A method for path selection and spectrum allocation to reduce the influence of stimulated Raman scattering

Abstract

This invention discloses a path selection and spectrum allocation method to reduce the impact of stimulated Raman scattering (SRS). The invention relates to the field of optical network technology and includes the following steps: S1: Calculate the average modulation level and average number of slots based on the modulation level of each modulation format and the bandwidth range of the service request; S2: Calculate the weight of each link based on the spectrum resource status in the link; S3: Request path calculation to obtain K candidate paths with the minimum cumulative link weights; S4: Select the modulation format with the corresponding modulation level based on the transmission distance of the candidate paths; S5: Calculate the number of slots required by the service request based on the modulation format; S6: Obtain the set of idle spectrum blocks within the current candidate paths that meet the slot requirement based on the number of slots required by the service request; S7: Execute the corresponding spectrum resource allocation strategy for the service request and establish a connection. This invention uses the above steps to reduce the degradation of service transmission quality caused by stimulated Raman scattering from both routing selection and spectrum allocation perspectives.

Description

Technical Field

[0001] This invention relates to the field of optical network technology, and in particular to a path selection and spectrum allocation method for reducing the effects of stimulated Raman scattering. Background Technology

[0002] With the emergence of applications such as high-definition television, short videos, and social networks, data traffic within backbone networks is growing exponentially, and the current backbone network capacity is insufficient to meet the ever-increasing traffic demands. C+L band elastic optical networks, utilizing the C and L bands of already deployed optical fibers for transmission, have attracted widespread attention from researchers as an effective solution to improve network capacity. However, in C+L band elastic optical networks, stimulated Raman scattering (SRS), as one of the main physical layer impairments, transfers power from short-wavelength optical paths to longer wavelengths. This results in nonlinear impairments such as self-phase modulation and cross-phase modulation becoming the main physical layer impairments for services near longer wavelengths, while linear impairments such as amplifier spontaneous emission noise dominate for services at shorter wavelengths. All of these physical layer impairments degrade the optical signal-to-noise ratio (SNR) of the path, and in severe cases, can lead to difficulties in normal service transmission. Therefore, how to reduce the impact of stimulated Raman scattering on services through low-cost resource allocation schemes to reduce the degradation of service transmission quality has become one of the research hotspots in C+L band elastic optical networks.

[0003] In existing C+L band flexible optical networks, resource allocation methods to reduce the impact of stimulated Raman scattering (SRS) only consider the relationship between service parameters and SRS during spectrum allocation. For example, the longer the service transmission distance, the more frequency slots required, and the larger the center frequency spacing between services, the greater the impact of SRS. Furthermore, the impact of SRS on services is also related to band selection; services allocated in the L band will experience more severe SRS compared to those allocated in the C band. However, existing methods lack analysis of the link spectrum resource utilization status in the network and the impact of SRS on services, i.e., they do not consider the influence of different routing methods on the SRS of services, which is detrimental to achieving the goal of reducing the degradation of service transmission quality caused by SRS.

[0004] Therefore, it is necessary to provide a path selection and spectrum allocation method to reduce the influence of stimulated Raman scattering in order to solve the above problems. Summary of the Invention

[0005] The purpose of this invention is to provide a path selection and spectrum allocation method to reduce the impact of stimulated Raman scattering. This method comprehensively considers the impact of service request parameters and the network link spectrum resource status on the stimulated Raman scattering effect on services, reduces service blocking rate, and further reduces the impact of stimulated Raman scattering during the spectrum allocation stage, thereby achieving the goal of reducing the degradation of service transmission quality caused by stimulated Raman scattering.

