Time-aware time-varying service routing spectrum allocation method in survivability elastic optical network

Abstract

The invention relates to a time-aware time-varying service routing spectrum allocation method in a survivability elastic optical network, and belongs to the technical field of optical communication and optical signal transmission. According to the method, the time-varying service transmission resources are allocated by adopting a mixed dedicated path and bandwidth segmentation multi-path protection strategy and a maximum time difference spectrum allocation strategy. When the time-varying service arrives at the elastic optical network, if the dedicated path protection cannot meet the bandwidth requirement of the time-varying service, transmitting the service by adopting a bandwidth segmentation multipath protection strategy; in order to increase frequency spectrum sharing, a maximum time difference frequency spectrum allocation strategy is adopted for a working path and a protection path of the time-varying service to allocate frequency spectrums; when the elastic optical network detects the bandwidth change of the time-varying service, in order to reduce the frequency spectrum fragments of an optical path, a frequency spectrum-time resource fragment value is designed to evaluate the availability of a frequency spectrum block, so that the frequency spectrum allocation on a working path and a protection path of the time-varying service is adjusted. The method can reduce the blocking rate of the time-varying service and improve the spectrum utilization rate of the network.

Description

Technical Field

[0001] The invention belongs to the field of optical fiber communication and optical transmission, and relates to a spectrum allocation method for time-aware time-varying service routing in a survivable elastic optical network. Background Art

[0002] In recent years, with the emergence of a large number of applications such as video on demand, cloud computing and grid computing, and online games, network traffic has exploded. Traditional optical transmission technology is limited by the bandwidth bottleneck in the electrical domain and it is difficult to meet the bandwidth requirements of optical networks, and the transmission distance of signals is also limited. Although wavelength division multiplexing optical networks are not restricted by the electrical domain and can achieve all-optical transmission, their fixed grids will cause a huge waste of spectrum bandwidth resources, which is not conducive to improving spectrum efficiency. Services such as cloud computing and grid computing have introduced a large amount of dynamic traffic (bandwidth requirements range from hundreds of bits per second to terabits). How to instantiate this traffic is a major challenge for network operators. In order to solve the above problems and meet the future optical network's requirements for efficiency, flexibility, and dynamism, elastic optical networks (EONs) based on orthogonal frequency division multiplexing (OFDM) technology came into being. EONs divide the spectrum into fine-grained frequency slots (FS), use OFDM technology to multiplex subcarriers, and flexibly allocate multiple consecutive idle FSs according to business needs to form available spectrum blocks for the business to meet the business transmission needs of different bandwidths.

[0003] In recent years, with the rapid development of Internet technology, new services have emerged, such as high-definition video live broadcast, online games, etc. The bandwidth of services often changes with time, which is called time-varying services. Traditional resource allocation methods are not flexible enough. In the face of increasingly precious spectrum resources, if resources can be allocated in real time according to the actual bandwidth requirements of the service to maximize spectrum efficiency, it will be of great benefit to operators to improve network service performance and resource utilization and enhance user service experience. In elastic optical networks, the transmission bandwidth resources allocated to services on the optical path are idle FS on the network link. Unlike traditional fixed grid optical networks, the optical path in EONs can dynamically adjust the modulation format of the grid according to real-time needs and network status, which can more flexibly allocate bandwidth to services and is conducive to improving bandwidth resource utilization. However, the spectrum blocks allocated by the network to the service need to meet the spectrum consistency and continuity constraints on each link of the optical path, which increases the complexity of service routing and spectrum allocation. Therefore, it is very necessary to study the routing and spectrum allocation (RSA) method of time-varying services in EONs.

[0004] Since some control protocols such as general protocol label switching and path control unit are used to manage dynamic optical paths, the network can dynamically perceive the time characteristics of the service and monitor the duration and termination time of the service. In order to improve resource utilization and meet the variable bandwidth requirements of the service, RSA is more complex. Combining the time characteristics of the service, studying the RSA problem of the service and optimizing the allocation of network resources is an important and meaningful work. Existing studies have shown that the RSA algorithm considering the service duration can be further optimized in terms of blocking rate, spectrum efficiency and fragmentation rate.

[0005] In addition, with the continuous development of optical network technology, the transmission capacity of a single optical fiber can reach 400Gbps or even more than 1Tbps. Therefore, the failure of a single optical fiber alone will cause serious and immeasurable losses to both operators and customers. With the increasing number of high-quality services that cannot be interrupted in the network, in order to improve the survivability transmission capability of the service against risks and disasters, and to ensure the rapid recovery capability of faults encountered during service transmission, these are quality assurance measures that operators need to consider. Furthermore, considering the increasing application of time-varying services in survivable elastic optical networks, it is very necessary to design a flexible RSA adjustment strategy for time-varying services in survivable elastic optical networks. Summary of the invention

[0006] In view of this, the purpose of the present invention is to provide a time-aware time-varying service routing spectrum allocation scheme in a survivable elastic optical network, which is used to improve the survivability transmission capability of the service against disasters, reduce the service blocking rate of the network, reduce the spectrum fragmentation rate of network resources and improve the utilization of spectrum-time resources.

[0007] In order to achieve the above object, the present invention provides the following technical solutions:

[0008] A method for allocating spectrum for time-aware time-varying service routing in a survivable elastic optical network. In the method, in order to reduce the service blocking rate, a hybrid dedicated path and a bandwidth split multipath protection strategy are used to transmit the time-varying service; in order to improve the resource utilization of the network, a maximum time difference spectrum allocation strategy is used to complete the spectrum allocation of the time-varying service; in order to reduce the spectrum fragments generated when the bandwidth of the time-varying service changes, the spectrum of the time-varying service is expanded or compressed according to the spectrum-time resource fragmentation value, and the spectrum allocation of the time-varying service after the required bandwidth changes is flexibly adjusted; the method specifically comprises the following steps:

[0009] S1: Input EONs topology and the remaining spectrum resources of each point and link, the spectrum allocation and remaining time of the services already allocated on the optical path, set K to the maximum integer of the average node degree of EONs; set the time-varying service r = (s, d, B, t h ,t d) arrives at EONs, where the time-varying service source node s, destination node d and bandwidth demand B, t h is the duration of the business, t d is the end time of the service; according to the source node s, destination node d and required bandwidth B value of the time-varying service, in the elastic optical network topology, the K shortest path algorithm is used to save the K shortest paths in the candidate working path set, and according to the required bandwidth value of the time-varying service, the number of FS required for the time-varying service to be transmitted on the candidate working path is calculated, and the spectrum cost value of the candidate working path of the service is calculated, and the candidate working paths are sorted in ascending order according to the spectrum cost value in the set P W middle;

[0010] The spectrum cost calculation formula of the path is as follows:

[0011]

[0012] In the above formula, cost(p i ) table path p i The spectrum cost value, E(p i ) represents the path p i The set of links on the path p i The e-th link on FS a (e) is the number of idle FS of link e, FS t (e) is the total number of FSs of link e, f(p i ) is the time-varying service on the candidate working path p i The number of FS required for transmission;

[0013] Among them, the time-varying service is on the candidate working path p i The calculation formula for the number of FSs required for the transmission service is:

