WO2018198261A1 - Base station, radio terminal, radio communication system, and communication control method - Google Patents

Abstract

The purpose of the invention is to suppress the risk of transmission delay and of degradation of efficiency. Provided is a radio terminal (20) comprising a control unit (23) that transmits buffer information (25) about a reception buffer (24) in response to a request from a base station (10) and receives control information (15) about aggregation of a plurality of radio resources from the base station (10) that, on the basis of the buffer information (25), controls whether or not to aggregate the plurality of radio resources.

Description

Base station, radio terminal, radio communication system, and communication control method

The present invention relates to a base station, a wireless terminal, a wireless communication system, and a communication control method.

In the LTE (Long Term Evolution) standard of 3GPP (Third Generation Partnership Project), radio resources used for uplink (UL) and downlink (DL) data transmission are allocated in units of subframes. One subframe has two slots. In the LTE standard, control information that defines communication conditions such as a modulation scheme is arranged in at least one slot included in one subframe.

Regarding the arrangement of control information, there has been proposed a method (SlotationAggregation) in which a plurality of slots are aggregated and a data transmission section is extended based on communication conditions defined by one control information. By collecting a large number of slots, the amount of data that can be transmitted can be increased.

A method for reporting the amount of DL data buffered in the transmission buffer of the base station to the wireless terminal has been proposed. Also, a method for reporting the amount of UL data buffered in the transmission buffer of the wireless terminal to the base station has been proposed. The LTE standard defines BSR (Buffer Status Reports) in order for a wireless terminal to report the buffer status of a transmission buffer to a base station. In addition, it is proposed that the wireless terminal reports CQI (Channel Quality Indicator) to the base station.

Special Table 2015-503865 Publication Special Table 2013-502850

A large size of data is transmitted in the data transmission section where many slots are aggregated. For example, when a data transmission section capable of transmitting data having a size larger than the free capacity of the reception buffer is set, there is a risk that the reception buffer overflows due to data transmitted in the data transmission section. If the data transmission interval setting (aggregation setting) is maintained, the reception buffer may overflow again due to the retransmitted data, even if the reception buffer overflows and data retransmission control is performed. As a result, retransmission control is repeated, leading to an increase in transmission delay and deterioration in transmission efficiency.

Note that the slot is an example of a transmission section (unit section) having a unit time width. Even when unit sections other than slots are aggregated, transmission delay and efficiency deterioration may occur for the same reason as described above. The unit section is an example of a radio resource. In the above description, for convenience of explanation, the method of aggregating unit sections in the time direction has been described. However, when a plurality of radio resources are aggregated in the frequency direction, transmission delay and efficiency degradation may occur for the same reason as described above. .

According to one aspect, an object of the present invention is to provide a base station, a wireless terminal, a wireless communication system, and a communication control method capable of suppressing the risk of transmission delay and efficiency deterioration.

According to one aspect, in response to a request from a base station, a plurality of radio resources are transmitted from a base station that transmits buffer information related to a reception buffer and controls whether to aggregate a plurality of radio resources based on the buffer information. There is provided a wireless terminal having a control unit that receives control information related to aggregation of data.

The risk of transmission delay and efficiency degradation can be suppressed.
These and other objects, features and advantages of the present invention will become apparent from the following description taken in conjunction with the accompanying drawings which illustrate preferred embodiments by way of example of the present invention.

It is the figure which showed an example of the radio | wireless communications system which concerns on 1st Embodiment. It is the figure which showed an example of the radio | wireless communications system which concerns on 2nd Embodiment. It is a sequence diagram for demonstrating the operation example (operation | movement regarding aggregation of a unit area) of a radio | wireless communications system. It is a figure for demonstrating the structure and application of a unit area. It is a sequence diagram for demonstrating the operation example (operation | movement regarding the aggregation control according to a reception buffer state) of a radio | wireless communications system. It is the block diagram which showed an example of the hardware which can implement | achieve the function of the base station which concerns on 2nd Embodiment. It is the block diagram which showed an example of the hardware which can implement | achieve the function of the radio | wireless terminal which concerns on 2nd Embodiment. It is the block diagram which showed an example of the function which the base station which concerns on 2nd Embodiment has. It is the block diagram which showed an example of the function which the radio | wireless terminal which concerns on 2nd Embodiment has. It is the flowchart which showed the flow of the process performed by the base station side among the processes regarding the reception buffer status report which concern on 2nd Embodiment. It is the flowchart which showed the flow of the process performed by the radio | wireless terminal side among the processes regarding the reception buffer status report which concern on 2nd Embodiment. It is the flowchart which showed the flow of the process performed by the base station side among the processes regarding DL data transmission control which concern on 2nd Embodiment. It is the flowchart which showed the flow of the process performed by the radio | wireless terminal side among the processes regarding DL data transmission control which concern on 2nd Embodiment. It is a figure for demonstrating the effective use of the surplus resource which may arise at the time of aggregation of a unit area. It is the flowchart which showed the flow of the process performed by the base station side among the processes regarding the DL data transmission control which concern on the modification (effective utilization of a surplus resource) of 2nd Embodiment. It is the flowchart which showed the flow of the process (pattern A) performed by the radio | wireless terminal side among the processes regarding DL data transmission control which concern on the modification (effective utilization of a surplus resource) of 2nd Embodiment. It is the flowchart which showed the flow of the process (pattern B) performed by the radio | wireless terminal side among the processes regarding DL data transmission control which concern on the modification (effective utilization of a surplus resource) of 2nd Embodiment. It is a sequence diagram for demonstrating the operation example (combination of pattern A and B) of the radio | wireless communications system regarding DL data transmission control which concerns on the modification (effective use of a surplus resource) of 2nd Embodiment.

Embodiments of the present invention will be described below with reference to the accompanying drawings. In addition, about the element which has the substantially same function in this specification and drawing, duplication description may be abbreviate | omitted by attaching | subjecting the same code | symbol.

<1. First Embodiment>
The first embodiment will be described with reference to FIG. The first embodiment relates to control for aggregating a plurality of radio resources, and relates to a method for dynamically controlling the number of radio resources to be aggregated in consideration of the state of a reception buffer in the control.

FIG. 1 is a diagram illustrating an example of a wireless communication system according to the first embodiment. The wireless communication system 5 illustrated in FIG. 1 is an example of a wireless communication system according to the first embodiment.
As shown in FIG. 1, the wireless communication system 5 includes a base station 10 and a wireless terminal 20. The base station 10 includes an antenna 11, a radio unit 12, and a control unit 13. The wireless terminal 20 includes an antenna 21, a wireless unit 22, a control unit 23, and a reception buffer 24. The number of antennas 11 and 21 may be two or more. The wireless communication system 5 may have two or more wireless terminals.

The antennas 11 and 21 are antennas used for transmission / reception of a radio (RF: Radio Frequency) signal. The radio units 12 and 22 are signal processing circuits that execute processing related to RF signals transmitted and received via the antennas 11 and 21, respectively. For example, the radio units 12 and 22 convert (frequency conversion) between an RF signal and a baseband (BB) signal (BB signal), and convert between an analog BB signal and a digital BB signal. (AD (Analog-to-Digital) / DA (Digital-to-Analog) conversion), modulation / demodulation, and the like are executed.

The control units 13 and 23 are processors such as a CPU (Central Processing Unit), a DSP (Digital Signal Processor), an ASIC (Application Specific Integrated Circuit), and an FPGA (Field Programmable Gate Array). The control units 13 and 23 execute processing using a memory (not shown) such as a RAM (Random Access Memory) mounted in the base station 10 and the wireless terminal 20, respectively.

