JP2008136055A - Radio communication system, radio communication equipment and radio communicating method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce a side lobe within a band without lowering an SNR and a data rate in the case of using OFDM to perform communication. <P>SOLUTION: This radio communication system for using OFDM to perform communication is provided with: a communication environment capturing means for capturing a communication environment with a receiving side after establishing synchronization with the receiving side; a reducible area determining means for determining a reducible area in a guard interval in accordance with the communication environment; a window function processing means for multiplying the reducible area of the guard interval by a prescribed window function in each symbol and adding expansion data obtained by multiplying data extracted from one portion of a data area immediately after the guard interval by the prescribed window function to the last of the data area; and a symbol arranging means for arranging symbols processed by the window function processing means in series so as not to overlap heads of the symbols on the data area of an adjacent symbol. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

 The present invention relates to a wireless communication system, a wireless communication apparatus, and a wireless communication method.

 In recent years, a wireless communication system that employs OFDMA (Orthogonal Frequency Division Multiple Access) as a multiple access technology in addition to TDMA (Time Division Multiple Access) / TDD (Time Division Duplex) has become a next-generation broadband mobile communication. It is attracting attention as a system. With OFDMA, subcarriers that are orthogonally related are shared by a plurality of terminals, any subcarriers are positioned as subchannels, and any communication timing (in a system employing TDMA, this communication timing corresponds to a slot or the like) This is a technique for realizing multiple access by adaptively assigning subchannels to each terminal.

  In such OFDMA, there is a problem that the side lobe in the band becomes large due to the influence of the discontinuity between symbols. To deal with this problem, there is ECP (Extended Cyclic Prefix) processing as a technique for reducing side lobes in the band by applying a window function to the discontinuous portions between the symbols and changing them smoothly. The ECP process will be specifically described below with reference to FIGS. 10 and 11.

  FIG. 10A is a schematic diagram of an OFDM signal. As shown in FIG. 10 (a), in the OFDM signal, each symbol is composed of a GI (Guard Interval) part and a data part, and discontinuities occur between the symbols. In the ECP process, first, data for which a window function is to be applied for each symbol (hereinafter, this data is referred to as window function target data) is extracted from each data portion. The window function target data needs to be data having continuity at discontinuous points. For example, in FIG. 10A, the discontinuous point viewed from the symbol 1 corresponds to the latter half of the data portion D1, and the original data of the GI portion g1 exists in the latter half. Therefore, as shown in FIG. 10B, the window function target data having continuity at the discontinuous point viewed from the symbol 1 is data immediately after the GI part g1, that is, data at the head part of the data part D1. Data at the beginning of the data portion D1 is extracted as the window function target data d1 of the symbol 1. Then, a predetermined window function is applied to the window function target data d1, and added to the tail of the data portion D1. It is assumed that the window function target data d1 after the window function is applied is extended data d1 '.

  On the other hand, the discontinuous point seen from the symbol 2 corresponds to the head part of the GI part g2, and the window function target data having continuity with respect to the head part is the GI part in the data part D2, as shown in FIG. This is the data immediately before the original data of g2. This data is extracted as the window function target data d2 of the symbol 2, applied with a predetermined window function, and added to the head of the GI part g2. It is assumed that the window function target data d2 after the window function is applied is extended data d2 '. The above processing is performed for each symbol.

Next, a serial arrangement process of symbols to which the extension data after the window function is added is performed. This serial arrangement processing includes a method defined by the IEEE802.11g standard and a method defined by the IEEE802.20 standard. FIG. 11A shows a case where the above-described symbol 1 and symbol 2 are arranged in series by a method defined by the IEEE802.11g standard. In this method, the extension data d1 ′ of symbol 1 overlaps the GI part g2 of symbol 2, and the extension data d2 ′ of symbol 2 overlaps the data part D1 of symbol 1. On the other hand, FIG. 11 (b) shows a case where the symbol 1 and the symbol 2 described above are arranged in series by a method defined in the IEEE802.20 standard. In this method, the extension data d1 ′ of the symbol 1 and the extension data d2 ′ of the symbol 2 overlap, but the extension data does not overlap the data part D1 and the GI part g2.
Special table 2003-535502 gazette

  According to the method defined in the IEEE802.11g standard described above, the discontinuity at the discontinuity point is alleviated and the side lobe in the band can be reduced. However, the extension data d2 ′ of symbol 2 is the symbol 1 symbol. Since it overlaps the data part D1, there is a problem that the SNR (Signal to Noise Ratio) is lowered. Further, according to the method defined in the above-mentioned IEEE802.20 standard, although the SNR does not decrease, there is a problem that the data rate decreases because the symbol time becomes long.