[0006] To achieve the above objectives, the present invention provides a path selection and spectrum allocation method for reducing the influence of stimulated Raman scattering, comprising the following steps:

[0007] S1: Calculate the average modulation level and average number of frequency slots based on the modulation level of each modulation format and the bandwidth range of the service request;

[0008] S2: Calculate the link weight of each link based on the spectrum resource status in the link;

[0009] S3: Based on the link weight and the source and destination nodes of the new service request, perform path calculation for the new service request to obtain the K candidate paths with the smallest cumulative link weight;

[0010] S4: Select the modulation format of the corresponding modulation level based on the transmission distance of the candidate path;

[0011] S5: Calculate the number of frequency slots required for the service request based on the modulation format;

[0012] S6: Based on the number of frequency slots required by the service request, obtain the set of idle spectrum blocks within the current candidate path that meet the frequency slot requirement;

[0013] S7: Based on the modulation format, the number of frequency slots required by the service request, and the set of idle spectrum blocks, execute the corresponding spectrum resource allocation strategy for the service request and establish a connection.

[0014] Preferably, in step S1, the average modulation level and the average number of frequency slots are calculated using the following formulas.

[0015]

[0016]

[0017] Where M is the average modulation level, M i Let be the modulation level of the i-th modulation format, n be the number of selectable modulation formats, F be the average number of frequency slots, a be the minimum requested bandwidth of the service request, c be the maximum requested bandwidth of the service request, b represent the value between a and c, and C be the maximum requested bandwidth of the service request. slot The spectral width of a single frequency slot.

[0018] Preferably, in step S2, the weight ρ of each link is calculated using the following formula.

[0019]

[0020] Among them, ρ is the link weight, N is the number of idle spectrum blocks included in the set of idle spectrum blocks, and F r is the number of frequency slots required for the service request after selecting the lowest-level modulation format, and F j is the number of idle frequency slots included in the j-th idle spectrum block in the set of idle spectrum blocks, and F l is the total number of idle frequency slots in link l, and SL l is the number of hops that link l needs to pass through.

[0021] Preferably, in step S3, the calculation method for calculating K candidate paths is the improved Dijkstra algorithm, and the calculation method for accumulating the path weight is:

[0022]

[0023] Among them, ρ sum is the accumulated link weight, and ρ i is the link weight of the i-th link.

[0024] Preferably, in step S4, according to the transmission distance of the candidate path, the corresponding modulation format is selected, including the following steps:

[0025] d ≤ D m , select the modulation format with modulation level m;

[0026] D m < d ≤ D m-1 , select the modulation format with modulation level m - 1;

[0027] D2 < d ≤ D1, select the modulation format with modulation level 1;

[0028] Among them, d is the transmission distance of the candidate path, m is the modulation level, and D m is the farthest transmission distance of the modulation format with modulation level m.

[0029] Preferably, the number of frequency slots required for the service request is calculated by the following formula

[0030]

[0031] Among them, f is the number of frequency slots required for the service request, B is the bandwidth of the service request, and C slot is the spectral width of a single frequency slot.

[0032] Preferably, step S6 specifically includes the following steps:

[0033] S61: Traverse the K candidate paths in sequence;

[0034] S62: Search within the C and L bands of the current candidate path for a set of available spectrum blocks that can meet the number of frequency slots required to satisfy the service request;

[0035] S63: The set of free spectrum blocks in the candidate path is not empty, proceed to step S6;

[0036] The set of free spectrum blocks within the candidate path is empty; search for the next candidate path.

[0037] When the set of free spectrum blocks in all candidate paths is empty, the traversal ends and the current service is blocked.

[0038] Preferably, step S7 specifically includes the following steps:

[0039] S71: Compare the modulation level and number of frequency slots of the service request with the average modulation level and average number of frequency slots;

[0040] S72: Based on the comparison results, select the free spectrum blocks in the set of free spectrum blocks by either starting from the beginning to the end or starting from the end to the beginning;

[0041] S73: Calculate the path optical signal-to-noise ratio based on the number of frequency slots required by the service request and the selected idle spectrum block;

[0042] S74: The path optical signal-to-noise ratio is not less than the optical signal-to-noise ratio threshold of the modulation format selected in the service request; establish the connection.

[0043] If the path optical signal-to-noise ratio is less than the optical signal-to-noise ratio threshold of the modulation format selected in the service request, select the next idle spectrum block from the set of idle spectrum blocks and calculate the path optical signal-to-noise ratio.

[0044] If none of the available spectrum blocks in the available spectrum block set can meet the optical signal-to-noise ratio threshold of the modulation format selected in the service request, then select the available spectrum block set of the next candidate path.

