JP6481711B2 - Wireless communication system, mobile station, base station, and wireless communication method - Google Patents

Description

  The present invention relates to a radio communication system, a mobile station, a base station, and a radio communication method.

  Conventionally, various devices have been devised to increase the transmission capacity (hereinafter sometimes referred to as “system capacity”) in a wireless communication system. For example, in 3GPP LTE (3rd Generation Partnership Project Radio Access Network Long Term Evolution), there is a discussion about a technique for increasing a system capacity by utilizing a “small cell (small cell)” in addition to a “macro cell”. Here, the “cell” is a term indicating a range covered by the radio base station in order for the radio terminal to transmit and receive radio signals. However, since the radio base station and the cell correspond to each other, In the description of “cell”, “cell” and “radio base station” may be appropriately replaced. The “macro cell” is a cell of a base station that can transmit with high transmission power, that is, a base station with a large range area. A “small cell” is a cell of a base station that transmits with low transmission power, that is, a base station with a small range area.

  In 3GPP LTE, as a configuration of a mobile communication system, for example, a configuration in which a plurality of small cells are included in a macro cell is being studied. And the technique in which a mobile station connects to a macro cell and a small cell simultaneously is examined. In addition, a technique in which a mobile station is simultaneously connected to two different small cells has been studied. As described above, communication in which a mobile station connects to both two different cells to perform communication may be referred to as dual connection. In addition, as the two-way connection, the base station may connect directly to a higher layer device. However, two-way connection is not limited to this configuration. In general, a terminal connects to a plurality of base stations and communicates with each other at the same time to transmit or receive different information simultaneously with each base station. Is. In the description here, a two-way connection is described, but the same discussion can be made for a three-way or more multiple connection. For this reason, the two-way connection in the following description may be considered as a concept including a multiple connection, or the two-way connection may be read as a multiple connection.

  When a mobile station is connected to a macro cell and a small cell at the same time, for example, a control plane that is a call for transmitting L3 control information for setting a transmission path for transmitting data and controlling a handover is connected to the macro cell. Is done. A data plane that is a call for transmitting and receiving data is connected to a small cell. Here, the control plane is also called C-plane or SRB (Signaling Radio Bearer). The data plane is also called a user plane, U-plane, DRB (Data Radio Bearer), or the like.

  In the case where the mobile station is connected to two different small cells at the same time, for example, the control plane is connected to one small cell and the data plane is connected to the other small cell. A configuration connected to a station is also conceivable. As described above, the two-way connection generally means that a terminal connects to a plurality of base stations and performs communication at the same time, thereby transmitting or receiving different information simultaneously with each base station.

  As described above, in the two-way connection, the radio base station to which the control plane is connected may be referred to as a primary radio base station (cell). In addition, a radio base station (cell) to which a data plane that performs data communication in cooperation with the primary radio base station (cell) is connected may be referred to as a secondary radio base station. Each of them may be called an anchor radio base station (cell) or an assisting radio base station (cell). Furthermore, each may be referred to as a master radio base station (cell) and a slave radio base station (cell). Here, in the case of two-way connection, in order to improve communication characteristics, when the wireless communication terminal has the ability to receive data from two wireless base stations, data is wirelessly communicated from both the primary and secondary wireless base stations. It can also be configured to be output to the terminal. However, the way of calling each radio base station is not limited to that described here. In general, if the radio base station that communicates with both the control plane and the data plane connected as in the conventional LTE communication system is the main base station, various names are used without departing from this intention. be able to. In the following, for simplicity, the terms “primary” and “secondary” are used.

  Various configurations have been proposed as the configuration of two-way connection depending on which layer the data plane is separated from.

  For example, there is a configuration in which the data plane is separated before the PDCP (Packet Data Convergence Protocol) layer. For example, there is a configuration in which a data plane is separated between a PDCP layer and an RLC (Radio Link Control) layer. For example, there is a configuration in which a data plane is separated between an RLC layer and a MAC (Medium Access Control) layer. Not only this but the structure isolate | separated within a layer can also be taken. For example, there may be a configuration in which a part of the functions of the PDCP layer is performed by the primary base station, and the remaining functions of the PDCP layer are performed by the secondary base station. The same applies to the RLC layer and the MAC layer.

  In the case of a two-way connection configuration, the primary wireless communication station and the secondary wireless base station are connected by a wired or wireless link. Then, after separating the data plane, the data is sent to the secondary radio base station via a link connecting the primary radio base station and the secondary radio base station.

3GPP TR 36.932 V12.1.0 (2013-03), 3rd Generation Partnership Project; Technical Specification Group Radio Access Network; Scenarios and requirements for small cell enhancements for E-UTRA and E-UTRAN (Release 12)

  However, in the two-way connection, the secondary wireless base station acquires and transmits the amount of data that the MAC layer can transmit from the RLC layer based on the transmitted data amount notified from the PHY (Physical) layer. Can be considered. Alternatively, it is conceivable that the MAC layer acquires and transmits data having a data amount that can be transmitted from the RLC layer based on data that can be transmitted according to the radio quality notified from the PHY layer. In this case, after the PDCP layer acquires the retention amount of the RLC layer data, the PDCP layer sends the amount of data corresponding to the acquired retention amount to the RLC layer. In this configuration, the PDCP layer acquires the RLC layer data retention amount via the link connecting the primary radio base station and the secondary radio base station. However, it is conceivable that the link connecting the primary radio base station and the secondary radio base station does not have high communication quality. In this case, there is a possibility that the acquisition of the data retention amount in the RLC layer by the PDCP layer may be delayed. In that case, the amount of data transmitted from the PDCP layer may not be properly controlled, and data delivery from the PDCP layer may be delayed. In addition, since the latest state cannot be reflected in the data retention amount of the RLC layer, the data is delivered from the PDCP layer to the RLC layer exceeding the amount of data that can be accommodated (bufferable) in the RLC layer, and therefore the data is discarded. May also occur.

  The disclosed technology has been made in view of the above, and an object thereof is to provide a wireless communication system, a mobile station, a base station, and a wireless communication method that improve the efficiency of communication between wireless communication stations.

  In one aspect, a wireless communication system, a mobile station, a base station, and a wireless communication method disclosed in the present application are such that a first wireless communication device operates in association with a first logical processing entity and the first logical processing entity. And a first communication unit that communicates with the second wireless communication device in a multiple manner, and a notification unit that notifies the second wireless communication device of data related information. The second wireless communication device includes a second communication unit that transmits data, and a control unit that controls the amount of data transmitted by the second communication unit by receiving the data related information from the notification unit. .

  According to one aspect of the wireless communication system, the mobile station, the base station, and the wireless communication method disclosed in the present application, it is possible to improve the efficiency of communication between the wireless communication stations.

FIG. 1 is a block diagram of a wireless communication system according to the first embodiment. FIG. 2 is a conceptual diagram summarizing various configurations of the wireless communication system. FIG. 3 is a schematic diagram of two-way connection in the wireless communication system according to the second embodiment. FIG. 4 is a block diagram of a wireless communication system according to the second embodiment. FIG. 5 is a diagram illustrating transmission / reception of user data executed using each link layer in the wireless communication system according to the first embodiment. FIG. 6 is a diagram for explaining the flow of user data to which numbers are regularly added. FIG. 7A is a diagram illustrating an example of a PDCP Status Report for a 12-bit sequence number. FIG. 7B is a diagram illustrating an example of PDCP Status Report for a 15-bit sequence number. FIG. 7C is a diagram illustrating an example of a PDCP Status Report for a 7-bit sequence number. FIG. 8 is a diagram illustrating information stored in the PDU Type. FIG. 9 is a sequence diagram for explaining the overall flow of data delivery amount control. FIG. 10 is a flowchart of control of the delivery amount of user data to the small base station in the communication system according to the second embodiment. FIG. 11A is a diagram for explaining transmission of user data at the time of two-way connection in a conventional communication system. FIG. 11B is a diagram for explaining transmission of user data at the time of two-way connection in the communication system according to the second embodiment. FIG. 12 is a hardware configuration diagram of the base station. FIG. 13 is a hardware configuration diagram of the mobile station. FIG. 14 is a schematic diagram of dual connection of a wireless communication system according to a modification of the second embodiment. FIG. 15 is a diagram illustrating transmission / reception of user data performed using each link layer in the wireless communication system according to the third embodiment. FIG. 16 is a diagram illustrating transmission / reception of user data performed using each link layer in the wireless communication system according to the fourth embodiment. FIG. 17 is a diagram illustrating transmission / reception of user data executed using each link layer in the wireless communication system according to the fifth embodiment. FIG. 18 is a diagram illustrating an example of a format of a transmission packet. FIG. 19 is a diagram illustrating a format of RLC Status Report. FIG. 20 is a diagram showing contents corresponding to values stored in the CPT. FIG. 21 is a diagram for explaining an example of a method for calculating the data retention amount. FIG. 22 is a sequence diagram for explaining the overall flow of transmission of RLC Status Report in the wireless communication apparatus according to the fifth embodiment.

  Embodiments of a wireless communication system, a mobile station, a base station, and a wireless communication method disclosed in the present application will be described below in detail with reference to the drawings. The wireless communication system, the mobile station, the base station, and the wireless communication method disclosed in the present application are not limited by the following embodiments.

  First, a method for realizing two-way connection will be briefly described. The carrier aggregation (CA) that is a technology defined in the conventional LTE system will be examined. Carrier aggregation realizes high-speed and large-capacity communication by using a plurality of component carriers (CC: Component Carrier) or cells that are frequency bands used for communication between a radio base station and a radio terminal. . The bandwidth supported by the LTE system is limited to a maximum of 20 MHz, but with the introduction of carrier aggregation, for example, a bandwidth of 40 MHz can be used by bundling two 20 MHz CCs.

  In the carrier aggregation framework, for example, a macro cell uses one CC and a small cell uses another CC, so that it seems that dual connection can be realized. However, it is considered difficult to realize a two-way connection based on carrier aggregation for the following reasons.

