Abstract:
In a mobile radio communication system including mobile stations; radio base stations which communicate with the mobile stations via connections on radio waves; base station controllers for controlling radio base stations thereunder; and mobile services switch centers, an upstream selection process section, which is provided to the base station controller for executing a selection process, operates in two operation modes (“normal mode” and “through mode”) with respect to each mobile station. In the case where the operation mode of the upstream selection process section with respect to a mobile station is the “through mode” (that is, when a “communicating connection number” with respect to the mobile station is 1), the upstream selection process section which received upstream data transmitted by the mobile station from a radio base station thereunder or from another lower base station controller directly transmits the received upstream data to the next upper device, without executing the selection process. By the “through mode”, wait delay for the selection process in inter-BSC (Base Station Controller) handover can be minimized.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to a device and a method for mobile radio communication, and in particular, to a mobile radio communication system, a mobile radio communication method and a base station controller employing data selection process. 
     DESCRIPTION OF THE PRIOR ART 
     Mobile stations such as portable cellular phones have become widely available these days, and mobile stations according to CDMA (Code Division Multiple Access) have been popular today because of their fine speech quality. 
     FIG. 1 shows an example of a CDMA mobile radio communication system. The mobile communication system shown in FIG. 1 includes a mobile station (MS)  101 , radio base stations (BS&#39;s)  102 A,  102 B,  102 C and  102 D, base station controllers (BSCs)  104  and  105 , and a mobile services switch center (MSC)  108 . The radio base stations  102 A,  102 B,  102 C and  102 D take charge of mobile service areas  103 A,  103 B,  103 C and  103 D, respectively. The radio base stations  102 A and  102 B are connected to the base station controller  104 , and the radio base stations  102 C and  102 D are connected to the base station controller  105 . 
     In the CDMA mobile radio communication system of FIG. 1, upstream data which is transmitted by the mobile station  101  which is located in the mobile service areas  103 A and  103 B is received by the radio base stations  102 A and  102 B, and the radio base stations  102 A and  102 B send the received data to the base station controller  104 . The base station controller  104  which receives the upstream data of the mobile station  101  from the radio base stations  102 A and  102 B executes “selection process for diversity hand-over” with regard to the received upstream data, according to timing which is provided in sync with radio frames. In the selection process, the base station controller  104  selects the upstream data from the radio base station  102 A or the upstream data from the radio base station  102 B based on radio quality information which is supplied from the radio base stations  102 A and  102 B. After the selection process is finished, the base station controller  104  sends the selected upstream data to the mobile services switch center  108 . 
     However, if there is a difference of data transmission time between the line from the radio base station  102 A to the base station controller  104  and the line from the radio base station  102 B to the base station controller  104  (for example, if the data transmission from the radio base stations  102 A and  102 B to the base station controller  104  is executed by means of ATM (Asynchronous Transfer Mode) data transmission and variations in cell delay occur), the base station controller  104  has to execute the selection process after waiting for the slowest upstream data corresponding to the longest data transmission time. While the base station controller  104  waits for the slowest upstream data, faster upstream data have to be temporarily stored in a buffer of the base station controller  104 , thereby processing delay due to the data buffering occurs. 
     Further, when the mobile station  101 , which has been located in the mobile service areas  103 A and  103 B and executing communication with the radio base stations  102 A and  102 B under the base station controller  104  (anchor-side base station controller (that is, a base station controller which started the communication with the mobile station  101  first)), moves into other mobile service areas  103 C and  103 D and starts communication with other radio base stations  102 C and  102 D under another base station controller  105  (drift-side base station controller) as shown in FIG. 1, a large number of connections become necessary if connections are established from the anchor-side base station controller  104  to all the radio base stations  102 C and  102 D which are communicating with the mobile station  101  under the drift-side base station controller  105 . Therefore, in such cases, the selection process is executed first in the drift-side base station controller  105  and only the selected upstream data is sent to the anchor-side base station controller  104 , and thereafter the selection process is executed again in the anchor-side base station controller  104 . 
     However, in the above method employing two stages of selection processes at the drift-side base station controller  105  and the anchor-side base station controller  104 , much data buffering time occurs in the drift-side base station controller  105  and the anchor-side base station controller  104 , and thereby delay is caused in the mobile radio communication service. 
