JP2005311638A - Mobile communication system, wireless base station, mobile station, and transmission power control method used for them - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a mobile communication system autonomously adjusting a transmission timing of a wireless state report by a mobile station and suppressing increase in an uplink wireless channel consumed amount. <P>SOLUTION: When each of mobile stations 2-1, 2-2 makes the wireless state report to wireless base stations 1-1 to 1-3, a timer function is used to determine the frequency of reports. The timer function is defined to allow mobile stations whose measured reception quality is highly divergent from target reception quality to use a short time timer and to allow mobile stations whose measured reception quality is nearly equal to the target reception quality to use a long time timer respectively. Since a result of weighting the wireless state of all the mobile stations 2-1, 2-2 receiving services is reflected on the transmission power control by the wireless base stations 1-1 to 1-3, a prescribed ratio of the mobile stations is controlled to have a level meeting the target reception quality with respect to the transmission power from the wireless base stations 1-1 to 1-3. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a mobile communication system, a radio base station, a mobile station, and a transmission power control method used for them, and more particularly to a transmission power control method in a common channel.

  In a mobile communication system, when a common channel is received by a plurality of mobile stations, an effective transmission power control method is necessary to reduce interference generated in the mobile communication system and increase system capacity. .

  As the transmission power control method, a method using a fixed value for the transmission power of the common channel, or a transmission power control method based on the worst channel quality information as disclosed in JP-A-2003-188818. (For example, refer to Patent Document 1).

  However, in this transmission power control method, since transmission power is controlled according to the mobile station, there is a high possibility that transmission power that always reaches the cell edge is required. For this reason, there is a concern that the above transmission power control method causes an increase in interference in the own cell and in other cells, which causes a reduction in system capacity.

JP 2003-188818 A

  However, in the conventional transmission power control method described above, when performing multimedia communication using a common channel from a radio base station to a plurality of mobile stations, good reception quality is guaranteed for the mobile stations existing at the cell edge. Therefore, there is a problem that a large transmission power is required in the radio base station, interference in the own cell and other cells increases, and the system capacity decreases.

  Accordingly, an object of the present invention is to solve the above-mentioned problems, mobile communication capable of autonomously adjusting the transmission timing of a radio status report by a mobile station, and suppressing an increase in uplink radio channel usage A system, a radio base station, a mobile station, and a transmission power control method used for them are provided.

A mobile communication system according to the present invention is a mobile communication system in which a radio base station performs transmission power control for a plurality of mobile stations receiving services on a common channel,
A timer function is used to determine the reporting frequency when the mobile station reports a radio status to the radio base station.

A radio base station according to the present invention is a radio base station that performs transmission power control for a plurality of mobile stations receiving services on a common channel,
Means for performing the transmission power control based on a radio status report from the mobile station;
The radio status report is performed using a timer function for determining the report frequency.

  A mobile station according to the present invention is a mobile station in which transmission power control when receiving a service on a common channel is performed in a radio base station, in order to determine a report frequency of a radio status report to the radio base station Means is provided for transmitting the radio status report using a timer function.

A transmission power control method according to the present invention is a transmission power control method in which a radio base station performs transmission power control on a plurality of mobile stations receiving services on a common channel,
The mobile station side includes a step of performing the radio status report using a timer function in order to determine a report frequency when performing radio status report to the radio base station.

  That is, the mobile communication system of the present invention uses a timer function to determine the reporting frequency when each mobile station reports a radio status to a radio base station. This timer function has control information periodically transmitted from the radio base station and the reception quality measured by each mobile station as variables, and a short timer for a mobile station having a large difference between the target reception quality and the measured reception quality. A timer function is defined so that a long timer is used for each mobile station whose measured reception quality is approximately equal to the target reception quality. However, it is set so that a mobile station receiving a quality better than the target reception quality uses a longer timer than a mobile station receiving a bad quality.

  As a result, in the mobile communication system of the present invention, the frequency of transmitting the radio status report from the mobile station to the radio base station is reduced, and the uplink radio channel usage is reduced. In addition, the transmission power control in the radio base station reflects the weighted result in the radio state of all mobile stations that receive the service. Control is performed to achieve a level that satisfies the target reception quality.

