JP2006295726A - Ofdm transmission equipment, and method therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide OFDM transmission equipment capable of reducing an influence of interference from a neighboring cell, when one cell frequency repetition is applied in a multi-cell environment. <P>SOLUTION: In the OFDM transmission equipment transmitting an orthogonal frequency division multiplex signal, there are provided a symbol repetition number set means for performing symbol repetition by fixing or varying the number of symbol repetitions to a data modulation signal in each channel, and an orthogonal code multiplying means for multiplying a predetermined orthogonal code by a transmission data in a frame generated by multiplexing each channel. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an OFDM transmission apparatus and method using 1-cell frequency repetition in a multi-cell environment.

  In recent years, communication speeds in wireless environments have been increased, frequency utilization efficiency is high, and orthogonal frequency division multiplexing (OFDM), or OFDM (Orthogonal Frequency Division Multiplexing), is a transmission method that enables high-speed communication even in harsh transmission paths. Is attracting attention.

FIG. 16 is a block diagram illustrating a configuration example of a conventional OFDM transmission apparatus to which the OFDM transmission scheme is applied. As shown in the figure, in this OFDM transmission apparatus, error correction coding is performed on input data by a channel encoder 101 and interleaved (rearranged) by a bit interleaver 102. Thereafter, the data modulator 103 performs data modulation (for example, QPSK modulation), and the serial / parallel converter 104 performs serial / parallel conversion. The transmission data subjected to serial-parallel conversion in this manner is subjected to frequency / time conversion (IFFT) processing by the inverse fast Fourier transform unit 105, and an OFDM signal by a plurality of subcarriers (N _c ) is generated. The generated OFDM signal is then subjected to parallel / serial conversion by the parallel / serial conversion unit 106, and then a guard interval is added to the head of each symbol by the guard interval insertion unit 107 and transmitted.

  FIG. 17 is a diagram illustrating the frequency spectrum of the OFDM signal. As shown in the figure, a plurality of subcarriers having different center frequencies are arranged to be orthogonal. In other words, OFDM has the advantage that the frequency utilization efficiency is very excellent because the spectra can be superimposed on each other. Further, by using the guard interval in combination, communication that is resistant to multipath is possible.

  By the way, with the spread of the Internet in recent years, data traffic is mainly used in mobile communication, and research on high-speed, high-efficiency, high-quality mobile packet communication has been actively conducted. When performing high-speed transmission, the above-mentioned OFDM that is resistant to multipath is suitable.

In addition, a technique related to a transmission apparatus for using the above-described OFDM and MC-CDMA mutually and applying to mobile communication configuring a cell is disclosed (for example, see Patent Document 1). Specifically, in an environment where the distance between the base station and the receiving apparatus is short and CINR is high, high-speed transmission is realized by using OFDM. Further, in an environment where the distance between the base station and the receiving apparatus is long or the CINR is low, MC-CDMA is used, the spreading factor is set large, and the communication quality is improved by obtaining the frequency diversity effect.
JP 2004-158901 A

As described above, the above-mentioned OFDM which is strong against multipath is suitable for high-speed transmission, but in order to use this OFDM in a multi-cell environment of a cellular system such as a cellular phone, interference in adjacent cells is avoided. It is necessary to. Therefore, it is conceivable to apply frequency repetition (for example, 3-cell frequency repetition) in order to reduce interference from adjacent cells. FIG. 18A is a diagram for explaining adjacent cell interference when 3-cell frequency repetition is applied in a multi-cell environment. As shown in the figure, in the case of this example, each of three cells is assigned a band of f _A , f _B , and f _{C obtained} by dividing the system bandwidth into three. Further, in this example, it is shown that a cell having a frequency f _A is receiving interference from five neighboring cells using the same frequency.

  That is, when 3-cell frequency repetition is performed in a multi-cell environment, the frequency bandwidth per cell is reduced due to the influence of interference in adjacent cells (decrease to 1/3 with 3-cell frequency repetition), resulting in the maximum information rate. Decrease. Also, as shown in FIG. 6B, when the frequency band is fixedly divided and allocated, the division loss due to the division occurs when the traffic amount of each cell is different. For this reason, even if there is a margin in capacity in a certain cell, a phenomenon occurs in which the capacity is insufficient in other cells. Also, a significant increase in system capacity due to an increase in the number of sectors cannot be expected.

