JP2009212954A - Wireless network system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To easily increase the number of terminals to be accommodated in a network by improving a frequency use efficiency, with respect to a wireless network system using multihop. <P>SOLUTION: Communication between a terminal 1 and sever 3 is carried out through a plurality of access points 2. The terminal 1 periodically transmits a packet to the server 3. Communication between a plurality of access points 2 is carried out by wireless, and a plurality of access points 2 relay the communication between the terminal 1 and server 3 using the multihop. The plurality of access points 2 do not transmit a receiving confirmation to a transmitter when relaying the packet transmitted from the terminal 1. The server 3 transmits a request for retransmission thereof to the terminal 1 when the packet transmitted from the terminal 1 is not received at a predetermined cycle. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a wireless network system. In particular, the present invention relates to a wireless network system using multi-hop.

  In recent years, wireless network systems using multi-hop have been proposed. For example, a sensor network is considered as an application of such a system. In a sensor network, data collected by a terminal can be transmitted to a server, or positioning of the terminal can be performed based on data from the terminal. Such a system is also applied to a health check of a terminal.

  In this wireless network system, communication between a terminal and a server is performed via a plurality of relay nodes. That is, communication (specifically, a packet) between the terminal and the server is transmitted by hopping through a plurality of relay nodes.

  Such a system is defined by IEEE802.15.4 as a standard. The ZigBee Alliance is known as a standardization body for such standards. ZigBee (trademark) is also known as a standard name for PAN (Parsonal Area Network). PAN is a network that covers a range of several tens of meters.

  By the way, in a wireless network using multihop, communication between relay nodes is basically performed via wireless. Since a carrier wave in wireless communication propagates in space, it is necessary to avoid interference between packets in a wireless network. In addition, in wireless communication, a usable frequency band is limited. For this reason, in wireless networks, for example, time slots and bandwidths are assigned according to predetermined rules, or communication is performed after confirming that no packets are sent (so-called CSMA / CA). Therefore, effective use of the frequency is achieved.

  However, in a wireless network, there is still a problem that if the number of packets becomes excessive, communication as a whole becomes difficult. That is, in a wireless network, problems due to communication capacity tend to appear more strongly than in a wired network. For this reason, it is desired to further improve the frequency utilization efficiency.

  In particular, in a network that performs positioning of a terminal, it is necessary to periodically transmit packets from the terminal to a server. For this reason, the number of packets increases, and as a result, there is a problem that it is difficult to increase the number of terminals.

  Further, since packets are concentrated between relay nodes close to the server or between the server and the relay node, there is a problem that it is difficult to increase the number of terminals from this point.

  The present invention has been made in view of such circumstances. An object of the present invention is to provide a wireless network system capable of increasing frequency utilization efficiency and increasing the number of terminals.

(Item 1)
A terminal, a plurality of access points, and a server,
The terminal and the server are configured to communicate via the plurality of access points,
The terminal is configured to periodically send packets to the server,
The plurality of access points are configured to communicate using radio,
And, the plurality of access points are configured to relay communication between the terminal and the server using multi-hop,
In addition, the plurality of access points, when relaying a packet sent from the terminal, is configured not to send a reception confirmation to the transmission source,
The wireless network system, wherein the server is configured to transmit a retransmission request to the terminal when the packet transmitted from the terminal is not received at a predetermined period.

  Here, the access point is a node for relaying packets transmitted between the terminal and the server.

  In general, when a node in a wireless network system receives a packet, it returns a packet for acknowledgment (so-called Ack) to the transmission source.

  In the present invention, since transmission of the reception confirmation packet is omitted, the communication amount can be reduced correspondingly, and frequency resources can be used for other packets.

  Further, the server sends a retransmission request to the terminal when the packet from the terminal is not periodically received. As a result, even if a slight delay occurs, it is possible to reliably perform communication with the terminal.

  In the present invention, the cycle for transmitting a packet from the terminal and the cycle for confirming reception of the packet by the server do not necessarily need to match. For example, the period at which the server confirms packet reception may be n times the packet transmission period from the terminal (n is an integer of 2 or more).

