JP2010087912A - Wireless communication system and method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wireless communication system and method capable of reducing processing necessary for handover. <P>SOLUTION: A first base station 100-1 in the wireless communication system creates a cell search report by performing cell search of all resources. The first base station 100-1 transmits the created cell search report to intermediate base stations 100-2 to 100-5. Each of the intermediate base stations 100-2 to 100-5 selects M resources of high reception quality from the cell search report received from the first base station 100-1 and performs cell search. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

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

  It is desired that wireless LAN communication can be comfortably performed even in a high-speed moving vehicle such as an automobile or a train, as in an office or home environment. Generally, in a wireless LAN system, a terminal (ST) is connected to a public Internet network via an access point (AP).

  Unlike an office or home environment, an access point provided in a high-speed moving vehicle communicates with a base station wirelessly in order to connect to a public Internet network. Therefore, it is necessary for the access point to perform handover for switching base stations as the high-speed moving body moves. In order to reduce the processing load when an access point provided in a high-speed moving body performs a handover, a technique using handover information of another moving body is known (for example, see Patent Document 1).

In the handover method described in Patent Document 1, the roadside device control server collects cell edge information from the mobile body that has performed the handover. The position information is loaded on the cell edge information, and the roadside machine control server distributes the cell edge information to the roadside machine based on the position information. A car navigation system mounted on a vehicle acquires cell edge information from a roadside device, and instructs a moving body in the vehicle to perform handover based on the cell edge information.
Japanese Patent Laid-Open No. 2003-9207

  In order for a mobile unit to perform a handover, it is necessary to acquire a cell search report periodically transmitted from a base station. This cell search report is not described in Patent Document 1, and the mobile body needs to acquire the cell search report every time. The cell search report needs to be acquired periodically, which causes a large processing burden on the moving body.

  Accordingly, the present invention has been made to solve the above-described problems, and an object of the present invention is to provide a wireless communication system and a wireless communication method that can reduce processing necessary for performing handover.

  In order to achieve the above object, a wireless communication system of the present invention is a wireless communication system having a first wireless communication device and a second wireless communication device respectively installed in a plurality of vehicles moving in the same direction. The first wireless communication apparatus is configured to change one or both of a frequency and a code sequence to receive information periodically transmitted by a base station, and a plurality of combinations of the frequency and code sequence And a search report generation unit that generates a search report that associates the reception quality of the information received at the time of the combination, and a transmission unit that transmits the search report to the second wireless communication device. The second radio communication device includes a second receiver that receives the search report from the first radio communication device, and a set of frequency and code sequence from the search report. A selection unit that selects M (M is an integer of 1 or more) in order of reception quality, and information that is periodically transmitted by the base station using a combination of frequencies and code sequences selected by the selection unit. And a third receiving unit.

  The wireless communication method of the present invention is a wireless communication method of the first wireless communication device and the second wireless communication device respectively installed in a plurality of vehicles moving in the same direction, wherein the first wireless communication A first receiving step in which a first receiving unit of the apparatus changes one or both of a frequency and a code sequence and receives information periodically transmitted by a base station; and a search report of the first wireless communication apparatus A generating step for generating a search report in which a plurality of combinations of the frequency and code sequence are associated with reception quality of the information received at the time of the combination, and transmission of the first wireless communication device A transmission and transmission step unit for transmitting the search report to the second wireless communication device; and a second reception unit of the second wireless communication device for transmitting the search report to the first wireless communication device. A second reception step of receiving from the device, and a selection unit of the second wireless communication apparatus, from the search report, a combination of frequency and code sequence M in descending order of reception quality (M is an integer of 1 or more) A selection step of selecting one, and a third reception unit of the second wireless communication apparatus receiving a information periodically transmitted by the base station at a combination of frequency and code sequence selected by the selection unit. And a receiving step.

  ADVANTAGE OF THE INVENTION According to this invention, the radio | wireless communications system and radio | wireless communication method which can reduce a process required in order to perform a handover can be provided.

  Embodiments of the present invention will be described below with reference to the drawings.

  A wireless communication system according to a first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a diagram illustrating an outline of a wireless communication system according to the present embodiment. The radio | wireless communications system concerning a present Example is provided in a high-speed moving body like a train.

