Patent Publication Number: US-2022217721-A1

Title: Wireless communication device and method

Description:
TECHNICAL FIELD 
     The present technology relates to a wireless communication device and method, and more particularly, to a wireless communication device and method that enable efficient data retransmission in communication using a plurality of frequency bands. 
     BACKGROUND ART 
     As a carrier aggregation technology or a channel bonding technology, there has been a technology for transmitting data using a plurality of frequency bands (bands). In that field, access control is performed on each frequency band, so that a series of data transmission can be performed. 
     First, which data should be transmitted through which frequency band is determined prior to data transmission. After the frequency band through which transmission is to be performed is determined, data is stored into the transmission buffers of the respective frequency bands through the respective frequency bands, and sequence numbers are set and managed for each frequency band (see Patent Document 1). 
     As a result, a receipt acknowledgement is sent through the frequency bands after the data transmission, and thus, the conventional access control technology can be used as it is. 
     CITATION LIST 
     Patent Document 
     Patent Document 1: Japanese Patent Application Laid-Open No. 2017-139595 
     SUMMARY OF THE INVENTION 
     Problems to be Solved by the Invention 
     As the amount of data transmission has increased these days, the amount of information that is used by applications has also increased, and a technology for transferring data using a plurality of frequency bands in combination is now being used. 
     By the technology described above, however, the sequence numbers are set and managed for each frequency band. Therefore, in a case where the radio wave propagation environment deteriorates in a specific frequency band, for example, it is difficult to receive a receipt acknowledgement and perform data retransmission using some other frequency band. 
     The present technology has been made in view of such circumstances, and is to enable efficient data retransmission in communication using a plurality of frequency bands. 
     Solutions to Problems 
     A wireless communication device according to one aspect of the present technology includes: a sequence management unit that sets a series of sequence numbers to data to be transmitted to one transmission destination through a plurality of frequency bands; a wireless transmission unit that transmits the data through the plurality of frequency bands; and a communication control unit that causes reception of receipt acknowledgment information through the frequency band in which the transmission of the data has been completed first among the plurality of frequency bands, the receipt acknowledgment information indicating a receipt acknowledgment regarding the data transmitted through the plurality of frequency bands. 
     A wireless communication device according to another aspect of the present technology includes: a wireless reception unit that receives data transmitted to one transmission destination through a plurality of frequency bands; a sequence management unit that manages a series of sequence numbers that have been set to the data received through the plurality of frequency bands; and a communication control unit that causes transmission of receipt acknowledgment information through the frequency band in which the reception of the data has been completed the earliest, the receipt acknowledgment information indicating a receipt acknowledgment regarding the data received through the plurality of frequency bands. 
     In one aspect of the present technology, a series of sequence numbers are set to the data to be transmitted to one transmission destination through a plurality of frequency bands, and the data is transmitted through the plurality of frequency bands. Receipt acknowledgment information indicating a receipt acknowledgment regarding the data transmitted through the plurality of frequency bands is received through the frequency band in which the transmission of the data has been completed first among the plurality of frequency bands. 
     In another aspect of the present technology, data transmitted to one transmission destination through a plurality of frequency bands is received, and a series of sequence numbers set to the data received through the plurality of frequency bands are managed. Receipt acknowledgment information indicating a receipt acknowledgment regarding the data received through the plurality of frequency bands is transmitted through the frequency band in which the reception of the data has been completed the earliest. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a diagram showing an example configuration of a wireless communication system according to an embodiment of the present technology. 
         FIG. 2  is a diagram showing the configurations of conventional transmission buffers. 
         FIG. 3  is a diagram showing a sequence of conventional data transmission. 
         FIG. 4  is a diagram showing an example of sequence number setting to data by the wireless communication system. 
         FIG. 5  is a chart showing a sequence of data transmission in the wireless communication system. 
         FIG. 6  is a chart showing another sequence of data transmission in the wireless communication system. 
         FIG. 7  is a block diagram showing an example configuration of a communication device. 
         FIG. 8  is a block diagram showing an example configuration of a wireless communication module. 
         FIG. 9  is a chart showing a communication sequence in the wireless communication system. 
         FIG. 10  is a diagram showing an example frame configuration according to the present technology. 
         FIG. 11  is a diagram showing an example configuration of a priority block ACK request frame. 
         FIG. 12  is a diagram showing an example configuration of a priority block ACK frame. 
         FIG. 13  is a diagram showing an example configuration of a priority sequence information element. 
         FIG. 14  is a flowchart for explaining a data transmission process to be performed by a communication device on the transmission side. 
         FIG. 15  is a flowchart for explaining the data transmission process to be performed by the communication device on the transmission side, continuing from  FIG. 14 . 
         FIG. 16  is a flowchart showing a data reception process to be performed by a communication device on the reception side. 
         FIG. 17  is a block diagram showing an example configuration of a computer. 
     
    
    
     MODES FOR CARRYING OUT THE INVENTION 
     The following is a description of modes for carrying out the present technology. Explanation will be made in the following order. 
     1. Wireless communication system 
     2. Configuration of a communication device 
     3. Operation of the wireless communication system 
     4. Frame configurations 
     5. Operations of communication devices 
     6. Other aspects 
     &lt;&lt;1. Wireless Communication System&gt;&gt; 
     &lt;Configuration of a Wireless Communication System&gt; 
       FIG. 1  is a diagram showing an example configuration of a wireless communication system according to an embodiment of the present technology. 
     The wireless communication system in  FIG. 1  includes communication devices  11 - 1  to  11 - 4 . The communication devices  11 - 1  to  11 - 4  are formed with smartphones, portable telephones, mobile terminals, personal computers, or the like. Note that, in a case where there is no particular need to distinguish the communication devices  11 - 1  to  11 - 4  from one another, the communication devices  11 - 1  to  11 - 4  will be referred to as the communication devices  11  in the description below. 
     In  FIG. 1 , circles with broken lines centered around circles representing the respective communication devices  11 - 1  to  11 - 4  indicate the effective wireless communication ranges of the respective communication devices  11 - 1  to  11 - 4 . 
     The communication devices  11 - 2  and  11 - 3  exist in the effective wireless communication range of the communication device  11 - 1 . The communication device  11 - 1  can transmit and receive data to and from at least one of the communication devices  11 - 2  and  11 - 3  by wireless communication. 
     The communication devices  11 - 1  and  11 - 4  exist in the effective wireless communication range of the communication device  11 - 2 . The communication device  11 - 2  can transmit and receive data to and from at least one of the communication devices  11 - 1  and  11 - 4  by wireless communication. 
     As indicated by a thick arrow, the communication device  11 - 1  transmits data through a plurality of frequency bands to the communication device  11 - 2  existing in the effective wireless communication range thereof. At that time, the communication device  11 - 1  sets a series of sequence numbers to the data to be transmitted through the plurality of frequency bands to the communication device  11 - 2  that is a transmission destination. The communication device  11 - 1  also causes reception of a block ACK that is an acknowledgment of receipt of the data transmitted through the plurality of frequency bands, through the frequency band in which the data transmission has been completed first. 
     The communication device  11 - 2  receives the data transmitted to one transmission destination through the plurality of frequency bands. The communication device  11 - 2  then manages the series of sequence numbers set for the data received through the plurality of frequency bands, and transmits the block ACK that is an acknowledgement of receipt of the data received through the plurality of frequency bands, through the frequency band in which the data reception has been completed first. 
     In this manner, receipt of data can be efficiently acknowledged in communication using a plurality of frequency bands. Thus, data retransmission can be efficiently performed. 
     &lt;Outline of Conventional Technologies&gt; 
     Meanwhile, as the amount of data transmission has increased these days, the amount of information that is used by applications has also increased, and a technology for transmitting data using a plurality of frequency bands in combination is now being used. 
     Among wireless communication standards compliant with IEEE 802.11 as a wireless LAN system, standards using a 2.4 GHz band, a 5 GHz band, a 920 MHz band, and a 60 GHz band are defined, and it is possible to transmit data by simultaneously operating a plurality of these frequency bands. 
     In a case where a plurality of pieces of data is transmitted through a plurality of frequency bands, the frequency bands are operated independently of one another. Therefore, the sequence numbers are managed independently for each frequency band, and a receipt acknowledgment is also recognized only with the sequence numbers. 
     As a result, a sequence number that has been set once is confused with a sequence number for another frequency band, and therefore, the frequency bands need to be closed when an acknowledgement of receipt of these pieces of data is transmitted. 
     Further, by an access control method according to Enhanced Distributed Channel Access (EDCA) defined in the IEEE 802.11 standard specification, a technology has been used for setting differences in transmission standby time, and preferentially transmitting data having the higher priority levels, in accordance with the type and the attribute information (Access Category (AC)) of the data to be transmitted. By EDCA, a sequence number is also set for each Transmit Identifier (TID). 
     &lt;Configurations of Conventional Transmission Buffers&gt; 
       FIG. 2  is a diagram showing the configurations of conventional transmission buffers. 
     In the case of  FIG. 2 , a transmission buffer is formed for each priority level, and the transmission buffer at each priority level stores data as described below, according to the categories defined in EDCA mentioned above. The categories include Voice, Video, Best Effort, and Back Ground in descending order of priority levels. 
     Note that, although  FIG. 2  shows an example in which the transmission buffers are formed in accordance with four priority levels for convenience, the number of priority levels may be five or larger, or may be three or smaller. 
