JP2007180902A - Multi-carrier signal transmission system, radio base station device, radio terminal device, and multi-carrier signal transmission method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To not only reduce the amount of control information exchanged between a transmission side and a reception side but also improve transmission quality, in an OFDMA system. <P>SOLUTION: A multi-carrier signal transmission system includes; a sub-channel assignment control circuit 102 which assigns sub-carriers to users with a sub-channel consisting of a plurality of sub-carriers as a unit; a feature extraction circuit 17 which generates feature extraction information representing propagation line characteristics of each sub-channel per user; a symbol modulating/multiplexing circuit which determines the most suitable spreading and multiplexing matrixes according with propagation line characteristics of sub-channels assigned to users on the basis of the feature extraction information per user and uses the spreading and multiplexing matrixes to spread and multiplex signals per user; and a transmission means which locates signals after spreading and multiplexing processing, in sub-channels assigned to users and transmits the signals. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a multicarrier signal transmission system, a radio base station apparatus, a radio terminal apparatus, and a multicarrier signal transmission method.

  In recent years, the Orthogonal Frequency Division Multiplexing (OFDM) system has attracted attention as one of the leading multi-carrier radio transmission systems. In the OFDM scheme, orthogonal frequency division multiple access (which realizes multiple access by assigning each subcarrier or subcarrier group obtained by grouping (subchannelizing) a plurality of subcarriers to individual users (wireless terminals) ( An Orthogonal Frequency Division Multiple Access (OFDMA) scheme has been proposed. This OFDMA system is being studied mainly by a working group that determines US standards for broadband wireless access (BWA), IEEE802.16a and IEEE802.16e.

The OFDMA scheme is a scheme in which access control is performed in units of subcarriers in an OFDM scheme in which information transmission is performed using N subcarriers that are orthogonal to each other. Is the same. Therefore, like the OFDM scheme, the modulation rate per subcarrier can be reduced to 1 / N compared to the single carrier scheme. In addition, the frequency of the sine wave signal c ₁ (t) having the time width T _S as a basic period is
f ₁ = Δf = 1 / T _S ,
It is expressed. At this time,
f _n = Δf × n (where n is an arbitrary integer),
All the sine wave signals c _n (t) represented by the relational expression are orthogonal to each other, that is, uncorrelated. Therefore, if transmitted simultaneously put the independent information to multiple subcarriers center frequency is f _n, without interfering with each other, can be performed without information transmission distortion.

  In the OFDMA scheme, allocation to users is performed in units of grouped continuous subchannels. For example, it is allocated to users in units of blocks (called data areas in the OFDMA scheme) composed of 4 subcarriers × 3 OFDM symbols. The data area is assigned to each user in the uplink (user-initiated link), and in the downlink (user-initiated link), each data area addressed to all users is transmitted simultaneously (this is a normal transmission). Same configuration as OFDM system). In addition, in the OFDMA scheme, a frequency hopping orthogonal frequency division multiplexing (FH-OFDM) scheme is proposed in which subcarriers allocated to each user are hopped in symbol periods in the subcarrier-based user allocation that is the basic concept. In the FH-OFDM scheme, each user performs communication while independently changing the subcarrier used for each symbol timing. Here, in the same cell, hopping patterns of independent subcarriers are assigned to individual users, and different hopping patterns are assigned between adjacent base stations, thereby reducing the influence of inter-channel interference at the same frequency. It is mitigating. By receiving the subcarrier allocation pattern in advance on the receiving side, the receiving station can receive only the subcarriers addressed to itself and obtain a baseband received data sequence.

Here, as a very significant feature of the OFDMA system (including the FH-OFDM system), an appropriate subcarrier is independent for each user according to the propagation path state between the wireless base station and each user (wireless terminal). As a result, the reception performance of the entire wireless system can be improved as compared with the OFDM method. In other words, in a multipath fading environment, the communication quality of individual subcarriers differs between the radio base station and each user. Therefore, subcarriers with good propagation path conditions are preferentially allocated to each user, and further optimal modulation is performed. By controlling so as to use the multi-value number and the coding rate, more efficient communication can be performed (for example, see Patent Document 1). Furthermore, the communication efficiency is improved by giving the right to use subcarriers according to the user's required transmission rate and the possibility of erroneous bits. Also, when communication services with different characteristics such as voice communication and packet communication are mixed, the subcarrier allocation is completed preferentially from the user who needs a fixed transmission rate, and the fixed transmission rate is set. By limiting the number of users required, the communication quality provided to each user can be improved.
JP 2004-248005 A

  However, in the conventional OFDMA system (including the FH-OFDM system) described above, the total communication capacity can be improved as a wireless system by allocating subcarriers with better communication quality for each user. The configuration is complicated. Specifically, in order to perform allocation control in units of subcarriers, each transmission path characteristic between the radio base station and each user is observed, and the observation information is shared between the radio base station and the user; A means for selecting a subcarrier group with good reception quality from the transmission path characteristics and a means for notifying the communication partner of identification information of single or plural subcarriers selected for data transmission are required. For example, N subcarriers are numbered from 1 to N in ascending order of carrier frequency, and subcarrier numbers k1, k2,. When selecting for transmission, it is necessary to notify the receiving side in advance of information on the subcarrier number, and information on the modulation scheme and coding rate used in each subcarrier. Further, in the case of an FDD (Frequency Division Duplex) system in which the frequency used is different between the uplink and the downlink, a means for informing the transmission side of the propagation path state on the reception side in advance is also required.

