JP4889290B2 - Wireless communication terminal and wireless communication method - Google Patents

Wireless communication terminal and wireless communication method Download PDF

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JP4889290B2
JP4889290B2 JP2005348155A JP2005348155A JP4889290B2 JP 4889290 B2 JP4889290 B2 JP 4889290B2 JP 2005348155 A JP2005348155 A JP 2005348155A JP 2005348155 A JP2005348155 A JP 2005348155A JP 4889290 B2 JP4889290 B2 JP 4889290B2
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terminal
communication
wireless communication
data
signal
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JP2007158529A (en
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正明 滝沢
務 鈴木
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株式会社日立製作所
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    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02DCLIMATE CHANGE MITIGATION TECHNOLOGIES IN INFORMATION AND COMMUNICATION TECHNOLOGIES [ICT], I.E. INFORMATION AND COMMUNICATION TECHNOLOGIES AIMING AT THE REDUCTION OF THIR OWN ENERGY USE
    • Y02D70/00Techniques for reducing energy consumption in wireless communication networks
    • Y02D70/10Techniques for reducing energy consumption in wireless communication networks according to the Radio Access Technology [RAT]
    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02DCLIMATE CHANGE MITIGATION TECHNOLOGIES IN INFORMATION AND COMMUNICATION TECHNOLOGIES [ICT], I.E. INFORMATION AND COMMUNICATION TECHNOLOGIES AIMING AT THE REDUCTION OF THIR OWN ENERGY USE
    • Y02D70/00Techniques for reducing energy consumption in wireless communication networks
    • Y02D70/10Techniques for reducing energy consumption in wireless communication networks according to the Radio Access Technology [RAT]
    • Y02D70/14Techniques for reducing energy consumption in wireless communication networks according to the Radio Access Technology [RAT] in Institute of Electrical and Electronics Engineers [IEEE] networks

Description

  The present invention relates to a wireless communication terminal that performs wireless communication using a wireless local area network (LAN) or the like, and a communication method therefor.

  In recent years, wireless LANs have become widespread as one of computer communication networks, and are actively used in offices, homes, urban areas (for example, stations, airports, fast food restaurants) and the like. As is well known, in such a wireless LAN, wireless communication is performed between a relay device called an AP (Access Point) and a wireless communication terminal.

  This wireless LAN generally conforms to IEEE (Institute of Electrical and Electronics Engineers) 802.11, which is one of the international standards, as a data link layer protocol, and conforms to IP (Internet Protocol) as a network layer protocol. It is compliant. Note that IEEE 802.11 is described in Non-Patent Document 1 below.

  Wireless communication terminals often operate on batteries in order to facilitate movement. In order to save battery consumption, IEEE802.11 defines a power saving mode. In this power saving mode, when data and voice (hereinafter referred to as data) are not transmitted / received wirelessly, a sleep state in which the wireless transmission / reception function is stopped to save power, and an active state in which the wireless transmission / reception function is activated only when wireless transmission / reception is performed. Next, the wireless transmission / reception function is switched.

  Here, the wireless communication procedure between the AP and the plurality of wireless communication terminals will be described according to the sequence shown in FIG. Here, it is assumed that there are three wireless communication terminals a, b, and c under the management of the relay device.

  Each terminal a, b, c in the power saving mode maintains the sleep state until immediately before the scheduled reception time of the beacon signal from the AP (S1), and shifts to the active state immediately before the scheduled reception time of the beacon signal (S2). ). On the other hand, when the beacon signal transmission time comes, the AP wirelessly transmits the beacon signal (S3), and the signal is transmitted for a time of DIFS (DCF Inter Frame Space) + random number (the random number is different for each device) from this point. Wait for.

  When the terminals a, b, and c in the active state receive a beacon signal from the AP, they analyze the beacon signal and grasp the presence / absence of data addressed to their own terminal. When there is data addressed to the own terminal, each terminal a, b, c waits for (DIFS + random number) time from reception of the beacon signal and then requests the AP to send data to the own terminal. Try to send. That is, the relay device and each terminal a, b, c try to send a signal after waiting for a different (DIFS + random number) time for each device so that signal transmission from each device does not compete. If the random number of the terminal “a” is the smallest, the terminal “a” acquires the transmission right and transmits the PS Poll signal “a” (S4).

  Upon receiving the PS Poll signal a from the terminal a, the AP transmits data Aa addressed to the terminal a after a SIFS (Short Inter Frame Space) time shorter than the DIFS time (S5).

  When the terminal a normally receives the data Aa from the AP, the terminal a sends out ACKa after SIFS time, notifies the AP that it has been normally received (S6), and again waits for (DIFS + random number) time. Further, upon receiving this ACKa, the AP and the terminals b and c also wait for each (DIFS + random number) time. Then, only a device that does not receive a radio signal from another device during each (DIFS + random number) time acquires a transmission right. Here, the terminal a acquires the transmission right, and the terminal a sends data Ta to the AP (S7).

  When the AP normally receives the data Ta from the terminal a, it returns an ACK after SIFS time (S8) and waits for (DIFS + random number) time. Upon receiving the ACK from the AP, the terminal a determines that the transmission / reception with the AP has been completed, and shifts to the sleep state until the next scheduled beacon reception time (S9).

  When the terminals b and c except the terminal a receive the ACK from the AP, they wait for each (DIFS + random number) time. Then, only a device that does not receive a radio signal from another device during each (DIFS + random number) time acquires a transmission right. Here, the AP acquires the transmission right, the AP sends out the data AD (S10), and then waits for (DIFS + random number) time.

  When the terminals b and c except the terminal a receive the data AD from the AP, they wait for each (DIFS + random number) time. Then, only a device that does not receive a radio signal from another device during each (DIFS + random number) time acquires a transmission right. Here, the terminal b obtains the transmission right and sends the PS poll signal b to the AP (S11).

  In the same manner as described above, the data Ab is transmitted from the AP to the terminal b (S12), the ACK b is transmitted from the terminal b to the AP (S13), the PS Poll signal c is transmitted from the terminal c to the AP (S14), the AP Data Ac sent from terminal c to terminal c (S15), ACKc sent from terminal c to AP (S16), data Tb sent from terminal b to AP (S17), ACK sent from AP to terminal b (S18), terminal b transitions to the sleeve state (S19), terminal C sends data Tc to the AP (S20), AP sends terminal ACK to the terminal c (S21), and terminal c transitions to the sleeve state (S22). The

  When only one terminal a is managed by the AP, the waiting time until the terminal a sends the PS Poll signal a after receiving the beacon signal from the AP, and the terminal a sends ACKa. The waiting time from when the data Ta is sent out is SIFS time.

"Wireless LAN Medium Control (MAC) and Physical Layer (PHY) Specifications" ANSI / IEEE Std 802.11, 1999 Edition

  In the above prior art, when there is only one terminal (hereinafter referred to as a power saving terminal) in which the AP is to transmit data in the power saving mode, communication between the AP and the terminal can be performed very well. When there are a plurality of power saving terminals, transmission right control is required to avoid contention between the power saving terminals, and there is a problem that transmission efficiency is lowered.

  The present invention has been made paying attention to such a conventional problem, and an object of the present invention is to provide a wireless communication terminal and a wireless communication method capable of improving transmission efficiency.

