JP2005260992A - Wireless communication apparatus and transmission rate decision method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wireless communication apparatus and transmission rate decision method for optimizing with high precision an assignment of transmission rate. <P>SOLUTION: In a Doppler frequency detector 117, a Doppler frequency of a relevant mobile station is detected using a demodulated received signal. A decoding part 119 decodes Ack/Nack information. A CIR (Carrier to Interference Ratio) report value storage part 123 stores CIR. An Ack/Nack information storage part 201 stores Ack/Nack information. An MCS assignment part 203 assigns, for each mobile station, optimal MCS to the relevant mobile station based on the CIR report value, Doppler frequency and Ack/Nack information of the mobile station. Physically, the MCS assignment part 203 further finely adjusts a correction amount based on the Doppler frequency using the Ack/Nack information. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a wireless communication apparatus and a transmission rate determination method.

  As a higher-speed IMT-2000 packet transmission method, a method called HSDPA (High Speed Downlink Packet Access) for the purpose of increasing the peak transmission speed of the downlink, low transmission delay, high throughput, and the like has been studied. As a technology that supports HSDPA, 3GPP (3rd Generation Partnership Project) TR25.848 "Physical layer aspects of UTRA High Speed Downlink Packet Access" is called AMC (Adaptive Modulation and Coding). A scheme is disclosed.

  This AMC technique is a technique for adaptively and rapidly changing the modulation scheme and error correction coding rate in accordance with fluctuations in channel quality. In the AMC technique, the higher the line quality, the higher the transmission rate by using a higher-speed modulation scheme and increasing the error correction coding rate. Specifically, the mobile station (or base station) measures the downlink propagation state for each mobile station at any time, and the base station determines the mobile station to transmit information and the optimal transmission rate based on the measurement results. And transmit information. Related to the transmission rate are modulation schemes (for example, QPSK (Quaternary Phase Shift Keying) and 16QAM (Quaternary Amplitude Modulation)), coding rates (for example, turbo coding at 1/3, puncture or repetition) (The coding rate is changed by repeating)). Examples of the line quality information include CIR (Carrier to Interference Ratio), SIR (Signal to Interference Ratio), TFRC (Transport Format and Resource Combination), and transmission power of a dedicated channel (for example, DPCH (Dedicated Physical Channel)). Used.

  For example, in one application example in determining the transmission rate in the AMC technique, the base station may use a modulation scheme and a coding rate (MCS) based on the CIR reported from the mobile station or the transmission power of the dedicated channel. Coding Scheme), that is, the one related to the transmission rate is determined.

  However, there are the following problems in determining such a transmission rate. In other words, even if the transmission rate is determined based on instantaneous information, the reliability of the information is reduced due to the delay in allocation, the moving speed of the mobile station, and the measurement accuracy of the channel quality at the mobile station or base station. To do. For example, when the moving speed of the mobile station is slow (the Doppler frequency is small), the fluctuation of the propagation environment is not so large, but when the moving speed is fast (the Doppler frequency is large), the fluctuation of the propagation environment becomes large, and the information The reliability of is reduced. As a result, transmission rate allocation cannot be optimized, and throughput may be greatly affected.

  Such a problem is not limited to the case of the above HSDPA, and is widely applied in a method for controlling a transmission rate. That is, in the above HSDPA, the spreading factor is fixed, but in general, the determination of the transmission rate involves not only the modulation method and coding rate but also the spreading factor and transmission power. If the reliability is lowered, the determination of the transmission rate cannot be optimized, and the performance of the transmission method may be greatly affected.

  The present invention has been made in view of this point, and an object of the present invention is to provide a wireless communication apparatus and a transmission rate determination method that can optimize transmission rate determination with high accuracy.

  The wireless communication apparatus of the present invention uses a relational expression that defines a relationship between channel quality information and a transmission rate, a determination unit that determines a transmission rate corresponding to the channel quality information, and retransmission necessity information from a communication partner. A configuration is provided that includes an acquisition unit that acquires and a correction unit that sets a correction amount based on the retransmission necessity information and corrects the relational expression by the correction amount.

  Further, the wireless communication apparatus of the present invention uses a relational expression that defines the relationship between the line quality information and the transmission rate to determine a transmission rate corresponding to the line quality information, and a relative movement speed of the communication partner. Detecting means for detecting; acquiring means for acquiring retransmission necessity information from the communication partner; and when Ack information is received as the retransmission necessity information, the correction amount set based on the relative movement speed is reduced. And a correction unit that corrects the relational expression by increasing a correction amount set based on the relative movement speed when the relational expression is corrected and Nack information is received as the retransmission necessity information. Take.

  The transmission rate determination method according to the present invention includes a determination step for determining a transmission rate corresponding to channel quality information using a relational expression that defines a relationship between channel quality information and a transmission rate, and retransmission necessity information from a communication partner. And a correction step of setting a correction amount based on the retransmission necessity information and correcting the relational expression by the correction amount.

  The transmission rate determination method of the present invention includes a determination step of determining a transmission rate corresponding to the channel quality information using a relational expression that defines a relationship between the channel quality information and the transmission rate, and a relative movement speed of the communication partner. A detection step for detecting the retransmission request, an acquisition step for acquiring retransmission necessity information from the communication partner, and a correction amount set based on the relative movement speed when the Ack information is received as the retransmission necessity information. A correction step of correcting the relational expression by increasing a correction amount set based on the relative movement speed when the relational expression is corrected and Nack information is received as the retransmission necessity information. I tried to do it.

