JP2010109939A - Radio communication device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve a hidden terminal problem without lowering throughput. <P>SOLUTION: A radio communication device 1 includes a transmission frame generation unit 13 which generates a transmission frame including a first field containing a physical header having added information showing a schedule period wherein a wireless line is used for communication with a destination, and a second field following the first field and containing a payload, and a transmission and reception unit 12 which transmits the second field in a second mode wherein a directional beam is generated toward the destination after transmitting the first field in a first mode wherein a plurality of directional beams differing in direction are switched and generated so as to transmit the transmission frame. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a wireless communication apparatus that performs communication between a plurality of wireless stations such as a wireless LAN (Local Area Network).

  There has been proposed a directional repetitive transmission technique in which transmission is performed while switching a plurality of directional beams having different directions in a millimeter wave radio system having strong straightness of radio waves (see, for example, Patent Document 1). By using this directivity repeat transmission technology, it is possible to repeatedly transmit a radio signal for reserving a channel while controlling beam directivity in different directions, so that it is possible to notify channel reservation information to a wide range of wireless terminals. it can. That is, by using the directional repeat transmission technique, a wide range of wireless terminals can receive channel reservation information, and the hidden terminal problem can be expected to be solved. On the other hand, an increase in overhead due to repeated transmission of radio signals, resulting in a decrease in throughput. For example, when the number of repeated transmissions is four, the throughput is reduced to ¼.

  In addition, if reception of a radio signal for channel reservation transmitted by directional repeat transmission fails, the radio signal carrying the payload is transmitted even though it is actually transmitted. Otherwise there is a possibility of making a wrong judgment. If the radio signal carrying the payload is also transmitted repeatedly with directivity, the above-mentioned misjudgment can be reduced, but the overhead increases and the throughput deteriorates. That is, the reliability when notifying information necessary for carrier sense was low.

Further, the next process cannot be executed until all the radio signals repeatedly transmitted with directivity are received. Therefore, the effect of reducing the power consumption of the reception process cannot be sufficiently obtained.
JP 11-136735 A

  As described above, the conventional directional repeat transmission technology has problems that the throughput is lowered, the efficiency of directional beam control is degraded, the reliability of information transmission is low, and the low power consumption is not sufficient.

  The present invention has been made paying attention to the above circumstances, and an object of the present invention is to provide a wireless communication apparatus capable of solving the hidden terminal problem without reducing the throughput.

  To achieve the above object, according to an aspect of the present invention, there is provided a first field including a physical header to which information indicating a scheduled period for using a wireless line for communication with a destination is added, and the first field. A transmission frame generation unit that generates a transmission frame including a second field including a payload, and a first mode in which a plurality of directional beams having different directions are switched to transmit the transmission frame. And a transmitter that transmits the second field in a second mode in which a directional beam is formed in the direction of the destination after transmitting the first field.

  According to another aspect of the present invention, there is provided a first field including a physical header to which information indicating a scheduled period for using a wireless line for communication with a destination is added, and a payload subsequent to the first field. A transmission frame generation unit that generates a transmission frame including a second field including the first field and a second field that switches and forms a plurality of directional beams having different directions for each of the first field and the second field. There is provided a wireless communication apparatus including a transmission unit that selectively transmits a first mode and a second mode that forms a directional beam in the direction of the destination.

  Therefore, according to the present invention, it is possible to provide a wireless communication apparatus that can solve the hidden terminal problem without reducing the throughput.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
(First embodiment)
FIG. 1 is a block diagram showing a configuration of a wireless communication apparatus according to the first embodiment of the present invention. The wireless communication device 1 includes an antenna unit 11, a transmission / reception unit 12, a transmission frame generation unit 13, and a reception frame analysis unit 14. The transmission / reception unit 12 includes an RF unit 121, a beam forming unit 122, and a control unit 123.

  The antenna unit 11 is configured by an adaptive array antenna including a plurality of antenna elements. The transmission / reception unit 12 converts the transmission frame generated by the transmission frame generation unit 13 into an RF signal via the beam forming unit 122 and the RF unit 121 and transmits the RF signal from the antenna unit 11. Further, the transmission / reception unit 12 converts the RF signal arriving at the antenna unit 11 into a reception signal via the RF unit 121 and the beam forming unit 122, and supplies frame data included in the reception signal to the reception frame analysis unit 14.

  The beam forming unit 122 switches and forms a plurality of directional beams having different directions by the antenna unit 11 in accordance with directivity control by the control unit 123. FIG. 2 shows an example of a directional beam formed by the wireless communication device 1. In the example of FIG. 2, since the directional beams 1 to 4 in four directions are switched and transmitted, the sum of the communication areas of the directional beams 1 to 4 becomes the communication area of the wireless communication device 1. Hereinafter, such a beam control method is referred to as directional repeat transmission (first mode). On the other hand, a transmission system that forms a directional beam only in a specific direction, for example, only in the direction of a communication partner is referred to as non-repetitive transmission (second mode).

  FIG. 3 is an example of a format of a transmission frame generated by the transmission frame generation unit 13. In the example of FIG. 3, the transmission frame includes a signal synchronization preamble, a physical header, a frame check sequence (FCS1) of the physical header, a MAC header, a payload, and a frame check sequence (FCS2) of the MAC header and payload. It consists of. Since FCS1 is a check sequence for a header, it may be called a header error check (HEC).

  FIG. 4 shows an example of a conventional physical header format. The physical header includes information regarding the packet length, the subsequent MAC header, the payload, and the transmission rate at which the FCS 2 is transmitted. The packet length can be expressed in bit length or time length. If the transmission rate information is used, the bit length can be converted into a time length, and the time length can be converted into a bit length.

