WO2008065901A1

WO2008065901A1 - Radio communication system, radio communication device, and radio communication method

Info

Publication number: WO2008065901A1
Application number: PCT/JP2007/072202
Authority: WO
Inventors: Takeshi Nakano; Mitsuharu Senda
Original assignee: Kyocera Corporation
Priority date: 2006-11-29
Filing date: 2007-11-15
Publication date: 2008-06-05

Abstract

It is possible to provide a radio communication system capable of reducing a side robe within a band without lowering an SNR and a data rate when performing communication by using the OFDM. The communication system includes: communication environment recognizing means (1a) which recognizes a communication environment with a reception side after establishing a synchronization with the reception side; reduction-enabled region deciding means (1b) which decides a reduction-enabled region in a guard interval in accordance with the communication environment; window function processing means (16a) which applies a predetermined window function to the reduction-enabled region of the guard interval for each symbol and adds extension data obtained by applying the predetermined window function to the data extracted from a part of the data region immediately after the guard interval, to the end of a data region; and a symbol arranging means (16b) which arranges the symbols processed by the window function processing means in series so that symbol heads are not superimposed on the adjacent symbol data region.

Description

Specification

Wireless communication system, wireless communication apparatus, and wireless communication method

Technical field

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

This application claims priority to Japanese Patent Application No. 2006-321533 filed on November 29, 2006, and Japanese Patent Application No. 2007-018098 filed on January 29, 2007. Incorporated into.

Background art

[0002] In recent years, a wireless communication system that performs packet communication by adopting TOFDMA (Orthogonal Frequency Division Multiple Access) in addition to TDMA (Time Division Multiple Access) / TDD (Time Division Duplex) as a multiple access technology suspension is the next generation. It is attracting attention as a broadband mobile communication system. In this OFDMA, orthogonal subcarriers are shared by a plurality of terminals, and a plurality of arbitrary subcarriers are positioned as subchannels. In addition, multiple access is realized by adaptively allocating subchannels to each terminal at any communication timing (in a system employing TDMA, this communication timing is equivalent to a slot).

[0003] In such OFDMA, there is a problem that side lobes in the band increase due to the influence of discontinuous portions 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 part between symbols and changing it 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. 10A, in an OFDM signal, each symbol is composed of a GI (Guard Interval) portion and a data portion, 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 for each data part. This window function target data must be data that has continuity at discontinuities. For example, in Figure 10A, the discontinuity seen from symbol 1 is the data Part 2 is the second half of Dl. In the latter half, the original data of the GI part gl exists. Therefore, as shown in FIG. 10B, the window function target data having continuity at the discontinuity point as seen from symbol 1 is data immediately after the GI part gl, that is, data at the head part of the data part D1. Data at the beginning of this data part D1 is extracted as the window function target data dl of symbol 1. Then, a predetermined window function is applied to the window function target data dl and added to the end of the data part D1. The window function target data dl after the window function is applied is the extended data dl '.

[0005] On the other hand, the discontinuity point seen from symbol 2 corresponds to the head part of GI part g2, and the window function target data having continuity with respect to this head part is shown in data part D2 as shown in FIG. 10C. This is the data immediately before the original data of GI part g2. This data is extracted as the window function target data d2 of symbol 2, applied with a predetermined window function, and added to the head of the GI part g2. The window function target data d2 after the window function is applied is defined as extended data d2 ′. The above processing is performed for each symbol.

[0006] Next, a serial arrangement process of symbols to which extension data after application of a window function is added is performed. This serial arrangement process includes a method defined in the IEEE802.11g standard and a method defined in the IEEE802.20 standard. Fig. 11A shows the case where symbol 1 and symbol 2 described above are arranged in series according to the method defined in the IEEE802.11g standard. In this method, the extension data dl ′ of symbol 1 overlaps with the GI part g2 of symbol 2, and the extension data d2 ′ of symbol 2 overlaps with the data part D1 of symbol 1. On the other hand, FIG. 11B shows a case where the above-described symbol 1 and symbol 2 are arranged in series by the method defined in the IEEE802.20 standard. In this method, the extension data d1 'of symbol 1 and the extension data d2' of symbol 2 overlap. The extension data does not overlap the data part D1 or GI part g2.

