Abstract:
Disclosed is a wireless communication system using white spaces and a base station that does not have its own backhaul, starts wireless communications without radiating radio waves of frequencies causing interference with primary users. A BS being in isolation starts a wireless communication with a CPE, connected to the internet, so as to access a database to acquire a list of frequencies available for transmission. The BS uses a predetermined frequency to perform the wireless communication with the CPE, and acquires, via this wireless communication, the list of frequencies available for transmission. Thereafter, the BS performs wireless communications with the CPE and with another CPE on the basis of the acquired list of frequencies available for transmission. The BS can hold, in advance, information of the predetermined frequency for which it has been estimated that the BS will cause no interference with the wireless communications of the primary users.

Description:
TECHNICAL FIELD 
       [0001]    This invention relates to a wireless communication system using white space. In particular, this invention relates to a method for allocation of frequencies used in radio communication equipment. 
       BACKGROUND ART 
       [0002]    The recent progress of the information-oriented society is really remarkable. As a communication method for information communication equipment or information communication service, wireless communication is often used for other than cable communication. With this situation, the demand for the limited resource of radio frequencies is increasing. Therefore, lack of a frequency which can be assigned to the communication is becoming a big problem in some countries. Generally, the frequencies are managed by the country under the license. Only the authorized licensees can use the frequencies in limited places and times, with severe managements. The demand for the frequencies will continue increasing in future. Therefore, corresponding to the demand for the frequencies, the new method of the use of the frequency, not to be seized with past method of the use of the frequency, is needed. 
         [0003]    Recently, in order to resolve the problem of lack of frequency, a new method of the utilization of the frequency is being studied. The method may use a frequency band, which has been already assigned to the licensee, but the frequency band is not used in certain spatial and temporal conditions. Such a frequency band may be called a white space. For example, regarding the cognitive wireless communication system, the research and development, or the standardization for this system is currently being enforced. In the cognitive wireless communication system, under the condition that avoiding the influence on the use of the specific frequency for the existing system which is operated by licensed user, the user who has not been licensed to use the frequency can use the frequency flexibly, as a white space. Hereinafter, the user who has an authorized license to use the specific frequency is referred to as a primary user, and the user who has not been licensed to use the specific frequency corresponding to the white space is referred to as a secondary user. For example, those are referred to Non-Patent Literature 1. 
         [0004]    As an example, in Wireless Regional Area Network (WRAN) system, using white spaces, being standardizing in IEEE802.22, by accessing a white space database or a coexistence manager on the IP network (hereinafter, database etc.), each radio station can get a list of frequencies available for transmission and allowable maximum transmission electricities, based on its location information. The list of frequencies available for transmission includes the frequency information that can perform wireless communication without giving a primary user interference. The list of frequencies available for transmission is managed collectively while updating the list at any time, by Spectrum Manager (SM) in Base Station (BS), which is connected to Customer Premises Equipment (CPE). In this way, BS can decide an operative frequency based on the list of frequencies available for transmission. 
         [0005]    In another case, each radio station (BS or CPE, the same applies hereinafter) may include a spectrum sensing functionality. When each radio station detects the condition that the frequency which is decided by the spectrum sensing functionality, has already been used by a primary user, each radio station notifies Spectrum Manager (SM) of this information. Then, SM can exclude this frequency from the list of frequencies available for transmission. By performing a dynamic spectrum access based on the information changing moment by moment in this way, the wireless communication system using a white space can realize the communication for a secondary user while avoiding influence on use of the frequency for a primary user. 
         [0006]    As for the wireless communication system using a white space, various kinds of techniques have been suggested so far. For example, patent literature 1 discloses a wireless communication method using a first base station and a second base station. The first base station can provide first backhaul information to the second base station, by using a shared channel. The shared channel can be supported by a white space channel, Authorized Shared Multi-user (ASM) channel, or Industry Science Medical (ISM) channel. Furthermore, the first base station can provide second backhaul information to the second base station, by using a legacy backhaul channel. 
