KR20070093996A - Base station and interference reduction method in the base station - Google Patents

Abstract

A base station performs communication with a mobile terminal existing in a slave cell and controls to reduce interference from a mobile terminal existing in an adjacent cell. The base station measures a total interference power received from the mobile terminals of all the adjacent cells. If the total interference power is greater than a predetermined value, the base station requests a base station of all the adjacent cells to reduce the interference. The base station which has received the interference reduction request judges a mobile terminal which may give an interference to the base station which has requested the interference reduction and temporarily lowers the transmission rate of upstream data or temporarily stops transmission of the upstream data in the mobile terminal, thereby reducing the interference.

Description

A base station and a method for reducing interference in the base station {BASE STATION AND INTERFERENCE REDUCTION METHOD IN THE BASE STATION}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a base station and a method for reducing interference in the base station. In particular, the base station communicates with a mobile terminal existing in a cell under management and performs control to reduce interference from a mobile terminal existing in an adjacent cell. And a method for reducing interference at the base station.

Commercialization of Code Division Multiple Access (CDMA) communication systems is rapidly progressing, and commercial services of wideband CDMA systems (W-CDMA) for exchanging large data such as moving images as well as voice and still images are being disclosed. . Specifications of the wideband CDMA system, the third generation mobile communication will enacted in the standardization organization 3GPP (3 ^rd Generation Partnership Project) systems, are also a variety of specifications continue to review with the aim of the system that can achieve a high quality of service than It is being added.

14 is a network configuration diagram of a W-CDMA system of the current 3GPP specification. The system includes a core network (CN) 100, a radio network controller (RNC) (101 # 0 to 101 # n), a radio base station (NodeB) 102 # 0 to 102 # n, and A mobile terminal (UE: User Equipment) 103 is composed of four types of nodes. Each node 100, 101 # 0 to 101 # n, 102 # 0 to 102 # n is physically connected by an ATM (Asynchronous Transfer Mode) transmission path or the like (wired section). The radio base stations 102 # 0 to 102 # n and the mobile terminal 103 are connected by radio signals (wireless sections). Iu is an interface between the radio network controllers 10O1 # O-1O1 # n and the core network 100, Iur is an interface between the radio network controllers 101- # O-1O1 # n, and Iub is a radio network controller. An interface between 101 # 0 to 101 # n and the wireless base stations 102 # 0 to 102 # n, Uu is an interface between the wireless base stations 102 # 0 to 102 # n and the mobile terminal 103.

The user data is transmitted to the RNC 101 # 0 to RNC101 # 1 via the Iu line from the CN 100 that houses the exchange, server, database, and the like. When the mobile terminal UE 103 of the destination belongs to the cell 104 # 1 under the management of the RNC 101 # 0, the user data is stored in the cell via the Iub line from the RNC 101 # 0. Transmitted to NodeB102 # 1, and transmitted to the mobile terminal UE 103 via the Uu interface.

In the mobile CDMA communication system composed of a plurality of cells as described above, the signal (uplink signal or reverse link signal) transmitted to the base station to which the mobile terminal is connected reaches the base station of the adjacent cell and is the same in the uplink between the cells. If a frequency band is used, this results in an interference signal for an adjacent cell. In particular, when a mobile terminal exists in the boundary region where a plurality of cells overlap, the level of the interference signal to the adjacent cell by the transmission signal from the mobile terminal is increased. FIG. 15 shows an image in which two terminals interfere with a base station of a neighboring cell by a mobile terminal in one cell. For ease of explanation, the number of base stations (cells) is two and the number of mobile terminals is three.

The mobile terminal MS1 in the cell CL1 is communicating with the base station BTS1, but the transmission signal from the mobile terminal MS1 also reaches the base station BTS2 of the adjacent cell CL2 and becomes an interference signal. In addition, although the mobile terminals MS2 and MS3 in the cell CL2 are communicating with the base station BTS2, the transmission signals from the mobile terminals MS2 and MS3 also reach and interfere with the base station BTS1 of the neighboring cell CL1. It becomes a signal. In this case, the interference of the mobile terminal MS3 present in the border region where the cells CL1 and CL2 overlap is larger than the interference of the mobile terminal MS2 not present in the border region.

FIG. 16 shows an image of the received signal component at the base stations BTS1 and BTS2 of the cells CL1 and CL2 shown in FIG. As shown in FIG. 16, the received signal power of the base station BTS1 includes the received signal power from the mobile terminal MS1 in the cell CL1 under management, the mobile terminal MS2 in the adjacent cell (cell CL2), and the like. The sum of the received signal powers from MS3). In addition, thermal noise is precisely included but omitted. The received signal power of the base station BTS2 includes the received signal power from the mobile terminals MS2 and MS3 in the cell CL2 under management, and the received signal from the mobile terminal MS1 in the adjacent cell (cell CL1). It is the sum of power.

