JP5845786B2 - Transmission power control method and radio base station apparatus - Google Patents

Description

  The present invention relates to a transmission power control method and a radio base station apparatus.

  In recent years, wireless communication systems such as LTE (Long Term Evolution) systems have been developed. In a cell formed by an LTE radio base station apparatus (also referred to as an eNB: evolved NodeB), the mobile terminal is connected to the radio communication system when the power is turned on or the mobile terminal Signal transmission is performed by determining transmission power based on a fixed target power value possessed.

  By the way, in a place where there is no change in the connection environment with the base station device such as home or office, information necessary for communication is registered in advance between the mobile terminal and the base station device, and even in an environment where the common channel is not connected, A technique has been proposed in which fixed communication environment information is set in both base station apparatuses, and communication is performed using only individual channels by transmitting / receiving larger transmission power than the common channel from the individual channels (see, for example, Patent Document 1).

  It also selects one service from among the active services delivered to the physical channel using a predetermined selection method, and selects the carrier / interference target of the service selected to lead the physical channel power control. A technique for setting has been proposed (see, for example, Patent Document 2).

JP 2004-350196 A JP-T-2002-511720

  In an environment where communication quality is deteriorated such as in the shade of a building in a cell formed by a radio base station apparatus, an RRC (Radio Resource Control) connection, that is, a radio, is caused by loss of synchronization in a radio section when a mobile terminal is attached or during communication. The link may be broken. In this case, there is a case where the mobile terminal continues the reconnection operation because the RRC connection is not connected even if the reconnection operation of the RRC connection is performed, and it takes time until the mobile terminal can perform data communication again. There was a problem that it took.

  The disclosed transmission power control method is intended to suppress disconnection of a radio link with a mobile terminal in a quality degradation area.

A transmission power control method according to an embodiment of the disclosure is a transmission power control method for a wireless communication system in which a wireless base station device and a mobile terminal are connected by a wireless link,
Based on the measurement information transmitted from the radio base station apparatus, the mobile terminal measures the downlink quality, and when the measured downlink quality is less than a first threshold included in the measurement information, the mobile terminal Notifying the wireless base station device of the quality degradation area,
The radio base station apparatus that has received the quality degradation area presence notification receives the reference signal transmitted from the mobile terminal, measures the uplink quality, and the measured uplink quality is preset. When the threshold is less than 2, the target power for determining the transmission power of the mobile terminal is increased and notified to the mobile terminal .

  According to the present embodiment, disconnection of a radio link with a mobile terminal in a quality degradation area can be suppressed.

It is a block diagram of one Embodiment of a wireless base station apparatus. It is a block diagram of one Embodiment of a mobile terminal. It is explanatory drawing of one Embodiment of threshold value determination operation | movement. It is explanatory drawing of one Embodiment of target electric power variable operation | movement. It is a figure which shows one Embodiment of a call information management table. It is a flowchart of one Embodiment of the process at the time of measurement report reception. It is a flowchart of one Embodiment of the process at the time of SRS signal reception. It is a figure which shows the time change of RSRQ and a target electric power value.

  Embodiments will be described below with reference to the drawings.

<Configuration of radio base station device>
FIG. 1 shows a configuration diagram of an embodiment of a radio base station apparatus. In FIG. 1, the radio base station apparatus 10 includes a transmission path interface 11, an L2 (layer 2) switch 12, a control management unit 13, a baseband processing unit 14, and a radio interface 15.

  The transmission path interface 11 is connected to an upper exchange S-GW (Serving-Gateway) 21 and MME (Mobility Management Entity) 22 via an IP network 20, and SON (Self Optimizing) via a base station monitoring device 23. Network) server 24 is connected. The transmission path interface 11 transmits / receives information to / from the S-GW 21, the MME 22, the base station monitoring device 23, and the SON server 24.

  The L2 switch 12 is connected to the transmission line interface 11, and is also connected to the control management unit 13, the baseband processing unit 14, and the wireless interface 15 in the radio base station apparatus 10, respectively. 13, the baseband processing unit 14 and the wireless interface 15 are switched between layer 2 packets.

