JP2001069110A - Ofdm communication equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To guarantee communication efficiency and communication quality even when maximum delay time is changed by the installation place or use time band of orthogonal frequency division multiplex(OFDM) communication equipment. SOLUTION: A measuring symbol transmitting part 22 successively transmits series of measuring symbols. A measuring symbol receiving part 23 successively receives the measuring symbols transmitted through a communication channel 21 and detects a shortest guard interval length κ, which can be confirmed. A notice transmitting part 25 reports κ to a notice receiving part 26. The notice receiving part 26 outputs the reported κ to a data symbol transmitting part 30. While using the guard interval length κ, the data symbol transmitting part 30 generates a data symbol ω of OFDM from inputted transmission data X and transmits it. While using the guard interval length κ, a data symbol receiving part 31 is receives the transmitted data symbol ω of OFDM and outputs received data Y.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an orthogonal frequency division multiplex (Orthogonal Frequency Div.).
edition Multiplexing: Hereinafter, OFD
M), more specifically OFDM
The present invention relates to adaptive control of a guard interval in a communication device.

[0002]

2. Description of the Related Art Generally, an OFDM signal includes an effective symbol period and a guard interval. The effective symbol period is a symbol period including a signal for transmitting data. The guard interval is a period inserted to reduce the effect of multipath. For example, the guard interval includes a redundant signal such as a signal in which valid symbols are repeated. By inserting the guard interval into the OFDM signal, it is possible to avoid the influence of the delayed wave within the guard interval length.

Conventionally, a guard interval length in an OFDM communication apparatus may be determined in advance by taking into account a maximum delay time of a multiplex wave in a general environment.

In some cases, a predetermined value is not determined in advance. Conventionally, for example, Japanese Patent Application Laid-Open No. 9-1
As disclosed in Japanese Patent No. 35230, there is a method in which a data symbol transmitting apparatus notifies a data symbol receiving apparatus of a certain system parameter to change the guard interval length. Further, for example, Japanese Patent Application Laid-Open No. 10-308
As disclosed in Japanese Patent No. 716, there is a method of detecting a guard interval length changed on the data symbol transmitting side on the data symbol receiving side. Each of these methods
This is a method in which the data symbol receiving side responds to the change of the guard interval length by the data symbol transmitting side.

[0005]

In general, the propagation delay time greatly varies depending on the installation location of the apparatus and the time of use. Therefore, if the actual delay time is shorter than the delay time preset in the system, an unnecessary guard interval is used. In such a case, the communication efficiency decreases. If the actual delay time is longer than the delay time preset in the system, the influence of the delay wave cannot be absorbed by the guard interval. In such a case, the communication quality is degraded.

[0006] In the above conventional example,
Since the data symbol receiving side only responds to the change of the guard interval length by the data symbol transmitting side, the changed guard interval does not always match the actual delay time.

Therefore, there is a need for a method of optimizing the guard interval length by measuring the changing propagation environment and adaptively adjusting the guard interval period suitable for the actual delay time.

It is an object of the present invention to provide an OFDM communication apparatus for measuring such a fluctuating propagation environment using measurement symbols and adaptively optimizing a guard interval period.

[0009]

According to a first aspect of the present invention, when an OFDM signal is transmitted from a transmitting station to a receiving station, a guard interval included in an OFDM symbol in the OFDM signal is adaptively adjusted. An OFDM communication device for adjusting the length of the delay wave, a measurement symbol transmitting means for transmitting a measurement symbol for obtaining a guard interval length corresponding to the maximum delay time of the delay wave, and an optimum guard interval length for receiving the measurement symbol. And a guard interval adjusting unit that adaptively adjusts a guard interval included in the OFDM symbol by using the calculated guard interval length.

[0010] In the first aspect of the present invention, an optimum guard interval is used by measuring a fluctuating propagation environment and adaptively adjusting a guard interval period suitable for an actual delay time. Therefore, communication efficiency can be improved.

A second invention is directed to the OFD according to the first invention.
M communication device, wherein the measurement symbol transmission means is provided on the transmission station side, the measurement symbol reception means is provided on the reception station side, the guard interval adjustment means is provided on the reception station side, and the measurement symbol reception means Notification transmitting means for transmitting a notification including the calculated guard interval length to the transmitting station side, and a notification provided at the transmitting station side for receiving the notification from the notification transmitting means and obtaining the calculated guard interval length A receiving means, a data symbol transmitting means provided on the transmitting station side for setting a guard interval length obtained by the notification receiving means as a parameter, and transmitting a data symbol having the guard interval length to the receiving station side; The guard interval length provided at the station side and calculated by the measurement symbol receiving means is set as a parameter. And a data symbol reception means for receiving data symbols having the guard interval length.

In the second invention, the guard interval period on the data symbol transmitting side and the data symbol receiving side is adaptively adjusted using the notification transmitting means and the notification receiving means, and an optimal guard interval is used.
Therefore, communication efficiency can be improved. Further, the data symbol transmission side can take the initiative in performing the measurement.

A third invention is directed to the OFD according to the second invention.
M communication apparatus, wherein one transmitting station communicates with a plurality of receiving stations, the guard interval adjusting means is provided on the transmitting station side, and the guard interval adjusting means is provided for each of the plurality of receiving stations inputted from the notification receiving means. The transmitting side guard interval length storing means for storing the interval length in association with each receiving station, wherein the transmitting side guard interval length storing means, when a receiving station of a communication destination is selected, the selected receiving station Is read out and output to the data symbol transmitting means.

[0014] In the third aspect of the present invention, on the transmitting station side,
A different guard interval is set for each communication destination and stored. Thereby, an optimum guard interval is set for each communication destination, and communication efficiency can be improved.

A fourth invention is directed to the OFD according to the second invention.
In the M communication apparatus, when a plurality of transmitting stations communicate with one receiving station, the guard interval adjusting means is provided on the receiving station side and is provided for each of the plurality of transmitting stations calculated by the measurement symbol receiving means. Guard interval length further includes a receiving side guard interval length storing means for storing the transmitting station corresponding to each transmitting station, the receiving side guard interval length storing means, when the transmitting station of the communication destination is selected,
The guard interval length corresponding to the selected transmitting station is read out and output to the data symbol receiving means.

[0016] In the fourth aspect, on the receiving station side,
A different guard interval is set for each communication destination and stored. Thereby, an optimum guard interval is set for each communication destination, and communication efficiency can be improved.

The fifth invention is directed to the OFD according to the second invention.
In the M communication apparatus, when a plurality of transmitting stations communicate with a plurality of receiving stations, the guard interval adjusting means is provided on the transmitting station side, and the guard interval adjusting means is provided for each of the plurality of receiving stations inputted from the notification receiving means. Transmitting side guard interval length storing means for storing an interval length in association with each receiving station; and a guard interval length for each of a plurality of transmitting stations, which is provided on the receiving station side and calculated by the measurement symbol receiving means. A receiving-side guard interval length storing means for storing in correspondence with the station, wherein the transmitting-side guard interval length storing means, when a receiving station of a communication destination is selected, a guard interval corresponding to the selected receiving station; The length is read out and output to the data symbol transmitting means, and the receiving side guard interval length storing means stores the data when the transmitting station of the communication destination is selected. Reading a guard interval length corresponding to the selected transmission station and outputs to the data symbol reception means.

In the fifth invention, different guard intervals are set and stored for each communication destination on both the transmitting station side and the receiving station side. As a result, an optimal guard interval is set for each destination,
Communication efficiency can be improved.

A sixth invention is directed to the OFD according to the first invention.
M communication device, wherein the measurement symbol transmitting means is provided on the receiving station side, the measurement symbol receiving means is provided on the transmitting station side, the guard interval adjusting means is provided on the transmitting station side, and the measurement symbol receiving means Notification transmitting means for transmitting a notification including the calculated guard interval length to the receiving station side, and a notification provided on the receiving station side for receiving the notification from the notification transmitting means and obtaining the calculated guard interval length Receiving means, provided on the transmitting station side, a data symbol transmitting means for setting a guard interval length calculated by the measurement symbol receiving means as a parameter, and transmitting a data symbol having the guard interval length to the receiving station side; The guard interval length provided on the receiving station side and obtained by the notification receiving means is set as a parameter. And a data symbol reception means for receiving data symbols having the guard interval length.

