JP5362131B2 - COMMUNICATION DEVICE, COMMUNICATION DEVICE CONTROL METHOD, AND PROGRAM - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To avoid wastefully occupying a communication band and to provide a technology to efficiently obtain synchronous data. <P>SOLUTION: Reception states of data sent at an N-th cycle on other communication devices are determined, and according to the determination results, data to other communication devices are sent at a cycle at an N-th cycle or later. <P>COPYRIGHT: (C)2013,JPO&amp;INPIT

Description

  The present invention relates to a communication apparatus that transmits received data, a communication apparatus control method, and a program.

  A wireless communication system is used as a network system having excellent portability, and is rapidly spreading due to an improvement in transmission speed in a wireless communication section, a spread of mobile terminals, and the emergence of applications suitable for mobile communication. In particular, WLAN systems that use radio waves in the 2.4 GHz and 5 GHz bands are widely used as a method for wirelessly connecting computer devices in a relatively short distance such as indoors or premises. The technical specifications are defined in the IEEE 802.11 standard group.

  In addition, there is an increasing demand for not only computer peripheral devices but also consumer devices such as digital still cameras and digital video cameras, and wireless communication between devices such as connecting a printer or a mobile phone. At present, these are generally connected by a wired cable such as USB or IEEE1394, but a method by which a user can easily connect these devices is also considered by wireless connection.

  The wireless communication system between devices at such a short distance is different from WLAN, and is aimed at wireless connection within the environment of one person, which is considered to be about 10 meters at the most. It is distinguished from WLAN and called WPAN. At present, regarding the WPAN, specifications of the physical layer and the MAC layer are defined as ECMA-368 standards from ECMA international, which is a standard-defining organization, that uses UWB (Ultra Wide Band) communication methods. Furthermore, the Wireless USB standard is defined as a protocol that operates above the ECMA-368.

  In WLAN and WPAN, in order to prevent collision of radio frames that may occur when a plurality of radio terminals transmit radio frames at the same time, the timing at which each radio terminal accesses the radio medium is controlled. The media access control (MAC) protocol defines this control method. There are various methods for such a MAC protocol, but as a typical classification method, it can be classified into two types, an asynchronous data transfer method and a synchronous data transfer method.

  In general, in asynchronous data transfer, a terminal that has obtained an access right to a medium through a CSMA / CA (Carrier Sense Multiple Access / Collision Avoidance) protocol transmits data. When the data destination terminal correctly receives the data, it returns a recognition response generally called an acknowledge frame to the transmitting terminal. When receiving the recognition response, the data transmitting terminal determines that the data transfer has been completed normally. On the other hand, when the recognition response is not received, the data transmitting terminal determines that the data transfer has failed and tries to retransmit the data after a certain period.

  In this way, the asynchronous data transfer method can reliably transfer the data to the destination terminal. However, on the other hand, the data transfer delay amount due to the failure to acquire the media access right or the above-mentioned data retransmission, etc. fluctuate. Here, such a variation in delay amount in data transfer is referred to as delay jitter.

  Note that applications that transfer audio, video, etc. require synchronicity or isochronism with respect to data transfer, so asynchronous data transfer methods that increase delay jitter are not suitable for such applications. Not suitable.

  On the other hand, in the synchronous data transfer method, each terminal transmits data within a time slot assigned to itself by a TDMA (Time Division Multiple Access) protocol or the like. In such a protocol, each terminal can acquire the right to transmit data at regular intervals, so that the delay jitter for data transfer is small. Therefore, the synchronous data transfer method is suitable for data transfer that requires synchronization or isochronism.

  Further, in the synchronous data transfer method, since the delay jitter in data transfer is kept within a certain range, generally, a recognition response is not exchanged between the transmitting and receiving terminals, and a retransmission process when data transfer fails is not performed. For this reason, in the synchronous data transfer method, a data packet may be lost depending on the communication state.

  However, in audio and video transmission, maintaining the constant average transfer rate and average delay is always given the highest priority as communication characteristics, so the application protocol is designed to allow a certain amount of packet loss. .

  As described above, the synchronous data transfer method is suitable for applications that require synchronization such as voice and moving images, but application data is lost due to packet loss. Such data loss has a drawback in that the quality of the application is deteriorated due to interruption of the reproduced sound, block noise of the moving image, and the like.

  To solve such problems in synchronous data transfer systems, relay transmission that transfers the same data redundantly multiple times as a highly reliable communication system that suppresses the occurrence of data loss while maintaining synchronization A method is considered. Therefore, such a relay transmission method will be described.

  FIG. 16 is a system configuration diagram illustrating an example of the configuration of the relay transmission system. This system is composed of, for example, a control station 11 as a generation source of synchronous data such as voice and moving images and four subordinate stations 12 to 15 as destinations of the synchronous data.

