JP2009065352A - Communication control device, communication control method, communication control program and communication system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce communication delay by finding communication timing, in accordance with transmission path information of a data signal, when mutually adjusting the communication timing between each node and another node to determine communication timing of own node. <P>SOLUTION: This communication control device is provided with a communication means for receiving a timing control signal, showing the timing of data transmission of other nodes and transmitting a timing control signal, showing the timing of data transmission of own node; a communication timing calculating means for calculating communication timing of own node by changing phase states in own node, on the basis of the timing control signal received from the other node; a phase sequence confirming means for confirming a sequence of phase states calculated by the communication timing calculating means, with reference to transmission path information of a data signal; and a phase-adjusting means for changing phases of its own node, when the sequence of phase states by the phase sequence confirming means does not correspond to the transmission path information. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a communication control device, a communication control method, a communication control program, a node, and a communication system, such as a system composed of a plurality of devices connected to a sensor network, an ad hoc network, or a LAN (Local Area Network). Thus, the present invention relates to a method for avoiding communication data collision due to radio wave interference or the like when a large number of nodes arranged in a distributed manner or nodes installed in a mobile body perform data communication with each other.

  There is a technique disclosed in Patent Literatures 1 to 7 as a method of avoiding a transmission collision by not adjusting the communication timing in an autonomous and distributed manner without requiring a centralized management server.

  In the method described in Patent Literature 1 to Patent Literature 7, each node performs mutual adjustment of communication timing by periodically transmitting and receiving impulse signals (control signal indicating the transmission timing of the own node) with neighboring nodes. Do. This realizes autonomous time slot allocation that divides a period of one period (impulse signal transmission period) between nodes within a radio wave reach of the impulse signal. Here, the impulse signal is not necessarily a signal having an impulse-like waveform, and can be composed of a packet or the like as in the case of a general control signal. Therefore, hereinafter, this impulse signal is also referred to as a timing control signal. Hereinafter, the transmission cycle of the timing control signal is simply referred to as a cycle. The radio wave arrival range of the timing control signal transmitted by each node corresponds to the interaction range in which the node adjusts the communication timing.

  There are several forms of transmission / reception methods of timing control signals between neighboring nodes. In the first form, as shown in FIG. 2A, the radio wave arrival range of the timing control signal is made wider than the radio wave arrival range of the data signal, and the ratio is, for example, about twice. In this case, the ratio of the radio wave coverage is set by adjusting the transmission power ratio between the timing control signal and the data signal. The reason for setting the ratio of the radio wave arrival range between the timing control signal and the data signal in this way is to avoid the occurrence of a transmission collision caused by a hidden terminal or the like.

  In the second form, as shown in FIG. 2B, the radio wave arrival ranges of the timing control signal and the data signal are the same (that is, the transmission power is the same), and based on the timing control signal received from another node, This is a method of adding a virtual phase for the node generated inside itself when transmitting a timing control signal (see Patent Document 5).

  The node that has received the timing control signal from the target node (the node in the solid circle in FIG. 2B) is newly generated if the virtual phase for the target node does not exist within the own node, and already exists Adjust its value. The generated or adjusted virtual phase value thereafter changes at a constant speed corresponding to the natural angular frequency. Then, when the own node transmits the timing control signal, the value is added with the value of the virtual phase for the node of interest at the current time. By doing so, the phase information of the node of interest is indirectly 2 hops ahead (a dotted line in FIG. 2B) via the 1 hop ahead node (node in the solid line circle in FIG. 2B). Nodes that are not included in the solid circle).

  In the above description, the mechanism in which the phase information of the node of interest is indirectly transmitted to the node that is 2 hops ahead has been described. However, the phase information of all the nodes is similarly transmitted to the node that is 2 hops away. Therefore, the interaction range in the communication timing adjustment is a 2-hop neighborhood range of each node.

Japanese Patent Laying-Open No. 2005-094663 JP 2006-74617 A JP 2006-74619 A JP 2006-157438 A JP 2006-157441 A Japanese Patent Application Laid-Open No. 2006-211585 Japanese Patent Laid-Open No. 2006-211564

  When using the communication timing control method disclosed in the above Patent Document 1 to Patent Document 7, generally, since the transmission order of each node in a cycle is randomly determined under the condition of avoiding transmission collision, communication is often performed. There is a problem that the delay may become very large. This problem will be specifically described below.

  FIG. 3 is a diagram illustrating an example of spatial arrangement of nodes and transmission paths. In FIG. 3, a situation is assumed in which traffic periodically occurs in all nodes.