[0007] 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. Symbol 2 expansion data d2 ' Has a problem that the SNR (Signal to Noise Ratio) decreases. In addition, according to the method defined in the above-mentioned IEEE802.20 standard, the SNR does not decrease, but the symbol time increases, so the data rate increases. There was a problem of lowering.

[0008] Also, since the guard interval period is set longer with a margin, the symbol length becomes longer even after synchronization is established between the base station and the wireless communication terminal, and the data rate cannot be improved. .

Patent Document 1: Japanese Translation of Special Publication 2003-535502

Disclosure of the invention

[0009] 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 reducing the SNR and data rate when performing communication using OFDM. To do.

[0010] It is another object of the present invention to obtain a reducible amount in the guard interval period after synchronization is established between the base station and the radio communication terminal.

In order to achieve the above object, the present invention has the following aspects, for example.

[0012] A first aspect is a wireless communication system that performs communication using OFDM (Orthogonal Frequency Division Multiplexing), and grasps the communication environment with the receiving side after establishing synchronization with the receiving side. A reduction area determination unit that determines a reduction area in the guard interval according to the unit and the communication environment, and for each symbol, a predetermined window function is applied to the reduction area of the guard interval and a guard interval is applied. A window function processing unit that adds extended data obtained by applying a predetermined window function to data extracted from a part of the immediately following data area, and a symbol processed by the window function processing unit. A symbol placement unit that places each other in series so that the beginning of the symbol does not overlap the data area of an adjacent symbol. It is obtain a wireless communication system.

[0013] A second aspect is the above-described wireless communication system, further comprising a storage unit that stores in advance a correspondence between a distance between a transmission side and a reception side and the reducible region, and The communication environment grasping unit grasps the distance between the transmission side and the receiving side as the communication environment, and the reducible area determination unit comprises the distance grasped by the communication environment grasping unit, the storage unit The wireless communication system determines a reducible area corresponding to the distance based on the correspondence relationship stored in! /. [0014] A third aspect is the wireless communication system described above, wherein the storage unit stores the correspondence relationship according to a line-of-sight environment with respect to the receiving side, and the communication environment grasping unit is configured as the communication environment. The distance between the transmitting side and the receiving side and the line-of-sight environment are grasped, and the reducible area determination unit is stored in the storage unit and the distance and line-of-sight environment grasped by the communication environment grasping unit. The wireless communication system determines a reducible area corresponding to the distance and the line-of-sight environment based on the correspondence relationship according to the line-of-sight environment.

[0015] A fourth aspect is a wireless communication apparatus that performs communication using OFDM, and after establishing synchronization with the receiving side, a communication environment grasping unit that grasps a communication environment with the receiving side, and the communication A wireless communication device comprising: a reducible area determination unit that determines a reducible area in a guard interval according to a communication environment.

[0016] A fifth aspect is the above-described wireless communication apparatus, in which for each symbol, a predetermined window function is applied to the area where the guard interval can be reduced and extracted from a part of the data area immediately after the guard interval. A window function processing unit for adding extended data obtained by applying a predetermined window function to the processed data at the end of the data area, and symbols processed by the window function processing unit are Is a radio communication apparatus further comprising a symbol arrangement unit arranged in series so as not to overlap the data area of adjacent symbols.

[0017] A sixth aspect is the wireless communication apparatus, further comprising a storage unit that stores in advance a correspondence relationship between a distance between the own apparatus and the receiving side and the reducible area, The environment grasping unit grasps the distance between the own device and the receiving side as the communication environment, and the reducible area determining unit grasps the distance grasped by the communication environment grasping unit and the memory The wireless communication apparatus determines a reducible area corresponding to the distance based on the correspondence relationship stored in the unit.

