RADIO MOBILE COMMUNICATION SYSTEM, RADIO BASE STATION APPARATUS, MOBILE TERMINAL APPARATUS, AND RADIO COMMUNICATION METHOD IN RADIO MOBILE COMMUNICATION SYSTEM

A radio mobile communication system including: a radio base station apparatus; and a mobile terminal apparatus, wherein radio communication is performed between the radio base station apparatus and the mobile terminal apparatus, the radio base station apparatus includes: a first transmission unit which transmits a first notification signal to notify a shift to a first mode; and a first mode switching control unit which transmits the first notification signal and switches to the first mode in which the first transmission unit is shifted to a condition of a suspension state, and the mobile terminal apparatus includes: a second mode switching control unit which switches to a second mode in which power of the mobile terminal apparatus is in an ON state and power consumption is smaller than in an outside coverage area mode, on receiving the first communication signal.

DESCRIPTION OF EMBODIMENTS

Hereafter, embodiments of the present invention will be described in detail by reference to the drawings.

First Embodiment

FIG. 1is a diagram illustrating a configuration example of a radio mobile communication system10according to the first embodiment. The radio mobile communication system10includes a radio base station apparatus100and a mobile terminal apparatus200.

The radio base station apparatus100includes a first transmission unit170and a first mode switching control unit171. The first transmission unit170transmits a first notification signal for the notification of a shift to a first mode. Further, after transmitting the first notification signal, the first mode switching control unit171switches to the first mode in which the first transmission unit170is shifted to a suspension state.

On the other hand, the mobile terminal apparatus200includes a second mode switching control unit270. The second mode switching control unit270, when receiving the first notification signal from the mobile base station apparatus100, is switched to a second mode in which the power of the mobile terminal apparatus200is ON and power consumption thereof is smaller than in the outside coverage area mode.

In the mobile base station apparatus100, on shifting to the first mode after the transmission of the first notification signal, the first transmission unit170is shifted to the suspension state, and therefore, it is possible to reduce power consumption as compared to the normal mode in which the first transmission unit170does not be shifted to the suspension mode.

Meanwhile, the mobile terminal apparatus200is switched to the second mode on receiving the first notification signal. When the mobile terminal apparatus200shifts to the second mode, it is possible to reduce power consumption because the power consumption is smaller than in the outside coverage area mode.

As such, the radio mobile communication system10can reduce power consumption in both the mobile base station apparatus100and the mobile terminal apparatus200.

Second Embodiment

FIG. 2is a diagram illustrating a configuration example of a radio mobile communication system10according to the second embodiment. The radio mobile communication system10includes radio base station apparatuses (hereinafter, “base stations”)100-1to100-3, mobile terminal devices (hereinafter, “terminals”)200-1,200-2and a control apparatus (hereinafter, “control station”)300.

The base stations100-1to100-3are radio communication apparatuses that perform radio communication through radio connection with the terminals200-1,200-2. The base stations100-1to100-3can provide various services such as voice communication and video distribution to the terminals200-1,200-2.

On the other hand, the terminals200-1,200-2are radio communication apparatuses which perform radio communication through radio connection with the base stations100-1to100-3, and are mobile telephone sets, information mobile terminal apparatuses, etc. The terminals200-1,200-2can receive data signals (hereinafter, “data”) from the base stations100-1to100-3, and also can transmit data to the base stations100-1to100-3.

In the example depicted inFIG. 2, the base station100-3performs radio communication with the terminal200-2. Further, the base station100-1is unable to transmit a radio signal because of being in the suspension mode, and the terminal200-1is in a state of a station suspension mode. Details of the suspension mode and the station suspension mode will be described later.

In the present description, communication links from the base stations100-1to100-3to the terminals200-1,200-2are referred to as downlinks (DL), and communication links from the terminals200-1,200-2to the base stations100-1to100-3are referred to as uplinks (UL).

FIG. 3Ais a diagram illustrating a configuration example of a base station100, andFIG. 3Bis a diagram illustrating a configuration example of a terminal200. Incidentally, the base stations100-1to100-3illustrated inFIG. 2are of identical configuration and each base station100-1to100-3is described as the base station100unless otherwise specified. Also, the same is applicable to the terminal200, namely, the terminals200-1,200-2are of identical configuration and each terminal200-1,200-2is described as the terminal200.

The base station100includes a radio unit110, a control function unit130and an external interface unit150. Further, the radio unit110includes a receiver111and a transmitter112.

Also, the terminal200includes a radio unit210, a control function unit220, a display unit240and an input unit250.

Incidentally, configuration examples of the base station100and the terminal200are represented inFIG. 6andFIG. 7, respectively, and the description on the configuration examples of the base station100and the terminal200will be made later by reference toFIG. 6andFIG. 7.

In the present second embodiment, as a mode of the base station100, a suspension mode is further provided. Also, as a mode of the terminal200, a station suspension mode is further provided. By that the base station100shifts (or transitions) to the suspension mode and the terminal200shifts to the station suspension mode, it is possible to respectively reduce power consumption in the base station100and the terminal200. Therefore, examples of state transition in the base station100and the terminal200including the above modes will be described first.

<State Transition in the Base Station100>

First, an example of state transition in the base station100will be described.FIG. 4is a diagram illustrating an example of state transition in the base station100according to the second embodiment.

As illustrated inFIG. 4, a suspension mode (M3) is provided in the base station100. The suspension mode (M3) signifies a state in which the transmitter112in the radio unit110of the base station100is not in operation (or in a power OFF condition). At this time, the base station100is configured to suspend the transmission of broadcast information, so as not to transmit the broadcast information to the inside of the service area. Additionally, in the base station100placed in the suspension mode (M3), the receiver111in the radio unit110, the external interface unit150and a portion of the control function unit130are in operation, so as to be continuously operable even in the suspension mode (M3). In the base station100placed in the suspension mode (M3), because the transmitter112of the radio unit100is not in operation, power consumption can be reduced as compared to the normal mode (M1) in which the transmitter112is in operation.

As illustrated inFIG. 4, the base station100can shift from the normal mode (M1) to the suspension mode (M3). For example, the base station100can shift to the suspension mode (M3), when a constant time passes from the last communication (S11) and no shift prohibition control is made by the control station300etc. (“No” in S12).

The shift prohibition control signifies control to prohibit shift to the suspension mode (M3), for example. The control function unit130controls the base station100not to shift to the suspension mode (M3) when a control signal representing shift prohibition is input from the control station300through the external interface unit150, for example. For example, when an event is held in the service area of the base station100, it is possible to prohibit shift to the suspension mode (M3) even after the lapse of a certain time after the last communication. Also, the set shift prohibition control can be canceled by the control station300or the base station100. For example, on receipt of a cancellation signal from the external interface unit150, the control function unit130performs control to cancel the shift prohibition to the suspension mode (M3).

On the other hand, when there is shift prohibition control (“Yes” in S12), the base station100maintains a state of the normal mode (M1).

