JP2015226283A - User equipment, and power headroom transmission method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve throughput by controlling transmission priority of PHR in Dual Connectivity.SOLUTION: User equipment for performing communication by using component carriers subordinate to different evolved NodeBs includes: a power headroom calculation unit that determines whether or not a power headroom transmission condition is satisfied and calculates power headroom; a priority control unit for controlling, when the power headroom transmission condition is satisfied for any evolved NodeB, transmission priority in transmitting power headroom depending on whether or not the power headroom transmission condition is satisfied for the evolved NodeB; and a transmission unit for transmitting the power headroom on the basis of the transmission priority.

Description

  The present invention relates to a mobile station and a power headroom transmission method.

  Currently, the 3rd Generation Partnership Project (3GPP) is proceeding with the formulation of specifications for improving the functionality of LTE-Advanced as the next generation communication standard of LTE (Long Term Evolution). In the LTE-Advanced system, carrier aggregation (CA) technology is introduced in order to achieve a throughput higher than that of the LTE system while ensuring backward compatibility with the LTE system. In carrier aggregation, a component carrier (CC: Component Carrier) having a maximum bandwidth of 20 MHz supported by the LTE system is used as a basic component. By using these multiple component carriers at the same time, higher bandwidth communication is realized. It is planned to do.

  In carrier aggregation, a mobile station (UE: User Equipment) can communicate with a base station (eNB: evolved NodeB) using a plurality of component carriers simultaneously. In carrier aggregation, a highly reliable primary cell (PCell: Primary Cell) that ensures connectivity with a mobile station, and a secondary cell (SCell: Secondary Cell) that is additionally set in a mobile station connected to the primary cell And are set.

  The primary cell is a cell similar to the serving cell of the LTE system, and is a cell for ensuring connectivity between the mobile station and the network. On the other hand, the secondary cell is a cell that is added to the primary cell and set in the mobile station. The addition and deletion of the secondary cell are executed by RRC (Radio Resource Control) configuration.

  In carrier aggregation up to LTE Release 11 (Rel-11), as shown in FIG. 1A, it is defined that a mobile station communicates simultaneously using a plurality of component carriers provided by the same base station. ing. Also, a coordinated multipoint transmission / reception system (CoMP: Coordinated MultiPoint) that performs coordinated transmission / reception using a plurality of transmission / reception points arranged at different points by the same base station is also defined. CA and CoMP by the same base station are also referred to as Intra-eNB CoMP / CA.

  On the other hand, in Rel-12, the carrier aggregation of Rel-10 is further expanded, and as shown in FIG. 1B, the mobile station performs simultaneous communication using a plurality of component carriers provided by a plurality of base stations. Dual connectivity is being considered. CA and CoMP in Dual Connectivity are also called Inter-eNB CoMP / CA. For example, when all the component carriers cannot be accommodated in a single base station, it is considered that Dual Connectivity is effectively used in order to achieve the same throughput as Rel-11. On the other hand, in Inter-eNB CoMP / CA, a plurality of base stations are connected by a backhaul whose delay cannot be ignored. Therefore, a study different from Intra-eNB CoMP / CA is required (see Non-Patent Document 1).

3GPP TR36.842 V12.0.0 (2013-12), "Study on Small Cell enhancements for E-UTRA and E-UTRAN; Higher layer aspects"

The mobile station controls transmission power based on a transmission power control command from the base station. For example, the transmission power P _{PUSCH, c} (i) of a physical uplink channel (PUSCH: Physical Uplink Shared Channel) is determined according to the following equation.

ただし、P_PUSCH,c(i)は第ｉサブフレームにおけるＰＵＳＣＨの送信電力値である。P_CMAX,c(i)は移動局の最大送信電力（必要な電力バックオフの考慮後）である。M_PUSCH,c(i)は第ｉサブフレームに割り当てられたＰＵＳＣＨ送信用のリソースブロック数である。P_{O_PUSCH,c}(j)は予め決められたＰＵＳＣＨの基準となる電力オフセット（報知パラメータ）である。α_c(j)はパスロスに乗算する係数（報知パラメータ）である。PL_cはパスロス（伝搬損）である。Δ_TF,c(i)は変調方式及び符号化率に基づく電力オフセットである。f_c(i)は基地局から指示されたＰＵＳＣＨに関する送信電力制御コマンドの累積値である。

