Patent Publication Number: US-2016242116-A1

Title: Radio access system and base station apparatus

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a continuation application of International Application Number PCT/JP2013/079405 filed on Oct. 30, 2013 and designated the U.S., the entire contents of which are incorporated herein by reference. 
    
    
     FIELD 
     The embodiments discussed herein are related to a radio access system and a base station apparatus. 
     BACKGROUND 
     Radio access systems such as a mobile telephone system and a wireless LAN (Local Area Network) are widely in use today. Also, in the field of the radio access system, continuous discussion is being made on a next generation communication technology to further improve the speed and the capacity of communication. For example, in the 3GPP (3rd Generation Partnership Project), which is a standardization association, the standardization of a communication specification called LTE (Long Term Evolution) and LTE-A (LTE-Advanced) based on LTE is completed or under discussion. 
     Further, the use of a radio access system by a novel terminal represented by a smartphone and a tablet is increasing today. To cope therewith, also in the 3GPP, the standardization of a communication specification in consideration of such a terminal is in progress. 
     The smartphone performs operation on the premise of continuous (always-on) connection. Therefore, when an application is used in the smartphone, there is continued a state that the smartphone is connected to a radio network such as a base station. For such reason, there is a problem of faster battery consumption in the smartphone than in a feature phone. 
     To cope with such a problem, a terminal manufacturer introduces, for example, a “Fast Dormancy” function into the smartphone etc. The “Fast Dormancy” function is a function to “disconnect” the connection to the radio network to shift to an “IDLE” state after the completion of data communication, based on the decision on the smartphone side, for example. In the “IDLE” state, the smartphone is disconnected from the radio network, for example. Therefore, the “Fast Dormancy” function enables the suppression of power consumption in the smartphone to elongate a battery available time. 
     On the other hand, there is a case that the smartphone periodically performs connection confirmation (Keep Alive) to the radio network even after the shift to the “IDLE” state. The connection confirmation is, for example, processing for confirming that the connection between the smartphone and the radio network is valid even in a non-communication state. 
     In this case, the smartphone performs the connection confirmation after reconnected to the “disconnected” radio network. Since the connection confirmation is performed periodically, the smartphone repeats reconnection and disconnection to/from the radio network for a multiplicity of times. Therefore, there is a case that, because of the connection confirmation, signal traffic (or signaling traffic) between the smartphone and the base station increases even in the smartphone in which the “Fast Dormancy” function is introduced. 
     As such, although the “Fast Dormancy” function is introduced, for example, to suppress battery consumption in the smartphone, from a differentiate viewpoint, signal traffic is not remarkably reduced, causing a factor to burden a heavy load on the radio network side. Further, the rapid spread of the smartphone produces a larger increase of signal traffic, causing a factor to burden a heavier load on the radio network. 
     To cope therewith, the 3GPP specifies a “Network Controlled Fast Dormancy” function (which may hereafter be referred to as a “Fast Dormancy (NW)” function). 
     In the “Fast Dormancy (NW)” function, a radio network, on receiving a request for the “Fast Dormancy (NW)” function from a smartphone, makes the smartphone shifted to an “URA_PCH” state, instead of the “IDLE” state, for example. 
     In the “URA_PCH” state, although connection to the radio network is contained, the terminal becomes a standby state in which the occurrence of new data or a call from the base station is awaited, for example, without data transmission or reception. Further, in the “URA_PCH” state, for example, the terminal maintains the standby state even if moving within a URA (UTRAN Registration Area) (or a plurality of cell groups), whereas when moving to another URA, the terminal shifts to an active state to transmit/receive a signal. 
     Accordingly, in the smartphone, when the connection confirmation is performed from the “IDLE” state, connection processing to the radio network is performed, whereas when connection confirmation is performed from the “URA_PCH” state, no connection processing to the radio network is performed because the smartphone is in the state of already connected to the radio network. 
     Thus, by the “Fast Dormancy (NW)” function, it is possible to reduce signal traffic as compared to a case in which reconnection is made from the “IDLE” state, to thereby suppress power consumption in the smartphone and elongate the battery available time. 
     Furthermore, there has been adopted new network architecture called HetNet (Heterogeneous Network) in order to cope with an increased communication volume in the overall network accompanying a remarkable spread of the smartphone. 
     The HetNet can improve the overall capacity of a radio access system by the use of a hierarchical configuration composed of a variety of sizes of cells, such as a microcell, a pico cell, etc. 
     CITATION LIST 
     Non-Patent Document 
     
         
         Non-patent document 1: 3GPP TS25.331 V9.15.0 (2013-06) 
       
    
     Although the “Fast Dormancy (NW)” function is specified in the 3GPP, there has been no specification on a method for further signal traffic suppression to enable the long-time use of a battery in a terminal such as a smartphone. 
     Also, no solution has been given on a generic method for signal traffic suppression, even taking network architecture such as the HetNet into consideration. 
     SUMMARY 
     According to one aspect of the embodiments, a radio access system including: a terminal apparatus, and a base station apparatus, wherein a first and second communicable areas of different size are located in hierarchy, the terminal apparatus moving from the first communicable area to the second communicable area and the base station apparatus perform radio communication, the base station apparatus includes: a control unit configured to change a time to maintain connection with the base station apparatus in the terminal apparatus and maintain a first state confirming connection to the base station apparatus at predetermined time interval without performing data transmission and reception, to a time longer than a reference time, according to an attribute of the first or second communicable area in which the terminal apparatus locates; and a transmission unit configured to transmit the changed time to maintain the first state to the terminal apparatus, and the terminal apparatus includes: a reception unit configured to receive the changed time to maintain the first state. 
     The object and advantages of the invention will be realized and attained by means of the elements and combinations particularly pointed out in the claims. 
     It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are not restrictive of the invention. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a diagram illustrating a configuration example of a radio access system. 
         FIG. 2  is a diagram illustrating a configuration example of a radio access system. 
         FIG. 3  is a diagram illustrating a configuration example of a radio base station apparatus. 
         FIG. 4  is a diagram illustrating a configuration example of a terminal apparatus. 
         FIG. 5  is a diagram illustrating a configuration example of a HetNet in a radio access system. 
         FIG. 6A  is a diagram illustrating an example of state transition when terminal controlled FD is applied, and  FIG. 6B  is a diagram illustrating an example of state transition when network controlled FD is applied, respectively. 
         FIGS. 7A through 7C  are diagrams illustrating examples of state transition operation when FD is applied. 
         FIG. 8  is a sequence chart illustrating an operation example of a radio access system. 
         FIG. 9  is a flowchart illustrating an operation example of a base station apparatus. 
         FIGS. 10A and 10B  are flowcharts illustrating operation examples of a base station apparatus. 
         FIGS. 11A and 11B  are flowcharts illustrating operation examples of a base station apparatus. 
         FIG. 12  is a flowchart illustrating an operation example of a base station apparatus. 
         FIGS. 13A and 13B  are diagrams illustrating examples of bearer hold timer set values. 
         FIG. 14  is a diagram illustrating a configuration example of a radio access system. 
         FIG. 15A  is a diagram illustrating a HetNet configuration example;  FIGS. 15B and 15C  are diagrams illustrating examples of information update timing when a terminal in each state moves;  FIG. 15D  is a diagram illustrating an example of information update timing when a terminal is in a URA_PCH state and stationary; and  FIGS. 15E and 15F  are diagrams illustrating examples of information update timing when a terminal in each state moves. 
         FIG. 16  is a diagram illustrating a configuration example of a radio base apparatus. 
         FIG. 17  is a diagram illustrating a configuration example of a radio base apparatus. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Hereinafter the present embodiments will be described in detail by reference to the drawings. 
     First Embodiment 
       FIG. 1  is a diagram illustrating a configuration example of a radio access system  10 . The radio access system  10  includes a base station apparatus  100  and a terminal apparatus  200 . 
