JP5424086B2 - Wireless communication system, transmission terminal, reception terminal, and data retransmission method - Google Patents

Description

  The present invention relates to a radio communication system that uses a common frequency band with other systems having different radio standards, and a data retransmission method in the radio communication system.

  Wireless standards (examples: IEEE 802.11, IEEE 802.15, ARIB-STD-T67, etc.) are used in a wireless communication system in order to avoid effective use of frequencies and interference between users. It defines the modulation method. Usually, in order to prevent interference, the use frequency bands are defined not to overlap between wireless communication systems having different wireless standards.

  In order to improve the reception quality in the wireless communication system defined in this way, it is necessary to take measures against fading and interference. However, in the wireless communication system according to the prior art, the propagation environment is improved by taking either one of the measures, and the influence from both fading and interference is reduced. For example, the influence of interference can be suppressed by taking a fading countermeasure. For this reason, normally, in order to improve the reception quality, one of fading countermeasures and interference countermeasures is selectively applied according to the propagation characteristics according to the radio standard, the radio wave environment, the intended use, and the like.

  As a countermeasure against fading, antenna diversity is performed in which data is transmitted and received by switching a transmission antenna or a reception antenna. For example, Japanese Patent Application Laid-Open No. 2003-244041 describes a wireless communication system that switches antennas every time data is transmitted or received (see Patent Document 1).

  Further, as a countermeasure against interference, frequency diversity is performed in which data is transmitted and received by changing a frequency channel (hereinafter referred to as a channel).

  On the other hand, in the case of a system with low output power, such as a specific low power radio or weak radio, there is little influence on other radio communication systems. For this reason, in recent years, a wireless standard that uses a frequency band common to other wireless communication systems has been defined.

  As a system using specific low power radio, for example, there is a short-range radio communication system and an active tag system. The short-range wireless communication system comprises a network of wireless nodes equipped with sensors and wireless stations equipped with actuators that control various devices. Temperature control in facilities, factory monitoring, hospital management, meter meter reading, home Used for security. In addition, the active tag system has a tag that performs communication with the reader / writer by spontaneously outputting radio waves, and can communicate within a wide range.

  As described above, a communication system using specific low-power radio is often used in a space with many reflectors such as in a building or in a room, that is, in an environment in which reception quality is likely to deteriorate due to fading. For this reason, a communication system using specific low-power radio requires a fading countermeasure in order to improve reception quality.

  Usually, by taking measures against fading, reception quality can be improved and the probability of occurrence of data errors can be reduced. However, when a wireless standard in which other wireless standards and the used frequency band coexist is adopted, interference due to wireless signals from other wireless communication systems cannot be avoided. For this reason, it is necessary to avoid both fading and interference in a wireless communication system that shares a used frequency band with other wireless communication systems.

  The radio standard sharing the used frequency band is not limited to the specific low-power radio but can be applied to other radio communication systems in the future. For this reason, it is thought that the scene which must avoid both the above fading and interference increases.

JP2003-244041A

  An object of the present invention is to improve the reception quality of a radio communication system that shares a use frequency band with other radio communication systems.

  The wireless communication system according to the present invention includes a transmission terminal and a reception terminal that use a common frequency band with other systems having different wireless standards. When the data transmitted from the transmitting terminal has not reached the receiving terminal, the transmitting terminal retransmits the data using another channel different from the transmission time. The receiving terminal receives the retransmission data by another antenna different from that at the time of receiving the transmission data.

  In the wireless communication system according to the present invention, when data is retransmitted, the transmission channel and the reception antenna are changed, so that both interference and fading due to signals from other communication systems can be avoided.

  ADVANTAGE OF THE INVENTION According to this invention, the reception quality of the radio | wireless communications system which shares a use frequency band with another radio | wireless communications system can be improved.

FIG. 1 is a diagram showing a configuration in an embodiment of a wireless communication system according to the present invention. FIG. 2 is a diagram showing the configuration of the communication apparatus according to the first embodiment of the present invention. FIG. 3 is a diagram showing an example of the structure of the used channel table according to the present invention. FIG. 4 is a diagram showing an example of the structure of the antenna table used according to the present invention. FIG. 5 is a flowchart showing data transmission and retransmission operations on the transmitter side of the wireless communication system in the first and third embodiments. FIG. 6 is a flowchart showing a data reception operation on the receiver side of the wireless communication system in the first and third embodiments. FIG. 7 is a diagram showing a modification of the configuration of the communication apparatus according to the first embodiment of the present invention. FIG. 8 is a flowchart showing data transmission and retransmission operations on the transmitter side of the wireless communication system according to the second embodiment. FIG. 9 is a conceptual diagram of data transmission and retransmission operations in the second embodiment. FIG. 10 is a diagram showing the configuration of the communication apparatus according to the third embodiment of the present invention. FIG. 11 is a flowchart illustrating a data transmission operation on the transmitter side of the wireless communication system in the fourth embodiment. FIG. 12 is a conceptual diagram of data transmission and retransmission operations in the fourth embodiment. FIG. 13 is a diagram showing an example of a simple configuration of a communication apparatus according to the present invention.