[0045] The set of available spectrum blocks for all candidate paths is insufficient to meet the requirements, thus blocking the current service.

[0046] Preferably, in step S72, the following criteria are performed:

[0047] Standard 1: The modulation level requested by the service is not less than the average modulation level, and the number of frequency slots required is not less than the average number of frequency slots required. Idle frequency blocks in the C-band idle frequency block set are selected in a tail-to-head manner.

[0048] Standard 2: The modulation level requested by the service is not less than the average modulation level, and the number of frequency slots required is less than the average number of frequency slots required. Idle frequency blocks in the C-band idle frequency block set are selected in a first-to-last manner.

[0049] Standard 3: If the modulation level requested by the service is less than the average modulation level and the number of frequency slots required is not less than the average number of frequency slots required, an idle spectrum block in the set of idle spectrum blocks in the L-band is selected in a first-to-last manner.

[0050] Standard 4: When the requested modulation level is less than the average modulation level and the required number of frequency slots is less than the average required number of frequency slots, an idle frequency block in the L-band idle frequency block set is selected in a tail-to-head manner.

[0051] Preferably, in step S73, the method for calculating the path optical signal-to-noise ratio is as follows:

[0052]

[0053] Where OSNR is the path optical signal-to-noise ratio, P is the transmit power of the service request, and P ASE P represents the amplifier's spontaneous radiated noise power received by the service request. NLI The power of the nonlinear effects on the business request.

[0054] Therefore, the path selection and spectrum allocation method for reducing the influence of stimulated Raman scattering described above in this invention has the following beneficial effects:

[0055] (1) This invention uses an improved Dijkstra algorithm to search for candidate paths, which can prioritize paths that occupy less spectrum resources and have shorter transmission distances. This reduces the degradation of service transmission quality caused by stimulated Raman scattering in advance during the routing stage, thereby effectively reducing the service blocking rate.

[0056] (2) In the spectrum allocation stage, this invention analyzes the relationship between service parameters and the degree of influence of stimulated Raman scattering on the service, concentrates the services with a large number of required frequency slots, and selects the corresponding bands for allocation according to the modulation format of the service. This allocation scheme not only meets the normal transmission requirements of the service, but also further reduces the degradation of service transmission quality caused by stimulated Raman scattering.

[0057] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0058] Figure 1 This is a flowchart of a path selection and spectrum allocation method for reducing the influence of stimulated Raman scattering according to the present invention;

[0059] Figure 2 This is a schematic diagram showing the relationship between the degree of influence of stimulated Raman scattering on the business operations of this invention and the business parameters;

[0060] Figure 3 This is a schematic diagram of the spectrum allocation method of the present invention;

[0061] Figure 4 This is a schematic diagram illustrating the impact of stimulated Raman scattering on the current service within the link of this invention. Detailed Implementation

[0062] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0063] Unless otherwise defined, the technical or scientific terms used in this invention shall have the ordinary meaning as understood by one of ordinary skill in the art to which this invention pertains.

[0064] The terms "comprising" or "including" as used in this invention mean that the element preceding the term encompasses the element listed after the term, and do not exclude the possibility of encompassing other elements. Terms such as "inner," "outer," "upper," and "lower" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. When the absolute position of the described object changes, the relative positional relationship may also change accordingly. In this invention, unless otherwise explicitly specified and limited, the term "attached" and similar terms should be interpreted broadly. For example, it can refer to a fixed connection, a detachable connection, or an integral part; it can refer to a direct connection or an indirect connection through an intermediate medium; it can refer to the internal communication of two elements or the interaction relationship between two elements. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0065] like Figures 1-4 As shown, this invention provides a path selection and spectrum allocation method to reduce the influence of stimulated Raman scattering, comprising the following steps:

[0066] S1: Calculate the average modulation level M and the average number of frequency slots F based on the modulation level of each modulation format and the bandwidth range [a,b] of the service request; in step S1, the average modulation level and the average number of frequency slots are calculated using the following formulas.

