WO2013145519A1

WO2013145519A1 - Apparatus and methods for managing resource among multiple communication devices

Info

Publication number: WO2013145519A1
Application number: PCT/JP2013/000483
Authority: WO
Inventors: Yan Steven ZHANG; Chan Wah Ng
Original assignee: Panasonic Corporation
Priority date: 2012-03-30
Filing date: 2013-01-30
Publication date: 2013-10-03

Abstract

A communication control method for use in communication performed through a network between a plurality of mobile terminals and a communication device, which is a communication partner of the plurality of mobile terminals, the method comprising:- generating, when a mobile terminal performing the communication through the network among the plurality of mobile terminals releases a dedicated bearer, by the mobile terminal, a message for releasing the bearer and requesting to transfer the bearer to be released to a mobile terminal for which bearer establishment is rejected, the message including the identity of the mobile terminal for which the bear establishment is rejected; and- transmitting the message to a mobility management device which performs the mobility management of the plurality of mobile terminals.

Description

APPARATUS AND METHODS FOR MANAGING RESOURCE AMONG MULTIPLE COMMUNICATION DEVICES

This disclosure relates to the field of telecommunications in a packet-switched data communications network. More particularly, it concerns the behaviour of communication devices when it is preparing to release any network resource.

The cellular telecommunications has been under constant evolution, from the earlier days of GSM (Global System for Mobile communications) networks, to GPRS (General Packet Radio Service), to the modern system of UMTS (Universal Mobile Telecommunications System) and Long Term Evolution (LTE) which can be found in various big cities around the world. Along with different access technologies, the experiences provided to end-user are also continuing to be enhanced. However, today's cellular network is no longer only providing services for human oriented communications (such as voice, short text message transmission and access to the global Internet).

Recently, new services have even been expanded to cover non-human communications, such as machine-to-machine (M2M) or machine-type communications. Machine-type communications can cover a very wide range of applications, from measurement collection from sensors, to remote control of devices. For such communications, delay need not be the foremost consideration, since they have a set of characteristics that is different from human oriented communications.

The Third Generation Partnership Project (3GPP) has started defining the requirements for a cellular network to support machine-type communications (MTC) in [NPL 1]. Typically, MTC in 3GPP consists of various communication devices that access the 3GPP cellular network to communicate with a server that is outside of the cellular network or to communicate with other communication devices in the cellular network. By having network improvement optimizations that take advantage of unique characteristics of MTC, the cellular network will be even more suitable to support MTC.

In 3GPP, devices are usually identified by network with the Temporary Mobile Subscriber Identity (TMSI) and International Mobile Subscriber Identity (IMSI). TMSI is the identity that is most commonly sent between the mobile and the network. TMSI is randomly assigned by network to every mobile in the area, the moment it is switched on. The number is local to a location area, and so it has to be updated each time the mobile moves to a new geographical area. An IMSI is a unique identification associated with all GSM and UMTS network mobile phone users. It is stored as a 64 bit field in the subscriber identification module (SIM) inside the phone and is sent by the phone to the network. Furthermore, the real telephone number of a mobile station is the mobile subscriber ISDN number (MSISDN) which is assigned by the network to the subscriber.

MTC involves MTC devices communicating using 3GPP radio network access. In many MTC applications, a large number of MTC devices are affiliated with a single MTC user. These MTC devices together are part of a MTC Group. MTC devices can be grouped together for the control, management or charging facilities etc. to meet the need of operators. MTC devices within the same group can be in the same area, and/or have the same MTC features attributed, and/or belong to the same MTC user. The MTC user associated with a MTC group owns a MTC server which is connected to the PS network of a mobile network operator via an Access Point Name (APN) using the Gi interface. All MTC devices in the MTC group can communicate with the MTC server in user plane.

This optimization of organizing MTC devices into groups provides easier means to control, update, or charge the MTC devices, and also decreases the redundant and unnecessary signaling to avoid network congestion. Furthermore, by using group based optimization, especially in the case where the number of MTC devices in a group is very large, network resources can be utilized more efficiently and the unnecessary signaling can be avoided.

According to the current architecture of MTC in 3GPP Evolved Packet Core (EPC) in [NPL 1] and [NPL 2], an exemplary network 110 is shown in Fig. 11, comprising a MTC server (MTC-Server) 1143, a Packet Data Network Gateway (PGW) 1120, a Serving Gateway (SGW) 1130, a Mobility Management Entity (MME) 1140, an MTC Interworking Function (IWF) 1122 and multiple base stations (eNB) 1150 and 1152. Mobile devices (also known as User Equipment or UE), or sometimes referred to as

MTC devices

1100 and 1102 obtain communication services from the 3GPP network by attaching to the radio access network of the base stations eNB 1150 and 1152, as shown by the

attachment

1190 and 1192. The interface 1170 allows packet forwarding on the User Plane (U-Plane) between the PGW 1120 and SGW 1130.