  That is, the mobile communication system of the present invention does not guarantee the reception quality for all mobile stations that receive a service, but provides a certain level of service to a group of mobile stations that receive the service. . Here, the mobile communication system of the present invention can be used when a plurality of mobile stations share one radio channel.

  As described above, in the mobile communication system of the present invention, transmission power control is performed in a radio base station for a plurality of mobile stations receiving services from a radio base station through a common channel, and interference in the radio system is reduced. Decreasing and increasing system capacity.

  Therefore, in the mobile communication system of the present invention, each mobile station sharing one radio channel uses a timer function that periodically uses control information transmitted from the radio base station and measured reception quality as variables. Since the transmission frequency is adjusted, the transmission timing of the radio status report by the mobile station can be adjusted autonomously, and an increase in the uplink radio channel usage can be suppressed.

  Further, in the mobile communication system of the present invention, the transmission power in the radio base station is weighted according to the radio conditions of all mobile stations receiving the service using the radio condition report transmitted from the mobile station. Therefore, the transmission power in the radio base station is autonomously adjusted to a level that satisfies the target reception quality in a certain percentage of the mobile stations that receive the service in the cell. It can be kept low.

  Furthermore, in the mobile communication system of the present invention, the transmission frequency can be adjusted by changing the parameter of the timer function used by each mobile station, so that the target reception quality within the cell can be adjusted according to the service provider policy. It is possible to adjust the ratio of mobile stations that satisfy the above.

  Furthermore, in the mobile communication system of the present invention, by referring to the worst value among BLER (Block Error Rate) included in the radio status report transmitted from each mobile station, Since the target reception quality can be changed, the BLER in the mobile station in the cell can be controlled to be a constant level. When the target reception power increases, the transmission power also increases, and as a result, BLER decreases.

  By adopting the configuration and operation as described below, the present invention can autonomously adjust the transmission timing of a radio status report by a mobile station, and can suppress an increase in uplink radio channel usage. An effect is obtained.

  Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing the configuration of a mobile communication system according to an embodiment of the present invention. In FIG. 1, a mobile communication system according to an embodiment of the present invention includes radio base stations 1-1 to 1-3, a radio network controller 3, and mobile stations 2-1 and 2-2. A radio access network of a system using a code division multiplexing system such as CDMA (Wideband-Code Division Multiple Access) is configured.

  The radio base stations 1-1 to 1-3, the radio network controller 2, and the mobile stations 2-1 and 2-2 constituting the radio access network can perform multimedia communication by broadcast or multicast. The radio network controller 3 manages radio resources and controls a plurality of radio base stations 1-1 to 1-3. The radio base stations 1-1 to 1-3 communicate with the mobile stations 2-1 and 2-2 by using radio.

  2 is a sequence chart showing the operation of the mobile communication system according to one embodiment of the present invention, FIG. 3 is a flowchart showing the operation of the radio base stations 1-1 to 1-3 in FIG. 1, and FIG. 2 is a flowchart showing operations of mobile stations 2-1 and 2-2 in FIG. The operation of the mobile communication system according to one embodiment of the present invention will be described with reference to FIGS.

  The radio network controller 3 periodically notifies the radio base stations 1-1 to 1-3 of information regarding the number of mobile stations that receive a specific multimedia service in a cell (not shown) (a1 in FIG. 2). The radio base stations 1-1 to 1-3 periodically receive information on the number of received mobile stations and information indicating the target reception quality on the mobile stations 2-1 and 2-2 in a specific multimedia communication in the cell. (A2 in FIG. 2, steps S1 and S2 in FIG. 3).

  In the mobile stations 2-1 and 2-2, a timer is set using a timer function having the received control information and the reception quality measured by each mobile station 2-1 and 2-2 as variables (a 3 in FIG. 2). FIG. 4 steps S11 and S12).

