JP6223665B2 - Communications system - Google Patents

Description

  The present invention relates to a communication system that performs wireless communication such as carrier sense multiple access / collision avoidance (CSMA / CA), and relates to power saving.

  Various techniques have been proposed for communication systems that perform wireless communication. For example, in the communication system shown in FIG. 9 disclosed in Non-Patent Document 1, first, a main access point (hereinafter also referred to as “main AP”) 51 having the function of First PAN Coordinator is connected to its own radio wave. It communicates with a terminal 53 outside the PAN area 61 via a terminal 52 that is located in a PAN (Personal Area Network) area 61.

  Then, the main AP 51 designates the terminal 53 as a relay access point having a PAN Coordinator function equivalent to the First PAN Coordinator. Then, the main AP 51 causes the designated terminal 53 (hereinafter referred to as “relay terminal 53”) to construct a new PAN area 62 and relays communication between terminals in the adjacent PAN areas 61 and 62 to the relay terminal 53. Let By constructing such a PAN area and relaying communication in a relay manner, the communication system disclosed in Non-Patent Document 1 constitutes a network capable of wide-ranging communication.

  In the communication system as described above, the main AP 51 and the relay terminal 53 transmit beacons in the respective PAN areas 61 and 62, and other terminals in the PAN areas 61 and 62 receive the beacons. It has been proposed to perform data communication and sleep repeatedly in synchronization.

IEEE Std 802.15.4, 2006, p. 13-17

  However, in the proposed technique described above, since the relay terminal needs to periodically transmit a beacon, there is a problem that the power consumption of the relay terminal is larger than that of other terminals. Further, in order to perform communication between the PAN areas, the relay terminal must perform relay with a large load. From this viewpoint, there is a problem that the power consumption of the relay terminal is larger than that of other terminals. is there.

  Therefore, the present invention has been made in view of the above problems, and an object thereof is to provide a technique capable of suppressing an increase in power consumption in a specific terminal.

A communication system according to the present invention includes a main AP (access point) and a subordinate terminal capable of wireless communication with the main AP. The main AP groups the subordinate terminals into a plurality of layers, and the subordinate Predetermined information including an activation mode time and a power saving mode time of the subordinate terminal is generated for the terminal to perform data communication according to the hierarchy. Then, based on the predetermined information, the main AP and the subordinate terminal of the highest layer that receives the predetermined information from the main AP are divided into the layer, the activation mode time, and the power saving mode time. done by synchronizing data communication with a communication start time in accordance, with each said dependent terminal, and said dependent terminal of one lower level for receiving the predetermined information from the slave terminal, based on said predetermined information, the Data communication is performed synchronously at a communication start time corresponding to the hierarchy, the activation mode time, and the power saving mode time . The subordinate terminals in the same hierarchy can start data communication at the same communication start time .

  According to the present invention, the main AP and the subordinate terminal of the highest hierarchy perform data communication in synchronization based on the predetermined information, and each subordinate terminal and the subordinate terminal of the next lower hierarchy Data communication is performed synchronously based on information. Therefore, beacon transmission and relay loads, which are the causes of increasing power consumption, can be distributed throughout the subordinate terminals, so that it is possible to suppress a intensive increase in power consumption at specific relay terminals.

1 is a diagram illustrating a configuration of a communication system according to Embodiment 1. FIG. 2 is a block diagram showing a configuration of a main AP according to Embodiment 1. FIG. 3 is a block diagram showing a configuration of a subordinate terminal according to Embodiment 1. FIG. 3 is a diagram illustrating an example of communication time of the communication system according to Embodiment 1. FIG. 6 is a diagram illustrating a configuration of a communication system according to Embodiment 2. FIG. 6 is a diagram illustrating a configuration of a communication system according to Embodiment 3. FIG. FIG. 10 is a diagram illustrating a configuration of a communication system according to a fourth embodiment. FIG. 10 is a diagram illustrating a configuration of a communication system according to a fourth embodiment. It is a figure which shows an example of a structure of a communication system.

<Embodiment 1>
FIG. 1 is a diagram showing a configuration of a communication system according to Embodiment 1 of the present invention. As shown in FIG. 1, this communication system is capable of wireless communication with a main access point (main AP) 101 that controls the entire system, and the main AP 101, and subordinate terminals 201-1 to 201-l subordinate to the main AP 101. , 301-1 to 301-m, 401-1 to 401-n. Hereinafter, when it is not necessary to distinguish the subordinate terminals 201-1 to 201-l, they are referred to as subordinate terminals 201. Similarly, the subordinate terminals 301-1 to 301-m and 401-1 to 401-n are respectively shown. 301 and 401 are described.

  In the following description, it is assumed that the main AP 101 has the function of First PAN Coordinator, and the subordinate terminals 201, 301, and 401 are distinguished as terminals (Devices), but the functions of both are almost the same. You can think about it.

