JP2010206588A - Radio communication device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To avoid impatient route search in a communication-disabled state caused by an influence of multipath fading varying temporarily without increasing the number of times for changing antennas and also without lengthening reception acknowledgement time of ACKs. <P>SOLUTION: In a radio communication device, a transmission source node SL1 designates a destination node MS from the antenna ANT1 to transmit a request message, and changes to the next antenna ANT2 to retransmit the request message (short-period retry) when ACKs from an adjacent node cannot be received within prescribed time T1 (approximately 1 ms). When a response message from a destination node MS cannot be received within prescribed time T2 (several 10 ms) after the transmission of the request message, the antenna is returned to a top antenna ANT1 to retransmit the request message (long-period retry) after prescribed time T3 (several 100 ms). Also, prescribed time T2 may be set to a few 100 ms, and long-period retry may be performed without waiting for prescribed time T3. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a wireless communication device suitable for use in a wireless communication system having a mesh network structure.

  In recent years, systems that perform environmental measurement, monitoring, control, and the like using wireless communication are increasing. In a wireless communication system that performs environmental measurement, monitoring, control, and the like, there are many cases where the target area is relatively wide or there are many obstacles for wireless communication in the target area. In such a case, in order to cover the target area, even if it is not possible to communicate directly depending on the environment such as the installation position of the receiver and the transmitter and the radio wave condition, it is possible to perform communication by relaying other devices. It is advantageous to use a communication network.

  As this type of wireless communication network, a mesh network such as a wireless communication network using a Zigbee (registered trademark) protocol (see, for example, Patent Documents 1 and 2) has been proposed. In this mesh network, bidirectional communication between a master node (destination node) and a slave node (source node) is performed by relaying other slave nodes (relay nodes) in the direct communication range. Even if one communication path is affected by multipath fading and becomes unable to communicate, this is a technology that can search for another communication path and continue communication. Multipath fading refers to a phenomenon in which a received radio wave is canceled due to a phase difference generated between a plurality of communication radio wave reflection paths, and reception becomes impossible.

  In Patent Document 3, each node has a plurality of antennas in a mesh network, and when communication with another node becomes impossible with one antenna, switching to another antenna is still impossible. In this case, a technique for searching for another communication path and continuing communication is described.

  The outline of the technique described in Patent Document 3 will be described with reference to FIG. In this figure, MS ′ is a destination node, SL1 ′ is a transmission source node, and SL2 ′ is a relay node. These nodes MS ′, SL1 ′, and SL2 ′ are two transmission / reception antennas (hereinafter simply referred to as antennas) ANT1. , ANT2. In this example, a communication path is directly established between the destination node MS ′ and the source node SL1 ′, and the destination node MS ′ and the source node SL1 ′ communicate with each other using the antenna ANT1. It shall be.

  In this case, the source node SL1 ′ designates the destination node MS ′ and transmits a request message (FIG. 18: arrow (1)), and the destination node MS ′ that has received the request message sends ACK as a reception confirmation notification. Return to the node SL1 ′ (FIG. 18: arrow (2)). If the transmission source node SL1 ′ fails to receive the ACK from the destination node MS ′ within a predetermined time (for example, about 1 ms), the request message is generated by switching the antenna to the antenna ANT2 and designating the destination node MS ′. Is transmitted again (FIG. 19: arrow (3)). If the source node SL1 ′ does not receive an ACK from the destination node MS ′ even in the retransmission of the request message after switching the antenna (FIG. 19: arrow (4)), the source node SL1 ′ Search for communication paths. This communication path search (route search) is performed by broadcast.

  When the transmission source node SL1 'succeeds in searching for the communication path, the transmission source node SL1' switches to the successful communication path and continues communication with the destination node MS '. For example, as shown in FIG. 20, the relay node SL2 'is interposed, and the communication with the destination node MS' is continued.

JP 2006-5928 A JP 2006-42370 A JP 2006-352436 A

  However, according to the technique described in Patent Document 3 described above, it is effective when one antenna is incapable of communication due to steady multipath fading, but temporarily due to movement of a person or the like. When communication becomes impossible due to the effect of fluctuating multipath fading, the route search is performed too quickly, so there is a problem that the communication load in the network temporarily increases and the network is adversely affected. .