     A transmission buffer # 1  of a priority level # 1  has TID # 1  allotted as the TID, and stores data (AC VO (Voice)) of Voice, which is a category with the highest priority level. In the data stored in the transmission buffer # 1 , sequence numbers P:1 D:1, P:1 D:2, P:1 D:3, and P:1 D:4 are sequentially set as TID # 1 . Note that P:1 D:1 represents Data with the first data order and the first Priority (priority level). 
     A transmission buffer # 2  of a priority level # 2  has TID # 2  allotted as the TID, and stores video data (AC VI (Video)) of Video, which is a category with the second highest priority level. In the data stored in the transmission buffer # 2 , sequence numbers P:2 D:1, P:2 D:2, P:2 D:3, and P:2 D:4 are sequentially set as TID # 2 . 
     A transmission buffer # 3  of a priority level # 3  has TID # 3  allotted as the TID, and stores data (AC BE (Best Effort)) of Best Effort, which is a category with the second lowest priority level. In the data stored in the transmission buffer # 3 , sequence numbers P:3 D:1, P:3 D:2, P:3 D:3, and P:3 D:4 are sequentially set as TID # 3 . 
     A transmission buffer # 4  of a priority level # 4  has TID # 4  allotted as the TID, and stores data (AC BG (Back Ground)) of Back Ground, which is a category with the lowest priority level. In the data stored in the transmission buffer # 4 , sequence numbers P:4 D:1, P:4 D:2, P:4 D:3, and P:4 D:4 are sequentially set as TID # 4 . 
     Since sequence numbers are set for each TID, the same sequence number exists for each TID in a case where retransmission control is performed in a plurality of frequency bands. Further, in a case where a block ACK indicating an acknowledgment of data receipt is requested, for example, there is the need to set a bitmap for each TID. Since sequence numbers are set for each TID in conventional cases as described above, sequence management is complicated in a case where these pieces of data are transmitted through a plurality of frequency bands. 
     &lt;Conventional Transmission Sequence&gt; 
       FIG. 3  is a diagram showing a conventional transmission sequence. 
       FIG. 3  shows a transmission sequence in each of the frequency bands of Band  1 , Band  2 , and Band  3  in this order from the top. In this transmission sequence, priority levels based on conventional sequence numbers are used. Data transmitted from a communication device on the transmission side is shown above the line indicating the sequence in each frequency band. Data transmitted from a communication device on the reception side is shown below the line indicating the sequence in each frequency band. The abscissa axis direction indicates the flow of operation over time. 
     Note that, although  FIG. 3  shows an example in which three frequency bands (Bands) are used, the number of frequency bands to be used may be four or larger, or may be two or smaller. 
     In the communication device on the transmission side, data is buffered according to the priority levels shown in  FIG. 2 . At time t 1 , Band  1  becomes available. In a case where any signal from another communication device has not been detected during a predetermined transmission standby time w in Band  1 , an access right is acquired, and the communication device on the transmission side transmits first data (P:1 D:1) of the highest priority level at time t 1 +w through Band  1 . 
     After that, the communication device on the transmission side transmits data of the same priority level as (P:1 D:1) in the order of (P:1 D:2, P:1 D:3, and P:1 D:4) through Band  1 , which is the frequency band that has become available first. P:1 D:1 to P:1 D:4 are an aggregation MAC protocol data unit (A-MPDU) that is aggregated and includes the respective MAC protocol data units (MPDUs) of P:1 D:1, P:1 D:2, P:1 D:3, and P:1 D:4. Note that the respective MPDUs of P:1 D:1, P:1 D:2, P:1 D:3, and P:1 D:4 are the respective data pieces of a data group of the same priority level. 
     Next, at time t 2 , Band  3  becomes available. In a case where any signal from another communication device has not been detected during the predetermined transmission standby time w in Band  3 , an access right is acquired, and the communication device on the transmission side transmits first data (P:2 D:1) of the second highest priority level at time t 2 +w through Band  3 . 
     After that, the communication device on the transmission side transmits data of the same priority level as (P:2 D:1) in the order of (P:2 D:2, P:2 D:3, and P:2 D:4) through Band  3 , which is the frequency band that has become available second. 
     Further, at time t 3 , Band  2  becomes available. In a case where any signal from another communication device has not been detected during the predetermined transmission standby time w in Band  2 , an access right is acquired, and the communication device on the transmission side transmits first data (P:3 D:1) of the low priority level at time t 3 +w through Band  2 . 
     After that, the communication device on the transmission side transmits data of the same priority level as (P:3 D:1) in the order of (P:3 D:2, P:3 D:3, and P:3 D:4) through Band  2 , which is the frequency band that has become available third. 
     Here, regarding the end time of data transmission, in Band  2 , which is a frequency band for transmission at a high transmission rate (MCS), the data transmission is ended earlier than in Band  1  and Band  3 , which are the other frequency bands, though the transmission was started the latest in Band  2 , as shown in  FIG. 3 . 
     As described above, not only the transmission start time varies, but also the available transmission rate (MCS) varies depending on the states of the transmission paths in the respective frequency bands, and each data piece is formed with a variable length. Therefore, the end time of data transmission is not always the same. 
     Further, in  FIG. 3 , Error seen in some pieces of data to be transmitted indicates that an error has occurred at the time of reception in the communication device on the reception side, and the data has not been correctly received. In Band  1 , the first and last data (P:1 D:1, and P:1 D:4) have not been correctly received. In Band  2 , intermediate data (P:3 D:3) has not been correctly received. In Band  3 , intermediate data (P:2 D:2) has not been correctly received. 
     Further, the communication device on the reception side transmits a block ACK (BA), after data transmission through each frequency band. BA is information indicating an acknowledgment of data receipt by the communication device on the reception side. The communication device on the transmission side that has received the BA can retransmit the data that has not been received through each frequency band. 
     In other words, in a case where some of the transmitted data has been correctly received after the end of the data transmission through Band  2 , which is the frequency band in which the data transmission has been completed the earliest, the communication device on the reception side transmits the BA at time t 4 . The communication device on the transmission side that has received the BA retransmits data (P:3 D:3) at time t 5 . In a case where the data retransmission has ended, and the retransmitted data has been correctly received, the communication device on the reception side transmits the BA through Band  2  at time t 8 . 
     Next, in a case where some of the transmitted data has been correctly received after the end of the data transmission through Band  1 , which is a frequency band in which the data transmission has been completed, the communication device on the reception side transmits the BA at time t 6 . The communication device on the transmission side that has received the BA retransmits data (P:1 D:1) at time t 7 , and retransmits data (P:1 D:4) at time t 9 . In a case where the data retransmission has ended, and the retransmitted data has been correctly received, the communication device on the reception side transmits the BA through Band  1  at time t 10 . 
     In a case where some of the transmitted data has been correctly received after the end of the data transmission through Band  3 , which is the frequency band in which the data transmission has been completed at the same timing as Band  1 , the communication device on the reception side transmits the BA at time t 6 . The communication device on the transmission side that has received the BA retransmits data (P:2 D:2) at time t 8 . In a case where the data retransmission has ended, and the retransmitted data has been correctly received, the communication device on the reception side transmits the BA through Band  3  at time t 9 . 
     In the above manner, the sequence of the conventional data transmission is completed. 
     In the case of the data transmission sequence shown in  FIG. 3 , transmission of all the data is completed the earliest in Band  2 , which is the frequency band in which transmission is started the latest, and transmission of data is completed the latest in Band  1 , which is the frequency band in which transmission is started the earliest. 
     As described above, in a conventional case, a sequence number is set for each TID, and data is transmitted TID by TID in each frequency band. Therefore, in a case where the radio wave propagation environment deteriorates in a specific frequency band, it is difficult for the communication device on the transmission side to receive an acknowledgement of receipt and retransmit data using another frequency band. 
     That is, a sequence number is set for each TID, and data is transmitted TID by TID in each frequency band. Therefore, the communication device on the transmission side can retransmit data only through the frequency band in which the data has been once transmitted. 
     In a case where the radio wave propagation environment deteriorates in a specific frequency band, it is difficult for the communication device on the transmission side to receive an acknowledgement of receipt and retransmit data using another frequency band. 
     Therefore, even if the communication device on the transmission side transmits data having a high priority level through the frequency band that has acquired the access right first, it takes time to acknowledge receipt, and it takes a long time to complete retransmission. 
     Further, depending on the state of the transmission path in the frequency band that has become available for use and acquired the access right, an encoding method (MCS) with a low transmission rate is used, and it takes time for the communication device on the transmission side to complete data transmission. 
     That is, even if data is transmitted through the frequency band that become available first among a plurality of frequency bands, there is a possibility that data transmission through a frequency band that becomes available later will be completed earlier. 
     In such a case, it is possible to control the transmission standby time, but controlling the transmission standby time will hinder data transmission having priority levels set thereto. This is because, even though the user has set priority levels and stores data into a buffer, the order in which the data is eventually delivered to the reception side will change. 
     Therefore, in the present technology, a communication device sets a series of sequence numbers to data to be transmitted to one transmission destination through a plurality of frequency bands, transmits the data through the plurality of frequency bands, and causes reception of information through the frequency band in which the data transmission has been completed first, the information indicating an acknowledgment of receipt of the data transmitted through the plurality of frequency bands. As a result, in communication using a plurality of frequency bands, data receipt acknowledgement or data retransmission can be efficiently performed. 
     &lt;Example of Sequence Number Setting According to the Present Technology&gt; 
       FIG. 4  is a diagram showing an example of sequence number setting to data by the wireless communication system shown in  FIG. 1 . 
       FIG. 4  shows data to be buffered in the case of the wireless communication system in  FIG. 1  among the transmission buffers # 1  to # 3  shown in  FIG. 2 . The explanations that have already been made will not be repeated below. 
