JP2010161647A - Transmission apparatus, communication system, transmission method, and, receiving apparatus - Google Patents

Abstract

Provided is a transmission apparatus capable of performing communication for improving the accuracy of propagation path estimation using pilot symbols in an environment in which a delayed wave having a delay exceeding a normal guard interval section arrives without substantially deteriorating transmission efficiency. To do.
A transmission apparatus using a multi-carrier transmission scheme with a plurality of symbols including either a modulation symbol obtained by data modulation of an information data signal or a pilot symbol as a unit of symbol length, the normal GI symbol generation unit includes the symbol. A normal GI (guard interval) is added to a part of the symbol, the long GI symbol generator adds a long GI longer than the normal GI to the rest of the symbols, and the multiplexing unit generates a normal GI symbol generator and a long GI symbol The symbols generated by the first and second parts are multiplexed. At this time, the symbol to which the long GI is added is arranged on a subcarrier adjacent to the subcarrier on which the pilot symbol is arranged.
[Selection] Figure 1

Description

  The present invention relates to a transmission device, a communication system, and a transmission method.

Communication systems used in recent wireless communications, such as OFDM (Orthogonal Frequency Division Multiplexing), OFDMA (Orthogonal Frequency Division Multiple Access), MC-CDM (Multi Carrier-Code Division Multiplexing) In transmission such as multi-carrier code division multiplexing (SC) and SC-FDMA (single carrier frequency division multiple access), a cyclic prefix (Guard Interval: GI) is used as a guard interval (GI) in a transmission apparatus. : CP) section (length) can be added to reduce communication quality degradation due to multipath interference.
In addition, since the amplitude and phase of the transmission signal fluctuate due to a propagation path such as multipath fading, the receiving apparatus needs to perform processing for compensating for fluctuations in amplitude and phase. A pilot symbol, which is a known signal between the transmitter and receiver, is inserted into a part of the transmission signal, and the receiver estimates the propagation path by detecting fluctuations in the amplitude and phase of the received pilot symbol. Compensation for variations in signal amplitude and phase. In order to prevent deterioration of communication quality, it is desirable to perform propagation path estimation with high accuracy.

In particular, in wideband transmission and high-speed moving environments, it is desirable to be able to follow fluctuations in the amplitude and phase of the transmission signal in the frequency direction and the time direction. As a method for estimating time variation and frequency variation of a transmission signal, there is a method of mapping pilot symbols scattered in the frequency direction and the time direction (hereinafter, this pilot symbol is a scattered pilot symbol (Scattered Pilot Symbol). Signal)).
FIG. 34 is a schematic diagram illustrating a configuration example of a transmission frame in multicarrier transmission using OFDM, in which the vertical axis indicates subcarriers (frequency) and the horizontal axis indicates OFDM symbol numbers (time). As shown in the figure, the transmission frame is composed of 8 subcarriers and 12 OFDM symbols. In the transmission frame, pilot symbols are mapped to be scattered over every third subcarrier and every other OFDM symbol. Furthermore, the subcarriers to which the pilot symbols are mapped are sequentially shifted with respect to the frequency direction. As described above, one frame on which pilot symbols are mapped is received, and transmission path estimation using the pilot symbols included in the received frame is performed, so that estimation that follows time variation and frequency variation of amplitude and phase is performed. be able to.

    As described above, the receiving apparatus maps the pilot symbol to the frame, receives the frame transmitted from the transmitting apparatus, and performs propagation path estimation based on fluctuations in the amplitude and phase of the subcarrier to which the pilot symbol is mapped. . In addition, the receiving apparatus performs interpolation for subcarriers to which pilot symbols are not mapped by interpolating from propagation path estimation results of subcarriers having close frequencies. As a result, it is possible to perform estimation following the time variation and frequency variation of the amplitude and phase. For example, Non-Patent Document 1 discloses a wireless communication system that performs propagation path estimation using scattered pilot symbols.

By the way, in the above-described multicarrier transmission, when there is an incoming wave exceeding the guard interval, the channel estimation accuracy, the demodulation accuracy, etc. are lowered, which causes the communication quality to deteriorate. FIG. 35 is a schematic diagram illustrating a signal that reaches a receiving apparatus from a transmitting apparatus through a multipath environment in multicarrier transmission such as OFDM. In FIG. 35, the horizontal axis direction represents time, and the incoming waves are shown in order. A guard interval obtained by copying a part of the second half of the effective symbol is added before each effective symbol.
FIG. 35 shows a case where FFT (Fast Fourier Transform) processing is performed in a section t4 in synchronization with the preceding wave s1 (wave that first arrived at the receiving device). The delayed wave s2 arrives after a time t1 with respect to the preceding wave s1 (the first wave that has arrived at the receiving device), the delayed wave s3 arrives with a delay of time t2 with respect to the preceding wave s1, and the delayed wave s4 is Arriving after time t3 with respect to the preceding wave s1. Note that each of the preceding wave s1 and the delayed waves s2, s3, and s4 indicates a wave of a signal in which all subcarriers are multiplexed. The preceding wave and the delayed wave are also called incoming waves.

Here, when the receiving device receives the preceding wave s1 and the delayed wave s2, the delay time t1 of the delayed wave s2 is a delay in which the delay with respect to the preceding wave s1 falls within the guard interval. When the FFT process is performed in the interval t4 that is the effective symbol interval of s1, the interval between the symbols of the delayed wave s2 is not included in the interval t4.
On the other hand, when the reception apparatus receives the preceding wave s1, the delay wave s2, the delay wave s3, and the delay wave s4, the delay time t2 of the delay wave s3 and the delay time t3 of the delay wave s4 are the preceding wave s1. When the receiving apparatus performs the FFT process in the interval t4, the interval between the symbols of the delayed wave s3 and the delayed wave s4 is included in the interval t4. As a result, the spectrum of each subcarrier spreads.
As described above, due to the presence of an incoming wave having a delay exceeding the guard interval length with respect to the reference incoming wave, the receiving device cannot correctly demodulate the modulation symbol, and communication quality deteriorates.

  Next, FIG. 36 is a schematic diagram showing the spectrum of the FFT interval for explaining the relationship between subcarriers in signal transmission / reception by the multicarrier transmission method. In FIG. 36, the horizontal axis direction represents frequency, and the vertical axis direction represents signal intensity. FIG. 36A shows a case where subcarriers in the multicarrier scheme are orthogonal to each other, and FIG. 36B is a schematic view showing a case where interference occurs between subcarriers due to intercarrier interference (hereinafter referred to as ICI). FIG. When there is no incoming wave exceeding the guard interval interval, that is, when there is no break between symbols of the delayed wave in the FFT processing interval (interval t4), as shown in FIG. At the frequency f1 shown, the spectrum of adjacent subcarriers 3 and 5 is 0, and the interference component of subcarrier 4 is not included. Such a state is a state in which the orthogonality between the subcarriers is maintained, and ICI does not occur.

  On the other hand, when there is a delayed wave exceeding the guard interval, there is a break between the symbols of the delayed wave in the FFT interval as described above, and as shown in FIG. At the frequency f1 indicating the component of the carrier 4, the spectrum of the adjacent subcarriers 3 and 5 is included, and interference occurs. In FIG. 36, only the main lobe of each subcarrier is shown for the sake of simplification, but subcarriers 1 to 3 and 5 at frequency f1 indicating the component of subcarrier 4 by the side lobe of each subcarrier. ˜8 spectra are included, resulting in interference. Such a state is a state in which the orthogonality between the subcarriers is not maintained. In a state where the orthogonality between subcarriers is not maintained, communication characteristics are degraded by ICI. This ICI is a factor that greatly deteriorates the accuracy of propagation path estimation and the error rate in demodulation.

  As a method for removing the influence of ICI, for example, as shown in Non-Patent Document 1, the guard interval of each OFDM symbol included in a transmission frame is set to a section longer than the delay time of the delay wave, and the carrier There is a method of maintaining the orthogonality between them.

"3rd Generation Partnership Project; Technical Specification Group Radio Access Network; Evolved Universal Terrestrial Radio Access (E-UTRA); Physical Channels and Modulation (Release 8)" 3GPP TS 36.211 V8.3.0 (2008-05).

  However, in the above method, since the guard interval interval is set for each transmission frame, the guard interval interval is lengthened not only for the subcarriers to which the scattered pilot symbols are mapped but also for all subcarriers. There is a need to. Also, the guard interval interval is lengthened for all symbols other than the scattered pilot symbol of the same transmission frame including the scattered pilot symbol. For this reason, the redundant section due to the guard interval increases in the transmission band, and there is a problem that the transmission efficiency is deteriorated.

  The present invention has been made in view of the above problems, and an object of the present invention is to use pilot symbols in an environment in which a delayed wave having a delay exceeding a normal guard interval section arrives, with almost no deterioration in transmission efficiency. It is an object of the present invention to provide a transmission device, a communication system, a transmission method, and a communication method that can perform communication for improving the accuracy of propagation path estimation.

  (1) In order to solve the above problem, the present invention provides a transmitting apparatus that transmits a symbol, which is a basic unit of a digital signal, by multicarrier modulation and transmits the symbol in a first multicarrier symbol having a normal guard interval. And a subcarrier in which the symbol is arranged in a second multicarrier symbol having a long guard interval longer than the normal guard interval, and a plurality of subcarriers that constitute the multicarrier at the same time The subcarriers scattered among the subcarriers and in which the second multicarrier symbol is arranged occupy subcarriers close to the subcarrier in which the first multicarrier symbol is arranged. This is a characteristic transmission device.

  (2) Moreover, the present invention provides the first multicarrier according to the invention described above, in which the transmission device adds a normal guard interval to a first symbol that is a part of the symbols. A long guard interval longer than the normal guard interval is added to a first multicarrier symbol generation unit that generates symbols and a second symbol that is a part of the symbols that is different from the first symbol. A second multicarrier symbol generator for generating the second multicarrier symbol generated; and a multiplexer for multiplexing the first multicarrier symbol and the second multicarrier symbol, The second multicarrier symbol is the first multicarrier symbol or the second multicarrier symbol. Yariashinboru is characterized in that to occupy the sub-carrier adjacent to a sub-carrier occupied.

  (3) Further, in the present invention described in the above, the first multicarrier symbol generation unit includes a first guard interval insertion unit that adds a normal guard interval, and the second multicarrier symbol. The generation unit includes a second guard interval insertion unit that adds a long guard interval, and the multiplexing unit multiplexes the first multicarrier symbol and the second multicarrier symbol in a time domain. It is characterized by.

  (4) Furthermore, in the present invention described above, the second multicarrier symbol generation unit may perform phase rotation on the symbols that are the partial symbols and to which the long guard interval is added, Generating a plurality of consecutively arranged symbols in the time direction of the same subcarrier as that of the partial symbol and constituting a part of the long guard interval to be added to the partial symbol And a phase control unit configured to arrange at least one second symbol that is phase-rotated continuously in the forward direction with respect to a time direction of a subcarrier in which the second symbol is arranged, and the multiplexing unit includes: The first multicarrier symbol and the second multicarrier symbol are multiplexed in a frequency domain.

  (5) Further, in the present invention according to the above aspect, the transmitter includes a pilot symbol in which the symbol is a predetermined known symbol, and the second multicarrier symbol is the pilot. A subcarrier adjacent to a subcarrier occupied by the first multicarrier symbol or the second multicarrier symbol including a symbol is occupied.

  (6) Further, the present invention is characterized in that, in the above-described invention, the first multicarrier symbol generation unit adds the normal guard interval to the pilot symbol.

  (7) Further, the present invention is characterized in that, in the above-described invention, the second multicarrier symbol generation unit adds the long guard interval to the pilot symbol.

  (8) Further, according to the present invention, in the above-described invention, the second multicarrier symbol is arranged on either one of a subcarrier having a higher frequency and a subcarrier having a lower frequency than the first symbol. It is characterized by being.

  (9) Further, in the present invention described above, the second symbol includes a control symbol for controlling communication, and the second multicarrier symbol having the long guard interval is the pilot symbol. It arrange | positions to the subcarrier adjacent to the subcarrier by which the said 1st symbol containing 2 or the said 2nd multicarrier symbol is arrange | positioned.

  (10) Further, in the present invention described in the above, the symbol includes a modulation symbol obtained by modulating data to be transmitted, and the first multicarrier symbol generation unit or the second multicarrier symbol generation unit Is characterized in that the control symbols are arranged on subcarriers with priority over the modulation symbols.

  (11) Further, according to the present invention, in the invention described above, the symbol interval included in the first multicarrier symbol and the symbol interval included in the second multicarrier symbol are arranged in a time direction. It is characterized by matching.

