Abstract:
A wireless communication terminal comprises a detection section, an acquisition section and a control section. The detection section detects activation of a voice telephone service application. The acquisition section acquires wireless station information transmitted from a wireless station that is a communication partner. The control section is set so as to ensure that a wireless receiver that receives wireless station information from the wireless station is always put in the ON condition when activation of the voice telephone service application is detected by the detection section. The control section sets the reception processing interval for which wireless station information is received and processed by the wireless receiver to a first interval in accordance with the wireless station information acquired by the acquisition section. The first interval is a time interval in which reception of voice telephone service incoming calls during standby is enabled.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation application of International Application PCT/JP2012/058013, filed on Mar. 27, 2012 and designating the U.S., the entire contents of which are incorporated herein by reference. 
    
    
     FIELD 
     The embodiments discussed herein are related to a radio communications terminal and a radio communications method. 
     BACKGROUND 
     Recently, in a system using radio communications terminals such as mobile telephones and smartphones, a voice communications service employing a voice over internet protocol (VoIP) and the voice communications service such as Skype (registered trademark) employing a peer-to-peer (P2P) technology are provided. Among the radio communications terminals is a terminal capable of connecting with both of a mobile telephone network such as a 3rd generation (3G) line and a wireless local area network (WLAN). 
     One conventional radio communications terminal has been designed to set according to an operation state of an application running on the radio communications terminal, the interval at which a beacon from an access point is received (see, e.g., Japanese Laid-Open Patent Publication No. 2004-128949). There is a method in which the access point calculates a beacon transmission period, changes the beacon transmission period to the calculated transmission period, and transmits the beacon with the changed transmission period (see, e.g., Japanese Laid-Open Patent Publication No. 2010-147672). According to this method, the beacon reception interval of the radio communications terminal becomes the beacon transmission interval of the access point. There is a radio communications terminal that receives the beacon transmitted by the access point, obtains a maximum listen interval from the beacon, and sets the maximum listen interval as the beacon reception interval (see, e.g., Published Japanese-Translation of PCT Application, Publication No. 2009-529299). 
     The radio communications terminal described above capable of connecting with plural networks can connect with either network and perform voice communication with the counterpart call destination radio communications terminal through a voice communications service such as VoIP and Skype. In the case of connecting with the WLAN to receive the voice communications service, the radio communications terminal can respond to a received call during a standby state by constantly remaining in a state capable of communicating with the access point, i.e., a WLAN wireless station. The radio communications terminal can maintain the state of being capable of communicating with the access point by constantly receiving the beacon transmitted by the access point. 
     During the standby state, if the radio communications terminal is to receive the beacon at the transmission interval of the access point, a transceiver for the WLAN has to operate frequently, arising in a problem that power consumption is increased during the standby state. On the other hand, during the standby state, if the radio communications terminal is to receive the beacon at a maximum listen interval, the beacon reception interval is too long and therefore, a delay is caused in the timing of notifying a user of a received call when there is a call is received during the standby state. For this reason, there is a problem in that it is possible that the user cannot respond to the received call. 
     SUMMARY 
     According to an aspect of an embodiment, a radio communications terminal includes a processor configured to detect that an application of a voice communications service is activated in the radio communications terminal; obtain wireless station information transmitted from a wireless station, which is a communication counterpart; and set a wireless receiver that receives the wireless station information from the wireless station to be in an always-on state and sets based on the wireless station information obtained, a reception processing interval at which the wireless receiver performs reception processing of the wireless station information, the reception processing interval being set to be a first interval, upon detecting that the application of the voice communications service is activated. The first interval is a time interval that enables an incoming call of the voice communications service to be received during a standby 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 block diagram of a radio communications terminal according to a first embodiment; 
         FIG. 2  is a flowchart of a radio communications method according to the first embodiment; 
         FIG. 3  is a block diagram of a hardware configuration of the radio communications terminal according to a second embodiment; 
         FIG. 4  is a block diagram of a functional configuration of the radio communications terminal according to the second embodiment; 
         FIG. 5  is a block diagram of a system of a voice communications service by Skype; 
         FIG. 6  is a block diagram of a system of a voice communications service by VoIP; 
         FIG. 7  is a table of an example of WLAN connection information; 
         FIG. 8  is a flowchart of an example of the radio communications method according to the second embodiment; 
         FIG. 9  is a flowchart of details of steps S 14  and S 15  of the flowchart depicted in  FIG. 8 ; 
         FIG. 10  is a flowchart of details of steps S 18  and S 19  of the flowchart depicted in  FIG. 8 ; 
         FIG. 11  is a timing chart relating a transmission interval of base station information and a reception interval of a beacon; 
         FIG. 12  is a flowchart of another example of the radio communications method according to the second embodiment; and 
         FIG. 13  is a flowchart of yet another example of the radio communications method according to the second embodiment. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Embodiments of a radio communications terminal and a radio communications method will be described in detail with reference to the accompanying drawings. The present invention is not limited by the embodiments. 