  The present invention has been made in view of the above-described circumstances, and an object of the present invention is to reduce side lobes in a band without lowering the SNR and data rate when performing communication using OFDM.

 In order to achieve the above object, in the present invention, as a first solving means related to a wireless communication system, in a wireless communication system that performs communication using OFDM (Orthogonal Frequency Division Multiplexing), after establishing synchronization with a receiving side, A communication environment grasping means for grasping a communication environment with the receiving side, a reducible area determining means for determining a reducible area in the guard interval according to the communication environment, and a reducible area for the guard interval for each symbol A window function processing means for applying a predetermined window function to the data area, and adding extended data obtained by applying a predetermined window function to data extracted from a part of the data area immediately after the guard interval, at the end of the data area; and If the symbols processed by the window function processing means overlap with the adjacent symbol data area, Symbol arrangement means arranged in series so as not to be present.

 Further, in the present invention, as a second solving means relating to the radio communication system, in the first solving means, a correspondence relationship between the distance between the transmitting side and the receiving side and the reducible area is stored in advance. Storage means, the communication environment grasping means grasps the distance between the transmission side and the receiving side as the communication environment, and the reducible area determination means is grasped by the communication environment grasping means A reducible area corresponding to the distance is determined based on the distance and the correspondence relationship stored in the storage means.

 Further, in the present invention, as a third solving means relating to a radio communication system, in the second solving means, the storage means stores the correspondence relationship according to a line-of-sight environment with respect to the receiving side, and the communication environment The grasping means grasps the distance between the transmitting side and the receiving side and the line-of-sight environment as the communication environment, and the reducible area determining means is the distance and line-of-sight environment grasped by the communication environment grasping means. And a reducible area corresponding to the distance and the line-of-sight environment is determined based on the correspondence relationship corresponding to the line-of-sight environment stored in the storage unit.

 Further, in the present invention, as a first solving means related to a wireless communication apparatus, in a wireless communication apparatus that performs communication using OFDM (Orthogonal Frequency Division Multiplexing), communication with the receiving side is established after synchronization is established with the receiving side. A communication environment grasping means for grasping the environment; a reducible area determining means for determining a reducible area in the guard interval according to the communication environment; and a predetermined window function in the reducible area of the guard interval for each symbol. And window function processing means for adding extended data obtained by applying a predetermined window function to data extracted from a part of the data area immediately after the guard interval, and processing by the window function processing means Symbols that are placed in series so that the symbol heads do not overlap the data area of adjacent symbols It is characterized by comprising a map placement means.

 Further, in the present invention, as a second solving means relating to the wireless communication apparatus, in the first solving means, the correspondence between the distance between the own apparatus and the receiving side and the reducible area is stored in advance. The communication environment grasping means grasps the distance between the own device and the receiving side as the communication environment, and the reducible area determining means grasps by the communication environment grasping means. A reducible area corresponding to the distance is determined based on the distance and the correspondence stored in the storage unit.

 Further, in the present invention, as a third solving means relating to the wireless communication apparatus, in the second solving means, the storage means stores the correspondence relationship according to a line-of-sight environment with respect to the receiving side, and the communication environment The grasping means grasps the distance between the device and the receiving side and the line-of-sight environment as the communication environment, and the reducible area determining means is the distance and line-of-sight environment grasped by the communication environment grasping means. And a reducible area corresponding to the distance and the line-of-sight environment is determined based on the correspondence relationship corresponding to the line-of-sight environment stored in the storage unit.

