Radio transmitting apparatus, radio receiving apparatus, radio transmitting method and radio receiving method

A radio transmitting apparatus and the like for improving the reception error rate characteristic. In this apparatus, a data modulating part (121) modulates a data signal to provide a modulated symbol. A Q-inverting part (125) generates a symbol that corresponds to the modulated symbol provided by the data modulating part (121) and that, when combined with the modulated symbol, becomes a signal having a particular value. A multiplexing part (110) multiplexes the modulated symbol provided by the data modulating part (121) with the corresponding symbol generated by the Q-inverting part (125) to provide a multiplexed signal.

TECHNICAL FIELD

The present invention relates to a radio transmission apparatus, radio reception apparatus, radio transmission method and radio reception method used in a radio communication network system where channel estimation is performed along with transmission of streams.

BACKGROUND ART

As one approach to achieve high-speed transmission in a radio communication network system, a multiple-input multiple-output (MIMO) scheme has attracted attention. In the MIMO scheme, a plurality of data signal sequences are transmitted in parallel from a transmitting side having a plurality of antennas to a receiving side having a plurality of antennas, using the same frequency (band).

Further, as another approach to achieve high-speed transmission, there is a multicarrier scheme. In the multicarrier scheme, a plurality of data signal sequences respectively superimposed on a plurality of subcarriers are transmitted in parallel.

In recent years, various studies have been conducted on communication schemes that combine the MIMO scheme and multicarrier scheme. One example is a MIMO-OFDM scheme that combines the orthogonal frequency division multiplexing (OFDM) scheme, which is one example of the multicarrier scheme, with the MIMO scheme (see, for example, Patent Document 1).

In one example of a conventional radio communication network system that adopts the MIMO-OFDM scheme, data signals and pilot signals are time division multiplexed and transmitted. On the receiving side, channel estimation is performed using the received pilot signals. Then, coefficients for demultiplexing a plurality of streams are calculated using a channel estimation value, and the plurality of streams are demultiplexed and demodulated based on that coefficients. Furthermore, the pilot signal is a known signal, and the data signal is not a known signal. That is, the signal sequence of pilot signals transmitted from the transmitting side is known in advance on the receiving side, and the signal sequence of data signals transmitted from the transmitting side is not known in advance on the receiving side.

DISCLOSURE OF INVENTION

Problems to be Solved by the Invention

However, in the above-described conventional radio communication network system, the problem arises that the reception error rate characteristics deteriorate due to a decrease in channel estimation accuracy on the receiving side when the transmitting side or receiving side moving speed is fast.

It is therefore an object of the present invention to provide a radio transmission apparatus, radio reception apparatus, radio transmission method and radio reception method capable of improving reception error rate characteristics.

Means for Solving the Problem

The radio transmission apparatus of the present invention adopts a configuration having: a modulation section that modulates a data signal to obtain a modulation symbol; a generation section that generates a corresponding symbol that corresponds to the modulation symbol and becomes a signal having a specific value when combined with the modulation symbol; and a multiplexing section that multiplexes the modulation symbol and the corresponding symbol to obtain a multiplexed signal.

According to this configuration, channel estimation can be performed using a combined signal comprised of the modulation symbol of a data signal and its corresponding symbol on the receiving side, so that it is possible to improve the frequency at which channel estimation is performed, improve the channel estimation accuracy when the moving speed on the transmitting side or receiving side becomes fast, and improve the reception error rate characteristics.

The radio reception apparatus of the present invention adopts a configuration having: an extraction section that extracts from a multiplexed signal a modulation symbol of a data signal and a corresponding symbol that corresponds to the modulation symbol and is generated to become a signal having a specific value when combined with the modulation symbol; a generation section that generates a combined signal comprised of the modulation symbol and the corresponding symbol; and an estimation section that performs channel estimation based on the combined signal.

According to this configuration, channel estimation can be performed using a combined signal comprised of a modulation symbol of a data signal and its corresponding symbol, so that it is possible to improve the frequency at which channel estimation is performed, improve the channel estimation accuracy when the moving speed on the transmitting side or receiving side becomes fast, and improve the reception error rate characteristics.

The radio transmission method of the present invention includes: a modulation step of modulating a data signal to obtain a modulation symbol; a generation step of generating a corresponding symbol that corresponds to the modulation symbol and becomes a signal having a specific value when combined with the modulation symbol; and a multiplexing step of multiplexing the modulation symbol and the corresponding symbol to obtain a multiplexed signal.

According to this method, channel estimation using a combined signal comprised of a modulation symbol of a data signal and its corresponding symbol can be performed on the receiving side, so that it is possible to improve the frequency at which channel estimation is performed, improve the channel estimation accuracy when the moving speed on the transmitting side or receiving side becomes fast, and improve the reception error rate characteristics.

The radio reception method of the present invention includes: an extraction step of extracting from a multiplexed signal a modulation symbol of a data signal and a corresponding symbol that corresponds to the modulation symbol and is generated to become a signal having a specific value when combined with the modulation symbol; a generation step of generating a combined signal comprised of the modulation symbol and the corresponding symbol; and an estimation step of performing channel estimation based on the combined signal.

According to this method, channel estimation can be performed using a combined signal comprised of a modulation symbol of a data signal and its corresponding symbol, so that it is possible to improve the frequency at which channel estimation is performed, improve the channel estimation accuracy when the moving speed on the transmitting side or receiving side becomes fast, and improve the reception error rate characteristics.

Advantageous Effect of the Invention

According to the present invention, it is possible to improve the reception error rate characteristics.

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiments of the present invention will now be described in detail with reference to the accompanying drawings. In the embodiments, components having the same function will be assigned the same reference numerals, and descriptions thereof will be omitted.

FIG. 1is a configuration diagram of the radio communication system according to Embodiment 1 of the present invention. In radio communication system1ofFIG. 1, base station apparatus (hereinafter “base station”)10and mobile station apparatus (hereinafter “mobile station”)20perform radio communication via MIMO channel30. The radio transmission apparatus according to Embodiment 1 of the present invention is applied to base station10, and the radio reception apparatus according to Embodiment 1 of the present invention is applied to mobile station20.

In radio communication system1, a radio signal transmitted from base station10is received by mobile station20via MIMO channel30. Further, in this embodiment, a case will be described where M (where M is an even number of 2 or higher) subcarriers are used for transmission and reception of data signals. Furthermore, M subcarriers are orthogonal each other. Identification numbers 1 to M are respectively assigned to the M subcarriers.

Both base station10and mobile station20have a plurality of antennas. In this embodiment, it is assumed that both have two antennas. Thus, MIMO channel30is defined by combinations of four channels. The four channel estimation values h(1,1), h(1,2), h(2,1), and h(2,2) can be obtained by estimating the characteristics C(1,1), C(1,2), C(2,1) and C(2,2) of the four channels. Furthermore, characteristic C (p, r) indicates the actual characteristic of the channel specified by the combination of the pth antenna provided in base station10and the rth antenna provided in mobile station20, and channel estimation value h(p, r) indicates the estimation result of characteristic C(1,2) (in this case, p=1, 2 and r=1, 2).

Furthermore, the number of antennas of base station10and mobile station20is not limited to two, but may be three or more. That is, when base station10has P (where P is an integer of 2 or higher) antennas and mobile station20has R (where R is an integer of 2 or higher) antennas, the P×R channel estimation values h(p, r) are calculated (in this case, p=1, 2, . . . , P and r=1, 2, . . . , R).

FIG. 2is a block diagram showing a configuration of base station10. Base station10has N (N=M/2) data symbol generation sections102-1to102-N, N data symbol generation sections104-1to104-N, pilot assignment section106, two pilot modulation sections108-1and108-2, two multiplexing sections110-1and110-2, two inverse fast Fourier transform (IFFT) sections112-1and112-2, two guard interval (GI) addition sections114-1and114-2, two transmission radio processing sections116-1and116-2and two antennas118-1and118-2.

Data symbol generation sections102-1to102-N, pilot modulation section108-1, multiplexing section110-1, IFFT section112-1, GI addition section114-1, and transmission radio processing section116-1are provided in association with antenna118-1, and data symbol generation sections104-1to104-N, pilot modulation section108-2, multiplexing section110-2, IFFT section112-2, GI addition section114-2and transmission radio processing section116-2are provided in association with antenna118-2.

N data symbol generation sections102-1to102-N have the same configuration, and therefore, are referred to as “data symbol generation section102” in descriptions for arbitrary one of N data symbol generation sections102-1to102-N. Additionally, N data symbol generation sections104-1to104-N have the same configuration, and therefore, are referred to as “data symbol generation section104” in descriptions for arbitrary one of N data symbol generation sections104-1to104-N.

Data symbol generation section102and data symbol generation section104are each provided in association with two adjacent subcarriers out of M subcarriers. For example, data signals transmitted using subcarriers f1and f2are inputted to data symbol generation section102-1.

More specifically, data signals inputted to data symbol generation section102-1include data signal D(1,1) transmitted from antenna118-1using subcarrier f1and data signal D(1,2) transmitted from antenna118-1using subcarrier f2. Additionally, data signals inputted to data symbol generation section104-1include data signal D(2,1) transmitted from antenna118-1using subcarrier f1and data signal D(2,2) transmitted from antenna118-2using subcarrier f2.