  In general, since the payload has a data length larger than that of the physical header, a code with higher error detection performance is required in FCS2 than in FCS1. Therefore, FCS2 requires a larger number of bits than FCS1. Further, even if there is an erroneous detection or missed detection of an error in the physical header, this is an effect on the communication characteristics such as throughput and efficiency, but the missed detection of the MAC header or payload may lead to a malfunction. Therefore, a code with higher error detection capability is used in FCS2 than in FCS1.

  Although the preamble includes a signal for synchronization, other methods such as a channel estimation field for estimating the state of the radio channel and a method for providing transmission rate information of the subsequent physical header are also considered. It is done. When the transmission rate of the physical header is fixed in advance, it is not always necessary to include the transmission rate information in the preamble.

  Hereinafter, as shown in FIG. 3, the frame check sequence of the preamble, physical header, and physical header is defined as the first field, and the MAC header, payload, MAC header, and payload frame check sequence (FCS2) are set as the second field. Define as field.

  FIG. 5 illustrates a network configuration example configured by the wireless communication device 1. FIG. 5 shows a network example in which the wireless communication device 1 operates as a base station (access point) or a terminal station (station). The terminal stations STA1 and STA2 are connected to the network via the base station AP.

  FIG. 6 shows an example of conventional directional repeat transmission. In the example of FIG. 6, when transmission using four types of directional beams is necessary, a certain unit of radio signal for wireless transmission of a transmission frame is defined, and the unit of the radio signal is sequentially changed to a directional beam. Transmit four times repeatedly while switching. In the case of OFDM transmission, if one symbol is used as a unit, the same symbol is repeatedly transmitted four times while switching the directional beam. For example, when the preamble is composed of eight symbols, the first symbol is transmitted four times, and then the second symbol is transmitted four times. Since the same symbol is repeatedly transmitted while switching the beam directivity, a wide range of wireless communication devices can receive this frame. However, there is a problem that the transmission efficiency is deteriorated by the number of repeated transmissions.

  FIG. 7A shows a typical frame exchange (RTS-CTS-Data-Ack) defined in the IEEE802.11 wireless LAN. The terminal station to be transmitted transmits an RTS (Request to Send: transmission request) toward the destination, and after receiving a CTS (Clear to Send: reception preparation complete) transmitted from the destination according to the RTS, Data is transmitted. FIG. 7B shows an example in which the directional repeat transmission shown in FIG. 6 is applied to this frame exchange. In FIG. 7B, since the transmission time length of each frame is quadrupled, as is clear from FIGS. 7A and 7B, it can be seen that the transmission efficiency is greatly reduced when directional repeat transmission is used. .

  On the other hand, as shown in FIG. 2 above, in the case of directional repeat transmission, the communication area of this wireless communication apparatus is the sum of the communication areas of the directional beams 1 to 4. In addition, when the communication partner is located in any one of the directional beams 1 to 4, it is possible to indicate that communication is being performed to terminals located in other communication areas. It is possible to avoid unnecessary radio signal collision due to a problem. In order to avoid the hidden terminal problem, as shown in FIG. 7B, there is a method in which a radio signal is always transmitted to each communication area to indicate that the channel is busy. There is also a method of reserving a channel using the period information including period information to be used (channel scheduled period).

  When this channel reservation method is used, for example, as shown in FIGS. 8A and 8B, only RTS and CTS frames are transmitted by directional repeat transmission, and subsequent frames (Data, Ack) are transmitted by a normal transmission method (non-repetitive transmission). ). In this method, RTS and CTS frames are used to notify surrounding wireless communication devices that a channel will be used from now on, and subsequent transmission of Data and Ack has directivity that covers only the communication area where the communication partner is located. This is a method of transmitting using a beam. When this method is used, the transmission efficiency can be improved as compared with FIG. 7B. Similarly, as shown in FIGS. 8C and 8D, only the RTS or CTS frame transmitted by the base station is notified of channel reservation information to the radio communication apparatus located in the communication area of the base station using the directional repeat transmission method. There is also a method. 8C and 8D, the communication efficiency can be improved as compared with FIGS. 8A and 8B. However, the transmission efficiency is reduced by transmitting RTS and CTS by directional repetitive transmission. Will not change.

In the first embodiment, a method capable of further improving the transmission efficiency will be described.
FIG. 9 shows a configuration example of the physical header in the first embodiment. FIG. 9 is obtained by adding a channel reservation period (PHY duration (NAV: Network Allocation Vector)) to the physical header of FIG. This PHY Duration is not the packet length (length) of the packet itself, but information relating to a scheduled frame exchange period that follows thereafter.

FIG. 10 is a flowchart showing a procedure of transmission frame generation processing.
First, the transmission frame generation unit 13 generates a signal synchronization preamble (step S1a). Next, a scheduled channel period to be added to the physical header is calculated (step S2a). A method for calculating the scheduled channel period will be described later. The transmission frame generation unit 13 generates a physical header to which the calculated channel scheduled period is added (step S3a), and generates a frame check sequence (FCS1) for the physical header (step S4a). Thus, a first field including a preamble, a physical header, and a frame check sequence (FCS1) for the physical header is generated. Then, the transmission frame generation unit 13 generates a MAC address and payload following the first field (step S5a), and generates a MAC address and payload frame check sequence (FCS2) (step S6a). Thus, the second field including the MAC address, the payload, the MAC address, and the frame check sequence (FCS2) for the payload is generated.

