TERMiNAL DEVECE, BASE STATEON DEVECE, AND WiRELESS
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`COMMUNECATEQN SYSTEM
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`t. Technicai Fieid
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`BACKGRGUND
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`{seat} The present disciosure reiates to terminai devices, base station devices,
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`and wireiess communication systems.
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`2. Description of the Rotated Art
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`{9992} With increased teveis ot tunctionaiity of digitai devices, access points and
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`terminai devices provided with wireiess iocai area networks (LANs) are
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`widespread.
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`in recent years, increased needs tor high~capacity, high~soeed
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`wireiess communication have ted to the spread of high—speed wireiess LANs that
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`go beyond gigabit speed.
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`{seas} To impiement high-capacity, high~speed wireiess communication, high—
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`speed wireiess communication in miiiimeter~wave bands (eg, SO—Gi—tz band) in
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`which directionai communication is carried out with the use of a oiuraiity of
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`antenna eiernents is attracting attention (eg, EEEE 802d tad—2012 standard,
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`December 28, 2012).
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`{aorta} Some of the characteristics of wireiess signais in miiiimetenwave hands
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`are their strong straightness and high soatiai propagation iosses. As such,
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`according to EEEE 802d tad—2012 standard, December 28, 2012, a wireiess
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`communication device (eg, access point, base station device, terminai device)
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`executes procedures caiied heamtorming training (BFT) in which the wireiess
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`communication device transmits and receives training signais to and from each
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`communicating party and determines the direction with high communication ouaiity,
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`and carries out wireiess communication by forming an antenna pattern (hereinafter,
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`referred to as a ”beam") that is highiy directionai in the determined direction.
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`SUMMARY
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`{9605} However, wireiess communication devices of existing techniques carry
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`out the EFT oeriodicaiiy and change the beams, which thus ieads to an increase in
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`the frequency of transmitting and receiving training signais and to a decrease in
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`the communication throughput.
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`{sees} One non—iimiting and exemoiary embodiment provides a terminai device,
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`a base station device, and a wireiess communication system that suppress a
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`decrease in the communication throughput.
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`{poor}
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`in one genera! aspect, the techniques disciosed here feature a terminai
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`device that inciudes a communicator that carries out first data communication with
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`a base station device by using a first beam and then receives, by using a reception
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`beam, a piuraiity of first signats transmitted by the base station device by using
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`respective transmission beams; and a determiner that caicuiates a reception
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`duaiity of the piuraiity of first signais and determines a second beam of which the
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`reception guaiity is the highest among the piuraiity of transmission beams. The
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`communicator transmits a feedback signai inciuding information indicating the
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`second beam to the base station device by using the first beam and starts second
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`data communication with the base station device by using the first beam in a case
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`in which the communicator has received, from the base station device, a response
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`signai indicating that the base station device has received the feedback signai.
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`{page} According to an aspect of the present disciosure, a decrease in the
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`communication throughput can be suppressed.
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`{bobs}
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`it is to be noted that generai or specific embodiments of the above mayi
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`be impiemented in the form of a system, an integrated circuit, a computer program,
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`or a recording medium, orthrough any desired combination of a system, an
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`apparatus, a method, an integrated circuit, a computer program, and a recording
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`medium.
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`{0016} Additionai benefits and advantages of the disciosed embodiments wiii
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`become apparent from the specification and drawings. The benefits and/or
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`advantages may be individuaiiy obtained by the various embodiments and
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`features of the specification and drawings, which need not aii be provided in order
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`to obtain one or more of such benefits and/or advantages.