  In addition, as a method of preventing route search from being performed suddenly when communication is disabled due to the influence of multipath fading that fluctuates temporarily, it is impossible to communicate even if the antenna is repeatedly switched and switched a predetermined number of times. If there is, a method of performing route search can be considered. However, when considering the influence of multipath fading that fluctuates temporarily, a long time of, for example, about several hundreds ms is expected as the time when the movement of a person is eliminated, and when the ACK reception confirmation time is about one ms, several hundreds The antennas must be switched once and again, and a large amount of useless communication occurs, which reduces the communication bandwidth and increases the power consumption.

  In addition, it is conceivable to lengthen the ACK reception confirmation time. However, if the ACK reception confirmation time is lengthened, the ACK cannot be received because the radio wave condition is bad, and communication is possible by switching the antenna immediately. Even under circumstances, antenna switching is performed with a long waiting time, which deteriorates the communication performance of the entire system.

  The present invention has been made to solve such a problem, and the object of the present invention is to temporarily increase the number of antenna switching times without increasing the ACK reception confirmation time. An object of the present invention is to provide a wireless communication device capable of avoiding a sudden route search when communication becomes impossible due to the influence of fluctuating multipath fading.

  In order to achieve such an object, the present invention provides a plurality of transmission / reception antennas and a request message transmission means for transmitting a request message by designating one of these transmission / reception antennas as a head antenna and specifying a destination device from the head antenna. A reception confirmation notification monitoring means for monitoring whether a reception confirmation notification for the request message transmitted by designating the destination device is received within a first predetermined time, and a reception confirmation notification monitoring means for the first predetermined If reception of the reception confirmation notification cannot be confirmed within the time, the first retry means for switching the transmission / reception antenna and transmitting the request message again, and after transmitting the request message, The response message sent back from the received destination device is the first Response message monitoring means for monitoring whether or not the message is received within a second predetermined time longer than the predetermined time, and the response message monitoring means cannot confirm the reception of the response message within the second predetermined time In this case, the request message transmitting means is provided with a second retry means for causing the request message from the head antenna to be transmitted again.

  The wireless communication device of the present invention is used, for example, as a transmission source device (transmission source node) in a wireless communication system having a mesh network structure. One of a plurality of transmission / reception antennas is used as a head antenna, and the destination device ( Specify the destination node and send the request message. This request message is received by the first device (adjacent device) in the communication path. For example, if a communication path is directly established with the destination device, the destination device receives it as an adjacent device. If there is a relay device (relay node) between the destination device, it is received by the relay device as an adjacent device. The adjacent device that has received this request message returns an acknowledgment (ACK) to the device of the present invention (source device).

  The device of the present invention (transmission source device) monitors the reception of ACKs from neighboring devices, and if this ACK is not received within a first predetermined time (for example, about 1 ms), it switches the transmission / reception antenna and makes a request. Send the message again. This re-transmission of the request message by switching the transmission / reception antenna (hereinafter referred to as a short cycle retry) is repeated until the final antenna when the reception of the ACK cannot be confirmed.

  On the other hand, after transmitting the request message, the device of the present invention (monitoring source device) monitors reception of a response message returned from the destination device that received the request message, and transmits the response message for a second predetermined time ( For example, if it cannot be received within several tens of ms), the request message is transmitted again from the top antenna. For example, after waiting for several 100 ms, the request message is transmitted again from the top antenna. This re-transmission of the request message from the head antenna (hereinafter referred to as long-period retry) is repeated when the reception of the response message from the destination device cannot be confirmed.

  Thus, in the present invention, a double retry structure of a short cycle retry and a long cycle retry is formed as a whole, and antenna switching is performed at a very short interval by the short cycle retry, and a relatively long time is obtained by the long cycle retry. Then, antenna switching can be started again from the top antenna.

  In the present invention, when the reception of the response message from the destination device cannot be confirmed, the long cycle retry is repeated. Here, when the long-period retry reaches a predetermined number of times, another communication path with the destination device is searched. That is, when the long-cycle retry reaches the predetermined number of times, it is determined that communication is not possible due to the influence of temporarily changing multipath fading, but communication due to steady multipath fading is not possible, Other communication paths are searched, and the request message is transmitted on the other communication paths that have been successfully searched.