  Therefore, in general, it is possible to increase the system capacity in a multi-cell environment by repeating 1-cell frequency without repeating 3-cell frequency.

  However, when 1-cell frequency repetition is performed in a multi-cell environment, as shown in FIG. 19, the influence of interference from adjacent cells becomes larger, so it is necessary to suppress this interference. It has not been studied so far.

  From the viewpoint of facilitating suppression of interference, it is necessary to make the influence of interference from neighboring cells appear as random as possible with respect to the desired received signal, but a solution to this problem has also been studied. Absent.

  Therefore, an object of the present invention is to provide an OFDM transmission apparatus and method that can reduce the influence of interference from adjacent cells when 1-cell frequency repetition is applied in a multi-cell environment.

  In order to solve the above problems, according to the present invention, as described in claim 1, in an OFDM transmitter for transmitting orthogonal frequency division multiplex signals, the number of symbol repetitions is fixed or variable for the data modulation signal of each channel. Symbol repetition number setting means for performing symbol repetition, and orthogonal code multiplication means for multiplying transmission data in a frame generated by multiplexing each channel by an orthogonal code for multiplying a predetermined orthogonal code. It is characterized by that.

  According to claim 2 of the present invention, in the OFDM transmission apparatus, a scramble code unique to a sector or a cell is used as the orthogonal code.

  According to a third aspect of the present invention, in the OFDM transmission apparatus, the symbol repetition number setting means includes symbol repetition number fixing means for performing symbol repetition for a fixed number of times on the data modulation signal of the control channel, and data And a symbol repetition number adaptive control means for adaptively controlling the symbol repetition number for the data modulation signal of the channel and performing symbol repetition.

  According to a fourth aspect of the present invention, in the OFDM transmission apparatus, the symbol repetition number setting means performs symbol repetition for performing a fixed number of symbol repetitions on a data modulation signal of a common control channel among the control channels. Characterized by comprising: number fixing means; and symbol repetition number adaptive control means for performing symbol repetition by adaptively controlling the symbol repetition number for the data modulation signals of the individual control channel and the data channel among the control channels. It is said.

  According to claim 5 of the present invention, in the OFDM transmitter, the symbol repetition number adaptive control means adaptively controls the symbol repetition number according to communication quality.

  According to claim 6 of the present invention, the OFDM transmission apparatus uses SINR as the communication quality.

  In order to solve the above problems, the present invention provides, as described in claim 7, channel coding applied to transmission data of each channel in an OFDM transmission apparatus that transmits orthogonal frequency division multiplexed signals. Coding rate setting means for performing the channel coding with a fixed or variable coding rate, and orthogonal codes for multiplying transmission data in a frame generated by multiplexing each channel by a predetermined orthogonal code And orthogonal code multiplication means for multiplication.

  According to claim 8 of the present invention, in the OFDM transmitter, a scramble code unique to a sector or cell is used as the orthogonal code.

  According to a ninth aspect of the present invention, in the OFDM transmission apparatus, the coding rate setting means sets a coding rate of channel coding applied to transmission data of the control channel to a fixed low coding rate. Coding rate fixed setting means for performing channel coding by setting to, and coding rate adaptation for performing channel coding by adaptively controlling the coding rate of channel coding applied to transmission data of the data channel And a control means.

  According to claim 10 of the present invention, in the OFDM transmission apparatus, the coding rate setting means sets a coding rate of channel coding applied to transmission data of a common control channel among the control channels. A coding rate fixed setting means for performing channel coding by setting a fixed low coding rate, and a coding rate of channel coding applied to transmission data of the individual control channel and the data channel among the control channels And coding rate adaptive control means for adaptively controlling and performing channel coding.

  According to claim 11 of the present invention, in the OFDM transmitter, the coding rate adaptive control means adaptively controls the coding rate of channel coding according to communication quality. .

  According to claim 12 of the present invention, the OFDM transmission apparatus uses SINR as the communication quality.

  According to the present invention, by applying fixed symbol repetition for the control channel and variable symbol repetition for the data channel, it is possible to obtain a gain that suppresses interference from adjacent cells. Become. Further, by multiplying the channel-multiplexed signal OFDM signal by a cell-specific scramble code, it is possible to randomize the influence of interference from adjacent cells.

