GB2414901A

GB2414901A - Adjusting the timing of radio status reports for transmission power control

Info

Publication number: GB2414901A
Application number: GB0507992A
Authority: GB
Inventors: Mitsuhiro Kubota
Original assignee: NEC Corp
Current assignee: NEC Corp
Priority date: 2004-04-21
Filing date: 2005-04-20
Publication date: 2005-12-07
Anticipated expiration: 2025-04-20
Also published as: GB0507992D0; JP2005311638A; JP4438493B2; GB2414901B

Abstract

A mobile communications system autonomously adjusts the transmission timing of radio status reports from mobile stations. When each of a plurality of mobile stations makes a radio status report a5 to a radio base station, such as power up of power down commands, a timer a3 decides the reporting frequency. A mobile station showing a large difference between a target received-signal quality a2 and a measured received-signal quality employs a short time between reports, whereas a mobile station showing a smaller difference employs a longer time between reports. Since the transmission power control a7 in the radio base station is weighted according to the radio statuses of all the mobile stations receiving the service, the transmission power in the radio base station is controlled so that a certain percentage of mobile stations may be at a level meeting the target received-signal quality.

Description

24l49ol Mobile Communications System, Radio Base Station, Mobile Station

and Transmission Power Control Method for Use therewith

BACKGROUND OF lilE INVENTION

Field of the Invention

The present invention relates to a mobile communications system, a radio base station, a mobile station, and a transmission power control method for use therewith, and more particularly to a transmission power control method on a common channel.

Description of the Prior Art

In the mobile communications system, when a plurality of mobile stations receive data through a common channel, there is a need for an effective transmission power control method to reduce interference occurring in the mobile communications system and increase the system capacity.

his transmission power control method involves employing a fixed value of transmission power for the common channel, or controlling the transmission power based on the worst channel quality information as disclosed in Japanese Patent Laid-Open No. 2003-188818 (e.g., refer to patent document 1).

However, with this transmissionpowercontrolmethod, since the transmission power is controlled in accordance with the mobile station, there is possibility that the transmission power to reach the cell end may be required at any time. Therefore, with the above transmission power control method, the interference between the self cell and other cells is increased, possibly causing the system capacity to be decreased.

BRIEF SUMMARY OF THE INVENTION

However, with the conventional transmission power control method, when multimedia communication is performed through the common channel from the radio base station to a plurality of mobile stations, the radio base station needs a large transmis sionpower to assure an excellent receivedsignal quality for the mobile station residing at the cell end, whereby the interference between the self cell and the other cell is increased, resulting in a problem that the system capacity is decreased.

The present invention is directed to this problem, and it is an object of the preferred embodiment of the subject invention to provide a mobile communications system, a radio base station, a mobile station and a transmission power control method for use therewith, all capable of autonomously adjusting the trans mission timing of a radio status report from the mobile station, and of deterring an increase in the amount of uplink radio network use.

The present invention provides a mobile communications system in which a radio base station performs the transmission power control to a plurality of mobile stations receiving service through a common channel, wherein the mobile stations employ a timer function for deciding a report frequency thereof in making a radio status report to the radio base station.

Also, the invention provides a radio base station for performingthetransmissionpowercontroltoapluralityofmobile stationsreceivingaservicethroughacommonchannel,comprising means for performing the transmission power control based on a radio status report from the mobile station, wherein the radio status report is made employing a timer function for deciding a report frequency thereof.

Also, the invention provides a mobile station for which the transmission power control in receiving a service through acommonchannelisperformedinaradiobasestation,comprising means for sending out a radio status report employing a timer function for deciding a report frequency of the radio status report to the radio base station.

Also, the invention provides a transmission power control method in which a radio base station performs the transmission powercontroltoapluralityofmobilestationsreceivingaservice throughacommonchannel,themethodcomprising,onmobilestation, a step of making a radio statue report employing a timer function to decide a report frequency thereof in making the radio status report to the radio base station.

Thatis,inthemobilecommunicationssystemoftheinvention, when each mobile station makes a radio statue report to the radio basestations, thetimerfunctionto decide its report frequency is employed. This timer function has the control information periodically transmitted from the radio base station and the received signal quality measured at each mobile station as the variables, and is defined to enable the mobile station having alarge dissociation between the target received signal quality - 4 - and the measured received signal quality to employ a shorter timer, and the mobile station having almost no dissociation between the target received signal quality and the measured received signal quality to employ a longer timer. The mobile station receiving the service at the target received signal quality or better is set up to employ a longer timer than the mobile station receiving the service below the target received signal quality.

