JP2010161650A - Communication device, communication system, transmission method, reception method, and communication method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress degradation of transmission efficiency while improving reliability of a recovered symbol, in an environment where delay waves crossing a normal guard interval zone arrive. <P>SOLUTION: A first communication device 100 includes: a normal GI symbol generation part 200 for generating a first pilot symbol having a first guide interval; and a long GI symbol generation part 250 for generating a second pilot symbol, having a second guard interval longer than the first guard interval. The first pilot symbol and the second pilot symbol are mixed in the same frame. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

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

  The multicarrier transmission scheme is a scheme in which information is divided into a plurality of carrier waves (carriers) called subcarriers. The multicarrier transmission scheme is a multiple access method using OFDM (Orthogonal Frequency Division Multiplexing), which assigns an independent modulation symbol to each subcarrier, and OFDM technology. OFDMA assigns subcarriers to each user. (Orthogonal Frequency Division Multiple Access), an application of code spreading technology to OFDM, MC-CDM (Multi Carrier-Code Division Multiplexing; mapping of modulation symbols to subcarriers) Multicarrier code division multiplexing).

  In multicarrier transmission, if the amplitude or phase of a transmission signal varies due to multipath fading or the like, the communication device on the receiving side needs to compensate for the variation. As a method of compensating for such fluctuations in amplitude and phase, a known symbol called a pilot symbol between communication devices that perform transmission and reception is inserted into a part of a transmission signal, and propagation path estimation is performed from a deviation between the transmission symbol and the reception symbol. There is a way to do it.

FIG. 33 is a conceptual diagram illustrating an example of a transmission signal in which pilot symbols are inserted.
In the figure, in a frame composed of 8 subcarriers and 12 OFDM symbols, every 3 subcarriers in the frequency direction, every 1 OFDM symbol in the time direction, and subcarrier 1 A pilot symbol is arranged with a shift.
These pilot symbols are used to estimate the propagation path at the frequency and time at which the pilot symbols are arranged. For areas where the pilot symbols are not arranged, the propagation path estimation values of the areas where the pilot symbols are arranged are used. Interpolated to obtain a propagation path estimate. This makes it possible to estimate time variation and frequency variation in amplitude and phase.
Note that, as shown in FIG. 33, pilot symbols scattered and arranged in the frequency direction and the time direction are referred to as scattered pilot symbols (Scattered Pilot Symbols).

Also, in multicarrier transmission, due to the effects of multipath, three problems of intersymbol interference, intercarrier interference, and signal-to-interference noise ratio reduction associated with signal power reduction of delayed wave occur, and the reliability of the restored signal is reduced. descend.
FIG. 34 is a conceptual diagram illustrating an example of multipath of three waves. In FIG. 34, W1101 represents the earliest wave, and W1102 and W1103 represent delayed waves.
First, when FFT is performed on the FFT (Fast Fourier Transform) section of FIG. 34 to obtain the symbol Sj, a part of the symbol Si of the delayed waves W1102 and W1103 is included in the FFT section. Intersymbol interference in which the resulting phase, amplitude, and frequency are shifted occurs.
Next, since the boundary between the symbols Si and Sj of the delayed waves W1102 and W1103 exists in the FFT interval, the periodicity of Sj is not maintained, and the discontinuous part interferes with other subcarriers as harmonics. Inter-carrier interference occurs.
Furthermore, as a result of including a part of the symbol Si instead of the symbol Sj in the FFT interval, the power of the radio wave of the symbol Sj is reduced, and a signal to interference and noise ratio (SINR) is reduced. .

  As a countermeasure against these three problems caused by multipath, there is a method of adding a copy of the portion after the own symbol to the head of the OFDM symbol in the time domain in the communication apparatus on the transmission side. This is called a guard interval (GI) or a cyclic prefix (CP). In this specification, the term guard interval is used, and a time when a copy of a later part is given. A section shall be designated.

  FIG. 35 is a conceptual diagram illustrating an example of a 3-wave multipath of a transmission signal to which a guard interval is added. In the figure, W1201 represents the earliest wave, and W1202 and W1203 represent delayed waves. For simplicity, it is assumed that a wave in which W1201, W1202, and W1203 are superimposed is a received signal.

  Since the waveform of the guard interval is a copy of the subsequent portion of the symbol, the delayed waves W1202 and W1203 are cyclic delays in the FFT interval of FIG. 35, and the periodicity is maintained. For this reason, the subcarriers are orthogonal to each other and no intercarrier interference occurs. Further, as shown in FIG. 35, since there is no leakage into the FFT section of Si, no intersymbol interference occurs. Furthermore, the power reduction of Sj in the delayed wave can be prevented. The signal after FFT also has a phase and amplitude shift, but the same as the transmission symbol by estimating (compensating for the propagation path) and compensating for the amplitude and phase shift (frequency response) between the transmission signal and the reception signal. Symbol is obtained.

The degree to which the effect of multipath can be reduced depends on the length of the guard interval.
FIG. 36 is a conceptual diagram illustrating an example of a channel impulse response value when a delayed wave that exceeds the guard interval section (guard interval section on the time axis) arrives. In the figure, the top four waves are within the guard interval section, and the other eight waves exceed that section.
FIG. 37 is a conceptual diagram showing an example in which the delayed wave of FIG. 36 causes interference. In the same figure, the symbol section before the next eight waves extends beyond the guard interval section to the FFT section, causing intersymbol interference, intercarrier interference, and signal power reduction of the corresponding eight paths.
As a countermeasure against the delayed wave exceeding the guard interval section, it can be considered to lengthen the guard interval. For example, Non-Patent Document 1 discloses a method of making the guard interval of each symbol in the same subframe (frame, slot) longer than a normal one.

`` 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 conventional method including the method of Non-Patent Document 1, since the guard interval interval is set for each frame, that is, for each of a plurality of OFDM symbols, for example, in order to lengthen the guard interval interval of the pilot symbol Requires a longer guard interval section for all symbols in the same OFDM symbol, and transmission efficiency decreases.

  The present invention has been made in view of such circumstances, and an object of the present invention is to reduce transmission efficiency while improving the reliability of restored symbols in an environment where a delayed wave exceeding the normal guard interval section arrives. Is to provide a communication device, a communication system, a transmission method, a reception method, and a communication method.

  The present invention has been made to solve the above-described problems, and a first communication device according to the present invention is a first communication device that performs multi-carrier modulation on a symbol that is a basic unit of a digital signal and performs communication. The first pilot symbols to which the first guard interval is added are interspersed among the subcarriers constituting the multicarrier at the same time, and the multicarrier is constituted at the same time as the first multicarrier symbol. A transmission symbol generation unit for generating a signal including a second multicarrier symbol in which second pilot symbols added with a second guard interval longer than the first guard interval are interspersed between subcarriers It is characterized by comprising.

  The first communication apparatus of the present invention is the first communication apparatus described above, wherein some of the second multicarrier symbols include information data symbols that are symbols of an information data signal. And

  The first communication apparatus of the present invention is the first communication apparatus described above, wherein some of the second multicarrier symbols include control symbols that are symbols of a control signal. .

  The first communication apparatus of the present invention is the first communication apparatus described above, wherein the transmission symbol generation unit adds the first guard interval to a symbol including the first pilot symbol. A first multicarrier symbol generating section configured to generate the first multicarrier symbol; and generating the second multicarrier symbol by adding the second guard interval to a symbol including the second pilot symbol. A second multicarrier symbol generation unit, a multiplexing unit that multiplexes the first multicarrier symbol and the second multicarrier symbol in a time domain are provided.

  The first communication device of the present invention is the first communication device described above, and the symbol to which the second multicarrier symbol generation unit adds the second guard interval is a pilot symbol, The transmission symbol generation unit includes a second multicarrier symbol storage unit that stores the second multicarrier symbol generated by the second multicarrier symbol generation unit.

  The first communication device of the present invention is the first communication device described above, wherein the transmission symbol generation unit phase-rotates a symbol to which the second guard interval is added, A phase rotation unit that generates a symbol that is arranged immediately before in the time direction of the same subcarrier as a symbol to which a guard interval is added, and that forms a part of the second guard interval; A frequency domain symbol multiplexing unit that multiplexes a symbol to which one guard interval is added, a symbol to which the second guard interval is added, and a symbol generated by the phase rotation unit in the frequency domain; and the frequency domain symbol An inverse Fourier transform unit that performs inverse Fourier transform on the symbols multiplexed by the multiplexing unit to convert the symbol into a time domain signal, and the inverse Fourier transform unit converts the symbol The signal of the time domain, characterized by comprising a guard interval inserting unit that adds a guard interval length of the first guard interval.

  The first communication device of the present invention is the first communication device described above, wherein the symbol to which the second guard interval is added is a pilot symbol, and the transmission symbol generator is And a second symbol storage unit that stores a symbol to which two guard intervals are added and a symbol generated by the phase rotation unit.

  The first communication device of the present invention is the first communication device described above, wherein the transmission symbol generation unit phase-rotates symbols constituting a part of the second guard interval, and A phase rotation unit that generates a symbol that is placed one time behind in the time direction of the same subcarrier as a symbol that constitutes a part of the guard interval of two, and to which the second guard interval is added; A frequency domain symbol multiplexing unit that multiplexes, in the frequency domain, a symbol to which a first guard interval is added, a symbol to which the second guard interval is added, and a symbol that forms part of the second guard interval. And inverse Fourier transform that converts the symbols multiplexed by the frequency domain symbol multiplexing unit into symbols in the time domain. And parts, the symbol in the time the inverse Fourier transform unit is converted area, characterized by comprising a guard interval inserting unit that adds a guard interval length of the first guard interval.

  A first communication device of the present invention is the first communication device described above, wherein the transmission symbol generation unit includes a low power allocation unit that allocates transmission power of the first pilot symbol, and the second And a high power allocating unit that allocates higher transmission power of pilot symbols than the transmission power allocated by the low power allocating unit.

  The first communication device of the present invention is the first communication device described above, and the transmission symbol generator does not need the second pilot symbol from the second communication device of the communication partner. Or a notification indicating that the number of the second pilot symbols may be reduced, the second pilot symbols are not mapped, or the number of mapping the second pilot symbols is reduced. Features.

  The first communication device of the present invention is the first communication device described above, and the transmission symbol generation unit does not need the second pilot symbol from the second communication device of the communication partner. Or the notification that the number of the second pilot symbols may be reduced, the first guard is placed at a position where the second pilot symbols are scheduled to be mapped. It is characterized by mapping symbols to which intervals are added.

  The second communication apparatus of the present invention is a second communication apparatus that receives a signal obtained by multi-carrier modulation of a symbol, which is a basic unit of a digital signal, to which a first guard interval is added at the same time. 1, the first pilot symbols scattered between the subcarriers constituting the multicarrier and the second guard interval longer than the first guard interval are added, and the subcarriers constituting the multicarrier at the same time A radio reception unit that receives a signal including second pilot symbols interspersed between, a pilot separation unit that separates the first pilot symbol and the second pilot symbol from the received signal; From the extracted first pilot symbol and the second pilot symbol, each sub-carrier Characterized by comprising a propagation path channel estimation unit for calculating an estimated value.

  The second communication device of the present invention is the second communication device described above, wherein the propagation path estimation unit includes a first propagation path estimated value calculated from the first pilot symbol, The second propagation path estimated value calculated from the two pilot symbols is weighted and combined.

  Further, the second communication device of the present invention is the second communication device described above, wherein the first propagation path estimated value and the second propagation path estimated value are estimated values of frequency response, The propagation path estimator weights and synthesizes the first propagation path estimated value and the second propagation path estimated value for the same subcarrier, and interpolates the weighted combined result in the frequency direction to obtain each subcarrier. The propagation path estimated value of is calculated.

  Further, the second communication device of the present invention is the second communication device described above, wherein the first propagation path estimated value and the second propagation path estimated value are estimated values of frequency response, The propagation path estimation unit calculates the first propagation path estimated value of each subcarrier by interpolating the first propagation path estimated value in the frequency direction, and uses the second propagation path estimated value in the frequency direction. By calculating the second propagation path estimated value of each subcarrier, and weighting and combining the first propagation path estimated value and the second propagation path estimated value in each subcarrier. In addition, the channel estimation value of each subcarrier is calculated.

  The second communication device of the present invention is the above-described second communication device, wherein the synthesis performed by the propagation path estimation unit is weighted synthesis, and the weighting coefficient of the weighted synthesis includes an Includes a weight component in the time direction that has different values.

  Moreover, the 2nd communication apparatus of this invention is the above-mentioned 2nd communication apparatus, Comprising: The said 1st propagation path estimated value and the said 2nd propagation path estimated value are estimated values of a channel impulse response. The channel estimation unit calculates a channel impulse response estimated value calculated by weighting and combining components having the same delay time among the first channel estimated value and the second channel estimated value as a time frequency. Conversion is performed to calculate a propagation path estimation value of each subcarrier.

  The second communication device of the present invention is the second communication device described above, wherein the propagation path estimation unit includes the first propagation path estimation value and the second propagation path estimation value. An estimated value of the channel impulse response calculated by arithmetically averaging components whose delay time is within the length of the first guard interval and weighting and combining components whose delay time exceeds the length of the first guard interval. A propagation frequency estimated value of each subcarrier is calculated by time-frequency conversion.

The second communication device of the present invention is the above-described second communication device, wherein the propagation path estimation unit adds a delay in a component of the first propagation path estimation value to the weighting coefficient of the weighting synthesis. Weighting is performed using a value based on a time exceeding the first guard interval among the times.

  The second communication device of the present invention is the above-described second communication device, wherein the propagation path estimation unit is configured to process a signal included in a received signal of each subcarrier in the weighting coefficient of the weighting synthesis. Weighting synthesis is performed using a value based on the ratio of interference and noise intensity.

  Further, the second communication device of the present invention is the second communication device described above, wherein the propagation path estimation unit receives the weighting combination weight coefficient from the first communication device of the communication partner. A value based on a value indicating the transmission power of the first pilot symbol and a value indicating the transmission power of the second pilot symbol is used.

