JP3806389B2 - Receiver - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a receiving apparatus.
[0002]
[Prior art]
In recent years, in a wireless communication system, a CDMA (Code Division Multiple Access) method has attracted attention as a multiple access method for a plurality of mobile stations to communicate simultaneously using the same frequency band. The CDMA system can achieve higher frequency utilization efficiency than technologies such as the FDMA (Frequency Division Multiple Access) system and the TDMA (Time Division Multiple Access) system. Many users can be accommodated.
[0003]
Further, as a transmission method for transmitting signals in both directions of uplink and downlink between a mobile station and a base station in a wireless communication system, an FDD (Frequency Division Duplex) method and a TDD (Time Division Duplex: Time division multiplexing). The FDD system is a system that uses different frequency bands for the uplink and the downlink, whereas the TDD system is a transmission and reception same band system, and the same radio frequency is time-divisionally communicated between the uplink and the downlink alternately. It is a method to do. Therefore, in the CDMA / TDD system, transmission signal processing is performed by the CDMA system, and uplink and downlink transmissions are performed by the TDD system.
[0004]
FIG. 6 is a diagram illustrating an example of a signal frame configuration in a wireless communication system using the CDMA / TDD scheme. As shown in the figure, one frame is composed of a plurality of slots each consisting of one pilot symbol block, two information symbol blocks, and one guard symbol block. That is, in one slot, the pilot symbol block Pi (i = 1 to n) is sandwiched between the information symbol block Ii1 (i = 1 to n) and the information symbol block Ii2 (i = 1 to n). Thereafter, guard symbol blocks Gi (i = 1 to n) are arranged.
[0005]
Each pilot symbol block Pi is composed of a known symbol string having a predetermined length (for example, 10 symbols). Each information block Ii1 and Ii2 has a predetermined number (maximum 61 symbols) of information symbols. Each guard symbol block Gi is composed of a symbol string having no information and having a predetermined length (for example, two symbols). The signal configured in this way is subjected to information modulation by, for example, QPSK modulation in a transmission side apparatus such as a base station, and then spread-modulated with a predetermined spreading code and transmitted to a reception side apparatus such as a mobile station.
[0006]
Specifically, as described in Non-Patent Document 1, for example, the transmission bit sequence is mapped to symbol positions as shown in FIG. 7 by performing QPSK modulation, and symbol data is obtained. The symbol data is transmitted after being subjected to a phase rotation in accordance with the channelization code assigned to each receiving-side apparatus that is a transmission partner and subjected to spreading processing.
[0007]
Then, the transmission signal is received by the receiving side device and despread by using the channelization code. Also, channel estimation is performed by using the pilot symbol block Pi included in the reception signal, and synchronous detection of the reception signal is performed by using the despread result and the channel estimation result. Further, the synchronous detection result is RAKE-combined, and phase rotation corresponding to the channelization code is added.
[0008]
The symbol data obtained by the above processing is demapped to symbol positions as shown in FIG. Here, when turbo decoding and Viterbi decoding are performed on the symbol data, each bit included in the symbol data needs to be output as a soft decision value, so the symbol data is (−π / 4). By rotating the phase, the I-axis component is used as the soft decision value of the first bit among the two bits demapped to the symbol position as shown in FIG. A Q-axis component is used as the determination value.
[0009]
[Non-Patent Document 1]
3GPP standard TS25.223 "3rd Generation Partnership Project; Technical Specification Group Radio Access Network; Spreading and modulation (TDD)"
[0010]
[Problems to be solved by the invention]
However, the above-described receiving-side apparatus has a problem that the amount of calculation becomes large because it is necessary to apply phase rotation to all symbol data.
[0011]
For example, in the case of the above-described slot configuration, the number of symbols of the information symbol block Ii1 and the information symbol block Ii2 is 122 (61 × 2) at the maximum, and the calculation for applying phase rotation to all these symbols is enormous. Amount.
[0012]
The present invention has been made in view of this point, and an object of the present invention is to provide a receiving apparatus that can efficiently convert symbol data into a received bit sequence with a small amount of calculation.