  Here, carrier aggregation is considered from the viewpoint of a protocol stack in the LTE system. The protocol stack of the LTE system includes a PHY layer, a MAC layer, an RLC layer, and a PDCP layer in order from the lower layer (there are further higher layers, but are omitted here). When corresponding to a commonly used OSI (Open Systems Interconnection) reference model, the PHY layer in the LTE system corresponds to the physical layer which is the first layer of the OSI reference model. The MAC layer, RLC layer, and PDCP layer in the LTE system correspond to the data link layer that is the second layer of the OSI reference model. The MAC layer is responsible for the scheduler function, the RLC layer is responsible for sequence control, and the PDCP layer is responsible for security and the like.

  When carrier aggregation is viewed from the viewpoint of a protocol stack, it can be said that data to be transmitted is separated at the physical layer. It can also be said that the received data is integrated in the physical layer. This means that in carrier aggregation, there are a plurality of physical layer entities on both the transmitting and receiving sides, and there is one entity such as a higher MAC layer. Here, the entity is a term meaning a logical (or virtual) processing subject. An entity exists in each layer of the protocol stack, and is not necessarily one-to-one with a device that is a physical processing entity, but may be N-to-one. For example, according to carrier aggregation as described above, there are a plurality of physical layer entities on both the transmission and reception sides.

  Here, in the protocol stack in general data communication in the LTE system, the entities of the PHY layer, the MAC layer, the RLC layer, and the PDCP layer operate in a single serial line in each of the radio base station and the radio terminal.

  On the other hand, in data communication based on carrier aggregation in the LTE system, entities of the PHY layer, the MAC layer, the RLC layer, and the PDCP layer operate in each of the radio base station and the radio terminal. However, data communication based on carrier aggregation is different from general data communication in the LTE system in that only the physical layer is separated into two entities. In this way, when carrier aggregation is viewed from the viewpoint of a protocol stack, it can be said that data to be transmitted is separated by the PHY layer and data to be received is integrated by the PHY layer.

  By the way, as described above, the MAC layer in the LTE system is responsible for the scheduler function. The scheduler function is a function that determines at which frequency and at what timing data is transmitted. In the carrier aggregation, it is described that there is one MAC layer entity. This means that there is one scheduler.

  If two-way connection is realized by carrier aggregation, for example, a MAC entity (scheduler) that exists in a macro radio base station corresponds to a PHY entity (CC) that exists in each of the macro radio base station and the small radio base station. Scheduling will be performed. This is difficult to realize due to the latency problem of communication between radio base stations. This is because scheduling in the LTE system needs to be performed in a very minute cycle in units of 1 millisecond (1 subframe). Therefore, according to carrier aggregation, one radio base station can perform transmission / reception using a plurality of carriers, but it is not realistic for a plurality of radio base stations to perform transmission / reception using a plurality of carriers. Conceivable. From the above, it is considered extremely difficult to realize a two-way connection based on carrier aggregation.

  By the way, based on the consideration regarding the carrier aggregation described above, it is necessary to separate data in the data link layer above the physical layer in order to realize the two-way connection. As described above, in the LTE system, the data link layer is further subdivided into three layers: a MAC layer, an RLC layer, and a PDCP layer. For example, if data is separated at the MAC layer, there are a plurality of MAC layer entities. Thereby, there are a plurality of schedulers, and for example, the macro radio base station and the small radio base station can be provided with separate schedulers. Therefore, by separating the data at the MAC layer, it is possible to avoid the problem based on the latency of the communication between the radio base stations described above, and to realize a two-way connection. Similarly, even when data is separated at the RLC layer or PDCP layer, it is possible to realize two-way connection.

  Note that data separation in the data link layer is not equivalent to two-way connection. This is because there may be a single connection even when data is separated at the data link layer, as in the case where one radio base station has a plurality of MAC entities.

  Next, a radio communication system according to the first embodiment will be described with reference to FIG. FIG. 1 is a block diagram of a wireless communication system according to the first embodiment. As illustrated in FIG. 1, the wireless communication system according to the present embodiment includes a wireless communication device 1, a wireless communication device 2, a wireless communication device 3, and an upper layer communication device 4.

  The wireless communication device 1 and the wireless communication device 2 are connected in two ways. The wireless communication device 1 is a primary wireless communication device in a two-way connection, and the wireless communication device 2 is a secondary wireless communication device in a two-way connection.

  The wireless communication device 1 and the wireless communication device 2 are connected, for example, by wire. The wireless communication device 1 and the wireless communication device 2 transmit / receive data to / from each other using a wired link connecting each other. The wireless communication device 1 and the wireless communication device 2 and the wireless communication device 3 are connected wirelessly.

  The wireless communication device 1 includes a communication unit 11 having a reception unit 12 and a transmission unit 13, and a control unit 14.

  The receiving unit 12 receives control data and user data from the upper layer communication apparatus 4. The receiving unit 12 outputs the received control data and user data to the transmitting unit 13. The control data may be data generated by the wireless communication device 1 itself.

  In addition, the receiving unit 12 transmits data related information (for example, information indicating the data retention amount of the buffer and information related to data such as data reception status) included in the receiving unit 32 of the wireless communication device 3. Received from the transmitter 33. Then, the reception unit 12 outputs the data related information received from the transmission unit 33 to the control unit 14.

  The transmission unit 13 transmits the control data to the reception unit 32 of the wireless communication device 3. Further, the transmission unit 13 receives a notification of the data delivery amount to the wireless communication device 2 from the control unit 14. Then, the transmission unit 13 transmits data to the wireless communication device 2 via the wired link with the data delivery amount notified from the control unit 14.

  The control unit 14 performs overall control of the operation of the communication unit 11 including the reception unit 12 and the transmission unit 13. In addition, the control unit 14 receives data-related information included in the reception unit 32 of the wireless communication device 3 from the reception unit 12. Then, the control unit 14 determines the data delivery amount of the data to the wireless communication device 2 using the data related information received from the receiving unit 12. Thereafter, the control unit 14 notifies the transmission unit 13 of the determined data delivery amount to the wireless communication device 2.

  The wireless communication device 2 includes a communication unit 21 having a reception unit 22 and a transmission unit 23, and a control unit 24.

  The reception unit 22 receives data from the transmission unit 13 of the wireless communication device 1 via a wired link. Then, the reception unit 22 outputs the received data to the transmission unit 23.

  The transmission unit 23 receives data input from the reception unit 22. Then, the transmission unit 23 transmits the received data to the reception unit 32 of the wireless communication device 3.

  The control unit 24 performs overall control of the operation of the communication unit 21 including the reception unit 22 and the transmission unit 23.

  The wireless communication device 3 includes a communication unit 31 including a reception unit 32 and a transmission unit 33, and a control unit 34.

  The reception unit 32 receives data from the transmission unit 23 of the wireless communication device 2. Then, the receiving unit 32 transmits data-related information (for example, information related to data such as information indicating the data retention amount of the buffer and data reception status) to the control unit 34.

  The transmission unit 33 receives the data related information included in the reception unit 32 from the control unit 34. Then, the transmission unit 33 transmits the data related information included in the reception unit 32 to the reception unit 12 of the wireless communication device 1.

  The control unit 34 performs overall control of the operation of the communication unit 31 including the reception unit 32 and the transmission unit 33. In addition, the control unit 34 acquires data related information that the receiving unit 32 has. Then, the control unit 34 transmits the data related information included in the reception unit 32 to the transmission unit 33.

  Furthermore, FIG. 2 is a conceptual diagram summarizing various configurations of the wireless communication system. Radio communication apparatuses 1-1 to 1-N in FIG. 2 correspond to radio communication apparatuses 1 and 3 in FIG. As shown in FIG. 2, it is possible to separate the data flow at each entity and any location before and after the entity and make a two-way connection. In any case, the wireless communication system according to the present embodiment is appropriately applied. be able to. Further, as shown in FIG. 2, the radio communication system according to the present embodiment can be applied regardless of whether it is uplink communication or downlink communication.

  As described above, in the wireless communication system according to the present embodiment, the wireless communication device 3 such as a mobile station has information in the buffer (for example, information indicating the data retention amount of the buffer, data reception status, and the like). Information related to the wireless communication device 1 and the wireless communication device 1 controls the amount of data delivered to the wireless communication device 2 in accordance with the notified information. Since the wireless communication device 3 and the wireless communication device 1 communicate with each other wirelessly, the wireless communication system according to the present embodiment is configured so that the wireless communication device 2 can receive information to the wireless communication device 1 via a wired link ( For example, it is possible to notify the wireless communication apparatus 1 that controls the delivery amount at a higher speed than when notifying information indicating data retention amount in the buffer and information related to data such as data reception status). Therefore, in the wireless communication system according to the present embodiment, the wireless communication device 1 has a more appropriate delivery amount compared to the case where data is transmitted to the wireless communication device 2 using information received via the wired link. Data can be sent to the wireless communication device 2. That is, the wireless communication system according to the present embodiment can improve the efficiency of communication between wireless communication devices.

  Next, Example 2 will be described. FIG. 3 is a schematic diagram of two-way connection in the wireless communication system according to the second embodiment. The radio communication system according to the present embodiment includes a macro base station 100 as the radio communication device 1 in FIG. Moreover, it has the small base station 200 as the radio | wireless communication apparatus 2 in FIG. In addition, the mobile station 300 is provided as the wireless communication device 3 in FIG.

  The mobile station 300 is connected to the macro base station 100 as a primary base station. The mobile station 300 is connected to the macro base station 100 by a control plane 350 represented by a solid line arrow and a user plane 351 represented by a broken line arrow. In addition, the mobile station 300 is connected to the small base station 200 as a secondary base station. The mobile station 300 is connected to the small base station 200 by the user plane 351. The user plane 351 in FIG. 3 represents each user plane 351 that connects the mobile station 300 and the small base station 200 when a handover is performed. The control plane 350 corresponds to an example of “first logical processing subject”. The user plane 351 corresponds to an example of “second logical processing subject”.

