JP5462396B2 - Base station and communication control method - Google Patents

Description

  The present invention relates to a base station and a communication control method including a layer 2 buffer that temporarily stores data transmitted to a mobile station and is shared by a plurality of mobile stations.

  In the Long Term Evolution (LTE) standardized by the 3rd Generation Partnership Project (3GPP), a layer 2 level (RLC / PDCP) buffer that temporarily stores data (IP packets) transmitted to the mobile station (UE) ( Hereinafter, a layer 2 buffer) is provided in the base station (eNB). The data stored in the layer 2 buffer is transmitted to the mobile station, and is discarded after confirming that the mobile station has received the data normally by ACK in the RLC layer.

  The layer 2 buffer is shared by a plurality of mobile stations / bearers residing in a cell formed by the base station. Thus, the layer 2 buffer can be efficiently used by sharing the layer 2 buffer among a plurality of mobile stations.

3GPP TS 36.300 V10.3.0, 3rd Generation Partnership Project; Technical Specification Group Radio Access Network; Evolved Universal Terrestrial Radio Access (E-UTRA) and Evolved Universal Terrestrial Radio Access Network (E-UTRAN); Overall description; Stage 2 (Release 10 ), March 2011

  However, the above-described conventional layer 2 buffer has the following problems. That is, when the layer 2 buffer overflows due to the staying data, the overflowed data is sequentially discarded. Since the layer 2 buffer is shared by a plurality of mobile stations, if a large amount of data addressed to a specific mobile station occurs, the layer 2 buffer may be occupied by the data.

  In particular, when there is an upper limit on the amount of data coming from higher layers, such as File Transfer Protocol (FTP), this situation is unlikely to occur, but the sender confirms data delivery as in User Datagram Protocol (UDP). In the case of a protocol that does not perform the above, such a state is likely to occur.

  If the layer 2 buffer is occupied by data addressed to a specific mobile station, the data of other mobile stations that arrived at the base station later will overflow and be discarded. Can not.

  Therefore, the present invention has been made in view of such a situation, and it is an object of the present invention to provide a base station and a communication control method for controlling data staying in a layer 2 buffer while ensuring fairness between mobile stations. To do.

  A first feature of the present invention is that a layer 2 buffer (a second layer level buffer) that temporarily stores data to be transmitted to mobile stations (mobile stations 200A and 200B) and is shared by a plurality of the mobile stations. A base station (base station 100) having a layer 2 buffer 103), and a buffer control unit (buffer control unit 105) that controls data discarded from the layer 2 buffer among data stored in the layer 2 buffer ) And an upper limit holding unit (upper limit holding unit 107) that acquires an upper limit for each mobile station of data that can be stored in the layer 2 buffer, and the buffer control unit holds the upper limit Based on the upper limit value acquired by the mobile station, data exceeding the upper limit value for each mobile station and data for which transmission processing in the radio link control layer has not been started are received from the layer 2 buffer. The gist is to discard.

  According to a second aspect of the present invention, communication using a communication apparatus that temporarily stores data transmitted to a mobile station and includes a layer 2 buffer that is a second layer level buffer shared by the plurality of mobile stations. A control method, the step of obtaining an upper limit value for each mobile station of data that can be stored in the layer 2 buffer, and the upper limit value for each mobile station based on the obtained upper limit value. And a step of discarding the excess data and data for which transmission processing in the radio link control layer has not started from the layer 2 buffer.

  According to the characteristics of the present invention, it is possible to provide a base station and a communication control method for controlling data staying in a layer 2 buffer while ensuring fairness between mobile stations.

1 is an overall schematic configuration diagram of a wireless communication system according to an embodiment of the present invention. FIG. 3 is a functional block configuration diagram of a base station 100 according to the embodiment of the present invention. It is a figure which shows the control operation | movement flow of the layer 2 buffer 103 by the base station 100 which concerns on embodiment of this invention. It is a figure which shows a mode that data are stored in the layer 2 buffer 103 which concerns on embodiment of this invention.

