JP2008228178A - Radio device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To attain an efficient relay processing for a radio technique. <P>SOLUTION: A sensor network system is formed in a form of tree by a plurality of radio devices with a basic device 10 in a plurality of radio devices 20 as a root. For each radio device 20 for constituting a network, characteristic transmission timing is prescribed. In the radio device 20, timing allocated to other radio devices 20 is used, when relaying data to the other radio devices 20, thus avoiding collisions. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a radio technology, and more particularly to a radio device in a multi-hop radio network formed by a plurality of radio devices.

Currently, a multi-hop wireless network method has been proposed in which a network is formed by a plurality of wireless terminals, and packets are relayed between adjacent wireless terminals, thereby enabling communication between wireless terminals that do not receive direct radio waves. . However, as the number of wireless terminals participating in the network increases, there is a problem that areas where wireless resources are used in the network overlap and communication collisions occur frequently. Conventionally, the occurrence of a collision has been suppressed by determining the timing to be transmitted in accordance with the number of relays from the transmission source wireless terminal (see, for example, Patent Document 1).
JP 2006-157737 A

  In general, in the case of a sensor network that is an application example of a multi-hop wireless network, efficient relay processing that can avoid an increase in power consumption is desired. The present invention has been made in view of such circumstances, and an object of the present invention is to provide a technique capable of preventing collision and realizing efficient relay processing.

  In order to solve the above problems, a radio apparatus according to an aspect of the present invention is a radio apparatus that requests participation in a multi-hop radio network formed by a plurality of radio apparatuses, and includes an uplink communication time domain and an uplink random A frame formed by an uplink time slot including an access time region and a downlink time slot including a downlink communication time region and a downlink random access time region is continuous, and is used for uplink random access. A determination unit that determines a common first offset amount from the beginning of each of the time domain and the downlink random access time domain, and a first offset amount that is determined by the determination unit for a management device that manages the multi-hop wireless network In the time domain for uplink random access, the time domain for uplink communication and the time for downlink communication An allocation requesting unit that requests allocation of a common second offset amount from the head of each area, and the allocation requesting unit in the time domain for downlink random access while using the first offset amount determined by the determining unit Multi-hop in the time domain for uplink communication and the time domain for downlink communication while using the second offset amount included in the response acquired in the offset amount acquisition unit A communication unit that performs communication within the wireless network.

  According to this aspect, since the second offset amount is requested and acquired using the random access area, it is possible to avoid a collision with a relay process using an area other than the random access area, and to realize an efficient relay process.

  In a multi-hop wireless network formed in a tree shape with a core device among a plurality of wireless devices as a root, a hop number acquisition unit that acquires the number of hops to the core device and a hop acquired by the hop number acquisition unit A first specifying unit for specifying an uplink time slot and a downlink time slot to be used by the radio apparatus from a plurality of uplink time slots and a plurality of downlink time slots forming a frame according to the number, The transmission timing is specified by a combination of the second offset amount acquired by the offset amount acquisition unit and the uplink communication time region included in the uplink time slot specified by the first specification unit, and the offset amount acquisition unit Included in the second offset amount acquired in step 1 and the downlink time slot specified by the first specifying unit. A second specifying unit configured to specify the reception timing by the combination of the downlink communication time region may further comprise a. The communication unit may perform communication at the transmission timing and the reception timing specified by the second specifying unit.

  Here, “the number of hops” indicates the number of relays to reach the backbone device, for example, a value obtained by adding 1 to the number of relay devices existing between the backbone device and the wireless device. In this case, by determining the timing based on the combination of the time slot specified in the number of hops and the second offset amount allocated individually, the influence on the relay processing in other wireless devices can be reduced, and collision can be avoided. it can.

  It is specified that the request from the allocation request unit is relayed to the backbone device using the uplink time slot specified by the number of hops in the other radio device and the first offset amount determined by the determination unit. The response acquired by the offset amount acquisition unit is relayed using the downlink time slot specified by the number of hops in the other wireless device and the first offset amount determined by the determination unit. It is stipulated in. In this case, in the request for the second offset amount, the transmission processing at the time of acquisition, and the relay processing, it is possible to avoid collision with the relay processing in other wireless devices by using the first offset amount in common, and efficiently. Relay processing can be realized.

  Another aspect of the present invention is also a wireless device. This device is based on a backbone device among a plurality of wireless devices, and in a multi-hop wireless network formed by a plurality of wireless devices in a tree shape, a wireless device that requests communication with the backbone device, and the backbone device A wireless device included in the path between the first acquisition unit that acquires the number of hops to reach the backbone device, and a plurality of time slots according to the number of hops acquired by the first acquisition unit Any one of a plurality of subslots that are uniquely defined for a first specifying unit that specifies any of the above and a wireless device that requests communication with a backbone device, and form a time slot The transmission timing is specified by a combination of the second acquisition unit that acquires the sub slot acquired by the second acquisition unit and the time slot specified by the first specification unit. To comprises a second identifying unit, at the transmission timing specified in the second identifying unit, a transmission unit for transmitting a signal for the wireless device requesting communication with the backbone device.

  Here, the “tree shape” includes a tree structure, for example, a hierarchical structure in which a parent-child relationship has a one-to-many relationship. According to this aspect, by determining the transmission timing by a combination of a time slot allocated according to the number of hops and a sub-slot that is uniquely defined for the wireless device that requests communication with the backbone device, Collisions can be avoided.

  A third specifying unit for specifying the reception timing by a combination of a time slot different from the time slot specified by the first specifying unit and the subslot acquired by the second acquiring unit, and a reception timing specified by the third specifying unit And a receiver that receives a signal about a wireless device requesting communication with the backbone device. The transmission unit may relay the signal received by the reception unit. Here, the “different time slot” may be determined depending on the time slot specified in the first specifying unit, for example, a time slot obtained by subtracting 1 from the time slot specified in the first specifying unit. Also good. In this case, since the reception timing is defined in relation to the transmission timing, it can be relayed efficiently.