  In the example of FIG. 1, the wireless communication system has an in-vehicle base station 100-n in each vehicle 10-n (n is an integer of 1 or more) of the train 1.

  The in-vehicle base station 100-n communicates between a terminal 200-k in the vehicle 10-n (k is an integer of 1 or more) and a base station 300-1 outside the vehicle (hereinafter referred to as an out-of-vehicle base station). Relay.

  The train 1 proceeds in the direction of the arrow shown in FIG. 1 and gradually moves from the cell 310 of the out-of-vehicle base station 300-1 to the cell 320 of the out-of-vehicle base station 300-2. With this movement, the in-vehicle base station provided in each vehicle 10-n performs handover from the out-of-vehicle base station 300-1 to the out-of-vehicle base station 300-2 instead of the terminal 200-k. The terminal 200-k does not need to perform a handover with a heavy processing load.

  Next, the detail of the train 1 concerning a present Example is demonstrated using FIG. A train 1 (high-speed moving body) illustrated in FIG. 2 includes a plurality of vehicles 10-n (n is an integer equal to or greater than 1. FIG. 2 illustrates an example of n = 5) connected in a row. . Each vehicle 10-n is provided with one in-vehicle base station 100-n, and there are a plurality of terminals 200-k.

  The in-vehicle base stations 100-n provided in each vehicle 10-n are connected by wire or wirelessly. The in-vehicle base station 100-1 (hereinafter referred to as the head base station) provided in the head vehicle 10-1 of the train 1 periodically performs a cell search and generates a cell search report. The leading base station 100-1 transmits the generated cell search report to other in-vehicle base stations.

  On-vehicle base stations (hereinafter referred to as intermediate base stations) provided in vehicles (hereinafter referred to as intermediate vehicles) other than the leading vehicle 10-1 are based on a cell search report transmitted from the leading base station 100-1. Cell search. Details of the cell search performed by the in-vehicle base station 100-n will be described later.

  Next, the configuration of the leading base station 100-1 will be described using FIG. The leading base station 100-1 (first wireless communication device) includes an antenna 101 for vehicle exterior, a vehicle exterior radio unit 102 (receiver), and a vehicle exterior communication unit for communicating with the vehicle base station 300-1 (not shown). 103, an in-vehicle antenna 111 for communicating with the terminal 200-k in the vehicle, an in-vehicle wireless unit 112, an in-vehicle communication unit 113, a cell search unit 130 (search report generating unit) for performing cell search, It has an out-of-vehicle communication control unit 140 that controls communication with an out-of-vehicle base station, and an inter-base station communication unit 150 (transmitting unit) that communicates with other in-vehicle base stations.

  The outside radio unit 102 is connected to the outside antenna 101, the outside communication unit 103, and the cell search unit 130. The outside radio unit 102 performs radio processing such as signal amplification, frequency conversion (down conversion), orthogonal demodulation, and the like on the radio signal received via the outside antenna 101 to generate a baseband signal.

  In addition, the outside radio unit 102 performs radio processing such as orthogonal modulation, frequency conversion (up-conversion), and power amplification on the baseband signal generated by the outside communication unit 103 to generate a radio signal. This radio signal is transmitted to the outside base station via the outside antenna 101.

  The vehicle exterior communication unit 103 is connected to the vehicle exterior radio unit 102 and the vehicle interior communication unit 113. The out-of-vehicle communication unit 103 performs signal processing such as error correction and demodulation processing on the baseband signal generated by the out-of-vehicle wireless unit 102, and generates relay data. The out-of-vehicle communication unit 103 performs signal processing such as addition of an error correction code and modulation processing on the relay data generated by the in-vehicle communication unit 113 to generate a baseband signal.

  The in-vehicle communication unit 113 is connected to the in-vehicle wireless unit 112 and the out-of-vehicle communication unit 103. The in-vehicle communication unit 113 performs signal processing such as addition of an error correction code and modulation processing on the relay data generated by the out-of-vehicle communication unit 103 to generate a baseband signal. The in-vehicle communication unit 113 performs signal processing such as error correction and demodulation processing on the baseband signal generated by the out-of-vehicle wireless unit 112, and generates relay data.

