JP2003158499A - Method and equipment for communication - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a communication method capable of realizing enhancement of system throughput and enhancement of transmission power efficiency as realizing satisfactory state estimation of a propagation path and sufficient compensation of transmission power efficiency. SOLUTION: In the communication method, communication is performed by using a multi-carrier modulation and demodulation system and furthermore, when at least any one of a modulation system, encoding ratio and information transmission rate are adaptively changed to sub-carrier units, at least any one of positions, the number and power of the sub-carriers (pilot sub-carriers) to be used as pilot signals are changed in accordance with the adapted modulation system, encoding ratio and information transmission rate.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a communication method for performing data communication in a wireless communication system such as a wireless LAN or a mobile communication system, and more particularly to an OFD.
The present invention relates to a communication method and a communication device that employ a multicarrier modulation / demodulation method such as an M (Orthogonal Frequency Division Multiplexing) modulation / demodulation method.

[0002]

2. Description of the Related Art A conventional communication method will be described below. FIG. 15 is a document “Low Power Data Communication System Wideband Mobile Access System (HiSWANa) Standard (Draft) 0.3 Edition” by the Radio Industries Association (October 1, 2000).
FIG. 2 is a diagram showing a slot configuration of the OFDM modulation / demodulation system shown in (2nd).

In FIG. 15, 1 is a pilot subcarrier, 2 is a data subcarrier, and the position, number, and power of pilot subcarriers are fixed.

Generally, when a wide band signal is transmitted in a wireless section, the received waveform is distorted due to the effect of frequency selective fading. Therefore, in the OFDM modulation / demodulation method, as shown in FIG.
As described above, the pilot carrier is inserted into the transmission symbol, the propagation path state is estimated by using the pilot carrier on the receiver side, and the received waveform is compensated.

[0005]

However, the above
In the conventional communication method, since the number of pilot subcarriers and the power of pilot subcarriers are the same in all subcarriers, a sufficient signal power to noise power ratio (SNR) is obtained due to the influence of frequency selective fading.
In some cases, there is a subcarrier that cannot be obtained. In that case, there is a problem that the accuracy of propagation path condition estimation deteriorates and the received waveform cannot be sufficiently compensated.

Further, in the conventional communication method, since the frequency selective fading characteristic is deteriorated depending on the magnitude of the modulation multi-level number, the modulation method of each subcarrier is adaptively adjusted in the OFDM modulation method. If you change, enough SNR
In some cases, there is a subcarrier that cannot be obtained. In that case, there is a problem that the accuracy of propagation path condition estimation deteriorates and the received waveform cannot be sufficiently compensated.

Further, in order to realize the accuracy of the propagation path condition estimation necessary to sufficiently compensate the received waveform, it is necessary to improve the SNR of the pilot carrier. However, in the conventional communication method, when the number of pilot subcarriers is increased in order to improve the SNR of pilot carriers, there is a problem that system throughput decreases. Also, the SNR of the pilot carrier
If the pilot subcarrier power is increased to improve the transmission power, there is a problem that the transmission power efficiency is reduced.

The present invention has been made in view of the above, and in radio communication adopting the OFDM modulation / demodulation method, it is possible to improve the system throughput while realizing good propagation path condition estimation and sufficient reception waveform compensation. Another object of the present invention is to obtain a communication method and a communication device that can improve the transmission power efficiency.

[0009]

[Means for Solving the Problems]
In order to achieve the object, in the communication method according to the present invention, communication is performed using a multi-carrier modulation / demodulation method,
When adaptively changing at least one of a modulation method, a coding rate, and an information transmission rate to a predetermined subcarrier unit, a parameter related to a subcarrier (pilot subcarrier) used as a pilot signal is applied to the modulated signal. It is characterized in that it is changed according to the method, the coding rate, and the information transmission rate.

In the communication method according to the next invention,
It is characterized in that the predetermined subcarrier unit is a single subcarrier.

In the communication method according to the next invention,
It is characterized in that the predetermined subcarrier unit is a subband composed of an arbitrary number of subcarriers.

In the communication method according to the next invention,
It is characterized in that the predetermined subcarrier unit is a single symbol, arbitrary plural symbols, single slot, arbitrary plural slots, single frame, or arbitrary plural frames.

In the communication method according to the next invention,
At least one of a modulation method, a coding rate, and an information transmission rate is set for each subcarrier in units of a single symbol,
For each subcarrier in units of multiple symbols, for each subcarrier in units of single slot, for each subcarrier in units of multiple slots, for each subcarrier in units of single frame, or for each subcarrier in units of multiple frames, It is characterized by being adaptively changed.

In the communication method according to the next invention,
At least one of the modulation method, the coding rate, and the information transmission rate is set for each subband in a unit of a single symbol, each subband in a unit of a plurality of symbols, each subband in a unit of a single slot, and a plurality of slots for each subband. For each subband as a unit, for each subband as a single frame,
Alternatively, it is characterized in that it is adaptively changed for each subband in units of a plurality of frames.

In the communication method according to the next invention,
The parameters are the position of the pilot subcarrier,
It is characterized in that it is at least one of the number and the power.

In the communication method according to the next invention,
When communication is performed using a multi-carrier modulation / demodulation method and the modulation method, coding rate, and information transmission rate used for retransmission are the same as before retransmission, at least any of the position, number, and power of subcarriers used as pilot signals. It is characterized by changing one of them.

In the communication device according to the next invention,
It is configured to perform communication using a multi-carrier modulation / demodulation method, and is used as a pilot signal when adaptively changing at least one of a modulation method, a coding rate, and an information transmission rate to a predetermined subcarrier unit. Parameters related to carriers (pilot subcarriers)
It is characterized in that it is provided with a modulation means that changes according to the applied modulation method, coding rate, and information transmission rate.

In the communication device according to the next invention,
It is characterized in that the predetermined subcarrier unit is a single subcarrier.

In the communication device according to the next invention,
It is characterized in that the predetermined subcarrier unit is a subband composed of an arbitrary number of subcarriers.

