JP2005065323A - Base station system and radio communication method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To transmit a DSCH with the optimum transmission method and transmission power appropriate for a downlink line quality, and to prevent degradation of the DSCH reception quality. <P>SOLUTION: SIR (Signal to Interference Ratio) information extraction section 106 extracts an SIR-related information, determined by a communication terminal from an incoming data. A fluctuation calculation section 109 calculates an SIR fluctuation between SIR determination time and DSCH (Downlink Shared Channel) transmission start time, using a TPC command. An SIR correction section 201 corrects the SIR notified by the communication terminal by adding the SIR fluctuation to the SIR information. A destination determination section 107 determines an optimum DSCH destination communication terminal, based on the corrected SIR of the each communication terminal. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a base station apparatus and a radio communication method used for high-speed data communication.

  One of the multiple access systems of digital wireless communication systems is a CDMA (Code Division Multiple Access) system. In addition, in the standard established by 3GPP (3rd Generation Partnership Project), which is one of standards organizations related to mobile radio communication systems, this CDMA system is adopted, and is one of channels shared by a plurality of communication terminals. In addition, DSCH (Downlink Shared CHannel) used for high-speed data communication in the downlink (line from the base station to the communication terminal) is defined.

  Since this DSCH is used by being assigned to each communication terminal for each predetermined transmission unit (for example, every frame), it is expected to be used for high-speed packet communication in the downlink.

  Hereinafter, a communication procedure of high-speed packet communication using DSCH will be described. FIG. 6 is a conceptual diagram of a high-speed packet communication system using DSCH, and FIG. 7 is a diagram illustrating a relationship between a conventional communication procedure of high-speed packet communication using DSCH and a reception SIR at a communication terminal.

  In high-speed packet communication using DSCH, the base station BS compares SIR (Signal to Interference Ratio) information notified from each communication terminal MS # 1 to MS # n as shown in FIG. DSCH is allocated to a communication terminal (here, MS # 1) and DSCH data (that is, high-speed packet data) is transmitted.

  Further, the communication procedure from the measurement of the received SIR at each communication terminal to the transmission of the DSCH data to each communication terminal is as shown in FIGS. That is, as shown in FIG. 7A, first, at t0 to t1, each of the communication terminals MS # 1 to #n measures SIR for one frame of downlink DPDCH (Dedicated Physical Data CHannel) data. Each communication terminal, for example, averages one frame of SIR measured in each slot of DPDCH data.

  In the next frame (t1 to t2), each communication terminal MS # 1 to #n uses the DPDCH on the uplink (the line from the communication terminal to the base station) as shown in FIG. The SIR for the frame is notified to the base station BS.

  In the next frame (t2 to t3), the base station BS compares the SIR notified from each communication terminal, and the communication terminal having the best line status, that is, the communication terminal having the largest SIR (here, MS #) 1) is determined as the DSCH data transmission destination. In addition, the base station BS, according to the SIR notified from the communication terminal that is the transmission destination of the DSCH data, collects the optimum modulation scheme, encoding scheme and transmission power for the SIR (hereinafter referred to as “transmission” as necessary). System ") is determined as the DSCH data transmission system. That is, the base station BS determines the modulation scheme, coding scheme, and transmission power optimum for the channel conditions at the past time points t0 to t1 as the DSCH data transmission scheme. Note that the optimum transmission method for the SIR is predetermined according to the size of the SIR.

  Then, in the next frame (t3 to t4), the base station BS transmits DSCH data to the communication terminal determined as the transmission destination using the downlink DSCH using the determined transmission method.

  However, when high-speed packet communication is performed according to the procedure shown in FIG. 7, a frame (t0 to t1) in which each communication terminal measures the SIR of DPDCH data and a frame (t3 to t4) in which the base station BS transmits DSCH data. ) There are two frames. For this reason, the propagation environment changes between the two frames, and the SIR of the DSCH data received by the communication terminal may be greatly degraded. That is, in the communication terminal, there is a possibility that the SIR of the DSCH data received at t3 to t4 is greatly degraded from the SIR of the DPDCH data received at t0 to t1.

  Since the base station BS determines the optimum modulation scheme, coding scheme and transmission power for the SIR measured from t1 to t2 as the transmission scheme for DSCH data, the SIR and DSCH notified from the communication terminal in this way If the SIR of the data is different, the DSCH data transmission method is not necessarily the optimum transmission method. Therefore, there is a possibility that the quality of the DSCH data is deteriorated.

