Patent Publication Number: US-2009225729-A1

Title: Radio base station

Description:
TECHNICAL FIELD 
     The present invention relates to a radio base station apparatus that is connectable to an upper communication network via a base station control apparatus. 
     BACKGROUND ART 
     The communication system for holding communication by connecting an access point such as a wireless LAN, or the like to an upper communication network is spreading rapidly. In such communication system, as the system for connecting the radio base station apparatus such as the access point, or the like and the upper communication network, the system in which a plurality of radio base station apparatuses are connected to the upper communication network via a control equipment such as a mobile access controller (MoAC), or the like and then a plurality of radio base station apparatuses are controlled in cooperation mutually by the control equipment is devised, in addition to the system in which the radio base station apparatus is connected directly to the upper communication network (see Non-Patent Literature 1, for example). 
     Non-Patent Literature 1: P. Calhoun and five others, “Light Weight Access Point Protocol (LWAPP)”, [online], 2003, IETF (Internet Engineering Task Force) Internet draft, [2005 May 18 searched], Internet &lt;URL:http://web.archive.org/web/20031209115721/http://www.ieff.org/internet-drafts/draft-calhoun-seamoby-lwapp-03.txt&gt; 
     DISCLOSURE OF THE INVENTION 
     Problems that the Invention is to Solve 
     However, in the system in which the radio base station apparatus is controlled by using the above control equipment, the radio base station control apparatus and the radio base station must be connected by the connecting cable. Therefore, such a circumstance existed that the radio base station apparatus cannot be installed in a radio wave dead zone such as a conference room that is surrounded by walls, or the like, a location such as a separate building in which the cable cannot be physically laid, or the like, and others, for example. 
     The present invention has been made in view of the above circumstances in the prior art, and it is an object of the present invention to provide a radio base station apparatus that can be simply installed. 
     Means for Solving the Problems 
     A radio base station apparatus of the present invention for a radio communication system including a base station control apparatus and the radio base station apparatus which holds communication with a radio terminal device via radio communication and is connectable to an upper communication network via the base station control apparatus, includes an inter-base station connecting radio portion for holding communication with a first radio base station apparatus which is connected to the base station control apparatus; a terminal connecting radio portion for holding radio communication with the radio terminal device; and a communication controlling portion for holding communication from the terminal connecting radio portion to the radio terminal device and controlling the inter-base station connecting radio portion; wherein the communication controlling portion searches the first radio base station apparatus, executes a connecting process to the first radio base station apparatus, acquires configuration information from the base station control apparatus via the first radio base station apparatus, and holds communication with the base station control apparatus via the first radio base station apparatus by using the inter-base station connecting radio portion. 
     According to this configuration, it is possible to establish more radio base station apparatuses that do not need the cable connection to the base station control apparatus, and the radio base station apparatus can be installed simply because the automatic connection and configuration can be made after the installation. 
     Also, the radio base station apparatus of the present invention further includes a cable connecting portion for connecting a cable communication line which holds communication with a second radio base station apparatus serving as a lower radio base station apparatus; wherein the communication controlling portion controls the cable connecting portion and the inter-base station connecting radio portion to interconnect the communication between the first radio base station apparatus and the second radio base station apparatus. 
     According to this configuration, it is possible to establish more lower radio base station apparatuses via the cable communication line. Therefore, the radio base station apparatus can be installed more simply. 
     Also, in the radio base station apparatus of the present invention, the inter-base station connecting radio portion holds communication with a third radio base station apparatus serving as a lower radio base station apparatus, and the communication controlling portion controls the inter-base station connecting radio portion to interconnect the communication between the first radio base station apparatus and the second radio base station apparatus. 
     According to this configuration, it is possible to establish more lower radio base station apparatuses via the cable communication line. Therefore, the radio base station apparatus can be installed more simply. 
     A radio base station system of the present invention which holds communication with a terminal device via radio communication and is connectable to an upper communication network, includes the radio base station apparatus; a first base station controlling device for connecting the radio base station apparatus and the communication network by using a first communication path; and a second base station controlling device for connecting the radio base station apparatus and the communication network by using a second communication path different from the first communication path; wherein a redundancy is applied to the first base station controlling device and the second base station controlling device by using a VRRP protocol. 
