JP4595911B2 - Transmission power control system, control method, base station, and mobile station - Google Patents

Description

  The present invention relates to a transmission power control system, a control method, a base station, and a mobile station, and in particular, when a soft handover is performed in a cellular communication system, a balance adjustment start is performed when transmission power balance adjustment is performed from a plurality of base stations to one mobile station. The present invention relates to a timing determination method.

  Since many lines use the same frequency in a code division multiplexing cellular system, the received power (desired signal power) of a signal on one line is interference wave power that interferes with other lines. . Accordingly, in the uplink transmitted from the mobile station and received by the base station, if the desired wave power exceeds a predetermined value, the interference wave power increases, and therefore the intra-channel capacity decreases. In order to prevent this, it is necessary to strictly control the transmission power of the mobile station. In the uplink transmission power control, the base station measures the desired signal power, compares it with the control target value, and when the desired signal power is large, the uplink transmission power (hereinafter “ Also, an uplink control command for reducing uplink transmission power is transmitted. When the desired signal power is small, an uplink control command for increasing uplink transmission power is transmitted to the mobile station. Then, the mobile station increases or decreases the uplink transmission power according to the uplink control command. Transmission of the uplink control command in this transmission power control uses a downlink transmitted from the base station to the mobile station.

  On the other hand, also in the downlink, a high channel capacity is realized by performing transmission power control so that the ratio of desired wave power and interference wave power becomes a predetermined amount. Specifically, in downlink transmission power control, the mobile station measures the downlink reception quality, compares it with the control target value, and if the reception quality is higher than the control target value, A downlink control command for reducing downlink transmission power (hereinafter also referred to as “downlink transmission power”) is transmitted, and when the reception quality is lower than the control target value, the downlink is configured to increase the downlink transmission power to the base station. Send a control command. Then, the base station increases or decreases the downlink transmission power according to the downlink control command.

  However, in this method, when the propagation loss from the mobile station to the base station increases rapidly as the location of the mobile station moves, the base station cannot receive the downlink control command from the mobile station. At the same time, the mobile station may not be able to receive an uplink control command from the base station. At this time, in the conventional method in which the base station controls the downlink transmission power only by the downlink control command from the mobile station, if the state in which the propagation loss continues to increase continues, the base station sends the downlink control command from the mobile station. Since the base station does not increase the downlink transmission power while the mobile station cannot receive the uplink, the mobile station cannot receive the uplink control command from the base station, and the uplink transmission power of the uplink signal can be increased. However, the problem that communication with the base station is interrupted continues.

  In general, the portion of user information, such as voice and data, of the signal received by the base station is relatively comparative so that it can be accurately decoded by performing error correction even if a reception error occurs instantaneously. A long amount of information is encoded together, and a long amount of information is decoded together over a relatively long time during decoding.

  However, when the mobile station moves at high speed, when performing high-speed transmission power control that keeps the reception quality constant by following high-speed fading fluctuations in the propagation path, even if user information is accurately decoded Even if it is possible, the determination of the control command needs to be performed instantaneously. Therefore, the determination of the control command cannot obtain an effect such as error correction and is relatively erroneous.

  Such a determination error in the control command is generated in connection with increase / decrease in the propagation loss, and therefore is likely to occur continuously. If the control command determination error continues, the base station cannot control the downlink transmission power of the downlink signal according to the downlink control command from the mobile station, and the mobile station cannot accurately receive the downlink signal. There is a possibility. On the other hand, in this state, since the mobile station cannot receive the uplink control command from the base station included in the downlink signal, the uplink transmission power of the uplink signal may not be controlled. In this case, the base station may not only frequently receive downlink control command determination errors among uplink signals, but may also be unable to receive user information accurately. Even in such a case, there is a problem that communication between the base station and the mobile station continues to be interrupted.

  In cellular systems, when a mobile station moves between cells, there is a technique called soft handover that switches a line between cells while setting a line simultaneously with a plurality of base stations near the boundary. This technique is particularly important in a cellular system that employs a code division multiplexing system.

  It is important that the uplink transmission power control during the execution of soft handover is performed so that the mobile station can receive the uplink control commands of all base stations that may minimize the uplink propagation loss.

  For this reason, a method is conceivable in which the downlink transmission power is controlled so that the desired signal power from each base station is equal in the mobile station. However, in this method, since the base station with a large propagation loss to the mobile station sets the downlink transmission power to that extent, the interference wave power increases and the downlink capacity decreases. As a method for suppressing a decrease in downlink capacity, there is a method of performing control so that the downlink transmission power of each base station is equal to each other.