The communication system of the present invention is a communication system comprising a first communication device and a second communication device, which communicate by performing multicarrier modulation on a symbol that is a basic unit of a digital signal. In the communication apparatus, the first guard interval is added, and at the same time, the first pilot symbols scattered between the subcarriers constituting the multicarrier and the second guard longer than the first guard interval. An interval is added, and at the same time, a transmission symbol generation unit that generates a signal including second pilot symbols scattered between subcarriers constituting a multicarrier is provided. A radio receiver for receiving a signal including a first pilot symbol and the second pilot symbol;
A pilot demultiplexer that separates the first pilot symbol and the second pilot symbol from the received signal, and each subcarrier from the extracted first pilot symbol and the second pilot symbol. And a propagation path estimator that calculates a propagation path estimated value.

  The transmission method of the present invention is a transmission method of a first communication device that performs communication by multicarrier modulation of symbols that are basic units of a digital signal, and the first communication device is configured to Between the first multicarrier symbols in which the first pilot symbols added with the first guard interval are interspersed between the subcarriers constituting the carrier and the subcarriers constituting the multicarrier at the same time, And a transmission symbol generation step of generating a signal including a second multicarrier symbol in which second pilot symbols added with a second guard interval longer than the first guard interval are scattered. .

  The receiving apparatus of the present invention is a receiving method of a second communication apparatus that performs multi-carrier modulation on a symbol that is a basic unit of a digital signal, and the second communication apparatus includes a first guard interval. Is added, and at the same time, a first pilot symbol scattered between subcarriers constituting the multicarrier and a second guard interval longer than the first guard interval are added. A radio reception process for receiving a signal including second pilot symbols interspersed between subcarriers constituting a carrier, and the second communication apparatus receives the first pilot symbol from the received signal, and A pilot separation process for separating a second pilot symbol; and the second communication apparatus includes the extracted first pattern. And a lot symbol and the second pilot symbol, characterized in that it comprises a channel estimation step of calculating a channel estimation value of each subcarrier.

  The communication method of the present invention is a communication method of a communication system including a first communication device and a second communication device, which performs communication by performing multicarrier modulation on a symbol that is a basic unit of a digital signal, At the same time as the first multicarrier symbol, in which the first communication apparatus is interspersed with the first pilot symbols to which the first guard interval is added among the subcarriers constituting the multicarrier at the same time. Generating a signal including a second multicarrier symbol in which second pilot symbols added with a second guard interval longer than the first guard interval are interspersed between subcarriers constituting the multicarrier A transmission symbol generation process, and the second communication device includes the first pilot symbol and the second pi A radio reception process for receiving a signal including a first symbol, a pilot separation unit for separating the first pilot symbol and the second pilot symbol from the received signal by the second communication apparatus; The second communication apparatus includes a channel estimation process for calculating a channel estimation value of each subcarrier from the extracted first pilot symbol and the second pilot symbol.

  According to the present invention, in multicarrier transmission, the accuracy of channel estimation obtained from pilot symbols can be increased, and high transmission efficiency can be obtained.

It is a schematic block diagram which shows the structure of the 1st communication apparatus by 1st Embodiment of this invention. In the embodiment, it is a conceptual diagram which shows the example which mapped the information data symbol and the normal GI pilot symbol. In the same embodiment, it is a conceptual diagram which shows the example which the 2nd mapping part mapped the long GI pilot symbol. In the same embodiment, it is a conceptual diagram showing the example of a structure of the OFDM symbol contained in the signal which the multiplexing part multiplexed. FIG. 3 is a conceptual diagram showing an information data symbol or pilot symbol to which a normal GI is added and a pilot symbol to which a long GI is added in the same embodiment. In the same embodiment, it is a conceptual diagram which shows the case where the wave which arrives earliest and two delay waves of the symbol to which normal GI was added arrived. In the same embodiment, it is a conceptual diagram which shows the case where the wave which arrives earliest and two delay waves of the symbol to which long GI was added arrived. It is a schematic block diagram which shows the structure of the 1st communication apparatus by 2nd Embodiment of this invention. It is a schematic block diagram which shows the structure of the 1st communication apparatus by 3rd Embodiment of this invention. In the same embodiment, it is a conceptual diagram showing the symbol to which long GI was added. It is a schematic block diagram which shows the structure of the 1st communication apparatus by 4th Embodiment of this invention. In the same embodiment, it is a figure which shows the structural example of the symbol which the multiplexing part multiplexed. It is a schematic block diagram which shows the structure of the 2nd communication apparatus by 5th Embodiment of this invention. In the embodiment, it is a schematic block diagram which shows the structural example of a propagation path estimation part. In the same embodiment, it is a flowchart which shows the process of a propagation path estimation part. In the embodiment, a propagation path estimation part is a conceptual diagram which shows the example which produces | generates the estimated value of the frequency response of the resource element in which the pilot symbol is not arrange | positioned. In the same embodiment, it is a conceptual diagram showing an example when there is at most one pilot symbol in each subcarrier. In the same embodiment, it is a conceptual diagram showing the example in case the arrangement | positioning of a normal GI pilot symbol differs temporally between subcarriers. In the same embodiment, it is a conceptual diagram showing the example in case the arrangement | positioning of a long GI pilot symbol differs temporally between subcarriers. In the same embodiment, it is a conceptual diagram showing the example in case three pilot symbols are mapped by the same subcarrier. It is a schematic block diagram showing the structural example of the 2nd communication apparatus in the modification of the embodiment. It is a schematic block diagram which shows the structural example of the propagation path estimation part in 6th Embodiment of this invention. In the same embodiment, it is a flowchart which shows the process of a propagation path estimation part. In the embodiment, it is a conceptual diagram which shows the example in which a propagation path estimation part produces | generates the estimated value of a frequency response. It is a schematic block diagram which shows the structural example of the propagation path estimation part in 7th Embodiment of this invention. In the same embodiment, it is a flowchart which shows the process of propagation path estimation. In the embodiment, it is a conceptual diagram which shows the example in which a propagation path estimation part produces | generates the estimated value of a frequency response. It is a schematic block diagram which shows the structure of the 1st communication apparatus by 8th Embodiment of this invention. It is a schematic block diagram which shows the structure of the 1st communication apparatus by 9th Embodiment of this invention. In the same embodiment, it is a conceptual diagram which shows the example when not mapping a long GI pilot symbol to the reservation position of long GI. In the embodiment, it is a conceptual diagram which shows the example in the case of mapping a long GI pilot symbol to the reservation position of long GI. FIG. 3 is a schematic block diagram illustrating a configuration example of a second communication device that is a communication counterpart corresponding to the first communication device in the embodiment. It is a conceptual diagram showing the example of the transmission signal with which the pilot symbol was inserted which the conventional communication apparatus produced | generated. It is a conceptual diagram which shows the example of the multipath of 3 waves received by the conventional communication apparatus. It is a conceptual diagram which shows the example of the multipath of 3 waves of the transmission signal which was received by the conventional communication apparatus and to which the guard interval was added. In the conventional communication apparatus, it is a conceptual diagram showing the example of the channel impulse response value when the delay wave exceeding a guard interval area arrives. FIG. 37 is a conceptual diagram showing an example in which the delayed wave of FIG. 36 interferes with the earliest wave in the conventional communication device.

<First Embodiment>
Embodiments of the present invention will be described below with reference to the drawings. In the following description, a communication device that transmits a signal including a pilot symbol is a first communication device, and a communication device that receives the signal and estimates a propagation path using the pilot symbol included in the signal is a second communication device. Although both are distinguished by calling an apparatus, these may be a communication apparatus having both functions. That is, a communication apparatus that transmits a signal including a pilot symbol at the time of transmission, receives a signal including a pilot symbol at the time of reception, and performs channel estimation using the pilot symbol. The first communication device includes a transmission device that performs only transmission, and the second communication device includes a reception device that performs only reception.
FIG. 1 is a schematic block diagram showing the configuration of a first communication device according to the first embodiment of the present invention.

In FIG. 1, first communication apparatus 100 includes transmission symbol generation section 190, radio transmission section 360, and antenna 370.
Transmission symbol generation section 190 includes normal GI symbol generation section (first multicarrier symbol generation section) 200, long GI symbol generation section (second multicarrier symbol generation section) 250, and multiplexing section 350. .
The normal GI symbol generation unit 200 includes an encoding unit 300, a modulation unit 310, a first mapping unit 320, an IFFT (Inverse Fast Fourier Transform) unit 330a, and a normal GI insertion unit (first GI). Guard interval insertion section) 340. The normal GI symbol generation unit 200 generates a symbol with a guard interval added. Hereinafter, the normal GI symbol generation unit 200 adds a guard interval “normal GI (first guard interval, normal guard interval)”, and a symbol added with the normal GI “normal GI symbol (first symbol)”. That's it.
The long GI symbol generation unit 250 includes a mapping unit 2 (second mapping unit) 325, an IFFT unit 330b, and a long GI insertion unit (second guard interval insertion unit) 345. The long GI symbol generation unit 250 adds a long GI symbol (second symbol) to which a guard interval (long guard interval, long GI, second guard interval) whose interval section (length) is longer than a normal guard interval is added. ).

  An information data signal that is a digital signal of information data to be transmitted is first input to the encoding unit 300 of the normal GI symbol generation unit 200. The encoding unit 300 performs error correction encoding such as a convolutional code and a turbo code. The signal subjected to error correction coding is output to modulation section 310.

  Modulation section 310 modulates the signal input from encoding section 300 using a modulation scheme such as QPSK (Quadrature Phase Shift Keying) or QAM (Quadrature Amplitude Modulation), and converts the information data signal. An information data symbol, which is a modulation symbol, is generated. The information data symbol is output to first mapping section 320.

First mapping section 320 receives the output from modulation section 310 and normal GI pilot symbols. Hereinafter, the pilot symbols input to the first mapping section 320 are referred to as “first pilot symbols”.
As will be described later, first mapping section 320 provides modulation elements 310 to resource elements other than the preset resource elements to which the long GI pilot symbols are mapped among the positions (resource elements) in the frame. One input information data symbol or pilot symbol is mapped. Here, the resource element is an area divided by a predetermined width of time and frequency, and is an area where one modulation symbol is arranged. When transmitting as scattered pilot symbols, mapping is performed so that pilot symbols are scattered in the frequency direction and the time direction. The mapping is performed before the inverse Fourier transform, and can be said to be multiplexing of symbols in the frequency domain.
The mapped symbol is output to IFFT section 330a.

IFFT section 330a performs IFFT processing on the information data symbols and pilot symbols mapped by first mapping section 320, and converts the mapped modulation symbols, which are frequency domain signals, into time domain signals. The converted time domain signal is output to normal GI insertion section 340.
The normal GI insertion unit 340 adds a normal guard interval to the time domain signal input from the IFFT unit 330a to generate a normal GI-OFDM symbol (first multicarrier symbol). The normal GI-OFDM symbol is output to multiplexing section 350.
The output of the normal GI insertion unit 340 is a signal in which a normal GI symbol obtained by adding a normal GI to a modulation symbol such as an information data symbol or a pilot symbol is multiplexed in the frequency direction. A pilot symbol to which a normal GI is attached is also referred to as a normal GI pilot symbol.

Another pilot symbol, that is, a long GI pilot symbol is input to long GI symbol generation section 250. The second mapping unit 325 of the long GI symbol generation unit 250 maps the input pilot symbol to a preset resource element. When a scattered pilot symbol is used, mapping is performed so as to be scattered in the frequency direction and the time direction in the same manner as the normal GI pilot symbol.
The mapped pilot symbol is output to IFFT section 330b.
In the following, the pilot symbol input to the second mapping section 325 is referred to as “second pilot symbol” and is distinguished from the “first pilot symbol”. However, there is no difference as a modulation symbol of the pilot signal.

IFFT section 330b performs IFFT processing on the pilot symbols mapped by second mapping section 325, and converts the mapped pilot symbols that are frequency domain signals into time domain signals. The converted time domain signal is output to long GI insertion section 345.
The long GI insertion unit 345 adds a guard interval (second guard interval) that is longer than the normal guard interval added by the normal GI insertion unit 340 to the time domain signal input from the IFFT unit 330b. A GI-OFDM symbol (second multicarrier symbol) is generated.

The multiplexing unit 350 generates a normal GI-OFDM symbol time domain signal generated by the normal GI symbol generation unit 200 and a long GI-OFDM symbol time domain signal generated by the long GI symbol generation unit 250. Add (multiplex) each.
Radio transmitting section 360 performs digital-analog conversion, frequency conversion, etc. on the OFDM symbol multiplexed by multiplexing section 350 and transmits the result from antenna 370.

FIG. 2 is a conceptual diagram illustrating an example in which the first mapping unit 320 maps information data symbols and normal GI pilot symbols.
In the frame composed of 4 OFDM symbols and 8 subcarriers in the figure, the second and third subcarriers in the third and sixth subcarriers from the lowest frequency indicated by dotted circles, respectively. The resource elements (B223, B233, B226, B236) of the OFDM symbol are positions where the long GI pilot symbols are mapped. The position where the long GI pilot symbol is mapped is determined in advance as a default value of the system, for example, or is input to the first mapping unit as an externally assigned signal according to the state of the propagation path, The mapping unit has the position set in advance. Alternatively, the position for mapping the information data symbol and the position for mapping the pilot symbol to which the normal GI is attached are set in advance. The first mapping unit does not map any symbol at a position where the long GI pilot symbol is mapped, and maps a blank (zero). The normal GI pilot symbol is mapped to the position of the third OFDM symbol in the second, fifth and eighth subcarriers (B232, B235, B238). Information data symbols are mapped at other positions.

  FIG. 3 is a conceptual diagram illustrating an example in which the second mapping unit 325 maps the long GI pilot symbols. Similarly to the first mapping unit, the second mapping unit previously sets a position where the long GI pilot symbol is mapped. 3, as in FIG. 2, the resource elements (B323, B333, B326, B336) of the second and third OFDM symbols in the third and sixth subcarriers are mapped with the long GI pilot symbols. It is a position. Among these, pilot symbols are mapped to resource elements (B333, B336) of the third OFDM symbol. The resource element (B323, 326) of the second OFDM symbol is mapped with zero in order to add a long GI.

  FIG. 4 is a conceptual diagram illustrating a configuration example of an OFDM symbol included in the signal multiplexed by the multiplexing unit 350. FIG. 4 shows frequency components and time components of OFDM symbols multiplexed after IFFT processing is performed on the symbols mapped in FIGS. 2 and 3 and normal GI and long GI are inserted. Since the symbols mapped by the normal GI symbol generation unit 200 and the symbols mapped by the long GI symbol generation unit 250 do not overlap each other, the carriers are orthogonal to each other. Therefore, multiplexing can be performed by adding the complex amplitudes of both signals in the time domain.