[0020] In the sixth aspect of the present invention, the guard interval period on the data symbol transmitting side and the data symbol receiving side is adaptively adjusted using the notification transmitting means and the notification receiving means, and an optimal guard interval is used.
Therefore, communication efficiency can be improved. Further, the data symbol receiving side can take the initiative in the measurement.

According to a seventh aspect, the OFD according to the sixth aspect is provided.
In the M communication device, when one transmitting station communicates with a plurality of receiving stations, the guard interval adjusting means is provided on the transmitting station side and is provided for each of the plurality of receiving stations calculated by the measurement symbol receiving means. Guard interval length further includes a transmission-side guard interval length storage unit that stores in association with each receiving station, the transmission-side guard interval length storage unit, when a receiving station of the communication destination is selected,
The guard interval length corresponding to the selected receiving station is read and output to the data symbol transmitting means.

In the seventh aspect, the transmitting station side
A different guard interval is set for each communication destination and stored. Thereby, an optimum guard interval is set for each communication destination, and communication efficiency can be improved.

An eighth invention is directed to the OFD according to the sixth invention.
In the M communication apparatus, when a plurality of transmitting stations communicate with one receiving station, the guard interval adjusting means is provided on the receiving station side, and the guard interval adjusting means is provided for each of the plurality of transmitting stations input from the notification receiving means. The receiving side guard interval length storing means for storing the interval length in association with each transmitting station, wherein the receiving side guard interval length storing means stores the selected transmitting station when the transmitting station of the communication destination is selected. Is read out and output to the data symbol receiving means.

In the eighth aspect, the receiving station side
A different guard interval is set for each communication destination and stored. Thereby, an optimum guard interval is set for each communication destination, and communication efficiency can be improved.

The ninth invention is directed to the OFD according to the sixth invention.
In the M communication apparatus, when a plurality of transmitting stations communicate with a plurality of receiving stations, the guard interval adjusting means is provided on the transmitting station side and is provided for each of the plurality of receiving stations calculated by the measurement symbol receiving means. A transmitting-side guard interval length storing means for storing the guard interval length in association with each receiving station; and a guard interval length for each of a plurality of transmitting stations provided at the receiving station side and inputted from the notification receiving means. A receiving-side guard interval length storing means for storing in correspondence with the station, wherein the transmitting-side guard interval length storing means, when a receiving station of a communication destination is selected, a guard interval corresponding to the selected receiving station; The length is read out and output to the data symbol transmitting means, and the receiving side guard interval length storing means stores the data when the transmitting station of the communication destination is selected. Reading a guard interval length corresponding to the selected transmission station and outputs to the data symbol reception means.

In the ninth aspect, a different guard interval is set for each communication destination on both the transmitting station side and the receiving station side and stored. As a result, an optimal guard interval is set for each destination,
Communication efficiency can be improved.

The tenth invention is directed to the OF according to the first invention.
In a DM communication device, the measurement symbol transmitting unit transmits a plurality of measurement symbols. The first
In the invention of No. 0, a guard interval length having an optimal time length can be selected by using a plurality of measurement symbols.

According to an eleventh aspect of the present invention, the O
In the FDM communication apparatus, the plurality of measurement symbols each include an effective symbol containing access control data. According to the eleventh aspect, control such as an access request can be performed simultaneously with the transmission of the measurement symbol, and the bandwidth can be used efficiently. In addition, since the latest delay time is measured for each access, adaptability is increased.

A twelfth invention is a device according to the tenth invention,
In the FDM communication apparatus, the plurality of measurement symbols include guard intervals each having a different time length. In the tenth aspect, an optimal guard interval length can be obtained by using guard intervals having different time lengths included in a plurality of measurement symbols.

A thirteenth invention is a method according to the twelfth invention.
In the FDM communication apparatus, the measurement symbol receiving unit determines the shortest guard interval length in the measurement symbol that was recognizable among the plurality of measurement symbols transmitted by the measurement symbol transmission unit, to the optimum guard interval length. Is calculated as

According to the thirteenth aspect, it is only necessary to receive measurement symbols having guard intervals of different lengths and select an optimum guard interval length from among the guard intervals included therein. Therefore, the maximum delay time can be easily obtained, and the device can be simply configured.

A fourteenth invention is directed to the OF of the first invention.
In the DM communication device, the measurement symbol transmitting unit transmits one measurement symbol including a predetermined guard interval and a predetermined effective symbol.

In the fourteenth aspect, the guard interval period can be easily and adaptively adjusted by using measurement symbols having a simple configuration. Therefore, communication efficiency can be improved.

The fifteenth invention is directed to the fourteenth invention in which
An FDM communication apparatus, wherein a predetermined guard interval is defined by: data stored in the latter half of an effective symbol;
And null data having an amplitude of 0.

In the fifteenth aspect, a long guard interval is generated by adding null data to the latter half data of the effective symbol. This makes it possible to easily determine the maximum delay time without generating unnecessary correlation peaks.

A sixteenth aspect of the present invention is directed to the fourteenth aspect of the present invention.
In the FDM communication apparatus, the measurement symbol receiving means detects, by a correlation operation, a delayed wave that affects the quality of the received signal by a predetermined value or more, from among the delayed waves included in the received signal, and detects the detected delayed wave. An optimum guard interval length is calculated from the maximum delay time.

In the sixteenth aspect, the delay time of the delayed wave is detected from the correlation peak obtained by the correlation operation. Therefore, the guard interval period can be easily and adaptively adjusted from the maximum delay time to improve communication efficiency.

The seventeenth invention is a modification of the sixteenth invention, wherein O
In the FDM communication apparatus, the measurement symbol receiving means obtains the head of the symbol from the received signal and outputs the timing, and a symbol synchronization means, which receives the timing, and sets the length of the effective symbol from the head of the measurement symbol to the effective symbol length. A first buffer means for outputting an equal data group β, and a length of an effective symbol while sliding in a time axis direction from a head of a measurement symbol in a period corresponding to a length of a guard interval included in the symbol. Second buffer means for sequentially extracting the data group α having the data, correlation calculating means for obtaining a correlation value between the data groups α and β, and correlation data among the time when the second buffer means slides from the start of the measurement symbol as a starting point. The time when the value exceeds a predetermined threshold value γ is sequentially detected as the delay time of the delayed wave, and when the detected delayed wave is delayed. And delay time detecting means for calculating a maximum delay time as an optimum guard interval length.

In the seventeenth aspect, the time when the correlation value satisfies the threshold value γ and corresponds to the largest sliding position is defined as the maximum delay time. Therefore, a correlation peak is obtained at the sliding position where the delay wave exists, and the maximum delay time can be accurately detected by specifying the correlation peak using the threshold value γ.

The eighteenth invention is a device according to the seventeenth invention, wherein
In the FDM communication apparatus, the delay time detecting means includes a predetermined coefficient Δ for normalizing the time average value of the correlation value.
Is multiplied to calculate the threshold value γ.

In the eighteenth aspect, the optimum threshold value γ
Since f varies depending on the distribution of correlation values, it is normalized using a time average value. Thus, the maximum delay time can be accurately obtained.

[0042]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described below.
The eighth to eighth embodiments are directed to the OF according to these embodiments.
In configuring the DM communication device, three distinctive features are combined so as to be different from each other. The first difference in the configuration is whether the measurement symbol transmission unit (or measurement symbol reception unit) is on the data symbol reception side or on the transmission side. The second difference is whether or not a guard interval length storage unit is provided. A third difference is whether the measurement symbol transmission unit 22 and the measurement symbol reception unit 23 are used for the measurement symbol transmission unit and the measurement symbol reception unit, or the measurement symbol transmission unit 32 and the measurement symbol reception unit 33 are used for the measurement symbol reception unit. That is the point. The embodiments of the present invention will be described below in order, taking into account the combinations of the above differences.

