JP5152324B2 - Wireless communication system, base station, terminal, wireless communication method, program - Google Patents

Description

  The present invention relates to a technique for controlling transmission power of downlink data signals and pilot signals transmitted from a base station to a wireless communication terminal (hereinafter referred to as a terminal) in a wireless communication system.

  In a wireless communication system, a plurality of base stations are arranged, and each base station communicates with a terminal in its own communication area. This communication area is called a cell.

  Furthermore, in the wireless communication system, in order to increase the number of terminals with which the base station communicates at the same time, the cell can be divided into a plurality of parts by providing directivity to the transmission antenna of the base station. This divided area is called a sector.

  When the same frequency is used in a plurality of cells, the communication quality of the cell may be deteriorated by interference from an adjacent cell (hereinafter referred to as adjacent cell interference).

  Similarly, when the same frequency is used in a plurality of sectors, there is a possibility that the communication quality of a sector may deteriorate due to interference from an adjacent sector (hereinafter referred to as adjacent sector interference).

  Generally, adjacent sector interference is considered to be sufficiently small due to the directivity of the transmitting antenna. However, in reality, when the distance from the base station is the same, the distance is the same regardless of the directivity, so that the interference is not reduced and the deterioration of the communication quality is not improved.

  As a technique for reducing adjacent cell interference, for example, Patent Document 1 discloses a technique for reducing adjacent cell interference in the downlink of OFDMA (Orthogonal Frequency Division Multiple Access).

  According to the technique described in Patent Literature 1, a central entity connected to a plurality of base stations assigns a frequency group to each base station, and further assigns a frequency group of each base station to terminals in the cell. Such allocation of radio resources (frequency) is called scheduling. The terminal measures the received power of the pilot signal from each base station, and the central entity performs scheduling based on the received power reported by the terminal. And when a terminal is located at a cell boundary in a cell of a certain base station, an adjacent base station reduces transmission power uniformly for a terminal in its own cell to which the same frequency group as that terminal is assigned. Send a signal.

  When the technology described in Patent Document 1 is used for an adjacent sector, when a terminal is located at a sector boundary in a certain sector, the base station can perform the following operations on terminals in the adjacent sector to which the same frequency group as that terminal is assigned. The signal is transmitted with the transmission power reduced uniformly.

  By the way, in a radio communication system, a phase modulation method or a phase amplitude modulation method can be used as a method for modulating a signal by a phase.

  When this type of modulation method is used, the transmission side generally modulates and transmits a pilot signal, which is a known control signal, together with a data signal. On the receiving side, first, the pilot signal is demodulated, and the data signal is demodulated based on the phase change and amplitude change of the demodulated pilot signal. Thereby, highly accurate demodulation of the data signal can be realized.

  However, in the wireless communication system, it is also required to increase the frequency utilization efficiency. For this purpose, it is desirable to use a phase amplitude modulation method with high transmission efficiency.

  In the phase / amplitude modulation method, the amplitude is also an element representing signal information, and therefore the power ratio between the pilot signal and the data signal is information necessary for demodulation of the data signal.

  However, in downlink transmission power control as described in Patent Document 1, when the base station controls only the transmission power of the data signal, the power ratio between the pilot signal and the data signal varies with time. . In this case, unless the power ratio between the pilot signal and the data signal is notified from the base station to the terminal, the terminal cannot know the accurate power ratio, and thus cannot demodulate the data signal with high accuracy.

  Conversely, it is conceivable to control not only the data signal but also the transmission power of the pilot signal so that the power ratio between the pilot signal and the data signal is constant. In this case, the terminal can demodulate the data signal with high accuracy because the power ratio is known without any notification from the base station.

  However, as described above, in downlink transmission power control, scheduling is performed based on the received power of pilot signals from each base station measured at the terminal.

  In other words, the pilot signal is not used only for the demodulation of the data signal by the terminal, but is a reference for the reception power measured by the terminal. Therefore, if the transmission power of the pilot signal fluctuates, scheduling will be affected. End up.

As described above, in transmission power control in the downlink, when the power ratio between the pilot signal and the data signal is constant, it is an important issue to prevent the scheduling from being affected.
JP 2006-33826 A

  Therefore, an object of the present invention is to provide a wireless communication system, a base station, a terminal, a wireless communication method, and a program that solve the above-described problems.

The wireless communication system of the present invention includes:
A wireless communication system comprising a base station forming a communication area and a plurality of terminals located in different communication areas,
The base station
A detection unit for detecting whether the current time is the first interval or the second interval;
An allocating unit that allocates radio resources to the plurality of terminals based on reception power of pilot signals reported from the plurality of terminals in a first section;
When the same radio resource is allocated to the plurality of terminals, the transmission power of the data signal and pilot signal to be transmitted to the plurality of terminals is kept at a predetermined value in the first section, and in the second section, A power control unit that changes transmission power of a data signal and a pilot signal transmitted to a specific terminal among the plurality of terminals from a predetermined value while keeping a power ratio of the data signal and the pilot signal constant. ,
The terminal
A detection unit for detecting whether the current time is the first interval or the second interval;
And a signal measurement unit that reports reception power of pilot signals received from each communication region to the base station.