Although the maximum allowable received signal power at the base station is considered to be a radio resource in the uplink, the radio resource is limited by the interference signal from the neighboring cell described above. On the other hand, a mobile terminal in a cell dominated by a base station subjected to interference from an adjacent cell interferes with the adjacent cell, thereby limiting radio resources of the adjacent cell.

In the current 3GPP W-CDMA system, the radio network controller RNC located above the base station BTS does not perform call admission control (admission control, congestion control) based on the total received signal power of the base station. However, no control is performed to reduce the power of the interference signal from the adjacent cell. That is, the base station can control the received signal power from the mobile terminal in the cell under management, but cannot control the interference signal power from the adjacent cell.

There is a conventional technique (see Patent Document 1, for example) for controlling interference from neighboring base stations. This prior art is a technique aimed at mitigating interference received by a mobile terminal due to a downlink signal from another station in a communication system in which frequency bands are the same in uplink and downlink. That is, the mobile terminal monitors the strength and frequency of the interference signal by the downlink signal transmitted from the other station, and when the interference level exceeds the threshold, notifies the base station during the communication that there is interference, and also generates the interference. Notify the time information. The base station received the notification cancels the interference received by the mobile terminal by changing the subband (subchannel) used for data transmission to the mobile terminal. However, if there is no empty band and the base station cannot solve the problem, the higher level apparatus of the base station notifies interference information (interference occurrence, interference occurrence time). The host apparatus checks the neighbor base stations of the base station, identifies the base station that caused the interference based on the time of the occurrence of interference, and changes the subbands used for data transmission to the interference causing base station. The base station instructed by the host apparatus changes the subband used for downlink data transmission. If there is no empty portion of the subband, transmission is stopped.

However, this prior art does not reduce the interference caused by the mobile terminal in the cell adjacent to the cell of interest, in particular, the mobile terminal in the adjacent cell near the cell edge, to the base station of the cell of interest by the uplink signal.

As mentioned above, the objective of this invention is to reduce the interference power from an adjacent cell.

Another object of the present invention is to reduce the interference power by requesting the neighbor base station to reduce the interference when the total interference power received from the mobile terminal of the neighbor cell is larger than the set value.

Another object of the present invention is to determine a mobile terminal which exists at a cell boundary and may generate a large interference signal, and reduces interference power by reducing the interference signal from the mobile terminal.

Another object of the present invention is to improve the throughput of the entire system by reducing and controlling the interference signal that the mobile terminal gives to the base station of the adjacent cell during communication with each base station.

Patent Document 1: Japanese Patent Application Laid-Open No. 2003-259414

<Start of invention>

This problem is solved by an interference reduction method of a base station which performs communication with a mobile terminal existing in a cell under management, and controls to reduce interference from the mobile terminal existing in an adjacent cell.

The first interference reduction method includes the steps of measuring the total interference power received from the mobile terminals of all neighboring cells, and if the total interference power is larger than a set value, requesting the base stations of all neighboring cells to reduce the interference. . The measuring step of the total interference power is a step of measuring the total received power of the base station, measuring the received power from all mobile terminals under management as the desired power, subtracting the desired power from the total received power, and the total interference power. It has a step of calculating.

The second interference reduction method includes measuring interference power received from all mobile terminals in the adjacent cell for each adjacent cell, and calculating total interference power received from the mobile terminals of all adjacent cells by adding interference power for each adjacent cell. And if the total interference power is larger than the set value, the step of requesting the base station of the predetermined number of neighboring cells with large interference power or the base station of the neighboring cell with the interference power larger than the set value to reduce the interference. have.

In the first and second interference reduction methods, when the interference reduction request is received, a step of determining a mobile terminal that may be interfering with the base station of the interference reduction request source, and a transmission rate of uplink data of the mobile terminal It further has a step of temporarily lowering or temporarily stopping transmission of upstream data.

Furthermore, the said subject is solved by the base station which communicates with the mobile terminal which exists in the cell under management, and performs control which reduces the interference from the mobile terminal which exists in an adjacent cell.

