JP2011135264A - Mobile communication system and wireless communication method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a mobile communication system which reduces a connection time from a mobile station to a base station and secures communication resources necessary for connection of mobile stations, and also to provide a wireless communication method. <P>SOLUTION: A base station assigns a wireless communication channel in a communication frame after a specified timing to a connected mobile station from the communication frame to transmit and receive communication data. Based on the assigned wireless communication channel, the base station generates communication resource information indicating the using rate of wireless communication channels in communication frames, adds the generated communication resource information to notification information, and transmits it to a mobile station. The mobile station receives communication resource information from a plurality of base stations, and detects wireless quality values, based on wireless signals transmitted from the plurality of base stations. When starting wireless communication, the mobile station selects a base station that is a connection destination, based on the communication resource information and wireless quality values of the plurality of base stations. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a mobile communication system and a wireless communication method.

  In a conventional mobile communication system, a mobile station selects a base station as a connection destination based on the reception quality of radio signals transmitted from neighboring base stations.

  For example, XGP (eXtended Global Platform) adopting OFDMA (Orthogonal Frequency Division Multiple Access) and TDMA / TDD (Time Division Multiple Access / Time Division Duplex) ), The mobile station selects a base station to be connected based on RSSI (Received Signal Strength Indication) of radio signals transmitted from neighboring base stations (see Non-Patent Document 1).

  However, even when a mobile station makes a connection request to a base station selected as a connection destination, the mobile station may be refused connection depending on the usage status of communication resources of the base station. In such a case, the mobile station needs to make a connection request to another neighboring base station again, and depending on the communication status between the surrounding base station and the mobile station, it takes time to connect to the base station. It was.

  Then, for such a problem, there is a possibility that the mobile station is refused to connect to the base station by notifying the surrounding mobile stations of the current communication resource usage status of the base station with broadcast information. A technique for avoiding a connection request to a base station has been proposed (see, for example, Patent Document 1).

JP 2000-324553 A

“ARIB STD-95 Version 1.2“ OFDMA / TDMA TDD Broadband Wireless Access System (Next Generation PHS) ””, March 18, 2009, Radio Industry

  However, in a mobile communication system such as XGP in which the communication resource used between the base station and the mobile station changes for each communication frame, the mobile station notifies the usage status of the communication resource transmitted from the base station. Even if a connection request is made to the selected base station after confirmation from the information, the connection is rejected because there is no communication resource available at that time, or a communication resource that satisfies the throughput according to the communication type of the mobile station is allocated. It may not be possible.

  The present invention has been made in view of the above problems, and provides a mobile communication system and a wireless communication method capable of shortening the connection time of a mobile station to a base station and securing a communication resource necessary for the mobile station to connect. The purpose is to do.

  In order to solve the above-described problems, a mobile communication system according to a first aspect of the present invention is a mobile communication system in which at least a part of a plurality of radio communication channels constituting a communication frame is allocated to a base station and the base station performs communication. The base station assigns a radio communication channel in a communication frame after a predetermined timing from the communication frame, which is assigned to a connected mobile station to transmit and receive communication data. A generation unit that generates communication resource information indicating a usage rate of the radio communication channel in the communication frame based on the radio communication channel allocated by the allocation unit, and the communication resource generated by the generation unit A transmitter that transmits information included in broadcast information, and the mobile station is transmitted by the transmitter. A reception unit that receives communication resource information of each of the plurality of base stations, a detection unit that detects a radio quality value based on a radio signal transmitted from each of the plurality of base stations, and when starting radio communication, Based on the communication resource information and the radio quality value of each of the plurality of base stations, a selection unit that selects a base station that is a connection destination, and a connection request to the base station selected by the selection unit And a controller for performing the operation.

  In order to solve the above-described problems, a wireless communication method according to a second aspect of the invention communicates with a base station and at least a part of a plurality of wireless communication channels constituting a communication frame assigned to the base station. A wireless communication method of a mobile communication system including the mobile station, wherein the base station assigns a wireless communication channel in a communication frame after a predetermined timing to be assigned to a connected mobile station to transmit and receive communication data. Allocating from the communication frame, generating communication resource information indicating a usage rate of the wireless communication channel in the communication frame after the predetermined timing based on the allocated wireless communication channel, and the generated Transmitting communication resource information in broadcast information, and the mobile station transmits the transmission information. When receiving the communication resource information of each of the plurality of base stations, detecting the radio quality value based on the radio signal transmitted from each of the plurality of base stations, and starting radio communication, A step of selecting a base station to be a connection destination based on the communication resource information and the radio quality value of each of the plurality of base stations, and a step of making a connection request to the selected base station; It is characterized by including.

