JP5561646B2 - Wireless communication terminal and wireless communication method - Google Patents

Description

  The present invention relates to a technique for avoiding control signal collision in a multi-hop wireless communication system.

  In recent years, there is a wireless communication network based on ZigBee (registered trademark) as a system expected to be utilized and spread in a sensor network or the like (Non-Patent Documents 1 and 2). In this wireless communication network, for example, two topologies can be used. One topology is a star topology, and a node called an end device is arranged around a wireless communication terminal (node) called a coordinator. A star topology is a simple network with only one hop. The other topology is a PtoP (Peer to Peer) type topology, which basically performs one-to-one communication between nodes. In a PtoP type topology, a multi-hop network can be constructed by having all nodes have router functions. For example, in a tree-type topology based on PtoP, a node called a coordinator is a vertex (root), and a node called a router having a relay function and a node called an end device having no relay function are arranged. The relay function is a function that includes a routing table and transfers data based on the routing table.

  In this wireless communication network, a CSMA / CA (Carrier Sense Multiple Access / Collision Avoidance) system is adopted. In CSMA / CA, a node performs carrier sense before transmission. Then, the node transmits after confirming that the signal is not transmitted to the wireless channel. Therefore, even when the node is not transmitting a signal, the node needs to be on standby to receive a signal from another node. Therefore, there is a problem that power consumption is large.

  In response to such a problem, in this wireless communication network, a beacon mode using a superframe configuration is prepared. In the beacon mode, the time from when a beacon signal is transmitted until the next beacon signal is transmitted is divided into an active (active) period and an inactive (inactive) period. The coordinator transmits information including an active period and an inactive period in a beacon signal. In the active period, an allocation period (GTS) in which communication is permitted only to a specific node can be provided. The beacon signal is forcibly transmitted at a constant period without performing carrier sense. In the active period, signal transmission / reception is performed, while in the inactive period, signal transmission / reception is not performed. Therefore, the node does not need to grasp the transmission status of other nodes during the inactive period, and power consumption can be reduced.

“IEEE Std 802.15.4”, [online], [searched on November 25, 2010], Internet <URL: http://www.ieee802.org/15/pub/TG4.html> Tatetsu, “ZigBee Development Handbook”, Rick Telecom, February 2006

  However, the beacon mode has been defined only considering application to a star network topology. Therefore, if it is applied as it is to a multi-hop network represented by a tree-type network topology, a problem occurs. For example, in a multi-hop network, since a beacon signal needs to be transmitted to all nodes, the router relays the beacon signal. At this time, if a plurality of routers are connected to one network, beacons transmitted from the plurality of routers may collide. Therefore, it becomes difficult for all the nodes to receive the beacon signal normally. Unlike the data signal, the beacon signal is automatically transmitted periodically without performing carrier sense, and thus the above-described problem occurs. Since the beacon signal includes control information for configuring a superframe, if this is lost due to a collision, the network breaks down. As a result, there is a problem that the beacon mode cannot be used in a multi-hop network.

  In view of this problem, the present invention provides a technique for realizing an operation in a beacon mode in a multi-hop network.

  In order to solve the above-described problem, the present invention provides that a plurality of wireless communication terminals connected in a hierarchical structure are themselves within a predetermined active period among output intervals of beacon signals output at a predetermined beacon period. A wireless communication terminal in a wireless communication system that communicates with another wireless communication terminal within an assignment period assigned to the self-communication from a higher-layer communication terminal that is a wireless communication terminal in a hierarchy one level higher in the hierarchical structure. In the hierarchical structure, a beacon signal receiving unit that receives a beacon signal including information indicating an allocation period allocated to the beacon signal, and a period within its own allocation period indicated by information included in the beacon signal received by the beacon signal receiving unit A beacon that generates a beacon signal including information indicating an allocation period to be assigned to a lower-layer communication terminal that is a lower-layer wireless communication terminal. A plane generator, within the allotted time period allocated to itself, a beacon signal generated by the beacon generation unit, characterized in that it comprises a beacon transmission unit for transmitting to the lower-level communication terminal.

  Further, according to the present invention, the above-described active period is a period indicated by a power of 2 of a predetermined basic period, and the allocation period is a time slot that is 1/16 of the active period. The beacon generation unit assigns any number of time slots among 1, 2, 4, and 8 among the 16 time slots included in its active period to the lower layer communication. A beacon signal including information indicating an allocation period to be allocated to a terminal is generated.

