Method of data retransmission in multi-carrier transmission and communication apparatus having data retransmission control device

The present invention relates to a data retransmission method in multicarrier transmission and a communication device including a data retransmission control device.

It is known that OFDM (Orthogonal Frequency Division Multiplex), which is a kind of multi-carrier communication, is effective as one of the measures against frequency selective fading in mobile communication.

OFDM lengthens the symbol length by allocating a time-series data symbol sequence to subcarriers (carrier waves) having multiple orthogonal frequencies, and by adding a guard interval, the effect of intersymbol interference of delayed waves is affected. It is mitigating.

In recent years, attention has been focused on technologies that realize high-speed multimedia mobile communication by combining wired network communication using optical fibers (for example, ATM (Asynchronous Transfer Mode) communication) and highly reliable wireless communication such as OFDM. There is.

For example, in ATM communication, four service classes (CBR, VBR, ABR, UBR) are provided, and QoS (Quality of Service) is defined for each class. When transferring files, 10 including the application layer^-9A low cell loss rate may be required.

Therefore, in order to realize a seamless connection between an ATM network using a high-quality optical fiber and a wireless communication path, error control (QoS control) in the wireless section is required.

Several ARQ (Automatic Repeat reQuest) methods suitable for multicarrier communication (OFDM) have been proposed as effective error control methods in the frequency selective fading communication path.

A code error detection code is added to the publicly known document 1 (H. Atarashi et al "Partial Frequency ARQ System for Multi-carrier Packet Communication" IEICE TRAN.COMMUN.vol.E78-B August 1995) for each data corresponding to each carrier. The technology to be used is described.

In Known Document 2 (Japanese Unexamined Patent Publication No. 11-55206), since transmission efficiency decreases when an error detection code is added for each carrier, one error detection code is added to the transmitted packet, and an error is detected on the receiving side. When this is done, the carrier whose reception quality does not reach a predetermined level is identified, it is estimated that an error has occurred for that carrier, and the carrier whose reception quality exceeds the threshold value is used to send to the sender. A technique for transmitting a retransmission request is described.

If the technique described in the above-mentioned known document 2 is used, the transmission efficiency is improved as compared with the technique described in the known document 1.

However, in order to transmit the retransmission request, the reception quality is checked for each of a large number of carriers (carrier waves), all the information of the carriers that do not meet the predetermined quality is stored, and the retransmission request is desired to be retransmissiond. It is necessary to include information to identify the carrier corresponding to the data. As the number of carriers used increases, the number of bits of the information also increases, which contributes to a decrease in transmission efficiency.

It is also necessary to select a carrier to be used when transmitting the retransmission request.

For example, in OFDM, the number of carriers to be used is assumed to be tens to thousands, and the above-mentioned known technology has problems to be overcome in order to actually use it in multimedia communication or the like where high speed is required. It is thought that there are many.

<p> An object of the present invention is a novel data retransmission method and data retransmission in the ARQ method in multicarrier communication, which simplifies the retransmission process, reduces the burden on the transmitter / receiver, and secures a practical level in terms of retransmission efficiency. It is to provide a communication device provided with a control device.</p>

<p> According to one embodiment of the present invention, the data retransmission method in multicarrier transmission is a case where a plurality of carrier waves used for multicarrier transmission are divided into a plurality of groups in advance and error compensation of the ARQ method is performed. Retransmission processing is performed in units of the group of a plurality of carrier waves.</p><p> According to another embodiment of the present invention, in the data retransmission method in multi-carrier transmission, the transmitting side device transmits data using a plurality of carrier waves composed of a plurality of groups, and the receiving side device is the transmitting side. Receives the plurality of carriers sent from the device, performs demodulation processing for each carrier to obtain received data, determines the presence or absence of an error by error detection processing, and generates a retransmission request when there is an error. A data retransmission method in multicarrier transmission in which the retransmission request is transmitted to the transmitting side device, and the transmitting side device retransmits data to the receiving side device in response to the retransmission request. The retransmission request includes information indicating which group among the plurality of groups of the carrier wave is the target of the retransmission request.</p>

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

(Embodiment 1) FIG. 1 is a block diagram showing a configuration of a mobile terminal provided with a data retransmission control device according to the present invention.

The mobile terminal device 100 and the base station device 150 in FIG. 1 perform OFDM communication. As shown in Fig. 2, the carriers (subcarriers) used are divided into four groups in advance, and each group is assigned a number from "1" to "4". The group can be identified.