Also, when the base station100shifted to the suspension mode (M3) receives either a restart request signal from the terminal200or incoming call information destined to the terminal200from the control station300(S14), the base station100restarts and shifts to the normal mode (M1). The restart request signal signifies, for example, a signal transmitted from the terminal200to the base station100in order to restart the base station in the suspension mode (M3). By the transmission of the restart request signal from the terminal200, the base station100in the suspension mode (M3) can be restarted to shift from the suspension mode (M3) to the normal mode (M1). Further, there is a case when the base station100in the suspension mode (M3) receives from the control station300incoming call information destined to a terminal200located in the coverage area. In such a case also, the base station100can shift from the suspension mode (M3) to the normal mode (M1), and transmit a data signal (hereinafter, “data”) etc. to the terminal200located in the coverage area. Additionally, because most portions other than the transmitter112are in operation, for example, the base station100in the suspension mode (M3) can receive a restart request signal transmitted from the terminal200and can also receive incoming call information transmitted from the control station300.

Incidentally, in regard to the state transition of the base station100, other portions are identical toFIG. 19Aand therefore, description is omitted.

<State Transition in the Terminal200>

Next, state transition in the terminal200will be described.FIG. 5is a diagram illustrating an example of a state transition diagram of the terminal200. In the terminal200, a station suspension mode (M14) is further provided. The station suspension mode (M14) signifies, for example, a mode when the terminal200is located in the service area of the base station100placed in the suspension mode (M3). The station suspension mode (M14) is also a mode in which the terminal200retrieves any one of the operator identification code, the radio communication method and the frequency bandwidth, or the combination thereof, of an operator immediately before the terminal200shifts to the station suspension mode (M14). Further, the station suspension mode (M14) is a mode in which, for example, the power of the terminal200is in an ON state, and power consumption is smaller than in the outside coverage area mode (M11).

The terminal200in the station suspension mode (M14) does not retrieve all operator identification codes, radio communication methods and frequency bandwidths with which the own terminal is compatible, as is performed in the outside coverage area mode (M11). The terminal200in the station suspension mode (M14) retrieves any one of the identification code, the radio communication method and the frequency bandwidth, or the combination thereof (or broadcast information) of the operator immediately before shifting to the station suspension mode (M14). Therefore, in the terminal200placed in the station suspension mode (M14), retrieval objects are narrower as compared to the terminal200in the outside coverage area mode (M11), and accordingly, power consumption can be reduced. Further, the terminal200in the outside coverage area mode (M11) continuously performs such the above retrieval, whereas the terminal200in the station suspension mode (M14) performs retrieval at constant time intervals. Therefore, a retrieval time in the station suspension mode (M14) is shorter than a retrieval time in the outside coverage area mode (M11), and accordingly, power consumption can be reduced.

Incidentally, in the terminal200placed in the outside coverage area mode (M11), for example, the radio unit210, the control function unit220, the display unit240and the input unit250can be brought into operation.

As illustrated inFIG. 5, when the terminal200in the standby mode (M12) receives a suspension mode shift notification signal transmitted from the base station100(S20), the terminal200can shift to the station suspension mode (M14). The suspension mode shift notification signal signifies a signal to notify that the base station100shifts to the suspension mode (M14), to the terminal200located in the service area of the own station. On receipt of the suspension mode shift notification signal (S20), the terminal200can grasp that the base station100currently in connection shifts to the suspension mode (M3).

The terminal200, after shifting to the station suspension mode (M14), can shift to the communication mode (M13), the standby mode (M12) and further, the outside coverage area mode (M11).

A shift from the station suspension mode (M14) to the communication mode (M13) is, for example, as follows. Namely, when a communication request is generated by the operation of a calling button or a start-to-talk button by a human operator (S22), the terminal in the station suspension mode (M14) transmits a restart request signal to the base station100in the suspension mode (M3) (S23). By this, the base station100restarts and shifts to the normal mode (M1), so as to transmit broadcast information. If the terminal200can detect the above broadcast information (“Capable” in S24), the terminal200shifts to the communication mode (M13) (in the case of the “station suspension mode” in S25). Based on the detected broadcast information, the terminal200performs, for example, location registration and authentication between with the base station100, and can shift to the communication mode (M13).

Also, a shift from the station suspension mode (M14) to the suspension mode (M3) is, for example, as follows. Namely, by a restart request signal transmitted from another terminal in the station suspension mode (M14), the base station100can shift from the suspension mode (M3) to the normal mode (M1). Then, the base station100shifted to the normal mode (M1) transmits broadcast information, and therefore the terminal200in the station suspension mode (M14), on receiving the broadcast information (S26), can shift to the standby mode (M12). Also, when the terminal200in the station suspension mode (M14) detects the broadcast information after moving to the service area of the base station100(S26), the terminal200can shift to the standby mode (M12).

Furthermore, a shift from the station suspension mode (M14) to the outside coverage area mode (M11) is, for example, as follows. Namely, if the terminal200in the station suspension mode (M14) makes a communication request (S22) and transmits a restart request signal (S23), and if the terminal200fails to receive broadcast information from the base station100(“Incapable” in S24), the terminal200can shift to the outside coverage area mode (M11). When the terminal200transmits the restart request signal, the base station100is expected to shift to the normal mode (M1) and transmit broadcast information, but it can be considered that the reason of the failure to receive the broadcast information is that the terminal200moves to the outside of the service area of the base station100.

Transitions to the other modes M11-M13are identical to the above-mentionedFIG. 19B, and therefore, the description will be omitted.

<Configuration Example of the Radio Base Station Apparatus>

Next, a configuration example of the base station100will be described.FIG. 6is a diagram illustrating a configuration example of the base station100. The same symbols are attached to the same configuration parts depicted inFIG. 3A.

The base station100includes the radio unit110, the control function unit130, and the external interface unit150. The radio unit110includes the receiver111and the transmitter112.

Further, the control function unit130includes a RACH signal detection unit131, a last communication time recording unit132, an incoming call information processing unit133, a suspension mode shift prohibition determination unit134, a suspension prohibition recording unit135, a suspension mode switching control unit136, a transmitter power control unit (hereinafter “power control unit”)137and a broadcast information generation unit138.

Here, for example, the first transmission unit170in the first embodiment corresponds to the broadcast information generation unit138and the transmitter112. Also, for example, the first mode switching control unit171corresponds to, for example, the RACH signal detection unit131, the last communication time recording unit132, the incoming call information processing unit133, the suspension mode shift prohibition determination unit134, the suspension prohibition recording unit135, the suspension mode switching control unit136and the power control unit137.

The receiver111receives a radio signal transmitted from the terminal200, converts (downconverts) the received radio signal into a baseband signal. To perform radio signal reception, conversion, etc., the receiver111includes a reception antenna, an A/D converter circuit, a D/A converter circuit, a frequency converter, a band pass filter (BPF), etc.

The RACH signal detection unit131detects a RACH signal from a baseband signal being output from the receiver111. The RACH signal is transmitted from the terminal200using a radio resource allocated by the base station100, for example, and accordingly, the RACH signal detection unit131can detect the radio signal using radio resources (time and frequency, for example) allocated for the RACH signal. As the radio signal, for example, there is a restart request signal transmitted from the terminal200, for example. The RACH signal detection unit131, when detecting the restart request signal for example, can output a control signal representing that effect to the suspension mode switching control unit136.

The last communication time recording unit132is, for example, a memory that records the last communication time of the base station100with the terminal200. The last communication time recording unit132is connected to the transmitter112. The transmitter112is configured to be able to output the time of a radio signal transmitted to the terminal200, to the last communication time recording unit132for each terminal200, for example, so that the time finally overwritten into the last communication time recording unit132is the last communication time of the terminal200. To output such the time, the transmitter112may provide, for example, a timer and a counter internally.