  Another aspect of the present invention is also a wireless device. This device is a wireless device that performs communication with a backbone device in a multi-hop wireless network formed in a tree shape by a plurality of wireless devices, with a backbone device among a plurality of wireless devices as a base, A first acquisition unit that acquires the number of hops up to the backbone device, a first specification unit that specifies one of a plurality of time slots according to the number of hops acquired by the first acquisition unit, and A subslot uniquely defined for the wireless device, a second acquisition unit that acquires any of a plurality of subslots forming a time slot; a subslot acquired by the second acquisition unit; The second specifying unit that specifies the transmission timing based on the combination with the time slot acquired by the first specifying unit, and the transmission timing specified by the second specifying unit Te, and a transmission unit for transmitting a signal for the wireless device. According to this aspect, the collision can be avoided by executing the transmission process based on the specific timing defined in advance in the wireless device.

  After the transmission timing is specified, when the first acquisition unit newly acquires the number of hops, the second acquisition unit newly acquires the number of hops without causing the second acquisition unit to acquire a new subslot. The transmission timing may be re-specified based on the subslot already acquired by the second acquisition unit. In this case, even when the slot specified by the change in the number of hops changes, the transmission timing can be specified without reassigning the subslot.

  It should be noted that any combination of the above-described constituent elements and a conversion of the expression of the present invention between a method, an apparatus, a system, a recording medium, a computer program, etc. are also effective as an aspect of the present invention.

  According to the present invention, efficient relay processing can be realized.

  Before the embodiments of the present invention are specifically described, an outline is first described. Embodiments described herein relate generally to a sensor network system. The sensor network system is a system for providing various services autonomously and wirelessly and providing services suitable for the situation from collected data. This system is considered to be applied to a wide variety of fields, such as grasping the damage situation at the time of disaster, building deterioration diagnosis, crime prevention / fire prevention device in a house.

  In general, a multi-hop wireless network is formed in a sensor network system. In general, in a multi-hop wireless network, as the number of wireless devices in the network increases, the possibility that the same wireless resource is used simultaneously increases, and wireless packet collisions occur frequently.

  Each wireless device has a function as a sensor and a communication function for transmitting acquired sensor information or relaying sensor information notified from another wireless device to a backbone device. Thus, in a wireless device in a multi-hop wireless network, it is necessary to relay not only its own communication but also data transmitted from another wireless device, which increases power consumption.

  In general, there are many types of wireless devices used in sensor network systems that are driven by batteries. Therefore, it is desired to realize an efficient relay process that can prevent the occurrence of a collision as described above and avoid an increase in power consumption.

  Therefore, in the embodiment of the present invention, collision is avoided by defining a unique transmission timing for each wireless device constituting the network. By taking such an aspect, efficient relay processing can be realized. Details will be described later.

  FIG. 1 shows a configuration example of a sensor network system 100 according to an embodiment of the present invention. The sensor network system 100 includes a server 90, a first backbone device 10a and a second backbone device 10b represented by the backbone device 10, and a first wireless device 20a to a fifth wireless device 20e represented by the wireless device 20. Including. The backbone device 10 is a gate node, and each wireless device 20 is a sensor node. In FIG. 1, two backbone devices 10 and five wireless devices 20 are shown, but other numbers may be used. The server 90 and the backbone device 10 may be connected to another network (not shown) via the wired network 80.

  The server 90 is a device that manages the sensor network system 100. The server 90 is connected to the first backbone device 10 a and the second backbone device 10 b via the wired network 80, and a path is formed for each backbone device 10 and between each backbone device 10. The timing to be used is assigned to the wireless device 20. Here, since the timing that can be assigned to the backbone device 10 and the wireless device 20 is limited, the server 90 manages the upper limit of the number of wireless devices 20 that participate in the sensor network system 100, and exceeds the upper limit. The new participation in the sensor network system 100 is rejected.

  The backbone apparatus 10 may be a computer having a wireless communication function, for example. The backbone device 10 establishes and controls wireless paths in the sensor network system 100 and manages sensor information reported from each wireless device 20. In addition, the backbone apparatus 10 reports the managed sensor information to the server 90. Prior to communication with the plurality of wireless devices 20, the backbone device 10 executes a process of joining the wireless device 20 to the wireless network to form a route. In the sensor network system 100 shown in FIG. 1, the first backbone device 10a is in a state in which a route is formed with the first wireless device 20a. Further, the second backbone device 10b is in a state in which a route is formed with the third wireless device 20c.

  On the other hand, the second wireless device 20b, the fourth wireless device 20d, and the fifth wireless device 20e other than the first wireless device 20a and the third wireless device 20c are far from the backbone device 10 and communicate directly with the backbone device 10. I can't. Therefore, the second radio apparatus 20b can execute communication with the first backbone apparatus 10a by forming a route with the first radio apparatus 20a and passing through the first radio apparatus 20a. . Similarly, a route is formed so that the fourth wireless device 20d and the fifth wireless device 20e pass through the third wireless device 20c, respectively. The path has a hierarchical relationship in a tree shape with each core device 10 as a root.

  In the following, in the direct path between the two wireless devices 20 in the sensor network system 100, the wireless device 20 closer to the backbone device 10 is referred to as a parent, higher-order, or upper-layer wireless device 20, The radio device 20 farther from the backbone device 10 is referred to as a child, lower level, or lower level radio device 20. For example, in the 1st radio | wireless apparatus 20a and the 2nd radio | wireless apparatus 20b, the 1st radio | wireless apparatus 20a becomes high rank and the 2nd radio | wireless apparatus 20b becomes low rank.

