Invention title: Transmitter and buffer control method
Technical field
[0001]
　The present invention relates to a transmitter and a buffer control method.
Background technology
[0002]
　In today's networks, the traffic of mobile terminals (smartphones and feature phones) occupies most of the network resources. In addition, the traffic used by mobile terminals tends to increase in the future.
[0003]
　On the other hand, in line with the development of IoT (Internet of a things) services (for example, monitoring systems for transportation systems, smart meters, devices, etc.), it is required to support services with various requirements. Therefore, in the communication standard of the 5th generation mobile communication (5G or NR (New Radio)), in addition to the standard technology of 4G (4th generation mobile communication) (for example, Non-Patent Documents 1 to 11), the communication standard is further higher. There is a demand for technology that realizes higher data rates, larger capacities, and lower delays. Regarding the 5th generation communication standard, technical studies are being carried out by the 3GPP working group (for example, TSG-RAN WG1, TSG-RAN WG2, etc.). (Non-Patent Documents 12 to 39). Currently, the first edition of the 5G standard specifications specified by 3GPP has been released.
[0004]
　As mentioned above, in 5G, many uses classified into eMBB (Enhanced Mobile BroadBand), Massive MTC (Machine Type Communications) and URLLC (Ultra-Reliable and Low Latency Communication) in order to support a wide variety of services. Case support is expected.
[0005]
　Further, in the communication standard of a wireless communication system, specifications are generally defined as a protocol stack (also referred to as a hierarchical protocol) in which a wireless communication function is divided into a series of layers. For example, the physical layer is defined as the first layer, the data link layer is defined as the second layer, and the network layer is defined as the third layer. In the 4th generation mobile communication system such as LTE (Long Term Evolution), the second layer is divided into a plurality of sublayers, which are a MAC (Medium Access Control) layer, an RLC (Radio Link Control) layer, and a PDCP (Packet). Data Convergence Protocol) Consists of layers. Further, in the 4th generation mobile communication system, the first layer is composed of a PHY (Physical) layer, and the third layer is composed of an RRC (Radio Resource Control) layer (the RRC layer is only a control plane). Since the MAC layer, RLC layer, and PDCP layer are sublayers of the second layer as described above, they may be referred to as MAC sublayer, RLC sublayer, and PDCP sublayer.
[0006]
　Each layer in the transmission device of the wireless communication system performs processing conforming to a predetermined protocol such as adding a header to a data block (also called a service data unit (SDU)) from an upper layer. By doing so, a protocol data unit (PDU) is generated and transferred to a lower layer. For example, in the LTE RLC layer, PDCP-PDU, which is a data block from the PDCP layer, which is the upper layer, is designated as RLC-SDU, and a plurality of RLC-SDUs are within the TB (Transport Block) length notified from the lower layer. RLC-PDU is generated by concatenating. Such an RLC-PDU is attached with an RLC header having a sequence number (SN: Sequence Number) in the RLC layer, and then transferred to a MAC layer which is a lower layer.
[0007]
　Each layer in the receiving device of the wireless communication system receives the data block (that is, PDU) from the lower layer, and transfers the data block (that is, SDU) taken out by removing the header or the like to the upper layer. For example, in the RLC layer of LTE, the RLC header attached to the data block (also referred to as MAC-SDU or RLC-PDU) from the MAC layer which is a lower layer is referred to and stored in one RLC-PDU. Processing such as reconstructing the plurality of RLC-SDUs is performed, and the RLC-SDU is transferred to the PDCP layer which is an upper layer. At that time, in order to compensate the order of RLC-SDU for the upper layer, in the reconstruction of RLC-SDU, an ordering process based on the RLC sequence number of the RLC header is performed. Then, when it is detected that the RLC sequence number is missing, the RLC retransmission control for requesting the transmission device to retransmit the RLC-PDU is executed.
[0008]
　In the 5G specification, priority control of uplink data called LCP (Logical Channel Prioritization) is performed in the MAC layer (Non-Patent Document 22). In LCP, for example, priority control is performed for each data in order to suppress the occurrence of characteristic deterioration (starvation) due to preferential radio resource allocation according to the request delay. Specifically, parameters such as a bit rate are set for the logical channel (LCH: Logical CHannel) through which each data is transmitted, and priority control is performed so as to satisfy these parameters (which are also requirements). To. However, if priority control is performed for each channel, the granularity becomes excessively fine and the amount of data processed by the terminal device increases. Therefore, a logical channel with the same requirements may be aggregated to generate an LCG (Logical Channel Group), and priority control may be performed for each LCG.