  The in-vehicle wireless unit 112 is connected to the in-vehicle antenna 111 and the in-vehicle communication unit 113. The in-vehicle wireless unit 112 performs wireless processing such as orthogonal modulation, frequency conversion (up-conversion), and power amplification on the baseband signal generated by the in-vehicle communication unit 113 to generate a wireless signal. This radio signal is transmitted to the base station outside the vehicle via the in-vehicle antenna 111.

  In addition, the in-vehicle wireless unit 112 performs wireless processing such as signal amplification, frequency conversion (down conversion), and orthogonal demodulation on the wireless signal received via the in-vehicle antenna 111 to generate a baseband signal.

The cell search unit 130 is connected to the out-of-vehicle radio unit 102, the out-of-vehicle communication control unit 140, and the inter-base station communication unit 150. The cell search unit 130 performs cell search by extracting broadcast information transmitted from the base stations 300-1, 300-2, ... from the baseband signal generated by the radio unit 102 outside the vehicle . Cell search is periodically performed for all resources such as frequency and code sequence. The cell search unit 130 generates a cell search report based on the extracted broadcast information and the received power of each cell.

  The vehicle exterior communication control unit 140 is connected to the cell search unit 130. The out-of-vehicle communication control unit 140 selects a cell (out-of-vehicle base station) to which the base station 100-1 is connected based on the cell search report. The out-of-vehicle communication control unit 140 controls the out-of-vehicle communication unit 103 so as to communicate with the selected cell (outside vehicle base station).

  The inter-base station communication unit 150 is connected to the cell search unit 130 and the intermediate base station. The inter-base station communication unit 150 distributes the cell search report to the intermediate base station.

  Then, the structure of an intermediate | middle base station is demonstrated using FIG. Here, although the in-vehicle base station 100-2 of FIG. 2 will be described, the configurations of the other intermediate base stations (in-vehicle base stations 100-3 to 100-5) are the same.

  The intermediate base station 100-2 (second radio communication apparatus) shown in FIG. 4 has substantially the same configuration as the top base station 100-1, except that it includes a cell search control unit 160 (selection unit). ing.

  Cell search control unit 160 is connected to cell search unit 131 and inter-base station communication unit 150. The cell search control unit 160 selects a resource for the cell search unit 131 to perform a cell search based on the cell search report input from the inter-base station communication unit 150.

  The cell search unit 131 is connected to the outside radio unit 102, the outside communication control unit 140, and the cell search control unit 160. Similar to the cell search unit 130 of the leading base station 100-1, the cell search unit 131 performs cell search by extracting broadcast information transmitted by the out-of-vehicle base station from the baseband signal generated by the out-of-vehicle radio unit 102. . This cell search is performed only for the resource selected by the cell search control unit 160. This is different from the cell search unit 130 of the leading base station 100-1 that performs cell search for all resources.

  Next, the operation of the wireless communication system according to the present embodiment will be described. First, a relay operation in which each in-vehicle base station 100-n relays exchanges between the terminal 200-k and the out-of-vehicle base station 300-1 will be described. Since the relay operation is the same for all in-vehicle base stations 100-n, the case of the head base station 100-1 will be described here.

(Relay operation for relaying signal from terminal 200-1 to base station 300-1 outside vehicle)
A radio signal transmitted from the terminal 200-1 is input to the in-vehicle wireless unit 102 via the in-vehicle antenna 111. The radio signal is converted into a baseband signal by radio processing such as signal amplification, frequency conversion (down conversion), quadrature demodulation and the like in the in-vehicle radio unit 112.

  The baseband signal is passed from the in-vehicle wireless unit 112 to the in-vehicle communication unit 113. The baseband signal is subjected to signal processing such as error correction and demodulation processing in the in-vehicle communication unit 113, and converted into relay data.

  The relay data is passed from the in-vehicle communication unit 113 to the out-of-vehicle communication unit 103. The relay data is subjected to signal processing such as addition of an error correction code, modulation processing, and the like in the external communication unit 103, and is converted into a baseband signal.

  The baseband signal is passed from the vehicle exterior communication unit 103 to the vehicle exterior radio unit 102. The baseband signal is converted into a radio signal by radio processing such as quadrature modulation, frequency conversion (up-conversion), signal amplification and the like in the radio unit outside the vehicle. The radio signal is transmitted to the base station outside the vehicle via the antenna 101 outside the vehicle.