An invention relating to a wireless communication terminal for solving the above problems
In a wireless communication terminal that communicates with another communication terminal via a relay device that transmits a beacon signal including control data indicating whether there is communication data addressed to the wireless communication terminal for each wireless communication terminal,
Transmitting and receiving means for transmitting and receiving various signals to and from the relay device;
When analyzing the control data contained in the beacon signal from the relay device received by the transmission / reception means and determining that there is communication data to be received by the terminal, based on the control data, A signal analysis means for determining a communication order in one or more wireless communication terminals under the control of the relay device;
In accordance with the communication order of the own terminal determined by the signal analysis means, the timing of the communication time zone is determined between the own terminal and the wireless relay device, and between the relay device during the communication time zone Communication control means for causing the transmission / reception means to transmit / receive the communication data signal, and to refrain from transmitting the communication data signal to the relay device in a time period excluding the communication time period;
It is characterized by having.

Here, the above wireless communication terminals are
Power supply control means for controlling power supplied to at least a part of the transmission / reception means to change the state of the transmission / reception means between an active state capable of transmission / reception operation and a sleep state where transmission / reception operation is disabled; The power supply control means causes the power supply control means to make the transmission / reception means in the active state and receive the beacon signal in the time zone for receiving the beacon signal and the communication time zone of the terminal itself. The power supply control means may be set to the sleep state in a time zone other than the time zone and the communication time zone of the terminal itself.

In addition, a wireless communication method for achieving the above object is as follows:
A control signal including control data indicating whether there is communication data addressed to the wireless communication terminal and the wireless communication terminal for each wireless communication terminal is transmitted and relayed between the wireless communication terminal and another communication terminal In a wireless communication method of a wireless communication system comprising a relay device,
The wireless communication terminal is
A control signal receiving step for receiving the control signal from the relay device;
When the control data included in the control signal received in the control signal receiving step is analyzed and it is determined that there is communication data to be received by the terminal, the relay device is based on the control data. A signal analysis step for determining a communication order in one or more wireless communication terminals having communication data to be transmitted from;
A communication time setting step for determining the timing of a communication time zone between the terminal and the wireless relay device according to the communication order of the terminal determined by the signal analysis unit,
Communication that causes the communication data signal to be transmitted to and received from the relay device during the communication time zone of its own terminal, and to refrain from transmitting the communication data signal to the relay device in a time zone other than the communication time. Control process;
It is characterized by performing.

  According to the present invention, when there are a plurality of wireless communication terminals having data to be transmitted from the relay device, each terminal determines its own communication time zone based on control data included in a beacon signal or the like from the relay device. Since the communication data is transmitted / received to / from the relay device in this communication time zone, the transmission efficiency can be improved.

  Hereinafter, various embodiments of a wireless communication system according to the present invention will be described in detail with reference to the drawings.

  First, the first embodiment of the wireless communication system will be described with reference to FIGS.

  As shown in FIG. 1, the wireless communication system according to the present embodiment includes a plurality of APs 30 and a plurality of computers 3 connected to LANs (A) and (B) via routers 2A and 2B, and an AP 10. Wireless communication terminals 10a, 10b, and 10c that communicate with other terminals are provided. LAN (A) and LAN (B) are connected by an IP (Internet Protocol) network 1. Each of the wireless communication terminals 10a, 10b, and 10c is an information communication terminal having a wireless LAN communication function that operates in compliance with IEEE802.11. For example, a telephone terminal such as a wireless IP telephone, a personal computer, or a PDA (Personal Digital Assistant) A wireless LAN card connected to an information terminal.

  Each AP 30 has a wireless LAN communication function that operates in conformity with IEEE802.11 and a wired LAN communication function such as Ethernet (registered trademark) that operates in conformity with IEEE802.3, and wireless communication terminals 10a and 10b. , 10c, and wired LAN communication with other devices (such as the computer 3 and the router 2A or 2B) connected to the LAN (A) or (B).

  The routers 2A and 2B are interposed between the LANs (A) and (B) and the IP network 1, and monitor IP packets flowing on the LANs (A) and (B) and IP packets obtained from the IP network 1. , A communication device that routes IP packets based on IP header information (destination IP address information, port number information, etc.) of the IP packets, and the IP packets flowing on the LANs (A) and (B) are transferred to the IP network 1 side. If it is determined that it should be routed, it is transmitted to the IP network 1 side, and the IP packet obtained from the IP network 1 is determined to be routed to the LAN (A), (B) side. In this case, this is sent to the LAN (A), (B) side.

  Each computer 3 has a normal wired LAN board, and is connected to LANs (A) and (B) to transmit and receive IP packets and perform IP communication (LAN communication).

  With the above configuration, the wireless communication terminals 10a, 10b and 10c on the LAN (A) side perform IP communication with other wireless communication terminals on the LAN (A) side and the computer 3 via the AP 30, and the router 2A It is possible to perform IP communication with the wireless communication terminals 10a, 10b, and 10c on the LAN (B) side and the computer 3 via the IP network 1 and the router 2B. Similarly, the wireless communication terminals 10a, 10b, 10c on the LAN (B) side perform IP communication with other wireless communication terminals on the LAN (B) side and the computer 3 via the AP 30, and the router 2B It is possible to perform IP communication with the wireless communication terminals 10a, 10b, and 10c on the LAN (A) side and the computer 3 via the IP network 1 and the router 2A.

  As shown in FIG. 2, each AP 30 includes an antenna 31, an RF (Radio Frequency) unit 32, a baseband unit 33, a MAC (Media Access Controller) layer processing unit 34, a router unit 35, A communication processing unit 40, a program memory 44, and a work memory 45 are provided. The RF unit 32, the baseband unit 33, and the MAC layer processing unit 34 are connected to the communication processing unit 40 via the bus 38.

  The communication processing unit 40 controls the RF unit 32, the baseband unit 33, and the MAC layer processing unit 34 while using the work memory 45 according to the control program and setting data in the program memory 44. The communication processing unit 40 includes a beacon data generation unit 41 that generates beacon data included in a beacon signal, an analysis unit 42 that analyzes a signal input from the antenna 31 or the router unit 35, and an analysis result of the analysis unit 42. And a control unit 43 that controls the RF unit 32, the baseband unit 33, and the MAC layer processing unit 34.

  The router unit 35 refers to an IP header including an IP address of an IP packet received from a network (LAN (A) or (B)), a TCP (Transmission Control Protocol) port number, or a UDP (User Datagram Protocol) port number. Then, the IP packet is routed based on a preset rule.

  The MAC layer processing unit 34 converts the MAC layer of the IP packet between the data link layer of IEEE802.3 that is the Ethernet (registered trademark) standard and the data link layer of IEEE802.11 that is the wireless LAN standard. . The baseband unit 33 modulates an IP packet subjected to MAC processing for IEEE802.11 into a baseband signal, or demodulates the baseband signal and restores the original IP packet. The RF unit 32 uses the baseband signal received from the baseband unit 33 in accordance with IEEE802.11, for example, carrier radio defined by the DS-SS (Direct Sequence Spread Spectrum) method or the FH-SS method (Frequency Hopping Spread Spectrum). The signal is placed on the frequency and transmitted from the antenna 31 as a radio signal. On the contrary, the carrier radio frequency is removed from the radio signal received from the antenna 31 to restore the original baseband signal, which is sent to the baseband unit 33.

  Next, the basic operation of the AP 30 when an IP packet is transmitted from the network (LAN (A) or LAN (B)) via the antenna 31 will be described below.