In a communication device according to the next invention,
It is characterized in that the predetermined subcarrier unit is a single symbol, arbitrary plural symbols, single slot, arbitrary plural slots, single frame, or arbitrary plural frames.

In the communication device according to the next invention,
At least one of a modulation method, a coding rate, and an information transmission rate is set for each subcarrier in units of a single symbol,
For each subcarrier in units of multiple symbols, for each subcarrier in units of single slot, for each subcarrier in units of multiple slots, for each subcarrier in units of single frame, or for each subcarrier in units of multiple frames, It is characterized by being adaptively changed.

In the communication device according to the next invention,
At least one of the modulation method, the coding rate, and the information transmission rate is set for each subband in a unit of a single symbol, each subband in a unit of a plurality of symbols, each subband in a unit of a single slot, and a plurality of slots for each subband. For each subband as a unit, for each subband as a single frame,
Alternatively, it is characterized in that it is adaptively changed for each subband in units of a plurality of frames.

In the communication device according to the next invention, the modulating means sets the parameter to at least one of the position, number and power of pilot subcarriers.

In the communication device according to the next invention,
Position, number, and power of subcarriers used as pilot signals when the configuration is such that communication is performed using the multicarrier modulation / demodulation method and the modulation method, coding rate, and information transmission rate used for retransmission are the same as before retransmission. And a modulation means for changing at least one of the values before the retransmission.

[0025]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of a communication method and a communication device according to the present invention will be described in detail below with reference to the drawings. The present invention is not limited to this embodiment.

Embodiment 1. FIG. 1 is a diagram showing a configuration of a communication device according to the present invention. In FIG. 1, 3 is a demodulation unit, 4 is a transmission parameter estimation unit, 5 is a channel condition estimation unit, 6 is a transmission parameter control unit, 7 is a modulation unit, and 8 is a receiving antenna. And 9 is a transmitting antenna.

The transmission parameter estimation unit 4 in the communication device estimates (extracts) parameters such as the modulation method used for transmission in each subcarrier from the signal received by the reception antenna 8 and demodulates the extraction result. Notify 3 The demodulation unit 3 demodulates the signal received by the reception antenna 8 using the extraction result of the transmission parameter estimation unit 4. The channel condition estimation unit 5 estimates the channel condition from the signal received by the receiving antenna 8 and notifies the transmission parameter control unit 6 of the estimation result. The transmission parameter control unit 6 uses the estimation result of the channel condition estimation unit 5 to determine the transmission parameter of the modulation scheme applied to each subcarrier, and notifies the modulation unit 7 of the determination result. The modulator 7 modulates the information data sequence using the determination result of the transmission parameter controller 6.

At this time, modulating section 7 inserts pilot symbols according to the communication method of the present embodiment shown below.

FIG. 2 is a diagram showing an example of subcarrier arrangement of the OFDM modulation / demodulation method used in the communication method of the first embodiment. In FIG. 2, 10 is a pilot subcarrier, 11 is a data subcarrier, and 12 is one symbol. Here, it is assumed that the power of each pilot subcarrier is equal.

In the present embodiment, when the modulation method is adaptively changed in subcarrier units in the OFDM modulation / demodulation method, as shown in FIG. 2, pilot subcarriers are used according to the modulation method applied to each subcarrier. Change the position and number of.

For example, there are three subcarriers to which the BPSK modulation method is applied to the subcarriers at time t (1), and the QPSK modulation method is applied to the remaining subcarriers at time t (1). The subcarrier at time t (2) has one subcarrier to which the BPSK modulation scheme is applied, and the remaining subcarriers at time t (2) have QPSK.
A case where the modulation method is applied will be described as an example. When a BPSK modulation method with good frequency selective fading characteristics is used as a pilot subcarrier, the propagation path condition can be estimated with high accuracy even if the number of pilot subcarriers is reduced. Therefore, a BPSK modulation method such as a QPSK modulation method can be used. Also, the number of pilot subcarriers can be reduced as compared with the case where a modulation scheme with a large number of modulation levels is used as pilot subcarriers.

Therefore, at time t (1), BPSK
Three subcarriers to which the modulation method is applied are pilot subcarriers, and at time t (2), one subcarrier to which the BPSK modulation method is applied and QPSK
Any three of the subcarriers to which the K modulation method is applied are pilot subcarriers.

As described above, in this embodiment, the total number of pilot subcarriers is reduced by changing the position and number of pilot subcarriers according to the modulation method applied to each subcarrier, and the system throughput is reduced. Improve. Although the modulation method described above (BPSK or the like) is applied in the present embodiment, the present invention is not limited to this and any method may be used. Also, the position and number of pilot subcarriers are arbitrary within a range in which desired propagation path condition estimation quality can be obtained.

Next, a case will be described where the power of pilot subcarriers is changed in accordance with the modulation scheme applied to each subcarrier in the configuration of the first embodiment. FIG. 3 shows the O used in the communication method of the first embodiment.
It is a figure which shows an example of the subcarrier arrangement | positioning of a FDM modulation / demodulation system, 13 is a data subcarrier, 14 is a pilot subcarrier. In addition, here, the magnitude of the power is represented by the length of the vertical axis of each subcarrier. Further, the subcarriers of frequencies f (3) and f (6) are pilot subcarriers, and the frequencies f (3) and f of time t (1) are used.
The QPSK modulation method is applied to (6), and the time t
16Q for each of the frequencies f (3) and f (6) in (2)
The AM and BPSK modulation method is applied.

Therefore, the time t (2) when the BPSK modulation method having good frequency selective fading characteristics is applied.
The pilot subcarrier of frequency f (6) at
The pilot subcarrier power is reduced because the propagation path condition can be estimated with high accuracy even if the power is reduced. On the other hand, the pilot subcarrier of frequency f (3) at the time t (2) to which the 16QAM modulation scheme having poor frequency selective fading characteristics is applied improves the SNR of the pilot subcarrier by increasing the pilot subcarrier power. , Keep the accuracy of channel condition estimation at a desired level.

As described above, in the present embodiment, the transmission power efficiency can be improved by making the power variable according to the modulation method applied to the pilot subcarrier.

