JPH06140975A - Controller for transmission power of mobile station - Google Patents

Abstract

PURPOSE:To improve the efficiency of the entire system by uniformizing a signal to interference noise ratio of each base station in the mobile communication system of code division multiple access. CONSTITUTION:A reception power setting value Sc(i+1) of the present station is increased by a multiple of k(i):SIRm(i)/SIRc(i) of a setting value Sc(i) at a just preceding control time with a present station total reception power observation means 1, an adjacent station power observation means 2, a revision parameter arithmetic operation means 3 and a reception power setting value revision means 4 to revise the setting value. Furthermore, a transmission power control means 5 controls transmission power of each mobile station so that the reception power of the present station is the setting value Sc(i+1). Thus the SIR of adjacent base stations is set in a direction to be the same value and the efficiency in the entire system is improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for controlling transmission power of a mobile station in a mobile communication system based on a code division multiple access communication system.

[0002]

2. Description of the Related Art Code Division Multiple Access
A near-far problem occurs in a reverse link (connection from a mobile station to a base station) in a mobile communication system based on the iple access communication method. In code division multiple access, communication is performed in the same frequency band, so for a signal from a certain mobile station at the base station,
Signals from other mobile stations become interference noise. The perspective problem is that the received signal power at the base station is small because the signal from the mobile station far from the base station is small and the signal from the mobile station close to the base station is large, so the signal from the mobile station far from the base station is large. This is a problem that the power ratio to interference noise becomes small and the signal quality deteriorates. Therefore, the transmission signal power of the mobile station must be controlled so that the transmission signal power of the mobile station is large for the mobile station far from the base station and small for the mobile station close to the base station.

The perspective problem of this kind is shown in, for example, the following document. That is, all the base stations control the transmission signal power of the managed mobile station so that the reception signal power of each base station becomes a predetermined value (1.0 in the following document). By this control method, the signal-to-interference noise power ratio of the signal from the mobile station under management can be made uniform in each 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 ", IEICETRANS. C
OMMUN., Vol.E75-B, No.6, June 1992

[0004]

However, the method of this document alone is still insufficient. That is, if there are sparse and dense distributions of mobile stations within the service area, the SIRs of base stations where the distribution of mobile stations is dense are
Becomes smaller and the quality of the signal deteriorates. On the other hand, in a base station where the distribution of mobile stations is sparse, the SIR becomes large and the quality of the signal becomes excessive. This means that if the distribution is sparse or dense, the SIRs of the respective base stations will be significantly biased, and the efficiency of the entire system will be poor. Therefore, it is an object of the present invention to provide a transmission power control device that adaptively changes the reception power setting value and makes the SIR in each base station as uniform as possible.

[0005]

The present invention relates to a mobile station transmission power control device used in a mobile communication system in which a base station and a mobile station communicate with each other based on a code division multiple access communication system. The present invention relates to an own station total received power observing means for outputting total received power in an own base station (hereinafter referred to as own station), and a received power set value regarding a plurality of adjacent base stations (hereinafter referred to as adjacent stations). Adjacent station observation means for outputting a ratio of total received power (hereinafter referred to as power ratio). In addition, the power ratio SIRc (i) of the own station is calculated from the reception power setting value of the own station and the total reception power, and the power ratio SIRc (i) of the own station is compared with the power ratio of the adjacent station. When the power ratio SIRc (i) of the station is the minimum, the minimum power ratio of the adjacent stations is SIRm.
(I) and update parameter k (i) is set to k (i) = SI
It has an update parameter calculation means for calculating and updating and setting in the relation of Rm (i) / SIRc (i). Furthermore, the reception power setting value Sc (i + 1) of the own station at the current time is set to Sc
(I + 1) = k (i) × Sc (i) The calculated reception power setting value updating means and the transmission power control command to the managed mobile station to receive the own station. Transmission power control means for controlling the power to reach the reception power setting value Sc (i + 1).

Further, it is desirable that the update parameter computing means of the present invention uses the maximum power ratio SIRc (i) of its own stations as the maximum power ratio SI of the adjacent stations.
Rmax (i) and update parameter k (i) to k
(I) = SIRmax (i) / SIRc (i) is calculated, and a function for reducing and updating setting is added.

