Method and system for communication between groups in wireless communication network

This application is a national stage application of International Application No. PCT/JP2015/004006 entitled “Method and System for Communication Between Groups in Wireless Communication Network” filed on Aug. 10, 2015, which claims priority to Japanese Application No. 2014-164034 filed on Aug. 12, 2014, the disclosures of which are hereby incorporated by reference in their entirety.

The present invention relates to a wireless communication network including terminals that are capable of peer-to-peer (hereinafter, abbreviated as “P2P”) wireless connection to each other (P2P terminals), and a communication technique in the same.

In recent years, Wi-Fi Direct has attracted attention as a terminal-to-terminal communication scheme in view of broader bandwidth, increased security, and the like. While conventional Wi-Fi networks work in the infrastructural mode with a specific device serving as an access point (AP), Wi-Fi Direct-compliant networks enable communication to be performed within a group, with any P2P terminal, not a specific device, serving as a group owner (NPL 1). A group owner is a P2P terminal that operates as an access point of a group and, as the parent of that group, can form the group including other P2P terminals as clients.

Within a P2P group formed as described above, terminals can share data and transfer data at high speed without connecting to the Internet or the like. Wi-Fi Direct, in particular, supports a robust security protocol and therefore can realize a higher level of security than the conventional ad-hoc mode (IBSS: Independent Basic Service Set and the like).

Non Patent Literature

[NPL 1]

Wi-Fi Alliance Technical Committee PSP Task Group, Wi-Fi Peer-to-Peer (P2P) Technical Specification Version 1.1

Technical Problem

However, in the above-described wireless P2P network, since each group is formed and operates independently, data sharing is limited to within a group. Moreover, in general, there is a physical upper limit to the maximum number of terminals in one group. If the above-described Wi-Fi Direct is implemented by using inexpensive wireless LAN devices, the number of members of a group is limited to an upper limit of about five to ten that can be supported by each device. Such a limitation of group size limits message sharing to those terminals within a single group and hinders information sharing in a larger network that includes a plurality of groups. In the above-described wireless P2P network, for example, urgent disaster information, traffic information, SOS signals, or voice signals cannot be notified beyond a local group.

Accordingly, an object of the present invention is to provide a communication method and system that make it possible to transfer information between groups.

Solution to Problem

A communication method according to the present invention is a communication method in a wireless communication network including a plurality of nodes that can form a peer-to-peer group, and is characterized in that an owner node operating as an access point in one group selects one or a plurality of client nodes in this group as delivery nodes; the delivery node disconnects from the group and connects to another group that is present in vicinity; and information is transferred between the delivery node and an owner node of the another group.

A communication system according to the present invention is a communication system in a wireless communication network including a plurality of nodes that can form a peer-to-peer group, and is characterized in that an owner node operating as an access point in one group selects one or a plurality of client nodes within this group as delivery nodes, the delivery node disconnects from the group and connects to another group that is present in vicinity, and information is transferred between the delivery node and an owner node of the another group.

Advantageous Effects of Invention

According to the present invention, it is possible to share information between groups through a delivery node.

FIG. 1 is a network architecture diagram showing an example of a group-to-group communication system according to a first exemplary embodiment of the present invention.

FIG. 2 is a flowchart showing operation in the group-to-group communication system shown in FIG. 1 .

FIG. 3 is a block diagram showing the functional configuration of a node according to the first exemplary embodiment.

FIG. 4 is a schematic network architecture diagram showing an example of a group-to-group communication system according to a second exemplary embodiment of the present invention.

FIG. 5 is a sequence chart showing operation in the group-to-group communication system shown in FIG. 4 .

FIG. 6A is a flowchart showing a first example of a method for selecting a delivery node.

FIG. 6B is a flowchart showing a second example of the method for selecting a delivery node.

FIG. 7 is a schematic network architecture diagram showing an example of a group-to-group communication system according to a third exemplary embodiment of the present invention.

FIG. 8 is a sequence chart showing operation in the group-to-group communication system shown in FIG. 7 .

FIG. 9 is a schematic network architecture diagram showing an example of a group-to-group communication system according to a fourth exemplary embodiment of the present invention.

FIG. 10 is a sequence chart showing operation in the group-to-group communication system shown in FIG. 9 .

FIG. 11 is a schematic network architecture diagram showing an example of a group-to-group communication system according to a fifth exemplary embodiment of the present invention.