  In addition, since the operation | movement which relays the signal from the base station 300-1 to the terminal 200-1 should just perform the operation | movement contrary to the case where the signal from the terminal 200-1 is relayed to the base station 300-1 outside, The description here is omitted.

  Subsequently, a cell search operation performed by the leading base station 100-1 will be described with reference to FIG. The leading base station 100-1 periodically performs a cell search.

(Cell search operation of leading base station 100-1)
The cell search is performed for N carrier frequencies and K spreading codes from among a frequency band and a plurality of spreading codes that can be received by the in-vehicle base station 100-n. Therefore, the leading base station 100-1 periodically repeats a total of N × K cell searches.

First, the cell search unit 130 selects one carrier frequency for cell search, and instructs the vehicle exterior communication control unit 140. (Steps S101 and S102)
The vehicle exterior communication control unit 140 controls the vehicle exterior communication unit 103 to receive a signal having a carrier frequency instructed from the cell search unit 130.

  The cell search unit 130 performs signal processing such as demodulation processing on the baseband signal received by the outside radio unit 102. At this time, cell search section 130 performs demodulation processing using a plurality (K) (spreading) codes. Thus, the cell search unit obtains broadcast information transmitted from the base station outside the baseband signal. (Steps S103 to S108)

Furthermore, cell search section 130 measures the received power of the baseband signal when broadcast information can be acquired. (Step S109) The above cell search is repeated by changing the carrier frequency. (Steps S110 and S111)
When cell search is performed for all resources, cell search unit 130 creates a cell search report based on the cell search result. (Step S112)

  FIG. 6 shows an example of a cell search report created by the cell search unit 130. As shown in FIG. 6, cell search section 130 creates a report by associating the frequency at which broadcast information is received, the type of spreading code, and received power. At this time, the order is set in descending order of the received power.

  As shown in FIG. 6, the order may be associated as a part of the table, or the table may be created in descending order of received power.

  Further, the order is not limited to the received power, but may be any order that represents the reception quality. For example, the cell search reports may be created in the order of large (or small) variation in received signal SN ratio, variation in received power compared to the previous cell search result, and the like.

  The intermediate base stations 100-2 to 100-5 perform a cell search based on a cell search report created by the leading base station 100-1.

(Cell search operation of intermediate base station)
The cell search control unit 160 that has received the cell search report via the inter-base station communication unit 150 selects the top M resources with high reception quality from among the resources described in the cell search report.

  The cell search unit 131 performs a cell search for the M resources selected by the cell search control unit 160. Since the specific operation of the cell search performed by the cell search unit 131 is the same as the cell search operation of the cell search unit 130 of the leading base station 100-1, description thereof will be omitted.

  The out-of-vehicle communication control unit 140 of the intermediate base stations 100-2 to 100-5 selects a cell (out-of-vehicle base station) to which the intermediate base stations 100-2 to 100-5 are connected based on the cell search result of the cell search unit 131. To do. The out-of-vehicle communication control unit 140 controls the out-of-vehicle communication unit 103 so as to communicate with the selected cell (outside vehicle base station). Note that the cell search unit 131 may create a cell search report for M resources for which cell search has been performed in order to select a cell to which the out-of-vehicle communication control unit 140 is connected.

  As described above, according to the first embodiment, the cell search report of the leading base station 100-1 is transmitted to the intermediate base stations 100-2 to 100-5, and the intermediate base station By selecting a resource with high communication quality and performing a cell search, the number of cell searches of the intermediate base stations 100-2 to 100-5 can be reduced.

  The cell search is periodically performed regardless of the handover timing, and reducing the number of cell searches greatly contributes to the reduction of processing necessary for performing the handover.

  Next, a second embodiment of the present invention will be described with reference to FIG. For example, when a high-speed moving body is matched by a train, there is a possibility that the leading vehicle and the trailing vehicle are switched depending on the traveling direction. In addition, the intermediate vehicle may become the leading vehicle due to the connection of the vehicles.

  In this embodiment, in order to deal with the above-described case, a case where a leading base station is provided in a plurality of vehicles will be described. Hereinafter, an in-vehicle base station that performs cell search for all resources is referred to as a head base station, and other in-vehicle base stations are referred to as intermediate base stations. Therefore, a leading base station may be provided in addition to the leading vehicle.