  The configuration of the wireless communication system as shown in FIG. 3 is often adopted for traffic offloading and reducing the number of handovers.

  Next, details of the wireless communication system according to the present embodiment will be described with reference to FIG. FIG. 4 is a block diagram of a wireless communication system according to the second embodiment. In the wireless communication system according to the present embodiment, in FIG. 4, each part having the same reference numeral as in FIG. 1 has the same function unless otherwise specified.

  A macro cell which is a cell of the macro base station 100 includes a plurality of small cells including the cell of the small base station 200. The wireless communication system according to the present embodiment performs two-way connection with the mobile station 300 with the macro base station 100 as a primary wireless communication device and the small base station 200 as a secondary wireless communication device.

  In addition, the macro base station 100, the small base station 200, and the mobile station 300 perform communication using link layer protocols corresponding to a plurality of link layers such as a PDCP layer, an RLC layer, a MAC layer, and a PHY layer, for example.

  Therefore, here, the process executed for each link layer will be described with reference to FIG. FIG. 5 is a diagram illustrating transmission / reception of user data executed using each link layer in the wireless communication system according to the second embodiment. Here, in this embodiment, the case where the mobile station 300 acquires user data from both the macro base station 100 and the small base station 200 will be described.

  The reception unit 12 and the transmission unit 13 in the communication unit 11 of the macro base station 100 perform data transmission / reception using the PDCP layer, the downlink RLC layer, the MAC layer, and the PHY layer. In FIG. 5, for convenience of explanation, the PDCP layer 101, the RLC layer 102, the RLC layer 103, and the MAC layer 104 are illustrated among the layers for the communication unit 11 to perform communication. The RLC layer 102 is a downlink RLC layer, and the RLC layer 103 is an uplink RLC layer.

  In such a configuration, RLC AM (Acknowledged Mode) is used in the RLC layer. In RLC AM, since it is necessary to receive uplink feedback (transmission confirmation (ACK and NACK) and communication control information for transmitted data) for downlink data, a bi-directional bearer (Bi-directional Bearer) is used as a bearer. ) Is used (mapped). Similarly, in the case of uplink communication, a bidirectional bearer is used (mapped) in order to receive downlink feedback for uplink data. When clearly indicating the type of bearer, it may be referred to as AM-DRB.

  As another configuration of the RLC layer, there is a configuration using RLC UM (Unacknowledged Mode). In RLC UM, a bidirectional bearer may be used (mapped) as in RLC AM, or a unidirectional bearer may be used. In the case of a one-way bearer, only one PDCP layer, RLC layer, and MAC layer are used (mapped) for both downlink communication and uplink communication. When the bearer type is specified, it may be called UM-DRB.

  As another configuration of the RLC layer, there is a configuration using RLC TM (Transparent Mode). This configuration is a configuration that substantially does not use the RLC layer, and PDCP layer data is directly delivered to the MAC layer in both downlink and uplink communications.

  For example, an application using TCP (Transmission Control Protocol) that provides reliable communication is mapped to the RLC AM. For example, an application using UDP (User Datagram Protocol) that provides communication (for example, VoIP) requiring real-time property is mapped to the RLC UM.

  In the radio communication system according to the present embodiment, the macro base station 100 that is a primary radio communication device separates the data plane between the PDCP layer 101 and the RLC layer 102. Specifically, the data plane is separated between the PDCP layer 101 and the RLC layer 102, one going to the RLC layer 102 of the macro base station 100 and the other going to the RLC layer 201 of the small base station 200.

(Processing of macro base station)
Processing of the communication unit 11 when transmitting user data to the mobile station 300 will be described.

  The communication unit 11 receives user data of the PDCP layer 101 from the upper layer communication device 4. Then, the communication unit 11 regularly adds numbers to the received user data packets in the PDCP layer 101 (for example, consecutive numbers are added in ascending order). This number is also used for handover. In the present embodiment, for example, the communication unit 11 sequentially adds odd numbers to data to be sent to the RLC layer 102 of its own device. Further, the communication unit 11 sequentially adds even numbers to the user data packets to be sent to the RLC layer 201 of the small base station 200. Further, the communication unit 11 performs header compression, security check, and encryption on the user data in the PDCP layer 101.

  Then, the communication unit 11 transmits user data to which the odd number is added from the PDCP layer 101 to the RLC layer 102. In addition, the communication unit 11 transmits user data with an even number added thereto to the RLC layer 201 of the small base station 200 via a wired link.

  Here, the distribution of user data by the communication unit 11 will be described with reference to FIG. FIG. 6 is a diagram for explaining the flow of user data to which numbers are regularly added. The square represented by the dotted line in FIG. 6 represents user data sent. And the number in user data represents the number provided to each user data. For example, # 1 represents user data assigned a number of 1.

  The communication unit 11 transmits data assigned with numbers 1, 3, 5, and 7 in the PDCP layer 101 to the RLC layer 102 as indicated by an arrow 111. In addition, the communication unit 11 transmits the data assigned numbers 2, 4, 6, and 8 in the PDCP layer 101 to the RLC layer 201 of the small base station 200 as indicated by an arrow 112.

  Furthermore, transmission of user data to the RLC layer 201 of the small base station 200 by the communication unit 11 will be described in detail.

  The communication unit 11 receives, from the communication unit 31 of the mobile station 300, PDCP Status Report representing information indicating the buffer state of the mobile station 300 (for example, data retention amount and data reception state). Then, the communication unit 11 transmits the received PDCP Status Report to the control unit 14. Thereafter, the communication unit 11 receives a notification of the amount of user data delivered to the RLC layer 201 of the small base station 200 from the control unit 14. Then, the communication unit 11 transmits user data to the RLC layer 201 of the small base station 200 with the delivery amount specified by the control unit 14.

  Returning to FIG. The communication unit 11 receives user data (PDCP PDU) from the PDCP layer in the RLC layer 102. It is also possible to change the packet size by dividing or integrating the packet that is the user data as required. Further, in the RLC layer 102, the communication unit 11 sequentially assigns an RLC layer number to a packet (PDCP PDU) received from the PDCP layer. Then, the communication unit 11 accumulates packets (RLC PDUs) that are user data in the buffer of the RLC layer 102.

  Thereafter, the communication unit 11 receives the amount of user data that can be transmitted to the mobile station 300 from the MAC layer 104. Then, the communication unit 11 transmits user data corresponding to the data amount received from the MAC layer 104 from the buffer of the RLC layer 102 to the MAC layer 104.

  In the MAC layer 104, the communication unit 11 assembles data for transmission using user data (RLC PDU) received from the RLC layer 102 (for example, adds a MAC header and generates a MAC PDU). Then, the communication unit 11 performs data transmission scheduling in the MAC layer 104 and outputs data assembled in accordance with the schedule to the mobile station 300. Here, in FIG. 5, the MAC layer 104 of the communication unit 11 and the MAC layer 301 of the mobile station 300 are described as communicating with each other, but actually, communication is performed via the PHY layer or the like. Is going.

  Next, processing of the communication unit 11 when receiving user data from the mobile station 300 will be described.

  The communication unit 11 performs user data reception scheduling in the MAC layer 104 and receives the user data from the MAC layer 301 of the mobile station 300 in accordance with the scheduling. Next, the communication unit 11 reconstructs (reassembles) the received user data in the MAC layer 104 (for example, removes the MAC header from the MAC PDU and extracts the RLC PDU). Then, the communication unit 11 transmits (distributes) user data (MAC SDU) from the MAC layer 104 to the RLC layer 103.

  The communication unit 11 divides and integrates received user data (RLC PDU) in the RLC layer 103. Further, the communication unit 11 corrects the order of the packets in the RLC layer 103 using the RLC layer number added to the packet. Then, the communication unit 11 transmits (distributes) user data (RLC SDU) from the RLC layer 103 to the PDCP layer 101 in the order of sequence numbers.

  In the PDCP layer 101, the communication unit 11 performs decryption, security check, and release of header compression on user data (PDCP PDU).

  Then, the communication unit 11 transmits user data from the PDCP layer 101 to the upper layer communication apparatus 4.

  In addition, when a handover occurs, the communication unit 11 cancels the multiple connection and transitions to communication with only a single connection. And the communication part 11 acquires the packet which exists in a lower layer in PDCP layer 101 from lower layers, such as an RLC layer. And the communication part 11 rearranges the acquired packet in numerical order in PDCP layer 101, and performs number guarantee.

  When a handover occurs, the source base station forwards (transfers) a packet that has not been transmitted to the destination base station. Then, the destination base station transmits the packet received by forwarding to the mobile station 300.

  Next, the operation of the control unit 14 will be described. The control unit 14 notifies the mobile station 300 of the PDCP Status Report parameter setting for notifying the buffer state of the mobile station 300 (for example, the data retention amount and the data reception state) via the communication unit 11. To do. Here, the parameter setting of PDCP Status Report includes a notification period and a staying amount threshold value for determining whether to perform notification. In the present embodiment, the control unit 14 stores the staying amount threshold as 10% of the buffer in the PDCP layer 307 of the mobile station 300. In the present embodiment, the control unit 14 stores 100 ms as the notification cycle. However, the staying amount threshold and the notification cycle can take other values, and are preferably determined according to the operation.

  Then, after starting the wireless communication by the two-way connection, the control unit 14 receives the PDCP Status Report of the mobile station 300 from the communication unit 11. FIG. 7A is a diagram illustrating an example of a PDCP Status Report for a 12-bit sequence number. FIG. 7B is a diagram illustrating an example of PDCP Status Report for a 15-bit sequence number. FIG. 7C is a diagram illustrating an example of a PDCP Status Report for a 7-bit sequence number. In the PDCP Status Report, the size of the sequence number varies depending on data to be transmitted / received. For example, in VoIP (Voice of Internet Protocol), a 7-bit sequence number may be used.

