JP5544573B2 - Wireless communication terminal and wireless communication method - Google Patents

Description

  The present invention relates to a wireless communication terminal and a wireless communication method for coexistence of a wireless PAN (Personal Wireless Network) and a wireless LAN (Local Area Network) in a multi-hop wireless communication system.

  In recent years, there is a wireless communication network based on ZigBee (registered trademark, the same applies hereinafter) as a system expected to be utilized and spread in sensor networks and the like. In this wireless communication network, for example, two topologies can be used. The first 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 ZigBee coordinator is used as 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 / Collection Aidance) system is adopted. In CSMA / CA, a node performs carrier sense (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 cycle (beacon cycle) 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, in the inactive period, the node does not need to grasp the transmission status of other nodes, and can reduce power consumption.

“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 Robert Morrow, “Active Coexistence,” in Wireless Network Coexistence: McGraw-Hill, 2004. pp.374: Alternating Wireless Medium Access (AWMA).

  Although many sensor networks generally have a small amount of traffic, for example, when a control system signal is transmitted / received to / from a sensor, the communication quality of such traffic may be important. On the other hand, the frequency band used by ZigBee is also used for wireless LAN systems. Therefore, the frequency band is divided and used in these systems in time, but when ZigBee is operated in the beacon mode, the ZigBee node needs to periodically transmit a beacon signal. is there.

  However, if a wireless LAN signal is transmitted in a time zone in which the beacon signal is scheduled to be transmitted, the ZigBee node cannot transmit the beacon signal. Alternatively, if a wireless LAN node transmits a beacon signal while the ZigBee node is transmitting a beacon signal, a collision occurs and the ZigBee node cannot normally receive the beacon signal. In any situation, if a beacon signal cannot be received, subsequent communication cannot be performed, and there is a problem that communication cannot be performed between the ZigBee nodes.

  To deal with this problem, Non-Patent Document 3 provides a technique in which a period between beacons is divided in time and used by each system in a time division manner when a wireless LAN and Bluetooth coexist. Yes. The same can be done by replacing Bluetooth with ZigBee. However, since this technique requires a change to the wireless LAN, it is not realistic in the current situation where there are a large number of wireless LAN nodes.

  The present invention has been made in view of the above points, and even in an environment in which different wireless communication systems coexist, communication is reliably performed in any wireless communication system without changing existing terminals. An object of the present invention is to provide a wireless communication terminal and a wireless communication method.

The present invention has been made to solve the above-described problem, and communicates with other wireless communication terminals within a predetermined active period within an output interval of a beacon signal output at a predetermined beacon cycle. A wireless communication terminal provided with a wireless interface for performing communication between a first wireless communication system to be performed and a second wireless communication system that performs autonomous distributed communication by carrier sense, wherein the first wireless First transmission means for transmitting a beacon signal in a communication system, and second transmission means for transmitting a channel reservation signal for reserving a channel to be used in the first wireless communication system prior to transmission of the beacon signal If, based on the maximum time a packet is likely to occupy a channel in said second wireless communication system, transmitting the second Determine the timing to transmit instructions to the stage, a wireless communication terminal; and a transmission control means for instructing the transmission to the second transmitting means to the timing.

  In the present invention, the channel reservation signal includes information for reserving a channel over a period from the end of transmission of the channel reservation signal to the end of an active period allocated after transmission of the beacon signal. The wireless communication terminal according to claim 1.

  The radio communication terminal according to claim 1, wherein the second transmission means is activated earlier by a predetermined period than the transmission time of the beacon signal by the first transmission means. It is.

  Further, according to the present invention, after the transmission of the channel reservation signal, the second transmission unit transmits a reception preparation completion signal addressed to itself again before the transmission of the beacon signal by the first transmission unit. A wireless communication terminal according to any one of claims 1 to 3.

