The present invention relates to a radio base station apparatus and radio communication method in a next-generation mobile communication system.
Aiming at improvements in frequency utilization efficiency and data rates of a UMTS (Universal Mobile Telecommunications System) network, HSDPA (High Speed Downlink Packet Access) or HSUPA (High Speed Uplink Packet Access) is being adopted to make the most of features of a W-CDMA (Wideband Code Division Multiple Access)-based system. For this UMTS network, Long Term Evolution (LTE) is being studied for the purpose of achieving a faster data rate and lower delay or the like (Non-Patent Document 1). As a multiplexing scheme, LTE uses OFDMA (Orthogonal Frequency Division Multiple Access) which is different from W-CDMA for a downlink and uses SC-FDMA (Single Carrier Frequency Division Multiple Access) for an uplink.
An uplink signal transmitted via an uplink is transmitted from a mobile terminal apparatus to a radio base station apparatus as shown in
PUCCH adopts a sub-frame configuration which differs between CQI and ACK/NACK (
When uplink control channel signals of a plurality of users are multiplexed in a PUCCH, the uplink control channel signals are orthogonally multiplexed so that the radio base station apparatus can separate the uplink control channel signals for different users. Examples of such an orthogonal multiplexing method include an orthogonal multiplexing method using a cyclic shift of a CAZAC (Constant Amplitude Zero Auto Correlation) code sequence and an orthogonal multiplexing method using block spreading.
The orthogonal multiplexing method using a cyclic shift of a CAZAC code sequence is an orthogonal multiplexing method taking advantage of the fact that sequence CAZAC#1(Δp) which is a CAZAC code sequence of a code length of L cyclically shifted by Δp and sequence CAZAC#1(Δq) which is a CAZAC code sequence cyclically shifted by Δq are orthogonal to each other. Therefore, by modulating SC-FDMA symbols with which control information is multiplexed using a CAZAC code sequence of a different cyclic shift amount, this method causes uplink control channel signals to be orthogonally multiplexed for different users. For example, as shown in
The orthogonal multiplexing method using block spreading is an orthogonal multiplexing method using orthogonal codes. Therefore, this method applies spread spectrum modulation to SC-FDMA symbols using orthogonal codes and maps the spread signals to the SC-FDMA symbols. For example, as shown in
According to an orthogonal multiplexing method using cyclic shifts of a CAZAC code sequence, the number of multiplexed users is determined by the number of cyclic shifts within one SC-FDMA symbol, the number of multiplexed users is typically 6 and a maximum of 12. On the other hand, according to an orthogonal multiplexing method using block spreading, the number of multiplexed users is determined by the number of SC-FDMA symbols with which control information within one slot is multiplexed and the number of multiplexed users is a maximum of 5. In this way, according to the orthogonal multiplexing method using cyclic shifts of a CAZAC code sequence, it is basically assumed that the number of users that can be multiplexed can be increased by increasing the number of cyclic shifts.
However, in the case of the orthogonal multiplexing method using cyclic shifts of a CAZAC code sequence, when the delay spread is large relative to the cyclic shift length, a correlation between CAZAC code sequences increases and orthogonality is lost. For this reason, required average receiving power for satisfying required receiving quality on the radio base station apparatus side increases and its reception characteristic deteriorates.
The present invention has been implemented in view of the above described problems and it is an object of the present invention to provide a radio base station apparatus and radio communication method whose reception characteristic does not deteriorate even when the number of multiplexed users of an uplink control channel signal is increased.
The radio base station apparatus of the present invention includes receiving section configured to receive an uplink control channel signal orthogonally multiplexed among users including reference signals and demodulation section configured to demodulate the uplink control channel signal using maximum likelihood detection.
The radio communication method of the present invention includes a transmission step of a mobile terminal apparatus transmitting an uplink control channel signal orthogonally multiplexed among users including reference signals, a reception step of a radio base station apparatus receiving the uplink control channel signal and a demodulation step of demodulating the uplink control channel signal using maximum likelihood detection.
