JP6548225B2 - Wireless communication system and communication method thereof - Google Patents

Description

  The present invention relates to a wireless communication system.

  Mobile communication has rapidly spread in recent years, and a standard cellular radio communication system developed by the Third Generation Partnership Project (3GPP) called 3G or Long Term Evolution (LTE) is widely used. The mobile communication service provided by the cellular wireless communication system is generally operated in a license band, and a licensed carrier using a frequency performs the mobile communication service using the frequency band. On the other hand, in the frequency band of wireless communication, a frequency band called an unlicensed band is prepared. Although the frequency band of the unlicensed band needs to meet the criteria for the device, it is characterized by a frequency band that can be used by anyone. For example, in an unlicensed band of 2.4 GHz band or 5 GHz band, a wireless LAN or the like of the IEEE 802.11 standard is widely used.

  Mobile communication traffic continues to increase rapidly due to the spread of smartphones and the like, and in the future there may be a shortage of frequencies only in license bands to which mobile operators are assigned. For this reason, in mobile communication, a method of operating LTE even in an unlicensed band is being studied. For example, LAA (Licensed Assisted Access) (prior art document 1) studied in 3GPP is an example. LAA is a technology that simultaneously uses a license band and an unlicensed band of 5 GHz band between UE (terminal, User Equipment) and base station (eNodeB), assuming that there is a communication path in the license band. It is a technology that uses the unlicensed band for downlink communication by LTE in an added form. Based on this technology, a technology called MulteFire has been proposed by MulteFire Alliance (http://www.multefire.org/), and it will be a technology that enables unlicensed bands to perform LTE service alone. It is. While LAA requires integrated use with a licensed band, MulteFire can be used as an unlicensed band alone, and can be used not only in the downstream direction but in both the upstream and downstream directions. Therefore, for example, there is a merit that a telecommunications carrier without a license of a license band can provide a mobile communication service conforming to LTE, and the future practical use is expected.

  MulteFire can provide mobile communication in the unlicensed band, and anyone can realize mobile communication if they prepare the equipment. However, since MulteFire basically conforms to the LTE standard and is used in an unlicensed band, a device on the network side of MulteFire requires a mobile core network device in addition to a base station. In LTE, these devices are called EPC (Enhanced Packet Core) (prior art document 2). The EPC is composed of a plurality of function groups, and provides functions such as UE authentication, mobility management, and policy control. As a component of the EPC, a Home Subscriber Server (HSS) stores subscriber information for authenticating an LTE UE. MME (Mobility Management Entity) controls mobility management of the UE. The S-GW (Serving Gateway) and the P-GW (PDN Gateway) operate in cooperation to perform the function of handover of traffic when the UE moves. The PCRF (Policy and Charging Rules Function) provides a function of policy control such as QoS.

  Since the base station of MulteFire operates on the premise that the EPC function exists as a core network, it is necessary to prepare an EPC for use. Therefore, it can not operate as a base station alone like, for example, a wireless LAN. EPC is premised on providing LTE mobile services on a relatively large scale, and cost becomes an issue to prepare the equipment. Also, EPC is basically supposed to be used in a single operator network, provides functions such as mobility management of UE in the operator's network, and the access to the Internet is P -Take the configuration aggregated in the GW. However, as a use case for MulteFire, it can be considered that it can be installed freely using various network circuits, taking advantage of the free installation. When providing a mobile service in such a use case, it is conceivable to deploy the EPC function on a cloud server on the Internet and accommodate a base station connected to any line.

3GPP, TR 36.889 V13.0.0 (2015-06), Technical Specification Group Radio Access Network; Study on Licensed-Assisted Access to Unlicensed Spectrum (Release 13) 3GPP, TS 23.401 V13.6.1 (2016-03), Technical Specification Group Services and System Aspects; General Packet Radio Service (GPRS) enhancements for Evolved Universal Terrestrial Radio Access Network (E-UTRAN) access (Release 13)

  When the EPC function is deployed on the cloud, the P-GW of the EPC serves as an anchor point for user data, and communication traffic is aggregated, causing bottlenecks such as congestion, and accessing the Internet via the anchor point. There is a problem that the delay also increases. On the other hand, it is conceivable to deploy and distribute the P-GW function on the base station side, but in this case, in LTE, the movement of the UE is managed with the P-GW as the anchor point to realize handover. There is a problem that the distributed P-GW can not perform handover.