[0009]
　Further, in a wireless communication system, data may be temporarily held in a buffer in, for example, an RLC layer or a PDCP layer before the transmitting device transmits data. The data held in the buffer is discarded, for example, when the preset discard timer expires.
Prior art literature
Non-patent literature
[0010]
Non-Patent Document 1: 3GPP TS 36.133 V15.2.0 (2018-03)
Non-Patent Document 2: 3GPP TS 36.211 V15.1.0 (2018-03)
Non-Patent Document 3: 3GPP TS 36.212 V15.1.0 (2018-03)
Non -Patent Document Document 4: 3GPP TS 36.213 V15.1.0 (2018-03)
Non-Patent Document 5: 3GPP TS 36.300 V15.1.0 (2018-03)
Non-Patent Document 6: 3GPP TS 36.321 V15.1.0 (2018-03)
Non-Patent Document 7 : 3GPP TS 36.322 V15.0.1 (2018-04)
Non-Patent Document 8: 3GPP TS 36.323 V14.5.0 (2017-12)
Non-Patent Document 9: 3GPP TS 36.331 V15.1.0 (2018-03)
Non-Patent Document 10: 3GPP TS 36.413 V15.1.0 (2018-03)
Non-Patent Document 11: 3GPP TS 36.423 V15.1.0 (2018-03)
Non-Patent Document 12: 3GPP TS 36.425 V14.1.0 (2018-03)
Non-Patent Document 13: 3GPP TS 37.340 V15.1.0 (2018-03)
Non-Patent Document 14: 3GPP TS 38.201 V15.0.0 (2017-12)
Non-Patent Document 15: 3GPP TS 38.202 V15.1.0 (2018-03)
Non-Patent Document 16: 3GPP TS 38.211 V15.1.0 (2018-03)
Non -Patent Document Document 17: 3GPP TS 38.212 V15.1.1 (2018-04)
Non-Patent Document 18: 3GPP TS 38.213 V15.1.0 (2018-03)
Non-Patent Document 19: 3GPP TS 38.214 V15.1.0 (2018-03)
Non-Patent Document 20 : 3GPP TS 38.215 V15.1.0 (2018-03)
Non-Patent Document 21: 3GPP TS 38.300 V15.1.0 (2018-03)
Non-Patent Document 22: 3GPP TS 38.321 V15.1.0 (2018-03)
Non-Patent Document 23: 3GPP TS 38.322 V15.1.0 (2018-03)
Non-Patent Document 24: 3GPP TS 38.323 V15.1.0 (2018-03)
Non-Patent Document 25: 3GPP TS 38.331 V15.1.0 (2018-03)
Non-Patent Document 26: 3GPP TS 38.401 V15.1.0 (2018-03)
Non-Patent Document 27: 3GPP TS 38.410 V0.9.0 (2018-04)
Non-Patent Document 28: 3GPP TS 38.413 V0.8.0 (2018-04)
Non-Patent Document 29: 3GPP TS 38.420 V0.8.0 (2018-04)
Non -Patent Document Document 30: 3GPP TS 38.423 V0.8.0 (2018-04)
Non-Patent Document 31: 3GPP TS 38.470 V15.1.0 (2018-03)
Non-Patent Document 32: 3GPP TS 38.473 V15.1.1 (2018-04)
Non-Patent Document 33 : 3GPP TR 38.801 V14.0.0 (2017-04)
Non-Patent Document 34: 3GPP TR 38.802 V14.2.0 (2017-09)
Non-Patent Document 35: 3GPP TR 38.803 V14.2.0 (2017-09)
Non-Patent Document 36: 3GPP TR 38.804 V14.0.0 (2017-03)
Non-Patent Document 37: 3GPP TR 38.900 V14.3.1 (2017-07)
Non-Patent Document 38: 3GPP TR 38.912 V14.1.0 (2017-06)
Non-Patent Document 39: 3GPP TR 38.913 V14.3.0 (2017-06)
Outline of the invention
Problems to be solved by the invention
[0011]
　However, when the data is held in the buffer in the RLC layer or the PDCP layer, there is a problem that the delay condition required for the data may not be satisfied by the data staying in the buffer. For example, when the discard timer is set to a relatively long time such as 10 ms, the time until the data staying in the buffer is discarded increases and HOL (Head of Line blocking) occurs. As a result, for example, when newly generated data having a required delay amount of less than 1 ms (low delay data), it may take time for the low delay data to be transmitted, and the delay request may not be satisfied.