FIG. 11 shows a beam control method when transmitting the generated transmission frame.
The transmission / reception unit 1 transmits a first field including a preamble, a physical header, and a frame check sequence (FCS1) for the physical header in the transmission frame by directional repetitive transmission. That is, the control unit 123 repeatedly transmits each symbol in the first field four times while the beam forming unit 122 switches a plurality of directional beams having different directions.

  On the other hand, the second field including the MAC address, payload, MAC address and payload frame check sequence (FCS2) following the first field is transmitted by non-repetitive transmission. The control unit 123 forms a directional beam in the direction of the destination included in the MAC address by the beam forming unit 122 and transmits the second field.

  By transmitting in this way, it becomes possible to notify the channel scheduled period to a wide range of radio stations without reducing the throughput.

FIG. 12 is a flowchart showing the procedure of the receiving operation when the frame including the physical header shown in FIG. 9 is received.
When receiving the first field (step S1b), the reception frame analysis unit 14 acquires the scheduled channel period included in the physical header (step S2b). Further, when the second field is received (step S3b), the MAC header is acquired from the received second field (step S4b). When the destination address included in the acquired MAC header is addressed to the own station (step S5b), the transmission / reception unit 12 performs subsequent transmission / reception processing (step S6b). On the other hand, if the second field cannot be received in step S3b, or if the destination address is not addressed to the own station in step S5b, the reception frame analysis unit 14 notifies the control unit 123 so that the transmission / reception unit 12 Transmission of the scheduled channel period is prohibited (step S7b).

  Here, the scheduled channel period will be described with reference to FIGS. 13A and 13B. The start of the scheduled channel period added to the physical header is immediately after the end of transmission of the first field. That is, the scheduled time when transmission of the second field is started. In addition, when a scheduled channel period is added to the MAC header, the transmission completion time in the second field is set as the start time of the scheduled channel period. That is, the start time of the scheduled channel period added to the physical header is different from the start time of the scheduled channel period added to the MAC header. However, the end time of the scheduled channel period is the same, and is the end time of frame exchange.

  For example, the scheduled channel period included in the physical header of the RTS in FIG. 13A is 500 [us], and the frame length of the second field of the RTS is 30 [us]. At this time, the scheduled channel period included in the RTS MAC header is 470 (= 500-30) [us]. Accordingly, in the third-party wireless communication device that has received the frame exchange of FIG. 13A, the wireless station that has received RTS but has not received CTS, and the wireless station that has not received RTS but has received CTS. The channel scheduled period recognized by can be set to the same value. Moreover, when calculating the channel scheduled period described in the physical header at the time of Data transmission, it can be calculated based on the channel scheduled period included in the received CTS MAC frame.

  Also, in the case of CTS-Data-Ack frame exchange as shown in FIG. 13B, the channel scheduled period is similarly calculated and set.

  14A and 14B show an example of frame exchange in the first embodiment. In FIG. 14A, only the first field of the RTS frame on the base station side is transmitted by the directional repeat transmission method, and the second and subsequent fields of the RTS are non-repeatedly transmitted using a directional beam in the destination direction. . Thereby, it is possible to further improve the communication efficiency while obtaining the same effect as in FIG. 8C described above. In FIG. 14B, only the first field of the CTS frame on the base station side is transmitted by the directional repeat transmission method, and the second and subsequent CTS fields are transmitted non-repetitively using a directional beam in the destination direction. In this way, it is possible to further improve communication efficiency while obtaining the same effect as in FIG. 8D described above.

  15A to 15D show another example of frame exchange in the first embodiment. In FIGS. 15A and 15B, only the first field of the RTS and CTS frames is transmitted by the directional repeat transmission method, and the second and subsequent fields of the RTS and CTS frames are non-repeatedly transmitted using the directional beam in the destination direction. It is. Thereby, it is possible to improve the communication efficiency while obtaining the same effect as in FIGS. 8A and 8B described above.

  In the directional repeat transmission method, only information necessary for confirming whether or not a channel is used is repeatedly transmitted, so that communication efficiency is good. Therefore, as shown in FIGS. 15C and 15D, the first field of the Data and Ack frames following the RTS / CTS exchange may be transmitted by the directional repeat transmission method. As a result, even if reception of the physical header included in the RTS or CTS frame fails, if the physical header of the Data or Ack frame can be received, the scheduled channel period can be grasped. Reliability can be improved. This is particularly effective when data and Ack frames are continuously transmitted in bursts.

  Furthermore, other examples of frame exchange are shown in FIGS. As an application of FIGS. 15A to 15D, as shown in FIGS. 16A and 16C, only the first field of the frame transmitted by the base station may be transmitted by the directional repeat transmission method. As a result, it is possible to efficiently notify the terminal station in the communication area of the base station of information related to the scheduled channel period.

FIG. 16D is a flowchart showing the procedure of the transmission control process of the control unit 123 in such a case.
The control unit 123 selects the transmission method of the first field according to information (base station / terminal station) indicating the device type (step S1). For example, when the device type is a base station, the directional repeat transmission method is selected, and when the device type is a terminal station, the non-repetitive transmission method is selected. When the control unit 123 selects the directional repeat transmission method in Step S1 (Step S2), the control unit 123 transmits the first field by the directional repeat transmission method (Step S3), and transmits the second field by the non-repetitive transmission method. (Step S4). On the other hand, when the non-repetitive transmission method is selected in step S1, the control unit 123 transmits the first field and the second field by the non-repetitive transmission method (steps S4 and S5).

