Patent Publication Number: US-2022231803-A1

Title: Communication device and method

Description:
TECHNICAL FIELD 
     The present technology relates to a communication device and method, and more particularly to a communication device and method capable of correctly specifying a same frame. 
     BACKGROUND ART 
     There is a wireless communication system for Internet of Things (IoT) in which a sensor terminal is assigned to a person or an object and information acquired from the sensor terminal is periodically transmitted by wireless communication. Using the wireless communication system for IoT makes it possible to create a new service. For example, a watching service can be realized by mounting a sensor terminal with GPS on an elderly person or a child and periodically transmitting location information as sensor data. In such a wireless communication system for IoT, long-distance transmission and low power consumption are required. 
     As a method of realizing long-distance transmission, a method of synthesizing a reception signal is considered. By a transmission terminal repeatedly transmitting a same frame and a reception terminal synthesizing a reception signal, an S/N can be increased. As a result, long-distance transmission can be performed. 
     In order for the transmission terminal to repeatedly transmit the same frame and the reception terminal to synthesize the reception signal, the reception terminal needs to specify the same frame. 
     As a method of specifying the same frame, a method of selecting and transmitting a wireless resource on the basis of a hopping pattern is generally used. 
     For example, in a technique described in Patent Document 1, the same frame can be specified by uniquely determining a wireless resource of a repeatedly transmitted frame on the basis of time synchronization and a notification of information on a wireless resource of a head frame, and on the basis of a known hopping pattern. 
     However, beacon reception for time synchronization and transmission and reception of control signaling for providing notification of information on the wireless resource of the head frame consume power of the transmission terminal, which is undesirable. 
     Therefore, a wireless communication system that performs repetitive transmission and synthesis asynchronously and without control signaling is considered. First, the transmission terminal selects a hopping pattern and starts repetitive transmission. 
     A device of a base station detects a frame by using all usable codes for all usable frequencies, and specifies a same frame on the basis of the detected frame. By regarding a frame at the earliest detection time as a head frame and performing pattern matching on the detected frame by using the hopping pattern, the same frame is specified. 
     CITATION LIST 
     Patent Document 
     
         
         Patent Document 1: International Publication No. 2017/212810 
       
    
     SUMMARY OF THE INVENTION 
     Problems to be Solved by the Invention 
     However, the device of the base station cannot always detect the head frame of the repetitive transmission, due to an influence of interference or the like. In this case, it has been difficult to correctly specify the same frame. 
     The present technology has been made in view of such a situation, and is intended to enable correct specification of a same frame. 
     Solutions to Problems 
     A communication device of one aspect of the present technology includes: a wireless resource determination unit configured to determine a first wireless resource including a frequency for transmission of a same frame that is a frame of same data, a code of the same frame, and a time for transmission of the same frame, on the basis of pattern information indicating a unique relationship between a frame number of the same frame and at least one of the frequency or the code; and a transmission unit configured to repeatedly transmit the same frame by using the first wireless resource. 
     A communication device of another aspect of the present technology includes: a frame detection unit configured to detect a data frame being transmitted with use of a wireless resource including a frequency for transmission of the data frame, a code of the data frame, and a time for transmission of the data frame; a frame specification unit configured to specify, from the detected data frame on the basis of pattern information, a same frame being transmitted with use of a first wireless resource determined on the basis of the pattern information indicating a unique relationship between a frame number of the same frame that is a frame of same data and at least one of the frequency or the code; and a demodulation unit configured to synthesize and demodulate the same frame. 
     In one aspect of the present technology, a first wireless resource including a frequency for transmission of a same frame that is a frame of same data, a code of the same frame, and a time for transmission of the same frame is determined on the basis of pattern information indicating a unique relationship between a frame number of the same frame and at least one of the frequency or the code. Then, the same frame is repeatedly transmitted by using the first wireless resource. 
     In another aspect of the present technology, a data frame is detected that is being transmitted with use of a wireless resource including a frequency for transmission of the data frame, a code of the data frame, and a time for transmission of the data frame. Then, from the detected data frame on the basis of pattern information, the same frame is specified that is being transmitted with use of the first wireless resource determined on the basis of the pattern information indicating a unique relationship between a frame number of the same frame that is a frame of same data, and at least one of the frequency or the code, and the same frame is synthesized and demodulated. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a diagram illustrating a configuration example of a wireless communication system of the present technology. 
         FIG. 2  is a block diagram illustrating a configuration example of a communication device. 
         FIG. 3  is a table illustrating an example of a frequency hopping pattern. 
         FIG. 4  is a view illustrating an example of a wireless resource to be used by a user terminal. 
         FIG. 5  is a block diagram illustrating a configuration example of the communication device. 
         FIG. 6  is a view illustrating an example of a wireless resource to be used by the communication device. 
         FIG. 7  is a view illustrating an example of a wireless resource to be used by the communication device in a case where detection of a head frame fails. 
         FIG. 8  is a block diagram illustrating another configuration example of the wireless communication system of the present technology. 
         FIG. 9  is a block diagram illustrating a configuration example of the user terminal. 
         FIG. 10  is a block diagram illustrating a configuration example of the communication device. 
         FIG. 11  is a view illustrating a configuration example of a frame. 
         FIG. 12  is a table illustrating an example of a time hopping pattern. 
         FIG. 13  is a table illustrating an example of a frequency hopping pattern. 
         FIG. 14  is a table illustrating an example of a code hopping pattern. 
         FIG. 15  is a diagram illustrating a configuration example of a gold code generator as a pseudo random number generator. 
         FIG. 16  is a table illustrating a detection frame list in the communication device. 
         FIG. 17  is a view illustrating an example in which DL transmission is performed after a same frame is specified from detected frames. 
         FIG. 18  is a flowchart for explaining processing of the entire wireless communication system. 
         FIG. 19  is a flowchart for explaining frame transmission/reception processing of the user terminal. 
         FIG. 20  is a flowchart for explaining repetitive transmission processing in step S 154  in  FIG. 19 . 
         FIG. 21  is a flowchart for explaining repetitive reception processing in step S 156  in  FIG. 19 . 
         FIG. 22  is a flowchart for explaining the repetitive reception processing in step S 156  in  FIG. 19  subsequent to  FIG. 21 . 
         FIG. 23  is a flowchart for explaining frame detection processing of the communication device. 
         FIG. 24  is a flowchart for explaining frame reception processing of the communication device. 
         FIG. 25  is a flowchart for explaining same frame specification processing in step S 235  in  FIG. 24 . 
         FIG. 26  is a flowchart for explaining frame synthesis/demodulation processing in step S 236  in  FIG. 24 . 
         FIG. 27  is a flowchart for explaining repetitive transmission processing of the communication device. 
         FIG. 28  is a table illustrating an example of a time hopping pattern. 
         FIG. 29  is a table illustrating an example of a frequency hopping pattern. 
         FIG. 30  is a table illustrating an example of a code hopping pattern. 
         FIG. 31  is a table illustrating a detection frame list in the communication device. 
         FIG. 32  is a view illustrating an example in which DL transmission is performed after a same frame is specified from detected frames. 
         FIG. 33  is a flowchart for explaining another example of the same frame specification processing in step S 235  in  FIG. 24 . 
         FIG. 34  is a table illustrating an example of a time hopping pattern. 
         FIG. 35  is a table illustrating an example of a frequency hopping pattern. 
         FIG. 36  is a table illustrating an example of a code hopping pattern. 
         FIG. 37  is a table illustrating a detection frame list in the communication device. 
         FIG. 38  is a view illustrating an example in which DL transmission is performed after a same frame is specified from detected frames. 
         FIG. 39  is a flowchart for explaining another example of the same frame specification processing in step S 235  in  FIG. 24 . 
         FIG. 40  is a block diagram illustrating a configuration example of a computer. 
     
    
    
     MODE FOR CARRYING OUT THE INVENTION 
     Hereinafter, an embodiment for implementing the present technology will be described. The description will be given in the following order. 
     1. First embodiment (example with control signaling) 
     2. Second embodiment (example without control signaling) 
     3. Third embodiment (example of specifying frame number on basis of code) 
     4. Fourth embodiment (example of specifying frame number on basis of frequency) 
     5. Fifth embodiment (example of specifying frame number on basis of combination of frequency and code) 
     6. Other 
     1. First Embodiment (Example with Control Signaling) 
     &lt;Configuration Example of Wireless Communication System&gt; 
       FIG. 1  is a view illustrating a configuration example of a wireless communication system according to a first embodiment of the present technology. 
     A wireless communication system  1  of  FIG. 1  is configured by connecting user terminals  11 - 1  to  11 - 3  and a communication device  12  by wireless communication. 
     The wireless communication between the user terminals  11 - 1  to  11 - 3  and the communication device  12  is two-way communication including UL (UP LINK) communication from the user terminals  11 - 1  to  11 - 3  to the communication device  12  and DL (DOWN LINK) communication from the communication device  12  to the user terminals  11 - 1  to  11 - 3 . 
     The user terminals  11 - 1  to  11 -N are Internet of things (IoT) devices including one or more sensors. 
     Hereinafter, in a case where it is not necessary to individually distinguish the user terminals  11 - 1  to  11 - 3 , they are collectively referred to as a user terminal  11 , as appropriate. 
     For example, as the UL communication, the user terminal  11  measures a measurement target and transmits a data frame containing sensor data representing a measurement result, to the communication device  12 . 
     In a case of  FIG. 1 , the user terminal  11  and the communication device  12  are time-synchronized in advance. The user terminal  11  selects a wireless resource by using a hopping pattern. The user terminal  11  repeatedly transmits a same frame, which is a same data frame, for example, four times by using the selected wireless resource. 
     The hopping pattern is shared as pattern information between the user terminal  11  and the communication device  12 . The hopping pattern includes one or a plurality of patterns indicating a combination of a wireless resource and a frame number. The wireless resource includes a frequency, a time, and a code. The frequency is a frequency at which a frame is transmitted. The time is a transmission time interval (transmission interval) at which a frame is transmitted. The code is information regarding a code of a frame, and is an initial value to be used for generating a code in a case of the present technology. 
     The user terminal  11  transmits a control frame including control signaling to the communication device  12  prior to transmission of the data frame. The control frame includes information on a wireless resource of a head frame. 
     Furthermore, the user terminal  11  determines a wireless resource of the DL communication on the basis of the wireless resource used in the UL communication. The user terminal  11  receives the data frame being transmitted from the communication device  12 , as the DL communication. 
     The communication device  12  constitutes a base station. The communication device  12  performs frame detection after receiving the control frame being transmitted from the user terminal  11 . The communication device  12  specifies a same frame from the detected frames by using information on the wireless resource of the head frame obtained by receiving the control frame and using the known hopping pattern. The communication device  12  synthesizes the specified same frame and performs demodulation. 
     Furthermore, the communication device  12  determines the wireless resource of the DL communication on the basis of the wireless resource used in the UL communication, and transmits the data frame to the user terminal  11 , as the DL communication. 
     &lt;Configuration Example of Communication Device&gt; 
       FIG. 2  is a block diagram illustrating a configuration example of the communication device  12 . 
     The communication device  12  includes a frame detection unit  31 , a detection frame list storage unit  32 , a head frame information storage unit  33 , a hopping pattern storage unit  34 , a same frame specification unit  35 , a reception signal synthesis unit  36 , and a demodulation unit  37 . 
     A reception signal is supplied to the frame detection unit  31  and the reception signal synthesis unit  36 . 
     The frame detection unit  31  calculates a correlation between a reception signal and a known pattern, and determines that a frame is detected in a case where the calculated correlation value exceeds a predetermined threshold value. The frame detection unit  31  adds information on a wireless resource (a frequency, a time, and a code) of the detected frame to the detection frame list storage unit  32 . The detection frame list storage unit  32  stores information on the wireless resource of the detected frame. 