The first base station includes an interference power measurement unit for measuring the total interference power received from the mobile terminals of all neighboring cells, a comparison unit for comparing the total interference power with a setting value, and if the total interference power is larger than the setting value, An interference reduction request unit for requesting the base station of an adjacent cell to reduce interference is provided. The interference power measurement unit includes a total reception power measurement unit for measuring the total received power of the base station, a desired power measurement unit for measuring the received power from all mobile terminals under management as desired power, and the desired power from the total received power. In addition, an interference power calculating section for calculating the total interference power is provided.

The second base station includes: an interference power measurement unit for measuring interference power received from all mobile terminals in the adjacent cell for each adjacent cell; a total interference power calculator for calculating total interference power received from the mobile terminals of all neighbor cells; If the interference power is larger than the first set value, the interference reduction requiring the base station of the predetermined number of neighboring cells with large interference power or the base station of the neighboring cell with the interference power larger than the second set value to reduce the interference. The request part is provided.

The first and second base stations intermittently reduce the transmission rate of the uplink data of the mobile terminal, the interfering mobile terminal determination unit for determining a mobile terminal that may be interfering with the base station that has issued the interference reduction request, Or a schedule section for temporarily stopping transmission of upstream data.

1 is a network configuration to which the present invention can be applied.

FIG. 2 is an image diagram of a mobile station in an adjacent cell interfering with a base station of a cell of interest in three cells; FIG.

3 is an explanatory diagram of details of received signal power.

4 is a processing flow of a base station under interference in the first embodiment;

Fig. 5 is a processing flow of a base station accommodating a mobile terminal which is interfering in the first embodiment.

6 is an explanatory diagram of a method for discriminating a mobile terminal that may be interfering.

7 is an explanatory diagram of an example of a common pilot signal in a W-CDMA system.

8 is a processing flow for determining a mobile terminal that may be interfering.

9 is a configuration diagram of a base station of the first embodiment.

10 is an explanatory diagram of a second embodiment;

11 is a processing flow of a base station under interference in the second embodiment.

12 is another processing flow of the base station under interference in the second embodiment;

Fig. 13 is a configuration diagram of a base station of the second embodiment.

14 is a network configuration diagram of a W-CDMA system of the current 3GPP specification.

Fig. 15 is an image diagram in which a mobile terminal in one cell interferes with a base station of an adjacent cell for two cells.

FIG. 16 illustrates that interference from adjacent cells limits radio resources. FIG.

<Best Mode for Carrying Out the Invention>

(A) First embodiment

(a) Network configuration

1 is a diagram illustrating a network to which the present invention can be applied. A plurality of base stations BTS1 to BTSn are connected to a core network CN, and each base station is wirelessly connected to a mobile terminal MSij in cells CL1 to CLn. It can communicate with. The core network CN has functions of both the core network and the radio network controller shown in FIG. 14. In addition, each base station is connected to an adjacent base station by wire (or wireless using a microwave band, for example) and has an interface for communicating with each other. This network configuration of FIG. 1 is a network proposed in, for example, 3GPP TR 25.897 V0.3.0 (2003-08).

FIG. 2 shows an image in which the mobile terminals MS2j and MS3k in the adjacent cells CL2 and 3 interfere with the base station BTS1 of the cell of interest CL1 in the three cells CL1 to CL3. In FIG. 2, the cell number is shown as 3 for ease of explanation. In these three cells, the same frequency band is used in the uplink.

Referring to the base station BTS1 of the cell CL1, the mobile terminals MS21 and MS22 in the adjacent cell CL2 are communicating with the base station BTS2, but the uplink signals transmitted from the mobile terminals MS21 and MS22 are The base station BTS1 of the cell of interest CL1 also arrives and becomes an interference signal. In this case, the mobile terminal MS23 which does not exist in the cell terminal or the mobile terminal which exists in the cell terminal on the opposite side to the base station BTS1 of interest does not interfere with the base station BTS1, or the interference is weak even if given. Similarly, the mobile terminal MS32 in the neighbor cell CL3 is in communication with the base station BTS3, but the uplink signal transmitted from the mobile terminal MS32 also reaches the base station BTS1 of the cell of interest CL1, thereby interfering with the interference signal. It becomes

(b) received signal power

As shown in FIG. 3, the total received signal power P received by the base station BTS1 is the received signal power Pa from the mobile terminal in the self cell CL1 and the neighboring signals CL2 and CL3. The sum of the total neighboring received signal power Pother from the mobile terminal (P = Pa + Pother) (where thermal noise is ignored). The host apparatus in the core performs call admission control, and monitors whether the difference between the maximum allowable received signal power Pmax and the total received signal power P at the base station BTS1 is equal to or less than the set value, If no, the mobile station in the base station BTS1 rejects the request for a new call, and if abnormal, the call is accepted. Therefore, as the total neighboring received signal power (Pother) increases, reducing this power (Pother) leads to the use of radio resources.

