JPH1032540A - Transmission power control method and device therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To uniform the quality of communication and to improve the efficiency of the whole system by calculating communication quality at the discrete time based on the total power of received signals and the average of the received power of incoming information signals, and adjusting the number of mobile stations while increasing the number of mobile stations to be managed when the communication quality is excessive and reducing the number of the mobile stations to be managed when the communication quality is bad. SOLUTION: A total receiving power observing part 2 observes and outputs the total power of signals received at the time of discretizing (i). An information signal receiving part 3 calculates the average of the received power of the upward information signal transmitted from each mobile station at the time of discretizing (i) to output as a signal power S. A communication quality arithmetic part 4 calculates the quality of communication at the time of discretizing (i) based on the total received power outputted by the part 2 and the signal power S outputted by the part 3. The transmission power of a pilot signal is controlled based on this quality of communication. Namely, when the communication quality is excessive, the transmission power is made large to manage a part of the mobile stations under management by an adjacent base station.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for controlling the transmission power of a control signal and a downlink information signal transmitted by a base 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 (Code Division)
In a mobile communication system based on a session multiple access (communication system), a service area is configured by a plurality of small wireless zones, and a base station is installed in each of the small wireless zones. Each base station constantly transmits a control signal called a pilot signal, and the mobile station receives pilot signals from a plurality of surrounding base stations, and is under the control of the base station that transmitted the pilot signal with the highest received power. And exchanges an uplink information signal and a downlink information signal.

[0003] With regard to such conventional communication control between a mobile station and a base station, see "Digital Mobile Communication", 1st edition, pp. 1-95.
179-180, supervised by Kagaku Shimbun, Moruji Kuwahara, 199
There is 2.9. As shown in this document, the transmission power of the pilot signal is equal and constant in each base station.
Therefore, when the base stations are arranged at equal intervals, the boundary of the coverage area of each base station is the midpoint with the adjacent base station, and the area of the coverage area of each base station is equal.

[0004]

However, if the transmission power of each base station is constant and equal and the area of the coverage area is constant as described above, the distribution of mobile stations in each base station varies. In this case, the number of managed mobile stations increases in a base station where the distribution of mobile stations is dense, and the number of managed mobile stations decreases in a base station where the distribution of mobile stations is sparse.

In the code division multiple access communication system, as the number of multiplexes simultaneously communicating increases, that is, as the number of mobile stations to be managed increases, the communication quality of the base station deteriorates. Therefore, in a base station where the distribution of mobile stations is dense, the communication quality is greatly deteriorated compared to the reference quality, while in a base station where the distribution of mobile stations is sparse, the communication quality is excessive compared to the reference quality. . When such communication quality variation occurs, the efficiency of the entire mobile communication system becomes very poor.

Therefore, there is a demand for a transmission power control method and apparatus that makes the communication quality of each base station as uniform as possible and improves the efficiency of the entire system even when the distribution of mobile stations is uneven in location. Was.

[0007]

According to the power control method of the present invention, a service area is constituted by a plurality of small radio zones, and a control signal constantly transmitted from a base station installed in each small radio zone is moved. A station receives from a plurality of base stations, wirelessly connects to a base station with the highest control signal reception power to transmit an uplink information signal, and a base station with the highest control signal reception power transmits to a wirelessly connected mobile station. A base station having a discrete time i in a transmission power control method of controlling the power of a signal transmitted by a base station at a constant time interval T in a mobile communication system of a code division multiple access communication system for transmitting a downlink information signal to a station. Measuring the total power of all received signals, calculating the average of the received power of each uplink information signal of the wirelessly connected mobile station, and calculating the total power of all the received signals and the uplink information signal. Based of the average of the received power,
Calculating the communication quality at the discrete time i; calculating the communication quality difference between the communication quality at the discrete time i and the target value; calculating the update transmission power difference based on the communication quality difference; Calculating the transmission power at the discrete time i based on the value obtained by adding the power difference and the transmission power calculated at the discrete time i-1 before the predetermined time interval T; And transmitting a downlink information signal.

