JP2006324728A - Multicarrier communication apparatus and multicarrier communication method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent operation amount from increasing while minimizing loss in transmission efficiency due to GI. <P>SOLUTION: A GI adding section 104 adds a GI having a length stored in a GI length holding section 105 to the head of OFDM data. The GI length holding section 105 is holding a GI length optimal for the cell of its own apparatus depending on the fact whether the cell attributes of its own apparatus are cellular or hot spot. An extension data IFFT section 106 performs inverse fast Fourier transform of modulation data of such an amount as confined to a length obtained by subtracting two times of the GI length of its own apparatus from extension of fixed length. An extension data GI adding section 107 adds a GI having a length stored in the GI length holding section 105 to the head of the extension data. An extension data adding section 108 adds extension data attached with a GI in front of the GI of the OFDM data added with GI. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a multicarrier communication apparatus and a multicarrier communication method, and more particularly to a multicarrier communication apparatus and a multicarrier communication method for transmitting a multicarrier signal in which a guard interval is added to the head of a data portion included in a symbol.

  In general, in multicarrier communication using an OFDM (Orthogonal Frequency Division Multiplex) system or the like, a guard interval (hereinafter abbreviated as “GI”) is provided between symbols in order to prevent intersymbol interference. Provided. The GI is provided between symbols by duplicating the end of the data portion in the symbol and adding it to the beginning of the data portion.

  The GI time length (hereinafter referred to as “GI length”) may be longer than the delay time of the delayed wave that reaches the receiving side with the greatest delay (hereinafter referred to as “maximum delay”). The delayed wave of one symbol does not interfere with the next symbol. However, since the maximum delay changes according to the propagation environment such as the cell radius, the GI length needs to be longer than the maximum maximum delay assumed in the radio communication system.

  On the other hand, since GI is a duplicate of the end of the data portion and is a redundant component that does not include information to be transmitted, it is preferable to shorten the GI length from the viewpoint of transmission efficiency. That is, the GI length is preferably equal to the largest maximum delay assumed in the wireless communication system, and it is not preferable that the GI length be longer or shorter than that.

  However, when the GI length is determined in this way, even in the same wireless communication system, for example, in a propagation environment where the maximum delay is small, the GI length is longer than necessary, and transmission efficiency is wasted. That is, for example, in the case of a radio communication system having cells with different cell radii, the maximum delay assumed in a cell having a large cell radius is large, and the maximum delay assumed in a cell having a small cell radius is small. In such a case, the GI length is determined to be equal to the maximum delay assumed in a cell having a large cell radius. However, when communication is performed in a cell having a small cell radius, the GI length is larger than the actual maximum delay. The GI length is long, and potential transmission efficiency loss occurs.

To solve this problem, for example, as disclosed in Patent Document 1, it is conceivable to make the GI length variable. That is, in a propagation environment with a small maximum delay, the ratio of the GI length in the OFDM symbol is reduced as shown in FIG. 13A, and in a propagation environment with a large maximum delay, as shown in FIG. What is necessary is just to enlarge the ratio of GI length which occupies for an OFDM symbol.
JP-A-8-88617

  By the way, in the receiving apparatus of multicarrier communication, a received signal is subjected to orthogonal transform such as Fast Fourier Transform (FFT) and Discrete Fourier Transform (DFT), for example. Data superimposed on the subcarrier is extracted. This orthogonal transformation is performed on the data portion of each symbol obtained by removing GI from the received signal. At this time, the length of the data portion is the power of 2 (2) in terms of the number of samples in the orthogonal transformation. , 4, 8, 16,... In other words, if the length of the data part is a power-of-two sample, FFT can be easily performed as orthogonal transform, and the amount of calculation can be reduced and the processing speed can be improved.

  However, in the technique disclosed in Patent Document 1 described above, since the GI length is changed without changing the OFDM symbol length, it is difficult to always maintain the length of the data portion at a power of 2 samples. There's a problem. Specifically, for example, when the length of the data portion is 1024 samples, in order to shorten the GI length while keeping the length of the data portion as a power-of-two sample, the GI length is shortened by 1024 samples and the data portion is shortened. The length should be 2048 (= 1024 + 1024) samples. However, since the GI length is usually much shorter than the length of the data portion, it is impractical to shorten the GI length by 1024 samples when the data portion is 1024 samples.

  For this reason, the ratio of the GI and the data portion in the OFDM symbol is appropriately changed without maintaining the length of the data portion to be a power-of-two sample. In this case, however, the FFT is easily performed as an orthogonal transformation. There is a need to apply a DFT that cannot be applied and has a large amount of calculation.

  The present invention has been made in view of the above points, and provides a multicarrier communication apparatus and a multicarrier communication method capable of preventing an increase in the amount of computation while minimizing loss of transmission efficiency due to GI. For the purpose.

  The multi-carrier communication apparatus according to the present invention is an extension that adds a guard interval having a length corresponding to a propagation environment to fixed-length multi-carrier data, and makes the sum of the lengths of the added guard intervals constant. A configuration having data generating means and transmitting means for transmitting a symbol composed of multicarrier data after addition of a guard interval and the extension data is adopted.

  The multi-carrier communication method according to the present invention is a method of adding a guard interval having a length corresponding to a propagation environment to fixed-length multi-carrier data, and extended data for making the sum of the lengths of the added guard intervals constant. And a step of transmitting a symbol composed of the multi-carrier data after the addition of the guard interval and the extension data.

  According to these, since a fixed-length extension portion consisting of a guard interval and extension data is added to the fixed-length multicarrier data to form a transmission symbol, the multicarrier can be changed even if the GI length is changed according to the propagation environment. The data length can be fixed to a power-of-two sample, and fast Fourier transform can be performed on the receiving side. As a result, it is possible to prevent an increase in the amount of computation while minimizing transmission efficiency loss due to GI.

  According to the present invention, it is possible to prevent an increase in the amount of computation while minimizing a loss in transmission efficiency due to GI.