In the following description, the name "subcarrier" generally used in OFDM communication is used for convenience, but this is a synonym for, for example, "carrier (carrier wave)" in the case of multicarrier transmission. , In particular, there is no distinction.

Further, when performing the error compensation of the ARQ method, it is a prerequisite that the device on the receiving side detects an error in the received data. In the case of multi-carrier transmission such as OFDM, the method of adding an error detection code to each data corresponding to each subcarrier, or the method of adding an error detection code to each data, or for each transmission symbol (for example, packet or cell) as in normal communication. A method is conceivable in which a code for error detection is added to the unit), and when an error is detected, the location of the error is estimated and a retransmission request is made.

The data retransmission method of the present invention belongs to the latter method for the time being. However, the former method can also be applied.

As shown in FIG. 1, the mobile terminal device 100 includes a transmission system 110, a reception system 120, a subcarrier information acquisition unit 130, and a communication control unit 140.

The subcarrier information acquisition unit 130 is a portion that examines the reception level of the subcarrier and acquires information for determining which group is to be retransmitted.

The receiving system 120 includes an antenna 121, a receiving unit 122, a memory 123, a P / S (parallel serial conversion) unit 124, a determination unit (error correction unit) 125 that performs Viterbi decoding, and an error detection unit 126. Has. The receiving unit 122 includes a radio unit 127, an FFT (Fast Fourier Transform) unit 128, and an equalization unit 129.

For example, the error detection unit 126 performs a syndrome calculation on the cyclic code and determines the presence or absence of an error (CRC method: Cyclic Redundancy Check).

The subcarrier information acquisition unit 130 includes a P / S unit 131, a size comparison unit 132, a counter unit 133, and a determination unit 134.

The P / S unit 131 distributes a signal indicating the level (reception level) of the received signal to each of the four groups shown in FIG.

The magnitude comparison unit 132 compares the reception level of each group with the threshold value, and outputs a determination signal indicating that when the reception level is less than the threshold value.

The counter unit 133 counts the number of times the reception level falls below the threshold value for each group.

The determination unit 134 determines whether or not there is a group in which the count value of the counter unit 133 exceeds a predetermined threshold value, and if there is a corresponding group, the retransmission control unit in the communication control unit 140 determines that there is a corresponding group. Notify 142. In FIG. 2, group 1 is the target of retransmission.

The communication control unit 140 includes a reception data memory 141 that temporarily stores received data, a retransmission control unit 142, a transmission control unit 143, a retransmission request transmission unit 144, and a transmission data memory 145.

The received data is temporarily stored in the received data memory 141. However, in reality, when an error is found by the error detection unit 126 and the retransmission process is performed, only the data corresponding to the group other than the group to be the retransmission target is retained.

In response to the signal indicating the determination result from the determination unit 134 of the subcarrier information acquisition unit 130, the retransmission control unit 142 sends the retransmission request transmission unit 144 and the reception data memory 141 the number of the group that wishes to retransmit (in FIG. 2). Notify 1).

The retransmission request transmission unit 144 outputs a retransmission request signal (including information on the number of the group to be retransmissiond). This retransmission request signal is transmitted to the base station apparatus 150 via the transmission system 110.

Then, when the data is retransmitted from the base station apparatus and can be received without error, the received retransmitted data and the data stored in the received data memory 141 are combined and output as received data.

On the other hand, when the mobile terminal device 600 is on the transmitting side and a retransmission request is received from the base station device 150 on the receiving side, the transmission control unit 143 receives the retransmission control information included in the received retransmission request signal in the received data memory. Read from 141 to detect the group to be retransmitted.

Then, from the transmission data memory 145, only the data corresponding to the group to be retransmitted is output from the data transmitted in the past. The retransmission data is transmitted to the base station apparatus 150 via the transmission system 110.

Further, the transmission system 110 includes a modulation unit 111, a transmission unit 112, and a transmission antenna 113. The modulation unit 111 includes an S / P (serial-parallel transform) unit 114 and an IFFT (Inverse Fast Fourier Transform) unit 115. The transmitter 112 has a multiplier 116 for multiplying the carrier fc and a bandpass filter 117.

As described above, in the present embodiment, all the subcarriers are divided into four groups, and it is determined whether or not to retransmit each group.