  Here, each mobile station 2-1, 2-2 uses a long timer if it is communicating with a quality close to the target reception quality, and a short timer if the difference between the target reception quality and the measured reception quality is large. A timer function is defined to be used (steps S13 to S15 in FIG. 4). However, it is set so that a mobile station receiving a quality better than the target reception quality uses a longer timer than a mobile station receiving a bad quality. Note that the length of the timer is controlled by providing an upper limit and a lower limit.

  When the timer expires (timer value = 0) (step S16 in FIG. 4), each of the mobile stations 2-1 and 2-2 performs the radio base stations 1-1 to 1-3 for the radio frame received immediately before that. A radio status report is transmitted to (step S17 in FIG. 4). The radio status report includes Power down (hereinafter referred to as Pdown) when the reception quality is better than the target reception quality, Power up (hereinafter referred to as Pup) when the reception quality is poor, and BLER (BLock). Also included is Error Rate (block error rate).

  The radio base stations 1-1 to 1-3 have a window for a fixed time, and compare the number of times Pdown is received and the number of times Pup is received within the window time (a6 in FIG. 2, steps S5 and S6 in FIG. 3). Then, transmission power control to each of the mobile stations 2-1 and 2-2 is performed according to the comparison result (a7 in FIG. 2).

  That is, the radio base stations 1-1 to 1-3 reduce the transmission power when the number of times Pdown is received is larger than the number of times Pup is received within a certain window time (steps S6 and S7 in FIG. 3). Nothing is performed when the number of receptions of Pup and the number of receptions of Pup are equal, and the transmission power is increased when the number of receptions of Pup is greater than the number of receptions of Pdown (steps S6 and S8 in FIG. 3).

  However, in the radio base stations 1-1 to 1-3, the transmission power control is set such that the increase width of the transmission power is larger than the decrease width, and the transmission power is gradually decreased. In addition, an upper limit and a lower limit are set for the transmission power of the radio base station, and the transmission power is controlled to fall within the range.

  When the mobile stations 2-1 and 2-2 receive the control information notification from the radio base stations 1-1 to 1-3 again (a8 in FIG. 2, step S11 in FIG. 4), the timer function is used in step S12. Then recalculate the timer and restart the timer.

  In the radio base stations 1-1 to 1-3, the target reception quality is updated at a sufficiently longer cycle than when the transmission power is changed (a9 in FIG. 2, steps S9 and S10 in FIG. 3). Here, the radio base stations 1-1 to 1-3 record the worst BLER among the BLERs received from the mobile stations 2-1 and 2-2 (steps S3 and S4 in FIG. 3), and the target reception quality is recorded. In updating, it is determined whether to increase or decrease the target value based on the recorded BLER (step S10 in FIG. 3).

  When performing multimedia communication using a common channel from a radio base station to a plurality of mobile stations, a large transmission power is required in the radio base station in order to guarantee good reception quality for mobile stations existing at the cell edge. There is a problem that interference in the own cell and other cells increases, leading to a reduction in system capacity.

  In the present embodiment, the mobile stations 2-1 and 2-2 sharing one radio channel periodically transmit control information and measured reception quality transmitted from the radio base stations 1-1 to 1-3. Since the transmission frequency is adjusted using a timer function used as a variable, the timing at which the mobile stations 2-1 and 2-2 transmit the radio status report can be adjusted autonomously, and the amount of uplink radio channel usage increases. Can be suppressed.

  Further, in this embodiment, the transmission power in the radio base stations 1-1 to 1-3 is determined using all radio status reports transmitted from the mobile stations 2-1 and 2-2. Since adjustment is performed by weighting according to the radio state of the mobile station, the transmission power in the radio base stations 1-1 to 1-3 is a certain percentage of the mobile stations that receive the service in the cell. Can be autonomously adjusted to a level that satisfies the target reception quality, and transmission power can be kept low.

  Furthermore, in this embodiment, since the transmission frequency can be adjusted by changing the parameter of the timer function used by each mobile station 2-1, 2-2, the third effect is according to the policy of the service provider, The ratio of mobile stations satisfying the target reception quality in the cell can be adjusted.