  For example, consider the magnitude of communication delay in the case where traffic generated in node 1 is transmitted in a multi-hop manner through adjacent nodes and finally reaches node 6.

  Since traffic is occurring at all nodes, some way to avoid outgoing collisions is required. On the other hand, if the communication timing control method disclosed in Patent Literature 1 to Patent Literature 7 is used, each node autonomously acquires a time slot in order to avoid a transmission collision between neighboring nodes.

  However, the time slot order relationship acquired by each node is independent of the transmission path. Therefore, in the worst case, the configuration is as shown in FIG. 4 and a problem that the communication delay becomes large occurs. Hereinafter, the contents represented by FIG. 4 will be described.

  FIG. 4 is a diagram showing the relationship between the position of the time slot acquired by each node within the period T and the communication delay. Within the period, node 1 acquired the first slot, node 2 acquired the last slot, node 3 acquired the slot immediately before node 2, node 4 acquired the slot immediately before node 3, and node 5 acquired the slot immediately before node 4. Shows the case.

  In this case, the traffic generated in the node 1 at a certain time is held in the node 1 until the start time of the next head slot, and then transmitted to the node 2 using the head slot. The traffic that reaches the node 2 is held in the node 2 until the start time of the last slot, and then transmitted to the node 3 using the last slot. In the same manner, the transmission data finally reaches the node 6 after being held in each node until the time slot of its own node is reached.

  In the above process, each node has time to hold traffic for almost one period, so it takes time for the traffic to reach the transmission destination and communication delay increases. In the case of the example in FIG. 4, a communication delay of nearly 5 cycles occurs after the node 1 reaches the node 6 that is 5 hops away.

  Therefore, each node adjusts the communication timing with other nodes to determine the communication timing of the own node, and follows the transmission path information (including transmission path information and relay order information) of the data signal. There is a need for a communication control device, a communication control method, a communication control program, a node, and a communication system that can determine the communication timing.

  In order to solve such a problem, a communication control apparatus according to a first aspect of the present invention is a communication control apparatus mounted on each of a plurality of nodes constituting a communication system, and (1) indicates a data transmission timing of another node. Timing control signal communication means for receiving a timing control signal or transmitting a timing control signal indicating the timing of data transmission of the own node; (2) Based on the timing control signal received from another node, A communication timing calculation means for obtaining the communication timing of the own node by changing the phase state; and (3) a phase for confirming the order of the phase states obtained by the communication timing calculation means with reference to the transmission path information of the data signal. If the order of the phase states by the order confirmation means and (4) phase order confirmation means does not correspond to the transmission path information, Characterized in that it comprises a phase adjusting means for changing the over de phase.

  A communication control method according to a second aspect of the present invention is a communication control method for a communication control device mounted on each of a plurality of nodes constituting a communication system. (1) The timing control signal communication means transmits data from other nodes. A timing control signal communication step of receiving a timing control signal indicating timing or transmitting a timing control signal indicating timing of data transmission of the own node; and (2) timing received by the communication timing calculation means from another node. A communication timing calculation step of obtaining a communication timing of the own node by changing a phase state in the own node based on the control signal; and (3) a phase order confirmation unit refers to the transmission path information of the data signal and performs communication. A phase order confirmation step for confirming the order of the phase states obtained by the timing calculation means; and (4) phase adjustment. Stage, if the order of phase states by the phase sequence confirmation means does not correspond to the transmission path information, and having a phase adjustment step of changing the phase of the node.

  A communication control program according to a third aspect of the present invention is a communication control program for causing a communication control device mounted in each of a plurality of nodes constituting a communication system to function, wherein (1) data transmission of other nodes is performed. Timing control signal communication means for receiving a timing control signal indicating timing or transmitting a timing control signal indicating timing of data transmission of the own node; (2) based on the timing control signal received from another node; Communication timing calculation means for determining the communication timing of the own node by changing the phase state at the node, (3) Checking the order of the phase states determined by the communication timing calculation means with reference to the transmission path information of the data signal Phase order confirmation means, (4) The phase state order by the phase order confirmation means is the transmission path information. If not respond, the communication control program to function as a phase adjusting means for changing the phase of the node.

  In the node of the fourth aspect of the present invention, a node constituting the communication system includes the communication control apparatus of the first aspect of the present invention.

  A communication system according to a fifth aspect of the present invention includes a plurality of nodes according to the fourth aspect of the present invention.

  According to the present invention, in each node, when the communication timing of the own node is determined by mutually adjusting the communication timing with other nodes, the communication timing according to the transmission path information of the data signal can be obtained. As a result, communication delay can be reduced.