At a certain base station at discrete time i, the total power of the received signal is measured. Further, it calculates the average of the received power of each uplink information signal from the connected mobile station. The communication quality at discrete time i is calculated based on the total power of the received signal and the average of the received power of the uplink information signal of each mobile station. The communication quality difference between the calculated communication quality and the target value is obtained, and the updated transmission power difference is calculated based on the communication quality difference. The updated transmission power difference and the discrete time i−
The transmission power at the discrete time i is calculated based on the value obtained by adding the transmission power at 1 and the transmission power at 1 to transmit the control signal and the downlink information signal. The communication quality is calculated at a certain time interval, and the communication quality is smaller than the target value,
If the communication quality is poor, reduce the power for transmitting the signal, reduce the range of the coverage area where the mobile station can obtain a sufficient control signal and downlink information signal to connect to the base station, and manage the mobile station. The number of stations is reduced, and the communication quality is improved to a target value. When the communication quality is higher than the target value and the communication quality is excessive, the power for transmitting the signal is increased, and a sufficient control signal and downlink information signal for the mobile station to connect to the base station are transmitted. The range of the obtained coverage area is widened, the number of mobile stations to be managed is increased, the communication quality is reduced to a target value, and the communication quality is made uniform.

[0009] The communication quality of the transmission power control method according to the present invention is determined by the difference between the total power of the received signal and the average of the reception power of the uplink information signal of the connected mobile station, and the uplink of the connected mobile station. It is calculated by the ratio with the average of the reception power of the information signal.

Further, since the communication quality and the communication quality difference are in units of decibels, the calculated values are evaluated based on a relative ratio, and the updated transmission power amount difference is calculated based on the ratio. The difference can be easily converted to the updated transmission power difference, and the calculation of the updated transmission power difference is facilitated.

In the transmission power control method according to the present invention, the communication quality and the communication quality difference are expressed in decibels, and the step of calculating the updated transmission power difference is substituted into a non-decreasing function using the communication quality difference as a variable. The calculated dependent value is calculated as an updated transmission power difference. The communication quality and the communication quality difference are calculated in decibels so that the calculated values become relative ratios.

The target value of the transmission power control method according to the present invention is a preset constant. The target value is set as a constant, and the configuration for calculating the target value is omitted.

Further, the target value in the transmission power control method according to the present invention is set to an average value of the communication quality at discrete time i and the communication quality at discrete time i of an adjacent base station. The target value of the communication quality is determined by the distribution of the mobile stations connected at the discrete time i and the mobile stations connected to the adjacent base station, that is, the communication quality at the discrete time i and the communication quality of the adjacent base station. Fluctuates.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiment 1 FIG. FIG. 1 is a configuration block diagram of an apparatus for implementing a power control method according to the first embodiment of the present invention. The apparatus shown in FIG. 1 performs a predetermined operation at regular time intervals T. In the present embodiment, an operation of the apparatus in a situation of the mobile station at a certain discrete time i will be described.

In FIG. 1, reference numeral 1 denotes a communication quality target value input terminal to which a communication quality target value which is a preset constant value is input. Reference numeral 2 denotes a total received power observation unit that observes and outputs the total power of the signal received at the discrete time i. The total received power includes not only the sum of the powers of the uplink information signals of the connected mobile stations, but also the power of the uplink information signals of the mobile stations connected to the adjacent base station. Reference numeral 3 denotes an information signal receiving unit that calculates the average of the received power of uplink information signals such as voices transmitted from each mobile station at a discrete time i and outputs the average as the signal power S. Originally, the reception powers of the uplink information signals transmitted from each mobile station by the mobile station transmission power control should be all equal. However, the power value of the uplink information signal transmitted from each mobile station is not always equal due to the presence of a control error. Therefore,
For the signal power S, the average of the received power of the uplink information signal of each mobile station is calculated and output.

Reference numeral 4 denotes a communication quality calculating unit which performs communication at a discrete time i based on the total received power at the discrete time i output by the total received power observation unit 2 and the signal power S output by the information signal receiving unit 3. Calculate and output quality. The communication quality is calculated by using the value obtained by subtracting the signal power S from the total received power as the interference power I of the signal power S, and calculating the following equation (1) based on the ratio of the signal power S to the interference power I. Equation (1)
Is given in decibels. 10 × log ₁₀ (S / I) [dB] (1)

Numeral 5 denotes a subtracter for calculating a difference between the communication quality at the discrete time i input from the communication quality calculation unit 4 and the communication quality target value input from the communication quality target value input terminal 1 and calculating the discrete time i. Is calculated to be higher or lower than the communication quality target value. Reference numeral 6 denotes an update amount calculation unit, which converts the subtraction result of the subtractor 5 as an update amount of the transmission power and outputs it. For the update, the subtraction result is substituted, for example, as a variable of a linear function having a positive slope and passing through the origin, and the dependent value is output as the transmission power update amount. 7
Denotes an adder, which outputs the sum of the update amount output from the update amount calculation unit 6 and the transmission power value at the discrete time i-1. 9 is a limiter, and the transmission power value at the discrete time i is
Adjust to fit within a certain range. This is because the power value transmittable by the hardware has an upper limit and a lower limit. When the value output from the adder 7 is larger than the upper limit, the specified upper limit value is output. The lower limit value is output, and in other cases, the value output by the adder 7 is output as it is to adjust the transmission power value.

