JP5137806B2 - Communication control method and communication apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a communication control method with which slot assignment information can be exchanged with another node with further reduced overhead. <P>SOLUTION: In the communication control method, each node notify an adjacent node of slot assignment information indicating a situation of using each time slot over a multi-hop ad-hoc network. The communication control method includes: a slot assignment information determination step of determining which is to be adopted as slot assignment information between a use slot list constituted of each identification information of use slots in one frame and a free slot list constituted of each identification information of time slots that are not use slots in one frame, on the basis of the number of use slots; and a slot assignment information transmission step of transmitting a data packet stored the use slot list or the free slot list into a header as slot assignment information in accordance with results of the determination. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a communication control method in a multi-hop ad hoc network adopting a TDMA system and a communication apparatus using the same.

  Conventionally, in order to avoid a transmission collision by a plurality of terminal devices existing in a communication area, a plurality of slots divided by a TDMA (Time Division Multiple Access) method or the like are allocated as time slots used by each terminal device. ing.

  By the way, since an ad hoc network does not have a device for managing the entire network, each terminal device negotiates with each other and autonomously determines time slot allocation. In order to perform time slot allocation, it is necessary to obtain slot allocation information indicating a time slot in use. As a technique for exchanging slot allocation information, techniques described in Patent Document 1 and Non-Patent Document 1 are known.

Japanese Patent No. 4023341 F. Borgonovo et al., “ADHOC MAC: New MAC architecture for ad hoc networks providing efficient and reliable Point-to-Point and broadcast services”, Wireless Networks 10, 359-366, 2004, Kluwer Academic Publishers, Netherlands

  However, in the method described in Patent Document 1, for example, packet allocation information is exchanged using an empty slot list that lists available slot information. Therefore, when there are few nodes in the ad hoc network, empty slots are used. There is a problem that the list becomes large and the overhead increases.

  The present invention has been made in view of the above, and in a multi-hop ad hoc network employing TDMA, obtains a communication control method and communication apparatus for exchanging slot allocation information with other nodes with less overhead. Objective.

  In order to solve the above-described problems and achieve the object, the present invention provides a plurality of nodes that transmit data packets using a part of a plurality of time slots obtained by time-sharing frames having a constant period. In the multi-hop ad hoc network formed by the communication method, each node notifies the adjacent node of slot allocation information indicating the usage status of each of the plurality of time slots. Based on the number of used slots indicating the number of used slots that are used time slots in one frame, a used slot list including identification information of each used slot in one frame and used slots in one frame Which of the empty slot lists consisting of identification information of time slots that are not A slot allocation information determining step for determining whether to adopt as information, and a slot allocation information transmitting step for transmitting a data packet storing the used slot list or the empty slot list in the header as the slot allocation information according to the determination result; It is characterized by including.

  According to the present invention, each node that has already entered the ad hoc network can use the slot allocation information to be transmitted to other nodes as a slot allocation information according to the time slot allocation status to itself and adjacent nodes. Since it is possible to select a list having a smaller number of time slots (a smaller amount of information) in the list, it is possible to suppress an increase in the overhead of the header, and to reduce the other overhead with a smaller overhead than before. There is an effect that the slot allocation information can be exchanged with the node.

  Embodiments of a communication control method and a communication apparatus according to the present invention will be described below in detail with reference to the drawings. Note that the present invention is not limited to the embodiments.

Embodiment 1 FIG.
FIG. 1 is a diagram illustrating a configuration example of a multi-hop ad hoc network to which the communication control method according to the present embodiment is applied. The ad hoc network 100 of FIG. 1 includes wireless mobile nodes 10, 11, and 12 and performs wireless packet communication between wireless mobile nodes. In addition, 10C, 11C, and 12C shown in the figure are wireless communication ranges that indicate communication ranges as viewed from the wireless mobile nodes 10, 11, and 12, respectively. Further, the packet communication performed by this ad hoc network employs a TDMA system in which a frame composed of a plurality of time slots TS is taken as one cycle.

