JP5470634B2 - Wireless communication system and wireless communication method for performing wireless communication using directional beam - Google Patents

Description

  The present invention relates to a wireless communication system and a wireless communication method for performing wireless communication using a directional beam between a transmitting device and a receiving device.

  In recent years, a wireless personal area network (WPAN) has been proposed as a technique for transmitting broadband signals with high quality over a short distance. As the WPAN, there is a wireless communication system using a radio wave in a millimeter wave band (for example, 60 GHz) (for example, see Non-Patent Documents 1 and 2 below). Such a wireless communication system using millimeter-wave radio waves is expected as a wireless communication system that realizes large-capacity transmission and low cost.

  In a wireless communication system, association processing is performed in order to perform wireless communication between two devices. Here, in the association process, for example, a beacon is transmitted using a quasi-omni beam. Here, the beacon is used to set time allocation and to communicate management information for the piconet.

  However, since the above-described Kwasomuni beam has a low gain at the receiving antenna, the area that can be received by the receiving device is limited to a radius of 10 meters from the transmitting device. In addition, if the gain is low in this way, the beacon signal is easily lost when there is a channel fluctuation or device movement during data transmission. Therefore, it is necessary to increase the reliability of the beacon.

  Also, depending on the beam width used for wireless communication, the two devices may not be able to find each other. In this case, the result is a hidden node. The presence of hidden nodes increases the possibility of interference.

Federal Communications Commission, “Amment of parts 2, 15 and 97 of the Commission's rules to permit use of radio frequencies above 40 GHz for 40 GHz. 94-124, RM-8308, December 1995 H. Ikeda, Y .; Shoji, “60 GHz Japan regulations”, IEEE 802.15-05-0525-03, October 2006

  Therefore, an object of the present invention is to provide a wireless communication system and a wireless communication method that can increase the gain of an antenna during association processing.

  The present invention basically relates to a wireless communication system 1 and the like. In the wireless communication system 1, wireless communication is performed between the transmitting device (10) and the receiving device (20).

  Here, the receiving device (20) is configured to be capable of generating a directional beam and includes an antenna capable of transmitting and receiving the directional beam. The transmitting device (10) includes an antenna capable of transmitting and receiving a directional beam and a piconet controller (PNC) that performs control for performing association processing with the receiving device (20). The piconet controller (PNC) is configured to be able to generate a directional beam, and is configured to be able to transmit and receive the directional beam via the antenna of the transmitting device (10). The piconet controller (PNC) transmits a directional beam in a predetermined transmission direction together with a beacon necessary for association processing. As a result, the area including the receiving device (20) becomes the target area for wireless communication.

  As described above, by using a directional beam, the gain at the antenna of the receiving device can be made higher than that of the Kwasomuni beam. Also, interference at hidden nodes is avoided.

  In another aspect of the present invention, the piconet controller (PNC) includes a plurality of beacons in a directional beam and directs one directional beam including the plurality of beacons toward the predetermined transmission direction. Transmit or multiplex a directional beam including one beacon, and transmit the multiplexed directional beam in a plurality of transmission directions as the predetermined transmission direction. In this way, it is possible to reliably eliminate the need to use the Kwasomuni beam.

  Furthermore, in still another aspect of the present invention, a CAP in frame data corresponding to a directional beam is divided into a plurality of sub-CAPs for association processing. Here, the number of sub-CAPs is a number corresponding to the receiving direction of the piconet controller (PNC). Further, the plurality of sub-CAPs are expanded into a plurality of super-frame data so that one sub-CAP is included in one super-frame data. Thereby, the buffer of the receiving device (20) can be reduced.

  In another aspect of the present invention, MCTA having the same data structure as that of CAP is generated in CTAP in frame data corresponding to a directional beam. The receiving device (20) transmits feedback information to the piconet controller (PNC) using MCTA. Thereby, since feedback information can be transmitted without using CAP, collision in CAP can be avoided.

  Furthermore, another aspect of the present invention is a wireless communication method. This wireless communication method is for performing wireless communication between the transmitting device (10) and the receiving device (20). Here, the receiving side device (20) is configured to generate a directional beam and includes an antenna capable of transmitting and receiving the directional beam. The transmitting device (10) includes an antenna capable of transmitting and receiving a directional beam and a piconet controller (PNC) that performs control for performing association processing with the receiving device (20). . The piconet controller (PNC) is configured to be able to generate a directional beam, and is configured to be able to transmit and receive the directional beam via the antenna of the transmitting device (10).

  The method includes an association step of performing an association process between the transmitting device (10) and the receiving device (20). In this association step, a piconet controller (PNC) transmits a directional beam in a predetermined transmission direction together with a beacon necessary for association processing, and a receiving device (20) includes a piconet controller (PNC). Receiving a beacon transmitted from. Also by this method, an effect equivalent to the effect described above can be achieved.

  According to the present invention, since a directional beam is used during the association process, it is not necessary to use a quadriom beam, and the gain at the antenna of the receiving device (20) can be increased. It is also possible to avoid interference at hidden nodes.

