JP2005252362A - Method for storing broadcasting communication causal relation order, and system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain an order storage broadcasting communication method, capable of suppressing quantity of data to be added to a broadcast message to a predetermined quantity or lower, even if the scale of a stationary network is increased, to increase the number of mobile supporting stations. <P>SOLUTION: The stationary network 3 is configured, in such a way that subnetworks in which the number of mobile supporting stations 2 is not more than a predetermined number are connected tree-like, and a causal relation order is stored and a range of performing communication is used as each subnetwork. Second mobile support stations 2b connected to two different subnetworks each receive a broadcast message from one of the subnetworks. The station 2b delivers the message to a terminal 4, connected to own station, and transmits it to another subnetwork, if the broadcast message is in a delivery enabling state, simultaneously transmits the broadcast message to both the two subnetworks if receiving a broadcast message from the terminal 4 connected to its own station or from own station, and delivers the message to the terminal 4 connected to own station and to own station, if the message can be delivered in both the subnetworks. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a causal order preserving broadcast type communication for executing causal order preserving broadcast type communication in a system comprising a mobile communication terminal and a fixed network comprising a mobile support station for performing wireless communication by the mobile communication terminal. It relates to a method and its system.

  In a wireless communication system comprising a mobile communication terminal and a fixed network composed of a movement support station for performing wireless communication by the mobile communication terminal, all mobile messages transmitted by one mobile communication terminal participating in the communication are transmitted. After receiving a broadcast message A in any mobile communication terminal, when a mobile communication terminal receives another broadcast message B after receiving one broadcast message A, it receives in the order transmitted in the communication terminal. As a communication method (protocol) that is guaranteed to receive the broadcast message B, there is a causal order preserving broadcast communication method (protocol) (for example, see Non-Patent Document 1).

  Below, the outline | summary of the causal order preservation | save broadcast type | mold communication method described in this nonpatent literature 1 is demonstrated. A wireless communication system in which causal sequence preserving broadcast communication is performed performs wireless communication with a mobile communication terminal in a predetermined area (generally referred to as a cell) using a predetermined wireless communication method. The mobile network is composed of a fixed network in which mobile support stations that perform part of the broadcast-type communication processing performed are connected to each other, and a mobile communication terminal (hereinafter referred to as a terminal) that performs communication via the fixed network.

  Here, it is assumed that the terminal is connected to a maximum of one mobility support station at a certain moment. In addition, it is assumed that all the mobile support stations existing in the fixed network recognize what kind of mobile support station exists in the fixed network. Furthermore, it is assumed that there is no increase or decrease in the number of terminals and mobility support stations existing in the fixed network. Furthermore, in the broadcast message transfer between the terminal and the mobile support station, and in the broadcast message transfer performed by the mobile support station on the fixed network, reliable message transfer is performed so that missing, duplicated, or rearranged messages do not occur. Assume that it is guaranteed to be done.

  The mobile support station manages vector data SENT including information on the context of broadcast messages, and vector data DELIV including the number of broadcast messages that have been delivered among broadcast messages from other mobile support stations. These SENT and DELIV have a data amount proportional to the number of mobile support stations existing in the fixed network. The mobile support station adds SENT to the broadcast message transmitted by the terminal, and determines the timing for delivering the broadcast message received from another mobile support station or mobile terminal to the subordinate mobile terminal between SENT and DELIV. By determining whether or not a specific condition is satisfied, causal order-preserving broadcast communication by the terminal is realized.

  Further, in order to support handoff in which the terminal moves and switches the connected mobile support station, the mobile support station transmits vector data indicating packet information delivered to the terminal for each terminal connected to the mobile station. It also manages RECV. When the terminal hands off from the mobile support station A to the mobile support station B, the mobile support station A notifies the mobile support station B of the RECV for the mobile terminal, and the mobile support station B has moved based on the RECV. By confirming the reception status of the broadcast message of the terminal, it is possible to prevent omission and duplication of delivery of the broadcast message to the terminal.

  Furthermore, since there is a possibility that delivery to the terminal that is moving by handoff may be required, the mobile support station holds the broadcast message even after delivering the broadcast message to the currently connected terminal. However, this broadcast message cannot be discarded simply by delivering the broadcast message to the terminal currently connected to the mobile support station, but it can be sent to all terminals connected to the fixed network. Can not be disposed of without confirmation that it has been delivered. Therefore, in order to enable the mobile support station to determine that the received broadcast message can be discarded, each mobile support station transmits a broadcast message to be transmitted to another mobile support station. Vector data REDUCE for managing the number of broadcast messages transmitted from all terminals connected to the mobile support station, obtained from the RECV for the mobile terminal, is added. This vector data REDUCE also has a data amount proportional to the number of mobile support stations. Each mobile support station records the REDUCE received from all mobile support stations in RECV_RDC, determines a broadcast message that can be discarded from the information of this RECV_RDC, and discards the held broadcast message.

Tsutomu Ohori, et al., "Conservation and Preservation Broadcast Protocol for Distributed Mobile Systems", IEICE Transactions, The Institute of Electronics, Information and Communication Engineers, February 1999, Vol. J82-DI, No. 2, pp. 425-435

  However, in the communication method described in Non-Patent Document 1, it is necessary to add vector data SENT and REDUCE having a data amount proportional to the number of mobile support stations existing in the fixed network to the broadcast message transmitted by the mobile support station. For this reason, when the fixed network scale increases and the number of mobile support stations increases, the amount of vector data SENT and REDUCE added to the broadcast message increases, and the use efficiency of the network bandwidth becomes very poor. There was a problem.

  The present invention has been made in view of the above. Even when the size of the fixed network is increased and the number of mobile support stations is increased, the amount of vector data SENT and REDUCE added to a broadcast message is suppressed to a predetermined amount or less. It is an object of the present invention to obtain an order-storing broadcast communication method that can be used and a system that implements the method.