  The present invention has been made in view of the above points, and can transmit DSCH data by an optimum modulation scheme, encoding scheme, and transmission scheme in accordance with downlink channel conditions, and the reception quality of DSCH data is degraded. It is an object of the present invention to provide a base station apparatus and a wireless communication method that can prevent this from happening.

  The base station apparatus of the present invention includes an acquisition unit that acquires channel quality information related to downlink quality measured at each of a plurality of communication terminals, a reception unit that receives TPC commands transmitted from the plurality of communication terminals, Calculating means for calculating the fluctuation amount of the downlink quality of each communication terminal using the TPC command of each communication terminal, and calculating the channel quality information of each communication terminal acquired by the acquiring means by the calculating means Correction means for correcting using the fluctuation amount of each communication terminal, selection means for comparing the line quality information of the plurality of communication terminals after correction, and selecting a communication terminal as a data transmission destination based on the comparison result The structure which comprises is taken.

  According to this configuration, it is possible to transmit DSCH data with an optimal transmission scheme and transmission power according to downlink channel conditions, and therefore it is possible to prevent the reception quality of DSCH data from deteriorating.

  The base station apparatus of the present invention includes an acquisition unit that acquires a line status observed in a communication terminal at a time before a transmission start time of data of a shared channel shared by a plurality of communication terminals; Detection means for detecting a change in line status until the transmission start time, and estimating the line status at the transmission start time by adding the change in the line status to the line status acquired by the acquisition means The configuration includes an estimation unit, and a transmission unit that transmits the data of the shared channel to the communication terminal by an optimal transmission method according to the channel state estimated by the estimation unit.

  According to this configuration, since the current line condition can be estimated from the past line condition, the data of the shared channel can be transmitted by an optimum transmission method according to the current line condition.

  In the base station apparatus of the present invention, the acquisition unit acquires the line status notified from the communication terminal for each predetermined transmission unit, and the detection unit receives from the communication terminal for each transmission unit shorter than the predetermined transmission unit. A configuration is adopted in which a change in line status is detected using a plurality of notified transmission power control information.

  According to this configuration, since the fluctuation of the line status is detected by observing the transmission power control information notified at a cycle earlier than the notification cycle of the channel status, the current channel is detected at a cycle earlier than the notification cycle of the channel status. The situation can be estimated accurately.

  The base station apparatus according to the present invention employs a configuration in which the detecting means detects a change in the channel status using transmission power control information for channels other than the shared channel.

  According to this configuration, since the transmission power control information for other channels is also used for detecting the fluctuation of the line status, it is not necessary to separately notify the information for detecting the fluctuation of the line status. And the configuration of the communication system can be simplified. In addition, since transmission power control information has already been notified in the existing channel, there is no need to newly provide information for detecting line state fluctuations. Therefore, it is possible to suppress an increase in the scale of the apparatus. In addition, it is not necessary to newly construct a communication system provided with information for detecting fluctuations in the line status, and it is possible to detect fluctuations in the line status using the current communication system. The shared channel data can be transmitted by an optimal transmission method according to the current line status without incurring new costs.

  The base station apparatus according to the present invention employs a configuration in which the transmission means includes coding means for coding the data of the shared channel by an optimum coding scheme according to the channel status estimated by the estimation means.

  According to this configuration, since the data of the shared channel is encoded with the optimum encoding method according to the estimated current line condition, the line between the observation time of the line condition and the transmission start point of the shared channel data is used. Even if the situation fluctuates, the error rate of the data of the shared channel can be maintained at a desired error rate.

  The base station apparatus of the present invention employs a configuration in which the transmission means includes modulation means for modulating the data of the shared channel with an optimum modulation scheme corresponding to the channel condition estimated by the estimation means.

  According to this configuration, since the data of the shared channel is modulated by the optimum modulation method according to the estimated current line condition, the line condition is determined between the observation time of the line condition and the transmission start time of the shared channel data. Even if it fluctuates, the error rate of the data of the shared channel can be maintained at a desired error rate.

  The base station apparatus of the present invention employs a configuration in which the transmission means includes control means for controlling the transmission power of the shared channel data to the optimum transmission power according to the channel status estimated by the estimation means.

  According to this configuration, in order to control the transmission power of the shared channel data to the optimum transmission power according to the estimated current channel status, the transmission status between the channel status observation time and the shared channel data transmission start time is determined. Even if the line status fluctuates, the reception quality of the data of the shared channel at the communication terminal can be maintained at a desired quality.

  The wireless communication method of the present invention includes an acquisition step of acquiring a line status observed in a communication terminal at a time before a transmission start time of data of a shared channel shared by a plurality of communication terminals, and from the previous time A detection step for detecting a change in line status until the transmission start time, and a line status at the transmission start time is estimated by adding the line status change to the line status acquired in the acquisition step. An estimation step, and a transmission step of transmitting the data of the shared channel to the communication terminal by an optimal transmission method according to the channel status estimated in the estimation step.