  FIG. 17 is a diagram illustrating the media access timing of the relay transmission system. Here, the system employs TDMA as an access protocol, and the access timing to the medium is managed in units of a fixed period called a superframe 21. The super frame 21 is divided into time slots 31 to 35 for data transmission by the control station 11 and the dependent stations 12 to 15 respectively.

  In the superframe 21, the time slot 31 is the time for the control station 11 to transmit data, and the time slots 32 to 35 are the time for the dependent stations 12 to 15 to transmit data in order.

  FIG. 18 is a diagram illustrating a radio frame transmitted in each time slot in a super frame. First, the control station 11 broadcasts a broadcast frame 41 holding synchronization data addressed to each dependent station in a time slot 31 in the superframe toward all the dependent stations.

  FIG. 19 is a diagram showing a frame format of a broadcast frame transmitted by broadcast. In the broadcast frame 41, an ISO_DATA1 field is arranged in the field 51, and this field 51 stores a synchronization data body addressed to the dependent station 12. Similarly, the fields 52 to 54 store synchronization data addressed to the dependent stations 13 to 15, respectively. In the field 55, a CHECKSUM_FRAME field is arranged, and a station that receives the broadcast frame 41 detects a bit error occurring in the broadcast frame 41 by verifying the checksum. In this example, the length of each synchronization data is fixed.

  FIG. 20 is a schematic diagram showing the direction of data transfer in each time slot. (A) shown in FIG. 20 shows a situation where a broadcast frame 41 is transmitted from the control station 11 to each of the dependent stations 12 to 15 in the first time slot 31. Each of the dependent stations 12 to 15 that have received the broadcast frame 41 determines its own transmission timing with reference to a predetermined transmission order on the basis of the time when the broadcast frame 41 is received. Further, the dependent stations 12 to 15 use data addressed to the own station from among the synchronization data included in the received broadcast frame 41 as application data. At the same time, the dependent stations 12 to 15 store the entire broadcast frame 41 in order to relay the broadcast frame 41 to other dependent stations.

  The dependent station 12 that has received the broadcast frame 41 and determined its own transmission timing transmits the relay frame 42 in the time slot 32 as a duplicate of the broadcast frame 41 received from the control station 11. This state is shown in FIG. Then, the other dependent stations 13 to 15 other than the dependent station 12 receive and store this relay frame 42. Similarly, in the time slot 33, the dependent station 13 transmits the relay frame 43 as a duplicate of the broadcast frame 41, and the other dependent stations 12, 14, 15 other than the dependent station 13 receive this relay frame 43.

  In this manner, the broadcast frame 41 transmitted from the control station 11 in the time slot 31 is relayed from the dependent stations 12 to 15 in the time slots 32 to 35 as shown in FIGS. Is done. The relay frames 42 to 45 that are relayed and transmitted have the same format as the broadcast frame 41. Therefore, each subordinate station has an opportunity to receive the same synchronization data four times in total as a broadcast frame from the control station 11 and a relay frame from another subordinate station.

  In this system, since the data is transferred a plurality of times in this way, even if the dependent station cannot correctly receive the broadcast frame from the control station, it is possible to synchronize from the relay frame transmitted by another dependent station to the local station. Data can be acquired. Therefore, in this system, even when a communication path is interrupted, data transfer is completed within one superframe, so that data transfer synchronization can be maintained.

  Patent Document 1 proposes a technique for reliably transmitting broadcast data to a destination node (see, for example, Patent Document 1).

JP 2007-266876

  In the relay transmission system described above, the same data is relayed and transmitted between subordinate stations, whereby packet loss can be suppressed and highly reliable synchronous data communication can be performed. However, this method also has an aspect in which the communication band is wasted because the same data is repeatedly transmitted five times redundantly from the viewpoint of communication band utilization efficiency.

  For example, if a dependent station can normally receive broadcast data from the control station, relay transmission in subsequent time slots becomes unnecessary communication, and the communication band is wasted. In such a redundant relay transmission system, the communication band is essentially occupied by data relay transfer, and it is impossible to transfer more data.

  As a result, there is a problem that it is difficult to optimize the use of the communication band and increase the data transfer amount of the entire system.

  An object of the present invention is to flexibly perform transmission of received data.

The present invention is a first communication device,
Receiving means for receiving data transmitted from the second communication device in an N-th period including at least a transmission period of the first communication device and a transmission period of the second communication device;
Determining means for determining a reception status of the third communication device of data transmitted from the second communication device in the Nth cycle;
Transmitting means for transmitting at least data addressed to the third communication device received by the receiving means in a period after the Nth period, according to a determination result by the determining means;
It is characterized by having.

