JP4616030B2 - Wireless transmission device, wireless reception device, transmission / reception method, and computer program - Google Patents

Description

  The present invention relates to a wireless transmission device, a wireless reception device, a transmission / reception method, and a computer program used in a transmission diversity method for orthogonal frequency division multiplexing / code division multiplexing in a mobile communication system.

  In recent years, with the development of mobile communication systems, further broadband, high frequency and high reliability have been demanded. In mobile communication systems, there is a transmission diversity technique for improving transmission quality without expanding the radio unit of a terminal. It is an effective means. Also, when transmitting low rate data or control data, or when transmitting in an environment where interference from other cells is severe, orthogonal frequency division multiplexing / code division multiplexing (hereinafter referred to as OFDM-CDM: Orthogonal). (Frequency Division Multiplexing-Code Division Multiplexing) is known as an effective means. Therefore, first, a conventional technique using the transmission diversity method and a conventional technique using the OFDM-CDM method will be described.

Two conventional techniques will be described below as conventional techniques in the transmission diversity system. The first prior art of the transmission diversity system is a transmission diversity system that uses two antenna branches. FIG. 11 shows a radio transmitter 1d having two transmission antennas 112-1 and 112-2 using a space-time code (STBC: Space Time Block Code) of 2 rows and 2 columns, and the radio transmitter 1d. It is the block diagram which showed the radio | wireless receiver 2d which receives the signal to receive. The wireless transmitter 1d uses a 2 × ₂ space-time encoder 100 to convert a transmission symbol pair s = [s ₁ , s ₂ ] ^{T based} on a ₂ × ₂ space-time coding matrix of the following equation (1). Space-time coding is performed, and the space-time coded transmission symbols are transmitted from the transmission antennas 112-1 and 112-2.

The 2-row 2-column space-time encoder 100 transmits s ₁ from the transmission antenna 112-1 at time ₁ and transmits s ₂ from the transmission antenna 112-2 simultaneously. Further, it sends _-s ^{2 *} from the transmission antenna 112-1 at the next time 2, and transmits from the transmission antenna 112-2 _s ^{1 *} simultaneously. In this case, the signal received by the receiving antenna 120 of the radio receiver 2d and r ₁ at time 1, when the signal received at time 2, r _2, the received signal r ₁ and r ₂ is expressed by the following equation ( 2).

In Expression (2), h ₁ and h ₂ are channel responses on the receiving side of the transmitting antennas 112-1 and 112-2, respectively. h ₁ and h ₂ are values calculated by the channel estimator 102 based on the received signal. When the received signal vector r is displayed in matrix using h ₁ and h ₂ , the following expression (3) is obtained.

Further, the channel matrix H is defined as in the following equation (4) using h ₁ and h ₂ .

The estimated value vector s ^ of the transmission signal in the space-time decoder 101 of the radio receiver 2d can be decoded as in the following equation (5) using the conjugate transpose matrix H ^H of the channel matrix H.

  As shown in Expression (5), since two symbols are transmitted in two time slots, the transmission rate is a full rate, and maximum ratio combining diversity for two transmission antenna branches can be realized.

  Next, as a second conventional technique in the transmission diversity scheme, a closed-loop transmission antenna diversity scheme of four antenna branches using two sets of 2 × 2 space-time codes will be described. FIG. 12 is a block diagram showing a radio transmitter 1e and a radio receiver 2e that realize a closed-loop transmit antenna diversity system having four transmit antennas 112-1 to 112-4 (for example, Non-Patent Document 1). reference).

  A 2 × 4 space-time coding performed by the 2 × 4 space-time encoder 110 in the wireless transmitter 1e is shown in the following equation (6).

  Here, b in the matrix is a binary code calculated by the feedback value calculator 126 of the wireless receiver 2e, and a value of +1 or −1 is set. A method using b (hereinafter referred to as control information) is called STBC-Group Coherent Code (STBC-GCC).

  The received signal vector r in the radio receiver 2e is represented by the following expression (7) in matrix display.

Therefore, the equivalent channel matrix ^{H ~} is represented by the following formula (8).

The time estimate vector s of the transmission signal ^ is able to use the conjugate transpose matrix H ^{to H} of the equivalent channel matrix H ^~ is decoded as shown in the following equation (9).

  Α and β in the equation (9) are as shown in the following equations (10) and (11), respectively.

  In the STBC-GCC scheme, b is controlled on the transmission side in advance so that the value of β becomes a positive value. Accordingly, since two symbols can be transmitted in two time slots, the transmission rate is a full rate. Further, an array gain β can be obtained in addition to the spatial diversity gain α for the four transmitting antenna branches.

Next, the prior art in the OFDM-CDM system will be described. FIG. 13 is a block diagram showing an OFDM-CDM wireless transmitter 1f and a wireless receiver 2f. FIG. 14 is a diagram illustrating the concept of two-dimensional spreading applied to the OFDM-CDM scheme. As shown in FIG. 14, two-dimensional spreading is performed by spreading one original symbol in the frequency direction and the time direction. In the spread in the frequency direction, a transmission symbol is serial-parallel converted by the serial-parallel converter 131 of the radio transmitter 1f, and then one original symbol is frequency-frequency spread ratio (SF _Freq ) by the replicators 132-1 to 132-n. This is done by duplicating the number of symbols corresponding to. The spreading in the time direction is performed for each symbol duplicated by the duplicators 132-1 to 132-n based on different spreading codes corresponding to the spreading factor (SF _Time ) in the time direction. 1321-m is performed by being diffused by 132n-1 to 132n-m. At this time, the spreading factor SF in the two-dimensional spreading is SF = SF _Time × SF _Freq . Since the above two-dimensional spreading is performed in the frequency direction, the SF _Time is set using a spreading code having a spreading length of SF. It means that it is folded and spread every time. Further, the two-dimensionally spread signal is assigned to each subcarrier in the frequency domain, and is input to the code multiplexer 133 as a subcarrier signal.