  The wireless communication method of the present invention acquires the line status notified from the communication terminal for each predetermined transmission unit in the acquisition step, and from the communication terminal for each transmission unit shorter than the predetermined transmission unit in the detection step. A change in the line status is detected using a plurality of notified transmission power control information.

  In the wireless communication method of the present invention, in the detection step, a change in the line status is detected using transmission power control information for channels other than the shared channel.

  According to the present invention, it is possible to transmit DSCH data with an optimal transmission scheme and transmission power in accordance with downlink channel conditions, and therefore it is possible to prevent the reception quality of DSCH data from deteriorating.

  The present inventors provide a TPC for instructing the base station to increase or decrease the transmission power of the downlink DPDCH data between the time when the downlink channel quality is measured by the communication terminal and the transmission start time of the DSCH data. Pay attention to the fact that the (Transmit Power Control) command is transmitted from the communication terminal to the base station for each slot using the uplink DPCCH (Dedicated Physical Control Channel), and observe this TPC command for a plurality of slots. As a result, it was found that the current channel status of the downlink can be estimated from the past channel status of the downlink, leading to the present invention.

  That is, the essence of the present invention is that DSCH is added to the channel status notified from the communication terminal by adding the fluctuation of the channel status from the time when the channel quality is measured at the communication terminal to the transmission start time of the DSCH data. The channel status at the time of starting data transmission is estimated, and the DSCH data is transmitted by an optimal transmission method according to the estimated channel status.

  Therefore, in the present invention, the DSCH data modulation scheme, coding scheme, and transmission power are determined by the following procedure.

  That is, the communication terminal measures the SIR of downlink DPDCH data in a certain frame, and notifies the measured SIR to the base station in the next frame. In addition, the communication terminal transmits a TPC command instructing increase / decrease in the transmission power of the DPDCH data to the base station for each slot using the DPCCH while notifying the base station of the SIR.

  In the next frame, the base station determines the communication terminal to be the DSCH data transmission destination according to the SIR notified from the communication terminal. In addition, the communication terminal transmits a TPC command for instructing increase / decrease in transmission power of DPDCH data to the base station for each slot using the DPCCH while the base station determines a communication terminal to which the DSCH data is to be transmitted. Send to.

  That is, since the TPC command for two frames is transmitted to the base station, the base station calculates the SIR fluctuation amount in the two-frame section from the TPC command, and adds the SIR fluctuation amount to the SIR notified from the communication terminal. Then, the SIR at the time when the DSCH data is received by the communication terminal is estimated. Then, the base station determines a DSCH data transmission method based on the estimated SIR. Thereby, DSCH data can be prevented from being transmitted to a communication terminal with a modulation scheme, a coding scheme and transmission power that are optimal for the channel condition at the time of DSCH data transmission, and the quality of the DSCH data being deteriorated. .

  Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. In the following description, a case where DSCH is used as a shared channel shared by a plurality of communication terminals will be described. However, the present invention is not limited to this, and this embodiment is used when a channel other than DSCH is used as a shared channel. Can also be implemented.

  FIG. 1 is a principal block diagram showing a schematic configuration of a base station apparatus according to an embodiment of the present invention. In the base station apparatus shown in FIG. 1, transmission / reception switching section 102 outputs the data received via antenna 101 to DPCCH data receiving section 103 and DPDCH data receiving section 105 and is output from DSCH data transmitting section 115. The DSCH data is output to the antenna 101.

  The DPCCH data receiving unit 103 performs predetermined radio processing on the received data, and then despreads the received data with a spreading code for DPCCH data, thereby extracting DPCCH data from the received data. The extracted DPCCH data is subjected to a predetermined demodulation process by the DPCCH data receiving unit 103 and then output to the TPC command detecting unit 104. The TPC command detection unit 104 detects the TPC command stored in each slot of the DPCCH data and outputs it to the TPC command selection unit 108. The TPC command output to the TPC command selection unit 108 is stored in the TPC command selection unit 108 for a predetermined frame (here, two frames) for each communication terminal.

  The DPDCH data receiving unit 105 performs predetermined radio processing on the received data, and then despreads the received data with a spreading code for DPDCH data, thereby extracting DPDCH data from the received data. The extracted DPDCH data is subjected to predetermined demodulation processing by the DPDCH data receiving unit 105 and then output to the SIR information extracting unit 106. The SIR information extraction unit 106 extracts the SIR information notified from each of the communication terminals MS # 1 to #n from the DPDCH data, and outputs it to the transmission destination determination unit 107.

