JP2003283426A - Transmission power control system, control method, base station, and mobile station - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent transmission power between base stations from being unbalanced due to asynchronization of balance adjustment in the case that a reception timing of transmission power valance control signals is different caused by dispersion in a transmission delay of the control signals from a control station to each of the base stations in soft handover in a cellular communication system. <P>SOLUTION: When a frame number of a transmission frame to a mobile station is referred to as a CFN and a balance adjustment period is referred to as an Nperiod frame, the start of the balance adjustment period is controlled on the basis of a frame with the frame number CFN wherein a relation of mod (CFN, m×Nperiod)=L (where m is a natural number, and L is 0 or a natural number smaller than m×Nperiod, which is common to all the base stations) holds. Thus, a calculation timing of a succeeding balancing period is synchronized between the base stations to balance the transmission power between the base stations. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transmission power control system, a control method, a base station, and a mobile station, and particularly to a balance adjustment of transmission power from a plurality of base stations to one mobile station during soft handover in a cellular communication system. The present invention relates to a method of determining the balance adjustment start timing when performing the.

[0002]

2. Description of the Related Art In a code division multiplexing cellular system, since many lines use the same frequency, the received power (desired wave power) of a signal on one line interferes with another line. It becomes the interference wave power. Therefore, in the uplink transmitted by the mobile station and received by the base station, when the desired wave power exceeds a predetermined value, the interference wave power increases and the intra-line 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 wave power, compares it with the control target value, and when the desired wave power is large, the uplink transmission power to the mobile station (hereinafter " (Also referred to as "uplink transmission power") is transmitted, and if the desired wave power is small, an uplink control command to increase the 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. The transmission of the uplink control command in this transmission power control uses the downlink which is transmitted from the base station to the mobile station.

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

However, according to this method, the base station cannot receive the downlink control command from the mobile station when the propagation loss from the mobile station to the base station rapidly increases as the location of the mobile station moves. At the same time, the mobile station may not be able to receive the 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 causes the downlink control command from the mobile station. Since the base station does not increase the downlink transmission power while it is unable to receive, the mobile station is unable to receive the uplink control command from the base station, and the uplink transmission power of the uplink signal can be increased. However, there is a problem that communication with the base station continues to be interrupted.

In general, in a signal received by a base station, a portion of user information such as voice and data can be accurately decoded by performing error correction or the like even if a reception error occurs momentarily. A relatively long amount of information is collectively coded, and a relatively long time is also required for decoding to collectively decode a long amount of information.

However, when the mobile station moves at a high speed, when performing high-speed transmission power control that keeps the reception quality constant by following the high-speed fading fluctuation of the propagation path, even if the user information is accurate. Even if it can be decoded to, since it is necessary to determine the control command instantaneously, the determination of the control command cannot obtain an effect such as error correction,
There are relatively many mistakes.

Since such a determination error of the control command occurs in relation to the increase / decrease of the propagation loss, it is relatively likely to occur continuously. When the control command judgment 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 that On the other hand, in this state, the mobile station cannot receive the uplink control command from the base station included in the downlink signal, so that the uplink transmission power of the uplink signal may not be controlled. At this time, in the base station, not only the downlink control command determination error frequently occurs in the uplink signal, but also the user information may not be correctly received. Even in this case,
There arises a problem that the communication between the base station and the mobile station continues to be interrupted.

In the cellular system, there is a technique called soft handover in which when a mobile station moves between cells, the lines are set up at the same time as a plurality of base stations near the boundary and the lines are switched between cells. This technique is an important technique especially in a cellular system that employs a code division multiplex system.

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

Therefore, a method is conceivable in which the transmission power of the downlink is controlled so that the desired wave power from each base station becomes equal in the mobile station. However, in this method, the base station, which has a large propagation loss to the mobile station, sets the downlink transmission power to a correspondingly large amount, so that the interference wave power increases and the downlink capacity decreases. As a method of suppressing the decrease in the capacity of the downlink, there is a method of controlling the downlink transmission power of each base station to be equal to each other.