  FIG. 2 is a block diagram illustrating an internal configuration example of a wireless mobile node (hereinafter simply referred to as a node). Each node includes an antenna 1, a wireless communication unit 2 that performs wireless communication, a time slot allocation unit 3 that performs time slot allocation, and a memory 4 that holds information on its own time slot. Yes. When a packet is transmitted from a certain node to another node, the packet is transmitted using the wireless communication unit 2.

  FIG. 3 is a conceptual diagram showing a configuration example of the frame F including the plurality of time slots TS described above. Each time slot TS is numbered with a unique time slot number “TS # N” (N = 0, 1, 2,...). Here, it is assumed that the frame F is composed of eight time slots of TS # 0 to TS # 7.

  Each node transmits a data packet including its own node ID and the current time slot number in the time slot TS # N assigned to itself, regardless of the presence or absence of transfer traffic. Each node receives a data packet from an adjacent node to confirm connection maintenance with the adjacent node.

  Next, a slot assignment notification operation when a new node enters the ad hoc network 100 configured as described above will be described. Here, an example (see FIG. 4) when the node 13 newly enters the ad hoc network 100 shown in FIG. 1 will be described. FIG. 4 is a diagram illustrating a state in which the node 13 moves within the wireless communication range 10 </ b> C of the node 10 in order to enter the ad hoc network 100.

  FIG. 5 is a diagram showing an example of time slot allocation of the ad hoc network 100, and shows which time slot is allocated to each node before the node 13 joins (time slot allocation status). Also, the time slot assigned to itself is painted in black, and the time slot assigned to the adjacent node is represented by “−”. In this example, TS # 0 and TS # 4 are assigned to the node 10. Therefore, the columns of TS # 0 and TS # 4 of the nodes 11 and 12 adjacent to the node 10 are “-”.

  When each node transmits a data packet, the slot assignment information for identifying the time slot assigned to the header portion and the time slot assigned to the adjacent node on the receiving side (see FIG. 6). (See FIG. 7). The joining node obtains slot assignment information from an adjacent node (a node located at a place where communication is possible) among nodes that have already entered the ad hoc network, thereby grasping a time slot that can be assigned to itself. Specifically, the data packet is received over one period (one frame) or more, slot allocation information is collected, and a time slot that is not allocated to any adjacent node is set as a time slot that can be allocated to itself.

  FIG. 6 shows a list of used slots (USList (10), each of which is held by each of the node 10, the node 11 and the node 12 when the time slot allocation status for each node of the ad hoc network 100 is as shown in FIG. It is a figure which shows USList (11), USList (12)). Each used slot list includes black slotted time slots in FIG. 5 and time slot in which “-” is described (hereinafter, such time slots are described as used slots) (in the time slot number). Equivalent) is listed for each node. That is, the use slot list is a list including a time slot that can be transmitted by each node and a time slot number TS # N of a time slot that has received a data packet from an adjacent node.

  FIG. 7 shows an empty slot list (ESList (10),) held by each of the node 10, the node 11, and the node 12 when the time slot allocation state for each node of the ad hoc network 100 is as shown in FIG. It is a figure which shows ESList (11) and ESList (12)). Each empty slot list is information in which time slot information that is blank in FIG. 5 is listed for each node. That is, the empty slot list is a time slot number TS of a time slot that is not assigned to itself at each node and is not assigned to an adjacent node (hereinafter, such a time slot is referred to as an empty slot). A list including #N.

  At the time of data packet transmission, each node confirms the time slot allocation status between itself and the adjacent node, selects a use slot list (see FIG. 6) or an empty slot list (see FIG. 7), and selects the selected list. Stored in the header as slot allocation information. Which list is selected is determined by the procedure shown in FIG. 8, for example. FIG. 8 is a flowchart showing an example of a procedure for determining slot allocation information.