That is, when an error is detected on the receiving side, the group to be retransmitted is specified, and the information for specifying the group is sent to the receiving side. Then, all the data corresponding to all the carriers included in the specified group are retransmitted.

For example, if the carriers are divided into four groups, the group to be retransmitted can be specified if there is two bits of information. Therefore, the amount of information of the retransmission request signal can be reduced.

By doing so, it is possible to efficiently make a retransmission request without increasing the control information (in this case, it is possible to specify the group with 2 bits), and the transmission efficiency is improved.

Further, since it is assumed that the group is used as a unit, it is not necessary to manage the information of each subcarrier in detail, and the retransmission process is simplified. This also helps to realize high-speed communication.

In the present embodiment, all subcarriers are divided into four groups, but the present invention is not limited to this.

Conventionally, in the ARQ method, it has been considered that only the data with an error is retransmitted to compensate for the error. On the other hand, in the present invention, when an error is detected, it is estimated from the reception level and the like which group is likely to include the subcarrier corresponding to the data in which the error has occurred, and for each group. A new method is adopted in which the retransmission process is performed.

OFDM is originally a highly reliable wireless communication method that is resistant to frequency selective fading, and which frequency band of subcarriers is affected by fading without strictly identifying the data in which the error occurred. If is known, it is considered that the desired reliability of ARQ control can be ensured by retransmitting the data of the frequency band (group belonging to).

In addition, OFDM uses a method of batch transforming data using an FFT calculator or IFFT calculator, so it supports subcarriers included in one group (a group of subcarriers adjacent to each other). The data resending process to be performed can also be realized without much difficulty by using this batch process.

INDUSTRIAL APPLICABILITY The present invention focuses on such characteristics of multi-carrier transmission represented by OFDM and realizes a realistic ARQ method in consideration of use in actual communication equipment.

The retransmission control device (a part that realizes retransmission control, and the subcarrier information acquisition unit 130 and the retransmission control unit 142 are at least its components) shown in FIG. 1 is not only a mobile terminal device but also a base. It can also be mounted on station equipment.

However, when the retransmission control device according to the present invention is mounted on the base station device, the base station device needs to hold information on which group of retransmissions are requested for all users, and the retransmission process. The amount of processing of the device may increase, the required memory capacity may become very large, and the load on the hardware may become heavy.

Therefore, it can be said that the retransmission control device according to the present invention is most suitable for mounting on a mobile terminal. That is, when the present invention is applied to a downlink, there is almost no concern about a decrease in throughput, and in reality, it can be said that application to a downlink is desirable.

Figure 3 summarizes the characteristic operations of the ARQ method of the present invention described above.

That is, all the subcarriers are divided into a plurality of groups (step S1000), and when an error is detected by the receiving device (step S2000), it is determined whether or not retransmission is necessary for each group (step S2000). S3000).

Then, the group (data corresponding to the subcarrier included in the group) determined to be retransmitted is requested to be retransmitted (step S4000).

(Embodiment 2) FIG. 4 is a block diagram showing a configuration of the mobile terminal device according to the second embodiment.

The feature of this embodiment is that the threshold value (threshold value for checking whether or not the reception level is a subcarrier whose reception level has dropped) in the magnitude comparison unit 132 of FIG. 1 is set according to the data modulation method. To change.

It can also be changed depending on the coding rate of error correction.

In the case of multi-value modulation, the larger the number of multi-values, the more likely it is that an error will occur even if the drop in reception level is small. For this reason, in the case of a modulation method such as 16QAM (Quadrature Amplitude Modulation) or 64QAM where errors are likely to occur, the threshold value is set higher and the necessity of retransmission is determined more strictly.

This enhances the function of error compensation.

In FIG. 4, two threshold values used by the magnitude comparison unit 132 are provided (threshold value 1 and threshold value 2), and are selected based on, for example, a signal indicating a modulation method given by a control unit (not shown). In part 201, the threshold value to be used is appropriately selected.

Other parts are the same as the configuration shown in FIG. 1, and the description thereof will be omitted. The same reference numerals are given to the same parts as those in FIG. This point is the same in the following description.

(Embodiment 3) FIG. 5 is a block diagram showing a configuration of the mobile terminal device according to the third embodiment.

The feature of this embodiment is that the threshold value (threshold value for checking whether or not the reception level is a lowered subcarrier) in the magnitude comparison unit 132 in FIG. 1 is set to the received electric field level (RSSI: Received Signal). It is to change adaptively according to the Strength Indicator (received signal strength display signal).