  In order to achieve the above object, according to the causal sequence preserving broadcast communication method according to the present invention, a sub-network including a predetermined number or less of mobile support stations that perform radio communication with a terminal is connected to three or more sub-networks. Causal order storage in a mobile support station of a communication system including a fixed network configured to be connected in a tree shape so as not to generate a mobile support station, and a terminal that performs radio communication with one of the mobile support stations of the fixed network In the broadcast communication method, when receiving a broadcast message from a terminal connected to the own station or from the own station, the transmission information indicating the context of the broadcast message and the erasable message information indicating the erasable broadcast message are Broadcasting process that is given to a broadcast message and broadcast, and when the broadcast message is received, the transmission information and the mobile support station have already delivered A delivery process of delivering the received broadcast message to the terminal connected to the own station and the terminal when the delivered information indicating the number of broadcast messages satisfying a predetermined condition is deliverable. In addition, the causal order in the terminal and the fixed network is stored and broadcast messages are broadcast, and in the delivery step, the mobile support station connected to two different sub-networks broadcasts from one sub-network. When a message is received, when the broadcast message is available for delivery, the message is delivered to the terminal connected to the local station and transmitted to the other subnetwork, and the broadcast message is received from the terminal connected to the local station or the local station. In the case, the broadcast message is simultaneously transmitted to both of the two sub-networks to transmit the two sub-networks. Becomes possible delivery in both, characterized in that delivery to the terminal and the own station to be connected to the own station.

  According to the present invention, the fixed network is configured such that a sub-network consisting of a predetermined number or less of mobile support stations is connected in a tree shape, and the conventional causal order-preserving broadcast communication is limited to within the sub-network. When transmitting a broadcast message, the amount of header information proportional to the number of mobile support stations attached to the broadcast message can be suppressed. In addition, a plurality of sub-networks generated by division are connected in a tree shape so that the maximum number of sub-networks to which the mobile support station connects is 2, and the mobile support stations connected to the two sub-networks are: When a broadcast message from one subnetwork is received, the other subnetwork is regarded as a terminal, and in the case of a broadcast message from the own station, two subnetworks are regarded as transmission targets, and the causal order is stored. Since the delivery process is executed, the causal order-preserving broadcast type communication can be guaranteed even in the entire tree-like fixed network.

  Exemplary embodiments of a causal order preserving broadcast communication method and system according to the present invention will be described below in detail with reference to the accompanying drawings.

Embodiment 1 FIG.
FIG. 1 is a diagram schematically showing a configuration of a causal order preserving broadcast communication system according to the present invention. The causal order preserving broadcast communication system is a mobile support station that performs wireless communication with a communication terminal 4 in a predetermined area using a predetermined wireless communication method, and performs a part of broadcast communication processing performed by the communication terminal 4. 2 are connected to each other, and a communication terminal (hereinafter referred to as a terminal) 4 that performs communication via the fixed network 3 is configured.

  In the present invention, the fixed network 3 is divided into a plurality of sub-networks SN, and the sub-networks SN have a hierarchical structure. Specifically, the fixed network 3 is divided into one or more sub-networks SN in which the number of mobile support stations 2 to which the mobile network 2 belongs is equal to or less than a predetermined value. It is configured to be connected to each other. At this time, only one type of the mobile support station 2 of the mobile support station 2a belonging to one sub-network SN or the mobile support station 2b belonging to two sub-networks SN should be present in the fixed network 3. And In this specification, when the mobility support station 2a belonging to one subnetwork SN and the mobility support station 2b belonging to two subnetworks SN need to be described separately, the former is referred to as the first mobility support. The latter will be referred to as a second mobile support station. In addition, it is assumed that the mobility support station 2 existing in the subnetwork SN recognizes what type of mobility support station 2 exists in the subnetwork SN.

  FIG. 2 is a block diagram schematically showing a schematic configuration of the terminal. The terminal 4 includes a broadcast communication calculation processing unit 41, a storage unit 42, a mobile support station communication processing unit 43, and an application process processing unit 44.

  The broadcast communication processing unit 41 is a terminal among the processes performed in the causal order preserving broadcast communication method in the causal order preserving broadcast communication system configured by connecting the sub-networks SN shown in FIG. 1 in a tree shape. 4 has a function of processing a portion to be executed.

  The storage unit 42 stores information used in the causal order preservation broadcast type communication executed by the terminal 4. In the present invention, SENDER_LIST, which is information related to the received broadcast message, is stored. SENDER_LIST is information composed of a set having a sender identifier and a sequence number maximum value assigned to a broadcast message received from the sender as elements. The initial value of SENDER_LIST is empty.

  The mobile support station communication processing unit 43 uses an ARQ (Automatic Repeat Request) technology such as an existing HLDC (High-level Data Link Control procedure) or PIAFS (Personal Handyphone System Internet Access Forum Standard). It has a function to guarantee that the receiving side receives the broadcast message transfer with the support station 2 in the order in which the transmitting side transmits without missing or overlapping.

  The application process processing unit 44 has a function of executing application processing on the terminal 4 using a broadcast message transmission / reception function.

  FIG. 3 is a block diagram schematically showing a schematic configuration of the mobility support station. The mobile support station 2 includes an inter-terminal communication processing unit 21 that performs processing of communication with the terminal 4, and an arithmetic process for broadcast communication that performs an operation for performing a broadcast message transmission process while maintaining a causal order storage relationship. Unit 22, a storage unit 23 that stores various information for executing communication that retains the causal order storage relationship, and a broadcast communication processing unit 24 that performs communication processing with other mobile support stations 2. It is prepared for.

  The inter-terminal communication processing unit 21 uses, for example, the existing ARQ technology such as HLDC or PIAFS, and the transmission side transmits the broadcast message between the terminal 4 and the mobile support station 2 without omission or duplication. The receiving side has a function of guaranteeing reception in the order.

  The broadcast communication arithmetic processing unit 22 is a causal order storage broadcast communication system configured by connecting the sub-networks SN shown in FIG. 1 in a tree shape, and performs causal order storage broadcast communication processing on the received broadcast message. It has a function.

  The storage unit 23 stores information used in the causal order storage broadcast communication executed by the mobile support station 2. The information stored in the storage unit 23 is data including MH, SENT, DELIV, and DELIV_MES used in the conventional causal order storage broadcast type communication of Non-Patent Document 1 in addition to SENDER_LIST. Below, these data are demonstrated. SENDER_LIST is information similar to the SENDER_LIST of the terminal 4 and is composed of a set having a sender identifier and a sequence number maximum value attached to a broadcast message received from the sender as elements. The MH is information indicating a set of identifiers of the terminals 4 connected to the mobility support station 2. There is one MH regardless of the number of sub-networks to which the mobility support station 2 is connected.

  SENT is vector information for managing the context of broadcast messages in each mobile support station 2. This SENT has the dimension of the number of elements of the mobility support station 2 in the subnetwork SN. In the second mobile support station 2b, when the two sub-networks SN connected to the second mobile support station 2b are sub-networks A and B, respectively, SENTa and SENTb are used to indicate which of the sub-networks A and B is data. Is described. The order of the vector information in this case is the number of mobility support stations on the subnetwork A and the number of mobility support stations on the subnetwork B, respectively. The initial value of this SENT data is 0. This SENT corresponds to the transmission information in the claims.