FIG. 1 is a diagram illustrating a configuration example of a wireless communication system 1 according to the present invention. FIG. 2 is a flowchart showing a procedure of a wireless communication method implemented in the wireless communication system 1 shown in FIG. FIG. 3 is a schematic diagram useful for explaining the processing in each step of FIG. FIG. 4 is a diagram schematically showing an example of a beam pattern when a code book is used. FIG. 5 is a diagram schematically showing fields related to beam forming. FIG. 6 is a diagram schematically showing data at the time of association processing. FIG. 7 is a diagram schematically showing data when notifying the device of information elements (IEs) related to device capabilities. FIG. 8 is a diagram schematically showing data at the time of CTA (channel time allocation). FIG. 9 is a diagram schematically illustrating data corresponding to a training sequence for beam forming. FIG. 10 is a diagram schematically illustrating data including an information element (IE) for feedback during beamforming. FIG. 11 is a diagram showing in detail the data related to the link establishment process between devices in the CTA. FIG. 12 is a diagram schematically showing data including an information element (IE) for sector search. FIG. 13 is a diagram showing in detail the data related to the sector search process in the CTA. FIG. 14 is a diagram schematically showing data including an information element (IE) for beam search. FIG. 15 is a diagram showing in detail the data related to the beam search process in the CTA. FIG. 16 is a diagram schematically illustrating frame data including multiplexed directional beacons and multiplexed directional sub-CAPs. FIG. 17 is a diagram schematically illustrating a group of superframe data including one directional beacon and multiplexed sub-CAPs. FIG. 18 is a diagram schematically illustrating a group of superframe data including multiplexed beacons and one sub-CAP. FIG. 19 is a diagram schematically showing frame data including a directional beacon in a CTA for special users. FIG. 20 is a diagram schematically showing frame data used for feedback during the association process and including MCTA instead of CAP.

  Hereinafter, the best mode for carrying out the present invention will be described with reference to the drawings. However, the form described below is an example, and can be appropriately modified within a range obvious to those skilled in the art.

  FIG. 1 is a diagram illustrating a configuration example of a wireless communication system 1 according to the present invention. As shown in FIG. 1, the system 1 includes a first device 10 capable of wireless communication and a second device 20 capable of wireless communication. The system 1 includes the two devices 10 and 20, but may further include another communicable device.

  In the wireless communication system 1, wireless communication is performed between the devices 10 and 20 using a general beamforming technique. As wireless communication, data transfer in a home video system can be considered. Beam forming (BF) is performed according to a code book based on the MAC layer protocol. The code book is generated using four types of phase shifts of 0 °, 90 °, 180 °, and 270 ° without changing the amplitude.

  Wireless communication is performed using radio waves in the 60 GHz band, for example, in a wireless personal area network (WPAN). The system 1 is configured to be capable of transmitting data from the first device 10 to the second device 20, transmitting data from the second device 20 to the first device 10, and bidirectional data transmission. ing. The frequency band of radio waves is not limited to that in the 60 GHz band, but in WPAN, the frequency band of radio waves is preferably selected from 59 to 76 GHz. Although details will be described later, according to this aspect, the data streaming performance increases and the data rate increases. Therefore, when this mode is applied to data transfer in a home video system, large-capacity data transfer is possible, and for example, video data restored from a compressed state or uncompressed video data can be easily transmitted. It becomes possible.

Next, the devices 10 and 20 will be described.
As illustrated in FIG. 1, the first device 10 includes a transmission unit that functions as a transmitter that transmits radio waves and a reception unit that functions as a receiver. Similarly to the first device 10, the second device 20 includes a transmission unit that functions as a transmitter and a reception unit that functions as a receiver. Each transmission unit has a plurality (t) of antenna elements and constitutes an antenna array. Each receiving unit has a plurality (r pieces) of antenna elements and constitutes an antenna array. Then, the first device 10 and the second device 20 establish a link with each other by using a beamforming technique, and perform data transmission / reception (communication).

  Various antennas can be used for the devices 10 and 20. Examples of the antenna include a single antenna element, a sectorized antenna, a switching antenna, a one-dimensional (1D) beamforming antenna array, and a two-dimensional (2D) beamforming antenna array.

  FIG. 2 is a flowchart showing a procedure of a wireless communication method implemented in the wireless communication system 1 shown in FIG. S in FIG. 2 indicates each step. By implementing this method, the first device 10 and the second device 20 establish a link with each other, and data can be transmitted and received (communication). Therefore, a program corresponding to the method shown in FIG. 2 is stored in the first device 10 and the second device 20 as a beam selection algorithm. FIG. 3 is a schematic diagram useful for explaining the processing in each step of FIG.

  As shown in FIG. 2, the wireless communication method transmits a beacon to perform beamforming to establish a device-device link (S10), and beamforming. By performing the first adjustment (coarse beamforming), the second stage (S20) of performing sector search, and performing the second adjustment (fine beamforming) following the first adjustment of beamforming, the beam search ( A third stage (S30) for performing beam tracking) and a step for performing data communication (S40) are included. As will be described later, in the first stage (S10), a quasi-omni search is also performed to establish a device-device link.

