JP5565577B2 - Traffic accommodation design method in variable bandwidth communication system - Google Patents

Description

  The present invention relates to a method for accommodating traffic demand in a variable bandwidth communication system, and in particular, selects an optical path by selecting a modulation format that can be transmitted and has a narrow spectral band in accordance with optical signal quality degradation in the optical path. The present invention relates to a method of accommodating and designing the traffic demand generated in a suboptimal manner in a system using a variable bandwidth communication apparatus that transmits and receives and changes the passable frequency band of a section through which an optical path passes in accordance with the band of the optical path.

  The optical path network that supports the current backbone network is mainly a group of optical communication devices such as a wavelength division multiplexing transmission device, an optical add / drop device, and an optical cross-connect device, and a transmission path group such as an optical fiber that connects them, and It is configured by a path group such as a wavelength for connecting optical communication apparatuses via a transmission path. In particular, research and development of a transparent optical path network for connecting optical communication apparatuses from end to end of an optical path network by a path without optical signal regenerative processing in a relay section is attracting attention.

  A traffic accommodation design method for a conventional transparent optical path network will be described.

  FIG. 11 shows an example of a conventional ring type optical path network. The optical path network includes optical communication devices 201-208. As shown in FIG. 12, each of the optical communication apparatuses 201 to 208 mainly includes a transmission unit 211 having a main signal transmission function, a reception unit 212 having a reception function, a wavelength multiplexer / demultiplexer, an optical switch, and the like. And a control unit (not shown) (see, for example, Non-Patent Document 1).

  The optical communication device on the entrance side of the optical path converts the electrical signal sent from the client into an optical signal in the transmission unit 211 and outputs the optical signal, and appropriately switches the destination of the optical path output in the path switching unit 213. The optical communication apparatus on the exit side of the optical path switches the optical path destination to the receiving unit 212 in the path switching unit 213, and converts the optical signal into an electrical signal in the receiving unit 212. The optical communication device on the relay side switches the path for each optical path.

  The optical communication method as described above is expected to realize economic, space and power savings of the optical path network in order to reduce the electrical signal processing of the optical communication device group in the relay section.

  On the other hand, in recent years, research and development for improving the frequency utilization efficiency of an optical signal by performing optical modulation with multiple values has been actively carried out (for example, see Non-Patent Document 2), and limited wavelength resources in an optical fiber. Further effective use of (frequency resources) is expected.

K. Sato et al., "Network performance and integrity enhancement with optical path layer technologies", IEEE J-SAC, Vol.12, No.1, pp.159-170. 1994 H. Goto et al., "Polarization-multiplexed 1 Gsymbol / s, 128 QAM (14Gbit / s) coherent optical transmission over 160 km using a 1.4 GHz Nyquist filter", OFC / NFOEC 2008, HThA45, 2008

  However, in the conventional optical path network, a modulation scheme is used in which all length optical paths can be transmitted with respect to an optical signal quality degradation amount in the longest optical path.

  FIG. 13 shows the relationship between various modulation schemes and SNR (Signal to Noise Ratio) penalties. In the case of a modulation scheme with a low multi-level number such as PSK (Phase Shift Keying) and QPSK (Quadrature Phase Shift Keying), the SNR penalty is small, so that it is suitable for transmission on an optical path having a long distance and a large number of nodes. On the other hand, since the SNR penalty increases as the multi-value number increases as in 8PSK, 16QAM, and 64QAM, the transmission distance and the number of nodes that can be transferred are reduced.

  Therefore, in the conventional optical path network, PSK or QPSK with a small SNR penalty is used so that transmission is possible with respect to the amount of optical signal quality degradation due to the influence of OSNR (Optical SNR) degradation or nonlinear optical effect in the longest optical path. The modulation method with a low multi-value number was used. For this reason, even for a short optical path (for example, optical path A in FIG. 11), as with the longest optical path (for example, optical path B in FIG. 11), a wide range necessary for a low-level modulation scheme (QPSK) is required. Spectral bands were used, and excessive spectral bands were allocated in most optical paths.

  In addition, in ADSL (Asymmetric Digital Subscriber Line) and wireless LAN, there is an adaptive modulation scheme that secures connectivity by lowering the transmission bit rate when the transmission path environment deteriorates. Proposals have also been made to apply this method to the optical communication method (see Japanese Patent Application Laid-Open No. 2008-167126). However, these conventional examples are point-to-point (P2P) cases. In the prior art, since the band allocated per optical path is fixed, even if the spectrum band is changed when the modulation method is changed, the frequency utilization efficiency is not improved.

