JPH10108249A - System and method for controlling transmission power - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the deterioration of communication quality by calculating transmission power in respective mobile stations based on the additive average value of the average value (average SIR) of signal power-to-interference noise power ratio (reference SIR)/SIR so as to transmit it to respective mobile stations and permitting the respective mobile stations which receive it to control transmission power based on it. SOLUTION: A signal transmitted from the antenna 102 of the mobile station inside a cell is received by the antenna 101. The signal is detected by an SIR detecting part 105 by way of a sharing equipment 107 and a high frequency receiving part 106 as the signal power-to-interference noise power ratio. Before the individual transmission power of the mobile station is controlled, the SIR ratios concerning the whole mobile stations are measured. Measured detection result is inputted to a mobile station transmission power control information arithmetic part 104 so as to obtain an average signal power-to-interference noise power ratio inside the cell. Then, the ratio between reference SIR and the in-cell average signal power-to-interference noise power ratio is obtained so that the transmission power control of the mobile stations is executed based on it.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a code division multiple access communication system having a service area of outdoor or indoor.
The present invention relates to a transmission power control method and method in a mobile communication system using ivision multiple access (CDMA).

[0002]

2. Description of the Related Art In a code division multiple access communication system, a mobile station and all mobile stations in a cell communicate using the same frequency. FIG. 6 is a diagram showing an uplink interference model in the CDMA system, where numerals 601 to 603 indicate cells, 61
1 to 613 are base stations, 621 to 623 are mobile stations, 631
634 represents an interference wave, and 635 represents a desired wave.

In the uplink (communication from a mobile station to a base station), as shown in FIG. 6, interference waves from mobile stations 622-2 other than the mobile station 622-1 performing communication in the own cell, In addition, the base station 612 receives interference waves from the mobile stations 621 and 623 in other cells. In the code division multiple access communication system, a transmission power technique is indispensable in order to reduce the level of an interference wave near a base station.

In the uplink, the transmission power of the mobile station is controlled so that the communication quality (ratio of signal power to interference noise power) at the base station becomes constant. The base station sets a signal power-to-interference noise power ratio that gives a required communication quality, and calculates the ratio between the signal power of the mobile station performing communication and the interference power from the own cell and the mobile station of another cell. The difference from the value is transmitted to the mobile station as control information. The mobile station controls the transmission power of the mobile station based on the control information.

FIG. 7 shows the operation of uplink transmission power control. Numerals 701 to 703 indicate cells, 711
713 denotes a base station, 721 to 723 denote mobile stations, and mobile station transmission power with respect to the distance when the base stations 711 to 713 are linearly arranged one-dimensionally.

The positions of the cell edges in the base stations 711 to 713 are E1 to E4, and the installation positions of the base stations are CS1 to CS3. The received signal power in CS1 to CS3 is Pd0,
The interference noise power is expressed as Pu0. At this time, the received signal power to interference noise power ratio (Pd0 / Pu0) is P0
Is assumed to be equal to

[0007] The signal level transmitted from the mobile station to the base station is attenuated by r ^-a (r: base station-mobile station distance, a: attenuation constant of the propagation path). The position of the mobile station is A, and the position of the base station is B
When the distance between the mobile station and the base station is expressed by “Equation 1”, the transmission powers P1, P2, and P3 of the mobile stations in PS1, PS2, and PS3 are expressed by Equation 2, “Equation 3,” and “Equation 4,” respectively. "become that way.

[0008]

(Equation 1)

[0009]

(Equation 2)

[0010]

(Equation 3)

[0011]

(Equation 4)

The mobile station transmission power is highest at cell edges E1 to E4. Assuming that the transmission power at the cell edge takes the same value and this is the maximum transmission power Pm of the mobile station, base stations 1 to 3 shown by "Equation 4", "Equation 5", and "Equation 6"
Have the same cell radius.

[0013]

(Equation 5)

[0014]

(Equation 6)

[0015]

(Equation 7)

[0016]

In a code division multiple access communication system, it is generally ideal that traffic within a cell is uniform. However, in an actual system, the traffic around a station, a downtown area, or the like is considered. Then, the traffic is not uniform. And traffic fluctuates spatially and temporally,
When traffic concentrates on a particular base station, the interference noise power increases and the signal power to interference noise power ratio degrades. An object of the present invention is to improve the degradation of communication quality due to a reduction in the signal power to interference noise power ratio when traffic concentrates on a specific base station.