  Next, spread signals spread with different spreading codes are code-multiplexed by the code multiplexer 133, and the code-multiplexed signal is subjected to inverse Fourier transform (hereinafter referred to as IFFT: Inverse First Fourier Transform) by the transform transmitter 134. After the carrier signal is converted into a time domain signal, a guard interval (GI) is inserted to avoid intersymbol interference and transmitted via the transmission antenna 135.

On the other hand, in the radio reception device 2f, the reception conversion unit 142 removes the guard interval from the signal received by the reception antenna 141 and performs Fourier transform (hereinafter referred to as FFT: First Fourier Transform) to convert it into a subcarrier signal. To do. Then, despreading in the time direction is performed by the despreaders 1431-1 to 1431-m and 143n-1 to 143n-m, and further, the combining is performed in the frequency direction by the synthesizers 143-1 to 143-n. Finally, the parallel / serial converter 144 performs parallel / serial conversion on the signal synthesized in the frequency direction and outputs a reproduction signal.
J.Akhtar and D.Gesbert, “Partial feedback based orthogonal block coding,” Proc. VTC'03-Spring, pp.287-291, Korea, April 2003.

In an environment where the above-described communication method is actually used, there are a plurality of receivers on the receiving side. At this time, in the closed loop transmission antenna diversity system using four transmission antenna branches, that is, the second conventional technique in the transmission diversity system, that is, the closed loop STBC-GCC system, feedback of control information from the reception side is required. Therefore, control information is received from a plurality of receivers. Figure 15 is a block diagram showing a configuration in which control information b ₁ respectively from the radio transmitter 1g and the wireless receiver 2 g-1 of the two one and 2 g-2 and b ₂ is fed back.

By the way, in an actual cellular phone communication network, when transmitting a signal common to a plurality of users, the wireless transmitter 1g corresponds to a base station or an access point, and the wireless receivers 2g-1 and 2g-2 have a plurality of signals. It corresponds to the mobile phone used by the user. In such a case, since the channel gains of the wireless transmitter 1g and the wireless receiver 2g-1 and the channel gains of the wireless transmitter 1g and the wireless receiver 2g-2 are different, the feedback control information does not necessarily match. There is. As a specific example, the channel responses from the four transmission antennas 112-1 to 112-4 of the wireless transmitter 1 g to the wireless receiver 2 g-1 are h ₁ , h ₂ , h ₃ , h _4, and wireless The channel responses to the receiver 2g-2 are h ₅ , h ₆ , h _{7 and} h ₈ . At this time, the array gains β ₁ and β ₂ in the wireless receiver 2g-1 and the wireless receiver 2g-2 are as shown in the following equations (12) and (13), respectively.

Here, a b ₁ is 1 to the beta ₁ a positive value, when b ₂ to the beta ₂ and positive value is -1, the radio transmitter 1g because the value of the control information is contradictory There arises a problem that it cannot be controlled. If all the control information values are 1, the array gain β ₂ in the radio receiver 2g-2 becomes a negative value, and the total gain α ₂ + β ₂ in the radio receiver 2g-2 becomes a gain smaller than α ₂ and the transmission quality becomes low. Will be reduced.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to perform transmission without feedback of control information from the radio receiver side in the STBC-GCC system, and further, OFDM of the STBC-GCC system. -To provide a wireless transmitter, a wireless receiver, a transmission / reception method, and a computer program that can be applied to a CDM communication system.

  In order to solve the above-described problem, the present invention extracts encoding means for encoding transmission data into a plurality of space-time codes, and a plurality of combinations from the plurality of space-time codes encoded by the encoding means. Then, for each set of extracted space-time codes, a spread signal is generated by associating each of a plurality of spreading codes consisting of a combination of repeating in-phase and anti-phase with a certain spreading length to spread the space-time code A wireless transmission apparatus comprising: a spreading unit configured to transmit; and a transmission unit configured to transmit a spread signal generated by the spreading unit using a plurality of transmission antennas. As a result, when the wireless receiver side performs space-time decoding on a spread signal spread by a plurality of spread codes that repeat in-phase and reverse-phase, the array gain is canceled and data can be reproduced.

  Further, the present invention provides a plurality of spreading units comprising a combination of receiving means for receiving signals transmitted from a plurality of transmitting antennas and outputting a spreading signal included in the signals and repeating in-phase and anti-phase with a certain spreading length. A spreading signal output from the receiving means by any one of the codes is despread for each of the constant spreading lengths to restore the space-time code, and the time restored by the despreading means A radio receiving apparatus comprising: a decoding unit that decodes a space code; and a combining unit that combines the space-time code decoded by the decoding unit to reproduce data. As a result, a spread signal is generated by spreading with a plurality of spreading codes that repeat the same phase and opposite phase in the wireless transmitter, thereby canceling array gain and reproducing data when performing space-time decoding on the wireless receiver side. can do.

  According to the present invention, in the STBC-GCC system, a radio transmitter that performs transmission without feedback of control information from the radio receiver side and can be applied to the OFDM-CDM communication system of the STBC-GCC system. A wireless receiver, a transmission / reception method, and a computer program can be obtained.

(First embodiment)
Hereinafter, a wireless transmitter and a wireless receiver according to a first embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing the internal configuration of the wireless transmitter 1a according to the first embodiment and the relationship of wireless signal propagation between the wireless transmitter 1a and the wireless receiver 2a.

In the radio transmitter 1a of FIG. 1, the 2 × 4 space-time encoder 10 performs space-time coding on the transmission symbol pair s = [s ₁ , s ₂ ] ^T. The spreaders 11-1 to 11-4 transmit the transmission symbols space-time encoded by the 2 rows and 4 columns space-time encoder 10 to the Walsh-Hadhard (hereinafter, referred to as “Walsh-Hadmard”) in the branches of the transmission antennas 12-1 to 12-4. Spreading is performed using a code (abbreviated as WH) to generate a spread signal. The transmission antennas 12-1 to 12-4 transmit signals spread by the spreaders 11-1 to 11-2.