  By acquiring information about communication resources transmitted from the base station by the mobile station, it is possible to shorten the connection time and secure communication resources necessary for the mobile station to connect.

It is a figure which shows the structure of the mobile communication system which concerns on embodiment of this invention. It is a figure which shows the radio channel structure in the mobile communication system which concerns on this embodiment. It is a functional block diagram of the base station which concerns on this embodiment. It is a functional block diagram of the mobile station which concerns on this embodiment. It is a figure which shows an example at the time of selecting the base station used as the connection destination of a mobile station. It is a flowchart which shows the process of the base station in the mobile communication system which concerns on this embodiment. It is a flowchart which shows the process of the mobile station in the mobile communication system which concerns on this embodiment.

  Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a diagram showing a configuration of a mobile communication system 10 according to an embodiment of the present invention. As shown in FIG. 1, a mobile communication system 10 includes a mobile station 12 (only one is shown here), a plurality of base stations 14 (here, base stations 14-1 to 14- located around the mobile station 12). 3 is shown). Here, it is assumed that the cells 16-1 to 16-3 of the base stations 14-1 to 14-3 overlap each other.

  The base station 14 performs radio communication with the mobile station 12 located in the cell 16 of the own station by the OFDMA method and the TDMA / TDD method. Examples of the mobile station 12 include a mobile phone, a communication card, and a portable information terminal with a built-in communication function.

  FIG. 2 is a diagram showing a radio channel configuration in the mobile communication system 10 (vertical axis: frequency, horizontal axis: time). As shown in FIG. 2, in the mobile communication system 10, a TDMA frame having a predetermined period (here, 5 ms) is divided into an uplink subframe (2.5 ms) and a downlink subframe (2.5 ms), and each subframe is further divided. Are equally divided into a plurality of time slots (here, Slot 1 to Slot 4). Between the base stations 14-1 to 14-3, the radio signal transmission / reception timing is synchronized (frame) so that the boundary of the TDMA frame (radio signal transmission / reception cycle) falls within a predetermined time (for example, within ± 10 μs). Is synchronized). In addition, a plurality of OFDMA subchannels (here, Sch1 to Sch18) in a predetermined frequency band are defined.

  The minimum unit of the radio channel that the base station 14 allocates to the mobile station 12 is called a PRU (Physical Resource Unit), and each PRU is one of time slots (Slot 1 to Slot 4) and one of subchannels (Sch 1 to Sch 18). , Belonging to. In both the uplink subframe and the downlink subframe, each PRU is determined to be identified by consecutive PRU numbers (1, 2, 3,...) Starting from 1, and PRUs having the same PRU number are It is supposed to be used in pairs. That is, the PRU is assigned symmetrically in the vertical direction.

  Among these, a PRU belonging to a specific subchannel (here, Sch1) is defined as a CCH (Common Channel) shared by one or more mobile stations 12. Also, non-overlapping CCH transmission / reception timings (hereinafter simply referred to as “CCH timings”) that are repeated at a predetermined cycle are assigned to each base station 14. For example, any one of 80 time slot pairs (4 pairs of upper and lower time slots × 20 frames) included in 20 consecutive frames is assigned to each base station 14 as CCH timing. Each base station 14 transmits / receives various control signals to / from one or more mobile stations 12 located in the cell 16 of the own station at the CCH timing assigned to the own station.

  On the other hand, PRUs belonging to subchannels other than the specific subchannel (here, Sch2 to Sch18) are used as ICH (Individual Channel) individually assigned to each mobile station 12. In principle, one ICH is assigned to each mobile station 12 as an individual control channel and is mainly used for transmission of control information. One or more communication channels are assigned to each mobile station 12 and mainly communication data. EXCH (Extra Channel) and the like used for transmission.