  The DPCCH data receiving unit 103, the TPC command detecting unit 104, the DPDCH data receiving unit 105, and the SIR information detecting unit 106 are provided for each communication terminal.

  The transmission destination determination unit 107 determines the transmission destination of the DSCH data according to the SIR notified from each communication terminal, and outputs a signal indicating the determined communication terminal to the TPC command selection unit 108 and the DSCH data selection unit 111. Also, transmission destination determining section 107 selects the SIR notified from the communication terminal determined as the DSCH data transmission destination from the SIR notified from each communication terminal, and outputs the selected SIR to transmission scheme determining section 110.

  The TPC command selection unit 108 selects the TPC command transmitted from the communication terminal determined as the DSCH data transmission destination from the TPC commands stored for each communication terminal, and outputs the selected TPC command to the fluctuation amount calculation unit 109. To do. That is, two frames of the TPC command transmitted from the communication terminal determined as the DSCH data transmission destination are output to the fluctuation amount calculation unit 109.

  The fluctuation amount calculation unit 109 uses the TPC command output from the TPC command selection unit 108 to calculate the SIR fluctuation amount in the two-frame section at the communication terminal determined as the DSCH data transmission destination. That is, fluctuation amount calculation section 109 calculates the SIR fluctuation amount in the two-frame section by adding two frames of TPC commands for instructing increase / decrease of transmission power of downlink DPDCH data. The calculated SIR fluctuation amount is output to transmission method determining section 110.

  The transmission method determination unit 110 adds the SIR fluctuation amount output from the fluctuation amount calculation unit 109 to the SIR output from the transmission destination determination unit 107, and determines the DSCH data at the communication terminal determined as the transmission destination of the DSCH data. Determines the most suitable transmission method for the SIR at the time when is actually received. That is, the transmission method determining unit 110 estimates the current channel status of the downlink by adding the fluctuation of the channel status in the two frame sections indicated by the TPC command to the past channel status of the downlink, A modulation scheme, a coding scheme, and transmission power optimum for the estimated current line condition are determined. A signal indicating the determined modulation scheme is output to modulation section 113, and a signal indicating the determined encoding scheme is output to encoding section 112. A signal indicating the determined transmission power is output to transmission power control section 114.

  The DSCH data selection unit 111 selects the DSCH data for the communication terminal determined as the transmission destination of the DSCH data from the DSCH data for the communication terminals MS # 1 to MS # n, and outputs the DSCH data for the communication terminal to the encoding unit 112 To do.

  Encoding section 112 encodes the DSCH data using the encoding scheme determined by transmission scheme determining section 110 and outputs the encoded DSCH data to modulating section 113. Modulation section 113 modulates the encoded DSCH data with the modulation scheme determined by transmission scheme determination section 110 and outputs the result to transmission power control section 114. The transmission power control unit 114 controls the transmission power of the modulated DSCH data to the transmission power determined by the transmission method determination unit 110, and outputs the DSCH data after the transmission power control to the DSCH data transmission unit 115.

  The DSCH data transmission unit 115 performs predetermined spreading processing and predetermined radio processing on the DSCH data after transmission power control, and then outputs the DSCH data to the transmission / reception switching unit 102.

  Next, the operation of the base station apparatus having the above configuration will be described. FIG. 2 is a diagram showing a relationship between a communication procedure in the present embodiment of high-speed packet communication using DSCH and a reception SIR at a communication terminal.

  In the following description, a case where 5 slots are included in one frame of a DPCCH signal will be described as an example. However, the present embodiment is not limited to this, and the present embodiment is not limited to the number of slots included in one frame. It can be implemented.

  First, as shown in FIG. 2A, at t0 to t1, each of the communication terminals MS # 1 to #n measures SIR for one frame of downlink DPDCH data. Each communication terminal, for example, averages one frame of SIR measured in each slot of DPDCH data.

  Further, in each slot of all frames of DPDCH data, each communication terminal compares the measured SIR with a predetermined desired SIR. If the measured SIR is smaller than the desired SIR, transmission of DPDCH data is performed. A TPC command for requesting the base station to increase the power is generated. If the measured SIR is equal to or higher than the desired SIR, a TPC command for requesting the base station to decrease the transmission power of the DPDCH data is generated. . Specifically, each communication terminal generates a TPC command indicating +1 dB when the measured SIR is smaller than the desired SIR, and indicates -1 dB when the measured SIR is equal to or greater than the desired SIR. Generate a TPC command. That is, when the line condition is bad and the reception quality is lower than the desired quality, an instruction to increase the transmission power of the DPDCH data is notified to the base station, and the line condition is good and the reception quality is higher than the desired quality. Is instructed to the base station to reduce the transmission power of the DPDCH data.