 Furthermore, in the present invention, as a means for solving the wireless communication method, in a wireless communication method that performs communication using OFDM (Orthogonal Frequency Division Multiplexing), after establishing synchronization with the communication partner, the communication environment with the communication partner is grasped. A communication environment grasping step, a reducible area determining step for determining a reducible area in the guard interval according to the communication environment, and applying a predetermined window function to the reducible area of the guard interval for each symbol, A window function processing step of adding extended data obtained by applying a predetermined window function to data extracted from a part of the data region immediately after the guard interval, and a symbol processed by the window function processing step Make sure that the beginning of the symbol does not overlap the data area of the adjacent symbol. And a symbol arrangement step of arranging the columns.

  According to the present invention, when performing communication using OFDM, it is possible to reduce the side lobes in the band without reducing the SNR and the data rate.

Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings, taking an OFDMA communication system as an example. As shown in FIG. 1, the radio communication system of this embodiment includes a base station CS, a radio communication terminal (hereinafter abbreviated as a terminal) PS, and a network (not shown). In addition to TDMA) and time division duplex (TDD), communication is performed using orthogonal frequency division multiple access (OFDMA) as a multiple access technique. A plurality of base stations CS are provided at fixed distance intervals, and perform multiple communications with a plurality of terminals PS to perform radio communication.
The terminal PS and the base station CS correspond to the radio communication apparatus according to the present invention. However, since both have the same configuration in the characteristic part of the present invention, the following description will be given using the terminal PS as a representative. To do.

 As is well known, the OFDMA scheme shares all subcarriers in an orthogonal relationship with all terminals PS, positions a group of arbitrary subcarriers as one group, and each terminal PS has one or more groups. Is a technology for realizing multiple access by adaptively assigning. In the wireless communication system of this embodiment, the above-described OFDMA method is further combined with a TDMA method and a TDD method. That is, each group is divided into uplink and downlink in the time axis direction as TDD, and the uplink and downlink are further divided into four TDMA slots. In this embodiment, one unit obtained by dividing each group as a TDMA slot in the time axis direction is called a subchannel. FIG. 2 shows the relationship among frequencies, TDMA slots, and subchannels in the wireless communication system of this embodiment. The vertical axis represents frequency and the horizontal axis represents time. As shown in FIG. 2, 112 subchannels obtained by multiplying 28 frequency directions and 4 time axis directions (4 slots) are allocated for uplink and downlink, respectively.

 In the wireless communication system of the present embodiment, as shown in FIG. 2, the most subchannel in the frequency direction (number 1 in FIG. 2) is used as a control channel (CCH) among all the subchannels, and the remaining subchannels are used. The channel is used as a traffic channel (TCH). Hereinafter, this traffic channel is referred to as a traffic subchannel. Then, the base station CS and the terminal PS that perform wireless communication have arbitrary traffic subchannels belonging to each of the uplink and downlink (in this case, 108 subchannels of 27 × 4 slots excluding CCH). One or more traffic subchannels are assigned. Note that the same traffic channel is allocated to the traffic subchannels for uplink and downlink as communication channels.

 Next, the configuration of the terminal PS will be described. As illustrated in FIG. 3, the terminal PS includes a terminal control unit 1, a wireless communication unit 2, an operation unit 3, a display unit 4, a voice input / output unit 5, and a storage unit (storage unit) 6. Further, the terminal control unit 1 includes a communication environment grasping unit (communication environment grasping unit) 1a and a GI reducible region determining unit (reducible region determining unit) 1b as functional elements.

 The terminal control unit 1 controls the operation of the terminal PS based on a terminal control program stored in the storage unit 6, a received signal acquired via the wireless communication unit 2, and an operation signal input from the operation unit 3. Control. The communication environment grasping unit 1a of the terminal control unit 1 grasps the distance between the terminal PS and the base station CS and the line-of-sight environment based on the received signal acquired from the base station CS via the wireless communication unit 2. Specifically, the communication environment grasping unit 1a grasps whether the prospect environment is an environment that is within the prospect or an environment that is outside the prospect.

