JP2007049390A - Wireless communication apparatus and method therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wireless communication apparatus and method in which a time-direction diffusion rate can be accurately grasped by comparatively simple configuration even when the time-direction diffusion rate is not notified in performing two-dimensional diffusion OFDM-CDMA type communication, and two-dimensional reverse diffusion of a two-dimensionally diffused data can be performed by using an accurate time-direction diffusion rate and a frequency-direction diffusion rate. <P>SOLUTION: A time-direction diffusion rate selection part 115 selects a time-direction diffusion rate corresponding to the value of estimated receiving quality by comparing the estimated receiving quality with a prescribed threshold. When there are a plurality of time-direction diffusion rates selected by the time-direction diffusion rate selection part 115, a decision part 108 decides the diffusion rates as time-direction diffusion rates to which a time-direction diffusion rate corresponding to an individual control channel in which a correlation value obtained by reverse diffusion is maximum is applied by using frequency-direction diffusion rates corresponding to respective time-direction diffusion rates, and when only one time-direction diffusion rate is selected, decides the time-direction diffusion rate as a time-direction diffusion rate to which the selected time-direction diffusion rate is applied. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a wireless communication device and a wireless communication method, and more particularly, to a wireless communication device and a wireless communication method for performing two-dimensional spread OFDM-CDMA (Orthogonal Frequency Division Multiplex-Code Division Multiple Access) communication.

  In recent years, in the field of wireless communication, particularly mobile communication, not only voice but also various information such as video and data are the targets of wireless communication. Therefore, a communication method that can perform high-speed and highly reliable transmission is required.

  On the other hand, when performing high-speed transmission in mobile communication, it is known that the influence of a delayed wave due to multipath is large, and transmission characteristics deteriorate due to frequency selective fading. As one countermeasure against this frequency selective fading, a multi-carrier modulation scheme such as OFDM and a CDMA (code division multiplexing) scheme have been proposed.

  Currently, in the field of mobile communications, an OFDM-CDMA system combining these OFDM modulation system and CDMA modulation system is drawing attention. In the OFDM-CDMA method, a symbol is spread in the frequency direction (frequency domain spreading method), a symbol is spread in the time direction (time domain spreading method), and two-dimensionally distributed in both the frequency direction and the time direction. A method (two-dimensional diffusion method) has been proposed (see, for example, Patent Document 1, Patent Document 2, and Patent Document 3).

  In particular, in the two-dimensional spreading method, by setting the spreading factor in the frequency direction and the spreading factor in the time direction in accordance with the channel state, a path diversity gain and a frequency diversity gain can be obtained. It attracts attention as a method that can suppress a decrease in system capacity. In the two-dimensional spreading method, it has been reported that the reception performance is improved by associating the spreading factor in the time direction with the modulation multi-level number. For example, Non-Patent Document 1 discloses that when the multi-level modulation number is changed to 16 QAM larger than QPSK, the reception performance is improved by increasing the spreading factor in the time direction.

However, using the two-dimensional spreading method, if the transmitting device selects and spreads the spreading factor in the time direction suitable for the channel state and the number of multi-level modulations, the receiving device cannot recognize the spreading factor in the time direction, There is a problem that the despreading operation is performed with a spreading factor in the time direction different from the spreading factor in the time direction actually used. Therefore, in order to solve this problem, a method of informing the spreading factor in the time direction can be considered.
JP 2002-190788 A JP 2003-46474 A JP 2003-101511 A Characteristics of VSF-OFCDM using two-dimensional diffusion with preferential use of time domain diffusion, IEICE Technical Report, RCS2002-85 (2002-6)

  However, when a channel for reporting the spreading factor in the time direction is used separately, there is a problem that the power consumption of the system is increased or the frequency utilization efficiency is reduced as the number of channels increases.

  The present invention has been made in view of the above points, and when performing communication in the two-dimensional spread OFDM-CDMA system, the spread in the time direction can be achieved with a relatively simple configuration without reporting the spread rate in the time direction. An object of the present invention is to provide a wireless communication apparatus and a wireless communication method capable of accurately grasping the rate and two-dimensionally despreading the two-dimensionally spread data using the accurate time direction spreading factor and frequency direction spreading factor. To do.

  In order to solve this problem, the wireless communication apparatus according to the present invention determines a spreading factor candidate in the time direction of the dedicated control channel signal included in the received two-dimensional spread OFDM-CDMA signal based on information on the channel state. A selection means for selecting; a candidate for a spreading factor in the frequency direction determined from a candidate for the spreading factor in the selected time direction and a two-dimensional spreading factor predetermined for the dedicated control channel signal; and a spreading factor in the time direction Among the DPCCH two-dimensional despreading means for two-dimensionally despreading the dedicated control channel signal using the candidates, and the spreading factor candidates in the time direction based on the despreading result obtained by the DPCCH two-dimensional despreading means Determining means for determining a spreading factor in the time direction that is actually used, and the dedicated data channel notified by the dedicated control channel signal. DPDCH frequency direction spreading factor calculating means for calculating a spreading factor in the frequency direction of the dedicated data channel signal using a two-dimensional spreading factor of the signal and the spreading factor in the time direction determined by the determining unit; A dedicated data channel included in the received two-dimensional spread OFDM-CDMA signal using the spreading factor in the time direction determined by the determining unit and the spreading factor in the frequency direction calculated by the DPDCH frequency direction spreading factor calculating unit And a DPDCH two-dimensional despreading means for two-dimensionally despreading the signal.