Also, a control method of the first communication device,
A receiving step of receiving data transmitted from the second communication device in an Nth cycle of a period including at least a transmission period of the first communication device and a transmission period of the second communication device;
A determination step of determining a reception status of a third communication device of data transmitted in the Nth cycle from the second communication device;
In accordance with the determination result in the determination step, at least a transmission step of transmitting data addressed to the third communication device received in the reception step in a cycle after the Nth cycle,
It is characterized by having.

  Furthermore, the present invention provides a computer program that causes a computer to function as the communication device of the present invention.

  According to the present invention, since received data is transmitted according to the data reception status of other communication devices, it is possible to flexibly transmit received data.

It is a figure which shows an example of a structure of the radio relay transmission system in 1st embodiment. It is a figure which shows an example of a structure of the control station in 1st embodiment. It is a figure which shows an example of the internal structure of the dependent station in 1st embodiment. It is a figure which shows the structure of the super frame in 1st embodiment. It is a figure which shows the structure of the relay frame in 1st embodiment. It is a figure which shows the frame format of the relay frame 407 of the dependent station 102, and the relay frame 410 of the dependent station 105. FIG. It is a figure which shows the frame format of the relay frame 408 of the dependent station 103, and the relay frame 409 of the dependent station 104. FIG. It is a figure which shows the super frame in case the dependent stations 102 and 103 transmit asynchronous data as data other than synchronous data. It is a figure which shows the frame format of the relay frame which the dependent station 102 transmits asynchronous data. 3 is a diagram illustrating a frame format of a relay frame 808. FIG. It is a figure which shows the structure of a super frame in case a control station transmits an asynchronous frame. It is a figure which shows an example of a structure of the asynchronous frame which a control station transmits. It is a figure for demonstrating the problem in 3rd embodiment. It is a figure which shows the example of a format of the broadcast frame which a control station transmits. It is a figure which shows the structure of the super frame in 3rd embodiment. It is a system configuration diagram showing an example of a configuration of a relay transmission system. It is a figure which shows the media access timing of a relay transmission system. It is a figure which shows the radio | wireless frame transmitted with each time slot in a super frame. It is a figure which shows the frame format of the broadcast frame transmitted by broadcast. It is a schematic diagram which shows the direction of the data transfer in each time slot.

  The best mode for carrying out the invention will be described below in detail with reference to the drawings.

[First embodiment]
The configuration and operation of the wireless relay transmission system according to the first embodiment will be described with reference to FIGS.

  FIG. 1 is a diagram illustrating an example of a configuration of a wireless relay transmission system according to the first embodiment. As shown in FIG. 1, the wireless relay transmission system includes a control station 101 as a generation source of synchronization data such as voice and moving images and dependent stations 102 to 105 as destinations of the synchronization data. In this example as well, TDMA is adopted, and the media access timing is managed in units of superframes 21 shown in FIG. The super frame 21 is divided into a plurality of time slots 31 to 35 for data transmission by the control station 101 and the dependent stations 102 to 105, respectively.

  FIG. 2 is a diagram illustrating an example of the configuration of the control station in the first embodiment. In FIG. 2, a super frame timing generation unit 206 generates a super frame timing to be described later. Timing information generated by the superframe timing generation unit 206 is transmitted to the transmission timing generation unit 207. In accordance with the instruction from the transmission timing generation unit 207, the transmission frame generation unit 204 generates a transmission frame using the synchronization data addressed to each dependent station received from the application processing unit 201 via the synchronization data generation unit 202. Similarly, in the case of asynchronous data received via the asynchronous data generation unit 203, a transmission frame is generated. This asynchronous data will be further described later.

  Here, a checksum for error detection is added to the generated transmission frame in the checksum generation unit 205, converted into a radio signal by the modulation unit 250 and the high frequency unit 252, and then transmitted from the antenna 253 to the wireless medium. Sent out.

  On the other hand, the relay frame from each dependent station is received by the antenna 253 and input to the checksum verification unit 210 via the high frequency unit 252 and the demodulation unit 251. Then, the checksum is verified and sent to the frame length determination unit 208 or the asynchronous data reception unit 209.

  FIG. 3 is a diagram illustrating an example of the internal configuration of the dependent station in the first embodiment. In FIG. 3, the application processing unit 301, the asynchronous data generation unit 302, the transmission frame generation unit 303, the checksum generation unit 304, the transmission timing generation unit 305, and the super frame timing synchronization unit 308 are components of the control station shown in FIG. It is the same. Also, the modulation unit 350, the demodulation unit 351, the high frequency unit 352, and the antenna 353 have the same functions as each unit of the control station.

  In FIG. 3, the broadcast frame received by the antenna 353 is converted into received data by the high frequency unit 352 and the demodulation unit 351. The received data is verified by the checksum verification unit 312 whether it contains a bit error. If it is determined that there is no bit error in the received data, the received data is sent to the received frame analysis unit 309 and the relay data storage unit 306. All the synchronization data normally received by each dependent station is temporarily stored in the relay data storage unit 306 for relay transmission to other dependent stations. Further, the received data is sent to the synchronous data receiving unit 310 or the asynchronous data receiving unit 311 according to the result analyzed by the received frame analysis unit 309.