[0012]
　The disclosed technique has been made in view of such a point, and an object of the present invention is to provide a transmission device and a buffer control method capable of satisfying a delay request for low-delay data.
Means to solve problems
[0013]
　In one embodiment, the transmission device disclosed in the present application has a first layer processing unit that has a buffer for holding transmission data and executes processing of the first layer on the transmission data, and the first layer processing unit on the transmission data. It has a second layer processing unit that executes processing of a second layer different from the first layer, and a transmission unit capable of transmitting transmission data processed by the first layer processing unit and the second layer processing unit. The first layer processing unit discards the transmission data held in the buffer according to the parameters used for transmission control in the processing of the second layer.
Effect of the invention
[0014]
　According to one aspect of the transmission device and the buffer control method disclosed in the present application, there is an effect that the delay requirement of low delay data can be satisfied.
A brief description of the drawing
[0015]
FIG. 1 is a block diagram showing a configuration of a terminal device according to the first embodiment.
FIG. 2 is a flow chart showing a buffer control method according to the first embodiment.
FIG. 3 is a block diagram showing a configuration of a terminal device according to a second embodiment.
FIG. 4 is a diagram showing a specific example of a maximum transmission time.
FIG. 5 is a flow chart showing a buffer control method according to the second embodiment.
[Fig. 6] Fig. 6 is a diagram showing an example of description of the contents according to the second embodiment in a standard specification.
FIG. 7 is a flow chart showing a buffer control method according to the third embodiment.
FIG. 8 is a diagram showing an example of description of the contents according to the third embodiment in a standard specification.
Mode for carrying out the invention
[0016]
　Hereinafter, embodiments of the transmission device and the buffer control method disclosed in the present application will be described in detail with reference to the drawings. The present invention is not limited to this embodiment. In the following, a terminal device will be described as an example of the transmitting device, but the transmitting device is not necessarily limited to the terminal device, and for example, a base station device is also included in the transmitting device. Further, unless otherwise specified, the SDU (Service Data Unit) and PDU (Protocol Data Unit) of each layer are simply referred to as "packets".
[0017]
(Embodiment 1)
　FIG. 1 is a block diagram showing a configuration of a terminal device 100 according to the first embodiment. The terminal device 100 shown in FIG. 1 includes a processor 110, a memory 120, and a wireless communication unit 130.
[0018]
　The processor 110 includes, for example, a CPU (Central Processing Unit), an FPGA (Field Programmable Gate Array), a DSP (Digital Signal Processor), or the like, and controls the entire terminal device 100 in an integrated manner. Specifically, the processor 110 includes an application processing unit 111, a first layer processing unit 112, and a second layer processing unit 113.
[0019]
　The application processing unit 111 executes processing of various applications. For example, the application processing unit 111 generates transmission data transmitted by an uplink from the terminal device 100 to a base station device (not shown). The transmitted data also includes, for example, low delay data in which the required delay amount is less than 1 ms.
[0020]
　The first layer processing unit 112 executes the processing of the first layer. For example, the first layer processing unit 112 adds the header of the first layer to the packet (SDU) of the transmission data generated by the application processing unit 111, and generates the PDU of the first layer. Here, the first layer processing unit 112 has a buffer, and temporarily holds the packet to be processed in the buffer. Then, the first layer processing unit 112 controls the discarding of the packet held in the buffer.
[0021]
　Specifically, when the packet is stored in the buffer, the first layer processing unit 112 sets the first information that defines the condition for discarding the packet. At this time, the first layer processing unit 112 acquires the second information used for transmission control in the second layer processing unit 113, and sets the first information according to the second information. That is, the first layer processing unit 112 sets the packet discard condition using the parameters of the second layer, which is a different layer (for example, a lower layer).
[0022]
　After setting the packet discard condition, the first layer processing unit 112 monitors whether or not the discard condition is satisfied, and if the discard condition is satisfied, discards the corresponding packet from the buffer.
[0023]
　The second layer processing unit 113 executes the processing of the second layer lower than the first layer. For example, the second layer processing unit 113 uses the PDU of the first layer generated by the first layer processing unit 112 as an SDU, adds a header of the second layer to the SDU, and generates a PDU of the second layer. The second layer processing unit 113 controls the transmission of packets using the second information. That is, the second layer processing unit 113 performs priority control of packet transmission and retransmission control according to, for example, the second information. As described above, the second information is used to set the packet discard condition of the first layer processing unit 112.