  Embodiments of a wireless communication system according to the present invention will be described below with reference to the accompanying drawings. In the drawings, the same or similar reference numerals indicate the same, similar, or equivalent components. Hereinafter, a sensor network using a specific low power radio in the 950 MHz band will be described as an example. The specific low-power radio in the 950 MHz band uses a frequency band common to RF tag systems that are other radio standards.

1. First Embodiment A first embodiment of a radio communication system according to the present invention will be described with reference to FIGS.

(Constitution)
FIG. 1 is a diagram illustrating a configuration of a wireless communication system according to an embodiment. The wireless communication system includes a plurality of wireless terminals 101 to 103 and a totaling terminal 200. The wireless terminals 101 to 103 have a built-in sensor 6, detect surrounding environmental information (for example, temperature, humidity, luminous intensity, etc.) and transmit it to the totaling terminal 200. Further, the wireless terminals 101 to 103 may be either fixedly provided or mounted on a mobile body. The aggregation terminal 200 is a computer device that analyzes and aggregates data transmitted from the wireless terminals 101 to 103 and records the data in a storage device. The wireless communication system in the present embodiment forms an ad hoc network, and packet communication is performed between terminals.

  The wireless terminals 101 to 103 and the totaling terminal 200 can transmit / receive data to / from each other. For this reason, the wireless terminals 101 to 103 and the aggregation terminal 200 in the first embodiment include the communication device 300 illustrated in FIG. 2 as a transmitter and a receiver. However, the totaling terminal 200 may not include the sensor 6. For example, when the wireless terminal 101 transmits data to the aggregation terminal 200, the communication device 300 mounted on the wireless terminal 101 functions as a transmitter, and the communication device 300 mounted on the aggregation terminal 200 functions as a receiver. . In addition, the wireless terminals 101 to 103 may have a function of relaying data transmitted from the wireless terminals 101 to the aggregation terminal 200. In this case, the communication device 300 mounted on the wireless terminals 101 to 103 functions as a receiver and a transmitter.

  With reference to FIG. 2, the structure of the communication apparatus 300 in 1st Embodiment is demonstrated. The communication device 300 includes an arithmetic processing device 1, a storage device 2, a packet control device 3, wireless modules 41 and 42, and antennas 51 and 52. The wireless terminals 101 to 103 include the sensor 6 in addition to the communication device 300. The arithmetic processing apparatus 1 includes a transmission data generation unit 11 and a reception data analysis unit 12 realized by software, hardware, or cooperation between software and hardware.

  The communication apparatus 300 according to the first embodiment includes a plurality of wireless modules that are connected to different antennas and transmit or receive data through different channels. Here, as an example, two wireless modules 41 and 42 are provided. In the first embodiment, the antenna and channel can be changed when data is retransmitted by switching the wireless module used for transmission.

  First, the configuration of the case where the communication apparatus 300 functions as a transmitter will be described in detail.

  The transmission data generation unit 11 extracts data from the storage device 2 and generates transmission data by adding a header including a transmission source identifier, a destination identifier, an error correction code, and the like to the data. At this time, divided data obtained by dividing the extracted data may be attached to the header as transmission data. Further, the transmission data generation unit 11 extracts transmitted data from the storage device 2 in response to the retransmission instruction 120 issued from the reception data analysis unit 12, and generates transmission data in the same manner as described above. The generated transmission data is output to the packet control device 3.

  The reception data analysis unit 12 analyzes the reception data input from the packet control device 3 and issues a retransmission instruction 120 to the transmission data generation unit 11 based on the analysis result. When the ACK signal notifying the arrival of data is not received for a predetermined time, the received data analysis unit 12 issues a module switching instruction 110 and a retransmission instruction 120. Here, the arrival of data means that data is received without error at the receiving terminal. Note that the time from the transmission of data to the reception of the ACK signal notifying the arrival is measured by a timer (not shown), for example.

  If the data does not reach the receiving terminal due to a reception error or the like (data has not been reached), the receiving data analysis unit 12 on the transmitting side issues a module switching instruction 110 to the packet control device 3 and performs wireless communication. Switch modules. In the first embodiment, since a use channel and a use antenna are determined for each radio module, data can be retransmitted by switching the channel and the antenna by switching the radio module. The wireless module switching instruction is preferably made with reference to the used channel table shown in FIG. 3 and the used antenna table shown in FIG. The used channel table includes information for specifying a channel to be used in the transmitting side and receiving side terminals. The used antenna table includes information for designating antennas to be used by the transmitting and receiving terminals. It is preferable that the wireless terminals 101 to 103 and the aggregation terminal 200 in the wireless communication system each hold a common used channel table.