  According to the present invention, transmission rate determination can be optimized with high accuracy.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

(Embodiment 1)
FIG. 1 is a block diagram showing a configuration on the transmission side of the wireless communication apparatus according to Embodiment 1 of the present invention.

  A transmission-side wireless communication apparatus 100 illustrated in FIG. 1 is, for example, a wireless communication apparatus using AMC technology, and includes an encoding unit 101, a modulation unit 103, a spreading unit 105, a transmission wireless unit 107, an antenna 109, a reception wireless device. Unit 111, despreading unit 113, demodulation unit 115, Doppler frequency detector 117, decoding unit 119, CIR report value extraction unit 121, CIR report value storage unit 123, and MCS allocation unit 125. Here, in order to be able to handle transmission data for a plurality of users, a plurality of units 101 to 105 and 113 to 125 other than the transmission radio unit 107, the antenna 109, and the reception radio unit 111 are provided. . The transmitting-side radio communication apparatus 100 is mounted on, for example, a base station apparatus (hereinafter simply referred to as “base station”) in a mobile communication system.

  FIG. 2 is a block diagram showing a configuration on the receiving side of the wireless communication apparatus according to Embodiment 1 of the present invention.

  2 is a wireless communication device that performs wireless communication with the transmission-side wireless communication device 100 of FIG. 1 using AMC technology, for example, an antenna 151, a reception wireless unit 153, A despreading unit 155, a demodulation unit 157, a decoding unit 159, a pilot signal extraction unit 161, a CIR measurement unit 163, an encoding unit 165, a modulation unit 167, a spreading unit 169, and a transmission radio unit 171 are included. The radio communication device 150 on the receiving side is mounted on, for example, a mobile station device (hereinafter simply referred to as “mobile station”) in a mobile communication system.

  Next, operations of transmitting and receiving side wireless communication apparatuses 100 and 150 having the above-described configuration will be described.

  The radio communication apparatus 100 (base station) on the transmission side first encodes transmission data by the encoding unit 101 and then modulates the encoded transmission data by the modulation unit 103 for each transmission data for each user. To do. Here, encoding section 101 and modulation section 103 perform error correction encoding processing and modulation processing, respectively, according to the allocation results (encoding rate and modulation scheme) in MCS allocation section 125. The encoding rate is encoded by, for example, 1/3, the encoding rate is changed by puncturing or repetition of the parity part, and the modulation scheme is selected from, for example, QPSK and 16QAM. The determination of the transmission rate (encoding rate and modulation scheme) here is based on the previously acquired information. The processing of the MCS allocation unit 125 will be described in detail later. The modulated transmission data is output to spreading section 105.

  Spreading section 105 spreads the modulated transmission data using a unique spreading code. The spread transmission data is output to the transmission radio section 107, where predetermined radio processing such as up-conversion is performed, and then radio transmission is performed from the antenna 109.

  Thereafter, radio communication apparatus 150 (mobile station) on the reception side receives the signal wirelessly transmitted from the base station by antenna 151 and outputs the signal to reception radio section 153.

  Reception radio section 153 performs predetermined radio processing such as down-conversion on the signal received by antenna 151. The output signal (baseband signal) of reception radio section 153 is output to despreading section 155.

  Despreading section 155 despreads the received signal using the same spreading code as at the time of transmission, and demodulating section 157 demodulates the received signal after despreading. The demodulated received signal is output to decoding section 159 and pilot signal extraction section 161.

  Decoding section 159 decodes the demodulated received signal to obtain desired received data.

  On the other hand, pilot signal extraction section 161 extracts a predetermined pilot signal (known signal) from the demodulated received signal. The extracted pilot signal is output to CIR measurement section 163.

  The CIR measurement unit 163 measures CIR using the extracted pilot signal. CIR is one piece of information indicating reception quality, and is an index indicating channel quality. The measured CIR value is output to encoding section 165 as a CIR report value.

  The encoding unit 165 encodes the measured CIR value together with other information, then sequentially modulates the encoded information by the modulation unit 167, and the spreading unit 169 modulates it using a unique spreading code. Spread later information. The spread information is output to transmission radio section 171, where predetermined radio processing such as up-conversion is performed and then radio transmission is performed from antenna 151.

  Thereafter, radio communication apparatus 100 (base station) on the transmission side receives a signal wirelessly transmitted from the mobile station by antenna 109 and outputs the signal to reception radio section 111.

  Reception radio section 111 performs predetermined radio processing such as down-conversion on the signal received by antenna 109. The output signal (baseband signal) of reception radio section 111 is output to despreading section 113.

  Despreading section 113 despreads the received signal for each mobile station using the same spreading code as at the time of transmission, and demodulation section 115 demodulates the despread received signal. The demodulated received signal is output to Doppler frequency detector 117 and decoding section 119.

  The Doppler frequency detector 117 detects the Doppler frequency (that is, moving speed) of the mobile station using the demodulated received signal. The Doppler frequency (movement speed) is detected for each mobile station that is communicating with the base station. The detected Doppler frequency (movement speed) of each mobile station is output to the MCS allocating unit 125.