  In this method, the received power of the uplink control command from the base station with a small propagation loss to the mobile station is larger than the received power of the uplink control command from the base station with a large propagation loss. The probability of failing to receive an uplink control command from a base station with a large loss increases. In such a case, the uplink transmission power is mainly controlled by an uplink control command from a base station having a small propagation loss, and therefore it does not become a problem. On the other hand, when the difference in propagation loss is small, it is important to control the uplink transmission power according to both base stations. In such a case, since each uplink control command can be received with substantially equal power, the probability that both uplink control commands can be accurately received is increased. Therefore, for uplink transmission power control, it is possible to receive all uplink control commands from base stations that may minimize uplink propagation loss.

  In addition, during execution of soft handover, when the magnitude of the propagation loss from the mobile station to each base station is switched at a high speed due to fading fluctuation, etc., the base station that transmits to the mobile station is changed accordingly. The base station with the smallest propagation loss is transmitting at any moment without switching to high speed. At this time, if the downlink transmission powers of the base stations are not equal to each other, the reception quality is likely to deteriorate because the reception quality increases and decreases when the base station with the smallest propagation loss is switched. However, if the downlink transmission powers of the respective base stations are equal to each other, the reception quality is further improved by the diversity effect that the reception quality is kept substantially constant even when the base station that minimizes the propagation loss is switched. You can also.

  In such downlink transmission power control, the mobile station measures the downlink reception quality, compares it with the control target value, and if the reception quality is higher than the control target value, A downlink control command for decreasing the downlink transmission power is transmitted. When the reception quality is lower than the control target value, a downlink control command for increasing the downlink transmission power is transmitted to the base station. During execution of soft handover, a plurality of base stations receive a downlink control command transmitted by the mobile station. Each base station performs control while increasing or decreasing the downlink transmission power in the same manner according to the downlink control command. Therefore, if the initial values of the downlink transmission power of the respective base stations are equal to each other, the increase and decrease are repeated in the same manner. Therefore, if there is no error in receiving the downlink control command, the downlink transmission power remains the same as each other. Will be controlled.

  However, in this method, the base station with the smallest propagation loss to the mobile station can receive the downlink control command from the mobile station almost accurately, but the base station with the large propagation loss from the mobile station can receive the downlink control command. Since telegraph power is small, reception of downlink control commands from mobile stations often fails. Therefore, the downlink transmission powers of the respective base stations cannot be kept equal to each other.

  Therefore, even if an error occurs in receiving a downlink control command in each base station during execution of soft handover, the cellular stations are configured so that each base station can transmit with substantially the same power to obtain a high line capacity. Patent Document 1 proposes a transmission power control method in a communication system.

  FIG. 6 shows a schematic configuration of the cellular communication system. In FIG. 6, the service area is divided into first and second cells 11 and 12, and the first and second base stations (# 1) 21 and 22 are respectively included in the first and second cells. (# 2) is arranged, and there are first and second mobile stations 61 and 62. The first and second base stations 21 and 22 are connected to a common control station 71, and the control station 71 is further connected to a communication network (not shown) including other control stations. Although not shown in the figure, this cellular communication system includes a number of other base stations, and a number of mobile stations exist in each cell.

  The first and second base stations 21 and 22 transmit the first and second pilot signals 31 and 32 with constant transmission power, respectively. Each of the mobile stations 61 and 62 includes an SIR (ratio between desired wave and interference power) measuring device for measuring the power of the pilot signal, and the received power of the first and second pilot signals 31 and 32 is measured. Measure each. The mobile station switches the pilot signal measuring unit to a short time slot unit as shown in FIG. 7, and measures each of the pilot signals of a plurality of base stations once for each frame. In the example of FIG. 7, since there are 6 slots in one frame, pilot signals from up to 6 base stations can be measured. In FIG. 6, 41, 41a, 41b, and 42 are downlink signals, and 51 and 52 are uplink signals.

  Next, transmission power control for the downlink in the cellular communication system shown in FIG. 6 will be described with reference to FIG. FIG. 8 is a flowchart for determining the downlink transmission power of the downlink in response to the downlink control command from the mobile station during execution of the soft handover. Here, it is assumed that the downlink transmission power P is represented by a decibel value.