[0014]

[0015] In the above formula, B is the bandwidth value required by the time-varying service, C f It represents the bandwidth provided by the unit FS, m represents the modulation efficiency corresponding to the modulation format M, the highest modulation format M of the service is determined by the length of the candidate path, and different modulation formats have different modulation efficiencies, GB is the number of protected FS, which is generally 1, Indicates the operation of rounding up to an integer;

[0016] Among them, the corresponding relationship between path length, maximum modulation efficiency, and modulation format is as follows:

[0017]

[0018] In the above table, O mis the path length in km, MF (Modulation Format), BPSK (Binary Phase Shift Keying), QPSK (Quadrature Phase ShiftKeying), 8QAM (8Quadrature Amplitude Modulation) and 16QAM (16Quadrature Amplitude Modulation);

[0019] S2: Select the candidate working path set P in turn W Select the number of FSs f(p i ) of the available spectrum block. If the spectrum block exists, mark the candidate path where the spectrum block is located as the working path p1; delete the working path p1 from the elastic optical network topology, use the K shortest path algorithm, and save the found K shortest paths in the candidate protection path set P B In P B If an available spectrum block that meets the number of FSs required by the service is found, the dedicated path protection method is used to select the protection path and spectrum block with the minimum spectrum cost for the time-varying service; otherwise, bandwidth split multipath protection is used to determine the protection path combination and spectrum block combination for the time-varying service;

[0020] S3: For both the working path and the protection path of the service, the maximum time difference spectrum allocation strategy is used to allocate spectrum resources to the service;

[0021] S4: If the elastic optical network detects that the bandwidth required by the time-varying service has changed, an extended / compressed spectrum allocation scheme is adopted, and the extended / compressed spectrum allocation scheme with the smallest spectrum-time resource fragmentation metric is selected to adjust the spectrum allocation of the time-varying service; otherwise, the current spectrum allocation of the service is maintained.

[0022] Further, the hybrid dedicated path and bandwidth split multipath protection strategy in S2 specifically includes the following steps:

[0023] S201: Select candidate working path set P in turn W Select an available spectrum block that meets the number of FSs required by the time-varying service. If an available spectrum block exists, mark the candidate path where the spectrum block is located as the working path p1;

[0024] S202: Delete the working path p1 from the elastic optical network topology. In the elastic optical network, use the K shortest path algorithm to find K candidate shortest paths for the service, and save the K candidate shortest paths in the candidate protection path set. According to formula (2), calculate the number of FSs f(p1) required for the time-varying service on each candidate protection path. i ) value; According to formula (1), the spectrum cost value cost(p i ), sort the candidate protection paths in ascending order according to the spectrum cost value in the set P B In; if P B If it is empty, the service is blocked and the algorithm ends;

[0025] S203: Select from the candidate protection path set P in turn B Select an available spectrum block that meets the number of FS required by the time-varying service. The number of FS required by the time-varying service is calculated by formula (2). An available spectrum block refers to a continuous idle FS combination whose number of continuous idle spectrum on the optical path is not less than the number of FS required by the time-varying service. If an available spectrum block exists, mark the candidate path where the spectrum block is located as the protection path p2 and save it in the set P B1 If yes, go to S3; otherwise, go to S204;

[0026] S204: Select from the candidate protection path set P in turn B Select the first two candidate paths with the smallest path length difference. If the sum of the number of free FSs of two available spectrum blocks from the two candidate protection paths is not less than the number of FSs required by the time-varying service, then divide the bandwidth requested by the time-varying service into two sub-services in proportion according to the size of the two spectrum blocks, combine the candidate protection paths where the two spectrum blocks are located, record the information of the sub-path combination and the service bandwidth division ratio ρ: (1-ρ), and save it in the set P B2 In; if P B2 If it is an empty set, the service is blocked. Otherwise, the process goes to S3.

[0027] The bandwidth division ratio of the sub-service is ρ:(1-ρ), which means that the bandwidth required by sub-service 1 is ρ×B, and the bandwidth required by sub-service 2 is (1-ρ)×B. Substituting the sub-service bandwidth value into formula (2), the number of FSs required by sub-service 1 and sub-service 2 on a path of a certain length can be calculated.

[0028] Furthermore, the maximum time difference spectrum allocation strategy in S3 specifically includes the following steps:

[0029] S301: Let p i =p1;

[0030] S302: Calculate the service on the working path p i The number of FS blocks required for transmission on thei ), statistics p i The index information of the available spectrum blocks that are larger than the number of FS required by the time-varying service is stored in the set , go to S303;

[0031] in, and They represent the starting FS index and ending FS index of the jth available spectrum block, j∈[1,n];

[0032] S303: Calculate the time matching value of each available spectrum block in the set ψ, and select the available spectrum block with the largest time matching value in ψ. in, and are the start / end FS indexes of the spectrum block with the largest time matching value, and then go to S304;

[0033] Among them, the available spectrum block F j The time matching degree DT(F j ) is calculated as follows:

[0034]

[0035] In the above formula, t is the current time; t0 is the remaining duration of service r; is the available spectrum block F on link e j The remaining duration of the nearest service on the right, is the available spectrum block F on link e j The end time of the nearest business on the right; is the available spectrum block F on link e j The remaining duration of the nearest service on the left, is the available spectrum block F on link e j The end time of the nearest business on the left, if F j If it is the start / end available spectrum block on the path, then mark is 0;

[0036] S304: The spectrum required by the time-varying service is allocated to the index value of the maximum time difference spectrum block [f start ,f end ], and add the path information and its allocated spectrum block index information to the set P r middle;

[0037] The calculation formula of the index value of the maximum time difference spectrum block is as follows:

[0038]

[0039] f end =fstart +f(p i )-1 (6)

[0040] S305: If the set P B1 is not empty, let p i =p2, execute steps S302 to S304, and add the path information of p2 and its allocated spectrum block index information to the set P r If yes, go to S4; otherwise, go to S306;

[0041] S306: From the set P B2 Select the first path and bandwidth split ratio information, and record the first path as p2, because the bandwidth split ratio is ρ:(1-ρ), that is, the bandwidth required for sub-service 1 is ρ×B, and the bandwidth required for sub-service 2 is (1-ρ)×B; let p i

[0042] =p2, execute steps S302 to S304, and add the path information of p2 and its allocated spectrum block index information to the set P r In the middle; let the second path be p3, let p i = p3, execute steps S302 to S304, and add the path information of p3 and its allocated spectrum block index information to the set P r , go to S4;

[0043] Furthermore, the expansion / compression spectrum allocation scheme in S4 specifically includes the following steps to adjust the bandwidth allocation of the time-varying service:

[0044] S401: If the bandwidth required by the time-varying service changes within the detection time period, go to S402;

[0045] S402: According to the set P r The number of paths in the formula (2) is used to calculate the number of FS changes on each path after the bandwidth of the time-varying service demand changes, and then go to S403;

[0046] Among them, if the set P r If the number of paths is 2, the number of FS changes of the time-varying service on the working path and the protection path is:

[0047] If the set P r If the number of paths is 3, the number of FS changes of the time-varying service on the working path is Δf, and the number of FS changes on the protection path p1 and the protection path p2 are respectively: and