Reference numeral 10 denotes a control signal transmitting unit, and the limiter 9
A pilot signal is transmitted based on the transmission power value at time i, which is the output of. An information signal transmission unit 11 transmits an information signal such as voice to each mobile station based on a transmission power value at time i, which is an output of the limiter 9. Reference numeral 8 denotes a delay unit that delays the transmission power value at time i, which is the output of the limiter 9, and outputs it to the adder 7 as the transmission power value at the discrete time i-1 at the time of the next transmission power calculation. By repeating this operation, the transmission power is adjusted at regular time intervals T.

In the device configured as described above,
Since the communication quality at a certain discrete time i is measured and the transmission power of the pilot signal is controlled based on the measured communication quality, if the measured communication quality is excessive, the transmission power is increased to expand the coverage area. A part of the mobile stations under the control of the adjacent base station is managed. As a result, the number of mobile stations to be managed is increased, so that excessive communication quality is suppressed and the target communication quality is approached. If the measured communication quality is poor, the transmission power is reduced to reduce the coverage area, so that part of the managed mobile stations are transferred to the adjacent base station, and as a result, the number of managed mobile stations is reduced. Thus, the communication quality is improved and approaches the target communication quality. Also, with the increase and decrease of the coverage area due to the increase and decrease of the transmission power of the pilot signal,
If the area of the coverage area is widened, so that the power of the necessary and sufficient information signal can be obtained even in a distant mobile station,
When the transmission power of the information signal to each mobile station under management increases, and when the area of the cover area decreases, the transmission power of the information signal to each mobile station under management decreases so that the power of the information signal does not become excessive. Become. Since the target communication quality is the same at each base station, the communication quality of the signals being communicated at each base station is uniform even if the distribution of mobile stations is uneven, resulting in improved overall system efficiency. I do. Since the target value is set in advance, the system configuration is simplified.

Embodiment 2 FIG. 2 is a configuration block diagram of an apparatus for realizing the power control method according to the second embodiment of the present invention. In FIG. 2, the same operations as those in FIG. 1 are denoted by the same reference numerals. Reference numeral 12 denotes an adjacent base station communication quality receiving unit, which receives the communication quality calculated by the adjacent base station. Further, 14 transmits the calculated communication quality to the adjacent base station.

Reference numeral 13 denotes a communication quality target value calculation unit, and K-
A communication quality target value is calculated based on the past M communication qualities calculated by one adjacent base station. The communication quality of the target base station at discrete time i is Q (0, i), and the communication quality of a certain adjacent base station k at discrete time i is Q (k, i).
If (k = 1,..., K−1), the average of the past M communication qualities calculated by the K base stations including the target base station is given by the following equation (2).

[0022]

(Equation 1)

This is output to the subtracter 5 as a target value of the communication quality. The subtractor 5 calculates the difference between the communication quality at the discrete time i and the calculated target value as in the first embodiment, and converts the calculated difference into an update amount of the transmission power in the update amount calculation unit 6. Is done. The converted update amount is added to the transmission power amount at the discrete time i-1 measured before the certain time interval T,
It is adjusted by the limiter 9. Using the value adjusted by the limiter 9 as the transmission power value at the discrete time i, the control signal transmission unit 10 and the information signal transmission unit 11 transmit the pilot signal and the information signal respectively at the transmission power value. The above operation is repeated, and the transmission power value is updated at regular time intervals T.

In the second embodiment, the target value of the communication quality is set by the average value of the communication quality calculated in the target base station and a plurality of base stations adjacent to the base station. The target value can be accurately set based on the communication quality of the adjacent base station, and the distribution of mobile stations in the vicinity of the target base station and a plurality of base stations adjacent to the base station varies. Even when the communication is performed, the communication quality of the signal communicated by each base station becomes uniform, and as a result, the efficiency of the entire system is improved.

[0025]

According to the present invention, the communication quality at the discrete time i is calculated based on the total power of the received signal and the average of the reception power of the uplink information signal, and if the calculated communication quality is excessive, The transmission power of the control signal and the downlink information signal is increased to increase the number of mobile stations to be managed by connecting the mobile stations managed by the adjacent base station. If the calculated communication quality is poor, the control signal and the downlink information signal Since the transmission power of the mobile station is reduced and the number of mobile stations managed is reduced by connecting the mobile station under management to an adjacent base station and the number of mobile stations is adjusted, the communication quality becomes uniform and the efficiency of the entire system is improved. improves.