  The essence of the present invention is that, in a multi-cell environment, in an OFDM transmission apparatus to which one-cell frequency repetition is applied, symbol repetition or channel coding with a low coding rate is performed to obtain a gain that suppresses the influence of interference from adjacent cells. Is to apply.

  Further, in order to randomize interference from adjacent cells, it is to multiply by a scramble code.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

(Embodiment 1)
FIG. 1 is a block diagram showing a configuration of an OFDM transmission apparatus according to Embodiment 1 of the present invention.

  The OFDM transmitter 1 shown in FIG. 1 includes channel encoders 11-1 and 11-2, bit interleavers 12-1 and 12-2, and data modulators 13-1 and 13 for the control channel and the data channel, respectively. -2, and further includes a frame generation unit 14 that multiplexes a control channel, a data channel, and a pilot channel, a cell-specific scramble code multiplication unit 15, a serial-parallel conversion unit 16, an inverse fast Fourier transform unit 17, and a parallel-serial conversion unit 18. , And a guard interval insertion portion 19.

  In the figure, control data transmitted on the control channel and transmission data transmitted on the data channel are respectively input to the corresponding channel encoders 11-1 and 11-2, where errors for countermeasures against transmission errors are input. Detection / correction encoding processing is performed. The control data and transmission data encoded by the channel encoders 11-1 and 11-2 are then interleaved by the corresponding bit interleavers 12-1 and 12-2. The interleaved control data and transmission data are digitally modulated by the corresponding data modulators 13-1 and 13-2 and then input to the frame generation unit 14. The frame generation unit 14 multiplexes the control channel, the data channel, and the pilot channel (reference signal for propagation path estimation) into a frame to generate a transmission frame.

  The channel-multiplexed transmission frame is input to the cell-specific scramble code multiplication unit 15 and the cell-specific scramble code generated in the unit 15 (for example, the OFDM transmission apparatus of the present invention is used in the mobile communication system). When applied to a base station, it is multiplied by a spreading code for identifying the base station. The scramble code is a spreading code unique to each base station.

  Next, the transmission frame multiplied by the cell-specific scramble code is subjected to the series-parallel conversion processing, inverse fast Fourier transform processing, parallel-serial conversion processing, and guard interval insertion processing similar to those of the conventional OFDM transmitter shown in FIG. , Transmitted as an OFDM signal.

  As described above, according to this embodiment, by multiplying a frame in which a pilot channel, a control channel, and a data channel are multiplexed by a cell-specific scramble code (random noise), interference from adjacent cells using the same frequency is randomized. As a result, it is possible to easily suppress the influence of interference.

(Embodiment 2)
In the first embodiment, the case where a frame in which a pilot channel, a control channel, and a data channel are multiplexed is multiplied by a cell-specific scramble code (random noise) is exemplified. However, the OFDM transmission apparatus 2 in the second embodiment is In addition to the cell-specific scramble code multiplication described above, fixed symbol repetition is applied to the control channel and variable symbol repetition is applied to the data channel in order to obtain a gain for suppressing interference from adjacent cells. The configuration.

  Specifically, as illustrated in FIG. 2, additional configurations in the OFDM transmission apparatus 2 in the present embodiment are a fixed symbol repetition unit 21-1 and a variable symbol repetition unit 21-2. Hereinafter, differences from the first embodiment will be described. In addition, the same code | symbol is attached | subjected to the component same as 1st Embodiment, and the description is abbreviate | omitted.

  The symbol repetition applied in the OFDM transmission apparatus 2 of the present embodiment is a technique that has been studied as a technique for improving frequency use efficiency in an uplink isolated cell environment, that is, applying symbol repetition to a transmission signal sequence. After generating a signal having a comb-shaped frequency spectrum, the frequency spectrum of each transmitting station is orthogonal to each other by multiplying each transmitting station (for example, a mobile station in a mobile communication system) by a unique phase sequence. It is the method of arranging to do.

  In the present embodiment, fixed symbol repetition section 21-1 receives as input control data in a control channel with a constant information rate. In general, the information rate of the control channel is constant, and there is no need to change the information rate by making the symbol repetition variable. Therefore, fixed symbol repetition section 21-1 sets fixed symbol repetition that can satisfy the required quality in an environment where interference from other cells is severe. For example, the number of symbol repetitions may be determined based on the user at the cell edge.