  The generated TPC command is stored in each slot of the DPCCH data, and is transmitted to the base station BS using the uplink DPCCH as shown in FIG. As shown in FIG. 2 (e), one slot of DPCCH data includes a pilot part (PL), a TPC command part (TPC), and a TFCI part (Transport Format Combination Indicator).

  In the base station, sequentially received TPC commands are detected from the DPCCH data by the TPC command detection unit 104 and output to the TPC command selection unit 108.

  In the next frame (t1 to t2), each communication terminal notifies the SIR of one frame to the base station using the uplink DPDCH as shown in FIG. 2 (b). The SIR information notified to the base station is extracted from the DPDCH data by the SIR information extraction unit 106 and output to the transmission destination determination unit 107.

  In addition, at the time t1 when the SIR notification using the uplink DPDCH is started, in the base station, the TPC command selection unit 108 starts accumulating the TPC commands output from the TPC command detection unit 104. The accumulation of TPC commands is continued until t3 when transmission of DSCH data is started. That is, TPC commands for two frames (ie, 10 slots) from t1 to t3 are sequentially accumulated in the TPC command selection unit 108.

  In the next frame (t2 to t3), the DSCH data transmission destination and the DSCH data transmission method are determined. That is, first, the transmission destination determination unit 107 compares the SIR notified from each communication terminal, and the communication terminal with the best downlink channel state measured at t0 to t1 (here, MS # 1). ) Is determined as the transmission destination of the DSCH data. Then, a signal indicating MS # 1 is output to TPC command selection section 108 and DSCH data selection section 111. In accordance with the signal indicating MS # 1, DSCH data selection section 111 selects MS # 1 DSCH data from MS # 1 to MS # n DSCH data, and outputs the selected data to encoding section 111.

  Also, the SIR notified from communication terminal MS # 1 is selected at t3 from the SIR notified from each communication terminal by transmission destination determining section 107 and output to transmission method determining section 110.

  When a signal indicating communication terminal MS # 1 is output from transmission destination determination unit 107 at t3, TPC command selection unit 108 selects a TPC command transmitted from communication terminal MS # 1 from among the accumulated TPC commands. The selected value is output to the fluctuation amount calculation unit 109. That is, TPC command selection section 108 outputs TPC commands for two frames (that is, 10 slots) transmitted from communication terminal MS # 1 between t1 and t3 to variation calculation section 109.

  In the fluctuation amount calculation unit 109, all TPC commands for two frames output from the TPC command selection unit 108 are added together, and the base station transmits the DSCH data from time t1 when the communication terminal MS # 1 starts SIR notification. The SIR fluctuation amount in the two-frame period up to the time point t3 at which the transmission is started is calculated and output to the transmission method determination unit 110. Specifically, the SIR fluctuation amount is calculated as follows.

  That is, for example, in a 2-frame section, if the TPC command for 6 slots is a TPC command indicating +1 dB and the TPC command for 4 slots is a TPC command indicating -1 dB, the SIR in the 2-frame section is The fluctuation amount is calculated as -2 dB. That is, in this case, the downlink channel status at t3 is 2 dB worse than the channel status notified at t1.

  Also, for example, in a 2-frame section, if the TPC command for 4 slots is a TPC command indicating +1 dB and the TPC command for 6 slots is a TPC command indicating -1 dB, the SIR in the 2-frame section is The fluctuation amount is calculated as +2 dB. That is, in this case, the downlink channel status at t3 is 2 dB better than the channel quality notified at t1.

  As described above, the fluctuation amount calculation unit 109 can calculate the SIR fluctuation amount in the two-frame section using the TPC command.

  First, transmission scheme determination section 110 selects a DSCH data modulation scheme, coding scheme, and transmission power by a conventional method. That is, in transmission method determining section 110, first, a transmission method optimal for the SIR is selected according to the SIR notified from t1 to t2 from communication terminal MS # 1 that is the transmission destination of the DSCH data. That is, first, the transmission scheme determination unit 110 selects a modulation scheme, a coding scheme, and transmission power that are optimal for the channel conditions at past times t0 to t1. Note that the optimum transmission method for SIR is determined in advance corresponding to the size of SIR, as in the prior art.

  Next, the transmission method determination unit 110 determines an optimal transmission method according to the current line status. Specifically, the DSCH data modulation scheme, coding scheme, and transmission power are determined as follows.

