JP2009260895A - Csg cell wireless communication base station device, wireless communication mobile management device, wireless communication control method, and wireless communication system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To establish a substitutive communication path to UE, in the case that a band of a backhaul interval between a CSG base station and an MME/S-GW is occupied by another device and sufficient capacity can not be secured in the CSG base station, when the UE performs a handover to the CSG base station or when the UE starts or continues a service at the CSG base station. <P>SOLUTION: A band monitoring unit 134 uses a signal for estimating an available band to perform available band estimation of a backhaul interval between a present station and an MME/S-GW with a band monitoring unit in the MME/S-GW. An input unit 131 receives control information, based on the available band estimation, indicating a congestion status of the backhaul interval from the MME/S-GW and notifies an RRC control unit 133 of the control information. On the basis of the control information, reported from the input unit 131, indicating the congestion status of the backhaul interval, the RRC control unit 133 determines whether to perform a handover of UE to a neighboring cell. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a CSG cell radio communication base station apparatus, radio communication mobility management apparatus, radio communication control method, and radio communication system.

  The LTE / SAE (Long Term Evolution / System Architecture Evolution) system is a next generation mobile communication system that has evolved from the UMTS (Universal Mobile Telecommunications System), and aims to provide improved mobile communication services.

  In the LTE / SAE system, in addition to a macrocell wireless communication base station device (Evolved NodeB: eNB) having a large cell radius, which is mainly installed outdoors, a femtocell ( The installation of a small cell radio communication base station apparatus with a cell radius of about several tens of meters, called a “Femto Cell”, is being studied. A small cell radio communication base station apparatus studied by 3GPP (3rd Generation Partnership Project) is being considered to permit access only to a limited group member. Such a cell is called a closed subscriber group (CSG) cell.

  A radio communication terminal apparatus (User Equipment: UE) to which access is permitted is controlled from the network so as to preferentially connect to a radio communication base station apparatus (hereinafter simply referred to as a CSG base station) that forms a CSG cell. That is, when the UE enters the area of the CSG base station, it is controlled to preferentially connect to the CSG base station even if it can receive radio waves from the eNB.

  As an example of a handover control method between base stations in the 3GPP LTE / SAE system, FIG. 24 illustrates a UE handover control method from an eNB to a CSG base station.

  Usually, the UE in the active state measures the reception quality of the neighboring cell (for example, the CSG base station shown in FIG. 24) according to the setting (measurement control) related to the reception quality measurement of the neighboring cell from the connected eNB, The reception quality measurement result is notified (measurement report) to the eNB periodically or for each set event (step (hereinafter abbreviated as “ST”) 1, ST2).

  Here, it is assumed that the UE has moved near the boundary of the CSG cell. Then, the eNB that has received the reception quality measurement result of the CSG base station notified from the UE detects that the UE is in the vicinity of the boundary of the CSG cell, and determines the handover (Handover: HO) of the UE to the CSG base station. (ST3).

  Next, the eNB inquires of the CSG base station whether the UE may be handed over (HO request). When the CSG base station allows the UE handover, the CSG base station reserves a radio resource corresponding to the service provided to the UE in advance and performs reception control, and a signal that allows the eNB to perform the UE handover (HO). Ack) for the request is transmitted (ST4 to ST6).

  The eNB instructs the UE to move to the CSG base station (HO command), and the UE starts handover to the instructed CSG base station (ST7).

  When the UE establishes synchronization with the CSG base station and is assigned an uplink transmission opportunity from the CSG base station, the UE transmits a signal (HO confirm) indicating the completion of handover to the CSG base station (ST8 to 10). ).

  When the handover is completed, the CSG base station transmits a signal (HO complete) indicating the completion of the handover in the core network so as to switch the communication path established between the UE and the eNB to the CSG base station. It transmits to Mobility Management Entity (MME) (ST11).

  The MME that has received the signal indicating the completion of the handover makes a request (user plane update request) to a serving gateway (Serving Gateway: S-GW) located in the core network to switch the communication path for the UE to the CSG base station. (ST12).

  The S-GW switches the communication path for the UE to the CSG base station (ST13), and notifies the MME that the path switching has been completed (user plane update response) (ST14).

  Then, the MME notifies the CSG base station that the path switching has been completed (Ack for HO complete) (ST15).

  When the CSG base station is notified from the MME that the path switching for the UE is completed, the CSG base station notifies the eNB that the handover of the UE is completed, and requests the release of resources related to the UE (ST16).

  After confirming that all of the processes related to the UE have been completed, the eNB releases the resources related to the UE (ST17).

  As described above, a series of handover processes for the UE is completed, and the UE can continue to receive services via the CSG base station.

In the above-described handover control method, the case where an active UE that has already started communication is handed over from an eNB to a CSG base station has been described. Then, the standby state is continued.
3GPP TS 36.300v8.3.0 “3rd Generation Partnership Project; Technical Specification Group Radio Access Network, Evolved Universal Terrestrial Radio Access (E-UTRA) and Evolved Universal Terrestrial Radio Access Network (E-UTRAN), Overall description, Stage 2”, 2007 -12 3GPP TSG-RAN WG3 # 56 Tdoc R3-070780 “Network transport QoS for Home NodeBs (HNB)”, 2007-05

  However, when the UE is handed over to the CSG base station using the above-described handover control method, there are the following problems.

  Some CSG base stations may be installed in homes or small offices. FIG. 25 shows a system configuration when installed in a home. As shown in FIG. 25, in each home, it is assumed that in addition to the CSG base station, an IP phone, an IP-TV, and a plurality of personal computers share one Internet connection fixed network such as xDSL or FTTH. .

  In such a case, there are few UEs to be connected in the radio section between the CSG base station and the UE, and even when a sufficient capacity can be secured, the fixed section (xDSL section) between the CSG base station and the MME / S-GW. Alternatively, it may be considered that the FTTH section (backhaul section) occupies a band by another device and the CSG base station cannot secure a sufficient capacity.

  In such a situation, when the UE is handed over to the CSG base station even though the UE is instructed to connect to the CSG base station in preference to the eNB, data communication is performed via the CSG base station. It is conceivable that the necessary bandwidth (Quality of Service: QoS) cannot be secured. In addition, when the idle UE tries to start communication with the CSG base station or when the UE is communicating with the CSG base station, the QoS necessary for data communication may not be secured in the same manner. It is possible.

  The present invention has been made in view of such points, and when the UE hands over to the CSG base station and when the UE starts or continues the service at the CSG base station, the CSG base station and the MME / S-GW The CSG cell radio communication base station apparatus, which establishes an alternative communication path for the UE when the backhaul interval between them is occupied by other devices and a sufficient capacity cannot be secured in the CSG base station. An object of the present invention is to provide a communication mobility management device, a radio communication control method, and a radio communication system.

  The CSG cell radio communication base station apparatus of the present invention shows a band estimation means for estimating a band of a network between itself and a radio communication mobility management apparatus, and indicates a network congestion state based on the estimated band estimation result. It adopts a configuration comprising control information receiving means for receiving control information from the radio communication mobility management apparatus and handover means for determining whether or not to perform handover of the radio communication terminal apparatus based on the control information.

  The wireless communication control method of the present invention includes a bandwidth estimation step for performing bandwidth estimation of a network between a CSG cell wireless communication base station device and a wireless communication mobility management device, and a network congestion state based on the estimated bandwidth estimation result A control information receiving step for receiving control information indicating the radio communication terminal device from the radio communication mobility management device, and a handover step for determining whether or not to perform a handover of the radio communication terminal device based on the control information. .

  According to the present invention, when the UE hands over to the CSG base station and when the UE starts or continues service at the CSG base station, the backhaul section between the CSG base station and the MME / S-GW When the device is occupied with a band and sufficient capacity cannot be secured in the CSG base station, an alternative communication path can be established for the UE.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the following embodiments, description will be made based on a radio access technology standardized by 3GPP, such as GPRS (General Packet Radio Service), UMTS, LTE, and the like. However, the present invention is not limited to the wireless access technology standardized by 3GPP, and is not limited to WLAN (Wireless Local Area Network), IEEE802.16, IEEE802.16e, IEEE802.16m, etc. WiMAX (Worldwide Interoperability for Microwave Access), 3GPP2 The present invention may be applied to a wireless access technology such as

(Embodiment 1)
FIG. 1 is a diagram showing a configuration of a wireless communication system according to the present embodiment. The radio communication system illustrated in FIG. 1 includes a UE, an eNB 120, a CSG base station 130, and an MME / S-GW 140. Here, for simplicity of explanation, the MME and the S-GW are integrated. Moreover, eNB120, MME / S-GW140, and CSG base station 130 are mutually connected via the IP network.

