JP2012151869A - Radio communication system, base station device, and radio communication method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make a scheduler function effectively by avoiding postponing of transmitting transmission data to a transmission destination reception device having high reception quality while preferentially transmitting retransmission data to a retransmission destination reception device requiring retransmission, in the case that the retransmission by an HARQ occurs.SOLUTION: A radio base station 1 comprises a scheduler 114 and a control part 112. The scheduler 114 sets priority, with which radio resources used for data transmission are allocated, of a reception device having high reception quality to high proportionally. The control part 112 allocates the radio resources to both transmission destination reception device and retransmission destination reception device, and transmits both transmission data and retransmission data by using the allocated radio resources; when priority β set to the transmission destination reception device by the scheduler 114 is higher than priority α set to the retransmission destination reception device.

Description

  The present invention relates to a radio communication system, a radio communication apparatus, and a radio communication method to which hybrid automatic retransmission control is applied.

  Generally, in a wireless communication system, transmission errors frequently occur as compared with a wired communication system. In order to ensure communication reliability in such a wireless communication system, in recent years, hybrid automatic retransmission control (HARQ) using both automatic retransmission control (ARQ) and forward error correction (FEC) is widely used.

  In HARQ, a reception-side wireless communication device (hereinafter referred to as a reception device) transmits a retransmission request to a transmission device when decoding of data received from a transmission-side wireless communication device (hereinafter referred to as a transmission device) fails. When receiving the retransmission request, the transmission device transmits the transmitted transmission data (initial transmission data) as retransmission data to the reception device.

  The receiving device stores transmission data that has failed in decoding. When receiving retransmission data from the transmitting device, the receiving device combines the stored transmission data and the received retransmission data to perform decoding. Thereby, the error correction capability can be improved. As described above, the transmission device and the reception device hold the transmission data until the retransmission processing by HARQ is completed.

  In addition, when a transmission device such as a radio base station communicates with a plurality of reception devices such as a radio terminal, the transmission device responds to a plurality of reception devices according to reception quality (for example, reception SNR) in each reception device. And a scheduler for controlling allocation of radio resources such as time or frequency. Usually, the scheduler enables data transmission using radio resources with high reception quality preferentially by setting a high allocation priority (hereinafter referred to as priority) for a receiving apparatus with high reception quality. Is effectively utilized and throughput is improved.

  When the above-described HARQ is applied to a transmission apparatus having such a scheduler, for the purpose of reducing the storage amount of transmission data and reducing the retransmission delay, the transmission apparatus can retransmit data regardless of the priority set by the scheduler. Is generally transmitted with the highest priority (see, for example, Patent Document 1).

JP 2005-39726 A ([0028], [0029] paragraphs, etc.)

  However, the conventional method for transmitting retransmission data with the highest priority has the following problems. Specifically, as a result of the retransmission data being transmitted with the highest priority, transmission of transmission data to the receiving apparatus set with a high priority by the scheduler is postponed.

  As described above, the scheduler sets a high priority for a receiving apparatus with high reception quality, but the reception quality is unstable in wireless communication, and at the time of transmission of transmission data that has been postponed, the reception is performed. Quality may be degraded. In other words, if retransmission data is always transmitted with the highest priority, there is a problem that the scheduler does not function effectively.

  In particular, a wireless communication system employing HARQ is configured to actively perform retransmission in anticipation of an improvement in error correction capability, and such a problem becomes significant because retransmission is frequently performed.

  Therefore, the present invention has been made to solve the above-described problem. When retransmission by HARQ occurs, the reception quality is improved while preferentially transmitting retransmission data to a receiving apparatus that requests retransmission. It is an object of the present invention to provide a radio communication system, a radio communication apparatus, and a radio communication method that enable a scheduler to function effectively by preventing transmission of transmission data to a high receiving apparatus from being delayed.