(First Embodiment) FIG. 1 shows a first embodiment of the present invention.
FIG. 3 is a block diagram showing a configuration of an OFDM communication device according to an embodiment. In FIG. 1, the OFDM communication apparatus includes a measurement symbol transmission unit 22 that transmits a predetermined measurement symbol, and a measurement symbol reception unit that receives the measurement symbol and outputs the shortest guard interval length κ that can be recognized. Unit 23 and a data symbol receiving unit 31 that sets the guard interval length to κ, receives OFDM data symbol ω, and outputs received data Y.
And the notification transmission unit 25 for notifying the guard interval length κ
And the received guard interval length κ
Receiving section 26 for outputting the data symbol to data symbol transmitting section 30
, The guard interval length is set to κ, and the transmission data X is input, and the OFDM data symbol ω
And a data symbol transmission unit 30 that transmits

The above-described units are provided on the data symbol transmitting side and the data symbol receiving side, respectively. On the data symbol transmission side, a measurement symbol transmission unit 2
2, a notification receiving unit 26, and a data symbol transmitting unit 30. On the data symbol receiving side, a measurement symbol receiving unit 23, a notification transmitting unit 25, and a data symbol receiving unit 31 are provided. As described above, the OFDM communication apparatus according to the first embodiment of the present invention is characterized in that the measurement symbol transmission unit 22 is provided on the data symbol transmission side.

In FIG. 1, the measurement symbol transmission unit 22
Transmits a plurality of measurement symbols including a guard interval having a predetermined length. FIG. 2 is a schematic diagram illustrating a configuration of a plurality of measurement symbols to be transmitted. As shown in FIG. 2, the measurement symbol includes a guard interval having a predetermined length and an effective symbol.

In FIG. 2, four measurement symbols are shown, and the lengths of the guard intervals have different predetermined lengths. Typically, the guard interval length of the first transmitted measurement symbol is
It is set to be relatively long, and is set to be relatively short as it is transmitted later. Of course, the number of measurement symbols to be transmitted is not limited to four.

FIG. 3 is a schematic diagram showing the configuration of a measurement symbol. In FIG. 3, the measurement symbol is composed of a guard interval and an effective symbol. The guard interval has, for example, a time length of κ. The effective symbol typically has predetermined access control data including an access request.

Further, the access control data includes identifiers of a communication source and a communication destination. A unique code or value is assigned to each identifier in advance so that the transmitting side and the receiving side of the access control data can be distinguished from other stations.

Needless to say, the contents of the effective symbols need only be those that can be recognized by the measurement symbol receiving unit 23. Therefore, the contents of the effective symbols need not necessarily have access control data, and are not particularly limited.

However, if the effective symbol has access control data, control such as an access request can be performed simultaneously with transmission of the measurement symbol. In that case, it is preferable because the band can be used efficiently. Therefore, hereinafter, the effective symbol will be described as having predetermined access control data.

First, when the transmission data X is generated, the measurement symbol transmission section 22 sequentially transmits a series of measurement symbols as described above. Regarding the timing of the transmission, if there is one communication destination, it is not necessary to transmit the measurement symbol every time the transmission data X occurs.

However, when there are a plurality of communication destinations, the optimum guard interval length is different for each communication destination. Therefore, it is preferable that a measurement symbol is transmitted each time transmission data X is generated. The following description is based on the premise that a measurement symbol is transmitted each time transmission data X occurs.

Next, the measurement symbol receiving section 23 sequentially receives a series of measurement symbols transmitted via the communication channel 21 and recognizes the access control data in the effective symbols. More specifically, the measurement symbol receiving unit 23
It recognizes that the identifier of the transmission destination among the identifiers included in the access control data is addressed to the own station.

For example, as shown in FIG. 2, the guard interval length of the measurement symbol is set to be relatively long for the first transmission, and is set to be relatively short for the next transmission. .

In this case, the measurement symbol receiving unit 23 may not be able to recognize the access control data transmitted later due to the effect of the multiplex wave as a result of the guard interval being too short. At this time, the measurement symbol receiving unit 23 can obtain the shortest guard interval length κ of the last symbol that was able to recognize the access control data. The same applies when all the access control data can be recognized.

FIG. 4 shows a case where a plurality of measurement symbols as shown in FIG.
Is a schematic diagram showing how to obtain the shortest guard interval length κ. As shown in FIG.
The guard interval length κ is the guard interval length of the last symbol that was able to recognize the access control data.

As described above, the measurement symbol receiving unit 23
The shortest guard interval length κ that can recognize the access control data is detected, and κ is notified to the notification transmitting unit 25.
And to the data symbol receiving section 31.

Next, the notification transmitting section 25 notifies the guard interval length κ input from the measurement symbol receiving section 23 to the notification receiving section 26 provided on the data symbol transmitting side. This notification includes the identifiers of the transmission source and the transmission destination. As described above, the transmitting side and the receiving side can be distinguished from other stations by the identifier.

The notification receiving unit 26 receives the notification transmitted via the communication channel 21 and determines the guard interval length κ included in the notification by using the data symbol transmitting unit 30.
Output to

Data symbol transmitting section 30 sets the guard interval length on the data symbol transmitting side to κ. Subsequently, the data symbol transmission unit 30 generates an OFDM data symbol ω from the input transmission data X using the set guard interval length κ, and transmits the generated data symbol ω to the data symbol reception unit 31.

The data symbol receiving section 31 sets κ input from the measurement symbol receiving section 23 as a guard interval length on the data symbol receiving side. Subsequently, the data symbol receiving unit 31 receives the OFDM data symbol ω transmitted via the communication channel 21 using the set guard interval length κ, and outputs received data Y.

As described above, the OFDM communication apparatus according to the first embodiment of the present invention adaptively uses the optimum guard interval corresponding to the delay time by using the measurement symbols. Therefore, communication efficiency can be improved. In addition, control such as access request,
Since the measurement can be performed at the same time as the transmission of the measurement symbol, the band can be used efficiently.

(Second Embodiment) FIG. 5 shows a second embodiment of the present invention.
FIG. 3 is a block diagram showing a configuration of an OFDM communication device according to an embodiment. In FIG. 5, the OFDM communication apparatus includes a measurement symbol transmission unit 22 that transmits a predetermined measurement symbol including a communication source identifier ρ and a communication destination identifier ψ.
And the measurement symbol receiving section 23 that receives the measurement symbol and outputs the shortest guard interval length κ and identifier ρ that can be recognized, and stores the input guard interval length κ and identifier ρ as a set. And
A guard interval length storage unit 28 that outputs a corresponding guard interval length κ when a communication destination identifier ρ is input.
And set the guard interval length to κ and
A data symbol receiver 31 for receiving FDM data symbol ω and outputting received data Y, and a notification transmitter 2 for notifying guard interval length κ and identifiers ρ and ψ
5, a notification receiving unit 26 that receives the notification and outputs the notified guard interval length κ and the identifier ψ, and stores the input guard interval length κ and the identifier に し て as a set, and the communication destination identifier ψ A guard interval length storage unit 29 that outputs a corresponding guard interval length κ when input, and a data symbol transmission that sets a guard interval length to κ, receives transmission data X, and transmits an OFDM data symbol ω. And a unit 30.

The above-described units are provided on the data symbol transmitting side and the data symbol receiving side, respectively. On the data symbol transmission side, a measurement symbol transmission unit 2
2, a notification receiving unit 26, a guard interval length storage unit 29, and a data symbol transmitting unit 30. On the data symbol receiving side, a measurement symbol receiving unit 23,
Notification transmission unit 25 and guard interval length storage unit 28
And a data symbol receiving unit 31.

As described above, in the OFDM communication apparatus according to the second embodiment of the present invention, the measurement symbol transmission section 22 is provided on the data symbol transmission side, and the guard interval length storage sections 28 and 29 are further provided. It is characteristic.

The OF according to the second embodiment of the present invention
Since the DM communication apparatus is based on the premise that there are a plurality of data symbol transmission sides and a plurality of data symbol reception sides, guard interval length storage sections 28 and 29 are provided, respectively. However, when only one of the data symbol transmitting side and the data symbol receiving side exists, the guard interval length storage unit 28 or 29 is provided only on the device side where only one exists. You may comprise.