  (12) Further, in the present invention described in the above, the length of the second multicarrier symbol output from the second multicarrier symbol generation unit is an output of the first multicarrier symbol generation. It is an integral multiple of the length of the first multicarrier symbol.

(13) Further, in order to solve the above problem, the present invention is a communication system including a transmission device and a reception device that transmit multi-carrier modulation of a symbol, which is a basic unit of a digital signal, and the transmission device includes: , A first multicarrier symbol generator for generating the first multicarrier symbol in which a normal guard interval is added to a first symbol that is a part of the symbols, and the first of the symbols A second multicarrier symbol generation unit that generates the second multicarrier symbol in which a long guard interval longer than the normal guard interval is added to a second symbol that is a part of a symbol different from the one symbol And the first multi-carrier symbol and the second multi-carrier symbol And a transmission unit that transmits the transmission symbol generated by the multiplexing unit to the reception device, and the reception device transmits the transmission symbol transmitted from the transmission device. A reception unit that receives a transmission symbol, and a first multicarrier symbol processing unit that extracts the symbol by removing the normal guard interval from the first multicarrier symbol among the transmission symbols received by the reception unit A second multicarrier symbol processing unit that removes the long guard interval from the second multicarrier symbol among the transmission symbols received by the receiving unit and extracts the symbol; and the first multicarrier symbol The symbol extracted by the carrier symbol processing unit or the second multi-carrier symbol processing unit A pilot symbol processing unit that performs channel estimation using known pilot symbols included in the signal to calculate a channel estimation value, and includes the first multicarrier symbol processing unit, the second multicarrier symbol processing unit, Is a channel distortion compensation based on a channel estimation value which is a channel estimation result by the pilot symbol processing unit, detects the symbol, the subcarrier in which the first multicarrier symbol is arranged, The subcarriers in which the second multicarrier symbols are arranged are scattered among a plurality of subcarriers constituting the multicarrier at the same time, and the symbols are arranged in the second multicarrier symbols. Subcarriers adjacent to the subcarrier in which the first multicarrier symbol is arranged It is a communication system characterized by occupying a subcarrier to be operated.
.

  (14) Further, in order to solve the above problem, the present invention provides a transmission method in which a symbol, which is a basic unit of a digital signal, is transmitted after multi-carrier modulation, in the first multi-carrier symbol having a normal guard interval. The subcarrier in which the symbol is arranged and the subcarrier in which the symbol is arranged in the second multicarrier symbol having a long guard interval longer than the normal guard interval form the multicarrier at the same time. The subcarriers that are interspersed among a plurality of subcarriers and in which the second multicarrier symbol is arranged occupy subcarriers close to the subcarrier in which the first multicarrier symbol is arranged. This is a transmission method characterized by the above.

  (15) Moreover, in order to solve the above problem, the present invention is a receiving apparatus that receives a transmission signal including a normal guard interval and a long guard interval that are part of a multicarrier symbol subjected to multicarrier modulation. The outputs from the normal guard interval-FFT section extracting unit, the long guard interval-FFT section extracting unit, the normal guard interval-FFT section extracting unit, and the long guard interval-FFT section extracting unit are used as signals on the frequency axis. A receiving apparatus comprising: a propagation path distortion compensator that regenerates a modulation symbol by performing propagation path compensation after conversion.

  According to the present invention, it is possible to reduce the occurrence of inter-carrier interference and improve communication quality in multicarrier transmission using digital technology.

It is a schematic block diagram which shows the structure of the transmitter in 1st Embodiment. It is a schematic diagram which shows the structure of the transmission frame in the embodiment. It is the figure which showed the normal guard interval insertion method by the normal GI insertion part in the embodiment. FIG. 3 is a schematic diagram illustrating a transmission frame in which a mapping unit of a normal GI symbol generation unit in the embodiment maps pilot symbols, modulation symbols, and zeros to the data arrangement information illustrated in FIG. 2. FIG. 3 is a schematic diagram illustrating a transmission frame in which a mapping unit of a long GI symbol generation unit in the embodiment maps a modulation symbol and zero to the data arrangement information illustrated in FIG. 2. It is the schematic diagram which showed the output of the multiplexing part in the same embodiment. FIG. 3 is a schematic diagram illustrating a transmission frame in which a mapping unit of a normal GI symbol generation unit in the present embodiment maps pilot symbols, modulation symbols, and zeros to resource elements with respect to the data arrangement information illustrated in FIG. 2. FIG. 3 is a schematic diagram showing a transmission frame in which a mapping unit of a long GI symbol generation unit in the embodiment maps modulation symbols and zeros to resource elements with respect to the data arrangement information shown in FIG. 2. It is the schematic diagram which showed the symbol contained in the output for 1 transmission frame which the multiplexing part in the embodiment outputs. It is a schematic block diagram which shows the structure of the receiver in the same embodiment. FIG. 7 is a schematic diagram illustrating a modulation symbol period that a normal GI-FFT interval extraction unit extracts from an input signal input from the reception unit when the reception device in the embodiment receives the transmission frame illustrated in FIG. 6 from the transmission device. is there. FIG. 6 is a schematic diagram illustrating a modulation symbol period that is extracted from an input signal input from the reception unit by the long GI-FFT section extraction unit when the reception apparatus according to the present embodiment receives the transmission frame illustrated in FIG. 6 from the transmission apparatus. is there. It is a schematic diagram which shows the orthogonality of the signal which the receiver in the embodiment received from the transmitter. It is a schematic diagram which shows the orthogonality between the subcarriers of the signal which the receiver in the embodiment received from the transmitter. FIG. 6 is a schematic diagram illustrating a transmission frame in which a mapping unit of a normal GI symbol generation unit in the second embodiment maps modulation symbols, pilot symbols, and zeros to resource elements with respect to the data arrangement information illustrated in FIG. is there. FIG. 3 is a schematic diagram illustrating a transmission frame in which a mapping unit of a long GI symbol generation unit in the embodiment maps modulation symbols and zeros to resource elements with respect to the data arrangement information illustrated in FIG. 2. FIG. 14 is a schematic diagram illustrating an output for one transmission frame output from the multiplexing unit when the mapping unit in this embodiment maps modulation symbols, pilot symbols, and zeros to resource elements as illustrated in FIGS. 14 and 15. is there. It is a schematic block diagram which shows the structure of the transmitter in 3rd Embodiment. FIG. 3 is a schematic diagram illustrating a transmission frame in which a mapping unit of a normal GI symbol generation unit in the embodiment maps modulation symbols and zeros to resource elements with respect to the data arrangement information illustrated in FIG. 2. FIG. 3 is a schematic diagram illustrating a transmission frame in which a mapping unit of a long GI symbol generation unit in the embodiment maps pilot symbols, modulation symbols, and zeros to resource elements with respect to the data arrangement information illustrated in FIG. 2. FIG. 13 is a schematic diagram showing symbols included in the output of one transmission frame output from the multiplexing unit when the mapping unit in the embodiment maps pilot symbols and modulation symbols as illustrated in FIGS. 13 and 14. is there. It is a schematic block diagram which shows the structure of the receiver in the same embodiment. It is a schematic block diagram which shows the structure of the transmitter in 4th Embodiment. 5 is a flowchart of an operation in which a mapping unit of a long GI symbol generation unit in the embodiment selects which of a pilot symbol, a modulation symbol, and a control symbol is arranged in a resource element. FIG. 21 is a schematic diagram illustrating symbols included in the output for one transmission frame output from the multiplexing unit when the mapping unit in the embodiment performs symbol mapping as illustrated in FIGS. 19 and 20. It is a schematic block diagram which shows the structure of the receiver in the same embodiment. It is the schematic block diagram which showed the structure of the transmitter in 5th Embodiment. FIG. 3 is a schematic diagram illustrating a transmission frame in which a mapping unit in the embodiment maps modulation symbols of information data signals and zeros to resource elements based on the data arrangement information illustrated in FIG. 2. It is the schematic diagram which showed the symbol contained in the output for 1 transmission frame which a multiplexing part outputs, when mapping of the mapping part symbol in the same embodiment was performed. It is the schematic diagram which showed the symbol contained in the output for 1 transmission frame which a multiplexing part outputs, when mapping of the mapping part symbol in the same embodiment was performed. It is the figure which showed the result of carrying out IFFT processing of the subcarrier. It is the figure which showed the production | generation method of the long guard interval in the same embodiment. It is the figure which showed another example of the production | generation method of the long guard interval in the embodiment. It is the schematic which showed the structural example of the frame in the multicarrier transmission by OFDM in a prior art example. It is the schematic which shows the signal which reaches | attains a receiver from a transmitter via the multipath environment in a prior art example. It is the schematic of the spectrum which shows the relationship between the subcarriers in the signal transmission / reception by a multicarrier system in a prior art example.

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

(First embodiment)
The communication system according to the first embodiment includes a transmission device and a reception device that communicate using the OFDM scheme.
FIG. 1 is a schematic block diagram illustrating the configuration of the transmission device 100 according to the first embodiment. Transmitting apparatus 100 includes transmitting section 102, multiplexing section 103, normal GI symbol generating section 104 (first multicarrier symbol generating section), long GI symbol generating section 105 (second multicarrier symbol generating section), and encoding section 106. And a modulation unit 107, to which an antenna unit 101 is connected.
In transmission apparatus 100 in the first embodiment, symbols such as modulation symbols (first symbols) of information data signals, pilot symbols used for propagation path estimation, control symbols for transmitting control information, and the like are used for OFDM communication. Guard interval that is longer than the subcarrier that is mapped to one of the subcarriers and that is mapped to a subcarrier adjacent to the subcarrier to which a part of the symbols (second symbol) is mapped. Is added. The symbols are preferably symbols that need to be demodulated with high accuracy compared to modulation symbols of information data signals such as control symbols and pilot symbols among symbols transmitted by the transmitting apparatus 100. The partial symbols may be modulation symbols of an information data signal and the modulation symbols having high data importance. Below, the case where a long guard interval is added to the subcarrier adjacent to the subcarrier to which the pilot symbol is mapped will be described.

In transmitting apparatus 100, encoding section 106 performs error correction encoding on an information data signal that is a digital signal input from an apparatus constituting an upper layer (not shown), and outputs the information data signal to modulating section 107. Here, the error correction encoding performed by the encoding unit 106 is performed using, for example, a convolutional code, a turbo code, a low density parity check code (LDPC), or the like.
Modulation section 107 performs data modulation on the error correction encoded information data signal input from encoding section 106 to generate a modulation symbol, and generates the generated symbol as a normal GI symbol generation section 104 and a long GI symbol. Output to the unit 105. Here, the data modulation performed by the modulation unit 107 is performed using QPSK (Quadrature Phase Shift Keying), QAM (Quadrature Amplitude Modulation), or the like.

The normal GI symbol generation unit 104 receives a modulation symbol from the modulation unit 107 and pilot symbols and data arrangement information input from the outside. Also, the normal GI symbol generation unit 104 is a normal OFDM symbol (first multicarrier symbol) composed of a modulation symbol to which a normal guard interval (hereinafter referred to as normal GI) is added or a pilot symbol to which a normal GI is added. ) (Hereinafter also referred to as an OFDM symbol) in the time domain is generated and output to the multiplexing unit 103.
Here, the pilot symbol is a known signal used by the receiving apparatus for channel estimation, and may be a symbol modulated by a modulation scheme such as QPSK, similar to a modulation symbol obtained by data modulation of an information data signal. In order to maintain pilot symbol orthogonality for each user and each transmission antenna, it is preferable to use orthogonal codes such as Hadamard codes and Zadoff-Chu CAZAC (Constant Amplitude Zero Auto Correlation).
The long GI symbol generation unit 105 receives a modulation symbol from the modulation unit 107 and receives data arrangement information from the outside. The long GI symbol generation unit 105 adds a long guard interval (hereinafter referred to as a long GI) to the modulation symbol input from the modulation unit 107, and adds a long OFDM symbol (first OFDM symbol) to which the long GI is added. 2 multi-carrier symbols) in the time domain is generated and output to the multiplexing unit 103.

  Multiplexer 103 is a signal (transmission symbol) obtained by adding (multiplexing) the normal OFDM symbol output from normal GI symbol generator 104 and the time domain signal of the long OFDM symbol output from long GI symbol generator 105. Is output to the transmission unit 102. The antenna unit 101 is connected to the transmission unit 102 and transmits a signal generated by the transmission device 100. The transmission unit 102 converts the signal output from the multiplexing unit 103 into an analog signal (Digital to Analogue conversion), performs a filtering process to limit the band of the signal converted into the analog signal, and further performs the filtering process. The received signal is converted into a transmittable frequency band and transmitted via the antenna unit 101.

