Patent Publication Number: US-2019173566-A1

Title: Wireless communication device and wireless communication method

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2017-115443, filed on Jun. 12, 2017, the entire contents of which are incorporated herein by reference. 
     FIELD 
     Embodiments described herein relate to a wireless communication device and a wireless communication method. 
     BACKGROUND 
     A wireless relay device (referred to as a relay device, hereinafter) is a wireless communication device that relays radio waves when a reaching distance of the radio waves is limited due to limitation of transmission power or attenuation or interference of the radio waves or the like. The relay device once receives the radio waves, performs signal amplification or the like, and then retransmits the radio waves. 
     In the case where transmission processing and reception processing are simultaneously performed in the relay device, when carrier frequencies of transmission signals and reception signals are the same, signals transmitted from the relay device are received by the device, and occurrence of sneak path interference that a circuit oscillates becomes a problem. Further, in the case where the same carrier frequency is used in a channel of the respective relay devices with each other, a channel between the relay device and a portable station and a channel between the relay device and a base station, interference waves are generated mutually between the different channels, and degradation of communication quality becomes unneglectable. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a block diagram of a wireless relay device as a wireless communication device according to a first embodiment; 
         FIG. 2  is a diagram illustrating examples of a wireless relay network according to the first embodiment; 
         FIG. 3  is a diagram time-sequentially illustrating changeover processing of a carrier frequency of the wireless relay device according to the first embodiment; 
         FIG. 4  is a diagram time-sequentially illustrating a relation between a physical arrangement and the carrier frequency of the wireless relay device according to the first embodiment; 
         FIG. 5  is a diagram time-sequentially illustrating the changeover processing of the carrier frequency of the wireless relay device according to a first modification of the first embodiment; 
         FIG. 6  is a diagram time-sequentially illustrating a relation between a physical arrangement and a utilization frequency of the plurality of wireless relay devices for the first modification of the first embodiment; 
         FIG. 7  is a diagram illustrating a range of synchronizing timings of carrier frequency changeover in the wireless relay network using the wireless relay device; 
         FIG. 8  is a functional block diagram of the wireless relay device as the wireless communication device according to a second embodiment; 
         FIG. 9  is a diagram illustrating a format of a frame transmitted by the wireless relay device according to the second embodiment; 
         FIG. 10A  is a diagram illustrating processing performed to the frame by the wireless relay device according to the second embodiment; 
         FIG. 10B  is a diagram illustrating processing performed to the frame by the wireless relay device according to the second embodiment; 
         FIG. 11A  is a diagram illustrating processing performed to the frame by the wireless relay device according to a first modification of the second embodiment; 
         FIG. 11B  is a diagram illustrating processing performed to the frame by the wireless relay device according to the first modification of the second embodiment; 
         FIG. 12  is a functional block diagram of the wireless relay device as the wireless communication device according to a third embodiment; 
         FIG. 13  is a diagram illustrating a format of the frame transmitted by the wireless relay device according to the third embodiment; 
         FIG. 14A  is diagram illustrating processing performed to the frame by the wireless relay device according to the third embodiment; 
         FIG. 14B  is a diagram illustrating processing performed to the frame by the wireless relay device according to the third embodiment; 
         FIG. 15A  is a diagram illustrating processing performed to the frame by the wireless relay device according to a first modification of the third embodiment; 
         FIG. 15B  is a diagram illustrating processing performed to the frame by the wireless relay device according to the first modification of the third embodiment; 
         FIG. 16  is a functional block diagram of the wireless relay device as the wireless communication device according to a fourth embodiment; 
         FIG. 17  is a diagram illustrating a format of the frame transmitted by the wireless relay device according to the fourth embodiment; 
         FIG. 18A  is diagram illustrating processing performed to the frame by the wireless relay device according to the fourth embodiment; 
         FIG. 18B  is a diagram illustrating processing performed to the frame by the wireless relay device according to the fourth embodiment; 
         FIG. 19  is a diagram illustrating a format of the frame transmitted by the wireless relay device according to the fifth embodiment; 
         FIG. 20A  is diagram illustrating processing performed to the frame by the wireless relay device according to the fifth embodiment; 
         FIG. 20B  is a diagram illustrating processing performed to the frame by the wireless relay device according to the fifth embodiment; 
         FIG. 21  is a functional block diagram of the wireless relay device as the wireless communication device according to a sixth embodiment; 
         FIG. 22  is a diagram illustrating an example of a wireless relay network connecting the wireless relay device according to the sixth embodiment and a base station; and 
         FIG. 23  is a functional block diagram of the wireless relay device as the wireless communication device according to a seventh embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     According to one embodiment, a wireless communication device includes a first receiver; a second transmitter; a controller; and a pre-equalizer. The controller switches a reception frequency of the first receiver from a first frequency to a second frequency and a transmission frequency of the first transmitter from the second frequency to the first frequency, at a first timing. The pre-equalizer pre-equalizes a second signal, based on channel state information of a first signal received in the first receiver before the first timing. The first transmitter transmits the pre-equalized second signal, after the first timing. 
     Hereinafter, embodiments of the present invention will be described with reference to the drawings. In addition, for same components in the drawings, identical numbers are attached and description is appropriately omitted. 
     First Embodiment 
       FIG. 1  is a block diagram illustrating an example of a wireless relay Device (relay device, hereinafter) as a wireless communication device according to the present embodiment. A relay device  1  includes an antenna  10 , an antenna  13 , an antenna  14  and an antenna  17 . The antenna  10  is arranged so as to receive signals from a first direction. The antenna  13  is arranged so as to transmit signals in a second direction. The antenna  14  is arranged so as to receive signals from the second direction. The antenna  17  is arranged so as to transmit signals in the first direction. Sizes and shapes of the antenna  10 , the antenna  13 , the antenna  14  and the antenna  17  are not limited in particular. For example, the antenna may be a parabola antenna or an array antenna for which each antenna is configured from a plurality of antenna elements or the like. The first direction and the second direction here mean respectively different directions in a view from the relay device  1 . An angle between the first direction and the second direction is not limited in particular. The relay device  1  further includes a receiver  11  electrically connected with the antenna  10 , a transmitter  12  electrically connected with the antenna  13 , a receiver  15  electrically connected with the antenna  14 , and a transmitter  16  electrically connected with the antenna  17 . By the electric connection, radio waves received by the antenna  10  are delivered to the receiver  11  as electric signals. By the electric connection, the antenna  13  can transmit the electric signals outputted by the transmitter  12  as the radio waves. Similarly, the radio waves received by the antenna  14  are delivered to the receiver  15  as the electric signals. Similarly, the antenna  17  can transmit the electric signals outputted by the transmitter  16  as the radio waves. A same single antenna may be shared for the antenna  10  and the antenna  17 . In addition, a same single antenna may be shared for the antenna  13  and the antenna  14 . In at least either case, a duplexer is inserted, though not illustrated, between the shared antenna and the receiver and the transmitter. 
     The relay device  1  further includes a controller  18 , a local oscillator  20 , a local oscillator  21 , a relay processor  22  and a relay processor  23  as components. The controller  18  controls and monitors the receiver  11 , the transmitter  12 , the receiver  15 , the transmitter  16 , the local oscillator  20 , the local oscillator  21 , the relay processor  22  and the relay processor  23 . In addition, the controller  18  includes a synchronizer  18 A and a time manager  18 B. All or part of the transmitter  12 , the transmitter  16 , the receiver  11 , the receiver  15 , the controller  18 , the local oscillator  20 , the local oscillator  21 , the relay processor  22  and the relay processor  23  may be realized by software by making a processor such as a CPU execute a program, may be realized by an exclusive hardware circuit or a programmable circuit, or may be realized by both. 
     The synchronizer  18 A of the controller  18  is in charge of a function of synchronizing a timing at which the controller  18  performs frequency changeover for a transmission frequency which is a frequency of the radio wave used for transmission, a reception frequency which is a frequency of the radio wave used for reception or both of the transmission frequency and the reception frequency, with another relay device or a terminal device (the terminal device is also one form of the wireless communication device) which mutually performs the transmission and the reception with the relay device  1 . Hereinafter, when changeover of a carrier frequency is described, all the cases of the changeover of only the transmission frequency, the changeover of only the reception frequency and the changeover of both transmission frequency and reception frequency are included. As a communicator used for synchronizing a carrier frequency changeover timing, a data transmission/reception function that the receiver  11 , the transmitter  12 , the receiver  15  and the transmitter  16  have may be used, a wireless communication function provided by the other component may be used, or a wired electric telecommunication line may be used. 
     The time manager  18 B is in charge of a time management function of the controller  18 . The time manager  18 B may include a real-time clock or a timer for time management. The time management function includes each processing of management of the present time, measurement of elapsed time and time adjustment. The frequency changeover timing of the controller  18  is measured based on the time provided by the time manager  18 B as an example. In order to guarantee accuracy of the time of the time manager  18 B, the time may be synchronized with an external server using a Network Time Protocol (NTP), or a standard radio wave transmitted by a standard frequency station may be received and synchronization may be performed with the time. In order to communicate with the external server and a terminal, the controller  18  may use a data communication function of the receiver  11 , the transmitter  12 , the receiver  15  and the transmitter  16 , or may use the electric telecommunication line separately provided for management. The electric telecommunication line for management may be wired or wireless, and a communication protocol to be used is not limited in particular. An implementation of the time manager may be by hardware, by software, or by a combination of both hardware and software. 
     As a method of matching the carrier frequency changeover timing of the relay device  1  with another relay device or a terminal device, there is a method of synchronizing all the time of the relay device or the terminal device which is a carrier frequency changeover target using the synchronizer  18 A and the time manager  18 B of the controller  18  described above and then executing the frequency changeover at the specified time. When this method is used, at the specified time or cycle, the changeover of the transmission frequency and the reception frequency of the relay device and the terminal device which are the frequency changeover targets is simultaneously performed. In addition, there is a method of detecting a frame boundary by acquiring synchronization of a reception frame as described later and performing the frequency changeover with detection of the frame boundary as a trigger. The above methods of synchronizing the timing of performing the frequency changeover are just examples, and the method is not limited to either method in particular. Further, the frequency changeover target may be both of the reception frequency and the transmission frequency, or may be one of the reception frequency and the transmission frequency. 
     The receiver  11  includes a mixer  11 A, a filter  11 B, and an amplifier  11 C. Similarly, the receiver  15  includes a mixer  15 A, a filter  15 B, and an amplifier  15 C. The filter  11 B and the filter  15 B are band-pass filters which pass only a frequency band of a reception target. When the frequency of the reception target changes, the frequency band to pass is changeable. For a purpose of noise elimination or the like, another filter such as a low-pass filter may be further added to the receiver  11  and the receiver  15 . The amplifier  11 C and the amplifier  15 C have a function of amplifying the electric signal for frequency conversion or processing in the relay processor  22  or the relay processor  23 . Even though only one amplifier is illustrated respectively in the receiver  11  and the receiver  15  in  FIG. 1 , the amplifier may be further added as needed. A function and a configuration of the mixer  11 A and the mixer  15 A will be described later. 
     The transmitter  12  includes a mixer  12 A, a filter  12 B, and an amplifier  12 C. Similarly, the transmitter  16  includes a mixer  16 A, a filter  16 B, and an amplifier  16 C. The filter  12 B and the filter  16 B are band-pass filters which pass only the electric signal of a transmission frequency band. For a purpose of noise elimination or the like, another filter such as a low-pass filter may be further added also to the transmitter  12  and the transmitter  16 . The amplifier  12 C and the amplifier  16 C have a function of amplifying the electric signal to transmission power. The amplifier may be the one of a multistage structure. In addition, a configuration with an increased number of the amplifiers may be used as needed. The function and the configuration of the mixer  12 A and the mixer  16 A will be described later. 