  In addition, the eNB 120 and the CSG base station 130 are responsible for radio resource allocation and management, receive information transferred from the physical layer of the UE via the uplink (Uplink: UL), and downlink (DL). ) To transfer data to the UE. That is, the eNB 120 and the CSG base station 130 are responsible for the access point role of the radio access network for the UE.

  In addition, the MME / S-GW 140 performs signaling related to setting, modification, and release of a communication path with the eNB 120 or the CSG base station 130, and transfers user data to the eNB 120 or the CSG base station 130 according to the setting for each service. . Note that the MME / S-GW 140 forms a core network.

  FIG. 2 is a block diagram showing a configuration of MME / S-GW 140 shown in FIG.

  In FIG. 2, the input unit 141 outputs user data received from the external network, the eNB 120, and the CSG base station 130 to the user plane control unit 144. Further, the input unit 141 outputs a signal for estimating the available band received from the CSG base station 130 to the band monitoring unit 142. Further, the input unit 141 notifies the control plane control unit 143 of the control signal received from the eNB 120 or the CSG base station 130.

  The bandwidth monitoring unit 142 monitors the bandwidth of the backhaul section by estimating the bandwidth of the backhaul section between the local station and the CSG base station 130. Specifically, when the bandwidth monitoring unit 142 is notified of a bandwidth monitoring request from the control plane control unit 143 to be described later, the available bandwidth that can be communicated with the bandwidth monitoring unit 142 in the CSG base station 130 to be described later The available bandwidth is estimated to estimate how much there is. For example, the bandwidth monitoring unit 142 performs usable bandwidth estimation using Pathload which is a general usable bandwidth estimation tool. Then, the bandwidth monitoring unit 142 determines whether or not the estimated available bandwidth estimation result can satisfy the requested bandwidth (QoS) included in each of the handover request or the service start request, and the determination result is transmitted to the control plane control unit. 143 is notified. Here, the determination result when the available bandwidth estimation result does not satisfy the requested bandwidth (QoS) included in each request (congestion status in the backhaul section) is defined as “congested”. Further, the determination result (congestion status in the backhaul section) when the available bandwidth estimation result after being determined as 'congested' satisfies the requested bandwidth (QoS) included in each request is referred to as 'congestion elimination'.

  Here, Pathload used for available bandwidth estimation will be described. Pathload is a tool for estimating the available bandwidth of a link on a communication path (path) between transmitting and receiving terminals. Pathload reduces the effects of cross traffic by continuously transferring measurement packets called probe packets, and estimates the available bandwidth by using the increasing trend of one-way transfer delay between probe packets. Do. Here, the available estimated bandwidth is A, and the probe packet transmission rate is R. When an increasing tendency of the transfer delay is observed on the receiving side, R> A holds, and it can be predicted that the available bandwidth of the path is smaller than the transmission rate. On the other hand, when the increasing tendency of the transfer delay is not observed on the receiving side, it can be predicted that R ≦ A. From this result, the transmission rate of the probe packet used in the next trial is increased or decreased, and measurement is repeated until a predetermined estimation error range is satisfied, thereby estimating the available bandwidth.

  When the control plane control unit 143 extracts a handover request or a service start request for the UE from the control signal notified from the input unit 141, the control plane control unit 143 outputs a band monitoring request to the band monitoring unit 142. Further, the control plane control unit 143 receives a control signal (backhaul congestion indicator) indicating the congestion status (congestion or congestion elimination) in the backhaul section according to the band monitoring determination result input from the band monitoring unit 142. Output to the output unit 145.

  In addition, when there is at least one UE communicating with the CSG base station 130 and when the UE handover request and the service start request are rejected due to backhaul congestion, Periodically outputs a bandwidth monitoring request to the bandwidth monitoring unit 142. Then, the control plane control unit 143 outputs a control signal (backhaul congestion indicator) indicating the congestion status (congestion or congestion elimination) of the backhaul section to the eNB 120 or the CSG base station 130 to the output unit 145.

  In addition, when the available bandwidth estimation result does not satisfy the requested bandwidth (QoS), the control plane control unit 143 outputs a control signal that notifies the UE of rejection of the service start request to the output unit 145.

  The user plane control unit 144 adds appropriate header information to the user data input from the input unit 141 based on the control information set for each service, and sends the user data to which the header information is added to the output unit 145. Output.

  The output unit 145 outputs to the CSG base station 130 a signal for estimating the available bandwidth input from the bandwidth monitoring unit 142 and control information for notifying the congestion status of the backhaul section. Also, the output unit 145 sends the control signal input from the control plane control unit 143 and the user data input from the user plane control unit 144 to any of the external network, the eNB 120, and the CSG base station 130, respectively.

  Next, bandwidth monitoring processing in the MME / S-GW 140 will be described with reference to FIG. FIG. 3 is a flowchart illustrating monitoring of the available bandwidth in the backhaul section between the MME / S-GW 140 and the CSG base station 130 in the MME / S-GW 140.

  In ST601, when control plane control section 143 receives a handover request for the UE (ST601: Yes), band monitoring section 142 estimates the available bandwidth of the backhaul section between the own station and CSG base station 130 in ST602. I do. In ST603, bandwidth monitoring section 142 determines whether or not the available bandwidth estimation result satisfies the requested bandwidth (QoS) included in the handover request.

  When the available bandwidth estimation result does not satisfy the requested bandwidth (QoS) included in the handover request (ST603: No), in ST604, the control plane control unit 143 uses the control signal (back) indicating that the backhaul section is congested. The CSG base station 130 is notified of the hall congestion indicator (congestion)).

  On the other hand, when the control plane control unit 143 has not received a handover request for the UE (ST601: No), and when the control plane control unit 143 has received a service start request for the UE (ST605: Yes), a bandwidth monitoring unit 142, similarly to ST602, performs estimation of the available bandwidth of the backhaul section between the own station and the CSG base station 130 in ST606. When control plane control section 143 has not received a service start request for UE (ST605: No), it returns to ST601 again.

  In ST607, bandwidth monitoring section 142 determines whether or not the available bandwidth estimation result satisfies the requested bandwidth (QoS) included in the service start request. When the available bandwidth estimation result does not satisfy the requested bandwidth (QoS) included in the service start request (ST607: No), the control plane control unit 143 performs the above-described ST604.

  When the available bandwidth estimation result satisfies the requested bandwidth (QoS) included in the handover request (ST603: Yes), or when the available bandwidth estimation result satisfies the requested bandwidth (QoS) included in the service start request (ST607: Yes) In ST608, MME / S-GW 140 waits for processing until the timer expires. When the timer has expired (ST608: Yes), the bandwidth monitoring unit 142 in ST609 and ST610, in the same manner as ST602 and ST603 (ST606 and ST607), in the backhaul section between the own station and the CSG base station 130 Available bandwidth estimation is performed, and it is determined whether or not the available bandwidth estimation result satisfies a requested bandwidth (QoS) included in each request.

  When the available bandwidth estimation result does not satisfy the requested bandwidth (QoS) included in each request (ST610: No), the control plane control unit 143 performs the above-described ST604, and the request including the available bandwidth estimation result in each request. When the bandwidth (QoS) is satisfied (ST610: Yes), the process returns to ST608 again. That is, when a handover request or a service start request for the UE is received, the MME / S-GW 140 periodically monitors the bandwidth of the backhaul section at a constant time interval set by the reception timer.

  On the other hand, when a control signal indicating that the backhaul section is congested (backhaul congestion indicator (congestion)) is notified to the CSG base station 130 in ST604, in ST611, the MME / S-GW 140 performs ST608. As with, the process waits until the timer expires.