  According to this configuration, first, based on the channel state, the time direction spreading factor is obtained using an individual control channel signal having a constant two-dimensional spreading factor (time spreading factor × frequency spreading factor), and then The frequency direction spreading factor of the individual data channel signal is obtained from the time direction spreading factor and the two-dimensional spreading factor of the individual data channel signal notified by the individual control channel signal, and the time direction spreading factor and the frequency direction spreading factor are obtained. Since the individual data channel signal is two-dimensionally despread using the, the time-direction spreading factor is accurately grasped with a relatively simple configuration without reporting the spreading factor in the time direction. Data can be two-dimensionally despread using an accurate time direction spreading factor and frequency direction spreading factor.

  According to the present invention, in the two-dimensional spreading method of the OFDM-CDMA scheme, the spreading factor in the time direction can be accurately grasped without reporting the spreading factor in the time direction, and the two-dimensionally spread data can be accurately timed. Two-dimensional despreading can be performed using the direction spreading factor and the frequency direction spreading factor.

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

(principle)
A radio communication apparatus according to an embodiment of the present invention is a radio communication apparatus that receives a dedicated control channel (DPCCH) and a dedicated data channel (DPDCH) transmitted from a communication partner. . The DPCCH and DPDCH are code division multiplexed in order to improve frequency utilization efficiency. Further, DPCCH and DPDCH are two-dimensionally spread in both the frequency direction and the time direction, respectively.

  Between the two-dimensional spreading factor (SF), the spreading factor for time (SFT), and the spreading factor for frequency (SFF), the formula (1) There is a relationship.

SF = SFT × SFF (1)

In this embodiment, the two-dimensional spreading factor (SF) of the DPCCH is known and always constant in the system. On the other hand, the two-dimensional despreading rate (SF) of DPDCH is variable. Also, the spreading factor (SFT) in the time direction is the same between the DPCCH and DPDCH.

  This will be specifically described. On the transmission side, the spreading factor in the time direction is selected based on the reception quality notified from the wireless communication apparatus of the communication partner, and the two-dimensional spreading factor of the known constant DPCCH and the selected spreading factor in the time direction are Substituting into (1), the spreading factor in the frequency direction is determined. Then, the DPCCH signal is two-dimensionally spread using this time direction spreading factor and frequency direction spreading factor and transmitted.

  On the other hand, for DPDCH, the spreading factor in the time direction is the same as the spreading factor in the time direction of DPCCH, while the spreading factor in the frequency direction is not necessarily the same as the spreading factor in the frequency direction of DPCCH. Vary with. That is, on the transmission side, the DPDCH signal is two-dimensionally spread and transmitted using the time direction spreading factor common to the DPCCH and the changing frequency direction spreading factor.

  Further, since the two-dimensional spreading factor of DPDCH is changed on the transmission side as described above, information on the two-dimensional spreading factor (SF) of DPDCH is allocated in the DPCCH frame to the wireless communication apparatus of the communication partner. Notify.

  The inventors of the present invention consider such a DPCCH and DPDCH channel configuration, first obtain a time direction spreading factor using an individual control channel signal having a constant two-dimensional spreading factor, and then calculate the time spreading factor. The frequency direction spreading factor of the individual data channel signal is obtained from the direction spreading factor and the two-dimensional spreading factor of the individual data channel signal notified by the individual control channel signal, and individually obtained using the time direction spreading factor and the frequency direction spreading factor. If the data channel signal is two-dimensionally despread, it is possible to accurately grasp the spreading factor in the time direction with a relatively simple configuration without informing the spreading factor in the time direction, and to accurately time the two-dimensionally spread data. It was considered that two-dimensional despreading can be performed using the directional spreading factor and the frequency directional spreading factor, leading to the present invention.

(Constitution)
FIG. 1 shows a configuration of a wireless communication apparatus according to an embodiment of the present invention. The wireless communication apparatus 100 includes a duplexer 101, an RF (Radio Frequency) receiving unit 102, an FFT (Fast Fourier Transform) unit 103, a reception quality estimating unit 104, an encoding unit 105, an RF transmitting unit 106, and a DPCCH two-dimensional despreading unit 107. -1, 107-2, determination unit 108, DPCCH decoding unit 109, DPDCH frequency direction spreading factor calculation unit 110, DPDCH two-dimensional despreading unit 111, DPDCH error correction decoding unit 112, error detection unit 113, reception quality fluctuation amount measurement unit 114 and a time direction spreading factor selection unit 115.

  The duplexer 101 shares an antenna between the transmission system and the reception system.

  The RF receiving unit 102 performs wireless reception processing (down-conversion, A / D conversion, etc.) on the received signal and outputs a signal obtained thereby to the FFT unit 103.

  The FFT unit 103 converts the time domain signal into a frequency domain signal by performing fast Fourier transform on the signal subjected to the radio reception processing, and converts the obtained frequency domain signal into a DPCCH two-dimensional despreading unit. While outputting to 107-1 and 107-2, it outputs to DPDCH two-dimensional despreading section 111.

  Reception quality estimation section 104 estimates the reception quality of the propagation path such as SIR (Signal to Interference Ratio) from the signal in the frequency domain, outputs the estimated reception quality to encoding section 105, and also receives the reception quality variation measurement section. To 114.