The

interfaces

1174 and 1176 allow packet forwarding between the SGW 1130 and the respective base stations of the mobile devices. To do so, one or more Evolved Packet System (EPS) bearers are established between the PGW 1120 and the mobile device through the SGW 1130 and eNB 1150. The interface 1172 between SGW 1130 and MME 1140, and the

interfaces

1178 and 1180 between MME 1140 and the base stations eNB 1150 and 1152 allow Control Plane (C-Plane) signaling to be performed. For example, when there is a downlink packet to be delivered to one of the mobile device (say, MTC device 1100) but the MTC device 1100 is currently not in connected mode, the C-plane interfaces 1172 allow the SGW 1130 to send a downlink data notification to the MME 1140, and the MME 1140 can send paging messages to trigger the MTC device 1100 to establish a connection via the base stations eNB 1150. The interface 1145 allows the MME 1140 to retrieve subscribers' information from the HSS 1144 in C-plane. The interface 1121 allows the data forwarding between the MTC-Server 1143 and the network 1110. The interface 1146 allows data forwarding between the MTC-Server 1143 and the PGW 1120.

In many MTC group related applications, MTC devices from the same MTC group may operate in a similar fashion during a certain period of time. For example, a group of MTC devices may be triggered during a short interval by a group trigger request generated by a MTC server. After receiving the group trigger, MTC devices will get connected by setting up their default EPS bearer. In some situations, MTC devices need to activate more dedicated bearer so as to meet the Quality of Service (QoS) requirement, e.g. for transferring video streaming.

The procedure of activating dedicated EPS bearers is illustrated in Fig. 12. MTC server 1205 initiates a device trigger request 1216 to MME 1201 via IWF 1204. MME 1201 sends the device trigger 1218 to respective MTC device 1200 so that they can setup their Packet Data Network (PDN) connections. A bearer modification request 1219 may be sent by a UE 1200 to MME 1201 so as to establish new dedicated bearers. MME 1201 can either reject (in case 1221) or accept (in case 1222) the bearer modification request. When congestion control for the corresponding APN is activated for case 1221, MME 1201 rejects the bearer modification request with a reject message 1220 which usually contains a session management back-off timer. On the other hand (in case 1222), if the bearer modification request is accepted by MME 1201, a bearer setup request 1223 will be generated and sent to SGW 1202 and PGW 1204. A response message 1225 received by MME 1201 indicates that the dedicated bearers in SGW 1202 and PGW 1203 are successfully activated. It is followed by a request 1227 sent from MME 1201 to activate the dedicated bearers in the UE 1200. Finally, uplink data 1228 can be transferred after completion of the above descried steps.

However, in some cases, UEs' dedicated bearers could not be activated successfully, for example, due to APN congestion. In 3GPP specification TS24.301 [NPL 3], it has specified the mechanism for APN based congestion control. When the APN based congestion control is active, network may store an APN congestion back-off time on a per UE and congested APN basis and reject any subsequent session management requests from UEs targeting towards the congested APN before the APN congestion back-off time for the congested APN elapses. When a session management request is sent to a congested APN, the UE will receive a back-off time and cannot initiate any session management request to this APN except requests for emergency or high priority requests until the session management back-off time is expired.

As depicted in Fig. 13, a group of MTC devices are triggered by MTC server 1143 with a Trigger request 1302. UE 1321 and UE 1322 are MTC devices in the same MTC group. After their connections are established, they may request for new bearer resource with messages 1303 1306. MME 1140 accepts the request message 1303 with an Accept message 1304. However, network rejects the request with a message 1307 containing a back-off time if session management congestion control is activated 1305 due to the APN congestion. After a certain period of time, UE 1321 may decide to release its resource by sending a Release Bearer Request 1308 to MME 1140 for UE 1322 to request for the released resource.

[PTL 1] US Patent US20120033551A1 Liao Ching-Yu, "Handling Signaling Congestion And Related Communication Device", Feb, 2012.
[PTL 2] US Patent US20110292893A1 LEE Kidong, et al., "NAS-BASED SIGNALING PROTOCOL FOR OVERLOAD PROTECTION OF RANDOM ACCESS IN MASSIVE MACHINE TYPE COMMUNICATION", Dec 2011.
[PTL 3] EP Patent EP2369890A1 Bachmann Jens, et al., "Connection peak avoidance for machine-type-communication (MTC) devices." Sep, 2011.

Non-Patent Literature

[NPL 1] 3GPP TS 22.368v11.3.0, "Service Requirements for Machine-Type Communications (MTC); Stage 1", Oct 2011.
[NPL 2] 3GPP TS 23.401v10.6.0, "General Packet Radio Service (GPRS) enhancements for Evolved Universal Terrestrial Radio Access network (E-UTRAN) access", Dec 2011.
[NPL 3] 3GPP TS 24.301v11.1.0, "Group Core Network and Terminals; Non-Access-Stratum (NAS) protocol for Evolved Packet System (EPS); Stage 3", Dec 2011.

However, as the APN based session management congestion control may be deactivated (1309) after UE 1321 released its resource, a following request 1310 for new bearer to that APN sent from UE 1323 could be accepted with an accept message 1311. Consequently, when the back-off timer of UE 1322 is expired as shown by 1313, the APN may fall into a congested condition again shown by 1312 and the new bearer request 1314 from UE 1322 will be again rejected with a Reject message 1315 containing a session management back-off time. As a result, the resource released by UE 1321 cannot be successfully received by UE 1322. A MTC group application would be interrupted by pending data from UE 1322.