  As described above, it is conceivable to deploy the EPC on the cloud server when deploying on the network an EPC that is connected to various networks and accommodates the base station of MulteFire freely installed by the user. In EPC, traffic concentration may cause a bottleneck, and there is a problem that EPC becomes expensive. On the other hand, it is conceivable to deploy and distribute the P-GW function on the base station side, but in this case, in LTE, the movement of the UE is managed with the P-GW as the anchor point to realize handover. There is a problem that the distributed P-GW can not perform handover.

  In order to achieve the above object, the present invention is a radio communication system comprising a radio base station having a radio access function unit forming a radio access section and a core network accommodating a plurality of radio base stations, Among the functional units that form a core network, a gateway functional unit that transmits user data and has a function of connecting to an external network including the Internet is deployed in the wireless base station, and control is performed among the functional units that form the core network. At least a part of a control plane function unit related to a plane is deployed on the Internet, and the wireless base station performs handover with a handover determination unit that determines whether a user terminal belonging to itself is to be handed over to another wireless base station In the case of own gateway function and handover destination Characterized in that it comprises a bearer setting unit for setting a bearer between the gateway function of the other radio base station.

  According to the present invention, deployment of core network functions on the network side when providing a mobile communication service by a wireless base station can be realized easily and at low cost, and without decentralizing traffic in the core network, autonomous distributed It is possible to provide the function of mobility management. Further, in the present invention, there is no need to change the function to the user terminal, and the function can be provided by the network side device.

A diagram showing a topology of a wireless communication system according to the present invention Diagram showing LTE topology Configuration of wireless base station according to one embodiment of the present invention A configuration diagram of a P-GW function unit of a wireless base station according to an embodiment of the present invention Configuration diagram of S-GW function unit of the radio base station according to one embodiment of the present invention Diagram of MME according to one embodiment of the present invention Diagram of HSS according to one embodiment of the present invention An example of management information of P-GW management DB belonging to UE in HSS according to an embodiment of the present invention Example of management information of inter-radio base station connection management DB in HSS according to one embodiment of the present invention Diagram showing traffic flow during handover Diagram showing traffic flow during handover of multiple terminals Diagram showing traffic flow during multiple handovers Diagram explaining formation of autonomous inter-base station connection Sequence diagram explaining the standard handover procedure in LTE A sequence diagram (1/2) explaining a handover procedure in an embodiment of the present invention A sequence diagram (2/2) explaining the handover procedure in one form of the present invention Flow chart for explaining execution decision processing of handover in one embodiment of the present invention Flowchart illustrating bearer release processing in an embodiment of the present invention Flow chart for explaining opening process of encrypted communication path in one embodiment of the present invention

  A wireless communication system according to an embodiment of the present invention will be described with reference to the drawings. The radio communication system according to the present embodiment is a radio communication system similar to LTE or the like, and deploys (HSS, MME, PCRF) which is a processing function of C-Plane (Control Plane) of EPC on a cloud server. In addition, the U-Plane (User Plane) function of the EPC S-GW / P-GW is deployed in the base station.

  FIG. 1 shows the topology of a wireless communication system according to the present invention. Each wireless base station 100 in FIG. 1 is a function deployment in which the function of the eNodeB, which is a base station of the LTE standard, and the P-GW and S-GW are integrated. In the present invention, by deploying the P-GW and S-GW functions in each base station 100, one base station 100 has a function equivalent to one P-GW and S-GW. All the base stations 100 connect to the EPC 200 installed on the cloud server of the Internet 300, and transmit and receive C-Plane signals. It is a feature that all the base stations 100 have a P-GW, resulting in a multi-P-GW configuration as a whole. Here, the functional units of the EPC 200 deployed in the cloud server, ie, deployed on the Internet 300, include at least the MME 210 and the HSS 220.

  On the other hand, FIG. 2 shows the topology of a standard LTE system for comparison. Basically, in the LTE standard, one P-GW is provided for a connection point to a packet data network (PDN), so the P-GW provides a path for access to the Internet to a mobile network under its control. Therefore, it is common for P-GW to be deployed in a very small number of places, such as one place, for one managed mobile network.