  The control management unit 13 is connected to the L2 switch 12, and the control management unit 13 includes a CPU 131, a memory (MEM) 132, and a call information management table 133. The CPU 131 performs various controls according to programs stored in the memory 132. The memory 132 stores a program for causing the radio base station apparatus 10 to function. The call information management table 133 stores target power value information and event information for each mobile terminal ID for identifying the mobile terminal (see FIG. 5).

  The control management unit 13 performs call processing. Further, the control management unit 13 performs resource management. In addition, the control management unit 13 performs connection control between the radio base station apparatus 10 and the mobile terminal 50. Furthermore, the control management unit 13 performs connection management between the radio base station apparatus 10 and the mobile terminal 50.

  The control management unit 13 notifies the mobile terminal 50 of the target power. In addition, the control management unit 13 instructs the mobile terminal 50 to measure downlink reception quality. Further, the control management unit 13 analyzes the RSRQ (Reference Signal Received Quality), which is the downlink reception quality notified from the mobile terminal 50 in response to the instruction, and transmits the RSRQ (Reference Signal Received Quality) to the SON server 24. Further, the control management unit 13 generates an RRC connection signal for notifying the mobile terminal 50 of the target power value and transmits the RRC connection signal to the mobile terminal 50. Further, the control management unit 13 monitors and controls each unit of the radio base station apparatus 10.

  The baseband processing unit 14 is connected to the L2 switch 12, and the baseband processing unit 14 includes a DSP (Digital Signal Processor) 141 and a memory (MEM) 142. The DSP 141 performs various controls according to programs stored in the memory 142. The baseband processing unit 14 inputs and outputs information to and from the control management unit 13. The baseband processing unit 14 performs traffic management and transfer processing. Specifically, GTP (General Packet Radio Service (GPRS) Tunneling Protocol) management and GTP transfer processing are performed. Further, the baseband processing unit 14 monitors traffic, that is, a cell state. In addition, the baseband processing unit 14 performs concealment setting and cancellation, performs MAC (Media Access Control) multiplexing and demultiplexing, performs synchronization processing, and performs paging processing.

  Further, the baseband processing unit 14 measures the quality of the location where the mobile terminal that has transmitted the SRS signal from the reception level of the SRS signal received from the mobile terminal 50, compares the measured quality with the quality threshold value, and compares the result. Is notified to the control management unit 13.

  The wireless interface 15 includes an I / O port 151, an A / D and D / A conversion circuit 152, a broadband AMP 153, and an antenna 154. The I / O port 151 is connected to the L2 switch 12 and inputs / outputs signals. The A / D and D / A conversion circuit 152 converts the digital signal from the I / O port 151 into an analog signal and supplies the analog signal to the broadband AMP 152. The A / D and D / A conversion circuit 152 converts an analog signal from the broadband AMP 152 into a digital signal and supplies the digital signal to the I / O port 151.

  The broadband AMP 152 amplifies the analog signal from the A / D and D / A conversion circuit 152 and transmits the amplified signal from the antenna 154 to the corresponding cell 40. The broadband AMP 152 amplifies an analog signal received from the cell 40 by the antenna 154 and supplies the amplified signal to the A / D and D / A conversion circuit 152.

<Configuration of mobile terminal>
FIG. 2 shows a block diagram of an embodiment of a mobile terminal. In FIG. 2, the mobile terminal 50 includes an antenna 51, an RF (high frequency) circuit unit 52, a CPU / memory controller / graphic controller 53, a memory 54, an audio unit 55, a display unit 56, and a GPS receiving unit 57.

  The RF circuit unit 52 performs radio communication with the radio base station 10 using the antenna 51, and performs modulation / demodulation of high-frequency signals, data encoding and decoding.

  The CPU / memory controller / graphics controller 53 performs various controls according to a program stored in the memory 54. The CPU in the CPU / memory controller / graphics controller 53 uses the memory 54 to execute various processes of the mobile phone. The memory controller controls writing and reading of the memory 54. The graphic controller displays an image on the display unit 56.

