JP5610340B2 - Wireless device, wireless system - Google Patents

Description

  The present invention relates to a radio apparatus and a radio system for preventing interference in a radio system sharing a frequency band to be used.

  In the radio wave related industry, development of a system that uses TVWS (TV White Space) is underway. In order to realize communication using TVWS, it is necessary to modify existing wireless communication systems so that the operation of these systems conforms to radio wave-related laws and regulations.

  In TVWS, a radio station based on a conventional license system and a radio station that does not require a license share the same frequency band. That is, since a plurality of different radio systems share the same frequency band, a function for preventing interference (in particular, interference with a radio system having a high priority for use of the frequency band) is required.

  As a mechanism for preventing interference with other radio systems, CSMA / CA (Carrier Sense Multiple Access / Collision Avoidance) is known. However, since a detection method such as CSMA / CA detects the presence of another wireless system based on the strength of the received signal, when wireless systems with different transmission power (different communication ranges) coexist, a system with high transmission power is used. It was difficult to prevent interference given to a system with low transmission power.

JP 2007-166470 A

  As described above, the conventional radio apparatus and radio system have a problem that it is difficult to prevent interference when radio systems having different communication ranges coexist. An embodiment described below is made to solve such a problem, and aims to provide a wireless device and a wireless system that can prevent interference even when wireless systems with different communication ranges coexist. .

  In order to solve the above-described problem, the wireless device according to the embodiment exchanges a transmission request signal transmitted prior to data transmission and a transmission permission signal transmitted in response to the transmission request signal, thereby obtaining a predetermined A wireless device in a wireless system that stops emission of radio waves from a wireless device that is irrelevant to the transmission and reception of data, a receiving unit that receives a transmission request signal, and an analysis that analyzes the content of the transmission request signal received by the receiving unit And a determination unit that determines whether the transmission request signal analyzed by the analysis unit includes its own identification information as a receiver or a relayer, and as a result of the determination, its own identification information is received. A communication control unit that replies a transmission permission signal to the transmission source wireless device when included as a relay person, and relays a transmission request signal to another wireless device when included as a relay person. Characterized in that was.

  In addition, the wireless device according to the embodiment exchanges the transmission request signal transmitted prior to data transmission and the transmission permission signal transmitted in response to the transmission request signal, thereby transmitting and receiving the data for a predetermined period. The wireless device in the wireless system that stops the emission of radio waves from an irrelevant wireless device, the identification information of other wireless device including at least one of its own or data receiver in the communication range, and the communication range information indicating the communication range A storage unit that stores other station information including data, a determination unit that determines whether data transmission / reception can receive interference based on the location of the data receiver and the other station information stored in the storage unit, and a determination As a result, when data transmission / reception can receive interference, based on the location of the data receiver and other station information, the wireless device to which the transmission request signal should be reached and the arrival A relay information generation unit that generates a relay information including identification information by identifying a wireless device that should relay the transmission request signal to the wireless device to be transmitted, and a transmission request signal based on the relay information generated by the relay information generation unit. And a signal generation unit for generation.

  According to the present invention, it is possible to provide a wireless device and a wireless system that can prevent interference even when wireless systems with different communication ranges coexist.

It is a block diagram which shows the structure of the radio | wireless system which concerns on 1st Embodiment. It is a conceptual diagram explaining the operation | movement of a RTS / CTS system. It is a conceptual diagram explaining the operation | movement of a RTS / CTS system. It is a timing chart explaining operation | movement of a RTS / CTS system. It is a conceptual diagram in case the transmission power of a radio | wireless apparatus is not uniform. It is a conceptual diagram explaining the interference generation | occurrence | production in case the transmission power of a radio | wireless apparatus is not uniform. It is a conceptual diagram explaining the interference generation | occurrence | production in case the transmission power of a radio | wireless apparatus is not uniform. It is a conceptual diagram explaining the interference generation | occurrence | production in case the transmission power of a radio | wireless apparatus is not uniform. It is a conceptual diagram explaining the interference generation | occurrence | production in case the transmission power of a radio | wireless apparatus is not uniform. It is a conceptual diagram explaining operation | movement of the radio | wireless system which concerns on 1st Embodiment. 5 is a flowchart for explaining the operation of the wireless system according to the first embodiment. 5 is a timing chart for explaining the operation of the wireless system according to the first embodiment. It is a figure which shows an example of the RTS frame of the radio | wireless system which concerns on 1st Embodiment. It is a figure which shows the update of the RTS frame of the radio | wireless system which concerns on 1st Embodiment. It is a conceptual diagram explaining operation | movement of the radio | wireless system which concerns on 2nd Embodiment. It is a conceptual diagram explaining operation | movement of the radio | wireless system which concerns on 3rd Embodiment. 6 is a flowchart for explaining the operation of the wireless system according to the second embodiment. 10 is a flowchart for explaining the operation of the wireless system according to the third embodiment.