  FIG. 3 shows a functional configuration diagram of the radio base station in the present embodiment. The radio base station 100 includes a P-GW function unit 121 corresponding to the P-GW function of LTE and an S-GW function unit 122 corresponding to the S-GW function, and also corresponds to a standard LTE eNodeB function. The eNodeB function unit 110 is provided. Furthermore, the wireless base station 100 includes an encrypted path setting function unit 130.

  The functional block diagram of the P-GW function part of a wireless base station is shown in FIG. As shown in FIG. 4, the P-GW function unit 121 includes an inter-base station bearer setting function unit 121-2 in addition to the standard P-GW function unit 121-1 of LTE.

  FIG. 5 shows a functional block diagram of the S-GW function unit of the wireless base station. As shown in FIG. 5, the S-GW function unit 122 includes an inter-base station bearer setting function unit 122-2 in addition to the standard S-GW function unit 122-1 of LTE.

  FIG. 6 shows a functional configuration of MME in the present technology. The MME 210 includes, in addition to the standard MME functional unit 211 of LTE, a P-GW management unit 212 to which the UE belongs, a base station connection implementation determination unit 213, and an inter-base station connection management unit 214.

  Fig. 7 shows the functional configuration of the HSS. The HSS 220 according to the present invention includes, in addition to the functional section 221 of the LTE standard HSS, a P-GW management DB (Data Base) 222 to which the UE belongs, and an inter-radio base station connection management DB 223.

  FIG. 8 shows a configuration example of the belonging destination P-GW management DB of the UE. As shown in FIG. 6, the UE has a base station ID for identifying the radio base station 100 to which it is affiliated, and a base station ID for identifying the radio base station 100 for which bearer configuration has been set from the radio base station 100 to which it belongs. The current assignee is managed in the database by the IP address of the bearer setting destination base station.

  FIG. 9 shows an example of management information in the radio base station connection management DB. As shown in FIG. 9, the radio base station 100 is managed by a database that manages the setting status of encrypted paths with other base stations 100.

  The flow of handover traffic in the present invention will be described in several patterns in FIGS. FIG. 10 shows an example in which one UE 10 performs a handover. In the following description, in order to distinguish a plurality of radio base stations and their functional units, subscripts "a" and "b" etc. are added after the reference numerals.

  Under the radio base station 100a connected before the handover, the UE 10 uses the IP address assigned from the P-GW function unit 121a of the radio base station 100a, and accesses the Internet 300 via the P-GW function unit 121a. Do. After the handover, using the encrypted communication path set between the base station 100a and the base station 100b that performs the handover, the wireless base station before the handover from the S-GW function unit 122b of the wireless base station 100b after the handover A tunneling connection is formed in the P-GW functional unit 121a of 100a, and Internet access is performed via the base station 100a before handover.

  Here, the tunneling connection is a tunneling protocol such as GTP (GPRS Tunneling Protocol) used between the S-GW and the P-GW in normal LTE, and the IP packet is encapsulated with a header using a specific identifier. Transmission technology. The communication path formed by these tunneling connections is also called a bearer. Further, the encrypted communication path between the wireless base stations is assumed to be an Internet VPN function by the function such as IPsec, Point to Point Tunneling Protocol (PPTP), Secure Socket Layer (SSL) technology, or the like.

  FIG. 11 shows an example of a plurality of UEs 10. Since the handover source base station 100 may be different for each UE 10, the handover source base station 100 is independently managed for each UE 10, and encrypted communication paths and bearers are set. Also, the newly connected UE 10c that is not a handover accesses the Internet 300 via the P-GW function unit 121b of the radio base station 100b connected according to the normal procedure.

  FIG. 12 shows an example of handover in a plurality of stages. Even in multiple stages, that is, even if the handover is repeated multiple times, the encrypted communication path and bearer are set up to the first base station 100a which has started the handover, and the P-GW function of the first wireless base station 100a The Internet 300 is accessed via the unit 121a.

  FIG. 13 shows an example of autonomous formation of encrypted communication paths and bearers between base stations 100 in the present invention. When there is an area where a plurality of connectable base stations 100a and 100b are simultaneously visible from the moving UE 10, a handover is required based on the radio wave observation status by the UE 10, so encryption between the base station 100a and base station 100b A standardized communication path is formed, and a bearer for carrying traffic is set up between the P-GW and S-GW of both base stations in response to a request for handover. An encrypted communication path and a bearer between the base stations are not formed between the base station 100c where such overlapping area of the service area of the base station does not occur. The formation of these connections is determined autonomously depending on whether or not the base station 100 needs to be handed over based on the radio wave observation status by the UE 10.