  Encoding section 105 encodes reception quality information, retransmission request information (ACK / NACK), and transmission data, and outputs the encoded data obtained thereby to RF transmission section 106.

  The RF transmission unit 106 performs predetermined wireless transmission processing (D / A conversion, up-conversion, etc.) on the encoded data, and transmits the encoded data to the communication partner via the shared unit 101.

  The DPCCH two-dimensional despreading sections 107-1 and 107-2 perform two-dimensional despreading on the frequency domain signal after the fast Fourier transform in accordance with the instruction output from the time direction spreading factor selection section 115. Specifically, the DPCCH two-dimensional despreading units 107-1 and 107-2 are configured such that the two-dimensional spreading factor is the same, and the spreading factor in the time direction and the spreading factor in the frequency direction are different from each other. . That is, as described above, since the two-dimensional spreading factor of DPCCH is known and constant, DPCCH two-dimensional despreading units 107-1 and 107-2 perform despreading with this known two-dimensional spreading factor. However, in the DPCCH two-dimensional despreading units 107-1 and 107-2, different time direction spreading factors are designated from the time direction spreading factor selection unit 115, and the time direction spreading factor, the time direction spreading factor, and the known 2 Two-dimensional despreading is performed using a frequency direction spreading factor that is uniquely determined from the dimensional spreading factor. In other words, the DPCCH two-dimensional despreading units 107-1 and 107-2 perform two-dimensional despreading with the same two-dimensional spreading factor, but perform two-dimensional despreading using different time direction spreading factors and frequency direction spreading factors. To do. DPCCH two-dimensional despreading sections 107-1 and 107-2 output despread signals to determination section 108. A method of selecting the time direction spreading factor by the time direction spreading factor selecting unit 115 will be described in detail later.

  In the present embodiment, since it is assumed that there are two candidates for the spreading factor in the time direction (SFT1 or SFT16) selected on the transmission side, radio communication apparatus 100 has two DPCCH two-dimensional despreading. Parts 107-1 and 107-2. Therefore, when there are three or more candidates for the spreading factor in the time direction for each channel state, it is sufficient to provide three or more two-dimensional despreading units. Alternatively, two-dimensional despreading may be performed by switching between the spreading factor in the time direction and the spreading factor in the frequency direction by using one two-dimensional despreading unit.

  The determination unit 108 compares the despreading results from the DPCCH two-dimensional despreading units 107-1 and 107-2, and the time used by the DPCCH two-dimensional despreading unit 107-1 or 107-2 having the larger despread value. It is determined that the directional spreading factor is the spreading factor in the time direction actually used. The determination unit 108 outputs the determined spreading factor in the time direction to the DPDCH frequency direction spreading factor calculation unit 110, and the DPCCH decoding unit 109 outputs the despread signal two-dimensionally despread using the determined spreading factor in the time direction. Output to.

  The DPCCH decoding unit 109 obtains information transmitted through the DPCCH by decoding the despread signal. Then, DPCCH decoding section 109 extracts information about the two-dimensional spreading factor of DPDCH included in the DPCCH information, and outputs this to DPDCH frequency direction spreading factor calculating section 110.

  The DPDCH frequency direction spreading factor calculation unit 110 substitutes the spreading factor in the time direction determined by the determination unit 108 and the two-dimensional DPDCH two-dimensional spreading factor extracted from the DPCCH decoding unit 109 into the above equation (1). The spreading factor in the frequency direction of DPDCH is calculated. The DPDCH frequency direction spreading factor calculation unit 110 outputs the calculated DPDCH spreading factor in the frequency direction and the spreading factor in the time direction to the DPDCH two-dimensional despreading unit 111.

  The DPDCH two-dimensional despreading unit 111 performs two-dimensional despreading on the frequency domain signal using a spreading code corresponding to the spreading factor in the time direction and the frequency direction of the DPDCH, and the despread signal is subjected to DPDCH error correction decoding. Output to the unit 112.

  The DPDCH error correction decoding unit 112 obtains data (received data) transmitted through the DPDCH by performing demodulation processing and error correction decoding on the despread signal. Further, DPDCH error correction decoding section 112 outputs CRC (Cyclic Redundancy Check) bits for error detection included in the decoded bits to error detection section 113.

  The error detection unit 113 performs error detection of the decoded bit string using the CRC bits, and determines whether or not to request retransmission of the bit string in which the error is detected based on the error detection result. Further, the error detection unit 113 calculates a PER (Packet Error Rate) from the number of retransmission request information (ACK / NACK) indicating whether or not to request retransmission of a bit string in which an error is detected, and uses the PER as a time direction spreading factor. While outputting to the selection part 115, resending request information is output to the encoding part 105. Specifically, the error detection unit 113 calculates the PER from the number of ACKs / (number of ACKs + number of NACKs).

  Reception quality fluctuation amount measuring section 114 measures a fluctuation amount of reception quality such as SIR output from reception quality estimation section 104 and outputs the fluctuation amount and reception quality to time direction spreading factor selection section 115. The reception quality is not limited to SIR, but may be other ones indicating communication states such as delay spread, Doppler frequency, reception power, interference power.

