JP6748004B2 - Path selection device and path selection method - Google Patents

Description

The present invention relates to a path selection device and a path selection method.

There is a radio base station in which an antenna unit (RRH: Remote Radio Head) and a signal processing unit (BBU: Base Band Unit) are separated. The RRH and the BBU are connected via an optical section having an optical device and an optical fiber. An optical section including an optical device and an optical fiber is called a mobile front haul (MFH).

FIG. 9 is a diagram showing an example of the configuration of a radio base station having a mobile fronthaul. In order to reduce the cost of the mobile fronthaul, which used to be point-to-point connection in the past, in recent years, networking the mobile fronthaul has been considered. The mobile fronthaul network system is, for example, a PON (Passive Optical Network) network system or a network system in which layer-2 switches (L2SW) are connected in multiple stages.

A network system (hereinafter referred to as “L2NW”) in which layer 2 switches (L2SW), which are signal transfer devices, are connected in multiple stages is attracting attention because it is more economical than other network systems. In a mobile fronthaul with strict requirements regarding signal delay, there is a problem in reducing signal delay when configuring an L2NW.

Standardization of a TSN (Time Sensitive Network) for the purpose of accommodating a network having strict requirements regarding signal delay in an L2NW is in progress. In the standardization of TSN, the mobile fronthaul is also the target of standardization (see Non-Patent Document 1).

“Time-Sensitive Networks for Fronthaul”, IEEE P802.1CM/D0.5, October 15, 2016

The TSN method for interrupting or discarding the transfer of low-priority signals and transferring high-priority signals with the highest priority and low delay has been widely studied. However, when a large amount of high-priority signals flow into the L2NW in a short time, a long waiting time occurs before the signal transfer device transfers the high-priority signals.

In the 5th generation mobile communication system (5G), adoption of a time division duplex (TDD: Time Division Duplex) is being considered as a communication method in a wireless section. When the time division duplex method is adopted as the communication method in the wireless section, since the time information of the RRHs is synchronized, the RRHs may transmit or receive the radio signals at substantially the same timing. As a result, the signal transmitted by the RRH in a burst and in a short time flows into the section of the mobile fronthaul, so that the waiting time until the signal transfer device transfers the high priority signal increases.

For example, the traffic of a signal that flows into the section of the mobile fronthaul (hereinafter referred to as “mobile traffic”) is the traffic of a signal of high priority in the L2NW. In the L2NW in which a plurality of RRHs and BBUs are connected, a large amount of high-priority signals flow into the signal transfer device in a burst and in a short time, so that the signal transfer device waits until the high-priority signal is transferred. Time will increase.

In addition, a fixed node between a start point node (hereinafter referred to as “s node”) which is a signal transfer device (node) at the beginning of signal inflow into the L2NW and a signal destination node (hereinafter referred to as “d node”). There is a method in which a signal transfer device transfers a signal from an s node to a d node via a specific path (hereinafter, referred to as “fixed path”). The fixed path is defined by a path selection device, which is a device that defines a path for transferring a signal.

The path selection device defines an arbitrary path such as the shortest path from the s node to the d node as a fixed path from the s node to the d node. The path selection device is connected to any signal transfer device of the L2NW. The path selection device, in each transfer information table stored in each signal transfer device such as the signal transfer device connected to the path selection device, stores the route of the L2NW representing the node to which the signal (packet) is transferred. Register the information to represent.

Hereinafter, in the case where a signal transfer failure occurs in a link between specific nodes, a path for transferring a signal from the s node to the d node, which is a path bypassing the failed link, will be described. , "Detour pass".

Each signal transfer device transfers a signal to the d node via the detour path. When each signal transfer device transfers a signal from the s node to the d node via the detour path, the number of signal transfers and the physical distance between the nodes change. Therefore, each signal transfer device may not be able to transfer a signal to the BBU or RRH within the transfer time required to be satisfied (hereinafter referred to as “request transfer time”).

Further, the signal being transferred flows into the signal transfer device via the detour path, and the transfer of the signal is placed in a waiting state in the signal transfer device (hereinafter referred to as “queuing delay”). May increase. That is, the signal transferred via the detour path additionally delays the signal transferred via a path other than the detour path, which may impair the entire L2NW.