  The main AP 101 groups subordinate terminals into a plurality of hierarchies as shown in FIG. Here, the main AP 101 has the slave terminals 201-1 to 201-l in the same HOP layer, the slave terminals 301-1 to 301-m in the same HOP layer, and the slave terminals 401-1 to 401-n in the same HOP layer. Group into Here, in order to transmit data from the main AP 101 to a desired subordinate terminal, it is HOP that the data is transmitted in a relay manner between the main AP 101 and the subordinate terminal 201 or in a radio section between the subordinate terminals 201. That's it. Further, when the subordinate terminal receives data from the main AP 101 by HOP, a value obtained by adding 1 to the number of other subordinate terminals that have passed through the HOP is referred to as the number of HOPs. The above-mentioned dependent terminals in the same HOP layer mean a set of dependent terminals having the same number of HOPs.

  In the first embodiment, it is defined that the level of the HOP layer becomes lower as the number of HOPs increases. Specifically, the main AP 101 groups the subordinate terminals 201-1 to 201-l having one HOP number into the HOP-1 layer of the upper layer (here, the highest layer). Similarly, the main AP 101 groups the subordinate terminals 301-1 to 301-m having two HOPs into the HOP-2 layer of the middle hierarchy, and subordinate terminals 401-1 to 401-n having the HOP number k. Are grouped in the lower-layer HOP-k layer.

  As will be described later, the subordinate terminals 201, 301, and 401 according to the first embodiment perform data communication at different times for each layer. The main AP 101 has a function of determining a time during which the main AP 101 and the subordinate terminals 201, 301, 401 perform data communication according to the hierarchy of the HOP layer, and can generate power saving information indicating the time. It has become. In addition, the main AP 101 has a function of holding and updating an accurate time, and can generate time information indicating the time. This time information is used to synchronize the time managed by the main AP 101 and the subordinate terminals 201, 301, 401 respectively. Hereinafter, the predetermined information including the power saving information and the time information is referred to as synchronization information.

  The main AP 101 transmits synchronization information for the subordinate terminals 201, 301, 401 to perform data communication according to the hierarchy of the HOP layer to the subordinate terminal 201 of the highest HOP-1 layer. Each subordinate terminal 201 transmits the received synchronization information to the subordinate terminal 301 of the next lower HOP-2 layer. Similarly, each subordinate terminal transmits the synchronization information received by itself to the lower HOP layer. To the subordinate terminal.

  The main AP 101 and the subordinate terminals 201, 301, and 401 have a function of performing data communication based on synchronization information (power saving information and time information).

  Further, the main AP 101 and the subordinate terminals 201, 301, and 401 have a function of performing data communication by a carrier sense multiple access / collision avoidance method (CSMA / CA) that uses an unused radio resource among predetermined radio resources. ing.

  Next, detailed configurations of the main AP 101 and the subordinate terminals 201, 301, and 401 will be described. FIG. 2 is a block diagram showing the configuration of the main AP 101.

  As shown in FIG. 2, the main AP 101 includes a time circuit 501 for managing time, a device control circuit 502 for controlling the entire main AP 101, and a HOP control circuit for determining and managing the HOP layers of the subordinate terminals 201, 301, and 401. 503 and a HOP memory 504 for storing information (HOP information) of the HOP layer determined by the HOP control circuit 503. In addition, the main AP 101 performs wireless communication and RSSI (Received Signal Strength Indication) with a transmission / reception control memory 505 that stores information about the activation time, activation time, upper transmission destination and lower transmission destination of the subordinate terminals 201, 301, 401. And an activation control circuit 507 are provided.

  The device control circuit 502 generates the above-described synchronization information. Then, the activation control circuit 507 determines the time circuit 501, the device control circuit 502, the HOP control circuit 503, the HOP memory 504, the transmission / reception control memory 505, and the RF circuit 506 based on the synchronization information generated by the device control circuit 502. Control startup.

  FIG. 3 is a block diagram showing the configuration of the subordinate terminals 201, 301, 401. Here, for convenience, the configuration of the subordinate terminals 201, 301, and 401 is assumed to be the same, and the configuration of the subordinate terminal 201 will be described as an example.

  As shown in FIG. 3, the subordinate terminal 201 includes a time circuit 601 that manages time, a device control circuit 602 that controls the subordinate terminal 201 itself, a start time, a start time, an upper transmission destination, and a lower subordinate of the subordinate terminal 201 itself. A transmission / reception control memory 603 that stores information regarding a transmission destination, an RF circuit 604 that performs radio communication and measures RSSI, and an activation control circuit 605 are provided. The activation control circuit 605 controls activation of the time circuit 601, the device control circuit 602, the transmission / reception control memory 603, and the RF circuit 604 based on the synchronization information received by the RF circuit 604.

<Operation>
Next, the operation of the communication system according to the first embodiment configured as described above will be described.

<Grouping of subordinate terminals>
Hereinafter, an operation in which the main AP 101 groups subordinate terminals will be described. Here, for convenience, a case where k = 3, that is, an operation in which the main AP 101 assigns the subordinate terminal to any one of the three layers (HOP-1 layer to HOP-3 layer) will be described.

  At the beginning of the system startup, since none of the subordinate terminals is synchronized with the main AP 101, a continuous connection request is made. In this case, the main AP 101 (device control circuit 502) groups the subordinate terminals into the HOP-1 layer to the HOP-3 layer based on RSSI.