[0017]

According to the invention, the above-mentioned object is solved by the means described in the claims.

That is, the first aspect of the present invention aims to maintain a constant communication quality in a base station that performs two-way communication with a plurality of mobile stations, and the transmission power of each mobile station within the communication area of the base station. In the transmission power control method for controlling

The base station receives a radio wave from each mobile station and measures a signal power to interference noise power ratio (SIR), and an average value of each SIR (average SIR)
And a third means for calculating a ratio of a signal power to interference noise power ratio (reference SIR) that gives a predetermined required communication quality and the average SIR (reference SIR / average SIR). When,

Based on the arithmetic mean or geometric mean value of the (reference SIR / average SIR), the transmission power at each mobile station is calculated, and the calculation result is transmitted to each mobile station. Means, and each mobile station is a transmission power control system including means for controlling its own transmission power based on the received calculation results.

According to a second aspect of the present invention, there is provided a transmission system for controlling transmission power of each mobile station within a communication area of the base station for the purpose of maintaining a constant communication quality in a base station which performs bidirectional communication with a plurality of mobile stations. In the power control method,

The base station includes a first unit for measuring a signal power to interference noise power ratio (SIR) for each mobile station, a second unit for calculating an average value of each SIR (average SIR), Third means for calculating a ratio (average SIR / reference SIR) between the average SIR and a signal power to interference noise power ratio (reference SIR) that provides a predetermined required communication quality;

The maximum transmission power for each mobile station calculated based on the arithmetic mean or geometric mean value of the (average SIR / reference SIR), the distance between each mobile station and the base station, and the attenuation of the propagation path Calculating the transmission power corresponding to each mobile station from the amount, and transmitting the calculation result to the corresponding mobile station, each mobile station has its own station based on the received calculation result. This is a transmission power control method including means for controlling transmission power.

According to a third aspect of the present invention, the transmission power of each of the mobile stations within a communication area of the base station is controlled in order to maintain a constant communication quality in a base station that performs bidirectional communication with a plurality of mobile stations. In the transmission power control method,

The base station measures a signal power to interference noise power ratio (SIR) for each mobile station, calculates an average value of each SIR (average SIR), and gives a predetermined required communication quality. Signal power to interference noise power ratio (reference SI
R) and the ratio of the average SIR (reference SIR / average SI)
R), and calculates the transmission power in each of the mobile stations based on the arithmetic mean (reference SIR / average SIR) or the geometric mean value k (k is a positive real number). Send the result to each applicable mobile station,

Each of the mobile stations controls its own transmission power based on each of the received calculation results, and if the calculation result is greater than or equal to its own maximum transmission power, the mobile station's transmission power is controlled. The power is the maximum transmission power, the transmission power of the mobile station communicating with the base station, and the mobile station communicating with the peripheral base station in the communication area of the base station (peripheral base station) located around the base station. The interrelationship of station transmit power is

When the distance between the mobile station communicating with the base station and the base station is equal to the distance between the mobile station communicating with the peripheral base station and the peripheral base station, the value of k is larger than 1. A transmission power control method for controlling the transmission power of the mobile station located in the communication area shown in the communication area to be larger than the transmission power of the mobile station located in the communication area in which the k indicates a value of 1 or less. is there.

According to a fourth aspect of the present invention, in order to maintain a constant communication quality in a base station that performs bidirectional communication with a plurality of mobile stations, a transmission for controlling the transmission power of each mobile station within a communication area of the base station is provided. In the power control method,

The base station measures a signal power to interference noise power ratio (SIR) for each mobile station, and
An average value of R (average SIR) is calculated, and a ratio (average SIR / standard SIR) of the average SIR and a signal power to interference noise power ratio (reference SIR) that provides a predetermined required communication quality is obtained.
IR), and

The maximum transmission power for each mobile station calculated based on the arithmetic mean or geometric mean value Δp (Δp is a positive real number) of the (average SIR / reference SIR), Calculating the transmission power corresponding to each mobile station from the distance between the base stations and the attenuation of the propagation path, and transmitting the respective calculation results to the mobile stations,