FIG. 12 is a schematic network architecture diagram showing a group-to-group communication system according to a sixth exemplary embodiment of the present invention.

FIG. 13 is a flowchart showing operation in the group-to-group communication system shown in FIG. 12 .

FIG. 14 is a block diagram showing the functional configuration of a node according to an example of the present invention.

FIG. 15 is a flowchart showing cases of Wi-Fi Direct connection in the present example.

FIG. 16 is a schematic sequence chart showing operation of device discovery in the present example.

FIG. 17 is a schematic sequence chart showing operation of device discovery toward an existing group in the present example.

FIG. 18 is a schematic sequence chart showing operation of group owner negotiation between nodes in the present example.

FIG. 19 is a schematic sequence chart showing operation of connection to an existing group in the present example.

FIG. 20 is a schematic sequence chart showing operation of connection to a persistent GO in the present example.

FIG. 21A is a schematic sequence chart showing operation of client-led disconnection from a group in the present example.

FIG. 21B is a schematic sequence chart showing operation of group owner-led disconnection from a group in the present example.

Outline of Embodiments

According to exemplary embodiments of the present invention, one or a plurality of client nodes within a P2P group are designated as delivery nodes, and each of these delivery nodes leaves the group to which the delivery node itself belongs, and joins another group that is present in its vicinity. Thus a message shared in the original group is transferred to the other group via the delivery node, whereby information sharing between different groups is possible. For example, urgent disaster information, traffic information, SOS signals, voice signals, or the like can be broadly transferred beyond a local group.

It is preferable to select a delivery node from the viewpoint of efficiency in transferring information. For example, a delivery node can be selected based on the number of neighboring groups or nodes discovered by each client node, or based on the distance from the group owner, or based on the combination thereof. Information can be propagated more quickly and more widely in particular if a client node having a larger number of neighboring groups is selected as a delivery node. In addition, a delivery node may be selected at random, or may be selected depending on the temporal order of joining the group (new/old), the amount of communication, the timing of terminating communication, or the like.

If a delivery node joins a plurality of neighboring groups and transfers information thereto, there is a possibility that the same message is duplicately transferred to a group to which the message has been already transferred. To avoid such duplicate transfer, it is preferable that each delivery node keep a history of all groups the delivery node joined in the past.

Moreover, it is also possible to set a time interval from a delivery node's disconnection until its return to the original group. During that time, the delivery node that has disconnected sequentially joins neighboring groups and transfers a message while acquiring information of the neighboring groups, and then returns to the original group after timeout.

A limit to the number of members of a group can be eased by configuring a virtual application group at an upper layer of the group. If communication between groups as described above is possible, it is also possible to make rules for rearrangement of the constituent members (nodes) of the group under a constraint of a upper group that includes a plurality of groups. For example, rules can be made as follows: if a node is one registered with an upper application group, control is performed such that even if the node is designated as a delivery node, the node will return after a certain period of time, but such control is not imposed on the other nodes; or alternatively, to begin with such a node shall not be designated as a delivery node.

Next, each of the above-mentioned exemplary embodiments will be described in more detail with reference to drawings.

1. FIRST EXEMPLARY EMBODIMENT

According to a first exemplary embodiment of the present invention, a delivery node is selected among client nodes within a group, and this delivery node periodically leaves the group and joins another group that is present in vicinity, thereby delivering information to the other group.

1.1) System Architecture and Operation

Referring to FIG. 1 , in a system according to the present exemplary embodiment, it is assumed that a plurality of nodes (here, seven nodes N 10 to N 16 ) form two groups G 1 and G 2 . The group G 1 is formed with the node N 10 serving as the parent (group owner) and the nodes N 11 to N 14 as its clients. The group G 2 is formed with the node N 15 serving as the group owner and the node N 16 as its client. Here, it is assumed that messages MSG 1 and MSG 2 are shared within the groups G 1 and G 2 , respectively.

In the system having the above-described architecture, operation for delivering information from the group G 1 to the group G 2 will be described. Note that this is an example, and group-to-group communication from any group to its neighboring group can be performed similarly.

Referring to FIG. 2 , in the group G 1 , one or more client nodes become delivery nodes (Operation S 101 ). Hereinafter, it is assumed that the client node N 13 , which is a member of the group G 1 , becomes a delivery node.