  In the present invention, “transmission source” means a terminal or an upstream access point. In the present invention, only some access points may be configured to omit transmission of reception confirmation.

  In the present invention, the “predetermined period” at which the server should receive a packet may be, for example, a specific numerical value (for example, 10 minutes) stored on the server side, or may be based on a predetermined function. It may be a period generated automatically. Similarly, it is possible to dynamically generate a cycle in which a terminal transmits a packet to a server.

(Item 2)
The wireless network system, wherein the terminal and the plurality of access points are configured to communicate using radio.

  By performing communication between the terminal and the access point wirelessly, the terminal can be moved relatively freely.

(Item 3)
Any one or all of the plurality of access points are configured to transmit packets received from the terminal to the access point or the server on the downstream side after accumulating for a certain period of time. Or the wireless network system according to 2;

  When the access point receives a packet from the terminal or the upstream access point, it is possible to store the packet for a certain period of time instead of transferring the packet immediately. In this way, the communication volume can be further reduced.

(Item 4)
Any one of Items 1 to 3, wherein among the plurality of access points, the access point closer to the server has a higher communication priority than the other access points. The wireless network system according to item.

  The amount of communication between nodes is considered to increase as it approaches the server. Therefore, the frequency band can be used effectively by setting the communication priority to be higher as it is closer to the server.

(Item 5)
The plurality of access points are distributed on different floors,
And among the plurality of access points, access points arranged on the same floor are configured to communicate using the radio,
The wireless network system according to any one of items 1 to 4, wherein among the plurality of access points, access points arranged on different floors are configured to communicate using wired communication. .

  It is considered that the communication amount between floors tends to be larger than the communication amount between access points on the same floor. Therefore, communication between floors can be easily handled with respect to an increase in the amount of communication by performing wire communication (cable).

(Item 6)
The plurality of access points, when the same access point is directly communicating with the terminal, is configured to set a longer transmission cycle of packets to be transmitted to the server,
Furthermore, the access point set to a longer transmission cycle of the packet to be transmitted to the server is configured to transmit information indicating a new transmission cycle to the server,
Any one of Items 1 to 5, wherein the server is configured to transmit the retransmission request to the terminal when a packet from the terminal is not received in the new transmission cycle. The wireless network system according to claim 1.

  The fact that the access point with which the terminal is communicating directly does not change means that the moving amount of the terminal is small or not moving. In such a case, for example, for positioning of the terminal, it is less necessary to receive a packet from the terminal. Therefore, in such a case, the communication amount can be further reduced by extending the packet transmission period.

  When the access point directly communicating with the terminal does not change because the terminal is not moving, especially in the case of positioning, it is less necessary for the access point to relay the packet. However, if there is no communication from the terminal, it is difficult to distinguish from the case of terminal failure. Therefore, in the invention of this item, even when the terminal does not move, it is configured not to transmit any packet at all, but to set a longer transmission cycle of packets transmitted to the server.

(Item 7)
The new transmission period is an integer multiple of the original transmission period;
The wireless network system according to item 6, wherein the access point is configured to transmit the integer as information indicating the new transmission cycle.

  In the invention of this item, the packet from the terminal is relayed intermittently, so to speak. That is, the new transmission cycle is an integral multiple of the terminal transmission cycle. Therefore, if only the integer value instead of the transmission cycle value is sent to the server, the amount of communication can be further reduced.

(Item 8)
The wireless server according to any one of items 1 to 7, wherein the server is configured to perform positioning of the terminal based on the packet received from the terminal via the access point. Network system.

  In the case of a wireless network that performs terminal positioning, the present invention is particularly effective because it is necessary to periodically transmit packets from the terminal. However, the present invention can also be applied to purposes other than positioning.

(Item 9)
A wireless communication method using a terminal, a plurality of access points, and a server,
The terminal and the server are configured to communicate via the plurality of access points,
The plurality of access points are configured to communicate using radio,
And, the plurality of access points are configured to relay communication between the terminal and the server using multi-hop,
When the plurality of access points relay a packet sent from the terminal, it is configured not to send a reception confirmation to the transmission source,
In addition, the method includes the following steps:
(1) The server determines whether or not a packet sent from the terminal has been received at a predetermined period;
(2) The step in which the server transmits a retransmission request to the terminal when a packet transmitted from the terminal is not received at a predetermined period.