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`BREEF DESCRiFTiQN OF THE DRAWiNGS
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`{Obit}
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`Fig. 1A iiiustrates an exampie of an operation A in BFT;
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`Fig. 18 iiiustrates an exampie of an operation 8 in EFT;
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`Fig. 1C) iiiustrates an exampie of an operation (3 in EFT;
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`Fig. 1E} iiiustrates an exampie of an operation D in BFT;
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`Fig. 2 is a sequence diagram iiiustrating an exampie of the fiovii of the operation A
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`to the operation D iiiustrated in Fig. “EA to Fig. t9;
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`Fig. 3 iiiustrates an exampie of a configuration of a wireiess communication device
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`according to a first embodiment of the present disciosure;
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`Fig. 4 is a sequence diagram iiiustrating an exampie of a series of operations
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`according to the first embodiment of the present disciosure;
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`Fig. 5A iiiostrates exampies of operation patterns according to the first
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`embodiment of the present disciosure;
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`Fig. 58 iiiustrates a correspondence of the operation patterns iiiostrated in Fig. 5A
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`with a base station device and a terminai device;
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`Fig. 6 is a flowchart iiiustrating processing of a base station device according to
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`the first embodiment of the present disciosure;
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`Fig. 7 is a flowchart iiiostratihg processing of a terminai device according to the
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`first embodiment of the present disciosure;
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`Fig. 8A is a sequence diagram iiiustrating an exampie of a series of operations
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`according to a second embodiment of the present disciosure;
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`Fig. 88 is a sequence diagram iiidstrating an exampie of a series of operations
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`according to the second embodiment of the present disciosure;
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`Fig. 9A iiiustrates exampies of operation patterns according to the second
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`embodiment of the present disciosure;
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`Fig. QB iiiostrates a correspondence of the operation patterns iiiustrated in Fig. 9A
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`with a base station device, a terminai device, and a iink disconnecting timing;
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`Figs. 10A and 108 are a flowchart iiiustrating processing of a base station device
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`according to the second embodiment of the present disciosure; and
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`Figs. 11A and MB are a flowchart iiiustrating processing of a terminai device
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`according to the second embodiment of the present disciosure.
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`DEEMLEDDESCMPHON
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`{G912}
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`First, beamtorming training (EFT) of existing techniques wiii be described.
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`in the EFT of the existing techniques, primariiy tour operations are carried out.
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`Hereinafter, these tour operations wiii be referred to sequentiaiiy as an operation A,
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`an operation B, an operation (3, and an operation D.
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`{9613}
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`Fig. 1A iiiostrates an exampie of the operation A in the EFT. Fig. 18
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`iiiustrates an exampie of the operation B in the EFT. Fig. 10 iiiustrates an
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`exampie of the operation (3 in the EFT. Fig. 1D iiiustrates an exampie of the
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`operation D in the EFT. Fig. 2 is a sequence diagram iiiustrating an exampie of
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`the tiow of the operation A to the operation D iiiustrated in Fig. 1A to Fig. it). The
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`operation A to the operation i3 iiiustrated in Fig. 2 correspond to Fig. 1A to Fig. it),
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`respectiveiy.
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`{@914}
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`Fig. 1A to Fig. ”it? iiiustrate the respective operations in the EFT
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`impiemented between a wireiess communication device "id and another wireiess
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`communication device 2t).
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`in the toiiowing description, the characteristics of
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`transmitting antenna patterns and the characteristics of receiving antenna patterns
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`are substantiaiiy eduai between the wireiess communication device 10 and the
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`wireiess communication device 20.
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`root 5} The wireiess communication device “to and the wireiess communication
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`device 20 each inciude a piuraiity of antenna eiements and each carry out
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`beamforming of eiectrohicaiiy switching the beam direction by seiecting an
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`antenna eiement and by controiiing the phase of the reception and transmission
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`radio waves of the seiected antenna eiement. The BFT is an operation of
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`determining the beamtorm suitabie for communication (eg, the beam direction
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`suitabie for communication) in response to a change in the communication
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`environment between the wireiess communication device to and the wireiess
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`communication device 20.
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`{dot at
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`in Fig. 1A, first, the wireiess communication device it) transmits training
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`signais fix in respective beam directions by using (narrowiy directionai)
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`transmission beams “i"xn (Txnmt to Txnmn) with a narrow directionaiity white
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`switching the beam direction of the transmission beam Txn among a piuraiity of
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`beam directions. The training sighais 3x transmitted with the use of the
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`transmission beams "i'xn in the respective beam directions inciude the
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`identification information of the corresponding beam directions. The (narrowiy
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`directionai) beam with a narrow directionaiitv is a beam having a smaii beam~hait—
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`vaiue angie.
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`it is to be noted that each beam indicates the transmitting direction or
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`the receiving direction, and aithough the transmission beams Txn and a reception
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`beam Ryw do not overiap in Fig. 1A, the communication is possihie.