  The packet control device 3 outputs the transmission data input from the transmission data generation unit 11 to one selected from a plurality of wireless modules. Here, based on the module switching instruction 110, the packet control device 3 determines a wireless module that is an output destination of transmission data (used for data transmission).

  In this embodiment, initially, wireless modules used for transmission are set based on the tables shown in FIGS. 3A and 4A, and at the time of retransmission, FIG. 3B and FIG. It is set by the table shown in (b). As an example, with reference to FIG. 3 and FIG. 4, a channel and an antenna used when transmitting data from the wireless terminal A will be described. As an initial setting, in the wireless terminal A, a channel and an antenna (wireless module) to be used are set based on the tables shown in FIGS. 3 (a) and 4 (a). Here, when data is transmitted to the wireless terminal B, the channel f1 and the antenna A1 (for example, the wireless module 41) are used, and when the data is transmitted to the wireless terminal C, the channel f2 and the antenna A2 (for example, the wireless module 42) are used. In the case of addressing to the aggregation terminal, the channel f1 and antenna A1 (wireless module 41) are set to be used. On the other hand, when data is retransmitted, the channel and antenna (wireless module) to be used are changed according to the module switching instruction 110 based on the tables shown in FIGS. 3B and 4B. Here, when data is transmitted to the wireless terminal B, the channel f2 and the antenna A2 (for example, the wireless module 42) are switched, and when the data is transmitted to the wireless terminal C, the channel f1 and the antenna A1 (for example, the wireless module 41) are switched. In the case of addressing to the aggregation terminal, the channel f2 and antenna A2 (wireless module 42) are switched.

  In the first embodiment, the use channel, the use antenna, and the radio module are associated with each other. For this reason, the channel and antenna may be switched using a wireless module table that designates a wireless module used for data transmission instead of the used channel table and the used antenna table. Note that the wireless modules 41 and 42 may be connected to the same antenna. In this case, the transmission antenna is not switched during data retransmission.

  As described above, when communication apparatus 300 according to the present embodiment determines that transmission data has not reached, it retransmits the data by switching the transmission antenna and the used channel.

  The communication device 300 includes wireless modules 41 and 42 that transmit and receive wireless signals using different channels. Therefore, it is possible to wait for all available channels. That is, the communication device 300 can function not only as a transmitter but also as a receiver. Hereinafter, the configuration of the communication device 300 functioning as a receiver will be described in detail.

  Data transmitted from the terminal on the transmission side is received by the antennas 51 and 52 and input to the packet control device 3 via the wireless modules 41 and 42. The packet control device 3 receives data from a plurality of wireless modules and outputs the data to the received data analysis unit 12.

  When the communication device 300 functions as a receiver, the reception data analysis unit 12 performs error detection on the data input from the packet control device 3. Error detection methods include parity check, cyclic redundancy check, Hamming code method, checksum, and the like, which can be selectively applied as appropriate. If there is no error in the received data, the received data analysis unit 12 extracts the data from the received data by removing the header, and if necessary, combines it with other data and stores it in the storage device 2.

  If there is no error in the received data, the communication device 300 transmits an ACK signal to the transmission source terminal (not shown). Moreover, the communication apparatus 300 may output a NACK signal when an error is detected from the received data. In this case, information specifying a channel and an antenna to be used together with the NACK signal may be transmitted.

  The reception data analysis unit 12 that has received no ACK signal within a predetermined time or has received a NACK signal and determined a reception error issues a module switching instruction 110 to the packet control device 3. The packet control device 3 switches the wireless module used for reception according to the module switching instruction 110. At this time, it is preferable that switching of the wireless module (issue of the module switching instruction 110) is performed based on the used channel table and the used antenna table as in the transmission.

  As described above, communication apparatus 300 according to the present embodiment functions as a receiver that receives retransmitted data by switching antennas and channels when a data reception error is detected. On the transmitting side and the receiving side, channels are switched using the same used channel table. This enables communication using the same channel on the transmission side and the reception side. The antenna table used is preferably a table corresponding to each terminal.

  Although not shown, a wireless module that is not used for data transmission or reception may be stopped according to the module switching instruction 110.

(Operation)
Next, with reference to FIG. 5 and FIG. 6, the data retransmission operation of the wireless communication system in the first embodiment will be described. Hereinafter, the wireless terminal 101 will be described as a transmitting terminal, and the aggregation terminal 200 as a receiving terminal.