[0067]

[0068]

[0069] Where M is the average modulation level, M i Let be the modulation level of the i-th modulation format, n be the number of selectable modulation formats, F be the average number of frequency slots, a be the minimum requested bandwidth of the service request, c be the maximum requested bandwidth of the service request, b represent the value between a and c, and C be the maximum requested bandwidth of the service request. slot The spectral width of a single frequency slot.

[0070] S2: Calculate the link weights of each link according to the spectrum resource status in the link; in step S2, calculate the weight ρ of each link through the following formula

[0071]

[0072] where ρ is the link weight, N is the number of idle spectrum blocks in the idle spectrum block set, F r is the number of frequency slots required for the service request after selecting the lowest-level modulation format, F j is the number of idle frequency slots in the j-th idle spectrum block in the idle spectrum block set, F l is the total number of idle frequency slots in link l, SL l is the number of hops that link l needs to pass through.

[0073] S3: According to the link weights and the source node and destination node of the new service request, use the improved Dijkstra algorithm to calculate the path for the new service request, and obtain the K candidate paths P sum with the smallest cumulative link weight ρ k ; each candidate path consists of l links; the calculation method of the cumulative path weight is:

[0074]

[0075] where ρ sum is the cumulative link weight, ρ i is the link weight of the i-th link.

[0076] S4: Traverse P k in turn, and determine the modulation level m of the highest available modulation format for the service request according to the transmission distance d of P k ; in step S4, select the corresponding modulation format according to the transmission distance of the candidate path, including the following steps: max If d ≤ D

[0077] m , select the modulation format with modulation level m;

[0078] If D m < d ≤ D m-1 , select the modulation format with modulation level m - 1;

[0079] If D2 < d ≤ D1, select the modulation format with modulation level 1;

[0080] where d is the transmission distance of the candidate path, m is the modulation level, and D m is the farthest transmission distance of the modulation format with modulation level m.

[0081] S5: Calculate the number of frequency slots f required for the service request based on the modulation level m of the modulation format selected in the service request; the number of frequency slots required for the service request is calculated using the following formula.

[0082]

[0083] Where f is the number of frequency slots required for the service request, B is the bandwidth of the service request, and C is the bandwidth of the service request. slot The spectral width of a single frequency slot.

[0084] S6: Based on the number of frequency slots f required by the service request, obtain the set of idle spectrum blocks within the current candidate path that meet the frequency slot requirement; specifically including the following steps:

[0085] S61: Iterate through the K candidate paths P in sequence;

[0086] S62: In the current candidate path p i Within the C and L bands, a set of available spectrum blocks that can satisfy the number of frequency slots required to meet the service request is searched and recorded in set B. c and B l ;

[0087] S63: The set of free spectrum blocks in the candidate path is not empty, proceed to step S6;

[0088] If the set of free spectrum blocks within a candidate path is empty, search for the next candidate path p. i+1 ;

[0089] When the set of free spectrum blocks in all candidate paths is empty, the traversal ends and the current service is blocked.

[0090] S7: Based on the modulation format, the number of frequency slots required by the service request, and the set of available spectrum blocks, execute the corresponding spectrum resource allocation strategy for the service request and establish a connection. Specifically, this includes the following steps:

[0091] S71: Compare the modulation level m and the required number of frequency slots f of the service request with the average modulation level M and the average number of frequency slots F;

[0092] S72: Based on the comparison results, select the free spectrum blocks from the free spectrum block set using either a first-to-last or last-to-first method; in step S72, the following criteria are applied:

[0093] Standard 1: The requested modulation level is not less than the average modulation level, and the required number of frequency slots is not less than the average required number of frequency slots. The set of C-band idle spectrum blocks B is selected from tail to head. c The free spectrum block in;

[0094] Standard 2: The requested modulation level is not less than the average modulation level, and the required number of frequency slots is less than the average required number of frequency slots. The set of C-band idle spectrum blocks B is selected according to a first-to-last method. c The free spectrum block in;

[0095] Standard 3: If the requested modulation level is lower than the average modulation level, and the required number of frequency slots is not less than the average required number of frequency slots, the set of L-band idle spectrum blocks B is selected according to the first-to-last method. l The free spectrum block in;

[0096] Standard 4: When the requested modulation level is lower than the average modulation level and the required number of frequency slots is lower than the average required number of frequency slots, the set of L-band idle spectrum blocks B is selected from tail to head. l The free spectrum block in.

