Wireless communication system, wireless relay unit and wireless terminal constituting the wireless communication system, and wireless communication method

• US 20060271969A1
• Filed: 03/13/2006
• Published: 11/30/2006
• Est. Priority Date: 05/18/2005
• Status: Active Grant

• Current Assignee: Hitachi, Ltd.
• Original Assignee: Hitachi, Ltd.
• Inventors: Suzuki, Tsutomu, Takizawa, Masaaki
• Granted Patent: US 7,542,719 B2
• Time in Patent Office: Days
• US Class Current: 725/81
• CPC Class Codes: H04W 72/12 Wireless traffic scheduling
• CPC Class Codes: H04W 74/0808 using carrier sensing, e.g. carrier sense multiple access [CSMA]
• CPC Class Codes: H04W 84/12 WLAN [Wireless Local Area Networks]
• CPC Class Codes: H04W 88/04 adapted for relaying to or from another terminal or user

Abstract

The present invention is to provide a wireless LAN system which achieves a relatively effective use of communication band, while suppressing occurrence of hidden terminal problems.

When wireless terminal A and wireless terminal B respectively transmit signals (T123, T133), and Access Point (AP) in the wireless LAN system recognizes occurrence of contention, if AP successfully recognizes an address of sending source of this signal and a duration of this signal as a result of analyzing any signal from the wireless terminal A, AP transmits a CTS signal which gives a clearance for transmission to the wireless terminal A which is the source of sending the signal (T113). The wireless terminal A which is given the clearance for transmission by the CTS signal, resends a signal identical to the one previously sent (T127), whereas the wireless terminal B which is not given the clearance for transmission by the CTS signal withholds a signal transmission during the duration indicated by the CTS signal.

Claims

1. A wireless relay unit comprising a wireless communication means which establishes a wireless communication with a wireless terminal, and relays communication between the wireless terminal and another terminal, comprising,

a receive judging means which determines whether or not said wireless communication means receives a signal from the outside,

a contention judging means which determines whether or not the signal received by said wireless communication means is in a state of contention where signals from multiple wireless terminals are overlapping,

an analyzing means which analyzes the signal received by said wireless communication means,

a control signal generating means which accepts a transmission from a particular wireless terminal among said multiple wireless terminals and generates a transmission clearance signal defining a duration indicating a time necessary for data transmission from the particular wireless terminal, and

a transmission directive means which instructs said wireless communication means, when said receive judging means determines that a signal is not received from the outside, to transmit said transmission clearance signal generated by said control signal generating means, wherein,

in the course of receiving a signal from any one of said multiple wireless terminals, if said contention judging means determines there is contention and if a sending source address and a duration of this signal are successfully obtained, as a result of analyzing a part of the signal by said analyzing means, said control signal generating means accepts the data transmission from the wireless terminal having the sending source address, and generates said transmission clearance signal defining the duration necessary for the data transmission from the wireless terminal.

2. The wireless relay unit according to claim 1, wherein,

said control signal generating means generates a dummy signal which does not define any wireless terminal as a sending source, and when said contention judging means determines there is contention, said transmission directive means makes said wireless communication means to transmit the dummy signal, until said receive judging means determines that no signal is received from the outside.

3. A wireless terminal comprising a wireless communication means, and the wireless communication means establishes wireless communication with a wireless relay unit and establishes communication with another terminal via the wireless relay unit, comprising,

a receive judging means which determines whether or not said wireless communication means receives a signal from the outside,

a waiting time setting means which generates a random number and sets a random backoff interval corresponding to the random number,

a transmission directive means which makes said wireless communication means to transmit a data signal when said receive judging means determines that no wireless signal is received after a lapse of said random backoff interval from the time when said receive judging means determined that no signal was received from the outside, and

an analyzing means which analyzes a signal received by said wireless communication means, wherein,

after transmitting said data signal, if it is found that the signal received by said wireless communication means is a transmission clearance signal which gives a transmission clearance to own terminal as a result of analysis by said analyzing means, said transmission directive means makes said wireless communication means to resend the data signal to said wireless relay unit.

4. The wireless terminal according to claim 3, wherein,

if the signal received by said wireless communication means is found to be the transmission clearance signal which permits data transmission from another terminal and defines a duration indicating a time necessary for the data transmission from the another terminal, according to an analysis by said analyzing means, said transmission directive means does not instruct the wireless communication means to perform data transmission during this duration.

