JP5286186B2 - Wireless communication system, relay device, and route search destination device - Google Patents

Description

  The present invention relates to a wireless communication system having a mesh network structure, and a relay device and a route search destination device used therefor.

  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 has been proposed (for example, see Patent Documents 1 and 2). In this mesh network, a large number of communication nodes (devices) are arranged in a mesh shape, and bidirectional communication between the communication nodes is performed by directly relaying other communication nodes in the communication area. Even if communication is disabled due to the influence of multipath fading, it is a technique that can continue communication by searching for another communication path. 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.

  Here, a technique for searching for another communication route (relay route) and continuing communication is called route search. In this route search, a transmission packet (route search issuer node) is a communication packet called a discovery packet ( (Route search packet) is broadcasted directly to other communication nodes in the communication area, and the other communication node (relay node) receiving this discovery packet accumulates information (route information) about the route between them in the discovery packet. The discovery packet storing the route information is broadcasted and further transmitted to other communication nodes directly in the communication area in order, so that the discovery packet passing through all the routes in the mesh network is sent to the destination node (route search). Finally reach the destination node. The destination node determines an optimal relay route between the transmission source node and the destination node based on the route information accumulated in the reached discovery packet. Note that a maximum relayable number N is determined for the mesh network, and discovery packets having the number of relays (number of relay hops) exceeding the maximum relayable number N are excluded from search targets.

  Here, it is important how the optimum relay route is determined in the destination node. Non-Patent Document 1, for example, describes a technique for performing a route search using a link cost. The link cost is an index representing the communication quality between two communication nodes (relay hops) linked by 1 hop, and the received radio wave intensity at the relay hop is divided into, for example, seven stages of evaluation. In this case, the link cost is increased by one each time the received radio wave strength evaluation step is increased by one step, such as the first step link cost being 1, and the second step link cost being 2. At this time, it is assumed that the link cost 1 is very good and the link cost 7 is very bad. Also, a link cost field is provided in the discovery packet, and each time the discovery packet is relayed, the link cost at the relay hop is added to the value (initial value 0) written in the link cost field of the received discovery packet. go. Then, in the destination node, the value written in the link cost field of the reached discovery packet (link cost integrated value) is checked, and the route having the smallest link cost integrated value is determined as the optimum relay route.

JP 2006-5928 A JP 2006-42370 A

"Practical introductory network Zigbee development handbook", 127-131 pages, author: Tatetsu, publisher: Masazumi Tsuchioka, publisher: Rick Telecom Co., Ltd., February 22, 2006, first edition first edition issued.

  However, in the route search method using the link cost described in Non-Patent Document 1 (hereinafter referred to as the conventional link cost method), the communication path with the best received radio wave intensity at all relay hops is the optimal relay. There is no guarantee that it will be selected as a route.

  For example, as shown in FIG. 16, the communication path A with the link cost integrated value “5” and the relay count “3”, and the link cost integrated value “6” and the relay count “3”. Suppose there is B. In the communication path A, the link cost between the communication nodes N0 and N2 is “3”, and the link cost between the communication nodes N2 and N3 and between the communication nodes N3 and N1 is “1”. . In the communication path B, it is assumed that the link costs between the communication nodes N0 and N2, between the communication nodes N2 and N3, and between the communication nodes N3 and N1 are “2”, respectively. In this case, according to the conventional link cost method, the communication route A with the link cost integrated value “5” is selected as the optimum relay route.

  Here, when the communication path A and the communication path B are compared, the communication path A includes a relay hop having a link cost of “3”. On the other hand, the communication path B does not include a relay hop having a link cost of “3”. That is, the communication path A includes a relay hop having a higher link cost than the communication path B, and there is a high possibility that the communication path A will eventually become unable to communicate with the relay hop having a higher link cost. When communication becomes impossible, route search is performed again, and the communication performance of the system is extremely deteriorated although temporarily. Therefore, the communication path B has a larger link cost integrated value than the communication path A, but is more suitable as a relay path than the communication path A in that it does not include a relay hop having a higher link cost. It can be said. Nevertheless, in the conventional link cost method, the communication path A is selected as the relay path.