The maximum transmission power of a mobile station located in a communication area where Δp is greater than 1 is as follows.
Set the maximum transmission power of the mobile station to be smaller than the maximum transmission power of the mobile station located in the communication area indicating the following value,

The set maximum transmission power Pm (Pm is a positive real number) is the maximum transmission power (Pm (max)) of the mobile station.
(Pm (max) is a positive real number)
= Pm (max), where Pm is the minimum transmission power Pm (min) of the mobile station (Pm (min) is a positive real number)
If it falls below

Assuming that Pm = Pm (min), the value of Pm is transmitted to each mobile station, and each mobile station controls its own transmission power based on the received calculation result, and the calculation result is A transmission power control method in which the transmission power of a station is set to Pm when the transmission power is greater than or equal to Pm.

According to the present invention, by diversifying traffic, deterioration of a signal power to interference noise power ratio in a base station where traffic is concentrated is reduced to improve communication quality.

According to the first and third aspects of the present invention, the "reception power level of each base station" and the "maximum transmission power level of the mobile station at the cell edge" are each set to a constant level irrespective of traffic. / Average SIR) based on the arithmetic mean or geometric mean value of the mobile station so that the base station having a high traffic has a small cell radius and the base station having a low traffic has a large cell radius. Features.

Further, according to the second and fourth aspects of the present invention, the reception power level of each base station is set to a fixed level, and the (average SIR)
By changing the maximum transmission power of the mobile station at the cell edge according to the traffic based on the arithmetic mean or the geometric mean of the (reference SIR), the cell radius at the base station with high traffic is small and the traffic is low. The transmission power of the mobile station is controlled so that the cell radius in the base station is increased.

[0037]

FIG. 1 is a diagram showing an example of the configuration of a base station and a mobile station according to the present invention. Numerals 101 and 102 denote antennas, 103 denotes a reference SIR value storage unit, and 104 denotes a mobile station transmission. A power control information calculation unit, 105 is an SIR detection unit,
Reference numerals 06 and 112 denote high frequency receiving units, 107 and 110 denote duplexers, 108 denotes a mobile station transmission power control information transmitting unit, and 109 and 112.
Reference numeral 111 denotes a high-frequency transmitting unit, and 113 denotes a mobile station transmission power control information receiving unit. The control of the mobile station transmission power according to the present invention is shown as a flowchart in FIGS.

First, the control algorithm of FIG. 2 will be described with reference to FIG. The signal transmitted from the antenna 102 of the mobile station in the cell is received by the antenna 101 and passed through the duplexer 107 and the high frequency
Signal power to interference power ratio (SI) in IR detection section 105
R) is detected.

Before controlling the individual transmission power of the mobile stations, the signal power to interference noise power ratio for all mobile stations in the cell is measured. The detection result is input to the mobile station transmission power control information calculation section 104, and the mobile station transmission power control information calculation section 104 calculates the average signal power to interference noise power ratio (Pav) in the cell.

Here, as in the conventional example, the reference received signal power at the base station is Pd0, and the interference noise power is Pu.
Notated as 0. The ratio P0 / Pav between the reference SIR (Pd0 / Pu0 = P0) and the above-mentioned average signal power to interference noise power ratio (Pav) in the cell is obtained. Based on this, the transmission power of the mobile station is controlled.

As shown in FIG. 2, the mobile station transmission power P is
= Pd0 × r ^ka (r: base station-mobile station distance, a: propagation path attenuation constant) is set by weighting the transmission power of the mobile station. Assuming that the number of times of control is N, the control variable k is represented by, for example, the following equation. In other words, the arithmetic mean is given as "Equation 8", and the geometric mean is given as "Equation 9".

[0042]

(Equation 8)

[0043]

(Equation 9)

In the conventional method, the transmission power of the mobile station is expressed as P =
Although Pd0 × r ^a was set, in the present invention, P = Pd0 ×
The transmission power of the mobile station is weighted and controlled by changing the value of k according to the above equation as r ^ka . That is, when the intra-cell average signal power to interference noise power ratio (Pav) is larger than the reference signal power to interference noise power ratio (P0), k ≦ 1 in the above equation, and the mobile station transmission power is equal to the conventional system. By comparison, the increase in the transmission power of the mobile station with respect to the distance is moderated.