  When the timer expires (ST611: Yes), the bandwidth monitoring unit 142 estimates the available bandwidth of the backhaul section between the local station and the CSG base station 130 in ST612 as in ST609, and ST613 as in ST610. In step (1), it is determined whether or not the available bandwidth estimation result satisfies a requested bandwidth (QoS) included in each request.

  When the available bandwidth estimation result does not satisfy the requested bandwidth (QoS) included in each request (ST613: No), the control plane control unit 143 performs the above-described ST604. When the available bandwidth estimation result satisfies the requested bandwidth (QoS) included in each request (ST613: Yes), the control plane control unit 143, in ST614, indicates that the control signal indicating that congestion in the backhaul section has been resolved ( A backhaul congestion indicator (resolved)) is notified to the CSG base station 130. Thus, the MME / S-GW 140 periodically monitors the bandwidth of the backhaul section while the backhaul section is congested.

  The details of the bandwidth monitoring process have been described above.

  FIG. 4 is a block diagram showing a configuration of eNB 120 shown in FIG. In FIG. 4, input section 121 outputs a signal received from MME / S-GW 140 or UE to parameter section 122 and RRC control section 123.

  The parameter unit 122 manages various parameters related to the data path. Then, the parameter unit 122 sets the control information of the radio bearer corresponding to the service and the user data acquired from the MME / S-GW 140 in accordance with the parameter setting regarding the bearer included in the control signal notified from the MME / S-GW 140. The data is output to the RRC control unit 123 and the output unit 124.

  The RRC control unit 123 determines an RRC message notified from the UE, and outputs a service start request to the output unit 124 when a service start request is included. In addition, when the RRC message from the UE includes the neighbor cell reception quality measurement result, the RRC control unit 123 determines whether to perform handover to the neighbor cell. When a handover is necessary, the RRC control unit 123 outputs a handover request to the output unit 124. Furthermore, when the approval for the handover request is notified from the input unit 121, the RRC control unit 123 outputs a handover instruction for the UE to the output unit 124.

  The output unit 124 sends user data and control information input from the parameter unit 122 and control information input from the RRC control unit 123 to the UE, and transmits user data received from the UE to the MME / S-GW 140. Send it out.

  FIG. 5 is a block diagram showing a configuration of CSG base station 130 shown in FIG. In FIG. 5, the input unit 131 notifies the bandwidth monitoring unit 134 of a signal for estimating the available bandwidth received from the MME / S-GW 140. Further, the input unit 131 receives control information indicating the congestion status of the backhaul section based on the available bandwidth estimation from the MME / S-GW 140 and notifies the RRC control unit 133 of the control information.

  Similar to the parameter unit 122 of the eNB 120 (FIG. 4), the parameter unit 132 manages various parameters related to the data path. Then, the parameter unit 132 sets the control information of the radio bearer corresponding to the service and the user data acquired from the MME / S-GW 140 in accordance with the parameter setting regarding the bearer included in the control signal notified from the MME / S-GW 140. The data is output to the RRC control unit 133 and the output unit 135.

  When the control signal notified from the input unit 131 includes control information indicating the congestion status of the backhaul section, the RRC control unit 133 determines whether to perform the UE handover to the adjacent cell based on the control information. To decide. Then, the RRC control unit 133 outputs a handover request for the eNB 120 to the output unit 135 when a handover is necessary. Further, the RRC control unit 133 outputs a handover instruction for the UE to the output unit 135 when the eNB 120 has accepted the handover request.

  The bandwidth monitoring unit 134 uses the signal for estimating the available bandwidth input from the input unit 131, and the bandwidth monitoring unit 142 in the MME / S-GW 140 (FIG. 2) between itself and the MME / The available bandwidth of the backhaul section with the S-GW 140 is estimated.

  The output unit 135 outputs to the MME / S-GW 140 a signal for estimating the available bandwidth input from the bandwidth monitoring unit 134. In addition, the output unit 135 sends user data input from the parameter unit 132, control information, and control information input from the RRC control unit 133 to the UE, and receives user data received from the UE as MME / S- Send to GW 140.

  Next, a procedure for handover to the eNB 120 when the backhaul section between the CSG base station 130 and the MME / S-GW 140 is congested while the UE is communicating with the CSG base station 130 will be described with reference to FIG.

  In FIG. 6, in ST 101, the UE communicates with an external network via the CSG base station 130.

  In ST102, CSG base station 130 and MME / S-GW 140 perform available band estimation of the backhaul section between MME / S-GW 140 and CSG base station 130. And MME / S-GW140 determines whether the backhaul area between MME / S-GW140 and CSG base station 130 is congested. Specifically, the MME / S-GW 140 determines that the backhaul section is congested when the available bandwidth estimation result is smaller than the bandwidth (QoS) required for the service. In ST103, MME / S-GW 140 notifies CSG base station 130 that the backhaul section between MME / S-GW 140 and CSG base station 130 is congested (backhaul congestion indicator).

  In ST 104, CSG base station 130 that is notified that the backhaul section between itself and MME / S-GW 140 is congested determines the handover of the UE to eNB 120. In ST105, CSG base station 130 transmits a UE handover request (HO request) to eNB 120.

  In ST106, eNB 120 confirms whether or not a UE handed over from CSG base station 130 can be accepted. If it is acceptable, in ST107, the eNB 120 notifies the CSG base station 130 that preparation for accepting handover of the UE has been completed (Ack for HO request).

  Next, in ST108, the CSG base station 130 transmits a handover instruction (HO command) to cause the UE to be handed over to the eNB 120.

  In ST109, the UE instructed to perform handover from the CSG base station 130 to the eNB 120 disconnects the connection with the CSG base station 130, and newly establishes synchronization with the cell managed by the instructed eNB 120.

  In ST110, a signal (HO confirm) indicating that the handover is completed is transmitted from the UE to the eNB 120. In ST111, the eNB 120 transmits a signal (HO complete) including a path switching request for switching the communication path from the CSG base station 130 to the eNB 120 to the MME / S-GW 140.

  In ST112, MME / S-GW 140 that has received the signal including the path switching request switches the communication path to eNB 120, and transmits a signal indicating completion of path switching (Ack for HO complete) to eNB 120 in ST113. .

  In ST114, the UE communicates with an external network via the eNB 120.

  With the above processing, the procedure for the UE to handover to the eNB 120 is completed.

  In this way, the available band in the backhaul section between the CSG base station 130 and the MME / S-GW 140 is estimated, and the CSG base station 130 performs the UE handover based on the band estimation in the backhaul section. As a result, when there is not enough space for the required bandwidth (QoS) in the backhaul interval, that is, the backhaul interval between the CSG base station 130 and the MME / S-GW 140 provides bandwidth to other devices. Even when occupied and sufficient capacity cannot be secured for communication with the CSG base station 130, the required QoS can be obtained by handing over the UE in communication via the CSG base station 130 to an adjacent cell (here, the eNB 120). Data communication can be performed.

  Here, since the eNB 120 regards the CSG base station 130 as a handover destination having a high priority, if the reception quality report indicating the reception quality of the CSG base station 130 is received from the UE, the eNB 120 performs a handover to the CSG base station 130. . However, if the backhaul section between the CSG base station 130 and the MME / S-GW 140 occupies a band by another device and sufficient capacity cannot be secured in the CSG base station 130, the CSG base station 130 performs handover. The request cannot be accepted. Therefore, even if the eNB 120 performs handover of the UE to the CSG base station 130, the eNB 120 is rejected by the CSG base station 130, and thus performs unnecessary handover processing.

  Therefore, after transmitting a handover instruction to the UE, the CSG base station 130 further receives control information indicating the congestion status of the backhaul section from the MME / S-GW 140 (ST103 shown in FIG. 6), and receives the control information (back Whole load information) is transmitted to the eNB 120 (ST115 shown in FIG. 6). That is, when the UE is handed over from the CSG base station 130 to the eNB 120, the available band estimation (ST102 shown in FIG. 6) is periodically performed. For example, in ST115 shown in FIG. 6, the CSG base station 130 indicates the congestion status of the backhaul section between the CSG base station 130 and the MME / S-GW 140 with reliability such as SCTP (Stream Control Transmission Protocol). The eNB 120 is notified using a certain protocol.