[0024]
　The memory 120 includes, for example, a RAM (Random Access Memory) or a ROM (Read Only Memory), and stores information used by the processor 110 to execute processing.
[0025]
　The wireless communication unit 130 performs wireless transmission processing such as D / A (Digital / Analog) conversion and up-conversion on the transmission data generated by the processor 110, and wirelessly transmits the transmission data via the antenna. Further, the wireless communication unit 130 performs wireless reception processing such as down-conversion and A / D (Analog / Digital) conversion on the received data wirelessly received via the antenna, and outputs the received data to the processor 110.
[0026]
　Next, the buffer control method in the terminal device 100 configured as described above will be described with reference to the flow chart shown in FIG. The following buffer control method is a buffer control method included in the first layer processing unit 112.
[0027]
　The transmission data generated by the application processing unit 111 is output to the first layer processing unit 112, divided into packets having a predetermined length, and then stored in the buffer of the first layer processing unit 112 (step S101). .. When the packets are stored in the buffer, the first information defining the discard condition is set for each packet (step S102). That is, the first layer processing unit 112 acquires the second information used for the transmission control by the second layer processing unit 113, and the first information is set according to the second information.
[0028]
　When the packet discard condition is set, the first layer processing unit 112 executes the first layer processing on the packet and determines whether or not the discard condition is satisfied for each packet stored in the buffer. Monitor (step S103). That is, it is monitored whether or not the discard condition indicated by the first information is satisfied, and if the packet satisfies the discard condition (step S103Yes), the packet is discarded by the first layer processing unit 112 (step). S104). As a result, the packets of the first layer are discarded under the discard conditions according to the parameters used for the transmission control of the lower second layer, and the residence time of the packets in the buffer of the first layer is shortened. As a result, even when low-delay data is generated as new transmission data, the processing of the first layer for the low-delay data packet is executed quickly, and the low-delay data can be transmitted with a small delay. Further, as a result of shortening the retention time of packets in the buffer, the buffer size can be reduced.
[0029]
　As described above, according to the present embodiment, the first information defining the packet discard condition of the first layer is set according to the second information regarding the transmission control of the second layer, and the discard condition is set. Discard the filled packet from the first layer buffer. Therefore, the dwell time of the packet in the buffer can be shortened, and even when low-delay data is generated as new transmission data, the delay until the low-delay data is transmitted can be reduced. As a result, the delay demand for low latency data can be met.
[0030]
　In the first embodiment, the buffer control method for the buffer of the first layer has been mainly described, but another layer processing unit (for example, a third layer processing unit) different from the first layer and the second layer has been described. May have a buffer. Then, when the packet is stored in the buffer of the third layer, the buffer control method described in the first embodiment may be applied to the buffer of the third layer. In this case, this buffer control method may not be applied to the first packet and the retransmission packet that are already being wirelessly transmitted.
[0031]
(Embodiment 2)
　FIG. 3 is a block diagram showing a configuration of a terminal device 100 according to the second embodiment. In FIG. 3, the same parts as those in FIG. 1 are designated by the same reference numerals, and the description thereof will be omitted. In the terminal device 100 shown in FIG. 3, the internal configuration of the processor 110 is different from that of the terminal device 100 shown in FIG. That is, the processor 110 shown in FIG. 3 has a PDCP processing unit 201, an RLC processing unit 202, and a MAC processing unit 203 in addition to the application processing unit 111.
[0032]
　The PDCP processing unit 201 executes the processing of the PDCP layer. For example, the PDCP processing unit 201 adds a header of the PDCP layer to the transmission data packet (PDCP-SDU) generated by the application processing unit 111 to generate the PDCP-PDU. The PDCP processing unit 201 has a buffer, and temporarily holds the packet to be processed in the buffer. Then, the PDCP processing unit 201 controls the discarding of the packet held in the buffer.
[0033]
　Specifically, the PDCP processing unit 201 sets a discard timer that defines the time until the packet is discarded when the packet is stored in the buffer. Further, the PDCP processing unit 201 acquires the maximum transmission time used for transmission control in the MAC processing unit 203, and sets the time until the packet is discarded in addition to the above-mentioned discard timer according to the maximum transmission time. That is, the PDCP processing unit 201 sets the packet discard condition using the parameters of the MAC layer, which is a lower layer than the PDCP layer.