Thereby, in the mobile communications system of the invention, thefrequencyoftransmittingtheradiostatusreport from the mobile station to the radio base station is lower, and the uplink radio network use amount is decreased. Since the transmission power control in the radio tease station is weighted according to the radio statuses of all the mobile stations receiving the service, the transmission power in the radio base station is controlled so that a certain percentage of mobile stations may be at a level meeting the target received signal quality.

That is, the mobile communications system of the invention does not assure the received signal quality for all the mobile stations receiving the service, but provides a fixed level of service to a group of mobile stations receiving the service.

Herein, in the mobile communications system of the invention, one radio channelis shared among a plurality of mobile stations.

As described above, in the mobile communications system oftheinvention, theradiobasestationperformsthetransmission power control to the plurality of mobile stations receiving the service through the common channel from the radio base station, - 5 - decreasing interference in the radio system and increasing the system capacity.

Accordingly, in the mobile communications system of the invention,eachof the mobile stations sharing one radio charnel adjusts the transmission frequency by employing the timer function with the control information periodically transmitted from the radio base station and the measured received signal quality as the variables, whereby the transmission timing of theradiostatusreportfromthemobilestationcanbeautonomously adjusted, deterring an increase in the uplink radio network use amount.

Alsoginthemobilecommunicationssystemoftheinvention, the transmission powerin the radio tease stationsis autonomously adjusted by being weighted according to the radio statuses of all the mobile stations receiving the service, employing the radio statue report transmitted from the mobile station, so that a certain percentage of mobile stations receiving the service within the cell may be at a level meeting the target received signal quality, thereby keeping the transmission power lower.

Moreover, in the mobile communications system of the invention, thetransmissionfrequencycanbeadjustedbychanging the parameters of the timer function employed by each mobile station, whereby the percentage of mobile stations meeting the target received signal quality within the cell is adjusted in accordance with the policy of the service agent.

Moreover, in the mobile communications system of the invention, the target received signal quality is periodically changed by referring to the worst value of BLER (Block Error - 6 - Rate) containedin the radio statue report transmitted from each mobile station, whereby the BLERat the mobile stationwithin the cell is controlled to be at a certain level. If the target received power is increased, the transmission power is also increased, resulting in a lower BLER.

In the present invention with the following configuration and operation, there is the effect that the transmission timing of the radio status report at the mobile station is autonomously adjusted, deterring an increase in the amount of uplink-radio network use.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred features of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which: FIG. 1 is a block diagram showing the configuration of a mobile communications system according to an embodiment of the present invention; FIG. 2 is a sequence chart showing the operation of the mobile communications system according to the embodiment of the present invention; FIG. 3 is a flowchart showing the operation of a radio base station of the mobile communications system of FIG. 1; FIG. 4 is flowchart showing the operation of a mobile station of the mobile communications system of FIG. 1; FIG. 5is a graph showing the relationship between received signal quality and timer magnitude according to the embodiment of the subject invention; FIG. 6 is a chart showing a transmission power control method according to the embodiment of the subject invention; - 7 FIG. 7 is a diagram showing the parameters transmitted or received between nodes in the embodiment of the invention; FIG. 8isadiagramshowingapracticalperiodofoontrolling the transmission power according to the embodiment of the invention; and FIG. 9 is a diagram showing the influence of a parameter change on the received signal quality of the mobile station in the embodiment of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The preferred embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing the configuration of a mobile communications system according to one embodiment of the present invention. InFIG.l, themobilecommunicationssystemaccording to one embodiment of the invention comprises the radio base stationsl-lto1-3, a radio network controllers, end the mobile stations 2-1, 2-2, and constitutes a radio access network for the system employing a code division multiple system such as W-CDMA (Wideband-Code Division Multiple Access).