[0048] In the above formula, B newrepresents the required bandwidth value after the time-varying service changes, m1 and m2 represent the modulation efficiency of the highest modulation format selected by the sub-service according to the length of the protection path p1 and the protection path p2 respectively;

[0049] S403: Let p i =p1,p1∈P r , if B new >B, go to S404, otherwise, go to S408;

[0050] S404: On path p i , counting the number of idle FSs on the left and right sides of the spectrum block originally allocated to the service, and increasing the number of Δf FSs according to the service needs, so as to count the feasible frequency slot extension schemes of the time-varying service on the working path and the protection path respectively; if no feasible frequency slot extension scheme of the time-varying service is found on the working path or the protection path, the time-varying service request is blocked; otherwise, go to S405;

[0051] Among them, the feasible time-varying service frequency slot expansion scheme refers to a specific implementation method of allocating available spectrum blocks after the service bandwidth is increased by frequency slot expansion. The feasible frequency slot expansion scheme for time-varying services needs to satisfy the following formula:

[0052] LEFN+REFN=Δf (7)

[0053] LEFN≤d L , REFN≤d R (8)

[0054] Where, LEFN represents the number of FSs that the time-varying service extends to the left, REFN represents the number of FSs that the time-varying service extends to the right, LEFN and REFN are both natural numbers, and (LFEN, REFN) is called a frequency slot expansion variation scheme; d L Indicates the number of consecutive idle FSs adjacent to the left side of the spectrum block allocated to the service on the path, d R Indicates the number of consecutive idle FSs adjacent to the right side of the spectrum block allocated to the service on the path. The calculation formula is as follows:

[0055]

[0056] In the formula, For path p i The number of consecutive idle FSs on the left side of the spectrum block allocated to the service on uplink e,

[0057] For path p i The number of consecutive idle FSs on the right side of the spectrum block allocated to the service on uplink e;

[0058] S405: Calculate the spectrum-time resource fragmentation value of each frequency slot extension scheme, and go to S406;

[0059] The calculation formula of the spectrum-time resource fragmentation value of the frequency gap expansion solution is as follows:

[0060]

[0061] In the formula, Frag E When the frequency slot of a time-varying service is expanded, the spectrum-time resource fragmentation value generated is The remaining duration difference between the service on link e and the adjacent service on the left, The remaining duration difference between the service on link e and the adjacent service on the right is calculated as follows:

[0062]

[0063] Where t0 is the remaining duration of the service, The remaining duration of the service on link e and the adjacent service on the right,

[0064] The remaining duration of the left adjacent service on link e;

[0065] S406: Select the frequency slot extension scheme corresponding to the minimum spectrum-time resource fragmentation value as the final frequency slot extension scheme for the time-varying service, and assign the FS of the spectrum block of the time-varying service after the bandwidth changes to the index value [f start -LEFN,f end +REFN], the path p i The changed spectrum block index information is saved in the collection In the set P r Delete the path p i and spectrum block allocation index information;

[0066] S407: If the set P r The number of paths is 1, and the set The number of paths from P is 1. r Select the second path and let p i =p2, go to S404; if the set P r The number of paths is 2, and the set The number of paths is 1, then let p i =p2, Δf=Δf1, go to S404; if the set P r The number of paths is 1, and the set The number of paths is 2, then let p i =p3, Δf=Δf2, go to S404; if the set P rIf the number of paths is 0, the time-varying service completes the expansion adjustment of bandwidth allocation and the algorithm ends;

[0067] S408: If the bandwidth B changes after time-varying new = 0, the service is released and the algorithm ends; otherwise, on path p i Determine the number of FSs occupied by other services on the left and right sides of the anchor frequency of the original allocated spectrum block, and go to S409;

[0068] Wherein, the anchor frequency of the service allocation spectrum block is assumed to be the center frequency f of the service allocation spectrum block. c , whose value is

[0069] The anchor frequency f of the service c The calculation formulas for the number of occupied frequency slots on the left and right sides are:

[0070] f L =f c -f start (14)

[0071] f R =f end -f c (15)

[0072] In the formula, f L is the number of FSs occupied on the left side of the service anchor frequency, f R The number of FSs occupied on the right side of the service anchor frequency;

[0073] S409: according to the time-varying service, i The number of FS changes of the service bandwidth on the service is Δf, and a feasible FS compression scheme for the service is determined, and the process goes to S410;

[0074] Among them, the feasible frequency slot compression scheme of the service needs to satisfy the following formula:

[0075] LCFN+RCFN=Δf (16)

[0076] LCFN≤f L , RCFN≤f R (17)

[0077] Where, LCFN represents the number of frequency slots compressed to the left by the time-varying service, and RCFN represents the number of frequency slots compressed to the right by the time-varying service. Both LCFN and RCFN are natural numbers. (LCEN, RCFN) is called a frequency slot compression variation scheme.

[0078] S410: Calculate the spectrum-time resource fragmentation value of the feasible frequency slot compression solution for each time-varying service, and go to S411;

[0079] The calculation formula of the spectrum-time resource fragmentation value of the feasible frequency slot compression solution is as follows:

[0080]

[0081] In the formula, Frag C It is the spectrum-time resource fragmentation value generated when the frequency slot of the time-varying service is compressed;

[0082] S411: Select the feasible frequency slot compression scheme with the smallest spectrum-time resource fragmentation value as the spectrum allocation scheme after the service bandwidth is compressed, that is, allocate the spectrum block of the time-varying service after bandwidth compression to the index value [f start +LCFN,f end -RCFE], the path p i The changed spectrum block index information is saved in the collection In the set P r Delete the path p i and spectrum block allocation index information;

[0083] S412: If the set P r The number of paths is 1, and the set The number of paths from P is 1. r Select the second path and let p i =p2, go to S408; if the set P r The number of paths is 2, and the set The number of paths is 1, then let p i =p2, Δf=Δf1, go to S408; if the set P r The number of paths is 1, and the set The number of paths is 2, then let p i =p3, Δf=Δf2, go to S408; if the set P r If the number of paths is 0, the time-varying service completes the compression adjustment of bandwidth allocation and the algorithm ends.