(A) First Embodiment Hereinafter, a first embodiment of a communication control device, a communication control method, a communication control program, a node, and a communication system according to the present invention will be described in detail with reference to the drawings.

  The first embodiment exemplifies an embodiment in which each of a plurality of nodes constituting a wireless communication network (wireless system) includes the present invention, and each node acquires a time slot according to transmission path information.

  In the following first embodiment, it is assumed that transmission path information is given to each node in advance. That is, it is assumed that each node holds information on which node it receives data from and to which node the data is transmitted.

(A-1) Configuration of First Embodiment FIG. 1 is an internal configuration diagram illustrating an internal configuration of a node according to the first embodiment. In FIG. 1, the node 10 of the first embodiment is configured to include at least a timing control signal reception unit 11, a communication timing calculation unit 12, a timing control transmission unit 13, and a data communication unit 14.

  The timing control signal receiving unit 11 receives an output timing control signal transmitted from a neighboring node as an input timing control signal, and gives the received timing control signal of another node to the communication timing calculation unit 12.

  Upon receiving the timing control signal of the other node from the timing control signal receiving unit 11, the communication timing calculation unit 12 forms a phase signal that defines the communication timing of the own node based on the timing control signal of the other node, and this phase A signal phase value (also referred to as phase information) is given to the timing control signal transmitter 13 and the data communication unit 14.

  Here, the phase model formation method (communication timing control method) of the phase signal by the communication timing calculation unit 12 is not particularly limited, and the methods described in Patent Documents 1 to 7 are widely applied. Can do.

  In the first embodiment, a case where the communication timing calculation unit 12 applies the virtual phase model forming method described in Patent Document 5 will be described as an example.

  That is, when receiving the timing control signal of another node, the communication timing calculation unit 12 generates a virtual phase model (hereinafter referred to as a virtual phase model) for the transmission source node in its own node. Using this virtual phase model, the phase of the other node is calculated in a pseudo manner, and the phase difference between the own node and the other node can be continuously observed.

  Here, the phase model of the phase signal formed by the communication timing calculation unit 12 will be described with reference to FIGS. 5 and 6. Note that the state changes shown in FIGS. 5 and 6 are also related to the function of the timing control signal transmitter 13.

  5 and 6 show a relationship formed between a target node (own node) and a neighboring node (another node) when attention is paid to a certain node, that is, a phase relationship between respective nonlinear vibration rhythms. Shows how the changes over time.

  FIG. 5 shows a case where there is one neighboring node j for the node i of interest. In FIG. 5, the motion of two mass points rotating on a circle represents a non-linear vibration rhythm corresponding to the node of interest and neighboring nodes, and the angle of the mass point on the circle is the value of the phase signal (phase) at that time. Value). The motion of the point where the rotational motion of the mass point is projected on the vertical or horizontal axis corresponds to the nonlinear vibration rhythm. By the operation based on the equation (1.1) described later, the two mass points try to be in opposite phases to each other, and even if the two mass points are close to each other in the initial state as shown in FIG. With the passage of time, the state (transient state) shown in FIG. 5B is changed to a steady state where the phase difference between the two mass points is almost π as shown in FIG. 5C.

  Each of the two mass points rotates with the natural angular frequency parameter ω as a basic angular velocity (corresponding to a basic velocity that changes its own operation state). Here, when an interaction based on transmission / reception of a timing control signal occurs between nodes, these mass points change (slow and steep) their respective angular velocities, and consequently reach a steady state that maintains an appropriate phase relationship. . This operation can be regarded as forming a stable phase relationship by repelling each other while the two mass points rotate. In the steady state, as described later, when each node transmits an output timing control signal at a predetermined phase α (for example, α = 0), the transmission timing at each node is appropriate. A time relationship is formed.

  FIG. 6 shows a case where there are two neighboring nodes j1 and j2 for the node of interest i. Even in the case where there are two neighboring nodes, a stable phase relationship (stability related to temporal relationship) is formed by repelling each other while rotating the respective mass points as described above. The same applies to the case where the number of neighboring nodes is 3 or more.

  The formation of the stable phase relationship (steady state) described above has a very adaptive (flexible) property with respect to changes in the number of neighboring nodes. For example, it is assumed that one neighboring node is added when there is one neighboring node with respect to the node of interest and a stable phase relationship (steady state) is formed. The steady state once collapses, but after passing through the transient state, a new steady state in the case where there are two neighboring nodes is reformed. In addition, when a neighboring node is deleted or does not function due to a failure or the like, an adaptive operation is performed in the same manner. The above is the basic function of the communication timing calculation unit 12.