[0013]
[Means for Solving the Problems]
The receiving apparatus of the present invention uses channel estimation means for obtaining a channel estimation value using a received signal, phase rotation means for phase rotating the channel estimation value, and a corrected channel estimation value obtained by phase rotation. have a, synchronous detection means for synchronously detecting the received signal, the phase rotation means, the configuration of a phase rotation amount of phase rotation by the channel estimation value determined in accordance with the channelization code assigned to the own device take.
[0014]
According to this configuration, since the channel estimation value is phase-rotated and the received signal is synchronously detected using the obtained corrected channel estimation value, the channel estimation value is smaller than the number of symbols included in the reception signal. It is only necessary to perform phase rotation calculation, and symbol data can be efficiently converted into a received bit sequence with a small amount of calculation. Furthermore, since the channel estimation value is phase-rotated by the phase rotation amount determined according to the channelization code, the phase rotation necessary to obtain the received bit sequence from the spread-modulated received signal in the CDMA system can be efficiently performed with a small amount of computation. Can be done well.
[0023]
The radio communication terminal apparatus of the present invention employs a configuration having the receiving apparatus.
[0024]
According to this configuration, the same function and effect as those of the receiving device can be realized in the wireless communication terminal device.
[0025]
The radio communication base station apparatus of the present invention employs a configuration having the receiving apparatus.
[0026]
According to this configuration, the same operational effects as those of the receiving apparatus can be realized in the radio communication base station apparatus.
[0029]
DETAILED DESCRIPTION OF THE INVENTION
The gist of the present invention is to eliminate the need for phase rotation during demodulation by performing synchronous detection of a despread signal using a channel estimation result to which phase rotation has been added.
[0030]
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0031]
(Embodiment 1)
FIG. 1 is a block diagram showing a main configuration of the receiving apparatus according to Embodiment 1 of the present invention. The receiving apparatus shown in the figure includes a despreading section 110, a synchronous detection section 120, a RAKE combining section 130, a phase rotation section 140, a QPSK demapping section 150 comprising a P / S (parallel / serial) conversion section 152, a channel estimation section. 160 and an estimated value correction unit 170.
[0032]
The despreading unit 110 performs despreading processing on a signal received via an antenna using a channelization code assigned to the own device.
[0033]
The synchronous detection unit 120 performs synchronous detection on the despread signal obtained by despreading the received signal using the correction channel estimation value output from the estimation value correction unit 170.
[0034]
The RAKE combining unit 130 performs RAKE combining of the synchronously detected signals.
[0035]
The phase rotation unit 140 adds phase rotation to the RAKE-combined signal by a phase rotation amount W corresponding to the channelization code assigned to the receiving device.
[0036]
The QPSK demapping unit 150 demodulates the signal output from the phase rotation unit 140 and outputs a received bit sequence. Specifically, the QPSK demapping unit 150 demodulates the output signal of the phase rotation unit 140 that has been subjected to QPSK modulation, acquires bits of the I-axis component and the Q-axis component, and the P / S conversion unit 152 performs parallel / The received bit sequence is output by serial conversion.
[0037]
Channel estimation section 160 performs channel estimation using the signal received via the antenna, and outputs the obtained channel estimation value to estimated value correction section 170. Here, as many channel estimation values as the number of paths detected in the time corresponding to one slot are obtained as a result of channel estimation. That is, as shown in FIG. 2, for example, when four paths 1 to 4 are detected by channel estimation within one slot time, four channel estimation values are obtained.
[0038]
Estimated value correcting section 170 adds (π / 4) phase rotation to each channel estimated value output from channel estimating section 160. Therefore, as shown in FIG. 2, when four paths 1 to 4 are detected within one slot time, (π / 4) phase rotation is added to each of the four channel estimation values.
[0039]
Next, the operation of the receiving apparatus configured as described above will be described.
[0040]
First, the received signal received via the antenna is input to despreading section 110 and channel estimation section 160. Then, the despreading unit 110 uses the channelization code assigned to the device itself, despreads the received signal, and outputs the despread signal to the synchronous detection unit 120.