Here, P _{PUSCH, c} (i) is the transmission power value of PUSCH in the i-th subframe. P _{CMAX, c} (i) is the maximum transmission power of the mobile station (after considering the necessary power back-off). M _{PUSCH, c} (i) is the number of resource blocks for PUSCH transmission allocated to the i-th subframe. P _{O_PUSCH, c} (j) is a power offset (broadcast parameter) serving as a reference for a predetermined PUSCH. α _c (j) is a coefficient (broadcast parameter) by which the path loss is multiplied. PL _c is a path loss (propagation loss). Δ _{TF, c} (i) is a power offset based on the modulation scheme and coding rate. f _c (i) is a cumulative value of a transmission power control command related to PUSCH instructed from the base station.

Further, since the path loss of each component carrier used for calculation of transmission power is unknown in the base station, for example, when the path loss changes in the mobile station, a power headroom (PHR) is fed back. The power headroom PH _{type1, c} (i) of the mobile station is determined according to the following equation.

なお、上記の式におけるPH_type1,c(i)は、Type 1と呼ばれるＰＨＲであり、Type 2のＰＨＲが用いられる場合には、Type 1のＰＨＲに加えてType 2のＰＨＲも報告される。

Note that PH _{type1, c} (i) in the above equation is a PHR called Type 1, and when Type 2 PHR is used, Type 2 PHR is also reported in addition to Type 1 PHR.

When the transmission power is stuck to the maximum transmission power P _{CMAX, c} (i), the actual transmission power is P _{CMAX, c} (i), and the power headroom PH _{type1, c} (i) is based on the above formula. Negative value is reported.

  In Dual Connectivity, PHR is reported to the following base stations when the following transmission conditions are satisfied.

  (1) When path loss changes, it is reported to both base stations.

  (2) When the power management back-off (P-MPR: Power Management Maximum Power Reduction) changes, it is reported to both base stations.

  (3) When the SCell is activated, it is reported to both base stations.

  (4) When a PHR configuration is added, it is reported only to the corresponding base station.

  (5) When the PHR reporting period is reached (when the Periodic PHR Timer expires), it is reported only to the corresponding base station.

  Thus, the base station to which the PHR is reported varies depending on the PHR transmission conditions. For example, regarding the transmission conditions (1) to (3) above, PHR reporting is useful for one base station, but PHR reporting may not be necessary for the other base station.

  If a PHR that is not highly urgent is stored in a MAC PDU (Media Access Control Protocol Data Unit) before other data, the base station cannot receive necessary data quickly, resulting in a decrease in throughput. There is a risk of reducing connectivity.

  An object of the present invention is to improve throughput by controlling the transmission priority of PHR in Dual Connectivity.

A mobile station according to an aspect of the present invention is:
A mobile station that communicates using component carriers under different base stations,
A power headroom calculation unit that determines whether or not the transmission condition of the power headroom is satisfied, and calculates the power headroom;
When the transmission conditions of the power headroom are satisfied for any of the base stations, the transmission priority when transmitting the power headroom depends on whether the transmission conditions of the power headroom are satisfied for the base station. A priority control unit for controlling the degree,
Based on the transmission priority, a transmission unit that transmits the power headroom,
It is characterized by having.

A power headroom transmission method according to one aspect of the present invention is as follows.
A power headroom transmission method in a mobile station that communicates using component carriers under different base stations,
Determining whether the transmission condition of the power headroom is satisfied, and calculating the power headroom;
When the transmission conditions of the power headroom are satisfied for any of the base stations, the transmission priority when transmitting the power headroom depends on whether the transmission conditions of the power headroom are satisfied for the base station. A step of controlling the degree;
Transmitting power headroom based on transmission priority;
It is characterized by having.

  According to the present invention, it is possible to improve throughput by controlling the transmission priority of PHR in Dual Connectivity.

Schematic diagram of CoMP / CA 1 is a schematic diagram of a wireless communication system according to an embodiment of the present invention. Configuration diagram of a mobile station according to an embodiment of the present invention 7 is a flowchart illustrating a PHR transmission method of a mobile station according to an embodiment of the present invention. Schematic diagram of PHR transmission when using PHR transmission timer (Part 1) Schematic diagram of PHR transmission when using PHR transmission timer (Part 2) Schematic diagram of PHR transmission when using PHR transmission timer (Part 3) Schematic diagram of PHR transmission when using BSR considering PHR data volume

  Embodiments of the present invention will be described below with reference to the drawings.