  The gist of the present invention is to generate a symbol by adding a fixed-length extension portion including a variable-length GI and variable-length extension data to the head of the fixed-length data portion.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the following description, it is assumed that communication using the OFDM method is applied as multicarrier communication.

(Embodiment 1)
In Embodiment 1 of the present invention, it is assumed that a mobile station apparatus can communicate with a base station apparatus in each cell in both a cell for a normal mobile phone and a cell for a wireless LAN.

  FIG. 1 is a block diagram showing a main configuration of the base station apparatus according to the present embodiment. 1 includes an error correction encoding unit 101, a modulation unit 102, an IFFT (Inverse Fast Fourier Transform) unit 103, a GI addition unit 104, a GI length holding unit 105, and an extended data IFFT unit. 106, extended data GI adding unit 107, extended data adding unit 108, RF (Radio Frequency) transmitting unit 109, RF receiving unit 110, GI removing unit 111, FFT unit 112, demodulating unit 113, and error correction decoding unit 114.

  Error correction coding section 101 performs error correction coding on transmission data and outputs the obtained coded data to modulation section 102.

  Modulating section 102 modulates the encoded data and outputs the obtained modulated data to IFFT section 103 and extension data IFFT section 106.

  IFFT section 103 performs inverse fast Fourier transform on the modulated data, superimposes the modulated data on a plurality of subcarriers having different frequencies, and outputs the obtained OFDM data to GI adding section 104. The IFFT unit 103 always performs inverse fast Fourier transform on a certain amount of modulation data. Therefore, the length of the obtained OFDM data is constant.

  The GI adding unit 104 adds a GI having a length specified by the GI length holding unit 105 to the beginning of the OFDM data, and outputs the OFDM data to which the GI is added to the extension data adding unit 108. Note that the GI addition unit 104 duplicates the end of the OFDM data to obtain a GI.

  The GI length holding unit 105 holds the optimum GI length for the cell of the own device depending on whether the own device is a base station device of a cell such as a mobile phone or a base station device of a cell such as a wireless LAN. ing. That is, the GI length holding unit 105 holds a long GI length because the cell of the own device is considered to have a relatively large cell radius and a large maximum delay if the own device is a base station device of a cell such as a mobile phone. is doing. In addition, if the device itself is a base station device of a cell such as a wireless LAN, the GI length holding unit 105 holds a short GI length because the cell of the device itself is considered to have a relatively small cell radius and a maximum delay. is doing. Then, the GI length holding unit 105 notifies the held GI length to the GI adding unit 104, the extended data IFFT unit 106, and the extended data GI adding unit 107.

  Hereinafter, a cell attribute of a cell such as a mobile phone is referred to as cellular, and a cell attribute of a cell such as a wireless LAN is referred to as a hot spot.

  The extended data IFFT unit 106 is a length obtained by subtracting twice the GI length held in the GI length holding unit 105 of the own device from the extended portion set to a length equal to or longer than the longest GI length in the entire wireless communication system. The amount of modulation data that falls within this range is subjected to inverse fast Fourier transform, the modulation data is superimposed on a plurality of subcarriers, and the obtained extension data is output to extension data GI adding section 107.

  That is, in the present embodiment, an extension portion having a certain length is added to OFDM data having a certain length generated by IFFT section 103. At this time, the extended portion is fixed to a length equal to or longer than the longest GI length in the entire wireless communication system. In this embodiment, the extended portion is fixed to a length equal to or longer than the GI length when the cell attribute is cellular. Yes. The extension portion is composed of a GI portion of OFDM data and a portion other than the GI, but the extension data IFFT unit 106 generates extension data by performing inverse fast Fourier transform on the amount of modulation data that fits in the portion other than the GI. . The amount that can be accommodated in the portion other than the GI is not an amount that is equal to the portion other than the GI but an amount that takes into account the GI added to the generated extension data. Therefore, the extended data IFFT unit 106 performs inverse fast Fourier transform on the modulated data equal to the length obtained by subtracting the GI length of both OFDM data and extended data (that is, twice the GI length) from the extended portion.

  The extension data GI adding unit 107 adds a GI having a length specified by the GI length holding unit 105 to the head of the extension data, and outputs the extension data to which the GI is added to the extension data adding unit 108. Note that the extension data GI adding unit 107 duplicates the end of the extension data to obtain a GI.

  The extension data addition unit 108 adds the extension data after the GI addition output from the extension data GI addition unit 107 before the GI of the OFDM data after the GI addition output from the GI addition unit 104. As a result, an OFDM symbol is generated in which a fixed-length OFDM data is added to the fixed-length OFDM data, and the fixed-length extension portion including the GI of OFDM data, the extension data, and the GI of extension data.

  The RF transmission unit 109 configures a frame from the OFDM symbol, performs predetermined wireless transmission processing (D / A conversion, up-conversion, etc.) on the obtained frame, and transmits the frame via an antenna.

  The RF receiving unit 110 receives a frame composed of OFDM symbols via an antenna, and performs predetermined radio reception processing (down-conversion, A / D conversion, etc.) on the received OFDM symbols.

  The GI removal unit 111 removes the GI added to the head of the OFDM symbol, and outputs the obtained OFDM data to the FFT unit 112.

  The FFT unit 112 performs fast Fourier transform on the OFDM data, and outputs the modulation data superimposed on each subcarrier to the demodulation unit 113.

  Demodulation section 113 demodulates the modulated data and outputs the obtained encoded data to error correction decoding section 114.

  Error correction decoding section 114 performs error correction decoding on the encoded data and outputs received data.

  FIG. 2 is a block diagram showing a main configuration of the mobile station apparatus according to the present embodiment. The mobile station apparatus shown in FIG. 2 includes an RF receiving unit 201, an extended part removing unit 202, an FFT unit 203, a GI length holding unit 204, an extended data GI removing unit 205, an extended data FFT unit 206, a demodulating unit 207, and error correction decoding. Unit 208, error correction coding unit 209, modulation unit 210, IFFT unit 211, GI addition unit 212, and RF transmission unit 213.

  The RF receiving unit 201 receives a frame composed of OFDM symbols via an antenna, and performs predetermined radio reception processing (down-conversion, A / D conversion, etc.) on the received OFDM symbols.