[0097] S73: Calculate the path optical signal-to-noise ratio (OSNR) based on the number of frequency slots required by the service request and the selected idle spectrum block; the method for calculating the path optical signal-to-noise ratio is as follows:

[0098]

[0099] Where OSNR is the path optical signal-to-noise ratio, P is the transmit power of the service request, and P ASE P represents the amplifier's spontaneous radiated noise power received by the service request. NLI The power of the nonlinear effects on the business request.

[0100] S74: The path optical signal-to-noise ratio (OSNR) is not less than the OSNR threshold of the modulation format selected in the service request. threshold Establish a connection;

[0101] If the path optical signal-to-noise ratio is less than the optical signal-to-noise ratio threshold of the modulation format selected in the service request, select the next idle spectrum block from the set of idle spectrum blocks and calculate the path optical signal-to-noise ratio.

[0102] If none of the available spectrum blocks in the available spectrum block set can meet the optical signal-to-noise ratio threshold of the modulation format selected in the service request, then select the available spectrum block set of the next candidate path.

[0103] The set of available spectrum blocks for all candidate paths is insufficient to meet the requirements, thus blocking the current service.

[0104] Therefore, this invention employs the aforementioned path selection and spectrum allocation method to reduce the impact of stimulated Raman scattering. In the path selection method based on the improved Dijkstra algorithm, the path with the minimum cumulative link weight is planned for the service, thus reducing the degradation of service transmission quality caused by stimulated Raman scattering in advance. Services requiring a large number of frequency slots are concentrated in the allocation, further reducing the degradation of service transmission quality caused by stimulated Raman scattering while meeting the normal transmission requirements of services with higher modulation levels. Through reasonable path selection and spectrum allocation, the degradation of service transmission quality caused by stimulated Raman scattering is effectively reduced, and service congestion is minimized.

[0105] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A path selection and spectrum allocation method for reducing the influence of stimulated Raman scattering, applied to the C and L bands, characterized in that: It includes the following steps: S1: Calculate the average modulation level and the average number of frequency slots according to the modulation levels of each modulation format and the bandwidth range required by the service request; S2: Calculate the link weights of each link according to the spectral resource status in the link; In step S2, the weight of each link is calculated using the following formula. ρ , ； in, ρ For link weight, N This represents the number of free spectrum blocks contained in the set of free spectrum blocks. F r To determine the number of frequency slots required for the service request after selecting the lowest level modulation format. F j The first in the set of free spectrum blocks j The number of free frequency slots contained within a free spectrum block. F l For link l The total number of free frequency slots in the frequency range, SL l For link l The number of spans required; S3: Perform path calculation on the new service request according to the link weights and the source node and destination node of the new service request, and obtain K candidate paths with the minimum cumulative link weight; S4: Select the modulation format of the corresponding modulation level according to the transmission distance of the candidate path; S5: Calculate the number of frequency slots required by the service request according to the modulation format; S6: Obtain the set of idle spectrum blocks that meet the frequency slot number requirement within the current candidate path according to the number of frequency slots required by the service request; S7: Execute the corresponding spectrum resource allocation strategy for the service request according to the modulation format, the number of frequency slots required by the service request, and the set of idle spectrum blocks, and establish a connection; The specific steps of step S7 include the following steps: S71: Compare the modulation level and the number of frequency slots of the service request with the average modulation level and the average number of frequency slots; S72: Select the idle spectrum blocks in the set of idle spectrum blocks in the C-band or L-band in the order from the head to the tail or from the tail to the head according to the comparison result; S73: Calculate the path optical signal-to-noise ratio according to the number of frequency slots required by the service request and the selected idle spectrum blocks; S74: If the path optical signal-to-noise ratio is not less than the optical signal-to-noise ratio threshold of the modulation format selected by the service request, establish a connection; If the path optical signal-to-noise ratio is less than the optical signal-to-noise ratio threshold of the modulation format selected by the service request, select the next idle spectrum block from the set of idle spectrum blocks and calculate the path optical signal-to-noise ratio; If all the idle spectrum blocks in the set of idle spectrum blocks cannot meet the optical signal-to-noise ratio threshold of the modulation format selected by the service request, select the set of idle spectrum blocks of the next candidate path; If the sets of idle spectrum blocks of all candidate paths cannot meet the requirements, block the current service.