In this method, the received power of the uplink control command from the base station having a small propagation loss to the mobile station is larger than the received power of the uplink control command from the base station having a large propagation loss, and the difference between them is large. At times, the probability of failure to receive an uplink control command from a base station with large propagation loss increases. In such a case, the uplink transmission power is mainly controlled by the uplink control command from the base station having a small propagation loss, so that there is not much 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 the respective uplink control commands can be received with substantially the same power, the probability that both uplink control commands can be accurately received becomes high. Therefore, it is possible to receive all the uplink control commands from the base station that may minimize the uplink propagation loss due to the uplink transmission power control.

Also, during execution of soft handover, when the magnitude of the propagation loss from the mobile station to each base station is switched at high speed due to fading fluctuations, etc., the base station transmitting to the mobile station is Accordingly, the base station having the minimum propagation loss is transmitting at any moment without switching at high speed.
At this time, if the downlink transmission power of the base station is not equal to each other, when the base station that minimizes the propagation loss is switched,
Since the reception quality increases or decreases, the reception quality is likely to deteriorate. However, if the downlink transmission powers of the respective base stations are equal to each other, even if the base station with the smallest propagation loss is switched, the reception quality is kept substantially constant, and the reception quality is further improved. 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, sends a downlink control command to reduce the downlink transmission power to the base station. If the reception quality is lower than the control target value, the downlink control command for increasing the downlink transmission power is transmitted to the base station. During execution of the soft handover, the plurality of base stations receive the downlink control command transmitted by the mobile station. Then, each base station controls the downlink transmission power while similarly increasing or decreasing it according to the downlink control command. Therefore, if the initial values of the downlink transmission powers of the respective base stations are equal to each other, the increase or decrease is repeated in the same manner, so if there is no error in receiving the downlink control command,
The downlink transmission power is controlled while maintaining the same state.

However, according to 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 the telegraphic power of the control command is small, it often fails to receive the downlink control command from the mobile station. Therefore, it becomes impossible to keep the downlink transmission power of each base station equal to each other.

Therefore, during soft handover execution, even if an error occurs in the reception of the downlink control command at each base station, each base station can transmit with substantially the same power so that high line capacity can be obtained. A transmission power control method in a cellular communication system according to the above is disclosed in JP-A-11-3.
It is proposed in Japanese Patent No. 40910.

FIG. 6 shows a schematic structure of the cellular communication system. In FIG. 6, the service area is the first
And the second cell 11 and 12, and the first and second cells are respectively provided with the first and second base stations (# 1) 21 and 22 (# 2). , There are first and second mobile stations 61, 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, this cellular communication system is provided with a large number of other base stations, and a large number of mobile stations are present in each cell.

The first and second base stations 21 and 22 respectively transmit the first and second pilot signals 31 and 32 with constant transmission power. Each of the mobile stations 61 and 62 is equipped with an SIR (ratio of desired wave to interference power) measuring device for measuring the power of the pilot signal, and measures the reception power of the first and second pilot signals 31 and 32. Measure each. The mobile station switches the pilot signal measuring device in units of short time slots as shown in FIG. 7, and measures each of the pilot signals of the plurality of base stations once for each frame. In the example of FIG. 7, there are 6 slots in one frame, so 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.

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 flow chart in which the base station receives the downlink control command from the mobile station and determines the downlink transmission power of the downlink during the execution of the soft handover. Here, the downlink transmission power P is represented by a decibel value.

When the base station initiates a soft handover with the mobile station, if the base station is the main base station that has already transmitted to the mobile station, the downlink transmission power P will be If the base station is the auxiliary base station that has newly started transmission to the mobile station, the downlink transmission power P is set to the initial value P0.
Shall be set to. 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 within the control range of the downlink transmission power.

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 S20).
1), I is incremented by 1 for each frame (step S20)
2). Here, the downlink control command (TPC: Transmission P
(ower Control) is notified from the mobile station at regular intervals, but if this newly notified downlink control command exists (step S203) and the downlink control command instructs to increase the power ( In step S204, the downlink transmission power P is increased by a predetermined value ΔP (step S20).
5) If the downlink control command instructs power reduction, the downlink transmission power P is reduced by a predetermined value ΔP (S206).