  First, the operation of the wireless terminal 101 on the transmission side will be described with reference to FIG. Here, as an initial setting, the channel f1 and the antenna A1 (antenna 51) are used for communication with the totaling terminal 200 in accordance with the tables set in FIGS. 3A and 4A.

  The wireless terminal 101 generates data detected by the sensor 6 as transmission data, and transmits it to the totaling terminal 200 (step S101). At this time, data is transmitted by the wireless module (wireless module 41) using the channel f1 and the antenna A1 (antenna 51). The wireless terminal 101 determines whether the data has arrived based on whether or not an ACK signal has been received from the totaling terminal 200 within a predetermined time (step S102). Upon confirming the arrival of data, the wireless terminal 101 extracts data to be transmitted next, generates transmission data, and transmits the data from the wireless module 41 (step S102 arrival, S105 Yes). Alternatively, the wireless terminal 101 confirms the arrival of data, and when there is no data to be transmitted next, ends the transmission operation (No in step S102, No in S105).

  When detecting that the data has not been reached, the wireless terminal 101 switches the channel and antenna used for data transmission based on the used channel table and the used antenna table (step S103). The transmitted data is re-extracted and re-generated, and transmitted to the aggregation terminal 200 using the switched channel and antenna (step S104). Here, based on FIG. 3B and FIG. 4B, data is retransmitted from the wireless module 42 using the channel f2 and the antenna A2 (antenna 52).

  After the data is retransmitted, the process proceeds to step S102 to determine whether the data has arrived. Thereafter, as described above, data is generated and transmitted using the channel f2 and the antenna A2 (antenna 52) switched in step S103.

  In step S103, a predetermined waiting time may be provided after the channel and antenna are switched until data is retransmitted. The reception environment may be improved when a predetermined time elapses. For example, the influence of fading or interference may be reduced by the movement of the wireless terminal 101 or other wireless terminals 102 or 103, or by changing the surrounding propagation environment or the radio wave output status of another wireless system. By waiting until such a state is reached and retransmitting data, it is possible to improve reception quality that does not improve even if a channel or antenna is changed or initialized without consuming unnecessary power for transmission. Can do. However, the number of times that the channel and antenna to be used are initialized and the data is retransmitted is preferably limited to a predetermined number (including 0).

  In this embodiment, a channel and an antenna to be used for transmission and retransmission are selected from two channels and antennas (wireless modules), but may be selected from three or more channels and antennas (wireless modules). I do not care. In this case, it is preferable that priority is given to the channel and antenna to be used, and the channel and antenna are switched according to the priority. This priority order is shared between the transmitting terminal and the receiving terminal.

  With reference to FIG. 6, the operation of the receiving terminal 200 will be described. Here, as an initial setting, the channel f1 and the antenna A1 (antenna 51) are used for communication with the wireless terminal 101 in accordance with the tables set in FIGS. 3A and 4A.

  Aggregation terminal 200, when receiving data from wireless terminal 101, performs error detection (steps S201 Yes, S202). Here, when no reception error is detected, the data body (for example, temperature information detected by the sensor 6) in the reception data is recorded in the storage device 2 (No in Steps S202 and S204).

  On the other hand, if a reception error is detected and it is determined that error correction is necessary, the aggregation terminal 200 switches the channel and antenna used for data standby based on the used channel table and the used antenna table (Yes in step S202). , S203). Here, based on FIGS. 3B and 4B, the channel f2 and the antenna A2 (antenna 52) are switched as the standby channel and the used antenna. After switching between channels and antennas, it waits until data to be retransmitted is received (No in step S201).

  Aggregation terminal 200 receives the retransmitted data by antenna 52 and performs error detection on the retransmitted data (step S202). Here, if no reception error is detected, the data in the received data is recorded in the storage device 2 (No in steps S202 and S204). On the other hand, when a reception error is detected and it is determined that error correction is necessary, the aggregation terminal 200 switches the standby channel and the antenna to be used (steps S202 Yes, S203). Here, when all the channels and antennas set in the table have been used, initialization may be set. Here, data standby is performed by using the used channel f1 and the antenna A1 again. However, the number of channel and antenna switching and initialization is preferably limited to a predetermined number (including 0).

  As described above, in the wireless communication system according to the present invention, when data is retransmitted, the use channel and the use antenna are changed in the terminal on the transmission side and the reception side. As a result, not only fading but also interference from a wireless communication system sharing other frequencies is avoided, and reception quality is improved.

  In the communication apparatus 300 according to the first embodiment, the channel and the antenna to be used are switched by switching the wireless modules connected to different antennas according to the detection of the reception error. Not exclusively. For example, as in the communication device 301 shown in FIG. 7, the use channel is switched by switching the radio modules 41 and 42 that output radio signals of different channels, and the antenna to be used is switched by the antenna switch 8. good.