2. The path selection and spectrum allocation method for reducing the influence of stimulated Raman scattering according to claim 1, characterized in that: In step S1, the average modulation level and the average number of frequency slots are calculated by the following formula in, M For average modulation level, M i For the first i Modulation levels of various modulation formats n The number of selectable modulation formats. F The average number of frequency slots, a This is the minimum request bandwidth for the business request. c The maximum request bandwidth for the business request. b express a arrive c The values ​​between, C slot The spectral width of a single frequency slot.

3. The path selection and spectrum allocation method for reducing the influence of stimulated Raman scattering according to claim 2, characterized in that: In step S3, the calculation method for calculating K candidate paths is the improved Dijkstra algorithm, and the calculation method for the cumulative path weight is: in, ρ sum To accumulate link weights, ρ i For the first i Link weights of each link.

4. The path selection and spectrum allocation method for reducing the influence of stimulated Raman scattering according to claim 3, characterized in that: In step S4, according to the transmission distance of the candidate path, select the corresponding modulation format, including the following steps: d≤D m Select the modulation format with modulation level m; D m <d≤D m-1 Select the modulation format with modulation level m-1; When D2 < d ≤ D1, select the modulation format with a modulation level of 1; Where d is the transmission distance of the candidate path, m is the modulation level, and D m This represents the maximum transmission distance for a modulation format with modulation level m.

5. The path selection and spectrum allocation method for reducing the influence of stimulated Raman scattering according to claim 4, characterized in that: Calculate the number of frequency slots required by the service request through the following formula in, f The number of frequency slots required for the service request. B For the bandwidth of the service request, C slot The spectral width of a single frequency slot.

6. The path selection and spectrum allocation method for reducing the influence of stimulated Raman scattering according to claim 5, characterized in that: The specific steps of step S6 include the following steps: S61: Traverse the K candidate paths in turn; S62: Search for the set of idle spectrum blocks that can meet the number of frequency slots required by the service request within the C and L bands of the current candidate path; S63: If the set of idle spectrum blocks within the candidate path is not empty, execute step S6; If the set of idle spectrum blocks within the candidate path is empty, search for the next candidate path; If the sets of idle spectrum blocks within all candidate paths are empty, the traversal ends, and the current service is blocked.

7. The path selection and spectrum allocation method for reducing the influence of stimulated Raman scattering according to claim 6, characterized in that: In step S72, the following criteria are executed: Criterion 1: When the modulation level of the service request is not less than the average modulation level and the number of required frequency slots is not less than the average required number of frequency slots, select the idle spectrum blocks in the set of idle spectrum blocks in the C-band according to the method from the tail to the head; Standard 2: The modulation level requested by the service is not less than the average modulation level, and the number of frequency slots required is less than the average number of frequency slots required. Idle frequency blocks in the C-band idle frequency block set are selected in a first-to-last manner. Standard 3: If the modulation level requested by the service is less than the average modulation level and the number of frequency slots required is not less than the average number of frequency slots required, an idle spectrum block in the set of idle spectrum blocks in the L-band is selected in a first-to-last manner. Standard 4: When the requested modulation level is less than the average modulation level and the required number of frequency slots is less than the average required number of frequency slots, an idle frequency block in the L-band idle frequency block set is selected in a tail-to-head manner.

8. The path selection and spectrum allocation method for reducing the influence of stimulated Raman scattering according to claim 7, characterized in that: In step S73, the path optical signal-to-noise ratio is calculated as follows: in, OSNR The path light signal-to-noise ratio. P For the transmit power requested by the service, P ASE The amplifier's spontaneously radiated noise power received by the service request. P NLI The power of the nonlinear effects on the business request.

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