(Configuration of the first embodiment)
An RTS-CTS method (Request To Send / Clear To Send: transmission request / transmission permission method) is known as a mechanism for preventing a radio system transmission collision. In the RTS-CTS system, a wireless device that is to transmit data transmits a transmission request signal (RTS signal) prior to data transmission, and a wireless device that is to receive data transmits a transmission permission signal (CTS) in response to the RTS signal. Signal). The RTS signal includes destination information indicating a destination to receive the RTS signal, and the wireless device that has received the RTS signal emits a radio wave for a certain period of time when the destination information does not include its own identification information. To stop. Similarly, the CTS signal includes destination information indicating the destination to which the CTS signal should be received. When the wireless device that has received the CTS signal does not include its own identification information, the CTS signal receives radio waves for a certain period of time. Stop firing. That is, a wireless device unrelated to the transmission / reception of the data operates so as to stop emission of radio waves because it does not cause interference. The embodiments described below overcome the limitations of the RTS-CTS scheme.

  The configuration of the wireless system according to the first embodiment will be described below with reference to FIG. As shown in FIG. 1, the wireless system of this embodiment includes a wireless device 1 that is a data transmission source, a wireless device 2a that is a transmission destination of the data, a wireless device 2b that assists the wireless device 1, and a wireless device. The wireless device 3 belongs to a system different from 1 · 2a · 2b and has different transmission power.

  The wireless device 1 includes an antenna 10, a reception unit 11 that demodulates radio waves received by the antenna 10 to generate reception data, a transmission unit 12 that modulates transmission data and transmits radio waves via the antenna 10, and reception It has an interface unit (I / F) 13 that exchanges received data demodulated by the unit 11 and transmission data transmitted by the transmitting unit 12 with a terminal PC connected to the outside. The receiving unit 11, the transmitting unit 12, and the interface unit 13 can be realized by a wireless system based on a standard such as IEEE802.11. That is, the wireless device 1 functions as an access point device such as a wireless LAN or a client device.

  The wireless device 1 also includes a frame generation unit 14, a frame analysis unit 15, a wireless control unit 16, and a storage unit 17.

  The frame generation unit 14 is a data calculator that generates an RTS frame and the like to be sent to a data transmission destination wireless device. The frame analysis unit 15 is a data computing unit that analyzes a CTS frame or the like transmitted from a data transmission destination wireless device. The radio control unit 16 controls operations of the frame generation unit 14, the frame analysis unit 15, and the transmission unit 12. The storage unit 17 is a database that stores information of at least another wireless system that exists around the wireless device 1 and uses a common frequency band. The storage unit 17 may be directly connected to the wireless device 1 or may be connected via a network such as the Internet.

  The wireless devices 2a and 2b have the same configuration as the wireless device 1. That is, the wireless devices 2 a and 2 b correspond to the antenna 10, the reception unit 11, the transmission unit 12, the interface unit 13, the frame generation unit 14, the frame analysis unit 15, the wireless control unit 16, and the storage unit 17 of the wireless device 1. Antennas 20a and 20b, receiving units 21a and 21b, transmitting units 22a and 22b, interface units 23a and 23b, frame generating units 24a and 24b, frame analyzing units 25a and 25b, radio control units 26a and 26b, and storage units 27a and 27b.

  The wireless device 3 has the same configuration as the wireless devices 1, 2 a, and 2 b except for the antenna and the transmission unit. That is, the wireless device 3 includes a reception unit 31, an interface unit 33, a reception unit 11, an interface unit 13, a frame generation unit 14, a frame analysis unit 15, a wireless control unit 16, and a storage unit 17 corresponding to the wireless device 1. A frame generation unit 34, a frame analysis unit 35, a wireless control unit 36, and a storage unit 37 are included. The antenna 30 and the transmission unit 32 of the wireless device 3 are a combination having different effective radiated power from the antenna 10 and the transmission unit 12 of the wireless device 1 (or the antennas 20a and 20b and the transmission units 22a and 22b of the wireless devices 2a and 2b). ing. That is, if the antenna 30 of the wireless device 3 and the antenna 10 of the wireless device 1 have the same gain, the transmission unit 32 of the wireless device 3 has a larger transmission power than the transmission unit 12 of the wireless device 1. Alternatively, if the transmission unit 32 of the wireless device 3 and the transmission unit 12 of the wireless device 3 have the same transmission power, the antenna 30 of the wireless device 3 has a higher gain than the antenna 10 of the wireless device 1. ing. That is, the communication range of the wireless device 3 is wider than the communication range (radio wave reachable range) of the wireless device 1.

(Frames generated by the frame generation unit 14)
The wireless device 1 of this embodiment transmits an RTS signal to a wireless device that exists outside its communication range. That is, the wireless device 1 transmits an RTS signal to a wireless device that exists outside the communication range of the wireless device 1 and has a wider communication range than the wireless device 1, so that the wireless device 1 transmits data while the wireless device 1 transmits data. The emission of radio waves from a wireless device outside the communication range of 1 is also stopped. Therefore, the frame generation unit 14 of the wireless device 1 includes transmitting station information indicating a transmission source, receiving station information indicating a destination to which the RTS signal is finally delivered, and relay information indicating a wireless device that relays the RTS signal. An RTS frame is generated.

  The frame generation unit 14 of the wireless device 1 searches the storage unit 17 for the presence of a wireless device having a wider communication range than itself. When the search result is obtained, the frame generation unit 14 further searches for a relay wireless device necessary for transmitting the RTS signal to the wireless device having a wide communication range. The frame generation unit 14 specifies the relay path of the RTS signal from these search results, and generates an RTS frame included in the RTS signal based on the relay path.