  DELIV is vector information that records the number of broadcast messages that have already been delivered from the mobile support station 2 that is each element of the mobile support station 2 in the subnetwork SN. This DELIV has a dimension of the number of elements of the mobility support station 2 in the subnetwork SN. In the second mobile support station 2b, DELIBa and DELIVb are described to indicate which of the sub-networks A and B is the data. The order of the vector information in this case is the number of mobile support stations on the network A and the number of mobile support stations on the network B, respectively. The initial value of this DELIV data is 0. This DELIV corresponds to the delivered information in the claims.

  DELIV_MES is a queue that stores broadcast messages already delivered by the mobile support station 2 in the order of delivery. The initial value is empty. There is one DELIV_MES regardless of the number of sub-networks to which the mobility support station 2 is connected. This DELIV_MES corresponds to broadcast message storage information.

  The broadcast communication processing unit 24 has a function of guaranteeing that the receiving side receives the transfer of the broadcast message between the mobile support stations in the order in which the transmitting side has transmitted without omission or duplication. In order to realize such a function, for example, Reliable Multicast Transport Protocol discussed in IETF (Internet Engineering Task Force) can be used. The causal order-preserving broadcast type communication is not limited to the order relationship between broadcast messages transmitted from one mobile support station 2, but also within a certain range of order relationships between broadcast messages transmitted from a plurality of different mobile support stations 2. The causal order preserving broadcast communication cannot be realized only by the function of the broadcast communication processing unit 24, and can be realized together with other processing units.

  Next, processing by the terminal 4 and the movement support station 2 in the system having such a configuration will be described. Similarly to the conventional communication method described in Non-Patent Document 1, the terminal 4 transmits cbcast (broadcast message) processing that transmits a broadcast message using a causal order storage broadcast communication protocol, and receives (moves) the broadcast message from the transmission source. (Support station, broadcast message) processing. FIG. 4 is a flowchart showing a procedure of broadcast message transmission processing (cbcast processing) by the terminal. When the terminal 4 transmits a broadcast message, the broadcast message to be transmitted is transmitted to the mobile support station 2 to which the terminal 4 is currently connected (step S41), and the broadcast message transmission process ends. Note that a broadcast message to be transmitted is given a sequence number that is incremented by a serial number and an identifier for identifying the broadcast message transmitted by the broadcast message.

  FIG. 5 is a flowchart illustrating a procedure of a broadcast message reception process (receive process) by the terminal. When the terminal 4 receives a broadcast message from the mobile support station 2 (step S51), it is determined whether or not the broadcast message has already been received using the SENDER_LIST data from the sender and sequence number of the broadcast message (step S52). To S53). That is, it is determined whether or not duplicate transmission is performed from the sender and the sequence number. As a result of the determination, if it has been received (Yes in step S53), the received broadcast message is discarded because it is duplicate reception (step S54), and the process ends. On the other hand, if it has not been received (No in step S53), broadcast message reception processing is performed (step S55). Further, the set of the sender and sequence number of the received broadcast message is added to SENDER_LIST (step S56), and the reception process ends. The broadcast message transmitted by the terminal 4 or the mobile support station 2 includes an identifier indicating the terminal 4 or the mobile support station 2 that is the transmission source of the broadcast message, and a sequence number assigned by the transmission source.

  On the other hand, each mobile support station 2 in one subnetwork SN according to the first embodiment performs processing based on the causal order storage broadcast protocol shown in Non-Patent Document 1 of the prior art, It is limited to the subnetwork SN to which the mobility support station 2 belongs. Therefore, the dimension of the vector that the mobile support station 2 adds to each broadcast message is the number of mobile support stations 2 in the subnetwork SN.

  In addition, in order to enable broadcasting with the causal order preserved even in the entire fixed network 3, it is necessary to cause the second mobile support station 2b to execute processing different from that of the normal first mobile support station 2a. The second mobile support station 2b connected to the two sub-networks A and B regards the broadcast message to be transmitted / received on the sub-network A, regards the sub-network B as a terminal connected to the own station, and transmits / receives on the sub-network B. For broadcast messages to be transmitted, the sub-network A is regarded as a terminal connected to the own station, and for broadcast messages transmitted and received by the terminal 4 connected to the own station, both the sub-networks A and B are set as separate transmission targets. I do.

  That is, when the second mobile support station 2b receives a broadcast message from the sub-network A, when the SENT and DELIV satisfy a predetermined condition and the broadcast message can be delivered, the terminal 4 connected to its own station The broadcast message is transmitted to the network B at the same time as transmitting the broadcast message. Then, a set of (SENT, vector of all elements 0, broadcast message given when received in subnetwork A) is added to DELIV_MES. When a broadcast message is received from the subnetwork B, when the SENT and DELIV satisfy a predetermined condition and the broadcast message can be delivered, the broadcast message is transmitted to the terminal 4 connected to the own station, A broadcast message is also transmitted to the network A. Then, a set of (vector of all elements 0, SENT given when received by subnetwork B, broadcast message) is added to DELIV_MES. Further, in the case of a broadcast message from the terminal 4 connected to the own station or a broadcast message transmitted by the own station, both sub-networks A and B can be individually transmitted and can be delivered to both sub-networks A and B. For the first time, delivery to the terminal 4 connected to the own station is enabled. Then, a set of (SENT given when transmitted in the subnetwork A, SENT given when transmitted in the subnetwork B, broadcast message) is added to DELIV_MES.

  By causing the second mobile support station 2b to execute the delivery process in this way, the terminal performs causal order preservation broadcasting communication not only in the subnetwork SN but also in the entire fixed network 3 including the set of subnetworks SN. Make it possible.

  According to the first embodiment, the fixed network 3 is divided into sub-networks SN composed of a predetermined number or less of the mobility support stations 2, and the mobility support station 2 connects a plurality of sub-networks SN generated by the division. When the second mobile support station 2b connected to the two sub-networks SN receives a broadcast message from one of the sub-networks SN while being connected in a tree shape so that the number of sub-networks SN is two at the maximum Since the other sub-network SN is regarded as a terminal and in the case of a broadcast message from the own station, the two sub-networks SN are regarded as transmission targets, and the delivery process storing the causal order is executed. Even in the entire fixed network 3, the causal order-preserving broadcast type communication can be guaranteed. In addition, since the plurality of sub-networks SN are connected in a tree shape and the conventional causal order-preserving broadcast type communication is limited to within the sub-network SN, the mobile support station 2 attached to the broadcast message when transmitting the broadcast message The amount of header information proportional to the number of headers can be suppressed.