     According to this configuration, a redundancy of the base station control apparatus is applied. Therefore, the radio base station system with high certainty of communication can be provided. 
     ADVANTAGE OF THE INVENTION 
     According to the present invention, the radio base station apparatus that can be simply installed can be provided. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  An explanatory view showing an outline of a radio communication system according to a first embodiment of the present invention. 
         FIG. 2  A block diagram showing a schematic configuration of a base station control apparatus according to the first embodiment of the present invention. 
         FIG. 3  A block diagram showing a schematic configuration of a radio base station apparatus according to the first embodiment of the present invention. 
         FIG. 4  A flowchart showing procedures of a communication connection method of the radio communication system according to the first embodiment of the present invention. 
         FIG. 5  A sequence diagram showing data exchange between the radio base station apparatus and the base station control apparatus according to the first embodiment of the present invention. 
         FIG. 6  A view showing a status transition of the radio base station apparatus according to the first embodiment of the present invention. 
         FIG. 7  A view showing a status transition of the base station control apparatus according to the first embodiment of the present invention. 
         FIG. 8  An explanatory view showing an outline of a radio communication system according to a second embodiment of the present invention. 
         FIG. 9  An explanatory view showing an outline of a radio communication system according to a third embodiment of the present invention. 
         FIG. 10  A view showing a schematic configuration of a radio communication system when VRPP is used. 
     
    
    
     DESCRIPTION OF REFERENCE NUMERALS AND SIGNS 
     
         
           100 R,  100 L base station control apparatus 
           101  cable connecting portion 
           102  communication controlling portion 
           103  terminal connecting radio portion 
           103   a  antenna 
           104  cryptography authenticating portion 
           105  inter-AP connecting radio portion 
           105   a  antenna 
           200  base station control apparatus 
           201  communication network connecting portion 
           202  base station controlling portion 
           203  base station connecting portion 
           400  radio terminal device 
           500  cable terminal device 
       
    
     BEST MODE FOR CARRYING OUT THE INVENTION 
     First Embodiment 
       FIG. 1  is an explanatory view showing an outline of a radio communication system according to a first embodiment of the present invention. In the present embodiment, as the radio communication system, the case where a wireless LAN stipulated in IEEE802.11, for example, is used as a radio communication system between a base station apparatus and a radio terminal device will be explained hereinafter. However, the present invention is not limited to the wireless LAN, and can be applied to various radio communication systems such as a mobile communication network, and the like. 
     As shown in  FIG. 1 , the radio communication system according to a first embodiment of the present invention includes a base station control apparatus  200  connected to a communication network  300  by using a communication line L 1  such as an optical fiber cable, or the like, a base station control apparatus  100 R connected to the base station control apparatus  200  via a communication line L 2  such as an Ethernet (registered trademark) type LAN, or the like, for example, and a base station control apparatus  100 L connected to the base station control apparatus  100 R via radio communication. 
     The base station control apparatus  200  has a configuration that can be connected to a plurality of radio base station apparatuses via the communication line L 2 , and controls the connected radio base station apparatuses in cooperation. The base station control apparatuses  100 R,  100 L get into radio communication with a radio terminal device  400 . 
     Here, the communication system stipulated in IEEE802.11a or IEEE802.11g, for example, is used in the communication between the base station control apparatus  100 L and the base station control apparatus  100 R, and the communication system stipulated in IEEE802.11b, for example, is used in the communication between the base station control apparatuses  100 R,  100 L and the radio terminal device  400 . 
     In this manner, the base station control apparatus  100 R and the base station control apparatus  100 L are connected to communicate with each other via radio. Therefore, the radio base station apparatus can be installed in a radio wave dead zone such as a conference room that is surrounded by walls, or the like, a location such as a separate building in which the cable cannot be physically laid, or the like, and others. 
