JPH06132872A - Mobile station transmission power controler - Google Patents

Abstract

PURPOSE:To equalize an S/N at each base station. CONSTITUTION:A present station SIR evaluated value calculating part 5 calculates an SIR evaluated value corresponding to difference between a present station SIR value and the average SIR value of entire service areas. In that case, a parameter setting part 6 and a received signal power set value calculation part 7 update and set a received signal power set value by subtracting an amount in proportion to the present station evaluated value from the received signal power set value at preceding control time when the present station SIR value is smaller than an upper limit threshold value or update and set the received signal power set value by adding that amount reversely when the SIR value is smaller. A transmission power control part 8 controls the transmission power of mobile. stations under the control so that received signal power from each mobile station can be the received signal power set value. Thus, the SIR is improved at the base station where the mobile stations are locally concentrated.

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 system. In the code division multiple access, all communication is performed in the same frequency band, so that in the base station, a signal from one mobile station causes a signal from another mobile station to cause 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. The problem is that the power ratio to interference noise (hereinafter referred to as SIR) becomes small and the signal quality deteriorates. Therefore, the transmission signal power of the mobile station should be large for mobile stations far from the base station and small for mobile stations close to the base station, and the transmission signal power of the mobile stations should be the same so that the reception power at the base station is the same. Have to control.

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 SIR of the signals from the managed mobile stations can be adjusted to a constant value in each base station. Reference name Eisuke KUDOH and Tadashi MATSUMOTO: "Effect
of Power Control Error on the System User Capac
City of DS / CDMA Cellular Mobile Radios ", IEICE TRAN
S. COMMUN., Vol.E75-B, No.6, June 1992

[0004]

SUMMARY OF THE INVENTION The present invention eliminates the above-mentioned problem that the efficiency of the system deteriorates when the spatial distribution of the mobile stations is uneven, so that the transmission power of the mobile station is reduced. In this control, the control method is adaptively changed based on the SIR distribution, and the SIR at the base station with a sparse distribution of mobile stations is deteriorated within an allowable range to thereby increase the density of mobile stations. It is an object of the present invention to provide a transmission power control device that does not deteriorate the efficiency of the entire system by maintaining the quality of the system.

[0005]

The present invention relates to a mobile station transmission power control apparatus in each base station in a mobile communication system based on a code division multiple access communication system composed of a plurality of base stations. This invention is S
The average SIR value of the entire service area is received from the own station SIR value observing means that observes and outputs the IR value and the service area control station that controls the service area to which the own station belongs,
It has a reception setting means for setting the upper and lower threshold values centered on the average SIR value, or a reception setting means for receiving the average SIR value and the upper and lower threshold values from the service area control station. Also, the SIR value of the own station from the SIR value observation means of the own station and the average SIR from the reception setting means
It has its own SIR evaluation value calculation means for calculating an SIR evaluation value corresponding to the difference between the SIR values of the two from the value. Also,
The own station SIR value is compared with the upper and lower threshold values. If the own station SIR value is larger than the upper threshold value, at least the own station S is set in the received signal power setting value at the immediately preceding control time.
The received signal power set value is updated and set by subtracting an amount proportional to the IR evaluation value, and if the SIR value of the local station is smaller than the lower limit threshold, at least the received signal power set value at the immediately preceding control time is set to at least the set value. It has a reception signal power design value calculation means for updating and setting the reception signal power setting value by adding an amount proportional to the SIR evaluation value of the own station. Further, it has a transmission power control means for controlling the transmission power of the managed mobile station based on the reception signal power setting value from the reception signal power setting value calculating means.

[0006]