     The head frame information storage unit  33  is notified of and stores information on the wireless resource of the head frame by control signaling before transmission of the data frame. The hopping pattern storage unit  34  stores a hopping pattern. 
     The same frame specification unit  35  specifies a repeatedly transmitted same frame from the detected frames. The same frame specification unit  35  uniquely determines a wireless resource to be used in the repeatedly transmitted same frame, on the basis of the information on the wireless resource of the head frame and on the basis of the hopping pattern, to specify the same frame. 
     The reception signal synthesis unit  36  segments a reception signal of the wireless resource specified by the same frame specification unit  35  as the same frame from the received reception signal, and synthesizes the reception signal. The demodulation unit  37  demodulates the signal synthesized by the reception signal synthesis unit  36 . 
     As described above, in the communication device  12  of  FIG. 2 , on the basis of time synchronization, acquisition of information on the wireless resource of the head frame, and the known hopping pattern, the wireless resource to be used for the repeatedly transmitted same frame is uniquely determined. As a result, the same frame can be specified. 
     However, beacon transmission for time synchronization and transmission and reception of control signaling for providing notification of information on the wireless resource of the head frame consume power of the user terminal  11 , which is undesirable. 
     2. Second Embodiment (Example without Control Signaling) 
     Therefore, as a second embodiment of the present technology, a system that performs repetitive transmission and synthesis asynchronously and without control signaling will be described. Note that the description will be made with reference to the wireless communication system  1  of  FIG. 1  again. 
     A user terminal  11  selects any pattern from a hopping pattern shared in advance as pattern information in the wireless communication system  1 , and repeatedly transmits a same frame at any time. 
     &lt;Example of Hopping Pattern&gt; 
       FIG. 3  is a table illustrating an example of a frequency hopping pattern. 
     The frequency hopping pattern defines a frequency to be used for each frame to be repeatedly transmitted.  FIG. 3  illustrates a hopping pattern including a plurality of patterns in which the number of times of repetitive transmission is four and the number of usable frequencies is nine. 
     In a case where a pattern of pattern number 1 is selected, frequencies f 8 , f 5 , f 7 , and f 0  are used to transmit frames of frame numbers 1 to 4, respectively. In a case where the pattern of pattern number 2 is selected, frequencies f 7 , f 8 , f 0 , and f 5  are used to transmit the frames of frame numbers 1 to 4, respectively. In a case where the pattern of pattern number 3 is selected, frequencies f 6 , f 3 , f 0 , and f 2  are used to transmit the frames of frame numbers 1 to 4, respectively. In a case where the pattern of pattern number 4 is selected, frequencies f 5 , f 4 , f 6 , and f 8  are used to transmit the frames of frame numbers 1 to 4, respectively. 
     In a case where the pattern of pattern number 5 is selected, frequencies f 4 , f 1 , f 2 , and f 7  are used to transmit the frames of frame numbers 1 to 4, respectively. In a case where the pattern of pattern number 6 is selected, frequencies f 3 , f 0 , f 5 , and f 1  are used to transmit the frames of frame numbers 1 to 4, respectively. In a case where the pattern of pattern number 7 is selected, frequencies f 2 , f 6 , f 1 , and f 3  are used to transmit the frames of frame numbers 1 to 4, respectively. 
     In a case where the pattern of pattern number 8 is selected, frequencies f 1 , f 7 , f 4 , and f 6  are used to transmit the frames of frame numbers 1 to 4, respectively. In a case where the pattern of pattern number 9 is selected, frequencies f 0 , f 2 , f 3 , and f 4  are used to transmit the frames of frame numbers 1 to 4, respectively. 
     As described above, the combination of the frame number and the frequency is different for each pattern. 
     For example, in a case where the user terminal  11  selects the pattern of pattern number 1, a same frame is transmitted by using frequencies f 8 , f 5 , f 7 , and f 0 . Here, for convenience of description, a time and a code that are the wireless resource other than the frequency are fixed. However, the hopping pattern may be defined and made variable also for the time and the code. Furthermore, as described above, the time here refers to a transmission interval at which the same frame is transmitted. The code represents an initial value to be used for generating a preamble/SYNC and a scramble pattern (code). 
     Furthermore, in the wireless communication system  1 , by using this hopping pattern, the wireless resource to be used for the DL communication is determined on the basis of the wireless resource used for the UL communication. For example, the DL communication is started after Δt from a transmission start time of a head frame to be repeatedly transmitted. For the DL communication, there is used a wireless resource indicated by a pattern of a pattern number obtained by adding ΔP to pattern number 1 used for the UL communication. 
     &lt;Wireless Resource to be Used by User Terminal&gt; 
       FIG. 4  is a view illustrating an example of a wireless resource to be used by the user terminal  11 . 
     In  FIG. 4 , a vertical axis represents a frequency, and a horizontal axis represents a time. Furthermore, a rectangle represents a frame. This similarly applies to subsequent figures. 
     The user terminal  11  uses the pattern of pattern number 1 as the hopping pattern of the UL communication. Therefore, as the UL communication, the user terminal  11  transmits a frame F1 by using the frequency f 8 , transmits a frame F2 by using the frequency f 5 , transmits a frame F3 by using the frequency f 7 , and transmits a frame F4 by using the frequency f 0 . 
     In the DL communication, there is used a wireless resource indicated by a pattern of pattern number 4, which is obtained by adding ΔP (=3) to pattern number 1 used in the UL communication, after Δt from a transmission start time of the head frame F1 to be repeatedly transmitted as the UL communication. 
     Therefore, as the DL communication, the user terminal  11  can receive the frame F1 transmitted with use of the frequency f 5  and receive the frame F2 transmitted with use of the frequency f 4 . Then, the user terminal  11  can receive the frame F3 transmitted by using the frequency f 6  and receive the frame F4 transmitted by using the frequency f 8 . 
     As described above, the wireless resource to be used in the DL communication is uniquely determined from the wireless resource used in the UL communication. Therefore, the user terminal  11  only needs to perform reception processing by using the corresponding code for the corresponding frequency, only during the time when the reception processing needs to be performed. The reception processing is processing including frame detection, synthesis, and demodulation. 
     &lt;Configuration Example of Communication Device&gt; 
       FIG. 5  is a block diagram illustrating a configuration example of a communication device  12 . 
       FIG. 5  illustrates a configuration example of the communication device in a case where the wireless communication system  1  is a system that performs repetitive transmission and synthesis asynchronously and without control signaling. 
     The communication device  12  includes a frame detection unit  51 , a detection frame list storage unit  32 , a hopping pattern storage unit  34 , a same frame specification unit  52 , a reception signal synthesis unit  36 , and a demodulation unit  37 . In the configuration illustrated in  FIG. 5 , the same components as those described with reference to  FIG. 2  are denoted by the same reference numerals. Redundant description will be omitted as appropriate. 
     A reception signal is supplied to the frame detection unit  51  and the reception signal synthesis unit  36 . 
     The frame detection unit  51  does not know which wireless resource is used by the user terminal  11  to transmit a frame. The frame detection unit  51  detects a frame at all times by using all usable codes for all usable frequencies. 
     The same frame specification unit  52  specifies a repeatedly transmitted same frame from the detected frames. Specifically, the same frame specification unit  52  refers to the detection frame list storage unit  32  and determines a focused frame, which is the frame of interest, in ascending order of a detection time. 
     The same frame specification unit  52  regards the focused frame as a head frame, and estimates a hopping pattern used for transmission on the basis of a frequency of the head frame and a hopping pattern. In the same frame specification unit  52 , a pattern in which the frequency of the head frame matches the frequency of frame number 1 in the hopping pattern is estimated to be the hopping pattern used for the transmission. On the basis of the time and the frequency indicated by the estimated hopping pattern, the same frame specification unit  52  specifies the second and subsequent frames from among the detected frames. 
     The reception signal synthesis unit  36  segments a reception signal transmitted with the wireless resource specified by the same frame specification unit  52  from the received reception signal, and synthesizes the reception signal. The demodulation unit  37  demodulates the signal synthesized by the reception signal synthesis unit  36 . 
     In a case where the demodulation is successful, the communication device  12  determines the wireless resource to be used for the DL communication by a method similar to that of the user terminal  11 , on the basis of the detection time of the focused frame and the estimated hopping pattern. The communication device  12  transmits the frame by using the determined wireless resource. 
     &lt;Example of Case where Head Frame is Detected&gt; 
       FIG. 6  is a view illustrating an example of a wireless resource to be used by the communication device  12 . 
     As illustrated in  FIG. 6 , the communication device  12  sequentially detects a frame B:F1, a frame B:F2, a frame C:F1, a frame B:F3, a frame C:F2, a frame B:F4, a frame C:F3, and a frame C:F4, as the UL communication. 
     The frame B:F1, the frame B:F2, the frame B:F3, and the frame C:F4 are frames transmitted from the user terminal  11  that is the reception target. The frame C:F1, the frame C:F2, the frame C:F3, and the frame C:F4 are frames transmitted from the user terminal  11  different from the user terminal  11  that is the reception target. 
     The communication device  12  determines the frame B:F1 with the earliest detection time, as the focused frame. The communication device  12  regards the focused frame as the head frame. The communication device  12  estimates, as a hopping pattern used for transmission, a hopping pattern (pattern of pattern number 1 in  FIG. 3 ) in which the same frequency as the frequency f 8  of the frame B:F1 that is the head frame is used for frame number 1. 
     The communication device  12  performs pattern matching on the detected frame by using the pattern (frequencies f 8 , f 5 , f 7 , and f 0 ) of pattern number 1. As a result of the pattern matching, the communication device  12  specifies the frame B:F2, the frame B:F3, and the frame B:F4 received using the frequency f 5 , the frequency f 7 , and the frequency f 0 , as the same frame. 
     Note that an interval between a detection time of the frame B:F1 and a detection time of the frame B:F2, an interval between a detection time of the frame B:F2 and a detection time of the frame B:F2, and an interval between a detection time of the frame B:F3 and a detection time of the frame B:F4 are time intervals in which an allowable error is added or subtracted for each transmission interval. 
     Furthermore, the communication device  12  determines the transmission start time of the DL communication to be after Δt from the transmission start time of the head frame B:F1 to be repeatedly transmitted. The communication device  12  determines the frequency of the DL communication as the frequency of the pattern of pattern number 4 obtained by adding ΔP (=3) to pattern number 1 used in the UL communication. The communication device  12  can receive, as the DL communication, the frame B:F1, the frame B:F2, the frame B:F3, and the frame B:F4 by using the wireless resource (frequencies f 5 , f 4 , f 6 , and f 8 ) indicated by the determined pattern of pattern number 4. 
     As described above, by regarding a frame having the earliest detection time as a head frame, and performing pattern matching on the detected frame by using the hopping pattern, the repeatedly transmitted same frame can be specified. 
     However, the communication device  12  cannot always detect the head frame of the repetitive transmission, due to an influence of interference or the like. 
     &lt;Example of Case where Detection of Head Frame Fails&gt; 
       FIG. 7  is a view illustrating a state of a wireless resource to be used by the communication device  12  in a case where detection of the head frame fails. 
     In a case where detection of the frame B:F1 of the head frame fails, the communication device  12  determines the frame B:F2 having the earliest detection time as the focused frame. The communication device  12  regards the focused frame as the head frame. The communication device  12  is to estimate, as a hopping pattern used for transmission, a hopping pattern (pattern number 4 in  FIG. 3 ) in which the same frequency as the frequency f 8  of the frame B:F2 that is the head frame is used for frame number 1. 