  On the other hand, the decoding unit 119 decodes the demodulated received signal. The decrypted information is output to the CIR report value extraction unit 121.

  The CIR report value extraction unit 121 extracts a CIR report value from the decoded information. The extracted CIR report value is stored in the CIR report value storage unit 123 in association with the reporter mobile station. The CIR report value of each mobile station stored in the CIR report value storage unit 123 is provided to the MCS allocation unit 125 as appropriate.

  The MCS assigning unit 125 assigns an optimum MCS (coding rate and modulation scheme) to each mobile station based on the CIR report value and Doppler frequency (moving speed) of the mobile station.

  Specifically, for example, in the MCS allocating unit 125, a relational expression between MCS (encoding rate and modulation scheme) and CIR is set in advance. The relational expression for allocating MCS to the reported CIR value may be in the form of a table or the form of a calculation expression. In the case of the table format, the MCS corresponding to the CIR report value is read from the table stored in the ROM or the like, and in the case of the calculation formula format, the calculation formula is converted each time by a DSP (Digital Signal Processor) or the like. Will be used to calculate the MCS from the CIR report value each time.

  FIG. 3 is a diagram illustrating an example of a relational expression between MCS and CIR. Here, for example, five threshold values TH1, TH2, TH3, TH4, and TH5 are set as CIR, and MCS allocation is performed depending on which threshold range the CIR report value is in. It has become. Specifically, in the example shown in FIG. 3, MCS1 is selected when the CIR report value is in the range from TH1 to less than TH2, and MCS2 is selected when the CIR report value is in the range from TH2 to less than TH3. When the CIR report value is in the range of TH3 or more and less than TH4, MCS3 is selected. When the CIR report value is in the range of TH4 or more and less than TH5, MCS4 is selected, and when the CIR report value is in the range of TH5 or more. MCS5 is selected. Here, each of MCS1 to MCS5 is a combination of a coding rate and a modulation scheme, and is a combination that increases the transmission rate as the MCS number increases.

  In the present embodiment, the MCS allocating unit 125 determines the optimum MCS for the CIR report value by correcting the relational expression based on the detected Doppler frequency (moving speed). Specifically, the threshold value in the above relational expression is corrected based on the detected Doppler frequency (moving speed). More specifically, since the channel quality may be deteriorated due to the influence of the Doppler frequency, the threshold value is corrected so that the transmission rate is switched to the low speed direction (in the example of FIG. 3, the right direction). ).

  At this time, for example, as shown in the control table of FIG. 4, when the Doppler frequency (moving speed) of the mobile station is large, the threshold value is largely corrected by increasing the correction amount in selection. Also, if the mobile station's Doppler frequency (moving speed) is medium, the correction amount in the selection is medium and the threshold is corrected to medium, and if the mobile station's Doppler frequency (moving speed) is small, The threshold value is corrected to be small by reducing the correction amount in selection. That is, since the fluctuation speed of the line quality varies depending on the magnitude of the Doppler frequency (moving speed), the threshold value is set by a necessary correction amount (margin) in order to compensate for the fluctuation at each transmission rate (each MCS). move.

  In this way, by correcting the CIR thresholds TH1 to TH5 (see FIG. 3) in the above relational expression according to the magnitude of the Doppler frequency (moving speed) of the mobile station, optimal transmission according to degradation of the channel quality is achieved. The rate (MCS) can be selected. At this time, the method of detecting the Doppler frequency includes not only a case where a fine value is detected but also a case where the determination is made in three stages, for example, large, medium and small as described above.

  The allocation result (optimum encoding rate and modulation scheme) in the MCS allocation unit 125 is output to the encoding unit 101 and the modulation unit 103 and reflected in the next transmission data transmission.

  Thus, according to the present embodiment, in the AMC technique, the Doppler frequency (moving speed) of each mobile station is detected, and the MCS (coding rate and modulation scheme) is based on the obtained Doppler frequency (moving speed). ) And the CIR relational expression are corrected to determine the optimum MCS, so that the allocation of the modulation scheme and the coding rate can be optimized with high accuracy in the AMC technique.

(Embodiment 2)
FIG. 5 is a block diagram showing a configuration on the transmission side of the wireless communication apparatus according to Embodiment 2 of the present invention. The transmitting-side radio communication apparatus 200 (base station) has the same basic configuration as the transmitting-side radio communication apparatus 100 (base station) shown in FIG. 1, and the same components are the same. The description is omitted. Further, the receiving-side radio communication device (mobile station) that performs radio communication with the transmitting-side radio communication device 200 (base station) is exactly the same as the receiving-side radio communication device 150 (mobile station) shown in FIG. Therefore, the description thereof is omitted.

  A feature of the present embodiment is that, in addition to the Doppler frequency (moving speed) of the mobile station, MCS (encoding rate) using Ack (Acknowledgment) / Nack (Negative acknowledgment) information from the mobile station. And the modulation scheme) and the CIR relational expression are corrected. Therefore, the Ack / Nack information decoded by the decoding unit 119 is stored in the Ack / Nack information storage unit 201 in association with the transmission source mobile station. The Doppler frequency (movement speed) of each mobile station detected by the Doppler frequency detector 117 and the Ack / Nack information from each mobile station stored in the Ack / Nack information storage unit 201 are provided to the MCS allocation unit 203. .