As described above, in the present embodiment, the case where the position and number of pilot subcarriers are made variable and the case where the power of pilot subcarriers is made variable have been described, but the present invention is not limited to this. If the modulation / demodulation system is configured to adaptively change the modulation system for each subcarrier, for example, at least any one of the position, number, and power of pilot subcarriers depending on the modulation system applied to each subcarrier. You may change one. Further, the position, the number, and the power are arbitrary within a range in which a desired propagation path condition estimation accuracy is maintained. As a result, at least one of system throughput and transmission power efficiency can be improved as compared with the conventional case.

Embodiment 2. FIG. 4 is a diagram showing an example of subcarrier arrangement of the OFDM modulation / demodulation method used in the communication method of the second embodiment. In FIG. 4, 15 is a pilot subcarrier, 16 is a data subcarrier, and 17 is one symbol. Here, it is assumed that the power of each pilot subcarrier is equal.

Here, the operation of the communication apparatus of this embodiment will be described. The configuration of the communication device is the same as that of the first embodiment described above, and therefore, the same reference numerals are given and the description thereof is omitted. Here, the transmission parameter estimation unit 4, the transmission parameter control unit 6, and the modulation unit 7, which have different operations, will be described. Transmission parameter estimation unit 4
Then, parameters such as the modulation method used for transmission in each subband are estimated (extracted) from the signal received by the reception antenna 8 and the extraction result is notified to the demodulation unit 3. The transmission parameter control unit 6 uses the estimation result of the propagation path condition estimation unit 5 to determine the transmission parameter of the modulation scheme applied to each subband, and the determination result is used by the modulation unit 7
Notify.

Then, modulating section 7 inserts pilot symbols according to the communication method of the present embodiment shown below. In this embodiment, when the modulation method is adaptively changed in subband units in the OFDM modulation / demodulation method, as shown in FIG. 4, the number and position of pilot subcarriers are changed according to the modulation method applied in each subband. To change.

For example, at time t (1), frequencies f (1) and f (2) and f (3) and frequencies f (4) and f
(5) and f (6), frequencies f (7), f (8) and f
The case where the BPSK modulation method, the QPSK modulation method, and the BPSK modulation method are applied to the individual subbands of (9) will be described as an example.

First, the frequencies f (1), f (2) and f (3), f (7), f (8) and f (to which the BPSK modulation method having good frequency selective fading characteristics is applied. In each subband of 9), the channel condition can be estimated with high accuracy even if the number of pilot subcarriers is small, so the number of pilot subcarriers is set to one of the frequencies f (1) and f (7). Secondly, the sub-bands of frequencies f (4), f (5) and f (6) to which the QPSK modulation system with poor frequency selective fading characteristics is applied compared to the BPSK modulation system are
The accuracy of channel estimation is improved by increasing the number of pilot subcarriers.

As described above, in this embodiment, the position and number of pilot subcarriers are variable for each subband, so that the total number of pilot symbols is reduced and the system throughput is improved. In the present embodiment, the above-mentioned modulation method is applied, but the present invention is not limited to this, and any method may be used. The position and number of pilot subcarriers in each subband are also arbitrary. Also, the method of dividing the subbands is not limited to this, but is arbitrary.

As described above, in the present embodiment, OFDM
When the modulation method is adaptively changed in sub-band units in the modulation / demodulation method, the position and number of pilot sub-carriers are made variable according to the modulation method applied in sub-band units. As a result, the system throughput can be significantly improved as compared with the conventional case.

In the present embodiment, the case has been described in which the position and number of pilot subcarriers are variable, but the present invention is not limited to this, and pilot subcarriers can be changed according to the modulation scheme applied in each subband. At least one of the position, the number, and the power of the carriers may be changed. In this case, the position, the number, and the power are arbitrary as long as the desired channel state estimation accuracy is maintained. As a result, at least one of system throughput and transmission power efficiency can be improved as compared with the related art.

Embodiment 3. FIG. 5 is a diagram showing an example of subcarrier arrangement of the OFDM modulation / demodulation method used in the communication method of the third embodiment. In FIG. 5, 18 is a pilot subcarrier, 19 is a data subcarrier, and 20 is one symbol. Here, it is assumed that the power of each pilot subcarrier is equal.

Here, the operation of the communication apparatus of this embodiment will be described. The configuration of the communication device is the same as that of the first embodiment described above, and therefore, the same reference numerals are given and the description thereof is omitted. Here, the transmission parameter estimation unit 4, the transmission parameter control unit 6, and the modulation unit 7, which have different operations, will be described. Transmission parameter estimation unit 4
Then, the parameters of the modulation method used for transmission in each symbol are estimated (extracted) from the signal received by the receiving antenna 8, and the extraction result is notified to the demodulation unit 3. In the transmission parameter control unit 6, the propagation path condition estimation unit 5
The transmission parameter of the modulation scheme applied to each symbol is determined using the estimation result of and the determination result is notified to the modulation unit 7.

Then, modulating section 7 inserts pilot symbols in accordance with the communication method of the present embodiment shown below. In the present embodiment, when the modulation method is adaptively changed on a symbol-by-symbol basis in the OFDM modulation / demodulation method, FIG.
As shown in, the number and position of pilot subcarriers are changed according to the modulation scheme applied in each symbol.

For example, the case where the BPSK modulation method is applied to the symbol starting at time t (1) and the QPSK modulation method is applied to the symbol starting at time t (n + 1) will be described as an example.

First, since the symbols starting from time t (1) to which the BPSK modulation method with good frequency selective fading characteristics is applied can estimate the channel condition with high accuracy even if the number of pilot subcarriers is small. , Pilot subcarriers are arranged at intervals of 4 subcarriers. Second
In addition, as compared with the BPSK modulation method, the time t when the QPSK modulation method having poor frequency selective fading characteristics is applied.
The symbols starting from (n + 1) improve the propagation path condition estimation accuracy by increasing the number of pilot subcarriers.