  Next, an embodiment of the present invention will be described. In the following description of the drawings, the same or similar parts are denoted by the same or similar reference numerals. However, it should be noted that the drawings are schematic and ratios of dimensions and the like are different from actual ones.

  Accordingly, specific dimensions and the like should be determined in consideration of the following description. Moreover, it is a matter of course that portions having different dimensional relationships and ratios are included between the drawings.

(1) Overall Schematic Configuration of Radio Communication System FIG. 1 is an overall schematic configuration diagram of a radio communication system according to the present embodiment. As shown in FIG. 1, the radio communication system according to the present embodiment employs a Long Term Evolution (LTE) scheme, and includes a core network 50, a base station 100 (eNB), and mobile stations 200A and 200B (UE). Including.

  Base station 100 is connected to core network 50. Base station 100 forms cell C1 and performs radio communication with mobile stations 200A and 200B according to the LTE scheme. In particular, in this embodiment, as will be described later, the base station 100 includes a layer 2 buffer that temporarily stores data transmitted to the mobile station 200A (and the mobile station 200B), and stores data stored in the layer 2 buffer. Control (send or discard). Note that the mobile stations controlled by the base station 100 are not limited to the mobile stations 200A and 200B, and the base station 100 can control a larger number of mobile stations.

(2) Functional Block Configuration of Radio Communication System Next, a functional block configuration of the radio communication system according to the present embodiment will be described. Specifically, the functional block configuration of base station 100 will be described. FIG. 2 is a functional block configuration diagram of the base station 100. As illustrated in FIG. 2, the base station 100 includes an upper layer processing unit 101, a layer 2 buffer 103, a buffer control unit 105, an upper limit holding unit 107, a data type acquisition unit 109, and a radio communication unit 111.

  The upper layer processing unit 101 executes processing in the upper layer, specifically, the RLC / PDCP layer. In particular, in the present embodiment, the upper layer processing unit 101 generates an RLC / PDCP SDU (Service Data Unit), and sequentially outputs the generated RLC / PDCP SDU to the layer 2 buffer 103. The RLC / PDCP SDU includes data according to FTP and UDP.

  The layer 2 buffer 103 temporarily stores data transmitted to the mobile stations 200A and 200B via the base station 100. The layer 2 buffer 103 is a second layer level buffer shared by a plurality of mobile stations.

  Specifically, the layer 2 buffer 103 temporarily stores RLC / PDCP SDU (Service Data Unit). The layer 2 buffer 103 (RLC / PDCP buffer) is shared by a plurality of mobile stations (users) and radio access bearers.

  The buffer control unit 105 controls the layer 2 buffer 103. In particular, the buffer control unit 105 controls data (SDU) discarded from the layer 2 buffer 103 among the data stored in the layer 2 buffer 103.

  Specifically, based on the upper limit value (Discard Buffer Threshold) for each mobile station held by the upper limit value holding unit 107, the buffer control unit 105 stores data exceeding the upper limit value for each mobile station in the layer 2 buffer. Discard from 103. The buffer control unit 105 stores, for a specific mobile station, the data stored in the layer 2 buffer 103, that is, if the amount of retained data exceeds the Discard Buffer Threshold, Discard.

  Note that the mobile station (user) identification of the data stored (stayed) in the layer 2 buffer 103 is to confirm the TEID (Tunnel Endpoint Identifier) that is the delivery destination identifier assigned to the SDU. (See 3GPP TS29.060).

  In addition, the buffer control unit 105 selects a predetermined type of data (for example, normal data communication) from the RLC / PDCP SDU 300 addressed to a predetermined mobile station based on the data type acquired by the data type acquisition unit 109. Only the data packet) is discarded from the layer 2 buffer 103. Specifically, based on the logical channel priority (LCP) acquired by the data type acquisition unit 109, the buffer control unit 105 applies only the data mapped to the logical channel having a predetermined priority to the layer 2 buffer 103. Discard from. Specifically, a flag indicating whether or not to discard is set for the LCP associated with the data to be discarded. Note that the buffer control unit 105 can discard only data mapped to a logical channel having a predetermined priority from the layer 2 buffer 103 based on QoS (Quality of Service) or QCI (QoS Class Identifier).