  Here, the Ack / Nack information is information regarding the necessity of retransmission in packet communication, and the Ack information indicates that there is no error in the received signal, that is, retransmission is unnecessary. It indicates that there is an error in the received signal, that is, retransmission is necessary. The transmission form of Ack / Nack information includes a case where both Ack information and Nack information are transmitted, and a case where only one of Ack information and Nack information (for example, Ack information) is transmitted. In the latter case, for example, when the Ack information is not received, it is assumed that the Nack information has been acquired.

  In the MCS allocating unit 203, for each mobile station, based on the CIR report value, Doppler frequency (moving speed), and Ack / Nack information of the mobile station, the MCS (coding rate and modulation scheme) optimum for the mobile station Assign. Specifically, in the MCS allocation method in the first embodiment (see FIGS. 3 and 4), the correction amount based on the Doppler frequency (movement speed) is further finely adjusted using the Ack / Nack information. For example, when the Ack information is received, the correction amount based on the Doppler frequency (movement speed) is made smaller than the set value, and when the Nack information is received, the correction amount based on the Doppler frequency (movement speed) is made larger than the set value. To do.

  Thus, according to the present embodiment, in the AMC technique, the Doppler frequency (moving speed) of each mobile station is detected, and the MCS (code) is based on the obtained Doppler frequency (moving speed) and Ack / Nack information. Since the optimum MCS is determined by correcting the relational expression between the conversion rate and the modulation method) and the CIR, the allocation of the modulation method and the coding rate can be optimized with higher accuracy in the AMC technique.

(Embodiment 3)
FIG. 6 is a block diagram showing a configuration on the transmission side of the wireless communication apparatus according to Embodiment 3 of the present invention. The transmitting-side radio communication apparatus 300 (base station) has the same basic configuration as the transmitting-side radio communication apparatus 200 (base station) shown in FIG. 2, and the same components are the same. The description is omitted. Further, the receiving-side wireless communication device (mobile station) that performs wireless communication with the transmitting-side wireless communication device 300 (base station) is exactly the same as the receiving-side wireless communication device 150 (mobile station) shown in FIG. Therefore, the description thereof is omitted.

  The feature of the present embodiment is that, instead of correcting the relational expression between MCS and CIR itself using Ack / Nack information from the mobile station, the Doppler frequency of the mobile station (using the Ack / Nack information from the mobile station) (Moving speed) is directly corrected. Therefore, the Ack / Nack information from each mobile station stored in the Ack / Nack information storage unit 201 is provided to the Doppler frequency detector 301.

  The Doppler frequency detector 301 detects the Doppler frequency (movement speed) of each mobile station using the demodulated received signal. At this time, the Ack / Nack information from the mobile station is used for each mobile station. Correct the Doppler frequency calculation. Specifically, for example, when Ack information is received, the Doppler frequency (moving speed) is corrected so as to decrease, and when Nack information is received, the Doppler frequency (moving speed) is corrected. . The Doppler frequency (moving speed) corrected by the Ack / Nack information is output to the MCS allocation unit 125.

  The MCS allocating unit 125 allocates the optimum MCS (coding rate and modulation scheme) to each mobile station by the same MCS allocating method (see FIGS. 3 and 4) as in the first embodiment.

  As described above, according to the present embodiment, since the Ack / Nack information from the mobile station is used to correct the Doppler frequency (movement speed) of the mobile station, the MCS allocation method according to the first embodiment (FIG. 3). The effect similar to that of the first embodiment can be obtained without correcting itself.

  In the second and third embodiments, the Ack / Nack information is used in an auxiliary manner, but the usage mode of the Ack / Nack information is not limited to this. For example, it is also possible to determine the optimum MCS by correcting the relational expression between MCS (coding rate and modulation scheme) and CIR using only Ack / Nack information. Specifically, for example, when Ack information is received, the correction amount for selection is made smaller than the previous set value, and when Nack information is received, the correction amount for selection is made larger than the previous set value. . Alternatively, for example, when Ack information is received, “+ A” is set, when Nack information is received, “−B” is set, and when the accumulation exceeds a threshold value “+ C”, the correction amount in the selection is set to the previous time. When the accumulated value falls below the threshold value “−D”, the correction amount in the selection is made larger than the previous set value (where A, B, C, and D are respectively The same value or different values).

(Embodiment 4)
FIG. 7 is a block diagram showing a configuration on the transmission side of the wireless communication apparatus according to Embodiment 4 of the present invention. The transmitting-side radio communication apparatus 400 (base station) has the same basic configuration as the transmitting-side radio communication apparatus 100 (base station) shown in FIG. 1, and the same components are the same. The description is omitted. Also, the receiving-side radio communication device (mobile station) that performs radio communication with the transmitting-side radio communication device 400 (base station) is exactly the same as the receiving-side radio communication device 150 (mobile station) shown in FIG. Therefore, the description thereof is omitted.