As described above, in the present embodiment, the position and number of pilot subcarriers are variable for each symbol, so that the total number of pilot symbols is reduced and the system throughput is improved. In the present embodiment, the above-mentioned modulation method is applied, but the present invention is not limited to this, and any method may be used. The position and number of pilot subcarriers for each symbol are also arbitrary.

As described above, in the present embodiment, OFDM
When the modulation method is adaptively changed in symbol units in the modulation / demodulation method, the position and number of pilot subcarriers are made variable according to the modulation method applied in symbol units. As a result, the system throughput can be significantly improved as compared with the conventional case.

In this embodiment, the case has been described in which the position and number of pilot subcarriers are variable, but the present invention is not limited to this, and pilot subcarriers can be changed according to the modulation scheme applied to each symbol. At least one of the position, the number, and the power may be changed. In this case, the position, the number, and the power are arbitrary as long as the desired channel state estimation accuracy is maintained. As a result, at least one of system throughput and transmission power efficiency can be improved as compared with the related art.

Further, in the present embodiment, the modulation system is adaptively changed in symbol units, but the present invention is not limited to this, and the modulation system change unit may be, for example, a plurality of symbol units, a slot unit, or a plurality of slots. Unit, frame unit,
Alternatively, a plurality of frames may be used.

Fourth Embodiment FIG. 6 is a diagram showing an example of subcarrier arrangement of the OFDM modulation / demodulation method used in the communication method of the fourth embodiment. In FIG. 6, 21 is a pilot subcarrier, 22 is a data subcarrier, and 23 is one symbol. Here, it is assumed that the power of each pilot subcarrier is equal.

Here, the operation of the communication apparatus of this embodiment will be described. The configuration of the communication device is the same as that of the first embodiment described above, and therefore, the same reference numerals are given and the description thereof is omitted. Here, the transmission parameter estimation unit 4, the transmission parameter control unit 6, and the modulation unit 7 which have different operations will be described. Transmission parameter estimation unit 4
Then, the parameters of the modulation scheme used for transmission in each subcarrier are estimated (extracted) from the signal received by the receiving antenna 8 in units of symbols, and the extraction result is notified to the demodulation unit 3. The transmission parameter control unit 6 uses the estimation result of the propagation path condition estimation unit 5 to determine the transmission parameter of the modulation scheme to be applied to each subcarrier in symbol units, and notifies the modulation unit 7 of the determination result. .

Then, modulating section 7 inserts pilot symbols in accordance with the communication method of the present embodiment shown below. In this embodiment, when the modulation method is adaptively changed in the symbol modulation unit and the subcarrier unit in the OFDM modulation / demodulation method, as shown in FIG. 6, the pilot subcarriers of pilot subcarriers are changed according to the modulation method applied to each subcarrier. Change the number and position.

For example, the frequencies f (1), f (4), f (5), f (9) ... Of symbols starting from time t (1).
The BPSK modulation method is applied to the sub-carriers of frequencies f (2), f (3), f (6), f (7), f (8) ...
Is applied to the subcarriers of the symbol frequencies f (2), f (18) ... Starting from time t (n + 1), the BPSK modulation method is applied to
(1), f (3), f (4), f (5), f (6), f
The case where the QPSK modulation method is applied to (7), f (8), f (9) ... Is described as an example.

First, the subcarriers of the frequencies f (1), f (4), f (5), and f (9) of the symbols starting from the time t (1) have good BPSK resistance against frequency selective fading. Since the modulation system is applied, it is suitable as a pilot subcarrier. Therefore, the frequency f
Subcarriers (1), f (5), and f (9) are used as pilot subcarriers.

Secondly, since the BPSK modulation scheme with good frequency selective fading characteristics is applied to the subcarrier of the frequency f (2) of the symbol starting from the time t (n + 1), it is suitable as a pilot subcarrier. There is. Therefore, the subcarrier of frequency f (2) is used as the pilot subcarrier. Further, the subcarrier of frequency f (6) is applied with the QPSK modulation method, which has poorer frequency selective fading characteristics than the BPSK modulation method, but the subcarrier to which the BPSK modulation method is applied next has the frequency f. Since it is (18), it is used as a pilot subcarrier in order to prevent the pilot subcarrier interval from becoming too large. This allows
The propagation path condition estimation accuracy is maintained at a desired quality.

As described above, in the present embodiment, the total number of pilot symbols is reduced by changing the position and number of pilot subcarriers when the modulation method is changed for each subcarrier in units of symbols. And improve system throughput. In the present embodiment, the above-mentioned modulation method is applied, but the present invention is not limited to this, and any method may be used. The position and number of pilot subcarriers are also arbitrary.

As described above, in the present embodiment, OFDM
When the modulation method is adaptively changed for each subcarrier in units of symbols in the modulation / demodulation method, the position and number of pilot subcarriers are made variable according to the applied modulation method. As a result, the system throughput can be significantly improved as compared with the conventional case.

In the present embodiment, the case has been described in which the position and number of pilot subcarriers are variable, but the present invention is not limited to this, and the pilot subcarriers may be changed according to the modulation scheme applied to each subcarrier. At least one of the position, the number, and the power of the carriers may be changed. In this case, the position, the number, and the power are arbitrary as long as the desired channel condition estimation accuracy is maintained. As a result, at least one of system throughput and transmission power efficiency can be improved as compared with the related art.

Further, in the present embodiment, the modulation method of each subcarrier is adaptively changed for each subcarrier in units of symbols, but the present invention is not limited to this. It may be changed for each carrier, for each subcarrier in units of slots, for each subcarrier in units of multiple slots, for each subcarrier in units of frames, or for each subcarrier in units of multiple frames.

Embodiment 5. FIG. 7 is a diagram showing an example of subcarrier arrangement of the OFDM modulation / demodulation method used in the communication method of the fifth embodiment. In FIG. 7, 24 is a pilot subcarrier, 25 is a data subcarrier, and 26 is one symbol. Here, it is assumed that the power of each pilot subcarrier is equal.