  That is, each node, when selecting the used slot list or the empty slot list as the slot allocation information, first checks whether “number of used slots ≦ total number of slots / 2” is satisfied (step S11). The number of used slots is the number of used slots included in one frame, and the total number of slots is the number of time slots included in one frame. And if the said conditions are satisfied (step S11, Yes), a use slot list is selected (step S12). On the other hand, if the above condition is not satisfied (step S11, No), an empty slot list is selected (step S13).

  Since the sum of the number of used slots and the number of empty slots (the number of empty slots included in one frame) at a certain node is always the total number of slots, it is determined in step S11 whether the number of used slots or the number of empty slots is larger. Is done. Therefore, by selecting any of the above lists according to the procedure shown in FIG. 8, it is possible to always transmit slot allocation information with the minimum data size. The slot allocation information determination procedure shown in FIG. 8 is executed by the time slot allocation unit 3. That is, in the present embodiment, the time slot allocation unit 3 has a function as a determination unit.

  If the time slot allocation status to each node is as shown in FIG. 5, according to the selection procedure of FIG. 8, the nodes 10 constituting the ad hoc network 100 store the empty slot list ESList (10) The node 11 stores the used slot list USList (11) and the empty slot list ESList (12) in the header of the data packet and transmits them (see FIG. 9). In the header portion of the data packet, an identifier for identifying whether the stored slot allocation information is a used slot list or an empty slot list is prepared. FIG. 9 is a diagram illustrating a state in which each node that has already entered the ad hoc network 100 stores and transmits slot allocation information in the header of the data packet.

  In the case illustrated in FIG. 4, that is, when the node 13 moves into the wireless communication range 10 </ b> C of the node 10 in order to enter the ad hoc network 100, the time is obtained by receiving the ESList (10) from the node 10. The node 13 determines that only the slot TS # 3 can be used, and the node 13 starts a sequence for entering the ad hoc network by transmitting a time slot allocation request message in the time slot TS # 3.

  When the node 10 receives the time slot allocation request from the node 13, the node 10 allocates the time slot TS # 3 to the node 13 and transmits an allocation notification to the node 13. At this time, the slot allocation information is updated.

  Upon receiving the above allocation notification from the node 10, the node 13 determines that the time slot TS # 3 has been allocated to itself, and the allocated time slot TS # 3 and the time at which the data packet has been received from the node 10. The slots TS # 0 and TS # 4 are determined to be used slots, and the remaining time slots are determined to be empty slots and stored. As a result, the slot allocation status to each node entering the ad hoc network 100 is as shown in FIG. Further, the used slot list and the empty slot list at each node at this time are as shown in FIGS. 11 and 12, respectively. FIG. 10 is a diagram illustrating an example of time slot allocation after the node 13 enters the ad hoc network 100, and FIG. 11 is a diagram illustrating an example of a use slot list after the node 13 enters the ad hoc network 100. FIG. 12 is a diagram illustrating an example of an empty slot list after the node 13 has entered the ad hoc network 100. In this example, all time slots have already been allocated in the node 10, and the empty slot list EList (10) of the node 10 indicates that there is no empty slot (see FIG. 12).

  As described above, in this embodiment, each node that has already entered the ad hoc network has, as slot allocation information, a list of available slot lists and empty slot lists according to the time slot allocation status to itself and adjacent nodes. The list having the smaller number of time slots (the amount of information is smaller) is selected, stored in the header of the data packet, and transmitted. As a result, it is possible to suppress an increase in header overhead as compared with the case where either the use slot list or the empty slot list is fixedly used as the slot allocation information, and the other nodes can be connected with a smaller overhead. Slot assignment information can be exchanged and time slots can be assigned.