  In order to solve the above-described problems, the present invention has the following aspects. First, a first aspect of the present invention is a wireless communication station apparatus that performs wireless communication with a plurality of communication apparatuses, and transmission of transmission data that is one of the plurality of communication apparatuses and is not requested to be retransmitted. A wireless communication system including: a first communication device that is a destination; and a second communication device that is one of the plurality of communication devices and is a transmission destination of retransmission data for which retransmission is requested, The wireless communication station device includes: a setting unit that sets priority for each communication device according to reception quality when each communication device receives a signal from the wireless communication station device; and And a transmission control unit that controls data transmission to each of the communication devices, the setting unit sets a higher priority as the reception quality is higher, and the transmission control unit is configured to control the first communication. The first priority set in the device is the second communication device. When it is higher than the set second priority, the transmission data for the first communication device and the retransmission data for the second communication device are controlled so as to share and transmit one radio resource. And

  According to such a wireless communication system, when the first priority set for the first communication device is higher than the second priority set for the second communication device, the transmission control unit In order to control the transmission data for one communication device and the retransmission data for the second communication device so as to share and transmit one radio resource, the retransmission data to the receiving device that requests retransmission is preferentially transmitted. However, it is possible to make the scheduler (setting unit) function effectively by avoiding the transmission of transmission data to a receiving apparatus having a high reception quality.

  A second aspect of the present invention provides a plurality of communications including a first communication device that is a transmission destination of transmission data for which retransmission is not requested and a second communication device that is a transmission destination of retransmission data for which retransmission is requested. A wireless communication station device that performs wireless communication with a device, wherein priority is set for each communication device according to reception quality when each communication device receives a signal from the wireless communication station device And a transmission control unit that controls data transmission to each communication device based on the priority, and the setting unit sets a higher priority as the reception quality is higher, When the first priority set for the first communication device is higher than the second priority set for the second communication device, the transmission control unit and the transmission data for the first communication device and the second The retransmission data for the communication device is 1 And summarized in that it controls to the transmission by sharing radio resources.

  According to a third aspect of the present invention, when the first priority is higher than the second priority, the transmission control unit is configured to change the first priority according to a ratio between the first priority and the second priority. The gist is to perform control so as to determine the sizes of the transmission data and the retransmission data in one radio resource.

  According to a fourth aspect of the present invention, the transmission control unit reduces the size of the retransmission data to be smaller than the size of the initial transmission data corresponding to the retransmission data transmitted to the second communication device. The gist is to determine the difference between the size of the corresponding initial transmission data and the size of the retransmission data as the size of the transmission data to be transmitted to the first communication device.

  In a fifth aspect of the present invention, the transmission control unit is configured such that the first priority set for the first communication device is A, the second priority set for the second communication device is B, The gist is that the size D of the retransmission data is determined by D = C × (B / (A + B)) where C is the size of the initial transmission data corresponding to the retransmission data.

  According to a sixth aspect of the present invention, the transmission control unit is configured such that the first communication device and the second communication device receive the first communication according to reception quality when the signal is received from the wireless communication station device. A first modulation scheme used for data transmission to a device and a second modulation scheme used for data transmission to the second communication device are determined, and the determined first modulation scheme and second modulation scheme are determined The gist is to determine the sizes of the transmission data and the retransmission data according to the above.

  According to a seventh aspect of the present invention, in the transmission control unit, when the first priority is higher than the second priority, the transmission control unit determines the first priority according to a ratio between the first priority and the second priority. According to each reception quality when the first communication device and the second communication device receive a signal from the wireless communication station device, respectively determining the sizes of the transmission data and the retransmission data in one wireless resource Determining a first modulation scheme used for data transmission to the first communication device and a second modulation scheme used for data transmission to the second communication device, and determining the determined first modulation scheme and The gist is to adjust the sizes of the determined transmission data and retransmission data in accordance with the second modulation scheme.

  According to an eighth aspect of the present invention, in the transmission control unit, the information amount per symbol defined in the second modulation scheme is smaller than the information amount per symbol defined in the first modulation scheme. In this case, the size of the determined retransmission data is reduced, the size of the determined transmission data is increased, and the information amount per symbol specified in the second modulation scheme is the first modulation. When the amount of information is larger than the information amount per symbol specified in the system, the gist is to increase the size of the determined retransmission data and decrease the size of the determined transmission data.

According to a ninth aspect of the present invention, when the first priority is higher than the second priority and the second priority is lower than a predetermined threshold, the transmission control unit assigns the radio resource to the radio resource. The gist is to perform control so that only the transmission data is transmitted while being allocated only to the first communication device.

  In a tenth aspect of the present invention, when the first priority is lower than the second priority, the transmission control unit allocates the radio resource only to the second communication device and transmits only the retransmission data. The gist is to control so as to.