In general, as RSSI decreases, errors are more likely to occur even if the reception level drops less. Therefore, RSSI changes the threshold value used to determine whether or not the reception level is a lowered subcarrier.

That is, when the RSSI is large, the judgment threshold is reduced, and when the RSSI is small, the judgment threshold is increased.

This enhances the function of error compensation.

In FIG. 5, a magnitude comparison unit 301 is provided, RSSI is compared with the threshold value 3, and the selection unit 201 determines whether to select the threshold value 1 or the threshold value 2 based on the comparison result. There is.

(Embodiment 4) FIG. 6 is a block diagram showing a configuration of the mobile terminal device according to the fourth embodiment.

The feature of this embodiment is that it is compared not only with the threshold value in the magnitude comparison unit 132 (threshold value for checking whether or not the reception level is a subcarrier whose reception level has dropped) but also with the count value of the counter unit 133. The threshold value for this is also changed according to the modulation method and RSSI.

In FIG. 6, a selection unit 601 is further added to the configuration of FIG. 5, and which of the threshold value 4 and the threshold value 5 is selected is determined according to the comparison result of the size comparison unit 301. ..

As a result, it is possible to accurately determine the necessity of retransmission under conditions suitable for the receiving environment.

(Embodiment 5) FIG. 7A is a block diagram showing the configuration of the mobile terminal device according to the fifth embodiment, and FIG. 7B is a block diagram showing the configuration of the delay dispersion generation unit.

The feature of this embodiment is that it is compared with the threshold value (threshold value for checking whether or not the reception level is a subcarrier whose reception level has dropped) in the magnitude comparison unit 132 and the count value of the counter unit 133. The threshold is changed according to the delay time of multipath.

When the delay time of the multipath becomes large, the interference between the front and rear signals becomes large, so that the change in the error rate characteristic becomes large. Therefore, it is effective to appropriately change the threshold value, which is a criterion for determining the retransmission processing, according to the delay time of the multipath, in terms of achieving both the transmission efficiency and the error rate.

Specifically, when the delay time of multipath is large, it is desirable to set the threshold value to a large value.

In the mobile terminal device of FIG. 7A, the delay dispersion generator 501 generates multipath delay time information based on the signal after FFT.

Then, the magnitude comparison unit 301 determines whether or not the delay variance is larger than the threshold value 6, and based on the determination result, the threshold value (in the subcarrier whose reception level has dropped) in the magnitude comparison unit 132. (Threshold value for checking whether or not there is) and the threshold value for comparison with the count value of the counter unit 133 are changed.

As shown in FIG. 7B, the delay dispersion generator 501 includes a delay device 502, a subtractor 503, a circuit 504 for obtaining an absolute value, a circuit 505 for obtaining an average value, and a division circuit 506.

The larger the delay variance, the larger the difference in reception levels between adjacent subcarriers. Utilizing this, delay distribution information can be generated based on the difference information of the reception levels of adjacent subcarriers.

(Embodiment 6) FIG. 8 is a block diagram showing a configuration of the mobile terminal device according to the sixth embodiment.

A feature of this embodiment is that the target of the retransmission request is limited to only one group that is most presumed to require retransmission.

In reality, it can be very difficult to request resending for all groups that meet certain conditions. For example, if the number of groups to be retransmitted increases, the transmission efficiency decreases accordingly, and there is a risk that the high speed of communication cannot be ensured.

Therefore, in such a case, as a realistic process, only one group that is presumed to require the most retransmission is targeted for retransmission. For example, the maximum value detection unit 601 detects the maximum count value by comparing the count values of a plurality of groups having a count value exceeding the threshold value 4. Then, only the group having the maximum count value is targeted for retransmission. As a result, it is possible to satisfy the high speed of communication while executing the error compensation of the ARQ method.

(Embodiment 7) FIG. 9 is a block diagram showing a configuration of the mobile terminal device according to the seventh embodiment.

The feature of this embodiment is that a method of dividing all subcarriers into a plurality of groups and using the group as a retransmission unit is being studied as a next-generation communication method. OFDM-CDMA (Orthogonal Frequency Division Multiplex --Code) This applies to communication devices that perform Division Multiple Access) communication.

In OFDM-CDMA communication, as shown in FIG. 9, after the transmission signal is spread by the spreading unit 701, one spreading chip is assigned to one subcarrier for communication. At the time of reception, the despreading unit 702 performs despreading, and the demodulation unit 703 performs demodulation processing to extract information.