Control units 13 and 23 control transmission and reception by the radio units 12 and 22, respectively. For example, the control unit 23 controls the radio unit 22 so as to receive an RF signal under communication conditions (such as a modulation scheme) set by the base station 10. Examples of the modulation method include QPSK (QuadratureQuPhase Keying), 16QAM (Quadrature Amplitude Modulation), and 64QAM. Note that the communication condition includes, for example, a coding rate in addition to the modulation method. The setting of the coding rate can be applied to coding / decoding by the control units 13 and 23.

The reception buffer 24 is a buffer memory in which data received by the wireless unit 22 is stored. As the buffer memory, for example, a volatile memory such as DRAM (Dynamic Random Access Memory) or SRAM (Static Random Access Memory) or a non-volatile memory such as a flash memory can be used. The state of the reception buffer 24 (used amount, used rate, free capacity, unused rate, etc.) is monitored by the control unit 23.

In the radio communication system 5, a plurality of radio resources (unit resources) having a unit width are aggregated, and DL data is transmitted from the base station 10 to the radio terminal 20 using a set of unit resources (aggregation resources) obtained by aggregation. Sent.

For example, a time interval (unit interval) having a unit time width is an example of a unit resource. In the case of the LTE standard, when the unit time width is 0.5 ms, the slot corresponds to the unit section, when 1 ms, the subframe corresponds to the unit section, and when 10 ms, the frame corresponds to the unit section. . One symbol may be set as a unit section.

A frequency band (unit band) having a unit frequency width is an example of a unit resource. In the case of the LTE standard, when the unit frequency width is 180 kHz (12 subcarriers), a band corresponding to 1 RB (Resource Block) corresponds to the unit band. If the unit width in the time direction is set to 0.5 ms and the unit width in the frequency direction is set to 180 kHz, 1 RB corresponds to a unit resource.

As described above, the technology according to the first embodiment can be applied to aggregation of radio resources in various forms. The example of the radio resource described above is merely an example, and the unit time width, unit frequency width, resource block size, and the like can be modified.

A transmission of a control signal (Ctrl) including communication conditions such as a modulation scheme and a coding rate is assigned to a unit resource located at one end of the aggregate resource. Control signal transmission is not allocated to the remaining unit resources. For data transmission in the remaining unit resources, communication conditions of control signals received by the unit resources located at one end of the aggregated resource are applied.

The control unit 13 can control the number of unit resources (aggregation number) included in the aggregation resource.
For example, the control unit 13 controls the aggregation number based on the state of the reception buffer 24. In this case, the control unit 13 requests the wireless terminal 20 for buffer information 25 indicating the state of the reception buffer 24 (buffer information request 14). In the wireless terminal 20 that has received this request 14, the control unit 23 confirms the state of the reception buffer 24 and generates buffer information 25. Then, as a response to the request 14, the control unit 23 transmits buffer information 25 regarding the reception buffer 24 to the base station 10.

In the base station 10 that has received the buffer information 25, the control unit 13 controls whether or not the above-described unit resource aggregation is performed based on the buffer information 25.
For example, as shown in FIG. 1A, when the free capacity 25a of the reception buffer 24 is twice or more the unit width, the control unit 13 controls the radio unit 12 so that unit resources are aggregated. In this example, since the free capacity 25a of the reception buffer 24 is larger than three times the unit width, the control unit 13 sets the aggregation number to 3, and performs DL data transmission with the aggregation resource 30 including the unit resources 31, 32, and 33. carry out.

On the other hand, as shown in FIG. 1B, when the free capacity 25b of the reception buffer 24 is less than twice the unit width, the control unit 13 controls the radio unit 12 so that unit resources are not aggregated. In this case, the control unit 13 performs DL data transmission using the unit resources 34 and 35 each including a control signal (Ctrl).

Before executing the DL data transmission, the control unit 13 transmits the control information 15 related to the aggregation to the wireless terminal 20. The control information 15 includes information such as the presence / absence of aggregation and the number of aggregations, for example. In the wireless terminal 20 that has received the control information 15, the control unit 23 controls reception by the wireless unit 22 based on the control information 15.

For example, when the DL data 16 is transmitted by the aggregate resource 30, the control unit 23 sets the communication condition of the control signal (Ctrl) received by the unit resource 31 based on the aggregation number included in the control information 15 as the unit resource 32. , 33 is applied to reception. Further, when the DL data 16 is transmitted by the unit resources 34 and 35 without being aggregated, the control unit 23 sets the communication condition of the control signal (Ctrl) received by the unit resources 34 and 35 to the unit resources 34 and 35, respectively. Applies to reception at

As described above, the buffer information 25 is notified from the radio terminal 20 to the base station 10 via UL, and the reception buffer 24 overflows and is retransmitted by controlling the presence / absence of aggregation and the number of aggregations according to the state of the reception buffer 24. Risk of control being implemented can be suppressed. As a result, it is possible to suppress the risk of transmission delay and efficiency degradation due to repeated retransmission.

The first embodiment has been described above.
<2. Second Embodiment>
Next, a second embodiment will be described. The second embodiment relates to control for aggregating a plurality of radio resources, and relates to a method for dynamically controlling the number of radio resources to be aggregated in consideration of the state of a reception buffer in the control.

[2-1. system]
The wireless communication system 50 will be described with reference to FIG. FIG. 2 is a diagram illustrating an example of a wireless communication system according to the second embodiment. The wireless communication system 50 illustrated in FIG. 2 is an example of a wireless communication system according to the second embodiment.

As illustrated in FIG. 2, the wireless communication system 50 includes a base station 100 and a wireless terminal 200. Note that the radio communication system 50 may have two or more base stations and radio terminals.
In the wireless communication system 50, data transmission is performed using a unit section L0 having a unit time width. The communication section L1 to which UL and DL transmission resources are allocated includes at least one unit section L0.

The subframe is an example of a communication section L1. A slot and a symbol are examples of the unit interval L0. In the example of (A), two unit sections L0 are included in one communication section L1. In the example of (B), four unit sections L0 are included in one communication section L1.

The transmission of the control signal Ctrl used for data transmission in the communication section L1 is assigned to the unit section L0 located at the head of the communication section L1. The control signal Ctrl includes information indicating communication conditions such as a modulation scheme (QPSK, 16QAM, 64QAM, etc.) and a coding rate. That is, in each unit section L0 included in the communication section L1, data transmission is performed under the same communication conditions.

As the number of unit sections L0 (aggregation number) included in the communication section L1 increases, the allocated resource of the control signal Ctrl in one communication section L1 decreases, so that more data can be transmitted. For example, compared with the example of (A) in which one communication section L1 includes two unit sections L0, more data can be transmitted in (B) in which one communication section L1 includes four unit sections L0. It is.

(Aggregation of unit sections)
FIG. 3 shows a control (aggregation control) sequence that enables use of a communication section L1 in which a plurality of unit sections L0 are aggregated. FIG. 3 is a sequence diagram for explaining an operation example of the wireless communication system (operation related to unit section aggregation).

(S101) Base station 100 transmits a known pilot signal to radio terminal 200 using communication section L1 including a predetermined number (two or more) of unit sections L0. Note that a modification may be made such that a reference signal for DL data demodulation is transmitted instead of a known pilot signal. As a reference signal for DL data demodulation, for example, there is RS (Cell specific reference signal // UE specific reference signal). This RS is a reference signal used for channel estimation performed when demodulating DL data, and is an example of a known signal.

(S102, S103) The radio terminal 200 measures a CQI (Channel Quality Indicator) using a pilot signal. Then, the radio terminal 200 transmits the measured CQI to the base station 100. The CQI is transmitted from the base station 100 by a base station 100 as a transmission destination of DL data, a transmission method (such as whether or not MIMO (Multiple-Input-and Multiple-Output) is implemented), data amount, allocation resource, and MCS (Modulation and). Used for selecting Coding Scheme).