In FIG. 4, resource elements indicated by hatching with hatching are mapped as scattered pilot symbols, and normal GI pilot symbols and long GI pilot symbols into which guard intervals are inserted are shown.
The modulation symbol interval of the OFDM symbol to which the long GI is added (the hatched portion with a white background diagonal line) is the same as the modulation symbol interval of the third OFDM symbol to which the normal GI is added (the portion without the white background hatching) in the time direction. There is no deviation (matches). For this reason, the second communication apparatus on the receiving side can set an FFT interval common to each subcarrier.

Next, the resistance to interference of the normal GI and the long GI will be described.
FIG. 5 is a conceptual diagram showing an information data symbol or pilot symbol to which a normal GI is added and a pilot symbol to which a long GI is added. In the figure, the symbol to which the long GI is added has an OFDM symbol length twice that of the symbol to which the normal GI is added. On the other hand, the lengths of both modulation symbol sections are the same. Therefore, the long GI length in the figure is longer by one OFDM symbol length than the normal GI length. Note that the guard interval interval is realized by adding the rear portion of the modulation symbol interval in the front, but even if the entire modulation symbol interval is added in the front, the guard symbol interval is less than the long GI OFDM symbol length. In addition, a long GI is realized by adding a rear portion of the modulation symbol period to the front and repeating this.

FIG. 6 is a conceptual diagram showing a case where the earliest arriving wave and two delayed waves arrive in a symbol to which a normal GI is added.
When the second communication apparatus that has received the radio wave performs the FFT process on the FFT interval in FIG. 6, the second symbol W622 from the left of the delayed wave 2 is included in the FFT interval beyond the guard interval interval. Intersymbol interference occurs.
Further, the boundary between the second symbol W622 and the third symbol W623 in the delay wave 2 is included in the FFT interval. For this reason, the periodicity of W623 is not maintained, and inter-carrier interference occurs in the symbol after FFT processing.
In addition, since part of the delayed wave 2 in the FFT interval is the second symbol and not the third symbol, the power of the radio wave of the third symbol is insufficient, and the signal-to-interference noise ratio is reduced. .

On the other hand, FIG. 7 is a conceptual diagram showing a case where the earliest arriving wave and two delayed waves arrive for a symbol to which a long GI is added. In the normal GI shown in FIG. 6, when the second communication device that has received the radio wave performs FFT processing on the FFT interval in FIG. 7, the symbol before the delayed wave 2 has exceeded the guard interval interval. Since the long GI is longer than the normal GI, the symbol W721 before the delayed wave 2 does not exceed the guard interval interval, and the intersymbol interference, the intercarrier interference, and the signal-to-interference noise ratio decrease do not occur.
Therefore, the channel estimation value obtained from the long GI pilot symbol is more accurate than that obtained from the normal GI pilot symbol. As described later, the second communication device that has received the radio wave performs weighted synthesis to reduce the influence of interference and noise, thereby improving the accuracy of the propagation path estimation. Thus, the reliability of the restored symbol can be improved. Further, in the present embodiment, since the long GI is added only to a part of the OFDM symbol, that is, a part of the symbol in the frame, the conventional method in which the GI of all the symbols in the frame is lengthened, A decrease in transmission efficiency can be suppressed.

In the above description, the case where the long GI pilot symbol is twice the OFDM symbol length of the information data symbol to which the normal GI is added and the OFDM symbol length of the normal GI pilot symbol has been described. This is not a limitation. It is sufficient that the OFDM symbol length of the pilot symbol of the long GI is longer than the OFDM symbol length of the information data symbol of the normal GI, for example, the OFDM symbol length of 3 times, the OFDM symbol length of 1.5 times, or the like.
In the above description, two types of symbols, normal GI and long GI, have been described. However, the present invention is not limited to this, and can be applied to symbols having three or more types of guard interval sections. That is, a normal GI that is the first guard interval and a long GI that is a plurality of types of second guard intervals may be used. The same applies to the following embodiments.

<Second Embodiment>
FIG. 8 is a schematic block diagram showing the configuration of the first communication device according to the second embodiment of the present invention. In the figure, the same reference numerals (200, 300, 310, 320, 330a, 340, 350, 360, 370) are assigned to portions corresponding to the respective portions in FIG.
FIG. 8 differs from FIG. 1 in that a long GI pilot symbol storage unit (second multicarrier symbol storage unit) 260 is provided instead of the long GI symbol generation unit 250.

The first communication apparatus 101 in FIG. 8 includes a transmission symbol generation unit 191, a wireless transmission unit 360, and an antenna 370.
Transmission symbol generation section 191 includes normal GI symbol generation section 200, long GI pilot symbol storage section 260, and multiplexing section 350.
The normal GI symbol generation unit 200 outputs a normal GI-OFDM symbol time-domain signal to the multiplexing unit 350 as in the first embodiment, and the output timing is controlled by a control unit (not shown). ).

The long GI pilot symbol storage unit 260 stores in advance the time domain signal of the long GI-OFDM symbol generated by the long GI symbol generation unit 250 of the first embodiment. Long GI pilot symbol storage section 260 outputs the stored signal to multiplexing section 350, and the output timing is controlled by a control section (not shown).
The time domain signal of the normal GI-OFDM symbol output from the normal GI symbol generation unit 200 and the time domain signal of the long GI-OFDM symbol output from the long GI pilot symbol storage unit 260 are the first As in the first embodiment, the signals are multiplexed by the multiplexing unit 350 and transmitted from the antenna 370 through the wireless transmission unit 360.

As described above, since the same signal as that of the first embodiment is transmitted, the same effect as that of the first embodiment can be obtained, and the processing in the pilot symbol generation unit is unnecessary. Also, the circuit scale and the calculation amount are reduced.
In the present embodiment, only the long GI-OFDM symbol including the long GI pilot symbol is stored, but an OFDM symbol obtained by multiplexing the long GI pilot symbol and the normal GI pilot symbol may be stored. In this case, when performing transmission, only the output from modulation section 310 is input to first mapping section 320 without inputting pilot symbols.

<Third Embodiment>
FIG. 9 is a schematic block diagram showing the configuration of the first communication device according to the third embodiment of the present invention. In the figure, the same reference numerals (300, 310, 330a, 340, 360, 370) are assigned to the parts corresponding to the respective parts in FIG.
FIG. 9 differs from FIG. 1 in that long GI mapping symbol generation section 270 is provided instead of long GI symbol generation section 250 and that no multiplexing section 350 is provided.

The first communication apparatus 102 in FIG. 9 includes a transmission symbol generation unit 192, a wireless transmission unit 360, and an antenna 370.
The transmission symbol generation unit 192 includes a normal GI symbol generation unit 201 and a long GI mapping symbol generation unit 270.
The long GI mapping symbol generation unit 270 includes a phase rotation unit 385.

  Long GI mapping symbol generation section 270 outputs the input pilot symbol and the pilot symbol phase-rotated by phase rotation section 385 to mapping section (frequency domain symbol multiplexing section) 321.

Similar to the first mapping unit 320 of the first embodiment, the mapping unit 321 maps symbols and pilot symbols of information data input from the modulation unit 310. In addition, mapping section 321 maps the pilot symbol input from long GI mapping symbol generation section 270 and the phase-rotated symbol. At this time, mapping section 321 maps the phase-rotated symbol to the position of the previous OFDM symbol on the same subcarrier as the position where the long GI pilot symbol is mapped.
Thereafter, the same processing as that performed by the normal GI symbol generation unit described in the first embodiment is performed. However, since no multiplexing process is required in the time domain, the output of the normal GI insertion unit 340 is immediately input to the radio transmission unit 360. And transmitted from the antenna 370.

  FIG. 10 is a conceptual diagram showing a symbol to which a long GI is added. In the figure, B101 represents a modulation symbol, and B102 represents a long GI. Also, A and B in the figure are both the same length as the normal GI. The symbol to be mapped to the position of the previous OFDM symbol on the same subcarrier as the position where symbol B101 is mapped, that is, the symbol generated by phase rotation section 385 is part of B103. Since the symbol is (B, plain color, A) and is a cyclic delay of the symbol B101 (plain color, A, B), it is equivalent to phase rotation in the frequency domain.

Accordingly, the amount of phase rotation performed by the phase rotation unit 385 is expressed as k, the number of subcarriers to which the phase-rotated symbol is mapped, the number of FFT points, and the normal GI interval (the length of the normal GI interval is expressed in FFT points). G) is 2πkG / N.
Further, (B) at the end of B102 is generated by the normal GI insertion unit 340 copying (B) at the end of the symbol B101, and (A) at the beginning of B102 is generated by the normal GI insertion unit 340 as a symbol. It is generated by copying (A) at the end of B103.

  As described above, since the same transmission signal as that in the first embodiment is transmitted, the same effect as in the first embodiment can be obtained. In addition, since it is not necessary to prepare a mapping unit, an IFFT unit, and a GI insertion unit for the long GI separately from those for the normal GI, the calculation amount and the circuit scale are reduced as compared with the first embodiment. In addition, when introducing into an existing first communication apparatus in which only normal GI symbols are used, the mapping unit may be changed and a phase rotation unit may be added. Therefore, the mapping unit, the IFFT unit, the long GI insertion unit, and the multiplexing unit need to be added more easily than the change to the first communication device of the first embodiment.

In the present embodiment, the maximum effect is obtained when the length of the symbol to which the long GI is added is an integral multiple of the OFDM symbol length.
In the above description, the phase-rotated pilot symbol is mapped to the resource element of the previous OFDM symbol on the same subcarrier, but may be the resource element of the next OFDM symbol. In this case, the amount of phase rotation is −2πkG / N, which is equivalent to adding a long GI to the symbol subjected to phase rotation. That is, since the phase-rotated symbol becomes a long GI pilot symbol, processing on the receiving side is performed in consideration of the phase rotation.
In the above description, the case where the long GI pilot symbol is twice the OFDM symbol length as compared with the OFDM symbol length of the normal GI information data symbol and the normal GI pilot symbol has been described. Instead, the pilot symbol of long GI may be an integer multiple of the OFDM symbol length of the information data symbol of normal GI. For example, a triple OFDM symbol length or a quadruple OFDM symbol length may be used.
In the above description, phase rotation is performed. However, pilot symbols and pilot symbols subjected to phase rotation may be stored in the storage unit (second symbol storage unit). This eliminates the need for phase rotation, thereby reducing the circuit scale and the amount of calculation.

<Fourth Embodiment>
FIG. 11 is a schematic block diagram showing the configuration of the first communication device according to the fourth embodiment of the present invention. In the figure, the same reference numerals (300, 320, 330a, 330b, 340, 345, 350, 360, 370) are assigned to portions corresponding to the respective portions in FIG.
FIG. 11 differs from FIG. 1 in that the output from the modulation unit 311 in the normal GI symbol generation unit 202 is input to the second mapping unit 326 in the long GI symbol generation unit 251. Therefore, in addition to the long GI pilot symbols, information data symbols that are a part of the output of modulation section 311 are also input to second mapping section 325.

The first communication apparatus 103 in FIG. 11 includes a transmission symbol generation unit 193, a radio transmission unit 360, and an antenna 370.
Transmission symbol generation section 193 includes normal GI symbol generation section 202, long GI symbol generation section 251, and multiplexing section 350.

The normal GI symbol generation unit 202 includes a coding unit 300, a modulation unit 311, a first mapping unit 320, an IFFT unit 330a, and a normal GI insertion unit 340.
The long GI symbol generation unit 251 includes a second mapping unit 326, an IFFT unit 330b, and a long GI insertion unit 345.

  Modulation section 311 modulates the input from coding section 300, and uses the modulated symbols as an information data symbol (first modulation symbol) for setting normal GI and an information data symbol (second second) for setting long GI. Modulation symbols), the first modulation symbols are output to the first mapping section 320, and the second modulation symbols are output to the second mapping section 326.

FIG. 12 is a diagram illustrating a configuration example of symbols multiplexed by the multiplexing unit 350 in the present embodiment.
In the figure, modulation symbols indicated by hatching with hatching indicate normal GI pilots and long GI pilot symbols, and modulation symbols without hatching with hatching indicate information data symbols. There are two types of information data symbols, one assigned a long GI and one assigned a normal GI. Since the long GI is longer than the normal GI, as described above, the data symbols in which the long GI is set are less likely to cause inter-carrier interference to other subcarriers, and pilot symbols, particularly adjacent subcarriers, in the same time zone. The reception quality of carrier pilot symbols is improved.

In the above description, the long GI is set only for a part of the pilot symbols and data symbols. However, for example, when the propagation path condition is bad, all pilot symbols and data symbols are temporarily long. GI may be set.
In the above description, the setting of the long GI to the data symbol uses the time domain multiplexing method as in the first embodiment, but the frequency domain phase as in the third embodiment. Rotation may be used.
In FIG. 12, the long GI is set for the information data symbol of the subcarrier one higher (higher frequency) than the long GI pilot symbol, but in addition, the information data symbol of the subcarrier lower by one is added. May also be set. In FIG. 12, the long GI is set for the information data symbol of the next subcarrier, but it may be set next to two or three. If the number of subcarriers for setting the long GI is increased, the transmission efficiency is sacrificed, but the influence of intercarrier interference on the pilot symbols can be reduced.

  In the above description, a long GI is set for an information data symbol obtained by encoding and modulating an information data signal, but a control symbol obtained by encoding and modulating a control signal may also be used. The control signal is a signal necessary for the second communication apparatus on the receiving side to correctly receive, and if the control signal fails to be received, there is a possibility that the subsequent series of information data signals cannot be received. When a long GI is added to the control signal, interference with the pilot symbol can be prevented and the control signal itself can be expected to be received correctly with reduced intersymbol interference.

  Control signals include, for example, modulation schemes used for information data signals, mapping methods (resource allocation methods), error correction coding information (eg, coding methods, coding rates, puncture patterns), interleaving methods, and scrambling. Method, Hybrid Automatic Repeat reQuest (HARQ) control information (for example, packet reception notification information (ACK (Acknowledgement), NACK (Negative Acknowledgement), retransmission count, etc.), synchronization signal, MIMO (Multi-Input-Multi-Input Information)) (Eg, number of layers (number of streams) and precoding method), base station information, terminal information, format information of control information, format information of data information, Feedback information (for example, CQI (Channel Quality Indicator), etc.), transmission power control information, and the like are included, but not limited thereto.