  The feature of this embodiment is that, instead of correcting the Doppler frequency (moving speed) of the mobile station using Ack / Nack information from the mobile station, the Doppler frequency (moving speed) of the mobile station using CIR variation information. ) Is corrected. Here, the CIR fluctuation information is a difference (calculated value) between the CIR report value used at the time of MCS allocation and the report value of the received CIR when transmitted and received by the allocation. Therefore, in this embodiment, a CIR variation information storage unit 401 that stores CIR variation information is provided, and the CIR variation information stored in the CIR variation information storage unit 401 is provided to the Doppler frequency detector 403.

  The Doppler frequency detector 403 detects the Doppler frequency (moving speed) of each mobile station using the demodulated received signal. At that time, the mobile station stores the movement stored in the CIR fluctuation information storage unit 401 for each mobile station. The station's CIR variation information is used to correct the Doppler frequency calculation. Specifically, for example, when the CIR fluctuation amount is small, it is determined that the Doppler frequency (moving speed) is small. If the Doppler frequency is detected to be large, the Doppler frequency (moving speed) is decreased. When the CIR fluctuation amount is large, it is determined that the Doppler frequency (moving speed) is large. If the Doppler frequency is detected to be small, the Doppler frequency (moving speed) is increased. to correct. The Doppler frequency (moving speed) corrected by the CIR variation information is output to the MCS allocation unit 125.

  The MCS allocating unit 125 allocates the optimum MCS (coding rate and modulation scheme) to each mobile station by the same MCS allocating method (see FIGS. 3 and 4) as in the first embodiment.

  Thus, according to the present embodiment, since the mobile station's CIR fluctuation information is used to correct the Doppler frequency (moving speed) of the mobile station, the MCS allocation method in Embodiment 1 (FIGS. 4)) The same effect as in the first embodiment can be obtained without correcting itself.

(Embodiment 5)
FIG. 8 is a block diagram showing a configuration on the transmission side of the wireless communication apparatus according to Embodiment 5 of the present invention. The transmitting-side radio communication apparatus 500 (base station) has the same basic configuration as the transmitting-side radio communication apparatus 100 (base station) shown in FIG. 1, and the same components are the same. The description is omitted. Further, the receiving-side wireless communication device (mobile station) that performs wireless communication with the transmitting-side wireless communication device 500 (base station) is exactly the same as the receiving-side wireless communication device 150 (mobile station) shown in FIG. Therefore, the description thereof is omitted.

  The feature of this embodiment is that instead of correcting the MCS-CIR relational expression itself by the Doppler frequency (moving speed) of the mobile station, the CIR report value from the mobile station is calculated by the Doppler frequency (moving speed) of the mobile station. It is to correct directly. Therefore, the Doppler frequency (movement speed) of each mobile station detected by the Doppler frequency detector 117 is output to the CIR correction unit 501.

  The CIR correction unit 501 uses, for each mobile station, the Doppler frequency (movement speed) of the mobile station when reading the CIR report value of the mobile station from the CIR report value storage unit 123 and providing it to the MCS allocation unit 125. To correct the CIR report value. Specifically, as described above, since the channel quality fluctuates due to the influence of the Doppler frequency, the CIR report value is corrected so as to switch the transmission rate in the low speed direction, that is, the CIR report value is reduced.

  At this time, for example, as shown in the control table of FIG. 9, when the Doppler frequency (moving speed) of the mobile station is large, the CIR report value is largely corrected by increasing the correction amount of the CIR report value. Also, when the Doppler frequency (movement speed) of the mobile station is medium, the correction amount of the CIR report value is set to medium, the CIR report value is corrected to medium, and the Doppler frequency (movement speed) of the mobile station is small. Takes a smaller correction amount of the CIR report value and corrects the CIR report value to be smaller.

  Thus, according to the present embodiment, since the CIR report value from the mobile station is corrected by the Doppler frequency (moving speed) of the mobile station, the relational expression in the MCS allocation method in Embodiment 1 (FIG. 3). Reference) The same effect as in the first embodiment can be obtained without correcting itself.

(Embodiment 6)
FIG. 10 is a block diagram showing the configuration of the transmission side of the wireless communication apparatus according to Embodiment 6 of the present invention. The transmitting-side radio communication apparatus 600 (base station) has the same basic configuration as the transmitting-side radio communication apparatus 100 (base station) shown in FIG. 1, and the same components are the same. The description is omitted. Further, the receiving-side wireless communication device (mobile station) that performs wireless communication with the transmitting-side wireless communication device 600 (base station) is exactly the same as the receiving-side wireless communication device 150 (mobile station) shown in FIG. Therefore, the description thereof is omitted.

  The feature of this embodiment is that, instead of correcting the relational expression between MCS (encoding rate and modulation scheme) and CIR based on the Doppler frequency (moving speed) of the mobile station, the above relational expression is obtained using CIR variation information. It is to correct. Here, as described above, the CIR fluctuation information is a difference (calculated value) between the CIR report value used at the time of MCS assignment and the report value of the received CIR when transmitted and received at that assignment. Therefore, in the present embodiment, as in the fifth embodiment, a CIR variation information storage unit 401 that stores CIR variation information is provided. The CIR variation information stored in the CIR variation information storage unit 401 is provided to the MCS allocation unit 601.