     The wireless communication system in  FIG. 1  allocates a series of sequence numbers (SN), starting from the data having the highest priority level among the data to be transmitted to one transmission destination. 
     For example, a series of sequence numbers are set, starting from the data P:1 having the highest priority level. Accordingly, SN:01 is set to P:1 D:1, SN:02 is set to P:1 D:2, SN:03 is set to P:1 D:3, and SN:04 is set to P:1 D:4. 
     Next, the series of sequence numbers continuing from the data P:1 are set to the data P:2 having the second highest priority level. Accordingly, SN:05 is set to P:2 D:1, SN:06 is set to P:2 D:2, SN:07 is set to P:2 D:3, and SN:08 is set to P:2 D:4. 
     Lastly, the series of sequence numbers continuing from the data P:1 and the data P:2 are set to the data P:3 having the third highest priority level. Accordingly, SN:09 is set to P:3 D:1, SN:10 is set to P:3 D:2, SN:11 is set to P:3 D:3, and SN:12 is set to P:3 D:4. 
     Further, priority start frames (PSFs) are added to P:1 D:1, P:2 D:1, and P:3 D:1. A PSF is information indicating the first data among data having the same priority level. Priority center frames (PCFs) are added to P:1 D:2, P:2 D:2, P:3 D:2, P:1 D:3, P:2 D:3, and P:3 D:3. A PCF is information indicating the intermediate data among data having the same priority level. 
     Priority end frames (PEFs) are added to P:1 D:4, P:2 D:4, and P:3 D:4. A PEF is information indicating the last (delimiter) data among data having the same priority level. The PSFs, the PCFs, and the PEFs are information indicating the positions of the respective data pieces in the data group having the same priority level, or positional information about the data at the same priority level. 
     Note that, for the sake of convenience,  FIG. 4  illustrates a state in which the data P:4 having the lowest priority level is not stored. However, in a case where the data P:4 is stored in the transmission buffer, a sequence number SN:13 and those that follow are set to the data P:4. 
     As described above, a communication device of the wireless communication system sets a series of sequence numbers for data to be transmitted to one transmission destination through a plurality of frequency bands, and performs centralized management. Accordingly, it is possible to acknowledge receipt of data transmitted through another frequency band. As a result, receipt through a plurality of frequency bands can be acknowledged at once, and thus, retransmission control can be simplified. 
     Further, a series of sequence numbers are set in accordance with the priority levels. Thus, it is possible to determine which priority level is higher, from the sequence numbers. 
     &lt;Transmission Sequence According to the Present Technology&gt; 
       FIG. 5  is a diagram showing a transmission sequence according to the present technology. 
     The transmission sequence in  FIG. 5  is a transmission sequence depending on priority levels using the series of sequence numbers of the present technology described above. 
     In  FIG. 5 , the sequence is basically similar to the sequence shown in  FIG. 3 , until the data transmission in Band  2  is completed the earliest. The explanations that have already been made will not be repeated below. 
     In the case shown in  FIG. 5 , up to the last (delimiter) data in a data group of the same priority level is transmitted through a frequency band that has become available. As a result, the respective MPDUs of P:1 D:1 to P:1 D:4 are transmitted as an aggregated A-MPDU through Band  1 . The respective MPDUs of P:2 D:1 to P:2 D:4 are transmitted as an aggregated A-MPDU through Band  2 . The respective MPDUs of P:3 D:1 to P:3 D:3 are transmitted as an aggregated A-MPDU through Band  3 . 
     The communication device  11  on the transmission side transmits a block ACK request (BAR) of the present technology at time t 24  after the end of the data transmission through Band  2 , which is the frequency band in which the data transmission has been completed the earliest. A BAR is a frame for discriminating between data that has been successfully received and data that has not been successfully received at that point of time, and requesting a notification of a discrimination result to the data transmission source. Note that a BAR of the present technology will be hereinafter referred to as a priority block ACK request (Priority BAR: PBAR) to be distinguished from a conventional BAR. 
     A PBAR can include a request for returning block ACK information about the sequence numbers for data transmitted to one transmission destination through a plurality of frequency bands, for example. In this case, a block ACK for P:1 D:1, P:1 D:2, P:1 D:3, P:2 D:1, P:2 D:2, P:2 D:3, P:3 D:1, P:3 D:2, P:3 D:3, and P:3 D:4, excluding the data that is being transmitted or has not been transmitted yet, is required through PBAR transmission. 
     Alternatively, a PBAR can include a request for a return of block ACK information about that sequence numbers for all the data that is scheduled to be transmitted through all the frequency bands. 
     In this case, through PBAR transmission, a block ACK is requested for all of P:1 D:1 to P:1 D:4, P:2 D:1 to P:2 D:4, and P:3 D:1 to P:3 D:4, including untransmitted data that has not been transmitted. That is, through PBAR transmission, a request for the received data, the unreceived data, and a response to the unreceived data can be sent to the communication device  11  on the reception side. 
     In a case where a PBAR is received, the communication device  11  on the reception side transmits a block ACK of the present technology at time t 25 . Note that the block ACK of the present technology transmitted from the communication device  11  on the reception side in response to the PBAR will be hereinafter referred to as a priority block ACK (Priority BA:PBA) to be distinguished from a conventional block ACK. A PBA includes receipt acknowledgment information about the sequence numbers for all the data in all the frequency bands, for example. 
     According to the PBA of Band  2  transmitted from the communication device  11  on the reception side, P:1 D:2, P:1 D:3, P:2 D:1, P:3 D:1, P:3 D:2, P:3 D:3, and P:3 D:4 have been received, and the others are regarded as unreceived. 
     Receiving the PBA, the communication device  11  on the transmission side can recognize that the data that has been transmitted but has not reached is P:1 D:1, P:2 D:2, and P:3 D:3, and the data that has not been received or is being received is P:1 D:4 and P:2 D:4. 
     As a result, through Band  2  as a frequency band that has become available again, the communication device  11  on the transmission side can retransmit P:1 D:1, P:2 D:2, and P:3 D:3, which are the data that has not reached through any frequency band at that time. In the case shown in  FIG. 5 , retransmission of P:1 D:1, P:2 D:2, and P:3 D:3 is started through Band  2  at time t 27 , and, after the end of the retransmission, a BA of the retransmission data is transmitted from the reception side at time t 30 . 
     As for P:1 D:4 and P:2 D:4 that are the data being received, on the other hand, in a case where an error has occurred in the communication device  11  on the reception side or where reception is correctly completed, a BA is transmitted through each frequency band at time t 26  immediately after that. As a result, the communication device  11  on the transmission side is notified of the data reception state. Thus, the communication device  11  on the transmission side can retransmit P:1 D:4, which had the error, through Band  3 . 
     Although a BA is returned almost simultaneously through Band  1  and Band  3  in  FIG. 5 , Band  3  that is a frequency band unlikely to have transmission errors may be used for data retransmission. 
     In the above manner, the communication device  11  on the reception side can receive data starting from the highest priority level, in accordance with the priority levels intended by the transmission side. 
     &lt;Another Data Transmission Sequence According to the Present Technology&gt; 
       FIG. 6  is a diagram showing another data transmission sequence according to the present technology. 
     Like the transmission sequence in  FIG. 5 , the transmission sequence in  FIG. 6  is a transmission sequence depending on priority levels using the series of sequence numbers of the present technology described above. 
     In  FIG. 6 , only transmission of the first P:1 D:1 is the same sequence as the sequence in  FIG. 3 . The explanations that have already been made will not be repeated below. 
     At time t 41 , Band  1  becomes available. In a case where any signal from another communication device has not been detected during a predetermined transmission standby time w in Band  1 , an access right is acquired, and the communication device  11  on the transmission side transmits the first data (P:1 D:1) of the highest priority level at time t 41 +w through Band  1 . 
     Next, at time t 42 , Band  3  becomes available. In a case where any signal from another communication device has not been detected during the predetermined transmission standby time w in Band  3 , an access right is acquired, and the communication device  11  on the transmission side transmits the second data (P:1 D:2) of the highest priority level at time t 42 +w through Band  3 . 
     At time t 44 , which is the point of time when the transmission of the first data (P:1 D:1) through Band  1  is completed, the communication device  11  on the transmission side transmits the third data (P:1 D:3) of the highest priority level through Band  1 . 
     At time t 43 , Band  2  becomes available. In a case where any signal from another communication device has not been detected during the predetermined transmission standby time w in Band  2 , an access right is acquired, and the communication device  11  on the transmission side transmits the fourth data (P:1 D:4) of the highest priority level at time t 43 +w through Band  2 . 
     At time t 45 , which is the point of time when the transmission of the first data (P:1 D:2) through Band  3  is completed, the communication device  11  on the transmission side transmits the first data (P:2 D:1) of the second highest priority level through Band  3 . 
     At time t 46 , which is the point of time when the transmission of the first data (P:1 D:4) through Band  2  is completed, the communication device  11  on the transmission side transmits the second data (P:2 D:2) of the second highest priority level through Band  2 . 
     At time t 47 , which is the point of time when the transmission of the second data (P:1 D:3) through Band  1  is completed, the communication device  11  on the transmission side transmits the third data (P:2 D:3) of the second highest priority level through Band  1 . 
     At time t 48 , which is the point of time when the transmission of the second data (P:2 D:2) through Band  2  is completed, the communication device  11  on the transmission side transmits the fourth data (P:2 D:4) of the second highest priority level through Band  2 . 