FIG. 2 is a diagram illustrating an internal configuration of the wireless receiver 2a corresponding to the wireless transmitter 1a. The partial despreader 21 is a mother for a reception signal received by the receiving antenna 20 and corresponding to a certain diffusion length described in the appended claims over the length of two diffusion regions, that is, 2SF. Partial despreading is performed for each spreading length SF _Time of the code layer. At this time, the WH code used for partial despreading is the WH code input to the spreaders 11-1 and 11-2 of the radio receiver 1a or the spreader 11-3 and 11-4. Either one of the WH codes is used. The number M of partial diffusion segments at this time is M = SF / SF _Time .

The channel estimator 23 calculates channel response estimates h ₁ , h ₂ , h ₃ , h ₄ , based on the received signal received by the receiving antenna 20, and uses the calculated channel response estimates. Output. Equivalent channel matrix calculator 24 calculates an equivalent channel matrix H ^~ based on an estimate of the channel response calculated by the channel estimator 23. The space-time decoder 22 decodes a signal on the basis of the signal for each despread partial spread segment output from the partial despreader 21 and the equivalent channel matrix H ^~ output from the equivalent channel matrix calculator 24. I do. The synthesizer synthesizes the signals for the partial spread segments output from the space-time decoder 22.

Next, operations of the above-described wireless transmitter 1a and wireless receiver 2a will be described.
When a transmission symbol pair s = [s ₁ , s ₂ ] ^T is input, space-time coding is performed by the 2-row 4-column space-time encoder 10 of the wireless transmitter 1a, and two rows shown in the following equation (14) are obtained. A four-column space-time code matrix S is generated.

  This encoding matrix S is expanded for four branch transmission antennas by repeating 2 rows and 2 columns STBC for transmission antennas having two branches.

Next, the generated space-time code matrix S is spread by the spreaders 11-1 to 11-4 using the WH code to generate a spread signal. At this time, at this time, the WH code applied to the STBC of 2 rows and 2 columns on the right side of Equation (14), that is, the WH code input to the spreaders 11-1 and 11-2, and the expanded left 2 A different WH code is applied to the WH code applied to the STBC of the row 2 column, that is, the WH code input to the spreaders 11-3 and 11-4. That is, setting is performed so that a WH code is applied so that the polarity of the spreading code alternately repeats in-phase and inversion for each spreading length of the upper layer of the code, that is, the mother code layer. Specifically, when the spreading length SF _Time = 8 of the mother code layer, when the spreading factor SF = 64, the two applied WH codes w ₅₇ and w ₆₁ are expressed by the following equations (15) and (16): Can show.

Here, when the code portion of the SF _Time length is a partial diffusion segment, the above-mentioned polarity alternately repeats in-phase and inversion in the expressions (15) and (16). In (3), the same code sequence is used, whereas in partial spread segments (2) and (4), the code is inverted. Signal vectors u ₁ (1), u ₂ (1), u ₃ for each of the transmission antennas 12-1 to 12-4 in which the first row of STBC symbols of 2 rows and 4 columns, that is, the symbols of the first time slot are spread (1) and u ₄ (1) are expressed as the following equation (17).

Similarly, signals u ₁ (2), u ₂ (2), u ₃ (2), u ₄ (2) for each of the transmission antennas 12-1 to 12-4 in which the transmission symbols of the second time slot are spread are It is shown as the following formula (18).

Next, the wireless receiver 2a receives a signal transmitted from the wireless transmitter 1a. At this time, the received signal vector r ₁ corresponding to the transmission signal of the first row of the space-time coding matrix S generated based on the transmission symbol transmitted from the wireless transmitter 1a, that is, the transmission signal of the first time slot. Is represented by the following equation (19).

Also, the received signal vector r ₂ for the transmission signal in the second row of the space-time coding matrix, that is, the transmission signal in the second time slot is represented by the following equation (20).

The partial despreader 21 performs partial despreading on the received signal vector using one of the two WH codes used by the wireless transmitter 1a for each partial spread segment. In this embodiment, a case where _w57 is applied will be described. The partial despreading for the first partial spreading segment of the vector r ₁ is shown by the following equation (21).

Further, partial despreading for the first partial spread segment of the vector r ₂ is expressed by the following equation (22).

Further, partial despreading for the second partial spread segment of the vector r ₁ is represented by the following equation (23).

Further, partial despreading for the second partial spread segment of the vector r ₂ is expressed by the following equation (24).

Vector y ₁ which is a partially despread the first signal y ₁ for the partial diffusion segment and y ₂ and the equivalent channel matrix H ^~ matrix display using a ₁ is expressed by the following equation (25).

Furthermore, the vector y ₂ which was the matrix display and a signal y ₃ and y ₄ for the second partial diffusion segments further portion despread using the equivalent channel matrix H ^~ _-1, as the following equation (26) Indicated.

When performing decoding on the vectors _{y 1} and vector _{y 2} using the conjugate transpose matrix ^{H to H} ₁ and ^H _{to H -1} of equivalent channel matrix calculated by the equivalent channel matrix calculator 24 ^H _{~ 1} and ^H _{~ -1} The decoded signal vector z ₁ and vector z ₂ are expressed by the following equations (27) and (28), respectively.

  Then, when the signal vector z decoded by the synthesizer 25 is synthesized, an estimated value vector s ^ of the transmission signal is represented by the following equation (29).

  As shown in Expression (29), by applying the WH code such that the polarity of the spreading code alternately repeats in-phase and inversion for each spreading length of the mother code layer in the configuration as described above, the array gain β is It is canceled out and only the space diversity gain α is obtained. As a result, it is possible to realize an open-loop transmission diversity method that does not require control information fed back at the expense of the array gain β.

(Second Embodiment)
Next, a radio transmitter and a radio receiver that realize an open-loop transmission diversity scheme in the OFDM-CDM scheme according to the second embodiment of the present invention will be described with reference to the drawings. FIG. 3 is a block diagram showing the internal configuration of the wireless transmitter 1b according to the second embodiment and the relationship of wireless signal propagation between the wireless transmitter 1b and the wireless receiver 2b.

