JPH07273722A - Power controller - Google Patents

Abstract

PURPOSE:To control the base station request power and the pilot signal power to improve the SIR degradation of a base station in the code division multiple access mobile communication system. CONSTITUTION:SIR measurement is performed in an SIR measurement part 2 of each base station, and a signal power control part 3 performs such control in accordance with the deviation from an SIR reference value that a base station request power PBD(t) is raised and a pilot signal power PP(t) is reduced or the power PBD(t) is reduced and the power PP(t) is raised. Thus, the degradation of the quality is improved if traffic is concentrated to a base station to degrade the quality in the base station, and the quality is restored to the reference if traffic is reduced to bring about an excessive quality, thereby leveling the qualities in base stations.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to reverse link base station required power and forward link pilot signal power in a base station in a mobile communication system based on a code division multiple access (CDMA) communication system. The present invention relates to a power control device.

[0002]

2. Description of the Related Art In the CDMA communication system, all mobile stations communicate using the same frequency band. Therefore, in the base station that receives the signals from these mobile stations, the signals from the mobile stations interfere with each other. In the reverse link (connection from the mobile station to the base station), the base station controls the transmission power of each mobile station so that the received signal powers from the mobile stations are all equal (reverse link power control). That is, the base station sets a required value of received signal power (base station required power), and transmits control information to each mobile station so that the received power from each mobile station becomes the required value.
Each mobile station controls the transmission power based on the control information. The power control of the reverse link makes the quality of each mobile station signal, that is, the signal-to-interference ratio (SIR), all equal in the base station (see the following document). The quality at this time is the quality of the base station. Reference name Eisuke KUDOH and Tadashi MATSUMOTO: "Effect
of Power Control Error on the System User Capacit
y of DS / CDMA Cellular Mobile Radios ", IEICE Trans.C
ommun., Vol. E75-B, No. 6, June 1992 In general, the received signal power required by a base station for each mobile station is the same and unchanged for each base station. Further, the pilot signal power transmitted from the base station depends on the size of the cell area, but is unchanged in one base station.
An example of this is shown in FIGS. In this example, base stations BS0-B
S2 is arranged in one dimension. The mobile station receives the pilot signal from each base station, compares the received strengths, and connects with the base station having the pilot signal having a strong strength. As the distance from the base station increases, the pilot signal strength becomes weaker, and conversely, the adjacent base station pilot signal strength becomes stronger and becomes equal at a certain position. This position is the cell boundary, and CL0-1, C in the figure
It is represented by L1-2 (Fig. 6). When the pilot signal powers at each base station are equal, the cell boundary is in the middle between base stations. Considering this two-dimensionally, when the base stations are uniformly arranged, the cell area areas surrounded by the cell boundaries are all equal. When the received signal power required by each base station is PBD0 to PBD2, the following is obtained. PBD0 = PBD1 = PBD2 Generally, the signal attenuates in proportion to the power of the propagation distance, so the mobile station transmission power PT for satisfying the base station required power
Is as follows, where the propagation distance is r. PT = PBD × (power of r) That is, the mobile station has to increase the transmission power as the distance from the base station increases. When the cell boundary is located at the center between the base stations, the loci of the mobile station transmission power PT satisfying both base station required powers intersect at the cell boundary (FIG. 7). That is, CL1-
If 2 is between BS1 and BS2, the intersection of PT1 and PT2 is CL1-2
Will be on top. In this case, the maximum interference from the mobile station connected to the adjacent base station is PBD. When the mobile station connected to the closest base station BS2 is on CL1-2, the interference power to the base station BS1 is PBD1. When the mobile station is closer to the base station BS2 than CL1-2, the interference power to the base station BS1 becomes weaker.

[0003]

The quality of a base station on the reverse link of a CDMA system is roughly determined by the number of mobile stations connected to the base station and the strength of interference signals from other cells. That is, the number of connected mobile stations
If N is the total amount of interference from other cells and Z is the base station SIR,
It looks like this: SIR = PBD / ((N-1) × PBD + Z) However, since the traffic distribution of mobile stations fluctuates depending on the location, time, etc., the traffic concentrates on the base station with traffic (N increase in the above equation), and the SIR May be deteriorated, or conversely traffic may be reduced, resulting in excessive quality. However, since the pilot signal power is constant, the cell area is also unchanged, and it is impossible to cope with the traffic distribution. Also, in a base station with increased traffic, when the pilot signal power is reduced and the cell area is reduced in order to reduce the number of connected mobile stations, interference from adjacent cells becomes large (Z increase in the above equation). That is, in FIG. 6, it is assumed that the traffic is concentrated on the base station BS1 and the base station SIR of the BS1 is degraded, and in order to reduce the number of connected mobile stations, the pilot signal power of the base station BS1 is lowered and the cell boundary CL0. If -1 is set to CL '0-1, the transmission power PT0 of the mobile station connected to BS0 becomes high,
The reception power PR ′ of the interference wave at the base station BS1 becomes higher than PBD1 and the amount of interference increases. In the present invention, when traffic is concentrated on a certain base station and a quality deterioration occurs at the base station,
By improving it to the standard value, and conversely, if the traffic decreases and the quality becomes excessive, by returning the quality to the standard,
It is an object of the present invention to propose a method that makes the quality of each base station uniform and enables signal power control according to the traffic distribution.