  The MAC layer processing unit 34 converts the MAC layer of the IP packet received from the network (LAN (A) or LAN (B)) via the router unit 35 from IEEE802.3 for Ethernet (registered trademark) to a wireless LAN. The data is converted into IEEE802.11 and sent to the baseband unit 33. The baseband unit 33 modulates the received IP packet according to IEEE802.11 for wireless LAN, generates a baseband signal, and sends it to the RF unit 32. The RF unit 32 puts the baseband signal from the baseband unit 33 on the carrier radio frequency, and sends out the radio signal from the antenna 31 to the radio terminals 10a, 10b, and 10c.

  Next, a basic operation of the AP 30 when wireless signals are received from the wireless communication terminals 10a, 10b, and 10c will be described.

  When the antenna 31 receives radio signals from the radio communication terminals 10a, 10b, and 10c, the antenna 31 transmits the radio signals to the RF unit 32. The RF unit 32 removes the carrier radio frequency from the radio signal received by the antenna 31 to restore the original baseband signal, and sends it to the baseband unit 33. The baseband unit 33 demodulates the baseband signal, restores it to the original IP packet, and sends it to the MAC layer processing unit 34. The MAC layer processing unit 34 converts the MAC layer of the IP packet from IEEE802.11 for wireless to IEEE802.3 for Ethernet (registered trademark), and sends it to the router unit 34. The router unit 34 transfers the received IP packet to a LAN or the like using the IP address of the received IP packet.

  As shown in FIG. 3, each of the wireless communication terminals 10a, 10b, and 10c includes an antenna 11, an RF unit 12, a baseband unit 13, a MAC layer processing unit 14, an upper layer processing unit 15, and an input unit. The output interface unit 16, the input / output unit 17, the communication processing unit 20, the program memory 24, the work memory 25, the power source 26, and the power supply control unit 27 are provided.

  The RF unit 12, the baseband 13, the MAC layer processing unit 14, the upper layer processing unit 15, and the input / output interface unit 16 are all connected to the communication processing unit 20 via the bus 18. Note that the “transmission / reception means” described in the claims includes the antenna 11, the RF unit 12, and the baseband unit 13 in the present embodiment.

  The communication processing unit 20 uses the work memory 25 in accordance with the control program and setting data in the program memory 24, while the RF unit 12, the baseband processing unit 13, the MAC layer processing unit 14, and the upper layer processing unit 15. And the input / output interface unit 16. The communication control unit 20 includes an analysis unit 21 that analyzes the content of a signal received by the input / output unit 17 or the antenna 11, and an RF unit 12, a baseband processing unit 13, and the like according to an analysis result in the analysis unit 21. The MAC layer processing unit 14, the upper layer processing unit 15, and the control unit 22 that controls the power supply control unit 27 are included.

  The power supply control unit 27 converts the power from the power source 26 into an appropriate voltage and supplies the power to each unit. Further, the power supply control unit 27 turns on / off the power supply to the RF unit 12 in accordance with an instruction from the control unit 22 of the communication processing unit 20. That is, the power supply control unit 27 is an execution part of the power saving mode in which the function is changed between the active state in which the wireless transmission / reception function is operated and the wireless transmission / reception function is stopped and the sleep state is set.

  For example, when the wireless communication terminal is a wireless IP phone, the input / output unit 17 is a voice / data input / output unit, specifically, a speaker, a microphone, an input key, and the like. When the wireless communication terminal is a wireless LAN card, the input / output unit 17 is an input / output unit for data signals, audio signals, and the like from a computer.

  The input / output interface unit 16 performs processing related to an interface for transferring a data signal and a speech encoded signal from the input / output unit 17 to the upper layer processing unit 15 or from the upper layer processing unit 15 to the input / output unit 17. The upper layer processing unit 15 performs IP packet processing related to the network layer / transport layer. Specifically, IP header including IP address, TCP port number, or UDP port number is added / deleted. The MAC layer processing unit 14 performs IP packet processing related to the data link layer. Specifically, in accordance with IEEE802.11, an IP packet storing data and voice bucket data is assembled or disassembled, and MAC address assignment / deletion processing is performed in order to transmit between data link layers. The baseband unit 13 modulates the IP packet to generate a baseband signal, or demodulates the baseband signal to restore the original IP packet. The RF unit 12 puts the baseband signal received from the baseband unit 13 on the carrier radio frequency according to IEEE802.11, and transmits it from the antenna 11 as a radio signal. Conversely, the carrier radio frequency is removed from the radio signal received from the antenna 11 to restore the baseband signal, and the baseband signal is sent to the baseband unit 13.

  Next, the basic operation of the radio communication terminals 10a, 10b, and 10c when the data signal or voice encoded signal received or generated by the input / output unit 17 is transmitted as a radio signal from the antenna 11 will be described.

  The input / output interface unit 16 sends the data signal and the voice encoded signal from the input / output unit 17 to the upper layer processing unit 15. The upper layer processing unit 15 performs IP header processing such as IP address assignment / TCP / UDP port number assignment, generates an IP packet, and then sends the IP packet to the MAC layer processing unit 14. The MAC layer processing unit 14 subjects the IP packet from the higher layer processing unit 15 to MAC processing such as MAC address assignment in accordance with IEEE802.11 and sends the IP packet to the baseband unit 13. The baseband unit 13 modulates this IP packet according to IEEE802.11 to generate a baseband signal, and sends it to the RF unit 12. The RF unit 12 puts the baseband signal from the baseband unit 13 on the carrier radio frequency according to IEEE802.11, and transmits it from the antenna 11 to the AP 30 as a radio signal.

  Next, a basic operation of the radio communication terminals 10a, 10b, and 10c when receiving a radio signal transmitted from the AP 30 and outputting a signal to the input / output unit 17 will be described.

  The antenna 11 receives a radio signal from the AP 30 and sends it to the RF unit 12. The RF unit 12 removes the carrier radio frequency from the radio signal, restores the original baseband signal, and sends it to the baseband unit 13. The baseband unit 13 demodulates the baseband signal, restores it to the original IP packet, and sends it to the MAC layer processing unit 14. The MAC layer processing unit 14 deletes the MAC address from this IP packet according to IEEE802.11 and sends it to the upper layer processing unit 15. The upper layer processing unit 15 deletes the TCP / UDP header and the IP header from the IP packet from the MAC layer processing unit 14 based on the setting data, and transmits the obtained data and the audio encoded signal via the input / output interface unit 16. The data is sent to the input / output unit 17.

  Next, the data structure of the beacon signal transmitted from the AP 30 will be described with reference to FIG.

  The AP 30 transmits a beacon signal at a constant cycle to notify each wireless communication terminal whether or not there is data to be transmitted to the wireless communication terminal in the power saving mode. This period is often about 100 ms, for example.

  This beacon signal is defined in IEEE 802.11, a frame control unit 61 in which data of a signal type for indicating that it is a beacon signal is entered, a duration / ID unit 62 in which data of wireless communication time is entered, A DA unit 63 for receiving a destination address, an SA unit 64 for receiving a source address, a BSSID unit 65 for storing an AP 30 address, a sequence control unit 66 for storing a sequence number in a series of sequences, and a notification It has a data main body section 67 for storing data to be received and an FCS section 68 for storing data for transmission error detection.

  The main body data section 67 has a fixed length field 69 for storing management / control data of a predetermined length and a variable length field 70 for storing variable length management / control data.