However, the conventional path selection device has a problem in that the transfer time of a signal when a failure occurs in the mobile fronthaul cannot be set within the transfer time required when the failure does not occur. ..

In view of the above circumstances, the present invention provides a path selection device capable of setting a signal transfer time when a failure occurs in a mobile fronthaul within a transfer time required when no failure occurs, and It is intended to provide a path selection method.

One aspect of the present invention is a path selection device that selects a path from a plurality of paths connecting a node at a start point to a node at an end point of a communication network having a plurality of nodes and links, in which a failure has occurred. Even when the signal is transferred by bypassing the link, a detection unit that detects a selectable path that is a path in which the transfer time of the bypassed signal and the signal that is not bypassed is less than a predetermined transfer time, and a failure occurs A path selecting device comprising: a selection unit that selects a predetermined path when the failure occurs, and a selection unit that selects the selectable path when a failure occurs.

One aspect of the present invention is the path selection device described above, further comprising a deletion unit that deletes the selected link from the logical topology information of the communication network, and the detection unit deletes the selected link. The selectable path is detected based on the logical topology information thus obtained.

One aspect of the present invention is the path selection device described above, wherein the deleting unit waits for a transfer time of the signal that has not been detoured in a path including the selected link and a transfer of the signal in the node. When the sum of the transfer delay time and the transfer delay time exceeds the predetermined transfer time, the selected link is deleted from the logical topology information.

One aspect of the present invention is a path selection method executed by a path selection device that selects a path from among a plurality of paths connecting a node at a start point to a node at an end point of a communication network having a plurality of nodes and links, A step of detecting a selectable path that is a path in which each transfer time of the bypassed signal and the non-rerouted signal is equal to or shorter than a predetermined transfer time even when the signal is transferred by bypassing the failed link And a step of selecting a predetermined path when no failure has occurred and selecting the selectable path when a failure has occurred.

According to the present invention, it is possible to set the signal transfer time in the case where a failure occurs in the mobile fronthaul within the transfer time required when the failure does not occur.

It is a figure which shows the example of a structure of the wireless base station in 1st Embodiment. It is a figure which shows the example of a structure of the path selection server in 1st Embodiment. It is a figure which shows the example of a logical topology in 1st Embodiment. FIG. 5 is a diagram showing an example of a path in the case where a link has not failed in the first embodiment. FIG. 6 is a diagram showing an example of a bypass path in the case where a link has a failure in the first embodiment. FIG. 6 is a diagram showing an example of a logical topology in which a link selected as a failed link is deleted in the first embodiment. 6 is a flowchart showing an example of the operation of the path selection server in the first embodiment. 6 is a flowchart showing an example of an operation of detecting a bypass path in the first embodiment. It is a figure which shows the example of a structure of the wireless base station which has a mobile fronthaul.

Embodiments of the present invention will be described in detail with reference to the drawings.
(First embodiment)
FIG. 1 is a diagram illustrating an example of the configuration of the wireless base station 1. The wireless base station 1 is a path selection device as a base station that executes wireless communication. The radio base station 1 includes a BBU 2 and an upper device such as an optical device 3, a path selection server 4, one or more signal transfer devices 5, one or more optical devices 6 and an RRH 7 (lower device). , As a network system (communication network system).

The BBU2 is a signal processing unit. The BBU 2 assigns a signal transfer priority to a downlink signal for each VLAN. The optical device 3 transmits to the signal transfer device 5-1 an optical signal based on a downlink signal to which a signal transfer priority is assigned. The optical device 3 acquires the optical signal based on the upstream signal to which the signal transfer priority is assigned, from the signal transfer device 5-1 via the optical fiber.

The path selection server 4 is an information processing device such as a server that defines a path for transferring a signal. The path selection server 4 may be realized as an external device connected to the signal transfer device 5, or may be realized as a device included in the signal transfer device 5. Hereinafter, a path connecting the s-node to the d-node when a link has a failure is referred to as a "detour path". The path selection server 4 defines a path (hereinafter referred to as “non-selectable path”) (transfer prohibited path) in which the signal transfer time exceeds the requested transfer time when the signal is bypassed. The path selection server 4 may set a path (hereinafter, referred to as “selectable path”) in which the signal transfer time is equal to or less than the request transfer time even if the signal is bypassed.