The radio base stations 1-1 to 1-3, the radio network controller3, andthemobilestations 2-1, 2-2 constituting this radio access network can make the multi-media communications bybroadcastormulticast. Theradionetworkcontroller3manages the radio resources, and controls a plurality of radio base stations 1-1 to 1-3. The radio base stations 1-1 to 1-3 make the communications with the mobile stations 2-1, 2-2 by radio. - 8 -

FIG. 2 is a sequence chart showing the operation of the mobile communications system according to one embodiment of the invention. FIG. 3 is a flowchart showing the operation of the radio base stations 1-1 to 1-3 as shown in FIG. 1. FIG. 4 is a flowchart showing the operation of the mobile stations 2-1, 2-2 as shown in FIG. 1. Referring to FIGS. 1 to 4, the operation of the mobile communications system according to one embodiment of the present invention will be described below.

me radio network controller 3 periodically notifies the information regarding the number of mobile stations receiving a specific multimedia service within a cell, not shown, to the radio base stations 1-1 to 1-3 (al in FIG. 2), and the radio base stations 1-1 to 1-3 periodically notifies the received information regarding the number of mobile stations and the information indicating the target received signal quality to the mobile stations 2-1, 2-2 during a specific multimedia communication within the cell (a2 in FIG. 2 and steps S1, S2 in FIG. 3).

In each mobile station 2-1, 2-2, the timer is set up, employing a timer function having the received control information and the received signal quality measured at each mobile station 2-1, 2-2 as the variables (as in FIG. 2 and steps Sll, S12 in FIG. 4).

Herein, each mobile station 2-1, 2-2 defines the timer function to employ a longer timer if the communication occurs near the target received signal quality, or a shorter timer if thereisalarge dissociation between the target received signal quality and the measured received signal quality (steps S13 to 9 - S15inFIG.4). However,themobilestationreceivingtheservice at the target received signal quality or better is set to employ a longer timer than the mobile station receiving the service below the target received signal quality. The length of the timer is regulated by the upper limit length and the lower limit length provided.

When the timer runs out (time value = 0) (step S16 in FIG. 4), each mobile station 2-1, 2-2 transmits a radio status report for the radio frame received immediately before to the radio 10base stations 1-1 to 1-3 (step S17 in FIG. 4). m e radio status reportcontainsPowerdown(hereinafterPdown),whenthereceived signalqualityis better than the target received signalquality, or otherwise, Power up (hereinafter Pup), and additionally the BLER (Block Error Rate).

15Theradiobasestationsl-ltol-3haveawindowforacertain time, compare the number of receiving Pdown and the number of receiving Pup within the certain time of the window (as in FIG. 2 aid steps S5, S6 in FIG. 3), and make the transmission power control to each mobile station 2-1, 2-2 in accordance with its comparison result (a7 in FIG. 2).

That is, the radio base stations 1-1 to 1-3 decrease the transmission power if the number of receiving Pdown is greater than the number of receiving Pup within the certain time of the window (steps S6, S7 in FIG. 3), perform no operation if the number of receiving Pdown is equal to the number of receiving Puprorincreasethetransmissionpowerifthenumberofreceiving Pdown is smaller than the number of receiving Pup (steps S6, So in FIG. 3). -

Intheradiobasestationsl-ltol-3,theabovetransmission powercontrolissetupsuchthatanincreasewidthoftransmission power is greater than a decrease width, to gradually decrease the transmission power. Also, the upper limit and the lower limit are set up for the transmission power of the radio base station,andthe transmission power is controlled tofallwithin its range.

When each mobile station 2-1, 2-2 is notified again of the control information from the radio base stations 1-1 to 1-3 (as in FIG. 2 and step Sll in FIG. 4), the timer is recalculated employing the timer function at step S12, and restarted.

In the radio base stations 1-1 to 1-3, the target received signal quality is updated at a fully longer period than that of changing the transmission power passed (as in FIG. 2, steps S9, S10 in FIG. 3). Herein, the radio base stations 1-1 to 1-3 record the worst value of the BLERs received from the mobile stations 2-1, 2-2 (step S3, S4 in FIG. 3), and in updating the target received signal quality, determine whether the target value is increased or decreased depending on the recorded BLER (step S10 in FIG. 3).

In making the multimedia communications through a common channel from the radio base stations to a plurality of mobile stationsetheradiobasestationsneedalargetransmissionpower to assure an excellent received signal quality for the mobile stationresidingatthecellend,increasinginterferencawithin the self cell and the other cell, and leading to a lower system capacity. - 11

In this embodiment, each of the mobile stations 2-1, 2-2 sharing one radio channelregulates the transmission frequency, employing a timer function having the control information periodically transmitted from the radio base stations 1-1 to 1-3 and the measured received signal quality as the variables, and is capable of autonomously adjusting the timing of transmitting the radio status report, and deterring an increase in the uplink radio network use amount.