  The variable length field 70 indicates whether there is an element ID portion 71 in which an element ID is entered, an element length portion 72 in which data of the element length is entered, and data to be notified to the terminal in the power saving mode by broadcast or multicast. Before a beacon including a DTIM (D traffic notification map) is transmitted, a DTIM count unit 72 in which the number of general beacons (a beacon including a TIM) is transmitted is transmitted between the DTIM and the next DTIM. A DTIM interval unit 73 for storing the number of general beacons, and a bitmap control unit 75 and a partial virtual bitmap unit 76 described later (the data entering these portions 75 and 76 is the control data described in the claims). Have.

  The element ID portion 71 contains “5” indicating that this element is a TIM (traffic notification map). The bit map control unit 75 and the partial virtual bit map unit 76 contain data indicating the presence / absence of data to be notified from the AP to the terminal in the power saving mode with a unicast address.

  In the data indicating the presence or absence of data, “1” is set when there is data and “0” is set when there is no data for each ID for terminal identification called AID assigned to each terminal. . The partial virtual bitmap unit 76 into which this data is stored has a variable length of 1 to 251 bytes. For example, as shown in the figure, “1” is set for the terminal c and the terminal h, that is, the terminal c and the terminal h. When there is transmission data to the other terminal and there is no transmission data in the other terminal, the bit containing significant data in all the virtual bitmap data, that is, from the terminal c of the third bit, for example, a predetermined number of bits, Only the partial virtual bitmap data for 8 bits up to the terminal j is entered. The bitmap control unit 75 stores the start bit (bitmap offset) of the partial virtual bitmap in the entire virtual bitmap and the number of bits (bitmap length) of the partial virtual bitmap.

  Each data included in the above beacon signal is generated by the beacon data generation unit 41 of the AP 30 based on data received from each terminal or data set in advance.

  Next, a wireless communication procedure between the AP 30 and the plurality of wireless communication terminals 10a, 10b, and 10c will be described with reference to a timing chart shown in FIG. In the following description, it is assumed that all data signals transmitted and received between the AP 30 and the plurality of wireless communication terminals 10a, 10b, and 10c are audio signals.

  Each wireless communication terminal 10a, 10b, 10c notifies the AP 30 when it enters the power saving mode. In response to this notification, the AP 30 assigns the AID to each of the wireless communication terminals 10a, 10b, and 10c, and manages the wireless communication terminals 10a, 10b, and 10c in the power saving mode using the AID as an ID for terminal identification. Then, when data or the like is transmitted from any other terminal or the like to any one of the wireless communication terminals 10a, 10b, and 10c, this terminal indicates that there is data to be transmitted to the terminal in the power saving mode. It is stored in correspondence with the ID. The stored contents are stored in the beacon signal bitmap control unit 75 and the partial virtual bitmap unit 76 described above with reference to FIG.

  Each terminal 10a, 10b, 10c in the power saving mode maintains the sleep state until immediately before the scheduled reception time of the beacon signal from the AP 30 (S1), and shifts to the active state immediately before the scheduled reception time of the beacon signal (S2). ). On the other hand, when the beacon signal transmission time comes, the AP 30 wirelessly transmits the beacon signal (S3), and waits for signal transmission from this point (DIFS + random number) time.

  When receiving the beacon signal from the AP, each of the active terminals 10a, 10b, and 10c analyzes the beacon signal. Temporarily, in the bitmap control unit 75 in the beacon signal described above with reference to FIG. 8, “first bit” is indicated as the start bit, and “8” is indicated as the number of bits of the partial virtual bitmap. If the data “11100000” is stored in the partial virtual bitmap section 76, each terminal 10a, 10b, 10c has communication data addressed to its own terminal, and there is data to be received from the AP 30. And the communication order of the own terminal with respect to the AP 30 is grasped.

  Here, what is important is that, in the prior art, the data contained in the partial virtual bitmap unit 76 is used only for determining whether there is communication data addressed to the terminal itself. In the present embodiment, as described above, there are three terminals having data to be received from the AP 30 based on the quantity of “1 (data present)” in the data stored in the partial virtual bitmap unit 76. To grasp. Further, in the present embodiment, among the terminals set to “1” in the data included in the partial virtual bitmap unit 76, the number of the own terminal is grasped based on the own terminal ID, This X-th is set as the communication order X of the own terminal with respect to the AP 30. Specifically, in the case of the terminal 10a, “1” is set to the first corresponding to its own terminal ID in the data contained in the partial virtual bitmap unit 76, so that the communication order of its own terminal is the first. In the case of the terminal 10c, “1” is set in the third corresponding to its own terminal ID in the data stored in the partial virtual bitmap unit 76, and the terminal 10c before that is recognized. Since “1” is set for the first and second, respectively, it is recognized that the communication order of the own terminal is the third. Here, depending on what number “1” is set in the data stored in the partial virtual bitmap unit 76, the X-th is used as it is as the communication order of the own terminal. For example, the communication order of the own terminal may be determined by substituting the Xth X. That is, using the data stored in the bitmap control unit 75 and the partial virtual bitmap unit 76, the communication order of the terminal itself may be determined according to a predetermined rule.

  As described above, when “11100000” is included in the partial virtual bitmap unit 76 in the beacon signal, each of the terminals 10a, 10b, and 10c has three terminals with data, and the communication order is It is recognized that the order is terminal 10a, terminal 10b, and terminal 10c.

  In this case, the terminal 10a with the first communication order transmits a PS Poll signal a for requesting the AP 30 to transmit data addressed to itself after SIFS time after receiving the beacon signal (S4a). .

  Upon receiving the PS Poll signal a from the terminal 10a, the AP 30 sends out data Aa addressed to the terminal a after SIFS time (S5). When the terminal 10a normally receives the data Aa from the AP 30, the terminal 10a sends ACKa after the SIFS time to notify the AP that it has been normally received (S6). Then, when there is data to be sent from the own terminal to the AP 30, the terminal 10 a sends data Ta to the AP 30 after SIFS time (S 7 a).

  When the AP 30 normally receives the data Ta from the terminal 10a, it returns an ACK after SIFS time (S8) and waits for (DIFS + random number) time. When receiving the ACK from the AP 30, the terminal 10 a determines that the transmission / reception with the AP 30 has ended, and shifts to the sleep state until the next scheduled beacon reception time (S <b> 9).

  What is important in the wireless communication between the terminal 10a and the AP 30 described above is that the terminal 10a transmits the PS Poll signal a (S4a) after SIFS time after receiving the beacon signal, and the terminal 10a. However, the data Ta is transmitted to the AP 30 (S7a) after SIFS time since the transmission of ACKa. On the other hand, in the conventional technique shown in FIG. 9, in any case (S4, S7), a signal is transmitted at (DIFS + random number) time in order to avoid competition with other devices. In this embodiment, in any case (S4a, S7a), the signals are sent after SIFS time because all the terminals 10a, 10b, 10c are communicating wirelessly between the terminal 10a and the AP 30. This is because it recognizes that the time zone is a dedicated radio communication time zone between the terminal 10a and the AP 30, and does not cause competition with other devices, and can be handled as if there is no other radio communication terminal. .