       FIG. 2  is a block diagram showing a schematic configuration of the base station control apparatus according to the first embodiment of the present invention. As shown in  FIG. 2 , the base station control apparatus  200  includes a communication network connecting portion  201  connected to the communication network  300 , a base station controlling portion  202  for controlling the base station control apparatus  100 , and a base station connecting portion  203  connected to the base station control apparatus  100 . 
     The communication network connecting portion  201  is connected to the communication network  300 . The base station controlling portion  202  controls a configuration of the connected base station control apparatus  100 , a status monitoring of the base station control apparatus  100 , and the like. The base station connecting portion  203  holds communication with the base station control apparatus  100  by using a radio base station control protocol. 
       FIG. 3  is a block diagram showing a schematic configuration of the radio base station apparatus according to the first embodiment of the present invention. As shown in  FIG. 3 , each of the base station control apparatuses  100 R,  100 L includes a cable connecting portion  101  connected to the cable communication line, a communication controlling portion  102  for controlling an operation of the radio base station apparatus by the base station control apparatus  200 , a terminal connecting radio portion  103  for holding the radio communication with the radio terminal device  400  via an antenna  103   a , a cryptography authenticating portion  104  for executing the authentication by encrypting the data in transmitting the data between the base stations and decrypting the data in receiving the data, and an inter-base station connecting radio portion  105  for holding communication with other radio base station apparatuses via an antenna  105   a . In the following explanation, the base station control apparatus  100 R connected to the base station control apparatus  200  via cable is referred to as a root AP, and the base station control apparatus  100 L connected to the base station control apparatus  100 R via radio is referred to as a leaf AP. 
     In the root AP  100 R, the cable connecting portion  101  is connected to the cable communication line L 2 , and performs communication with the base station control apparatus  200  by using the radio base station control protocol. The communication controlling portion  102  executes the control in response to the instruction from the base station control apparatus  200 , and also switches communication with the radio terminal device  400  via the terminal connecting radio portion  103  and communication with the leaf AP  100 L via the inter-base station connecting radio portion  105  to hold communication with the base station control apparatus  200  via the cable connecting portion  101 . In this case, preferably the communication controlling portion  102  should control the communication with the leaf AP  100 L prior to the communication with the radio terminal device  400 . 
     In the leaf AP  100 L, the inter-base station connecting radio portion  105  holds radio communication with the root AP  100 R by the radio base station control protocol. The cryptography authenticating portion  104  handles the encryption and the authentication in the communication with the root AP  100 R. Like the root AP  100 R, the terminal connecting radio portion  103  holds radio communication with the radio terminal device  400 . The cable connecting portion  101  can be connected a cable terminal device  500  via the cable communication line L 2  (for example, Ethernet (registered trademark) type LAN, or the like). The communication controlling portion  102  executes the control in response to the instruction from the base station control apparatus  200 , and also switches communication with the radio terminal device  400  via the terminal connecting radio portion  103  and communication with the cable terminal device  500  via the cable connecting portion  101  to hold communication with the base station control apparatus  200  via the inter-base station connecting radio portion  105  and the root AP  100 R. 
       FIG. 4  is a flowchart showing procedures of a communication connection method of the radio communication system according to the first embodiment of the present invention. When the leaf AP  100 L is installed and a power supply is turned ON, the communication controlling portion  102  scans the presence of the root APs  100 R by using a beacon, or the like via the inter-base station connecting radio portion  105  to search the root AP  100 R that can be connected via radio (step S 101 ). 
     When the root AP  100 R detects the beacon transmitted from the leaf AP  100 L, it makes a response to the beacon. Then, the leaf AP  100 L detects a response from the root AP  100 R to decide whether or not the root AP  100 R is found (step S 102 ). 
     In this case, if a plurality of root APs  100 R are detected by the leaf AP  100 L, the nearest root AP  100 R may be selected by measuring an electric field strength in the response, an error rate of data, or the like. 
     If no root AP  100 R is found (No in step S 102 ), the leaf AP  100 L goes back to step S 101  and searches successively the root AP  100 R. In contrast, if the root AP  100 R is found, a connection is established by using an encryption key being set previously between the leaf AP  100 L and the root AP  100 R (step S 103 ). 