  The present invention has been made to solve such a problem, and the object of the present invention is to select a communication path having the best received radio wave intensity at all relay hops as an optimal relay path. To provide a wireless communication system, a relay device, and a route search destination device that can be guaranteed.

In order to achieve such an object, the present invention relays a route search issuer device, a route search destination device, and a route search packet transmitted by broadcast from the route search issuer device to the route search destination device. In a wireless communication system including a plurality of relay devices , m is a plurality of evaluation stages indicating the state of received radio wave strength on the relay device, and the maximum number of relayable signals in the wireless communication system is N. In this case, the link cost LC (m) expressed as m = 0 link cost LC (0) = 1 and m + 1 link cost LC (m + 1) = (N × LC (m)) + 1 is evaluated. a route search determination indicator of m, and route search determination index storage means for storing a relationship between each of the evaluation phase and the route search determination index, root A received radio field strength measuring unit that measures the received radio field strength at the time of receiving the search packet, and an evaluation stage determining unit that determines to which evaluation stage the measured received radio field intensity belongs to Route search determination index reading means for reading out the route search determination index corresponding to the evaluation stage from the route search determination index stored in the route search determination index storage means, and route search that has received the read route search determination index Route search determination index adding means for adding to the value written in the write area of the route search determination index of the packet for use as the integrated value of the route search determination index, and route search in which the integrated value of the route search determination index is written A route search packet transfer means for transferring a packet for broadcast to the route search destination device. Based on the integrated value of the route search determination index received from the route search packet transmitted from the device and sent via all the routes in the wireless communication system, and written in the received route search packet And a relay route determining means for determining a route having the smallest integrated value of the route search determination index as an optimal relay route.

In the present invention, when m is a plurality of evaluation stages (good, acceptable, bad, etc.) showing the good / bad state of received radio wave intensity for a relay device, and the maximum number of relayable signals in a wireless communication system is N, The link cost LC (m) expressed as m = 0 link cost LC (0) = 1 and m + 1 link cost LC (m + 1) = (N × LC (m)) + 1. As a route search determination index, the relationship between the route search determination index and each of the evaluation stages is stored. In this case, for example, when the evaluation stage m is m = 0, 1, 2 (the smaller the evaluation is, the better the evaluation), the link cost of m = 1 stage is LC (1) = (N × LC (0)) + 1 = (N X1) + 1 = N + 1, and the link cost of m = 2 stages is LC (2) = (N * LC (1)) + 1 = (N * (N + 1)) + 1.

  The relay device measures the received radio wave intensity at the time of receiving the route search packet (discovery packet), determines which evaluation stage the measured received radio wave intensity belongs to, and the determined evaluation stage The link cost corresponding to is read, and the read link cost is added to the value written in the write area (link cost field) of the route search determination index of the received discovery packet to obtain an integrated value of the link cost. Then, the discovery packet in which the integrated value of the link cost is written is transferred by broadcasting.

  On the other hand, the route search destination device receives a route search packet (discovery packet) transmitted from the route search issuer device and sent via all routes in the wireless communication system, and the received discovery packet Based on the written link cost integrated value, the route having the smallest link cost integrated value is determined as the optimum relay route.

Here, in the relay device, the relationship between each of the received radio wave strength evaluation stages and the route search determination index (link cost) is that the link cost of m = 0 stage is LC (0) = 1, and the link cost of m + 1 stage is LC. Since (m + 1) = (N × LC (m)) + 1 is stored , if the evaluation at all the relay devices is better than the m-th stage, in the discovery packet received by the route search destination device The integrated value of the link cost is always N × LC (m) or less. If at least one relay device with an evaluation worse than the m-th stage is included, the integrated value of the link cost in the discovery packet received by the route search destination device is at least (N × LC (m )) +1 or more. That is, if the integrated value of the minimum link cost is N × LC (m) or less, the relay route determined from the integrated value of the link cost includes a relay hop with a worse evaluation than the m-th stage. Absent.