Data symbol generation section102has two data modulation sections121and122, two repetition sections123and124, Q inversion section125and IQ inversion section126. Data modulation section121, repetition section123and Q inversion section125are provided in association with D (1,2n−1) transmitted from subcarriers having odd identification numbers, out of D(1,2n−1) and D(1,2n) inputted to data symbol generation section102.

Data modulation section122, repetition section124and IQ inversion section126are provided in association with D(1,2n) transmitted from subcarriers having even identification numbers, out of D(1,2n−1) and D(1,2n) inputted to data symbol generation section102. Furthermore, n is an arbitrary integer between 1 to N.

Data modulation section121modulates D(1,2n−1) using quadrature phase shift keying (QPSK) and generates a modulated data symbol. The modulated data symbol generated by data modulation section121is outputted to repetition section123. Data modulation section122modulates D (1,2n) and generates a modulated data symbol. The modulated data symbol generated by data modulation section122is outputted to repetition section124.

Repetition section123duplicates (repeats) the modulated data symbol inputted from data modulation section121according to the number of repetitions. In this embodiment, the number of repetitions is “2.” That is, repetition section123outputs the inputted modulated data symbol as is to Q inversion section125, and following the output of the modulated data symbol, generates a duplicate data symbol having the same value as the modulated data symbol and outputs the duplicate data symbol to Q inversion section125.

Repetition section124repeats the modulated data symbol inputted from data modulation section122according to the number of repetitions. In this embodiment, the number of repetitions is “2.” That is, repetition section124outputs the inputted modulated data symbol as is to IQ inversion section126and then, following the output of the modulated data symbol, generates a duplicate data symbol having the same value as the modulated data symbol and outputs the duplicate data symbol to IQ inversion section126.

Q inversion section125as a generation means of a radio transmission apparatus, outputs the modulated data symbol inputted from repetition section123as is to multiplexing section110-1. Q inversion section125inverts the positive/negative sign of the value of the quadrature (Q) component of the duplicate data symbol inputted after the modulated data symbol from repetition section123and generates a Q inverted data symbol. The generated Q inverted data symbol is outputted to multiplexing section110-1following the output of the modulated data symbol. This Q inverted data symbol corresponds to the modulated data symbol generated by data modulation section121and becomes a signal having a specific value when combined with the modulated data symbol. Further, the average symbol obtained when the Q inverted symbol and modulated data symbol are combined is substantially the same as the binary phase shift keying (BPSK) modulated signal.

IQ inversion section126as a generation means of a radio transmission apparatus, outputs the modulated data symbol inputted from repetition section124as is to multiplexing section110-1. IQ inversion section126inverts the positive/negative sign of the value of the in-phase (I) component and the positive/negative sign of the value of the Q component of the duplicate data symbol inputted after the modulated data symbol from repetition section124and generates an IQ inverted data symbol. That is, this IQ inverted data symbol corresponds to the modulated data symbol generated by data modulation section122and becomes a signal having a specific value when combined with the modulated data symbol. The generated IQ inverted data symbol is outputted to multiplexing section110-1following the output of the modulated data symbol. In the following descriptions, the Q inverted symbol and the IQ inverted symbol are generically referred to as “inverted symbol.”

Data symbol generation section104has two data modulation sections131and132, two repetition sections133and134, IQ inversion section135and Q inversion section136. Data modulation section131, repetition section133and IQ inversion section135are provided in association with D(2,2n−1) transmitted from subcarriers having odd identification numbers, out of D(2,2n−1) and D(2,2n) inputted to data symbol generation section104.

On the other hand, data modulation section132, repetition section134and Q inversion section136are provided in association with D(2,2n) transmitted from subcarriers having even identification numbers, out of D(2,2n−1) and D(2,2n) inputted to data symbol generation section104.

Data modulation section131modulates D(2,2n−1) to generate a modulated data symbol. The modulated data symbol generated by data modulation section131is outputted to repetition section133. Data modulation section132modulates D(2,2n) using QPSK to generate a modulated data symbol. The modulated data symbol generated by data modulation section132is outputted to repetition section134.

Repetition section133repeats the modulated data symbol inputted from data modulation section131according to the number of repetitions. In this embodiment, the number of repetitions is “2.” That is, repetition section133outputs the inputted modulated data symbol as is to IQ inversion section135and then, following the output of the modulated data symbol, generates a duplicate data symbol having the same value as the modulated data symbol and outputs the duplicate data symbol to IQ inversion section135.

Repetition section134repeats the modulated data symbol inputted from data modulation section132according to the number of repetitions. In this embodiment, the number of repetitions is “2.” That is, repetition section134outputs the inputted modulated data symbol as is to Q inversion section136and then, following the output of the modulated data symbol, generates a duplicate data symbol having the same value as the modulated data symbol and outputs the duplicate data symbol to Q inversion section136.

IQ inversion section135as a generation means of a radio transmission apparatus, outputs the modulated data symbol inputted from repetition section133as is to multiplexing section110-2. IQ inversion section135inverts the positive/negative sign of the value of the I component and the positive/negative sign of the value of the Q component of the duplicate data symbol inputted after the modulated data symbol from repetition section133and generates an IQ inverted data symbol. This IQ inverted data symbol corresponds to the modulated data symbol generated by data modulation section131and becomes a signal having a specific value when combined with the modulated data symbol. The generated IQ inverted data symbol is outputted to multiplexing section110-2following the output of the modulated data symbol.

Q inversion section136as a generation means of a radio transmission apparatus, outputs the modulated data symbol inputted from repetition section134as is to multiplexing section110-2. Q inversion section136inverts the positive/negative sign of the value of the Q component of the duplicate data symbol inputted after the modulated data symbol from repetition section134and generates a Q inverted data symbol. This Q inverted data symbol corresponds to the modulated data symbol generated by data modulation section132and becomes a signal having a specific value when combined with the modulated data symbol. The generated Q modulated data symbol is outputted to multiplexing section110-2following the output of the modulated data symbol.

Pilot assignment section106assigns pilot signals to the odd number subcarriers and the even number subcarriers. The pilot signals assigned to the odd number subcarriers are outputted to pilot modulation section108-1, and the pilot signals assigned to the even number subcarriers are outputted to pilot modulation section108-2. Further, pilot assignment section106generates a zero signal having a zero value. The generated zero signal is outputted to multiplexing sections110-1and110-2. Furthermore, the pilot signal and zero signal are known signals.

Pilot modulation section108-1modulates the pilot signals inputted from pilot assignment section106and generates a pilot symbol. The generated pilot symbol is outputted to multiplexing section110-1. In this embodiment, BPSK is used for modulation of the pilot signals.

Pilot modulation section108-2modulates the pilot signals inputted from pilot assignment section106and generates a pilot symbol. In this embodiment, BPSK is used for this modulation. The generated pilot symbol is outputted to multiplexing section110-2.

That is, the combination of the pilot assignment section106and pilot modulation sections108-1and108-2configures a known signal generation section that generates a known signal.

Multiplexing section110-1multiplexes the modulated data symbol and Q inverted data symbol inputted from Q inversion section125, the modulated data symbol and IQ inverted data symbol inputted from IQ inversion section126, the pilot symbol inputted from pilot modulation section108-1, and the zero signal inputted from pilot assignment section106and generates a multiplexed signal to be transmitted from antenna118-1. The format of the multiplexed signal generated by multiplexing section110-1will be specifically described later.

Multiplexing section110-2multiplexes the modulated data symbol and IQ inverted data symbol inputted from IQ inversion section135, the modulated data symbol and Q inverted data symbol inputted from Q inversion section136, the pilot symbol inputted from pilot modulation section108-2, and the zero signal inputted from pilot assignment section106and generates a multiplexed signal to be transmitted from antenna118-2. The format of the multiplexed signal generated by multiplexing section110-2will be specifically described later.

IFFT section112-1as an assignment means, performs IFFT processing on the multiplexed signal generated by multiplexing section110-1, and thereby assigns the multiplexed signal to subcarriers. IFFT section112-2as an assignment means, performs IFFT processing on the multiplexed signal generated by multiplexing section110-2, and thereby assigns the multiplexed signal to subcarriers.

GI addition section114-1adds a GI at a predetermined position of the multiplexed signal subjected to IFFT processing by IFFT section112-1. GI addition section114-2adds a GI at a predetermined position of the multiplexed signal subjected to IFFT processing by IFFT section112-2.

Transmission radio processing section116-1generates a radio signal by performing predetermined transmission radio processing (such as D/A conversion and up-conversion) on the multiplexed signal to which GI is added by GI addition section114-1, and transmits the generated radio signal from antenna118-1. Transmission radio processing section116-2generates a radio signal by performing predetermined transmission radio processing on the multiplexed signal to which GI is added by GI addition section114-2, and transmits the generated radio signal from antenna118-2.

Next, the format of the multiplexed signal generated at base station10having the above-described configuration will be explained. Here, the format will be explained for multiplexed signals transmitted using subcarriers f1and f2during a period between time t1and time t5.