     Here, the encryption key used in the connection between the leaf AP  100 L and the root AP  100 R can be changed after the connection is established. When the encryption key is changed, the base station control apparatus  200  transmits the encryption key data to be changed (referred to as “new encryption key data” hereinafter) to the root AP  100 R. When the root AP  100 R receives the new encryption key data, it updates the data in the cryptography authenticating portion  104  and also transmits the updated data to the leaf AP  100 L. When the leaf AP  100 L receives the new encryption key data, it updates the data in the cryptography authenticating portion  104  and holds communication with the root AP  100 R by using the new encryption key data. Accordingly, improvement of security can be further achieved. Here, when a plurality of leaf APs  100 L are connected, update of the encryption key data may be applied simultaneously to all leaf APs  100 L or may be applied individually to respective leaf APs  100 L. 
     When the root AP  100 R established the connection with the leaf AP  100 L, it opens a path to connect the leaf AP  100 L and the base station control apparatus  200  (step S 104 ). Then, the base station control apparatus  200  and the leaf AP  100 L execute a connecting process via the root AP  100 R (step S 105 ). In the meantime, the root AP  100 R causes the cryptography authenticating portion  104  to execute the cryptography authentication and causes the inter-base station connecting radio portion  105  to execute the connecting process between the base stations via radio, and also causes to pass the data between the base station control apparatus  200  and the leaf AP  100 L. As a result, the connection equivalent to the communication that is held directly between the leaf AP  100 L and the base station control apparatus  200  can be built up between them. This connecting process will be explained with reference to  FIG. 5  to  FIG. 7  hereunder. 
       FIG. 5  is a sequence diagram showing data exchange between the radio base station apparatus and the base station control apparatus according to the first embodiment of the present invention.  FIG. 6  is a view showing a status transition of the radio base station apparatus according to the first embodiment of the present invention. Also,  FIG. 7  is a view showing a status transition of the base station control apparatus according to the first embodiment of the present invention. 
     The exchange of data between the leaf AP  100 L and the base station control apparatus  200  and the status transition between the leaf AP  100 L and the base station control apparatus  200  will be explained with reference to  FIG. 5  to  FIG. 7  hereunder. The case where the connection should be established between the leaf AP  100 L and the base station control apparatus  200  will be explained hereunder. This explanation is similarly true of the case where the connection is established between the root AP  100 R and the base station control apparatus  200 . 
     First, the leaf AP  100 L in its initial process (step S 201 ) establishes the connection with the root AP  100 R, and then transmits a search request message to the base station control apparatus  200  (step S 202 ). At this time, the leaf AP  100 L transfers from an initial status  301  to a search status  302 . The radio base station apparatus  100  continues to transmit periodically this search request message until it receives a search response message from the base station control apparatus  200 . 
     When the base station control apparatus  200  receives the search request message from the leaf AP  100 L, it transmits the search response message to inform the leaf AP  100 L of its own existence (step S 203 ). 
     The leaf AP  100 L transmits the search request message to the base station control apparatus  200  at a predetermined time. When the base station control apparatus  200  receives the search request message from the leaf AP  100 L, it sends back the search response message to inform the leaf AP  100 L of the presence of the base station control apparatus  200 . 
     When the leaf AP  100 L receives the search response message from the base station control apparatus  200 , it demands a connection of the base station control apparatus  200  by transmitting a connection request message to the base station control apparatus  200  via the root AP  100 R to make its own entry (step S 204 ). At this time, the leaf AP  100 L shifts from the search status  302  to a connection status  303 . 
     When the base station control apparatus  200  receives the connection request message from the leaf AP  100 L, it shifts from a no status  401  to a connection status  402  and registers the information of the entered leaf AP  100 L. Then, the base station control apparatus  200  checks a MAC address of the leaf AP  100 L to decide whether the connection of the leaf AP  100 L should be allowed or not. If the connection should not be allowed, the base station control apparatus  200  interrupts the connection at this point of time and transmits a connection response message of NG to the MAC address of the entered leaf AP  100 L. When the leaf AP  100 L receives the connection response message of NG, it returns to the search status  302  from the connection status  303  and executes the process over again from the initial process. In contrast, if the connection should be allowed, the base station control apparatus  200  transmits a connection response message to the MAC address of the entered leaf AP  100 L (step S 205 ). 