  The extension removal unit 202 removes the fixed-length extension added to the beginning of the OFDM symbol and outputs the obtained OFDM data to the FFT unit 203.

  The FFT unit 203 performs fast Fourier transform on the OFDM data, and outputs the modulation data superimposed on each subcarrier to the demodulation unit 207.

  The GI length holding unit 204 refers to the neighboring cell information transmitted from the control station device via the base station device, and the GI length added by the base station device of the cell to which the own device belongs and the base station device of the neighboring cell, respectively. Hold. Then, the GI length holding unit 204 notifies the extended data GI removing unit 205 and the extended data FFT unit 206 of the GI length of the base station apparatus that is the communication partner.

  The extended data GI removing unit 205 extracts the extended portion added to the head of the OFDM symbol, and removes the GI length GI notified from the GI length holding unit 204 from the extended portion. That is, the extension data GI removal unit 205 removes the extension data GI included at the beginning of the extension part and the OFDM data GI included at the end of the extension part, and the obtained extension data is sent to the extension data FFT unit 206. Output.

  Extension data FFT section 206 performs fast Fourier transform on the extension data and outputs the modulation data superimposed on each subcarrier to demodulation section 207.

  Demodulation section 207 demodulates the modulated data output from FFT section 203 and extended data FFT section 206, and outputs the obtained encoded data to error correction decoding section 208.

  Error correction decoding section 208 performs error correction decoding on the encoded data, and outputs received data.

  The error correction coding unit 209 performs error correction coding on the transmission data and outputs the obtained coded data to the modulation unit 210.

  Modulation section 210 modulates the encoded data and outputs the obtained modulated data to IFFT section 211.

  The IFFT unit 211 performs inverse fast Fourier transform on the modulated data, and outputs the obtained OFDM data to the GI adding unit 212.

  The GI adding unit 212 adds a GI to the head of the OFDM data, and outputs the OFDM data with the added GI to the RF transmitting unit 213.

  The RF transmission unit 213 performs predetermined wireless transmission processing (D / A conversion, up-conversion, etc.) on the OFDM data after the GI is added, and transmits the result via the antenna.

  Next, operations of the base station apparatus and mobile station apparatus configured as described above will be described with reference to the sequence diagram shown in FIG. In the following description, an operation when the mobile station apparatus performs handover from the base station apparatus # 0 to the base station apparatus # 1 will be described. Further, the cell attribute of the cell of the base station apparatus # 0 is assumed to be cellular (GI length is large), and the cell attribute of the cell of the base station apparatus # 1 is assumed to be a hot spot (GI length is small).

  First, a control station device (not shown) transmits neighboring cell information to the mobile station device via the communicating base station device # 0 (301). In the neighboring cell information, for example, as shown in FIG. 4, an ID of a cell around the cell to which the mobile station device currently belongs, a cell attribute of each cell, a GI length corresponding to the cell attribute of each cell, and the like are recorded. Has been. Then, the GI length of the neighboring cell included in the neighboring cell information is acquired by the mobile station apparatus shown in FIG. 2 (302), and the GI length of each neighboring cell is held in the GI length holding unit 204. In the sequence diagram shown in FIG. 3, only base station apparatus # 1 is shown among the base station apparatuses of the neighboring cells.

  Further, data addressed to the mobile station apparatus is transmitted from the control station apparatus (not shown) as needed via the base station apparatus # 0 (303), and a common pilot channel signal is transmitted from each base station apparatus (304). Then, the reception quality of the signal of the common pilot channel is measured by a processing unit (not shown) of the mobile station apparatus shown in FIG. 2 (305), and the reception quality measurement result for each base station apparatus determines the base station apparatus # 0 that is communicating (306).

  A control station apparatus (not shown) refers to the reception quality measurement result notified from the mobile station apparatus and determines whether or not to hand over from the base station apparatus # 0 to another base station apparatus (307). Specifically, a control station device (not shown) decides to hand over to the mobile station device when the reception quality related to another base station device becomes higher than the reception quality related to the base station device # 0 in communication, for example. To do. Here, it is assumed that the control station apparatus has decided to hand over the mobile station apparatus to base station apparatus # 1.

  Then, the control station device (not shown) transmits an instruction to release the communication link with the mobile station device to the base station device # 0 (308), and at the same time establishes the communication link with the mobile station device. An instruction to do so is transmitted to the base station apparatus # 1 (309). Further, a control station device (not shown) transmits an instruction to hand over from the base station device # 0 to the base station device # 1 to the mobile station device (310).

  Upon receiving these instructions, the mobile station apparatus starts reception from the base station apparatus # 1 (311), the base station apparatus # 1 starts transmission to the mobile station apparatus (312), and the base station apparatus # 0 Transmission to the mobile station apparatus is stopped (313). Specifically, the mobile station apparatus selects the GI length of the base station apparatus # 1 from the GI lengths of the neighboring cells held in the GI length holding unit 204, and the extended data GI removing unit 205 and the extended data FFT unit 206. To notify. Here, since the base station apparatus # 0 is a base station apparatus of a cell with a cell attribute cellular, the base station apparatus # 1 is a base station apparatus of a cell with a cell attribute hotspot, so the neighboring cell information is shown in FIG. In the case shown in FIG. 4, the GI length is changed from 10 μs to 1 μs. By doing so, the mobile station apparatus prepares for handover to the base station apparatus # 1. When the setting of the GI length in extension data GI removal section 205 and extension data FFT section 206 is completed, the mobile station apparatus notifies the control station apparatus that a handover to base station apparatus # 1 is possible (314). .

  When the mobile station apparatus can perform handover, the control station apparatus (not shown) resumes data transmission via the handover destination base station apparatus # 1 (315). At this time, specifically, base station apparatus # 1 transfers the GI length (1 μs) held in GI length holding unit 105 to GI adding unit 104, extended data IFFT unit 106, and extended data GI adding unit 107. Notice. Then, the GI length GI notified from the GI length holding unit 105 is added to the OFDM data subjected to inverse fast Fourier transform by the IFFT unit 103. Also, the modulated data having a length obtained by subtracting twice the GI length from the fixed-length extended portion is subjected to inverse fast Fourier transform by the extended data IFFT unit 106, and the obtained extended data is converted into a GI by the extended data GI adding unit 107. Added to the extended data adding unit 108. Then, the extension data adding unit 108 adds the extension data after adding the GI to the OFDM data after adding the GI output from the GI adding unit 104.