Embodiment 2. FIG.
In the first embodiment, the causal order preserving broadcast communication method that does not consider the handoff of the terminal has been described. Therefore, in the second embodiment, a causal order preserving broadcast communication system that supports terminal handoff will be specifically described. This second embodiment will also be described using the network configuration shown in FIG. However, the terminal 4 is a communication terminal capable of wireless communication while moving.

  In addition to the DELIV, SENT, RECV, RECV_RDC, REDUCE, WAITING, DELIV_MES, and MOVING data used in the conventional causal order preserving broadcast type communication of Non-Patent Document 1, the storage unit 23 of the mobile support station 2 In the present invention, RECV_A, RECV_B, RECLIST_A, and RECLIST_B data for enabling handoff of the terminal 4 are stored. Below, the data which did not come out in Embodiment 1 among these data are demonstrated.

  RECV is vector information for managing the number of broadcast messages delivered by each terminal 4 connected to each mobile support station 2, and is a normal mobile support station (mobile support connected to only one subnetwork SN). Only station 2a holds. This RECV has the dimension of the number of elements of the mobility support station 2 existing in the subnetwork SN to which it belongs.

  RECV_A and RECV_B are data similar to the RECV and are data used only by the second mobility support station 2b. RECV_A is a mobile support station 2 existing in a subnetwork group beyond subnetwork B as data used for performing causal order-preserving broadcast type communication on subnetwork A, and terminals connected to those mobile support stations 2 4 is vector information for recording information relating to broadcast messages received on the subnetwork A that have been delivered. This RECV_A has the order of the number of mobile support stations on the subnetwork A. Similarly, RECV_B is used as data used for performing causal order-preserving broadcast-type communication on the subnetwork B, and the mobile support stations 2 existing in the subnetwork group beyond the subnetwork A and the mobile support stations 2 thereof. This is vector information for recording information related to a broadcast message received on the subnetwork B that has been delivered to the terminal 4 to be connected. This RECV_B has the order of the number of mobile support stations on the subnetwork B. These RECV-A and RECV-B become broadcast message information that is guaranteed to be delivered due to the effect of hierarchization by the sub-network SN, and in reality there is a possibility that more broadcast messages have already been delivered. However, in the steady state, RECV-A and RECV-B match the information of the broadcast message that has actually been delivered. Since the use purpose of RECV-A and RECV-B has already been delivered to all the terminals 4 and the mobile support station 2, it is an input for determining a broadcast message that can be discarded. It is not inconvenient for the broadcast message to be treated as undelivered.

  The REDUCE is vector information for managing the number of broadcast messages that have been delivered by all the terminals 4 connected to the mobile support station 2. This REDUCE has the dimension of the number of elements of the mobility support station 2 existing in the subnetwork SN to which it belongs. In the second mobile support station 2b, REDUCEa and REDUCEb are described to indicate which of the sub-networks A and B is the data. The order of the vector information in this case is the number of mobile support stations on the network A and the number of mobile support stations on the network B, respectively. This REDUCE corresponds to deleteable message information in the claims.

  RECV_RDC is arrangement information for managing REDUCE received by each mobile support station 2 and represents broadcast message information that can be deleted from DELIV_MES among broadcast messages received from other mobile support stations 2.

  WAITING is information indicating a broadcast message received by the mobile support station 2 but postponed in order to maintain the causal order and held in the buffer. In the second mobility support station 2b, data received from each of the two sub-networks A and B and data received from the terminal 4 connected to the own station or from the own station are managed separately. In this specification, WAITINGa, WAITINGb, and WAITINGs are respectively described in order to indicate data for any of the sub-networks A and B and the own station (terminal connected to the own station).

  The MOVING is an identifier of the terminal 4 that has been handed off from its own station but has not confirmed the connection with the mobile support station 2 that is the handoff destination, and a RECV for the terminal 4 (in the case of the second mobile support station 2b, This is information consisting of a set whose elements are two sets of RECV_A and RECV_B. The initial value is empty, and there is one regardless of the number of subnetworks SN to which the mobility support station 2 is connected.

  RECLIST-A and RECLIST-B are information used only in the second mobility support station 2b. RECLIST-A is a list that records a set of SENTa to be given to the broadcast message when transmitting a broadcast message to the subnetwork A and DELIVb on the subnetwork B side at that time. RECLIST-B is a list that records a set of SENTb to be given to the broadcast message when transmitting a broadcast message to the subnetwork B and DELIVa on the subnetwork A side at that time. These RECLIST-A and RECLIST-B are used to update RECV-A and RECV-B.

  Here, the processing performed by the terminal 4 and the mobile support station 2 in the causal order preserving broadcast communication system corresponding to the handoff of the terminal 4 will be described. As processing performed by the terminal 4, in addition to the processing described in the first embodiment, a disconnection (mobile support station) process for disconnecting from the currently connected mobile support station and starting handoff, and a mobile support station after handoff And a connect (mobile support station) process for completing the handoff.

  FIG. 6 is a flowchart illustrating a procedure of processing (disconnect processing and connect processing) when the terminal performs handoff. For example, when the terminal 4 moves in FIG. 1 to handoff from the currently connected mobile support station 2a-1 to another mobile support station 2b-1, the terminal 4 is connected to the currently connected mobile support station 2a-1. Is disconnected (step S61), and it is confirmed whether or not it is connected to the new mobility support station 2b-1 after movement (step S62). It will be in a waiting state until it can connect with the new movement assistance station 2b-1 (in the case of No at step S62). After that, when a new connection is made with the mobile support station 2b-1 (Yes in step S62), the mobile support station 2b-1 newly connected is notified of its own terminal identifier information (step S63). The process waits until there is a communication permission from the mobile support station 2b-1 (in the case of No in step S64). At this time, the transmission of the broadcast message from the terminal 4 to the new mobile support station 2b-1 is stopped. When there is a communication permission from the new mobile support station 2b-1 (Yes in step S64), the processing at the time of handoff of the terminal 4 is completed, and the broadcast message to the new mobile support station 2b-1 thereafter. Can be transmitted.