     Further, in the radio access system  10 , a first communicable area  100 -C 1  and a second communicable area  100 -C 2  are located in hierarchy. In the example of  FIG. 1 , the second communicable area  100 -C 2  is disposed in the first communicable area  100 -C 1 . However, inversely, the first communicable area  100 -C 1  may be disposed in the second communicable area  100 -C 2 . The terminal apparatus  200  moves from the first communicable area  100 -C 1  to the second communicable area  100 -C 2 . 
     The base station apparatus  100  includes a control unit  150  and a transmitter unit  151 . 
     The control unit  150  changes a time to maintain a first state, in which the terminal apparatus  200  maintains connection with the base station apparatus  100  and confirms the connection to the base station apparatus  100  without data transmission and reception at predetermined time intervals, to a longer time than a reference time according to the attribute of the first or second communicable area  100 -C 1 ,  100 -C 2  in which the terminal apparatus  200  is located. 
     The transmitter unit  151  transmits the changed time to maintain the first state to the terminal apparatus  200 . 
     The terminal apparatus  200  includes a receiver unit  230 . The receiver unit  230  receives the changed time to maintain the first state. 
     As such, in the present first embodiment, the time to maintain the first state is changed to a time longer than the reference time, according to the attribute of the first or second communicable area  100 -C 1 ,  100 -C 2 . This enables the terminal apparatus  200  in the first state to confirm connection with the base station apparatus  100 , for example. 
     In this case, the terminal apparatus  200  is not transmit or receive a control signal for reconnection, as compared to, for example, a case of performing connection confirmation after becoming a second state in which the connection with the base station apparatus  100  is disconnected. This enables the suppression of signal traffic accordingly. 
     Further, by the suppressed signal traffic, for example, the number of transmitted and received control signals is suppressed in the terminal apparatus  200 . The non-execution of control signal transmission and reception can cause the suppression of power consumption and the elongation of the battery available time than a threshold. 
     Second Embodiment 
     Next, a second embodiment will be described. The second embodiment will be described in the following order. 
     &lt;1. Configuration example of radio access system&gt; 
     &lt;2. Configuration examples of base station and terminal&gt; 
     &lt;3. Configuration example of HetNet&gt; 
     &lt;4. Examples of state transition&gt; 
     &lt;5. Operation examples&gt; 
     1. Configuration Example of Radio Access System 
       FIG. 2  is a diagram illustrating a configuration example of a radio access system  10 . The radio access system  10  includes a base station apparatus (which may hereafter be referred to as “base station”)  100 , a terminal apparatus (which may hereafter be referred to as “terminal”)  200 , a CN (Core Network)  300  and a content server  500 . Also, in the radio access system  10 , the CN  300  and the content server  500  are connected through the Internet  400 . 
     In the present radio access system  10 , the terminal  200  is, for example, a smartphone, a tablet, etc., and includes the “Fast Dormancy” function. The “Fast Dormancy” function according to the second embodiment is performed under control from the radio network (NW) side, such as the base station  100  and the CN  300 . The detail of the NW controlled “Fast Dormancy” function by will be described later. 
     The base station  100  is a radio communication apparatus which performing radio communication with the terminal  200 . Also, the base station  100  can perform bidirectional radio communication with the terminal  200  in a communicable area (which may be referred to as a “cell area” or a “cell”). 
     More specifically, there are data transmission (or downlink communication) from the base station  100  to the terminal  200  and data transmission (or uplink communication) from the terminal  200  to the base station  100 . The base station  100  performs scheduling etc. to allocate each radio resource (for example, a time resource and a frequency resource) to the terminal  200 . The base station  100  transmits the allocated radio resource to the terminal  200  as a control signal. The base station  100  and the terminal  200  perform downlink communication and uplink communication using the radio resource. 
     The terminal  200  is, for example, a movable radio communication apparatus. Through radio communication with the base station  100 , the terminal  200  can receive a variety of services including speech communication and home page reading. In the example of  FIG. 2 , the terminal  200  can receive a content distribution service from the content server  500 . 
     The CN  300  is connected to the content server  500  through the base station  100  and the Internet  400 . The CN  300  is switching equipment which manages subscriber information and controls related to call connection, for example. Typically, the CN  300  performs the management of a user contract state, charging control, position registration, moving control including handover etc., bearer establishment and deletion, and so on. 
     The content server  500  includes, for example, a large capacity storage medium and stores a variety of contents including video and music, so as to distribute a content in response to a request from the terminal  200 . 
     2. Configuration Examples of Base Station and Terminal 
     Next, the configuration examples of the base station  100  and the terminal  200 .  FIG. 3  illustrates a configuration example of the base station  100  and  FIG. 4  illustrates a configuration example of the terminal  200 , respectively. 
     The base station  100  includes an antenna  101 , a radio unit  110 , and a control and baseband unit  120 . Further, the radio unit  110  includes a modulation and demodulation unit  111 , a transmitter unit  112 , a PA (Power Amplifier)  113 , a DUP (Duplexer)  114 , an LNA (Low Noise Amplifier)  115  and a receiver unit  116 . Further, the control and baseband unit  120  includes an interface unit  121 , a control unit  122 , a baseband unit  123 , a power unit  124  and a timing control unit  125 . 
     Here, the control unit  150  in the first embodiment corresponds to, for example, the control unit  122  and the timing control unit  125 . Also, the transmitter unit  151  in the first embodiment corresponds to, for example, the baseband unit  123 , the radio unit  110  and the antenna  101 . 
     The modulation and demodulation unit  111  performs IFFT (Inverse Fast Fourier Transform) processing etc. on a signal which is output from the baseband unit  123 , to convert the signal in the frequency domain into a signal in the time domain. Also, the modulation and demodulation unit  111  performs FFT (Fast Fourier Transform) processing etc. on a signal which is output from the receiver unit  116 , to convert the signal in the time domain into a signal in the frequency domain. In order to enable such processing, the modulation and demodulation unit  111  may be configured to internally include an IFFT circuit, an FFT circuit, etc. 
     The transmitter unit  112  converts (upconverts) the time domain signal which is output from the modulation and demodulation unit  111  into a radio signal in a radio band, to output the radio signal to the PA  113 . For this purpose, the transmitter unit  112  may be configured to internally include a frequency conversion circuit. 
     The PA  113  amplifies the radio signal output from the transmitter unit  112 . 
     The PA  113  may be configured to internally include an amplifier circuit. 
     The DUP  114  outputs the radio signal output from the PA  113  to the antenna  101 , and also outputs a radio signal output from the antenna  101  to the LNA  115 . The DUP  114  is, for example, an antenna duplexer or an antenna splitter. 
     The antenna  101  transmits the radio signal output from the DUP  114  to the terminal  200 . Also, the antenna  101  receives a radio signal transmitted from the terminal  200  to output to the DUP  114 . 
     The LNA  115  amplifies the radio signal output from the DUP  114 . The LNA  115  is, for example, a high frequency amplifier or a low noise amplifier, and may internally include an amplifier circuit. 
     The receiver unit  116  converts (downconverts) a radio band signal output from the LNA  115  into a baseband signal, to output the converted signal to the modulation and demodulation unit  111 . The receiver unit  116  may also be configured to internally include a frequency conversion circuit. 
     The interface unit  121  converts data, a control signal, etc. which are output from the control unit  122  into a format capable of transmission to the CN  300 , such as, for example, packet data, to transmit the converted packet data to the CN  300 . Also, the interface unit  121  receives packet data from the CN  300 , and extracts data, a control signal, etc. from the packet data to output to the control unit  122 . 
     The control unit  122  outputs data, a control signal, etc. output from the baseband unit  123 , to the interface unit  121  to instruct the interface unit  121  to transmit to the CN  300 . By this, the data, the control signal, etc. are transmitted to the CN  300 . 