  The OFDM symbol generated in this way is frame-configured by the RF transmission unit 109, subjected to predetermined radio transmission processing, and then transmitted to the mobile station apparatus via the antenna (316). This frame includes a plurality of OFDM symbols as shown in FIG. Each OFDM symbol is composed of a fixed-length data portion and a fixed-length extension portion.

In FIG. 5, the length τ _max of the fixed-length extension is equal to or longer than the longest GI length in the entire wireless communication system. In the present embodiment, the GI length in a cell having a cell attribute of 10 μs or more is used. Is the length of Furthermore, the fixed length extension portion includes extension data, OFDM data, and GI of each extension data. The GI length τ is the GI length held in the GI length holding unit 105, and here is 1 μs because the cell attribute of the cell of the base station apparatus # 1 is a hot spot.

By the way, in this Embodiment, if cell attributes differ, GI length will change. However, if the GI length changes, the length of the extension data changes accordingly, and the length of the extension part as a whole can be fixed. At this time, since the length τ _max of the extended portion is equal to or longer than the longest GI length in the entire wireless communication system, the changing GI length τ does not exceed the length τ _max of the extended portion. The length τ _{max of the} part can be fixed.

Furthermore, since the length τ _max of the extended portion is fixed, the length of the OFDM data in the OFDM symbol can also be fixed. Therefore, the length of OFDM data can be fixed to a power of 2 samples (for example, 1024 samples), and fast Fourier transform can be easily performed by the FFT unit 203 of the mobile station apparatus. For this reason, it is not necessary to apply discrete Fourier transform (DFT) or the like in the mobile station apparatus, and an increase in the amount of computation can be prevented.

In addition, although the length τ _max of the extension portion is fixed, the GI length τ included in the extension portion is variable, and the GI length τ can be freely changed according to the propagation environment such as the cell attribute of the cell that performs communication. be able to. Then, transmission data can be superimposed as extension data on a portion other than the GI of the extension portion, and loss of transmission efficiency due to the GI can be suppressed to a minimum. Since extended data is also subjected to fast Fourier transform in the mobile station apparatus, it is preferable to adjust the length of the extended data to a power-of-two sample by adjusting the GI length τ and the length of the extended data. Since the extension part is shorter than the OFDM data, the GI length τ and the extension data length can be changed relatively easily inside the extension part. That is, when OFDM data is set to a power of 2 samples, for example, the length needs to be adjusted to about several thousand samples. On the other hand, in order to set extended data to a power of 2 samples, for example, a length of about several tens of samples is required. Adjustment is enough.

  A frame including an OFDM symbol of such a format is received by the RF receiving unit 201 via the antenna of the mobile station apparatus shown in FIG. 2, and an extended portion of each OFDM symbol is removed by the extended portion removing unit 202. The OFDM data is fast Fourier transformed by the FFT unit 203. Further, the extended data GI removing unit 205 removes the GI of each of the OFDM data and the extended data from the extended portion of each OFDM symbol, and the obtained extended data is subjected to fast Fourier transform by the extended data FFT unit 206.

  The result of the fast Fourier transform by the FFT unit 203 and the extended data FFT unit 206 is demodulated by the demodulation unit 207, error-corrected by the error correction decoding unit 208, and becomes reception data.

  As described above, according to the present embodiment, an OFDM symbol is composed of fixed-length OFDM data and a fixed-length extension part, and a GI whose GI length is variable and extension data whose length is variable according to cell attributes. Is included in the extended portion, the loss of transmission efficiency due to GI can be suppressed to the minimum by setting the GI length to an optimum length according to the propagation environment, and the length of the OFDM data is set to a power of 2 samples. By fixing to, it is possible to apply a fast Fourier transform with a small amount of calculation and prevent an increase in the amount of calculation.

(Embodiment 2)
A feature of Embodiment 2 of the present invention is that known pilot data is used as extension data included in the extension part.

  Also in Embodiment 2 of the present invention, the base station of each cell in both a cell (cell attribute cellular) for a normal mobile phone and a cell (cell attribute hot spot) for a wireless LAN etc. It is assumed that communication with the station apparatus is possible.

  FIG. 6 is a block diagram showing a main configuration of the base station apparatus according to the present embodiment. In the figure, the same parts as those in FIG. The base station apparatus shown in FIG. 6 includes an error correction coding unit 101, a modulation unit 102, a switching unit 401, an IFFT unit 103, a GI adding unit 104, a GI length holding unit 105, an extended data IFFT unit 106a, and an extended data GI adding unit. 107, an extended data adding unit 108, an RF transmitting unit 109, an RF receiving unit 110, a GI removing unit 111, an FFT unit 112, a demodulating unit 113, and an error correction decoding unit 114.

  Switching section 401 outputs either modulation data or pilot data output from modulation section 102 to IFFT section 103 while switching. Specifically, switching section 401 outputs modulated data to IFFT section 103 at the timing of generating data symbols in the frame, and outputs pilot data to IFFT section 103 at the timing of generating pilot symbols. A data symbol is an OFDM symbol in which transmission data is superimposed on all subcarriers of OFDM data, and a pilot symbol is an OFDM symbol in which pilot data is superimposed on all subcarriers of OFDM data. The arrangement of data symbols and pilot symbols in a frame may be arbitrary. For example, one symbol at the beginning and end of the frame and two symbols at the center of the frame may be used as pilot symbols.

  The extended data IFFT unit 106a is a length obtained by subtracting twice the GI length held in the GI length holding unit 105 of the own device from the extended portion set to a length equal to or longer than the longest GI length in the entire wireless communication system. The extension pilot data of a sufficient amount is subjected to inverse fast Fourier transform, the known extension pilot data is superimposed on a plurality of subcarriers, and the obtained extension data is output to extension data GI adding section 107.