The base station of the present invention
A base station forming a communication area,
A detection unit for detecting whether the current time is the first interval or the second interval;
An allocating unit that allocates radio resources to the plurality of terminals based on reception power of pilot signals reported from a plurality of terminals located in different communication areas in the first section;
When the same radio resource is allocated to the plurality of terminals, the transmission power of the data signal and pilot signal to be transmitted to the plurality of terminals is kept at a predetermined value in the first section, and in the second section, A power control unit configured to change transmission power of a data signal and a pilot signal transmitted to a specific terminal among the plurality of terminals from a predetermined value while keeping a power ratio of the data signal and the pilot signal constant.

The terminal of the present invention
A terminal located in a communication area formed by a base station,
A detection unit for detecting whether the current time is the first interval or the second interval;
And a signal measurement unit that reports reception power of pilot signals received from each communication region to the base station.

The first wireless communication method of the present invention includes:
A wireless communication method using a wireless communication system comprising a base station forming a communication area and a plurality of terminals located in different communication areas,
A detecting step in which the base station and the terminal detect whether a current time is a first interval or a second interval;
A reporting step in which the terminal reports the received power of a pilot signal received from each communication area to the base station in a first interval;
The base station assigning radio resources to the plurality of terminals based on reception power of pilot signals reported from the plurality of terminals in the first section;
When the same radio resource is allocated to the plurality of terminals, the base station keeps transmission powers of data signals and pilot signals to be transmitted to the plurality of terminals at predetermined values in a first interval, A power control step of changing a transmission power of a data signal and a pilot signal to be transmitted to a specific terminal among the plurality of terminals from a predetermined value while keeping a power ratio of the data signal and the pilot signal constant And having.

The second wireless communication method of the present invention includes:
A wireless communication method by a base station forming a communication area,
A detection step of detecting whether the current time is the first interval or the second interval;
Allocating radio resources to the plurality of terminals based on reception power of pilot signals reported from a plurality of terminals located in different communication areas in the first section;
When the same radio resource is allocated to the plurality of terminals, the transmission power of the data signal and pilot signal to be transmitted to the plurality of terminals is kept at a predetermined value in the first section, and in the second section, And a power control step of changing transmission power of a data signal and a pilot signal transmitted to a specific terminal among the plurality of terminals from a predetermined value while keeping a power ratio of the data signal and the pilot signal constant.

The third wireless communication method of the present invention is:
A wireless communication method by a terminal located in a communication area formed by a base station,
A detection step of detecting whether the current time is the first interval or the second interval;
And a reporting step of reporting received power of pilot signals received from each communication area to the base station in a first section.

The first program of the present invention is:
To the base station that forms the communication area,
A detection procedure for detecting whether the current time is the first interval or the second interval;
An allocation procedure for allocating radio resources to the plurality of terminals based on reception power of pilot signals reported from a plurality of terminals located in different communication areas in the first section;
When the same radio resource is allocated to the plurality of terminals, the transmission power of the data signal and pilot signal to be transmitted to the plurality of terminals is kept at a predetermined value in the first section, and in the second section, A power control procedure for changing transmission power of a data signal and a pilot signal to be transmitted to a specific terminal among the plurality of terminals from a predetermined value while keeping a power ratio of the data signal and the pilot signal constant .

The second program of the present invention is:
To terminals located in the communication area formed by the base station,
A detection procedure for detecting whether the current time is the first interval or the second interval;
In a first section, a reporting procedure for reporting received power of pilot signals received from each communication area to the base station is executed.

  According to the present invention, when the same radio resource is allocated to a plurality of terminals located in different communication areas, the base station changes the transmission power of data signals and pilot signals transmitted to any of the plurality of terminals. In this case, the power ratio is changed from a predetermined value while keeping the power ratio constant.

  Therefore, even when the transmission power is changed, the power ratio between the pilot signal and the data signal is constant, so that the terminal can demodulate the data signal with high accuracy without the notification of the power ratio from the base station. The effect is obtained.

  Further, according to the present invention, the base station distinguishes between the first section in which the transmission power is not changed and the second section in which the transmission power is changed, and the base station sets the transmission power to a predetermined value in the first section. A pilot signal having a constant value is transmitted to a plurality of terminals, and scheduling is performed to allocate radio resources to the plurality of terminals based on the received power when the pilot signal is received by the terminal.

  Therefore, even if the base station changes the transmission power of the pilot signal, there is an effect that the base station does not affect the scheduling.

It is a figure which shows the structure of the radio | wireless communications system of one Embodiment of this invention. It is a figure which shows the example of a power change permission area and a power change prohibition area. It is a figure which shows the example of 1 structure of the terminal shown in FIG. It is a figure which shows one structural example of the base station shown in FIG. 3 is a flowchart for explaining the overall operation of the base station shown in FIG. 3 is a flowchart for explaining the overall operation of the terminal shown in FIG. 1. 3 is a flowchart for explaining a power control operation in a power change permission section of the base station shown in FIG. 1. It is a figure which shows the condition of adjacent sector interference.

  The best mode for carrying out the present invention will be described below with reference to the drawings.

  In the embodiments described below, a case where the wireless communication system is an LTE (Long Term Evolution) wireless communication system of 3GPP (3rd Generation Partnership Project) will be described as an example. However, the present invention is not limited thereto. The present invention is not limited to this, and the present invention can also be applied to a wireless communication system using other communication methods such as WIMAX (Worldwide Interoperability for Microwave). In the LTE downlink, OFDMA is employed as a radio access scheme.