  The mobile station 12 receives a radio signal transmitted from each of the surrounding base stations 14 (including the connected base station 14). Radio signals transmitted from the base station 14 include BCCH (Broadcasting Control Channel) transmitted via the CCH, PCH (Paging Channel), control signals transmitted via the ICH, There are communication signals.

  At this time, the base station 14 transmits communication resource information indicating the usage status of the PRU in the BCCH. And the mobile station 12 grasps | ascertains the usage condition of PRU of each base station 14 contained in BCCH received from the surrounding base station 14. FIG. Then, one of the base stations 14 is selected as a connection destination based on the usage status of the PRU and the reception quality of the radio signal from each base station 14. That is, the mobile station 12 selects a base station 14 that can expect a communication quality higher than a predetermined quality and can secure a communication resource (PRU) necessary for communication as a connection destination. For this reason, in the mobile communication system 10, the mobile station 12 can shorten the connection time to the base station 14 and can secure communication resources required when the mobile station 12 is connected.

  Below, in order to implement | achieve the said process, the structure with which the mobile station 12 in the mobile communication system 10 and the base station 14 are provided is demonstrated concretely.

  First, the structure with which the base station 14 is provided is demonstrated. FIG. 3 is a functional block diagram of the base station 14. As shown in FIG. 3, the base station 14 includes an antenna 20, a reception RF unit 22, a reception baseband unit 24, a control unit 26, a transmission baseband unit 28, and a transmission RF unit 30.

  The antenna 20 receives a radio signal transmitted from each of the surrounding mobile stations 12 and outputs the received radio signal (reception signal) to the reception RF unit 22. Further, the antenna 20 transmits a radio signal supplied from the transmission RF unit 36 to the mobile station 12.

  The reception RF unit 22 includes a low noise amplifier, a frequency converter, a band pass filter, and an A / D converter. The reception RF unit 22 amplifies the radio signal input from the antenna 20 with a low noise amplifier, down-converts it to an intermediate frequency signal, further converts it into a digital signal, and then outputs it to the reception baseband signal unit 24 .

  The reception baseband unit 24 includes a serial-parallel converter, an FFT (Fast Fourier Transform) unit, a parallel-serial converter, and a demodulation unit (not shown). The reception baseband unit 24 performs serial-parallel conversion, CP removal, primary demodulation (fast Fourier transform), parallel-serial conversion, secondary demodulation (symbol demapping), and the like on the digital signal input from the reception RF unit 22. The received data obtained is output to an upper layer (not shown).

  The control unit 26 includes, for example, a CPU and a program that controls the operation of the CPU, and controls each unit of the base station 14. In particular, the control unit 26 functionally includes a message analysis unit 40, a radio quality detection unit 42, a channel allocation unit 44, a communication resource information generation unit 46 and a message generation unit 48, and assigns PRU (ANCH, EXCH) to the mobile station 12. Etc.).

  The message analysis unit 40 extracts various messages from the mobile station 12 from the reception data input from the reception baseband unit 24 and analyzes the contents of the messages. The message from the mobile station 12 extracted from the received data includes an LCH assignment request message, an LCH reassignment request message, a link setting request message, a function extension request message, a connection request message, an ANCH / CSCH switching request message, an ANCH / CSCH. There is a switching confirmation message.

  The radio quality detection unit 42 detects a radio quality value representing the radio quality of each PRU belonging to the use frequency band of the base station 14 based on the complex symbol sequence input from the reception baseband unit 24. Examples of the radio quality value detected by the radio quality detection unit 42 include RSSI (Received Signal Strength Indication) detected by carrier sense (interference wave measurement) and SNR (Signal to Noise Ratio). Power ratio).

  The channel allocating unit 44 is configured such that the wireless quality value detected by the wireless quality detecting unit 42, the PRU availability, the amount of data transmitted to and received from the mobile station 12, the communication type (voice communication, packet communication, etc.), movement The PRU to be allocated to the mobile station 12 is determined based on the contract information of the station 12 (information relating to the upper limit number of PRUs that can be allocated to the mobile station 12). For example, the channel allocation unit 44 determines a PRU to be allocated to the mobile station 12 as an ANCH (Dedicated Control Channel) based on an LCH allocation request message from the mobile station 12. In addition, the channel allocation unit 44 determines one or more PRUs to be allocated to the mobile station 12 as EXCH (communication channel) for each frame or a plurality of frames after a predetermined timing. Further, the channel allocation unit 44 changes the PRU allocated to the mobile station 12 as an ANCH based on the ANCH / CSCH switching request message from the mobile station 12.