  Specifically, the main AP 101 measures the RSSI value of each slave terminal that can directly communicate, and records the RSSI value in the HOP memory 504. Then, the main AP 101 (HOP control circuit 503) assigns subordinate terminals (in this case, subordinate terminals 201-1 to 201-l) whose recorded RSSI values are equal to or greater than a predetermined threshold to the HOP-1 layer, and stores the result in the HOP memory. Register at 504.

  At this time, the main AP 101 is stable as a dependent terminal other than the dependent terminal 201 (that is, a dependent terminal having a small RSSI or a dependent terminal for which RSSI measurement itself has not been performed, hereinafter collectively referred to as “weak reception strength terminal”). Cannot be connected directly. Therefore, the main AP 101 performs control for transmitting a signal for a certain period to the weak reception strength terminal via the slave terminal 201 and causes each slave terminal 201 to receive a signal from the weak reception strength terminal for a certain period. Then, control is performed to measure the RSSI value of the signal.

  After the above-described fixed period, the subordinate terminal 201 transmits the measured RSSI value of the weak reception strength terminal to the main AP 101. The main AP 101 records the RSSI value received from the subordinate terminal 201 in the HOP memory 504. Then, the main AP 101 (HOP control circuit 503) assigns predetermined weak reception strength terminals (here, the dependent terminals 301-1 to 301-m) to the HOP-2 layer based on the received information such as the RSSI value. Then, the main AP 101 (HOP control circuit 503) uniquely determines a communication path between the subordinate terminal 201 in the HOP-1 layer and the subordinate terminal 301 in the HOP-2 layer, and registers the result in the HOP memory 504.

  Thereafter, the main AP 101 (HOP control circuit 503) assigns predetermined weak reception strength terminals (subordinate terminals 401-1 to 401-n in this case) to the HOP-3 layer by performing the same operation as described above. Then, the main AP 101 (HOP control circuit 503) uniquely determines the communication path between the subordinate terminal 301 in the HOP-2 layer and the subordinate terminal 401 in the HOP-3 layer, and registers the result in the HOP memory 504.

  Through the above operation, the HOP layer and communication path to which the subordinate terminals 201, 301, 401 belong are registered in the HOP memory 504 of the main AP 101. In the above description, the case where the subordinate terminals are grouped into three hierarchies has been described. Of course, the subordinate terminals are divided into two hierarchies (k = 2) or four or more hierarchies (k ≧ 4) may be grouped. Further, after subordinate terminals are grouped once, the main AP 101 may cause the subordinate terminals 201, 301, and 401 to transition to the reception state. When a communication terminal that is not registered as a subordinate terminal (a communication terminal that has become communicable after performing the above grouping) is detected in this reception state, the same grouping as described above is performed. By doing so, the communication terminal may be registered as a subordinate terminal. This will be described in detail in the second embodiment.

<Generation of synchronization information>
The main AP 101 (apparatus control circuit 502) generates power saving information indicating a time (communication timing schedule) during which the subordinate terminal performs data communication according to the hierarchy after grouping of subordinate terminals is completed.

  FIG. 4 is a diagram illustrating an example of a time (communication timing schedule) indicated in the power saving information. Next, the communication timing indicated by the power saving information will be described with reference to FIG. In the following description, some information (signal) is transmitted in the direction from the main AP 101 to the subordinate terminal 201, from the subordinate terminal 201 to the subordinate terminal 301, or from the subordinate terminal 301 to the subordinate terminal 401. The direction is called “down”. Conversely, the direction in which some information (signal) is transmitted in the direction from the subordinate terminal 401 to the subordinate terminal 301, from the subordinate terminal 301 to the subordinate terminal 201, and from the subordinate terminal 201 to the main AP 101 is “uplink”. "

  Referring to the outline of the communication shown in FIG. 4, a data signal (data) is transmitted in the upstream direction in the front period (time interval from the downlink reception start time to the downlink transmission start time) Trxtx in one cycle. (Solid arrow), synchronization information and Ack signal are transmitted in the downstream direction (dotted arrow, but Ack signal is appropriate). On the other hand, in the rear period Ttxrx of one cycle, the data signal (data) is transmitted in the downlink direction (solid arrow), and the Ack signal is appropriately transmitted in the uplink direction (dotted arrow).

  Next, the communication shown in FIG. 4 will be described in detail.

  In the front period Trxtx, Rxd receives data from the lower HOP layer as indicated by the solid arrow, and sends synchronization information and an Ack signal (Ack signal is appropriate) to the lower HOP layer as indicated by the dotted arrow. It is in a state to transmit. Txu is a state in which data is transmitted to the upper HOP layer as indicated by a solid arrow, and synchronization information and an Ack signal (Ack signal is appropriately selected) are received from the upper HOP layer as indicated by a dotted arrow.

  In the rear period Ttxrx, Txd is a state in which data is transmitted to the lower HOP layer as indicated by a solid arrow, and an Ack signal is appropriately received from the lower HOP layer as indicated by a dotted arrow. Rxu is a state in which data is received from the upper HOP layer as indicated by a solid arrow, and an Ack signal is appropriately transmitted to the upper HOP layer as indicated by a dotted arrow.