In FIG. 5, the measurement symbol transmitting section 22
Transmits a plurality of measurement symbols including a guard interval having a predetermined length as shown in FIG. The measurement symbol includes, for example, a guard interval having a time length of κ and an effective symbol having predetermined access control data, as shown in FIG. 3 described above.

The access control data includes an identifier. A unique code or value is assigned to the identifier in advance so that the transmitting side and the receiving side of the access control data can be distinguished from each other. In the following description, the identifier of the measurement symbol transmitting side is ρ, and the identifier of the measurement symbol receiving side is ψ.

As in the OFDM communication apparatus according to the first embodiment, the measurement symbol transmitting section 22 sequentially transmits a series of measurement symbols. Here, even if there are a plurality of communication destinations, the optimum guard interval length for each communication destination is stored together with the corresponding identifier as described later. Therefore, it is sufficient that the measurement symbol is transmitted at a timing with a predetermined time interval. Of course, the measurement symbol may be transmitted each time transmission data is generated, although the communication efficiency is reduced.

In the following, the operation in the case where the communication destination is the first communication station and the optimum guard interval is not stored in the communication destination will be described.
The operation when the communication destination is not the first communication station will be described.

The measurement symbol receiving section 23 sequentially receives the measurement symbols transmitted via the communication channel 21 and recognizes the identifiers ρ and ψ in the effective symbols. By recognizing the identifier ψ of the own station, the measurement symbol receiving section 23 identifies that the symbol is transmitted to the own station. Subsequently, the measurement symbol receiving unit 23
Detects the shortest guard interval length κ that can recognize the identifiers ρ and ψ.

Next, measurement symbol receiving section 23 outputs guard interval length κ and identifier ρ to notification transmitting section 25 and guard interval length storage section 28. First, the guard interval length storage unit 28 stores the input guard interval length κ and the identifier ρ of the measurement symbol transmitting side as a set.

For example, as described above, if the identifier of the data symbol transmitting side provided with the measurement symbol transmitting unit 22 is ρ, the identifier ρ is stored as a set with the corresponding guard interval length κ. If the identifier of another data symbol transmission side is ν, the identifier ν is stored as a set with a guard interval length τ which is optimal for communication with another corresponding communication destination. In this manner, the guard interval length storage unit 28 sets the identifier of the communication destination and the guard interval length optimal for the communication destination and stores them one after another.

The notification transmitting unit 25 includes the measurement symbol receiving unit 2
Then, the guard interval length κ and the identifiers ρ and ψ input from 3 are notified to the notification receiving unit 26 provided on the data symbol transmitting side.

The notification receiving section 26 receives the notification by recognizing its own identifier ρ included in the notification transmitted via the communication channel 21. After receiving, the notification receiving unit 26
Outputs the guard interval length κ and the identifier ψ included in the notification to the guard interval length storage unit 29.

The guard interval length storage unit 29 first stores the input guard interval length κ and identifier ψ
Is stored as a set. The operation is the same as that of the guard interval length storage unit 29 described above. Next, the guard interval length storage unit 29 stores the guard interval length κ corresponding to the identifier ψ of the communication destination in the data symbol transmission unit 30.
Output to

The data symbol transmitting section 30 sets the input guard interval length κ as the guard interval length on the data symbol transmitting side. Next, the data symbol transmission unit 30 uses the guard interval length κ to
An OFDM data symbol ω is generated from the input transmission data X and transmitted to the data symbol receiving unit 31.

The guard interval length storage unit 28
Outputs the guard interval length κ corresponding to the identifier へ to the data symbol receiving unit 31.

The data symbol receiving section 31 sets the input guard interval length κ as the guard interval length on the data symbol receiving side. Next, the data symbol receiving unit 31 uses the guard interval length κ to
It receives the OFDM data symbol ω transmitted via the communication channel 21 and outputs received data Y.

The above description relates to the operation when the communication destination is the first communication station and the optimum guard interval is not stored in the communication destination. Next, the operation when the communication destination is not the first communication station will be described.

When the transmission data X is generated, the judgment unit (not shown) sets the guard interval length storage unit 29
Refers to whether the identifier of the communication destination is stored.
If the corresponding identifier is not stored, the above-mentioned operation is performed because the communication destination is the first communication station.

If the corresponding identifier is stored, the determining unit further refers to the elapsed time to determine whether it is time to periodically send a measurement symbol. If it is determined that it is time to send the measurement symbol periodically, the same operation as that performed when the communication destination is the first communication station is performed. The time interval at which measurement symbols are periodically transmitted is predetermined in consideration of, for example, changes in propagation conditions in the transmission path.

When it is determined that it is not the timing to send the measurement symbol periodically, the determination unit issues an access request to, for example, a communication destination having the identifier ψ. This access request is made on a communication channel (not shown) different from the communication channel 21.

When an access request is made, identifiers of respective communication destinations are input to guard interval length storage units 28 and 29. For example, the identifier ρ is input to the guard interval length storage unit 28, and the identifier ψ is input to the guard interval length storage unit 29.

The guard interval length storage unit 29 receives the identifier ψ of the communication destination and stores it as a set with ψ.
Is output to the data symbol transmission unit 30.

The data symbol transmitting section 30 sets the input guard interval length κ as the guard interval length on the data symbol transmitting side. Next, the data symbol transmission unit 30 uses the guard interval length κ to
An OFDM data symbol ω is generated from the input transmission data X and transmitted to the data symbol receiving unit 31.

The guard interval length storage unit 28
Receives the identifier ρ of the communication destination from the measurement symbol receiving unit 23 and outputs the guard interval length κ corresponding to ρ to the data symbol receiving unit 31.

The data symbol receiving unit 31 sets the input guard interval length κ as the guard interval length on the data symbol receiving side. Next, the data symbol receiving unit 31 uses the guard interval length κ to
It receives the OFDM data symbol ω transmitted via the communication channel 21 and outputs received data Y.

As described above, the OFDM communication apparatus according to the second embodiment of the present invention uses the measurement symbols to adaptively use the optimum guard interval corresponding to the delay time so that the communication efficiency can be improved. Can be improved. Further, by setting a different guard interval for each communication destination, the guard interval is optimized for each communication destination, and communication efficiency can be improved.

(Third Embodiment) FIG. 6 shows a third embodiment of the present invention.
FIG. 3 is a block diagram showing a configuration of an OFDM communication device according to an embodiment. In FIG. 6, the OFDM communication apparatus includes a measurement symbol transmitting unit 22 that transmits a predetermined measurement symbol, and a measurement symbol reception unit that receives the measurement symbol and outputs the shortest guard interval length κ that can be recognized. Unit 23, the guard interval length is set to κ, transmission data X is input, and OFDM
Data symbol transmitting unit 3 for transmitting data symbol ω
Notification transmitting unit 2 for notifying 0 and guard interval length κ
5, a notification receiving unit 26 that receives the notification and outputs the notified guard interval length κ, and receives the output from the notification receiving unit 26, sets the guard interval length to κ, and sets the OFDM data symbol and a data symbol receiving unit 31 that receives ω and outputs received data Y.

The above-described units are provided on the data symbol transmitting side and the data symbol receiving side, respectively. On the data symbol receiving side, a measurement symbol transmitting unit 2
2, a notification receiving unit 26, and a data symbol receiving unit 31. On the data symbol transmitting side, a measurement symbol receiving unit 23, a notification transmitting unit 25, and a data symbol transmitting unit 30 are provided. As described above, the OFDM communication apparatus according to the third embodiment of the present invention is characterized in that the measurement symbol transmitting unit 22 is provided on the data symbol receiving side.

In FIG. 6, measured symbol transmitting section 22
Is similar to the OFDM communication device according to the first embodiment,
A series of measurement symbols are transmitted sequentially. The measurement symbol receiving unit 23 sequentially receives the measurement symbols transmitted via the communication channel 21, and first recognizes the access control data in the effective symbols. Then, the measurement symbol receiving unit 23 detects the shortest guard interval length κ at which the access control data can be recognized, and outputs κ to the notification transmitting unit 25 and the data symbol transmitting unit 30.