(c) treatment of the base station under interference;

4 is a processing flow of the base station under interference in the first embodiment.

In the base station BTS1, the total neighbor received signal power Pother from all neighbor cells is measured (step 201). The method of measuring the interference power Pother measures the total received signal power of the base station BTS1, measures the total received signal power from all mobile terminals in the cell under management as desired power, and measures the total power of the base station BTS1. It is found by subtracting the desired power from the total received signal power.

Subsequently, the total neighboring received signal power Pother and the threshold power Pth are compared (step 202), and if the total neighboring received signal power is greater than or equal to the threshold power (Pother? Pth), the base station BTS1 is the entire neighboring base station. On the other hand, the flag signal Fint requesting the interference reduction is transmitted (step 203). In addition, as will be described later, the neighboring base stations BTS2 and BTS3 that have received this flag signal Fint have a predetermined time and up with respect to the mobile terminal near the cell terminal on the target base station BTS1 side of the mobile terminals under management. Control is made to reduce the data rate at the time of link transmission or not to allow transmission. This reduces the total neighboring received signal power Pother.

Subsequently, the process waits for the predetermined time to elapse (step 204), and when the elapsed time passes, the process after the above step 201 is repeated. In step 202, if the total adjacent received signal power is smaller than the threshold power (Pother <Pth), since the interference is small, the processor waits for a predetermined time to elapse without doing anything (step 204). The subsequent processing is repeated.

(d) the processing of the base station accommodating the interfering mobile terminal;

5 is a processing flow of the base station, for example, the base station BTS2, which accommodates the mobile terminal that is interfering in the first embodiment.

The base station BTS2 monitors whether the flag signal Fint has been received (step 301). If no flag signal Fint is received, the base station BTS2 waits for a predetermined time to elapse (step 304). The subsequent processing is repeated.

On the other hand, when the flag signal Fint is received in step 301, a mobile terminal that may interfere with the base station BTS1 that has transmitted the flag signal Fint is determined (step 302). That is, the mobile terminal in the vicinity of the cell end on the base station side which transmitted the flag signal Fint is identified.

When the determination of the mobile terminal interfering with the base station BTS1 is completed, the neighboring base station BTS2 temporarily reduces the transmission rate of the upstream data of the mobile terminal or temporarily stops the transmission of the uplink data by the scheduling function. Control to stop (step 303). After that, the process waits for the predetermined time to elapse (step 304), and if so, the process after the above step 301 is repeated.

The transmission restriction of upstream data ends when the flag signal Fint is no longer received and when the mobile terminal no longer exists at the cell end. Moreover, it can also be made to end when a fixed time elapses after transmission transmission start.

As described above, when receiving a flag signal (Fint) requesting interference reduction, the transmission rate of the upstream data of the mobile terminal which may be interfering is temporarily lowered or the transmission of the upstream data is temporarily stopped. The interference with the base station BTS1 can be reduced.

(e) Identification of the mobile terminal at the cell end

6 is an explanatory diagram of a discriminating method of a mobile terminal which is interfering.

As shown in FIG. 6, when the mobile terminal MS22 communicating with the base station BTS2 exists in or near the boundary area of the cells CL1 and CL2 of the base stations BTS1 and BTS2, the downlink from both base stations Receive the signal. Each downlink signal includes a common pilot signal (CPICH signal). The mobile terminal MS22 measures the received power P1, P2 of each common pilot signal from the base stations BTS1, BTS2, and exists near the cell end if the absolute value of the difference ΔP between the two received powers is less than or equal to the set value. It is determined that there is a possibility of interfering with the transmission source base station BTS1 of the flag signal Fint, and if it is equal to or larger than the set value, it is determined that the transmission source base station BTS1 of the flag signal Fint is not interfered.

FIG. 7 is an explanatory diagram showing an example of a common pilot signal transmitted from each base station in a W-CDMA system. One frame is 10 msec and is composed of 15 slots (S0 to S14). However, the present invention does not depend on the physical channel configuration of the downlink.

The primary common control physical channel (P-CCPCH) and the common pilot channel (CPICH) (CPICH in this example represents the primary common pilot channel P-CPICH), one for each cell in the downlink common channel. exist. Among them, the primary common control channel (P-CCPCH) is used to transmit BCH (notification information), and the BCH includes information about a base station, a base station code of an adjacent base station, and the like. On the other hand, the common pilot channel (CPICH) transmits a common pilot signal, thereby spreading the common pilot signal by the base station code (for example, the cell-specific scramble code of the cell under the base station management) and the channelization code for the CPICH. Send. The receiving side performs control such as channel estimation and reception power measurement using the common pilot signal. In FIG. 7, the S-SCH is a secondary synchronization channel.