[0007]

According to the present invention, the power ratio SIRc of the own station is controlled by the total received power observation means of the own station, the adjacent station observation means, the update parameter calculation means, and the received power set value update means.
When (i) is the minimum, the power ratio SIRc of the own station
Based on (i) and the minimum power ratio SIRm (i) among the adjacent stations and the reception power setting value Sc (i) at the immediately preceding control time, the reception power setting value Sc (i
+1), Sc (i + 1) = (SIRm (i) / SIR
The update setting is performed in the relationship of c (i)) × Sc (i). Then, for example, a command to increase or decrease the transmission power is transmitted from the transmission power control means to each mobile station, and in cooperation with each mobile station, the reception power at the local station becomes the set value Sc (i + 1), The transmission power of each mobile station is controlled. Therefore,
When the power ratio SIRc (i) of the own station is smaller than that of the surrounding base stations, the reception power of the own station is controlled to be large, and as a result, the communication quality of the own station is improved. On the other hand, the increase control of received power increases interference noise for adjacent stations, but it is limited only when the own station's power ratio is minimum (when communication quality is worst), and there are multiple controls. Since the adjacent station with the smallest power ratio among the adjacent stations is used as a reference and the power ratio is controlled to be the same as the power ratio SIRm (i), the influence on the adjacent station is very limited. Therefore, the efficiency of the entire system will be maintained.

Further, when the power ratio SIRc (i) of the own station is the maximum, a communication function of the own station as compared with that of the adjacent station is added by adding a function of reducing and setting the update parameter k (i). Is too good, the received power setting value Sc
(I + 1) is set to be reduced so that the power ratio SIRc (i) of the own station is the same as the power ratio SIRmax (i), and therefore the interference noise with respect to the adjacent station is decreased, and as a result, the system as a whole is reduced. The efficiency can be improved.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1 is a block diagram showing an embodiment of the present invention, showing the structure of one base station. In FIG. 1, 1 is a total received power observation unit of the own station, 2 is a received power observation unit of an adjacent station, 3 is an update parameter calculation unit, 4 is a received power set value updating unit, 5 is a transmission power control unit, and the adjacent station is The received power setting values S2 and S3 and the total received powers I2 and I3 from two adjacent base stations are input to the received power observing unit 2. The output Ic of the own station total received power observation unit 1 is
Outputs SIR2 and SIR of the adjacent station reception power observation unit 2 sent to the adjacent station and input to the update parameter calculation unit 3
3 is input to the update parameter calculation unit 3, the output k of the update parameter calculation unit 3 is input to the reception power setting value update unit 4, the output Sc of the reception power setting value update unit 4 is sent to the adjacent station, and the update parameter is updated. It is input to the calculation unit 3 and the transmission power control unit 5.

Next, the transmission power operation will be described. The control operation is performed at discrete times (T = 0,
1, 2, ..., 1, ...). Each control time T = i
In, the own station total received power observing section 1 observes and calculates an average value of the total received power of the own station for a predetermined time,
The total received power Ic (i) is output. The adjacent station reception power observing section 2 receives the reception power set value S2 from the adjacent station.
(I), S3 (i) and total received power I2 (i), I3
From (i), the power ratio SIR2 (i), S of each adjacent station
Calculate and output IR3 (i).

The update parameter calculation unit 3 calculates the power ratio SIRc (i) (= Sc (i) / I of its own station) from the received power setting value Sc (i) of its own station and the total received power Ic (i).
c (i)) is calculated, and the power ratio SIR2 of each adjacent station is calculated.
(I) and SIR3 (i) are compared. Then, when the power ratio SIRc (i) of the own station is the minimum, the minimum SIRm (i) of the power ratios SIR2 (i) and SIR3 (i) of the adjacent stations is selected, and the update parameter k ( i)
Is calculated from the following equation and output. k (i) = SIRm (i) / SIRc (i) (1)

The update parameter calculator 3 also determines the power ratio SIRc (i) of its own station and the power ratio SIR2 of the adjacent station.
(I) and SIR3 (i) are compared, and the power ratio S
When IRc (i) is the maximum, the power ratio S of the adjacent station
The largest of IR2 (i) and SIR3 (i) SI
Rmax (i) is selected and the update parameter k (i) is
Calculated by the following formula and output. k (i) = SIRmax (i) / SIRc (i) (2) When the power ratio SIRc (i) of the own station is an intermediate value of the adjacent stations, the state of the control time immediately before is maintained. ,
That is, k (i) = 1.

