JP2993561B2 - Transmission power control method in mobile communication system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transmission power control method for controlling transmission power in a mobile communication system for performing wireless communication between a base station and a mobile station.

[0002]

2. Description of the Related Art Conventionally, a transmission power control method as described in, for example, the following publication is known. SUMMARY OF THE INVENTION A bit error rate of a signal transmitted from a transmitter of a transmitting station is detected, and when the bit error rate is equal to or less than a first threshold, the transmission power of the transmitter is set to a predetermined amount. And if it is greater than or equal to a second threshold greater than the first threshold, the transmission power is increased by a predetermined amount. SUMMARY OF THE INVENTION The maximum value and the minimum value of the transmission power accessed by the mobile station for each of a plurality of transmission control channels are reported to the mobile station in advance,
The mobile station accesses the transmission control channel with the minimum transmission power at the time of transmission, and if the communication between the radio base station and the control signal is unsuccessful, the mobile station sequentially increases the transmission power up to the maximum transmission power. Access. As the radio base station controls the transmission power for the mobile unit, the transmission power of the radio base station is controlled at the same time.

[0003]

However, in the conventional method, the initial setting power of the uplink and downlink traffic channels has a fixed fixed value, and after shifting to the traffic channel, the transmission power is stabilized at an appropriate level. Therefore, power control is performed, and it is necessary to repeat the correction.

SUMMARY OF THE INVENTION An object of the present invention is to determine the appropriate transmission power for a call before setting a communication channel, to eliminate the need for subsequent correction of the transmission power, to reduce the load on the base station and the mobile station, and to reduce the load. It is an object of the present invention to provide a transmission power control method that can prevent the occurrence of interference between channels due to the transmission of the above power and that can set an appropriate initial transmission power even for a mobile station located in a place where the wireless state is unstable. .

[0005]

According to the transmission power control method of the present invention, the initial transmission power of the uplink traffic channel and the initial transmission power of the downlink traffic channel are determined in the following steps.

A first step in which the base station measures the electric field strength and the bit error rate of the uplink control channel from the mobile station a plurality of times. A second step of measuring the electric field strength and the bit error rate of the downlink control channel from the base station a plurality of times on the mobile device side, and reporting the measurement result to the base station via the uplink control channel. In the base station, by observing the transition of the measured field strength and bit error rate of the uplink control channel a plurality of times, only one data of the field strength or the bit error rate is taken, and the initial initial transmission power is calculated from the average value of one of them. Third step to calculate. In the base station, the transition of the electric field strength and the bit error rate of the reported downlink control channel a plurality of times is taken, and only one data of the electric field strength or the bit error rate is taken, and the downlink initial transmission power is calculated from the average value of one of them. Fourth step to calculate. A fifth step of reporting the calculated uplink initial transmission power to the mobile station via the downlink control channel. A sixth step of setting the reported uplink initial transmission power in the mobile station as the initial transmission power of the uplink traffic channel when the control channel shifts to the traffic channel; A seventh step in which the base station sets the downlink communication channel as the initial transmission power of the downlink communication channel using the calculated downlink initial transmission power when shifting from the control channel to the communication channel.

In the third step, when the bit error rate has not changed, the initial uplink transmission power is calculated only from the average value of the electric field strength.

In the fourth step, when the bit error rate has not changed, the downlink initial transmission power is calculated only from the average value of the electric field strength.

[0009]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows an outline of a mobile communication system to which a transmission power control method according to the present invention is applied. The base station 1 and each mobile station 2 are connected to the uplink control channel 10 from the mobile station 2 to the base station 1, the downlink control channel 11 from the base station 1 to the mobile station 2, and the mobile station 2 to the base station 1 in the same manner as in the prior art. An uplink communication channel 12 to the mobile station 2 and a downlink communication channel 14 from the base station 1 to the mobile station 2 are set and communication is possible. The base station 1 includes, in addition to the conventional equipment, an uplink control channel measurement device 3, an initial transmission power calculation device 4, and an initial transmission power setting device 5, and each mobile device 2 has a downlink control channel measurement device. A device 6 and an initial transmission power setting device 7 are provided. An exchange 8 is connected to the base station 1 by wire.