The node N 13 as a delivery node disconnects from the group owner (hereafter, abbreviated as GO) node N 10 through a predetermined procedure and connects to the GO node N 15 of the neighboring group G 2 as a client. Thus the delivery node N 13 can transfer the message MSG 1 shared in the group G 1 to the GO node N 15 of the group G 2 (Operation S 102 ). Signals used in a procedure for joining the group G 2 may be utilized for this transfer of the message MSG 1 . Note that the GO node N 15 transfers the message MSG 1 to the client node N 16 in its own group G 2 .

In the case where the number of members of the neighboring group G 2 reaches the upper limit, the delivery node N 13 cannot join this group G 2 . This greatly reduces the advantage of a delivery node. Accordingly, it is preferable that the GO node of each group set the upper limit of the number of nodes it supports to a number obtained by subtracting one from the maximum number of nodes in a group in this system. Since a delivery node leaves as soon as it finishes delivering information, the chance of each group's accepting a delivery node is greatly increased. As another method, the GO node of each group may perform control such that a delivery node is preferentially accepted by temporarily disconnecting a relatively low-priority client node within the group, such as a node that is not performing communication or a node that has spent a relatively short time since the node joined the group.

Once delivery of the message MSG 1 to the GO node N 15 is finished, the delivery node N 13 disconnects from the GO node N 15 and reconnects to the original group G 1 (Operation S 103 ). However, not all of the delivery nodes necessarily have to return to the original group G 1 .

1.2) Node Configuration

The nodes N 10 to N 16 shown in FIG. 1 basically have the same functional configuration, and hereinafter the functional configuration of the nodes will be described with reference to FIG. 3 . Here, it is assumed that the nodes include wireless terminals having a function of configuring a P2P group, for example, mobile stations and communication terminals such as mobile information terminals and mobile telephone terminals equipped with this function.

Referring to FIG. 3 , the node N includes a wireless communication section 201 , a user control section 202 , an information storage section 203 , a program storage section 204 , and a control section 205 for the node. The wireless communication section 201 is capable of P2P communication, which will be described later, and may be additionally capable of communicating with a radio base station of a mobile communication system or with a wireless LAN base station. Moreover, the wireless communication section 201 can detect the presence of another P2P group and the presence of another wireless LAN by scanning beacons broadcast from nodes that are present in vicinity.

The user control section 202 has a P2P automatic connection function that manages predetermined procedures for P2P group formation, joining, disconnection, and the like, and controls the wireless communication section 201 on behalf of a communication application. Note that similar control can be also performed by using a communication application. The information storage section 203 stores information such as a message shared within a group to which the own node is connected, a message acquired from a delivery node that joins from another group, a group history in case of functioning as a delivery node, or the like, which will be described later.

The program storage section 204 stores communication applications and the like in addition to programs for functioning as a node, and the control section 205 executes these programs and applications, thereby controlling P2P node operation. Further, it is also possible that the operation of the user control section 202 for group formation and the like is restricted by executing a predetermined application, which will be described later.

Furthermore, the node N may be provided with a location detector for detecting the geographical location of the own station, a communication amount monitor for monitoring the amount of communication, and the like. The location detector only needs to be capable of identifying the location of the own station to some degree. For example, the location may be detected by utilizing signals from fixed base stations, or a GPS (Global Positioning System) receiver may be used.

1.3) Effects

As described above, according to the first exemplary embodiment of the present invention, a delivery node is designated as appropriate within a group, whereby group-to-group communication is possible, and widespread deployment of a P2P network can be achieved beyond a limit of the number of members of a group. Since a message shared within an original group can be spread over to another group in particular, it is possible to share information between different groups. For example, it can be easily achieved to share urgent traffic information among many moving vehicles, and to share a disaster-related message among many smartphones and the like.

2. SECOND EXEMPLARY EMBODIMENT

According to a second exemplary embodiment of the present invention, a delivery node is selected based on the number of neighboring groups or the number of nodes discovered by each client node within a group. The selected delivery node leaves the original group periodically, or when a predetermined condition is met, and joins another group that is present in vicinity, whereby information shared in the original group can be transferred to the other group.

2.1) System Architecture

Referring to FIG. 4 , in a system according to the present exemplary embodiment, it is assumed that a plurality nodes (here, five nodes N 10 to N 14 ) form a group G 1 , with the node 10 serving as the parent (group owner) and the nodes N 11 to N 14 as its clients. Moreover, it is assumed that a message MSG 1 is stored in the information storage section 303 of each member node of the group G 1 .