       FIG. 1  is a block diagram of a radio communications terminal according to a first embodiment. As depicted in  FIG. 1 , a radio communications terminal  1  has a detecting unit  2 , an obtaining unit  3 , and a control unit  4 . The detecting unit  2  detects a voice communications service application. The obtaining unit  3  obtains wireless station information transmitted from a wireless station (not depicted) that is a communication counterpart. 
     The control unit  4  performs setting such that a wireless receiver  5  that receives the wireless station information from the wireless station will be in an always-on state when the detecting unit  2  detects that the application of the voice communications service is activated. Based on the wireless station information obtained by the obtaining unit  3 , the control unit  4  sets, at a first interval, a reception processing interval at which the wireless receiver  5  performs reception processing. The first interval is a time interval that enables an incoming call of the voice communications service to be received during the standby state. 
       FIG. 2  is a flowchart of a radio communications method according to the first embodiment. As depicted in  FIG. 2 , when the radio communications method starts, the radio communications terminal  1  uses the detecting unit  2  to detect whether an application of the voice communications service is activated (step S 1 ). If not (step S 1 : NO), the radio communications terminal  1  returns to step  1 . If an application of the voice communications service is detected to be activated (step S 1 : YES), the radio communications terminal  1  uses the control unit  4  to perform setting such that the wireless receiver  5  that receives the wireless station information from the communication counterpart wireless station will be in the always-on state (step S 2 ). 
     The radio communications terminal  1  uses the obtaining unit  3  to obtain the wireless station information transmitted by the wireless station and received by the wireless receiver  5  (step S 3 ). The radio communications terminal  1  uses the control unit  4 , to set based on the obtained wireless station information, the reception processing interval at which the wireless receiver  5  performs reception processing of the wireless station information, the reception processing interval being set such that it is possible to receive an incoming call of the voice communications service during the standby state (step S 4 ). The radio communications terminal  1  then ends a sequence of operations. The order in which steps S 2  to S 4  are performed is arbitrary. 
     According to the first embodiment, while the voice communications service is in use, the wireless receiver is in the always-on state even in the standby state and the wireless receiver receives the wireless station information at a time interval that enables an incoming call to be received during the standby state. Thus, it becomes possible for the user of the radio communications terminal  1  to respond to an incoming call of the voice communications service during the standby state. 
     A second embodiment is an example of an application of the radio communications terminal  1  according to the first embodiment, to a radio communications terminal such as a mobile telephone and a smartphone. In the second embodiment, the radio communications terminal is assumed to be able to connect with plural networks of both a mobile telephone network such as a 3G line and a WLAN, for example. 
     In the second embodiment, the wireless station that is the communication counterpart when the radio communications terminal connects with a mobile telephone network is referred to as a base station and the wireless station that is the communication counterpart when the radio communications terminal connects with a WLAN is referred to as an access point. The radio communications terminal may be connectable to a network of a worldwide interoperability for microwave access (WiMax) (registered trademark) system or other system. 
       FIG. 3  is a block diagram of a hardware configuration of the radio communications terminal according to the second embodiment. As depicted in  FIG. 3 , a radio communications terminal  11  has a first radio frequency (RF) transceiver  12 , for example, a second RF transceiver  13  as a wireless receiver, a display  14 , an input key  15 , memory  16 , a speaker  17 , a microphone  18 , a central processing unit (CPU)  19 , and a voice circuit  20 . 
     The first RF transceiver  12  is connected to an antenna  21  and the CPU  19 . The first RF transceiver  12  receives a radio signal from the mobile telephone network by the antenna  21 , generates received data from the received signal, and transfers the data to the CPU  19 . The first RF transceiver  12  generates a transmission signal from transmission data transferred from the CPU  19  and transmits the radio signal to the mobile telephone network by the antenna  21 . 