Here, the operation of the communication apparatus of this embodiment will be described. The configuration of the communication device is the same as that of the first embodiment described above, and therefore, the same reference numerals are given and the description thereof is omitted. Here, the transmission parameter estimation unit 4, the transmission parameter control unit 6, and the modulation unit 7 which have different operations will be described. Transmission parameter estimation unit 4
Then, the parameters of the modulation method used for transmission in each subband are estimated (extracted) from the signal received by the receiving antenna 8 in units of symbols, and the extraction result is notified to the demodulation unit 3. The transmission parameter control unit 6 determines the transmission parameter of the modulation scheme to be applied to each subband on a symbol-by-symbol basis using the estimation result of the channel condition estimation unit 5, and notifies the modulation unit 7 of the determination result. .

Then, modulating section 7 inserts pilot symbols according to the communication method of the present embodiment shown below. In this embodiment, when the modulation method is adaptively changed for each subband in units of symbols in the OFDM modulation / demodulation method, as shown in FIG. 7, pilot subcarriers are used according to the modulation method applied in each subband. Change the number and position of.

For example, the BPSK modulation method is applied to the subband (1) and the subband (3) of the symbol starting from the time t (1), the QPSK modulation method is applied to the subband (2), and the time t (n + 1). The case where the QPSK modulation method is applied to the subband (1) of the symbol starting from () and the BPSK modulation method is applied to the subband (2) and the subband (3) will be described as an example.

First, the subbands (1) and (3) of the symbol, which start at time t (1) to which the BPSK modulation method with good frequency selective fading characteristics is applied, can be used even if the number of pilot subcarriers is small. Since the propagation path condition can be estimated with high accuracy, the number of pilot subcarriers is one in the subband.

Secondly, the number of pilot subcarriers is increased in the subband (2) of the symbol starting from time t (1) to which the QPSK modulation system having poor frequency-selective fading characteristics is applied as compared with the BPSK modulation system. This improves the accuracy of channel estimation.

Third, the time t (n + 1) when the BPSK modulation method with good frequency selective fading characteristics is applied.
In the subbands (2) and (3) of symbols starting with, the propagation path condition can be estimated with high accuracy even if the number of pilot subcarriers is small, so that there is one pilot subcarrier in the subband.

Fourth, as compared with the BPSK modulation method, the subband (1) of the symbol starting from time t (n + 1) to which the QPSK modulation method having poor frequency selective fading characteristics is applied increases the number of pilot subcarriers. This improves the accuracy of channel estimation.

As described above, in this embodiment, the total number of pilot symbols is reduced and the system throughput is improved by making the position and number of pilot subcarriers variable for each subband in units of symbols. Although the above-described modulation method is applied in the present embodiment, the present invention is not limited to this and may be any method. The position and number of pilot subcarriers are also arbitrary. Also, the method of dividing the subbands is not limited to this, and may be arbitrary.

As described above, in the present embodiment, OFDM
In the modulation / demodulation method, when the modulation method is adaptively changed in subband units in units of symbols, the position and number of pilot subcarriers are made variable according to the applied modulation method. As a result, the system throughput can be significantly improved as compared with the conventional case.

In this embodiment, the case has been described in which the position and number of pilot subcarriers are variable, but the present invention is not limited to this, and, for example, according to the modulation scheme applied to each subcarrier. At least one of the position, the number, and the power of the pilot subcarriers may be changed. In this case, the position, the number, and the power are arbitrary as long as the desired channel state estimation accuracy is maintained. As a result, at least one of the system throughput and the transmission power efficiency is improved as compared with the conventional one.
Can improve one.

In the present embodiment, the modulation method of each subcarrier is adaptively changed for each subband in units of symbols, but the present invention is not limited to this, and submodulation is performed in units of a plurality of symbols, for example. It may be changed for each band, for each subband in units of slots, for each subband in units of multiple slots, for each subband in units of frames, or for each subband in units of multiple frames.

Sixth Embodiment 8 and 9 are diagrams showing an example of subcarrier arrangement of the OFDM modulation / demodulation method used in the communication method of the sixth embodiment, and more specifically, FIG.
Shows the subcarrier arrangement before retransmission, and FIG.
The subcarrier arrangement at the time of retransmission is shown. In FIG. 8, 28 is a pilot subcarrier, 27 is a data subcarrier, and 29 is one symbol. Further, in FIG. 9, 31 is a pilot subcarrier, 30 is a data subcarrier, and 32 is one symbol. Here, it is assumed that the power of each pilot subcarrier is equal.

Here, the operation of the communication apparatus of this embodiment will be described. FIG. 10 is a diagram showing the configuration of the sixth embodiment of the communication device according to the present invention. In FIG.
33 is a transmission parameter estimation unit, 34 is a pilot subcarrier storage unit, 35 is a pilot subcarrier changing unit, 36 is a demodulation unit, 37 is a modulation unit, 38 is a receiving antenna, 39 is a transmitting antenna.

In the transmission parameter estimation unit 33 in the communication device, from the signal received by the receiving antenna 38,
The subcarriers used as pilot subcarriers are estimated (extracted), and the extraction result is notified to demodulation section 36. The demodulation unit 36 demodulates the signal received by the reception antenna 38 using the extraction result of the transmission parameter estimation unit 33. In the pilot subcarrier storage unit 34, if there is no retransmission request, the stored information about the position, number, and power of pilot subcarriers is notified to the modulation unit 37, and if there is a retransmission request, the retransmission request is sent to the pilot subcarrier changing unit 35. To notify. Upon receiving the retransmission request from the pilot subcarrier storage unit 34, the pilot subcarrier changing unit 35 changes at least one of the position, number, and power of the pilot subcarriers, and notifies the modulating unit 37 of the information. Modulation section 37 uses the pilot subcarrier information notified from pilot subcarrier storage section 34 or pilot subcarrier changing section 35 to insert pilot subcarriers and modulate the information data sequence.

Then, modulating section 37 inserts pilot symbols in accordance with the communication method of the present embodiment shown below. In the present embodiment, when there is retransmission in the OFDM modulation / demodulation method, the number and position of pilot subcarriers are changed as shown in FIG.

For example, as shown in FIG. 8, an example will be described in which subcarriers of frequencies f (5) and f (7) are used as pilot subcarriers at time t (1) before retransmission.