[0041]
On the other hand, channel estimation is performed by channel estimation unit 160, direct wave and delayed wave paths are detected, and channel estimation values in each path are output to estimated value correction unit 170. Channel estimation values in each path are respectively subjected to (π / 4) phase rotation by the estimation value correction unit 170, and the obtained correction channel estimation values are output to the synchronous detection unit 120.
[0042]
Here, since the number of paths detected within one slot time by the channel estimation unit 160 is very small compared to the number of symbols included in the received signal, the calculation of the phase rotation for the channel estimation value corresponding to each path is as follows: A small amount is enough.
[0043]
Then, the synchronous detector 120 performs synchronous detection of the despread signal by using the corrected channel estimation value. In this synchronous detection, a correction channel estimation value to which (π / 4) phase rotation is added is used, so that the signal after synchronous detection is obtained by adding (π / 4) phase rotation to each symbol. Is equivalent to
[0044]
The signal after the synchronous detection is RAKE combined by the RAKE combining unit 130 to obtain a RAKE combined signal in which signals corresponding to the respective paths are combined. The RAKE composite signal is subjected to phase rotation by the phase rotation unit 140 by the phase rotation amount W corresponding to the channelization code, demodulated by the QPSK demapping unit 150, and P / S converted. Parallel / serial conversion is performed by unit 152, and a received bit sequence composed of I-axis component and Q-axis component bits is output.
[0045]
As described in the above prior art, for example, in the signal having the frame configuration shown in FIG. 6, when the information symbol block Ii1 and the information symbol block Ii2 included in each slot are each composed of 61 symbols, the conventional technique has 122 symbols. On the other hand, it is necessary to apply (π / 4) phase rotation to the present embodiment. In the present embodiment, for example, as shown in FIG. 2, when four paths are detected within one slot time, four channels are detected. What is necessary is just to add ((pi) / 4) phase rotation with respect to an estimated value.
[0046]
As described above, according to the present embodiment, only the channel estimation value obtained within one slot time from the received signal is rotated by (π / 4) phase to obtain the correction channel estimation value, and the correction channel estimation value is used. Since the despread signal is synchronously detected, the symbol data can be efficiently converted to the received bit sequence with a smaller amount of computation than when the phase rotation is performed on each symbol of the RAKE-combined signal.
[0047]
(Embodiment 2)
A feature of the second embodiment of the present invention is that a phase rotation determined corresponding to the channelization code is added to the channel estimation value.
[0048]
FIG. 3 is a block diagram showing a main configuration of the receiving apparatus according to the second embodiment. In the figure, the same parts as those in FIG.
[0049]
3 includes a despreading section 110, a synchronous detection section 120, a RAKE combining section 130, a P / S conversion section 152, and a (−π / 4) phase shifter 154, a QPSK demapping section 150a, a channel An estimation unit 160 and an estimated value correction unit 210 are included.
[0050]
The QPSK demapping unit 150a demodulates the signal output from the RAKE combining unit 130 and outputs a received bit sequence. More specifically, the QPSK demapping unit 150a rotates and demodulates the output signal of the RAKE combining unit 130 subjected to QPSK modulation by (−π / 4) phase shifter 154 and demodulates it. The bits of the axis component and the Q-axis component are acquired, and parallel / serial conversion is performed by the P / S conversion unit 152 to output a received bit sequence.
[0051]
The estimated value correcting unit 210 adds a phase rotation to each channel estimated value output from the channel estimating unit 160 by a phase rotation amount W determined corresponding to the channelization code.
[0052]
Next, the operation of the receiving apparatus configured as described above will be described.
[0053]
First, the received signal received via the antenna is input to despreading section 110 and channel estimation section 160. Then, the despreading unit 110 uses the channelization code assigned to the device itself, despreads the received signal, and outputs the despread signal to the synchronous detection unit 120.
[0054]
On the other hand, channel estimation is performed by channel estimation unit 160, direct wave and delayed wave paths are detected, and channel estimation values in each path are output to estimated value correction unit 210. Channel estimation values in each path are subjected to phase rotation by an estimated value correction unit 210 by a phase rotation amount W determined corresponding to each channelization code, and the obtained corrected channel estimation values are output to the synchronous detection unit 120. Is done.