According to the present invention, the mobile terminal apparatus transmits an uplink control channel signal orthogonally multiplexed among users including reference signals and the radio base station apparatus receives the uplink control channel signal, demodulates the uplink control channel signal using maximum likelihood detection, and therefore the reception characteristic does not deteriorate even when the number of multiplexed users of the uplink control channel signal is increased.
a) and (b) are diagrams illustrating a sub-frame configuration of an uplink control channel signal;
a) is a diagram illustrating orthogonal multiplexing by cyclic shifts using a CAZAC code sequence and
a) and (b) are diagrams illustrating a configuration of a maximum likelihood detection section of the radio base station apparatus;
Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
The present embodiment will describe a case where uplink control information is user-multiplexed using an orthogonal multiplexing method using cyclic shifts of a CAZAC code sequence.
The BCH signal generation section 401 generates a BCH signal including broadcast information to be broadcast from the radio base station apparatus. The BCH signal generation section 401 outputs the BCH signal to the OFDM signal generation section 403. The BCH signal includes a CAZAC number indicating a CAZAC code sequence, a resource block number indicating a resource block (RB) to which an uplink control channel is mapped and a cyclic shift number corresponding to a cyclic shift amount or the like.
The downlink L1/L2 control signal generation section 402 generates a downlink L1/L2 control signal to be transmitted through a downlink control channel (PDCCH: Physical Downlink Control Channel). The downlink L1/L2 control signal generation section 402 outputs the downlink L1/L2 control signal to the OFDM signal generation section 403. The downlink L1/L2 control signal includes a CAZAC number indicating a CAZAC code sequence, a resource block number indicating a resource block (RB) to which the uplink control channel is mapped and a cyclic shift number corresponding to a cyclic shift amount or the like.
The CAZAC number, resource block number and cyclic shift number may also be transmitted to the mobile terminal apparatus through a BCH or may be transmitted to the mobile terminal apparatus through a PDCCH. Alternatively, the CAZAC number, resource block number and cyclic shift number may also be reported to the mobile terminal apparatus through a higher layer.
The OFDM signal generation section 403 applies discrete Fourier transform (DFT) to a downlink signal including at least the BCH signal and downlink L1/L2 control signal, maps the downlink signal to subcarriers, applies inverse fast Fourier transform (IFFT) thereto, adds a CP (Cyclic prefix) thereto and thereby generates a downlink OFDM signal.
The processing section of reception system includes a CP removing section 404 that removes a CP from a received signal, a cyclic shift separating section 405 that separates an orthogonally multiplexed received signal using a cyclic shift number, an FFT section 406 that applies fast Fourier transform (FFT) to the separated received signal, a subcarrier demapping section 407 that demaps the signal after the FFT, an IDFT section 408 that applies inverse discrete Fourier transform (IDFT) to the demapped signal, a despreading section 409 that dispreads the signal after the IDFT using a CAZAC number and a maximum likelihood detection section 410 that performs maximum likelihood detection using the despread signal.
The CP removing section 404 removes a portion corresponding to a CP from the received signal and extracts a valid signal portion. The CP removing section 404 outputs the signal after the CP removal to the cyclic shift separating section 405.
Using cyclic shift numbers, the cyclic shift separating section 405 separates the received signal orthogonally multiplexed using cyclic shifts. An uplink control channel signal from the mobile terminal apparatus is cyclically shifted by a cyclic shift amount which differs from one user to another. Therefore, by cyclically shifted in a reverse direction by the same cyclic shift amount as the cyclically shifted amount by the mobile terminal apparatus, it is possible to obtain an uplink control channel signal not cyclically shifted. The cyclic shift amount varies from one user to another and is associated with a cyclic shift number. For this reason, the cyclic shift separating section 405 applies the cyclic shift in the reverse direction using a cyclic shift amount corresponding to the cyclic shift number. In this way, it is possible to separate a signal (uplink control channel signal) of a user corresponding to the cyclic shift number. The cyclic shift separating section 405 outputs the separated signal to the FFT section 406.