  The communication timing calculation unit 12 of the present invention includes at least a phase order relationship evaluation unit 121, a phase shift execution unit 122, and a phase calculation unit 123.

  Here, the phase order evaluation unit 121 refers to the phase of the own node and the virtual phase model for all other nodes in the interaction range, and determines whether the phase order relationship is consistent with the transmission path information. To do.

  Here, the transmission path information is given in advance as described above. For example, when the timing control signal transmitted from the final destination node is transferred between the nodes in a multihop manner, each node observes the number of hops from the destination node of the received timing control signal. Then, the one with the smallest number of hops from the destination node is held as the number of hops from the own node to the destination node. In this case, the number of hops from this node to the destination node can be used as transmission path information.

  A method for determining the phase order relationship by the phase order evaluation unit 121 will be described in detail in the section of operation.

  The phase shift execution unit 122 shifts the phase of its own node (changes the phase order relationship) when the phase order evaluation unit 121 determines that the phase order relationship does not match the transmission path information. is there. Further, the phase shift execution unit 122 gives the phase shift result of the own node to the phase calculation unit 123. The details of the method of phase shift of the own node by the phase shift execution unit 122 will be described in the operation section. By this, the own node autonomously acquires the time slot of the order relation depending on the transmission path information. be able to.

  The phase calculator 123 forms the phase of the phase signal that defines the communication timing of the own node based on the timing control signal of the other node. The phase shift calculation unit 123 takes in the phase shift result from the phase shift execution unit 122 and also forms a phase signal after the phase shift of the own node. The phase calculation unit 123 forms a phase signal using Expression (1.1) and Expression (1.2) described later.

  When receiving the phase information (phase signal phase value) from the communication timing calculation unit 12, the timing control signal transmission unit 13 transmits an output timing control signal based on the phase information.

  Here, as the transmission timing of the output timing control signal, for example, a method of transmitting the phase signal at a timing where the phase value of the phase signal is a predetermined phase α (0 ≦ α <2π) can be applied. In addition, it is preferable that the predetermined phase α is previously unified in the entire system. For example, in the first embodiment, it is assumed that the predetermined phase α is uniform throughout the system with α = 0.

  The data communication unit 14 transmits data as an output data signal when transmission data is generated in the own node. The data communication unit 14 receives data transmitted from another node as input data, and transmits this data as output data to a transmission destination.

  The data communication unit 14 receives the phase information from the communication timing calculation unit 12, and when the phase relationship indicates a steady state, the data communication unit 14 is a time slot (which is not a fixed time interval allocated by the system or the like described later, In the embodiment, the term “time slot” is used). Note that the data communication unit 14 stops the transmission operation when the phase relationship indicates a transient state. The output data signal may be a transmission frequency in the same frequency band as the output timing control signal.

The time slot is a period in which the phase θ _i (t) of the phase signal is δ ₁ ≦ θ _i (t) ≦ β ₁ −δ ₂ . The start point of the time slot (the value of the phase signal at that time is δ ₁ ) is the timing when the transmission of the output timing control signal is completed, and the end point of the time slot (the value of the phase signal at that time is β ₁ −δ ₂ ) is set to a timing slightly before the offset δ ₂ from the reception timing of the first timing control signal for each period of the phase signal. δ ₁ and δ ₂ are a wireless space in the vicinity of the node, and a timing control signal (including both the case where the transmission source is the own node and the other node) and a data signal (when the transmission source is the own node) Phase width corresponding to a very short time to compensate for the absence of both at the same time. For example, δ ₁ and δ ₂ can be determined experimentally under node installation conditions.

For example, in the “steady state” as shown in FIG. 5C, the node i starts transmitting the output timing control signal from the phase θ _i of 0, and before the phase θ _i becomes δ ₁ , the output timing The transmission of the control signal is terminated, and when the phase θ _i starts to transmit the output data signal from δ ₁ and the phase θ _i becomes β ₁ −δ ₂ (where β ₁ ≈π), the output data signal is transmitted. Thereafter, the transmission of the output timing control signal and the transmission of the output data signal are stopped until θ _i becomes 0 again. The other node j performs the same operation based on the phase θ _j , but the transmission operation does not compete because the phase θ _i and the phase θ _j are shifted by approximately π. Similarly, when the number of nodes is three or more, transmission operations do not compete.

(A-2) Operation of the First Embodiment Next, the operation of the communication timing control process in the node of the first embodiment will be described in detail with reference to the drawings.

  In the following, as shown in FIG. 3, in a situation where a large number of nodes having the configuration of FIG. 1 are distributed in a distributed manner, operation when a virtual phase model calculation method is adopted as a method of transmitting and receiving timing control signals between neighboring nodes. Will be explained. Of course, the method for transmitting and receiving the timing control signal is not particularly limited, and other methods (for example, the method shown in FIG. 2A) can be applied.