  An eleventh aspect of the present invention provides a plurality of communications including a first communication device that is a transmission destination of transmission data for which retransmission is not requested and a second communication device that is a transmission destination of retransmission data for which retransmission is requested. A wireless communication method applied to a wireless communication station device that performs wireless communication with a device, wherein each of the communication devices is in accordance with reception quality when the communication device receives a signal from the wireless communication station device. A step A for setting priority to the communication device, and a step B for controlling data transmission to each communication device based on the priority set in the step A. In the step A, the reception is performed. The higher the quality, the higher the priority is set. In the step B, when the first priority set for the first communication device is higher than the second priority set for the second communication device, the first The above for one communication device The retransmission data for the signal data and the second communication device, and summarized in that control to transmit by sharing a single radio resource.

  According to the present invention, when retransmission by HARQ occurs, transmission of transmission data to a receiving apparatus with high reception quality is delayed while transmitting retransmission data to a receiving apparatus that requests retransmission with priority. By avoiding the above, it is possible to provide a wireless communication system, a wireless communication apparatus, and a wireless communication method that enable the scheduler to function effectively.

1 is an overall schematic configuration diagram of a wireless communication system according to an embodiment of the present invention. It is a functional block block diagram of the radio base station which concerns on embodiment of this invention. It is a figure for demonstrating an example of the priority setting process which concerns on embodiment of this invention. It is a conceptual diagram for demonstrating the data size determination process and data size adjustment process which concern on embodiment of this invention. It is a figure which shows an example of matching with CQI and reception SNR. It is a figure for demonstrating the modulation system used in adaptive modulation. It is a flowchart which shows operation | movement of the radio base station which concerns on embodiment of this invention.

  Next, a radio communication system according to an embodiment of the present invention will be described with reference to the drawings. Specifically, (1) overall schematic configuration of radio communication system, (2) configuration of radio base station, (3) example of priority setting process, (4) example of data size determination / adjustment process, (5) The operation of the radio base station, (6) operations and effects, (7) other embodiments will be described. In the description of the drawings in the following embodiments, the same or similar parts are denoted by the same or similar reference numerals.

(1) Overall schematic configuration of wireless communication system
FIG. 1 is an overall schematic configuration diagram of a wireless communication system 10 according to the present embodiment. As shown in FIG. 1, the wireless communication system 10 includes a wireless base station 1, a wireless terminal 2, and a wireless terminal 3.

  The wireless terminal 2 and the wireless terminal 3 are located in the service area of the wireless base station 1 and communicate with the wireless base station 1 via a wireless section. In the example of FIG. 1, only a total of two wireless terminals, the wireless terminal 2 and the wireless terminal 3, are illustrated, but many wireless terminals may communicate with the wireless base station 1.

  In the present embodiment, the wireless terminal 2 and the wireless terminal 3 constitute a plurality of receiving apparatuses that receive data from the wireless base station 1. The wireless base station 1 constitutes a wireless communication device that performs wireless communication with the plurality of receiving devices.

  The radio terminal 2 and the radio terminal 3 periodically measure the reception quality of a radio signal transmitted by the radio base station 1, specifically, a pilot signal that is a broadcast signal, and receive the reception quality information indicating the reception quality Transmitting to station 1 regularly. In the present embodiment, the reception quality measured by the wireless terminal 2 and the wireless terminal 3 is a reception SNR (Signal to Interference plus Noise power Ratio). Hereinafter, the reception quality information transmitted by the wireless terminal 2 and the wireless terminal 3 is referred to as CQI (Channel Quality Indicator).

  The wireless communication system 10 employs the above-described HARQ. In the present embodiment, the wireless terminal 2 fails to decode the initial transmission data received from the wireless base station 1, and transmits a Nack, which is a negative response message requesting retransmission of the initial transmission data, to the wireless base station 1. Yes. That is, the wireless terminal 2 is a transmission destination of retransmission data for which retransmission is requested. On the other hand, the wireless terminal 3 is a transmission destination of transmission data (initial transmission data) for which retransmission is not requested.

  In general HARQ, the receiving side transmits an acknowledgment message (Ack) indicating successful decoding when the data (data packet) transmitted by the transmitting side is successfully decoded, and when decoding is unsuccessful. A negative acknowledgment message (Nack) indicating a decoding failure is transmitted to the transmission side.