  That is, the transmission method determination unit 110 adds the SIR fluctuation amount calculated by the fluctuation amount calculation unit 109 to the transmission power optimum for the channel status at the past time points t0 to t1, and thereby optimizes the transmission power optimum for the current channel status. Ask for. Specifically, for example, when the SIR fluctuation amount calculated by the fluctuation amount calculation unit 109 is −2 dB, the downlink channel status at t3 is 2 dB worse than the channel quality notified at t1. Therefore, the transmission scheme determination unit 110 determines a value 2 dB larger than the transmission power optimum for the channel state at the past time points t0 to t1 as the transmission power of the DSCH data.

  As described above, according to the present embodiment, in order to control the transmission power of DSCH data to the optimum transmission power according to the estimated current channel status, the observation time of the channel status and the transmission start time of DSCH data Even if the line condition varies between the two, the reception quality of the DSCH data at the communication terminal can be maintained at a desired quality.

  In addition, the transmission method determination unit 110 adds the SIR fluctuation amount calculated by the fluctuation amount calculation unit 109 to the modulation method and coding method optimal for the channel state at the past time points t0 to t1, and sets the current channel state. Determine the optimal modulation and coding scheme. Specifically, the optimum modulation scheme and encoding scheme for the current line condition are determined as follows. FIG. 3 is a graph for explaining a modulation scheme determination method in the base station apparatus according to one embodiment of the present invention. FIG. 4 is a graph in the base station apparatus according to one embodiment of the present invention. It is a graph for demonstrating the determination method of an encoding system.

First, a modulation method determination method will be described. The relationship among the modulation method, SIR, and bit error rate is generally as shown in the graph of FIG. Therefore, for example, when the modulation scheme optimal for the channel condition at the past time points t0 to t1 is QPSK and the SIR fluctuation amount calculated by the fluctuation amount calculation unit 109 is −2 dB, the transmission method determination unit 110 At a bit error rate of 10 ⁻³ , BPSK, which is a modulation scheme corresponding to SIR 2 dB smaller than QPSK, is determined as a modulation scheme for DSCH data. At this time, BPSK can obtain the same communication quality as QPSK (that is, bit error rate 10 ⁻³ ). That is, when the current line condition is deteriorated as compared with the past line condition, a modulation method having a value that can be represented by one symbol is determined as the DSCH data modulation method, which is less than the modulation method optimal for the past line condition. .

  As described above, according to the present embodiment, since the DSCH data is encoded by the optimum encoding method according to the estimated current channel state, the channel state observation time and the DSCH data transmission start point are Even if the line status fluctuates between them, the error rate of DSCH data can be maintained at a desired error rate.

Next, a coding method determination method will be described. The relationship between coding rate R, SIR and bit error rate is generally as shown in the graph of FIG. Therefore, for example, when the coding rate R optimum for the channel condition at the past time points t0 to t1 is 1/3 and the SIR fluctuation amount calculated by the fluctuation amount calculation unit 109 is −2 dB, the transmission method The determination unit 110 determines R = 1/4, which is a coding rate corresponding to an SIR 2 dB smaller than the coding rate R = 1/3, as the coding rate of the DSCH data at the bit error rate 10 ⁻³ . . At this time, at the coding rate R = 1/4, the same communication quality as the coding rate R = 1/3 (that is, the bit error rate 10 ⁻³ ) can be obtained. In other words, when the current line condition deteriorates compared to the past line condition, an encoding method having a higher coding rate than the coding method optimal for the past line condition is determined as the DSCH data encoding method. The

  As described above, according to the present embodiment, since the DSCH data is modulated by the optimum modulation method according to the estimated current channel state, the channel state is observed between the time point when the channel state is observed and the transmission start point of the DSCH data. Even if the line status fluctuates, the error rate of DSCH data can be maintained at a desired error rate.

In the above specific example, the case where the value required as the bit error rate of the DSCH data is assumed to be 10 ⁻³ , for example, and this embodiment is applied to the required bit error rate. It can be arbitrarily determined in the wireless communication system. Further, the bit error characteristics shown in FIGS. 3 and 4 are merely examples, and the modulation scheme and the coding scheme are determined in accordance with the bit error characteristics in each wireless communication system as appropriate.

  Signals indicating the determined encoding scheme, modulation scheme, and transmission power are output to encoding section 112, modulation section 113, and transmission power control section 114, respectively.

  In encoding section 112, MS # 1 DSCH data is encoded by the encoding scheme determined by transmission scheme determining section 110 and output to modulation section 113. Also, in modulation section 113, the encoded DSCH data is modulated by the modulation scheme determined by transmission scheme determination section 110 and output to transmission power control section 114.