  Further, the tree shape indicates that the relationship between the parent and the child is a one-to-many relationship. In other words, there are one or more routes from the backbone device 10 to the arbitrary wireless device 20, and conversely, there is only one upstream route from the arbitrary wireless device 20 to the backbone device 10. By such an aspect, in uplink communication, communication explosion due to an increase in the number of relay stations can be avoided. On the other hand, since there is only one upstream route, communication failure due to collision or the like must be avoided as much as possible. Although details will be described later, in the present embodiment, communication failure due to a collision is prevented by setting a transmission timing unique to each core device 10 and each wireless device 20.

  Each wireless device 20 acquires various sensor information according to the sensor function of each wireless device 20 and reports it to the backbone device 10. Prior to such a reporting process, the wireless device 20 first executes a participation process in order to participate in the sensor network system 100. In the participation process, the wireless device 20 selects another wireless device 20 that should form a parent-child relationship. The backbone device 10 may be selected instead of the other wireless device 20. Further, this selection is performed so that the number of other wireless devices 20 existing with the backbone device 10 is minimized. In the following, a value obtained by adding 1 to “the number of other wireless devices 20 existing with the backbone device 10” is referred to as “the number of hops”.

  Here, the frame configuration in the sensor network system 100 and the relationship between slots and subslots will be described. FIG. 2A is a diagram illustrating a configuration example of the frame format 200 in the sensor network system 100 of FIG. As illustrated, in the frame format 200, one superframe may be defined as Fsec (F is an integer). The superframe is time-division-multiplexed (Time Division Duplex), and the first m slots (m is an integer) in one frame are allocated for downlink communication, and the latter m slots are allocated for uplink communication. The number of slots allocated for downlink communication and uplink communication may be determined by the maximum number of hops allowed in the system.

  FIG. 2B is a diagram showing an example of the slot format 210 of the slot in FIG. The slot includes n sub-slot sections 212 from 1 to n and a spare section 214. In the subslot section 212, data, hello packets, and the like are transmitted. Note that the number of subslots existing in the subslot section 212 may be determined by the maximum number of sensor nodes allowed in the system. The data includes sensor information measured by a sensor provided in each sensor node. The hello packet is broadcast information for establishing a route, and includes identification information indicating the broadcast source wireless device 20, the number of hops from the backbone device 10 to the broadcast source wireless device 20, and the like. The configuration of the slot format 210 shown in FIG. 2B is common to the downlink slot and the uplink slot shown in FIG.

  FIG. 2C is a diagram illustrating an example of a format included in the subslot section 212 of FIG. The subslot section 212 includes a communication time area 216 and a random access time area 218. Communication time region 216 includes k subslots. The random access time region 218 includes (n−k) subslots.

  The server 90 determines a subslot allocated to each wireless device 20 from the communication time area 216. Further, the server 90 manages participation so that the total number of wireless devices 20 participating in the sensor network system 100 does not exceed k. The random access time region 218 is used when the wireless device 20 newly participating in the sensor network system 100 requests the server 90 to assign a subslot. In this case, the radio apparatus 20 randomly selects a subslot to be used from among (n−k + 1) subslots.

  Here, (1) participation processing and (2) relay processing will be specifically described. FIG. 3 is a diagram illustrating a second configuration example of the sensor network system 100 of FIG. In the second configuration example, the first backbone device 10a forms a route with the first wireless device 20a. The second backbone device 10b forms a route with the third wireless device 20c. The first wireless device 20a forms a route with the second wireless device 20b, and the third wireless device 20c forms a route with the fifth wireless device 20e. The case where the 4th radio | wireless apparatus 20d newly participates in the sensor network system 100 under the above condition is demonstrated.

(1) Participation process (1-1) Identification of transmission slot A slot is composed of a plurality of subslots as shown in FIG. Therefore, each wireless device 20 needs to determine both a slot and a subslot as transmission timing. Here, the specification of the transmission slot will be described.

  First, the fourth wireless device 20d receives a hello packet notified from the backbone device 10 or the wireless device 20 already participating in the network. As illustrated, the fourth wireless device 20d includes a hello packet A notified from the first wireless device 20a, a hello packet C notified from the third wireless device 20c, and a hello packet E notified from the fifth wireless device 20e. Are received respectively. Each received hello packet includes information indicating the radio device 20 that is the notification source of the hello packet and the number of hops in the radio device 20 that is the notification source.

  As described above, the route is formed so that the number of other wireless devices 20 existing between the backbone device 10 is reduced. Here, the hello packet A includes “1” as the number of hops, the hello packet C includes “1” as the number of hops, and the hello packet E includes “2” as the number of hops. "It is included. Therefore, the fourth radio apparatus 20d selects the first radio apparatus 20a and the third radio apparatus 20c that have transmitted the hello packet for the minimum hop number “1” among the acquired hop numbers. By selecting in this way, the fourth radio apparatus 20d can reduce the number of relays with the backbone apparatus 10 and improve the reliability of communication.

  As described above, since only one wireless device 20 can be connected as an upper layer of the fourth wireless device 20d, it is necessary to narrow down to one of the first wireless device 20a and the third wireless device 20c here. In such a case, the fourth radio apparatus 20d selects the one with the better propagation quality. This is because the number of retransmissions can be reduced by connecting to the radio apparatus 20 with better propagation quality. Here, it is assumed that the propagation quality with the third radio apparatus 20c is better than that with the first radio apparatus 20a. In this case, a route is formed with the third radio apparatus 20c as the upper level. Then, the number of hops in the fourth radio apparatus 20d is “2” obtained by adding “1” to the number of hops of the third radio apparatus 20c.

  Next, the fourth radio apparatus 20d specifies its own transmission slot using the selected number of hops. Here, for example, the fourth radio apparatus 20d adds “1” to “2” in accordance with the number of hops “2”, and identifies the third slot in FIG. 2A as the transmission slot. In this way, smooth communication is possible by determining the timing of the transmission slot according to the number of hops.