         [0007]    For example, patent literature 2 disclose a wireless communication method, the wireless communication method is comprised of receiving a first signal under using a first channel, deciding a second channel based on the first signal, receiving a second signal under using the second channel, and communicating with a wireless device under using the second channel based on the communication quality of the second signal. 
       PRIOR ART DOCUMENTS 
     Patent Literature 
       [0000]    
       
         Patent Literature 1, Japanese Patent Application Laid-Open Publication No. 2013-523024 
         Patent Literature 2, Japanese Patent Application Laid-Open Publication No. 2013-529047 
       
     
       Non Patent Literature 
       [0000]    
       
         Non Patent Literature 1, Cognitive Wireless RAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications: Policies and Procedures for Operation in the TV Bands, IEEE Std 802.22-2011, 1 Jul. 2011, Part 22 
       
     
       SUMMARY OF INVENTION 
     Technical Problem 
       [0011]    As described above, the system, being standardizing in IEEE802.22, may be the system performing a secondary use while avoiding the interference in the primary user, by referring to the list of frequencies available for transmission retrieved from a database etc. or by using spectrum sensing functionality in each base station. Here, as illustrated in  FIG. 7 , is a relay communication system using radio communication link prescribed in IEEE 802.22. The relay communication system illustrated in  FIG. 7  includes a first base station (BS 1 )  710  which is connected to the Internet through a backhaul line, a first terminal station (CPE 1 )  711  communicating with BS 1  by radio under using frequency f 1 , a second base station (BS 2 )  720  which is connected to CPE 1   711  by cables, and a second terminal station (CPE 2 )  721  communicating with BS 2   720  by radio under using frequency f 2 . BS 2   720  and CPE 1   711  in  FIG. 7  can function as a relay station. 
         [0012]    The system described in IEEE802.22 is a Time Division Duplex (TDD) system. Then, to reduce interference, it is essential that each BS in the system synchronizes the transmit/receive timing of Superframe or frame, by using a clock function of Global Positioning System (GPS), etc., respectively. Therefore, in the configuration for relay communication as illustrated in  FIG. 7 , transmit/receive timing between BS 2   720  and CPE 1   711 , located closely each other as a relay station, becomes the relations as illustrated in  FIG. 8 . For example, in the timing to transmit a downlink signal (a signal from a higher device to a lower device), CPE 1   711  can receive a downlink signal from BS 1   710  under using frequency f 1 , and BS 2   720  can transmit a downlink signal under using frequency f 2 . As a result, the downlink signal transmitted from BS 2   720 , under using frequency f 2 , may jump into CPE 1   711  with the high electricity and becomes interference. In addition, in the timing to transmit an uplink signal (a signal from a lower device to a higher device), CPE 1   711  can transmit an uplink signal to BS 1   710  under using frequency f 1 , and BS 2   720  can receive an uplink signal under using frequency f 2 . As a result, the downlink signal transmitted from CPE 1   711 , under using frequency f 2 , may jump into BS 2   720  with the high electricity and becomes interference. 
         [0013]    Therefore, the relay station, which is configured by the two radio stations as base station (BS 2 )  720  and the terminal station (CPE 1 )  711 , has problems that an outbreak of the blocking caused by the situation that the electric wave which is radiated from one radio station is received by the other radio station as a high level, a deterioration of signal-to-noise ratio (SNR) caused by the situation that a leakage ingredient out of the band, included in the electric wave which is radiated from one radio station, is received by the other radio station as a high level, and any other interference on the receiving operation of each radio station, configuring the relay station. 
         [0014]    To resolve these problems, the configuration for relay is illustrated in  FIG. 9 . The relay communicating system illustrated in  FIG. 9  includes a first base station (BS 1 )  910  which is connected to the Internet through a backhaul line, a first terminal station (CPE 1 )  911  communicating with BS 1   910  by radio under using frequency f 1 , a second terminal station (CPE 2 )  921  communicatively connected with CPE 1   911  by cables, and a second base station (BS 2 )  920  which is communicatively connected to CPE 2   921  by radio under using frequency f 2 . CPE 1   911  and CPE 2   921  in  FIG. 9  can be cooperating as a relay station. 