     Also, the control unit  122  outputs the data and the control signal output from the interface unit  121  to the baseband unit  123 , to control to transmit to the terminal  200 . For example, the control unit  122  determines radio resource allocation (for example, frequency and time) to the terminal  200 , a modulation system, etc. to schedule. The control unit  122  generates a control signal including scheduling information, to transmit to the terminal  200  through the baseband unit  123 . 
     Further, the control unit  122  instructs the power unit  124  to switch on or off the power of the base station  100  to thereby control the power of the base station  100 . 
     In the present second embodiment, the control unit  122  and the timing control unit  125  perform processing related to the change of bearer hold timer setting. The detail thereof will be described later. 
     The baseband unit  123  performs error correction coding processing, modulation processing such as QPSK (Quadrature Phase Shift Keying) on the data, the control signal, etc. output from the control unit  122 , to output a signal after the modulation processing to the modulation and demodulation unit  111 . Also, the baseband unit  123  performs demodulation processing, error correction decoding processing, etc. on a signal output from the modulation and demodulation unit  111 , to extract data, a control signal, etc. to output to the control unit  122 . 
     The power unit  124  switches on and off the power of the overall base station  100  or the radio unit  110  in the base station  100 , according to the instruction from the control unit  122 . 
     As depicted in  FIG. 4 , the terminal  200  includes an antenna  201 , a radio unit  210  and a control and baseband unit  220 . Further, the radio unit  210  includes a modulation and demodulation unit  211 , a transmitter unit  212 , a PA  213 , a DUP  214 , an LNA  215  and a receiver unit  216 . Further, the control and baseband unit  220  includes a control unit  222 , a baseband unit  223  and a power unit  224 . 
     Here, the receiver unit  230  in the first embodiment corresponds to, for example, the antenna  201 , the radio unit  210  and the baseband unit  223 . 
     The antenna  201  receives a radio signal transmitted from the base station  100 , and outputs the received radio signal to the DUP  214 . Also, the antenna  201  transmits a radio signal output from the DUP  214  to the base station  100 . 
     The modulation and demodulation unit  211  performs IFFT processing etc. on a signal output from the baseband unit  223 , to convert into a time domain signal. Also, the modulation and demodulation unit  211  performs FFT processing etc. on a signal output from the receiver unit  216 , to convert into a frequency domain signal. 
     The transmitter unit  212  converts (upconverts) the time domain signal output from the modulation and demodulation unit  211  into a radio band signal. 
     The PA  213  amplifies the radio signal output from the transmitter unit  212 . 
     The DUP  214  outputs the radio signal, output from the PA  213 , to the antenna  201 , and outputs a radio signal, output from the antenna  201 , to the LNA  215 . 
     The LNA  215  amplifies the radio signal output from the DUP  214  to output to the receiver unit  216 . 
     The receiver unit  216  converts the radio signal into a baseband signal, to output to the modulation and demodulation unit  211 . 
     The baseband unit  223  performs demodulation processing, error correction decoding processing, etc. on a signal output from the modulation and demodulation unit  111  to extract data, a control signal, etc. Also, the baseband unit  223  performs error correction coding processing, modulation processing on data, a control signal, etc. which are output from the control unit  222 , to output the signal after modulation processing to the modulation and demodulation unit  211 . 
     The control unit  222  receives the control signal and the data from the baseband unit  223 , to output the data etc. to a monitor, a speaker, etc. to perform the output control of video and voice. Also, the control unit  222 , on receiving video and voice data from the monitor and a microphone, outputs the received data to the baseband unit  223  so as to be transmitted to the base station  100 . 
     In the present second embodiment, the control unit  222 , on detecting that the terminal  200  is in a non-communication state for a certain period, generates a disconnection request signal including SCRI (or a disconnection request message, which may hereafter be referred to as an “SCRI message”) to transmit to the base station  100 . The detail will be described later. 
     The power unit  224  switches on or off the power of the terminal  200 , according to an instruction from the control unit  222 . 
     3. Configuration Example of HetNet 
     In the present second embodiment, the radio access system  10  configures a HetNet environment. The HetNet signifies a hierarchical network constituted by various sizes of cells. The example of the radio access system  10  depicted in  FIG. 2  illustrates an example of one base station  100  for easy explanation. However, the HetNet environment may be constituted by a plurality of base stations, for example. 
       FIG. 5  is a diagram illustrating an example of a HetNet environment in the radio access system  10 . In the example of  FIG. 5 , there are included 6 macro cells  100 -M 1  to  100 -M 6  in the radio access system  10 . 
     Also, pico cells  100 -P 1  to  100 -P 6  are included in each macro cell  100 -M 1  to  100 -M 6 . For example, three pico cells  100 -P 1  to  100 -P 3  are included in the macro cell  100 -M 1 , and two pico cells  100 -P 4  to  100 -P 5  are included in the macro cell  100 -M 2 . 
     In the following, a cell having a smaller cell area than the macro cell  100 -M 1  to  100 -M 6  may be referred to as a “small cell”, for example. In the small cell, there are included a pico cell, a micro cell, a femto cell, etc. 
     “Cell” is a service provision area by the base station  100 , for example, and also a radio communicable area of the base station  100 . The base station  100  may include one cell or a plurality of cells, for example. The base station  100  and each cell thereof may integrally be referred to as “cell”, for example. 
     In the example of the HetNet environment depicted in  FIG. 5 , there is illustrated an example such that macro cells  100 -M 1  to  100 -M 6  include a plurality of small cells  100 -P 1  to  100 -P 16 . However, each macro cell  100 -M 1  to  100 -M 6  may include one small cell. 
     In the example of the HetNet environment depicted in  FIG. 5 , a plurality of cells are grouped into URA (UTRAN Registration Area)  1  ( 100 -U 1 ) to URA 3  ( 100 -U 3 ). The URA 1  ( 100 -U 1 ) includes the macro cells  100 -M 1  and  100 -M 2 , the URA 2  ( 100 -U 2 ) includes the macro cells  100 -M 3  and  100 -M 4 , and the URA 3  ( 100 -U 3 ) includes the macro cells  100 -M 5  and  100 -M 6 , respectively. 
     The URA is constituted by a plurality of grouped cells. If a terminal  200  which is in the “URA_PCH” state moves from one cell to another within the same URA, the terminal  200  does not notify the base station  100  of new cell information. On the other hand, if the terminal  200  in the “URA_PCH” state moves to another cell in a different URA, the terminal  200  notifies the base station  100  of new cell information. In other words, the terminal  200  in the “URA_PCH” state does not perform cell information notification processing etc. if moving to the other cell within the same URA. This enables the prevention of a signal traffic increase in comparison with a case of performing such cell information notification processing. The details of the “URA_PCH” state will be described later. 
     Incidentally, notification processing of the new cell information by the terminal  200  may also be referred to as, for example, Cell_update. For example, when the terminal  200  detects, in comparison with a reception signal level from the connected base station, a larger reception signal level from another base station, the terminal  200  performs the Cell_update by notifying the connected base station about the reception signal level of the other base station. 
     In the example of the HetNet environment depicted in  FIG. 5 , there is further provided a paging area. The paging area signifies an area in which the CN  300 , on receiving an incoming call from another CN etc., distributes the incoming call, for example. In the example of  FIG. 5 , the URA 1  ( 100 -U 1 ) to the URA 3  ( 100 -U 3 ) constitute one paging area. 
     In this case, the terminal  200  in the “IDLE” state does not perform position registration processing (for example, Location Registration) or the like while the terminal  200  is located in the same paging area, whereas performs position registration processing (for example, Location Registration) when moving to another paging area. The description of the “IDLE” state will also be given later. 
     4. Examples of State Transition 
     The terminal  200  can receive data or become a sleep state while shifting the state thereof. Now, the state transition of the terminal  200  will be described below. 
       FIGS. 6A and 6B  illustrate examples of state transition in the terminal  200 . The terminal  200  shifts among four states: “Cell_DCH”, “Cell_FACH”, “URA_PCH” and “IDLE”.  FIG. 6A  illustrates a state transition example when the terminal controlled “Fast Dormancy” function (which may hereafter be referred to as “FD (terminal)”) is performed, whereas  FIG. 6B  illustrates a state transition example when the network controlled “Fast Dormancy” function (which may hereafter be referred to as “FD (NW)”) is performed. 