  In an embodiment of the present invention, a communication system including a mobile station that performs communication using component carriers under the control of different base stations will be described. In carrier aggregation (CA), a connection form in which mobile stations communicate using component carriers (CC) under the control of different base stations is called dual connectivity. In Dual Connectivity, a base station corresponding to a primary cell (PCell) is called a master base station (MeNB: Master eNB), and a base station corresponding to a secondary cell (SCell) is a secondary base station (SeNB: Secondary eNB). Called.

  The base station controls the transmission power of the mobile station using the transmission power control command. In order to control the transmission power, since the path loss of each component carrier used for calculating the transmission power is unknown, the base station feeds back a power headroom (PHR) to the mobile station. PHR is the difference between the maximum transmission power of the mobile station and the actual transmission power.

  In Dual Connectivity, both MeNB and SeNB control transmission power. Therefore, the PHR may be reported to both the MeNB and the SeNB. However, in the embodiment of the present invention, when the PHR is transmitted to a base station that does not satisfy the PHR transmission conditions, the transmission priority of the PHR The throughput is improved by lowering.

<Configuration of communication system>
FIG. 2 shows a schematic diagram of a wireless communication system according to an embodiment of the present invention. The wireless communication system includes a mobile station (UE) and a base station (MeNB and SeNB). The wireless communication system supports dual connectivity in which a mobile station performs simultaneous communication using component carriers provided by a plurality of base stations. The mobile station uses a dual connectivity function to provide a master base station (MeNB) and a secondary base station. It communicates with a base station (SeNB).

  The mobile station has a dual connectivity function for simultaneous communication with a plurality of base stations. Typically, the mobile station may be any appropriate information processing apparatus having a wireless communication function such as a smartphone, a mobile phone, a tablet, or a mobile router. The mobile station includes a CPU (Central Processing Unit) such as a processor, a memory device such as a RAM (Random Access Memory) and a flash memory, a wireless communication device for transmitting and receiving radio signals to and from the base station, and the like. For example, each function and process of the mobile station described later may be realized by the CPU processing or executing data or a program stored in the memory device. However, the mobile station is not limited to the hardware configuration described above, and may be configured by a circuit that realizes one or more of the processes described below.

  The base station wirelessly connects to the mobile station, thereby transmitting a downlink (DL) packet received from a network device such as an upper station or a server connected to a core network (not shown) to the mobile station. The uplink (UL) packet received from the mobile station is transmitted to the network device. In the illustrated embodiment, one base station functions as a master base station (MeNB) or a primary base station, and the other base station functions as a secondary base station (SeNB). In Dual Connectivity, the MeNB controls simultaneous communication between the mobile station and both base stations by Dual Connectivity, and also controls communication with the upper core network (not shown). On the other hand, for transmission power control, both the MeNB and SeNB control transmission power independently.

  For example, when the path loss changes, the mobile station transmits PHR to both base stations. However, as illustrated in FIG. 2A, when the path loss for only the MeNB changes and the path loss for the SeNB does not change, it is assumed that the urgency of the PHR for the SeNB is low. Thus, when the transmission conditions of PHR are satisfied in the cells under the MeNB, the transmission priority when transmitting the PHR to the SeNB is lowered. The transmission priority when transmitting the PHR to the MeNB is assumed to be a normal transmission priority.

  Similarly, as illustrated in FIG. 2B, when the path loss for only the SeNB changes and the path loss for the MeNB does not change, it is assumed that the urgency level of the PHR for the MeNB is low. Thus, when the transmission conditions of PHR are satisfied in the cell under SeNB, the transmission priority when transmitting PHR to MeNB is lowered. The transmission priority when transmitting the PHR to the SeNB is a normal transmission priority.

  The transmission condition for transmitting the PHR to both base stations is not limited to a change in path loss, but may be a change in power management back-off (P-MPR), SCell activation, or the like.

  By lowering the transmission priority of PHR, for example, from the transmission priority of specific data or control information, it becomes possible to transmit specific data or control information quickly.

<Configuration of mobile station>
FIG. 3 shows a configuration diagram of the mobile station 10 according to the embodiment of the present invention. The mobile station 10 includes a downlink (DL) signal reception unit 101, an uplink (UL) signal transmission unit 103, a PHR calculation unit 105, a data management unit 107, a priority control unit 109, and a timer management unit 111. And a resource request unit 113.