  In the above system configuration, the UE 10 attaches to and connects to the base station 100 as in a normal LTE system, sets a bearer for communication in the S / P-GW and eNodeB functions, and performs communication to the Internet 300. The IP address of the UE 10 at this time is assigned by the P-GW function unit 121. The UE 10 periodically performs a channel scan of the radio base station 100 for handover, and reports information such as received power of radio waves left from other base stations 100 discovered to the base station 100. Based on this report, the eNodeB functional unit 110 determines whether the UE 10 should perform handover and starts a handover procedure.

  Here, as a comparison object, FIG. 14 shows a handover procedure in the normal LTE standard. This is a scheme called S1 handover in LTE. As shown in FIG. 14, the base station 1a that has decided to carry out the handover transmits a handover request to the MME 2, and the MME 2 notifies the target base station 1b of the handover destination that the handover will be performed, and obtains approval. Take the procedure. After that, the actual handover proceeds in cooperation with the S-GW 3b, eNodeB 1b, and UE 10, performs position registration operation of the terminal called Tracking Update, and cancels the bearer setting of the eNodeB 1a and S-GW 3a of the handover source. Is complete.

  On the other hand, the procedure of the handover in the present embodiment is shown in FIG. 15 and FIG. In this embodiment, basically, the standard procedure shown in FIG. 14 is followed, but after eNodeB 110a determines execution of handover ((A) in FIG. 15), MME 210 notifies MME 210 of the start of handover and MME 210 executes handover. The difference is that the judgment is made.

  The determination of the base station is performed by the inter-base station connection implementation determination unit 213 of the MME 210 to determine whether an encrypted communication path is formed between the two base stations 100a and 100b with which the UE 10 is to perform handover. If it is not formed, the formation of the encrypted communication path is executed to determine the connection. The flow of this process is shown in FIG.

  If it is determined that the encrypted communication path is available, handover processing is performed. At this time, the MME 210 transmits the P-source of the handover source to the S-GW function unit 122b of the base station 100b of the handover destination and the P-GW function unit 121a of the base station 100a of the handover source -Instructs setting of a bearer to the GW function unit 121a ((B) in FIG. 15). In this instruction, it is necessary to notify the handover destination S-GW function unit 122b of the information for tunneling connection to the P-GW function unit 121a of the handover source, so the MME 210 controls the inter-base station connection management unit 214 The connection destination information of the P-GW function unit 121a of the radio base station 100a of the handover source is notified with reference to the belonging destination P-GW management DB 222 of the UE stored in the HSS 220. Also, the MME 210 notifies the P-GW function unit 121 a of the handover source of connection source information of the S-GW function unit 122 b of the handover destination wireless base station 100 b. The connection destination information and the connection source information are, for example, IP addresses. After bearer setting, data transfer from the handover source base station 100a to the handover destination base station 100b is started.

  The UE 10 performs the Tracking Area Update procedure as usual. At this time, in MME 210, together with the eNodeB information of the handover destination of UE 10, the information of base station 100a of the handover source having the P-GW function setting the bearer is grasped by P-GW management section 212 to which the UE belongs. , And stored in the P-GW management DB 222 to which the UE of the HSS 220 belongs.

  In this way, the mobility function is realized by the UE 10 autonomously forming the encrypted communication path and bearer on the network side of the handover between the base stations as needed.

  When the handover is performed as described above, although the continuity of communication can be realized, since the communication is performed via the P-GW of a distant wireless base station, there is a problem that the delay increases. Therefore, as a feature of the present invention, when there is no use of the bearer set for the handover for a certain period of time, the bearer is released and the base station performs detach processing on the UE to promote reconnection. The flow is shown in FIG.

  Further, the connection of the encrypted communication path between the base stations formed for the handover operation is characterized in that the connection is released when there is no use for a fixed time. This prevents an increase in unused encrypted communication paths. The flow is shown in FIG.

  As mentioned above, although one embodiment of the present invention was explained in full detail, the present invention is not limited to this. For example, although the MME 210 and the HSS 220 are deployed in the cloud server in the above embodiment, the deployment mode is not questioned if installed in the Internet 300.