On the other hand, when the average signal power to interference noise power ratio in the cell is smaller than the reference signal power to interference noise power ratio (P0), k> 1. Steep increase in transmission power. The transmission power control information to be controlled in this way is input to the mobile station transmission power control information transmitting section 108, and the high frequency transmitting section 109, the duplexer 1
07, transmitting via the antenna 101.

In the mobile station, the antenna 102 and the duplexer 110
, After receiving by the high frequency receiving section 112, the control signal is extracted by the mobile station transmission power control information receiving section 113, and the transmission power of the high frequency transmitting section 111 is set to a required value. Further, in the uplink, the transmission power of the mobile station is maximized at the end of the cell. Therefore, as shown in FIG. 2, the control is performed within the cell at the maximum transmission power Pm (max) of the mobile station.

FIG. 4 is a diagram showing the relationship between the traffic distribution and the mobile station transmission power with respect to the distance when the base stations are linearly arranged one-dimensionally and the transmission power control shown in FIG. 2 is performed. In the figure, numerals 401 to 403 are cells, 4
11 to 413 are base stations, 421 to 423 are mobile stations, CS1 to CS3 are base station installation positions, E1 to E4 are cell edge positions, Pd0 is a reference received signal power in the base station, Pm is a base station 411 to This is the maximum transmission power of the base station 413.

The traffic has a distribution that attenuates in the direction of the base station 411 and the base station 413 with the base station 412 as the center. By applying this control algorithm, P = Pd0 × r ^ka (k>) in the cell of the base station 412.
The transmission power of the mobile station is controlled so as to satisfy 1), and P = Pd0 × r ^ka (k ≦
Transmission power control is performed so as to satisfy 1).

Therefore, the radius of a cell with high traffic like the cell of the base station 412 is small, and the radius of the cell with low traffic like the cells of the base station 411 and the base station 413 is large. As in the case of FIG. 4, when the traffic in the cell of the base station 412 is higher than that of the base stations 411 and 413, the interference noise power increases and the signal power to interference noise power ratio deteriorates.

In order to reduce this deterioration, it is necessary to control the transmission power of the mobile station so as to increase the transmission power of the mobile station. As in the conventional system shown in FIG.
When the base stations 721 to 723 are located at the same distance from the communicating base stations 711 to 713, the traffic distribution according to the traffic distribution according to the conventional method is notwithstanding the distribution shown in FIG. Since the transmission power control of the stations is not performed, the mobile stations 721 to 723 have the same transmission power.

However, according to the transmission power control method of the present invention, since the traffic in the cell of the base station 412 in FIG. 4 is higher than that of the base stations 411 and 413, the mobile station 412
Is controlled to be higher than the transmission powers of the mobile stations 411 and 413. As described above, it is a feature of the present invention that the transmission power of the mobile station is controlled according to the traffic. By performing the control as described above, traffic is dispersed and communication quality in an area with high traffic can be improved.

Next, the control algorithm of FIG. 3 will be described. The method of detecting the signal power to interference noise power ratio and the method of calculating the average signal power to interference noise power ratio in the cell are the same as those in FIG. 2, and the detection result is the mobile station transmission power control information calculation unit 104 in FIG. And the mobile station transmission power control information calculation section 104 calculates the average signal power to interference noise power ratio (Pav) in the cell.

In this embodiment, the maximum transmission power of the mobile station in the cell is determined by determining the average signal power to interference noise power ratio (Pav) and the reference signal power to interference noise power ratio (P0) in the cell.
Set according to. That is, assuming that the control variable of the maximum transmission power is ΔP and the number of times of control is N, for example, “Equation 10”
, Or the geometric mean shown by "Equation 11".

[0054]

(Equation 10)

[0055]

[Equation 11]

The reference maximum transmission power Pm0 at the cell edge is defined as Pm0
= (Pm (max) + Pm (min)) / 2. Here, Pm (max) is the maximum transmission power on the system, and Pm (min) is the minimum transmission power on the system. The cell-edge maximum transmission power Pm in the present invention is obtained by multiplying Pm0 by ΔP, and Pm = ΔP × (Pm (max) + Pm
(Min)) / 2.