In addition, the present invention provides a plurality of wireless communication terminals connected in a hierarchical structure within an allocation period allocated to themselves within a predetermined active period among output intervals of beacon signals output at a predetermined beacon period. A wireless communication method of a wireless communication terminal in a wireless communication system that communicates with another wireless communication terminal, which is assigned to itself from an upper-layer communication terminal that is a wireless communication terminal in a hierarchy higher in the hierarchical structure. A step of receiving a beacon signal including information indicating an allocation period and a period within its allocation period indicated by the information included in the received beacon signal are a wireless communication terminal in a hierarchy lower than itself in the hierarchical structure. Generating a beacon signal including information indicated as an allocation period allocated to the hierarchical communication terminal, and within the allocation period allocated to itself, The beacon signals generated by the generating unit, characterized in that it comprises the steps of: transmitting at a lower hierarchy communication terminal.

  As described above, according to the present invention, a beacon including a wireless communication terminal including information indicating an allocation period allocated to itself from an upper layer communication terminal that is a wireless communication terminal in the hierarchy one level higher in the hierarchical structure. Information indicating a period within the allocation period of the receiver indicated by the information included in the received beacon signal as an allocation period to be allocated to a lower hierarchy communication terminal that is a radio communication terminal of a hierarchy lower than itself in the hierarchical structure. The beacon signal is generated, and the beacon signal generated by the beacon generator is transmitted to the lower layer communication terminal within the allocation period allocated to itself. Therefore, the operation in the beacon mode is performed in the multi-hop network. Can be realized.

It is a block diagram which shows the structural example of the radio | wireless communication terminal by one Embodiment of this invention. It is a figure which shows the structure of the communication network by one Embodiment of this invention. It is a figure which shows the example of control by the beacon mode of the communication network by one Embodiment of this invention. It is a figure which shows the example of control by the beacon mode of the communication network by one Embodiment of this invention. It is a figure which shows the example of the slot number of GTS allocated by one Embodiment of this invention. It is a figure which shows the example of GTS allocated by one Embodiment of this invention. It is a figure which shows the example of the topology which allocates GTS by one Embodiment of this invention. It is a flowchart which shows the operation example of the communication system by one Embodiment of this invention. It is a figure which shows the operation example of the communication system by one Embodiment of this invention. It is a figure which shows the collision example of the beacon by a prior art.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a block diagram illustrating a configuration of a wireless communication terminal 10 according to the present embodiment.
The radio communication terminal 10 is connected to the hierarchical structure of a plurality of radio communication terminals 10 and within an allocation period allocated to itself within a predetermined active period among output intervals of beacon signals output at a predetermined beacon period. The communication terminal forms a wireless communication network (ZigBee (registered trademark) network) that communicates with other wireless communication terminals 10.

  FIG. 2 is a diagram illustrating an example of the communication network 1 to which the wireless communication terminal 10 is connected. Here, a communication network 1 having a tree topology is formed, all wireless communication terminals connected to the communication network 1 are referred to as nodes, and one wireless communication terminal 10 that is the top of the hierarchical structure is referred to as a coordinator. The wireless communication terminal 10 connected to the coordinator and having a relay function is called a router. Nodes that do not have a relay function are called end devices. The upper hierarchy and the lower hierarchy are relative relationships as seen from a certain node. For example, when viewed from a certain node, the node that connects itself as the lower layer, that is, the node that is the upper layer for itself is called the upper layer node (upper layer communication terminal), and the node that connects itself as the upper layer node is the lower layer It is called a hierarchical node (lower hierarchical communication terminal).

  In this figure, a wireless communication terminal 10-1-1 and a wireless communication terminal 10-2-1 as routers are connected to a lower layer of the wireless communication terminal 10-0 as a coordinator, and the wireless communication terminal 10-1- A wireless communication terminal 10-1-2 that is a router is further connected to a lower layer of 1, and an end device 20-1 is connected to a lower layer of the wireless communication terminal 10-1-2. An end device 20-2 is connected to the radio communication terminal 10-2-1 in the lower layer. Here, the wireless communication terminal 10-0, the wireless communication terminal 10-1-1, the communication network 10-1-2, and the wireless communication terminal 10-2-1 have the same configuration and need not be particularly distinguished. Will be described as a wireless communication terminal 10. The end device 20 is a wireless communication terminal that communicates with the wireless communication terminal 10. The end device 20 is a sensor, for example, and transmits data acquired by sensing to the wireless communication terminal 10.