  In transmission power control section 114, the modulated DSCH data is controlled to the transmission power determined by transmission scheme determination section 110, and then output to DSCH data transmission section 115 for transmission to communication terminal MS # 1. .

  Note that, as described below, the transmission method determination unit 110 may determine an optimal transmission method according to the current line status. That is, first, transmission method determination section 110 adds the SIR variation output from variation calculation section 109 to the SIR output from transmission destination determination section 107, and communication terminal MS # 1 actually performs DSCH. The SIR at the time of reception is estimated. That is, in the transmission method determination unit 110, first, the SIR fluctuation amount at t1 to t3 is added to the SIR notified at the past t1, and the downlink channel status at the current t3 is estimated.

  Next, the transmission destination determination unit 107 selects a transmission method optimal for the SIR according to the estimated SIR. That is, the transmission scheme determining unit 110 selects a modulation scheme, a coding scheme, and transmission power that are optimal for the estimated SIR. Note that the optimum transmission method for SIR is determined in advance corresponding to the size of SIR, as in the prior art.

  As described above, according to the present embodiment, by observing the TPC command, it is possible to estimate the current channel status of the downlink from the past channel status of the downlink. DSCH data can be transmitted by an optimal transmission method.

  In addition, according to the present embodiment, since the fluctuation of the line status is detected by observing the TPC command notified at a cycle earlier than the notification cycle of the channel status, the current status is detected at a cycle earlier than the notification cycle of the channel status. It is possible to accurately estimate the line status of the network.

  Further, according to the present embodiment, since the TPC command for controlling the transmission power of DPDCH data is also used for detecting the fluctuation of the line condition, there is no need to separately notify the communication terminal of the information for detecting the fluctuation of the line condition. Therefore, the line utilization efficiency can be improved and the configuration of the communication system can be simplified. In addition, since the TPC command has already been transmitted on the existing DPCCH, it is not necessary to newly provide information for detecting the fluctuation of the line status. Therefore, it is not necessary to provide a new device, and an increase in the device scale can be suppressed. In addition, it is not necessary to newly construct a communication system provided with information for detecting fluctuations in the line status, and it is possible to detect fluctuations in the line status using the current communication system. The shared channel data can be transmitted by an optimal transmission method according to the current line status without incurring new costs.

  In addition, according to the present embodiment, one of the modulation scheme, the coding scheme, and the transmission power is changed in order to change the modulation scheme, the coding scheme, and the transmission power in combination in accordance with the fluctuation of the line condition. Rather than the case, the optimal transmission method can be determined more reliably according to various line conditions.

  Note that the configuration of the base station apparatus according to the present embodiment may be the configuration shown in FIG. 5 instead of the configuration shown in FIG. FIG. 5 is a principal block diagram showing another schematic configuration of the base station apparatus according to one embodiment of the present invention. 5 that are the same as those shown in FIG. 1 are assigned the same reference numerals as in FIG. 1, and detailed descriptions thereof are omitted.

  In the configuration illustrated in FIG. 1, the fluctuation amount calculation unit 109 calculates the SIR fluctuation amount using the TPC command selected by the TPC command selection unit 108. On the other hand, in the configuration shown in FIG. 5, the fluctuation amount calculation unit 109 and the SIR correction unit 201 are provided for each communication terminal. For each communication terminal, the calculation of the SIR fluctuation amount and the correction of the SIR notified from each communication terminal are performed. Is done.

  That is, the fluctuation amount calculation unit 109 calculates the SIR fluctuation amount using the TPC command output from the TPC command detection unit 104 in the same manner as described above. The calculated SIR fluctuation amount is output to the SIR correction unit 201. The SIR correction unit 201 corrects the SIR notified from the communication terminal by adding the SIR fluctuation amount to the SIR information output from the SIR information extraction unit 106. The corrected SIR is output to the transmission destination determination unit 107.

  Then, transmission destination determination section 107 determines the transmission destination of DSCH data according to the corrected SIR. By using the corrected SIR, the communication terminal having the best downlink channel condition is determined as the DSCH data transmission destination. The transmission destination determination unit 107 outputs a signal indicating the determined communication terminal to the DSCH data selection unit 111, and selects the SIR corresponding to the communication terminal determined as the transmission destination of the DSCH data from the corrected SIR. And output to the transmission method determination unit 110.

  The transmission method determination unit 110 determines an optimal transmission method for the corrected SIR output from the transmission destination determination unit 107. By using the corrected SIR, the optimum transmission method is determined for the current channel condition of the downlink. This is the same as the configuration shown in FIG.