[0018] A seventh aspect is the wireless communication apparatus, wherein the storage unit stores the correspondence relationship according to a line-of-sight environment with respect to the receiving side, and the communication environment grasping unit includes the communication As the environment, the distance between the own device and the receiving side and the visibility environment are grasped, and the reducible area determination unit is grasped by the communication environment grasping unit. Based on the distance and line-of-sight environment and the correspondence relationship stored in the storage unit according to the line-of-sight environment! /, The reduction possible area corresponding to the distance and line-of-sight environment is determined. , A wireless communication device.

[0019] An eighth aspect is a wireless communication method that performs communication using OFDM, and grasps a communication environment between the transmission side and the reception side after establishing synchronization between the transmission side and the reception side A wireless communication method comprising: a communication environment grasping step; and a reducible area determining step for determining a reducible area in a guard interval according to the communication environment.

[0020] A ninth aspect is the above wireless communication method, further comprising a storage step of previously storing a correspondence relationship between a distance between a transmission side and a reception side and the reduction possible region, The boundary grasping step grasps the distance between the transmission side and the receiving side as the communication environment, and the reducible area determination step comprises the distance grasped in the communication environment grasping step, and the storage step The wireless communication method determines a reducible area corresponding to the distance based on the correspondence relationship stored in! /.

[0021] A tenth aspect is the wireless communication method, wherein the storing step stores the correspondence relationship according to a line-of-sight environment between the transmission side and the reception side, and determines the communication environment. In the step, the distance between the transmitting side and the receiving side and the line-of-sight environment are grasped as the communication environment, and the reducible area determination step is performed in the communication environment grasping step! A wireless communication method for determining a reducible area corresponding to the distance and line-of-sight environment based on the grasped distance and line-of-sight environment and the correspondence relationship corresponding to the line-of-sight environment stored in the storing step. is there.

[0022] An eleventh aspect is the wireless communication method described above, in which a predetermined window function is applied to the area where the guard interval can be reduced for each symbol, and extracted from a part of the data area immediately after the guard interval. A window function processing step of adding extended data obtained by applying a predetermined window function to the processed data at the end of the data area, and the symbol placement step includes the symbols processed by the window function processing step. The leading power of the symbol is a wireless communication method that is arranged in series so as not to overlap the data area of the adjacent symbol.

[0023] According to the above solution, when performing communication using OFDM, SNR and data It is possible to reduce side lobes in the band without lowering the tartrate.

[0024] According to the above solution, when performing communication using OFDM, it is possible to reduce side lobes within a band without reducing the SNR and data rate. In addition, by acquiring the amount that can be reduced in the guard interval period, the time corresponding to the amount that can be reduced can be reduced, and the symbol length can be shortened, so that the data rate can be improved.

Brief Description of Drawings

FIG. 1 is a schematic configuration diagram of a wireless communication system in an embodiment of the present invention.

FIG. 2 is a schematic diagram showing a relationship among frequencies, slots, and subchannels of a wireless communication system in an embodiment of the present invention.

FIG. 3 is a configuration block diagram of a wireless communication terminal (terminal) PS in an embodiment of the present invention.

FIG. 4A is a first explanatory diagram showing a correspondence relationship between a Gr reduction possible area and a distance between a terminal PS and a base station CS in an embodiment of the present invention.

FIG. 4B is a first explanatory diagram showing a correspondence relationship between a Gr reduction possible area and a distance between the terminal PS and the base station CS in an embodiment of the present invention.

FIG. 5A is a second explanatory diagram showing a correspondence relationship between the Gr reduction possible area and the distance between the terminal PS and the base station CS in one embodiment of the present invention.

FIG. 5B is a second explanatory diagram showing a correspondence relationship between the Gr reduction possible area and the distance between the terminal PS and the base station CS in one embodiment of the present invention.

FIG. 6 is a detailed explanatory diagram of the wireless communication unit 2 in one embodiment of the present invention.

[FIG. 7] FIG. 7 is an operation flow chart of a wireless communication terminal (terminal) PS according to an embodiment of the present invention.

FIG. 8 is a first explanatory diagram showing an ECP process in one embodiment of the present invention.

FIG. 9 is a second explanatory diagram showing an ECP process in one embodiment of the present invention.