The incoming call information processing unit133inputs incoming call information transmitted from the control station300or an adjacent base station, through the external interface unit150. When the incoming call information being input through the control station300is destined to a terminal200located in the coverage area of the base station100, the incoming call information processing unit133outputs to the suspension mode switching control unit136a control signal representing that there is an incoming call destined to the terminal200.

Also, when the incoming call information is a suspension mode shift notification signal and a start notification signal transmitted from the adjacent base station, the incoming call information processing unit133outputs a control signal representing that effect to the suspension mode switching control unit136. The suspension mode shift notification signal from the adjacent base station is, for example, a signal to notify the base station100that the adjacent base station shifts to the suspension mode (M3). Also, the start notification signal is a signal to notify the base station100that the adjacent base station restarts from the suspension mode (M3). Details will be described later.

The suspension mode shift prohibition determination unit134determines whether or not signals input through the external interface unit150includes a signal corresponding to suspension mode shift prohibition control, and if there is a signal corresponding to suspension mode shift prohibition control, the suspension mode shift prohibition determination unit134records that effect into the suspension prohibition recording unit135. The determination can be made by using, for example, a flag that indicates suspension mode shift prohibition control or whether or not a predetermined number that represents the suspension mode shift prohibition control is included in a signal input from the external interface unit150. There are two signals associated with the suspension mode shift prohibition control, namely, one is to prohibit shifting to the suspension mode (M3) and another is to cancel prohibition of shifting to the suspension mode (M3). Therefore, for example, when a signal representing prohibition of shifting to the suspension mode (M3) is input, the suspension mode shift prohibition determination unit134records that effect into the suspension prohibition recording unit135. Also, when a signal representing cancellation of prohibition of shifting to the suspension mode (M3) is input, the indication of prohibition of shifting to the suspension mode (M3) recorded in the suspension prohibition recording unit135can be deleted from the suspension prohibition recording unit135.

The suspension prohibition recording unit135is a memory to record the suspension mode shift prohibition control therein. For example, the suspension prohibition recording unit135can record an effect representing prohibition of shifting to the suspension mode (M3).

The suspension mode switching control unit136determines to switch from the normal mode (M1) to the suspension mode (M3), and determines to restart from the suspension mode (M3) to switch to the normal mode (M1), so as to perform a variety of types of control according to the respective cases.

In regard to a shift from the normal mode (M1) to the suspension mode (M3), the suspension mode switching control unit136refers to the last communication time recording unit132and the suspension prohibition recording unit135, to determine whether or not a shift to the suspension mode (M3) is to be made. For example, the suspension mode switching control unit136determines to shift to the suspension mode (M3) when a set time passes after the last communication time and a shift to the suspension mode is not prohibited. At this time, the suspension mode switching control unit136controls to notify a terminal200located in the coverage area and an adjacent base station that the own base station shifts to the suspension mode (M3). Details will be described later. Thereafter, the suspension mode switching control unit136outputs to the power control unit137a control signal to switch off the power (or halt the operation) of the transmitter112. By this, the operation of the transmitter112halts and the base station100shifts to the suspension mode (M3).

Further, in regard to a shift to the normal mode (M1) after restarting from the suspension mode (M3), the suspension mode switching control unit136can perform determination on the basis of a signal from the RACH signal detection unit131or the incoming call information processing unit133. Namely, when inputting from the RACH signal detection unit131a control signal representing that a restart request signal is received, the suspension mode switching control unit136determines to shift from the suspension mode (M3) to the normal mode (M1). Also, when inputting from the incoming call information processing unit133a control signal representing that there is incoming call information destined to the terminal200, the suspension mode switching control unit136determines to shift from the suspension mode (M3) to the normal mode (M1). On determining to shift to the normal mode (M1) after restarting, the suspension mode switching control unit136outputs to the power control unit137a control signal to restart the transmitter112. By this, the base station100in the suspension mode (M3) shifts to the normal mode (M1). Further, the suspension mode switching control unit136controls to notify the adjacent base station that the own base station restarts from the suspension mode (M3) and shifts to the normal mode (M1). Details will be described later.

Additionally, the suspension mode switching control unit136can receive a signal representing that the own station shifts to the suspension mode (M3) and a signal representing that the own station restarts from the suspension mode (M3) and shifts to the normal mode (M1), from the adjacent base station through the incoming call information processing unit133. The details thereof will also be described later.

The power control unit137can switch off the power of the transmitter112to halt the operation or can switch on the power to restart, based on a control signal from the suspension mode switching control unit136. Accordingly, the power control unit137can output, for example, a control signal representing power ON or OFF to the transmitter112.

The broadcast information generation unit138can generate broadcast information on the basis of an instruction from the suspension mode switching control unit136. The broadcast information generation unit138can generate, for example, the suspension mode shift notification signal, an adjacent base station in-suspension notification signal and an adjacent base station start notification signal, as the broadcast information. The adjacent base station in-suspension notification signal is, for example, a signal to notify a terminal200located in the coverage area of the base station100that the adjacent base station is in the suspension mode (M3). Also, the adjacent base station start notification signal is, for example, a signal to notify the terminal200located in the coverage area of the base station100that the adjacent base station restarts from the suspension mode (M3) (or restarts and shifts to the normal mode (M1)). The details of the above signals will be described later. The broadcast information includes an operator identification code, a frequency bandwidth, an identification number (such as cell ID) of the own station, etc., as described earlier. During the normal mode (M1), the broadcast information generation unit138can generate the broadcast information at constant intervals.

The transmitter112can transmit to the terminal200the broadcast information etc. being output from the broadcast information generation unit138after converting (upconverting) from a baseband signal to a radio signal. Therefore, the transmitter112may include an A/D converter circuit, a D/A converter circuit, a frequency converter, a band pass filter (BPF), a transmission antenna, etc. Also, the transmitter112can halt or restart the operation on the basis of a control signal from the power control unit137.

<Configuration Example of the Terminal200>

Next, a configuration example of the terminal200will be described. The terminal200, as depicted inFIG. 7, includes the radio unit210, the control function unit220, the display unit240and the input unit250. The radio unit210includes a transmitter211, a receiver212and a power measurement unit213. Further, the control function unit220includes a broadcast information detection unit221, a mode switching control unit222, a display control unit223, a RACH signal generation unit224, an adjacent base station suspension recording unit225and a measurement result processing unit226.

Here, the mode switching control unit270according to the first embodiment corresponds to the receiver212, the broadcast information detection unit221, the mode switching control unit222, the display control unit223, the adjacent base station suspension recording unit225and the measurement result processing unit226, for example.

The transmitter221can convert (upconvert) an RACH signal being output from the RACH signal generation unit224into a radio signal, to transmit to the base station100. To perform such conversion and transmission, the transmitter221may include, for example, an A/D converter circuit, a D/A converter circuit, a frequency converter, a band pass filter (BPF) and a transmission antenna. The RACH signal to be transmitted includes a restart request signal, for example.

The receiver212receives a radio signal transmitted from the terminal200, so as to convert (downconvert) into a baseband signal. To perform such reception and conversion, the receiver212may also include, for example, a reception antenna, an A/D converter circuit, a D/A converter circuit, a frequency converter, a band pass filter (BPF), etc.

The power measurement unit213measures the receiving power of the radio signal received in the receiver212. The power measurement unit213can output the measured receiving power to the measurement result processing unit226.