[0084] The beneficial effects of the present invention are as follows: the present invention provides a spectrum partitioning strategy for time-aware time-varying service routing in a survivable elastic optical network, which takes into account the characteristics of time-varying service bandwidth changing with time while satisfying service survivability transmission, maximizes the duration difference of adjacent services through time perception of service bandwidth changes, increases spectrum sharing between time-varying services, improves the efficiency of network resource utilization, and optimizes the utilization rate of network spectrum-time resources; when the time-varying service bandwidth changes, selects the frequency slot expansion or compression scheme that produces the smallest time-frequency resource fragmentation value through the designed spectrum-time resource fragmentation value, thereby reducing spectrum fragmentation in the network; and reduces the blocking rate of time-varying service survivability transmission through the combined dedicated protection path and bandwidth splitting multipath protection strategy. BRIEF DESCRIPTION OF THE DRAWINGS

[0085] In order to make the purpose, technical solution and beneficial effects of the present invention clearer, the present invention provides the following drawings for illustration:

[0086] Attached Figure 1 Flowchart of multipath protection strategy for hybrid dedicated paths and bandwidth splitting;

[0087] Attached Figure 2 This is a schematic diagram of maximum time difference spectrum allocation;

[0088] Attached Figure 3 Flowchart of the maximum time difference spectrum allocation strategy

[0089] Attached Figure 4 Schematic diagram of spectrum expansion strategy based on spectrum-time resource fragmentation;

[0090] Attached Figure 5 A schematic diagram of spectrum compression allocation based on spectrum-time resource fragmentation;

[0091] Attached Figure 6 Flowchart of spectrum expansion / compression based on spectrum-time resource fragmentation

[0092] Figure 7 Flowchart of a spectrum allocation method for time-aware time-varying service routing in survivable elastic optical networks. DETAILED DESCRIPTION

[0093] The preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0094] The purpose of the spectrum allocation method for time-aware time-varying service routing in a survivable elastic optical network provided by the present invention is to better optimize the spectrum resources of time-varying services in the elastic optical network. The present invention can also be implemented or applied through other different specific implementation methods, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the illustrations provided in the following embodiments only illustrate the basic concept of the present invention in a schematic manner, and the following embodiments and the features in the embodiments can be combined with each other without conflict.

[0095] Among them, the figures are only used for illustrative explanations, and they only represent schematic diagrams rather than actual pictures, and should not be understood as limitations on the present invention. In order to better illustrate the embodiments of the present invention, some parts in the figures may be omitted, enlarged or reduced, and do not represent the size of the actual product. For those skilled in the art, it is understandable that some well-known structures in the figures and their descriptions may be omitted.

[0096] Example:

[0097] The following will be combined with the attached Figure 1 The overall process of the hybrid dedicated path and bandwidth split multipath protection transmission strategy of the present invention is introduced. The specific overall process can be divided into the following steps:

[0098] Input: EONs topology and node and link resource distribution status, determine the remaining spectrum resources of the current elastic optical network, set the K value, K is the maximum integer of the average node degree of EONs; input time-varying service r = (s, d, B, t h ,t d ), let p1=φ,P B1 ={φ},P B2 ={φ};

[0099] Output: working path p1 for time-varying service r, dedicated protection path P B1 or bandwidth partitioning multipath combination P B2 ;

[0100] S1: When the variable service r = (s, d, B, t h ,t d ) arrives at the network, executes the K shortest path algorithm according to the source s and the destination node d, and constructs the candidate working path set P of the time-varying service r sd ={p1,p2,...,p K};

[0101] S2: According to formula (2), count the candidate paths p i length, determine the modulation efficiency of the modulation format used for task transmission, and calculate the time-varying service if the candidate path p is used i The number of FS required f(p i ), i=1,2,...,K, go to S3;

[0102] S3: According to formula (1), calculate each candidate path p i The spectrum cost cost(p i ), according to the spectrum cost of the path (p i ), sort the candidate working paths in ascending order in the set P sd ={p1,p2,...,p K}, go to S4;

[0103] S4: Select from the candidate working path set one by one the candidate paths with the number of continuous idle FSs not less than the number of FSs required for the service transmission on the path as the working path for the service transmission, denoted as p1, and go to S5; if P sd If there is no candidate path that satisfies the number of FSs required for the time-varying service to be transmitted on the candidate path, the service is blocked and the algorithm ends;

[0104] S5: Remove the working path p1 from the EONs topology, and mark the available spectrum block allocated to the working path p1 as occupied in the EONs; in the updated EONs, use the K shortest path algorithm to find K candidate shortest paths for the service, and save the K candidate shortest paths in the candidate protection path set. According to formula (2), calculate the number of FSs f(p) required by the time-varying service on each candidate protection path. i ) value; According to formula (1), the spectrum cost value cost(p i ), sort the candidate protection paths in ascending order according to the spectrum cost value in the set P B In; if P B If it is empty, the service is blocked and the algorithm ends. Otherwise, go to S6.

[0105] S6: Select the candidate protection path set P in turn B In the above example, select the number of FSs f(p i ), where the number of FS required by the time-varying service is calculated by formula (2). An available spectrum block refers to a continuous idle FS combination whose number of continuous idle spectrum on the optical path is not less than the number of FS required by the time-varying service. If an available spectrum block exists, the candidate path where the spectrum block is located is marked as the protection path p2 and saved in the set P B1 If yes, go to S8; otherwise, go to S7;

[0106] S7: Select the candidate protection path set P in turn B Select the first two candidate paths with the smallest path length difference. If the sum of the number of free FSs of two available spectrum blocks from the two candidate protection paths is not less than the number of FSs required by the time-varying service, then divide the bandwidth requested by the time-varying service into two sub-services in proportion according to the size of the two spectrum blocks, combine the candidate protection paths where the two spectrum blocks are located, record the sub-path combination and the service bandwidth division ratio ρ: (1-ρ) information, and save it in the set P B2 In; if P B2 If it is an empty set, the service is blocked. Otherwise, go to S8.

[0107] Among them, the bandwidth division ratio of the sub-service ρ is: (1-ρ), which means that the bandwidth required by sub-service 1 is ρ×B, and the bandwidth required by sub-service 2 is (1-ρ)×B. Substituting the sub-service bandwidth value into formula (2), the number of FSs required by sub-service 1 and sub-service 2 on the path of a certain length can be calculated;

[0108] S8: Output working path p1 of time-varying service r, dedicated protection path P B1 or bandwidth partitioning multipath combination P B2 .

[0109] As attached Figure 2As shown in the diagram of maximum time difference spectrum allocation, each square represents a FS, squares of different colors represent FSs in different states, the numbers in the squares represent the remaining duration of the service occupying the FS, and the numbers above the squares represent the index value of the FS, where green represents the FS already occupied by other services, i.e., unavailable FS, and white represents that the FS is in an idle state. Figure 2 (a) indicates the use of attached Figure 1 The FS status on links AB and BC included in a path calculated by dedicated path protection or bandwidth split multipath protection.

[0110] Assume that at time t=5, a time-varying service r(s,b,B,5,10) arrives at the network. Figure 2 (a) shows the path status information. Assuming that the number of FSs required by the service is 4, the example process of using the maximum time difference spectrum allocation strategy is as follows: First, Figure 2 From the path resource state diagram (a), it can be found that path ABC contains two available spectrum blocks, namely F 1 and F 2 . Calculate the time matching degree of each available spectrum block, the calculation formula is as follows:

[0111]

[0112] t o =t d -t

[0113]

[0114]

[0115] In the above formula, t o is the remaining duration of the time-varying service, t is the current time, and t d The business end time, and is the end time of the adjacent business, and is the remaining duration of the adjacent service. Figure 2 (a), and The value of Figure 2 As shown in the green box in (a), due to t d =10,t o =5, and the time matching degree of the two available spectrum blocks is calculated as D F1 =(5-4)+(5-2)+(5-4)+(5-3)=7 and D F2=(5-3)+(5-1)+(5-2)+5=14. By comparison, the available spectrum block F with the largest time matching degree is selected. 2 For spectrum allocation, the calculation formula for the start and end FS index values ​​of the available spectrum block is:

[0116]

[0117] f end =f start +f(p i )-1

[0118] In the above formula, are the start / end FS index values ​​of the spectrum block with the largest time matching value, f(p i ) is the path p i The number of frequency slots required. In this example, f(p i )=4, and substitute it into the maximum time difference spectrum allocation calculation formula to obtain f start =12,f end =15. Therefore, the 4 FSs of the time-varying service are allocated to the index value [FS12, FS15] in path ABC, such as Figure 2 (b) In the figure, orange indicates that the time-varying services occupy the FS state on the optical path after spectrum allocation.