The path selection server 4 disables the non-selectable path so that the signal transfer apparatus 5 does not use a predetermined non-selectable path when a failure occurs in the mobile fronthaul including each signal transfer apparatus 5. Is applied to the signal transfer device 5. For example, the path selection server 4 includes, in the transfer information table stored in the signal transfer apparatus 5 connected to the path selection server 4, the signal transfer apparatus 5 as the destination to transfer the signal based on the non-selectable path. Register the information to represent. For example, the path selection server 4 registers, in the transfer information table, information indicating a route that prohibits signal transfer.

That is, the path selection server 4 uses the selectable path so that the signal transfer apparatus 5 uses the predetermined selectable path when the mobile fronthaul including each signal transfer apparatus 5 has a failure. The signal transfer device 5 is set to be permitted. For example, the path selection server 4 represents the signal transfer device 5 to which the signal is transferred based on the selectable path in the transfer information table stored in the signal transfer device 5 connected to the path selection server 4. Register the information. For example, the path selection server 4 registers, in the transfer information table, information indicating the route for which signal transfer is permitted.

The signal transfer device 5 is a device that transfers an optical signal. The signal transfer device 5 is, for example, a layer 2 switch, a layer 3 switch, or a router. Below, the signal transfer apparatus 5 is a layer 2 switch as an example. The signal transfer device 5 stores a transfer information table including information indicating a fixed path. The transfer information table further includes information indicating unselectable paths. The transfer information table may include information indicating a selectable path instead of including information indicating a non-selectable path. The signal transfer device 5 transfers the downstream optical signal to the signal transfer device 5 or the optical device 6 at the next stage based on the transfer information table. The signal transfer device 5 transfers the upstream optical signal to the signal transfer device 5 or the optical device 3 at the next stage based on the transfer information table. The signal transfer device 5 autonomously detects a failure in the mobile fronthaul and autonomously resets a path based on table information of selectable paths.

FIG. 3 is a diagram showing an example of the logical topology. In FIG. 3, each node of the logical topology is the signal transfer devices 5-1 to 5-16. In FIG. 3, the s node is the signal transfer device 5-1. The d node is the signal transfer device 5-16. The path selection server 4 is connected to the signal transfer device 5-4 as an example.

Hereinafter, the link included in the detour path is referred to as a "detour link". Hereinafter, a path that includes at least one detour link when no failure has occurred in the link (during normal operation) is referred to as a “normal path”.

FIG. 4 is a diagram showing an example of a path when a link has not failed. In FIG. 4, the path selection server 4 includes a signal transfer device 5-1, a signal transfer device 5-2, a signal transfer device 5-3, a signal transfer device 5-7, and a signal transfer device 5-11. The fixed path connecting the signal transfer device 5 in the order of the signal transfer device 5-15 and the signal transfer device 5-16 is selected as the normal path 50 connecting the s node to the d node.

FIG. 5 is a diagram showing an example of a detour path when a failure occurs in a link. In FIG. 5, as an example, a failure occurs in the link connecting the signal transfer device 5-2 and the signal transfer device 5-3. In FIG. 5, the path selection server 4 includes a signal transfer device 5-1, a signal transfer device 5-2, a signal transfer device 5-6, a signal transfer device 5-10, and a signal transfer device 5-14. The path connecting the signal transfer apparatus 5-15 and the signal transfer apparatus 5-16 in this order is selected as the detour path 51 connecting the s node to the d node. The detour path 51 has a detour link between the signal transfer devices 5 adjacent to each other in the detour path 51.

Returning to FIG. 1, the description of the configuration example of the wireless base station 1 will be continued. The optical device 6 acquires the downstream optical signal from the signal transfer device 5 that is the d node. The optical device 6 transmits the upstream optical signal to the signal transfer device 5. The RRH 7 is an antenna unit. The RRH 7 forms a small cell 8 for wireless communication. The RRH 7 wirelessly communicates with the wireless terminal in the small cell 8 based on the downstream optical signal acquired by the optical device 6.