  Further, as shown in FIG. 16B, the terminal station may transmit only one field of RTS that is transmitted first to acquire a channel by the directional repeat transmission method. Thereby, it is possible to promptly notify the information related to the scheduled channel period to other terminal stations located around the terminal station that transmits the RTS.

  In the normal RTS / CTS procedure, the wireless communication apparatus 1 transmits a CTS signal triggered by the reception of an RTS signal addressed to itself, but a CTS signal that can be transmitted without receiving an RTS addressed to itself. It may be defined. That is, since it is a CTS signal addressed to its own station, it is also called “CTS-to-self”.

  17A and 17B show an example of frame exchange in the case of CTS-to-self. FIG. 17A shows a case of transmitting from the base station to the terminal station by CTS-to-self, and FIG. 17B shows a case of transmitting from the terminal station to the base station by CTS-to-self. In FIG. 17A, only the first field of the CTS frame transmitted from the base station is transmitted by the directional repeat transmission method. In FIG. 17B, only the first field of the CTS frame transmitted from the terminal station is transmitted by the directional repeat transmission method.

  18A and 18B show another example of frame exchange in the case of CTS-to-self. 18A shows a case where transmission is performed from the base station to the terminal station by CTS-to-self, and FIG. 18B shows a case where transmission is performed from the terminal station to the base station by CTS-to-self. In FIGS. 18A and 18B, the first field of each frame of CTS, Data, and Ack is transmitted by the directional repeat transmission method.

  19A, 19B, and 19C show other examples of frame exchange in the case of CTS-to-self. FIG. 19A shows a case where only the first field of the frame transmitted from the base station is transmitted by the directional repeat transmission method, and FIG. 19B shows the first field of the frame transmitted from the base station and the first field transmitted by the terminal station. The first field of the CTS frame is transmitted by the directional repeat transmission method. In FIG. 19C, only the first field of the frame transmitted first from the base station is transmitted by the directional repeat transmission method.

  20A to 20D show examples of frame exchange when RTS / CTS exchange and CTS-to-self transmission are not performed. 20A and 20B show a case where data is transmitted from the base station to the terminal station, and FIGS. 20C and 20D show a case where data is transmitted from the terminal station to the base station. 20A and 20C transmit the first field of the transmission frame from both the base station and the terminal station by the directional repeat transmission method, and FIGS. 20B and 20D only show the first field of the transmission frame from the base station. Is transmitted by the directional repeat transmission method.

  21A to 21D show frame exchange examples when data is transmitted in bursts. 21A and 21C show a case where data is burst transmitted from the base station to the terminal station, and FIGS. 21B and 21D show a case where data is burst transmitted from the terminal station to the base station. 21A and 21B transmit the first field of the transmission frame from both the base station and the terminal station by the directional repeat transmission method, and FIGS. 21C and 21D only show the first field of the transmission frame from the base station. Is transmitted by the directional repeat transmission method. 21A to 21D show frame exchange examples in the case of burst transmission of only Data without transmitting RTS / CTS, CTS-to-self, etc., but before the Data burst, RTS / CTS is shown. An exchange or a method of transmitting CTS-to-self may be used.

(Second Embodiment)
In the second embodiment, a method of transmitting by switching between a directional repetitive transmission method and a non-repetitive transmission method according to the type of transmission frame and the like will be described. Since the configuration of the second embodiment is the same as the configuration of FIG. 1, the description will be made with reference to FIG. In the second embodiment, the configuration of the physical header and the operation of the control unit 123 are different.

  FIG. 22 shows a configuration example of the physical header in the second embodiment. FIG. 22 is obtained by adding information related to the beam control identifier to the physical header of FIG. This beam control identifier is an identifier for indicating how to transmit the second field. By using this identifier, it is notified to the other party whether the second field is transmitted by the non-repetitive transmission method using one directional beam, or is transmitted by the directional repetitive transmission method similarly to the first field. can do. For example, when the destination address is a broadcast, if the destination address is a specific terminal station, the MAC header and the subsequent part are transmitted using the directional repeat transmission method so that all terminals communicable with the local station can receive it. Then, transmission is performed using a directional beam in a direction that the terminal station can receive. Thus, an appropriate value is set to this beam control identifier depending on whether the destination address is broadcast or unicast. If the destination address is a broadcast address, the beam control identifier may be omitted if it is determined in advance that transmission is always performed by the directional repeat transmission method.

  Next, the operation of the control unit 123 will be described. FIG. 23 is a flowchart illustrating the procedure of the transmission control process of the control unit 123.

  When the frame type information of the transmission frame is notified from the transmission frame generation unit 13, the control unit 123 selects the transmission method of the first field according to the frame type information (step S1c). For example, when the frame type information is an RTS frame, the directional repeat transmission method is selected. When the control unit 123 selects the directional repeat transmission method in step S1c (step S2c), the control unit 123 transmits the first field by the directional repeat transmission method (step S3c).

  Next, when the destination address is broadcast (step S4c), the second field is transmitted by the directional repeat transmission method (step S4c). Further, in step S4c, when the destination address is unicast, the control unit 123 transmits the second field by the non-repetitive transmission method (step S7c). On the other hand, when the non-repetitive transmission method is selected in step S1c, the control unit 123 transmits the first field and the second field by the non-repetitive transmission method (steps S6c and S7c).