  The normal GI symbol generation unit 104 includes a mapping unit 108, an IFFT unit 109, and a normal guard interval insertion unit 110 (hereinafter referred to as a normal GI insertion unit 110 (first guard interval insertion unit)).

  In normal GI symbol generation section 104, mapping section 108 determines the modulation symbol input from modulation section 107, which is a symbol obtained by modulating the information data signal, and the input pilot symbol based on the input data arrangement information. And mapping to the resource elements constituting the transmission frame. Here, the transmission frame includes a plurality of OFDM symbols including a plurality of subcarriers, and is represented by a predetermined frequency and time interval. The transmission frame will be described with reference to FIG.

  FIG. 2 is a schematic diagram showing the configuration of the transmission frame in the first embodiment, where the vertical axis indicates the subcarrier number k (subcarrier index) and the horizontal axis indicates the OFDM symbol number l (OFDM symbol index). Show. Further, as shown in the figure, an example of mapping between modulation symbols and pilot symbols of an information data signal is shown. The transmission frame includes 14 OFDM symbols including 12 subcarriers, and includes 168 resource elements. The resource element indicated by the kth subcarrier included in the lth OFDM symbol is referred to as resource element (k, l).

A resource element is a minimum unit constituting a transmission frame, and is a unit for mapping a modulation symbol obtained by modulating an information data signal and a pilot symbol by the modulation unit 107. The data arrangement information is a signal indicating to which resource element the modulation symbol and the pilot symbol are mapped. The data arrangement information may include information indicating the position of the modulation symbol and information indicating the position of the pilot symbol, may include only information indicating the position of the pilot symbol, or may be a normal guard interval. May be information indicating a resource element to which the GI is added and a resource element to which the long GI is added.
In FIG. 2, pilot symbols are mapped to resource elements indicated by diagonal lines, and modulation symbols are mapped to white resource elements.

  Returning to FIG. 1, mapping section 108 identifies a resource element that maps a pilot symbol from input data arrangement information, maps the pilot symbol, and in the frequency direction with respect to the resource element to which the pilot symbol is mapped. Zero (null) is mapped to a plurality of adjacent resource elements, and modulation symbols are mapped to resource elements other than the resource elements to which pilot symbols and zeros are mapped.

IFFT section 109 receives from transmission section 108 a transmission frame in which modulation symbols, pilot symbols, and zeros are mapped. Also, IFFT section 109 converts each symbol from a frequency domain signal to a time domain signal by performing IFFT processing for each OFDM symbol transmitted at the same time constituting the input transmission frame.
The normal GI insertion unit 110 adds a guard interval to the signal converted by the IFFT unit 109. The guard interval added by the normal GI insertion unit 110 is also referred to as a normal guard interval (first guard interval).

Here, the guard interval insertion processing performed by the normal GI insertion unit 110 will be described. FIG. 3 is a diagram showing a normal guard interval insertion method by the normal GI insertion unit 110 in the same embodiment. A time domain signal converted by the IFFT unit 109, for example, a time domain signal having an effective symbol length A shown in FIG. A part of the end (signal G having a predetermined guard interval length B) is copied and inserted in front of the signal. The effective symbol period is a period of a signal output from the IFFT unit 109 and the IFFT unit 112 (described later). The symbol shown in FIG. 3C generated by inserting the signal G forward is an OFDM symbol, and the length (A + B) of the OFDM symbol is called an OFDM symbol length.
A signal G having a predetermined length B that is copied and inserted forward is a normal guard interval (hereinafter referred to as a normal GI), and the length of the signal G is a guard interval length. The guard interval length is called normal GI length. A guard interval longer than the normal GI is a long guard interval (expanded guard interval, extended GI, hereinafter referred to as long GI). The process of inserting the guard interval is the same as the known guard interval insertion process that is normally performed in ODFM communication.

Returning to FIG. 1, long GI symbol generation section 105 includes mapping section 111, IFFT section 112, and long guard interval insertion section 113 (hereinafter referred to as long GI insertion section 113 (second guard interval insertion section)).
In long GI symbol generation section 105, mapping section 111 identifies a resource element to which a pilot symbol is mapped from data arrangement information input from the outside, and modulates the resource element adjacent to the resource element in the frequency direction. The modulation symbol in which the information data signal is modulated by unit 107 is mapped, and zero is mapped to other resource elements.

The IFFT unit 112 receives a transmission frame in which a modulation symbol and zero are mapped from the mapping unit 111, and performs IFFT processing for each OFDM symbol transmitted at the same time constituting the input transmission frame. Convert symbols from frequency domain signals to time domain signals.
Similarly to the normal GI insertion unit 110, the long GI insertion unit 113 adds a guard interval to the time domain signal output from the IFFT unit 112. Here, the guard interval added by the long GI insertion unit 113 is longer than the guard interval added by the normal GI insertion unit 110, and is referred to as a long GI (second guard interval). When the guard interval length added by the normal GI insertion unit 110 is τ ₁ and the guard interval length added by the long GI insertion unit 113 is τ ₂ , τ ₂ > τ ₁ is satisfied.

  In addition, when data arrangement information for mapping pilot symbols to resource elements (K, L) is input, mapping section 108 uses resource elements (K ± n, L) in the vicinity of resource elements that map pilot symbols in a transmission frame. -M) (where n = 1, 2,..., N, m = 0, 1,... M) is mapped to zero (null). Here, N and M are values that allow the receiving apparatus to decode pilot symbols with respect to temporal fluctuation and frequency fluctuation of a propagation path in which communication is performed. N and M may be dynamically changed, or a fixed value calculated from a statistical average value of temporal variation and frequency variation of the propagation path may be used. It is also possible to select N and M according to available resource elements among resource elements that map pilot symbols for other users or other streams.

The long GI insertion unit 113 adds a guard interval that satisfies τ ₂ ≦ M × T _sym −T _eff . However, T _sym is the OFDM symbol length output from the normal GI insertion unit 110, and T _eff is the symbol length (effective symbol period) output from the IFFT unit 112.
Note that M is preferably set to a length that satisfies τ ₂ ≧ τ _MAX . Here, τ _MAX is the maximum delay time with respect to the preceding wave of the delayed wave arriving at the receiving device.
For example, the transmission apparatus 100 obtains the maximum delay time based on feedback from the reception apparatus, and determines resource elements in the vicinity of pilot symbols to which the mapping unit 108 maps zeros. For feedback from the receiving device, a known configuration can be used for such feedback, and illustration and detailed description thereof are omitted. The guard interval added by the long GI insertion unit 113 is also referred to as a long guard interval (long GI).
In the following description, a case where M = 2 will be described. At this time, the long GI insertion unit 113 can add a long GI that satisfies τ ₂ ≦ 2 × T _sym −T _eff . The long GI length of the guard interval added by the long GI insertion unit 113 is preferably set as τ ₂ = 2 × T _sym −T _eff .

  Next, an example of mapping modulation symbols, pilot symbols, and zeros by the mapping units 108 and 111 will be described with reference to FIGS. Here, the resource elements near the resource element (K, L) to which the pilot symbol in the transmission frame is mapped are (K ± n, L−m) (where n = 1, 2, m = 0, 1). There are 8 resource elements represented. At this time, in long GI symbol generation section 105, mapping section 111 modulates two subcarriers having a high frequency in the vicinity and two subcarriers having a low frequency in the vicinity with respect to the subcarrier in which the pilot symbol is arranged. Map symbols.

First, FIG. 4 is a schematic diagram showing a transmission frame in which the mapping unit 108 of the normal GI symbol generation unit 104 maps pilot symbols, modulation symbols, and zeros to the data arrangement information shown in FIG.
At this time, the mapping unit 108 maps the modulation symbols to the white resource elements marked with solid lines, maps the pilot symbols to the resource elements marked with solid lines and filled with diagonal lines, and resources marked with broken lines Map zeros to elements. Mapping section 108 maps zeros to resource elements in the vicinity of resource elements to which pilot symbols are mapped. For example, the mapping unit 108 sets zero to (6, 1), (6, 2), (7, 1), (7, 2), (9, 1), for the pilot symbol (8, 2), Mapping is performed on eight resource elements (9, 2), (10, 1), and (10, 2).

FIG. 5 is a schematic diagram showing a transmission frame in which the mapping unit 111 of the long GI symbol generation unit 105 maps the modulation symbol and zero to the data arrangement information shown in FIG.
At this time, the mapping unit 111 maps a modulation symbol to a white resource element marked with a solid line and maps zero to a resource element marked with a broken line. Mapping section 111 arranges modulation symbols in subcarriers near the subcarrier in which pilot symbols are arranged in the OFDM symbols to which mapping section 108 maps pilot symbols. For example, the mapping unit 111 has four resource elements (6, 2), (7, 2), (9, 2), and (10, 2) as modulation symbols for the pilot symbol (8, 2). To map. In OFDM symbol number 2, neighboring subcarriers are subcarriers (k = 1, 3, 7, 9) adjacent to subcarriers (k = 2, 8) in which pilot symbols are arranged, and the subcarriers. Adjacent subcarriers (k = 4, 6, 10).

  The number of adjacent subcarriers to which long GI is added is set according to the degree of inter-carrier interference (ICI) that occurs in the communication environment. When ICI occurs between a wide range of subcarriers, long GI is added. When the number of adjacent subcarriers is increased and ICI occurs only between adjacent subcarriers, a long GI may be added only to adjacent subcarriers, or may be determined in advance.

Next, FIG. 6 is included in the output of one transmission frame of the multiplexing unit 103 when the mapping units 108 and 111 map modulation symbols, pilot symbols, and zeros as illustrated in FIGS. 4 and 5. It is the schematic diagram which showed the symbol. The horizontal axis direction indicates the OFDM symbol number l. The vertical axis direction indicates the subcarrier number k.
The shaded portion (the second and eighth subcarriers in the second OFDM symbol (l = 2)) indicates that pilot symbols are mapped. Also, a portion filled with dots indicates a guard interval.

Normal GI symbol generation section 104 outputs an OFDM symbol (first multicarrier symbol) obtained by adding normal GI to the pilot symbol and modulation symbol to multiplexing section 103.
Long GI symbol generation section 105 has a length equivalent to two normal OFDM symbols for each of two adjacent subcarriers having a high frequency adjacent to the subcarrier to which the pilot symbol is mapped and two adjacent subcarriers having a low frequency. And outputs a long OFDM symbol (second multicarrier symbol) including a long GI to the multiplexing unit 103.

  In the signal transmitted by transmitting apparatus 100, the effective symbol interval of the signal output from long GI symbol generation section 105 and the effective symbol interval of the signal output from normal GI symbol generation section 104 are the start position of the symbol interval and Since the timings of the end positions coincide with each other, the receiving apparatus that receives the transmitted signal can set the FFT interval without distinguishing between the modulation symbol and the pilot symbol as in the conventional case without considering the long guard interval. Thus, the pilot symbol and the modulation symbol can be separated. Thus, the receiving device does not have to perform new processing when receiving and demodulating the signal transmitted by the transmitting device 100.

In the present embodiment, a configuration in which a long guard interval is added to a symbol mapped to both a subcarrier with a high frequency and a subcarrier with a low frequency close to the subcarrier to which the pilot symbol is mapped is provided. However, a long guard interval may be added to only one of a high-frequency subcarrier and a low-frequency subcarrier, and is selected according to the degree of ICI generated.
Hereinafter, as a modified example of the present embodiment, a long guard interval is used for symbols mapped to two neighboring subcarriers (N = 2) on either one of the high and low frequencies with respect to the subcarriers on which pilot symbols are mapped. The case where is added will be described.

FIG. 7 is a schematic diagram showing a transmission frame in which the mapping unit 108 of the normal GI symbol generation unit 104 maps pilot symbols, modulation symbols, and zeros to resource elements with respect to the data arrangement information shown in FIG.
The mapping unit 108 maps the modulation symbol to the white resource element marked with a solid line, maps the pilot symbol to the resource element marked with a solid line and filled with diagonal lines, and zeros to the resource element shown with a broken line To map. The mapping unit 108 maps zeros to resource elements in the vicinity of either the high frequency or the low frequency for the resource elements to which pilot symbols are mapped. For example, the mapping unit 108 assigns zero to four resource elements (9, 1), (9, 2), (10, 1), and (10, 2) for the pilot symbol (8, 2). Map.