         [0015]    In the configuration for relay communication as illustrated in  FIG. 9 , transmit/receive timing between CPE 1   911  and CPE 2   921 , located closely to each other as a relay station, relations illustrated in  FIG. 10 . For example, in the timing to transmit a downlink signal, CPE 1   911  can receive a downlink signal from BS 1   910  under using frequency f 1 , and CPE 2   921  can receive a downlink signal from BS 2   920  under using frequency f 2 . In addition, in the timing to transmit an uplink signal, CPE 1   911  can transmit an uplink signal to BS 1   910  under using frequency f 1 , and CPE 2   921  can transmit an uplink signal under using frequency f 2 . 
         [0016]    In this configuration for relay communication, transmit/receive timing between CPE 1   911  and CPE 2   921 , located closely to each other, is matching. Therefore, CPE 1   911  and CPE 2   921  are not interfering with each other. For example, by allocating the terminal stations (CPE 1   911  and CPE 2   921 ) for two radio stations which configure the relay station, respectively, transmit/receive timing becomes the timing as illustrated in  FIG. 10 . Then, the situation that the other radio station is transmitting a signal when one radio station is receiving a signal can be avoided. In addition, due to the method arranging the terminal stations as relay stations in the domain near the border of the communication area, the efficiency of the arrangement of radio stations can improve, because the domains near the borders of the two communication areas are overlapped. 
         [0017]    BS 2   920  in the configuration for relay communication illustrated in  FIG. 9 , is isolated under the situation that BS 2   920  cannot connect to the Internet because the BS 2   920  cannot establish a radio link with CPE 2   921 . Hereinafter, such a base station (BS) will be called as an isolated base station (an isolated BS). In order to establish a second hop of radio communication, BS 2   920  as an isolated BS tries to start a radio communication using a new white space. But, BS 2   920  cannot get a list of frequencies available for transmission based on its location information, being provided by the database etc. on the Internet, because BS 2   920  has not established a radio link with CPE 2   921 . For example, BS 2   920  radiates electric waves without knowing the frequency which is available to transmit at its location. When BS 2   920  does not have a spectrum sensing functionality, a risk for giving a primary user interference may be increased. 
         [0018]    In view of the problem mentioned above, an embodiment of the present invention provides the wireless communication system using a white space. The wireless communication system includes the isolated BS, can start a radio communication without radiating the electric waves which may interfere with a primary user, before the isolated BS gets the white space information (for example, the list of frequencies available for transmission) based on its location information, from the database etc. 
       Solution to Problem 
       [0019]    To resolve the problem mentioned above, the composition of the wireless communication system regarding an embodiment of the present invention may be as follows. A wireless communication system to conduct communications between a base station and a terminal station uses a white space secondarily. The white space is the frequency that is not used by a primary user among the frequencies licensed to the primary user. The wireless communication system includes a managing apparatus for managing the information of white spaces and the base station, having information of a predetermined frequency, which is estimated so that the base station does not cause interference with the wireless communication of the primary users. 
         [0020]    In order to acquire the information of the white space that is available in the base station, when the base station needs to access the managing apparatus through the wireless communication with a terminal station, being within the cell of the base station, the base station communicated with the terminal station using the predetermined frequency. 
         [0021]    After retrieving the white space information which is available for the base station by accessing the managing apparatus through the radio communication, the base station performs a radio communication with a terminal station within the cell of the base station, by using the white space. 
         [0022]    In addition, an embodiment of the present invention includes the following configuration. 
         [0023]    The terminal station has information of a predetermined frequency, which is estimated so that the base station does not cause interference with the wireless communication of the primary users. 
         [0024]    When the terminal station can access the managing apparatus, the terminal station can search a base station based on the predetermined frequency information. When the terminal station cannot access the managing apparatus, the terminal station searches the base station without making a limit for frequencies. 
         [0025]    In addition, an embodiment of the present invention includes the following configuration. 