Next, the notification transmitting unit 25 notifies the guard interval length κ input from the measurement symbol receiving unit 23 to the notification receiving unit 26 provided on the data symbol receiving side. The notification receiving unit 26 outputs the guard interval length κ notified via the communication channel 21 to the data symbol receiving unit 31.

Data symbol transmitting section 30 sets κ input from measurement symbol receiving section 23 as a guard interval length on the data symbol transmitting side. Subsequently, the data symbol transmitting unit 30 uses the set guard interval length κ to convert the input transmission data X into OFDM data.
And generates a data symbol ω of
Send to 1.

Data symbol receiving section 31 sets κ inputted from notification receiving section 26 as a guard interval length on the data symbol receiving side. Subsequently, the data symbol receiving unit 31 uses the set guard interval length κ to transmit the OF transmitted through the communication channel 21.
It receives the DM data symbol ω and outputs received data Y.

As described above, the OFDM communication apparatus according to the third embodiment of the present invention uses the measurement symbols to adaptively use the optimum guard interval corresponding to the delay time so that the communication efficiency can be improved. Can be improved. Further, the data symbol receiving side can take the initiative in the measurement.

(Fourth Embodiment) FIG. 7 shows a fourth embodiment of the present invention.
FIG. 3 is a block diagram showing a configuration of an OFDM communication device according to an embodiment. In FIG. 7, the OFDM communication apparatus includes a measurement symbol transmission unit 22 that transmits a predetermined measurement symbol including identifiers ρ and ψ, and a shortest guard interval length that can receive and recognize the measurement symbol. a measurement symbol receiving unit 23 that outputs κ and identifiers ρ and 、, and an input guard interval length κ
And an identifier ρ as a set, and when the identifier ρ of the communication destination is input, outputs a guard interval length κ corresponding to the guard interval length storage unit 28, sets the guard interval length to κ, and transmits the transmission data X Is input, a data symbol transmitting unit 30 for transmitting the OFDM data symbol ω, a notification transmitting unit 25 for notifying the guard interval length κ and the identifiers ρ and ψ, and a guard interval length κ for receiving and notifying the notification. And a notification receiving unit 26 for outputting an identifier ψ, a guard interval length κ and an identifier ψ which are inputted and stored as a set, and a guard interval length κ which is output when the identifier の of the communication destination is inputted. The length storage unit 29, the guard interval length is set to κ, and the OFDM data symbol ω Receiving, and a data symbol reception unit 31 for outputting the received data Y.

[0098] The above-described units are provided on the data symbol transmitting side and the data symbol receiving side, respectively. On the data symbol receiving side, a measurement symbol transmitting unit 2
2, a notification receiving unit 26, a guard interval length storage unit 29, and a data symbol receiving unit 31. On the data symbol transmitting side, a measurement symbol receiving unit 23;
Notification transmission unit 25 and guard interval length storage unit 28
And a data symbol transmission unit 30.

As described above, in the OFDM communication apparatus according to the fourth embodiment of the present invention, the measurement symbol transmitting section 22 is provided on the data symbol receiving side, and the guard interval length storage sections 28 and 29 are further provided. It is characteristic.

The OFDM communication apparatus according to the present embodiment is similar to the OFDM communication apparatus according to the second embodiment,
Since it is assumed that there are a plurality of data symbol transmission sides and a plurality of data symbol reception sides, guard interval length storage units 28 and 29 are provided, respectively. However, when only one of the data symbol transmitting side and the data symbol receiving side exists, the guard interval length storage unit 28 or 29 is provided only on the device side where only one exists. You may comprise.

The measurement symbol transmitting section 22 sequentially transmits a series of measurement symbols, similarly to the OFDM communication apparatus according to the first embodiment. The measurement symbol receiving unit 23 sequentially receives the measurement symbols transmitted via the communication channel 21 and recognizes the identifiers ρ and ψ in the effective symbols.

Next, the measurement symbol receiving section 23 detects the shortest guard interval length κ at which the identifiers ρ and ψ can be recognized, and sends the guard interval length κ and the identifier ρ to the notification transmitting section 25 and the guard Output to the interval length storage unit 28. The guard interval length storage unit 28 first stores the guard interval length κ and the identifier ρ that have been input.

The notification transmitting unit 25 includes the measurement symbol receiving unit 2
3 to the notification receiving unit 26 provided on the data symbol receiving side.

The notification receiving unit 26 recognizes its own identifier ρ included in the notification transmitted via the communication channel 21, and determines the guard interval length κ and the identifier ψ included in the notification, Output to the storage unit 29.

The guard interval length storage unit 29 first stores the input guard interval length κ and identifier た
Is stored as a set. Next, the guard interval length storage 29 stores the guard interval length κ corresponding to ψ as a set with the identifier ψ,
Output to 1. The guard interval length storage unit 28
Outputs the guard interval length κ corresponding to the identifier ρ to the data symbol transmission unit 30.

The data symbol transmitting section 30 sets the input guard interval length κ as the guard interval length on the data symbol transmitting side. Next, the data symbol transmission unit 30 uses the guard interval length κ to
An OFDM data symbol ω is generated from the input transmission data X and transmitted to the data symbol receiving unit 31.

The data symbol receiving section 31 sets the input guard interval length κ as the guard interval length on the data symbol receiving side. Next, the data symbol receiving unit 31 uses the guard interval length κ to
It receives the OFDM data symbol ω transmitted via the communication channel 21 and outputs received data Y.

The above description is based on the OF according to the second embodiment.
Similar to the DM communication device, this is an operation in a case where the communication destination is the first communication station and the optimum guard interval is not stored in the communication destination. The operation in the case where the communication destination is not the first communicating station is also described in the OF according to the second embodiment.
The operation is almost the same as that of the DM communication device.

That is, the access request between the data symbol transmitting side and the data symbol receiving side is transmitted to the communication channel 21.
It is assumed that the communication is performed on a communication channel (not shown) other than the above. When the transmission data X occurs, this access request is made, and the identifiers of the respective communication destinations are input to the guard interval length storage unit 28 and the guard interval length storage unit 29.

The guard interval length storage unit 28 receives the identifier ρ and stores it as a set with ρ, and stores the guard interval length κ corresponding to ρ in the data symbol transmission unit 30.
Output to

The data symbol transmitting section 30 sets the input guard interval length κ as the guard interval length on the data symbol transmitting side. Next, the data symbol transmission unit 30 uses the guard interval length κ to
An OFDM data symbol ω is generated from the input transmission data X and transmitted to the data symbol receiving unit 31.

The guard interval length storage unit 29
Receives the identifier ψ and outputs the guard interval length κ corresponding to the identifier へ to the data symbol receiving unit 31 in the same manner as the guard interval length storage unit 28.

The data symbol receiving unit 31 sets the input guard interval length κ as the guard interval length on the data symbol receiving side. Next, the data symbol receiving unit 31 uses the guard interval length κ to
It receives the OFDM data symbol ω transmitted via the communication channel 21 and outputs received data Y.

As described above, the OFDM communication apparatus according to the fourth embodiment of the present invention adaptively uses the optimum guard interval corresponding to the delay time by using the measurement symbol, and therefore, the communication efficiency is improved. Can be improved.

In the OFDM communication apparatus according to the present embodiment, by setting a different guard interval for each communication destination, the guard interval is optimized for each communication destination and communication efficiency can be improved. Further, in the OFDM communication apparatus according to the present embodiment, the data symbol receiving side can perform measurement initiatively.

(Fifth Embodiment) FIG. 8 shows a fifth embodiment of the present invention.
FIG. 3 is a block diagram showing a configuration of an OFDM communication device according to an embodiment. In FIG. 8, the OFDM communication apparatus includes a measurement symbol transmission unit 32 that transmits a predetermined measurement symbol, a measurement symbol reception unit 33 that receives the measurement symbol, and outputs a guard interval length κ, and a guard interval length. Set to κ, receive the OFDM data symbol ω and output the received data Y, a data symbol receiving unit 31, a notification transmitting unit 25 that notifies the guard interval length κ, receive the notification, and receive the notified guard. A notification receiving unit 26 that outputs the interval length κ and a data symbol transmitting unit 30 that sets the guard interval length to κ, receives the transmission data X, and transmits the OFDM data symbol ω.