Embodiment 2. FIG.
In the first embodiment described above, a case is described in which slot allocation information is expressed by two types of expression methods, a used slot list or an empty slot list, and an expression with a small data size is appropriately selected to reduce overhead. did. In contrast, in Embodiment 2, a technique for reducing overhead by expressing a slot sequence as a bit string (hereinafter referred to as a slot map) in which time slot allocation positions are mapped will be described. The configuration of the ad hoc network and the internal configuration of each node are the same as those in the first embodiment (see FIGS. 1 and 2). Further, the description will be made assuming that the concept of the frame used in TDMA communication and the allocation state of the time slot to each node that has already entered the ad hoc network are the same as in the first embodiment (see FIGS. 3 and 5).

  FIG. 13 is a diagram showing the allocation status of time slots to each node shown in FIG. 5 in a slot map. In this slot map, the time slot allocated to itself and the time slot allocated to the adjacent node are expressed by “1” indicating an allocation ant, and the others are expressed by “0” indicating the allocation no.

  Then, in the ad hoc network 100 of the present embodiment, when each node transmits a data packet, as a slot allocation information for each header portion, as a slot allocation information, a used slot list (see FIG. 6) and an empty slot list (see FIG. 7). ) And a slot map. The joining node obtains this slot assignment information from the adjacent nodes (nodes located at a place where communication is possible) among the nodes that have already joined the ad hoc network, thereby grasping slots that can be assigned to the joining node.

  At the time of data packet transmission, each node confirms the time slot allocation status of itself and adjacent nodes, selects a used slot list, an empty slot list, or a slot map, and stores it in the header as slot allocation information. Which of these is to be selected is determined by the procedure shown in FIG. 14, for example.

  That is, each node, when selecting slot allocation information to be stored in the header of the data packet, first confirms whether or not “total number of slots <number of used slots × slot ID size” (condition 1) is satisfied (step 1). S21).

  Here, as described in Embodiment 1, the total number of slots is the number of time slots included in one frame, and this is the same as the size (number of bits) of the slot map. For example, in the case of the frame configuration shown in FIG. The slot ID is time slot identification information, and the slot ID size is the minimum number of bits necessary to represent the slot ID. That is, the slot ID size is “the total number of Log slots (the base of Log is 2 and rounded up after the decimal point)”. Therefore, the condition 1 is a condition for determining whether the slot allocation status can be notified to other nodes with a smaller number of bits when the slot map is used as the slot allocation information or when the used slot list is used. It is.

  If the total number of slots is 3 or more, the slot ID size is 2 bits or more. In the present embodiment, the case where the total number of slots = 8 (see FIG. 3) is described. Therefore, the slot ID size is 3, and the above condition 1 is satisfied when the number of slots used is 3 or more.

  When the condition 1 is satisfied, that is, when it is determined that the slot allocation information is a slot map and the amount of information is smaller (overhead becomes smaller) (Yes in step S21), “total number of slots < It is confirmed whether “the number of empty slots × slot ID size” (condition 2) is satisfied (step S22). This condition 2 is a condition for determining whether the slot allocation status can be notified to other nodes with a smaller number of bits when the slot map is used as the slot allocation information or when the empty slot list is used. is there.

  In the example of the present embodiment, the above condition 2 is established when the number of empty slots is 3 or more, as in the above-described condition 1.

  If condition 2 is satisfied (step S22, Yes), a slot map is selected (step S25). In the example of the present embodiment, when the number of empty slots is in the range of 3 to 6 (the number of used slots is also in the range of 3 to 6 at this time), the slot map is selected.

  If condition 1 is not satisfied (No in step S21), the number of used slots is 2 or less. At this time, the number of empty slots is 6 or more, that is, the number of used slots is smaller than the number of empty slots. A slot list is selected (step S23).

  If the condition 2 is not satisfied (No in step S22), the number of empty slots is 2 or less, and the number of used slots is 6 or more, that is, the number of empty slots is smaller than the number of used slots. A slot list is selected (step S24).

  The slot allocation information determination procedure shown in FIG. 14 is executed by the time slot allocation unit 3 having a function as a determination unit.