  First, in the first stage (S10), a device functioning as a transmitter (here, referred to as first device 10) transmits a beacon defined by the MAC layer protocol. A beacon is a signal for notifying other devices of basic information of a device that is a wireless communication terminal. When a device functioning as a receiver (here, the second device 20) succeeds in receiving a beacon, that is, when a device-device link is established, a beam transmitted as a beacon is selected. , A beam for data communication between the two is selected. Here, a plurality of (for example, two types) quasi-omni beams that are different from each other are selected as a beam for performing data communication (search for quasi-omni). Kwasomuni beam means a quasi-omnidirectional beam. In the example shown in FIG. 3, the two types of quasi-omni beam are a first best quasi-omni beam and a second best quasi-omni beam.

  By the way, each of the two types of quasi-omni beams transmitted by the first device 10 forms a beam pattern in a space around the first device 10 (beam forming). Here, the beam pattern is determined by obstacles around the first device 10 and the second device 20. And if the 2nd device 20 is arrange | positioned in the part with little energy loss of an electromagnetic wave in the pattern of the beam which the 1st device 10 transmitted, the 2nd device 20 will stabilize an electromagnetic wave from the 1st device 10. It becomes possible to receive. That is, the device-device link is established when the second device 20 can receive the radio wave transmitted from the first device 10.

  Subsequently, in the second step (S20), the pattern of the beam formed by beam forming is adjusted. Specifically, the beam is narrowed as an adjustment to give the beam directivity. In accordance with this narrowing, the beam pattern (region where the energy loss of radio waves is low or high) also changes. And the area | region which can maintain the link between the 1st device 10 and the 2nd device 20 is determined by narrowing down a beam by a some pattern. Here, the region where the beam is narrowed is such that the pattern region of the beam formed by the Kwasomuni beam is divided into, for example, four equal parts. The region divided into four in this way is hereinafter also referred to as “sector”. Then, among the sectors in which the link between the first device 10 and the second device 20 can be maintained, the sector that is most easily maintained and has the lowest radio wave energy loss is defined as the best sector. This completes the sector search.

  In the third stage (S30), beam tracking is performed. Similar to the sector search described above, beam tracking is the energy of radio waves that is most easily maintained in the area where the link between the first device 10 and the second device 20 can be maintained (area smaller than the sector). The area with the least loss is obtained. This beam tracking need only be performed within the best sector defined in the second stage. Here, a code book may be used for beam tracking. It can be considered that the beam having the highest resolution (hereinafter also referred to as “center beam”) is localized in the area thus determined. Here, as shown in FIG. 3, a set of a center beam and adjacent beams (adjacent beams) is referred to as a “best cluster”.

  By the way, in this aspect, in the first stage, two types of quasi-omni beams are transmitted. Therefore, in the third stage, the center beam is determined for each Kwasomuni beam. That is, two types of center beams and two types of best clusters (first best cluster and second best cluster) are determined.

  In step S40, data communication is performed. Specifically, the first device 10 transmits data to the second device 20 using one of the two types of beams (center beam). Thereby, data transmission from the first device 10 to the second device 20 can be performed efficiently. Further, the second device 20 has directivity so that the radio wave transmitted from the second device 20 is localized at the position corresponding to the other beam, and the data to the first device 10 in that state is provided. Send. Thereby, the gain of the radio wave can be sufficiently increased, and as a result, data transmission from the second device 20 to the first device 10 can be performed efficiently. That is, according to this aspect, bidirectional data communication can be performed efficiently. Note that, as in this aspect, specifying the beam position and performing data communication centered on that position is a pseudo channel for data communication between the first device 10 and the second device 20. It can be said that this corresponds to providing the

  According to the aspect described above, three types of beams having different widths (quasi-omni beam, beam corresponding to the best sector, and center beam) are generated. Specifically, the center beam can be obtained by narrowing the beam width from the Kwasomuni beam. By doing so, it is possible to increase the efficiency of the gain of the antenna. In addition, since the link between devices is established at the stage of the quasi-omni beam, even if the beam width is narrowed after that, the established link is not broken. Since the antenna gain can be made highly efficient, the data rate can be increased and high performance can be exhibited in the scenario of data transmission. In addition, power consumption can be reduced by narrowing the beam width.

  Hereinafter, a system configuration and a data structure necessary for realizing each processing as described above will be described in detail.

  In this aspect, the first device 10 handles a controller for realizing a wireless terminal management function (SME) for causing the device to function as a wireless terminal, and a MAC (Medium Access Control) layer. A piconet controller (PNC) that implements a MAC layer management function (MLME) is implemented. Similarly to the first device 10, the second device 20 also includes a controller for realizing SME and a piconet controller (PNC). The controller included in the first device 10 is not limited to a piconet controller (PNC), and any controller that can control beamforming may be used. Such a controller is realized by software. It may be realized by a combination of software and hardware.

  Further, the first device 10 is configured to be able to handle a beam codebook for adjusting the beam width. Here, the code book is preferably designed to comply with the MAC layer protocol. In this case, the code book can be handled by a piconet controller (PNC). The code book may be handled by a controller other than the piconet controller (PNC). In any case, the code book is stored in the memory as the storage means of the corresponding device, and is read and used as necessary. Similarly to the first device 10, the second device 20 is configured to handle a code book.