  As processing of one mobile support station 2, cbcast (broadcast message) processing for transmitting a broadcast message by a causal order storage broadcast communication protocol, receive (transmission source [terminal or mobile support station], receiving a broadcast message from the transmission source, Broadcast message) process, remove (terminal) process performed when the terminal connected to the local station starts handoff and disconnects from the local station, the new terminal completes the handoff, There is an accept (terminal) process for the connection to the station.

  FIG. 7 shows the procedure of the broadcast request process (cbcast process) executed when the second mobile support station itself connected to the two sub-networks becomes a transmission source and transmits a broadcast message using the causal order storage broadcast communication protocol. It is a flowchart which shows an example. First, when the second mobile support station 2b transmits a broadcast message to the subnetwork A, the second mobile support station 2b is included in the vector information SENTa having the order of the number of mobile support stations belonging to the subnetwork A, and RECV-A, DELIVA, and MOVING. REDUCEa, which is the minimum value of RECV-A, is added to the broadcast message, and the broadcast message is transmitted to the subnetwork A (step S71).

  Similarly, when the second mobile support station 2b transmits a broadcast message to the subnetwork B, the second mobile support station 2b includes the vector information SENTb whose order is the number of mobile support stations belonging to the subnetwork B, and RECV-B, DELIVb, and MOVING. REDUCEb, which is the minimum value of RECV-B, is added to the broadcast message, and the broadcast message is transmitted to the sub-network B (step S72).

  Note that RECV-A is used as an input for calculating the vector REDUCE to be added to the broadcast message transmitted by the second mobile support station 2b in steps S71 and S72, when RECV-A is transmitted on the subnetwork A. At the time of transmission on B, RECV_B is added to obtain REDUCE, thereby preventing the undelivered broadcast message from being discarded on the other subnetwork.

  Next, the delivery possibility of whether or not the broadcast message broadcast by the second mobile support station 2b, which is the own station, can be delivered to the own station is checked (step S73). Then, when the second mobile support station 2b transmits the broadcast message to the subnetwork A, the SENTa assigned to the broadcast message and the number of mobile support stations belonging to the subnetwork B on the subnetwork B side at that time A set of vector information DELIVb (SENTa, DELIVb) having the order of is added to RECLIST-A. Similarly, when the second mobile support station 2b transmits a broadcast message to the subnetwork B, SENTb to be given to the broadcast message and the number of mobile support stations belonging to the subnetwork A on the subnetwork A side at that time A set of vector information DELIVa (SENTb, DELIVa) having the order of is added to RECLIST-B (step S74). Thus, the broadcast message transmission process by the second mobile support station 2b is completed.

  FIG. 8 is a flowchart showing the procedure of the delivery possibility check process and the delivery process in step S73 of FIG. This process is executed when an event of ireceive (SENTa, SENTb, broadcast message) occurs. First, the second mobile support station 2b determines whether or not it is possible to deliver a broadcast message to itself (step S81). Whether delivery is possible is determined according to the algorithm described in Non-Patent Document 1 using SENT and DELIV. Here, it is determined that delivery is possible when the SENT of a certain mobile support station becomes DELIVa + 1 of the mobile support station and the SENT other than the mobile support station is equal to or lower than DELIVa other than the mobile support station. . As a result, when delivery is not possible (No in step S81), a broadcast message to be transmitted is added to WAITINGa (step S82), and the process returns to step S74 and subsequent steps in FIG.

  If the second mobile support station 2b can deliver the broadcast message to itself in step S81 (Yes in step S81), the other mobile support station 2 notifies that the terminal 4 is handed off. It is determined whether or not a movement notification message has been received (step S83). If the movement notification message has not been received (No in step S83), a broadcast message is transmitted to the terminal 4 connected to the own station (step S84), and the process returns to step S74 and subsequent steps in FIG. Further, when the movement notification message is received (Yes in step S83), an accept process for giving communication permission to the terminal 4 that has handed off is performed (step S85), and the processes after step S74 in FIG. Return.

  FIG. 9 is a flowchart showing the procedure of the accept process in step S85 of FIG. First, when the second movement support station 2b receives a movement notification message from another movement support station 2, the second movement support station 2b confirms that the terminal corresponding to the movement notification message exists in its own station, and moves about the terminal that has moved. A confirmation message is transmitted (step S91). Next, the information of the terminal 4 stored in the movement notification message is added to MH which is information indicating the set of terminals 4 connected to the own station (step S92). Then, communication permission is given to the terminal 4 that has handed off, an undelivered broadcast message in DELIV_MES specified from the RECV included in the movement notification message described later is transmitted to the terminal (step S93), and the accept process ends.

  In the description of FIGS. 7 to 9 described above, the broadcast message transmission processing by the second mobile support station 2b connected to the two sub-networks has been described. However, the terminal to which the second mobile support station 2b connects to the own station. The same processing is performed when a message is received from 4.

  Next, a broadcast message transmission process of the first mobile support station 2a connected to one subnetwork will be described. FIG. 10 shows a procedure of broadcast request processing (cbcast processing) executed when the first mobile support station itself connected to one sub-network is a transmission source and transmits a broadcast message using a causal order storage broadcast communication protocol. It is a flowchart which shows an example. First, when the first mobile support station 2a transmits a broadcast message to the subnetwork to which the first mobile support station 2a belongs, the first mobile support station 2a includes the vector information SENT having the order of the number of mobile support stations belonging to the subnetwork, and RECV, DELIV, and MOVING. REDUCE, which is the minimum value of RECV, is added to the broadcast message (step S101). Then, the broadcast message is transmitted to the sub-network (step S102), and the process ends. In the description of FIG. 10 described above, the transmission process of the broadcast message by the first mobile support station 2a connected to one subnetwork has been described. However, the first mobile support station 2a sends a message from the terminal 4 connected to the own station. The same processing is also performed when receiving.

  Next, processing of the received broadcast message (receive processing) by the second mobility support station 2b located at the connection point of the two sub-networks SN will be described. FIG. 11 is a flowchart illustrating an example of a procedure for receiving a broadcast message from the subnetwork A by the second mobile support station. When the second mobile support station 2b receives the broadcast message from the subnetwork A (step S111), the second mobile support station 2b uses the vector REDUCE (having the order of the number of mobile support stations in the subnetwork A) indicated in the broadcast message. The RECV_RDCA for the subnetwork A is updated by the same method as in step 1 (step S112). Specifically, the largest of REDUCD and RECV_RDCA is RECV_RDCA for subnetwork A. Next, a vector MIN_RA (having the order of the number of mobility support stations in subnetwork A) having the minimum value of each element of the vector included in RECV_RDC as an element is obtained (step S113). Thereafter, a set of (SENTa, DELIVb) including the maximum SENTa that is equal to or smaller than MIN_RA among the set of (SENTa, DELIVb) included in RECLIST-A is obtained. The value of RECV-B is updated with (the order of the number of B mobile support stations) (step S114).