  Further, a radio communication system in which a base station forms a communication area in units of sectors and reduces adjacent sector interference will be described as an example. However, the present invention is not limited to this, and the base station forms a communication area in units of cells. However, the present invention is also applicable to a radio communication system that reduces adjacent cell interference.

  Referring to FIG. 1, the wireless communication system according to the present embodiment includes three base stations BS1, BS2, and BS3.

  The base station BS1 has a configuration of a three-sector cell in which the cell C1 that provides a wireless communication service is formed and the transmitting antenna has directivity so that the cell C1 is divided into three sectors S11, S12, and S13. . Similarly, the other base stations BS2 and BS3 have a three-sector cell configuration.

  In addition, the wireless communication system according to the present embodiment includes a terminal MS111 located in the sector S11 being served by the base station BS1. Similarly, it has terminals MS112 and MS113 respectively located in other sectors S12 and S13 under the base station BS1.

  In FIG. 1, the terminals MS located in the cells C2 and C3 are omitted for the sake of simplicity. Further, in order to simplify the description, the number of base stations BS is three, but the present invention is not limited to this. Further, although the base stations BS1, BS2, and BS3 have a three-sector cell configuration, other multi-sector cell configurations may be used. Although not shown, the base stations BS1, BS2, and BS3 are connected via a network and can transmit and receive data to and from each other.

  Also, in this specification, “adjacent sector” refers to a sector that is adjacent via a sector boundary in the same cell, and “adjacent base station sector” is different in cell and adjacent via a cell boundary. Refers to the sector in question. In FIG. 1, adjacent sectors of sector S11 are sectors S12 and S13 that are adjacent via a sector boundary, and adjacent base station sectors of sector S11 are sectors S22, S23, and S32 that are adjacent via a cell boundary. It becomes.

  In LTE, the frequency band is divided in units of frequency blocks (RBs), and the divided RBs are allocated to the terminal MS as radio resources. The RB is composed of one or more subcarriers. In each sector, one RB is assigned to one terminal.

  Here, the terminal MS and the base station BS will be described in detail.

  In the present embodiment, two sections of a power change prohibition section (first section) and a power change permission section (second section) are alternately repeated, and the terminal MS and the base station BS The operation according to the section is performed.

  The power change prohibition section and the power change permission section may be repeated at a predetermined cycle. In this case, for example, the period can be set in advance for the terminal MS and the base station BS, and the period can be notified from an upper node (not shown) of the base station BS at the start of connection. FIG. 2 is an example when the power change prohibition section and the power change permission section are periodically repeated.

  Alternatively, the power change prohibition section and the power change permission section may be instructed by an upper node (not shown) of the base station BS. In this case, for example, when each base station BS is instructed by an upper node, the base station BS notifies the instructed section to a terminal MS located in its own cell as a control signal or a broadcast channel message. Can do.

  The lengths of the power change prohibition section and the power change permission section may be freely determined.

  Further, the transmission power of the data signal and pilot signal of the base station BS in the power change prohibition section may be set in the terminal MS in advance, or even if the base station BS changes in time and notifies the terminal MS Good.

  Next, the configuration of the terminal MS will be described. Below, although the structure of terminal MS111 is demonstrated, the structure of the other terminal MS is also the same.

  Referring to FIG. 3, the terminal MS 111 includes a terminal operation unit 101, a section detection unit 102, and a signal measurement unit 103.

  The terminal operation unit 101 has a function equivalent to that of a terminal generally used in an LTE wireless communication system, for example, a function of receiving a data signal and a pilot signal from the base station BS1. Since the configuration and operation of the terminal operation unit 101 are well known, description thereof will be omitted.

  The section detection unit 102 has a function of detecting whether the current time is a power change permission section or a power change prohibition section. If two sections are repeated with a predetermined period, the current period is determined and the section is detected. If the upper node of the base station BS1 indicates the section, the base station BS1 The section may be detected by this notification.

  The signal measurement unit 103 calculates a propagation loss (PL) based on the received power of the pilot signal transmitted from the sector where the terminal MS111 is located or an adjacent sector in the power change prohibition section, and PL information representing the calculated PL To the base station BS1. In the present embodiment, the received power is reported to the base station BS1 as a propagation loss. However, the present invention is not limited to this, and the received power itself may be reported to the base station BS1.

  Next, the configuration of the base station BS will be described. Below, although the structure of base station BS1 is demonstrated, the structure of other base station BS is also the same.

  Referring to FIG. 4, the base station BS1 includes a base station operation unit 201 serving as an allocation unit, a section detection unit 202, a PL information management unit 203, a resource management unit 204, and a transmission power control unit 205. .

  The base station operation unit 201 has a function equivalent to that of a base station generally used in an LTE radio communication system, for example, RB to terminals MS111, MS112, and MS113 located in the sector for each of the sectors S11, S12, and S13. For each sector S11, S12, and S13, a function for transmitting data signals and pilot signals to terminals MS111, MS112, and MS113 located in each sector, and PL from terminals MS111, MS112, and MS113. It has a function of receiving information. Since the configuration and operation of the base station operation unit 201 are well known, detailed description thereof is omitted.

  The section detection unit 202 has a function of detecting whether the current time is a power change permission section or a power change prohibition section. If two sections are repeated at a predetermined period, the current period is determined to detect the section, and if the upper node of the base station BS1 indicates the section, the upper node A section may be detected by an instruction.