Here, the code book will be described in detail with a specific example.
A codebook is a matrix. Each column of the matrix corresponds to one type of beam (that is, one antenna element), and by designing (specifying) each column, a beamforming weight vector (that is, a beam pattern) is obtained. It will be fixed. By using a code book, for example, a non-directional beam can have a desired directivity.

For the generation of the code book, it is preferable to use four types of phase shifts of 0 °, 90 °, 180 ° and 270 °. When the phase 0 ° is “+ I”, the phase 180 ° is “−I”, the phase 90 ° is “+ Q”, and the phase 270 ° is “−Q”, the codebook is represented by these combinations. For example, when creating eight types of beam patterns from eight types of antenna elements alone, a code book W corresponding to a matrix as shown in the following equation 1 is used. In this aspect, amplitude adjustment is not performed in order to minimize power loss. FIG. 4 schematically shows a beam pattern when the matrix shown in the following equation 1 is used as a code book.

  Such a codebook is highly versatile because it can be adapted to wireless communication standards. That is, the wireless communication method according to the present invention can be easily applied to an existing wireless communication method.

  Next, wireless communication performed between the first device 10 and the second device 20 configured as described above will be described in more detail.

  First, the first stage (S10) described above will be described in detail. In the first stage, a pair of best quadomni beams is detected between the transmission unit of the first device 10 and the reception unit of the second device 20.

In order to realize the detection, first, the first device 10 transmits N _t quasi-omni beams from the transmission unit. These beams comply with the MAC layer protocol (for example, IEEE802.15.3b), and beacons and beamforming (BF) are preset as fields. In the field related to beam forming, information elements (IE: information element) are set for some of the beam forming capabilities of the first device 10, and specifically, as shown in FIG. Information indicating the number, beam switching (beam switching), and antenna type is set.

When N _t quasi-omni beams are transmitted from the transmission unit of the first device 10, the second device 20 can receive up to M _r quasi-omni beams at the reception unit. If successful, it notifies the first device 10 to that effect.

Data exchange until the second device 20 successfully receives the Kwasomuni beam will be described in detail.
<First stage>
First, processing (association request and association response) defined in the MAC layer is performed. At this time, each device exchanges data having a structure as shown in FIG. 6 with the piconet controller (PNC). Specifically, each device informs the piconet controller (PNC) of the information element (IE) related to the capability of the device and registers it in the register of the piconet controller (PNC). In this way, the association is established.

<Second stage>
Subsequently, the piconet controller (PNC) uses the data having the structure shown in FIG. 7 to transmit the information element (IE) relating to the device capability within the CAP to the devices that have already established the association (the first device 10 and the second device 20). To inform. Here, CAP refers to a contention access period. At the time of this notification, the piconet controller (PNC) uses an announcement command. As a result, both devices (the first device 10 and the second device 20) acquire information on the capability of the other device.

<Third stage>
One of the first device 10 and the second device 20 calculates a CTA based on the obtained device capability of the object. Here, CTA refers to channel time allocation. As shown in FIG. 8, the first device 10 that is the signal generation source (Src.DEV) transmits a CTA request command to the piconet controller (PNC). In response to this, the piconet controller (PNC) allocates a CTA for the first device 10 by transmitting a CTA response command to the first device 10. As a result, a device-device link is established within the assigned CTA.

<4th stage>
The first device 10 transmits data corresponding to the training sequence shown in FIG. 9 (hereinafter also referred to as “TS data”) for N _t groups. As the training sequence, in this embodiment, a sequence determined by Tensor com is used. As shown in FIG. 9, the TS data includes a sync (SYNC) field and a channel estimation (CE) field. Here, transmission of TS data for N _t groups starts when the first device 10 transmits each quadomni beam. That is, TS data is transmitted M _t times for each group. By doing so, it can be expected that the second device 20 receives at least one TS data from any one of the receiving side quasi-omni beams of the second device 20 itself.

<5th stage>
While transmitting TS data for a plurality of groups from the first device 10 to the second device 20, the second device 20 switches its own quasi-omni beam one by one and sets the time for each quasi-omni beam. Wait for T _s . Thereby, it can be expected that the second device 20 receives TS data from its own arbitrary quasi-omni beam. Here, the time T _s is a period required for the training sequence. The second device 20 repeats such scanning from the first Kwasomuni beam after a period of M _r × T _s .

<6th stage>
After the first device 10 has transmitted all the TS data for N _t groups, the second device 20 has received at least one TS data. By the way, whenever the second device 20 receives the TS data, the second device 20 selects the best quadmomni beam from among the multiple quadrature beams transmitted by the first device 10 according to the estimated SNR of the communication link. At the same time, the receiving side best quadmuni beam of the second device 20 itself is determined. Here, the SNR of the communication link is obtained for each training sequence. Therefore, every time a training sequence is performed, an information element (IE) for feedback at the time of beam forming as shown in FIG. 10 is transmitted from the second device 20 to the first device 10.

<7th stage>
As the TS data is transmitted from the first device 10 to the second device 20, the second device 20 repeats N _r times for each group in the same way as the decryption in the fourth stage, while the M _t group Minutes of TS data is transmitted. By doing so, it can be expected that the first device 10 receives at least one TS data from any one of the receiving side quasi-omni beams of the first device 10 itself.

