JP2008079212A - Radio communication apparatus and power control method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a radio communication apparatus capable of controlling transmission power even when the reception quality can not be calculated. <P>SOLUTION: A Viterbi decoding part 4 Viterbi decodes the signal received by a receiving part 8. A CRC judgement part 5 judges whether the error is in the Viterbi decoded signal. A control part 6 judges whether or not the transport format of transport channel of the signal can be specified. When the transport format can not be specified, the control part 6 estimates the reception quality of the signal based on the judgement result by the CRC judgement part 5 and the likelihood of the Viterbi decoded signal by the Viterbi decoding part 4. The control part 6 calculates the target SIR based on the reception quality. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a radio communication apparatus and a power control method for performing outer loop power control.

  In a W-CDMA (Wideband-Code Division Multiple Access) mobile communication system, transmission power at which a base station apparatus transmits information using a dedicated channel is controlled. In this transmission power control, power control is performed based on SIR (Signal to Interference Ratio) so that predetermined reception quality is maintained and transmission power is low. High-speed TPC (High-speed Transmission Power Control) is used.

  In high-speed TPC, outer loop power control (OLPC) and inner loop power control (ILPC) are used.

  In the inner loop power control, the SIR is measured every time slot (0.667 milliseconds) from the data received on the dedicated channel, and the increase or decrease in transmission power is indicated so that the measured SIR becomes the target SIR. A TPC command is generated. Further, the TPC command is transmitted through a dedicated DPCCH channel (Dedicated Physical Control Channel).

  In outer loop power control, first, for each transport channel, the reception quality (BLER (Block Error Rate) or BER (Bit Error Rate)) is longer than a predetermined time slot. Measured. Thereafter, the target SIR is updated according to the reception quality.

  However, in the conventional outer loop power control, if data is not received for a certain time, the reception quality cannot be measured and the target SIR cannot be corrected. In this case, a method of setting the target SIR to an initial value when data is not received for a certain time can be considered. However, in this method, there is a possibility that the target SIR changes greatly every certain time and the transmission power is not stable.

  The mobile phone device described in Patent Document 1 (Japanese Patent Application Laid-Open No. 2003-318818) does not set the target SIR to an initial value when data is not received for a certain period of time, according to the current target SIR. The updated target SIR is controlled within a certain allowable range.

Thereby, even when data is not received for a certain time, it is possible to reduce the change in the target SIR and to stabilize the transmission power.
JP 2003-318818 A

  In the transport channel, a transport block is defined as a basic unit for data transfer. A collection of transport blocks is called a transport block set. Also, the time interval at which the transport block set is transferred between the MAC layer and layer 1 is referred to as TTI (Transmission Time Interval).

  Also, in the transport channel, the format (transport block size, multiplexing number, etc.) in which the transport block set is transferred between the MAC layer and the layer 1 in each TTI is referred to as a transport format (TF: Transport Format).

  Usually, a TFCI (Transport Format Combination Indicator) bit for specifying a transport format is mapped to the DPCCH. The wireless communication device identifies the transport format by checking the TFCI bit.

  However, the TFCI bit may not be mapped to the DPCCH. In this case, the wireless communication apparatus performs BTFD (Blind Transport Format Detection) to estimate the transport format.

  Specifically, first, when the wireless communication apparatus receives a signal, the wireless communication apparatus performs Viterbi decoding of the signal in each of a plurality of predetermined candidate transport formats.

  Subsequently, the wireless communication apparatus performs CRC (Cyclic Redundancy Check) on each of the plurality of signals that are Viterbi-decoded in each of the plurality of candidate transport formats. Thereafter, the wireless communication apparatus estimates the candidate transport format of the signal indicating that the CRC determination result indicates OK as the genuine transport format of the signal.

  Alternatively, the wireless communication apparatus uses the candidate transport format of the signal with the highest likelihood as a genuine transport format of the signal among the plurality of signals that are Viterbi-decoded in each of the plurality of candidate transport formats. presume.

  At this time, the wireless communication apparatus performs Viterbi decoding even when there is a transport format without a transport block in the transport format set of the received signal.