  In addition, since the propagation path state changes every moment in the mobile communication environment, the best subcarrier and the modulation scheme and coding rate used by each subcarrier differ from time to time. The amount of control information exchanged to share information about subcarriers is enormous. For this reason, the ratio of the amount of control information to the communication capacity increases, resulting in a problem that the radio system capacity decreases. In order to avoid the problem of an increase in the amount of control information, a method is conceivable in which a plurality of subcarriers are grouped into subchannels, and subchannels with good characteristics are assigned based on an average propagation path state. However, if the number of subcarriers included per subchannel increases, the propagation path state is averaged, and as a result, there is no significant difference from the case of randomly assigning subcarriers. In addition, a method of reducing the amount of control information by applying a multi-carrier code division multiplexing (MC-CDM) method that performs code spreading on the frequency axis is conceivable. However, in the MC-CDM method, communication quality is improved when code multiplexing is performed. There is a fundamental problem of deterioration, and it is difficult to use together with the OFDMA method.

  The present invention has been made in consideration of such circumstances, and the object thereof is to reduce the amount of control information exchanged between the transmission side and the reception side and improve the transmission quality in the OFDMA system. To provide a multicarrier signal transmission system, a radio base station apparatus, a radio terminal apparatus, and a multicarrier signal transmission method.

  In order to solve the above problems, a multicarrier signal transmission system according to the present invention includes a plurality of subcarriers in a multicarrier signal transmission system having an orthogonal frequency division multiple access (OFDMA) type radio base station apparatus and radio terminal apparatus. Subchannel allocation control means for assigning subcarrier users in units of subchannels composed of carriers, feature extraction means for generating feature extraction information representing characteristics of propagation path characteristics for each subchannel for each user, and for each user And, based on the feature extraction information, spreading multiplex transform matrix determining means for determining an optimum spreading multiplex transform matrix according to the propagation path characteristics of the subchannel assigned to the user, the radio base station apparatus, Signal multiplexing means for spreading and multiplexing signals using the spread multiplex transform matrix for each user, and the spreading and multiplexing Transmitting means for arranging and transmitting the processed signal in the subchannel as a result of the user assignment, and the wireless terminal device receiving means for receiving the signal of the subchannel as a result of the user assignment; Signal division means for performing signal division processing on the received signal using the same spread multiplex transformation matrix as that at the time of transmission.

  In the multicarrier signal transmission system according to the present invention, the spread multiplex transform matrix is an orthogonal matrix composed of a trigonometric function having an adjustment parameter as an argument, and the spread multiplex transform matrix determination means is based on the feature extraction information. A setting value of the adjustment parameter is determined.

  In the multicarrier signal transmission system according to the present invention, the subchannel allocation control means determines a priority order of subchannels for each user based on the feature extraction information.

  A radio base station apparatus according to the present invention comprises: an orthogonal frequency division multiple access (OFDMA) radio base station apparatus; subchannel allocation control means for allocating subcarriers in units of subchannels composed of a plurality of subcarriers; , For each user, feature extraction means for generating feature extraction information representing the characteristics of the propagation path characteristics for each subchannel, and for each user, based on the feature extraction information, the channel characteristics of the subchannel assigned to the user Spreading multiplex transformation matrix determining means for determining the optimum spreading multiplex transformation matrix according to the signal, signal multiplexing means for spreading and multiplexing the signal using the diffusion multiplex transformation matrix for each user, and the processing of the spreading and multiplexing Transmission means for transmitting a subsequent signal in a subchannel as a result of the user assignment.

  A radio terminal apparatus according to the present invention, in an orthogonal frequency division multiple access (OFDMA) system radio terminal apparatus, receives a subchannel signal of a user allocation result, and transmits the received signal with respect to the received signal. And signal division means for performing signal division processing using the same spread multiplex transform matrix.