The mobile terminal MS22 (see FIG. 6) separates the common pilot signal transmitted from the base station BTS2 during the communication by using the base station code of the base station BTS2 and the CPICH channelization code during communication, and the common pilot. The received power P2 of the signal is measured. Further, the base station code of the neighboring base station BTS1 is obtained from the BCH (notification information) transmitted by the primary common control channel (P-CCPCH), and the neighboring base station is used by using the base station code and the channelization code for the CPICH. The common pilot signal transmitted from (BTS1) is separated, and the received power P1 of the common pilot signal is measured.

8 is a processing flow for determining a mobile terminal that may be interfering.

In each mobile terminal communicating with the base station BTS2, for example, the mobile terminal MS22 measures the reception power of the common pilot signal transmitted through the common pilot channel CPICH of the base station BTS2 during communication ( Step 401). Subsequently, a base station code (scramble code) of the neighboring base station BTS1 is obtained from the BCH (notification information) transmitted by the PCCPCH (step 402), and the neighboring base station (the base station code and the channelization code for the CPICH are used). The common pilot signal transmitted from the BTS1) is separated and the received power P1 of the common pilot signal is measured (step 403).

When the measurement of the received powers P1 and P2 is completed, the mobile terminal calculates the absolute value of the difference ΔP between the received powers P2 and P1 of the common pilot signal from the base station BTS2 and the adjacent base station BTS1 during communication. (? P = | P2-P1 |), step 404, it is determined whether the difference? P is equal to or greater than the threshold (step 405). If the difference ΔP is equal to or greater than the threshold value, it is determined that there is no presence in the vicinity of the neighboring base station BTS1, and the base station name of the neighboring base station is attached to the determination result and notified to the base station BTS2 during communication (step 406). In addition, although the determination result is notified to the base station BTS2 during communication here, the determination result in this case does not necessarily need to be notified, and it is not necessary to notify it.

On the other hand, if the difference ΔP is less than or equal to the threshold, it is determined that the cell is present in the vicinity of the cell end, and the base station name of the adjacent base station is attached to the determination result and notified to the base station BTS2 during communication (step 407). Alternatively, only a flag signal indicating that the neighboring cell may be interfering is transmitted.

The base station BTS2 identifies the mobile terminal that is interfering with the source base station BTS1 of the flag signal Fint based on the determination result received from each mobile terminal, and determines the uplink data of the mobile terminal by the scheduling function. Temporarily reduce the transmission rate or temporarily stop the transmission of upstream data.

(f) configuration of the base station

9 is a configuration of a base station of the first embodiment.

The receiving radio section 11 amplifies the radio signal received by the antenna 10 and downconverts the frequency from the high frequency band to the baseband. The total received signal power measuring unit 12 measures the total received signal power P from the output signal of the receiving radio unit 11, and the demodulator 13 inverts the scramble code unique to each terminal after the orthogonal demodulation. By spreading and despreading with a predetermined channelization code, (1) user data or control signals, (2) signals for measuring the total received signal power from the mobile terminal under management, and (3) movement The cell-end notification signal from the terminal is separated. In addition, the total received signal power from all mobile terminals in communication is referred to as desired signal power (or desired power).

The signal for measuring the desired signal power is obtained by despreading the received signal with a despreading code specific to the mobile terminal. The decoding unit 14 performs decoding processing and error detection correction processing on the demodulated data and the control signal, and outputs the obtained data and control information.

The desired signal power calculating unit 15 measures the desired signal power Pa using the signal obtained by despreading, and the interference power calculating unit 16 uses the following equation.

The received signal power Pother received from the mobile terminals of all neighboring cells is calculated as interference power. Also, the received signal power Pother is hereinafter referred to as the total adjacent received signal power. The comparator 17 compares the total neighboring received signal power Pother with the threshold power Pth and inputs a comparison result to the flag generator 18. The flag generator 18 generates a flag signal Fint requesting the neighbor base station to reduce interference when the total neighbor received signal power is greater than or equal to the threshold power (Pother? Pth) with reference to the comparison result. It enters in the part 19. The transmitting unit 19a of the neighbor base station communication interface unit 19 attaches the sender base station ID to the flag signal Fint and transmits it to all neighbor base stations. Also, if the total neighbor received signal power is less than or equal to the threshold power, no flag signal is generated.

