JP5793373B2 - Base station and wireless communication method - Google Patents

Description

  The present invention relates to a base station and a radio communication method that request a mobile station to report reception channel quality in a mobile station.

  In Long Term Evolution (LTE), which is standardized in the 3rd Generation Partnership Project (3GPP), the transmission timing (Transmission timing) is considered in consideration of the frequency selectivity of the reception channel quality within the frequency band (system band) used by the wireless communication system. Frequency scheduling that assigns a block (RB) of a frequency resource used in the subframe is applied for each (Time Interval), that is, for each subframe (for example, Non-Patent Document 1). By applying frequency scheduling, the capacity of the wireless communication system can be greatly increased.

  When applying frequency scheduling, the base station (eNB), in order to determine the frequency selectivity of the reception channel quality in the connected mobile station (UE), the reception channel quality (for each subband into which the system band is divided ( sub-band CQI) is received from each mobile station. The base station can select either “periodic transmission” or “aperiodic CQI” as the transmission method of the reception channel quality by the mobile station.

  In periodic transmission, the reception channel quality is periodically transmitted using an uplink physical control channel (PUCCH) specified by L3 signaling. On the other hand, in non-periodic transmission, the base station instructs the mobile station to transmit reception channel quality at an arbitrary timing through L1 signaling using a downlink physical control channel (PDCCH). The mobile station transmits the reception channel quality of all subbands only once using the uplink physical shared channel (PUSCH) designated by the base station.

  In the case of periodic transmission, in order to transmit the reception channel quality of all subbands, transmission across multiple transmission timings is necessary due to the relationship between the number of allocated bits. Since the reception channel quality can be transmitted at one transmission timing, even when the reception channel quality fluctuates rapidly due to fading or the like, the followability to the fluctuation is good.

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

  However, the above-described conventional aperiodic transmission of reception channel quality has the following problems. That is, in the case of aperiodic transmission, radio resources in both directions of the downlink physical control channel and the uplink physical shared channel are used for acquisition of the reception channel quality by the base station. There is a problem that increases.

  Therefore, the present invention has been made in view of such a situation, and an object of the present invention is to provide a base station and a radio communication method capable of acquiring reception channel quality at an appropriate timing while suppressing consumption of radio resources. To do.

  A first feature of the present invention is a base station (base station 100) that requests the mobile station to report reception channel quality (CQI) in the mobile stations (mobile stations 200A and 200B), the mobile station A channel allocating unit (PUSCH scheduler 111) for allocating an uplink physical shared channel (PUSCH) to the mobile station, and when the uplink physical shared channel is allocated by the channel allocating unit, the received channel quality for the mobile station A report control unit (CQI report control unit 107) that requests a report of the received channel, and a reception channel quality management unit (CQI management unit 121) that acquires the report of the reception channel quality transmitted from the mobile station, the report The control unit requests the mobile station to report the reception channel quality when the elapsed time from the transmission of the previous reception channel quality by the mobile station exceeds a first threshold. The gist of the door.

  According to a second aspect of the present invention, there is provided a wireless communication method in a wireless communication system that requests the mobile station to report a reception channel quality in the mobile station, wherein the wireless communication system transmits an uplink to the mobile station. Allocating a link physical shared channel; requesting the mobile station to report the received channel quality when the uplink physical shared channel is allocated; and Transmitting the reception channel quality to the wireless communication system based on a request, and obtaining the reception channel quality report transmitted from the mobile station, and requesting the reception channel quality report In the step, the elapsed time from the previous transmission of the reception channel quality by the mobile station exceeds a first threshold value. When, and spirit to request the receive channel quality reports to the mobile station.

  According to the features of the present invention, it is possible to provide a base station and a radio communication method that can acquire reception channel quality at an appropriate timing while suppressing consumption of radio resources.

1 is an overall schematic configuration diagram of a wireless communication system according to an embodiment of the present invention. FIG. 3 is a functional block configuration diagram of a base station 100 according to the embodiment of the present invention. It is a figure which shows the CQI report request | requirement operation | movement flow (the 1) by 200 A of base stations by the base station 100 which concerns on embodiment of this invention. It is a figure which shows the CQI report request | requirement operation | movement flow (the 2) to 200 A of mobile stations by the base station 100 which concerns on embodiment of this invention. FIG. 6 is a diagram showing an operation flow for setting a threshold for CQI reporting by the base station 100 according to the embodiment of the present invention. It is a figure which shows an example of the table which matches the radio | wireless resource block (RB) usage rate of the uplink and downlink bearer or PUSCH which concerns on embodiment of this invention, and a 2nd threshold value.