  When the received data is a broadcast frame from the control station 101, a synchronization control signal is sent from the received frame analysis unit 309 to the superframe timing synchronization unit 308. In this way, the dependent stations 102 to 105 can follow the superframe managed by the control station 101 synchronously, and transmit the relay frame in the time slot assigned to the dependent station.

  In addition, the dependent stations 102 to 105 that have received the broadcast frame determine their own transmission timing with reference to a predetermined transmission order on the basis of the time at which the broadcast frame is received, and respectively transmit the relay frame. .

  FIG. 4 is a diagram illustrating a configuration of a super frame in the first embodiment. In this example, for convenience of drawing, the Nth superframe is illustrated in the upper stage and the (N + 1) th superframe is illustrated in the lower stage. However, the Nth superframe is temporally consecutive so that the Nth superframe comes first. Be placed.

  First, in the first time slot of the Nth superframe, the control station 101 broadcasts the Nth broadcast frame 401 holding the synchronization data addressed to the dependent station to all the dependent stations. The frame format of the broadcast frame 401 is the same as that shown in FIG.

  4, 402 is a relay frame transmitted from the dependent station 102, 403 is a relay frame transmitted from the dependent station 103, 404 is a relay frame transmitted from the dependent station 104, and 405 is a relay frame transmitted from the dependent station 105.

  Here, a frame format example of the relay frame, which is a feature of the present invention, will be described with reference to FIGS.

  FIG. 5 is a diagram showing the configuration of the relay frame in the first embodiment. The relay frame has a LEN_FRAME field indicating the length of the entire frame at the frame start portion and an ACKNOWLEDGE field indicating a recognition response to the broadcast frame received in the same super frame. The unit of the frame length indicated by the LEN_FRAME field may be a byte (8 bits) or a word (16 bits) depending on the implementation, but the present invention can be applied to any unit. Is possible.

  The station that receives these relay frames can know the length of the relay frame by referring to the value of the LEN_FRAME field, and can also calculate the time for which the frame occupies the communication band.

  Examples of values stored in the ACKNOWLEDGE field include ACK and NACK. In this example, the dependent station that has successfully received the broadcast frame sets ACK as a value in the ACKNOWLEDGE field. On the other hand, the dependent station that failed to receive the broadcast frame sets NACK as a value in the ACKNOWLEDGE field.

  The third field of the relay frame shown in FIG. 5 is a data payload portion. Here, synchronous data and other asynchronous data that are relayed and transmitted are stored in the data payload portion, which will be described in detail later.

  The fourth field at the end of the relay frame is a checksum for detecting whether a bit error is included in the entire relay frame. As the checksum, a CRC (Cyclic Redundancy Code) such as 16 bits or 32 bits is generally used, but any code can be applied as long as a bit error can be detected.

  Here, as shown in FIG. 1, the dependent station 102 and the dependent station 105 have successfully received the broadcast frame 401 transmitted from the control station 101, but the dependent station 103 and the dependent station 104 have failed to receive. think of.

  Each dependent station determines a value set in the ACKNOWLEDGE field by the recognition response generation unit 307 with reference to the error detection result in the checksum verification unit 312. Now, the ACKNOWLEDGE field in the relay frame 402 of the dependent station 102 and the relay frame 405 of the dependent station 105 stores the value ACK because these dependent stations have normally received the Nth broadcast frame 401. In the ACKNOWLEDGE field in the relay frame 403 of the dependent station 103 and the relay frame 405 of the dependent station 104, NACK is stored as a value because these dependent stations have failed to receive the Nth broadcast frame 401.

  As a result, each dependent station receives a recognition response transmitted using the ACKNOWLEDGE field, so that each dependent station determines whether or not the synchronization data included in the broadcast frame needs to be transferred. can do. For example, the dependent station 102 understands that its own station has normally received the Nth broadcast frame 401, and has further received an ACKNOWLEDGE frame holding the value ACK transmitted by the dependent station 105 as a recognition response. .

  Therefore, the dependent station 102 determines that only the synchronization data addressed to the dependent station 103 and the dependent station 104 in the Nth synchronization frame should be relayed in the (N + 1) th superframe. Further, the dependent station 105 understands that the own station has normally received the Nth broadcast frame 401, and has further received an ACKNOWLEDGE frame holding the value ACK transmitted as a recognition response by the dependent station 102. .

  Therefore, the dependent station 105 similarly determines that only the synchronization data addressed to the dependent station 103 and the dependent station 104 in the Nth synchronization frame should be relayed in the (N + 1) th superframe.