On the other hand, when the reception unit 19b of the neighbor base station communication interface unit 19 receives the flag signal Fint from the neighbor base station, the reception unit 19b receives the flag signal Fint and the source base station name of the flag signal Fint. The uplink schedule unit 20 is notified. When the uplink scheduler 20 receives the flag signal reception notification, the uplink scheduler 20 inputs the name of the sender base station of the flag signal Fint to the terminal near terminal specification unit 21.

Since the cell-end near-terminal specification part 21 inputs the cell-end vicinity determination result sent by the mobile terminal according to the process of FIG. 8 during a communication, if the mobile terminal exists in a cell-end among each communication based on the result, in other words, During the communication, the mobile terminal identifies whether the mobile terminal interferes with the base station that sent the flag signal Fint, and notifies the uplink scheduler 20 of the mobile terminal that is interfering.

Upon receiving this notification, the uplink scheduler 20 instructs the control signal generator 22 to limit the uplink data transmission of the mobile terminal that is causing the interference. The control signal generator 22 generates a control signal for limiting uplink data transmission of the indicated mobile terminal. That is, a control signal for temporarily lowering the transmission rate of upstream data or a control signal for temporarily stopping transmission of the upstream data is created. The multiplexer 23 multiplexes the control signal and the user data generated by the user data generator 24, and the encoder / modulator 25 encodes the multiple data and spreads by a predetermined spreading code. Orthogonal modulation is performed by the spreading result, and the transmission radio section 26 performs frequency up-conversion, high frequency amplification, and the like on the modulated output signal to transmit the transmission signal from the antenna 27.

The mobile terminal which receives the signal transmitted from the antenna 27 and restricts the uplink data transmission temporarily lowers the transmission rate of the uplink data or temporarily stops the uplink data transmission. The uplink scheduler 20 controls to cancel the restriction on the uplink transmission data of the mobile terminal when the flag signal Fint is not received or when a predetermined time elapses after the transmission rate is lowered or paused. do.

According to the first embodiment, interference power from adjacent cells can be reduced. Further, according to the first embodiment, when the total interference power received from the mobile terminal of the neighbor cell is larger than the set value, the neighbor base station can be requested to reduce the interference, thereby reducing the interference power, thereby reducing the throughput of the entire system. Can be improved. Further, according to the first embodiment, the interference power can be reduced by determining the mobile terminal existing at the cell boundary and generating a large interference signal, and reducing the interference signal from the mobile terminal.

(B) Second embodiment

In the first embodiment, the total received signal power (total neighbor received signal power) (Pother) from the mobile terminals of all neighboring cells was measured based on the equation (1). In the second embodiment, as shown in Fig. 10, the total received signal power (adjacent received signal power) from the mobile terminals in the cell (Pcell 1 to Pcell N) for each cell of all adjacent cells (cell 1 to cell N). ), And the following equation

In other words, the total neighboring received signal power Pother is calculated by summing the neighboring received signal powers Pcell 1 to Pcell N for each neighboring cell (wherein each terminal performs scramble with a cell-specific scramble code). After that, the uplink data is transmitted). The adjacent received signal powers Pcell 1 to Pcell N for each cell of the adjacent cells (cells 1 to cell N) are measured by despreading the received signal by the scramble code of each adjacent cell and separating the common pilots of the respective base stations. .

11 is a processing flow of the base station under interference in the second embodiment.

For each cell of all adjacent cells (cell 1 to cell N), the adjacent received signal powers Pcell 1 to Pcell N from the mobile terminals in the cell are measured (step 501), and the total adjacent received signals by Equation (2). The power is calculated (step 502). Subsequently, the total neighboring received signal power Pother and the threshold power Pth are compared (step 503). If the total neighboring received signal power is equal to or greater than the threshold power (Pother? Pth), the neighboring received signal power Pcell 1 to Pcell N) is ranked in ascending order (step 504). Subsequently, a flag signal Fint for requesting interference reduction is transmitted to the base stations according to the top m ranked cells, for example, the top two cells (step 50). The adjacent base station that has received this plug signal (Fint) has a fixed time and uplink transmission time to the mobile terminal near the cell end on the base station (BTS1) side of interest, as in the first embodiment (see the processing flow of FIG. 5). Control to lower the data rate or control to disallow transmission is performed. This reduces the total neighboring received signal power Pother.

Thereafter, the controller waits for a predetermined time to elapse (step 506), and if it elapses, the processing after step 501 is repeated. In step 503, when the total neighboring received signal power is smaller than the threshold power (Pother <Pth), the processor waits for a predetermined time to elapse (step 506), and when it passes, the process after step 501 is repeated.