  Also, when the terminal station moves, it is not necessary to transmit in all directions using directional repeat transmission, but it is possible to transmit with multiple directional beams including directions that may move. Is good. Therefore, for example, when there are eight types of directional beams, the first field is transmitted by the eight-way directional repeat transmission method, and the second field is three of the eight types of directional beams. Are transmitted in a three-way directional repeat transmission system. When the directional repeat transmission method is used, the receiving side needs to grasp the number of repetitions. However, if this embodiment is used, the number of repetitions is considered in consideration of the destination address, the moving direction of the communication partner, and the like. Thus, the necessary number of times can be selected as appropriate.

  In the first embodiment, the transmission method of the second field has been described using an example of transmission using one directional beam. However, if a beam control identifier is used, the number of repetitions is dynamically changed as necessary. Can be applied to.

(Third embodiment)
24A and 24B show an example in which the beam directivity at the time of Data transmission is not appropriate in the frame exchange using the directivity repeat transmission shown in FIGS. 9A and 9B. As shown in FIG. 24A, the base station AP transmits Data using a directional beam suitable for transmission to the terminal station STA. However, if there is a change in the wireless communication environment, the directional beam is not appropriate, and as a result Data may not be correctly transmitted to the destination terminal station STA. In such a case, the base station AP performs data retransmission processing using a directional repetitive transmission method or the like, but this method determines whether or not the directional beam is correct unless data transmission is actually performed. I can't judge. In addition, when Data transmission is transmitted by a highly efficient multilevel modulation method, it is determined whether SINR is insufficient due to an inappropriate directional beam or whether SINR is insufficient even though the directional beam is appropriate. Is difficult. In the former case, it is desirable to change the directional beam at the time of retransmission, and in the latter case, the modulation method and the coding method are more robust without changing the directional beam at the time of retransmission (for example, a multi-level number). It is desirable to change the setting to reduce the error correction or strengthen the error correction. However, since the cause of the error cannot be specified, the conventional retransmission method tends to be inefficient. Further, when the Data frame length is long, the efficiency is particularly lowered. The same applies when the data transmitted from the terminal station STA to the base station AP is incorrect as shown in FIG. 24B.

  Therefore, the third embodiment proposes a method for solving this problem. 25A and 25B are block diagrams illustrating a configuration example of a wireless communication apparatus according to the third embodiment. FIG. 25A is obtained by providing a channel estimation signal generation unit 15 in the configuration of FIG. FIG. 25B is obtained by providing a beam selection signal generation unit 16 in the configuration of FIG. Note that both the channel estimation signal generation unit 15 and the beam selection signal generation unit 16 may be provided in the configuration of FIG. In FIG. 25A, the channel estimation signal generation unit 15 generates a sounding signal (channel estimation signal) used by the transmission source to estimate an appropriate channel. In FIG. 25B, the beam selection signal generation unit 16 generates information (beam selection signal) for enabling the transmission source to select an optimum directional beam.

  FIG. 26 shows a configuration example of a physical header in the third embodiment. FIG. 26 is obtained by adding destination address information to the physical header of FIG. 6A. This destination address is information that should normally be added to the MAC header, but here it is also added to the physical header. A destination address may or may not be added to the MAC header.

FIG. 27 is a flowchart illustrating a reception operation of the wireless communication apparatus according to the third embodiment.
When receiving the first field (step S1d), the reception frame analysis unit 14 acquires the scheduled channel period included in the physical header (step S2d) and also acquires the destination address included in the physical header (step S3d). . When the acquired destination address is addressed to the own station (step S4d), the reception frame analysis unit 14 attempts to receive the second field (step S5d). In step S5d, when the second field is received, the transmission / reception unit 12 performs subsequent transmission / reception processing (step S6d). On the other hand, if the destination address is not addressed to the own station in step S4d, the transmission / reception unit 12 stops transmission in the scheduled channel period (step S7d). If the second field cannot be received in step S5d in FIG. 27, the channel estimation signal generation unit 15 performs channel estimation signal generation processing, or the beam selection signal generation unit 16 performs beam selection signal generation processing. Perform (step S8d).

  Further, if the destination address is not addressed to the own station in step S4d, the reception process may be stopped. As shown in FIG. 28, when the terminal station STA2 receives a radio frame addressed to the terminal station STA1, communication between the base station AP and the terminal station STA1 is performed during the scheduled channel period included in the physical header. The reception processing during that time is stopped (power supply is stopped or clock supply is stopped). Since the second field transmitted by the base station AP or the terminal station STA1 is transmitted using a directional beam directed toward the destination direction, the terminal station STA2 may not be able to detect the power. It is determined that communication between the base station AP and the terminal station STA1 is being performed during the included scheduled channel period. As a result, wasteful power consumption can be reduced, leading to lower power consumption.

An operation when a channel estimation signal is transmitted when the second field cannot be received because the beam directivity is not appropriate in step S8d will be described.
29A and 29B show a case where the first field including the physical header to which the destination address addressed to the own station is added is received. In FIG. 29A, when the first field transmitted by the directional repeat transmission can be received, but the information after the second field subsequent thereto cannot be correctly received (error in the frame check sequence), The received frame analysis unit 14 of the terminal station STA can determine that the beam formed by the base station AP addressed to itself is not appropriate. In particular, when the modulation method and error correction method used for the first field transmission are the same as the modulation method and error correction method used for the second field transmission, the modulation method used for the second field transmission, The determination is more appropriate when the error correction method is more robust. Also, as shown in FIG. 29B, even when the reception level after the second field deteriorates rapidly and reception is hardly possible, the terminal station STA determines that the beam formed by the base station AP addressed to itself is not appropriate. Can do. Further, the received power of the first field and the received power of the second field are compared, and if the difference is equal to or greater than a predetermined threshold, it can be determined that the beam is not appropriate.