  On the other hand, the variable symbol repetition unit 21-2 receives user data in a data channel with a variable information rate as an input. In the data channel, the information rate required by the user differs, and the magnitude of interference from adjacent cells differs depending on the position of the user. Therefore, the variable symbol repetition unit 21-2 adaptively varies the number of symbol repetitions so that the information rate desired by the user is achieved as much as possible while satisfying the required quality for each user.

  Here, the relationship between the number of symbol repetitions, the interference suppression effect, and the information rate will be described. The number of symbol repetitions indicates how many symbols are repeatedly transmitted. If the number of symbol repetitions is large, the received symbols are combined on the receiving side, resulting in a large interference suppression effect. Although quality reception is possible, the information rate is reduced according to the number of symbol repetitions. On the contrary, if the symbol repetition number is small, the interference suppression effect is small, but the information rate is large.

  Therefore, the number of symbol repetitions varied in the variable symbol repetition unit 21-2 is determined and varied by the trade-off between the interference suppression effect and the information rate.

  As described above, according to the OFDM transmitter 2 in the present embodiment, interference from adjacent cells is reduced by applying fixed symbol repetition to the control channel and variable symbol repetition to the data channel. A gain to be suppressed can be obtained.

  Further, by multiplying the channel-multiplexed signal OFDM signal by a cell-specific scramble code, it is possible to randomize the influence of interference from adjacent cells.

  That is, according to the OFDM transmitter 2 according to the present invention, one-cell frequency repetition can be realized in a multi-cell environment, and as a result, the system capacity can be increased.

(Embodiment 3)
In the second embodiment, a mode in which fixed symbol repetition is applied to the control channel is exemplified. However, in the OFDM transmission apparatus 3 in the present embodiment, symbol repetition is fixed according to the type of the control channel. -Equipped with a function that selectively uses variable.

  As shown in FIG. 3, the OFDM transmission apparatus 3 according to the third embodiment has the same basic configuration as that of the OFDM transmission apparatus 2 described in the second embodiment, but separates the control channel from the common control channel. The control channel is divided into two types, and is different in that fixed symbol repetition is applied to the common control channel and variable symbol repetition is applied to the individual control channel. That is, in the OFDM transmitter 3 in the present embodiment, the channel encoder 31-1, the bit interleaver 32-1, the data modulator 33-1, the fixed symbol repetition unit 34-1, the dedicated control channel corresponding to the common control channel. Are provided with a channel encoder 31-2, a bit interleaver 32-2, a data modulator 33-2, and a variable symbol repetition unit 34-2.

  Hereinafter, differences from the second embodiment will be described in detail. In addition, the same code | symbol is attached | subjected to the component same as 1st Embodiment, and the description is abbreviate | omitted.

  As described above, in this embodiment, the control channels shown in the second embodiment are classified into two types: common control channels for all users in the cell and individual control channels for each user. In the fixed symbol repetition unit 34-1 corresponding to, a fixed symbol repetition number is set. For example, as in the second embodiment, the number of symbol repetitions is determined based on the user at the cell edge.

  On the other hand, in variable symbol repetition section 34-2 corresponding to the dedicated control channel, it is considered that the number of symbol repetitions required for each user to satisfy the required quality is different (mainly due to different user positions in the cell). Although it is conceivable, the difference in information rate for each user is also considered as a factor), and the number of symbol repetitions is adaptively varied for each user.

  As described above, according to the OFDM transmitter 3 in the present embodiment, by applying fixed symbol repetition to the common control channel, adaptive symbol repetition to the dedicated control channel, and adaptive symbol repetition to the data channel, It is possible to obtain a gain that suppresses interference from adjacent cells with high accuracy.

  Next, a variable control method of the number of symbol repetitions adaptively varied by the variable symbol repetition units 21-2, 34-2, and 34-3 in the above embodiments will be described with reference to FIG. The OFDM transmission device 4 shown in FIG. 4 is configured by adding a repetition number variable control unit 22 corresponding to a data channel, compared to the configuration of the OFDM transmission device 2 shown in FIG. Hereinafter, variable control of the symbol repetition number performed by the repetition number variable control unit 22 will be described.