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`{961?} The wireiess communication device 20 forms a (wideiy directionai)
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`reception beam Ryw with a wide directionaiity and stands by uhtii the wireiess
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`communication device 20 receives the training signais Sx transmitted from the
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`wireiess communication device to. Then, the wireiess communication device 20
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`caicuiates the reception duaiity of the received training signais fix and determines
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`the training signai fix with the highest reception guaiity (Sxflf-f-i in Fig. 1A). The
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`beam direction indicated by the identification information inciuded in the training
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`signai Sx with the highest reception guaiity is the beam direction of the wireiess
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`communication device to that is optimai in the communication with the wireiess
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`communication device 20 (the pest beam of the vvireiess communication device
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`10). The (wideiy directionai) beam with a wide directiohaiity is a beam having a
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`iarge beam—haif~vaiue angie.
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`{9618} Upon having finished receiving the training signais fix in Fig. 1A, the
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`wireiess communication device 20 transmits training signais Sy by using (narrowiy
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`directionai) transmission beams Tyn (Tynmt to Tynmm) with a narrow directionaiity
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`in respective beam directions white switching the beam direction of the
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`transmission beam Tyn among a piuraiity of beam directions in Fig. 18. The
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`wireiess communication device 29 incorporates, into the training signais Sy, the
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`identification information of the beam direction inciuded in the training signai 3x
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`with the highest reception guaiitv (in Fig. 1A, the identification information of the
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`beam direction inciuded in the training signai ijfi) among the training signais Sx
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`received by using the reception beam Ryw. The identification information of the
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`beam direction inciuded in the training signai fix with the highest reception guaiity
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`indicates the beam direction information of the wireiess communication device 10
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`that is optimai in the communication with the vvireiess communication device 20.
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`{Got 9} Upon having finished transmitting the training signais 8x in Fig. 1A, the
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`wireiess communication device to forms a wideiy directionai reception beam vav
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`and stands by untii the wireiess communication device 10 receives the training
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`signais Sy transmitted from the vvireiess communication device 28 in Fig. 18.
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`Then, the wireiess communication device to caicuiates the reception guaiity of the
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`received training signais Sy and determines the training sighai 3y with the highest
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`reception guaiity (Syjtj in Fig. f8). The beam direction indicated by the
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`identification information inciuded in the training signai Sy with the highest
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`reception guaiity is the beam direction of the wireiess communication device 20
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`that is optimai in the communication with the wireiess communication device 10
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`(the pest beam of the wireiess communication device 20).
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`geese} Upon having finished receiving the training signais 8y in Fig. 18, the
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`wireiess communication device to sets the transmission beam cptimai in the
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`communication with the vvireiess communication device 20 (the narrowiy
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`directionai transmission beam Txnmi in Fig. 10) on the basis of the identification
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`information of the beam direction inciuded in the training signai Sy in Fig. 10.
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`Then, the wireiess communication device til) transmits a feedback (hereinafter,
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`abbreviated to F8) by using the transmission beam Txnmi. The F8 inciudes the
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`identification information of the beam direction inciuded in the training signai Sy
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`with the highest reception duaiity (the identification information of the beam
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`direction inciuded in the training signai Sywrti in Fig. t8) among the training signais
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`8y received by using the reception beam vav. The identification information of
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`the beam direction inciuded in the training signai Sy with the highest reception
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`duaiity indicates the beam direction information of the wireiess communication
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`device 20 that is optimai in the communication with the vvireiess communication
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`device to.
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`{(3021} Upon having finished transmitting the training signais Sy in Fig. t8, the
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`wireiess communication device 2i.) forms the Wideiy directionai reception beam
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`Ryvv and receives the FB transmitted from the Wireiess communication device to
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`in Fig. 1C.
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`{M322} Upon having finished receiving the F8 in Fig. 10, the Wireiess
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`communication device 20 sets the transmission beam optima! in the
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`communication with the wireiess communication device to (the narrowiy
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`directionai transmission beam Tynmi in the exampie iiiustrated in Fig. ti?) on the
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`basis of the identification information of the beam direction inciuded in the FB in
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`Fig. til). Then, the wireiess communication device 20 transmits an
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`acknowiedgement (ACK) to the wireiess communication device 10.