12 is another processing flow of the base station under interference in the second embodiment.

For each cell of all adjacent cells (cell 1 to cell N), the adjacent received signal powers Pcell 1 to Pcell N from the mobile terminals in the cell are measured (step 601), and the total adjacent received signals by equation (2). The power is calculated (step 602). Subsequently, the total neighboring received signal power Pother and the threshold power Pth1 are compared (step 603). If the total neighboring received signal power is equal to or greater than the threshold power (Pother? Pth1), the neighboring received signal power Pcell 1 to The power of the Pcell N) is searched for power equal to or greater than the threshold Pth2 (step 604), and a flag signal Fint is requested to reduce the interference to the base station of the cell corresponding to the power of the adjacent received signal equal to or greater than the threshold Pth2 (step P604). 6O5). The neighboring base station that has received this flag signal Fint has a constant time and uplink transmission time for the mobile terminal near the cell end on the base station BTS1 of interest, as in the first embodiment (see the processing flow in FIG. 5). Control to lower the data rate or control to disallow transmission is performed. This reduces the total neighboring received signal power Pother.

Subsequently, the controller waits for a predetermined time to elapse (step 606), and when it elapses, the process after the above step 601 is repeated. In step 603, when the total neighboring received signal power is smaller than the threshold power (Pother <Pth2), the processor waits for a predetermined time to elapse (step 606), and when it elapses, the process after the step 601 is repeated.

FIG. 13 is a configuration diagram of the base station of the second embodiment, wherein a configuration different from the first embodiment of FIG. 9 determines a configuration for calculating the total neighboring received signal power Pother and a source base station for the flag signal Fint. Configuration.

The demodulator 13 despreads the baseband signal after orthogonal demodulation by a cell-specific scramble code to obtain a despread signal, and then a predetermined channelization code (for example, each channel temporarily used by each terminal). Despreading, which is assigned to (1), separates (1) user data and control signals, and (2) cell-end notification signals from the mobile terminal.

The adjacent received signal power calculating unit 31 receives the despread signal obtained by despreading, calculates the adjacent received signal power Pcell N (n = 1 to N), and the total adjacent received signal power calculating unit 32 The total neighbor received signal power (Pother) is calculated by Equation (2). The comparator 33 compares the total neighboring received signal power Pother with the threshold power Pth1, and inputs the comparison result to the flag generator 18 and the sender base station determiner 34 of the flag signal. When the total neighboring received signal power is equal to or greater than the threshold power (Pother? Pth), the transmission destination base station determination unit 34 determines the transmission base station of the flag signal and inputs it to the flag generation unit 18. The base station to which the flag signal is to be transmitted is a base station according to the ranked upper m cells, which ranks adjacent received signal powers Pcell 1 to Pcell N in ascending order. Alternatively, the base station to which the flag signal is transmitted is a base station corresponding to a cell equal to or greater than the threshold Pth2 among the neighboring received signal powers Pcell 1 to Pcell N.

If the total neighboring received signal power is equal to or greater than the threshold power (Pother? Pth), the flag generation unit 18 generates a flag signal Fint for requesting interference reduction, and the sender base station name and the destination to the flag signal Fint. The base station name is attached to the neighboring base station communication interface unit 19, and the transmitting unit 19a transmits the flag signal Fint to the transmitting base station.

On the other hand, when the reception unit 19b of the neighbor base station communication interface unit 19 receives the flag signal Fint from the neighbor base station, the reception unit 19b receives the flag signal Fint and the source base station name of the flag signal Fint. The uplink schedule unit 20 is notified. When the uplink scheduler 20 receives the flag signal reception notification, the uplink scheduler 20 inputs the name of the sender base station of the flag signal Fint to the terminal near terminal specification unit 21.

Since the cell-end near terminal specification part 21 inputs the cell-end vicinity determination result which the mobile terminal sent according to the process of FIG. 8 during communication is input, based on the result, the mobile terminal exists in a cell terminal, ie, During each communication, the mobile terminal identifies whether the mobile terminal is interfering with the base station which sent the flag signal Fint, and notifies the uplink scheduler 20 of the mobile terminal that is interfering.

Upon receiving this notification, the uplink scheduler 20 instructs the control signal generator 22 to limit the uplink data transmission of the mobile terminal that is causing the interference. The control signal generation section 22 generates a control signal for instructing to temporarily lower the transmission rate of the upstream data or temporarily stops the transmission of the upstream data by the instruction, and transmits it to the indicated mobile terminal. The multiplexer 23 multiplexes the control signal and the user data generated by the user data generator 24, and transmits the mobile terminal from the antenna 27 through the encoder / modulator 25 and the transmitter radio 26. To transmit.