  On the other hand, after receiving the beacon signal from the AP 30 (S3), the second and third terminals 10b and 10c having the communication order set their communication time zone timer value to (n-1) T and set the timer. At the same time as starting, it shifts to the sleeve state (S23). In the above, n is the communication order. Further, T is a fixed time shorter than the beacon signal interval p, for example, the time obtained by dividing the beacon signal interval p by the maximum number of terminals that can be accommodated by the AP 30, and is the time of the communication time zone of the own terminal.

  After receiving the beacon signal from the AP 30 (S3), the second and third terminals 10b and 10c in the communication order are active as the communication time zone of their own terminal when the communication time zone timer value of their own terminal becomes 0. After shifting to the state (S24, S25), and further waiting for (DIFS + random number) time, the PS Poll signal b and PS Poll signal c are sent to the AP 30 (S11a, S14a). The terminal 10b with the second communication order receives the beacon signal (S3), and the T (= (2-1) T) time when the communication time zone of the terminal 10a with the first communication order has ended. The terminal 10b whose communication order is the third terminal 10b later receives the beacon signal (S3), and the communication time period of the second terminal 10b whose communication order is the second 2T (= (3-1) T) The communication time zone of the terminal will be reached after a time.

  Upon receiving the PS Poll signal b and PS Poll signal c from the terminals 10b and 10c, the AP 30 sends data Ab and Ac addressed to the terminals 10b and 10c after SIFS time (S12, S15a). When the terminals 10b and 10c normally receive the data Ab and Ac from the AP 30, the terminals 10b and 10c send ACKb and ACKc after the SIFS time to notify the AP 30 that the data has been normally received (S13 and S16). Then, when there is data to be transmitted from the terminal 10 to the AP 30, the terminals 10 b and 10 c transmit the data Tb and Tc to the AP 30 after SIFS time after transmitting ACKb and ACKc (S 17 a and S 20 a). In this case as well, if the data Tb and Tc are sent to the AP 30 not after (DIFS + random number) time after sending ACKb and ACKc but after SIFS time, radio contention with other devices occurs. Because there is no.

  When the AP 30 normally receives the data Tb, Tc from the terminals 10b, 10c, the AP 30 returns an ACK after SIFS time (S18a, S21). When receiving the ACK from the AP 30, the terminals 10 b and 10 c determine that the transmission / reception with the AP 30 has ended and shift to the sleep state until the next scheduled beacon reception time (S 19 a and S 22).

  Next, focusing on only the radio communication terminals 10a, 10b, and 10c, the operation of the radio communication terminals 10a, 10b, and 10c will be described with reference to the flowchart shown in FIG. In addition, in the figure, the code | symbol in () among the codes | symbols shown with a leader line is a code | symbol of the corresponding | compatible process in FIG.

  The control unit 22 of the wireless communication terminal determines whether or not a beacon timer for recognizing the reception time of the beacon signal is set (S30). If the beacon timer is not set, the reception time of the next beacon signal is determined. Until the beacon timer is started (S31). When the beacon timer is already set and when the beacon timer is set and activated (S31), the control unit 22 cuts off the power supply to the RF unit 12 with respect to the power supply control unit 27. The transmission / reception function is set to the sleeve state (S32).

The control unit 22 determines whether or not the beacon timer has reached 0, that is, whether or not it is just before the scheduled reception time of the beacon signal (S33), waits until just before the scheduled beacon reception time, and immediately before the scheduled beacon time. Then, the power supply control unit 27 is instructed to start supplying power to the RF unit 12, and the transmission / reception function is activated (S34). When the transmission / reception function of the wireless communication terminal becomes active and the antenna 11 receives a beacon signal from the AP 30 (S35), the control unit 22 sets and activates the beacon timer (S36), and then the analysis unit 21 Determines whether or not the beacon signal is normally received (S37). If the beacon signal is not normally received, the process returns to step 30, and if the beacon signal is normally received, the beacon signal is further analyzed. do it,
a. Whether there is data addressed to own terminal, etc. b. If there is data, etc. addressed to own terminal, N
c. Communication order n of all terminals N
(S38).

  Subsequently, the control unit 22 determines whether or not the communication order n of the own terminal is the first (S39), and when the communication order n of the own terminal is the first, the transmission waiting time timer Is set to the SIFS time, which is activated (S40), and proceeds to step 46. If the communication order n of the own terminal is not the first, the own communication time zone timer is set to the aforementioned (n−1) T (where n is the communication order and T is a fixed time), and this is started. After that, the transmission / reception function is shifted to the sleeve state (S41).

  When starting the own communication time zone timer, the control unit 22 determines whether or not this timer has become 0, that is, whether or not the own terminal communication time zone has been reached (S42), and the own terminal communication time zone. If it is determined that the transmission / reception function has been established, the transmission / reception function is shifted to the active state (S43). If wireless reception is not currently being performed (S44), the transmission waiting time timer is set to (DIFS + random number) time, and this is started (S45).

  When starting the transmission waiting time timer (S40, S45), the control unit 22 determines whether or not a wireless signal is being received. If the wireless signal is being received, the control unit 22 returns to step 45; Until the end of, the PS Poll signal is transmitted, and the transmission of data from the AP 30 is requested (S48). The analysis unit 21 determines whether or not the radio signal corresponding to the PS Poll signal has been normally received (S49). If the radio signal has been normally received, the control unit 22 causes the ACK to be transmitted and the feature of the present embodiment. The transmission waiting time timer is set to the SIFS time and started (S50). After the SIFS time elapses, that is, when the waiting time timer becomes 0, the terminal that sent ACK in step 50 is the own communication time zone among the terminals 10a, 10b, and 10c of this embodiment, and the remaining terminals Is not in its own communication time zone, so it does not send out radio signals. In addition, since the AP 30 or a terminal that is not the present embodiment (for example, the terminal described in the related art) waits for longer than the SIFS time (DIFS + random time) after receiving the ACK, the terminal that sent the ACK in step 50 Always secure the next transmission right.

  When the transmission waiting time timer becomes 0 (S51), as described above, since the terminal secures the transmission right, the control unit 22 sends data to the AP 30 as necessary and waits for transmission. The time timer is set to the SIFS time and started (S52).

  And the analysis part 21 judges whether ACK from AP30 was received, and if it has received, it will return to step 30. In this case, since the beacon timer is already set in step 36, the control unit 22 immediately shifts the transmission / reception function to the sleeve state (S32). If no ACK is received, the process waits until the transmission waiting time timer expires and returns to step 52.

  As described above, in the present embodiment, when there are a plurality of wireless communication terminals 10a, 10b, and 10c as compared with the prior art shown in FIG. 9, each terminal 10a, 10b, and 10c has its own communication time zone and beacon signal. Since the transmission / reception function is activated only when the terminal 10a is received, the power consumption of the terminals 10a, 10b, and 10c can be reduced. Furthermore, in this embodiment, when there are a plurality of wireless communication terminals 10a, 10b, and 10c, data is exchanged with the AP 30 only in the communication time zone assigned to the own terminal. Etc., and transmission efficiency is improved.

  Specifically, transmission efficiency is improved for the following two reasons.