  In the example of the present embodiment in which the time slot allocation state to each node is as shown in FIG. 5, according to the selection procedure of FIG. 14, the nodes 10 constituting the ad hoc network 100 are free slot lists. The ESList (10), the node 11 stores the slot map SM (11), and the node 12 stores the slot map SM (12) in the header of the data packet and transmits them (see FIG. 15). In the header portion of the data packet, an identifier for identifying whether the stored slot allocation information is a used slot list, an empty slot list, or a slot map is prepared. FIG. 15 is a diagram illustrating a state in which each node that has already entered the ad hoc network 100 stores slot assignment information in the header of a data packet and transmits it.

  The procedure when a new node enters the ad hoc network 100 is as described in the first embodiment.

  For simplification, in steps S21 and S22 in FIG. 14, in order to identify whether the slot allocation information included in the header portion of the data packet is a used slot list, an empty slot list, or a slot map. Although the description has been made using the determination condition that does not consider the identifier, the determination condition considering the identifier may be used. For example, instead of the total number of slots for each condition, a value obtained by subtracting the size (number of bits) of this identifier from the total number of slots is used.

  As described above, in this embodiment, each node that has already entered the ad hoc network has, as slot allocation information, the allocation status of each time slot in one frame (in accordance with the time slot allocation status to itself and an adjacent node ( A slot map which is information of a total of n bits (n is the number of time slots in one frame) indicating 1 bit of a used slot or an empty slot, and a used slot list and an empty slot list used in the first embodiment From those, the time slot allocation status that can be notified with the least amount of information is selected, stored in the header of the data packet, and transmitted. As a result, the data length of the slot allocation information can always be less than or equal to the bit size of the total number of slots, and the overhead amount can be further reduced as compared with the case of the first embodiment.

  In each of the above embodiments, the slot allocation information is always described in the header of the data packet. However, each node that has already entered the ad hoc network receives the slot allocation information from a node that newly wishes to enter. After receiving a request to transmit the packet included in the header, the slot allocation information may be described in the header and transmitted.

  As described above, the communication control method according to the present invention is useful for a control procedure when notifying an adjacent node of a time slot allocation status in a multi-hop ad hoc network that employs a TDMA scheme, and particularly increases overhead. It is suitable as a method for notifying as much as possible.

1 is a diagram illustrating a configuration example of a multi-hop ad hoc network according to a first embodiment. It is a block diagram which shows the internal structural example of a radio | wireless mobile node. 3 is a conceptual diagram illustrating a configuration example of a frame used in the multi-hop ad hoc network according to Embodiment 1. FIG. It is a figure which shows a mode that a new node moves in order to enter an ad hoc network. It is a figure which shows the example of time slot allocation. It is a figure which shows an example of a use slot list. It is a figure which shows an example of an empty slot list. It is a flowchart which shows an example of the determination procedure of slot allocation information. It is a figure which shows a mode that each node stores slot allocation information in the header of a data packet, and transmits. It is a figure which shows the example of time slot allocation. It is a figure which shows an example of a use slot list. It is a figure which shows an example of an empty slot list. It is the figure which showed the allocation situation of the time slot to each node with the slot map. It is a flowchart which shows an example of the determination procedure of slot allocation information. It is a figure which shows a mode that each node stores slot allocation information in the header of a data packet, and transmits.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Antenna 2 Wireless communication part 3 Time slot allocation part 4 Memory 10-13 Radio | wireless mobile node (node)

Claims (8)