  In the present invention, when reception of ACK can be confirmed within the first predetermined time, the transmission / reception antenna that has transmitted the request message that is the source of this ACK may be registered as the head antenna. In this way, for example, when the first head antenna is incapable of communication due to steady multipath fading, another communicable transmission / reception antenna is registered as the head antenna, and during a long period retry Can reduce the possibility of communication failure with the first antenna.

  According to the present invention, it is monitored whether or not a reception confirmation notification for a request message transmitted by designating a destination device is received within a first predetermined time, and the reception confirmation notification is received within the first predetermined time. If the request message cannot be confirmed, the transmission / reception antenna is switched so that the request message is transmitted again, while the response message returned from the destination device that received the request message is longer than the first predetermined time. Monitor whether it is received within a long second predetermined time, and if the reception of the response message cannot be confirmed within the second predetermined time, the request message is transmitted from the head antenna again. As a whole, a double-retry structure consisting of a short-cycle retry and a long-cycle retry is used to cut off the antenna. It is possible to avoid a hasty route search in the case of communication failure due to the effect of multipath fading that fluctuates temporarily, without increasing the number of transmissions and without increasing the ACK reception confirmation time. .

It is a block diagram which shows one Embodiment (Embodiment 1) of the radio | wireless communications system using the radio | wireless communication device which concerns on this invention. It is a figure which shows the state which transmitted the request message from the transmission origin node in this radio | wireless communications system. It is a figure which shows the state (short cycle retry) which switched the antenna from the transmission origin node in this radio | wireless communications system, and transmitted the request message. It is a figure which shows the state (long-cycle retry) which transmitted the request message by returning an antenna to the head antenna from the transmission origin node in this radio | wireless communications system. It is a figure which shows the example which switched the communication path | route between a transmission source node and a destination node by route search. 3 is a functional block diagram of a main part of a transmission source node in the wireless communication system according to the first embodiment. FIG. It is a figure which shows other embodiment (Embodiment 2) of the radio | wireless communications system using the radio | wireless communication device which concerns on this invention. 10 is a flowchart for illustrating a processing operation at a transmission source node in the wireless communication system according to the second embodiment. 10 is a flowchart for explaining processing operations at a destination node and a relay node in the wireless communication system according to the second embodiment. FIG. 11 is a diagram for explaining short-cycle retry and long-cycle retry performed when a request message is transmitted from a transmission source node to a destination node and a response message is returned from the destination node to the transmission source node in the wireless communication system according to the second embodiment. . It is a figure which shows the example which switched the communication path | route between a transmission source node and a destination node by route search. FIG. 11 is a functional block diagram of nodes (destination node, transmission source node, relay node) used in the second embodiment. It is a figure which shows the case where this node operate | moves as a transmission source node. It is a figure which shows the case where this node operate | moves as a relay node. It is a figure which shows the case where this node operate | moves as a destination node. FIG. 10 is a diagram for explaining the merit in the case where an antenna to be transmitted is determined for each adjacent node in the second embodiment. It is a figure which shows the minimum structure of the radio | wireless communications system for demonstrating the outline | summary of the technique described in patent document 3. FIG. It is a figure which shows the state which transmitted the request message from the transmission origin node in this radio | wireless communications system. It is a figure which shows the state (retry) which switched the antenna from the transmission origin node in this radio | wireless communications system, and transmitted the request message. It is a figure which shows the example which switched the communication path | route between a transmission source node and a destination node by route search.

Hereinafter, the present invention will be described in detail with reference to the drawings.
(Embodiment 1)
FIG. 1 is a block diagram showing an embodiment of a wireless communication system using a wireless communication device according to the present invention. In this figure, the same reference numerals as those in FIG. 17 denote the same or equivalent components as those described with reference to FIG. 17, and the description thereof will be omitted. Note that this wireless communication system also shows the minimum configuration as the simplest example, similar to the conventional wireless communication system shown in FIG.

  In this wireless communication system, the destination node MS, the source node SL1, and the relay node SL2 have the same function, and the destination node MS can be the source node SL1 and the relay node SL2, or the source The node SL1 can be the destination node MS or the relay node SL2, and the relay node SL2 can be the destination node MS or the source node SL1.