  Further, the CPU / memory controller / graphic controller 53 stores the target power notified from the radio base station apparatus 10 by the broadcast information in the memory 54 and determines the transmission power based on the target power. Then, the RF circuit unit 52 is controlled to transmit with the determined transmission power. Further, when the CPU / memory controller / graphics controller 53 receives the measurement information from the radio base station apparatus 10, the CPU / memory controller / graphics controller 53 causes the RF circuit unit 52 to measure RSRQ, and determines each of the events A1 / A2 / A3 from the RSRQ. When the event A1 / A2 / A3 occurs, a measurement report including the event information, the measured RSRQ, and the location information of the own mobile terminal is generated and transmitted to the radio base station apparatus 10.

  The audio unit 55 performs sound processing such as processing of input sound from the microphone and processing of received sound data supplied from the CPU / memory controller / graphic controller 53.

  The GPS receiving unit 57 measures and measures the three-dimensional (or two-dimensional) position information of the own mobile terminal from four (or three) or more captured satellite information, and the CPU / memory controller / graphic controller 53 as the position information of the own mobile terminal. Notify

<Threshold determination operation>
FIG. 3 is an explanatory diagram of an embodiment of the threshold value determining operation.

  Sequence SQ1: Each mobile terminal measures RSRQ (Reference Signal Received Quality), which is the quality of a signal at each position in the cell, at a constant period. The mobile terminal 50 notifies the radio base station apparatus 10 of the measured RSRQ and position information by a measurement report.

  Sequence SQ2: The radio base station apparatus 10 transmits the RSRQ and location information received from the mobile terminal 50 to the SON server 24 via the IP network 20 and the base station monitoring apparatus 23.

  Sequence SQ3: The SON server 24 determines an RSRQ threshold value that causes quality degradation in the cell based on the RSRQ and the location information. This RSRQ threshold corresponds to the first threshold.

  Sequence SQ4: The SON server 24 transmits the determined RSRQ threshold value to the radio base station apparatus 10 via the base station monitoring apparatus 23.

  Sequence SQ5: The radio base station apparatus 10 notifies the mobile terminal 50 of the RSRQ threshold as measurement configuration information of the RRC connection reconfiguration message at the time of attachment.

<Target power variable operation>
FIG. 4 is an explanatory diagram of an embodiment of the target power variable operation. First, a case where the mobile terminal 50 exists in a good quality area will be described.

  Sequence SQ11: The radio base station apparatus 10 notifies the target power to the mobile terminal 50 in the cell by p0-Nominal PUSCH of the broadcast information, that is, the uplink power control IE (information element) of the RRC connection reconfiguration message. . Note that the RRC connection reconfiguration message is also referred to as an “RRC connection signal”, and the target power notified by the broadcast information is referred to as an “initial value of the target power value”.

  The mobile terminal 50 that has received the broadcast information determines transmission power using a calculation formula defined by standardization based on the received initial value of the target power value and performs data communication (for example, 3GPP TS36.213, 5. See 1.1.1).

  Sequence SQ12: When the mobile terminal 50 is attached, measurement information is notified from the radio base station apparatus 10 to the mobile terminal 50. This measurement information notifies the report type (event A1 / A2 / A3) in the measurement configuration IE of the RRC connection reconfiguration message, and includes an RSRQ threshold value.

  Event A1 occurs when the reception quality RSRQ of the serving cell (cell 40 to which the mobile terminal 50 is connected) becomes better than the RSRQ threshold, and the mobile terminal 50 measures the occurrence of the event A1 and the measured RSRQ and location information. The radio base station apparatus 10 is notified by a report.

  The event A2 occurs when the quality of the serving cell becomes lower than the RSRQ threshold, and the mobile terminal 50 notifies the radio base station apparatus 10 of the occurrence of the event A2 and the measured RSRQ and position information by a measurement report. However, handover is not performed.

  Event A3 occurs when the quality of the neighboring cell becomes better than a predetermined offset value set in advance for the quality of the serving cell, and the mobile terminal 50 generates the event A1 for performing handover and the measured RSRQ and The location information is notified to the radio base station apparatus 10 by a measurement report.