The FFT section 406 applies FFT to the separated received signal to transform the signal to a frequency domain signal. The FFT section 406 outputs the signal after FFT to the subcarrier demapping section 407.
The subcarrier demapping section 407 extracts the uplink control channel signal from the frequency domain signal. The subcarrier demapping section 407 extracts the uplink control channel signal using a resource block number to which the uplink control channel signal is assigned. The subcarrier demapping section 407 outputs the extracted uplink control channel signal to the IDFT section 408.
The IDFT section 408 applies IDFT to the extracted uplink control channel signal to transform the signal into a time domain signal. Furthermore, the IDFT section 408 outputs the signal transformed into the time domain to the despreading section 409.
The despreading section 409 despreads the signal after IDFT using a CAZAC number. Therefore, the despreading section 409 identifies a CAZAC code sequence from the CAZAC number corresponding to the CAZAC code sequence, dispreads the signal after IDFT using the CAZAC code sequence and obtains an SC-FDMA symbol. The despreading section 409 outputs the obtained SC-FDMA symbol to the maximum likelihood detection section 410.
The maximum likelihood detection section 410 performs maximum likelihood detection (demodulation) on the signal after IDFT. The maximum likelihood detection section 410 performs maximum likelihood detection on the despread SC-FDMA symbol. As shown in
In the maximum likelihood detection section 410 in the configuration shown in
The maximum likelihood detection section 410 may also have a configuration shown in
In the maximum likelihood detection section 410 in the configuration shown in
By performing maximum likelihood detection in this way, a CQI (Channel Quality Indicator) bit sequence which is a transmission bit sequence (control signal) or ACK/NACK bit is obtained.
The CAZAC code generation section 601 prepares a CAZAC code sequence corresponding to a CAZAC number assigned to the user. The CAZAC code generation section 601 outputs the prepared CAZAC code sequence to the block modulation section 602.
The block modulation section 602 modulates every predetermined number of symbols (block) using the CAZAC code sequence. That is, assuming a predetermined number of SC-FDMA symbols as one block, the block modulation section 602 performs modulation on this unit block using the CAZAC code sequence. To be more specific, individual SC-FDMA symbols are multiplied by individual codes of the CAZAC code sequence. The block modulation section 602 outputs the block modulated signal to the subcarrier mapping section 604.
The subcarrier mapping section 604 maps a frequency domain signal to a subcarrier. Using a resource block number to which the uplink control channel signal is assigned, the subcarrier mapping section 604 maps the uplink control channel signal to a subcarrier of a resource block having the resource block number. The subcarrier mapping section 604 outputs the mapped uplink control channel signal to the IFFT section 605.
The IFFT section 605 applies IFFT to the mapped signal to transform the signal into a time domain signal. The IFFT section 605 outputs the signal after the IFFT to the cyclic shift section 606.
The cyclic shift section 606 shifts the time domain signal by a predetermined cyclic shift amount. The order of the SC-FDMA symbols included in the unit block is shifted by this cyclic shift. The cyclic shift amount differs from one user to another and is associated with the cyclic shift number. The cyclic shift section 606 outputs the cyclically shifted signal to the CP adding section 607.
CP adding section 607 adds a CP to the cyclically shifted signal. A transmission signal including the uplink control channel signal is thereby generated.
The processing section of reception system includes an OFDM signal receiving section 608 that receives an OFDM signal, a BCH signal receiving section 609 that receives a BCH signal, a downlink L1/L2 control signal receiving section 610 that receives a downlink control signal (L1/L2 control signal), a CQI estimation section 611 that estimates CQI using reference signals included in the downlink signal and a determining section 612 that determines whether or not the received downlink shared data channel signal has been received without errors.
The OFDM signal receiving section 608 receives a downlink OFDM signal and separates the downlink OFDM signal into signals of their respective channels. That is, the OFDM signal receiving section 608 removes a CP from the downlink OFDM signal, applies fast Fourier transform, performs demapping from subcarriers and performs inverse discrete Fourier transform. This received signal is outputted to the BCH signal receiving section 609 and the downlink L1/L2 control signal receiving section 610. Furthermore, the reference signals are outputted to the CQI estimation section 611 and the downlink shared data channel signal is outputted to the determining section 612.