  In FIG. 3, for the wireless transmitter 1 b, OFDM-CDM modulators 31-1 to 31-4 having a different configuration from the wireless transmitter 1 a of the first embodiment will be described below, and other configurations are the same. Since it is a structure, the same code | symbol as the wireless transmitter 1a of 1st Embodiment is attached | subjected, and description is abbreviate | omitted.

  The OFDM-CDM modulators 31-1 to 31-4 have the configuration of the above-described wireless transmitter 1 f in order to realize the OFDM-CDM system. That is, in each of the OFDM-CDM modulators 31-1 to 31-4, the input signal is subjected to serial-parallel conversion, and each of the parallel-converted signals is converted into the frequency direction and the time direction based on the spreading code. In this configuration, the spread signal that has been two-dimensionally spread is subjected to inverse Fourier transform for each subcarrier signal, and transmitted after inserting a guard interval in order to avoid intersymbol interference. In the second embodiment, different spreading codes are input to the OFDM-CDM modulators 31-1, 31-2 and the OFDM-CDM modulators 31-3, 31-4. Here, spreading code # 1 is set in OFDM-CDM modulators 31-1, 31-2, and spreading code # 2 is set in OFDM-CDM modulators 31-3, 31-4. Details of how to assign codes # 1 and # 2 will be described later.

FIG. 4 is a block diagram showing an internal configuration of the wireless receiver 2b with respect to the wireless transmitter 1b. In FIG. 4, the reception conversion unit 41 removes the guard interval from the signal received by the reception antenna 20, performs Fourier transform to convert the signal into subcarrier signals, and outputs each subcarrier signal. The time-direction despreader 42-1 performs despreading on the signal output from the reception conversion unit 41 based on a spread code set in advance in the time direction. Channel estimator 43-1, the receiving antenna 20 is received by, based on a sub-carrier signal output is converted by the reception converter unit 41, the estimated value of the channel response in the frequency of the subcarrier h _{1 ^,} h _2, ^ H ₃ ^ and h ₄ ^ are calculated. The equivalent channel matrix calculator 44-1 calculates an equivalent channel matrix at the frequency of the subcarrier based on the channel response estimation value calculated by the channel estimator 43-1. The space-time decoder 45-1 decodes a signal based on the despread signal output from the time direction despreader 42-1 and the equivalent channel matrix output from the equivalent channel matrix calculator 44-1. I do. The frequency direction synthesizer 46-1 synthesizes the signals output from the space-time decoder 45-1 and other space-time decoders that decode other subcarriers in the frequency direction, and reproduces the reproduced signals s _{1 １} and s ₂ ＾. Is output.

  FIG. 5 shows a generation tree of WH codes input to the OFDM-CDM modulators 31-1 to 31-4 of the OFDM-CDM wireless transmitter 1b shown in FIGS. 3 and 4, and allocation to the physical layer. It is the figure which showed the example of. As shown in FIG. 5, the WH code # 57 and the WH code # 61, which are different spreading codes, are used in the OFDM-CDM modulators 31-1 and 31-2 and the OFDM-CDM modulators 31-3 and 31-4. Entered.

  WH codes # 57 and WH # 67 are WH codes belonging to the same generation tree of the mother code layer. For example, the polarity of the spreading code is the same for each spreading length 8 shown in the above-described equations (15) and (16). The sign which repeats and inversion alternately is applied. Here, the reason why the WH codes belonging to the generation tree of the same mother code layer are used is that the number of WH codes used for the time direction spreading is not reduced. In other words, the code of the mother code layer, which is an orthogonal code, must be used in time-direction spreading. If WH # 57 and # 61 belong to different mother code layers, they are used. The remaining mother code layer WH codes that can be generated are six, which limits the amount of data that can be transmitted. In the present embodiment, as shown in FIG. 5, since the WH codes # 57 and # 61 belong to the generation tree of the mother code layer # 8, the remaining WH codes that can be used for time-direction spreading are the same as those in the past. Seven mother code layers # 1 to # 7 can be applied. That is, by using WH codes belonging to the same mother code layer generation tree, the effect of the present invention can be obtained while maintaining the same amount of transmission data as in the past.

FIG. 6 is a diagram illustrating a mechanism in which transmission symbols are assigned to two-dimensional spreading areas in each of the transmission antennas 12-1 to 12-4. The signals u ₁ (1), u ₂ (1), u ₃ (1), and u ₄ (1) in the first spread time slot are respectively expressed as u ₁ (1) = s _1. It can be shown as w ₅₇ , u ₂ (1) = s ₂ · w ₅₇ , u ₃ (1) = s ₁ · w ₆₁ , u ₄ (1) = s ₂ · w ₆₁ . If the diffusion lengths of w ₅₇ and w ₆₁ are 64, the 64 spread symbols are folded for each SF _Time and assigned to the two-dimensional diffusion region. At this time, since the frequencies of the subcarriers assigned to the transmission antennas 12-1 to 12-4 are the same, u ₁ (1), u ₂ (1), u ₃ (1), u ₄ (1) The eight partial spreading segments for each block of SF _Freq are allocated to the same subcarrier and transmitted.

Next, operations of the wireless transmitter 1b in FIG. 3 and the wireless receiver 2b in FIG. 4 will be described. The 2 × 4 space-time encoder 10 of the wireless transmitter 1b converts the input transmission symbols s ₁ and s ₂ into a ₂ × 4 matrix S shown in the above equation (14). The OFDM-CDM modulators 31-1 and 31-2 perform time direction spreading based on the WH code # 57, and the OFDM-CDM modulators 31-3 and 31-4 perform time direction based on the WH code # 61. Perform diffusion. Furthermore, in the time slot 1, the OFDM-CDM modulator 31-1 uses the signal u ₁ (1) = s ₁ · w _57, which has been spread in the time direction, in the time direction in the two-dimensional spreading region as shown in FIG. When the time-direction spreading factor SF _Time = 8 is exceeded, folding is performed and the adjacent subcarriers are arranged in the time direction. Similarly, the OFDM-CDM modulators 31-2 to 31-4 have their spread signals u ₂ (1) = s ₂ · w ₅₇ , u ₃ (1) = s ₁ · w ₆₁ , u ₄ (1 ) = S ₂ · w ₆₁ is assigned to the two-dimensional diffusion region, inverse Fourier transformed to convert it into a time domain signal, and transmitted after inserting a guard interval. Similarly, in the next time slot 2, u ₁ (2) = − s ₂ ^* · w ₅₇ , u ₂ (2) = s ₁ ^* · w ₅₇ , u ₃ (2) = − s ₂ ^* · w ₆₁ , U ₄ (2) = s ₁ ^* · w ₆₁ is assigned to the two-dimensional diffusion region and transmitted as shown in FIG.