  The PL information management unit 203 has a function of registering and managing the PL information as shown in Table 1 below because PL information is reported from the terminals MS111, MS112, and MS113 in the power change prohibition section.

リソース管理部２０４は、セクタＳ１１，Ｓ１２，Ｓ１３毎に、そのセクタに位置する端末ＭＳ１１１，ＭＳ１１２，ＭＳ１１３に割り当てられたＲＢのＲＢ情報（例えば、ＲＢの識別情報となるＲＢ番号）を、以下の表２のように登録し管理する機能を有する。

For each sector S11, S12, and S13, the resource management unit 204 uses the following RB information (for example, an RB number that serves as RB identification information) assigned to the terminals MS111, MS112, and MS113 located in the sector. It has a function to register and manage as shown in Table 2.

送信電力制御部２０５は、リソース管理部２０４に登録されたＲＢ情報に基づいて、端末ＭＳ１１１，ＭＳ１１２，ＭＳ１１３のうち２以上の端末ＭＳに割り当てられたＲＢを検索する。

Based on the RB information registered in the resource management unit 204, the transmission power control unit 205 searches for RBs assigned to two or more terminals MS among the terminals MS111, MS112, and MS113.

  Also, the transmission power control section 205 keeps the transmission power of the data signal and pilot signal to be transmitted to two or more terminals MS to which the same RB is assigned at a predetermined value in the power change prohibition section. In addition, although an initial value is mentioned as a predetermined value, for example, this invention is not restricted to this, You may change temporally.

  In addition, the transmission power control unit 205 changes the transmission power from two or more terminals MS to which the same RB is assigned based on the PL information registered in the PL information management unit 203 in the power change permission section. The terminal MS to be determined is determined, and the transmission power of the data signal and pilot signal transmitted to the terminal MS is changed from a predetermined value while the power ratio is kept constant. Specifically, if the predetermined values of the transmission power of the data signal and the pilot signal are both 1 W, the power ratio is kept constant at 1: 1, for example, both are changed to 0.5 W.

  Hereinafter, operations of the base station BS and the terminal MS of the present embodiment will be described.

  First, the operation of the base station BS will be described. Hereinafter, the operation of the base station BS1 will be described, but the operations of the other base stations BS are the same.

  Referring to FIG. 5, in the base station BS1, first, the section detecting unit 202 detects whether the current time is a power change permission section or a power change prohibition section in step S101.

  In step S101, when it is a power change prohibition section, since PL information is reported from terminals MS111, MS112, and MS113, PL information management section 203 registers the reported PL information in step S102.

  Next, in step S103, the base station operation unit 201 moves to the terminals MS111, MS112, and MS113 located in the sector for each of the sectors S11, S12, and S13 based on the PL information registered in the PL information management unit 203. RBs are allocated (scheduled). Note that since a general scheduling method may be applied, description thereof is omitted here. The RB information of the RB allocated in step S103 is registered in the resource management unit 204.

  Next, in step S104, the transmission power control unit 205 searches for RBs assigned to two or more terminals MS among the terminals MS111, MS112, and MS113 based on the RB information registered in the resource management unit 204. Here, assuming that the RB assigned to terminals MS111, MS112, and MS113 is searched, the transmission power of the data signal and pilot signal transmitted to terminals MS111, MS112, and MS113 is kept at a predetermined value.

  Thereafter, in step S105, the base station operation unit 201 transmits both the data signal and the pilot signal to the terminals MS111, MS112, and MS113 while keeping the transmission power at a predetermined value.

  On the other hand, in step S101, when it is a power change permission section, PL information is not reported from terminals MS111, MS112, and MS113, so scheduling is not performed, and the RB assigned in the power change prohibition section is used as it is. However, the present invention is not limited to this, and the scheduling may be performed again based on the PL information already registered in the PL information management unit 203.

  Next, in step S106, the transmission power control unit 205 searches for RBs assigned to two or more terminals MS among the terminals MS111, MS112, and MS113, based on the RB information registered in the resource management unit 204. Further, based on the PL information registered in the PL information management unit 203, the terminal MS whose transmission power is to be changed is determined from the terminals MS to which the searched RBs are assigned. Here, if the RBs assigned to terminals MS111, MS112, and MS113 are searched and it is further determined that the transmission power to terminal MS111 is to be changed, the transmission power of the data signal and pilot signal to be transmitted to terminal MS111 is determined. The power ratio is changed from a predetermined value while keeping it constant.

  Thereafter, in step S105, the base station operation unit 201 transmits the data signal and the pilot signal to the terminal MS111 after changing the transmission power while keeping the power ratio of a predetermined value constant. Note that the transmission power of data signals and pilot signals transmitted to other terminals MS112 and MS113 is kept at a predetermined value.

  Next, the operation of the terminal MS will be described. Hereinafter, the operation of the terminal MS111 will be described, but the operations of the other terminals MS are the same.

  Referring to FIG. 6, in terminal MS111, section detection unit 102 first detects whether the current time is a power change permission section or a power change prohibition section in step S201.

  In step S201, when it is a power change prohibition section, the signal measurement unit 103 calculates the PL of the pilot signal transmitted from the sector S11 in which the terminal MS111 is located or the adjacent sectors S12 and S13 in step S202.