  Here, when the wireless communication terminal 10 connects to the communication network 1, another wireless communication terminal 10 is connected as an upper layer node, and an address in the communication network 1 is given from the upper layer node. When the wireless communication terminal 10 detects a plurality of communicable nodes that can be in the upper hierarchy when connecting to the communication network 1, the reception power of the beacon signal transmitted by each detected node is measured, and the most received It is possible to connect to a node that transmits a high-level beacon signal.

  FIG. 3 is a diagram illustrating a control example of the communication network 1 in the beacon mode. Here, a beacon signal is output every fixed period (Tb). As described above, the time (beacon period) from when a beacon signal is transmitted until the next beacon signal is transmitted is divided into an active (active) period and an inactive (inactive) period. The coordinator and the router transmit information including a beacon period and an active period in a beacon signal. The inactive period is calculated from the difference between the beacon period and the active period. The active period started by the beacon signal is called a super frame.

  Such a superframe is divided into 16 time slots. The time slot is divided into a mandatory CAP (Contention Access Period) period and an optional CFP (Contention Free Period) period. In the CFP period, a GTS (Guaranteed Time Slot) (allocation period) in which only one communicable node is limited is provided. One GTS is assigned to a specific node, and a node to which a GTS is assigned can exclusively transmit a signal without performing carrier sense in the GTS. The maximum number of GTS is 7. The CAP period is multiple access based on Slotted-CSMA / CA, and each node performs carrier sense and transmits / receives after confirming availability. The GTS assigns one or more dedicated time slots to a specific node in advance, and there is no need for carrier sense because no collision occurs. In each time slot, two-way bi-directional communication is performed from the upper hierarchy node to the lower hierarchy node and from the lower hierarchy node to the upper hierarchy node.

Returning to FIG. 1, the wireless communication terminal 10 includes a reception processing unit 11, a beacon generation timing calculation unit 12, a beacon generation unit 13, a transmission processing unit 14, a switch 15, a control unit 16, and a data processing unit 17. And.
The reception processing unit 11 receives a signal transmitted from another wireless communication terminal 10 or end device 20 connected to the communication network 1. For example, the reception processing unit 11 receives a beacon signal including information indicating the GTS allocated to itself from an upper layer node that is the radio communication terminal 10 of the layer one level higher in the hierarchical structure of the communication network 1. Here, the beacon signal includes information indicating the beacon period in which the beacon signal is output, information indicating the superframe length, information indicating the CAP period and CFP period of the time slot, information indicating allocation of GTS in the CFP period, and the like Is included.

  Here, the reception processing unit 11 performs processing such as A / D conversion, frequency conversion, and demodulation on the radio signal received via the antenna, and extracts a baseband signal. The baseband signal is input to the control unit 16, and when it is a data signal, it is output to the data processing unit 17. In other cases, for example, when the signal received by the router is a beacon signal, slot allocation information included therein is extracted, and the time slot timing of the GTS allocated to the local station is the beacon generation timing. Processing according to the signal, such as being output to the calculation unit 12, is performed.

  The beacon generation timing calculation unit 12 calculates the timing at which it outputs a beacon signal. For example, the beacon generation timing calculation unit 12 in the wireless communication terminal 10 (wireless communication terminal 10-0) serving as a coordinator outputs a signal instructing the beacon generation unit 13 to generate a beacon at a predetermined beacon period. On the other hand, the beacon generation timing calculation unit 12 in the wireless communication terminal 10 (wireless communication terminal 10-1-1, wireless communication terminal 10-1-2, wireless communication terminal 10-2-1), which is a router, is assigned to the own station. When the timing of the received GTS is input by the control unit 16, a signal instructing the beacon generation unit 13 to generate a beacon is output according to the timing of the GTS. As described above, the beacon generation timing calculation unit 12 calculates the timing at which the beacon is output without overlapping with the other wireless communication terminals 10.

  Here, the timing calculated by the beacon generation timing calculation unit 12 will be described with reference to the drawings. FIG. 4 is a diagram illustrating timings calculated by the beacon generation timing calculation unit 12. In this way, in the relationship between the upper hierarchy node and the lower hierarchy node, one GTS in the superframe of the upper hierarchy node includes the active period of the lower hierarchy node to which the GTS is assigned so that A beacon generation timing is calculated. In this way, the superframe of the lower hierarchy node is configured by subdividing the GTS of the upper hierarchy node.