As described above, the OFDM communication apparatus according to the present embodiment differs from the OFDM communication apparatus according to the first embodiment in that measurement symbol transmission section 32 is provided in place of measurement symbol transmission section 22, and measurement symbol transmission section 32 is provided. The feature is that a measurement symbol receiving unit 33 is provided instead of the receiving unit 23. Therefore, in the following, only the different points will be described in detail, and the O according to the first embodiment will be described.
A description of the same points as those of the FDM communication device will be omitted.

FIG. 9 is a block diagram showing a detailed configuration of the measurement symbol transmitting section 32. In FIG. 9, the measurement symbol transmission unit 32 receives the output from the common unit acquisition unit 1 and the common unit acquisition unit 1 that extracts the second half of the effective symbol, and converts the data of amplitude 0 to the end of the guard interval. A null data adding unit 2 for adding a valid symbol after the guard interval.

First, the common part acquisition unit 1 receives the valid symbol data A and inputs the first half of the valid symbol data A.
The portion of / 2 is extracted as a common portion and output to the null data adding portion 2.

The null data adding unit 2 adds null data having an amplitude of 0 to the end of the guard interval after the input common unit. The added data is output as a guard interval.

The measurement symbol generation unit 3 receives the guard interval and adds a valid symbol after the guard interval to generate a measurement symbol B. FIG.
It is a schematic diagram showing the measurement symbol B generated in such a manner. FIG. 10A shows the measurement symbol B when the guard interval length exceeds half the length of the effective symbol data A.

The above is the operation in the case where the guard interval length is set in advance so as to exceed half the length of the effective symbol data A. Usually, it is set as described above.

If the guard interval length is set to be equal to or less than half the length of the effective symbol data A, the operation is different from the above. First, the common unit acquisition unit 1
Receives the effective symbol data A, extracts the part corresponding to the guard interval length from the latter half of the effective symbol data A as a common part,
Output to The null data adding unit 2 outputs the input common unit as a guard interval as it is.

The measurement symbol generator 3 receives the guard interval and adds a valid symbol after the guard interval to generate a measurement symbol B. FIG.
(B) shows the measurement symbol B when the guard interval length generated in this way is equal to or less than half the length of the effective symbol data A.

The generated measurement symbol B is converted into an OFDM signal by an inverse discrete Fourier transform (IDFT) unit and a modulation unit (not shown) and transmitted to the measurement symbol receiving unit 33.

FIG. 11 is a block diagram showing a detailed configuration of the measurement symbol receiving section 33. In FIG. 11, a measurement symbol receiving unit 33 detects a synchronization timing of a measurement symbol from a received signal, and a symbol synchronizing unit 4 sequentially samples the received signal and outputs the data α by an effective data length.
A buffer 5 for buffering data α inputted from the buffer 5 as data β at a synchronization timing, a correlation operation unit 7 for calculating a correlation value between the data α and the data β, A delay time detecting section for calculating a delay time from the correlation value input from the correlation calculating section and a predetermined threshold value and outputting a guard interval length;

First, the received measurement symbol is generated as symbol data C via a demodulation unit and a discrete Fourier transform (DFT) unit (not shown) and input to the symbol synchronization unit 4 and the buffer 5. You.

The symbol synchronization section 4 obtains the head of the symbol from the input signal, and outputs the symbol synchronization timing to the buffer 6. The buffer 5 samples the input signal one after another and buffers the effective signal length. The buffered data is sequentially output to the buffer 6 and the correlation calculator 7 as data α. The buffer 6 buffers the data α at the symbol synchronization timing input from the symbol synchronization unit 4 and outputs the data α to the correlation calculation unit 7 as data β. FIG. 12 schematically shows the above operation.

FIG. 12 is a schematic diagram showing how data α and data β are output. As shown in FIG. 12, data β is extracted at the detected symbol synchronization timing, and data α is extracted sequentially until the time length corresponding to the guard interval is reached. That is, since the data α is sequentially extracted at a certain timing, the parts extracted from the symbol data are slid to the latter half one after another.

The data α and data β extracted as described above are input, and the correlation operation unit 7
And calculates a correlation value between the data and the data β, and outputs the calculated value to the delay time detecting unit 8.

The delay time detector 8 calculates a time average of the input correlation values. Further, the delay time detection unit 8
For normalization, a value obtained by multiplying the calculated value by a coefficient Δ is calculated and set as a threshold value γ. FIG. 13 is a graph showing the process of calculating the delay time.

FIG. 13 is a graph showing the relationship between the value obtained by multiplying the correlation value by the coefficient Δ and the amount of delay. In FIG. 13, the vertical axis represents the value obtained by multiplying the correlation value by the coefficient Δ, and the horizontal axis represents the delay amount. The delay amount is, as described above, the data α
Is sequentially taken out at a certain timing, and is expressed by the number of taken out samples.

As shown in FIG. 13, when the delay amount is 0, the value obtained by multiplying the correlation value by the coefficient Δ becomes maximum.
This is because, as described above, synchronization is achieved by the symbol synchronization unit 4, and the symbol correlation unit 4 has the maximum correlation value.

Thereafter, the data α is sequentially taken out at a certain timing, and the number of samples increases. As the number of samples increases, the value obtained by multiplying the correlation value by the coefficient Δ
It may exceed the threshold value γ. The largest delay amount is determined as the delay time.

The delay time detector 8 outputs a guard interval length signal D based on the delay time determined as described above. The guard interval length signal D is a signal including the above-described guard interval length κ, and is input to the notification transmitting unit 25 and the data symbol receiving unit 31. The following operation is performed according to the OF according to the first embodiment of the present invention.
The description is omitted because it is the same as the DM communication device.

As described above, the OFD in this embodiment is
The M communication device obtains a correlation peak at a sliding position where a delayed wave exists, and further detects a maximum delay time using a threshold γ. Therefore, O in the present embodiment is
The FDM communication apparatus is an OFDM communication apparatus according to the first embodiment of the present invention.
By using a plurality of measurement symbols in the DM communication device, the delay time can be calculated more accurately than the method of detecting the maximum delay time.

In the OFDM communication apparatus according to the present embodiment, a long guard interval generated by adding null data to the second half data of an effective symbol does not generate an unnecessary correlation peak. Therefore, the maximum delay time can be accurately obtained.

(Sixth Embodiment) FIG. 14 is a block diagram showing a configuration of an OFDM communication apparatus according to a sixth embodiment of the present invention. In FIG. 14, the OFDM communication apparatus includes a measurement symbol transmitting unit 32 that transmits a predetermined measurement symbol including identifiers ρ and ψ, and a measurement that receives the measurement symbol and outputs a guard interval length κ and an identifier ρ. A symbol receiving unit 33, a guard interval length storage unit 28 that stores the guard interval length κ and the identifier ρ that are input as a set, and outputs a corresponding guard interval length κ when the identifier ρ of the communication destination is input, A data symbol receiving unit 31 that sets the guard interval length to κ, receives an OFDM data symbol ω, and outputs received data Y, a notification transmitting unit 25 that notifies the guard interval length κ and the identifiers ρ and ψ, Notification receiving unit 26 that receives the notification and outputs the notified guard interval length κ and identifier ψ ,
A guard interval length storage unit 29 that stores the guard interval length κ and the identifier ψ as a set and outputs the corresponding guard interval length κ when the identifier の of the communication destination is input, and sets the guard interval length to κ. When the transmission data X is input and the OFDM
Data symbol transmitting unit 3 for transmitting data symbol ω
0.

As described above, the OFDM communication apparatus according to the present embodiment differs from the OFDM communication apparatus according to the second embodiment in that the measurement symbol transmission section 32 is provided instead of the measurement symbol transmission section 22 and the measurement symbol transmission section 32 is provided. The feature is that a measurement symbol receiving unit 33 is provided instead of the receiving unit 23. Therefore, description of the same points as those of the OFDM communication apparatus according to the second embodiment will be omitted.

