JP2003174428A - OFDM transceiver - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To improve an effective data transmission speed by setting an optimal transmission condition according to a transmission path response for each subcarrier. An OFDM transmitting / receiving apparatus for transmitting and receiving an OFDM signal to / from a partner station transmitting / receiving apparatus includes:
A receiving section 16 for receiving an OFDM signal transmitted from a partner station transmitting / receiving apparatus, a transmission path response calculating section 2 for calculating a transmission path response for each subcarrier from the received OFDM signal
1. A subcarrier transmission line response comparison unit 2 that compares the calculated characteristic value of the transmission line response with a threshold value and calculates the ratio of the subcarriers whose characteristic value exceeds the threshold value to all the subcarriers.
2, and a transmission condition setting unit 12 that sets a transmission condition when the OFDM transmission / reception device transmits an OFDM signal to a partner station transmission / reception device using at least the calculated ratio as a transmission condition setting index.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an OFDM (Orthogonal Frequency Division Multiplex).
exing) OF in a wireless communication system for transmitting signals
The present invention relates to a DM transceiver.

[0002]

2. Description of the Related Art Generally, in a wireless communication system, a transmitted signal is received through a plurality of various paths (multipaths) due to reflection of radio waves by a building or the like, so that the received signal is distorted. This distortion varies with location and time. Under such a propagation environment, the effective speed of data transmission can be maximized by changing the transmission conditions such as the modulation method and the coding rate according to the propagation environment. Usually, the receiver can set the transmission condition suitable for the propagation environment by obtaining the received electric field strength and the transmission line response from the known reference sequence and data sequence.

When the transmitted signal is a wideband signal such as an OFDM signal, frequency selective fading occurs due to multipath. When frequency-selective fading occurs, as a result of the received electric field strength being different for each of a plurality of subcarriers having different frequencies that form an OFDM signal,
Subcarriers with excellent reception characteristics and subcarriers with poor reception characteristics coexist. The presence of subcarriers with poor reception characteristics increases the possibility of error even if the average reception field strength of all subcarriers and the transmission line response are excellent. Therefore, even if a transmission condition suitable for the average propagation environment of all subcarriers is selected, there may be a case where a large effect is not obtained in improving the effective speed of data transmission (for example, refer to Patent Document 1).

[0004]

[Patent Document 1] US Pat. No. 6,175,550

[0005]

As described above, the conventional O
In the FDM transmitter / receiver, the transmission conditions are set according to the average transmission line response of all subcarriers and the received electric field strength. Therefore, if there are subcarriers with poor reception characteristics, the effective speed of data transmission under the set transmission conditions is set. There was a problem that I could not raise.

An object of the present invention is to provide an OFDM transmitter / receiver capable of improving the effective speed of data transmission by setting the optimum transmission condition according to the transmission path response for each subcarrier.

[0007]

In order to solve the above problems, an OFDM transceiver according to the first aspect of the present invention is
OF having a plurality of subcarriers via a predetermined transmission path
In an OFDM transmitter / receiver that transmits and receives a DM signal to and from a partner station transmitter / receiver, receiving means for receiving an OFDM signal transmitted from the partner station transmitter / receiver;
Transmission path response calculation means for calculating a transmission path response indicating response characteristics of the transmission path to the plurality of subcarriers from the received OFDM signal, and a predetermined characteristic value of the calculated transmission path response to a predetermined threshold value. Comparing means for calculating the ratio of the number of subcarriers whose characteristic value exceeds the threshold value to the total number of subcarriers, and the transmission condition setting index using at least the ratio calculated by the comparing means as the transmission condition setting index. Based on the above, the OFDM transmitter / receiver comprises a transmission condition setting means for setting a transmission condition when the OFDM signal is transmitted to the partner station transmitter / receiver, and a transmitting means for transmitting the OFDM signal according to the set transmission condition. .

An OFDM transmitting / receiving apparatus according to a second aspect of the present invention is an OFDM transmitting / receiving apparatus for transmitting / receiving an OFDM signal having a plurality of subcarriers to / from a partner station transmitting / receiving apparatus via a predetermined transmission line, Receiving means for receiving an OFDM signal transmitted from the partner station transmitting / receiving device, and transmission path response calculating means for calculating a transmission path response indicating the response characteristics of the transmission path for the plurality of subcarriers from the received OFDM signal. A comparison means for comparing a predetermined characteristic value of the calculated transmission line response with a predetermined threshold value, and calculating a ratio of the number of subcarriers whose characteristic value exceeds the threshold value to the total number of subcarriers, and at least the comparison Using the ratio calculated by the means as a transmission condition setting index, the partner station transmitter / receiver sends an OF signal to the OFDM transmitter / receiver.
Transmission condition setting information generating means for generating transmission condition setting information for setting transmission conditions when transmitting a DM signal;
And a transmitting means for transmitting the transmission condition setting information to the partner station transmitting / receiving device.

An OFDM transmitting / receiving apparatus according to a third aspect of the present invention is an OFDM transmitting / receiving apparatus for transmitting / receiving an OFDM signal having a plurality of subcarriers to / from a partner station transmitting / receiving apparatus via a predetermined transmission line, Receiving means for receiving an OFDM signal transmitted from the partner station transmitting / receiving device, and transmission path response calculating means for calculating a transmission path response indicating the response characteristics of the transmission path for the plurality of subcarriers from the received OFDM signal. A comparison means for comparing a predetermined characteristic value of the calculated transmission line response with a predetermined threshold value, and calculating a ratio of the number of subcarriers whose characteristic value exceeds the threshold value to the total number of subcarriers, and at least the comparison The ratio calculated by the means is set as a transmission condition when the partner station transmitter / receiver transmits an OFDM signal to the OFDM transmitter / receiver. A transmission condition setting index information synthesizing unit for synthesizing the information of the transmission condition setting index as a transmission condition setting index in this case, and a transmitting unit for transmitting the information of the transmission condition setting index to the partner station transmitting / receiving apparatus. .

According to the above configuration, by setting the optimum transmission condition according to the transmission path response for each subcarrier based on the received OFDM signal, the data transmitted by the OFDM transmitter / receiver receiving the OFDM signal is It is possible to improve the effective speed of data transmission.