     The local oscillator  20  and the local oscillator  21  generate signals for the frequency conversion used when converting each reception frequency to an intermediate frequency in the receiver  11  or the receiver  15 . The signals for the frequency conversion generated by the local oscillator  20  and the local oscillator  21  are also used when converting the signals of the intermediate frequency to the signals of the transmission frequency in the transmitter  12  or the transmitter  16 . As the local oscillator  20  and the local oscillator  21 , there are various implementations such as a synthesizer by a Phase Locked Loop (PLL) or a Direct Digital Synthesizer (DDS), but a system to be used is not limited in particular. In addition, two or more times of the frequency conversion may be used such as double conversion or triple conversion. Furthermore, in the case where the local oscillator  20  and the local oscillator  21  can be integrated by the combination of the reception frequency used in the receiver  11  and the receiver  15  and the transmission frequency used in the transmitter  12  and the transmitter  16 , the configuration of using only one local oscillator may be used. Conversely, the configuration with a further increased number of the local oscillators is not excluded either. 
     The signals generated by the local oscillator  20  are used for converting the electric signals of the reception frequency of the receiver  11  to the intermediate frequency used in the relay processor  22 , in the mixer  11 A. Further, the signals generated by the local oscillator  20  are used for converting the electric signals of the intermediate frequency outputted from the relay processor  23  to the transmission frequency of the transmitter  12 , in the mixer  16 A of the transmitter  16 . In the mixer  11 A and the mixer  16 A, the frequency conversion is realized by taking out the signals of a frequency which is a sum or a difference of mixed frequencies. 
     The signals generated by the local oscillator  21  are used for converting the electric signals of the intermediate frequency outputted from the relay processor  22  to the transmission frequency of the transmitter  12 , in the mixer  12 A of the transmitter  12 . Further, the signals generated by the local oscillator  21  are used for converting the electric signals of the reception frequency of the receiver  15  to the intermediate frequency used in the relay processor  23 . Also in the mixer  12 A and the mixer  15 A, the frequency conversion is realized by taking out the signals of the frequency which is the sum or the difference of the mixed frequencies. For the mixer, there are a plurality of circuit configurations using various parts such as a diode, a transistor or an integrated circuit, but an mounting method is not limited in particular. 
     The controller  18  can issue a command of changing a reception frequency f t1  of the antenna  10  and the receiver  11 , a transmission frequency f t1  of the antenna  13  and the transmitter  12 , a reception frequency f r2  of the antenna  14  and the receiver  15 , and a transmission frequency f t2  of the antenna  17  and the transmitter  16 , an intermediate frequency f i1  of the relay processor  22  and an intermediate frequency f i2  of the relay processor  23 . A frequency change command can be issued for all the frequencies or issued for only some of the frequencies. Specific frequency change processing is executed by changing an oscillation frequency of the local oscillator  20  and changing an oscillation frequency of the local oscillator  21 . 
     The relay processor  22  performs equalization processing (channel equalization or pre-equalizing or both) to the electric signals received by the antenna  10  and converted to the intermediate frequency in the receiver  11 . Thus, the signals for relay are sent to the transmitter  12  in the state that a data transmission characteristic of the signals is improved. In the transmitter  12 , the frequency conversion, amplification and transmission by the antenna  13  are performed. Similarly, the relay processor  23  performs the equalization processing (channel equalization or pre-equalizing or both) to the electric signals received by the antenna  14  and converted to the intermediate frequency in the receiver  15 . Thus, the signals for relay are sent to the transmitter  16  in the state that the data transmission characteristic of the signals is improved. In the transmitter  16 , the frequency conversion, the amplification and the transmission by the antenna  17  are performed. The components inside the relay processor  22  and the relay processor  23  and detailed processing performed therein will be described later. 
       FIG. 2  illustrates three examples of a wireless relay network using the relay device of the present embodiment. In an upper stage of  FIG. 2 , the wireless relay network in which a relay device  1   a , the relay device  1  and a relay device  1   b  are used and the three relay devices are arranged successively is illustrated as an example. The relay device  1   a  includes an antenna  13   a  which transmits the radio waves to the relay device  1 , and an antenna  14   a  which receives the radio waves from the relay device  1 . The relay device  1   b  includes an antenna  17   b  which transmits the radio waves to the relay device  1 , and an antenna  10   b  which receives the radio waves from the relay device  1 . The number of the successive relay devices is not limited to three and may be two, four or more. By arranging the relay devices at every interval determined in consideration of a range of the radio waves used in communication in this way, periodical signal amplification and improvement of the transmission characteristic are repeated, and data communication can be performed at remote locations with each other. When the radio waves reach, the radio waves can be relayed by only one relay device without successively arranging the plurality of relay devices. 
     In a middle stage of the  FIG. 2 , the wireless relay network in which the relay device  1  relays the radio waves transmitted and received by a terminal device  3  which is a wireless communication device to the relay device  1   b  is illustrated as an example. The terminal device  3  includes an antenna  3   a  which transmits the radio waves to the relay device  1 , and an antenna  3   b  which receives the radio waves from the relay device  1 . The radio waves transmitted and received by the terminal device  3  carries data inputted or outputted by a computer  2 . An example of uses of the computer  2  is a server for management/control of the wireless relay network. The configuration is just an example, and the wireless relay network in which a connection destination of the terminal device  3  is not one computer but another device or a combination of other devices may be constructed. 
     In a lower stage of  FIG. 2 , the wireless relay network in which the relay device  1  relays the radio waves transmitted by a terminal device  4  which is the wireless communication device and the radio waves received by a terminal device  5  which is the wireless communication device to the relay device  1   b  or from the relay device  1   b  is illustrated as an example. The terminal device  4  includes an antenna  4   a  which transmits the radio waves to the relay device  1 . The terminal device  5  includes an antenna  5   a  which receives the radio waves transmitted from the relay device  1 . In this way, the number of the terminal devices that the relay device  1  faces is not limited to one and may be two or more. 
     By constructing the wireless relay network as described above, large-capacity information transmission can be realized while solving a problem of a limited reaching distance of the radio waves. In a millimeter wave region, since an effect of attenuation by vapor and gaseous molecules is strongly shown as a frequency becomes higher, a demand for solving the problem of the attenuation of the radio waves is high and a need of constructing a system using the relay device is high. In addition, since the limitation of the transmission power exists also in regions other than the millimeter wave region, the information transmission of a distance longer than the reaching distance of the radio waves can be realized using the wireless relay network as described above, also in the wireless communication using other frequency bands. 
     In the case of configuring the wireless relay network as described above, when the transmission frequency and the reception frequency are set to the same frequency, various problems arise. In the case where the radio waves are simultaneously transmitted and received, the signals transmitted from the relay device are received by the device, and sneak path interference that a circuit oscillates may occur.  FIG. 2  illustrates a combination  24  of the antennas with a risk of occurrence of the sneak path interference as described above as an example. Further, when the same carrier frequency is used in a plurality of channels in the wireless relay network, interference waves not only between the antennas but also between the channels are generated, and communication quality may be deteriorated.  FIG. 2  illustrates a combination  25  of the channels with a risk of generation of such interference waves as an example. 
     Then, in the relay device in the embodiment of the present invention, processing of switching the transmission frequency and the reception frequency with each other by the time is performed so that channel information in the transmission frequency can be estimated from the signals received before the most recent frequency changeover time. By performing pre-equalizing using the estimated channel information, the communication quality of the signals to be relayed is improved. It is not needed to perform a sounding process beforehand in order to acquire the channel information in the transmission frequency from the signals received before the most recent frequency changeover time, and processing loads on the relay device are reduced as well. 
       FIG. 3  illustrates an example that the respective parts of the relay device time-sequentially perform processing of switching the frequency used in data transmission/reception. A horizontal axis expresses time “t” and it is assumed that the time advances from left to right. In  FIG. 3 , changeover processing of the carrier frequency is performed at the respective timings time-sequentially in an order of the times t 1 , t 2 , t 3 , t 4 , and t 5 . A first period indicates a period between the time t 1  and the time t 2 . A second period indicates a period between the time t 2  and the time t 3 . A third period indicates a period between the time t 3  and the time t 4 . A fourth period indicates a period between the time t 4  and the time t 5 . Hereinafter, details of the processing at the timing at which the frequency is switched will be described. 
     At the time t 1 , the controller  18  sets the reception frequency of the receiver  11  to 72 GHz. Thus, the receiver  11  can receive the radio waves at the frequency 72 GHz by the antenna  10 . Further, the controller  18  sets the transmission frequency of the transmitter  12  to 82 GHz. Thus, the transmitter  12  can frequency-convert the signals received in the receiver  11  to 82 GHz and transmit the signals from the antenna  13 . At the same time t 1 , the controller  18  sets the reception frequency of the receiver  15  to 75 GHz. Thus, the receiver  15  can receive the radio waves at the frequency 75 GHz by the antenna  14 . Further, the controller  18  sets the transmission frequency of the transmitter  16  to 85 GHz. Thus, the transmitter  16  can frequency-convert the signals received in the receiver  15  to 85 GHz and transmit the signals from the antenna  17 . 
     At the time t 1 , since 82 GHz and 85 GHz which are the frequencies used in the data transmission are different from 72 GHz and 75 GHz which are the frequencies used in the data reception, even when the data are transmitted and received at the same time, occurrence of the sneak path interference within the same relay device can be suppressed. Further, since the frequencies for the transmission are separated into 82 GHz and 85 GHz and the frequencies for the reception are separated into 72 GHz and 75 GHz respectively, occurrence of interference between channels can be also suppressed. 
     At the time t 2 , the controller  18  sets the reception frequency of the receiver  11  to 85 GHz. Thus, the receiver  11  can receive the radio waves at the frequency 85 GHz by the antenna  10 . Further, the controller  18  sets the transmission frequency of the transmitter  12  to 75 GHz. Thus, the transmitter  12  can frequency-convert the signals received in the receiver  11  to 75 GHz and transmit the signals from the antenna  13 . At the same time t 2 , the controller  18  sets the reception frequency of the receiver  15  to 82 GHz. Thus, the receiver  15  can receive the radio waves at the frequency 82 GHz by the antenna  14 . Further, the controller  18  sets the transmission frequency of the transmitter  16  to 72 GHz. Thus, the transmitter  16  can frequency-convert the signals received in the receiver  15  to 72 GHz and transmit the signals from the antenna  17 . 
     The transmission frequency 75 GHz set to the transmitter  12  at the time t 2  is the same as the reception frequency 75 GHz set to the receiver  15  at the time t 1 . Further, the transmission frequency 72 GHz set to the transmitter  16  at the time t 2  is the same as the reception frequency 72 GHz set to the receiver  11  at the time t 1 . Since the reception frequency before the carrier frequency changeover is equal to the transmission frequency after the carrier frequency changeover, transmission channel state information can be estimated from reception channel state information acquired before the carrier frequency changeover timing. 
     The reception channel state information is information indicating a state of a channel from the other device to the present device, and the transmission channel state information is information indicating a state of a channel from the present device to the other device. The reception channel state information can be expressed by a channel matrix formed of components for the number of pieces of a value for which the number of transmission antennas of the other device and the number of reception antennas of the present device are multiplied for example. Each element includes an amplitude variation amount and phase rotation of the pertinent channel as the information. When symmetry of the channel is assumed, the transmission channel state can be calculated from the reception channel state. For example, when the number of the transmission antennas of the other device and the number of the reception antennas of the present device are the same, the reception channel state information can be considered as being identical to the transmission channel state information. 
       FIG. 4  is a diagram time-sequentially illustrating a relation between a physical arrangement and the carrier frequency of the plurality of relay devices. It is assumed that the time advances from the first period in the order of the second period, the third period and the fourth period. During each period, the changeover processing of the carrier frequency is performed. Next, the processing in each period will be described. While it is expressed that the signals of the reception frequency are converted to the signals of the transmission frequency in the description, the description is omitted for the conversion from the reception frequency to an intermediate frequency and conversion from the intermediate frequency to the transmission frequency performed in the middle of the conversion. 
     In the first period, the relay device  1  receives a signal  301  of 72 GHz transmitted from the relay device  1   a . The relay device  1  converts the signal  301  to the transmission frequency 82 GHz, and transmits the signal to the relay device  1   b  as a signal  309  of 82 GHz. Further, the relay device  1  receives a signal  310  of 75 GHz transmitted from the relay device  1   b . The relay device  1  converts the signal  310  to the transmission frequency 85 GHz, and transmits the signal to the relay device  1   a  as a signal  302  of 85 GHz. 