  Sleep indicates the state of the power saving mode.

  Tsrt indicates the system operation start time based on the grouping end time of the subordinate terminal, and Trxtx, Ttxrx, Trxtx,... Are repeated in order after Tsrt. Twt indicates the transmission / reception time (start-up mode time) of the main AP 101 and the subordinate terminals 201, 301, 401. Tst is the power saving mode time from Txu to Rxd (from Rxu to Txd) of the subordinate terminals 201 and 301, the power saving mode time from Txu of the subordinate terminal 401 to Txd of the main AP 101, and the Rxu of the subordinate terminal 401. The power saving mode time up to Rxd of the main AP 101 is shown.

  The main AP 101 (device control circuit 502) determines Tsrt, Trxtx (Ttxrx), Twt, and Tst after the grouping of subordinate terminals is completed. For example, the main AP 101 (device control circuit 502) calculates (determines) the time obtained by multiplying the total time of Twt and Tst by the total number of HOPs as Trxtx (Ttxrx). The main AP 101 (device control circuit 502) stores the determined Tsrt, Trxtx (Ttxrx), Twt, and Tst in the transmission / reception control memory 505, and generates power saving information indicating these times.

  Further, the main AP 101 (device control circuit 502) matches the time managed by the time circuit 501 with the time acquired from the high-performance oscillator (not shown) mounted on the main AP 101 or from the outside of the main AP 101. Then, time information indicating the time is generated. The generation of time information may be performed in parallel with grouping of dependent terminals.

  Thus, the main AP 101 (device control circuit 502) generates power saving information and time information, thereby generating synchronization information including these information.

<Transmission of synchronization information>
The main AP 101 (device control circuit 502) transmits (notifies) the generated synchronization information to the subordinate terminal 201 in the HOP-1 layer via the RF circuit 506. Of the power saving information included in the synchronization information, Tsrt may be transmitted (notified) in order from the main AP 101 to the dependent terminals 201, 301, 401 after the processing of the dependent terminals 201, 301, 401 is completed.

  The device control circuit 602 of the subordinate terminal 201 stores the power saving information included in the synchronization information received from the main AP 101 by the RF circuit 604 in its own transmission / reception control memory 603. Then, the device control circuit 602 switches between an activation mode in which data communication is performed and a power saving mode in which data communication is not performed based on the power saving information. For example, the device control circuit 602 uses the time obtained by adding the time calculated by (Twt + Tst) × (HOP number−1) to the end time of Tsrt as the start time of Txu. In the case of the subordinate terminal 201, since the number of HOPs = 1, the subordinate terminal 201 changes to the Txu state and the main AP 101 changes to the Rxd state at the end time of Tsrt.

  Further, the device control circuit 602 of the dependent terminal 201 performs control to reset the time of the time circuit 601 based on the time information included in the synchronization information. As a result, the time of the subordinate terminal 201 is synchronized with the time of the main AP 101.

  As described above, in the first embodiment, the main AP 101 and the subordinate terminal 201 in the highest HOP layer can perform data communication in synchronization based on the synchronization information. In parallel with this operation, the device control circuit 602 of the subordinate terminal 201 transmits (notifies) the synchronization information to the subordinate terminal 301 of the next lower layer (HOP-2 layer) via its own RF circuit 604. . Each slave terminal 301 performs the same operation as that of the slave terminal 201.

  Thereby, in this Embodiment 1, it becomes possible for each subordinate terminal 201 and the subordinate terminal 301 of the HOP hierarchy one level lower to perform data communication synchronously based on synchronous information. In parallel with this operation, the device control circuit 602 of the subordinate terminal 301 transmits (notifies) the synchronization information to the subordinate terminal 401 of the next lower layer (HOP-3 layer) via its own RF circuit 604. . Each slave terminal 401 performs the same operation as that of the slave terminal 301.

<Downlink transmission of synchronization information and Ack signal and uplink transmission of data>
Up to this point, only the transmission of the synchronization information has been described, but hereinafter, the downlink transmission of the synchronization information and the Ack signal and the uplink transmission of data performed in the preceding period Trxtx will be described.

  As shown in FIG. 4, after Tsrt, the main AP 101 transitions to the Rxd state, and the subordinate terminal 201 transitions to the Txu state. Then, the main AP 101 and the subordinate terminal 201 are activated only during the time period Twt, and the device control circuit 602 of the subordinate terminal 201 transmits data to the main AP 101 in accordance with CSMA / CA. When the data from the dependent terminal 201 is normally received, the device control circuit 502 of the main AP 101 transmits an Ack signal to the dependent terminal 201 and notifies the synchronization information. The device control circuit 602 of the subordinate terminal 201 recognizes that its own data has been normally transmitted to the main AP 101 based on the Ack signal from the main AP 101.

  The main AP 101 maintains the Sleep state until the time (Trxtx−Twt) elapses from the time when the Rxd state ends (until the time when Ttxrx starts).