The above steps S203 to S206 are repeated for a predetermined number Nframe of frames as a balance adjustment period, and when that period has elapsed (step S207), that is, when I = Nperiod, A difference (CP) between a predetermined reference power (also referred to as a target value and a reference value) C and the downlink transmission power P before updating is calculated by a coefficient (1-
The value obtained by multiplying r) is added to the downlink transmission power P to obtain P = P + (1-r) (CP) (step S208). The coefficient r is a predetermined constant value, and the coefficient r is a value of 0 or more and less than 1. Also, 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 the maximum power Pma
When it is larger than x, the downlink transmission power P is set to the maximum power P.
max (steps S209 and S210), and when the updated transmission power P is smaller than the minimum power Pmin, the downlink transmission power P is set to the minimum power Pmin (step S21).
1, S212). Then, the process is repeated again from step S202.

According to this method, since the initial values of the downlink transmission powers 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 of the auxiliary base station are different. Difference between power P2 | P
There is 1-P2 |. If one or more base stations fail to receive the downlink control command, the downlink transmission power P
The difference | P1-P2 | between 1 and P2 may increase. However, in the control of steps S203 to S206, that is, in the part of increasing or decreasing the downlink transmission power 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, it will increase or decrease the downlink transmission powers P1 and P2 in the same way.
The difference | P1-P2 | between the downlink transmission powers P and P2 does not change.

On the other hand, at the same time, for each number of frames of I = Nperiod, the main base station and the auxiliary base station transmit downlink transmission powers P1 and P2.
To P1 + (1-r) (C-P1) and P2 +, respectively.
Since it is updated at the same time as (1-r) (C-P2), the difference | P1-P2 | between these downlink transmission powers P1 and P2 is r | P.
1-P2 | Thus, the difference in downlink transmission power | P
1-P2 | becomes r times every time Nperiod. And
Since the coefficient r is smaller than 1, unless the downlink transmission power difference | P1-P2 | increases due to a new downlink control command reception error, the control amount difference decreases in geometric progression and converges to 0. . Further, even if the difference | P1-P2 | in downlink transmission power increases due to the occurrence of a new downlink control command reception error, the difference | P1-P2 | can be reduced. Therefore, even if the reception of the downlink control command fails, the transmission power Pi of the downlink (i = 1, 2) can be exchanged between the base stations without exchanging information about the downlink transmission power between the base stations. Can be adjusted to a value approximately equal to.

That is, after the downlink transmission power is increased or decreased by the control in the steps S203 to S206, the difference in the downlink transmission power of the plurality of base stations is reduced by the control in the steps S207 to S212 ( Along with the balance adjustment), the downlink transmission power is updated so as to approach the reference power C commonly set among a plurality of base stations.

As described above, while the mobile station is performing the soft handover, each base station transmits an uplink control command for uplink transmission power control to the mobile station with substantially equal power between the base stations. Therefore, when the propagation loss from each base station to the mobile station is almost the same, and there is a possibility that the uplink propagation loss is minimized in any of the base stations,
The mobile station can receive all 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.

Also, during execution of soft handover, even if the magnitude of the propagation loss from the mobile station to each base station is changed at high speed due to fading fluctuation or the like, the diversity effect that the reception quality is kept almost constant is provided. As a result, it is possible to further improve the reception quality at the mobile station. In this way, by controlling the uplink transmission power so that the desired wave power does not become excessive, the line capacity of the uplink increases, and if the reception quality at the mobile station can be improved by the diversity effect, the reception quality will be constant. Then, the line capacity of the downlink will increase.

[0028]

As described above, in each base station, the transmission power is reduced by the adjustment amount in the transmission power balance adjustment period. This adjustment amount is transmitted at the start of the adjustment period. Electric power and reference value C which is a standard 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 are the adjustment timings. Note that in the figure, Pbali is set with r = 0.
Shows the width of.