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`{9923} Upon having finished transmitting the F8 in Fig. 10, the wireiess
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`communication device to forms the Wideiy directionai reception beam Rxw and
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`stands by untii the wireiess communication device 10 receives the ACK
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`transmitted front the wireiess communication device 20 in Fig. 10.
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`{(3024} The wireiess communication device 10 compietes the EFT operation
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`upon having received the ACK and starts data communication with the wireiess
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`communication device 20. The wireiess communication device 10 transmits and
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`receives data signais by using the narrowiy directionai beam Txnmi, and the
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`wireiess communication device 20 transmits and receives data signais by using
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`the narrowivi directionai beam Tyn__i.
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`{G925} Through the EFT operation iiiustrated in Fig. 1A to Fig. ti) and Fig. 2, the
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`wireiess communication device to and the wireiess communication device 20
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`determine their respective best beams.
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`it is to be noted that the wireiess
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`communication device 20 may start the EFT described above.
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`{@926}
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`For exambie, in a case in which at ieast one of the wireiess
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`communication device it) and the wireiess communication device 20 is a oortabie
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`information terminai device {mobiie terminai device) and the other one of the two is
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`a base station device, an area with a high density of mobiie terminai devices is
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`iiiteiy to appear, and the reiative position of the base station device and the mobiie
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`terminai device is iikeiy to change. Therefore, in the existing techniques, the EFT
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`is carried out beriodicaiiy to retain the communication. The base station device
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`extends the communication distance by reducing the hait—vaiue angie of the beam,
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`and thus the number of beams to scan increases as compared to that of the
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`mobiie terminai device. Consequentiy, the increase in the number of beams and
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`the increase in the frequency of the EFT iead to an increase in the frequency of
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`transmitting training signais, which thus ieads to a decrease in the throughput in
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`data communication.
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`{soar}
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`in the meantime, tor exampie, in an environment in which the density of
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`the mobiie terminai devices and/or the reiative position of the base station device
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`and the mobiie terminai device do/does not change, the best beam determined in
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`the EFT may be identicai to the best beam used in the data communication prior to
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`the EFT,
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`in such a case, the base station device and the mobiie terminai device
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`can refrain from changing their beam directions.
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`{9628} Accordingiy, by checking, in the second and subsequent instances of
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`BFT, Whether the best beam used by a wireiess communication device in the first
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`instance of data communication carried out prior to carrying out the second and
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`subsequent instances of BFT can continue to be used in the second and
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`subsequent instances of data communication, the second and subsequent
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`instances of BFT may possibiy be abbreviated. This observation has iead to the
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`present disciosure.
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`{962%} Hereinafter, embodiments of the present disciosure wiii be described in
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`detaii with reference to the drawings.
`
`it is to be noted that the embodiments
`
`described hereinafter are mereiy exampies, and the present disciosure is not
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`iimited by the toiiovving embodiments.
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`First Embodiment
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`{9639}
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`Fig. 3 iiiustrates an exampie of a configuration of a wireiess
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`communication device 100 according to a first embodiment.
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`in the toiicwing, an
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`exampie in which the wireiess communication device 100 carries out miiiimeter—
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`wave communication with a wireiess communication device 200, which serves as
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`a communicating party, wiii be described. The configuration of the wireiess
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`communication device 200 is simiiar to that of the vvireiess communication device
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`1013) described hereinafter, and thus detaiied descriptions thereof wiii be omitted.
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`{111631} The wireiess communication device 1013 inciudes a piuraiity of antenna
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`eiements 101, a beam tormer102, a transmission processor 103, a reception
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`processor 104, a communication controiier 105, a guaiity information acquirer 105,
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`a beam controiier 107', and an information storage 108.
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`{@332} The piuraiity of antenna eiements 1131 are array antennas arrayed in a
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`predetermined arrangement.
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`{ease} The beam former 102 excites the piuraiit},i of antenna eiements 101 and
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`controis the ampiitude and the phase of an excitation current in orderto form a
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`beam for transmitting or receiving a wireiess signai, under the oontroi of the beam
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`controiier 107, which wiii be described tater.
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`{@034} The piuraiity of antenna eiements 101 and the beam former 102 Wiii
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`coiiectiveiy be referred to as an antenna unit 121, as appropriate. Specificaiiy, the
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`antenna unit 121 switches the directions of the respective beams by using the
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`pturaiity of antenna eiements 11.31.