(Item 10)
A computer program for causing a computer to execute each step according to item 9.

(Item 11)
An access point in a wireless network system using multihop,
The access point is configured to relay packets transmitted between the terminal and the server,
Further, the access point for a wireless network system is configured such that when the packet sent from the terminal is relayed, a reception confirmation to the transmission source is not sent.

(Item 12)
An access point in a wireless network system using multihop,
The access point is configured to relay packets transmitted between the terminal and the server,
An access point for a wireless network system, wherein the access point is configured to store packets received from the terminal for a certain period of time and then transmit the packets to another access point downstream or the server.

  Note that the number of terminals in the present invention is not limited to one. Rather, it is considered normal to use a plurality of terminals.

  According to the wireless network system of the present invention, it is possible to increase the utilization efficiency of the frequency band. Thereby, for example, it becomes easy to increase the number of terminals that can be accommodated in this system.

  Hereinafter, a wireless network system according to a first embodiment of the present invention will be described with reference to the accompanying drawings.

(Configuration of the first embodiment)
The system according to the present embodiment includes a terminal 1, a plurality of access points 2, and a server 3. Since the terminals 1 have basically the same configuration, the same reference numerals are used for both. Similarly, the same reference numerals are used for the plurality of access points 2. The terminal 1 and the server 3 are configured to communicate via a plurality of access points 2.

  Here, FIG. 2 shows a general basic configuration of a node used in the wireless network system. In the case of wirelessly connected nodes, the same components are basically provided regardless of whether the node is used as a terminal, an access point, or a server.

  This node includes an RF unit 61, a CPU 62, a memory 63, an interface unit 64, and an antenna 65. Such a node may have the same configuration as the node used in, for example, the ZigBee (trade name) standard, and detailed description of each component will be omitted.

  The terminal 1 is configured to periodically transmit packets toward the server 3. In addition, the terminal 1 in the present embodiment and any one of the plurality of access points 2 are configured to communicate using radio.

  Specifically, the terminal 1 includes a reception unit 11, a transmission unit 12, a timer 13, and a storage unit 14 as functional elements (see FIG. 3).

  The receiving unit 11 is a part that receives a packet sent to the terminal 1. The transmission unit 12 is a part that transmits a packet from the terminal 1 to the access point 2. The transmission unit 12 is configured to transmit packets to the server 3 at a predetermined cycle. The timer 13 is a part for determining that a predetermined period stored in the storage unit 14 has arrived. The storage unit 14 further records the ID of the terminal.

  The plurality of access points 2 communicate with each other using radio. And the some access point 2 becomes a structure which relays communication between the terminal 1 and the server 3 using multihop. In other words, the plurality of access points 2 transmit packets by performing hops between the access points 2. Of course, when the access point 2 that can transmit to the server 3 with only one hop receives the packet directly from the terminal 1, the packet can be transmitted to the server 3 with one hop.

  The access point 2 of the present embodiment is configured not to send a reception confirmation to the transmission source when relaying a packet sent from the terminal 1.

  The access point 2 includes a receiving unit 21, a transmitting unit 22, a timer 23, and a storage unit 24 as functional elements (see FIG. 4).

  The receiving unit 21 is a part that receives a packet from the terminal 1 or the upstream access point 2. The transmission unit 22 is a part that transmits a packet to the access point 2 or the server 3 on the downstream side. The timer 23 is not particularly necessary in this embodiment (described in other embodiments described later). The storage unit 24 is a part that appropriately stores data necessary for the operation of the access point 2 and the ID of the access point.

  The server 3 is configured to transmit a retransmission request to the terminal 1 when the packet transmitted from the terminal 1 is not received at a predetermined period.

  The server 3 includes a receiving unit 31, a transmitting unit 32, a timer 33, a storage unit 34, and a retransmission request unit 35 as functional elements (see FIG. 5).