  The time direction spreading factor selection unit 115 selects a candidate for the spreading factor in the time direction corresponding to the value of the reception quality by comparing the reception quality with a predetermined threshold value. In general, when the two-dimensional spreading method is used, on the transmission side, when the channel condition is good and the reception quality is good, the spreading factor in the time direction is increased, and when the channel condition is bad and the reception quality is bad, the time is Reduce the diffusivity in the direction. Considering this, the time direction spreading factor selecting unit 115 selects a candidate for the spreading factor in the time direction. This will be specifically described below with reference to the drawings.

  FIG. 2 is an example of mapping of reception quality and time direction spreading factor tables held in the time direction spreading factor selecting unit 115 inside. As shown in FIG. 2, the time direction spreading factor selection section 115 preferentially selects a larger time direction spreading factor candidate as the reception quality is better, and the smaller the time direction spreading factor is as the reception quality is worse. Select candidates preferentially. Moreover, the time direction spreading factor selecting section 115 selects a plurality of time direction spreading factor candidates depending on the reception quality. For example, when the reception quality is β or more, the time direction spreading factor selection unit 115 selects SFT 16 as a candidate, and when the reception quality is less than α, the time direction spreading factor selection unit 115 selects SFT 1 as a candidate. When the reception quality is not less than α and less than β, the time direction spreading factor selection unit 115 selects SFT16 and SFT1 as candidates. Although FIG. 2 shows two cases of SFT16 and SFT1 as candidates for the time direction spreading factor, the number of candidates for the spreading factor in the time direction is not limited to this and may be three or more.

  Further, the time direction spreading factor selection unit 115 corrects the correspondence between the reception quality and the time direction spreading factor according to the amount of variation in reception quality such as SIR and the result of error detection such as PER. FIG. 3 shows a mapping example of a table of reception quality and time direction spreading factor corresponding to the variation amount of reception quality. FIG. 3A shows an example where the amount of fluctuation in reception quality is larger than a predetermined threshold, and FIG. 3B shows an example where the amount of fluctuation in reception quality is smaller than a predetermined threshold. The time direction spreading factor selecting unit 115 selects a plurality of candidates when there is a large amount of variation in reception quality, there is a variation in the state of the communication channel, and the time direction spreading factor used on the transmission side is likely to vary from time to time. Increase the range of reception quality to be selected. Thereby, the rate of erroneously determining the time-direction spreading factor actually used is reduced, and the determination accuracy of the time-direction spreading factor can be increased.

  On the other hand, the time direction spreading factor selection unit 115 may change the time direction spreading factor used on the transmission side for each time when the variation amount of the reception quality is small and the state of the communication channel is small. Since it is low, the range of reception quality for selecting a plurality of candidates is narrowed. As a result, the rate at which multiple two-dimensional despreading is performed is reduced, and power consumption can be reduced. Note that the range of reception quality for selecting a plurality of candidates may be changed in proportion to the amount of change in reception quality, or may be changed by comparing the amount of change with a predetermined threshold.

  FIG. 4 shows a mapping example of a table of reception quality and time direction spreading factor according to PER. FIG. 4A shows an example in the case where PER is higher than a predetermined threshold and the communication path condition is bad. FIG. 4B shows an example in which PER is lower than the predetermined threshold and the communication path condition is good. As shown in FIG. 4, the time direction spreading factor selection section 115 is a reception quality range in which a plurality of time direction spreading factor candidates are selected as the PER is lower than a predetermined threshold and the channel condition is better in the long term. The center value of the reception quality range in which a plurality of candidates are selected is lowered as the PER is higher than the predetermined threshold and the channel condition is worse in the long term.

  As described above, when the applied modulation scheme is used, the transmission side adopts a modulation scheme with a larger multi-level modulation number as the communication path state is better, and a time direction spreading factor as the multi-level modulation number increases. It is known that the reception performance is improved when the value is increased. Therefore, by correcting the center value of the reception quality range in which a plurality of time direction spreading factor candidates are selected according to PER, the time direction spreading factor selecting unit 115 can be used on the transmission side when adopting an applied modulation scheme. The candidate of the time direction spreading factor to be used can be selected more reliably.

  The time direction spreading factor selecting unit 115 uses the above-described method to determine the reception quality range in which a plurality of time direction spreading factor candidates are selected, the center value of the range in which a plurality of candidates are selected, The spreading factor in the time direction is selected while correcting according to PER or the like, and an instruction to despread is output to the DPCCH two-dimensional despreading units 107-1 and 107-2 corresponding to the spreading factor in the selected time direction. .

(Operation)
Next, the determination operation of the spreading factor in the time direction of the wireless communication apparatus configured as described above will be specifically described with an example.

  First, on the transmission side (not shown), a time direction spreading factor candidate is selected according to reception quality information notified from the wireless communication apparatus 100. And the spreading factor of each frequency direction is determined from the two-dimensional spreading factor (SF) of each of DPCCH and DPDCH. As described above, the two-dimensional spreading factor (SF) of DPCCH is known and always constant, and the two-dimensional spreading factor (SF) of DPDCH is variable according to the data rate and the like. Further, the spreading factor (SFT) in the time direction is the same between the DPCCH and DPDCH. There is a relationship of the above equation (1) among the two-dimensional spreading factor (SF), the temporal spreading factor (SFT), and the frequency spreading factor (SFF). Therefore, information about the two-dimensional spreading factor of DPDCH is allocated in the DPCCH frame and transmitted to radio communication apparatus 100. The DPCCH and DPDCH that are two-dimensionally spread using the spreading factor in the time direction and the spreading factor in the frequency direction are encoded and multiplexed, and then predetermined radio transmission processing (D / A conversion, up-conversion), etc. Is transmitted to the wireless communication apparatus 100.