  Each PDCP Status Report 400, 410, and 420 has a different size of FMS (First Missing Sequence number) 401, 411, and 421 that represents the sequence number of the oldest packet among unreachable packets. Hereinafter, the PDCP Status Report for a 12-bit sequence number shown in FIG. 7A will be described as an example.

The format of PDCP Status Report 400 shown in FIG. 7A is used to notify the PDCP sequence number from the mobile station to the base station. The FMS 401 stores the PDCP sequence number of the oldest packet among unreachable packets. Here, since the PDCP Status Report 400 is for a 12-bit PDCP sequence number, the FMS 401 uses 12 bits. Bitmap _{1 to} Bitmap _N are used as options.

The FMS 401 stores the sequence number of the oldest packet among unreachable packets. In other words, the FMS 401 stores a sequence number of a packet that should be received earliest among packets of user data that have not arrived from the small base station 200. Hereinafter, the oldest unreachable packet may be referred to as an “FMS packet”. Further, in Bitmap ₁ to Bitmap _N of PDCP Status Report 400, information indicating the arrival status of packets after the packet corresponding to FMS 401 is stored. In this embodiment, information indicating that the bit representing arrival is “1” and the bit representing unreached is “0” is stored in Bitmap ₁ to Bitmap _N of PDCP Status Report 400. For example, in a case where a certain packet has not arrived and the subsequent six packets have arrived and unreached in order, information “101010” is stored in Bitmap _{1 to} Bitmap _N.

  FIG. 8 is a diagram illustrating information stored in the PDU Type. Table 430 describes information on each bit of the PDU Type of PDCP Status Report and the contents of the PDU Type corresponding thereto. When each bit of the PDU Type is “000”, this represents a PDCP status report indicating the PDCP sequence number of user data received by the mobile station 300. Further, when each bit of the PDU Type is “001”, this indicates that it is a scattered ROHC feedback packet. The scattered ROHC feedback packet includes feedback information for the PDCP PDU transmitted from the receiving side. And each bit of PDU Type is left in reserve from “010” to “111”. In the present embodiment, a bit string “001” is stored in the PDU Type of the PDCP Status Report 400.

  However, another value of PDU Type may be designated to indicate notification of information indicating the buffer status (for example, data retention amount and data reception status). For example, any one of “010” to “111” may be stored as each bit, and a predetermined value may be stored in the bit string of the PDU Type.

  In this embodiment, as shown in FIG. 7C, a PDCP Status Report 420 for a 7-bit sequence number is created. Therefore, in the radio communication system according to the present embodiment, even when an RLC UM (Unacknowledge mode) bearer is used, PDCP Status Report can be used, and the reliability of packet order guarantee can be improved.

The control unit 14 acquires the number of the FMS packet from the FMS 401 of the received PDCP Status Report 400. Further, the control unit 14 acquires the reception state of the packets after the FMS packet from Bitmap ₁ to Bitmap _N of the PDCP Status Report 400. And the control part 14 calculates | requires the data retention amount in the buffer of the mobile station 300 from the packet amount after the packet which has the number stored in FMS401.

  Thereafter, the control unit 14 notifies the communication unit 11 of the obtained buffer state.

  Here, a case where the sequence number is given to the user data packet as shown in FIG. 6 will be described as an example. For example, it is assumed that the packet whose sequence number is 2 in FIG.

  In this case, since packets having odd sequence numbers are transmitted from the macro base station 100, packets with sequence numbers 1, 3, 5 and 7 reach the mobile station 300. On the other hand, since packets having even sequence numbers are sent from the small base station 200, packets with sequence numbers 4, 6, and 8, which are even packets after the second, do not reach the mobile station 300. This is because when the second packet does not reach the PDCP layer, the subsequent packets stay in the lower layer and do not reach the PDCP layer.

  However, in the case of handover, even if the second packet does not reach the PDCP layer, the packets with sequence numbers 4, 6, and 8 are forwarded to the PDCP layer. In the PDCP layer, number guarantee for the packet is performed.

  In addition, assuming the worst case, the operation at the time of handover can be applied to the case of two-way connection (multi-way connection). That is, in the case where the second packet is not delivered from the macro base station to the small base station (for example, a packet loss occurs or a bit error is detected on the small base station side), the sequence number 4, The packets 6 and 8 are not forwarded to the PDCP layer and fall into a deadlock state. In such a case, retransmission must be performed end-to-end in the upper layer, the TCP layer or the application layer.

  Therefore, even if there is a missing sequence number, the PDCP layer can grasp which packet has not arrived by forwarding the packet to the PDCP layer. For example, in the above example, if the packet of sequence number 2 has not reached the PDCP layer, the state of the PDCP layer buffer is “1, 3, 4, 5, 6, 7, 8”, and packet 2 has not arrived. I understand that. If the packet 2 is not delivered to the small base station as described above, the deadlock state is set as described above. Therefore, timer control can be considered in order to eliminate the state.

  Specifically, for example, when it is detected that a packet with sequence number 2 has not arrived, a timer is started. If the second packet does not arrive within the set time and the timer expires, it is assumed that the timer 2 has not reached the small base station, and all packets are forwarded to the upper layer.

  By performing such control, the deadlock state can be eliminated as soon as possible, and end-to-end retransmission can be speeded up (the delay time required for retransmission can be shortened).

  Note that the set value of the timer may be set in advance at the time of line setting or may be set when performing two-way connection (multi-way connection). The timer may be managed by the PDCP layer or may be managed by another layer (MAC layer or RLC layer). What is tolerant is to perform timer control at the terminal.

In this case, the control unit 14 receives PDCP Status Report in which information of sequence number 2 is stored in the FMS, and information “101010” is stored in Bitmap _{1 to} Bitmap _N. Then, the control unit 14 acquires No. 2 stored in the FMS as the FMS packet number. Then, from the subsequent bit string, the control unit 14 has the packets of sequence numbers 3, 5, and 7 stored in the buffer of the mobile station 300, and the packets of sequence numbers 4, 6, and 8 have arrived from the small base station 200. Make sure there is no. The packets of sequence numbers 3, 5, and 7 stored in the buffer of the mobile station 300 and the packets of sequence numbers 2, 4, 6, and 8 that have not arrived from the small base station 200 become the data retention amount in the buffer of the mobile station 300. . And the control part 14 calculates the delivery amount of the user data transmitted from the macro base station 100 to the small base station 200 using the data retention amount in the buffer of the mobile station 300.

  For example, the control unit 14 stores in advance a function in which the delivery amount decreases when the data retention amount increases and the delivery amount increases when the data retention amount decreases. The delivery amount may be calculated using a function. Further, the delivery amount in the case of sending data is fixed, and the control unit 14 stops the delivery of the data if the data retention amount is larger than a predetermined threshold value, and then the stage in which the data retention amount falls below the threshold value. The data delivery may be resumed. Further, the correspondence between the data retention amount and the delivery amount may be stored in stages, and the control unit 14 may determine the delivery amount in accordance with the stored correspondence relationship.

  The control unit 14 stores the sequence number assigned to each packet transmitted to the macro base station 100 and the small base station 200, and thereby determines the data retention amount on the small base station side based on the received PDCP Status Report. It is possible to calculate the data delivery amount.

(Small base station processing)
Returning to FIG. The process at the time of user data transmission to the mobile station 300 in the small base station 200 is demonstrated. In FIG. 5, only the RLC layer 201, the RLC layer 202, and the MAC layer 203 used for explanation among the layers of the small base station 200 are described. Here, the RLC layer 201 is a downlink RLC layer, and the RLC layer 202 is an uplink RLC layer (an RLC layer associated with downlink).

  The communication unit 21 receives user data sent from the PDCP layer 101 of the macro base station 100 via a wired link in the RLC layer 201.

  Next, the communication unit 21 receives user data (PDCP PDU) from the PDCP layer in the RLC layer 201. If necessary, the communication unit 21 can change the size of the packet by dividing or integrating the packet that is the user data. Further, in the RLC layer 201, the communication unit 21 receives the number for the RLC layer from the PDCP layer and sequentially assigns the packet (PDCP PDU). Then, the communication unit 21 accumulates packets (RLC PDUs) that are user data in the buffer of the RLC layer 201.

  Thereafter, the communication unit 21 receives from the MAC layer 203 the amount of user data that can be transmitted to the mobile station 300. Then, the communication unit 21 transmits user data corresponding to the data amount received from the MAC layer 203 from the buffer of the RLC layer 201 to the MAC layer 203.

  In the MAC layer 203, the communication unit 21 assembles data for transmission using user data (RLC PDU) received from the RLC layer 201 (for example, adds a MAC header and generates a MAC PDU). Then, the communication unit 21 performs data transmission scheduling in the MAC layer 203 and outputs data (RLC SDU) assembled according to the schedule to the mobile station 300.

  Next, processing when user data is received from the mobile station 300 in the small base station 200 will be described.

  The communication unit 21 performs user data reception scheduling in the MAC layer 203 and receives the user data from the MAC layer 302 of the mobile station 300 in accordance with the scheduling. Next, the communication unit 21 reconstructs (reassembles) the received user data in the MAC layer 203. Then, the communication unit 21 transmits (distributes) user data (MAC SDU) from the MAC layer 203 to the RLC layer 202.

  The communication unit 21 divides and integrates received user data (RLC PDU) in the RLC layer 202. Further, the communication unit 21 corrects the order of the packets in the RLC layer 202 based on the RLC layer number added to the packet. Then, the communication unit 21 transmits (distributes) user data (RLC SDU) from the RLC layer 202 to the PDCP layer 101 of the macro base station 100 in the order of sequence numbers via the wired link.