(S104) The base station 100 performs aggregation control based on the CQI received from the radio terminal 200. For example, the base station 100 specifies the number of unit sections L0 that can be aggregated (aggregation number) based on the CQI. In addition, the base station 100 determines whether or not aggregation is possible based on the identified aggregation number. For example, when the aggregation number is larger than a predetermined number (a number of 2 or more), the base station 100 determines that aggregation is possible. Note that the base station 100 may determine whether or not aggregation is possible in consideration of conditions other than the number of aggregations (cell congestion status, retransmission rate, and the like).

(S105) The base station 100 transmits control information including information such as the presence / absence of aggregation and the number of aggregations to the radio terminal 200. The presence / absence of aggregation is information indicating whether or not aggregation is performed when DL data is transmitted. The number of aggregations indicates the number of aggregations applied to DL data transmission, and is a number of 1 or more (1 when there is no aggregation, 2 or more when there is aggregation). The control information is notified using, for example, at least one of a PHY (Physical) layer, a MAC (Medium Access Control) layer, and an RRC (Radio Resource Control) layer.

When notifying in the PHY layer, a dedicated bit is defined in DL control information such as DCI (Downlink Control Information), and the base station 100 uses the dedicated bit for transmission of control information. When notifying in the MAC layer, the base station 100 transmits control information using a dedicated header (for example, MAC CE (Control Element)). When notifying in the RRC layer, the base station 100 transmits control information using a dedicated message or a change notification message (for example, Measurement Report or UE Capability Information).

(S106) When the radio terminal 200 completes the reception setting based on the control information, the base station 100 transmits DL data to the radio terminal 200. At this time, the base station 100 transmits DL data in the communication section L1 including the unit section L0 of the aggregation number set in S104. The DL data transmitted in the communication section L1 is stored in the reception buffer of the wireless terminal 200. When the process of S106 is completed, the series of processes shown in FIG.

(Subframe structure)
Here, the structure and application of the unit section L0 will be described with reference to FIG. FIG. 4 is a diagram for explaining the structure and usage of a unit section. Symbols, slots, subframes, and frames are examples of the unit interval L0.

In the LTE standard, as shown in FIG. 4A, one frame (10 ms) is formed of 10 subframes (1 ms), and each subframe includes two slots (0.5 ms). One slot includes, for example, seven symbols. Of the two slots included in one subframe, at least one slot is provided with a control signal Ctrl that defines communication conditions such as a modulation scheme and a coding rate.

In the LTE standard, DL, UL, and S (Special Subframe) are assigned to each subframe. S is arranged in a section where a transition is made from DL to UL. On the other hand, in the next generation communication method, as shown in FIG. 4B, expansion to a mechanism (Self-contained operation method) that flexibly operates a communication section is under consideration. In this scheme, one or both of UL and DL can be assigned to each subframe.

In the example of (B), a transmission section of DL control signal (DL Ctrl), DL data (DL Data), UL control signal (UL Ctrl), and UL data (UL Data) is arranged in one subframe. Further, a gap (Gap) section is arranged between the DL data transmission section and the UL control signal transmission section. Even when such a subframe is adopted, the above-described aggregation can be performed with the subframe as the unit interval L0.

(Buffer amount at the time of aggregation)
When the aggregation of the unit section L0 is performed, the amount of transmission data increases as the number of aggregations increases. However, if the size of the communication section L1 increases, the reception buffer (buffer 200f described later) overflows and the risk of occurrence of retransmission occurs. Becomes larger. There is also a risk that retransmission will occur repeatedly due to insufficient free space in the reception buffer. As a result, transmission delay and efficiency deterioration may occur.

For example, when n unit intervals L0 are aggregated, as compared with the case where one unit interval L0 is used as the communication interval L1, n times as much free space (buffer amount) is used in reception in simple calculation. However, when MIMO transmission, multi-level modulation, turbo code, HARQ (Hybrid ARQ), and SAW (Stop and Wait) of multiple channels are applied, the buffer amount used at the time of reception is larger than n times. As an example, when 256QAM, MIMO transmission with two streams, turbo code, HARQ, and 4-channel SAW are applied, 96 times the buffer amount is used.

(Receive buffer status report sequence)
In order to suppress the risk of transmission delay and efficiency deterioration as described above, in the second embodiment, the radio terminal 200 reports the state of a reception buffer (a buffer 200f described later) to the base station 100. In response to this report, the base station 100 performs aggregation control so that the reception buffer does not overflow.

For example, in the wireless communication system 50, the base station 100 and the wireless terminal 200 operate as in the sequence shown in FIG. FIG. 5 is a sequence diagram for explaining an operation example of the wireless communication system (operation related to aggregation control according to the reception buffer state).

(S111) The base station 100 transmits a known pilot signal to the radio terminal 200 using a communication section L1 including a predetermined number (two or more) of unit sections L0. Note that a modification may be made such that a reference signal for DL data demodulation is transmitted instead of a known pilot signal.

(S112, S113) The radio terminal 200 measures the CQI using the pilot signal. Then, the radio terminal 200 transmits the measured CQI to the base station 100. The CQI is used by the base station 100 to select a radio terminal that is a DL data transmission destination, a transmission method (such as whether or not MIMO is performed), a data amount, an allocation resource, and an MCS.

The radio terminal 200 may measure information related to radio quality other than CQI and transmit the information to the base station 100. For example, the radio terminal 200 may measure RI (Rank Indication) indicating the number of normally received symbols and transmit the RI together with the CQI to the base station 100.

(S114) The base station 100 transmits a reception buffer status report request for requesting a status report of the reception buffer to the radio terminal 200. For example, the reception buffer status report request is transmitted using PDCCH (Physical Downlink Control Channel), MAC CE, or the like. The PDCCH is an example of a downlink control channel.

(S115) In response to the reception buffer status report request received from the base station 100, the radio terminal 200 confirms the status of the reception buffer (buffer confirmation). For example, the radio terminal 200 confirms the reception buffer usage, usage rate, free capacity, and free rate (unused rate) as the receive buffer status. Then, the wireless terminal 200 generates reception buffer state information including information indicating the confirmed state of the reception buffer.

Note that information regarding the amount of receivable data (amount of user data receivable by the wireless terminal 200) obtained in consideration of the situation regarding reception quality such as CQI and RI may be included in the reception buffer status information.

(S116) The radio terminal 200 transmits reception buffer status information to the base station 100 as a response to the reception buffer status report request. The reception buffer status information is transmitted using, for example, PUCCH (Physical / Uplink / Control / Channel) or MAC CE. PUCCH is an example of an uplink control channel.

(S117) The base station 100 performs aggregation control based on the CQI received from the radio terminal 200 and the reception buffer status information.
For example, the base station 100 specifies the number of unit sections L0 that can be aggregated (aggregation number) based on the CQI. Further, the base station 100 sets the number of unit sections L0 that can transmit the amount of data that can be received in the current state as the aggregation number, according to the state of the reception buffer indicated by the reception buffer state information. For example, if the reception buffer has a free capacity of the same size as the amount of data that can be transmitted using m unit intervals L0, the base station 100 sets the aggregation number to m.

The base station 100 determines whether or not aggregation is possible based on the identified aggregation number. For example, when the aggregation number is larger than a predetermined number (a number of 2 or more), the base station 100 determines that aggregation is possible. Note that the base station 100 may determine whether or not aggregation is possible in consideration of conditions other than the number of aggregations (cell congestion status, retransmission rate, and the like).

(S118) The base station 100 transmits control information including information such as the presence / absence of aggregation and the number of aggregations to the wireless terminal 200. The presence / absence of aggregation is information indicating whether or not aggregation is performed when DL data is transmitted. The number of aggregations indicates the number of aggregations applied to DL data transmission, and is a number of 1 or more (1 when there is no aggregation, 2 or more when there is aggregation). The control information is notified using at least one of a PHY layer, a MAC layer, and an RRC layer, for example.