  In this example, MS is a destination node, SL1 is a source node, SL2 is a relay node, and a communication path is directly established between the destination node MS and the source node SL1, and the destination node MS and the source node It is assumed that communication is performed with SL1 using the antenna ANT1 of each other.

[Send request message from source node]
The transmission source node SL1 uses the antenna AT1 as a head antenna, and transmits a request message by designating the destination node MS from the head antenna AT1 (FIG. 2: arrow (1)). The destination node MS that has received the request message from the transmission source node SL1 returns an ACK to the transmission source node SL1 (FIG. 2: arrow (2)).

[Short cycle retry]
If the source node SL1 fails to receive an ACK from the destination node MS within a predetermined time T1 (in this example, about 1 ms), the request message is sent by switching the antenna to the antenna ANT2 and designating the destination node MS. Is transmitted again (FIG. 3: arrow (3)). In the present embodiment, the retransmission of the request message by switching the antenna is referred to as a short cycle retry. The destination node MS that has received the request message from the transmission source node SL1 returns an ACK to the transmission source node SL1 (FIG. 3: arrow (4)).

  If the transmission source node SL1 fails to receive the ACK from the destination node MS within the predetermined time T1 even after re-transmission of the request message after switching to the antenna ANT2, the switching of the antenna once ends. In this case, the antenna ANT2 is the final antenna.

[Long cycle retry]
On the other hand, after transmitting the request message specifying the destination node MS, the transmission source node SL1 monitors reception of a response message returned from the destination node MS that received the request message.

  When the transmission source node SL1 fails to receive the response message within a predetermined time T2 (for example, several tens of ms) after transmitting the request message specifying the destination node MS (FIG. 4: arrow (5)), Waiting for the elapse of a predetermined waiting time T3 (for example, several 100 ms), the request message is transmitted again from the top antenna AT1 (FIG. 4: arrow (6)). In the present embodiment, this re-transmission of the request message from the head antenna is called a long cycle retry.

  The source node SL1 repeats this long-period retry when it cannot confirm the reception of the response message from the destination node MS.

  Thus, in this embodiment, a double retry structure of a short cycle retry and a long cycle retry is formed as a whole, and antenna switching is performed at a very short interval (about 1 ms) by the short cycle retry. After a relatively long time (several hundreds of milliseconds) due to the retry, the antenna switching is restarted from the top antenna.

  As a person moves, the state of multipath fading changes dynamically in units of 100 ms. Therefore, by performing retry at intervals of several hundreds ms in this way, even if the antennas are affected by multipath fading between all antennas, the multipath fading state is steady at the time of retransmission. Since it has returned to the state, it is possible to succeed in resending

[Switching communication path]
When the number of long-period retries reaches a predetermined number of times (maximum number of retries) N, the source node SL1 is not incapable of communication due to the influence of temporarily changing multipath fading, and is not able to communicate with a steady multi It is determined that communication is impossible due to path fading, and another communication path with the destination node MS is searched. This communication path search (route search) is performed by broadcast.

  In this case, the maximum number of retries N may be arbitrarily determined in advance for each type of message to be transmitted, from the balance between the importance of the message and the increase in the amount of communication expected by the retry.

  When the transmission source node SL1 succeeds in searching for the communication path, the transmission source node SL1 switches to the successful communication path and continues communication with the destination node MS. For example, as shown in FIG. 5, the relay node SL2 is interposed, and the communication with the destination node MS is continued.

  In this way, in the present embodiment, as a whole, a double retry structure of a short cycle retry and a long cycle retry is used, without increasing the number of antenna switching times and without increasing the ACK reception confirmation time, This makes it possible to avoid a sudden route search when communication is disabled due to the temporarily changing multipath fading.

  In this embodiment, the predetermined time T2 is set to several tens of milliseconds and a waiting time T3 of several hundreds of milliseconds is provided to perform a long cycle retry. However, the predetermined time T2 is set to several hundreds of milliseconds and the waiting time T3 is not provided. A long cycle retry may be performed.