(Frames generated by the frame generators 24a and 24b)
The wireless devices 2a and 2b of this embodiment transmit the RTS signal of the wireless device 1 outside the communication range of the wireless device 1. The frame generation units 24a and 24b of the wireless devices 2a and 2b generate an RRTS frame (Relay Request To Send frame) based on the contents of the RTS frame of the received RTS signal. The frame generators 24a and 24b of the wireless devices 2a and 2b update the relay information included in the RTS frame to generate a new RRTS frame.

  The radio apparatuses 2a and 2b relay the RTS signal as the RRTS signal, so that the RTS signal can be delivered over a wider range than the original communication range. This makes it possible to prevent in advance potential interference that may occur when there is a wireless device having a larger effective radiation power than the wireless device 1 at a position outside the communication range of the wireless device 1.

(Frames generated by the frame generation unit 34)
The wireless device 3 of this embodiment transmits a CTS signal according to the RTS signal of the wireless device 1 sent via the wireless devices 2a and 2b. That is, the frame generation unit 34 of the wireless device 3 generates a CTS frame.

  As described above, in the RTS-CTS method, for example, when data is transmitted from the wireless device 1 to the wireless device 2a, the wireless device 2a transmits a CTS signal. On the other hand, in this embodiment, the wireless device 3 that has a wider communication range than the wireless device 1 (and the wireless device 2a) and is likely to cause interference transmits a CTS signal instead of the wireless device 2a. Since the communication range of the wireless device 3 is wider than the communication range of the wireless devices 1, 2 a, and 2 b, it is possible to stop radio wave emission of a wider range of wireless devices by transmitting the CTS signal from the wireless device 3. Become. Further, by causing the RTS signal to be transferred to the wireless device 3, interference from the wireless device 3 to the wireless device 1 can be prevented.

(Outline of RTS-CTS method)
Here, with reference to FIG. 2 thru | or 4, the communication procedure by a RTS-CTS system is demonstrated easily.

As shown in FIG. 2, a case is considered where there is a wireless device V ₁ having a communication range VN and a wireless device I ₁ having a communication range IN, and a wireless device V ₂ is present in a region where the communication ranges VN and IN overlap. . The wireless device V ₂ can receive both radio waves from the wireless device V ₁ and radio waves from the wireless device I ₁ .

As shown in FIG. 3, when the wireless device _{V 1} is to transmit an RTS signal to the wireless device _{V 2,} the wireless device _{V 2} transmits a CTS signal in response to the RTS signal. At this time, if the communication ranges of the wireless devices V ₁ , V _2, and I ₁ are approximately the same, the wireless device I ₁ can receive either the RTS signal or the CTS signal. FIG. 3 shows that the wireless device I ₁ is ready to receive the CTS signal of the wireless device V ₂ .

That is, as shown in FIG. 4, after a lapse of the DIFS (Distributed Inter-Frame Space) is a period for determining the radio wave state of another wireless device, the wireless device V ₁ was transmitting an RTS signal. Wireless device _{V 2} which has received the RTS signal, after the minimum frame interval SIFS (Short Inter-Frame Space) , transmits a CTS signal. The wireless device I _{1 that} is adjacent to the wireless devices V ₁ and V ₂ is in a period indicated by NAV (RTS) or NAV (CTS) (NAV: Network Allocation Vector) in response to reception of these RTS signal or CTS signal. The transmission is stopped, and radio wave emission is stopped during the access suspension period including the DIFS period.

In the example shown in FIGS. 2 to 4, the wireless device I ₁ is because present within the communication range of the wireless device V ₂ outside the communication range of the wireless device V _1, the wireless device I ₁ includes transmission stop in response to CTS signal It becomes a state. The wireless devices V ₁ and V ₂ transmit data and ACK during this transmission stop state. Thus, if the communication ranges of the wireless device V ₁ (V ₂ ) and the wireless device I ₁ are approximately the same, the wireless device I ₁ stops transmitting during the communication between the wireless devices V ₁ and V ₂ . Interference can be prevented.

(Limit of RTS-CTS method)
Next, the limitations of the RTS-CTS method will be described with reference to FIGS. As shown in FIG. 5, consider a case where there are a wireless device I ₂ having a communication range IN and wireless devices V ₁ to V ₈ having communication ranges VN ₁ to VN ₈ and located in the communication range IN. The transmission power P ₂ of the wireless device I ₂ is larger than the transmission power P ₁ of the wireless devices V ₁ to V ₈ and the communication range is wide. That is, the radio waves of the radio device I ₂ reach all of the radio devices V ₁ to V ₈ , but the radio waves of the radio devices V ₁ to V ₈ may not reach the radio device I ₂ .