     When the leaf AP  100 L receives the connection response message from the base station control apparatus  200 , it shifts from the connection status  303  to a configuration status  304  and then transmits a configuration request message to the base station control apparatus  200  (step S 206 ). 
     When the base station control apparatus  200  receives the configuration request message from the leaf AP  100 L, it shifts from the connection status  402  to a configuration status  403  and informs the leaf AP  100 L of a configuration that is adaptable to the leaf AP  100 L by a configuration data message (step S 207 ). 
     The leaf AP  100 L receives the configuration data message from the base station control apparatus  200 , then sets the configuration in the hardware register by expanding the message, and then transmits a configuration data response message to the base station control apparatus  200  (step S 208 ). Here, processes in steps S 207  to S 208  are repeated until the transmission of all configuration data to be set (referred to as “configuration data” hereinafter) is finished. 
     After all configuration data are transmitted from the base station control apparatus  200  and the configuration data response message is returned in response to the final configuration data message, the base station control apparatus  200  transmits a configuration set request message to the leaf AP  100 L (step S 209 ). A start of the operation of the leaf AP  100 L is triggered by this transmission of the configuration set request message 
     When the leaf AP  100 L receives the configuration set request message from the base station control apparatus  200 , the configuration is completed and the leaf AP  100 L transmits a configuration set response message to the base station control apparatus  200  and shifts from the configuration status  304  to an operation status  305  to enter into its operation state (step S 210 ). In contrast, in the case of the configuration failure, or the like, the leaf AP  100 L returns to the search status  302  from the configuration status  304  and executes the process over again from the initial process. When the base station control apparatus  200  receives the configuration set response message, it shifts from the configuration status  403  to the operation status  404 . 
     Then, the leaf AP  100 L transmits a connection acknowledge request message to the base station control apparatus  200  at a predetermined interval of time during the operation to inform the base station control apparatus  200  of a normal operation of the leaf AP  100 L (step S 211 ). 
     The base station control apparatus  200  receives the connection acknowledge request message from the leaf AP  100 L, and transmits a connection acknowledge response message to the leaf AP  100 L as the response (step S 212 ). 
     The processes in steps S 211  to S 212  are repeated during the operation of the leaf AP  100 L and the base station control apparatus  200 . 
     In this manner, according to the first embodiment of the present invention, it is possible to establish more radio base station apparatuses that do not need the cable connection to the base station control apparatus, and the radio base station apparatus can be installed simply because the automatic connection and configuration can be made after the installation. 
     Second Embodiment 
       FIG. 8  is an explanatory view showing an outline of a radio communication system according to a second embodiment of the present invention. In the present embodiment, the same reference symbols are affixed herein to the redundant portions with those in the first embodiment explained with reference to  FIG. 1  to  FIG. 7 . 
     As shown in  FIG. 8 , in the radio communication system according to the present embodiment, at least one radio base station apparatus  110 L (referred to as the “leaf AP” hereinafter) is connected to the base station control apparatus (root AP)  100 R via radio. Also, a radio base station apparatus  110 R (referred to as the “root AP” hereinafter) is connected to the leaf AP  110 L via a cable communication line L 3 . Also, a radio base station apparatus  111 L (referred to as the “leaf AP” hereinafter) is connected to the root AP  110 R via a radio line. 
     The root APs  100 R,  110 R and the leaf APs  110 L,  111 L have the same configurations as those in the radio base station apparatus shown in  FIG. 3 . 
     The communication line L 3  is connected to the cable connecting portion  101  of the leaf AP  110 L, and the leaf AP  110 L and the root AP  110 R can communicate with each other. As the communication line L 3 , the Ethernet (registered trademark) type LAN, or the like, for example, can be applied. Also, the communication controlling portion  102  of the leaf AP  110 L switches the cable connecting portion  101  and the terminal connecting radio portion  103  to establish the communication connection with the root AP  100 R via the inter-base station connecting radio portion  105 . 