  A multicarrier signal transmission method according to the present invention is an orthogonal frequency division multiple access (OFDMA) multicarrier signal transmission method, which is a first method for assigning subcarriers in units of subchannels composed of a plurality of subcarriers. And a second step of generating feature extraction information representing characteristics of propagation path characteristics for each subchannel for each user, and for each user, the subchannel assigned to the user based on the feature extraction information. A third process for determining an optimum spread multiplex transform matrix according to propagation path characteristics, a fourth process for spreading and multiplexing signals using the spread multiplex transform matrix for each user, and the spread and multiplex A fifth step of transmitting the signal after the conversion processing in the subchannel as a result of the user assignment, and a sixth step of receiving a signal of the subchannel as a result of the user assignment. And processes, with respect to the received signal and a seventh step of performing a signal division processing using the same spreading multiplex conversion matrix and during its transmission, characterized in that it comprises a.

  According to the present invention, the amount of control information exchanged between the transmission side and the reception side can be reduced by performing user assignment of subcarriers in units of subchannels. Furthermore, by performing spreading and multiplexing of the signal using the optimum spreading multiplex transform matrix for each user based on the feature extraction information of each user, the “propagation” that is optimum for the channel characteristics of the subchannel assigned to the user is performed. Adjustment of the influence received from the road ”becomes possible, and transmission quality can be improved.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

  First, subchannels in the OFDMA multicarrier signal transmission system are defined. A subchannel refers to a subcarrier group obtained by grouping a plurality of subcarriers. More specifically, all the subcarriers (n) are grouped into L groups of J subcarriers, and one group is associated with one subchannel. Here, J is an integer equal to or greater than 2, and is basically a power of 2. However, the present invention is not limited to this. Further, the J subcarriers constituting one subchannel do not have to be adjacent to each other, and may be selected from all the subcarriers randomly or according to a certain rule.

  Hereinafter, a mobile communication system will be described as a specific example of a multicarrier signal transmission system having an OFDMA wireless base station apparatus and a wireless terminal apparatus.

  FIG. 1 is a block diagram showing a configuration of a radio base station apparatus of an OFDMA mobile communication system according to an embodiment of the present invention. FIG. 2 is a block diagram showing a configuration of a mobile station apparatus (wireless terminal apparatus) in the OFDMA mobile communication system according to the embodiment. Here, a case of a TDD (Time Division Duplex) method will be described. In addition, a subchannel number is assigned to each subchannel, and a subcarrier number is assigned to each subcarrier in advance. In addition, grouping information indicating the correspondence relationship between the predefined subchannels and subcarriers is shared in advance between the radio base station apparatus and the mobile station apparatus. The grouping information includes a combination of a subchannel number and a plurality of subcarrier numbers, and indicates which subchannel includes which subcarrier.

First, a radio base station apparatus will be described with reference to FIG.
In the radio base station apparatus of FIG. 1, in the transmission system, downlink data sequences 1-1 to L transmitted to users (mobile station apparatuses) 1 to L are input to the subchannel allocation control circuit 2. The data series consists of information data symbols. The feature extraction information 102 is input from the feature extraction circuit 17 to the subchannel allocation control circuit 2. The feature extraction information 102 is information representing the characteristics of propagation path characteristics for each subchannel for each user.

  The subchannel allocation control circuit 2 prioritizes subchannels for each user based on the feature extraction information 102. The subchannel allocation control circuit 2 determines a subchannel to be allocated to each user using the subchannel priority information for each user and the priority information between users 1 to L. The subchannel allocation control circuit 2 associates the determined subchannel with the information data symbol for each user. Specifically, a set of information data symbols and subchannel numbers for each user is configured. A set of information data symbols and subchannel numbers for each user is input to the symbol modulation / multiplexing circuit 3. Further, the feature extraction information 102 is input from the feature extraction circuit 17 to the symbol modulation / multiplexing circuit 3.

  The symbol modulation / multiplexing circuit 3 determines, for each user, an optimum spread multiplex transform matrix corresponding to the propagation path characteristic of the subchannel assigned to the user, based on the feature extraction information 102. This spread multiple conversion matrix will be described later. The symbol modulation / multiplexing circuit 3 performs spreading and multiplexing processing of information data symbols using the determined spread multiplexing conversion matrix for each user. Specifically, the copy of the information data symbol is multiplied by the spread code obtained from the spread multiplex transform matrix. Here, the information data symbols are copied by the number corresponding to the spreading code length. By the processing of the symbol modulation / multiplexing circuit 3, a spread multiplexed signal for each user is obtained. The spread multiplex signal is input to the inverse fast Fourier transform (IFFT) circuit 4 together with the subchannel number that forms a pair.

  The IFFT circuit 4 performs inverse fast Fourier transform on each spread multiplexed signal and then multiplies the frequency signal of the associated subcarrier according to the subchannel number. Each signal after the multiplication is added by the adder 5 and then a guard interval for avoiding the influence of multipath is added by the guard interval adding circuit 6. The signal after the addition of the guard interval is input to the multiplier 8 via the switch 7, is multiplied by the carrier signal output from the high frequency oscillator 9, and is converted from a baseband signal to a multicarrier radio frequency signal (multicarrier signal). Is transmitted from the antenna 10.