[0034]
　After setting the packet discard condition, the PDCP processing unit 201 monitors whether or not the discard condition is satisfied, and if the discard condition is satisfied, discards the corresponding packet from the buffer.
[0035]
　The RLC processing unit 202 executes the processing of the RLC layer lower than the PDCP layer. For example, the RLC processing unit 202 uses the PDCP-PDU generated by the PDCP processing unit 201 as the RLC-SDU, adds the header of the RLC layer to the RLC-SDU, and generates the RLC-PDU. The RLC layer processing executed by the RLC processing unit 202 includes, for example, packet retransmission control.
[0036]
　The RLC processing unit 202 has a buffer, and for example, when preprocessing is performed, the packet of transmission data generated by the application processing unit 111 is temporarily held in the buffer instead of the PDCP processing unit 201. Therefore, the RLC processing unit 202 may control the discarding of the packets held in the buffer, similarly to the PDCP processing unit 201.
[0037]
　The MAC processing unit 203 executes processing of the MAC layer lower than the PDCP layer and the RLC layer. For example, the MAC processing unit 203 uses the RLC-PDU generated by the RLC processing unit 202 as the MAC-SDU, adds a header of the MAC layer to the MAC-SDU, and generates the MAC-PDU. The MAC layer processing executed by the MAC processing unit 203 includes, for example, packet scheduling and priority control. In the priority control executed by the MAC processing unit 203, for example, LCP (Logical Channel Prioritization) for controlling the priority of the logical channel is executed. Specifically, logical channels with the same required Quality of Service (QoS) are aggregated to generate an LCG (Logical Channel Group), and priority control is performed for each LCG.
[0038]
　In the LCP of the MAC layer, priority control is performed by, for example, the following three parameters (1) to (3).
[0039]
　(1) allowedSCS-List: A parameter that specifies the subcarrier space of the LCG that transmits low-delay data.
[0040]
　(2) maxPUSCH-Duration: A parameter indicating the maximum transmission time of PUSCH (Physical Uplink Shared CHannel) used in wireless transmission by LCG. More specifically, this parameter defines the time from the timing when transmission using PUSCH is permitted to the timing when transmission is actually executed by PUSCH. It can be said that the smaller the set maxPUSCH-Duration is, the lower the delay is required for the LCG. As maxPUSCH-Duration, a value selected from multiple candidates is set. That is, for example, as shown in FIG. 4, there are 0.02 ms, 0.04 ms, 0.0625 ms, 0.125 ms, 0.25 ms and 0.5 ms as candidates for maxPUSCH-Duration, and LCG has priority among them. A value is set according to the degree.
[0041]
　(3) configuredGrantType1Allowed: The radio resource used in the radio transmission by the LCG is a predetermined radio resource such as a periodic radio resource, or is dynamically determined by a UL grant, for example. It is a parameter indicating whether it is a wireless resource.
[0042]
　As described above, the maximum transmission time indicated by maxPUSCH-Duration is set separately from the discard timer as the time until packet discard of the PDCP processing unit 201.
[0043]
　Next, the buffer control method in the terminal device 100 configured as described above will be described with reference to the flow chart shown in FIG. The following buffer control method is a buffer control method included in the PDCP processing unit 201. In FIG. 5, the same parts as those in FIG. 2 are designated by the same reference numerals.
[0044]
　The transmission data generated by the application processing unit 111 is output to the PDCP processing unit 201, divided into packets having a predetermined length, and then stored in the buffer of the PDCP processing unit 201 (step S101). When the packets are stored in the buffer, a discard timer that defines the time until discard is set for each packet (step S201). The discard timer corresponds to the expiration date of the data for the application, and for example, a time of about 10 ms may be set.
[0045]
　Further, the PDCP processing unit 201 acquires the maximum transmission time, which is one of the priority control parameters in the MAC processing unit 203 (step S202). This maximum transmission time is used as the time until the packet is discarded, in addition to the above-mentioned discard timer. That is, the PDCP processing unit 201 acquires the parameters used for controlling the lower MAC layer, and sets the time until the packet is discarded according to the acquired parameters. As shown in FIG. 4, the maximum transmission time is a relatively short time of less than 1 ms.