  For this reason, if the CRC determination result of the Viterbi-decoded signal indicates that there is an error, the wireless communication apparatus indicates that there is an error because there is no transport block. It cannot be determined whether there is an error because the signal is really incorrect. Therefore, the wireless communication apparatus cannot calculate the reception quality of the signal and cannot control the transmission power.

  Patent Document 1 does not describe transmission power control when reception quality cannot be calculated because a transport format cannot be specified.

  An object of the present invention is to provide a radio communication apparatus and a power control method capable of controlling transmission power even when reception quality cannot be calculated.

  In order to achieve the above object, a wireless communication apparatus of the present invention includes a receiving unit that receives a signal mapped to a transport channel, a measuring unit that measures an SIR of a signal received by the receiving unit, and the receiving unit. A decoding unit that performs Viterbi decoding on the signal received by the unit, a determination unit that determines whether or not the signal that has been Viterbi decoded by the decoding unit includes an error, and whether or not the transport format of the transport channel can be specified. If the transport format is not identifiable, the reception quality of the signal is estimated based on the determination result by the determination unit and the likelihood of the signal Viterbi-decoded by the decoding unit, and the reception Based on the control unit that calculates the target value of SIR based on quality, the target value of SIR calculated by the control unit, and the SIR measured by the measurement unit, A generation unit that generates, including a transmission section for transmitting a power control signal, wherein the generating unit has generated.

  The power control method of the present invention is a power control method performed by a radio communication apparatus, and includes a receiver that receives a signal mapped to a transport channel, and a measurement that measures the SIR of the signal received by the receiver. A decoding unit that performs Viterbi decoding on the signal received by the receiving unit, a determination unit that determines whether the signal that has been Viterbi decoded by the decoding unit includes an error, and a transport format of the transport channel is specified If the transport format is not identifiable, the reception quality of the signal is determined based on the determination result by the determination unit and the likelihood of the signal Viterbi-decoded by the decoding unit. A control unit that estimates and calculates a target value of SIR based on the reception quality, a target value of SIR calculated by the control unit, and an SIR measured by the measurement unit Zui and includes a generating unit for generating a power control signal, and a transmission unit for transmitting the power control signal, wherein the generating unit has generated.

  According to the above invention, when the transport format cannot be specified, the reception quality of the signal is estimated based on the likelihood of the signal and the determination result indicating the presence or absence of the signal error. When the determination result indicates that there is an error, the likelihood of the signal indicates the high possibility that the signal has an error.

  For this reason, it is possible to estimate whether there is no transport block or whether there is an error in the signal based on the likelihood of the signal, and it is possible to estimate the reception quality. Become. Therefore, even when reception quality cannot be calculated, transmission power can be controlled.

  Further, the control unit holds the number of error blocks and the total number of blocks, and when the transport format is not identifiable and the determination result indicates that there is an error in the signal, the likelihood of the signal is determined in advance. It is determined whether or not the threshold is greater than or equal to the threshold, and if the likelihood of the signal is greater than or equal to the threshold, the number of error blocks and the total number of blocks are increased. If the determination result indicates that there is no signal error, the total number of blocks It is desirable to estimate the reception quality based on the number of previous error blocks and the total number of blocks every predetermined time.

  According to the present invention, the number of error blocks and the total number of blocks are increased when the likelihood of the signal is equal to or greater than the threshold, and the number of error blocks and the total number of blocks are increased when the likelihood of the signal is less than the threshold. Not.

  For this reason, when the determination result indicates that there is an error, the higher the likelihood of the signal, the higher the possibility that the signal really has an error. Therefore, it is possible to improve the accuracy of the reception quality.

  In addition, it is preferable that the determination unit determines whether or not there is an error in the signal decoded by the decoding unit by a cyclic redundancy check.

  According to the present invention, it is possible to control transmission power even when reception quality cannot be calculated.

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

  FIG. 1 is a block diagram showing a configuration of a wireless communication apparatus according to an embodiment of the present invention.

  In FIG. 1, the wireless communication apparatus includes a despreading unit 1, a demodulating unit 2, an SIR measuring unit 3, a Viterbi decoding unit 4, a CRC determining unit 5, a control unit 6, a TPC command generating unit 7, A reception unit 8 and a transmission unit 9 are included.