FIG. 6 shows a first scenario in which all of the wireless devices V ₁ , V ₂ , and I ₂ are located within the communication range VN ₁ . In this case, all radio waves of the wireless devices V ₁ , V ₂ , and I ₂ can reach each of them. It is shown in FIG. 7, the wireless device V ₂ is a second scenario which is located in a region overlapping the communication range IN of the communication range VN ₁ and the wireless device I ₂ of the wireless device V _1. In this case, the radio device V ₂ can receive the radio wave from the radio device V ₁ and the radio wave from the radio device I ₂ , but the radio device V ₁ does not receive the radio wave of the radio device I ₂ . FIG. 8 shows a third scenario in which the wireless devices V ₁ and V ₂ are located within the communication range IN of the wireless device I ₂ . In this case, the radio wave of the wireless device _V 1 · _{V 2} is not reached the wireless device _{I 2,} the radio wave of the wireless device _{I 2} is in a state of reaching the wireless device _V 1 · _{V 2.}

Of the three scenarios shown in Figure 6-8, in the second and third scenario, likely RTS signal and CTS signal of the wireless device V ₁ · V ₂ does not reach the wireless device I _2, the wireless device I ₂ may cause interference to the wireless devices V ₁ and V ₂ . In order to prevent this, the reach of the RTS signal or CTS signal may be expanded (FIG. 9). In the wireless system according to the first embodiment, interference from other wireless devices having a wide communication range is prevented by extending the range in which the RTS signal reaches.

(Operation of the wireless system of the first embodiment)
Subsequently, the operation of the wireless system according to the first embodiment will be described with reference to FIGS. In the following description, as shown in FIG. 10, it is assumed that the wireless device 1 transmits data to the wireless device 2a, the wireless devices 2a and 2b transfer RTS signals, the wireless device 3 transmits CTS signals, and wireless Assume that the devices 1, 2 a, and 2 b are located within the communication range IN of the wireless device 3. In the following description, the symbols T ₁ , T _2a , T _2b, and T ₃ in the figure represent the wireless devices 1, 2 a, 2 b, and 3, respectively.

(RTS transmission of _{T 1)}
When the wireless device 1 performs data transmission, the wireless control unit 16 searches the storage unit 17 for destination information indicating the location of the wireless device 2a that is the destination of data transmission (step 101; hereinafter referred to as “S101”). ). At the same time, the wireless control unit 16 searches the storage unit 17 for other station information indicating the presence and location of other wireless devices that can interfere with the wireless device 1.

For example, in the example illustrated in FIG. 10, the wireless control unit 16 has destination information including the location of the wireless device 2a and a wireless device having a communication range IN (> communication range VN) with transmission power P ₂ (> P ₁ ). 3 is obtained from the storage unit 17.

  When the search result is obtained, the wireless control unit 16 determines whether or not there is a possibility of receiving interference in data transmission to the wireless device 2a based on the destination information and the other station information (S102). For example, when the location of the wireless device 2a is sufficiently close to the wireless device 1 and no other wireless device having a different communication range exists in the vicinity (No in S102), the wireless control unit 16 determines that there is no possibility of interference. . When there is no possibility of interference, the frame generation unit 14 generates an RTS frame including the ID of the wireless device 1 as the transmitting station information and the ID of the wireless device 2a as the receiving station information indicating the final destination of the RTS signal (S104). ). In this case, the destination information as the data destination and the receiving station information as the final destination of the RTS signal have the same contents, and the wireless device 2a transmits the CTS signal. Other station information can be searched based on the location of the wireless device, effective radiated power (communication range), and the like.

  On the other hand, when the presence of the wireless device 3 having a communication range IN wider than the communication range VN of the wireless device 1 is searched (Yes in S102), the wireless control unit 16 determines that there is a possibility of interference. When there is a possibility of interference, the wireless control unit 16 searches the storage unit 17 for a wireless device that relays the RTS signal to the wireless device 3 that can give interference to itself, and obtains route information from the wireless device 1 to the wireless device 3. The relay information including it is generated (S103).

  For example, in the example illustrated in FIG. 10, the wireless control unit 16 obtains, as other station information, the wireless device 3 that is located outside the communication range VN of the wireless device 1 and includes the wireless device 1 in the communication range IN. Therefore, the wireless control unit 16 searches and calculates a route passing through the wireless device 2a and the wireless device 2b that can relay the RTS signal to the wireless device 3 as route information, and generates relay information.

  The radio control unit 16 sends the generated relay information to the frame generation unit 14, and the frame generation unit 14 causes the ID of the radio apparatus 1 as the transmission station information and the counterpart (= CTS signal) that delivers the RTS signal as the reception station information. An RTS frame including the ID of the wireless device 3 that is the partner and the IDs of the wireless devices 2a and 2b as relay wireless devices is generated (S104).

  FIG. 13 shows an example of an RTS frame generated by the frame generation unit 14. In the example shown in FIG. 13, as elements included in the RTS frame, the station that has received the RTS frame generates transmission stop period information that should stop the radio wave, receiving station information that indicates the partner to which the RTS frame is finally delivered, and the RTS frame. The relay station information, the relay control information indicating the number of relays, and the like, and RE0 to RE3 indicating the ID of the relay wireless device that relays the RTS frame are included.

  That is, in the example shown in FIG. 10, the transmission stop period information includes the RTS signal transmitted from the wireless device 1 via the wireless devices 2a and 2b, and the CTS signal transmitted from the wireless device 3 to the wireless device 1. This is information indicating the time until data and an ACK signal are exchanged between the wireless device 1 and the wireless device 2a (the time indicated by “NAV (RTS)” in FIG. 12). Similarly, the wireless device 3 that transmits the CTS signal is defined as the receiving station information, the wireless device 1 is defined as the transmitting station information, the relay number information indicating the number of relays of the RTS signal as the relay control information, and the current relay state Relay status information is defined. Further, the ID of the wireless device 2a is defined in RE0 as the first RTS signal relay station, and the ID of the wireless device 2b is defined in RE1 as the second RTS signal relay station.