  Next, the second mobile support station 2b determines whether or not the transmission source of the received broadcast message is another mobile support station 2 of the subnetwork A (step S115). If the transmission source of the broadcast message is another mobile support station 2 of the sub-network A (Yes in step S115), a broadcast message delivery process is performed (step S116), and WAITINIGa, If broadcast messages held in WAITINGb and WAITINGs can be delivered, the broadcast messages are delivered (step S117).

  Next, the second mobility support station 2b obtains a vector MIN_RB having the order of the number of mobility support stations in the subnetwork B having the minimum value of each element of the vector included in the RECV_RDC for the subnetwork B (step S118). . Then, in the set of (mobile support station, SENTa, SENTb, broadcast message) included in DELIV_MES, processing that deletes from DELIV_MES those in which SENTa is MIN_RA or less and SENTb is MIN_RB or less is performed (step S119), the processing of the received broadcast message ends.

  FIG. 12 is a flowchart showing a detailed procedure of broadcast message delivery processing in step S116 of FIG. This broadcast message delivery process is performed by the occurrence of an event of a deliver_check (mobile support station, SENT, broadcast message). First, the second mobile support station 2b determines whether or not the received broadcast message can be delivered (step S131). As in the case of step S81 in FIG. 8, the determination as to whether or not the delivery is possible is made such that the SENT of a certain mobile support station becomes DELIVa + 1 of the mobile support station and the SENTs other than the mobile support station receive the mobile support station. It is determined that delivery is possible when the DELIVa is less than or equal to. As a result, when delivery is not possible (No in step S131), since it is a broadcast message received from the subnetwork A, the second mobile support station 2b adds the broadcast message to WAITINGa (step S132). ), Returning to FIG. 11, the processing from step S117 is performed. On the other hand, if the received broadcast message is deliverable (Yes in step S131), it is further determined whether or not it is a broadcast message transmitted by the own station (step S133). If the broadcast message is transmitted by the own station (Yes in step S133), the process returns to FIG. However, if it is not a broadcast message transmitted by the own station (No in step S133), it is determined whether a movement notification message has been received from another movement support station 2 (step S134).

  When a movement notification message is received from another mobile support station 2 (Yes in step S134), the second mobile support station 2b gives communication permission to the terminal 4 that has handed off and is held in DELIV_MES. Messages are transmitted to the terminal 4 in the order of delivery (step S135). In addition, a movement confirmation message for the movement notification message is transmitted as a broadcast message (step S136). On the other hand, when a movement notification message is not received from another movement support station 2 (No in step S134), the received broadcast message is transmitted to the terminal 4 connected to the own station (step S137). . After step S136 or step S137, the second mobile support station 2b adds SENTb and REDUCEb, which is the minimum value of RECV-B included in RECV-B, DELIVb, and MOVING, to the broadcast message. It transmits to the network B (step S138). Then, a set of (SENTb, DELIVa) is added to RECLIST-B (step S139), and the processing after step S117 is performed by returning to FIG.

  When the second mobile support station 2b receives a broadcast message from the subnetwork B, in the processes of FIGS. 11 to 12, a process of replacing the subnetwork B, the subnetwork A, and variables related thereto may be performed. In addition, the mobile support station 2 that has received the broadcast message receives information on which mobile support station is the mobile support station that transmitted the transmission message, in addition to the transmission source indicated (stored) in the broadcast message. .

  Next, the broadcast message reception process of the first mobile support station 2a connected to one subnetwork will be described. FIG. 13 is a flowchart showing the procedure of the broadcast message reception process (receive process) of the first mobile support station. First, the first mobile support station determines whether or not the received broadcast message can be delivered (step S151). As in the case of step S81 in FIG. 8, the determination as to whether or not the delivery is possible is made such that the SENT of a certain mobile support station becomes DELIVa + 1 of the mobile support station and the SENTs other than the mobile support station receive the mobile support station. It is determined that delivery is possible when the DELIVa is less than or equal to. As a result, if delivery is not possible (No in step S151), the received broadcast message is added to WAITING (step S152). On the other hand, if the received broadcast message is deliverable (Yes in step S151), it is further determined whether or not a movement notification message has been received from another mobile support station 2 (step S153).

  When a movement notification message is received from another mobility support station 2 (Yes in step S153), the first mobility support station 2a gives communication permission to the terminal 4 that has handed off and is held in DELIV_MES. Messages are transmitted to the terminal 4 in the order of delivery (step S154). In addition, a movement confirmation message for the movement notification message is transmitted as a broadcast message (step S155). On the other hand, when a movement notification message is not received from another mobile support station 2 (No in step S153), the received broadcast message is transmitted to all terminals 4 connected to the own station (step S153). S156). After step S152, S154, or step S156, the first mobile support station 2a performs the above-described steps S151 to S156 on the broadcast message included in WAITING to deliver a deliverable broadcast message (step S157). ). Then, MIN_R having the minimum value of each element of the vector included in RECV_RDC as an element is calculated (step S158), and DELIV_MES (mobile support station, SENT, m) having SENT less than MIN_R is deleted. (Step S159), the broadcast message reception processing by the first mobile support station 2a is completed.

  Next, processing of the mobile support station (remove processing) that is performed when a terminal connected to the mobile support station 2 moves away from the mobile station by handoff will be described with reference to the flowchart of FIG. When the movement support station 2 detects that the terminal 4 to be connected moves away from its own station by handoff, the information on the terminal 4 that moves is removed from the MH (step S171), and the broadcast message that has been delivered for the terminal is removed. The number RECV (RECV-A, RECV-B) is added to MOVING (step S172). For example, the first mobile support station 2a adds (terminal, RECV) to MOVING, and the second mobile support station 2b adds (terminal, RECV-A, RECV-B) to MOVING.

  Next, the mobility support station 2 transmits a movement notification message including an identifier indicating the moving terminal 4 and an identifier indicating its own station as a broadcast message of causal order preserving broadcast type communication (step S173). The movement support station 2 transmits a movement notification message transmitted as a causal order preserving broadcast type broadcast message in the same procedure as the normal causal order preserving broadcast type communication message shown in FIGS. However, when the movement notification message is transmitted, the message is not delivered to the terminal 4 but delivered only to the movement support station 2.

