JP2012244401A - Communication system, base station thereof and communication control method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a communication system with an improved fault resistance performance.SOLUTION: The communication system includes: a connection device that connects an interface between a terminal and a best-effort type communication network; a base station that spreads a radio zone to connect a mobile station located within the radio zone to the communication network; and a detour processing module that, when a trouble occurs on the interface, detours a communication path between the terminal and a communication partner to another route through the base station. The base station includes a release processing unit. When there is no available radio resource for detouring in the radio zone, the release processing unit forcibly releases a channel which is occupied by some mobile station located within the radio zone to ensure a detouring radio resource.

Description

  Embodiments described herein relate generally to a communication system using an IP (Internet Protocol) network, a base station thereof, and a communication control method.

In various forms of communication systems, a communication path is bypassed when a failure occurs. For example, the following method has been proposed in a system in the form of passing through an IP network in peer-to-peer communication between a calling side terminal and a called side terminal.
A PHS (Personal Handy-phone System) will be described as an example. That is, it has been proposed that when a failure occurs in an interface connecting one terminal to an IP network, the communication path to the other terminal is reconfigured using PHS radio resources. The failure can be detected by, for example, the absence of a response to the health check. In the above proposal, for example, it is considered that voice packets are encapsulated and transmitted by data communication based on PIAFS (Personal handy phone Internet Access Forum Standard). In this system, a device called a PHS wireless communication module has been proposed, and the communication system and protocol stack have been studied in detail.

JP 2001-333114 A

By the way, the radio resources of the PHS and the so-called cellular phone system are limited. For example, the current PHS has a maximum of 4 channels per base station. If all of these channels are used for other communications, the line is blocked, and a communication path passing through the wireless section cannot be set. As a result, a detour route cannot be formed and there is room for improvement in fault tolerance performance, and therefore, provision of a new technology is demanded.
An object is to provide a communication system, a base station, and a communication control method with improved fault tolerance performance.

  According to the embodiment, the communication system includes a connection device that connects an interface between a best-effort communication network and a terminal, and a base that expands a wireless zone and connects a mobile station in the wireless zone to the communication network. And a detour processing module for detouring a communication path between the terminal and the communication partner to a route via the base station when a failure occurs in the interface. The base station includes an opening processing unit. The release processing unit forcibly releases a channel occupied by one of the mobile stations in the radio zone if there is no available radio resource for the detour in the radio zone, and releases the radio resource for the detour. Secure.

1 is a system diagram showing an example of a communication system according to an embodiment. The figure which shows the principal part of the communication system shown by FIG. The functional block diagram which shows an example of the base stations 41-48. The sequence diagram which shows an example of the process sequence at the time of the failure generation in the communication system concerning embodiment. The figure which shows the state in which there is no empty channel in the radio | wireless resource of the base station 41 when a line failure arises in the IP line L1. The figure which shows the state by which one channel was open | released from the state shown by FIG. The sequence diagram which shows an example of the process sequence at the time of the failure recovery in the communication system concerning embodiment. The figure which shows that the allocation state of the communication resource of the base station 41 changes in the detouring process. The figure which shows an example of the normal route and detour route in the system shown by FIG.

FIG. 1 is a system diagram illustrating an example of a communication system according to an embodiment. The IP network 5 in FIG. 1 is a best-effort communication network that transmits IP packets, and the type of the data link layer that is Layer 2 and the type of the physical layer that is Layer 1 are not limited.
The IP exchanges 11 and 12 and the connection device 2 are connected to the IP network 5 through the IP line L1, respectively. The IP exchanges 11 and 12 and the connection device 2 are also connected to an ISDN (Integrated Services Digital Network) line L2. The IP exchanges 11 and 12 and the connection device 2 interconnect the ISDN line L2 and the IP line L1. Among these, the connection device 2 further includes a wireless module 21. That is, the connection device 2 connects an interface between the IP network 5 and the packet terminal 33. This interface includes a terminal adapter T3.

  The wireless module 21 has a function for wirelessly connecting to the base station 41. The wireless module 21 has a function of diverting traffic related to the packet terminal 33 to the IP switch 11 via the base station 41 when a failure occurs in the interface to the IP network 5. That is, when a failure occurs in the interface between the packet terminal 33 and the IP network 5, the wireless module 21 changes the communication path between the packet terminal 33 and its communication partner (for example, the packet terminal 32) to the base station 41. Detour to the route that goes through.