  Hereinafter, the wireless terminal 2 that is the transmission destination of the retransmission data requested to be retransmitted is appropriately referred to as “retransmission destination wireless terminal 2”. In addition, the wireless terminal 3 that is the transmission destination of transmission data for which retransmission is not requested is appropriately referred to as “destination wireless terminal 3”.

  Based on the CQI received from each of the retransmission destination wireless terminal 2 and the transmission destination wireless terminal 3, the wireless base station 1 assigns a wireless resource to each of the retransmission destination wireless terminal 2 or the transmission destination wireless terminal 3, and assigns the assigned wireless resource to The data is transmitted to the retransmission destination wireless terminal 2 or the transmission destination wireless terminal 3 by using it. Here, the radio resource used for data transmission means a transmission time frame (hereinafter referred to as a transmission slot) or a frequency channel. In the following embodiments, for convenience of explanation, a transmission slot will be described as an example of radio resources allocated by the radio base station 1.

  Further, for the purpose of increasing the communication speed, the wireless communication system 10 employs an adaptive modulation method. Based on the CQI received from each of the retransmission destination wireless terminal 2 and the transmission destination wireless terminal 3, the wireless base station 1 dynamically switches the modulation scheme (hereinafter referred to as “modulation class” as appropriate). Specifically, the radio base station 1 selects an appropriate modulation scheme from a plurality of modulation schemes such as BPSK (Binary Phase Shift Keying) and 24QAM (Quadrature Amplitude Modulation).

  In HARQ, retransmission gain can be obtained by combining transmission data (initial transmission data) and retransmission data. In particular, selecting a high modulation class in anticipation of retransmission gain leads to higher overall system performance than selecting a low modulation class to be completed in one transmission. Therefore, retransmission is frequently performed in such a system.

(2) Configuration of radio base station
Next, the configuration of the radio base station 1 will be described. FIG. 2 is a functional block configuration diagram of the radio base station 1.

  As shown in FIG. 2, the radio base station 1 includes an antenna 110, a transmission / reception unit 111, a control unit 112, a data storage unit 113, a scheduler 114, and a data size control unit 115.

  The transmission / reception unit 111 transmits and receives a radio signal including data via the antenna 110. In the present embodiment, the transmission / reception unit 111 constitutes an information reception unit that receives CQI indicating the reception SNR of the radio signal transmitted by the radio base station 1 from each of the radio terminals 2 and 3.

  The data storage unit 113 temporarily stores transmission data to be transmitted to the wireless terminals 2 and 3 and stores the transmitted data that has been transmitted until an acknowledgment message (Ack) indicating successful reception is received.

  The control unit 112 controls the operation of the entire radio base station 1. Specifically, the control unit 112 controls data transmission and data reception with respect to the wireless terminals 2 and 3. In the present embodiment, the control unit 112 allocates a radio resource used for data transmission to one of the radio terminals 2 and 3, and uses the allocated radio resource to transmit a transmission processing unit that transmits transmission data or retransmission data. Constitute.

  Further, the control unit 112 uses the first modulation method used for data transmission to the transmission destination wireless terminal 3 and the second transmission data used for data transmission to the retransmission destination wireless terminal 2 according to the CQI received by the transmission / reception unit 111. A modulation scheme determining unit that determines the modulation scheme is configured.

  The scheduler 114 sets the priority with which the control unit 112 allocates radio resources for each radio terminal according to the above-described CQI. Hereinafter, the priority (second priority) set by the scheduler 114 for the retransmission destination wireless terminal 2 is referred to as “priority α”, and the priority (first priority) set by the scheduler 114 for the transmission destination wireless terminal 3. ) Is called “priority β”. Details of the scheduler 114 will be described later.

  Here, when the priority β set for the transmission destination wireless terminal 3 is at least higher than the priority α set for the retransmission destination wireless terminal 2, the control unit 112 assigns radio resources to the transmission destination wireless terminal 3 and the retransmission destination. While assigning to both the radio | wireless terminals 2, both transmission data and retransmission data are transmitted using the allocated radio | wireless resource.

  Further, the control unit 112 determines that the priority β set for the transmission destination wireless terminal 3 is higher than the priority α set for the retransmission destination wireless terminal 2 and the priority α set for the retransmission destination wireless terminal 2. Is less than a predetermined threshold, radio resources are allocated only to the destination radio terminal 3, and only transmission data is transmitted using the allocated radio resources.

