CN109905172B - Frequency spectrum allocation method for minimizing adjacency reduction in elastic optical network - Google Patents
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Abstract
The invention discloses a frequency spectrum allocation method for minimizing adjacency reduction in a flexible optical network, when allocating spectrum for a connection request on a path, by calculating the amount of decrease in the degree of adjacency on the path that is caused when each available spectrum block is used, the one that minimizes the amount of adjacency reduction is then selected from all available spectral blocks, allocated to the connection request, thereby realizing the frequency spectrum allocation which minimizes the reduction of the adjacency degree, considering the influence on the path adjacency degree after using one frequency spectrum block when allocating the frequency spectrum for the connection request in the elastic optical network, further ensuring that after the frequency spectrum is distributed to each connection request, the adjacency of the rest idle frequency slots on the path is maximum, the measure can reduce the fragmentation degree of the frequency spectrum on the path, further reduce the blocking rate of the connection request and improve the utilization rate of network resources.
Description
Technical Field
To a method of spectrum allocation in a resilient optical network that minimizes adjacency reduction.
Background
In a conventional optical network, signal transmission is performed by using a Wavelength Division Multiplexing (WDM) technology, which can only provide a transmission channel with a fixed bandwidth in terms of Wavelength. With the development of technologies such as cloud computing, mobile internet, internet of things and the like, the requirement of users on the diversity of network bandwidths is higher and higher, and the WDM technology cannot adapt to the requirement. An Elastic Optical Network (EON) is a Network architecture based on Optical Orthogonal Frequency Division Multiplexing (O-OFDM) technology. In the elastic optical network, the spectrum resource is divided into hundreds of Frequency Slots (FS), and the spectrum width occupied by each Frequency slot is much smaller than that occupied by one wavelength in the WDM optical network. In the elastic optical network, a plurality of frequency slots can be flexibly allocated to users according to the transmission rate requested by the users, so that the elastic optical network can fully meet the bandwidth diversity requirements of the users.
In an optical network, a path between two nodes is called a light-path (light-path), and a light path may include multiple links. In the elastic optical network, if the frequency resources on each link are divided into F frequency slots, the frequency slots are numbered 1,2, …, F from small to large. When allocating a frequency band for a connection request of a user in a flexible optical network, the following three limiting conditions need to be satisfied:
(1) band non-overlapping limitation: on any one link, the frequency slots allocated for different connection requests cannot overlap with each other. In other words, any two connection requests cannot use the same number of frequency slots on the same link at the same time.
(2) Band continuity limitation: the frequency slots allocated for the same connection request must be identical on all links of a lightpath. That is, if a frequency slot with the number f is allocated to a connection request on one link of an optical path, the frequency slot with the number f is allocated to the connection request on all links of the optical path.
(3) Band adjacency limitation: on any link in the network, the frequency slots allocated for the same connection request must have consecutive numbers. For example, if 3 frequency slots are allocated for a connection request, the three frequency slots may be numbered 2, 3, 4 or 3, 4, 5, but not 2, 3, 5.
The above restriction conditions make more consideration to the allocation of spectrum resources for connection requests in the elastic optical network. If the spectrum allocation method is not reasonable, the fragmentation phenomenon of the spectrum resources in the network is serious, and the consequence that although the idle frequency slot resources exist, the idle resources do not meet the above limiting conditions, and thus cannot be allocated to the connection request for use is caused. The reasonable spectrum resource allocation mode can more efficiently use the spectrum resources, thereby reducing the blocking rate of connection requests in the network and improving the utilization rate of the network resources.
Disclosure of Invention
The present invention aims to overcome the above-mentioned shortcomings and provide a technical solution to solve the above-mentioned problems.