In addition, the present invention provides a first wireless communication system that communicates with other wireless communication terminals within a predetermined active period in a beacon signal output interval that is output at a predetermined beacon period, and carrier sense. A wireless communication method in a wireless station having a wireless interface for performing respective communication with a second wireless communication system that performs communication in an autonomous distributed manner, and transmitting a beacon signal in the first wireless communication system A first transmission process, and a transmission control process for determining a timing for instructing transmission based on a maximum time during which one packet may occupy a channel in the second wireless communication system, and instructing transmission at the timing If, on the timing determined, prior to transmission of the beacon signal, used in the first wireless communications system It is a wireless communication method characterized by comprising a second transmission step of transmitting a channel reservation signal to reserve that channel.

  Further, according to the present invention, the channel reservation signal includes information for reserving a channel over a period from the end of transmission of the channel reservation signal to the end of the active period after transmission of the beacon signal. The wireless communication method according to claim 5, wherein the method is a wireless communication method.

  Further, according to the present invention, the second transmission process is started earlier by a predetermined period than the transmission time of the beacon signal transmitted in the first transmission process. A wireless communication method.

  Further, according to the present invention, in the second transmission process, after transmission of the channel reservation signal, a transmission preparation completion signal addressed to itself is transmitted again prior to transmission of the beacon signal in the first transmission process. The wireless communication method according to claim 5, wherein the wireless communication method is a wireless communication method.

According to the present invention, prior to the beacon signal transmission time of the first wireless communication system, a channel reservation signal for reserving a channel to be used in the first wireless communication system is transmitted by the second transmission means, and channel reservation is performed. I do.
Thereby, even in an environment where different wireless communication systems coexist, it is possible to reliably communicate with any wireless communication system without changing existing terminals.

It is a block diagram for demonstrating the structure of a radio | wireless communications system using the hybrid terminal (wireless communication terminal) by 1st Embodiment of this invention, and a substantially operation | movement. It is a figure which shows the example of control by the beacon mode of the hybrid terminal by 1st Embodiment of this invention. It is a block diagram which shows the structure of the hybrid terminal by 1st Embodiment of this invention. 4 is a timing chart illustrating an operation of the hybrid terminal according to the first embodiment of the present invention. 4 is a timing chart illustrating an operation of the hybrid terminal according to the first embodiment of the present invention. It is a block diagram for demonstrating the structure of a radio | wireless communications system using the hybrid terminal by 2nd Embodiment of this invention, and a substantially operation | movement. 6 is a timing chart illustrating an operation of the hybrid terminal according to the second embodiment of the present invention. It is a conceptual diagram for demonstrating the evaluation result at the time of simulating using the hybrid terminal by 1st and 2nd embodiment of this invention. It is a conceptual diagram for demonstrating the effect by operating the minimum value CWmin of the contention window size when the hybrid terminal by 1st and 2nd embodiment of this invention is used.

  An embodiment of the present invention will be described in detail with reference to the drawings. In the present invention, a hybrid terminal (wireless communication terminal) having both ZigBee and wireless LAN wireless interfaces is prepared, and the hybrid terminal first reserves a channel through the wireless LAN interface, and the wireless LAN is ZigBee. Avoid sending signals at beacon transmission timing. By doing so, the ZigBee coordinator reliably sends out a beacon signal at the beacon period and can receive the subordinate node, so even in an environment where a wireless LAN exists in the vicinity, it is possible to communicate with ZigBee in the beacon mode. It becomes like this. Note that the wireless LAN interface only needs to operate from a predetermined period before sending out the beacon signal, so that the other period can be set to the power saving operation.

A. First Embodiment FIG. 1 is a block diagram for explaining a configuration and a schematic operation of a wireless communication system using a hybrid terminal (wireless communication terminal) according to a first embodiment of the present invention. In the figure, a wireless communication system includes a wireless LAN base station (WLAN AP) 1-1, wireless LAN terminals (WLAN nodes) 1-2 to 1-4, and a plurality of ZigBee terminals (ZigBee nodes) 2-1. 2-3 and one hybrid terminal (wireless communication terminal) 3. The hybrid terminal 3 includes both a wireless LAN interface (communication function) 3-1 and a ZigBee interface (communication function) 3-2.