     In the second period, the relay device  1  receives a signal  303  of 85 GHz transmitted from the relay device  1   a . The relay device  1  converts the signal  303  to the transmission frequency 75 GHz, and transmits the signal to the relay device  1   b  as a signal  311  of 75 GHz. The frequency 75 GHz of the signal  311  is equal to the frequency of the signal  310  received from the relay device  1   b  in the first period. Further, the relay device  1  receives a signal  312  of 82 GHz transmitted from the relay device  1   b . The relay device  1  converts the signal  312  to the transmission frequency 72 GHz, and transmits the signal to the relay device  1   a  as a signal  304  of 72 GHz. The frequency 72 GHz of the signal  304  is equal to the frequency of the signal  301  received from the relay device  1   a  in the first period. 
     In the third period, the relay device  1  receives a signal  305  of 72 GHz transmitted from the relay device  1   a . The relay device  1  converts the signal  305  to the transmission frequency 82 GHz, and transmits the signal to the relay device  1   b  as a signal  313  of 82 GHz. The frequency 82 GHz of the signal  313  is equal to the frequency of the signal  312  received from the relay device  1   b  in the second period. Further, the relay device  1  receives a signal  314  of 75 GHz transmitted from the relay device  1   b . The relay device  1  converts the signal  314  to the transmission frequency 85 GHz, and transmits the signal to the relay device  1   a  as a signal  306  of 85 GHz. The frequency 85 GHz of the signal  306  is equal to the frequency of the signal  303  received from the relay device  1   a  in the second period. 
     In the fourth period, the relay device  1  receives a signal  307  of 85 GHz transmitted from the relay device  1   a . The relay device  1  converts the signal  307  to the transmission frequency 75 GHz, and transmits the signal to the relay device  1   b  as a signal  315  of 75 GHz. The frequency 75 GHz of the signal  315  is equal to the frequency of the signal  314  received from the relay device  1   b  in the third period. Further, the relay device  1  receives a signal  316  of 82 GHz transmitted from the relay device  1   b . The relay device  1  converts the signal  316  to the transmission frequency 72 GHz, and transmits the signal to the relay device  1   a  as a signal  308  of 72 GHz. The frequency 72 GHz of the signal  308  is equal to the frequency of the signal  305  received from the relay device  1   a  in the third period. 
     When performing the transmission to the relay device  1   a , the relay device  1  uses the same frequency as the frequency received from the same relay device  1   a  before the frequency is switched. Since the frequency is equal, the relay device  1  can estimate the information regarding the channel state used when performing the transmission to the relay device  1   a  from the signals received from the relay device  1   a  before the frequency is switched. Therefore, the relay device  1  can perform the equalization processing (here, pre-equalizing) to the signals to be transmitted to the relay device  1   a  by using the channel state estimated from the signals received from the relay device  1   a . Similarly, also for the signals to be transmitted to the relay device  1   b  by the relay device  1 , the equalization processing (here, pre-equalizing) can be performed by using the channel state estimated from the signals received before the frequency changeover. By performing pre-equalizing, distortion of the channel can be equalizeed beforehand so that it can be expected to receive the signals in the state that the distortion of the channel is canceled or reduced on a reception side. 
     The value of the transmission frequency, the value of the reception frequency and the combination thereof used in the processing according to the first embodiment illustrated in  FIG. 3  and  FIG. 4  are just an example, and using the combination of the carrier frequencies different from them is not excluded. When the combination of the carrier frequencies is generalized, it can be said that the relay device  1  repeats the changeover of two carrier frequency patterns. First, in a first carrier frequency pattern, a first frequency is set to the reception frequency of the receiver  11 , a second frequency is set to the transmission frequency of the transmitter  12 , a third frequency is set to the reception frequency of the receiver  15 , and a fourth frequency is set to the transmission frequency of the transmitter  16 . In the next second carrier frequency pattern, the fourth frequency is set to the reception frequency of the receiver  11 , the third frequency is set to the transmission frequency of the transmitter  12 , the second frequency is set to the reception frequency of the receiver  15 , and the first frequency is set to the transmission frequency of the transmitter  16 . When applied to the processing exemplified in the first embodiment, it can be said that the relay device  1  repeats the first carrier frequency pattern and the second carrier frequency pattern. 
     First Modification 
       FIG. 5  illustrates another example that the respective parts of the relay device time-sequentially perform the processing of switching the frequency used in the data transmission/reception. While the total of four frequencies are used in transmission/reception processing of the relay device in the processing illustrated in  FIG. 3 , the total of two frequencies are used in the processing illustrated in  FIG. 5 . 
     At the time t 1 , the controller  18  sets the reception frequency of the receiver  11  to 72 GHz. Thus, the receiver  11  can receive the radio waves at the frequency 72 GHz by the antenna  10 . Further, the controller  18  sets the transmission frequency of the transmitter  12  to 85 GHz. Thus, the transmitter  12  can frequency-convert the signals received in the receiver  11  to 85 GHz and transmit the signals from the antenna  13 . At the same time t 1 , the controller  18  sets the reception frequency of the receiver  15  to 72 GHz. Thus, the receiver  15  can receive the radio waves at the frequency 72 GHz by the antenna  14 . Further, the controller  18  sets the transmission frequency of the transmitter  16  to 85 GHz. Thus, the transmitter  16  can frequency-convert the signals received in the receiver  15  to 85 GHz and transmit the signals from the antenna  17 . 
     At the time t 1 , since 85 GHz which is the frequency used in the data transmission is different from 72 GHz which is the frequency used in the data reception, even when the data are transmitted and received at the same time, occurrence of the sneak path interference within the same relay device can be suppressed. 
     At the time t 2 , the controller  18  sets the reception frequency of the receiver  11  to 85 GHz. Thus, the receiver  11  can receive the radio waves at the frequency 85 GHz by the antenna  10 . Further, the controller  18  sets the transmission frequency of the transmitter  12  to 72 GHz. Thus, the transmitter  12  can frequency-convert the signals received in the receiver  11  to 72 GHz and transmit the signals from the antenna  13 . At the same time t 2 , the controller  18  sets the reception frequency of the receiver  15  to 85 GHz. Thus, the receiver  15  can receive the radio waves at the frequency 85 GHz by the antenna  14 . Further, the controller  18  sets the transmission frequency of the transmitter  16  to 72 GHz. Thus, the transmitter  16  can frequency-convert the signals received in the receiver  15  to 72 GHz and transmit the signals from the antenna  17 . 
     The transmission frequency 72 GHz set to the transmitter  12  and the transmitter  16  at the time t 2  is the same as the reception frequency 72 GHz set to the receiver  11  and the receiver  15  at the time t 1 . Since the reception frequency before the carrier frequency changeover is equal to the transmission frequency after the carrier frequency changeover, transmission channel state can be estimated from the information regarding the reception channel state acquired before the carrier frequency changeover timing. 
       FIG. 6  is a diagram time-sequentially illustrating a relation between the physical arrangement and the carrier frequency of the plurality of wireless relay devices for the first modification of the first embodiment. 
     In the first period, the relay device  1  receives a signal  601  of 72 GHz transmitted from the relay device  1   a . The relay device  1  converts the signal  601  to the transmission frequency 85 GHz, and transmits the signal to the relay device  1   b  as a signal  609  of 85 GHz. Further, the relay device  1  receives a signal  610  of 72 GHz transmitted from the relay device  1   b . The relay device  1  converts the signal  610  to the transmission frequency 85 GHz, and transmits the signal to the relay device  1   a  as a signal  602  of 85 GHz. 
     In the second period, the relay device  1  receives a signal  603  of 85 GHz transmitted from the relay device  1   a . The relay device  1  converts the signal  603  to the transmission frequency 72 GHz, and transmits the signal to the relay device  1   b  as a signal  611  of 72 GHz. The frequency 72 GHz of the signal  611  is equal to the frequency of the signal  610  received from the relay device  1   b  in the first period. Further, the relay device  1  receives a signal  612  of 85 GHz transmitted from the relay device  1   b . The relay device  1  converts the signal  612  to the transmission frequency 72 GHz, and transmits the signal to the relay device  1   a  as a signal  604  of 72 GHz. The frequency 72 GHz of the signal  604  is equal to the frequency of the signal  601  received from the relay device  1   a  in the first period. 
     In the third period, the relay device  1  receives a signal  605  of 72 GHz transmitted from the relay device  1   a . The relay device  1  converts the signal  605  to the transmission frequency 85 GHz, and transmits the signal to the relay device  1   b  as a signal  613  of 85 GHz. The frequency 85 GHz of the signal  613  is equal to the frequency of the signal  612  received from the relay device  1   b  in the second period. Further, the relay device  1  receives a signal  614  of 72 GHz transmitted from the relay device  1   b . The relay device  1  converts the signal  614  to the transmission frequency 85 GHz, and transmits the signal to the relay device  1   a  as a signal  606  of 85 GHz. The frequency 85 GHz of the signal  606  is equal to the frequency of the signal  603  received from the relay device  1   a  in the second period. 
     In the fourth period, the relay device  1  receives a signal  607  of 85 GHz transmitted from the relay device  1   a . The relay device  1  converts the signal  607  to the transmission frequency 72 GHz, and transmits the signal to the relay device  1   b  as a signal  615  of 72 GHz. The frequency 72 GHz of the signal  615  is equal to the frequency of the signal  614  received from the relay device  1   b  in the third period. Further, the relay device  1  receives a signal  616  of 85 GHz transmitted from the relay device  1   b . The relay device  1  converts the signal  616  to the transmission frequency 72 GHz, and transmits the signal to the relay device  1   a  as a signal  608  of 72 GHz. The frequency 72 GHz of the signal  608  is equal to the frequency of the signal  605  received from the relay device  1   a  in the third period. 
     Also for the relay device  1  according to the first modification of the first embodiment, when performing the transmission to the relay device  1   a , the same frequency as the frequency received from the same relay device  1   a  before the frequency is switched is used. The relay device  1  can perform pre-equalizing to the signals to be transmitted to the relay device  1   a  at the same frequency, using the channel state estimated from the signals received from the relay device  1   a . Similarly, also for the signals to be transmitted to the relay device  1   b  by the relay device  1 , pre-equalizing can be performed by using the channel state estimated from the signals received before the frequency changeover. 
     The value of the transmission frequency, the value of the reception frequency and the combination thereof used in the processing according to the first modification of the first embodiment illustrated in  FIG. 5  and  FIG. 6  are just an example, and using the combination of the carrier frequencies different from them is not excluded. When the combination of the carrier frequencies is generalized, it can be said that the relay device  1  repeats the changeover of two carrier frequency patterns here as well. First, in the first carrier frequency pattern, the first frequency is set to the reception frequency of the receiver  11 , the second frequency is set to the transmission frequency of the transmitter  12 , the first frequency is set to the reception frequency of the receiver  15 , and the second frequency is set to the transmission frequency of the transmitter  16 . In the next second carrier frequency pattern, the second frequency is set to the reception frequency of the receiver  11 , the first frequency is set to the transmission frequency of the transmitter  12 , the second frequency is set to the reception frequency of the receiver  15 , and the first frequency is set to the transmission frequency of the transmitter  16 . When applied to the exemplified processing, it can be said that the relay device  1  repeats the first carrier frequency pattern and the second carrier frequency pattern. 
     In the wireless relay network illustrated in  FIG. 4  and  FIG. 6 , the plurality of relay devices are successively arranged. In  FIG. 4  and  FIG. 6 , not only the carrier frequency pattern is switched in the relay device  1  but also the carrier frequency pattern is switched in the relay device  1   a  and the relay device  1   b . At the time, a mode of the frequency pattern changeover between the adjacent relay devices has regularity. That is, in the first period, when it is assumed that the relay device  1  is set to the first carrier frequency pattern, the adjacent relay device  1   a  and the adjacent relay device  1   b  are set to the second carrier frequency pattern. In the second period, when it is assumed that the relay device  1  is set to the second carrier frequency pattern, the adjacent relay device  1   a  and the adjacent relay device  1   b  are set to the first carrier frequency pattern. In the third period, when it is assumed that the relay device  1  is set to the first carrier frequency pattern, the adjacent relay device  1   a  and the adjacent relay device  1   b  are set to the second carrier frequency pattern. In the fourth period, when it is assumed that the relay device  1  is set to the second carrier frequency pattern, the adjacent relay device  1   a  and the adjacent relay device  1   b  are set to the first carrier frequency pattern. In the case where another relay device is present on a left side of the relay device  1   b , the carrier frequency pattern of another relay device coincides with the relay device  1  in each period. 