The receiving unit 31 is a part that receives packets from the access point 2 on the upstream side. The transmission unit 32 is a part that transmits a packet toward a node connected to the server 3. The timer 33 is a part that can determine whether or not a predetermined period stored in the storage unit 34 has arrived. The retransmission request unit 35 is a part for sending a retransmission request to the terminal 1 when a packet from the terminal 1 is not received within a predetermined period. Here, the predetermined period (T ₃ ) stored in the server 3 and the predetermined transmission period (T ₁ ) stored in the terminal 1 may be different, but are the same in this embodiment. Has been. If these periods are different, it is preferable to satisfy T ₃ > T ₁ .

(Operation of the first embodiment)
Next, the operation of the wireless network system according to the present embodiment will be described with reference mainly to the flowchart shown in FIG.

(Step SA-1)
First, each terminal 1 transmits a packet toward the server 3 in a predetermined cycle according to the count in the timer 13. When transmitting a packet, it is confirmed in advance whether another packet is transmitted (so-called carrier sense). Since this method is known as CSMA / CA (Carrier Sense Multiple Access with Collision Avoidance), detailed description thereof is omitted. In subsequent wireless packet transmissions at the nodes, packet collision is avoided by performing this carrier sense. Each terminal 1 transmits the terminal ID in a packet.

(Step SA-2)
Next, the access point 2 close to the terminal 1 receives each packet from the terminal 1 and relays it to the next access point 2. The packets from each terminal 1 usually follow different paths, but in the following description, only the packet from one terminal 1 will be described for convenience of explanation.

  The access point 2 further adds the received electric field strength and its own ID to the packet carrying the ID information of the terminal 1, and forwards it to the downstream node.

  Here, the access point 2 that received the packet does not transmit a reception confirmation to the transmission source node. In general, when a node in a wireless network system receives a packet, it returns a packet for acknowledgment (so-called Ack) to the transmission source. However, in this embodiment, since transmission of the reception confirmation packet is omitted, there is an advantage that the communication amount can be reduced correspondingly and frequency resources can be used for other packets.

(Step SA-3 and Step SA-4)
Thereafter, similarly, the downstream access point 2 relays the packet toward the server 3. Note that if it is possible to relay in one hop from the access point 2 closest to the terminal 1 to the server 3, these steps SA-3 and SA-4 need not be executed.

(Step SA-5 and Step SA-6)
Next, the server 3 receives the packet sent from the terminal 1. Further, the server 3 determines whether or not the packet from the terminal 1 has been received at a predetermined cycle.

  Here, an example of a specific method for determining whether or not a packet from the terminal 1 has been received at a predetermined cycle will be further described.

  First, when the packet from the terminal 1 is the first one, the server 3 stores the period in which the packet should arrive next in the storage unit 34 in accordance with the ID of the terminal 1 based on the packet arrival time. Remember. This storage is performed for each terminal 1 from which the packet has arrived.

  Thereafter, the server 3 uses the timer 33 to monitor whether a packet from the terminal 1 having the ID arrives in the stored cycle. If the packet does not arrive at the predetermined period, the process proceeds to step SA-7.

  If a packet has arrived at the server 3 in a predetermined cycle, the process returns to step SA-2 to wait for the next packet.

  Further, the server 3 determines the position of the terminal 1 from the position of the access point 2 that directly receives the packet from the terminal 1. When a plurality of access points 2 receive packets from the same terminal 1 at the same time, the position of the access point 2 having a strong received electric field strength from the terminal 1 can be set as the position of the terminal 1. Alternatively, the position of the terminal 1 can be obtained by weighting the coordinates of the access point 2 based on the received electric field strength.

(Step SA-7)
In step SA-6, when it is determined that the packet from the terminal 1 does not arrive at a predetermined cycle, the retransmission request unit 35 of the server 3 uses the transmission unit 32 to request a retransmission from the terminal 1. Send the packet.

(Step SA-8 and Step SA-9)
The retransmission request packet sent from the server 3 reaches the access point 2 close to the terminal 1 via the access point 2. The access point 2 close to the terminal 1 sends a retransmission request packet to the terminal 1.

(Step SA-10)
The terminal 1 that has received the retransmission request packet retransmits the packet to the server 3.

  In the present embodiment, there is an advantage that communication between the terminal 1 and the server 3 can be reliably performed by the operation of the retransmission request.