  In such a case, the channel estimation signal generation unit 15 of the terminal station STA is necessary for the base station AP to perform channel estimation with respect to the base station AP after the reception of the RTS is completed and a predetermined time has elapsed. A channel estimation signal is transmitted. Further, as shown in FIG. 29B, even when the second field and subsequent fields of the RTS cannot be received at all, since the information regarding the RTS frame length is added to the physical header of the RTS, the terminal station STA Since the end time of the RTS frame can be grasped, it is possible to recognize the timing for transmitting the channel estimation signal.

In addition, an operation in the case where the beam control signal is transmitted when the second field cannot be received because the beam directivity is not appropriate in step S8d will be described.
30A and 30B show a case where the first field including the physical header to which the destination address addressed to the own station is added is received. In FIGS. 30A and 30B, when the identifier of the beam being used can be recognized from the signal of the first field that is repeatedly transmitted with directivity, the terminal station STA is most suitable among the beams used by the base station AP. The correct beam can be selected. In such a case, if the beam selection signal generation unit 16 of the terminal station STA does not receive the RTS frame correctly or fails to receive the second field of the RTS, the reception of the RTS is completed. After a predetermined time has elapsed, a beam selection signal for notifying the base station AP of an optimum beam is transmitted.

  By doing so, the base station AP can quickly determine the optimum beam and execute the retransmission process efficiently as compared with the methods shown in FIGS. 24A and 24B. If the Data frame is not received correctly even though the RTS frame is correctly received, it is determined that the selected modulation method is inappropriate, although the beam directivity is correct. It is possible to change to a more robust modulation method and coding method while maintaining the above.

  In addition, by transmitting a radio signal with a physical header shown in FIG. 26, a channel schedule period is notified to a wide range of radio stations, and to which radio station the radio frame is addressed. You can be notified. Therefore, a radio station not designated as a destination does not need to receive data after the second field of the frame after analyzing the physical header, so that the reception process can be stopped to save power. it can. It can also be understood that the reception process may be stopped during the scheduled channel period.

  Note that the destination address added to the physical header may compress the information amount by a reversible compression method such as a hash function in order to reduce overhead. Alternatively, compression may be performed using an irreversible compression method. As an irreversible compression method, it is also possible to simply use it as a destination address for adding a few lower bits of a MAC address to a physical header. When compressed with an irreversible compression method, destination address information is also added to the MAC header, and the information related to the destination address included in the physical header is analyzed, so that the wireless packet can be addressed to the local station. Judge whether there is sex or not. If there is a possibility that it is addressed to the own station, the receiving process may be continued, and the destination address added to the MAC header may be viewed to finally determine whether it is addressed to the own station.

(Fourth embodiment)
FIG. 31 shows a network configuration example configured by the wireless communication apparatus according to the fourth embodiment. In FIG. 31, the terminal stations STA1-1 to 1-2 are connected to the base station AP1, and the terminal stations STA2-1 to 2-2 are connected to the base station 2. The terminal station STA2-2 is located in the communication area of both the base station AP1 and the base station AP2. Therefore, the terminal station STA2-2 can receive not only the radio signal transmitted by the base station AP2, but also the radio signal transmitted by the base station AP1. Then, the base station AP1 reserves a channel also for the terminal station STA2-2 connected to the base station 2, and there is a possibility that the channel efficiency improvement effect by spatial multiplexing may be reduced.

Therefore, the fourth embodiment proposes a technique for solving such a problem.
Since the configuration of the fourth embodiment is the same as the configuration of FIG. 1, the description will be made with reference to FIG. In the fourth embodiment, the configuration of the physical header and the operation of the control unit 123 are different. FIG. 32 shows a configuration example of a physical header in the fourth embodiment. FIG. 32 is obtained by adding a network identifier (information for identifying a radio channel) for identifying a radio channel to the physical header of FIG. 6A.

FIG. 33 is a flowchart showing a reception operation of the wireless communication apparatus according to the fourth embodiment.
When receiving the first field (step S1e), the reception frame analysis unit 14 acquires the scheduled channel period included in the physical header (step S2e) and also acquires the network identifier included in the physical header (step S3e). . The received frame analysis unit 14 determines whether or not the network identifier of the network to which the own station belongs is the same as the acquired network identifier (step S4e), and is different from the network identifier to which the own station belongs. Ignores channel reservation information included in the physical header. That is, it is not determined that the channel is reserved.

  On the other hand, if it is determined in step S4e that the network identifier of the network to which the station belongs is the same as the acquired network identifier, and if the second field is received (step S5e), the received second The MAC header is acquired from the field (step S6e). When the destination address included in the acquired MAC header is addressed to the own station (step S7e), the transmission / reception unit 12 performs subsequent transmission / reception processing (step S8e). On the other hand, if the second field cannot be received in step S5e, transmission in the scheduled channel period is stopped (step S9e). When the destination address is not addressed to the own station in step S7e, the transmission / reception unit 12 stops transmission / reception in the scheduled channel period (step S10e).

  For example, as shown in FIG. 34A, it is assumed that the terminal stations STA1-1, STA1-2, and STA2-2 receive a radio signal transmitted from the base station AP1 to the terminal station STA1-1. Since the terminal station STA1-1 is a radio signal addressed to itself, the terminal station STA1-1 communicates with the base station AP1 thereafter.