The OF received from the transmitting / receiving device of the partner station
Transmission condition setting information for setting transmission conditions when the partner station transmitter / receiver transmits an OFDM signal to the own station transmitter / receiver based on the transmission path response of each subcarrier of the DM signal Sent to the station transceiver. By setting the transmission condition based on the transmitted transmission condition setting information, the partner station transceiver device can improve the effective speed of data transmission of the data transmitted by the partner station transceiver device to the own station transceiver device. It will be possible.

Further, the O received from the transmitting / receiving device of the partner station
Based on the transmission path response for each subcarrier of the FDM signal,
A transmission condition setting index used when the transmission / reception device of the opposite station sets transmission conditions when transmitting an OFDM signal to the transmission / reception device of the own station is transmitted from the transmission / reception device of the own station to the transmission / reception device of the other station. By setting the transmission condition based on the transmitted transmission condition setting index, the partner station transceiver device can improve the effective speed of data transmission of the data transmitted by the partner station transceiver device. Here, the transmission condition setting index is information serving as an index for setting the transmission condition, and has a smaller data amount than the transmission condition setting information. Therefore, there is an effect that the amount of data transmitted from the own station transceiver device to the partner station transceiver device can be small.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. OF according to an embodiment of the present invention
The DM transmitter / receiver is applied to a mobile radio communication system including a base station and a terminal or a wireless LAN system. OFD
The M transmission / reception device may be mounted on the terminal or may be mounted on the base station. In the former case, the partner station transmitter / receiver may be an OFDM transmitter / receiver installed in a base station or an OFDM transmitter / receiver installed in another mobile terminal. In the latter case, the partner station transmitting / receiving device is installed in the terminal or another base station.

(First Embodiment) FIG. 1 shows a first embodiment of the present invention.
3 is a block diagram showing a configuration of an OFDM transmitting / receiving apparatus according to the embodiment of FIG. The OFDM transmission / reception device of this embodiment uses the O
The reception field strength of the FDM signal and the ratio at which the characteristic value of the transmission path response corresponding to each of the plurality of subcarriers forming the OFDM signal exceeds a predetermined threshold are used as transmission condition setting indexes, and based on these transmission condition setting indexes. Set the transmission conditions for transmitting an OFDM signal to the transmitter / receiver of the partner station.

First, the structure of the transmitting side for the OFDM transmitting / receiving apparatus (self station transmitting / receiving apparatus) of this embodiment to transmit to the transmitting apparatus of the opposite station will be described. Transmission data series 10
Is converted into a plurality of subcarrier signals that are orthogonal on the frequency axis by being input to the subcarrier modulator 11. The subcarrier modulation unit 11 generates each subcarrier signal based on transmission conditions (for example, modulation scheme, coding rate, packet length, and transmission power) set by the transmission condition setting unit 12 as described below.

Each subcarrier signal output from the subcarrier modulator 11 is IFFT (Fast Inverse Fourier Transform).
IFFT processing is performed by the unit 13 and each is converted into a time waveform signal. These time waveform signals are transmitted by the transmission unit 14
Entered in. The transmitting unit 14 adds a preamble including a known signal sequence and a guard time to each time waveform signal, and further converts the added signal into an analog signal. After that, the transmission unit 14 frequency-converts the analog signal according to a predetermined local oscillation signal to thereby perform RF conversion.
A band OFDM signal (OFDM modulated signal) is generated. The generated OFDM signal is radiated as a radio wave from the antenna 15. In the transmission unit 14, the transmission power of the OFDM signal is set by the transmission condition setting unit 12 as necessary.

Next, the configuration of the receiving side for the own station transmitting / receiving apparatus to receive the OFDM signal transmitted from the partner station transmitting / receiving apparatus will be described. The antenna 15 receives the radio wave of the OFDM signal transmitted from the transmitter / receiver of the partner station. The received OFDM signal in the RF band received by the antenna 15 is input to the receiving unit 16. The receiving unit 16 receives O
The FDM signal is frequency-converted into a baseband signal in accordance with a predetermined local oscillation signal, and then analog / digital converted to perform time synchronization and frequency synchronization processing.

The received OFDM signal of the base band output from the receiving unit 16 is an FFT (Fast Fourier Transform) unit 1
Input to 7. By the synchronization processing of the receiving unit 16, the FF
The FFT conversion window in the T section 17 is set. FFT section 17
Then, the input baseband reception OFDM signal is subjected to FFT processing for each conversion window set in the reception unit 16 to generate a plurality of reception subcarrier signals. Each received subcarrier signal generated is generated by the subcarrier demodulation unit 1
The data is demodulated by 8, and the reception data sequence 19 that is the same as the transmission data sequence of the transmitting / receiving device of the other station is reproduced.

The reception OFDM signal having an analog waveform or the reception OFDM signal having a digital waveform after analog / digital conversion, which is output from the reception unit 16, is input to the reception electric field strength measuring unit 20, where the reception electric field strength is measured. It Information on the measured received electric field strength is input to the transmission condition setting unit 12.

On the other hand, the output from the FFT section 17 is also input to the transmission line response calculation section 21. The transmission line response calculation unit 21 uses the preamble added to the received OFDM signal included in the output of the FFT unit 17 to transmit the transmission line response for each subcarrier, that is, the transmission from the partner station transceiver device to the own station transceiver device. Calculate the response characteristics of the road. The information on the transmission path response calculated by the transmission path response calculation unit 21 is input to the subcarrier demodulation unit 18.

Of the output of the FFT unit 17, the data subcarrier contained in the data symbol of the subcarrier is transmitted to the transmission line response calculation unit 2 in the subcarrier demodulation unit 18.
The transmission path response calculated in 1 is used for distortion compensation and demodulation. At this time, the distortion of the data subcarrier can be further compensated by the pilot carrier which is a known subcarrier included in the data symbol.

The information on the transmission path response calculated by the transmission path response calculating section 21 is also input to the subcarrier transmission path response comparing section 22. In the subcarrier transmission line response comparison unit 22,
A predetermined characteristic value of the transmission path response of each subcarrier is compared with a predetermined threshold value, and the ratio A of subcarriers whose characteristic value exceeds the threshold value to all subcarriers (number of subcarriers whose characteristic value exceeds the threshold value / total subcarriers Number) is calculated. Here, the predetermined characteristic value is, for example, at least one of the amplitude, power, and phase rotation of the transmission path response of each subcarrier. In this case, the subcarrier transmission line response comparison unit 22 uses, for example, an amplitude attenuation amount, a power attenuation amount, a phase rotation amount, etc. for the average transmission line response of all subcarriers as the threshold value. In the subcarrier transmission line response comparison unit 22, it is not always necessary to compare the characteristic values of the transmission line responses of all the subcarriers with the threshold value in this way, and it is assumed that the transmission line responses of the neighboring subcarriers are almost equal, and several subcarriers are set. The predetermined characteristic value of the transmission path response of the subcarrier may be compared with the threshold value.