  The base station 41 is connected to the IP exchange 11 via the ISDN line L2 or the IP line L1. The base station wirelessly connects to a PHS terminal (hereinafter referred to as a mobile station) 71. Terminal adapters (TA) T1, T2, T3 terminate the ISDN line L2. The packet terminals 31, 32, and 33 are provided with a packet calling function and a packet receiving function, thereby enabling mutual packet transmission / reception between the packet terminals. Each packet terminal is connected to the network via a TA. The PIAFS termination device 6 is connected to the IP network 5 and terminates PIAFS (PHS Internet Access Forum Standard). That is, in the system shown in FIG. 1, communication by a PHS terminal and data communication by a packet terminal are mixed.

  FIG. 2 is a diagram showing a main part of the communication system shown in FIG. In FIG. 2, base stations 41, 42, 47, 48 are connected to the IP switch 11, and base stations 43, 44, 45, 46 are connected to the IP switch 12. The IP exchanges 11 and 12 communicate via the IP network 5. The packet terminals 31 and 32 communicate binary data and the like via the terminal adapter T1, the IP exchange 11, the IP network 5, the IP exchange 12, and the terminal adapter T2.

  The mobile station 74 is connected to the IP exchange 12 via the base station 44. The mobile station 73 is connected to the IP exchange 12 via the base station 43. The packet terminals 31 and 33 communicate binary data and the like via the terminal adapter T3, the connection device 2, the IP network 5, the IP exchange 12, and the terminal adapter T2. The mobile stations 71, 72 and 75 are connected to the IP exchange 11 via the base station 41. The mobile stations 71 to 75 can perform data communication using, for example, PIAFS in addition to voice communication.

  FIG. 3 is a functional block diagram illustrating an example of the base station 41 illustrated in FIGS. 1 and 2. The same applies to the base stations 42 to 48. In FIG. 3, the base station 41 includes an antenna ANT, a radio unit (RF) 102, a communication control unit 103, a data exchange unit 104, a network interface unit 105, and a control unit 106.

  The radio unit 102 radiates a gigahertz band radio wave from the antenna ANT to develop a radio zone, and exchanges radio signals with mobile stations located in the radio zone. As a result, the mobile station is connected to the IP network 5 via the base station 41 and the IP exchange 11. The communication control unit 103 performs signal processing and control related to wireless communication such as modulation and demodulation of communication data. The data exchange unit 104 multiplexes transmission data to a plurality of transmission channels, separates received data received through a plurality of reception channels, and the like. The network interface unit 105 performs interface processing for transmitting transmission / reception data to / from the IP exchange 11. The control unit 106 comprehensively controls communication signal processing by the communication control unit 103, data demultiplexing processing in the data exchange unit 104, and interface processing in the network interface unit 105.

The control unit 106 includes a release processing unit 106a and a reconnection processing unit 106b as processing functions according to this embodiment.
If there is no available radio resource for forming a detour route led by the radio module 21 in the radio zone deployed by the release processing unit 106a, the release processing unit 106a selects a channel occupied by any mobile station in the radio zone. Force open. This secures radio resources for detouring.

  In particular, the release processing unit 106a releases at least one of the plurality of channels if the plurality of channels are occupied by the same mobile station. Also, the release processing unit 106a preferentially releases channels in order from channels occupied by mobile stations with a large number of occupied channels (during high-speed data communication or the like).

  The reconnection processing unit 106b converts the channel used by the release processing unit 106a and used to form the detour route according to switching back from the detour route of the communication path to the normal route, to any mobile station in the radio zone. Reassign to The reassignment target may be the occupying mobile station that occupied the channel before detouring, or may be another mobile station. For example, an empty channel may be assigned to a device having the smallest number of channels in use. Alternatively, an empty channel may be preferentially assigned to a device that requests data communication, and the priority of assignment to a device that performs voice communication may be lowered. Next, the operation in the above configuration will be described.

  FIG. 4 is a sequence diagram illustrating an example of a processing procedure when a failure occurs in the communication system according to the embodiment. For example, when a line failure of the IP line L1 is detected in the connection device 2 (step S1), the occurrence of the failure is notified to the wireless module 21 (step S2). Then, the wireless module 21 notifies the detour request message to the base station 41 (step S3). Upon receiving this message, the base station 41 determines whether there is a free radio resource for forming a bypass route, that is, whether there is a free channel (step S4). If there is a free resource, a detour process is executed (step S5).

  If there is no free resource, the base station 41 performs channel release control (step S6). That is, the base station 41 transmits a channel release request message to the mobile station 71 (FIG. 2) that occupies two channels (step S7). Receiving this, the mobile station 71 releases at least one channel in use, and returns a channel release notification message describing the channel ID (identifier) of the released channel to the base station 41 (step S8).