  When the RTS frame is generated, the transmission unit 12 generates an RTS signal including the RTS frame and transmits it via the antenna 10 (S105).

(T _2a RRTS transmission)
The wireless device 2a receives the RTS signal of the wireless device 1. The receiving unit 21a demodulates the RTS signal received from the antenna 20a and extracts the RTS frame (S106). The extracted RTS frame is sent to the frame analysis unit 25a.

  The frame analysis unit 25a analyzes the RTS frame (S107). The frame analysis unit 25a reads the transmission suspension period, receiving station information, relay information, etc. from the RTS frame and analyzes the contents (S108). As a result of the analysis, if the local station ID is included in the receiving station information included in the RTS frame (Yes in S108), that is, if the radio apparatus 2a is the final recipient of the RTS signal, the radio control unit 26a The frame generation unit 24a is instructed to generate a CTS frame, the frame generation unit 24a generates a CTS frame, and the transmission unit 22a modulates the CTS frame and transmits it as a CTS signal (S109).

  When the reception station information included in the RTS frame does not include the own station ID (No in S108), the frame analysis unit 25a determines whether the relay information includes the own station ID (S110). ). As a result of the determination, if the relay information does not include the ID of the own station (No in S110), the RTS signal received by the receiving unit 21a is irrelevant to the radio device 2a. The transmission unit 22a is set in a transmission prohibited state based on the transmission stop period read from (S111). The transmission stop period here is a period represented by “NAV (RTS)” in the example shown in FIG.

  As a result of the determination, if the ID of the local station is included in the relay information (Yes in S110), the wireless device 2a starts the relay process of the RTS frame. First, the radio control unit 26a reads the transmission stop period from the RTS frame and sets the transmission prohibition period NAV (RTS) in the transmission unit 22a (S112). In the examples shown in FIGS. 10 and 13, since the ID of the wireless device 3 is defined in the receiving station information included in the RTS frame, the wireless control unit 26a does not perform the CTS frame generation process but the RTS frame. Relay processing will be started.

  When the transmission prohibition period is set, the radio control unit 26a updates the transmission stop period information and the relay control information included in the analyzed RTS frame (S113). First, the radio control unit 26a generates transmission stop period information to be sent to the relay destination of the RTS signal. As shown in FIG. 12, the transmission suspension period NAV (RRTS1) generated here is shorter than the transmission suspension period NAV (RTS) of the RTS frame received by the wireless device 2a. Subsequently, the radio control unit 26a updates the relay count information and the relay status information included in the relay information, and records that the relay has been performed once.

  When the relay control information is updated, the frame generator 24a generates an RRTS frame based on the RTS frame sent from the wireless device 1 and sends it to the transmitter 22a. The transmitter 22a modulates the RRTS frame to generate an RRTS signal, and transmits the RRTS signal to the wireless device 2b via the antenna 20a (S114).

(T _2b RRTS transmission)
The wireless device 2b receives the RRTS signal of the wireless device 2a. The receiving unit 21b demodulates the RRTS signal received from the antenna 20b and extracts the RRTS frame (S115). The extracted RRTS frame is sent to the frame analysis unit 25b.

  The frame analysis unit 25b analyzes the RRTS frame (S116). The frame analysis unit 25b reads the transmission stop period, receiving station information, relay information, and the like from the RRTS frame and analyzes the contents (S117). As a result of the analysis, when the local station ID is included in the receiving station information included in the RRTS frame (Yes in S117), that is, when the radio apparatus 2b is the final recipient of the RTS signal, the radio control unit 26b The frame generation unit 24b is instructed to generate a CTS frame, the frame generation unit 24b generates a CTS frame, and the transmission unit 22b modulates the CTS frame and transmits it as a CTS signal (S118).

  When the reception station information included in the RRTS frame does not include the own station ID (No in S117), the frame analysis unit 25b determines whether the relay information includes the own station ID (S119). ). As a result of the determination, if the relay information does not include the ID of the own station (No in S119), since the RRTS signal received by the receiving unit 21b is irrelevant to the radio apparatus 2b, the radio control unit 26b The transmission unit 22b is set in a transmission prohibited state based on the transmission stop period read from (S120). The transmission stop period here is a period represented by “NAV (RRTS1)” in the example shown in FIG.

  As a result of the determination, if the ID of the local station is included in the relay information (Yes in S119), the wireless device 2b starts the relay process of the RRTS frame. First, the radio control unit 26b reads the transmission stop period from the RRTS frame and sets the transmission prohibition period NAV (RRTS1) in the transmission unit 22b (S121). In the examples shown in FIGS. 10 and 13, since the ID of the wireless device 3 is defined in the receiving station information included in the RRTS frame, the wireless control unit 26b does not perform the CTS frame generation process but the RRTS frame. Relay processing will be started.

  When the transmission prohibition period is set, the radio control unit 26b updates the transmission stop period information and the relay control information included in the analyzed RRTS frame (S122). First, the radio control unit 26b generates transmission stop period information to be sent to the relay destination of the RRTS signal. As shown in FIG. 12, the transmission suspension period NAV (RRTS2) generated here is shorter than the transmission suspension period NAV (RRTS1) of the RRTS frame received by the wireless device 2b. Subsequently, the radio control unit 26b updates the relay count information and the relay status information included in the relay information, and records that the relay has been performed a total of two times.