The intra-cell average signal power to interference noise power ratio (P
av)> Reference signal power to interference noise power ratio (P0), ΔP shown in the above equation is ΔP> 1, and Pm> (Pm
(Max) + Pm (min)) / 2. When the average signal power to interference noise power ratio (Pav) ≦ reference signal power to interference noise power ratio (P0), ΔP ≦ 1, and Pm ≦ (Pm (max) + Pm (min)) / 2. Become.

When the maximum transmission power Pm exceeds Pm (max), Pm = Pm (max), and Pm (mi)
If it is less than n), Pm = Pm (min). After defining the maximum transmission power at the cell edge of the mobile station in the cell communicating with the base station in this way, the mobile station transmission power is set to P = Pd0 in accordance with the distance attenuation for each mobile station. ×
to control the r ^a.

When the mobile station exists at the cell edge, the maximum transmission power Pm defined above is reached. As in the case of FIG. 2, the control information of the mobile station transmission power is input to the mobile station transmission power information transmission unit 108 of FIG. 1, and transmitted via the high frequency transmission unit 109, the duplexer 107, and the antenna 101.

In the mobile station, the antenna 102 and the duplexer 110
, After receiving by the high frequency receiving section 112, the control signal is extracted by the mobile station transmission power control information receiving section 113, and the transmission power of the high frequency transmitting section 111 is set to a required value.

FIG. 5 shows the relationship between the traffic distribution and the distance and the mobile station transmission power when the transmission power control shown in FIG. 3 is performed when the base stations are linearly arranged one-dimensionally. In FIG. 5, reference numerals 501 to 503 indicate cells, 511 to 513 indicate base stations, CS1 to CS3 indicate base station installation positions, E1 to E4 indicate cell edge positions, and Pd0 indicates a reference reception signal. Power, Pm1 indicates the maximum transmission power of the base station 512, and Pm2 indicates the maximum transmission power of the base station 511 and the base station 513. In the figure, the traffic has a distribution that attenuates in the directions of the base station 511 and the base station 513 with the base station 512 as the center. First,
As can be seen from the interference model described in FIG.
, The interference noise power increases as the cell radius increases. To solve this, the maximum transmission power of the mobile station at the cell edge of a cell with high traffic is reduced as described above.

As a result, the cell radius is reduced, and the amount of interference can be reduced. As shown in FIG. 5, the maximum transmission power is set in a relationship of Pm2> Pm1. As a result, mobile stations in an area with high traffic can communicate with a base station having a larger cell radius, so that deterioration of communication quality is improved.

[0063]

According to the present invention, it is possible to equalize the traffic and improve the deterioration of the communication quality due to the concentration of traffic at a specific base station.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating an example of a configuration of a base station and a mobile station according to the present invention.

FIG. 2 is a flowchart showing a first example of mobile station transmission power control.

FIG. 3 is a flowchart showing a second example of mobile station transmission power control.

4 is a diagram showing a mobile station transmission power with respect to a traffic distribution and a distance when the algorithm of FIG. 2 is used.

FIG. 5 is a diagram showing a mobile station transmission power with respect to a traffic distribution and a distance when the algorithm of FIG. 3 is used.

FIG. 6 is a diagram showing a line interference model in the CDMA system.

FIG. 7 is a diagram illustrating mobile station transmission power with respect to distance when conventional base stations are linearly arranged.

[Explanation of symbols]

 101, 102 Antenna 103 Reference SIR value storage unit 104 Mobile station transmission power control information calculation unit 105 SIR detection unit 106, 112 High frequency reception unit 107, 110 Duplexer 108 Mobile station transmission power control information transmission unit 109, 111 High frequency transmission unit 113 Mobile station transmission power control information receiving section 401-403, 501-503 Cell 411-413, 511-513 Base station 421-423 Mobile station

Claims (4)