  In the case of an optical path with a short transmission distance and a small number of nodes, there is little degradation of the optical signal quality, so that a desired transmission bit rate can be ensured by using a modulation method having a high multi-level number. However, in the case of an optical path with a long distance or a large number of passing nodes, the optical signal quality is greatly deteriorated, and a modulation scheme with a low multi-level number is used, so that the bit rate is reduced and a desired transmission bit rate cannot be secured. There was a problem.

  The present invention has been made in view of the above points. In accordance with optical signal quality degradation in an optical path route, the optical path is transferred by selecting a combination of a multi-value number and a symbol rate that can be transmitted and has a narrow spectrum band. An object of the present invention is to provide a traffic accommodation design method in a variable bandwidth communication system in which the bit rate is constant in all optical paths and the frequency band can be effectively used.

In order to solve the above-described problems, the present invention (Claim 1) provides a bandwidth in an optical path network having a network management apparatus that connects a group of communication apparatuses by optical transmission and has a function of setting and managing an optical path A method for accommodating traffic in a variable communication system, comprising:
Input means, traffic accommodation design means, path allocation means, physical topology database, path allocation information database storing link information between communication devices for each frequency slot, each having a required physical network configuration and a required traffic pattern as input, In a communication management device that gives a frequency slot number assigned to an optical path,
A traffic pattern input step in which the input means acquires one traffic pattern from a plurality of traffic demands;
A route extraction step in which the traffic accommodation design means extracts one route from possible routes on the network with reference to the physical topology database;
The traffic accommodation design means refers to the path allocation information database, and determines a necessary frequency slot from the route length or the number of hops to determine a required frequency slot;
The traffic accommodation design means disassembles the route into a plurality of fiber sections constituting it, and refers to the path allocation information database and the physical topology database for each of the disassembled fiber sections to determine whether they can be used. A determination step for determining;
A path allocation step of determining path allocation when the path allocation unit determines that the path allocation unit is usable in the determination step and updating the path allocation information database and the physical topology database; it repeatedly until no,
In the determination step,
When there are some fiber sections that cannot be secured, the physical topology database is referenced to determine whether there are other candidates for using different fiber sections on the same route. Returning to the step of referring to the path allocation information database to determine whether or not each section can be used, the allocation is performed again .

Further, according to the present invention (Claim 2), in the route extraction step,
Including preferentially extracting a route having a short hop count.

Further, according to the present invention (Claim 3 ), in the determination step,
If there are some fiber sections that cannot be secured and there are no other candidates that use different fiber sections on the same route, determine whether there is another candidate that passes through a different route with reference to the physical topology database, In some cases, the process returns to the route extraction step of extracting one route from possible routes on the network, and reassignment is performed.

Further, the present invention (Claim 4 ) is characterized in that in the determination step,
As a result of referring to the path allocation information database, when there are some fiber sections that cannot be secured and there are no other candidates for using different fiber sections on the same route, the physical topology database is referred to and a different route is passed. It is determined whether there is another candidate. If there is no candidate, it is assumed that a fiber is added to the necessary link. With reference to the path allocation information database and the physical topology database, for each fiber section, It returns to the step which judges whether it can be utilized, and it is characterized by assigning again.

Further, the present invention (Claim 5 ) is characterized in that in the traffic pattern input step,
It is characterized by sequentially accommodating and designing traffic generated according to demand.

Further, the present invention (Claim 6 ) is characterized in that in the traffic pattern input step,
When the traffic demand is known in advance, it is characterized in that a long hop number is first designed to be accommodated.

Further, the present invention (invention 7 ) provides the traffic pattern input step,
When the traffic demand is known in advance, it is characterized in that the one with a short hop number is first designed to be accommodated.

In the traffic pattern input step, the present invention (claim 8 )
When the traffic demand is known in advance, the accommodation design is random regardless of the number of hops.

  As described above, according to the present invention, an optical path is transferred by selecting a combination of a multi-value number and a symbol rate that can be transmitted according to optical signal quality degradation in an optical path route and has a narrow spectrum band, and transferring the optical path. In a system that can improve the use efficiency of the optical frequency band without changing the bit rate of the optical path of the path network, efficient traffic accommodation design can be performed.