  The effect of slot assignment is shown using another figure. FIG. 4 is a diagram showing an example of slot allocation according to the embodiment of the present invention. Here, it is assumed that a multi-hop wireless network having a maximum hop count of m hops is formed with the backbone device 10 as a base. In FIG. 4, the vertical axis indicates the slot number in an arbitrary frame. The horizontal axis indicates the number of hops in each wireless device 20. The first hop corresponds to the hop from the backbone device 10 to the wireless device 20 in FIG. 3, and the second hop or more corresponds to the hop between the wireless devices 20 in FIG. In FIG. 4, the backbone device 10 and the wireless device 20 are not shown.

  In timeslots 1 to m, the downlink signal is transmitted to the wireless device 20 of the second hop from the backbone device 10 of the first hop, and the wireless device 20 of the third hop is transmitted in the order of the wireless device 20 of the fourth hop. It is shown that the data is transmitted to the wireless device 20 at the m-hop. Here, the downlink signal includes a hello packet and the like. The hello packet includes, for example, information for establishing a route and a subslot number to be assigned to each wireless device 20.

  From time slot (m + 1) to 2m, starting from the m-hop wireless device 20, the uplink signal is transmitted to the (m-1) -hop wireless device 20, relayed in order, and transmitted to the backbone device 10 Is shown. The uplink signal includes signals such as monitor data, path information, and subslot allocation request.

  As shown in the figure, the timing of the downlink transmission slot of each wireless device 20 is shifted by one slot as it goes to the lower layer. For this reason, the downlink signal reaches the m-th hop wireless device 20 without stagnation. The same applies to uplink transmission. According to such an aspect, in any of the radio apparatuses 20, it is not necessary to hold the relay data for an excessively long time, so that power consumption can be reduced. Moreover, since the amount of buffer held can be reduced, downsizing can be promoted.

  As shown in FIG. 4, when different slots are used for uplink transmission and downlink transmission, one slot may be specified depending on the other. For example, in the case of the above-described example, the fourth wireless device 20d specifies the third slot as the transmission slot. In this case, the (2m-2) th slot may be specified as the uplink slot. The value “(2m−2)” is a value obtained by subtracting the number of hops “2” from the number of slots “2 m” per frame shown in FIG.

(1-2) Subslot allocation Return to FIG. In assigning subslots, the server 90 sets a unique value for each wireless device 20. By setting the subslot number to a value unique to the backbone device 10 and the wireless device 20, collision in the same network can be completely prevented. Further, even when the wireless device 20 moves and switches to another route on the same network, the subslot number can be continuously used. In the following, for the convenience of explanation, a uniquely assigned subslot number is referred to as a communication subslot number.

  This will be specifically described. After the slot assignment, the fourth wireless device 20d can execute communication with the backbone device 10 via the third wireless device 20c. However, no communication subslot number is assigned at this stage. Accordingly, the fourth radio apparatus 20d determines a subslot number (hereinafter referred to as “random subslot number”) used when requesting the communication apparatus 10 for a communication subslot number. Specifically, the fourth radio apparatus 20d randomly selects a random subslot number from the random access time area 218 shown in FIG.

  It can be said that the selected random sub-slot number is an offset amount based on the sub-slot number indicated by “1” in FIG. It may be an offset amount based on the head of the random access time area 218 indicated by “k + 1” instead of “1”. This offset amount is commonly used in the random access time region 218 in the upstream and the random access time region 218 in the downstream.

  That is, the random subslot number is used when an uplink signal related to the allocation request is transmitted to the server 90, and further, information on the communication subslot number allocated by the server 90 is transmitted toward the fourth radio apparatus 20d. It is also used when transmitting. In this way, by using both the uplink and downlink in common, it is possible not only to easily manage the random subslot number, but also to reduce the possibility of a collision with the random subslot number selected by another radio apparatus 20. .

  After determining the random subslot number, the fourth radio apparatus 20d transmits an allocation request signal to the server 90 at the timing of the random subslot number in the already determined slot. In response to the request, the server 90 assigns, for example, X as a unique communication subslot number to the fourth radio apparatus 20d. X is selected from the communication time area 216 in FIG. As described above, the random subslot number is used as the subslot number used to notify the fourth radio apparatus 20d of the assigned X.

  The fourth radio apparatus 20d stores the assigned communication subslot number X. Thereafter, the fourth radio apparatus 20d executes transmission processing in the X subslot of the third slot. After the participation process is completed, the fourth radio apparatus 20d periodically notifies the hello packet. This hello packet includes its own identification information and 2 that is its own hop count. In addition, the fourth wireless device 20d executes its own transmission processing and relay processing of signals transmitted from other wireless devices 20.

(2) Relay Process Next, the relay process will be described. The relay process is executed in the slot specified at the time of the participation process. However, the communication subslot number is not the communication subslot number assigned to itself, but the communication subslot number assigned to the wireless device 20 that requests communication with the backbone device 10. The wireless device 20 that requests communication with the backbone device 10 indicates the wireless device 20 that generates data to be transmitted and transmits the data to the backbone device 10. Hereinafter, for convenience of explanation, such a wireless device 20 is referred to as a starting wireless device.

  An example of relay processing will be described with reference to the drawings. FIG. 5 is a diagram schematically illustrating an example of transmission timing in the sensor network system 100 of FIG. FIG. 5 shows the relationship of the transmission timing in each wireless device 20 in the sensor network system 100 shown in FIG. In FIG. 5, the second radio apparatus 20b and the fourth radio apparatus 20d are the origin radio apparatuses. Here, it is assumed that X is assigned to the second radio apparatus 20b as a unique communication subslot number. Further, it is assumed that Y is assigned to the fourth radio apparatus 20d as a unique communication subslot number. X and Y indicate subslots included in the communication time area 216 in FIG. That is, X and Y are values of 1 or more and k or less.