  In the above embodiment, the P-GW function unit 121 and the S-GW function unit 122 are individually implemented in the wireless base station 100, but both function units are integrated as one P / S-GW function unit. It may be implemented in

  In the above embodiment, the bearer (tunneling connection) to be set from the S-GW function unit 122 at the handover destination to the P-GW function unit 121 at the handover source is the handover source wireless base station 100 and the handover destination wireless base For example, in the case where both functional units 121 and 122 can directly communicate, for example, when both functional units 121 and 122 are in an internet-reachable environment, they are formed on the encrypted communication path formed in station 100. A direct bearer may be set up between both functional units 121 and 122 without forming an encrypted communication path between base stations. In this case, in the process of “determination of handover permission” shown in (A) of FIG. 15 and FIG. 17, the process of confirming the presence or absence of the encrypted communication path and the process of forming the encrypted communication path become unnecessary.

  Moreover, although the LTE base station of the unlicensed band like MulteFire was explained in full detail in the said embodiment, this invention can be implemented also with the wireless base station which uses a license band.

100 ... radio base station 110 ... eNodeB functional unit 121 ... P-GW functional unit 121-1 ... standard P-GW functional unit 121-2 ... inter-base station bearer setting functional unit 122 ... S-GW functional unit 122-1 ... standard S-GW function unit 122-2 ... Inter-base station bearer setting function unit 130 ... Encrypted route setting function unit 200 ... EPC
210 ... MME
211 Standard MME function unit 212 Assigned destination P-GW management unit of UE 213 Inter-base station connection execution judgment unit 214 Inter-base station connection management unit 220 HSS
221 ··· Standard HSS function unit 222 ··· Target UE P-GW management DB
223 ... Radio base station connection management DB
300 ... Internet

Claims (7)

A wireless communication system comprising: a wireless base station having a wireless access function unit forming a wireless access section; and a core network accommodating a plurality of wireless base stations,
Among the functional units forming the core network, a gateway functional unit that transmits user data and has a function of connecting to an external network including the Internet is provided in the wireless base station,
Among the functional units forming the core network, at least a part of the control plane functional unit related to the control plane is deployed on the Internet,
The wireless base station is a handover determination unit that determines whether a user terminal belonging to itself is to be handed over to another wireless base station, and in the case of handover, a gateway function unit of its own and another wireless base station of a handover destination And a bearer setting unit configured to set a bearer between the gateway function unit and the wireless communication system. The wireless base station includes an encrypted communication path setting function unit that forms an encrypted communication path via the Internet between the wireless base station of its own and another wireless base station of the handover destination when performing handover.
The wireless communication system according to claim 1, wherein the bearer setting unit sets a bearer on the encrypted communication path formed by the encrypted communication path setting function unit. 3. The wireless communication system according to claim 2, wherein the encrypted communication path setting function unit opens the encrypted communication path when the encrypted communication path is not used for a predetermined time. The bearer setting unit releases the bearer when the bearer set for the handover is not used for a fixed time, and instructs the radio access function unit to perform the detach process with the user terminal. The wireless communication system according to any one of claims 1 to 3, characterized in that: The wireless communication system according to any one of claims 1 to 4, wherein each functional unit in the wireless communication system has a function and an interface defined by LTE (Long Term Evolution). The wireless access function unit has an eNodeB function and an interface for providing a wireless access function,
The gateway function unit has at least the functions and interface of Serving-Gateway and PDN (Packet Data Network) -Gateway,
The control plane function unit deployed on the Internet has at least functions and interfaces of MME (Mobility Management Entity) and functions and interface of Home Subscriber Server (HSS),
The radio communication according to claim 5, characterized in that the bearer for the handover is formed between the functional unit of the Serving-Gateway of the radio base station of the handover destination and the PDN-Gateway of the radio base station of the handover source. system. A communication method in a wireless communication system comprising: a wireless base station having a wireless access function unit forming a wireless access section; and a core network accommodating a plurality of wireless base stations,
Among the functional units forming the core network, a gateway functional unit that transmits user data and has a function of connecting to an external network including the Internet is provided in the wireless base station,
Among the functional units forming the core network, at least a part of the control plane functional unit related to the control plane is deployed on the Internet,
The wireless base station determines whether the user terminal belonging to itself is to be handed over to another wireless base station, and in the case of handover, the gateway function unit of its own and the gateway function unit of another wireless base station of handover destination. A communication method in a wireless communication system, comprising setting up a bearer via an encrypted communication path between

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