  FIG. 7 is a block diagram showing a main configuration of the mobile station apparatus according to the present embodiment. In this figure, the same parts as those in FIG. The mobile station apparatus shown in FIG. 7 includes an RF receiving unit 201, an extended part removing unit 202, an FFT unit 203, a separating unit 402, a GI length holding unit 204, an extended data GI removing unit 205, an extended data FFT unit 206a, and a channel estimating unit. 403, a demodulation unit 207, an error correction decoding unit 208, an error correction coding unit 209, a modulation unit 210, an IFFT unit 211, a GI addition unit 212, and an RF transmission unit 213.

  Separation section 402 outputs the modulated data output from FFT section 203 to demodulation section 207, and outputs pilot data to channel estimation section 403. Here, the modulation data is superimposed on the data symbols in the frame, but the pilot data is superimposed on the pilot symbols in the frame.

  Extension data FFT section 206a performs fast Fourier transform on the extension data and outputs the extension pilot data superimposed on each subcarrier to channel estimation section 403.

  Channel estimation section 403 performs channel estimation using pilot data and extended pilot data, and outputs the obtained channel estimation value to demodulation section 207. Note that the channel estimation unit 403 may perform interpolation in the frequency direction, for example, with reference to the GI length notified from the GI length holding unit 204 when using the extended pilot data for channel estimation. That is, depending on the length of the GI length in the extended portion, the extended data included in the extended portion is short, and the extended pilot data may be insufficient to perform channel estimation for all subcarriers. Therefore, processing such as interpolation of pilot data may be performed with reference to the GI length to improve channel estimation accuracy.

  In the present embodiment, unlike the first embodiment, known extended pilot data is used as the extended data of the extended portion. For this reason, pilot data is superimposed on an extended portion of all OFDM symbols in the frame, and channel estimation accuracy can be improved as compared with the case where channel estimation is performed using only the pilot symbols in the frame.

  As described above, according to the present embodiment, the known pilot data, not the transmission data, is superimposed on the extended portion of the OFDM symbol, so that the channel estimation accuracy is improved even when the number of pilot symbols is small in the frame. can do.

  In Embodiments 1 and 2 described above, the GI length of each base station apparatus is notified to the mobile station apparatus by neighboring cell information from a control station apparatus (not shown), but before the handover is performed. If there is, the notification of the GI head may be anytime. Therefore, for example, a GI length of the handover destination base station apparatus may be notified at the same time when an instruction to perform handover is transmitted from a control station apparatus (not shown) to the mobile station apparatus.

(Embodiment 3)
The feature of Embodiment 3 of the present invention is that each mobile station apparatus measures the maximum delay and determines the GI length in the extended portion from this measurement result.

  FIG. 8 is a block diagram showing a main configuration of the base station apparatus according to the present embodiment. In the figure, the same parts as those in FIG. 8 includes an error correction coding unit 501, a modulation unit 102, an IFFT unit 103, a GI adding unit 104, an extended data IFFT unit 106, an extended data GI adding unit 107, an extended data adding unit 108, and an RF transmission. Unit 109, RF receiving unit 110, GI removing unit 111, FFT unit 112, demodulating unit 113, error correction decoding unit 114, maximum delay totaling unit 502, and scheduler 503.

  Error correction encoding section 501 performs error correction encoding on transmission data, scheduling information described later, and GI length information described later, and outputs the obtained encoded data to modulating section 102.

  Maximum delay totaling section 502 totalizes the maximum delays reported from mobile station devices in the cell, and groups mobile station devices. Specifically, maximum delay totaling section 502 performs grouping for grouping mobile station devices having maximum delays within a predetermined range. Then, the maximum delay totaling unit 502 notifies the scheduler 503 of the grouping result.

  The scheduler 503 performs scheduling using the reception quality and the grouping result in the mobile station apparatus in the cell. Specifically, the scheduler 503 determines to perform transmission to a mobile station apparatus whose reception quality is better than a predetermined reference and a mobile station apparatus in the same group as the mobile station apparatus. At this time, if there is a mobile station device with poor reception quality in the same group as a mobile station device with good reception quality, scheduler 503 performs transmission by excluding mobile station devices with poor reception quality. May be determined.

  Then, scheduler 503 outputs scheduling information for reporting the mobile station apparatus that has performed transmission to error correction coding section 501, and notifies the GI length corresponding to the group to which these mobile station apparatuses belong. The information is output to error correction coding section 501, GI adding section 104, extended data IFFT section 106, and extended data GI adding section 107.

  FIG. 9 is a block diagram showing a main configuration of the mobile station apparatus according to the present embodiment. In this figure, the same parts as those in FIG. The mobile station apparatus shown in FIG. 9 includes an RF receiving unit 201, an extended part removing unit 202, an FFT unit 203, a GI length holding unit 204a, an extended data GI removing unit 205, an extended data FFT unit 206, a demodulating unit 207, and error correction decoding. Unit 208, maximum delay measurement unit 504, error correction coding unit 209, modulation unit 210, IFFT unit 211, GI addition unit 212, and RF transmission unit 213.

  The GI length holding unit 204a refers to the GI length information transmitted from the base station apparatus, and holds the GI length added by the base station apparatus that performs transmission to the own apparatus.

  Maximum delay measurement section 504 measures the maximum delay using a common pilot channel signal transmitted from the base station apparatus. Specifically, the maximum delay measurement unit 504 creates, for example, a delay profile, and sets the length of a section in which a path having a reception level equal to or higher than a predetermined level from the arrival timing of the preceding wave as the maximum delay. Maximum delay measurement section 504 outputs the measured maximum delay to error correction encoding section 209.

  Next, operations of the base station apparatus and mobile station apparatus configured as described above will be described with reference to the sequence diagram shown in FIG. In the following description, it is assumed that n mobile station apparatuses # 1 to #n belong to a cell covered by the base station apparatus shown in FIG. The configuration of mobile station apparatuses # 1 to #n is the same as that of the mobile station apparatus shown in FIG.