         [0026]    In order to access the management apparatus, a first base station does not need to go through wireless communication with the terminal station within the cell of the first base station. In order to access the management apparatus, a second base station needs to go through wireless communication with the terminal station within the cell of the second base station. A relay station relays the communication between the first base station and the second base station. The relay station is configured to connect the first terminal station within the cell of the first base station and the second terminal station within the cell of the second base station by a wire line. In order to acquire the information of the white space that is available in the second base station from the managing apparatus, the second base station communicates with the terminal station in the distance that can communicate by using the predetermined frequency. 
         [0027]    After getting the white space information which is available for the second base station by accessing the managing apparatus through the radio communication, the second base station performs a radio communication with a terminal station within the cell of the second base station by using the white space. 
       Advantageous Effects of the Embodiments 
       [0028]    As stated above, according to this embodiment, the following wireless communication system using white spaces is disclosed. In the multi-hop wireless communication system including a base station which cannot get the information of the white space (for example, the list of frequencies available for transmission) except for via a terminal station, the base station can start communication without radiating any radio waves of frequencies having a possibility to cause interference with primary users, though the condition is before getting white space information. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0029]      FIG. 1  Schematic configuration diagram of the wireless communication system according to the exemplary embodiment of the present invention. 
           [0030]      FIG. 2  Figure depicting the example of concrete configuration of BS. 
           [0031]      FIG. 3  Figure depicting the example of concrete configuration of CPE. 
           [0032]      FIG. 4  Figure depicting the example of frequency utilization under the situation that BS 20  is isolated. 
           [0033]      FIG. 5  Figure depicting the example of frequency utilization just after that CPE 21  was connected to BS 20  by wireless communication. 
           [0034]      FIG. 6  Figure depicting the example of frequency utilization under the situation that BS 22  is connected to the Internet via CPE 21 . 
           [0035]      FIG. 7  Figure depicting the example of system configuration for the relay communication system using IEEE802.22 wireless link. 
           [0036]      FIG. 8  Figure depicting the example of transmitting/receiving timing between CPE 2  and BS 2 , which configure the relay station in the relay communication system illustrated in  FIG. 7 . 
           [0037]      FIG. 9  Figure depicting the example of system configuration for the relay communication system using IEEE802.22 wireless link. 
           [0038]      FIG. 10  Figure depicting the example of transmitting/receiving timing between CPE 1  and CPE 2 , which configure the relay station in the relay communication system illustrated in  FIG. 9 . 
       
    
    
     DESCRIPTION OF EXEMPLARY EMBODIMENTS 
       [0039]    An exemplary embodiment of the present invention will be described with reference to the drawings. 
       [Overview of the Embodiment] 
       [0040]    As an exemplary embodiment of the present invention, a wireless communication system includes a base station and a terminal station. They are performing radio communications, respectively. The wireless communication system performs multi-hop wireless communication, using a white space. The outline of the configuration of the wireless communication system will be explained below. In the situation that the base station is isolated from the network, thereby there are no means to get a list of frequencies which are available for transmission, except for the wireless communication. The base station may include a radio communication means using a predetermined frequency. The predetermined frequency is estimated so as to get the list of frequencies which are available for transmission. The predetermined frequency is except for the frequency that the wireless communication system may use as a white space. Until the base station gets the list of frequencies which are available for transmission, the base station transmits or receives the information under the predetermined frequency. Therefore, unless the base station radiates the waves which frequency may not be permitted to radiate, the base station can use the frequency, included in the list of frequencies which are available for transmission, the list being based on the information of its own location. 
       [Outline of the Wireless Communication System] 
       [0041]      FIG. 1  is a schematic configuration diagram of the wireless communication system according to the exemplary embodiment of the present invention. An exemplary embodiment of wireless communication system  1  performs multi-hop wireless communication, using a white space. 