  As described above, in the configuration shown in FIG. 5, in order to determine the destination according to the corrected SIR, that is, the current line status, the destination is determined according to the SIR notified from the communication terminal as it is. Compared with, it is possible to select an optimal destination more reliably.

  In the above embodiment, the SIR has been described as an example of the value indicating the communication quality. However, the present embodiment is not limited to this, and the present embodiment uses any value as long as the value indicates the communication quality. However, it can be implemented.

  In the above-described embodiment, the DSCH data modulation scheme, coding scheme, and transmission power are determined for each frame, but may be performed for each slot.

  Further, the above embodiment can be applied to a communication system in which retransmission of DSCH data is performed when there is an error in DSCH data. That is, it is also possible to determine the modulation scheme, coding scheme, and transmission power for the retransmitted DSCH data by the method described in the above embodiment. Also in this case, it is possible to determine the DSCH data modulation scheme, encoding scheme, and transmission power for each slot.

  In the above embodiment, a radio communication system that performs high-speed downlink data communication using DSCH has been described as an example. However, the present invention is not limited to this, and in this embodiment, the base station is a communication terminal. The present invention can be applied to all wireless communication systems that perform high-speed downlink data communication by deciding shared channel assignment based on a value indicating communication quality transmitted from the mobile station.

  Further, in the above embodiment, the case where the modulation scheme, the coding scheme, and the transmission power are all changed has been described. However, the present invention is not limited to this, and one selected from the modulation scheme, the coding scheme, and the transmission power. It is also possible to change one or two.

The principal part block diagram which shows schematic structure of the base station apparatus which concerns on one embodiment of this invention The figure which shows the relationship between the communication procedure in one Embodiment of this invention of high-speed packet communication using DSCH, and reception SIR in a communication terminal. The graph for demonstrating the determination method of the modulation system in the base station apparatus which concerns on one embodiment of this invention The graph for demonstrating the determination method of the encoding system in the base station apparatus which concerns on one embodiment of this invention The principal part block diagram which shows another schematic structure of the base station apparatus which concerns on one embodiment of this invention Conceptual diagram of high-speed packet communication system using DSCH The figure which shows the relationship between the conventional communication procedure of the high-speed packet communication using DSCH, and reception SIR in a communication terminal.

Explanation of symbols

DESCRIPTION OF SYMBOLS 103 DPCCH data receiving part 104 TPC command detection part 105 DPDCH data receiving part 106 SIR information extraction part 107 Transmission destination determination part 108 TPC command selection part 109 Fluctuation amount calculation part 110 Transmission method determination part 111 DSCH data selection part 112 Encoding part 113 Modulation unit 114 Transmission power control unit 115 DSCH data transmission unit 201 SIR correction unit

Claims (4)

Acquisition means for acquiring channel quality information related to downlink quality measured by each of a plurality of communication terminals;
Receiving means for receiving TPC commands transmitted from the plurality of communication terminals;
Calculating means for calculating a fluctuation amount of downlink quality of each communication terminal using the received TPC command of each communication terminal;
Correction means for correcting the line quality information of each communication terminal acquired by the acquisition means using the fluctuation amount of each communication terminal calculated by the calculation means;
Selecting means for comparing the channel quality information of the plurality of communication terminals after correction, and selecting a communication terminal of a data transmission destination based on the comparison result;
A base station apparatus comprising: The calculating means includes
Summing up the TPC commands of each communication terminal received by the receiving means after obtaining the line quality information by the obtaining means, the TPC command after the summation as the variation amount of each communication terminal,
The correction means includes
Adding the fluctuation amount of each communication terminal calculated by the calculation means to the line quality information of each communication terminal acquired by the acquisition means, and correcting the acquired line quality information;
The base station apparatus according to claim 1. A determination unit that determines a modulation scheme and a coding scheme of data to be transmitted to the communication terminal selected by the selection unit according to the channel quality information corrected by the correction unit;
The base station apparatus according to claim 1, further comprising: An acquisition step of acquiring channel quality information relating to downlink quality respectively measured by a plurality of communication terminals;
Receiving a TPC command transmitted from the plurality of communication terminals;
A calculation step of calculating a fluctuation amount of the downlink quality of each communication terminal using the received TPC command of each communication terminal;
A correction step of correcting the channel quality information of each communication terminal acquired in the acquisition step using the fluctuation amount of each communication terminal calculated in the calculation step;
A comparison step of comparing line quality information of the plurality of communication terminals after correction;
A selection step of selecting a communication terminal as a data transmission destination based on the comparison result;
A wireless communication method comprising:

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