     SUMMARY OF THE INVENTION 
     It is therefore the primary object of the present invention to provide a mobile radio communication system, a mobile radio communication method and a base station controller employing the selection process for diversity hand-over, by which the wait delay for the selection process in the case of the inter-BSC (Base Station Controller) handover can be decreased and thereby the processing delay can be minimized. 
     In accordance with a first aspect of the present invention, there is provided a mobile radio communication system comprising: mobile stations; radio base stations which communicate with the mobile stations via connections on radio waves; base station controllers for controlling radio base stations thereunder, each of which including an upstream selection process section for executing a selection process, in which received upstream data which have been transmitted by a mobile station and supplied from radio base stations thereunder to the base station controller are temporarily stored in a buffer and data having the highest quality is selected from the stored upstream data corresponding to the same radio frame based on radio quality information and the selected data having the highest quality is sent to the next upper device; and mobile services switch centers each of which is provided as the interface between a network and base station controllers which are connected thereunder. In the mobile radio communication system, the operation mode of the upstream selection process section of the base station controller can be set to through mode with respect to a mobile station. When the operation mode of an upstream selection process section of a base station controller is the through mode with respect to a mobile station and the upstream selection process section received upstream data transmitted by the mobile station from a radio base station thereunder or a lower base station controller which is communicating with the base station controller, the upstream selection process section directly sends the received upstream data to the next upper device without temporarily storing the received upstream data and executing the selection process. 
     In accordance with a second aspect of the present invention, in the first aspect, the operation mode of the upstream selection process section of the base station controller is set to normal mode with respect to a mobile station and thereby the selection process is executed normally with respect to the mobile station when a communicating connection number with respect to the mobile station, which means the number of radio base stations and lower base station controllers which are communicating with the base station controller with respect to the mobile station, is 2 or more. The operation mode of the upstream selection process section is set to the through mode with respect a mobile station when the communicating connection number with respect to the mobile station is 1. 
     In accordance with a third aspect of the present invention, in the first aspect, when a mobile station, which has been executing communication in a mobile service area of a radio base station under a first base station controller, moved and started communication with another radio base station under a second base station controller, the operation mode of the upstream selection process section of the second base station controller is set to the through mode with respect to the mobile station. 
     In accordance with a fourth aspect of the present invention, in the first aspect, when a mobile station, which has been executing communication in a mobile service area of a radio base station under a first base station controller, moved and started communication with another radio base station under a second base station controller and thereby the first base station controller finishes the communication with the radio base station thereunder and thereafter executes communication with the another radio base station under the second base station controller, the operation mode of the upstream selection process section of the first base station controller is set to the through mode with respect to the mobile station. 
     In accordance with a fifth aspect of the present invention, in the first aspect, the communication between the mobile station and the radio base stations is executed by means of CDMA (Code Division Multiple Access). 
     In accordance with a sixth aspect of the present invention, there is provided a base station controller for controlling radio base stations thereunder which communicate with mobile stations via connections on radio waves. The base station controller includes an upstream selection process section which includes an upstream data reception means, a timing control means, a selection process means, an upstream frame transmission means and a control means. The upstream data reception means receives upstream data which have been transmitted by a mobile station, received by one or more radio base stations and supplied from the radio base stations or another lower base station controller to the base station controller. The timing control means provides processing timing for selection process to the selection process means. The selection process means is provided with functions for operating depending on whether the present operation mode with respect to a mobile station is normal mode or through mode when the upstream data reception means received upstream data transmitted by the mobile station, storing/reading upstream data to/from a received data buffer and executing the selection process for upstream data according to the processing timing which is provided by the timing control means. The upstream frame transmission means transmits the upstream data outputted by the selection process means to the next upper device. The control means controls the operations of the upstream frame reception means, the upstream frame transmission means, the selection process means and the received data buffer. When a communicating connection number with respect to a mobile station, which means the number of radio base stations and lower base station controllers which are communicating with the base station controller with respect to the mobile station, is 2 or more, the operation mode of the upstream selection process section of the base station controller is set to normal mode with respect to the mobile station and thereby the selection process is executed by the selection process means normally with respect to the mobile station. When the communicating connection number with respect to a mobile station is 1, the operation mode of the upstream selection process section is set to the through mode with respect the mobile station and thereby the received upstream data is directly transmitted to the next upper device without temporarily storing the received upstream data in the received data buffer and executing the selection process. 