  The subordinate terminal 201 maintains the Sleep state until the time Tst elapses from the time when the Txu state ends. Then, at the time when time has elapsed by Tst, the dependent terminal 201 transitions to the Rxd state, and enters a data reception state from the dependent terminal 301. At the same time, the subordinate terminal 301 transitions to the Txu state and enters a data transmission state to the subordinate terminal 201.

  Communication between the subordinate terminal 201 and the subordinate terminal 301 is the same as the communication between the main AP 101 and the subordinate terminal 201 described above. The communication between the dependent terminal 301 and the dependent terminal 401 is also the same as the communication between the main AP 101 and the dependent terminal 201 (similar to the communication between the dependent terminal 201 and the dependent terminal 301).

<Ack signal uplink transmission and data downlink transmission>
Next, Ack signal uplink transmission and data downlink transmission performed in the rear period Ttxrx will be described.

  The main AP 101 transitions to the Txd state when (Trxtx−Twt) has elapsed from the time when the Rxd state ends (when Ttxrx starts). At the same time, the subordinate terminal 201 transitions to the Rxu state. Then, the main AP 101 and the subordinate terminal 201 are activated only during the time period Twt, and the device control circuit 502 of the main AP 101 transmits data to the subordinate terminal 201 in accordance with CSMA / CA. The device control circuit 602 of the subordinate terminal 201 transmits an Ack signal to the main AP 101 when the data from the main AP 101 is normally received. The device control circuit 502 of the main AP 101 recognizes that its own data has been normally transmitted to the dependent terminal 201 based on the Ack signal from the dependent terminal 201.

  The main AP 101 maintains the Sleep state until the time (Ttxrx−Twt) elapses from the time when the Txd state ends (until the time when Trxtx starts).

  The subordinate terminal 201 maintains the sleep state until the time of Tst elapses from the time when the Rxu state ends. Then, at the time when time has elapsed by Tst, the subordinate terminal 201 transitions to the Txd state and enters a data transmission state to the subordinate terminal 301. At the same time, the subordinate terminal 301 transitions to the Rxu state and enters a data receiving state from the subordinate terminal 201.

  Communication between the subordinate terminal 201 and the subordinate terminal 301 is the same as the communication between the main AP 101 and the subordinate terminal 201 described above. The communication between the dependent terminal 301 and the dependent terminal 401 is also the same as the communication between the main AP 101 and the dependent terminal 201 (similar to the communication between the dependent terminal 201 and the dependent terminal 301).

  According to the communication system according to the first embodiment as described above, the main AP 101 and the subordinate terminal 201 in the highest hierarchy perform data communication in synchronization based on synchronization information (predetermined information), and The slave terminal and the slave terminal in the next lower hierarchy perform data communication in synchronization based on the synchronization information (predetermined information). Therefore, the load of beacon transmission or relay, which is an increase factor of power consumption, can be distributed throughout the subordinate terminals, so that an increase in power consumption at a specific relay terminal can be suppressed.

  Here, in general, the accuracy of time management in the time circuit 501 of the main AP 101 and the time circuit 601 of the subordinate terminals 201, 301, 401 is low, so that the timing deviation gradually increases with time and communication is performed. It may not be possible. On the other hand, according to the first embodiment, the synchronization information (predetermined information) includes time information for the main AP 101 and the subordinate terminals 201, 301, 401 to synchronize their respective times. Thereby, since the subordinate terminals 201, 301, 401 can reset the time of each time circuit 601, the synchronization with the main AP 101 can be maintained.

  Further, according to the first embodiment, when one of the main AP (each subordinate terminal) and the subordinate terminal of the highest hierarchy (subordinate terminal of the lower hierarchy) receives data from the other, An Ack signal is transmitted to the other side. Thereby, one side can recognize that the other received data.

  Moreover, according to this Embodiment 1, since main AP101 groups a subordinate terminal into a some hierarchy based on RSSI, the said grouping can be performed appropriately.

  In the above description, the subordinate terminals are arranged in the lower hierarchy of the main AP 101. However, the grouping is not limited to this. For example, another subordinate terminal such as the subordinate terminal 201 can be arranged under the subordinate terminal 401-1, using the subordinate terminal 401-1 as a substitute for the main AP 101. .

<Embodiment 2>
FIG. 5 is a diagram showing a configuration of a communication system according to Embodiment 2 of the present invention. Since the communication between the main AP 101 and the subordinate terminal according to the second embodiment is basically the same as that of the first embodiment, differences from the first embodiment will be mainly described below.

  The communication system according to the second embodiment is configured by adding a secondary AP (access point) 102 having the same function as the main AP 101 that controls the entire system to the communication system according to the first embodiment. In the communication system according to the second embodiment, when communication cannot be performed using the main communication path of the main AP 101 and the subordinate terminal (for example, when the main AP 101 fails), the sub communication path of the sub AP 102 and the subordinate terminal It is comprised so that it may communicate using.

  Hereinafter, the configuration related to the secondary AP 102 will be described in detail. The block configuration of the secondary AP 102 will be described below assuming that it is the same as the block configuration of the main AP 101 shown in FIG.