  In the radio base station apparatus of FIG. 1, in the reception system, the multicarrier signal received by the antenna 10 is multiplied by the carrier signal output from the high frequency oscillator 9 by the multiplier 8 and frequency-converted into a baseband signal. Then, the signal is input to the guard interval removing circuit 11 via the switch 7, and the guard interval is removed. Note that a low-pass filter, a timing recovery circuit, and the like necessary for frequency conversion are omitted and not shown.

  A fast Fourier transform (FFT) circuit 12 performs fast Fourier transform on the signal after removal of the guard interval to obtain a baseband signal for each subcarrier. The data determination circuit 13 performs demodulation processing and data determination on the spread multiplexed signal for the baseband signal for each subcarrier, and obtains information data symbols for each subcarrier. Here, the data determination circuit 13 performs equalization processing of the received signal based on the transmission path distortion input from the channel estimation circuit 16. The information data symbol for each subcarrier is input to the data demapping circuit 14. Further, the sub-channel allocation information 103 is input from the sub-channel allocation control circuit 2 to the data demapping circuit 14. The subchannel allocation information 103 includes a subchannel number for each user.

  Based on the subchannel allocation information 103, the data demapping circuit 14 grasps the correspondence relationship between the subchannel and the subcarrier for each user, and determines each user from the information data symbol for each subcarrier after the data determination circuit 13 outputs. The information data symbol is determined. The data demapping circuit 14 outputs the uplink data sequences 15-1 to 15-L of the users 1 to L from the determination result.

  The channel estimation circuit 16 receives the baseband signal for each subcarrier from the FFT circuit 12. The channel estimation circuit 16 measures the received signal strength, the interference signal strength, the noise level, and the transmission path distortion generated in the propagation path for each subcarrier from the baseband signal for each subcarrier. Further, the channel estimation circuit 16 performs propagation path estimation for each user. For the propagation path estimation, every symbol period or head preamble portion of the received signal, or a known pilot symbol or data symbol inserted periodically is used. The channel estimation circuit 16 outputs transmission characteristic information 101 including the measurement result for each subcarrier and the transmission path estimation result for each user. The transmission characteristic information 101 is input to the feature extraction circuit 17.

  The feature extraction circuit 17 performs feature extraction of transmission path characteristics for each subchannel of each user based on the transmission characteristics information 101. Thereby, the feature extraction information 102 representing the characteristics of the propagation path characteristics for each subchannel is obtained for each user.

Next, the mobile station apparatus will be described with reference to FIG.
In the mobile station apparatus of FIG. 2, in the transmission system, the uplink data sequence transmitted on the uplink to the radio base station apparatus is input to the subchannel selection control circuit 21. Also, the subchannel selection control circuit 21 receives the mapping control information 201 detected from the downlink reception data by the subchannel selection control information detection circuit 35. The mapping control information 201 includes a subchannel number for each user.

  The subchannel selection control circuit 21 associates the subchannel to be used, which is indicated by the mapping control information 201, with the uplink data sequence. Specifically, a set of an uplink data sequence information data symbol and a subchannel number is configured. The combination of the information data symbol and the subchannel number is input to the symbol modulation / multiplexing circuit 22. Also, the symbol modulation / multiplexing circuit 22 receives the spread multiplex transform matrix information 202 detected from the downlink received data by the subchannel selection control information detection circuit 35. The spread multiplex transform matrix information 202 is information for specifying a spread multiplex transform matrix for each user.

  The symbol modulation / multiplexing circuit 22 determines the spread multiplex transform matrix to be used based on the spread multiplex transform matrix information 202. The symbol modulation / multiplexing circuit 3 multiplies the copy of the information data symbol by the spread code obtained from the determined spread multiplex transformation matrix. Here, the information data symbols are copied by the number corresponding to the spreading code length. A spread multiplexed signal is obtained by the processing of the symbol modulation / multiplexing circuit 22. The spread multiplex signal is input to the IFFT circuit 23 together with the subchannel number forming a pair.

  The IFFT circuit 23 performs inverse fast Fourier transform on each spread multiplexed signal, and then multiplies the frequency signal of the corresponding subcarrier according to the subchannel number. Each signal after the multiplication is added by an adder 24, and then a guard interval for avoiding the influence of multipath is added by a guard interval adding circuit 25. The signal after adding the guard interval is input to the multiplier 27 via the switch 26, multiplied by the carrier signal output from the high frequency oscillator 28, converted from the baseband signal to the multicarrier signal, and then transmitted from the antenna 29. Is done.