Hereinafter, for simplified description, a case will be described as an example where a plurality of groups G 2 to G 5 are present in the vicinity of the group G 1 , the client nodes N 13 and N 14 each send a probe request for Device Discovery processing, and the client node N 13 detects probe responses 302 , 303 and 304 from the Groups G 3 , G 4 and G 5 , respectively, and the client node N 14 detects a probe response 301 from the group G 2 .

2.2) Operation

Referring to FIG. 5 , each of the client nodes N 11 to N 14 belonging to the group G 1 , when receiving a probe response to a probe request it has sent from a group node that is present in vicinity (Operation S 401 ), notifies information on the group owner discovered with this probe response, as neighboring node information, to the GO node N 10 (Operation S 402 ).

The control section 205 of the GO node N 10 selects a delivery node based on the number of neighboring nodes, which is obtained from the neighboring node information notified from each client node (Operation S 403 ). Assuming that a client node that has discovered the largest number of neighboring nodes is selected as a delivery node, the client node N 13 is selected as a delivery node, and the GO node N 10 notifies a disconnection instruction to the node N 13 (Operation S 404 ). For disconnection of the node N 13 , the GO node N 10 may disconnect the node N 13 , or the node N 13 may disconnect itself. Note that the selected delivery node is not always one. It is also possible that the control section 205 of the GO node N 10 sorts the numbers of neighboring nodes of the plurality of client nodes in descending order and selects two or more client nodes that have the most neighboring nodes as delivery nodes. In this case as well, the operation of each of the selected delivery nodes is as described below.

When being designated as a delivery node, the control section 205 of the node N 13 instructs the user control section 202 to perform a procedure for disconnecting from the GO node N 10 (Operation S 405 ). The node N 13 that has thus left the group G 1 initiates a procedure for joining a discovered neighboring group. Illustrating a case of joining the group G 3 , the node N 13 sends a connection request to the GO node of the group G 3 (Operation S 406 ). When receiving a permission response thereto (Operation S 407 ), the node N 13 , as a client of the group G 3 , transfers the information shared in the group G 1 to the GO node of the group G 3 , and the GO node of the group G 3 distributes that shared information to client nodes under its coverage (Operation S 408 ). Information transfer from the delivery node N 13 to the group G 3 may be performed as data transmission from a client to the group owner, or the information can be also sent by using the connection request message in Operation S 406 . Moreover, the delivery node N 13 can also receive information shared in the group G 3 from the GO node of the group G 3 and stores it in the information storage section 203 (Operation S 409 ).

Note that the GO node of each group can set the upper limit of the number of nodes it supports to a number obtained by subtracting one from the maximum number of nodes in a group in this system in order to increase the chance of a delivery node's joining. Alternatively, it is also possible that the GO node of each group preferentially accepts a delivery node by temporarily disconnecting a relatively low-priority client node within the group.

When information transfer is thus finished, the control section 205 of the delivery node N 13 instructs the user control section 202 to perform a procedure for disconnecting from the GO node of the group G 3 (Operation S 410 ). Alternatively, it is also possible that the group G 3 initiates the disconnection procedure when information transfer is finished. The delivery node N 13 that has thus left the group G 3 sends a connection request to the GO node N 10 of the original group G 1 (Operation S 411 ) and, when receiving a permission response thereto (Operation S 412 ), returns to a client of the group G 1 and transfers the information shared in the group G 3 to the GO node N 10 of the group G 1 , whereby the GO node N 10 of the group G 1 can distribute this shared information to the client nodes under its coverage (Operation S 413 ).

2.3) Delivery Node Selection Criterion

Referring to FIG. 6A , a GO node can select a client node to become a delivery node based on the number of neighboring groups/nodes discovered by each client node. That is, the GO node N 10 collects neighboring group/node information from each of all client nodes N 11 to N 14 (Operation S 501 ) and selects a client node that has the largest number of neighboring groups/nodes as a delivery node (Operation S 502 ). Subsequently, the GO node N 10 notifies a disconnection instruction to the client node selected as a delivery node (Operation S 503 ).

2.4) Modification Example of Delivery Node Selection Criterion

Referring to FIG. 6B , it is also possible that a GO node selects a client node to become a delivery node based on the distance of each client node from the GO node in addition to the above-described number of neighboring groups/nodes. For example, when the GO node N 10 , as described above, collects neighboring group/node information from each of all client nodes N 11 to N 14 (Operation S 511 ) and selects among them one or more client nodes as delivery node candidates in the descending order of the number of neighboring groups/nodes (Operation S 512 ), then the GO node N 10 calculates the distance of each delivery node candidate from the GO node N 10 by using location information obtained by a location detector (Operation S 513 ) and determines the most distant candidate as a delivery node (Operation S 514 ). Thereafter, the GO node N 10 notifies a disconnection instruction to the client node selected as a delivery node (Operation S 515 ).