  For example, when discarding data from the layer 2 buffer 103, the buffer control unit 105 may discard data having a long buffer residence time (old data). In addition, the buffer control unit 105 transmits data packets for normal data communication based on types such as control data (C-Plane data), voice packets, and data packets for normal data communication included in the Signal Radio Bearer (SRB). You may make it discard preferentially. As a result, discarding of control data and voice packets that are greatly affected by discarding can be suppressed.

  Alternatively, when the overflow of the layer 2 buffer 103 occurs, the buffer control unit 105 may discard from the layer 2 buffer 103 data that has not started transmission processing in the radio link control (RLC) layer. Specifically, the buffer control unit 105 discards SDUs for which transmission processing in the RLC has not started among the RLC / PDCP SDUs stored in the layer 2 buffer 103. More specifically, the buffer control unit 105 can discard only an SDU that is a part of an RLC / PDCP SDU and has not yet been mapped to a transport block.

  The upper limit holding unit 107 holds an upper limit (Discard Buffer Threshold) for each mobile station of data that can be stored in the layer 2 buffer 103. Specifically, the upper limit holding unit 107 may be for each mobile station type (or for each system bandwidth, for each mobile station category, for each protocol used in the upper layer, for each traffic type, and for each application used in the upper layer. ) Is stored, and Discard Buffer Threshold corresponding to the type of mobile station is notified to the buffer control unit 105.

  Further, the upper limit holding unit 107 may acquire and hold a Discard Buffer Threshold for each mobile station via an external communication device.

  The data type acquisition unit 109 acquires the type of data stored in the layer 2 buffer 103. Specifically, as described above, the data type acquisition unit 109 acquires the priority (LCP) of the logical channel to which the data is mapped as the data type. The data type acquisition unit 109 can also acquire QoS or QCI. The data type acquisition unit 109 notifies the buffer control unit 105 of the acquired LCP.

  The radio communication unit 111 performs radio communication with the mobile station 200A (200B) according to the LTE scheme. In particular, in this embodiment, the radio communication unit 111 schedules the data (SDU) output from the layer 2 buffer 103 to the corresponding radio resource block based on the type of the data, and the mobile station 200A (and Transmit to mobile station 200B).

(3) Operation of Radio Communication System Next, the operation of the radio communication system according to the present embodiment will be described. Specifically, the control operation of the layer 2 buffer 103 by the base station 100 will be described. FIG. 3 shows a control operation flow of the layer 2 buffer 103 by the base station 100.

  As shown in FIG. 3, the base station 100 sequentially stores data arriving from an upper layer (RLC / PDCP layer) in the layer 2 buffer 103 (S10). Here, FIG. 4 shows how data is stored in the layer 2 buffer 103.

  As illustrated in FIG. 4, the base station 100 sequentially stores the RLC / PDCP SDU 300 arriving from the RLC / PDCP layer in the layer 2 buffer 103. As described above, the layer 2 buffer 103 is shared by a plurality of mobile stations. In the example shown in FIG. 4, the RLC / PDCP SDU 300 (data) of the user A and the user B (mobile station) is the layer 2 buffer. Stored in 103.

  In the example illustrated in FIG. 4, the upper limit value Discard Buffer Threshold for each mobile station that can stay in the layer 2 buffer 103 is set to “9”.

  The base station 100 determines whether or not the data staying in the layer 2 buffer 103 for each mobile station is greater than or equal to the Discard Buffer Threshold (S20).

  When the data staying in the layer 2 buffer 103 is equal to or greater than the Discard Buffer Threshold, the base station 100 discards the RLC / PDCP SDU 300 addressed to the mobile station (for example, user A, see FIG. 4) (S30).