It is an example of the physical model of the assumed network of the 1st Embodiment of this invention. It is an example of the relationship between the number of hops and a required frequency slot in the 1st Embodiment of this invention. It is a communication system block diagram in the 1st Embodiment of this invention. It is a block diagram of the network management apparatus in the 1st Embodiment of this invention. It is a flowchart of the accommodation design method in the 1st Embodiment of this invention. It is a flowchart of the accommodation design method in the 2nd Embodiment of this invention. It is the example of determination of the use fiber in the 2nd Embodiment of this invention, a use collection, and several slots. It is a flowchart of the accommodation design method in the 3rd Embodiment of this invention. It is a flowchart of the accommodation design method in the 4th Embodiment of this invention. It is a flowchart of the accommodation design information in the 5th Embodiment of this invention. It is an example of the conventional optical path network. It is a structural example of the conventional communication apparatus. This is the relationship between various modulation methods and SNR penalty.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[First Embodiment]
A first embodiment of the present invention will be described with reference to FIGS. The present embodiment corresponds to claims 1 to 4.

  FIG. 1 shows a physical model of a network assumed in the first embodiment. In this embodiment, a ring network composed of 16 nodes is assumed. This assumption does not consider path protection. Consider the full mesh traffic demand between all nodes for this network. Furthermore, the relationship between the number of hops and the number of required frequency slots as shown in FIG. 2 is used when extracting the traffic pattern. At this time, in the present invention, as shown in FIG. 2, the optimum value of the number of slots to be assigned according to the number of hops is used. On the other hand, conventionally, only the number of slots at the longest hop number is employed as the number of slots, and the same number of slots is employed even if the distance changes.

  FIG. 3 shows the configuration of the communication system according to the first embodiment of the present invention, and FIG. 4 shows the configuration of the network management apparatus according to the first embodiment of the present invention.

  The network management apparatus 100 shown in the figure has a function of connecting a communication apparatus group by optical transmission and setting and managing an optical path. The network management device 100 is connected to each communication device 200.

  The network management apparatus 100 includes a control unit 110, a traffic accommodation design unit 120, a storage unit 130, an input unit 140, and a path allocation unit 150. The storage unit 130 includes a traffic pattern database (DB) 131, a physical topology DB 132, A path allocation information DB 133 is stored.

  The traffic pattern DB 131 stores the start point and end point of the path of the input traffic demand (traffic pattern).

  The physical topology DB 132 stores information about links between communication devices and physical fibers. By combining with the allocation path information DB, it is possible to determine whether or not to secure fiber resources.

  The path allocation information DB 133 stores allocated path information.

  The traffic accommodation design unit 120 includes a route extraction unit 122, a required frequency slot determination unit 123, and a used fiber / use frequency slot number determination unit 124. Detailed operation will be described later.

  The path allocation unit 150 reserves a combination of fiber sections for the optical path, and updates the contents of the physical topology DB 132 and the path allocation information DB 133.

  The operation in the above configuration is shown below.

  The present embodiment is an example in the case where two or more traffic demands are generated together, and is applied, for example, when accommodation design is performed again when a communication network that has already been constructed is relocated.

  FIG. 5 is a flowchart of accommodation design information in the first exemplary embodiment of the present invention.

  First, the communication manager considers that a new traffic demand has occurred when the actual traffic volume with respect to the traffic volume that can be accommodated exceeds a certain value, or when a new service application occurs. Then, the traffic demand (traffic pattern) is input to the input unit 140 of the network management apparatus 100. The input unit 140 stores the start point and end point of the traffic pattern path in the traffic pattern DB 131 (step 101).

  The traffic accommodation design unit 120 of the network management apparatus 100 uses the route extraction unit 122 to extract one arbitrary traffic pattern from the traffic pattern DB 131, and based on the start point and the end point of the optical path, based on the physical model. The entire route search of the path assignment information DB 133 is performed, and the reachable route and the number of hops are temporarily stored in a route list in a memory (not shown) (step 102). The required frequency slot determination unit 123 extracts the shortest hop number from the optical path route searched by the route extraction unit 122 (step 103), and determines the number of slots corresponding to the hop number based on FIG. (Step 104). Next, the used fiber / used frequency slot number determination unit 124 decomposes the determined optical path route information into a plurality of fiber sections constituting the same (step 105), and extracts one decomposed fiber section. (Step 106), it is determined whether each disassembled fiber section can be used with reference to the physical topology DB 132 and the path allocation information DB 133 (Step 107). If all the fiber sections are available (step 107, Yes), the path allocation unit 150 reserves the combination of the sections for the optical path and updates the contents of the path allocation DB 133 (step). 108).