  The mobile terminal 50 notified of the measurement information from the radio base station apparatus 10 measures the RSRQ that is the quality of the signal at the current position at a constant period based on the notified measurement information. The mobile terminal 50 notifies the radio base station apparatus 10 of the RSRQ and position information measured by the measurement report when the event occurs.

  Sequence SQ13: The mobile terminal 50 transmits an SRS (Sounding Reference Signal) signal to the radio base station device 10 during data communication, and the radio base station device 10 that has received the SRS signal indicates the quality status of the location where the mobile terminal 50 is currently located. Check. If it is determined that the quality of the location where the mobile terminal 50 is currently located is good, the communication is continued with the current target power value.

  Next, a case where the mobile terminal 50 moves to the quality deterioration area will be described.

  Sequence SQ14: When the mobile terminal 50 moves to the quality degradation area, the mobile terminal 50 reports a measurement report of the event A2 to the radio base station apparatus 10 as a measurement result. The radio base station apparatus 10 that has received the measurement report of the event A2 stores the event A2 in the event information of the mobile terminal ID corresponding to the mobile terminal 50 in the call information management table 133, and the mobile terminal 50 Recognize that it has moved to a quality degradation environment. The call information management table 133 shown in FIG. 5 indicates that the event A2 has occurred in the mobile terminal whose mobile terminal ID is “C”.

  Sequence SQ15: The mobile terminal 50 transmits an SRS signal to the radio base station apparatus 10 during data communication, and measures the quality status of the location where the mobile terminal 50 is present at the radio base station apparatus 10 that has received the signal. When the radio base station apparatus 10 determines that the quality measured from the SRS signal is equal to or less than a preset quality threshold, it calls whether or not the measurement report of the event A2 is reported from the corresponding mobile terminal 50 Confirm with the information management table 133. This quality threshold corresponds to the second threshold.

  Sequence SQ16: When the radio base station apparatus 10 receives the report of the event A2 in sequence SQ14, the target power value for the mobile terminal 50 is updated by, for example, 1 dBm, and updated to the call information management table 133 And the updated target power value is notified to the mobile terminal 50 through RRC connection reconfiguration.

  In the call information management table 133 shown in FIG. 5, the target power value of the mobile terminal ID corresponding to the mobile terminal with the mobile terminal ID “C” is updated from “5”, which is the initial value of the target power, to “6”. Is shown. The mobile terminal 50 determines transmission power based on the notified updated target power value and performs data communication.

  Radio base station apparatus 10 confirms the quality status from mobile terminal 50 again in sequence SQ15, and repeats the operation of sequence SQ16 when it is determined that the quality is poor from the SRS signal. When the target power value finally reaches a predetermined upper limit value, reconnection is promoted or another RAT (Radio Access Technology) such as W-CDMA (Wideband Code Division Multiple Access) is used. ).

  Sequence SQ17: The quality status from the mobile terminal 50 is measured in sequence SQ15, and the mobile terminal 50 performs data communication at the target power value when the finally measured quality is better than the quality threshold. .

  Sequence SQ18: When it is determined from the measurement result in the mobile terminal 50 that the RSRQ at the current position of the mobile terminal 50 has exceeded the RSRQ threshold, the mobile terminal 50 notifies the radio base station apparatus 10 of the measurement of event A1 as the measurement result. Report a report. The radio base station apparatus 10 that has received the report determines that the mobile terminal 50 has moved to a good quality environment, and sets the initial value of the target power value as the transmission power corresponding to the mobile terminal 50 in the call information management table 133. Remember and update. Thereafter, “the initial value of the target power value” is notified to the mobile terminal 50 through the RRC connection reconfiguration message.

<Processing when receiving a measurement report>
FIG. 6 shows a flowchart of an embodiment of processing executed by the radio base station apparatus 10 when receiving a measurement report. The control management unit 13 of the radio base station apparatus analyzes the measurement report information received in step S1.