  When the base station starts a soft handover with the mobile station, if the base station is a main base station that has been transmitting to the mobile station, the downlink transmission power P is transmitted to the mobile station. If the base station is an auxiliary base station that newly starts transmission to the mobile station, the downlink transmission power P is set to the initial value P0. Further, the main base station and the auxiliary base station are notified of the frame number for starting the soft handover from the control station 71. The initial value P0 is an arbitrary value in the downlink transmission power control range.

  First, when a transmission power balance control message between a plurality of base stations arrives from the control station 71, the base station resets the frame counter to I = 0 (step S201), and increments I by 1 for each frame (step S202). Here, the downlink control command (TPC: Transmission Power Control) is notified from the mobile station at regular intervals, but this newly notified downlink control command exists (step S203), and the downlink control command is the power. If an increase is instructed (step S204), the downlink transmission power P is increased by a predetermined value ΔP (step S205), and if the downlink control command indicates a decrease in power, the downlink The transmission power P of the line is decreased by a predetermined value ΔP (S206).

The above processes S203 to S206 are repeated for the number Nperiod of frames as a predetermined balance adjustment period, and when that period has elapsed (step S207), that is, when I = Nperiod, A value obtained by multiplying the difference (C−P) between the reference power (also referred to as a target value or a reference value) C and the downlink transmission power P before update by the coefficient (1−r) is added to the downlink transmission power P. ,
P = P + (1-r) (CP)
(Step S208). The coefficient r is a predetermined constant value, and the coefficient r is 0 or more and less than 1. C is an intermediate power between the maximum power Pmax and the minimum power Pmin of the downlink transmission power P.

  If the updated transmission power P is larger than the maximum power Pmax, the downlink transmission power P is set to the maximum power Pmax (steps S209 and S210). If the updated transmission power P is smaller than the minimum power Pmin, The downlink transmission power P is set to the minimum power Pmin (steps S211 and S212). Then, the process is repeated again from step S202.

  According to this method, since the initial values of the downlink transmission power of the main base station and the auxiliary base station are different at the time of starting the soft handover, the downlink transmission power P1 of the main base station and the downlink transmission power P2 of the auxiliary base station There is a difference | P1-P2 | If one or more base stations fail to receive the downlink control command, the difference | P1-P2 | between the downlink transmission powers P1 and P2 may increase. However, in the control of steps S203 to S206, that is, in the part where the downlink transmission power is increased or decreased by the downlink control command from the mobile station, each base station receives the notification of the same downlink control command. If the station does not fail to receive the downlink control command, the downlink transmission powers P1 and P2 are increased or decreased in the same manner, so that the difference | P1-P2 | between these downlink transmission powers P and P2 does not change.

  On the other hand, for each frame number of I = Nperiod, the main base station and the auxiliary base station respectively set the downlink transmission powers P1 and P2 to P1 + (1−r) (C−P1) and P2 + (1−r) (C− Since the update is performed simultaneously with P2), the difference | P1-P2 | between these downlink transmission powers P1 and P2 is r | P1-P2 |. Thus, the downlink transmission power difference | P1-P2 | becomes r times every time Nperiod. Since the coefficient r is smaller than 1, unless the downlink transmission power difference | P1−P2 | increases due to a reception error of a new downlink control command, the difference in control amount decreases to 0 by a geometric series. Converge. Also, even if the downlink transmission power difference | P1-P2 | increases due to the occurrence of a new downlink control command reception error, the difference | P1-P2 | can be reduced. Accordingly, even if reception of the downlink control command fails, the downlink transmission power Pi (i = 1, 2) is exchanged between the base stations without exchanging information regarding the downlink transmission power between the base stations. Can be set to a value approximately equal to.

  That is, after increasing or decreasing the downlink transmission power by the control in steps S203 to S206, the difference in the downlink transmission power of the plurality of base stations is reduced by the control in steps S207 to S212 (balance adjustment). At the same time, the downlink transmission power is updated so as to approach the reference power C defined in common among the plurality of base stations.

  In this way, while the mobile station is executing soft handover, each base station transmits an uplink control command for uplink transmission power control to the mobile station with approximately equal power between the base stations. When the propagation loss from each base station to the mobile station is almost the same, and there is a possibility that the uplink transmission loss may be minimized in any base station, the mobile station can receive all the uplink control commands. Therefore, the mobile station can control the uplink transmission power so that the desired wave power does not become excessive for any base station.