         [0042]    As depicted in  FIG. 1 , wireless communication system  1  may include CPE 11 , CPE 21  and CPE 22  as a terminal station, respectively. Wireless communication system  1  may include BS 10  and BS 20  as a base station, respectively, connected to the terminal stations. Wireless communication system  1  may include backhaul line  30  for BS 10 , Internet  40 , white space database (DB)  50  (hereinafter, database  50 ), and white space coexistence manager (CM)  60  (hereinafter, coexistence manager  60 ). In this embodiment, database  50  and/or coexistence manager  60  may be corresponding to a managing apparatus. Unless otherwise mentioned, BS or CPE may include functions which are required in IEEE802.22. 
         [0043]    BS 10  may be connected to Internet  40  through backhaul line  30 . Thereby, BS 10  can access database  50  or coexistence manager  60 , which exists on Internet  40 . BS 10  configures cell  1  including CPE 11  which exist within the radio communication area of BS 10 . BS 20  configures cell  2  including CPE 21  and CPE 22  which exist within the radio communication area of BS 20 . CPE 11  and CPE 21  may operate as a relay station by being connected each other using a cable. 
         [0044]    BS 20  and CPE 22  may be connected to Internet  40  through the radio link between BS 10  and CPE 11  (a first hop of radio link), and the radio link between CPE 21  and BS 20  (a second hop of radio link). According to this configuration for the relay, CPE 22  being in the location where the radio wave from BS 10  cannot be reached, may be provided the Internet service via BS 20 . 
         [0045]    A communication system being operated by the primary user who is licensed to frequency utilization (hereinafter, existing system  2 ) may include transmitting station  70  and receiving station  80 . Existing system  2  may be using frequency f 1  and f 2 , under licenses, respectively. In the following explanation, a secondary user who does not have licenses regarding frequency f 1  and f 2 , shall use frequency f 1  and f 2  as a white space, respectively. 
         [0046]    Here, as illustrated in  FIG. 1 , even existing system  2  is using frequency f 1  and f 2  for communication, on condition that a service area of wireless communication system  1  is far enough away from the service area of existing system  2 , and transmission power of the radio station in wireless communication system  1  is lowered enough, wireless communication system  1  can communicate using frequency f 1  or f 2  without giving existing system  2  interference. In this embodiment, one of the roles of database  50  is to provide information of the frequency which is available to radio communication without affecting the primary use system in certain spatial and temporal conditions. 
         [0047]    Furthermore, BS 10  and BS 20 , constituting wireless communication system  1 , can perform wireless communication using a different frequency as a secondary use, respectively. For example, BS 10  may use frequency f 1 , and BS 20  may use frequency f 2 , respectively. In this embodiment, in the situation that the plurality of wireless communication systems exist, and each of the wireless communication system uses a frequency as a secondary use, the role of coexistence manager  60  is to restructure the list of frequencies available for transmission so as to communicate appropriately under the situation avoiding the interference between the second use systems. In this way, the wireless communication system using white spaces can utilize the source of frequencies, which are available in spatial conditions, effectively. 
         [0048]    Here, the frequency, which is used in BS 10  as a secondary use, shall be provided by accessing database  50  or coexistence manager  60  on the Internet. In other words, firstly, BS 10  accesses database  50  and provide its location information, etc. to database  50 . Then, BS 10  can get the list of frequencies available for transmission and the allowable maximum transmission power, corresponding to each of the available frequencies in its setting location. Next, BS 10  notifies coexistence manager  60  about the information of its setting location, the list of frequencies available for transmission and the allowable maximum transmission powers. Based on the list of frequencies available for transmission of BS 10  and the operative channel information of another second use system existing around BS 10 , coexistence manager  60  can restructure the list of frequencies available for transmission of BS 10 . Thereafter, coexistence manager  60  may respond to BS 10  by the list of frequencies available for transmission, including restructured information. BS 10  selects an operative channel among the list of frequencies available for transmission, including restructured information. Then, BS 10  notifies coexistence manager  60  of the operative channel of BS 10 . In this way, coexistence manager  60  can know the frequency used by BS 10  as the secondary use. 