When notifying in the PHY layer, a dedicated bit is defined in DL control information such as DCI, and the base station 100 uses the dedicated bit for transmission of control information. When notifying in the MAC layer, the base station 100 transmits control information using a dedicated header (for example, MAC CE). When notifying in the RRC layer, the base station 100 transmits control information using a dedicated message or a change notification message.

(S119) When the radio terminal 200 completes the reception setting based on the control information, the base station 100 transmits DL data to the radio terminal 200. At this time, the base station 100 transmits DL data in the communication section L1 including the unit section L0 of the aggregation number set in S117. The DL data transmitted in the communication section L1 is stored in the reception buffer of the wireless terminal 200. When the process of S119 is completed, the series of processes shown in FIG.

When aggregation is performed, there may be a difference between the amount of data that can be transmitted in the communication section L1 (transmittable data amount) and the amount of data that can be received by the reception buffer (receivable data amount). For example, if the reception buffer has a free space of the same size as the data amount that can be transmitted in 1.5 unit sections L0, and a communication section L1 in which two unit sections L0 are aggregated is set, the unit section L0 A radio resource equivalent to half is set in an extra state. Hereinafter, the radio resources that are set in this way may be referred to as surplus resources.

When the allocation method shown in FIG. 4B is adopted, when a surplus resource occurs in a section to which DL transmission is allocated, UL transmission can be allocated to the surplus resource. In this case, the base station 100 may allocate surplus resources for UL transmission of the radio terminal 200. When allocating surplus resources for UL transmission, the base station 100 notifies the radio terminal 200 of allocation resources for UL transmission using control information. The wireless terminal 200 uses, for example, the allocated resource for delivery confirmation and reception buffer status information update.

The effective use of surplus resources as described above will be described later as a modified example.
[2-2. hardware]
Here, hardware capable of realizing the functions and operations of the base station 100 and the wireless terminal 200 described above will be described.

(base station)
The base station 100 has hardware as shown in FIG. 6, for example. FIG. 6 is a block diagram illustrating an example of hardware capable of realizing the functions of the base station according to the second embodiment.

As shown in FIG. 6, the base station 100 includes an antenna 100a, an RF circuit 100b, a signal processing circuit 100c, a network interface (NIF) circuit 100d, a CPU 100e, and a memory 100f.

The antenna 100a is an antenna used for transmission / reception of radio band signals (RF signals). Note that the number of antennas mounted on the base station 100 may be two or more. The RF circuit 100b executes processing such as modulation / demodulation and frequency conversion on the RF signal. The signal processing circuit 100c executes encoding / decoding processing, AD (Analog to Digital) / DA (Digital to Analog) conversion processing, and the like for a baseband signal (baseband signal). The NIF circuit 100d is a communication circuit connected to the core network.

The CPU 100e controls the operation of the base station 100 using programs and data stored in the memory 100f. For example, the CPU 100e executes processing such as determination and control related to aggregation of unit sections. In addition, the CPU 100e performs control such as transmission mode switching and radio resource allocation.

Of the processes shown in FIG. 5, processes related to aggregation control (such as determining the number of aggregations and determining whether aggregation is possible) are mainly implemented using the CPU 100e. In addition, processing related to transmission of pilot signals, transmission of reception buffer status report and control information, reception of CQI and reception buffer status information, and transmission of DL data is mainly performed by the signal processing circuit 100c, RF according to control by the CPU 100e. The circuit 100b executes.

The CPU 100e can be replaced with a DSP, ASIC, FPGA, or the like. The memory 100f is, for example, an HDD, an SSD (Solid State Drive), a RAM, a ROM (Read Only Memory), or the like.

(Wireless terminal)
The wireless terminal 200 has hardware as shown in FIG. 7, for example. FIG. 7 is a block diagram illustrating an example of hardware capable of realizing the function of the wireless terminal according to the second embodiment.

As shown in FIG. 7, the radio terminal 200 includes an antenna 200a, an RF circuit 200b, a signal processing circuit 200c, a CPU 200d, a memory 200e, and a buffer 200f. Note that the number of antennas included in the wireless terminal 200 may be two or more. The memory 200e and the buffer 200f may be realized by the same storage device.

The antenna 200a is an antenna used for transmission / reception of RF signals. The RF circuit 200b executes processing such as modulation / demodulation and frequency conversion on the RF signal. The signal processing circuit 200c executes encoding / decoding processing, AD / DA conversion processing, and the like for the baseband signal. The CPU 200d controls the operation of the wireless terminal 200 using programs and data stored in the memory 200e.

Among the processes shown in FIG. 5, processes such as quality measurement such as CQI, buffer confirmation, reception buffer status information generation and transmission are mainly implemented using the CPU 200d. In addition, processes related to reception of pilot signals, transmission of CQI and reception buffer status information, reception of reception buffer status report requests and control information, and reception of DL data are mainly performed in accordance with control by the CPU 200d. The circuit 200b executes.

The CPU 200d can be replaced with a DSP, ASIC, FPGA, or the like. The memory 200e is, for example, an HDD, SSD, RAM, ROM, or the like. The buffer 200f is a memory such as a RAM or a ROM used as a reception buffer. The function of the transmission buffer can be provided by, for example, the memory 200e or another buffer memory (not shown). When the buffer 200f is shared by the transmission buffer and the reception buffer, the transmission buffer area and the reception buffer area are distinguished from each other, and the state (such as free space) is managed for each area.

[2-3. function]
Hereinafter, functions of the base station 100 and the wireless terminal 200 will be further described.
(base station)
First, the function of the base station 100 will be described with reference to FIG. FIG. 8 is a block diagram illustrating an example of functions of the base station according to the second embodiment.

As illustrated in FIG. 8, the base station 100 includes a transmission / reception unit 111, a modem unit 112, an encoding / decoding unit 113, a control unit 114, and a storage unit 115.
The functions of the transmission / reception unit 111 and the modulation / demodulation unit 112 can be realized mainly by the above-described RF circuit 100b, signal processing circuit 100c, and CPU 100e. The functions of the encoding / decoding unit 113 and the control unit 114 can be realized mainly by the signal processing circuit 100c and the CPU 100e. The function of the storage unit 115 can be realized mainly by the memory 100f.

The transmission / reception unit 111 transmits a pilot signal used for quality measurement by the radio terminal 200 and receives a quality measurement result (CQI or the like). In addition, the transmission / reception unit 111 transmits a reception buffer status report request to the radio terminal 200 and receives reception buffer status information from the radio terminal 200. In addition, the transmission / reception unit 111 transmits the control information including the result of aggregation control (existence of aggregation, the number of aggregations, and the like) and DL data to the radio terminal 200.

The modem unit 112 modulates a signal transmitted to the radio terminal 200 and demodulates a signal received from the radio terminal 200. The encoding / decoding unit 113 performs encoding of a signal transmitted to the wireless terminal 200 and decoding of a signal received from the wireless terminal 200.

The control unit 114 controls the transmission / reception unit 111, the modulation / demodulation unit 112, the encoding / decoding unit 113, and manages radio resources. For example, the control unit 114 has functions such as terminal information reception 114a, terminal information request 114b, resource control 114c, scheduling 114d, and control information transmission 114e.

The terminal information reception 114a is a function of controlling the transmission / reception unit 111 and the like to receive quality measurement results, reception buffer status information, and the like from the wireless terminal 200. The terminal information request 114b is a function for transmitting a reception buffer status report request received by controlling the transmission / reception unit 111 and the like. The resource control 114c is a function that implements aggregation control of the unit section L0.

Scheduling 114d is a function that performs selection of wireless terminals, allocation of DL transmission and UL transmission to wireless resources, and the like. The control information transmission 114e is a function of transmitting control information including the presence / absence of aggregation and the number of aggregations to the wireless terminal 200. Here, for convenience of explanation, the function is classified with a name attached thereto, but the name and classification of the function are not limited to this.