     When the mode of the frequency pattern changeover described above is generalized, in the case where the plurality of relay devices are successively arranged, the relay devices are divided into the ones belonging to a first group and the ones belonging to a second group. Here, the first group and the second group mean sets of the relay devices to which the same carrier frequency pattern is set in the same period. In the case where the plurality of relay devices are successively arranged, the relay devices belonging to the first group and the relay devices belonging to the second group are alternatingly installed. 
     The two of the processing according to the first embodiment illustrated in  FIG. 3  and  FIG. 4  and the processing according to the first modification of the first embodiment illustrated in  FIG. 5  and  FIG. 6  are described as examples so far. Between the carrier frequency patterns used in the two types of the processing, there is a difference in the number of the frequencies being used. It is assumed that the carrier frequency is switched time-sequentially for two or more times, but the timing at which the carrier frequency is switched for two or more times is not limited in particular. When various kinds of the timing of switching the frequency are assumed, further more modifications can be realized. The changeover of the carrier frequency may be performed at every fixed cycle, or may be the one of an event driven type to be executed when some conditions are satisfied. In the case that the changeover of the carrier frequency is cyclic, a length of the cycle does not matter. 
     Even though a selection of the carrier frequency changeover timing is not limited in particular as described above, the timing at which the wireless communication device or the relay device that transmits and receives the radio waves to/from the relay device  1  switches the carrier frequency needs to be synchronized with the timing at which the relay device  1  switches the carrier frequency. The synchronization of the carrier frequency changeover timing will be specifically described using  FIG. 7 . 
     It is described that the carrier frequency changeover timings of the transmitter and the receiver of the relay device and the wireless communication device configuring the wireless relay network become identical in the description so far, but the frequency changeover timings of the receiver and the transmitter do not need to strictly coincide. For example, in the case where the processing of the transmission or the reception of data is not completed yet for any direction even when a specified carrier frequency changeover timing comes, the frequency changeover of the transmitter or the receiver may be performed after the transmission or the reception of the data being performed at present is completed. 
     For example, in the case where the data reception in the receiver  11  continues even when the carrier frequency changeover timing comes and the received data needs to be continuously transmitted by the transmitter  12 , the frequency changeover timing of the receiver  11  and the transmitter  12  may be after that of the transmitter  16  and the receiver  15 . 
     In addition, even when a command to simultaneously switch the frequency in all of the receiver  11 , the transmitter  12 , the receiver  15  and the transmitter  16  is issued, the timings of actually switching the frequency in the receiver  11 , the transmitter  12 , the receiver  15  and the transmitter  16  sometimes vary due to factors on program processing of the controller  18  or the circuit implementation of the local oscillators  20  and  21  and the mixers  11 A,  12 A,  15 A and  16 A or the like, but it can be said that even such a device is included in the scope of the embodiment of the present invention as long as the occurrence of the interference is suppressed. 
     In the wireless relay network in a top stage illustrated in  FIG. 7 , one relay device is used for a purpose of relaying the communication performed between a terminal device  6   a  and a terminal device  6   b . In the case of using such a configuration, for the transmission antenna of the terminal device  6   a , the reception antenna of the terminal device  6   a , the transmission antenna of the terminal device  6   b , the reception antenna of the terminal device  6   b , and the one relay device, the timings of switching the carrier frequency need to be synchronized. The components filled with oblique lines in  FIG. 7  correspond to the range where the carrier frequency changeover timings are synchronized. The terminal device  6   a  and the terminal device  6   b  also include the configuration equivalent to that excluding a function regarding relay in the configuration in  FIG. 1 . 
     In the wireless relay network in a second stage from top in  FIG. 7 , two relay devices are used for the purpose of relaying the communication performed between a terminal device  6   c  and a terminal device  6   d . In the case of using such a configuration, for the transmission antenna of the terminal device  6   c , the reception antenna of the terminal device  6   c , the transmission antenna of the terminal device  6   d , the reception antenna of the terminal device  6   d , and the two relay devices, the timings of switching the carrier frequency need to be synchronized. The components filled with oblique lines in  FIG. 7  correspond to the range where the carrier frequency changeover timings are synchronized. The terminal device  6   c  and the terminal device  6   d  also include the configuration equivalent to that excluding the function regarding the relay in the configuration in  FIG. 1 . 
     In the wireless relay network in a third stage from the top in  FIG. 7 , three relay devices are used for the purpose of relaying the communication performed between a terminal device  6   e  and a terminal device  6   f . In the case of using such a configuration, for the transmission antenna of the terminal device  6   e , the reception antenna of the terminal device  6   e , the transmission antenna of the terminal device  6   f , the reception antenna of the terminal device  6   f , and the three relay devices, the timings of switching the carrier frequency need to be synchronized. The components filled with oblique lines in  FIG. 7  correspond to the range where the carrier frequency changeover timings are synchronized. The terminal device  6   e  and the terminal device  6   f  also include the configuration equivalent to that excluding the function regarding the relay in the configuration in  FIG. 1 . 
     In the wireless relay network in a fourth stage from the top in  FIG. 7 , three relay devices are used for the purpose of relaying the communication performed between a terminal device  6   g  and a terminal device  6   i  and the communication performed between a terminal device  6   h  and a terminal device  6   j . In the case of using such a configuration, for the transmission antenna of the terminal device  6   g , the reception antenna of the terminal device  6   i , the transmission antenna of the terminal device  6   j , the reception antenna of the terminal device  6   h , and the three relay devices, the timings of switching the carrier frequency need to be synchronized. The components filled with oblique lines in  FIG. 7  correspond to the range where the carrier frequency changeover timings are synchronized. A set of the terminal device  6   g  and the terminal device  6   h  and a set of the terminal device  6   i  and the terminal device  6   j  also include the configuration equivalent to that excluding the function regarding the relay in the configuration in  FIG. 1 . 
     When the relation described above is generalized, in the case where “n” relay devices that perform relay processing of the radio waves are successively installed, it can be said that the range where the frequency changeover timings are synchronized includes, in addition to the “n” relay devices, the antennas of the terminal device or the relay device that transmit or receive the radio waves directly with the antennas positioned at both ends of a series of the “n” relay devices. The synchronization processing of the frequency changeover timing may be autonomously performed by the function of the synchronizers of the “n” relay devices, may be performed by receiving an external command from a management terminal or a management server or the like, or may be performed by the combination thereof, and an mounting method is not limited in particular. 
     Second Embodiment 
       FIG. 8  is a functional block diagram of the relay device as the wireless communication device according to the second embodiment. The relay Processor  22  according to the second embodiment includes a channel estimator  70 , a channel equalizer  71 , a combiner  72 , and a pilot signal generator  73 . Similarly, the relay processor  23  includes a channel estimator  74 , a channel equalizer  75 , a combiner  76 , and a pilot signal generator  77 . The antenna  10 , the receiver  11 , the transmitter  12 , the antenna  13 , the antenna  14 , the receiver  15 , the transmitter  16 , the antenna  17  and the controller  18  of the relay device according to the second embodiment have the functions respectively equivalent to that of the antenna  10 , the receiver  11 , the transmitter  12 , the antenna  13 , the antenna  14 , the receiver  15 , the transmitter  16 , the antenna  17  and the controller  18  according to the first embodiment, respectively. Even though not illustrated in  FIG. 8 , the relay device according to the second embodiment also includes the local oscillator having the function equivalent to that of the local oscillator  20  and the local oscillator  21  of the relay device according to the first embodiment. 
       FIG. 9  is a diagram illustrating a format of a frame transmitted by the relay device according to the second embodiment. The frame according to the second embodiment includes a pilot portion including a pilot signal configured from a plurality of pilot symbols, and a payload portion including a data main body. 
       FIG. 10A  and  FIG. 10B  are diagrams illustrating the processing performed to the frame by the relay device according to the second embodiment. The carrier frequency is switched respectively at the time t 1 , the time t 2 , the time t 3 , the time t 4 , and the time t 5 . The first period indicates the period between the time t 1  and the time t 2 . The second period indicates the period between the time t 2  and the time t 3 . The third period indicates the period between the time t 3  and the time t 4 . The fourth period indicates the period between the time t 4  and the time t 5 . In  FIG. 10A  and  FIG. 10B , for the respective periods, an outline of the processing performed to the frame received by the relay device  1  is illustrated in a direction from top to bottom. Hereinafter, the processing performed for the frame will be described along  FIG. 10A  and  FIG. 10B . 
     First, the processing for the first period will be described. At the time t 1 , the controller  18  sets the reception frequency of the receiver  11  to 72 GHz. The frame transmitted at the transmission frequency 72 GHz from the relay device  1   a  is received by the antenna  10 , and converted to the intermediate frequency used by a baseband signal in the receiver  11 . The channel estimator  70  refers to the pilot signal included in a pilot portion  90  of the received frame, and estimates a channel state H 1a ( 72 ) between the relay device  1  and the relay device  1   a . The channel equalizer  71  performs channel equalization to a payload portion  91  of the frame by using an inverse characteristic H 1a   −1 ( 72 ) of the channel state. The combiner  72  combines a equalizeed payload portion  93  and a new pilot portion  92  generated by the pilot signal generator  73  to configure a new frame. The controller  18  sets the transmission frequency of the transmitter  12  to 82 GHz at the time t 1 . Therefore, the transmitter  12  converts the baseband signal to the transmission frequency 82 GHz, and then transmits signals including the new frame from the antenna  13  to the relay device  1   b.    
     In the same first period, the processing for the frame received by the receiver  15  will be also described. At the time t 1 , the controller  18  sets the reception frequency of the receiver  15  to 75 GHz. The frame transmitted at the transmission frequency 75 GHz from the relay device  1   b  is received by the antenna  14 , and converted to the intermediate frequency used by the baseband signal in the receiver  15 . The channel estimator  74  refers to the pilot signal included in a pilot portion  94  of the received frame, and estimates a channel state H 1b ( 75 ) between the relay device  1  and the relay device  1   b . The channel equalizer  75  performs the channel equalization to a payload portion  95  of the frame by using an inverse characteristic H 1b   −1 ( 75 ) of the channel state. The combiner  76  combines a equalizeed payload portion  97  and a new pilot portion  96  generated by the pilot signal generator  77  to configure a new frame. The controller  18  sets the transmission frequency of the transmitter  16  to 85 GHz at the time t 1 . Therefore, the transmitter  16  converts the baseband signal to the transmission frequency 85 GHz, and then transmits signals including the new frame from the antenna  17  to the relay device  1   a.    
     Next, the processing in the second period will be described. At the time t 2 , the controller  18  sets the reception frequency of the receiver  11  to 85 GHz. The frame transmitted at the transmission frequency 85 GHz from the relay device  1   a  is received by the antenna  10 , and converted to the intermediate frequency used by the baseband signal in the receiver  11 . The channel estimator  70  refers to the pilot signal included in a pilot portion  98  of the received frame, and estimates a channel state H 1a ( 85 ) between the relay device  1  and the relay device  1   a . The channel equalizer  71  performs the channel equalization to a payload portion  99  of the frame by using an inverse characteristic H 1a   −1 ( 85 ) of the channel state. The combiner  72  combines a equalizeed payload portion  101  and a new pilot portion  100  generated by the pilot signal generator  73  to configure a new frame. The controller  18  sets the transmission frequency of the transmitter  12  to 75 GHz at the time t 2 . Therefore, the transmitter  12  converts the baseband signal to the transmission frequency 75 GHz, and then transmits signals including the new frame from the antenna  13  to the relay device  1   b.    