First, an example of the format of the multiplexed signal transmitted from antenna118-1will be explained with reference toFIG. 3. At a position of subcarrier f1and time t1, a BPSK modulated signal having a value of “1”—a pilot symbol generated by pilot modulation section108-1—is arranged. At a position of subcarrier f1and time t2, a modulated data symbol (QPSK symbol) generated by data modulation section121is arranged. At a position of subcarrier f1and time t3, a Q inverted data symbol generated by Q inversion section125—a Q inverted symbol corresponding to the QPSK symbol arranged at the position of subcarrier f1and time t2—is arranged. At a position of subcarrier f1and time t4, a QPSK symbol generated by data modulation section121(that is, a modulated data symbol generated following the QPSK symbol arranged at the position of subcarrier f1and time t2) is arranged. At a position of subcarrier f1and time t5, a Q inverted data symbol generated by Q inversion section125—a Q inverted symbol corresponding to the QPSK symbol arranged at the position of subcarrier f1and time t4—is arranged.

That is, in the multiplexed signal transmitted from antenna118-1, the subcarrier signal corresponding to subcarrier f1is a signal obtained by time division multiplexing a signal having a known value (that is, the pilot symbol generated by pilot modulation section108-1) the QPSK symbol generated by data modulation section121and the Q inverted symbol generated by Q inversion section125.

Further, at a position of subcarrier f2and time t1, the zero signal is arranged (that is, a pilot symbol is not arranged at this position). At a position of subcarrier f2and time t2, a QPSK symbol generated by data modulation section122is arranged. At a position of subcarrier f2and time t3, an IQ inverted data symbol generated by IQ inversion section126—an IQ inverted symbol corresponding to the QPSK symbol arranged at the position of subcarrier f2and time t2—is arranged. At a position of subcarrier f2and time t4, a QPSK symbol generated by data modulation section122(that is, a modulated data symbol generated following the QPSK symbol arranged at the position of subcarrier f2and time t2) is arranged. At a position of subcarrier f2and time t5, an IQ inverted data symbol generated by IQ inversion section126—an IQ inverted symbol corresponding to the QPSK symbol arranged at the position of subcarrier f2and time t4—is arranged.

That is, in the multiplexed signal transmitted from antenna118-1, the subcarrier signal corresponding to subcarrier f2is a signal obtained by time division multiplexing a signal having a known value (that is, the zero signal), the QPSK symbol generated by data modulation section122and the IQ inverted symbol generated by IQ inversion section126.

Next, an example of the format of the multiplexed signal transmitted from antenna118-2will be explained with reference toFIG. 4. At a position of subcarrier f1and time t1, the zero signal is arranged (that is, a pilot symbol is not arranged at this position). At a position of subcarrier f1and time t2, a QPSK symbol generated by data modulation section131is arranged. At a position of subcarrier f1and time t3, an IQ inverted data symbol generated by IQ inversion section135—an IQ inverted symbol corresponding to the QPSK symbol arranged at the position of subcarrier f1and time t2—is arranged. At a position of subcarrier f1and time t4, a QPSK symbol generated by data modulation section131(that is, a modulated data symbol generated following the QPSK symbol arranged at the position of subcarrier f1and time t2) is arranged. At a position of subcarrier f1and time t5, an IQ inverted data symbol generated by IQ inversion section135—an IQ inverted symbol corresponding to the QPSK symbol arranged at the position of subcarrier f1and time t4—is arranged.

That is, in the multiplexed signal transmitted from antenna118-2, the subcarrier signal corresponding to subcarrier f1is a signal obtained by time division multiplexing a signal having a known value (that is, the zero signal), the QPSK symbol generated by data modulation section131and the IQ inverted symbol generated by IQ inversion section135.

At a position of subcarrier f2and time t1, a BPSK modulated signal having a value of “1”—a pilot symbol generated by pilot modulation section108-2—is arranged. At a position of subcarrier f2and time t2, a QPSK symbol generated by data modulation section132is arranged. At a position of subcarrier f2and time t3, a Q inverted data symbol generated by Q inversion section136—a Q inverted symbol corresponding to the QPSK symbol arranged at the position of subcarrier f2and time t2—is arranged. At a position of subcarrier f2and time t4, a QPSK symbol generated by data modulation section132(that is, a modulated data symbol generated following the QPSK symbol arranged at the position of subcarrier f2and time t2) is arranged. At a position of subcarrier f2and time t5, a Q inverted data symbol generated by Q inversion section136—a Q inverted symbol corresponding to the QPSK symbol arranged at the position of subcarrier f2and time t4—is arranged.

That is, in the multiplexed signal transmitted from antenna118-2, the subcarrier signal corresponding to subcarrier f2is a signal obtained by time division multiplexing a signal having a known value (that is, the pilot symbol generated by pilot modulation section108-2), the QPSK symbol generated by data modulation section132and the Q inverted symbol generated by Q inversion section136.

Here, the correspondence relationship between the QPSK symbol and Q inverted symbol will be explained with reference toFIG. 5.FIG. 5Ashows an example of a QPSK symbol.FIG. 5Bshows a Q inverted symbol obtained by inverting the positive/negative sign of the Q component of the QPSK symbol. When the QPSK symbol ofFIG. 5Aand the Q inverted symbol ofFIG. 5Bare combined through averaging processing, an average symbol as shown inFIG. 5Cis obtained. This average symbol is substantially the same as the BPSK modulated signal. That is, the Q inverted symbol generated by Q inversion sections125and136is a signal of information of “−1” or “1” when combined with the corresponding QPSK symbol through averaging processing.

The correspondence relationship between the QPSK symbol and IQ inverted symbol will now be explained with reference toFIG. 6.FIG. 6Ashows an example of a QPSK symbol.FIG. 6Bshows an IQ inverted symbol obtained by inverting the positive/negative sign of the I component and the positive/negative sign of the Q component of the QPSK symbol. When the QPSK symbol ofFIG. 6Aand the IQ inverted symbol ofFIG. 6Bare combined through averaging processing, an average symbol as shown inFIG. 6Cis obtained. This average symbol is substantially the same as the zero signal. That is, the IQ inverted symbol generated by IQ inversion sections126and135is a signal having the specific value “0” when combined with the corresponding QPSK symbol through averaging processing.

The configuration of mobile station20will now be described. As shown inFIG. 7, mobile station20has two antennas202-1and202-2, two reception radio processing sections204-1and204-2, two GI removal sections206-1and206-2, two fast Fourier transform (FFT) sections208-1and208-2, two subcarrier demultiplexing sections210-1and210-2and N MIMO reception sections212-1to212-N. Furthermore, N MIMO reception sections212-1to212-N have the same configuration, and therefore, are hereinafter referred to as “MIMO reception section212” in descriptions for arbitrary one of N MIMO reception sections212-1to212-N.

Reception radio processing section204-1, GI removal section206-1, FFT section208-1, and subcarrier demultiplexing section210-1are provided in association with antenna202-1, and reception radio processing section204-2, GI removal section206-2, FFT section208-2and subcarrier demultiplexing section210-2are provided in association with antenna202-2.

Reception radio processing section204-1receives via antenna202-1a radio signal transmitted from base station10and obtains the received signal by performing predetermined reception radio processing (such as down-conversion and A/D conversion) on the radio signal. Reception radio processing section204-2receives via antenna202-2a radio signal transmitted from base station10and obtains the received signal by performing predetermined reception radio processing (such as down-conversion and A/D conversion) on the radio signal.

GI removal section206-1removes the GI added in a predetermined position of the received signal obtained by reception radio processing section204-1. GI removal section206-2removes the GI added in a predetermined position of the received signal obtained by reception radio processing section204-2.

FFT section208-1performs FFT processing on the received signal from which the GI is removed by GI removal section206-1. FFT section208-2performs FFT processing on the received signal from which the GI is removed by GI removal section206-2.

Subcarrier demultiplexing section210-1demultiplexes on a per channel estimation unit basis the received signal subjected to FFT processing by FFT section208-1. In this embodiment, as an example, the combination of two subcarriers f2n-1and f2nis used as a channel estimation unit. Thus, subcarrier demultiplexing section210-1outputs to MIMO reception section212received signal RS(2,2n−1) of subcarrier f2n-1and received signal RS(1,2n) of subcarrier f2n. More specifically, RS (1,1) and RS (1,2) are outputted to MIMO reception section212-1, and RS(1,2N−1) and RS(1,2N) are outputted to MIMO reception section212-N.

Furthermore, the received signal of subcarrier fkreceived by antenna202-i(i=1, 2) is expressed as RS(i, k).

Subcarrier demultiplexing section210-2demultiplexes on a per channel estimation unit basis the received signal subjected to FFT processing by FFT section208-2. In this embodiment, as an example, the combination of two subcarriers f2n-1and f2nis used as a channel estimation unit. Thus, subcarrier demultiplexing section210-2outputs to MIMO reception section212received signal RS(2,2n−1) of subcarrier f2n-1and received signal RS(2,2n) of subcarrier f2n. More specifically, RS(2,1) and RS(2,2) are outputted to MIMO reception section212-1, and RS(2,2N−1) and RS(2,2N) are outputted to MIMO reception section212-N.