Thus, according to the present invention, the link cost of the m = 0 stage is represented as LC (0) = 1, and the link cost of the m + 1 stage is represented as LC (m + 1) = (N × LC (m)) + 1. The link cost LC (m) to be used is the route search determination index of the evaluation stage m, and by defining the relationship between this route search determination index and each of the evaluation stages, the integrated value of the link cost is the smallest in the route search destination device When a route is selected, it is possible to select a communication route having the best received radio wave intensity at all relay hops as the optimum relay route.

In the present invention, a plurality of evaluation stages such as “good”, “acceptable”, “bad” and the like are defined as the evaluation stage of the received radio wave intensity. This evaluation stage is “good” or “bad”. Including the case of stages. If there are two evaluation stages,
(1) As a first priority criterion, a communication path having a good received radio wave intensity is selected at all relay hops.
(2) If there are multiple communication paths with good received signal strength at all relay hops, the path with the smallest number of relays is selected.
In this way, it is possible to select a route with as few relays as possible.
If you want to evaluate the received signal strength more safely, you can set the evaluation stage to 3 or more stages, or you can configure it with only the minimum available relay hops, and you want to reduce the amount of communication as much as possible. Therefore, the evaluation stage may be made into two stages.

According to the present invention, the link cost LC (m expressed as m = 0 link cost LC (0) = 1, and the m + 1 link cost LC (m + 1) = (N × LC (m)) + 1. ) Is used as a route search determination index at the evaluation stage m, the relationship between the route search determination index and each of the evaluation stages is determined, and the evaluation stage to which the measured received radio wave intensity belongs is determined. since such added to the value written in the link cost field of the discovery packet reads the corresponding link cost, if the integrated value of the link cost selects the smallest path in its root search destination device, all It is possible to guarantee that the communication path with the best received radio wave intensity at the relay hop is selected as the optimum relay path.

It is a block diagram which shows the outline of one Embodiment (when the evaluation stage is made into three stages) of the radio | wireless communications system (mesh network) which concerns on this invention. It is a figure which shows the relationship between each relay hop now in this mesh network, and the state (evaluation) of received radio wave strength. It is a figure which shows the table in which the relationship between each of the evaluation steps (good, tolerance, bad) of received radio wave intensity and the link cost weighted by the maximum number N of relayable is set. It is a flowchart for demonstrating operation | movement of the transmission origin node in this mesh network. It is a flowchart for demonstrating operation | movement of the relay node in this mesh network. It is a figure which shows the relationship between permissible reception radio wave intensity Eth1 and safe reception radio wave intensity Eth2 used as the evaluation criteria at the time of evaluating reception radio wave intensity. It is a flowchart for demonstrating operation | movement of the destination node in this mesh network. It is a figure which shows the integrated value of the arrival path | route of each discovery packet received in the destination node, the link cost in each relay hop, the frequency | count of relay, and link cost. It is the figure which rearranged the arrival cost of each discovery packet received in this destination node, the link cost at each relay hop, the number of relays, and the integrated value of the link cost in ascending order of the integrated value of the link cost. It is a functional block diagram of the principal part at the time of making a communication node function as a relay node. It is a functional block diagram of the principal part at the time of making a communication node function as a destination node. It is a block diagram which shows the outline of other embodiment (when the evaluation stage is made into two steps) other radio | wireless communications systems (mesh network) which concern on this invention. It is a figure which shows the relationship between each relay hop now in this mesh network, and the state (evaluation) of received radio wave strength. It is a figure which shows the table in which the relationship between each of the evaluation steps (good and bad) of received radio wave intensity and the link cost weighted by the maximum relayable number N is set. It is a figure which shows the integrated value of the arrival path | route of each discovery packet received in the destination node, the link cost in each relay hop, the frequency | count of relay, and link cost. It is a figure explaining the problem which arises with the conventional link cost method.