[0119] The following will be combined with the attached Figure 3 The overall process of the maximum time difference spectrum allocation strategy of the present invention is introduced, and the specific overall process can be divided into the following steps:

[0120] Input: EONs topology and node and link resource distribution status, determine the remaining spectrum resources of the current elastic optical network, set the K value; input time-varying service r = (s, d, B, t h ,t d ) request and its working path p1, dedicated protection path P B1 or bandwidth partitioning multipath combination P B2 , let ψ = {φ}, the path and resource set P of time-varying service r r ={φ};

[0121] Output: Resource set P of working path, protection path and spectrum block allocation for time-varying service r r .

[0122] S1: Let p i =p1;

[0123] S2: Calculate the service on the working path p using formula (2). i The number of FS spectrum blocks required for transmission is denoted as f(p i), statistics p i is greater than f(p i ) is stored in the collection , go to S3;

[0124] in, and They represent the starting FS index and ending FS index of the jth available spectrum block, j∈[1,n];

[0125] S3: Calculate the time matching value of each available spectrum block in the set ψ according to formula (3), and select the available spectrum block with the largest time matching value in ψ in, and are the start / end FS indexes of the spectrum block with the largest time matching value, and go to S4;

[0126] S4: According to formula (5) and formula (6), determine the index value [f start ,f end ], and add the path information and its allocated spectrum block index information to the set P r middle;

[0127] S5: If the set P B1 is not empty, let p i = p2, execute steps S2 to S4 of this strategy, and add the path information of p2 and its allocated spectrum block index information to the set P r If yes, go to S8; otherwise, go to S6;

[0128] S6: From the set P B2 Select the first path and bandwidth split ratio information, and record the first path as p2. Since the bandwidth split ratio is ρ:(1-ρ), the bandwidth required for sub-service 1 is ρ×B. Let p i = p3, execute steps S2 to S4, and add the path information of p2 and its allocated spectrum block index information to the set P r , go to S7;

[0129] S7: From the set P B2 Select the second path and record it as p3. The bandwidth required by sub-service 2 is (1-ρ)×B. Let p i = p3, execute steps S2 to S4, add the path information of p3 and its allocated spectrum block index information to the set P r , go to S8;

[0130] S8: Output the resource set P of the working path, protection path and spectrum block allocation of the time-varying service r r .

[0131] As attached Figure 4 The schematic diagram of spectrum expansion strategy based on spectrum-time resource fragmentation is shown in FIG. Figure 4 It is shown that when the time-varying service is running on the EONs network at time t=7, the bandwidth required by the service is expanded, resulting in the number of frequency slots required by the time-varying service on path ABC increasing from 4 to 6. It is necessary to adjust the frequency slot index value of the spectrum block originally allocated to the time-varying service. Figure 4 The spectrum expansion strategy based on spectrum-time resource fragmentation is introduced.

[0132] The frequency slot index of the spectrum block allocated on the transmission path ABC before the service bandwidth changes is [FS12, FS15]. First, the number of frequency slots that need to be extended on the path after the bandwidth expansion of the time-varying service is calculated. The calculation formula is:

[0133]

[0134] In the attached Figure 4 In the example, assuming that Δf = 2, the number of idle frequency slots on both sides of the spectrum block originally allocated to the time-varying service is calculated. The specific calculation formula is as follows:

[0135]

[0136] where d L and d R Used to determine the number of idle frequency slots on the left and right sides of the spectrum block originally allocated to the time-varying service. and are the number of idle frequency slots on both sides of the service on link e, and p i is the transmission path, including links AB and BC. Figure 4 In, due to So d L =3,d R =2. Based on d L , d R and Δf values, and according to formulas (7) and (8), the feasible frequency slot expansion schemes for time-varying services are determined to be: (2, 0), (1, 1) and (0, 2); Figure 4 , t o =3, According to formula (11), the spectrum-time resource fragmentation values ​​of the three feasible frequency slot extension schemes (2, 0), (1, 1) and (0, 2) are calculated as 4.33, 4.75 and 3.87 respectively. By comparison, the frequency slot extension scheme (0, 2) corresponding to the minimum spectrum-time resource fragmentation value is selected as the final spectrum extension scheme for the service. Figure 4In the figure, the time-varying service is extended by 0FS to the left and 2FS to the right on the path ABC, that is, the frequency slot index value of the spectrum block allocated to the time-varying service on the transmission path ABC is extended from [FS12, FS15] to: [FS12, FS17], such as Figure 4 As shown in the red dashed box.

[0137] Attached Figure 5 Schematic diagram of spectrum compression allocation based on spectrum-time resource fragmentation, Figure 5 It shows that the bandwidth of the time-varying service is compressed at the time t=7 of EONs, resulting in the number of frequency slots required by the time-varying service on the originally allocated path ABC being reduced from 4 to 3. It is necessary to adjust the frequency slot index of the originally allocated spectrum block of the time-varying service. Figure 5 , the spectrum compression strategy based on spectrum-time resource fragmentation is introduced.

[0138] The frequency slot index of the spectrum block allocated before the service bandwidth changes is [FS12, FS15], with a total of 4 consecutive frequency slots. When the time-varying service bandwidth changes, firstly, according to formula (2), the number of changed frequency slots required to be compressed by the time-varying service on the path is calculated; Figure 5 In the example, Δf = 1, taking working path ABC as an example, the frequency slot compression scheme process of the spectrum block of the time-varying service is as follows: Calculate the anchor frequency f of the time-varying service c The number of frequency slots occupied by the left and right sides are:

[0139] f L =f c -f start

[0140] f R =f end -f c

[0141] In the attached Figure 5 In, f c =13,f start =12,f end =15,f L =1,f R =2. According to f L , f R and Δf, and by using formula (16) and formula (17), the feasible frequency slot compression schemes for time-varying services are calculated as: (1, 0) and (0, 1); by using formula (18), the spectrum-time resource fragmentation values ​​of the two feasible frequency slot compression schemes are calculated respectively;

[0142] The calculation formula of the spectrum-time resource fragmentation value of the frequency slot compression scheme is:

[0143]

[0144] In the attached Figure 5 In, t o =3, Therefore, the spectrum-time resource fragmentation values ​​of the feasible frequency slot compression schemes (1, 0) and (0, 1) are calculated to be 2.67 and 2.58 respectively. By comparison, the frequency slot compression scheme (0, 1) with the smallest spectrum-time resource fragmentation value is selected to perform frequency slot compression of the spectrum block, that is, the index value of the spectrum block allocation of the service on optical path ABC changes from [FS12, FS15] to [FS12, FS14], as shown in the attached figure. Figure 5 As shown in the red dashed box.