(Mobile station processing)
Next, the mobile station 300 will be described. In FIG. 5, among the layers of the mobile station 300, the MAC layer 301, the MAC layer 302, the RLC layers 303 to 306, and the PDCP layer 307 used for explanation are shown. Here, in this embodiment, the mobile station 300 has a function of receiving user data from two base stations in parallel. The MAC layer 301, RLC layer 303, RLC layer 304, and PDCP layer 307 are layers for transmitting and receiving data to and from the macro base station 100. The RLC layer 303 is a downlink RLC layer, and the RLC layer 304 is an uplink RLC layer. Further, the MAC layer 302, the RLC layer 305, the RLC layer 306, and the PDCP layer 307 are layers for transmitting and receiving data to and from the small base station 200. The RLC layer 305 is a downlink RLC layer, and the RLC layer 306 is an uplink RLC layer (an RLC layer associated with downlink).

  Processing when the mobile station 300 receives user data from the macro base station 100 will be described.

  The communication unit 31 performs user data reception scheduling in the MAC layer 301 and receives the data from the MAC layer 104 of the macro base station 100 in accordance with the scheduling. Next, the communication unit 31 reconstructs (reassembles) the received user data in the MAC layer 301. Then, the communication unit 31 transmits user data (MAC SDU) from the MAC layer 301 to the RLC layer 303.

  The communication unit 31 divides and integrates received user data (RLC PDU) in the RLC layer 303. Further, the communication unit 31 corrects the order of the packets in the RLC layer 303 based on the RLC layer number added to the packet. Then, the communication unit 31 transmits (distributes) user data (RLC SDU) from the RLC layer 303 to the PDCP layer 307.

  In the PDCP layer 307, the communication unit 31 performs decryption, security check, and release of header compression on user data.

  The communication unit 31 performs data processing such as data display and calculation using the data on the received user data.

  Next, processing at the time of user data transmission to the macro base station 100 in the mobile station 300 will be described.

  In the PDCP layer 307, the communication unit 31 regularly adds numbers to user data packets to be transmitted (for example, continuously in ascending order). Further, the communication unit 31 performs header compression, security check, and encryption on user data in the PDCP layer 307.

  Then, the communication unit 31 transmits user data from the PDCP layer 307 to the RLC layer 304.

  Next, the communication unit 31 receives user data (PDCP PDU) from the PDCP layer in the RLC layer 304. The communication unit 31 can also change the size of the packet by dividing or integrating the packet that is the user data as necessary. Further, in the RLC layer 304, the communication unit 31 sequentially assigns an RLC layer number to a packet (PDCP PDU) received from the PDCP layer. Then, the communication unit 31 accumulates packets (RLC PDUs) that are user data in the buffer of the RLC layer 304.

  Thereafter, the communication unit 31 receives from the MAC layer 301 the amount of user data that can be transmitted to the macro base station 100. Then, the communication unit 31 transmits user data corresponding to the data amount received from the MAC layer 301 from the buffer of the RLC layer 304 to the MAC layer 301.

  In the MAC layer 301, the communication unit 31 assembles data for transmission using user data (RLC PDU) received from the RLC layer 304 (for example, adds a MAC header and generates a MAC PDU). Then, the communication unit 31 performs data transmission scheduling in the MAC layer 301 and outputs data assembled in accordance with the schedule to the macro base station 100.

  A process when the mobile station 300 receives user data from the small base station 200 will be described.

  The communication unit 31 performs user data reception scheduling in the MAC layer 302 and receives the user data from the MAC layer 203 of the small base station 200 in accordance with the scheduling. Next, the communication unit 31 reconstructs (reassembles) the received user data in the MAC layer 302. Then, the communication unit 31 transmits (distributes) user data (MAC SDU) from the MAC layer 302 to the RLC layer 305.

  The communication unit 31 divides and integrates received user data (RLC PDU) in the RLC layer 305. Further, the communication unit 31 corrects the order of the packets in the RLC layer 305 based on the RLC layer number added to the packet. Then, the communication unit 31 transmits (distributes) user data (RLC SDU) from the RLC layer 305 to the PDCP layer 307 in the order of sequence numbers.

  In the PDCP layer 307, the communication unit 31 performs decryption, security check, and header compression cancellation on user data (PDCP PDU).

  The communication unit 31 performs data processing such as data display and calculation using the data on the received user data.

  Next, processing at the time of user data transmission to the small base station 200 in the mobile station 300 will be described.

  In the PDCP layer 307, the communication unit 31 regularly adds numbers to user data packets to be transmitted (for example, consecutive numbers are added in ascending order). Further, the communication unit 31 performs header compression, security check, and encryption on user data in the PDCP layer 307.

  Then, the communication unit 31 transmits user data from the PDCP layer 307 to the RLC layer 306.

  Next, the communication unit 31 receives user data (PDCP PDU) from the PDCP layer in the RLC layer 306. If necessary, the communication unit 31 can change the size of the packet by dividing or integrating the packet that is user data. Further, in the RLC layer 306, the communication unit 31 sequentially assigns the RLC layer number to the packet (PDCP PDU) received from the PDCP layer. Then, the communication unit 31 accumulates packets (RLC PDUs) that are user data in the buffer of the RLC layer 306.

  Thereafter, the communication unit 31 receives the amount of user data that can be transmitted to the macro base station 100 from the MAC layer 302. Then, the communication unit 31 transmits user data corresponding to the data amount received from the MAC layer 302 from the buffer of the RLC layer 306 to the MAC layer 302.

  In the MAC layer 302, the communication unit 31 assembles data for transmission using user data (RLC PDU) received from the RLC layer 306 (for example, generates a MAC PDU by adding a MAC header or the like). Then, the communication unit 31 performs data transmission scheduling in the MAC layer 302 and outputs data (RLC SDU) assembled in accordance with the schedule to the small base station 200.

  Next, notification of information indicating the data state (for example, the data retention amount and the data reception state) to the macro base station 100 in the mobile station 300 will be described.

  The control unit 34 receives the parameter setting of PDCP Status Report via the communication unit 31. And the control part 34 sets various parameters of PDCP Status Report, such as a notification period of a regular notification, and a residence amount threshold value, using the parameter setting of PDCP Status Report.

  The control unit 34 monitors the amount of packets received in the PDCP layer 307 in the buffer in the PDCP layer 307 when receiving user data. Then, when the staying amount exceeds the staying amount threshold, the control unit 34 acquires the FMS packet number among the user data packets that have not arrived from the small base station 200. Further, the control unit 34 acquires a reception state of a packet to be processed after the FMS packet.

  And the control part 34 produces | generates PDCP Status Report400 which has a format shown to FIG. 7A using the acquired information.

  Here, in the case where the sequence number is given to the packet of user data as shown in FIG. 6 and the packet with the sequence number of 2 has not reached the mobile station 300, the control unit 34 creates the PDCP Status Report. explain.

  In this case, packets with sequence numbers 1, 3, 5, and 7 reach mobile station 300, but packets with sequence numbers 4, 6, and 8 do not reach mobile station 300. This is because when the second packet does not reach the PDCP layer, the subsequent packets stay in the lower layer and do not reach the PDCP layer.

  However, in the case of handover, even if the second packet does not reach the PDCP layer, the packets of sequence numbers 4, 6, and 8 are sucked up to the PDCP layer. In the PDCP layer, number guarantee for the packet is performed.

  Therefore, the control unit 34 obtains No. 2 as the FMS packet number among user data packets that have not arrived from the small base station 200. Further, as a reception state of packets processed after the FMS packet, the control unit 34 has received packets with sequence numbers 1, 3, 5, and 7 and has not received packets with sequence numbers 4, 6, and 8. Get information that there is. Here, the control unit 34 may acquire an FMS packet number from user data not received from the macro base station 100, and may acquire a reception state of a packet to be processed after the FMS packet.

Then, the control unit 34 stores information that the packet is sequence number 2 in the FMS area of the PDCP Status Report. Further, the control unit 34 stores 101010 from the beginning in each bit of Bitmap _{1 to} Bitmap _N. Further, the control unit 34 stores data representing a packet for notifying information indicating the buffer retention amount in the PDU Type area.

  After that, the control unit 34 transmits the generated PDCP Status Report to the communication unit 31.

  The communication unit 31 transmits the PDCP Status Report received from the control unit 34 to the macro base station 100.

  In addition, the control unit 34 generates a PDCP Status Report for each stored cycle. Then, the communication unit 31 transmits PDCP Status Report to the macro base station 100.

  Here, in this embodiment, two timings are used as the notification timing of the buffer retention amount, when the threshold is exceeded and when it is periodic, but the notification timing is not limited to this. For example, the control unit 34 may use only a regular case as the notification timing. Moreover, the control part 34 may notify until it falls below a threshold value for every fixed period using the case where a threshold value is exceeded as a notification timing.

  Next, the overall flow of data delivery amount control at the time of two-way connection will be described with reference to FIG. FIG. 9 is a sequence diagram for explaining the overall flow of data delivery amount control. Here, the macro base station 100 stops the transmission of user data to the small base station 200 when the data retention amount in the buffer of the mobile station 300 exceeds the threshold value, and then the user when the buffer of the mobile station 300 becomes empty. This will be described in the case of restarting data transmission. Here, states 501 to 503 in FIG. 9 represent the data retention state of the buffer of the mobile station 300, and states 511 to 514 represent the data retention state of the buffer of the macro base station 100. Further, the arrows and data descriptions in states 511 to 514 indicate that user data is being transmitted from the buffer of the macro base station 100 to the small base station 200 at that time.

  The macro base station 100 transmits user data to the small base station 200 via a wired link (step S1). The small base station 200 transmits user data to the mobile station 300 (step S2).

  At this time, data is accumulated in the buffer of the macro base station 100 as in the state 511. User data is transmitted from the buffer of the macro base station 100. Further, a small amount of data is stored in the buffer of the mobile station 300 with respect to the buffer capacity as in the state 501.