  First, the base station apparatus transmits a common pilot channel signal as needed (601), and the mobile station apparatuses # 1 to #n in the cell receive the common pilot channel signal. The received signal of the common pilot channel is received by the RF receiving unit 201 via the antenna of the mobile station apparatus shown in FIG. 9 and output to the maximum delay measuring unit 504 via the extended portion GI removing unit 202. Then, the maximum delay is measured by creating a delay profile, for example, by the maximum delay measuring unit 504 (602). Since the propagation environments of the mobile station apparatuses # 1 to #n are different, the maximum delays measured by the maximum delay measuring unit 504 of each mobile station apparatus are different from each other.

  The measured maximum delay is subjected to error correction coding by the error correction coding unit 209, processed by the modulation unit 210 by the RF transmission unit 213, and then transmitted to the base station apparatus via the antenna (603). Then, the maximum delay transmitted from the mobile station apparatuses # 1 to #n is received by the RF receiving unit 110 via the antenna of the base station apparatus, and the maximum delay is summed from the GI removing unit 111 via the error correction decoding unit 114. Is output to the unit 502.

  The maximum delay totaling unit 502 totalizes the maximum delay from each mobile station device, and groups the mobile station devices. That is, for example, as shown in FIG. 11, the range of the maximum delay is divided every 2 μs, and the mobile station apparatuses # 1 to #n are allocated to the group of the range including the measured maximum delay. In the right column of FIG. 11, the GI length assigned to each group of mobile station apparatuses is shown. Since this GI length is an upper limit value in each range of the maximum delay, if an OFDM symbol provided with this GI length GI is transmitted to the mobile station apparatus of each group, the GI is longer than the maximum delay, It is considered that the influence of interfering interference can be effectively suppressed.

  Here, for example, the maximum delay measurement results of mobile station apparatuses # 1 to # 6 are as shown in FIG. 12, and the description will proceed assuming that the group of each mobile station apparatus is determined according to the grouping shown in FIG. . That is, mobile station apparatuses # 1 and # 2 are allocated to group 1, mobile station apparatus # 3 is allocated to group 4, mobile station apparatuses # 4 and # 5 are allocated to group 2, and mobile station apparatus # 6 is allocated to mobile station apparatus # 6. It is assumed that they are assigned to group 3. In the right column of FIG. 12, the GI length assigned to each mobile station apparatus is shown.

  The result of such grouping is notified to the scheduler 503, and scheduling is performed by the scheduler 503 (604). That is, the scheduler 503 compares the reception quality separately reported from each mobile station apparatus, and determines to perform transmission to the mobile station apparatus with good reception quality.

  Then, the scheduler 503 determines that transmission is also performed for mobile station apparatuses belonging to the same group as the mobile station apparatus that is to perform transmission, and all the mobile station apparatuses that are to perform transmission are determined. The scheduling information to be notified is output to error correction coding section 501. That is, in FIG. 12, for example, when it is determined to transmit to the mobile station apparatus # 1, it is also determined to transmit to the mobile station apparatus # 2 belonging to the group 1, and the scheduling to that effect is performed. Information is output to error correction coding section 501. However, when the reception quality of the mobile station apparatus belonging to the same group as the mobile station apparatus to which transmission is to be performed is inferior, this mobile station apparatus may be excluded.

  Also, the scheduler 503 determines the GI length corresponding to the group to which the mobile station apparatus to be transmitted belongs as the GI length until the next scheduling (605), and this GI length information is the error correction coding unit. 501, the GI adding unit 104, the extended data IFFT unit 106, and the extended data GI adding unit 107.

  As described above, in the present embodiment, as a result of scheduling, a GI length corresponding to the maximum delay in the mobile station apparatus is adopted for a mobile station apparatus with good reception quality. The loss can be minimized and the GI length suitable for the propagation environment can be determined flexibly. Moreover, since transmission is performed collectively for mobile station apparatuses having the same maximum delay, the frequency of changing the GI length can be reduced, and an increase in processing load can be suppressed.

  After scheduling and GI length determination, scheduling information is transmitted from the error correction encoding unit 501 via the RF transmission unit 109 via the antenna (606), and similarly, GI length information is transmitted from the error correction encoding unit 501. The signal is transmitted via the antenna via the RF transmitter 109 (607). FIG. 10 shows a sequence when it is determined that transmission is performed to mobile station apparatus # 1 and mobile station apparatus # 2 as a result of scheduling.

  Thereafter, the base station apparatus shown in FIG. 8 starts transmission of the OFDM symbol to which the GI length GI specified by the GI length information is added (608). That is, the transmission data is processed by the error correction coding unit 501 by the IFFT unit 103, and the length of GI notified from the scheduler 503 is added to the obtained OFDM data. Also, the modulated data having a length obtained by subtracting twice the GI length from the fixed-length extended portion is subjected to inverse fast Fourier transform by the extended data IFFT unit 106, and the obtained extended data is converted into a GI by the extended data GI adding unit 107. Added to the extended data adding unit 108. Then, the extension data adding unit 108 adds the extension data after adding the GI to the OFDM data after adding the GI output from the GI adding unit 104.

  The OFDM symbol generated in this way is frame-configured by the RF transmission unit 109, subjected to predetermined radio transmission processing, and then transmitted to the mobile station apparatus via the antenna (609).

  Then, reception of the frame including the OFDM symbol is started by the mobile station apparatus # 1 and the mobile station apparatus # 2 (610). That is, the frame is received by the RF receiving unit 201 via the antenna of the mobile station apparatus shown in FIG. 9, the extended portion of each OFDM symbol is removed by the extended portion removing unit 202, and the obtained OFDM data is transformed into the FFT unit 203. Is fast Fourier transformed. Further, the extended data GI removing unit 205 removes the GI of each of the OFDM data and the extended data from the extended portion of each OFDM symbol, and the obtained extended data is subjected to fast Fourier transform by the extended data FFT unit 206.

  The result of the fast Fourier transform by the FFT unit 203 and the extended data FFT unit 206 is demodulated by the demodulation unit 207, error-corrected by the error correction decoding unit 208, and becomes reception data.