MIMO reception section212performs MIMO reception processing on RS(1,2n−1) and RS(1,2n) inputted from subcarrier demultiplexing section210-1, and RS(2,2n−1) and RS(2,2n) inputted from subcarrier demultiplexing section210-2, and outputs D(j,2n−1) and D(j,2n) transmitted from base station10.

Here, the internal configuration of MIMO reception section212will be described with reference to the block diagram of MIMO reception section212-1shown inFIG. 8.

MIMO reception section212has two data/pilot demultiplexing sections221and222, two channel estimation sections223and224, two channel estimation value correction sections225and226, two average symbol generation sections227and228, demultiplexing coefficient calculation section229, two stream demultiplexing sections230and231, two Q inversion sections232and233, two IQ inversion sections234and235, four symbol combination sections236,237,238and239, and four data demodulation sections240,241,242and243.

Data/Pilot demultiplexing section221as an extraction means, demultiplexes the data symbols and pilot symbols of RS(1,2n−1) and RS(1,2n) inputted from subcarrier demultiplexing section210-1.

Specifically, data/pilot demultiplexing section221extracts the signal RD(1,2n−1) of the portion corresponding to the data symbol and the signal of the portion corresponding to the pilot symbol from RS(1,2n−1) outputs the signal of the portion corresponding to the pilot symbol to channel estimation section223, and outputs RD(1,2n−1) to stream demultiplexing section230and average symbol generation section227.

Further, data/pilot demultiplexing section221extracts signal RD(1,2n) of the portion corresponding to the data symbol and the signal of the portion corresponding to the pilot symbol from RS (1,2n), outputs the signal of the portion corresponding to the pilot symbol to channel estimation section223, and outputs RD(1,2n) to stream demultiplexing section231and average symbol generation section227.

RD(1,2n−1) and RD(1,2n) are comprised of a portion corresponding to a modulated data symbol and a portion corresponding to an inverted symbol generated to become a signal having a specific value when combined with the modulation symbol through averaging processing.

Channel estimation section223performs channel estimation using an input signal from data/pilot demultiplexing section221, and obtains channel estimation values h(1,1) and h(2,1). The obtained channel estimation values h(1,1) and h(2,1) are outputted to channel estimation value correction section225.

RD(1,2n−1) and RD(1,2n) are inputted from data/pilot demultiplexing section221to average symbol generation section227used as a generation means of the radio reception apparatus. Average symbol generation section227combines through averaging processing the portion corresponding to the modulated data symbol in RD(1,2n−1) and the portion arranged at the position immediately after the portion, that is, the portion corresponding to the inverted symbol. As a result, an average symbol is generated.

Further, average symbol generation section227combines through averaging processing the portion corresponding to the modulated data symbol in RD(1,2n) and the portion arranged at the position immediately after the portion, that is, the portion corresponding to the inverted symbol. As a result, an average symbol is generated. The generated average symbols are outputted to channel estimation value correction section225.

Channel estimation value correction section225corrects channel estimation values h(1,1) and h(2,1) inputted from channel estimation section223using the average symbols inputted from average symbol generation section227. The corrected channel estimation values h (1,1) and h(2,1) are outputted to demultiplexing coefficient calculation section229. That is, the combination of channel estimation section223and channel estimation value correction section226configure an estimation section used as an estimation means of the radio reception apparatus. A specific example of the operation of the estimation section will be described later.

Data/Pilot demultiplexing section222as an extraction means, demultiplexes the data symbols and pilot symbols of RS(2,2n−1) and RS(2,2n) inputted from subcarrier demultiplexing section210-2.

Specifically, data/pilot demultiplexing section222extracts signal RD(2,2n−1) of the portion corresponding to the data symbol and the signal of the portion corresponding to the pilot symbol from RS (2,2n−1) outputs the signal of the portion corresponding to the pilot symbol to channel estimation section224, and outputs RD(2,2n−1) to stream demultiplexing section230and average symbol generation section228.

Further, data/pilot demultiplexing section222extracts signal RD(2,2n) of the portion corresponding to the data symbol and the signal of the portion corresponding to the pilot symbol from RS (2,2n), outputs the signal of the portion corresponding to the pilot symbol to channel estimation section224, and outputs RD(2,2n) to stream demultiplexing section231and average symbol generation section228. RD(2,2n−1) and RD(2,2n) is comprised of a portion corresponding to a modulated data symbol and a portion corresponding to an inverted symbol generated to become a signal having a specific value when combined with the modulation symbol through averaging processing.

Channel estimation section224performs channel estimation using an input signal from data/pilot demultiplexing section222, and obtains channel estimation values h(1,2) and h(2,2). The obtained channel estimation values h (1,2) and h (2,2) are outputted to channel estimation value correction section226.

RD(2,2n−1) and RD(2,2n) are inputted from data/pilot demultiplexing section222to average symbol generation section228used as a generation means of the radio reception apparatus. Average symbol generation section228combines through averaging processing the portion corresponding to the modulated data symbol in RD(2,2n−1) and the portion arranged at the position immediately after the portion, that is, the portion corresponding to the inverted symbol. As a result, an average symbol is generated.

Further, average symbol generation section228combines through averaging processing the portion corresponding to the modulated data symbol in RD(2,2n) and the portion arranged at the position immediately after the portion, that is, the portion corresponding to the inverted symbol. As a result, an average symbol is generated. The generated average symbols are outputted to channel estimation value correction section226.

Channel estimation value correction section226corrects channel estimation values h(1,2) and h(2,2) inputted from channel estimation section224using the average symbols inputted from average symbol generation section228. The corrected channel estimation values h (1,2) and h(2,2) are outputted to demultiplexing coefficient calculation section229. That is, the combination of channel estimation section224and channel estimation value correction section226configures an estimation section used as an estimation means of the radio reception apparatus, similar to the combination of channel estimation section223and channel estimation value correction section225. A specific example of the operation of the estimation section will be described later.

Demultiplexing coefficient calculation section229calculates demultiplexing coefficients for demultiplexing a plurality of streams transmitted via MIMO channel30using channel estimation values h(1,1), h(1,2), h(2,1) and h(2,2) inputted from channel estimation value correction sections225and226. The demultiplexing coefficients are calculated by, for example, obtaining the inverse matrix of channel matrix H obtained from channel estimation values h(1,1), h(1,2), h(2,1) and h(2,2). The calculated demultiplexing coefficients are outputted to stream demultiplexing sections230and231.

Stream demultiplexing section230performs stream demultiplexing on RD(1,2n−1) inputted from data/pilot demultiplexing section221and RD(2,2n−1) inputted from data/pilot demultiplexing section222. The demultiplexing coefficients inputted from demultiplexing coefficient calculation section229are used in this stream demultiplexing processing. Further, D(1,2n−1) and D(2,2n−1) are obtained through the stream demultiplexing processing of stream demultiplexing section230. D(1,2n−1) and D(2,2n−1) are outputted to Q inversion section232and IQ inversion section234, respectively.

Q inversion section232outputs the modulated data symbol in D(1,2n−1) inputted from stream demultiplexing section230as is to symbol combination section236. Further, Q inversion section232inverts the positive/negative sign of the value of the Q component of the Q inverted symbol in D (1,2n−1) inputted from stream demultiplexing section230and restores the duplicate symbol. Then, Q inversion section232outputs the restored duplicate symbol to symbol combination section236following the output of the modulated data symbol.

Symbol combination section236combines the modulated data symbol inputted from Q inversion section232and the duplicate symbol inputted from Q inversion section232after the modulated data symbol to obtain a combined data symbol. The obtained combined symbol is inputted to data demodulation section240.

Data demodulation section240demodulates the combined data symbol inputted from symbol combination section236and outputs D(1,2n−1). In this embodiment, QPSK is used for demodulation of D(1,2n−1), and therefore data demodulation section240uses QPSK for demodulation processing.

IQ inversion section234outputs the modulated data symbol of D(2,2n−1) inputted from stream demultiplexing section230as is to symbol combination section237. Further, IQ inversion section234inverts the positive/negative sign of the I component and the positive/negative sign of the Q component of the IQ inverted symbol in D(2,2n−1) inputted from stream demultiplexing section230and restores the duplicate symbol. Then, IQ inversion section234outputs the restored duplicate symbol to symbol combination section237following the output of the modulated data symbol.

Symbol combination section237combines the modulated data symbol inputted from IQ inversion section234and the duplicate symbol inputted from IQ inversion section234after the modulated data symbol to obtain a combined data symbol. The obtained combined symbol is inputted to data demodulation section241.

Data demodulation section241demodulates the combined data symbol inputted from symbol combination section237and outputs D(2,2n−1).

Stream demultiplexing section231performs stream demultiplexing on RD(1,2n) inputted from data/pilot demultiplexing section221and RD(2,2n) inputted from data/pilot demultiplexing section222. The demultiplexing coefficients inputted from demultiplexing coefficient calculation section229are used in this stream demultiplexing processing. Further, D(1,2n) and D(2,2n) are obtained through the stream demultiplexing processing of stream demultiplexing section231. D(1,2n) and D(2,2n) are outputted to IQ inversion section235and Q inversion section233, respectively.