<Eighth stage>
While the TS data is being transmitted from the second device 20 to the first device 10, the first device 10 attempts to receive a training sequence from any of the quasi-omni beams in the same manner as the decoding at the fifth stage. .

<9th stage>
After the second device 20 finishes transmitting all TS data for the M _t group, the first device 10 has received at least one of the TS data. Each time the first device 10 receives TS data, the first device 10 determines a best quasi-omni beam from a plurality of quasi-omni beams transmitted by the second device 20 according to the estimated SNR of the communication link. , The receiving side best quadmuni beam of the first device 10 itself is determined.

<10th stage>
After the training period, the second device 20 feeds back the offset index of the best quadomni beam of the first device 10. This feedback is performed by the second device 20 transmitting data having the structure shown in FIG. 10 (information element (IE) for feedback related to beamforming) to the first device 10. The data transmission direction shown in FIG. 10 corresponds to each of M _t transmissions, and an announcement command is used for the transmission.

<11th stage>
While the second device 20 is transmitting feedback to the first device 10, the first device 10 attempts to obtain feedback information from the receiving-side best quadmuni beam. Here, the receiving-side best quadmuni beam is determined during the above-described ninth stage training step.

<12th stage>
In accordance with the information element (IE) received as feedback related to beamforming (BF), the first device 10 grasps the transmission side quasi-omni beam that is best for itself. The first device 10 performs subsequent transmission using the grasped quasi-omni beam as the best quasi-omni beam.

<13th stage>
In response to the feedback from the second device 20 to the first device 10, the first device 10 feeds back the offset index of the best quadomni beam of the second device 20. This feedback is performed when the first device 10 transmits an information element (IE) for feedback related to beamforming (see FIG. 10) to the second device 20. An announcement command is used for this transmission. However, the first device 10 needs to transmit feedback once from the best quadmuni beam. The best quadmuni beam is determined during the training step of the twelfth stage described above.

<14th stage>
While the first device 10 is sending feedback to the second device 20, the second device 20 receives feedback by using the best Kwasomuni beam among the receiving side Kwasomuni beams. try to.

<15th stage>
By performing all the operations described above, data is exchanged as shown in FIG. 11, and finally both transmission directions (transmission direction from the first device 10 to the second device 20, And the transmission direction from the second device 20 to the first device 10), the best quadmuni beam pair is determined.

  When the second device 20 does not receive any TS data from the first device 10 during the fifth stage, or when the second device 20 does not receive any feedback from the first device 10 at the fourteenth stage. If not received, the second device 20 declares “beam forming failure”. Specifically, this declaration is performed by the second device 20 transmitting an information element indicating that beamforming has failed together with the announcement command to the piconet controller (PNC). In response to this, the piconet controller (PNC) notifies the first device 10 of this by using an announcement command. Thereafter, the first device 10 selects one of resuming or abandoning this process.

  When the first device 10 does not receive any TS data from the second device 20 during the eighth stage, or the first device 10 receives no feedback from the second device 20 at the eleventh stage If not, the first device 10 declares “beamforming failure”. Specifically, this declaration is performed by the first device 10 transmitting an information element indicating that beamforming has failed together with the announcement command to the piconet controller (PNC). Then, the piconet controller (PNC) notifies the second device 20 to that effect by using an announcement command. Thereafter, the second device 20 selects one of resuming or abandoning this process.

  Next, the second stage (S20) will be described in detail. In this second stage, a sector search is performed, and a pair of the first best sector and the second best sector between the first device 10 and the second device 20 is detected. In order to realize this detection, the first device 10 and the second device 20 are configured or set as follows.

  First, both the first device 10 and the second device 20 have a fine beam code book with a narrow width. This codebook was created to cover the entire target area of interest around these devices.

  Second, both the first device 10 and the second device 20 group fine beams into sectors. Even in this way, it is possible to cover the entire area covered by the quasi-omni beam (hereinafter also referred to as “selected quasi-omni beam”) determined in the first step (S10).

  Third, the first device 10 and the second device 20 can communicate with each other by using the quasi-omni beam determined in the first stage (S10).

Fourth, the first device 10 has J _t sectors for the transmitter, and these sectors cover the selected quadomni beam for the transmitter. Further, the first device 10 has J _r sectors for the receiving unit, and these sectors cover the selected quadomni beam for the receiving unit. Accordingly, the second device 20 has K _t sectors for the transmitter, which cover the selected quadomni beam for the transmitter and K _r for the receiver. This sector covers the selected quadomni beam for the receiver. These pieces of information are included in the information element (IE) for sector search shown in FIG. 12, and can be referred to by both the first device 10 and the second device 20.

  Then, by using the first device 10 and the second device 20 configured or set as described above, the sector search in the second stage (S20) is performed in the following procedure.

<First stage>
First, the first device 10 and the second device 20 transmit sector candidate information to each other using an announcement command. Specifically, the first device 10 transmits J _t and J _r as sector candidate information to the second device 20, and accordingly, the second device 20 uses K _t and K _r as sector candidate information. Is transmitted to the first device 10.