  Thereafter, returning to step 101, the next new traffic demand is searched for the one with the longest hop count, and one is extracted. This traffic demand will have the next longest hop count of what we chose earlier.

  This series of operations is repeated until all input traffic demands are exhausted (step 109, No). This completes the accommodation design for all traffic demands.

  Among the above, when the specification fiber / used frequency slot number determination unit 124 of the traffic accommodation design unit 120 determines whether each of the decomposed fiber sections can be used, there is no empty slot in the path allocation information DB 133. When even one that cannot be used is found (step 107, No), the physical topology DB 132 and the path allocation information DB 133 are referred to and it is confirmed whether there are other candidates that use different fibers on the same route. (Step 110). If it exists (step 110, Yes), the process returns to the operation (step 106) for determining whether or not each of the disassembled fiber sections can be used, and the same operation is performed. However, if there are no other candidates that use different fibers on the same route (step 110, No), the physical topology DB 132 is referenced to check whether there is a candidate that passes through a different route (step 111). In step 111, Yes), the operation returns to the assignment operation of the frequency slot number (step 103) again for the route, and a series of operations are performed. This route should have the second shortest number of hops. However, if there is no candidate that passes through a different route (step 111, No), it is impossible to perform accommodation design, and thus the series of operations is terminated.

  That is, this embodiment is applied under the condition that the total number of fibers is constant.

  The first embodiment of the present invention repeats the above until there is no traffic demand.

[Second Embodiment]
A second embodiment of the present invention will be described with reference to FIG. This embodiment corresponds to the fifth aspect.

  In the present embodiment, as in the first embodiment described above, a case where two or more traffic demands are generated together is shown.

  The configuration of the present invention is in accordance with the first embodiment.

  FIG. 6 is a flowchart of the accommodation design method according to the second embodiment of the present invention. The same steps as those in FIG. 5 are denoted by the same step numbers, and the description thereof is omitted.

  In the present embodiment, in the above-described first embodiment, when a candidate passing through a different route is not found (No in step 111), a fiber necessary for passing the link is added, and the physical topology The DB 132 is updated (step 201). In this process, as shown in FIG. 7A, the fiber 1 and the fiber 2 are set between the communication device A and the communication device B (link A), and the communication device B and the communication device C. If the empty slot of the path allocation information DB 133 when the fiber 3 is set between (link B) is in the state of FIG. 7B, the fiber that is an empty slot is used. For example, when a demand for a path connecting the communication device A and the communication device C (necessary number of slots: 1) occurs, the frequency slot number “2” of the fibers 2 and 3 can be used. When it is assumed that the frequency slot number “2” is used, the fibers 2 and 3 of the frequency slot number “2” in the path allocation information DB 133 are updated as used slots.

  And it returns to the process (step 106) which judges again whether all the fiber sections on a path | route are usable, It is characterized by performing a series of operation | movement. If there are a plurality of traffic patterns as in this embodiment, the processing shown in FIG. 6 is not stopped until the fiber addition is completed, but the fiber addition is performed based on the updated path allocation information DB 133. The process proceeds as if it were broken.

  The present embodiment is characterized in that a solution that accommodates all traffic is found in order to allow an additional fiber.

[Third Embodiment]
A third embodiment of the present invention will be described with reference to FIG. This embodiment corresponds to the sixth aspect.

  In the first and second embodiments, the case where the traffic demand is known in advance has been described. However, in the present embodiment, the traffic demand occurs sequentially (when the traffic demand is not known in advance). Yes, for example, when a new traffic demand occurs during operation of the communication network.

  The configuration of the present invention is in accordance with the first and second embodiments.

  FIG. 8 is a flowchart of the accommodation design method according to the third embodiment of the present invention.

  This embodiment is processing when traffic demand occurs sequentially.

  In the present embodiment, instead of extracting one traffic pattern, each time a traffic demand is input to the input unit 140 by the administrator, the accommodation is designed sequentially (the processing after step 102 is performed) (step 301). Since other processes are the same as those of the second embodiment, description thereof is omitted.

[Fourth Embodiment]
A fourth embodiment of the present invention will be described with reference to FIG. This embodiment corresponds to the seventh aspect. This embodiment is applied mainly when the traffic demand is known in advance, as in the first and second embodiments described above.

  The configuration and operation of the present invention are in accordance with the first and second embodiments.