     In accordance with a seventh aspect of the present invention, there is provided a mobile radio communication method for a mobile radio communication system which is provided with: mobile stations; radio base stations which communicate with the mobile stations via connections on radio waves; base station controllers for controlling radio base stations thereunder, each of which including an upstream selection process section for executing a selection process, in which received upstream data which have been transmitted by a mobile station and supplied from radio base stations thereunder to the base station controller are temporarily stored in a buffer and data having the highest quality is selected from the stored upstream data corresponding to the same radio frame based on radio quality information and the selected data having the highest quality is sent to the next upper device; and mobile services switch centers each of which is provided as the interface between a network and base station controllers which are connected thereunder. In the mobile radio communication method, the operation mode of the upstream selection process section of the base station controller is set to through mode with respect to a mobile station when necessary. When the operation mode of an upstream selection process section of a base station controller is the through mode with respect to a mobile station and the upstream selection process section received upstream data transmitted by the mobile station from a radio base station thereunder or a lower base station controller which is communicating with the base station controller, the upstream data received by the upstream selection process section is directly sent to the next upper device without temporarily storing the received upstream data and executing the selection process. 
     In accordance with an eighth aspect of the present invention, in the seventh aspect, the operation mode of the upstream selection process section of the base station controller is set to normal mode with respect to a mobile station and thereby the selection process is executed normally with respect to the mobile station when a communicating connection number with respect to the mobile station, which means the number of radio base stations and lower base station controllers which are communicating with the base station controller with respect to the mobile station, is 2 or more. The operation mode of the upstream selection process section is set to the through mode with respect a mobile station when the communicating connection number with respect to the mobile station is 1. 
     In accordance with a ninth aspect of the present invention, in the seventh aspect, when a mobile station, which has been executing communication in a mobile service area of a radio base station under a first base station controller, moved and started communication with another radio base station under a second base station controller, the operation mode of the upstream selection process section of the second base station controller is set to the through mode with respect to the mobile station. 
     In accordance with a tenth aspect of the present invention, in the seventh aspect, when a mobile station, which has been executing communication in a mobile service area of a radio base station under a first base station controller, moved and started communication with another radio base station under a second base station controller and thereby the first base station controller finishes the communication with the radio base station thereunder and thereafter executes communication with the another radio base station under the second base station controller, the operation mode of the upstream selection process section of the first base station controller is set to the through mode with respect to the mobile station. 
     In accordance with an eleventh aspect of the present invention, in the seventh aspect, the communication between the mobile station and the radio base stations is executed by means of CDMA (Code Division Multiple Access). 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The objects and features of the present invention will become more apparent from the consideration of the following detailed description taken in conjunction with the accompanying drawings, in which: 
     FIG. 1 is a schematic block diagram for explaining a mobile radio communication system in accordance with an embodiment of the present invention; 
     FIG. 2 is a block diagram showing an example of the composition of an upstream selection process section of a base station controller which is shown in FIG. 1; and 
     FIGS. 3A and 3B are flow charts showing the operation of a selection process section of the upstream selection process section of FIG.  2 . 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring now to the drawings, a description will be given in detail of a preferred embodiment in accordance with the present invention. 
     FIG. 1 is a schematic block diagram for explaining a mobile radio communication system in accordance with an embodiment of the present invention. The mobile communication system shown in FIG. 1 includes a mobile station (MS)  101 , radio base stations (BS&#39;s)  102 A,  102 B,  102 C and  102 D, base station controllers (BSCs)  104  and  105 , and a mobile services switch center (MSC)  108 . 
     The radio base stations  102 A,  102 B,  102 C and  102 D take charge of mobile service areas  103 A,  103 B,  103 C and  103 D, respectively. The mobile station  101  shown in FIG. 1, which is executing mobile radio communication in the mobile service areas  103 A and  103 B of the radio base stations  102 A and  102 B, is moving toward the mobile service areas  103 C and  103 D of the radio base stations  102 C and  102 D. 
     The radio base stations  102 A and  102 B are connected to the base station controller  104 , and the radio base stations  102 C and  102 D are connected to the base station controller  105 . 
     The base station controller  104  (anchor-side base station controller) includes an upstream selection process section  106 . The upstream selection process section  106  executes selection from data which have been received by the radio base stations  102 A and  102 B from the mobile station  101  and which have been supplied from the radio base stations  102 A and  102 B to the base station controller  104 , and sends the selected data to the mobile switching exchange  108 . 