[0145] The following will be combined with the attached Figure 6 The overall process of the spectrum expansion / compression strategy based on spectrum-time resource fragmentation of the present invention is introduced, and the specific overall process is:

[0146] Input: elastic optical network topology and resource status of each node and link, input time-varying service request r(s,d,B,t h ,t d ), r's transmission path and spectrum allocation set P r , after the required bandwidth changes r(s,d,B new ,t h ,t d );

[0147] Output: Time-varying service request r(s,d,B new ,t h ,t d )After bandwidth demand changes

[0148] S1: If the bandwidth requirement of a time-varying service changes during the detection period, the bandwidth requirement changes from B to B new , go to S2, otherwise, let Go to S13;

[0149] S2: According to the set P r The number of paths in the middle, by formula (2), calculate the number of FS changes on each path after the bandwidth of the time-varying service demand changes, and go to S3;

[0150] Among them, if the set P r If the number of paths is 2, the number of FS changes of the time-varying service on the working path and the protection path is:

[0151] If the set P r If the number of paths is 3, the number of FS changes of the time-varying service on the working path is Δf, and the number of FS changes on the protection path p1 and the protection path p2 are respectively: and

[0152] In the above formula, m1 and m2 represent the modulation efficiency of the highest modulation format selected by the sub-service according to the length of the protection path p1 and the protection path p2 respectively. If the bandwidth ratio of the service is ρ:(1-ρ), after the service request bandwidth changes, the bandwidth of sub-service 1 transmitted on protection path 1 is ρ×B new , the bandwidth of the sub-service transmitted on protection path 2 is (1-ρ)×B new ;

[0153] S3: Let p i =p1,p1∈P r , if B new > B, the bandwidth required by the business is expanded, and the process goes to S4; otherwise, the bandwidth required by the business is compressed, and the process goes to S8;

[0154] S4: On path p i On the left and right sides of the spectrum block originally allocated to the service, the number of idle FSs on the left and right sides is counted, and the number of Δf FSs is increased according to the service needs. According to formula (7) and formula (8), the set of feasible frequency slot extension schemes (LFEN, REFN) of the time-varying service on the working path and the protection path can be counted respectively; if no feasible frequency slot extension scheme (LFEN, REFN) of the time-varying service is found on the working path or the protection path, the time-varying service request is blocked; otherwise, go to S5;

[0155] S5: According to formula (11), calculate the spectrum-time resource fragmentation value Frag for each frequency slot extension scheme (LFEN, REFN) E , go to S6;

[0156] S6: Select the minimum spectrum-time resource fragmentation value Frag E The corresponding frequency slot extension scheme (LFEN,REFN) is used as the final frequency slot extension scheme for time-varying services. The FS of the spectrum block of the time-varying service after the bandwidth change is assigned to the index value [f start -LEFN,f end +REFN], the path p i and the changed spectrum block index information (p i ,[f start -LEFN,f end +REFN]) is stored in the collection In the set P r Delete the path p i and spectrum block allocation index information;

[0157] S7: If the set P r The number of paths is 1, and the set The number of paths from P is 1. r Select the second path and let p i =p2, go to S4; if the set P r The number of paths is 2, and the set The number of paths is 1, then let p i =p2, Δf = Δf1, go to S4; if the set P r The number of paths is 1, and the set The number of paths is 2, then let p i =p3, Δf = Δf2, go to S4; if the set P r If the number of paths is 0, the time-varying service completes the expansion adjustment of bandwidth allocation, and the process goes to S13;

[0158] S8: If the bandwidth B changes after time variation new =0, the service is released and the process goes to S13; otherwise, according to formula (14) and formula (15), on path p i Determine the anchor frequency f of the original allocated spectrum block c The number of FSs occupied by other services on the left and right sides is transferred to S9;

[0159] S9: according to the time-varying service, the path p i The number of FS changes of the service bandwidth on the network is Δf. According to formula (16) and formula (17), the set of feasible FS compression schemes (LCEN, RCFN) of the service is determined, and then the process goes to S10;

[0160] S10: Calculate the spectrum-time resource fragmentation value Frag of the feasible frequency slot compression scheme (LCEN, RCFN) for each time-varying service according to formula (18): C , go to S11;

[0161] S11: Select the spectrum-time resource fragmentation value Frag C The minimum feasible frequency slot compression scheme (LCEN, RCFN) is used as the spectrum allocation scheme after the service bandwidth is compressed, that is, the spectrum block of the time-varying service after bandwidth compression is allocated to the index value [f start +LCFN,f end -RCFE], the path p i and the changed spectrum block index information (p i ,[f start +LCFN,f end -RCFE)) is saved in the collection In the set P r Delete the path p i and spectrum block allocation index information, and go to S12;

[0162] S12: If the set P r The number of paths is 1, and the set The number of paths from P is 1. r Select the second path and let p i =p2, go to S8; if the set P r The number of paths is 2, and the set The number of paths is 1, then let p i =p2, Δf=Δf1, go to S8; if the set P r The number of paths is 1, and the set The number of paths is 2, then let p i =p3, Δf = Δf2, go to S8; if the set P r If the number of paths is 0, the time-varying service completes the compression adjustment of bandwidth allocation, and the process goes to S13;

[0163] S13: Output time-varying service request r(s, d, B new ,t h ,t d )After bandwidth demand changes

[0164] The following will be combined with the attached Figure 7 The overall process of the spectrum allocation method for time-aware time-varying service routing in a survivable elastic optical network of the present invention is introduced. The specific overall process can be divided into the following steps:

[0165] Input: EONs topology and node and link resource distribution status, determine the remaining spectrum resources of the current elastic optical network, set the K value; input time-varying service r = (s, d, B, t h ,t d ) request and its working path p1, dedicated protection path P B1 or bandwidth partitioning multipath combination P B2 , let ψ = {φ}, the path and resource set P of time-varying service r r ={φ}, let p1 = φ, P B1 ={φ},P B2 ={φ}, ψ ={φ},

[0166] Output: Resource set of working path, protection path and spectrum block allocation for time-varying service r

[0167] S1: Determine the FS status information of each link of the current EONs, set the K value to be the maximum integer of the average node degree of EONs, and the time-varying service r = (s, d, B, t h ,t d ) arrives, go to S2;

[0168] S2: Execute the attached Figure 1 The hybrid dedicated path and bandwidth split multipath protection strategy shown in the figure obtains the working path p1 of the time-varying service r and the dedicated protection path P B1 or bandwidth partitioning multipath combination P B2 ;

[0169] S3: For working path p1, dedicated protection path P B1 or bandwidth partitioning multipath combination P B2 For each path in the time-varying service, according to formula (2), the candidate path p is calculated. i The number of frequency slots required f(p i ), execute the attached Figure 3 The maximum time difference spectrum allocation strategy shown in the figure converts the time-varying service request r = (s, d, B, t h ,t d )'s working path p1 and the assigned spectrum block index value, protection path combination information and respective spectrum block index value information are added to the set P r , go to S4;

[0170] S4: If the EONs control center detects that the bandwidth demand of the time-varying service whose transmission time has not ended has changed, the bandwidth demand B changes from B new , go to S5; otherwise, go to S7;