  First, in each node 10, when the arithmetic processing for forming the phase of the phase signal is performed by the communication timing calculation unit 12 and the phase value (phase information) of the phase signal is obtained, the timing control signal transmission unit 13 outputs the output timing. A control signal is transmitted.

  Thereby, each node 10 transmits / receives a timing control signal between the nodes near 1 hop, and mutual adjustment of a communication timing is performed.

  Further, the timing control signal transmission unit 13 transmits the timing control signal transmitted by the own node with information of “node numbers for all other nodes existing in the vicinity of one hop” and “virtual phase” added thereto.

  Therefore, when each node 10 receives a timing control signal from another node existing in the vicinity of one hop, each node 10 has “node numbers for all other nodes existing in the vicinity of one hop” and “virtual phase”. Based on the information, it is possible to indirectly obtain phase information for other nodes in the vicinity of the 2-hop range.

  When each node 10 receives the timing control signal of the other node, the communication timing calculation unit 12 generates a virtual phase model for the node using the phase information for the other node in the vicinity of the 2-hop at the reception timing, Thereafter, the value of the virtual phase is adjusted for each reception.

  And the calculation in the communication timing calculation part 12 is performed using the virtual phase with respect to all the other nodes of the 2-hop vicinity range. As described above, the interaction range in the communication timing adjustment by the communication timing calculation unit 12 is performed in the 2-hop neighborhood of each node 10.

  Next, calculation processing in the communication timing calculation unit 12 will be described. The arithmetic processing of the communication timing calculation unit 12 is performed using, for example, the following expressions (1.1) and (1.2).

Expressions (1.1) and (1.2) are obtained by appropriately modifying a mathematical expression that models a system in which nonlinear oscillators are coupled.

Here, the variable t represents time, and θ _i (t) represents the phase of the own node i at time t. It is assumed that θ _i (t) always takes a value of section 0 ≦ θ _i (t) <2π by performing an operation of mod 2π (the remainder divided by 2π).

d / dt is a symbol representing a differential operation with respect to time t, and dθ _i (t) / dt represents a state variable obtained by differentiating phase θ _i (t) with respect to time t.

ω _i is a natural angular frequency parameter and represents a vibration rhythm unique to each node. Here, as an example, it is assumed that the value of ω _i is previously unified to the same value in all nodes.

ΔΘ _ij (t) is a phase difference between the virtual phase Θ _ij (t) with respect to another node j in the interaction range and the phase θ _i (t) of the own node i. However, the phase difference ΔΘ _ij (t) takes a value of section 0 ≦ ΔΘ _ij (t) <2π for the sake of convenience by performing an operation of mod 2π (the remainder after dividing by 2π) on the value obtained by adding 2π. And

R (ΔΘ _ij (t)) is a phase response function that expresses a response characteristic that changes the vibration rhythm of the node according to the phase difference ΔΘ _ij (t). FIG. 7 is an explanatory diagram showing a specific example of the phase response function R (ΔΘ _ij (t)). This phase response function has a mechanical characteristic that makes the phase difference between its own node and a neighboring node greater than or equal to the phase φc.

  In equations (1.3) to (1.5), φd and α represent constant parameters, and these values are determined experimentally.

  The constant parameter φd takes a value greater than or equal to the minimum phase width φc necessary for data transmission (φd ≧ φc). However, it should be noted that in the first embodiment, the function form of the phase response function is not limited to the above form. A function that gives a mechanical characteristic that makes the phase difference between its own node and a neighboring node greater than or equal to the phase width φc can be realized by using various function forms.

In the term including R (ΔΘ _ij (t)), N ＾ (hat) _i represents the total number of virtual phase models at time t, and K represents a coupling constant parameter. Here, the coupling constant parameter K is a parameter that determines the contribution of a term including R (ΔΘ _ij (t)) to the time evolution of the phase, and its value can be determined experimentally.

^{_{{Θ ij (t) | ∀}} j} denotes the set of generated inside the own node "virtual phase theta _ij to other nodes i within an interaction range _(t)", all elements are function Z of the set ({Θ _ij (t) | ^∀ j}, θ _i (t)) is an independent variable (an input variable to the function).

_{Z ({Θ ij (t)} | ∀ j}, θ i (t)) includes a phase θ _i (t) of the node i, the virtual phase theta _ij (t to all other nodes j in interaction range ), When the phase order relationship is not consistent with the transmission path information, the function of shifting the phase of its own node i (changing the phase order relationship) accordingly. The function _{Z ({Θ ij (t)} | ∀ j}, θ i (t)) is a function that is the arithmetic processing by the phase shift execution unit 122.