     The “FD (terminal)” is, for example, a function in which after the completion of data communication, the terminal  200  “disconnects” connection with the radio network on the basis of the decision of the terminal  200 , to shift to the “IDLE” state. Therefore, as depicted in  FIG. 6A , the terminal  200  can shift from the “Cell_DCH” or the “Cell_FACH” to the “IDLE”. 
     On the other hand, the “FD (NW)” is, for example, a function in which the base station  100  or the CN  300  (which may hereafter be referred to as a “radio network”), on receiving from the terminal  200  an execution request of the “Fast Dormancy” function, shifts the state of the terminal  200  to the “URA_PCH” state, not to the “IDLE” state. Accordingly, as depicted in  FIG. 6B , the terminal  200  can shift from the “Cell_DCH” or the “Cell_FACH” to the “URA_PCH”, not to the “IDLE”. 
     When shifting to the “IDLE”, the terminal  200  is disconnected from the radio network. Therefore, in order that the terminal  200  shifts to the “Cell_DCH” to reconnect to the radio network, the terminal  200  transmits a connection request message, such as RRC Connection Reconfiguration, for example. 
     On the other hand, if shifting to the “URA_PCH”, the terminal  200  does not transmit a connection request message like RRC Connection Reconfiguration because connection with the radio network is continued. 
     Therefore, a signal traffic amount, which is to be transmitted and received when the terminal  200  shifts from the “URA_PCH” to the “Cell_DCH”, becomes smaller than a signal traffic amount to be transmitted and received when the terminal  200  shifts from the “IDLE” to the “Cell_DCH”. 
     Accordingly, as compared to the “FD (terminal)”, the “FD (NW)” can reduce a load on the radio network. More specific examples related to the number of control signals etc. will be described later. 
     Now, each state of the terminal  200  will be described below. 
     The “Cell_DCH” is a state in which, for example, the terminal  200  and the base station  100  are connected through an individual channel (DCH: Dedicated Channel). 
     In the “Cell_DCH” state, because data transmission/reception is performed, power consumption in the terminal  200  becomes larger as compared to other states. 
     The “Cell_FACH” is a state in which, for example, the terminal  200  and the base station  100  are connected through a common channel (FACH: Forward Access Channel). In the “Cell_FACH”, because data transmission/reception is performed in the case of necessity, power consumption is smaller than in the “Cell_DCH”. Further, in the case of the “Cell_FACH” state, a data amount capable of transmission/reception becomes smaller than in the “Cell_DCH”, because a plurality of terminals transmit data using each limited shared channel. 
     The “URA_PCH” is, for example, a state (or a sleep state) in which the terminal  200 , which is connected to the base station  100  etc., waits for the occurrence of new data or a call from the base station  100  without data transmission and reception. Further, in the URA, the terminal  200  in the “URA_PCH” state moves in the sleep state, and therefore, the power consumption is smaller than in the “Cell_DCH”. Further, the terminal  200  in the “URA_PCH” state does not perform Cell_update if the terminal  200  moves from one cell to another cell in the same URA, whereas performs Cell_update if moving to another cell in a different URA. 
     The “IDLE” is, for example, a state in which the terminal  200 , whose connection with the radio network is disconnected, waits for the occurrence of new data or a call from the base station  100 , without data transmission and reception. The terminal  200  in the “IDLE” state does not perform Cell_update if moving from one cell to another in the same paging area, whereas performs notification of new paging area information (for example, Location Registration) when moving to another paging area. 
     The “Cell_DCH” and the “Cell_FACH” states may be referred to as an active state, for example. 
       FIGS. 7A through 7C  illustrate operation examples of shift transition in the terminal  200 . In  FIGS. 7A through 7C , the horizontal axis represents time, whereas the vertical axis represents state transition. 
       FIG. 7A  illustrates an example of state transition in the terminal  200  without provision of the “Fast Dormancy” function (which may hereafter be referred to as “without FD”). 
     In the case of “without FD”, the terminal  200  is continuously in the “Cell_DCH” when an application is in use. The terminal  200  maintains the “Cell_DCH” even when no communication state exists. 
     Here, the terminal  200  performs Keep Alive (or connection confirmation) to the base station  100  and the CN  300  after the lapse of each predetermined period (or at predetermined time intervals). Such Keep Alive enables the terminal  200  to confirm a valid connection with the radio network side. 
     In the case of “without FD”, because the terminal  200  maintains the “Cell_DCH” during the use of application, the terminal  200  can perform the Keep Alive without particular state transition. 
       FIG. 7B  is an operation example of state transition in the terminal  200  in a case based on the “FD (terminal)”. 
     In the case of the “FD (terminal)” also, when the use of application is started, transition is made from the “IDLE” to the “Cell_DCH”. the When non-communication state continues after shifting to the “Cell_DCH”, the terminal  200  shifts to the “Cell_FACH”, and transmits an SCRI message to the base station  100 . Thereafter, the terminal  200  shifts to the “IDLE” by its own decision. 
     In the case of the “FD (terminal)” also, the terminal  200  performs the Keep Alive after the lapse of each predetermined time.  FIG. 7B  illustrates an example in which the terminal  200 , after shifting to the “IDLE”, performs the Keep Alive from the “IDLE” state because the predetermined time elapses. 
     In this case, in order to perform processing related to the Keep Alive, the terminal  200  shifts from the “IDLE” to the “Cell_DCH”. The terminal  200  then transmits and receives each control signal related to the Keep Alive, so as to perform the Keep Alive. 
     To perform the Keep Alive, the terminal  200  shifts from the “IDLE” to the “Cell_DCH”, and the number of control signals to be transmitted and received at the shift is “30”, as an example. 
       FIG. 7C  illustrates an operation example of state transition in the terminal  200  in a case based on the “FD (NW)”. 
     In the case of the “FD (NW)”, if non-communication state continues in the “Cell_DCH”, the terminal  200  shifts to the “Cell_FACH”, and transmits an SCRI message. Thereafter, the terminal  200 , on receiving notification from the base station  100 , shifts to the “URA_PCH”, for example. 
     In the case of the “FD (NW)” also, the terminal  200  performs the Keep Alive whenever a predetermined time elapses. In  FIG. 7C , there is illustrated an example in which, after shifting to the “URA_PCH”, the terminal  200  performs the Keep Alive from the “URA_PCH” state because the predetermined time elapses. 
     In this case, to perform processing related to the Keep Alive, the terminal  200  shifts from the “URA_PCH” to the “Cell_DCH” through the “Cell_FACH”. Then, the terminal  200  in the “Cell_FACH” transmits and receives each control signal related to the Keep Alive, so as to perform the Keep Alive. The number of control signals transmitted and received when shifting from the “URA_PCH” to the “Cell_DCH” is “15”, as an example. 
     As such, the number of control signals transmitted and received at the shift from the “URA_PCH” to the “Cell_DCH” is smaller than the number of control signals transmitted and received at the shift from the “IDLE” to the “Cell_DCH”. The reason is that, because the terminal  200  in the “URA_PCH” state is connected to the radio network, no transmission and reception of a connection request message etc., for example, is performed, as described earlier. 
     In the “FD (terminal)” and the “FD (NW)”, in each state among the existent four states, a time to maintain the state is fixed in advance, as a reference time (or a reference value), for example. Such a reference time may be held in the memory of the terminal  200 , for example. 
     For example, in the case of the “FD (NW)”, a set time in which the terminal  200  maintains the “URA_PCH” state is also fixed as a reference value. 
     The reason for such fixation of time to maintain the “URA_PCH” state etc. as the reference time is as follows, for example. 