In [PTL 1], MTC device receives a group paging message with a time period for MTC devices in the group to transmit data. Then MTC devices select a random value to determine a sub-time period to transmit data and respond to the paging. Although this invention provides a method to handle signal congestion for a MTC device and/or a MTC server, it does not consider the limitation of number of bearers that an APN can provide and thus a group based MTC application still can be interrupted.

[PTL 2] introduces a scheme of minimizing the random access load on the network to support MTC devices. In particular, the concept of grouping (e.g., collecting, combining, aggregating, etc.) MTC devices based on non-access stratus (NAS) signalling is performed. Various types of grouping schemes for MTC devices are proposed to minimize random access load. It has MME based and eNB based solutions. For MME based solution, the MME decides upon group configuration, namely which nodes (slave or secondary) to belong to which node (master or principal), in response to those RRC Connection Setup Complete messages received from one or more MTC devices. MTC devices send its periodicity to MME and MME will decide who should be the slave and master, or providing a subframe for MTC devices. The scheduling is based on device capacity of being master or slave devices. This invention is about the method of grouping MTC devices which may have the effect in helping to alleviate network congestion.

In [PTL 3], it introduces a method for controlling connection establishment of devices to a network to avoid a connection peak when all devices would simultaneously connect to the network due to a trigger event. In the embodiments, the invention distributes the connection of devices to the network over a time period after the trigger. In the other word, devices do not connect to the network at the same time but during a determined period of time. Doing so results in reduced the signalling overload on the network such that a large number of MTC devices can be accommodated.

All these prior arts do not provide a method to manage network resource.

It is a one non-limiting and exemplary embodiment of the present disclosure to overcome or at least substantially ameliorate the afore-mentioned disadvantages and shortcomings of the prior art. Specifically, it is a one non-limiting and exemplary embodiment of the present disclosure to provide a mechanism that a device can pass its resource to another device with the aid of some other network nodes, for example, MME or MTC server. More specifically, this disclosure lets a device to request for resource on behalf of another device, and transferring back-off timer from one device to another such that a group application can be guaranteed.

Accordingly, in an example embodiment of the present disclosure, it is provided a communication control method. The communication control method for use in communication performed through a network between a plurality of mobile terminals and a communication device, which is a communication partner of the plurality of mobile terminals, the method comprising: generating, when a mobile terminal performing the communication through the network among the plurality of mobile terminals releases a dedicated bearer, by the mobile terminal, a message for releasing the bearer and requesting to transfer the bearer to be released to a mobile terminal for which bearer establishment is rejected, the message including the identity of the mobile terminal for which the bear establishment is rejected; and transmitting the message to a mobility management device which performs the mobility management of the plurality of mobile terminals.

These general and specific aspects may be implemented using a system and a computer program, and any combination of systems, apparatuses, and computer programs.

The disclosure has the advantage of managing network resource.

Additional benefits and advantages of the disclosed embodiments will be apparent from the specification and Figures. The benefits and/or advantages may be individually provided by the various embodiments and features of the specification and drawings disclosure, and need not all be provided in order to obtain one or more of the same.

Fig. 1 depicts an example functional architecture of a device apparatus according to an example embodiment of the present disclosure. Fig. 2 illustrates a flowchart for transferring network resource from one device to another device by interacting of UE with MME and MTC server according to an example embodiment of the present disclosure. Fig. 3 illustrates a flowchart for a further identified problem when resource transfer request is rejected according to an example embodiment of the present disclosure. Fig. 4 depicts a message sequence chart of communications between multiple MTC devices and network nodes for transferring network resource to some other devices according to an example embodiment of the present disclosure. Fig. 5 depicts a message sequence chart of communications between multiple MTC devices and network nodes for transferring network resource to some other devices according to another example embodiment of the present disclosure. Fig. 6 illustrates a message sequence chart of communications between multiple MTC devices and network nodes for transferring network resource to some other devices according to an example embodiment of the present disclosure. Fig. 7 depicts a message sequence chart of communications between multiple MTC devices and network nodes for transferring network resource to some other devices according to a variant of the present disclosure used in mobility management procedure. Fig. 8 shows the flowchart of UE's decision process of sending resource transfer request according to an example embodiment of the present disclosure. Fig. 9 illustrates a suggested information element for Transfer Request sent by a device according to an example embodiment of the present disclosure. Fig. 10 illustrates a suggested information element for Target UE Query sent by a device according to an example embodiment of the present disclosure. Fig. 11 illustrates the network architecture of machine type communications in a cellular network according to a prior art. Fig. 12 depicts the PDN connection setup procedure initiated by a UE in cellular network according to a prior art. Fig. 13 illustrates various device operations upon receiving a device trigger from network according to a prior art.

In the following description, for purposes of explanation, specific numbers, times, structures, protocol names, and other parameters are set forth in order to provide a thorough understanding of the present disclosure. However, it will be apparent to anyone skilled in the art that the present disclosure may be practiced without these specific details.

The present disclosure applies to the situation where a communication device intends to release its network resource when some other devices need to acquire the said resource. This requires a communication device to discover which communication device has tried to request for the resource but unsuccessful. It may involve interaction between a communication device and network or interaction between a communication device and a server. Particularly, this disclosure allows a communication device to initiate a network resource transfer request for another communication device which is temporally unable to send such a request, e.g. due to a running session management back-off timer to that particular APN.