[0046]
　When the time until packet discard is set, the PDCP processing unit 201 executes PDCP layer processing on the packet and monitors whether the discard condition is satisfied for each packet stored in the buffer. To do.
[0047]
　Specifically, it is determined whether or not the discard timer set for each packet has expired (step S203). As a result of this determination, when the discard timer expires (step S203Yes), the packet is discarded by the PDCP processing unit 201 (step S104). On the other hand, if the discard timer has not expired (step S203No), it is determined whether or not it has been notified that the packet reception has been successful (step S204). That is, in the PDCP layer, since the status report (SR: Status Report) is periodically transmitted from the device on the receiving side, it is possible to determine whether or not the packet reception is successful based on this status report. Therefore, when the PDCP processing unit 201 notifies that the packet has been successfully received (step S204Yes), the PDCP processing unit 201 discards the packet (step S104). On the other hand, if there is no notification of successful reception (step S204 No), it is determined whether or not the maximum transmission time has elapsed since the packet was stored in the buffer (step S205). That is, it is determined whether or not the maximum transmission time for priority control in the MAC layer has elapsed. Then, when the maximum transmission time has elapsed since the packet was stored (step S205Yes), the packet is discarded by the PDCP processing unit 201 (step S104).
[0048]
　In this way, whether or not the discard condition is satisfied is monitored, and the packet that satisfies the discard condition is discarded from the buffer, so that the retention time of the packet in the buffer of the PDCP layer is shortened. In particular, by using the maximum transmission time used in the priority control of the MAC layer lower than the PDCP layer as a discard condition, packets are discarded in a shorter time than the discard timer corresponding to the application, and the delay of wireless transmission is reduced. It can be reduced. In other words, even when low-delay data is generated as new transmission data, the PDCP layer processing for the low-delay data packet is executed quickly, and the low-delay data can be transmitted with a small delay.
[0049]
　As described above, according to the present embodiment, the time for defining the packet discard condition of the PDCP layer is set according to the maximum transmission time for priority control of the MAC layer, and the maximum transmission time after being stored. Drops the old packet from the PDCP layer buffer. Therefore, the dwell time of the packet in the buffer can be shortened, and even when low-delay data is generated as new transmission data, the delay until the low-delay data is transmitted can be reduced. As a result, the delay demand for low latency data can be met.
[0050]
　According to the buffer control method according to the second embodiment, for example, the item related to SDU disposal described in Non-Patent Document 24 (TS38.323) can be amended as shown in FIG. 6, for example. That is, the PDCP-SDU is discarded when the discard timer for PDCP-SDU expires, when the status report confirms that the PDCP-SDU has been successfully received, or when maxPUSCH-Duration has elapsed. It may be specified in.
[0051]
　Further, in the second embodiment, the buffer control method regarding the buffer of the PDCP layer has been mainly described, but as described above, the RLC processing unit 202 also has a buffer. Then, for example, when preprocessing is performed, the packet is stored in the buffer of the RLC layer, so that the buffer control method described in the second embodiment may be applied to the buffer of the RLC layer. In this case, this buffer control method may not be applied to the first packet and the retransmission packet that are already being wirelessly transmitted.
[0052]
　Further, in the second embodiment, since the process of fitting into the cross layer between the layers having similar properties (for example, between the PDCP layer and the MAC layer in layer 2) is executed, the layers having different properties (for example) For example, the protocol (eg, terminal protocol) can be simplified rather than the processing between the application layer and layer 2 being performed.
[0053]
(Embodiment 3) Since
　the configuration of the terminal device according to the third embodiment is the same as that of the terminal device 100 (FIG. 3) according to the second embodiment, the description thereof will be omitted. In the third embodiment, the buffer control method in the PDCP processing unit 201 is different from that of the second embodiment.
[0054]
　FIG. 7 is a flow chart showing a buffer control method according to the third embodiment. The following buffer control method is a buffer control method included in the PDCP processing unit 201. In FIG. 7, the same parts as those in FIGS. 2 and 5 are designated by the same reference numerals.
[0055]
　The transmission data generated by the application processing unit 111 is output to the PDCP processing unit 201, divided into packets having a predetermined length, and then stored in the buffer of the PDCP processing unit 201 (step S101). When the packets are stored in the buffer, a discard timer that defines the time until discard is set for each packet (step S201). The discard timer corresponds to the expiration date of the data for the application, and for example, a time of about 10 ms may be set.