[0004]

The present invention relates to control of reverse link base station required power and forward link pilot signal power in a base station in a mobile communication system based on a code division multiple access communication system. . The present invention provides means for receiving a signal, means for measuring a signal-to-interference ratio at a base station from the received signal, and transmission of control information relating to transmission power requested to each mobile station according to base station required power. Reverse link power control means, a forward link power control means for controlling the transmission power of the pilot signal according to the pilot signal power, and a signal power control means. This signal power control means lowers the pilot signal power in a base station whose measured base station SIR is worse than the reference SIR, thereby reducing the cell area covered by the base station and connecting mobile stations. To increase the power required by the base station at the same time,
This suppresses interference from adjacent cells and functions to improve the base station SIR to the reference SIR,
In a base station where the measured base station SIR is better than the reference SIR, it raises the pilot signal power, thereby making it function to expand the cell area covered by the base station, and at the same time base station request. It lowers the power, thereby suppressing the interference given to the adjacent cell and suppressing the excessive quality up to the reference SIR.

[0005]

According to the present invention, when traffic is concentrated on a certain base station and a quality deterioration occurs at the base station, it is improved,
On the contrary, when the traffic decreases and the quality becomes excessive, the quality is returned to the standard to make the quality uniform in each base station. The concept of the present invention is shown in FIGS. Base station BS1
When the traffic is concentrated on the base station S1 and the base station SIR at the base station BS1 deteriorates, the pilot signal power PP1 at the base station BS1 is lowered (FIG. 4). The cell boundary is the intersection of the received power PR of the pilot signal and is indicated by CL0-1 and CL1-2. By reducing the pilot signal power PP1, the cell boundary approaches the base station BS1, the cell area is reduced, and the number of connected mobile stations in the base station BS1 is reduced. At the base station BS1, the power required by the base station BS0 and BS2 is set so that the amount of interference from the cells does not increase.
Raise PBD1 (Figure 5). At this time, the mobile station transmission power PT is set to be equal at the cell boundary. Base stations BS0 to C
If the distance to L0-1 is r0, the distance from CL0-1 to BS1 is r1, and the distance attenuation constant is w, PP0 / r0w = PP1 / r1w PBD0 × r0w = PBD1 × r1w. Relationship is obtained. PP0 x PBD0 = PP1 x PBD1 That is, when one side is a constant, the pilot signal power PP
When multiplied by X, the base station required power PBD becomes 1 / X. As a result, the mobile station transmission power PT becomes equal at the cell boundary,
The power of the interference wave from the adjacent cell mobile station is less than or equal to the required power at the base station. That is, the most effective control becomes possible by setting PP x PBD = constant. This reduces the cell area at the base station BS1, reduces some intra-cell interference by allocating part of the traffic to adjacent cells, and suppresses adjacent cell interference by increasing the power required by the base station. Make improvements. In addition, FIG. 4 and FIG.
It also serves as the following explanation. When the traffic decreases in the base stations BS0 and BS2 and the base station SIR becomes excessive, the pilot signal powers PP0 and PP2 are increased and the base station required powers PBD0 and PBD2 are decreased to improve the quality of the base stations BS0 and BS2. Suppress to the standard value.

[0006]

1 is a block diagram of a power control device according to an embodiment of the present invention, and FIG. 2 is a block diagram of a signal power control unit in FIG.
FIG. 3 shows a flowchart for explaining the operation of FIG. These are all on the base station side. Shown in the figure
SIR and signal power are all displayed in decibels. First, a signal is received by the signal receiving unit 1 of FIG. 1 (ST of FIG. 3).
1). Next, the SIR measuring section 2 in FIG. 1 measures the SIR at the base station from the received signal (ST2). CDM
The quality of the base station on the reverse link of the A system is
It is roughly determined by the number of mobile stations connected to the base station and the strength of interference signals from other cells. That is, if the number of connected mobile stations is N and the total amount of interference from other cells is Z,
The base station SIR is as follows. SIR = PBD / ((N-1) × PBD + Z)

The measured result is represented by SIR (t) because it varies with time. The measured SIR value is sent to the signal power control unit 3. In the signal power control unit, the difference between the SIR measurement value SIR (t) and the SIR reference value SIRo is calculated by using the subtractor 8 in FIG.
D_SIR (t) is taken (ST3). That is, it becomes as follows. D_SIR (t) = SIRo-SIR (t) The SIR reference value is the control target value of the SIR measurement value, and the entire system is controlled so that the measurement value is always this value. The SIR reference value is set slightly higher than the quality assurance value (when the SIR is below that value, quality cannot be guaranteed).