Fig. 1 depicts the example functional architecture 100 of a communication device, comprising a Radio Interface 101, a Non-Access Stratum Layer 102, a Requesting Means 105, a Receiving Means 110, a Time Control Means 104, and an Application Layer 103.

Radio interface 101 is a functional block comprises of the hardware and firmware necessary to enable a device to communicate with the cellular base station. It may include the antenna, transmitting circuitry and receiving circuitry. It also implements the radio access control and signalling to the cellular radio network and the transport of data packets over the cellular radio access. It is obvious to anyone skilled in the art that this does not preclude the system to be used in a wired environment, i.e. the radio interface 101 can be replaced with wired transmission means as long as interface 106 is kept intact. It is also possible that the radio interface 101 is in fact running on top of another layer of communication stack, e.g. the Unlicensed Mobile Access (UMA) or any variance of the Generic Access Network (GAN).

Non-Access Stratum (NAS) layer 102 is functional block that implements the control plane signalling and initiation of user plane transport of data between the mobile device and the cellular network. The signal path 106 allows the NAS layer 102 and radio interface 101 to exchange control information and signalling messages. NAS messages sent from the network are processed by the NAS layer 102. NAS messages sent from the device to the network are generated by the NAS layer 102. The Application Layer 103 is an abstraction of applications running on the MTC device that require communications with an external node (such as other MTC Devices or MTC Server).

The Requesting Means 105 is used to generate requests to Application Layer 103 via the signal path 107 or to NAS layer 102 via signal path 108. Receiving Means 110 allows the communication device to receive messages from Application Layer 103 via signal path 111 or from NAS Layer 102 via signal path 112. The Receiving Means 110 also provides a time value, which is contained in received messages from NAS Layer 102, to Time Control Means 104 via the signal path 114. The Time Control Means 104 stores the received time value and runs a timer. The Requesting Means 105 needs to check the remaining time value running in the Time Control Means 104 via signal path 113 before generating new requests.

In one aspect of present disclosure as illustrated in Fig. 2, UE 221 and UE 222 are MTC devices. UE 221's New Bearer Request 223 is accepted by MME 1140 with an Accept message 224. Network may become congested after accepting the New Bearer Request 223 and therefore session management congestion control for that APN will be activated as shown by 225. The following New Bearer Request 226 sent from UE 222 will be rejected by MME with a reject message 227 containing a back-off time. When UE 221 is going to release its bearer resource, it has to send a query message 201 to MTC server 1143. MTC server 1143 provides a target UE in the response message 202, based on which UE 221 can transfer its bearer resource to the target UE specified in the message 202. One method for a MTC server to identify a target UE is to communicate with UEs via application layer so that it could find out UEs which have requested for additional bearer resource unsuccessfully. Subsequently, UE 221 initiates a Bearer Transfer Request 203 comprising the target UE 222's identity to MME 1140. Upon receiving the Bearer Transfer Request 203, MME 1140 will setup new bearers for UE 222 by initiating a Bearer Setup Request 204 to UE 222. UE 222 responds the Bearer Setup Request 204 with a Bearer Setup Response message 205. At last, MME acknowledges UE 221 about the successful bearer transfer with an Accept message 206. In this way, UE 221 can successfully transfer bearer resources to UE 222.

This transfer of resources is especially useful when the two UEs belong to the same MTC group. It allows the MTC applications to proceed instead of being suspended due to the inability of one UE in the MTC group to obtain network resources due to congestion.

A back-off time may be optionally contained in the Accept message 206 which could be equal to the remaining value of back-off timer in UE 222. The objective of assigning the remaining value of back-off timer in the target UE to the source UE is to keep the overall back-off time of the MTC group constant and it could also avoid misusing this disclosure as a method for removing running back-off timer.

In a further consideration of this aspect of present disclosure as shown in Fig. 2, after data transmission is completed at UE 221, UE 222 sends a Query message 208 to MME 1140 or to MTC server 1143 via MME 1140 on whether its bearer could be released or will be returned to UE 221. If 'Nil' is indicated in the response message 210, UE 222 will start a procedure to release its bearers with a Release Bearer Request; otherwise a similar bearer transfer procedure will be carried out as described in the present disclosure.

One limitation of this aspect is that network is usually implemented with thresholds N_Hand N_L in network congestion control. N_Hand N_Lare the upper bound and lower bound of number of connections or bearers occupied. In session management congestion control, once the number of bearers of an APN exceeds the said threshold N_H, network should activate session management congestion control and reject further request to that APN, until the number of bearers falls below N_L. If session management congestion control is activated and the number of bearers has not dropped to N_Hyet, Bearer Transfer Requests may also be rejected.