The output of the subcarrier transmission line response comparison unit 22, that is, information indicating the ratio A of the subcarriers whose transmission line response characteristic value exceeds the threshold value to all the subcarriers is
It is input to the transmission condition setting unit 12. Transmission condition setting unit 12
Then, the transmission condition is set using the ratio A calculated by the subcarrier transmission path response comparison unit 22 and the reception electric field intensity obtained by the reception electric field intensity measurement unit 20 as the transmission condition setting index. Further, the transmission condition setting unit 12 further refers to the communication quality setting information 23 as necessary to set the transmission condition.

Here, the transmission conditions are, for example, a modulation method, a coding rate in error correction coding, a packet length, and a transmission power when the OFDM transmitting / receiving apparatus of this embodiment, which is a local station transmitting / receiving apparatus, transmits an OFDM signal. is there. In the transmission condition setting unit 12, the subcarrier transmission line response comparison unit 2
At least one of these transmission conditions is based on the ratio A of the subcarriers whose characteristic value of the transmission path response calculated by 2 exceeds the threshold value to all the subcarriers and the reception electric field strength obtained by the reception electric field strength measuring unit 20. One is set. Hereinafter, the transmission condition setting method in the transmission condition setting unit 12 will be described more specifically.

[0025]

[Table 1] Table 1 shows a specific example of the transmission condition setting method in this embodiment. The received electric field strength is, for example, less than −70 dBm, more than −70 dBm and less than −50 dBm, −50 dB.
It is classified into three levels of Bm and above. The ratio A of subcarriers whose transmission path response characteristic value exceeds a threshold value to all subcarriers is classified into two levels, for example, less than 30% and 30% or more. By such classification, the modulation method and the coding rate can be set to appropriate values.

In the example of Table 1, first, a modulation method is used in which the noise resistance is increased as the received electric field strength of the received OFDM signal is weakened, and the coding rate is reduced. Specifically, three modulation methods, BPSK, QPSK, and 16QAM, are prepared, and the noise immunity is BPSK>QPSK> 16.
It becomes smaller in the order of QAM. In this way, by selecting the modulation method and the coding rate according to the received electric field strength, it becomes possible to provide stable communication quality,
The effective speed of data transmission can be improved.

Further, in this embodiment, the ratio A of the subcarriers whose characteristic value of the transmission line response exceeds the threshold value to all the subcarriers is added as the transmission condition setting index of the transmission condition, so that the transmission line response, that is, the reception characteristic is deteriorated. When subcarriers are present, it is possible to set a modulation method that is more resistant to noise and a lower coding rate. Therefore, even if severe frequency-selective fading occurs due to the radio wave propagation environment of the transmission path, stable communication quality can be provided, and the effective speed of data transmission can be dramatically improved.

The transmission condition setting unit 12 may further set the packet length and the transmission power according to the received electric field strength and the ratio A of the subcarriers whose characteristic value of the transmission path response exceeds the threshold value to all the subcarriers. . That is, as the received electric field strength becomes smaller or the ratio A becomes smaller, the packet length is set smaller or the transmission power is set larger. Even in this case, the same effect can be obtained. That is, the transmission condition set using the reception electric field strength and the ratio A as the transmission condition setting index may be at least one of the modulation method, the coding rate in error correction coding, the packet length, and the transmission power.

[0029]

[Table 2] Table 2 shows another specific example of the transmission condition setting method in the present embodiment. In addition to the ratio A of the subcarriers whose characteristic values of the reception electric field strength and the transmission path response exceed the threshold values shown in Table 1 to all the subcarriers, the transmission conditions (modulation method and coding rate) are set in consideration of the required communication quality. It is an example of a method of setting.

Here, the required communication quality is given by the communication quality setting information 23 shown in FIG. 1, and is defined by the packet error rate (PER) in the example of Table 2. PER
Is categorized into two levels, 1% or more and less than 1%. As the required PER conditions become stricter, as shown in Table 2, by using a noise-resistant modulation method or reducing the coding rate, the communication quality is improved and the required PER is satisfied. You can

In the above description, the received electric field strength, the ratio A of the subcarriers whose characteristic value of the transmission path response exceeds the threshold value to all the subcarriers, and the required communication quality are used as the transmission condition setting index of the transmission condition. Although the transmission condition is set according to one or three transmission condition setting indexes, it is also possible to set the transmission condition using only the ratio A as the transmission condition setting index.

(Second Embodiment) Next, a second embodiment of the present invention will be described with reference to FIG. The same parts as those in FIG.
The M transmitter / receiver differs from the first embodiment in that the subcarrier transmission line response comparison unit 22 shown in FIG. 1 is replaced with a pilot carrier transmission line response comparison unit 24.

As described in the first embodiment,
The pilot carrier, which is a known subcarrier included in the data symbol, of the output of the FFT unit 17 is used for distortion compensation of the data subcarrier, and therefore when the reception characteristic of the pilot carrier becomes poor, the reception characteristic of the entire subcarrier becomes It may deteriorate. Therefore, in this embodiment, the communication quality is stabilized by setting the transmission condition according to the reception characteristic of the pilot carrier, and the effective speed of data transmission is improved.

Among the outputs of the transmission path response calculation section 21, information on the transmission path response of the pilot carrier is input to the pilot carrier transmission path response comparison section 24. The pilot carrier transmission line response comparison unit 24 compares a predetermined characteristic value of the transmission line response of each pilot carrier with a predetermined threshold value, and determines a ratio B of the pilot carriers whose characteristic value exceeds the threshold value to all pilot carriers (the characteristic value is a threshold value). The number of pilot carriers exceeding / the total number of pilot carriers) is calculated. The predetermined characteristic value here is, for example, at least one of the amplitude, power, and phase rotation of the transmission path response of each pilot carrier, like the characteristic value of the transmission path response of each subcarrier in the first embodiment. . In this case, the pilot carrier transmission line response comparison unit 24 uses, for example, an amplitude attenuation amount, a power attenuation amount, a phase rotation amount or the like with respect to the average transmission line response of all subcarriers or all pilot carriers as a threshold value.