Since the configurations and operations of the measurement symbol transmitting section 32 and the measurement symbol receiving section 33 have been described in the description of the fifth embodiment, the description is omitted here.

As described above, in the OFDM communication apparatus according to the sixth embodiment of the present invention, the measurement symbol transmission section 32 is provided on the data symbol transmission side, and the guard interval length storage sections 28 and 29 are provided. It is a characteristic that

Therefore, the OFDM communication apparatus according to the present embodiment uses the plurality of measurement symbols in the OFDM communication apparatus according to the second embodiment, similarly to the above-described OFDM communication apparatus according to the fifth embodiment. The delay time can be calculated more accurately than the method of detecting the delay time.

Further, similarly to the OFDM communication apparatus according to the second embodiment, by setting a different guard interval for each communication destination, the guard interval is optimized for each communication destination and communication efficiency can be improved. .

(Seventh Embodiment) FIG. 15 is a block diagram showing a configuration of an OFDM communication apparatus according to a seventh embodiment of the present invention. In FIG. 15, the OFDM communication apparatus includes a measurement symbol transmission unit 32 for transmitting a predetermined measurement symbol, a measurement symbol reception unit 33 for receiving the measurement symbol and outputting a guard interval length κ, and a guard interval length. When the transmission data X is input and the transmission data X is input, the data symbol transmission unit 30 that transmits the OFDM data symbol ω, the notification transmission unit 25 that notifies the guard interval length κ, and the notification is received and notified. Notification receiving unit 26 that outputs guard interval length κ
And a data symbol receiving unit 31 that receives the output from the notification receiving unit 26, sets the guard interval length to κ, receives the OFDM data symbol ω, and outputs the received data Y.

As described above, the OFDM communication apparatus according to the present embodiment is different from the OFDM communication apparatus according to the third embodiment in that the measurement symbol transmission section 32 is provided instead of the measurement symbol transmission section 22 and the measurement symbol transmission section 32 is provided. The feature is that a measurement symbol receiving unit 33 is provided instead of the receiving unit 23. Therefore, description of the same points as those of the OFDM communication apparatus according to the third embodiment will be omitted.

Since the configurations and operations of the measurement symbol transmitting section 32 and the measurement symbol receiving section 33 have been described in the description of the fifth embodiment, the description is omitted here.

As described above, the OFDM communication apparatus according to the seventh embodiment of the present invention is characterized in that the measurement symbol transmitting section 32 is provided on the data symbol receiving side.

Therefore, the OFDM in this embodiment is
The communication device is more accurate than the method of detecting the maximum delay time using a plurality of measurement symbols in the OFDM communication device according to the third embodiment, like the OFDM communication device according to the fifth embodiment. The delay time can be calculated. Further, similarly to the OFDM communication apparatus of the third embodiment, the data symbol receiving side can take the initiative in measurement.

(Eighth Embodiment) FIG. 16 is a block diagram showing a configuration of an OFDM communication apparatus according to an eighth embodiment of the present invention. In FIG. 16, the OFDM communication apparatus includes a measurement symbol transmitting unit 32 that transmits a predetermined measurement symbol including identifiers ρ and ψ, and a measurement that receives the measurement symbol and outputs a guard interval length κ and an identifier ρ. A symbol receiving unit 33, a guard interval length storage unit 28 that stores the guard interval length κ and the identifier ρ that are input as a set, and outputs a corresponding guard interval length κ when the identifier ρ of the communication destination is input, A data symbol transmission unit 30 that sets the guard interval length to κ and receives the transmission data X and transmits the OFDM data symbol ω, and a notification transmission unit 25 that notifies the guard interval length κ and the identifiers ρ and ψ Receiving unit for receiving the notification and outputting the notified guard interval length κ and identifier ψ 6
And the input guard interval length κ and identifier ψ
Is stored as a set, and when the identifier 通信 of the communication destination is input, a guard interval length storage unit 29 that outputs a corresponding guard interval length κ,
And receives the OFDM data symbol ω and outputs the received data Y.
1 is provided.

As described above, the OFDM communication apparatus according to the present embodiment differs from the OFDM communication apparatus according to the fourth embodiment in that measurement symbol transmission section 32 is provided instead of measurement symbol transmission section 22, and measurement symbol transmission section 32 is provided. The feature is that a measurement symbol receiving unit 33 is provided instead of the receiving unit 23. Therefore, description of the same points as those of the OFDM communication apparatus according to the fourth embodiment will be omitted.

Since the configurations and operations of the measurement symbol transmitting section 32 and the measurement symbol receiving section 33 have been described in the description of the fifth embodiment, the description thereof will be omitted.

As described above, the OFDM communication apparatus according to the eighth embodiment of the present invention is characterized in that the measurement symbol transmitting section 32 is provided on the data symbol receiving side.

Therefore, the OFDM in this embodiment is
The communication device is more accurate than the method of detecting the maximum delay time using a plurality of measurement symbols in the OFDM communication device according to the fourth embodiment, similarly to the OFDM communication device according to the fifth embodiment. The delay time can be calculated.

In the OFDM communication apparatus according to the present embodiment, similarly to the OFDM communication apparatus according to the fourth embodiment, by setting different guard intervals for each communication destination, the guard interval is optimized for each communication destination. , Communication efficiency can be improved. Further, in the OFDM communication apparatus according to the present embodiment, the data symbol receiving side can perform measurement initiatively.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of an OFDM communication device according to a first embodiment of the present invention.

FIG. 2 is a schematic diagram illustrating a configuration of a plurality of measurement symbols to be transmitted.

FIG. 3 is a schematic diagram showing a configuration of a measurement symbol.

FIG. 4 is a schematic diagram showing how the measurement symbol receiving unit 23 obtains the shortest guard interval length κ.

FIG. 5 is a block diagram showing a configuration of an OFDM communication device according to a second embodiment of the present invention.

FIG. 6 is a block diagram illustrating a configuration of an OFDM communication device according to a third embodiment of the present invention.

FIG. 7 is a block diagram showing a configuration of an OFDM communication device according to a fourth embodiment of the present invention.

FIG. 8 is a block diagram illustrating a configuration of an OFDM communication device according to a fifth embodiment of the present invention.

FIG. 9 is a block diagram showing a detailed configuration of a measurement symbol transmission unit 32.

FIG. 10 is a schematic diagram illustrating measurement symbols B generated by a measurement symbol generation unit 3.

FIG. 11 is a block diagram showing a detailed configuration of a measurement symbol receiving unit 33.

FIG. 12 is a schematic diagram showing how data α and data β are output.

FIG. 13 is a graph showing a relationship between a value obtained by multiplying a correlation value by a coefficient Δ and a delay amount.

FIG. 14 is a block diagram illustrating a configuration of an OFDM communication device according to a sixth embodiment of the present invention.

FIG. 15 is a block diagram showing a configuration of an OFDM communication device according to a seventh embodiment of the present invention.

FIG. 16 is a block diagram showing a configuration of an OFDM communication device according to an eighth embodiment of the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 common part acquisition part 2 null data addition part 3 measurement symbol generation part 4 symbol synchronization part 5 buffer 6 buffer 7 correlation operation part 8 delay time detection part 21 communication channel 22 measurement symbol transmission part 23 measurement symbol reception part 25 notification transmission part 26 notification Reception unit 28 Guard interval length storage unit 29 Guard interval length storage unit 30 Data symbol transmission unit 31 Data symbol reception unit 32 Measurement symbol transmission unit 33 Measurement symbol reception unit

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yuji Hayashino 1006 Kadoma Kadoma, Kadoma, Osaka Prefecture Inside Matsushita Electric Industrial Co., Ltd. Terms (reference) 5K022 DD00 DD13 DD17 DD19 DD24 DD34 DD42

Claims (18)