[0171] S5: According to the set P r The number of paths in the process is calculated, and the number of frequency slots changed on each path after the bandwidth required by the time-varying service changes, and the process goes to S6;

[0172] Among them, if the set P r If the number of paths is 2, the number of frequency slots that change for time-varying services on both the working path and the protection path is:

[0173] If the set P r If the number of paths is 3, the number of frequency slots that change on the working path for the time-varying service is Δf, and the number of frequency slots that change on the protection path p1 and the protection path p2 are: and

[0174] S6: for the set P r For each path, use the attached Figure 6 The spectrum expansion / compression strategy based on spectrum-time resource fragmentation shown in FIG. adjusts the index value of the spectrum block of the time-varying service on each path, and adds the path information and the adjusted spectrum block index information to the set , go to S8;

[0175] S7: Order

[0176] S8: Output the resource set of the working path, protection path and spectrum block allocation for the time-varying service r

[0177] Finally, it should be noted that the above preferred embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail through the above preferred embodiments, those skilled in the art should understand that various changes can be made in form and details without departing from the scope defined by the claims of the present invention.

Claims

1. A spectrum allocation method for time-aware time-varying service routing in a survivable elastic optical network, characterized by: In this method, a hybrid dedicated path and bandwidth split multipath protection strategy are used to transmit time-varying services; a maximum time difference spectrum allocation strategy is used to complete spectrum allocation for time-varying services; when the elastic optical network detects that the bandwidth of the time-varying service has changed, the spectrum allocation for the time-varying service is adjusted according to the spectrum-time resource fragmentation value; the method specifically includes the following steps: S1: According to the source node s, destination node d and required bandwidth B value of the time-varying service, in the elastic optical network topology, the K shortest path algorithm is used to save the K shortest paths in the candidate working path set. According to the required bandwidth value of the time-varying service, the number of frequency slots required by the time-varying service on the candidate working path is calculated, and the spectrum cost value of the candidate working path of the service is calculated. The candidate working paths are sorted in ascending order according to the spectrum cost value in the set P. W middle; The formula for calculating the number of frequency slots required for a time-varying service to transmit the service on a candidate working path is as follows: In the above formula, f(p i ) indicates that the time-varying service adopts the candidate working path p i The number of required frequency slots, B is the bandwidth value required by the time-varying service, C is f It represents the bandwidth provided by the unit frequency slot, m represents the modulation efficiency corresponding to the modulation format M, the modulation format M of the service is determined by the length of the candidate path, and different modulation formats have different modulation efficiencies, GB is the protection frequency slot, which is generally 1, Indicates the operation of rounding up to an integer; The spectrum cost calculation formula of the path is as follows: In the above formula, cost(p i ) table path p i The spectrum cost value, E(p i ) represents the path p i The set of links on the path p i The e-th link on FS a (e) is the number of idle frequency slots of link e, FS t (e) is the total number of frequency slots of link e; S2: Using the method of claim 2, select the candidate working path set P in turn. W Select an available spectrum block that meets the number of frequency slots required by the time-varying service. If the spectrum block exists, mark the candidate path where the spectrum block is located as the working path p1; delete the working path p1 from the elastic optical network topology, use the K shortest path algorithm, and save the K shortest paths found in the candidate protection path set P B In P B If an available spectrum block that meets the number of frequency slots required by the service is found, a dedicated path protection method is used to select a protection path and spectrum block with the minimum spectrum cost for the time-varying service; otherwise, bandwidth split multipath protection is used to determine the protection path combination and spectrum block combination for the time-varying service; S3: Using the method described in claim 3, for the working path and protection path of the service, using the maximum time difference spectrum allocation strategy described in claim 3 of the present invention to allocate spectrum resources to the service; S4: If the elastic optical network detects that the bandwidth required by the time-varying service has changed, the extended / compressed spectrum allocation scheme described in claim 4 is adopted, the extended / compressed spectrum allocation scheme with the smallest spectrum-time resource fragmentation metric is selected, and the spectrum allocation of the time-varying service is adjusted; otherwise, the current spectrum allocation of the service is maintained.

2. The method for allocating spectrum for time-aware time-varying service routing in a survivable elastic optical network according to claim 1, characterized in that: The S2 is specifically implemented in the following manner: S201: Select candidate working path set P in turn W Select an available spectrum block that meets the number of frequency slots required by the time-varying service, and if an available spectrum block exists, mark the candidate path where the spectrum block is located as the working path p1; S202: Delete the working path p1 from the elastic optical network topology. In the elastic optical network, use the K shortest path algorithm to find K candidate shortest paths for the service. Save the K candidate shortest paths in the candidate protection path set, calculate the number of frequency slots required for the time-varying service on each candidate protection path, calculate the spectrum cost value of each candidate protection path of the service, and sort the candidate protection paths in ascending order according to the spectrum cost value in the set P. B In; if P B If it is empty, the service is blocked and the algorithm ends; S203: Select from the candidate protection path set P in turn B Select an available spectrum block that meets the number of frequency slots required by the time-varying service. If an available spectrum block exists, mark the candidate path where the spectrum block is located as the protection path p2 and save it in the set P. B1 If yes, go to S3; otherwise, go to S204; S204: Select from the candidate protection path set P in turn B Select the first two candidate paths with the smallest path length difference. If the sum of the number of idle frequency slots of two available spectrum blocks from the two candidate protection paths is not less than the number of frequency slots required by the time-varying service, then divide the bandwidth requested by the time-varying service into two sub-services in proportion according to the size of the two spectrum blocks, combine the candidate protection paths where the two spectrum blocks are located, record the sub-path combination and the service bandwidth division ratio information, and save them in the set P B2 In; if P B2 If the set is empty, the service is blocked; otherwise, the process goes to S3.

3. The method for allocating spectrum for time-aware time-varying service routing in a survivable elastic optical network according to claim 1, characterized in that: The S3 is specifically implemented in the following manner: S301: Let p i =p1; S302: Calculate the service on the working path p i The number of frequency slots f(p i ), statistics p i The index information of the available spectrum blocks that are larger than the number of frequency slots required by the time-varying service is stored in the set , go to S303; in, and They represent the starting frequency slot index and the ending frequency slot index of the jth available spectrum block, j∈[1,n]; S303: Calculate the time matching value of each available spectrum block in the set ψ, and select the available spectrum block with the largest time matching value in ψ in, and are the start / end frequency slot indexes of the spectrum block with the largest time matching value, and then go to S304; Among them, the available spectrum block F j The time matching degree DT(F j ) is calculated as follows: t o =t d -t In the above formula, t is the current time; t0 is the remaining duration of service r; is the available spectrum block F on link e j The remaining duration of the nearest service on the right, is the available spectrum block F on link e j The end time of the nearest business on the right; is the available spectrum block F on link e j The remaining duration of the nearest service on the left, is the available spectrum block F on link e j The end time of the nearest business on the left, if F j If it is the start / end available spectrum block on the path, then mark is 0; S304: The spectrum required by the time-varying service is allocated to the index value of the maximum time difference spectrum block [f start ,f end ], and add the path information and its allocated spectrum block index information to the set P r middle; The calculation formula of the index value of the maximum time difference spectrum block is as follows: f end =f start +f(p i )-1 S305: If the set P B1 is not empty, let p i =p2, execute steps S302 to S304, and add the path information of p2 and its allocated spectrum block index information to the set P r If yes, go to S4; otherwise, go to S306; S306: From the set P B2 Select the first path and bandwidth split ratio information, and record the first path as p2, because the bandwidth split ratio is ρ:(1-ρ), that is, the bandwidth required for sub-service 1 is ρ×B, and the bandwidth required for sub-service 2 is (1-ρ)×B; let p i =p2, execute steps S302 to S304, and add the path information of p2 and its allocated spectrum block index information to the set P r In the middle; let the second path be p3, let p i = p3, execute steps S302 to S304, and add the path information of p3 and its allocated spectrum block index information to the set P r , go to S4.