When there is a retransmission request, at time tr (1), subcarriers of frequencies f (1), f (3), and f (5) are used as pilot subcarriers, as shown in FIG. That is, the propagation path condition estimation accuracy is improved by increasing the number of pilot subcarriers.

As described above, in the present embodiment, the position and number of pilot subcarriers are made variable at the time of retransmission, so that the accuracy of channel condition estimation is improved. In the present embodiment, the above-mentioned modulation method is applied, but the present invention is not limited to this, and any method may be used. The position and number of pilot subcarriers are also arbitrary.

Further, although the case has been described with the present embodiment where the position and number of pilot subcarriers are variable, the present invention is not limited to this, and, for example, the position, number and power of pilot subcarriers can be used at the time of retransmission. It is good also as changing at least any one of these. In this case, the position, the number, and the power are arbitrary as long as the desired channel state estimation accuracy is maintained.

In the OFDM modulation / demodulation method, the modulation method may be adaptively changed. At this time, if the transmission parameters at the time of retransmission are the same as those before the retransmission, the position and number of pilot subcarriers are variable.

Next, the operation of the communication apparatus of this embodiment different from the above will be described. FIG. 11 is a diagram showing the configuration of the sixth embodiment of the communication device according to the present invention. The same components as those in the first embodiment described above are designated by the same reference numerals and the description thereof will be omitted. Further, the subcarrier arrangement of the OFDM modulation / demodulation method is the same as that in FIGS. 8 and 9 above. Here, the operations of the transmission parameter storage unit 40, the transmission parameter comparison unit 41, and the pilot subcarrier changing unit 42 which are different in operation will be described.

The transmission parameter storage unit 40 stores the information from the transmission parameter control unit 6 and notifies the transmission parameter comparison unit 41 of the information. The transmission parameter comparison unit 41 compares the information from the transmission parameter control unit 6 with the information from the transmission parameter storage unit 40. If the results are different, the modulation unit 7 uses the information from the transmission parameter control unit 6. When the result is the same, the pilot subcarrier changing unit 42 is notified to change the position and number of pilot subcarriers. When the pilot subcarrier changing unit 42 receives the change notification of the position and number of pilot subcarriers from the transmission parameter comparing unit 41, it notifies the modulating unit 7 of the changed position and number of pilot subcarriers.

Then, modulating section 7 inserts pilot symbols according to the communication method of the present embodiment shown below. In the present embodiment, the modulation method is adaptively changed in the OFDM modulation / demodulation method, and, for example, when the transmission parameters at the time of retransmission are the same as before retransmission, the position and number of pilot subcarriers are changed.

Here, the case has been described where the position and number of pilot subcarriers are variable, but the present invention is not limited to this, and at the time of retransmission, at least one of the position, number and power of pilot subcarriers is used. May be changed. In this case, the position, the number, and the power are arbitrary as long as the desired channel state estimation accuracy is maintained.

In the first to sixth embodiments, the OFD is used.
Although the parameter that is made variable in the M modulation / demodulation method has been described as the modulation method, the present invention is not limited to this, and the same applies even when at least one of the modulation method, the coding rate, and the information transmission rate is made variable. The effect of can be obtained.

Seventh Embodiment In the first to sixth embodiments described above, the operation of the modulation unit 7 and the modulation unit 37, which are the features of the present invention, has been described using the communication device shown in FIG. 1, FIG. 10 or FIG. 11, but the overall configuration of the communication device is described. For example, any of FIG. 12, FIG. 13 and FIG. 14 may be used. Further, the modulator 7 and the modulator 37, which are the features of the present invention, operate in the same manner as in each of the above-described embodiments. As a result, the first to third embodiments described above
The effect similar to that of 6 can be obtained.

12 to 14, the above-mentioned FIG.
Only the operation different from that will be described. For example, in FIG.
In the channel condition estimation unit 43, the reception antenna 8
The state of the propagation path is estimated from the signal received in step 1 and the estimation result is notified to the modulator 7. Channel condition estimation unit 44
Then, the propagation path condition of the reverse channel is estimated from the signal received by the receiving antenna 8, and the estimation result is notified to the transmission parameter control unit 6. In the transmission parameter control unit 6,
The parameters of the modulation method (coding rate, information transmission rate) applied to each subcarrier (subband, symbol, etc.) are determined using the estimation result of the channel condition estimation unit 44, and the determination result is used as the modulation unit 7 Notify. The modulation unit 7 modulates the information data sequence and the information from the propagation path condition estimation unit 43 using the determination result of the transmission parameter control unit 6.

In FIG. 13, the propagation path condition estimation unit 46 estimates the propagation path condition from the signal received by the receiving antenna 8, and the estimation result is used as the transmission parameter selection unit 4
Notify 5 In the transmission parameter selection unit 45,
By using the estimation result of the propagation path condition estimation unit 46, the modulation unit 7 sets parameters such as a modulation method used by the other side for the next transmission.
Notify. The transmission parameter estimation unit 47 estimates the parameter such as the modulation scheme notified from the other party from the signal received by the reception antenna 8 and notifies the modulation unit 7 of the estimation result. The modulator 7 uses the estimation result of the transmission parameter estimator 47 to modulate the information data sequence and the information from the transmission parameter selector 45.

In FIG. 14, the propagation path condition estimating unit 50 estimates the propagation path condition from the signal received by the receiving antenna 8, and the estimation result is used as the transmission parameter selecting unit 4
Notify 9. In the transmission parameter selection section 49,
Using the estimation result of the propagation path condition estimation unit 50, the other side notifies the transmission parameter storage unit 48 and the modulation unit 7 of parameters such as the modulation method used at the next transmission. The transmission parameter storage unit 48 stores the information from the transmission parameter selection unit 49, and the contents thereof are demodulated by the demodulation unit 3 at the next demodulation.
Notify. The demodulation unit 3 demodulates the signal received by the reception antenna 8 using the information from the transmission parameter storage unit 48. The transmission parameter estimation unit 51 estimates the parameters such as the modulation scheme notified from the other side from the signal received by the reception antenna 8 and notifies the estimation unit 7 of the estimation result. The modulator 7 uses the information from the transmission parameter estimator 51 to modulate the information data sequence and the information from the transmission parameter selector 49.