  Further, in this embodiment, when reception of ACK can be confirmed within a predetermined time T1, the antenna that transmitted the request message that is the source of this ACK may be registered as the head antenna. In this way, for example, when the leading antenna AT1 is incapable of communication due to steady multipath fading, the communicable antenna AT2 is registered as the leading antenna, and at the time of initial transmission and long cycle retry Can reduce the possibility of communication failure with the first antenna.

  FIG. 6 shows a functional block diagram of the main part of the source node SL1 in the first embodiment. Source node SL1 transmits / receives antennas AT1 and AT2, request message transmitter 1A for transmitting / receiving antenna AT1 as a head antenna and a destination node from this head antenna to transmit a request message, and a destination node. The reception confirmation notification monitoring unit 1B that monitors whether or not an ACK for the request message is received within the predetermined time T1, and the reception confirmation notification monitoring unit 1B could not confirm the reception of the ACK within the predetermined time T1. The short-cycle retry unit 1C for switching the antenna and transmitting the request message from the request message transmission unit 1A again.

  In addition, after transmitting the request message, a response message monitoring unit 1D for monitoring whether or not a response message returned from the destination node that has received the transmitted request message is received within a predetermined time T2, and a response message monitoring When the unit 1D cannot confirm the reception of the response message within the predetermined time T2, the request message transmitting unit 1A waits for the elapse of the predetermined time T3 to retransmit the request message from the head antenna AT1. The periodic retry unit 1E, the long cycle retry number counting unit 1F that counts the number of request message transmissions by the long cycle retry unit 1E as the number of long cycle retry times, and the long cycle retry number that the long cycle retry number counting unit 1F counts are the maximum. retry When it reaches the number N, and a communication route searching unit 1G to explore other communication paths between the destination node.

(Embodiment 2)
FIG. 7 shows another embodiment of a wireless communication system using the wireless communication device according to the present invention. In this wireless communication system, the relay node SL2 is located between the transmission source node SL1 and the destination node MS, and a communication path via the relay node SL2 is established between the transmission source node SL1 and the destination node MS.

  A communication path is also established between the transmission source node SL4 and the destination node MS via the relay node SL3. Hereinafter, a communication path established between the transmission source node SL1 and the destination node MS will be described. The side will be described as a representative. Further, it is assumed that the transmission source node SL1 and the relay node SL2, and the relay node SL2 and the destination node MS communicate with each other using the antenna ANT1.

  In this embodiment, the transmission source node SL1, the relay node SL2, and the destination node MS are realized by hardware including a processor and a storage device and a program that realizes various functions in cooperation with these hardware. As functions unique to the present embodiment, a short cycle retry function and a long cycle retry function are provided.

  Hereinafter, the processing operation specific to the present embodiment executed in the transmission source node SL1 will be described according to the flowchart shown in FIG. 8, and the processing operation specific to the present embodiment executed in the master node MS and the relay node SL2 according to the flowchart shown in FIG. The processing operation will be described.

[Send request message from source node]
The source node SL1 creates a request message to the destination node MS (FIG. 8: step S101), sets the antenna AT1 as the head antenna (step S102), specifies the destination node MS from the head antenna AT1, and sends a request message. Transmit (FIG. 10A: arrow (1), step S103). This request message is transmitted to the adjacent relay node SL2 in accordance with a predetermined routing table. And it waits for reception of ACK from relay node SL2 (step S104).

  When the relay node SL2 receives a request message specifying the destination node MS from the transmission source node SL1 (FIG. 9: YES in step S202), the relay node SL2 returns an ACK to the transmission source node SL1 (FIG. 10A). : Arrow (2), step S203).

[Short-cycle retry at the source node]
When the transmission source node SL1 receives an ACK from the relay node SL2 within a predetermined time T1 (for example, about 1 ms) (YES in step S105), the transmission source node SL1 waits for a response message from the destination node MS (step S109).

  When the ACK from the relay node SL2 cannot be received within the predetermined time T1 (YES in step S106), the transmission source node SL1 sets the transmission antenna as the next antenna AT2 (step S108), and selects the destination node MS from the antenna AT2. The request message is specified and retransmitted (FIG. 10A: arrow (1), step S103). Then, after retransmitting the request message with the antenna switched, the reception of ACK from the relay node SL2 is awaited (step S104).