In one example solution as illustrated by Fig. 3, a group of new bearer requests 611 from UE 301 to UE 305 were setup successfully. A following group of requests 328 from UE 306 to UE 308 were rejected due to session management congestion control activated as shown by 312. After each UE301 and UE302 performs a Query and Response interaction with

messages

313, 335 with MTC server or with network, UE 301 and UE 302 request for transferring bearer resource to UE 306 and UE 307 with

messages

314 and 316 respectively, which however are rejected by MME 1140 with

messages

315, 317 due to session management congestion control being activated. UE 301 and UE 302 will run a back-

off timer

330 and 331 which could be either received from

reject messages

315, 317 from network or a self-generated back-off timer. The value of a self-generated back-off timer could be retrieved by communicating with MTC server via application layer or based on some predefined subscription agreement. MTC server may detect that the transfer was failed to the target UE based on no data transmission from the target UE. Meanwhile, MME 1140 releases the bearers belonging to UE 301 and UE 302 after receiving the

Bearer Transfer Request

314 and 316.

After UE302 performs a Query and Response interaction with message 332, UE302 requests for transferring bearer resource to UE308 with message 318. When another Bearer Transfer Request 318 initiated by UE 303 is received, MME 1140 first releases the bearer belonging to UE 303 and session management congestion control is off due to the number of bearers occupied falls below N_L. Thus, MME 1140 can help UE 308 to setup its bearer which is indicated in message 318, and an Accept message will be sent to UE 303 as an acknowledgement. MTC server may be aware of the recovery of the APN congestion, e.g. by receiving data from UE 308, and it can appoint some other UEs which decide to release their bearer resource to carry out bearer transfer procedure, e.g. UE 304/305 with a group of messages 321-327, 333 and 334.

In another example solution based on the solution in the last paragraph, MTC server 1143 can proactively inform UE 301 and UE 302 to stop their back-

off timer

330 and 331 after detecting bearer transfer procedure was successful for UE 308. Meanwhile, MTC server 1143 lets UE 301 and UE 302 to re-initiate bearer transfer procedure for

UE

306 and 307. Compared to the solution in the last paragraph, this solution allows UE to transfer bearer resource to other UEs immediately after the number of bearers dropped below NL. However, it also requires network to keep at least the default bearers of UE 301 and UE 302 so that they can communicate with MTC server. In addition, the back-off timer of UE 301 and UE 302 should be controllable by MTC server.

In another aspect of the present disclosure as depicted in Fig. 6, a group of UEs from UE 601 to UE 608 are triggered by a Trigger request 610 generated by MTC server 1143 via MME 1140. After all devices establish their connections, they may intend to get additional bearer by sending New Bearer Requests 611 to MME 1140.

As what has been described, during session management congestion control when the number of bearers to an APN exceeds a threshold N_H, congestion control for that APN would be activated. Some of the requests from UE 601 to UE 605 are accepted while the remaining requests 612 from UE 606 to UE 608 are rejected with a group of messages 612 due to the session management congestion control is activated as shown by 633. When a UE is going to release bearer resource, it has to initiate a Query and response procedure 613 with MTC server 1143 or MME 1140 to get a target UE identity. After the procedure is completed, the UEs, e.g. UE 601 and UE 602, sends a Bearer Transfer Request 614/616 to MME 1140 for transferring bearer resource to UE 606 and UE 607.

However, they are rejected with

messages

615 and 617 because session management congestion control is activated. A short back-off time could be contained in the reject messages 615/617 to prevent

UE

601 and 602 resending same message during the specified period. Alternatively, UE could use a pre-agreed back-off time to control resending the message. This allows UE 601 and UE 602 to retry in a more frequent manner so that the delay of transferring the resource to UE 606 and UE 607 can be reduced. On the other hand, resent Bearer Transfer Request 618/620 may be rejected again with reject messages 619/621.

This will repeatedly take place until the session management congestion control is deactivated, i.e. when a new Bearer Transfer Request 623 from UE 604 is received by MME 1140. After MME 1140 releases the bearer resource of UE 604, the session management congestion control can be lifted. A procedure to setup the bearer resource for UE 606 UE 607 will be started upon receiving Bearer Transfer Request 625/627 from UE 601 and UE 602 which will receive Accept messages 626/628 eventually. The disadvantage of this method is that it generates a lot of signalling to the network, which even worsen the network congestion situation.

In yet another example solution of the present disclosure, MTC server analyzes and determine whether the previous Bearer Transfer Request was successful based on whether the MTC server has received the data from target UEs after the command of transferring bearer resource being sent out. If not, MTC server will respond the query from a UE with multiple target UEs. On the other hand, one UE can request to setup the bearer resource for a number of UEs.

A more detailed description of the example solution addressed in the last paragraph is illustrated in Fig. 5. A group of UEs from UE 501 to UE 508 receive a group trigger request 510 generated by MTC server 1143 sent via MME 1140. After their connections are established, they may intend to get additional bearers by sending New Bearer Requests 511 to MME 1140. Some of the requests from UE 501 to UE 505 are accepted while remaining requests from UE 506 to UE 508 are rejected with a group of messages 512 due to the session management congestion control is activated as shown in 523.

After data transmission is completed, UE 501 decides to release its bearers. It needs to inform MTC server 1143 with a Query message 513 and MTC server can send a response message 513 containing a target UE identity, e.g. UE 506, to UE 501. Following that, UE 501 initiates a Bearer Transfer Request 514 to release its bearers and transfer the released resource to UE 506. However the number of bearers may be still beyond N _L. Consequently, the Bearer Transfer Request would be rejected with a message in 514. MTC server did not receive the expected data from UE 506 as shown by 523 and thus suspects that the Bearer Transfer Request initiated by UE 501 was unsuccessful.