[0055]
Here, since the number of paths detected within one slot time by the channel estimation unit 160 is very small compared to the number of symbols included in the received signal, the calculation of the phase rotation for the channel estimation value corresponding to each path is as follows: A small amount is enough.
[0056]
Then, the synchronous detector 120 performs synchronous detection of the despread signal by using the corrected channel estimation value. In this synchronous detection, a correction channel estimation value obtained by adding phase rotation by the amount of phase rotation W is used, so that the signal after synchronous detection is obtained by adding phase rotation by the amount of phase rotation W to each symbol. Is equivalent to
[0057]
The signal after the synchronous detection is RAKE combined by the RAKE combining unit 130 to obtain a RAKE combined signal in which signals corresponding to the respective paths are combined. The RAKE composite signal is demodulated by (−π / 4) phase rotation by the (−π / 4) phase shifter 154 in the QPSK demapping unit 150 a and is also demodulated by the P / S conversion unit 152. Parallel / serial conversion is performed, and a received bit sequence including bits of the I-axis component and the Q-axis component is output.
[0058]
As described in the above prior art, for example, in the signal having the frame configuration shown in FIG. 6, when the information symbol block Ii1 and the information symbol block Ii2 included in each slot are each composed of 61 symbols, the conventional technique has 122 symbols. On the other hand, it is necessary to apply phase rotation by the amount of phase rotation W. In this embodiment, for example, when four paths are detected within one slot time as shown in FIG. 2, four channels are detected. What is necessary is just to add the phase rotation of the phase rotation amount W to the estimated value.
[0059]
Thus, according to the present embodiment, only the channel estimation value obtained within one slot time from the received signal is phase-rotated by the phase rotation amount determined corresponding to the channelization code to obtain the corrected channel estimation value. Since acquisition and synchronization detection of the despread signal is performed using the corrected channel estimation value, the received bit sequence can be efficiently received with a small amount of calculation compared to the case where phase rotation is performed on each symbol of the RAKE-combined signal. Can be converted to
[0060]
(Embodiment 3)
The feature of the third embodiment of the present invention is that both the phase rotation required in QPSK demapping and the phase rotation determined in accordance with the channelization code are added to the channel estimation value.
[0061]
FIG. 4 is a block diagram showing a main configuration of the receiving apparatus according to the third embodiment. In the figure, the same parts as those in FIG.
[0062]
4 includes a despreading section 110, a synchronous detection section 120, a RAKE combining section 130, a QPSK demapping section 150 including a P / S conversion section 152, a channel estimation section 160, and an estimated value correction section 310. is doing.
[0063]
Estimated value correcting section 310 adds a phase rotation amount W and (π / 4) phase rotation determined in accordance with the channelization code to each channel estimated value output from channel estimating section 160.
[0064]
Next, the operation of the receiving apparatus configured as described above will be described.
[0065]
First, the received signal received via the antenna is input to despreading section 110 and channel estimation section 160. Then, the despreading unit 110 uses the channelization code assigned to the device itself, despreads the received signal, and outputs the despread signal to the synchronous detection unit 120.
[0066]
On the other hand, channel estimation is performed by channel estimation unit 160, direct wave and delayed wave paths are detected, and channel estimation values in each path are output to estimated value correction unit 310. The channel estimation value in each path is added with the phase rotation amount W and (π / 4) phase rotation determined in accordance with the channelization code by the estimation value correction unit 310, and the obtained correction channel estimation value is synchronized. It is output to the detector 120.
[0067]
Here, since the number of paths detected within one slot time by the channel estimation unit 160 is very small compared to the number of symbols included in the received signal, the calculation of the phase rotation for the channel estimation value corresponding to each path is as follows: A small amount is enough.
[0068]
Then, the synchronous detector 120 performs synchronous detection of the despread signal by using the corrected channel estimation value. In this synchronous detection, the correction channel estimation value to which the phase rotation amount W and (π / 4) phase rotation are added is used, so that the signal after the synchronous detection has a phase rotation amount W and (π / 4) Equivalent to a phase rotation added.