In addition, when soft handover is executed, even if the magnitude of the propagation loss from the mobile station to each base station changes at high speed due to fading fluctuations, etc., the diversity effect that keeps the reception quality almost constant The reception quality at the station can be further improved. In this way, by controlling the uplink transmission power so that the desired signal power does not become excessive, the channel capacity of the uplink increases, and if the reception quality at the mobile station can be improved by the diversity effect, the reception quality becomes constant. As a result, the line capacity of the downlink increases.
JP 11-340910 A

  In this way, in each base station, the transmission power is decreased by the adjustment amount during the transmission power balance adjustment period. This adjustment amount is determined based on the transmission power at the start of the adjustment period and the reference value C that is the reference value. Is a predetermined percentage of the difference. This state is shown in FIG. In the figure, Pbali (i = 1, 2) is the amount of power to be adjusted, and T1, T2, T3 indicate the adjustment timing. In the figure, the width of Pbali is shown with r = 0.

  Since the transmission power of each base station increases / decreases in accordance with the same transmission power control command (TPC bit) from the mobile station, the transmission power increases / decreases in the same way if there is no reception error in the transmission power control command. At this time, if the start time of the adjustment period is the same timing in each base station, when the transmission power of one of the two base stations is large (P1> P2), the transmission power at the start time of the adjustment period Since the difference Pbal from the reference value C is also larger than that of the other base station (Pbal1> Pbal2), the one transmission power (P1) is greatly reduced during the adjustment period. In this way, since the base station having a large transmission power greatly reduces the transmission power, the difference in the transmission power between the base stations becomes small, and the balance is adjusted.

  However, as shown in FIG. 9B, if the start time of the adjustment period is different for each base station, such as T1 and T1 ′, the transmission power constantly changes according to the transmission power control command. Even if the transmission power of one base station is larger than that of the other base station (P1> P2), the adjustment start time T1 of the former base station is a moment when the transmission power is relatively small, and the latter If the base station adjustment start time is a moment when the transmission power is relatively large, the latter base station has a larger difference between the transmission power at the start time of the adjustment period and the reference value C than the former (Pbal1 < Pbal2), the transmission power during the adjustment period is greatly reduced. For this reason, the difference in transmission power between base stations becomes large, and power balance becomes difficult. As a result, there is a problem that transmission power balance between base stations cannot be achieved and the line capacity is reduced.

  As described above, the phenomenon that the start time of the adjustment period is different for each base station, such as T1 and T1 ′, is that the control message for adjusting the transmission power balance from the control station 71 to each of the base stations 21 and 22 is This is caused by variations in transmission delay between base stations. The example in case the reception timing of the control message for the conventional power balance adjustment concerning Fig.2 (a) differs between base stations is shown. In FIG. 2A, Nperiod = 2 is set as the balance adjustment period, and the frame numbers are assumed to be a total of 8 numbers from 0 to 7, and this is repeated. In this way, in the conventional example, since the difference in the reception timing of the power balance control message always continues thereafter, the calculation timing of Pbal between the base stations is always shifted, as shown in FIG. 9B. The reverse phenomenon of Pbal1 and Pbal2 occurs.

  The object of the present invention is that even if there are variations in the transmission delay of control messages between the control station and the base station and the transmission power balance adjustment start time is different, the adjustment start timings coincide with each other while the adjustment period Nperiod is repeated. It is to obtain a transmission power control system, a method thereof, a base station and a mobile station that can achieve synchronization and can balance the transmission power between base stations to increase the channel capacity.

According to the present invention,
A plurality of cells, a plurality of base stations respectively disposed in the plurality of cells, a mobile station moving in the cells, and a plurality of base stations are provided in common. A transmission power control system in a cellular communication system, comprising: a control station that transmits a control command including a balance adjustment period for adjusting the balance of transmission power to a mobile station to the base station;
Each of the base stations
Means for controlling to start the balance adjustment period from a frame number determined based on the number of frames in the balance adjustment period;
When the frame number of the transmission frame to the mobile station is CFN , a transmission power control system is provided that includes means for resuming the balance adjustment at a frame where CFN becomes 0 .

According to the present invention,
A plurality of cells, a plurality of base stations respectively disposed in the plurality of cells, a mobile station moving in the cells, and a plurality of base stations are provided in common. A transmission power control method in a cellular communication system, including a control station that transmits a control command including a balance adjustment period for adjusting the balance of transmission power to a mobile station to the base station,
In each of the base stations:
Controlling to start the balance adjustment period from a frame number determined based on the number of frames in the balance adjustment period;
And a step of resuming the balance adjustment at a frame in which CFN is 0 when the frame number of a transmission frame to the mobile station is CFN .