[0095]

As described above, according to the present invention, by changing the modulation method, the coding rate, or the information transmission rate adaptively for each predetermined subcarrier in the OFDM modulation / demodulation method, the pilot sub Change the parameters related to the carrier. As a result, there is an effect that at least one of the system throughput and the transmission power efficiency can be improved as compared with the related art.

According to the next invention, the position and number of pilot subcarriers are changed according to the modulation scheme, coding rate, or information transmission rate applied to each subcarrier. By this means, it is possible to reduce the total number of pilot subcarriers, and thus it is possible to significantly improve the system throughput. Further, by varying the power according to the modulation method, the coding rate, or the information transmission rate applied to the pilot subcarriers, it is possible to significantly improve the transmission power efficiency.

According to the next invention, when the modulation method, the coding rate, or the information transmission rate is adaptively changed for each sub-band, depending on the applied modulation method, the coding rate, or the information transmission rate, The position, number and power of pilot subcarriers are made variable. As a result, compared to the conventional
It is possible to significantly improve at least one of the system throughput and the transmission power efficiency.

According to the next invention, a modulation method, a coding rate, a single symbol, an arbitrary plural symbol, a single slot, an arbitrary plural slot, a single frame, or an arbitrary plural frame unit, Alternatively, when the information transmission rate is adaptively changed, the position, number, and power of pilot subcarriers are made variable according to the applied modulation scheme, coding rate, or information transmission rate. As a result, it is possible to significantly improve at least one of system throughput and transmission power efficiency as compared with the related art.

According to the next invention, for example, when the modulation method is adaptively changed for each subcarrier in units of symbols, the pilot subcarriers are changed according to the applied modulation method, coding rate, or information transmission rate. Variable position, number and power of. As a result, compared to the conventional
It is possible to significantly improve at least one of the system throughput and the transmission power efficiency.

According to the next invention, when the modulation method is adaptively changed for each subband in units of symbols, the position of the pilot subcarrier is determined according to the applied modulation method, coding rate, or information transmission rate. , Variable in number and power. As a result, it is possible to significantly improve at least one of system throughput and transmission power efficiency as compared with the related art.

According to the next invention, at least one of the position, number, and power of pilot subcarriers is adjusted by adaptively changing the modulation method, coding rate, or information transmission rate for each predetermined subcarrier unit. Change one. As a result, there is an effect that at least one of the system throughput and the transmission power efficiency can be improved as compared with the related art.

According to the next invention, the position, number and power of the pilot subcarriers can be made variable at the time of retransmission, so that there is an effect that the accuracy of channel condition estimation can be greatly improved.

According to the next invention, the modulation means adaptively changes the modulation method, the coding rate, or the information transmission rate for each predetermined subcarrier unit so that the modulation means changes the parameter relating to the pilot subcarrier. And As a result, it is possible to obtain a communication device capable of improving at least one of system throughput and transmission power efficiency as compared with the related art.

According to the next invention, the modulation means changes the position and number of pilot subcarriers according to the modulation method, coding rate, or information transmission rate applied to each subcarrier. By this means, it is possible to reduce the total number of pilot subcarriers, and thus it is possible to obtain a communication device capable of significantly improving system throughput. Also,
By varying the power according to the modulation method, the coding rate, or the information transmission rate applied to the pilot subcarriers, it is possible to obtain a communication device capable of significantly improving the transmission power efficiency. Produce an effect.

According to the next invention, when the modulation method, the coding rate, or the information transmission rate is adaptively changed for each subband, according to the applied modulation method, the coding rate, or the information transmission rate, The position, number and power of the pilot subcarriers are variable. As a result, it is possible to obtain a communication device capable of significantly improving at least one of system throughput and transmission power efficiency as compared with the related art.

According to the next invention, a modulation method, a coding rate, a single symbol, an arbitrary plural symbol, a single slot, an arbitrary plural slot, a single frame, or an arbitrary plural frame unit, Alternatively, when the information transmission rate is adaptively changed, the position, the number, and the power of the pilot subcarriers are made variable according to the applied modulation method, coding rate, or information transmission rate. As a result, it is possible to obtain a communication device capable of significantly improving at least one of system throughput and transmission power efficiency as compared with the related art.

According to the next invention, for example, when the modulation method is adaptively changed for each subcarrier in units of symbols, the pilot subcarriers can be changed according to the applied modulation method, coding rate, or information transmission rate. The position, the number, and the electric power of the are variable. As a result, it is possible to obtain a communication device capable of significantly improving at least one of system throughput and transmission power efficiency as compared with the related art.

According to the present invention, when the modulation method is adaptively changed for each subband in units of symbols, the position of the pilot subcarrier is determined according to the applied modulation method, coding rate, or information transmission rate. The number and power are variable. As a result, it is possible to obtain a communication device capable of significantly improving at least one of system throughput and transmission power efficiency as compared with the related art.

According to the next invention, at least one of the position, number and power of pilot subcarriers is adjusted by adaptively changing the modulation method, the coding rate or the information transmission rate for each predetermined subcarrier unit. It is configured to change one. As a result, at least one of the system throughput and the transmission power efficiency is improved as compared with the conventional one.
Thus, there is an effect that it is possible to obtain a communication device that can improve the above.

According to the next invention, the position, the number and the power of the pilot subcarriers can be made variable at the time of retransmission, so that it is possible to obtain a communication apparatus capable of greatly improving the accuracy of propagation path condition estimation. Has the effect.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of a communication device according to the present invention.

FIG. 2 is an OFD used in the communication method according to the first embodiment.
It is a figure which shows an example of the subcarrier arrangement | positioning of a M modulation / demodulation system.

FIG. 3 is an OFD used in the communication method according to the first embodiment.
It is a figure which shows an example of the subcarrier arrangement | positioning of a M modulation / demodulation system.

FIG. 4 is an OFD used in the communication method according to the second embodiment.
It is a figure which shows an example of the subcarrier arrangement | positioning of a M modulation / demodulation system.