  Returning to FIG. 1, the beacon generator 13 generates a beacon signal according to the timing calculated by the beacon generation timing calculator 12. Here, the beacon generation unit 13 sets the period in its own GTS indicated by the information included in the beacon signal received by the reception processing unit 11 to the lower hierarchy that is the radio communication terminal 10 in the hierarchy lower than itself in the hierarchical structure. A beacon signal including information indicated as GTS to be allocated to the node is generated. Here, when there is a router connected to the own station, the beacon generation unit 13 allocates at least one GTS to the router, and then notifies the GTS timing for each router by a beacon signal. To do. Thereby, the lower hierarchy node can know the timing of the GTS slot allocated to the own station.

  Here, the number of slots allocated to the lower layer node (the number of slots constituting the GTS) is added such as the number of nodes connected to itself, the number of nodes connected to the lower layer router, or the amount of traffic handled by the lower layer node. It is determined based on the conditions. Further, the lower layer node further divides the allocated GTS into 16 slots and performs allocation as CAP or CFP. That is, a superframe generated by a lower-layer router assigned a GTS composed of one upper-layer superframe time slot and a GTS composed of two or more upper-layer superframe time slots The time slot length of the superframe generated by the lower layer router to which is assigned is different, and the latter generates a longer time slot than the former.

  Here, in the ZigBee (registered trademark) network, the active period is a period indicated by a power of 2 of a predetermined basic period, and GTS is a time slot that is 1/16 of the active period. Is assigned as a unit. Therefore, the beacon generating unit 13 is information indicating GTS that allocates any number of time slots 1, 2, 4, and 8 among the 16 time slots included in its active period as a lower layer node. A beacon signal including is generated.

Specifically, the super frame length SD is defined to be expressed by a power of 2 as expressed by the following equation (1) with respect to BSD (basic super frame length).
SD = BSD × 2 ^SO (1)
Here, SO is a variable for substantially defining SD, and is notified to the lower hierarchy node by a beacon signal. Since the minimum unit of GTS allocated to the lower layer node is 1/16 of the SD length, the number of slots to be allocated is any one of 1, 2, 4, and 8 as shown in FIG. Here, the upper layer superframe is divided into 16 frames, and a frame is allocated to one of them. Therefore, the frame of the frame allocated to itself with respect to the length of the parent frame (relatively one frame above) is allocated. The length is 1/16, and the index is -4. Thereby, for example, even if three time slots are assigned as GTSs to the lower layer, the above formula (1) is not satisfied, and only the same length as when two are assigned can be used. Similarly, for example, when the number of slots allocated to the GTS is 4 to 7, all have the same child superframe (relatively lower superframe) length. That is, a slot that cannot be expressed by a power of 2 with respect to the BSD cannot be used and is discarded. FIG. 6 is a diagram showing an example of such assignment.

  Here, according to the standard, the SO of the formula (1) is specified as 14 being the maximum value. That is, when the index of 2 in equation (1) becomes 0, it becomes the basic length (shortest length) of the superframe, and beacon relay using GTS beyond that becomes impossible. An example of GTS allocation at this time is shown in FIG. If a GTS composed of 8 time slots is assigned to a child router and a grandchild router, a maximum of 14 relay stages can be relayed. On the other hand, the number of child routers that can be connected per router is 7 depending on the number of GTS that can be set.

  The transmission processing unit 14 receives signals from other wireless communication terminals 10 connected to the communication network 1. The transmission processing unit 14 performs processes such as modulation, D / A conversion, and frequency conversion on the beacon signal input by the beacon generation unit 13 and the data signal input by the data processing unit 17 via the control unit 16. And transmit as a radio signal via a switch and an antenna. For example, the transmission processing unit 14 transmits the beacon signal generated by the beacon generation unit 13 to the lower layer node in the GTS assigned to itself.

The switch 15 switches between reception processing by the reception processing unit 11 and transmission processing by the transmission processing unit 14 performed via the antenna.
The control unit 16 controls each unit included in the wireless communication terminal 10.
The data processing unit 17 performs data communication processing with other wireless communication terminals 10 performed during the CAP period.

Next, an operation example of the wireless communication terminal 10 according to the present embodiment will be described. FIG. 8 is a flowchart illustrating an operation example of beacon transmission processing by the wireless communication terminal 10.
FIG. 8 shows beacon signal generation processing and transmission processing of the wireless communication terminal 10 which is a router according to the present embodiment. First, when the beacon generation timing calculation unit 12 inputs a beacon generation instruction to the beacon generation unit 13, the beacon generation unit 13 inquires of 16 whether or not a subordinate router is performing a relay process (step S1). ).