  As described above, according to the present embodiment, the GI length is determined according to the maximum delay reported from the mobile station apparatus, and transmission is performed collectively to mobile station apparatuses having the same maximum delay. The loss of transmission efficiency due to the GI can be suppressed to a minimum by setting the GI length to an optimum length according to the propagation environment, and an increase in processing load for changing the GI length can be suppressed.

  In the present embodiment, the mobile station apparatuses are grouped according to the maximum delay, but the GI length is calculated from the maximum delay of the mobile station apparatus determined to be transmitted by scheduling without performing grouping. You may only decide. Even in this case, it is possible to determine the GI length according to the propagation environment and suppress the loss of transmission efficiency to the minimum.

  In each of the above embodiments, the extension data in the extension portion has been described as multi-carrier data obtained by inverse fast Fourier transform. However, the present invention is not limited to this, and the extension data is a single carrier. It is good as data. Further, in each of the above embodiments, the downlink from the base station apparatus to the mobile station apparatus has been described. However, in the uplink from the mobile station apparatus to the base station apparatus, variable length GI and variable length extension data are transmitted. The fixed-length extension part that includes it may be added to the fixed-length data part.

  The multicarrier communication apparatus according to the first aspect of the present invention includes an adding means for adding a guard interval having a length corresponding to a propagation environment to fixed-length multicarrier data, and a sum of the lengths of the added guard intervals. The generating means for generating the extension data that keeps constant and the transmission means for transmitting the symbol composed of the multi-carrier data after the addition of the guard interval and the extension data are employed.

  According to this configuration, since a fixed-length extension portion consisting of a guard interval and extension data is added to fixed-length multicarrier data to form a transmission symbol, even if the GI length is changed according to the propagation environment, the The length of the carrier data can be fixed to a power of 2 samples, and fast Fourier transform can be performed on the receiving side. As a result, it is possible to prevent an increase in the amount of computation while minimizing transmission efficiency loss due to GI.

  The multicarrier communication apparatus according to a second aspect of the present invention is the multicarrier communication apparatus according to the first aspect, wherein the adding means adds a longer guard interval as the cell radius of the cell covered by the own apparatus increases, and the cell radius is The smaller the interval, the shorter the guard interval is added.

  According to this configuration, since the length of the guard interval is changed according to the cell radius, an optimum GI length can be employed depending on whether the cell attribute is cellular or hot spot, for example.

  The multicarrier communication apparatus according to a third aspect of the present invention employs a configuration in which, in the first aspect, the adding means adds a guard interval having a length equal to or longer than a maximum delay in a communication partner.

  According to this configuration, since the guard interval has a length equal to or longer than the maximum delay at the communication partner, intersymbol interference at the communication partner can be reliably prevented.

  The multicarrier communication apparatus according to a fourth aspect of the present invention is the multicarrier communication apparatus according to the third aspect, wherein the adding means totals the maximum delays reported from a plurality of mobile station apparatuses, and A maximum delay totaling unit for grouping mobile station devices, a scheduler for determining a mobile station device having a reception quality equal to or higher than a predetermined standard among the plurality of mobile station devices, and a mobile station device in the same group as the mobile station device as a communication partner And adopting a configuration in which a guard interval having the same length is added to the mobile station device of the determined communication partner.

  According to this configuration, in order to transmit a symbol by adding a guard interval of the same length to a group to which a mobile station apparatus with good reception quality belongs among groups of mobile station apparatuses with the same maximum delay, The loss of transmission efficiency due to the GI can be suppressed to the minimum, and the frequency of changing the GI length can be reduced to suppress an increase in processing load.

  The multicarrier communication apparatus according to a fifth aspect of the present invention is the multicarrier communication apparatus according to the first aspect, wherein the generation means includes an orthogonal inverse transform unit that orthogonally transforms transmission data, and the addition to the orthogonally inversely transformed transmission data. And a guard interval adding unit that generates extension data by adding a guard interval having the same length as the guard interval added by the means.

  According to this configuration, transmission data can be improved by orthogonally transforming transmission data and adding a guard interval to obtain extended data.

  The multicarrier communication apparatus according to a sixth aspect of the present invention is the multicarrier communication apparatus according to the first aspect, wherein the generation means includes an orthogonal inverse transform unit that orthogonally transforms known pilot data, and the orthogonal inversely transformed pilot data A guard interval adding unit for generating extended data by adding a guard interval having the same length as the guard interval added by the adding means is adopted.

  According to this configuration, since the pilot data is inversely orthogonally transformed and the guard interval is added to obtain the extended data, the channel estimation accuracy on the receiving side can be improved.

  In the multicarrier communication apparatus according to the seventh aspect of the present invention, a guard interval having a length corresponding to a propagation environment and extension data that makes the sum of the lengths of the guard interval constant are added to the fixed-length multicarrier data. Receiving means for receiving the generated symbols, first acquisition means for acquiring the multicarrier data by removing the guard interval and extension data from the received symbols, and the extension from the received symbols using the length of the guard interval A configuration having second acquisition means for acquiring data and demodulation means for performing demodulation based on the acquired multicarrier data and extension data is adopted.

  According to this configuration, a fixed-length multicarrier data is received with a symbol having a fixed-length extension portion composed of a guard interval and extension data, and is extended using the guard interval length separately from the multicarrier data. Since data is acquired, even if the length of the guard interval is changed, the multicarrier data and the extended data can be accurately demodulated.

  In the multicarrier communication method according to the eighth aspect of the present invention, a step of adding a guard interval having a length corresponding to a propagation environment to fixed-length multicarrier data and a sum of the lengths of the added guard intervals are provided. A step of generating constant extension data; and a step of transmitting a symbol composed of the multi-carrier data after the addition of the guard interval and the extension data.

  According to this method, since a fixed-length extension portion consisting of a guard interval and extension data is added to fixed-length multicarrier data to form a transmission symbol, even if the GI length is changed according to the propagation environment, the The length of the carrier data can be fixed to a power of 2 samples, and fast Fourier transform can be performed on the receiving side. As a result, it is possible to prevent an increase in the amount of computation while minimizing transmission efficiency loss due to GI.