     The communication device  12  performs pattern matching on the detected frame by using the pattern (frequencies f 5 , f 4 , f 6 , and f 8 ) of pattern number 4. As a result of the pattern matching, a frame received by using the frequency f 4  has not been detected. A frame received by using the frequency f 6  is the frame C:F4. A frame received by using the frequency f 8  has not been detected. Therefore, the communication device  12  specifies the frame C:F4, which is the frame received by using the frequency f 6 , as the same frame. 
     That is, as a result of the pattern matching, the communication device  12  erroneously specifies and synthesizes the frame C:F4 transmitted from different user terminals  11 , as the same frame. 
     Furthermore, the communication device  12  is to determine the transmission start time of the DL communication to be after Δt from the transmission start time of the head frame B:F2 to be repeatedly transmitted. The communication device  12  is to determine, as the frequency of the DL communication, the pattern of pattern number 7, which is obtained by adding ΔP (=3) to pattern number 4 used in the UL communication. The pattern of pattern number 7 is frequencies f 2 , f 6 , f 1 , and f 3  as indicated by frames B:F1 to B:F4 of the DL communication of  FIG. 7 . 
     However, the actual head frame is the frame B:F1. In a case where the head frame is the frame B:F1, the transmission start time of the DL communication is after Δt from the transmission start time of the head frame B:F1 to be repeatedly transmitted, as illustrated in  FIG. 6 . Furthermore, in a case where the head frame is the frame B:F1, the hopping pattern to be actually used in the DL communication is the pattern (frequencies f 5 , f 4 , f 6 , and f 8 ) of pattern number 4 as illustrated in the frames B:F1 to B:F4 of the DL communication of  FIG. 6 . 
     Therefore, the wireless resources used by the communication device  12  and the user terminal  11  do not match, and the user terminal  11  cannot receive a DL frame, which is the frame for the DL communication. 
     Therefore, it is necessary to specify the same frame by regarding frames of frame number 2 to a frame number obtained by subtracting 1 from number of times of repetitive transmission as frames that may be the head frame, in addition to regarding the frame with the earliest detection time as the head frame. 
     However, in this method, the number of patterns for specifying the same frame increases. As a result, there are concerns about an increase in a reception processing time due to an increase in the search time for specifying the same frame and an increase in an operation amount of the base station due to an increase in the number of combinations of the same frame to be demodulated. 
     Therefore, in the present technology, there is used a code hopping pattern that is limited such that the frame number for repetitive transmission is uniquely determined on the basis of the code. As a result, the reception side can uniquely determine what number of frames a detected frame is. 
     3. Third Embodiment (Example of Specifying Frame Number on Basis of Code) 
     &lt;Configuration Example of Wireless Communication System&gt; 
       FIG. 8  is a block diagram illustrating a configuration example of a wireless communication system according to a third embodiment of the present technology. 
     A wireless communication system  101  of  FIG. 8  is configured by connecting user terminals  111 - 1  to  111 - 3  and a communication device  112  by wireless communication. 
     The wireless communication between the user terminals  111 - 1  to  111 - 3  and the communication device  112  is two-way communication including UL communication from the user terminals  111 - 1  to  111 - 3  to the communication device  112  and DL communication from the communication device  112  to the user terminals  111 - 1  to  111 - 3 . 
     The user terminals  111 - 1  to  111 -N are IoT devices including one or more sensors. The user terminals  111 - 1  to  111 -N include at least one sensor of, for example, a camera, a microphone, an acceleration sensor, an angular velocity sensor, a geomagnetic sensor, an illuminance sensor, a temperature sensor, a humidity sensor, a moisture sensor, an optical sensor, an atmospheric pressure sensor, a positioning sensor, and the like. 
     Hereinafter, in a case where it is not necessary to individually distinguish the user terminals  111 - 1  to  111 - 3 , they are collectively referred to as a user terminal  111 , as appropriate. 
     In the wireless communication system  101 , the user terminal  111  and the communication device  112  share a frequency hopping pattern, a code hopping pattern, and a time hopping pattern. The frequency hopping pattern, the code hopping pattern, and the time hopping pattern are configured such that a frame number is specified on a reception side on the basis of the code. 
     For example, as the UL communication, the user terminal  111  measures a measurement target and transmits a data frame containing sensor data representing a measurement result, to the communication device  112 . 
     The user terminal  111  selects a wireless resource by using each frequency hopping pattern, a code, and a time. The user terminal  111  repeatedly transmits a same frame, which is a same data frame, for example, four times by using the selected wireless resource. 
     Furthermore, the user terminal  111  determines a wireless resource of the DL communication on the basis of the wireless resource used in the UL communication. The user terminal  111  receives, as the DL communication, the same frame being transmitted from the communication device  112  by using the wireless resource of the DL communication. 
     The communication device  112  constitutes a base station. The communication device  112  detects a frame being transmitted from the user terminal  111 . The communication device  112  specifies the same frame from the detected frames by using the hopping pattern. 
     The communication device  112  determines the hopping pattern by specifying a frame number of the detected frame on the basis of the code. The communication device  112  specifies the same frame by pattern matching between the detected frame and the determined hopping pattern. The communication device  112  synthesizes the specified same frame and performs demodulation. 
     Furthermore, the communication device  112  determines the wireless resource of the DL communication on the basis of the wireless resource used in the UL communication, and transmits the data frame to the user terminal  111  by using the wireless resource of the DL communication, as the DL communication. 
     As described above, the frame number of the detected frame is specified on the basis of the code. As a result, it is possible to accurately specify the same frame without time synchronization or transmission of a control frame. 
     &lt;Configuration Example of User Terminal&gt; 
       FIG. 9  is a block diagram illustrating a configuration example of the user terminal  111 . 
     The user terminal  111  includes a wireless communication unit  121 , a wireless control unit  122 , a frame generation unit  123 , a sensor  124 , a wireless resource determination unit  125 , a storage unit  126 , a frame detection unit  127 , and a frame demodulation unit  128 . 
     The wireless communication unit  121  transmits and receives wireless signals to and from the communication device  112 . In accordance with a control signal supplied from the wireless control unit  122 , the wireless communication unit  121  converts a frame generated by the frame generation unit  123  into a wireless signal, and transmits to the communication device  112 . 
     In accordance with a control signal supplied from the wireless control unit  122 , the wireless communication unit  121  receives a wireless wave being transmitted from the communication device  12 , and converts into a wireless signal. The wireless communication unit  121  outputs the converted wireless signal to the frame detection unit  127  and the frame demodulation unit  128 . 
     The wireless control unit  122  includes a central processing unit (CPU), a read only memory (ROM), a random access memory (RAM), and the like. The wireless control unit  122  executes a program stored in the ROM or the like, and controls the wireless communication unit  121 . 
     The wireless control unit  122  controls the wireless communication unit  121  to transmit a frame supplied from the frame generation unit  123 , by using a transmission time and a transmission frequency supplied from the wireless resource determination unit  125 . Furthermore, the wireless control unit  122  controls the wireless communication unit  121  to receive a frame, by using a reception time and a reception frequency supplied from the wireless resource determination unit  125 , as necessary. 
     The frame generation unit  123  generates a data frame including sensor data supplied from the sensor  124 , and outputs the generated data frame to the wireless control unit  122 . For generating the data frame, a code supplied from the wireless resource determination unit  125  is used. 
     The sensor  124  measures information outside and inside the terminal, and outputs sensor data indicating a measurement result to the frame generation unit  123 . 
     The wireless resource determination unit  125  determines a wireless resource for transmission of each data frame, by using the hopping pattern acquired from the storage unit  126 . The wireless resource determination unit  125  individually generates a preamble/SYNC and a scramble pattern by using the determined code as an initial value. Furthermore, the wireless resource determination unit  125  determines the wireless resource to be used for the DL communication on the basis of the wireless resource used for the UL communication. 
     The storage unit  126  stores a hopping pattern to be used for determining a wireless resource. 
     The frame detection unit  127  detects a frame from a reception signal supplied from the wireless communication unit  121 . Specifically, the frame detection unit  127  extracts a signal of a target frequency from a wide area signal from the reception signal supplied from the wireless communication unit  121 , and generates a known pattern by using the preamble/SYNC and the scramble pattern. 
     The frame detection unit  127  calculates a correlation value between the signal and the known pattern, and determines that a frame has been detected in a case where the correlation value is a certain value or more. In a case where the frame detection is successful, the frame detection unit  127  outputs the detected wireless resource to the frame demodulation unit  128 . 
     The frame demodulation unit  128  synthesizes and demodulates the frame by using the reception signal supplied from the wireless communication unit  121 . Specifically, the frame demodulation unit  128  extracts a signal of a portion corresponding to the frame from the reception signal, on the basis of a wireless resource corresponding to the number of frames detected by the frame detection unit  127 . 
     The frame demodulation unit  128  descrambles the extracted signal with the scramble pattern supplied from the wireless resource determination unit  125 , and synthesizes the descrambled signal. The frame demodulation unit  128  extracts a Payload from the synthesized signal, and performs error correction code decoding processing and error detection processing using CRC. In a case where the frame demodulation is successful, the frame demodulation unit  128  notifies an upper layer of data. 
     Note that, in a case where the DL communication is not performed, the user terminal  111  may be configured without the frame detection unit  127  and the frame demodulation unit  128 . 
     &lt;Configuration Example of Communication Device&gt; 
       FIG. 10  is a block diagram illustrating a configuration example of the communication device  112 . 
     The communication device  112  includes a wireless communication unit  141 , a wireless control unit  142 , a frame generation unit  143 , a wireless resource determination unit  144 , a storage unit  145 , a frame detection unit  146 , a same frame specification unit  147 , and a frame demodulation unit  148 . 
     The wireless communication unit  141  transmits and receives wireless signals to and from the user terminal  111 . The wireless communication unit  141  receives a wireless wave being transmitted from the user terminal  111  in accordance with a control signal supplied from the wireless control unit  142 , and converts into a wireless signal. The wireless communication unit  141  outputs the converted wireless signal to the frame detection unit  146  and the frame demodulation unit  148 . 
     In accordance with a control signal supplied from the wireless control unit  142 , the wireless communication unit  141  converts a frame generated by the frame generation unit  143  into a wireless signal, and transmits to the user terminal  111 . 
     The wireless control unit  142  includes a CPU, a ROM, a RAM, and the like. The wireless control unit  142  executes a program stored in the ROM or the like, and controls the wireless communication unit  141 . 
     The wireless control unit  142  controls the wireless communication unit  141  to receive a frame, by using a reception time and a reception frequency supplied from the wireless resource determination unit  144 . Furthermore, the wireless control unit  142  controls the wireless communication unit  141  to transmit a frame supplied from the frame generation unit  143 , by using a transmission time and a transmission frequency supplied from the wireless resource determination unit  144 , as necessary. 
     The frame generation unit  143  generates a data frame to be transmitted by the communication device  112 , by using a code supplied from the wireless resource determination unit  144 . The frame generation unit  143  outputs the generated data frame to the wireless control unit  142 . 
     The wireless resource determination unit  144  determines a wireless resource (a frequency, a time, and a code) for transmission of each data frame, by using the hopping pattern acquired from the storage unit  145 . The wireless resource determination unit  144  individually generates a preamble/SYNC and a scramble pattern by using the determined code as an initial value. 
     Furthermore, the wireless resource determination unit  144  has a DL transmission list in which a terminal ID and the wireless resource that is to be used for the DL transmission are registered. The wireless resource determination unit  144  determines the wireless resource to be used for the DL communication on the basis of the wireless resource used for the UL communication. The wireless resource determination unit  144  registers the terminal ID and the wireless resource that is to be used for the DL transmission, in the DL transmission list. 