  First, the hybrid terminal 3 transmits an RTS (Request to Send) signal to the wireless LAN base station 1-1 using the wireless LAN interface 3-1 (Sa1). The RTS signal includes period information for reserving a channel by ZigBee. The wireless LAN base station 1-1 returns a CTS (Clear To Send) signal to the hybrid terminal 3 and the other wireless LAN terminals 1-2 to 1-4 according to the received RTS signal (Sa2). ). Thereby, it is avoided that the wireless LAN terminals 1-1 to 1-4 transmit signals during the reserved period. Meanwhile, the ZigBee terminals 2-1 to 2-3 including the wireless interface (communication function) 3-2 of the hybrid terminal 3 perform ZigBee communication including transmission of a beacon signal (Sa3).

  FIG. 2 is a diagram illustrating a control example of the hybrid terminal 3 in the beacon mode. Here, a beacon signal is output every fixed period (Tb). The time from when a beacon signal is transmitted until the next beacon signal is transmitted is divided into active (active interval) and inactive (inactive interval). In the inactive (inactive period), each ZigBee node does not perform transmission / reception (sleep). The ZigBee coordinator and the router transmit information including an active period and an inactive period in a beacon signal. 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 an essential CAP (Contention Access Period) period and an optional CFP (Contention Free Period) period. In the CFP period, a GTS (Guaranteed Time Slot) in which the number of communicable nodes is limited to one is provided. One GTS is assigned to a specific node, and the node to which the GTS is assigned can transmit a signal exclusively without performing carrier sense in the GTS. The maximum number of GTSs is 7. The CAP period is multiple access by Slotted-CSMA / CA, and each node performs transmission / reception after performing carrier sense to confirm availability. The GTS assigns one or more dedicated time slots to a specific node in advance, and collision does not occur, so there is no need for carrier sense. Within 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.

  FIG. 3 is a block diagram showing a configuration of the hybrid terminal 3. The hybrid terminal 3 includes an antenna 10, a first switch 11, a second switch 12, a reception processing unit 13, a transmission processing unit 14, a control unit 15, a beacon generation unit 16, a beacon generation timing calculation unit 17, and a data processing unit 18. The wireless LAN processing unit 19 is configured.

  The beacon generation unit 16 generates a beacon signal in ZigBee communication according to the timing calculated by the control unit 15 and outputs the beacon signal to the transmission processing unit 14. 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. .

  The transmission processing unit 14 performs processes such as modulation, D / A conversion, and frequency conversion on the beacon signal supplied from the beacon generation unit 16 and the data signal supplied from the data processing unit 18 via the control unit 15. The second switch 12, the first switch 11, and the antenna 10 are transmitted as radio signals. The second switch 12 switches between reception processing by the reception processing unit 13 and transmission processing by the transmission processing unit 14 performed via the antenna 10. The first switch 11 switches between wireless LAN signal transmission / reception processing by the wireless LAN processing unit 19 and ZigBee signal transmission / reception processing performed by the reception processing unit 13 and the like. That is, the first switch 11 transmits and receives signals while switching between the signals of the wireless LAN and ZigBee.

  The data processing unit 18 performs data communication processing with other ZigBee nodes performed during the CAP period. The reception processing unit 13 receives a signal transmitted from another ZigBee node, for example, a beacon signal, a data signal, or the like via the antenna 10, and performs A / D conversion, frequency conversion, demodulation on the received radio signal. The baseband signal is extracted by performing the above process.

  The baseband signal is supplied to the control unit 15, and when it is a data signal, it is output to the data processing unit 18. In other cases, for example, when the signal received by the router is a beacon signal, the slot allocation information included therein is extracted, and the timing of the time slot of the GTS allocated to the local station is acquired. For example, processing corresponding to the signal is performed via the control unit 15.

  The wireless LAN processing unit 19 is activated by an instruction from the control unit 15 and transmits / receives a wireless LAN signal. Signal transmission / reception in a wireless LAN is generally performed by a procedure called CSMA / CA. That is, it is determined whether or not a signal is transmitted to the channel based on the received power (carrier sense). If no signal is output, signal transmission is started.