The transmission power of each base station increases / decreases according to the same transmission power control command (TPC bit) from the mobile station. Therefore, unless the transmission power control command has a reception error, it similarly increases / decreases. 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 high (P1> P2), the transmission power at the start time of the adjustment period is Since the difference Pbal from the reference value C is also larger than that of the other base station (Pbal1> Pbal2),
During the adjustment period, the one transmission power (P1) is greatly reduced. In this way, a base station with a large transmission power greatly reduces the transmission power, so that the difference in the transmission power between the base stations becomes small and the balance adjustment is performed.

However, as shown in FIG. 9 (b), when the start time of the adjustment period is different for each base station, such as T1 and T1 ', the transmission power is constantly changed by the transmission power control command, and therefore 2 Even if the transmission power of one of the two base stations is higher than that of the other base station (P1> P
2) If the adjustment start time T1 of the former base station is a moment when the transmission power is relatively small, and the adjustment start time T1 of the latter base station is a moment when the transmission power is relatively large, the latter base station than the former In this case, the difference between the transmission power at the start of the adjustment period and the reference value C becomes larger (Pbal1 <Pbal2), and the transmission power during the adjustment period is greatly reduced. for that reason,
The difference in transmission power between the base stations becomes large, and it becomes difficult to balance the power. As a result, there is a problem that the transmission power cannot be balanced between the base stations and the line capacity is reduced.

As described above, the phenomenon that the start time of the adjustment period differs from base station to base station such as T1 and T1 'is that the control message for the transmission power balance adjustment from the control station 71 to the base stations 21 and 22 is transmitted. , Caused by variations in transmission delay between the control station and the base station. FIG. 3A shows an example in which the reception timing of the control message for conventional power balance adjustment according to FIG. 2A differs between base stations. In FIG. 2A, Nperi is set as the balance adjustment period.
It is assumed that od = 2, the frame number is 0 to 7 in total, and this is repeated. As described above, in the conventional example, since the difference in the reception timing of the power balance control message always continues thereafter, Pba between the base stations is increased.
The calculation timing of l always shifts.
The reversal phenomenon between Pbal1 and Pbal2 as shown in (b) occurs.

An object of the present invention is to adjust the adjustment period Nperiod even if the transmission power balance adjustment start time differs due to variations in the transmission delay of the control message from the control station to the base station.
The transmission power control system, the method, the base station, and the base station capable of increasing the line capacity by balancing the transmission power between the base stations so that the adjustment start timings can be synchronized with each other To get a mobile station.

[0033]

According to the present invention, a plurality of cells, a plurality of base stations respectively arranged in the plurality of cells, a mobile station moving in these cells, and a plurality of these Power control system in a cellular communication system including a control command which is provided in common to all the base stations and sends a control command for balancing the transmission power from the base stations to the mobile station to the base station. In addition, a transmission power control system is obtained in which the plurality of base stations are controlled to synchronize the timing of the balance adjustment.

According to the present invention, a plurality of cells, a plurality of base stations respectively arranged in the plurality of cells, a mobile station moving in the cells, and a plurality of base stations common to the plurality of base stations A transmission power control method in a cellular communication system, comprising: a control station which is provided and sends a control command for balancing the transmission power from the base station to the mobile station to the base station; Between the base stations of
There is provided a transmission power control method characterized by controlling so as to synchronize the timing of the balance adjustment.

According to the present invention, a plurality of cells, a plurality of base stations respectively arranged in these plurality of cells, a mobile station moving in these cells, and a plurality of base stations common to these base stations. A base station in a cellular communication system including a control station which is provided and sends a control command to the base station to balance the transmission power from the base station to the mobile station, which is another base station. A base station is obtained which operates so as to synchronize the timing of the balance adjustment between the above and the above.

According to the present invention, a plurality of cells, a plurality of base stations respectively arranged in the plurality of cells, a mobile station moving in the cells, and a plurality of base stations common to the plurality of base stations Provided, including a control station for sending to the base station a control command to balance the transmission power from these base stations to the mobile station, among the plurality of base stations,
A mobile station in a cellular communication system that is controlled to synchronize the timing of the balance adjustment, wherein the mobile station transmits a transmission power control bit that controls the transmission power to the base station. Is obtained.