     At time t 48 , which is the point of time when the transmission of the second data (P:2 D:1) through Band  3  is completed, the communication device  11  on the transmission side transmits the first data (P:3 D:1) of the third highest priority level through Band  3 . 
     At time t 49 , which is the point of time when the transmission of the third data (P:2 D:4) through Band  2  is completed, the communication device  11  on the transmission side transmits the second data (P:3 D:2) of the third highest priority level through Band  2 . 
     At time t 50 , which is the point of time when the transmission of the third data (P:2 D:3) through Band  1  is completed, the communication device  11  on the transmission side transmits the third data (P:3 D:3) of the third highest priority level through Band  1 . 
     Lastly, at time t 51 , which is the point of time when the transmission of the third data (P:3 D:1) through Band  3  is completed, the communication device  11  on the transmission side transmits the fourth data (P:3 D:4) of the third highest priority level through Band  3 . 
     As untransmitted data of higher priority levels is sequentially transmitted through a frequency band that has become available in the above manner, the respective MPDUs of P:1 D:1, P:1 D:3, P:2 D:3, and P:3 D:3 are transmitted as an aggregated A-MPDU through Band  1  in the case shown in  FIG. 6 . The respective MPDUs of P:1 D:4, P:2 D:2, P:2 D:4, and P:3 D:2 are transmitted as an aggregated A-MPDU through Band  2 . The respective MPDUs of P:1 D:2, P:2 D:1, P:3 D:1, and P:3 D:4 are transmitted as an aggregated A-MPDU through Band  3 . Although each four MPDUs are aggregated herein, a padding may be added to an A-MPDU as necessary in a case where its size is smaller than a predetermined size. 
     Meanwhile, the communication device  11  on the reception side transmits a PBA at time t 52  after the end of data transmission through Band  2 , which is the frequency band in which the data transmission has been completed the earliest. A PBA includes receipt acknowledgment information about the sequence numbers for all the data in all the frequency bands, for example. 
     In the case shown in  FIG. 6 , a PBA includes received data and unreceived data, and a response to the unreceived data, regarding that a block ACK is requested for all of P:1 D:1 to P:1 D:4, P:2 D:1 to P:2 D:4, and P:3 D:1 to P:3 D:4, including data that has not been transmitted. 
     According to the priority block ACK (PBA) of Band  2  transmitted at time t 52 , P:1 D:2, P:1 D:3, P:2 D:1, P:2 D:3, P:2 D:4, P:3 D:1, and P:3 D:2 have been received, and the others are regarded as unreceived. 
     Receiving the PBA, the communication device  11  on the transmission side can recognize that the data that has been transmitted but has not reached is P:1 D:1, P:1 D:4, and P:2 D:2, and the data that has not been received or is being received is P:3 D:3 and P:3 D:4. 
     After that, P:1 D:1, P:1 D:4, and P:2 D:2, which are data that has not reached at that time, can be retransmitted through Band  2 , which is a frequency band that has become available again. At this point of time, the respective MPDUs of P:1 D:1, P:1 D:4, and P:2 D:2 are transmitted as an aggregated A-MPDU through Band  2 . In  FIG. 6 , at time t 53 , the communication device  11  on the transmission side starts retransmission of P:1 D:1, P:1 D:4, and P:2 D:2. At time t 58  after the end of the retransmission, the communication device  11  on the reception side transmits a BA for the retransmitted data. 
     As for P:3 D:3 and P:3 D:4 that are the data being received, on the other hand, in a case where an error has occurred in the communication device  11  on the reception side or where reception is correctly completed, a BA is transmitted to the transmission side at time t 55  immediately after that. As a result, the communication device  11  on the transmission side is notified of the data reception state. Thus, the communication device  11  on the transmission side can retransmit P:1 D:4, which had the error, through Band  3 . 
     Although a BA is returned almost simultaneously through Band  1  and Band  3  at time t 55  in  FIG. 6 , Band  3  that is a frequency band unlikely to have transmission errors may be used at time t 56  for retransmitting P:3 D:3 that has become an error. At time t 57  after the end of the retransmission, the communication device  11  on the reception side transmits a BA for the retransmitted data. 
     In the above manner, the communication device  11  on the reception side can receive data starting from the highest priority level, in accordance with the priority levels intended by the transmission side. 
     Note that, in the transmission sequences shown in  FIGS. 5 and 6 , examples in which a BA is transmitted in the case of an acknowledgement of retransmission receipt have been described. However, a PBA may be transmitted in the case of an acknowledgement of retransmission receipt. 
     Further, the transmission sequences in  FIGS. 5 and 6  will be hereinafter also referred to as priority sequences (Priority Sequences) of the present technology. 
     &lt;&lt;2. Configuration of a Communication Device&gt;&gt; 
     &lt;Configuration of a Communication Device&gt; 
       FIG. 7  is a block diagram showing an example configuration of a communication device  11 . 
     The communication device  11  in  FIG. 7  includes a network connection module  51 , an information input module  52 , a device control module  53 , an information output module  54 , and a wireless communication module  55 . 
     The network connection module  51  is designed to implement the functions of a communication modem or the like for connecting to the Internet network in a case where it operates as a device at an access point, under the control of the device control module  53 . The network connection module  51  performs connection between a public communication channel and the Internet via an Internet service provider. 
     The information input module  52  outputs information indicating an instruction that is input by the user, to the device control module  53 . The information input module  52  includes push buttons, a keyboard, a touch panel, or the like. 
     The device control module  53  includes a central processing unit (CPU), a read only memory (ROM), and a random access memory (RAM). The device control module  53  executes a program stored in the ROM or the like, causes an application to function in a higher layer, and performs control to cause each component of the communication device  11  intended by the user to operate as a communication device or a device at an access point. 
     The information output module  54  outputs information that is supplied from the device control module  53  and relates to the operating state of the communication device  11 , or information obtained via the Internet. The information output module  54  includes a display element such as an LED, a liquid crystal panel, or an organic display, or a speaker or the like that outputs sound or music. The information output module  54  performs display and notification of information required for the user. 
     The wireless communication module  55  performs wireless communication, to transmit data supplied from the device control module  53  to another communication device  11 . The wireless communication module  55  performs wireless communication, to receive data transmitted from another communication device  11 , and output the received data to the device control module  53 . 
     &lt;Configuration of the Wireless Communication Module&gt; 
       FIG. 8  is a block diagram showing an example configuration of the wireless communication module  55 . 
     The wireless communication module  55  includes an interface  101 , a priority level determination unit  102 , a transmission buffer  103 , an operation control unit  104 , a transmission sequence management unit  105 , a communication control unit  106 , a frame construction unit  107 , and an access control unit  108 . The wireless communication module  55  also includes high-frequency processing units  109 - 1  to  109 - 4 , a frame analysis unit  110 , a reception sequence management unit  111 , a reception buffer  112 , and an output sequence management unit  113 . 
     The interface  101  functions as an interface for exchanging information that is input from the user through the device control module  53 , data that is supplied from the Internet network, or information to be provided to the user, in a predetermined signal format. 
     The interface  101  outputs data supplied from the device control module  53  to the priority level determination unit  102  and the operation control unit  104 . The interface  101  outputs data supplied from the output sequence management unit  113  to the device control module  53 . 
     The priority level determination unit  102  recognizes the setting of the priority level of the data to be transmitted. The priority level determination unit  102  determines the priority level in accordance with the access category (AC), and stores the data into the transmission buffer  103  in accordance with the priority level. 
     In a case where information input from a user or a signal for performing wireless transmission is received, the transmission buffer  103  temporarily stores the received signal. The transmission buffer  103  includes transmission buffers # 1  to # 4  that store data in accordance with priority levels. 
     The operation control unit  104  is a component that manages the operating state of the wireless communication module  55  in an integrated manner. On the basis of information supplied from the interface  101 , the transmission buffer  103 , the communication control unit  106 , and the reception buffer  112 , the operation control unit  104  sequentially performs necessary settings with respect to transmission and reception of data for the communication control unit  106  and the reception buffer  112 . 
     In response to an instruction from the communication control unit  106 , the transmission sequence management unit  105  sets a series of transmission sequence numbers for data to be transmitted, in accordance with the priority level of the data. The transmission sequence management unit  105  also acquires data from the transmission buffer  103  in descending order of priority levels, and outputs the data to the frame construction unit  107 . 
     The communication control unit  106  manages operations for transmitting and receiving data through a plurality of frequency bands, on the basis of information supplied from the access control unit  108 , the frame analysis unit  110 , and the reception sequence management unit  111 . The communication control unit  106  recognizes the frame construction and the data transmission/reception state in each frequency band, and controls the transmission sequence management unit  105  and the frame construction unit  107  on the basis of a priority sequence of the present technology. 
     The frame construction unit  107  constructs a data (MPDU) frame or an MPDU (A-MPDU) frame aggregated from a plurality of pieces of data (MPDUs), in response to an instruction from the communication control unit  106 . The frame construction unit  107  constructs a PBAR frame, a BAR frame, a BA frame, a PBA frame, and the like, in accordance with an instruction from the communication control unit  106 . 
     The frame construction unit  107  outputs constructed frames to the high-frequency processing units  109 - 1  to  109 - 4  corresponding to the frequency bands being used for transmission. 
     The access control unit  108  manages access control in a plurality of frequency bands in an integrated manner, on the basis of information indicating signal detection states supplied from the respective high-frequency processing units  109 - 1  to  109 - 4 . The access control unit  108  outputs information indicating that one of the frequency bands has become available, to the communication control unit  106 . 