IQ inversion section235outputs the modulated data symbol in D(1,2n) inputted from stream demultiplexing section231as is to symbol combination section238. Further, IQ inversion section235inverts both the positive/negative sign of the value of the I component and the positive/negative sign of the value of the Q component of the IQ inverted symbol in D(1,2n) inputted from stream demultiplexing section231and restores the duplicate symbol. Then, IQ inversion section235outputs the restored duplicate symbol to symbol combination section238following the output of the modulated data symbol.

Symbol combination section238combines the modulated data symbol inputted from IQ inversion section235and the duplicate symbol inputted from IQ inversion section235after the modulated data symbol to obtain a combined data symbol. The obtained combined symbol is inputted to data demodulation section242.

Data demodulation section242demodulates the combined data symbol inputted from symbol combination section238and outputs D(1,2n).

Q inversion section233outputs the modulated data symbol in D(2,2n) inputted from stream demultiplexing section231as is to symbol combination section239. Further, Q inversion section233inverts the positive/negative sign of the Q component of the Q inverted symbol in D(2,2n) inputted from stream demultiplexing section231and restores the duplicate symbol. Then, Q inversion section233outputs the restored duplicate symbol to symbol combination section239following the output of the modulated data symbol.

Symbol combination section239combines the modulated data symbol inputted from Q inversion section233and the duplicate symbol inputted from Q inversion section233after the modulated data symbol to obtain a combined data symbol. The obtained combined symbol is inputted to data demodulation section243.

Data demodulation section243demodulates the combined data symbol inputted from symbol combination section239and outputs D(2,2n). In this embodiment, QPSK is used for modulation of D(2,2n), and therefore data demodulation section243uses QPSK for demodulation processing.

Next, an operation example of the estimation section of mobile station20will be described with reference toFIG. 9. Here, multiplexed signals transmitted using subcarriers f1and f2during a period between time t1and time t5will be described.

The multiplexed signal shown inFIG. 9Ais transmitted from antenna118-1of base station10. The format of the multiplexed signal ofFIG. 9Ais the same as that shown inFIG. 3. Furthermore, the numbers in parentheses shown at the arranged positions of the QPSK symbol and Q inverted symbol are the I component values and Q component values of the symbols.

The multiplexed signal shown inFIG. 9Bis transmitted from antenna118-2of base station10. The format of the multiplexed signal ofFIG. 9Bis the same as that shown inFIG. 4. Furthermore, the numbers in parentheses shown at the arranged positions of the QPSK symbol and IQ inverted symbol are the I component values and Q component values of the symbols.

The multiplexed signal ofFIG. 9Aand the multiplexed signal ofFIG. 9Bare affected by characteristics C(1,1), C(2,1), C(1,2) and C(2,2) of MIMO channel30, and arrive at mobile station20. Characteristics C(1,1), C(2,1), C(1,2) and C(2,2) for each timing of MIMO channel30are shown inFIG. 9C.

A radio signal in which the multiplexed signal ofFIG. 9Aand the multiplexed signal ofFIG. 9Baffected by characteristics C(1,1) and C(2,1) of MIMO channel30are present arrives at antenna202-1of mobile station20. The received signal of antenna202-1is shown inFIG. 9D. The numbers in parentheses shown at the arranged positions of the symbols of the received signal ofFIG. 9Dare the I component value and Q component value of the symbols.

Further, a radio signal in which the multiplexed signal ofFIG. 9Aand the multiplexed signal ofFIG. 9Baffected by characteristics C(1,2) and C(2,2) of MIMO channel30are present arrives at antenna202-2of mobile station20. The received signal of antenna202-2is shown inFIG. 9E. The numbers in parentheses shown at the arranged positions of the symbols of the received signal ofFIG. 9Eare the I component value and Q component value of the symbols.

Then, in mobile station20, channel estimation section223performs channel estimation using the pilot symbol arranged in the portion of time t1of the received signal ofFIG. 9D, and obtains channel estimation values h(1,1) and h(2,1).

Further, average symbol generation section227combines the modulated data symbol of time t2and the Q inverted symbol of time t3to generate an average symbol for the subcarrier signal corresponding to subcarrier f1in the received signal ofFIG. 9D. Furthermore, average symbol generation section227combines the modulated data symbol of time t4and the Q inverted symbol of time t5to generate an average symbol for the subcarrier signal corresponding to subcarrier f1in the received signal ofFIG. 9D. Furthermore, average symbol generation section227combines the modulated data symbol of time t2and the IQ inverted symbol of time t3to generate an average symbol for the subcarrier signal corresponding to subcarrier f2in the received signal ofFIG. 9D. Furthermore, average symbol generation section227combines the modulated data symbol of time t4and the IQ inverted symbol of time t5to generate an average symbol for the subcarrier signal corresponding to subcarrier f2in the received signal ofFIG. 9D.

As shown inFIG. 9F, channel estimation values h(1,1) and h(2,1) and the average symbols generated by average symbol generation section227are inputted to channel estimation value correction section225.

Channel estimation value correction section225regards the average symbols inputted from average symbol generation section227as BPSK modulated pilot symbols and performs channel estimation using the average symbols. The average symbols are regarded as BPSK modulated pilot symbols, and therefore there are two possibilities in channel estimation results depending on whether the BPSK symbol is (−1, 0) or (1, 0). Channel estimation value correction section225lines up channel estimation value candidates based on the possibilities. For example, for the average symbol of subcarrier f1and times t2to t3, (1, 0.3) and (−1, −0.3) are lined up as channel estimation value candidates. The channel estimation value candidates lined up for each average symbol are shown inFIG. 9H.

Then, channel estimation value correction section225compares each candidate with the channel estimation value (the channel estimation value of time t1in this illustration) obtained from the pilot symbol and selects the candidate having the value closest to the channel estimation value obtained from the pilot symbol (in other words, the value having a smaller square error with respect to the channel estimation value obtained from the pilot symbol).

For example, the above-described candidates (1, 0.3) and (−1, −0.3) correspond to subcarrier f1and therefore are compared with the channel estimation value (1, 0.3) corresponding to subcarrier f1. As a result of comparison, candidate (1, 0.3) has a value having a smaller square error with respect to channel estimation value (1, 0.3) compared to (−1, −0.3), and therefore (1, 0.3) is selected. The selected candidate (1, 0.3) is determined as the channel estimation value h (1,1) corresponding to times t2to t3. The candidates encircled inFIG. 9Hare the candidates selected as a result of the comparison. The determined channel estimation value is used for calculating the demultiplexing coefficients at demultiplexing coefficient calculation section229.

Further, the same operation as that described above is performed in channel estimation section224, average symbol generation section228and channel estimation value correction section226.

That is, channel estimation section224performs channel estimation using the pilot symbol arranged in the portion of time t1of the received signal ofFIG. 9E, and obtains channel estimation values h(1,2) and h(2,2).

Further, average symbol generation section228combines the modulated data symbol of time t2and the IQ inverted symbol of time t3and generates an average symbol for the subcarrier signal corresponding to subcarrier f1in the received signal ofFIG. 9E. Furthermore, average symbol generation section228combines the modulated data symbol of time t4and the IQ inverted symbol of time t5to generate an average symbol for the subcarrier signal corresponding to subcarrier f1in the received signal ofFIG. 9E. Furthermore, average symbol generation section228combines the modulated data symbol of time t2and the Q inverted symbol of time t3to generate an average symbol for the subcarrier signal corresponding to subcarrier f2in the received signal ofFIG. 9E. Furthermore, average symbol generation section228combines the modulated data symbol of time t4and the Q inverted symbol of time t5to generate an average symbol for the subcarrier signal corresponding to subcarrier f2in the received signal ofFIG. 9E.

As shown inFIG. 9G, channel estimation values h(1,2) and h(2,2) obtained by channel estimation section224and the average symbols generated by average symbol generation section228are inputted to channel estimation value correction section226.

Channel estimation value correction section226regards the average symbols inputted from average symbol generation section228as BPSK modulated pilot symbols and performs channel estimation using the average symbols. The average symbols are regarded as BPSK modulated pilot symbols, and therefore there are two possibilities in the channel estimation results depending on whether the BPSK symbol is (−1, 0) or (1, 0). Channel estimation value correction section226lines up channel estimation value candidates based on the possibilities. For example, for the average symbol of times t2to t3of subcarrier f1, (0.5, 1) and (−0.5, −1) are lined up as channel estimation value candidates. The channel estimation value candidates lined up for each average symbol are shown inFIG. 9I.

Then, channel estimation value correction section226compares each candidate with the channel estimation value (the channel estimation value of time t1in this illustration) obtained from the pilot symbol and selects the candidate having the value closest to the channel estimation value obtained from the pilot symbol.