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

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

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

  Base station 100 is connected to core network 50. Base station 100 forms cell C1 and performs radio communication with mobile stations 200A and 200B according to the LTE scheme.

  In the present embodiment, the base station 100 requests the mobile station 200A to report the reception channel quality in the mobile station 200A (or the mobile station 200B, hereinafter the same), specifically, Channel Quality Indicator (CQI). In particular, in this embodiment, the base station 100 requests the mobile station 200A to perform aperiodic transmission (Aperiodic CQI) of sub-band CQI that is CQI for each subband in which the system band is divided.

(2) Functional Block Configuration of Base Station Next, a functional block configuration of the wireless communication system according to the present embodiment will be described. Specifically, the functional block configuration of base station 100 will be described. FIG. 2 is a functional block configuration diagram of the base station 100.

  As shown in FIG. 2, the base station 100 includes a transmission buffer 101, a PDSCH scheduler 103, a transmission data generation unit 105, a CQI report control unit 107, a control information generation unit 109, a PUSCH scheduler 111, a signal multiplexing unit 113, and a signal transmission unit. 115, a signal reception unit 117, a signal separation unit 119, and a CQI management unit 121.

  The transmission buffer 101 stores data transmitted in the downlink direction, that is, from the base station 100 toward the mobile station 200A. The transmission buffer 101 sets a Queue for each bearer set with the mobile station 200A, stores transmission data for the mobile station 200A, and manages a retention amount of the transmission data.

  The PDSCH scheduler 103 allocates a downlink physical shared channel (PDSCH) to the mobile station 200A.

  The transmission data generation unit 105 performs channel coding and data modulation on the transmission data stored in the transmission buffer 101, and generates transmission data to be output to the signal multiplexing unit 113.

  The CQI report control unit 107 acquires information indicating the retention amount of transmission data for each bearer from the transmission buffer 101, and sets a mobile station having the retention data as a CQI report target. The CQI report control unit 107 manages the elapsed time from the previous CQI report for the mobile station that is the target of CQI report.

  Specifically, when PUSCH is assigned to the mobile station 200A by the PUSCH scheduler 111, the CQI report control unit 107 requests the mobile station 200A to report CQI. In addition, when the elapsed time from the previous CQI transmission by the mobile station 200A exceeds the first threshold, the CQI report control unit 107 requests the mobile station 200A to report the CQI.

  When the CQI report control unit 107 determines to request the CQI report from the mobile station 200A, the CQI report control unit 107 notifies the control information generation unit 109 to include the CQI report request in the downlink physical control channel (PDCCH).

  Also, the CQI report control unit 107, when no PUSCH is allocated to the mobile station 200A, and when the elapsed time from the previous CQI transmission by the mobile station 200A exceeds the second threshold, the mobile station 200A Can be requested to report CQI.

  Note that the CQI report control unit 107 may change the second threshold based on the congestion degree of the cell C1 formed by the base station 100. Specifically, the CQI report control unit 107 lengthens the second threshold as the congestion degree of the cell C1 increases. As described later, the degree of congestion of the cell C1 can be determined based on the number of uplink or downlink set bearers.

  Control information generation section 109 performs PDCCH channel coding and data modulation. In addition, the control information generation unit 109 generates a control signal (UL grant) for notifying resource allocation for PUSCH, and sets a bit indicating a CQI report request to ON based on the notification from the CQI report control unit 107 To do.

  Note that, when receiving a UL grant, the mobile station 200A generates transmission data, performs encoding and data modulation using a designated transport block size (TBS) and modulation coding scheme (MCS). Also, when the CQI report is requested, the mobile station 200A generates the CQI and multiplexes it with the transmission data in the designated PUSCH radio resource block. At this time, if a predetermined condition is satisfied, the information (BSR) of the accumulated data amount in the upstream direction is also multiplexed.

  The PUSCH scheduler 111 allocates PUSCH to the mobile station 200A. In this embodiment, the PUSCH scheduler 111 constitutes a channel allocation unit. The BSR described above is notified to the PUSCH scheduler 111. The PUSCH scheduler 111 determines a mobile station to be scheduled for PUSCH based on the notified BSR.

  The signal multiplexing unit 113 multiplexes the data output from the transmission data generation unit 105 and the control information generation unit 109, and outputs the multiplexed signal to the signal transmission unit 115.

  The signal reception unit 117 outputs the received signal to the signal separation unit 119. The signal separator 119 separates the signal output from the signal receiver 117 into uplink data, BSR, and CQI.

  The CQI management unit 121 manages the CQI separated by the signal separation unit 119. In the present embodiment, the CQI management unit 121 constitutes a reception channel quality management unit that acquires a CQI report transmitted from the mobile station 200A. The CQI of the mobile station 200A acquired by the CQI management unit 121 is notified to the PDSCH scheduler 103 and used for PDSCH scheduling.