In the OFDM-CDMA communication device to which the present invention is applied, it is possible to obtain a new effect that the signal multiplexing number can be further increased, which is not found in the communication method of OFDM alone.

(Embodiment 8) FIG. 10 is a block diagram showing a configuration of the mobile terminal device according to the eighth embodiment. The feature of this embodiment is that the number of groups that can be requested per one retransmission request (the number of upper limit groups) is changed based on the delay variance and RSSI.

For example, as the delay dispersion increases, the reception level difference between adjacent subcarriers increases. Therefore, changing the number of groups that can request retransmission according to the delay dispersion helps to achieve both transmission efficiency and error rate. Specifically, it is desirable to increase the number of groups that can request retransmission as the delay distribution increases.

Similarly, changing the number of groups that can be retransmitted according to RSSI helps to achieve both transmission efficiency and error rate. Specifically, it is desirable to increase the number of retransmittable groups as RSSI becomes smaller.

In FIG. 10, a magnitude comparison unit 801 is provided, RSSI and the threshold value 7 are compared, and the number of groups that can be selected by the selection unit 802 is changed according to the comparison result.

(Embodiment 9) FIG. 11 is a block diagram showing a configuration of the mobile terminal device according to the ninth embodiment.

The feature of this embodiment is that the group including the subcarrier corresponding to the data of the DC component of the analog circuit is subject to retransmission in preference to the other groups.

When the DC offset of the analog circuit is large, the retransmission request of the group including the subcarrier corresponding to the DC component tends to increase. In consideration of this point, the group including the subcarrier corresponding to the data of the DC component of the analog circuit is to be retransmitted in preference to the other groups.

In FIG. 11, the determination unit 901a determines the necessity of retransmission for the group including the subcarrier corresponding to the DC component, and the determination unit 901b determines the other groups.

By making the threshold value 8 used by the determination unit 901a smaller than the threshold value 9 used by the determination unit 901b, the group including the subcarrier corresponding to the DC component can be easily targeted for retransmission.

(Embodiment 10) FIG. 12 is a block diagram showing a configuration of the mobile terminal device according to the tenth embodiment.

The feature of this embodiment is that the group including the subcarriers located at both ends on the frequency axis among all the subcarriers (that is, the lowest frequency subcarrier and the highest frequency subcarrier among all the subcarriers) , It is to be the target of retransmission in preference to other groups.

Subcarriers located at both ends on the frequency axis have worse error rate characteristics than other subcarriers when adjacent channel interference is present or when there is a group delay deviation of an analog filter.

Therefore, the group including the subcarriers located at both ends on the frequency axis is subject to retransmission in preference to the other groups.

In FIG. 12, the determination unit 1001a determines whether or not retransmission is necessary for a group including subcarriers located at both ends on the frequency axis. In addition, the determination unit 1001b makes a determination about another group.

By making the threshold value 10 used by the determination unit 1001a smaller than the threshold value 11 used by the determination unit 1001b, the group including the subcarriers located at both ends on the frequency axis is likely to be the target of retransmission.

(Embodiment 11) FIG. 13 is a block diagram showing a configuration of the mobile terminal device according to the eleventh embodiment.

The feature of this embodiment is that for a group containing subcarriers located at both ends on the frequency axis or a group containing subcarriers corresponding to DC component data, the multivalues in the multivalued modulation can be obtained from other groups. It is also necessary to make it smaller so that errors are less likely to occur.

When the level of adjacent channel interference is large or the DC offset of the analog circuit is large, retransmission is performed for the group containing subcarriers located at both ends on the frequency axis and the group containing subcarriers corresponding to the DC component. The number of times becomes very large, and the transmission efficiency may be extremely lowered.

Therefore, in order to suppress a decrease in transmission efficiency, for a group containing subcarriers located at both ends on the frequency axis or a group containing subcarriers corresponding to DC component data, a multivalue in multivalue modulation is used. Make it smaller than the other groups to make it less error prone.

In FIG. 13, two multi-value modulation units 1101a and 1101b are provided in the transmission system, and the selection unit 1102 selects which modulation signal to use.