  In the present embodiment, the terminal 1 and any one of the plurality of access points 2 are configured to communicate using radio. For this reason, this embodiment has an advantage that the terminal can be moved relatively freely.

(Second Embodiment)
Next, a wireless network system according to the second embodiment of the present invention will be described with reference mainly to FIG. In the description of the second embodiment, elements that are basically the same as the components in the first embodiment described above are denoted by the same reference numerals to simplify the description.

  In the second embodiment, the plurality of access points 2 are configured to transmit the packets received from the terminal 1 to the access point 2 or the server 3 on the downstream side after accumulating the packets for a certain period. Note that the number of terminals 1 is not limited to one. Rather, it is considered that a plurality of terminals 1 are usually used. Hereinafter, it will be described in more detail with reference to FIG.

(Step SB-1)
First, the terminal 1 transmits a packet toward the server 3 at a predetermined cycle.

(Step SB-2)
The access point 2 nearest to the terminal 1 receives the packet from the terminal 1 to the server 3. Further, the access point 2 stores the received packet in its memory.

(Step SB-3)
Further, the access point 2 that has received the packet uses the timer 23 to determine whether a predetermined time has elapsed. Then, as long as the predetermined time has not elapsed, the packet is not transferred to the next access point 2 but stored in its own memory. In the access point 2 of the present embodiment, the cycle (T ₂ ) for storing packets is stored in the storage unit 24 in advance. The relationship between the period T2 and the period (T ₁ ) at which the terminal 1 transmits a packet is preferably T ₂ > T ₁ .

(Step SB-4)
When the predetermined time elapses, the access point 2 collects the packets received so far and transfers the packets to the next access point 2. Of course, if the next node of the access point 2 is the server 3, the packet is transferred to the server 3.

  The access point 2 of the first embodiment described above immediately transfers the packet received from the terminal 1 to the downstream node. On the other hand, in the second embodiment, after the packet received from the terminal 1 is accumulated for a certain period, the packet is transferred to the downstream node. According to the system of the second embodiment, since packets are transferred together at a constant cycle, there is an advantage that the amount of communication can be further reduced.

  A packet generally includes not only transmission information but also a preamble and a synchronization word as data. When a plurality of packets are transmitted together, redundant portions can be omitted, and the total time required for communication can be shortened.

  Furthermore, by reducing the number of packets, there is an advantage that the possibility of packet collisions is reduced and the capacity of the communication path is increased as a whole.

(Step SB-5 to Step SB-7)
Also in the access point 2 on the downstream side, the packets are accumulated for a certain period in the same manner as described in Step SB-3 and Step SB-4, and then sent to the next access point 2. In this way, packets can be sequentially transferred to the access point 2 on the downstream side.

(Step SB-8)
Through the above steps, the packet can finally be delivered to the server 3. Similarly to the first embodiment, the server 3 sends a retransmission request to the terminal 1 when it does not receive a packet from the terminal 1 at a predetermined cycle. In the second embodiment, since the packets are accumulated at each access point 2, the time for the packets to arrive at the server 3 from the terminal 1 tends to be longer than in the case of the first embodiment. Therefore, in consideration of this point, it is desirable to set a cycle (a predetermined cycle in the server 3) at which a packet should arrive from the terminal 1 to the server 3. Specifically, for example, when a packet arrives from the terminal 1 to the server 3, the time at which the next packet should arrive is set from the number of hops of the packet and the accumulation time at each access point 2. be able to. In general, the period T ₃ server to receive the packet, the relationship between the period T ₂ to the access point 2 forwards packets, the period T ₁ in which the terminal 1 transmits a packet, _{T 3>} T _2> T ₁ is preferable.

  Other configurations and advantages of the system of the second embodiment are the same as those of the first embodiment, and thus detailed description thereof is omitted.

(Third embodiment)
Next, a wireless network system according to a third embodiment of the present invention will be described with reference mainly to FIG. In the description of the third embodiment, elements that are basically the same as those in the first embodiment described above are denoted by the same reference numerals to simplify the description.

  In the third embodiment, among the plurality of access points 2, the access point 2 that is closer to the server 3 has a higher communication priority than the other access points.