The radio receiver 2b receives the signal transmitted from the radio transmitter 1b, and after the reception conversion unit 41 removes the guard interval, it performs Fourier transform to convert it into a subcarrier signal. The time-direction despreader 42-1 corresponds to the first subcarrier signal, that is, the first eight symbols of u ₁ (1), u ₂ (1), u ₃ (1), u ₄ (1). The subcarrier signal including the partial spread segment is despread in the time direction based on the code of WH # 57 used for spreading in the wireless transmitter 1b. The space-time decoder 45-1 decodes and outputs a signal despread in the time direction based on the equivalent channel matrix calculated by the channel estimator 43-1 and the equivalent channel matrix calculator 44-1. . The frequency direction synthesizer 46-1 synthesizes the signal output from the space-time decoder 45-1 in the frequency direction over the subcarriers in the two-dimensional diffusion region, and outputs reproduced signals s ₁ ｓ and s ₂ ＾. .

  With the configuration of the second embodiment described above, the spreading factor of partial despreading performed in the time direction despreader 42-1 is the time direction spreading factor of the two-dimensional spread OFDM-CDM. The response values are almost equal, and the absolute values of the array gains in adjacent subcarriers are almost equal, and the signs are out of phase. Therefore, by combining in the frequency direction, the array gain is canceled, but in the open loop configuration, a spatial diversity gain can be obtained.

In FIG. 4, the time-direction despreader 42-1, the space-time decoder 45-1, the channel estimator 43-1 and the equivalent channel matrix calculator 44-1 are equivalent to the number of subcarrier signals, that is, In the case of SF _Freq = 8 shown in FIG. 6, eight are provided. The frequency direction synthesizer 46-1 is provided for each unit to be synthesized in the frequency direction. When SF _Freq = 8, eight space-time decoders are connected to the input side with one frequency direction synthesizer. It will be.

FIG. 7 is a diagram illustrating a signal allocation state in one transmission antenna when chip interleaving is performed on symbols constituting a spread signal, that is, spread chips. As shown in FIG. 7, when chip spreading is assigned to subcarriers, chip interleaving is a sub-frequency separated by a certain frequency (in FIG. 7, every SF _Freq ) corresponding to a predetermined frequency described in the appended claims. This means that signals are distributed and arranged in the frequency domain by being assigned to carrier signals.

It is the figure which showed that it is necessary to perform interleaving for every two adjacent subcarriers, since a WH code repeats an in-phase and a reverse phase for every SF _Time . By performing chip interleaving as shown in FIG. 7, the array gain is the same in two adjacent subcarriers after interleaving is returned on the receiving side (after deinterleaving), and the reverse phase property is maintained. Therefore, the array gain can be canceled out. In addition, when combining in the frequency direction, subcarrier pairs that are separated from each other are added, so even if the subcarrier received power is reduced across consecutive subcarriers, the effect of the reduction Can be dispersed. In other words, frequency diversity gain can be obtained by chip interleaving.

(Third embodiment)
Next, a radio transmitter 1c and a radio receiver 2c to which the two-dimensional spread OFDM-CDM scheme in the third embodiment is applied will be described with reference to FIGS.
FIG. 8 is a block diagram showing an internal configuration of the wireless transmitter 1c. The wireless transmitter 1c can set control information individually for high-speed data whose control information can be changed for each user terminal, that is, data corresponding to information transmitted and received for each user terminal. Control data including information such as a modulation scheme when transmitting transmission data common to all user terminals is transmitted by STBC-GCC, and cannot be individually controlled, so transmission is performed by open loop STBC-GCC according to the present invention. I do.

  In FIG. 8, the wireless transmitter 1 c includes a plurality of high-speed data channels 50-1 to 50-n and one control data channel 60. For example, the high-speed data channels 50-1 to 50-n are provided corresponding to individual radio receivers. Since the internal configuration of each high-speed data channel is the same, the internal configuration will be described here taking the high-speed data channel 50-1 as an example. In the high-speed data channel 50-1, the error correction encoder 51-1 gives an error correction code to the input transmission data. The modulation mapping unit 52-1 maps the transmission data to the modulation signal using a modulation scheme such as QPSK (Quadrature Phase Shift Keying) for the transmission signal output from the error correction encoder 51-1, and generates a symbol. . The closed-loop STBC-GCC encoder 53-1 performs space-time encoding of 2 rows and 4 columns based on a control value fed back from the reception side. The time direction spreading sections 541-1 to 541-4 spread the four symbols output from the closed loop STBC-GCC encoder 53-1 in the time direction based on a preset spreading code, Generate.

  Next, in the control channel 60, the error correction encoder 61 adds an error correction code to the input control data. The modulation mapping unit 62 maps the control data to the modulation signal with respect to the transmission signal output from the error correction encoder 61 by a modulation method such as QPSK, and generates a symbol. The open loop STBC-GCC encoder 63 performs space-time encoding of 2 rows and 4 columns without using a control value fed back from the receiving side. The two-dimensional spreading units 64-1 to 64-4 spread in the time direction based on a preset spreading code to generate a spread signal.