Further, according to the present invention, a plurality of cells, a plurality of base stations respectively arranged in the plurality of cells,
A mobile station that moves in these cells and a plurality of base stations that are provided in common, and send a control command to the base station to balance the transmission power from these base stations to the mobile station. In order to synchronize the timing of the balance adjustment among the plurality of base stations, each of the base stations has a balance adjustment period for performing the balance adjustment. A mobile station in a cellular communication system having a control means for controlling to start from a frame number determined based on the number of frames, wherein a transmission power control bit for controlling the transmission power is transmitted to the base station. A characteristic mobile station is obtained.

The operation of the present invention will be described. When a mobile station is in soft handover with multiple base stations and the balance of the transmission power from multiple base stations to the mobile station is adjusted, the balance adjustment period for adjusting the balance at each base station is started. Is performed from the frame number determined based on the number of frames in this balance adjustment period. Thereby, even when the reception timing of the balance control message from the control station is deviated in each base station due to the variation of the transmission delay, the balance calculation timing for the balance adjustment during the balance adjustment period is repeated, Since the base stations are synchronized with each other, the transmission power balance between the base stations can be accurately performed.

Further, the frame number of the transmission frame to the mobile station is from the maximum value to the minimum value (or from the minimum value to the maximum value).
When the balance control message is received by each base station before and after the discontinuous change, the balance adjustment timing may deviate between the base stations due to the relationship between the balance adjustment cycle and the total number of frames. However, even if the frame number returns from the maximum value to the minimum value and is repeated by restarting the balance adjustment period from the frame defined by the same rule as the rule for defining the frame, the balance adjustment period is started. 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 can be accurately balanced between the base stations.

Further, CFN is the total number of frame numbers of the frames transmitted to the mobile station, and Nperiod is a balance adjustment period which is a period of balance calculation, and this Nperiod is k × Npe.
By selecting a value that has k satisfying the relation of riod = CFNmax (k is an integer), 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 is To be immutable. Therefore,
Even when 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 synchronized between the base stations. Therefore, it is possible to accurately balance the transmission power between the base stations.

[0041]

BEST MODE FOR CARRYING OUT THE INVENTION 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, and a system configuration example is shown in FIG.
Is the same as that shown in FIG.
And the frame structure of the downlink from (# 2) 22 to the mobile station 61 is the same as the example of FIG. 7, and the frame numbers of the frames transmitted at the same time between the base stations are the same. .

Referring to FIG. 1, the base station includes an antenna 2
01, a transmission / reception shared unit 202, and a reception circuit 203 that performs reception processing of a reception signal and outputs the reception signal to a terminal 207.
And an SIR measurement section 204 for performing downlink SIR measurement
And the transmission power control unit 205 that controls the transmission power by referring to the SIR measurement result and the like, and the transmission signal from the terminal 208 and the SIR measurement result signal by superimposing the transmission power control unit 2
And a transmission circuit 206 that performs amplification control according to the control from 05. Further, it also includes a CPU (control device) 209 for controlling the operation of each of these units, and a read-only recording medium (ROM) 210 in which a program for controlling the operation of the CPU is stored in advance. And

In the present invention, as shown in FIG. 9B, the power balance control message from the control station 71 is
The base stations # 1 and # 2 prevent the transmission power difference between the base stations from becoming large due to a shift such as T1 or T1 ′, which prevents the balance from being lost. Therefore, as shown in FIG. 2B, the power balance adjustment start timings are made the same between the base stations so that they are synchronized with each other.

In the example of FIG. 2B, the frame number C
FN is 0 to 7 (total number of frames (number) is CFNmax,
This is a case where it is composed of 8 frames of CFNmax-1 = 7) and this is repeated, and the adjustment period is Nperiod = 2.

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 and L is 0 or a natural number smaller than m × Nperiod and is common to all base stations) This is a case where the start control of the balance adjustment period is started from the frame of frame number CFN. That is, the frame number CFN
The balance adjustment is started with a frame having a frame number such that the remainder obtained by dividing m by N × period becomes “L”. After that, the balance is adjusted every N period. The example of FIG. 2B 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 in practice, it may be a predetermined timing of these frames (for example, the S slot).