  When the secondary AP 102 acquires the time from the outside of the secondary AP 102, the time managed from the time circuit 501 of the secondary AP 102 is matched with the time acquired from the outside in the same manner as the main AP 101 to generate the reference time. Further, when the main AP 101 generates time with a high-performance oscillator mounted on the main AP 101, the sub AP 102 synchronizes the time circuit 501 of the sub AP 102 based on the time information transmitted by the main AP 101. It has a function.

<Operation>
Next, the operation of the communication system according to the second embodiment will be described. First, as in the first embodiment, the main AP 101 allocates subordinate terminals (in this case, subordinate terminals 201-1 to 201-l) to the HOP-1 layer based on RSSI. At this time, the main AP 101 cannot stably connect directly to the above weak reception strength terminal. Therefore, the main AP 101 performs control for transmitting a signal for a certain period to the weak reception strength terminal via the slave terminal 201 and causes each slave terminal 201 to receive a signal from the weak reception strength terminal for a certain period. Then, control is performed to measure the RSSI value of the signal.

  After the above-described fixed period, the subordinate terminal 201 transmits the measured RSSI value of the weak reception strength terminal to the main AP 101. Based on information such as the RSSI value received from the slave terminal 201, the main AP 101 (HOP control circuit 503) sends predetermined weak reception strength slave terminals (here, slave terminals 301-1 to 301-m) to the HOP-2 layer. The communication path between the subordinate terminal 201 in the HOP-1 layer and the subordinate terminal 301 in the HOP-2 layer is determined. Here, in the second embodiment, the main AP 101 (HOP control circuit 503) determines two types of communication paths assuming a failure of the main AP 101 and a failure of the subordinate terminal 201. The main AP 101 (HOP control circuit 503) notifies the subordinate terminals 201 and 301 of one of the two types of communication paths as the main communication path and the remaining as the sub communication path. Three or more types of communication paths may be prepared, may be determined at random, or may be determined so that the number of times the communication path passes is equal.

  Thereafter, the main AP 101 (HOP control circuit 503) assigns predetermined weak reception strength terminals (subordinate terminals 401-1 to 401-n in this case) to the HOP-3 layer by performing the same operation as described above. Then, the main AP 101 (HOP control circuit 503) determines two types of communication paths (main and sub communication paths) between the subordinate terminal 301 in the HOP-2 layer and the subordinate terminal 401 in the HOP-3 layer.

  At this time, communication paths between the subordinate terminal 201 and the subordinate terminal 301 and between the subordinate terminal 301 and the subordinate terminal 401 in the sub communication path are determined. The communication path between them has not been secured yet. Therefore, next, an operation for securing a communication path between the secondary AP 102 and the subordinate terminal 201 is performed.

  Specifically, the main AP 101 controls the slave terminal 201 to transmit a signal for a certain period, and causes the sub AP 102 to receive a signal from the slave terminal 201 for a certain period and measures the RSSI value of the signal. To control.

  After the above-described fixed period, the secondary AP 102 transmits the measured RSSI value of the dependent terminal 201 to the main AP 101. The main AP 101 uniquely determines a communication path between the sub AP 102 and the subordinate terminal 201 based on information such as an RSS value received from the sub AP 102, registers the result in the HOP memory 504, and The terminal 201 is notified. By performing the operations as described above, a secondary communication path that passes through the secondary terminals 102, 301, and 401 in order from the secondary AP 102 is defined. Thereafter, transmission of synchronization information and transmission / reception of data as described in the first embodiment are performed.

  According to the communication system according to the second embodiment as described above, for example, even when the main AP 101 fails, communication can be continued using the sub AP 102 as an alternative. Moreover, it can be expected that such an operation is realized without canceling the power saving mode.

<Embodiment 3>
FIG. 6 is a diagram showing a configuration of a communication system according to Embodiment 3 of the present invention. In the communication system according to the third embodiment, the same or similar components as those described in the second embodiment are denoted by the same reference numerals, and different points will be mainly described.

  In the communication system according to the third embodiment, a communication terminal 701 having a function equivalent to that of the subordinate terminal is added to the communication system according to the second embodiment. The communication terminal 701 has a function of transmitting an entry flag signal indicating whether or not a communication system has been entered.

  Each of the main AP 101, the sub AP 102, and the subordinate terminals 201, 301, and 401 has a function of receiving an entry flag signal from the communication terminal 701 and a function of measuring an RSSI value of an entry flag signal indicating non-entry. And. When the main AP 101, the sub AP 102, and the subordinate terminals 201, 301, 401 receive an entry flag signal indicating non-entry from the communication terminal 701, the main AP 101 or the sub AP 102 re-establishes the communication terminal 701 and the subordinate terminal. By grouping, the communication terminal 701 can be included in the subordinate terminal.

<Operation>
Next, in a state where transmission of synchronization information and transmission / reception of data have already been performed between the main AP 101 and the subordinate terminals 201, 301, 401, any of the main AP 101 and the subordinate terminals 201, 301, 401 is not An operation performed by the communication system when receiving an entry flag signal indicating entry from the communication terminal 701 (hereinafter also referred to as “new entry terminal 701”) will be described.