  The despreading unit 1 despreads and restores the signal received by the receiving unit 8. It is assumed that the signal is mapped to a transport channel and spread with a despread code.

  The signal includes transmission data and control data. The control data includes at least a pilot signal and an error correction code. The control data may include a TFCI bit that specifies a transport format, or may not include a TFCI bit. Furthermore, it is assumed that the symbol data of the signal is encoded with a convolutional code. Hereinafter, this signal is referred to as a received signal. In this embodiment, the error correction code is a CRC bit (CRC code).

  The demodulating unit 2 demodulates the symbol data from the received signal restored by the despreading unit 1.

  The SIR measurement unit 3 is an example of a measurement unit. The SIR measuring unit 3 measures the SIR of the received signal based on the pilot signal included in the received signal restored by the despreading unit 1. Hereinafter, this SIR is referred to as measurement SIR.

  The Viterbi decoding unit 4 is an example of a decoding unit. The Viterbi decoding unit 4 performs Viterbi decoding on the symbol data demodulated by the demodulation unit 2.

  In the present embodiment, when the transport format cannot be specified, first, the Viterbi decoding unit 4 performs Viterbi decoding of the symbol data with a plurality of predetermined candidate transport formats. Subsequently, it is assumed that the Viterbi decoding unit 4 uses the symbol data having the highest likelihood among the plurality of symbol data that are Viterbi-decoded in each of the plurality of candidate transport formats as the decoding result.

  Although the demodulated symbol data may be turbo-decoded, since it is not directly related to the present invention, a turbo decoding unit that turbo-decodes symbol data is not shown.

  The CRC determination unit 5 determines whether or not there is an error in the symbol data (transmission data) decoded by the Viterbi decoding unit 4. Specifically, first, the CRC determination unit 5 generates CRC bits from the transmission data of the decoded symbol data. Subsequently, the CRC determination unit 5 performs CRC by comparing the generated CRC bits with the CRC bits included in the control data of the decoded symbol data. Note that the CRC determination unit 5 performs CRC for each transport block.

  The CRC determination unit 5 is an example of a determination unit. In this embodiment, the determination unit determines whether or not there is an error in the symbol data by CRC, but actually, the determination unit is not limited to CRC and can be changed as appropriate.

  The control unit 6 calculates the SIR target value based on the symbol data decoded by the Viterbi decoding unit 4, the likelihood of the symbol data, and the determination result of the CRC determination unit 5 for the symbol data. Hereinafter, the target value of SIR is referred to as target SIR.

  Specifically, first, the control unit 6 confirms whether or not the TFCI bit is included in the control data of the symbol data, thereby determining whether or not the transport format of the transport channel of the symbol data can be specified. Determine.

  If the control data includes the TFCI bit, the control unit 6 determines that the transport format can be specified. If the control data does not include the TFCI bit, the control format cannot be specified. judge.

  When the transport format can be specified, the control unit 6 calculates the reception quality based on the determination result of the CRC determination unit 5 for the symbol data. Hereinafter, the reception quality is assumed to be BLER. The reception quality is not limited to BLER and can be changed as appropriate.

  On the other hand, when the transport format cannot be specified, the control unit 6 estimates the BLER of the symbol data based on the determination result and the likelihood of the symbol data.

  Specifically, when the determination result indicates NG (with signal error), the control unit 6 estimates whether or not the symbol data really has an error based on the likelihood of the symbol data.

  For example, the control unit 6 holds a predetermined threshold and determines whether or not the likelihood of the symbol data is equal to or greater than the threshold. When the likelihood of the symbol data is equal to or greater than the threshold, the control unit 6 determines that the symbol data is truly erroneous, while when the likelihood of the symbol data is less than the threshold, the transport is performed. It is determined that there is no block. This is because the greater the likelihood of the symbol data, the higher the possibility that the symbol data has an error.

  If it is estimated that the symbol data is really erroneous, the control unit 6 increases the number of error blocks and the total number of blocks. On the other hand, if it is estimated that there is no transport block, the control unit 6 enters a standby state. Note that the control unit 6 holds the number of error blocks and the total number of blocks.