  When the priority β set in the transmission destination wireless terminal 3 is lower than the priority α set in the retransmission destination wireless terminal 2, the control unit 112 assigns the radio resource only to the retransmission destination wireless terminal 2 and Only retransmit data is transmitted using radio resources.

  When the priority β set in the transmission destination wireless terminal 3 is higher than the priority α set in the retransmission destination wireless terminal 2, the data size control unit 115 depends on the ratio of the priority β and the priority α. The sizes of the transmission data and retransmission data to be transmitted are determined.

  The data size control unit 115 adjusts the sizes of the determined transmission data and retransmission data according to the first modulation scheme and the second modulation scheme determined by the control unit 112. As described above, the data size control unit 115 constitutes a size determination unit that determines the sizes of the transmission data and the retransmission data, and a size adjustment unit that adjusts the sizes of the determined transmission data and the retransmission data. Constitute.

(3) Example of priority setting process
Next, an example of priority setting processing executed by the scheduler 114 will be described. FIG. 3 is a diagram for explaining an example of the priority setting process.

  FIG. 3 illustrates an example in which the scheduler 114 sets the radio resource allocation priority (Priority) for each of the three radio terminals A to C.

  As described above, in the radio communication system 10, the scheduler 114 is used for the radio base station 1 to manage a large number of radio terminals and effectively utilize radio resources. The scheduler 114 sets the priority according to the CQI indicating the instantaneous reception SNR. As a method of the scheduler 114, there are a Max CIR method and a PF (Proportional fair) method.

  The Max CIR scheme is a scheme for setting a high priority for a wireless terminal having a high instantaneous reception SNR (hereinafter, instantaneous reception SNR). In the example of FIG. 3, the wireless terminal A has the highest instantaneous reception SNR in the transmission slots # 1, # 2, and # 6, and the wireless terminal B has the highest instantaneous reception SNR in the transmission slots # 3 to 5. The solid line in FIG. 3A indicates the instantaneous reception SNR, and the broken line in FIG. 3A indicates an average value of the instantaneous reception SNR (hereinafter, average reception SNR).

  For this reason, when the scheduler 114 adopts the Max CIR method, as shown in FIG. 3B, the priority of the radio terminal A in the transmission slots # 1, # 2, and # 6 is maximized, and the transmission slots # 3 to # 3 are used. 5, the priority of the wireless terminal B is maximized.

  On the other hand, in the PF scheme, a high priority is set for a wireless terminal having a relatively high instantaneous reception SNR with respect to the average reception SNR. Specifically, in the PF method, the scheduler 114 calculates the priority according to priority = DRC / R. Here, DRC is an instantaneous data rate calculated from CQI, and R is a value obtained by averaging the data rate by an exponential function weighted average using a certain time constant. Therefore, the ratio of the instantaneous data rate (instantaneous reception SNR) to the average rate (average reception SNR) is calculated as the priority.

  When the scheduler 114 employs PF, as shown in FIG. 3C, the priority of the wireless terminal A is the highest in the transmission slots # 1 and # 6, and the priority of the wireless terminal C is the transmission slots # 2 and # 3. The wireless terminal B has the highest priority in the transmission slots # 4 and # 5.

  As described above, the PF scheme can impart transmission opportunities to a plurality of wireless terminals fairly compared to the Max CIR scheme. In the following embodiment, a case where the scheduler 114 adopts the PF method will be described.

(4) An example of data size determination / adjustment processing
As described above, when the priority β set for the transmission destination wireless terminal 3 is at least higher than the priority α set for the retransmission destination wireless terminal 2, the control unit 112 of the wireless base station 1 In the embodiment, the transmission slot) is allocated to both the transmission destination wireless terminal 3 and the retransmission destination wireless terminal 2, and both the transmission data and the retransmission data are transmitted using the allocated radio resources. At that time, the data size control unit 115 determines the sizes of transmission data and retransmission data to be transmitted according to the ratio of the priority β and the priority α.

  Here, data size determination processing and data size adjustment processing executed by the data size control unit 115 will be described with reference to FIG.

  As shown in FIGS. 4B and 4C, the data size control unit 115 makes the retransmission data size SIZE1 smaller than the size SIZE0 of the initial transmission data corresponding to the retransmission data transmitted to the retransmission destination wireless terminal 2. To do.