According to the present invention,
A plurality of cells, a plurality of base stations respectively disposed in the plurality of cells, a mobile station moving in the cells, and a plurality of base stations are provided in common. A base station in a cellular communication system including a control station that transmits a control command including a balance adjustment period for adjusting balance of transmission power to a mobile station to the base station,
Means for controlling to start the balance adjustment period from a frame number determined based on the number of frames in the balance adjustment period;
When the frame number of the transmission frame to the mobile station is CFN , a base station is provided that includes means for resuming the balance adjustment at a frame where CFN becomes 0 .

According to the present invention,
A plurality of cells, a plurality of base stations respectively disposed in the plurality of cells, a mobile station moving in the cells, and a plurality of base stations are provided in common. To cause a computer to execute a transmission power control method at a base station in a cellular communication system including a control station including a control instruction including a balance adjustment period for adjusting balance of transmission power to a mobile station to the base station The program of
Control to start the balance adjustment period from a frame number determined based on the number of frames in the balance adjustment period;
When the frame number of the transmission frame to the mobile station is CFN , a program is obtained that includes a process of resuming the balance adjustment with a frame in which CFN becomes 0 .

According to the present invention,
A plurality of cells, a plurality of base stations respectively disposed in the plurality of cells, a mobile station moving in the cells, and a plurality of base stations are provided in common. look including a control station for transmitting a control command including a balance adjustment period for making the balance adjustment of the transmission power to the mobile station to the base station,
Each of the base stations controls the start of the balance adjustment period to start from a frame number determined based on the number of frames in the balance adjustment period, and sets the frame number of a transmission frame to the mobile station as CFN A mobile station in a cellular communication system having means for resuming the balance adjustment in a frame in which CFN is 0,
A mobile station characterized in that a transmission power control command for controlling the transmission power is transmitted to the base station.

  The operation of the present invention will be described. When a mobile station is in soft handover with a plurality of base stations, when a balance adjustment of transmission power from a plurality of base stations to the mobile station is performed, the start of a balance adjustment period for performing the balance adjustment in each base station Is controlled from a frame number determined based on the number of frames in the balance adjustment period. Thereby, even when the reception timing of the balance control message from the control station is deviated at each base station due to variations in transmission delay, the balance calculation timing for balance adjustment with each other while repeating the balance adjustment period, Synchronization between base stations is achieved, and transmission power balance between base stations can be accurately achieved.

  When the balance control message is received by each base station before and after the frame number of the transmission frame to the mobile station changes discontinuously from the maximum value to the minimum value (or from the minimum value to the maximum value), the balance adjustment is performed. Due to the relationship between the period and the total number of frames, the balance adjustment timing may shift between base stations. However, even if the frame number is repeated from the maximum value to the minimum value by resuming the balance adjustment period from the frame defined by the same rule as that for determining the frame, the balance adjustment period starts from the maximum value to the minimum value. The frame number that is a candidate for the start of the adjustment period remains unchanged. Therefore, the balance calculation timing can be synchronized between the base stations, and the transmission power balance between the base stations can be accurately obtained.

  Further, assuming that the total number of frame numbers of transmission frames to the mobile station is CFN and the balance adjustment period that is the period of balance calculation is Nperiod, there exists k satisfying the relationship of k × Nperiod = CFNmax (k is an integer). By selecting the value to be used, even if the frame number returns from the maximum value to the minimum value and repeats, the frame number that is a candidate for the start of the balance adjustment period remains unchanged. Therefore, even if the balance control message is received by each base station before and after the frame number changes discontinuously from the maximum value to the minimum value (or from the minimum value to the maximum value), the balance calculation timing is not changed between the base stations. Synchronization can be established and the transmission power balance between the base stations can be accurately obtained.

  According to the present invention, when the reception timing of the control signal due to variations in the transmission delay of the control signal from the control station to the base station is different, the starting point of the first adjustment period may be different, but Since the balance adjustment timing is synchronized, this has the effect of improving the balance of transmission power between the base stations and increasing the line capacity.