  A two-dimensional spread signal transmitted from a transmission side (not shown) is received by the RF receiver 102 via the antenna and duplexer 101, and subjected to predetermined radio reception processing. The received signal is subjected to fast Fourier transform by the FFT unit 103 and output to the reception quality estimation unit 104 to measure the reception quality and output to the DPCCH two-dimensional despreading units 107-1 and 107-2.

  Information about the reception quality estimated by the reception quality estimation unit 104 is encoded together with the transmission data by the encoding unit 105 and transmitted to a communication partner on the transmission side (not shown) via the RF transmission unit 106. Then, it is output to the time direction spreading factor selection unit 115 via the reception quality fluctuation amount measurement unit 114.

  Then, the time direction spreading factor selection unit 115 selects a spreading factor in the time direction from a table held therein according to the reception quality output from the reception quality variation measuring unit 114. For example, when the time direction spreading factor selection unit 115 holds a table of reception quality and spreading factor in the time direction as shown in FIG. 2, the SIR estimated by the reception quality estimation unit 104 is the lower limit of the SFT 16. When the threshold value α is greater than or equal to the threshold value β and less than the upper threshold value β of SFT1, the time direction spreading factor selecting unit 115 selects both SFT16 and SFT1 as candidates for the spreading factor in the time direction. Then, an instruction to perform two-dimensional despreading is output to both DPCCH two-dimensional despreading units 107-1 and 107-2.

  Then, each DPCCH two-dimensional despreading section 107-1, 107-2 performs two-dimensional despreading using the spreading code corresponding to the selected spreading factor in the time direction and spreading factor in the frequency direction. Is output to the determination unit 108. The determination unit 108 compares the results output from the DPCCH two-dimensional despreading units 107-1 and 107-2, and the time direction spreading factor corresponding to the largest result is actually used on the transmission side. It is determined as the directional spreading factor.

  On the other hand, when the estimated SIR is less than the lower threshold α of SFT16 or greater than the upper threshold β of SFT1, only one of SFT1 and SFT16 is selected as a candidate for the spreading factor in the time direction. Then, an instruction is output to perform two-dimensional despreading only to the DPCCH two-dimensional despreading unit corresponding to the selected spreading factor in the time direction. The result of the two-dimensional despreading is output to the determination unit 108, and the selected spreading factor in the time direction is determined as the spreading factor in the time direction used by the transmission side.

  The spreading factor in the time direction determined by the determining unit 108 is output to the DPDCH frequency direction spreading factor calculating unit 110, and the despread signal two-dimensionally despread using the determined spreading factor in the time direction is subjected to DPCCH decoding. The data is output to the unit 109 and decoded. Then, information about the two-dimensional spreading factor (SF) of DPDCH is extracted from the decoded bits, and information about the two-dimensional spreading factor is output to DPDCH frequency direction spreading factor calculation section 110.

  Then, DPDCH frequency direction spreading factor calculation section 110 substitutes the two-dimensional spreading factor of DPDCH and the spreading factor in the time direction into the above equation (1), and calculates the spreading factor in the frequency direction of DPDCH. Information about the obtained spreading factor in the frequency direction and spreading factor in the time direction is output to DPDCH two-dimensional despreading section 111.

  Two-dimensional despreading is performed by the DPDCH two-dimensional despreading unit 111 using the spreading factor in the time direction and the spreading factor in the frequency direction of the DPDCH, and the obtained despread signal is output to the DPDCH error correction decoding unit 112 The

  Then, DPDCH error correction decoding section 112 performs demodulation processing and error correction decoding, and outputs CRC bits included in the decoded bit string to error detection section 113.

  The error detection unit 113 uses the CRC bits to detect errors in the decoded bit string, and calculates the PER from the number of retransmission request information (ACK / NACK) indicating whether or not to request retransmission of the decoded bit string. The obtained PER is output to the time direction spreading factor selection unit 115.

  The time direction spreading factor selection unit 115 selects a candidate for the spreading factor in the time direction by comparing the reception quality with a predetermined threshold value. In addition, the time direction spreading factor selection unit 115 corrects the reception quality range in which a plurality of time direction spreading factor candidates are selected and the center value of the range in which the candidates are selected in accordance with the amount of SIR variation and PER. Is done.

  Specifically, the reception quality for selecting multiple candidates when the amount of fluctuation in reception quality is large, the channel conditions vary, and the time-direction spreading factor used on the transmission side is likely to vary from time to time. The range of is set wide. Thereby, the rate of erroneously determining the time-direction spreading factor actually used is reduced, and the determination accuracy of the time-direction spreading factor can be increased.

  On the other hand, when the amount of fluctuation in reception quality is small and the communication channel state is small, the time-direction spreading factor used on the transmission side is unlikely to change from time to time. The range is set narrow. As a result, the rate at which multiple two-dimensional despreading is performed is reduced, and power consumption can be reduced.

  Further, as the PER is lower than a predetermined threshold and the channel condition is better in the long term, the center value γ of the reception quality range in which a plurality of time direction spreading factors are selected is set higher, and the PER is higher than the predetermined threshold. As the channel condition becomes worse in the long term, the center value γ of the reception quality range in which a plurality of time direction spreading factors are selected is set lower. In this way, by correcting the center value of the reception quality range in which a plurality of time direction spreading factors are selected in accordance with the PER, candidates for the time direction spreading factor used on the transmission side are more reliably selected. .