The BCH signal receiving section 609 receives a BCH signal including broadcast information to be broadcast from the radio base station apparatus. When this BCH signal includes a CAZAC number indicating a CAZAC code sequence, a resource block number indicating a resource block (RB) to which an uplink control channel is mapped and a cyclic shift number corresponding to the cyclic shift amount, the BCH signal receiving section 609 outputs the CAZAC number to the CAZAC code generation section 601, outputs the resource block number to the subcarrier mapping section 604 and outputs the cyclic shift number to the cyclic shift section 606.
The downlink L1/L2 control signal receiving section 610 receives the downlink L1/L2 control signal transmitted through the downlink control channel. When the downlink L1/L2 control signal includes a CAZAC number indicating a CAZAC code sequence, a resource block number indicating a resource block (RB) to which the uplink control channel is mapped and a cyclic shift number corresponding to the cyclic shift amount or the like, the BCH signal receiving section 609 outputs the CAZAC number to the CAZAC code generation section 601, outputs the resource block number to the subcarrier mapping section 604 and outputs the cyclic shift number to the cyclic shift section 606.
The CQI estimation section 611 estimates CQI used for scheduling or adaptive control in the radio base station apparatus using reference signals and generates a CQI bit sequence. The CQI estimation section 611 outputs the CQI bit sequence to the block modulation section 602.
The determining section 612 determines whether or not the received downlink shared data channel signal (PDSCH signal) has been received without errors or even when there is an error, whether or not the error is within an allowable range and outputs the determination result. The determination result is expressed with acknowledgement information indicating an affirmative response (ACK bit) or negative response (NACK bit). The determining section 612 outputs the ACK/NACK bit to the block modulation section 602.
A radio communication method according to the present invention using the radio base station apparatus and the mobile terminal apparatus in the above described configuration will be described. In the radio communication method according to the present invention, the mobile terminal apparatus transmits an uplink control channel signal including reference signals orthogonally multiplexed among users, the radio base station apparatus receives the uplink control channel signal and demodulates the uplink control channel signal using maximum likelihood detection. A case will be described here where CQI information having the sub-frame configuration shown in
First, the BCH signal generation section 401 of the radio base station apparatus generates a BCH signal including a CAZAC number, resource block number and cyclic shift number. This BCH signal is broadcast to the mobile terminal apparatus by OFDM signal generation section 403 as a downlink OFDM signal. In the mobile terminal apparatus, when the OFDM receiving section 608 receives the downlink OFDM signal, the BCH signal receiving section 609 extracts the CAZAC number, resource block number and cyclic shift number, outputs the CAZAC number to the CAZAC code generation section 601, outputs the resource block number to the subcarrier mapping section 604 and outputs the cyclic shift number to the cyclic shift section 606.
The CAZAC code generation section 601 of the mobile terminal apparatus prepares a CAZAC code sequence corresponding to the CAZAC number and the block modulation section 602 modulates CQI information which is control information with the CAZAC code sequence. This CQI information is a CQI bit sequence estimated by CQI estimation section 611 using reference signals included in the downlink signal.
Next, the subcarrier mapping section 604 maps block-modulated signals to subcarriers corresponding to respective resource block numbers and the IFFT section 605 applies IFFT to the mapped signal to transform the signal into a time domain signal.
Next, the cyclic shift section 606 applies a cyclic shift corresponding to the cyclic shift number to the signal after the IFFT. In this case, since different cyclic shifts are applied to different users, control information (CQI information) is orthogonally multiplexed among users. Next, the CP adding 607 adds a CP to the cyclically shifted signal and this signal is transmitted to the radio base station apparatus as an uplink control channel signal.