     In the same second period, the processing for the frame received by the receiver  15  will be also described. At the time t 2 , the controller  18  sets the reception frequency of the receiver  15  to 82 GHz. The frame transmitted at the transmission frequency 82 GHz from the relay device  1   b  is received by the antenna  14 , and converted to the intermediate frequency used by the baseband signal in the receiver  15 . The channel estimator  74  refers to the pilot signal included in a pilot portion  102  of the received frame, and estimates a channel state H 1b ( 82 ) between the relay device  1  and the relay device  1   b . The channel equalizer  75  performs the channel equalization to a payload portion  103  of the frame by using an inverse characteristic H 1b   −1 ( 82 ) of the channel state. The combiner  76  combines a equalizeed payload portion  105  and a new pilot portion  104  generated by the pilot signal generator  77  to configure a new frame. The controller  18  sets the transmission frequency of the transmitter  16  to 72 GHz at the time t 2 . Therefore, the transmitter  16  converts the baseband signal to the transmission frequency 72 GHz, and then transmits signals including the new frame from the antenna  17  to the relay device  1   a . The processing performed for the frame received by the relay device  1  in the third period and the fourth period is also similar to the processing in the first period and the second period described above. 
     First Modification 
     While the total of four frequencies are used in the transmission/reception processing of the relay device in the processing illustrated in  FIG. 10A  and  FIG. 10B , the processing in the case of using the total of two frequencies in the transmission/reception processing is illustrated in  FIG. 11A  and  FIG. 11B  as the first modification of the second embodiment. The carrier frequency is switched respectively at the time t 1 , the time t 2 , the time t 3 , the time t 4 , and the time t 5  also in  FIG. 11A  and  FIG. 11B . 
     First, the processing for the first period will be described. At the time t 1 , the controller  18  sets the reception frequency of the receiver  11  to 72 GHz. The frame transmitted at the transmission frequency 72 GHz from the relay device  1   a  is received by the antenna  10 , and converted to the intermediate frequency used by the baseband signal in the receiver  11 . The channel estimator  70  refers to the pilot signal included in a pilot portion  106  of the received frame, and estimates a channel state H 1a ( 72 ) between the relay device  1  and the relay device  1   a . The channel equalizer  71  performs the channel equalization to a payload portion  107  of the frame by using the inverse characteristic H 1a   −1 ( 72 ) of the channel state. The combiner  72  combines a equalizeed payload portion  109  and a new pilot portion  108  generated by the pilot signal generator  73  to configure a new frame. The controller  18  sets the transmission frequency of the transmitter  12  to 85 GHz at the time t 1 . Therefore, the transmitter  12  converts the baseband signal to the transmission frequency 85 GHz, and then transmits signals carrying the new frame from the antenna  13  to the relay device  1   b.    
     In the same first period, the processing for the frame received by the receiver  15  will be also described. At the time t 1 , the controller  18  sets the reception frequency of the receiver  15  to 72 GHz. The frame transmitted at the transmission frequency 72 GHz from the relay device  1   b  is received by the antenna  14 , and converted to the intermediate frequency used by the baseband signal in the receiver  15 . The channel estimator  74  refers to the pilot signal included in a pilot portion  110  of the received frame, and estimates a channel state H 1b ( 72 ) between the relay device  1  and the relay device  1   b . The channel equalizer  75  performs the channel equalization to a payload portion  111  of the frame by using an inverse characteristic H 1b   −1 ( 72 ) of the channel state. The combiner  76  combines a equalizeed payload portion  113  and a new pilot portion  112  generated by the pilot signal generator  77  to configure a new frame. The controller  18  sets the transmission frequency of the transmitter  16  to 85 GHz at the time t 1 . Therefore, the transmitter  16  converts the baseband signal to the transmission frequency 85 GHz, and then transmits signals carrying the new frame from the antenna  17  to the relay device  1   a.    
     Next, the processing in the second period will be described. At the time t 2 , the controller  18  sets the reception frequency of the receiver  11  to 85 GHz. The frame transmitted at the transmission frequency 85 GHz from the relay device  1   a  is received by the antenna  10 , and converted to the intermediate frequency used by the baseband signal in the receiver  11 . The channel estimator  70  refers to the pilot signal included in a pilot portion  114  of the received frame, and estimates the channel state H 1a ( 85 ) between the relay device  1  and the relay device  1   a . The channel equalizer  71  performs the channel equalization to a payload portion  115  of the frame by using the inverse characteristic H 1a   −1 ( 85 ) of the channel state. The combiner  72  combines a equalizeed payload portion  117  and a new pilot portion  116  generated by the pilot signal generator  73  to configure a new frame. The controller  18  sets the transmission frequency of the transmitter  12  to 72 GHz at the time t 2 . Therefore, the transmitter  12  converts the baseband signal to the transmission frequency 72 GHz, and then transmits signals including the new frame from the antenna  13  to the relay device  1   b.    
     In the same second period, the processing for the frame received by the receiver  15  will be also described. At the time t 2 , the controller  18  sets the reception frequency of the receiver  15  to 85 GHz. The frame transmitted at the transmission frequency 85 GHz from the relay device  1   b  is received by the antenna  14 , and converted to the intermediate frequency used by the baseband signal in the receiver  15 . The channel estimator  74  refers to the pilot signal included in a pilot portion  118  of the received frame, and estimates a channel state H 1b ( 85 ) between the relay device  1  and the relay device  1   b . The channel equalizer  75  performs the channel equalization to a payload portion  119  of the frame by using an inverse characteristic H 1b   −1 ( 85 ) of the channel state. The combiner  76  combines a equalizeed payload portion  121  and a new pilot portion  120  generated by the pilot signal generator  77  to configure a new frame. The controller  18  sets the transmission frequency of the transmitter  16  to 72 GHz at the time t 2 . Therefore, the transmitter  16  converts the baseband signal to the transmission frequency 72 GHz, and then transmits signals including the new frame from the antenna  17  to the relay device  1   a . The processing performed for the frame received by the relay device  1  in the third period and the fourth period is also similar to the processing in the first period and the second period described above. 
     As described above, by obtaining the inverse characteristic based on the information of the channel state at the time of the reception and equalizing the distortion of the signals for the payload portion, an effect of improving the transmission characteristic (suppressing degradation of transmission signals) can be obtained. For example, for the data carried by the radio waves relayed by the relay device, an SER (Symbol Error Rate) is reduced, and more efficient data transfer is made possible. 
     Third Embodiment 
       FIG. 12  is a functional block diagram of the relay device as the wireless communication device according to the third embodiment. The relay processor  22  according to the third embodiment includes the channel estimator  70 , the combiner  72 , the pilot signal generator  73 , a storage  122 , and a pre-equalizer  123 . Similarly, the relay processor  23  includes the channel estimator  74 , the combiner  76 , the pilot signal generator  77 , a storage  124  and a pre-equalizer  125 . The antenna  10 , the receiver  11 , the transmitter  12 , the antenna  13 , the antenna  14 , the receiver  15 , the transmitter  16 , the antenna  17  and the controller  18  of the relay device according to the third embodiment have the functions respectively equivalent to that of the antenna  10 , the receiver  11 , the transmitter  12 , the antenna  13 , the antenna  14 , the receiver  15 , the transmitter  16 , the antenna  17  and the controller  18  according to the first embodiment, respectively. In addition, the relay device according to the third embodiment also includes the local oscillator having the function equivalent to that of the local oscillator  20  and the local oscillator  21  of the relay device according to the first embodiment. 
     The storages  122  and  124  are configured from any one of a nonvolatile storage device such as a NAND flash memory, an NOR flash memory, an MRAM, a ReRAM, a hard disk or an optical disk or a storage device such as a DRAM or the combination thereof. 
     The third embodiment is an example of the relay device which estimates the transmission channel state by the information regarding the reception channel state acquired before the carrier frequency changeover timing, and performs pre-equalizing utilizing the estimated transmission channel state. 
       FIG. 13  is a diagram illustrating a format of the frame transmitted by the relay device according to the third embodiment. The frame according to the third embodiment includes the payload portion including the data main body and the pilot portion including the pilot symbol. 
       FIG. 14A  and  FIG. 14B  are diagrams illustrating the processing performed to the frame by the relay device according to the third embodiment. The carrier frequency is switched respectively at the time t 1 , the time t 2 , the time t 3 , the time t 4 , and the time t 5 . The first period indicates the period between the time t 1  and the time t 2 . The second period indicates the period between the time t 2  and the time t 3 . The third period indicates the period between the time t 3  and the time t 4 . The fourth period indicates the period between the time t 4  and the time t 5 . In  FIG. 14A  and  FIG. 14B , for the respective periods, an outline of the processing performed to the frame received by the relay device  1  is illustrated in the direction from top to bottom. Hereinafter, the processing performed for the frame will be described along  FIG. 14A  and  FIG. 14B . 
     First, the processing for the first period will be described. At the time t 1 , the controller  18  sets the reception frequency of the receiver  11  to 72 GHz. The frame transmitted at the transmission frequency 72 GHz from the relay device  1   a  is received by the antenna  10 , and converted to the intermediate frequency used by the baseband signal in the receiver  11 . The channel estimator  70  refers to the pilot signal included in a pilot portion  130  of the received frame, and estimates a channel state H 1a ( 72 ) between the relay device  1  and the relay device  1   a . The channel estimator  70  further obtains the inverse characteristic H 1a   −1 ( 72 ) of the channel state, and preserves the inverse characteristic H 1a   −1 ( 72 ) of the channel state in the storage  122 . The pre-equalizer  123  performs pre-equalizing (pre-equalization) to a payload portion  131  of the frame by using the inverse characteristic H 1b   −1 ( 82 ) of the channel state with the relay device  1   b  in the period before the time t 1 , which is preserved in the storage  124 . The pre-equalizing is performed before the transmission to the relay device  1   b . The combiner  72  combines a payload portion  132  pre-equalized by the pre-equalizer  123  and a new pilot portion  133  generated by the pilot signal generator  73  to configure a new frame. The controller  18  sets the transmission frequency of the transmitter  12  to 82 GHz at the time t 1 . Therefore, the transmitter  12  converts the baseband signal to the transmission frequency 82 GHz, and then transmits signals carrying the new frame from the antenna  13  to the relay device  1   b.    
     In the same first period, the processing for the frame received by the receiver  15  will be also described. At the time t 1 , the controller  18  sets the reception frequency of the receiver  15  to 75 GHz. The frame transmitted at the transmission frequency 75 GHz from the relay device  1   b  is received by the antenna  14 , and converted to the intermediate frequency used by the baseband signal in the receiver  15 . The channel estimator  74  refers to the pilot signal included in a pilot portion  134  of the received frame, and estimates the channel state H 1b ( 75 ) between the relay device  1  and the relay device  1   b . The channel estimator  74  further obtains the inverse characteristic H 1b   −1 ( 75 ) of the channel state, and preserves the inverse characteristic H 1b   −1 ( 75 ) of the channel state in the storage  124 . The pre-equalizer  125  performs the pre-equalizing (pre-equalization) to a payload portion  135  of the frame by using the inverse characteristic H 1a   −1 ( 85 ) of the channel state with the relay device  1   a  in the period before the time t 1 , which is preserved in the storage  122 . The pre-equalizing is performed before the transmission to the relay device  1   a . The combiner  76  combines a payload portion  136  pre-equalized by the pre-equalizer  125  and a new pilot portion  137  generated by the pilot signal generator  77  to configure a new frame. The controller  18  sets the transmission frequency of the transmitter  16  to 85 GHz at the time t 1 . Therefore, the transmitter  16  converts the baseband signal to the transmission frequency 85 GHz, and then transmits signals carrying the new frame from the antenna  17  to the relay device  1   a.    