[0069]
The signal after the synchronous detection is RAKE combined by the RAKE combining unit 130 to obtain a RAKE combined signal in which signals corresponding to the respective paths are combined. The RAKE composite signal is demodulated by the QPSK demapping unit 150 and parallel / serial converted by the P / S conversion unit 152, and a received bit sequence including bits of the I-axis component and the Q-axis component is output.
[0070]
As described in the above prior art, for example, in the signal having the frame configuration shown in FIG. 6, when the information symbol block Ii1 and the information symbol block Ii2 included in each slot are each composed of 61 symbols, the conventional technique has 122 symbols. On the other hand, while it is necessary to add the phase rotation amount W and the (π / 4) phase rotation, in this embodiment, for example, when four paths are detected within one slot time as shown in FIG. The phase rotation amount W and the (π / 4) phase rotation may be added to the four channel estimation values.
[0071]
Thus, according to the present embodiment, only the channel estimation value obtained within one slot time from the received signal is rotated by the phase rotation amount and (π / 4) phase rotation determined in accordance with the channelization code. Since the correction channel estimation value is acquired and the despread signal is synchronously detected using the correction channel estimation value, the symbols can be efficiently calculated with a smaller amount of computation than when phase rotation is performed on each symbol of the RAKE-combined signal. Data can be converted into a received bit sequence.
[0072]
(Embodiment 4)
A feature of the fourth embodiment of the present invention is that interference cancellation is performed on a signal after RAKE combining.
[0073]
FIG. 5 is a block diagram showing a main configuration of the receiving apparatus according to the fourth embodiment. In this figure, the same parts as those in FIG.
[0074]
5 includes a despreading section 110, a synchronous detection section 120, a RAKE combining section 130, a QPSK demapping section 150 including a P / S conversion section 152, a channel estimation section 160, an estimated value correction section 310, and an arithmetic operation. An interference removal unit 400 including a variable generation unit 410 and an interference removal calculation unit 420 is provided. Note that the despreading unit 110 in the present embodiment applies fast Hadamard transform, and simultaneously performs despreading processing on the signals of other users.
[0075]
Interference removal section 400 removes interference of the signal after RAKE combining using the corrected channel estimation value and spreading information regarding the multiplexed codes of all users in the same cell as the own apparatus. Specifically, the interference removal unit 400 generates a calculation variable for interference removal by using the correction channel estimation value and the spreading information regarding the multiplexed codes of all users in the calculation variable generation unit 410, and performs interference removal. By using a calculation variable for the RAKE-combined signal in the calculation unit 420, a calculation for removing the influence of intersymbol interference and other user interference such as JD (Joint Detection) calculation is performed. For the interference canceller 400, for example, “Interference Cancellation vs. Channel Equalization and Joint Detection for the Downlink of C / TDMA Mobile Radio Concepts” (Bernd Steiner, Proceedings of EPMCC Conference Germany 1997, No. 145, pp.253-260 ) Or techniques described in documents such as “EFFICIENT MULTI-RATE MULTI-USER DETECTION FOR THE ASYNCHRONOUS WCDMA UPLINK” (HRKarimi, VTC'99, pp.593-597) can be applied.
[0076]
Next, the operation of the receiving apparatus configured as described above will be described.
[0077]
First, the received signal received via the antenna is input to despreading section 110 and channel estimation section 160. Then, the despreading unit 110 uses the channelization code assigned to the device itself, despreads the received signal, and outputs the despread signal to the synchronous detection unit 120.
[0078]
On the other hand, channel estimation is performed by channel estimation unit 160, direct wave and delayed wave paths are detected, and channel estimation values in each path are output to estimated value correction unit 310. The channel estimation value in each path is added with the phase rotation amount W and (π / 4) phase rotation determined in accordance with the channelization code by the estimation value correction unit 310, and the obtained correction channel estimation value is synchronized. This is output to the detection variable generation unit 410 in the detection unit 120 and the interference removal unit 400.