  On the other hand, if the determination result indicates OK (no signal error), the control unit 6 determines that the symbol data is not a block error and increases the total number of blocks.

  Further, the control unit 6 estimates the BLER for each predetermined time (for example, one time slot) based on the number of error blocks and the total number of blocks held therein. The control unit 6 calculates the target SIR based on the BLER.

  The TPC command generation unit 7 generates a TPC command based on the measurement SIR measured by the SIR measurement unit 3 and the target SIR calculated by the control unit 6. The TPC command generation unit 7 is an example of a generation unit, and the TPC command is an example of a power control signal.

  The receiving unit 8 receives a signal from the base station device.

  The transmission unit 9 transmits the TPC command generated by the TPC command generation unit 7 to the base station apparatus.

  Next, the operation will be described.

  FIG. 2 is a flowchart for explaining an example of the operation of the wireless communication apparatus.

  When receiving the signal from the base station apparatus, the receiving unit 8 executes Step S1.

  In step S <b> 1, the reception unit 8 transmits the signal (reception signal) to the despreading unit 1. When the despreading unit 1 receives the received signal, the despreading unit 1 executes Step S2.

  In step S2, the despreading unit 1 despreads and restores the received signal, and transmits the restored received signal to the demodulating unit 2 and the SIR measuring unit 3.

  When receiving the received signal, the SIR measuring unit 3 measures the SIR of the received signal based on a pilot signal included in the received signal. The SIR measurement unit 3 transmits the SIR (measurement SIR) to the TPC command generation unit 7. The TPC command generator 7 receives the measurement SIR.

  On the other hand, when the demodulator 2 receives the received signal, the demodulator 2 executes step S3.

  In step S <b> 3, the demodulator 2 demodulates the symbol data from the received signal and transmits the symbol data to the Viterbi decoder 4. When receiving the symbol data, the Viterbi decoding unit 4 executes Step S4.

  In step S4, the Viterbi decoding unit 4 performs Viterbi decoding on the symbol data. Specifically, it is confirmed whether or not the TFCI bit is included in the control data of the symbol data.

  When the control data includes a TFCI bit, the Viterbi decoding unit 4 performs Viterbi decoding of the symbol data in a transport format specified by the TFCI bit.

  On the other hand, if the control data does not include the TFCI bit, the Viterbi decoding unit 4 performs Viterbi decoding of the symbol data in a plurality of candidate transport formats, and Viterbi decoding is performed in each of the plurality of candidate transport formats. Among the plurality of symbol data, the symbol data having the highest likelihood is used as a decoding result.

  When the Viterbi decoding unit 4 performs Viterbi decoding on the symbol data, the Viterbi decoding unit 4 transmits the Viterbi decoded symbol data (decoding result) to the CRC determination unit 5. Further, the Viterbi decoding unit 4 transmits the likelihood of the decoded symbol data to the control unit 6. The control unit 6 receives the likelihood of the symbol data.

  On the other hand, when the CRC determination unit 5 receives the symbol data, it executes Step S5.

  In step S5, the CRC determination unit 5 generates CRC bits from the transmission data of the symbol data, compares the generated CRC bits with the CRC bits included in the control data of the symbol data, and generates the symbol data. Determine if there is an error. The CRC determination unit 5 generates the determination result and transmits the determination result and symbol data to the control unit 6. The CRC determination unit 5 generates a determination result indicating NG if the symbol data has an error, and generates a determination result indicating OK if the symbol data has no error.

  When receiving the determination result and the symbol data, control unit 6 executes step S6.

  In step S6, the control unit 6 calculates a target SIR based on the likelihood report of the symbol data, the determination result, and the symbol data. The control unit 6 transmits the calculated target SIR to the TPC command generation unit 7. When receiving the target SIR, the TPC command generation unit 7 executes step S7.

  In step S <b> 7, the TPC command generation unit 7 generates a TPC command based on the measurement SIR received from the SIR measurement unit 3 and the target SIR received from the control unit 6.

  Specifically, the TPC command generation unit 7 compares the measurement SIR with the target SIR. The TPC command generation unit 7 generates a TPC command indicating an increase in transmission power when the measured SIR is lower than the target SIR, while a TPC indicating a decrease in transmission power when the measured SIR is higher than the target SIR. Generate a command.