For example, the candidates (0.5, 1) and (−0.5, −1) corresponding to times t2to t3of subcarrier f1are compared with channel estimation value (0.5, 1) corresponding to subcarrier f1. As a result of comparison, candidate (0.5, 1) has a value closer to the channel estimation value (0.5, 1) compared to (−0.5, −1), and therefore (0.5, 1) is selected. The selected candidate (0.5, 1) is determined as channel estimation value h(1,2) corresponding to times t2to t3. The candidates encircled inFIG. 9Iare the candidates selected as a result of the comparison. The determined channel estimation value is used for calculating demultiplexing coefficients at demultiplexing coefficient calculation section229.

In this way, according to Embodiment 1, channel estimation using the average symbol obtained from a modulated data symbol and an inverted symbol corresponding to that symbol can be performed in mobile station20, that is, pilot symbols as well as data symbols can be used for channel estimation. As a result, it is possible to increase the frequency at which channel estimation is performed, thereby improve channel estimation accuracy as well as reception error rate characteristics when the moving speed of mobile station20becomes fast.

Furthermore, in this embodiment, the case has been described where a radio transmission apparatus is applied to base station10and a radio reception apparatus is applied to mobile station20, but the radio transmission apparatus may be applied to mobile station20and the radio reception apparatus may be applied to base station10.

Further, in this embodiment, a repeated symbol is arranged by time division, but may be arranged in the frequency direction if within a coherent band.

Further, in this embodiment, the subcarrier for mapping the Q inverted symbol used for channel estimation value correction and the subcarrier for mapping the IQ inverted symbol not used for channel estimation value correction are made adjacent, non-adjacent subcarriers may also be used if within a coherent band.

In Embodiment 1, the case has been described as an example where QPSK is applied as the modulation scheme. However, when the 16QAM is applied, as shown inFIG. 10, the average symbols of the modulated data symbols and Q inverted data symbols becomes four values on the I axis, and, out of the signal points of the four values, the signal points of the two values having smaller absolute values have low SNR, and therefore channel estimation accuracy deteriorates. Here, in Embodiment 2 of the present invention, a case will be described where 16QAM is applied as the modulation scheme.

FIG. 11is a block diagram showing a configuration of base station40according to Embodiment 2 of the present invention. The differences betweenFIG. 11andFIG. 2is that data modulation section121is changed to data modulation section321, data modulation section122is changed to data modulation section322, data modulation section131is changed to data modulation section331, data modulation section132is changed to data modulation section332, Q inversion section125is changed to mapping change section325, and Q inversion section136is changed to mapping change section336.

Data modulation section321modulates D(1,2n−1) using 16QAM and generates a modulated data symbol. The modulated data symbol generated by data modulation section321is outputted to repetition section123. Data modulation section322modulates D(1,2n) and generates a modulated data symbol. The modulated data symbol generated by data modulation section322is outputted to repetition section124.

Mapping change section325as a generation means of the radio transmission apparatus, outputs the modulated data symbol inputted from repetition section123as is to multiplexing section110-1. Mapping change section325changes the mapping of the duplicate data symbol inputted after the modulated data symbol from repetition section123and generates a mapping change symbol. The generated mapping change symbol is outputted to multiplexing section110-1following the output of the modulated data symbol. This mapping change symbol corresponds to the modulated data symbol generated by data modulation section321, and the average symbol obtained when the mapping change symbol is combined with this modulated data symbol is substantially the same as the BPSK modulated signal.

Data modulation section331modulates D(2,2n−1) to generate a modulated data symbol. The modulated data symbol generated by data modulation section331is outputted to repetition section133. Data modulation section332modulates D(2,2n) using 16QAM and generates a modulated data symbol. The modulated data symbol generated by data modulation section332is outputted to repetition section134.

Mapping change section336as a generation means of the radio transmission apparatus, outputs the modulated data symbol inputted from repetition section134as is to multiplexing section110-2. Mapping change section336changes the mapping of the duplicate data symbol inputted after the modulated data symbol from repetition section134and generates a mapping change symbol. The generated mapping change symbol is outputted to multiplexing section110-2following the output of the modulated data symbol. This mapping change symbol corresponds to the modulated data symbol generated by data modulation section332, and the average symbol obtained when the mapping change symbol is combined with this modulated data symbol is substantially the same as the BPSK modulated signal.

Here, the correspondence relationship between the 16QAM symbol and mapping change symbol will be explained with reference toFIG. 12.FIG. 12Ashows the arrangement pattern of the modulated data symbols generated by data modulation sections321and332. In this 16QAM symbol arrangement pattern, with regard to the quadrants on the right of the Q axis (first and fourth quadrants), the I component of each of the signal points takes two values, and mapping change sections325and336change the mapping by moving signal points symmetrically using the point on the I axis that indicates the average of these two values as the point of symmetry.

Similarly, for the quadrants on the left of the Q axis as well (second and third quadrants), mapping change sections325and336change the mapping by moving signal points symmetrically in the I component of the signal points using the point that indicates the average value obtained from the two values as the point of symmetry. By this means, the mapping change symbol arrangement pattern becomes that shown inFIG. 12B.

When the 16QAM symbols ofFIG. 12Aand the mapping change symbols ofFIG. 12Bare combined through averaging processing, average symbols of two values are obtained on the I axis, as shown inFIG. 12C. These average symbols are substantially the same as the BPSK modulated signal. That is, the average symbol combined by performing averaging processing on the mapping change symbol generated by mapping change section325and336and the corresponding 16QAM symbol is a signal of information of −1 or “1.”

FIG. 13summarizes the I components and Q components of the modulated data symbols, mapping change symbols and average symbols thereof. Furthermore, R in the figure indicates 0.3162. In this figure, it is clear that the average symbols are all 0 for the Q component, and the two values 4R and −4R for the I component.

The configuration of the mobile station according to Embodiment 2 of the present invention is the same as the configuration shown inFIG. 7of Embodiment 1, and thereforeFIG. 7will be employed and a duplicate description thereof will be omitted.FIG. 14is a block diagram showing an internal configuration of MIMO reception section212according to Embodiment 2 of the present invention. The differences betweenFIG. 14andFIG. 8is that average symbol generation section227is changed to average symbol generation section427, average symbol generation section228is changed to average symbol generation section428, Q inversion section232is changed to mapping change section432, and Q inversion section233is changed to mapping change section433.

Average symbol generation section427combines through averaging processing the portion corresponding to the modulated data symbol in RD(1,2n−1) and the portion arranged at the position immediately after the portion, that is, the portion corresponding to the mapping change symbol. As a result, an average symbol is generated.

Further, average symbol generation section427combines through averaging processing the portion corresponding to the modulated data symbol in RD(1,2n) and the portion arranged at the position immediately after the portion, that is, the portion corresponding to the mapping change symbol. As a result, an average symbol is generated. The generated average symbols are outputted to channel estimation value correction section225.

Average symbol generation section428combines through averaging processing the portion corresponding to the modulated data symbol in RD(2,2n−1) and the portion arranged at the position immediately after the portion, that is, the portion corresponding to the mapping change symbol. As a result, an average symbol is generated.

Further, average symbol generation section428combines through averaging processing the portion corresponding to the modulated data symbol in RD(2,2n) and the portion arranged at the position immediately after the portion, that is, the portion corresponding to the mapping change symbol. As a result, an average symbol is generated. The generated average symbols are outputted to channel estimation value correction section226.

Mapping change section432outputs the modulated data symbol in D(1,2n−1) inputted from stream demultiplexing section230as is to symbol combination section236. Further, mapping change section432changes the mapping of the mapping change symbol in D(1,2n−1) inputted from stream demultiplexing section230in the same way as mapping change section325ofFIG. 11and restores the duplicate symbol. Then, mapping change section432outputs the restored duplicate symbol to symbol combination section236following the output of the modulated data symbol.

Mapping change section433outputs the modulated data symbol in D(2,2n) inputted from stream demultiplexing section231as is to symbol combination section239. Further, mapping change section433changes the mapping of the mapping change symbol in D(2,2n) inputted from stream demultiplexing section231in the same way as mapping change section336ofFIG. 11, and restores the duplicate symbol. Then, mapping change section433outputs the restored duplicate symbol to symbol combination section239following the output of the modulated data symbol.

In this way, according to Embodiment 2, in a 16QAM symbol arrangement pattern, by changing the mapping by symmetrically moving the signal points of the right quadrants and left quadrants centering around the Q axis of the IQ plane using the point that indicates the average value of the I component of two values of each of the signal points as the point of symmetry, two values for the average symbols can be obtained from the modulated data symbols and corresponding mapping change symbols even with the modulation scheme is 16QAM, and it is thereby possible to improve channel estimation accuracy and reception error rate characteristics by making the mobile station perform channel estimation using the average symbols.

In Embodiment 2, the case has been described where 16QAM is applied as the modulation scheme, but in Embodiment 3 of the present invention, a case will be described where 64QAM is applied as the modulation scheme. The configuration of the base station according to Embodiment 3 of the present invention is the same as the configuration shown inFIG. 11of Embodiment 2, and thereforeFIG. 11will be employed, and the configuration of the mobile station according to Embodiment 3 of the present invention is the same as the configuration shown inFIG. 7of Embodiment 1, and thereforeFIG. 7will be employed, and duplicate descriptions thereof will be omitted.