Then, as shown in FIG. 4C, the data size control unit 115 determines the difference (SIZE0) between the size SIZE0 of the initial transmission data corresponding to the retransmission data transmitted to the retransmission destination wireless terminal 2 and the size SIZE1 of the retransmission data. -SIZE1) is determined as the size SIZE2 of the transmission data to be transmitted to the destination wireless terminal 3. That is, the following relationship is established between the size SIZE0 of the initial transmission data corresponding to the retransmission data transmitted to the retransmission destination wireless terminal 2, the size SIZE1 of the retransmission data, and the size SIZE2 of the transmission data transmitted to the transmission destination wireless terminal 3.
SIZE2 = SIZE0-SIZE1 (1)

In this embodiment, the data size control unit 115 includes the priority β set for the transmission destination wireless terminal 3, the priority α set for the retransmission destination wireless terminal 2, the size SIZE0 of the initial transmission data corresponding to the retransmission data, The following relationship holds for the size SIZE1 of the retransmission data.
SIZE1 = SIZE0 × (α / (α + β)) (2)

  Here, when there are a plurality of transmission destination wireless terminals 3, the priority of the transmission destination wireless terminal 3 that has the highest priority among the plurality of transmission destination wireless terminals 3 is set as the priority β.

  Next, the data size control unit 115 determines whether the control unit 112 determines the first modulation scheme determined for the transmission destination wireless terminal 3 and the second modulation scheme determined for the retransmission destination wireless terminal 2. The sizes (SIZE1, SIZE2) calculated by (2) are adjusted.

  Here, the modulation scheme determined by the control unit 112 will be briefly described with reference to FIGS. 5 and 6.

  As shown in FIG. 5, the CQI is associated with the received SNR. As shown in FIG. 6, the modulation class is associated with the threshold value of the reception SNR. In the example of FIG. 6, a total of nine modulation classes of modulation classes 0 to 8 are prepared. Modulation class 8 is the fastest modulation class, and modulation class 0 is the slowest modulation class. Specifically, 24QAM is used in modulation class 8, and π / 2-BPSK is used in modulation class 0. That is, the information amount per symbol differs in each modulation class.

Each modulation class has a threshold value for reception SNR. For example, modulation class 8 is applied when the received SNR exceeds a threshold SNR ₈ . Modulation class 7 is applied if the received SNR is below threshold SNR ₈ and above threshold SNR ₇ . Similarly, the received SNR is below the threshold SNR _7, when above a threshold SNR ₆ is modulation class 6 is applied.

  In this way, the control unit 112 determines the modulation class. When the amount of information per symbol defined in the second modulation scheme is smaller than the amount of information per symbol defined in the first modulation scheme, the data size control unit 115 determines that the equations (1) and (2) The size SIZE1 of the retransmission data calculated in step (1) is reduced and the size SIZE2 of the transmission data is increased.

  On the other hand, the data size control unit 115 uses the information amount per symbol defined in the second modulation scheme used for data transmission to the retransmission destination wireless terminal 2 for data transmission to the transmission destination wireless terminal 3. When the amount of information per symbol is larger than that defined in one modulation scheme, the size SIZE1 of retransmission data calculated by the equations (1) and (2) is increased and the size SIZE2 of transmission data is decreased.

  It should be noted that the total size of the retransmission data size SIZE1 and the transmission data size SIZE2 does not change before and after the size adjustment.

  Specifically, for example, the data size control unit 115 sets the modulation class (second modulation scheme) for the retransmission destination wireless terminal 2 to Xbit / symbol and the modulation class for the transmission destination wireless terminal 3 to Ybit / symbol. At this time, the size of the retransmission data for the retransmission destination wireless terminal 2 is ((100 × α / (α + β)) × (X / (X + Y)) + (100-100 × α / () of the initial transmission packet size SIZE0. α + β)) × (Y / (X + Y)))%.

(5) Operation of the radio base station
Next, the operation of the radio base station 1 will be described. FIG. 7 is a flowchart showing the operation of the radio base station 1.

  In step S11, the scheduler 114 and the control unit 112 allocate radio resources (in this embodiment, transmission slots) to the retransmission destination radio terminal 2 based on the CQI of the retransmission destination radio terminal 2 and the CQI of the transmission destination radio terminal 3. The transmission data is transmitted to the retransmission destination wireless terminal 2.