  In particular, in the invention for performing resumption control, even if k is selected as a value that does not have k × CFNmax, Nperiod can be selected regardless of the value of CFNmax because the balance adjustment timing can be synchronized. . In order to satisfy a predetermined requirement standard for transmission power balance between base stations, the frequency of balance adjustment needs to be equal to or higher than a predetermined frequency, but Nperiod can be selected regardless of the value of CFNmax. The frequency of adjustment can be minimized above a predetermined frequency. For this reason, there is an effect that it is possible to reduce the control processing for synchronizing the timing of balance adjustment.

  Further, in the invention in which k period is selected such that k × Nperiod = CFNmax as Nperiod, restart control is not required even when the total number of frames is limited, so that the timing of balance adjustment is synchronized. There is an effect that the control processing can be reduced.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic configuration diagram of a base station used in the embodiment of the present invention. The system configuration example is the same as that shown in FIG. 6, and each of the base stations (# 1) 21 and (# 2) 22 Assume that the downlink frame configuration from the mobile station 61 to the mobile station 61 is the same as in the example of FIG. 7, and the frame numbers of frames transmitted at the same time are the same between base stations.

  Referring to FIG. 1, the base station includes an antenna 201, a transmission / reception sharing unit 202, a reception circuit 203 that performs reception processing of a reception signal and outputs the reception signal to a terminal 207, and SIR measurement that performs downlink SIR measurement. Unit 204, a transmission power control unit 205 that controls transmission power with reference to the SIR measurement result, etc., and a control from transmission power control unit 205 by superimposing a transmission signal and SIR measurement result signal from terminal 208 And a transmission circuit 206 that performs amplification control according to the above. Also included is a CPU (control device) 209 for controlling the operation of these units, and a read-only recording medium (ROM) 210 in which a program is stored in advance for controlling the operation of the CPU. And

  In the present invention, as shown in FIG. 9 (b), the power balance control message from the control station 71 is caused by the base station # 1 and the base station # 2 being shifted like T1 or T1 ′. This is to prevent the difference in transmission power between them becoming large and becoming unbalanced. For this purpose, as shown in FIG. 2B, the power balance adjustment start timing is the same between the base stations so as to synchronize with each other.

  In the example of FIG. 2B, the frame number CFN is composed of 8 frames of 0 to 7 (the total number of frames (numbers) is CFNmax, CFNmax −1 = 7), and this is repeated. In which Nperiod = 2 is shown.

If this is generally expressed, the following three modes can be considered. First, as a first aspect,
mod (CFN, m × Nperiod) = L
(Where m is a natural number, L is a natural number less than 0 or m × Nperiod and is common to all base stations), and the balance adjustment period is controlled to start. That is, the balance adjustment is started with a frame having a frame number such that the remainder obtained by dividing the frame number CFN by m × Nperiod is “L”. Thereafter, the balance is adjusted every Nperiod. In the example of FIG. 2B, this corresponds to the case of m = 1 and L = 0. In FIG. 2, the calculation timing of Pbal is shown as the head of the frame, but actually, it may be a predetermined timing (for example, the S slot) of these frames.

  As a second aspect, when the frame number CFN is expressed by an m × Nperiod base number (m is a natural number), the balance adjustment is started from a frame in which the number of the first digit becomes a predetermined value. Thereafter, the balance is similarly adjusted every Nperiod. In the example of FIG. 2B, this corresponds to the case where m = 1 and the predetermined value = 0.

  As a third aspect, the balance adjustment is started from a frame in which the frame number CFN is m × Nperiod + L. Note that m is 0 or a natural number, and L is 0 or a natural number common to all base stations. In the example of FIG. 2B, this corresponds to the case of m = 1 and L = 0.

  FIG. 3 is a flowchart showing the operation of the base station in each aspect described above, and the control operation of FIG. 3 is started in response to the arrival (reception) of the power balance control message from the control station. First, the current frame number CFN is acquired (step S11), and a frame counter (not shown) I is set to I = mod (CFN, Nperiod) (step S12). Then, Pbal = (1-r) (CP) shown in FIG. 9 is reset to 0 (step S13). In FIG. 9, the reference value C is depicted as a level that is smaller than the transmission power P1 and P2 of each base station. In this case, Pbal = (1-r) (PC). In this example, the case where the reference value C is set larger than the transmission powers P1 and P2 of each base station will be described below.