  At this time, the calculation of PLj, p of the pilot signal from the sector Sp in the terminal MSj is performed by the following equation.

PLj, p [dB] = P_txt [dBm] −P_rxj, p [dBm]
Here, P_txt and P_rxj, p represent the average transmission power of the pilot signal in the sector Sp and the average reception power of the pilot signal in the terminal MSj, respectively. The average transmission power of the pilot signal in the sector Sp can be broadcasted as a control signal to all terminals located in the subordinate sector from the base station.

  Next, in step S203, the signal measuring unit 103 creates PL information in which the calculated PL and a sector number (IDp) that is identification information of each of the sectors S11, S12, and S13 are combined, and step S204. The generated PL information is reported to the base station BS1.

  On the other hand, in step S201, when it is a power change permission section, the signal measurement unit 103 does not create and report the PL information described above.

  Here, the power control operation (corresponding to step S106 in FIG. 5) in the power change permission section of the base station BS1 will be described in detail.

  Referring to FIG. 7, in base station BS1, first, transmission power control section 205, based on the RB information registered in resource management section 204 in step S301, two or more of terminals MS111, MS112, and MS113. Select the RB assigned to the terminal MS. Here, in the example of Table 2, it is assumed that the RB with the RB number 1 assigned to the terminals MS111, MS112, and MS113 is selected.

  Next, in step S302, the transmission power control unit 205 determines whether or not the terminal MS has received adjacent sector interference for each of the terminals MS111, MS112, and MS113 based on the PL information registered in the PL information management unit 203. Determine whether. For example, in the example of Table 1, regarding the terminal MS111, if the PL information of the pilot signal received from the adjacent sectors S12 and S13 is within a predetermined value, it is determined that the terminal MS111 has received adjacent sector interference.

  For example, when the terminal MS111 receives adjacent sector interference from the adjacent sector S12 in step S302, the transmission power control unit 205 determines whether the terminal MS112 receives adjacent sector interference from the adjacent sector S11 in step S303, that is, It is determined whether the terminals MS111 and MS112 located in each of the two sectors S11 and S12 adjacent to each other receive adjacent sector interference from the other sector.

  If terminal MS112 has not received adjacent sector interference from adjacent sector S11 in step S303, transmission power control section 205 reduces only the transmission power of the data signal and pilot signal transmitted to terminal MS112 in step S304. .

  On the other hand, when terminal MS112 receives adjacent sector interference from adjacent sector S11 in step S303, that is, terminals MS111 and MS112 located in each of two adjacent sectors S11 and S12 are adjacent to each other from the other sector. There may be sector interference. In this case, for example, when the transmission power to the terminal MS111 is decreased, the adjacent sector interference from the adjacent sector S12 to the terminal MS111 becomes relatively large. Further, if both transmission powers to terminals MS111 and MS112 are reduced, the communication quality of the sector is deteriorated. Therefore, in this case, in step S305, transmission power control section 205 does not change the transmission power of the data signal and pilot signal transmitted to terminals MS111 and MS112 at a predetermined value.

  Steps S303 to S305 described above are examples in the case where adjacent sector interference occurs between the sectors S11 and S12, but also when adjacent sector interference occurs between the sectors S11 and S13 and between the sectors S12 and S13. A similar operation is performed.

  Also, if none of terminals MS111, MS112, and MS113 has received adjacent sector interference in step S302, transmission power control section 205 determines the data signal and pilot signal to be transmitted to terminals MS111, MS112, and MS113 in step S306. The transmission power is not changed to a predetermined value.

  After that, the transmission power control unit 205 ends the process when all the RBs assigned to two or more terminals MS among the terminals MS111, MS112, and MS113 are selected in step S307.

  Here, the power control operation in the power change permission section of the base station BS1 shown in FIG. 7 will be described in more detail with a specific example.

Referring to FIG. 8, the base station BS1 classifies adjacent sector interference situations in the cell C1 into six cases based on the PL information reported from the terminals MS111, MS112, and MS113 to which the same RB is assigned. To do. However, these six cases are merely examples, and the present invention is not limited thereto.
[Power Control Pattern of Step S304]
Cases 1 to 3 are cases where the power control pattern of step S304 is applicable.
(1) Case 1
In case 1, two terminals MS112 and MS113 are located at the sector center in sectors S12 and S13, respectively, and the remaining terminal MS111 is located at a sector boundary with sector S13 in sector S11.

  At this time, the adjacent sector interference in the cell C1 is as follows.

-Data signal and pilot signal to terminal MS111 do not cause adjacent sector interference-Data signal and pilot signal to terminal MS112 do not cause adjacent sector interference-Data signal and pilot signal to terminal MS113 are not related to terminal MS111 Therefore, in order to avoid adjacent sector interference, it is only necessary to reduce the transmission power of the data signal and pilot signal to terminal MS113.

  Therefore, the transmission power of data signals (or pilot signals) to terminals MS111, MS112, and MS113 is as follows.

P (S11, n) = P (S12, n) = P0
P (S13, n) = P0−Δ1
Here, P (Sp, n) represents the transmission power of the data signal (or pilot signal) to the terminal MS, which is located in the sector Sp and assigned the RB of the RB number n, and P0 represents the transmission to the terminal MS. A predetermined value of the data signal (or pilot signal) is represented, and Δ1 represents an arbitrary power value that can be changed (hereinafter the same).
(2) Case 2
In Case 2, one terminal MS112 is located at the sector center in sector S12, and the remaining terminals MS111 and MS113 are located at sector boundaries with sector S12 in sectors S11 and S13, respectively.