     The wireless resource determination unit  144  extracts a wireless resource of the DL transmission list, and outputs a code in the wireless resource to the frame generation unit  143 . The wireless resource determination unit  144  outputs a frequency and a time in the wireless resource to the wireless control unit  142 . 
     The storage unit  145  stores a hopping pattern to be used for determining a wireless resource. 
     The frame detection unit  146  detects a frame from a reception signal supplied from the wireless communication unit  141 . A method of detecting the frame is similar to the method of detecting a frame in the frame detection unit  127  in  FIG. 9 . 
     In a case where the frame detection is successful, the frame detection unit  146  registers information on the detected wireless resource as an entry, in a detection frame list included in the same frame specification unit  147 . 
     The same frame specification unit  147  has the detection frame list in which wireless resources of detected frames are registered. The same frame specification unit  147  specifies the repeatedly transmitted same frame from the detected frames by using the information on the wireless resource in the detection frame list and the hopping pattern acquired from the storage unit  145 . 
     In a case where the same frame is successfully specified, the same frame specification unit  147  registers information on the wireless resource of the specified same frame as an entry in a same frame list included in the frame demodulation unit  148 . 
     The frame demodulation unit  148  has the same frame list in which wireless resources of the same frame are registered. In a case where there is a plurality of entries in the same frame list, the frame demodulation unit  148  synthesizes and demodulates the frame by using a reception signal supplied from the wireless communication unit  121 . A method of synthesizing and demodulating the frame is a method of synthesizing and demodulating similar to the method of synthesizing and demodulating in the frame demodulation unit  128  in  FIG. 9 . 
     In a case where the frame demodulation is successful, the frame demodulation unit  148  notifies an upper layer of data. Furthermore, in a case where the frame demodulation is successful, the frame demodulation unit  148  outputs the wireless resource of the same frame to the wireless resource determination unit  144  as the wireless resource of the UL communication. 
     Note that, in a case where the DL communication is not performed, the communication device  112  may be configured without the frame generation unit  143 . 
     &lt;Configuration Example of Frame&gt; 
       FIG. 11  is a view illustrating a configuration example of a frame transmitted and received by the wireless communication system  101 . 
     The frame includes fields of Preamble/SYNC and Payload. The Payload has fields such as ID, DATA, and cyclic redundancy check (CRC). 
     The ID includes a terminal-specific identifier. The DATA contains sensor data. The CRC contains a value that is calculated for the ID and the DATA and to be used for determining reception success on a reception side. 
     The frame generation unit  123  and the frame generation unit  143  perform error correction and interleave on a sequence in which the ID, the DATA, and the CRC are concatenated, and generates the Payload. 
     After concatenating the Payload and the Preamble/SYNC of the data frame, the frame generation unit  123  and the frame generation unit  143  take an exclusive OR for every bit with a scramble pattern of the data frame, and generate a data frame (frame). 
     The preamble/SYNC and the scramble pattern used in the frame are patterns generated from (an initial value of) a code in the wireless resource determination unit  125  and the wireless resource determination unit  144 . 
     &lt;Example of Hopping Pattern&gt; 
     Next, a hopping pattern to be used for generating a wireless resource will be described. In the wireless communication system  101  of  FIG. 7 , a hopping pattern is defined for each of the time, the frequency, and the code. Note that, in the following figures, an example of the number of times of repetitive transmission is four is shown. 
     &lt;Time Hopping Pattern&gt; 
       FIG. 12  is a table illustrating an example of a time hopping pattern. 
     The time hopping pattern indicates a transmission interval at which each frame is repeatedly transmitted. In a case of the third embodiment, the number of patterns is limited to one. A value of the transmission interval is not particularly limited. 
     In a case of  FIG. 12 , the time hopping pattern includes one pattern. In a case where the pattern of pattern number 1 is selected, transmission interval 0, transmission interval T 1 , transmission interval T 1 , and transmission interval T 1  are used to transmit frames of frame numbers 1 to 4, respectively. 
     &lt;Frequency Hopping Pattern&gt; 
       FIG. 13  is a table illustrating an example of a frequency hopping pattern. 
     The frequency hopping pattern indicates a frequency to be used for each frame to be repeatedly transmitted.  FIG. 13  illustrates a pattern in which there are nine usable frequencies and all the frequencies are uniformly assigned. The frequency hopping pattern is not limited to the example of  FIG. 13 . 
     In a case where a pattern of pattern number 1 is selected, frequencies f 3 , f 5 , f 7 , and f 0  are used to transmit frames of frame numbers 1 to 4, respectively. In a case where the pattern of pattern number 2 is selected, frequencies f 7 , f 8 , f 0 , and f 5  are used to transmit the frames of frame numbers 1 to 4, respectively. In a case where the pattern of pattern number 3 is selected, frequencies f 6 , f 3 , f 3 , and f 2  are used to transmit the frames of frame numbers 1 to 4, respectively. In a case where the pattern of pattern number 4 is selected, frequencies f 5 , f 4 , f 6 , and f 3  are used to transmit the frames of frame numbers 1 to 4, respectively. 
     In a case where the pattern of pattern number 5 is selected, frequencies f 4 , f 1 , f 2 , and f 7  are used to transmit the frames of frame numbers 1 to 4, respectively. In a case where the pattern of pattern number 6 is selected, frequencies f 3 , f 0 , f 5 , and f 1  are used to transmit the frames of frame numbers 1 to 4, respectively. In a case where the pattern of pattern number 7 is selected, frequencies f 2 , f 6 , f 1 , and f 3  are used to transmit the frames of frame numbers 1 to 4, respectively. 
     In a case where the pattern of pattern number 8 is selected, frequencies f 1 , f 7 , f 4 , and f 6  are used to transmit the frames of frame numbers 1 to 4, respectively. In a case where the pattern of pattern number 9 is selected, frequencies f 0 , f 2 , f 3 , and f 4  are used to transmit the frames of frame numbers 1 to 4, respectively. 
     &lt;Hopping Pattern of Code&gt; 
       FIG. 14  is a table illustrating an example of a code hopping pattern. 
     The code hopping pattern indicates a combination of initial values to be used for generating a preamble/SYNC and a scramble pattern to be used for generating each frame to be repeatedly transmitted. In the third embodiment, it is necessary to limit such that a frame number for repetitive transmission is uniquely determined on the basis of a code. The number of patterns is not limited, and a plurality of patterns may be included. 
     In a case of  FIG. 14 , the code hopping pattern includes one pattern. In a case where a pattern of pattern number 1 is selected, codes C 1 , C 2 , C 3 , and C 4  are used to transmit frames of frame numbers 1 to 4, respectively. 
     Note that, V 1 , V 2 , V 3 , and V 4  are respectively used as Value 1 to Value 4, for the code C 1 . V 2 , V 3 , V 4 , and V 5  are respectively used as Value 1 to Value 4, for the code C 2 . V 3 , V 4 , V 1 , and V 2  are respectively used as Value 1 to Value 4, for the code C 3 . V 4 , V 1 , V 2 , and V 3  are respectively used as Value 1 to Value 4, for the code C 1 . 
     &lt;Configuration of Pseudo Random Number Generator&gt; 
       FIG. 15  is a diagram illustrating a configuration example of a gold code generator as a pseudo random number generator to be used for generating a preamble/SYNC and a scramble pattern. 
     The gold code generator  151  illustrated in  FIG. 15  includes four pseudo random number generators  161 - 1  to  161 - 4  configured to output two M-sequences, and two exclusive OR (XOR) arithmetic units  171 - 1  and  171 - 2 . This gold code generator  151  is used for the wireless resource determination unit  125  and the wireless resource determination unit  144 . 
     Value 1 of a code C is inputted as an initial value to the pseudo random number generator  161 - 1 . Value 2 of the code C is inputted as an initial value to the pseudo random number generator  161 - 2 . The pseudo random number generator  161 - 1  and the pseudo random number generator  161 - 2  input the initial values to generate random numbers. A value (random number) outputted from the pseudo random number generator  161 - 1  is inputted to the arithmetic unit  171 - 1 . A value (random number) outputted from the pseudo random number generator  161 - 2  is inputted to the arithmetic unit  171 - 1 . The arithmetic unit  171 - 1  obtains a Preamble/SYNC (pseudo random number) by integrating the values supplied from the pseudo random number generators  161 - 1  and  161 - 2 . At this time, the preamble/SYNC obtains a length that matches a preamble/SYNC length of the frame. 
     Similarly, Value 3 of the code C is inputted as an initial value to the pseudo random number generator  161 - 3 . Value 4 of the code C is inputted as an initial value to the pseudo random number generator  161 - 4 . The pseudo random number generator  161 - 3  and the pseudo random number generator  161 - 4  input the initial values to generate random numbers. A value (random number) outputted from the pseudo random number generator  161 - 3  is inputted to the arithmetic unit  171 - 2 . A value (random number) outputted from the pseudo random number generator  161 - 2  is inputted to the arithmetic unit  171 - 2 . The arithmetic unit  171 - 2  obtains a scramble pattern (pseudo random number) by integrating the values supplied from the pseudo random number generators  161 - 3  and  161 - 4 . At this time, the scramble pattern obtains a length that matches a frame length. 
     In this way, in a case where the preamble/SYNC and the scramble pattern are generated, the known pattern to be used for frame detection is to be a different pattern except for a combination in which all of Value 1 to Value 4 have the same value. 
     Effects of Third Embodiment 
     Next, a description is given to an example in which the first frame in same frames has been unable to be detected correctly on the reception side, in a case of using a hopping pattern ( FIGS. 12 to 14 ) limited such that the frame number for repetitive transmission is uniquely determined on the basis of the code. 
       FIG. 16  is a table illustrating a detection frame list in the communication device  112 . 
     In the detection frame list of  FIG. 16 , information on wireless resources of detected frames of entries 1 to 7 is registered. 
     As entry 1, information on a wireless resource whose time is T′+T 1 , frequency is f 5 , and code is C 2  is registered. As entry 2, information on a wireless resource whose time is T′+2T 1 , frequency is f 2 , and code is C 1  is registered. As entry 3, information on a wireless resource whose time is T′+2T 1 , frequency is f 7 , and code is C 3  is registered. As entry 4, information on a wireless resource whose time is T′+3T 1 , frequency is f 0 , and code is C 4  is registered. 
     As entry 5, information on a wireless resource whose time is T′+3T 1 , frequency is f 6 , and code is C 2  is registered. As entry 6, information on a wireless resource whose time is T′+4T 1 , frequency is f 1 , and code is C 3  is registered. As entry 7, information on a wireless resource whose time is T′+5T 1 , frequency is f 3 , and code is C 4  is registered. 
       FIG. 17  is a view illustrating an example in which the communication device  12  performs DL transmission after specifying a same frame from detected frames. 
     In  FIG. 17 , the frames of entries 1 to 7 registered in the detection frame list of  FIG. 16  are assigned with entry numbers, and are shown at positions of respectively corresponding frequencies in order of detection time. Furthermore, on the right side of the DL repetitive transmission start time, frames F1 to F4 to be subjected to the DL transmission are indicated in order of respective transmission times at respective frequencies. Moreover, the frames of entries 1 to 7 and frames F1 to F4 to be subjected to the DL transmission also indicate the respective codes. 
     As illustrated in  FIG. 17 , in a case where same frame specification processing is performed with entry 1 of the detection frame list as the focused entry, the detected code is (C 2 ). Therefore, a code of the focused frame is specified as the code of frame number 2 on the basis of the code hopping pattern ( FIG. 14 ). 
     Furthermore, on the basis of the frequency (f 5 ) at which the frame of the focused entry has been detected and the frequency of frame number 2 in the frequency hopping pattern ( FIG. 13 ), the pattern used for repetitive transmission can be correctly extracted as pattern number 1. 