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`in the present embodiment, the antenna unit
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`121 inciudes a transmitting antenna and a receiving antenna, and a substantiaiiy
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`identicai beam pattern can be obtained in each beam direction.
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`{@935} The transmission processor 1133 moduiates various controi signais
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`inciuding a training signai used in EFT and various pieces of information to be
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`transmitted into miiiimeter—vvave signais and transmits the miiiimeter—wave signais
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`via the antenna unit 121.
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`{(39363 The reception processor 104 demoduiates, from a miiiimeter—vvave signai
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`received by the antenna unit 121, information inciuded in the miiiimeter—vvave
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`signai. Such information inciudes various oontroi signais inciuding a received
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`training signai and various pieces of information.
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`{near} The communication controtier 105 generates a packet for communicating
`
`with the wireiess communication device 200. The communication controiier105
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`receives information from the guaiity information acquirer 106, which wiii be
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`described iater, and carries out processing of incorporating, into a packet,
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`information on the best beam direction for communicating with the wireiess
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`communication device 200, for exampie. The transmission processor 103, the
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`reception processor 104, and the communication controiier 105 wiii coiiectiveiy be
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`referred to as a communicator 122, as appropriate. Specifioaiiy, the communicator
`
`122 carries out wireiess communication with the wireiess communication device
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`200 by using the antenna unit 121.
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`{0038}
`
`in the EFT, the duaiity information acquirer 100 caisuiates the reception
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`duaiity (ed, the received signai strength indicator (RSS1) and the signai—tounoise
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`ratio (Shim) ot the signai received from the vvireiess communication device 200 via
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`the communicator 122 and acquires the caicuiated reception ouaiity as ouaiity
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`information. The ouaiity information is the reception duaiity. in the wireiess
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`communication device 100, of the signai transmitted from the wireiess
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`communication device 200. The duaiity information acouirer106 may transmit the
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`duaiity information indicating the reception duaiity in the wireiess communication
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`device 100 to the wireiess communication device 200 via the communicator 122 or
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`may receive the quaiity information indicating the reception duaiity in the wireiess
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`communication device 200 from the vvireiess communication device 200 via the
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`communicator 122.
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`{00393
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`in addition, the ouaiity information acduirer 100 functions as a determiner
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`that caicuiates the reception duaiity of each training signai transmitted by the
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`wireiess communication device 200 and determines the beam number with the
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`highest reception duaiity. The duaiity information acquirer 106 outputs the
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`determined beam number to the communication controiier 105.
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`{(11140} The beam controiier 107 controis the beam formed by the antenna unit
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`121. For exampie, in the EFT, in response to an instruction from the duaiity
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`information acauirer100. the beam controiier107 causes the antenna unit 121 to
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`successiveiy form narrowiy directionai beams in respective directions and aiso
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`causes the antenna unit 121 to form a wideiy directionai beam. Then, upon the
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`compietion of the EFT, the beam controiier 107 forms a narrowiy directionai beam
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`in the direction determined to be the best (the best beam) and starts data
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`communication.
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`{0041}
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`in addition, the beam controiier 107’ outputs an instruction to the antenna
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`unit 121 directing the antenna unit 121 to form a narrowiy directionai transmission
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`beam used in the previous instance of communication (is, the best beam of the
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`previous instance) on the basis of the beam direction information stored in the
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`information storage 108, which wiii be described tater. The instruction forthe
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`beam formation is impiemented in conjunction with an instance in which the
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`communication oontroiier 105 outputs, to the transmission processor 103, an
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`instruction for transmitting a feedback signai inciuding the beam number output
`
`from the duaiity information acquirer 105, for exampie.
`
`{9642} The information storage “i055 stores the best beam direction information
`
`up to the current moment of the wireiess communication device 100 and the
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`wireiess communication device 200. The information storage ӣ08 may store the
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`beam direction information used in the entire instances of communication up to the
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`current moment. The beam controiier 107 uses the information in the information
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`storage t08 when comparing the best beam direction up to the current moment
`
`with the current best beam direction.
`
`{0043} The wireiess communication device 100 inciudes, for exampie, a centrai
`
`processing unit (CPU), a storage medium such as a read~oniy memory (ROM)
`
`storing a controi program, a work memory such as a random~access memorji,i
`
`(RAM), and a communication circuit. The functions of the components described
`
`above are impiemented as the CPU executes the controi program.