<Fifth Embodiment>
The signal transmitted by the first communication apparatus from the first embodiment to the fourth embodiment includes a long GI pilot symbol and a normal GI pilot symbol. In an environment where a delayed wave exceeding the guard interval section of the normal GI (hereinafter referred to as “normal GI section”) arrives, the long GI pilot symbol is less susceptible to inter-symbol interference than the normal GI pilot symbol. The channel estimation value obtained from the GI pilot symbol is more accurate than the channel estimation value obtained from the normal GI pilot symbol.
In the second communication apparatus of the present embodiment, in an environment where a delayed wave exceeding the normal GI interval arrives, the first communication apparatus arranges pilot symbols at positions of several OFDM symbols in the same subcarrier, When a long GI is added to only a part of the pilot symbol, the channel estimation is improved by weighting and combining channel estimation values having different accuracy.
As the first communication device that transmits a radio signal to the second communication device of the present embodiment, for example, the first communication device of the first to third embodiments can be used.

FIG. 13 is a schematic block diagram showing the configuration of the second communication device according to the fifth embodiment of the present invention.
The second communication device 500 includes an antenna 370, a radio reception unit 710, an FFT section extraction unit 600, an FFT unit 610, a data / pilot separation unit (pilot separation unit) 620, a propagation path estimation unit 750, A filter unit 760, a demapping unit 770, a demodulation unit 780, and a decoding unit 790 are provided.
The FFT interval extraction unit 600 includes a first FFT interval extraction unit 720 and a second FFT interval extraction unit 725.
The FFT unit 610 includes a first FFT unit 730 and a second FFT unit 735.
The data / pilot separation unit 620 includes a data / normal GI pilot separation unit 740 and a long GI pilot extraction unit 745.

The radio reception unit 710 performs processing such as frequency conversion and analog-digital conversion on the reception signal received by the antenna 370. The signal output from the wireless reception unit 710 is input to the FFT interval extraction unit 600.
In the FFT interval extraction unit 600, the first FFT interval extraction unit 720 extracts the FFT interval of the normal GI-OFDM symbol, and the second FFT interval extraction unit 725 extracts the FFT interval of the long GI-OFDM symbol. .

Here, the FFT section of the normal GI symbol extracted by the first FFT section extraction unit 720 is, for example, sections L1, L2, L3, and L4 that are sections of the effective symbol length in FIG. 4, and the normal GI is added. This is a section in which modulation symbols are arranged, that is, a section having a predetermined length immediately after the normal GI. Further, the FFT section of the long GI symbol extracted by the second FFT section extraction unit 725 is, for example, the section L3 in FIG. 4, and is determined in advance after the modulation symbol section to which the long GI is added, that is, immediately after the long GI. It is a section of the specified length.
In the FFT unit 610, the first FFT unit 730 performs FFT processing on the FFT interval extracted by the first FFT interval extraction unit 720, and converts the signal from the time domain to the frequency domain. Similarly, the second FFT section 735 performs FFT processing on the FFT section extracted by the second FFT section extraction section 725, and converts the signal from the time domain to the frequency domain.
In data / pilot demultiplexing section 620, data / normal GI pilot demultiplexing section 740 obtains in advance information on mapping performed by the first communication apparatus that has performed transmission, and uses this information, and uses this information, The information data symbol and the first pilot symbol to which the normal GI is added at the time of transmission are extracted from the inside, and the information data symbol is output to the filter unit 760 and the pilot symbol is output to the propagation path estimation unit 750. Similarly, the long GI pilot extraction unit 745 obtains in advance information on mapping performed by the first communication apparatus, and uses this to add the second GI to which the long GI is added from the frequency domain signal. Pilot symbols are extracted and output to the propagation path estimation unit 750.

In FIG. 13, the FFT interval extraction unit 600 includes a first FFT interval extraction unit 720 and a second FFT interval extraction unit 725, but is not limited thereto. For example, when there is no difference between the FFT section of the normal GI-OFDM symbol and the FFT section of the long GI-OFDM symbol as shown in FIG. 4, the FFT section of the normal GI-OFDM symbol is obtained by one FFT section extraction unit 600. Is extracted, the FFT section of the long GI-OFDM symbol is also included in the extracted FFT section.
In this case, also for the FFT unit, one FFT unit 610 performs an FFT process on the FFT section extracted by the FFT section extraction unit 600.
Also for the data / pilot separation unit, one data / pilot separation unit 620 performs processing. The data / pilot separation unit 620 adds the information data symbol (representing signal) and the normal GI to the frequency domain signal generated by the FFT unit 610 using the mapping information performed by the first communication device. The first pilot symbol (representing the signal) that has been added, the second pilot symbol having the long GI added (representing the signal), and a signal in which a part of the long guard interval has been subjected to FFT processing. The information data symbols are output to the filter unit 760, the first pilot symbol and the second pilot symbol are output separately to the propagation path estimation unit 750, and a signal in which a part of the long guard interval is subjected to FFT processing is discarded. (Do nothing) to obtain the same output as in FIG.

The propagation path estimation unit 750 obtains a frequency response estimation value (propagation path estimation value) by a method described later and outputs it to the filter unit 760.
Filter section 760 performs channel compensation of the information data symbol according to the frequency response estimation value input from channel estimation section 750 and outputs the information data symbol to demapping section 770.
The demapping unit 770 obtains in advance the information of the mapping performed by the first communication device, and uses this information to extract the information data symbols compensated for the propagation path by the filter unit 760, and the original (during transmission) Arrange them in the same order as the information data symbols.

FIG. 14 is a schematic block diagram illustrating a configuration example of the propagation path estimation unit 750.
In FIG. 14, the propagation path estimation unit 750 includes frequency response estimation units 900a and 900b, a weighting synthesis unit 910, and a frequency response interpolation unit 920.

FIG. 15 is a flowchart showing the processing of the propagation path estimation unit of the present embodiment.
The frequency response estimation units 900a and 900b perform frequency response estimation (step S1).
Specifically, frequency response estimation section 900a obtains in advance information on the amplitude and phase of the first pilot symbol. When the first pilot symbol is input from data / normal GI pilot separation section 740 of FIG. 13, frequency response estimation section 900a compares the input symbol with amplitude and phase information obtained in advance. Thus, the amplitude and phase variation (frequency response) due to fading or the like in the resource element to which the first pilot symbol is mapped is estimated and output to the weighting synthesis section 910.
Similarly, frequency response estimation section 900b compares the second pilot symbol input from long GI pilot extraction section 745 of FIG. 13 with the amplitude and phase information of the second pilot symbol obtained in advance. Thus, amplitude and phase fluctuations (frequency response) due to fading or the like in the resource element to which the second pilot symbol is mapped are estimated and output to the weighting synthesis section 910.

  The weighting combining unit 910 has a frequency response estimation value (first frequency response estimation value) obtained from the first pilot symbol and a frequency response estimation value (second frequency response estimation) obtained from the second pilot symbol. As will be described later, the value is weighted and synthesized in accordance with the accuracy of estimation, and output to the frequency response interpolation unit 920 (step S2a).

  When the frequency response estimation value weighted and synthesized from weighting synthesis section 910 is input to frequency response interpolation section 920, frequency response interpolation section 920 obtains the frequency response estimation values (propagation path estimation values) of resource elements other than the resource elements in which pilot symbols are arranged. Interpolate (step S3a). Interpolation is performed using, for example, linear interpolation. Alternatively, time domain estimated based on FFT interpolation, interpolation using DCT (Discrete Cosine Transform), frequency domain filtering based on delay profile, and MMSE (Minimum Mean Square Error) standard A method of converting a channel impulse response into a frequency response by FFT may be used.

FIG. 16 is a conceptual diagram illustrating an example in which the propagation path estimation unit 750 generates an estimated value of the frequency response of a resource element in which no pilot symbol is arranged.
In the present embodiment, the pilot symbol to which the long GI is added and the pilot symbol to which the normal GI is added are arranged on the same subcarrier. In the present embodiment, the time variation of the frequency response is moderate, and the time variation between the pilot symbol to which the long GI is added and the pilot symbol to which the normal GI is added is sufficiently small. Assuming a frequency response.
In the frame composed of 6 OFDM symbols and 8 subcarriers in the figure, long GI scattered pilot symbols (B1622, B1626 are respectively located at the positions of the 2nd and 6th subcarriers and the 2nd and 5th OFDM symbols. ), Normal GI scattered pilot symbols (B1652, B1656) are mapped.

H1602 in the figure is a frequency response estimation value in the second subcarrier estimated by frequency response estimation section 900b using long GI pilot symbol B1622, and H1606 is estimated using long GI pilot symbol B1626. It is a frequency response estimated value in the sixth subcarrier.
H1612 is a frequency response estimation value in the second subcarrier estimated by frequency response estimation section 900a using normal GI pilot symbol B1652, and H1616 is estimated using normal GI pilot symbol B1656. It is a frequency response estimation value in the th subcarrier.

  The estimated values H1602 and H1606 using the long GI pilot symbols are less susceptible to delay waves exceeding the guard interval interval than the estimated values H1612 and H1616 using the normal GI pilot symbols, so that higher accuracy is expected. Is done. Therefore, the weighting combining section 910 gives a larger weighting factor to the estimated value H1602 using the long GI pilot symbol, the estimated value of the same subcarrier as the estimated value H1602, and sets the estimated value H1612 using the normal GI pilot symbol. Are multiplied by a smaller weighting coefficient to obtain a frequency response estimation value H1622. Similarly, an estimated value H1626 is obtained from the estimated value H1606 and the estimated value H1616.

The obtained frequency response estimated values H1622 and H1626 are output to the frequency response interpolation unit 920. The frequency response interpolation unit 920 uses the input from the weighting synthesis unit 910 to generate frequency response estimation values (H1621 to H1628) in other subcarriers by interpolation.
The frequency response estimation value H1621 is the frequency response estimation value of the first subcarrier from the lowest frequency, H1622 is that of the second subcarrier, and H1628 is the eighth subcarrier in the same manner. belongs to.

Next, the weighting coefficient used by the weighting synthesis unit 910 will be described.
Assume that the estimated value of the frequency response using the long GI pilot symbol is H _L , the estimated value using the normal GI pilot symbol is H _N , and the respective weighting factors are w _L and w _N in the subcarriers to be weighted. The frequency response estimation value H _S generated by the weighting synthesis unit 910 is H _S = w _L H _L + w _N H _N.

As the weighting factors w _L and w _N , for example, values based on the ratio of interference to a desired signal and the strength of noise are used. For example, as the ratio of interference and noise strength for a desired signal, the power of inter-symbol interference for pilot symbols, inter-carrier interference, and noise sum (hereinafter collectively referred to as “sum of interference and noise”) And w _L = P _N / (P _L + P _N ) and w _N = P _L / (P _L + P _N ). Here, P _L is an ensemble average of the sum of interference and noise for all occurrences of long GI pilot symbols (set average; hereinafter, the ensemble average for all occurrences is simply referred to as ensemble average), and P _N is normal It is an ensemble average of the power of the sum of interference and noise of GI pilot symbols.

In the following, by using the above weighting factor, it is possible to minimize the ensemble average of the power of the sum of interference and noise after weighted combining, and the same power is the sum of interference and noise in the long GI pilot symbols. It will be described that the power decreases to P _N / (P _L + P _N ) times with respect to the ensemble average.
Let H be the frequency response when there is no influence of the sum of interference and noise, and let n _L = H _L -H, n _N = H _N -H, and n _S = H _S -H. n _L , n _N , and n _S are so-called frequency response shifts caused by the sum of interference and noise. Here, it is assumed that interference also behaves as noise.
Using H, n _L , and n _N , the above formula H _S = w _L H _L + w _N H _N can be expressed as H _S = w _L H _L + w _N H _N = w _L (H + n _L ) + w _N (H + n _N ) = (W _L + w _N ) H + w _L n _L + w _N n _N
Here, w _L + w _N = 1 is set as a constraint condition so that the power of H does not increase or decrease. _Then, the _{n S = H S -H = w} L n L + w N n N.

Further, E [] represents an ensemble average, ^* represents a complex conjugate, and P _S is an ensemble average of the sum of interference and noise after weighted synthesis, P _L = E [n _L n _L ^* ], P _N = E [n _N n _N ^* ] and P _S = E [n _S n _S ^* ].
Power sum of the interference and noise of the weighted _{^{synthesis, P S = E [n S}} n S *] = E [(H S -H) (H S -H) *] = E [(w L H L + w _{N H N -H) (w L} H L + w N H N -H) *] = E [(w L n L + w N n N) (w L n L + w N n N) *] = E [w L _{^{2 n L n L * + w}} N 2 n N n N * + w L w N n L n N * + w L w N n L * n N] = w L 2 E [n L n L *] + w N 2 E [ _{^{n N n N *] * +}} w L w N E [n L n N] is a ^{_{+ w L w N E [n}} L * n N].

Here, assuming that n _L and n _N are uncorrelated, E [n _L n _N ^* ] = 0, E [n _L ^* n _N ] = 0, and P _S = w _L ² E [n _L a ^{_{n L *] + w N 2}} E [n N n N *] = w L 2 P L + w N 2 P N.
Therefore, w _L and w _N that minimize w _L ² P _L + w _N ² P _N under the constraint condition w _L + w _N = 1 are obtained using the Lagrange's undetermined multiplier method.
A function f of w _L , w _N , and λ is set as f = w _L ² P _L + w _N ² P _N −λ (w _L + w _N −1), where λ is a variable.
Solving the following two equations obtained by partial differentiation of f, ∂f / ∂w _L = 2w _L P _L −λ = 0, ∂ f / ∂w _N = 2w _N P _N −λ = 0, w _L = λ / 2P _L , w _N = λ / 2P _N This is substituted into the constraint condition w _L + w _N = 1 to obtain λ = 2P _L P _N / (P _L + P _N ). Substituting this into the previous formulas w _L = λ / 2P _L , w _N = λ / 2P _N , w _L = P _N / (P _L + P _N ), w _N = P _L / (P _L + P _N )
From the _{above, / w L = P N (} P L + P N), w N = P L / (P L + P N) , because the only solutions that the _{P S} minimized, this time _{P S} is minimized.