 Here, the line-of-sight environment is an environment in which there is no obstacle between the terminal PS and the base station CS in the communication area and the occurrence of multipath is small as shown in FIG. In such a line-of-sight environment, as shown in FIG. 4B, the GI reduction possible area becomes smaller in inverse proportion to the distance between the terminal PS and the base station CS. This is because the delay time increases as the terminal PS is farther away from the base station CS. On the other hand, the unforeseen environment is an environment in which there are obstacles between the terminal PS and the base station CS in the communication area and multipaths occur frequently as shown in FIG. In such an out-of-sight environment, the delayed wave power may be larger than in the out-of-sight environment, and as shown in FIG. 5B, the distance between the terminal PS and the base station CS The GI reduction possible area becomes exponentially smaller. Correspondence relationship between the distance between the terminal PS and the base station CS in the environment within the line-of-sight and the environment outside the line-of-sight as shown in FIG. 4B and FIG. This correspondence relationship is called GI reduction information) is stored in the storage unit 6 in advance. Such GI reduction information may be stored as table-like data or as a function.

 The GI reducible area determination unit 1b is based on the distance and the line-of-sight environment between the terminal PS and the base station CS that are grasped by the communication environment grasping unit 1a, and the GI reduction information that is stored in the storage unit 6. The GI reduction possible region corresponding to the distance between the terminal PS and the base station CS and the line-of-sight environment is determined. The terminal control unit 1 outputs the GI reducible area determined by the GI reducible area determination unit 1b and the ECP processing start request to the ECP processing unit 16 described later.

 Under the control of the terminal control unit 1, the wireless communication unit 2 performs error correction coding, modulation, and multiplexing by OFDM of the control signal or data signal output from the terminal control unit 1, and a multiplexed signal (OFDM signal) Is converted to an RF frequency band and then transmitted to the base station CS as a transmission signal.

 Specifically, as shown in FIG. 6, the transmitter side of the wireless communication unit 2 includes an error correction coding unit 10, an interleaver 11, a serial-parallel conversion unit 12, a digital modulation unit 13, an IFFT (Inverse Fast Fourier Transform). ) Unit 14, a GI (Guard Interval) adding unit 15, an ECP (Extended Cyclic Prefix) processing unit 16, and a transmission unit 17.

 The error correction coding unit 10 is, for example, an FEC (Forward Error Correction) encoder, and based on the coding rate instructed to the terminal control unit 1, a bit string of a control signal or a data signal input from the terminal control unit 1 Is added with error correction code, which is redundant information, and output to the interleaver 11. The interleaver 11 performs an interleaving process on the bit string to which the error correction code is added by the error correction encoding unit 10. The serial-parallel conversion unit 12 divides the bit string after the interleaving process in units of bits for each subcarrier included in the subchannel instructed by the terminal control unit 1 and outputs the result to each digital modulation unit 13.

 The digital modulation unit 13 is provided in the same number as the subcarriers, digitally modulates the bit data divided for each subcarrier using the subcarrier corresponding to the bit data, and outputs the modulation signal to the IFFT unit 14 To do. Each digital modulation unit 13 uses a modulation method instructed by the terminal control unit 1, for example, BPSK (Binary Phase Shift Keying), QPSK (Quadrature Phase Shift Keying), 16QAM (Quadrature Amplitude Modulation), 64QAM, or the like. Perform digital modulation. The IFFT unit 14 generates an OFDM signal by performing inverse Fourier transform and orthogonal multiplexing on the modulation signal input from each digital modulation unit 13, and outputs the OFDM signal to the GI addition unit 15. The GI adding unit 15 adds a guard interval (GI) to the OFDM signal input from the IFFT unit 14 and outputs the result to the ECP processing unit 16.

 The ECP processing unit 16 includes a window function processing unit 16a and a symbol arrangement unit 16b, and starts the ECP processing in response to the ECP processing start request input from the terminal control unit 1. On the other hand, if the ECP processing start request is not input, the GI The added OFDM signal is output to the transmitter 17 without processing. Based on the GI reducible region input from the terminal control unit 1, the window function processing unit 16a applies a predetermined window function to the GI reducible region for each symbol included in the OFDM signal after GI addition, and immediately after the GI. The extension data obtained by applying a predetermined window function to the window function target data extracted from the head portion of the data portion is added to the end of the data portion. The symbol arrangement unit 16b arranges the symbols processed by the window function processing unit 16a in series so that the heads of the symbols do not overlap the data portions of adjacent symbols, and outputs the symbols to the transmission unit 17. The transmission unit 17 frequency-converts the OFDM signal input from the symbol arrangement unit 16b into an RF frequency band, and transmits it to the base station CS as a transmission signal.