  Thereafter, when the terminal 4 starts connection with a new mobility support station and a movement confirmation message is delivered from the new mobility support station to itself (step S174), the mobility support station 2 assumes that the movement of the terminal is completed. The information of the terminal 4 that has moved from MOVING is deleted (step S175). Thus, the process associated with the handoff of the terminal 4 at the mobile support station 2 where the terminal 4 has been separated ends.

  Next, the process of the mobile support station 2 performed when the terminal 4 connected to another mobile support station 2 connects to the local station by handoff will be described. In this invention, when the movement support station 2 detects that a new terminal 4 has newly connected to its own station as a result of handoff, the movement notification message including the identifier of the terminal 4 is delivered to its own station. In the meantime, communication permission is not given to the terminal 4, and broadcast message delivery to the terminal 4 and transfer processing of the broadcast message transmitted by the terminal 4 are not performed.

  FIG. 15 is a flowchart showing a processing procedure of the mobility support station when a new terminal is connected to the local station as a result of handoff. When the movement support station 2 has detected that a new terminal 4 has newly connected to its own station as a result of handoff, it has already received a movement notification message including the identifier of the terminal 4 or the terminal 4 When a movement notification message including the identifier of the terminal 4 is received after connecting to the own station (step S181), the movement including the identifier of the terminal 4 indicated in the received movement notification message and the identifier of the movement support station that is the source of the movement notification message The confirmation message is transmitted as a causal order storage broadcast type broadcast message (step S182). At this time, the mobile support station 2 transmits the movement confirmation message in the same procedure as the broadcast message of the normal causal order preservation broadcast type communication shown in FIGS. 7 to 9, but delivers only to the mobile support station 2, It is not delivered to the terminal 4. Then, communication permission is given to the terminal 4 that has moved (step S183), and all broadcast messages included in the DELIV_MES of the local station are delivered to the terminal 4 in the order added to the DELIV_MES (step S184). The process performed by the mobile support station 2 is completed. Thereafter, the broadcast message newly delivered by the mobile support station 2 is also delivered to the terminal 4 and the transfer process of the broadcast message transmitted by the terminal 4 is also performed.

  On the other hand, when the movement support station 2 receives the movement notification message, if the terminal 4 that has been handed off to the local station and is currently connected and there is no terminal 4 that has not received the corresponding movement notification message, the movement support station 2 receives the movement notification message. The movement notification message is recorded in the storage unit 23, and the movement confirmation message corresponding to the movement notification message from another movement support station 2 is delivered to the own station when the corresponding terminal 4 has handed off to the own station. If this happens, the recorded movement notification message is discarded.

  By the way, in the conventional communication method described in Non-Patent Document 1, when a terminal is handed off, omission and duplication of broadcast messages delivered to the moving terminal are avoided, and the causal order of the broadcast messages transmitted by the moving terminal is not preserved. For the purpose of avoiding the problem, the mobile support station connected to the terminal before the handoff from the mobile support station connected to the terminal after the handoff to the mobile support station connected after the handoff (one-to-one communication) Data and SENT data when the terminal is moved). The RECV data for the moved terminal is used to avoid missing and duplicated broadcast messages delivered to the moving terminal, and the SENT data at the time of moving the terminal is the causal order of broadcast messages transmitted by the moving terminal. It is used to avoid storage.

  However, in the present invention, when the fixed network 3 is divided into sub-networks SN that are coupled in a tree shape, a case where a terminal handoffs between mobile support stations belonging to different sub-networks SN occurs. In this case, if the method of Non-Patent Document 1 is applied as it is, the exact values of the RECV data for the moved terminal and the SENT data at the time of moving the terminal are changed from the movement support station of the movement source to the movement support station of the movement destination. Cannot be transferred to.

  As for RECV data, it is possible to guarantee that a broadcast message that has already been delivered to the mobile terminal is actually delivered to the mobile terminal, even if the broadcast message that has already been delivered to the mobile terminal is treated as not being delivered. If it is possible to transfer information on what a broadcast message is, it is possible to avoid missing broadcast messages. This is because by adding RECV-A and RECV-B and correcting the REDUCE value accordingly, a broadcast message that may be undelivered to the moving terminal is stored in DELIV_MES of the movement support station of the moving destination. It is satisfied by being guaranteed. For duplicate avoidance, each sender assigns a sequence number to the broadcast message and manages the received sequence number for each sender on the terminal side, thereby performing duplicate reception detection processing on the terminal side. This is possible. As described above, it is possible to avoid omission and duplication of broadcast messages for a moving terminal.

  For SENT data, for the purpose of using SENT data, a value that is greater than or equal to the SENT data given by the destination subnetwork SN to the broadcast message transmitted by the mobile terminal is transmitted to the destination mobile support station, It is sufficient if it is reflected in the SENT data of the destination mobile support station. As shown in the second embodiment, this condition can be satisfied by transmitting a movement notification message as a broadcast message of causal order preserving broadcast communication at the time of handoff of the terminal.

  According to the second embodiment, the fixed network 3 that performs causal order-preserving broadcast communication considering the mobility of the terminal 4 is divided into sub-networks SN and the Cebu networks SN are connected in a tree shape. Even if the number of mobile support stations 2 constituting the fixed network 3 increases, the amount of vector data that needs to be added to the broadcast message can be suppressed to a predetermined amount or less. As a result, there is an effect that the use efficiency of the network bandwidth can be suppressed even if the scale of the fixed network 3 is increased.

  In the networks of the first and second embodiments, the multicast message transmitted by the terminal 4 is transferred between the mobility support stations 2 as a causal order storing broadcast message, thereby enabling the causal order storing multicast communication by the terminal 4. be able to.

  As described above, the causal order preserving broadcast communication method and system according to the present invention broadcast information that needs to be communicated by storing the context of system monitoring, resource allocation, electronic news, electronic conference, etc. Suitable for

It is a figure which shows typically the structure of the causal order preservation | save broadcast type | mold communication system by this invention. It is a block diagram which shows typically schematic structure of a terminal. It is a block diagram which shows typically schematic structure of a movement assistance station. It is a flowchart which shows the procedure of the transmission process of the broadcast message by a terminal. It is a flowchart which shows the process sequence in which a terminal receives a broadcast message. It is a flowchart which shows the process sequence at the time of a terminal handing off. It is a flowchart which shows an example of the process sequence which a 2nd mobility support station becomes a transmission source and transmits a broadcast message. It is a flowchart which shows the procedure of the delivery possibility check process and delivery process in step S73 of FIG. It is a flowchart which shows the procedure of the accept process in step S85 of FIG. It is a flowchart which shows an example of the procedure of the transmission process of the broadcast message by a 1st mobile assistance station. It is a flowchart which shows an example of the procedure of the reception process of the broadcast message by a 2nd movement assistance station. 12 is a flowchart showing a detailed procedure of broadcast message delivery processing in step S116 of FIG. It is a flowchart which shows an example of the procedure of the reception process of the broadcast message by a 1st mobile assistance station. It is a flowchart which shows the process sequence of the movement assistance station performed when the terminal connected to a movement assistance station leaves | separates from an own station by handoff. It is a flowchart which shows the process sequence of the movement assistance station when a new terminal has connected to the local station as a result of handoff.