2.5) Other Modification Examples of Delivery Node Selection Criterion

Not only the above-described delivery node selection based on the number of neighboring nodes, but it is also possible that a delivery node is selected based on the distance from the GO node N 10 . That is, the GO node N 10 may calculate the distance of each client node from the GO node N 10 by using location information obtained by a location detector and may select the most distant client node as a delivery node.

Moreover, a delivery node can be also selected based on the above-described number of neighboring groups/nodes, distance from GO, a time stamp indicating a time point when a client node joins, or a combination of any of these items. Further, a delivery node may be selected at random among the client nodes, or may be selected at random among the delivery node candidates that have been selected based on the above-described various selection criteria.

2.6) Delivery Node Disconnection Timing

The GO node N 10 can be triggered to disconnect a delivery node, for example, by a condition as listed below.

When a client node to become a delivery node discovers a new neighboring group When timeout of a timer for measuring a certain period of time occurs (periodical disconnection) When a client node that has joined as a delivery node finishes delivering a content

2.7) Effects

As described above, according to the second exemplary embodiment of the present invention, in addition to the above-described effects of the first exemplary embodiment, quick information sharing between different groups is possible because a delivery node is selected from the viewpoint of efficiency in transferring information. A delivery node is selected based on the number of neighboring nodes discovered by each client node within a group as described above, whereby information can be propagated quickly and widely.

3. THIRD EXEMPLARY EMBODIMENT

According to a third exemplary embodiment of the present invention, when a delivery node joins a plurality of neighboring groups and transfers information, the delivery node keeps a history of all groups it joined to deliver information in the past, whereby the possibility of duplicate delivery to a group where delivery has been already made can be reduced.

3.1) System Architecture

Referring to FIG. 7 , in a system according to the present exemplary embodiment, it is assumed that a plurality of nodes (here, five nodes N 10 to N 14 ) form a group G 1 , with the node N 10 serving as the parent (group owner) and the nodes N 11 to N 14 as its clients. Moreover, it is assumed that a message MSG 1 is stored in the information storage section 303 of each member node of the group G 1 .

Hereinafter, for simplified description, a case will be described as an example where a plurality of groups G 2 to G 5 are present in the vicinity of the group G 1 , the client node N 13 detects beacons 302 , 303 and 304 from the Groups G 3 , G 4 and G 5 , respectively, and the client node N 14 detects beacons 301 and 302 from the groups G 2 and G 3 , respectively.

3.2) Operation

Referring to FIG. 8 , the GO node N 10 of the group G 1 selects at least one delivery node among the client nodes N 11 to N 14 as described in the second exemplary embodiment above (Operation S 600 ) and gives a delivery node designation to each selected delivery node (Operation S 601 ). Here, it is assumed that the nodes N 13 and 14 are selected as delivery nodes, as shown in FIG. 7 . The nodes N 13 and N 14 designated as delivery nodes each perform a procedure for disconnecting from the GO node N 10 (Operation S 602 ), join their respective neighboring groups while referring to their respective delivery histories, and update the respective delivery histories after performing information transfer.

For example, the delivery node N 13 first refers to the delivery history stored in the information storage section 203 and determines whether or not delivery has been already made to the GO node of the group G 3 (Operation S 603 a ). If delivery has not yet been made, the delivery node N 13 becomes a client of the group G 3 and performs information delivery, and thereafter leaves the group G 3 and updates the delivery history (Operation S 603 b ).

Subsequently, the delivery node N 13 refers to the delivery history stored in the information storage section 203 and determines whether or not delivery has been already made to the GO node of the group G 4 (Operation S 604 a ). If delivery has not yet been made, the delivery node N 13 becomes a client of the group G 4 and performs information delivery, and thereafter leaves the group G 4 and updates the delivery history (Operation S 604 b ). Thereafter, the delivery node N 13 repeats information delivery and history update in a similar manner while referring to the delivery history for each neighboring group discovered, and updates the delivery history each time. When information delivery to the neighboring groups is thus finished, the delivery node N 13 returns to the original group G 1 (Operation S 605 ).