[FIG. 10A] FIG. 1 OA is an explanatory diagram showing a conventional ECP process.

FIG. 10B is an explanatory view showing a conventional ECP process.

FIG. 10B is an explanatory view showing a conventional ECP process. FIG. 11A is an explanatory view showing conventional ECP processing.

FIG. 11B is an explanatory diagram showing a conventional ECP process.

Explanation of symbols

[0026] CS ', base station

PS '*' wireless communication terminal (terminal)

1. Terminal control unit

2 ... Wireless communication part

3 Operation section

4 Display section

5 ... Audio input / output section

6 ··· Storage section (storage means)

la- ··· Communication environment grasping section (Communication environment grasping means)

lb-- · θΓ reduction possible area determination part (reducible area determination means)

10 ... Coding encoder

11 ... Interleaver

12 ... 'Serial parallel conversion part

13 Digital modulation section

14 ... IFFT section

15 ΟΙ Additional section

16 "'ECP processor

17 ··· Transmitter

16a * Window function processing section

16b 'Symbol placement part

BEST MODE FOR CARRYING OUT THE INVENTION

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

The present embodiment relates to an OFDMA communication system. As shown in FIG. 1, the wireless communication system of this embodiment includes a base station CS, a wireless communication terminal (hereinafter abbreviated as a terminal) PS, and a network (not shown). Base station CS and terminal PS are time-division multiplex connections Communication is performed using orthogonal frequency division multiple access (OFDMA) as a multiple access technique in addition to system (TDMA) and time division duplex (TDD). A plurality of base stations CS are provided at regular distance intervals, and multiple connections are made with a plurality of terminals PS to perform wireless communication. Note that the terminal PS and the base station CS have the same configuration in the present embodiment in the force characteristic portion corresponding to the wireless communication device. For this reason, the following explanation will be given using the terminal PS as a representative.

[0028] As is well known, the OFDMA scheme is that all subcarriers in an orthogonal relationship are shared by all terminal PSs, and a set of arbitrary subcarriers is positioned as one group, one for each terminal PS. Alternatively, it is a technology that realizes multiple access by adaptively assigning multiple groups. In the wireless communication system of this embodiment, the TDMA method and the TDD method are further combined with the OFDMA method described above. In other words, each group is divided into an uplink and a downlink in the time axis direction as a TDD, and these uplink and downlink are each divided into four TDMA slots. In this embodiment, one unit obtained by dividing each dulpe as a TDMA slot in the time axis direction is called a subchannel. Figure 2 shows the relationship among frequency, TDMA slot, and subchannel 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, which are multiplied by 28 in the frequency direction and 4 in the time axis direction (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 subchannels. The remaining subchannel is used as a traffic channel (TCH). In the following, this traffic channel is called a traffic subchannel. The base station CS and the terminal PS that perform radio communication can be arbitrarily selected from all traffic subchannels belonging to the uplink and downlink (in this case, 108 subchannels of 27 X 4 slots excluding CCH). One or more traffic subchannels are assigned. The same traffic channel is assigned to the traffic subchannel for uplink and downlink as communication channels.

[0030] Next, the configuration of terminal PS will be described. As shown in Fig. 3, the terminal PS controls the terminal A 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 means) 6 are provided. Further, the terminal control unit 1 includes a communication environment grasping unit (communication environment grasping unit) la and a GI reducible region determining unit (reducible region determining unit) lb as functional elements.

[0031] Based on the terminal control program stored in the storage unit 6, the received signal obtained via the wireless communication unit 2, and the operation signal input from the operation unit 3, the terminal control unit 1 Control the overall operation. The communication environment grasping unit la of the terminal control unit 1 is based on the received signal acquired from the base station CS via the wireless communication unit 2! /, Based on the distance between the terminal PS and the base station CS and the line-of-sight environment. To figure out. Specifically, the communication environment grasping unit la grasps whether the prospect environment is an environment that is within the prospect or an environment that is not the prospect.

