1)-(N-2) -2 = N (N-2). The number becomes N (N-2) / 2. Therefore, in the even case, the remaining optical paths except the optical path having the maximum distance are equally allocated for each wavelength, and four optical paths may be configured for each wavelength.

How to configure four optical paths for each wavelength

1. Select nodes (n, n + N / 2) as reference nodes. The following steps 2 and 3 are repeated with n being the variable and increasing by 1 in the interval [1, (N-1) / 2].

2. Any node a and [(n + 1 + N / 2), N) in the interval [(n + 1), N / 2] (where n + 1≥N / 2) , select n + 1 + N / 2≥N). Then, a light path from nodes {n, a, n + N / 2, b} to nodes {a, n + N / 2, b, n} is configured.

3. In the interval [(n + 2), N / 2] (where n + 1≥N / 2), select any node a 'not selected in the above process, and select [(n + 1 + N / 2), in the interval of N] (where n + 1 + N / 2≥N), select any node b 'not selected in the above process and select nodes {n, a', n + N / 2, b '} Constitutes a light path leading to nodes {a', n + N / 2, b ', n}. This process is repeated until all nodes are selected.

The number of optical paths configured through the above process is 4 (N / 2-1 + ... + 1) = N (N-2) / 2 to configure all desired optical paths.

Example 2

10 to 13 are diagrams for describing a wavelength allocation method when the number of nodes is an even number according to another embodiment of the present invention.

FIG. 10 is a view for explaining a method of configuring an optical path having a maximum distance in a ring-shaped communication network of a wavelength division multiplex method having 6 nodes. As shown, two wavelengths are required for the optical path with the maximum distance. Two wavelengths for the optical path from nodes {1, 4} to nodes {4, 1} in the clockwise optical fiber link and the light path from nodes {2, 5} to nodes {5, 2} W ₁ and W ₂ are required, in the counterclockwise optical fiber link one wavelength W ₃ (for the optical fiber link in the clockwise direction) is used for the optical path from nodes {3, 6} to nodes {6, 3}. One of the wavelengths required).

11A and 13 are diagrams for describing a method of configuring four optical paths for each wavelength in the ring network shown in FIG. 10. In FIGS. 11A-12B, the reference node is set to nodes {1, 4}, further selects nodes {2, 5} in FIG. 11A, and further selects nodes {3, 6} in FIG. 11B. In addition, nodes {2, 6} are additionally selected in FIG. 12A, and nodes {3, 5} are additionally selected in FIG. 12B.

In the case of FIG. 11A, four light paths are configured from nodes {1, 2, 4, 5} to nodes {2, 4, 5, 1}. In the case of FIG. 11B, four light paths are configured leading from nodes {1, 3, 4, 6} to nodes {3, 4, 6, 1}. In the case of FIG. 12A, four light paths are configured, leading from nodes {1, 2, 4, 6} to nodes {2, 4, 6, 1}. In the case of FIG. 12B, four light paths are configured from nodes {1, 3, 4, 5} to nodes {3, 4, 5, 1}.

11A to 12B illustrate two different methods for configuring four optical paths per wavelength for the reference nodes {1, 4}. The remaining case is for the reference node {2, 5}, in which case there is only one method.

In FIG. 13, the reference node is set to nodes {2, 5} and further selects nodes {3, 6}. In the case of FIG. 13, four light paths are formed from nodes {2, 3, 5, 6} to nodes {3, 5, 6, 2}.

Table 8 below shows the optical path construction method corresponding to FIGS. 10, 11A and 11B, and FIG. 13 by using a matrix, and Table 9 below shows FIGS. 12B and the optical path construction method corresponding to the case shown in FIG. 13 are displayed by using a matrix.

One 2 3 4 5 6 W ₁ 3 X X 3 X X W ₂ X 3 X X 3 X W ₃ One 2 X One 2 X W ₄ 2 X One 2 X One W ₅ X One 2 X One 2

One 2 3 4 5 6 W ₁ 3 X X 3 X X W ₂ X 3 X X 3 X W ₃ One 2 X 2 X One W ₄ 2 X One One 2 X W ₅ X One 2 X One 2

Modified Wavelength Allocation Method

As described above, when the configuration and assigned wavelengths of each optical path are expressed in a matrix, the rows are exchanged with each other (meaning different wavelengths are allocated) or the nodes are fixed and the columns are cycled. The wavelength allocation method can be obtained. This method takes into account the characteristics of a ring network. Here, a method of obtaining a different optical path configuration and a wavelength allocation method by modifying a basic optical path configuration and a wavelength allocation method according to the present invention will be described.

When compared with the configuration in the optical path of the two wavelengths, the wavelength _{W 1 {..., a → c} , ...} has a structure in the optical path of the wavelength W ₂ {..., a → b, b → c, ...} in the case of wavelength W ₁ , the existing optical path configuration at wavelength W ₁ is maintained at {..., a → b, b → c, ...}. And replace a → c with {a → b, b → c}, and configure the optical path with {..., a → c, ...} for wavelength W ₂ You can get it. For example, in FIG. 6A, the light path is composed of {1 → 2, 2 → 5, 5 → 1}, and in FIG. 7A, the light path is {1 → 3, 3 → 5, 5 → 7, 7 → 1}. Consists of In this case, even if the optical path configuration is changed to {1 → 2, 2 → 5, 5 → 7, 7 → 1} and {1 → 3, 3 → 5, 5 → 1}, the configuration method is different, The configuration using the two wavelengths does not change. By such a modified wavelength allocation method, more various types of optical path configurations and wavelength allocation methods can be obtained.