(1) First reason In order to prevent multiple wireless communication terminals and APs from transmitting and transmitting radio signals simultaneously, IEEE802.11 waits for (DIFS + random number) time after receiving no radio signal and waits for the radio signal. It is specified to start sending. Since this random number is generally different for each wireless communication terminal and AP, the risk of interference by starting transmission / reception at the same time is reduced. In a certain wireless communication terminal, when another wireless communication terminal or AP starts wireless transmission before the (DIFS + random number) time expires, this wireless communication terminal is next generated because the wireless transmission path is congested. The random number is set to a value larger than the previously generated random number, and the risk of transmitting radio at the same time is reduced. Then, when a radio signal is received from another radio communication terminal or AP again before the (DIFS + random number) time has elapsed since the next radio signal was received, the above random number is further increased. That is, if the reception of radio signals from other radio communication terminals or APs is repeated before the (DIFS + random number) time ends, the random numbers gradually increase and the transmission waiting time of the radio communication terminals becomes longer.

  On the other hand, in the present embodiment, since a dedicated communication time zone is determined for each wireless communication terminal 10a, 10b, 10c, each wireless communication terminal 10a, 10b, 10c The reception of radio signals is basically eliminated, and the number of cases where the random number waiting time becomes long is extremely small. In addition, in this embodiment, the number of times (DIFS + random number) time is set as the transmission waiting time is smaller than that in the prior art, so that the transmission waiting time can be shortened for the entire wireless communication system.

  By the way, if there is a wireless communication terminal of the prior art in addition to the wireless communication terminals 10a, 10b, and 10c of the present embodiment under the management of the AP 30, this wireless communication terminal and the wireless communication of the present embodiment will be provided. There is a risk of competing with any of the terminals 10a, 10b, and 10c. However, even in such a case, only one of the wireless communication terminals 10a, 10b, and 10c competes with the wireless communication terminal, and the number of competing devices is small. As compared with the case of the above, it is possible to suppress a decrease in transmission efficiency due to an increase in the transmission waiting time described above.

  That is, in this embodiment, transmission efficiency can be improved from the viewpoint that the transmission waiting time can be shortened.

(2) Second reason A wireless communication terminal may not be able to detect transmissions of other wireless communication terminals. This is because an AP is generally installed near a ceiling with a good view, but a terminal may be placed on a desk or near a pillar or wall. This is because the transmission of can be detected, but the transmission of other wireless communication terminals may not be received. In general, another wireless communication terminal in such a case is called a hidden terminal.

  As described above, since the transmission of the other wireless communication terminal cannot be detected between the hidden terminals, two wireless communication terminals may simultaneously transmit to the AP and interfere with each other. Since the AP cannot normally receive the interfering signal, the AP does not return a reception confirmation signal ACK for both. Then, since both wireless communication terminals cannot receive ACK, they retransmit the wireless signal. Thereafter, transmission of radio signals of both radio communication terminals is repeated until interference is eliminated. As a result, the transmission efficiency is reduced in the wireless communication terminal as in the prior art.

  On the other hand, in this embodiment, based on a beacon signal from an AP generally installed in a place with a good view, the communication time zone assigned to itself is grasped from a partial virtual bitmap in this beacon signal, Since the wireless communication terminal wirelessly communicates with the AP only during its own communication time zone, even if there is a hidden terminal, the probability that two wireless communication terminals transmit to the AP at the same time can be greatly reduced.

  That is, in this embodiment, transmission efficiency can be improved from the viewpoint that interference due to hidden terminals can be reduced.

  Moreover, in this embodiment, since the transmission efficiency between AP30 and each terminal 10a, 10b, 10c is raised without changing the specification of AP30 at all, in implementing this embodiment, equipment cost can be suppressed. it can.

  Next, the radio | wireless communications system as 2nd embodiment which concerns on this invention is demonstrated using FIG. In this embodiment, the basic system configuration is the same as the system configuration of the first embodiment shown in FIG. 1, and the configuration of the AP 30 is also the same as the AP 30 of the first embodiment shown in FIG. There is a different point only in the communication time zone of the own terminal set by the control unit 22 of the wireless communication terminals 10a, 10b, and 10c.

  That is, in the first embodiment, the communication time zone of each of the terminals 10a, 10b, and 10c is the fixed time T. However, in this embodiment, the AP 30 transmits the beacon signal at the transmission interval p of the beacon signal by the AP 30. The time (p / N) divided by the total number N of terminals with data that is grasped at the time is set as the time of the communication time zone of the own terminal. Therefore, if the total number N of terminals with data that is grasped when the AP 30 transmits a beacon signal changes, the time of the communication time zone of the own terminal also changes. Note that, as described above, the number of terminals having data to be transmitted from the AP 30 is calculated based on the number of “1 (data present)” in the partial virtual bitmap unit 76 in the beacon signal. 21 asks.

  Specifically, as shown in FIG. 6, when the number of terminals 10a, 10b, and 10c having data to be transmitted from the AP 30 is 3, the communication time zone of each terminal 10a, 10b, and 10c is p / 3. Become. For this reason, regarding the terminal 10b with the second communication order, the timing at which the transmission / reception function becomes active again (S24b) after receiving the beacon signal is p / 3 hours after receiving the beacon signal. For the third terminal 10c, the timing at which the transmission / reception function becomes active again (S25b) after receiving the beacon signal is 2p / 3 hours after receiving the beacon signal. Note that the timing chart shown in FIG. 6 is basically the same as the timing chart of FIG. 5 except for the timing when the active state (24b, 25b) described above and the time of the communication time zone are described.

  In this embodiment, the communication time zone of each terminal is determined according to the number of terminals that have data to be transmitted from the AP 30. Therefore, even when the number of terminals increases, the communication time zone of each terminal is secured. can do. On the other hand, when the number of terminals is small, the communication time zone of each terminal becomes longer. Therefore, PS Poll and data from each terminal are transmitted at intervals apart from those of the first embodiment. As a result, the probability of crosstalk is reduced and transmission efficiency can be increased.

  Next, the radio | wireless communications system as 3rd embodiment which concerns on this invention is demonstrated using FIG. In this embodiment, the basic system configuration is the same as the system configuration of the first embodiment shown in FIG. 1, and the configuration of the AP 30 is the same as that of the AP 30 of the first embodiment shown in FIG. The only difference is the start timing of the communication time zone of the own terminal set by the control unit 22 of the wireless communication terminals 10a, 10b, and 10c.

  In each of the above embodiments, the start time of the communication time zone of each terminal 10a, 10b, 10c is determined based on the beacon reception time. In this embodiment, the time included in the beacon signal is determined. The start timing of the communication time zone of each terminal 10a, 10b, 10c is determined with reference to the time of the clock synchronized with the stamp.

  In the beacon signal, a 64-bit time stamp is always included in the fixed-length field 69 shown in FIG. 8 according to the IEEE 802.11 standard. This time stamp represents a time that is an integer multiple of 1 microsecond. Since the terminals 10a, 10b, and 10c can receive the beacon signal in common, if the terminals 10a, 10b, and 10c generate a clock synchronized with the time stamp, the clocks of the terminals 10a, 10b, and 10c are almost equal to each other. Will be shown.

Therefore, for example, the start timing of the communication time zone of the terminal 10a whose communication order is the first is
Clock time = 20 ms x m (m is an arbitrary integer)
The time becomes. The start time of the communication time zone of the terminal 10a becomes the reference time of the communication time zone start timing of the other terminals 10b and 10c.

Also, the start timing of the communication time zone of the second terminal 10b with the communication order is
Clock time = 20ms × m + T
(T is the same value as the time of the communication time zone in the first embodiment)
The time becomes.