  Furthermore, in the present embodiment, the target reception quality is periodically changed by referring to the worst value among the BLERs included in the radio status reports transmitted from the mobile stations 2-1 and 2-2. Therefore, it is possible to control the BLER in the mobile station in the cell so as to be a constant level. When the target reception power increases, the transmission power also increases, and as a result, BLER decreases.

  FIG. 5 is a diagram showing the relationship between the reception quality and the timer size according to an embodiment of the present invention, FIG. 6 is a diagram showing a transmission power control method according to an embodiment of the present invention, and FIG. FIG. 8 is a diagram showing parameters transmitted and received between nodes in one embodiment of the invention, FIG. 8 is a diagram showing an implementation period of transmission power control according to one embodiment of the present invention, and FIG. 9 is one embodiment of the present invention. It is a figure which shows the influence which the parameter change in gives to the reception quality of a mobile station. With reference to FIGS. 5 to 9, an example of an algorithm for performing transmission power control in a multimedia service using a common channel in a cellular mobile communication system using a W-CDMA system according to an embodiment of the present invention. explain.

  In MBMS (Multimedia Broadcast Multicast Service) that provides broadcast and multicast services, information on the mobile stations 2-1 and 2-2 receiving services is managed by the MBMS context by the radio network controller 3.

In this embodiment, the radio network controller 3 notifies the radio base stations 1-1 to 1-3 of the number M of mobile stations in the connected mode receiving each service at a period τ. 1-3 notifies the parameter v _T indicating a target reception quality in the mobile stations 2-1 and 2-2 and the number of mobile station M to the mobile stations 2-1 and 2-2 in the service reception.

・・・（１）
という式によってタイマＴを求める。 In the mobile stations 2-1 and 2-2, the timer T is started at the timing when the notification is received from the radio base stations 1-1 to 1-3. Each of the mobile stations 2-1 and 2-2 uses the measured value v of the size of the timer T, the frame transmission interval I of the application to be used, the constant N that determines the upper limit value of the timer, and the constants α and β. do it,

... (1)
The timer T is obtained by the following equation.

  At this time, the size of the timer T is MI <T ≦ NI. As the measurement value v representing the reception quality used here, SIR (Signal-to-Interference power Ratio: signal power to interference power ratio) or Ec / No (energy per desired wave chip to in-band received power density ratio) ) Etc. are considered.

  A constant α = a is set for a mobile station receiving with a quality better than the target reception quality, and a constant α = b is set for a mobile station receiving with a bad quality, and whether the quality is better or worse than the target reception quality. Judgment is made and the size of the timer T is determined. Here, a <b. FIG. 5 shows the relationship between the reception quality according to the above equation (1) and the size of the timer T.

As a result, in this embodiment, a mobile station with a large difference between the measurement value v and the target value v _T and a poor reception quality uses a shorter timer, and thus the radio base stations 1-1 to 1-3 are wirelessly connected. Increasing frequency of status reports. Each of the mobile stations 2-1 and 2-2 reports a radio status only for the frame received immediately before the timer expires.

  This report includes BLER in each of the mobile stations 2-1, 2-2, Pdown reported when the reception quality is better than the target reception quality, and Pup reported when the reception quality is bad. That is, the mobile station that has not received the data uses Pup.

In this embodiment, for transmission power control, the radio base station 1-1 to 1-3 has a window t _w, compares the count of the number and Pdown of Pup received during the window t _w, Pdown When the number of Pup is large, the transmission power is decreased by Δdown. When the number of Pup is equal to the number of Pdown, the transmission power is not changed. When the number of Pup is larger than the number of Pdown, the transmission power is Δup. Just raise.

However, Δdown <Δup is set in order to avoid abrupt deterioration of reception quality in the cell. Here, an upper limit W _sup and a lower limit W _inf are set for the transmission power in the radio base stations 1-1 to 1-3, and the transmission power is controlled to be within the range. FIG. 6 shows a transmission power control method.

In the transmission power control method shown in FIG. 6, a timer having an arbitrary size is started using the parameter M and the target value v _T received by the mobile stations 2-1 and 2-2 at the period τ. The radio base stations 1-1 to 1-3 may not receive the radio status reports from the mobile stations 2-1 and 2-2 with respect to the transmission frame because the radio status reports are transmitted only when the signal is disconnected.