III. Wavelength Allocation Method for Node Expansion

After constructing a ring-type communication network of wavelength division multiplexing with the minimum number of wavelengths, if a new node is added, a new communication network may be configured without considering the existing communication network in order to configure the communication network with the minimum number of wavelengths. It would be more efficient to reconfigure the network with a minimum number of wavelengths while reducing the network's change. Here, we describe a wavelength allocation method for node expansion with less change compared to the conventional method. This method maximizes the effect when the number of nodes extends from odd to even rather than a multiple of four.

Wavelength allocation method when the number of nodes extends from odd to even rather than a multiple of four

1. Determine the position of the column to be added in the given matrix.

2. Look left for each row centered on the added column and find that the first number is L _max . In this case, L _max is (N _odd -1) / 2, and N _odd means an _odd number of nodes.

2-1. Select one of them, increment it by one, and assign X to that row in the added column.

2-1. If there is anything left, change the value by calculating the distance from the node to the added node, and assign the value by calculating the distance from the added column to the node where the next number appears in the row of the added column.

3. Continue left for each row around the added column, incrementing by 1 for the first non-L _max , and assigning X to that row in the added column.

4. Add rows by the number of wavelengths added, and complete the matrix for each row added.

By using the above-described method, the matrixes when the number of nodes N is extended from 5 are as shown in Tables 10 and 11, where node F is added between node B and node C. FIG.

A B F C D E W ₁ One One 2 X 2 X W ₂ 2 X One One One One W ₃ X 2 X 2 X 2 W ₄ 3 X X 3 X X W ₅ X X 3 X X 3

Table 10 shows the results by Elinas.

A B F C D E W ₁ One 3 X X 2 X W ₂ 2 X One One One One W ₃ X 2 X 2 X 2 W ₄ X One 2 X 3 X W ₅ 3 X X 3 X X

Table 11 shows the results according to the present invention. In other words, the result of Elinas, but the change in the wavelength W1 and W2 occurred, it can be seen that the result according to the present invention changed only W2.

As described above, the wavelength allocation method of the ring-type communication network using the wavelength division multiplexing method according to the present invention has an advantage in that flexibility in wavelength allocation is improved by setting a reference node and configuring optical paths in various ways.

In addition, the wavelength allocation method of the ring-type communication network using the wavelength division multiplexing method according to the present invention can configure the optical path between each node using the minimum wavelength without changing the previous network configuration possible when any node is added. There is an advantage that it can.

Claims (3)

In the wavelength allocation method of a ring-shaped communication network using a wavelength division multiplexing method having N nodes and a pair of optical fibers connecting the N nodes in turn, and a predetermined wavelength is allocated between the two different nodes, First lightpath constituting a first lightpath leading from nodes {n, n + 1, n + (N + 1) / 2} to nodes {n + 1, n + (N + 1) / 2, n} Configuration process; Node selection process for selecting node a in interval of ((n + 2), (N + 1) / 2) and node b in interval of ((n + 1 + (N + 1) / 2), N) and; A second light path constituting a second light path from nodes {n, a, n + (N + 1) / 2, b} to nodes {a, n + (N + 1) / 2, b, n} Including the configuration process, N is an odd number, n is a unique identification factor of the wavelength W _n assigned to the corresponding optical path, and the first optical path configuration process, node selection process, and second optical path configuration process are performed using n as a variable [ 1, (N-1) / 2] are repeated a plurality of times, and a and b are the wavelength allocation method of a ring-type communication network using a wavelength division multiplexing method characterized in that not selected in duplicate in the iteration process. In the wavelength allocation method of a ring-shaped communication network using a wavelength division multiplexing method comprising N nodes and a pair of optical fibers connecting the N nodes in turn, and a predetermined wavelength is allocated between the two different nodes. A node selection process of selecting node a in a section of [(N / 2), (n + 1)] and node b in a section of [N, (n + 1 + N / 2)]; A process of constructing a light path constituting a light path from nodes {n, a, n + N / 2, b} to nodes {a, n + N / 2, b, n}, N is an even number, n is a unique identification factor of the wavelength W _n assigned to the corresponding optical path, and the node selection process and the optical path construction process are performed using n as a variable [1, (N-1) / 2] A plurality of repetitions in the interval, the a and b wavelength allocation method of a ring-shaped communication network using a wavelength division multiplexing method characterized in that the overlapping process is not selected. Wavelength allocation in the case of extending the number of nodes in a ring-shaped communication network having a wavelength division multiplexing system having N nodes and a pair of optical fibers connecting the N nodes in turn and allotting a predetermined wavelength between the two different nodes. In the method, Expressing the optical path configuration and wavelength assignment before the node expansion in a matrix; Adding a column corresponding to node expansion to the matrix; Proceeding to the left for each row about the added column and finding that the first value is the maximum distance; Select one of the rows whose first value is the maximum distance, increment it by 1, assign X to that row in the added column, change the value by calculating the distance from that node to the added node, if any Assigning this value to the corresponding row of the added column by calculating a distance from the added column to the node where the next value appears; Proceeding to the left for each row about the added column, increasing the value by 1 for the first value not being the maximum distance, and assigning X to the corresponding row of the added column; Adding rows by the number of added wavelengths, and completing a matrix for each added row, The value used in the matrix represents a distance between nodes, and the X value does not constitute an optical path of the node. The wavelength allocation method of the ring-type communication network using the wavelength division multiplexing method.