     The high-frequency processing units  109 - 1  to  109 - 4  perform predetermined high-frequency processing on frames supplied from the frame construction unit  107 , and construct a signal in each frequency band among a plurality of frequency bands. The high-frequency processing units  109 - 1  to  109 - 4  transmit the constructed signals to the communication device  11  at the other end. 
     The high-frequency processing units  109 - 1  to  109 - 4  receive the signals transmitted from the communication device  11  at the other end through the respective frequency bands, and recognize the signal detection states in the respective frequency bands. The high-frequency processing units  109 - 1  to  109 - 4  output information indicating the signal detection states in the respective frequency bands to the access control unit  108 . The high-frequency processing units  109 - 1  to  109 - 4  each perform predetermined processing on the received signal to extract a frame, and output the frame to the frame analysis unit  110 . 
     Note that the high-frequency processing units  109 - 1  to  109 - 4  will be hereinafter referred to as the high-frequency processing units  109  in a case where there is no particular need to distinguish them from one another. A predetermined antenna is attached to each of the high-frequency processing units  109 , so that radio signals are transmitted and received at predetermined frequencies. 
     The frame analysis unit  110  extracts a header portion and individual data (MPDUs) from an A-MPDU frame received through each frequency band. The frame analysis unit  110  analyzes the frame from the information written in the extracted header portion. The frame analysis unit  110  outputs the information written in the extracted header portion to the communication control unit  106 . The frame analysis unit  110  decodes the extracted MPDUs, and outputs the MPDUs to the reception sequence management unit  111 . 
     The reception sequence management unit  111  extracts and manages parameters such as sequence numbers from the MPDUs supplied from the frame analysis unit  110 . The reception sequence management unit  111  determines the MPDUs that have been correctly received, and generates a PBA or a BA that is an acknowledgment of receipt of the MPDUs that have been correctly received. The reception sequence management unit  111  outputs the extracted parameters and the generated PBA or BA to the communication control unit  106 . 
     The reception sequence management unit  111  checks the start flags (PSFs), the intermediate flags (PCFs), and the end flags (PEFs) of the MPDUs described above with reference to  FIG. 4 , collects data in accordance with the respective priority levels, and stores the MPDUs into the reception buffer  112 . 
     The reception buffer  112  stores the collected data (MPDUs) in accordance with the priority levels. Note that the priority levels are determined in accordance with the transmission sequence numbers, and accordingly, the output sequence management unit  113  recognizes the priority levels in accordance with the order of sequence numbers. 
     In a case where data of each predetermined priority level is stored into the reception buffer  112 , the output sequence management unit  113  performs control to output the data to the information output module  54  or a device connected to the communication device  11 , via the interface  101 . 
     Note that the communication device  11  may include only the necessary modules among the modules shown in  FIG. 7 , or may have a configuration in which unnecessary modules are simplified or are not incorporated. 
     &lt;&lt;3. Operation of the Wireless Communication System&gt;&gt; 
     &lt;Communication Sequence in the Wireless Communication System&gt; 
       FIG. 9  is a chart showing a communication sequence in the wireless communication system shown in  FIG. 1 . 
     In  FIG. 9 , the communication device  11 - 1  is a communication device on the transmission side, and is a communication terminal. The communication device  11 - 2  is a communication device on the reception side, and serves as a device at an access point. The communication devices  11 - 1  and  11 - 2  perform communication based on a priority sequence of the present technology, using frequency bands # 1  to # 3  that are shown as Bands # 1  to # 3 , respectively. 
     In step S 11 , the communication device  11 - 1  transmits an association request frame to the communication device  11 - 2 , to conduct association. Association is a procedure for a communication terminal to enter a wireless network. An association request frame is a frame for a communication terminal to enter a wireless network. The association request frame is transmitted through the frequency band # 1 , for example. 
     At that point of time, the communication device  11 - 1  transmits a priority sequence information element (Priority Sequence IE) included in the association request frame. The priority sequence information element is information for exchanging the setting of the priority sequence described above with reference to  FIG. 5  or  FIG. 6 , information about the plurality of frequency bands to be used, and the like, between the device at an access point and the communication terminal at the time of association as described above. 
     In step S 51 , the communication device  11 - 2  receives the association request frame transmitted from the communication device  11 - 1  using the frequency band # 1 . 
     In step S 52 , the communication device  11 - 2  returns an association response (Association Response) frame to the communication device  11 - 1 . An association response frame is a frame for a device at an access point to allow a communication terminal to enter a wireless network. 
     At that point of time, the communication device  11 - 2  transmits a priority sequence information element (Priority Sequence IE) that is agreed by both sides and is included in the association response frame. 
     In step S 12 , the communication device  11 - 1  receives the association response frame transmitted from the communication device  11 - 2  using the frequency band # 1 . 
     As a result, in a case where the frequency bands # 1  to # 3  are available, the channels to be used in the respective frequency bands are specified, and the respective operations are set. 
     After that, the communication terminal and the device at an access point serve as the transmission side and the reception side, respectively, perform communication based on the priority sequence of the present technology, and return a priority block ACK (PBA) frame for acknowledging the receipt. 
     For example, in a case where the frequency bands # 1  to # 3  become available in this order, the communication device  11 - 1  in step S 13  transmits an A-MPDU (Priority Sequence) frame according to the priority sequence of the present technology, to the communication device  11 - 2  through the frequency band # 1 . 
     In step S 53 , the communication device  11 - 2  receives the A-MPDU (Priority Sequence) frame transmitted from the communication device  11 - 1  through the frequency band # 1 . In step S 54 , the communication device  11 - 2  transmits a PBA frame for acknowledging receipt of the A-MPDU (Priority Sequence) to the communication device  11 - 1  through the frequency band # 1 . 
     In step S 14 , the communication device  11 - 1  receives the PBA frame transmitted from the communication device  11 - 2  through the frequency band # 1 . In step S 15 , the communication device  11 - 1  transmits an A-MPDU (Priority Sequence) frame to the communication device  11 - 2  through the frequency band # 2 . 
     In step S 55 , the communication device  11 - 2  receives the A-MPDU (Priority Sequence) frame transmitted from the communication device  11 - 1  through the frequency band # 2 . In step S 56 , the communication device  11 - 2  transmits a PBA frame for acknowledging receipt of the A-MPDU (Priority Sequence) to the communication device  11 - 1  through the frequency band # 2 . 
     In step S 16 , the communication device  11 - 1  receives the PBA frame transmitted from the communication device  11 - 2  through the frequency band # 2 . In step S 17 , the communication device  11 - 1  transmits an A-MPDU (Priority Sequence) frame to the communication device  11 - 2  through the frequency band # 3 . 
     In step S 57 , the communication device  11 - 2  receives the A-MPDU (Priority Sequence) frame transmitted from the communication device  11 - 1  through the frequency band # 3 . In step S 58 , the communication device  11 - 2  transmits a PBA frame for acknowledging receipt of the A-MPDU (Priority Sequence) to the communication device  11 - 1  through the frequency band # 3 . 
     In step S 18 , the communication device  11 - 1  receives the PBA frame transmitted from the communication device  11 - 2  through the frequency band # 3 . 
     On the other hand, the communication device  11 - 2 , which is an access point, transmits an A-MPDU (Priority Sequence) frame to the communication device  11 - 1  through the frequency band # 1  in step S 59 . 
     In step S 19 , the communication device  11 - 1  receives the A-MPDU (Priority Sequence) frame transmitted from the communication device  11 - 2  through the frequency band # 1 . In step S 20 , the communication device  11 - 1  transmits a PBA frame for acknowledging receipt of the A-MPDU (Priority Sequence) to the communication device  11 - 2  through the frequency band # 1 . 
     In step S 60 , the communication device  11 - 2  receives the PBA frame transmitted from the communication device  11 - 1  through the frequency band # 1 . In step S 61 , the communication device  11 - 2  transmits an A-MPDU (Priority Sequence) frame to the communication device  11 - 1  through the frequency band # 2 . 
     In step S 21 , the communication device  11 - 1  receives the A-MPDU (Priority Sequence) frame transmitted from the communication device  11 - 2  through the frequency band # 2 . In step S 22 , the communication device  11 - 1  transmits a PBA frame for acknowledging receipt of the A-MPDU (Priority Sequence) to the communication device  11 - 2  through the frequency band # 2 . 
     In step S 62 , the communication device  11 - 2  receives the PBA frame transmitted from the communication device  11 - 1  through the frequency band # 2 . In step S 63 , the communication device  11 - 2  transmits an A-MPDU (Priority Sequence) frame to the communication device  11 - 1  through the frequency band # 3 . 
     In step S 23 , the communication device  11 - 1  receives the A-MPDU (Priority Sequence) frame transmitted from the communication device  11 - 2  through the frequency band # 3 . In step S 24 , the communication device  11 - 1  transmits a PBA frame for acknowledging receipt of the A-MPDU (Priority Sequence) to the communication device  11 - 2  through the frequency band # 3 . 
     In step S 64 , the communication device  11 - 2  receives the PBA frame transmitted from the communication device  11 - 1  through the frequency band # 3 . 
     The communication sequence as described above is performed between the communication terminal and the device at an access point. 
     &lt;&lt;4. Frame Configurations&gt;&gt; 
     &lt;Example Configuration of a Frame&gt; 
       FIG. 10  is a diagram showing an example frame configuration according to the present technology. 
     The frame shown in  FIG. 10  includes a preamble (Preamble) and a data frame including an A-MPDU frame. Note that information indicated by shaded portions in the frame in  FIG. 10  is information according to the present technology. 
     The preamble includes L-STF, L-LTF, L-SIG, RL-SIG, HE-SIG-A, HE-SIG-B, HE-STF, and a HE-LTF group. 