The local SIR value observing means and the reception setting means determine the SIR value of the local station, the average SIR value of the entire service area to which the local station belongs, and the upper and lower thresholds centered around the average SIR value. Detect or set. Own SIR
The SIR evaluation value corresponding to the difference between the local SIR value and the average SIR value is calculated by the evaluation value calculation means. The received signal power design value calculation means compares the SIR value of the own station with the upper and lower threshold values, and if the SIR value of the own station is larger than the upper threshold value, the received signal power setting at the immediately preceding control time is set. At least an amount proportional to the SIR evaluation value of the own station is subtracted from the value to update and set the received signal power setting value. Conversely, if the SIR value of the own station is smaller than the lower limit threshold value,
The received signal power setting value is updated and set by adding at least an amount proportional to the SIR evaluation value of the own station to the received signal power setting value at the immediately preceding control time. The transmission power control means controls the transmission power of the managed mobile station so that the reception signal power from each mobile station becomes the reception signal power set value. Thus, when the SIR value is below the lower limit (that is, when the communication quality is poor), the received Shingo power is increased, and when the SIR value is above the upper limit (that is, when the communication quality is too good), the received signal power is lowered. By doing so, even if the distribution of mobile stations becomes locally dense or dense, the communication quality of the entire service area can be maintained good.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a block diagram showing an embodiment of the present invention, in which 1 is a local SIR value observing section, 2 is a local SIR value transmitting section, 3 is an average SIR value receiving section, and 4 is a threshold. Value setting part, 5
Is a local SIR evaluation value calculation unit, 6 is a parameter setting unit, 7
Is a received signal power set value calculation unit, and the output D of the local SIR value observation unit 1 is input to the local SIR value transmission unit 2, the local SIR evaluation value calculation unit 5, and the parameter setting unit 6, and the average SIR is calculated. The output Dav of the value receiving unit 3 is input to the threshold value setting unit 4 and the local SIR evaluation value calculation unit 5, and the output Dsa of the local SIR evaluation value calculation unit 5 is input to the reception power setting value calculation unit 7. The output α of the parameter setting unit 6 is input to the reception signal power setting value calculation unit 7, and the output P (i) of the reception signal power setting value calculation unit 7 is input to the transmission power control unit 8 and the reception signal power setting value calculation unit 7. Is entered.

Next, the operation will be described. The operation is performed at discrete times (I = 0, 1, 2, ..., At predetermined time intervals).
i), and the operation at time I = i will be described. The own station SIR value observing section 1 observes and outputs the signal-to-interference noise power ratio D in the own station. The own station SIR value transmission unit 2 receives the output D of the own station SIR value observation unit 1 and transmits it to the service area control station 10. The service area control station 10 calculates the average SIR value Dav of the entire service area. The average SIR value receiving unit 3 receives and outputs the average SIR value Dav calculated by the service area control station. The threshold setting unit 4 outputs the output Dav of the average SIR value receiving unit 3
In response to a predetermined positive constant Dth and average SIR value receiving unit D
From av and a threshold value Dthlo, D according to the following equations (1) and (2)
Calculate and output thhi. Dthlo = Dav-Dth (1) Dthhi = Dav + Dth (2)

The own station SIR evaluation value calculation unit 5 is
The output D of the value observing unit 1 and the output Dav of the average SIR value receiving unit 3 are received, and the SIR evaluation value Dsa of the own station is calculated based on the following equation (3) and output. Dsa = | D−Dav | (3) The parameter setting unit 6 outputs the output D of the SIR value observation unit 1 of its own station.
Also, the outputs Dthlo and Dthhi of the threshold value setting unit are received, and the parameter α is set and output under the condition of Expression (4). α = Positive constant (D <Dthlo) α = Negative constant (D> Dthhi) α = 0 (other than that) (4) The received power setting value calculation unit 7 outputs the output Dsa of the local SIR evaluation value calculation unit 5 and the parameter Output α of setting unit 6 and received signal power set value P (i-1) at time I = i-1
In response, the received signal power set value P (i) at time I = i is calculated and output according to the following equation (5). P (i) = P (i-1) + α × Dsa (5)

Based on the output P (i) of the received signal power setting value calculation unit 7, the transmission power control unit 8 transmits power to the managed mobile station so that the received power becomes P (i). Control to do so. This operation is performed by the signal reception power from a certain mobile station and the own station reception power set value P (i).
And if P (i) is larger, send a command to the mobile station to increase the power by a predetermined value,
If P (i) is smaller, the mobile station transmits a command to reduce the power by a predetermined value. Further, this operation is performed for all the mobile stations under management, and is repeatedly performed at high speed within the control time interval described above.