  When the relay control information is updated, the frame generation unit 24b generates an RRTS frame based on the RRTS frame sent from the wireless device 2a and sends it to the transmission unit 22b. The transmitter 22b modulates the RRTS frame to generate an RRTS signal, and transmits the RRTS signal to the wireless device 3 via the antenna 20b (S123).

(CTS transmission of _{T 3)}
The wireless device 3 receives the RRTS signal of the wireless device 2b. The receiving unit 31 demodulates the RRTS signal received from the antenna 30 and extracts the RRTS frame (S124). The extracted RRTS frame is sent to the frame analysis unit 35.

  The frame analysis unit 35 analyzes the RRTS frame (S125). The frame analysis unit 35 reads the transmission stop period, receiving station information, relay information, and the like from the RRTS frame and analyzes the contents (S126). As a result of the analysis, when the local station ID is included in the receiving station information included in the RRTS frame (Yes in S126), that is, when the radio apparatus 3 is the final recipient of the RTS signal, the radio control unit 36 The frame generation unit 34 is instructed to generate a CTS frame, the frame generation unit 34 generates a CTS frame, and the transmission unit 32 modulates the CTS frame and transmits it as a CTS signal (S127).

  If the receiving station information included in the RRTS frame does not include the own station ID (No in S126), the frame analyzing unit 35 determines whether the relay information includes the own station ID (S128). ). As a result of the determination, if the relay information does not include the own station ID (No in S128), since the RRTS signal received by the receiving unit 31 is irrelevant to the radio apparatus 3, the radio control unit 36 Based on the transmission stop period read out from, the transmission unit 32 is set in a transmission prohibited state (S129). The transmission stop period here is a period represented by “NAV (RRTS2)” in the example shown in FIG.

  As a result of the determination, if the ID of the local station is included in the relay information (Yes in S128), the wireless device 3 starts the relay process of the RRTS frame. First, the radio control unit 36 reads the transmission stop period from the RRTS frame and sets the transmission prohibition period NAV (RRTS2) in the transmission unit 32 (S130).

  When the transmission prohibition period is set, the wireless control unit 36 updates the transmission stop period information and the relay control information included in the analyzed RRTS frame (S131). The radio control unit 36 generates transmission stop period information to be sent to the relay destination of the RTS signal. The wireless control unit 36 updates the relay count information and the relay status information included in the relay information, and records that the relay has been performed three times in total.

  When the relay control information is updated, the frame generation unit 34 generates an RRTS frame based on the RRTS frame sent from the wireless device 2 b and sends it to the transmission unit 32. The transmission unit 32 modulates the RRTS frame to generate an RRTS signal, and transmits the RRTS signal to the next-stage radio apparatus via the antenna 30 (S132).

  In the example shown in FIGS. 10 and 13, since the ID of the wireless device 3 is defined in the receiving station information included in the RRTS frame, the wireless control unit 36 does not perform the RRTS frame relay process but the CTS frame. Generation processing is started (S127). When the CTS frame is generated and the CTS signal is transmitted, the radio control unit 36 sets the transmission prohibition period NAV (CTS) in the transmission unit 32.

(Data transmission from _{T 1} to _{T 2a)}
When the receiving unit 11 receives the CTS signal via the antenna 10, the receiving unit 11 demodulates the received CTS signal and extracts a CTS frame (S133). The frame analysis unit 15 analyzes the extracted CTS frame and confirms whether or not it corresponds to the RTS frame transmitted by the wireless device 1 previously. When the CTS frame is confirmed to be correct, the radio control unit 16 instructs the frame generation unit 14 to convert the data from the terminal PC into a data frame, and the frame generation unit 14 generates a data frame using the data. To do. The transmission unit 12 modulates the generated data frame to generate a data signal, and transmits the data signal to the wireless device 2a (S134).

  The receiving unit 21a receives and demodulates the data sent from the wireless device 1, and sends it to the terminal PC via the interface unit 23a (S135). When all the data is received, the radio control unit 26a causes the frame generation unit 24a to generate an ACK frame, and the transmission unit 22a modulates the generated ACK frame and transmits it as an ACK signal via the antenna 20a (S136). .

  When the receiving unit 11 receives the ACK signal, a series of communication procedures is completed (S137).

  As described above, according to the wireless device and the wireless system of this embodiment, when the wireless device that transmits data determines whether or not there is interference in transmission to the destination wireless device, and can receive the interference, the RTS signal transfer path Is generated. Therefore, the RTS signal can be transferred to a wireless device that is located farther than the destination wireless device, and interference caused by radio waves from outside the communication range can be prevented.

(Specific example of RTS frame)
Here, with reference to FIG. 13 and FIG. 14, a specific example of the RTS frame in the wireless system of this embodiment will be described. In the RTS frame shown in FIG. 13, relay count information RT and relay status information RI indicating the current relay status are defined as relay control information. The relay count information RT is a data string indicating how many times the RTS signal is relayed. For example, “00” for the conventional RTS-CTS method, “01” for relaying the RRTS frame once, “10” for relaying twice, “11” for relaying the same three times, and so on. It can be expressed as 2-bit value data.