With reference toFIG. 11, data modulation section321modulates D(1,2n−1) using 64QAM to generate a modulated data symbol. The modulated data symbol generated by data modulation section321is outputted to repetition section123. Data modulation section322modulates D(1,2n) to generate a modulated data symbol. The modulated data symbol generated by data modulation section322is outputted to repetition section124.

Mapping change section325as a generation means of the radio transmission apparatus, outputs the modulated data symbol inputted from repetition section123as is to multiplexing section110-1. Mapping change section325changes the mapping of the duplicate data symbol inputted after the modulated data symbol from repetition section123and generates a mapping change symbol. The generated mapping change symbol is outputted to multiplexing section110-1following the output of the modulated data symbol. This mapping change symbol corresponds to the modulated data symbol generated by data modulation section321, and the average symbol obtained when the mapping change symbol is combined with this modulated data symbol is substantially the same as the BPSK modulated signal.

Data modulation section331modulates D(2,2n−1) to generate a modulated data symbol. The modulated data symbol generated by data modulation section331is outputted to repetition section133. Data modulation section332modulates D(2,2n) using 64QAM to generate a modulated data symbol. The modulated data symbol generated by data modulation section332is outputted to repetition section134.

Mapping change section336as a generation means of the radio transmission apparatus, outputs the modulated data symbol inputted from repetition section134as is to multiplexing section110-2. Mapping change section336changes the mapping of the duplicate data symbol inputted after the modulated data symbol from repetition section134and generates a mapping change symbol. The generated mapping change symbol is outputted to multiplexing section110-2following the output of the modulated data symbol. This mapping change symbol corresponds to the modulated data symbol generated by data modulation section332and the average symbol obtained when the mapping change symbol is combined with this modulated data symbol is substantially the same as the BPSK modulated signal.

Here, the correspondence relationship between the 64QAM symbols and mapping change symbols will be explained with reference toFIG. 15.FIG. 15Ashows the arrangement pattern of the modulated data symbols generated by data modulation sections321and332. In this 64QAM symbol arrangement pattern, with regard to the quadrants on the right of the Q axis (first and fourth quadrants), the I component of each of the signal points takes four values, and mapping change sections325and336change the mapping by moving signal points symmetrically using the point on the I axis that indicates the average of these four values as the point of symmetry.

Similarly, for the quadrants on the left of the Q axis as well (second and third quadrants), mapping change sections325and336change the mapping by moving signal points symmetrically in the I component of each of the signal points using the point that indicates the average value obtained from the four values as the point of symmetry. By this means, the mapping change symbol arrangement pattern becomes that shown inFIG. 15B.

When the 64QAM symbols ofFIG. 15Aand the mapping change symbols ofFIG. 15Bare combined through averaging processing, average symbols of two values are obtained on the I axis. These average symbols are substantially the same as the BPSK modulated signal. That is, the average symbol combined by performing averaging processing on the mapping change symbol generated by mapping change section325and336and the corresponding 64QAM symbol is a signal of information of “−1” or “1.”

FIG. 16summarizes the I components and Q components of the modulated data symbols, mapping change symbols and average symbols thereof. Furthermore, R in the figure indicates 0.154. In this figure, it is clear that the average symbols are all 0 for the Q component, and the two values 8R and −8R for the I component.

In this way, according to Embodiment 3, in a 64QAM symbol arrangement pattern, by changing the mapping by symmetrically moving the signal points of the right quadrants and left quadrants centering around the Q axis of the IQ plane using the point that indicates the average value of the I component of four values of each of the signal points as the point of symmetry, two values for the average symbols can be obtained from the modulated data symbols and corresponding mapping change symbols even with the 64QAM modulation scheme, and it is thereby possible to improve channel estimation accuracy and reception error rate characteristics by making the mobile station perform channel estimation using the average symbols.

In Embodiments 1 to 3, the case has been described where QPSK, 16QAM and 64QAM are applied as modulation schemes, but, in this embodiment, a case will be described where 8PSK is applied as the modulation scheme. The configuration of the base station according to Embodiment 4 of the present invention is the same as the configuration shown inFIG. 11of Embodiment 2, and thereforeFIG. 11will be employed, and the configuration of the mobile station according to Embodiment 4 of the present invention is the same as the configuration shown inFIG. 7of Embodiment 1, and thereforeFIG. 7will be employed, and duplicate descriptions thereof will be omitted.

With reference toFIG. 11, data modulation section321modulates D(1,2n−1) using 8PSK to generate a modulated data symbol. The modulated data symbol generated by data modulation section321is outputted to repetition section123. Data modulation section322modulates D(1,2n) to generate a modulated data symbol. The modulated data symbol generated by data modulation section322is outputted to repetition section124.

Mapping change section325as a generation means of the radio transmission apparatus, outputs the modulated data symbol inputted from repetition section123as is to multiplexing section110-1. Mapping change section325changes the mapping of the duplicate data symbol inputted after the modulated data symbol from repetition section123and generates a mapping change symbol. The generated mapping change symbol is outputted to multiplexing section110-1following the output of the modulated data symbol. This mapping change symbol corresponds to the modulated data symbol generated by data modulation section321, and the average symbol obtained when the mapping change symbol is combined with this modulated data symbol is substantially the same as the BPSK modulated signal.

Data modulation section331modulates D(2,2n−1) to generate a modulated data symbol. The modulated data symbol generated by data modulation section331is outputted to repetition section133. Data modulation section332modulates D(2,2n) using 8PSK to generate a modulated data symbol. The modulated data symbol generated by data modulation section332is outputted to repetition section134.

Mapping change section336as a generation means of the radio transmission apparatus, outputs the modulated data symbol inputted from repetition section134as is to multiplexing section110-2. Mapping change section336changes the mapping of the duplicate data symbol inputted after the modulated data symbol from repetition section134and generates a mapping change symbol. The generated mapping change symbol is outputted to multiplexing section110-2following the output of the modulated data symbol. This mapping change symbol corresponds to the modulated data symbol generated by data modulation section332, and the average symbol obtained when the mapping change symbol is combined with this modulated data symbol is substantially the same as the BPSK modulated signal.

Here, the correspondence relationship between the 8PSK symbols and mapping change symbols will be explained with reference toFIG. 17.FIG. 17Ashows the arrangement pattern of the modulated data symbols generated by data modulation sections321and332. In this 8PSK symbol arrangement pattern, with regard to the quadrants on the right of the Q axis (first and fourth quadrants), the I component of each of the signal points takes two values, and mapping change sections325and336change the mapping by moving signal points symmetrically using the point on the I axis that indicates the average of these two values as the point of symmetry.

Similarly, for the quadrants on the left of the Q axis as well (second and third quadrants), mapping change sections325and336change the mapping by moving signal points symmetrically in the I component of each of the signal points using the point that indicates the average value obtained from the two values as the point of symmetry. By this means, the mapping change symbol arrangement pattern becomes that shown inFIG. 17B.

When the 8PSK symbols ofFIG. 17Aand the mapping change symbols ofFIG. 17Bare combined through averaging processing, average symbols of two values are obtained on the I axis. These average symbols are substantially the same as the BPSK modulated signal. That is, the average symbol combined by performing averaging processing on the mapping change symbol generated by mapping change section325and336and the corresponding 8PSK symbol is a signal of information of “−1” or “1.”

FIG. 18summarizes the I components and Q components of the modulated data symbols, mapping change symbols and average symbols thereof. In this figure, it is clear that the average symbols are all Q for the Q component, and the two values 1.307 and −1.307 for the I component.

In this way, according to Embodiment 4, in an 8PSK symbol arrangement pattern, by changing the mapping by symmetrically moving the signal points of the right quadrants and left quadrants centering around the Q axis of the IQ plane using the point that indicates the average value of the I component of two values of each of the signal points as the point of symmetry, two values for the average symbols can be obtained from the modulated data symbols and corresponding mapping change symbols even with the 8PSK modulation scheme, and it is thereby possible to improve channel estimation accuracy and reception error rate characteristics by making the mobile station perform channel estimation using the average symbols.

In Embodiment 4, the case has been described where 8PSK is applied as the modulation scheme, but, in Embodiment 5 of the present invention, a case will be described where 16PSK is applied as the modulation scheme. The configuration of the base station according to Embodiment 5 of the present invention is the same as the configuration shown inFIG. 11of Embodiment 2, and thereforeFIG. 11will be employed, and the configuration of the mobile station according to Embodiment 5 of the present invention is the same as the configuration shown inFIG. 7of Embodiment 1, and thereforeFIG. 7will be employed, and duplicate descriptions thereof will be omitted.

With reference toFIG. 11, data modulation section321modulates D(1,2n−1) using 16PSK to generate a modulated data symbol. The modulated data symbol generated by data modulation section321is outputted to repetition section123. Data modulation section322modulates D(1,2n) to generate a modulated data symbol. The modulated data symbol generated by data modulation section322is outputted to repetition section124.