  In the present embodiment, the center value γ is changed in consideration of PER, but BER (Bit Error Rate) may be used instead of PER. That is, instead of calculating the PER from the decoded bit in the error detection unit 113, if the BER is higher than a predetermined threshold, the center value γ of the reception quality range in which both SFT16 and SFT1 are selected is set. If the BER is higher and the BER is lower than the predetermined threshold, the center value γ of the reception quality range in which both the SFT 16 and the SFT 1 are selected may be lowered.

(effect)
As described above, according to the present embodiment, based on the information on the channel state, a candidate for the spreading factor in the time direction of the dedicated control channel signal included in the received two-dimensional spread OFDM-CDMA signal is selected, The individual control channel signal is two-dimensionally despread using a time direction spreading factor candidate and a frequency direction spreading factor candidate determined from a predetermined two-dimensional spreading factor and a time spreading factor candidate. Based on the obtained two-dimensional despreading inverse result, the spreading factor in the time direction actually used is determined from the spreading factor candidates in the time direction, and the dedicated data channel signal notified by the dedicated control channel signal The spread factor in the frequency direction of the dedicated data channel signal is calculated using the two-dimensional spreading factor of the data and the determined spread factor in the time direction, and the determined spread factor in the time direction and the calculated spread in the frequency direction are calculated. Since the dedicated data channel signal is two-dimensionally despread using the rate, the information about the spreading factor in the time direction is not reported, the reduction in frequency utilization efficiency is prevented, and the spreading factor in the time direction is accurately determined. The individual data channel signal can be two-dimensionally despread.

  Further, according to the present embodiment, the amount of variation in reception quality is measured, and when the amount of variation in reception quality is large and the state of the communication path varies, a plurality of candidates for spreading factors in the time direction are selected. Correct the reception quality range widely. On the other hand, when the fluctuation amount of the reception quality is small and there is no variation in the state of the communication channel, the reception quality range in which a plurality of candidates for the spreading factor in the time direction are selected is narrowed. As a result, when there is a large variation in the state of the communication channel, it prevents the deterioration of the accuracy of determination of the spreading factor in the time direction due to narrowing down of the candidates, reliably determines the spreading factor in the time direction, and the variation in the state of the communication channel When is small, two-dimensional despreading processing can be reduced and power consumption can be reduced.

  In addition, according to the present embodiment, error detection is performed, and when the error detection result is bad and the state of the communication channel is determined to be inferior, the rate at which a small spreading factor in the time direction is selected is increased, and error detection is performed. If the result is good and the channel condition is determined to be good, the time direction spreading factor used on the transmission side can be selected more reliably in order to increase the rate at which a large spreading factor in the time direction is selected. it can.

  The radio communication apparatus according to the first aspect of the present invention selects a spreading factor candidate in the time direction of the dedicated control channel signal included in the received two-dimensional spread OFDM-CDMA signal based on information on the channel state. A selection means; a candidate for a spreading factor in the frequency direction determined from a candidate for the spreading factor in the selected time direction and a two-dimensional spreading factor predetermined for the dedicated control channel signal; and a candidate for the spreading factor in the time direction And DPCCH two-dimensional despreading means for two-dimensionally despreading the dedicated control channel signal, and based on the result of despreading obtained by the DPCCH two-dimensional despreading means, from among the candidates for the spreading factor in the time direction Determination means for determining a spreading factor in the time direction used for the two-dimensional of the dedicated data channel signal notified by the dedicated control channel signal DPDCH frequency direction spreading factor calculating means for calculating a spreading factor in the frequency direction of the dedicated data channel signal using a spreading factor and the spreading factor in the time direction determined by the determining means; The received data channel signal included in the received two-dimensional spread OFDM-CDMA signal is two-dimensionally converted using the spread factor in the time direction and the spread factor in the frequency direction calculated by the DPDCH frequency-direction spread factor calculator. A configuration having DPDCH two-dimensional despreading means for despreading is adopted.

  According to this configuration, first, based on the channel state, the time direction spreading factor is obtained using an individual control channel signal having a constant two-dimensional spreading factor (time spreading factor × frequency spreading factor), and then The frequency direction spreading factor of the individual data channel signal is obtained from the time direction spreading factor and the two-dimensional spreading factor of the individual data channel signal notified by the individual control channel signal, and the time direction spreading factor and the frequency direction spreading factor are obtained. Since the individual data channel signal is two-dimensionally despread using the, the time-direction spreading factor is accurately grasped with a relatively simple configuration without reporting the spreading factor in the time direction. Data can be two-dimensionally despread using an accurate time direction spreading factor and frequency direction spreading factor.

  The wireless communication apparatus according to a second aspect of the present invention is the wireless communication apparatus according to the first aspect, wherein the DPCCH two-dimensional despreading means have the same two-dimensional spreading factor, a spreading factor in the time direction, and a spreading factor in the frequency direction. A configuration including a plurality of DPCCH two-dimensional despreaders having different rates is adopted.

  According to this configuration, since the dedicated control channel signal can be two-dimensionally despread simultaneously with different spreading factors in the time direction, the processing speed can be improved when a plurality of spreading factors in the time direction are selected. It becomes.