     The second RF transceiver  13  is connected to an antenna  22  and the CPU  19 . The second RF transceiver  13  receives a radio signal from the WLAN by the antenna  22 , generates the received data from the received signal and transfers the data to the CPU  19 . The second RF transceiver  13  generates the transmission signal from the transmission data transferred from the CPU  19  and transmits the radio signal to the WLAN by the antenna  22 . 
     The display  14  is connected to the CPU  19 . The display  14  displays characters and images, based on data output from the CPU  19 . The display  14  may have a touch panel attached to the surface thereof and characters and symbols may be input through the touch panel. 
     The input key  15  is connected to the CPU  19 . The input key  15  is used for inputting characters and symbols into the CPU  19 . 
     The memory  16  is connected to the CPU  19 . The memory  16  stores an operating system (OS) and various programs such as applications to be executed by the CPU  19 . A program of the voice communications service such as, for example, VoIP and Skype can be cited as an example of an application program. The memory  16  stores connection information corresponding to the time when the radio communications terminal  11  connects to the WLAN. 
     The speaker  17  is connected to the voice circuit  20 . The speaker  17  outputs sound, based on a signal output by the voice circuit  20 . 
     The microphone  18  is connected to the voice circuit  20 . The microphone  18  is used for inputting a voice signal into the voice circuit  20 . 
     The voice circuit  20  is connected to the CPU  19 . The voice circuit  20  generates voice data from the voice signal transferred from the microphone  18  and transfers the data to the CPU  19 . The voice circuit  20  generates the voice signal from the voice data transferred from the CPU  19  and transfers the signal to the speaker  17 . 
     The CPU executes the operating system and various programs such as applications. The CPU  19  processes the data input from the first RF transceiver  12 , the second RF transceiver  13 , the input key  15 , the memory  16 , and the voice circuit  20  and outputs the data to the first RF transceiver  12 , the second RF transceiver  13 , the display  14 , the memory  16 , and the voice circuit  20 . The CPU  19  controls the overall operation of the radio communications terminal  11 . The radio communications terminal  11  may have a CPU for radio communication and another CPU for execution of application programs. 
       FIG. 4  is a block diagram of a functional configuration of the radio communications terminal according to the second embodiment. As depicted in  FIG. 4 , the radio communications terminal  11  has, for example, an application detecting unit  31  as the detecting unit, for example, a beacon information obtaining unit  32  as the obtaining unit, and, for example, a WLAN control unit  33  as the control unit. 
     The application detecting unit  31  detects the application of the voice communications service such as the VoIP and the Skype. The application detecting unit  31  may detect whether, for example, the Skype program is activated and the terminal or the user using the terminal is authenticated by a sign-in. It may be assumed that the application detecting unit  31  has detected the application of the voice communications service by the Skype when the terminal or the user using the terminal is authenticated. 
     For example, a task manager to be implemented as a function of the operating system can detect that the Skype program is activated. Configuration may be such that that the activation of the Skype program will be detected by downloading an application program that implements the same function as that of the task manager from the Internet and executing the application program. 
     The application detecting unit  31  may detect whether information of a session initiation protocol (SIP) server that controls connection to, for example, the WLAN is stored in the terminal and the terminal is connected to the SIP server. It may be assumed that the application detecting unit  31  has detected the application of the voice communications service by VoIP when the terminal is connected to the SIP server. 
     The beacon information obtaining unit  32  obtains the wireless station information from a beacon. The beacon is transmitted from the access point of the WLAN and is received by the second RF transceiver  13  of the radio communications terminal  11 . The beacon information obtaining unit  32  may be a function of a WLAN driver to be implemented as a function of the operating system. For example, a beacon interval value and a delivery traffic indication message (DTIM) value can be cited as an example of the wireless station information to be obtained by the beacon information obtaining unit  32 . 
     With the beacon interval value from the access point, the radio communications terminal  11  can know the interval at which the access point transmits the beacon. For example, if the beacon interval value is 100, the beacon is transmitted from the access point every 100 milliseconds. 
     With the DTIM value from the access point, the radio communications terminal  11  can know the interval at which the beacon including the DTIM is transmitted. For example, if the DTIM value is 5, the DTIM is transmitted every 5 beacons from the access point. The DTIM means a traffic indication message (TIM) giving notification of the presence of data addressed to a radio client. 
     The WLAN control unit  33  controls the operation of the WLAN driver and the second RF transceiver  13 , based on results of detection of the application by the application detecting unit  31  and the wireless station information obtained by the beacon information obtaining unit  32 . The WLAN control unit  33  may be implemented by executing a program that implements the radio communications method to be described later. 