<Second stage>
Subsequently, the first device 10 and the second device 20 perform the same operations as those defined in the fourth stage to the fifteenth stage of the first stage (S10) described above. However, N _t , N _r , M _t , and M _r need to be replaced with J _t , J _r , K _t , and K _r , respectively. Then, during the sector search, the first device 10 and the second device 20 record the SNR for all combinations (combinations) of sector candidates.

<Third stage>
By performing all the operations described above, data exchange as shown in FIG. 13 is performed. Eventually, based on the SNR table, the best sector of both transmission directions (the transmission direction from the first device 10 to the second device 20 and the transmission direction from the second device 20 to the first device 10) is determined. A pair (that is, a pair of the first best sector and the second best sector) is determined.

  Even in the second stage (S20), the first device 10 and the second device 20 may declare "Beamforming (BF) failure". The case where this declaration is made is the same as that defined in the first stage (S10) described above.

  Next, the third stage (S30) will be described in detail. In this third stage, a beam search (beam tracking) is performed, and a pair of the first best beam and the second best beam between the first device 10 and the second device 20 is detected. In order to realize this detection, the first device 10 and the second device 20 are configured or set as follows.

  First, both the first device 10 and the second device 20 have a codebook for a super fine beam that is further narrowed. This codebook was created to cover the entire target area of interest around these devices.

  Second, both the first device 10 and the second device 20 group superfine beams within the sector determined in the second step (S20) (hereinafter also referred to as “selected sector”). In other words, the selected sector is disassembled with a super fine beam. Therefore, the entire area covered by the selected sector is surely covered.

  Third, the first device 10 and the second device 20 can communicate with each other by using the best sector determined in the second step (S20).

Fourth, the first device 10 has a beam area for S _t pieces of beam for transmission portion, by their radiation field covers the selected sector for transmission portion. The first device 10 has a S _r pieces of beam space for receiving part, by their radiation field covers the selected sector of the receiver unit. Correspondingly, the second device 20 has T _t beam regions for the transmitter, which cover the selected sector for the transmitter and T _r for the receiver. The selected sector for the receiving unit is covered by these beam regions. These pieces of information are included in the beam search information element (IE) shown in FIG. 14 and can be referred to by both the first device 10 and the second device 20.

  Then, by using the first device 10 and the second device 20 configured or set as described above, the beam search in the third stage (S30) is performed in the following procedure. The following procedure is performed not only for the first best sector but also for the second best sector. That is, the beam search is performed twice.

<First stage>
First, the first device 10 and the second device 20 mutually transmit beam area candidate information using an announce command. Specifically, the first device 10, as the beam area candidate information, and sends the S _t and S _r to the second device 20, in response thereto, the second device 20, as the beam area candidate information, T _t and T _r is transmitted to the first device 10.

<Second stage>
Subsequently, the first device 10 and the second device 20 perform the same operations as those defined in the fourth stage to the fifteenth stage of the first stage (S10) described above. _{However, N t, N r, M} t, and M _r are each, it is necessary to replace the _{S t, S r, T t} , and T _r. During the beam search, the first device 10 and the second device 20 record the SNR for every combination (combination) of beam region candidates.

<Third stage>
By performing all the operations described above, data exchange as shown in FIG. 15 is performed. Finally, based on the SNR table, the best beam region for both transmission directions (transmission direction from the first device 10 to the second device 20 and transmission direction from the second device 20 to the first device 10). (Ie, the first best beam and second best beam pair) are determined.

  Also in the third stage (S30), the first device 10 and the second device 20 may declare “Beamforming (BF) failure”. The case where this declaration is made is the same as that defined in the first stage (S10) described above.

  By the way, in the aspect mentioned above, the association process is performed using a quasi-omni beam. Here, when the quasi-omni beam is used, there is a possibility that the gain at the antenna of the second device 20 that is the receiving device is not sufficiently high. Therefore, in another aspect of this embodiment, a directional beam is used instead of the quasi-omni beam. Hereinafter, the configuration of the wireless communication system 1 in the case of using a directional beam and the processing to be executed will be described in detail.

  First, the configuration of the wireless communication system 1 is the same as that described above. Also in this aspect, the first device 10 functions as a transmitting device, and the second device 20 functions as a receiving device. However, the first device 10 and the second device 20 are configured to be capable of generating a directional beam and transmitting / receiving a directional beam. The first device 10 includes a piconet controller (PNC) in the same manner as described above in order to perform control for performing association processing with the second device 20. The piconet controller (PNC) of the first device 10 can transmit the directional beam of the first device 10 and can receive the directional beam from the second device 20 via the antenna of the first device 10. is there.

  Next, processing executed in the wireless communication system 1 will be described. First, association processing is performed. For this reason, the piconet controller (PNC) of the first device 10 transmits a directional beam in a predetermined transmission direction together with a beacon necessary for association processing. By doing so, an area including the second device 20 is attempted to be a target area for wireless communication. In practice, a directional beam is transmitted so that all of the target area around the piconet controller (PNC) is covered (for example, an area within a communicable distance in any direction of 360 °). .