  The control manager 13 determines whether or not the report type of the measurement report received in step S2 is event A1. If the report type is event A1, the control management unit 13 adds “event A1” to the event information of the mobile terminal ID corresponding to the mobile terminal (the mobile terminal that transmitted the measurement report) in the call information management table 133 in step S3. Set.

  Thereafter, in step S4, the control management unit 13 determines whether or not the target power value information corresponding to the mobile terminal in the call information management table 133 is the “initial value of the target power value”. When the target power value information is not “initial value of target power value”, the control management unit 13 adds “initial value of target power value” to the target power value information corresponding to the mobile terminal in the call information management table 133 in step S5. Set.

  In step S6, the control management unit 13 transmits an RRC connection signal for notifying the mobile terminal of the “initial value of the target power value”, and ends this process. Note that this processing is also terminated when the target power value information corresponding to the mobile terminal in the call information management table 133 is “initial value of target power value” in step S4.

  On the other hand, if the report type is other than event A1 in step S2, the control management unit 13 determines whether the report type is event A2 in step S7. If the report type is event A2, the control management unit 13 sets “event A2” in the event information of the mobile terminal ID corresponding to the mobile terminal in the call information management table 133 in step S8.

  If the report type is not event A2 in step S7, or after executing step S8, in step S9, the control management unit 13 determines whether the report type is event A3 in step S10. If the report type is event A3, the control management unit 13 executes the handover process in step S10 and ends this process. If the report type is not event A3 in step S9, this process ends.

<SRS signal reception processing>
FIG. 7 shows a flowchart of an embodiment of processing executed by the radio base station apparatus 10 when an SRS signal is received. The baseband processing unit 14 of the radio base station apparatus measures the quality of the location where the mobile terminal that transmitted the SRS signal is currently based on the reception level of the SRS signal received in step S21. The baseband processing unit 14 determines whether or not the quality measured in step S22 is less than a preset quality threshold value. Note that the quality threshold value is a value that is regarded as poor quality at the location where the mobile terminal is currently located when the measured quality, that is, the reception level of the SRS signal is less than a predetermined reception level. If the measured quality is equal to or higher than the quality threshold, this process is terminated.

  If the measured quality is less than the quality threshold, the baseband processing unit 14 notifies the measured quality to the control management unit 13 in step S23. Next, in step S24, the control management unit 13 refers to the event information of the mobile terminal ID corresponding to the mobile terminal in the call information management table 133. In step S <b> 25, the control management unit 13 determines whether the event information referred to from the call information management table 133 is event 2. If the event information is not event 2, this process ends.

  If the event information is event 2, the control management unit 13 acquires target power value information corresponding to the mobile terminal from the call information management table 133 in step S26. Next, the control management unit 13 determines whether or not the target power value acquired in step S27 is greater than or equal to a preset upper limit value. If the target power value is less than the upper limit value, the control management unit 13 adds the target power value by, for example, 1 dBm in step S28. If the added result exceeds the upper limit value, the control management unit 13 changes the upper limit value. The target power value information corresponding to the mobile terminal in the table 133 is updated. Then, the control management unit 13 transmits the updated target power value to the mobile terminal using the RRC connection signal in step S29, and ends this process.

  On the other hand, if the target power value is greater than or equal to the upper limit value in step S27, the control management unit 13 prompts reconnection in step S30 or prompts connection to another RAT, and ends this process.

<SRS signal reception processing>
FIG. 8 shows temporal changes in RSRQ and target power value due to movement of the mobile terminal. In the period T1, the RSRQ measured by the mobile terminal indicated by the solid line I is larger than the RSRQ threshold indicated by the broken line J, and the current position of the mobile terminal is a good quality area. In this case, the target power value of the mobile terminal maintains the initial value of the target power value as indicated by the alternate long and short dash line K.

  In the next period T2, the RSRQ measured by the mobile terminal indicated by the solid line I becomes equal to or less than the RSRQ threshold value indicated by the broken line J, and the current position of the mobile terminal is the quality degradation area. In this case, the mobile terminal reports a measurement report of event A2 to the radio base station apparatus 10, and the quality measured from the SRS signal is equal to or lower than the quality threshold in the radio base station apparatus 10, so that the target power of the mobile terminal The value gradually increases in units of 1 dBm, for example, as indicated by a dashed line K.