Next, an example of the configuration of the path selection server 4 will be described.
FIG. 2 is a diagram showing an example of the configuration of the path selection server 4. The path selection server 4 includes a storage unit 40, a creation unit 41, an extraction unit 42, a detection unit 43, a determination unit 44, a deletion unit 45, a registration unit 46, and a selection unit 47. As described above, the path selection server 4 may be realized as an external device connected to the signal transfer device 5, or may be realized as a device included in the signal transfer device 5. When the path selection server 4 is realized as an external device connected to the signal transfer device 5, at least one of the functional units of the path selection server 4 may be included in the signal transfer device 5.

Some or all of the creation unit 41, the extraction unit 42, the detection unit 43, the determination unit 44, the deletion unit 45, the registration unit 46, and the selection unit 47 are stored in a processor such as a CPU (Central Processing Unit). It may be realized by executing a program stored in the unit, or may be realized using hardware such as an LSI (Large Scale Integration) or an ASIC (Application Specific Integrated Circuit).

The storage unit 40 is a storage device having a non-volatile recording medium (non-temporary recording medium) such as a magnetic hard disk device or a semiconductor storage device. The storage unit 40 stores information indicating a logical topology in which the signal transfer device 5 is a node (hereinafter referred to as “logical topology information”). The storage unit 40 stores information indicating unselectable paths. The storage unit 40 may store information indicating a selectable path instead of storing information indicating a non-selectable path.

FIG. 6 is a diagram showing an example of a logical topology in which a link selected as a failed link is deleted. The creation unit 41 selects the link i (=l _i ) as the failed link. Here, i represents a link number. In FIG. 6, the link i is a link connecting the signal transfer device 5-2 and the signal transfer device 5-3. As illustrated in FIG. 6, the creating unit 41 creates the logical topology information using the links other than the selected link i.

The creation unit 41 searches the logical topology information for a path p _i,j (j=0,1,..., N) passing through the link i when no failure has occurred in the link i (normal time). j represents the pass number. If the link i has not failed, (n+1) paths include the link i.

Returning to FIG. 2, the description of the configuration example of the path selection server 4 will be continued. The extraction unit 42 extracts the path p _i,j from the logical topology information. Extraction unit 42, bypass links are included in the detour path _{p 'i, j k (=} l k) (k = 0,1, ..., m) and extracted from the logical topology information. k represents the number of the detour link.

The detection unit 43 detects a selectable path based on the logical topology information in which the selected detour link k(l _k ) is deleted by the deletion unit 45. Detector 43, the path _{p i,} for _j, detour path p _'i, and _j, the detour path p' _i, the transfer time _{t i} of the signal at _j, and _j, detected by any calculation method. Detector 43, the normal path p _k including bypass link l _k when the link i is no _failure, the transfer time t _a signal in _a, to detect the bypass link l _k.

The detection unit 43 detects the queuing delay d _c due to the signal transfer waiting due to the addition of the detour path p′ _i,j for the signal transfer device 5 (node) that terminates the detour link 1 _k. To detect. Here, the detection unit 43 detects the worst value of the queuing delay d _c . The worst value of the queuing delay d _c is, for example, when the detection unit 43 sets four normal paths and two detour paths in the signal transfer device 5 terminating the detour link l _k. When the signal of the normal path and the signal of the two bypass paths flow into the signal transfer apparatus 5 almost at the same time, the queuing of the signal transferred last by the signal transfer apparatus 5 via the bypass path p′ _i,j The delay d _c .

The determination unit 44 determines whether or not a failure has occurred in the mobile fronthaul including each signal transfer device 5. Determining unit 44, the transfer time t _i which is detected by the detection unit _{43, j} is equal to or below the required transfer time t _r. The determination unit 44, the normal path p _k, determines whether or not exceed the total demand transfer time t _r of the transfer time t _a and queuing delay d _c of the signal that has not been diverted in _a.

Whether or not the determination unit 44 determines whether or not the number k of the detour links exceeds the total number m of the detour links, whether or not the detour links are to be deleted from the logical topology information, for all the detour links. Determine whether or not. The determination unit 44 determines whether or not all the paths p _i,j are the selectable paths by determining whether or not the path number j exceeds the total number (n) of the paths. Determine whether.