  Here, the operation of each station in the (N + 1) th superframe when the dependent stations 103 and 104 fail to receive the Nth broadcast frame 401 will be described. Also in the (N + 1) th superframe, the control station 101 broadcasts the N + 1th broadcast frame 406 holding the synchronization data addressed to each dependent station in the first time slot. Then, the dependent stations 102 to 105 that have received the broadcast frame 406 determine their own transmission timing in the same manner as the Nth superframe and transmit the relay frame.

  In FIG. 4, 407 is a relay frame transmitted from the dependent station 102, 408 is a relay frame transmitted from the dependent station 103, 409 is a relay frame transmitted from the dependent station 104, and 410 is a relay frame transmitted from the dependent station 105.

  FIG. 6 is a diagram illustrating the frame formats of the relay frame 407 of the dependent station 102 and the relay frame 410 of the dependent station 105. These relay frames also have a header portion including a LEN_FRAME field and an ACKNOWLEDGE field, as shown in FIG.

  First, the LEN_FRAME field indicates the length of the entire relay frame, and the ACKNOWLEDGE field is a recognition response indicating whether or not a broadcast frame in the same super frame has been normally received. The relay frame has a synchronization data part in which synchronization data to be relayed is stored.

  In FIG. 6, a DATA_TYPE field is shown as the third field, and this field is set to ISO2 as a value in order to indicate that this synchronization data is data addressed to the dependent station 103. The fourth field has an ISO_DATA field, in which the synchronization data body addressed to the dependent station 103 is stored.

  Similarly, it has a DATA_TYPE field as the fifth field, and this field is set to ISO3 as a value to indicate that the next synchronization data is data addressed to the dependent station 104. The sixth field has an ISO_DATA field, in which the synchronization data body addressed to the dependent station 104 is stored.

  By transmitting relay data in such a format, only synchronous data addressed to the dependent stations 103 and 104 is relayed from the dependent stations 102 and 105.

  FIG. 7 is a diagram illustrating the frame formats of the relay frame 408 of the dependent station 103 and the relay frame 409 of the dependent station 104. Since the dependent stations 103 and 104 have not normally received the Nth broadcast frame 401 transmitted from the control station 101, they hold synchronization data that can be relayed to other dependent stations in the (N + 1) th superframe. Absent.

  Therefore, the dependent stations 103 and 104 only transmit a recognition response to the (N + 1) th broadcast frame 406, and do not relay synchronous data.

  As described above, unnecessary relay transmission of synchronous data is suppressed by using the recognition response. For this reason, as shown in FIG. 4, the relay frames 407 to 410 to which the present invention is applied have a shorter frame length than the relay frames 42 to 45 in the conventional relay transmission system already shown in FIG.

  As a result, as shown in FIG. 4, the period reserved for relay transmission (the second half of the time slot) is not actually used for relay transmission, and an unoccupied time can be provided on the communication medium. Further, since each dependent station can receive at least the (N + 1) th superframe in the Nth superframe, the synchronization data transmitted from the control station to each subordinate station can be received. A system is built.

  In the description so far, the formats shown in FIGS. 5 to 7 have been used as relay frames on the assumption that each dependent station does not hold other data such as asynchronous data that is required to be transmitted. Hereinafter, how each substation uses the non-occupation time obtained in this way for other data transmission will be described.

  FIG. 8 is a diagram illustrating a super frame when the dependent stations 102 and 103 transmit asynchronous data as data other than the synchronous data. Asynchronous data is data other than data transmitted synchronously by relay transmission, and data having various formats and characteristics can be transmitted as asynchronous data.

  In FIG. 8, reference numerals 801 to 806, 809, and 810 are the same frames as 401 to 406, 409, and 410 shown in FIG. Reference numeral 807 denotes a relay frame transmitted by the dependent station 102. FIG. 9 is a diagram illustrating a frame format of a relay frame in which the dependent station 102 transmits asynchronous data.

  In FIG. 9, the first to sixth fields are the same as those shown in FIG. By using these fields, the dependent station 102 recognizes and responds to the (N + 1) th broadcast frame 806, and simultaneously relays the synchronization data included in the Nth broadcast frame 801 to the dependent stations 103 and 104. To transmit. Here, when the dependent station 102 holds asynchronous data to be transmitted, the seventh to ninth fields are added as fields for asynchronous data transmission as in the frame format shown in FIG.

  First, the DATA_TYPE field, which is the seventh field, holds ASYNC as a value. Each station that has received the relay frame 807 can identify that asynchronous data is being transmitted by referring to this field. Next, the LEN_ASYNC field, which is the eighth field, indicates the data length of asynchronous data. Unlike synchronous data, the data length of asynchronous data is generally variable, and each station that receives the relay frame 807 can know the data length of asynchronous data by referring to this field. Finally, asynchronous data is stored in the ASYNC_DATA field, which is the ninth field having a variable length.

