CN108833142B - Network planning method for multi-core optical fiber planning service - Google Patents
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- CN108833142B CN108833142B CN201810522958.5A CN201810522958A CN108833142B CN 108833142 B CN108833142 B CN 108833142B CN 201810522958 A CN201810522958 A CN 201810522958A CN 108833142 B CN108833142 B CN 108833142B
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04Q—SELECTING
- H04Q11/00—Selecting arrangements for multiplex systems
- H04Q11/0001—Selecting arrangements for multiplex systems using optical switching
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04Q—SELECTING
- H04Q11/00—Selecting arrangements for multiplex systems
- H04Q11/0001—Selecting arrangements for multiplex systems using optical switching
- H04Q11/0062—Network aspects
- H04Q2011/0086—Network resource allocation, dimensioning or optimisation
Abstract
The invention discloses a network planning method of multi-core optical fiber planning service, in a given series of planning services, assuming that the path of each planning service is fixed and is the shortest route between a source node and a destination node; and calculating and finding out the optical core and the frequency spectrum which are suitable for distribution on each link on the planned traffic path, and selecting the most suitable establishment time and release time to reduce the time-weighted crosstalk factor between the optical cores. The invention adopts the plan light path algorithm based on RCSA, effectively reduces the crosstalk between the optical cores while meeting the plan service requirement, and optimizes the network plan of plan service transmission.
Description
Technical Field
The invention relates to a network planning method, in particular to a network planning method of a multi-core optical fiber planning service.
Background
With the rapid development of internet applications, network traffic shows exponential growth, and the demand for network bandwidth is also growing at a very rapid rate. Nowadays, the provision of bandwidth by network architectures based on single-core single-mode fibers has tended to saturate, and researchers have developed a study on space division multiplexing networks (SDMs), in which a multi-core fiber (MCF) is one of the fast-developing and promising ones. However, crosstalk between optical cores has been the biggest impediment to the development of multi-core optical fibers. Currently, there are several studies that show that crosstalk between adjacent optical cores affects signal transmission. Meanwhile, current SDM research based on MCF has been developed around static services and dynamic services. However, in real life, a client usually has some planning business, which is a business for determining the setup time and the release time in advance. However, the study of crosstalk between optical cores for planned services is not uncommon.
Therefore, a new technical solution is needed to solve the above technical problems.
Disclosure of Invention
The invention provides a network planning method of multi-core optical fiber planning service, namely, service transmission is carried out through non-adjacent optical cores in the same time, so that the service requirement can be met, and meanwhile, the crosstalk between the optical cores can be greatly reduced.
In order to achieve the purpose, the invention provides the following technical scheme:
a network planning method for multi-core optical fiber planning service is provided, which carries out service transmission between non-adjacent optical cores in the same time so as to reduce crosstalk factors between the optical cores while meeting the requirements of planning service. That is, in a given series of planned services, the path of each planned service is assumed to be fixed, being the shortest route between the source node and the destination node; and calculating and finding out the optical core and the frequency spectrum which are suitable for distribution on each link on the planned traffic path, and selecting the most suitable establishment time and release time to reduce the time-weighted crosstalk factor between the optical cores.
Since each scheduled service has its own earliest setup time and latest release time, we need to select the most appropriate time window within its time interval and assign the most appropriate spectral window to obtain the lowest time-weighted cross-core crosstalk factor.
Assuming a fixed route between the source node and the destination node, a secondary graph is built for each available spectral window for selecting the optical core and the spectrum with the lowest time-weighted crosstalk factor between the optical cores. Based on the auxiliary graph, for the multi-core fiber under the current route, it needs to calculate whether each optical core is available for the current spectral window, for the optical core that is not available for the current spectral window, no corresponding auxiliary link is established in the auxiliary graph, for those available optical cores, its corresponding auxiliary link is established in the auxiliary graph, and the cost value of its link is established as the inter-optical-core crosstalk factor value, and the time-weighted inter-optical-core crosstalk factor of the available optical core is calculated by using formula (2),
wherein the content of the first and second substances,
represents a set of time slots, and
then it means that at time slot t, the optical core
And
the total number of spectral overlaps when occupied by an optical path,
represents a weighted value of the crosstalk of the optical core,
respectively representing the serial number of the optical core.