Therefore, when MTC server 1143 receives another Query message 516 from UE 502, a response 516 containing a list of UEs including both UE 506 and UE 507 will be replied to UE 502. The Bearer Transfer Request from UE 502 for UE 507 and UE 506 is also rejected due to APN congestion. Similarly, after receiving a Query 517 from UE 503, MTC server further provides UE 503 a list of UEs including UE 506 UE 507 and UE 508. When network APN congestion is lifted as the number of bearers drop below N_L, e.g. after releasing the resource of UE 503, MME 1140 can accept the Bearer Transfer Request 519 sent by UE 503 and setup the bearers for UE 506, UE 507 and UE 508 with the respective bearer setup procedures 520/521/522.

In yet another solution as illustrated by Fig. 4, the initial procedure is similar to above described example solutions, where a group of UEs from UE 401 to UE 408 receive a group trigger request 410 generated by MTC server 1143 sent via MME 1140. After connections are established, they may intend to get additional bearers by sending New Bearer Requests to MME 1140 as shown in the

procedure

411 and 412. However, only requests from UE 401 to UE 405 are accepted while others are rejected due to session management congestion control is activated as shown by 426. MTC server responds to the received Query message in the procedure 413 and provides a target UE for each source UE.

Because network session management congestion control is still on, network rejects the first Bearer Transfer Request with a back-off time T₁ with a message in 414 and rejects following Bearer Transfer Request with a message in 415 by providing a back-off time T₂ in the reject message based on the remaining value of T₁. Meanwhile, network will release the corresponding bearer resource indicated in the Bearer Transfer Request. The back-off time for each respective device can be controlled by network based on the remaining value of the first back-off timer. The advantage of this is that back-off timer of following devices can be synchronized with T₁which shortens the timeout duration and reduces the delay of resending Bearer Transfer Request.

As shown in Fig. 4, the Bearer Transfer Request sent by UE 402 can be synchronized with UE1 which shorten the duration of back-off timer. If the Bearer Transfer Requests 418/419 are rejected again, network can assign a shorter back-off time T₃ in the reject message based on the value of T₁ in the sense that the back-off time for a MTC group could be proportional to the level of congestion. When APN congestion is alleviating, the back-off time assigned by network could be shorter. When the number of occupied bearers falls below N_L, e.g. after receiving Bearer Transfer Request 421 from UE 403, MME 1140 can deactivate the session management congestion control and setup bearers for UE 408. Consequently, Bearer Transfer Requests from UE 401 and UE 402 in the third attempt 422/423 after the back-off timer 424/425 has expired can finally be accepted.

In one variation of this solution in the present disclosure, when network receives a Bearer Transfer Request but unable to accept it due to network congestion, network replies the Bearer Transfer Request with a reject message. However, network may not initiate bearer release procedure immediately instead just assign a back-off time in the reject message. When another Bearer Transfer Request is received and congestion control for that APN is still activated, network rejects the request with a new back-off timer based on the first assigned back-off time. Such that, when the back-off timer for the group is expired, network will receive a batch of Bearer Transfer Requests simultaneously.

Network can decide whether to accept the batch of requests by comparing the number of bearers occupied with N_L if the bearers corresponding to the batch of requests could be released. Before establishing bearers for target UEs, network first releases those bearers corresponding to the batch of requests so that the APN congestion can be lifted. This variant provides flexibility of using the bearer resource continuously if the attempt of transferring network resource was unsuccessful. For example, a UE wants to retain its bearer resource if the transfer is unsuccessful. The back-off time for a group of source UEs, which are sending the Bearer Transfer Request, could be proportional to the number of UEs in a batch of sending requests. For example, the current number of bearers being occupied is N=90 while N_L=80; a batch of 9 requests should receive a shorter back-off time than a batch of 5 requests, because network needs fewer requests to recover from network congestion for a larger batch of requests.

One enhancement to the present disclosure is a means to retain resource for a short period of time. When the Bearer Transfer Request is unsuccessful, the source UE's bearer may not be released immediately. Instead, network will hold it for a while in case some other UEs may request for that resource during the interval before the Bearer Transfer Request is resent. Network could also delay responding the Bearer Transfer Request for a short while if network deems the APN based network congestion control will be removed soon. This allows network to wait for other Bearer Transfer Requests or bearer release requests so that the number of bearers can drop below N_L.

In another variation of this disclosure, a UE can interact with network instead of MTC server to obtain a target UE for performing network resource transferring procedure. Network may store back-off time for each individual UE. When a Bearer Transfer Request is received by the network, network can select a target UE having a session management back-off timer running to allocate the resource to that UE. Selection criteria of the target UE could be based on the same group identification, or the last UE rejected by network congestion control for that APN. The UE can communicate with the target UE or MTC server whether bearer transfer request is still needed or not.

Another variation of this disclosure is its applicability to mobility management procedure as illustrated in Fig. 7. The resource transfer technique can also be applied during mobility management congestion control. The initial procedure of triggering is similar as what has been described in this disclosure. UE responds the trigger with a service request procedure. The group of service requests 711 from UE 701 to UE 705 are accepted by MME 1140 while the rest are rejected as shown by 712 due to mobility management congestion control being activated 733. As shown by procedure 713, after data transmission is completed, a UE queries MTC server which may respond with a target UE identity. The target UE could be selected based on whether the MTC server 1143 has received the expected data from the UEs after a group trigger request. The source UE initiates a resource transfer request 714 which contains the identity of the target UE.