Pilot carrier transmission line response comparison unit 24
Of the pilot carrier whose characteristic value of the transmission path response exceeds the threshold value, that is, the ratio B to all pilot carriers is input to the transmission condition setting unit 12. The transmission condition setting unit 12 sets the transmission condition by using the ratio B calculated by the pilot carrier transmission line response comparison unit 24 and the reception electric field strength obtained by the reception electric field strength measurement unit 20 as a transmission condition setting index. Further, the transmission condition setting unit 12 refers to the communication quality setting information 23 as necessary to set the transmission condition.

[0036]

[Table 3] Table 3 shows an example of a transmission condition setting method in the transmission condition setting unit 12 in this embodiment. Similar to Tables 1 and 2, the received electric field strength is less than −70 dBm, −70 dBm or more and less than −50 dBm, −50 d.
It is classified into three levels of Bm and above. The ratio B of the pilot carriers whose transmission path response characteristic value exceeds the threshold value to all the pilot carriers is classified into two levels, for example, less than 50% and 50% or more. By such classification, the modulation method and the coding rate can be set appropriately.

That is, according to the present embodiment, by using a modulation method that is more resistant to noise as the received electric field strength of the received signal is weaker and by reducing the coding rate, it is possible to supply stable communication quality and It is possible to improve the effective speed of transmission.

Further, by adding the ratio B of the pilot carriers having the characteristic value of the transmission path response exceeding the threshold value to all the pilot carriers as a transmission condition setting index of the transmission condition, there is a pilot carrier having a poor transmission path response, that is, a reception characteristic. In this case, it is possible to set a low noise-resistant modulation method and coding rate. This allows
Even if severe frequency selective fading occurs due to the radio wave propagation environment of the transmission path, stable communication quality can be provided, so that the effective speed of data transmission can be dramatically improved.

Further, as shown in Table 3, the required communication quality can be defined by PER, and the transmission condition can be changed depending on the required PER of 1% or more or less than 1%. That is, depending on the required PER condition, it is possible to stabilize the communication quality by using a noise-resistant modulation method or reducing the coding rate.

In the transmission condition setting section 12, according to the received electric field strength and the ratio B of the pilot carriers whose characteristic value of the transmission path response exceeds the threshold value to all the pilot carriers,
Further, the packet length and the transmission power may be set. That is, as the received electric field strength decreases, or the ratio B
As is smaller, the packet length is set to be smaller or the transmission power is set to be larger. Even in this case, the same effect can be obtained. That is, the transmission condition set using the reception electric field strength and the ratio B as the transmission condition setting index may be at least one of the modulation method, the coding rate in error correction coding, the packet length, and the transmission power.

Further, in the above description, the received electric field strength,
The ratio B of the pilot carriers whose characteristic value of the transmission path response exceeds the threshold value to all the pilot carriers, and the required communication quality are used as the transmission condition setting index of the transmission condition.
Although the transmission condition is set according to one or three transmission condition setting indexes, it is also possible to set the transmission condition using only the ratio B as the transmission condition setting index.

(Third Embodiment) FIG. 3 shows the third embodiment of the present invention.
2 shows a configuration of an OFDM transmitter / receiver according to the exemplary embodiment. The same parts as those in FIG. 1 and FIG. 2 are denoted by the same reference numerals and explained.
It has a configuration in which the above embodiments are combined.

That is, in the output of the transmission path response calculation unit 21, the information of the transmission path response of the subcarrier is sent to the subcarrier transmission path response comparison unit 22, and the information of the transmission path response of the pilot carrier is sent to the pilot carrier transmission path response. It is input to the comparison unit 24. The subcarrier transmission path response comparison unit 22 compares a predetermined characteristic value of the transmission path response of each subcarrier with a first threshold value, and calculates a ratio of subcarriers whose characteristic value exceeds the first threshold value to all subcarriers. To do. The pilot carrier transmission line response comparison unit 24 sets a predetermined characteristic value of the transmission line response of each pilot carrier to the second characteristic value.
And the ratio of pilot carriers whose characteristic value exceeds the second threshold to all pilot carriers is calculated.

In the transmission condition setting unit 12, the ratio A calculated by the subcarrier transmission line response comparison unit 22, the ratio B calculated by the pilot carrier transmission line response comparison unit 24, and the reception field strength measurement unit 20 are obtained. The transmission condition is set using the received electric field strength as a transmission condition setting index, and the transmission condition is set by referring to the communication quality setting information 23 as necessary.

[0045]

[Table 4] Table 4 shows an example of a transmission condition setting method in the transmission condition setting unit 12 in this embodiment. The received electric field strength is -70 dB as in Table 1, Table 2 and Table 3.
less than m, -70 dBm or more and less than -50 dBm, -5
It is classified into 3 levels of 0 dBm or more. The ratio A of subcarriers whose transmission path response characteristic value exceeds the first threshold value to all subcarriers is classified into two levels of less than 30% and 30% or more, as in Tables 1 and 2. The ratio B of the pilot carriers whose characteristic value of the transmission path response exceeds the second threshold value to all the pilot carriers is 50 as in Table 3.
It is classified into two levels of less than 50% and 50% or more.

According to this classification, a stable communication quality can be provided by using a modulation method that is more resistant to noise as the received electric field strength of the received signal becomes weaker and by reducing the coding rate. The effective speed of data transmission can be improved. Further, a ratio A of subcarriers whose transmission path response characteristic value exceeds a first threshold value to all subcarriers, and a ratio B of pilot carriers whose transmission path response characteristic value exceeds a second threshold value to all pilot carriers are transmitted. By adding it as a transmission condition setting index of the condition, it becomes possible to set a modulation method and coding rate that are even more resistant to noise when there are subcarriers or pilot carriers with poor channel response, that is, reception characteristics. . Therefore, even if severe frequency selective fading occurs due to the radio wave propagation environment of the transmission path,
Since it is possible to provide stable communication quality, it is possible to dramatically improve the effective speed of data transmission.