     When the application of the voice communications service such as VoIP and Skype is detected, the WLAN control unit  33  sets the WLAN driver and the second RF transceiver  13  to be in the always-on state. The WLAN control unit  33  sets the interval at which the beacon is to be received such that an incoming call of the voice communications service can be responded to during the standby state. 
     For example, the time on the order of 1 to 2.5 seconds can be cited as an example of the time that enables an incoming call to be responded to during the standby state. The interval at which the base station in the mobile telephone network such as, for example, the 3G line gives notification of position information is, for example, 2.56 seconds and therefore, the above time is sufficient for responding to an incoming call from the mobile telephone network. Further, in the mobile telephone network of a long term evolution (LTE) system, the base station gives notification of the position information, for example, every 1.28 seconds. 
     Namely, if the interval at which the beacon is to be received is on the order of 1 to 2.5 seconds, the radio communications terminal  11  can notify the user of an incoming call of the voice communications service during the standby state. Accordingly, the user of the radio communications terminal  11  can respond to the incoming call of the voice communications service during the standby state. 
     When the application of the voice communications service such as VoIP and Skype is not detected, the WLAN control unit  33  performs settings such that the WLAN driver and the second RF transceiver  13  will be in the off-state at a point in time after an elapse of a given period. The WLAN control unit  33  sets the interval at which the beacon is to be received, to be a period longer than the beacon reception interval in the case of the detection of the application of the voice communications service as described above. For example, a period on the order of 3 seconds can be cited as an example of a period that is longer than the beacon reception interval in the case of the detection of the application of the voice communications service. 
       FIG. 5  is a block diagram of a system of the voice communications service by Skype. As depicted in  FIG. 5 , radio communications terminals  44  and  45  can use the voice communications service by Skype in an environment  41  of the mobile telephone network such as the 3G line as well as in an environment  42  of a wireless fidelity (WiFi) (registered trademark). 
     When the radio communications terminal  44  as a call source makes a voice call to the radio communications terminal  45  as a call destination, using the voice communications service by Skype, the radio communications terminal  45  (call destination) is required to activate Skype, log onto a Skype server (not depicted), and sign in. The radio communications terminal  45  (call destination) is connected to a supernode  43  by way of the Internet at the time of activation of a client. 
     The procedure to start the voice communication by Skype is as follows. The radio communications terminal  44  (call source) transmits a call request message indicating a desire to make a call to the radio communications terminal  45  (call destination) to the supernode  43  to which the radio communications terminal  45  (call destination) is connected. Upon receiving the call request message from the radio communications terminal  44  (call source), the supernode  43  to which the radio communications terminal  45  (call destination) is connected instructs the radio communications terminal  45  (call destination) to access the radio communications terminal  44  (call source). 
     Upon receiving the instruction from the supernode  43 , the radio communications terminal  45  (call destination) accesses the radio communications terminal  44  (call source). This enables the radio communications terminal  44  (call source) and the radio communications terminal  45  (call destination) to start the voice communication therebetween, through a firewall (not depicted). 
     The radio communications terminal  44  (call source) and the radio communications terminal  45  (call destination) may be connected wirelessly to a WiFi router  49  in the WiFi environment  42 . The WiFi router  49  serves as the access point of the WLAN. The WiFi router  49  is connected wirelessly or by a line to Internet  47  by way of a provider  48 . 
     In the WiFi environment  42 , a supernode  46  different from the supernode  43  in the mobile telephone network environment  41  may be connected to the Internet  47 . Another terminal  50  to be connected to the supernode  46  may be connected by wire or radio to the Internet  47 . If the supernode  43  to which the radio communications terminal  44  (call source) and the supernode  46  to which the radio communications terminal  45  (call destination) is connected are different, the radio communications terminal  44  (call source) transmits the call request message to the supernode  46  to which the radio communications terminal  45  (call destination) is connected, by way of the supernode  43  to which the terminal  44  is connected. 
     The Internet protocol (IP) address of the supernode  43  in the mobile telephone network environment  41  is different from the IP address of the supernode  46  in the WiFi environment  42 . For this reason, the radio communications terminals  44  and  45 , at the time of going back and forth between the mobile telephone network environment  41  and the WiFi environment  42 , are required to re-perform the sign-in to the Skype server. 