The start timing of the communication time zone of the third terminal 10c whose communication order is
Clock time = 20ms × m + 2T
The time becomes. That is, the communication time zone start timings of the second and third terminals 10b and 10c with the communication order are times obtained by adding + T and + 2T to the above-described reference time, respectively. Moreover, the time of the communication time zone of each terminal 10a, 10b, 10c is the same T as in the first embodiment.

  As described above, when each terminal 10a, 10b, 10c sets the communication time zone of its own terminal, it operates as follows.

  Each terminal 10a, 10b, 10c maintains the sleep state until just before the scheduled reception time of the beacon signal from the AP 30 (S1), as in the above embodiment, and becomes active when just before the scheduled reception time of the beacon signal. (S2). On the other hand, when the beacon signal transmission time comes, the AP 30 wirelessly transmits the beacon signal (S3), and waits for signal transmission from this point (DIFS + random number) time. When each terminal 10a, 10b, 10c in the active state receives a beacon signal from the AP, it analyzes the beacon signal and, as described above, determines the communication time zone of the terminal that is determined based on the clock generated from the time stamp. While grasping, it shifts to a sleep state (S23).

  And each terminal 10a, 10b, 10c will each transfer to an active state, if it becomes the start timing of the communication time slot | zone of an own terminal (S2c, S24c, S25c). When the first terminal 10a in the communication sequence becomes active, in this example, since the AP 30 is transmitting data AD (S10c), it waits for the end of the transmission, and when the transmission ends (DIFS + random number) Wait for a time, and if no other radio signal is received during that time, PS Polla is transmitted (S4c). Thereafter, each terminal 10a, 10b, 10c basically performs the same operation as in the above embodiment. However, to be repeated, the terminal 10b shifts to the active state at the time when + T is added to the reference time (20 ms × m) (S24c), and the terminal 10c shifts to the active state at the time when the reference time + 2T is added. (S25c).

  The scheduled reception time of the beacon signal may not be received at an accurate cycle timing due to interference with other signals. For this reason, when the data signal transmitted / received between AP30 and each terminal 10a, 10b, 10c is a voice signal, a jitter will arise and a delay may arise in a voice signal, or a packet may be lost. Therefore, in this embodiment, a reference time is generated from a time stamp included in the beacon signal, and a communication time zone is determined based on the reference time.

As mentioned above, although various embodiment which concerns on this invention was described, this invention is not restricted to the above embodiment, For example, the modification of the following (1)-(6) is also included.
(1) In the above embodiments, the number N of terminals having data to be transmitted from the AP 30 and the communication order of each terminal in the power saving mode and the communication order of each terminal are in the partial virtual bitmap of the beacon signal received from the AP 30. Although it is grasped from the data, the AP may notify each terminal of the above information by a unique procedure. Also in this case, basically, it is preferable to include the above information at any location in the beacon signal.
(2) In the above embodiment, the transmission function and the reception function are activated in the active state. However, in some cases, only the transmission function or only the reception function is activated to further save power. Good. For example, only the reception function may be activated at the scheduled reception time of the beacon signal.
(3) When the data signal is an audio signal, the following a) to d) may be made.

  In order to shorten the delay time of the voice signal, in other words, in order to secure the real-time level, the voice signal is usually transmitted in a short cycle of about 20 to 40 ms. On the other hand, as described above, the beacon signal is normally transmitted at a cycle of about 100 ms. For this reason, a plurality of voice packets can be transmitted during one period of the beacon signal.

Therefore,
a) Even if a plurality of packets transmitting voice signals are integrated, for example, five voice packets with a period of 20 ms are integrated into one large packet, and one packet is transmitted during one period of a beacon signal. good.

  As a method of integration into a large packet, a plurality of packets may be integrated with one MAC layer, and the IP headers of the IP layer may be integrated as they are, or the IP header and UDP header of the IP layer and UDP layer may be integrated. It is also possible to integrate and integrate only the audio signal as it is.

b) Both the beacon signal period and the voice packet period may be unified to 40 ms, and one voice packet may be transmitted in one beacon period.
c) Since the cycle of the beacon signal and the cycle of the voice packet are different, the number of voice packets that the AP should send to each wireless terminal in one beacon cycle is 0, or 2 or more in the case of 1 There may be cases. For that, it may be as follows.

  In the case of 0: Since the beacon signal indicates that there is no data addressed to its own wireless terminal, PS Poll is not transmitted in this beacon period, and its own audio signal is not transmitted to the AP.

  In the case of one: Since the beacon signal indicates that there is data for the own wireless terminal, PS Poll is transmitted, the data is received from the AP, and its own audio signal is also transmitted to the AP. When there are two or more voice packets to be transmitted from the own wireless terminal, both packets are preferentially transmitted by transmitting with a waiting time of SIFS time.

  When there are two or more: Since the beacon signal indicates that there is data or the like addressed to the own wireless terminal, PS Poll is transmitted and the data or the like is received from the AP. When there are two or more, the “more data” bit in the frame control signal in the packet header of the data header transmitted from the AP is “1” in accordance with the 802.11 standard, so the first data is read, After returning ACK, by sending PS Poll again during the SIFS time waiting time, the second and subsequent data are preferentially sent from the AP. When the reception of data from the AP is completed, its own audio signal is sent to the AP as in the case of one.

d) Predicting that there is data addressed to itself without looking at the above-mentioned more data, with the reception time of the beacon signal as a reference, at different phases between the power-saving communication wireless terminals, for example, in a general cycle of a voice packet PS Poll may be sent to the AP every 20 ms to request transmission of data.
(4) In radio, reception of radio signals often fails due to transmission errors or the like. Since the beacon signal is also a radio signal, the radio terminal may not be able to receive due to a transmission error. In this case, that is, when the beacon signal cannot be normally received at the scheduled reception time of the beacon signal, in the above embodiment, the data addressed to itself is requested to the AP by the PS Poll signal until the next beacon signal is normally received. Can not be done and delays occur. Therefore, if the beacon signal cannot be received normally at the scheduled reception time of the beacon signal, the number of all terminals and the communication order of the own terminal are determined according to the contents of the partial virtual bitmap of the beacon signal received last time, and this A communication time zone may be determined. Specifically, the number of all terminals grasped in step S38 in the flowchart of FIG. 4 and the communication order of the own terminal are temporarily stored, and it is determined that the beacon signal has not been normally received at the subsequent beacon reception scheduled time. If this is the case (step 37), without returning to step 30, the number of previously stored terminals and the communication order of the own terminal are called and the process moves to step 39.
(5) In the above embodiments, only the time zone including the scheduled reception time of the beacon signal and the communication time zone of the own terminal are activated, but the communication time of the own terminal from the scheduled reception time of the beacon signal. It may be in an active state until the band ends. In other words, the active state maintenance time may be substantially the same as that of the prior art. However, it goes without saying that the power consumption can be reduced if only the time zone including the scheduled reception time of the beacon signal and the communication time zone of the own terminal are in the active state as in the above embodiment.
(6) In the above embodiment, the data signal transmitted / received between the AP and each terminal is an audio signal, but signals other than the audio signal, for example, data such as image data and character data may be handled. Good. In this case, since the data length of these data is not constant like an audio signal, there is a possibility that communication cannot be performed in the own communication time zone. For this reason, when handling such data, it is preferable that the length of data transmitted and received between the terminal and the AP is determined in advance between the AP and each terminal.