[0047]

[Table 5] Table 5 shows another specific example of the transmission condition setting method in the present embodiment. Ratio A of subcarriers whose characteristic values of reception electric field strength and transmission line response shown in Table 4 exceed a first threshold value to all subcarriers, and all pilots of pilot carriers whose characteristic value of transmission line response exceeds a second threshold value This is an example of a method of setting transmission conditions (modulation method and coding rate) in consideration of required communication quality in addition to the ratio B to the carrier. The required communication quality is P as in Tables 2 and 3.
ER is defined, and the required PER is added to two levels of classification of 1% or more and less than 1%. As the required PER condition becomes stricter as described above, a communication method is improved by using a noise-resistant modulation method or a coding rate is reduced to satisfy the required PER. can do.

In the transmission condition setting unit 12, the ratio A of the sub-carriers having the characteristic value of the reception electric field strength and the transmission path response exceeding the first threshold value to all the sub-carriers and the characteristic value of the transmission path response the second threshold value. The packet length and the transmission power may be further set according to the ratio B of the excess pilot carriers to all the pilot carriers. That is, as the received electric field strength becomes smaller or the ratio A or B becomes smaller, the packet length becomes smaller,
By setting to increase the transmission power,
The same effect can be obtained. That is, the transmission condition set using the reception electric field strength or the ratio A or B as the transmission condition setting index may be at least one of the modulation method, the coding rate in error correction coding, the packet length, and the transmission power.

Further, in the above description, the received electric field strength,
In addition to a ratio A of subcarriers whose transmission path response characteristic value exceeds a first threshold value to all subcarriers and a ratio B of pilot carriers whose transmission path response characteristic value exceeds a second threshold value to all pilot carriers, Uses the required communication quality as the transmission condition setting index of the transmission condition, and these 3
The transmission condition is set according to one or four transmission condition setting indexes. However, it is possible to set the transmission condition using only the ratio A and the ratio B as the transmission condition setting index.

Next, some embodiments according to another aspect of the present invention will be described. In the first, second, and third embodiments described above, based on the OFDM signal transmitted from the partner station transceiver device to the local station transceiver device,
A transmission condition setting index (reception electric field strength, ratios A, B, required communication quality, etc.) for setting transmission conditions when the own station transmission / reception device transmits an OFDM signal to the other station transmission / reception device is obtained, and based on this You have set the transmission conditions. In the first, second and third embodiments, the transmission path response when transmitting from the local station transmitting / receiving apparatus to the partner station transmitting / receiving apparatus and the transmission path response when transmitting from the remote station transmitting / receiving apparatus to the local station transmitting / receiving apparatus Are substantially equal (for example, when the respective transmission frequency bands are equal).

On the other hand, if the transmission line response when transmitting from the local station transmitting / receiving device to the partner station transmitting / receiving device and the transmission line response when transmitting from the remote station transmitting / receiving device to the local station transmitting / receiving device are different, Based on the OFDM signal transmitted from the station transmitter / receiver to the own station transmitter / receiver, the transmission condition setting index for setting the transmission condition when the partner station transmitter / receiver transmits to the own station transmitter / receiver is obtained, It suffices to set the transmission condition of the transmitting device of the partner station based on this. Less than,
Specific examples in such a case will be described in the fourth, fifth, and sixth embodiments.

(Fourth Embodiment) FIG. 4 shows a fourth embodiment of the present invention.
It is a figure which shows the structure of the OFDM transmission / reception apparatus (local station transmission / reception apparatus) which concerns on embodiment of this, Comprising: It is comprised based on 3rd Embodiment shown in FIG. In the present embodiment, the same parts as those in FIG. 3 are designated by the same reference numerals, and in the present embodiment, the transmission condition setting unit 12 in FIG. 3 is replaced with the transmission condition setting information generating unit 31, and the output of the transmission condition setting information is the transmitting unit. 14 is different from the third embodiment in that it is input to 14.

The transmission condition setting information generating unit 31 inputs the outputs of the reception electric field strength measuring unit 20, the subcarrier transmission line response comparing unit 22 and the pilot carrier transmission line response comparing unit 24 as a transmission condition setting index. The transmission condition setting information generation unit 31 calculates the transmission condition setting index based on the input transmission condition setting index.
The transmission conditions (modulation method, coding rate, packet length, transmission power, etc.) when the counterpart station transmission / reception device transmits to the OFDM transmission / reception device (self-station transmission / reception device) of this embodiment are the transmission conditions in the third embodiment. It is obtained by the same procedure as the setting unit 12. Then, the transmission condition setting information generation unit 31 generates transmission condition setting information for the partner station device to set the transmission condition based on the calculated transmission condition. The transmission condition setting information generated in this way is transmitted to the transmission unit 14
Is transmitted to the transmitting / receiving device of the other station. The partner station transmitter / receiver sets transmission conditions according to the transmitted transmission condition setting information.

FIG. 5 shows the configuration of an OFDM transmitter / receiver as a partner station transmitter / receiver in this embodiment. The transmission condition setting information transmitted from the OFDM transmitter / receiver shown in FIG. 4 is input to the transmission condition setting unit 32 via the antenna 15 and the receiving unit 16. The transmission condition setting unit 32 sets the modulation method and the coding rate for the subcarrier modulation unit 11 according to the input transmission condition setting information, and further sets the transmission power for the transmission unit 14.

As described above, in the present embodiment, the reception field strength measuring unit 20, the subcarrier transmission line response comparison unit 22 and the pilot carrier transmission line response comparison unit 24 in the local station transmission / reception device of FIG. Own station OFDM
A transmission condition setting index for setting the transmission condition when transmitting to the transmission / reception device is obtained. Transmission condition setting information generation unit 3
1 generates transmission condition setting information for setting the transmission condition of the partner station transmitting device based on this transmission condition setting index. The transmission unit 14 displays the generated transmission condition setting information in FIG.
To the other station's transceiver device. In the partner station transmitting / receiving device, the transmission condition setting unit 32 sets the transmission condition based on the transmitted transmission condition setting information. That is,
The partner station transceiver device does not execute the operation of generating the transmission condition setting information for setting the transmission condition. The transmission condition setting information is generated by the local station transmitting / receiving device.