  The wireless communication apparatus according to a third aspect of the present invention is the wireless communication apparatus according to the first aspect, wherein when the selection unit selects a plurality of spread rate candidates in the time direction, the determination unit performs the DPCCH two-dimensional despreading unit. The candidate of the spreading factor in the time direction in which the despreading result obtained by the above is the maximum is determined as the actually used spreading factor in the time direction, and is selected when there is one selected spreading factor in the time direction. A configuration is adopted in which a candidate for the spreading factor in the time direction is determined as the spreading factor in the time direction actually used.

  According to this configuration, since the method of determining the spreading factor in the time direction actually used is changed according to the number of spreading factor candidates in the time direction selected, when there are a plurality of selected candidates, The accuracy of determining the spreading factor can be increased, and when the number of selected candidates is one, the processing amount of two-dimensional despreading can be reduced and the power consumption can be reduced.

  The wireless communication apparatus according to a fourth aspect of the present invention further comprises a fluctuation amount measuring means for measuring the fluctuation amount of the communication path state in the first aspect, wherein the selection means measures the fluctuation amount. A configuration is adopted in which the number of candidates to be selected is variable according to the fluctuation amount of the communication channel state measured by the means.

  According to this configuration, since the number of candidates to be selected is made variable according to the fluctuation amount of the communication path state, the number of candidates to be selected can be increased when the fluctuation amount is large, and the number of candidates is excessively narrowed down. It is possible to prevent deterioration in determination accuracy of the spreading factor in the time direction.

  The wireless communication apparatus according to a fifth aspect of the present invention is the wireless communication apparatus according to the fourth aspect, wherein the selecting means is a spreading factor in a time direction according to the fluctuation amount of the communication path state measured by the fluctuation amount measuring means. The candidate is mapped in association with the channel state, the threshold value of the channel state for each mapped spreading factor in the time direction and the actual channel state are determined as a threshold, and the spreading factor candidate in the time direction is selected. Take the configuration.

  According to this configuration, since the selection unit maps the spreading factor candidates in the time direction in association with the channel state according to the channel state variation amount, the channel state variation amount is large and the channel state is changed. If it is determined that there is variation, the range of channel conditions in which multiple candidates for the spreading factor in the time direction are selected is expanded, and deterioration of the accuracy of judging the spreading factor in the time direction due to narrowing down of the candidates is prevented. If the channel state fluctuation amount is small and there is no variation in the channel state, a range of channel state in which a plurality of time direction spreading factor candidates are selected. , And the power consumption can be reduced by reducing the processing amount of two-dimensional despreading.

  The wireless communication apparatus according to a sixth aspect of the present invention further comprises error detection means for performing error detection by decoding the dedicated data channel signal output from the DPDCH two-dimensional despreading means in the first aspect. The selection means preferentially selects a candidate having a small time direction spreading factor as a candidate for the time direction spreading factor as the error detection result detected by the error detecting unit is worse, As the result of error detection detected by the detection means is better, a configuration is adopted in which a candidate having a larger spreading factor in the time direction is preferentially selected as a candidate for the spreading factor in the time direction.

  According to this configuration, when the error detection result is poor and the channel condition is judged to be poor, the ratio of selecting a small spreading factor in the time direction is increased, and the error detection result is good and the communication channel condition is good. When the state is determined to be good, the ratio of selecting a large time direction spreading factor increases, and the time direction spreading factor candidate used on the transmission side is selected more reliably.

  The wireless communication method according to the seventh aspect of the present invention selects a spreading factor candidate in the time direction of the dedicated control channel signal included in the received two-dimensional spread OFDM-CDMA signal based on information on the channel state. A candidate for a spreading factor in a frequency direction determined from a step, a candidate for a spreading factor in a time direction, and a two-dimensional spreading factor predetermined for the dedicated control channel signal, and a candidate for a spreading factor in the time direction A time direction actually used from among the candidates for the spreading factor in the time direction, based on a step of two-dimensionally despreading the dedicated control channel signal and a result of despreading obtained by two-dimensional despreading Determining the spreading factor, the two-dimensional spreading factor of the dedicated data channel signal notified by the dedicated control channel signal, and the time direction determined by the determining means Using the spreading factor, calculating the spreading factor in the frequency direction of the dedicated data channel signal, the determined spreading factor in the time direction, and the calculated spreading factor in the frequency direction of the dedicated data channel signal. And two-dimensional despreading of the individual data channel signal included in the received two-dimensional spread OFDM-CDMA signal.

  According to this method, first, based on the channel state, the time direction spreading factor is obtained using an individual control channel signal having a constant two-dimensional spreading factor (time spreading factor × frequency spreading factor), and then The frequency direction spreading factor of the individual data channel signal is obtained from the time direction spreading factor and the two-dimensional spreading factor of the individual data channel signal notified by the individual control channel signal, and the time direction spreading factor and the frequency direction spreading factor are obtained. Since the individual data channel signal is two-dimensionally despread using, so that the spreading factor in the time direction can be accurately grasped without reporting the spreading factor in the time direction, and the two-dimensional despread data can be accurately timed. Two-dimensional despreading can be performed using the spreading factor and the frequency direction spreading factor.

  The wireless communication apparatus and wireless communication method of the present invention can accurately grasp the spreading factor in the time direction and perform two-dimensional spreading in the OFDM-CDMA two-dimensional spreading method without reporting the spreading factor in the time direction. Data can be two-dimensionally despread using an accurate time-direction spreading factor and frequency-direction spreading factor, for example, in a radio communication apparatus and a radio communication method to which the OFDM-CDMA two-dimensional spreading method is applied. Useful.