4. The method for allocating spectrum for time-aware time-varying service routing in a survivable elastic optical network according to claim 1, characterized in that: The S4 is specifically implemented in the following manner: S401: If the bandwidth required by the time-varying service changes within the detection time period, go to S402; S402: According to the set P r Calculate the number of paths in the process, and calculate the number of frequency slots changed on each path after the bandwidth of the time-varying service demand changes, and then go to S403; Among them, if the set P r If the number of paths is 2, the number of frequency slots that change for time-varying services on both the working path and the protection path is: If the set P r If the number of paths is 3, the number of frequency slots that change on the working path for the time-varying service is Δf, and the number of frequency slots that change on the protection path p1 and the protection path p2 are: and In the above formula, B new represents the required bandwidth value after the time-varying service changes, m1 and m2 represent the modulation efficiency of the highest modulation format selected by the sub-service according to the length of the protection path p1 and the protection path p2 respectively; S403: Let p i =p1,p1∈P r , if B new >B, go to S404, otherwise, go to S408; S404: On path p i , counting the number of idle frequency slots on the left and right sides of the spectrum block originally allocated to the service, and increasing the number of Δf frequency slots according to the service needs, so as to count the feasible frequency slot extension schemes of the time-varying service on the working path and the protection path respectively; if no feasible frequency slot extension scheme for the time-varying service is found on the working path or the protection path, the time-varying service request is blocked; otherwise, go to S405; Among them, the feasible time-varying service frequency slot expansion scheme refers to a specific implementation method of allocating available spectrum blocks after the service bandwidth is increased by frequency slot expansion. The feasible frequency slot expansion scheme for time-varying services needs to satisfy the following formula: LEFN+REFN=Δf LEFN≤d L REFN≤d R Where, LEFN represents the number of frequency slots that the time-varying service extends to the left, REFN represents the number of frequency slots that the time-varying service extends to the right, LEFN and REFN are both natural numbers, and (LFEN, REFN) is called a frequency slot extension variation scheme; d L Indicates the number of consecutive idle frequency slots adjacent to the left side of the spectrum block allocated to the service on the path, d R Indicates the number of continuous idle frequency slots adjacent to the right side of the spectrum block allocated to the service on the path. The calculation formula is as follows: In the formula, For path p i The number of consecutive idle frequency slots on the left side of the spectrum block allocated to the service on uplink e, For path p i The number of consecutive idle frequency slots on the right side of the spectrum block allocated to the service on uplink e; S405: Calculate the spectrum-time resource fragmentation value of each frequency slot extension scheme, and go to S406; The calculation formula of the spectrum-time resource fragmentation value of the frequency gap expansion solution is as follows: In the formula, Frag E When the frequency slot of a time-varying service is expanded, the spectrum-time resource fragmentation value generated is The remaining duration difference between the service on link e and the adjacent service on the left, The remaining duration difference between the service on link e and the adjacent service on the right is calculated as follows: Where t0 is the remaining duration of the service, The remaining duration of the service on link e and the adjacent service on the right, The remaining duration of the left adjacent service on link e; S406: Select the frequency slot extension scheme corresponding to the minimum spectrum-time resource fragmentation value as the final frequency slot extension scheme for the time-varying service, and allocate the frequency slot of the time-varying service after the bandwidth changes to the index value [f start -LEFN,f end +REFN], the path p i The changed spectrum block index information is saved in the collection In the set P r Delete the path p i and spectrum block allocation index information; S407: If the set P r The number of paths is 1, and the set The number of paths from P is 1. r Select the second path and let p i =p2, go to S404; if the set P r The number of paths is 2, and the set The number of paths is 1, then let p i =p2, Δf=Δf1, go to S404; if the set P r The number of paths is 1, and the set The number of paths is 2, then let p i =p3, Δf=Δf2, go to S404; if the set P r If the number of paths is 0, the time-varying service completes the expansion adjustment of bandwidth allocation and the algorithm ends; S408: If the bandwidth B changes after time-varying new = 0, the service is released and the algorithm ends; otherwise, on path p i Determine the number of frequency slots occupied by other services on the left and right sides of the originally allocated time-varying service anchor frequency, and transfer to S409; The anchor frequency of the service is assumed to be the center frequency f of the spectrum block originally allocated to the service. c , whose value is The anchor frequency f of the service c The calculation formulas for the number of occupied frequency slots on the left and right sides are: f L =f c -f start f R =f end -f c In the formula, f L is the number of occupied frequency slots to the left of the service anchor frequency, f R The number of occupied frequency slots on the right side of the service anchor frequency; S409: according to the time-varying service, i The number of frequency slots of the service bandwidth change Δf is determined, and a feasible frequency slot compression scheme for the service is determined, and the process goes to S410; Among them, the feasible frequency slot compression scheme of the service needs to satisfy the following formula: LCFN+RCFN=Δf LCFN≤f L RCFN≤f R Where, LCFN represents the number of frequency slots compressed to the left by the time-varying service, and RCFN represents the number of frequency slots compressed to the right by the time-varying service. Both LCFN and RCFN are natural numbers. (LCEN, RCFN) is called a frequency slot compression variation scheme. S410: Calculate the spectrum-time resource fragmentation value of the feasible frequency slot compression solution for each time-varying service, and go to S411; The calculation formula of the spectrum-time resource fragmentation value of the feasible frequency slot compression solution is as follows: In the formula, Frag C It is the spectrum-time resource fragmentation value generated when the frequency slot of the time-varying service is compressed; S411: Select the feasible frequency slot compression scheme with the smallest spectrum-time resource fragmentation value as the spectrum allocation scheme after the service bandwidth is compressed, that is, allocate the spectrum block of the time-varying service after bandwidth compression to the index value [f start +LCFN,f end -RCFE], the path p i The changed spectrum block index information is saved in the collection In the set P r Delete the path p i and spectrum block allocation index information; S412: If the set P r The number of paths is 1, and the set The number of paths from P is 1. r Select the second path and let p i =p2, go to S408; if the set P r The number of paths is 2, and the set The number of paths is 1, then let p i =p2, Δf=Δf1, go to S408; if the set P r The number of paths is 1, and the set The number of paths is 2, then let p i =p3, Δf=Δf2, go to S408; if the set P r If the number of paths is 0, the time-varying service completes the compression adjustment of bandwidth allocation and the algorithm ends.

Images