Also, in this embodiment, the radio base stations 1-1 to 1-3autonomouslyadjustthetransmissionpowerbybeingweighted according to the radio statuses of all the mobile stations receiving the service, employing the radio status report transmitted from the mobile stations 2- 1, 2-2, so that a certain percentage of mobile stations receiving the service within the cellmaybeatalevelmeetingthetargetreceivedsignalquality, thereby keeping the transmission power low.

Moreover, in this embodiment, each mobile station 2-1, 2-2 can adjust the transmission freguencyby changing the parameters of the timer function for use, in which there is a third effect that thepercentageofmobilestationsmeetingthetarget received signal quality within the cell can be adjusted in accordance with the policy of the service agent.

Moreover, in this embodiment, since the target received signalqualityis periodically charged by referring to the worst valueoftheBLERscontainedintheradiostatusreporttransmitted fromeachmobilestation2-1, 2-2,theBLER et the mobile station within the cell is kept at the certain level. If the target - 12 received power is increased, the transmission power is also increased, so that the BLER is decreased.

FIG. 5 is a graph showing the relationship between received signal quality and timer magnitude according to one embodiment of the invention. FIG. 6 is a chart showing a transmission power control method according to one embodiment of the invention.

FIG. 7 is a diagram showing the parameters transmitted or received between nodes in one embodiment of the invention. FIG. 8 is a diagram showing a practical period of controlling the transmission power according to one embodiment of the invention.

FIG. 9 is a diagram showing the influence of a parameter change on the received signal quality of the mobile station in one embodiment of the invention. Referring to FIGS. 5 to 9, an example of an algorithm for controlling the transmission power in the multimedia service through the common channel in a cellularmobile communications system employing the WCDMA system according to one embodiment of the invention will be described below.

In an MBMS (Multimedia Broadcast Multicast Service) providing the broadcast and multimedia service, the information of the mobile stations 2-1, 2-2 receiving the service is managed according to an MBMS context by the radio network controller 3.

In this embodiment, the radio network controller 3 notifies the number M of mobile stations in a connected mode receiving each service to the radio base stations 1-1 to 1-3 at a period T. and the radio base stations 1-1 to 1-3 notify the number M of mobile stations and a parameter VT indicating the target - 13 received signal quality at the mobile stations 2-1, 2-2 to the mobile stations 2-1, 2-2 while receiving the service.

The mobile stations 2-1, 2-2 start the timer at the timing of receiving a notification from the radio base stations 1-1 to 1-3. Each mobile station 2-1, 2-2 obtains the magnitude of the timer T. employing the measured value v, the frame sending interval I of application for use, the constant N deciding the upperlimitvalueofthetimer,andtheconstantsa, pinaccordance with the following formula.

[Formula 1] T = MI +(N - Mica . (1) At this time, the magnitude of the timer satisfies the relationMI<TNI. Asthemeasuredvaluevindicatingthereceived signal quality for use herein, the SIR (Signal-to-Interference power Ratio) or Ec/No (ratio of desired wave energy per chip to in-band received power density) may be employed.

Supposing that the constant a is equal to a at the mobile station receiving the service at the target received signal quality or better, and the constant a is equal to b at the mobile station receiving the service below the target received signal quality, it is determined whether or not the quality is better than the target received signal quality, deciding the magnitude of the timer T. Where a is smaller than b. The relationship between the received signal quality and the magnitude of the timer T in accordance with the expression (1) is shown in FIG. 5.

Thereby, in this embodiment, the mobile station with worse received signal quality in which there is a large dissociation - 14 between the measured value v and the target value VT employs ashortertimer, wherebythefrequencyofmakingtheradiostatus report to the radio base stations 1-1 to 1-3 increases. Each mobile station 2-1, 2-2 makes the radio status report for the frame alone received immediately before the timer runs out.

This report contains the BLER at each mobile station 2-1, 2-2,andPdownreportedwhenthereceivedsignalqualityisabove the target received signal quality, or Pup reported when it is below the target received signal quality. That is, the mobile station receiving no data employs Pup.