In the example shown in FIG. 14, when RT is defined as “11”, the RTS frame transmitted from the radio apparatus TA is sent to the relay radio apparatus RE0, and the RRTS frame generated in the relay radio apparatus RE0 is relayed. through three relays by use wireless device RE1 / RE2 / RE3 reach the wireless device RA _3. The wireless device RA ₃ transmits a CTS frame in response to the RRTS frame. On the other hand, when RT is defined as “00”, the RTS frame transmitted from the radio apparatus TA is sent to the relay radio apparatus RE0, and the RRTS frame generated in the relay radio apparatus RE0 is not relayed. That is, the radio apparatus RA ₀ transmits a CTS frame.

In the first embodiment, the RTS signal generated by the wireless device 1 becomes an RRTS signal in the wireless device 2a, and reaches the wireless device 3 after being relayed once by the wireless device 2b. Therefore, if RT is set to “01”, the RRTS signal reaches RA ₁ corresponding to the wireless device 3.

  On the other hand, the relay status information RI indicates the position of the RTS frame in the relay path, that is, the relay status of the RTS frame. For example, as shown in FIG. 14, when RT is “11”, the initial value of RI is also “11”. When the radio control unit 26a of the radio apparatus 2a updates the relay control information, if the process of subtracting one RI is executed, the RI becomes “00” when there is no RTS frame relay destination. The position on the relay route can be found from the value of.

In the example shown in FIG. 14, the initial value “11” of RI is subtracted by 1 in RE0 / RE1 / RE2, and the RI value in RE3 is “00”. That is, RE3 is the last relay station of the RTS frame, and the next RA ₃ transmits the CTS signal.

  In the first embodiment, since RT is “01”, the initial value of RI may be “01”. When the wireless device 1 transmits the RTS frame, the wireless device 2a that has received the RTS frame subtracts one RI value from “01” to “00”. When the wireless device 2a sends an RRTS frame including the RI value “00” to the wireless device 2b, the wireless device 2b is the last relay station because the RI value is “00”, and the next wireless device 3 receives the CTS signal. Will know that should be sent.

  As described above, by defining the relay count information and the relay state information in the RTS frame, it is possible to identify the wireless device to which the RTS frame should be delivered.

(Second Embodiment)
Next, a radio system according to the second embodiment will be described in detail with reference to FIGS. 15 and 17. In the wireless system according to the first embodiment, an RTS signal (RRTS signal) is relayed as a method of extending the reach of an RTS signal or a CTS signal. In the wireless system according to the second embodiment, in addition to the transfer of the RTS signal, the CTS signal is also transferred. Since the configuration of the wireless system according to the second embodiment is the same as that of the wireless system according to the first embodiment, in the following description, common elements are denoted by the same reference numerals and overlapped. Description is omitted.

  As shown in FIG. 15, in the wireless system of this embodiment, the communication range of the wireless device 1 that transmits the RTS signal and the communication range of the wireless device 3 that has a wide communication range and may cause interference exist. The wireless device (wireless device 2a in FIG. 15) relays the CTS signal transmitted from the wireless device 3. That is, the frame generation unit 24a and the radio control unit 26a of the radio apparatus 2a generate an RCTS frame (Relay Clear To Send) that relays the CTS frame.

  As shown in FIG. 17, the wireless system of this embodiment has the same operation as that of the first embodiment except for the operation of step 228 in which the wireless device 2a transfers the CTS signal.

  That is, when the transmitting unit 22b of the wireless device 2b transmits a CTS signal or the transmitting unit 32 of the wireless device 3 transmits a CTS signal (S118 / S127), the receiving unit 21a of the wireless device 2a transmits the CTS signal. Receive and demodulate to extract CTS frame. When the CTS frame is extracted, the frame generation unit 24a and the radio control unit 26a of the radio apparatus 2a generate an RCTS frame that relays the CTS frame in the same manner as the relay process of the RRTS signal from step 112 to step 114, It transmits as a RCTS signal (S228).

  When the receiving unit 11 receives a CTS signal or RCTS via the antenna 10, the receiving unit 11 demodulates the received CTS signal or RCTS signal and extracts a CTS frame (S133). The frame analysis unit 15 analyzes the extracted CTS frame and confirms whether or not it corresponds to the RTS frame transmitted by the wireless device 1 previously. When the CTS frame is confirmed to be correct, the radio control unit 16 instructs the frame generation unit 14 to convert the data from the terminal PC into a data frame, and the frame generation unit 14 generates a data frame using the data. To do. The transmission unit 12 modulates the generated data frame to generate a data signal, and transmits the data signal to the wireless device 2a (S134). Subsequent operations are the same as those in the first embodiment.

  Thus, according to the wireless system of this embodiment, since the wireless device that relays the RCTS signal also relays the CTS signal, the communication range of the wireless device that transmits data and the communication range of the wireless device that can give interference Even if there is only a partial overlap, interference can be prevented.