  Here, how the dependent station transmits asynchronous data using the non-occupancy time is described, and a detailed internal format for the ASYNC_DATA field is not particularly mentioned. However, the internal configuration of the ASYNC_DATA field is assumed to include various tags for identifying the address and data type of the destination station of the asynchronous data, for example, according to the asynchronous data communication protocol.

  In addition, the ASYNC_DATA field can be divided into a plurality of subfields in order to transmit asynchronous data to a plurality of destination stations. It goes without saying that the present invention can be applied no matter what method of use is adopted for the inside of the ASYNC_DATA field.

  Next, the operation of the dependent station 103 will be described. As shown in FIG. 8, the dependent station 103 transmits a relay frame 808 in the (N + 1) th super frame. The frame format of this relay frame 808 is shown in FIG. In this frame format, the first and second fields are the same as those shown in FIG. 7, and the dependent station 103 transmits a recognition response to the N + 1th broadcast frame 806.

  Here, when the dependent station 103 holds asynchronous data to be transmitted, the third to fifth fields are added as fields for asynchronous data transmission as shown in FIG. These fields correspond to the seventh to ninth fields in the relay frame 807 transmitted by the dependent station 102 shown in FIG.

  The dependent station 103 does not perform relay transmission in the (N + 1) th superframe, but can use the third to fifth fields to transmit asynchronous data using the unoccupied time in the same manner as the dependent station 102. It becomes possible.

  As described above, when the dependent station transmits the recognition response, a non-occupancy time is provided in the communication band, and the dependent station can transmit asynchronous data using this non-occupied time. As a result, asynchronous data can be transferred anew, and the entire data transfer amount including both synchronous data and asynchronous data can be increased.

  In general, since synchronization data is often handled as a fixed length, the description has been given using the fixed-length synchronization data. However, the present invention can also be applied to synchronization data having a variable length. Furthermore, although the format for transmitting the recognition response, the relay transmission of the synchronous data, and the transmission of the asynchronous data in a single frame has been illustrated, it is also possible to transmit these from the subordinate station as individual frames.

[Second Embodiment]
Next, a second embodiment according to the present invention will be described in detail with reference to the drawings. In the first embodiment, it has been described that a dependent station can transmit asynchronous data in a wireless relay transmission system to which the present invention is applied. In the second embodiment, a method in which the control station 101 transmits asynchronous data in the same manner as the dependent stations 102 and 103 will be described.

  The configuration of the wireless relay transmission system in the second embodiment is the same as the configuration of the first embodiment described with reference to FIG. The internal configurations of the control station 101 and the dependent stations 102 to 105 are also the same as the internal configuration of the first embodiment described with reference to FIGS.

  As an example of the operation of the relay transmission system in the second embodiment, a case of transmitting the frame shown in FIG. 8 described in the first embodiment will be described. As described in the first embodiment, the dependent stations 102 to 105 simultaneously execute relay transmission and asynchronous data transmission by transmitting relay frames 807 to 810 in the (N + 1) th superframe.

  In the (N + 1) th superframe shown in FIG. 8, the dependent station 103 transmits the relay frame 808, but the non-occupancy time still remains from the end of the relay frame 808 to the next time slot. In the second embodiment, the control station 101 transmits an asynchronous frame holding asynchronous data during this non-occupation time.

  Here, the control station 101 receives the relay frame shown in FIG. Since each relay frame includes the LEN_FRAME field as described above, the control station 101 can know the length of the relay frame by the frame length determination unit 208 referring to the value of the LEN_FRAME field. Furthermore, since the control station 101 controls the TDMA protocol, the start time of each time slot is also known.

  Therefore, the control station 101 can accurately detect the non-occupation time during which the communication medium is not used from the end of the relay data transmitted in each time slot until the next time slot.

In FIG. 2, the transmission timing generation unit 207 obtains information on the reception frame end point from the frame length determination unit 208 and information on the next time slot start point from the super frame timing generation unit 206. Based on these pieces of information, the transmission timing generation unit 207 instructs the transmission frame generation unit 204 to transmit a frame. As described above, the control station 101 can transmit asynchronous data without causing a frame collision with other dependent stations by transmitting an asynchronous frame during the non-occupancy time.

  FIG. 11 is a diagram illustrating a superframe configuration when the control station transmits an asynchronous frame. 11, 1101 to 1110 are the same frames as 801 to 810 shown in FIG. 8 in the first embodiment.

In the (N + 1) th superframe, the control station 101 that has received the relay frame 1108 of the dependent station 103 detects the end of the relay frame 1108 and immediately starts transmission of the asynchronous frame 1111.