  The retransmission destination wireless terminal 2 receives the transmission data from the wireless base station 1 and decodes it. If the CRC is checked and decoded correctly, the retransmission destination wireless terminal 2 transmits Ack as a response message to the wireless base station 1 and cannot correctly decode it. Nack is transmitted as a response message.

  In step S <b> 12, the transmission / reception unit 111 receives a response message (Ack or Nack) from the retransmission destination wireless terminal 2. Further, the transmission / reception unit 111 receives the CQI from each of the wireless terminals 2 and 3 (step S13).

  In step S14, the control unit 112 determines whether the response message received by the transmission / reception unit 111 is Ack or Nack. If the response message is Ack, the process proceeds to step S15. If the response message is Nack, the process proceeds to step S17.

  In step S15 and step S16, the scheduler 114 and the control unit 112 perform allocation processing and transmission processing for the next data as usual.

  In step S17 in the case where the response message is Nack, the scheduler 114 sets the priority to which the control unit 112 allocates radio resources for each radio terminal using the PF method described above.

  In step S18, the control unit 112 determines whether or not the priority α set for the retransmission destination wireless terminal 2 by the scheduler 114 is the highest priority. In other words, the control unit 112 determines whether or not the priority α set for the retransmission destination wireless terminal 2 is higher than the priority β set for the transmission destination wireless terminal 3.

  If the priority α set in the retransmission destination wireless terminal 2 is the highest priority, the process proceeds to step S19. If the priority α is not the highest priority, the process proceeds to step S20.

  In step S19, the control unit 112 allocates radio resources only to the retransmission destination radio terminal 2 and transmits only retransmission data using the allocated radio resources. Specifically, the control unit 112 acquires retransmission data from the data storage unit 113 to the retransmission destination wireless terminal 2, and transmits the acquired retransmission data via the transmission / reception unit 111.

  In step S <b> 20, the control unit 112 determines whether or not the priority α set for the retransmission destination wireless terminal 2 is equal to or greater than a threshold value. For example, in the PF system, this threshold is set to 0.5, which has an instantaneous reception SNR (instantaneous data rate) only about half of the average reception SNR (average data rate).

  If the priority α set in the retransmission destination wireless terminal 2 is greater than or equal to the threshold, the process proceeds to step S22. If the priority α is less than the threshold, the process proceeds to step S21.

  In step S21, the control unit 112 allocates radio resources only to the transmission destination radio terminal 3 and transmits only transmission data using the allocated radio resources. Specifically, the control unit 112 acquires transmission data to the transmission destination wireless terminal 3 from the data storage unit 113 and transmits the acquired transmission data via the transmission / reception unit 111.

  In step S22 and step S23, the data size control unit 115 performs the data size determination process corresponding to the priority α and the priority β according to the procedure described in “(4) Example of data size determination / adjustment process”. After that, data size adjustment processing according to the modulation class is executed.

(6) Action and effect
As described above, the control unit 112 of the radio base station 1 determines that the priority β set in the transmission destination radio terminal 3 by the scheduler 114 is higher than the priority α set in the retransmission destination radio terminal 2. Radio resources are allocated to both the transmission destination radio terminal 3 and the retransmission destination radio terminal 2, and both transmission data and retransmission data are transmitted using the allocated radio resources.

  For this reason, the scheduler avoids the transmission of the transmission data to the transmission destination wireless terminal 3 having a high reception SNR being delayed while transmitting the retransmission data to the retransmission destination wireless terminal 2 that requests retransmission with priority. 114 can function effectively.

  Specifically, the data size control unit 115 makes the retransmission data size SIZE1 smaller than the size SIZE0 of the initial transmission data corresponding to the retransmission data transmitted to the retransmission destination wireless terminal 2. Then, the data size control unit 115 determines the difference (SIZE0-SIZE1) between the size SIZE0 of the initial transmission data corresponding to the retransmission data to be transmitted to the retransmission destination wireless terminal 2 and the size SIZE1 of the retransmission data (SIZE0-SIZE1). Is determined as the size SIZE2 of the transmission data to be transmitted to.

  Therefore, when the transmission data and the retransmission data share one radio resource, both the transmission data and the retransmission data can be transmitted by making the best use of the radio resource.

  In the present embodiment, since the data size control unit 115 determines the size of retransmission data according to Equation (2), it can determine the size of retransmission data reflecting the priority set by the scheduler 114.