     Next, the processing in the second period will be described. At the time t 2 , the controller  18  sets the reception frequency of the receiver  11  to 85 GHz. The frame transmitted at the transmission frequency 85 GHz from the relay device  1   a  is received by the antenna  10 , and converted to the intermediate frequency used by the baseband signal in the receiver  11 . The channel estimator  70  refers to the pilot signal included in a pilot portion  138  of the received frame, and estimates the channel state H 1a ( 85 ) between the relay device  1  and the relay device  1   a . The channel estimator  70  further obtains the inverse characteristic H 1a   −1 ( 85 ) of the channel state, and preserves the inverse characteristic H 1a   −1 ( 85 ) of the channel state in the storage  122 . The pre-equalizer  123  performs the pre-equalizing (pre-equalization) to a payload portion  139  of the frame by using the inverse characteristic H 1b   −1 ( 75 ) of the channel state with the relay device  1   b  in the first period before the time t 2 , which is preserved in the storage  124 . The pre-equalizing is performed before the transmission to the relay device  1   b . The combiner  72  combines a payload portion  140  pre-equalized by the pre-equalizer  123  and a new pilot portion  141  generated by the pilot signal generator  73  to configure a new frame. The controller  18  sets the transmission frequency of the transmitter  12  to 75 GHz at the time t 2 . Therefore, the transmitter  12  converts the baseband signal to the transmission frequency 75 GHz, and then transmits signals carrying the new frame from the antenna  13  to the relay device  1   b.    
     In the same second period, the processing for the frame received by the receiver  15  will be also described. At the time t 2 , the controller  18  sets the reception frequency of the receiver  15  to 82 GHz. The frame transmitted at the transmission frequency 82 GHz from the relay device  1   b  is received by the antenna  14 , and converted to the intermediate frequency used by the baseband signal in the receiver  15 . The channel estimator  74  refers to the pilot signal included in a pilot portion  142  of the received frame, and estimates the channel state H 1b ( 82 ) between the relay device  1  and the relay device  1   b . The channel estimator  74  further obtains the inverse characteristic H 1b   −1 ( 82 ) of the channel state, and preserves the inverse characteristic H 1b   −1 ( 82 ) of the channel state in the storage  124 . The pre-equalizer  125  performs the pre-equalizing (pre-equalization) to a payload portion  143  of the frame by using the inverse characteristic H 1a   −1 ( 72 ) of the channel state with the relay device  1   a  in the first period before the time t 2 , which is preserved in the storage  122 . The pre-equalizing is performed before the transmission to the relay device  1   a . The combiner  76  combines a payload portion  144  pre-equalized by the pre-equalizer  125  and a new pilot portion  145  generated by the pilot signal generator  77  to configure a new frame. The controller  18  sets the transmission frequency of the transmitter  16  to 72 GHz at the time t 2 . Therefore, the transmitter  16  converts the baseband signal to the transmission frequency 72 GHz, and then transmits signals carrying the new frame from the antenna  17  to the relay device  1   a . The processing performed for the frame received by the relay device  1  in and after the third period and the fourth period is also similar to the processing in the second period described above. 
     First Modification 
     While the total of four frequencies are used in the transmission/reception processing of the relay device in the processing illustrated in  FIG. 14A  and  FIG. 14B , the processing in the case of using the total of two frequencies in the transmission/reception processing is illustrated in  FIG. 15A  and  FIG. 15B , as the first modification of the third embodiment. 
     First, the processing for the first period will be described. At the time t 1 , the controller  18  sets the reception frequency of the receiver  11  to 72 GHz. The frame transmitted at the transmission frequency 72 GHz from the relay device  1   a  is received by the antenna  10 , and converted to the intermediate frequency used by the baseband signal in the receiver  11 . The channel estimator  70  refers to the pilot signal included in a pilot portion  150  of the received frame, and estimates a channel state H 1a ( 72 ) between the relay device  1  and the relay device  1   a . The channel estimator  70  further obtains the inverse characteristic H 1a   −1 ( 72 ) of the channel state, and preserves the inverse characteristic H 1a   −1 ( 72 ) of the channel state in the storage  122 . The pre-equalizer  123  performs the pre-equalizing (pre-equalization) to a payload portion  151  of the frame by using the inverse characteristic H 1b   −1 ( 85 ) of the channel state with the relay device  1   b  in the period before the time t 1 , which is preserved in the storage  124 . The pre-equalizing is performed before the transmission to the relay device  1   b . The combiner  72  combines a payload portion  152  pre-equalized by the pre-equalizer  123  and a new pilot portion  153  generated by the pilot signal generator  73  to configure a new frame. The controller  18  sets the transmission frequency of the transmitter  12  to 85 GHz at the time t 1 . Therefore, the transmitter  12  converts the baseband signal to the transmission frequency 85 GHz, and then transmits signals carrying the new frame from the antenna  13  to the relay device  1   b.    
     In the same first period, the processing for the frame received by the receiver  15  will be also described. At the time t 1 , the controller  18  sets the reception frequency of the receiver  15  to 72 GHz. The frame transmitted at the transmission frequency 72 GHz from the relay device  1   b  is received by the antenna  14 , and converted to the intermediate frequency used by the baseband signal in the receiver  15 . The channel estimator  74  refers to the pilot signal included in a pilot portion  154  of the received frame, and estimates the channel state H 1b ( 72 ) between the relay device  1  and the relay device  1   b . The channel estimator  74  further obtains the inverse characteristic H 1b   −1 ( 72 ) of the channel state, and preserves the inverse characteristic H 1b   −1 ( 72 ) of the channel state in the storage  124 . The pre-equalizer  125  performs the pre-equalizing (pre-equalization) to a payload portion  155  of the frame by using the inverse characteristic H 1a   −1 ( 85 ) of the channel state with the relay device  1   a  in the period before the time t 1 , which is preserved in the storage  122 . The pre-equalizing is performed before the transmission to the relay device  1   a . The combiner  76  combines a payload portion  156  pre-equalized by the pre-equalizer  125  and a new pilot portion  157  generated by the pilot signal generator  77  to configure a new frame. The controller  18  sets the transmission frequency of the transmitter  16  to 85 GHz at the time t 1 . Therefore, the transmitter  16  converts the baseband signal to the transmission frequency 85 GHz, and then transmits signals carrying the new frame from the antenna  17  to the relay device  1   a.    
     Next, the processing in the second period will be described. At the time t 2 , the controller  18  sets the reception frequency of the receiver  11  to 85 GHz. The frame transmitted at the transmission frequency 85 GHz from the relay device  1   a  is received by the antenna  10 , and converted to the intermediate frequency used by the baseband signal in the receiver  11 . The channel estimator  70  refers to the pilot signal included in a pilot portion  158  of the received frame, and estimates the channel state H 1a ( 85 ) between the relay device  1  and the relay device  1   a . The channel estimator  70  further obtains the inverse characteristic H 1a   −1 ( 85 ) of the channel state, and preserves the inverse characteristic H 1a   −1 ( 85 ) of the channel state in the storage  122 . The pre-equalizer  123  performs the pre-equalizing (pre-equalization) to a payload portion  159  of the frame by using the inverse characteristic H 1b   −1 ( 72 ) of the channel state with the relay device  1   b  in the first period before the time t 2 , which is preserved in the storage  124 . The pre-equalizing is performed before the transmission to the relay device  1   b . The combiner  72  combines a payload portion  160  pre-equalized by the pre-equalizer  123  and a new pilot portion  161  generated by the pilot signal generator  73  to configure a new frame. The controller  18  sets the transmission frequency of the transmitter  12  to 72 GHz at the time t 2 . Therefore, the transmitter  12  converts the baseband signal to the transmission frequency 72 GHz, and then transmits signals carrying the new frame from the antenna  13  to the relay device  1   b.    
     In the same second period, the processing for the frame received by the receiver  15  will be also described. At the time t 2 , the controller  18  sets the reception frequency of the receiver  15  to 85 GHz. The frame transmitted at the transmission frequency 85 GHz from the relay device  1   b  is received by the antenna  14 , and converted to the intermediate frequency used by the baseband signal in the receiver  15 . The channel estimator  74  refers to the pilot signal included in a pilot portion  162  of the received frame, and estimates the channel state H 1b ( 85 ) between the relay device  1  and the relay device  1   b . The channel estimator  70  further obtains the inverse characteristic H 1b   −1 ( 85 ) of the channel state, and preserves the inverse characteristic H 1b   −1 ( 85 ) of the channel state in the storage  124 . The pre-equalizer  125  performs the pre-equalizing (pre-equalization) to a payload portion  163  of the frame by using the inverse characteristic H 1a   −1 ( 72 ) of the channel state with the relay device  1   a  in the first period before the time t 2 , which is preserved in the storage  122 . The pre-equalizing is performed before the transmission to the relay device  1   a . The combiner  76  combines a payload portion  164  pre-equalized by the pre-equalizer  125  and a new pilot portion  165  generated by the pilot signal generator  77  to configure a new frame. The controller  18  sets the transmission frequency of the transmitter  16  to 72 GHz at the time t 2 . Therefore, the transmitter  16  converts the baseband signal to the transmission frequency 72 GHz, and then transmits signals carrying the new frame from the antenna  17  to the relay device  1   a . The processing performed for the frame received by the relay device  1  in and after the third period and the fourth period is also similar to the processing in the second period described above. 
     As described above, by using the inverse characteristic of the channel state obtained from the channel state obtained when the reception is previously performed from the same wireless communication device, and performing the pre-equalizing before the transmission for the payload portion received this time, the high transmission characteristic can be obtained. For example, an effect that a channel capacity increases can be obtained. Thus, for the data carried by the radio waves relayed by the relay device, the efficient data transfer can be performed. 
     Fourth Embodiment 
       FIG. 16  is a functional block diagram of the relay device as the wireless communication device according to the fourth embodiment. The relay processor  22  according to the fourth embodiment includes the channel estimator  70 , the channel equalizer  71 , the storage  122 , the pre-equalizer  123 , a pilot signal generator  170 , a combiner  171 , a pilot signal generator  172 , and a combiner  173 . Similarly, the relay processor  23  includes the channel estimator  74 , the channel equalizer  75 , the storage  124 , the pre-equalizer  125 , a pilot signal generator  174 , a combiner  175 , a pilot signal generator  176 , and a combiner  177 . The antenna  10 , the receiver  11 , the transmitter  12 , the antenna  13 , the antenna  14 , the receiver  15 , the transmitter  16 , the antenna  17  and the controller  18  of the relay device according to the fourth embodiment have the configuration and the functions respectively equivalent to that of the antenna  10 , the receiver  11 , the transmitter  12 , the antenna  13 , the antenna  14 , the receiver  15 , the transmitter  16 , the antenna  17  and the controller  18  according to the first embodiment, respectively. In addition, the relay device according to the fourth embodiment also includes the local oscillator having the function equivalent to that of the local oscillator  20  and the local oscillator  21  of the relay device according to the first embodiment. 
       FIG. 17  is a diagram illustrating a format of the frame transmitted by the relay device according to the fourth embodiment. The frame according to the fourth embodiment includes the two pilot portions and the payload portion including the data main body. The two pilot portions are a pilot portion  1  including a first pilot signal and a pilot portion  2  including a second pilot signal, respectively. The case where the pilot portion  1  and the payload portion are pre-equalized and the pilot portion  2  is not pre-equalized is assumed. Note that the configuration may be such that the pilot portion  2  and the payload portion are pre-equalized and the pilot portion  1  is not pre-equalized. 
       FIG. 18A  and  FIG. 18B  are diagrams illustrating the processing performed to the frame by the relay device according to the fourth embodiment. The carrier frequency is switched respectively at the time t 1 , the time t 2 , the time t 3 , the time t 4 , and the time t 5 . The first period indicates the period between the time t 1  and the time t 2 . The second period indicates the period between the time t 2  and the time t 3 . The third period indicates the period between the time t 3  and the time t 4 . The fourth period indicates the period between the time t 4  and the time t 5 . In  FIG. 18A  and  FIG. 18B , for the respective periods, an outline of the processing performed to the frame received by the relay device  1  is illustrated in the direction from top to bottom. Hereinafter, the processing performed for the frame will be described along  FIG. 18A  and  FIG. 18B . Note that, in the figures, the pre-equalized pilot portion  1  is described as “Pilot1” and the pilot portion  1  before being pre-equalized is described as “Pilot1”. First, the processing for the first period will be described. 