[0032] More specifically, the communication environment grasping unit la grasps the distance between the terminal PS and the base station CS based on the synchronization timing. The base station CS uses the power of the response frame from the terminal PS to the frame sent to the synchronized terminal PS that is the other party of communication (how long the deviation time is based on the time axis). calculate. Furthermore, the base station CS instructs the terminal PS in advance to transmit at a timing that allows for the time difference. The base station CS can calculate and grasp the distance from the terminal PS based on the deviation time. For example, (distance between terminal PS and base station CS) = (deviation time) / (radio wave propagation speed). Understanding the outlook environment means that the communication environment between the terminal PS and the base station CS is to understand whether the outlook environment is in the outlook environment or in the out of view environment.

Here, the line-of-sight environment, as shown in FIG. 4A, is an environment in which there are few occurrences of multipaths between the terminal PS and the base station CS in the communication area. In such a line-of-sight environment, as shown in Fig. 4B, the Gr 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 located at a longer distance from the base station CS. On the other hand, the unforeseen environment is an environment where multiple paths occur frequently because there are obstacles between the terminal PS and the base station CS in the communication area, as shown in Fig. 5A. 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, an exponential function is used for the distance between the terminal PS and the base station CS. Therefore, the area where Gr can be reduced becomes smaller. [0034] In addition, whether or not the force is a line-of-sight environment and an environment that is not a line-of-sight environment is determined as follows. If the received signal level of the delayed wave arriving after the direct wave arriving at the base station CS from the terminal PS is lower than that of the direct wave, the line-of-sight environment is determined. In addition, it is judged that the environment is out of sight when there are delay waves with more delay waves than a certain number and a signal level higher than that of the direct waves.

[0035] As shown in FIG. 4B and FIG. 5B, the correspondence between the distance between the terminal PS and the base station CS in the sight-line environment and the non-line-of-sight environment and the Gr reduction possible area (hereinafter, this correspondence relationship). Is called “Gr reduction information”). Such Gr reduction information may be stored as table-like data or as a function.

[0036] The Gr reducible area determination unit lb includes the distance between the terminal PS and the base station CS, which is grasped by the communication environment grasping unit la, the line-of-sight environment, and the Gr reduction information stored in the storage unit 6. Based on the above, the Gr reduction possible area 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 Gr reducible region determined by the Gr reducible region determining unit lb and the ECP processing start request to the ECP processing unit 16 described later.

[0037] Under the control of the terminal control unit 1, the radio communication unit 2 performs error correction coding, modulation, and multiplexing by OFDM on the control signal or data signal output from the terminal control unit 1 to multiplex Get the digitized signal (OFDM signal). Further, the radio communication unit 2 frequency-converts the multiplexed signal into the RF frequency band, and transmits it to the base station CS as a transmission signal.

More 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 IF FT (Inverse Fast Fourier Transform) unit 14, GI (Guard Interval) attached calorie unit 15, ECP (Ext ended Cyclic Prefix) processing unit 16, and transmission unit 17.

[0039] The error correction encoding unit 10 is, for example, a FEC (Forward Error Correction) encoder. The error correction coding unit 10 adds an error correction code, which is redundant information, to the bit string of the control signal or data signal input from the terminal control unit 1 based on the coding rate specified by the terminal control unit 1. , Output to 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 coding unit 10. The serial / parallel conversion unit 12 converts the bit string after the interleaving process into the terminal control unit. Each subcarrier included in the subchannel indicated in 1 is divided in bit units and output to each digital modulation section 13.

[0040] The same number of digital modulation units 13 as subcarriers are provided. The digital modulation unit 13 digitally modulates the bit data divided for each subcarrier using the subcarrier corresponding to the bit data, and outputs the modulated signal to the IFFT unit 14. Each digital modulation unit 13 is a modulation method instructed by the terminal control unit 1, for example, BPSK (Binary Phase Shift Keying), QPSK (Quadrature Phase Shift Keying), 16Q AM (Quadrature Amplitude Modulation), Digital modulation is performed using 64QAM. The IFFT unit 14 generates an OFDM signal by performing inverse Fourier transform on the modulated signal input from each digital modulation unit 13 and performing orthogonal multiplexing, and outputs the OFDM signal to the GI adding unit 15. The GI adding unit 15 adds a guard interval (GI) to the OFDM signal input from the IFFT unit 14 and outputs it to the ECP processing unit 16.