  In the mobile station apparatus of FIG. 2, in the receiving system, the multicarrier signal received by the antenna 29 is multiplied by the carrier signal output from the high frequency oscillator 28 by the multiplier 27 and frequency-converted into a baseband signal. The signal is input to the guard interval removal circuit 30 via the switch 26, and the guard interval is removed. Note that a low-pass filter, a timing recovery circuit, and the like necessary for frequency conversion are omitted and not shown.

  The FFT circuit 31 performs fast Fourier transform on the signal after removal of the guard interval to obtain a baseband signal for each subcarrier. The baseband signal for each subcarrier is input to the subchannel selection / determination circuit 32. The subchannel selection / determination circuit 32 receives mapping control information 201 from the subchannel selection control information detection circuit 35.

  The subchannel selection / determination circuit 32 performs demodulation processing and data determination of the spread multiplexed signal on the baseband signal of the subcarrier constituting the subchannel to be used indicated by the mapping control information 201, and performs subcarrier Each information data symbol is obtained. Here, the subchannel selection / determination circuit 32 performs equalization processing of the received signal based on the transmission path distortion input from the channel estimation circuit 36. The information data symbol for each subcarrier is output as a serial data series by the parallel / serial conversion circuit 33. The switch 34 switches the connection destination according to the timing of the received frame, and inputs the serial data sequence output from the parallel / serial conversion circuit 33 to the subchannel selection control information detection circuit 35 or outputs it as a downlink data sequence. To do.

  The channel estimation circuit 36 receives a baseband signal for each subcarrier from the FFT circuit 31. Further, the mapping control information 201 is input to the channel estimation circuit 36 from the subchannel selection control information detection circuit 35. The channel estimation circuit 36 receives the received signal strength, the interference signal strength, the noise level, and the propagation path for each subcarrier with respect to the baseband signal of the subcarrier constituting the subchannel to be used indicated by the mapping control information 201. Measure the transmission line distortion that occurs in

Next, a characteristic configuration according to the present embodiment will be described in detail.
FIG. 3 is a block diagram showing a configuration of subchannel allocation control circuit 2 shown in FIG. FIG. 4 is a block diagram showing a configuration of the feature extraction circuit 17 shown in FIG.

First, the subchannel assignment control circuit 2 will be described with reference to FIG.
In FIG. 3, the feature extraction information 102-1 to L of each user 1 to L generated by the feature extraction circuit 17 is input to the subchannel allocation control circuit 2. The subchannel allocation control circuit 2 includes determination criteria 41-1 to L and subchannel priority determination circuits 42-1 to L for each user, a subchannel selection / allocation control circuit 43, and a data mapping circuit 44. .

  The criterion 41-1 is prepared in advance for each of the users 1 to L. The subchannel priority order determination circuits 42-1 to L select subchannels for the users 1 to L to be processed based on the determination criteria 41-1 to L. Further, priorities are assigned to the selected sub-channels based on the feature extraction information 102-1 to L of the users 1 to L. Thereby, the priority order of subchannels is determined for each user.

  Note that subchannel priorities can be assigned in the order of, for example, higher average power, lower average interference power, average CIR (Carrier to Interference Ratio), average CNR (Carrier to Noise Ratio), or average CNIR (Carrier to Noise and Interference Ratio) in descending order, received signal strength dispersion value of each subcarrier constituting a subchannel in ascending order, interference power received by each subcarrier in order of decreasing dispersion value, noise received by each subcarrier The order in which the power dispersion value is small and the order in which the CIR or CNR or CNIR dispersion value of each subcarrier is small are listed.

  Information on the priority order of subchannels of each user is input to the subchannel selection / assignment control circuit 43. Also, the user priority information 301 is input to the subchannel selection / allocation control circuit 43. The priority order information 301 indicates the priority order among the users 1 to L and is prepared in advance.

  The subchannel selection / assignment control circuit 43 assigns subchannels to the users 1 to L based on the priority order information of each user and the priority order information 301. Here, the subchannel selection / allocation control circuit 43 controls the allocation order between users based on the priority information 301. In addition, for each user, subchannel allocation is controlled so as to follow the priority order of the subchannels. As a control result, the subchannel selection / allocation control circuit 43 outputs subchannel allocation information 103 indicating which subchannel is allocated to which user. The subchannel allocation information 103 is transmitted as mapping control information 302 to each mobile station apparatus via a downlink control channel.

  Based on the subchannel assignment information 103, the data mapping circuit 44 associates the information data symbols of the users 1 to L with the subchannels. Specifically, a set of information data symbols and subchannel numbers for each user is configured.

Next, the feature extraction circuit 17 will be described with reference to FIG.
In FIG. 4, FFT circuit 12 (FFT unit 12a, the sub-carrier de-interleaving unit 12b) from the subcarrier _f 1 ~f _n subcarriers _f 1 ~f _n which is subcarrier deinterleaving on the signal Baseband signals s _{1 to} s _n are input to the channel estimation circuit 16. The channel estimation circuit 16 determines the amplitude distortion h _k (t), the phase rotation amount φ _k (t), the received signal strength r _k (t) for each of the subcarriers f _{1 to} f _n from the baseband signals s _{1 to} s _n. ), Measuring the interference signal intensity i _k (t) and the noise level n _k (t) (where k is 1 to n). The measurement result is input to the feature extraction circuit 17 is included in the transmission characteristic information 101-1~n of subcarriers _f 1 ~f _n.