When spectrum is allocated for a connection request on a path, the method for allocating the spectrum with the minimum adjacency reduction amount in the elastic optical network is realized by calculating the reduction amount of the adjacency on the path caused by each available spectrum block when used, then selecting one with the minimum adjacency reduction amount from all the available spectrum blocks and allocating the selected one to the connection request, and the specific steps are as follows:
the method comprises the following steps: when a connection request r comes from a source node s to a destination node d, a path from the source node to the destination node is denoted as P, a link set on the path P is denoted as e (P), a frequency slot number is F ═ 1,2, …, F, and a state of an F-th frequency slot on the path is represented as:
calculating the number of idle spectrum blocks on a path
And number of idle spectrum blocks
Further calculate the adjacency degree on the path P
Step two: recording the number of frequency slots required by the connection request as S, finding out all available frequency spectrum blocks on the path, and recording the available frequency spectrum blocks as b1,b2,…,bBWherein the ith spectrum block is bi＝[istart(b),iend(b)]；
Step three, for each frequency spectrumBlock bi＝[istart(b),iend(b)]Calculating the adjacency degree C of the path P after it is usedP(bi) And further calculates the usage spectrum block biDecrease Δ C in adjacency on path P when usedP(bi)＝CP-CP(bi)；
Step four: one of all available spectrum blocks that minimizes the reduction in adjacency on path P is selected and allocated to connection request r.
As a further scheme of the invention: the idle frequency slot hinge refers to a frequency slot group formed by two idle frequency slots which are numbered continuously.
As a further scheme of the invention: in the third step: if there is more than one spectrum block with the smallest reduction of the adjacency, the first spectrum block is selected to be allocated to the connection request r.
As a further scheme of the invention: in the first step: when there are no free spectrum blocks available on path P, the connection request r is blocked from stopping.
Compared with the prior art, the invention has the beneficial effects that: the method and the device consider the influence on the adjacency degree of the path after using one spectrum block when allocating the spectrum for the connection request in the elastic optical network, further ensure that the adjacency degree of the rest idle frequency gaps on the path is maximum after allocating the spectrum for each connection request, reduce the fragmentation degree of the spectrum on the path by the measure, further reduce the blocking rate of the connection request and improve the utilization rate of network resources.
Additional aspects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.
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In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to these drawings without creative efforts.
Fig. 1 is a specific operation flow of the spectrum allocation method based on minimizing the adjacency reduction amount.
Fig. 2 is a diagram for explaining an example in which a path is formed by a plurality of links.
Fig. 3 is an example of a method for determining busy/idle status of each frequency slot on path P, and shows all available spectrum blocks on path P.
Fig. 4 is used to explain the adjacency and the decrease amount of the adjacency on the path P when different spectrum blocks are used.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Referring to fig. 1 to 4, in an embodiment of the present invention, a method for allocating a spectrum of a minimum adjacency reduction amount in a flexible optical network, when allocating a spectrum for a connection request on a path, the method calculates a reduction amount of adjacency on the path caused when each available spectrum block is used, and then selects one of all available spectrum blocks that minimizes the reduction amount of adjacency to allocate to the connection request, thereby implementing the spectrum allocation of the minimum adjacency reduction amount, including the following specific steps:
the method comprises the following steps: when a connection request r comes from a source node s to a destination node d, a path from the source node to the destination node is denoted as P, a link set on the path P is denoted as e (P), a frequency slot number is F ═ 1,2, …, F, and a state of an F-th frequency slot on the path is represented as:
calculating the number of idle spectrum blocks on a path
And number of idle spectrum blocks
Further calculate the adjacency degree on the path P
Step two: recording the number of frequency slots required by the connection request as S, finding out all available frequency spectrum blocks on the path, and recording the available frequency spectrum blocks as b1,b2,…,bBWherein the ith spectrum block is bi＝[istart(b),iend(b)]；
Step three, for each frequency spectrum block bi＝[istart(b),iend(b)]Calculating the adjacency degree C of the path P after it is usedP(bi) And further calculates the usage spectrum block biDecrease Δ C in adjacency on path P when usedP(bi)＝CP-CP(bi)；
Step four: one of all available spectrum blocks that minimizes the reduction in adjacency on path P is selected and allocated to connection request r.
As a further scheme of the invention: the idle frequency slot hinge refers to a frequency slot group formed by two idle frequency slots which are numbered continuously.
As a further scheme of the invention: in the third step: if there is more than one spectrum block with the smallest reduction of the adjacency, the first spectrum block is selected to be allocated to the connection request r.
As a further scheme of the invention: in the first step: when there are no free spectrum blocks available on path P, the connection request r is blocked from stopping.