Based on the auxiliary graph, values of crosstalk factors between optical cores that are weighted in time can be selected
Minimum spectral and temporal windows, however, different combinations of spectral and temporal windows will yield different values of time-weighted inter-core crosstalk, for which there are two strategies, the first hit strategy and the cost minimum strategy, the first one
The optical channel is established and time slots and frequency slots are allocated by combining the spectral windows and the time windows, and the time slot and the frequency slot are selected by scanning all the combinations to select the one with the lowest cost, namely
And judging the used optical core according to the link passed by the path, thereby establishing the optical path of the current service.
The invention adopts the plan light path algorithm based on RCSA, effectively reduces the crosstalk between the optical cores while meeting the plan service requirement, and optimizes the network plan of plan service transmission.
Drawings
The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention and not to limit the invention.
In the drawings:
figure 1 is a schematic representation of a 19-core MCF.
Fig. 2 is a schematic diagram of calculation of crosstalk factors between optical cores.
Fig. 3 is a construction aid diagram.
Figure 4 is a schematic representation of simulation results for the NSFNET network using a 7-core MCF.
Figure 5 is a graph showing similar results for the COST239 network of a 19-core MCF.
Detailed Description
The preferred embodiments of the present invention will be described in conjunction with the accompanying drawings, and it will be understood that they are described herein for the purpose of illustration and explanation and not limitation.
Crosstalk level for different adjacent characteristics between optical cores in an MCF, we define different levels for crosstalk between optical cores. Fig. 1 is an example of a 19-core MCF, in which we define 3 levels of cross-talk between optical cores. The first level, designated by L1 in the figure, is between the immediately adjacent cores 1 and 2, which produce the strongest cross-talk between cores when signals are simultaneously transmitted. At the second level, denoted by L2, between core 1 and core 14, it can be seen that there are 1 cores spaced apart, such indirectly adjacent cores are further apart than the directly adjacent L1, and crosstalk between cores occurring during simultaneous signal transmission is also weaker than that of L1. Finally, for the third type of cross-talk between cores L3, between core 11 and the core17, with more than 1 core spaced apart, it is clear that cross-talk between cores in this case is the weakest. As used herein
To express optical core crosstalk weight values, wherein
Representing the number of the optical cores, respectively, the first level of cross-talk between the optical cores obviously has the highest weighting factor, in this example set to 100, and similarly the second and third levels are set to 10 and 1, respectively.
Inter-core crosstalk factor, which is the crosstalk between cores that occurs when the same spectrum of different cores is occupied simultaneously. Thus, in addition to addressing the adjacency of different cores to each other, we also consider how much spectral overlap there is between the two cores. If there is no spectral overlap between the two cores being used, no crosstalk between the cores exists. Based on this spectral overlap, we define the crosstalk factor between the optical cores as
 | (1) |
Wherein the content of the first and second substances,
representing optical core
And
the total number of Frequency Slots (FSs) occupied by the optical path overlap.
Fig. 2 shows an example of crosstalk factor calculation between optical cores. In the optical core 1, the frequency gap of the optical path has two sections, from 1 to 3 and from 14 to 3 respectively28. In the optical core 2, the frequency gap occupied by the optical path is 2 to 4. For these two cores, the total number of overlapping frequency slots is 2FSs, i.e.,
from the formula defining the crosstalk factor between the optical cores, it can be derived
Similarly, an inter-core crosstalk factor between cores 1 and 8 can be calculated
The crosstalk factor between the optical cores of the optical core 8 and the optical core 14 is
。
Time-weighted cross-talk factor between optical cores: the condition for crosstalk between optical cores must be that when two optical paths exist simultaneously and have overlapping frequency spectrums, the longer the two optical paths exist simultaneously, the more crosstalk between optical cores is generated. Therefore, considering the time factor, we need to define further the crosstalk between the optical cores:
 | (2) |
here, the
Represents a set of time slots, and
then it means that at time slot t, the optical core
And
the total number of spectral overlaps when occupied by the optical path.