Hereinafter, the present invention will be described in detail with reference to the drawings.
[Embodiment 1: Example with three evaluation stages]
FIG. 1 is a block diagram showing an outline of an embodiment of a radio communication system according to the present invention. In the figure, N0 to N4 are communication nodes, and a mesh network is configured by these communication nodes N0 to N4.

  In this embodiment, the received radio wave strength at the relay hop between the communication nodes N0 and N1 is “bad”, the received radio wave strength at the relay hop between the communication nodes N0 and N2 is “good”, and the communication node The received radio wave strength at the relay hop between N0 and N3 is “permitted”, the received radio wave strength at the relay hop between the communication nodes N0 and N4 is “good”, and at the relay hop between the communication nodes N1 and N2. The received radio wave intensity is “permitted”, the received radio wave intensity at the relay hop between the communication nodes N1 and N3 is “good”, and the received radio wave intensity at the relay hop between the communication nodes N1 and N4 is “bad”. The received radio wave strength at the relay hop between N2 and N3 is “good”, and the received radio wave strength at the relay hop between the communication nodes N2 and N4 is “acceptable”. Received signal strength in the relay hop between the de N3 and N4 are intended to be "bad" state. FIG. 2 shows the relationship between each relay hop and the state (evaluation) of the received radio wave intensity in this case. The evaluation criteria for “good”, “acceptable”, and “bad” of the received radio wave intensity will be described later.

  Further, in this embodiment, the communication nodes N0 to N4 are weighted according to each of the received radio wave intensity evaluation stages and the maximum number N of relayable nodes in this mesh network as a table specific to this embodiment. A table TB1 (FIG. 3) showing the relationship with the cost is provided. In this embodiment, the maximum relayable number N is set to N = 3, the link cost is set as LC (0) = 1 for “good”, and the link cost is set to LC (1) = for “allowed”. (N × LC (0)) + 1 = N + 1 = 3 + 1 = 4, and the link cost for “bad” is LC (2) = (N × LC (1)) + 1 = (N × (N + 1)) + 1 = (3 × 4) + 1 = 13.

  Hereinafter, each of the cases where the route search is performed with the communication node N0 as the transmission source node (route search issuer node), the communication node N1 as the destination node (route search destination node), and the communication nodes N2 to N4 as the relay mode is taken as an example. The operation will be described with the function of the communication node.

[Source node]
When the source node N0 is instructed to start a route search (FIG. 4: YES in step S101), the source node N0 adds its own address as route information, and designates the communication node N1 as a destination node to perform direct communication. The discovery packet P is transmitted by broadcast to other communication nodes in the vicinity (step S102). The discovery packet P is provided with a link cost field F, and an initial value 0 is initially written in the link cost field F as the link cost.

[Relay node]
When the communication node N2 receives the discovery packet P from the transmission source node N0 (FIG. 5: YES in step S201), the communication node N2 measures the received radio wave intensity at the time of receiving the discovery packet P (step S202), and this measured reception The radio wave intensity is evaluated (step S203). In this case, the communication node N2 evaluates the measured received radio wave intensity as follows.

  In the communication node N2, an allowable reception radio wave intensity Eth1 and a safe reception radio wave intensity Eth2 are set as threshold values. FIG. 6 shows the relationship between the allowable reception radio wave intensity Eth1 and the safe reception radio wave intensity Eth2. In this example, a theoretical reception radio wave intensity E1 is obtained for the guaranteed maximum communication distance, and a margin M1 is added to the theoretical reception radio wave intensity E1 in consideration of deterioration of radio wave conditions to obtain an allowable reception electric field intensity Eth1. Yes. Further, a margin M2 is further added to the allowable received electric field strength Eth1 to obtain a safe received radio wave strength Eth2.