  When the terminal station STA1-2 receives the first field of the RTS frame and determines that the signal belongs to the network to which the terminal station belongs by the network identifier added to the physical header, the terminal station STA1-2 continues to receive the RTS frame. When the second field is received, it is determined that the frame is not addressed to the own station. Therefore, the transmission / reception process is stopped during the period in which the communication between the base station AP1 and the terminal station STA1-1 is performed, that is, during the scheduled channel period.

  On the other hand, when the terminal station STA2-2 receives the first field of the RTS frame, the terminal station STA2-2 detects that the signal is a network signal different from the network to which the terminal station STA2-2 belongs based on the network identifier added to the physical header. Then, the terminal station STA2-2 cancels the scheduled channel period included in the physical header, and continues the reception process thereafter. Transmission processing can also be performed as necessary. As shown in FIG. 31, when the networks are different as shown in FIG. 31, generally, a signal transmitted from the terminal station STA2-2 to the base station AP2 is transmitted to the communication of the terminal station STA1-1 belonging to the base station AP1. This is because the spatial communication efficiency is considered to be improved by continuing normal transmission / reception rather than suppressing transmission, because the influence is considered to be small.

  However, in the system shown in FIG. 34A, when the terminal station STA1-2 receives the first field of the RTS frame, but receives the second field after that, it is addressed to itself. Therefore, there remains a problem that the transmission / reception process cannot be stopped at that time.

  Therefore, as shown in FIG. 35, both the destination address and the network identifier are added to the physical header shown in FIG. In this way, as shown in FIG. 34B, when the terminal station STA1-2 receives the first field of the RTS frame, the terminal station STA1-2 determines that the frame is not addressed to itself from the destination address included in the physical header. Since the determination can be made, compared to the method of FIG. 34A, the transmission / reception process can be stopped more quickly, which is effective in further reducing power consumption.

  According to the fourth embodiment, by using the physical header to which the network identifier is added, the terminal station can grasp not only the information on the scheduled channel period but also the network identifier information, and therefore belongs to another base station. There is no longer unnecessary suppression of transmission up to the terminal station. That is, simultaneous transmission between different network devices becomes possible, and space utilization efficiency can be improved. Note that the network identifier may be subjected to lossless compression or lossy compression in the same manner as the destination address to reduce the amount of information.

  Moreover, although the said embodiment demonstrated based on the structural example of the radio | wireless communication apparatus of FIG. 1, it is applicable also to the structural example of the radio | wireless communication apparatus of FIG. 36 using a sector antenna. That is, directivity repeat transmission may be realized by transmitting an RF signal while sequentially switching a plurality of sector antennas having directivity. Based on this configuration, the channel estimation signal generation unit 15 as shown in FIG. 25A or the beam selection signal generation unit 16 in FIG. 25B may be provided.

  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. Further, various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, you may combine suitably the component covering different embodiment.

1 is a block diagram illustrating a configuration example of a wireless communication device according to a first embodiment. FIG. 3 is a diagram illustrating an example of a directional beam formed by the wireless communication apparatus in FIG. 1. The figure which shows an example of the format of a transmission frame. The figure which shows an example of the format of the conventional physical header. The figure which shows the network structural example which the radio | wireless communication apparatus of FIG. 1 comprises. The figure which shows an example of the conventional directional repetition transmission. The figure which shows the typical frame exchange example defined by wireless LAN. The figure which shows the example which applied the directional repetition transmission in the frame exchange of FIG. 7A. The figure which shows the other example to which directional repetition transmission is applied. The figure which shows the other example to which directional repetition transmission is applied. The figure which shows the other example to which directional repetition transmission is applied. The figure which shows the other example to which directional repetition transmission is applied. The figure which shows the structural example of the physical header in 1st Embodiment. The flowchart which shows the procedure of a transmission frame production | generation process. The figure which shows the beam control method at the time of transmitting a transmission frame. 10 is a flowchart showing a procedure of a reception operation when a frame including the physical header shown in FIG. 9 is received. The figure explaining a channel scheduled period. The figure explaining a channel scheduled period. The figure which shows an example of the flame | frame exchange in 1st Embodiment. The figure which shows an example of the flame | frame exchange in 1st Embodiment. The figure which shows the other example of the flame | frame exchange in 1st Embodiment. The figure which shows the other example of the flame | frame exchange in 1st Embodiment. The figure which shows the other example of the flame | frame exchange in 1st Embodiment. The figure which shows the other example of the flame | frame exchange in 1st Embodiment. The figure which shows the other example of the flame | frame exchange in 1st Embodiment. The figure which shows the other example of the flame | frame exchange in 1st Embodiment. The figure which shows the other example of the flame | frame exchange in 1st Embodiment. 16 is a flowchart showing a procedure of transmission control processing in the frame exchange of FIGS. 16A and 16C. The figure which shows an example of the frame exchange in the case of CTS-to-self. The figure which shows an example of the frame exchange in the case of CTS-to-self. The figure which shows the other example of the frame exchange in the case of CTS-to-self. The figure which shows the other example of the frame exchange in the case of CTS-to-self. The figure which shows the other example of the frame exchange in the case of CTS-to-self. The figure which shows the other example of the frame exchange in the case of CTS-to-self. The figure which shows the other example of the frame exchange in the case of CTS-to-self. The figure which shows an example of the flame | frame exchange when not performing RTS / CTS exchange and CTS-to-self transmission. The figure which shows an example of the flame | frame exchange when not performing RTS / CTS exchange and CTS-to-self transmission. The figure which shows an example of the flame | frame exchange when not performing RTS / CTS exchange and CTS-to-self transmission. The figure which shows an example of the flame | frame exchange when not performing RTS / CTS exchange and CTS-to-self transmission. The figure which shows an example of the frame exchange in the case of carrying out burst transmission of data. The figure which shows an example of the frame exchange in the case of carrying out burst transmission of data. The figure which shows an example of the frame exchange in the case of carrying out burst transmission of data. The figure which shows an example of the frame exchange in the case of carrying out burst transmission of data. The figure which shows the structural example of the physical header in 2nd Embodiment. 9 is a flowchart showing a procedure of transmission control processing of the wireless communication apparatus according to the second embodiment. The figure which shows the example when the directivity of the beam at the time of Data transmission is not appropriate. The figure which shows the example when the directivity of the beam at the time of Data transmission is not appropriate. The block diagram which shows the structural example of the radio | wireless communication apparatus which concerns on 3rd Embodiment. The block diagram which shows the other structural example of the radio | wireless communication apparatus which concerns on 3rd Embodiment. The figure which shows the structural example of the physical header in 3rd Embodiment. 10 is a flowchart illustrating a reception operation of the wireless communication apparatus according to the third embodiment. The figure which shows a process when a destination address is not addressed to an own station. The figure which shows the operation | movement which transmits a channel estimation signal. The figure which shows the operation | movement which transmits a channel estimation signal. The figure which shows the operation | movement which transmits a beam control signal. The figure which shows the operation | movement which transmits a beam control signal. The figure which shows the network structural example which the radio | wireless communication apparatus which concerns on 4th Embodiment comprises. The figure which shows the structural example of the physical header in 4th Embodiment. 10 is a flowchart illustrating a reception operation of a wireless communication device according to a fourth embodiment. The figure which shows an example of the frame exchange of the radio | wireless communication apparatus which concerns on 4th Embodiment. The figure which shows an example of the frame exchange of the radio | wireless communication apparatus which concerns on 4th Embodiment. The figure which shows the other example of a structure of a physical header. The block diagram which shows the other structural example of a radio | wireless communication apparatus.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Wireless communication apparatus, 11 ... Antenna part, 12 transmission / reception part, 13 transmission frame production | generation part, 14 ... Reception frame analysis part, 121 ... RF unit, 122 ... Beam formation part, 123 ... Control part, 1A ... Wireless communication apparatus, 15 ... Channel estimation signal generator, 16 ... Beam selection signal generator.