  Furthermore, the macro base station 100 transmits user data to the small base station 200 via a wired link (step S3). The small base station 200 transmits user data to the mobile station 300 (step S4). However, at this time, there is a delay in data transmission from the small base station 200 to the mobile station 300.

  Therefore, in this case, the amount of data stored in the buffer of the mobile station 300 increases as in the state 502. In this state, user data is accumulated in the buffer of the macro base station 100 as in the state 512, and user data is transmitted from the buffer of the macro base station 100.

  When the amount of data stored in the buffer of the mobile station 300 exceeds the threshold, the mobile station 300 transmits information indicating the data retention amount of the buffer to the macro base station 100 (step S5). In response to this, the macro base station 100 stops transmitting user data to the small base station 200.

  As a result, data is accumulated in the buffer of the macro base station 100 as in the state 513, but user data is not transmitted from the buffer of the macro base station 100. Then, the mobile station 300 receives the delayed data from the small base station 200 and performs data processing, so that the data retention amount in the buffer decreases. Then, as in the state 503, there is no data remaining in the buffer of the mobile station 300.

  After that, the mobile station 300 transmits information indicating that the data retention amount of the buffer is 0 to the macro base station 100 at the periodic data retention amount notification timing (step S6).

  When the macro base station 100 confirms that the data retention amount in the buffer of the mobile station 300 is 0, the macro base station 100 reunites the transmission of user data to the small base station 200 (step S7). At this time, data is accumulated in the buffer of the macro base station 100 as in the state 514, and the accumulated user data is transmitted from the buffer. Then, the small base station 200 transmits user data to the mobile station 300 (step S8).

  Next, with reference to FIG. 10, control of the delivery amount of user data from the macro base station 100 to which the two-way connection is made in the communication system according to the present embodiment to the small base station 200 will be described. FIG. 10 is a flowchart of control of the delivery amount of user data to the small base station in the communication system according to the second embodiment.

  The control unit 14 of the macro base station 100 instructs the communication unit 11 to manage the delivery amount of user data to the small base station 200 by adding a regular sequence number (step S101).

  The transmission unit 13 regularly adds a sequence number to the user data packet in the PDCP layer 101, and transmits the user data to the small base station 200 via the wired link (step S102). The small base station 200 transmits user data received from the macro base station 100 to the mobile station 300.

  The transmission unit 13 transmits PDCP Status Report parameter settings including a threshold value and a notification cycle to the mobile station 300 (step S103).

  The receiving unit 32 of the mobile station 300 receives the parameter setting of the PDCP Status Report from the macro base station 100 (Step S104).

  The control unit 34 acquires the parameter setting of PDCP Status Report from the reception unit 32. Then, the control unit 34 sets PDCP Status Report parameters such as a threshold value and a notification cycle (step S105).

  The control unit 34 determines whether the data retention amount in the buffer of the mobile station 300 exceeds a threshold value or the notification cycle has arrived (step S106). When neither the threshold of the data retention amount nor the arrival of the notification cycle has occurred (Step S106: No), the control unit 34 either exceeds the threshold of the data retention amount or the notification cycle has occurred. Wait until.

  On the other hand, if either the threshold of the data retention amount exceeds or the notification cycle arrives (step S106: Yes), the control unit 34 notifies the PDCP Status Report for notifying information indicating the data retention amount. Is generated. Then, the transmission unit 33 transmits the PDCP Status Report generated by the control unit 34 to the macro base station 100 (Step S107).

  The receiving unit 12 of the macro base station 100 receives the PDCP Status Report for notifying the information indicating the data retention amount from the mobile station 300 (step S108).

  The control unit 14 acquires PDCP Status Report from the receiving unit 12. And the control part 14 calculates the data retention amount of the buffer of the mobile station 300 using PDCP Status Report (step S109).

  Next, the control unit 14 determines a delivery amount of user data to the small base station 200 from the calculated data retention amount (step S110).

  The transmission unit 13 receives a notification of the delivery amount of user data to the small base station 200 determined by the control unit 14. And the transmission part 13 changes the delivery amount of the user data to the small base station 200 to the designated delivery amount (step S111). Then, the transmission unit 13 transmits user data to which the regular sequence number is added with the changed delivery amount to the small base station 200.

  Here, in the flowchart of FIG. 10, a series of processes in which one change process is performed is described in order to explain the process of changing the delivery amount of user data, but actually, the macro base station 100 and the mobile station 300 are changed. Repeats the processing from step S106 to step S111 in FIG.

  Next, referring to FIG. 11A and FIG. 11B, a comparison between user data transmission from the macro base station 100 connected in a binary manner to the small base station 200 in the communication system according to the present embodiment and a conventional dual connection. Will be described. FIG. 11A is a diagram for explaining transmission of user data at the time of two-way connection in a conventional communication system. FIG. 11B is a diagram for explaining transmission of user data at the time of two-way connection in the communication system according to the second embodiment.

  The connection between the macro base station 110 and the small base station 210 in FIG. 11A and the connection between the macro base station 100 and the small base station 200 in FIG. 11B are connections represented by dashed arrows, It shall be connected using.

  As shown in FIG. 11A, in the conventional communication system, the MAC layer of the small base station 210 is called radio quality (UCI: Uplink Channel Information) by the PHY layer, and is downlink radio quality measured by the mobile station. CQI: Channel Quality Information, SRS: Sounding Reference Signal, which is uplink radio quality, and the like) are acquired. Then, the RLC layer of the small base station 210 acquires the data size to be transmitted from the MAC layer, and transmits user data corresponding to the data size to the MAC layer.

  Then, the size of the user data transmitted from the RLC layer of the small base station 210 to the MAC layer is notified to the macro base station 110 via a wired link. The PDCP layer of the macro base station 110 transmits user data to the RLC layer of the small base station 210 according to the size of the user data transmitted from the RLC layer of the small base station 210.

  In this case, the macro base station 110 determines a delivery amount of user data to be transmitted to the RLC layer of the small base station 210 using information transmitted from the small base station 210 via a wired link. The wired link may cause a delay in information transmission depending on the quality of communication. That is, there is a possibility that information transmitted from the small base station 210 via the wired link may be delayed, and when the delay occurs, the macro base station 110 transmits the user data in accordance with the transmission state of the small base station 210. There is a possibility that transmission cannot be performed properly.

  In contrast, as illustrated in FIG. 11B, in the communication system according to the present embodiment, the MAC layer of the small base station 200 acquires the data size determined from the wireless quality by the PHY layer. And the RLC layer of the small base station 200 acquires the data size transmitted from a MAC layer, and transmits the user data for the data size to a MAC layer.

  In addition, information indicating the buffer data retention amount in the PDCP layer of the mobile station 300 is transmitted from the mobile station 300 to the macro base station 100 by radio. Then, the macro base station 100 determines the user data delivery amount from the buffer data retention amount information in the PDCP layer of the mobile station 300 and transmits the user data to the RLC layer of the small base station 200 with the determined delivery amount. To do.

  In this case, the macro base station 100 determines a delivery amount of user data to be transmitted to the RLC layer of the small base station 200 using information transmitted from the mobile station 300 by radio. Wireless is faster than wired links with poor communication quality. That is, in the communication system according to the present embodiment, the macro base station 100 quickly acquires information for determining the delivery amount of user data to be transmitted to the RLC layer of the small base station 200 as compared with the conventional case. Can do. For this reason, the macro base station 100 according to the present embodiment can appropriately transmit user data in accordance with the transmission state of the small base station 200.

  As described above, in the wireless communication system according to the present embodiment, the user data transmitted from the primary wireless communication station to the secondary wireless communication station using the data retention amount of the buffer of the mobile station in the two-way connection. Determine the delivery amount. Accordingly, the primary wireless communication station can transmit user data with an appropriate delivery amount from the primary wireless communication station to the secondary wireless communication station. Therefore, according to the wireless communication system according to the present embodiment, the efficiency of communication between wireless communication stations can be improved.

  In addition, the existing data (signaling) PDCP Status Report is used to notify the buffer data retention amount, so that the various functions described above can be realized with only a small change to the existing system. Can do. That is, the wireless communication system according to the present embodiment can be easily constructed.

(Hardware configuration)
FIG. 12 is a hardware configuration diagram of the base station. The base stations are, for example, the wireless communication apparatuses 1 and 2 in FIG. 1, the macro base station 100 and the small base station 200 shown in FIG.

  The base station includes an antenna 901, a control unit 902, an RF circuit 903, a memory 904, a CPU 905, and a network interface 906.

  The control unit 902 realizes the function of the control unit 14 illustrated in FIGS. 1 and 4, for example.

  The network interface 906 is an interface for connecting a network using a wired link. For example, the macro base station 100 and the small base station 200 are connected by a wired link via the network interface 906.

  The CPU 905, the memory 904, and the RF circuit 903 realize the functions of the communication unit 11 including the reception unit 12 and the transmission unit 13 and the communication unit 21 including the reception unit 22 and the transmission unit 23 illustrated in FIGS. .

  For example, the memory 904 stores various programs such as a program for realizing the function of the communication unit 11 or the communication unit 21.

  The CPU 905 reads the program stored in the memory 904 and realizes the function of the communication unit 11 or the communication unit 21 by cooperating with the RF circuit 903 or the like.

  FIG. 13 is a hardware configuration diagram of the mobile station. The mobile station is, for example, the wireless communication device 3 in FIG. 1 or the mobile station 300 shown in FIG.

  The mobile station includes an antenna 911, a control unit 912, an RF circuit 913, a memory 914, and a CPU 915.

  The control unit 912 realizes the function of the control unit 34 illustrated in FIGS. 1 and 4, for example.

  The CPU 915, the memory 914, and the RF circuit 913 realize the function of the communication unit 31 including the reception unit 32 and the transmission unit 33 illustrated in FIGS.

  For example, the memory 914 stores various programs such as a program for realizing the function of the communication unit 31.

  The CPU 915 implements the function of the communication unit 31 by reading the program stored in the memory 914 and cooperating with the RF circuit 913 and the like.