Therefore, according to the present embodiment, the own station OFDM
Even if the transmission line response when transmitting from the transmitting / receiving device to the partner station transmitting / receiving device and the transmission line response when transmitting from the partner station transmitting / receiving device to the own station OFDM transmitting / receiving device are different, the partner station transmitting / receiving device is optimal It is possible to set various transmission conditions, and it is possible to obtain the same effect as that of the third embodiment in the partner station transmitting / receiving device.

That is, in the transmitter / receiver of the other station of FIG. 5, a modulation method that is more resistant to noise is used as the received electric field strength of the transmitter / receiver of the own station of FIG. Can be provided and the effective speed of data transmission can be improved. Further, the ratio A of the subcarriers whose characteristic value of the transmission path response exceeds the first threshold value to all the subcarriers A
And a ratio B of pilot carriers whose transmission path response characteristic value exceeds the second threshold value to all pilot carriers is added as a transmission condition setting index of the transmission condition, so that there is a subcarrier whose transmission path response, that is, reception characteristic is poor. In this case, it is possible to set a modulation method and a coding rate that are more resistant to noise. Therefore, even if severe frequency-selective fading occurs due to the radio wave propagation environment of the transmission path, stable communication quality can be provided, and the effective speed of data transmission can be dramatically improved.

In the present embodiment, as in the third embodiment, the received electric field strength, the ratio A of the subcarriers whose transmission path response characteristic value exceeds the first threshold value to all the subcarriers, and the transmission path response characteristic. The ratio B of pilot carriers whose value exceeds the second threshold to all pilot carriers, and the required communication quality are used as the transmission condition setting indexes of the transmission conditions, and the transmission conditions are set according to these three or four transmission condition setting indexes. However, the ratio A or the ratio B
It is also possible to set the transmission condition using only the ratio A or B as the transmission condition setting index.

(Fifth Embodiment) FIG. 6 shows a fifth embodiment of the present invention.
It is a figure which shows the structure of the OFDM transmitter-receiver (self-station transmitter-receiver) which concerns on embodiment of FIG. In the present embodiment, the same parts as those in FIG. 4 are designated by the same reference numerals. In this embodiment, the transmission condition setting information output from the transmission condition setting information generating unit 31 in FIG. The point of input is different from that of the third embodiment.

FIG. 7 is a diagram showing the structure of an OFDM transmitter / receiver as a partner station transmitter / receiver in this embodiment. The same parts as those in FIG. 5 will be described with the same reference numerals. In the present embodiment, as shown in FIG. 6, the transmission condition setting information is input to the subcarrier modulator 11 in the local station transmitter / receiver. The difference is that transmission condition setting information is extracted from the output of the subcarrier demodulation unit 18 and input to the transmission condition setting unit 32 in the transmitter / receiver of the partner station.

As described above, the transmission / reception of the transmission condition setting information may be performed via the subcarrier modulation section 11 and the subcarrier demodulation section 18, whereby the same effect as that of the fourth embodiment can be obtained.

(Sixth Embodiment) FIG. 8 shows a sixth embodiment of the present invention.
It is a figure which shows the structure of the OFDM transmission / reception apparatus (local station transmission / reception apparatus) which concerns on embodiment of this, Comprising: It is comprised based on 3rd Embodiment shown in FIG. In the description of the present embodiment, the same parts as those in FIG. 3 are designated by the same reference numerals, and in this embodiment, the transmission condition setting unit 12 in FIG.
The third embodiment is different from the third embodiment in that the transmission condition setting index information that is the output is input to the transmission unit 14.

The transmission condition setting index information synthesizing section 41 includes a reception field strength measuring section 20 and a subcarrier transmission line response comparing section 2.
2 and the output of the pilot carrier transmission line response comparison unit 24 are input as transmission condition setting index information, and the transmission condition setting index information is combined. The transmission condition setting index information generated in this way is transmitted to the partner station transmitting / receiving device via the transmitting unit 14. The partner station transmitter / receiver sets transmission conditions according to the transmitted transmission condition setting index information.

FIG. 9 shows the configuration of an OFDM transmitter / receiver as a partner station transmitter / receiver in this embodiment. The transmission condition setting index information transmitted from the OFDM transmitting / receiving apparatus shown in FIG. 8 is input to the transmission condition setting index information separating unit 42 via the antenna 15 and the receiving unit 16. The transmission condition setting index information separating unit 42, based on the input transmission condition setting index, transmits the transmission condition (modulation method, modulation scheme,
The coding rate, the packet length, the transmission power, etc.) are obtained by the same procedure as the transmission condition setting unit 12 in the third embodiment. Then, the transmission condition setting index information separating unit 42 generates transmission condition setting information for the partner station device to set the transmission condition based on the calculated transmission condition. Then, the transmission condition setting index information separation unit 42 outputs the transmission condition setting information to the transmission condition setting unit 43. The transmission condition setting unit 43 sets the transmission condition according to the input transmission condition setting index information. The transmission condition setting unit 43 sets the modulation method and the coding rate for the subcarrier modulation unit 11 and the transmission power for the transmission unit 14 as the transmission condition.

As described above, in the present embodiment, the transmitting section 14 in the own station transmitting / receiving apparatus of FIG. 8 has the receiving electric field strength measuring section 20, the subcarrier transmission line response comparing section 22 and the pilot carrier transmission in the own station transmitting / receiving apparatus. Road response comparison unit 24
9 is transmitted to the partner station transceiver device of FIG. 9 as transmission condition setting index information for setting the transmission condition when the partner station transceiver device transmits to the own station transceiver device. The partner station transmitting / receiving device sets transmission conditions based on the received transmission condition setting index information. As a result, even if the transmission line response when transmitting from the local station transmitting / receiving device to the remote station transmitting / receiving device and the transmission line response when transmitting from the remote station transmitting / receiving device to the local station transmitting / receiving device are different, It is possible to set the optimum transmission conditions. Therefore, it is possible to obtain the same effect as that of the fourth and fifth embodiments in the partner station transmitting / receiving device. In the present embodiment, the information transmitted from the local station transmitting / receiving apparatus to the partner station transmitting / receiving apparatus is not the transmission condition setting information as in the fourth and fifth embodiments, but the transmission condition setting index information. The transmission condition setting index information has a smaller data amount than the transmission condition setting information. Therefore, this embodiment has an effect that the transmission data amount transmitted from the own station transmission / reception device to the partner station transmission / reception device is smaller than that in the fourth and fifth embodiments.