FIG. 8 is a schematic diagram showing a transmission frame in which mapping section 111 of long GI symbol generation section 105 maps modulation symbols and zeros to resource elements with respect to the data arrangement information shown in FIG.
At this time, the mapping unit 111 maps a modulation symbol to a white resource element marked with a solid line and maps zero to a resource element marked with a broken line. Mapping section 111 arranges modulation symbols on neighboring subcarriers on either one of the high and low frequencies for subcarriers to which pilot symbols are mapped. For example, mapping section 111 maps modulation symbols to two resource elements (9, 2) and (10, 2) with high subcarrier frequencies for pilot symbols (8, 2).

Next, FIG. 9 is a schematic diagram illustrating symbols included in the output for one transmission frame output from the multiplexing unit 103 when the mapping units 108 and 111 perform the mapping illustrated in FIGS. 7 and 8. . The horizontal axis direction indicates the OFDM symbol number l. The vertical axis direction indicates the subcarrier number k.
The shaded portion (second and eighth subcarriers in the second OFDM symbol (l = 2)) indicates a section in which pilot symbols are mapped. Also, a portion filled with dots indicates a guard interval.
Normal GI symbol generation section 104 adds normal GI to the pilot symbols and modulation symbols arranged by mapping section 108 and outputs the result to multiplexing section 103.
Long GI symbol generation section 105 is one of two subcarriers having a high frequency close to the subcarrier to which the pilot symbol is mapped, or two subcarriers having a low frequency close to the subcarrier to which the pilot symbol is mapped. An OFDM symbol having a double OFDM symbol length (long OFDM symbol) including a modulation symbol with a long GI added to each subcarrier is generated and output to multiplexing section 103.

Thus, by reducing the number of subcarriers that map the long guard interval, it is possible to suppress a decrease in transmission efficiency caused by mapping the long guard interval.
7 to 9, the mapping unit 111 maps the modulation symbols to the third, fourth, ninth, and tenth subcarriers. However, the mapping is not limited to this, and the pilot symbols are mapped. Any of the adjacent subcarriers with high subcarrier frequencies or adjacent subcarriers with low frequencies may be used, or they may be selected at random. At this time, mapping section 108 maps zero to the resource element corresponding to the subcarrier selected by mapping section 111.

  In the present embodiment, a configuration has been described in which a subcarrier to which a long guard interval (second guard interval) is added is a subcarrier that is adjacent to a subcarrier in which a pilot symbol is arranged. However, a modulation symbol to which a normal guard interval is added may be mapped between a subcarrier in which a pilot symbol is arranged and a neighboring subcarrier to which a long guard interval is added.

Next, FIG. 10 is a schematic block diagram illustrating a configuration of the receiving device 200 in the present embodiment.
As illustrated, receiving apparatus 200 includes receiving section 202, pilot symbol processing section 203, normal GI symbol processing section 204 (first multicarrier symbol processing section), and long GI symbol processing section 205 (second multicarrier symbol). A processing unit), a demodulation unit 206, and a decoding unit 207, to which an antenna unit 201 is connected.
In the receiving device 200, when the receiving unit 202 receives a signal transmitted from the transmitting device 100 via the antenna unit 201, the receiving unit 202 converts the signal into a frequency band capable of digital signal processing, such as signal detection processing, and further performs a band limiting filtering process. Then, the filtered signal is converted from an analog signal to a digital signal (analogue to digital conversion), and output to the normal GI symbol processing unit 204 and the long GI symbol processing unit 205.

Pilot symbol processing section 203 performs channel estimation using pilot symbols included in the received signal input from normal GI symbol processing section 204. The normal GI symbol processing unit 204 performs modulation symbol detection processing on a normal OFDM symbol (first multicarrier symbol) including a normal guard interval in the received signal input from the receiving unit 202. Long GI symbol processing section 205 performs modulation symbol detection processing on a long OFDM symbol (second multicarrier symbol) including a long guard interval in the received signal input from receiving section 202.
Demodulation section 206 performs demodulation processing such as QPSK and 16QAM on the signals input from normal GI symbol processing section 204 and long GI symbol processing section 205 and outputs the demodulated signal to decoding section 207. Decoding section 207 performs error correction decoding processing on the signal input from demodulation section 206, and calculates and outputs an information data signal from the error correction decoded signal.

The normal GI symbol processing unit 204 includes a normal GI-FFT section extraction unit 210, an FFT unit 211, a channel distortion compensation unit 212, and a demapping unit 213. The normal GI-FFT interval extraction unit 210 removes the normal guard interval interval of the guard interval length τ ₁ from the input signal input from the reception unit 202, and the normal GI symbol generation unit 104 maps the modulation symbols and pilot symbols. The FFT interval T _eff of the normal OFDM symbol is extracted.
11 shows a normal OFDM symbol extracted from the input signal input from the receiving section 202 by the normal GI-FFT section extracting section 210 when the receiving apparatus 200 receives the transmission frame shown in FIG. It is a schematic diagram which shows a FFT area. The normal GI-FFT section extraction unit 210 removes the other than the FFT section (guard interval) extracted from the received signal, thereby removing all normal OFDM symbols from the first to the 14th with the normal guard interval added. The FFT interval T _eff of the modulation symbol and pilot symbol is extracted. Here, the shaded portion indicates a section in which pilot symbols are mapped. A white portion indicates a section in which a modulation symbol is mapped. Also, a portion filled with dots indicates a section in which the guard interval is mapped.

Returning to FIG. 10, the FFT unit 211 removes the normal guard interval by the normal GI-FFT section extraction unit 210 and performs FFT processing on the extracted section T _eff to convert the time domain signal into the frequency domain signal. The signal is converted and output to pilot symbol processing section 203 and propagation path distortion compensation section 212. That is, FFT section 211 performs FFT processing on each of the modulation symbol and pilot symbol FFT sections extracted by normal GI-FFT section extraction section 210 shown in FIG.
Pilot symbol processing section 203 includes pilot extraction section 208 and propagation path estimation section 209. The pilot extraction unit 208 extracts pilot symbols included in the frequency domain signal input from the FFT unit 211. The propagation path estimation unit 209 performs propagation path estimation for estimating fluctuations in amplitude and phase due to fading and the like using the pilot symbols extracted by the pilot extraction unit 208, and normalizes the propagation path estimation value as a propagation path estimation result. The data is output to the GI symbol processing unit 204 and the long GI symbol processing unit 205. Here, in the propagation path estimation performed by the propagation path estimation unit 209, a known propagation path estimation technique such as linear interpolation or FFT interpolation is used as a propagation path estimation method for resource elements other than resource elements to which pilot symbols are mapped. To do.

  The propagation path distortion compensation unit 212 calculates a weighting factor based on the propagation path estimation value estimated by the propagation path estimation unit 209 according to a ZF (Zero Forcing) standard, an MMSE (Minimum Mean Square Error) standard, and the like. Then, compensation of the amplitude variation and the phase variation (propagation channel compensation) is performed on the frequency domain signal input from the FFT unit 211 using the calculated weighting factor. The demapping unit 213 extracts (demapping) a modulation symbol mapped to a subcarrier by the mapping unit 108 of the transmission apparatus 100 and added with a normal guard interval from the signal input from the propagation path distortion compensation unit 212. To the demodulator 206.

The long GI symbol processing unit 205 includes a long GI-FFT section extraction unit 214, an FFT unit 215, a propagation path distortion compensation unit 216, and a demapping unit 217. The long GI-FFT section extraction unit 214 performs the guard interval length τ ₂ at the timing of the second, sixth, ninth, and thirteenth long OFDM symbols constituting the reception signal with respect to the reception signal input from the reception unit 202. The long GI symbol generator 105 extracts the FFT section of the long OFDM symbol to which the modulation symbol is mapped.
FIG. 12 shows a long OFDM symbol extracted by the long GI-FFT section extraction unit 214 from the reception signal input from the reception unit 202 when the reception device 200 receives the transmission frame shown in FIG. It is a schematic diagram which shows a FFT area. The long GI-FFT interval extraction unit 214 removes the long guard interval interval τ ₂ from the received signal, thereby the modulation symbols of the second, sixth, ninth and thirteenth long OFDM symbols to which the long guard interval is added. An FFT interval T _eff is extracted.

Returning to FIG. 10, the FFT unit 215 removes the long guard interval by the long GI-FFT interval extraction unit 214 and performs FFT processing on the extracted interval T _eff to convert the time domain signal into the frequency domain signal. The converted signal is output to the propagation path distortion compensation unit 216. That is, FFT section 215 performs FFT processing on each FFT section of the modulation symbol extracted by long GI-FFT section extraction section 214 shown in FIG.
Similarly to the propagation path distortion compensation unit 212, the propagation path distortion compensation unit 216 calculates a weighting factor based on the propagation path estimation value estimated by the propagation path estimation unit 209 according to the ZF criterion, the MMSE criterion, and the like, and calculates the calculated weight. Compensation of the amplitude variation and the phase variation (propagation channel compensation) is performed on the frequency domain signal input from the FFT unit 215 using the coefficient. The demapping unit 217 extracts a modulation symbol mapped to a subcarrier by the mapping unit 111 of the transmission apparatus 100 and added with a long guard interval from the signal input from the propagation path distortion compensation unit 216, and outputs the modulation symbol to the demodulation unit 206. Output.

FIG. 13 is a schematic diagram illustrating orthogonality of signals received from the transmission device 100 by the reception device 200. At this time, the signal received by the receiving apparatus 200 includes a delayed wave that exceeds the normal guard interval length and has a delay equal to or shorter than the long guard interval length. The horizontal axis direction indicates normalized frequencies, and each numerical value indicates a frequency (subcarrier number) to which a subcarrier is mapped. In addition, the subcarrier of x = 0 is shown as a reference. The vertical axis direction indicates the normalized power (signal strength) of the received signal.
A spectrum indicated by a solid line is a spectrum of a subcarrier to which a modulation symbol to which a long guard interval is added is mapped. The spectrum of the subcarrier indicated by the solid line indicates that the amplitude is zero (null) at a point indicating another subcarrier and does not interfere with another subcarrier.
On the other hand, a spectrum indicated by a broken line is a spectrum of a subcarrier to which a modulation symbol to which a normal guard interval is added is mapped. The spectrum of the subcarrier indicated by the broken line indicates that the amplitude is not zero at the point indicating the other subcarrier and interferes with the other subcarrier.

  Next, FIG. 14 is a schematic diagram illustrating orthogonality between subcarriers of a signal received by the receiving apparatus 200 from the transmitting apparatus 100. At this time, the signal received by the receiving apparatus 200 includes a delayed wave that has a delay exceeding the normal guard interval length and not longer than the long guard interval length. The spectrum of each subcarrier is a frequency domain signal obtained by performing FFT processing on the second OFDM symbol (l = 2) shown in FIG. In addition, although the signal of each subcarrier becomes a sinc function, only the main lobe is illustrated and the side lobe is omitted.

As shown in FIG. 6, modulation symbols to which a long guard interval is added are mapped to neighboring subcarriers (k = 1, 3, 4, 6, 7, 9, 10). Accordingly, when the FFT unit 211 performs the FFT process on the second OFDM symbol, the normal GI-FFT interval extraction unit 210 for the pilot symbol extracts the neighboring subcarriers (k = 1, 3, It is possible to prevent the presence of the previous modulation symbol due to a delay longer than the long guard interval length of 4, 6, 7, 9, 10). As a result, the spread of the spectrum of neighboring subcarriers can be suppressed, and the spectrum of adjacent subcarriers can be (zero) null in the subcarriers (k = 2, 8) including the pilot symbols. Therefore, receiving apparatus 200 can receive a signal that does not include signal components of adjacent subcarriers (k = 1, 3, 4) at the subcarrier point of subcarrier number k = 2. In addition, receiving apparatus 200 can receive a signal that does not include signal components of neighboring subcarriers (k = 6, 7, 9, 10) at the subcarrier point of subcarrier number k = 8.
That is, in receiving apparatus 200, the spectrum of neighboring subcarriers (k = 1, 3, 4, 6, 7, 9, 10) output from FFT section 211 is the spectrum indicated by the solid line in FIG. Inter-carrier interference to the included subcarriers (k = 2, 8) can be reduced. Therefore, with respect to the signal transmitted from the transmission apparatus 100 of the present embodiment, the reception apparatus 200 can perform propagation path estimation using pilot symbols that are less affected by inter-carrier interference and improve propagation path estimation accuracy. Can be made.