     Namely, in each state like the “Cell_DCH”, each radio resource for the individual channel and the shared channel is secured. However, when considering other data communication, it is not appropriate to secure the secured radio resource continuously and permanently. It is rather appropriate to release the secured radio resource after the lapse of a certain time. Therefore, in each state like the “URA_PCH” etc. for example, a set time to maintain the state is fixed as the reference value. 
     In the present second embodiment, the set time to maintain the “URA_PCH” in the “FD (NW)” is fixed as a reference time, for example. However, the set time can be set longer than the reference time according to the attribute of the cell. This enables further suppressing a signal traffic amount when the “FD (NW)” is performed, for example. Hereafter, the detail thereof will be described in an operation example. 
     5. Operation Example 
     An operation example in the present second embodiment will be described below. 
       FIG. 8  is a sequence chart illustrating the overall operation example of the radio access system  10 , and  FIG. 9  through  FIG. 12  are flowcharts illustrating the operation example of the base station  100 . 
     First, an example of the overall operation of the radio access system  10  will be described, and next, an operation example of the base station  100  will be described. 
     &lt;5-1. Overall Operation Example of Radio Access System&gt; 
     As depicted in  FIG. 8 , the terminal  200  transmits and receives user data etc. between with the base station  100  and the CN  300 , so as to use a service content (S 10 ). In this case, the terminal  200  is in the “Cell_DCH” state. 
     Next, when non-communication state continues for a predetermined time, the terminal  200  transmits an SCRI message (S 11 ). 
     For example, the control unit  222  of the terminal  200  (for example,  FIG. 4 ) monitors data, each signal, etc. which are input and output from/to the baseband unit  223 , to count a time having no input/output of the data and the signal by use of a “timer”. The control unit  222 , when counting up the predetermined time by the “timer”, discriminates that the terminal  200  is in a non-communication state, so as to generate the SCRI message. 
     In this case, the control unit  222  transmits the SCRI message by including therein request information for requesting the execution of the “Fast Dormancy” function. 
     Here, the “timer” may be provided separately from the control unit  222 , or may be actualized by the execution of a program in the control unit  222 , as a “timer” function. 
     Returning back to  FIG. 8 , the base station  100 , on receiving the SCRI message, activates the “Fast Dormancy” function according to the “Fast Dormancy” request included in the SCRI message (S 12 ). 
     For example, the control unit  122  of the base station  100  (for example,  FIG. 3 ) determines to activate the “Fast Dormancy” function when the request information for requesting the execution of the “Fast Dormancy” function is successfully extracted from the SCRI message. 
     Returning back to  FIG. 8 , next, the base station  100  changes a bearer hold timer set value according to the attribute of the cell (S 13 ). The bearer hold timer set value signifies a time to maintain the “URA_PCH”, for example. As described earlier, the bearer hold timer set value is fixed in advance as a reference value, for example. However, in the present second embodiment, the reference value can be changed according to the cell attribute. The detail thereof will be described later. 
     Returning back to  FIG. 8 , next, by the activation of the “Fast Dormancy” function, the base station  100  instructs the terminal  200  to shift the state of the terminal  200  to the “URA_PCH” (S 14 ). 
     For example, the control unit  122  of the base station  100  (for example,  FIG. 3 ) generates an instruction message to instruct to shift the state of the terminal  200  to the “URA_PCH”, so as to transmit to the terminal  200 . In this case, the control unit  122  generates the instruction message which includes the changed bearer hold timer set value. Here, the control unit  122 , when not changing the bearer hold timer set value, may include the fixed reference value of the bearer hold timer set value in the instruction message. 
     Returning back to  FIG. 8 , the terminal  200 , on receiving the instruction message instructing to shift to the “URA_PCH” (S 14 ), shifts the state of the terminal  200  from the “Cell_DCH” to the “URA_PCH”, and transmits a response message to the base station  100  (S 15 ). 
     For example, the control unit  222  of the terminal  200  (for example,  FIG. 4 ), on receiving the instruction message from the baseband unit  223 , shifts the state of the terminal  200  to the “URA_PCH”. 
     In the above “URA_PCH” state, as described earlier, there comes to a state in which, although connection to the radio network is maintained, there is no data transmission and reception. For example, in the base station  100  and the CN  300  on the radio network side, a bearer ID indicative of connection with the terminal  200  is held if the terminal  200  becomes the “URA_PCH” state, and also, the control unit  222  of the terminal  200  holds the bearer ID or information related to the bearer ID. 
     Further, in the “URA_PCH” state, the control unit  222  does not perform data transmission and reception, and maintains the “URA_PCH” state until the occurrence of data, processing by the Keep Alive, or the lapse of a time set by the bearer hold timer set value. 
     Here, the control unit  222  extracts the bearer hold timer set value from the instruction message received from the baseband unit  223 , so that can obtain a set time to maintain the “URA_PCH” state. Further, when shifting the state of the terminal  200  to the “URA_PCH”, the control unit  222  activates the “bearer hold timer” to start counting. 
     In this case, the set time is set into the “bearer hold timer”, and counting is continued until the set time elapses. When the count value reaches the set time, the “bearer hold timer” expires. On the expiration of the “bearer hold timer”, the control unit  222  shifts the state of the terminal  200  from the “URA_PCH” state to the “IDLE” state. 
     Here, the count operation may be performed using a “bearer hold timer” which is provided separately from the control unit  222 , for example, or alternatively, by the execution of a program in the control unit  222 , the “bearer hold timer” may be actualized as a function of the control unit  222 . 
     Returning back to  FIG. 8 , the base station  100 , on receiving a response message from the terminal  200  (S 15 ), generates a response message to transmit to the CN  300  (S 16 ). 
     For example, on receiving the response message from the baseband unit  123 , the control unit  122  of the base station  100  generates a response message indicating that the terminal  200  is shifted to the “URA_PCH”, so as to transmit to the CN  300  through the interface unit  121 . 
     Returning back to  FIG. 8 , if transmission data occurs before the lapse of the set time set in the “bearer hold timer”, the terminal  200  transmits to the base station  100  a control signal which indicates the occurrence of data communication (S 17 ). 
     For example, on detection of the occurrence of the transmission data which includes a character, voice, etc. from a display unit, a microphone, etc., the control unit  222  of the terminal  200  (for example,  FIG. 4 ) generates a control signal indicative of the occurrence of data communication, so as to transmit to the base station  100 . In this case, the control unit  222  transmits the control signal by shifting the state of the terminal  200  from the “URA_PCH” to the “Cell_FACH”. 
     Returning back to  FIG. 8 , on receiving from the terminal  200  the control signal indicative of the occurrence of data communication, the base station  100  generates a message indicating that transmission data occurs in the terminal  200 , and transmits the message to the CN  300  (S 18 ). 
     For example, on receiving from the baseband unit  123  the control signal indicative of the occurrence of data communication, the control unit  122  of the base station  100  (for example,  FIG. 3 ) generates a message indicating that transmission data occurs in the terminal  200 , to transmit to the CN  300  through the interface unit  121 . 
     Returning back to  FIG. 8 , next, the base station  100  instructs the terminal  200  to shift the state of the terminal  200  to the “Cell_DCH” (S 19 ). 
     For example, the control unit  122  of the base station  100  (for example,  FIG. 3 ) generates an instruction message to instruct to shift the state of the terminal  200  to the “Cell_DCH”, so as to transmit to the terminal  200 . 
     Returning back to  FIG. 8 , the terminal  200 , on receiving the instruction message (S 19 ), shifts the state of the self-terminal  200  from the “Cell_FACH” to the “Cell_DCH”, and transmits the data to the base station  100  and the CN  300  through the base station  100 . 
     For example, on receiving from the baseband unit  223  the instruction message to shift to the “Cell_DCH”, the control unit  222  of the terminal  200  (for example,  FIG. 4 ) shifts the state of the terminal  200  to the “Cell_DCH”, so as to resume data communication. 