     At the time t 1 , the controller  18  sets the reception frequency of the receiver  11  to 72 GHz. The frame transmitted at the transmission frequency 72 GHz from the relay device  1   a  is received by the antenna  10 , and converted to the intermediate frequency used by the baseband signal in the receiver  11 . The channel estimator  70  refers to the first pilot signal included in the pilot portion  1  ( 190 ) of the received frame, and obtains a channel state H′ 1a ( 72 ). Since the first pilot signal is pre-equalized, influence of channel variation from the channel state information used during the pre-equalizing is included in the H′ 1a ( 72 ). The channel estimator  70  further refers to the second pilot signal included in the pilot portion  2  ( 191 ), and estimates the channel state H 1a ( 72 ) between the relay device  1  and the relay device  1   a . Since the second pilot signal is not pre-equalized, the channel state H 1a ( 72 ) indicates the channel state when the frame is received this time. In addition, the channel estimator  70  obtains the inverse characteristic H 1a   −1 ( 72 ) of the channel state, and preserves the inverse characteristic H 1a   −1 ( 72 ) of the channel state in the storage  124 . The channel equalizer  71  obtains H′ 1a   −1 ( 72 ) which is the inverse characteristic of the above-described H′ 1a ( 72 ), and performs the equalization to a payload portion  192  using the H′ 1a   −1 ( 72 ). The combiner  171  combines a new pilot portion  1  generated by the pilot signal generator  170  and the channel-equalizeed payload portion. The pre-equalizer  123  performs the pre-equalizing to the channel-equalizeed payload portion and the new pilot portion  1 , using the inverse characteristic H 1b   −1 ( 82 ) of the channel state with the relay device  1   b  in the period before the time t 1 , which is preserved in the storage  122 . The pre-equalizing is performed before the transmission to the relay device  1   b . The combiner  173  configures a new frame by inserting the pilot portion  2  generated by the pilot signal generator  172  between the pre-equalized pilot portion  1  and the pre-equalized payload portion. Note that the inserted pilot portion  2  is not pre-equalized. The controller  18  sets the transmission frequency of the transmitter  12  to 82 GHz at the time t 1 . Therefore, the transmitter  12  converts the baseband signal to the transmission frequency 82 GHz, and then transmits signals carrying the new frame from the antenna  13  to the relay device  1   b.    
     In the same first period, the processing for the frame received by the receiver  15  will be also described. At the time t 1 , the controller  18  sets the reception frequency of the receiver  15  to 75 GHz. The frame transmitted at the transmission frequency 75 GHz from the relay device  1   b  is received by the antenna  14 , and converted to the intermediate frequency used by the baseband signal in the receiver  15 . The channel estimator  74  refers to the first pilot signal included in the pilot portion  1  ( 193 ) of the received frame, and obtains a channel state H′ 1b ( 75 ). The channel estimator  74  further refers to the second pilot signal included in the pilot portion  2  ( 194 ), and estimates the channel state H 1b ( 75 ). In addition, the channel estimator  74  obtains the inverse characteristic H 1b   −1 ( 75 ) of the channel state, and preserves the inverse characteristic H 1b   −1 ( 75 ) of the channel state in the storage  122 . The channel equalizer  71  obtains H′ 1b   −1 ( 75 ) which is the inverse characteristic of the above-described H′ 1b ( 75 ), and performs the equalization to a payload portion  195  using the H′ 1b   −1 ( 75 ). The combiner  175  combines a new pilot portion  1  generated by the pilot signal generator  174  and the channel-equalizeed payload portion. The pre-equalizer  125  performs the pre-equalizing to the channel-equalizeed payload portion and the new pilot portion  1 , using the inverse characteristic H 1a   −1 ( 85 ) of the channel state with the relay device  1   a  in the period before the time t 1 , which is preserved in the storage  124 . The pre-equalizing is performed before the transmission to the relay device  1   b . The combiner  177  configures a new frame by inserting the pilot portion  2  generated by the pilot signal generator  176  between the pre-equalized pilot portion  1  and the pre-equalized payload portion. The controller  18  sets the transmission frequency of the transmitter  16  to 85 GHz at the time t 1 . Therefore, the transmitter  16  converts the baseband signal to the transmission frequency 85 GHz, and then transmits signals carrying the new frame from the antenna  17  to the relay device  1   a.    
     Next, the processing in the second period will be described. At the time t 2 , the controller  18  sets the reception frequency of the receiver  11  to 85 GHz. The frame transmitted at the transmission frequency 85 GHz from the relay device  1   a  is received by the antenna  10 , and converted to the intermediate frequency used by the baseband signal in the receiver  11 . The channel estimator  70  refers to the first pilot signal included in the pilot portion  1  ( 196 ) of the received frame, and obtains a channel state H′ 1a ( 85 ). The channel estimator  70  further refers to the second pilot signal included in the pilot portion  2  ( 197 ), and estimates the channel state H 1a ( 85 ) between the relay device  1  and the relay device  1   a . In addition, the channel estimator  70  obtains the inverse characteristic H 1a   −1 ( 85 ) of the channel state, and preserves the inverse characteristic H 1a   −1 ( 85 ) of the channel state in the storage  124 . The channel equalizer  71  obtains H′ 1a   −1 ( 85 ) which is the inverse characteristic of the above-described H′ 1a ( 85 ), and performs the equalization to a payload portion  198  using the H′ 1a   −1 ( 85 ). The combiner  171  combines the new pilot portion  1  generated by the pilot signal generator  170  and the channel-equalizeed payload portion. The pre-equalizer  123  performs the pre-equalizing to the channel-equalizeed payload portion and the new pilot portion  1 , using the inverse characteristic H 1b   −1 ( 75 ) of the channel state with the relay device  1   b  in the first period before the time t 2 , which is preserved in the storage  122 . The pre-equalizing is performed before the transmission to the relay device  1   b . The combiner  173  configures a new frame by inserting the pilot portion  2  generated by the pilot signal generator  172  between the pre-equalized pilot portion  1  and the pre-equalized payload portion. The controller  18  sets the transmission frequency of the transmitter  12  to 75 GHz at the time t 2 . Therefore, the transmitter  12  converts the baseband signal to the transmission frequency 75 GHz, and then transmits signals carrying the new frame from the antenna  13  to the relay device  1   b.    
     In the same second period, the processing for the frame received by the receiver  15  will be also described. At the time t 2 , the controller  18  sets the reception frequency of the receiver  15  to 82 GHz. The frame transmitted at the transmission frequency 82 GHz from the relay device  1   b  is received by the antenna  14 , and converted to the intermediate frequency used by the baseband signal in the receiver  15 . The channel estimator  74  refers to the first pilot signal included in the pilot portion  1  ( 199 ) of the received frame, and obtains a channel state H′ 1b ( 82 ). The channel estimator  74  further refers to the second pilot signal included in the pilot portion  2  ( 200 ), and estimates the channel state H 1b ( 82 ) between the relay device  1  and the relay device  1   b . In addition, the channel estimator  74  obtains the inverse characteristic H 1b   −1 ( 82 ) of the channel state, and preserves the inverse characteristic H 1b   −1 ( 82 ) of the channel state in the storage  122 . The channel equalizer  71  obtains H′ 1b   −1 ( 82 ) which is the inverse characteristic of the above-described H′ 1b ( 82 ), and performs the equalization to a payload portion  201  using the H′ 1b   −1 ( 82 ). The combiner  175  combines the new pilot portion  1  generated by the pilot signal generator  174  and the channel-equalizeed payload portion. The pre-equalizer  125  performs the pre-equalizing to the channel-equalizeed payload portion and the new pilot portion  1 , using the inverse characteristic H 1a   −1 ( 72 ) of the channel state with the relay device  1   a  in the first period before the time t 2 , which is preserved in the storage  124 . The pre-equalizing is performed before the transmission to the relay device  1   b . The combiner  177  configures a new frame by inserting the pilot portion  2  generated by the pilot signal generator  176  between the pre-equalized pilot portion  1  and the pre-equalized payload portion. The controller  18  sets the transmission frequency of the transmitter  16  to 72 GHz at the time t 2 . Therefore, the transmitter  16  converts the baseband signal to the transmission frequency 72 GHz, and then transmits signals carrying the new frame from the antenna  17  to the relay device  1   a.    
     As described above, the channel state is calculated by the pre-equalized pilot signal, and the inverse characteristic is obtained based on the calculated channel state. Then, the distortion of the signal is equalizeed for the similarly pre-equalized payload portion, using the information of the inverse characteristic. Further, the pilot signal and the equalizeed payload portion are pre-equalized using the inverse characteristic of the channel state obtained from the channel state obtained when the reception is previously performed from the same wireless communication device. Thus, the transmission characteristic of the relay can be further improved. For example, for the data to be carried, the effect that the SER (Symbol Error Rate) is reduced and the channel capacity increases simultaneously can be obtained. Thus, for the data carried by the radio waves relayed by the relay device, the efficient data transfer can be performed. 
     Fifth Embodiment 
     A functional block diagram of the relay device as the wireless communication device according to the fifth embodiment is the same  FIG. 16  as the fourth embodiment. 
       FIG. 19  is a diagram illustrating a format of the frame transmitted by the relay device according to the fifth embodiment. The frame according to the fifth embodiment includes the pilot portion  1  including the first pilot signal, the payload portion including the data, and a pilot portion  3  including a third pilot signal. By arranging the pilot portion  3  at the end of the frame, a newer condition of the channel can be reflected so that estimation accuracy of the channel state can be improved when the pre-equalizing is performed compared to the case of arranging the pilot portion  3  at the head of the frame. 
       FIG. 20A  and  FIG. 20B  are diagrams illustrating the processing performed to the frame by the relay device according to the fifth embodiment. The carrier frequency is switched respectively at the time t 1 , the time t 2 , the time t 3 , the time t 4 , and the time t 5 . The first period indicates the period between the time t 1  and the time t 2 . The second period indicates the period between the time t 2  and the time t 3 . The third period indicates the period between the time t 3  and the time t 4 . The fourth period indicates the period between the time t 4  and the time t 5 . In  FIG. 20A  and  FIG. 20B , for the respective periods, an outline of the processing performed to the frame received by the relay device  1  is illustrated in the direction from top to bottom. Hereinafter, the processing performed for the frame will be described along  FIG. 20A  and  FIG. 20B . Note that, in the figures, the pre-equalized pilot portion  1  is described as “Pilot1′” and the pilot portion  1  before being pre-equalized is described as “Pilot1”. 
     First, the processing for the first period will be described. At the time t 1 , the controller  18  sets the reception frequency of the receiver  11  to 72 GHz. The frame transmitted at the transmission frequency 72 GHz from the relay device  1   a  is received by the antenna  10 , and converted to the intermediate frequency used by the baseband signal in the receiver  11 . The channel estimator  70  refers to the first pilot signal included in the pilot portion  1  ( 210 ) of the received frame, and obtains the channel state H′ 1a ( 72 ). The channel estimator  70  further refers to the third pilot signal included in the pilot portion  3  ( 211 ), and estimates the channel state H 1a ( 72 ) between the relay device  1  and the relay device  1   a . In addition, the channel estimator  70  obtains the inverse characteristic H 1a   −1 ( 72 ) of the channel state, and preserves the inverse characteristic H 1a   −1 ( 72 ) of the channel state in the storage  124 . The channel equalizer  71  obtains H′ 1a   −1 ( 72 ) which is the inverse characteristic of the above-described H′ 1a ( 72 ), and performs the equalization to a payload portion  212  using the H′ 1a   −1 ( 72 ). The combiner  171  combines the new pilot portion  1  generated by the pilot signal generator  170  and the channel-equalizeed payload portion. The pre-equalizer  123  performs the pre-equalizing to the channel-equalizeed payload portion and the new pilot portion  1 , using the inverse characteristic H 1b   −1 ( 82 ) of the channel state with the relay device  1   b  in the period before the time t 1 , which is preserved in the storage  122 . The pre-equalizing is performed before the transmission to the relay device  1   b.    