     When the radio communications terminal is connected to the supernode  46  in the WiFi environment  42  and is in the state of waiting for an incoming call of Skype, a display screen of the radio communications terminal may be put in an off-state to suppress power consumption. Even if the screen is in the off-state, the radio communications terminal can wait for an incoming call of Skype if the WLAN driver and the WLAN RF transceiver of the radio communications terminal are in the on-state. 
     If the screen is in the off-state and further, the WLAN driver and the WLAN RF transceiver of the radio communications terminal are put in the off-state, however, the supernode to which the radio communications terminal is connected does not automatically switch to the supernode  43  in the mobile telephone network environment  41 . For this reason, the radio communications terminal can no longer standby for an incoming call of Skype. 
     In the second embodiment, when the application of Skype is detected, the WLAN driver and the WLAN RF transceiver are put in the always-on state. This enables the radio communications terminal to remain standing by for an incoming call while Skype is in use. 
       FIG. 6  is a block diagram of a system of the voice communications service by VoIP. As depicted in  FIG. 6 , the radio communications terminal  53  (call source) and the radio communications terminal  56  (call destination) connect wirelessly with WiFi routers  54  and  55  and connect with a provider or an intra-company network  52  by way of the WiFi routers  54  and  55 . 
     The WiFi routers  54  and  55  serve as the access points of the WLAN. If the address of a SIP server  51  is registered at the access points, the radio communications terminals  53  and  56  are registered in the SIP server  51 , by the radio communications terminals  53  and  56  connecting with the access points. The information for connection with the SIP server  51  is retained in the radio communications terminals  53  and  56  as WLAN connection information. The WLAN connection information may be stored in, for example, the memory  16  of the radio communications terminal  11  (see  FIG. 3 ). 
       FIG. 7  is a table of an example of the WLAN connection information. As depicted in  FIG. 7 , WLAN connection information  59  is a data table having fields for “profile name”, “extended service set identifier (ESSID)”, “SIP connection information”, etc., and indicates communication networks as connection candidates. 
     In the example depicted in  FIG. 7 , “office3F” and “office2F” are profiles at the time of using the voice communications service by VoIP by connecting with the SIP server  51  and have effective SIP connection information. “eigyosho-1” and “home” are the profiles at the time of using the voice communications service by, for example, Skype, without a need to connect to the SIP server, and do not have the effective SIP connection information. 
       FIG. 8  is a flowchart of an example of the radio communications method according to the second embodiment. As depicted in  FIG. 8 , when the radio communications method starts in the radio communications terminal  11 , the WLAN control unit  33  determines whether the application of the voice communications service by Skype or VoIP has been detected by the application detecting unit  31  (step S 11 ). 
     If it is determined that the application of the voice communications service has been detected (step S 11 : YES), then the WLAN control unit  33  sets the WLAN driver and the second RF transceiver  13  to be in the always-on state (step S 12 ). If the radio communications terminal  11  is not connected to the WLAN (step S 13 : NO), the radio communications terminal  11  performs an operation of connecting to the WLAN and connects to the WLAN. 
     If the radio communications terminal is already connected to the WLAN or if the radio communications terminal connects to the WLAN by performing the operation of connecting thereto (step S 13 : YES), the WLAN control unit  33  obtains from the beacon information obtaining unit  32 , the wireless station information obtained by the beacon information obtaining unit  32  (step S 14 ). The wireless station information may be, for example, the beacon interval value and the DTIM value. 
     The WLAN control unit  33 , based on the obtained wireless station information, sets the beacon reception interval to be less than or equal a period that enables response to an incoming call of the voice communications service during the standby state (step S 15 ), and ends a sequence of operations. 
     On the other hand, if it is determined that the application of the voice communications service has not been detected (step S 11 : NO), the WLAN control unit  33  performs settings such that the WLAN driver and the second RF transceiver  13  will be in the off-state a given period after the screen of the display  14  of the radio communications terminal  11  is put into the off-state (step S 16 ). If the radio communications terminal  11  is not connected to the WLAN (step S 17 : NO), the radio communications terminal  11  performs the operation of connecting to the WLAN and connects thereto. 
     If the radio communications terminal is already connected to the WLAN or if the radio communications terminal connects to the WLAN by performing the operation of connecting thereto (step S 17 : YES), the WLAN control unit  33  obtains the wireless station information such as the beacon interval value and the DTIM value from the beacon information obtaining unit  32  (step S 18 ). The WLAN control unit  33 , based on the obtained wireless station information, sets the beacon reception interval to be equal to or longer than the time that enables response to an incoming call of the voice communications service during the standby state, namely, a period equal to or longer than the beacon reception interval is set at step S 15  (step S 19 ). The WLAN control unit  33  returns to step  11  and repeats the operations at the steps S 11  to S 19 . 