  Specifically, the communication device 301 includes an antenna switch 8 and a wireless control device 7 that controls the antenna switch 8. The antenna switch 8 is connected between the plurality of wireless modules 41 and 42 and the plurality of antennas 51 and 52, and connects the antenna selected according to the antenna switching signal 131 from the wireless control device 7 and the wireless module. To do. The wireless control device 7 outputs an antenna switching signal 131 corresponding to the antenna switching instruction 130 issued from the reception data analysis unit 12 to the antenna switch 8. The reception data analysis unit 12 of the communication device 301 issues an antenna switching instruction 130 when a reception error is detected. Other operations are the same as those of the communication apparatus 300 shown in FIG.

  In the communication apparatus 301, since the wireless modules 41 and 42 transmit and receive wireless signals using different channels, the use channel can be switched by switching the wireless modules. Further, since the antenna to be used can be switched by the antenna switcher 8, the communication device 301 can arbitrarily set the combination of the channel to be used and the antenna. Furthermore, since the channel and the antenna are switched depending on whether or not the transmission data has arrived, the data can be retransmitted by switching the channel and the antenna. Furthermore, since the wireless modules 41 and 42 transmit and receive wireless signals using different channels, they can wait for all usable channels. For this reason, the communication apparatus 301 can function not only as a transmitter but also as a receiver.

2. Second Embodiment In the first embodiment, data is retransmitted by changing the channel and antenna. However, the antenna power (output power and transmission power) may be further changed to retransmit the data. . In the retransmission method according to the second embodiment, at the time of data retransmission, not only the channel and antenna but also the antenna power is switched to high power. FIG. 8 is a flowchart illustrating a data retransmission method according to the second embodiment. FIG. 9 is a conceptual diagram of data transmission and retransmission operations in the second embodiment.

  Prior to data transmission, the transmission terminal performs interference confirmation by carrier sense. The transmission terminal according to the second embodiment performs carrier sense using a channel and an antenna that are not used for data transmission in parallel with data transmission. Depending on the wireless standard, the antenna power that can be transmitted in a long carrier sense time is higher than the antenna power that can be transmitted in a short carrier sense time in order to change the limit value of the antenna power according to the observation accuracy of the surrounding wireless environment. There may be. For example, a certain wireless standard stipulates that when data is transmitted with an antenna power exceeding 1 mW, carrier sense of 10 ms or more is performed, and otherwise, carrier sense of 128 μs or more is performed. In such a case, the transmitting terminal in the second embodiment transmits data at a low output (for example, 1 mW), and uses a different output channel and antenna for a long time (for example, 10 ms) at a high output (for example, 10 mW). Perform a career sense. When transmission of data with low output fails, the transmitting terminal retransmits data with high output using another channel and antenna for which carrier sense has succeeded.

  Details of the data retransmission method according to the second embodiment will be described with reference to FIGS. 8 and 9. The data retransmission method according to the second embodiment can be suitably applied to communication apparatuses 300 and 301 including a plurality of wireless modules 41 and 42 that are different for each channel. Hereinafter, as an example, a data retransmission method according to the second embodiment when the communication apparatus 300 mounted on the wireless terminal 101 is used as a transmitter will be described.

  Here, it is assumed that the channel f1 and the antenna A1 (antenna 51) are assigned to the wireless module 41, and the channel f2 and the antenna A2 (antenna 52) are assigned to the wireless module 42 in advance. First, carrier sense is executed in each of the wireless modules 41 and 42 (step S301). Here, the wireless module 41 performs a carrier sense (low output) of 128 μs for the channel f1, and the wireless module 42 performs a carrier sense (high output) of 10 ms for the channel f2.

  When it is determined that transmission is possible by the carrier sense of 128 μs, the wireless module 41 transmits data with low output (1 mW) (step S302 transmission is possible, S303). At this time, the channel f1 and the antenna A1 are used.

  The wireless terminal 101 determines whether the data has arrived based on whether or not an ACK signal has been received from the totaling terminal 200 within a predetermined time (step S102). Upon confirming the arrival of data, the wireless terminal 101 extracts data to be transmitted next, generates transmission data, and transmits data from the wireless module 41 (step S102 arrival, S108 Yes). Alternatively, the wireless terminal 101 confirms the arrival of data, and when there is no data to be transmitted next, ends the transmission operation (arrival at step S102, No at S108).