  Code multiplexers 70-1 to 70-4 are provided corresponding to transmission antennas 73-1 to 74-4, respectively, and time-direction spreaders 54-1 to 54-4 and two-dimensional spreaders 64-1 to 64-64. -4. The code multiplexers 70-1 to 70-4 and the high-speed data spread in the time direction output from the corresponding time direction spreaders 54-1 to 54-4 and the two-dimensional spreaders 64-1 to 64-4. 2 is code-multiplexed on the spread code axis.

  Pilot signal time multiplexers 71-1 to 71-4 are connected to code multiplexers 70-1 to 70-4, respectively, and are code-multiplexed transmission frames output from code multiplexers 70-1 to 70-4. In contrast, the pilot signal is time-multiplexed in the time axis direction.

  Conversion transmitting units 72-1 to 72-4 are connected to pilot signal time multiplexers 71-1 to 71-4 and transmission antennas 73-1 to 73-4, respectively, and pilot signal time multiplexers 71-1 to 71-4 are connected. 4 is converted into a time domain signal by performing inverse fast Fourier transform (hereinafter referred to as IFFT: Inverse First Fourier Transform) on the transmission frame output from 4, and a guard interval (GI: Guard Interval) to avoid intersymbol interference. Is transmitted through the corresponding transmission antennas 73-1 to 74-4.

  FIG. 9 is a block diagram showing an internal configuration of the wireless receiver 2c with respect to the wireless transmitter 1c. In FIG. 9, the reception conversion unit 81 removes the guard interval from the signal received by the reception antenna 20, performs Fourier transform to convert it to a subcarrier signal, and outputs each subcarrier signal. The time-direction despreader 82a-1 performs despreading in the time direction using a spreading code obtained by spreading high-speed data in the time direction with respect to the spread signal output from the reception conversion unit 41. On the other hand, the time direction despreader 82b-1 performs despreading in the time direction based on the spread code obtained by spreading the control data in the time direction with respect to the signal output from the reception conversion unit 41.

The channel estimator 83-1 is based on the pilot signal included in the subcarrier signal output from the reception conversion unit 41, and the channel response estimation values h ₁ ^, h ₂ , ^ h ₃ ^ at the frequency of the subcarrier. h ₄ ^ is calculated, and an estimated value of the calculated channel response is output. The equivalent channel matrix calculator 85a-1 calculates an equivalent channel matrix corresponding to the high-speed data channel. The equivalent channel matrix calculator 85b-1 calculates an equivalent channel matrix corresponding to the control data channel.

  The space-time decoder 84a-1 converts the high-speed data despread in the time direction output from the time-direction despreader 82a-1 based on the equivalent channel matrix output from the equivalent channel matrix calculator 85a-1. Decode the containing signal. The space-time decoder 84b-1 receives the control data despread in the time direction output from the time direction despreader 82b-1 based on the equivalent channel matrix output from the equivalent channel matrix calculator 85b-1. Decode the containing signal.

  The parallel-serial converter (P / S in the figure) 86-1 parallelizes signals output from the space-time decoder 84 a-1 and other space-time decoders that decode signals including high-speed data from other subcarrier signals. High-speed data is output in a state including an error correction code after serial conversion. The error correction encoder 87-1 performs error correction decoding on the high speed data output from the parallel / serial converter 86-1, and reproduces the high speed data.

  The frequency direction synthesizer 90-1 synthesizes a signal including control data output from the space-time decoder 84b-1 and the space-time decoder that decodes other subcarriers in the frequency direction. The parallel-serial converter (P / S in the figure) 91-1 performs parallel-serial conversion on the signal output from the space-time decoder 84b-1 and the space-time decoder that has decoded control data from other subcarrier signals. Control data including the error correction code is output. The error correction encoder 92-1 performs error correction decoding on the control data output from the parallel / serial converter 91-1, and reproduces the control data.

  In FIG. 9, time-direction despreaders 82a-1 and 82b-1, space-time decoders 84a-1 and 84b-1, a channel estimator 83-1, and equivalent channel matrix calculators 85a-1 and 85b- 1 is provided by the number of subcarriers. The frequency direction synthesizer 90-1 receives a signal despread in the time direction from a space-time encoder corresponding to the number of spread lengths in the frequency direction when two-dimensionally spread. The parallel-to-serial converters 86-1 and 91-1 receive as many signals as parallelized when data transmitted from the wireless transmitter 1 c is serial-parallel converted to reproduce the original data.

  FIG. 10 is a diagram illustrating a transmission frame transmitted from the wireless transmitter 1c. In FIG. 10, transmission data and control data are code-multiplexed, but the pilot signal is time-multiplexed with respect to control data and transmission data, and is assigned to a time slot different from control data and high-speed data.

  Next, operations of the wireless transmitter 1c in FIG. 8 and the wireless receiver 2c in FIG. 9 will be described. When high-speed data is input to the wireless transmitter 1c, corresponding control data is input. The input high-speed data is subjected to error correction coding by an error correction encoder 51-1, and then mapped to a modulation signal point by a modulation mapping unit 52-1, thereby generating a transmission symbol. The transmission symbol is subjected to space-time coding of 2 rows and 4 columns corresponding to the above-described equation (6) based on the control information from the wireless reception device 2 c by the closed loop STBC-GCC encoder 53-1. The encoded transmission symbols are spread by the time direction spreaders 54-1 to 54-4 and assigned to the time direction spread segment.

On the other hand, the input control data is error correction encoded by the error correction encoder 61 and then mapped to the modulation signal point by the modulation mapping unit 62 to generate a transmission symbol. The transmission symbols are subjected to space-time coding of 2 rows and 4 columns corresponding to the above-described equation (14) by the open loop STBC-GCC encoder 63, and in the time direction by the two-dimensional spreaders 64-1 to 64-4. After being spread, it is assigned to the two-dimensional spread segment by the assigning means shown in FIG. At this time, every two subcarriers are allocated to the two-dimensional spreading segment while performing the above-described chip interleaving. As a spreading code input to the two-dimensional spreading units 64-1 to 64-4, the WH code # 1 is input to the two-dimensional spreading units 64-1 and 64-2, and the two-dimensional spreading unit 64-3. And 64-4 are supplied with the WH code # 2. For the WH code # 1 and the WH code # 2, w ₅₇ , w _{61 and the} like shown in the above-described formulas (15) and (16) are applied.