  In the transmission apparatus 100 of the present embodiment, in an environment where an incoming wave exceeding the normal guard interval section arrives, the normal GI symbol generation unit 104 arranges a scattered pilot symbol in the resource element of the transmission frame, and a long GI symbol Generation section 105 arranges a modulation symbol obtained by adding a long guard interval to a signal of a subcarrier adjacent to a subcarrier on which the scattered pilot symbol is arranged. Thus, when decoding the transmission frame configured as described above, receiving apparatus 200 can reduce transmission errors due to inter-carrier interference due to neighboring subcarriers with respect to subcarriers where scattered pilot symbols are arranged. In addition, it is possible to improve the accuracy of channel estimation for calculating the channel estimation value from the scattered pilot symbols.

Transmitting apparatus 100 of the present embodiment has a normal guard interval and a long guard interval longer than the normal guard interval, and an OFDM symbol including the long guard interval (second multicarrier symbol) includes an OFDM that includes the normal guard interval. Arranged in a subcarrier adjacent to a subcarrier in which a symbol (first multicarrier symbol) is arranged. Since an OFDM symbol including a long guard interval includes a longer guard interval than an OFDM symbol including a normal guard interval, a carrier due to a delay in the propagation path is compared with a case where only an OFDM symbol including a normal guard interval is arranged on a Cebu carrier. Interference can be suppressed.
In addition, OFDM symbols arranged in subcarriers close to OFDM symbols including long guard intervals are less likely to deteriorate communication quality due to inter-carrier interference, and channel estimation using symbols included in the OFDM symbols is It is possible to obtain a highly accurate estimation result. By performing propagation path compensation in which the obtained propagation path estimation result is reflected not only on the subcarrier on which the OFDM symbol is arranged but also on adjacent subcarriers, in a plurality of subcarriers used for multicarrier modulation, Communication quality can be improved.

Also, receiving apparatus 200 performs channel compensation for subcarriers in which no scattered pilot symbols are arranged based on the channel estimation value calculated from the received signal with normal GI and long GI of the present invention. By doing so, transmission path errors of the entire subcarrier can be reduced. In addition, since the receiving apparatus 200 can perform propagation path estimation with high accuracy in an environment where an incoming wave exceeding a normal guard interval section arrives, for example, iterative processing (such as interference cancellation or turbo equalization for removing inter-symbol interference) ( By using turbo processing, it is possible to accurately decode an information data signal and improve communication transmission efficiency.
Furthermore, since the transmission apparatus 100 replaces some guard intervals with long guard intervals compared to the case where all the guard interval sections are lengthened, it improves the accuracy of channel estimation without reducing the overall transmission efficiency. be able to.

In this embodiment, the case of using two types of guard intervals, that is, the normal guard interval and the long guard interval has been described. You may make it the structure added to a symbol. That is, a normal guard interval that is a first guard interval and a long guard interval that is a plurality of types of second guard intervals may be used. In that case, transmitting apparatus 100 includes a plurality of symbol generation units that generate OFDM symbols whose length of a long OFDM symbol including a long guard interval is an integer multiple of the length of a normal OFDM symbol including a normal guard interval. .
In the present embodiment, the symbols to which the long GI is added are mapped with one symbol to which the normal GI is added (in FIG. 6, one pilot symbol), but are mapped with a plurality of symbols. May be.

In the present embodiment, the case where a long guard interval is added to a signal mapped to subcarriers close to all input pilot symbols has been described, but the present invention is not limited to this. For example, a long guard interval may be added to signals mapped to subcarriers close to some pilot symbols, and normal guard intervals may be added to other pilot symbols. Thereby, a reduction in transmission efficiency can be suppressed.
In this embodiment, a long guard interval is added to a signal mapped to a subcarrier adjacent to a subcarrier to which a pilot symbol is mapped. However, the present invention is not limited to this. By adding a long guard interval to a signal that maps to a subcarrier adjacent to a subcarrier that maps a signal that includes control information that controls the reception information, the receiving apparatus 200 can accurately acquire control information, Transmission efficiency can be improved.

(Second Embodiment)
The second embodiment is a modification of the first embodiment, and differs from the first embodiment in the mapping of modulation symbols, pilot symbols, and zeros by the mapping units 108 and 111 of the transmission apparatus 100.
FIG. 15 illustrates a transmission in which the mapping unit 108 of the normal GI symbol generation unit 104 in the second embodiment maps modulation symbols, pilot symbols, and zeros to resource elements with respect to the data arrangement information illustrated in FIG. It is a schematic diagram which shows a frame. The horizontal axis direction represents time and represents the OFDM symbol number l. The vertical axis direction indicates the frequency and indicates the subcarrier number k.
In FIG. 15, modulation symbols or pilot symbols are mapped to resource elements marked with a solid line, and zeros (null, null) are mapped to resource elements marked with a broken line. Mapping section 108 maps zero to resource elements on both sides adjacent in the frequency direction to resource elements to which pilot symbols are mapped, maps pilot symbols to resource elements to map pilot symbols, and maps to other resource elements The modulation symbol in which the information data signal is modulated is mapped.

Next, FIG. 16 illustrates a transmission frame in which the mapping unit 111 of the long GI symbol generation unit 105 in the second embodiment maps modulation symbols and zeros to resource elements with respect to the data arrangement information illustrated in FIG. It is a schematic diagram which shows. The horizontal axis direction represents time and represents the OFDM symbol number l. The vertical axis direction indicates the frequency and indicates the subcarrier number k.
In FIG. 16, the mapping unit 111 maps modulation symbols to resource elements marked with solid lines, and maps zeros to resource elements marked with broken lines. That is, mapping section 111 maps modulation symbols only to resource elements on both sides adjacent to each other in the frequency direction with respect to resource elements to which pilot symbols are mapped, and maps zeros to resource elements other than the resource elements to which the modulation symbols are mapped. To do.

Next, FIG. 17 is included in the output of one transmission frame output from the multiplexing unit 103 when the mapping units 108 and 111 map modulation symbols, pilot symbols, and zeros as illustrated in FIGS. 15 and 16. It is the schematic diagram which showed the symbol. Here, the hatched portion indicates the section where the pilot symbol is arranged, and the filled portion indicates the section where the guard interval is arranged.
The long GI included in the long OFDM symbol output by the long GI symbol generation unit 105 is longer than the normal GI added by the normal GI symbol generation unit 104, and the long OFDM symbol length is double the normal OFDM symbol length. .
In OFDM, since the signal of each subcarrier becomes a sinc function, the subcarrier to which the pilot symbol is mapped receives the largest interference from adjacent subcarriers. Therefore, long GI symbol generation section 105 adds a long guard interval to the subcarrier adjacent to the subcarrier to which the pilot symbol is mapped, so that the subcarrier to which the pilot symbol is mapped and the adjacent subcarrier are mapped. It is possible to reduce intersubcarrier interference occurring between the subcarrier and the subcarrier. Further, in this embodiment, only the guard interval added to the subcarrier adjacent to the subcarrier to which the pilot symbol is mapped is replaced with the long guard interval, so that the accuracy of the channel estimation can be improved without reducing the overall transmission efficiency. Can be improved.

  In this embodiment, the long guard interval is added to the signal mapped to the subcarriers on both sides of the high frequency subcarrier and the low frequency subcarrier adjacent to the subcarrier to which the pilot symbol is mapped. A long guard interval may be added only to one of the adjacent subcarriers.

(Third embodiment)
FIG. 18 is a schematic block diagram illustrating a configuration of the transmission device 300 according to the third embodiment.
Transmitting apparatus 300 includes transmitting section 102, multiplexing section 303, normal GI symbol generating section 304 (first multicarrier symbol generating section), long GI symbol generating section 305 (second multicarrier symbol generating section), and encoding section 106. The modulation unit 107 is provided, and the antenna unit 101 is connected.
The transmission apparatus 300 replaces the multiplexing unit 103, normal GI symbol generation unit 104, long GI symbol generation unit 105, and mapping units 108 and 111 in the transmission apparatus 100 of the first embodiment illustrated in FIG. Unlike the transmission apparatus 100 of the first embodiment, the normal GI symbol generation unit 304, the long GI symbol generation unit 305, and the mapping units 308 and 311 are provided. The input points are different. The other components are the same as those in the first embodiment, and thus the same reference numerals (101, 102, 106, 107, 109, 110, 112, 113) are given and description thereof is omitted.

  The normal GI symbol generation unit 304 includes a mapping unit 308, an IFFT unit 109, and a normal GI insertion unit 110. Based on data arrangement information input from the outside, mapping section 308 is in the frequency domain for resource elements that map the pilot symbols and resource elements that map the pilot symbols among the resource elements that make up the transmission frame. Zero (null) is mapped to a plurality of adjacent predetermined resource elements. In addition, among the resource elements constituting the transmission frame, the modulation unit 107 maps the modulation symbol obtained by modulating the information data signal to the resource elements excluding the resource element to which zero is mapped.

  The long GI symbol generation unit 305 includes a mapping unit 311, an IFFT unit 112, and a long GI insertion unit 113. Based on data arrangement information input from the outside, mapping section 311 maps pilot symbols to resource elements that map pilot symbols among resource elements that constitute a transmission frame, and for resource elements that map pilot symbols Thus, a modulation symbol in which the information data signal is modulated is mapped to a plurality of predetermined resource elements close to the frequency domain. Further, the mapping unit 311 maps zero to resource elements excluding resource elements to which the pilot symbols are mapped and resource elements to which the modulation symbols are mapped.

  The modulation symbol MCS (Modulation and Coding) input to the normal GI symbol generation unit 304 by the modulation unit 107 and the modulation symbol input to the long GI symbol generation unit 305 by the modulation unit 107 The MCS may be different. In consideration of the length of the guard interval, the modulation symbol mapped to the resource element to which the long guard interval is added has a larger modulation multi-level than the modulation symbol to be mapped to the resource element to which the normal guard interval is added. Further, it is possible to suppress a decrease in transmission efficiency due to the provision of the long guard interval.

FIG. 19 is a schematic diagram illustrating a transmission frame in which the mapping unit 308 of the normal GI symbol generation unit 304 maps modulation symbols and zeros to resource elements with respect to the data arrangement information illustrated in FIG. 2 in the present embodiment. is there.
FIG. 20 is a schematic diagram illustrating a transmission frame in which the mapping unit 311 of the long GI symbol generation unit 305 maps pilot symbols, modulation symbols, and zeros to the data arrangement information illustrated in FIG. 2 in the present embodiment. FIG.
The mapping unit 311 has a guard interval (long guard interval) longer than a normal guard interval period for the subcarrier to which the pilot symbol is mapped and the modulation symbol mapped to each of the subcarriers adjacent to the subcarrier. Add a section. At this time, the long guard interval added by the mapping unit 311 adds a length τ ₂ that satisfies τ ₂ = 2 × T _sym −T _eff . This relational expression has already been explained.
In this embodiment, a long guard interval is added to a subcarrier to which a pilot symbol is mapped and a modulation symbol to be mapped to a subcarrier adjacent to the subcarrier, but the pilot symbol is mapped. A long guard interval may be added to a plurality of subcarriers close to the subcarrier.

  As illustrated in FIG. 19, the mapping unit 308 maps modulation symbols to resource elements marked with solid lines, and maps zeros to resource elements marked with broken lines. That is, the mapping unit 308 has resource elements (K, L) = (2, 2), (8, 2), (5, 6), (11, 6), (2, 9) to which pilot symbols are mapped. , (8, 9), (5, 13), (11, 13), the resource element (K ± 1, L) of the subcarrier adjacent to the resource element, the resource element to which the pilot symbol is mapped, and the To the resource elements (K, L−1) and (K ± 1, L−1) that are immediately before the resource element of the subcarrier adjacent to the resource element (the ODFM symbol number is one less). Map zero and map modulation symbols to other resource elements in the transmission frame.

  As illustrated in FIG. 20, the mapping unit 311 maps pilot symbols to resource elements marked with a solid line and filled with diagonal lines, maps modulation symbols to outlined resource elements marked with a solid line, and Map zeros to resource elements marked with. That is, the mapping unit 311 has resource elements (K, L) = (2, 2), (8, 2), (5, 6), (11, 6) to which the pilot symbols indicated by the data arrangement information are mapped. , (2, 9), (8, 9), (5, 13), (11, 13) are mapped to pilot symbols, and resource elements (K ± 1, L) adjacent to the resource element in the subcarrier direction Map modulation symbols to zero and map zeros to other resource elements in the transmission frame.

