JP2013085031A - Base station and communications control method - Google Patents

Abstract

The present invention provides a base station and a communication control method capable of more reliably transmitting data, such as control data and voice packets, that are greatly affected by discarding to a mobile station.
A base station 100 includes: a buffer control unit 103 that controls data discarded from the layer 2 buffer 101 among data stored in the layer 2 buffer 101; and a data stored in the layer 2 buffer 101. And a data type acquisition unit 105 for acquiring the type. The buffer control unit 103 discards only data of a predetermined type from the layer 2 buffer 101 based on the data type acquired by the data type acquisition unit 105.
[Selection] Figure 2

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. Here, control data and voice packets included in Signal Radio Bearer (SRB), such as control data and voice packets, and data such as general data communication, even if the data is discarded, retransmission has a substantial effect on the user. There is a problem that data with almost no data is discarded without distinction.

  Therefore, the present invention has been made in view of such a situation, and provides a base station and a communication control method that can more reliably transmit data, such as control data and voice packets, that are greatly affected by discarding to a mobile station. With the goal.

  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 101), which controls data to be discarded from the layer 2 buffer among the data stored in the layer 2 buffer (buffer control unit 103) ) And a data type acquisition unit (data type acquisition unit 105) that acquires the type of data stored in the layer 2 buffer, and the buffer control unit includes the data acquired by the data type acquisition unit Based on this type, only the data of a predetermined type is discarded from the layer 2 buffer.

  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, wherein a step of acquiring a type of data stored in the layer 2 buffer and a predetermined type of data stored in the layer 2 buffer are determined based on the acquired type of data. And a step of discarding only the type of data from the layer 2 buffer.

  According to the features of the present invention, it is possible to provide a base station and a communication control method that can more reliably transmit data, such as control data and voice packets, that are greatly affected by discarding to a mobile station.

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 101 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 101 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 shown in FIG. 2, the base station 100 includes a layer 2 buffer 101, a buffer control unit 103, a data type acquisition unit 105, a scheduler control unit 106, and a radio communication unit 107.

  The layer 2 buffer 101 temporarily stores data transmitted to the mobile stations 200A and 200B via the base station 100. The layer 2 buffer 101 is a second layer level buffer shared by a plurality of mobile stations.

  Specifically, the layer 2 buffer 101 temporarily stores RLC / PDCP SDU (Service Data Unit). The layer 2 buffer 101 (RLC / PDCP buffer) is shared by a plurality of mobile stations (users) and radio access bearers. The layer 2 buffer 101 is prepared for each cell formed by the base station 100. In the present embodiment, the layer 2 buffer 101 is set to 32 Mbytes for a bandwidth of 5 MHz. Note that the capacity of the layer 2 buffer 101 is not limited to such a setting.

  The buffer control unit 103 controls the layer 2 buffer 101. In particular, the buffer control unit 103 controls data (SDU) discarded from the layer 2 buffer 101 among the data stored in the layer 2 buffer 101.

  Specifically, based on the data type acquired by the data type acquisition unit 105, the buffer control unit 103 receives only data of a predetermined type (for example, a data packet related to normal data communication) from the layer 2 buffer 101. Discard. In the present embodiment, the buffer control unit 103 uses only the data mapped to the logical channel having a predetermined priority based on the logical channel priority (LCP) acquired by the data type acquisition unit 105 as the layer 2 buffer 101. Discard from. Specifically, a flag indicating whether or not to discard is set for the LCP associated with the data to be discarded.

  Alternatively, the buffer control unit 103 corresponds to a predetermined QoS or QCI (QoS Class Identifier) based on QoS (Quality of Service) or QCI (QoS Class Identifier) of the data acquired by the data type acquisition unit 105. It is also possible to discard only the data to be processed from the layer 2 buffer 101. In this case, a flag indicating whether or not to discard is set for QoS or QCI (QoS Class Identifier) associated with the data to be discarded.