  The feature extraction circuit 17 includes feature extraction units 50-1 to 50-L for the users 1 to L, respectively. The feature extraction units 50-1 to 50-L generate feature extraction information 102-1 to L representing the characteristics of the propagation path characteristics for each subchannel for the users 1 to L to be processed. Specifically, the feature extraction units 50-1 to 50 -L perform an average value calculation process, a dispersion value calculation process, and the like on each measurement data included in the transmission characteristic information 101-1 to 101 -n, and the characteristics of the transmission path characteristics. Candidates are calculated. Candidates for characteristics of transmission path characteristics include, for example, the average received signal strength of all subcarriers constituting the subchannel, the average interference power received by all the subcarriers, the average noise power of all the subcarriers, and the average power ratio thereof. , Dispersion value of received signal strength of each subcarrier constituting the subchannel, dispersion value of interference power received by each subcarrier, dispersion value of noise power received by each subcarrier, CIR or CNR of each subcarrier, or CNIR dispersion value and the like.

  The feature extraction units 50-1 to 50 -L select candidates to be included in the feature extraction information 102-1 to 102 -L from the calculated candidate channel characteristics. The selection criteria are prepared in advance for each user. The feature extraction units 50-1 to 50-L output the feature extraction information 102-1 to L having the selection result candidates. The feature extraction information 102-1 to L represents the characteristics of the propagation path characteristics for each subchannel for the users 1 to L.

Next, the diffusion multiple conversion matrix used in this embodiment will be described.
In the present embodiment, a diffusion multiple transformation matrix expressed by equation (1) is used. Equation (1) is a diffusion multiplexing transform matrix corresponding to a case where the spreading factor is ^2N and the number of multiplexing is ^2N .

Specific examples of the above (1), (2) spreading multiplex conversion matrix T ₂ where spreading factor 2 and multiplex number corresponding to the case of 2 in _equation (3) spreading factor 4 and the equation A spread multiplex transformation matrix T ₄ corresponding to the case where the multiplex number is 4 is shown. These diffusion multiple transformation matrices can be modified in various mathematical formulas based on the characteristics of trigonometric functions.

The diffusion multiplex transformation matrix of the above equation (1) is an orthogonal matrix, and the row vectors are orthogonal vectors. Similarly, column vectors are orthogonal vectors. Thereby, a spread code is obtained as an orthogonal code from the row vector or column vector in the spread multiple transform matrix. Further, the diffusion multiple transformation matrix is a rotation matrix, and the adjustment parameter _PN is the rotation angle. Then, the spread code obtained from the Division Multiple transformation matrix, the adjustment parameter p _N, those capable of controlling the degree of diffusion of the in-phase component (I component) and quadrature component (Q component).

For example, when the spreading factor is 2 (N = 1), from the above equation (2), if “p ₁ = 0 (radian)”, signal diffusion is not performed, and “p ₁ = π / 4 (radian)”. Then, signal diffusion is performed at an equal ratio. If “0 <p ₁ <π / 4 (radian)”, signal diffusion is performed at a ratio corresponding to the adjustment parameter p ₁ .

  The diversity effect and the intersymbol interference can be adjusted by adjusting the degree of diffusion. That is, when the signal is not spread, no intersymbol interference occurs, but no diversity effect is obtained. On the other hand, when signal spreading is performed, a diversity effect corresponding to the degree of spreading is obtained, but intersymbol interference occurs with it.

In the present embodiment, diffusion is performed using the set value of the adjustment parameter p _N from the row vector or column vector in the diffusion multiple transformation matrix formed of the trigonometric function having the adjustment parameter p _N represented by the above equation (1) as an argument. A code (rotation orthogonal code) is generated, and signal transmission is performed by a modulation method that performs spreading and multiplexing of the signal using the spreading code. Then, the degree of diffusion is controlled by the set value of the adjustment parameter _PN . Thereby, the diversity effect and the intersymbol interference can be adjusted.

In each user's subchannel, there is an optimum adjustment parameter p _N according to the dispersion value such as interference power and CIR received individually by the subcarriers constituting the subchannel. From this, in this embodiment, based on the feature extraction information 102 of each user, the optimal setting value of the adjustment parameter _PN for each user is obtained, and the spread multiplex transformation matrix for each user is obtained from the setting value. Thus, the spread multiplex transform matrix becomes an optimum spread multiplex transform matrix according to the propagation path characteristics of the subchannel assigned to the user. By performing spreading and multiplexing of signals using the spread multiplex transform matrix, it is possible to adjust the diversity effect and intersymbol interference optimal for the propagation path characteristics of the subchannels assigned to the user. As a result, the transmission quality can be improved.