The mobile terminal limited to the uplink data transmission temporarily lowers the transmission rate of the uplink data or temporarily stops the uplink data transmission. If the uplink scheduler 20 does not receive the flag signal Fint, the uplink scheduler 20 controls to cancel the restriction of the uplink transmission data of the mobile terminal.

According to the second embodiment, the same effects as in the first embodiment can be obtained. Further, according to the second embodiment, when the total neighboring received signal power (interference power) becomes large, the interference power from neighboring cells which give a large interference is reduced, so that the throughput can be improved in the whole system.

Claims (12)

In the interference reduction method of the base station which performs communication with the mobile terminal which exists in the cell under management, and performs control which reduces the interference from the mobile terminal which exists in an adjacent cell, Measure the total interference power received from mobile terminals in all neighboring cells, If the total interference power is greater than a set value, the base station of all neighboring cells The interference reduction method of the base station characterized in that. The method of claim 1, The measuring step of the total interference power, While measuring the total received power of the base station, the received power from all mobile terminals under management is measured as desired power, The total interference power is calculated by subtracting the desired power from the total received power. In the interference reduction method of the base station which performs communication with the mobile terminal which exists in the cell under management, and performs control which reduces the interference from the mobile terminal which exists in an adjacent cell, For each adjacent cell, measure the interference power received from all mobile terminals in the neighbor cell, Calculating the total interference power received from the mobile terminals of all neighbor cells by summing the interference powers for each neighbor cell; If the total interference power is larger than a set value, the base station of a predetermined number of neighboring cells having a large interference power or a base station of a neighboring cell having an interference power larger than the set value is requested to reduce the interference. The interference reduction method of the base station characterized in that. The method according to any one of claims 1 to 3, The base station that has received the interference reduction request determines the mobile terminal that may be interfering with the base station of the interference reduction request source, And reducing the transmission rate of the uplink data of the mobile terminal temporarily or temporarily stopping the transmission of the uplink data. The method of claim 4, wherein The determining step of the interfering mobile terminal, For each mobile terminal, the reception power from the base station during communication and the reception power from the interference reduction request source base station are measured, and if the difference between the two reception powers is less than or equal to the set value, it is determined that the interference reduction request source base station is interfering. An interference reduction method of a base station. The method of claim 5, The reception power from the base station and the interference reduction request source base station during the communication is measured based on the downlink common pilot signal from each base station. A base station that communicates with a mobile terminal existing in a cell under management and controls to reduce interference from the mobile terminal existing in an adjacent cell. An interference power measurement unit for measuring total interference power received from mobile terminals of all adjacent cells; A comparator for comparing the total interference power with a set value; If the total interference power is greater than the set value, the interference reduction request unit for requesting to reduce the interference to the base stations of all neighboring cells Base station comprising a. The method of claim 7, wherein The interference power measuring unit, A total reception power measurement unit measuring a total reception power of a base station; A total desired power measurement section for measuring received power from all mobile terminals under management as desired power; An interference power calculating unit that calculates the total interference power by subtracting the desired power from the total received power. Base station comprising a. A base station that communicates with a mobile terminal existing in a cell under management and controls to reduce interference from the mobile terminal existing in an adjacent cell. An interference power measurement unit for measuring interference power received from all mobile terminals in the neighbor cell for each neighbor cell; A total interference power calculator for calculating total interference powers received from mobile terminals of all neighboring cells; If the total interference power is greater than the first set value, it is required to reduce the interference to the base station of a predetermined number of neighboring cells with large interference power or to the base station of the neighboring cell with the interference power larger than the second set value. Interference Reduction Request Base station comprising a. The method according to claim 7 or 9, The base station further comprises a communication interface for directly communicating with an adjacent base station. The method according to any one of claims 7 to 9, An interfering mobile terminal discrimination unit for discriminating a mobile terminal that may be interfering with the base station that has issued the interference reduction request; A scheduler for temporarily lowering a transmission rate of uplink data of the mobile terminal or temporarily stopping transmission of uplink data The base station further comprises. The method of claim 11, The interfering mobile terminal discrimination unit checks for each mobile terminal whether the difference between the received power from the base station during communication and the received power from the interference reducing request source base station is less than or equal to a set value, and if so, the mobile terminal determines the interference reducing requesting base station. A base station for determining that there is a possibility of interference.

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