[0041] The ECP processing unit 16 includes a window function processing unit 16a and a symbol arrangement unit 16b. The ECP processing unit 16 starts the ECP processing in response to an ECP processing start request input from the terminal control unit 1. On the other hand, when the ECP processing start request is not input, the ECP processing unit 16 outputs the OFDM signal after GI addition to the transmitting unit 17 without processing. Based on the Gr reducible region input from the terminal control unit 1, the window function processing unit 16a applies a predetermined window function to the Gr reducible region for each symbol included in the OFDM signal after GI addition. Further, the window function processing unit 16a adds the extended data obtained by applying a predetermined window function to the window function target data extracted from the head part of the data part immediately after the GI, at the end of the data part. The symbol arrangement unit 16b arranges the symbols processed by the window function processing unit 16a in series so as not to overlap the symbol leading force ^s and the data portion of the adjacent symbol, and outputs them to the transmission unit 17. The transmission unit 17 converts the frequency of 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 radio communication unit 2 extracts the received OFDM signal by frequency-converting the received signal received from the base station CS to the IF frequency band. Further, the receiver side of the wireless communication unit 2 applies the window function to the received OFDM signal and the GI. Remove. After that, the receiver side of the wireless communication unit 2 reconstructs the bit string by performing FFT processing, digital demodulation, parallel serial conversion processing, dintariba processing, and error correction decoding processing on the received OFDM signal. Output to control unit 1.

Subsequently, returning to FIG. 3, the description will be continued. The operation unit 3 is composed of operation keys such as a power key, various function keys, and a keypad. The operation unit 3 outputs an operation signal based on operation inputs from 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 predetermined images and characters based on display signals 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. On the other hand, the audio input / output unit 5 outputs the audio data input from the terminal control unit 1 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 terminal PS configured as described above will be described using the flowchart of FIG.

First, terminal control unit 1 receives an operation signal instructing data transmission from operation unit 3. The terminal control unit 1 controls the radio communication unit 2 to search for a control channel (CCH) transmitted from the base station CS. Furthermore, the terminal control unit 1 performs a process of establishing a communication connection with the base station CS that has successfully acquired and transmitted the control channel with the best reception state. Here, the terminal control unit 1 requests the base station CS to allocate a link channel (traffic subchannel) via the control channel, and the base station CS and the base station CS are based on the synchronization information included in the control channel. Establish synchronization (step Sl).

[0046] When the establishment of synchronization with the base station CS is completed, the communication environment grasping unit la establishes a communication 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 distance and the prospect environment (in-prospect or out-of-sight environment) are ascertained (step S2).

[0047] Specifically, the communication environment grasping unit la synchronizes the distance between the terminal PS and the base station CS. Get based on ming. Then, the communication environment grasping unit la determines that it is a line-of-sight environment when the received signal level of the delayed wave that arrives after the direct wave that reaches the base station CS from the terminal PS is lower than the direct wave. In addition, the communication environment grasping unit la determines that the environment is an out-of-look environment when there are delay waves that have more than a predetermined number of delay waves and a signal level higher than that of the direct waves.

[0048] Subsequently, the Gr reducible area determination unit lb determines the distance between the terminal PS and the base station CS, which is grasped by the communication environment grasping unit la, the line-of-sight environment, and the Gr stored in the storage unit 6. Based on the reduction information, the Gr reduction possible area corresponding to the distance between the terminal PS and the base station CS and the line-of-sight environment is determined (step S3). Specifically, for example, when the outlook environment grasped by the communication environment grasping unit la is an unforeseen environment, the Gr reducible area determination unit lb displays the Gr reducible area shown in FIG. The Gr reduction possible area is determined based on the correspondence with the distance to the station CS.