FIG. 5 is an OFD used in the communication method according to the third embodiment.
It is a figure which shows an example of the subcarrier arrangement | positioning of a M modulation / demodulation system.

FIG. 6 is an OFD used in the communication method according to the fourth embodiment.
It is a figure which shows an example of the subcarrier arrangement | positioning of a M modulation / demodulation system.

FIG. 7 is an OFD used in the communication method according to the fifth embodiment.
It is a figure which shows an example of the subcarrier arrangement | positioning of a M modulation / demodulation system.

FIG. 8 is an OFD used in the communication method according to the sixth embodiment.
It is a figure which shows an example of the subcarrier arrangement | positioning of a M modulation / demodulation system.

FIG. 9 is an OFD used in the communication method according to the sixth embodiment.
It is a figure which shows an example of the subcarrier arrangement | positioning of a M modulation / demodulation system.

FIG. 10 is a diagram showing a configuration of a sixth embodiment of a communication device according to the present invention.

FIG. 11 is a diagram showing a configuration of a sixth embodiment of a communication device according to the present invention.

FIG. 12 is a diagram showing a configuration of a seventh embodiment of a communication device according to the present invention.

FIG. 13 is a diagram showing a configuration of a seventh embodiment of a communication device according to the present invention.

FIG. 14 is a diagram showing a configuration of a seventh embodiment of a communication device according to the present invention.

FIG. 15 is a diagram showing a slot configuration of an OFDM modulation / demodulation system disclosed in a conventional document.

[Explanation of symbols]

3,36 demodulation section, 4,33,47,51 transmission parameter estimation section, 5,43,44,46,50 propagation path condition estimation section, 6 transmission parameter control section, 7,37 modulation section,
8,38 receiving antenna, 9,39 transmitting antenna, 3
4 pilot subcarrier storage unit, 35, 42 pilot subcarrier change unit, 40, 48 transmission parameter storage unit, 41 transmission parameter comparison unit, 45, 49
Transmission parameter selection unit.

Claims (16)

[Claims] 1. A communication method between devices that perform communication using a multi-carrier modulation / demodulation method, wherein at least one of a modulation method, a coding rate, and an information transmission rate is adaptive in a predetermined subcarrier unit. The communication method is characterized in that the parameters relating to subcarriers (pilot subcarriers) used as pilot signals are changed according to the applied modulation scheme, coding rate, and information transmission rate. 2. The communication method according to claim 1, wherein the predetermined subcarrier unit is a single subcarrier. 3. The communication method according to claim 1, wherein the predetermined subcarrier unit is a subband composed of an arbitrary number of subcarriers. 4. The predetermined subcarrier unit is a single symbol, arbitrary plural symbols, single slot, arbitrary plural slots, single frame, or arbitrary plural frames. The communication method according to claim 1. 5. A subcarrier in which at least one of a modulation method, a coding rate, and an information transmission rate is set for each subcarrier in a unit of a single symbol, each subcarrier in a unit of a plurality of symbols, and a subcarrier in a unit of a single slot. The communication according to claim 1, wherein the communication is adaptively changed for each subcarrier in units of a plurality of slots, for each subcarrier in a unit of a single frame, or for each subcarrier in a unit of a plurality of frames. Method. 6. At least one of a modulation method, a coding rate, and an information transmission rate, for each subband in the unit of a single symbol, for each subband in the unit of a plurality of symbols,
It is characterized in that it is adaptively changed for each subband in a unit of a single slot, each subband in a unit of a plurality of slots, each subband in a unit of a single frame, or each subband in a unit of a plurality of frames. The communication method according to claim 1. 7. The communication method according to claim 1, wherein the parameter is at least one of position, number and power of pilot subcarriers. 8. A communication method between devices that perform communication using a multi-carrier modulation / demodulation method, wherein a pilot signal is used when the modulation method, the coding rate, and the information transmission rate used for retransmission are the same as before retransmission. A communication method characterized by changing at least one of the position, the number, and the power of the subcarriers used as. 9. In a communication device that performs communication using a multicarrier modulation / demodulation system, at least one of a modulation system, a coding rate, and an information transmission rate is adaptively changed in a predetermined subcarrier unit. In this case, the communication device is provided with a modulation unit that changes a parameter relating to a subcarrier (pilot subcarrier) used as a pilot signal in accordance with an applied modulation scheme, coding rate, and information transmission rate. 10. The communication device according to claim 9, wherein the predetermined subcarrier unit is a single subcarrier. 11. The communication apparatus according to claim 9, wherein the predetermined subcarrier unit is a subband composed of an arbitrary number of subcarriers. 12. The predetermined subcarrier unit is a single symbol, arbitrary plural symbols, single slot, arbitrary plural slots, single frame, or arbitrary plural frames. The communication device according to claim 9. 13. A subcarrier having at least one of a modulation method, an encoding rate, and an information transmission rate, for each subcarrier in the unit of a single symbol, for each subcarrier in the unit of a plurality of symbols, and for each single carrier in the unit of a single slot. 10. The communication according to claim 9, which is adaptively changed for each subcarrier in units of a plurality of slots, for each subcarrier in a unit of a single frame, or for each subcarrier in a unit of a plurality of frames. apparatus. 14. At least one of a modulation method, a coding rate, and an information transmission rate, for each subband in the unit of a single symbol, in each subband in the unit of a plurality of symbols, and in the subband for the unit of a single slot. 10. The communication according to claim 9, which is adaptively changed for each subband in units of a plurality of slots, for each subband in a unit of a single frame, or for each subband in a unit of a plurality of frames. apparatus. 15. The modulating means sets the parameter to a position of a pilot subcarrier,
The communication device according to any one of claims 9 to 14, wherein at least one of the number and the power is used. 16. A communication device for performing communication using a multicarrier modulation / demodulation method, which is used as a pilot signal when the modulation method, coding rate, and information transmission rate used for retransmission are the same as those before retransmission. A communication device, comprising: a modulation unit that changes at least one of the position, the number, and the power of the subcarriers to be used.