     The base station controller  105  (drift-side base station controller) includes an upstream selection process section  107 . When the mobile station  101  has moved into the mobile service areas  103 C and  103 D, the upstream selection process section  107  executes selection from data which have been received by the radio base stations  102 C and  102 D from the mobile station  101  and which have been supplied from the radio base stations  102 C and  102 D to the base station controller  105 , and sends the selected data to the base station controller  104  (anchor-side base station controller). 
     The mobile switching exchange  108  executes data communication with a network (PSTN (Public Switched Telephone Network), ISDN (Integrated Services Digital Network), etc.). 
     FIG. 2 is a block diagram showing an example of the composition of the upstream selection process section  106  of the base station controller  104 . Incidentally, the upstream selection process section  107  of the base station controller  105  also has the same composition. In FIG. 2, the upstream selection process section ( 106 ,  107 ) is shown as an upstream selection process section  200 . 
     Referring to FIG. 2, the upstream selection process section  200  ( 106 ,  107 ) includes an upstream frame reception section  201 , an upstream frame transmission section  202 , a selection process section  203 , a received data buffer  204 , a timing control section  205 , and a control section  206 . 
     The upstream frame reception section  201  receives upstream data from radio base stations which are connected thereto, and sends the upstream data to the selection process section  203 . 
     The control section  206  controls the operations of the upstream frame reception section  201 , the upstream frame transmission section  202 , the selection process section  203  and the received data buffer  204 . 
     The timing control section  205  provides processing timing to the selection process section  203 . 
     The selection process section  203  is provided with functions for storing information concerning an “operation mode” with respect to each mobile station  101  (in communication with the upstream selection process section  200 ) which is set by the control section  206 , operating according to the operation mode, storing/reading upstream data to/from the received data buffer  204 , executing selection process for upstream data according to the processing timing which is provided by the timing control section  205 , and sending the selected upstream data to the upstream frame transmission section  202 . When the operation mode of the selection process section  203  with respect to a mobile station  101  is “through mode” which will be explained later, the selection process section  203  does not execute the selection process with respect to the mobile station  101  and directly sends the upstream data from the mobile station  101  to the upstream frame transmission section  202 . 
     The upstream frame transmission section  202  receives the upstream data which have been selected by the selection process section  203  and transmits the selected upstream data to the next device (a mobile services switch center or a base station controller depending on whether the upstream selection process section  200  is anchor-side or drift-side). In the “through mode” which will be explained below, the upstream frame transmission section  202  receives the upstream data which have been directly outputted by the selection process section  203  without executing the selection process and transmits the upstream data to the next device. 
     FIGS. 3A and 3B are flow charts showing the operation of the selection process section  203  of the upstream selection process section  200  ( 106 ,  107 ) in accordance with the embodiment of the present invention. The operation of the selection process section  203  when the upstream selection process section  200  received data will be explained referring to FIGS. 3A and 3B. 
     The control section  206  of the upstream selection process section  200  of a base station controller constantly recognizes the number of radio base stations and lower base station controllers which are communicating with the base station controller, with respect to each mobile station  101  in communication with the upstream selection process section  200 . The number will hereafter be referred to as a “communicating connection number (with respect to a mobile station  101 )”. The control section  206  sets the operation mode of the selection process section  203  with respect to a mobile station  101  to “normal mode” when the communicating connection number with respect to the mobile station  101  is two or more, and to “through mode” when the communicating connection number with respect to the mobile station  101  is one. 
     When the selection process section  203  received upstream data which have been transmitted by a mobile station  101  (step  301 ), the selection process section  203  judges whether the operation mode of the selection process section  203  with respect to the mobile station  101  which has been set by the control section  206  is the through mode or not (i.e. the normal mode) (step  302 ). If the operation mode with respect to the mobile station  101  is the normal mode (“No” in the step  302 ), the selection process section  203  stores the received upstream data from the mobile station  101  in the received data buffer  204 . If the operation mode with respect to the mobile station  101  is the through mode (“Yes” in the step  302 ), the selection process section  203  directly transmits the received upstream data to the next device (that is, to the mobile switching exchange  108  (in the case where the upstream selection process section  200  is the upstream selection process section  106  (anchor-side)), or to the anchor-side base station controller  104  (in the case where the upstream selection process section  200  is the upstream selection process section  107  (drift-side))) via the upstream frame transmission section  202 , without storing the upstream data in the received data buffer  204  (step  304 ). 