When deleting unit 45, which exceeds the normal path p _k, the total demand transfer time t _r of the transfer time t _a and queuing delay d _c of the signal that has not been diverted in _a, selectable path p _{'i, The} detour link k(l _k ) is deleted from the logical topology information for extracting _j .

The registration unit 46 (selectable path determination unit) may detect the selectable path instead of the detection unit 43 detecting the selectable path. Registration unit 46, bypassing the remaining without being removed in order to successfully pass p _k, does not exceed the total demand transfer time t _r of the transfer time t _a and queuing delay d _c of the signal that has not been diverted in _a The detour path p′ _i,j including the link is determined as the selectable path. That is, the selectable paths, the sum of the transfer time t _a and queuing delay d _c is less required transfer time t _r.

The registration unit 46 registers information indicating a non-selectable path (hereinafter referred to as “non-selectable path information”) in the transfer information table and storage unit 40. Here, the non-selectable path information includes, for example, information indicating a port (blocking port) that prevents signal transfer in the signal transfer device 5. However, the unit that hinders signal transfer is not limited to the port unit. When each path is set for each VLAN, the unit for blocking the signal transfer may be the VLAN unit.

Instead of registering the non-selectable path information in the transfer information table and storage unit 40, the registration unit 46 registers information representing a selectable path (hereinafter referred to as “selectable path information”) in the transfer information table and storage unit 40. You may. The registration unit 46 may register information indicating that there is no selectable path in the transfer information table and storage unit 40.

The selection unit 47 selects a fixed path when there is no failure in the mobile fronthaul including each signal transfer device 5. When a failure occurs in the mobile fronthaul, the selecting unit 47 sets the registering unit 46 so that the signal transfer device 5 uses a predetermined selectable path so that the unselectable path is disabled. Via the transfer information table of the signal transfer device 5. That is, the selecting unit 47 sets the setting of permitting the use of the selectable path so that the signal transfer device 5 uses the predetermined selectable path when a failure occurs in the mobile fronthaul. It registers in the transfer information table of the signal transfer device 5 via 46. The reason why the non-selectable path is prohibited is to prevent flooding in the non-selectable path.

When a signal flows into the signal transfer device 5 from a port that is not registered as a blocking port in the transfer information table, the selection unit 47 selects a signal that has flowed in from a port that is not registered as a blocking port in the transfer information table as a selectable path. Flood to. As one of the embodiments, the path selection server 4 determines a selectable path in advance, and each signal transfer device 5 holds table information of the selectable path. Each signal transfer device 5 autonomously determines whether or not a failure has occurred in the mobile fronthaul, and when a failure has occurred, autonomously resets the path based on the table information. By doing so, a delay or the like associated with recalculation does not occur as compared with the case where the path selection server 4 recalculates a selectable path when a failure occurs, so the radio base station 1 is more resistant to delay. Can be increased. However, the embodiment is not limited to this, and the path selection server 4 may periodically recalculate the selectable paths.

Next, an example of the operation of the path selection server 4 will be described.
FIG. 7 is a flowchart showing an example of the operation of the path selection server. The path selection server 4 detects detour paths for all links in the mobile fronthaul (step S101). The path selection server 4 registers the non-selectable path information, which is the information indicating the non-selectable path, in each transfer information table stored in all the signal transfer devices 5 in the mobile front hall. The path selection server 4 may register the selectable path information, which is information indicating the selectable path, in each transfer information table stored in all the signal transfer devices 5 in the mobile front hall (step S102).

FIG. 8 is a flowchart showing an example of the operation of detecting a bypass path. The creation unit 41 selects the link i (=l _i ) as the failed link (step S201). As illustrated in FIG. 6, the creating unit 41 creates logical topology information using links other than the link i (step S202). The creation unit 41 searches the logical topology information for a path p _i,j (j=0,1,..., N) passing through the link i when no failure has occurred in the link i (normal time). The extraction unit 42 extracts the path p _i,j from the logical topology information (step S203).