  In the present embodiment, the data size control unit 115 adjusts the sizes of the determined transmission data and retransmission data according to the modulation scheme. For this reason, when a high-speed modulation scheme is used, by transmitting as much data as possible, radio resources can be effectively used, and throughput can be improved.

  In the present embodiment, the control unit 112 has the priority β set for the transmission destination wireless terminal 3 higher than the priority α set for the retransmission destination wireless terminal 2 and is set to the retransmission destination wireless terminal 2. When the priority α is lower than a predetermined threshold, radio resources are allocated only to the destination radio terminal 3 and only transmission data is transmitted using the allocated radio resources.

  Further, in the present embodiment, the control unit 112 transmits the radio resource to the retransmission destination wireless terminal 2 when the priority β set in the transmission destination wireless terminal 3 is lower than the priority α set in the retransmission destination wireless terminal 2. Only the retransmission data is transmitted using the allocated radio resources.

  That is, even when retransmission by HARQ occurs, the priority set by the scheduler 114 is emphasized, and the scheduler 114 can function effectively.

(7) Other embodiments
As mentioned above, although this invention was described by embodiment, it should not be understood that the description and drawing which form a part of this indication limit this invention. From this disclosure, various alternative embodiments, examples and operational techniques will be apparent to those skilled in the art.

  In the embodiment described above, the data size control unit 115 adjusts the sizes of the transmission data and the retransmission data calculated based on Expression (2) according to the modulation method. However, the data size control unit 115 may omit the calculation of the size using Expression (2) and determine the sizes of the transmission data and the retransmission data according to only the modulation scheme.

  In the above-described embodiment, the reception SNR is used as the reception quality. However, the received SNR is not limited to the reception SNR, and a received signal strength indicator (RSSI), a bit error rate (BER), or the like may be used.

  Furthermore, although the above-described embodiment has been described on the assumption that retransmission by HARQ occurs, the present invention can be applied not only to HARQ but also to normal ARQ.

  Note that although a portable wireless terminal is illustrated in FIG. 1, it may be a fixed wireless terminal, a card wireless terminal, or the like. Alternatively, a device that does not have a data transmission function may be used instead of the wireless terminal.

  Thus, it should be understood that the present invention includes various embodiments and the like not described herein. Therefore, the present invention is limited only by the invention specifying matters in the scope of claims reasonable from this disclosure.

  DESCRIPTION OF SYMBOLS 1 ... Wireless base station, 2 ... Wireless terminal (retransmission destination wireless terminal), 3 ... Wireless terminal (destination wireless terminal), 10 ... Wireless communication system, 110 ... Antenna, 111 ... Transmission / reception part, 112 ... Control part, 113 ... Data storage unit 114... Scheduler, 115.

The present invention relates to a radio communication system, a base station apparatus, and a radio communication method to which hybrid automatic retransmission control is applied.

Therefore, the present invention has been made to solve the above-described problem. When retransmission by HARQ occurs, the reception quality is improved while preferentially transmitting retransmission data to a receiving apparatus that requests retransmission. It is an object of the present invention to provide a radio communication system, a base station apparatus, and a radio communication method that allow a scheduler to function effectively by avoiding transmission of transmission data to a high receiving apparatus later.

Claims (3)

A wireless communication station device that performs wireless communication with a plurality of communication devices; a first communication device that is one of the plurality of communication devices and is a transmission destination of transmission data for which retransmission is not requested; A second communication device that is a transmission destination of retransmission data for which retransmission is requested, and a wireless communication system including:
The wireless communication station device
A wireless communication system, wherein the transmission data for the first communication device and the retransmission data for the second communication device are controlled so as to share one wireless resource. Wireless communication for performing wireless communication with a plurality of communication devices including a first communication device that is a transmission destination of transmission data for which retransmission is not requested and a second communication device that is a transmission destination of retransmission data for which retransmission is requested A station device,
A radio communication station apparatus that controls to transmit the transmission data for the first communication apparatus and the retransmission data for the second communication apparatus by sharing one radio resource. Wireless communication for performing wireless communication with a plurality of communication devices including a first communication device that is a transmission destination of transmission data for which retransmission is not requested and a second communication device that is a transmission destination of retransmission data for which retransmission is requested A wireless communication method applied to a station apparatus,
A wireless communication method for controlling to transmit the transmission data for the first communication device and the retransmission data for the second communication device by sharing one wireless resource.

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