  When the measured received radio wave intensity is equal to or greater than the safe received radio wave intensity Eth2, the communication node N2 evaluates the received radio wave intensity at the relay hop between the transmission source node N0 and the communication node N2 as “good”. When the measured received radio wave intensity is between the safe received radio wave intensity Eth2 and the allowable received electric field intensity Eth1, the received radio wave intensity at the relay hop between the transmission source node N0 and the communication node N2 is evaluated as “allowable”. . When the measured received radio wave intensity is equal to or less than the allowable received electric field intensity Eth1, the received radio wave intensity at the relay hop between the transmission source node N0 and the communication node N2 is evaluated as “bad”.

  Note that this evaluation of the received radio wave intensity may be performed by one reception, or may be performed by an average value of a plurality of reception results, or may be performed most frequently when a plurality of receptions are performed. You may make it carry out with a bad result.

  Next, the communication node N2 reads the link cost corresponding to the evaluation result of the received radio wave intensity from the table TB1 (FIG. 3) held by itself (step S204). In this case, if the evaluation result of the received radio wave intensity is “good”, the link cost LC (0) = 1 is read. If the evaluation result of the received radio wave intensity is “allowable”, the link cost LC (1) = 4. If the evaluation result of the received radio wave intensity is “bad”, the link cost LC (2) = 13 is read out. In this example, since the evaluation result of the received radio wave intensity at the relay hop between the transmission node N0 and the communication node N2 is obtained as “good”, the link cost LC (0) = 1 is read.

  Then, the communication node N2 adds the read link cost LC (0) = 1 to the value written in the link cost field F of the received discovery packet P to obtain an integrated value of the link cost (step S205). In this case, since the initial value 0 is written in the link cost field F of the discovery packet P from the transmission node N0, the value 1 obtained by adding the link cost LC (0) = 1 to the initial value 0 is the link cost. It is an integrated value.

  The communication node N2 broadcasts and transfers the discovery packet P in which the integrated value of the link cost is written, to the other communication nodes in the direct communication range, with its own address as route information (step S206).

  The discovery packet P is relayed in the other communication nodes N3 and N4 in the same manner as the communication node N2. For example, when the discovery packet P transferred from the communication node N2 is received by the communication node N3, the communication nodes N2 and N3 are set to the value (1) written in the link cost field F of the received discovery packet P. The link cost 1 of the relay hops between the two is added to obtain an integrated value (2) of the link cost. The communication node N3 broadcasts and transfers the discovery packet P, in which the link cost integrated value is written, directly to another communication node within the communication range, with its own address added as route information.

[Destination node]
For example, when the destination node N1 receives the discovery packet P from the communication node N3 (FIG. 7: YES in step S301), the destination node N1 measures the received radio wave intensity when the discovery packet P is received (step S302). The received radio wave intensity is evaluated (step S303). In this example, it is evaluated as “good”.

  Then, the link cost corresponding to the evaluation result of the received radio wave intensity is read from the table TB1 (FIG. 3) held by itself (step S304), and the read link cost is read in the link cost field F of the received discovery packet P. The value is added to the written value to obtain an integrated value of the link cost (step S305). In this example, the link cost LC (0) = 1 is read and added to the value (2) written in the link cost field F of the received discovery packet P to obtain the link cost integrated value (3).

  When the destination node N1 completes reception of the discovery packet P via all the routes in the mesh network (YES in step S306), the value (link cost) written in the link cost field F of each received discovery packet P (Step S306), and the route with the smallest link cost integration value is determined as the optimum relay route (step S308).

  FIG. 8 shows the arrival path of each discovery packet P received at the destination node N1, the link cost at each relay hop, the number of relays, and the integrated value of the link cost. When these are rearranged in ascending order of the integrated value of the link cost, it is as shown in FIG. In this example, the route of N0 → N2 → N3 → N1 is determined as the optimum relay route as the route having the smallest link cost integrated value.