Explanation of symbols

2 Mobile support station,
2a The first mobile support station,
2b Second mobility support station,
3 fixed network,
4 Terminal.

Claims (10)

A fixed network configured by connecting sub-networks of a predetermined number or less of mobile support stations that perform radio communication with terminals in a tree shape so as not to generate mobile support stations connected to three or more sub-networks; A causal order-preserving broadcast communication method in a mobile support station of a communication system comprising a mobile communication station with any mobile support station of the fixed network,
When receiving a broadcast message from a terminal connected to the local station or the local station, transmission information indicating the context of the broadcast message and deletable message information indicating a deletable broadcast message are added to the broadcast message and broadcast. Broadcasting process,
When the broadcast message is received, when the transmission information and the delivered information indicating the number of broadcast messages delivered by the mobile support station satisfy the predetermined condition and can be delivered, the received broadcast message is automatically received from the own station. A delivery process to deliver to a terminal connected to the station;
And a broadcast message broadcast to save the causal order in the terminal and the fixed network,
Furthermore, in the delivery process, when the mobile support station connected to two different sub-networks receives a broadcast message from one of the sub-networks, the mobile support station delivers the message to the terminal connected to the local station when the broadcast message can be delivered. When the broadcast message is received from a terminal connected to the own station or from the own station and transmitted to the other subnetwork, the broadcast message is simultaneously transmitted to both of the two subnetworks. A causal order-preserving broadcast communication method, characterized in that, when delivery is possible in both, a terminal connected to the own station and delivery to the own station. In the delivery process, the broadcast messages that have been delivered are stored in the order of delivery,
The mobile support station connected to the two sub-networks extracts a broadcast message that can be deleted using the transmission information, the delivered information, and the message information that can be deleted, and extracts the extracted broadcast message from the stored broadcast message. The causal order preservation broadcast type communication method according to claim 1, further comprising a deletion step of deleting. When a terminal connected to the first mobile support station on the fixed network moves to the second mobile support station on the fixed network,
When the first mobile support station detects that a terminal connected to the mobile station is moving away from the mobile station, the mobile support station excluding the mobile terminal sends a mobile notification message including information identifying the terminal and the mobile station. A movement notification message transmission step of transmitting as a causal order storage broadcast type broadcast message;
A notification message holding step in which another movement support station holds the received movement notification message;
The second mobile support station is
Upon detecting the connection of the terminal to its own station and receiving the movement notification message, a movement confirmation message that is a response to the movement notification message is transmitted as a causal order-preserving broadcast-type broadcast message to the movement support station other than the terminal. A movement confirmation message sending step to perform,
A storage message delivery step of giving a communication permission to the terminal and delivering a delivered broadcast message stored in the local station to the terminal;
The causal order preserving broadcast communication method according to claim 2, further comprising:   The information processing apparatus further includes a notification message discarding step of discarding the movement notification message when the other movement support station without a handoff of a terminal corresponding to the received movement notification message receives the movement confirmation message. Item 4. The causal order preserving broadcast communication method according to Item 3.   5. The causal order-preserving broadcast communication method according to claim 1, wherein the multicast message transmitted by the terminal is transmitted as the broadcast message in the fixed network. A fixed network configured by connecting sub-networks including a predetermined number or less of mobile support stations that perform radio communication with terminals in a tree shape so that no mobile support stations connected to three or more sub-networks are generated. A causal order storage broadcast communication system comprising a terminal that performs wireless communication with any mobile support station of the fixed network, and performs causal order storage broadcast communication,
When a mobile support station connected to two different sub-networks receives a broadcast message from one sub-network, when the broadcast message becomes deliverable, the mobile support station delivers the message to the terminal connected to its own station and the other sub-network. When a broadcast message is received from a terminal connected to the local station or from the local station, the broadcast message is simultaneously transmitted to both of the two sub-networks and can be delivered to both of the two sub-networks. In other words, a causal order-preserving broadcast communication system comprising a terminal connected to the own station and broadcast processing means for delivering to the own station. The mobile support station connected to the two sub-networks is
Broadcast messages that store transmission information that indicates the context of broadcast messages and delivery information that indicates the number of broadcast messages that have been delivered by the mobile support station for each subnetwork connected to the local station, and store delivered broadcast messages in the order of delivery Storage means for storing storage information and removable message information representing a removable broadcast message;
The broadcast processing means extracts a broadcast message that can be deleted so as not to delete an undelivered broadcast message on one subnetwork side using the transmission information, the delivered information, and the deleteable message information, The causal order preserving broadcast communication system according to claim 6, further comprising a function of deleting from broadcast message storage information. The broadcast processing means of the mobile support station is
When detecting that a terminal connected to the own station is moving away from the own station, a movement notification message including information for identifying the terminal and the own station is transmitted to the movement support station excluding the terminal as a causal order preserving broadcast type broadcast message. The ability to send,
When a movement notification message received from another mobility support station is received, it is temporarily stored in the storage means, and when a connection of the terminal corresponding to the movement notification message to its own station is detected, a movement confirmation message for the movement notification message A function to transmit the message as a causal order-preserving broadcast type broadcast message to a mobile support station other than the terminal,
Further comprising
8. The inter-terminal communication processing means for granting communication permission to the terminal and delivering a broadcast message constituting broadcast message storage information stored in the storage unit to the terminal. The causal order preservation broadcast type communication system.   The broadcast processing unit of the mobile support station further includes a function of discarding the mobile notification message from the storage unit when receiving a movement confirmation message from another mobile support station for the mobile notification message. The causal order preservation | save broadcast type | mold communication system of Claim 8.   The broadcast processing unit of the mobile support station further includes a function of transmitting a multicast message transmitted by the terminal as the broadcast message in the fixed network. The causal order preserving broadcast communication system described in 1.

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