  The MCS allocating unit 601 allocates an optimum MCS (encoding rate and modulation scheme) to each mobile station based on the CIR report value and the CIR fluctuation amount of the mobile station.

  Specifically, MCS allocating section 601 has a relational expression between MCS (coding rate and modulation scheme) and CIR, as in Embodiment 1, and CIR reports from each mobile station using the relational expression. The MCS is selected based on the value, and the MCS optimum for the mobile station is determined by correcting the relational expression based on the CIR fluctuation amount of the mobile station. Specifically, the threshold value in the above relational expression is corrected based on the CIR fluctuation amount of the mobile station.

  At this time, for example, as shown in the control table of FIG. 11, when the CIR fluctuation amount of the mobile station is large, the threshold value is largely corrected by increasing the correction amount in selection. Further, when the mobile station CIR fluctuation amount is medium, the correction amount in the selection is moderate, and the threshold value is corrected to medium. When the mobile station CIR fluctuation amount is small, the correction amount in the selection is reduced. The threshold value is corrected to be small. In other words, when the degradation of the line quality differs depending on the amount of CIR variation, the degradation at each transmission rate (each MCS) is estimated, and the threshold value is set by the necessary correction amount (margin). move.

  In addition, about how to move the threshold value, instead of moving the correction amount every time, move it while watching the situation, that is, instead of setting the correction amount for the first threshold value every time, it was decided once It is also possible to change the correction amount little by little.

  As described above, according to the present embodiment, in the AMC technique, an optimum MCS is determined by correcting the relational expression between MCS (coding rate and modulation scheme) and CIR using the CIR variation information of each mobile station. Therefore, it is possible to optimize the allocation of the modulation scheme and the coding rate with high accuracy in the AMC technique.

  In the first to sixth embodiments, the CIR is used as the channel quality, but the present invention is not limited to this. For example, any appropriate information such as SIR, TFRC, transmission power of a dedicated channel (for example, DPCH) may be used instead of CIR.

  Moreover, although each said Embodiment 1-6 demonstrated the case where MCS allocation processing (determination of a transmission rate) was performed in a base station, it is not necessarily limited to this. For example, it is also possible to perform the MCS allocation process in the mobile station in the same manner. It is also possible to report a transmission rate that can be received by the mobile station to the base station, and the base station can assign an optimal transmission rate based on the report result. In the latter case, the transmission rate assigned by the base station does not need to match the transmission rate reported by the mobile station, and the transmission rate report from the mobile station is only used as a reference by the base station for assignment. .

  In the first to sixth embodiments, the case where the AMC technique is used as the data transmission method has been described as an example. However, the present invention is not limited to this. The present invention can be applied to any data transmission method for controlling the transmission rate. That is, as described above, since the determination of the transmission rate involves not only the modulation method and the coding rate but also the spreading factor and the transmission power, the present invention sets the various parameters related to the determination of the transmission rate. The present invention can be widely applied to changing data transmission systems.

  Further, these pieces of information are effective not only in determining the transmission rate but also in determining which mobile station performs transmission (scheduling). For example, when a mobile station with a high transmission rate is prioritized, efficient scheduling can be performed by using this transmission rate after applying this correction.

  In the first to fourth embodiments, the transmission rate is corrected by correcting the relational expression between MCS (transmission rate) and CIR (line quality information) as an example of the transmission rate correction method. However, the present invention is not limited to this, and it is also possible to directly correct the transmission rate based on the predetermined parameter.

  In the above, in order to optimize transmission rate determination with high accuracy, it has been described that predetermined correction processing is performed when determining transmission rate, for example, when assigning MCS (coding rate and modulation scheme). It was. That is, in determining the transmission rate, an error occurs in information from the mobile station (for example, a report value such as CIR) due to fading, allocation delay, and the like. For example, in the allocation of MCS (coding rate and modulation scheme), It is desirable to perform correction processing as shown in each of the first to sixth embodiments. However, it is not always necessary to perform such correction processing, and it is desirable to perform correction processing only when necessary from the viewpoint of reducing the amount of processing and power consumption and performing optimal control.

  Further, such correction processing can be performed in both the base station and the mobile station as described above. Therefore, the mobile station is divided into those that perform correction processing and those that do not perform correction processing, and it is conceivable that the content of correction processing differs between those that perform correction processing. However, the correction process does not necessarily need to be performed simultaneously on both the mobile station and the base station. From the viewpoint of reducing the processing amount and power consumption of the mobile communication system as a whole and performing optimal control, the correction process is not necessary. It is desirable to take some adjustments.

  The seventh embodiment described below corresponds to the former problem, and the eighth embodiment corresponds to the latter problem.

(Embodiment 7)
FIG. 12 is a block diagram showing a configuration on the transmission side of the wireless communication apparatus according to Embodiment 7 of the present invention. The transmitting-side radio communication apparatus 700 (base station) has the same basic configuration as the transmitting-side radio communication apparatus 100 (base station) shown in FIG. 1, and the same components are the same. The description is omitted. Also, the receiving-side wireless communication device (mobile station) that performs wireless communication with the transmitting-side wireless communication device 700 (base station) is exactly the same as the receiving-side wireless communication device 150 (mobile station) shown in FIG. Therefore, the description thereof is omitted.