  In addition to the carrier sense based on the received power, virtual carrier sense is performed. Virtual carrier sense refers to acquiring the time required for transmission / reception of the signal from the received signal and transmitting the signal until the time elapses even if the received power is lower than the threshold value. Therefore, it does not transmit its own signal. In addition, in order to acquire the said time from the signal which the wireless LAN node received, the parameter for control called NAV (Network Allocation Vector) is contained in all the wireless LAN signals.

  If the wireless LAN processing unit 19 determines that no signal is output on the channel due to both carrier senses, the wireless LAN processing unit 19 transmits an RTS (Request To Send) signal. For example, when the hybrid terminal 3 is connected to the wireless LAN base station (wireless LAN base station 1-1 in FIG. 1) via the wireless LAN processing unit 19, the RTS signal is transmitted from the wireless LAN base station 1- 1 is sent as the destination.

  The wireless LAN base station 1-1 that has received the RTS signal transmits a CTS signal. In these signals, a time T for virtual carrier sense is stored by NAV. Therefore, the other wireless LAN terminals 1-2 to 1-4 that have received the RTS or CTS do not send signals to the channel during the time T. That is, the channel is temporarily reserved. When the channel reservation is completed, the wireless LAN processing unit 19 notifies the control unit 15 of success, enters the power saving state, and waits for the next activation instruction. On the other hand, if a channel cannot be reserved even after a predetermined time has elapsed, the control unit 15 inputs an instruction for shifting to the power saving state.

  On the other hand, when the cycle of transmitting the ZigBee beacon signal approaches, the control unit 15 notifies the instruction for starting the wireless LAN processing unit 19. Here, the timing for notifying the instruction for starting the wireless LAN processing unit 19 is determined based on, for example, the maximum time during which one packet occupies the channel in the wireless LAN. That is, when data of 2312 [Byte], which is the maximum data amount allowed at 6 [Mbit / s], which is the minimum transmission speed in the wireless LAN, is transmitted over 3156 [μs]. The channel is occupied.

  Therefore, if a signal is transmitted by the wireless LAN node during 3156 [μs] retroactively from the time of transmitting the ZigBee beacon signal, there is a possibility that the channel is occupied at the timing of transmitting the ZigBee beacon signal. In this case, a beacon signal cannot be transmitted. That is, the channel reservation needs to be completed before 3156 [μs] from the time when the ZigBee beacon signal is transmitted.

  Therefore, the control unit 15 sets the wireless LAN processing unit 19 at a time retroactive to the time of 3156 [μs] and the time required to transmit / receive the RTS signal and the CTS signal from the time of transmitting the ZigBee beacon signal. to start. At the time of activation, a ZigBee beacon signal is transmitted to the wireless LAN processing unit 19, and the time when the subsequent active period ends is also notified.

  The wireless LAN processing unit 19 starts up, counts down toward the time when the active period ends, and sets the time required to the time when the active period ends when the RTS signal is sent to the NAV. Send. By doing in this way, a channel can be reserved until an active period is complete | finished, and the period required for ZigBee communication can be ensured.

  In addition, when the wireless LAN processing unit 19 notifies the channel reservation success, the control unit 15 activates other processing units such as the beacon generation unit 16 based on the cycle of transmitting the beacon signal, The ZigBee signal transmission / reception process starting from signal generation is started. On the other hand, if the wireless LAN processing unit 19 does not notify the channel reservation success even when the beacon signal is transmitted, the channel reservation is canceled and the wireless LAN processing unit 19 shifts to the power saving operation. Notification of. In addition, about the processing part which transmits / receives another ZigBee signal, the power saving operation | movement is performed in the inactive period.

4 and 5 are timing charts showing the operation of the hybrid terminal 3 according to the first embodiment. When the hybrid terminal 3 confirms that no signal is transmitted to the channel by carrier sense, the hybrid terminal 3 transmits an RTS signal to the wireless LAN base station 1-1 (Sb1). In this case, the RTS signal, the time T required until the active period ends is stored (SIFS + CTS + GAPtime1 + T active).