  The DL signal receiving unit 101 receives a downlink signal from the base station. In order to control the transmission power, the DL signal reception unit 201 receives a transmission power control command from the base station. In Dual Connectivity, the transmission power control command is transmitted independently from both base stations of MeNB and SeNB.

  The UL signal transmission unit 103 transmits an uplink signal to the base station. In order to control transmission power, the UL signal transmission unit 103 transmits the PHR to the base station. In Dual Connectivity, PHR is transmitted to both base stations of MeNB and SeNB.

  The PHR calculation unit 105 determines whether or not the PHR transmission condition is satisfied, and calculates the PHR. The PHR transmission conditions include (1) path loss change, (2) power management back-off (P-MPR) change, (3) SCell activation, (4) PHR configuration addition, (5 ) PHR periodic reporting (expiration of Periodic PHR Timer). As described above, the PHR is calculated according to the following equation, for example.

データ管理部１０７は、基地局に送信するデータ及び制御情報を格納する送信バッファである。例えば、データ管理部１０７には、ＰＨＲに加えて、移動局の識別子を示すＣ−ＲＮＴＩ（Cell-Radio Network Temporary Identifier）ＭＡＣ ＣＥ（MAC Control Element）、共通制御チャネル（ＣＣＣＨ：Common Control Channel）の制御情報、バッファステータスレポート（ＢＳＲ：Buffer Status Report）ＭＡＣ ＣＥ（パディングＢＳＲ以外）、送信データ（ＣＣＣＨ以外）、パディングＢＳＲ等が格納される。

The data management unit 107 is a transmission buffer that stores data to be transmitted to the base station and control information. For example, in addition to the PHR, the data management unit 107 includes a C-RNTI (Cell-Radio Network Temporary Identifier) MAC CE (MAC Control Element) indicating a mobile station identifier, and a common control channel (CCCH). Control information, buffer status report (BSR) MAC CE (other than padding BSR), transmission data (other than CCCH), padding BSR, and the like are stored.

  When the priority control unit 109 satisfies the power headroom transmission condition for any base station, the priority control unit 109 transmits the PHR depending on whether the PHR transmission condition is satisfied for the base station. Control the transmission priority of. Specifically, when the PHR transmission condition is satisfied in the cell under the MeNB, the priority control unit 109 lowers the transmission priority when transmitting the PHR to the SeNB, and satisfies the PHR transmission condition in the cell under the SeNB. In this case, the transmission priority when the PHR is transmitted to the MeNB is lowered. The priority control unit 109 may notify the data management unit 107 of the PHR transmission priority, and rearrange the data and control information stored in the data management unit 107.

  The PHR is normally transmitted with the following transmission priority.

(1) C-RNTI MAC CE or CCCH
(2) BSR MAC CE (other than padding BSR)
(3) PHR
(4) Transmission data (other than CCCH)
(5) BSR MAC CE (padding BSR)
When transmitting PHR to a base station that does not satisfy the PHR transmission conditions, the priority control unit 109 may set the following transmission priorities.

(1) C-RNTI MAC CE or CCCH
(2) BSR MAC CE (other than padding BSR)
(3) Transmission data (other than CCCH)
(4) PHR
(5) BSR MAC CE (padding BSR)
Alternatively, the priority control unit 109 may set the following transmission priority.

(1) C-RNTI MAC CE or CCCH
(2) BSR MAC CE (other than padding BSR)
(3) Transmission data (other than CCCH)
(4) BSR MAC CE (padding BSR)
(5) PHR
Alternatively, the priority control unit 109 may set the following transmission priority.

(1) C-RNTI MAC CE or CCCH
(2) BSR MAC CE (other than padding BSR)
(3) Transmission data (specific logical channel other than CCCH, for example, mapping of SRB (Signaling Radio Bearer))
(4) PHR
(5) Transmission data (a specific logical channel other than CCCH, for example, a data radio bearer (DRB) is mapped)
(6) BSR MAC CE (padding BSR)
Alternatively, the priority control unit 109 may set the following transmission priority.