  When it is determined that transmission is impossible due to carrier sense of 128 μs (transmission is not possible in step S302), or when transmission of data fails (step S102 is not reached), the wireless terminal 101 waits for determination of carrier sense by the wireless module 42 (Step S304). When the carrier sense time (here, 10 mS) by the wireless module 42 has elapsed and it is determined that transmission is possible, the wireless terminal 101 regenerates transmission data and transmits the transmission data at a high output (10 mW) by the wireless module 42 (step S304). Transmission is possible, S305). The wireless terminal 101 performs data arrival determination and confirms arrival, extracts data to be transmitted next, generates transmission data, and transmits data from the wireless module 41 (step S306 arrival, S108 Yes). Alternatively, the wireless terminal 101 confirms the arrival of data, and when there is no data to be transmitted next, ends the transmission operation (arrival at step S306, No at S108).

  On the other hand, when it is determined that transmission is not possible due to carrier sense of 10 ms (step S304 cannot be transmitted), or when it is determined that the data transmitted from the wireless module 42 has not been reached (step S306 has not been reached), it waits for a predetermined time. Later, the process proceeds to step S301 (step S107). At this time, the combination of the channel, antenna, and output power (carrier sense time) used for transmission may be changed to perform the processing after step S301. However, it is preferable that the number of times the data is retransmitted after moving from step S107 to step S301 is limited to a predetermined number (including 0).

  As described above, in this embodiment, carrier sensing with different carrier sensing times is performed using a plurality of different channels and antennas, and data is retransmitted while switching antenna power, channels, and antennas. According to the data retransmission method in the present embodiment, since the antenna power is increased at the time of data retransmission, the data reception quality can be further improved. In addition, since carrier sense for data transmission and carrier sense for retransmission are simultaneously performed by different wireless modules, the time from transmission failure to retransmission can be shortened. Note that the receiving operation is the same as that of the first embodiment, and a description thereof will be omitted.

3. Third Embodiment In the first embodiment, since a channel and an antenna are changed when data is retransmitted, a plurality of radio modules are changed. However, a radio module that can use a plurality of channels is used. Can also be realized. FIG. 10 shows the configuration of the communication apparatus 302 according to the third embodiment. The communication device 302 according to the third embodiment includes a multi-channel wireless module (wireless module 4) that can use a plurality of channels instead of the wireless modules 41 and 42 mounted on the communication device 301 shown in FIG. . The radio control apparatus 7 shown in FIG. 7 outputs an antenna switching signal 131 to switch antennas. The radio control apparatus 7 in the third embodiment performs channel antenna switching from the received data analysis unit 12. In response to the instruction 140, the channel switching signal 132 is output together with the antenna switching signal 131. The wireless module 4 changes the channel used for data transmission according to the channel switching signal 132. In the communication devices 300 and 301 shown in the first embodiment, the packet control device 3 selects the radio module corresponding to the channel used, but in the communication device 302 in the third embodiment, the radio control device By switching the channel at 7, the channel at the time of retransmission is changed. Since other configurations and data retransmission methods are the same as those in the first embodiment, description thereof will be omitted.

  Note that since the communication device 302 according to the third embodiment has only one wireless module, it cannot stand by on a plurality of channels. For this reason, the communication apparatus 302 does not have a function as the above-mentioned receiver. For this reason, in order to use as mentioned above, it is preferable to use in combination with the communication apparatuses 300 and 301 in the first embodiment.

4). Fourth Embodiment A modification of the method for retransmitting data by switching the antenna power as well as the channel and antenna will be described as a fourth embodiment. The data retransmission method according to the second embodiment is suitable for the communication devices 300 and 301 according to the first embodiment in which a plurality of wireless modules are mounted, but the communication device 302 according to the third embodiment includes Not applicable. In the data retransmission method according to the fourth embodiment, by controlling the carrier sense start time for each channel, not only the communication devices 300 and 301 in the first embodiment but also the third embodiment. The present invention can be applied to the communication device 302. FIG. 11 is a flowchart illustrating a data retransmission method according to the fourth embodiment. FIG. 12 is a conceptual diagram of data transmission and retransmission operations in the fourth embodiment.

  In the data retransmission method according to the second embodiment, carrier sense for data transmission and carrier sense for retransmission are performed in parallel, but in the fourth embodiment, carrier sense for retransmission is This is executed after detecting that the transmission data has not been reached.

  The details of the data retransmission method according to the fourth embodiment will be described with reference to FIGS. In the following, the data retransmission method according to the fourth embodiment will be described by taking as an example the operation of the wireless terminal 101 using the communication device 302 according to the third embodiment as a transmitter.

  Here, it is assumed that the wireless module 4 can selectively use the channels f1 and f2 in advance. First, the wireless module 4 performs carrier sense (low output) on the channel f1 at 128 μs (step S401).

  When it is determined that transmission is possible by the carrier sense of 128 μs, the wireless module 4 transmits data at a low output (1 mW) (step S302 transmission possible, S303). At this time, the channel f1 and the antenna A1 are used.