The detection unit 43 sets an initial value 0 to the path number j so that the first target for determining the bypass path is the path p _i,0 . Note that the order of the paths that are the targets of the determination for determining the detour path is arbitrary (step S204). Detector 43, the path _{p i,} for _j, detour path p _{'i, j} and detour path p' _i, the transfer time of the signal in the _{j t i,} detects a _j. The detection unit 43 detects the detour path p′ _i,j and the transfer time t _i,j by an arbitrary calculation method (step S205).

Determining unit 44, the detected transmission time _{t i,} and determines whether or not _j is less than required transfer time _{t r} (step S206). Transfer time _{t i,} if _j is less than the required transfer time _{t r} (step S206: YES), the extraction unit 42, bypass path p _'i, bypass link k included in the _{j (=} l k) (k =0, 1,..., M) is extracted from the logical topology information (step S207). Detector 43, link i to a normal path p _k including bypass link l _k if no failure _occurs, the transfer time t _a signal in _a, to detect all of the bypass link l _k (step S208) .. The detection unit 43 detects the queuing delay d _c due to the signal transfer waiting due to the addition of the bypass path p′ _i,j for the signal transfer device 5 terminating the bypass link l _k ( Step S209).

Determining unit 44, the normal path _{p k,} determines whether or not the sum of the transfer time of the signals in _a t _a and queuing delay _{d c} is greater than the required transfer time _{t r} (step S210). Normal path _{p k,} if the total exceeds the required transfer time _{t r} of the transfer time t _a and queuing delay _{d c} of the signal in _a (Step S210: YES), the deleting unit 45, as shown in FIG. 6 Then, the detour link k(l _k ) is deleted from the logical topology for extracting the selectable path p′ _i,j (step S211). The deletion unit 45 returns the process to step S205.

Normal path _{p k,} if the sum of the transfer time t _a and queuing delay _{d c} of the signal is less than required transfer time _{t r} at _a (Step S210: NO), the extraction unit 42, the number k of the detour link Increment (step S213). Whether or not the determination unit 44 determines whether or not the number k of the detour links exceeds the total number m of the detour links, whether or not the detour links are to be deleted from the logical topology information, for all the detour links. It is determined whether or not (step S214).

When it is determined whether or not it is the detour link to be deleted for all the detour links (step S214: YES), the registration unit 46 selects the detour path p′ _i,j that includes the detour links remaining without being deleted. It is determined as a feasible path (step S215). When there is a detour link for which it is not determined whether or not the detour link is to be deleted (step S214: NO), the detection unit 43 returns the process to step S208.

Transfer time _{t i,} if _j is requested transfer time _{t r} or (step S206: NO), the registration unit 46, information indicating that there is no selectable paths and registers in the storage unit 40 (step S212). The detection unit 43 increments the path number j (step S216). The determination unit 44 determines whether or not all the paths p _i,j are the selectable paths by determining whether or not the path number j exceeds the total number (n) of the paths. It is determined (step S217).

When there remains a path p _i,j for which it has not been determined whether or not it is a selectable path (step S217: NO), the creating unit 41, as shown in FIG. Is used to create logical topology information (step S218). When it is determined whether or not the path is a selectable path for all the paths p _i,j (step S217: YES), the path selection server 4 advances the process to step S102 in FIG. 7.

As described above, the radio base station 1 according to the first embodiment is a device (path selection device) that selects a path from a plurality of paths that connect a node at the start point to a node at the end point of a communication network having a plurality of nodes and links. Device). The wireless base station 1 includes a detection unit 43 and a selection unit 47. The detection unit 43 can select a path in which the transfer time of the bypassed signal and the transfer time of the non-routed signal are equal to or less than a predetermined transfer time even when the signal is transferred by bypassing the link in which the failure has occurred. Find the path. The selection unit 47 selects a predetermined path such as a fixed path when no failure occurs in the communication network, and selects a selectable path when a failure occurs in the communication network.

As a result, the radio base station 1 of the first embodiment can set the signal transfer time in the case where a failure occurs in the mobile fronthaul within the transfer time required when the failure does not occur. Become. That is, the radio base station 1 of the first embodiment can prevent the mobile traffic from being given a transfer delay exceeding the transfer delay required for normal traffic.