Also, this w _L = P _N / (P _L + P _N ), w _N = P _L / (P _L + P _N ) is substituted into the above formula P _S = w _L ² P _L + w _N ² P _N , P _S = a ^{_{(P N 2 P L + P}} L 2 P N) / (P L + P N) 2 = P L P N / (P L + P N).
Therefore, the ratio of the ensemble average of the power of the sum of interference and noise after weighted combination to the ensemble average of the power of the sum of interference and noise included in the received signal of the long GI pilot symbol is P _S / P _L = P _N / (P _L + P _N ) times and the estimation accuracy is improved.

Next, an example of a method for obtaining estimated values of P _L and P _N will be described. This estimated value is obtained by the weighted combining unit 910 itself, for example, when the received signal power value is input to the weighted combining unit 910.
It is assumed that the frequency response and the average power of the transmission signal are normalized to 1 at the time of AD conversion. In this case, the received signal power of a long GI pilot symbols, ensemble average (ensemble average) becomes 1 + P _L. Assuming ergodicity and assuming that the ensemble average and the arithmetic average (time average) are equal, P _L is obtained by subtracting 1 from the arithmetic average of the received signal power of all long GI pilot symbols. As an approximate value of this arithmetic mean, the arithmetic mean of the received signal power is calculated for all the occurrences of the long GI pilot symbols within a predetermined time, and 1 is subtracted from the obtained arithmetic mean. the estimated value of P _L. Similarly, the estimated value of _PN is obtained for the normal GI.

  Filter section 760 calculates a filter coefficient using a ZF (Zero Forcing) standard, an MMSE standard, or the like based on the propagation path estimation value estimated by propagation path estimation section 750, and for the information data symbol, Compensation for fluctuations in amplitude and phase (propagation path compensation). The demapping unit 770 performs demapping processing on the information data symbols for which propagation path compensation has been performed. Demodulation section 780 converts the symbol after propagation path compensation and demapping into an information signal by performing demodulation processing. The decoding unit 790 performs maximum likelihood decoding (MLD), maximum a posteriori probability (MAP), log-MAP, Max-log-MAP on the error-corrected encoded signal. Decoding processing is performed using SOVA (Soft Output Viterbi Algorithm) or the like.

  As described above, even in an environment where a delayed wave exceeding the normal GI interval arrives, accurate channel estimation is performed using a pilot symbol with a long GI and a pilot symbol with a normal GI, and a normal GI is added. The signal can be accurately restored by using the propagation path estimation result for the information data symbol. For example, iterative processing such as interference cancellation or turbo equalization that removes inter-symbol interference or the like using the decoding result can be used. Further, by adding the long GI, inter-carrier interference from the long GI pilot symbol to the information data symbol transmitted at the same time is suppressed, and the decoding characteristic is improved.

In the above description, only the section (B101 in FIG. 10) extracted by the second FFT section extraction unit 725 among the long GI pilot symbols is used to perform weighting synthesis with normal GI pilot symbols of other symbols. However, in addition to this, a part (B103 in FIG. 10) corresponding to the modulation symbol of the previous symbol may be extracted from the long GI and used as a normal GI pilot symbol. In this part, propagation path estimation can be performed with the same accuracy as the normal GI pilot symbol, so that the number of weighted synthesis samples can be increased, and the amount of interference and noise reduction can be increased.
Alternatively, a section shifted backward from the portion corresponding to the modulation symbol of the preceding symbol may be extracted and used as a pilot symbol. In this case, since the modulation symbol interval between this pilot symbol and a symbol on another subcarrier does not match, inter-carrier interference from another subcarrier increases, but the guard interval of this pilot symbol is normal. Since it is longer than GI, it is possible to suppress the effects of intersymbol interference and power reduction due to delayed waves. In this case, there is a trade-off relationship between the increase in inter-carrier interference and the suppression of inter-symbol interference and power reduction.

In the above description, the case where the long GI pilot symbol and the normal GI pilot symbol are on the same subcarrier has been described, but the frequency response estimation value can also be generated when they are on different subcarriers.
FIG. 17 is a conceptual diagram showing an example in which there is at most one pilot symbol in each subcarrier for one frame. In the case of the figure, since weighted synthesis cannot be performed, the frequency response estimation value obtained from each pilot symbol is used as it is for frequency response interpolation.

FIG. 18 is a conceptual diagram illustrating an example in which the arrangement of normal GI pilot symbols is temporally different among subcarriers. Even in the case shown in the figure, when the time variation of the propagation path can be ignored, frequency interpolation may be performed using the frequency response estimation value obtained from each pilot symbol.
FIG. 19 is a conceptual diagram illustrating an example in which the arrangement of long GI pilot symbols is temporally different among subcarriers. Even in the case shown in the figure, when the time variation of the propagation path can be ignored, frequency interpolation may be performed using the frequency response estimation value obtained from each pilot symbol.

In the above description, the case of using two types of pilot symbols, a long GI pilot symbol and a normal GI pilot symbol, has been described, but three or more types may be used. For example, when two types of long GI pilot symbols and normal GI pilot symbols are used, frequency response estimation values using the two types of long GI pilot symbols and normal GI pilot symbols are expressed as H _L1 , H _L2 , H _N , and noise power. _Are P _L1 , P _L2 , and P _N , the estimated value by weighting synthesis is W _L1 H _L1 + W _L2 H _L2 + W _N H _N. Where W _L1 = P _L2 P _N / (P _L2 P _L1 + P _L2 P _N + P _L1 P _N ), W _L2 = P _L1 P _N / (P _L2 P _L1 + P _L2 P _N + P _L1 P _N ), W _N = P _L2 P _L1 / (P _L2 P _L1 + P _L2 P _N + P _L1 P _N ).

If the time variation of the propagation path cannot be ignored, weighting in the time direction may be performed when estimating the frequency response of the pilot subcarrier. In particular, in a broadband transmission and a high-speed moving environment, it is easy to be affected by the time variation of the transmission path.
For example, in the case of FIG. 20, when time variation is considered, the frequency response is estimated for each resource element. Taking the second subcarrier from the bottom as an example, the frequency response of resource elements B2022, B2052, and B2082 can be estimated using a long GI pilot symbol. The estimated values of the other resource elements B2012, B2032, B2042, B2062, B2072, and B2092 can be obtained by performing weighted synthesis on the three obtained estimated values.
Assuming that the frequency response estimation values obtained in B2022, B2052, and B2082 are H ₁ , H ₂ , and H ₃ , and the weighting factors are t ₁ , t ₂ , and t ₃ , the estimation values obtained by weighting synthesis are t ₁ H ₁ + t ₂ H ₂ + t ₃ H ₃ As a weighting factor, it is conceivable to use a forgetting factor λ (0 ≦ λ ≦ 1) and combine so as to forget the estimated value of the frequency response obtained from a distant pilot symbol. For example, for the estimate of the frequency response obtained from the OFDM symbol j number fraction separated pilot symbols is multiplied by lambda ^J. When the resource element B2032 example, B2022, B2052, B2082 and, because apart respectively 1,2,5 pieces of OFDM symbols, weighting _{factors, t 1 = λ / (λ} + λ 2 + λ 5), t 2 = λ ² / (λ + λ ² + λ ⁵ ), t ₃ = λ ⁵ / (λ + λ ² + λ ⁵ ) The denominator coefficient is for normalizing the power. Similarly, for other symbols, an estimated value of the frequency response obtained from a distant symbol is forgotten. For example, in the resource element B 2042, t ₁ = λ ² / (λ ² + λ + λ ⁴ ), t ₂ = λ / (λ ² + λ + λ ⁴ ), and t ₃ = λ ⁴ / (λ ² + λ + λ ⁴ ). Similar processing is performed for other subcarriers.

In the above description, the weighted combination in the resource element in which the pilot symbol is not inserted is shown. However, the weighted combination may be performed in the inserted resource element. For example, in the resource element B 2082, synthesis is performed with t ₁ = λ ⁶ / (λ ⁶ + λ ³ +1), t ₂ = λ ³ / (λ ⁶ + λ ³ +1), and t ₃ = 1 / (λ + λ ² + λ ⁵ ). . By doing in this way, the influence of interference and noise can be reduced.
Note that future information may not be referred to in order to prevent processing delay. In this case, for example, in B2022, the weighting factor is t ₁ = 1, and the estimated value of the frequency response is t ₁ H ₁ = H ₁ . In B2032, the weighting factor is t ₁ = λ / λ = 1, and the estimated value of the frequency response is t ₁ H ₁ = H ₁ . In B2062, the weighting factors are t ₁ = λ ⁴ / (λ ⁴ + λ), t ₂ = λ / (λ ⁴ + λ), and the estimated value of the frequency response is t ₁ H ₁ + t ₂ H ₂ = λ. ^{_{4 H 1 + λH 2 / (}} λ 4 + λ) = λ 3 H 1 + H 2 / become (λ ³ +1).
In the above description, an example in which three frequency responses are weighted has been shown, but the present invention is not limited to this, and more may be used. In either case, a weighting factor that forgets the estimated value of the frequency response obtained from a distant symbol and normalizes the power is used.

In addition, when frames as shown in FIG. 20 are continuously transmitted, it is possible to perform weighted synthesis for a long time with respect to the past. Particularly, in the case of the downlink, since symbols including pilot symbols are constantly transmitted from the base station, weighting synthesis can be started from the time when the terminal is synchronized with the base station. Although all the received past frequency response estimation values in which pilot symbols are inserted may be held, the following method can be used to reduce the memory used. First, two parameters, x and y, are prepared. The initial value of x is 1, and the initial value of y is the frequency response estimated for the first time. That is, when the frames in FIG. 20 are transmitted continuously, the frequency response is estimated in the resource element B 2022 of the first received frame. Next, these values are updated for each OFDM symbol. If the next resource element is a resource element in which no pilot symbol is inserted, x is updated to λx and y is updated to λy. The estimated value of the frequency response in this resource element is y / x. When the next symbol is a symbol in which a pilot symbol is inserted, first, an estimated value H ′ of a frequency response is calculated using the pilot symbol, and x is updated to λx + 1 and y is updated to λy + H ′. Assume that the final frequency response estimate in this resource element is y / x. Thereafter, this process is repeated. For example, the case where the estimated value of the frequency response in the resource element B2062 is obtained will be described. When the estimated value of the frequency response in B2052 is obtained, x = λ ³ +1 and y = λ ³ H ₁ + H ₂ are obtained. Since no resource element is inserted in B2062, the value of x is updated to λx = λ ⁴ + λ, and the value of y is updated to λy = λ ⁴ H ₁ + λH ₂ . Using the values of these post updated estimates ^{y / x = (λ 4 H} 1 + λH 2) / (λ 4 + λ) = (λ 3 H 1 + H 2) of the frequency response / obtain (λ ³ +1).
According to this method, in order to obtain the same frequency response estimation value as in the case of the weighted synthesis without referring to the future information described above, it is sufficient to store x and y. Can be reduced.

In the above description, an example is shown in which the long GI pilot symbol and the normal GI pilot symbol are mapped to different subcarriers, but they may exist on the same subcarrier. In that case, first, the frequency response may be estimated by each of the long GI pilot symbol and the normal GI pilot symbol, and then weighted synthesis based on the time direction, interference, and noise power may be performed. For example, in the sixth subcarrier from the bottom of FIG. 16, a long GI pilot symbol is inserted at the position B1626 and a normal GI pilot symbol is inserted at the position B1656. Therefore, first, a frequency response estimation value H _L of the long GI pilot symbol of B1626 and a frequency response estimation value H _N of the normal GI pilot symbol of B1656 are obtained. Next, using, for example, w _L = t _L P _N / (t _N P _L + t _L P _N ) and w _N = t _N P _L / (t _N P _L + t _L P _N ) as weighting factors, The weighted synthesized frequency response estimate H _S = w _L H _L + w _N H _N is obtained. Where P _L is the ensemble average of the sum of interference and noise in the long GI pilot symbol, P _N is the ensemble average of the sum of interference and noise in the normal GI pilot symbol, and t _L and t _N are Forgetting factor, where 0 <λ ≦ 1, for example, in the synthesis in B1626, t _L = 1 / (1 + λ ³ ) and t _N = λ ³ / (1 + λ ³ ).

Note that λ = 1 when time variation is not taken into account.
In the above description, an example of weighting combining using the forgetting factor is shown, but the weighting combining method is not limited to this. For example, the time correlation of the time variation of the propagation path may be measured to obtain a weight component in the time direction, and a weight coefficient based on the weight component may be used.
In the following embodiments, when time variation is taken into account, the method described above is used when processing in the time direction.

Next, a second communication device 501 that is a modification of the second communication device 500 in the present embodiment will be described.
In the first communication apparatus 103 of the fourth embodiment, the information signal symbol signal in which the long GI is set is included in the transmission signal. In this case, in the long GI pilot extraction unit 745, not only pilot symbols but also information data symbols are extracted. Therefore, in the second communication device 501 that receives the signal transmitted by the first communication device 103, the information data symbol is input to the filter unit 760.
FIG. 21 is a schematic block diagram illustrating a configuration example of the second communication device in the present modification.
The second communication apparatus 501 shown in the figure is different from the second communication apparatus 500 shown in FIG. 13 in that information data symbols are transmitted from the data / long GI pilot separation unit 746 to the filter unit 761. The other parts are the same as in FIG. 13, and the same numbers (370, 600, 710, 720, 725, 730a, 730b, 740, 750, 770, 780, 790) as in FIG. .

The data / long GI pilot separation unit 746 extracts a symbol for which a long GI is set, similar to the long GI pilot extraction unit 745 of FIG. Then, similarly to long GI pilot extraction section 745, pilot symbols are output to propagation path estimation section 750 in accordance with mapping information obtained in advance. In addition, unlike long GI pilot extraction section 745, information data symbols are output to filter section 761 according to the mapping information.
In addition to the information data symbol input from data / normal GI pilot demultiplexing section 740, filter section 761 also receives the information data symbol input from data / long GI pilot demultiplexing section 746 from propagation path estimating section 750. According to the input frequency response estimation value, the transmission path compensation of the information data symbol is performed and output to the demapping unit 770.
Thereafter, the demodulation unit 780 and the decoding unit 790 also decode the information data symbol set with the long GI included in the transmission signal of the first communication apparatus 103 into the information data signal.
As described above, since the symbol set with the long GI is also extracted and decoded, the information data signal can be obtained from the information data symbol signal set with the long GI included in the transmission signal.