[Claims] When transmitting an OFDM signal from a transmitting station to a receiving station, an OFD signal in the OFDM signal is transmitted.
An OFDM communication apparatus for adaptively adjusting a guard interval included in M symbols, a measurement symbol transmitting unit transmitting a measurement symbol for obtaining a guard interval length corresponding to a maximum delay time of a delay wave, A measurement symbol receiving unit for receiving a measurement symbol and calculating an optimum guard interval length; and using the calculated guard interval length, the OFD
A guard interval adjusting means for adaptively adjusting a guard interval included in the M symbols.
M communication device. 2. The measurement symbol transmitting means is provided on the transmitting station side, the measurement symbol receiving means is provided on the receiving station side, the guard interval adjusting means is provided on the receiving station side, A notification transmitting unit for transmitting a notification including the guard interval length calculated by the measurement symbol receiving unit to the transmitting station side, provided in the transmitting station side, receiving a notification from the notification transmitting unit, and calculating Notification receiving means for obtaining a guard interval length obtained by the transmitting station, and setting a guard interval length obtained by the notification receiving means as a parameter, and transmitting a data symbol having the guard interval length to the receiving station. Data symbol transmitting means for transmitting to the receiving station side, provided at the receiving station side, by the measurement symbol receiving means The OFDM communication apparatus according to claim 1, further comprising: a data symbol receiving unit configured to set the calculated guard interval length as a parameter and receive a data symbol having the guard interval length. 3. When one transmitting station communicates with a plurality of receiving stations, the guard interval adjusting means is provided on the transmitting station side, and the guard interval adjusting means is provided for each of the plurality of receiving stations input from the notification receiving means. The transmitting side guard interval length storing unit further stores a guard interval length corresponding to each receiving station, and the transmitting side guard interval length storing unit stores the guard interval length when the receiving station of the communication destination is selected. 3. The OFDM communication apparatus according to claim 2, wherein a guard interval length corresponding to a receiving station is read and output to said data symbol transmitting means. 4. When a plurality of transmitting stations communicate with one receiving station, the guard interval adjusting means is provided on the receiving station side, and the guard interval adjusting means is provided for each of the plurality of transmitting stations calculated by the measurement symbol receiving means. The receiving side guard interval length storing means further stores the guard interval length of the transmitting station in association with each transmitting station, and the receiving side guard interval length storing means, when the transmitting station of the communication destination is selected, 3. The OFDM communication apparatus according to claim 2, wherein a guard interval length corresponding to the transmitted transmitting station is read and output to the data symbol receiving means. 5. When a plurality of transmitting stations communicate with a plurality of receiving stations, the guard interval adjusting means is provided on the transmitting station side, and is provided for each of the plurality of receiving stations inputted from the notification receiving means. Guard interval length storing means for storing the guard interval length in association with each receiving station; and a guard interval length for each of the plurality of transmitting stations, which is provided on the receiving station side and calculated by the measurement symbol receiving means. A receiving-side guard interval length storing unit that stores the transmitting-side guard interval length in association with each transmitting station, wherein the transmitting-side guard interval length storing unit stores, when a receiving station of a communication destination is selected, the selected receiving station. The corresponding guard interval length is read and output to the data symbol transmitting means, and the receiving side guard interval length storing means is configured to When the transmitting station has been selected, characterized in that reading the guard interval length corresponding to the selected transmission station and outputs it to the data symbol receiving unit, OFDM communication apparatus according to claim 2. 6. The measurement symbol transmitting means is provided on the receiving station side, the measurement symbol receiving means is provided on the transmitting station side, the guard interval adjusting means is provided on the transmitting station side, Notification transmitting means for transmitting a notification including the guard interval length calculated by the measurement symbol receiving means to the receiving station side, provided on the receiving station side, receiving a notification from the notification transmitting means, and calculating A notification receiving means for acquiring the guard interval length, and a guard interval length calculated by the measurement symbol receiving means provided at the transmitting station side as a parameter, and receiving the data symbol having the guard interval length. Data symbol transmitting means for transmitting to the station side, provided on the receiving station side, by the notification receiving means The OFDM communication apparatus according to claim 1, further comprising: a data symbol receiving unit that sets the acquired guard interval length as a parameter and receives a data symbol having the guard interval length. 7. When one transmitting station communicates with a plurality of receiving stations, the guard interval adjusting means is provided on the transmitting station side, and the guard interval adjusting means is provided for each of the plurality of receiving stations calculated by the measurement symbol receiving means. The transmission side guard interval length storage unit further stores the guard interval length of the communication station in correspondence with each receiving station, and the transmission side guard interval length storage unit, when a receiving station of the communication destination is selected, 7. The OFDM communication apparatus according to claim 6, wherein a guard interval length corresponding to the received receiving station is read and output to the data symbol transmitting means. 8. When a plurality of transmitting stations communicate with one receiving station, the guard interval adjusting means is provided on the receiving station side, and is provided for each of the plurality of transmitting stations input from the notification receiving means. A receiving-side guard interval length storing means for storing a guard interval length in association with each transmitting station, wherein the receiving-side guard interval length storing means, when a transmitting destination transmitting station is selected, 7. The OFDM communication apparatus according to claim 6, wherein a guard interval length corresponding to a transmitting station is read and output to said data symbol receiving means. 9. When a plurality of transmitting stations communicate with a plurality of receiving stations, said guard interval adjusting means is provided on said transmitting station side, and said guard interval adjusting means is provided for each of said plurality of receiving stations calculated by said measurement symbol receiving means. A guard interval length storing means for storing the guard interval length of each of the receiving stations in association with each receiving station, and a guard interval length for each of the plurality of transmitting stations provided on the receiving station side and inputted from the notification receiving means. A receiving-side guard interval length storing means for storing in correspondence with each transmitting station, wherein the transmitting-side guard interval length storing means, when a receiving station of a communication destination is selected, the selected receiving station The corresponding guard interval length is read and output to the data symbol transmitting means, and the receiving side guard interval length storing means is configured to When the transmitting station has been selected, characterized in that reading the guard interval length corresponding to the selected transmission station and outputs it to the data symbol receiving unit, OFDM communication apparatus according to claim 6. 10. The OFDM communication apparatus according to claim 1, wherein said measurement symbol transmitting means transmits a plurality of measurement symbols. 11. The plurality of measurement symbols each include an effective symbol containing access control data.
The OFDM communication device according to claim 10. 12. The OFDM communication apparatus according to claim 10, wherein said plurality of measurement symbols include guard intervals each having a different time length. 13. The measurement symbol receiving means determines the shortest guard interval length in a measurement symbol that can be recognized among a plurality of measurement symbols transmitted by the measurement symbol transmission means, as the optimum guard interval. The OFDM communication apparatus according to claim 12, wherein the length is calculated as a length. 14. The measurement symbol transmission means according to claim 1, wherein said measurement symbol transmission means includes a predetermined guard interval and a predetermined effective symbol.
2. The OFDM communication apparatus according to claim 1, wherein one measurement symbol is transmitted. 15. The OF according to claim 14, wherein the predetermined guard interval includes data stored in the latter half of the effective symbol and null data having an amplitude of 0.
DM communication device. 16. The measurement symbol receiving means detects, by a correlation operation, a delayed wave that affects the quality of a received signal by a predetermined value or more, among delayed waves included in a received signal.
2. The optimum guard interval length is calculated from the maximum delay time of the detected delay wave.
5. The OFDM communication device according to 4. 17. The measurement symbol receiving means obtains a head of a symbol from a received signal and outputs a timing thereof. The symbol synchronization means receives the timing, and receives a length of an effective symbol from the head of the measurement symbol. A first buffer means for outputting a data group β equal to the length of the effective symbol while sliding in the time axis direction within a period corresponding to the length of the guard interval included in the measurement symbol from the head of the measurement symbol. Buffer means for sequentially taking out a data group α having a correlation value, correlation calculating means for obtaining a correlation value between the data groups α and β, and the second buffer means sliding the head of the measurement symbol as a starting point. Of the time, the time when the correlation value exceeds a predetermined threshold value γ is sequentially detected as the delay time of the delayed wave. , Of the delay time of the detected delayed wave,
17. The OFDM communication apparatus according to claim 16, further comprising: a delay time detecting unit that calculates a maximum delay time as the optimum guard interval length. 18. The delay time detecting means according to claim 1, wherein a predetermined coefficient Δ for normalizing the time average value of the correlation value.
The OFDM communication apparatus according to claim 17, wherein the threshold value γ is calculated by multiplying the threshold value by.