  Note that the feature extraction information according to the present embodiment can be used for optimization and selection of various transmission parameters in addition to the above-described determination of the spread multiplex transform matrix.

  According to the above-described embodiment, the amount of control information exchanged between the transmission side and the reception side can be reduced by performing user assignment of subcarriers in units of subchannels. Further, an optimum spread multiplex transform matrix for each user is obtained from the setting value of the optimum adjustment parameter for each user based on the feature extraction information of each user, and signal spreading and multiplexing are performed using the spread multiplex transform matrix. By doing so, it becomes possible to “adjust the influence from the propagation path” optimal for the propagation path characteristics of the subchannel assigned to the user, and to improve the transmission quality. In the present embodiment, specifically, it is possible to adjust the diversity effect and the intersymbol interference.

  Further, according to the present embodiment, the following effects can be obtained.

(1) For each user, prioritization is performed in order of subchannels with good reception quality based on transmission path characteristics between the radio base station and the user, and subchannels used by each user are selected from the prioritized subchannels. Since it is determined sequentially, it can be expected that a reception error occurring in a subcarrier having poor reception quality, which has been a problem in the conventional method, and a decrease in transmission efficiency caused by application of an error correction code having a low coding rate can be expected.

(2) In the multi-carrier code division multiplexing (MC-CDM) method, a spreading code is set using a setting value of an adjustment parameter from a row vector or a column vector in a spread multiplex transformation matrix composed of a trigonometric function having an adjustment parameter as an argument. Generate and transmit the signal using a modulation scheme that performs spreading and multiplexing of the signal using the spreading code, and selects the optimum adjustment parameter setting value for each user based on the feature extraction information of each user Thus, it is possible to improve the radio transmission quality.

(3) Since information transmission is performed using subchannels with good reception characteristics, not only communication quality can be improved, but also a multi-level modulation scheme with high transmission efficiency can be implemented at a high coding rate, and frequency utilization efficiency can be improved. It can be expected that a high wireless system can be realized.

The embodiment of the present invention has been described in detail with reference to the drawings. However, the specific configuration is not limited to this embodiment, and includes design changes and the like within a scope not departing from the gist of the present invention.
For example, the determination of the subchannel priority order and the adjustment parameter for each user described above is performed in advance, for example, every symbol, every regular symbol period, every irregular symbol period, every slot length decided beforehand. It can be performed in arbitrary time units, such as every frame period.

  Also, it is possible to change the subchannel assigned to each user in symbol period units or arbitrary symbol length units in accordance with a hopping pattern determined in advance without considering the priority order of the subchannels. In this case, by making the subchannel hopping pattern independent for each user or having a low correlation, the interference between adjacent cells is reduced and the resistance to the same channel interference between adjacent cells is increased. It is possible to provide a radio system with excellent characteristics that can provide a frequency diversity effect.

  In the above-described embodiment, the radio base station apparatus determines the setting value of the optimum adjustment parameter for the spread multiplex transform matrix and transmits the spread multiplex transform matrix information to the mobile station apparatus. A setting value of an optimum adjustment parameter of the spread multiplex transform matrix may be determined, and the spread multiplex transform matrix information may be transmitted to the radio base station apparatus.

  Further, generation of feature extraction information and prioritization of subchannels using the feature extraction information may be performed by either the radio base station or the mobile station device. Alternatively, the feature extraction information may be transmitted to the partner station, and the priority order of the subchannels may be determined based on the feature extraction information on the partner station side.

  In the above-described embodiment, the case of the TDD system has been described, but the present invention can also be applied to the case of the FDD system. In the case of the FDD scheme, since the use frequency is different between the uplink and the downlink, it is necessary to perform channel estimation independently for the uplink and the downlink. That is, for the uplink, the radio base station apparatus determines the communication priority (reception signal strength, etc.) of the uplink signal transmitted from each user, and determines the priority order of each user's subchannel based on the observation result. Then, the priority information is notified to each user. On the other hand, for the downlink, each user observes the communication quality (received signal strength, etc.) of the downlink signal transmitted from the radio base station apparatus, and the feature extraction information on the subchannel or the subchannel determined on the user side The priority information is fed back to the radio base station apparatus, and based on the feedback information, a subchannel to be allocated to each user by the radio base station apparatus is determined and notified to each user. These control procedures are the same for the determination of the optimum adjustment parameter setting value of the spread multiplex transform matrix and the transmission of the spread multiplex transform matrix information.