         [0049]    On the other hand, just after the initialization (before the establishment of radio communication link with CPE 21 ), BS 20  is not connected to Internet  40 . Therefore, as a frequency to use for wireless communication, BS 20  transmits or receives the radio wave using frequency f 10 , which is estimated so that BS 20  can use the frequency for transmitting or receiving. After completing the network entry under establishing a wireless link with CPE 21 , BS 20  accesses database  50  on Internet  40 , via CPE 21 , CPE 11  and BS 10 . BS 20  transmits at least its location information to database  50 . Thereafter, corresponding to the location of BS 20 , BS 20  gets the list of frequencies available for transmission and the allowable maximum transmission power corresponding to each frequency. Next, BS 20  notifies coexistence manager  60  about the information of its location, the list of frequencies available for transmission and the allowable maximum transmission powers. Based on the list of frequencies available for transmission of BS 20 , and if necessary, based on the operative channel information of another second use system existing around BS 20 , coexistence manager  60  can restructure the list of frequencies available for transmission of BS 20 . Thereafter, coexistence manager  60  may respond to BS 20  by the list of frequencies available for transmission, including restructured information. BS 20  selects an operative channel from among the list of frequencies available for transmission, including restructured information. Then, BS 20  notifies coexistence manager  60  of its own operative channel. In this way, coexistence manager  60  can know the frequency used by BS 20  as the secondary use. 
         [0050]    In this embodiment, frequency f 10 , which is used to get the list of frequencies available for transmission based on the location information of BS 20 , is estimated so that BS 20  does not give a primary user interference. In order that BS or CPE can use such a frequency, for example, the frequency which is estimated so as to transmit within the area specified by the location information, may be predetermined from among the available frequencies of the UHF zone. By having the information of the estimated frequency as one of the initial information, BS can select the frequency for the communication. In addition, in CPE, by having the information of the estimated frequency as one of the initial information, CPE can search BS by using the frequency in the state after a start of supply of the electricity. 
         [0051]    In another embodiment, it may be possible that BS 20  is allocated as a primary user of frequency f 10 . 
       [Configuration of BS 10  or BS 20 ] 
       [0052]    We will explain each configuration of BS 10  and BS 20  more concretely, by referring to  FIG. 2  as follows. As illustrated in  FIG. 2 , each of BS 10  and BS 20  may include antenna  101  for transmitting/receiving radio waves, data communication section  102  for transmitting/receiving data, Spectrum Manager (SM)  103  for managing the operational channel or the frequencies which are available for transmission, main control section  104  for controlling the base station, interface section  105  for interfacing with backhaul line  30  or an external device, and terminal  106  for connecting to backhaul line  30  or the external device. 
         [0053]    Data communication section  102  may include RF section  111 , baseband (BB) signal processing section  112  and MAC processing section  113 . RF section  111  may convert a baseband to a radio frequency band, convert the radio frequency band to the baseband, and amplify signals etc. Baseband (BB) signal processing section  112  may perform an error correction coding/decoding and modulation/demodulation processing etc. MAC processing section  113  may perform a control for the operational channel, the data transmission/reception timings, an addition of its station identifier to a communication packet, and a recognition of the wireless equipment which transmitted data etc. 
         [0054]    Spectrum Manager (SM)  103  may include a communicating section for frequency information  121  and managing section for frequency information  122 . Communicating section for frequency information  121  may transmit its location information etc. to database  50 . Thereby, communicating section for frequency information  121  can get the list of frequencies which are available for transmission in its setting location and the allowable maximum transmission powers, corresponding to each frequency. Next, communicating section for frequency information  121  may notify coexistence manager  60  about the information of its setting location, the list of frequencies available for transmission and the allowable maximum transmission powers. Thereby, communicating section for frequency information  121  can get the list of frequencies which are available for transmission, reconstructed by coexistence manager  60 . 
         [0055]    In the situation that its own station is connected to Internet  40  via interface section  105 , in other words, in the situation that its own station can access database  50  or coexistence manager  60 , the station may select an operational channel from among the list of frequencies available for transmission, received from coexistence manager  60 . Then, the operational channel may be set to data transmission section  102 . Then, the station may notify coexistence manager  60  about its operational channel. In the situation that its own station is not connected to Internet  40  via interface section  105 , in other words, in the situation that its own station cannot access database  50  or coexistence manager  60 , the station may read frequency f 10  from its internal memory etc., frequency f 10 , being guaranteed that there is no primary user using this frequency. Then frequency f 10  may be set to data transmission section  102  as the operational frequency of its own cell. 