On detecting broadcast information out of baseband signal output from the receiver212, the broadcast information detection unit221outputs to the mode switching control unit222a control signal representing that the broadcast information is detected. The broadcast information includes, for example, a suspension mode shift notification signal transmitted from the base station100, an adjacent base station start notification signal, etc. On detection of these signals, the broadcast information detection unit221can output control signals respectively representing that effect.

Further, on receiving from the mode switching control unit222a shift control signal to the station suspension mode (M14), the broadcast information detection unit221retrieves broadcast information immediately before, at certain time intervals. By this, the terminal200in the station suspension mode (M14) can retrieve any one of an operator identification code, a radio communication method and a frequency bandwidth, or the combination thereof, immediately before shifting to the station suspension mode (M14). Incidentally, the broadcast information detection unit221retrieves all of the broadcast information with which the terminal200is compatible, when receiving from the mode switching control unit222a shift control signal to shift to the outside coverage area mode (M11). The broadcast information to be retrieved in the outside coverage area mode (M11) includes, for example, all operator identification codes, radio communication methods and frequency bandwidths.

Further, when receiving from the mode switching control unit222a communication mode (M13) shift control signal or a standby mode (M12) shift control signal, the broadcast information detection unit221can detect an adjacent base station in-suspension notification signal or an adjacent base station start notification signal. At this time, the broadcast information detection unit221can record an adjacent base station suspension flag into the adjacent base station suspension recording unit225. By this, for example, the terminal200can detect at handover whether or not the adjacent handover-target base station is in the suspension mode (M3). Details will be described later.

When receiving from the broadcast information detection unit221a control signal to the effect that the suspension mode shift notification signal is detected, the mode switching control unit222determines to shift to the station suspension mode (M14) and outputs a shift control signal to the station suspension mode (M14) to both the display control unit223and the broadcast information detection unit221. By this, the terminal200can shift to the station suspension mode (M14).

Also, when receiving from the input unit250a control signal representing a communication request or power ON, the mode switching control unit222can output a shift control signal to shift from the station suspension mode (M14) to a corresponding mode to the RACH signal generation unit224, the broadcast information detection unit221, the display control unit223, etc. The mode switching control unit222executes, for example, processing such as determining to shift to the outside coverage area mode (M11), the standby mode (M12), the communication mode (M13) and the station suspension mode (M14), as depicted inFIG. 5, of which details will be described later.

The display control unit223, on receiving a mode shift control signal from the mode switching control unit222, can control the display unit240to display the present mode to the display unit240.

The RACH signal generation unit224generates an RACH signal. For example, the RACH signal generation unit224can generate a restart request signal, when receiving a shift control signal to shift to the station suspension mode (M14) from the mode switching control unit222, and when receiving an instruction to generate the restart request signal from the measurement result processing unit226.

The adjacent base station suspension recording unit225is a memory to record a flag representing that the adjacent base station is in the suspension mode (M3). When the terminal200is located in the coverage area of the base station100and located at the edge of the service area, receiving power from the base station100becomes smaller than a set value, and therefore, the terminal retrieves a handover target. Then, when the adjacent base station of the handover target is in the suspension mode (M3), there is a case that the terminal200shifts to the outside coverage area mode (M11) because detection of the receiving power from the base station100of concern is not possible. To avoid such a case, a flag that represents whether or not the adjacent base station is in the suspension mode (M3) is recorded in the adjacent base station suspension recording unit225, so as to prevent the terminal200from becoming the outside coverage area mode (M11) when the terminal200moves to the service area of the base station100in the suspension mode.

For example, in the adjacent base station suspension recording unit225, there is recorded each flag representing whether or not each base station is in the suspension mode (M3). For example, each of the adjacent base station in-suspension notification signal and the adjacent base station start notification signal includes each identification number (cell ID etc.) of a base station100in the suspension mode (M3) and a base station100restarted (returned to the normal mode (M1)). Therefore, the broadcast information detection unit221records each flag to be ON or OFF, according to the identification number and the signal type of each corresponding base station. For example, when detecting the adjacent base station in-suspension notification signal, the broadcast information detection unit221can record ON (or “1”) into the adjacent base station suspension recording unit225relative to the identification number of the corresponding base station, so as to record that the corresponding adjacent base station is in the suspension mode (M3). Also, when detecting the adjacent base station start notification signal, the broadcast information detection unit221can record OFF (or “0”) from ON in regard to the identification number of the related base station100, so as to record that the corresponding adjacent base station restarts.

The measurement result processing unit226refers to the adjacent base station suspension flag recorded in the adjacent base station suspension recording unit225and the measurement result of the power measurement unit213, determines whether or not to transmit a restart request signal, and on determining to transmit, outputs a generation instruction of the restart request signal to the RACH signal generation unit224. For example, when the terminal200hands over to the base station100in the suspension mode (M3), the generation of a restart request signal is instructed when the receiving power of the base station in connection is smaller than a set value, and the terminal200is unable to retrieve a handover-target base station, and the adjacent base station suspension flag is ON. Details thereof will also be described later.

Operation Example

Next, an operation example will be described. As an operation example of the present radio mobile communication system10, there are two types of shift operation: shift operation in which the base station100shifts to the suspension mode (M3) and shift operation in which the terminal200shifts to the station suspension mode (M14). Furthermore, there is operation to restart the base station100currently in the suspension mode (M3).

First, shift operation to the suspension mode (M3) and the station suspension mode (M14) will be described, and subsequently, restart operation from the suspension mode (M3) will be described.

<1. Shift Operation to the Suspension Mode (M3) and the Station Suspension Mode (M14)>

First, a description will be given on the shift operation to the suspension mode (M3) and the station suspension mode (M14).FIG. 8is a sequence diagram illustrating an example of the shift operation to the suspension mode (M3) and the station suspension mode (M14),FIGS. 9A and 9Billustrate diagrams respectively illustrating examples on what kind of signals are transmitted from the base station100and the terminal200. Also,FIGS. 10A and 1013are diagrams illustrating signal examples.

A description will be given onFIG. 8. As a premise, for example, a terminal200-1is in the communication mode (M13) and is connected to a base station100-1, and the base station100-1is in the normal mode (M1), as depicted inFIG. 9Aetc. Further, there is a base station100-3as an adjacent base station, and a terminal200-2is located in the service area of the adjacent base station100-3. The terminal200-2is in either the communication mode (M13) or the standby mode (M12). Here inFIG. 8, the same symbols as inFIG. 4are attached to the same processing portions in the state transition diagram ofFIG. 4.

In such a situation, the terminal200-1and the base station100-1perform radio communication, so as to mutually transmit and receive data signals (hereinafter, data) (S30). Then, on completion of communication, the terminal200-1executes RRC Release (or transmits an RRC Release message) to terminate radio communication with the base station100(S219). Thereafter, the terminal200-1shifts to the standby mode (M12).

On the other hand, after the execution of the RRC Release, the base station100-1confirms whether or not suspension mode shift prohibition control is activated (S31(or S12inFIG. 4)). For example, the suspension mode switching control unit136, by referring to the suspension prohibition recording unit135, can perform confirmation based on whether or not a flag that represents prohibition to the suspension mode (M3) is recorded.

When the suspension mode shift prohibition control is activated (Y in S31), a shift to the suspension mode (M3) is prohibited, and therefore, the base station100-1maintains the normal mode (M1).