  Here, when a directional beam is used instead of the quasi-omni beam, two types of methods (a first method and a second method) can be considered as a directional beam transmission method. The first method is to transmit a directional beam having directivity in a plurality of directions in a predetermined transmission direction. The second method is to transmit a directional beam having directivity in one direction in all transmission directions.

First, the first method will be described.
FIG. 16 shows frame data including a plurality of beacons. In the frame data shown in FIG. 16, a plurality of beacons associated with the direction corresponding to the directivity of the directional beam (that is, the transmission direction in which the piconet controller (PNC) of the first device 10 can transmit) is shown. That is, a beacon is multiplexed into one data (super frame). In the example shown in FIG. 16, since there are N _t types of transmission directions of the piconet controller (PNC) of the first device 10, only N _t beacons are prepared so as to correspond thereto.
When such a beacon is transmitted, the second device 20 has an opportunity to receive at least one of the plurality of beacons.

In contrast to the first method, the data is configured as follows in the second method.
FIG. 17 schematically shows a state in which a plurality of frame data including beacons associated with any one transmission direction that can be transmitted by the piconet controller (PNC) of the first device 10 is generated for each transmission direction. Show. That is, data (superframe) including one beacon is multiplexed. In the example shown in FIG. 17, since the transmission direction of the piconet controller of the first device 10 (PNC) is N _t kind, so as to correspond thereto, the number of beacons also the N _t only are prepared, in the N _t data Is distributed.
When the multiplexed data is transmitted according to the transmission direction in this way, the second device 20 has an opportunity to receive at least one of the plurality of data. If the reception is successful, the received data You can get a beacon from

  Therefore, the second device 20 can acquire at least one beacon regardless of the first method or the second method described above. That is, the 2nd device 20 which is a receiving device can receive a beacon by adopting the 1st method and the 2nd method. Therefore, it is possible to eliminate the need to use a quasi-omni beam whose gain at the antenna is not sufficiently high. If a directional beam is used instead of the quasi-omni beam, the gain at the antenna of the second device 20 can be increased.

And after the 2nd device 20 receives a beacon, the process for confirming whether the piconet controller (PNC) of the 1st device 10 can receive data from the 2nd device 20 is performed. Therefore, the CAP in the frame data is divided into N _r sub-CAPs (S-CAPs) according to the number N _r of reception directions of the piconet controller (PNC) of the first device 10. Then, the piconet controller (PNC) of the first device 10 listens (receives) the channel passing through the N _r sub-CAPs using a corresponding directional beam (FIG. 16 or FIG. 17).

On the other hand, the second device 20 communicates with the piconet controller (PNC) of the first device 10 in each of the M _r reception directions at least during the period in which the plurality of beacon groups described above are transmitted. Wait for the association process between them. As described above, the second device 20 is configured to be able to receive directional beams from M _r reception directions and to transmit directional beams in M _t transmission directions.

Each time the second device 20 detects a beacon from one of the reception directions of the second device, the second device 20 grasps the best transmission direction of the piconet controller (PNC) of the first device 10 and Figure out the best receiving direction for Subsequently, the second device 20 transmits the feedback information through each of the M _t transmission directions of the second device using the announcement command. The feedback information at this time includes information regarding the transmission direction of the piconet controller (PNC) of the first device 10. Here, if the plurality of feedback information is a feedback information group, the second device 20 repeatedly transmits such a feedback group to the piconet controller (PNC) of the first device 10 for each sub-CAP. It will be.

  Accordingly, every time the piconet controller (PNC) of the first device 10 receives feedback information from the second device 20, the piconet controller (PNC) grasps the best transmission direction from the information included in the feedback information. Further, the piconet controller (PNC) of the first device 10 detects the SNR using the preamble portion of the feedback information received by each of the sub-CAPs. Thereby, the piconet controller (PNC) of the first device 10 grasps the best reception direction of the piconet controller (PNC).

  Thereafter, the piconet controller (PNC) of the first device 10 notifies the best transmission direction of the second device 20. Specifically, this notification is performed by transmitting the extended beacon from the best transmission direction of the piconet controller (PNC).

  At this point, both the piconet controller (PNC) of the first device 10 and the second device 20 have grasped each other's best transmission direction and each other's best reception direction. In other words, the best beam direction pair is determined. Thereafter, normal association and CTA request operations will be performed through these best beam direction pairs. Note that both normal association and CTA request operations are those defined in IEEE 802.15.3.

By the way, the plurality of sub-CAPs described above can be spread over several superframes as shown in FIG. In the example shown in FIG. 18, N _r sub-CAPs are spread over N _r super frames. In this way, the buffer of the receiving side device (second device 20) can be reduced by widening.

  Also, here, in the case of the example shown in FIG. 17 (one directional beacon in one superframe), the association processing is performed over several superframes. Then, a beacon (synchronization beacon) is transmitted via the pair of best directions described above at the beginning of the allocated CTA so that the associated device (second device 20) does not miss the synchronization. The This process can be executed because the piconet controller (PNC) already knows the best transmission direction after the association. Therefore, the second device 20 can follow a synchronization beacon as shown in FIG.