  Next, the base station 41 notifies the wireless module 21 of an allocated channel notification message including the channel ID of the released channel (step S9). In response, a wireless connection process for connecting to the wireless module 21 and the base station 41 is executed between the wireless module 21 and the base station 41 (step S10). When this procedure is completed, a process for bypassing the communication path of the packet terminal 33 to the route via the base station 41 (a bypass process) is executed between the connection device 2 and the base station 41 (step S11). . When the detouring is completed, it may be notified to the packet terminal 33 (step S12).

  FIG. 5 is a diagram illustrating a state where there is no empty channel in the radio resource of the base station 41 when a line failure occurs in the IP line L1. For example, it is assumed that the mobile station 71 occupies two channels in a bundle for high-speed data communication, and the remaining channels are also occupied by any of the mobile stations, and there is no empty channel in the wireless zone developed by the base station 41. . Further, it is assumed that the packet terminal 33 is communicating with the packet terminal 32 via the IP network 5.

  If a failure occurs in the IP line L1 from this state, the wireless module 21 immediately tries to form a detour route via the base station 41, but there is no wireless resource available at this time. In addition, there is no room for wired resources such as the ISDN B channel between the base station 41 and the IP exchange 11, for example. Therefore, in the embodiment, one of the two channels occupied by the mobile station 71 is forcibly released.

  FIG. 6 is a diagram showing a state where one channel is released from the state shown in FIG. As shown in FIG. 6, in the embodiment, priority is given to communication between the packet terminals 33 and 32, and one of the channels in use by the mobile station 71 is released. As a result, the communication speed of the mobile station 71 becomes lower than before, but communication between the packet terminals 33 and 32 can be continued. Thereby, the availability of communication between important terminals (here, packet terminals 33 and 32) can be improved. In the embodiment, for example, data communication is more important than voice communication, and a terminal performing data communication may be regarded as an important terminal. Alternatively, it may be important to enable more terminals to communicate than the communication speed.

  In the embodiment, as a channel to be opened when a detour route is formed, for example, a policy of selecting a channel having the largest number allocated to the same allocation destination is adopted. If the number of channels in use at each allocation destination is the same, for example, the channel with the lowest channel number is released.

  FIG. 7 is a sequence diagram illustrating an example of a processing procedure at the time of failure recovery in the communication system according to the embodiment. In FIG. 7, for example, when failure recovery of the IP line L1 is detected by the connection device 2 (step S21), the connection device 2 notifies the wireless module 21 of a recovery notification message (step S22). In response to this, the radio module 21 notifies the base station 41 of a channel disconnection request message for disconnecting the channel assigned to itself in step S9 of FIG. 4 (step S24). Then, the base station 41 executes channel disconnection control for disconnecting the channel (step S25), and notifies the mobile station 71 of a reconnection request message for reconnecting to the mobile station 71 using this channel (step S26). . In response to this, a reconnection process for returning to the state of FIG. 2 is executed between the mobile station 71 and the base station 41 (step S27).

  In parallel with the above procedure, a switchback process is executed under the control of the connection device 2 (step S23). The switch-back process is a process for returning the route of the communication path that has been switched from the normal route to the detour route by the detour processing to the normal route along with the failure recovery. When the procedure of FIG. 7 is completed, the state shown in FIG. 2 is realized again.

FIG. 8 is a diagram illustrating that the communication resource allocation state of the base station 41 changes during the detour processing. The table shown in FIG. 8 is managed by, for example, the base station 41 related to route switching / switchback.
In a state where there is no failure in the system and before detouring, as shown in FIG. 8A, channels 1 to 4 in the radio zone of the base station 41 are assigned to mobile stations 71, 71, 72 and 75, respectively. Suppose that When a failure occurs in the IP line L1 from this state and the route is detoured, as shown in FIG. 8B, the channels 1 to 4 of the base station 41 are respectively connected to the radio module 21, the mobile station 71, 72, 75. Thereafter, when the IP line failure is recovered, the state before the detour is reproduced, and the channels 1 to 4 are assigned to the mobile stations 71, 71, 72, and 75, respectively, as shown in FIG. 8C.

  In addition, since the wireless module 21 does not use the channel 1 after the IP line failure recovery, the allocation of the channel 1 is reproduced as shown in FIG. 8C. In addition, in the base station 41, the mobile station 71, In this case, in addition to the method of selecting a channel to be forcibly released, it may be additionally allocated to the same allocation destination with the smallest number of channel specifications. When the number of channels in use at each assignment destination is the same, the assignment is made to the assignment destination using the re-number channel number. In this case, the allocation status of each channel allocated to the mobile station 71 and held in the base station 1 is the same as the status before detouring.