 On the other hand, although not shown, the receiver side of the wireless communication unit 2 includes components that perform the reverse operation of the transmitter side. That is, the receiver side of the wireless communication unit 2 converts the received signal received from the base station CS to the IF frequency band, extracts the received OFDM signal, and applies the window function to the received OFDM signal and the GI. The bit string is reconstructed by performing FFT processing, digital demodulation, parallel-serial conversion processing, deinterleaver processing, and error correction decoding processing, and is output to the terminal control unit 1.

 Subsequently, returning to FIG. The operation unit 3 includes operation keys such as a power key, various function keys, and a numeric keypad. The operation unit 3 outputs an operation signal based on an operation input using these operation keys to the terminal control unit 1. The display unit 4 is, for example, a liquid crystal monitor or an organic EL monitor, and displays a predetermined image or character based on a display signal input from the terminal control unit 1. The voice input / output unit 5 includes a microphone and a speaker. The voice input / output unit 5 converts voice input from the outside through the microphone into a digital signal and outputs the digital signal to the terminal control unit 1, while being input from the terminal control unit 1. Audio data is output to the outside through a speaker. The storage unit 6 stores various data such as a terminal control program and GI reduction information used by the terminal control unit 1 and has a function as a buffer used for retransmission control and the like.

 Next, the operation of the terminal PS configured as described above will be described using the flowchart of FIG.

First, the terminal control unit 1 receives an operation signal instructing data transmission from the operation unit 3.
Controls the radio communication unit 2 to search for a control channel (CCH) transmitted from the base station CS, and establishes a communication connection with the base station CS that has successfully acquired and is transmitting the control channel with the best reception state. Process. Here, the terminal control unit 1 makes a link channel (traffic subchannel) allocation request to the base station CS via the control channel, or synchronizes with the base station CS based on synchronization information included in the control channel. Is established (step S1).

 When the synchronization establishment with the base station CS is completed, the communication environment grasping unit 1a determines the distance between the terminal PS and the base station CS based on the received signal acquired from the base station CS via the wireless communication unit 2. The prospect environment (environment within the prospect or environment outside the prospect) is grasped (step S2). Subsequently, the GI reducible area determination unit 1b determines the distance between the terminal PS and the base station CS, which is grasped by the communication environment grasping unit 1a, the line-of-sight environment, and the GI reduction information stored in the storage unit 6. Based on the distance between the terminal PS and the base station CS and the GI reduction possible area corresponding to the line-of-sight environment is determined (step S3). Specifically, for example, when the line-of-sight environment grasped by the communication environment grasping unit 1a is an unforeseen environment, the GI reducible area determination unit 1b includes the GI reducible area shown in FIG. The GI reduction possible area is determined based on the correspondence relationship between the PS and the distance between the base station CS.

 And the terminal control part 1 outputs the bit sequence of the data signal which should be transmitted to base station CS to the error correction encoding part 10, and also the GI reduction possible area | region which the ECP process start request | requirement and GI reduction possible area | region determination part 1b determined Is output to the ECP processing unit 16. The bit string of the data signal is converted into an OFDM signal to which GI is added via an error correction coding unit 10, an interleaver 11, a serial-parallel conversion unit 12, a digital modulation unit 13, an IFFT unit 14, and a GI addition unit 15, and is converted into an ECP. The data is input to the window function processing unit 16a of the processing unit 16. Here, since the window function processing unit 16a receives the ECP processing start request and the signal indicating the GI reduction possible area from the terminal control unit 1, the ECP processing is performed on the OFDM signal input from the GI adding unit 15. Start (step S4).