FIG. 9 is a flowchart of the accommodation design method according to the fourth embodiment of the present invention.
In the present embodiment, in the first and second embodiments, among the traffic generated according to the demand input from the administrator to the input unit 140, the traffic having a large number of hops is first designed to be accommodated (steps). 401). Since other processes are the same as those of the second embodiment, description thereof is omitted.

[Fifth Embodiment]
A fifth embodiment of the present invention will be described with reference to FIG. This embodiment corresponds to the eighth aspect.

  The configuration and operation of the present invention are in accordance with the first and second embodiments. In the present embodiment, in the above-described embodiment, among the traffic generated according to the demand input from the administrator to the input unit 140, the traffic with a small number of hops is first designed to be accommodated (step 501). Since other processes are the same as those of the second embodiment, description thereof is omitted.

  The operation shown in FIGS. 5, 6, 8, 9, and 10 of the network management apparatus 100 is constructed as a program and installed in a computer used as the network management apparatus, or via a network. It can be distributed.

  Further, the constructed program can be stored in a portable storage medium such as a hard disk, a flexible disk, or a CD-ROM, and installed in a computer or distributed.

  The present invention is not limited to the above-described embodiment, and various modifications and applications can be made within the scope of the claims.

DESCRIPTION OF SYMBOLS 100 Network management apparatus 110 Control part 120 Traffic accommodation design part 122 Path extraction part 123 Required frequency slot determination part 124 Used fiber and use frequency slot number determination part 130 Storage part 131 Traffic pattern database 132 Physical topology database 133 Path allocation information database 140 Input Unit 150 path allocation unit 200 communication device

Claims (8)

A method for accommodating traffic in a bandwidth variable communication system in an optical path network having a network management device that connects a communication device group by optical transmission and has a function of setting and managing an optical path,
Input means, traffic accommodation design means, path allocation means, physical topology database, path allocation information database storing link information between communication devices for each frequency slot, each having a required physical network configuration and a required traffic pattern as input, In a communication management device that gives a frequency slot number assigned to an optical path,
A traffic pattern input step in which the input means acquires one traffic pattern from a plurality of traffic demands;
A route extraction step in which the traffic accommodation design means extracts one route from possible routes on the network with reference to the physical topology database;
The traffic accommodation design means refers to the path allocation information database, and determines a necessary frequency slot from the route length or the number of hops to determine a required frequency slot;
The traffic accommodation design means disassembles the route into a plurality of fiber sections constituting it, and refers to the path allocation information database and the physical topology database for each of the disassembled fiber sections to determine whether they can be used. A determination step for determining;
A path allocation step of determining path allocation when the path allocation means is determined to be usable in the determination step, and updating the path allocation information database and the physical topology database;
And to repeat until the traffic demand unallocated is eliminated,
In the determination step,
When there are some fiber sections that cannot be secured, the physical topology database is referenced to determine whether there are other candidates for using different fiber sections on the same route. The accommodation design method of returning to the step of judging whether or not each section can be used by referring to the path allocation information database and performing allocation again . In the route extraction step,
The accommodation design method according to claim 1, further comprising a step of preferentially extracting a route having a short hop number. In the determination step,
If there are some fiber sections that cannot be secured and there are no other candidates that use different fiber sections on the same route, determine whether there is another candidate that passes through a different route with reference to the physical topology database, from possible paths in the network in some cases, return to the path extracting step of extracting one path, accommodation design method according to claim 1, characterized in that the assignment again. In the determination step,
As a result of referring to the path allocation information database, when there are some fiber sections that cannot be secured and there are no other candidates for using different fiber sections on the same route, the physical topology database is referred to and a different route is passed. It is determined whether there is another candidate. If there is no candidate, it is assumed that a fiber is added to the necessary link. With reference to the path allocation information database and the physical topology database, for each fiber section, accommodation design method of claim 1, wherein the performing reassigned back to the step of determining whether available. In the traffic pattern input step,
The accommodation design method according to any one of claims 1 to 4 , wherein the traffic generated according to demand is sequentially accommodated. In the traffic pattern input step,
The accommodation design method according to any one of claims 1 to 4 , wherein when the traffic demand is known in advance, the accommodation design with a long hop number is performed first. In the traffic pattern input step,
Advance when traffic demand is known, accommodation design method according to any one of claims 1 to 4, characterized in that to accommodate design those short hops earlier. In the traffic pattern input step,
The accommodation design method according to any one of claims 1 to 4 , wherein when the traffic demand is known in advance, the accommodation design is performed randomly regardless of the number of hops.

Images