  The communication resource information generation unit 46 generates communication resource information indicating the PRU usage rate in the base station 14 based on the PRU allocation in the connected mobile station 12 determined by the channel allocation unit 44.

  The message generator 48 generates a message addressed to the mobile station 12 and outputs the message to the transmission baseband unit 32. The message addressed to the mobile station 12 includes an LCH assignment response message including the number of the PRU assigned to the mobile station 12 as an ANCH, an LCH reassignment response message, a link setup response message, a function extension response message, a connection response message, an ANCH / CSCH switching instruction message. In addition, a message related to broadcast information including communication resource information is also generated.

  The transmission baseband unit 28 includes a serial-parallel converter, an IFFT (Inverse Fast Fourier Transform) unit, a parallel-serial converter, and a modulation unit (not shown). The transmission baseband unit 28 performs primary modulation (symbol mapping) and serial parallel on transmission data addressed to a mobile station 12 being connected or a mobile station 12 around the base station 14 input from an upper layer (not shown). Conversion, secondary modulation (inverse fast Fourier transform), addition of CP, parallel serial conversion, and the like are performed, and the obtained digital signal is output to the transmission RF unit 30.

  The transmission RF unit 30 includes a power amplifier, a frequency converter, a band pass filter, and a D / A converter. The transmission RF unit 36 converts the digital signal input from the transmission baseband unit 34 into an analog signal, then up-converts it to a radio signal, amplifies it to a transmission output level with a power amplifier, and then supplies it to the antenna 20 .

  The storage unit 32 stores information on PRU allocation to the mobile station 12 in the channel allocation unit 44 and the radio quality value detected by the radio quality detection unit 42.

  Next, the structure with which the mobile station 12 is provided is demonstrated. FIG. 4 is a functional block diagram of the mobile station 12. As shown in FIG. 4, the mobile station 12 includes an antenna 50, a reception RF unit 52, a reception baseband unit 54, a control unit 56, a transmission baseband unit 58, a transmission RF unit 60, and a storage unit 62. The

  The antenna 50 receives a radio signal transmitted from each of the surrounding base stations 14 and outputs the received radio signal (reception signal) to the reception RF unit 52. Further, the antenna 50 transmits the radio signal supplied from the transmission RF unit 60 to the base station 14.

  The reception RF unit 52 includes a low noise amplifier, a frequency converter, a band pass filter, and an A / D converter. The reception RF unit 52 amplifies the radio signal input from the antenna 50 with a low noise amplifier, down-converts it to an intermediate frequency signal, further converts it to a digital signal, and then outputs it to the reception baseband signal unit 54 .

  The reception baseband unit 54 includes a serial-parallel converter, an FFT (Fast Fourier Transform) unit, a parallel-serial converter, and a demodulation unit (not shown). The reception baseband unit 24 performs serial-parallel conversion, CP removal, primary demodulation (fast Fourier transform), parallel-serial conversion, secondary demodulation (symbol demapping), and the like on the digital signal input from the reception RF unit 22. The received data obtained is output to an upper layer (not shown).

  The control unit 56 includes, for example, a CPU and a program that controls the operation of the CPU, and controls each unit of the mobile station 12. In particular, the control unit 50 functionally includes a message analysis unit 70, a radio quality detection unit 72, a connection destination selection unit 74, and a message generation unit 76, and performs communication processing such as a connection request to the base station 14 of the mobile station 12. Control related to

  The message analysis unit 70 extracts various messages from the base station 14 from the reception data input from the reception baseband unit 54 and analyzes the contents of the messages. For example, the message analysis unit 30 acquires an LCH (Link Channel) assignment response message from the base station 14 from the received data, and the PRU assigned to the mobile station 12 as an ANCH (Dedicated Control Channel) from the LCH assignment response message. A number (information for identifying an ANCH time slot and subchannel) is acquired. The message from the base station 14 extracted from the received data includes an LCH reassignment response message, a link setup response message, a function extension response message, a connection response message, an ANCH / CSCH switching instruction message in addition to the LCH assignment response message. and so on. Moreover, the content of the message regarding the broadcast information including the communication resource information is analyzed.