(Modification)
In the second embodiment described above, the case where the primary base station is the macro base station 100 and the secondary base station is the small base station 200 has been described. However, the configuration of the base station is not limited to this, and the radio communication system according to the present embodiment can operate even with a system configuration as shown in FIG.

  FIG. 14 is a schematic diagram of dual connection of a wireless communication system according to a modification of the second embodiment. The radio communication system according to the present embodiment includes a small base station 200A as the radio communication device 1 in FIG. Moreover, it has the small base station 200B as the radio | wireless communication apparatus 2 in FIG. In addition, the mobile station 300 is provided as the wireless communication device 3 in FIG.

  The mobile station 300 is connected to the small base station 200A as a primary base station. The mobile station 300 is connected to the small base station 200A by a control plane 350 represented by a solid line arrow and a user plane 351 represented by a broken line arrow. In addition, the mobile station 300 is connected to the small base station 200B as a secondary base station. The mobile station 300 is connected to the small base station 200B by the user plane 351.

  The configuration of the radio communication system as shown in FIG. 14 is often employed for improving the characteristics of uplink communication.

  Further, in FIG. 14, the small base station 200 is connected to the macro base station 100, but the small base station 200 may be directly connected to an upper layer communication apparatus of the macro base station 100.

  Next, Example 3 will be described. The wireless communication system according to the third embodiment is different from the wireless communication system according to the second embodiment in that the data plane is separated between the RLC layer and the MAC layer. In the following description, description of each part having the same function is omitted.

  FIG. 15 is a diagram illustrating transmission / reception of user data performed using each link layer in the wireless communication system according to the third embodiment.

  In the case of downlink communication, the communication unit 11 of the macro base station 100 transmits, to the RLC layer 102, user data packets that are regularly numbered in the PDCP layer 101.

  Then, the communication unit 11 receives a delivery amount of user data from the control unit 14. Next, the communication unit 11 performs processing such as packet division and integration and number addition in the RLC layer. Thereafter, the communication unit 11 extracts a packet to which a number as a packet to be transmitted to the small base station 200 by the PDCP layer 101 is added. Then, the communication unit 11 transmits the extracted packet of user data to the MAC layer 203 of the small base station 200 with a delivery amount designated by the control unit 14 via a wired link. Further, the communication unit 11 outputs a packet to which a number as a packet to be processed in the own station is added to the MAC layer 104.

  In the case of uplink communication, the communication unit 11 receives user data from the MAC layer 203 of the small base station 200 via the wired link in the RLC layer 103. Then, the communication unit 11 divides and integrates the received user data and arranges them in order of numbers. Thereafter, the communication unit 11 transmits user data received from the small base station 200 from the RLC layer 103 to the PDCP layer 101.

  In the case of downlink communication, the communication unit 21 of the small base station 200 acquires user data from the RLC layer 102 of the macro base station 100 via a wired link in the MAC layer 203. Then, the communication unit 21 transmits user data from the MAC layer 203 to the mobile station 300.

  In the case of uplink communication, the communication unit 21 of the small base station 200 transmits user data received from the mobile station 300 from the MAC layer 203 to the RLC layer 103 of the macro base station 100.

  As described above, even when the data plane is separated between the RLC layer and the MAC layer, the delivery amount of data to the secondary wireless communication station is determined according to the data retention amount in the buffer of the mobile station. be able to. That is, the primary wireless communication station can transmit user data with an appropriate delivery amount from the primary wireless communication station to the secondary wireless communication station. Therefore, according to the wireless communication system according to the present embodiment, the efficiency of communication between wireless communication stations can be improved.

  Next, Example 4 will be described. The wireless communication system according to the fourth embodiment is different from the wireless communication system according to the second embodiment in that the data plane is separated in the previous stage of the PDCP layer. In the following description, description of each part having the same function is omitted.

  FIG. 16 is a diagram illustrating transmission / reception of user data performed using each link layer in the wireless communication system according to the fourth embodiment.

  In the case of downlink communication, the communication unit 11 of the macro base station 100 receives a delivery amount of user data from the control unit 14. Then, the communication unit 11 transmits the user data packet received from the upper layer communication device 4 to the PDCP layer 204 of the small base station 200 with the delivery amount specified by the control unit 14. At this time, the communication unit 11 distributes the user data so that the order of the numbers added in the PDCP layers 101 and 204 is preserved. For example, when it is determined that an even number is added in the own station and an odd number is added in the small base station 200, the communication unit 11 transmits a packet to which the odd number is assigned when the packets are arranged to the small base station. 200.

  Further, the communication unit 11 transmits the remaining user data to the PDCP layer 101 of the own station.

  Next, the communication unit 11 adds a number to the user data packet in accordance with the rules determined by the PDCP layer 101. For example, the communication unit 11 adds an even number to the packet. Then, the communication unit 11 transmits a packet of user data from the PDCP layer 101 to the RLC layer 102.

  In the case of uplink communication, the communication unit 11 receives user data from the PDCP layer 204 of the small base station 200 via a wired link. Then, the communication unit 11 transmits the received user data to the upper layer communication device 4.

  In the case of downlink communication, the communication unit 21 of the small base station 200 acquires user data from the macro base station 100 via a wired link in the PDCP layer 204. Then, the communication unit 21 adds a number to the user data packet according to the rule determined in the PDCP layer 204. For example, the communication unit 21 adds an odd number to the packet in the PDCP layer 204. Then, the communication unit 200 transmits user data from the PDCP layer 204 to the MAC layer 203.

  In the case of uplink communication, the communication unit 21 of the small base station 200 transmits user data from the RLC layer 202 to the PDCP layer 204.

  Then, the communication unit 21 performs decryption and security check on the user data in the PDCP layer 204. Then, the communication unit 21 transmits user data from the PDCP layer 204 to the macro base station 200.

  Thus, even when the data plane is separated in the previous stage of the PDCP layer, the data delivery amount to the secondary wireless communication station can be determined according to the data retention amount in the buffer of the mobile station. That is, the primary wireless communication station can transmit user data with an appropriate delivery amount from the primary wireless communication station to the secondary wireless communication station. Therefore, according to the wireless communication system according to the present embodiment, the efficiency of communication between wireless communication stations can be improved.

  Next, a wireless communication system according to a fifth embodiment is described. The radio communication system according to the present embodiment is different from the second embodiment in that the RLC feedback information is used to notify the data retention amount of the RLC buffer of the small base station.

  FIG. 17 is a diagram illustrating transmission / reception of user data executed using each link layer in the wireless communication system according to the fifth embodiment. In the present embodiment, as illustrated in FIG. 17, a case where the data plane is separated between the RLC layer and the MAC layer in the macro base station 100 will be described as an example. Hereinafter, description of the same functions as those in the second embodiment will be omitted.

  The communication unit 11 of the macro base station 100 separates the data plane after the RLC layer 102 and transmits user data to the small base station 200. At this time, the communication unit 11 transmits user data with a delivery amount specified by the control unit 14.

  When the two-way connection is started, the control unit 14 notifies the mobile station 300 of the setting of RLC Status Report that is RLC feedback information via the communication unit 11.

  Thereafter, the control unit 14 manages the number of packets transmitted during execution of the two-way connection with a counter, and sets a flag for a packet to be transmitted to the mobile station 300 when the counter reaches a certain value. FIG. 18 is a diagram illustrating an example of a format of a transmission packet. For example, the control unit 14 sets the flag of P (Pall) 701 of the transmission packet 700 in FIG. 18 to “1”. P701 is a bit for setting a polling command. The control unit 14 notifies the mobile station 300 of the transmission of the RLC Status Report by transmitting the packet with the flag set to the mobile station 300. In normal data, for example, “0” is set as a flag in P701.

  In addition, the control unit 14 calculates the amount of transmitted data, and when the transmitted data amount exceeds a predetermined value, sets a flag in the same manner as when the counter reaches a constant value. In this case, after setting the flag, the control unit 14 clears the transmitted data amount, and then repeats calculating the transmitted data amount.

  In addition, the timing of the RLC Status Report transmission request is not particularly limited. For example, the control unit 14 may set a flag at a predetermined period.

  The control unit 14 acquires an RLC Status Report from the communication unit 11. And the control part 14 acquires the sequence number of the oldest packet which is not received by the mobile station 300 from RLC Status Report. Furthermore, when packet loss has occurred, the control unit 14 acquires the sequence number of the lost packet in the divided packets.

  Here, RLC Status Report for transmitting information indicating the amount of buffer data in mobile station 300 will be described. FIG. 19 is a diagram illustrating a format of RLC Status Report. RLC Status Report 600 includes ACK_SN 601. ACK_SN 601 indicates a sequence number of an unreceived RLC data PDU. However, it represents the sequence number of an RLC PDU (RLC data PDU) that has not been notified that it has not been received in the STATUS PDU. That is, once it is reported that “not received” in the STATUS PDU, the sequence number is not set as ACK_SN 601.

  Further, the RLC Status Report 600 includes a NACK_SN 602. NACK_SN 602 represents the sequence number of the AMD PDU (or part thereof) in which loss is detected at the receiving side of the AM RLC entity.

  Further, SOstart indicates a part of AMD PDU having a sequence number (NACK_SN, for example, NACK_SN related to SOstart) in which a loss is detected at the receiving side of the AM RLC entity. SOend indicates a part of an AMD PDU having a sequence number (NACK_SN, for example, NACK_SN related to SOend) in which a loss is detected on the receiving side of the AM RLC entity.

  The RLC Status Report 600 includes a CPT (Carrier Packet Type).

  FIG. 20 is a diagram showing contents corresponding to values stored in the CPT. As shown in FIG. 20, if the value of CPT is “001”, it indicates feedback information of secondary connection. Further, if the value of CPT is “002”, it indicates feedback information of third connection. The CPT values “003” to “111” are reserved. In the present embodiment, the bit string “001” is stored in the CPT of the RLC Status Report 600.