And (3) heuristic algorithm: given a series of planned light path services, define as
[3]Wherein
Representing the source node and the destination node of the traffic,
indicating the time at which the service can be established earliest and the time at which the service needs to be released latest, and
it indicates the duration of the service and,
FSs for business needs. In this example, we assume that the path of each traffic is fixed, being the shortest route between two points (source node and destination node). For each particular service requiring xFSs, we need to find the appropriate allocated optical core and spectrum on each link on its path and select the most appropriate setup and release times. Since each scheduled service has its own earliest setup time and latest release time, we need to select the most appropriate Time Window (TW) within his time interval and assign the most appropriate Spectral Window (SW) to achieve the lowest cross-talk between optical cores. For this selection of TW and SW, we developed a heuristic algorithm based on the auxiliary graph.
Heuristic algorithm based on auxiliary graph:
we now give an example of the creation of an auxiliary graph, based on which a new auxiliary topology is created that can pick out the lowest time-weighted cross-talk factor between the optical cores, assuming that a fixed route between the source node and the destination node is given and a specific SW is assigned for lightpath creation.
For each MCF under the current route, we first need to calculate whether each of its optical cores is available for the current SW, and if so, we calculate its time-weighted inter-core crosstalk factor using equation 2.
In fig. 3 (a), assuming that the current SW is from 1 to 4, we label the specific core usage of each core in the figure, for link Ns-N1 where the frequency slot of core 1 is occupied by other traffic from 1 to 3, and the frequency slot of the current spectral window of core 2 of link N1-Nd is all occupied. For the network utilization case of fig. 3 (a), we have established an auxiliary graph topology as in fig. 3(b), and first for optical cores (optical core 1 of link Ns-N1 and optical core 2 of link N1-Nd) for which the current spectral window is not available, no corresponding auxiliary links are established in the auxiliary graph. For those available optical cores, we establish their corresponding auxiliary links in the auxiliary map and establish the cost values of their links as the inter-core crosstalk factor values calculated using equation 1. For example, if frequency slots 1 through 3 of core 1 are occupied and the adjacent ranks of core 2 and core 1 are of the first rank, then
So can calculate
Then the cost of the auxiliary link s-D0- -N1-D0 is 300. Accordingly, the values of all the secondary links can be calculated in this way, we have labeled the links next to each other. Based on the newly established auxiliary graph topology, a path with the minimum cost is found out between the source node S-S and the destination node D-D by using a minimum cost routing algorithm, and the used optical core is judged according to a link passed by the path, so that the optical path of the current service is established.
SW and TW selection strategies based on the auxiliary map created above, we can select values of the crosstalk factor between the optical cores that make the weights in time
The smallest SW and TW. However, different SW and TW combinations result in different time-weighted inter-core crosstalk factor values, for which case we consider two strategies, namely the first hit strategy and the cost minimization strategy. The former being the first one used
SW and TW to establish an optical channel and allocate time slots and frequency slots, the latter being a combination of scanning all the combinations, selecting the one with the lowest cost, i.e.
。
Simulation and result analysis: we simulated the results of the proposed network planning strategy using the COST239 network of 11 nodes, 26 links and the NSFNET network of 14 nodes, 21 links. For each optical core of each MCF, 320FSs is available, and the spectral allocation for each optical channel is the same as for a conventional elastic optical network. In the simulation, the bandwidth of the planned service is randomly distributed between 5 and 20FSs, where the number of frequency slots is determined by the actual loan of the service and the modulation format selected for it. In addition, we generate a series of scheduled services immediately between the time slot intervals [0,260], with the duration of the services between [5, 2X-5] TSs (X denotes the average duration of the services). The simulation selects 500 of the planned traffic list from 100 to 200 TSs (without considering traffic congestion), and calculates the time-weighted value of the crosstalk factor between the optical cores for establishing the optical channel. In the optical channel establishment, the path selection follows the shortest routing path, and then the auxiliary graph algorithm is used for selecting the used TW and SW, and the simulation compares the results of the FF strategy and the LC strategy.