  At this time, the adjacent sector interference in the cell C1 is as follows.

-Data signal and pilot signal to terminal MS111 do not give adjacent sector interference-Data signal and pilot signal to terminal MS112 give adjacent sector interference to terminal MS111 and terminal MS113-Data signal and pilot to terminal MS113 The signal does not cause adjacent sector interference. Therefore, in order to avoid adjacent sector interference, the transmission power of the data signal and pilot signal to the terminal MS 112 may be reduced.

  Therefore, the transmission power of data signals (or pilot signals) to terminals MS111, MS112, and MS113 is as follows.

P (S11, n) = P (S13, n) = P0
P (S12, n) = P0−Δ1
(3) Case 3
In Case 3, one terminal MS112 is located at the sector center in sector S12, and the remaining terminals MS111 and MS113 are located at sector boundaries of the same positional relationship in sectors S11 and S13, respectively. That is, of the terminals MS111 and MS113, only the terminal MS113 is located at the sector boundary with the sector S12.

  At this time, the adjacent sector interference in the cell C1 is as follows.

-Data signal and pilot signal to terminal MS111 do not give adjacent sector interference-Data signal and pilot signal to terminal MS112 give adjacent sector interference to terminal MS113-Data signal and pilot signal to terminal MS113 are Therefore, adjacent sector interference is given to terminal MS111. Therefore, in order to avoid adjacent sector interference, the transmission power of data signals and pilot signals to terminal MS112 and terminal MS113 may be reduced.

  However, since the data signal and pilot signal to terminal MS112 give adjacent sector interference to terminal MS113, the transmission power to terminal MS112 needs to be lower than the transmission power to terminal MS113.

  Therefore, the transmission power of data signals (or pilot signals) to terminals MS111, MS112, and MS113 is as follows.

P (S11, n) = P0
P (S12, n) = P0−Δ2
P (S13, n) = P0−Δ1
Δ2> Δ1 Here, Δ2 represents an arbitrary power value that can be changed (the same applies hereinafter).
[Power Control Pattern of Step S305]
Case 4 is a case where the power control pattern of step S305 is applicable.
(4) Case 4
In Case 4, two terminals MS111 and MS113 are located at adjacent sector boundaries in sectors S11 and S13, respectively, and the remaining terminal MS112 is located at the sector center in sector S12.

  At this time, the adjacent sector interference in the cell C1 is as follows.

The data signal and pilot signal to terminal MS111 give adjacent sector interference to terminal MS113. The data signal and pilot signal to terminal MS112 give no adjacent sector interference. The data signal and pilot signal to terminal MS113 are Giving adjacent sector interference to terminal MS111 In this case, for example, if transmission power to terminal MS111 is reduced, adjacent sector interference from sector S13 to terminal MS111 becomes relatively large. Further, if both the transmission powers to terminals MS111 and MS113 are reduced, the communication quality of sectors S11 and S13 is deteriorated.

  Therefore, since adjacent sector interference cannot be avoided without causing other problems, the transmission power of the data signal and the pilot signal to terminal MS111 and terminal MS113 remains unchanged at a predetermined value.

  Therefore, the transmission power of data signals (or pilot signals) to terminals MS111, MS112, and MS113 is as follows.

P (S11, n) = P (S12, n) = P (S13, n) = P0
[Power Control Pattern of Steps S304 and S305]
Case 5 is a case where the power control patterns of both step S304 and step S305 can be applied.
(5) Case 5
In Case 5, the two terminals MS111 and MS113 are located at adjacent sector boundaries in the sectors S11 and S13, respectively, and the remaining terminals MS112 are located at the sector boundaries of the sector S12 with the sector S11.

  At this time, the adjacent sector interference in the cell C1 is as follows.

-Data signal and pilot signal to terminal MS111 give adjacent sector interference to terminal MS112 and terminal MS113-Data signal and pilot signal to terminal MS112 do not give adjacent sector interference-Data signal and pilot to terminal MS113 Signal gives adjacent sector interference to terminal MS111 In this case, focusing on the relationship between terminal MS111 and terminal MS112, the data signal and pilot signal to terminal MS111 give adjacent sector interference to terminal MS112. The data signal and pilot signal to the MS 112 do not cause adjacent sector interference. Therefore, the power control pattern in step S304 can be applied.

  On the other hand, paying attention to the relationship between terminal MS111 and terminal MS113, the data signal and pilot signal to terminal MS111 and terminal MS113 give each other adjacent sector interference. Therefore, the power control pattern in step S305 can be applied.

  As described above, when two power control patterns can be applied in the base station BS, priorities are set in advance, and it is determined which power control pattern is applied according to the priorities. Good.

  For example, when applying the power control pattern in step S304, the transmission power of the data signal and pilot signal to terminal MS111 may be reduced.

  Therefore, the transmission power of data signals (or pilot signals) to terminals MS111, MS112, and MS113 is as follows.