<Sixth Embodiment>
FIG. 22 is a schematic block diagram illustrating a configuration example of a propagation path estimation unit in the sixth embodiment. In the second communication device 500a of the present embodiment, the propagation path estimation unit 750 (FIG. 14) in the second communication device 500 (FIG. 13) of the fifth embodiment is changed to a propagation path estimation unit 751. Is.
In FIG. 22, the same reference numerals (900a, 900b, 910) are assigned to portions corresponding to the respective portions in FIG. 14, and the description thereof is omitted.
FIG. 22 differs from FIG. 14 in that there are two frequency response interpolation units 920a and 920b before the weighting synthesis unit 910.
The propagation path estimation unit 751 includes frequency response estimation units 900a and 900b, frequency response interpolation units 920a and 920b, and a weighting synthesis unit 910.

FIG. 23 is a flowchart showing processing of the propagation path estimation unit of the present embodiment.
In FIG. 15, S1 for performing frequency response estimation is the same as S1 in FIG. 15, but the order of frequency response interpolation S3b and weighting synthesis S2b is opposite to S2a and S3a in FIG.

Similar to the fifth embodiment, the frequency response estimation unit 900a receives the input of the normal GI pilot symbol, outputs the first frequency response estimation value to the frequency response interpolation unit 920a, and the frequency response estimation unit 900b In response to the input of the GI pilot symbol, the second frequency response estimation value is output to the frequency response interpolation unit 920b (step S1).
Frequency response interpolation section 920a uses the input from frequency response estimation section 900a to interpolate the frequency response estimation values of resource elements other than the resource element in which the scattered pilot symbols are arranged. The frequency response interpolation unit 920b uses the input from the frequency response estimation unit 900b to interpolate the frequency response estimation values of resource elements other than the resource element in which the scattered pilot symbols are arranged (step S3b).
The weighting synthesis unit 910 performs the frequency response estimation value of each resource element input from the frequency response interpolation unit 920a and the frequency response interpolation unit 920b of each resource element input from the frequency response interpolation unit 920b in the fifth implementation. Similarly to the form, the estimated values of the same resource elements are weighted and synthesized according to the estimation accuracy to obtain a propagation path estimated value (step S2b).

FIG. 24 is a conceptual diagram illustrating an example in which the propagation path estimation unit 751 generates an estimated value of the frequency response.
In the frame composed of 2 OFDM symbols and 8 subcarriers in the figure, the second and sixth subcarriers, the long GI pilot symbol at the position of the 2nd OFDM symbol, the 4th and 8th subcarriers, the 2nd Normal GI pilot symbols are mapped to the positions of the OFDM symbols.

First, frequency response estimation sections 900a and 900b estimate frequency responses in subcarriers of normal GI and long GI pilot symbols, respectively. The estimated value obtained at this time is high in accuracy using a long GI pilot symbol and low in accuracy using a normal GI pilot symbol. In FIG. 24, H2402 and H2406 represent frequency response estimation values using long GI pilot symbols, and H2414 and H2418 represent frequency response estimation values using normal GI pilot symbols.
The frequency response interpolation unit 920b performs interpolation on the frequency response estimation values H2402 and H2406, and the frequency response interpolation unit 920a performs interpolation on the frequency response estimation values H2414 and H2418, so that the scattered pilot symbols are changed. For resource elements other than the arranged resource elements, high-accuracy frequency response estimation values (H2401 to H2408) and low-accuracy frequency response estimation values (H24111 to H2418) are obtained. As in the fifth embodiment, the influence of interference and noise is reduced by weighting and synthesizing both, and more accurate frequency response estimation values (H2421 to H2428) are obtained for each subcarrier.

In the present embodiment, frequency response interpolation is performed before weighting, which is effective when normal GI pilot symbols and long GI pilot symbols exist only in different subcarriers. For example, the pilot configuration as shown in FIG. 16 does not differ from the fifth embodiment.
On the other hand, in the case of the pilot configuration as shown in FIG. 20, since the normal GI pilot symbol and the long GI pilot symbol exist in different subcarriers, in the fifth embodiment, , Will be divided into lower subcarriers. When frequency response interpolation is performed in such a state, the accuracy of the frequency response estimation value around the pilot subcarrier with low accuracy is lowered, and the accuracy of the frequency response estimation value around the pilot subcarrier with high accuracy is improved. Variations in accuracy occur. On the other hand, in this embodiment, by performing frequency response interpolation first, high-precision frequency response estimation values over the entire frequency range and low ones are estimated first, and then weighted synthesis is performed. There is no variation in accuracy.

<Seventh Embodiment>
In the fifth and sixth embodiments, the weighted synthesis is performed on the frequency response estimation value, whereas in this embodiment, the frequency response estimation value obtained from the long GI pilot symbol and the normal GI pilot symbol. The channel impulse response is estimated from, and processing is performed for each complex amplitude of each path. When the path delay time does not exceed the length of the normal GI, even if the complex amplitude is obtained from the normal GI pilot symbol, the path power does not decrease, so the path delay time is the length of the normal GI. Further improvement in estimation accuracy can be expected by performing weighted combining using different weighting factors depending on whether or not the number exceeds. In the following description, the path whose delay time exceeds the length of the normal GI and the corresponding complex amplitude are respectively “path exceeding normal GI” and “complex amplitude exceeding normal GI”, and the path not exceeding and the corresponding complex amplitude are “ This is called “path within normal GI” and “complex amplitude within normal GI”.

FIG. 25 is a schematic block diagram illustrating a configuration example of a propagation path estimation unit in the seventh embodiment. The second communication device 500b of the present embodiment is obtained by changing the propagation path estimation unit 750 to a propagation path estimation unit 753 in the communication device 500 of the fifth embodiment.
In FIG. 25, the channel estimation unit 753 includes frequency response estimation units 900a and 900b, channel impulse response estimation units 930a and 930b, complex amplitude extraction units 940a and 950a exceeding the normal GI, and complex amplitude extraction unit 940b within the normal GI. , 950b, weighting synthesis sections 960a and 960b, a channel impulse response reshaping section 970, and an FFT section 980.

FIG. 26 is a flowchart showing a propagation path estimation process according to this embodiment.
When the received signal of the normal GI pilot subcarrier is input, frequency response estimation section 900a estimates the frequency response in the resource element to which the normal GI pilot symbol is mapped. Specifically, the frequency response estimation unit 900a knows in advance the phase and amplitude of the transmission signal, and obtains the ratio between the phase and amplitude of the transmission signal and the phase and amplitude of the reception signal as the frequency response estimation value.
When the received signal of the long GI pilot subcarrier is input, frequency response estimation section 900b estimates the frequency response in the resource element to which the long GI pilot symbol is mapped (step S1).

When the frequency response estimation value is input from the frequency response estimation unit 900a, the channel impulse response estimation unit 930a receives the channel impulse response estimation value (first channel impulse) generated from the frequency response estimation value using the normal GI pilot symbol. Response estimate).
When the frequency response estimation value is input from the frequency response estimation unit 900b, the channel impulse response estimation unit 930b receives the channel impulse response estimation value (second channel impulse) generated from the frequency response estimation value using the long GI pilot symbol. Response estimate). When the first channel impulse response value (channel impulse response value generated from the normal GI pilot symbol) generated by the channel impulse response estimation unit 930a is input, the complex amplitude extraction unit 950a within the normal GI is input A complex amplitude within the normal GI is extracted from the first channel impulse response. Similarly, the within normal GI complex amplitude extraction unit 950b extracts the within normal GI complex amplitude from the second channel impulse response. Further, the normal GI exceeding complex amplitude extracting unit 940a extracts the normal GI exceeding complex amplitude from the first channel impulse response. Secondly, the complex amplitude 940b exceeding the normal GI extracts the complex amplitude exceeding the normal GI from the channel impulse response (step S11).
Here, the channel impulse response is a propagation path characteristic in the time domain expressed by a response (component, complex amplitude) for each sampling point (path), and is estimated from the frequency response by a known method such as a method based on the MMSE norm. The

When the complex amplitudes within normal GI extracted by the complex amplitude extraction units 950a and 950b within normal GI are input, the weighting synthesis unit 960b weights and synthesizes these complex amplitudes having the same delay time (steps). S12a).
When the complex amplitude exceeding normal GI extracted by the complex amplitude extraction units 940a and 940b exceeding normal GI is input, the weighting synthesis unit 960a performs weighted synthesis of those complex amplitudes having the same delay time (step) S12b).
The channel impulse response reshaping unit 970 converts the component exceeding the normal GI interval processed separately and the component not exceeding by the weighting combining units 960a and 960b into the original channel impulse response (step S13).
The FFT unit 980 converts the obtained channel impulse response estimation value into a frequency response by performing FFT (step S14).

FIG. 27 is a conceptual diagram illustrating an example in which the propagation path estimation unit 753 generates an estimated value of the frequency response.
In the frame composed of 2 OFDM symbols and 8 subcarriers in the figure, long GI pilot symbols are located at the positions of resource elements B2722 and B2726, normal GI pilot symbols are located at the positions of the 4th and 8th subcarriers, and B2724 and B2728. It is mapped.

First, frequency response estimation sections 900a and 900b estimate frequency responses in subcarriers of normal GI and long GI pilot symbols, respectively, and channel impulse response estimation sections 930a and 930b estimate channel impulse responses, respectively.
(3) and (4) shown in the center of the figure are the first channel impulse response estimation values generated by the channel impulse response estimation unit 930a, and (1) and (2) are generated by the channel impulse response estimation unit 930b. The second channel impulse response estimation value.
If the previous symbol exceeds the guard interval and enters the FFT interval, the complex amplitude (4) whose delay time exceeds the normal GI of the first channel impulse response has a reduced power and is susceptible to interference and noise. Thus, the accuracy of the channel estimation value is lower than the complex amplitude (2) in which the delay time of the second channel impulse response does not exceed the normal GI. Therefore, the weighting synthesis unit 960a performs weighting synthesis considering this fact.

_Let h _{N be} the complex amplitude of the first channel impulse response estimate and h _{L be} the complex amplitude of the second channel impulse response estimate in a certain path. Also, of the delay time in h _N, amount that exceeds the normal GI interval (which was expressed at a sampling point) d, the number of FFT points and N _f. Using the weighting coefficients a _L and a _N , an estimated value of a complex amplitude obtained by weighting and combining them is generated by a _L h _L + a _N h _N.
Of the delayed wave of the normal GI pilot symbol that is the source of h _N , the d points that exceed the normal GI section are signals representing the previous symbol and do not include the signal of the desired pilot symbol. For this reason, the power representing the desired pilot symbol is reduced by [(N _f −d) / N _f ] ² times compared to the case where the GI interval is sufficiently long and the previous symbol does not exceed the GI interval. ing. Here, when the ensemble averages of the sum of interference and noise power applied to h _L and h _N are P _L and P _N , respectively, a _L and a _N are a _L = P _N / (P _L + b ² When P _N ), a _N = bP _L / (P _L + b ² P _N ), the ensemble average of the power of the sum of interference and noise is minimized. Here, b = (N _f −d) / N _f .
On the other hand, the complex amplitude (3) of which the delay time of the first channel impulse response does not exceed the normal GI does not cause a reduction in power. , A _L = P _N / (P _N + P _L ) and a _N = P _L / (P _L + P _N ) are used to perform weighted synthesis.

In the following, the weighted coefficient calculation method is a _L = P _N / (P _L + b ² P _N ), a _N = bP _L / (P _L + b ² P _N ), so that the combined channel impulse response It is explained that the power of the sum of interference and noise can be minimized.
When there is no influence of the sum of interference and noise, the complex amplitude is h, the complex amplitude after weighted synthesis is h _S , n _L = h _L -h, n _N = h _N -bh, n _S = h _S -h And n _L , n _N , and n _S are so-called complex amplitude shifts caused by the sum of interference and noise. Here, it is assumed that interference also behaves as noise.
When h, n _L , and n _N are used, the complex amplitude h _S = a _L h _L + a _N h _N after weighted synthesis is expressed as h _S = a _L h _L + a _N h _N = a _L (h + n _L ) + a _N (H + bn _N ) = (a _L + ba _N ) h + a _L n _L + a _N n _N
Here, a _L + ba _N = 1 is set as a constraint condition so that the power of h does not increase or decrease. _Then, the _{n S = h S -h = a} L n L + a N n N.

Also, E [] represents the ensemble average (set average), ^* represents the complex conjugate, and P _S is the power of the sum of interference and noise after weighted synthesis, P _L = E [n _L n _L ^* ] , P _N = E [n _N n _N ^* ], and P _S = E [n _S n _S ^* ].
Power sum of the interference and noise of the weighted _{^{synthesis, P S = E [n S}} n S *] = E [(h S -h) (h S -h) *] = E [(a L h L + a _{N h N -h) (a L} h L + a N h N -h) *] = E [(a L h L + a N h N -a L h-ba N h) (a L h L + a N h N _{^{-a L h-ba n h)}} *] = E [(a L n L + a n n n) (a L n L + a n n n) *] = E [a L 2 n L n L * + a n 2 _{^{n n n n * + a L}} a n n L n n * + a L a n n L * n n] = a L 2 E [n L n L *] + a n 2 E [n n n n *] + a L a _N is _{^{E [n L n N *]}} + a L a N E [n L * n N].

Here, assuming that n _L and n _N are uncorrelated, E [n _L n _N ^* ] = 0, E [n _L ^* n _N ] = 0, and P _S = a _L ² E [n _L a ^{_{n L *] + a N 2}} E [n N n N *] = a L 2 P L + a N 2 P N.
Therefore, a _L and a _N that minimize a _L ² P _L + a _N ² P _N under the constraint condition a _L + ba _N = 1 are obtained by using Lagrange's undetermined multiplier method.
With λ as a variable, a function f of a _L , a _N , and λ is set as f = a _L ² P _L + a _N ² P _N −λ (a _L + ba _N −1).
Solving the following two equations obtained by partial differentiation of f, ∂f / ∂a _L = 2a _L P _L -λ = 0, ∂ f / ∂a _N = 2a _N P _N -bλ = 0, a _L = λ / 2P _L , a _N = bλ / 2P _N This is substituted into the constraint condition a _L + ba _N = 1 to obtain λ = 2P _L P _N / (P _L + b ² P _N ). This, above equation _{a L} = _{λ /} 2P _L, by substituting the _{a N = bλ / 2P N,} a L = P N / (P L + b 2 P N), a N = bP L / (P L + B ² P _N ).
From the ^{_{above, a L = P N / (}} P L + b 2 P N), a N = bP L / (P L + b 2 P N) , because the only solutions to minimize _{P S,} this time _{P S} is Minimal.