For example, UE 701 sends a Resource Transfer Request for UE 706 in the procedure 714. If MME 1140 cannot handle this request due to network congestion, it will reject this request with a back-off time T₁. Similarly, MME rejects the resource transfer request from UE 702 and UE 703 with back-off time T₂ and T₃ respectively, where T₂ and T₃ could be equal to the remaining value of T₁ so that the requests resent by UE 701, UE 702 and UE 703 could be synchronized at the timeout of these back-off timers 725 724 and 726.

The advantage of using the first back-off timer T₁ as a group back-off timer is to synchronize the resource transfer request so that network can calculate whether the mobility management congestion control could be removed if accepting a batch of requests of releasing their resource. If network decides to accept Resource Transfer Requests in the procedures of 722/723/731, MME 1140 will send a resource transfer accept message to each respective source UE with a mobility management back-off timer 727 728 729 which may be equivalent to the remaining values of the back-off timers assigned to UE 706 UE 707 and UE 708. Following that, MME sends a paging message to UE 706 UE 707 and UE 708 and a service request procedure will be carried out as shown in 732.

The UE decision process of initiating a resource transfer request or Bearer Transfer Request in the present disclosure can be described by the flowchart in Fig. 8. The process starts from UE about to release network resource in step 801. It is followed by sending a Query to MTC server or network in step 802. MTC server and Network can reply with a target UE's identity. The identity could be TMSI, IMSI, MSISDN or any other forms of unique identification to recognize the target UE. Subsequently, a network resource transfer request or Bearer Transfer Request will be generated and sent in step 803. If it is not accepted by the network in step 805, the UE will start to run a back-off timer and resend the request after its timeout as shown in step 807. This process is ended until the transfer request is accepted by the network in step 806.

Fig. 9 shows a suggested information element for Resource Transfer Request 901. It contains a Transfer Request Information Element Identifier 903, Type of identity 904 and Identity 905. Fig. 10 shows a suggested information element for a device to query network for a target device 1000. It contains a Target UE Query Request Information Element Identifier 1001 and MM/SM flag 1002. The MM/SM flag indicates whether the identity of a device provided by a UE will be used for sending a mobility management request or session management request.

Although the present disclosure has been herein shown and described in what is conceived to be the most practical and example embodiment, it will be appreciated by those skilled in the art that various modifications may be made in details of design and parameters without departing from the scope and ambit of the present disclosure.

For instance, in the explanation of the embodiments, the 3GPP evolved packet system architecture is assumed with the use of network architectural elements such as the MME, PGW and SGW. A person skilled in the art would appreciate that the disclosure may be applied to any other packet-switched network architectures, such as the 3GPP2, WiMax, the Generalized Packet Radio Service (GRPS) system, which involve the installation of filters to direct packets into different bearers or carrier mediums.

In an aspect of the present disclosure, wherein the message includes the identities of several mobile terminals for which the bearer establishment is rejected.

In an aspect of the present disclosure, wherein the mobile terminal, which releases the bearer, transmits an acquisition message for acquiring the identity of the mobile terminal, for which the bearer establishment is rejected, to the communication device before transmitting the message.

In an aspect of the present disclosure, wherein, in the case of receiving the message, the mobility management device determines whether or not the number of established bearers is a predetermined value or less and performs the bearer establishment for the mobile terminal corresponding to the identity included in the message if the number of established bearers is the predetermined value or less.

In one general aspect of the present disclosure, the present disclosure provides a mobile terminal. The mobile terminal for use in communication performed through a network between a plurality of mobile terminals and a communication device, which is a communication partner of the plurality of mobile terminals, the mobile terminal comprising: a generating unit which, when releasing a dedicated bearer to perform the communication through the network, generates a message for releasing the bearer and requesting to transfer the bearer to be released to a mobile terminal for which bearer establishment is rejected, the message including the identity of the mobile terminal for which the bear establishment is rejected; and a transmitting unit which transmits the message to a mobility management device which performs the mobility management of the plurality of mobile terminals.

In an aspect of the present disclosure, wherein the transmitting unit transmits an acquisition message for acquiring the identity of the mobile terminal, for which the bearer establishment is rejected, to the communication device before transmitting the message.

In one general aspect of the present disclosure, the present disclosure provides a mobility management device. The mobility management device which perform mobility management of a plurality of mobile terminals when communication is performed through a network between the plurality of mobile terminals and a communication device, which is a communication partner of the plurality of mobile terminals, the mobility management device comprising: a receiving unit which, when a mobile terminal performing the communication through the network among the plurality of mobile terminals releases a dedicated bearer, receives a message, which is transmitted by the mobile terminal which releases the bearer, for releasing the bearer and requesting to transfer the bearer to be released to a mobile terminal for which bearer establishment is rejected, the message including the identity of the mobile terminal for which the bear establishment is rejected; a determining unit which determines whether or not the number of established bearers is a predetermined value or less in the case of receiving the message; and an establishing unit which performs the bearer establishment for the mobile terminal included in the message if the number of established bearers is determined to be the predetermined value or less.