The uplink control channel measuring device 3 measures the radio condition of the uplink control channel 10, that is, the electric field strength and the bit error rate, and the downlink control channel measuring device 6 measures the radio condition of the downlink control channel 11, that is, the electric field intensity and the bit error rate. Measure the bit error rate. The initial transmission power calculation device 4 calculates the initial transmission power from the electric field strength and the bit error rate measured by the uplink control channel measurement device 3, and is measured by the downlink control channel measurement device 6 and reported by the mobile device 2. The initial downlink transmission power is calculated from the obtained electric field strength and bit error rate. The initial transmission power setting device 5 of the base station 1 sets the initial transmission power of the downlink communication channel 13 according to the downlink initial transmission power calculated by the initial transmission power calculation device 4. Initial transmission power setting device 7 for mobile device 2
Is calculated by the initial transmission power calculation device 4 and the base station 1
The initial transmission power of the uplink communication channel 12 is set according to the reported uplink initial transmission power.

FIG. 2 is a flowchart showing the operation of the mobile communication system shown in FIG. 1 until transmission power is controlled by controlling the transmission power by the method according to the present invention. In FIG. 2, when the downlink control channel 11 and the uplink control channel 12 are set (steps S1 and S2), the electric field strength and the bit error rate of the uplink control channel 10 are increased by the uplink control channel measuring device 3 of the base station 1 a plurality of times. It is measured (step S3), and the electric field strength and the bit error rate of the downlink control channel 11 are measured a plurality of times by the downlink control channel measuring device 6 of the mobile station 2, and the measurement results are reported to the base station 1 by the uplink control channel 10. Is performed (step S4).

FIG. 3 shows a measurement example in which the electric field strength and the bit error rate of the uplink control channel 10 are measured five times each. In this measurement example, the electric field strength is changed, but the bit error rate is the same “0.1” in all five measurements. FIG. 4 shows another measurement example in which the electric field strength and the bit error rate of the uplink control channel 10 are each measured five times. In this measurement example, both the electric field strength and the bit error rate change. FIG. 5 shows a measurement example in which the electric field strength and the bit error rate of the downlink control channel 11 are measured five times each. In this measurement example, the electric field strength is changed, but the bit error rate is the same “0.1” in all five measurements. FIG. 6 shows another measurement example in which the electric field strength and the bit error rate of the downlink control channel 11 are measured five times each. In this measurement example, both the electric field strength and the bit error rate change.

Next, the initial transmission power setting device 5 of the base station 1
Calculates the average of each of the electric field strength and the bit error rate of the uplink control channel 10 measured a plurality of times by the uplink control channel measuring device 3, and calculates the initial uplink transmission power from the average value (step S5). In this case, for example, by applying a lookup table method to the transmission power conversion table, the initial uplink transmission power corresponding to the average value can be easily obtained. In the example of FIG. 3, since the bit error rate does not change, the corresponding transmission power can be obtained from the transmission power conversion table using only the electric field strength as a parameter as shown in FIG. In the case of the example of FIG. 3, the third value out of the five measured electric field intensities is “60”, which is abnormally high. , The corresponding transmission power is “4” from the conversion table of FIG.

On the other hand, in the example of FIG. 4, both the electric field strength and the bit error rate change. The transmission power is determined only from the result. FIG. 8 shows a conversion table into transmission power using only the bit error rate as a parameter. In the case of the example of FIG. 4, since there is no abnormal value in the bit error rate measured five times, all five times are valid,
Since the average is "0.38", the transmission power corresponding to this is "3" from the conversion table of FIG.

The initial transmission power setting device 5 of the base station 1
Calculates the average of the electric field strength and the bit error rate of the downlink control channel 11 reported from the mobile station 2, and calculates the initial downlink transmission power from the average in the same manner as described above (step S6). In the case of the example of FIG. 5, the bit error rate is the same for the five measurements, and there is no abnormality in the five field strengths.
Therefore, the transmission power corresponding to this becomes “4” from the conversion table of FIG. However, since the electric field strength of the five measurements has been gradually increased, it is predicted that the wireless condition has been improved, and “3” obtained by subtracting “1” from “4” obtained from the conversion table of FIG. Is used as the downlink initial transmission power. In the example of FIG. 6, the average of the electric field intensities measured five times is “50.6”, which is a high value. Therefore, the downlink initial transmission power is determined only by the measurement result of the bit error rate. in this case,
Since there are no abnormalities in the measured five bit error rates, all are valid, and when the average is obtained, it is "0.18".
The transmission power corresponding to this is “2” from the conversion table of FIG.