In a multi-hop ad hoc network formed by a plurality of nodes that transmit data packets using a part of a plurality of time slots obtained by time-sharing frames of a certain period, each node is configured to transmit the plurality of times A communication control method for notifying an adjacent node of slot allocation information indicating an individual usage status of a slot,
Based on the number of used slots indicating the number of used slots that are time slots used by itself or adjacent nodes, a used slot list including identification information of each used slot in one frame; A slot allocation information determination step for determining which of the empty slot lists made up of identification information of time slots that are not used slots in one frame is adopted as the slot allocation information;
According to the determination result, a slot allocation information transmission step of transmitting a data packet in which the used slot list or the empty slot list is stored as a slot allocation information in a header;
The communication control method characterized by including.   In the slot allocation information determination step, if the number of used slots is equal to or less than the number of time slots that are not used slots in one frame, the used slot list is adopted as slot allocation information; otherwise, an empty slot list is used. The communication control method according to claim 1, wherein the communication control method is adopted as slot allocation information. In a multi-hop ad hoc network formed by a plurality of nodes that transmit data packets using a part of a plurality of time slots obtained by time-sharing frames of a certain period, each node is configured to transmit the plurality of times A communication control method for notifying an adjacent node of slot allocation information indicating an individual usage status of a slot,
Based on the number of used slots indicating the number of used slots that are allocated to itself or an adjacent node in one frame and the number of time slots in one frame, each of the used slots in one frame A used slot list composed of identification information, an empty slot list composed of identification information of time slots that are not used slots in one frame, and a slot map that is a bit string indicating whether or not each time slot in one frame is a used slot A slot allocation information determination step for determining which of the slot allocation information is to be adopted;
According to the determination result, a slot allocation information transmission step of transmitting a data packet storing the used slot list, the empty slot list or the slot map as the slot allocation information in a header;
The communication control method characterized by including.   In the slot allocation information determination step, when “(number of time slots in one frame) ≧ (number of used slots) × (number of bits of time slot identification information)” is satisfied, the used slot list is used as slot allocation information. If “(number of time slots in one frame) ≧ (number of time slots that are not used slots in one frame) × (number of bits of time slot identification information)” is satisfied, an empty slot list is 4. The communication control method according to claim 3, wherein the communication method is adopted as slot assignment information, and in other cases, a slot map is adopted as slot assignment information. A communication device that forms a multi-hop ad hoc network together with other communication devices and transmits data packets using a part of a plurality of time slots obtained by time-sharing frames of a certain period,
Based on the number of used slots indicating the number of used slots that are time slots used by itself or adjacent nodes, a used slot list including identification information of each used slot in one frame; Determining means for determining which of the empty slot lists made up of identification information of time slots that are not used slots in one frame is adopted as the slot allocation information;
Communication means for transmitting a data packet stored in a header as the slot allocation information according to the determination result, the used slot list or the empty slot list;
A communication apparatus comprising:   The determining means adopts the used slot list as slot allocation information when the number of used slots is equal to or less than the number of time slots that are not used slots in one frame, and uses the empty slot list as slot allocation information in other cases. The communication device according to claim 5, wherein the communication device is used as a communication device. A communication device that forms a multi-hop ad hoc network together with other communication devices and transmits data packets using a part of a plurality of time slots obtained by time-sharing frames of a certain period,
Based on the number of used slots indicating the number of used slots that are allocated to itself or an adjacent node in one frame and the number of time slots in one frame, each of the used slots in one frame A used slot list composed of identification information, an empty slot list composed of identification information of time slots that are not used slots in one frame, and a slot map that is a bit string indicating whether or not each time slot in one frame is a used slot A determining means for determining which one of the slot allocation information is to be adopted;
Communication means for transmitting a data packet stored in a header as the slot allocation information, according to the determination result, the used slot list, the empty slot list or the slot map;
A communication apparatus comprising:   The determination means adopts the used slot list as slot allocation information when “(number of time slots in one frame) ≧ (number of used slots) × (number of bits of identification information of time slot)” is satisfied, If “(number of time slots in one frame) ≧ (number of time slots that are not used slots in one frame) × (number of bits of time slot identification information)” is satisfied, the empty slot list is assigned to the slot allocation information. 8. The communication apparatus according to claim 7, wherein a slot map is adopted as slot allocation information in other cases.

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