     &lt;5-2. Operation Example of Base Station&gt; 
     Next, an operation example of the base station  100  will be described using  FIG. 9  through  FIG. 12 . The operation example of the base station  100  is partially duplicated with the aforementioned overall operation example of the radio access system  10 , so that the description will be made with appropriate omission. 
       FIG. 9  is a flowchart indicative of the overall operation example of the base station  100 .  FIGS. 10A through 12  are flowcharts indicative of each operation example. 
     The overall operation example of the base station  100  will be described using  FIG. 9 . The base station  100 , on starting processing (S 30 ), receives from the terminal  200  an SCRI message which includes information for requesting the execution of the “Fast Dormancy” function (S 31 ). 
       FIG. 10A  is a flowchart illustrating the operation example of the SCRI reception processing (S 31 ). The base station  100 , on starting the SCRI reception processing (S 40 ), receives the SCRI message from a user (or the terminal  200 ) (S 41 ), to activate the “FD (NW)” function (S 42 ). The base station  100  then completes a series of SCRI reception processing (S 43 ). 
     Returning back to  FIG. 9 , next, at the time point of receiving the SCRI message from the terminal  200 , the base station  100  determines whether to change the bearer hold timer set value according to the cell attribute (S 32 -S 33 ). 
     More specifically, if the cell type of an area in which the terminal  200  is communicating is “small cell” (YES in S 32 ), and if the area attribute of the cell is “high mobility” (YES in S 33 ), the base station apparatus  100  changes the bearer hold timer set value (S 34 ). 
     As described earlier, in the case of the “FD (NW)”, the bearer hold timer set value is, for example, a uniform reference value. 
     However, in the radio access system  10  like the HetNet, different types of cells are included. Also, there is a case that the terminal  200  moves from one cell to another which are of mutually different types. In such a case, if the bearer hold timer set value is fixed to the uniform reference value, it can hardly be said that a bearer hold timer set value fit to the terminal  200  which moves in the HetNet is set. 
     Accordingly, the base station  100  changes the bearer hold timer set value to a longer value than the reference value when the cell type of the area in which the terminal  200  is communicating is “small cell”, and when the area attribute of the area concerned (or the area attribute of the cell concerned) is “high mobility”. 
     For example, the base station  100  changes the bearer hold timer set value to a longer time than the execution time interval of the Keep Alive. 
     This enables the base station  100  to set a bearer hold timer set value according to the terminal  200  which moves in the HetNet, for example. In particular, by the change of the bearer hold timer set value to a longer time than the predetermined time interval of the execution of the Keep Alive, signal traffic caused by the Cell_update can be reduced further, as compared to the case when the bearer hold timer set value is set to the reference value. The reason will be described later. 
     Here, the cell attribute indicates, for example, whether or not the cell type of the area in which the terminal  200  is communicating is “small cell”, and also whether or not the area attribute of the area (of the cell) concerned is “high mobility”. 
     Returning back to  FIG. 9 , the detail of the processing of S 32  and after will be described. The base station  100 , on receiving the SCRI message (S 31 ), discriminates whether or not the cell type of the area in which the terminal  200  is communicating is “small cell” (S 32 ). 
       FIG. 10B  is a flowchart illustrating an operation example of small cell determination processing (S 32 ). The base station  100 , on starting the processing (S 50 ), activates a cell type determination function (S 51 ). For example, the control unit  122  of the base station  100  (for example,  FIG. 3 ) executes a program for cell type determination, so that can activate the function concerned. 
     Next, the base station  100  determines a cell ID (S 52 ). For example, the base station  100  determines from the cell ID the cell type of the area in which the terminal  200  is communicating. In this case, for example, the base station  100  may determine the cell type on the basis of the cell ID of a travel destination received from the terminal  200 , through the Cell_update processing which is performed in the terminal  200  during data communication (for example, S 10  in  FIG. 8 ). 
     Such determination of the cell ID is executed in, for example, the control unit  122  of the base station  100  (for example,  FIG. 3 ). There are a variety of determination methods using the cell ID. For example, the control unit  122  determines to be a “macro cell” if the cell ID received from the terminal  200  by the Cell_update is smaller than a predetermined number (for example, “50,000”), whereas a “small cell” if the cell ID is the predetermined number of greater. Alternatively, by the storage of each cell type item in a cell ID list held in a memory etc., the control unit  122  may determine by reading out the cell type corresponding to the received cell ID from the cell type item in the cell ID list. 
     Returning back to  FIG. 10B , on deciding that the cell type of the area in which the terminal  200  is communicating is “small cell” (YES in S 52 ), the base station  100  terminates the small cell determination processing, and shifts to mobility determination processing (S 53 , S 54 ). On the other hand, when the cell type is “macro cell” (NO in S 52 ), the base station  100  terminates the small cell determination processing, and shifts to state transition instruction notification processing (S 55 , S 56 ). 
     Returning back to  FIG. 9 , on deciding that the cell type is “small cell”, the base station  100  performs the mobility determination processing (S 33 ). For example, the base station  100  determines whether the area attribute of the area in which the terminal  200  is communicating indicates “high mobility” or “low mobility”. 
       FIG. 11A  is a flowchart illustrating an operation example of the mobility determination processing (S 33 ). On starting the mobility determination processing (S 60 ), the base station  100  activates an area attribute determination function (S 61 ). For example, the control unit  122  of the base station  100  (for example,  FIG. 3 ) executes a program for area attribute determination, so that can activate the area attribute determination function. 
     Returning back to  FIG. 11A , next, the base station  100  performs mobility determination (S 62 ). For example, the mobility determination is performed in the control unit  122  of the base station  100  (for example,  FIG. 3 ). As a determination method, for example, an “area having a railroad and a highway” in the cell concerned can be determined to be a “high mobility” area, whereas another area can be determined to be a “low mobility” area. 
     More specifically, the determination is made in the following manner, for example. Namely, the control unit  122  receives a cell ID notified from the terminal  200  by the Cell_update to thereby discriminate a cell in which the terminal  200  is communicating and obtain the position information of the cell of concern. The cell position information includes a predetermined area in a radius of 500 meters etc., for example. The control unit  122  then compares the cell position information with map information, to identify the area in the map information corresponding to the cell position information, so that can determine based on whether there is vector information related to “railroad” and “highway” in the identified area. The control unit  122 , for example, downloads the map information through the Internet  400 , to perform mobility determination using the most up-to-date map information. 
     When the base station  100  determines that the area attribute of the area in which the terminal  200  is communicating indicates “high mobility” (YES in S 62 ), the base station  100  terminates the mobility determination processing, to shift to bearer hold timer setting change processing (S 63 , S 64 ). On the other hand, on deciding that the area attribute of the area in which the terminal  200  is communicating indicates “low mobility” (NO in S 62 ), the base station  100  terminates the mobility determination processing, to shift to the state transition instruction notification processing (S 65 , S 66 ). 
     Returning back to  FIG. 9 , on the determination of “high mobility” (YES in S 33 ), the base station  100  performs the bearer hold timer setting change processing (S 34 ). 
       FIG. 11B  is a flowchart illustrating an operation example of the bearer hold timer setting change processing (S 34 ). On starting the bearer hold timer setting change processing (S 70 ), the base station  100  changes the setting of the bearer hold timer (S 71 ). 
     The setting change of the bearer hold timer is performed in, for example, the control unit  122  of the base station  100  (for example,  FIG. 3 ). The control unit  122  sets a bearer hold timer set value to be a longer value than the reference value. Here the value to be set may be either a fixed value or a variable value. In the case of the fixed value, the control unit  122  reads out the value held in the memory etc., so that can determine the value to be the bearer hold timer set value. 
     As an example of variable value setting, for example, there is an example as follows. 
     (Variable Value Setting Example 1) 
     Let t 1  [sec] be the reference value of the bearer hold timer set value, and a “n” be a variable, then a variable value T is expressed as 
         T=n·t 1 [sec]  (1)
 
     The variable “n” of the variable value T is determined in the following manner, for example. Namely, when a Keep Alive period while the terminal  200  uses an application is t 2  [sec], determine a variable “n” which satisfies 
         T&gt;t 2. 