The storage unit 115 stores reception buffer status information 115a. For example, the control unit 114 controls the transmission / reception unit 111 to transmit a reception buffer status report request, receives the reception buffer status information 115a transmitted from the wireless terminal 200 in response to the reception buffer status report request, and stores the reception buffer status report 115a. 115. The reception buffer status information 115a includes information indicating the status of the reception buffer, such as the reception buffer usage, usage rate, free capacity, and free rate (unused rate).

(Wireless terminal)
Next, functions of the wireless terminal 200 will be described with reference to FIG. FIG. 9 is a block diagram illustrating an example of functions of the wireless terminal according to the second embodiment.

As illustrated in FIG. 9, the wireless terminal 200 includes a transmission / reception unit 211, a modem unit 212, an encoding / decoding unit 213, a control unit 214, and a storage unit 215.
The functions of the transmission / reception unit 211 and the modulation / demodulation unit 212 can be realized mainly by the above-described RF circuit 200b, signal processing circuit 200c, and CPU 200d. The functions of the encoding / decoding unit 213 and the control unit 214 can be realized mainly by the signal processing circuit 200c and the CPU 200d. The function of the storage unit 215 can be realized mainly by the memory 200e.

The transmission / reception unit 211 receives a pilot signal used for quality measurement from the base station 100, and transmits a quality measurement result (CQI or the like). In addition, the transmission / reception unit 211 receives a reception buffer status report request from the base station 100 and transmits reception buffer status information to the base station 100. Further, the transmission / reception unit 211 receives control information including the result of aggregation control (such as aggregation presence / absence, the number of aggregations) and DL data from the base station 100.

The modem unit 212 modulates a signal transmitted to the base station 100 and demodulates a signal received from the base station 100. The encoding / decoding unit 213 performs encoding of a signal transmitted to the base station 100 and decoding of a signal received from the base station 100.

The control unit 214 controls the transmission / reception unit 211, the modulation / demodulation unit 212, the encoding / decoding unit 213, and manages the state of the reception buffer (buffer 200f). For example, the control unit 214 has functions such as information request reception 214a, information notification 214b, and buffer status management 214c.

The information request reception 214a is a function of receiving a reception buffer status report request from the base station 100 by controlling the transmission / reception unit 211 and the like. The information notification 214b is a function of transmitting the reception buffer status information to the base station 100 by controlling the transmission / reception unit 211 and the like. The buffer status management 214c is a function for generating reception buffer status information by confirming the status of the reception buffer, such as the usage amount, usage rate, free capacity, and free rate (unused rate) of the buffer 200f. Here, for convenience of explanation, the function is classified with a name attached thereto, but the name and classification of the function are not limited to this.

Also, the control unit 214 updates the reception setting based on the control information received from the base station 100. For example, when the presence / absence of aggregation or the number of aggregations is changed, the control unit 214 updates the reception setting so that reception can be performed with the number of aggregations after the change. As an example, when the aggregation number is changed from 2 to 3, the control unit 214 receives the control signal Ctrl in the unit section L0 located at the head of the communication section L1, and has three communication conditions defined by the control signal Ctrl. The reception setting is updated so as to control reception in the unit section L0.

The storage unit 215 stores data used temporarily or continuously when the control unit 214 executes processing. The storage unit 215 may store a program that defines the operation of the control unit 214, setting information that defines reception settings, and the like. Further, the storage unit 215 may store status information indicating the usage amount, usage rate, free capacity, free rate (unused rate), and the like of the reception buffer acquired by the buffer status management 214c.

[2-4. Process flow]
Here, a flow of processing executed by the base station 100 and the wireless terminal 200 will be described.
(Reception buffer status report)
First, the flow of processing on the base station side related to transmission / reception of a reception buffer status report request will be described with reference to FIG. FIG. 10 is a flowchart showing the flow of processing executed on the base station side in the processing related to the reception buffer status report according to the second embodiment. 10 is mainly executed by the base station 100.

(S131) The control unit 114 selects a wireless terminal (wireless terminal 200; selection terminal) to be subjected to DL data transmission.
(S132) The control unit 114 confirms the reception buffer status information (reception buffer status information 115a stored in the storage unit 115) of the selected terminal held in the base station 100. At this time, the control unit 114 confirms the presence / absence of the reception buffer status information 115a and whether the reception buffer status information 115a is the latest. Note that the reception buffer status information 115a can be managed by using, for example, time elapsed since the previous update, version information acquired from the wireless terminal 200, or the like.

(S133) The control unit 114 determines whether there is reception buffer status information 115a. In addition, when there is the reception buffer status information 115a, the control unit 114 determines whether or not the reception buffer status information 115a is the latest. If there is no reception buffer status information 115a, or if the reception buffer status information 115a is not the latest, the process proceeds to S134. On the other hand, when the reception buffer status information 115a is the latest, the series of processing illustrated in FIG.

According to the sequence illustrated in FIG. 5, the reception buffer status information is transmitted from the radio terminal 200 in response to the reception buffer status report request. However, it is also possible to employ a mechanism in which the radio terminal 200 notifies the base station 100 of reception buffer status information regardless of whether there is a reception buffer status report request. When this mechanism is employed, the reception buffer status information 115a may be stored in the storage unit 115 before the reception buffer status report request is transmitted. The confirmation of the reception buffer status information 115a performed in S132 and S133 functions effectively when such a mechanism is adopted.

(S134, S135) The control unit 114 controls the transmission / reception unit 111 and the like, and transmits a reception buffer status report request to the wireless terminal 200 which is the selected terminal. Then, the control unit 114 waits for reception of the reception buffer status information 115a transmitted from the wireless terminal 200. Note that the control unit 114 may execute another process in a standby state. When the reception buffer status information 115a is received, the process proceeds to S136.

(S136) The control unit 114 stores the reception buffer status information 115a received from the wireless terminal 200 in the storage unit 115, and sets it so that it can be used for resource control 114c and scheduling 114d. When the process of S136 is completed, the series of processes shown in FIG.

Next, the flow of processing on the terminal side related to transmission / reception of the reception buffer status report request will be described with reference to FIG. FIG. 11 is a flowchart showing a flow of processing executed on the wireless terminal side in processing related to the reception buffer status report according to the second embodiment. The process illustrated in FIG. 11 is mainly executed by the wireless terminal 200.

(S141, S142) The control unit 214 receives a reception buffer status report request from the base station 100. In response to the reception buffer status report request, the control unit 214 detects the usage amount, usage rate, free capacity, free rate (unused rate), and the like of the buffer 200f as the reception buffer status.

(S143, S144) The control unit 214 generates reception buffer state information indicating the state of the reception buffer. Then, the control unit 214 transmits the generated reception buffer state information to the base station 100. When the process of S144 is completed, the series of processes illustrated in FIG. 11 ends.

Note that the control unit 214 may autonomously confirm the state of the buffer 200f and transmit the reception buffer state information to the base station 100 before receiving the reception buffer state report request from the base station 100. For example, the control unit 214 may confirm the state of the buffer 200f at a predetermined cycle, and may transmit the reception buffer state information to the base station 100 by multiplying the transmission timing of the UL control channel. Such a modification also belongs to the technical scope of the second embodiment.

(DL data transmission control)
Next, the flow of processing on the base station side related to DL data transmission control will be described with reference to FIG. FIG. 12 is a flowchart showing a flow of processing executed on the base station side among the processing related to DL data transmission control according to the second embodiment. The process shown in FIG. 12 is mainly executed by base station 100.

(S151) The control unit 114 refers to the reception buffer status information 115a of the selected terminal (wireless terminal 200). If the latest reception buffer status information 115a is stored in the storage unit 115, the reception buffer status information 115a is referred to. Further, when the reception buffer status information 115a is received from the wireless terminal 200 in response to the reception buffer status report request, the received reception buffer status information 115a is referred to.