As a modification of this embodiment, the fourth and fifth embodiments are provided.
In the same manner as in the first embodiment, the reception electric field strength, the ratio A of the subcarriers whose transmission line response characteristic value exceeds the first threshold value to all the subcarriers, and the pilot carrier whose transmission line response characteristic value exceeds the second threshold value. The ratio B to all pilot carriers and the required communication quality are used as the transmission condition setting indexes of the transmission conditions, and the transmission conditions are not set according to these three or four transmission condition setting indexes. Only the ratio A or the ratio B is set. Alternatively, it is possible to set the transmission condition using both the ratios A and B as the transmission condition setting index.

(Seventh Embodiment) FIG. 10 is a diagram showing the structure of an OFDM transmitting / receiving apparatus according to a seventh embodiment of the present invention. The OFDM transmitting / receiving apparatus of the third embodiment shown in FIG. , And has a configuration in which the functions of the OFDM transmitter-receiver shown in FIG. 9 are combined. That is, O shown in FIG.
A transmission condition setting index information separating unit 51 is added to the FDM transmitting / receiving apparatus, and the transmission condition setting unit 52 further causes the receiving electric field strength measuring unit 20, the subcarrier transmission line response comparing unit 22 and the pilot carrier transmission line response in the own station transmitting / receiving device. The function of setting the transmission condition in the local station transmitting / receiving device by using the output of the comparing unit 24 as the transmission condition setting index information, and the transmission condition setting index transmitted from the partner station transmitting / receiving device and separated by the transmission condition setting index information separating unit 51. It has a function of setting transmission conditions in the local station transmitter / receiver according to the information.

According to this embodiment, when the transmission line response at the time of transmission from the local station transmission / reception device to the remote station transmission / reception device and the transmission line response at the transmission from the remote station transmission / reception device to the self station transmission / reception device are substantially equal to each other, In the same manner as the third embodiment, the output of the reception electric field strength measuring unit 20, the subcarrier transmission line response comparing unit 22 and the pilot carrier transmission line response comparing unit 24 in the local station transmitting / receiving apparatus is used as transmission condition setting index information. Set the transmission conditions for the local transceiver.

On the other hand, if the transmission line response at the time of transmission from the local station transmission / reception device to the remote station transmission / reception device and the transmission line response at the transmission from the remote station transmission / reception device to the self station transmission / reception device are different, Similar to the partner station transmitter / receiver shown in FIG. 9 in the sixth exemplary embodiment, the transmission condition setting is performed based on the OFDM signal transmitted from the partner station transmitter / receiver in the own station transmitter / receiver, that is, transmitted from the partner station transmitter / receiver. According to the transmission condition setting index information separated by the index information separating unit 51, the transmission condition setting unit 52 sets the transmission condition in the local station transmitting / receiving device.

That is, according to the present embodiment, it is possible to set the optimum transmission condition for both cases where the bidirectional transmission line responses of the local station transmitting / receiving apparatus and the partner station transmitting / receiving apparatus are equal or different. it can. As a modification of this embodiment, the ratio A of subcarriers whose transmission path response characteristic value exceeds the first threshold value to all subcarriers and all pilots of pilot carriers whose transmission path response characteristic value exceeds the second threshold value. It is also possible to set the transmission condition using only one or both of the ratios B to the carrier as the transmission condition setting index.

[0071]

According to the OFDM transmitter / receiver of the present invention,
The transmission condition can be set according to the transmission path response of each subcarrier of the OFDM signal, and the effective speed of data transmission can be effectively improved.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of an OFDM transmitting / receiving apparatus according to a first embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration of an OFDM transmitting / receiving apparatus according to a second embodiment of the present invention.

FIG. 3 is a block diagram showing a configuration of an OFDM transmitting / receiving apparatus according to a third embodiment of the present invention.

FIG. 4 is a block diagram showing a configuration of an OFDM transmitting / receiving apparatus (local station transmitting / receiving apparatus) according to a fourth embodiment of the present invention.

FIG. 5 is a block diagram showing a configuration of an OFDM transmitting / receiving apparatus (partner station transmitting / receiving apparatus) according to a fourth embodiment of the present invention.

FIG. 6 is a block diagram showing the configuration of an OFDM transmitter / receiver (own station transmitter / receiver) according to a fifth embodiment of the present invention.

FIG. 7 is a block diagram showing a configuration of an OFDM transmitting / receiving apparatus (partner station transmitting / receiving apparatus) according to a fifth embodiment of the present invention.

FIG. 8 is a block diagram showing a configuration of an OFDM transmitting / receiving apparatus (own station transmitting / receiving apparatus) according to a sixth embodiment of the present invention.

FIG. 9 is a block diagram showing the configuration of an OFDM transmitting / receiving apparatus (partner station transmitting / receiving apparatus) according to a sixth embodiment of the present invention.

FIG. 10 is a block diagram showing the configuration of an OFDM transmitting / receiving apparatus according to a seventh embodiment of the present invention.

[Explanation of symbols]

10 Transmission data series 11 Subcarrier modulator 12 Transmission condition setting section 13 IFFT (Fast Inverse Fourier Transform) section 14 Transmitter 15 antenna 16 Receiver 17 FFT (Fast Fourier Transform) section 18 subcarrier demodulator 19 Received data series 20 Received field strength measurement unit 21 Transmission line response calculator 22 Subcarrier transmission line response comparison unit 23 Communication quality setting information 24 Pilot carrier transmission line response comparison unit 31 Transmission condition setting information generator 32 Transmission condition setting section 41 Transmission condition setting index information synthesis unit 42 Transmission condition setting index information separation unit 43 Transmission condition setting section 51 Transmission condition setting index information separation unit 52 Transmission condition setting section

Claims (12)