 Hereinafter, the ECP processing by the window function processing unit 16a and the symbol arrangement unit 16b in the ECP processing unit 16 will be described in detail. The OFDM signal input from the GI adding unit 15 can be shown in FIG. FIG. 8 shows a symbol 1 extracted from the OFDM signal shown in FIG. As shown in FIG. 8, the window function processing unit 16a applies a predetermined window function (for example, a trigonometric function) to the GI reducible region r1 in the GI unit g1 of the symbol 1, and the data function D1 immediately after the GI unit g1. The extended data r2 ′ obtained by applying a predetermined window function to the window function target data r2 extracted from the head part is added to the end of the data part D1. As a result, the data r1 'obtained by applying the window function to the GI reducible region r1 is added to the head of the symbol 1, and the extension data r2' is added to the tail of the symbol 1. Then, as shown in FIG. 9, the same processing is performed for the symbol 2, and the data r 1 ″ obtained as a result of applying a predetermined window function to the GI reducible region in the GI part g 2 of the symbol 2 is applied to the symbol 2. And extended data r2 ″ obtained as a result of applying a predetermined window function to the window function target data r2 extracted from the head portion of the data D2 immediately after the GI part g2. As described above, the window function processing unit 16a performs the same processing as described above on all symbols.

 Then, as shown in FIG. 9, the symbol arrangement unit 16b is configured so that the symbols processed by the window function processing unit 16a are not overlapped with the data portion of the adjacent symbol. The extension data r2 ′ and the data r1 ″ are arranged in series so that only the data r1 ″ overlap and are output to the transmission unit 17. The transmission unit 17 converts the OFDM signal input from the symbol arrangement unit 16b into an RF frequency band, and transmits the transmission signal. Is transmitted to the base station CS (step S5), that is, adjacent symbols are arranged in series by a method similar to the conventional IEEE802.20 standard shown in Fig. 11 (b). The difference between the GI unit and the conventional one is that the GI length is shortened by reducing the GI part by the GI reducible area, thereby reducing the symbol time. It can suppress a decrease of the data rate. That is, not only the decrease in SNR, while reduction of the data rate, it is possible to reduce the side lobes of the band.

  By the way, when the ECP process is simply performed on the GI unit, it is possible to suppress a decrease in the SNR and the data rate. However, since the part on which the ECP process is performed in the GI unit is different from the original data, The effect is lost, and intersymbol interference is likely to occur due to signal delay. However, the delay of the signal after the synchronization is established can be assumed according to the previous communication situation, and is considered to be much smaller than the maximum delay defined by the GI. Therefore, as in this embodiment, by performing ECP processing on the GI unit in communication after establishment of synchronization, it is possible to reduce side lobes in the band while suppressing a decrease in SNR and data rate.

  In the above embodiment, the OFDMA communication system has been described. However, the present invention can be widely applied not only to OFDMA but also to communication systems using the OFDM method. Moreover, although terminal PS was illustrated and demonstrated as a radio | wireless communication apparatus, it is not limited to this, The same structure can be applied to the radio | wireless communication apparatus which communicates using base station CS or other OFDM.

1 is a schematic configuration diagram of a wireless communication system in an embodiment of the present invention. It is a schematic diagram which shows the relationship of the frequency of the radio | wireless communications system in one Embodiment of this invention, a slot, and a subchannel. 1 is a configuration block diagram of a wireless communication terminal (terminal) PS in an embodiment of the present invention. It is a 1st explanatory view which shows the correspondence of the GI reduction possible area | region and the distance between terminal PS-base station CS in one Embodiment of this invention. It is a 2nd explanatory view which shows the correspondence of the GI reduction possible area | region and the distance between terminal PS-base station CS in one Embodiment of this invention. It is detailed explanatory drawing of the radio | wireless communication part 2 in one Embodiment of this invention. It is an operation | movement flowchart of radio | wireless communication terminal (terminal) PS in one Embodiment of this invention. It is the 1st explanatory view showing ECP processing in one embodiment of the present invention. It is the 2nd explanatory view showing ECP processing in one embodiment of the present invention. It is the 1st explanatory view showing the conventional ECP processing. It is the 2nd explanatory view showing conventional ECP processing.