The radio base stations 1-1 to 1-3 record the largest value among the BLERs received from the mobile stations 2-1 and 2-2 during the time τ, that is, the worst quality value. From this value, it is determined whether appropriate transmission power control is performed in the cell. The period τ to change the target value v _T in the radio base station 1-1 to 1-3, is set sufficiently longer than the period t _w to change the transmit power.

In this embodiment, by changing the target value v _T , the size of the timer used by the mobile stations 2-1 and 2-2 and the reference value for determining whether Pup or Pdown is changed. As a result, since the ratio of Pup and Pdown transmitted from the mobile stations 2-1 and 2-2 to the radio base stations 1-1 to 1-3 changes, the radio base stations 1-1 to 1-3 are changed. Adjustment will be added to the transmission power control in. FIG. 7 shows parameters transmitted and received between nodes.

  As described above, in this embodiment, when the transmission power control is performed in the radio base stations 1-1 to 1-3, the transmission power is frequently changed, and the target reception quality that is performed at a longer cycle than that. And updating. FIG. 8 shows an execution cycle of transmission power control. In FIG. 8, the length of the cycle in which the control is performed is expressed using the size of the area.

Here, when the mobile stations 2-1 and 2-2 receive the parameter notifications from the radio base stations 1-1 to 1-3 through the control channel, the mobile stations 2-1 and 2-2 perform the recalculation of the timer value and restart the timer. Depending on the setting of the constant N and the period τ, the mobile station whose measurement value v is close to the target value v _T can be set not to return a radio status report. By setting as described above, it is possible to reduce the amount of uplink radio channel usage.

  FIG. 9 shows the influence of the parameter change in the present invention on the reception quality of the mobile stations 2-1 and 2-2. In FIG. 9, the horizontal axis indicates reception quality v represented by RSSI (Received Signal Strength Indicator) such as SIR and Ec / No, the vertical axis indicates BLER, and the vertical axis indicates the number M of mobile stations.

  Here, it is known that when the RSSI increases, the BLER is greatly improved. When the reception quality v and the BLER are expressed using logarithms, the relationship is almost a straight line. Assuming that the mobile stations 2-1 and 2-2 are uniformly distributed in the cell, the reception quality deteriorates rapidly as the distance from the radio base stations 1-1 to 1-3 increases. Therefore, the relationship between the reception quality v and the number of mobile stations M is considered that the number of mobile stations decreases when the reception quality is good.

In this embodiment, by changing the values of a, b and β used for the timer function, the mobile station ratio is changed as shown in (1) with the target reception quality v _T and v _T ′ as the center. Can be changed. Thereby, in the present embodiment, it is possible to adjust the ratio of mobile stations that receive a service with a quality higher than the target reception quality.

Next, in the radio base stations 1-1 to 1-3, the service quality in the cell is estimated from the worst value among the BLERs included in the radio status reports from the mobile stations 2-1 and 2-2. By increasing the target reception quality from v _T to v _T ′, the transmission power in the radio base stations 1-1 to 1-3 is increased, and the mobile station receives the service in the cell as shown in (2). It is thought that the BLER of the station can be lowered.

It is a block diagram which shows the structure of the mobile communication system by one Example of this invention. It is a sequence chart which shows operation | movement of the mobile communication system by one Example of this invention. 2 is a flowchart showing an operation of the radio base station of FIG. 2 is a flowchart showing the operation of the mobile station of FIG. It is a figure which shows the relationship between the reception quality and the magnitude | size of a timer by one Example of this invention. FIG. 6 is a diagram illustrating a transmission power control method according to an embodiment of the present invention. It is a figure which shows the parameter transmitted / received between nodes in one Example of this invention. It is a figure which shows the implementation period of transmission power control by one Example of this invention. It is a figure which shows the influence which the parameter change in one Example of this invention has on the reception quality of a mobile station.