Mapping change section325as a generation means of the radio transmission apparatus, outputs the modulated data symbol inputted from repetition section123as is to multiplexing section110-1. Mapping change section325changes the mapping of the duplicate data symbol inputted after the modulated data symbol from repetition section123and generates a mapping change symbol. The generated mapping change symbol is outputted to multiplexing section110-1following the output of the modulated data symbol. This mapping change symbol corresponds to the modulated data symbol generated by data modulation section321, and the average symbol obtained when the mapping change symbol is combined with this modulated data symbol is substantially the same as the four-value AM modulated signal.

Data modulation section331modulates D(2,2n−1) to generate a modulated data symbol. The modulated data symbol generated by data modulation section331is outputted to repetition section133. Data modulation section332modulates D(2,2n) using 16PSK to generate a modulated data symbol. The modulated data symbol generated by data modulation section332is outputted to repetition section134.

Mapping change section336as a generation means of the radio transmission apparatus, outputs the modulated data symbol inputted from repetition section134as is to multiplexing section110-2. Mapping change section336changes the mapping of the duplicate data symbol inputted after the modulated data symbol from repetition section134and generates a mapping change symbol. The generated mapping change symbol is outputted to multiplexing section110-2following the output of the modulated data symbol. This mapping change symbol corresponds to the modulated data symbol generated by data modulation section332, and the average symbol obtained when the mapping change symbol is combined with this modulated data symbol is substantially the same as the four-value AM modulated signal.

Here, the correspondence relationship between the 16PSK symbol and mapping change symbol will be explained with reference toFIG. 19.FIG. 19Ashows the arrangement pattern of the modulated data symbols generated by data modulation sections321and332. In this 16PSK symbol arrangement pattern, with regard to the quadrants on the right of the Q axis (first and fourth quadrants), the I component of each of the signal points takes four values, and mapping change sections325and336change the mapping by moving signal points symmetrically using the point on the I axis that indicates the average of these four values as the point of symmetry.

Similarly, for the quadrants on the left of the Q axis as well (second and third quadrants), mapping change sections325and336change the mapping by moving signal points symmetrically in the I component of each of the signal points using the point that indicates the average value obtained from the two values as the point of symmetry. By this means, the mapping change symbol arrangement pattern becomes that shown inFIG. 19B.

When the 16PSK symbols ofFIG. 19Aand the mapping change symbols ofFIG. 19Bare combined through averaging processing, four average symbol values are obtained on the I axis.

FIG. 20summarizes the I components and Q components of the modulated data symbols, mapping change symbols and average symbols thereof. In this figure, it is clear that the average symbols are all 0 for the Q component, and the four values 1.176, 1.387, −1.176, and −1.387 for the I component.

In this way, according to Embodiment 5, in a 16PSK symbol arrangement pattern, by changing the mapping by symmetrically moving the signal points of the right quadrants and left quadrants centering around the Q axis of the IQ plane using the point that indicates the average value of the I component of four values of each of the signal points as the point of symmetry, four values for the average symbols can be obtained from the modulated data symbols and the corresponding mapping change symbols even with the 16PSK modulation scheme, and it is thereby possible to improve channel estimation accuracy and reception error rate characteristics by making the mobile station perform channel estimation using the average symbols.

In Embodiment 2, the case has been described where 16QAM is applied as the modulation scheme and channel estimation is performed using average symbols of two values obtained by combining modulated data symbols and mapping change symbols, but, in Embodiment 6 of the present invention, a case will be described where channel estimation is performed using average symbols of one value.

FIG. 21is a block diagram showing a configuration of the base station according to Embodiment 6 of the present invention. The differences betweenFIG. 21andFIG. 11are that bit division section531, bit insertion section532and 16QAM modulation section533are added to data modulation section321to be data modulation section521, and bit division section541, bit insertion section542and 16QAM modulation section543are added to data modulation section322to be data modulation section522.

InFIG. 21, bit division section531divides inputted D(1,2n−1) per three bits, and outputs the signal sequences divided into three bits to bit insertion section532.

Bit insertion section532inserts 0 at the head of each signal sequence divided into three bits and outputted from bit division section531, and outputs each signal sequence of four bits with 0 at the head to 16QAM modulation section533.

16QAM modulation section533modulates using 16QAM each signal sequence of four bits outputted from bit insertion section532and generates a modulated data symbol. The modulated data symbol generated by 16QAM modulation section533is outputted to repetition section123.

Mapping change section325as a generation means of the radio transmission apparatus, outputs the modulated data symbol inputted from repetition section123as is to multiplexing section110-1. Mapping change section325changes the mapping of the duplicate data symbol inputted after the modulated data symbol from repetition section123and generates a mapping change symbol. The generated mapping change symbol is outputted to multiplexing section110-1following the output of the modulated data symbol. This mapping change symbol corresponds to the modulated data symbol generated by data modulation section321.

Bit division section541divides inputted D(2,2n) per three bits, and outputs the signal sequences divided into three bits to bit insertion section542.

Bit insertion section542inserts 0 at the head of each signal sequence divided into three bits and outputted from bit division section541, and outputs each signal sequence of four bits with 0 at the head to 16QAM modulation section543.

16QAM modulation section543modulates using 16QAM each signal sequence of four bits outputted from bit insertion section542to generate a modulated data symbol. The modulated data symbol generated by 16QAM modulation section543is outputted to repetition section134.

Mapping change section336as a generation means of the radio transmission apparatus, outputs the modulated data symbol inputted from repetition section134as is to multiplexing section110-2. Mapping change section336changes the mapping of the duplicate data symbol inputted after the modulated data symbol from repetition section134and generates a mapping change symbol. The generated mapping change symbol is outputted to multiplexing section110-2following the output of the modulated data symbol. This mapping change symbol corresponds to the modulated data symbol generated by data modulation section332.

Here, the correspondence relationship between the 16QAM symbol which always has 0 at the head of the signal sequence of four bits, and the mapping change symbol will be explained with reference toFIG. 22.FIG. 22Ashows the arrangement pattern of the modulated data symbols generated by data modulation sections321and332. In this 16QAM symbol arrangement pattern, the I component of each of the signal points takes two values, and mapping change sections325and336change the mapping by moving signal points symmetrically using the point on the I axis that indicates the average of these two values as the point of symmetry. By this means, the mapping change symbol arrangement pattern becomes that shown inFIG. 22B.

When the 16QAM symbols ofFIG. 22Aand the mapping change symbols ofFIG. 22Bare combined through averaging processing, average symbols of one value are obtained on the I axis as shown inFIG. 22C.

FIG. 23summarizes the I components and Q components of the modulated data symbols, mapping change symbols and average symbols thereof. Furthermore, R in the figure indicates 0.3162. In this figure, it is clear that the average symbols are all 0 for the Q component, and the single value 4R for the I component.

FIG. 24is a block diagram showing a configuration of MIMO reception section212-1according to Embodiment 6 of the present invention. The difference betweenFIG. 24andFIG. 14are that head bit removal sections602and604are added.

Head bit removal section602removes the head bit0of each signal sequence of four bits superimposed on each symbol, out of signal sequences outputted from data demodulation section240and then outputs the signal sequence of three bits from which the head bit0is removed.

Similarly, head bit removal section604outputs the signal sequences outputted from data demodulation section243with the head bits removed.

In this way, according to Embodiment 6, in a 16QAM symbol arrangement pattern having signal sequences with 0 at the head, by changing the mapping by symmetrically moving the signal points using the point that indicates the average value of the I component of two values of each of the signal points as the point of symmetry, one value for the average symbols can be obtained from the modulated data symbols and the corresponding mapping change symbols, and it is thereby possible to improve channel estimation accuracy and reception error rate characteristics by making the mobile station perform channel estimation using the average symbols.

Furthermore, in this embodiment, the case has been described where 0 is inserted at the head and modulation is performed, but the present invention is not limited to this, and, the present invention can be similarly applied to a case where 1 is inserted at the head and modulation is performed.FIG. 25shows the correspondence relationship between the 16QAM symbol and mapping change symbol at this time, andFIG. 26shows the I components and Q components of the modulated data symbols, mapping change symbols and average symbols thereof.

Further, each function block employed in the description of each of the aforementioned embodiments may typically be implemented as an LSI constituted by an integrated circuit. These may be individual chips or partially or totally contained on a single chip.

Furthermore, here, each function block is described as an LSI, but this may also be referred to as “IC”, “system LSI”, “super LSI”, “ultra LSI” depending on differing extents of integration.

Further, the method of circuit integration is not limited to LSI's, and implementation using dedicated circuitry or general purpose processors is also possible. After LSI manufacture, utilization of an FPGA (Field Programmable Gate Array) or a reconfigurable processor where connections and settings of circuit cells within an LSI can be reconfigured is also possible.

The present application is based on Japanese Patent Application No. 2004-376162, filed on Dec. 27, 2004 and Japanese Patent Application No. 2005-263014, filed on Sep. 9, 2005, the entire content of which is expressly incorporated by reference herein.

INDUSTRIAL APPLICABILITY

The radio transmission apparatus, radio reception apparatus, radio transmission method and radio reception method of the present invention can be applied to apparatuses such as a base station apparatus and a mobile station apparatus in a radio communication network system where a plurality of streams are transmitted in parallel.