In a second mode, when the frame number CFN is expressed by an m × Nperiod base number (m is a natural number), the balance adjustment is started from the frame where the first digit has a predetermined value. After that, the balance adjustment is similarly performed every N period. In the example of FIG. 2B,
This corresponds to the case where m = 1 and the predetermined value = 0.

In the third mode, the balance adjustment is started from the 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. The example of FIG. 2B corresponds to the case of m = 1 and L = 0.

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

Next, a slot counter (not shown)
J is reset to J = 0 (step S14), and TPC
It waits for the reception of bits (step S15). In response to the reception of the TPC bit, if this TPC bit is the power increase command (step S16), the transmission power P is the predetermined amount S.
The transmission power P is controlled to increase by a predetermined amount S1 (step S18). When 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).
Pbal is controlled to decrease by a predetermined amount S2 (step S21).

In step S19, if Pbal is smaller than the predetermined amount S2, Pbal is compared with -S2 (step S22), and if it is smaller than -S2, P-.
When the process of S2 is performed (step S23), Pba
The l is controlled to increase by a predetermined amount S2 (step S24). After steps S21 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
This is repeated for the number of slots Nslot that form one frame (step S26). When Nslot is repeated and J = Nslot, the frame counter I is incremented by 1 and the process for the next frame is started (step S
28). At this time, the above 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 S3).
0). Then, returning to step S14 again, the transmission power control is started from the first slot J = 0 of the next frame.

By the above processing, the transmission power of each downlink base station is controlled by the TPC bit in each slot, and the base stations transmit to each other due to the variation due to the transmission delay of the power balance control message from the control station. Therefore, the start timing of the power balance can be synchronized.

In the operation flow shown in FIG. 3, the frame number CFN is 0 to the maximum value (CFNmax -1) and the total number of frames is CFNmax (for example, 0 in FIG. 2).
In the case where the number of 8 frames from ~ 7 is repeated),
This is an operation flow that holds only when CFNmax is an integer multiple of Nperiod. However, when CFNmax is not an integral multiple of Nperiod, for example, as shown in FIG. 4, the calculation timing of Pbal of the base station # 1 is the frame number CFN.
= 4 and executed every Nperiod = 3 thereafter,
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 with each other, which causes a problem.

Therefore, in such a case, in the base station # 1, the frame number CFN is reset to "0" and m × N.
By restarting the calculation timing from the frame number of period + L (m is 0 or a natural number, L is 0 or a natural number common to all base stations), as shown in FIG.
1 and # 2 can be synchronized. In the example of FIG. 4, m = 0 and L = 1.

In this way, when the frame number changes discontinuously from the maximum value to the minimum value (or from the minimum value to the maximum value), it is determined by the same rule as the rule for determining the frame of the start of the balance adjustment period. Synchronization can be established by restarting the balance control period from the frame.

The operation flow of the base station in such a case is shown in FIG. 5, and the steps equivalent to the steps in the operation flow of FIG. 3 are designated by the same reference numerals. Explaining only the parts different from FIG. 3, a frame number counter CFN is provided after step S27 and the value of the 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 the ascending order, but it can be similarly applied to the case of the descending order.

In FIG. 5, Npe including CFN = 0
At the last power value P of each riod frame, Pbal
Is shown as being calculated. Also, FIG. 3 and FIG.
In both flows, Pbal is Pbal = (1-r)
It is calculated as (C−P), and Pbal is updated every calculation, but Pbal = Pbal + (1-r)
An example in which (CP) is integrated may be used.

As Nperiod, k × Nperiod = CFN
It goes without saying that the embodiment in which the frame number counter CFN is reset to "0" is not necessary by selecting a value that has an integer k such that it becomes max. In this case, the base station may select Nperiod for a value that has an integer k such that k × Nperiod = CFNmax, but in general, it is selected by the control station and this is notified to each base station. Will be done. Therefore, at each base station, m × Nperi
Even if the frame number CFN changes from the maximum value to the minimum value (or vice versa, when counting down from the minimum value to the maximum value) by starting the balance adjustment from the frame of od + L, Also, the calculation timings of both base stations can be synchronized. For example, CFNmax =
When 256, Nperiod is 1, 2, 4, 8,
It will be selected from 16, 32, 64, 128, 256.