[0049] Then, terminal control section 1 outputs a bit string of a data signal to be transmitted to base station CS to error correction coding section 10. Further, the terminal control unit 1 outputs an ECP processing start request and a signal indicating the Gr reducible region determined by the Gr reducible region determining unit lb to the ECP processing unit 16. The bit string of the data signal is converted into an OFDM signal to which GI is added through 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. The OFD M signal is input to the window function processing unit 16a of the ECP processing unit 16. Here, an ECP process start request and a signal indicating a Gr reduction possible area are input from the terminal control unit 1 to the window function processing unit 16a. Therefore, the window function processing unit 16a starts ECP processing on the OFDM signal input from the GI adding unit 15 (step S4).

[0050] 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 symbol 1 extracted from the OFDM signal shown in Fig. 10A. As shown in FIG. 8, the window function processing unit 16a applies a predetermined window function (for example, a trigonometric function) to the Gr reducible region rl in the GI unit gl of the symbol 1. The window function processing unit 16a starts from the head of the data part D1 immediately after the GI part gl. The extended data r2 ′ obtained by applying a predetermined window function to the extracted window function target data r2 is added to the end of the data part D1. As a result, data rl ′ obtained by applying a window function to the Gr reducible area rl is added to the beginning of symbol 1. Furthermore, the extension data r2 ′ is added to the end of the symbol 1. Then, as shown in FIG. 9, the same process is performed for symbol 2. For symbol 2, data rl "obtained as a result of applying a predetermined window function to the Gr reducible region in GI part g2 of symbol 2, and the window function target data extracted from the head part of data D2 immediately after GI part g2 Extended data r2 "obtained as a result of applying a predetermined window function to r2 is added. As described above, the window function processing unit 16a performs the same processing as described above for all symbols.

Then, as shown in FIG. 9, the symbol arrangement unit 16b serially processes the symbols processed by the window function processing unit 16a so that the head of the symbol does not overlap the data portion of the adjacent symbol. Deploy. Specifically, the symbol arrangement unit 16b arranges the symbols processed by the window function processing unit 16a in series so that only the extension data r2 ′ and the data rl ″ overlap, and outputs the symbols to the transmission unit 17. The transmission unit 17 inputs the OFDM signal from the symbol arrangement unit 16b, and the transmission unit 17 frequency-converts the OFDM signal to an RF frequency band to obtain a transmission signal, which is transmitted to the base station CS (step S5). In other words, adjacent symbols are arranged in series by a method similar to the conventional IEEE802.20 standard shown in Fig. 11B, where the difference between this embodiment and the conventional one is that Gr can be reduced in the GI section. By reducing the area, the GI length is shortened, which reduces the symbol time and suppresses the decrease in data rate, that is, while suppressing the decrease in data rate just by reducing the SNR. It is possible to reduce the side lobes of the band.

[0052] By the way, even when the ECP processing is simply performed on the GI unit, it is possible to suppress the decrease in the SNR and the data rate. The part of the GI section that has undergone ECP processing is different from the original data. For this reason, in this case, the effect of the GI unit is lost, and intersymbol interference due to signal delay is likely to occur. The delay of the signal after the synchronization is established can be assumed by the previous communication situation, and is considered to be much less than the maximum delay specified by GI. Therefore, as in this embodiment, in communication after establishment of synchronization, ECP processing is performed on the GI unit, thereby suppressing a decrease in SNR and data rate. In addition, side lobes in the band can be reduced.

[0053] Also, by obtaining the reducible amount of the guard interval period, the guard interval time corresponding to the reducible amount can be reduced, and the symbol length of the communication frame can be shortened, thereby improving the data rate in communication. be able to.

In the above embodiment, the power OF described for the communication system of the OFDMA system

The present invention can be widely applied to communication systems using OFDM systems that use only DMA. Further, although the terminal PS has been described as an example of the wireless communication apparatus, the present invention is not limited to this, and the same configuration can be applied to a wireless communication apparatus that performs communication using the base station CS or other OFDM. Monkey.

Note that the present invention is not limited to the above embodiment, and for example, addition or deletion of components to the above embodiment, substitution, combination of components, and the like may be appropriately performed.

Industrial applicability

[0055] When performing communication using OFDM, it is possible to reduce side lobes in the band without reducing the SNR and data rate.