On the other hand, the base station100-1, when suspension mode shift prohibition control is not made (N in S31), measures an elapsed time (S32(or S11)) and determines whether or not a set time passes (S33(or S11)). For example, the transmitter112records into the last communication time recording unit132the transmission time of a signal that represents an RRC Release message to the terminal200-1, and the suspension mode switching control unit136reads out the last communication time from the last communication time recording unit132and, by subtracting from the present time, measures an elapsed time T. Then, the suspension mode switching control unit136can determine whether or not the elapsed time T exceeds the set time. If communication starts before the elapsed time T passes, the present time is recorded into the last communication time recording unit132by the transmitter112as the last communication time, and the elapsed time T is reset, needless to say. For example, the set time is retained in an internal memory of the suspension mode switching control unit136, so as to be read out at discretion by the suspension mode switching control unit136.

When the elapsed time T does not exceed the set time (N in S33), the base station100-1moves to S31again and repeats the above-mentioned processing. For example, when communication is restarted, the elapsed time does not exceed the set time because the elapsed time T is reset.

On the other hand, when the elapsed time T exceeds the set time (Y in S33), the base station100-1generates a suspension mode shift notification signal to transmit to all terminals that are located in the coverage area (S34, S35). For example, when communication is not restarted if the elapsed time T passes, the suspension mode switching control unit136determines to shift to the suspension mode (M3). For example, when the elapsed time T exceeds the set time, the suspension mode switching control unit136determines to shift to the suspension mode (M3), so as to instruct the broadcast information generation unit138to generate a suspension mode shift notification signal. Based on the instruction, the broadcast information generation unit138generates the suspension mode shift notification signal, and transmits the suspension mode shift notification signal through the transmitter112. Additionally, inFIG. 8andFIG. 9A, the suspension mode shift notification signal is represented as STANDBY_UE_INFO.

FIG. 10Aillustrates an example of the suspension mode shift notification signal. For example, the suspension mode shift notification signal is transmitted through an X1 interface in appropriation of SI (System Information) of 3GPP. For example, it is possible to use the extension bits of Tracking Area Id in 3GPP TS 36.300 V8. 10.0 (2009-09) (3GPP TS 36.300 V8.10.0 (2009-09), Annex C, Table C.2.1-1, FFS (for further study)). As depicted inFIG. 10A, for example, the suspension mode shift communication signal can be configured to include a bit representing “own station” in the field subsequent to the “Tracking Area Id”, a bit representing “suspension” in the next field, and a cell ID of the base station100in the next.

Returning toFIG. 8, on receiving the suspension mode shift notification signal, the terminal200-1shifts to the station suspension mode (M14) (S37). For example, the broadcast information detection unit221outputs to the mode switching control unit222a control signal representing that the suspension mode shift communication signal is detected, and on receiving the above control signal, the mode switching control unit222determines to shift from the standby mode (M12) to the station suspension mode (M14). When shifting to the station suspension mode (M14), the terminal200-1outputs a station suspension mode shift control signal to the broadcast information detection unit221. On receiving the station suspension mode shift control signal, the broadcast information detection unit221retrieves any one of an operator identification code, a radio communication method and a radio frequency bandwidth, or the combination thereof, that are used immediately before the station suspension mode (M14). The retrieval may be performed, for example, at constant time intervals.

Meanwhile, the base station100transmits a suspension mode shift notification signal to an adjacent base station100-3(S36). By this, the base station100can notify the adjacent base station100-3that the own station shifts to the suspension mode (M3).FIG. 10Bis a diagram illustrating an example of the suspension mode shift notification signal to be transmitted to the adjacent base station100-3. The transmission to the adjacent base station100-3is made using, for example, the X2 interface. For example, an ERROR INDICATION message in X2-AP (Application Protocol) (3GPP TS 36.423 V8.9.0 (2010-03), Chapter 9.1.2.2) can be appropriated. For example, a flag “transmission standby” is set ON, and the identification number (for example, cell ID) of the own station is included in “Old EeNB UE X2AP ID” or “New eNB UE X2AP ID”. By this, the base station100-1can transmit the suspension mode shift notification signal to the adjacent base station100-3. Additionally, inFIG. 8,FIG. 9A, etc., the suspension mode shift notification signal to be transmitted to the adjacent base station100-3is represented as STANDBY_NEIGHBOR.

Returning toFIG. 8, the base station100-1shifts to the suspension mode (M3) after transmitting the suspension mode shift notification signal to the terminal located in the coverage area and the adjacent base station (S34-S36). For example, the suspension mode switching control unit136outputs to the power control unit137a control signal representing switching off the power, and on receiving the control signal, the power control unit137outputs to the transmitter112a control signal to switch off the power of the transmitter112. On receiving the control signal, the transmitter112switches off the power of the transmitter112, to halt the operation. By this, the base station100-1shifts to the suspension mode (M3). In the suspension mode (M3), it is also possible not to operate the broadcast information generation unit138, in addition to the transmitter112.

On the other hand, on receiving the suspension mode shift notification signal (S36), the adjacent base station100-3transmits an adjacent base station in-suspension notification signal to all terminals located in the service area of the own station (S38, S39). InFIG. 8,FIG. 9A, etc., the adjacent base station in-suspension notification signal is represented as NEIGHBOR_STANDBY_UE_INFO. The adjacent base station in-suspension notification signal can also be represented byFIG. 10A. For example, the signal is configured to include a bit representing “adjacent” in the field subsequent to the “Tracking Area Id”, a bit representing “suspension” in the next field, and a cell ID of the base station100-1in the next field. For example, on receiving the suspension mode shift communication signal from the incoming call information processing unit133, the suspension mode switching control unit136extracts the cell ID of the base station100-1included in the above signal, and instructs the broadcast information generation unit138to generate an adjacent base station in-suspension notification signal, and also outputs the extracted cell ID to the broadcast information generation unit138. Based on the instruction and the cell ID, the broadcast information generation unit138can generate the adjacent base station in-suspension notification signal to output to the terminal200-2.

Returning toFIG. 8, on receiving the adjacent base station in-suspension notification signal, the terminal200-2sets the adjacent base station suspension flag ON to the adjacent base station suspension recording unit225(S40). For example, on detecting the adjacent base station in-suspension notification signal, the broadcast information detection unit221searches the adjacent base station suspension recording unit225for an item corresponding to the cell ID included in the above signal, and records a flag representing that the adjacent base station is in the suspension mode (M3), into the item of concern. This flag is used at handover, for example.

Here, if the terminal200-2receives the adjacent base station in-suspension notification signal, the terminal200-2only recognizes that the adjacent base station shifts to the suspension mode (M3), and does not perform any mode shift.

In the above-mentioned manner, the base station100-1shifts to the suspension mode (M3), and the terminal200-1shifts to the station suspension mode (M14). Also, the adjacent base station100-3can notify the terminal200-2located in the coverage area that the base station100-1shifts to the suspension mode (M3).FIG. 9Billustrates a configuration example of the radio mobile communication system10after shift operation to the suspension mode (M3) and the station suspension mode (M14) is made. Because the base station100-1is in the suspension mode (M3), no broadcast information is transmitted thereto, and the terminal200-1, which is in the station suspension mode (M14), retrieves an operator identification code, a radio communication method and a radio frequency bandwidth immediately before shifting to the station suspension mode (M14).

<2. Restart Operation from the Suspension Mode (M3)>

Next, a description will be given on the operation of restarting the base station100shifted to the suspension mode (M3) to shift to the normal mode (M1). Hereinafter, such operation is referred to as restart operation. The following three cases exist when the base station100performs restart operation.