     As the communication line L 3 , the Ethernet (registered trademark) type LAN, or the like, for example, can be applied. Also, the leaf AP  110 L and the root AP  110 R can communicate with each other by connecting the cable connecting portion  101  of the leaf AP  110 L and the root AP  110 R. 
     The communication controlling portion  102  of the leaf AP  110 L switches the cable connecting portion  101  and the terminal connecting radio portion  103  to establish the communication connection with the root AP  100 R via the inter-base station connecting radio portion  105 . 
     Like the root AP  100 R, the communication controlling portion  102  of the root AP  110 R switches the inter-base station connecting radio portion  105  and the terminal connecting radio portion  103  to establish the communication connection with the base station control apparatus  200  via the cable connecting portion  101 , the leaf AP  110 L, and the root AP  100 R. 
     The communication controlling portion  102  of the leaf AP  111 L switches the cable connecting portion  101  and the terminal connecting radio portion  103  to establish the communication connection with the root AP  110 R via the inter-base station connecting radio portion  105 . 
     In this case, if a plurality of apparatuses can be connected to the cable connecting portion  101 , the leaf AP  110 L may be connected to a plurality of root APs  110 R. Also, the leaf AP  110 R may hold a radio communication with a plurality of leaf APs  111 L. In addition, like the leaf AP  110 L, the leaf AP  111 L may be connected to the radio base station apparatus, which acts as the root AP to hold the radio communication with the radio base station apparatus (lower leaf AP) via radio, via the cable connecting portion  101 . 
     In this manner, according to the second embodiment of the present invention, it is possible to establish more lower radio base station apparatuses to the radio base station apparatus that serves as the leaf AP. Therefore, the radio base station apparatus can be installed more simply. 
     Third Embodiment 
       FIG. 9  is an explanatory view showing an outline of a radio communication system according to a third embodiment of the present invention. In the present embodiment, the same reference symbols are affixed herein to the redundant portions with those in the first embodiment explained with reference to  FIG. 1  to  FIG. 7 . 
     As shown in  FIG. 9 , in the radio communication system of the present embodiment, at least one radio base station apparatus  120 L (referred to as the “leaf AP” hereinafter) is connected to the base station control apparatus (root AP)  100 R via radio. Also, a radio base station apparatus  121 L (referred to as the “leaf AP” hereinafter) is connected to the radio base station apparatus  120 L via radio. Also, a radio base station apparatus  122 L (referred to as the “leaf AP” hereinafter) is connected to the leaf AP  121 L via radio. 
     The leaf APs  120 L,  121 L,  122 L have the same configurations as those in the radio base station apparatus shown in  FIG. 3 . Also, the radio base station apparatuses serving as the leaf APs  120 ,  121 L,  122 L can be connected to the base station control apparatus  200  when they are connected to the upper root AP or leaf AP by using the inter-base station connecting radio portion  105 . Also, these radio base station apparatuses have the configuration that can be connected to the radio base station apparatus serving as the lower leaf AP by using the inter-base station connecting radio portion  105 . Also, when the radio base station apparatus serving as the lower leaf AP is connected, these radio base station apparatuses acts as the root AP that controls the data exchanged between the upper radio base station apparatus and the lower radio base station apparatus. 
     The inter-base station connecting radio portion  105  of the leaf AP  120 L has the same configuration that can communicate with the root AP  100 R and the leaf AP  121 L. Also, the communication controlling portion  102  of the leaf AP  120 L switches the cable connecting portion  101  and the terminal connecting radio portion  103  to establish the communication connection to the root AP  100 R via the inter-base station connecting radio portion  105 . Also, when the communication controlling portion  102  of the leaf AP  120 L receives the data (downstream data) addressed to the lower leaf AP or the cable or radio terminal device being communicated with the lower leaf AP from the root AP  100 R, it transmits the data to the lower leaf AP  121 L via the inter-base station connecting radio portion  105 . Also, when the communication controlling portion  102  of the leaf AP  120 L receives the data (upstream data) addressed to the upper root AP  100 R from the lower leaf AP  121 L, it transmits the data to the root AP  100 R via the inter-base station connecting radio portion  105 . 