  In the figure, the repetition number variable control unit 22 receives a desired signal received power to noise + interference power ratio (SINR) of each user as an input, and determines the number of symbol repetitions according to the SINR. Adaptively variable control. For example, control is performed to increase the number of symbol repetitions when the input SINR is low and to decrease the number of symbol repetitions when the SINR is large.

  The SINR is notified from, for example, a mobile station (in the case of a mobile communication system) to which an OFDM receiver that is a communication partner of the OFDM transmitter in the present embodiment is applied. In this embodiment, the method for variably controlling the symbol repetition number based on the SINR notification from the mobile station is referred to as a base station initiative type symbol repetition number changing method in this embodiment. Further, according to the present embodiment, a method of notifying the base station of a change in the number of symbol repetitions based on the SINR measured by the mobile station and changing the number of symbol repetitions based on this notification This is called a change method.

  Next, the sequence of the procedure for changing the number of symbol repetitions led by the base station and the mobile station will be described. Here, a case where the OFDM transmission apparatus according to the present embodiment is applied to a base station in a mobile communication system will be described as an example.

  FIG. 5 is a diagram showing a sequence of a procedure for changing the number of symbol repetitions led by the base station, and FIG. 6 is a diagram showing a sequence of a procedure for changing the number of symbol repetitions led by the mobile station.

  In FIG. 5, the mobile station measures SINR using a pilot channel multiplexed in the frame of the OFDM signal transmitted from the base station, and transmits (feeds back) the measurement result to the base station as SINR information. The repetition number variable control unit 22 of the base station determines the symbol repetition number based on the SINR information. Thereafter, the determined symbol repetition count after change is notified to each user (mobile station) through a control channel transmitted from the base station, and the mobile station recognizes the changed symbol repetition count from the base station. Data channel transmission is started.

  Next, a procedure for changing the number of symbol repetitions led by the mobile station will be described with reference to FIG.

  In the figure, the mobile station notifies the base station of the desired number of symbol repetitions. The repetition number variable control unit 22 of the base station determines the symbol repetition number based on the notification from the mobile station, and transmits the data channel with the determined symbol repetition number. In this aspect, the base station always transmits a data channel according to the number of symbol repetitions requested by the mobile station.

  The mobile station initiative type symbol repetition number changing procedure is advantageous in that the processing required for changing the symbol repetition number is simplified as compared with the base station initiative type symbol repetition number changing procedure. When there is an error in the number of symbol repetitions notified from the receiver, the received signal cannot be demodulated / decoded with the desired number of symbol repetitions. Therefore, as shown in FIG. 7, the base station notifies the mobile station of the changed symbol repetition number through the control channel. As a result, the transmission of the data channel by the base station starts after the mobile station confirms the number of symbol repetitions. In this aspect, in this aspect, compensation is made when the notification from the mobile station to the base station is incorrect. Is possible.

  In the above embodiment, the mode of changing the number of symbol repetitions of the data channel has been exemplified, but when changing the number of symbol repetitions of the dedicated control channel, a method for notifying the mobile station of the number of symbol repetitions after the change is as follows. There are two possible ways.

  (A) A method of notifying the number of symbol repetitions using a common control channel with a fixed number of symbol repetitions.

  (B) A method in which the mobile station is notified through the dedicated control channel before changing the symbol repetition number, and after the mobile station recognizes, the symbol repetition number is actually changed by transmission of the next dedicated control channel.

  Next, the symbol repetition method in this embodiment will be described. As a method of symbol repetition, for example, as shown in FIG. 8A, each symbol is repeated n times (in this example, n = 4) in the time domain, or as shown in FIG. It is preferable to repeat the symbol n times (in this example, n = 4) in the frequency domain (repeating across subcarriers). Further, as shown in FIG. 8C, two-dimensional repetition in the time / frequency domain may be performed by combining FIGS. 8A and 8B. In the example of FIG. 5C, each symbol is repeated n times (n = 2 in this example) in the time domain and n times (n = 2 in this example) in the frequency domain.

  In the above example, when symbol repetition is performed, a mode in which repeated symbols are allocated to adjacent OFDM symbols or adjacent subcarriers has been illustrated. However, symbol repetition is not limited to such a mode, and symbol positions are separated from each other. It is also possible to perform allocation to a plurality of OFDM symbols or distant subcarriers. In that case, a time diversity effect and a frequency diversity effect can be obtained, and as a result, high-quality transmission can be performed.