It is explanatory drawing which shows the structure of the radio | wireless communications system in 1st embodiment which concerns on this invention. It is a functional block diagram of AP in 1st embodiment which concerns on this invention. It is a functional block diagram of the radio | wireless communication terminal in 1st embodiment which concerns on this invention. It is a flowchart which shows operation | movement of the radio | wireless communication terminal in 1st embodiment which concerns on this invention. It is a timing chart which shows the transmission / reception timing between AP and each radio | wireless communication terminal in 1st embodiment which concerns on this invention. It is a timing chart which shows the transmission / reception timing between AP and each radio | wireless communication terminal in 2nd embodiment which concerns on this invention. It is a timing chart which shows the transmission / reception timing between AP and each radio | wireless communication terminal in 3rd embodiment which concerns on this invention. It is explanatory drawing which shows the data structure in a beacon signal. It is a timing chart which shows the transmission / reception timing between AP and each wireless communication terminal in a prior art.

Explanation of symbols

10a, 10b, 10c: wireless communication terminal, 11: antenna, 12: RF unit, 13: baseband unit, 14: MAC layer processing unit, 15: upper layer processing unit, 16: input / output interface unit, 17: input / output Unit: 20: communication processing unit, 21: analysis unit, 22: control unit, 26: power supply, 27: power supply control unit, 30: AP (relay device), 31: antenna, 32: RF unit, 33: baseband 34: MAC layer processing unit 35: Router unit 40: Communication processing unit 41: Beacon data generation unit 42: Analysis unit 43: Control unit

Claims (9)

  1. In a wireless communication terminal that communicates with another communication terminal via a relay device that transmits a beacon signal including control data indicating whether there is communication data addressed to the wireless communication terminal for each wireless communication terminal,
    Transmitting and receiving means for transmitting and receiving various signals to and from the relay device;
    When analyzing the control data contained in the beacon signal from the relay device received by the transmission / reception means and determining that there is communication data to be received by the terminal, based on the control data, A signal analysis means for determining a communication order in one or more wireless communication terminals under the control of the relay device;
    In accordance with the communication order of the own terminal determined by the signal analysis means, the timing of the communication time zone is determined between the own terminal and the wireless relay device, and between the relay device during the communication time zone Communication control means for causing the transmission / reception means to transmit / receive the communication data signal, and to refrain from transmitting the communication data signal to the relay device in a time period excluding the communication time period;
    Equipped with a,
    Communication between the relay device and the wireless communication terminal is performed in conformity with IEEE 802.11,
    In the control data, information indicating whether there is communication data for each terminal identification ID is set as binary information in the partial virtual bitmap of the variable-length field of the beacon signal defined in IEEE 802.11. And
    The signal analysis means includes
    Based on the terminal identification ID assigned to the wireless communication terminal in advance, it is determined whether there is communication data based on the binary information corresponding to the terminal identification ID, and the partial virtual bitmap is stored in the partial virtual bitmap. The communication order is determined by analyzing the quantity of information indicating the presence of communication data set before the terminal identification ID of the own wireless communication terminal.
    A wireless communication terminal characterized by the above.
  2. The wireless communication terminal according to claim 1,
    The communication control means causes the transmission / reception means to transmit a request signal for requesting transmission of the communication data to the relay device when the communication time zone of the own terminal comes.
    A wireless communication terminal characterized by the above.
  3. The wireless communication terminal according to any one of claims 1 and 2,
    When there is communication data to be transmitted from the own terminal to the relay device, the communication control means determines that no other wireless communication terminal exists during the communication time zone of the own terminal, and transmits a signal including the communication data. Preferentially transmitting from the other wireless communication terminal by the transmission / reception means,
    A wireless communication terminal characterized by the above.
  4. In the radio | wireless communication terminal as described in any one of Claim 1 to 3,
    The communication control means determines the timing of the communication time zone on the basis of the reception time of the beacon signal.
    A wireless communication terminal characterized by the above.
  5. In the radio | wireless communication terminal as described in any one of Claim 1 to 4,
    Power supply control means for controlling power supplied to at least a part of the transmission / reception means to change the state of the transmission / reception means between an active state capable of transmission / reception operation and a sleep state where transmission / reception operation is disabled,
    The communication control means causes the power supply control means to make the transmission / reception means in the active state by the power supply control means in a time zone for receiving the beacon signal and the communication time zone of the terminal itself. In the time zone other than the time zone for receiving the beacon signal and the communication time zone of the terminal itself, the power supply control means causes the device to enter the sleep state.
    A wireless communication terminal characterized by the above.
  6. In the radio | wireless communication terminal as described in any one of Claim 1 to 5,
    The communication control means sets a time obtained by dividing the transmission interval of the beacon signal by the relay device by a predetermined fixed number as the time of the communication time zone.
    A wireless communication terminal characterized by the above.
  7. In the radio | wireless communication terminal as described in any one of Claim 1 to 5,
    The signal analyzing means analyzes the control data included in the beacon signal, and obtains the number of wireless communication terminals having communication data to be transmitted from the relay device at the present time,
    The communication control means is a time obtained by dividing the transmission interval of the beacon signal by the relay device by a value determined by the number of the wireless communication terminals obtained by the signal analysis means, as the time of the communication time zone.
    A wireless communication terminal characterized by the above.
  8. A control signal including control data indicating whether there is communication data addressed to the wireless communication terminal and the wireless communication terminal for each wireless communication terminal is transmitted and relayed between the wireless communication terminal and another communication terminal In a wireless communication method of a wireless communication system comprising a relay device,
    The wireless communication terminal is
    A control signal receiving step for receiving the control signal from the relay device;
    When the control data included in the control signal received in the control signal receiving step is analyzed and it is determined that there is communication data to be received by the terminal, the relay device is based on the control data. A signal analysis step for determining a communication order in one or more wireless communication terminals having communication data to be transmitted from;
    A communication time setting step for determining the timing of a communication time zone between the terminal and the wireless relay device according to the communication order of the terminal determined by the signal analysis unit,
    Communication that causes the communication data signal to be transmitted to and received from the relay device during the communication time zone of its own terminal, and to refrain from transmitting the communication data signal to the relay device in a time zone other than the communication time. Control process;
    The execution,
    Communication between the relay device and the wireless communication terminal is performed in conformity with IEEE 802.11,
    In the control data, information indicating whether there is communication data for each terminal identification ID is set as binary information in the partial virtual bitmap of the variable-length field of the beacon signal defined in IEEE 802.11. And
    In the signal analysis step,
    Based on the terminal identification ID assigned to the wireless communication terminal in advance, it is determined whether there is communication data based on the binary information corresponding to the terminal identification ID, and the partial virtual bitmap is stored in the partial virtual bitmap. The communication order is determined by analyzing the quantity of information indicating the presence of communication data set before the terminal identification ID of the own wireless communication terminal.
    A wireless communication method.
  9. The wireless communication method according to claim 8, wherein
    The wireless communication terminal is configured to transmit / receive various signals to / from the relay device, and to control power supplied to the transmission / reception means so that the transmission / reception means can perform a transmission / reception operation and sleep incapable of transmission / reception operation Power supply control means for changing the state to a state,
    The time for the power supply control means to receive the beacon signal in the time zone for receiving the beacon signal and the communication time zone of the terminal itself, causing the power supply control means to activate the transmission / reception means in the active state. Performing a power saving mode control step of causing the power supply control means to enter the sleep state in a time zone excluding the communication time zone of the zone and the own terminal;
    A wireless communication method.
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