[0079]
Here, since the number of paths detected within one slot time by the channel estimation unit 160 is very small compared to the number of symbols included in the received signal, the calculation of the phase rotation for the channel estimation value corresponding to each path is as follows: A small amount is enough.
[0080]
Then, the synchronous detector 120 performs synchronous detection of the despread signal by using the corrected channel estimation value. In this synchronous detection, the correction channel estimation value to which the phase rotation amount W and (π / 4) phase rotation are added is used, so that the signal after the synchronous detection has a phase rotation amount W and (π / 4) Equivalent to a phase rotation added.
[0081]
The signal after the synchronous detection is RAKE combined by the RAKE combining unit 130 to obtain a RAKE combined signal in which signals corresponding to the respective paths are combined. The RAKE combined signal is output to the interference removal calculating unit 420. The
[0082]
In addition, the calculation variable generation unit 410 generates a calculation variable for interference removal by using the corrected channel estimation value and the spread information regarding the multiplexed codes of all users in the same cell as the own device, and the interference cancellation calculation. By using the calculation variable for the RAKE composite signal by the unit 420, for example, calculation such as JD calculation is performed, and the influence of intersymbol interference and other user interference is removed.
[0083]
The signal after interference cancellation is demodulated by the QPSK demapping unit 150 and parallel / serial converted by the P / S conversion unit 152 to output a received bit sequence including bits of the I-axis component and the Q-axis component. The
[0084]
Thus, according to the present embodiment, only the channel estimation value obtained within one slot time from the received signal is rotated by the phase rotation amount and (π / 4) phase rotation determined in accordance with the channelization code. Phase correction is performed on each symbol of the RAKE-combined signal in order to obtain a corrected channel-estimated value and perform synchronous detection of the despread signal using the corrected channel estimate and to remove interference of the signal after RAKE-combining. The symbol data can be efficiently converted into a highly accurate received bit sequence from which the influence of interference has been removed with a smaller amount of computation than in the case of performing.
[0085]
In each of the above embodiments, the case where QPSK is applied as a modulation scheme has been described. Therefore, the amount of phase rotation added to the channel estimation value is (π / 4), but the present invention is not limited to this. However, even when other modulation schemes are applied, the present invention can be implemented by changing as appropriate.
[0086]
【The invention's effect】
As described above, according to the present invention, symbol data can be efficiently converted into a received bit sequence with a small amount of calculation.
[Brief description of the drawings]
FIG. 1 is a block diagram showing the main configuration of a receiving apparatus according to Embodiment 1 of the present invention. FIG. 2 is a diagram for explaining the operation of a channel estimation section according to Embodiment 1. FIG. 4 is a block diagram showing the main configuration of a receiving apparatus according to Embodiment 2 of the present invention. FIG. 4 is a block diagram showing the main configuration of the receiving apparatus according to Embodiment 3 of the present invention. FIG. 6 is a diagram showing an example of a frame configuration of a signal used in the CDMA / TDD system. FIG. 7 is a diagram showing an example of symbol mapping in QPSK modulation. FIG. 8 is a diagram showing another example of symbol mapping in QPSK modulation.
110 Despreading section 120 Synchronous detection section 130 RAKE combining section 140 Phase rotation section 150, 150a QPSK demapping section 152 P / S conversion section 154 (-π / 4) phase shifter 160 Channel estimation section 170, 210, 310 Estimated value Correction unit 400 Interference removal unit 410 Calculation variable generation unit 420 Interference removal calculation unit

Claims (3)

Channel estimation means for obtaining a channel estimation value using a received signal;
Phase rotation means for phase rotating the channel estimation value;
Synchronous detection means for synchronously detecting the received signal using a correction channel estimation value obtained by phase rotation;
Have a,
The phase rotation means includes
A receiving apparatus characterized in that the channel estimation value is phase-rotated by an amount of phase rotation determined in accordance with a channelization code assigned to the own apparatus . A wireless communication terminal device comprising the receiving device according to claim 1 . A radio communication base station apparatus comprising the receiving apparatus according to claim 1 .

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