  Further, in the second radio apparatus 20b and the fourth radio apparatus 20d, the (2m-2) th slot is specified as the uplink slot, and in the first radio apparatus 20a and the third radio apparatus 20c, the (2m-1) slot is specified. Assume that the eye is specified as an upstream slot. In addition, the reception timing in each radio | wireless apparatus 20 is abbreviate | omitting illustration.

  In this case, when the second radio apparatus 20b transmits uplink data to the backbone apparatus 10, the second radio apparatus 20b transmits to the first radio apparatus 20a at the X timing of the (2m-2) slot. The first wireless device 20a that has received the uplink signal from the second wireless device 20b has the communication subslot number of the second wireless device 20b that is the originating wireless device at the (2m-1) th slot that is its own transmission slot timing. Is relayed to the backbone apparatus 10 at the timing of X.

  Similarly, the fourth radio apparatus 20d transmits to the third radio apparatus 20c at the timing of Y in the (2m-2) th slot. The third radio apparatus 20c transmits to the backbone apparatus 10 at the timing of Y in the (2m-1) th slot.

  As described above, in the first radio apparatus 20a to the fourth radio apparatus 20d, a plurality of transmission processes are executed in the same frame, but the respective transmission timings are shifted, so that they do not collide with each other. It is assumed that the first radio apparatus 20a knows the communication subslot number of the second radio apparatus 20b that is the origin radio apparatus. The first wireless device 20a may be notified of the communication subslot number when data is first transmitted to the first wireless device 20a after the second wireless device 20b joins the sensor network system 100. The first radio apparatus 20a may read the communication subslot number when relaying the communication subslot number to be assigned to the second radio apparatus 20b.

  As an example of another relay process, a case where a communication subslot number allocation request transmitted from a newly participating wireless device 20 is relayed will be described with reference to FIG. In FIG. 5, the second wireless device 20 b and the fourth wireless device 20 d are wireless devices 20 that have newly joined the sensor network system 100, respectively. Further, it is assumed that the second radio apparatus 20b and the fourth radio apparatus 20d request the first radio apparatus 20a and the third radio apparatus 20c to relay the communication subslot number assignment request, respectively. .

  Here, it is assumed that the second radio apparatus 20b has selected X as the random subslot number used in the communication subslot number allocation request. In addition, it is assumed that the fourth radio apparatus 20d has selected Y as the random subslot number. X and Y indicate subslots included in the random access time region 218 in FIG. That is, X and Y are values from (k + 1) to n. The details of the other processes, particularly the relay timing, are the same as described above, and thus the description thereof is omitted.

  As described above, the random subslot number used in the communication subslot number assignment request is selected from the random access time region 218 that is not assigned to the wireless device 20. There is no impact. As shown in FIG. 5, in the case where a plurality of radio apparatuses 20 request assignment of communication subslot numbers at the same time, if X and Y, which should have been selected at random, accidentally become the same value, both assignments are made. The request conflicts and the allocation process is interrupted. However, since a plurality of subslots are prepared in advance in the random access time area 218 as subslots that can be selected as the random subslot number, it is rare that the random subslot numbers overlap, and the random subslot number Is used only at the time of an allocation request, so there is no constant collision. Furthermore, even if an allocation request collides, it may be retransmitted, so that there is almost no problem. In other words, in this embodiment, the collision between the allocation requests and the communication of the other wireless device 20 is avoided by allowing a slight collision between the allocation requests.

  Here, the wireless device 20 will be described with reference to the drawings. Here, the wireless device 20 does not include the backbone device 10. FIG. 6 is a diagram illustrating a configuration example of the wireless device 20 of the sensor network system 100 of FIG. The wireless device 20 includes a reception unit 22, an analysis unit 24, a timing allocation unit 26, a storage unit 28, a timing setting unit 30, a transmission control unit 32, a transmission unit 34, and a sensor 36. In the following, description will be given separately for each case of the participation process, the transmission process for the measurement result by the own sensor 36, and the relay process of the transmission data by the other radio apparatus 20.

  First, the case of the participation process will be described. During the participation process, the receiving unit 22 receives a hello packet broadcast from the backbone device 10 or another wireless device 20. When the analysis unit 24 receives a hello packet from the reception unit 22, the analysis unit 24 reads the identification information indicating the number of hops and the notification source wireless device 20 from the hello packet and notifies the timing allocation unit 26 of the read information. Thereafter, the number of hops is also notified in the same manner for hello packets received during a certain period.

  The timing allocation unit 26 searches for the minimum number of hops among the number of hops notified from the analysis unit 24. Next, the timing allocation unit 26 stores “identification information of the wireless device 20 that has notified the hello packet including the searched hop number” in the storage unit 28. Further, the timing allocation unit 26 may specify a value obtained by adding 1 to the searched hop count as the number of its own downlink transmission slot and record it in the storage unit 28. Further, the timing allocation unit 26 may record the value obtained by subtracting the downlink transmission slot number from the number of slots in one frame in the storage unit 28 as the uplink transmission slot number.

  Next, the timing allocation unit 26 requests the transmission control unit 32 to allocate its own communication subslot number. Further, the timing allocation unit 26 notifies the timing setting unit 30 of the set uplink transmission slot number and a predetermined subslot number as the transmission timing of the communication subslot number allocation request.

  At this stage, a unique communication subslot number has not yet been assigned. Therefore, the timing allocation unit 26 determines a random subslot number. Since the random subslot number is determined from a subslot that is not assigned to another wireless device 20, it is possible to prevent communication interference with the existing wireless device 20 in the system. In summary, before the communication subslot number is assigned, the timing assignment unit 26 notifies the timing setting unit 30 of the combination of the set uplink transmission slot number and the random subslot number. After the communication subslot number is assigned, the timing assignment unit 26 notifies the timing setting unit 30 of the combination of the set uplink transmission slot number and the communication subslot number.