The above R (ΔΘ _ij (t)) has no function of changing the phase order relationship. Further, the stress response function ξ (S _i (t)) disclosed in Patent Document 5 and the like has a function of shifting the phase (changing the phase order relationship), but functions regardless of the transmission path information. . In _{contrast, Z ({Θ ij (t} ) | ∀ j}, θ i (t)) is that it has a function to depend on the transmission path information to change the order relation of the phase is different. The phase order relationship between the nodes directly corresponds to the time slot order relationship acquired by each node. Therefore, the function _{Z ({Θ ij (t)} | ∀ j}, θ i (t)) by newly adding the function of the each node autonomously, time slots and the order related depends on the transmission path information The operation of acquiring is executed.

  Next, the operation of the phase shift process depending on the transmission path information by the communication timing calculation unit 12 of the first embodiment will be specifically described with reference to FIG.

  FIG. 8 is an operation flowchart showing a process of shifting the phase according to the transmission path information by the communication timing calculation unit 12.

  Hereinafter, the final destination where each node transmits data in multi-hop is referred to as a destination node. For example, in the case of a network that collects data in a sink node, the sink node is the destination node. For example, in FIG. 3, if the node 6 is the final destination, the node 6 is the destination node. Here, it is assumed that the number of hops (transmission path information) from the destination node is given to each node in advance. The number of hops (transmission route information) from the destination node can be given as follows, for example. A signal equivalent to the timing control signal is transmitted from the destination node, the number of transfers is counted while being transferred in multihop, and the number of hops until reaching each node is observed. Each node holds the minimum value of the number of hops observed at the own node as “the number of hops from the own node to the destination node”. By performing such processing in advance, the number of hops can be given to each node in advance.

  First, in the communication timing calculation unit 12, the phase order relationship evaluation unit 121 determines whether or not the own node is a node having one hop number from the destination node based on the above “number of hops from the own node to the destination node”. Is determined (step S101).

Then, when the own node is a node having one hop number from the destination node, the phase shift execution unit 122 does not perform the phase shift (step S102). That is, the phase shift execution unit 122 sets the function Z ({Θ _ij (t) | ^∀ j}, θ by setting Z ({Θ _ij (t) | ^∀ j}, θ _i (t)) = 0. _i (t)) is not executed.

  On the other hand, when the own node is not a node having one hop number from the destination node, the following processing is performed.

First, the phase order relationship evaluation unit 121 refers to the phase θ _i (t) of the own node i and the virtual phase Θ _ij (t) for all other nodes j in the interaction range (step S103), Using the phase of the destination node of i as a reference, observations are sequentially made in the direction in which the phase increases, and a section in which the phase difference between the nodes is equal to or greater than a predetermined value C is detected (step S104). The predetermined value C can be determined experimentally.

  When a section in which the phase difference between the nodes is equal to or greater than the predetermined value C is detected, the phase order relationship evaluation unit 121 determines that the own node is between the phase of the leading node and the phase of the transmission destination node related to the detected section. It is determined whether or not a phase i exists (step S105).

  Then, when the phase of the own node i does not exist between the phase of the head node and the phase of the transmission destination node in the detection section, the phase shift execution unit 122 shifts to the section in which the phase of the own node i is detected. (Step S106).

  Note that if the phase difference between the nodes is not detected in step S104 in the phase difference of the predetermined value C or more, and the phase of the own node i is the phase of the first node and the phase of the destination node in the detection interval in step S105. If it exists, the process proceeds to step S102, and the phase shift execution unit 122 does not perform the phase shift.

  Here, the operation when the node 6 is the destination node as shown in FIG. 3 will be specifically described.

  First, the nodes 1 to 5 up to the destination node 6 refer to the number of hops to the destination node 6 held by each node, and determine whether or not to perform phase shift processing of the phase signal depending on the transmission path information. To do.

  For example, since the node 6 is the destination node, the node 5 whose hop count from the node 6 is 1 does not execute the phase shift process. On the contrary, since the number of hops from the node 6 is not 1, the node 1 to the node 4 execute the phase shift process.

  FIG. 9A is a diagram illustrating the phase state between the nodes immediately after the start of the operation of each of the nodes 1 to 5 (that is, the initial state). As shown in FIG. 9A, in the initial state, the phase order relationship of each of the nodes 1 to 5 is random.