  When the source node SL1 receives the ACK from the relay node SL2 within a predetermined time T1 after retransmitting the request message after switching the antenna (after a short cycle retry) (YES in step S105), the source node SL1 The response message is awaited (step S109).

  If the ACK from the relay node SL2 cannot be received within the predetermined time T1 (YES in step S106), the transmission source node SL1 determines that transmission with all the antennas has been completed (YES in step S107), and the destination node Wait for a response message from the MS (step S109). That is, the antenna AT2 is used as the final antenna, and antenna switching is temporarily ended to prepare for a long-period retry described later.

[Transfer request message at relay node]
On the other hand, when the relay node SL2 receives the request message specifying the destination node MS from the transmission source node SL1 (NO in step S202), the received request message is set as a transmission message addressed to the destination node MS (step S205). ), Using the antenna AT1 as the head antenna (step S207), the request message from the transmission source node SL1 is transferred from the head antenna AT1 (FIG. 10A: arrow (3), step S208). The request message is transferred to the destination node MS according to a predetermined routing table. Then, it waits for reception of ACK from the destination node MS (step S209).

  When the request message from the transmission source node SL1 is transferred from the relay node SL2 (YES in step S202), the destination node MS returns an ACK to the relay node SL2 (FIG. 10A: arrow (4), step S203. ).

[Short-cycle retry at relay node]
When the relay node SL2 receives an ACK from the destination node MS within the predetermined time T1 (YES in step S210), the relay node SL2 ends the process as a successful relay (step S214). When the ACK from the destination node MS cannot be received within the predetermined time T1 (YES in step S211), the relay node SL2 sets the transmission antenna as the next antenna AT2 (step S213), and from the antenna AT2 to the transmission source node SL1. The request message is retransmitted (FIG. 10 (a): arrow (3), step S208). Then, after the transmission message is retransmitted with the antenna switched, reception of an ACK from the destination node MS is awaited (step S209).

  The relay node SL2 receives the ACK from the destination node MS after retransmitting the request message after switching the antenna (after a short cycle retry) (YES in step S210), and ends the processing as a successful relay (step S214). ). If the ACK from the destination node MS cannot be received within the predetermined time T1 (YES in step S211), the relay node SL2 determines that transmission with all antennas has been completed (YES in step S212), and the relay failure is determined. The process ends (step S215).

[Returning a response message from the destination node]
When the destination node MS receives a transmission message addressed to itself (request message from the transmission source node SL1) from the relay node SL2 (YES in step S204), the destination node MS creates a response message to the transmission source node SL1 (step S204). In step S206, the antenna AT1 is set as the head antenna (step S207), and the response message is transmitted from the head antenna AT1 by designating the transmission source node SL1 (FIG. 10B: arrow (5), step S208). The response message is transmitted to the adjacent relay node SL2 in accordance with a predetermined routing table. Then, it waits for reception of ACK from the relay node SL2 (step S209).

  When the relay node SL2 receives a re-response message specifying the source node SL1 from the destination node MS (FIG. 9: YES in step S202), the relay node SL2 returns an ACK to the destination node MS (FIG. 10 (b)). : Arrow (6), step S203).

[Short-cycle retry at the destination node]
When receiving the ACK from the relay node SL2 within the predetermined time T1 (YES in Step S210), the destination node MS ends the process as a successful response (Step S214). If the ACK from the relay node SL2 cannot be received within the predetermined time T1 (YES in step S211), the destination node MS sets the transmission antenna to the next antenna AT2 (step S213), and sets the transmission source node SL1 from the antenna AT2. The response message is designated and retransmitted (FIG. 10B: arrow (5), step S208). Then, after retransmitting the response message with the antenna switched, reception of ACK from the relay node SL2 is awaited (step S209).

  When the destination node MS receives the ACK from the relay node SL2 within the predetermined time T1 after retransmitting the request message after switching the antenna (after a short cycle retry) (YES in step S210), the destination node MS performs the processing as a successful response. The process ends (step S214). If the ACK from the relay node SL2 cannot be received within the predetermined time T1 (YES in step S211), the destination node MS determines that transmission with all antennas has been completed (YES in step S212), and the response fails. The process ends (step S215).