  Since the new entry terminal 701 has not entered the communication system, it constantly transmits a signal in accordance with CSMA / CA. The main AP 101, the sub AP 102, and the subordinate terminals 201, 301, 401 monitor whether the signal received in the Rxd state and the Rxu state (FIG. 4) includes the entry flag signal, and the entry flag indicates that the entry has not entered. If it is, the terminal recognizes that there is a new entry terminal, and measures the RSSI of the entry flag signal.

  When the main AP 101 has not failed, the sub AP 102 and the subordinate terminals 201, 301, 401 notify the main AP 101 of information including the measured RSSI value via the subordinate terminal belonging to the higher HOP layer. Then, the main AP 101 recognizes that the new entry terminal 701 exists by reception of the main AP 101 itself and notification (report) from any one of the sub AP 102 and the subordinate terminals 201, 301, 401. At the same time, the main AP 101 determines the HOP layer and communication path to which the new entry terminal 701 should belong based on the received or notified RSSI value and the number of subordinate terminals 201, 301, 401 registered in each HOP layer. To decide. Then, the main AP 101 notifies the determined HOP layer and communication path to the secondary AP 102 and the subordinate terminals 201, 301, and 401, and notifies the newly entered terminal 701 of the determined HOP layer and communication path via these as appropriate. To do.

  On the other hand, when the main AP 101 is out of order, the subordinate terminals 201, 301, 401 notify the sub AP 102 of information including the measured RSSI value via the subordinate terminal belonging to the higher HOP layer. Then, the secondary AP 102 recognizes that the new entry terminal 701 exists by reception of the secondary AP 102 itself and notification (report) from any of the subordinate terminals 201, 301, 401. At the same time, the secondary AP 102 determines the HOP layer and communication path to which the new entry terminal 701 should belong based on the received or notified RSSI value and the number of subordinate terminals 201, 301, 401 registered in each HOP layer. To decide. Then, the secondary AP 102 notifies the determined HOP layer and communication path to the subordinate terminals 201, 301, and 401, and notifies the newly entered terminal 701 of the determined HOP layer and communication path through these as appropriate.

  According to the communication system according to the third embodiment as described above, data communication can be performed between a communication terminal 701 that has not yet entered, the main AP 101, the sub AP 102, and the subordinate terminal. Moreover, it can be expected that such an operation is realized without canceling the power saving mode.

  In the above description, the case has been described in which the third embodiment is applied to the duplex system (FIG. 5) using the main AP 101 and the sub AP 102 described in the second embodiment. However, the present invention is not limited to this, and the third embodiment may be applied to a single system (FIG. 1) using the main AP 101 described in the first embodiment.

<Embodiment 4>
FIG. 7 is a diagram showing a configuration of a communication system according to Embodiment 4 of the present invention. In the communication system according to the fourth embodiment, the same or similar components as those described in the first embodiment are denoted by the same reference numerals, and different points will be mainly described.

  In the communication system (FIG. 1) described in the first embodiment, for example, when the dependent terminal 301-2 fails or leaves the communication system, the lower HOP layer through which the communication path uniquely passes through the dependent terminal 301-2. The subordinate terminal 401-2 and the subordinate terminal 401-3 are isolated from each other.

  Therefore, in the communication system according to the fourth embodiment, when a subordinate terminal becomes unable to communicate with a subordinate terminal in the next higher hierarchy, a message to that effect is transmitted to the main AP 101 via another subordinate terminal. It is configured.

  Specifically, each of the subordinate terminals 201, 301, and 401 has a function of performing transmission / reception between the same HOP layers, and communication with a subordinate terminal of a higher-order HOP layer serving as a unique communication path is interrupted. It has a function of disabling the opposite terminal to detect When the slave terminals 201, 301, 401 detect a communication interruption due to the opposite terminal non-communication function, the slave terminals 201, 301, 401 transmit communication disable information to the main AP 101 via other slave terminals.

  In the communication system according to the fourth embodiment, the main AP 101 is configured to regroup the dependent terminals when receiving the communication disabling information.

  Specifically, the main AP 101 measures the RSSI value of the notification subordinate terminal with respect to the subordinate terminal belonging to the higher HOP layer of the subordinate terminal (hereinafter referred to as “notification subordinate terminal”) that is the transmission source of the above-described communication disable information. Then, control is performed to transmit the RSSI value to the AP 101 via other slave terminals as appropriate. The main AP 101 has a function of determining a new communication path based on information such as the transmitted RSSI value, and notifies each subordinate terminal of the determined new communication path and determines it through these as appropriate. A new communication path is notified to the notification subordinate terminal.

<Operation>
Next, a specific operation of the communication system according to the fourth embodiment will be described by taking as an example a case where the dependent terminal 301-2 cannot communicate for some reason. First, the subordinate terminal 401-2 detects that the communication with the subordinate terminal 301-2 of the upper HOP layer is interrupted, and in the Txu state, the subordinate terminal 401-2 determines that the subordinate terminal of the same HOP layer (for example, the subordinate terminal 401-1). Notify communication disabled information. The subordinate terminal 401-1 notifies the main AP 101 of communication disable information via its own communication path.