  The transmission control unit 32 transmits a communication subslot number allocation request to the backbone apparatus 10 via the transmission unit 34 in accordance with an instruction from the timing allocation unit 26. Here, when the number of hops retrieved by the timing allocation unit 26 is 2 or more, since the other wireless device 20 exists between the wireless device 20 and the backbone device 10, the destination is the other wireless device 20. Become. The other wireless device 20 is identified by “identification information of the wireless device 20 that has notified the hello packet including the searched hop count” stored in the storage unit 28.

  After the allocation request, the receiving unit 22 receives the communication subslot number allocated to its own radio apparatus 20. Random subslots are used for reception timing at the time of reception. In addition, when it cannot be received even after a certain period of time, the allocation request may be retransmitted. When the analysis unit 24 is notified of the communication subslot number uniquely assigned to its own radio apparatus 20 from the reception unit 22, the analysis unit 24 transfers it to the timing allocation unit 26 and stores it in the storage unit 28.

  The timing setting unit 30 controls the transmission unit 34 or the reception unit 22 according to the notified timing. The notified timing is an uplink transmission slot number and a communication subslot number or a random subslot number. The timing setting unit 30 derives a downlink transmission slot number from the notified uplink transmission slot number. Further, the timing setting unit 30 derives the uplink reception slot number and the downlink reception slot number by subtracting 1 from the uplink transmission slot number and the downlink transmission slot number, respectively. Note that the timing setting unit 30 may be notified of all uplink / downlink transmission slot numbers and uplink / downlink reception slot numbers. The process of the timing setting unit 30 is a common process regardless of the participation process, the transmission process, and the relay process.

  Next, a case at the time of transmission processing will be described. Here, the transmission processing refers to transmission processing when the wireless device 20 of its own transmits mainly. The upstream transmission process is started with a transmission request from the sensor 36 as a trigger. The sensor 36 observes sensor data such as temperature and humidity, and periodically requests the transmission control unit 32 to transmit the observed sensor data. The timing assignment unit 26 notifies the timing setting unit 30 of the identified transmission slot number and the communication subslot number uniquely assigned to the wireless device 20 to set the timing. The transmission control unit 32 transmits data to be transmitted to the backbone apparatus 10 via the transmission unit 34.

  In the downlink transmission process, the timing allocation unit 26 notifies the timing setting unit 30 of the specified downlink transmission slot number and its own communication subslot number. Further, the transmission control unit 32 causes the transmission unit 34 to notify the hello packet including its own identification number and the number of hops.

  Next, the case of relay processing will be described. First, uplink relay processing will be described. First, the reception unit 22 receives data to be relayed from the radio device 20 in the next lower layer and notifies the analysis unit 24 of the data. The data to be relayed here is, for example, sensor information or subslot allocation request signal observed in the originating wireless device. The analysis unit 24 determines the starting wireless device from the data to be relayed, and notifies the timing allocation unit 26 together with the data.

  When the uplink data to be relayed is a subslot allocation request, the communication subslot number is not allocated in the originating wireless device, so the timing allocating unit 26 uses the random subslot number determined in the originating wireless device as the timing setting unit 30. Notify This is to reduce interference with other radio apparatuses 20. The random subslot number determined in the originating wireless device may be included in a wireless packet to be relayed with information indicating the number. Further, the subslot number when the radio packet to be relayed is received may be estimated as the random subslot number. Since the slot to receive and the slot to relay are shifted by one slot, it can be said that there is enough time for executing the estimation process.

  On the other hand, when the uplink data to be relayed is information other than the subslot allocation request, for example, sensor information, the timing allocation unit 26 stores the communication subslot number stored in association with the originating wireless device from the storage unit 28. Is sent to the timing setting unit 30. Here, the timing allocation unit 26 transfers the data to be relayed notified from the analysis unit 24 to the transmission control unit 32. The transmission control unit 32 causes the transmission unit 34 to transmit the transferred data.

  Next, downlink relay processing will be described. First, the reception unit 22 receives data to be relayed from the radio device 20 of the layer above and notifies the analysis unit 24 of the data. The data to be relayed here is, for example, a communication subslot number to be assigned to the originating wireless device.

  The timing assignment unit 26 associates the communication subslot number to be relayed with the identification number indicating the originating wireless device to which the communication subslot number is assigned, and stores it in the storage unit 28. That is, the upper radio apparatus 20 manages communication subslot numbers of one or more radio apparatuses 20 in the lower rank.

  In addition, the timing allocation unit 26 notifies the timing setting unit 30 of the downlink transmission slot number and the communication subslot number itself to be relayed as the subslot number at the time of relaying. This is to prevent a collision. The transmission control unit 32 relays the communication subslot number to be assigned to the origin wireless device via the transmission unit 34 toward the origin wireless device that has requested the assignment of the communication subslot number.

  In uplink transmission / downlink transmission, the reception timing in an arbitrary radio apparatus 20 is one slot before its own transmission timing. In other words, since reception timing is defined based on its own transmission timing, timing management becomes easy.

  Next, the configuration of the backbone apparatus 10 will be described. In addition, about the structure equivalent to the structure of the radio | wireless apparatus 20 shown in FIG. 6, description is simplified using the same code | symbol.

  The backbone device 10 includes a wired communication unit (not shown) in addition to the configuration of the wireless device 20 illustrated in FIG. 6. The wired communication unit performs wired communication with the server 90 via the wired network 80. The wired communication unit converts the wireless packet received from the lower-layer wireless device 20 into a format for wired communication and transmits it to the server 90. Also, the packet configured in the wired communication format transmitted from the server 90 is converted into a wireless packet format and transmitted to the lower-layer wireless device 20. For wired communication, for example, a well-known wired LAN (Local Area Network) method may be used, and the description thereof is omitted.