  Here, SIFS is a short period in which a signal between RTS and CTS is not transmitted, and is a time for switching the switch from reception to transmission in the wireless LAN base station 1-1. GAPtime1 is a period from the transmission of CTS to the beacon signal cycle of ZigBee, and varies depending on the timing at which RTS is transmitted. GAPtime1 is automatically included as the value of NAV based on the countdown from the end time of the active period notified by the control unit 15 by the wireless LAN processing unit 19. With the NAV, the wireless LAN terminals 1-2, 1-3, etc. do not transmit by virtual carrier sense.

  When the hybrid terminal 3 receives the CTS signal from the wireless LAN base station 1-1 (Sb2), the hybrid terminal 3 determines that the channel reservation has been completed, and the wireless LAN processing unit 19 notifies the control unit 15 of the successful reservation. The beacon generation unit 16 generates a beacon signal in ZigBee communication according to the timing calculated by the beacon generation timing calculation unit 17, and the transmission processing unit 14 transmits the beacon signal from the antenna 10. Thereafter, signal transmission / reception is performed between the hybrid terminal 3 and the ZigBee terminals 2-1 to 2-3 in the CFP or CAP period over the active period (Sb3). In the inactive period, the processing units related to ZigBee of the ZigBee terminals 2-1 to 2-3 and the hybrid terminal 3 perform power saving operation, while the wireless LAN base station 1-1 and the wireless LAN terminals 1-2 to 1-4 starts communication because channel reservation by NAV is completed (Sb4).

  According to the first embodiment described above, the wireless terminal is reserved prior to the cycle of the ZigBee beacon signal by the hybrid terminal 3 including the wireless LAN processing unit 19, so that the wireless LAN is transmitted at the transmission timing of the ZigBee beacon signal. As a result, the possibility that the channel is occupied becomes low, and thus ZigBee communication is secured. At this time, since the virtual carrier sense included in all the wireless LAN nodes 1-1 to 1-4 is used for the channel reservation, no change is made to the wireless LAN nodes 1-1 to 1-4. unnecessary. In addition, since the wireless LAN processing unit 19 is activated based on the ZigBee beacon period and the wireless LAN processing unit 19 is set to a power saving operation in other periods, the hybrid terminal 3 also has an effect of power saving. Note that the power saving operation refers to, for example, a sleep mode defined in the IEEE 802.11 standard.

As described above, ZigBee that communicates with other wireless communication terminals within a predetermined active period in the output interval of beacon signals output at a predetermined beacon period, and autonomously distributed communication by carrier sense. A wireless communication terminal including a wireless interface for performing respective communications with the wireless LAN to be performed, and prior to the beacon period, a wireless LAN processing unit 19 that transmits a CTS signal that reserves a channel to be used in the wireless LAN; A transmission processing unit 14 that transmits a beacon signal in ZigBee.
Thereby, even in an environment where ZigBee and a wireless LAN coexist, communication by ZigBee can be reliably performed without changing the wireless LAN terminal. In addition, the wireless LAN processing unit 19 is activated based on the ZigBee beacon period, and the wireless LAN processing unit 19 is set to a power saving operation during other periods, thereby saving power of the hybrid terminal 3. Can do.

Further, the CTS signal includes information for reserving a channel over a period from the end of transmission of the CTS signal to the end of the active period assigned after transmission of the beacon signal.
Thereby, even in an environment where ZigBee and a wireless LAN coexist, communication by ZigBee can be performed reliably.

Further, the wireless LAN processing unit 19 is activated earlier than the transmission cycle of the beacon signal by the transmission processing unit 14 by a predetermined period.
Thereby, even in an environment where ZigBee and a wireless LAN coexist, communication by ZigBee can be reliably performed without changing the wireless LAN terminal.

B. Second Embodiment Next, a second embodiment of the present invention will be described.
In the second embodiment of the present invention, the RTS / CTS alone does not establish a NAV for the wireless LAN base station 1-1 that has received the RTS (the wireless LAN base station that has received the RTS addressed to itself does not establish the NAV. For the purpose of securing the NAV of the wireless LAN base station 1-1, the hybrid terminal 3 once again transmits the CTS-to-self (CTS addressed to itself) after transmitting the RTS / CTS. Frame).