The communication quality is calculated by calculating the difference between the total power of the received signal and the average of the received power of the uplink information signal of the connected mobile station, and the average of the received power of the uplink information signal of the connected mobile station. Since the ratio is calculated, the communication quality can be easily observed.

Further, since the communication quality and the communication quality difference are expressed in decibels, the calculated values are evaluated based on a relative ratio, and the updated transmission power difference is calculated based on the ratio. Can be easily converted to the updated transmission power difference, and the calculation of the updated transmission power difference is facilitated.

Further, since the communication quality target value is set in advance as a constant, there is no need to exchange communication quality information between base stations, and the system configuration is simplified.

According to the present invention, the target value is calculated from the average of the communication quality at the discrete time i and the communication quality of the adjacent base station at the discrete time i, so that the communication can be accurately performed according to the situation of the adjacent base station. Since the quality is set and the communication quality between the base stations becomes uniform, the efficiency of the entire system is improved.

[Brief description of the drawings]

FIG. 1 is a block diagram of an apparatus for implementing a transmission power control method according to a first embodiment of the present invention.

FIG. 2 is a block diagram of an apparatus for realizing a transmission power control method according to a second embodiment of the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 communication quality target value input terminal 2 total received power control unit 3 information signal receiving unit 4 communication quality calculation unit 5 subtractor 6 update amount calculation unit 7 adder 8 delay unit 9 limiter 10 control signal transmission unit 11 information signal transmission unit 12 Adjacent base station communication quality receiver 13 Communication quality target value calculator 14 Communication quality transmitter

Claims (6)

[Claims] A mobile station receives a control signal from a plurality of base stations, wherein a service area is constituted by a plurality of small wireless zones, and a control signal constantly transmitted from a base station installed in each of the small wireless zones. The received power of the signal is wirelessly connected to the base station to transmit the uplink information signal, and the received power of the control signal is the largest base station transmits the downlink information signal to the mobile station wirelessly connected, In a mobile communication system of a code division multiple access communication system, a transmission power control method for controlling the power of a signal transmitted by a base station at a constant time interval T is described. Measuring the power, calculating the average of the received power of each uplink information signal of the mobile station wirelessly connected, the total power of all the received signals and the received power of the uplink information signal Calculating the communication quality at the discrete time i based on the average; calculating the communication quality difference between the communication quality at the discrete time i and the target value; and updating the transmission power difference based on the communication quality difference. Calculating the transmission power at the discrete time i based on a value obtained by adding the updated transmission power difference and the transmission power calculated at the discrete time i−1 before the certain time interval T. Transmitting the control signal and the downlink information signal with the transmission power at the discrete time i. 2. The communication quality is a difference between the total power of the received signal and the average of the received power of the uplink information signal of the connected mobile station, and the reception of the uplink information signal of the connected mobile station. The transmission power control method according to claim 1, wherein the transmission power control method is calculated by a ratio to an average of the power. 3. The communication quality and the communication quality difference are in units of decibels, and the step of calculating the updated transmission power difference is substituted into a non-decreasing function having the communication quality difference as a variable,
The transmission power control method according to claim 1, wherein the calculated dependent value is calculated as the updated transmission power difference. 4. The transmission power control method according to claim 1, wherein the target value is a preset constant. 5. The transmission power control method according to claim 1, wherein the target value is set to an average value of the communication quality at the discrete time i and the communication quality of the adjacent base station at the discrete time i. 6. A service area is defined by a plurality of small radio zones, and a mobile station receives a control signal from a plurality of base stations, the control signal being constantly transmitted from a base station installed in each of the small radio zones. The received power of the signal is wirelessly connected to the base station to transmit the uplink information signal, and the received power of the control signal is the largest base station transmits the downlink information signal to the mobile station wirelessly connected, In a transmission power control device of the base station at a discrete time i in a mobile communication system of a code division multiple access communication system, a total reception power observation means for measuring a total power of a received signal; Receiving information signal calculating means for calculating the average of the received power of each uplink information signal; and at discrete time i, based on the total power of the received signals and the average of the received power of the uplink information signal. Communication quality calculating means for calculating the communication quality to be calculated, communication quality difference calculating means for calculating the communication quality difference between the communication quality at the discrete time i and the target value, and calculating the updated transmission power difference based on the communication quality difference An update amount calculating unit that calculates transmission power at a discrete time i based on a value obtained by adding the update transmission power difference and a transmission power at a discrete time i−1; A transmission means for transmitting the control signal and the downlink information signal at a transmission power of the transmission power control apparatus.