The received power set value updating unit 4 calculates the received power of the own station at the current time from the update parameter k (i) of the immediately preceding control time and the received power set value Sc (i) of the own station at the immediately preceding control time. The set value Sc (i + 1) is calculated by the following equation and output. Sd (i + 1) = k (i) × Sc (i) (3) The transmission power control unit 5 receives the mobile station under management based on the output Sc (i + 1) of the reception power setting value updating unit 4. The control is performed so that the power is transmitted so that the power becomes Sc (i + 1). In this operation, the signal reception power from a certain mobile station is compared with the reception power setting value Sc (i + 1) of its own station, and if Sc (i + 1) is larger, the mobile station is made to increase the power by a predetermined value. When a command is transmitted and Sc (i + 1) is smaller, a command that causes the mobile station to reduce the power by a predetermined value is transmitted. This operation is performed for all the mobile stations under management, and is repeatedly performed at high speed within the control time interval τ described above.

Next, the effects of the present invention will be shown by simulation. We are considering a situation in which mobile stations under the control of neighboring stations gradually gather under the control of their own stations, and then mobile stations under the control of their own stations move to the adjacent stations and return to the initial state. That is, with time, the distribution of mobile stations near the local station becomes dense, and the distribution of mobile stations near the adjacent station becomes sparse,
This is a situation in which the operation reverse to the above is performed to return to the initial state. FIG. 2A shows a temporal change of the density. The horizontal axis of the figure shows time, and the vertical axis shows the ratio of the distribution densities of the mobile station of the own station and the adjacent station. 1.0 indicates a state in which there is no bias and is uniform, and the larger the value, the higher the density of mobile stations near the own station is, compared to the density of mobile stations near the adjacent station. The simulation result is shown in B of FIG. The horizontal axis of the figure is time, and the vertical axis is S.
It represents IR [dB]. The dotted line in the figure is the SIR at the station,
The actual result represents the SIR at the adjacent station. In the figure, what is shown before improvement is the result when the conventional technique is used, and what is shown after improvement is the result when the method of the present invention is used. In this simulation, it is assumed that the power of the radio wave decreases in proportion to the reciprocal of the fourth power of the distance. As is clear from FIG. 2, when the conventional technique is used, the SIR of the local station deteriorates and the SIR of the adjacent station improves as the density of the mobile stations increases. On the other hand, in the method according to the present invention, the quality of the local station can be improved by sacrificing the excess quality in the communication of the adjacent station. That is, the SIR for each base station is made more uniform than in the conventional technique. From the above results, the effectiveness of the present invention can be seen.

In the above embodiment, when the power ratio SIRc (i) of the own station is an intermediate value of the adjacent stations, the control time immediately before is maintained.
The average of the power ratios of the adjacent stations including the own station was calculated, and the average value was not less than a predetermined threshold th, and the power ratio SIRc (i) of the own station was not less than the threshold th. In this case, the received power setting value Sc (i
+1) may be decreased and updated and set. Sc (i + 1) = (th / SIRc (i)) × Sc (i) (4)

[0016]

As described above in detail, according to the present invention, the reception power setting value is adaptively changed in relation to the adjacent station so that the SIR at each base station is as uniform as possible. Therefore, it is possible to improve the SIR in the base station where the distribution of mobile stations is dense, and it is possible to suppress a decrease in the efficiency of the entire system.

[Brief description of drawings]

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

FIG. 2 is a block diagram showing a simulation result of the present invention.

[Explanation of symbols]

 1 Own station total received power observation unit 2 Adjacent station received power observation unit 3 Update parameter calculation unit 4 Received power set value update unit 5 Transmission power control unit

Claims (1)

[Claims] 1. Use in a mobile communication system in which a base station and a mobile station communicate with each other based on a code division multiple access communication system, and output the total received power at its own base station at each control time. Own station total received power observation means, adjacent station observation means that outputs the ratio of received power set value to total received power of a plurality of adjacent base stations at each control time, and the own base station at the control time immediately before The reception power setting value of the own base station to the total reception power ratio SIRc (i) is calculated from the reception power setting value of the station and the total reception power, and the reception power setting value of the own base station to the total reception power ratio SIRc ( i) is compared with the reception power setting value to the total reception power ratio of the adjacent base station, and when the reception power setting value to the total reception power ratio SIRc (i) of the own base station is the minimum, Previous The update parameter k (i) is calculated by using SIRm (i), which is the smallest of the received power set value to the total received power ratio,
k (i) = SIRm (i) / SIRc (i), update parameter calculation means for updating and setting, and the update parameter k (i) and the reception power setting value of the own station at the immediately preceding control time. Using Sc (i), the reception power setting value Sc (i + 1) of the own station at the current time is set to Sc (i +
1) = k (i) × Sc (i) is calculated, and the transmission power control command is transmitted to the reception power setting value updating means for updating and setting, and the mobile station under management, and reception by the own station The power is the received power setting value Sc (i
A mobile station transmission power control device, comprising: transmission power control means for controlling the transmission power to be +1).