(Third embodiment)
Next, a radio system according to the third embodiment will be described in detail with reference to FIGS. 16 and 18. In the wireless system according to the first embodiment, the RTS signal (RRTS signal) is relayed as a method for extending the reach of the RTS signal and the CTS signal. In the wireless system according to the second embodiment, the relay wireless device Relays the CTS signal in addition to the RTS signal. In the wireless system according to the third embodiment, the relay wireless device relays only the RTS signal, and the CTS signal is not for the wireless device that gives interference, but for the relay that exists within the communication range of the wireless device that has transmitted the RTS signal. It is configured to be transmitted by a wireless device. Since the configuration of the radio system according to the third embodiment is the same as that of the radio system according to the first and second embodiments, in the following description, common elements are denoted by the same reference numerals and overlapped. Description to be omitted is omitted.

  As shown in FIG. 16, in the wireless system of this embodiment, the RTS signal is relayed similarly to the wireless system of the first embodiment, and the RTS signal is transmitted to a wireless device outside the communication range of the wireless device 1. . In the first embodiment, the wireless device 3 that has received the RTS signal lastly transmits the CTS signal. However, in the third embodiment, the wireless device (in the communication range of each of the wireless device 1 and the wireless device 3) ( In FIG. 16, the wireless device 2a) transmits a CTS signal.

  As shown in FIG. 18, in the wireless system of this embodiment, the wireless device 2b and the wireless device 3 perform the operation of steps 120 and 129 for setting transmission stop instead of transmitting the CTS signal, and the wireless device 2a transmits the CTS signal. The operation is the same as that of the first embodiment except for the operation of step 228 to transmit.

  That is, the frame analysis units 25b and 35 analyze the RRTS frame (S116 and S125), read the transmission suspension period, the receiving station information, the relay information, and the like from the RRTS frame and analyze the contents (S117 and S126). As a result of analysis, if the local station ID is included in the receiving station information included in the RRTS frame (Yes in S117 / S126), that is, if the wireless device 2b / 3 is the final recipient of the RTS signal, The control units 26b and 36 read the transmission stop period from the RRTS frame and set the transmission prohibition period in the transmission units 22b and 32 (S120 and S129). That is, in this embodiment, instead of transmitting the CTS signal, the transmission is set to be prohibited by performing its own transmission stop setting.

  On the other hand, the radio control unit 26a of the radio apparatus 2a instructs the frame generation unit 24a to generate a CTS frame at the timing when the RTS frame reaches the radio apparatus 3, and the frame generation unit 24a generates the CTS frame. The transmitter 22a modulates the generated CTS frame to generate a CTS signal, and transmits it via the antenna 20a (S228). The subsequent procedure is the same as in the first embodiment.

  The timing at which the RTS frame reaches the wireless device 3 can be obtained by various methods. For example, a timer can be set together with the transmission stop setting in step 112, and a CTS signal can be transmitted when a predetermined time arrives (for example, the time represented by NAV (RTS)). .

  As described above, according to the wireless system of this embodiment, since the wireless device that relays the RCTS signal transmits the CTS signal, it is possible to prevent interference by minimizing traffic.

  Note that the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. In addition, various inventions can be formed by appropriately combining a plurality of components disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment. And you may combine the component covering different embodiment suitably.

  1 to 3... 1 to 3 wireless devices, 10. F), 14, 24, 34, frame generation unit, 15, 25, 35, frame analysis unit, 16, 26, 36, radio control unit, 17, 27, 37, storage unit.

Claims (5)

By exchanging a transmission request signal transmitted prior to data transmission and a transmission permission signal transmitted in response to the transmission request signal, emission of radio waves unrelated to transmission / reception of the data for a predetermined period is stopped. A wireless device in a wireless system,
A receiver for receiving the transmission request signal;
An analysis unit for analyzing the content of the transmission request signal received by the reception unit;
A determination unit that determines whether the identification information of the self is included as a receiver in the transmission request signal analyzed by the analysis unit, or is included as a relayer;
As a result of the determination, when the self-identification information is included as the receiver, the transmission permission signal is returned to the transmission source wireless device, and when the identification information is included as the repeater, the process waits for a predetermined period. A wireless device, comprising: a communication control unit that later returns the transmission permission signal to a wireless device that is a transmission source. By exchanging a transmission request signal transmitted prior to data transmission and a transmission permission signal transmitted in response to the transmission request signal, emission of radio waves unrelated to transmission / reception of the data for a predetermined period is stopped. A wireless device in a wireless system,
A storage unit storing other station information including identification information of other wireless devices including at least one of the receiver of the data or the data in the communication range and communication range information indicating the communication range;
A determination unit that determines whether or not the transmission and reception of the data can receive interference based on the position of the receiver of the data and the other station information stored in the storage unit;
As a result of the determination, when the transmission / reception of the data can receive interference, based on the position of the receiver of the data and the other station information, the wireless device to reach the transmission request signal and the wireless device to reach A relay information generation unit for generating a relay information including identification information by specifying a wireless device to relay the transmission request signal;
A radio apparatus comprising: a signal generation unit configured to generate the transmission request signal based on relay information generated by the relay information generation unit. Relay information generation unit, a radio apparatus according to claim 1, wherein generating a relay information including the number of times information indicating the number of times to be relayed to the transmission request signal. Based on the originating transmission permission signal in response to the transmission request signal, wherein the signal generating unit has generated, the wireless device according to claim 1, further comprising that the said transmission unit for transmitting the data. Radio system comprising a radio apparatus according to claim 1, and a wireless device according to claim 2.

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