  A feature of the present embodiment is that MCS (coding rate and modulation scheme) is based on the probability (reception probability) that data transmitted first from the base station (not retransmission data) is received without error by the mobile station (reception probability). It is to determine whether or not to perform a predetermined correction process when assigning. Therefore, the reception probability observation unit 701 is provided between the decoding unit 119 and the MCS allocation unit 703. The reception probability observation unit 701 receives the Ack / Nack information from the mobile station for the data (packet data) initially transmitted from the base station from the decoding unit 119, records it for a predetermined number of times, and calculates the reception probability. To do. The calculated reception probability is output to the MCS allocating unit 703. Note that the MCS allocation unit 703 has an arbitrary correction function including the correction function of the MCS allocation units 125, 203, and 601 in the first to sixth embodiments. For this reason, the illustration of the input system of information necessary for the correction process is omitted here, and the description of the content of the correction process in the MCS allocating unit 703 is omitted.

  The MCS allocation unit 703 determines, for each mobile station, whether or not to perform a predetermined correction process at the time of MCS allocation based on the reception probability output from the reception probability observation unit 701. For example, when the reception probability is very high (for example, when the reception probability is 90% or more as an example), it is determined that the system is controlled so that the correction value converges to an excessive level. In order to correct the control, a predetermined correction process is executed. On the other hand, when the reception probability is low (for example, when the reception probability is 75% or less as an example), it is determined that the system is controlled so that the correction value converges to an unacceptable level. In order to correct the above, a predetermined correction process is executed. On the other hand, when the reception probability is within a certain range (for example, when the reception probability is between 75% and 90% as an example), the correction value is held at an appropriate level and correction processing is performed. It is determined that it is not necessary to perform the correction process, and correction processing is not performed from the viewpoint of reducing the processing amount and power consumption.

  Thus, according to the present embodiment, based on the reception probability at the mobile station, in order to determine whether or not to perform correction processing at the time of MCS allocation, correction processing is performed only when necessary, and the amount of processing is reduced. Reduction and reduction of power consumption can be achieved.

  In the present embodiment, only the data first transmitted from the base station is considered as the basis for calculating the reception probability. However, the present invention is not limited to this. For example, the reception probability at the mobile station for all data transmitted from the base station including retransmissions may be calculated, and the necessity of correction processing may be determined based on the calculation result.

  In the present embodiment, the case where the base station performs MCS allocation processing (determination of transmission rate) has been described. However, the present invention is not limited to this, as in the case of each of the first to sixth embodiments.

  In the present embodiment, the case where the AMC technique is used as the data transmission method has been described as an example. However, the present invention is not limited to this, as in the case of each of the first to sixth embodiments.

(Embodiment 8)
In the present embodiment, both the base station and the mobile station have a correction function. The content of the correction function is not particularly limited. For example, each of the base station and the mobile station has the above-described configuration on the transmission side (see FIGS. 1, 5, 6, 7, 8, and 10) and the configuration on the reception side (see FIG. 2). be able to.

  A feature of the present embodiment is that a signal notifying whether or not the mobile station is performing correction processing is transmitted from the mobile station to the base station, and when the base station performs the correction processing, the mobile station When it is necessary to stop the correction process in the mobile station, a signal for stopping the correction process in the mobile station is transmitted from the base station to the mobile station. These signals are transmitted using DPCH, for example.

  Specifically, for example, the mobile station transmits a signal (notification signal) notifying whether or not correction processing is being performed to the base station. At this time, the base station may be able to request the mobile station to transmit the notification signal (this request is also made using, for example, DPCH). The base station that has received the notification executes correction processing immediately if the mobile station is not performing correction processing, and if the mobile station is performing correction processing, results of correction processing in the mobile station for a predetermined period of time , And determine whether correction processing needs to be performed instead of or together with the mobile station. Note that the base station can also perform the correction process while observing the result of the correction process in the mobile station.

  Further, for example, when it is necessary to stop the correction process in the mobile station when the correction process is executed in the base station, the base station sends a signal (stop signal) for stopping the correction process in the mobile station to the mobile station. Send to. The mobile station that has received this stop signal stops the correction process according to the received stop signal. Thereby, the correction process in a base station can be reliably performed as intended.

  As described above, according to the present embodiment, when both the base station and the mobile station have the correction function, the mobile station performs the correction process to the base station according to a request from the base station, for example. When the base station performs correction processing at the base station, it is necessary to stop the correction processing at the mobile station when the base station performs correction processing. Since the signal for stopping the correction process at the station is transmitted, it is not necessary for both the mobile station and the base station to perform the correction process at the same time, and the entire mobile communication system can reduce the processing amount and reduce the power consumption. Reduction can be achieved and optimal control can be performed.

  The wireless communication apparatus and the transmission rate determination method according to the present invention are suitable for determining the transmission rate.