  Moreover, in this aspect, as shown in FIG. 20, MCTA may be generated in CTAP. This MCTA has the same structure as CAP (or sub-CAP). Then, all the operations for transmitting the feedback information described above are executed in this MCTA. By using MCTA in this way, it is not necessary to exchange some commands within the CAP. As a result, for example, feedback information does not enter the CAP. Therefore, collision (data collision) can be avoided. As a result, a situation in which the wireless communication system 1 is broken can be avoided, and the stability of the wireless communication system 1 is increased. Since CTAP is used, the efficiency of the protocol can be increased.

  According to another aspect described above, the piconet controller (PNC) of the first device 10 transmits a directional beam in a predetermined transmission direction together with a beacon necessary for the association process, and the second device 20 receives the directional beam. . That is, the area including the second device 20 is a target area for wireless communication. Here, the gain at the antenna of the second device 20 is increased by using the directional beam. Further, according to this aspect, it is possible to avoid interference of hidden nodes.

  Moreover, in this aspect, there are two types of directional beam transmission methods including beacons as described above. One is to include a plurality of beacons in a directional beam and transmit one directional beam (FIG. 16) including the plurality of beacons in a predetermined transmission direction. The other is to multiplex a directional beam including one beacon and transmit the multiplexed directional beam (FIG. 17) in a plurality of transmission directions as a predetermined transmission direction. . In any method, the target area can be easily secured, and the necessity of using a quasi-omni beam can be eliminated.

  The aspect described above mainly relates to the wireless communication system 1 and the wireless communication method. However, the devices 10 and 20 constituting the wireless communication system 1 of the present invention, antennas, transmitters, receivers, codebooks used in the wireless communication method of the present invention, beam search processing (sector search processing, beam The format or frame structure of data including fields relating to tracking processing, feedback processing, announcement commands, and beamforming also constitutes the present invention or a part of the present invention. Needless to say, a program (algorithm) corresponding to part or all of the above-described processing and an information storage medium storing the program also constitute the present invention or a part of the present invention.

  The present invention is not limited to data transfer in a home video system, but can be used in all fields of wireless communication (for example, a high-throughput file server for user communication). The present invention can also be used when switching wired communication to wireless communication. Furthermore, the present invention can be applied to any directional antenna that is mounted in a wireless communication system.

1 wireless communication system 10 first device (DEV1)
20 Second device (DEV2)

Claims (4)

A wireless communication system (1) for performing wireless communication between a transmitting device (10) and a receiving device (20),
The receiving device (20)
It is configured to generate a directional beam,
Including an antenna capable of transmitting and receiving directional beams,
The transmitting device (10)
An antenna capable of transmitting and receiving directional beams;
A piconet controller (PNC) that performs control for performing association processing with the receiving device (20),
The piconet controller (PNC)
It is configured to be able to generate a directional beam, and is configured to be able to transmit and receive a directional beam via the antenna.
The piconet controller (PNC)
The directional beam is transmitted in a predetermined transmission direction together with a beacon necessary for the association process,
Thereby, the area including the receiving device (20) is set as the target area of the wireless communication ,
A CAP (contention access period) in frame data corresponding to the directional beam is divided into a plurality of sub-CAPs for the association process,
The number of sub-CAPs is a number corresponding to the reception direction of the piconet controller (PNC),
The plurality of sub-CAPs are:
One sub-CAP is expanded to a plurality of superframe data so that it is included in one superframe data.
MCTA having the same data structure as the CAP is generated in the CTAP in the frame data corresponding to the directional beam,
The receiving device (20)
Sending feedback information to the piconet controller (PNC) using the MCTA,
Wireless communication system (1). The piconet controller (PNC)
Including a plurality of beacons in the directional beam and transmitting one directional beam including the plurality of beacons toward the predetermined transmission direction;
The wireless communication system (1) according to claim 1. The piconet controller (PNC)
Multiplex a directional beam including one of the beacons, and transmit the multiplexed directional beam toward a plurality of transmission directions as the predetermined transmission direction;
The wireless communication system (1) according to claim 1. A wireless communication method for performing wireless communication between a transmitting device (10) and a receiving device (20),
The receiving device (20) is configured to be capable of generating a directional beam and includes an antenna capable of transmitting and receiving a directional beam,
The transmitting device (10) includes an antenna capable of transmitting and receiving a directional beam and a piconet controller (PNC) that performs control for performing association processing with the receiving device (20), The piconet controller (PNC) is configured to be capable of generating a directional beam and configured to be capable of transmitting and receiving a directional beam via the antenna.
Said method is:
An association step for performing an association process between the transmitting device (10) and the receiving device (20);
The association step is
The piconet controller (PNC) transmitting the directional beam along with a beacon required for the association process in a predetermined transmission direction;
The receiving device (20) receiving the beacon transmitted from the piconet controller (PNC) ,
The CAP in the frame data corresponding to the directional beam is divided into a plurality of sub-CAPs for the association process,
The number of sub-CAPs is a number corresponding to the reception direction of the piconet controller (PNC),
The plurality of sub-CAPs are:
One sub-CAP is expanded to a plurality of superframe data so that it is included in one superframe data.
MCTA having the same data structure as the CAP is generated in the CTAP in the frame data corresponding to the directional beam,
The receiving device (20)
Sending feedback information to the piconet controller (PNC) using the MCTA,
Wireless communication method.

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