  When generating the TPC command, the TPC command generation unit 7 executes Step S8.

  In step S <b> 8, the TPC command generation unit 7 transmits the TPC command to the transmission unit 9. When receiving the TPC command, the transmission unit 9 transmits the TPC command to the base station apparatus.

  Next, an example of the operation of the control unit 6 will be described.

  FIG. 3 is a flowchart for explaining an example of the operation of the control unit 6.

  In step A1, the control unit 6 determines whether or not the transport format of the transport channel of the received signal can be specified. Specifically, the control unit 6 determines whether the TFCI bit is included in the symbol data received from the CRC determination unit 5. When the symbol data includes the TFCI bit, the control unit 6 determines that the transport format of the transport channel of the received signal can be specified, and when the symbol data does not include the TFCI bit, the received signal It is determined that the transport format of the transport channel cannot be specified.

  If the control unit 6 determines that the transport format is identifiable, it executes step A2, and if it determines that the transport format is not identifiable, it executes step A3.

  In step A <b> 2, the control unit 6 confirms the determination result received from the CRC determination unit 5. When the determination result indicates NG, the control unit 6 increases the number of retained error blocks and the total number of blocks. On the other hand, when the determination result indicates OK, the control unit 6 increases the total number of stored blocks.

  On the other hand, in step A3, the control unit 6 confirms the determination result.

  If the determination result indicates NG, the control unit 6 determines whether or not the likelihood received from the Viterbi decoding unit 4 is equal to or greater than the stored threshold value.

  When the likelihood of the symbol data is equal to or greater than the threshold, the control unit 6 determines that the symbol data is truly erroneous, while when the likelihood of the symbol data is less than the threshold, the transport is performed. It is determined that there is no block.

  If it is estimated that there is an error in the symbol data, the control unit 6 increases the number of error blocks and the total number of blocks. If it is estimated that the transport block does not exist, the control unit 6 enters a standby state.

  On the other hand, if the determination result indicates OK, the control unit 6 determines that the symbol data is not a block error, and increases the total number of blocks.

  The controller 6 repeats steps A1 to A3 for a predetermined time. Thereafter, when the predetermined time has passed, the control unit 6 executes Step A4.

  In Step A4, the control unit 6 measures BLER based on the number of error blocks and the total number of blocks held, and then initializes the number of error blocks and the total number of blocks held to zero. . The controller 6 executes Step A5 after completing Step A4.

  In step A5, the control unit 6 calculates a target SIR based on the BLER and transmits the target SIR to the TPC command generation unit 7.

  Note that the operation described with reference to FIG. 3 is performed for each transport channel multiplexed in a signal. Further, the control unit 6 holds the number of error blocks and the total number of blocks in association with each transport channel.

  According to the present embodiment, the Viterbi decoding unit 4 performs Viterbi decoding on the signal received by the receiving unit 8. The CRC determination unit 5 determines whether or not the Viterbi-decoded signal has an error. The control unit 6 determines whether or not the transport format of the transport channel of the signal can be specified. When the transport format cannot be specified, the control unit 6 estimates the reception quality of the signal based on the determination result by the CRC determination unit 5 and the likelihood of the signal Viterbi-decoded by the Viterbi decoding unit 4. The control unit 6 calculates the target SIR based on the reception quality.

  In this case, when the transport format cannot be specified, the BLER of the signal is estimated based on the likelihood of the signal and the determination result indicating the presence / absence of an error in the signal.

  When the determination result indicates that there is an error, the likelihood of the signal indicates the high possibility that the signal has an error.

  For this reason, it is possible to estimate whether there is no transport block or whether there is an error in the signal based on the likelihood of the signal, and it is possible to estimate the reception quality. Become. Therefore, even when reception quality cannot be calculated, transmission power can be controlled.

  In the present embodiment, when the transport format cannot be specified, the control unit 6 determines whether the likelihood of the signal is equal to or greater than a predetermined threshold when the determination result by the CRC determination unit 5 indicates NG. judge. When the likelihood of the signal is equal to or greater than the threshold, the control unit 6 increases the number of error blocks and the total number of blocks held. Further, when the determination result indicates OK, the control unit 6 increases the total number of blocks held. Furthermore, the control unit 6 estimates the reception quality based on the number of error blocks and the total number of blocks every predetermined time.