Example (b):
calculating the current state of the path: when a connection request comes, the busy-idle state of all frequency slots on the path is firstly judged. FIG. 2 shows aAn example of a path, path P, includes three links, and the state of each frequency slot on the path is determined by the state of the corresponding frequency slot on the three links. Fig. 3 shows a method for determining the status of each frequency slot on path P, in this example, it is assumed that there are 16 frequency slots on each link (the number of frequency slots in an actual network is generally 320 or more), and each frequency slot is represented by a rectangle: the black filled rectangle indicates that the frequency slot is busy, i.e. that the frequency slot has been occupied by other connection requests; the white filled rectangle indicates that the frequency slot is free and can be allocated to the current connection request. For the frequency slot numbered f on the path, it is idle on path P only if the corresponding frequency slots on the three links are idle. For example, frequency slot number 3 is in link e1Is idle at2And e3Is busy, so it is also busy on path P; the frequency slot numbered 4 is free on all links and therefore also on path P. The state of the f-th frequency slot on the path can be expressed as a Boolean variable
The states of all frequency slots on path P form an F-dimensional Boolean vector
For the example in the figure, we can obtain the state vector of path P as
Determining available spectrum blocks: after determining the busy-idle status of each frequency slot on the path, all available spectrum blocks can be found on the path according to the number of frequency slots required by the connection request. If the connection request requires 2 frequency slots, the available spectrum blocks on path P are four in total: b1、b2、b3、b4The specific position is shown in fig. 3.
Calculating the adjacency degree on the path: to calculate the adjacency on a path, two quantities need to be calculated first: the number of idle frequency slots on the path, and the number of idle frequency slot hinges on the path. For path P in the example, the number of free frequency slots on it is
The number of idle frequency gap hinges is
Whereby the adjacency on the path P of
Calculate the adjacency reduction amount caused by each spectrum block: the amount of decrease in the degree of adjacency on the path that results when different available spectrum blocks are allocated to the connection request r is calculated as follows. We first calculate the adjacency degree on the path after using each spectrum block, and the difference between the adjacency degree before and after using is the decrease of the adjacency degree on the path. The calculation results are as follows:
selecting a spectrum block that minimizes the amount of adjacency reduction: as can be seen from the calculation results, the spectrum block b is used1The resulting reduction in adjacency on path P is minimal, thus placing spectral block b in1The corresponding frequency slot is allocated to the connection request r.
It will be evident to those skilled in the art that the invention is not limited to the details of the foregoing illustrative embodiments, and that the present invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein. Any reference sign in a claim should not be construed as limiting the claim concerned.
Claims (3)
1. A method for allocating frequency spectrum in elastic optical network to minimize the reduction of adjacency is characterized in that when allocating frequency spectrum for a connection request on a path, the frequency spectrum allocation for minimizing the reduction of adjacency is realized by calculating the reduction of adjacency on the path caused by each available frequency spectrum block being used, then selecting one of all available frequency spectrum blocks which minimizes the reduction of adjacency to allocate it to the connection request, and the specific steps are as follows:
the method comprises the following steps: when a connection request r comes from a source node s to a destination node d, a path from the source node to the destination node is denoted as P, a link set on the path P is denoted as e (P), a frequency slot number is F ═ 1,2, …, F, and a state of an F-th frequency slot on the path is represented as:
calculating the number of idle spectrum blocks on a path
And number of idle spectrum blocks
Further calculate the adjacency degree on the path P
Step two: recording the number of frequency slots required by the connection request as S, finding out all available frequency spectrum blocks on the path, and recording the available frequency spectrum blocks as b1,b2,…,bBWherein the ith spectrum block is bi＝[istart(b),iend(b)]；
Step three, for each frequency spectrum block bi＝[istart(b),iend(b)]Calculating the adjacency degree C of the path P after it is usedP(bi) And further calculates the usage spectrum block biDecrease Δ C in adjacency on path P when usedP(bi)＝CP-CP(bi) If more than one frequency spectrum block with the minimum adjacency reduction amount is selected, a first frequency spectrum block is selected to be allocated to the connection request r;
step four: one of all available spectrum blocks that minimizes the reduction in adjacency on path P is selected and allocated to connection request r.
2. The method according to claim 1, wherein the free-slot hinge is a frequency slot group consisting of two consecutive free-slots.
3. The method according to claim 1, wherein the first step comprises: when there are no free spectrum blocks available on path P, the connection request r is blocked from stopping.
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