     As explained above, the received upstream data is stored in the received data buffer  204  in the normal mode. Next, the upstream data transmission from the received data buffer  204  to the next device (the mobile switching exchange  108  or the anchor-side base station controller  104 ) will be explained. 
     According to the processing timing for the selection process which is provided by the timing control section  205  (when upstream data transmission timing has come) (step  305 ), the selection process section  203  reads out appropriate upstream data (that is, data corresponding to the same radio frame from the mobile station  101  which have been supplied from the radio base stations under the base station controller) from the received data buffer  204  (step  306 ), executes the selection process (step  307 ), and transmits the selected upstream data to the next device (that is, to the mobile switching exchange  108  (in the case where the upstream selection process section  200  is the upstream selection process section  106  on the anchor-side), or to the anchor-side base station controller  104  (in the case where the upstream selection process section  200  is the upstream selection process section  107  on the drift-side)) via the upstream frame transmission section  202  (step  308 ). 
     Referring again to FIG. 1, when the mobile station  101 , which has been located in the mobile service area  103 A of the radio base station  102 A under the base station controller  104 , moved into another mobile service area  103 C and started communication with the radio base station  102 C under the base station controller  105 , the communicating connection number of the upstream selection process section  107  of the base station controller  105  becomes 1 with respect to the mobile station  101 , and thereby the operation mode of the selection process section  203  with respect to the mobile station  101  is set to the through mode in the upstream selection process section  107  of the base station controller  105 . By the setting to the through mode, the time for buffering the upstream data from the mobile station  101  in the received data buffer  204  of the upstream selection process section  107  becomes unnecessary, and thereby the processing delay due to the data buffering is eliminated. 
     When the moving mobile station  101  finishes communication with the radio base stations  102 A and  102 B under the base station controller  104  and starts communication with the radio base stations  102 C and  102 D under the base station controller  105  only, the communicating connection number of the upstream selection process section  106  of the base station controller  104  becomes 1 with respect to the mobile station  101  (the connection with the base station controller  105  only, with respect to the mobile station  101 ) and thus the operation mode with respect to the mobile station  101  is set to the through mode in the upstream selection process section  106 , thereby the processing delay at the base station controller  104  is shortened. 
     As described above, in the mobile radio communication system in accordance with the embodiment of the present invention, the wait delay for the selection process of the base station controller ( 104 ,  105 ) can be minimized, since the operation mode of the selection process section  203  of the base station controller with respect to a mobile station  101  can be set to the through mode when the communicating connection number with respect to the mobile station  101  is 1 and thereby the time for buffering the upstream data in the received data buffer  204  of the base station controller can be eliminated. 
     For example, first, when the mobile station  101  moved out of a mobile service area of a radio base station under the anchor-side base station controller ( 104 ) and started communication with another base station under a drift-side base station controller ( 105 ), the operation mode of the selection process section  203  of the upstream selection process section  200  of the drift-side base station controller ( 105 ) is set to the through mode with respect to the mobile station  101  since the communicating connection number with respect to the mobile station  101  becomes (from 0) to 1, thereby the data buffering time at the drift-side base station controller ( 105 ) does not occur at this stage, and thereby the processing delay at the drift-side base station controller is shortened. 
     Second, when the mobile station  101  moved out of a mobile service area ( 103 A) of a radio base station ( 102 A) under the anchor-side base station controller ( 104 ) and started communication with another radio base station ( 102 C) under a drift-side base station controller ( 105 ) and thereby the anchor-side base station controller ( 104 ) finishes the communication with the radio base station ( 102 A) thereunder and thereafter executes communication with the another radio base station ( 102 C) under the drift-side base station controller ( 105 ), the communicating connection number of the upstream selection process section  200  of the anchor-side base station controller ( 104 ) with respect to the mobile station  101  becomes 1 (connection with the drift-side base station controller ( 105 ) only) and thus the operation mode of the selection process section  203  of the anchor-side base station controller ( 104 ) is set to the through mode, thereby the processing delay at the anchor-side base station controller ( 104 ) can be shortened. 
     While the present invention has been described with reference to the particular illustrative embodiments, it is not to be restricted by those embodiments but only by the appended claims. For example, the mobile radio communication system is not limited to CDMA mobile radio communication system. The present invention can also be applied to other types of mobile radio communication systems which employ the selection process requiring the data buffering. It is to be appreciated that those skilled in the art can change or modify the embodiments without departing from the scope and spirit of the present invention.