Note that P _L and P _N used here are the same methods as in the fifth embodiment, assuming that the statistical properties of the frequency domain interference and noise do not change even when the conversion processing to the channel impulse response is performed. Can be calculated.
Note that P _L = P _N may be set assuming that the power of interference and noise applied to h _L and h _N are equal. In this case, the weights in the weighting synthesis unit 960a are a _L = 1 / (b ² +1) and a _N = b / (b ² +1). Further, the weights in the weighting / synthesizing unit 960b are a _L = 1/2 and a _N = 1/2, which are the addition average. In this method, since the power estimation of interference and noise is unnecessary, the amount of calculation can be reduced.

It should be noted that the same calculation method is used when the weighting coefficient calculation method used in the complex amplitude weighting synthesis whose delay time does not exceed the normal GI is the same as the weighting coefficient calculation method used in the complex amplitude weighting synthesis whose delay time exceeds the normal GI. The weighting / synthesizing unit may perform weighting / synthesizing both. For example, the above-described a _L = P _N / (P _L + b ² P _N ) and a _N = bP _L / (P _L + b ² P _N ) are used as weighting factors. Then, the same weighting synthesis as that performed by the weighting synthesis unit 960a can be performed for the complex amplitude whose delay time exceeds the normal GI. As for the complex amplitude within the normal GI, since d = 0, b = 1, and a _L = P _N / (P _L + P _N ), a _N = P _L / (P _L + P _N ) The same weighting synthesis as that performed by the weighting synthesis unit 960b can be performed.
In this case, the complex amplitude within the normal GI also requires a weighting factor for each path, but the amount of calculation increases. In addition, it is not necessary to provide a plurality of weighting synthesis units. And the complex amplitude within the normal GI need not be separated, so that it is not necessary to have a complex amplitude extraction unit exceeding the normal GI and a complex amplitude extraction unit within the normal GI, and the circuit scale can be reduced.

<Eighth Embodiment>
FIG. 28 is a schematic block diagram illustrating a configuration example of the first communication device according to the eighth embodiment.
In the figure, the same reference numerals (200, 300, 310, 320, 330a, 340, 350, 360, 370, 250, 325, 330b, 345) are given to the portions corresponding to the respective parts in FIG. Is omitted.
FIG. 28 differs from FIG. 1 in that the first communication device 104 includes a low power allocation unit 400 and a high power allocation unit 405. Low power allocating section 400 and high power allocating section 405 respectively determine signal power allocated to normal GI pilot symbols and long GI pilot symbols, and change the amplitudes of these symbols.
As the second communication device corresponding to the first communication device of the present embodiment, for example, the second communication devices 500, 500a, and 500b of the fifth to eighth embodiments can be used.

In FIG. 28, the reason why the low power is assigned to the normal GI pilot symbol is to keep the sum of the power of the increased long GI pilot symbol constant.
Since the high power is allocated, the SINR of the long GI pilot symbol increases, so that the accuracy of channel estimation can be improved. On the other hand, the normal GI pilot symbol is not greatly improved in estimation accuracy even if high power is allocated because the influence of inter-symbol interference and inter-carrier interference is large.

The amplified power value is notified to the second communication device on the receiving side as system control information. In the second communication apparatuses 500, 500a, and 500b according to the fifth to eighth embodiments, the weighting combining by the weighting combining units 910, 960a, and 960b may be performed based on the notified power value, so that the weight coefficient generation is performed. Can be reduced. Specifically, assuming that the power allocated to the long GI pilot symbol and the normal GI pilot symbol is P ₁ and P ₂ , w _L = P ₁ / (P ₁ + P ₂ ), w _N = P ₂ / (P ₁ + P ₂ ). Moreover, the power to be allocated need not be limited to two, and may be three or more. For example, when P1 is assigned to a part of a long GI pilot symbol, P2 is assigned to the rest, and P3 is assigned to a normal GI pilot symbol, W _L1 = P ₂ P ₃ / (P ₁ P ₂ + P ₂ P ₃ + P ₁ P ₃ ), W _L2 = P ₁ P ₃ / (P ₁ P ₂ + P ₂ P ₃ + P ₁ P ₃ ), W _N = P ₁ P ₂ / (P ₁ P ₂ + P ₂ P ₃ + P ₁ P ₃ ). Here, W _L1 and W _L2 are weighting coefficients to be applied to the frequency responses estimated using the long GI pilot symbols to which P ₁ and P ₂ are allocated, respectively.

  As described above, since the signal power higher than that of the normal GI pilot symbol is assigned to the long GI pilot symbol, the accuracy of channel estimation can be improved. In addition, since the allocated power value is notified to the second communication device on the receiving side, the value notified by the second communication device is used for weighting, thereby reducing the circuit scale and calculation amount of the weight coefficient calculation. it can.

In the present embodiment, the case where there are a normal GI pilot symbol and a long GI pilot symbol has been described. However, the present invention is not limited to this, and there may be a difference in signal power when only a long GI pilot symbol is present. Good.
In the present embodiment, the power allocated to the two types of pilot symbols, the long GI pilot symbol and the normal GI pilot symbol, has been described, but there may be a case where there are a plurality of long GI pilot symbols. In this case, there may be a plurality of powers allocated in the same manner as described above.
In the present embodiment, the power allocated to the two types of pilot symbols, the long GI pilot symbol and the normal GI pilot symbol has been described. However, only the normal GI pilot symbol may be transmitted and a plurality of powers may be allocated therein. .

<Tenth Embodiment>
FIG. 29 is a schematic block diagram illustrating a configuration example of the first communication device according to the tenth embodiment.
In the figure, the same reference numerals (300, 310, 330a, 340, 350, 360, 370, 330b, 345) are assigned to portions corresponding to the respective portions in FIG.
FIG. 29 differs from FIG. 1 in that the first communication device 105 includes a long GI control unit 410 and a wireless reception unit 711.

When the propagation path characteristics are good, accurate propagation path estimation can be performed without a long GI pilot symbol. In the present embodiment, when the propagation path estimation can be performed with high accuracy, the second communication apparatus of the communication partner transmits a notification that the long GI pilot symbol is unnecessary.
In the first communication device 105, the wireless reception unit 711 receives a notification from the second communication device of the communication partner and outputs it to the long GI control unit 410. Long GI control section 410 controls whether to map a long GI pilot symbol according to the notification. In addition, long GI control unit 410 notifies the second communication apparatus of the communication counterpart as information on whether or not the long GI pilot symbol has been mapped.

FIG. 30 is a conceptual diagram illustrating an example when a long GI pilot symbol is not mapped to a reserved position of the long GI.
In the figure, a position where insertion of a long GI pilot symbol is reserved (hereinafter referred to as “reserved position”) in the mapping performed by the first mapping unit 320 is filled with data symbols, and the second mapping is performed. Nothing is mapped to the reserved position of the mapping long GI performed by the unit 325. This control is performed by the long GI control unit 410. When receiving a notification that the long GI pilot symbol is unnecessary from the second communication apparatus of the communication partner, the long GI control unit 410 designates a reserved position to the first mapping unit 320 and sets the reserved position to the reserved position. Instructs to map data symbols. The long GI control unit 410 also designates a reserved position and instructs the second mapping unit 325 not to map anything to the reserved position. In addition, long GI control section 410 superimposes the reserved position where the long GI pilot symbol is not mapped on the control signal.
On the other hand, when the notification that the long GI pilot symbol is necessary is received from the second communication apparatus of the communication partner, the processing is performed in accordance with the predetermined mapping as in the first embodiment, and the control signal is processed. However, nothing is superimposed on the information on the reserved position where the long GI pilot symbol is not mapped.

FIG. 31 is a conceptual diagram illustrating an example in which a long GI pilot symbol is mapped to a reserved position of the long GI.
When the long GI control unit 410 receives a request to map the long GI pilot symbol from the second communication apparatus of the communication partner, the long GI control unit 410 designates a reserved position to the first mapping unit 320, and the reserved position To map nothing. In addition, long GI control unit 410 designates a reserved position and instructs second mapping unit 325 to map a long GI pilot symbol to the reserved position. In addition, long GI control section 410 superimposes the reserved position mapping the long GI pilot symbol on the control signal.

The second communication device of the communication partner changes the processing of the own communication device based on this control signal. For example, when a long GI pilot symbol exists, that is, when a long GI is set for some pilot symbols, the channel estimation shown in the fifth to eighth embodiments can be performed. Also, encoding on the transmission side and decoding on the reception side are performed using positions other than the position where the long GI pilot symbol is added.
FIG. 32 is a schematic block diagram illustrating a configuration example of the second communication apparatus of the communication counterpart corresponding to the first communication apparatus 105 in the present embodiment.
In the figure, the same reference numerals (370, 600, 710, 730a, 730b, 760, 770, 780, 790) are assigned to the portions corresponding to the respective portions in FIG.
32 includes a first FFT section extraction unit 721, a second FFT section extraction unit 726, a data / normal GI pilot separation unit 741, and a long GI pilot extraction unit 747. The information about the reserved position obtained by mapping the long GI pilot symbol superimposed on the control signal is used to correct the mapping information obtained in advance, from the propagation path estimation unit 754 to the long GI necessity determination unit 800, the first frequency. A point where a response estimation value (frequency response estimation value obtained from a normal GI pilot symbol) is output, and a point where the long GI necessity determination unit 800 transmits the necessity of a long GI pilot symbol via the wireless transmission unit 361 This is different from FIG.

Long GI necessity determination unit 800 determines whether or not the first frequency response estimation value input from propagation path estimation unit 754 is within a predetermined range. If it is within a certain range, the long GI necessity determination unit 800 determines that the propagation path characteristics are good and accurate channel compensation can be performed only with the normal GI pilot symbol. A notification that the long GI pilot symbol is unnecessary is transmitted to 105.
Conversely, when the first frequency response estimation value is outside a certain range, the propagation path characteristics are poor and a long GI pilot symbol is required, and the long GI necessity determining unit 800 requires a long GI pilot symbol. Send a notification.

  When the information on the position where the long GI pilot symbol is not mapped is superimposed by the first communication apparatus 105 in response to the notification that the long GI pilot symbol is unnecessary, the first FFT section extracting unit 721, The second FFT interval extraction unit 726 corrects the mapping information obtained in advance, and extracts the first FFT interval and the second FFT interval, respectively. Similarly, the data / normal GI pilot separating unit 741 and the long GI pilot extracting unit 747 correct the mapping information obtained in advance, and then separate the data symbol and the pilot symbol to extract the pilot symbol. Hereinafter, as in FIG. 1, the information data symbols separated by the data / normal GI pilot separation unit 741 are decoded into information data signals through the filter unit 760, the demapping unit 770, the demodulation unit 780, and the decoding unit 790. .

  As described above, the first communication apparatus 105 does not transmit the long GI pilot symbol, but instead maps the data symbol, and the second communication apparatus 502 maps the information data symbol mapped instead of the long GI pilot symbol. Is decoded together with other information data symbols, so that transmission efficiency can be improved.

In the above description, the data symbol is mapped to the reserved position when the long GI pilot symbol is unnecessary, but the present invention is not limited to this, and a normal GI pilot symbol or the like may be used.
In the above description, only the option of whether or not to set a long GI pilot symbol is shown, but some reserved positions may be long GI pilot symbols. For example, in FIG. 30, the positions of the second and third OFDM symbols in the third and sixth subcarriers are reserved positions, and in FIG. 31, both the third and sixth subcarriers are long GI pilot symbols. However, only one of them may be used. Moreover, although the case where the reservation position exists in two subcarriers is shown in the above description, the present invention is not limited to this, and three or four cases may be used. Also in this case, whether or not to assign a long GI pilot symbol may be designated for each reserved position.

  1, the normal GI symbol generation unit 200, the long GI symbol generation unit 250, the encoding unit 300, the modulation unit 310, the first mapping unit 320, and the second mapping. 325, IFFT units 330a and 330b, normal GI insertion unit 340, long GI insertion unit 345, multiplexing unit 350, radio transmission unit 360, transmission symbol generation unit 191 in FIG. 8, and normal GI symbol generation Unit 200, long GI pilot symbol storage unit 260, encoding unit 300, modulation unit 310, first mapping unit 320, IFFT unit 330a, normal GI insertion unit 340, multiplexing unit 350, and radio transmission Unit 360, transmission symbol generation unit 192 in FIG. 9, normal GI symbol generation unit 201, Long GI mapping symbol generation section 270, encoding section 300, modulation section 310, mapping section 321, IFFT section 330a, normal GI insertion section 340, multiplexing section 350, radio transmission section 360, and phase rotation 11, transmission symbol generator 193 in FIG. 11, normal GI symbol generator 202, long GI symbol generator 251, encoder 300, modulator 311, first mapping unit 320, second Mapping section 326, IFFT sections 330a and 330b, normal GI insertion section 340, long GI insertion section 345, multiplexing section 350, radio transmission section 360, FFT section extraction section 600 in FIG. 13, and FFT section 610, data / pilot separation unit 620, radio reception unit 710, and first FFT interval extraction unit 7 0, the second FFT interval extraction unit 725, the first FFT unit 730, the second FFT unit 735, the data / normal GI pilot separation unit 740, the long GI pilot extraction unit 745, and the channel estimation Unit 750, filter unit 760, demapping unit 770, demodulation unit 780, decoding unit 790, frequency response estimation units 900a and 900b in FIG. 14, weighting synthesis unit 910, frequency response interpolation unit 920, 21, FFT section 610, data / pilot separation section 621, radio reception section 710, first FFT section extraction section 720, second FFT section extraction section 725, 1 FFT section 730, second FFT section 735, data / normal GI pilot separation section 740, and data / long GI pilot Separating section 746, propagation path estimation section 750, filter section 760, demapping section 770, demodulation section 780, decoding section 790, propagation path estimation section 751 in FIG. 22, and frequency response estimation sections 900a and 900b A frequency response interpolation unit 920a, 920b, a weighting synthesis unit 910, a propagation path estimation unit 753 in FIG. 25, a frequency response estimation unit 900a, 900b, a channel impulse response estimation unit 930a, 930b, a complex exceeding normal GI Amplitude extraction units 940a and 940b, within normal GI complex amplitude extraction units 950a and 950b, weighting synthesis units 960a and 960b, channel impulse response reconfiguration unit 970, FFT unit 980, and transmission symbol generation unit 194 in FIG. A normal GI symbol generator 200 and a long GI symbol Generation unit 250, encoding unit 300, modulation unit 310, first mapping unit 320, second mapping unit 325, IFFT units 330a and 330b, normal GI insertion unit 340, and long GI insertion unit 345 A multiplexing unit 350, a wireless transmission unit 360, a low power allocation unit 400, a high power allocation unit 405, a transmission symbol generation unit 195, a normal GI symbol generation unit 203, and a long GI symbol generation unit in FIG. 252, coding section 300, modulation section 310, first mapping section 322, second mapping section 327, IFFT sections 330 a and 330 b, normal GI insertion section 340, long GI insertion section 345, Multiplexer 350, wireless transmitter 360, long GI controller 410, wireless receiver 711, and wireless transmission in FIG. 361, FFT section extraction section 600, FFT section 610, data / pilot separation section 620, radio reception section 710, first FFT section extraction section 721, second FFT section extraction section 726, 1 FFT section 730, second FFT section 735, data / normal GI pilot separation section 741, long GI pilot extraction section 747, propagation path estimation section 754, filter section 760, demapping section 770, The program for realizing the functions of the demodulation unit 780 and the decoding unit 790 is recorded on a computer-readable recording medium, and the program recorded on the recording medium is read into a computer system and executed. You may perform the process of. The “computer system” here includes an OS and hardware such as peripheral devices.