[Transmission of response message at relay node]
On the other hand, when the relay node SL2 receives the response message specifying the transmission source node SL1 from the destination node MS (NO in step S204), the relay message SL2 is set as a transmission message addressed to the transmission source node SL1 (step S205). The antenna AT1 is set as the head antenna (step S207), and the response message from the destination node MS is transferred from the head antenna AT1 (FIG. 10B: arrow (7), step S208). The response message is transferred to the transmission source node SL1 in accordance with a predetermined routing table. Then, it waits for reception of ACK from the transmission source node SL1 (step S209).

  The source node SL1 waits for reception of a response message from the destination node MS (step S109), and the response message from the destination node MS is transferred from the relay node SL2 (YES in step S110), and an ACK is sent to the relay node SL2. Is returned (FIG. 10B: arrow (8), step S115), and the processing is terminated as a communication success (step S116).

[Short-cycle retry at relay node]
When the relay node SL2 receives an ACK from the transmission source node SL1 within the predetermined time T1 (YES in step S210), the relay node SL2 ends the process as a successful relay (step S214). When the ACK from the transmission source node SL1 cannot be received within the predetermined time T1 (YES in step S211), the relay node SL2 sets the transmission antenna as the next antenna AT2 (step S213), and from the antenna AT2 to the destination node MS. Is retransmitted (FIG. 10B: arrow (7), step S208). Then, after retransmitting the response message with the antenna switched, the reception of the ACK from the transmission source node SL1 is waited (step S209).

  When the relay node SL2 receives an ACK from the transmission source node SL1 after retransmitting the response message after switching the antenna (after a short cycle retry) (YES in step S210), the relay node SL2 ends the processing as a successful relay (step S210). S214). If the ACK from the transmission source node SL1 cannot be received within the predetermined time T1 (YES in step S211), the relay node SL2 determines that transmission with all antennas has been completed (YES in step S212), and the relay fails. And the process is terminated (step S215).

[Long cycle retry at the source node]
The source node SL1 waits for reception of a response message from the destination node MS (step S109), and when the response message from the destination node MS cannot be received within a predetermined time T2 (for example, several tens of ms) (step S111). (YES), the number of retries is set to 1 (step S113), and after a predetermined waiting time T3 (for example, several 100 ms) has elapsed (step S114), the process returns to step S102, and the request message is transmitted again from the top antenna AT1. Perform (FIG. 10: arrow (9)). That is, the antenna is returned to the head antenna AT1, and a long period retry is performed.

  If the source node SL1 cannot receive the response message from the destination node MS within the predetermined time T2 (YES in step S111), the transmission source node SL1 repeats the long cycle retry while counting the number of retries (step S113).

  In this way, the second embodiment also has a double retry structure of short cycle retry and long cycle retry as a whole, and antenna switching is performed at a very short interval (about 1 ms) by the short cycle retry. The antenna switching can be started again from the top antenna after a relatively long time (several hundreds of milliseconds) by periodic retry.

[Switching communication path]
When the number of long-period retries reaches a predetermined number (maximum number of retries) N (YES in step S112), the transmission source node SL1 is not incapable of communication due to the influence of temporarily changing multipath fading and is stationary. It is determined that communication is not possible due to multipath fading, and another communication path with the destination node MS is searched (step S117). This communication path search (route search) is performed by broadcast.

  When the transmission source node SL1 succeeds in searching the communication path, the transmission source node SL1 switches to the successful communication path and continues communication with the destination node MS. For example, as shown in FIG. 11, the communication is continued with the destination node MS by switching to the detour route on the relay node SL3 side.

  Also in the second embodiment, as in the first embodiment, the maximum retry count N is arbitrarily determined in advance for each type of message to be transmitted, based on the balance between the importance of the message and the increase in the amount of communication expected by the retry. It is sufficient that the predetermined time T2 is set to several hundreds of milliseconds, and the long period retry may be performed without providing the waiting time T3.

  FIG. 12 shows a functional block diagram of the node 1 used in the second embodiment. This node 1 has all functions as a destination node, a transmission source node, and a relay node, and as a destination node MS, a transmission source node SL1, and a relay node SL2, depending on the role that behaves on the communication path during communication. Operate.