  Next, the slot counter (not shown) J is reset to J = 0 (step S14), and the system waits for reception of the TPC bit (step S15). In response to receiving the TPC bit, if the TPC bit is a power increase command (step S16), the transmission power P is controlled to increase by a predetermined amount S1 (step S17). P is controlled to decrease by a predetermined amount S1 (step S18). If Pbal is larger than the predetermined amount S2 (step S19), the transmission power P is controlled to increase by the predetermined amount S2 (step S20), and Pbal is controlled to decrease by the predetermined amount S2. (Step S21).

  In step S19, if Pbal is smaller than the predetermined amount S2, Pbal is compared with -S2 (step S22). If Pbal is smaller than -S2, P-S2 is processed (step S22). S23), Pbal is controlled to increase by a predetermined amount S2 (step S24). After steps S2l and S24 and if “NO” in step S22, the slot counter J is incremented by 1 (step S25).

  The above steps S15 to S25 are repeated for the number of slots Nslot constituting one frame (step S26). When Nslot is repeated and J = Nslot, the frame counter I is incremented by 1 and the processing of the next frame is started (step S28). At this time, the processes of steps S14 to S27 are repeated until I becomes equal to Nperiod.

  When I = Nperiod, the adjustment of Pbal is started. That is, Pbal = (1-r) (CP) is calculated (step S29), and the frame counter I = 0 is reset (step S30). Then, the process returns to step S14 again, and transmission power control is started from the first slot J = 0 of the next frame.

  With the above processing, the transmission power of each base station in the downlink is controlled by the TPC bit for each slot, and the power balance between the base stations due to variations due to the transmission delay of the power balance control message from the control station. Thus, the start timing can be synchronized.

  In the operation flow shown in FIG. 3, the frame number CFN takes 0 to the maximum value (CFNmax −1) and the total number of frames is repeated at CFNmax (for example, in FIG. In this case, the operation flow is satisfied only when CFNmax is an integral multiple of Nperiod. However, if CFNmax is not an integral multiple of Nperiod, for example, as shown in FIG. 4, the calculation timing of Pbal of base station # 1 starts from frame number CFN = 4 and is executed every Nperiod = 3 thereafter. Then, in the next frames 0 to 7, the frame number CFN = 2 is the calculation timing. At this time, if the arrival timing of the power balance control message to the base station # 2 is the frame number CFN = 1, the base station # 2 starts the calculation timing of Pbal from the frame number CFN = 4. . Then, the calculation timings of both base stations cannot be synchronized, and a problem still occurs.

  Therefore, in such a case, the base station # 1 resets the frame number CFN to “0”, and the frame number of m × Nperiod + L (m is 0 or a natural number, L is 0 or a natural number common to all base stations). Then, by restarting the calculation timing, the base stations # 1 and # 2 can be synchronized as shown in FIG. In the example of FIG. 4, m = 0 and L = 1.

  Thus, when the frame number changes discontinuously from the maximum value to the minimum value (or from the minimum value to the maximum value), from the frame defined by the same rule as the rule for determining the frame of the start of the balance adjustment period, By resuming the balance control period, synchronization can be achieved.

  FIG. 5 shows an operation flow of the base station in such a case, and steps equivalent to those in the operation flow of FIG. 3 are denoted by the same reference numerals. Explaining only the difference from FIG. 3, after step S27, a frame number counter CFN is provided, and the value of this frame number counter is incremented by 1 (step S31). Then, it is determined whether or not the value of the frame number counter has reached the maximum value CFNmax (step S32). If the result of this determination is “YES”, the frame number counter CFN is reset to “0” ( Step S33). Then, the process proceeds to step S29.

  In the description of FIGS. 4 and 5, the value of the frame number counter is in ascending order, but the same applies to the case of descending order.

  In FIG. 5, Pbal is calculated by calculating the last power value P of each Nperiod frame including CFN = 0. 3 and FIG. 5, Pbal is calculated as Pbal = (1−r) (C−P), and Pbal is updated for each calculation. Pbal = Pbal + (1-r) (CP) may be an example of integration.

  It should be noted that by selecting an integer k such that k × Nperiod = CFNmax as Nperiod, the above-described embodiment for resetting the frame number counter CFN to “0” is not necessary. is there. In this case, the N station may be selected by the base station so that the integer k exists such that k × Nperiod = CFNmax, but is generally selected by the control station, and this is notified to each base station. Will be. Therefore, in each base station, the balance adjustment is started from the frame of m × Nperiod + L, so that the frame number CFN includes the case of counting down from the maximum value to the minimum value (or vice versa, from the minimum value to the maximum value). ), The calculation timings of both base stations can be synchronized thereafter. For example, when CFNmax = 256, Nperiod is selected from 1, 2, 4, 8, 16, 32, 64, 128, and 256.