       FIG. 9  is a flowchart of details of steps S 14  and S 15  of the flowchart depicted in  FIG. 8 . As depicted in  FIG. 9 , when a beacon reception interval setting process starts, the WLAN control unit  33  obtains, for example, the beacon interval value A[sec] and the DTIM value B as the wireless station information (step S 21 ). The WLAN control unit  33  then calculates a beacon reception interval C[sec] (step S 22 ). A calculating formula may be, for example, [C=A×E]. 
     The WLAN control unit  33  then determines whether the beacon reception interval C is less than, for example, 2.5[sec] (step S 23 ). If the beacon reception interval C is less than, for example, 2.5[sec] (step S 23 : YES), the WLAN control unit  33  determines whether the beacon reception interval C is greater than, for example, 1.5[sec] (step S 24 ). If the beacon reception interval C is greater than, for example, 1.5[sec] (step S 24 : YES), the WLAN control unit  33  sets the beacon reception interval to be C[sec] (step S 25 ), and ends a sequence of operations. 
     On the other hand, if the beacon reception interval C is not greater than, for example, 1.5[sec] (step S 24 : NO), the beacon reception interval C is too small. When the beacon reception interval C is too small, the radio communications terminal  11  frequently receives the beacon and therefore, power consumption is increased. When the beacon reception interval C is too small, it is desirable to set the beacon reception interval to a period that enable response to an incoming call of the voice communications service during the standby state and that can suppress power consumption, by appropriately setting a listen interval value D. 
     Accordingly, the WLAN control unit  33  sets the repetition number N to 2 (step S 26 ) and obtains C by calculating, for example, [C=C×N] (step S 27 ). The WLAN control unit  33  determines whether the beacon reception interval C is greater than, for example, 1.5[sec] (step S 28 ). If the beacon reception interval C is greater than, for example, 1.5[sec] (step S 28 : YES), the WLAN control unit  33  sets the listen interval value D to, for example, [C/A] or sets a DTIM listen interval value E to the repetition number N (step S 29 ). The WLAN control unit  33  then sets the beacon reception interval to C[sec] (step S 25 ), and ends a sequence of operations. 
     When, despite the setting of the repetition number N, the beacon reception interval C is not greater than, for example, 1.5[sec] (step S 28 : NO), the beacon reception interval is still too small and therefore, the WLAN control unit  33  calculates [N=N+1] and updates the repetition number N (step S 30 ). The WLAN control unit  33 , using a new repetition number N, calculates, for example, [C=C×N] to obtain C (step S 27 ). 
     The WLAN control unit  33  repeats the updating of the repetition number N and the calculation of, for example, [C=C×N] until the beacon reception interval C becomes greater than, for example, 1.5[sec] (step S 27 , step S 28 , and step S 30 ). If the beacon reception interval C becomes greater than, for example, 1.5[sec] (step S 28 : YES), then the WLAN control unit  33  sets the listen interval value D to, for example, [C/A] (step S 29 ) and sets the beacon reception interval to C[sec] (step S 25 ), and ends a sequence of operations. 
     If the beacon reception interval C is not smaller than, for example, 2.5[sec] (step S 23 : NO), then the WLAN control unit  33  sets C directly as the beacon reception interval (step S 25 ), and ends a sequence of operations. 
     An example will be given. At step S 21 , it is assumed that the beacon interval value A is, for example, 100[msec] and that the DTIM value B is, for example, 5. In this case, at step S 22 , the beacon reception interval C becomes, for example, 500[msec] and since this value is too small, the flow at step S 24  branches to NO. When the repetition number N becomes 4, the beacon reception interval C becomes 2000[msec], i.e., becomes greater than 1.5[sec]. At this time, the listen interval value D is 20 and the DTIM listen interval value E is 4. 
       FIG. 10  is a flowchart of details of the steps S 18  and S 19  of the flowchart depicted in  FIG. 8 . As depicted in  FIG. 10 , when the beacon reception interval setting process starts, the WLAN control unit  33  obtains, for example, the beacon interval value A[sec] and the DTIM value B as the wireless station information (step S 41 ). The WLAN control unit  33  then calculates the beacon reception interval C[sec] (step S 42 ). A calculating formula may be, for example, [C=A×B]. 