The operation flows shown in FIGS. 3 and 5 are processed by the CPU 209 reading and executing the program stored in the recording medium such as the ROM 210 shown in FIG. Although the functional block diagram and operation flow in the control station are not shown,
Similarly, the operation control program is stored in advance in the recording medium and C
By executing this while reading it by PU, etc., transmission of transmission power balance control message and Nperiod
It is obvious that operations such as selection of are possible.

[0062]

As described above, according to the present invention, when the control signal reception timings due to variations in the control signal transmission delay from the control station to the base station are different, the first adjustment period is started. Even if the points are different, the timing of the subsequent balance adjustment will be synchronized, and this has the effect of improving the balance of the transmission power between the base stations and increasing the line capacity. .

Particularly, in the invention for performing the restart control, Nperiod
Even if a value such that k does not exist such that k × CFNmax is selected, since the timing of the balance adjustment can be synchronized, Nperiod can be selected regardless of the value of CFNmax.
The frequency of the balance adjustment must be equal to or higher than a predetermined frequency in order to satisfy the predetermined requirement standard for the balance of the transmission power between the base stations, but Np is not related to the value of CFNmax.
Since eriod can be selected, the frequency of balance adjustment can be minimized at a predetermined frequency or more. Therefore, there is an effect that the control processing for synchronizing the timing of the balance adjustment can be reduced.

As Nperiod, k × Nperiod = C
In the invention in which k is selected so that FNmax is present, restart control is not necessary even when the total number of frames is limited, so that it is possible to reduce the control processing for synchronizing the timing of balance adjustment. is there.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a base station according to an embodiment of the present invention.

FIG. 2 is a diagram showing a calculation timing of transmission power balance according to the present invention in comparison with a conventional example.

FIG. 3 is a flow chart showing an operation of one embodiment of the base station of the present invention, when CFNmax is an integral multiple of Nperiod.

FIG. 4 is a diagram showing an operation example when CFNmax is not an integral multiple of Nperiod.

FIG. 5 is a flow chart showing the operation of another embodiment of the base station of the present invention, when CFNmax is not an integral multiple of Nperiod.

FIG. 6 is a system configuration diagram to which the present invention is applied.

FIG. 7 is a frame configuration diagram in the present invention.

FIG. 8 is a base station operation flow chart in the conventional system.

FIG. 9 is a diagram illustrating a case where transmission power balance adjustment is not satisfactory when a power balance control message from a control station arrives at different timings between base stations due to variations in transmission delay. Is.

[Explanation of symbols]

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

Claims (17)