     Moreover, on the basis of a time (T′+T 1 ) at which the focused entry has been detected and a total transmission interval up to the second frame of the time hopping pattern ( FIG. 12 ), a start time (T′) of repetitive transmission of the UL communication is correctly calculated. 
     Here, in the wireless communication system  1 , in order to determine the wireless resource to be used for the DL communication, rules shown in Equations (1) and (2), which will be described later, are defined and shared by the user terminal  111  and the communication device  112 . For example, in a case of ΔP=2, the user terminal  111  and the communication device  112  individually calculate pattern number 4 (f 5 , f 4 , f 6 , and f 8 ) ( FIG. 13 ) to be used for repetitive transmission of the DL communication illustrated in  FIG. 17 , by Equation (1) and the frequency hopping pattern ( FIG. 13 ). Furthermore, the user terminal  111  and the communication device  112  individually calculate a start time (T′+Δt) of the repetitive transmission of the DL communication by Equation (2). In this way, since the wireless resource calculated by the user terminal  111  and to be used for the DL communication matches the wireless resource calculated by the communication device  112  and to be used for the DL communication, the user terminal  111  can receive a DL frame. 
     In this way, in the third embodiment of the present technology, there is used a code hopping pattern that is limited such that the frame number for repetitive transmission is uniquely determined on the basis of the code. As a result, since the reception side uniquely determines what number of frames a detected frame is, it is possible to correctly specify a same frame only by performing pattern matching once for the focused frame. 
     &lt;Operation of Entire Wireless Communication System&gt; 
       FIG. 18  is a flowchart for explaining processing of the entire wireless communication system  101 . 
     When receiving a data transmission request from an upper layer, the user terminal  111  starts the processing of  FIG. 18 . 
     In step S 101 , the user terminal  111  determines a wireless resource to be used for UL communication. 
     In step S 102 , the user terminal  111  repeatedly transmits UL frames (1 to n), which are frames of the UL communication, to the communication device  112 , by using the determined wireless resource. 
     In step S 121 , the communication device  112  performs frame detection at all times, and detects the UL frames (1 to n) being transmitted from the user terminal  111 . 
     In a case where a same frame specification request supplied from an upper layer is received, the communication device  112  performs the processing in and after step S 122 . 
     In step S 122 , the communication device  112  specifies the same frame from the frames detected in step S 121 , as the same frame specification processing. 
     In step S 123 , the communication device  112  synthesizes and demodulates the specified same frame, as frame synthesis/demodulation processing. 
     In step S 124 , the communication device  112  determines the wireless resource to be used for the DL communication, on the basis of the wireless resource estimated to have been used in the UL communication from a detection/demodulation result of a UL frame. 
     Note that, hereinafter, individual pieces of the processing in steps S 122  to S 124  will be collectively referred to as frame reception processing. 
     In step S 125 , the communication device  112  repeatedly transmits DL frames (1 to n), which are frames of the DL communication, to the user terminal  111  by using the determined wireless resource. 
     Whereas, after transmitting the UL frame, in step S 103 , the user terminal  111  determines the wireless resource to be used for the DL communication, on the basis of the wireless resource used for the UL communication. 
     In step S 104 , the user terminal  111  performs frame detection only at a time when the DL frame is transmitted, by using the determined wireless resource. 
     In step S 105 , the user terminal  111  synthesizes and demodulates the detected frame. 
     Note that determining the wireless resource to be used for the DL communication on the basis of the wireless resource used for the UL communication specifically means to determine a hopping pattern to be used for the DL communication and a start time of repetitive transmission. For example, in the wireless communication system  101 , rules as shown in the following Equations (1) and (2) are defined and shared. 
     [Formula 1] 
       PATTERN NUMBER TO BE USED FOR DL COMMUNICATION=(PATTERN NUMBER USED FOR UL COMMUNICATION+Δp) mod NUMBER OF PATTERNS+1   (1)
 
     Here, for example, ΔP=2 is used. 
       [Formula 2] 
       DL REPETITIVE TRANSMISSION START TIME=UL REPETITIVE TRANSMISSION START TIME+Δt  (2)
 
     By doing this way, the user terminal  111  can perform frame detection only at a time when the DL frame is transmitted. As a result, power saving can be achieved. 
     &lt;Operation of User Terminal&gt; 
       FIG. 19  is a flowchart for explaining frame transmission/reception processing of the user terminal  111 . 
     In step S 151 , the wireless control unit  122  determines whether or not a data transmission request has been received from an application of an upper layer (not illustrated). In a case where it is determined in step S 151  that the data transmission request has been received, the process proceeds to step S 152 . 
     In step S 152 , the wireless resource determination unit  125  selects any given pattern from a hopping pattern in the storage unit  126  (corresponding to step S 101  in  FIG. 18 ). A pattern of a frequency and a pattern of a time are outputted to the wireless control unit  122 . A pattern of a code is outputted to the frame generation unit  123 . 
     In step S 153 , the wireless control unit  122  sets a repetitive transmission start time to any given time. 
     In step S 154 , the wireless control unit  122  executes repetitive transmission processing (corresponding to step S 102  in  FIG. 18 ). This repetitive transmission processing will be described later with reference to  FIG. 20 . By the processing in step S 154 , the same frame is repeatedly transmitted a predetermined number of times. 
     In step S 155 , the wireless control unit  122  determines whether or not frame reception is necessary. In a case where it is determined that frame reception is necessary, the process proceeds to step S 156 . 
     In step S 156 , the wireless control unit  122  executes repetitive reception processing (corresponding to steps S 103  to S 105  in  FIG. 18 ). This repetitive reception processing will be described later with reference to  FIGS. 21 and 22 . By the processing in step S 156 , the same frame transmitted from the communication device  112  is repeatedly received a predetermined number of times. 
     After the frame is repeatedly received in step S 156 , the frame transmission/reception processing of the user terminal  111  ends. 
     Furthermore, similarly, also in a case where it is determined in step S 151  that the data transmission request has not been received, or in a case where it is determined in step S 155  that frame reception is not necessary, the frame transmission/reception processing ends. 
       FIG. 20  is a flowchart for explaining the repetitive transmission processing in step S 154  in  FIG. 19 . 
     In step S 171 , the wireless control unit  122  sets a frame transmission start time as a repetitive transmission start time. 
     In step S 172 , the wireless control unit  122  initializes a frame number F to 1. 
     In step S 173 , the wireless control unit  122  determines whether or not the frame number F is equal to or less than the number of times of repetitive transmission. In a case where it is determined in step S 173  that the frame number F is equal to or less than the number of times of repetitive transmission, the process proceeds to step S 174 . 
     In step S 174 , the wireless control unit  122  and the frame generation unit  123  extract a wireless resource (a frequency, a time, and a code) corresponding to the frame number F of the pattern selected by the wireless resource determination unit  125 . 
     In step S 175 , the frame generation unit  123  generates a frame to be transmitted, by using the extracted code. 
     In step S 176 , the wireless control unit  122  adds the extracted time (transmission interval) to the frame transmission start time. 
     In step S 177 , the wireless control unit  122  waits until the frame transmission start time is reached. In a case where it is determined in step S 177  that the frame transmission start time has been reached, the process proceeds to step S 178 . 
     In step S 178 , the wireless control unit  122  controls the wireless communication unit  121  to transmit the frame supplied from the frame generation unit  123 , by using the extracted frequency. 
     In step S 179 , the wireless control unit  122  increments the frame number F, and thereafter, the process returns to step S 173 . 
     In a case where it is determined in step S 173  that the frame number F is larger than the number of times of repetitive transmission, the repetitive transmission processing ends. 
       FIGS. 21 and 22  are flowcharts for explaining the repetitive reception processing in step S 156  in  FIG. 19 . 
     In step S 181  of  FIG. 21 , the wireless resource determination unit  125  calculates a pattern to be used for reception (DL communication) on the basis of the pattern selected in step S 152  of  FIG. 19 . For the calculation of the hopping pattern, Equation (1) or Equation (2) described above is used. A pattern of a frequency and a pattern of a time are outputted to the wireless control unit  122 . A pattern of a code is outputted to the frame generation unit  123 . 
     In step S 182 , the wireless control unit  122  calculates a repetitive reception start time on the basis of a repetitive transmission start time. 
     In step S 183 , the wireless control unit  122  sets a frame reception start time as a repetitive reception start time. 
     In step S 184 , the wireless control unit  122  initializes the frame number F to 1. 
     In step S 185  of  FIG. 22 , it is determined whether or not the frame number F is equal to or less than the number of times of repetitive transmission. In a case where it is determined in step S 185  that the frame number F is equal to or less than the number of times of repetitive transmission, the process proceeds to step S 186 . 
     In step S 186 , the wireless control unit  122  and the frame generation unit  123  extract a wireless resource (a frequency, a time, and a code) corresponding to the frame number F of the pattern selected by the wireless resource determination unit  125 . 
     In step S 187 , the wireless control unit  122  adds the time (transmission interval) extracted in step S 186  to the frame reception start time. 
     In step S 188 , the wireless control unit  122  waits until the frame reception start time is reached. In a case where it is determined in step S 188  that the frame reception start time has been reached, the process proceeds to step S 189 . 
     In step S 189 , the wireless communication unit  121  receives a wireless signal of the frequency extracted in step S 186 . The wireless communication unit  121  outputs the received wireless signal to the frame detection unit  127 . 
     In step S 190 , the frame detection unit  127  executes frame detection processing by using the code extracted in step S 186 . 
     In step S 191 , the frame detection unit  127  determines whether or not the frame detection is successful. In a case where it is determined in step S 191  that the frame detection is successful, the process proceeds to step S 192 . 
     In step S 192 , the frame detection unit  127  segments, descrambles, and holds a signal of the detected frame. 
     In a case where it is determined in step S 191  that the frame detection is not successful, step S 192  is skipped, and the process proceeds to step S 193 . 
     In step S 193 , the wireless control unit  122  increments the frame number F, and thereafter, the process returns to step S 185 . 
     In a case where it is determined in step S 185  that the frame number F is larger than the number of times of repetitive transmission, the process proceeds to step S 194 . 
     In step S 194 , the frame detection unit  127  determines whether or not there is a plurality of detected frames. In a case where it is determined in step S 194  that there is a plurality of detected frames, the process proceeds to step S 195 . 
     In step S 195 , the frame detection unit  127  synthesizes the signal held in step S 192 . 
     In a case where it is determined in step S 194  that there is not a plurality of detected frames, step S 195  is skipped, and the process proceeds to step S 196 . 
     In step S 196 , the frame demodulation unit  128  executes demodulation processing. 
     In step S 197 , the frame demodulation unit  128  determines whether or not the frame demodulation is successful. In a case where it is determined in step S 197  that the frame demodulation is successful, the process proceeds to step S 198 . 
     In step S 198 , the frame demodulation unit  128  notifies an upper layer of data acquired from the frame. 
     In a case where it is determined in step S 197  that frame demodulation has failed, the process skips step S 198 . 
     After the data is notified to the upper layer in step S 198  or after step S 198  is skipped, the repetitive reception processing ends. 
     &lt;Operation of Communication Device&gt; 
     As described above with reference to  FIG. 18 , processing of the communication device  12  is divided into three pieces: the frame detection processing ( FIG. 23 ) in step S 121 , the frame reception processing ( FIG. 24 ) in steps S 122  to S 124 , and the repetitive transmission processing ( FIG. 27 ) in step S 125 . These pieces of processing are individually executed in parallel. Hereinafter, each piece of processing will be described in detail. 
       FIG. 23  is a flowchart for explaining the frame detection processing of the communication device  112 . Note that the processing in  FIG. 23  is processing corresponding to the frame detection processing in step S 121  in  FIG. 18 . 