(4) Operation / Effect According to the base station 100, data destined for the mobile station exceeding the upper limit value is discarded from the layer 2 buffer 103 based on the upper limit value (Discard Buffer Threshold) for each mobile station. For this reason, it is possible to suppress the layer 2 buffer 103 from being occupied by data addressed to a specific mobile station, and overflowing and discarding data of other mobile stations that have arrived at the base station 100 later. That is, according to the base station 100, data staying in the layer 2 buffer 103 can be controlled while ensuring fairness between mobile stations.

  In the present embodiment, based on the type of RLC / PDCP SDU 300 acquired by the data type acquisition unit 109, data of a predetermined type (for example, data packet) among the RLC / PDCP SDU 300 addressed to a predetermined mobile station Only from the layer 2 buffer 103. For this reason, even when the layer 2 buffer 103 overflows, data such as a data packet is discarded preferentially even if it is discarded but has little substantial effect on the user due to retransmission. That is, according to the base station 100, data such as control data and voice packets that are greatly affected by discarding can be transmitted to the mobile stations 200A and 200B more reliably.

  In this embodiment, data for which transmission processing in the radio link control (RLC) layer has not started is discarded from the layer 2 buffer 103. For this reason, even if the data is discarded, retransmission in the RLC layer can be prevented.

(5) Other Embodiments As described above, the content of the present invention has been disclosed through one embodiment of the present invention. However, it is understood that the description and drawings constituting a part of this disclosure limit the present invention. should not do. From this disclosure, various alternative embodiments will be apparent to those skilled in the art.

  For example, in the embodiment described above, data for which transmission processing in the RLC layer has not been started has been discarded from the upper layer processing unit 101, but such an operation is not necessarily essential. In the above-described embodiment, based on the type of the RLC / PDCP SDU 300, only the data of a predetermined type is discarded from the layer 2 buffer 103 out of the RLC / PDCP SDU 300 addressed to the predetermined mobile station. Such an operation is not necessarily essential. That is, the base station 100 may discard the data addressed to the mobile station regardless of the data type.

  As described above, the present invention naturally includes various embodiments that are not described herein. Therefore, the technical scope of the present invention is defined only by the invention specifying matters according to the scope of claims reasonable from the above description.

50 ... Core network
100 ... Base station
101: Upper layer processing section
103 ... Layer 2 buffer
105 ... Buffer control section
107 ... Upper limit value acquisition unit
109 ... Data type acquisition part
111… Wireless communication part
200A, 200B ... Mobile station
300… RLC / PDCP SDU
C1 ... cell

Claims (2)

A base station that temporarily stores data transmitted to a mobile station and includes a layer 2 buffer that is a second layer level buffer shared by a plurality of the mobile stations,
Among the data stored in the layer 2 buffer, a buffer control unit that controls data discarded from the layer 2 buffer;
An upper limit that holds an upper limit value of data that can be stored in the layer 2 buffer for each system bandwidth, for each mobile station category, for each protocol used in an upper layer, for each traffic type, or for each application used in an upper layer A value holding unit,
The buffer control unit, based on the upper limit value held by the upper limit value holding unit, out of the data exceeding the upper limit value, one of RLC / PDCP Service Data Units stored in the layer 2 buffer. A base station that discards only Service Data Units that are not yet mapped to transport blocks from the layer 2 buffer. A communication control method using a communication device that temporarily stores data transmitted to a mobile station and includes a layer 2 buffer that is a second layer level buffer shared by a plurality of the mobile stations,
Obtaining an upper limit value of data that can be stored in the layer 2 buffer for each system bandwidth, for each mobile station category, for each protocol used in a higher layer, for each traffic type, or for each application used in a higher layer When,
Based on the acquired upper limit value, the data exceeding the upper limit value is a part of the RLC / PDCP Service Data Unit stored in the layer 2 buffer and has not yet been mapped to the transport block. And a step of discarding only service data units that are not present from the layer 2 buffer.

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