  For example, based on the notified LCP, the buffer control unit 103, for each type such as control data (C-Plane data), voice packet, and normal data communication data packet included in the Signal Radio Bearer (SRB) Whether to discard data from the layer 2 buffer 101 can be controlled.

  Further, when an overflow of the layer 2 buffer 101 occurs, the buffer control unit 103 can discard data from which transmission processing in the radio link control (RLC) layer has not been started from the layer 2 buffer 101. Specifically, the buffer control unit 103 discards SDUs for which RLC transmission processing has not started from among RLC / PDCP SDUs stored in the layer 2 buffer 101. More specifically, the buffer control unit 103 can discard only those SDUs that are part of the PDCP SDU and are not yet mapped to the transport block.

  The buffer control unit 103 can also control the layer 2 buffer 101 in a state where a predetermined margin is provided from the maximum size of the layer 2 buffer 101. Such control is effective when the layer 2 buffer 101 is controlled periodically at predetermined intervals. Specifically, the buffer control unit 103 manages the difference between the layer 2 buffer 101 and the total amount of data staying in the layer 2 buffer 101, that is, the free capacity of the layer 2 buffer 101.

When the amount of data stored in the layer 2 buffer 101 exceeds a predetermined threshold Th _{overflow, discard} , the buffer control unit 103 until the amount of data stored in the layer 2 buffer 101 falls below Th _{overflow, discard} The predetermined type of data described above is discarded from the layer 2 buffer 101. The predetermined threshold may be controlled based on the free capacity of the layer 2 buffer 101. Specifically, when the free capacity of the layer 2 buffer 101 falls below a predetermined threshold, the buffer control unit 103 stores a predetermined type of data until the free capacity of the layer 2 buffer 101 exceeds the threshold. You may make it discard from 101.

  Further, the buffer control unit 103 may discard the data from the layer 2 buffer 101 by the following method.

・ Discard from data with low priority ・ Discard from data with long buffer retention time (old data) ・ Round-robin discard in units of mobile stations (users) / radio access bearers ・ Random discard For example, among the data to be discarded, data that is mapped to a lower LCP, data that uses a specific protocol that is less affected when discarded, or the scheduler control unit 106 determines that the priority is low Data. In addition, the mobile station (user) identification of the data stored (residual) in the layer 2 buffer 101 is to confirm the TEID (Tunnel Endpoint Identifier) that is the delivery destination identifier assigned to the SDU. (See 3GPP TS29.060).

  The data type acquisition unit 105 acquires the type of data stored in the layer 2 buffer 101. Specifically, as described above, the data type acquisition unit 105 acquires the priority (LCP) of the logical channel to which the data is mapped as the data type. The data type acquisition unit 105 notifies the acquired LCP to the buffer control unit 103.

  The scheduler control unit 106 manages the amount of radio resources used by the mobile stations 200A and 200B (users), the amount of data (traffic) transmitted and received by the mobile stations, and the priority between users.

  The radio communication unit 107 performs radio communication with the mobile station 200A (200B) according to the LTE scheme. In particular, in this embodiment, the radio communication unit 107 schedules the data (PDU) output from the layer 2 buffer 101 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 101 by the base station 100 will be described. FIG. 3 shows a control operation flow of the layer 2 buffer 101 by the base station 100.

  As shown in FIG. 3, the base station 100 sequentially stores data arriving from an upper layer (IP layer) in the layer 2 buffer 101 (S10). Here, FIG. 4 shows how data is stored in the layer 2 buffer 101.

  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 101. Data included in the RLC / PDCP SDU 300 includes control data (C-Plane data), voice packets, and data packets for normal data communication. The layer 2 buffer 101 is shared by a plurality of mobile stations (users).

  The base station 100 determines whether or not an overflow from the layer 2 buffer 101 of the RLC / PDCP SDU 300 has occurred (or is likely to occur) (S20).