`
`in a simiiar
`
`manner, the wireiess communication device 200 inciudes, for exampie, a CPU, a
`
`storage medium such as a RQit/t storing a controi program, a work memorji,i such
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`as a RAM, and a communication circuit.
`
`in this case, the functions of the
`
`components described above are impiemented as the CPU executes the controi
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`program.
`
`goose} Next, a series of operations of the vvireiess communication device tilt}
`
`and the wireiess communication device 200 according to the first embodiment wiii
`
`be described with reference to Fig. 4.
`
`{(3045}
`
`Fig. 4 is a sequence diagram iiiustrating an exampie of a series of
`
`operations according to the first embodiment.
`
`in the foiiowing, a case in which the
`
`wireiess communication device 100 is a base station device (referred to as a base
`
`station device 100 for convenience) and the wireiess communication device 200 is
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`a terminai device (referred to as a terminai device 200 for convenience) wiii be
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`descnbed.
`
`{G946} The base station device 100 and the terminai device 280 carry out BFT
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`simiiar to the one of the existing techniques described with reference to Fig. 1A to
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`Fig. it) and Fig. 2 in the initiai instance of connection (when the iii‘ik is estabiished
`
`therebetween). Thereafter, in piace of the second and subsequent instances of
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`periodic BFT, the base station device 100 and the terminai device 200 carry out
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`the EFT operation according to the first embodiment described hereinafter. The
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`EFT operation according to the first embodiment described hereinafter is a kth
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`instance of EFT operation (it is an integer no smaiier than 2), and the terminai
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`device 200 retains the information on the narrowiy directionai transmission beam
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`that the terminai device 200 has used in data communication after the (it—t)th
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`instance tie, the previous instance) of BFT operation (hereinafter, referred to as
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`the best beam of the terminai device 200 of the previous instance ((it—t)th
`
`instance).
`
`{604?} The best beam of the terminai device 200 of the previous instance refers
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`to the best narrowiy directionai transmission beam set by the terminai device 200
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`prior to the current instance of BFT operation.
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`{@648}
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`in Fig. 4, a series of EFT operations according to the first embodiment
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`inciudes an operation 1, an operation 2, and an operation 3. Atthough the detaiis
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`wiii be given tater, in the series of BFT operations according to the first
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`embodiment, the base station device 100 and the terminai device 200 may start
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`data communication without carrying out the operation 3, depending on the
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`conditions. Hereinafter, each of the operations wiit be described.
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`Operation t
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`{964%}
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`in the operation 1, the terminai device 280 determines the best beam of
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`the base station device 100 of the current instance.
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`{tidbit}
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`in the operation 1, the base station device ttiO periodicaih,i transmits a
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`beacon, as in the existing techniques (eg, iEEE 802.1tad~2012 standard,
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`December 28, 2012). The base station device 100 transmits beacons white
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`switching the beam direction of the narrovviy directiohai transmission beam Txn
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`among a piuraiitji,i of beam directions. The beacons transmitted with the use of the
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`transmission beam Txn in the respective beam directions inciude the identification
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`information of the corresponding beam directions.
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`{@051} The terminai device 200 receives a piuraiity of beacons transmitted from
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`the base station device too by using the wideiy directionai reception beam Ryw,
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`as the terminai device 200 knows the transmission intervai of the beacons
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`i 1
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`transmitted from the base station device 100. Then, the terminai device 209
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`caicuiates the reception ouaiity of each beam direction and determines the best
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`beam for the base station device 100 to communicate with the terminai device 230
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`(the best beam). For exampie, the terminai device 206 determines the beam with
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`the highest reception duaiity, among the reception duaiities of the respective beam
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`directions, as the best beam. The determined best beam is the best beam of the
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`base station device 100 of the current instance (kth instance).
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`Operation 2
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`{9952}
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`in the operation 2, the base station device 100 is notified of the
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`information on the best beam of the base station device ”Edd of the current
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`instance determined by the terminai device 200 in the operation 1, and whether
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`the best beam used by the terminai device 280 in the previous instance of data
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`communication can continue to be used in the current instance of data
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`communication is checked.