Case 1) When a communication request occurs at the terminal200in the station suspension mode (M14).

Case 2) When the terminal200fails to receive a suspension mode shift notification signal because of the power OFF (M10) and the power is switched ON while the terminal200is located in the service area of the base station100shifted to the suspension mode (M3), or when the terminal200located outside the service area moves to the service area of the base station100in the suspension mode (M3) and the power is switched ON.

Case 3) When the terminal200located in the coverage area of the base station100moves to an adjacent base station in the suspension mode (M3) by handover.

Each of the above three cases will be described below.

<2.1 When a Communication Request Occurs at the Terminal200in the Station Suspension Mode (M14)>

FIG. 11is a sequence diagram illustrating an operation example when a communication request occurs at the terminal200in the station suspension mode (M14). Also,FIGS. 12A and 12Bare diagrams illustrating examples of signals transmitted and received at the base station100and the terminal200in the operation example.

As a premise, for example, the base station100-1is in the suspension mode (M3) and the terminal200-1located in the service area of the base station100-1is in the station suspension mode (M14). The adjacent base station100-3that neighbors the base station100-1is in the normal mode (M1), and performs radio communication with the terminal200-2in the service area of the own base station100-3. Further, it is assumed that another terminal200-3in the station suspension mode (M14) is also located in the service area of the base station100-1.

As illustrated inFIG. 11, at the terminal200-1in the station suspension mode (M14), a connection request is made by the operation of a calling button etc. by a human operator (S22), and the terminal200-1discriminates whether or not the number of transmissions of the restart request signal is smaller than a set value (S41). For example, when a connection request is input from the input unit250, the mode switching control unit222reads out the set value retained in the internal memory etc., so that the mode switching control unit222can discriminate whether or not the number of transmissions of the restart request signal is smaller than the set value.

Then, when the number of transmissions of the restart request signal is smaller than the set value (N in S41), the terminal200-1transmits the restart request signal (S23). For example, when the number of transmissions of the restart request signal is smaller than the set value, the mode switching control unit222instructs the RACH signal generation unit224to generate the restart request signal. Then, based on the instruction, the RACH signal generation unit224can generate the restart request signal and transmit to the base station100-1through the transmitter211. At this time, the mode switching control unit222can increment the number of transmissions by one, for example.

The restart request signal is represented inFIG. 11,FIG. 12A, etc. as WAKEUP. The restart request signal is transmitted, for example, using a PRACH (Physical Random Access Channel) of 3GPP. For example, to avoid interference by discriminating from another signal using the PRACH, the restart request signal is transmitted by using an unused Configuration Index No. 60 of the PRACH in Preamble format 3 (3GPP TS 36.211 V8.9.0 (2009-12), Table 5.7.1-2).

After transmitting the restart request signal, the terminal200-1detects whether or not broadcast information is received from the base station100-1(S24). For example, the broadcast information detection unit221detects whether or not the broadcast information is received.

Then, on detecting the broadcast information (Y in S24), the terminal200-1shifts from the station suspension mode (M14) to the communication mode (M13), and performs communication with the base station100-1(S241, S242). For example, the terminal200-1transmits to the base station100-1a radio signal that represents a connection request (for example, RRC Connection message) (S241), to perform data transmission or reception (for example,FIG. 12B). For example, on detecting the broadcast information, the broadcast information detection unit221outputs to the mode switching control unit222a control signal representing that effect, and on receipt of the above control signal, the mode switching control unit222determines to switch to the communication mode (M13). The mode switching control unit222outputs a shift control signal that represents the communication mode (M13) to the broadcast information detection unit221, the display control unit223, the RACH signal generation unit224, etc., and the terminal200shifts to the communication mode (M13).

On the other hand, when reception of the broadcast information is unsuccessful (N in S24), the terminal200-1goes to S41again, to discriminate whether or not the number of transmissions of restart is smaller than the set value (S41).

Thereafter, the terminal200-1repeats the above-mentioned processing, and when the terminal200-1fails to receive the broadcast information if the restart request signal is transmitted as many times as the set value or more (N in S24and N in S41), the terminal200shifts to the outside coverage area mode (M11) for the first time. For example, it is considered that the case of failure to receive the broadcast information in spite of the transmission of the restart request signal a lot of times is caused by that the terminal200-1moves outside the service area of the base station100-1, or the base station100-1fails to restart because of the occurrence of a failure in the base station100-1. In such a case, the terminal200-1is configured to shift to the outside coverage area mode (M11).

For example, if the number of transmissions of the restart request signal becomes equal to the set value, the mode switching control unit222determines to switch to the outside coverage area mode (M11) when receiving from the broadcast information detection unit221a control signal representing that the broadcast information does not be detected. Then, the mode switching control unit222outputs a shift control signal representing a shift to the outside coverage area mode (M11) to the display control unit223, the broadcast information detection unit221, the RACH signal generation unit224, etc., so as to shift to the outside coverage area mode (M11).

On the other hand, the base station100-1in the suspension mode (M3) supervises whether or not incoming call information to the terminal200-1located in the service area of the own station is received from the control station300, and whether or not a restart request signal is received from the terminal200-1(S43, S14).

On receiving the incoming call information to the terminal200-1(S43), the base station100-1restarts the transmitter112(S44). For example, when receiving from the control station300incoming call information destined to the terminal200-1, the incoming call information processing unit133notifies the suspension mode switching control unit136of that effect, and the suspension mode switching control unit136, on receiving this notification, outputs to the power control unit137a control signal to restart the transmitter112. Then, by the power switched ON, the transmitter112operates and restarts.

Also, when receiving the restart request signal from the terminal200-1(N in S14), the base station100-1restarts the transmitter112(S44). For example, on detecting the reception of the restart request signal, the RACH signal detection unit131notifies the suspension mode switching control unit136of that effect, and the suspension mode switching control unit136, on receiving this notification, outputs to the power control unit137a control signal to restart the transmitter112.

On the other hand, when there is no incoming call information to the terminal200-1(N in S43), the base station100-1supervises the reception of a restart request signal (S14), and maintains the suspension mode (M3) if no restart request signal is received (N in S14).

Next, the base station100-1transmits broadcast information (S45-S47). For example, the suspension mode switching control unit136instructs the broadcast information generation unit138to generate broadcast information, and then, in the broadcast information generation unit138, the broadcast information is generated and transmitted. The broadcast information is transmitted to all terminals located in the service area of the base station100-1, and therefore, not only the terminal200-1transmitted the restart request signal, the other terminal200-3in the station suspension mode (M14) that does not transmit the restart request signal can receive the restart request signal (S47).

Next, the base station100-1transmits the start notification signal to the adjacent base station (S48). InFIG. 12A, the start notification signal is represented as WAKEUP_NEIGHBOR. The transmission of the start notification signal will be described later (for example,FIG. 17).

Next, the base station100-1shifts from the suspension mode (M3) to the normal mode (M1), so as to be able to perform data transmission and reception between with the terminal200-1(S241, S242and, for example,FIG. 12B).

Meanwhile, on receiving the broadcast information from the base station100-1, the terminal200-3in the station suspension mode (M14) that is located in the service area of the restarted base station100-1shifts from the station suspension mode (M14) to the standby mode (M12). On the other hand, when the terminal200-3fails to receive the broadcast information (N in S26), the terminal200-3maintains the station suspension mode (M14).