     In this case, the variable “n” is 
         n·t 1&gt; t 2, 
       therefore 
         n &gt;( t 2/ t 1)  (2)
 
     is obtained. 
     For example, the control unit  122  holds the reference value “t 1 ” and the Keep Alive period “t 2 ” in the memory etc., and substitutes the above values into expression (2), so as to obtain a variable “n” which satisfies expression (2). The control unit  122  then substitutes the obtained variable “n” into expression (1) to obtain a variable value T. 
     (Variable Value Setting Example 2) 
     Supposing there are known values of a moving speed v [km/h] of the terminal  200  and a distance x [m] from the present position of the terminal  200  to a cell edge, let t [sec] be a time consumed when the terminal  200  moves from the present position to a cell edge, then 
         t= 3.6 x/v≧T&gt;t 2 
       therefore, 
         t= 3.6 x/v&gt;t 2  (3)
 
     is obtained. 
     Here, if expression (3) is not satisfied, in other words, 3.6x/v&lt;t 2  is held, the terminal  200  passes through a “small cell” area while moving in the cell. In this case, for example, the control unit  122  does not change the setting of the bearer hold timer. 
       FIG. 13A  illustrates an example of the values of the movement time t (=T) which can be taken in combination between the values of a distance x (=X) to the cell edge and a moving speed v (=V). It is assumed that the movement time t (=T) depicted in  FIG. 13A  satisfies expression (3). 
     For example, the control unit  122 , when acquiring the moving speed v and the distance x, confirms whether or not expression (3) is satisfied. Then, the control unit  122  may be configured to determine the variable set value when expression (3) is satisfied, using another setting example (for example, variable value setting example (1)), for example. 
     (Variable Value Setting Example 3) 
     It is also possible to perform statistic processing for each set variable value T in an OAM (Operation, Administration and Maintenance: monitor and control) apparatus (or system) etc., and based on the result thereof, obtain the average value of the variable value T, so as to set the variable “n” of the variable value T. 
       FIG. 14  is a diagram illustrating a configuration example of the radio access system  10  which includes an OAM apparatus  600 . The OAM apparatus  600  receives from the base station  100  and the CN  300  the feedback result of operation information, and receives the variable value T and the variable n included in the operation information. In this case, time, location or district, in which the variable value T and the variable n are set, is included in the operation information. The OAM apparatus  600  holds in a memory etc. the variable value T and the variable n according to the time and the place, as statistic information. 
       FIG. 13B  is a diagram illustrating an example of the statistic information held in the OAM apparatus  600 . In the example of  FIG. 13B , there are included “time zone”, “weekdays” and “holidays” as time, and “cell  1  (urban)” and “cell  2  (suburb)” as location. In this case, the control unit  122  of the base station  100  obtains the time and the location when the variable n is set from map information, a timer, etc., to transmit to the OAM apparatus  600  as operation information. The OAM apparatus  600  obtains such operation information to hold the statistic information as depicted in  FIG. 13B . 
     Then, when setting the variable value T, the control unit  122  of the base station  100  obtains a set time and a location from the timer and the map information, to transmit to the OAM apparatus  600 , so that the OAM apparatus  600  reads out the variable “n” corresponding to the received time and the location. The OAM apparatus  600  then transmits the variable “n” to the base station  100 , and the control unit  122  of the base station  100  sets the variable value T on the basis of the received variable “n”, using expression (1) etc. 
     Here, in an early stage of the setting of the variable value T, the above-mentioned (Variable value setting example 1) or (Variable value setting example 2) may be applicable, because of a lack of the number of statistic information items. 
     Also, although the description is given in the example of  FIG. 13B  on the example in which the variable “n” is included in the statistic information, the variable value T itself may be included in the statistic information. Also, although the description is given in the example of  FIG. 13B  on the example in which the time and the location are included as the statistic information, it is possible that either one of the time and the location is used according to the environment condition of the radio access system  10  and the values of a variety of set parameters, or information other than the time and the location is included. 
     (Variable Value Setting Example 4) 
     It is also possible that a system operator arbitrarily sets the variable value T. In this case, for example, the variable value T may be arbitrarily set by the system operator using the variable “n” of expression 1, or the variable value T itself may be set. As to a condition set to  FIG. 13B , another item than the time zone and the location is settable by the operator. Based on the set condition, the control unit  122  changes the setting of the bearer hold timer. 
     That is all for the description on the variable value setting examples. 
     Returning back to  FIG. 11B , the base station  100 , on completion of changing the setting of the bearer hold timer (S 71 ), completes the bearer hold timer setting change processing (S 72 ). 
     Returning back to  FIG. 9 , after changing the setting of the bearer hold timer, the base station  100  performs the state transition instruction notification processing (S 35 ).  FIG. 12  is a flowchart illustrating an operation example of the state transition instruction notification processing. 
     The base station  100 , on starting the state transition instruction notification processing (S 80 ), performs state transition instruction notification (S 81 ). For example, the control unit  122  of the base station  100  generates an instruction message to instruct the terminal  200  to shift to the “URA_PCH”, and transmits the generated instruction message to the terminal  200 . At this time, the control unit  122  transmits the instruction message by including therein the changed bearer hold timer set value. 
     Here, the control unit  122  transmits the instruction message to instruct to shift to the “URA_PCH” after deciding to be “macro cell” in the determination of a cell type (NO in S 32  of  FIG. 9 ) and after deciding to be “low mobility area” in the determination of mobility (NO in S 33  of  FIG. 9 ) also. In this case, because the control unit  122  maintains the reference value intact as the bearer hold timer set value, the control unit  122  transmits the instruction message by including therein the reference value, as the bearer hold timer set value. 
     Returning back to  FIG. 12 , the base station  100 , on completion of the state transition instruction notification (S 81 ), completes the state transition instruction notification processing (S 82 ). 
     Returning back to  FIG. 9 , on completion of the state transition instruction notification processing (S 35 ), the base station  100  completes a series of processing (S 36 ). 
     &lt;5-3. Example of Information Update in Each State&gt; 
     Next, an example of information update in the terminal  200  will be described.  FIG. 15A  illustrates an example of a HetNet environment, and  FIGS. 15B through 15F  illustrate the way of updating information by the terminal  200  in each state. 
       FIG. 15A  is a diagram illustrating an example of the HetNet environment in the radio access system  10 . In the example of  FIG. 15A , there are three paging areas i.e. a paging area 1  to a paging area 3 . The terminal  200  moves from the paging area 1  to the paging area 3  as depicted with an arrow. 
     The paging area 2  includes the URA 1  to the URA 3 , and the terminal  200  moves from the URA 1  to the URA 3 . There are two macro cells included in the URA 2 , and further, there are two small cells included in each macro cell. 
     As depicted in  FIG. 15A , the terminal  200  traverses two macro cells and four small cells in the URA 2 . The examples of information update when the terminal  200  moves as such are depicted in  FIGS. 15B through 15D . In  FIGS. 15B through 15D , the horizontal axes represent the time and the vertical axes represent states and examples of transmission information. 
       FIG. 15B  illustrates an example of information update when the terminal  200  moves in the “IDLE” state. 
     As described earlier, the terminal  200  in the “IDLE” state does not perform the Cell_update even when moving from one cell to another within the same paging area. In this case, if the terminal  200  moves to a different paging area, the terminal  200  performs information update (for example, Location Registration: LR). In the example of  FIG. 15B , the terminal  200  performs information update twice, namely, when moving from the paging area 1  to the paging area 2  and when moving from the paging area 2  to the paging area 3 . 
       FIG. 15C  illustrates an example of the information update when the terminal  200  in an active state moves. 