As can be seen from the relationship shown in FIG. 9, in the present embodiment, by performing route selection with the priority in ascending order of the integrated value of the link cost,
(1) Routes with all “good” received field strengths at relay hops are adopted with the highest priority.
(2) If there is only a route that includes something other than “good” in any of the relay hops, a route that does not include a relay hop in the “bad” state is adopted as the next priority (in which “permitted” ”Is used in the order of priority in ascending order of relaying).
(3) When “bad” is always included in any relay hop, the route with the fewest relay hops in the “bad” state is preferentially adopted.
It will be a thing.

  In this way, in the present embodiment, a table that defines the relationship between each of the received radio wave intensity evaluation stages and the link cost weighted by the maximum number N of relayable meshes in the mesh network (the zero-stage link cost is LC (0) = 1, m + 1 stage link cost LC (m + 1) = (N × LC (m)) + 1 table) TB1 is used to determine which evaluation stage the measured received radio wave intensity belongs to Then, by adopting a method of reading the link cost corresponding to the determined evaluation stage and adding it to the value written in the link cost field F of the discovery packet P, the integrated value of the link cost is the highest at the destination node N1. When a small route is selected, the communication route with the best received signal strength at all relay hops is optimally selected. It is possible to so as to select a path.

[Function block of relay node]
FIG. 10 shows a functional block diagram of the main part when the communication node functions as a relay node. In FIG. 10, the relay node is indicated by the symbol NA in order to distinguish it from the transmission source node and the destination node.

  The relay node NA includes a discovery packet receiving unit 1 that receives the discovery packet P, a received radio wave strength measuring unit 2 that measures the received radio wave strength when the discovery packet P is received by the discovery packet receiving unit 1, and an allowable received radio wave strength. A threshold value storage unit 3 for storing Eth1 and safe received radio wave intensity tEh2, and a threshold value indicating whether the received radio wave intensity measured by the received radio wave intensity measuring unit 2 belongs to an evaluation stage of “good”, “acceptable”, or “bad” An evaluation stage determination unit 4 for determining based on the allowable reception radio wave intensity Eth1 and the safe reception radio wave intensity Eth2 stored in the storage unit 3 is provided.

  Further, the maximum relayable number storage unit 5 that stores the maximum relayable number N in the mesh network, each of the received radio wave strength evaluation stages, and the maximum relayable number N stored in the maximum relayable number storage unit 4 are weighted. The link cost storage unit 6 that stores the table TB1 indicating the relationship with the link cost to be subjected to, and the link cost corresponding to the evaluation stage determined by the evaluation stage determination unit 4 from the table TB1 in the link cost storage unit 6 A link cost reading unit 7 for reading is provided.

  In addition, the link cost read by the link cost reading unit 7 is added to the value written in the link cost field F of the discovery packet P received by the discovery packet receiving unit 1 to obtain an integrated value of the link cost. An addition unit 8 and a discovery packet transfer unit 9 that adds the address of the discovery packet P in which the integrated value of the link cost is written and transfers it by broadcast are provided.

  In this configuration of the relay node NA, the link cost in the table TB1 in the link cost storage unit 6 is automatically changed when the maximum relayable number N stored in the maximum relayable number storage unit 5 is changed. Can be rewritten.

[Function block of destination node]
FIG. 11 shows a functional block diagram of the main part when the communication node functions as a destination node. In FIG. 11, the destination node is denoted by reference numeral NB in order to distinguish it from the transmission source node and relay node.

  The destination node NB includes a discovery packet reception unit 1, a received radio wave intensity measurement unit 2, a threshold storage unit 3, an evaluation stage determination unit 4, a maximum relayable number storage unit 5, a link cost storage unit 6, a link cost reading unit 7, a link In addition to the cost addition unit 8, a discovery packet reception completion determination unit 10, a link cost integrated value check unit 11, and an optimum relay route determination unit 12 are provided.