  The node 1 includes transmission / reception antennas AT1 and AT2, a communication transmission unit 1-1, a communication reception unit 1-2, an antenna switching unit 1-3, a message destination determination unit 1-4, and a request message transmission management unit. 1-5, a request message reception management unit 1-6, and a routing table 1-7.

  FIG. 13 shows a case of operating as the transmission source node SL1. When operating as the transmission source node SL1, the request message reception management unit 1-6 does not function. FIG. 14 shows a case where the relay node SL2 operates. When operating as the relay node SL2, the request message transmission management unit 1-5 and the request message reception management unit 1-6 do not function. FIG. 15 shows a case in which it operates as the destination node MS. When operating as the destination node MS, the request message transmission management unit 1-5 does not function.

[About the top antenna]
In the first and second embodiments, two antennas are used to simplify the description. However, the number of antennas used is not limited to two, and more antennas may be provided. In this case, when performing transmission to an adjacent node, as to which antenna is selected first, a fixed antenna may be used at all times, or an antenna to be transmitted may be determined for each adjacent node. .

  When a fixed antenna is always used, there is a merit that a required resource (RAM) is small and it can be simply implemented. On the other hand, when the antenna to be transmitted first is determined for each adjacent node, each node must store the antenna to be transmitted first for each adjacent node. There is merit in case.

  For example, as shown in FIG. 16, the node SLX is positioned as a relay node of a plurality of communication paths. In the communication path A, the relay node SLX can communicate only with the antenna a, but in the communication path B, the relay node Assume that SLX can communicate only with antenna b. In this case, if the antenna (first antenna) to be transmitted first is always set to a, for example, when communication is performed using the communication path B, a transmission retry always occurs once, and unnecessary communication occurs. End up. In order to prevent this, in the communication path B, it is desirable to set the head antenna to b.

  In order to determine the head antenna for each communication path, it is only necessary to store the number of the antenna that has been successfully transmitted to the relay destination corresponding to the relay destination address when relaying.

  The wireless communication device of the present invention can be used in various fields such as a medium-scale and large-scale monitoring control system having a mesh network structure in which a communication trunk line is wireless. More specifically, it can be used for an indoor air conditioning system by VAV (variable air volume adjustment).

  MS ... destination node, SL1 ... transmission source node, SL2 ... relay node, AT1, AT2 ... transmission / reception antenna, 1A ... request message transmission unit, 1B ... reception confirmation notification monitoring unit, 1C ... short cycle retry unit, 1D ... response message monitoring 1E ... long cycle retry unit, 1F ... long cycle retry count counting unit, 1G ... communication path search unit, 1-1 ... communication transmission unit, 1-2 ... communication reception unit, 1-3 ... antenna switching unit, 1 -4 ... message destination determination unit, 1-5 ... request message transmission management unit, 1-6 ... request message reception management unit, 1-7 ... routing table.

Claims (3)

Multiple transmit and receive antennas;
Request message transmission means for transmitting a request message by designating a destination device from the first antenna with any one of these transmission / reception antennas as a leading antenna;
A reception confirmation notification monitoring means for monitoring whether a reception confirmation notification for a request message transmitted by designating the destination device is received within a first predetermined time;
If the reception confirmation notification monitoring unit cannot confirm reception of the reception confirmation notification within the first predetermined time, a first retry is made to switch the transmission / reception antenna and transmit the request message again. Means,
After transmission of the request message, it is monitored whether or not a response message returned from the destination device that has received the transmitted request message is received within a second predetermined time longer than the first predetermined time. A response message monitoring means for
If the response message monitoring unit cannot confirm the reception of the response message within the second predetermined time, the request message transmitting unit causes the request message transmission unit to transmit the request message again from the first antenna. A wireless communication device comprising: a retry means. The wireless communication device of claim 1, wherein
Communication path search means for searching for another communication path with the destination device when the number of transmissions of the request message by the second retry means reaches a predetermined number of times.
A wireless communication device comprising: The wireless communication device according to claim 1 or 2,
When the reception confirmation notification monitoring unit can confirm reception of the reception confirmation notification within the first predetermined time, a transmission / reception antenna that transmits the request message that is a source of the reception confirmation notification is set as the leading antenna. A wireless communication device comprising: first antenna registration means for registering as:

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