The SIR deviation D_SIR (t) is calculated by the signal converter 9 of FIG.
Converted to base station required power update value U_PR (t) at (ST
Four). The conversion function is as follows, where a proportional function is used and its coefficient is α. U_PR (t) = α × D_SIR (t) The base station request power is updated using this update value (ST
Five). The update is obtained by adding the update value to the pre-update request power delayed by the delay unit 12 in FIG. 2 (ST7) by the adder 10. That is, the base station required power PR (t) is as follows. PR (t) = PR (t-1) + U_PR (t) = PR (t-1) + α × D_SIR (t) Here, PR (t-1) represents the required power value before update. For example, S
If the IR measurement value is worse than the reference value, the deviation D_SIR
(t) becomes positive (SIR value is indicated by negative decibel value), the updated value of required power also becomes positive, and required power increases. Since the SIR and the power value are shown in decibel values, they are multiplied by the updated value on a real number. The range is limited in the limiter 11 of FIG. 2 so that the obtained result falls within the dynamic range of the required power (ST
6). This prevents the control from running out of control.

The base station required power PR (t) is sent to the reverse link power control unit 4 in FIG. 1 (ST8).
The reverse link power control unit 4 compares the calculated base station required power with the received signal power from each mobile station, and transmits control information regarding power control to the mobile station. Each mobile station controls the transmission power based on the control information. The pilot signal power is calculated using the base station required power. The base station reference power value is the sum of the base station required power value and the pilot signal power value. The base station reference power value is set to be always constant. That is,
In FIG. 2, the base station required power is subtracted from the set base station reference power value 13 using the subtractor 14 to obtain the pilot signal power PP (t) shown below (ST9). PP (t) = PBSo-PR (t) Since these electric powers are decibel values, the following relation is obtained on a real number. PP '= PBSo' / PR '

The pilot signal power PP (t) is sent to the forward link power control section 5 (ST1
0), the pilot signal is transmitted with the pilot signal power. Of the base station reference power values, the initial value of the required power of the base station is constant regardless of the base station, and the initial value of the pilot signal power can be roughly determined by the size of the cell at the design stage. That is, the base station reference power value is
It is determined and set according to the initial cell size.

In this embodiment, the SIR deviation is converted into the update value of the base station required power, and the pilot signal power is updated according to the update value, whereby the base station required power and the pilot signal power are SIR. Although the SIR deviation is converted into the update value of the pilot signal power and the base station required power is updated according to the update value, the same is true. Although the SIR and signal power are all displayed in decibels, they can also be real values. In this case, the addition part of the decibel is the multiplication of the real number. Further, the function in the signal conversion unit is a proportional function, but a step function or a quadratic function is also possible. Further, although the SIR reference value is fixed, it can be made variable while observing the quality at the adjacent base station.

[0012]

As described above, by controlling the power required by the base station and the power of the pilot signal according to the traffic in each cell, the quality in each base station is kept constant and the control is performed according to the traffic distribution. Is possible.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a power control device showing an embodiment of the present invention.

FIG. 2 is a configuration diagram of a signal power control unit in FIG.

FIG. 3 is a flowchart for explaining the operation of the power control device in FIG.

FIG. 4 is an explanatory view of the concept of the present invention.

FIG. 5 is an explanatory view of the concept of the present invention.

FIG. 6 is an explanatory view of the concept of the prior art.

FIG. 7 is an explanatory view of the concept of the prior art.

[Explanation of symbols]

 1 signal receiving unit 2 SIR measuring unit 3 signal power control unit 4 reverse link power control unit 5 forward link power control unit BS0 to BS2 base station PBD0 to PBD2 base station required power PP0 to PP2 pilot signal power CL0-1, 1-2 Cell boundary SIR (t) Measured SIR value SIRo SIR reference value PBSo Base station reference power

Claims (1)

[Claims] 1. A means for receiving a signal, a means for measuring a signal-to-interference ratio at a base station from the received signal, and control information relating to transmission power requested to each mobile station according to a base station required power. Reverse link power control means for sending, forward link power control means for controlling the transmission power of the pilot signal according to the pilot signal power, if the measured signal to interference ratio is worse than the reference signal to interference ratio, According to the deviation between the measured signal-to-interference ratio and the reference signal-to-interference ratio, the pilot signal power is updated to be lowered and the base station required power is increased, and the measured signal pair is also updated. If the interference ratio is better than the reference signal-to-interference ratio, the pilot signal is adjusted according to the deviation between the measured signal-to-interference ratio and the reference signal-to-interference ratio. And a signal power control means for updating to reduce the and the base station requests the power-up power, and wherein the power control apparatus in a base station of a mobile communication system based on code division multiple access communication system.