We finally compare the results of the individual strategies with the average single TS and FS values of the crosstalk factors between the optical cores, expressed as
WhereinLA set of links is represented that is,Tis a set of time slots, and,Cis the set of optical cores in each MCF,Da traffic set indicating successful establishment of an optical channel.
Is indicated in a time slot
Time-link I optical core
And
the cross-talk factor between the optical cores in between,
then represents the time-weighted aggregate value of the cross-talk factor between the optical cores throughout the network topology.
Respectively representing services
The number of FSs required and its duration.
Fig. 4 is a simulation result of the NSFNET network using a 7-core MCF, in which labels "First-First" and "last-Cost" denote the selection strategies of SW and TW in the auxiliary graph algorithm, respectively, and "Normal" denotes the network planning strategy without considering the crosstalk factor between optical cores. From the figure we can see that a strategy that considers crosstalk between optical cores can significantly reduce the value of crosstalk factor between optical cores by up to 57%. In addition, the "least cost" strategy may also be optimized up to 43% over the result of the "first hit" strategy, because the "least cost" strategy tries all possible SWs and TWs combinations and then selects the combination with the smallest crosstalk factor to establish the optical channel. In addition, fig. 5 also shows similar results for the COST239 network of the 19-core MCF.
Claims (1)
1. A network planning method of multi-core optical fiber planning service is characterized in that: service transmission is carried out between nonadjacent optical cores in the same time so as to reduce crosstalk factors between the optical cores while meeting the requirement of planned service; in a given series of planned services, assuming that the path of each planned service is fixed, the shortest route between a source node and a destination node; calculating and finding out optical cores and frequency spectrums suitable for being distributed on each link on a planned service path, and selecting the most suitable establishment time and release time to reduce time-weighted crosstalk factors between the optical cores; because each planned service has the earliest establishment time and the latest release time, the time window which is most suitable for each planned service needs to be selected in the time interval of the planned service, and the most suitable frequency spectrum window is distributed to obtain the crosstalk factor between the optical cores with the lowest time weighting; establishing an auxiliary graph for each available spectral window based on a fixed route between a given source node and a given destination node for selecting the optical core and the spectrum with the lowest time-weighted crosstalk factor between the optical cores; based on the auxiliary graph, for the multi-core fiber under the current route, it needs to calculate whether each optical core is available for the current spectral window, for the optical core that is not available for the current spectral window, no corresponding auxiliary link is established in the auxiliary graph, for those available optical cores, its corresponding auxiliary link is established in the auxiliary graph, and the cost value of its link is established as the inter-optical-core crosstalk factor value, and the time-weighted inter-optical-core crosstalk factor of the available optical core is calculated by using formula (2),
where T denotes a set of time slots, and
then indicates the total number of spectral overlaps, alpha, when the optical cores i and j are occupied by the optical path during time slot ti，jExpressing the crosstalk weight value of the optical core, wherein i and j respectively represent the serial number of the optical core; based on the auxiliary graph, values of crosstalk factors between optical cores that are weighted in time can be selected
Minimum spectral and temporal windowsHowever, different spectral windows and time window combinations result in different time-weighted inter-core crosstalk factor values, and for this case, there are two strategies, namely a first hit strategy and a cost minimization strategy, the first one being used
The optical channel is established and time slots and frequency slots are allocated by combining the spectral windows and the time windows, and the time slot and the frequency slot are selected by scanning all the combinations to select the one with the lowest cost, namely
And judging the used optical core according to the link passed by the path, thereby establishing the optical path of the current service.
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