     The WLAN control unit  33  then determines if the beacon reception interval C is, for example, 3[sec] or greater (step S 43 ). If the beacon reception interval C is, for example, 3[sec] or greater (step S 43 : YES), the WLAN control unit  33  sets the beacon reception interval to be C[sec] (step S 44 ), and ends a sequence of operations. 
     On the other hand, if the beacon reception interval C is not, for example, 3[sec] or greater (step S 43 : NO), the beacon reception interval C is too small. When the beacon reception interval C is too small, the beacon reception interval can be extended by appropriately setting the listen interval value D. 
     Accordingly, the WLAN control unit  33  sets the repetition number N at 2 (step S 45 ) and obtains C by calculating, for example, [C=C×N] (step S 46 ). The WLAN control unit  33  determines if the beacon reception interval C is, for example, 3[sec] or greater (step S 47 ). If the beacon reception interval C is, for example, 3[sec] or greater (step S 47 : YES), the WLAN control unit  33  sets the listen interval value D to, for example, [C/A] or sets the DTIM listen interval value E to the repetition number N (step S 48 ). The WLAN control unit  33  then sets the beacon reception interval to C[sec] (step S 44 ), and ends a sequence of operations. 
     When, despite the setting of the repetition number N, the beacon reception interval C is not, for example, 3[sec] or greater (step S 47 : NO), the beacon reception interval is still too small and therefore, the WLAN control unit  33  calculates [N=N+1] and updates the repetition number N (step S 49 ). The WLAN control unit  33 , using a new repetition number N, calculates, for example, [C=C×N] to obtain C (step S 46 ). 
     The WLAN control unit  33  repeats the updating of the repetition number N and the calculation of, for example, [C=C×N] until the beacon reception interval C becomes, for example, 3[sec] or greater (step S 46 , step S 47 , and step S 49 ). If the beacon reception interval C becomes, for example, 3[sec] or greater (step S 47 : YES), then the WLAN control unit  33  sets the listen interval value D to, for example, [C/A] (step S 48 ) and sets the beacon reception interval to C[sec] (step S 44 ), and ends a sequence of operations. 
     An example will be given. At step S 41 , it is assumed that the beacon interval value A is, for example, 100[msec] and that the DTIM value B is, for example, 5. In this case, at step S 42 , the beacon reception interval C becomes, for example, 500[msec] and since this value is too small, the flow at step S 43  branches to NO. When the repetition number N becomes 6, the beacon reception interval C becomes 3000[msec], i.e., becomes 3[sec] or greater. At this time, the listen interval value D is 30 and the DTIM listen interval value E is 6. 
       FIG. 11  is a timing chart relating the transmission interval of base station information and the reception interval of the beacon. In  FIG. 11 , a case of no detection of the voice communications service is indicated in a timing chart  61 . A case of detection of the voice communications service is indicated in a timing chart  62 . 
     “Screen off processing” indicates the process of setting the screen of the display  14  of the radio communications terminal  11  to the off-state. “WLAN off processing” indicates the process of setting the WLAN driver and the second RF transceiver  13  of the radio communications terminal  11  to the off-state. “Base station position information reception interval” indicates the interval at which the radio communications terminal  11  is to receive the position information notified by the base station in the mobile telephone network. “Beacon reception interval” indicates the interval at which the radio communications terminal  11  is to receive the beacon transmitted from the access point. 
     As depicted in the timing chart  61  of  FIG. 11 , in the case of no detection of the voice communications service, the WLAN driver and the second RF transceiver  13  of the radio communications terminal  11  are put into the off-state a given period, for example, 15 minutes, after the screen is put into the off-state. Until the WLAN driver and the second RF transceiver  13  are put into the off-state, the beacon reception interval is longer than, for example, the base station position information reception interval. 
     In contrast, as depicted in the timing chart  62  of  FIG. 11 , when the voice communications service is detected, the WLAN driver and the second RF transceiver  13  remain in the on-state even after the screen is put into the off-state and time elapses. The beacon reception interval is on the order of, for example, the base station position information reception interval. 
       FIG. 12  is a flowchart of another example of the radio communications method according to the second embodiment. In this example, the user sets the operation state and the WLAN control unit  33  of the radio communications terminal  11  automatically sets the beacon reception interval in the case of an automatic state. 