  Next, the spread signals output from the time direction spreaders 54-1 to 54-4 and the spread signals output from the two-dimensional spreaders 64-1 to 64-4 are code multiplexers 70-1 to 70-. 4 is multiplexed on the spread code axis, and pilot signals are time-multiplexed by the pilot signal time multiplexers 71-1 to 71-4 to generate a transmission frame shown in FIG. The generated transmission frame is converted into a time domain signal by inverse Fourier transform operation of the conversion transmitting units 72-1 to 72-4, and then a guard interval is inserted to avoid intersymbol interference, thereby transmitting antennas 73-1 to 73-1. 73-4.

  On the other hand, in the radio receiver 2c, after the guard interval is removed by the reception conversion unit 81, the reception signal is converted into a subcarrier signal by Fourier transform. Then, based on the time-multiplexed pilot signal, each subcarrier is detected by a channel estimator 83 (only a channel estimator 83-1 corresponding to one subcarrier is shown in FIG. 9) provided for each subcarrier. An estimate of the carrier channel response is calculated. Equivalent channel matrices are calculated by the equivalent channel matrix calculators 85a-1 and 85b-1 using the estimated channel response values calculated by the channel estimator 83-1.

  At this time, the equivalent channel matrix calculator 85a-1 on the high-speed data side calculates an equivalent channel matrix based on the control information transmitted to the wireless transmitter 1c. Further, the equivalent channel matrix calculator 85b-1 on the control data side calculates an equivalent channel matrix by using another equivalent channel matrix calculation formula at the even-numbered and odd-numbered subcarriers.

  Next, based on the equivalent channel matrix calculated by the equivalent channel matrix calculator 85a-1, the space-time decoder 84a-1 performs space-time decoding of the high-speed data, and the equivalent channel matrix calculator 85b-1 calculates. Based on the equivalent channel matrix, the space-time decoder 84b-1 performs space-time decoding of the control data.

  The high-speed data output from the space-time decoder 84a-1 and the high-speed data space-time decoded from the other subcarrier signals are converted into serial data by the parallel-serial converter 86-1, and the error correction decoder 87- 1 outputs high-speed data subjected to error correction decoding.

  On the other hand, with respect to the control data, the control data output from the space-time decoder 84b-1 and the control data space-time decoded from other subcarrier signals are deinterleaved over the two-dimensional diffusion region, and the frequency is increased. The signal is synthesized in the frequency direction by the direction synthesizer 90-1, and further converted into serial data by the parallel-serial converter 91-1, together with the decoded data from other spreading segments, and the error-correcting decoder 92-1 performs error correction decoding. The controlled data is output.

  With the configuration of the third embodiment described above, it is possible to realize a transmission diversity scheme using four transmission antenna branches that do not require control information on the transmission side for control data that is information common to a plurality of wireless receivers. . Thereby, space diversity gain can be obtained, and furthermore, frequency diversity gain can be obtained by using chip interleaving together, and communication quality can be improved.

  In the first to third embodiments, the WH code is applied as the orthogonal code. However, the present invention is not limited to this configuration, and any code that is orthogonal may be used. A series or the like can also be applied. In the present invention, substantially the same effect can be obtained by applying a quasi-orthogonal code in addition to the orthogonal code.

  The encoding means, spreading means, converting means, and transmitting means in the wireless transmitter described in the appended claims correspond to the following in the first to third embodiments. That is, in the first embodiment, the encoding means corresponds to the 2-row 4-column space-time encoder 10, and the spreading means and transmitting means correspond to the spreaders 11-1 to 11-4. In the second embodiment, the encoding means corresponds to the 2-row 4-column space-time encoder 10, and the spreading means, conversion means, and transmission means correspond to the OFDM-CDM modulators 31-1 to 31-4. In the third embodiment, the encoding means is the open-loop STBC-GCC encoder 63, the spreading means is the two-dimensional spreaders 64-1 to 64-4, and the converting means is in the conversion transmitting units 72-1 to 72-4. Applicable.

  The receiving means, converting means, decoding means, and synthesizing means in the wireless receiver described in the claims correspond to the following in the first to third embodiments. That is, in the first embodiment, the receiving means corresponds to the partial despreader 21, the decoding means corresponds to the space-time decoder 22, and the combining means corresponds to the combiner 25. In the second embodiment, the reception means and conversion means correspond to the reception conversion unit 41, the decoding means corresponds to the space-time decoder 45-1, and the combining means corresponds to the frequency direction combiner 46-1. In the third embodiment, the reception means and the conversion means correspond to the reception conversion unit 41, the decoding means corresponds to the space-time decoder 84b-1, and the combining means corresponds to the frequency synthesizer 90-1.

  The wireless transmitters 1a, 1b, 1c and the wireless receivers 2a, 2b, 2c described above have a computer system inside. Then, the processing relating to the encoding, spreading, and conversion of the transmission data and reception data of the wireless transmitters 1a, 1b, 1c and the wireless receivers 2a, 2b, 2c in the first to third embodiments described above is performed by the program. It is stored in a computer-readable recording medium in a format, and the above processing is performed by the computer reading and executing this program. Here, the computer-readable recording medium means a magnetic disk, a magneto-optical disk, a CD-ROM, a DVD-ROM, a semiconductor memory, or the like. Alternatively, the computer program may be distributed to the computer via a communication line, and the computer that has received the distribution may execute the program.