(1) C-RNTI MAC CE or CCCH
(2) BSR MAC CE (other than padding BSR)
(3) Transmission data (RLC (Radio Link Control) / PDCP (Packet Data Convergence Protocol) control PDU) of a specific logical channel other than CCCH
(4) PHR
(5) Transmission data (RLC (Radio Link Control) / PDCP (Packet Data Convergence Protocol) control PDU) of a specific logical channel other than CCCH
(6) BSR MAC CE (padding BSR)
The timer management unit 111 manages a timer related to PHR transmission. As a timer related to PHR transmission, when the transmission priority of the PHR is lowered, the PHR used to restore the transmission priority of the PHR when a predetermined period elapses after the PHR transmission condition is satisfied. There is a transmission timer. In addition, in order to suppress frequent PHR transmission, there is a PHR transmission suppression timer (PHR prohibitTimer) that does not transmit PHR within a certain period after reporting PHR. Control of transmission priority using a timer will be described in detail below.

  The resource request unit 113 requests a resource for transmitting data stored in the data management unit 107 by transmitting a buffer status report (BSR) to the base station. The resource request unit 113 may request a resource having a data amount obtained by adding the data amount stored in the data management unit 107 and the data amount of the control information and the PHR data amount. For example, when a predetermined period has elapsed since the transmission priority of the PHR is lowered and the transmission priority of the PHR is restored, the resource request unit 113 requests the resource by taking the PHR data amount into account, The PHR can be transmitted together with the data and control information.

<Mobile station operation>
FIG. 4 shows a PHR transmission method of a mobile station according to an embodiment of the present invention.

  This method starts when a PHR transmission condition is satisfied. The priority control unit 109 determines whether a PHR transmission condition is satisfied in a cell under the MeNB (step S101). For example, when the path loss for only the MeNB changes and the path loss for the SeNB does not change, the priority control unit 109 determines that the PHR transmission condition is satisfied in the cell under the MeNB. Similarly, when the path loss for only the SeNB changes and the path loss for the MeNB does not change, the priority control unit 109 determines that the PHR transmission condition is satisfied in the cell under the SeNB.

  When the PHR transmission condition is satisfied in the cell under the MeNB (step S101: YES), the priority control unit 109 lowers the transmission priority when transmitting the PHR to the SeNB, and the PHR is transmitted from the UL signal transmission unit 103. Transmit (step S103). On the other hand, when the PHR transmission condition is satisfied in the cell under the SeNB (step S101: NO), the priority control unit 109 lowers the transmission priority when transmitting the PHR to the MeNB, and the UL signal transmission unit 103 PHR is transmitted (step S105).

  When the PHR transmission condition is satisfied, the timer management unit 111 activates a PHR transmission timer and manages whether the PHR is transmitted within a predetermined period (step S107). The PHR transmission timer is used to restore the transmission priority of the PHR when a predetermined period has elapsed after satisfying the transmission conditions of the PHR in order to avoid the transmission of the PHR with the transmission priority lowered for a long period of time. It is a timer.

  When the PHR is transmitted within the predetermined period (step S107: YES), this method ends. On the other hand, when the PHR is not transmitted within the predetermined period (step S107: NO), the priority control unit 109 restores the PHR transmission priority and transmits the PHR from the UL signal transmission unit 103 (step S109).

  With reference to FIGS. 5 to 7, PHR transmission when the PHR transmission timer is used will be further described. Here, it is assumed that the cell under the MeNB satisfies the PHR transmission condition.

  When the PHR transmission condition is satisfied in a cell under the MeNB, the PHR transmission priority for the SeNB is lowered. As shown in FIG. 5, when there is data with higher transmission priority than PHR for SeNB, data with higher priority is transmitted before PHR. The PHR is transmitted when high-priority data is exhausted before the PHR transmission timer expires. At this point, the PHR transmission timer may be stopped. Further, the PHR transmission suppression timer (PHR prohibitTimer) may be restarted.

  As shown in FIG. 6, when there is data with higher transmission priority than PHR for SeNB, data with higher priority is transmitted before PHR. If the PHR transmission timer expires during transmission of high-priority data, the priority of the PHR is restored, and high-priority data (relatively high priority due to lowering of the PHR priority). PHR is transmitted even if there is data in the transmission buffer. At this point, the PHR transmission timer may be restarted. Further, the PHR transmission suppression timer may be restarted.

  As illustrated in FIG. 7, when there is data with higher transmission priority than PHR for SeNB, data with higher priority is transmitted before PHR. When PHR transmission conditions are satisfied in a cell under the SeNB before the PHR transmission timer expires, high-priority data (data that has a relatively high priority because the PHR priority has been lowered) Is present in the transmission buffer, PHR is transmitted.