The radio base station 1 of the first embodiment can take countermeasures against failures without affecting traffic that is normally transferred. The radio base station 1 of the first embodiment can minimize the range affected by the delay even when a failure occurs in the mobile fronthaul.

(Second embodiment)
The second embodiment is different from the first embodiment in that when a failure occurs in a certain link, a failure also occurs in another link. In the second embodiment, only the differences from the first embodiment will be described.

When the second link also fails in the logical topology in which the first link has been deleted, the path selection server 4 applies the same processing to that in the first embodiment to the logical topology in which the first link and the second link have been deleted. By performing the above, the non-selectable path or the selectable path is determined in advance.

Thereby, the path selection server 4 of the second embodiment transfers the signal when the mobile fronthaul fails even when the second link fails when the first link fails. It is possible to make the time within the transfer time required when no failure occurs.

At least a part of the wireless base station, the path selection server, and the signal transfer device in the above-described embodiments may be realized by a computer. In that case, the program for realizing this function may be recorded in a computer-readable recording medium, and the program recorded in this recording medium may be read by a computer system and executed. The “computer system” mentioned here includes an OS and hardware such as peripheral devices. The "computer-readable recording medium" refers to a portable medium such as a flexible disk, a magneto-optical disk, a ROM, a CD-ROM, or a storage device such as a hard disk built in a computer system. Further, the "computer-readable recording medium" means that a program is dynamically held for a short time like a communication line when the program is transmitted through a network such as the Internet or a communication line such as a telephone line. In this case, a volatile memory inside the computer system that serves as a server or a client in that case may hold the program for a certain period of time. Further, the program may be for realizing a part of the functions described above, or may be a program that can realize the functions described above in combination with a program already recorded in a computer system, It may be realized by using a programmable logic device such as FPGA (Field Programmable Gate Array).

The embodiment of the present invention has been described in detail above with reference to the drawings, but the specific configuration is not limited to this embodiment, and includes a design etc. within the scope not departing from the gist of the present invention.

INDUSTRIAL APPLICABILITY The present invention is applicable to a server that selects a mobile fronthaul path.

1... Wireless base station, 2... BBU, 3... Optical device, 4... Path selection server, 5... Signal transfer device, 6... Optical device, 7... RRH, 8... Small cell, 40... Storage unit, 41... Creation unit , 42... Extraction unit, 43... Detection unit, 44... Judgment unit, 45... Deletion unit, 46... Registration unit, 50... Normal path, 51... Detour path

Claims (2)

A path selection device for selecting a path from a plurality of paths connecting from a start node to an end node of a communication network having a plurality of nodes and links,
Among the plurality of paths, each link included in a path that bypasses a link in which a failure has occurred is used as a bypass link, and a transfer time of a signal that has not been bypassed in a path including the bypass link and a signal in the node When the total of the transfer delay time due to the transfer of the transfer being in a waiting state exceeds a predetermined transfer time, a deletion unit that deletes the detour link from the logical topology information of the communication network,
Based on the logical topology information which the bypass link is deleted by the deletion unit, the even if a failure to transfer the signal to bypass the link has occurred, the signal and the bypassed so have no signal to bypass a detector for detecting a selectable path is a path that each transfer time is equal to or less than the predetermined transfer time,
A selection unit that selects a predetermined path when no failure has occurred, and selects the selectable path when a failure has occurred,
A path selection device comprising: A path selection method executed by a path selection device that selects a path from a plurality of paths connecting a node at a start point to a node at an end point of a communication network having a plurality of nodes and links,
Among the plurality of paths, each link included in a path that bypasses a link in which a failure has occurred is used as a bypass link, and a transfer time of a signal that has not been bypassed in a path including the bypass link and a signal in the node When the total of the transfer delay time due to the transfer of the transfer being in a waiting state exceeds a predetermined transfer time, a deletion step of deleting the detour link from the logical topology information of the communication network,
Based on the logical topology information which the bypass link is deleted by said deletion step, said even if a failure to transfer the signal to bypass the link has occurred, the signal and the bypassed so have no signal to bypass a detection step of detecting a selectable path is a path that each transfer time is equal to or less than the predetermined transfer time,
A selection step of selecting a predetermined path when no failure has occurred and selecting the selectable path when a failure has occurred.

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