  As described above, in each of the above embodiments, the mode in which the number of symbol repetitions is adaptively controlled in order to obtain a gain for suppressing interference from adjacent cells has been illustrated, but the present invention is limited to such a mode. Is not to be done. In the embodiment described below, a gain for suppressing interference from adjacent cells is obtained by controlling a coding rate for error correction and obtaining a coding gain.

(Embodiment 4)
The OFDM transmitter according to this embodiment has a function of obtaining a gain for suppressing interference from neighboring cells by controlling the coding rate of error correction coding and obtaining a coding gain.

  As shown in FIG. 9, the OFDM transmission apparatus 5 in the present embodiment has the same basic configuration as the OFDM transmission apparatus 1 in the first embodiment shown in FIG. 1, but the OFDM transmission apparatus 5 in the present embodiment. 1, the fixed symbol repetition unit 21-1 and the variable symbol repetition unit 21-2 shown in FIG. 1 are omitted, the coding rate fixed channel encoder 51-1 corresponding to the control channel, and the encoding corresponding to the data channel. A rate variable channel encoder 51-2 is provided. In the present embodiment, in order to suppress interference from other cells, the coding rate of the channel encoder 51-1 corresponding to the control channel is set to a fixed low coding rate, and the channel encoder 51-2 for the data channel is set. The coding rate is adaptively varied, and this is different from the first embodiment. Hereinafter, differences from the first embodiment will be described. Further, the same components as those in the first embodiment are denoted by the same reference numerals, and description thereof is omitted.

In FIG. 9, the fixed channel encoder 51-1 corresponding to the control channel can satisfy the required quality in an environment where interference from other cells is severe, similar to the concept of symbol repetition in the first embodiment described above. Possible fixed channel coding rates, for example, coding rates of 1/2 and 1/3 are set. On the other hand, in the variable channel encoder 51-2 corresponding to the data channel, the code rate is adaptively changed so that the information rate desired by the user can be obtained as much as possible while satisfying the required quality according to the user. For example, the coding rate can be changed to 1/8 and 1/16, which are larger than the fixed coding rates 1/2 and 1/3.
As described above, according to the OFDM transmitter 5 in the present embodiment, a fixed channel coding coding rate is applied to the control channel, and a variable channel coding coding rate is applied to the data channel. By doing so, it is possible to obtain a gain that suppresses interference from adjacent cells.

  Further, by multiplying the channel-multiplexed signal OFDM signal by a cell-specific scramble code, it is possible to randomize the influence of interference from adjacent cells.

  That is, according to the OFDM transmitter 5 according to the present invention, one-cell frequency repetition can be realized in a multi-cell environment, and as a result, the system capacity can be increased.

(Embodiment 5)
In the fourth embodiment, a mode in which a fixed coding rate is applied to the control channel is exemplified. However, in the OFDM transmitter 6 in the present embodiment, channel coding is further performed according to the type of the control channel. It has a function to use either fixed or variable coding rate.

  As shown in FIG. 10, the OFDM transmission apparatus 6 in the present embodiment has a fixed coding rate and individual coding for the common control channel among the control channels, as in the concept of symbol repetition in the third embodiment. A variable coding rate is applied to the control channel, and a variable coding rate is applied to the data channel.

  That is, according to the OFDM transmitter 6 in the present embodiment, a fixed coding rate is applied to the common control channel, an adaptive coding rate is applied to the dedicated control channel, and an adaptive coding rate is applied to the data channel. Thus, it is possible to obtain a gain that suppresses interference from adjacent cells with high accuracy.

  Next, a variable control method of the coding rate of channel coding that is varied in the variable channel encoders 51-2, 61-2, and 61-3 will be described with reference to FIG. In the coding rate variable control method according to the present embodiment, the coding rate of the channel coding is variable by the coding rate variable control unit 52 of the OFDM transmitter 7 shown in FIG. Be controlled. Specifically, the coding rate of channel coding is variably controlled according to the measured value of SINR of each user. For example, when the SINR is low, control is performed to decrease the coding rate, and when the SINR is large, control to increase the coding rate.

  As in the case of the symbol repetition described above, the coding rate is changed when the base station to which the OFDM transmitter of the present invention is applied performs the change based on the SINR notified from the mobile station (base station). And a case where the base station is notified of the change of the coding rate based on the SINR measured by the mobile station and the coding rate is changed based on this notification (mobile station led). The sequence of the coding rate changing procedure led by the base station and the mobile station is the same as the above-described symbol repetition concept as shown in FIGS.