<2.2 When the Power of the Terminal200is Switched ON>

Next, as case 2, a description will be given on an example when the base station100performs restart operation when the power of the terminal200is switched ON. Among such cases, there is a case when the terminal200is in the power OFF (M10) and fails to receive a suspension mode shift notification signal, and the power is switched ON while located in the service area of the base station100shifted to the suspension mode (M3). Also, there is a case when the terminal200located outside the service area moves to the service area of the base station100in the suspension mode (M3) and the power is switched ON while located in the service area of the base station100placed in the suspension mode (M3). In either case, the terminal200did not shift to the station suspension mode (M14), and the operation starts from the power OFF (M10) state. In this case, the base station100is in the suspension mode (M3).

FIG. 13is a sequence diagram illustrating an example of restart operation, andFIGS. 14A and 14Bare diagrams respectively illustrating examples of signals transmitted and received in the restart operation. Here, it is assumed that a terminal200-4is in the power OFF (M10) state and is located in the service area of the base station100-1.

The terminal200-4switches on the power from the power OFF (M10) state (S211).

Next, the terminal200-4confirms whether or not broadcast information is detected (S212). For example, confirmation can be made by whether or not the broadcast information detection unit221detects broadcast information.

When the detection of the broadcast information is unsuccessful (N in S212), the terminal200-4determines whether or not the number of transmissions of the restart request signal exceeds the set value (S50). For example, the broadcast information detection unit221notifies the mode switching control unit222that the detection of broadcast information is unsuccessful, and then, the mode switching control unit222compares the number of transmissions of the restart request signal with the set value, to determine whether or not the number of transmissions does not exceed the set value.

If the number of transmissions of the restart request signal does not exceed the set value (Y in S50), the terminal200-4transmits the restart request signal (S23). The restart request signal is transmitted using PRACH (Physical Random Access Channel), similar to the restart request signal in the operation example of the above-mentioned case 1 (S42). InFIGS. 13 and 14A, the restart request signal is represented as WAKEUP.

On the other hand, when the terminal200-4, after switching on the power, transmits the restart request signal and detects broadcast information (Y in S212), the terminal200-4shifts to the standby mode (M12). For example, the terminal200-4outputs to the mode switching control unit222a control signal representing that the broadcast information detection unit221detects the broadcast information. Based on the above control signal, the mode switching control unit222determines to shift to the standby mode (M12) and outputs a shift control signal that represents a shift to the standby mode (M12) to the display control unit223, the broadcast information detection unit221, etc. By this, the terminal200-4shifts to the standby mode (M12), and becomes a state in which communication can starts at any time (for example,FIG. 14B).

Also, after switching on the power, when the terminal200-4fails to detect broadcast information if the restart request signal is transmitted for the number of times equal to the set value (N in S212, N in S50), the terminal200-4shifts to the outside coverage area mode (M11).

On the other hand, the base station100-1, on receiving the restart request signal (Y in S14), restarts and shifts to the normal mode (M1) (S44, S45, S48). Also, the base station100-1in the suspension mode (M3) restarts and shifts to the normal mode (M1) (S44, S45, S48) if there is incoming call information to a terminal located in the coverage area (Y in S43). As to the operation of the base station100-1, the same operation as the operation in case 1 (when a communication request occurs at the terminal200in the station suspension mode (M14)) is performed.

<2.3 When the Terminal200Located in the Coverage Area of the Base Station Moves to an Adjacent Base Station in the Suspension Mode (M3) by Handover>

Next, a description will be given on an example of restart operation when the terminal200located in the coverage area of the base station100moves to an adjacent base station in the suspension mode (M3) by handover.FIG. 15is a sequence diagram illustrating the present operation example andFIGS. 16A and 16Bare diagrams respectively illustrating signal examples transmitted and received in the present operation example.

As a premise, as illustrated inFIG. 16Afor example, the terminal200-1is located in the coverage area of the base station100-3that is in the normal mode (M1), and is in either the communication mode (M13) or the standby mode (M12). Further, the terminal200-1moves to the adjacent base station100-1in the suspension mode (M3) by the handover. An operation example will be described on such an example.

The terminal200-1measures the receiving power of the base station100-3currently in connection, to discriminate whether or not the receiving power is smaller than a set value (falls down below a set value) (S70). For example, the power measurement unit213measures the receiving power of a radio signal received by the receiver212, and outputs a measurement result to the measurement result processing unit226. The measurement result processing unit226compares the receiving power with the set value, and discriminates whether or not the receiving power is smaller than the set value, and thus, the present processing is performed.

When the receiving power is larger than and including the set value (N in S70), the terminal200-1maintains the communication mode (M13) or the standby mode (M12) (loop at S70).

On the other hand, when the receiving power is smaller than the set value (Y in S70), the terminal200-1discriminates whether or not broadcast information of the adjacent base station100-1is received (S71). For example, the broadcast information detection unit221can discriminate whether or not the broadcast information of the adjacent base station is received. For example, because the broadcast information includes the identification information (for example, cell ID) of the base station100, the broadcast information detection unit221can discriminate from the identification information of the base station whether or not the broadcast information of the adjacent base station100-1is received.

The terminal200-1, on receiving the broadcast information of the adjacent base station100-1(Y in S71), measures the receiving power of the adjacent base station (S76). For example, the measurement is performed by the power measurement unit213.

Then, the terminal200-1performs a normal handover procedure between with the base station100-1. Namely, the terminal200-1notifies the base station100-3of the measured receiving power (S77), and the base station100-3determines the handover target of the terminal200-1on the basis of the above receiving power (S78). The base station100-3notifies the terminal200-1of the determined handover target (S79), and the terminal200-1executes the handover procedure (S80). For example, the terminal200-1hands over to the adjacent base station100-1(for example,FIG. 16B).

On the other hand, when the terminal200-1fails to receive the broadcast information from the adjacent base station100-1(N in S71), the terminal200-1discriminates whether or not the adjacent base station suspension flag is ON (S72). The terminal200-1confirms that the failure to receive the broadcast information of the adjacent base station100-1is caused by whether or not the adjacent base station100-1is in the suspension mode (M3). For example, when the measurement result processing unit226inputs from the broadcast information detection unit221a control signal representing that the broadcast information of the adjacent base station100-1does not be received, the measurement result processing unit226confirms whether or not the adjacent base station100-1becomes the suspension mode (M3) in the adjacent base station suspension recording unit225. Alternatively, when the measurement result processing unit226inputs from the broadcast information detection unit221a control signal representing that the reception of the broadcast information of the adjacent base station100-1is unsuccessful, it may also be possible to confirm by referring to the adjacent base station suspension recording unit225.

Then, when the adjacent base station suspension flag is ON (or when the adjacent base station100-1is in the suspension mode (M3)), the terminal200-1transmits to the adjacent base station100-1a restart request signal within the range not exceeding the set value (N in S73, S74, S75). The terminal200-1confirms that the adjacent base station100-1is in the suspension mode (M3), and transmits the restart request signal to the adjacent base station100-1to restart. For example, when the measurement result processing unit226, by referring to the adjacent base station suspension recording unit225, confirms that the adjacent base station suspension flag of the adjacent base station100-1is ON, the measurement result processing unit226compares the number of transmissions of the transmitted start request signal stored in the internal memory with the set value. Then, if the number of transmissions is smaller than the set value, the measurement result processing unit226instructs the RACH signal generation unit224to generate a restart request signal. By this, the restart request signal is transmitted to the base station100-1.