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`{0053}
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`in the operation 2, the terminai device 206 transmits, to the base station
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`device 100, a feedback signai (hereinafter, abbreviated to F8) by using the best
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`beam (Tyan—i )) of the terminai device 200 of the previous instance ((k—t)th
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`instance). The F8 stores the beam direction information indicating the best beam
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`of the base station device 100 of the current instance (kth instance) determined in
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`the operation 1.
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`{boss}
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`For the FB, a sector sweep feedback frame described in EEEE 802.11ad-
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`2012 standard, December 28, 2012, may be used, for exampie.
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`{9655} The base station device tot) determines whether the base station device
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`100 has received the F8 from the terminai device 200 by using the wideiy
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`directionai reception beam Rxw. Then, if the base station device 100 has received
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`the FE, the base station device 100 sets the best beam (Txnmiiitn of the base
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`station device ’itit‘i of the current instance (kth instance) indicated by the beam
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`direction information stored in the FB as the beam to be used in the current
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`instance of data communication. Then, the base station device 100 transmits, to
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`the terminai device 200, an acknowiedgement (ASK) by using the set best beam
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`(Txnmiikh of the base station device 100 of the current instance (kth instance).
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`goose}
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`it the terminai device 200 has received the ACK by using the best beam
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`(TynJ‘iit—th of the previous instance, the base station device 100 and the terminai
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`device 2630 start data communication without carrying out the operation 3.
`t2
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`{965?}
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`it the terminat device 200 has received the ACK from the base station
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`device 100 by using the best beam (Tynflfikuti) ot the previous instance, this
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`suggests that the FB transmitted by the terminai device 200 by using the best
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`beam (Tyng'dt-t )) of the previous instance has been received by the base station
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`device tut) and the received ACK satisfies the reception quaiity in the data
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`communication.
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`in other words, the termihai device 200 can confirm that the
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`terminai device 200 can communicate with the base station device tQQ by using
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`the best beam (Tynjio‘ih of the previous instance, and thus the base station
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`device 100 and the terminai device 200 can start data communication Without
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`carrying out the operation of determining the best beam of the terminai device 200
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`again by transmitting and receiving training signais.
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`{G958}
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`in a case in which the terminat device 200 does not carry out data
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`communication after receiving the ACK by using of the best beam (Tynmitit—tjj of
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`the previous instance, the terminai device 200 may set the wideiy directionai
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`reception beam Ryw to receive a subsequent beacon transmitted from the base
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`station device tOO (i.e., to carry out the next instance of operation 1). The terminai
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`device 200 mayi carry out an operation such as turning off the power source or
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`entering a steep state, for exampie, untii the timing of receiving the beacon.
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`{G959} On the other hand, it the terminai device 200 has received no ACK by
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`using the best beam (Tyn__i(it~t)) of the previous instance or it the terminai device
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`200 has received the ACK but the reception duaiity in the data communication is
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`not satisfied, the base station device 106 and the terminai device 200 carry out the
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`operation 3.
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`goose}
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`if the termihai device 200 has received no ACK by using the best beam
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`(Tyn_j(i<~t)_) of the previous instance, this suggests, tor exampie, that the FE from
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`the terminai device 200 has taiied to reach the base station device tQO, that the
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`terminai device 200 has had ditticuity receiving the ACK from the base station
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`device tut), orthat the reception duaiity in the data communication is not satisfied.
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`in other words, the terminai device 200 determines that it is ditticuit to
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`communicate with the base station device 100 with the best beam (Tynfliijio‘ih of
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`the previous instance and carries out the operation 3 of determining the best beam
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`of the terminai device 200.
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`{@661} The base station device tGO and the terminai device 206 carry out the
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`operation 3 in a case in which the FE does not reach the base station device 100
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`or it is ditticuit to receive the ACK from the base station device 100 due to an
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`intiuence of interference, tor exampie, even though the best beam (Tynmxku’ih of
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`the terminai device 200 of the previous instance satisfies the reception duaiity in
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`the data communication with the base station device tilt) in the operation 2.
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`Operation 3
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`{(39623
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`in the operation 3, the base station device 100 determines the best beam
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`of the terminai device 206 of the current instance and notifies the terminai device
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`200 of the information on the determined best beam.
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`roses}
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`in the operation 3, the terminai device 200 tran