(S152, S153) The control unit 114 determines the aggregation number of the unit section L0 according to the state of the reception buffer (buffer 200f) indicated by the reception buffer state information 115a. In addition, the control unit 114 determines the allocated resource size of the selected terminal (wireless terminal 200).

For example, the free capacity of the buffer 200f is expressed as RxBuff, the data size of the data waiting to be transmitted among the DL data transmitted from the base station 100 to the radio terminal 200 is expressed as TxData, and the aggregation number of the unit section L0 is expressed as AggNum. Also, the resource size allocated to the radio terminal 200 is denoted as AggSize, and the resource size that can be allocated to one unit section L0 is denoted as DurSize.

Using the above notation, the aggregation number AggNum can be determined by the following equation (1), for example. However, floor (•) is a function that rounds off the decimal part. Further, the allocation resource AggSize can be determined by the following equation (2), for example. In the following description, the above notation may be used again.

AggNum = floor {RxBuff / DurSize} +1 (1)
AggSize = DurSize × AggNum (2)
(S154) The control unit 114 determines whether or not aggregation is performed based on the aggregation number AggNum. For example, the control unit 114 determines that aggregation is present when the aggregation number AggNum is greater than or equal to a predetermined number (two or more). On the other hand, when the aggregation number AggNum is equal to or smaller than the predetermined number, the control unit 114 determines that there is no aggregation. In this case, the control unit 114 sets the aggregation number to 1, and arranges the control signal Ctrl in each unit section L0. In addition, the control unit 114 generates control information including the presence / absence of aggregation and the number of aggregations.

(S155, S156) The control unit 114 controls the transmission / reception unit 111 and the like, and transmits the generated control information to the selection terminal (wireless terminal 200). And the control part 114 transmits DL data by the communication area L1 set based on the aggregation number of control information with respect to the selection terminal (radio | wireless terminal 200) by which reception setting was updated according to control information. When the process of S156 is completed, the series of processes illustrated in FIG.

Next, the flow of processing on the terminal side related to DL data transmission control will be described with reference to FIG. FIG. 13 is a flowchart showing a flow of processing executed on the wireless terminal side among the processing related to DL data transmission control according to the second embodiment. The process illustrated in FIG. 13 is mainly executed by the wireless terminal 200.

(S161) The control unit 214 receives control information including information such as the presence / absence of aggregation and the number of aggregations from the base station 100. Then, the control unit 214 updates the reception setting based on the control information. For example, when aggregation is performed and the number of aggregations is 3, the control unit 214 receives the control signal Ctrl in the unit section L0 at the head of the communication section L1, and three unit sections with communication conditions defined by the control signal Ctrl The reception setting is updated so that reception at L0 can be controlled.

(S162, S163) The control unit 214 receives DL data from the base station 100 based on the reception setting updated in S161. DL data received from the base station 100 is stored in the buffer 200f. After storing the DL data, the control unit 214 confirms the state of the buffer 200f and updates the reception buffer state information. Note that the reception buffer state information may be autonomously transmitted to the base station 100 at this time.

(S164) The control unit 214 transmits a DL data delivery confirmation (ACK (ACKnowledgement) / NACK (Negative ACKnowledgement)) using a known UL resource that can be used by the terminal (wireless terminal 200). A method for transmitting a delivery confirmation using surplus resources will be described later as a modification. When the process of S164 is completed, the series of processes illustrated in FIG. 13 ends.

As described above, the radio terminal 200 notifies the base station 100 of the state of the reception buffer, and the base station 100 performs aggregation control in consideration of the state of the reception buffer, so that the risk of occurrence of retransmission due to overflow of the reception buffer In addition, transmission delay and efficiency degradation due to repeated retransmission can be suppressed.

[2-5. Modified example]
Hereinafter, modifications of the second embodiment will be described.
(Effective use of surplus resources)
As a modification, a mechanism for effectively using surplus resources will be described.

According to the above equation (1), as shown in FIG. 14, the amount of data that can be transmitted in the communication section L1 (transmittable data amount) and the amount of data that can be received by the reception buffer (receivable data amount). Differences can occur. FIG. 14 is a diagram for explaining effective use of surplus resources that may occur when unit sections are aggregated.

For example, if the reception buffer has a free space of the same size as the data amount that can be transmitted in 1.5 unit sections L0, and a communication section L1 in which two unit sections L0 are aggregated is set, the unit section L0 A radio resource corresponding to half becomes a surplus resource.

When the allocation method already introduced with reference to FIG. 4B is employed, when a surplus resource occurs in a section to which DL transmission is allocated, UL transmission can be allocated to the surplus resource. In this case, the control unit 114 of the base station 100 can allocate surplus resources to the UL transmission of the radio terminal 200.

In the present modification, the control unit 114 notifies the wireless terminal 200 of the surplus resources allocated for UL transmission using the control information. On the other hand, the control unit 214 of the wireless terminal 200 effectively uses the allocated surplus resource for confirmation of delivery, update of reception buffer status information, and the like. Below, the flow of the process which the base station 100 and the radio | wireless terminal 200 perform when implementing such effective use of a surplus resource is demonstrated.

First, the flow of processing on the base station side related to DL data transmission control will be described with reference to FIG. FIG. 15 is a flowchart illustrating a flow of processing executed on the base station side in the processing related to DL data transmission control according to a modification of the second embodiment (effective use of surplus resources). Note that the flow of processing related to the reception buffer status report is the same as in FIGS.

(S201) The control unit 114 refers to the reception buffer status information 115a of the selected terminal (wireless terminal 200). If the latest reception buffer status information 115a is stored in the storage unit 115, the reception buffer status information 115a is referred to. Further, when the reception buffer status information 115a is received from the wireless terminal 200 in response to the reception buffer status report request, the received reception buffer status information 115a is referred to.

(S202, S203) The control unit 114 determines the aggregation number of the unit section L0 according to the state of the reception buffer (buffer 200f) indicated by the reception buffer state information 115a. In addition, the control unit 114 determines the allocated resource size of the selected terminal (wireless terminal 200). For example, the aggregation number AggNum is determined by the above equation (1). The allocation resource AggSize is determined by, for example, the above equation (2).

(S204) The control unit 114 calculates the size of the surplus resource. For example, if the surplus resource size is expressed as FreeSize, the surplus resource size FreeSize can be determined by the following equation (3).

FreeSize = AggSize−RxBuff (3)
(S205) The control unit 114 determines the presence or absence of aggregation based on the aggregation number AggNum. For example, the control unit 114 determines that aggregation is present when the aggregation number AggNum is greater than or equal to a predetermined number (two or more). On the other hand, when the aggregation number AggNum is equal to or smaller than the predetermined number, the control unit 114 determines that there is no aggregation. In this case, the control unit 114 sets the aggregation number to 1, and arranges the control signal Ctrl in each unit section L0. In addition, the control unit 114 generates control information including the presence / absence of aggregation and the number of aggregations.

(S206) The control unit 114 determines whether or not the size (FreeSize) of the surplus resource is larger than zero. If FreeSize> 0, the process proceeds to S207. On the other hand, if FreeSize> 0 is not satisfied (if FreeSize = 0), the process proceeds to S208.

(S207) The control unit 114 adds information on surplus resources to the control information generated in S205. The surplus resource information includes, for example, notification information indicating that the surplus resource can be used for UL transmission, and information indicating a range in which the surplus resource is allocated in the unit section L0 at the end of the communication section L1 (allocation range) For example).

(S208, S209) The control unit 114 controls the transmission / reception unit 111 and the like, and transmits the generated control information to the selection terminal (wireless terminal 200). And the control part 114 transmits DL data by the communication area L1 set based on the aggregation number of control information with respect to the selection terminal (radio | wireless terminal 200) by which reception setting was updated according to control information. When the process of S209 is completed, the series of processes illustrated in FIG.