Inthisembodiment,tomakethetransmissionpowercontrol, the radio base stations 1-1 to 1-3 have a window to, a comparison is made between the number of receiving Pup and the number of receiving Pdown for the window t-, in which the transmission power is decreased by Adown when the number of Pdown is greater than the number of Pup, not changed when the number of Pup is equal to the number of Pdown, or increased by Aup when the number of Pup is greater than the number of Pdown. i

Toavoidanabruptdegradationofthereceivedsignalquality within the cell, it is supposed that Adown is smaller than Aup.

Where the upper limit W-= and the lower limit W-= are set for the transmission power in the radio base stations 1-1 to 1-3.

The transmission power is controlled to fall within its range.

A method of controlling the transmission power is shown in FIG. 6.

With the method of controlling the transmission power as shown in FIG. 6, each mobile station 2-1, 2-2 starts the timer of any magnitude, employing the parameter M end the target value - 15 VT received at period I, and transmits the radio status report only when the timer runs out, in which the radio base stations 1-1 to 1-3 may not receive the radio status report for the transmission frame from the mobile stations 2-1, 2-2.

In the radio base stations 1-1 to 1-3, the largest value, or the worst quality value among the BLERs received from the mobile stations 2-1, 2-2 for the time is recorded, and it is determined whether or not the appropriate transmission power control is performed within the cell based on this BLER. The periodfor changing the target value VT in the radio tease stations 1-1 to 1-3 is set up to be fully longer than the period t. for changing the transmission power.

In this embodiment, the magnitude of the timer employed by the mobile stations 2-1, 2-2 and the reference value for deciding Pup or Pdown are changed by changing the target value VT. As a result, since the ratio of Pup to Pdown transmitted from the mobile stations 2-1, 2-2 to the radio base stations 1-l to 1-3 is changed, the transmission power control in the r radio base stations 1-1 to 1-3 is adjusted. FIG. 7 shows the parameters transmitted or received between nodes.

In this way, in making the transmission power control in this embodiment, the radio base stations 1-1 to 1-3 change the transmission power frequently, and update the target received signal quality at a longer period. FIG. 8 shows a period of transmission power control to be performed. FIG. 8 shows the length of period to be controlled in terms of the magnitude of area. - 16

Herein, when each mobile station 2-1, 2-2 receives a notification of parameter from the radio base stations 1-1 to 1-3 through the controlchannel, it recalculates the timer value and restarts the timer upon, whereby the mobile station at which the measured value v is close to the target value VT may be set up not to return the radio statue report depending on the settings of the constant N and the period I. By making the settings as above, the uplink radio network use amount is decreased.

_

FIG. 9 shows the influence of a parameter change on the received signal quality of the mobile stations 2-1, 2-2 in the invention. InFIG.9, thetransverseaxisindicatesthereceived signal quality v in terms of an RSSI (Received Signal Strength Indicator)suchas SIRorEc/No, thelongitudinal axis indicates the BLER, and the vertical axis indicates the number M of mobile stations.

Herein, if the RSSI rises, the BLER is greatly improved, as well known. When the received signal quality v and the BLER are represented by logarithm, the relationship between them is almost linear. Supposing that the mobile stations 2-1, 2-2 are uniformly distributed within the cell, the received signal quality is abruptly degraded with a larger distance from the radiobasestationsl-ltol-3. Thereby,therelationshipbetween the received signalquality v end the number M of mobile stations is considered such that the number of mobile stations is smaller in the area with better received signal quality.

Inthisembodiment,themobilestationratio can tee charged around the target received signal quality VT and VT' by changing - 17 the values a, b and employed for the timer function, as shown in (1). Thereby, the percentage of mobile stations receiving the service at the target receiving signal quality or better can be adjusted in this embodiment.

In the radio base stations 1-1 to 1-3, the service quality within the cell is estimated from the worst value of the BLERs contained in the radio status report from the mobile stations2 1, 2-2, in which by raising the level of the target received signalquality from VT to VTi, the transmissionpowerin the radio base stations 1-1 to 1-3 can be increased and the BLER of the mobile stations receiving the service within the cell can be decreased as shown in (2).

While the present invention has been described in its preferred embodiment, itisto tee understood that the words which have been used are words of description rather than limitation, and that changes may be made to the invention without departing from its scope as defined by the appended claims.

Each feature disclosed in this specification (which term includes the claims) and/or shown in the drawings may be incorporated in the invention independently of other disclosed and/or illustrated features.

The text of the abstract filed herewith is repeated here as

part of the specification.