  FIG. 8 shows a specific example of priority. In this figure, the priority is described numerically inside each access point 2. The smaller the number, the higher the priority.

  The amount of communication between nodes is considered to increase as the server 3 is approached. Thus, there is an advantage that the frequency band can be used effectively by setting the communication priority to be higher as it is closer to the server 3.

  Further, if the packet does not reach the link where the communication is concentrated, the reliability of the entire communication system is greatly impaired. Thus, there is an advantage that the reliability of the entire system can be improved by increasing the reliability of communication in such a link.

  Other configurations and advantages of the system according to the third embodiment are the same as those of the first embodiment, and thus further detailed description is omitted.

(Fourth embodiment)
Next, a wireless network system according to a fourth embodiment of the present invention will be described with reference mainly to FIG. In the description of the fourth embodiment, elements that are basically the same as those in the first embodiment described above are denoted by the same reference numerals to simplify the description.

  The plurality of access points 2 in the present embodiment are distributed on different floors. Different floors are, for example, upper and lower floors in a building. In FIG. 9, floor boundaries 7 a and 7 b are schematically represented by alternate long and short dash lines. The number of floors in the present embodiment is not limited to the illustrated example, and may be plural.

  Among the plurality of access points in the present embodiment, the access points 2 arranged on the same floor are configured to communicate using radio as in the first embodiment.

  However, in this embodiment, the access points 2 arranged on different floors among the plurality of access points 2 are configured to communicate with each other using the cables 81 and 82 (see FIG. 9). That is, between the different floors, the access points 2 communicate with each other by wire. A wired communication method is, for example, Ethernet (registered trademark), but is not limited thereto.

  The amount of communication between floors is likely to be larger than the amount of communication between access points on the same floor. When communication between floors is wireless, there is a high possibility that communication between floors interferes with communication between other access points. Therefore, there is an advantage that it is possible to easily cope with an increase in communication amount by performing communication between floors via a cable (cable).

  In addition, since the amount of communication between floors is large, if the communication here receives interference, the stability of the communication is greatly affected. In this embodiment, communication between floors is wired, so that communication between floors is not subject to interference due to communication between other nodes. For this reason, according to this embodiment, there exists an advantage that the stability of communication can be improved.

  Other configurations and advantages of the system of the fourth embodiment are the same as those of the first embodiment, and thus detailed description thereof is omitted.

(Fifth embodiment)
Next, a wireless network system according to a fifth embodiment of the present invention is described with reference mainly to FIG. In the description of the fifth embodiment, elements that are basically the same as those in the first embodiment described above are denoted by the same reference numerals to simplify the description.

  In the fifth embodiment, when the access point 2 with which the terminal 1 is directly communicating is the same, the access point 2 is configured to set a longer transmission cycle for packets transmitted to the server 3. Yes. Furthermore, the access point 2 that has set a longer transmission cycle of packets to be transmitted to the server 3 is configured to transmit information indicating a new transmission cycle to the server. The server 3 is configured to transmit a retransmission request to the terminal 1 when the packet from the terminal 1 is not received in a new transmission cycle. Hereinafter, a more detailed description will be given based on FIG.

(Step SC-1)
First, the terminal 1 transmits a packet toward the server 3 at a predetermined cycle.

(Step SC-2)
The access point 2 nearest to the terminal 1 receives the packet from the terminal 1 to the server 3. Further, the access point 2 stores the received packet in its memory. The access point 2 records the ID of the terminal. The access point 2 stores the packet transmission cycle to the server 3 in the storage unit 24. In this embodiment, the received packets are not transferred immediately, but transferred together at regular intervals. Thereby, the amount of packets can be reduced.

(Step SC-3)
Furthermore, the access point 2 that has received the packet from the terminal 1 determines whether or not the same terminal ID has been received within a predetermined period (transmission cycle). That is, it is determined whether the terminal ID recorded in the packet received from the terminal 1 is the same as the recorded ID. If the same terminal ID is received within the predetermined period, the process proceeds to step SC-4.

  If the same terminal ID has not been received, the process proceeds to step SC-5.