Multiplexing section 303 adds (multiplexes) the time domain signal output from normal GI symbol generation section 304 and the time domain signal output from long GI symbol generation section 305. FIG. 21 illustrates symbols included in the output of one transmission frame output from the multiplexing unit 303 when the mapping units 308 and 311 map pilot symbols and modulation symbols as illustrated in FIGS. 19 and 20. It is a schematic diagram shown. In FIG. 21, the vertical axis represents subcarriers (frequency), and the horizontal axis represents OFDM symbol numbers (time). In FIG. 21, the shaded portion indicates a section where pilot symbols are arranged, and the portion filled with dots indicates a section where guard intervals are arranged.
Long GI symbol generation section 305 has a length twice as long as a normal OFDM symbol length in a subcarrier to which a pilot symbol is mapped in OFDM symbols and two subcarriers adjacent to the subcarrier. A long OFDM symbol including GI is arranged.

FIG. 22 is a schematic block diagram showing the configuration of the receiving device 400 in this embodiment. The receiving apparatus 400 includes a receiving unit 202, a pilot symbol processing unit 203, a normal GI symbol processing unit 404, a long GI symbol processing unit 405, a demodulation unit 206, and a decoding unit 207, to which an antenna unit 201 is connected.
The receiving apparatus 400 replaces the normal GI symbol processing section 204 and the long GI symbol processing section 205 in the receiving apparatus 200 of the first embodiment shown in FIG. 7 with a normal GI symbol processing section 404 (first multicarrier symbol processing). And a long GI symbol processing unit 405 (second multicarrier symbol processing unit), and there is no connection between the normal GI symbol processing unit 404 and the pilot symbol processing unit 203, and long GI symbol processing Connection between unit 405 and pilot symbol processing unit 203 is provided. The other parts are the same as those in the first embodiment, and thus the same reference numerals (201 to 203, 206 to 217) are given and description thereof is omitted, and different parts from the receiving apparatus 200 will be described.

The normal GI symbol processing unit 404 includes a normal GI-FFT section extraction unit 210, an FFT unit 211, a propagation path distortion compensation unit 212, and a demapping unit 213. The normal GI symbol processing unit 404 differs from the normal GI symbol processing unit 204 of the first embodiment in that the FFT unit 211 outputs the frequency domain signal after the FFT processing only to the propagation path distortion compensation unit 212.
Long GI symbol processing section 405 includes long GI-FFT section extraction section 214, FFT section 215, propagation path distortion compensation section 216, and demapping section 217. In the long GI symbol processing unit 405, compared to the long GI symbol processing unit 205 of the first embodiment, the FFT unit 215 outputs the frequency domain signal after the FFT processing to the pilot symbol processing unit 203 and the propagation path distortion compensation unit 216. The point is different.

  By using the transmission device 300 and the reception device 400 in the present embodiment, the long GI symbol generation unit 305 is input in an environment where an incoming wave exceeding the normal guard interval section added by the normal GI symbol generation unit 304 arrives. Scattered pilot symbols are arranged on any subcarrier in the same OFDM symbol based on the data arrangement information to be transmitted, and the scattered pilot symbols and the subcarriers on which the scattered pilot symbols are arranged A long GI (second guard interval) period longer than the normal guard interval period is set for adjacent subcarriers. As a result, the resistance to inter-carrier interference can be greatly improved with respect to scattered pilot symbols, without increasing the guard interval section of all subcarriers and without greatly degrading the overall transmission efficiency. . As a result, the propagation path estimation unit 209 included in the reception apparatus 400 can improve the accuracy of propagation path estimation using the scattered pilot symbols. Also, since the guard interval (long guard interval, second guard interval) longer than the normal guard interval is set for the scattered pilot symbol, the symbol for the subcarrier in which the pilot symbol is arranged The resistance to interfering interference can be greatly improved.

(Fourth embodiment)
FIG. 23 is a schematic block diagram illustrating a configuration of a transmission device 500 according to the fourth embodiment. Transmitting apparatus 500 includes transmission section 102, multiplexing section 503, normal GI symbol generation section 304 (first multicarrier symbol generation section), long GI symbol generation section 505 (second multicarrier symbol generation section), and encoding section 106. The modulation unit 107 is provided, and the antenna unit 101 is connected. Also, the transmission apparatus 500 includes a multiplexing unit 503 and a long GI symbol generation unit 505 instead of the multiplexing unit 303 and the long GI symbol generation unit 305, as compared with the transmission apparatus 300 in the third embodiment illustrated in FIG. Further, the long GI symbol generation unit 505 is different in that a pilot symbol, a control symbol, and a modulation symbol obtained by modulating the information data signal are input to the long GI symbol generation unit 505. In the transmission apparatus 500, the other configurations are the same, and the same reference numerals (101, 102, 106, 107, 109, 110, 112, 113, 304, 308) are given, and the description thereof is omitted.

  Here, the control symbol is a signal that controls transmission operations such as a transmission rate and transmission timing, for example, a modulation scheme used for an information data signal, a mapping method (resource allocation method), error correction coding information (for example, Encoding method, coding rate, puncture pattern), interleaving method, scrambling method, HARQ (Hybrid Automatic Repeat reQuest) control information (eg, packet reception notification information (ACK), retransmission) Request signal (Negative Acknowledgment; NACK) and number of retransmissions), synchronization signal, MIMO (Multi-Input Multi-Output) control information (for example, number of layers (number of streams) and precoding method), base station Information, terminal information, control information format information, data information format information Information, feedback information (for example, CQI (Channel Quality Indicator)), transmission power control information, and the like, but are not limited thereto.

The long GI symbol generation unit 505 is different from the long GI symbol generation unit 305 in the third embodiment in that a mapping unit 511 is provided instead of the mapping unit 311. Mapping section 511 receives as input modulation symbols, pilot symbols and control symbols obtained by modulating information data signals, and data arrangement information, and maps pilot symbols to resource elements based on the input data arrangement information. The modulation symbols or control symbols are mapped to resource elements adjacent to each other in the subcarrier direction. Long GI symbol generation section 505 can improve control symbol transmission characteristics by preferentially arranging control symbols in resource elements with respect to pilot symbols.
FIG. 24 is a flowchart of an operation in which mapping section 511 of long GI symbol generation section 505 selects which one of pilot symbols, modulation symbols, and control symbols is arranged in a resource element. Here, the resource elements in which symbols are arranged by mapping section 511 are resource elements in which pilot symbols are arranged, and resource elements adjacent to the resource elements in the subcarrier direction based on the data arrangement information.

First, the mapping unit 511 determines, based on the data arrangement information, whether or not to place a scattered pilot symbol for the resource element to be arranged (step S101).
When the resource element is a resource element that arranges a pilot symbol (step S101: YES), the long GI symbol generation unit 505 arranges a pilot symbol in the resource element (step S102), and performs the next step S106.
On the other hand, when the resource element is not a resource element that arranges a pilot symbol (step S101: NO), the mapping unit 511 determines whether there is a control symbol that is not yet arranged in the resource element among the input control symbols. Is determined (step S103).

If there is a control symbol that is not arranged in the resource element (step S103: YES), the long GI symbol generation unit 505 arranges the control symbol in the resource element (step S104).
When there is no control symbol not arranged in the resource element (step S103: NO), the long GI symbol generation unit 505 arranges the modulation symbol input from the modulation unit 107 in the resource element (step S105).
The mapping unit 511 determines in the long GI symbol generation unit 505 whether there is a resource element that can still arrange the pilot symbol, the modulation symbol, and the control symbol (step S106).
When there is a resource resource element that can still be arranged (step S106: YES), the mapping unit 511 repeats the operation from step S101 again.
On the other hand, when there is no resource resource element that can be arranged (step S106: NO), the mapping unit 511 ends the arrangement of the symbols in the resource element.
As described above, mapping section 511 places control symbols in resource elements with priority over modulation symbols.
In the present embodiment, control symbols are adaptively arranged in priority. However, in a communication system to which a transmitter belongs, resource elements for arranging control symbols may be determined in advance.

Returning to FIG. 23, in transmission apparatus 500, multiplexing section 503 adds the time domain symbols output from normal GI symbol generation section 304 and the time domain symbols output from long GI symbol generation section 505.
FIG. 25 is a schematic diagram illustrating symbols included in the output of one transmission frame output from the multiplexing unit 503 when the mapping units 308 and 511 perform symbol mapping as illustrated in FIGS. 19 and 20. It is. The horizontal axis direction indicates the OFDM symbol number l, and the vertical axis direction indicates the subcarrier number k. Long GI symbol generation section 505 adds a long guard interval to subcarriers to which pilot symbols are mapped and to two subcarriers adjacent to the subcarriers to which the pilot symbols are mapped in the subcarrier direction.

  In the transmission frame, as shown in the figure, the hatched portion indicates a section where pilot symbols are arranged, and the hatched portion indicates a section where control symbols are arranged. Also, a portion filled with dots indicates a section where guard intervals are arranged. The long GI symbol generation unit 505 generates a long OFDM symbol having a long GI longer than the normal GI in the pilot symbol and the control symbol having a length equivalent to two normal OFDM symbols, and outputs the generated long OFDM symbol to the multiplexing unit 503. .

  Next, FIG. 26 is a schematic block diagram illustrating a configuration of the receiving device 600 in the present embodiment. Receiving apparatus 600 includes receiving section 202, pilot symbol processing section 203, normal GI symbol processing section 404 (first multicarrier symbol processing section), long GI symbol processing section 605 (second multicarrier symbol processing section), demodulation Unit 206 and decoding unit 207, to which the antenna unit 201 is connected. The normal GI symbol processing unit 404 includes a normal GI-FFT section extraction unit 210, an FFT unit 211, a propagation path distortion compensation unit 212, and a demapping unit 213. Long GI symbol processing section 605 has long GI-FFT section extraction section 214, FFT section 215, propagation path distortion compensation section 216, and demapping section 617.

The receiving apparatus 600 is different from the receiving apparatus 400 of the third embodiment illustrated in FIG. 22 in that a long GI symbol processing unit 605 is provided instead of the long GI symbol processing unit 405. The long GI symbol processing unit 605 is different from the long GI symbol processing unit 405 of the third embodiment in that it includes a demapping unit 617 instead of the demapping unit 217.
In the receiving apparatus 600, other configurations are the same, and the same reference numerals (201 to 203, 206 to 216) are given, and the description thereof is omitted. Hereinafter, a different part from the receiver 400 is demonstrated.
The demapping unit 617 extracts modulation symbols from the subcarriers to which the modulation symbols are arranged among the subcarriers to which the long guard interval is added from the frequency domain signal input from the propagation path distortion compensation unit 216, The extracted modulation symbols are output to the demodulation unit 206, and control symbols are extracted from the subcarriers on which the control symbols are arranged. The extracted control symbols are demodulated, demodulated, and then output to an upper layer (not shown).
The control symbol includes a known pattern that allows the demapping unit 617 to distinguish between the control symbol and the modulation symbol.

  By using the transmitting apparatus 500 and the receiving apparatus 600 in the present embodiment, a long GI symbol generation unit in an environment where there is an incoming wave that arrives later than the normal guard interval section added by the normal GI symbol generation unit 304 505 assigns a scattered pilot symbol to any subcarrier in the transmission frame based on the input data arrangement information, and from a normal guard interval to a subcarrier adjacent to the subcarrier. A long long GI (second guard interval) section is added. Thereby, the tolerance with respect to the intercarrier interference between the subcarrier which mapped the scattered pilot, and the adjacent subcarrier can be improved significantly. Alternatively, a long GI (second guard interval) section longer than the normal guard interval is added to the subcarrier in which the scattered pilot is arranged and the subcarrier adjacent to the subcarrier. As a result, the tolerance to inter-symbol interference in subcarriers mapped to scattered pilot symbols and inter-carrier interference between subcarriers mapped to scattered pilots and adjacent subcarriers can be greatly improved. It is possible to improve the accuracy of channel estimation. Also, the accuracy of channel estimation is improved without significantly degrading the transmission efficiency compared to the case where the guard interval of all subcarriers is lengthened to improve the tolerance of intersymbol interference and intercarrier interference for pilot symbols. can do.

  Further, the long GI symbol generation unit 505 receives the control symbol by preferentially arranging the control symbol in the resource element as compared with the modulation symbol modulated by the modulation unit 107 and treating it like the pilot symbol. Apparatus 600 can receive control symbols with high accuracy, can prevent retransmission of control symbols, and can improve communication quality.