  Then, when the eNB 120 receives a control signal (backhaul load information) indicating that the congestion situation in the backhaul section has been eliminated from the CSG base station 130, that is, the requested QoS for the UE to be handed over by the available bandwidth estimation result. Only when the condition is satisfied, handover of the UE to the CSG base station 130 is started (ST104 shown in FIG. 6). In other words, the CSG base station 130 sends a control signal indicating that the backhaul section is congested to the adjacent cell while the backhaul section is congested, that is, while the available bandwidth estimation result does not satisfy the required QoS. By transmitting to the UE, it is possible to reject a UE handover request from a neighboring cell.

  As described above, according to the present embodiment, the usable bandwidth estimation of the backhaul section between the CSG base station and the MME / S-GW is performed, and the CSG base station determines the UE based on the usable bandwidth estimation result. Decide whether to perform a handover. That is, when the available bandwidth estimation result does not satisfy the required QoS, the CSG base station performs handover to the eNB for the UE in the active state via the CSG base station. As a result, even when the backhaul section between the CSG base station and the MME / S-GW occupies a band by another device and sufficient capacity cannot be secured in the CSG base station, alternative communication to the UE A route can be established.

(Embodiment 2)
In the first embodiment, when the backhaul section between the CSG base station and the MME / S-GW is congested, in order not to perform useless handover processing, the eNB transmits control information indicating the congestion status to the CSG. Receive from the base station. However, a large number of CSG base stations are expected to overlap within the communication area of one eNB. Therefore, in one eNB, since a congestion state is notified from a plurality of CSG base stations, a large number of SCTP signaling connections and message processing amounts are required.

  Hereinafter, this embodiment will be specifically described.

  FIG. 7 is a block diagram showing a configuration of CSG base station 170 according to the present embodiment. However, in FIG. 7, the same reference numerals as those in FIG. 5 are given to portions common to FIG. 5, and detailed description thereof is omitted.

  The P-SS signal control unit 171 of the CSG base station 170 illustrated in FIG. 7 controls transmission of a synchronization signal (Primary Synchronization Signal: P-SS) for detecting transmission frame synchronization. Specifically, the P-SS signal control unit 171 indicates that the backhaul section between the local station and the MME / S-GW 140 is congested from the MME / S-GW 140 via the input unit 131. When the control signal is received, the transmission of the P-SS signal is stopped. In addition, the P-SS signal control unit 171 stops the transmission of the P-SS signal, and then the backhaul section between the local station and the MME / S-GW 140 from the MME / S-GW 140 via the input unit 131. When the signal indicating that the congestion is eliminated, the transmission of the P-SS signal is resumed.

  Next, the handover procedure in this embodiment will be described. FIG. 8 is a sequence diagram showing a handover procedure in the present embodiment. However, in FIG. 8, the same reference numerals as those in FIG. 6 are given to portions common to FIG. 6, and detailed description thereof is omitted.

  The CSG base station 170 that is notified that the backhaul section between itself and the MME / S-GW 140 is congested in ST103 shown in FIG. 8 determines the handover of the UE to the eNB 120 in ST104.

  Furthermore, in ST201, CSG base station 170 stops transmission of the P-SS signal.

  Then, in ST105, CSG base station 170 transmits a UE handover request to eNB 120, as in the first embodiment. The UE instructed to perform handover from the CSG base station 170 to the eNB 120 completes the handover to the eNB 120 by performing the same handover process (ST106 to 113) as in the first embodiment, and communicates via the eNB 120. Continue.

  Next, in ST202, UE in communication via eNB 120 performs control (measurement control) to report a reception quality report indicating a measurement result of reception quality of a neighboring cell (here, CSG base station 170) from eNB 120. Is done. Normally, the UE should detect the P-SS signal from the CSG base station 170 and report the reception quality report of the CSG base station 170. However, since the CSG base station 170 stops transmission of the P-SS signal in ST201 here, the UE cannot detect the P-SS signal from the CSG base station 170. Therefore, the UE cannot report a reception quality report regarding the CSG base station 170 to the eNB 120. Therefore, since the reception quality measurement result of the CSG base station 170 is not reported, the eNB 120 does not recognize the CSG base station 170 as a cell that can be handed over.

  Next, if it is notified that the congestion of the backhaul section between the own station and the MME / S-GW 140 has been resolved, the CSG base station 170 resumes transmission of the P-SS signal in ST203. Therefore, since the UE can detect the P-SS signal from the CSG base station 170, the UE reports the reception quality report of the CSG base station 170 to the eNB 120 (measurement report) in ST204. And in ST104, eNB120 determines the hand-over to CSG base station 170. FIG.

  As described above, in this embodiment, when the backhaul section between the CSG base station 170 and the MME / S-GW 140 is congested, the CSG base station 170 connects to the eNB 120 in the same manner as in the first embodiment. Perform UE handover. However, in Embodiment 1, after that, the CSG base station rejected the handover to the own station by notifying the eNB of a control signal indicating the congestion status of the backhaul section. On the other hand, in this embodiment, the CSG base station 170 stops transmission of the P-SS signal, and the UE cannot detect the P-SS signal of the own station, thereby rejecting the handover to the own station. . Thereby, even when a plurality of CSG base stations overlap in the communication area of the eNB, the handover of the UE to the CSG base station can be rejected without increasing the message processing amount in the eNB.

  Note that the UE that is in an active state via the CSG base station is already synchronized with the CSG base station and does not need to receive the P-SS signal. Therefore, a best-effort UE that does not require a QoS request already in communication at the CSG base station can continue to communicate via the CSG base station.

  Thus, according to the present embodiment, when the CSG base station is notified from the MME / S-GW that the backhaul section is congested, the CSG base station performs handover of the UE to the eNB, and P -Stop sending SS signals. As a result, the UE handed over to the eNB cannot synchronize with the CSG base station, and therefore, until the transmission of the P-SS signal is resumed, that is, until the congestion in the backhaul section is eliminated. Handover to the base station is not possible. Therefore, according to the present embodiment, an alternative communication path can be established for the UE without notifying the eNB of the congestion status of the backhaul section as in the first embodiment. Furthermore, in this Embodiment, since it is not necessary to notify the control information from a CSG base station to eNB, the processing load of eNB by control information notification can be reduced.

(Embodiment 3)
After the congestion in the backhaul section between the CSG base station and the MME / S-GW is resolved, UEs that have performed handover to the eNB while communicating with the external network via the CSG base station return to the CSG base station all at once. When trying to do so, there is a possibility that the load caused by the handover process of the network device such as eNB becomes high. Moreover, when UEs return to the CSG base station all at once, the backhaul section between the CSG base station and the MME / S-GW may be congested again, and handover to the eNB may repeatedly occur.

  Hereinafter, this embodiment will be specifically described.

  FIG. 9 is a block diagram showing a configuration of MME / S-GW 150 according to the present embodiment. FIG. 10 is a block diagram showing a configuration of CSG base station 180 according to the present embodiment. However, in FIGS. 9 and 10, the same reference numerals as those in FIGS. 2 and 7 are given to portions common to FIGS. 2 and 7, and detailed description thereof will be omitted.

  In the MME / S-GW 150 illustrated in FIG. 9, the count unit 151 of the control plane control unit 143 counts the number of UEs that may be handed over to the CSG base station 180 and stores the counted number of UEs. Specifically, when the counting unit 151 is notified from the bandwidth monitoring unit 142 that the backhaul section between the CSG base station 180 and the MME / S-GW 150 has been eliminated, the backhaul section is congested. After that, the sum of the number of UEs handed over from the CSG base station 180 to the eNB 120 and the number of UEs rejected from the eNB 120 to the CSG base station 180 is counted as the number of UEs that may be handed over to the CSG base station 180. To do.

  When notified from the bandwidth monitoring unit 142 that the congestion in the backhaul period has been resolved, the control plane control unit 143 stores the UE stored in the counting unit 151 together with a signal indicating that the congestion in the backhaul period has been resolved. The number is transmitted to the CSG base station 180 via the output unit 145.

  In the CSG base station 180 shown in FIG. 10, the parameter unit 132 sets the correspondence relationship between the number of UEs in the eNB that may be handed over to the CSG base station 180 and the transmission power of the P-SS signal (FIG. 11). Hold.