  However, another value of CPT can also be designated to indicate notification of information indicating the data retention amount. For example, any one of “003” to “111” as CPT is determined in advance as a data retention amount in the buffer of the mobile station 300, and in the case of notification of information indicating the data retention amount A predetermined value may be stored in the CPT.

  The control unit 14 confirms whether or not the CPT value of the acquired RLC Status Report 600 is a predetermined value indicating that it is an RLC Status Report for transmitting information indicating the buffer data retention amount in the mobile station 300. . Then, the control unit 14 confirms ACK_SN 601 and obtains the sequence number of the oldest packet that has not reached the mobile station 300. Thereafter, the control unit 14 specifies the packet after the sequence number of the oldest packet that has not reached the mobile station 300, and obtains the data retention amount of the RLC buffer of the small base station 200. In addition, the control unit 14 obtains the data retention amount of the RLC buffer of the small base station 200 by obtaining, for example, the total amount in bytes of the area indicated by NACK_SN, SOstart, and SOend.

  FIG. 21 is a diagram for explaining an example of a method for calculating the data retention amount. In FIG. 21, it is assumed that the hatched portion is data for which delivery has not been confirmed. When RLC Status Report is received by the transmission side, it can be calculated as follows.

That is, the retention amount of RLC PDU = (b ₁ + h ₃ ) + (b ₄ + h ₂ ) or (SOend + h ₃ ) + (b ₄ + h ₂ ). Further, the retention amount of RLC SDU = B ₁ + B ₃ . Further, the retention amount of PDCP PDU = B ₁ + B ₂ . Further, the retention amount of PDCP SDU = (B ₁ −H ₁ ) + (B ₂ −H ₂ ).

  And the control part 14 determines the delivery amount of the user data according to the data retention amount of the buffer in the small base station 200. FIG. Then, the control unit 14 notifies the communication unit 11 of the determined delivery amount. Of the staying amounts, any staying amount used for determining the delivery amount of user data may be used.

  The control unit 34 of the mobile station 300 receives the RLC Status Report setting from the macro base station 100 at the start of the two-way connection. And the control part 34 sets the notification of RLC Status Rport.

  Then, the control unit 34 receives, from the macro base station 100, a packet in which the RLC Status Report transmission request flag is set during the two-way connection. Then, the control unit 34 generates an RLC Status Report using the sequence number of the received packet and the sequence number of the packet in which the loss is detected. Thereafter, the control unit 34 transmits the generated RLC Status Report to the small base station 200 via the communication unit 31 to perform RLC feedback, and transmits the RLC Status Report to the macro base station 100.

  Next, with reference to FIG. 22, the overall flow of transmission of the RLC Status Report will be described. FIG. 22 is a sequence diagram for explaining the overall flow of transmission of the RLC Status Report in the wireless communication apparatus according to the third embodiment. Here, states 801 and 802 in FIG. 22 represent data retention states in the RLC buffer of the small base station 200. Further, the arrows and data descriptions in states 801 and 802 indicate that user data is being output from the RLC buffer of the small base station 200 at that time.

  The macro base station 100 transmits a packet with a flag set to “0” to the mobile station 300 in order to notify that the RLC Status Report transmission request is not performed (step S11). Furthermore, the macro base station 100 transmits user data to the small base station 200 (step S12). The small base station 200 transmits user data to the mobile station 300 (step S13).

  At this time, data is accumulated in the RLC buffer of the small base station 200 as in the state 801. Then, user data is output from the RLC buffer of the small base station 200.

  After that, when the number of packets exceeds a certain value or the transmission data amount exceeds a threshold, the macro base station 100 is a packet whose flag is set to “1” in order to notify the transmission request of the RLC Status Report. Is transmitted to the mobile station 300 (step S14). Thereafter, the macro base station 100 continues to transmit user data to the small base station 200 (step S15). The small base station 200 continues to transmit user data to the mobile station 300 (step S16).

  Also at this time, data is accumulated in the RLC buffer of the small base station 200 as in the state 802. Then, user data is output from the RLC buffer of the small base station 200.

  When the mobile station 300 receives the packet with the flag “1”, the mobile station 300 transmits an RLC Status Report to the macro base station 100 (step S17). Furthermore, the mobile station 300 transmits RLC Status Report to the small base station 200, and performs RLC feedback (step S18).

  Thereafter, the macro base station 100 obtains the data retention amount of the RLC buffer in the small base station 200 from the received RLC Status Report, and controls the data delivery amount to the small base station 200 according to the obtained data retention amount.

  As described above, the primary wireless communication station according to the present embodiment determines the amount of user data delivered to the secondary wireless communication station according to the data retention amount of the secondary RLC buffer notified using the RLC Status Report. decide. Accordingly, the primary wireless communication station can transmit user data with an appropriate delivery amount from the primary wireless communication station to the secondary wireless communication station. Therefore, according to the wireless communication system according to the present embodiment, the efficiency of communication between wireless communication stations can be improved.

(Modification)
In the fifth embodiment, the macro base station 100 transmits a packet in which a flag is set and requests transmission of the RLC Status Report. However, the present invention is not limited to this. For example, the small base station 200 may transmit a packet in which a flag is set to request transmission of RLC Status Report.

  In this case, the control unit 24 of the small base station 200 monitors the number of packets and the data transmission amount in the same manner as the control unit 14 of the macro base station 100 of Example 2, and determines whether or not to set the flag. Also good.

  In addition, as in the fifth embodiment, after determining whether or not the macro base station 100 sets a flag, the packet with the flag set is transmitted to the small base station 200, and the small base station 200 The packet may be transferred to the mobile station 300.

  Further, in the fifth embodiment, the mobile station 300 wirelessly transmits the RLC Status Report to the macro base station 100, but the transmission method is not limited to this. For example, the RLC Status Report may be transmitted to the macro base station 100 using a wired link.

  In the fifth embodiment, a polling command that has been conventionally defined as a packet format is used for the RLC Status Report transmission request. However, the transmission request method is not limited to this. For example, a transmission request may be made by defining a new polling command.

  Further, instead of executing Status Report at the RLC level, the macro base station 100 may determine the data retention amount of the RLC buffer of the secondary radio communication station by causing the mobile station 300 to perform PDCP Status Reporting. Good.

  The embodiments disclosed above may be implemented in any combination without departing from the scope of the invention. Further, in the description, the downlink communication is mainly described for the uplink communication accompanying the downlink communication. However, the present embodiment can be similarly implemented even when the uplink communication is mainly used and the downlink communication is accompanied.

1, 2, 3 Wireless communication device 4 Upper layer communication device 11, 21, 31 Communication unit 12, 22, 32 Reception unit 13, 23, 33 Transmission unit 14, 24, 34 Control unit 100 Macro base station 200 Small base station 300 Mobile station 101,307 PDCP layer 102,103,201,202,303-306 RLC layer 104,203,301,302 MAC layer

Claims (10)

A first wireless communication device, and a second wireless communication device that transmits data from the first wireless communication device. A communication unit that communicates with the device in a multiple manner;
An accumulation unit for accumulating data received from the second wireless communication device;
A notification unit that directly notifies the first wireless communication device of the data reception status in the storage unit, and the amount of data transmitted from the first wireless communication device to the second wireless communication device receives the notification. The mobile station is controlled by the first wireless communication device.   The notifying unit stores at least the sequence number of the packet that should be received earliest in the packet of data that has not arrived from the second wireless communication device, and notifies the first wireless communication device The mobile station according to claim 1, wherein:   2. The communication unit according to claim 1 or 2, wherein the communication unit performs multi-way communication using the first logical processing entity for communicating with the first wireless communication device and the second wireless communication device. 2. The mobile station according to 2.   The said notification part notifies the reception status of the said data to the said 1st wireless communication apparatus according to the information regarding the period received from the said 1st wireless communication apparatus, The any one of Claims 1-3 characterized by the above-mentioned. The mobile station described in 1.   The mobile station according to any one of claims 1 to 3, wherein the notification unit performs notification when a data retention amount in the storage unit exceeds a threshold value.   The mobile station according to any one of claims 1 to 5, wherein the notification unit notifies the first wireless communication apparatus of a reception status of the data using a PDCP Status Report. A wireless communication system in which a wireless communication terminal , a first wireless communication device, and a second wireless communication device communicate with each other,
The wireless communication terminal is
A first communication unit that communicates in a multiple manner with the first wireless communication device and the second wireless communication device using a first logical processing entity and a second logical processing entity that operates in association with the first logical processing entity When,
An accumulation unit for accumulating data received from the second wireless communication device;
A notification unit that directly notifies the first wireless communication device of the data reception status in the storage unit,
The first wireless communication device is:
A second communication unit for transmitting data to the second wireless communication device;
A control unit that directly receives the data reception status in the storage unit from the notification unit of the wireless communication terminal and controls the amount of data transmitted by the second communication unit;
The second wireless communication device is
A wireless communication system, comprising: a third communication unit that transmits data received from the first wireless communication device to the wireless communication terminal . A base station that communicates data with a mobile station,
A communication unit for transmitting data directly to the mobile station;
A transfer unit that transfers a part of the data to the mobile station to another wireless communication device;
A control unit that receives a reception status of data received by the mobile station via the other radio communication device directly from the mobile station, and controls a data amount transferred from the transfer unit to the other radio communication device; A base station characterized by comprising:   The base station according to claim 8, wherein the transfer unit communicates with the other wireless communication device using a link layer protocol. Communicating in a multiple manner between a wireless communication terminal , a first wireless communication device, and a second wireless communication device using a first logical processing entity and a second logical processing entity operating in association with the first logical processing entity And
In the wireless communication terminal , the data received from the first wireless communication device via the second wireless communication device is stored in a buffer,
Notifying the first wireless communication device directly of the data reception status in the buffer;
The first wireless communication apparatus controls the amount of data transmitted to the second wireless communication apparatus in response to the notification.

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