  When an overflow occurs (or it is determined that there is a possibility of occurrence), the base station 100 determines an RLC / PDCP SDU 300 to be discarded from the layer 2 buffer 101. Specifically, base station 100 determines RLC / PDCP SDU 300 to be discarded based on the type of RLC / PDCP SDU 300 (control data, voice packet, and data packet) (S30). Note that the base station 100 preferably discards other data preferentially so that at least the control data is not discarded. In addition, since voice packets are also greatly affected by discarding (such as voice delay increase or quality degradation), the base station 100 preferably discards other data (that is, normal data) with priority.

Next, the base station 100 discards the data of the determined data type, for example, the RLC / PDCP SDU 300 including the data packet from the layer 2 buffer 101 (S40). As a result of discarding the determined type of RLC / PDCP SDU 300, the base station 100 determines whether or not the amount of data stored in the layer 2 buffer 101, that is, staying data has recovered below a predetermined threshold (Th _{overflow, discard} ) Is determined (S50).

(4) Operation / Effect According to the base station 100, the buffer control unit 103 determines whether or not data of a predetermined type (for example, a data packet) Only from the layer 2 buffer 101. For this reason, even if the layer 2 buffer 101 overflows, data such as a data packet is discarded with priority even if it is discarded, and data that does not have a 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 the present embodiment, based on the LCP acquired by the data type acquisition unit 105, only the data mapped to the logical channel having a predetermined priority is discarded from the layer 2 buffer 101. For this reason, in order to newly identify the type of data, the type of data to be preferentially discarded can be selected without adding new information.

  In the present embodiment, data for which transmission processing in the radio link control (RLC) layer has not started is discarded from the layer 2 buffer 101. For this reason, discarding the data does not affect the transmission processing in the RLC layer and below.

In this embodiment, a predetermined type of data (for example, a data packet) is discarded from the layer 2 buffer 101 until the amount of data stored in the layer 2 buffer 101 falls below a predetermined threshold (Th _{overflow, discard} ). . For this reason, even when the layer 2 buffer 101 is periodically controlled at predetermined intervals, the overflow of the layer 2 buffer 101 can be more reliably 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 above-described embodiment, a predetermined type of data is discarded from the layer 2 buffer 101 until the amount of data stored in the layer 2 buffer 101 falls below Th _{overflow, discard.} Not necessarily required. For example, a predetermined type of data may be discarded every time the layer 2 buffer 101 overflows without setting Th _{overflow and discard} .

  In the embodiment described above, data for which transmission processing in the RLC layer has not been started has been discarded from the layer 2 buffer 101, but such an operation is not necessarily essential. In the above-described embodiment, the data type to be discarded is determined based on the LCP. However, information for identifying the data type is newly added, and the data type is identified based on the information. Good.

  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 ... Layer 2 buffer
103: Buffer control unit
105 ... Data type acquisition unit
106 ... Scheduler controller
107… Wireless communication part
200A, 200B ... Mobile station
300… RLC / PDCP SDU
C1 ... cell

Claims (5)

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;
A data type acquisition unit for acquiring the type of data stored in the layer 2 buffer;
The buffer control unit is a base station that discards only data of a predetermined type from the layer 2 buffer based on the type of the data acquired by the data type acquisition unit. The data type acquisition unit acquires the priority of the logical channel to which the data is mapped as the data type,
The buffer control unit discards only data mapped to a logical channel having a predetermined priority from the layer 2 buffer based on the priority of the logical channel acquired by the data type acquisition unit. The listed base station.   The base station according to claim 1, wherein the buffer control unit discards, from the layer 2 buffer, data for which transmission processing in a radio link control layer has not been started.   When the amount of data stored in the layer 2 buffer exceeds a predetermined threshold, the buffer control unit is configured to output the predetermined amount until the amount of data stored in the layer 2 buffer falls below the predetermined threshold. The base station according to claim 1, wherein the type of data is discarded 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 a type of data stored in the layer 2 buffer;
And a step of discarding only a predetermined type of data from the layer 2 buffer based on the type of the acquired data among the data stored in the layer 2 buffer.

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