  The P-SS signal control unit 171 determines the number of UEs that are likely to be handed over to the own station from the MME / S-GW 150 via the input unit 131 together with control information indicating that congestion in the backhaul section has been resolved. Receive. Then, the P-SS signal control unit 171 controls the transmission power of the P-SS signal stepwise according to the number of UEs that may be handed over to the own station and the parameters set in the parameter unit 132.

  FIG. 11 shows a correspondence example between the number of UEs that may be handed over to the CSG base station 180 and the transmission power of the P-SS signal, held by the P-SS signal control unit 171 of the CSG base station 180. is there. In FIG. 11, the maximum transmission power of the P-SS signal is 100%. As shown in FIG. 11, the transmission power of the P-SS signal becomes smaller as the number of UEs that may be handed over to the CSG base station 180 increases. For example, when the number of UEs is 100 or more, the transmission power of the P-SS signal is 5%, and UEs that can receive the P-SS signal are limited to the vicinity of the center of the CSG base station 180. That is, the reach range of the P-SS signal is limited to the vicinity of the CSG base station 180. On the other hand, when the number of UEs is small from 0 to 9, the transmission power of the P-SS signal is 100% and is set to a predetermined maximum transmission power set in the CSG base station 180.

  That is, when the number of UEs that may be handed over to the CSG base station 180 is larger, the CSG base station 180 first transmits the P-SS signal so that the P-SS signal only reaches UEs near the cell center. To control. Then, the CSG base station 180 gradually increases the P-SS signal so that the P-SS signal reaches the entire cell as the number of UEs that may be handed over to the CSG base station 180 remaining in the eNB 120 decreases. To control the transmission power. In this way, the CSG base station 180 can perform handover of UEs that are likely to be handed over to its own station at different timings by controlling the transmission power of the P-SS signal in stages.

  Thus, according to this Embodiment, a CSG base station controls the transmission power of a P-SS signal in steps according to the number of UEs notified from MME / S-GW. Thereby, since the detection of the P-SS signal of the CSG base station depends on the position of the UE in the eNB, the timing of the handover to the CSG base station can be distributed. Therefore, according to this Embodiment, it can prevent UE returning to a CSG base station all at once after the congestion of the backhaul area between a CSG base station and MME / S-GW is eliminated. Furthermore, according to the present embodiment, it is possible to reduce the UEs from returning to the CSG base station all at once, so that the load caused by the handover process of the network device such as eNB or the handover to the eNB repeatedly occurs. This can be suppressed.

(Embodiment 4)
In the present embodiment, a case will be described in which a large number of UEs exist near the center of the CSG base station.

  In the third embodiment, the case has been described in which the transmission power of the P-SS signal is controlled stepwise according to the number of UEs that may be handed over to the CSG base station. However, when there are many UEs near the center of the CSG base station, there is a possibility that the UEs may return to the CSG base station all at once even though the transmission power of the P-SS signal is limited to the vicinity of the cell center. is there.

  Hereinafter, this embodiment will be specifically described.

  FIG. 12 is a block diagram showing a configuration of CSG base station 190 according to the present embodiment. However, in FIG. 12, the same reference numerals as those in FIG. 10 are given to portions common to FIG. 10, and detailed description thereof is omitted.

  In the CSG base station 190 shown in FIG. 12, when the position detection unit 191 of the RRC control unit 133 receives the reception quality report result from the UE, the UE that has transmitted the reception quality report from the reception quality report result It is detected how far away from the cell center.

  The count unit 192 of the RCC control unit 133 counts the number of UEs indicating that the location information of the UE detected by the location detection unit 191 exists near the CSG base station 190, that is, near the center of the CSG cell, Store the counted number of UEs.

  The RRC control unit 133 compares the number of UEs stored in the counting unit 192 with a predetermined threshold value. Then, when the counted number of UEs is greater than the threshold, the RRC control unit 133 transmits a handover request including a request for causing the UE to transmit a reception quality report stochastically to the eNB 120.

  Next, the handover procedure in this embodiment will be described. FIG. 13 is a sequence diagram illustrating a handover procedure when congestion in the backhaul section is resolved when there are a large number of UEs in the vicinity of the CSG base station 190. However, in FIG. 13, the same reference numerals as those in FIG. 8 are given to portions common to FIG. 8, and detailed description thereof is omitted.

  In FIG. 13, when the CSG base station 190 is notified from the MME / S-GW 150 that the backhaul section is congested in ST103, in ST201, the P-SS signal is transmitted in the same manner as in Embodiment 2. While stopping the transmission, a handover process to the eNB 120 of the UE that can no longer satisfy the QoS request existing in the CSG base station 190 is performed. At this time, when the number of UEs in the vicinity of the CSG base station stored in the counting unit 192 (FIG. 12) of the RRC control unit 133 is greater than a predetermined threshold, the CSG base station 190 makes a handover request to the eNB 120 in ST401. , The UE is also requested to transmit the reception quality report stochastically. Specifically, when the number of UEs in the vicinity of the CSG base station is greater than a predetermined threshold, the CSG base station 190 determines that the UE includes the CSG base station 190 in the counted reception quality report of the UE. On the other hand, a handover request (HO request (near center)) including information (near center) requesting that a reception quality report be transmitted stochastically is transmitted to the eNB 120.

  In ST402, the eNB 120 controls the UE so as to report the reception quality report of the CSG base station 190 stochastically to the UE notified from the CSG base station 190 and existing near the center of the CSG cell (major). Control (PF). As a control method, control similar to Probability Factor (PF: probability factor) used in MBMS Counting can be considered. For example, the UE reports the reception quality report of the CSG base station 190 to the eNB 120 in ST204 only when the random number generated inside the UE is larger than the probability factor.

  Thereby, only the UE that has generated a random number larger than the probability factor notifies the eNB 120 of the reception quality report of the CSG base station 190. Therefore, even when the number of UEs located in the vicinity of the CSG base station 190 is large, the number of UEs that perform handover can be limited by the probability factor. Therefore, the eNB can prevent the UEs located in the vicinity of the CSG base station 190 from being handed over to the CSG base station 190 all at once.

  Thus, according to the present embodiment, the CSG base station counts the number of UEs present in the vicinity of the CSG base station, and when the number of UEs is larger than the threshold, the probability factor is used for the UE. Request to report the reception quality report to the eNB. Thereby, even when many UE exists in the CSG base station vicinity, possibility that UE will return to a CSG base station all at once can be reduced. Therefore, according to this Embodiment, it can further suppress that the load resulting from the handover process of network devices, such as eNB, and the hand-over to eNB generate | occur | produce repeatedly.

  In the present embodiment, when the number of UEs present in the vicinity of the CSG base station is larger than a predetermined threshold, a handover request including a request for reporting a reception quality report using a probability factor to the UE is made. The case of sending was explained. However, in the present invention, when the CSG base station transmits a handover request to the eNB, the eNB 120 indicates information indicating the ease of return to the CSG base station according to the service and required bandwidth (QoS) received by the UE. You may make it notify in conjunction with. Moreover, you may make it eNB120 determine the hand-over to CSG base station of UE according to the service and required zone | band (QoS) which UE has received.

(Embodiment 5)
In the present embodiment, communication when UE in an idle state existing in a CSG cell transitions to an active state while the backhaul section between the CSG base station and the MME / S-GW is congested. A route establishment procedure will be described.

  In universities and corporate premises where a large number of CSG base stations are assumed to be installed, there may be a large number of idle UEs even if the number of active UEs is small. For example, many idle UEs may transition to the active state at the same time during a break. In such a case, each UE gives priority to a service start request to the MME / S-GW via the CSG base station, and when rejected from the CSG base station, the service to the MME / S-GW via the eNB Make a start request. Therefore, network resources may be wasted due to rejection of service start requests from a large number of UEs to the MME / S-GW via the CSG base station.

  Hereinafter, this embodiment will be specifically described.

  FIG. 14 is a block diagram showing a configuration of MME / S-GW 160 according to the present embodiment. FIG. 15 is a block diagram showing a configuration of CSG base station 200 according to the present embodiment. However, in FIGS. 14 and 15, the same reference numerals as those in FIGS. 2 and 7 are given to portions common to FIGS. 2 and 7, and the detailed description thereof is omitted.