  The present invention includes a digital cellular system, a digital mobile communication system, a high-speed wireless access system, a subscriber wireless access system, a fixed microwave transmission system, a wireless local area network (wireless LAN) system, a personal area network system, and a digital satellite. The present invention can be applied to various digital radio systems such as a communication system, a mobile satellite system, and a sensor network system.

It is a block diagram which shows the structure of the radio base station apparatus of the mobile communication system of the OFDMA system which concerns on one Embodiment of this invention. FIG. 2 is a block diagram showing a configuration of a mobile station apparatus (wireless terminal apparatus) in the OFDMA mobile communication system according to the embodiment. FIG. 2 is a block diagram showing a configuration of a subchannel allocation control circuit 2 shown in FIG. It is a block diagram which shows the structure of the feature extraction circuit 17 shown in FIG.

Explanation of symbols

2 ... subchannel allocation control circuit, 3, 22 ... symbol modulation / multiplexing circuit, 4, 23 ... inverse fast Fourier transform (IFFT) circuit, 5, 24 ... adder, 12, 31 ... fast Fourier transform (FFT) circuit , 13 ... Data determination circuit, 14 ... Data demapping circuit, 16, 36 ... Channel estimation circuit, 17 ... Feature extraction circuit, 21 ... Subchannel selection control circuit, 32 ... Subchannel selection / determination circuit, 33 ... Parallel / Serial conversion circuit, 35... Subchannel selection control information detection circuit, 41-1 to L... Judgment criteria, 42-1 to L... Subchannel priority determination circuit, 43. Mapping circuit, 50-1 to L ... feature extraction unit

Claims (6)

In a multicarrier signal transmission system having an orthogonal frequency division multiple access (OFDMA) wireless base station apparatus and a wireless terminal apparatus,
Subchannel allocation control means for performing user allocation of subcarriers in units of subchannels composed of a plurality of subcarriers;
Feature extraction means for generating feature extraction information representing characteristics of propagation path characteristics for each subchannel for each user;
For each user, comprising, based on the feature extraction information, a spread multiplex transform matrix determining means for determining an optimum spread multiplex transform matrix according to the propagation path characteristics of the subchannel assigned to the user,
The wireless base station device
Signal multiplexing means for spreading and multiplexing signals using the spread multiplex transform matrix for each user;
Transmission means for arranging and transmitting the signal after the spreading and multiplexing processing in a subchannel as a result of the user assignment,
The wireless terminal device
Receiving means for receiving a signal of a subchannel as a result of the user assignment;
Signal division means for performing signal division processing on the received signal using the same spread multiplex transformation matrix as that at the time of transmission;
A multi-carrier signal transmission system. The diffusion multiple transformation matrix is an orthogonal matrix composed of a trigonometric function with an adjustment parameter as an argument,
The spread multiple transform matrix determining means determines a setting value of the adjustment parameter based on the feature extraction information;
The multicarrier signal transmission system according to claim 1. The subchannel allocation control means determines a priority order of subchannels for each user based on the feature extraction information.
The multicarrier signal transmission system according to claim 1. In a radio base station apparatus of orthogonal frequency division multiple access (OFDMA) system,
Subchannel allocation control means for performing user allocation of subcarriers in units of subchannels composed of a plurality of subcarriers;
Feature extraction means for generating feature extraction information representing characteristics of propagation path characteristics for each subchannel for each user;
For each user, based on the feature extraction information, a spread multiplex transform matrix determining means for determining an optimum spread multiplex transform matrix according to the channel characteristics of the subchannel assigned to the user;
Signal multiplexing means for spreading and multiplexing signals using the spread multiplex transform matrix for each user;
Transmitting means for arranging and transmitting the signal after the spreading and multiplexing processing in a subchannel as a result of the user assignment;
A radio base station apparatus comprising: In an orthogonal frequency division multiple access (OFDMA) wireless terminal device,
Receiving means for receiving a signal of a subchannel of a user allocation result;
Signal division means for performing signal division processing on the received signal using the same spread multiplex transformation matrix as that at the time of transmission;
A wireless terminal device comprising: An orthogonal frequency division multiple access (OFDMA) multicarrier signal transmission method comprising:
A first step of performing user allocation of subcarriers in units of subchannels composed of a plurality of subcarriers;
A second process of generating feature extraction information representing characteristics of propagation path characteristics for each subchannel for each user;
A third step of determining, for each user, an optimum spread multiplex transform matrix according to the propagation path characteristics of the subchannel assigned to the user, based on the feature extraction information;
A fourth step of spreading and multiplexing signals using the spread multiplex transform matrix for each user;
A fifth step of transmitting the signal after the spreading and multiplexing processing in a subchannel as a result of the user assignment; and
A sixth step of receiving a signal of a subchannel as a result of the user assignment;
A seventh step of performing signal division processing on the received signal using the same spread multiplex transformation matrix as that at the time of transmission;
A multi-carrier signal transmission method comprising:

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