         [0056]    For example, main control section  104  can be configured by a processor, a data storage area defined on memory, and software. Each procedure in BB signal processing section  112 , MAC processing section  113  and Spectrum Manager (SM)  103  may be executed by the processor in main control section  104 . The programs for the processor were loaded from the data storage memory like a hard disk device or flash memories etc. to the internal memory in main control section  104 . 
       [Configuration of CPE 11 , CPE 21  or CPE 22 ] 
       [0057]    We will explain each configuration of CPE 11 , CPE 21  and CPE 22  more concretely, by referring to  FIG. 3  as follows. As illustrated in  FIG. 3 , each of CPE 11 , CPE 21  and CPE 22  may include antenna  201  for transmitting/receiving radio waves, data communication section  202  for transmitting/receiving data, control section for using frequency  203  for controlling own operational channel, main control section  204  for controlling its own station, interface section  205  for interfacing with an external line or an external device, and terminal  206  for connecting to the external line or the external device. 
         [0058]    Data communication section  202  may include RF section  211 , baseband (BB) signal processing section  212  and MAC processing section  213 . RF section  211  may convert a baseband to a radio frequency band, convert the radio frequency band to the baseband, and amplify signals etc. Baseband (BB) signal processing section  212  may perform an error correction coding/decoding and modulation/demodulation processing etc. MAC processing section  213  may perform a control for the operational channel, the data transmission/reception timings, an addition of its station identifier to a communication packet, and a recognition of the wireless equipment which transmitted data etc. 
         [0059]    In the situation that its own station is connected to Internet  40  via interface section  205 , in other words, in the situation that its own station can access database  50  or coexistence manager  60 , the station may read frequency f 10  from a memory etc., frequency f 10 , being guaranteed that there is no primary user using this frequency. Then the station may search BS using frequency f 10 . On the other hand, in the situation that its own station is not connected to Internet  40  via interface section  205 , in other words, in the situation that the station cannot access database  50  or coexistence manager  60 , the station may search BS without making a limit for frequency to use for a search. 
         [0060]    In addition, main control section  204  can be configured by a processor, a data storage area defined on memory and software. Each procedure in BB signal processing section  212  and MAC processing section  213  may be executed by the processor in main control section  204 . The programs for the processor were loaded from the data storage memory like a hard disk device etc. to its memory. 
         [0061]    [Example of the Changing Pattern of the Frequency to Use for Wireless Communication] 
         [0062]    We will explain the examples of the changing patterns of the frequencies to use for wireless communication in each of BS 10 , BS 20 , CPE 11 , CPE 21  and CPE 22 , by referring to  FIG. 4 ,  FIG. 5  or  FIG. 6  as follows. 
         [0063]      FIG. 4  depicts the example of frequency utilization under the situation that BS 20  is isolated. Each of BS 10  and CPE 11  has gotten the list of frequencies available for transmission, based on its location information, respectively. Then, each station is performing the radio communication using operational frequency f 1 , being included in the list of frequencies available for transmission. On the other hand, until BS 20  establishes radio communication link with CPE 21 , BS 20  is isolated and not connected to Internet  40 . Therefore, BS 20  cannot get the list of frequencies available for transmission, based on its location information. Then, BS 20  is performing a radio communication using frequency f 10 , guaranteed not to give a primary user interference. As CPE 22  had not connected to Internet  40  via interface section  205 , CPE 22  had been searching BS without making a limit for frequencies to use for a search. Thereafter, CPE 22  received the radio wave transmitted from BS 20  under using frequency f 10 , CPE 22  has been connecting with BS 20  under using frequency f 10 . 