  In the MME / S-GW 160 illustrated in FIG. 14, the state management unit 161 of the control plane control unit 143 is in the active state from the idle state while the backhaul section between the local station and the CSG base station 200 is congested. The number of UEs that have transitioned to is counted per unit time. That is, the state management unit manages the state transition rate from the idle state per unit time of the UE to the active state.

  The control plane control unit 143 compares the number of UEs counted by the state management unit 161 with a predetermined threshold value. Then, when the number of UEs counted is larger than the threshold, the control plane control unit 143 transmits the backhaul interval to all CSG base stations 200 sharing the same backhaul interval via the output unit 145. Instructing the UE to transmit the congestion status using system information (SI) of the CSG base station 200.

  In the CSG base station 200 shown in FIG. 15, the system information generation unit 201 of the RRC control unit 133 gives an instruction to transmit control information indicating the congestion status of the backhaul section to the UE from the MME / S-GW 160 (FIG. 14). When received, the control information indicating the congestion status of the backhaul section is transmitted using the system information.

  Next, in the present embodiment, the idle UE existing in the CSG cell enters the active state while the backhaul section between the CSG base station 200 and the MME / S-GW 160 is congested. A communication route establishment procedure in the case of transition will be described with reference to FIG. However, in FIG. 16, the same reference numerals as those in FIG.

  In FIG. 16, in ST501, the MME / S-GW 160 notifies the system information of the CSG base station 200 that the backhaul section is congested with respect to all the CSG base stations 200 sharing the same backhaul section. Control information (backhaul congestion indicator (SI)) including an instruction to be transmitted to the UE is transmitted.

  In ST502, the CSG base station 200 that has been notified that the backhaul section is congested, includes system information (system information (backhaul: congested)) that includes information indicating that the backhaul section is congested. To the UE. Moreover, UE detects that the backhaul area is congested from system information.

  Next, in ST503, an idle UE detects a service start request requiring QoS guarantee from the application layer.

  In ST504, since the UE recognizes that the backhaul section between the CSG base station 200 and the MME / S-GW 160 is congested, cell re-transmission from the CSG base station 200 to the eNB 120 remains in the idle state. Make a selection. The UE actually transitions to active in ST505, and performs a service start request process in ST506.

  In this way, the idle UE can grasp in advance the congestion status of the backhaul section. For this reason, when the UE transitions from the idle state to the active state, when the backhaul section between the CSG base station 200 and the MME / S-GW 160 is congested, the UE starts from the beginning via the eNB 120. A service start request to the MME / S-GW 160 can be made. That is, it is possible to prevent wasteful use of network resources such as connection to the CSG base station 200 every time each UE makes a transition from the idle state to the active state.

  As described above, according to the present embodiment, the MME / S-GW may provide the CSG base station with the UE according to the state transition rate from the idle state to the active state per unit time of the UE existing in the CSG cell. To notify the UE of the congestion status of the backhaul section. As a result, when a UE in an idle state requests a service that requires QoS guarantee and the backhaul section is congested, it transitions to active after performing cell reselection from the CSG base station to the eNB. To do. Therefore, according to the present embodiment, since the service start request to the MME / S-GW via the CSG base station 200 in which the backhaul section is congested is reduced, the consumption of useless network resources is reduced. be able to.

(Embodiment 6)
In Embodiments 1 to 4, the CSG base station controls movement from the outside of the CSG base station into the CSG base station by controlling transmission of the P-SS signal. For example, when the backhaul section between the CSG base station and the MME / S-GW is congested, the P-SS transmission is stopped to prevent new traffic from flowing into the CSG base station from the outside. . However, all users who are outside the CSG base station, for example, owners who purchase and install a CSG base station and pay for the access line and power supply are equally synchronized with the CSG base station. I can't. Therefore, in the present embodiment, the CSG base station uses a synchronization signal (Secondary Synchronization) for detecting radio frame synchronization instead of P-SS while the backhaul section with the MME / S-GW is congested. A case where transmission of (Signal: S-SS) is controlled will be described.

  Hereinafter, this embodiment will be specifically described.

  FIG. 17 is a block diagram showing a configuration of CSG base station 210 according to the present embodiment. However, in FIG. 17, the same reference numerals as those in FIG. 7 are given to portions common to FIG. 7, and detailed description thereof is omitted.

  In the CSG base station 210 illustrated in FIG. 17, the S-SS signal control unit 211 controls transmission of the S-SS signal. Specifically, the S-SS signal control unit 211 indicates that the backhaul section between the local station and the MME / S-GW 140 is congested from the MME / S-GW 140 via the input unit 131. When the control signal is received, the transmission of the S-SS signal is stopped. In addition, the S-SS signal control unit 211 stops the transmission of the S-SS signal, and then, from the MME / S-GW 140 via the input unit 131, the backhaul section between the own station and the MME / S-GW 140. When the signal indicating that the congestion is eliminated, the transmission of the S-SS signal is resumed.

  FIG. 18 shows a multiplexed configuration of P-SS and S-SS according to the present embodiment. As shown in FIG. 18, one radio frame having a length of 10 msec is composed of 10 subframes having a length of 1 msec, and the subframe is composed of two slots having a length of 0.5 msec. The synchronization signal is multiplexed in the first and eleventh slots. Furthermore, P-SS and S-SS are time-multiplexed to the seventh and sixth OFDM symbols in two slots, respectively.

  FIG. 19 is a flowchart showing a three-step cell search procedure in the present embodiment. Under the frame configuration as shown in FIG. 18, the UE detects the correlation between the P-SS replica signal and the received signal in the time domain, and thereby performs Fast Fourier Transform (FFT) window timing and synchronization. Signal symbol reception timing is detected.

  Next, the base station performs FFT processing on the S-SS using the detected synchronization signal symbol timing, extracts each subcarrier component, and detects the S-SS sequence multiplexed in the subcarrier direction. A cell ID group which is a unique physical layer ID is detected. Further, the radio frame timing is also detected at the same time by detecting S-SS. Here, the cell ID in the physical layer is synonymous with a cell-specific scramble code that is multiplied by a physical channel such as a reference signal (RS) in order to make peripheral cell interference noise.

  Note that the correlation probability of each code is subjected to in-phase addition averaging over a plurality of radio frames, thereby increasing the radio frame timing and the detection probability of the cell ID group.

  Further, the UE performs RS replica correlation detection. The RS is multiplied by a different scramble code for each sector, and the scramble code multiplied by the RS is specified by replica correlation detection. If the scramble code is specified, the sector index is determined, and the cell ID can be finally specified together with the detected cell ID group.

  Next, the handover procedure in this embodiment will be described. Here, a case will be described in which a special user such as the owner of the CSG base station 210 is handed over to the CSG base station 210 when the backhaul section of the CSG base station 210 is congested. FIG. 20 is a sequence diagram showing a handover procedure in the present embodiment. However, in FIG. 20, the same reference numerals as those in FIG. 8 are given to portions common to FIG. 8, and detailed description thereof will be omitted.

  In ST601, it is assumed that confirmation regarding the scramble code (physical layer cell ID) to be used has already been obtained between the CSG base station 210 and, for example, the special UE that is the owner.

  When the CME base station 210 is notified from the MME / S-GW 150 that the backhaul section is congested in ST103, the CSG base station 210 stops transmitting the S-SS signal in ST602.

  In ST603, two UEs 100 and 110 camping on or connected to eNB 120 attempt to detect CSG base station 210 by cell search. The UE 100 that does not know the scramble code used in the CSG base station 210 tries to detect the scramble code by the S-SS when detecting the P-SS, but the CSG base station 210 has stopped transmitting the S-SS. Therefore, the UE 100 cannot know the scramble code used in the CSG base station 210 and cannot perform handover to the CSG base station 210.

  On the other hand, the UE 110 that knows the predetermined scramble code used in the CSG base station 210 tries to detect the scramble code by the S-SS in the same manner as detecting the P-SS. When the UE 110 cannot detect the S-SS, the UE 110 performs channel estimation of the reference signal RS transmitted by the CSG base station 210 using a known scramble code.