(Step SC-4)
When the same terminal ID is received within the predetermined transmission cycle, the access point 2 lengthens the relay cycle to the server 3 regarding the terminal. Specifically, in this embodiment, an integer multiple of the previous transmission cycle (here, the integer means 2 or more) is set as the new transmission cycle. Such transmission can be easily realized, for example, by intermittently relaying packets. The new transmission cycle is stored in the storage unit 24 of the access point 2 and transmitted to the server 3.

(Step SC-5)
As a result of the determination in step SC-3, if the same terminal ID is not received within the predetermined transmission period or within the reset transmission period, the access point 2 determines the packet received so far. Collectively, the packet is transferred to the next access point 2. Of course, if the next node of the access point 2 is the server 3, the packet is transferred to the server 3.

  The access point 2 of the first embodiment described above immediately transfers the packet received from the terminal 1 to the downstream node. On the other hand, in the fifth embodiment, packets received from the terminal 1 are collectively transferred to downstream nodes when a new terminal ID is received and when a predetermined time has elapsed. According to the system of the fifth embodiment, since packets are transferred together, there is an advantage that the amount of communication can be further reduced.

  A packet generally includes not only transmission information but also a preamble and a synchronization word as data. When a plurality of packets are transmitted together, redundant portions can be omitted, and the total time required for communication can be shortened.

  Furthermore, by reducing the number of packets, there is an advantage that the possibility of packet collisions is reduced and the capacity of the communication path is increased as a whole.

(Step SC-6)
In the access point 2 on the downstream side, packets are sequentially sent to the next access point 2 as in the first embodiment. In this way, the packet can be transferred to the access point 2 on the downstream side.

(Step SC-7)
Through the above steps, the packet can finally be delivered to the server 3. Similarly to the first embodiment, the server 3 sends a retransmission request to the terminal 1 when it does not receive a packet from the terminal 1 at a predetermined cycle.

  Since the access point 2 of the fifth embodiment sends the reset transmission cycle to the server 3, the server 3 can know the cycle or time for receiving the packet. Therefore, in this embodiment, for example, it is possible to know that the terminal 1 is out of order.

  That the ID of the terminal 1 that is directly communicating with the access point 2 does not change means that the terminal 1 has a small amount of movement or has not moved. In such a case, for example, for positioning of the terminal 1, the necessity of receiving a packet from the terminal 1 is generally low. Therefore, in such a case, the communication amount can be reduced by extending the packet transmission period.

  Furthermore, the access point 2 can delete the packet from the terminal 1 when the packet from the terminal 1 is not received for a certain period. In this way, memory resources at the access point 2 can be used effectively.

  Furthermore, in the fifth embodiment described above, the new transmission cycle is an integer multiple of the original transmission cycle. Here, the access point 2 can transmit the integer value to the server 3 as information indicating a new transmission cycle. In this way, it is possible to further reduce the amount of communication between nodes.

  In the fifth embodiment described above, when a new terminal 1 is connected to the access point 2, the packets received so far are transferred together. For this reason, even if the terminal 1 originally connected to the access point 2 does not move, packet transfer for the terminal is performed collectively. Even in this case, the frequency resources can be effectively used by transferring the packets together. However, it is possible to set so that the packet of the terminal 1 that does not move is not relayed.

  Other configurations and advantages of the system of the fifth embodiment are the same as those of the first embodiment, and thus detailed description thereof is omitted.

  The steps in the communication method described in the present embodiment can be performed by a computer in which an appropriate computer program is installed.

  In addition, this invention is not limited to the said embodiment, Of course, a various change can be added in the range which does not deviate from the summary of this invention.

  Moreover, each component described above may exist as a functional block, and does not need to exist as independent hardware. As a mounting method, hardware or computer software may be used. Furthermore, one functional element in the present invention may be realized by a set of a plurality of functional elements, and a plurality of functional elements in the present invention may be realized by one functional element.