  FIG. 12 is a diagram illustrating an example of a configuration of an asynchronous frame transmitted by the control station. This first field is a LEN_FRAME field indicating the entire length of the asynchronous frame 1111. The unit of the frame length indicated by the LEN_FRAME field includes byte (8 bits), word (16 bits), etc. depending on the implementation, but the present invention can be applied to any unit. Is possible.

  The control station 101 determines the length of the asynchronous frame 1111 and sets the LEN_FRAME field so that the asynchronous frame 1111 ends before the start time of the next time slot.

  The second field shown in FIG. 12 is an ASYNC_DATA field, in which asynchronous data transmitted from the control station 101 is stored. The second embodiment describes how the control station 101 transmits asynchronous data using the non-occupancy time, and does not particularly refer to the detailed internal format for this ASYNC_DATA field. However, it goes without saying that the present invention can be applied no matter what method of use is adopted for the ASYNC_DATA field.

  As described above, when the dependent stations 102 to 105 transmit asynchronous data using the non-occupancy time, the control station 101 can also transmit asynchronous data in the same manner. By applying the present invention, it becomes possible for the control station and the dependent stations to transmit both synchronous data and asynchronous data.

  Furthermore, since the number of necessary relay transmissions can be optimized according to the communication state and almost all of the non-occupancy time can be used for asynchronous data transmission, the data transfer amount of the entire system can be increased.

[Third embodiment]
Next, a third embodiment according to the present invention will be described in detail with reference to the drawings. In the third embodiment, relay transmission is optimized.

  The configuration of the wireless relay transmission system according to the third embodiment is the same as the configuration of the first embodiment described with reference to FIG. The internal configurations of the control station 101 and the dependent stations 102 to 105 are also the same as the internal configuration of the first embodiment described with reference to FIGS.

  Also in the third embodiment, it is assumed that the dependent stations 103 and 104 have failed to receive the Nth broadcast frame 401. At this time, as shown in FIG. 13, a bit error may have occurred only in the ISO_DATA3 field that is the synchronization data addressed to the dependent station 104 stored in the third field in the received broadcast frame 401. obtain.

  Here, even if all the broadcast frames 401 cannot be received correctly, as long as the dependent station 103 can obtain the synchronization data addressed to itself, which is stored in the ISO_DATA2 field, it will relay from other dependent stations thereafter. No transmission is necessary. Nevertheless, in such a state, in the first embodiment, the dependent stations 102 and 105 relay and transmit synchronous data addressed to the dependent station 103, which wastes the communication band as wasteful communication. Become.

  In the third embodiment, in view of such a situation, the format shown in FIG. 14 is used as a format example of a broadcast frame transmitted by the control station 101. In FIG. 14, the synchronization data addressed to each dependent station is stored in the ISO_DATA1 to 4 fields, respectively. Further, immediately after the ISO_DATA 1 to 4 fields, CHECKSUM 1 to 4 fields are provided as checksums based on error detection codes for each synchronization data.

  FIG. 15 is a diagram illustrating a configuration of a superframe in the third embodiment. First, the control station 101 broadcasts a broadcast frame 1501 in the Nth superframe. The broadcast frame 1501 has a frame format shown in FIG. The dependent station 103 that has received the broadcast frame 1501 verifies CHECKSUM_ISO1 to CHECKSUM_ISO1 to 4 that are checksums for the respective synchronization data. Thereafter, the dependent station 103 transmits a relay frame 1503 in its own time slot, but the relay frame 1503 includes an ACKNOWLEDGE field as in the first embodiment.

  Here, when a bit error has occurred only in ISO_DATA3, the dependent station 103 has successfully received ISO_DATA2 as synchronization data addressed to itself, and therefore sets a value ACK in the ACKNOWLEDGE field of the relay frame 1503. . Then, it is recognized that the other dependent station receiving this ACKNOWLEDGE field does not need to relay and transmit the Nth broadcast frame 1501 to the dependent station 103.

  The relay transmission for the Nth broadcast frame 1501 is performed in the (N + 1) th superframe. The dependent station 102 transmits a relay frame 1507 and the dependent station 105 transmits a relay frame 1510. However, since the dependent stations 102 and 105 already know that there is no need to perform relay transmission to the dependent station 103 using the relay frame 1503, the relay frames 1507 and 1510 do not include synchronization data addressed to the dependent station 103.

  Therefore, the length of the relay frame 1507 transmitted from the dependent station 102 is shorter than the relay frame 407 shown in FIG. Similarly, the length of the relay frame 1510 transmitted from the dependent station 105 is also shorter than the relay frame 410 shown in FIG. Therefore, the unoccupied time in the (N + 1) th superframe is longer than that shown in FIG.

  As described above, by improving the checksum and the recognition response system, it becomes possible to optimize relay transmission and to provide a longer non-occupancy time.