  The main AP 101 controls the slave terminals 201 and 301 belonging to the higher HOP layer of the slave terminal 401-2 to receive the signal of the slave terminal 401-2 (notification slave terminal) and measure the RSSI value of the signal. Do. The subordinate terminals 201 and 301 measure the RSSI value of the subordinate terminal 401-2 (notification subordinate terminal) according to the control, and transmit (report) it to the main AP 101. Then, the main AP 101 determines (calculates) a new communication path to be taken by the subordinate terminal 401-2 (notification subordinate terminal), and sends the determined new communication path to the subordinate terminal 401- via the subordinate terminal 401-1. 2 (notification subordinate terminal). The subordinate terminal 401-2 (notification subordinate terminal) registers the received new communication path and performs data communication according to the communication path. In the example illustrated in FIG. 7, the slave terminal 401-2 (same as the slave terminal 401-3) that originally communicated with the slave terminal 301-2 continues to communicate with the slave terminal 301-1 by the above operation. The situation is shown.

  According to the communication system according to the fourth embodiment as described above, even when the subordinate terminal in the lower layer becomes unable to communicate with the subordinate terminal in the one higher layer, it bypasses to the main AP 101. A message to that effect can be sent. As a result, the subordinate terminal in the lower hierarchy can continue data communication. Moreover, it can be expected that such an operation is realized without canceling the power saving mode.

  In the above description, the case where the fourth embodiment is applied to the single system (FIG. 1) using the main AP 101 described in the first embodiment has been described. However, it is not limited to this.

  For example, also in the duplex system described in the second embodiment (FIG. 5), when the subordinate terminal 301-2 fails or leaves the communication system, the communication path uniquely passes through the subordinate terminal 301-2. There is a problem that the subordinate terminal 401-1, subordinate terminal 401-2 and subordinate terminal 401-n in the HOP layer are isolated.

  Therefore, as shown in FIG. 8, the above-described fourth embodiment may be applied to the duplex system (FIG. 5) using the main AP 101 and the sub-AP 102 described in the second embodiment. Specifically, when the subordinate terminals 201, 301, 401 detect communication interruption due to the opposite terminal non-communication function, the communication impossibility information is transmitted to the main AP 101 (sub AP 102 when the main AP 101 fails) via another subordinate terminal. Send. When the main AP 101 (the sub AP 102 when the main AP 101 fails) receives the communication disabling information, the main AP 101 regroups the subordinate terminals. Even in such a configuration, the same effect as described above can be obtained.

  It should be noted that the present invention can be freely combined with each other within the scope of the invention, and each embodiment can be appropriately modified or omitted.

  The present invention may be used in a system that requires power saving, such as a battery-driven system.

  101 Main AP, 102 Sub AP, 201, 301, 401 Subordinate terminal, 701 Communication terminal.

Claims (8)

The main AP (access point),
A subordinate terminal capable of wireless communication with the main AP,
The main AP is
Grouping the subordinate terminals into a plurality of layers, and generating predetermined information including a start mode time and a power saving mode time of the subordinate terminals for the subordinate terminals to perform data communication according to the layers,
Based on the predetermined information, the main AP and the subordinate terminal of the highest layer that receives the predetermined information from the main AP, according to the layer, the activation mode time, and the power saving mode time Synchronize data communication at the communication start time ,
Based on the predetermined information, each subordinate terminal and the subordinate terminal of the next lower hierarchy that receives the predetermined information from the subordinate terminal are divided into the hierarchy, the activation mode time, and the power saving mode time. Data communication is performed synchronously at the corresponding communication start time ,
The communication system in which the subordinate terminals in the same hierarchy can start data communication at the same communication start time . The communication system according to claim 1,
The predetermined information is
Said dependent terminal indicates time for performing the data communication in accordance with the hierarchy and saving information including the start-up mode time and the power saving mode time, the main AP and the subsidiary terminal synchronizes each time Communication system including time information for the communication. A communication system according to claim 1 or claim 2, wherein
When one of the main AP and the slave terminal of the highest layer receives data from the other, transmits an Ack signal to the other,
A communication system in which one of the subordinate terminals and the subordinate terminal of the lower layer transmits an Ack signal to the other when receiving data from the other. A communication system according to any one of claims 1 to 3,
The communication system in which the main AP and the subordinate terminal perform the data communication using a carrier sense multiple access / collision avoidance method (CSMA / CA). A communication system according to any one of claims 1 to 4,
Sub AP (access point) having the same function as the main AP
Further comprising
A communication system that performs communication using a sub-communication path between the sub-AP and the subordinate terminal when communication becomes impossible using the main communication path between the main AP and the subordinate terminal. A communication system according to any one of claims 1 to 5,
A communication terminal having a function equivalent to that of the subordinate terminal;
A communication system in which, when the main AP and the subordinate terminal receive an entry flag indicating non-entry from the communication terminal, the communication terminal is included in the subordinate terminal. A communication system according to any one of claims 1 to 6,
When the subordinate terminal becomes unable to communicate with the subordinate terminal in the next higher hierarchy, the subordinate terminal transmits a message to that effect to the main AP via the other subordinate terminal. A communication system according to any one of claims 1 to 7,
The main AP is
A communication system that groups the subordinate terminals into the plurality of layers based on RSSI (Received Signal Strength Indication).

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