5. A wireless relaying unit comprising a wireless communication means which establishes wireless communication with a wireless terminal, and relays communication between the wireless terminal and another wireless terminal, comprising,

an analyzing means which analyzes a signal received by said wireless communication means,

a communication request setting means which determines, in which timing within a predetermined communication cycle, a communication is established with the wireless terminal, if the signal received by said wireless communication means indicates a communication request from the wireless terminal, as a result of analyzing the signal by said analyzing means,

a communication release setting means which releases data regarding the wireless terminal defined by said communication request setting means, if the signal received by said wireless communication means indicates a communication release request from the wireless terminal, as a result of analyzing the signal by said analyzing means,

a control signal generating means which accepts a transmission from a particular wireless terminal among multiple wireless terminals, and generates a transmission clearance signal indicating a predetermined duration being a time necessary for data transmission from the particular wireless terminal, and

a transmission directive means which makes said wireless communication means to transmit said transmission clearance signal accepting the transmission from the wireless terminal, when a particular timing comes within the communication cycle, with respect to each communication cycle until receiving said communication release request from said wireless terminal that is determined by said communication request setting means to establish communication at the particular timing within the communication cycle.

6. The wireless relay unit according to claim 5, wherein,

said communication request setting means determines the wireless terminal as a destination for a slot period as to which the destination has not been decided yet among the multiple slot periods obtained by dividing the communication cycle by a predetermined number, if the signal is a communication request from said wireless terminal as a result of analyzing by said analyzing means the signal received by said wireless communication means, and

said transmission directive means makes said wireless communication means to transmit said transmission clearance signal accepting the transmission from the wireless terminal, when a particular slot period comes within the communication cycle, with respect to each communication cycle until receiving said communication release request from the wireless terminal that is determined by said communication request setting means to establish communication in the particular slot period within the communication cycle.

7. A wireless communication system comprising,

a wireless relay unit having a wireless communication means to relay communication between a wireless terminal and another terminal, and

multiple wireless terminals each having a wireless communication means, and the wireless communication means establishes wireless communication with said wireless relay unit, and further establishes communication with another terminal via the wireless relay unit, wherein,

said wireless relay unit comprises, a receive judging means which determines whether or not said wireless communication means receives a signal from the outside,

a contention judging means which determines whether or not the signal received by said wireless communication means is in a state of contention where signals from multiple wireless terminals are overlapping,

an analyzing means which analyzes the signal received by said wireless communication means,

a control signal generating means which accepts a transmission from a particular wireless terminal among said multiple wireless terminals and generates a transmission clearance signal defining a duration indicating a time necessary for data transmission from the particular wireless terminal, and

a transmission directive means which instructs said wireless communication means, when said receive judging means determines that a signal is not received from the outside, to transmit said transmission clearance signal generated by said control signal generating means, wherein,

in the course of receiving a signal from any one of said multiple wireless terminals, if said contention judging means determines there is contention and if a sending source address and a duration of this signal are successfully obtained, as a result of analyzing a part of the signal by said analyzing means, said control signal generating means accepts the data transmission from the wireless terminal having the sending source address, and generates said transmission clearance signal defining the duration necessary for the data transmission from the wireless terminal, and

said wireless terminal comprises,

a receive judging means which determines whether or not said wireless communication means receives a signal from the outside,

a waiting time setting means which generates a random number and sets a random backoff interval corresponding to the random number,

a transmission directive means which makes said wireless communication means to transmit a data signal when said receive judging means determines that no waveform is received after a lapse of said random backoff interval from the time when said receive judging means determined that no signal was received from the outside, and

an analyzing means which analyzes a signal received by said wireless communication means, wherein,

after transmitting said data signal, if it is found that the signal received by said wireless communication means is a transmission clearance signal which gives a transmission clearance to own terminal as a result of analysis by said analyzing means, said transmission directive means makes said wireless communication means to resend the data signal to said wireless relay unit.