(3) Operation of Base Station Next, the operation of the radio communication system according to this embodiment will be described. Specifically, the operation of the base station 100 for reporting the reception channel quality (CQI) to the mobile station 200A will be described.

(3.1) Operation example 1
FIG. 3 shows a CQI report request operation flow (part 1) from the base station 100 to the mobile station 200A. As shown in FIG. 3, the base station 100 allocates a PUSCH to the mobile station 200A (UE) in order to transmit a shared channel (UL-SCH) in the uplink (S10).

  The base station 100 determines whether or not the mobile station 200A to which the PUSCH is assigned meets the first predetermined condition (S20). The first predetermined condition is satisfied when any of the following six conditions is satisfied.

(1) When the elapsed time since the last CQI report was instructed does not exceed the first threshold (2) When retransmitted by hybrid ARQ (3) Subframe that transmits PUSCH is a sub that transmits Sounding Reference Signal (4) When the number of assigned radio resource blocks (RBs) is below a certain number and / or when the MCS used for PUSCH transmission is above a certain value (5) Specific to the mobile station When the radio bearer is set (6) When the synchronization state is not established with the mobile station Note that (1) is confirmed by the CRC of Msg 3 at the start of the Random Access procedure, including the start of communication Elapsed time is not measured until it is done, and the elapsed time is counted from the time when CRC of Msg 3 is confirmed.

  Specifically, (2) corresponds to the case of Adaptive retransmission in which the PURB transmission RB is redesignated by the PDCCH. This is to avoid reception errors caused by the increase in the UL-SCH coding rate due to CQI multiplexing.

  (3) and (4) are also for avoiding reception errors caused by an increase in the UL-SCH coding rate due to CQI multiplexing. In particular, allocation resources are small and CQI multiplexing is performed. This is because the coding rate changes greatly.

  This is because (5) may want to suppress UL-SCH reception errors due to CQI multiplexing, such as voice calls. Alternatively, the CQI transmission may not be requested except when a specific radio bearer is set.

  When the first predetermined condition is not met, the base station 100 requests the mobile station 200A to report CQI (S30). On the other hand, when the first predetermined condition is met, the base station 100 does not request the CQI report from the mobile station 200A (S40).

(3.2) Operation example 2
FIG. 4 shows a CQI report request operation flow (part 2) from the base station 100 to the mobile station 200A. As shown in FIG. 4, the base station 100 determines whether or not the elapsed time since the previous CQI report was requested from the mobile station 200A exceeded a second threshold (S50).

  When the elapsed time exceeds the second threshold, the base station 100 determines whether or not the mobile station 200A meets the second predetermined condition (S60). The second predetermined condition is satisfied when any of the following three conditions is satisfied.

(1) When a specific radio bearer is set for the mobile station (2) When the total data retention amount of all logical channels in the downlink is below a certain value (3) A synchronization state is established with the mobile station If not, if the second predetermined condition is not met, the base station 100 requests the mobile station 200A to report CQI (S70). On the other hand, when the first predetermined condition is met, the base station 100 resets the elapsed time from the previous CQI report request (S80).

(3.3) Operation example 3
FIG. 5 shows an operation flow for setting a threshold for CQI reporting by the base station 100. As shown in FIG. 5, the base station 100 acquires the number of uplink bearers set for the mobile station in the cell C1 (S110). Similarly, the base station 100 acquires the number of downlink bearers set in the mobile station in the cell C1 (S120). Furthermore, the base station 100 acquires the radio resource block usage rate of PUSCH (S130).

  Next, the base station 100 is used to determine the elapsed time since the mobile station 200A requested the previous CQI report based on the acquired number of uplink and downlink bearers or the radio resource block usage rate of PUSCH. A second threshold value to be determined is determined (S140).

  Specifically, since the total number of CQI report requests is considered to be proportional to the number of downlink bearers, the total number of CQI report requests may be controlled according to the number of downlink bearers. Further, since the degree of uplink congestion is considered to be proportional to the number of uplink bearers, it corresponds to the total number of CQI report requests (that is, CQI reports that constitute uplink overhead) according to the number of uplink bearers. ) May be controlled.

  For example, an average value per subframe can be used for the PUSCH radio resource block usage rate. Since the uplink congestion level is considered to be proportional to the PUSCH radio resource block usage rate, the total number of CQI report requests (that is, uplink overhead) is controlled according to the PUSCH radio resource block usage rate. That's fine.