Explanation of symbols

1,1-1 to 1-3 Radio base station 2,2-1,2-2 Mobile station
3 Radio network controller

Claims (18)

A mobile communication system in which a radio base station performs transmission power control for a plurality of mobile stations receiving services on a common channel,
A mobile communication system, wherein a timer function is used to determine a reporting frequency when the mobile station reports a radio status to the radio base station.   The timer function has control information periodically transmitted from the radio base station and reception quality measured by the mobile station as variables, and is short for a mobile station having a large difference between the target reception quality and the measured reception quality. 2. The mobile communication system according to claim 1, wherein a timer is used, and the mobile communication system is defined such that a long timer is used for a mobile station in which the target reception quality and the measured reception quality are substantially equal.   3. The mobile communication system according to claim 2, wherein the mobile station receiving the quality better than the target reception quality is set to use a longer timer than the mobile station receiving the bad quality. .   The radio base station performs transmission power control that is weighted according to radio conditions of all mobile stations that receive the service, and performs control so that a certain percentage of mobile stations satisfy the target reception quality. The mobile communication system according to claim 2 or claim 3, wherein   The radio base station periodically changes the target reception quality with reference to the worst value of BLER (BLOCK Error Rate) included in a radio status report transmitted from the mobile station. The mobile communication system according to any one of claims 2 to 4. A radio base station that performs transmission power control for a plurality of mobile stations receiving services on a common channel,
Means for performing the transmission power control based on a radio status report from the mobile station;
The radio base station, wherein the radio status report is performed using a timer function for determining the report frequency.   The timer function has control information periodically transmitted from the radio base station and reception quality measured by the mobile station as variables, and is short for a mobile station having a large difference between the target reception quality and the measured reception quality. 7. The radio base station according to claim 6, wherein a timer is used, and the mobile base station is defined such that a long timer is used for a mobile station having substantially the same target reception quality and the measured reception quality.   8. The radio base station according to claim 7, wherein a mobile station receiving a quality better than the target reception quality is set to use a longer timer than a mobile station receiving a bad quality. .   The transmission power control weighted according to the radio conditions of all mobile stations that receive the service is performed, and control is performed so that a certain percentage of mobile stations satisfy the target reception quality. The radio base station according to claim 7 or 8.   8. The target reception quality is periodically changed with reference to the worst value of BLER (BLOCK Error Rate) included in a radio status report transmitted from the mobile station. Item 10. The radio base station according to any one of Items 9.   A mobile station that performs transmission power control at the time of receiving a service on a common channel at a radio base station, and uses a timer function to determine the reporting frequency of radio status reports to the radio base station A mobile station comprising means for sending a radio status report.   The timer function has control information periodically transmitted from the radio base station and reception quality measured by the local station as variables, and uses a short timer when the difference between the target reception quality and the measured reception quality is large. The mobile station according to claim 11, wherein a long timer is used when the target reception quality and the measured reception quality are substantially equal.   13. The mobile station according to claim 12, wherein a longer timer is used when receiving with better quality than the target reception quality than when receiving with poor quality. A wireless base station is a transmission power control method for performing transmission power control for a plurality of mobile stations receiving services on a common channel,
Transmitting power characterized in that the mobile station side has a step of performing the radio status report using a timer function in order to determine the report frequency when performing radio status report to the radio base station Control method.   The timer function has control information periodically transmitted from the radio base station and reception quality measured by the mobile station as variables, and is short for a mobile station having a large difference between the target reception quality and the measured reception quality. 15. The transmission power control method according to claim 14, wherein a timer is used, and the mobile station is defined such that a long timer is used for the mobile station in which the target reception quality and the measured reception quality are substantially equal.   16. The transmission power control method according to claim 15, wherein the mobile station receiving the quality better than the target reception quality is set to use a longer timer than the mobile station receiving the quality lower than the target reception quality. .   The radio base station performs transmission power control that is weighted according to radio conditions of all mobile stations that receive the service, and controls so that a certain percentage of mobile stations satisfy the target reception quality. The transmission power control method according to claim 15 or 16, wherein: The radio base station periodically changes the target reception quality with reference to the worst value of BLER (BLOCK Error Rate) included in a radio status report transmitted from the mobile station. The transmission power control method according to any one of claims 16 to 17.

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