  The wireless terminal 101 determines whether the data has arrived based on whether or not an ACK signal has been received from the totaling terminal 200 within a predetermined time (step S102). Upon confirming the arrival of data, the wireless terminal 101 extracts data to be transmitted next, generates transmission data, and transmits data from the wireless module 41 (step S102 arrival, S108 Yes). Alternatively, the wireless terminal 101 confirms the arrival of data, and when there is no data to be transmitted next, ends the transmission operation (arrival at step S102, No at S108).

  When it is determined that transmission is not possible due to the carrier sense of 128 μs (step S302 transmission is impossible), or when data transmission fails (step S102 is not reached), the used channel and the used antenna are switched to another channel and antenna (step) S104). The wireless module 4 performs carrier sense (high output) for 10 ms using the channel and antenna after switching (step S402). Here, carrier sense is performed by channel f2 and antenna A2. When the wireless terminal 101 determines that transmission is possible after the carrier sense time (in this case, 10 ms) by the wireless module 4 has elapsed, the wireless terminal 101 regenerates transmission data, and the wireless module 4 whose channel has been switched has high output (10 mW). Transmit (step S304 transmission possible, S305).

  The wireless terminal 101 performs data arrival determination based on whether or not an ACK signal has been received from the totaling terminal 200 within a predetermined time (step S306). When the wireless terminal 101 confirms the arrival of data, the wireless terminal 101 extracts data to be transmitted next, generates transmission data, and transmits the data from the wireless module 41 (step S306 arrival, S108 Yes). Alternatively, the wireless terminal 101 confirms the arrival of data, and when there is no data to be transmitted next, ends the transmission operation (arrival at step S306, No at S108).

  On the other hand, when it is determined that transmission is not possible due to carrier sense of 10 ms (step S304 cannot be transmitted), or when it is determined in step S305 that the data transmitted from the wireless module 4 has not been reached (step S306 has not been reached), predetermined After waiting for a time, the process proceeds to step S401 (step S107). At this time, the combination of the channel, antenna, and antenna power (carrier sense time) used for transmission may be changed to perform the processing after step S401. However, the number of times (including 0) of retransmitting data from step S107 to step S401 is preferably limited to a predetermined number.

  As described above, in this embodiment, carrier sensing with different carrier sensing times is performed using a plurality of different channels and antennas, and data is retransmitted while switching antenna power, channels, and antennas. According to the data retransmission method in the present embodiment, since the antenna power is increased at the time of data retransmission, the data reception quality can be further improved. In addition, since carrier sense for retransmission is performed after confirming the arrival of data, channel, antenna, and antenna power can be switched while performing carrier sense with one wireless module during retransmission. . Note that the receiving operation is the same as that of the first embodiment, and a description thereof will be omitted.

  The embodiment of the present invention has been described in detail above, but the specific configuration is not limited to the above-described embodiment, and changes within a scope not departing from the gist of the present invention are included in the present invention. . According to the present invention, when data is retransmitted, the transmission channel and the receiving antenna are changed, thereby avoiding interference due to signals from other communication systems sharing the used frequency band and preventing reception deterioration due to fading. be able to. For this reason, the radio communication system according to the present invention can be suitably used for a radio communication system in which a radio frequency standard is different but a used frequency band is common to other radio communication systems. Note that any one of the communication devices 300, 301, and 302 in the first to fourth embodiments is used as a transmitter, and any one of the communication devices 300 and 301 in the first and second embodiments is a receiver. Can be used as Needless to say, the numbers of the wireless terminals 101 to 103 and the totaling terminal 200 are not limited to the above example.

  Further, as a simple configuration, the communication device 303 shown in FIG. 13 can be applied as a transmitter. Similar to the communication device 302 shown in FIG. 10, the communication device 303 includes the wireless module 4 that can be used by switching a plurality of channels, but does not switch the antenna. In this case, the channel to be used is switched according to the channel switching instruction 150 from the reception data analysis unit 12. The communication device 303 does not switch the transmission antenna and has a simple configuration, so that the cost of the terminal and the entire system can be reduced. Furthermore, when any one of the communication devices 300 and 301 in the first, second, and fourth embodiments is used as a transmitter, it is possible to set so that the transmission antenna is not switched when data is retransmitted. It is.