[Claims] 1. A plurality of cells, a plurality of base stations respectively arranged in the plurality of cells, a mobile station moving in the cells, and a base station common to the plurality of base stations. A transmission power control system in a cellular communication system including a control station for sending a control command for adjusting balance of transmission power from the base stations to the mobile stations, among the plurality of base stations. 2. The transmission power control system according to claim 1, wherein control is performed to synchronize the timing of the balance adjustment. 2. A control means for controlling each of the plurality of base stations to start a balance adjustment period for performing the balance adjustment from a frame number determined based on the number of frames of the balance adjustment period. The transmission power control system according to claim 1, further comprising: 3. The control means, when the frame number changes discontinuously from a maximum value to a minimum value or from a minimum value to a maximum value, is defined by the same rule as a rule for defining a frame for starting a balance adjustment period. From the frame
The transmission power control system according to claim 2, wherein restart control of the balance adjustment period is performed. 4. When the frame number of a frame transmitted to the mobile station is CFN and the balance adjustment period is Nperiod frame, the control means sets the CFN from a maximum value to a minimum value or from a minimum value to a maximum value. The balance adjustment period is restarted from a frame in which m × Nperiod + L (m is 0 or a natural number, L is a common 0 or natural number for all base stations) when continuously changing. The transmission power control system described. 5. The control means, when the transmission power at the start of the balance adjustment period is P, the reference value is C, and r is a coefficient of 0 or more and less than 1, the adjustment amount in the balance adjustment is: 1-r) (CP), The transmission power control system according to claim 2. 6. A plurality of cells, a plurality of base stations respectively arranged in the plurality of cells, a mobile station moving in the cells, and a base station common to the plurality of base stations. A transmission power control method in a cellular communication system including a control station that sends a control command for adjusting balance of transmission power from the base stations to the mobile stations, among the plurality of base stations. In the transmission power control method, the balance control timing is controlled so as to be synchronized with each other. 7. A control step of controlling, in each of the plurality of base stations, a balance adjustment period for performing the balance adjustment so as to start from a frame number determined based on the number of frames of the balance adjustment period. The transmission power control method according to claim 6, further comprising: 8. The control step is defined by the same rule as a rule for defining a frame for starting a balance adjustment period when the frame number changes discontinuously from the maximum value to the minimum value or from the minimum value to the maximum value. The transmission power control method according to claim 7, wherein the balance adjustment period is restarted from a different frame. 9. When the frame number of the frame transmitted to the mobile station is CFN and the balance adjustment period is Nperiod frame, the control step is such that the CFN is not changed from the maximum value to the minimum value or from the minimum value to the maximum value. 8. The balance adjustment period is restarted from a frame in which m × Nperiod + L (m is 0 or a natural number and L is a common 0 or natural number common to all base stations) when continuously changing. The transmission power control method described. 10. The control step includes the transmission power P at the start of the balance adjustment period, the reference value C, and the reference value C.
The transmission power control method according to any one of claims 7 to 9, wherein the adjustment amount in the balance adjustment is (1-r) (C-P) when is a coefficient of 0 or more and less than 1. 11. A plurality of cells, a plurality of base stations respectively arranged in the plurality of cells, a mobile station moving in these cells, and a common base station provided in the plurality of base stations,
A base station in a cellular communication system including a control station that sends a control command for balancing the transmission power from the base station to the mobile station to another mobile station, In the base station, the base station operates so as to synchronize the timing of the balance adjustment. 12. The control means for controlling the balance adjustment period for performing the balance adjustment to start from a frame number determined based on the number of frames in the balance adjustment period. The listed base station. 13. The control means is defined by the same rule as a rule for defining a frame for starting a balance adjustment period when the frame number discontinuously changes from the maximum value to the minimum value or from the minimum value to the maximum value. 13. The base station according to claim 12, wherein the balance adjustment period is restarted from a different frame. 14. When the frame number of a frame transmitted to the mobile station is CFN and the balance adjustment period is Nperiod frame, the control means sets the CFN from a maximum value to a minimum value or from a minimum value to a maximum value. 13. The balance adjustment period is restarted from a frame in which m × Nperiod + L (m is 0 or a natural number, L is a common 0 or natural number common to all base stations) when changing continuously. The listed base station. 15. The control means sets the transmission power at the start of the balance adjustment period to P, the reference value to C, and r to 0.
The base station according to any one of claims 12 to 14, wherein the adjustment amount in the balance adjustment is (1-r) (CP) when a coefficient of 1 or more and less than 1 is set. 16. A plurality of cells, a plurality of base stations respectively arranged in the plurality of cells, a mobile station moving in these cells, and a base station common to the plurality of base stations,
A control station that sends a control command for adjusting the balance of transmission power from the base station to the mobile station to the base station, and synchronizes the balance adjustment timing among the plurality of base stations. A mobile station in a cellular communication system that is controlled so as to transmit a transmission power control bit that controls the transmission power to the base station. 17. A plurality of cells, a plurality of base stations respectively arranged in the plurality of cells, a mobile station moving in these cells, and a base station common to the plurality of base stations,
A control station that sends a control command for adjusting the balance of transmission power from the base station to the mobile station to the base station, and synchronizes the timing of the balance adjustment among the plurality of base stations. For this purpose, each of the base stations has a control means for controlling the balance adjustment period for performing the balance adjustment so as to start from a frame number determined based on the number of frames of the balance adjustment period. The mobile station according to claim 1, which transmits a transmission power control bit for controlling the transmission power to the base station.