P (S11, n) = P0−Δ1
P (S12, n) = P (S13, n) = P0
However, if the transmission power of the data signal and pilot signal to terminal MS111 is reduced, the adjacent sector interference from sector S13 to terminal MS111 becomes relatively large, and therefore the data signal and pilot signal are transmitted to terminal MS113. The power may also be reduced.

  On the other hand, when the power control pattern of step S304 is applied, the transmission power of the data signal and pilot signal to terminal MS111 and terminal MS113 remains unchanged at a predetermined value.

  Therefore, the transmission power of data signals (or pilot signals) to terminals MS111, MS112, and MS113 is as follows.

P (S11, n) = P (S12, n) = P (S13, n) = P0
[Power Control Pattern of Step S306]
Case 6 is a case where the power control pattern of step S306 is applicable.
(6) Case 6
Case 6 is a case where all the terminals MS111, MS112, and MS113 are located at the sector centers in the sectors S11, S12, and S13, respectively.

  At this time, since the data signal and pilot signal to terminals MS111, MS112, and MS113 do not cause adjacent sector interference, neither transmission power is changed to a predetermined value.

  Therefore, the transmission power of data signals (or pilot signals) to terminals MS111, MS112, and MS113 is as follows.

P (S11, n) = P (S12, n) = P (S13, n) = P0
In FIG. 8, it has been described that the terminals MS111, MS112, and MS113 to which the same RB is assigned are located in all the sectors S11, S12, and S13. However, the sector without the terminal MS to which the RB is assigned is described. Is also present. In such a sector, since there is no data signal to be transmitted, transmission power 0 of the data signal is assigned.

  As described above, in the present embodiment, when the same radio resource is allocated to a plurality of terminals MS located in different sectors of the own station, the base station BS transmits a data signal to be transmitted to any of the plurality of terminals MS, When changing the transmission power of the pilot signal, the pilot signal is changed from a predetermined value while keeping the power ratio constant.

  Therefore, even when the transmission power is changed, the power ratio between the pilot signal and the data signal is constant, so that the terminal MS can demodulate the data signal with high accuracy without the notification of the power ratio from the base station BS. Can do.

  Further, in the present embodiment, the base station BS distinguishes between the power change prohibition section and the power change permission section, and the base station BS transmits a pilot signal whose transmission power is constant at a predetermined value in a plurality of terminals MS in the power change prohibition section. And scheduling based on the received power when this pilot signal is received by the terminal MS.

  Therefore, the base station BS does not affect scheduling even if the transmission power of the pilot signal is changed.

  In the present embodiment, the base station BS does not uniformly change the transmission power to the terminal MS that gives adjacent sector interference. For example, the base station BS causes problems such as deterioration in communication quality of both sectors when the transmission power is reduced together for the terminals MS located in two sectors that cause adjacent sector interference to each other. The transmission power is not changed.

  Therefore, the base station BS can avoid changing the transmission power when another problem occurs with the change in the transmission power.

  Although the present invention has been described with reference to the embodiments, the present invention is not limited to the above embodiments. Various changes that can be understood by those skilled in the art can be made to the configuration and details of the present invention within the scope of the present invention.

  Note that the methods performed in the base station BS and the terminal MS of the present invention may be applied to a program for causing a computer to execute. In addition, the program can be stored in a storage medium and can be provided to the outside via a network.

  This application claims the priority on the basis of Japanese application Japanese Patent Application No. 2008-095108 for which it applied on April 1, 2008, and takes in those the indications of all here.

Claims (17)