[Claims] 1. An OFDM transmitter / receiver for transmitting and receiving an OFDM signal having a plurality of subcarriers to and from a partner station transmitter / receiver via a predetermined transmission path, wherein the OFDM signal transmitted from the partner station transmitter / receiver device Receiving means for receiving a transmission path response calculating means for calculating a transmission path response indicating a response characteristic of the transmission path to the plurality of subcarriers from the received OFDM signal; Comparing the characteristic value of the above with a predetermined threshold value and calculating a ratio of the number of subcarriers whose characteristic value exceeds the threshold value to the total number of subcarriers; and a transmission condition setting index at least the ratio calculated by the comparing means. Based on the transmission condition setting index
An OFDM transmission / reception device comprising: transmission condition setting means for setting transmission conditions when an FDM transmission / reception device transmits an OFDM signal to the partner station transmission / reception device; and transmission means for transmitting an OFDM signal according to the set transmission conditions. 2. The transmission condition setting means sets at least one of a modulation method for generating an OFDM signal, a coding rate in error correction coding, a packet length and a transmission power as the transmission condition. OFDM described in 1
Transceiver. 3. The OF from the received OFDM signal
The OFDM according to claim 1, further comprising means for measuring a reception electric field strength of the DM signal, wherein the transmission condition setting means sets the transmission condition by adding the measured reception electric field strength to the transmission condition setting index. Transceiver. 4. The OF from the received OFDM signal
The transmission condition setting means sets the transmission condition by adding the measured reception electric field intensity and the required communication quality to the transmission condition setting index. The OFDM transmitter / receiver according to claim 1. 5. An OFDM transmitter / receiver for transmitting and receiving an OFDM signal having a plurality of subcarriers to and from a partner station transmitter / receiver via a predetermined transmission path, the OFDM signal transmitted from the partner station transmitter / receiver device. Receiving means for receiving a transmission path response calculating means for calculating a transmission path response indicating a response characteristic of the transmission path to the plurality of subcarriers from the received OFDM signal; Comparing the characteristic value of the above with a predetermined threshold value and calculating a ratio of the number of subcarriers whose characteristic value exceeds the threshold value to the total number of subcarriers; and a transmission condition setting index at least the ratio calculated by the comparing means. As the partner station transmitting / receiving device
Transmission condition setting information generating means for generating transmission condition setting information for setting a transmission condition when transmitting an OFDM signal to the transmitting / receiving device; and transmitting means for transmitting the transmission condition setting information to the partner station transmitting / receiving device. An OFDM transmitter / receiver provided. 6. The first transmission response indicating the response characteristic of the transmission channel with respect to a known subcarrier included in each area where data is stored, from the received OFDM signal. To calculate a second transmission response indicating a response characteristic of the transmission path with respect to a known subcarrier forming a preamble, and the comparing means calculates a predetermined characteristic value of the calculated first transmission path response. The ratio of the number of known subcarriers whose characteristic value exceeds the threshold to the total number of known subcarriers is calculated by comparing with a predetermined threshold value, and the predetermined characteristic value of the calculated second transmission path response is set to a predetermined threshold value. And calculating the ratio of the number of known subcarriers whose characteristic value exceeds the threshold value to the total number of known subcarriers, wherein the transmission condition setting means is at least the first and second transmission paths. The ratio calculated on the basis of the answer as the transmission condition setting index, the OFDM based on the transmission condition setting index
The transmission / reception apparatus sets transmission conditions when transmitting an OFDM signal to the partner station transmission / reception apparatus.
8. The OFDM transmitter / receiver described in. 7. The first transmission response indicating the response characteristic of the transmission channel from the received OFDM signal to the known subcarriers included in each area where data is stored, from the received OFDM signal. And calculating a second transmission response indicating a transmission path response indicating the response characteristics of the transmission path for the plurality of subcarriers, wherein the comparison means determines a predetermined value of the calculated first transmission path response. The characteristic value is compared with a predetermined threshold value, the ratio of the number of known subcarriers whose characteristic value exceeds the threshold value to the total number of known subcarriers is calculated, and the predetermined characteristic value of the calculated second transmission line response is calculated. A ratio of the number of subcarriers whose characteristic value exceeds the threshold to the total number of subcarriers is calculated by comparing with a predetermined threshold, and the transmission condition setting means is based on at least the first and second transmission path responses. As the transmission condition setting index calculated proportion come, the OFDM based on the transmission condition setting index
The transmission / reception apparatus sets transmission conditions when transmitting an OFDM signal to the partner station transmission / reception apparatus.
8. The OFDM transmitter / receiver described in. 8. The comparing means sets at least one of amplitude, power and distortion magnitude of the first and second transmission line responses to a predetermined characteristic value of the first and second transmission line responses. The OFDM transmitter / receiver according to claim 6 or 7, wherein the OFDM transmitter / receiver is compared with the first and second threshold values, respectively. 9. An OFDM transmitting / receiving apparatus for transmitting / receiving an OFDM signal having a plurality of subcarriers to / from a partner station transmitting / receiving apparatus via a predetermined transmission path, wherein the OFDM signal transmitted from the partner station transmitting / receiving apparatus. Receiving means for receiving a transmission path response calculating means for calculating a transmission path response indicating a response characteristic of the transmission path to the plurality of subcarriers from the received OFDM signal; Comparing a characteristic value of a subcarrier number with a predetermined threshold value and calculating a ratio of the number of subcarriers whose characteristic value exceeds the threshold value to the total number of subcarriers; The transmission condition setting as a transmission condition setting index when the device sets transmission conditions when transmitting an OFDM signal to the OFDM transmission / reception device OFDM transmitting and receiving apparatus comprising a transmission condition setting index information synthesizing means for synthesizing the information of target, and transmitting means for transmitting the information of the transmission condition setting index to the other station transceiver. 10. The transmission path response calculation means calculates, from the received OFDM signal, response characteristics of the transmission path with respect to known subcarriers included in respective areas in which data is stored, and the comparison means. Means for comparing a predetermined characteristic value of the calculated transmission path response with a predetermined threshold value, and calculating a ratio of the number of known subcarriers whose characteristic value exceeds the threshold value to the total number of known subcarriers. The OFDM transmitter / receiver according to claim 1, 5 or 9, further comprising: 11. The transmission path response calculation means calculates, from the received OFDM signal, response characteristics of the transmission path with respect to known subcarriers forming a preamble, and the comparison means calculates the transmission path response of the calculated transmission path response. The second comparison means for comparing a predetermined characteristic value with a predetermined threshold value, and calculating a ratio of the number of known subcarriers whose characteristic value exceeds the threshold value to the total number of known subcarriers. Alternatively, the OFDM transmitter / receiver according to claim 9. 12. The comparison means compares the at least one of amplitude, power and distortion magnitude of the transmission line response with the threshold value as a predetermined characteristic value of the transmission line response. 5 or the OFD according to claim 9.
M transceiver.