101-103: Wireless terminal 200: Totaling terminal 300-303: Communication device 1: Arithmetic device 2: Storage device 3: Packet control device 4, 41, 42: Wireless module 5, 51, 52: Antenna 6: Sensor 7: Wireless Control device 11: Transmission data generation unit 12: Reception data analysis unit 110: Module switching instruction 120: Retransmission instruction 130: Antenna switching instruction 140: Channel antenna switching instruction 150: Channel switching instruction

Claims (13)

In a wireless communication system using a common frequency band with other systems having different wireless standards,
A sending terminal that sends data;
A receiving terminal waiting for the transmission data by a plurality of channels and a plurality of antennas;
Comprising
If the transmission data does not reach the receiving terminal, the transmitting terminal retransmits the data using another channel and antenna different from the transmission time,
The wireless communication system, wherein the receiving terminal receives the retransmission data by another antenna different from that at the time of receiving the transmission data.   In a wireless communication system using a common frequency band with other systems having different wireless standards,
  A sending terminal that sends data;
  A receiving terminal waiting for the transmission data by a plurality of channels and a plurality of antennas;
  Comprising
  If the transmission data has not reached the receiving terminal, the transmitting terminal retransmits the data using another channel different from the transmission time,
  The receiving terminal receives the retransmission data by another antenna different from the reception time of the transmission data,
  The transmitting terminal is
  Multiple antennas,
  An arithmetic device that selects an antenna to be used for retransmission from the plurality of antennas according to a reception status of the transmission data, and selects a channel to be used for retransmission from a plurality of channels;
  A plurality of wireless modules that transmit and receive data using different channels, and
  With
  The arithmetic unit outputs the retransmission data to a radio module that uses the selected channel.
  Wireless communication system.   The wireless communication system according to claim 2,
  Each of the plurality of wireless modules performs carrier sensing at different times,
  The data is transmitted from a wireless module having a short carrier sense time, and when the transmission data has not reached the receiving terminal, the data is retransmitted from the wireless module having a long carrier sense time.
  Wireless communication system.   In a wireless communication system using a common frequency band with other systems having different wireless standards,
  A sending terminal that sends data;
  A receiving terminal waiting for the transmission data by a plurality of channels and a plurality of antennas;
  Comprising
  If the transmission data has not reached the receiving terminal, the transmitting terminal retransmits the data using another channel different from the transmission time,
  The receiving terminal receives the retransmission data by another antenna different from the reception time of the transmission data,
  The transmitting terminal is
  Multiple antennas,
  An arithmetic device that selects an antenna to be used for retransmission from the plurality of antennas according to a reception status of the transmission data, and selects a channel to be used for retransmission from a plurality of channels;
  The transmitting terminal includes a multi-channel wireless module that can use a plurality of channels,
  The arithmetic unit sets a channel to be used for the multi-channel wireless module and outputs the retransmission data
  Wireless communication system.   The wireless communication system according to claim 4, wherein
  The multi-channel wireless module transmits the data with a short carrier sense time, and when the transmission data has not reached the receiving terminal, changes the channel and lengthens the carrier sense time to retransmit the data.
  Wireless communication system. The wireless communication system according to any one of claims 1 to 5 ,
A wireless communication system, in which, when the transmission data does not reach the receiving terminal, the transmitting terminal retransmits the data with higher antenna power than at the time of transmission. The wireless communication system according to any one of claims 1 to 6 ,
Each of the transmitting terminal and the receiving terminal holds a table in which combinations of channels and antennas used for transmission and retransmission are set, and sets channels and antennas used for retransmission by referring to the table system. The wireless communication system according to any one of claims 1 to 7 ,
The receiving terminal is
Multiple antennas,
An arithmetic device that selects an antenna to be used for receiving the retransmission data from the plurality of antennas according to a reception status of the transmission data, and selects a channel to be used for reception of the retransmission data from a plurality of channels; ,
With
The wireless communication system, wherein the retransmission data is input to the arithmetic device from a wireless module that uses the selected channel. The wireless communication system according to claim 8 ,
The receiving terminal includes a plurality of wireless modules that transmit and receive data using different channels, respectively.
The wireless communication system, wherein the plurality of wireless modules are connected corresponding to the plurality of antennas and receive data via different antennas. The wireless communication system according to claim 9 , wherein
The receiving terminal is
A plurality of wireless modules that transmit and receive data using different channels, and
An antenna switch connected to the plurality of antennas;
With
The antenna switch is a wireless communication system that connects an antenna selected by the arithmetic unit among the plurality of antennas and a wireless module that receives the retransmission data. A communication terminal having a function of the transmission terminal and the receiving terminal to be used in a wireless communication system according to any one of claims 1 to 10. A retransmission method executed in a wireless communication system using a frequency band common to other systems having different wireless standards,
A transmitting terminal transmitting data;
A receiving terminal waiting for the transmission data on a plurality of channels and a plurality of antennas;
If the transmission data has not reached the receiving terminal, the transmitting terminal retransmits the data using another channel and antenna different from the transmission time; and
The receiving terminal receives the retransmission data at another antenna different from the reception time of the transmission data; and
A data retransmission method comprising: The data retransmission method according to claim 12 ,
When the transmission data does not reach the receiving terminal, the transmitting terminal further includes a step of retransmitting the data with higher antenna power than at the time of transmission.

Images