     HE-SIG-A includes, as a parameter, a Priority Sequence Identifier bit for identifying a priority sequence according to the present technology to be executed. 
     By checking this Priority Sequence Identifier bit, the communication device  11  on the reception side can recognize that data (MPDUs) having different priority levels is transmitted through a plurality of frequency bands, and that the A-MPDU includes MPDUs having different priority levels. 
     HE-SIG-B includes, as a parameter, Priority Sequence Info required for managing a series of sequence numbers in a plurality of frequency bands in accordance with priority levels. In Priority Sequence Info, various parameters such as information indicating a plurality of frequency bands are written. 
     In the case shown in  FIG. 10 , the A-MPDU formed as an A-MPDU frame is formed by aggregating eight MPDUs that are MPDU  1  to MPDU  8 . An EOF padding is added to the A-MPDU as necessary. 
     Each MPDU formed as an A-MPDU subframe has a predetermined delimiter (Delimiter) and a tail Padding added thereto as necessary. An MPDU includes a predetermined MAC header, a data payload (Data Payload), and a frame check sequence (FCS). Note that, in a case where the A-MPDU frame is shorter than a predetermined length, a padding Pad portion is added to the end of each MPDU as necessary. 
     The delimiter includes MPDU Length, flag information including Priority Start Flag, Priority END Flag, and Priority Continue Flag, and Priority. 
     MPDU Length is information indicating the length of an MPDU. Priority Start Flag is a flag indicating that the data is the first data in the data group having the same priority level. Priority END Flag is a flag indicating that the data is the last data in the data group having the same priority level. Priority Continue Flag is a flag indicating that the data is intermediate data in the data group having the same priority level. The priority level is written in Priority as necessary. With these flags, the communication device  11  on the reception side can recognize to which data the same priority level continues, and the delimiter for each priority level. Alternatively, in an exemplary mode in which these states are expressed with two bits, a case where data is formed with one MPDU, or incompatibility with a configuration of the present technology may be expressed with four identifiable values. 
     The MAC header (Header) includes Frame Control, Duration, Address  1  to Address  4 , Sequence Control, Qos Control, and New HT Control. 
     Frame Control is information indicating the frame format. Duration is information indicating the duration. Address  1  to Address  4  are information for appropriately designating communication devices. Sequence Control is information indicating the sequence number or the like. Qos Control is information indicating a Qos parameter. New HT Control is information indicating a high-speed transmission parameter. 
     Note that  FIG. 10  shows an example in which Priority Start Flag, Priority END Flag, Priority Continue Flag, and Priority, which are information regarding the priority sequence according to the present technology, are written in the delimiter. The site in which the information regarding the priority sequence according to the present technology is written is not necessarily the delimiter. For example, the information regarding the priority sequence according to the present technology may be written in New HT Control or the like as appropriate. 
     &lt;Example Configuration of a Block ACK Request Frame&gt; 
       FIG. 11  is a diagram showing an example configuration of a priority block ACK request frame (Priority BAR Frame) according to the present technology. 
     The priority block ACK request frame shown in FIG.  11  includes Frame Control, Duration, Transmit Address (TA), Receive Address (RA), BAR Control, BAR Information, Priority Sequence Info, Priority End Flags MAP, and FCS. Note that, in the priority block ACK request frame in  FIG. 11 , Priority Sequence Info and Priority End Flags MAP, which are information indicated by shaded portions, are information regarding a priority sequence according to the present technology. 
     Frame Control is information indicating the frame format. Duration is information indicating the duration. Transmit Address is information designating the communication device  11  on the transmission side. Receive Address is information designating the communication device  11  on the reception side. BAR Control is information indicating control information for requesting a block ACK. The BAR information is information including information about a start sequence number for requesting a block ACK, and bitmap information indicating the range to be requested. 
     Priority Sequence Info (priority sequence information) is information including various parameters required for managing a series of sequence numbers of a plurality of frequency bands in accordance with priority levels. For example, Priority Sequence Info includes information indicating the plurality of frequency bands to be used. Priority End Flags MAP is information indicating a list of the last (delimiter) data in the data group having the same priority level. FCS is a frame check sequence for error detection. 
     &lt;Example Configuration of a Block ACK Frame&gt; 
       FIG. 12  is a diagram showing an example configuration of a priority block ACK frame (Priority ACK Frame) according to the present technology. 
     In the priority block ACK frame shown in  FIG. 12 , BA Control and BA Information are provided simply in place of BAR Control and BAR Information, and the other information is similar to that shown in  FIG. 11 . The explanations that have already been made will not be repeated below. 
     The priority block ACK frame includes Frame Control, Duration, Transmit Address (TA), Receive Address (RA), BA Control, BA Information, Priority Sequence Info, Priority End Flags MAP, and FCS. 
     BA Control is information indicating control information for transmitting a block ACK. BA Information is information including information about a start sequence number for transmitting a block ACK and bitmap information indicating the range to be requested. 
     &lt;Example Configuration of a Priority Sequence Information Element&gt; 
       FIG. 13  is a diagram showing an example configuration of a priority sequence information element according to the present technology. 
     The priority sequence information element shown in  FIG. 13  includes Element ID, Length, Priority Type, Operation Band, Transmit Back-off Time, Sequence No. Management, A-MPDU Max Length, and FCS. 
     Element ID is information for identifying the information element as a priority sequence information element. Length is information indicating the length of information. Priority Type is information for designating the format of priority levels according to the present technology. Operation Band is information for designating the frequency band to be used. 
     Transmit Back-off Time is the transmission standby time that is set in accordance with the priority level. Sequence No. Management is information defining a sequence number management method. A-MPDU Max Length is information indicating the maximum length of an A-MPDU to be aggregated. FCS is a frame check sequence for error detection. 
     &lt;&lt;5. Operations of Communication Devices&gt;&gt; 
     &lt;Operation of the Communication Device on the Transmission Side&gt; 
       FIGS. 14 and 15  are flowcharts for explaining a data transmission process to be performed by the communication device  11 - 1  on the transmission side. 
     In  FIG. 14 , in a case where the data to be transmitted has been received beforehand from an application of a higher layer via the interface  101 , the data to be transmitted is stored in the transmission buffer  103  in accordance with the priority levels. In a case where a predetermined amount of information is stored in the transmission buffer  103 , an operation of transmitting a series of data is then started. 
     In step S 101 , the transmission sequence management unit  105  sets a series of sequence numbers in accordance with the priority levels of the data. The data for which the sequence numbers are set by the transmission sequence management unit  105  is supplied to the frame construction unit  107 . 
     In step S 102 , the communication control unit  106  sets a transmission standby time. 
     In step S 103 , the communication control unit  106  determines whether or not the operation is in a plurality of frequency bands. If the operation is determined to be in a plurality of frequency bands in step S 103 , the process moves on to step S 104 . 
     In step S 104 , the communication control unit  106  sets parameters (such as a maximum length and a transmission rate (MCS)) of the A-MPDU frame of each frequency band. 
     In step S 105 , the communication control unit  106  stands by until the standby time set in step S 102  elapses. If it is determined in step S 105  that the set standby time has elapsed, the process moves on to step S 106 . 
     In step S 106 , the communication control unit  106  stands by until determining that there is a frequency band in an available state, on the basis of information that is supplied from the access control unit  108  and indicates the states of a plurality of frequency bands. If it is determined in step S 106  that there is a frequency band in an available state, the process moves on to step S 107 . 
     In step S 107 , the communication control unit  106  specifies the frequency band to be used for transmission, on the basis of the information that is supplied from the access control unit  108  and indicates the states of the plurality of frequency bands. 
     In step S 108 , the communication control unit  106  determines whether or not an A-MPDU can be formed. If it is determined in step S 108  that an A-MPDU can be formed, the process moves on to step S 109 . 
     In step S 109 , the transmission sequence management unit  105  acquires data (MPDUs) from the transmission buffer  103  in descending order of priority levels, and outputs the data to the frame construction unit  107 . 
     In step S 110 , the frame construction unit  107  constructs (the MPDUs constituting) an A-MPDU frame or a (single) MPDU frame, using the data (MPDUs) supplied from the transmission sequence management unit  105 . The frame construction unit  107  outputs the constructed A-MPDU frame or MPDU frame to the high-frequency processing unit  109  corresponding to the frequency band to be used for transmission. As a result, an A-MPDU frame or a MPDU frame is transmitted from the high-frequency processing unit  109  corresponding to the frequency band to be used for transmission, to the communication device  11 - 2  at the other end. 
     Here, in the case of the example shown in  FIG. 5 , an A-MPDU including MPDUs having the same priority level is formed. Therefore, in step S 110 , an operation of transmitting an A-MPDU frame is set as a transmission operation in the corresponding frequency band. In the case of the example shown in  FIG. 6 , an operation of transmitting MPDUs having higher priority levels is set as a sequential transmission operation in the corresponding frequency band. 
     In step S 111 , the communication control unit  106  determines whether or not there is a remaining one of the MPDUs constituting the A-MPDU not smaller than a predetermined size. If it is determined in step S 111  that there is a remaining MPDU, the process returns to step S 106 . 
     If the operation is determined not to be an operation in a plurality of frequency bands in step S 103 , on the other hand, the process moves on to step S 112 . 
     In step S 112 , the transmission sequence management unit  105  acquires data (MPDUs) in the order of sequence numbers, and outputs the data to the frame construction unit  107 . 