Claims (15)

Transmission including a first field including a physical header to which information indicating a scheduled period in which a wireless line is used for communication with a destination is added, and a second field including a payload following the first field. A transmission frame generation unit for generating a frame;
A second directional beam is formed in the direction of the destination after transmitting the first field in a first mode in which a plurality of directional beams having different directions are switched to form the transmission frame. A wireless communication apparatus comprising: a transmission unit configured to transmit the second field according to a mode of Transmission including a first field including a physical header to which information indicating a scheduled period in which a wireless line is used for communication with a destination is added, and a second field including a payload following the first field. A transmission frame generation unit for generating a frame;
A first mode in which a plurality of directional beams having different directions are switched for each of the first field and the second field, and a second mode in which a directional beam is formed in the direction of the destination. And a transmitter that selectively transmits the transmission frame. The transmission unit according to claim 2, further comprising: selecting one of the first mode and the second mode according to a type of the transmission frame in order to transmit the first field. The wireless communication device described. The radio according to claim 2, wherein the transmission unit further selects one of the first mode and the second mode according to the destination in order to transmit the second field. Communication device.   The wireless communication apparatus according to claim 4, wherein the transmission unit transmits the second field in the first mode when the destination is broadcast.   The transmission frame generation unit further adds beam control information indicating whether the second field is transmitted in the first mode or the second mode to the physical header. 2. The wireless communication device according to 2.   The wireless communication apparatus according to claim 1, wherein the transmission frame generation unit further adds information for identifying the destination to the physical header.   When receiving a first field including a physical header to which information for identifying a destination different from the own station is added, a reception frame analysis unit for stopping transmission processing at least during the scheduled period is further provided. The wireless communication apparatus according to claim 7.   A signal for estimating channel information to the transmission source when the second field cannot be received after receiving the first field including the physical header to which information identifying the destination addressed to the own station is added. The wireless communication apparatus according to claim 7, further comprising a channel estimation signal generation unit that generates   For selecting a directional beam for a transmission source when the second field cannot be received after receiving the first field including a physical header to which information identifying a destination addressed to the own station is added. The radio communication apparatus according to claim 7, further comprising a beam selection signal generation unit that generates a signal.   The wireless communication apparatus according to claim 1, wherein the transmission frame generation unit further adds information identifying the wireless line to the physical header.   A reception frame analysis unit for stopping transmission processing at least during the scheduled period when receiving a first field including a physical header to which information identifying a wireless line to which the local station is connected is added; The wireless communication apparatus according to claim 11.   When receiving the first field including a physical header to which information identifying a radio channel different from the radio channel to which the local station is connected is received, a reception frame analysis unit for stopping transmission / reception processing of the scheduled period is further provided. The wireless communication apparatus according to claim 11.   The wireless communication apparatus according to claim 1, wherein the start time of the scheduled period is calculated to be a scheduled time at which transmission of the second field is started.   When the scheduled period is the first scheduled period and the information indicating the second scheduled period in which the wireless line is used for communication with the destination is added to the second field, the second scheduled period The wireless communication apparatus according to claim 14, wherein the start time of is further calculated to be a scheduled time at which transmission of the second field ends.

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