  When the CSG base station 210 is a base station accessible by the UE 110, channel estimation is performed correctly, the received power of the downlink transmission signal of the CSG base station 210 exceeds a predetermined threshold, and the UE 110 outputs a measurement report in ST204. Send it out. Thereafter, a predetermined handover process (ST104 to ST113) is performed, and the UE 110 can be handed over to the CSG base station 210.

  Thus, according to this Embodiment, a CSG base station stops transmission of an S-SS signal, while the backhaul area between MME / S-GW is congested. As a result, a specific UE that knows the predetermined scramble code used in the CSG base station performs channel estimation of the reference signal RS transmitted by the CSG base station using the known scramble code, and the CSG base station Is a base station accessible by the UE, channel estimation is performed correctly, the received power of the downlink transmission signal of the CSG base station exceeds a predetermined threshold, and the UE can be handed over to the CSG base station.

  In this embodiment, in ST103 of FIG. 20, when it is notified that the backhaul section between the CSG base station and the MME / S-GW is congested, the CSG base station transmits the S-SS. Explained the case of stopping. However, in the present invention, a maximum number of users that can be accommodated is set in the CSG base station, and when the maximum number of users that can be accommodated is exceeded, the CSG base station is S-SS. Transmission may be stopped.

  In addition, in this Embodiment, although the CSG base station demonstrated the case where transmission of S-SS was stopped while the backhaul area between MME / S-GW was congested, in this invention, Instead of stopping S-SS transmission, a predetermined S-SS sequence may be transmitted. In that case, the predetermined S-SS sequence is confirmed in advance between the CSG base station and the UE, and when the UE detects the predetermined S-SS sequence, the UE derives a scramble code corresponding to the sequence. Similarly, after performing channel estimation of the reference signal RS transmitted by the CSG base station, control is performed so as to be handed over to the CSG base station.

(Embodiment 7)
In order to reduce the power consumption of the CSG base station and interference with neighboring cells, the transmission power of the downlink signal of the CSG base station is suppressed or the transmission is completely stopped during a period when there is no user who can access the CSG base station. It is possible. However, if the transmission of the CSG base station is simply stopped, when the user approaches the CSG base station, the user cannot be aware of the presence of the CSG base station, and preferential camp-on to the CSG base station or Handover cannot be provided. Therefore, in the present embodiment, a case will be described in which the CSG base station transmits S-SS sequences with a predetermined interval.

  Hereinafter, this embodiment will be specifically described.

  FIG. 21 is a block diagram showing a configuration of CSG base station 210 according to the present embodiment. However, in FIG. 21, the same reference numerals as those in FIG. 17 are given to portions common to FIG. 17, and detailed description thereof is omitted.

  In the CSG base station 210 shown in FIG. 21, the RRC control unit 213 has that there is no UE that starts an RRC connection for a predetermined period, for example, at least twice the periodical location registration area update (Periodic Tracking Area Update) time. Is detected, the wireless transmission signal suppression request is output to the S-SS signal control unit 211 and the output unit 214.

  The S-SS signal control unit 211 further includes an interval control unit 212, and controls the transmission interval of the S-SS signal. Specifically, when the interval control unit 212 receives a wireless transmission signal suppression request from the RRC control unit 213, the interval control unit 212 transmits an S-SS signal with a predetermined interval. The predetermined S-SS transmission interval is assumed to be confirmed in advance between the CSG base station and the UE. In addition, after changing the transmission interval of the S-SS signal, the interval control unit 212 receives a signal indicating that an accessible UE exists in the vicinity from the MME / S-GW 150 via the input unit 131 The S-SS signal transmission interval is restored.

  When acquiring the radio transmission signal suppression request from the RRC control unit 213, the output unit 214 stops transmission of all radio signals other than the P / S-SS signal. In addition, the output unit 214 confirms that there is an accessible UE near the MME / S-GW 150 via the input unit 131 after stopping transmission of all radio signals other than the P / S-SS signal. When the signal shown is received, transmission of all radio signals is resumed.

  FIG. 22 shows a multiplexed configuration of P-SS and S-SS according to the present embodiment. As shown in the system frame number (SFN) = 3 in FIG. 22, the normal P-SS and S-SS are the first and eleventh slots in one radio frame having a length of 10 msec. Multiplexed at the rear end. In the present embodiment, a CSG base station that has detected that there is no UE that starts an RRC connection for a predetermined time or longer transmits an S-SS signal with a predetermined interval. For example, S-SS is not transmitted in the 11th slot of SFN = 0, the 1st slot of SFN = 1 (shown in FIG. 22), and the 1st and 11th slots of SFN = 2.

  Next, a handover procedure to the CSG base station in this embodiment will be described. Here, a case will be described in which a user who can access the CSG base station 210 is handed over to the CSG base station 210 when the CSG base station 210 stops transmitting all radio signals other than P / S-SS. FIG. 23 is a sequence diagram showing a handover procedure in the present embodiment. However, in FIG. 23, the same reference numerals as those in FIG. 20 are given to portions common to FIG. 20, and detailed description thereof will be omitted.

  In ST701, the confirmation regarding the transmission interval of the S-SS signal transmitted when there is no user accessible to the CSG base station between the CSG base station 210 and the UE 110 accessible to the CSG base station 210 has already been confirmed. It shall be taken.

  If the CSG base station 210 detects that there is no UE that starts an RRC connection for a predetermined period in ST702, the CSG base station 210 transmits an S-SS signal at a predetermined interval in ST703, and all other than the P / S-SS signal. Stops transmission of wireless signals.

  In ST704, two UEs 100 and 110 that are camping on or connected to eNB 120 start a cell search. The UE 100 that does not know the S-SS transmission interval of the CSG base station 210 does not know the next S-SS transmission timing even if it detects the S-SS once. 210 cannot be detected.

  On the other hand, once UE 110 that knows the S-SS transmission interval of CSG base station 210 detects P / S-SS, it does not take the correlation of the synchronization channel until the next P / S-SS is transmitted. Therefore, synchronization with the CSG base station 210 can be established as if P / S-SS is continuously transmitted, and the CSG base station 210 can be correctly detected.

  In ST705, UE 110 that has detected CSG base station 210 transmits a radio transmission request to MME / S-GW 150 so that CSG base station 210 transmits all radio signals as usual. This wireless transmission request includes an identifier CSG-ID indicating the CSG base station 210.

  The MME / S-GW 150 that has received the wireless transmission request determines whether or not the UE 110 that has transmitted the request can access the CSG base station 210. If it is determined that access is possible, in ST706, a CRS base station 210 is transmitted with a radio transmission request that requests all radio signals to be transmitted.

  In ST707, the CSG base station 210 restores the S-SS transmission interval and restarts transmission of all radio signals.

  After CSG base station 210 returns to normal operation, the received power of the downlink transmission signal of CSG base station 210 of UE 110 exceeds a predetermined threshold, and UE 110 transmits a measurement report in ST204. Thereafter, a predetermined handover process (ST104 to ST113) is performed, and the UE 110 can be handed over to the CSG base station 210.

  Thus, according to the present embodiment, the CSG base station transmits an S-SS sequence at a predetermined interval during a period when there is no accessible user, and the UE that can access the CSG base station is The CSG base station is detected using a known S-SS transmission interval. As a result, only a specific UE that knows the S-SS transmission interval of the CSG base station can provide an opportunity for the CSG base station to return to normal operation, while reducing the transmission power of the CSG base station as much as possible. , The UE can be handed over to the CSG base station.

  The embodiments of the present invention have been described above.

  Although cases have been described with the above embodiment as examples where the present invention is configured by hardware, the present invention can also be realized by software.

  Each functional block used in the description of each of the above embodiments is typically realized as an LSI which is an integrated circuit. These may be individually made into one chip, or may be made into one chip so as to include a part or all of them. The name used here is LSI, but it may also be called IC, system LSI, super LSI, or ultra LSI depending on the degree of integration.

  Further, the method of circuit integration is not limited to LSI's, and implementation using dedicated circuitry or general purpose processors is also possible. An FPGA (Field Programmable Gate Array) that can be programmed after manufacturing the LSI, or a reconfigurable processor that can reconfigure the connection and setting of circuit cells inside the LSI may be used.