In an aspect of the present disclosure, wherein the identity of the mobile terminal for which the bearer establishment is rejected included in the message is acquired by transmitting an acquisition message for acquiring the identity of the mobile terminal, for which the bearer establishment is rejected, to the communication device before the mobile terminal, which releases the bearer, transmits the message.

The above aspects may be implemented by combination. These aspects may be implemented by a program to let a computer implement the method and recording medium recorded the program in addition to the communication control method and the apparatus.

Further, functional blocks of the above-mentioned embodiment may be implemented by hardware, software, or any combination of the hardware and the software. For example, each functional block of Fig.1 may be implemented by hardware such as CPU or memory of any computer. In addition, any computer implements program that processes of each function are described, and the each functional block may be implemented. In addition, flow charts or sequence charts of the above-mentioned embodiment may be implemented by hardware such as CPU or memory.

Further, each functional block and each processing for sequence charts used in the description of the embodiments of the present disclosure as given above can be realized as LSI (Large Scale Integration), typically represented by the integrated circuit. These may be produced as one chip individually or may be designed as one chip to include a part or all. Here, it is referred as LSI, while it may be called IC, system LSI, super LSI, or ultra LSI, depending on the degree of integration.

Also, the technique of integrated circuit is not limited only to LSI and it may be realized as a dedicated circuit or a general-purpose processor. FPGA (Field Programmable Gate Array), which can be programmed after the manufacture of LSI, or a reconfigurable processor, in which connection or setting of circuit cell inside LSI can be reconfigured, may be used. Further, with the progress of semiconductor technique or other techniques derived from it, when the technique of circuit integration to replace LSI may emerge, the functional blocks may be integrated by using such technique. For example, the adaptation of biotechnology is one of such possibilities.

The disclosure has the advantage of managing network resource. Therefore, the disclosure can be used as the behaviour of communication devices when it is preparing to release any network resource.

Claims

A communication control method for use in communication performed through a network between a plurality of mobile terminals and a communication device, which is a communication partner of the plurality of mobile terminals, the method comprising:
- generating, when a mobile terminal performing the communication through the network among the plurality of mobile terminals releases a dedicated bearer, by the mobile terminal, a message for releasing the bearer and requesting to transfer the bearer to be released to a mobile terminal for which bearer establishment is rejected, the message including the identity of the mobile terminal for which the bear establishment is rejected; and
- transmitting the message to a mobility management device which performs the mobility management of the plurality of mobile terminals.
The communication control method according to claim 1, wherein the message includes the identities of several mobile terminals for which the bearer establishment is rejected.
The communication control method according to claim 1 or 2, wherein the mobile terminal, which releases the bearer, transmits an acquisition message for acquiring the identity of the mobile terminal, for which the bearer establishment is rejected, to the communication device before transmitting the message.
The communication control method according to claim 1, wherein, in the case of receiving the message, the mobility management device determines whether or not the number of established bearers is a predetermined value or less and performs the bearer establishment for the mobile terminal corresponding to the identity included in the message if the number of established bearers is the predetermined value or less.
A mobile terminal for use in communication performed through a network between a plurality of mobile terminals and a communication device, which is a communication partner of the plurality of mobile terminals, the mobile terminal comprising:
- a generating unit which, when releasing a dedicated bearer to perform the communication through the network, generates a message for releasing the bearer and requesting to transfer the bearer to be released to a mobile terminal for which bearer establishment is rejected, the message including the identity of the mobile terminal for which the bear establishment is rejected; and
- a transmitting unit which transmits the message to a mobility management device which performs the mobility management of the plurality of mobile terminals.
The mobile terminal according to claim 5, wherein the message includes the identities of several mobile terminals for which the bearer establishment is rejected.
The mobile terminal according to claim 5 or 6, wherein the transmitting unit transmits an acquisition message for acquiring the identity of the mobile terminal, for which the bearer establishment is rejected, to the communication device before transmitting the message.
A mobility management device which perform mobility management of a plurality of mobile terminals when communication is performed through a network between the plurality of mobile terminals and a communication device, which is a communication partner of the plurality of mobile terminals, the mobility management device comprising:
- a receiving unit which, when a mobile terminal performing the communication through the network among the plurality of mobile terminals releases a dedicated bearer, receives a message, which is transmitted by the mobile terminal which releases the bearer, for releasing the bearer and requesting to transfer the bearer to be released to a mobile terminal for which bearer establishment is rejected, the message including the identity of the mobile terminal for which the bear establishment is rejected;
- a determining unit which determines whether or not the number of established bearers is a predetermined value or less in the case of receiving the message; and
- an establishing unit which performs the bearer establishment for the mobile terminal included in the message if the number of established bearers is determined to be the predetermined value or less.
The mobility management device according to claim 8, wherein the message includes the identities of several mobile terminals for which the bearer establishment is rejected.
The mobility management device according to claim 8 or 9, wherein the identity of the mobile terminal for which the bearer establishment is rejected included in the message is acquired by transmitting an acquisition message for acquiring the identity of the mobile terminal, for which the bearer establishment is rejected, to the communication device before the mobile terminal, which releases the bearer, transmits the message.