     As depicted in  FIG. 12 , when the radio communications method starts in the radio communications terminal  11 , the WLAN control unit  33  determines the operation state set by the user (step S 51 ). If it is determined that the user has set the automatic state (step S 51 : Automatic Setting), the WLAN control unit  33  puts the setting of the beacon reception interval into the automatic setting (step S 52 ) and performs the operations at steps S 11  to S 19  described above. The operations at steps S 11  to S 19  are the same as those in the flowchart depicted in  FIG. 8 . Therefore, redundant description is omitted. 
     If it is determined that the user has set the state that puts the WLAN driver and the second RF transceiver  13  in the always-on state (step S 51 : Always-On Setting), the WLAN control unit  33  sets the WLAN driver and the second RF transceiver  13  to be in the always-on state (step S 53 ). If it is determined that the user has set the state in which the WLAN driver and the second RF transceiver  13  are put into the off-state at a point in time after an elapse of a given period (step S 51 : Off Setting after Elapse of Given Period), the WLAN control unit  33  performs the setting corresponding thereto. Namely, the WLAN control unit  33  performs setting such that the WLAN driver and the second RF transceiver  13  will be put into the off-state a given period after the screen is put into the off-state (step S 54 ). 
       FIG. 13  is a flowchart of yet another example of the radio communications method according to the second embodiment. In this example, the user sets the operation state and the WLAN control unit  33  of the radio communications terminal  11  sets the beacon reception interval, based on the set operation state. 
     As depicted in  FIG. 13 , the operations at steps S 51  to S 54  and the operations at steps S 11  to S 19  are the same as those in the flowchart depicted in  FIG. 12 . Therefore, the redundant description is omitted. 
     When, at step S 53 , the WLAN control unit  33  sets the WLAN driver and the second RF transceiver  13  to be in the always-on state, the radio communications terminal  11 , if not connected to the WLAN (step S 55 : NO), performs the operation of connecting to the WLAN and connects thereto. 
     If the radio communications terminal  11  is already connected to the WLAN or if the radio communications terminal  11  connects to the WLAN by the operation of connecting thereto (step S 55 : YES), the WLAN control unit  33  obtains the wireless station information such as the beacon interval value and the DTIM value from the beacon information obtaining unit  32  (step S 56 ). The WLAN control unit  33 , based on the obtained wireless station information, sets the beacon reception interval to a period equal to or shorter than the period that enables response to an incoming call of the voice communications service during the standby state (step S 57 ), and ends a sequence of operations. 
     On the other hand, at step S 54 , if the WLAN control unit  33  performs settings such that the WLAN driver and the second RF transceiver  13  will be put into the off-state a given period after the screen is put into the off-state, the radio communications terminal  11 , if not connected to the WLAN (step S 58 : NO), returns to step S 51  and repeats the operation at step S 51  and subsequent operations. 
     If the radio communications terminal  11  is already connected to the WLAN (step S 58 : YES), the WLAN control unit  33  obtains the wireless station information such as the beacon interval value and the DTIM value from the beacon information obtaining unit  32  (step S 59 ). The WLAN control unit  33 , based on the obtained wireless station information, sets the beacon reception interval to a period equal to or longer than the period that enables response to an incoming call of the voice communications service during the standby state (step S 60 ), returns to step S 51 , and repeats the operation at step S 51  and subsequent operations. 
     According to the second embodiment, while the voice communications service is in use, the WLAN driver and the second RF transceiver  13  are in the always-on state even in the standby state and the radio communications terminal  11  receives the beacon at a time interval that makes it possible to receive an incoming call during the standby state. This enables the user of the radio communications terminal  11  to respond to an incoming call of the voice communications service during the standby state. 
     According to the second embodiment, the interval at which the beacon is to be received during standby for the voice communications service is longer than the interval at which the access point transmits the beacon. This makes it possible to keep the power consumption low even if the WLAN driver and the second RF transceiver  13  are in the always-on state. For example, the interval at which the beacon is to be received is on the same order as the interval at which the position information notified by the base station disposed in the mobile telephone network is to be received. This makes it possible to suppress the power consumed for receiving the beacon during standby for the voice communications service to the same level as that for the power consumed by receiving the position information notified by the base station disposed in the mobile telephone network. 
     Configuration may be such that the above beacon reception interval control will be performed in the standby state with the screen light-off and such that in the light-on state of the screen, the beacon reception interval control will not be performed but the beacon reception will be performed based on ordinary information from the access point. 
     The embodiments enable response to a received call of a voice communications service during a standby state. 
     All examples and conditional language provided herein are intended for 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.