8. A wireless communication system comprising a wireless relay unit having a wireless communication means which establishes wireless communication with a wireless terminal and relays communication between the wireless terminal and another terminal, and also comprising the wireless terminal, wherein,

said wireless relay unit comprising,

an analyzing means which analyzes a signal received by said wireless communication means,

a communication request setting means which determines, in which timing within a predetermined communication cycle, a communication is established with the wireless terminal, if the signal received by said wireless communication means indicates a communication request from the wireless terminal, as a result of analyzing the signal by said analyzing means,

a communication release setting means which releases data regarding the wireless terminal defined by said communication request setting means, if the signal received by said wireless communication means indicates a communication release request from the wireless terminal, as a result of analyzing the signal by said analyzing means,

a control signal generating means which accepts a transmission from a particular wireless terminal among multiple wireless terminals, and generates a transmission clearance signal indicating a predetermined duration being a time necessary for data transmission from the particular wireless terminal, and

a transmission directive means which makes said wireless communication means to transmit said transmission clearance signal accepting the transmission from the wireless terminal, when a particular timing comes within the communication cycle, with respect to each communication cycle until receiving said communication release request from said wireless terminal that is determined by said communication request setting means to establish communication at the particular timing within the communication cycle.

9. A wireless communication method in which a wireless terminal communicates with another terminal via a wireless relay unit, wherein,

said wireless relay unit executes,

a receive judging step which determines whether or not a signal is received from the outside,

a contention judging step which determines whether or not the signal received from the outside is in a state of contention where signals from multiple wireless terminals are overlapping,

an analyzing step which analyzes the signal received from the outside,

a control signal generating step which accepts a transmission from a particular wireless terminal among said multiple wireless terminals and generates a transmission clearance signal defining a duration indicating a time necessary for data transmission from the particular wireless terminal, and

a transmission clearance signal sending step which sends wirelessly said transmission clearance signal that is generated by said signal generating step, when said receive judging step determines that a signal is not received from the outside, wherein,

in the course of receiving a signal from any one of said wireless terminals, if said contention judging step determines there is contention and if a sending source address and a duration of this signal are successfully obtained, as a result of analyzing a part of the signal by said analyzing step, said control signal generating step accepts the transmission from the wireless terminal having the sending source address, and generates said transmission clearance signal defining the duration necessary for the data transmission from the wireless terminal.

10. The wireless communication method according to claim 9, wherein,

said wireless terminal executes,

a receive judging step which determines whether or not a signal is received from the outside,

a waiting time setting step which generates a random number and sets a random backoff interval corresponding to the random number,

a transmission step which transmits a data signal wirelessly when the receive judging step determines that no waveform is received after a lapse of the random backoff interval from the time when the receive judging step determined that no signal was received from the outside, and

an analyzing step which analyzes a signal received from the outside, wherein,

after transmitting the data signal, if it is found that the signal received from the outside is a transmission clearance signal which gives a transmission clearance to own terminal as a result of analysis by said analyzing step, the transmission step resends said data signal to the wireless relay unit.

11. A wireless communication in which a wireless terminal establish connection with another terminal via a wireless relay unit, wherein,

said wireless relay unit executes,

an analyzing step which analyzes a signal received from the outside,

a communication request setting step which determines in which timing within a predetermined communication cycle, a communication is established with the wireless terminal, if the signal received from the outside indicates a communication request from said wireless terminal, as a result of analyzing the signal by said analyzing step,

communication release setting step which releases data regarding the wireless terminal determined by said communication request setting step, if the signal received from the outside indicates a communication release request from said wireless terminal, as a result of analyzing the signal by said analyzing step,

a control signal generating step which accepts a transmission from a particular wireless terminal among multiple wireless terminals, and generates a transmission clearance signal indicating a predetermined duration being a time necessary for data transmission from the particular wireless terminal, and

a transmission clearance signal sending step which sends the transmission clearance signal accepting the transmission from the wireless terminal, when a particular timing comes within the communication cycle, with respect to each communication cycle until receiving the communication release request from the wireless terminal that is determined by the communication request setting step to establish communication at the particular timing within the communication cycle.

12. The wireless communication method according to claim 11, wherein,

said wireless terminal executes,

an analyzing step which analyzes a signal received from the outside,

a communication request transmitting step which transmits said communication request to said wireless relay unit,

a communication release transmitting step which transmits said communication release request to said wireless relay unit, and

a data transmitting step which converts data that is to be transmitted to another terminal, into signals, and transmits the data thus converted to said wireless relay unit, wherein,

in said data transmitting step, if it is found that the signal received from the outside is a transmission clearance signal that permits a data transmission from its own terminal, according to an analysis by said analyzing step, said data is transmitted to said wireless relay unit.