It is a block diagram which shows the internal structure of the wireless transmitter by 1st Embodiment, and the relationship between the said wireless transmitter and a wireless receiver. It is a block diagram which shows the internal structure of the radio | wireless receiver in 1st Embodiment. It is a block diagram which shows the internal structure of the wireless transmitter in 2nd Embodiment, and the relationship between the said wireless transmitter and a wireless receiver. It is a block diagram which shows the internal structure of the radio | wireless receiver in 2nd Embodiment. It is the figure which showed the example of the allocation to the production | generation tree and physical layer of a WH code in 2nd Embodiment. It is the figure which showed allocation of the spreading | diffusion signal to the two-dimensional spreading | diffusion area | region in 2nd Embodiment. It is the figure which showed the allocation state in the case of performing chip interleaving about the spreading | diffusion chip which comprises the spreading | diffusion signal in 2nd Embodiment. It is the block diagram which showed the internal structure of the wireless transmitter in 3rd Embodiment. It is the block diagram which showed the internal structure of the radio receiver in 3rd Embodiment. It is the figure which showed the structure of the transmission frame in 3rd Embodiment. It is a figure for demonstrating the transmission diversity system by two transmission antennas which is a prior art. It is a figure for demonstrating the closed loop transmission diversity system by four transmission antennas which is a prior art. It is a figure for demonstrating the two-dimensional spreading | diffusion OFDM-CDM system which is a prior art. It is a figure for demonstrating the concept of the spreading | diffusion of the two-dimensional spreading | diffusion OFDM-CDM system which is a prior art. It is a figure for demonstrating the case where a some receiving terminal exists in the closed-loop transmission diversity system by four transmission antennas which is a prior art.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1a Radio transmitter 10 2 rows 4 columns space-time encoder 11-1 to 11-4 Spreader 12-1 to 12-4 Transmitting antenna

Claims (9)

Encoding means for encoding transmission data into a plurality of space-time codes;
Extracting a plurality of combinations from a plurality of space-time codes encoded by the encoding means, and a plurality of combinations of repeating the same phase and opposite phase with a constant spreading length for each set of the extracted plurality of space-time codes Spreading means for spreading a spatio-temporal code in association with each spreading code to generate a spread signal;
Transmitting means for transmitting the spread signal generated by the spreading means by a plurality of transmitting antennas;
A wireless transmission device comprising: A plurality of subcarrier signals having different frequencies are converted into time domain signals by inverse Fourier transform, and conversion means for outputting the converted time domain signals to the transmission means is provided.
The diffusion means is
Assigning the spread signal to each of the plurality of subcarrier signals for each constant spread length;
The transmission means includes
The radio transmission apparatus according to claim 1, wherein the time domain signal output from the conversion means is transmitted by a plurality of transmission antennas. The diffusion means is
When assigning the spread signal to each of the plurality of subcarrier signals for each constant spread length, assigning to two subcarrier signals of adjacent frequencies and then assigning to the subcarrier signals separated by a predetermined frequency interval The wireless transmission device according to claim 2, wherein: Receiving means for receiving signals transmitted from a plurality of transmitting antennas and outputting a spread signal included in the signals;
A spatio-temporal code is obtained by despreading the spread signal output from the receiving means for each of the fixed spread lengths by any one of a plurality of spread codes composed of a combination of repeating in-phase and reverse phase with a constant spread length. Despreading means to restore;
Decoding means for decoding the space-time code restored by the despreading means;
Combining means for combining the space-time code decoded by the decoding means to reproduce data;
A wireless receiver characterized by comprising: A Fourier transform of the signal received by the receiving means, a subcarrier signal having a different frequency is read out, and a conversion means for outputting a spread signal assigned to the subcarrier signal,
The synthesis means includes
The radio reception apparatus according to claim 4, wherein the space-time code decoded by the decoding means is combined in the frequency direction of the subcarrier signal to reproduce data. The synthesis means includes
When synthesizing the space-time code decoded by the decoding means in the frequency direction of the subcarrier signal, two space-time codes corresponding to adjacent frequency directions are set at predetermined frequency intervals. 6. The radio reception apparatus according to claim 5, wherein the data is synthesized and reproduced for each data. A transmission / reception method in a wireless communication system comprising a wireless transmitter for transmitting signals from a plurality of transmission antennas and a wireless receiver for receiving signals transmitted from the wireless transmitter,
The wireless transmitter encodes transmission data into a plurality of space-time codes;
The wireless transmitter extracting a plurality of combinations from a plurality of encoded space-time codes;
The wireless transmitter spreads the space-time code by associating each of a plurality of spread codes consisting of a combination of repeating in-phase and reverse phase with a constant spread length for each set of extracted space-time codes, Generating a spread signal;
The wireless transmitter transmitting the generated spread signal by a plurality of transmission antennas;
The wireless receiver receives signals transmitted from the plurality of transmitting antennas and outputs a spread signal included in the signals;
When the radio receiver despreads the output spread signal for each of the constant spread lengths by any one of a plurality of spread codes consisting of a combination of repeating in-phase and reverse phase with a constant spread length. Restoring a spatial code; and
The wireless receiver decoding the restored space-time code;
The wireless receiver combines the decoded space-time code to reproduce the data; and
A transmission / reception method characterized by comprising: A wireless transmitter computer that transmits signals from multiple transmitting antennas,
Encoding means for encoding transmission data into a plurality of space-time codes;
Extracting a plurality of combinations from a plurality of space-time codes encoded by the encoding means, and a plurality of combinations of repeating the same phase and opposite phase with a constant spreading length for each set of the extracted plurality of space-time codes Spreading means for spreading a spatio-temporal code in association with each spreading code and generating a spread signal;
Transmitting means for transmitting the spread signal generated by the spreading means by a plurality of transmitting antennas;
Computer program to function as. A wireless receiver computer that receives signals transmitted from a plurality of transmission antennas,
Receiving means for receiving signals transmitted from a plurality of transmitting antennas and outputting a spread signal included in the signals;
A spatio-temporal code is obtained by despreading the spread signal output from the receiving means for each of the fixed spread lengths by any one of a plurality of spread codes composed of a combination of repeating in-phase and reverse phase with a constant spread length. Despreading means to restore,
Decoding means for decoding the space-time code restored by the despreading means;
Combining means for combining the space-time code decoded by the decoding means to reproduce data;
Computer program to function as.

Images