Claims

The scope of the claims

[1] A non-spring communication system that uses OFDM (Orthogonal Frequency Division Multiplexing) to communicate.

After establishing synchronization with the receiving side, a communication environment grasping unit for grasping the communication environment with the receiving side,

A reducible area determination unit that determines 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 used as the end of the data area. A window function processing unit to be added to the tail,

A radio communication system comprising: a symbol arrangement unit arranged in series so that symbols processed by the window function processing unit are arranged such that a symbol head does not overlap a data area of an adjacent symbol.

[2] The storage unit further stores in advance the correspondence between the distance between the transmission side and the reception side and the reducible area,

The communication environment grasping unit grasps a distance between the transmitting side and the receiving side as the communication environment,

The reducible area determining unit determines a reducible area corresponding to the distance based on the distance grasped by the communication environment grasping unit and the correspondence relation stored in the storage unit.

The wireless communication system according to claim 1.

[3] The storage unit stores the correspondence relationship according to the line-of-sight environment with respect to the receiving side.

I think

The communication environment grasping unit 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 includes the distance and line-of-sight environment acquired by the communication environment determination unit, and the line-of-sight environment stored in the storage unit! / Based on the corresponding relationship according to! /, Determine the reducible area corresponding to the distance and the visibility environment,

The wireless communication system according to claim 2.

[4] A wireless communication device that performs communication using OFDM (Orthogonal Frequency Division Multiplexing),

A wireless communication device comprising:

[5] For each symbol, a predetermined window function is applied to the area where the guard interval can be reduced, 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 used as data. A window function processing unit to be added to the end of the area;

A symbol arrangement unit that arranges the symbols processed by the window function processing unit in series so that the top of the symbol does not overlap the data area of an adjacent symbol;

The wireless communication apparatus according to claim 4, further comprising:

[6] The apparatus further comprises a storage unit for storing in advance the correspondence between the distance between the device and the receiving side and the reducible area,

The communication environment grasping unit grasps a distance between the own device and the receiving side as the communication environment,

The wireless communication device according to claim 5.

[7] The storage unit stores the correspondence relationship according to a line-of-sight environment with respect to the receiving side.

I think The communication environment grasping unit grasps the distance between the own device and the receiving side and the line-of-sight environment as the communication environment,

The reducible area determination unit is based on the distance and line-of-sight environment grasped by the communication environment grasping unit and the correspondence relationship according to the line-of-sight environment stored in the storage unit! /, Determine a reducible area corresponding to the distance and line-of-sight environment,

The wireless communication device according to claim 6.

[8] OFDM (Orthogonal Frequency Division Multiplexing)

A communication environment grasping step for grasping a communication environment between the transmission side and the reception side after establishing synchronization between the transmission side and the reception side;

A reducible area determination step for determining a reducible area in the guard interval according to the communication environment;

A wireless communication method comprising:

[9] A storage step of previously storing a correspondence relationship between the distance between the transmission side and the reception side and the reducible area is further provided.

The communication environment grasping step grasps a distance between the transmission side and the reception side as the communication environment,

The reducible area determination step can reduce the distance corresponding to the distance based on the distance grasped in the communication environment grasping step and the correspondence stored in the storing step. Determine the area,

The wireless communication method according to claim 8.

[10] The storing step stores the correspondence relationship according to a line-of-sight environment between the transmitting side and the receiving side,

The communication environment grasping step grasps the distance between the transmitting side and the receiving side and the line-of-sight environment as the communication environment,

The reducible area determining step includes the distance and line-of-sight environment determined in the communication environment determination step and the line-of-sight environment stored in the storage step! / Based on the correspondence relationship according to the! /, Determine a reducible area corresponding to the distance and line-of-sight environment,

The wireless communication method according to claim 9.

For each symbol, a predetermined window function is applied to the area where the guard interval can be reduced, 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 used as the data area. A window function processing step to be added to the tail of

9. The radio communication method according to claim 8, wherein the symbol arrangement step arranges the symbols processed by the window function processing step in series so that the head of the symbol does not overlap with a data area of an adjacent symbol.