The block diagram which shows the structure of the transmission side of the radio | wireless communication apparatus which concerns on Embodiment 1 of this invention. The block diagram which shows the structure of the receiving side of the radio | wireless communication apparatus which concerns on Embodiment 1 of this invention. The figure which shows an example of the relational expression of MCS and CIR used in the case of MCS allocation in Embodiment 1. The figure which shows an example of the control table which shows the qualitative relationship between the Doppler frequency and correction amount in Embodiment 1. The block diagram which shows the structure of the transmission side of the radio | wireless communication apparatus which concerns on Embodiment 2 of this invention. FIG. 9 is a block diagram showing a configuration of a transmission side of a wireless communication apparatus according to Embodiment 3 of the present invention. FIG. 7 is a block diagram showing a configuration of a transmission side of a wireless communication apparatus according to Embodiment 4 of the present invention. FIG. 7 is a block diagram showing a configuration on the transmission side of a wireless communication apparatus according to a fifth embodiment of the present invention. The figure which shows an example of the control table which shows the qualitative relationship between the Doppler frequency and correction amount in Embodiment 5. FIG. 9 is a block diagram showing a configuration on the transmission side of a wireless communication apparatus according to a sixth embodiment of the present invention. The figure which shows an example of the control table which shows the qualitative relationship of the CIR variation | change_quantity and correction amount in Embodiment 6. FIG. 9 is a block diagram showing a configuration on the transmission side of a wireless communication apparatus according to a seventh embodiment of the present invention.

Explanation of symbols

100, 200, 300, 400, 500, 600 Radio communication device on transmission side (base station)
DESCRIPTION OF SYMBOLS 101 Coding part 103 Modulation part 117,301,403 Doppler frequency detector 121 CIR report value extraction part 123 CIR report value storage part 125,203,601,703 MCS allocation part 150 Radio | wireless communication apparatus (mobile station) of receiving side
163 CIR measurement unit 201 Ack / Nack information storage unit 401 CIR fluctuation information storage unit 501 CIR correction unit 701 reception probability observation unit

Claims (13)

Determining means for determining a transmission rate corresponding to the line quality information using a relational expression defining a relation between the line quality information and the transmission rate;
Acquisition means for acquiring retransmission necessity information from a communication partner;
A wireless communication apparatus, comprising: a correction unit that sets a correction amount based on the retransmission necessity information and corrects the relational expression by the correction amount.   The correction means reduces the correction amount below the previous set value when the retransmission necessity information is Ack information, and sets the correction amount to the previous amount when the retransmission necessity information is Nack information. The wireless communication apparatus according to claim 1, wherein the wireless communication apparatus is larger than a set value.   The correction means accumulates a predetermined value when the Ack information is received as the retransmission necessity information and when the Nack information is received, and when the accumulation exceeds a threshold value, the correction amount is set. 2. The wireless communication apparatus according to claim 1, wherein the wireless communication apparatus is smaller than a previous set value, and the correction amount is made larger than a previous set value when the accumulation falls below a threshold value. Determining means for determining a transmission rate corresponding to the line quality information using a relational expression defining a relation between the line quality information and the transmission rate;
Detecting means for detecting the relative movement speed of the communication partner;
Obtaining means for obtaining retransmission necessity information from the communication partner;
When Ack information is received as the retransmission necessity information, the correction amount set based on the relative movement speed is reduced to correct the relational expression. When Nack information is received as the retransmission necessity information, Correction means for correcting the relational expression by increasing a correction amount set based on the relative movement speed;
A wireless communication apparatus comprising: Comprising a reception probability observing means for acquiring a reception probability that transmission data is received without error in a communication partner;
5. The radio according to claim 1, wherein the correction unit determines whether or not to perform a correction process based on the reception probability acquired by the reception probability observation unit. Communication device.   The wireless communication apparatus according to claim 1, further comprising a transmission unit that transmits a signal notifying whether or not correction processing by the correction unit is being performed to a communication partner.   The wireless communication apparatus according to claim 1, further comprising: a transmission unit configured to transmit a signal for stopping correction processing at the communication partner to the communication partner. A wireless communication device on the receiving side that uses the wireless communication device according to claim 6 as a communication partner,
The receiving-side wireless communication device is:
A radio communication apparatus on the receiving side, which requests to transmit a signal notifying whether or not correction processing is being executed by the correction means. A wireless communication device on the receiving side that uses the wireless communication device according to claim 7 as a communication partner,
The receiving-side wireless communication device is:
Correction means for performing a predetermined correction process when determining the transmission rate;
Receiving means for receiving a signal transmitted from the communication partner to stop the correction process;
Control means for stopping correction processing by the correction means based on the signal received by the receiving means;
A receiving-side radio communication apparatus comprising:   A base station apparatus comprising the wireless communication apparatus according to claim 1.   A mobile station apparatus comprising the wireless communication apparatus according to claim 1. A determination step for determining a transmission rate corresponding to the line quality information using a relational expression defining a relation between the line quality information and the transmission rate;
An acquisition step of acquiring retransmission necessity information from the communication partner;
And a correction step for setting a correction amount based on the retransmission necessity information and correcting the relational expression by the correction amount. A determination step for determining a transmission rate corresponding to the line quality information using a relational expression defining a relation between the line quality information and the transmission rate;
A detection step for detecting the relative movement speed of the communication partner;
An acquisition step of acquiring retransmission necessity information from the communication partner;
When Ack information is received as the retransmission necessity information, the correction amount set based on the relative movement speed is reduced to correct the relational expression. When Nack information is received as the retransmission necessity information, A correction step of correcting the relational expression by increasing a correction amount set based on the relative movement speed;
A transmission rate determination method comprising:

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