Further, in the above embodiment, the case of changing the coding rate of the data channel has been shown. However, as a method of notifying the mobile station of the changed coding rate when changing the coding rate of the dedicated control channel, The following two ways can be considered.
(A) A method of reporting the coding rate using a common control channel with a fixed coding rate.
(B) A method in which the mobile station is notified using the dedicated control channel before the coding rate is changed, and the coding rate is actually changed by transmission of the next dedicated control channel after being recognized by the mobile station.

  Next, a method for assigning channel-coded bits in this embodiment will be described. As a channel-coded bit allocation method, for example, as shown in FIG. 15 (a), when the coding rate is 1/8, eight OFDM symbols are generated from the coded bits. Channel-coded bits are continuously allocated to the time domain by n symbols (in this example, n = 8), or channel-coded bits are allocated to frequency domain n subcarriers as shown in FIG. It is preferable to assign (n = 8 in this example). Also, as shown in FIG. 15C, FIGS. 15A and 15B may be combined to perform two-dimensional allocation to the time / frequency domain. In the example of coding rate = 1/8 in FIG. 8C, n symbols (in this example, n = 2) are allocated to channel encoded bits continuously in the time domain, and channel encoded bits are allocated. It is assigned to n subcarriers in the frequency domain (in this example, n = 4).

  In the above example, the mode in which encoded bits are allocated to adjacent OFDM or adjacent subcarriers has been illustrated. However, the allocation of encoded bits is not limited to such a mode, and OFDM symbols located at distant positions are used. Alternatively, it is possible to assign to remote subcarriers. In that case, a time diversity effect and a frequency diversity effect can be obtained, and as a result, high-quality transmission can be performed.

It is a block diagram which shows the structure of the OFDM transmitter which concerns on Embodiment 1 of this invention. It is a block diagram which shows the structure of the OFDM transmitter which concerns on Embodiment 2 of this invention. It is a block diagram which shows the structure of the OFDM transmitter which concerns on Embodiment 3 of this invention. It is a block diagram which shows the structure of the OFDM transmitter for demonstrating the variable control method of the symbol repetition number. It is a figure which shows the sequence of the change procedure of the symbol repetition number led by the base station. It is a figure which shows the sequence (the 1) of the change procedure of the symbol repetition number led by the mobile station. It is a figure which shows the sequence (the 2) of the change procedure of the symbol repetition number led by the mobile station. It is a figure for demonstrating the symbol repetition method. It is a block diagram which shows the structure of the OFDM transmitter which concerns on Embodiment 4 of this invention. It is a block diagram which shows the structure of the OFDM transmitter which concerns on Embodiment 5 of this invention. It is a block diagram which shows the structure of the OFDM transmitter for demonstrating a coding rate variable control method. It is a figure which shows the sequence of the change procedure of the encoding rate led by a base station. It is a figure which shows the sequence (the 1) of the change procedure of the encoding rate led by a mobile station. It is a figure which shows the sequence (the 2) of the change procedure of the encoding rate led by a mobile station. It is a figure for demonstrating the allocation method of the channel-coded bit. It is a block diagram which shows the structure of the conventional OFDM transmitter. It is a figure which shows the frequency spectrum of the OFDM signal in the conventional OFDM transmitter. It is a figure for demonstrating 3 cell frequency repetition in a multicell environment. It is a figure for demonstrating 1 cell frequency repetition in a multicell environment.

Explanation of symbols

1-7 OFDM transmitters 11-1, 11-2, 31-1 to 31-3, 101 channel encoders 12-1, 12-2, 32-1 to 32-3, 62-1 to 62-3 , 102 bit interleaver 13-1, 13-2, 33-1 to 33-3, 63-1 to 63-3, 103 Data modulator 14 Frame generator 15 Cell-specific scramble code multiplier 16, 104 Serial-parallel conversion Unit 17, 105 inverse fast Fourier transform unit 18, 106 parallel-serial conversion unit 19, 107 guard interval insertion unit 21-1, 34-1 fixed symbol repetition unit 21-2, 34-2, 34-3 variable symbol repetition unit 22 Symbol repetition number variable control unit 51-1, 61-1 fixed channel encoder 51-2, 61-2, 61-3 variable channel encoder 52 variable coding rate control Part