  FIG. 6 is a block diagram for explaining a configuration and a schematic operation of a wireless communication system using the hybrid 3. It should be noted that portions corresponding to those in FIG. In the figure, the wireless communication terminal (hybrid terminal) 3 first transmits an RTS signal using the wireless LAN interface 3-1 (Sc1). The RTS signal includes period information for reserving a channel by ZigBee.

  The wireless LAN base station 1-1 returns a CTS signal to the hybrid terminal 3 and the other wireless LAN terminals 1-2 to 1-4 according to the received RTS signal (Sc2). When the hybrid terminal 3 receives the CTS returned by the wireless LAN base station 1-1, the hybrid terminal 3 transmits CTS-to-self again (Sc3). When receiving the CTS-to-self transmitted to the destination other than the wireless LAN base station 1-1, the wireless LAN base station 1-1 enters the NAV section. As a result, the wireless LAN base station 1-1 and the wireless LAN terminals 1-2 to 1-4 avoid transmitting signals during the reserved period. Meanwhile, the ZigBee terminals 2-1 to 2-3 including the wireless interface (communication function) 3-2 of the hybrid terminal 3 perform ZigBee communication including transmission of a beacon signal (Sc4).

  FIG. 7 is a timing chart showing the operation of the hybrid terminal 3. When the hybrid terminal 3 confirms that no signal is transmitted to the channel by carrier sense, the hybrid terminal 3 transmits an RTS signal to the wireless LAN base station 1-1 (Sd1).

  When the hybrid terminal 3 receives the CTS signal from the wireless LAN base station 1-1 (Sd2), it transmits the CTS2self again (Sd3). When the wireless LAN base station 1-1 determines that the CTS is transmitted to a destination other than itself, the wireless LAN base station 1-1 enters the NAV section. As a result, the wireless LAN base station 1-1 and the wireless LAN terminals 1-2 to 1-4 avoid transmitting signals during the reserved period. Meanwhile, the ZigBee terminals 2-1 to 2-3 including the wireless interface 3-2 of the hybrid terminal 3 perform ZigBee communication including transmission of a beacon signal (Sd4).

  As described above, after transmitting the RTS signal, the wireless LAN processing unit 19 transmits the CTS-to-self addressed to itself again before the transmission processing unit 14 transmits the beacon signal. Thereby, the NAV of the wireless LAN base station 1-1 can be ensured more reliably.

  FIG. 8 is a conceptual diagram for explaining an evaluation result when a simulation is performed using the hybrid terminal 3. The simulation conditions are: beacon period: 245.76 [ms], superframe period: 30.72 [ms], RTS transmission period: 2 [ms] period before beacon transmission start time, one wireless LAN station to access point Saturated traffic transmission in 54 [Mbps] mode.

  When the simulation time was 600 [seconds], the wireless LAN was 26.943 [Mbps], the beacon failure rate was 0.0167964, and the delay was 623.396 [μs]. The throughput when there is no hybrid terminal 3 and the wireless LAN base station 1-1 performs communication in the saturation mode is 30.81 [Mbps].

  According to this simulation, although the traffic is saturated, a beacon loss rate of 1.6% is realized. If the time for starting to send the RTS packet is made earlier, the beacon loss rate can be further reduced. Furthermore, the throughput of the wireless LAN can be realized with a decrease of about 12%.

  FIG. 9 is a conceptual diagram for explaining the effect of operating the minimum contention window size CWmin when the hybrid terminal 3 is used. In FIG. 9, the horizontal axis represents the number of nodes and the vertical axis represents the beacon failure rate. “+” Is the minimum contention window size CWmin = 15, “×” is the minimum contention window size CWmin = 7, and “*” is the minimum contention window size CWmin = 3. It plots how the beacon failure rate changes with increasing number of nodes.

  It can be seen that when the hybrid terminal 3 transmits an RTS packet and the packet collides, the beacon failure rate decreases by manipulating (decreasing) the minimum contention window size CWmin. That is, it can be understood that the reliability of the RTS can be improved by manipulating (decreasing) the minimum contention window size CWmin. It is shown that the beacon loss rate of ZigBee is improved by the present invention.