The radio base station apparatus receives the uplink control channel signal orthogonally multiplexed among users and the CP removing section 404 removes the CP from the received signal. Next, the cyclic shift separating section 405 applies the cyclic shift amount corresponding to the cyclic shift number to the signal after the CP removal in the direction opposite to the direction in which the cyclic shift is applied in the mobile terminal apparatus. An uplink control channel signal not cyclically shifted is thereby obtained. Next, the FFT section 406 applies FFT to the user-separated signal to transform the signal into a frequency domain signal, the subcarrier demapping section 407 performs demapping from a subcarrier corresponding to the resource block number and the IDFT section 408 applies IDFT to the demapped signal to transform the signal into a time domain signal.
Next, the despreading section 409 despreads the signal after the IDFT using the CAZAC code sequence corresponding to the CAZAC number and obtains received SC-FDMA symbols. Next, the maximum likelihood detection section 410 performs maximum likelihood detection on the received SC-FDMA symbols and reproduces the most likely CQI information. The radio base station apparatus performs scheduling or adaptive control using the reproduced CQI information.
Thus, by applying maximum likelihood detection to the uplink control channel signal orthogonally multiplexed using the cyclic shift of the CAZAC code sequence, it is possible to prevent the reception characteristics from deteriorating even when the number of multiplexed users is increased in an environment in which the delay spread is greater than the length of cyclic shift. A case has been described above where control information is CQI information, but the present invention is likewise applicable to a case where the control information is ACK/NACK information which is retransmission necessity/unnecessity determination result of a PDSCH signal.
The present embodiment will describe a case where uplink control information is user-multiplexed according to an orthogonal multiplexing method using block spreading.
Embodiment 1 has described a case with an orthogonal multiplexing method using a cyclic shift of a CAZAC code sequence, but the technical thought of the present invention is also applicable to a case where uplink control information is user-multiplexed according to the orthogonal multiplexing method using block spreading.
When transmitting multi-bit information, a large coding gain of error correcting coding is generally preferable from the standpoint of widening coverage of a cell. This is because when the error correcting coding gain is large, transmission power necessary to achieve required quality can be reduced. In the case of the orthogonal multiplexing method using the CAZAC code sequence in Embodiment 1, the channel coding rate when information bits transmitted in one sub-frame are assumed to be 10 bits depends on the number of SC-FDMA symbols with which information data within one slot is multiplexed. For example, in the sub-frame configuration shown in
The processing section of reception system includes a CP removing section 704 that removes a CP from a received signal, a block despreading section 705 that dispreads the orthogonally multiplexed received signal with a spreading code corresponding to a block spreading code number, an FFT section 706 that applies FFT to the despread signal, a subcarrier demapping section 707 that demaps the signal after the FFT, an IDFT section 708 that applies IDFT to the demapped signal and a maximum likelihood detection section 709 that performs maximum likelihood detection using the signal after the IDFT. Since the CP removing section 704, FFT section 706, subcarrier demapping section 707, IDFT section 708 and maximum likelihood detection section 709 are identical to the CP removing section 404, FFT section 406, subcarrier demapping section 407, IDFT section 408 and maximum likelihood detection section 410 in Embodiment 1, detailed descriptions thereof will be omitted.
Using a block spreading code number, the block despreading section 705 separates the received signal orthogonally multiplexed using a block spreading code. The uplink control channel signal from the mobile terminal apparatus is subjected to spread spectrum modulation using different block spreading codes for different users. Therefore, it is possible to obtain an uplink control channel signal not subjected to spread spectrum modulation by despreading the signal with the same block spreading code as the block spreading code used for spread spectrum modulation in the mobile terminal apparatus. The block spreading code differs from one user to another and is associated with a block spreading code number. For this reason, the block despreading section 705 performs despreading using a block spreading code corresponding to the block spreading code number. This allows a signal (uplink control channel signal) of a user corresponding to the block spreading number to be separated. The block despreading section 705 outputs the separated signal to the FFT section 706.
The channel coding section 801 performs error correcting coding on a bit sequence representing control information. The channel coding section 801 outputs the signal after the error correcting coding to the data modulation section 802. The data modulation section 802 data-modulates the bit sequence after the error correcting coding. The data modulation section 802 outputs the data-modulated signal to the DFT section 803. The channel coding scheme and data modulation scheme are reported from the radio base station apparatus beforehand.