  In the next period T3, the RSRQ measured by the mobile terminal indicated by the solid line I is larger than the RSRQ threshold indicated by the broken line J, and the current position of the mobile terminal is a good quality area. In this case, the target power value of the mobile terminal decreases to the initial value of the target power value as indicated by the alternate long and short dash line K.

  In this way, in this embodiment, the target power value during attachment and communication is temporarily increased in a quality degradation area such as in the shade of a building, and the RRC connection is disconnected between the mobile terminal and the radio base station. Therefore, it is possible to reduce the reconnection rate and the time required for resuming data communication, and to improve user satisfaction.

  In this embodiment, after the downlink quality of the mobile terminal deteriorates and the mobile terminal notifies the radio base station apparatus 10 of the event A2, the radio base station apparatus 10 measures the SRS signal from the mobile terminal. When it is determined that the uplink quality has deteriorated, the target power value for the mobile terminal is increased from the initial value of the target power value.

  However, the present invention is not limited to this, and the target power value for the mobile terminal is increased from the initial value of the target power value when the downlink quality in the mobile terminal deteriorates and the mobile terminal notifies the radio base station apparatus 10 of the event A2. It is good also as a structure. However, as in this embodiment, after the notification of the event A2, the radio base station apparatus 10 determines that the quality of the uplink has deteriorated, and the configuration in which the target power value is increased is more accurate. Can be judged.

DESCRIPTION OF SYMBOLS 10 Radio base station apparatus 11 Transmission path interface 12 L2 switch 13 Control management part 131 CPU
132 Memory 133 Call Information Management Table 14 Baseband Processing Unit 141 DSP
142 memory 15 wireless interface 20 IP network 21 S-GW
22 MME
23 base station monitoring device 24 SON server 40 cell 50 mobile terminal 51 antenna 52 RF circuit unit 53 CPU / memory controller / graphic controller 54 memory 55 audio unit

Claims (4)

A transmission power control method for a radio communication system for connecting a radio base station apparatus and a mobile terminal via a radio link,
Based on the measurement information transmitted from the radio base station apparatus, the mobile terminal measures the downlink quality, and when the measured downlink quality is less than a first threshold included in the measurement information, the mobile terminal Notifying the wireless base station device of the quality degradation area,
The radio base station apparatus that has received the quality degradation area presence notification receives the reference signal transmitted from the mobile terminal, measures the uplink quality, and the measured uplink quality is preset. A transmission power control method characterized by increasing a target power for determining the transmission power of the mobile terminal when it is less than two thresholds and notifying the mobile terminal . The transmission power control method according to claim 1 ,
Good quality from the mobile terminal to the radio base station apparatus when the downlink quality measured by the mobile terminal based on the measurement information transmitted from the radio base station apparatus is equal to or higher than a first threshold included in the measurement information Make an area notification,
The radio base station apparatus that has received the good quality area presence notification changes the target power of the mobile terminal to an initial value and notifies the mobile terminal of the transmission power control method. A radio base station apparatus of a radio communication system for connecting a radio base station apparatus and a mobile terminal via a radio link,
Measurement information transmission means for transmitting measurement information instructing measurement of downlink quality to the mobile terminal; and downlink quality measured by the mobile terminal that has received the measurement information is less than a first threshold included in the measurement information After receiving the quality degradation area presence notification transmitted from the mobile terminal, the reference signal transmitted from the mobile terminal is received to measure the uplink quality, and the measured uplink quality is preset. Transmission power update means for increasing the target power for determining the transmission power of the mobile terminal and notifying the mobile terminal when it is less than the second threshold ;
A radio base station apparatus comprising: The radio base station apparatus according to claim 3 ,
The transmission power update means receives a good area coverage notification transmitted from the mobile terminal when the downlink quality measured by the mobile terminal that has received the measurement information is equal to or higher than a first threshold included in the measurement information. Then, the radio base station apparatus changes the target power of the mobile terminal to an initial value and notifies the mobile terminal.

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