3.3) Effects

As described above, according to the third exemplary embodiment of the present invention, in addition to the above-described effects of the first and second exemplary embodiments, when a single delivery node delivers information to a plurality of neighboring groups, the delivery node refers to the delivery history, whereby the possibility of duplicate delivery to a group where delivery has been already made can be reduced.

4. FOURTH EXEMPLARY EMBODIMENT

According to a fourth exemplary embodiment of the present invention, a time period from a delivery node's leaving the original group until its return thereto, or the number of neighboring groups to which a delivery node should connect, is set, whereby it is possible to secure time for which the delivery node performs information delivery, or ensure information delivery, and to ensure the return of the delivery node.

4.1) System Architecture

Referring to FIG. 9 , in a system according to the present exemplary embodiment, it is assumed that a plurality of nodes (here, five nodes N 10 to N 14 ) form a group G 1 , with the node N 10 serving as the parent (group owner) and the nodes N 11 to N 14 as its clients. Each node is provided with a timer function, with which a timer for defining a delivery period for a delivery node is set. Moreover, it is assumed that a message MSG 1 is stored in the information storage section 203 of each member node of the group G 1 .

Hereinafter, for simplified description, a case will be described as an example where a plurality of groups G 3 to G 5 are present in the vicinity of the group G 1 , and the client node N 13 detects beacons from the groups G 3 , G 4 and G 5 , respectively, and, as a delivery node, delivers information to each group.

4.2) Operation

Referring to FIG. 10 , the GO node N 10 of the group G 1 , as described in the second exemplary embodiment above, selects at least one delivery node among the client nodes N 11 to N 14 (Operation S 700 ) and gives a disconnection instruction to each selected delivery node (Operation S 701 ). Here, it is assumed that the node N 13 is selected as a delivery node, as shown in FIG. 9 . When the node N 13 designated as a delivery node disconnects from the GO node N 10 (Operation S 702 ), the node N 13 starts a timer on which a predetermined information delivery period is set (Operation S 703 ) so that the node N 13 will not return to the original group G 1 before timeout. That is, the delivery node N 13 sequentially performs information delivery to the discovered neighboring groups G 3 , G 4 and G 5 until timeout. In that event, it is also possible that the delivery node N 13 joins the neighboring groups while referring to the delivery history and updates the delivery history after performing information transfer, as in the third exemplary embodiment.

When timeout of the timer occurs (Operation S 704 ), the delivery node N 13 returns to the original groups G 1 after finishing information delivery to the neighboring groups (Operation S 705 ) and transfers, to the GO node N 10 , the accumulated information that was acquired from each neighboring group when the delivery node N 13 joined the neighboring group (Operation S 706 ), and the information is stored in the information storage section 203 of the GO node N 10 (Operation S 707 ).

Note that the GO node N 10 can also perform control such that the timer of a delivery node is not set. More specifically, if a delivery node should return to the original group, a timer is set for that delivery node, but otherwise a timer is not set. Alternatively, it is also possible that the control section 205 of a delivery node determines whether or not to set its own return timer. For example, if a group setting application that is the same as that of the GO node N 10 is activated, which will be described later, the return timer is set, but if not, the timer is not set.

Moreover, the information delivery operation of the delivery node N 13 is managed by using a timer in the present exemplary embodiment, but can be also managed by using the number of neighboring groups to which delivery is to be made. For example, it is also possible that the number of neighboring groups to which delivery is to be made is designated, and a delivery node returns after connecting to the designated number of neighboring groups. Alternatively, it is also possible to manage a delivery node so as not to return until the delivery node connects to the designated number of neighboring groups.

4.3) Effects

As described above, according to the fourth exemplary embodiment of the present invention, in addition to the above-described effects of the first to third exemplary embodiments, a time period from a delivery node's leaving the original group until its return thereto, or the number of neighboring groups to which a delivery node should connect, is set, whereby it is possible to increase the reliability of information delivery by the delivery node, and to ensure the return of the delivery node that should return.

5. FIFTH EXEMPLARY EMBODIMENT

According to a fifth exemplary embodiment of the present invention, an application group is formed at a higher layer than groups, and rules for the disconnection and joining operation of a delivery node are set within this higher-layer application group.

Referring to FIG. 11 , in a system according to the present exemplary embodiment, it is assumed that a plurality of nodes form three groups G 1 to G 3 , and that the node N 10 is the parent (group owner) of the group G 1 with the nodes N 11 to N 13 as its clients and the node N 14 is the parent (group owner) of the group G 2 with the nodes N 15 to N 17 as its clients. Further, it is assumed that a predetermined application is set on the nodes N 10 to N 16 , which form an application group Gap, and that the node N 17 and the group G 3 do not belong to the application group Gap.