The block spreading section 806 performs spread spectrum modulation on the time domain signal using a block spreading code. The block spreading code differs from one user to another and is associated with a block spreading code number. The block spreading section 806 outputs the signal subjected to spread spectrum modulation to the CP adding section 807.
The processing section of reception system includes an OFDM signal receiving section 808 that receives an OFDM signal, a BCH signal receiving section 809 that receives a BCH signal, a downlink L1/L2 control signal receiving section 810 that receives a downlink control signal (L1/L2 control signal), a CQI estimation section 811 that estimates CQI using reference signals included in a downlink signal and a determining section 812 that determines whether or not the received downlink shared data channel signal has been received without errors. Since the OFDM receiving section 808, BCH signal receiving section 809, downlink L1/L2 control signal receiving section 810, CQI estimation section 811 and determining section 812 are identical to the OFDM receiving section 608, BCH signal receiving section 609, downlink L1/L2 control signal receiving section 610, CQI estimation section 611 and determining section 612 in Embodiment 1 respectively, detailed descriptions thereof will be omitted.
The radio communication method according to the present invention using the radio base station apparatus and the mobile terminal apparatus in the above described configuration will be described. Here, a case will be described where CQI information having the sub-frame configuration shown in
First, the BCH signal generation section 701 of the radio base station apparatus generates a BCH signal including a resource block number and block spreading code number. This BCH signal is broadcast to the mobile terminal apparatus by the OFDM signal generation section 703 as a downlink OFDM signal. In the mobile terminal apparatus, when the OFDM receiving section 808 receives a downlink OFDM signal, the BCH signal receiving section 809 extracts the resource block number and block spreading code number, outputs the resource block number to the subcarrier mapping section 804 and outputs the block spreading code number to the block spreading section 806.
In the mobile terminal apparatus, the channel coding section 801 applies error correcting coding to CQI information which is control information and the data modulation section 802 performs data modulation. This CQI information is a CQI bit sequence estimated by the CQI estimation section 811 using reference signals included in the downlink signal.
Next, the DFT section 803 applies DFT to the modulated signal to transform the signal into a frequency domain signal, the subcarrier mapping section 804 maps the signal after the DFT to a subcarrier corresponding to the resource block number and the IFFT section 805 applies IFFT to the mapped signal to transform the signal into a time domain signal.
Next, the block spreading section 806 applies spread spectrum modulation to the signal after the IFFT using a block spreading code. In this case, since different block spreading codes are used for different users, control information (CQI information) is orthogonally multiplexed among users. Next, the CP adding 807 adds a CP to the signal subjected to block spread spectrum modulation and this signal is transmitted to the radio base station apparatus as an uplink control channel signal.
The radio base station apparatus receives the uplink control channel signal orthogonally multiplexed among users and the CP removing section 704 removes the CP from the received signal. Next, the block despreading section 705 despreads the signal after the CP removal using a block spreading code corresponding to the block spreading code number. Thus, an uplink control channel signal not subjected to block spread spectrum modulation is obtained. Next, the FFT section 706 applies FFT to the user-separated signal to transform the signal into a frequency domain signal, the subcarrier demapping section 707 performs demapping from a subcarrier corresponding to the resource block number and the IDFT section 708 applies IDFT to the demapped signal to obtain time domain reception SC-FDMA symbols. Next, the maximum likelihood detection section 709 performs maximum likelihood detection on the reception SC-FDMA symbols to reproduce the most likely CQI information. The radio base station apparatus performs scheduling and adaptive control using the reproduced CQI information.
Thus, maximum likelihood detection is also applicable to the uplink control channel signal orthogonally multiplexed using block spreading. In this case, it is possible to increase the coding gain and reduce transmission power necessary to achieve required quality. A case has been described above where control information is CQI information, but the present invention is likewise applicable to a case where control information is ACK/NACK information which is a retransmission necessity/unnecessity determination result of a PDSCH signal.