(Fifth embodiment)
FIG. 27 is a schematic block diagram illustrating a configuration of a transmission device 700 according to the fifth embodiment. Transmitting apparatus 700 includes coding section 106, modulation section 107, normal GI symbol generation section 705 (first multicarrier symbol generation section), long GI symbol generation section 706 (second multicarrier symbol generation section), and multiplexing section 702. , IFFT unit 703, GI insertion unit 704, and transmission unit 102, and antenna unit 101 is connected thereto. The normal GI symbol generation unit 705 includes a mapping unit 108. The long GI symbol generation unit 706 includes a mapping unit 711 and a phase control unit 701. In addition, the same code | symbol (101,102,106-108) is attached | subjected to the same structure as 1st Embodiment, and description is abbreviate | omitted.
The transmission apparatus 700 has a configuration in which the order of IFFT processing, guard interval insertion, and multiplexing processing is changed with respect to the transmission apparatus 100 of the first embodiment illustrated in FIG. Transmitting apparatus 700 receives pilot symbols, information data signals, and data arrangement information as inputs, multiplexes symbols generated by normal GI symbol generation section 705 and long GI symbol generation section 706, and then performs IFFT processing and Insert a guard interval and transmit. The mapping unit 711 maps the modulation symbols output from the modulation unit 107 to resource elements according to data arrangement information input from the outside.

Next, an example in which mapping sections 108 and 711 map modulation symbols and pilot symbols of information data signals based on the data arrangement information shown in FIG. Here, a case will be described where a long GI having a length twice that of a normal GI is added to two subcarriers adjacent to both sides of a subcarrier to which a pilot symbol is mapped.
The mapping unit 108 performs the mapping illustrated in FIG. 4 on the modulation symbols, pilot symbols, and zeros of the information data signal based on the data arrangement information illustrated in FIG.
FIG. 28 is a schematic diagram illustrating a transmission frame in which the mapping unit 711 maps modulation symbols of information data signals and zeros to resource elements based on the data arrangement information illustrated in FIG. The horizontal axis direction represents time and represents the OFDM symbol number l. The vertical axis direction indicates the frequency and indicates the subcarrier number k.

  In FIG. 28, mapping section 711 maps modulation symbols to resource elements marked with solid lines, and maps zeros to resource elements marked with broken lines. That is, the mapping unit 711 has resource elements (K ± n, L−m) that are close in the frequency direction to the resource elements (K, L) to which pilot symbols are mapped (where n = 1, 2, m = 0, 1) is mapped to modulation symbols, and zero is mapped to resource elements other than the resource elements. Further, the mapping unit 711 maps the same modulation symbol as the modulation symbol mapped to the resource element (K ± n, L) to the resource element (K ± n, L−1). For example, the mapping unit 711 maps the same modulation symbol to the resource elements (1, 2) and (1, 1).

Returning to FIG. 27, phase control section 701 performs phase rotation on the transmission frame in which modulation symbol 711 is mapped by mapping section 711, and outputs the result to multiplexing section 702. When the mapping unit 711 performs the mapping illustrated in FIG. 28, the phase control unit 701 converts the phase of the modulation symbol mapped to the resource element (K, L−1) to the normal GI length and subcarrier position ( controlling the phase rotating by the rotation amount = theta _k corresponding to the number). In FIG. 28, the phase rotation is given to the modulation symbols mapped to the resource elements filled with diagonal grids. A detailed description of the phase control according to the length of the normal GI and the position (number) of the subcarrier will be described later.

The multiplexing unit 702 includes modulation symbols, pilot symbols, and zeros mapped by the mapping unit 108 to each resource element, and modulation symbols mapped by the mapping unit 711 to each resource element and phase-rotated by the phase control unit 701, Then, zero is added (multiplexed) and output to the IFFT unit 703. That is, multiplexing section 702 multiplexes each symbol in the frequency domain.
The IFFT unit 703 converts the signal output from the multiplexing unit 702 from a frequency domain signal to a time domain signal by performing IFFT processing for each resource element (same OFDM symbol number) of the same time. The GI insertion unit 704 adds a guard interval (normal guard interval, first guard interval) to the signal converted by the IFFT unit 703. The transmission unit 102 converts the signal to which the guard interval is added by the GI insertion unit 704 into an analog signal, performs a filtering process for performing band limitation on the signal converted into the analog signal, and further processes the filtered signal. The frequency band is converted into a transmittable frequency band and transmitted via the antenna unit 101.

FIG. 29 is a schematic diagram showing symbols included in the output of one transmission frame output from the GI insertion unit 704. FIG. 29 shows an example in which the mapping unit 108 performs the mapping shown in FIG. 4 and the mapping unit 711 performs the mapping shown in FIG. A white portion indicates a section in which a modulation symbol of the information data signal is mapped. A portion filled with a lattice indicates a section in which a modulation symbol of an information data signal subjected to phase rotation is mapped.
At this time, for the modulation symbols mapped to the first, third, fourth, sixth, seventh, ninth and tenth subcarriers of the first OFDM symbol, the phase control unit 701 performs phase control according to the normal GI length. Therefore, the modulation symbols mapped to the first, third, fourth, sixth, seventh, ninth and tenth subcarriers of the first OFDM symbol are 1, 3, 4, This is equivalent to the guard interval of the modulation symbol mapped to the sixth, seventh, ninth and tenth subcarriers. That is, as shown in FIG. 30, an OFDM symbol in which a modulation symbol to which a normal GI is added or a pilot symbol to which a normal GI is added and a modulation symbol to which a long GI is added is mixed between subcarriers is generated. Is equivalent to In FIG. 30, a long OFDM symbol uses two OFDM symbols: a normal OFDM symbol composed of a modulation symbol with a normal GI added and a normal OFDM symbol with a normal GI added to a modulation symbol that has undergone phase rotation. The symbol to which the long GI is added is generated. For this reason, the length of the guard interval of this one long GI is significantly longer than that of the normal GI.

  As described above, modulation symbols and phase-controlled modulation symbols are mapped adjacent to each other in the time direction, and multiplexed in the frequency domain, thereby adding IFFT processing and normal GI normally performed in OFDM communication. By performing the processing only once, it is possible to generate an OFDM symbol in which normal GI and long GI are mixed between subcarriers.

Next, phase control performed by the phase control unit 701 in the transmission apparatus 700 of the present embodiment will be described. That is, with respect to the phase control for symbols mapped to the resource elements (K ± n, L−m) (n = 1, 2, m = 0, 1) in FIG. explain.
First, effects obtained by rotating the phase of the signal of each subcarrier in multicarrier transmission will be described. FIG. 31 is a diagram illustrating a result of IFFT processing on a subcarrier.
When phase rotation (phase offset) is not performed on each subcarrier, the modulation symbol of the kth subcarrier (k = 0, 1,..., Ns−1: Ns is the number of subcarriers) that is a frequency domain signal. A signal x (n) in the time domain, which is a result of performing IFFT processing on X (k), is expressed by the following equation (1). That is, the result of performing the IFFT process without performing phase rotation does not shift in the time direction as shown in FIG.

In the above equation (1), n (n = 0, 1,..., Ns−1) is time, i is an imaginary unit, and exp () is an exponential function.
On the other hand, when the phase rotation to the signal of each subcarrier, performs phase rotation of the rotation amount θ _{k =} 2πkm / Ns to modulation symbols of a k-th subcarrier, a signal in the time domain is a result of the IFFT processing x ' (N) is represented by the following formula (2). The following expression (2) deforms the right side, and further becomes x (n + m) from the above expression (1). Therefore, x ′ (n) = x (n + m). This is the result of performing IFFT processing on k = 0 to Ns−1 by performing phase rotation of the rotation amount θ _k = 2πkm / Ns on the modulation symbol of the _kth subcarrier, and x ′ (n) is the result of FIG. As shown in 31 (b), x (n) is x (n + m) obtained by shifting m points in the time direction.

Next, generation of a long OFDM symbol by the phase control unit 701 performing phase control will be described. FIG. 32 is a diagram illustrating a method for generating one long GI from two normal OFDM symbols (hereinafter, OFDM symbols).
FIG. 32A shows a subcarrier symbol to which a long GI is added (hereinafter referred to as “long OFDM symbol”), and the symbol length is 2 for a normal OFDM symbol as shown in FIG. The combined symbol length. Normally, when a long GI as shown in FIG. 8A is added, as shown in FIG. 32C, one effective symbol length and two normal GI lengths predetermined in the effective symbol length. The length of is repeatedly copied to make a long GI. For example, if the two normal GI length sections from the right end of the effective symbol in FIG. 32A are G1 and G2, respectively, the long GI length section from the left end is as shown in FIG. 32C. That is, the long GI length section is generated by first copying the effective symbol length including G1 and G2, copying G1 and G2, and inserting them in front of the previously copied effective symbol length.

When the view of the long OFDM symbol in which the guard interval of the long GI length shown in FIG. 32 (c) is generated is changed, as shown in FIG. 32 (d), an OFDM symbol with two normal GIs added (normal OFDM) Symbol). That is, the rear (right) symbol in FIG. 32D is an OFDM symbol to which a normal GI length signal G1 is added, and the front (left) symbol is an OFDM symbol to which a normal GI length signal G2 is added. It becomes.
At this time, when the effective symbol of the rear (right side) OFDM symbol in FIG. 32 (d) is compared with the effective symbol of the front (left side) OFDM symbol, the rear (right side) effective symbol is the same as the original effective symbol. Although it is the same, it can be seen that the front (left) effective symbol is shifted by the normal GI length of the rear (right) effective symbol, that is, the original effective symbol. Therefore, in the present embodiment, the effective symbol of the rear (right) OFDM symbol is not shifted to the original effective symbol without using the method shown in FIG. With respect to the effective symbol, a long GI symbol as shown in FIG. 32A is generated by shifting the original effective symbol according to the normal GI length.

  Next, the shift shown in FIG. 32 (d) will be described. The effective symbol of the OFDM symbol to be shifted is the front (left side) OFDM symbol as described above, and the effective symbol is shifted by the normal GI length. At this time, the time domain signal x (n−g) obtained by shifting the time domain signal x (n) by the normal GI length g, where g is the normal GI length, is expressed by the following equation (3).

As shown in FIG. 32 (e), the above equation (3) is obtained by modulating the front (left side) OFDM symbol to the modulation symbol, that is, the modulation symbol mapped by the mapping unit 711 to the resource element (k, L-1). The phase control unit 701 rotates the phase at a phase rotation amount θ _k = −2πkg / Ns according to the normal GI length, thereby shifting the time domain signal x (n) by the normal GI length g. The phase rotation also changes depending on the position (k) of the subcarrier.
In the above description, a method for generating one long OFDM symbol using two normal OFDM symbols has been described, but a long OFDM symbol having three or more OFDM symbol lengths is generated. Even if applicable. For example, FIG. 33 is a diagram illustrating a case where one long OFDM symbol is generated using three normal OFDM symbols.

  FIG. 33 (a) shows a long OFDM symbol having three OFDM symbol lengths. In FIG. 33 (a), the symbol length is three normal OFDM symbols as shown in FIG. 33 (b). The combined symbol length. Normally, when a long GI as shown in FIG. 33A is added, as shown in FIG. 33C, two effective symbol lengths and three normal GI lengths predetermined in the effective symbol length are used. The length of is repeatedly copied to make a long GI. For example, if the three normal GI length sections from the right end of the effective symbol in FIG. 33A are G1, G2 and G3, the long GI length sections from the left end are as shown in FIG. 33C. Become. That is, in the long GI length section, first, the effective symbol length including G1, G2, and G3 is copied twice, and G1, G2, and G3 are further copied and inserted in front of the previously copied effective symbol length. Is generated by

  When the way of viewing the long OFDM symbol generated by copying the effective symbol and G1, G2, and G3 repeatedly as described above is changed, as shown in FIG. 33 (d), the normal OFDM with three normal GIs added thereto. It can be regarded as a symbol. That is, the rear (right) symbol in FIG. 33D is an OFDM symbol to which a normal GI length signal G1 is added, and the central symbol is an OFDM symbol to which a normal GI length signal G2 is added. The symbol on the left side is an OFDM symbol to which a normal GI length signal G3 is added.

  Further, when the effective symbol of the rear (right side) OFDM symbol is compared with the effective symbol of the center OFDM symbol and the effective symbol of the front (left side) OFDM symbol in FIG. It can be seen that the symbols are the same as the original effective symbols, but the central effective symbol shifts the rear (right) effective symbol, that is, the original effective symbol by one normal GI length. Further, it can be seen that the front (left side) effective symbol is shifted from the rear (right side) effective symbol, that is, the original effective symbol by two normal GI lengths. Therefore, in this embodiment, instead of the method shown in FIG. 33C, the effective symbols of the rear (right) OFDM symbol are not shifted, and the effective symbols of the center and front (left) OFDM symbols are not shifted. Can generate a long OFDM symbol as shown in FIG. 33A by shifting the original effective symbol in accordance with the normal GI length.