  The discovery packet reception completion determination unit 10 determines that the reception of the discovery packet P has been completed when the link cost addition unit 8 finishes adding the link cost to the discovery packet P sent via all routes.

  The link cost integrated value check unit 11 confirms the completion of reception of the discovery packet P in the discovery packet reception completion determination unit 10 and then the value written in the link cost field F of each received discovery packet P (link cost integration) Value). Based on the check result of the link cost integrated value check unit 11, the optimum relay route determination unit 12 determines the route having the smallest link cost integrated value as the optimal relay route.

[Embodiment 2: Example in which evaluation stage is two stages]
In the first embodiment, the evaluation stage for the received radio wave intensity is three stages. However, the evaluation stage is not limited to three stages, and the evaluation stage may be further increased. Also, the evaluation stage may be reduced and two stages may be used. In the second embodiment, the evaluation stage is divided into two stages, “good” and “bad”.

  FIG. 12 shows a diagram corresponding to FIG. 1 when the evaluation stage is two stages. In this mesh network, the received radio wave strength at the relay hop between the communication nodes N0 and N1 is “bad”, the received radio wave strength at the relay hop between the communication nodes N0 and N2 is “good”, and the communication nodes N0 and N3 The received radio wave strength at the relay hop between the communication nodes N0 and N4 is “good”, the received radio wave strength at the relay hop between the communication nodes N0 and N4 is “good”, and the received radio wave strength at the relay hop between the communication nodes N1 and N2 Is “bad”, the received radio wave strength at the relay hop between the communication nodes N1 and N3 is “good”, the received radio wave strength at the relay hop between the communication nodes N1 and N4 is “bad”, and the communication nodes N2 and N3 The reception radio wave strength at the relay hop between the communication nodes N2 and N4 is “good”, and the reception radio wave strength at the relay hop between the communication nodes N2 and N4 is “good”. Received signal strength in the relay hop between the de N3 and N4 are intended to be "bad" state. FIG. 13 shows the relationship between each relay hop and the state (evaluation) of the received radio wave intensity in this case.

  Further, in the second embodiment, the communication nodes N0 to N4 are linked to each of the received radio wave intensity evaluation stages and the link cost weighted by the maximum relayable number N in this mesh network, as in the first embodiment. Table TB1 (FIG. 14) showing the relationship between the In the second embodiment, the maximum relayable number N is set to N = 4, the link cost is set as LC (0) = 1 for “good”, and the link cost is set to LC (1) for “bad”. = (N × LC (0)) + 1 = N + 1 = 4 + 1 = 5.

  Also in the second embodiment, a route search is performed using the communication node N0 as a transmission source node (route search issuer node), the communication node N1 as a destination node (route search destination node), and the communication nodes N2 to N4 as relay nodes. Shall. Since the route search process is the same as that in the first embodiment, a description thereof will be omitted.

  FIG. 15 shows the arrival path of each discovery packet P received at the destination node N1, the link cost at each relay hop, the number of relays, and the integrated value of the link cost. In this figure, the link costs are rearranged in ascending order. In this case, the route of N0 → N3 → N1 is determined as the optimum relay route as the route having the smallest link cost integrated value.

As can be seen from the relationship shown in FIG. 15, in the present embodiment, by performing route selection in order of priority in ascending order of link cost integrated value,
(1) Routes with all “good” received field strengths at relay hops are adopted with the highest priority (if there are multiple routes with “good” for all relay hops, priority is given to those with the smallest number of relays. Adopted).
(2) If any of the relay hops contains a “bad” state, a route with the fewest “hope” relay hops is adopted (multiple routes with the same number of “bad” relay hops exist) If this is the case, it will be preferentially adopted in ascending order of the number of relays).
It will be a thing.
That is, by setting the evaluation stage to two stages, it is possible to consider that the number of relays is small as the second priority determination criterion.

  The wireless communication system, relay device, and route search destination 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. Specifically, it can be applied to a room air conditioning system by VAV (variable air volume adjustment).