It is explanatory drawing for demonstrating the structure of the radio | wireless network system which concerns on 1st Embodiment of this invention. It is a block diagram for demonstrating the general internal structure of a node. It is a functional block diagram for demonstrating the internal structure of a terminal. It is a functional block diagram for demonstrating the internal structure of an access point. It is a functional block diagram for demonstrating the internal structure of a server. 5 is a flowchart for explaining an operation of the wireless network system according to the first embodiment of the present invention. 7 is a flowchart for explaining an operation of the wireless network system according to the second embodiment of the present invention. It is explanatory drawing for demonstrating the structure of the radio | wireless network system which concerns on 3rd Embodiment of this invention. It is explanatory drawing for demonstrating the structure of the radio | wireless network system which concerns on 4th Embodiment of this invention. It is a flowchart for demonstrating operation | movement of the radio | wireless network system which concerns on 5th Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Terminal 11 Reception part 12 Transmission part 13 Timer 14 Storage part 2 Access point 21 Reception part 22 Transmission part 23 Timer 24 Storage part 3 Server 31 Reception part 32 Transmission part 33 Timer 34 Storage part 35 Retransmission request part 61 RF part 62 CPU
63 Memory 64 Interface section 65 Antenna 7a, 7b Boundary between floors 81, 82 Cable (wired)

Claims (12)

A terminal, a plurality of access points, and a server,
The terminal and the server are configured to communicate via the plurality of access points,
The terminal is configured to periodically send packets to the server,
The plurality of access points are configured to communicate using radio,
And, the plurality of access points are configured to relay communication between the terminal and the server using multi-hop,
In addition, the plurality of access points, when relaying a packet sent from the terminal, is configured not to send a reception confirmation to the transmission source,
The wireless network system, wherein the server is configured to transmit a retransmission request to the terminal when the packet transmitted from the terminal is not received at a predetermined period. The wireless network system, wherein the terminal and the plurality of access points are configured to communicate using radio. 3. The configuration according to claim 1, wherein the plurality of access points are configured to accumulate packets received from the terminal for a certain period, and then transmit the packets to the access point or the server on the downstream side. Wireless network system. 4. The access point closer to the server among the plurality of access points has higher communication priority than the other access points. The wireless network system according to item 1. The plurality of access points are distributed on different floors,
And among the plurality of access points, access points arranged on the same floor are configured to communicate using the radio,
The wireless network according to any one of claims 1 to 4, wherein, among the plurality of access points, access points arranged on different floors are configured to communicate using wired communication. system. The plurality of access points, when the same access point is directly communicating with the terminal, is configured to set a longer transmission cycle of packets to be transmitted to the server,
Furthermore, the access point set to a longer transmission cycle of the packet to be transmitted to the server is configured to transmit information indicating a new transmission cycle to the server,
6. The server according to claim 1, wherein the server is configured to transmit the retransmission request to the terminal when a packet from the terminal is not received in the new transmission cycle. The wireless network system according to any one of the above. The new transmission period is an integer multiple of the original transmission period;
The wireless network system according to claim 6, wherein the access point is configured to transmit the integer as information indicating the new transmission cycle. 8. The server according to claim 1, wherein the server is configured to perform positioning of the terminal based on the packet received from the terminal via the access point. 9. Wireless network system. A wireless communication method using a terminal, a plurality of access points, and a server,
The terminal and the server are configured to communicate via the plurality of access points,
The plurality of access points are configured to communicate using radio,
And, the plurality of access points are configured to relay communication between the terminal and the server using multi-hop,
When the plurality of access points relay a packet sent from the terminal, it is configured not to send a reception confirmation to the transmission source,
In addition, the method includes the following steps:
(1) The server determines whether or not a packet sent from the terminal has been received at a predetermined period;
(2) The step in which the server transmits a retransmission request to the terminal when a packet transmitted from the terminal is not received at a predetermined period.   A computer program for causing a computer to execute each step according to claim 9. An access point in a wireless network system using multihop,
The access point is configured to relay packets transmitted between the terminal and the server,
Further, the access point for a wireless network system is configured such that when the packet sent from the terminal is relayed, a reception confirmation to the transmission source is not sent. An access point in a wireless network system using multihop,
The access point is configured to relay packets transmitted between the terminal and the server,
An access point for a wireless network system, wherein the access point is configured to store packets received from the terminal for a certain period of time and then transmit the packets to another access point downstream or the server.

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