A wireless communication system comprising a base station forming a communication area and a plurality of terminals located in different communication areas,
The base station
A detection unit for detecting whether the current time is the first interval or the second interval;
An allocating unit that allocates radio resources to the plurality of terminals based on reception power of pilot signals reported from the plurality of terminals in a first section;
When the same radio resource is allocated to the plurality of terminals, the transmission power of the data signal and pilot signal to be transmitted to the plurality of terminals is kept at a predetermined value in the first section, and in the second section, A power control unit that changes transmission power of a data signal and a pilot signal transmitted to a specific terminal among the plurality of terminals from a predetermined value while keeping a power ratio of the data signal and the pilot signal constant. ,
The terminal
A detection unit for detecting whether the current time is the first interval or the second interval;
A radio communication system comprising: a signal measurement unit that reports reception power of a pilot signal received from each communication region to the base station in a first section. The power control unit
In the second section, based on the received power of the pilot signal reported from the plurality of terminals in the first section, it is determined whether each of the plurality of terminals is receiving interference from the adjacent communication area, and the determination result The wireless communication system according to claim 1, wherein the specific terminal is determined based on the data signal, and transmission power of a data signal and a pilot signal transmitted to the specific terminal is changed. The power control unit
In the second section, a terminal located in one of the two communication areas adjacent to each other receives interference from the other communication area, and a terminal located in the other communication area receives interference from one communication area. 3. The wireless communication according to claim 2, wherein if it is determined that there is not, a terminal located in the other communication area is determined as the specific terminal, and transmission power of a data signal and a pilot signal transmitted to the specific terminal is changed. system. The power control unit
In the second interval, when it is determined that none of the plurality of terminals has received interference from the adjacent communication area, the transmission power of the data signal and pilot signal transmitted to the plurality of terminals is kept at a predetermined value. The wireless communication system according to claim 2. The power control unit
In the second section, when it is determined that the terminals located in each of the two communication areas adjacent to each other receive interference from the other communication area, the terminals are transmitted to the terminals located in each of the two communication areas. The wireless communication system according to claim 2, wherein transmission powers of the data signal and the pilot signal are kept at predetermined values. A base station forming a communication area,
A detection unit for detecting whether the current time is the first interval or the second interval;
An allocating unit that allocates radio resources to the plurality of terminals based on reception power of pilot signals reported from a plurality of terminals located in different communication areas in the first section;
When the same radio resource is allocated to the plurality of terminals, the transmission power of the data signal and pilot signal to be transmitted to the plurality of terminals is kept at a predetermined value in the first section, and in the second section, A power control unit that changes the transmission power of a data signal and a pilot signal to be transmitted to a specific terminal among the plurality of terminals from a predetermined value while keeping the power ratio of the data signal and the pilot signal constant, base station. The power control unit
In the second section, based on the received power of the pilot signal reported from the plurality of terminals in the first section, it is determined whether each of the plurality of terminals is receiving interference from the adjacent communication area, and the determination result The base station according to claim 6, wherein the base station determines the specific terminal and changes transmission power of a data signal and a pilot signal transmitted to the specific terminal. The power control unit
In the second section, a terminal located in one of the two communication areas adjacent to each other receives interference from the other communication area, and a terminal located in the other communication area receives interference from one communication area. The base station according to claim 7, wherein if it is determined that the terminal is located in the other communication area, the terminal is determined as the specific terminal, and the transmission power of the data signal and pilot signal transmitted to the specific terminal is changed. . The power control unit
In the second interval, when it is determined that none of the plurality of terminals has received interference from the adjacent communication area, the transmission power of the data signal and pilot signal transmitted to the plurality of terminals is kept at a predetermined value. The base station according to claim 7. The power control unit
In the second section, when it is determined that the terminals located in each of the two communication areas adjacent to each other receive interference from the other communication area, the terminals are transmitted to the terminals located in each of the two communication areas. The base station according to claim 7, wherein the transmission power of the data signal and the pilot signal is kept at a predetermined value. A wireless communication method using a wireless communication system comprising a base station forming a communication area and a plurality of terminals located in different communication areas,
A detecting step in which the base station and the terminal detect whether a current time is a first interval or a second interval;
A reporting step in which the terminal reports the received power of a pilot signal received from each communication area to the base station in a first interval;
The base station assigning radio resources to the plurality of terminals based on reception power of pilot signals reported from the plurality of terminals in the first section;
When the same radio resource is allocated to the plurality of terminals, the base station keeps transmission powers of data signals and pilot signals to be transmitted to the plurality of terminals at predetermined values in a first interval, A power control step of changing a transmission power of a data signal and a pilot signal to be transmitted to a specific terminal among the plurality of terminals from a predetermined value while keeping a power ratio of the data signal and the pilot signal constant And a wireless communication method. A wireless communication method by a base station forming a communication area,
A detection step of detecting whether the current time is the first interval or the second interval;
Allocating radio resources to the plurality of terminals based on reception power of pilot signals reported from a plurality of terminals located in different communication areas in the first section;
When the same radio resource is allocated to the plurality of terminals, the transmission power of the data signal and pilot signal to be transmitted to the plurality of terminals is kept at a predetermined value in the first section, and in the second section, A power control step of changing the transmission power of a data signal and a pilot signal to be transmitted to a specific terminal among the plurality of terminals from a predetermined value while keeping the power ratio of the data signal and the pilot signal constant. Wireless communication method. In the power control step,
In the second section, based on the received power of the pilot signal reported from the plurality of terminals in the first section, it is determined whether each of the plurality of terminals is receiving interference from the adjacent communication area, and the determination result The radio communication method according to claim 12 , wherein the specific terminal is determined based on and a transmission power of a data signal and a pilot signal transmitted to the specific terminal is changed. In the power control step,
In the second section, a terminal located in one of the two communication areas adjacent to each other receives interference from the other communication area, and a terminal located in the other communication area receives interference from one communication area. The wireless communication according to claim 13 , wherein if it is determined that there is not, the terminal located in the other communication area is determined as the specific terminal, and the transmission power of the data signal and pilot signal transmitted to the specific terminal is changed. Method. In the power control step,
In the second interval, when it is determined that none of the plurality of terminals has received interference from the adjacent communication area, the transmission power of the data signal and pilot signal transmitted to the plurality of terminals is kept at a predetermined value. The wireless communication method according to claim 13 . In the power control step,
In the second section, when it is determined that the terminals located in each of the two communication areas adjacent to each other receive interference from the other communication area, the terminals are transmitted to the terminals located in each of the two communication areas. The radio communication method according to claim 13 , wherein transmission powers of the data signal and the pilot signal are kept at predetermined values. To the base station that forms the communication area,
A detection procedure for detecting whether the current time is the first interval or the second interval;
An allocation procedure for allocating radio resources to the plurality of terminals based on reception power of pilot signals reported from a plurality of terminals located in different communication areas in the first section;
When the same radio resource is allocated to the plurality of terminals, the transmission power of the data signal and pilot signal to be transmitted to the plurality of terminals is kept at a predetermined value in the first section, and in the second section, A power control procedure for changing transmission power of a data signal and a pilot signal to be transmitted to a specific terminal among the plurality of terminals from a predetermined value while keeping a power ratio of the data signal and the pilot signal constant Program for.

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