[0056]
　In addition, the PDCP processing unit 201 acquires the maximum number of retransmissions, which is one of the retransmission control parameters in the RLC processing unit 202 (step S301). This maximum number of retransmissions is the maximum number of retransmissions allowed in the RLC layer that controls packet retransmission. That is, in the RLC layer, the packet is retransmitted when NACK indicating that the packet is not received correctly is returned from the receiving device, but if the retransmission is repeated indefinitely, the throughput decreases, which is allowed. The maximum number of retransmissions may be set. Therefore, the PDCP processing unit 201 acquires the maximum number of retransmissions used for controlling the lower RLC layer, and sets the packet discard condition according to the acquired maximum number of retransmissions.
[0057]
　When the packet discard condition is set, the PDCP processing unit 201 monitors whether or not the discard condition is satisfied for each packet stored in the buffer while executing the PDCP layer processing on the packet.
[0058]
　Specifically, it is determined whether or not the discard timer set for each packet has expired (step S203). As a result of this determination, when the discard timer expires (step S203Yes), the packet is discarded by the PDCP processing unit 201 (step S104). On the other hand, if the discard timer has not expired (step S203No), it is determined whether or not it has been notified that the packet reception has been successful (step S204). That is, in the PDCP layer, since the status report is periodically transmitted from the device on the receiving side, it is possible to determine whether or not the packet reception is successful based on this status report. Therefore, when the PDCP processing unit 201 notifies that the packet has been successfully received (step S204Yes), the PDCP processing unit 201 discards the packet (step S104). On the other hand, if there is no notification of successful reception (step S204 No), it is determined whether or not the number of retransmissions of the packet stored in the buffer has reached the maximum number of retransmissions (step S302). That is, it is determined whether or not the maximum number of retransmissions for retransmission control in the RLC layer has been reached. Then, when the number of retransmissions of the packet has reached the maximum number of retransmissions (step S302Yes), the packet is discarded by the PDCP processing unit 201 (step S104).
[0059]
　In this way, whether or not the discard condition is satisfied is monitored, and the packet that satisfies the discard condition is discarded from the buffer, so that the retention time of the packet in the buffer of the PDCP layer is shortened. In particular, by using the maximum number of retransmissions used in the retransmission control of the RLC layer lower than the PDCP layer as a discard condition, packets for which retransmission fails can be discarded early and the delay of wireless transmission can be reduced. it can. In other words, even when low-delay data is generated as new transmission data, the PDCP layer processing for the low-delay data packet is executed quickly, and the low-delay data can be transmitted with a small delay.
[0060]
　As described above, according to the present embodiment, the packet discard condition of the PDCP layer is set according to the maximum number of retransmissions for the retransmission control of the RLC layer, and the packet whose number of retransmissions reaches the maximum number of retransmissions is set. Discard from the PDCP layer buffer. Therefore, the dwell time of the packet in the buffer can be shortened, and even when low-delay data is generated as new transmission data, the delay until the low-delay data is transmitted can be reduced. As a result, the delay demand for low latency data can be met.
[0061]
　According to the buffer control method according to the third embodiment, for example, the item related to SDU disposal described in Non-Patent Document 24 (TS38.323) can be amended as shown in FIG. 8, for example. That is, when the discard timer for PDCP-SDU expires, when it is confirmed by the status report that the PDCP-SDU reception is successful, or when the number of retransmissions reaches maxRetxThreshold, which indicates the maximum number of retransmissions of the RLC layer. PDCP-SDU may be specified to be discarded.
[0062]
　Further, in each of the above embodiments, it is assumed that the information for determining the packet discard condition in the buffer of the upper layer is acquired from the processing unit of the lower layer, but the information is not necessarily obtained from the processing unit of the lower layer. It does not have to be acquired. That is, for example, RRC (Radio Resource Control) signaling may be used to notify the base station apparatus of information for determining packet discard conditions. Specifically, for example, a parameter indicating one of the values ​​(0.5ms, 1ms, 2ms, 3ms) as the second discard timer represented by 2 bits (for example, a parameter having a specified name such as discardTimer2 may be used). Is specified in RRC, and any value may be notified by RRC signaling (eg, RRC Reconfiguration message, RRC setup message, etc.). Further, as a parameter represented by 3 bits for the second discard timer, a value is specified from the same candidates as maxPUSCH-Duration of the second embodiment, or a value is specified from a candidate to which another value is added. It may be done.