Explanation of symbols

 CS ... base station, PS ... wireless communication terminal (terminal), 1 ... terminal control unit, 2 ... wireless communication unit, 3 ... operation unit, 4 ... display unit, 5 ... voice input / output unit, 6 ... storage unit (storage means) 1a ... Communication environment grasping unit (communication environment grasping means), 1b ... GI reducible area determining part (reducible area determining means), 10 ... Correction encoding part, 11 ... Interleaver, 12 ... Serial-parallel conversion part, DESCRIPTION OF SYMBOLS 13 ... Digital modulation part, 14 ... IFFT part, 15 ... GI addition part, 16 ... ECP processing part, 17 ... Transmission part, 16a ... Window function processing part, 16b ... Symbol arrangement part

Claims (7)

In a wireless communication system that performs communication using OFDM (Orthogonal Frequency Division Multiplexing),
A communication environment grasping means for grasping a communication environment with the receiving side after establishing synchronization with the receiving side;
Reducible area determining means for determining a reducible area in the guard interval according to the communication environment;
For each symbol, a predetermined window function is applied to the reducible area of the guard interval, and extended data obtained by applying a predetermined window function to data extracted from a part of the data area immediately after the guard interval is sent to the end of the data area. Window function processing means to be added to the tail;
Symbol placement means for placing the symbols processed by the window function processing means in series so that the beginning of the symbols does not overlap the data area of the adjacent symbol;
A wireless communication system comprising: Comprising storage means for storing in advance the correspondence between the distance between the transmission side and the reception side and the reducible area;
The communication environment grasping means grasps a distance between the transmission side and the reception side as the communication environment,
The reducible area determining means determines a reducible area corresponding to the distance based on the distance grasped by the communication environment grasping means and the correspondence relation stored in the storage means.
The wireless communication system according to claim 1. The storage means stores the correspondence according to the line-of-sight environment for the receiving side,
The communication environment grasping means grasps the distance between the transmitting side and the receiving side and the line-of-sight environment as the communication environment,
The reducible area determination unit is configured to determine the distance and the line-of-sight based on the distance and line-of-sight environment grasped by the communication environment grasping part and the correspondence relation according to the line-of-sight environment stored in the storage part. Determine the reducible areas corresponding to the environment,
The wireless communication system according to claim 2. In a wireless communication apparatus that performs communication using OFDM (Orthogonal Frequency Division Multiplexing),
A communication environment grasping means for grasping a communication environment with the receiving side after establishing synchronization with the receiving side;
Reducible area determining means for determining a reducible area in the guard interval according to the communication environment;
For each symbol, a predetermined window function is applied to the reducible area of the guard interval, and extended data obtained by applying a predetermined window function to data extracted from a part of the data area immediately after the guard interval is sent to the end of the data area. Window function processing means to be added to the tail;
Symbol placement means for placing the symbols processed by the window function processing means in series so that the beginning of the symbols does not overlap the data area of the adjacent symbol;
A wireless communication apparatus comprising: A storage means for storing in advance a correspondence between a distance between the own apparatus and the receiving side and the reducible area;
The communication environment grasping means grasps a distance between the own device and the receiving side as the communication environment,
The reducible area determining means determines a reducible area corresponding to the distance based on the distance grasped by the communication environment grasping means and the correspondence relation stored in the storage means.
The wireless communication apparatus according to claim 4. The storage means stores the correspondence according to the line-of-sight environment for the receiving side,
The communication environment grasping means grasps the distance between the device and the receiving side and the visibility environment as the communication environment,
The reducible area determination unit is configured to determine the distance and the line-of-sight based on the distance and line-of-sight environment grasped by the communication environment grasping part and the correspondence relation according to the line-of-sight environment stored in the storage part. Determine the reducible areas corresponding to the environment,
The wireless communication apparatus according to claim 5. In a wireless communication method for performing communication using OFDM (Orthogonal Frequency Division Multiplexing),
After establishing synchronization with the communication partner, a communication environment grasping step for grasping a communication environment with the communication partner;
A reducible area determination step for determining a reducible area in the guard interval according to the communication environment;
For each symbol, a predetermined window function is applied to the reducible area of the guard interval, and extended data obtained by applying a predetermined window function to data extracted from a part of the data area immediately after the guard interval is sent to the end of the data area. A window function processing step to be added to the tail;
A symbol placement step for placing the symbols processed in the window function processing step in series so that the head of the symbol does not overlap the data area of an adjacent symbol;
A wireless communication method comprising:

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