Next, the flow of processing on the terminal side related to DL data transmission control (when used for transmission of delivery confirmation: pattern A) will be described with reference to FIG. FIG. 16 is a flowchart showing a flow of a process (pattern A) executed on the wireless terminal side among the processes related to DL data transmission control according to a modified example (effective use of surplus resources) of the second embodiment. is there.

(S211) The control unit 214 receives control information including information such as the presence / absence of aggregation and the number of aggregations from the base station 100. Then, the control unit 214 updates the reception setting based on the control information. For example, when aggregation is performed and the number of aggregations is 3, the control unit 214 receives the control signal Ctrl in the unit section L0 at the head of the communication section L1, and three unit sections with communication conditions defined by the control signal Ctrl The reception setting is updated so that reception at L0 can be controlled.

(S212) The control unit 214 determines whether there is information on surplus resources in the control information. If surplus resource information is added to the control information, the process proceeds to S216. On the other hand, when the surplus resource information is not added to the control information, the process proceeds to S213.

(S213, S214) The control unit 214 receives DL data from the base station 100 based on the reception setting updated in S211. DL data received from the base station 100 is stored in the buffer 200f. After storing the DL data, the control unit 214 confirms the state of the buffer 200f and updates the reception buffer state information. Note that the reception buffer state information may be autonomously transmitted to the base station 100 at this time.

(S215) The control unit 214 transmits a DL data delivery confirmation (ACK / NACK) using a known UL resource that can be used by the terminal (wireless terminal 200). When the process of S215 is completed, the series of processes illustrated in FIG.

(S216, S217) The control unit 214 receives DL data from the base station 100 based on the reception setting updated in S211. DL data received from the base station 100 is stored in the buffer 200f. After storing the DL data, the control unit 214 confirms the state of the buffer 200f and updates the reception buffer state information. Note that the reception buffer state information may be autonomously transmitted to the base station 100 at this time.

(S218) The control unit 214 refers to the information on the surplus resource assigned to the control information, and transmits a delivery confirmation (ACK / NACK) using the surplus resource allocated to the selected terminal (wireless terminal 200). . When the process of S218 is completed, the series of processes illustrated in FIG.

Next, the flow of processing on the terminal side related to DL data transmission control (when used for transmission of reception buffer status information: pattern B) will be described with reference to FIG. FIG. 17 is a flowchart showing the flow of processing (pattern B) executed on the wireless terminal side among the processing related to DL data transmission control according to a modification of the second embodiment (effective use of surplus resources). is there.

(S221) The control unit 214 receives control information including information such as the presence / absence of aggregation and the number of aggregations from the base station 100. Then, the control unit 214 updates the reception setting based on the control information. For example, when aggregation is performed and the number of aggregations is 3, the control unit 214 receives the control signal Ctrl in the unit section L0 at the head of the communication section L1, and three unit sections with communication conditions defined by the control signal Ctrl The reception setting is updated so that reception at L0 can be controlled.

(S222) The control unit 214 determines whether or not there is surplus resource information in the control information. If surplus resource information is added to the control information, the process proceeds to S223. On the other hand, when the surplus resource information is not added to the control information, the process proceeds to S226.

(S223, S224) The control unit 214 receives DL data from the base station 100 based on the reception setting updated in S221. DL data received from the base station 100 is stored in the buffer 200f. After storing the DL data, the control unit 214 confirms the state of the buffer 200f and updates the reception buffer state information. Note that the reception buffer state information may be autonomously transmitted to the base station 100 at this time.

(S225) The control unit 214 refers to the information on the surplus resources assigned to the control information, and transmits the reception buffer status information using the surplus resources allocated to the selected terminal (wireless terminal 200). When the process of S225 is completed, the process proceeds to S228.

(S226, S227) The control unit 214 receives DL data from the base station 100 based on the reception setting updated in S221. DL data received from the base station 100 is stored in the buffer 200f. After storing the DL data, the control unit 214 confirms the state of the buffer 200f and updates the reception buffer state information. Note that the reception buffer state information may be autonomously transmitted to the base station 100 at this time.

(S228) The control unit 214 transmits a DL data delivery confirmation (ACK / NACK) using a known UL resource that can be used by the terminal (wireless terminal 200). When the process of S228 is completed, the series of processes shown in FIG.

As described above, the utilization efficiency of radio resources can be increased by effectively using surplus resources.
In the above description, an example in which the surplus resource is allocated to UL transmission when the surplus resource is not 0 has been shown. However, when the surplus resource size is smaller than a predetermined threshold, the use of the surplus resource is suppressed. It may be deformed. For example, in the example of the pattern B described above, the total data amount of the data amount of the UL control signal (UL Ctrl) and the reception buffer state information is set to a predetermined threshold value. That is, control may be performed so that surplus resources are allocated when there is a surplus resource of a size that allows UL transmission of desired information.

(Other variations)
So far, a method for aggregating radio resources in the time direction has been described. However, the technique of the second embodiment described above can also be applied to a method of consolidating radio resources in the frequency direction. For example, it can be applied to CA (Carrier Aggregation). Further, the present invention can also be applied to a method of aggregating radio resources such as RB and RE (Resource Element) having unit time width and unit bandwidth. Regardless of which method is applied, the radio terminal 200 notifies the base station 100 of reception buffer state information, and the base station 100 performs the same aggregation control based on the reception buffer state information.

In the above description, the base station 100 determines the aggregation number. However, the radio terminal 200 determines the aggregation number based on the measurement result of the radio quality, and notifies the base station 100 of the aggregation number. It is also possible to deform. In addition, the base station 100 and the wireless terminal 200 may both determine the aggregation number candidates, and the base station 100 may select one of the candidates. Such a modification naturally belongs to the technical scope of the second embodiment.

In the above description, the method of using surplus resources for transmission of delivery confirmation (pattern A) and transmission of reception buffer status information (pattern B) has been described with reference to FIGS. 16 and 17. The information that can be UL transmitted with the surplus resource is not limited to one of the delivery confirmation and the reception buffer status information, and information different from the delivery confirmation and the reception buffer status information may be UL transmitted with the surplus resource.

Therefore, as a modified example, a sequence in the case where both the delivery confirmation and the reception buffer status information are UL transmitted using surplus resources will be described with reference to FIG. FIG. 18 is a sequence diagram for explaining an operation example (a combination of patterns A and B) of the wireless communication system related to DL data transmission control according to a modified example (effective use of surplus resources) of the second embodiment.

(S231) Base station 100 transmits a known pilot signal to base station 100 using communication section L1 including a predetermined number (two or more) of unit sections L0.
(S232, S233) The radio terminal 200 measures CQI using a pilot signal. Then, the radio terminal 200 transmits the measured CQI to the base station 100.

(S234) The base station 100 transmits a reception buffer status report request for requesting a status report of the reception buffer to the radio terminal 200. For example, the reception buffer status report request is transmitted using PDCCH, MAC CE, or the like.

(S235) In response to the reception buffer status report request received from the base station 100, the radio terminal 200 confirms the status of the reception buffer (buffer confirmation). For example, the radio terminal 200 confirms the reception buffer usage, usage rate, free capacity, and free rate (unused rate) as the receive buffer status. Then, the wireless terminal 200 generates reception buffer state information including information indicating the confirmed state of the reception buffer.

(S236) The radio terminal 200 transmits reception buffer status information to the base station 100 as a response to the reception buffer status report request. The reception buffer status information is transmitted using, for example, PUCCH or MAC CE.

(S237) The base station 100 performs aggregation control (determination of aggregation presence / absence of aggregation, determination of the number of aggregations) based on the CQI and reception buffer status information received from the radio terminal 200. When performing aggregation, the base station 100 identifies surplus resources based on the number of aggregations.