  The intermediate base station 100-22 of the wireless communication system according to the present embodiment includes a report storage unit 170 (storage unit) that stores the cell search report received from the head base station. Since the other configuration is the same as that of the first embodiment, description thereof is omitted.

  FIG. 7 is a block diagram of the configuration of the intermediate base station 100-22 according to the present embodiment. As shown in FIG. 7, the report storage unit 170 is connected to the cell search control unit 160.

A cell search report received by the cell search control unit 160 via the inter-base station communication unit 150 is stored in the report storage unit 170.

  Next, the operation of the wireless communication system according to the present embodiment will be described. The operation of the radio communication system according to the present embodiment is the same as that of the radio communication system shown in FIG. 1 except for the cell search operation of the intermediate base station 100-22.

(Cell search operation of intermediate base station)
The cell search control unit 160 stores the cell search report received from the inter-base station communication unit 150 in the report storage unit 170.

  The cell search control unit 160 that has newly received a cell search report from the inter-base station communication unit 150 refers to the report storage unit 170 and compares the cell search report received last time with the latest cell search report.

  The cell search control unit 160 selects a resource whose reception quality is improved from the previous cell search and instructs the cell search unit 131 to perform a cell search. At this time, in addition to resources with improved reception quality, M resources with good reception quality may be selected from the latest cell search reports.

  The cell search control unit 160 that has selected the resource for cell search stores the latest cell search report in the report storage unit 170. At this time, the latest cell search report may be overwritten on the previous cell search report. If multiple cell search reports can be stored, the previous cell search report is deleted and the latest cell search report is overwritten. May be.

  When the report storage unit 170 can store a plurality of cell search reports, the contents of all cell search reports may be compared with the contents of the latest cell search report.

  As described above, according to the second embodiment, the same effect as in the first embodiment can be obtained, and the number of cell searches can be reduced even when the leading base station is provided in a vehicle other than the leading vehicle. Can be reduced.

  When the leading base station is provided in a plurality of vehicles, the intermediate base station may receive a plurality of cell search reports having different cell search results. The intermediate base station compares a plurality of cell search reports and selects a resource for cell search. As a result, the intermediate base station uses the cell search report transmitted from the head base station provided in the head vehicle (or the head base station closest to the head vehicle among the plurality of head base stations), based on the cell search report. Since a resource to be searched can be selected, a cell search can be performed more efficiently. This is because, as shown in FIG. 1, it is considered that the head base station located at the head in the traveling direction reaches the cell to be handed over first.

(Modification 1)
A modification 1 of the intermediate base station according to the second embodiment will be described. The cell search control unit 160 of the intermediate base station according to the present modification does not select a resource whose reception quality has improved from the previous time, but performs a cell search for the resource newly added to the cell search report. The cell search unit 131 is instructed. At this time, in addition to the resources newly added to the cell search report, M resources having good reception quality may be selected from the latest cell search reports.

(Modification 2)
A modification 2 of the intermediate base station according to the second embodiment will be described. The report storage unit 170 of the intermediate base station according to the present modification does not store the latest cell search report, but stores a cell search report in which cell search reports of a plurality of leading base stations are aggregated.

  The cell search control unit 160 compares the contents of the cell search report of each head base station, and stores the resource with the highest reception quality in the report storage unit 170 together with the reception quality.

  Specifically, when receiving the latest cell search report, the cell search control unit 160 refers to the aggregate cell search report stored in the report storage unit 170 and selects a resource for performing the cell search. As described above, this selection method may be a resource with improved reception quality or a newly added resource.

  The cell search control unit 160 that has selected the resource updates the aggregated cell search report. If there is a resource with a higher reception quality described in the latest cell search report than the aggregate cell search report, the reception quality is replaced with the latest one. If there are resources not listed in the aggregate cell search report, the resources and reception quality are newly added to the aggregate cell search report.

  As described above, the cell search control unit 160 creates the aggregated cell search report, so that the storage capacity of the report storage unit 170 can be reduced as compared with the case of storing a plurality of cell search reports.