Next, the shift shown in FIG. 33 (d) will be described. Since the shift for the central effective symbol in FIG. 33D is the same as that shown in FIG. 32, here, the shift for the front (left side) effective symbol in FIG.
The shift to the front (left side) effective symbol is performed by an amount corresponding to shifting the effective symbol by two normal GI lengths. Assuming that the normal GI length at this time is g and the phase rotation amount θ _k is θ _k = −2πkg / Ns, the time domain signal x (n−2g) at that time is expressed by the following equation (4). It is.

In the above equation (4), the phase control unit 701 rotates the effective symbol of the front (left side) OFDM symbol in FIG. 33 (d) by 2θ _k with respect to the effective symbol of the rear (right side) OFDM symbol. Indicates that it should be done. The phase rotation also changes depending on the position (k) of the subcarrier as in the case shown in FIG.

Similarly, later, even if you generate a long OFDM symbol that has four or more of the OFDM symbol _{length, 3θ k, 4θ k, ···} , (n-1) θ k ( normal OFDM n is possessed by the long OFDM symbol The number of symbol lengths) can be generated by phase rotation for each effective symbol.

In transmitting apparatus 700, phase control section 701 performs phase rotation on modulation symbols mapped to resource elements that are adjacent in the frequency direction to resource elements to which mapping section 711 maps pilot symbols. The mapping unit 711 maps the modulation symbol whose phase has been rotated to the resource element of the same subcarrier included in the OFDM symbol immediately before the resource element. Thereby, even in the configuration in which GI insertion section 704 inserts a normal guard interval, a long guard interval can be added to subcarriers close to the subcarrier to which the pilot symbol is mapped.
With the above-described configuration, the transmission apparatus 700 can be configured with fewer IFFT units and GI insertion units than the transmission apparatuses 100, 300, and 500 of the first to fourth embodiments, thereby reducing the circuit scale. it can.
Transmitting apparatus 700 may use the modulation symbol / pilot symbol mapping method in the second to fourth embodiments described above.

In the first to fifth embodiments described above, the case where the number of subcarriers (number of resource elements) to which a long guard interval is added and the subcarrier arrangement (resource element position) are fixed has been described. The number of subcarriers to which the long guard interval is added and the subcarrier arrangement may be changed for each transmission frame and each OFDM symbol according to the state of the propagation path, for example, delay dispersion and the amount of ICI.
In the first to fifth embodiments described above, the OFDM symbol length to which the long guard interval is added is twice as long as the OFDM symbol length to which the normal guard interval is added. The OFDM symbol length with the guard interval added may be an integer multiple of the OFDM symbol length with the normal guard interval added.

The present invention can be used for both fixed communication and mobile communication. When used in a mobile phone, the transmission apparatus of the present invention constitutes the transmission part of the base station, and the reception part constitutes the reception part of the mobile station apparatus, or vice versa. The present invention also relates to a radio communication system that performs communication using a multicarrier transmission scheme in which symbols, which are basic units of a digital signal, are distributed over a number of subcarriers and modulated and transmitted by multicarrier modulation. In the first to fifth embodiments, the case where the present invention is applied to a wireless communication system that uses the OFDM scheme as an example has been described. However, the present invention is limited to the OFDM scheme. Not. In this case, a symbol to which a guard interval is added is a multicarrier symbol.
Examples of other multicarrier transmission schemes include OFDMA, MC-CDM, DFT-S-OFDM, and the like. Also, in OFDM and OFDMA, modulation symbols correspond to the above symbols. As multicarrier modulation, modulation modulation is performed by distributing the modulation symbols and arranging them on subcarriers, performing inverse Fourier transform, and adding a guard interval. Further, in MC-CDM, a chip corresponds to the symbol, and as multicarrier modulation, a chip generated by multiplying a modulation symbol by a spreading code is distributed and arranged on subcarriers, and after performing inverse Fourier transform, a guard interval is used. MC-CDM modulation is added. In DFT-S-OFDM, discrete symbols correspond to the above symbols. Discrete spectra generated by Fourier transform of a plurality of symbols are dispersed and arranged on subcarriers, and guard intervals are added after inverse Fourier transform. DFT-S-OFDM modulation is performed.

  The transmitting apparatus and the receiving apparatus of the first to fifth embodiments described above may have a computer system inside. In this case, the processing steps of the normal GI symbol generation units 104 and 304 and the long GI symbol generation units 105, 305, and 505 described above are stored in a computer-readable recording medium in the form of a program. The above process is performed by reading and executing. Here, the computer-readable recording medium means a magnetic disk, a magneto-optical disk, a CD-ROM, a DVD-ROM, a semiconductor memory, or the like. Alternatively, the computer program may be distributed to the computer via a communication line, and the computer that has received the distribution may execute the program.

DESCRIPTION OF SYMBOLS 100, 300, 500, 700 ... Transmitting apparatus 101 ... Antenna part 102 ... Transmitting part 103, 303, 503, 702 ... Multiplexing part 104, 304, 705 ... Normal GI symbol generation part 105, 305, 505, 706 ... Long GI symbol Generation unit 106 ... encoding unit 107 ... modulation unit 108, 111, 308, 311 and 511 ... mapping unit 109, 112 and 703 ... IFFT unit 110 ... normal GI insertion unit 113 ... long GI insertion unit 200, 400 and 600 ... receiving device DESCRIPTION OF SYMBOLS 201 ... Antenna part 202 ... Reception part 203 ... Pilot symbol processing part 204, 404 ... Normal GI symbol processing part 205, 405, 605 ... Long GI symbol processing part 206 ... Demodulation part 207 ... Decoding part 208 ... Pilot extraction part 209 ... Propagation Route estimation unit 210 ... normal GI-FFT interval extraction unit 211, 215 ... FFT unit 212, 216 ... propagation path distortion compensation unit 213, 217, 617 ... demapping unit 214 ... long GI-FFT interval extraction unit 704 ... GI insertion unit 711 ... mapping unit

Claims (15)

In a transmitter for transmitting a symbol, which is a basic unit of a digital signal, by multi-carrier modulation,
A subcarrier in which the symbol is arranged in a first multicarrier symbol having a normal guard interval and a subcarrier in which the symbol is arranged in a second multicarrier symbol having a long guard interval longer than the normal guard interval Carriers are interspersed among a plurality of subcarriers constituting the multicarrier at the same time, and a subcarrier in which the second multicarrier symbol is arranged is the first multicarrier symbol. A transmission apparatus that occupies subcarriers close to arranged subcarriers. The transmitter is
A first multicarrier symbol generation unit that generates the first multicarrier symbol in which a normal guard interval is added to a first symbol that is a part of the symbols;
A second multi-carrier symbol is generated by adding a long guard interval longer than the normal guard interval to a second symbol which is a part of the symbols different from the first symbol. A multi-carrier symbol generator of
A multiplexing unit that multiplexes the first multicarrier symbol and the second multicarrier symbol;
The transmission apparatus according to claim 1, wherein the second multicarrier symbol occupies a subcarrier adjacent to a subcarrier occupied by the first multicarrier symbol or the second multicarrier symbol. . The first multicarrier symbol generation unit includes:
A first guard interval insertion unit for adding a normal guard interval;
The second multicarrier symbol generation unit includes:
A second guard interval insertion unit for adding a long guard interval;
The multiplexing unit includes:
The transmission apparatus according to claim 2, wherein the first multicarrier symbol and the second multicarrier symbol are multiplexed in a time domain. The second multicarrier symbol generation unit includes:
The symbols that are the partial symbols, the symbols to which the long guard interval is added are phase-rotated, and are symbols that are arranged before a plurality of consecutive symbols in the time direction of the same subcarrier as the partial symbols. A phase control unit for generating a symbol constituting a part of the long guard interval to be added to the partial symbol,
Arranging at least one second symbol that is phase-rotated continuously in front of the time direction of a subcarrier in which the second symbol is arranged;
The multiplexing unit includes:
4. The transmission apparatus according to claim 2, wherein the first multicarrier symbol and the second multicarrier symbol are multiplexed in a frequency domain. 5. The transmitter is
The symbols include pilot symbols that are predetermined known symbols;
The second multicarrier symbol occupies a subcarrier adjacent to a subcarrier occupied by the first multicarrier symbol including the pilot symbol or the second multicarrier symbol. The transmission device according to claim 4. The first multicarrier symbol generation unit includes:
The transmission apparatus according to any one of claims 2 to 5, wherein the normal guard interval is added to the pilot symbol. The second multicarrier symbol generation unit includes:
The transmission apparatus according to any one of claims 2 to 5, wherein the long guard interval is added to the pilot symbol. The second multi-carrier symbol is
The transmission apparatus according to any one of claims 2 to 7, wherein the transmission apparatus is arranged on one of a subcarrier having a high frequency and a subcarrier having a low frequency with respect to the first symbol. The second symbol includes a control symbol for controlling communication,
The second multicarrier symbol having the long guard interval is arranged in a subcarrier adjacent to the first symbol including the pilot symbol or a subcarrier in which the second multicarrier symbol is arranged. The transmission device according to any one of claims 2 to 8. The symbol includes a modulation symbol obtained by modulating data to be transmitted,
The first multicarrier symbol generator or the second multicarrier symbol generator is
The transmission apparatus according to claim 9, wherein the control symbol is arranged on a subcarrier with priority over the modulation symbol. The section of the symbol included in the first multicarrier symbol and the section of the symbol included in the second multicarrier symbol coincide with each other in the time direction. The transmission device according to any one of the above. The length of the second multicarrier symbol output from the second multicarrier symbol generation unit is an integral multiple of the length of the first multicarrier symbol output from the first multicarrier symbol generation. The transmission device according to claim 1, wherein the transmission device is a device. A communication system having a transmitting device and a receiving device that transmit multi-carrier modulated symbols that are basic units of a digital signal,
The transmitter is
A first multicarrier symbol generation unit that generates the first multicarrier symbol in which a normal guard interval is added to a first symbol that is a part of the symbols;
A second multi-carrier symbol is generated by adding a long guard interval longer than the normal guard interval to a second symbol which is a part of the symbols different from the first symbol. A multi-carrier symbol generator of
A multiplexing unit that multiplexes the first multicarrier symbol and the second multicarrier symbol to generate a transmission symbol;
A transmission unit that transmits the transmission symbol generated by the multiplexing unit to the reception device, and
The receiving device is:
A receiver that receives the transmission symbols transmitted from the transmitter;
A first multicarrier symbol processing unit for extracting the symbol by removing the normal guard interval from the first multicarrier symbol among the transmission symbols received by the receiving unit;
A second multicarrier symbol processing unit for extracting the symbol by removing the long guard interval from the second multicarrier symbol among the transmission symbols received by the receiving unit;
Pilot symbol processing for calculating a channel estimation value by performing channel estimation using a known pilot symbol included in the symbol extracted by the first multicarrier symbol processing unit or the second multicarrier symbol processing unit The department and
The first multicarrier symbol processing unit and the second multicarrier symbol processing unit perform channel distortion compensation based on a channel estimation value which is a channel estimation result by the pilot symbol processing unit, and Detect symbols,
The subcarriers in which the first multicarrier symbols are arranged and the subcarriers in which the second multicarrier symbols are arranged are scattered among a plurality of subcarriers constituting the multicarrier at the same time. The subcarrier in which the symbol is arranged in the second multicarrier symbol occupies a subcarrier adjacent to the subcarrier in which the first multicarrier symbol is arranged. . In a transmission method in which a symbol which is a basic unit of a digital signal is transmitted by multi-carrier modulation,
A subcarrier in which the symbol is arranged in a first multicarrier symbol having a normal guard interval and a subcarrier in which the symbol is arranged in a second multicarrier symbol having a long guard interval longer than the normal guard interval Carriers are interspersed among a plurality of subcarriers constituting the multicarrier at the same time, and a subcarrier in which the second multicarrier symbol is arranged is the first multicarrier symbol. A transmission method characterized by occupying subcarriers close to arranged subcarriers. A receiving apparatus that receives a transmission signal including a normal guard interval and a long guard interval that are part of a multicarrier symbol that has been subjected to multicarrier modulation,
A normal guard interval-FFT section extractor;
A long guard interval-FFT section extractor;
A propagation path distortion compensation section that regenerates a modulation symbol by converting the outputs from the normal guard interval-FFT section extraction section and the long guard interval-FFT section extraction section into a signal on the frequency axis and performing propagation path compensation. And a receiving device.

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