  In order to increase the transmission efficiency of PHR, when transmitting data with high transmission priority, a BSR that takes into account the amount of PHR data may be used. FIG. 8 shows a schematic diagram of PHR transmission when using BSR in consideration of the amount of PHR data.

  For example, when the PHR transmission conditions are satisfied in a cell under the MeNB, the PHR transmission priority for the SeNB is lowered. FIG. 8A shows a case where BSR is reported to the base station without taking into account the amount of PHR data when data with a high priority of 150 bytes is generated. When the mobile station reports a BSR indicating a 150-byte data amount without taking the PHR data amount into consideration, a resource for transmitting 150-byte data from the base station is allocated. At this time, since the resource for transmitting PHR is not allocated by resource allocation information (UL grant), the mobile station cannot transmit PHR. In order to transmit PHR, it is necessary to report to the base station a BSR indicating the amount of data necessary to transmit PHR MAC CE.

  On the other hand, FIG. 8B shows a case where BSR is reported to the base station in consideration of the amount of PHR data when 150-byte high-priority data is generated. When the mobile station reports a BSR in which the data amount (α) of the PHR MAC CE is added to the data amount of 150 bytes, a resource for transmitting the PHR is allocated from the base station in addition to the data of 150 bytes. Since the resource for transmitting the PHR is allocated by the resource allocation information (UL grant), the mobile station can transmit the PHR following the high priority data.

<Effect of the embodiment of the present invention>
According to the embodiment of the present invention, it is possible to improve the throughput by controlling the transmission priority of PHR in Dual Connectivity. Specifically, specific data or control information can be quickly transmitted by lowering the transmission priority of PHR to a base station that does not satisfy the transmission conditions of the power headroom.

  Further, by using the PHR transmission timer, it is possible to avoid that the PHR is not transmitted for a long period of time due to lowering the transmission priority of the PHR.

  Also, by using the BSR that takes into account the amount of PHR data, the transmission efficiency of the PHR can be increased.

  For convenience of explanation, the mobile station according to the embodiment of the present invention is described using a functional block diagram, but the mobile station according to the embodiment of the present invention is realized by hardware, software, or a combination thereof. May be. In addition, the functional units may be used in combination as necessary. In addition, the method according to the embodiment of the present invention may be performed in an order different from the order shown in the embodiment.

  As described above, the method for improving the throughput by controlling the transmission priority of PHR in Dual Connectivity has been described. However, the present invention is not limited to the above-described embodiments, and is within the scope of the claims. Various changes and applications are possible.

DESCRIPTION OF SYMBOLS 10 Mobile station 101 DL signal receiving part 103 UL signal transmission part 105 PHR calculation part 107 Data management part 109 Priority control part 111 Timer management part 113 Resource request part

Claims (6)

A mobile station that communicates using component carriers under different base stations,
A power headroom calculation unit that determines whether or not the transmission condition of the power headroom is satisfied, and calculates the power headroom;
When the transmission conditions of the power headroom are satisfied for any of the base stations, the transmission priority when transmitting the power headroom depends on whether the transmission conditions of the power headroom are satisfied for the base station. A priority control unit for controlling the degree,
Based on the transmission priority, a transmission unit that transmits the power headroom,
A mobile station.   The priority control unit lowers the transmission priority of the power headroom when transmitting the power headroom to a base station whose transmission conditions of the power headroom are not satisfied for the base station. The mobile station according to 1.   The mobile station according to claim 2, wherein the priority control unit lowers the transmission priority of power headroom from the transmission priority of specific data or control information.   The mobile station according to any one of claims 1 to 3, wherein the priority control unit increases the transmission priority of the power headroom when a predetermined period has elapsed after satisfying the transmission conditions of the power headroom. .   5. The mobile station according to claim 1, further comprising a resource request unit that requests a resource having a data amount including a data amount in the transmission buffer and a data amount of the power headroom. A power headroom transmission method in a mobile station that communicates using component carriers under different base stations,
Determining whether the transmission condition of the power headroom is satisfied, and calculating the power headroom;
When the transmission conditions of the power headroom are satisfied for any of the base stations, the transmission priority when transmitting the power headroom depends on whether the transmission conditions of the power headroom are satisfied for the base station. A step of controlling the degree;
Transmitting power headroom based on transmission priority;
A power headroom transmission method.

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