  3 and 5 are processed by the CPU 209 reading and executing a program stored in a recording medium such as the ROM 210 shown in FIG. Although a functional block diagram and an operation flow in the control station are not particularly shown, similarly, an operation control program is stored in advance in a recording medium and executed while being read by a CPU or the like. It is clear that operations such as transmission and selection of Nperiod are possible.

It is a schematic block diagram of the base station of the Example of this invention. It is a figure which shows the calculation timing of the transmission power balance by this invention by contrast with a prior art example. It is a flow which shows operation | movement of one Example of the base station of this invention, Comprising: When CFNmax is an integral multiple of Nperiod. It is a figure which shows the operation example when CFNmax is not an integral multiple of Nperiod. It is a flow which shows operation | movement of the other Example of the base station of this invention, and is when CFNmax is not an integral multiple of Nperiod. 1 is a system configuration diagram to which the present invention is applied. It is a frame block diagram in this invention. It is a base station operation | movement flowchart in a conventional system. It is a figure explaining the case where the balance adjustment of transmission power does not become favorable when the power balance control message from a control station arrives at the timing which differs between base stations due to the dispersion | variation in transmission delay.

Explanation of symbols

11, 12 cells 21, 22 base station 61, 62 mobile station 71 control station 201 antenna 202 transmission / reception shared circuit 203 reception circuit 204 SIR measurement unit 205 transmission power control unit 206 transmission circuit 209 CPU
210 ROM (recording medium)

Claims (5)

A plurality of cells, a plurality of base stations respectively disposed in the plurality of cells, a mobile station moving in the cells, and a plurality of base stations are provided in common. A transmission power control system in a cellular communication system, comprising: a control station that transmits a control command including a balance adjustment period for adjusting the balance of transmission power to a mobile station to the base station;
Each of the base stations
Means for controlling to start the balance adjustment period from a frame number determined based on the number of frames in the balance adjustment period;
A transmission power control system comprising: means for resuming the balance adjustment at a frame in which CFN is 0 when a frame number of a transmission frame to the mobile station is CFN . A plurality of cells, a plurality of base stations respectively disposed in the plurality of cells, a mobile station moving in the cells, and a plurality of base stations are provided in common. A transmission power control method in a cellular communication system, including a control station that transmits a control command including a balance adjustment period for adjusting the balance of transmission power to a mobile station to the base station,
In each of the base stations:
Controlling to start the balance adjustment period from a frame number determined based on the number of frames in the balance adjustment period;
And a step of resuming the balance adjustment at a frame in which CFN is 0 when a frame number of a transmission frame to the mobile station is CFN . A plurality of cells, a plurality of base stations respectively disposed in the plurality of cells, a mobile station moving in the cells, and a plurality of base stations are provided in common. A base station in a cellular communication system including a control station that transmits a control command including a balance adjustment period for adjusting balance of transmission power to a mobile station to the base station,
Means for controlling to start the balance adjustment period from a frame number determined based on the number of frames in the balance adjustment period;
And a means for resuming the balance adjustment at a frame in which CFN is 0 when a frame number of a transmission frame to the mobile station is CFN . A plurality of cells, a plurality of base stations respectively disposed in the plurality of cells, a mobile station moving in the cells, and a plurality of base stations are provided in common. To cause a computer to execute a transmission power control method at a base station in a cellular communication system including a control station including a control instruction including a balance adjustment period for adjusting balance of transmission power to a mobile station to the base station The program of
Control to start the balance adjustment period from a frame number determined based on the number of frames in the balance adjustment period;
And a process of resuming the balance adjustment with a frame in which CFN becomes 0, where CFN is a frame number of a transmission frame to the mobile station . A plurality of cells, a plurality of base stations respectively disposed in the plurality of cells, a mobile station moving in the cells, and a plurality of base stations are provided in common. look including a control station for transmitting a control command including a balance adjustment period for making the balance adjustment of the transmission power to the mobile station to the base station,
Each of the base stations controls the start of the balance adjustment period to start from a frame number determined based on the number of frames in the balance adjustment period, and sets the frame number of a transmission frame to the mobile station as CFN A mobile station in a cellular communication system having means for resuming the balance adjustment in a frame in which CFN is 0,
A mobile station, wherein a transmission power control command for controlling the transmission power is transmitted to the base station.

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