The block diagram which shows the structure of the radio | wireless communication apparatus which concerns on one embodiment of this invention The figure explaining an example of the method of determining the spreading factor of the time direction which concerns on the said embodiment of this invention (A) The figure explaining an example of the method of determining the spreading factor of the time direction which concerns on the said embodiment of this invention (b) An example of the method of judging the spreading factor of the time direction which concerns on the said embodiment of this invention Figure explaining (A) The figure explaining an example of the method of determining the spreading factor of the time direction which concerns on the said embodiment of this invention (b) An example of the method of judging the spreading factor of the time direction which concerns on the said embodiment of this invention Figure explaining

Explanation of symbols

DESCRIPTION OF SYMBOLS 101 Duplexer 102 RF receiving part 103 FFT part 104 Reception quality estimation part 105 Coding part 106 RF transmission part 107-1, 107-2 DPCCH two-dimensional despreading part 108 Judgment part 109 DPCCH decoding part 110 DPDCH frequency direction spreading factor calculation part 111 DPDCH two-dimensional despreading unit 112 DPDCH error correction decoding unit 113 Error detection unit 114 Received quality variation measurement unit 115 Time direction spreading factor selection unit

Claims (7)

Selecting means for selecting a spreading factor candidate in the time direction of the dedicated control channel signal included in the received two-dimensional spread OFDM-CDMA signal based on the information on the channel state;
A frequency direction spreading factor candidate determined from the selected time direction spreading factor candidate and a predetermined two-dimensional spreading factor for the dedicated control channel signal, and the time direction spreading factor candidate are used. DPCCH two-dimensional despreading means for two-dimensional despreading the dedicated control channel signal;
A determination unit that determines a spreading factor in the time direction actually used from the spreading factor candidates in the time direction based on a despreading result obtained by the DPCCH two-dimensional despreading unit;
Spreading in the frequency direction of the dedicated data channel signal using the two-dimensional spreading factor of the dedicated data channel signal notified by the dedicated control channel signal and the spreading factor in the time direction determined by the determining means DPDCH frequency direction spreading factor calculating means for calculating a rate;
Individual data included in the received two-dimensional spread OFDM-CDMA signal using the spreading factor in the time direction determined by the determining unit and the spreading factor in the frequency direction calculated by the DPDCH frequency direction spreading factor calculating unit DPDCH two-dimensional despreading means for two-dimensional despreading the channel signal;
A wireless communication apparatus comprising: The DPCCH two-dimensional despreading means is:
A plurality of DPCCH two-dimensional despreaders having the same two-dimensional spreading factor and different spreading factors in the time direction and in the frequency direction;
The wireless communication apparatus according to claim 1, further comprising: The determination means includes
When a plurality of spreading factor candidates in the time direction are selected by the selecting unit, the spreading factor candidate in the time direction that maximizes the despreading result obtained by the DPCCH two-dimensional despreading unit The determination as a spreading factor, and when there is one selected candidate for the spreading factor in the time direction, the candidate for the spreading factor in the selected time direction is determined as the actually used spreading factor in the time direction. Wireless communication device. A fluctuation amount measuring means for measuring the fluctuation amount of the communication path state;
The selection means includes
The radio communication apparatus according to claim 1, wherein the number of candidates to be selected is made variable according to the fluctuation amount of the communication path state measured by the fluctuation amount measuring unit. The selection means includes
In accordance with the fluctuation amount of the communication channel state measured by the fluctuation amount measuring means, the candidate for the spreading factor in the time direction is mapped in association with the communication channel state, and the channel state for each mapped spreading factor in the time direction is mapped. The wireless communication apparatus according to claim 4, wherein a threshold value and an actual communication path state are determined as a threshold value, and a candidate for the spreading factor in the time direction is selected. Error detecting means for detecting an error by decoding the dedicated data channel signal output from the DPDCH two-dimensional despreading means,
The selection means includes
When the error detection result detected by the error detection means is worse, a candidate having a smaller time direction spreading factor is preferentially selected as the time direction spreading factor candidate, and the error detected by the error detection means is selected. The radio communication apparatus according to claim 1, wherein a candidate having a larger spreading factor in the time direction is preferentially selected as the candidate for the spreading factor in the time direction as the detection result is better. Selecting a spreading factor candidate in the time direction of the dedicated control channel signal included in the received two-dimensional spread OFDM-CDMA signal based on information on the channel state;
The frequency direction spreading factor candidate determined from the selected time direction spreading factor candidate and a predetermined two-dimensional spreading factor for the dedicated control channel signal, and the time direction spreading factor candidate Two-dimensional despreading of the individual control channel signal;
Determining a spreading factor in the time direction actually used from the spreading factor candidates in the time direction based on a despreading result obtained by two-dimensional despreading;
Spreading in the frequency direction of the dedicated data channel signal using the two-dimensional spreading factor of the dedicated data channel signal notified by the dedicated control channel signal and the spreading factor in the time direction determined by the determining means Calculating a rate;
Using the determined spreading factor in the time direction and the calculated spreading factor in the frequency direction of the dedicated data channel signal, the dedicated data channel signal included in the received two-dimensional spread OFDM-CDMA signal is two-dimensionally despread. And a process of
A wireless communication method comprising:

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