  The radio quality detection unit 72 detects a radio quality value representing the radio quality of each PRU belonging to the use frequency band of the base station 14 based on the complex symbol sequence input from the reception baseband unit 54. Examples of the radio quality value detected by the radio quality detection unit 72 include RSSI (Received Signal Strength Indication) detected by carrier sense (interference wave measurement) and SNR (Signal to Noise Ratio). Power ratio).

  The connection destination selection unit 72 selects the base station 14 that is the connection destination of the mobile station 12. For example, when the mobile station 12 performs communication, the connection destination selection unit 72 determines the connection destination based on the communication resource information transmitted from each base station 14 and the radio quality value detected by the radio quality detection unit 72. Base station 14 is selected.

  The message generator 36 generates a message addressed to the base station 14 and outputs the message to the transmission baseband unit 58. Messages addressed to the base station 14 include an LCH allocation request message, an LCH reassignment request message, a link setting request message, a function extension request message, a connection request message, an ANCH / CSCH switching request message, an ANCH / CSCH switching confirmation message, and the like. .

  The transmission baseband unit 58 includes a serial-parallel converter, an IFFT (Inverse Fast Fourier Transform) unit, a parallel-serial converter, and a modulation unit (not shown). The transmission baseband unit 58 performs primary modulation (symbol mapping), serial-parallel conversion, secondary conversion on transmission data that is input from an upper layer (not shown) and is connected to or connected to the base station 14. Modulation (inverse fast Fourier transform), addition of CP, parallel serial conversion, and the like are performed, and the obtained digital signal is output to the transmission RF unit 60.

  The transmission RF unit 60 includes a power amplifier, a frequency converter, a band pass filter, and a D / A converter. The transmission RF unit 36 converts the digital signal input from the transmission baseband unit 34 into an analog signal, then up-converts it into a radio signal, amplifies it to a transmission output level with a power amplifier, and then supplies it to the antenna 50. .

  The storage unit 62 stores the communication resource information analyzed by the message analysis unit 70 and the radio quality value detected by the radio quality detection unit 72.

  Next, an example of connection destination selection in the connection destination selection unit 72 will be described. The mobile station 12 can receive radio signals transmitted from the base stations 14-1 to 14-3. And in selecting the base station 14 used as a connection destination, the radio | wireless quality value in each base station 14 and the communication resource information contained in alerting | reporting information are used. The table in FIG. 5A stores the wireless quality values in the base stations 14-1 to 14-3 acquired by the mobile station 12 and communication resource information (PRU usage rate in each base station) stored in the storage unit 62. Show. Then, the acquired communication resource information and radio quality value are replaced with parameters as shown in the table of FIG. 5B stored in the storage unit 62, for example. Then, the base station 14 having the highest value calculated by (communication resource parameter) × (radio quality value parameter) is selected as the connection destination. In the case of FIG. 5A, the base station 14-1 having the second highest usage rate and the second reception sensitivity in the PRU usage status is selected as the connection destination. In addition, the selection of the base station 14 in the connection destination selection unit 72 may have a function such as “preferentially connect to a base station 14 having a PRU usage rate of XX% or less”. In this case, the parameters are adjusted by weighting the items to be prioritized.

  Next, in the mobile communication system, an example of an operation related to connection destination selection of the mobile station 12 using communication resource information transmitted by the base station 14 will be described.

  FIG. 6 is a flowchart showing processing in which the base station 14 transmits communication resource information.

  As shown in FIG. 6, the base station 14 detects RSSI (one of the radio qualities) from radio signals transmitted from the base stations located in the vicinity and the mobile station 12 (S10). Then, based on the detected RSSI, the availability of PRU, the amount of data transmitted / received to / from the connected mobile station 12, the communication type, the contract information of the mobile station 12, etc., the PRU assigned to the mobile station 12 is determined. Determine (S12). Then, communication resource information indicating the usage rate of the PRU is generated from the allocation of the PRU to the connected mobile station 12 (S14). Then, the generated communication resource information is included in the broadcast information and transmitted (S16).

  Next, the base station 14 determines whether or not a connection request from the mobile station 12 has been made (S18). When a connection request is made (S18: Y), the process proceeds to S20, a connection process with the mobile station 12 that has made the connection request is performed, and communication is started. On the other hand, when the connection request is not made (S18: N), the process proceeds to S10.