     In step S 113 , the frame construction unit  107  determines whether or not to construct an A-MPDU. In a case where the length of the A-MPDU is smaller than a predetermined length, it is determined to continue to construct the A-MPDU, and the process moves on to step S 114 . 
     In step S 114 , the frame construction unit  107  constructs an A-MPDU frame. After an A-MPDU frame is constructed, the process returns to step S 112 , and the process after that is repeated. 
     In a case where the length of the A-MPDU becomes equal to the predetermined length or where a single MPDU is to be transmitted, it is determined that any A-MPDU is not to be constructed, and the process moves on to step S 115 . 
     If it is determined in step S 108  that any A-MPDU cannot be formed, the process also moves on to step S 115 . 
     In step S 115 , the frame construction unit  107  outputs a frame to the high-frequency processing unit  109  corresponding to a predetermined frequency band. As a result, an A-MPDU frame or a MPDU frame is transmitted as a data frame from the high-frequency processing unit  109  corresponding to the predetermined frequency band. 
     After the transmission in step S 115 , the process moves on to step S 116  in  FIG. 15 . Meanwhile, if it is determined in step S 111  that there are no remaining MPDUs, a padding Pad is inserted into the A-MPDU frame as necessary, and the process moves on to step S 116 . 
     In step S 116 , the communication control unit  106  determines whether or not transmission of a priority block ACK request (PBAR) is necessary. If it is determined that transmission of a priority block ACK request (PBAR) is necessary, the process moves on to step S 117 . 
     In step S 117 , in response to an instruction from the communication control unit  106 , the transmission sequence management unit  105  acquires the MPDU information already transmitted at that point of time from the transmission buffer  103 , and outputs the acquired transmitted MPDU information to the frame construction unit  107 . 
     In step S 118 , the frame construction unit  107  constructs a priority block ACK request (PBAR) frame in which the transmitted MPDU information is written, and outputs the constructed frame to the high-frequency processing unit  109  corresponding to the frequency band in which transmission has been completed the earliest. As a result, the priority block request (PBAR) frame in which the transmitted MPDU information is written is transmitted through the frequency band in which transmission has been completed the earliest. After the transmission of the PBAR frame, the process moves on to step S 119 . 
     Note that, as information about the series of sequence numbers scheduled to be transmitted is acquired, a priority block ACK request (PBAR) frame in which information about the series of sequence numbers scheduled to be transmitted is written may be transmitted. 
     If it is determined that transmission of a priority block ACK request (PBAR) is unnecessary, on the other hand, steps S 117  and S 118  are skipped, and the process moves on to step S 119 . 
     In step S 119 , the frame analysis unit  110  determines whether or not a PBA or a BA has been received. If it is determined in step S 119  that neither a PBA nor a BA has been received, the process returns to step S 116 , and the processes after that are repeated. 
     In a case where an ACK frame directed to the device is supplied from the high-frequency processing unit  109 , it is determined in step S 119  that a PBA or a BA has been received, and the process moves on to step S 120 . 
     In step S 120 , the reception sequence management unit  111  acquires the received sequence numbers from the ACK frame that is directed to the device and has been analyzed by the frame analysis unit  110 , and outputs the sequence numbers to the communication control unit  106 . 
     From the transmission sequence management unit  105 , the communication control unit  106  also acquires the sequence numbers transmitted from the device. 
     In step S 121 , the communication control unit  106  refers to the received sequence numbers and the transmitted sequence numbers, to determine whether or not there is data that has not reached yet. If it is determined in step S 121  that there is data that has not reached, the process moves on to step S 122 . 
     In step S 122 , the communication control unit  106  determines whether or not data retransmission is necessary. If it is determined in step S 122  that data retransmission is necessary, the process moves on to step 
     S 123 . 
     In step S 123 , the communication control unit  106  specifies data (a MPDU) that has not reached. After data that has not reached is specified, the process returns to step S 102  in  FIG. 14 , and the processes after that are repeated. 
     If it is determined in step S 121  that there is no data that has not reached, or if it is determined in step 
     S 122  that data retransmission is not necessary, on the other hand, the data transmission process by the communication device  11 - 1  comes to an end. 
     &lt;Operation of the Communication Device on the Reception Side&gt; 
       FIG. 16  is a flowchart showing a data reception process to be performed by the communication device  11 - 2  on the reception side. 
     In the case shown in  FIG. 16 , data frames transmitted from the communication device  11 - 1  on the transmission side through one frequency band are sequentially received with a configuration according to a predetermined preamble pattern in the corresponding high-frequency processing unit  109 . 
     The high-frequency processing unit  109  outputs the received data frames to the frame analysis unit  110 . 
     In step S 201 , the frame analysis unit  110  analyzes the data frames supplied from the high-frequency processing unit  109 , and determines whether or not a data frame directed to the device has been received. If it is determined in step S 201  that a data frame directed to the device has been received, the process moves on to step S 202 . 
     In step S 202 , the frame analysis unit  110  extracts the header portion, the delimiter portion, and individual data (MPDU) from a MPDU frame, and performs a decoding process on the MPDU. The frame analysis unit  110  outputs the information written in the extracted header portion to the communication control unit  106 . The frame analysis unit  110  outputs the decoded MPDU to the reception sequence management unit  111 . 
     In step S 203 , the reception sequence management unit  111  determines whether or not the MPDU has been correctly received. If it is determined in step S 203  that the MPDU has been correctly received, the process moves on to step S 204 . 
     In step S 204 , the reception sequence management unit  111  checks the start flag (PSF), the intermediate flags (PCFs), and the end flag (PEF) of the MPDU, collects data in accordance with the priority level of the MPDU, and stores the MPDU into the reception buffer  112 . 
     In step S 205 , the reception sequence management unit  111  extracts a sequence number from the MPDU. 
     In step S 206 , the reception sequence management unit  111  generates ACK information about the extracted sequence number. 
     In step S 207 , the output sequence management unit  113  determines whether or not the PSF to the PEF have been collected, from the flag information in the delimiter. If it is determined in step S 207  that the PSF to PEF have been collected, the process moves on to step S 208 . 
     In step S 208 , the output sequence management unit  123  outputs a series of data including the PSF to the PEF, to the interface  101 . 
     If it is determined in step S 203  that the MPDU has not been correctly received, on the other hand, the process skips steps S 204  to S 208 , and moves on to step S 209 . That is, ACK information is not generated. 
     If it is determined in step S 207  that the PSF to the PEF have not been collected, on the other hand, the process skips step S 208 , and moves on to step S 209 . 
     In step S 209 , the frame analysis unit  110  acquires A-MPDU Length information. 
     In step S 210 , the frame analysis unit  110  determines whether or not the A-MPDU continues, on the basis of the A-MPDU Length information. If it is determined that the A-MPDU continues, the process returns to step S 202 , and the processes after that are repeated. 
     If it is determined in step S 201  that any data frame directed to the device has not been received, on the other hand, the process moves on to step S 211 . 
     In step S 211 , the frame analysis unit  110  determines whether or not a BAR frame directed to the device has been received. If it is determined in step 
     S 211  that any BAR frame directed to the device has not been received, the process returns to step S 201 , and the processes after that are repeated. 
     If it is determined in step S 211  that a BAR frame directed to the device has been received, the process moves on to step S 212 . 
     In step S 212 , the frame analysis unit  110  acquires parameters from the BAR frame directed to the device. 
     In step S 213 , the frame analysis unit  110  determines whether or not the BAR frame directed to the device is a PBAR according to the present technology. If it is determined in step S 213  that the BAR frame directed to the device is a PBAR according to the present technology, the process moves on to step S 214 . 
     If it is determined in step S 210  that the A-MPDU does not continue, on the other hand, the process moves on to step S 214 . 
     In step S 214 , the frame analysis unit  110  acquires priority sequence information ( FIG. 11 ) from the BAR frame directed to the device. 
     In step S 215 , the frame analysis unit  110  acquires information indicating the frequency band to be used, from the priority sequence information. 
     After the processing in step S 215 , or if the BAR frame is determined not to be a PBAR according to the present technology in step S 213 , the process moves on to step S 216 . 
     In step S 216 , the frame analysis unit  110  acquires the start sequence number from the BAR frame directed to the device. 
     In step S 217 , the communication control unit  106  acquires ACK bitmap information of the MPDU that has been correctly received, from the BAR frame directed to the device. 
     In step S 218 , the communication control unit  106  generates PBA or BA information, on the basis of the acquired ACK bitmap information. The PBA or BA information is supplied from the communication control unit  106  to the frame construction unit  107 . 
     In step S 219 , the frame construction unit  107  transmits a PBA frame based on the PBA information supplied from the communication control unit  106 , or a BA frame generated on the basis of the BA information. 
     In step S 220 , the communication control unit  106  determines whether or not all the MPDUs have been completed. If it is determined in step S 220  that not all the MPDUs have been completed yet, the process returns to step S 201 , and the processes thereafter are repeated. 
     If it is determined in step S 220  that all the MPDUs have been completed, the data reception process in the communication device  11 - 2  comes to an end. 
     &lt;&lt;6. Other Aspects&gt;&gt; 
     &lt;Effects&gt; 
     As described above, in the present technology, a series of sequence numbers are set to data to be transmitted to one transmission destination through a plurality of frequency bands. Thus, it is possible to acknowledge receipt of data transmitted through another frequency band. 
     Further, by acknowledging receipt of data transmitted through another frequency band at the same time, it is possible to acknowledge receipt of a MPDU even when an A-MPDU is being transmitted through the another frequency band. 
     According to the present technology, a series of sequence numbers are set in accordance with priority levels. Thus, it is possible to determine which priority level is higher, from the sequence numbers. 