Next, the effect of this embodiment will be shown by a simulation of FIG. Consider a situation in which mobile stations gradually gather from the vicinity of a base station (own station) of interest. That is, with time, the distribution of mobile stations near the own station becomes dense, and the distribution of mobile stations near the base station (adjacent station) adjacent to the own station becomes sparse. FIG. 2A shows a temporal change of the density. The horizontal axis of A of FIG. 2 shows time, and the vertical axis of A of FIG. 2 shows the ratio of the maximum number of mobile stations to the minimum number of mobile stations. 1.0 represents a state in which there is no bias and is uniform, and the larger the number, the larger the number of mobile stations near the local station is, and the larger the number of mobile stations near the adjacent station. The change in SIR is shown in B of FIG. The horizontal axis of B in FIG. 2 represents time, and the vertical axis represents SIR (dB). AP of FIG.
Cc and FPCc are SIRs at the local station, and APCn and FPC
n represents the SIR at the adjacent station. 2 FPCc, FPC
n is according to the method of the prior art, APCc, AP
Cn is according to the method of the present invention. Here, in this simulation, the reception power setting value at the initial time 0 was set to 1, Dth = 0.1 (dB), and α = 0.1. Further, it is assumed that the power of the radio wave decreases in proportion to the reciprocal of the fourth power of the distance. In addition, the mobile station is assumed to be connected to the base station having the smallest required transmission power. Figure 2
Therefore, in the method according to the related art, the SIR of the local station deteriorates and the SIR of the adjacent station improves as the density of the mobile stations increases. The quality deteriorates at the own station, while the quality becomes excessive at the adjacent station. In other words, it means that the efficiency of the entire system has deteriorated. On the other hand, with the method according to the present invention, the quality of the local station can be improved, and the deterioration of the quality of the adjacent station is within an allowable range. That is,
The SIR for each base station is more uniform than prior art methods. From the above results, the effectiveness of the present invention can be seen.

In the above embodiment, the average SIR value Dav
Is received from the control station, the threshold value Dthlo, Dth is received at the base station.
Although hi is calculated, the base station may calculate it so that each base station receives the average SIR value Dav and the threshold values Dthlo and Dthhi. Further, in the above embodiment,
Although the thresholds Dthlo and Dthhi common to each base station are set, different thresholds may be set in consideration of the propagation characteristics of each base station. Also,
In the above embodiment, the received signal power setting value is updated by adding or subtracting an amount proportional to Dsa as shown in the equation (5). However, the received signal power of the own station line connection Mc and the received signal of the control time immediately before is updated. The larger the power set value P (i-1), the larger the average received power S by setting the larger received power.
Since it is close to IR, an amount proportional to them, for example, Dsa
The received signal power set value may be updated by adding or subtracting an amount proportional to × Mc × P (i-1).

[0013]

As described above in detail, according to the present invention, when the spatial distribution of mobile stations is uneven, based on the SIR value of the own station and the average SIR value of the service area to which the mobile station belongs. By adaptively changing the control method, it is possible to deteriorate the SIR in a base station with a sparse mobile station distribution within an allowable range and maintain the quality in a base station with a dense mobile station distribution. Therefore, it is possible to suppress SIR at each base station due to the uneven distribution of the spatial distribution of mobile stations, and it is possible to suppress a decrease in efficiency of the entire system.

[Brief description of drawings]

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

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

[Explanation of symbols]

 1 own station SIR observation section 2 own station SIR value transmission section 3 average SIR value reception section 4 threshold setting section 5 own station SIR evaluation value calculation section 6 parameter setting section 7 received signal power set value calculation section 8 transmission power control section

Claims (1)

[Claims] 1. A mobile communication system based on a code division multiple access communication system composed of a plurality of base stations,
A mobile station transmission power control device at each base station, which monitors and outputs the signal-to-interference noise ratio value of the mobile station.
The average signal-to-interference-plus-noise ratio value of the entire service area is received from the value observing means and the service area control station that controls the service area to which the own station belongs, and the upper and lower thresholds centering on the average value are set. Or a reception setting means for receiving the average signal-to-interference noise ratio value and the upper and lower threshold values from the service area control station, and the own-station signal-to-interference from the own-station SIR value observing means. From the noise ratio value and the average signal-to-interference noise ratio value from the reception setting means, a signal-to-interference noise ratio evaluation value corresponding to the difference between the signal-to-interference noise ratio values of the two is calculated. Means, comparing the local station signal-to-interference noise ratio value with the upper and lower threshold values, if the local station signal-to-interference noise ratio value is greater than the upper threshold value, the control time immediately before Received The received signal power set value is updated and set by subtracting at least an amount proportional to the own station signal to interference noise ratio evaluation value from the power set value, and the own station signal to interference noise ratio value is the lower threshold value. If it is smaller than, the received signal power design value for updating and setting the received signal power set value by adding at least an amount proportional to the own-station signal-to-interference noise ratio evaluation value to the received signal power set value at the immediately preceding control time. Based on the received signal power set value from the calculating means and the received signal power set value calculating means, the transmission power of the managed mobile station is adjusted so that the received signal power from each mobile station becomes the received signal power set value. And a transmission power control means for controlling the transmission power control device.