  The embodiment of the present invention has been described in detail with reference to the drawings. However, the specific configuration is not limited to this embodiment, and includes designs and the like that do not depart from the gist of the present invention.

  For example, the present invention can be applied not only to ZigBee but also to other wireless devices using the same frequency band. In other words, in the wireless system [a] using the same frequency band as the wireless LAN, when the wireless system [a] is desired to be temporarily suppressed and the wireless system [a] communicates, the RTS / CTS function is installed. A wireless communication terminal (hybrid terminal) is provided, and a NAV is set in a node of the wireless LAN. As a result, since the wireless LAN does not transmit radio waves during the NAV, the communication of the wireless system [a] is successful.

  A program for realizing the hybrid terminal described above may be recorded on a computer-readable recording medium, and the program may be read into a computer system and executed. Here, the “computer system” includes an OS and hardware such as peripheral devices. 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.

1-1 ... Wireless LAN base station (WLAN AP), 1-2 to 1-4 ... Wireless LAN terminal, 2-1 to 2-3 ... ZigBee terminal, 3 ... Hybrid terminal, 3-1 ... Wireless LAN interface, 3 -2 ... ZigBee interface, 10 ... antenna, 11 ... first switch, 12 ... second switch, 13 ... reception processing unit, 14 ... transmission processing unit, 15 ... control unit, 16 ... beacon generation unit, 17 ... beacon Generation timing calculation unit, 18 ... data processing unit, 19 ... wireless LAN processing unit

Claims (8)

The first wireless communication system that communicates with other wireless communication terminals within the determined active period in the output interval of the beacon signal output at the determined beacon period, and communicates autonomously and distributedly by carrier sense A wireless communication terminal comprising a wireless interface for performing respective communications with a second wireless communication system to be performed,
First transmission means for transmitting a beacon signal in the first wireless communication system;
Prior to transmission of the beacon signal, second transmission means for transmitting a channel reservation signal for reserving a channel to be used in the first wireless communication system;
Based on the maximum time that one packet may occupy a channel in the second wireless communication system, a timing for instructing transmission to the second transmission means is determined, and transmission to the second transmission means is performed at the timing. Transmission control means for instructing
A wireless communication terminal comprising:   The channel reservation signal includes information for reserving a channel over a period from the end of transmission of the channel reservation signal to the end of an active period allocated after transmission of the beacon signal. Item 2. A wireless communication terminal according to Item 1.   2. The wireless communication terminal according to claim 1, wherein the second transmission unit is activated earlier by a predetermined period than a transmission time of a beacon signal by the first transmission unit.   The second transmission means transmits a reception preparation completion signal addressed to itself again after transmission of the channel reservation signal and prior to transmission of the beacon signal by the first transmission means. Item 4. The wireless communication terminal according to any one of Items 1 to 3. The first wireless communication system that communicates with other wireless communication terminals within the determined active period in the output interval of the beacon signal output at the determined beacon period, and communicates autonomously and distributedly by carrier sense A wireless communication method in a wireless station comprising a wireless interface for performing respective communications with a second wireless communication system to perform,
A first transmission process of transmitting a beacon signal in the first wireless communication system;
A transmission control process for determining a timing for instructing transmission based on a maximum time that one packet may occupy a channel in the second wireless communication system;
A second transmission step of transmitting a channel reservation signal for reserving a channel to be used in the first wireless communication system, prior to transmission of the beacon signal , at the determined timing ;
A wireless communication method comprising:   6. The channel reservation signal includes information for reserving a channel over a period from the end of transmission of the channel reservation signal to the end of an active period after transmission of the beacon signal. The wireless communication method described in 1.   6. The wireless communication method according to claim 5, wherein the second transmission process is started earlier by a predetermined period than the transmission time of the beacon signal transmitted in the first transmission process.   In the second transmission process, after the transmission of the channel reservation signal, the reception preparation completion signal addressed to itself is transmitted again before the transmission of the beacon signal in the first transmission process. The wireless communication method according to claim 5.

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