  FIG. 7 is a flowchart showing processing in which the mobile station 12 selects the base station 14 to be connected. Here, as shown in FIG. 1, it is assumed that the mobile station 12 can receive radio signals transmitted from the base stations 14-1 to 14-1.

  As shown in FIG. 7, the mobile station 12 receives a RSSI (radio quality) from a radio signal transmitted from each of the base stations 14-1 to 3-1 located around the mobile station 12 in a predetermined cycle (for example, 20 frame cycle). Is detected (S100). Further, the mobile station 12 performs communication resource information in each base station 14 from the broadcast information transmitted from each of the base stations 14-1 to 14-3 (S102).

Next, the mobile station 12 determines whether or not a request to start communication with the base station 14 has been made by a user operation or the like (S104). When a request to start communication is made (S104: Y), the process proceeds to S106. On the other hand, if the request for starting communication has not been made (S104: N), the process proceeds to S100.
When a request to start communication is made (S104: Y), the mobile station 12 evaluates the base station 14 that is the connection destination based on the wireless quality values in the base stations 14-1 to 14-3 and the communication resource information. (S106). Then, the base station 14 to be connected (here, the base station 14-1) is selected (S108). Then, after making a connection request to the base station 14 selected as the connection destination, the mobile station 12 performs a connection process to start communication (S110), and ends this process.

  According to the mobile communication system 10 described above, the mobile station 12 selects a base station 14 that can be reliably connected in advance and can secure such communication resources as a connection destination. For this reason, it is possible to shorten the connection time of the mobile station 12 to the base station 14 and to secure communication resources necessary for the mobile station 12 at the time of connection.

  The present invention is not limited to the above embodiment.

  For example, the present invention is not limited to a scene where the mobile station 12 performs a new connection, but can also be applied to a scene where the mobile station 12 performs a handover.

  10 mobile communication systems, 12 mobile stations, 14 base stations, 16 cells, 20, 50 antennas, 22, 52 reception RF units, 24, 54 reception baseband units, 26, 56 control units, 28, 58 transmission baseband units, 30, 60 Transmission RF section, 32, 62 Storage section, 40, 70 Message analysis section, 42, 72 Radio quality detection section, 44 Channel allocation section, 46 Communication resource information generation section, 48, 76, 74 Connection destination selection section.

Claims (2)

A mobile communication system including a base station and a mobile station that performs communication by being assigned at least a part of a plurality of wireless communication channels that constitute a communication frame to the base station,
The base station
An assigning unit for assigning a wireless communication channel in a communication frame after a predetermined timing to be assigned to a connected mobile station for transmitting and receiving communication data, from the communication frame;
A generating unit that generates communication resource information indicating a usage rate of the wireless communication channel in the communication frame based on the wireless communication channel assigned by the assigning unit;
A transmission unit that includes the communication resource information generated by the generation unit and transmits the information in broadcast information,
The mobile station
A receiver that receives communication resource information of each of the plurality of base stations, transmitted by the transmitter;
A detection unit for detecting a radio quality value based on radio signals transmitted from each of the plurality of base stations;
When starting wireless communication, a selection unit that selects a base station to be connected based on the communication resource information and the wireless quality value of each of the plurality of base stations;
A control unit that makes a connection request to the base station selected by the selection unit,
A mobile communication system. A wireless communication method for a mobile communication system, comprising: a base station; and a mobile station that performs communication by assigning at least a part of a plurality of wireless communication channels that constitute a communication frame to the base station,
The base station
Assigning a wireless communication channel in a communication frame after a predetermined timing to be assigned to a connected mobile station to transmit and receive communication data, from the communication frame;
Generating communication resource information indicating a usage rate of the wireless communication channel in a communication frame after the predetermined timing based on the assigned wireless communication channel;
Including the generated communication resource information included in broadcast information, and
The mobile station
Receiving the transmitted communication resource information of each of the plurality of base stations;
Detecting a radio quality value based on radio signals transmitted from each of the plurality of base stations;
When starting wireless communication, selecting a base station to be connected based on the communication resource information and the wireless quality value of each of the plurality of base stations;
Making a connection request to the selected base station,
A wireless communication method.

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