  N0 to N4 ... communication node, P ... discovery packet, F ... link cost field, TB1 ... table, 1 ... discovery packet reception unit, 2 ... received radio wave intensity measurement unit, 3 ... threshold storage unit, 4 ... evaluation stage determination unit, DESCRIPTION OF SYMBOLS 5 ... Maximum relayable number memory | storage part, 6 ... Link cost memory | storage part, 7 ... Link cost reading part, 8 ... Link cost addition part, 9 is a discovery packet transfer part, 10 ... Discovery packet reception completion judgment part, 11 ... Link Cost integrated value check unit, 12... Optimum relay route determination unit, NA... Relay node, NB.

Claims (3)

Wireless communication comprising a route search issuer device, a route search destination device, and a plurality of relay devices that relay route search packets transmitted by broadcast from the route search issuer device to the route search destination device In the system,
The relay device is
When m is a plurality of evaluation stages indicating whether the received radio wave intensity is good or bad, and N is the maximum number of relayable signals in the wireless communication system, the link cost of m = 0 stage is LC (0) = 1, The link cost LC (m) represented as m + 1 stage link cost LC (m + 1) = (N × LC (m)) + 1 is used as the route search judgment index of the evaluation stage m, and this route search judgment index and the evaluation Route search determination index storage means for storing the relationship with each of the stages ;
A received radio wave intensity measuring means for measuring a received radio wave intensity at the time of receiving the route search packet;
An evaluation stage determination means for determining which of the plurality of evaluation stages the measured received radio wave intensity belongs to;
Route search determination index reading means for reading out the route search determination index corresponding to the determined evaluation stage from the route search determination index stored in the route search determination index storage means;
Route search determination index adding means for adding the read route search determination index to the value written in the write area of the route search determination index of the received route search packet to obtain an integrated value of the route search determination index When,
Route search packet transfer means for transferring the route search packet in which the integrated value of the route search determination index is written by broadcast,
The route search destination device is:
The route search determination index written in the received route search packet is received from the route search issuer device and sent via all routes in the wireless communication system. A wireless communication system comprising: a relay route determination unit that determines a route having the smallest integrated value of the route search determination index as an optimal relay route based on the integrated value of A relay device that is used in a wireless communication system including a route search issuer device and a route search destination device, and relays a route search packet that is broadcast from the route search issuer device to the route search destination device. In
When m is a plurality of evaluation stages indicating whether the received radio wave intensity is good or bad, and N is the maximum number of relayable signals in the wireless communication system, the link cost of m = 0 stage is LC (0) = 1, The link cost LC (m) represented as m + 1 stage link cost LC (m + 1) = (N × LC (m)) + 1 is used as the route search judgment index of the evaluation stage m, and this route search judgment index and the evaluation Route search determination index storage means for storing the relationship with each of the stages ;
A received radio wave intensity measuring means for measuring a received radio wave intensity at the time of receiving the route search packet;
An evaluation stage determination means for determining which of the plurality of evaluation stages the measured received radio wave intensity belongs to;
Route search determination index reading means for reading out the route search determination index corresponding to the determined evaluation stage from the route search determination index stored in the route search determination index storage means;
Route search determination index adding means for adding the read route search determination index to the value written in the write area of the route search determination index of the received route search packet to obtain an integrated value of the route search determination index When,
A route search packet transfer means for transferring a route search packet in which the integrated value of the route search determination index is written by broadcast. A wireless communication system comprising a route search issuing device that broadcasts a route search packet and a plurality of relay devices according to claim 2 that relay the route search packet from the route search issuing device. In a route search destination device used as a final destination of the route search packet,
The route search determination index written in the received route search packet is received from the route search issuer device and sent via all routes in the wireless communication system. A route search destination device comprising: a relay route determination unit that determines a route having the smallest integrated value of the route search determination index as an optimal relay route based on the integrated value of

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