An application group is manually input by a user, and therefore, in some cases, the number of members of such a group exceeds a predetermined limit of the number of members of a group. Accordingly, if communication between groups as described above is possible, a higher-layer group can be configured beyond the limit of the number of members of a group. In this case, rules for rearrangement of nodes between groups can be determined in accordance with a constraint of an application by which an application group Gap is configured. For example, the nodes N 10 to N 16 registered with the higher-layer application group are controlled so that they can mutually move in and out the groups and, even when designated as a delivery node, will be subject to timer setting so as to return after a certain period of time, but the other node N 17 is controlled so that a timer will not be set on it (or it will not be designated as a delivery node to begin with).

As described above, according to the fifth exemplary embodiment of the present invention, a user sets a constraint of an application in a higher-layer application group including a plurality of groups, whereby rules for a node's disconnecting from a group, joining a group, and moving between groups can be set as the user desires.

6. SIXTH EXEMPLARY EMBODIMENT

As described above, a delivery node can return to the original group after delivering information to neighboring groups. However, the present invention is not limited to such scenarios. In case of spreading emergency information in particular, priority can be placed on transferring information to as many neighboring groups as possible as in a sixth exemplary embodiment of the present invention, which will be described below.

Referring to FIG. 12 , in a system according to the present exemplary embodiment, it is assumed that a plurality of nodes N 10 to N 19 form four groups G 1 to G 4 . It is assumed that the node N 10 is the parent (group owner) of the group G 1 with the nodes N 11 to N 13 as its clients, the node N 14 is the parent (group owner) of the group G 2 with the nodes N 15 to N 17 as its clients, and further the nodes N 18 and N 19 are the group owners of the groups G 3 and G 4 , respectively.

Note that it is assumed that the GO node of each group operates in such a manner that it temporarily disconnects a relatively low-priority client node in its group and preferentially accepts a delivery node, in order to increase the chance of a delivery node's joining. It is also possible to keep the number of members of each group always smaller than the upper limit in the system as described above. Hereinafter, a case will be described as an example where a message MSG 1 shared within the group G 1 is delivered to the other groups.

Referring to FIG. 13 , in the group G 1 , one or more client nodes become delivery nodes (Operation S 801 ). Here, it is assumed that one client node N 12 in the group G 1 becomes a delivery node.

The node N 12 as a delivery node disconnects from the GO node N 10 and joins the GO node N 14 of the neighboring group G 2 as described above, and thereby transfers the message MSG 1 to the GO node N 14 of the group G 2 (Operation S 802 ). Since the delivery node N 12 can preferentially join, information delivery from the delivery node N 12 succeeds with a high probability.

When delivery of the message MSG 1 to the GO node N 14 is finished and sharing of the message MSG 1 in the group G 2 is completed, then the GO node N 14 of the group G 2 next selects one or more client nodes in the group G 2 as delivery nodes (Operation S 803 ). Here, it is assumed that two client nodes N 16 and N 17 in the group G 2 become delivery nodes.

The nodes N 16 and N 17 as delivery nodes each disconnect from the GO node N 14 as described above, join the neighboring groups G 3 and G 4 , respectively, and thereby deliver the message MSG 1 to the groups G 3 and G 4 , respectively (Operation S 804 ). Thereafter, information delivery is repeated similarly in downstream groups, whereby the same information MSG 1 is spread quickly in the P2P network over a wide range.

7. EXAMPLE

Next, a detailed description will be given of a case as an example of the present invention where the above-described systems according to the first to sixth exemplary embodiments of the present invention are applied to a Wi-Fi Direct-compliant P2P network. Since basic configurational components and functions are as described above, illustrated below is a case where such configurational components and functions are implemented based on Wi-Fi Direct.

7.1) Node Configuration

Referring to FIG. 14 , a node (wireless terminal) according to the present example includes a Wi-Fi device 901 for performing Wi-Fi communication, a Wi-Fi connection control section 902 , an application section 903 , and a WFD automatic connection control section 904 that performs automatic connection in accordance with Wi-Fi Direct. Here, the WFD automatic connection control section 904 corresponds to the user control section 202 in FIG. 3 . Note that the information storage section 203 described in FIG. 3 is not shown in FIG. 14 but is provided to the node in the present example.