     After data (an A-MPDU) is transmitted through a plurality of frequency bands, receipt acknowledgment information regarding all the received data is returned through the frequency band in which the transmission has been completed the earliest. Thus, it is possible to send a notification of the reception states of all the data that has been successfully received through the plurality of frequency bands at that point of time. As a result, receipt acknowledgment information can be efficiently collected, without transmission of receipt acknowledgment information through each frequency band. 
     By forming an A-MPDU frame in accordance with the priority levels, it is possible to start transmitting the data having the highest priority level first, in a case where an access right has been acquired through a specific frequency band. 
     As the data having the highest priority level is transmitted through a plurality of frequency bands each time an access right is acquired. Thus, the communication device on the reception side can collect the data having the higher priority levels at an earlier stage. 
     As the data to be transmitted includes positional information (flags) at the same priority level, the reception side can also identify which data has the same priority level. 
     Further, a series of received data can be output at an earlier stage, in accordance with the positional information at the same priority level. 
     A priority block ACK request (PBAR) frame requires return of ACKs regarding all the sequence numbers for which transmission through a plurality of frequency bands is scheduled. Thus, it is possible to notify the reception side of the sequence numbers of all the data to be transmitted through the plurality of frequency bands. 
     The data that has not arrived through a plurality of frequency bands can be recognized at an early stage. Thus, retransmission can be preferentially performed, starting from the data with the highest priority level. 
     Further, an A-MPDU frame is formed with the data having the highest priority level each time in a frequency band that has become available, in accordance with the priority levels of data. Thus, the data having the higher priority levels can be transmitted at an early stage. 
     &lt;Example Configuration of a Computer&gt; 
     The series of processes described above can be performed by hardware, and can also be performed by software. In a case where the series of processes are performed by software, the program that forms the software may be installed in a computer incorporated into special-purpose hardware, or may be installed from a program recording medium into a general-purpose personal computer or the like. 
       FIG. 17  is a block diagram showing an example configuration of the hardware of a computer that performs the above described series of processes in accordance with a program. 
     A central processing unit (CPU)  301 , a read only memory (ROM)  302 , and a random access memory (RAM)  303  are connected to one another by a bus  304 . 
     An input/output interface  305  is further connected to the bus  304 . An input unit  306  formed with a keyboard, a mouse, and the like, and an output unit  307  formed with a display, a speaker, and the like are connected to the input/output interface  305 . Further, a storage unit  308  formed with a hard disk, a nonvolatile memory, or the like, a communication unit  309  formed with a network interface or the like, and a drive  310  that drives a removable medium  311  are connected to the input/output interface  305 . 
     In the computer having the above described configuration, the CPU  301  loads a program stored in the storage unit  308  into the RAM  303  via the input/output interface  305  and the bus  304 , for example, and executes the program, so that the above described series of processes are performed. 
     The program to be executed by the CPU  301  is recorded in the removable medium  311  and is thus provided, for example, or is provided via a wired or wireless transmission medium, such as a local area network, the Internet, or digital broadcasting. The program is then installed into the storage unit  308 . 
     Note that the program to be executed by the computer may be a program for performing processes in chronological order in accordance with the sequence described in this specification, or may be a program for performing processes in parallel or performing a process when necessary, such as when there is a call. 
     It should be noted that, in this specification, a system means an assembly of a plurality of components (devices, modules (parts), and the like), and not all the components need to be provided in the same housing. In view of this, a plurality of devices that are housed in different housings and are connected to one another via a network forms a system, and one device having a plurality of modules housed in one housing is also a system. 
     Further, the advantageous effects described in this specification are merely examples, and the advantageous effects of the present technology are not limited to them or may include other effects. 
     Embodiments of the present technology are not limited to the embodiments described above, and various modifications may be made to them without departing from the scope of the present technology. 
     For example, the present technology may be embodied in a cloud computing configuration in which one function is shared among a plurality of devices via a network, and processing is performed by the devices cooperating with one another. 
     Further, the respective steps described with reference to the flowcharts described above may be carried out by one device or may be shared among a plurality of devices. 
     Furthermore, in a case where a plurality of processes is included in one step, the plurality of processes included in the one step may be performed by one device or may be shared among a plurality of devices. 
     &lt;Example Combinations of Configurations&gt; 
     The present technology may also be embodied in the configurations described below. 
     (1) 
     A wireless communication device including: 
     a sequence management unit that sets a series of sequence numbers to data to be transmitted to one transmission destination through a plurality of frequency bands; 
     a wireless transmission unit that transmits the data through the plurality of frequency bands; and 
     a communication control unit that causes reception of receipt acknowledgment information through a frequency band in which transmission of the data has been completed first among the plurality of frequency bands, the receipt acknowledgment information indicating a receipt acknowledgment regarding the data transmitted through the plurality of frequency bands. 
     (2) 
     The wireless communication device according to (1), in which 
     the communication control unit causes sequential transmission of the data through a frequency band that has entered an available state among the plurality of frequency bands, after a predetermined transmission standby time has passed. 
     (3) 
     The wireless communication device according to (1) or (2), in which, 
     in accordance with priority levels of the data, the sequence management unit sets the series of sequence numbers, starting from the data having the highest priority level. 
     (4) 
     The wireless communication device according to (3), in which 
     the sequence management unit adds information to the data, the information indicating a position of the data in a data group having the same priority level. 
     (5) 
     The wireless communication device according to (4), in which, 
     when the position of the data is the last position in the data group, the sequence management unit adds an end flag as the information indicating the position of the data. 
     (6) 
     The wireless communication device according to (4), in which, 
     when the position of the data is the first position in the data group, the sequence management unit adds a start flag as the information indicating the position of the data. 
     (7) 
     The wireless communication device according to (4), in which, 
     when the position of the data is an intermediate position in the data group, the sequence management unit adds an intermediate flag as the information indicating the position of the data. 
     (8) 
     The wireless communication device according to any one of (1) to (3), further including 
     a frame construction unit that constructs an A-MPDU frame including the data of a predetermined length. 
     (9) 
     The wireless communication device according to (8), in which, 
     when the A-MPDU frame is shorter than the predetermined length, the frame construction unit constructs the A-MPDU frame having a padding added to the end. 
     (10) 
     The wireless communication device according to (8), in which 
     the frame construction unit constructs an A-MPDU frame formed with a data group having the same priority level as the data to be transmitted through a frequency band that has entered an available state. 
     (11) 
     The wireless communication device according to (8), in which 
     the frame construction unit constructs an A-MPDU frame formed with the data that is high in the priority level and has not been transmitted, as the data to be transmitted through a frequency band that has entered an available state. 
     (12) 
     The wireless communication device according to (8), in which 
     the frame construction unit constructs an A-MPDU frame for retransmission as the data to be transmitted through a frequency band that has entered an available state. 
     (13) 
     The wireless communication device according to any one of (1) to (12), in which 
     the communication control unit causes transmission of a request for the receipt acknowledgment information. 
     (14) 
     The wireless communication device according to any one of (1) to (13), in which 
     the communication control unit causes retransmission of the data that has not arrived, the data being of the data transmitted through in the plurality of frequency bands. 
     (15) 
     A wireless communication method implemented in a wireless communication device, 
     the wireless communication method including: 
     setting a series of sequence numbers to data to be transmitted to one transmission destination through a plurality of frequency bands; 
     transmitting the data through the plurality of frequency bands; and 
     causing reception of receipt acknowledgment information through a frequency band in which transmission of the data has been completed first among the plurality of frequency bands, the receipt acknowledgment information indicating a receipt acknowledgment regarding the data transmitted through the plurality of frequency bands. 
     (16) 
     A wireless communication device including: 
     a wireless reception unit that receives data transmitted to one transmission destination through a plurality of frequency bands; 
     a sequence management unit that manages a series of sequence numbers that have been set to the data received through the plurality of frequency bands; and 
     a communication control unit that causes transmission of receipt acknowledgment information through a frequency band in which reception of the data has been completed first, the receipt acknowledgment information indicating a receipt acknowledgment regarding the data received through the plurality of frequency bands. 
     (17) 
     The wireless communication device according to (16), in which 
     the sequence management unit determines a priority level of the data, in accordance with information indicating a position of the data in a data group having the same priority level, the information having been added to the data received through the plurality of frequency bands. 
     (18) 
     The wireless communication device according to (16) or (17), further including 
     an output management unit that outputs the received data, in accordance with the information indicating the position of the data. 
     (19) 
     A wireless communication method implemented in a wireless communication device, 
     the wireless communication method including: 
     receiving data transmitted to one transmission destination through a plurality of frequency bands; 
     managing a series of sequence numbers that have been set to the data received through the plurality of frequency bands; and 
     causing transmission of receipt acknowledgment information through a frequency band in which reception of the data has been completed first, the receipt acknowledgment information indicating a receipt acknowledgment regarding the data received through the plurality of frequency bands. 
     REFERENCE SIGNS LIST 
     
         
           11 ,  11 - 1  to  11 - 4  Communication device 
           51  Network connection module 
           52  Information input module 
           53  Device control module 
           54  Information output module 
           55  Wireless communication module 
           101  Interface 
           102  Priority level determination unit 
           103  Transmission buffer 
           104  Operation control unit 
           105  Transmission sequence management unit 
           106  Communication control unit 
           107  Frame construction unit 
           108  Access control unit 
           109 ,  109 - 1  to  109 - 5  High-frequency processing unit 
           110  Frame analysis unit 
           111  Reception sequence management unit 
           112  Reception buffer 
           113  Output sequence management unit