  Here, whether or not the subordinate router is performing the relay processing is based on the fact that when the other node is connected to the subordinate router, the subordinate router has connected to the router. This can be grasped by notifying that the relay processing is started). If the subordinate router is not performing the relay processing (step S1: No), the process proceeds to step S3, where a beacon signal including control information and the like is generated, and the beacon is transmitted at the head of the GTS assigned to itself.

  On the other hand, when the subordinate router performs the relay process (step S1: Yes), a beacon including the information is assigned to the router with a GTS of at least one slot for the superframe that it constitutes (step S2). Is generated (step S3), and the beacon is transmitted at the head of the GTS allocated to itself (step S4). As described above, the number of time slots constituting a GTS is determined in consideration of the amount of traffic handled by a subordinate router to which the GTS is assigned. Here, if at least one time slot is assigned, the subordinate This router can also perform relay processing.

  FIG. 9 is a diagram illustrating an operation example when the present embodiment is applied to the network configuration illustrated in FIG. 2. Here, the CAP period is briefly described for convenience. The super frame of the radio communication terminal 10-0 that is a coordinator is started by a beacon signal and includes a CAP, a CFP, and an inactive period. The CFP is composed of a plurality of GTSs. Here, the case where there are two GTSs is shown. The transmitted beacon signal is received by the wireless communication terminal 10-1-1 and the wireless communication terminal 10-2-1 which are lower layer routers, and each router receives the wireless communication terminal 10- which is a coordinator in the CAP period. Data is transmitted to and received from 0.

  Also, the wireless communication terminal 10-1-1 that is a router forms a superframe having the same configuration as the superframe of the coordinator in the GTS1 allocated to itself in the superframe of the wireless communication terminal 10-0 that is the coordinator. . The beacon signal in the superframe of the wireless communication terminal 10-1-1 is received by the wireless communication terminal 10-1-2, which is a lower-layer router, and wirelessly communicates with the wireless communication terminal 10-1-1 during the CAP period. Data is transmitted / received to / from the communication terminal 10-1-2.

  Here, the wireless communication terminal 10-1-2, which is a lower-layer router, configures a superframe in the GTS in the superframe of the wireless communication terminal 10-1-1. The beacon signal in this super frame is received by the end device 20-1, and data is transmitted and received between the wireless communication terminal 10-1-2 and the end device 20-1 in the CAP period. In this example, since no other node is connected to the end device 20-1, the wireless communication terminal 10-1-2 does not set GTS. For example, when the end device 20-1 uses an application that requires bandwidth guarantee such as VoIP, one GTS may be assigned to the node 1. As described above, each router determines whether to assign a GTS based on whether or not a subordinate node performs relay processing and whether or not bandwidth compensation is necessary. By assigning GTS, it is possible to relay while avoiding beacon collisions.

  On the other hand, the wireless communication terminal 10-2-1 that is the router that has received the beacon signal transmitted from the wireless communication terminal 10-0 is the same as the superframe of the coordinator in the GTS2 allocated to the coordinator superframe. Configure the superframe by configuration. The beacon signal in the super frame of the wireless communication terminal 10-2-1 is received by the end device 20-2, and data is transmitted and received between the wireless communication terminal 10-2-1 and the end device 20-1 in the CAP period. Is done. Since no other node is connected to the end device 20-1, the wireless communication terminal 10-2-1 does not set GTS.

  As a result, when controlling the beacon mode in a communication network having a tree topology according to the prior art, it is conceivable that beacon signals collide and control information cannot be acquired as shown in FIG. According to the form, beacon signals do not collide. That is, according to the present embodiment, in the tree topology, the beacon signal transmitted by the lower layer router connected to the coordinator is transmitted at the head of the GTS assigned to the lower layer router in the super frame of the coordinator. And beacons will not collide between lower layer routers. In addition, the relationship between the superframe of the lower layer router and the superframe of the lower layer is the same as the relationship between the superframe of the coordinator and the superframe of the lower layer coordinator. But there is no collision. Since such a nested structure is repeated to form a super frame in each router, relaying is possible even in a tree topology without causing a beacon collision.