     The terminal  200  in the active state performs Cell_update when moving from one cell to another. By the execution of the Cell_update, the terminal  200  can notify the base station  100  of the present location, for example. Then, based on the notification, the base station  100  can grasp the ID of the cell in which the terminal  200  is currently located, and also the cell attribute. In the example of  FIG. 15C , the terminal  200  performs 11 times of information update. 
       FIG. 15D  illustrates an example of information update when the terminal  200  in the “URA_PCH” state is stationary. 
     The terminal  200  in the “URA_PCH” state performs the information update when moving from one URA to another, for example. In the example of  FIG. 15D , the terminal  200  performs URA_update when moving to the URA 2 , to perform the information update. By the URA_update, the base station  100  can grasp a URA in which the terminal  200  is located. 
       FIG. 15E  illustrates an example of information update when the terminal  200  in the “URA_PCH” state moves within the URA. In the example of  FIG. 15E , the set value of the bearer hold timer is the reference value. 
     The terminal  200  performs the URA_update when moving within the URA. In this case, the terminal  200  shifts from the “URA_PCH” to the active state and performs the URA_update. 
     After performing the URA_update, the terminal  200  shifts from the active state to the “URA_PCH” again. After shifting to the “URA_PCH”, when it becomes a set time (“URA_Timer” in  FIG. 15 ) set by the bearer hold timer set value, the terminal  200  shifts from the “URA_PCH” to the “IDLE”. 
     After shifting to the “IDLE” state, when it becomes a predetermined time to perform the Keep Alive, the terminal  200  shifts from the “IDLE” state to the active state and performs the Keep Alive. 
     The terminal  200  after performing the Keep Alive returns to the “URA_PCH” state again. Thereafter, the terminal  200  repeats the above-mentioned processing when moving within the URA. 
     Then, the terminal  200  performs the URA_update when moving to the outside of the URA. 
     In the example of  FIG. 15E , the terminal  200  performs at least 7 times of information update. 
     Here, a numeral described in  FIG. 15E  represents the number of messages (or the number of control signals) which are transmitted and received between the terminal  200  and the base station  100 . 
     For example, the terminal  200 , when shifting from the “URA_PCH” to the active state by the URA_update, transmits and receives “38” messages between with the base station  100 . Also, the terminal  200  transmits and receives “38” messages when shifting from the “IDLE” to the active state by the Keep Alive. More specifically, the terminal  200  transmits and receives “30” messages when shifting from the “IDLE” to the “Cell_FACH”, and “8” messages when shifting from the “Cell_FACH” to the “Cell_DCH”, which are totally “38” messages. 
       FIG. 15F  illustrates an example of information update when the terminal  200  in the “URA_PCH” state moves within the URA in a case when the bearer hold timer set value is set to a longer time than the reference value. As such, when the attribute of the cell in which the terminal  200  is located is “small cell” and “high mobility”, the bearer hold timer set value is set to a longer time than the reference value, as described earlier. 
     In the example of  FIG. 15F , when moving within the URA, the terminal  200  shifts from the “URA_PCH” to the active state and performs the URA_update, similar to the example of  FIG. 15E . 
     Because the bearer hold timer set value is set longer than the reference value, a time during which the terminal  200  maintains the “URA_PCH” state becomes longer than the case of  FIG. 15E . Desirably, the bearer hold timer set value which is set longer than the reference value is longer than a predetermined time interval of the execution of the Keep Alive. By such setting, at the time of the Keep Alive, the terminal  200  can be set to the “URA_PCH”, not the “IDLE”. 
     In the example of  FIG. 15F , on reaching a predetermined time to perform the Keep Alive, the terminal  200  shifts from the “URA_PCH” to the active state and performs the Keep Alive. In this case, when shifting from the “URA_PCH” to the active state, the terminal  200  transmits and receives “23” messages. More specifically, the terminal  200  transmits and receives “15” messages when shifting from the “URA_PCH” to the “Cell_FACH” and “8” messages when shifting from the “Cell_FACH” to the “Cell_DCH”, which are totally “23” messages. 
     The number of messages in one time of the Keep Alive is “38” in the case of the shift from the “IDLE” to the active state (for example,  FIG. 15E ), whereas “23” in the case of the shift from the “URA_PCH” to the active state (for example,  FIG. 15F ). Thus, in the case of the shift from the “URA_PCH” to the active state, “15” messages can be reduced as compared to the case of the shift from the “IDLE” to the active state. Also, the total number of messages is 38×7=266 in the example of  FIG. 15E , whereas 38+23×6+8=184 in the example of  FIG. 15F , and thus, “82” messages can be reduced. 
     Accordingly, in the radio access system  10 , by setting the bearer hold timer set value longer than the reference value, for example, there is produced a shift from the “URA_PCH” state to the active state, and thus, as compared to the case of the reference value, the number of messages can be reduced. As a result, the elongation of the bearer hold timer set value to be longer than the reference value enables the suppression of signal traffic, for example. 
     Further, by the suppression of the signal traffic, for example, the number of times of signal transmission and reception in the terminal  200  is reduced, which enables the suppression of power consumption in the terminal  200  and the elongation of the battery available time. 
     OTHER EMBODIMENTS 
     Next, other embodiments will be described. 
     In the second embodiment, for example as depicted in  FIG. 5 , the example in which one cell is included in one base station  100  is described. However, a plurality of cells may be included in one base station  100 , for example. 
     Also, in the second embodiment, for example as depicted in  FIG. 3 , the example in which one radio unit  110  is included in the base station  100  is described. For example, a plurality of radio units  110  may be included in the base station  100 . 
       FIG. 16  is a diagram illustrating a configuration example of the base station  100  when a plurality of radio units  110 - 1 ,  110 - 2 , . . . are included in the base station  100 . The plurality of radio units  110 - 1 ,  110 - 2 , . . . are connected to the control and baseband unit  120 . Further, radio units  110 - 1 ,  110 - 2 , . . . may be installed at mutually different locations. 
     Further, in the second embodiment, there is described the example in which the bearer hold timer set value is set longer than the reference value, to thereby elongate the time to maintain the “URA_PCH” state longer than the reference value. For example, the present embodiment is applicable if the terminal  200 , though not in the “URA_PCH” state, is in a state capable of maintaining connection with the base station  100  and performing processing to confirm the connection at predetermined time intervals to the base station  100  without data transmission and reception. 
     Further, in the second embodiment, as the configuration example of the base station  100 , the description is given based on the example of  FIG. 3 .  FIG. 17  is a diagram illustrating a hardware configuration example of the base station  100 . 
     The base station  100  further includes a DSP (Digital Signal Processor)  131 , a CPU (Central Processing Unit)  132 , a ROM (Read Only Memory)  133  and a RAM (Random Access Memory)  134 . 
     The DSP  131  performs processing of error correction coding, modulation, error correction decoding, demodulation, etc. on data and a signal which are output from the modulation and demodulation unit  111  and data, a signal, etc. which are output from the IF  121 , according to each instruction from the CPU  132 . The DSP  131  outputs the data and the signal on which the above processing is performed to the IF  121  and the modulation and demodulation unit  111 , according to the instruction of the CPU  132 . 
     The CPU  132  reads out a program stored in the ROM  133  to load on the RAM  134 , and executes the loaded program, to thereby actualize each function performed in the control unit  122  and the timing control unit  125 . 
     The CPU  132  corresponds to, for example, the control unit  122  and the timing control unit  125  in the second embodiment. Also, the DSP  131  corresponds to, for example, the baseband unit  123  in the second embodiment. Further, the IF  121  corresponds to, for example, the interface unit  121  in the second embodiment. 
     All examples and conditional language provided herein are intended for the pedagogical purposes of aiding the reader in understanding the invention and the concepts contributed by the inventor to further the art, and are not to be construed as limitations to such specifically recited examples and conditions, nor does the organization of such examples in the specification relate to a showing of the superiority and inferiority of the invention. Although one or more embodiments of the present invention have been described in detail, it should be understood that the various changes, substitutions, and alterations could be made hereto without departing from the spirit and scope of the invention.