  These configurations described above can be realized in hardware by a CPU, memory, or other LSI of an arbitrary computer, and in terms of software, it is realized by a program loaded in the memory. Describes functional blocks realized through collaboration. Accordingly, those skilled in the art will understand that these functional blocks can be realized in various forms by hardware only, software only, or a combination thereof.

  FIG. 7 is a diagram illustrating an example of an operation sequence in the sensor network system 100 of FIG. An example of this operation sequence is based on the example described with reference to FIG. That is, it is assumed that the third wireless device 20c and the fifth wireless device 20e have already participated in the sensor network system 100 based on the backbone device 10. In the following, hello packets other than the hello packet received by the fourth radio apparatus 20d are not shown.

  First, the third radio apparatus 20c broadcasts a hello packet (S10). This hello packet includes information indicating “the number of hops = 1”. The fifth radio apparatus 20e broadcasts a hello packet (S12). It is assumed that the hello packet includes information indicating “hop count = 2”. The fourth radio apparatus 20d receives the hello packet notified from the third radio apparatus 20c and the fifth radio apparatus 20e, respectively.

  The fourth radio apparatus 20d searches for the minimum number of hops out of the number of hops included in each received hello packet (S14). Here, “hop count = 1” is the smallest. Next, the fourth radio apparatus 20d adds 1 to the searched minimum hop count and sets its own hop count to 2. Further, the uplink transmission slot is specified according to the number of hops of the device (S18).

  Here, the fourth radio apparatus 20d requests the server 90 to allocate a communication subslot number via the backbone apparatus 10 at the timing of the specified transmission slot (S20). This request is received by the third radio apparatus 20c. Here, the third radio apparatus 20c sets its own uplink transmission slot (S22), and relays a signal related to the allocation request to the backbone apparatus 10 (S24).

  The backbone device 10 receives the assignment request relayed from the third wireless device 20c. Further, the core apparatus 10 converts the format of the received allocation request into a wired packet for wired communication (S28). Furthermore, the core device 10 relays the format-converted wired packet to the server 90 (S30).

  Here, as the subslot number used in the transmission process of S20 and the relay process of S24 and S30, a random subslot number existing in the time domain that is not assigned by the server 90 is used. For this reason, these processes do not interfere with the relay process in the existing radio apparatus 20.

  The server 90 allocates a unique subslot number to the fourth radio apparatus 20d when receiving the allocation request relayed by the backbone apparatus 10 (S32). The server 90 includes the assigned communication subslot number in a wired packet for wired communication and notifies the backbone apparatus 10 via the wired network 80 (S34). The backbone apparatus 10 receives the wired packet including the communication subslot number notified from the server 90. Here, the core apparatus 10 extracts the communication subslot number included in the received wired packet and converts the format so as to be included in the wireless packet (S36).

  Further, in order to transmit the communication subslot number included in the radio packet, the core apparatus 10 sets its own downlink transmission slot (S38), and notifies the third radio apparatus 20c of the communication subslot number. (S40). In order to transmit the received communication subslot number, the third radio apparatus 20c sets its own downlink transmission slot (S42), and relays the communication subslot number to the fourth radio apparatus 20d (S44). ). When relaying, the third radio apparatus 20c may store the communication subslot number of the fourth radio apparatus 20d and information indicating the fourth radio apparatus 20d in association with each other. The fourth radio apparatus 20d stores the communication subslot number received from the third radio apparatus 20c (S46).

  Note that the sub-slot numbers used in the notification process of S34 and the relay processes of S40 and S44 are the same as the random sub-slot numbers used in the transmission process of S20 and the relay processes of S24 and S30.

  FIG. 8 is a flowchart illustrating an operation example during the participation process in the wireless device 20 of FIG. This process may be started when the power of the wireless device 20 is turned on or when the route is disconnected and a route is newly established.

  First, the wireless device 20 receives a hello packet broadcast from another wireless device 20 (S50). The reception of the hello packet is repeated until a predetermined time elapses (N in S52). When the predetermined time has elapsed (Y in S52), the wireless device 20 searches for the minimum number of hops among the number of hops included in the received hello packet (S54). Next, the wireless device 20 adds 1 to the searched hop count and identifies its own transmission slot (S56).

  Here, the radio apparatus 20 determines a random subslot number. Furthermore, the wireless device 20 requests the backbone device 10 to assign a communication subslot number using the random subslot number in the assigned transmission slot (S58). If the communication subslot number cannot be received even after a predetermined time has elapsed (N in S60), the process of S58 is repeated until it can be received. When the communication subslot number is received (Y in S60), the wireless device 20 stores the received communication subslot number (S62). Note that the random subslot used in the request process in S58 is also used in common in the reception process in S60.

  FIG. 9 is a flowchart illustrating an operation example during relay processing in the wireless device 20 of FIG. This flowchart is a process performed after the participation process shown in FIG. 8 is completed. This process may be started when data to be transmitted is generated or when data to be relayed from another wireless device 20 is received.

  First, the wireless device 20 determines whether it is a relay process for another wireless device 20 or a transmission process for its own wireless device 20 (S80). When it is a relay process (Y of S80), the radio | wireless apparatus 20 reads the communication subslot number of an origin radio | wireless apparatus, and sets a timing (S82). When the relay data is a communication subslot number assignment request, the random subslot number determined by the originating wireless device is set. On the other hand, when it is not relay processing (N of S80), the radio | wireless apparatus 20 sets the intrinsic | native communication subslot number allocated to self as a transmission timing (S84).

  Next, the radio apparatus 20 determines whether it is uplink transmission or downlink transmission (S86). When it is uplink transmission (Y of S86), the radio | wireless apparatus 20 reads the stored uplink transmission slot number, and sets a timing (S88). If it is downlink transmission (N in S86), the downlink transmission slot number is read and the timing is set (S90). After setting the timing, the wireless device 20 executes a transmission process.