The present embodiment will describe a case where uplink control information is user-multiplexed by switching between an orthogonal multiplexing method using a cyclic shift of a CAZAC code sequence and an orthogonal multiplexing method using block spreading.
In an environment in which a delay spread is relatively small, orthogonal multiplexing using block spreading has a large coding gain, and can thereby reduce required receiving power to satisfy required receiving quality compared to orthogonal multiplexing using a cyclic shift. On the other hand, in an environment in which the delay spread is relatively large, orthogonal multiplexing using a cyclic shift can reduce required receiving power to satisfy required receiving quality compared to orthogonal multiplexing using the block spreading. This is because while orthogonal multiplexing using the block spreading realizes orthogonality in slot units, orthogonal multiplexing using a cyclic shift realizes orthogonality in SC-FDMA symbol units.
Thus, the present embodiment will describe a case where the delay spread is determined and the orthogonal multiplexing method for an uplink control channel signal is switched according to the determination result. That is, the orthogonal multiplexing method using block spreading is applied when the delay spread is small and the orthogonal multiplexing method using a cyclic shift is applied when the delay spread is large.
The sequence of orthogonal multiplexing using a cyclic shift of the processing section of reception system includes a CP removing section 904 that removes a CP from a received signal, a cyclic shift separating section 905 that separates the orthogonally multiplexed received signal using a cyclic shift number, an FFT section 906 that applies FFT to the separated received signal, a subcarrier demapping section 907 that demaps the signal after the FFT, an IDFT section 908 that applies IDFT to the demapped signal, a despreading section 909 that performs despreading on the signal after the IDFT using a CAZAC number and a maximum likelihood detection section 910 that performs maximum likelihood detection using the despread signal. Since the CP removing section 904, cyclic shift separating section 905, FFT section 906, subcarrier demapping section 907, IDFT section 908, despreading section 909 and maximum likelihood detection section 910 are identical to the CP removing section 404, cyclic shift separating section 405, FFT section 406, subcarrier demapping section 407, IDFT section 408, despreading section 409 and maximum likelihood detection section 410 of Embodiment 1 respectively, detailed descriptions thereof will be omitted.
The sequence of orthogonal multiplexing using block spreading of the processing section of reception system includes a CP removing section 911 that removes a CP from a received signal, a block despreading section 912 that despreads the orthogonally multiplexed received signal using a spreading code corresponding to a block spreading code number, an FFT section 913 that applies FFT to the despread signal, a subcarrier demapping section 914 that demaps the signal after the FFT, an IDFT section 915 that applies IDFT to the demapped signal and a maximum likelihood detection section 916 that performs maximum likelihood detection using the signal after the IDFT. Since the CP removing section 911, block despreading section 912, FFT section 913, subcarrier demapping section 914, IDFT section 915 and maximum likelihood detection section 916 are identical to the CP removing section 704, block despreading section 705, FFT section 706, subcarrier demapping section 707, IDFT section 708 and maximum likelihood detection section 709 in Embodiment 2 respectively, detailed descriptions thereof will be omitted.
The radio base station apparatus is provided with a delay spread determining section 918 that detects a delay spread and determines the level of the delay spread and a SW 919 that switches the processing section of reception system according to the level determination result of the delay spread. Here, as for the delay spread, the delay spread is detected using a reference signal included in an uplink signal and the level of the delay spread is determined through a comparison with a predetermined threshold. The information of the determination result, that is, switching information is outputted to the SW 919 and used as information for switching the processing section of reception system (orthogonally multiplexed sequence using a cyclic shift, orthogonally multiplexed sequence using block spreading). The separation scheme for the orthogonally multiplexed uplink control channel signal is thereby switched. The processing by the respective processing sections of reception system is the same as that of Embodiments 1 and 2.
Furthermore, the information of this determination result is included in a BCH signal, reported to the mobile terminal apparatus and used as information for switching the processing section of transmission system. This switching information may also be reported to the mobile terminal apparatus through a downlink L1/L2 control channel or may be reported to the mobile terminal apparatus via a higher layer.