Claims (14)

In an OFDM transmitter that transmits orthogonal frequency division multiplexing signals,
Symbol repetition number setting means for performing symbol repetition by fixing or varying the symbol repetition number for the data modulation signal of each channel;
An OFDM transmission apparatus, comprising: orthogonal code multiplication means for multiplying transmission data in a frame generated by multiplexing each channel by an orthogonal code for multiplying a predetermined orthogonal code. The OFDM transmitter according to claim 1, wherein
An OFDM transmitting apparatus, wherein a scramble code unique to a sector or a cell is used for the orthogonal code. In the OFDM transmitter according to claim 1 or 2,
The symbol repetition number setting means includes:
Symbol repetition number fixing means for performing symbol repetition for a fixed number of times on the data modulation signal of the control channel;
An OFDM transmission apparatus comprising: a symbol repetition number adaptive control unit that adaptively controls a symbol repetition number for a data modulation signal of a data channel to perform symbol repetition. In the OFDM transmitter according to claim 1 or 2,
The symbol repetition number setting means includes:
Symbol repetition number fixing means for performing symbol repetition for a fixed number of data modulation signals of a common control channel among the control channels;
An OFDM transmitter comprising: a symbol repetition number adaptive control unit that adaptively controls a symbol repetition number for a data modulation signal of an individual control channel and a data channel among the control channels, and performs symbol repetition. . In the OFDM transmitter according to claim 3 or 4,
The symbol repetition number adaptive control means adaptively controls the number of symbol repetitions according to communication quality. The OFDM transmitter according to claim 5, wherein
An OFDM transmission apparatus using SINR as the communication quality. In an OFDM transmitter that transmits orthogonal frequency division multiplexing signals,
Coding rate setting means for performing the channel coding with the coding rate of channel coding applied to the transmission data of each channel fixed or variable;
An OFDM transmission apparatus, comprising: orthogonal code multiplication means for multiplying transmission data in a frame generated by multiplexing each channel by an orthogonal code for multiplying a predetermined orthogonal code. The OFDM transmitter according to claim 7, wherein
An OFDM transmitting apparatus, wherein a scramble code unique to a sector or a cell is used for the orthogonal code. In the OFDM transmitter according to claim 7 or 8,
The coding rate setting means includes:
Coding rate fixed setting means for performing channel coding by setting the coding rate of channel coding applied to transmission data of the control channel to a fixed low coding rate;
An OFDM transmission apparatus comprising: coding rate adaptive control means for performing channel coding by adaptively controlling a coding rate of channel coding applied to transmission data of a data channel. In the OFDM transmitter according to claim 7 or 8,
The coding rate setting means includes:
Coding rate fixed setting means for performing channel coding by setting a coding rate of channel coding applied to transmission data of the common control channel among the control channels to a fixed low coding rate;
Coding rate adaptive control means for adaptively controlling the coding rate of channel coding applied to the transmission data of the dedicated control channel and the data channel among the control channels, and performing channel coding. A featured OFDM transmitter. In the OFDM transmitter according to claim 9 or 10,
The OFDM transmission apparatus characterized in that the coding rate adaptive control means adaptively controls the coding rate of channel coding according to communication quality. The OFDM transmitter according to claim 11, wherein
An OFDM transmission apparatus using SINR as the communication quality. In an OFDM transmission method for transmitting orthogonal frequency division multiplexed signals,
Performing a fixed number of symbol repetitions on the control channel data modulation signal;
Performing symbol repetition by adaptively controlling the number of symbol repetitions for the data modulation signal of the data channel;
Multiplying transmission data in a frame generated by multiplexing the control channel, the data channel, and the pilot channel by an orthogonal code of multiplying a predetermined orthogonal code, and an OFDM transmission method comprising: . In an OFDM transmission method for transmitting orthogonal frequency division multiplexed signals,
Setting the coding rate of channel coding applied to the transmission data of the control channel to a fixed low coding rate, and performing channel coding;
Performing channel coding by adaptively controlling a coding rate of channel coding applied to transmission data of a data channel;
An OFDM transmission method comprising: multiplying transmission data in a frame generated by multiplexing the control channel, the data channel, and the pilot channel by a predetermined orthogonal code.

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