  In this case, if the likelihood of the signal is equal to or greater than the threshold, the number of error blocks and the total number of blocks are increased, and if the likelihood of the signal is less than the threshold, the number of error blocks and the total number of blocks are not increased.

  For this reason, when the determination result indicates that there is an error, the higher the likelihood of the signal, the higher the possibility that the signal really has an error. Therefore, it is possible to improve the accuracy of the reception quality.

  In the embodiment described above, the illustrated configuration is merely an example, and the present invention is not limited to the configuration.

  For example, the control data of the received signal may include a case where a CRC bit is included and a case where a CRC bit is not included. In this case, when receiving the symbol data not including the CRC bit from the Viterbi decoding unit 4, the CRC determination unit 5 generates a CRC bit indicating NG.

It is the block diagram which showed the structure of the radio | wireless communication apparatus of one Example of this invention. 6 is a flowchart for explaining an example of the operation of the wireless communication device. It is a flowchart for demonstrating an example of operation | movement of a control part.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Despreading part 2 Demodulation part 3 SIR measurement part 4 Viterbi decoding part 5 CRC judgment part 6 Control part 7 TPC command generation part 8 Reception part 9 Transmission part

Claims (6)

A receiver for receiving a signal mapped to a transport channel;
A measuring unit for measuring the SIR of the signal received by the receiving unit;
A decoding unit for Viterbi decoding the signal received by the receiving unit;
A determination unit that determines whether or not there is an error in the Viterbi-decoded signal by the decoding unit;
It is determined whether or not the transport format of the transport channel can be specified, and when the transport format is not specified, the determination result by the determination unit and the likelihood of the signal Viterbi decoded by the decoding unit A control unit that estimates the reception quality of the signal based on the reception quality and calculates a target value of the SIR based on the reception quality;
A generating unit that generates a power control signal based on a target value of SIR calculated by the control unit and an SIR measured by the measuring unit;
And a transmitter that transmits a power control signal generated by the generator. The wireless communication device according to claim 1,
The control unit holds the number of error blocks and the total number of blocks, and when the transport format is not identifiable and the determination result indicates that there is a signal error, the likelihood of the signal is equal to or greater than a predetermined threshold value If the likelihood of the signal is equal to or greater than the threshold, the number of error blocks and the total number of blocks are increased. If the determination result indicates that there is no signal error, the total number of blocks is increased. A wireless communication apparatus that estimates the reception quality based on the number of previous error blocks and the total number of blocks every predetermined time. The wireless communication device according to claim 1 or 2,
The said determination part is a radio | wireless communication apparatus which determines whether the signal which the said decoding part carried out Viterbi decoding has an error by a cyclic redundancy check. A power control method performed by a wireless communication device,
A receiving step for receiving a signal mapped to a transport channel;
A measuring step of measuring the SIR of the received signal;
A decoding step of Viterbi decoding the received signal;
A determination step of determining whether or not the Viterbi decoded signal has an error;
Determining whether the transport format of the transport channel can be specified;
If the transport format is not identifiable, an estimation step for estimating the reception quality of the signal based on the determination result of the determination step and the likelihood of the Viterbi-decoded signal;
A calculation step of calculating a target value of SIR based on the estimated reception quality;
Generating a power control signal based on the calculated target SIR value and the measured SIR;
A transmission step of transmitting the generated power control signal. The power control method according to claim 4,
The estimation step includes
When the determination result indicates that there is a signal error, a threshold determination step for determining whether the likelihood of the signal is equal to or greater than a predetermined threshold;
If the likelihood of the signal is equal to or greater than the threshold, an error counting step for counting the number of determinations and the number of errors;
When the determination result indicates that there is no signal error, a determination counting step for counting the number of determinations;
And a frequency estimation step of estimating the reception quality based on the counted determination count and error count. The power control method according to claim 4 or 5,
The power control method, wherein in the determination step, it is determined by cyclic redundancy check whether the Viterbi-decoded signal has an error.

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