The present invention can be used for both fixed communication and mobile communication. When used for mobile communication, the transmitting device is used for the transmitting portion of the base station device, and the receiving device is used for the receiving portion of the mobile station device, but the reverse is also possible.

Further, the “computer system” includes a homepage providing environment (or display environment) if a WWW system is used.
The “computer-readable recording medium” refers to a portable medium such as a flexible disk, a magneto-optical disk, a ROM, and a CD-ROM, and a storage device such as a hard disk built in the computer system. Furthermore, the “computer-readable recording medium” dynamically holds a program for a short time like a communication line when transmitting a program via a network such as the Internet or a communication line such as a telephone line. In this case, a volatile memory in a computer system serving as a server or a client in that case, and a program that holds a program for a certain period of time are also included. The program may be a program for realizing a part of the functions described above, and may be a program capable of realizing the functions described above in combination with a program already recorded in a computer system.

  The embodiment of the present invention has been described in detail with reference to the drawings. However, the specific configuration is not limited to this embodiment, and includes design changes and the like within a scope not departing from the gist of the present invention.

  The present invention is suitable for use in a communication system using a mobile phone, but is not limited to this.

100, 101, 102, 103, 104, 105, 500, 500a, 500b, 501, 502 ... Communication devices 190, 191, 192, 193, 194, 195 ... Transmission symbol generators 200, 201, 202, 203 ... Normal GI Symbol generators 250, 251, 252 ... Long GI symbol generator 260 ... Long GI pilot symbol storage unit 270 ... Long GI mapping symbol generator 300 ... Encoder 310, 311 ... Modulator 320, 322 ... First mapping unit 321 ... Mapping units 325, 326, 327 ... Second mapping units 330a, 330b ... IFFT unit 340 ... Normal GI insertion unit 345 ... Long GI insertion unit 350 ... Multiplexing units 360, 361 ... Radio transmission unit 370 ... Antenna 385 ... Phase Rotating unit 400 ... low power allocation unit 405 ... High power allocation unit 410 ... Long GI control unit 600 ... FFT section extraction section 610 ... FFT section 620, 621 ... Data / pilot separation sections 710, 711 ... Radio reception sections 720, 721 ... First FFT section extraction section 725 726, second FFT section extraction unit 730, first FFT unit 735, second FFT unit 740, 741, data / normal GI pilot separation unit 745, 747, long GI pilot extraction unit 746, data / long GI. Pilot separation units 750, 751, 752, 753, 754 ... propagation path estimation units 760, 761 ... filter unit 770 ... demapping unit 780 ... demodulation unit 790 ... decoding unit 800 ... long GI necessity determination unit 900a, 900b ... frequency response Estimating unit 910 ... weighting synthesis unit 920, 920a, 920b ... frequency response interpolation unit 30a, 930 b ... channel impulse response estimation unit 940a, 940b ... Normal GI exceed complex amplitude extraction section 950a, 950b ... Normal GI within the complex amplitude extraction section 960a, 960b ... weighting combining unit 970 ... channel impulse response re-formed portions 980 ... FFT unit

Claims (25)

In the first communication device that performs multi-carrier modulation on symbols that are basic units of digital signals,
A first pilot symbol to which a first guard interval is added is scattered between subcarriers constituting a multicarrier at the same time, and subcarriers constituting a multicarrier at the same time. A transmission symbol generation unit that generates a signal including a second multicarrier symbol in which second pilot symbols added with a second guard interval longer than the first guard interval are scattered between carriers. A first communication device characterized in that:   2. The first communication apparatus according to claim 1, wherein some of the second multicarrier symbols include an information data symbol that is a symbol of an information data signal.   2. The first communication apparatus according to claim 1, wherein some of the second multicarrier symbols include a control symbol which is a symbol of a control signal. The transmission symbol generator is
A first multicarrier symbol generator for generating the first multicarrier symbol by adding the first guard interval to a symbol including the first pilot symbol;
A second multicarrier symbol generator for generating the second multicarrier symbol by adding the second guard interval to a symbol including the second pilot symbol;
4. The multiplex unit according to claim 1, further comprising: a multiplexing unit that multiplexes the first multi-carrier symbol and the second multi-carrier symbol in a time domain. 1. Communication device. The symbol to which the second multicarrier symbol generation unit adds the second guard interval is a pilot symbol,
The transmission symbol generation unit includes a second multicarrier symbol storage unit that stores the second multicarrier symbol generated by the second multicarrier symbol generation unit. First communication device. The transmission symbol generator is
The symbol to which the second guard interval is added is phase-rotated, and is a symbol arranged one time before in the time direction of the same subcarrier as the symbol to which the second guard interval is added. A phase rotator that generates symbols that form part of the guard interval of
A frequency domain symbol multiplexing unit that multiplexes in a frequency domain the symbol to which the first guard interval is added, the symbol to which the second guard interval is added, and the symbol generated by the phase rotation unit;
An inverse Fourier transform unit that performs inverse Fourier transform on the symbols multiplexed by the frequency domain symbol multiplexing unit and converts the symbols into a time domain signal;
The guard interval insertion part which adds the guard interval of the length of the said 1st guard interval to the signal of the time domain which the said inverse Fourier transform part transformed, The any one of Claim 1 to 3 characterized by the above-mentioned. The 1st communication apparatus as described in a term. The symbol to which the second guard interval is added is a pilot symbol,
The transmission symbol generation unit includes a second symbol storage unit that stores a symbol to which the second guard interval is added and a symbol generated by the phase rotation unit. 1st communication apparatus of description. The transmission symbol generator is
A symbol that is phase-rotated for a symbol that forms part of the second guard interval, and that is placed one time later in the time direction of the same subcarrier as the symbol that forms part of the second guard interval, A phase rotation unit for generating a symbol to which the second guard interval is added;
Frequency domain symbol multiplexing for multiplexing in the frequency domain a symbol to which the first guard interval is added, a symbol to which the second guard interval is added, and a symbol that forms part of the second guard interval. And
An inverse Fourier transform unit that performs inverse Fourier transform on the symbol multiplexed by the frequency domain symbol multiplexing unit, and converts the symbol into a time domain symbol;
The guard interval insertion part which adds the guard interval of the length of the said 1st guard interval to the symbol of the time domain which the said inverse Fourier transform part transformed, The any one of Claim 1 to 3 characterized by the above-mentioned. The 1st communication apparatus as described in a term. The transmission symbol generator is
A low power allocation unit that allocates transmission power of the first pilot symbol;
The high power allocating unit that allocates the transmission power of the second pilot symbol higher than the transmission power allocated by the low power allocating unit, according to any one of claims 1 to 4 A first communication device according to claim 6 or claim 8. The transmission symbol generator is
When receiving a notification from the second communication apparatus of the communication partner that the second pilot symbol is unnecessary or a notification that the number of the second pilot symbols may be reduced, the second pilot symbol The first communication apparatus according to claim 1, wherein the first communication apparatus is not mapped or the number of mapping of the second pilot symbols is reduced. The transmission symbol generation unit notifies the communication partner second communication device that the second pilot symbol is unnecessary, or the notification that the number of the second pilot symbols may be reduced. 11. The symbol to which the first guard interval is added is mapped at a position where the second pilot symbol is scheduled to be mapped. Communication device. In the second communication device that receives a signal that is a multi-carrier modulated symbol that is a basic unit of a digital signal,
A first guard interval is added, and at the same time, first pilot symbols scattered between subcarriers constituting a multicarrier, and a second guard interval longer than the first guard interval are added, A radio reception unit for receiving a signal including second pilot symbols scattered between subcarriers constituting a multicarrier at the same time;
A pilot separation unit for separating the first pilot symbol and the second pilot symbol from the received signal;
A second communication apparatus comprising: a propagation path estimation unit that calculates a propagation path estimated value of each subcarrier from the extracted first pilot symbol and the second pilot symbol.   The propagation path estimation unit weights and synthesizes a first propagation path estimated value calculated from the first pilot symbol and a second propagation path estimated value calculated from the second pilot symbol. The second communication device according to claim 12. The first propagation path estimated value and the second propagation path estimated value are frequency response estimated values,
The propagation path estimator weights and synthesizes the first propagation path estimated value and the second propagation path estimated value for the same subcarrier, and interpolates the weighted combined result in the frequency direction to obtain each subcarrier. The second communication apparatus according to claim 13, wherein an estimated propagation path value is calculated. The first propagation path estimated value and the second propagation path estimated value are frequency response estimated values,
The propagation path estimation unit calculates the first propagation path estimated value of each subcarrier by interpolating the first propagation path estimated value in the frequency direction, and calculates the second propagation path estimated value in the frequency direction. By calculating the second propagation path estimated value of each subcarrier and weighting and combining the first propagation path estimated value and the second propagation path estimated value in each subcarrier. The second communication apparatus according to claim 13, wherein a propagation path estimation value of each subcarrier is calculated. The combination performed by the propagation path estimation unit is weighted combining, and the weighting coefficient of the weighted combination includes a weight component in the time direction that varies in time. 15. The second communication device according to 15. The first channel estimation value and the second channel estimation value are channel impulse response estimates,
The propagation path estimation unit performs time-frequency conversion on an estimated value of a channel impulse response calculated by weighting and combining components having the same delay time among the first propagation path estimation value and the second propagation path estimation value The second communication apparatus according to claim 13, wherein a propagation path estimation value of each subcarrier is calculated.   The propagation path estimation unit arithmetically averages a component having a delay time within the length of the first guard interval from the first propagation path estimation value and the second propagation path estimation value, and delay time The channel impulse response estimated value calculated by weighting and combining components exceeding the length of the first guard interval is time-frequency converted to calculate the propagation path estimated value of each subcarrier. Item 18. The second communication device according to Item 17. The propagation path estimation unit uses the weighting combination weighting factor as
The weighted synthesis is performed using a value based on a time exceeding the first guard interval among delay times in the component of the first propagation path estimated value. The 2nd communication apparatus of description. The propagation path estimation unit performs weighting combining using a value based on a ratio of interference and noise strength included in a received signal of each subcarrier as a weighting coefficient of the weighting combining. The second communication device according to any one of claims 13 to 18. The propagation path estimator is
A value based on a value indicating the transmission power of the first pilot symbol and a value indicating the transmission power of the second pilot symbol received from the first communication device of the communication partner as the weighting coefficient of the weighting synthesis. The second communication device according to claim 13, wherein the second communication device is used. In a communication system including a first communication device and a second communication device that perform multi-carrier modulation on a symbol that is a basic unit of a digital signal,
The first communication device is:
A first guard interval is added, and at the same time, first pilot symbols scattered between subcarriers constituting a multicarrier, and a second guard interval longer than the first guard interval are added, A transmission symbol generation unit for generating a signal including second pilot symbols scattered between subcarriers constituting a multicarrier at the same time;
The second communication device is:
A radio receiver that receives a signal including the first pilot symbol and the second pilot symbol;
A pilot separation unit for separating the first pilot symbol and the second pilot symbol from the received signal;
A communication system comprising: a propagation path estimation unit that calculates a propagation path estimation value of each subcarrier from the extracted first pilot symbol and the second pilot symbol. In the transmission method of the first communication device that performs multi-carrier modulation on a symbol that is a basic unit of a digital signal,
The same time as the first multicarrier symbol, in which the first pilot symbol to which the first guard interval is added is scattered between the subcarriers constituting the multicarrier at the same time. , A signal including a second multicarrier symbol in which second pilot symbols added with a second guard interval longer than the first guard interval are interspersed between subcarriers constituting the multicarrier. A transmission method comprising: a transmission symbol generation step for generating. In the receiving method of the second communication apparatus for performing communication by performing multicarrier modulation on a symbol which is a basic unit of a digital signal,
The second communication device is provided with a first guard interval, and at the same time, a first pilot symbol scattered between subcarriers constituting a multicarrier and a first longer than the first guard interval. A radio reception process of receiving a signal including a second pilot symbol scattered between subcarriers constituting a multicarrier at the same time with two guard intervals added;
A pilot separation process in which the second communication device separates the first pilot symbol and the second pilot symbol from the received signal;
The second communication apparatus includes: a propagation path estimation process for calculating a propagation path estimated value of each subcarrier from the extracted first pilot symbol and the second pilot symbol. Reception method. In a communication method of a communication system including a first communication device and a second communication device that perform multi-carrier modulation on a symbol that is a basic unit of a digital signal.
The same time as the first multicarrier symbol, in which the first pilot symbol to which the first guard interval is added is scattered between the subcarriers constituting the multicarrier at the same time. , A signal including a second multicarrier symbol in which second pilot symbols added with a second guard interval longer than the first guard interval are interspersed between subcarriers constituting the multicarrier. A transmission symbol generation process to be generated;
A radio reception process in which the second communication apparatus receives a signal including the first pilot symbol and the second pilot symbol;
A pilot demultiplexing unit that demultiplexes the first pilot symbol and the second pilot symbol from the received signal;
The second communication apparatus includes a channel estimation process for calculating a channel estimation value of each subcarrier from the extracted first pilot symbol and the second pilot symbol. Communication method.

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