  Now, focus on node 4, for example. In the node 4, the phase order relation evaluating unit 121 observes in the direction in which the phase becomes larger with reference to the phase of the node 5 that is the transmission destination (counterclockwise direction in FIG. 9A), and A section whose phase is equal to or greater than a predetermined value C is detected. In FIG. 9A, when observing from the node 5 in the counterclockwise direction, it is detected that the phase difference between the phase immediately after the phase of the node 5 and the phase of the node 2 is a predetermined value C or more. .

  Next, in the node 4, the phase order relation evaluating unit 121 has the phase of the own node 4 between the phase of the node 2 that is the leading phase of the detected section and the phase of the node 5 that is the transmission destination. Judge whether or not.

  In this case, since the phase of the node 4 does not exist between the phase of the node 2 and the phase of the node 5, the phase shift execution unit 122 detects the phase of the detected node 2 and the subsequent phase (reverse with respect to the node 5). The phase of the own node 4 is shifted to the phase immediately after the node 5 (observed in the clockwise direction).

  In the above, the operation of the phase shift process has been described focusing on the node 4, but the same operation is performed in the nodes 1 to 3. Furthermore, since the phase shift process is not executed in the node 5, the phase of the node 5 becomes a reference for the other nodes 1 to 4. As a result, an order relationship is formed between the phases of the nodes 1 to 4 with the phase of the node 5 as a reference.

  FIG. 9B is a diagram illustrating a phase state when the node 1 to the node 5 are phase-shifted according to the transmission path information to be in a converged state. FIG. 10 is a diagram showing the relationship between the position of the communication time slot acquired by each node and the communication delay. Note that the communication time slots shown in FIG. 10 correspond to the order relationship shown in FIG.

  Note that each of the nodes 1 to 5 can observe only the phase of another node in the interaction range (another node in the 2-hop neighborhood). For example, the node 4 cannot observe the phase of the node 1. Therefore, in FIG. 9B, for easy understanding, all phases of the nodes 1, 2, 3, 4, and 5 are shown and shown on the same drawing. Note that this is done using only the phase information of other nodes.

  In FIG. 9B, there is a phase of another node between the phases of the node 4 and the node 5, but nodes other than the nodes 1 to 5 (surrounding nodes) are operating in the same manner. It can be in this form. However, the configurations shown in FIGS. 9B and 10 are merely examples. Further, the difference between adjacent phases existing between the phases between the node 4 and the node 5 is smaller than the constant value C described above. The same applies between the node 3 and the node 4 and between the node 1 and the node 2.

However, as can be seen by comparing the conventional communication delay shown in FIG. 4 with the example of the communication delay according to the first embodiment shown in FIG. 10, as in the first embodiment, the function Z ({Θ _ij ( t) | By introducing a phase shift operation based on | ^∀ j}, θ _i (t)), the position of the time slot acquired by each node is determined depending on the transmission path, and as a result, Communication delay is reduced.

(A-3) Effect of the First Embodiment As described above, according to the first embodiment, data in which a plurality of nodes mutually adjust communication timing in an autonomous and distributed manner by transmitting and receiving timing control signals. In the communication method, by shifting the phase of the phase signal indicating the communication timing according to the transmission path information, the position of the time slot acquired by each node can be set in the order according to the transmission path order, thereby reducing the communication delay. can do.

(B) Other Embodiments In the first embodiment, the calculation method of the phase of the timing control signal of the own node calculated by the communication timing calculation unit is an arithmetic expression represented by equations (1.1) and (1.2). It is not limited to the case of using, but can be widely applied.

  For example, it can be implemented on a node as software using a general numerical calculation method such as the Runge-Kutta method. The Runge-Kutta method is one of the techniques for calculating the change (time evolution) of a state variable using a difference equation (recurrence formula) obtained by differentiating a differential equation (discretizing a continuous time variable t). is there. Similarly to the form disclosed in Patent Document 2, it is also possible to calculate the change of the state variable using a difference equation obtained by another differentiating method simpler than the Runge-Kutta method. Furthermore, if an electronic circuit that operates in the same manner as in equations (1.1) and (1.2) is configured, it can be mounted on a node as hardware.

  In the first embodiment, a sensor network in which each node transmits sensor data is illustrated as an example of a wireless communication network. However, the present invention is not limited to a sensor network, and can be widely applied to a wireless communication network that realizes wireless communication by forming communication timing autonomously and distributed between nodes.