In the node according to the present example, the WFD automatic connection control section 904 controls Wi-Fi Direct commands on behalf of an existing communication application. Accordingly, it is possible to automate the control according to Wi-Fi Direct, without modifying the existing application. For example, when wireless terminals come close to each other, they can automatically form a group and implement terminal-to-terminal communication within the group. Moreover, when a new terminal approaches an already established group, the terminal can automatically join the established group. Further, even if already established groups are in proximity to each other, the composition of each group is maintained without changing.

7.2) Wi-Fi Direct Connection and Disconnection Flows

Referring to FIG. 15 , in case of forming a group between terminals (CASE 1 ), first, a node searches for a P2P node in its vicinity through Device Discovery processing, and when a P2P node is discovered, the nodes connect to each other through GO Negotiation processing, with one of them becoming the group owner (GO) and the other becoming a client. Subsequently, WPS Provision Phase-1 (authentication phase) and Phase-2 (encryption phase) are sequentially performed.

In case of connecting to an existing GO (CASE 2 ), first, a node searches for a P2P node in its vicinity through Device Discovery processing, and if a discovered P2P node is a GO, the node connects to this GO through Provision Discovery processing. Subsequently, WPS Provision Phase-1 (authentication phase) and Phase-2 (encryption phase) are sequentially performed.

In case of connecting to a Persistent GO (CASE 3 ), first, a node searches for a P2P node in its vicinity through Device Discovery processing, and if a discovered P2P node is a Persistent GO, the node connects to this Persistent GO through Invitation processing. Subsequently, WPS Provision Phase-1 (authentication phase) and Phase-2 (encryption phase) are sequentially performed.

The Device Discovery operation is performed as illustrated in FIG. 16 . That is, the Wi-Fi connection control section of each node, upon receiving a search request from the WFD automatic connection control section, starts searching for a neighboring node and repeats Search state and Listen state alternately. In Search state, the node sends out Probe Request while sequentially changing predetermined channels and waits for a response, Probe Response, thereto. In Listen state, the node waits for Probe Request from another node and, when receiving Probe Request, returns a response, Probe Response, thereto. Assuming that a node N 1 is a client of a group, the Wi-Fi connection control section of the node N 1 , when receiving Probe Response from a node N 2 , notifies information on this neighboring node N 2 as neighboring node information to the group owner of its own group.

The Device Discovery operation toward an existing GO is performed as illustrated in FIG. 17 . If a group is already established with a node N 2 as its group owner, the GO node N 2 returns Probe Response to Probe Request from a node N 1 . At that time, P2P Device Info Attribute in the Probe Response from the GO node N 2 contains a list of clients belonging to this group (here, information on the node N 2 and a node N 3 ).

The GO Negotiation operation in case of forming a group between terminals is performed as illustrated in FIG. 18 . GO Negotiation Request, GO Negotiation Response, and GO Negotiation Confirmation are sent and received between nodes, whereby one of the nodes becomes a GO and starts broadcasting a beacon.

The Provision Discovery operation for connecting to an existing GO is performed as illustrated in FIG. 19 . In response to Provision Discovery Request from a node N 1 to a node N 2 , the GO node N 2 returns Provision Discovery Response to the node N 1 , whereby the node N 1 is connected to the node N 2 .

The Invitation operation for connecting to a Persistent-GO is performed as illustrated in FIG. 20 . In response to Invitation Request from a node N 1 to a node N 2 , the Persistent-GO node N 2 returns Invitation Response to the node N 1 , whereby the node N 1 is connected to the node N 2 .

Referring to FIG. 21A , in client-led disconnection, a client node N 1 sends Deauthentication or Disassociation Indication to a GO node N 2 and thereby can disconnect therefrom. Conversely, referring to FIG. 21B , in group owner-led disconnection, the GO node N 2 sends Deauthentication or Disassociation Indication to the client node N 1 and thereby can disconnect the client.

Through the above-described Wi-Fi connection and disconnection flows, the above-described information sharing methods according to the first to sixth exemplary embodiments of the present invention can be implemented in a Wi-Fi P2P network.

The present invention can be implemented in a P2P network including a plurality of nodes (wireless terminals) that can dynamically form a group.

G 1 -G 5 Group

GO Group owner

N Node

MSG Message

201 Wireless communication section

202 User control section

203 Information storage section

204 Program storage section

205 Control section

301 - 304 Probe response, beacon