  FIG. 9 is a diagram showing an example of a normal route and a detour route in the system shown in FIG. Peer-to-peer communication between the packet terminals 33 and 32 is usually realized using a communication path of a route that passes through the packet terminal 33, the terminal adapter T 3, the connection device 2, and the IP network 5. When a line failure occurs from this state, a detour route is prepared via the packet terminal 33, the terminal adapter T3, the connection device 2, the wireless module 21, the base station 41, the IP switch 11 and the IP network 5, and the above route is provided on this route. A communication path for peer-to-peer communication is set.

  As described above, in this embodiment, when a failure occurs in the communication path between the packet terminals 33 and 32, the communication path is bypassed to the route passing through the base station 41. At that time, if all the resources in the wireless zone are occupied by a mobile station or the like in the wireless zone of the base station 41, any channel is forcibly released. A route that passes through the wireless module 21 and the base station 41 is prepared using the opened channel, and the communication path is reset along this route. Since it did in this way, it becomes possible to provide the communication system which improved fault tolerance performance, its base station, and the communication control method.

  In addition, although PHS was assumed in the said embodiment, it is possible to apply the said embodiment not only to this but the cellular phone system whole. In addition, the present embodiment is not limited to the current PHS, and the above-described embodiment can be applied to a next-generation PHS having more wireless communication channels.

  Although an embodiment of the present invention has been described, this embodiment is presented as an example and is not intended to limit the scope of the invention. The novel embodiment can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. This embodiment and its modifications are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

  DESCRIPTION OF SYMBOLS 5 ... IP network, L1 ... IP line, 11, 12 ... IP exchange, 2 ... Connection apparatus, L2 ... ISDN line, 21 ... Wireless module, 41-48 ... Base station, T1, T2, T3 ... Terminal adapter (TA) 31 to 33: Packet terminal, 6: PIAFS terminator, 71 to 75: Mobile station, ANT ... Antenna, 102 ... Radio unit (RF), 103 ... Communication control unit, 104 ... Data exchange unit, 105 ... Network interface unit 106 ... Control unit 106a ... Opening processing unit 106b ... Reconnection processing unit

Claims (12)

A connection device for connecting an interface between a best-effort communication network and a terminal;
A base station that expands a radio zone and connects a mobile station in the radio zone to the communication network; and
When a failure occurs in the interface, a detour processing module for detouring a communication path between the terminal and its communication partner to a route via the base station,
The base station
If there is no available radio resource for the detour in the radio zone, the channel occupied by any mobile station in the radio zone is forcibly released to secure the radio resource for the detour A communication system comprising an opening processing unit.   The communication system according to claim 1, wherein the release processing unit releases at least one of the plurality of channels if the plurality of channels are occupied by the same mobile station.   The communication system according to claim 2, wherein the release processing unit preferentially releases a channel occupied by a mobile station having a large number of occupied channels.   The base station further includes a reconnection processing unit that reallocates the released channel to a mobile station that has occupied the channel in response to switching back of the communication path in response to recovery of the failure. The communication system according to any one of 1 to 3. A connection device that connects an interface between a best-effort communication network and a terminal, and if a failure occurs in the interface, a communication path between the terminal and a communication partner is diverted to a route via a wireless zone In a base station provided in a communication system comprising a bypass processing module,
Means for expanding the radio zone and connecting a mobile station in the radio zone to the communication network;
If there is no available radio resource for the detour in the radio zone, the channel occupied by any mobile station in the radio zone is forcibly released to secure the radio resource for the detour A base station comprising an open processing unit.   The base station according to claim 5, wherein the release processing unit releases at least one of the plurality of channels if the plurality of channels are occupied by the same mobile station.   The base station according to claim 6, wherein the release processing unit preferentially releases a channel occupied by a mobile station having a large number of occupied channels.   The reconnection processing unit according to any one of claims 5 to 7, further comprising a reconnection processing unit that reallocates the released channel to a mobile station that has occupied the channel in response to switching back of the communication path in response to recovery of the failure. The base station according to claim 1. A connection device that connects an interface between a best-effort communication network and a terminal, a base station that expands a wireless zone and connects a mobile station in the wireless zone to the communication network, and a failure occurs in the interface And a communication control method used in a communication system comprising a detour processing module for detouring a communication path between the terminal and the communication partner to a route passing through the base station,
If there is no available radio resource for the detour in the radio zone, the base station forcibly releases a channel occupied by any mobile station in the radio zone, and A communication control method for securing radio resources.   10. The communication control method according to claim 9, wherein the releasing includes releasing at least one of the plurality of channels if a plurality of channels are occupied by the same mobile station.   The communication control method according to claim 10, wherein the releasing preferentially releases a channel occupied by a mobile station having a large number of occupied channels.   The base station according to any one of claims 9 to 11, wherein the base station reassigns the released channel to a mobile station that has occupied the channel in response to switching back of the communication path in response to recovery of the failure. The communication control method according to item 1.

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