  The first embodiment has been described assuming a system in which a large number of distributed nodes exchange data with each other wirelessly. However, the utilization form of the present invention is not limited to a system that performs wireless communication. The present invention can also be applied to a system in which a large number of nodes distributed in a space exchange data with each other by wire. For example, the present invention can be applied to a LAN system connected by wire such as Ethernet (registered trademark). Similarly, the present invention can be applied to a network in which different types of nodes are mixed, such as wired sensors or actuators or servers. Of course, the present invention can be applied to a network in which nodes connected by wire and nodes connected wirelessly are mixed.

  In FIG. 1, the timing control signal transmission unit, the timing control signal reception unit, and the data communication unit may have the same configuration.

  The function realized by the communication timing calculation means in the first embodiment is assumed to be based on software processing in which hardware resources are executed by executing a processing program. You may make it implement | achieve with the hardware made.

It is an internal block diagram which shows the internal structure of the node of 1st Embodiment. It is a figure which shows the transmission / reception form of the conventional communication timing control signal. It is a figure which illustrates the mode of a plurality of nodes distributed, and a transmission route. It is a figure which shows the relationship between the example of the position of the conventional time slot which each node acquired, and communication delay. It is a figure which shows the basic phase formation relationship which forms the phase of the phase signal which shows the communication timing of each node (the 1). It is a figure which shows the basic phase formation relationship which forms the phase of the phase signal which shows the communication timing of each node (the 2). It is a figure which shows the relationship between the phase response function of a node of 1st Embodiment, and a phase difference. It is an operation | movement flowchart which shows the phase shift process in the node of 1st Embodiment. It is a figure which shows a mode that the phase of each node is changed by the phase shift process in each node of 1st Embodiment. It is a figure which shows the relationship between the example of the position of the conventional time slot which each node acquired by the result of the phase shift of each node of 1st Embodiment, and communication delay.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Node, 11 ... Timing control signal receiving part, 12 ... Communication timing calculation part, 121 ... Phase order relation evaluation part, 122 ... Phase shift execution part, 123 ... Phase operation part, 13 ... Timing control signal transmission part, 14 ... Data communication department.

Claims (7)

In a communication control device mounted on each of a plurality of nodes constituting a communication system,
Timing control signal communication means for receiving a timing control signal indicating the timing of data transmission of another node or transmitting a timing control signal indicating the timing of data transmission of the own node;
Based on a timing control signal received from another node, a communication timing calculation means for changing a phase state in the own node and obtaining a communication timing of the own node;
Referring to the transmission path information of the data signal, phase order confirmation means for confirming the order of the phase states obtained by the communication timing calculation means,
A communication control apparatus comprising: a phase adjustment unit that changes a phase of the own node when an order of phase states by the phase order confirmation unit does not correspond to the transmission path information. The phase order confirmation means observes in order in the direction in which the phase increases with reference to the transmission destination of the own node, detects a section where the phase difference is equal to or greater than a predetermined value, and detects the leading phase and transmission destination of this detection section To check whether the phase of its own node exists between
When the phase order confirmation unit confirms that the phase of the own node does not exist between the start phase and the transmission destination phase of the detection interval, the phase adjustment unit shifts the phase of the own node to the detection interval. The communication control device according to claim 1, wherein   The communication control apparatus according to claim 1, wherein the phase order confirmation unit and the phase adjustment unit do not execute processing when the own node is one hop away from the destination node. In the communication control method of the communication control device mounted on each of a plurality of nodes constituting the communication system,
A timing control signal communication step in which the timing control signal communication means receives a timing control signal indicating the timing of data transmission of another node or transmits a timing control signal indicating the timing of data transmission of the own node;
A communication timing calculation step for determining a communication timing of the own node by changing a phase state in the own node based on a timing control signal received from another node,
A phase order confirming step for confirming the order of the phase states obtained by the communication timing calculating means with reference to the transmission path information of the data signal;
And a phase adjustment step of changing a phase of the own node when the phase order by the phase order confirmation unit does not correspond to the transmission path information. In a communication control program for causing a communication control device mounted on each of a plurality of nodes constituting a communication system to function,
The communication control device is
A timing control signal communication means for receiving a timing control signal indicating the timing of data transmission of another node or transmitting a timing control signal indicating the timing of data transmission of the own node;
Based on the timing control signal received from another node, the communication timing calculation means for changing the phase state in the own node and obtaining the communication timing of the own node,
Phase order confirmation means for confirming the order of the phase states obtained by the communication timing calculation means with reference to the transmission path information of the data signal,
A communication control program that functions as a phase adjustment unit that changes the phase of the own node when the phase state sequence by the phase sequence confirmation unit does not correspond to the transmission path information.   The node which comprises a communication system is provided with the communication control apparatus in any one of Claims 1-3, The node characterized by the above-mentioned.   A communication system comprising a plurality of nodes according to claim 6.

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