  In addition, the control station and the dependent stations transmit asynchronous data using this non-occupancy time in the same manner as in the first and second embodiments. Thereby, the data transfer amount as the whole synchronous data and asynchronous data in a relay transmission system can further be increased.

  According to the embodiment described above, it is possible to reduce the number of data relay transfers that are unnecessary when a receiving station normally receives a data frame in a wireless relay transmission system. Therefore, since the communication time that is no longer used for relay transmission can be used for other data transfer such as asynchronous data, an effect of increasing the data transfer amount as a whole network can be obtained.

  Even if the present invention is applied to a system constituted by a plurality of devices (for example, a host computer, an interface device, a reader, a printer, etc.), it is applied to an apparatus (for example, a copying machine, a facsimile machine, etc.) comprising a single device. It may be applied.

  In addition, a recording medium in which a program code of software for realizing the functions of the above-described embodiments is recorded is supplied to the system or apparatus, and the computer (CPU or MPU) of the system or apparatus stores the program code stored in the recording medium. Read and execute. It goes without saying that the object of the present invention can also be achieved by this.

  In this case, the program code itself read from the computer-readable recording medium realizes the functions of the above-described embodiments, and the recording medium storing the program code constitutes the present invention.

  As a recording medium for supplying the program code, for example, a flexible disk, a hard disk, an optical disk, a magneto-optical disk, a CD-ROM, a CD-R, a magnetic tape, a nonvolatile memory card, a ROM, or the like can be used.

  In addition, by executing the program code read by the computer, not only the functions of the above-described embodiments are realized, but also the following cases are included. That is, based on the instruction of the program code, an OS (operating system) running on the computer performs part or all of the actual processing, and the functions of the above-described embodiments are realized by the processing. .

  Further, the program code read from the recording medium is written in a memory provided in a function expansion board inserted into the computer or a function expansion unit connected to the computer. After that, based on the instruction of the program code, the CPU of the function expansion board or function expansion unit performs part or all of the actual processing, and the function of the above-described embodiment is realized by the processing. Needless to say.

101 Control Station 102 Dependent Station 103 Dependent Station 104 Dependent Station 105 Dependent Station

Claims (11)

A first communication device comprising:
Receiving means for receiving data transmitted from the second communication device in an N-th period including at least a transmission period of the first communication device and a transmission period of the second communication device;
Determining means for determining a reception status of the third communication device of data transmitted from the second communication device in the Nth cycle;
Transmitting means for transmitting at least data addressed to the third communication device received by the receiving means in a period after the Nth period, according to a determination result by the determining means;
A first communication device characterized by comprising:   When the third communication device cannot receive the data transmitted from the second communication device in the Nth cycle, the transmission unit is addressed to at least the third communication device received by the reception unit. When the third communication device can receive the data transmitted from the second communication device in the Nth cycle, the third communication 2. The communication apparatus according to claim 1, wherein a period for transmitting data addressed to the apparatus is used for transmitting other data.   When the third communication device cannot receive the data transmitted from the second communication device in the Nth cycle, the transmission unit is addressed to at least the third communication device received by the reception unit. When the third communication device can receive the data transmitted from the second communication device in the Nth cycle, the third communication The communication apparatus according to claim 1, wherein data destined for the apparatus is not transmitted.   4. The method according to claim 1, wherein the determination unit determines a reception status of the third communication device based on a reception confirmation signal transmitted by the third communication device. 5. 1st communication apparatus.   5. The determination unit according to claim 1, wherein the determination unit determines a reception status of the third communication device based on a signal indicating that the data could not be normally received. 1st communication apparatus.   The transmission means receives the data addressed to the third communication device by the reception means, and when the third communication device cannot receive the data, at least the third received by the reception means. 6. The communication apparatus according to claim 1, wherein data addressed to the communication apparatus is transmitted in a period after the Nth period.   The determination unit determines a reception status of data including data addressed to the first communication device and data addressed to the third communication device transmitted by the second communication device. The communication device according to any one of claims 6 to 6.   The communication according to any one of claims 1 to 6, wherein the determination unit determines a reception state of data transmitted from the second communication device and addressed to the third communication device. apparatus.   9. The communication apparatus according to claim 1, wherein data reception by the reception unit and data transmission by the transmission unit are performed by wireless communication. A control method for a first communication device, comprising:
A receiving step of receiving data transmitted from the second communication device in an Nth cycle of a period including at least a transmission period of the first communication device and a transmission period of the second communication device;
A determination step of determining a reception status of a third communication device of data transmitted in the Nth cycle from the second communication device;
In accordance with the determination result in the determination step, at least a transmission step of transmitting data addressed to the third communication device received in the reception step in a cycle after the Nth cycle,
A control method for a first communication device, comprising:   A computer program that causes a computer to function as the communication device according to claim 1.

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