  Note that the present invention is not limited to the above-described embodiments as they are, and can be embodied by modifying the components without departing from the scope of the invention in the implementation stage. Various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the above embodiments. For example, some components may be deleted from all the components shown in the embodiments. Furthermore, constituent elements over different embodiments may be appropriately combined.

1 is a diagram showing an outline of a wireless communication system according to a first embodiment of the present invention. The figure which shows the structure of the radio | wireless communications system which concerns on 1st Example of this invention. The block diagram which shows the structure of the head base station 100-1 which concerns on the 1st Example of this invention. The block diagram which shows the structure of the intermediate | middle base station 100-2 which concerns on 1st Example of this invention. The flowchart explaining the cell search operation | movement which concerns on 1st Example of this invention. The figure which shows an example of the cell search report which concerns on 1st Example of this invention. The block diagram which shows the structure of intermediate | middle base station 100-22 based on 2nd Example of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Train, 10-n ... Vehicle 101, 111 ... Antenna 102, 112 ... Radio | wireless part 103, 113 ... Communication part 130, 131 ... Cell search part 140 ... Outside a vehicle Communication control unit 150 ... Inter-base station communication unit 160 ... Cell search control unit 170 ... Report storage unit

Claims (8)

A wireless communication system having a first wireless communication device and a second wireless communication device respectively installed in a plurality of vehicles moving in the same direction,
The first wireless communication device is:
A first receiving unit that receives information periodically transmitted by the base station by changing one or both of the frequency and the code sequence;
A search report generating unit that generates a search report in which a plurality of combinations of the frequency and code sequence are associated with the reception quality of the information received at the time of the combination;
A transmission unit for transmitting the search report to the second wireless communication device;
With
The second wireless communication device is:
A second receiver for receiving the search report from the first wireless communication device;
A selection unit that selects M (M is an integer of 1 or more) combinations of frequencies and code sequences in descending order of reception quality from the search report;
A third receiving unit that receives information periodically transmitted by the base station using the combination of frequencies and code sequences selected by the selecting unit;
A wireless communication system comprising:   The second wireless communication apparatus further includes a storage unit that stores a search report, and the selection unit compares the search report received by the reception unit with the search report stored by the storage unit, The radio communication system according to claim 1, wherein a combination of a frequency and a code sequence with improved reception quality is selected.   The selection unit selects N (N is an integer of 1 or more) combinations of frequencies and code sequences with high reception quality in addition to combinations of frequencies and code sequences with improved reception quality. The wireless communication system described in 1.   The second wireless communication apparatus further includes a storage unit for storing a search report, and the selection unit is in a search report received by the reception unit and not in a search report stored by the storage unit. The wireless communication system according to claim 1, wherein a combination of a code sequence and a code sequence is selected.   The selection unit includes N (N is an integer of 1 or more) combinations of frequencies and code sequences having high reception quality, in addition to combinations of frequencies and code sequences not included in the search report stored in the storage unit, from the received search report. The wireless communication system according to claim 4, wherein the wireless communication system is selected.   The wireless communication system according to claim 2, wherein the selection unit deletes the search report stored in the storage unit and stores the received search report.   The selection unit selects the higher received quality from the received search report and the search report stored in the storage unit to generate an aggregate search report, and the storage unit stores the aggregate search report The wireless communication system according to claim 2 or 4, characterized by the above. A wireless communication method for a first wireless communication device and a second wireless communication device respectively installed in a plurality of vehicles moving in the same direction,
A first receiving step in which the first receiving unit of the first wireless communication apparatus receives information that the base station periodically transmits by changing one or both of a frequency and a code sequence;
A generation step in which a search report generation unit of the first wireless communication apparatus generates a search report in which a plurality of combinations of the frequency and code sequence are associated with reception quality of the information received at the time of the combination; ,
A transmission / transmission step unit for transmitting the search report to the second wireless communication device by the transmission unit of the first wireless communication device;
A second receiving step in which a second receiving unit of the second wireless communication device receives the search report from the first wireless communication device;
A selection step in which the selection unit of the second wireless communication device selects M (M is an integer of 1 or more) combinations of frequencies and code sequences in descending order of reception quality from the search report;
A third receiving step in which the third receiving unit of the second wireless communication apparatus receives information periodically transmitted by the base station with the combination of frequency and code sequence selected by the selecting unit;
A wireless communication method comprising:

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