  Further, if integrated circuit technology comes out to replace LSI's as a result of the advancement of semiconductor technology or a derivative other technology, it is naturally also possible to carry out function block integration using this technology. Biotechnology can be applied.

  In the present invention, when a UE is handed over from an SFN area to a non-SFN area, it is possible to reduce the interruption time of a service being received by the UE while suppressing the consumption of radio resources in the SFN area, and to provide an MBMS transmission. Applicable to control system.

The figure which shows the structure of the radio | wireless communications system which concerns on Embodiment 1 of this invention. The block diagram which shows the structure of MME / S-GW concerning Embodiment 1 of this invention. The flowchart figure which shows the usable bandwidth monitoring of the backhaul area which concerns on Embodiment 1 of this invention. The block diagram which shows the structure of eNB which concerns on Embodiment 1 of this invention. The block diagram which shows the structure of the CSG base station which concerns on Embodiment 1 of this invention. The sequence diagram which shows the hand-over procedure from the CSG base station to eNB which concerns on Embodiment 1 of this invention The block diagram which shows the structure of the CSG base station which concerns on Embodiment 2 of this invention. The sequence diagram which shows the hand-over procedure from CSG base station to eNB which concerns on Embodiment 2 of this invention The block diagram which shows the structure of MME / S-GW concerning Embodiment 3 of this invention. The block diagram which shows the structure of the CSG base station which concerns on Embodiment 3 of this invention. The figure which shows the example of a response | compatibility with the number of UEs in eNB which may be handed over to the CSG base station which concerns on Embodiment 3 of this invention, and the transmission power of a P-SS signal The block diagram which shows the structure of the CSG base station which concerns on Embodiment 4 of this invention. The sequence diagram which shows the hand-over procedure from the CSG base station to eNB which concerns on Embodiment 4 of this invention The block diagram which shows the structure of MME / S-GW concerning Embodiment 5 of this invention. The block diagram which shows the structure of the CSG base station which concerns on Embodiment 5 of this invention. The sequence diagram which shows the communication path establishment procedure of idle state UE which concerns on Embodiment 5 of this invention The block diagram which shows the structure of the CSG base station which concerns on Embodiment 6 of this invention. The figure which shows the multiplexing structure of the synchronizing signal which concerns on Embodiment 6 of this invention. The flowchart which shows the procedure of the three-step cell search which concerns on Embodiment 6 of this invention. The sequence diagram which shows the hand-over procedure from eNB which concerns on Embodiment 6 of this invention to a CSG base station The block diagram which shows the structure of the CSG base station which concerns on Embodiment 7 of this invention. The figure which shows the multiplexing structure of the synchronizing signal which concerns on Embodiment 7 of this invention. The sequence diagram which shows the hand-over procedure from eNB which concerns on Embodiment 7 of this invention to a CSG base station Sequence diagram showing a conventional handover control procedure between base stations The figure which shows the structure of a radio | wireless communications system

Explanation of symbols

120 eNB
121, 131, 141 Input unit 122, 132 Parameter unit 123, 133 RRC control unit 124, 135, 145 Output unit 130, 170, 180, 190, 200 CSG base station 140, 150, 160 MME / S-GW
134, 142 Band monitoring unit 143 Control plane control unit 144 User plane control unit 151, 192 Count unit 161 State management unit 171 P-SS signal control unit 191 Position detection unit 201 System information generation unit

Claims (16)

Bandwidth estimation means for performing network bandwidth estimation between the device itself and the wireless communication mobility management device;
Control information receiving means for receiving control information indicating network congestion based on the estimated bandwidth estimation result from the wireless communication mobility management device;
Handover means for determining whether or not to perform handover of the radio communication terminal apparatus based on the control information;
A CSG cell radio communication base station apparatus comprising: The handover means, when determining handover of the radio communication terminal apparatus, transmits a handover instruction to the radio communication terminal apparatus;
The control information receiving means, after transmitting the handover instruction to the radio communication terminal apparatus, further receives the control information from the radio communication mobility management apparatus, and transmits the control information to a macro cell radio communication base station apparatus.
The CSG cell radio communication base station apparatus according to claim 1. A synchronization signal control means for controlling transmission of the synchronization signal;
The synchronization signal control means stops transmission of the synchronization signal when the control information indicating that the network is congested is received from the wireless communication mobility management device.
The CSG cell radio communication base station apparatus according to claim 1. The synchronization signal control means, after stopping the transmission of the synchronization signal, when receiving the control information indicating that network congestion has been resolved from the wireless communication mobility management device, restarts the transmission of the synchronization signal;
The CSG cell radio communication base station apparatus according to claim 3. When the synchronization signal control means receives the control information indicating that network congestion has been resolved after stopping the transmission of the synchronization signal from the wireless communication mobility management device, the synchronization signal control means gradually increases the transmission power of the synchronization signal. To control,
The CSG cell radio communication base station apparatus according to claim 3. The synchronization signal control means controls the transmission power of the synchronization signal stepwise according to the number of radio communication terminal devices that may be handed over to the own station.
The CSG cell radio communication base station apparatus according to claim 5. The synchronization signal control means reduces the transmission power as the number of radio communication terminal devices that may be handed over to the own station increases.
The CSG cell radio communication base station apparatus according to claim 6. Position detecting means for detecting the position of the wireless communication terminal device in its own cell;
Counting means for counting the number of wireless communication terminal devices in which the detected position is in the vicinity of the own device; and
When the number of counted wireless communication terminal devices is greater than a threshold, the handover means sends a handover request to the macro cell wireless communication, including a request to cause the wireless communication terminal device to perform a quality measurement report using a probability factor. Send to base station equipment,
The CSG cell radio communication base station apparatus according to claim 1. The control information receiving means wirelessly transmits the control information using system information when the control information is received from the wireless communication mobility management device, including an instruction to transmit the control information to the wireless communication terminal device in an idle state. Send to communication terminal device,
The CSG cell radio communication base station apparatus according to claim 1. The synchronization signal control means stops transmission of a P-SS signal or an S-SS signal when the control information indicating that the network is congested is received from the wireless communication mobility management device.
The CSG cell radio communication base station apparatus according to claim 3. A synchronization signal control means for controlling transmission of the synchronization signal;
The synchronization signal control means controls the transmission interval of the S-SS signal when there is no accessible wireless communication terminal device for a predetermined period.
The CSG cell radio communication base station apparatus according to claim 1. Bandwidth estimation means for performing bandwidth estimation of the network between the own device and the CSG cell radio communication base station device;
Control information transmitting means for transmitting control information indicating network congestion based on the estimated bandwidth estimation result to the CSG cell radio communication base station device;
A wireless communication mobility management apparatus comprising: A counting means for counting the number of radio communication terminal devices that may be handed over to the CSG cell radio communication base station device,
The control information transmitting means transmits the counted number of the wireless communication terminal devices together with the control information to the CSG cell wireless communication base station device.
The wireless communication mobility management device according to claim 12. Counting means for counting the number of wireless communication terminal devices that have transitioned from the idle state to the active state;
An instruction means for instructing the CSG cell radio communication base station apparatus to transmit the control information to an idle radio communication terminal apparatus when the counted number of radio communication terminal apparatuses is greater than a threshold; , Further comprising
The wireless communication mobility management device according to claim 12. A bandwidth estimation step for performing bandwidth estimation of a network between the CSG cell radio communication base station device and the radio communication mobility management device;
A control information receiving step for receiving control information indicating network congestion based on the estimated bandwidth estimation result from the wireless communication mobility management device;
A handover step for determining whether or not to perform handover of the wireless communication terminal device based on the control information;
A wireless communication control method comprising: Bandwidth estimation means for performing bandwidth estimation of the network between the own device and the CSG cell radio communication base station device;
Control information transmitting means for transmitting control information indicating network congestion based on the estimated bandwidth estimation result to the CSG cell radio communication base station device;
A wireless communication mobility management device comprising:
Control information receiving means for receiving the control information from the wireless communication mobility management device;
Handover means for determining whether or not to perform handover of the radio communication terminal apparatus based on the control information;
A CSG cell radio communication base station apparatus comprising:
A wireless communication system composed of:

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