     The combiner  173  configures a new frame by combining the pilot portion  3  generated by the pilot signal generator  172  after the pre-equalized pilot portion  1  and the pre-equalized payload portion. The controller  18  sets the transmission frequency of the transmitter  12  to 82 GHz at the time t 1 . Therefore, the transmitter  12  converts the baseband signal to the transmission frequency 82 GHz, and then transmits signals carrying the new frame from the antenna  13  to the relay device  1   b.    
     In the same first period, the processing for the frame received by the receiver  15  will be also described. At the time t 1 , the controller  18  sets the reception frequency of the receiver  15  to 75 GHz. The frame transmitted at the transmission frequency 75 GHz from the relay device  1   b  is received by the antenna  14 , and converted to the intermediate frequency used by the baseband signal in the receiver  15 . The channel estimator  74  refers to the first pilot signal included in the pilot portion  1  ( 213 ) of the received frame, and obtains the channel state H′ 1b ( 75 ). The channel estimator  74  further refers to the third pilot signal included in the pilot portion  3  ( 214 ), and estimates the channel state H 1b ( 75 ). In addition, the channel estimator  74  obtains the inverse characteristic H 1b   −1 ( 75 ) of the channel state, and preserves the inverse characteristic H 1b   −1 ( 75 ) of the channel state in the storage  122 . The channel equalizer  71  obtains the H′ 1b   −1 ( 75 ) which is the inverse characteristic of the above-described H′ 1b ( 75 ), and performs the equalization to a payload portion  215  using the H′ 1b   −1 ( 75 ). The combiner  175  combines the new pilot portion  1  generated by the pilot signal generator  174  and the channel-equalizeed payload portion. The pre-equalizer  125  performs the pre-equalizing to the channel-equalizeed payload portion and the new pilot portion  1 , using the inverse characteristic H 1a   −1 ( 85 ) of the channel state with the relay device  1   a  in the period before the time t 1 , which is preserved in the storage  124 . The pre-equalizing is performed before the transmission to the relay device  1   b . The combiner  177  configures a new frame by combining the pilot portion  3  generated by the pilot signal generator  176  after the pre-equalized pilot portion  1  and the pre-equalized payload portion. The controller  18  sets the transmission frequency of the transmitter  16  to 85 GHz at the time t 1 . Therefore, the transmitter  16  converts the baseband signal to the transmission frequency 85 GHz, and then transmits signals carrying the new frame from the antenna  17  to the relay device  1   a.    
     Next, the processing in the second period will be described. At the time t 2 , the controller  18  sets the reception frequency of the receiver  11  to 85 GHz. The frame transmitted at the transmission frequency 85 GHz from the relay device  1   a  is received by the antenna  10 , and converted to the intermediate frequency used by the baseband signal in the receiver  11 . The channel estimator  70  refers to the first pilot signal included in the pilot portion  1  ( 216 ) of the received frame, and obtains the channel state H′ 1a ( 85 ). The channel estimator  70  further refers to the third pilot signal included in the pilot portion  3  ( 217 ), and estimates the channel state H 1a ( 85 ). In addition, the channel estimator  70  obtains the inverse characteristic H 1a   −1 ( 85 ) of the channel state, and preserves the inverse characteristic H 1a   −1 ( 85 ) of the channel state in the storage  124 . The channel equalizer  71  obtains H′ 1a   −1 ( 85 ) which is the inverse characteristic of the above-described H′ 1a ( 85 ), and performs the equalization to a payload portion  215  using the H′ 1a   −1 ( 85 ). The combiner  171  combines the new pilot portion  1  generated by the pilot signal generator  170  and the channel-equalizeed payload portion. The pre-equalizer  123  performs the pre-equalizing to the channel-equalizeed payload portion and the new pilot portion  1 , using the inverse characteristic H 1b   −1 ( 75 ) of the channel state with the relay device  1   b  in the first period before the time t 2 , which is preserved in the storage  122 . The pre-equalizing is performed before the transmission to the relay device  1   b . The combiner  173  configures a new frame by combining the pilot portion  3  generated by the pilot signal generator  172  to the pre-equalized pilot portion  1  and the pre-equalizeed payload portion. The controller  18  sets the transmission frequency of the transmitter  12  to 75 GHz at the time t 2 . Therefore, the transmitter  12  converts the baseband signal to the transmission frequency 75 GHz, and then transmits signals carrying the new frame from the antenna  13  to the relay device  1   b.    
     In the same second period, the processing for the frame received by the receiver  15  will be also described. At the time t 2 , the controller  18  sets the reception frequency of the receiver  15  to 82 GHz. The frame transmitted at the transmission frequency 82 GHz from the relay device  1   b  is received by the antenna  14 , and converted to the intermediate frequency used by the baseband signal in the receiver  15 . The channel estimator  74  refers to the first pilot signal included in the pilot portion  1  ( 219 ) of the received frame, and obtains the channel state H′ 1b ( 82 ). The channel estimator  74  further refers to the third pilot signal included in the pilot portion  3  ( 220 ), and estimates the channel state H 1b ( 82 ) between the relay device  1  and the relay device  1   b . In addition, the channel estimator  74  obtains the inverse characteristic H 1b   −1 ( 82 ) of the channel state, and preserves the inverse characteristic H 1b   −1 ( 82 ) of the channel state in the storage  122 . The channel equalizer  71  obtains H′ 1b   −1 ( 82 ) which is the inverse characteristic of the above-described H′ 1b ( 82 ), and performs the equalization to a payload portion  221  using the H′ 1b   −1 ( 82 ). The combiner  175  combines the new pilot portion  1  generated by the pilot signal generator  174  and the channel-equalizeed payload portion. The pre-equalizer  125  performs the pre-equalizing to the channel-equalizeed payload portion and the new pilot portion  1 , using the inverse characteristic H 1a   −1 ( 72 ) of the channel state with the relay device  1   a  in the first period before the time t 2 , which is preserved in the storage  124 . The pre-equalizing is performed before the transmission to the relay device  1   b . The combiner  177  configures a new frame by combining the pilot portion  3  generated by the pilot signal generator  176  to the pre-equalized pilot portion  1  and the pre-equalized payload portion. The controller  18  sets the transmission frequency of the transmitter  16  to 72 GHz at the time t 2 . Therefore, the transmitter  16  converts the baseband signal to the transmission frequency 72 GHz, and then transmits signals carrying the new frame from the antenna  17  to the relay device  1   a.    
     As described above, by arranging the pilot portion (pilot portion  3 ) at the end of the frame, the pre-equalizing in consideration of the condition of the channel at a closer point of time is made possible. Thus, the effect of the fourth embodiment can be improved more. 
     Sixth Embodiment 
       FIG. 21  is a functional block diagram of the relay device as the wireless communication device according to the sixth embodiment. The relay processor  22  according to the sixth embodiment includes the channel estimator  70 , the channel equalizer  71 , the storage  122 , the pre-equalizer  123 , the pilot signal generator  170 , the combiner  171 , the pilot signal generator  172 , the combiner  173 , and a multiplexer  270 . Similarly, the relay processor  23  includes the channel estimator  74 , the channel equalizer  75 , the storage  124 , the pre-equalizer  125 , the pilot signal generator  174 , the combiner  175 , the pilot signal generator  176 , the combiner  177 , and a demultiplexer  272 . The relay device according to the sixth embodiment further includes a modulator  271  provided with an input terminal, and a demodulator  273  provided with an output terminal. The modulator  271  is electrically connected to the multiplexer  270 , and the demodulator  273  is electrically connected to the demodulator  273 , respectively. The antenna  10 , the receiver  11 , the transmitter  12 , the antenna  13 , the antenna  14 , the receiver  15 , the transmitter  16 , the antenna  17  and the controller  18  of the relay device according to the sixth embodiment have the functions respectively equivalent to that of the antenna  10 , the receiver  11 , the transmitter  12 , the antenna  13 , the antenna  14 , the receiver  15 , the transmitter  16 , the antenna  17  and the controller  18  according to the first embodiment, respectively. In addition, the relay device according to the sixth embodiment also includes the local oscillator having the function equivalent to that of the local oscillator  20  and the local oscillator  21  of the relay device according to the first embodiment. At least one of the modulator  271  and the demodulator  273  may be realized by software by making a processor such as a CPU execute a program, may be realized by an exclusive hardware circuit or a programmable circuit, or may be realized by both. 
       FIG. 22  illustrates an example of the wireless relay network according to the present embodiment. The wireless relay network includes the relay device  1  and a base station  280 . The relay device  1  and the base station  280  are supported at an upper part of a region inside a cell  283  by a support member  285 . The base station  280  can transmit and receive the data to/from a terminal station  284  positioned inside the cell  283 . The input terminal of the relay device  1  is connected to an uplink processor  281  of the base station  280 . The output terminal of the relay device  1  is connected to a downlink processor  282  of the base station  280 . An uplink signal outputted from the uplink processor  281  of the base station  280  is inputted from the input terminal of the relay device  1  to the relay device  1 . The uplink signal is modulated in the modulator  271  in  FIG. 21 , and then multiplexed to a relay signal in the multiplexer  270 . At least one of the uplink processor  281  and the downlink processor  282  may be realized by software by making a processor such as a CPU execute a program, may be realized by an exclusive hardware circuit or a programmable circuit, or may be realized by both. 
     On the other hand, for a downlink, a range pertinent to a downlink signal is demultiplexed or duplicated in the demultiplexer  272  in  FIG. 21  and delivered to the demodulator  273 . The demodulator  273  demodulates the signal, and a demodulated downlink signal is outputted from the output terminal. The downlink signal is inputted to the downlink processor  282  of the base station  280 . The downlink processor  282  executes downlink processing, and transmits a downlink signal to the terminal station  284 . By connecting the relay device and the base station in this way, after multiplexing both of the uplink signal and the downlink signal of the plurality of base stations, the data can be relayed to a remote location outside the range of the cell  283  relating to the base station  280 . 
     Seventh Embodiment 
       FIG. 23  is a functional block diagram of the relay device as the wireless communication device according to the seventh embodiment. The configuration of the relay processor  22  according to the seventh embodiment is similar to that of the sixth embodiment. The relay processor  23  is configured similarly to the relay processor  23  of the sixth embodiment, except for a point that a synchronization acquirer  290  is present. The antenna  10 , the receiver  11 , the transmitter  12 , the antenna  13 , the antenna  14 , the receiver  15 , the transmitter  16 , the antenna  17 , the controller  18 , the modulator  271  and the demodulator  273  of the relay device according to the seventh embodiment have the functions respectively equivalent to that of the antenna  10 , the receiver  11 , the transmitter  12 , the antenna  13 , the antenna  14 , the receiver  15 , the transmitter  16 , the antenna  17  and the controller  18  according to the first embodiment, and the modulator  271  and the demodulator  273  according to the sixth embodiment, respectively. In addition, the relay device according to the seventh embodiment also includes the local oscillator having the function equivalent to that of the local oscillator  20  and the local oscillator  21  of the relay device according to the first embodiment. 
     By the synchronization acquirer  290  in the seventh embodiment, the carrier frequency changeover timing of the relay device  1  can be synchronized with the other relay device or the wireless communication device. Specific processing of an operation of the synchronization acquirer  290  will be described below. The synchronization acquirer  290  refers to the pilot portion arranged at the head of the frame, acquires the synchronization using the processing of serial search or matched filtering or the like, and detects a frame boundary. The frame boundary detected by the synchronization acquirer  290  is notified to the controller  18 . When a frame boundary detection notice is received, the controller  18  performs setting change to the respective parts of the local oscillator  20 , the local oscillator  21 , the receiver  11 , the transmitter  12 , the receiver  15  and the transmitter  16 , and executes the changeover processing of the transmission frequency and the reception frequency. The carrier frequency changeover target may be either one of the transmission frequency and the reception frequency, or may be both of the transmission frequency and the reception frequency. The configuration and the method of the seventh embodiment are an example, and other configurations and methods may be used. For example, the method of successively receiving a specific frame for two or more times and then executing the changeover processing of the transmission frequency and the reception frequency may be used. 
     While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Indeed, the novel embodiments described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the embodiments described herein may be made without departing from the spirit of the inventions. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the inventions.