  Moreover, according to this embodiment, all the radio | wireless communication terminals 10 can be controlled so that a beacon signal may not collide autonomously and distributedly. Furthermore, since no node communicates wirelessly during the interval designated by the coordinator as an inactive period, even when coexisting with other standard wireless communication systems, for example, communication with other standard wireless communication systems during the inactive period is possible. By doing so, wireless communication systems with different standards can coexist. Further, according to the present embodiment, the GTS assigned to the lower layer node in the tree topology is shorter. For example, when the end device in the communication network 1 is a sensor, the GTS is upgraded from the end device. Since there are many cases in which the information goes up by the link, it is assumed that the higher the hierarchy, the more information gathers and the more bandwidth is required. That is, a configuration in which a lower GTS is assigned to a lower layer node is considered to be a configuration suitable for such a communication network 1.

  Note that a program for realizing the function of the processing unit in the present invention is recorded on a computer-readable recording medium, and the program recorded on the recording medium is read into a computer system and executed to control wireless communication. May be performed. Here, the “computer system” includes an OS and hardware such as peripheral devices. The “computer system” includes a WWW system having a homepage providing environment (or display environment). The “computer-readable recording medium” refers to a storage device such as a flexible medium, a magneto-optical disk, a portable medium such as a ROM and a CD-ROM, and a hard disk incorporated in a computer system. Further, the “computer-readable recording medium” refers to a volatile memory (RAM) in a computer system that becomes a server or a client when a program is transmitted via a network such as the Internet or a communication line such as a telephone line. In addition, those holding programs for a certain period of time are also included.

  The program may be transmitted from a computer system storing the program in a storage device or the like to another computer system via a transmission medium or by a transmission wave in the transmission medium. Here, the “transmission medium” for transmitting the program refers to a medium having a function of transmitting information, such as a network (communication network) such as the Internet or a communication line (communication line) such as a telephone line. The program may be for realizing a part of the functions described above. Furthermore, what can implement | achieve the function mentioned above in combination with the program already recorded on the computer system, what is called a difference file (difference program) may be sufficient.

DESCRIPTION OF SYMBOLS 1 Communication network 10 Wireless communication terminal 11 Reception processing part 12 Beacon generation timing calculation part 13 Beacon generation part 14 Transmission processing part 15 Switch 16 Control part 17 Data processing part 20 End device

Claims (2)

A plurality of wireless communication terminals connected in a hierarchical structure may receive other wireless signals within an assigned period assigned to itself within a predetermined active period of the output interval of beacon signals output at a predetermined beacon period. The wireless communication terminal in a wireless communication system that communicates with a communication terminal,
A beacon signal receiving unit that receives a beacon signal including information indicating the allocation period allocated to itself from an upper layer communication terminal that is the wireless communication terminal in a layer higher than itself in the hierarchical structure;
Allocating a period within its own allocation period indicated by the information included in the beacon signal received by the beacon signal receiving unit to a lower-layer communication terminal that is the wireless communication terminal at a lower layer than itself in the hierarchical structure A beacon generator that generates a beacon signal including information indicated as the allocation period;
A beacon transmitter that transmits the beacon signal generated by the beacon generator to the lower-layer communication terminal within the allocation period allocated to itself;
Equipped with a,
The active period is a period indicated by a power of 2 of a predetermined basic period, and the allocation period is allocated in units of time slots that are 1/16 of the active period. And
The beacon generation unit indicates any number of time slots of 1, 2, 4, and 8 among 16 time slots included in its active period as an allocation period for allocating to the lower-layer communication terminal. Generate a beacon signal containing information
A wireless communication terminal characterized by the above. A plurality of wireless communication terminals connected in a hierarchical structure may receive other wireless signals within an assigned period assigned to itself within a predetermined active period of the output interval of beacon signals output at a predetermined beacon period. A wireless communication method of the wireless communication terminal in a wireless communication system for communicating with a communication terminal,
Receiving a beacon signal including information indicating the allocation period allocated to itself from an upper-layer communication terminal which is the wireless communication terminal in a hierarchy one higher than itself in the hierarchical structure;
Including information indicating a period in its own allocation period indicated by the information included in the received beacon signal as an allocation period to be allocated to a lower-layer communication terminal that is the lower-layer communication terminal in the hierarchical structure. Generating a beacon signal;
Transmitting the beacon signal generated in the step of generating the beacon signal to the lower layer communication terminal within the allocation period allocated to itself;
Equipped with a,
The active period is a period indicated by a power of 2 of a predetermined basic period, and the allocation period is allocated in units of time slots that are 1/16 of the active period. And
In the step of generating the beacon signal, an allocation in which any one of 1, 2, 4, and 8 time slots among the 16 time slots included in its active period is allocated to the lower layer communication terminal. A radio communication method comprising generating a beacon signal including information indicated as a period .

Images