[0063]
　Further, the scaling factor for scaling the value of the discard timer may be defined in the RRC by RRC signaling, and the value of the scaling factor may be notified. For example, if the value that can be set as the discard timer of the PDCP layer is (10ms, 20ms, 30ms, 40ms, 50ms, 60ms, 75ms, 100ms, 150ms, 200ms, 250ms, 300ms, 500ms, 750ms, 1500ms, infinity), scaling When 0.002 is notified as a factor, each value of the discard timer may be multiplied by 0.002 and used as the discard condition. In this case, the values ​​that can be used as the disposal conditions are (0.02ms, 0.004ms, 0.06ms, 0.08ms, 0.1ms, 0.12ms, 0.15ms, 0.2ms, 0.3ms, 0.4ms, 0.5ms, 0.6ms, 1.0ms, 1.5ms, 3.0ms, infinite). Therefore, as compared with using the value of the discard timer as it is, the time until the packet is discarded can be shortened, and the delay request for low delay data can be satisfied. The scaling factor may be dynamically selected from a plurality of candidates.
[0064]
　Further, the parameters conventionally defined may be changed. For example, the value that can be set as the conventional discard timer of the PDCP layer is (10ms, 20ms, 30ms, 40ms, 50ms, 60ms, 75ms, 100ms, 150ms, 200ms, 250ms, 300ms, 500ms, 750ms, 1500ms, infinity). You may delete infinity and add 1ms by referring to. As a result, the values ​​that can be set as the discard timer are (1ms, 10ms, 20ms, 30ms, 40ms, 50ms, 60ms, 75ms, 100ms, 150ms, 200ms, 250ms, 300ms, 500ms, 750ms, 1500ms).
[0065]
　When the above-described first embodiment and the second embodiment are combined, the first layer may be a PDCP layer and the second layer may be a MAC layer. Further, the first information may be the value of the discard timer, and the second information may be maxPUSCH-Duration. Further, when the first embodiment and the third embodiment are combined, the first layer may be a PDCP layer, the second layer may be a MAC layer, and the third layer may be an RLC layer.
Description of the sign
[0066]
　110 Processor
　111 Application processing unit
　112 First layer processing unit
　113 Second layer processing unit
　120 Memory
　130 Wireless communication unit
　201 PDCP processing unit
　202 RLC processing unit
　203 MAC processing unit
The scope of the claims
[Claim 1]
　A first layer processing unit that has a buffer for holding transmission data and executes processing of the first layer on the
　transmission data, and a second layer processing different from the first layer is executed on the transmission data. It has a second layer processing unit,
　a transmission unit capable of transmitting transmission data processed by the first layer processing unit and the second layer processing unit, and
　the first layer processing unit is of
　the second layer.
　A transmission device characterized in that transmission data held in the buffer is discarded according to a parameter used for transmission control in processing .
[Claim 2]
　The second layer processing unit
　executes MAC (Medium Access Control) layer processing on
　the
　transmission data , and the first layer processing unit performs priority control of the MAC layer after the transmission data is held in the buffer.
　The transmission device according to claim 1 , wherein when the time corresponding to the maximum transmission time of the PUSCH (Physical Uplink Shared CHannel) used in the above has elapsed, the transmission data held in the buffer is discarded .
[Claim 3]
　The first layer processing unit
　executes processing of the PDCP (Packet Data Convergence Protocol) layer on the transmitted data, and the
　maximum transmission time is
　larger than the disposal timer indicating the time until disposal predetermined in the PDCP layer.
　The transmission device according to claim 2, wherein the time is short .
[Claim 4]
　The first layer processing unit
　executes RLC (Radio Link Control) layer processing on the transmission data, and the
　maximum transmission time is
　shorter than the disposal timer indicating the time until disposal predetermined in the RLC layer.
　The transmitting device according to claim 2 , wherein the time is used.
[Claim 5]
　The second layer processing unit
　executes RLC layer processing on the transmission data, and
　the first layer processing unit uses the
　number of retransmissions of the transmission data held in the buffer to control the retransmission of the RLC layer.
　The transmission device according to claim 1 , wherein when the maximum number of retransmissions is reached, the transmission data held in the buffer is discarded .
[Claim 6]
　The processing of the first layer is executed for the transmission data held in the buffer, the processing of
　the second layer different from the first layer is executed for the transmission data
　, and the transmission control is performed in the processing of the second layer.
　A buffer control method comprising a process of discarding transmission data held in the buffer according to a parameter used .