FIG. 6 shows an example of a table associating the number of uplink and downlink bearers or the PUSCH radio resource block (RB) usage rate with the second threshold. As illustrated in FIG. 6, the base station 100 includes a second threshold value (T _Threshold2, T2) corresponding to the number of uplink and downlink bearers or a radio resource block (RB) usage rate (such as N _{0 to} N ₂ ) of PUSCH _{. 0 to} T _Threshold2,3 ). As described above, it is preferable that the second threshold value increases as the number of bearers or the radio resource block usage rate increases.

(4) Operation / Effect According to the base station 100, when the PUSCH is assigned by the PDSCH scheduler 103, the CQI report control unit 107 requests the mobile station 200A to report CQI. Then, when the elapsed time from the previous CQI transmission by the mobile station 200A exceeds the first threshold, the CQI report control unit 107 requests the mobile station 200A to report the CQI.

  For this reason, even in the case of Aperiodic CQI in which CQI is transmitted aperiodically, radio resources are used only in PUSCH, that is, only in the uplink direction, so that base station 100 can appropriately use radio resources while suppressing consumption of radio resources. The CQI can be acquired from the mobile station 200A at the timing.

  In the present embodiment, the CQI report control unit 107 is a case where no PUSCH is assigned to the mobile station 200A, and when the elapsed time from the previous CQI transmission by the mobile station 200A exceeds the second threshold, Request CQI report to mobile station 200A. For this reason, the base station 100 can acquire the CQI from the mobile station 200A at a constant cycle while suppressing the consumption of radio resources.

  In the present embodiment, the CQI report control unit 107 increases the second threshold based on the congestion degree of the cell C1 formed by the base station 100, specifically, as the congestion degree of the cell C1 increases. can do. For this reason, when the degree of congestion of the cell C1 is high, the minimum CQI necessary for control can be acquired from the mobile station 200A while further suppressing the consumption of radio resources.

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

  For example, in the embodiment described above, the CQI report control unit 107, based on the congestion degree of the cell C1 formed by the base station 100, specifically, as the congestion degree of the cell C1 increases, Although the threshold value has been lengthened, such control is merely an example, and such control is not necessarily performed. For example, as shown in FIGS. 5 and 6, the second threshold may be controlled based on the number of uplink or downlink bearers or the radio resource block usage rate of PUSCH.

  In the above-described embodiment, when the elapsed time from the previous CQI transmission by the mobile station 200A exceeds the second threshold, the mobile station 200A is requested to report the CQI. If the elapsed time from the transmission of the CQI does not exceed the second threshold, the mobile station 200A may be requested to report the CQI.

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

50 ... Core network
100 ... Base station
101 ... Transmission buffer
103… PDSCH scheduler
105 ... Transmission data generator
107… CQI Report Control Department
109 ... Control information generator
111 ... PUSCH scheduler
113 ... Signal multiplexer
115 ... Signal transmitter
117 ... Signal receiver
119 signal separator
121CQI Management Department
200A, 200B ... Mobile station
C1 ... cell

Claims (5)

A base station that instructs a mobile station to report reception channel quality by signaling using a downlink physical control channel ,
A channel allocation unit that allocates an uplink physical shared channel to the mobile station;
A report control unit that requests the mobile station to report the received channel quality when the uplink physical shared channel is allocated by the channel allocation unit;
A reception channel quality management unit for obtaining a report of the reception channel quality transmitted from the mobile station,
The report control unit is a base station that requests the mobile station to report the reception channel quality when the elapsed time from the transmission of the previous reception channel quality by the mobile station exceeds a first threshold.   The report control unit is a case where the uplink physical shared channel is not allocated to the mobile station, and the elapsed time from the previous transmission of the reception channel quality by the mobile station exceeds a second threshold value The base station according to claim 1, wherein the base station requests the mobile station to report the reception channel quality.   The base station according to claim 2, wherein the report control unit changes the second threshold based on a congestion degree of a cell formed by the base station.   The base station according to claim 3, wherein the report control unit lengthens the second threshold as the degree of congestion of the cell increases. A radio communication method in a radio communication system instructing a mobile station to report reception channel quality by signaling using a downlink physical control channel ,
The wireless communication system assigns an uplink physical shared channel to the mobile station;
Requesting the mobile station to report the received channel quality if the uplink physical shared channel is allocated;
The mobile station transmitting the reception channel quality to the wireless communication system based on the reception channel quality report request;
Obtaining a report of the received channel quality transmitted from the mobile station,
In the step of requesting the report of the reception channel quality, if the elapsed time from the previous transmission of the reception channel quality by the mobile station exceeds a first threshold, the reception channel quality report is sent to the mobile station. The requested wireless communication method.

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