  In the multicarrier communication method according to the ninth aspect of the present invention, a guard interval having a length corresponding to a propagation environment and extension data for making the sum of the lengths of the guard intervals constant are added to the fixed-length multicarrier data. Receiving the received symbol, removing the guard interval and extension data from the received symbol to obtain the multicarrier data, and obtaining the extension data from the received symbol using the length of the guard interval And a step of performing demodulation based on the acquired multicarrier data and extension data.

  According to this method, a fixed-length multicarrier data received with a fixed-length extension portion consisting of guard intervals and extension data is received and extended using the guard interval length separately from the multicarrier data. Since data is acquired, even if the length of the guard interval is changed, the multicarrier data and the extended data can be accurately demodulated.

  The multicarrier communication apparatus and multicarrier communication method of the present invention can prevent an increase in the amount of computation while minimizing loss of transmission efficiency due to GI. For example, the GI is placed at the head of a data portion included in a symbol. It is useful as a multicarrier communication apparatus and a multicarrier communication method for transmitting a multicarrier signal to which is added.

The block diagram which shows the principal part structure of the base station apparatus which concerns on Embodiment 1 of this invention. FIG. 3 is a block diagram showing a main configuration of the mobile station apparatus according to Embodiment 1. FIG. 7 is a sequence diagram showing a handover operation according to the first embodiment. The figure which shows an example of a response | compatibility with the cell attribute which concerns on Embodiment 1, and GI length The figure which shows an example of the frame format which concerns on Embodiment 1. The block diagram which shows the principal part structure of the base station apparatus which concerns on Embodiment 2 of this invention. FIG. 3 is a block diagram showing a main configuration of a mobile station apparatus according to Embodiment 2. The block diagram which shows the principal part structure of the base station apparatus which concerns on Embodiment 3 of this invention. Block diagram showing main configuration of mobile station apparatus according to Embodiment 3 FIG. 11 is a sequence diagram showing a scheduling operation according to the third embodiment. The figure which shows an example of the relationship between the maximum delay and group which concerns on Embodiment 3. The figure which shows an example of grouping of the mobile station apparatus which concerns on Embodiment 3. (A) Diagram showing an example of an OFDM symbol (b) Diagram showing another example of an OFDM symbol

Explanation of symbols

101, 209, 501 Error correction encoding unit 102, 210 Modulation unit 103, 211 IFFT unit 104, 212 GI adding unit 105, 204, 204a GI length holding unit 106, 106a Extended data IFFT unit 107 Extended data GI adding unit 108 Extension Data adding unit 109, 213 RF transmitting unit 110, 201 RF receiving unit 111 GI removing unit 112, 203 FFT unit 113, 207 demodulating unit 114, 208 Error correction decoding unit 202 Extended portion removing unit 205 Extended data GI removing unit 206, 206a Extended data FFT unit 401 Switching unit 402 Separating unit 403 Channel estimating unit 502 Maximum delay totaling unit 503 Scheduler 504 Maximum delay measuring unit

Claims (9)

An adding means for adding a guard interval having a length corresponding to the propagation environment to the fixed-length multicarrier data;
Generating means for generating extended data for making the sum of the lengths of the added guard intervals constant;
Transmitting means for transmitting a symbol composed of multi-carrier data after adding a guard interval and the extension data;
A multi-carrier communication apparatus comprising: The adding means includes
2. The multicarrier communication apparatus according to claim 1, wherein a longer guard interval is added as the cell radius of a cell covered by the own apparatus increases, and a shorter guard interval is added as the cell radius decreases. The adding means includes
The multicarrier communication apparatus according to claim 1, wherein a guard interval having a length equal to or longer than a maximum delay at a communication partner is added. The adding means includes
A maximum delay totaling unit that aggregates the maximum delays reported from a plurality of mobile station devices, and groups the plurality of mobile station devices according to a range of maximum delays;
A mobile station device having a reception quality of a predetermined reference or higher among the plurality of mobile station devices and a scheduler that determines a mobile station device in the same group as the mobile station device as a communication partner;
4. The multicarrier communication apparatus according to claim 3, wherein a guard interval having the same length is added to the determined mobile station apparatus of the communication counterpart. The generating means includes
An orthogonal inverse transform unit for orthogonally transforming transmission data;
A guard interval adding unit that generates extended data by adding a guard interval having the same length as the guard interval added by the adding means to the orthogonally inversely transformed transmission data;
The multicarrier communication apparatus according to claim 1, further comprising: The generating means includes
An orthogonal inverse transformer that orthogonally transforms known pilot data;
A guard interval adding unit for generating extended data by adding a guard interval having the same length as the guard interval added by the adding means to the orthogonally inversely transformed pilot data;
The multicarrier communication apparatus according to claim 1, further comprising: Receiving means for receiving a symbol having a guard interval having a length according to a propagation environment and extension data that makes the sum of the lengths of the guard interval constant fixed to multi-carrier data having a fixed length;
First acquisition means for acquiring the multicarrier data by removing the guard interval and extension data from a received symbol;
Second acquisition means for acquiring the extension data from a received symbol using the length of the guard interval;
Demodulation means for performing demodulation based on the acquired multicarrier data and extension data;
A multi-carrier communication apparatus comprising: Adding a guard interval of a length according to the propagation environment to fixed-length multicarrier data;
Generating extended data that makes the sum of the lengths of the added guard intervals constant; and
Transmitting a symbol consisting of multi-carrier data after adding a guard interval and the extension data;
A multi-carrier communication method comprising: Receiving a symbol having a guard interval having a length corresponding to a propagation environment and extension data that makes the sum of the lengths of the guard interval constant added to multi-carrier data having a fixed length;
Removing the guard interval and extension data from a received symbol to obtain the multicarrier data;
Obtaining the extension data from a received symbol using the length of the guard interval;
Performing demodulation based on the acquired multi-carrier data and extension data;
A multi-carrier communication method comprising:

Images