         [0064]      FIG. 5  depicts the example of frequency utilization just after the situation that CPE 21  was connected to BS 20  by wireless communication. CPE 21  is connected to CPE 11  via interface section  205 . Furthermore, CPE 21  is connected to Internet  40  through the radio communication between CPE 11  and BS 10 . In this situation, CPE 21  may be connected to BS 20  by searching BS using frequency f 10 , guaranteed not to give a primary user interference. As a result, BS 20  is connected to Internet  40  by having been connected to CPE 21 . Then, BS 20  can get the list of frequencies available for transmission based on its location information by accessing database  50  or coexistence manager  60 . 
         [0065]    As a result that BS 20  was connected to CPE 21 , BS 20  is able to get the list of frequencies available for transmission based on its location information, from database  50 , etc. on Internet  40 .  FIG. 6  depicts the example of frequency utilization after the situation that BS 20  can get the list of frequencies available for transmission based on its location. In this situation, BS 20  can select frequency f 2  from among the list of frequencies available for transmission, based on its location information. Then, BS 20  can change the frequency f 10  to frequency f 2  for wireless communication. In response to this frequency changing procedure in BS 20 , each frequency for wireless communication, used in CPE 21  and CPE 22  is changed from frequency f 10  to frequency f 2 , respectively. 
       CONCLUSION 
       [0066]    As stated above, according to this embodiment, following wireless communication system using white spaces is disclosed. In the situation that a base station which needs to perform a radio communication with a terminal station before retrieving a list of frequencies available for transmission from database etc., the base station can get the list of frequencies available for transmission by the radio communication using the frequency which is guaranteed to be able to transmit. Therefore, the base station can perform the radio communication using a white space, without emitting the radio waves whose frequencies may not be allowed to use for transmitting. 
         [0067]    In addition, this embodiment can apply to the base station desiring to use white spaces as frequency resources, except predetermined available frequencies. In this case, the base station can also perform the radio communication using white spaces, without emitting the radio waves whose frequencies may not be allowed to use for transmitting. Here, example for the cases that uses white spaces as frequency resources, except predetermined available frequencies are as follows: 
         [0068]    to use white spaces for off-road communication, under a situation that available frequencies are in a busy condition, 
         [0069]    to use white spaces as additional frequencies, under a shortage of available frequencies for configuring a relay system, and 
         [0070]    to use white spaces as data communication frequencies, under a situation that the band of the available frequency is narrowband, and cannot use the band for broadband data communications. 
         [0071]    In addition, this invention is particularly suitable for a wireless communication system, prescribed in IEEE802.22, but not limited to such a system. The preceding description has been provided to enable others skilled in the art to best utilize various aspects of the exemplary embodiments disclosed herein. This exemplary description is not intended to be exhaustive or to be limited to any precise form disclosed. Many modifications and variations are possible without departing from the spirit and scope of the instant disclosure. The embodiments disclosed herein should be considered in all respects illustrative and not restrictive. Reference should be made to the appended claims and their equivalents in determining the scope of the instant disclosure. 
       DESCRIPTION OF THE PREFERRED EMBODIMENT(S) 
       [0072]    This invention can apply to the various kind of wireless communication system, which is using a white space. 
       REFERENCE SIGNS LIST 
       [0000]    
       
           1 : wireless communication system 
           2 : existing system 
           10 : base station (BS) 
           11 , 21 , 22 : Customer Premises Equipment (CPE) 
           30 : backhaul line 
           40 : Internet 
           50 : database (DB) 
           60 : coexistence manager (CM) 
           70 : transmitting station 
           80 : receiving station 
           101 : antenna 
           102 : data transmission section 
           103 : Spectrum Manager (SM) 
           104 : main control section 
           105 : interface section 
           106 : terminal 
           111 : RF section 
           112 : BB signal processing section 
           113 : MAC processing section 
           121 : communicating section for frequency information 
           122 : managing section for frequency information 
           201 : antenna 
           202 : data transmission section 
           203 : control section for using frequency 
           204 : main control section 
           205 : interface section 
           206 : terminal 
           211 : RF section 
           212 : BB signal processing section 
           213 : MAC processing part