[Claims] A transmission power control method for controlling transmission power of each mobile station within a communication area of the base station for the purpose of keeping communication quality at a base station performing bidirectional communication with a plurality of mobile stations, A base station that receives radio waves from each mobile station and measures a signal power to interference noise power ratio (SIR) thereof; and a second unit that calculates an average value (average SIR) of the SIRs. Means for calculating a signal power-to-interference noise power ratio (reference SIR) that gives a predetermined required communication quality and the average SIR (reference SIR / average SIR); Fourth means for calculating transmission power in each of the mobile stations based on an arithmetic mean or geometric mean of SIR / average SIR, and transmitting each calculation result to each of the mobile stations. The mobile station receives Transmission power control method characterized by comprising means for controlling the transmission power of the own station based on the each calculation result. 2. A transmission power control system for controlling transmission power of each mobile station within a communication area of the base station for the purpose of maintaining constant communication quality in a base station performing bidirectional communication with a plurality of mobile stations, The base station has a signal power to interference noise power ratio (SIR) for each mobile station.
, A second means for calculating an average value of the SIRs (average SIR), and a signal power-to-interference noise power ratio (A / S) which gives the average SIR and a predetermined required communication quality ( Third means for calculating a ratio (average SIR / reference SIR) to the reference SIR), and for each mobile station calculated based on the arithmetic mean or geometric mean value of the (average SIR / reference SIR). The fourth transmission means for calculating the maximum transmission power, the transmission power corresponding to each mobile station from the distance between each mobile station and the base station and the attenuation of the propagation path, and transmitting the calculation result to the corresponding mobile station. A transmission power control system, wherein each mobile station includes means for controlling its own transmission power based on the received calculation results. 3. A transmission power control method for controlling transmission power of each mobile station within a communication area of the base station in order to keep communication quality in a base station performing bidirectional communication with a plurality of mobile stations. The base station comprises: a signal power to interference noise power ratio (SI
R), calculate the average value of the SIRs (average SIR), and determine the ratio of the signal power to interference noise power ratio (reference SIR) that gives a predetermined required communication quality and the average SIR ratio (reference SIR). / Average SIR), and calculates the transmission power in each mobile station based on the arithmetic mean or geometric mean value k (k is a positive real number) of the (reference SIR / average SIR). The result is transmitted to each applicable mobile station, and each mobile station controls its own transmission power based on each received calculation result, and the calculation result is larger than its own maximum transmission power, or If they are equal, the transmission power of the own station is set to the maximum transmission power, and the transmission power of the mobile station communicating with the base station and the transmission power of the base station (peripheral base station) located around the base station are determined. Mobile that communicates with neighboring base stations The correlation between the transmission powers of the stations is as follows: when the distance between the mobile station communicating with the base station and the base station is equal to the distance between the mobile station communicating with the peripheral base station and the peripheral base station, Is controlled so that the transmission power of the mobile station located in the communication area where the value of k is greater than 1 is higher than the transmission power of the mobile station located in the communication area where the value of k is 1 or less. A transmission power control method. 4. A transmission power control method for controlling transmission power of each mobile station within a communication area of the base station for the purpose of keeping communication quality in a base station performing bidirectional communication with a plurality of mobile stations, The base station includes a signal power to interference noise power ratio (SI
R), calculate an average value (average SIR) of the respective SIRs, and calculate a ratio (average) between the average SIR and a signal power-to-interference noise power ratio (reference SIR) that provides a predetermined required communication quality. SIR / reference SIR), and the maximum transmission power for each mobile station calculated based on the arithmetic mean or geometric mean value Δp (Δp is a positive real number) of the (average SIR / reference SIR) Calculating the transmission power corresponding to each mobile station from the distance between each mobile station and the base station and the attenuation of the propagation path, transmitting each calculation result to each mobile station; The maximum transmission power of a mobile station located in a communication area having a large value is smaller than the maximum transmission power of a mobile station located in a communication area having a value of Δp of 1 or less. Set power and set The maximum transmission power Pm (Pm is a positive real number) is the maximum transmission power (Pm (max)) (Pm (ma) of the mobile station.
x) is a positive real number), Pm = Pm (max), where Pm is the minimum transmission power Pm (min) of the mobile station.
When (Pm (min) is a positive real number), the value of Pm is transmitted to each mobile station as Pm = Pm (min), and each mobile station performs its own calculation based on the received calculation results. A transmission power control method comprising: controlling the transmission power of a station; and, when the calculation result is greater than or equal to the Pm, setting the transmission power of the own station to the Pm.