     The inter-base station connecting radio portion  105  of the leaf AP  1211 L has the same configuration that can communicate with the leaf AP  120 L and the leaf AP  122 L. Also, the communication controlling portion  102  of the leaf AP  121 L switches the cable connecting portion  101  and the terminal connecting radio portion  103  to establish the communication connection to the leaf AP  120 L via the inter-base station connecting radio portion  105 . Also, when the communication controlling portion  102  of the leaf AP  121 L receives the data addressed to the lower leaf AP or the cable or radio terminal device being communicated with the lower leaf AP from the leaf AP  120 L, it transmits the data to the lower leaf AP  122 L via the inter-base station connecting radio portion  105 . Also, when the communication controlling portion  102  of the leaf AP  121 L receives the data addressed to the upper root AP  100 R from the lower leaf AP  122 L, it transmits the data to the leaf AP  120 L via the inter-base station connecting radio portion  105 . 
     Here, the method of connecting the radio base station apparatus to the upper radio base station apparatus after the radio base station apparatus serving as the leaf AP is installed is given as explained in the first embodiment. In case the communicatable radio base station apparatus is present in plural in circumference, the connection to the radio base station apparatus that is estimated as the nearest one, for example, is established. Each leaf AP may communicate with a plurality of lower leaf APs via radio. 
     In this manner, according to the third embodiment of the present invention, it is possible to establish more lower radio base station apparatuses to the radio base station apparatus that serves as the leaf AP. Therefore, the radio base station apparatus can be installed more simply. 
     In the explanation in the above first to third embodiments, the example in which one base station control apparatus  200  is provided is explained. In this case, the present invention may be similarly embodied by using VRRP (Virtual Router Redundancy Protocol), or the like as a redundancy protocol to realize the redundancy of the base station control apparatus. 
       FIG. 10  is a view showing a schematic configuration of the radio communication system when VRPP is used. As shown in  FIG. 10 , in this communication system, a back-up base station control apparatus  200   b  as well as a base station control apparatus  200   a  is installed, and both control equipments are connected to the base station control apparatus (root AP)  100 R via a communication network  801  such as the Ethernet (registered trademark) type LAN, or the like, for example. Also, the base station control apparatus  200   a  and the back-up base station control apparatus  200   b  are connected to an opposing apparatus  802  via a different communication line (via upper communication networks  800   a ,  800   b ) respectively. 
     Here, the base station control apparatus  200   a  and the back-up base station control apparatus  200   b  have the same configuration as the base station control apparatus  200  explained above. The base station connecting portions  203  of the base station control apparatuses  200   a ,  200   b  execute the control using VRRP. 
     The base station control apparatus  200   a  and the back-up base station control apparatus  200   b  monitor whether or not any trouble is caused in the communication respectively, and advertises based on VRRP when some trouble is caused. Thus, the back-up base station control apparatus  200   b  acts as the master control apparatus instead of the base station control apparatus  200   a.    
     Therefore, the radio base station apparatus  100 R is connected to the communication network  800   a  via the base station control apparatus  200   a  in the normal operation. When any trouble is caused in the base station control apparatus  200   a , between the radio base station apparatus  100 R and the base station control apparatus  200   a  or in the upper communication network  800   a  of the base station control apparatus  200   a , the radio base station apparatus  100 R is connected to the communication network  800   b  via the back-up base station control apparatus  200   b . As a result, when any trouble is caused, the communication is held via the different communication path to make sure the redundancy of the base station control apparatus and therefore the radio base station system with high certainty of communication can be provided. 
     The present invention is explained in detail with reference to the particular embodiments. But it is apparent for those skilled in the art that various variations and modifications can be applied without departing from a spirit and a scope of the present invention. 
     This application is based upon Japanese Patent Application (Patent Application 2005-174179) filed Jun. 14, 2005; the entire contents of which are incorporated herein by reference. 
     INDUSTRIAL APPLICABILITY 
     The radio base station apparatus of the present invention possesses such an advantage that such apparatus can be installed simply, and is useful to a radio system such as a wireless LAN, or the like.