  According to the present embodiment, the communication subslot number assigned to the wireless device 20 that requests communication with the backbone device 10 among the plurality of subslots forming the slot assigned according to the number of hops. A collision can be avoided by executing a transmission process in the subslot. By selecting a route so that the number of other wireless devices 20 existing with the backbone device 10 is reduced, the number of relays can be reduced, and the reliability of communication can be improved. Since reception timing can be defined based on its own transmission timing, control such as intermittent reception can be executed effectively.

  Further, since the sub-slot allocation is requested and obtained using the random access area, collision with communication processing and relay processing in another radio apparatus 20 using an area other than the random access area can be avoided, and efficient relaying is achieved. Processing can be realized. In addition, in the uplink transmission / relay process when requesting a subslot and the downlink transmission / relay process when acquiring, a random subslot number is used in common, so that the basic apparatus and other wireless apparatuses can be used. Control of transmission / relay processing related to sub-slot number assignment processing can be facilitated without instructing and notifying random sub-slot numbers. Further, by determining the timing based on the combination of the time slot defined in the number of hops and the uniquely assigned subslot, it is possible to reduce the influence on the relay processing in other radio apparatuses, and to avoid collision.

  The present invention has been described based on the embodiments. This embodiment is an exemplification, and it will be understood by those skilled in the art that various modifications can be made to the combination of each component and each processing process, and such modifications are also within the scope of the present invention. .

  In the present embodiment described above, when a plurality of wireless devices 20 to be connected exist when newly joining the sensor network system 100, the selection is made based on the propagation quality. However, the present invention is not limited to this. For example, the wireless device 20 to be selected may be determined according to the system load in the connected tree. In particular, as shown in FIG. 3, when the selected first wireless device 20 a and third wireless device 20 c are connected to different backbone devices 10, in the tree rooted at each backbone device 10, What is necessary is just to select the radio | wireless apparatus 20 which belongs to the tree with the few number of the participating radio | wireless apparatuses 20. This is because the smaller the number, the smaller the relay load and the more the load of the entire sensor network system 100 can be distributed.

  In the above-described embodiment, the server 90 and the backbone device 10 have been described as separate configurations. However, the server 90 and the backbone device 10 may be integrally configured.

It is a figure which shows the structural example of the sensor network system concerning embodiment of this invention. FIG. 2A is a diagram illustrating a configuration example of a frame format in the sensor network system of FIG. FIG. 2B is a diagram showing an example of the slot format of the slots included in the frame of FIG. FIG. 2C is a diagram illustrating an example of a format included in the subslot section of FIG. It is a figure which shows the 2nd structural example of the sensor network system of FIG. It is a figure which shows the example of the slot allocation concerning embodiment of this invention. It is a figure which shows the example of the transmission timing in the sensor network system of FIG. It is a figure which shows the structural example of the radio | wireless apparatus of the sensor network system of FIG. It is a figure which shows the example of the operation | movement sequence in the sensor network system of FIG. 6 is a flowchart illustrating an operation example during a participation process in the wireless device in FIG. 5. 6 is a flowchart illustrating an operation example during relay processing in the wireless device of FIG. 5.

Explanation of symbols

  10 core devices, 20 wireless devices, 22 receiving units, 24 analyzing units, 26 timing assigning units, 28 storage units, 30 timing setting units, 32 transmission control units, 34 transmitting units, 36 sensors, 80 wired networks, 90 servers, 100 Sensor network system, 200 frame format, 210 slot format, 212 subslot section, 214 spare section, 216 communication time area, 218 random access time area.

Claims (3)

A wireless device requesting participation in a multi-hop wireless network formed by a plurality of wireless devices,
Consecutive frames formed by an upstream time slot including an upstream communication time region and an upstream random access time region and a downstream time slot including a downstream communication time region and a downstream random access time region A determination unit that determines a common first offset amount from the head of each of the time domain for uplink random access and the time domain for downlink random access;
Using the first offset amount determined by the determination unit for the management device that manages the multi-hop wireless network, the upstream communication time domain and the downstream communication time domain in the upstream random access time domain An allocation requesting unit for requesting allocation of a common second offset amount from each head;
An offset amount acquisition unit that acquires a response to the request in the allocation request unit in the time domain for downlink random access while using the first offset amount determined in the determination unit;
A communication unit that performs communication in the multi-hop wireless network in the time domain for uplink communication and the time domain for downlink communication while using the second offset amount included in the response acquired in the offset amount acquisition unit When,
A wireless device comprising: In a multi-hop wireless network formed in a tree shape with the backbone device among the plurality of wireless devices as a root, a hop number acquisition unit that acquires the number of hops to the backbone device;
In accordance with the number of hops acquired by the hop number acquisition unit, an uplink time slot and a downlink time slot to be used by the radio apparatus from a plurality of uplink time slots and a plurality of downlink time slots forming a frame. A first specifying unit for specifying each of
The transmission timing is specified by a combination of the second offset amount acquired by the offset amount acquisition unit and the uplink communication time domain included in the uplink time slot specified by the first specification unit, and the offset amount A second specifying unit for specifying a reception timing by a combination of the second offset amount acquired by the acquiring unit and the downlink communication time region included in the downlink time slot specified by the first specifying unit;
Further comprising
The radio apparatus according to claim 1, wherein the communication unit performs communication at the transmission timing and the reception timing specified by the second specifying unit. The request from the allocation request unit is relayed to the backbone device using the uplink time slot specified by the number of hops in the other wireless device and the first offset amount determined by the determination unit. Stipulated in
The response acquired by the offset amount acquisition unit is specified to be relayed while using the downlink time slot specified by the number of hops in another wireless device and the first offset amount determined by the determination unit. The wireless device according to claim 1, wherein the wireless device is a wireless device.

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