     In step S 211 , the wireless control unit  142  waits until it is determined that the frame reception start time has been reached. In a case where it is determined in step S 211  that the frame reception start time has been reached, the process proceeds to step S 212 . 
     In step S 212 , the wireless communication unit  141  receives a wireless signal of a target frequency in accordance with a control signal supplied from the wireless control unit  142 . 
     In step S 213 , the frame detection unit  146  executes the frame detection processing by using a target code. 
     In step S 214 , the frame detection unit  146  determines whether or not the frame detection is successful. In a case where it is determined in step S 214  that the frame detection is successful, the process proceeds to step S 215 . 
     In step S 215 , the frame detection unit  146  registers information on a wireless resource (a frequency, a time, and a code) with which the frame is detected, in the detection frame list included in the same frame specification unit  147 . 
     After the registration in the detection frame list in step S 215  or in a case where it is determined in step S 214  that the frame detection is not successful, the frame detection processing ends. 
     Note that the communication device  112  of the base station does not know which wireless resource is used by the user terminal  111  to transmit the frame, and thus the processing of  FIG. 23  is repeatedly executed at all times. Furthermore, the processing of  FIG. 23  needs to be executed in parallel by designating the target frequency and the target code such that the processing with all usable codes is performed on all usable frequencies. 
       FIG. 24  is a flowchart for explaining frame reception processing of the communication device  112 . 
     In step S 231 , the same frame specification unit  147  determines whether or not a same frame specification request has been received. For example, in a case where the same frame specification request is supplied from an upper layer of the communication device  112 , it is determined in step S 231  that the same frame specification request has been received, and the process proceeds to step S 232 . 
     In step S 232 , the same frame specification unit  147  determines whether or not there is an entry in the detection frame list. In a case where it is determined in step S 232  that there is an entry in the detection frame list, the process proceeds to step S 233 . 
     In step S 233 , the same frame specification unit  147  focuses on an entry having the earliest detection time. 
     In step S 234 , the same frame specification unit  147  temporarily clears the same frame list included in the frame demodulation unit  148 . 
     In step S 235 , the same frame specification unit  147  executes the same frame specification processing (corresponding to step S 122  in  FIG. 18 ). This same frame specification processing will be described later with reference to  FIG. 25 . By the processing in step S 235 , the same frame is specified. 
     In step S 236 , the frame demodulation unit  148  executes the frame synthesis/demodulation processing (corresponding to steps S 123  and S 124  in  FIG. 18 ). The frame synthesis/demodulation processing will be described later with reference to  FIG. 26 . By the processing in step S 236 , the same frame is synthesized, and frame demodulation processing is performed. 
     In step S 237 , the same frame specification unit  147  deletes the focused entry. 
     After step S 237 , the process returns to step S 232 , and the subsequent processing is repeated. 
     In a case where it is determined in step S 231  that the same frame specification request has not been received, or in a case where it is determined in step S 232  that there is no entry in the detection frame list, the frame reception processing ends. 
     Note that, depending on a timing at which the same frame specification request has been received, the user terminal  111  may still be in the middle of repetitive transmission for the focused entry (detected frame). In this case, as in this processing, if an entry focused once is immediately deleted from the detection frame list, the number of frames determined to be the same frame decreases, and the gain obtained by the synthesis may decrease. 
     Therefore, in consideration of such a case, whether or not to delete the focused entry may be determined by using the number of frames specified as the same frame, whether demodulation is successful, a detection time of the focused entry, or the like. 
       FIG. 25  is a flowchart for explaining the same frame specification processing in step S 235  in  FIG. 24 . 
     In step S 251 , the same frame specification unit  147  adds a focused entry to the same frame list. 
     In step S 252 , the same frame specification unit  147  extracts a pattern (code) and a frame number that match a code of the focused entry. 
     In step S 253 , the same frame specification unit  147  sets a frame number to F. 
     In step S 254 , the same frame specification unit  147  extracts a pattern (frequency) in which the frame number F and a frequency of the focused entry match. 
     In step S 255 , the same frame specification unit  147  calculates a repetitive transmission start time from the detection time of the focused entry and the frame number F. 
     In step S 256 , the same frame specification unit  147  determines whether or not F is smaller than the number of times of repetitive transmission. In a case where it is determined in step S 256  that F is smaller than the number of times of repetitive transmission, the process proceeds to step S 257 . 
     In step S 257 , the same frame specification unit  147  calculates a wireless resource to be used for a frame of a frame number F+1, from the extracted pattern and the repetitive transmission start time. 
     In step S 258 , the same frame specification unit  147  determines whether or not there is an entry whose detection time is within a range of (calculated time±a) in the detection frame list. In a case where it is determined in step S 258  that there is an entry whose detection time is within the range of (calculated time±a) in the detection frame list, the process proceeds to step S 259 . 
     In step S 259 , the same frame specification unit  147  determines whether or not the frequency/code of the entry matches the calculated frequency/code. In a case where it is determined in step S 259  that the frequency/code of the entry matches the calculated frequency/code, the process proceeds to step S 260 . 
     In step S 260 , the same frame specification unit  147  adds the entry to the same frame list. After the entry is added, the process proceeds to step S 261 . 
     Furthermore, similarly, also in a case where it is determined in step S 258  that there is no entry whose detection time is within the range of (calculated time±a) in the detection frame list, or in a case where it is determined in step S 259  that the frequency/code of the entry does not match the calculated frequency/code, the process proceeds to step S 261 . 
     In step S 261 , the same frame specification unit  147  increments F. After F is incremented, the process returns to step S 256 , and the subsequent processing is repeated. 
     Whereas, in a case where it is determined in step S 256  that F is larger than the number of times of repetitive transmission, the same frame specification processing ends. 
       FIG. 26  is a flowchart for explaining the frame synthesis/demodulation processing in step S 236  in  FIG. 24 . 
     In step S 271 , the frame demodulation unit  148  segments, descrambles, and holds a signal for all the entries (frames) in the same frame list. 
     In step S 272 , the frame demodulation unit  148  determines whether or not there is a plurality of entries in the same frame list. In a case where it is determined in step S 272  that there is a plurality of entries in the same frame list, the process proceeds to step S 273 . 
     In step S 273 , the frame demodulation unit  148  synthesizes the held signal. After the synthesis of the signal, the process proceeds to step S 274 . 
     In a case where it is determined in step S 272  that there is not a plurality of entries in the same frame list, step S 273  is skipped, and the process proceeds to step S 274 . 
     In step S 274 , the frame demodulation unit  148  executes demodulation processing. 
     In step S 275 , the frame demodulation unit  148  determines whether or not the frame demodulation is successful. In a case where it is determined in step S 275  that the frame demodulation is successful, the process proceeds to step S 276 . 
     In step S 276 , the frame demodulation unit  148  notifies the upper layer of data acquired from the frame. 
     In step S 277 , the wireless control unit  142  determines whether or not DL transmission is necessary. In a case where it is determined in step S 277  that DL transmission is necessary, the process proceeds to step S 278 . At this time, the frame demodulation unit  148  outputs a wireless resource of the specified same frame to the wireless resource determination unit  144 , as the wireless resource of the UL communication. 
     In step S 278 , the wireless resource determination unit  144  calculates a wireless resource to be used for the DL transmission. 
     In step S 279 , the wireless resource determination unit  144  registers the terminal ID and the wireless resource that is to be used for the DL transmission, in the DL transmission list. After the wireless resource is registered, the frame synthesis/demodulation processing ends. 
     Furthermore, similarly, also in a case where it is determined in step S 275  that the demodulation of the frame is not successful, or in a case where it is determined in step S 277  that DL transmission is not necessary, the frame synthesis/demodulation processing ends. 
       FIG. 27  is a flowchart for explaining the repetitive transmission processing of the communication device  112 . 
     This repetitive transmission processing is processing corresponding to step S 125  in  FIG. 18 , and is processing performed for each entry of the DL transmission list by the communication device  112 . 
     In step S 291 , the wireless control unit  142  sets a frame transmission start time as a repetitive transmission start time. 
     In step S 292 , the wireless control unit  142  initializes the frame number F to 1. 
     In step S 293 , the wireless control unit  142  determines whether or not the frame number F is equal to or less than the number of times of repetitive transmission. In a case where it is determined in step S 293  that the frame number F is equal to or less than the number of times of repetitive transmission, the process proceeds to step S 294 . 
     In step S 294 , the wireless control unit  142  extracts a wireless resource (a frequency, a time, and a code) corresponding to the frame number F of the pattern of the focused entry. 
     In step S 295 , the frame generation unit  143  generates a frame to be transmitted, by using the extracted code. 
     In step S 296 , the wireless control unit  142  adds the extracted time (transmission interval) to the frame transmission start time. 
     In step S 297 , the wireless control unit  142  waits until the frame transmission start time is reached. In a case where it is determined in step S 297  that the frame transmission start time has been reached, the process proceeds to step S 298 . 
     In step S 298 , the wireless control unit  142  controls the wireless communication unit  141  to transmit the frame by using the extracted frequency. 
     In step S 299 , the wireless control unit  142  increments the frame number F, and thereafter, the process returns to step S 293 . 
     In a case where it is determined in step S 293  that the frame number F is larger than the number of times of repetitive transmission, the repetitive transmission processing ends. 
     As described above, in the third embodiment, there is used a code hopping pattern that is limited such that the frame number for repetitive transmission is uniquely determined on the basis of the code. As a result, since the reception side uniquely determines what number of frames a detected frame is, it is possible to correctly specify a same frame only by performing pattern matching once for the focused frame. 
     4. Fourth Embodiment (Example of Specifying Frame Number on Basis of Frequency) 
     As described above in the third embodiment, in a case of enabling determination as to what number of frames a detection frame is on the basis of a code, the code corresponding to the number of times of repetitive transmission x the number of patterns is required. Since the communication device  112  of the base station does not know which wireless resource is used by the user terminal  111  to transmit the frame, it is necessary to execute the frame detection processing in parallel so as to be performed at all times for all usable frequencies with all usable codes. 
     Therefore, when the number of codes to be used in the wireless communication system  101  increases, a processing amount for the frame detection processing of the communication device  112  increases. 
     Therefore, a fourth embodiment makes it makes possible to determine what number of frames a detected frame is on the basis of a frequency in a wireless resource. 
     A configuration of a wireless communication system  101 , a configuration of a user terminal  111 , and a configuration of a communication device  112  of the fourth embodiment are similar configurations to those of the third embodiment. Description overlapping with the description of the third embodiment described above will be appropriately omitted. 
     &lt;Example of Hopping Pattern&gt; 
     Next, a hopping pattern to be used for generating a wireless resource will be described. Also in the wireless communication system  101  of the fourth embodiment, a hopping pattern is defined for each of a frequency, a time, and a code. 
     &lt;Time Hopping Pattern&gt; 
       FIG. 28  is a table illustrating an example of a time hopping pattern. 
     The time hopping pattern indicates a transmission interval of each frame to be repeatedly transmitted. Also in a case of the fourth embodiment, similarly to the third embodiment, the number of patterns is limited to one. A value of the transmission interval is not particularly limited. 
     In a case of  FIG. 28 , the time hopping pattern includes one pattern. In a case where the pattern of pattern number 1 is selected, transmission interval 0, transmission interval T 1 , transmission interval T 1 , and transmission interval T 1  are used to transmit frames of frame numbers 1 to 4, respectively. 
     &lt;Frequency Hopping Pattern&gt; 
       FIG. 29  is a table illustrating an example of a frequency hopping pattern. 
     The frequency hopping pattern indicates a frequency to be used for each frame to be repeatedly transmitted. In a case of the fourth embodiment, it is necessary to limit such that a frame number for repetitive transmission is uniquely determined on the basis of a frequency. Therefore, the number of the frequency hopping patterns is to be an integer obtained by dividing the number of usable frequencies by the number of times of repetitive transmission. 