The sequence of orthogonal multiplexing using a cyclic shift of the processing section of transmission system includes a CAZAC code generation section 1008 that generates a CAZAC code sequence corresponding to a CAZAC number, a block modulation section 1009 that modulates every predetermined number of symbols (block) using the CAZAC code sequence, a subcarrier mapping section 1011 that maps the signal after the block modulation to subcarriers, an IFFT section 1012 that applies IFFT to the mapped signal, a cyclic shift section 1013 that assigns a cyclic shift to the signal after the IFFT and a CP adding section 1014 that adds a CP to the signal assigned the cyclic shift. Since the CAZAC code generation section 1008, block modulation section 1009, subcarrier mapping section 1011, IFFT section 1012, cyclic shift section 1013 and CP adding section 1014 are identical to the CAZAC code generation section 601, block modulation section 602, subcarrier mapping section 604, IFFT section 605, cyclic shift section 606 and CP adding section 607 of Embodiment 1 respectively, detailed descriptions thereof will be omitted.
The processing section of reception system includes an OFDM signal receiving section 1015 that receives an OFDM signal, a BCH signal receiving section 1016 that receives a BCH signal, a downlink L1/L2 control signal receiving section 1017 that receives a downlink control signal (L1/L2 control signal), a CQI estimation section 1018 that estimates CQI using reference signals included in the downlink signal, a determining section 1019 that determines whether or not the received downlink shared data channel signal has been received without errors. Since the OFDM receiving section 1015, BCH signal receiving section 1016, downlink L1/L2 control signal receiving section 1017, CQI estimation section 1018 and determining section 1019 are identical to the OFDM receiving section 608, BCH signal receiving section 609, downlink L1/L2 control signal receiving section 610, CQI estimation section 611 and determining section 612 in Embodiment 1 respectively, detailed descriptions thereof will be omitted.
The mobile terminal apparatus is provided with a SW 1020 that switches the processing section of transmission system according to switching information generated based on a delay spread detected by the radio base station apparatus. The switching information as a result of determination of the level of the delay spread in the radio base station apparatus is received with a BCH signal by the mobile terminal apparatus and outputted to the SW 1020. The of transmission system processing section (orthogonally multiplexed sequence using a cyclic shift, orthogonally multiplexed sequence using block spreading) is switched according to this switching information. The processing by the respective processing sections of transmission system is similar to that in Embodiments 1 and 2. Furthermore, this switching information may be reported through a downlink L1/L2 control channel or reported via a higher layer.
Thus, the radio communication method according to the present embodiment can appropriately select an orthogonal multiplexing method with low required receiving power to satisfy the required receiving quality according to the level of the delay spread.
Although a case has been described above where the orthogonal multiplexing method is selected according to the level of the delay spread, the present invention is not limited to this, but is also applicable to a case of switching between the orthogonally multiplexed sequence using a cyclic shift and the orthogonally multiplexed sequence using block spreading according to requirements for the number of multiplexed users. That is, the orthogonally multiplexed sequence using a cyclic shift is selected when the number of multiplexed users exceeds a threshold, while the orthogonally multiplexed sequence using block spreading is selected when the number of multiplexed users is equal to or below the threshold. The radio base station apparatus determines the number of multiplexed users and the determination result is reported to the mobile terminal apparatus as switching information as described above.
The present invention is not limited to the above-described embodiments, and can be implemented with various changes. For example, the number of processing sections and the processing procedure in the above description can be changed as appropriate without departing from the scope of the present invention. Furthermore, the elements illustrated in the drawings represent functions and each function block may be implemented by hardware or by software. In addition, the present invention may be implemented with other various changes as appropriate without departing from the scope of the present invention.
The present application is based on Japanese Patent Application No. 2009-002063 filed on Jan. 7, 2009, entire content of which is expressly incorporated by reference herein.
Number | Date | Country | Kind |
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2009-002063 | Jan 2009 | JP | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/JP2010/050044 | 1/6/2010 | WO | 00 | 9/13/2011 |