For example, when the multi-value modulator 1101a includes a 16QAM modulator and the multi-value modulator 1101b includes a QPSK (Quadrature Phase Shift Keying) modulator, a group containing subcarriers located at both ends on the frequency axis, or a DC component. For the group including the subcarrier corresponding to the data of, the QPSK signal output from the multi-value modulation unit 1101b is selected, and for the other groups, the 16QAM signal output from the multi-value modulation unit 1101a is selected.

(Embodiment 12) In the present embodiment, when a group including a subcarrier corresponding to the DC component data is to be retransmitted, the transmitting side device (base station device in the above-described embodiment) is a sub corresponding to the DC component. Send only carriers.

Data on the DC component of analog circuits is very important, and quality deterioration is a particular problem. On the other hand, due to various restrictions, the amount of data that can be retransmitted may be considerably limited.

In this case, only the subcarriers corresponding to the direct current, in which the deterioration of quality is particularly problematic, are first retransmitted preferentially.

In FIG. 14, when group 2 is a group including a subcarrier corresponding to the direct current (DC) component data and this group 2 is the target of retransmission, first, the subcarrier corresponding to the direct current component data ( In the figure, only those marked with DSB) are subject to retransmission.

As described above, the present invention focuses on the characteristics of multi-carrier transmission represented by OFDM, and introduces a novel method of grouping subcarriers and using a subcarrier group belonging to one group as a retransmission unit. Then, the ARQ method suitable for practical use is realized.

For example, when constructing a wireless ATM network by directly connecting a wireless communication system to a high-speed ATM network using an optical fiber, the accuracy and high speed of error compensation in wireless communication are the key points. Therefore, the present invention is effective in realizing high-speed mobile communication (high-speed mobile multimedia communication).

Further, when the group to be retransmitted is specified based on at least one of the reception level of each carrier, the index indicating the reception quality, and the delay variance, for example, the reception level included in each group is set to a predetermined standard. It is determined whether or not the number of carriers that does not meet exceeds a predetermined threshold value, and a group to be retransmitted is specified. Since only a simple comparison process with a predetermined reference or threshold value is required for each group, the retransmission process is simplified, and the complexity of the circuit is prevented.

Further, the receiving device discards the data corresponding to the group that is the target of the retransmission request among the first received data, temporarily retains the data of the other group, and causes an error as a result of the retransmission. When no data is obtained, the data and the temporarily stored data may be combined and output. Since the processing of the received data is also simple, the present invention is easy to realize in this respect as well.

This specification is based on Japanese Patent Application No. 2002-097468 filed on March 29, 2002. All this content is included here.

The present invention can be applied to mobile terminal devices and base station devices used in wireless communication systems.

<figref num="1">A block diagram showing a configuration of a communication device (portable terminal device) according to the first embodiment of the present invention.</figref><figref num="2">Diagram for explaining grouping of all subcarriers in OFDM</figref><figref num="3">The flow chart which shows the main procedure of the data retransmission method which concerns on this invention.</figref><figref num="4">A block diagram showing a configuration of a communication device (portable terminal device) according to the second embodiment of the present invention.</figref><figref num="5">A block diagram showing a configuration of a communication device (portable terminal device) according to the third embodiment of the present invention.</figref><figref num="6">A block diagram showing a configuration of a communication device (portable terminal device) according to the fourth embodiment of the present invention.</figref><figref num="7A">A block diagram showing a configuration of a communication device (portable terminal device) according to the fifth embodiment of the present invention.</figref><figref num="7B">The block diagram which shows the structure of the delay dispersion generation part of the communication device (portable terminal device) which concerns on Embodiment 5 of this invention.</figref><figref num="8">A block diagram showing a configuration of a communication device (portable terminal device) according to a sixth embodiment of the present invention.</figref><figref num="9">A block diagram showing a configuration of a communication device (portable terminal device) according to a seventh embodiment of the present invention.</figref><figref num="10">A block diagram showing a configuration of a communication device (portable terminal device) according to the eighth embodiment of the present invention.</figref><figref num="11">A block diagram showing a configuration of a communication device (portable terminal device) according to a ninth embodiment of the present invention.</figref><figref num="12">A block diagram showing a configuration of a communication device (portable terminal device) according to a tenth embodiment of the present invention.</figref><figref num="13">A block diagram showing a configuration of a communication device (portable terminal device) according to the eleventh embodiment of the present invention.</figref><figref num="14">The figure for demonstrating the data retransmission method (the method of resending only the subcarrier corresponding to a DC component) which concerns on Embodiment 12 of this invention.</figref>