(S238) The base station 100 generates control information including information such as the presence / absence of aggregation and the number of aggregations. When there is a surplus resource, the base station 100 gives information on the surplus resource to the control information. Then, the base station 100 transmits control information to the wireless terminal 200. The control information is notified using at least one of a PHY layer, a MAC layer, and an RRC layer, for example.

(S239) When the radio terminal 200 completes the reception setting based on the control information, the base station 100 transmits DL data to the radio terminal 200. At this time, the base station 100 transmits DL data in the communication section L1 including the unit section L0 of the aggregation number set in S237. The DL data transmitted in the communication section L1 is stored in the reception buffer of the wireless terminal 200.

(S240) When surplus resource information is added to the control information, the radio terminal 200 transmits the UL data delivery confirmation using the surplus resource and the reception buffer status information updated after receiving the UL data. . Of the surplus resources, other information may be UL-transmitted using the remainder of the allocation resources for the delivery confirmation and reception buffer status information. When the process of S240 is completed, the series of processes shown in FIG.

As described above, various modifications can be made to the technology according to the second embodiment. Such a modification naturally belongs to the technical scope of the second embodiment.
The second embodiment has been described above.

The above merely shows the principle of the present invention. In addition, many modifications and changes can be made by those skilled in the art, and the present invention is not limited to the precise configuration and application shown and described above, and all corresponding modifications and equivalents may be And the equivalents thereof are considered to be within the scope of the invention.

5 wireless communication system 10 base station 11, 21 antenna 12, 22 wireless unit 13, 23 control unit 14 request 15 control information 16 DL data 24 reception buffer 25 buffer information 25a, 25b free capacity 30 aggregated resources 31, 32, 33, 34 35 unit resource Ctrl control signal

Claims (21)

1. In response to a request from a base station, buffer information related to a reception buffer is transmitted, and whether or not a plurality of radio resources are aggregated is controlled based on the buffer information. And a control unit that receives control information.
2. The radio terminal according to claim 1, wherein each of the plurality of radio resources is a communication section having a unit time width.
3. The wireless terminal according to claim 2, wherein the communication section is any one of a symbol, a slot, and a subframe.
4. The buffer information includes at least one of a usage amount, a usage rate, a free capacity, and an unused rate of the reception buffer.
   The wireless terminal according to claim 1.
5. The control unit receives the control information including information related to the setting of the communication section, and receives at least one of uplink data, a response of a downlink reception result, and the buffer information according to reception of the control information. The wireless terminal according to claim 2, which transmits to a base station.
6. The radio terminal according to claim 2, wherein the communication section is divided into an uplink transmission resource and a downlink transmission resource by the base station based on information on the radio terminal.
7. The control unit receives information on the uplink transmission resource, uses the uplink transmission resource, uses the uplink transmission resource, information about a downlink reception result, information about the reception buffer after the downlink reception, the downlink The wireless terminal according to claim 6, wherein at least one of information related to reception quality is transmitted to the base station.
8. The aggregation of the plurality of radio resources is an aggregation of a first communication section including a section for transmitting and receiving control information and a plurality of second communication sections that are sections for transmitting and receiving data using the control information. Item 3. The wireless terminal according to Item 2.
9. A transmission / reception unit that requests buffer information related to a reception buffer of the wireless terminal to the wireless terminal and receives the buffer information from the wireless terminal;
   A control unit that controls whether or not to aggregate a plurality of radio resources using information about the radio terminals received from the radio terminal, and transmits control information about the aggregation of the plurality of radio resources to the radio terminal; Have a base station.
10. The control unit refers to the buffer information, and when the size of the aggregate resource obtained by aggregating the plurality of radio resources is larger than the empty size of the reception buffer, the control unit is a difference between the aggregate resource size and the empty size. The base station according to claim 9, wherein surplus resources are allocated to uplink transmission and the uplink transmission allocation is notified to the radio terminal.
11. The control unit divides at least one radio resource among the plurality of radio resources allocated to the radio terminal into an uplink transmission resource and a downlink transmission resource based on information on the radio terminal. 10. A base station according to 10.
12. Aggregating the plurality of radio resources by requesting buffer information related to the reception buffer of the radio terminal from the radio terminal, controlling whether or not to aggregate a plurality of radio resources based on the buffer information received from the radio terminal, A base station having a first control unit for transmitting control information relating to the wireless terminal;
    The wireless terminal comprising: a second control unit that receives the buffer information request from the base station, transmits the buffer information to the base station in response to the request, and receives the control information from the base station When;
    A wireless communication system.
13. The base station requests the wireless terminal for buffer information related to the reception buffer of the wireless terminal,
    The wireless terminal receives the buffer information request from the base station, and transmits the buffer information to the base station;
    The base station controls whether or not to aggregate a plurality of radio resources based on the buffer information received from the radio terminal, and transmits control information related to the aggregation of the plurality of radio resources to the radio terminal. Control method.
14. In a wireless communication system for transmitting data between a wireless terminal and a base station,
    The base station
    A first notification unit that transmits a buffer notification request for requesting the wireless terminal to notify buffer information related to a reception buffer;
    A first receiving unit for receiving the buffer information notified from the wireless terminal;
    A first controller that controls whether to aggregate a plurality of radio resources based on the buffer information;
    A first transmitter that transmits control information related to aggregation of the plurality of radio resources to the radio terminal;
    Have
    The wireless terminal is
    The receive buffer;
    A second receiving unit for receiving the buffer notification request and the control information from the base station;
    A second notification unit for notifying the buffer information to the base station;
    A wireless communication system.
15. The radio communication system according to claim 14, wherein the first control unit controls whether or not the plurality of radio resources are aggregated with any one of a symbol, a slot, and a subframe.
16. When the first control unit aggregates the plurality of radio resources, a first resource that aggregates the plurality of radio resources and a second resource that corresponds to the amount of data that can be received by the reception buffer. Calculate the surplus resource that is the difference,
    The first transmission unit transmits surplus resource information regarding the surplus resource to the wireless terminal,
    The second receiving unit receives the surplus resource information from the base station,
    The radio communication system according to claim 15, wherein the radio terminal further includes a second control unit that controls uplink transmission using the surplus resource based on the control information and the surplus resource information.
17. The wireless communication system according to claim 16, wherein the buffer information includes at least one of a buffer usage amount, a buffer usage rate, a buffer free space, and a buffer unused rate of the reception buffer.
18. The first control unit includes a first section including a section in which uplink control information is transmitted and a section in which the uplink data is transmitted, a section in which downlink control information is transmitted, and the downlink. Performing allocation control for allocating at least one of the second sections including a section in which link data is transmitted to a subframe;
    The first transmission unit gives the result of the allocation control to the control information,
    The second notification unit is configured to transmit at least one of the uplink data, a response to the downlink reception result, and the buffer information based on a result of the allocation control given to the control information to the base station The wireless communication system according to claim 14.
19. For the downlink radio resource allocated to the radio terminal, the first control unit determines an area in the downlink radio resource based on the buffer information as an area for downlink transmission and an area for uplink transmission. The wireless communication system according to claim 14.
20. The first receiving unit receives uplink control information used for uplink transmission from the wireless terminal,
    The first control unit allocates a radio resource designated by the uplink control information to the radio terminal, information on a reception result of downlink transmission, the buffer information on the reception buffer after the downlink transmission, The wireless communication system according to claim 14, wherein the wireless terminal is caused to perform uplink transmission for transmitting at least one of quality information related to communication quality of downlink transmission.
21. The first control unit allocates the surplus resource to another radio terminal, uses the surplus resource for transmission of the buffer notification request to the other radio terminal, or performs signaling performed with the other radio terminal The wireless communication system according to claim 16.

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