     In a case of the example of  FIG. 29 , in a case where there are nine usable frequencies and the number of times of repetitive transmissions is four, the definable frequency hopping pattern is to be two patterns. 
     In a case where a pattern of pattern number 1 is selected, frequencies f 0 , f 5 , f 7 , and f 0  are used to transmit frames of frame numbers 1 to 4, respectively. In a case where the pattern of pattern number 2 is selected, frequencies f 2 , f 6 , f 1 , and f 3  are used to transmit the frames of frame numbers 1 to 4, respectively. 
     &lt;Hopping Pattern of Code&gt; 
       FIG. 30  is a table illustrating an example of a code hopping pattern. 
     The code hopping pattern indicates a combination of initial values to be used for generating a preamble/SYNC and a scramble pattern to be used for generating each frame to be repeatedly transmitted. In the fourth embodiment, the code is fixed, but is not limited to the example of  FIG. 30 . 
     In a case of  FIG. 30 , the code hopping pattern includes one pattern. In a case where a pattern of pattern number 1 is selected, codes C 1 , C 1 , C 1 , and C 1  are used to transmit frames of frame numbers 1 to 4, respectively. 
     Note that V 1 , V 2 , V 3 , and V 4  are respectively used as values 1 to 4, for the code C 1 . 
     Effects of Fourth Embodiment 
     Next, a description is given to an example in which the first frame in same frames has been unable to be detected correctly on the reception side, in a case of using a hopping pattern ( FIGS. 28 to 30 ) limited such that the frame number for repetitive transmission is uniquely determined on the basis of the frequency. 
       FIG. 31  is a table illustrating a detection frame list in the communication device  112 . 
     In the detection frame list of  FIG. 31 , wireless resources of detected frames of entries 1 to 7 are registered. 
     As entry 1, information on a wireless resource whose time is T′+T 1 , frequency is f 5 , and code is C 1  is registered. As entry 2, information on a wireless resource whose time is T′+2T 1 , frequency is f 2 , and code is C 1  is registered. As entry 3, information on a wireless resource whose time is T′+2T 1 , frequency is f 7 , and code is C 1  is registered. As entry 4, information on a wireless resource whose time is T′+3T 1 , frequency is f 0 , and code is C 1  is registered. 
     As entry 5, information on a wireless resource whose time is T′+3T 1 , frequency is f 6 , and code is C 1  is registered. As entry 6, information on a wireless resource whose time is T′+4T 1 , frequency is f 1 , and code is C 1  is registered. As entry 7, information on a wireless resource whose time is T′+5T 1 , frequency is f 3 , and code is C 1  is registered. 
       FIG. 32  is a view illustrating a state in which the communication device  12  performs DL transmission after specifying a same frame from detected frames. 
     In  FIG. 32 , the frames of entries 1 to 7 registered in the detection frame list of  FIG. 31  are assigned with entry numbers, and are shown at positions of respectively corresponding frequencies in order of detection time. Furthermore, on the right side of the DL repetitive transmission start time, frames F1 to F4 to be subjected to the DL transmission are indicated in order of respective transmission times at respective frequencies. Moreover, the frames of entries 1 to 7 and frames F1 to F4 to be subjected to the DL transmission also indicate the respective codes. 
     As illustrated in  FIG. 32 , in a case where the same frame specification processing is performed with entry 1 of the detection frame list as the focused entry, the detected frequency is (f 5 ). Therefore, on the basis of the frequency hopping pattern ( FIG. 29 ), it is specified that the frequency of the focused frame is the frequency of frame number 2, and the pattern number is 1. 
     Furthermore, on the basis of the code (C 1 ) with which the frame of the focused entry has been detected and the code of frame number 2 of the code hopping pattern ( FIG. 30 ), the pattern used for repetitive transmission can be correctly extracted as pattern number 1. 
     Moreover, on the basis of a time (T′+T 1 ) at which the focused entry has been detected and a total transmission interval up to the second frame of the time hopping pattern, a start time (T′) of repetitive transmission as the UL communication is correctly calculated. 
     Here, in the wireless communication system  1 , in order to determine a wireless resource to be used for the DL communication, Equations (1) and (2) described above are shared by the user terminal  111  and the communication device  112 . For example, in a case of ΔP=2, the user terminal  111  and the communication device  112  individually calculate pattern number 2 (f 2 , f 6 , f 1 , and f 3 ) ( FIG. 29 ) to be used for repetitive transmission of the DL communication illustrated in  FIG. 32 , by Equation (1) and the frequency hopping pattern ( FIG. 29 ). Furthermore, the user terminal  111  and the communication device  112  individually calculate a start time (T′+Δt) of the repetitive transmission of the DL communication by Equation (2). In this way, since the wireless resource calculated by the user terminal  111  and to be used for the DL communication matches the wireless resource calculated by the communication device  112  and to be used for the DL communication, the user terminal  111  can receive a DL frame. 
     In this way, in the fourth embodiment of the present technology, there is used a frequency hopping pattern that is limited such that the frame number for repetitive transmission is uniquely determined on the basis of the frequency. As a result, since the reception side uniquely determines what number of frames a detected frame is, it is possible to correctly specify a same frame only by performing pattern matching once for the focused frame. 
     Note that, in the fourth embodiment, processing of the entire wireless communication system  101  is similar to the processing described above with reference to  FIG. 18 . The processing of the user terminal  111  is also similar to the processing described above in the third embodiment. In the processing of the communication device  112 , processing other than the following same frame specification processing is similar to the processing described above in the third embodiment. 
     Therefore, in the processing in the fourth embodiment, description of processing similar to the processing described above in the third embodiment will be redundant, and thus to be omitted. 
     &lt;Operation of Communication Device&gt; 
       FIG. 33  is a flowchart for explaining another example of the same frame specification processing in step S 235  in  FIG. 24 . 
     In step S 311 , the same frame specification unit  147  adds a focused entry to a same frame list. 
     In step S 312 , the same frame specification unit  147  extracts a pattern (frequency) and a frame number that match a frequency of the focused entry. 
     In step S 313 , the same frame specification unit  147  sets a frame number to F. 
     In step S 314 , the same frame specification unit  147  extracts a pattern (code) in which the frame number F and a code of the focused entry match. 
     Note that, since processing in steps S 315  to S 321  in  FIG. 33  is similar to processing in steps S 255  to S 261  in  FIG. 25 , the description thereof will be omitted. 
     As described above, in the fourth embodiment of the present technology, there is used a pattern of a frequency that is limited such that a frame number for repetitive transmission is uniquely determined on the basis of a frequency. As a result, since the reception side uniquely determines what number of frames a detected frame is, it is possible to correctly specify a same frame only by performing pattern matching once for the focused frame. 
     5. Fifth Embodiment (Example of Specifying Frame Number on Basis of Combination of Frequency and Code) 
     As described above in the fourth embodiment, in a case of enabling determination as to what number of frames a detection frame is on the basis of a frequency, the number of hopping patterns that can be defined is to be small with respect to usable frequencies. When the number of frequency hopping patterns is small, a collision of frames transmitted by the user terminal  111  is likely to occur in the wireless communication system  101 . 
     Therefore, in a fifth embodiment, it makes possible to determine what number of frames a detected frame is on the basis of a combination of a frequency and a code in a wireless resource. 
     Since a configuration of a wireless communication system  101 , a configuration of a user terminal  111 , and a configuration of a communication device  112  of the fifth embodiment are similar configurations to those of the third embodiment, description overlapping with the description of the third embodiment described above will be appropriately omitted. 
     &lt;Example of Hopping Pattern&gt; 
     Next, a hopping pattern to be used for generating a wireless resource will be described. Also in the wireless communication system  101  of the fifth embodiment, a hopping pattern is defined for each of a frequency, a time, and a code. 
     &lt;Time Hopping Pattern&gt; 
       FIG. 34  is a table illustrating an example of a time hopping pattern. 
     The time hopping pattern indicates a transmission interval of each frame to be repeatedly transmitted. Also in a case of the fifth embodiment, similarly to the third embodiment, the number of patterns is limited to one. A value of the transmission interval is not particularly limited. 
     In a case of  FIG. 34 , the time hopping pattern includes one pattern. In a case where the pattern of pattern number 1 is selected, transmission interval 0, transmission interval T 1 , transmission interval T 1 , and transmission interval T 1  are used to transmit frames of frame numbers 1 to 4, respectively. 
     &lt;Frequency Hopping Pattern&gt; 
       FIG. 35  is a table illustrating an example of a frequency hopping pattern. 
     The frequency hopping pattern indicates a frequency to be used for each frame to be repeatedly transmitted. In a case of the fifth embodiment, it is necessary to limit such that the frame number for repetitive transmission is uniquely determined on the basis of a combination of a frequency and a code in  FIG. 36  described later. 
     In a case of the example of  FIG. 35 , in a case where there are nine usable frequencies, the definable frequency hopping pattern is to be four patterns. 
     In a case where a pattern of pattern number 1 is selected, frequencies f 8 , f 5 , f 7 , and f 0  are used to transmit frames of frame numbers 1 to 4, respectively. In a case where the pattern of pattern number 2 is selected, frequencies f 2 , f 6 , f 1 , and f 3  are used to transmit the frames of frame numbers 1 to 4, respectively. In a case where the pattern of pattern number 3 is selected, frequencies f 5 , f 2 , f 3 , and f 7  are used to transmit the frames of frame numbers 1 to 4, respectively. In a case where the pattern of pattern number 4 is selected, frequencies f 6 , f 8 , f 0 , and f 1  are used to transmit the frames of frame numbers 1 to 4, respectively. 
     &lt;Hopping Pattern of Code&gt; 
       FIG. 36  is a table illustrating an example of a code hopping pattern. 
     In a case of  FIG. 36 , the code hopping pattern includes one pattern. In a case where a pattern of pattern number 1 is selected, codes C 1 , C 2 , C 1  and C 2  are used to transmit frames of frame numbers 1 to 4, respectively. 
     Note that, V 1 , V 2 , V 3 , and V 4  are respectively used as Value 1 to Value 4, for the code C 1 . V 2 , V 3 , V 4 , and V 1  are respectively used as Value 1 to Value 4, for the code C 2 . 
     Effects of Fifth Embodiment 
     Next, a description is given to an example in which the first frame in same frames has been unable to be detected correctly on the reception side, in a case of using a hopping pattern ( FIGS. 34 to 36 ) limited such that the frame number for repetitive transmission is uniquely determined on the basis of the combination of the frequency and the code. 
       FIG. 37  is a table illustrating a detection frame list in the communication device  112 . 
     In the detection frame list of  FIG. 37 , wireless resources of detected frames of entries 1 to 7 are registered. 
     As entry 1, information on a wireless resource whose time is T′+T 1 , frequency is f 5 , and code is C 2  is registered. As entry 2, information on a wireless resource whose time is T′+2T 1 , frequency is f 2 , and code is C 1  is registered. As entry 3, information on a wireless resource whose time is T′+2T 1 , frequency is f 7 , and code is C 1  is registered. As entry 4, information on a wireless resource whose time is T′+3T 1 , frequency is f 0 , and code is C 2  is registered. 
     As entry 5, information on a wireless resource whose time is T′+3T 1 , frequency is f 6 , and code is C 2  is registered. As entry 6, information on a wireless resource whose time is T′+4T 1 , frequency is f 1 , and code is C 1  is registered. As entry 7, information on a wireless resource whose time is T′+5T 1 , frequency is f 3 , and code is C 2  is registered. 
       FIG. 38  is a view illustrating a state in which the communication device  112  performs DL transmission after specifying a same frame from detected frames. 