After calculating the uplink initial transmission power as described above, the base station 1 reports the value to the mobile station 2 via the downlink control channel 11 (step S7). Upon receiving this, the mobile station 2 uses the reported uplink initial transmission power as the initial transmission power of the uplink traffic channel 12 when transitioning from the control channel to the traffic channel.
Is set (step S8). Also, the base station 1 uses the downlink initial transmission power calculated by the initial transmission power setting device 5 as described above as the initial transmission power of the downlink communication channel 13 when shifting from the control channel to the communication channel. It is set (step S9). Then, a call is started with such initial transmission power (step 10).

[0018]

As described above, according to the present invention, before setting the communication channel, the electric field strength and the bit strength are set for each of the uplink control channel from the mobile station to the base station and the downlink control channel from the base station to the mobile station. The error rate is measured a plurality of times, and only one of the electric field strength and the bit error rate is taken by observing the transition of the measured data for the plurality of times, and the initial transmission of the uplink control channel and the downlink control channel is performed from the average value of one of the data. Since the power is determined and thereafter the communication channel is established with the initial transmission power, the following effects are obtained.

The minimum required transmission power value is known before the start of a call, and power correction for correcting the transmission power to an appropriate value after the start of a call becomes unnecessary. Therefore, the load on the base station and the mobile device can be reduced, and since both the base station and the mobile device do not need to transmit more power than necessary, the occurrence of interference between channels can be prevented.

The respective changes in the electric field strength and the bit error rate are determined, one of the electric field strength and the bit error rate is adopted as a parameter from the degree of the change, and the initial transmission power and the downlink Since the initial transmission power of the communication channel is determined, an appropriate initial transmission power that takes into account both the relationship between the reception level (field strength) and the quality (bit error rate) and that is not greatly affected by sudden changes in one of them. Can be set.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an example of a mobile communication system to which a transmission power control method of the present invention is applied.

FIG. 2 is a flowchart illustrating an operation of an example of a transmission power control method according to the present invention.

3 is a diagram illustrating a measurement example of a radio state of an uplink control channel measured by the uplink control channel measuring device in FIG. 1;

FIG. 4 is a diagram illustrating another measurement example of the radio state of the uplink control channel measured similarly to the example of FIG. 3;

5 is a diagram illustrating a measurement example of a radio state of a downlink control channel measured by the downlink control channel measurement device in FIG. 1;

FIG. 6 is a diagram illustrating another measurement example of the radio state of the downlink control channel measured similarly to the example of FIG. 5;

FIG. 7 is a diagram showing a conversion table from electric field strength to transmission power.

FIG. 8 is a diagram showing a conversion table from a bit error rate to transmission power.

[Explanation of symbols]

 Reference Signs List 1 base station 2 mobile station 3 uplink control channel measuring device 4 initial transmission power calculating device 5 initial transmission power setting device 6 downlink control channel measuring device 7 initial transmission power setting device 8 exchange

Claims (3)

(57) [Claims] 1. A first step of measuring the electric field strength and bit error rate of an uplink control channel from a mobile station a plurality of times at a base station, and moving the electric field strength and bit error rate of a downlink control channel from the base station. A second step of measuring a plurality of times on the mobile station side and reporting the measurement result to the base station using the uplink control channel; and, in the base station, a change in the measured field strength and bit error rate of the uplink control channel a plurality of times. A third step of taking only one data of the electric field strength or the bit error rate, and calculating the uplink initial transmission power from the average value of one of the data; and A fourth step of taking only one data of the electric field strength or the bit error rate by observing the transition of the electric field strength and the bit error rate, and calculating the downlink initial transmission power from the average value of one of the data. A fifth step of reporting the calculated uplink initial transmission power to the mobile station via the downlink control channel; and, in the mobile station, transmitting the reported uplink initial transmission power at the time of transition from the control channel to the communication channel. A sixth step of setting the uplink communication channel as the initial transmission power of the channel; and, in the base station, converting the calculated downlink initial transmission power as the initial transmission power of the downlink communication channel when shifting from the control channel to the communication channel. A transmission power control method in a mobile communication system, comprising: a seventh step of setting a communication channel. 2. The mobile communication system according to claim 1, wherein in the third step, when the bit error rate has not changed, the uplink initial transmission power is calculated only from the average value of the electric field strength. Transmission power control method in the embodiment. 3. The mobile communication system according to claim 1, wherein in the fourth step, when the bit error rate has not changed, the downlink initial transmission power is calculated only from the average value of the electric field strength. Transmission power control method in the embodiment.