A mobile communications system is capable of autonomously adjusting the transmission timing of a radio status report from a mobile station, and of deterring an increase in the amount of uplink-radio-network use. When each of a plurality of mobile stations makes a radio status report to a radio base station, a - 18 - timer function decides the reporting frequency. The timer function is defined so as to enable a mobile station showing a large difference between a target received-signal quality and a measured received-signal quality to employ a short time between reports, whereas a mobile station showing a smaller difference employs a longer time between reports. Since the transmission power control in the radio base station is weighted according to the radio statuses of all the mobile stations receiving the service, the transmission power in the radio base station is controlled so that a certain percentage of mobile stations may be at a level meeting the target received-signal quality.

Claims

- 19 - CLAIMS: 1. A radio base station for controlling transmission power

to a plurality of mobile stations receiving service through a common channel, the radio base station comprising means for performing said transmission power control based on a radio status report from each of the mobile stations, wherein each mobile station employs a timer for deciding on a frequency at which to make the radio status report to said radio base station
2. The radio base station according to claim 1, wherein each timer utilizes, as variables, control information periodically transmitted from said radio base station and the received-signal quality measured at the respective mobile station, and wherein the timer functions such that the length of time employed in the timer increases as a difference decreases between a target received-signal quality and a measured received-signal quality.
3. The radio base station according to claim 2, wherein the mobile station receiving service at said target receiving-signal quality or better is set up to employ a longer time in the respective timer than a mobile station receiving the service at less than said target receiving- signal quality.
4. The radio base station according to claim 2, wherein said radio base station controls transmission power weighted according to the radio statuses of all the mobile stations - 20 - receiving said service, and controls a certain percentage of mobile stations to be at a level meeting said target received- signal quality.
5. The radio base station according to claim 2, wherein said radio base station periodically changes said target received- signal quality by referring to the worst value of Block Error Rate(BLER) containedin the radio statue report transmitted from said mobile station.
6. A mobile station for which transmission power control in receiving a service through a common channel is performed in a radio base station, the mobile station comprising means for sending out a radio status report to the radio base station performing the transmission power control, the mobile station employing a timer for deciding on a frequency at which to make the radio status report to said radio base station.
7. Themobile station according to claim 6, wherein said timer utilizes, as variables, control information periodically transmitted from said radio base station and the received signal quality measured at said mobile station, and wherein the timer functions such that the length of time employed in the timer increases as a difference decreases between a target received- signal quality and a measured received-signal quality.
8. Themobile station according to claim 6, wherein the mobile station employs a longer time when receiving the service et said - 21 - target receiving-signal quality or better than when receiving the service at less than said target receiving-signal quality.
9. Amobile communications system thatincludes the radio base station of any of claims 1 to 5, and also includes the mobile station of any of claims 6 to 8.
10. A transmission power control methodin which a tease station controls transmission power to a plurality of mobile stations receiving service through a common channel, said method comprising each mobile station making a respective radio-status report to said radio base station, a respective timer being employed by each mobile station for deciding on a respective frequency at which the respective radio status report is made.
11. The transmission power control method according to claim 10, wherein each timer utilizes, as variables, control information periodically transmitted from said radio base station and the received- signal quality measured at the respective mobile station, and wherein the timer functions such that the length of time employed in the timer increases as a difference decreases between a target received-signal quality and a measured received-signal quality.
12. The transmission power control method according to claim 11, wherein the mobile station receiving service at said target receiving- signal quality or better is set up to employ a longer timein the respective timer than a mobile station receiving the service at less than said target receiving-signal quality.
13. The transmission power control method according to claim 11, wherein said radio base station controls transmission power weighted according to the radio statuses of all the mobile stations receiving said service, and controls a certain percentage of mobile stations to be at a level meeting said target received-signal quality.
14. The transmission power control method according to claim 12, wherein said radio base station periodically changes said target received-signal quality by referring to the worst value of BLER contained in the radio status report transmitted from said mobile station.
15. A radio base station substantially as herein describedwith reference to and as shown in the accompanying drawings.
16. A mobile station substantially as herein described with reference to and as shown in the accompanying drawings.
17. A mobile communications system substantially as herein described with reference to and as shown in the accompanying drawings.
18. Atransmissionpowercontrolmethodeubstantiallyas herein described with reference to and as shown in the accompanying drawings.