     In  FIG. 38 , the frames of entries 1 to 7 registered in the detection frame list of  FIG. 37  are assigned with entry numbers, and are shown at positions of respectively corresponding frequencies in order of detection time. Furthermore, on the right side of the DL repetitive transmission start time, frames F1 to F4 to be subjected to the DL transmission are indicated in order of respective transmission times at respective frequencies. Moreover, the frames of entries 1 to 7 and frames F1 to F4 to be subjected to the DL transmission also indicate the respective codes. 
     As illustrated in  FIG. 38 , in a case where the same frame specification processing is performed with entry 1 of the detection frame list as the focused entry, the detected code is (C 2 ). Therefore, it is specified that the frequency of the focused frame is the frequency of frame number 2 or the frequency of frame number 4 on the basis of the pattern of codes ( FIG. 36 ). 
     Furthermore, on the basis of the frequency (f 5 ) at which the frame of the focused entry has been detected and the frequency of frame number 2 or the frequency of frame number 4 of the frequency hopping pattern ( FIG. 35 ), a frame of the focused entry can be correctly extracted as the frame of frame number 2. Moreover, the pattern used for repetitive transmission can be correctly extracted as pattern number 1. 
     Moreover, on the basis of the time (T′+T 1 ) at which the focused entry has been detected and a total transmission interval up to the second frame of the time hopping pattern, a start time (T′) of repetitive transmission as the UL communication and a start time (T′+Δt) of repetitive transmission of the DL communication can also be calculated correctly. 
     Here, in the wireless communication system  1 , in order to determine a wireless resource to be used for the DL communication, Equations (1) and (2) described above are shared by the user terminal  111  and the communication device  112 . For example, in a case of ΔP=2, the user terminal  111  and the communication device  112  individually calculate pattern number 4 (f6, f8, f0, and f1) ( FIG. 35 ) to be used for repetitive transmission of the DL communication illustrated in  FIG. 38 , by Equation (1) and the frequency hopping pattern ( FIG. 35 ). Furthermore, the user terminal  111  and the communication device  112  individually calculate a start time (T′+Δt) of the repetitive transmission of the DL communication by Equation (2). Therefore, since the wireless resource calculated by the user terminal  111  and to be used for the DL communication coincides with the wireless resource calculated by the communication device  112  and to be used for the DL communication, the user terminal  111  can receive a DL frame. 
     In this way, in the fifth embodiment of the present technology, there are used a frequency hopping pattern and a code hopping pattern that are limited such that the frame number for repetitive transmission is uniquely determined on the basis of the combination of the frequency and the code. As a result, since the reception side uniquely determines what number of frames a detected frame is, it is possible to correctly specify a same frame only by performing pattern matching once for the focused frame. 
     Note that, in the fifth embodiment, processing of the entire wireless communication system  101  is similar to the processing described above with reference to  FIG. 18 . The processing of the user terminal  111  is also similar to the processing described above in the third embodiment. In the processing of the communication device  112 , processing other than the following same frame specification processing is similar to the processing described above in the third embodiment. 
     Therefore, in the processing in the fifth embodiment, description of processing similar to the processing described above in the third embodiment will be redundant, and thus to be omitted. 
     &lt;Operation of Communication Device&gt; 
       FIG. 39  is a flowchart for explaining another example of the same frame specification processing in step S 235  in  FIG. 24 . 
     In step S 351 , the same frame specification unit  147  adds a focused entry to a same frame list. 
     In step S 352 , the same frame specification unit  147  extracts a pattern (code) and a frame number candidate that match a code of the focused entry. 
     In step S 353 , the same frame specification unit  147  extracts a pattern (frequency) and a frame number in which the frame number candidate and a frequency of the focused entry match. 
     In step S 354 , the same frame specification unit  147  sets a frame number to F. 
     Note that, since processing in steps S 355  to S 361  in  FIG. 39  is similar to processing in steps S 255  to S 261  in  FIG. 25 , the description thereof will be omitted. 
     As described above, in the fifth embodiment of the present technology, there are used a frequency hopping pattern and a code hopping pattern that are limited such that the frame number for repetitive transmission is uniquely determined on the basis of a combination of a frequency and a code. As a result, since the reception side uniquely determines what number of frames a detected frame is, it is possible to correctly specify a same frame only by performing pattern matching once for the focused frame. 
     6. Other 
     Effects 
     In the present technology, a wireless resource to be used for repetitive transmission of a same frame is limited. As a result, even in a case where there is a frame that has been unable to be detected in the base station among repeatedly transmitted same frames, a frame number of the detected frame can be uniquely determined. 
     According to the present technology, the same frame can be correctly specified. 
     According to the present technology, it is possible to suppress the time required for the same frame specification processing, as compared with a round robin method on wireless resources. 
     According to the present technology, it is possible to suppress the number of combinations determined to be the same frame and to suppress a processing amount required for the demodulation processing, as compared with a round robin method on wireless resources. 
     According to the present technology, it is possible to correctly specify a pattern with which the wireless resource used for the UL communication is determined. Further, the wireless resources individually calculated by the user terminal and the base station and to be used for the DL communication match each other, and the user terminal can receive a DL frame. 
     &lt;Computer Configuration Example&gt; 
     The series of processes described above can be executed by hardware or software. In a case of executing the series of processes by software, a program that forms the software is installed from a program recording medium to a computer incorporated in dedicated hardware, to a general-purpose personal computer, or the like. 
       FIG. 40  is a block diagram illustrating a configuration example of hardware of a computer that executes the series of processes described above in accordance with a program. 
     A CPU  301 , a ROM  302 , and a RAM  303  are connected to each other by a bus  304 . 
     The bus  304  is further connected with an input/output interface  305 . The input/output interface  305  is connected with an input unit  306  including a keyboard, a mouse, and the like, and an output unit  307  including a display, a speaker, and the like. Furthermore, the input/output interface  305  is connected with a storage unit  308  including a hard disk, a non-volatile memory, and the like, a communication unit  309  including a network interface and the like, and a drive  310  that drives a removable medium  311 . 
     In the computer configured as described above, the series of processes described above are performed, for example, by the CPU  301  loading a program recorded in the storage unit  308  into the RAM  303  via the input/output interface  305  and the bus  304 , and executing. 
     The program to be executed by the CPU  301  is provided, for example, by being recorded on the removable medium  311  or via wired or wireless transfer media such as a local area network, the Internet, and digital broadcasting, to be installed in the storage unit  308 . 
     Note that the program executed by the computer may be a program that performs processing in a time series according to an order described in this specification, or may be a program that performs processing in parallel or at necessary timing such as when a call is made. 
     Note that, in this specification, the system means a set of a plurality of components (a device, a module (a part), and the like), and it does not matter whether or not all the components are in the same housing. Therefore, a plurality of devices housed in separate housings and connected via a network, and a single device with a plurality of modules housed in one housing are both systems. 
     Furthermore, the effects described in this specification are merely examples and are not limited, and other effects may also be present. 
     The embodiment of the present technology is not limited to the above-described embodiments, and various modifications can be made without departing from the scope of the present technology. 
     For example, the present technology can have a cloud computing configuration in which one function is shared and processed in cooperation by a plurality of devices via a network. 
     Furthermore, each step described in the above-described flowchart can be executed by one device, and also shared and executed by a plurality of devices. 
     Moreover, in a case where one step includes a plurality of processes, the plurality of processes included in the one step can be executed by one device, and also shared and executed by a plurality of devices. 
     &lt;Combination Example of Configuration&gt; 
     The present technology can also have the following configurations. 
     (1) 
     A communication device including: 
     a wireless resource determination unit configured to determine a first wireless resource including a frequency for transmission of a same frame that is a frame of same data, a code of the same frame, and a time for transmission of the same frame, on the basis of pattern information indicating a unique relationship between a frame number of the same frame and at least one of the frequency or the code; and 
     a transmission unit configured to repeatedly transmit the same frame by using the first wireless resource. 
     (2) 
     The communication device according to (1) described above, in which 
     the wireless resource determination unit determines the first wireless resource on the basis of the pattern information indicating a unique relationship between the frame number and the code. 
     (3) 
     The communication device according to (1) described above, in which 
     the wireless resource determination unit determines the first wireless resource on the basis of the pattern information indicating a unique relationship between the frame number and the frequency. 
     (4) 
     The communication device according to (1) described above, in which 
     the wireless resource determination unit determines the first wireless resource on the basis of the pattern information indicating a unique relationship between the frame number and a combination of the frequency and the code. 
     (5) 
     The communication device according to any one of (1) to (4), in which 
     the wireless resource determination unit determines a second wireless resource required for reception of the same frame, on the basis of the first wireless resource. 
     (6) 
     The communication device according to (5) described above, further including: 
     a reception unit configured to repeatedly receive the same frame by using the second wireless resource. 
     (7) 
     A communication method including, 
     by the communication device: 
     determining a first wireless resource including a frequency for transmission of a same frame that is a frame of same data, a code of the same frame, and a time for transmission of the same frame, on the basis of pattern information indicating a unique relationship between a frame number of the same frame and at least one of the frequency or the code; and 
     repeatedly transmitting the same frame by using the first wireless resource. 
     (8) 
     A communication device including: 
     a frame detection unit configured to detect a data frame being transmitted with use of a wireless resource including a frequency for transmission of the data frame, a code of the data frame, and a time for transmission of the data frame; 
     a frame specification unit configured to specify, from the detected data frame on the basis of pattern information, a same frame being transmitted with use of a first wireless resource determined on the basis of the pattern information indicating a unique relationship between a frame number of the same frame that is a frame of same data and at least one of the frequency or the code; and a demodulation unit configured to synthesize and demodulate the same frame. 
     (9) 
     The communication device according to (8) described above, in which 
     the same frame is being transmitted with use of the first wireless resource determined on the basis of the pattern information indicating a unique relationship between the frame number and the code. 
     (10) 
     The communication device according to (8) described above, in which 
     the same frame is being transmitted with use of the first wireless resource determined on the basis of the pattern information indicating a unique relationship between the frame number and the frequency. 
     (11) 
     The communication device according to (8) described above, in which 
     the same frame is being transmitted with use of the first wireless resource determined on the basis of the pattern information indicating a unique relationship between the frame number and a combination of the frequency and the code. 
     (12) 
     The communication device according to any one of (8) to (11), further including: 
     a wireless resource determination unit configured to determine a second wireless resource to be used for transmission of the same frame, on the basis of the first wireless resource. 
     (13) 
     The communication device according to (12) described above, further including: 
     a transmission unit configured to repeatedly transmit the same frame by using the second wireless resource. 
     (14) 
     A communication method including, 
     by the communication device: 
     detecting a data frame being transmitted with use of a wireless resource including a frequency for transmission of the data frame, a code of the data frame, and a time for transmission of the data frame; 
     specifying, from the detected data frame on the basis of pattern information, a same frame being transmitted with use of a first wireless resource determined on the basis of the pattern information indicating a unique relationship between a frame number of the same frame that is a frame of same data and at least one of the frequency or the code; and 
     synthesizing and demodulating the same frame. 
     REFERENCE SIGNS LIST 
     
         
           101  Wireless communication system 
           111 - 1  to  111 - 3 ,  111  User terminal 
           112  Communication device 
           121  Wireless communication unit 
           122  Wireless control unit 
           123  Frame generation unit 
           124  Sensor 
           125  Wireless resource determination unit 
           126  Storage unit 
           127  Frame detection unit 
           128  Frame demodulation unit 
           141  Wireless communication unit 
           142  Wireless control unit 
           143  Frame generation unit 
           144  Wireless resource determination unit 
           145  Storage unit 
           146  Frame detection unit 
           147  Same frame specification unit 
           148  Frame demodulation unit