When the terminal200-1fails to detect the broadcast information in spite of the transmission of the restart request signal for the set number of transmissions (N in S71and Y in S73), the terminal200-1shifts to the outside coverage area mode (M11). For example, the terminal200-1is configured to shift to the outside coverage area mode (M11) due to a reason that either the terminal200-1moves to outside the service area or the base station100-1in the suspension mode (M3) fails to restart due to a fault.

On the other hand, when the adjacent base station suspension flag is OFF (N in S72), the terminal200-1shifts to the outside coverage area mode (M11). In this case, for example, the adjacent base station100-1is in the normal mode (M1), and the reason for the failure to receive the broadcast information (N in S71) is that the terminal200-1is located outside the service area of the adjacent base station100-1.

Here, operation in the adjacent base station100-1after the reception of the restart request signal is identical to case 1 and case 2 (for example, S14and S44-S48inFIG. 11andFIG. 13), and therefore, description is omitted.

Next, as other operation examples, detailed processing of S48in case 1 to case 3 will be described. The processing of S48is an example when the base station100in the suspension mode (M3) received the restart request signal transmits the start notification signal to the adjacent base station, for example. InFIGS. 12,14and16, the start notification signal is represented as WAKEUP_NEIGHBOR.

FIG. 17is a diagram illustrating the detailed operation example of the processing of S48. As a premise, it is assumed that the base station100-1is in the suspension mode (M3), the adjacent base station100-3is in the normal mode (M1), and the terminal200-2is located in the service area of the adjacent base station100-3.

The base station100-1in the suspension mode (M3), when receiving the restart request signal from the terminal200-1(S14), restarts the transmitter112to transmit broadcast information (S44, S45). Then, the base station100-1transmits a start notification signal to the adjacent base station (S48, S60). For example, on receiving a control signal representing that the restart request signal is received from the RACH signal detection unit131, the suspension mode switching control unit136instructs the external interface unit150to generate the start notification signal and transmit to the adjacent base station100-3. On receiving this instruction, the external interface unit150generates the start notification signal to transmit to the adjacent base station100-3. Alternatively, it may also be possible that the suspension mode switching control unit136generates the start notification signal to transmit to the adjacent base station100-3through the external interface unit150.

As the start notification signal, an X2-AP ERROR INDICATION message by 3GPP (3GPP TS 36.423 V8.9.0 (2010-03), Chapter 9.1.2.2) can be appropriated, similar to the suspension mode shift notification signal (STANDBY_NEIGHBOR). In the example depicted inFIG. 10B, the start notification signal is transmitted using a message in which a flag “transmission wakeup” is set ON and the identification number of the own station is included in “Old EeNB UE X2AP ID” or “New eNB UE X2AP ID”.

Returning toFIG. 17, after transmitting the start notification signal (S48), the base station100-1in the suspension mode (M3) can shift to the normal mode (M1).

On the other hand, the adjacent base station100-3, on receiving the start notification signal, transmits an adjacent base station start notification signal to a terminal located in the service area of the adjacent base station100-3(S36, S61). The adjacent base station start notification signal is a signal to notify the terminal200-2located in the coverage area of the adjacent base station100-3that the base station100-1restarts from the suspension mode (M3) (or restarts and shifts to the normal mode (M1)).

As the adjacent base station start notification signal, similar to the above-mentioned suspension mode shift notification signal, the adjacent base station in-suspension notification signal, etc., it is possible to use, for example, the extension bits of Tracking Area Id in 3GPP TS 36.300 V8. 10.0 (2009-09) (3GPP TS 36.300 V8.10.0 (2009-09), Annex C, Table C.2.1-1, FFS (for further study)).FIG. 10Aillustrates an example of the adjacent base station start notification signal. For example, there are inserted a bit representing “adjacent” in the field subsequent to the “Tracking Area Id”, a bit representing “restart” in the next field, and a cell ID of the base station100-1restarted in the next field, respectively.

For example, on receiving the start notification signal through the external interface unit150, the incoming call information processing unit133in the adjacent base station100-3outputs to the suspension mode switching control unit136a control signal including that effect and a cell ID included in the start notification signal. Then, the suspension mode switching control unit136outputs the cell ID included in the start notification signal to the broadcast information generation unit138, to instruct to generate a adjacent base station start notification signal. By this, the adjacent base station start notification signal is transmitted from the broadcast information generation unit138to the terminal200-2located in the coverage area.

Returning toFIG. 17, on receiving the adjacent base station start notification signal, the terminal200-2switches off the adjacent base station suspension flag (S62). By this, for example, the terminal200-2can grasp that the adjacent base station100-1is not in the suspension mode (M3). For example, on receiving the adjacent base station start notification signal, the broadcast information detection unit221searches the adjacent base station suspension recording unit225for an item corresponding to the cell ID that is included in the adjacent base station start notification signal. Then, the broadcast information detection unit221switches off the adjacent base station suspension flag that is ON in the item corresponding to the cell ID (for example, rewrites the flag is “1” to “0”).

Then, thereafter, the terminal200-2maintains the communication mode (M13) or the standby mode (M12) intact.

Through one of the above three cases, the base station in the suspension mode (M3) restarts and can shift to the normal mode (M1).

As described above, according to the present second embodiment, the suspension mode (M3) is newly provided for the base station100, and during the suspension mode (M1), the transmitter112does not operate, and thus, power consumption in the base station100can be reduced as compared to the normal mode (M1) in which the transmitter112is in operation.

Further, the station suspension mode (M14) is newly provided for the terminal200, and during the station suspension mode (M14), broadcast information immediately before shifting to the station suspension mode (M14) is retrieved at constant time intervals. For example, the terminal200is configured to retrieve any one of the operator identification code, the radio communication method and the radio frequency bandwidth immediately before, or the combination thereof, at constant time intervals. Therefore, as compared to the outside coverage area mode (M11) in which the terminal200continuously retrieves all operator identification codes, radio communication methods and radio frequency bandwidths with which the terminal200is compatible, the terminal in the station suspension mode (M14) can reduce power consumption thereof.

Further, the base station100, on shifting to the suspension mode (M3), is configured to distribute a notification that represents the shift to the suspension mode (M3) to the terminal200located in the coverage area of the base station100(for example, S35inFIG. 8). On receiving the notification, the terminal200shifts to the station suspension mode (M14) without shifting to the outside coverage area mode (M11) (for example, S37inFIG. 8). Accordingly, because the terminal200shifts to the station suspension mode (M14), the number of types and the frequency of broadcast information to be retrieved become smaller than in the outside coverage area mode (M11), and it is possible to reduce power consumption in the terminal200and extend the battery life, as compared to the case of the outside coverage area mode (M11).

Further, by shifting the terminal200that is located in the coverage area of the base station100shifted to the suspension mode (M3), to the station suspension mode (M14), it is also possible for the user of the terminal200to distinguish from the outside coverage area mode (M11) and determine whether or not communication is possible. For example, making the display control unit223display an indication representing the station suspension mode (M14) on the display unit240enables the user to determine whether or not communication is possible.

Further, the base station100-1is configured to notify the terminal200-2, which is located in the coverage area of the adjacent base station100-3, of the shift to the suspension mode (M3) through the adjacent base station100-3(for example, S36inFIG. 8) (S36, S39). By this, if the terminal200-2moves to the service area of the base station100-1in a suspension state by handover, the terminal200-2does not shift to the outside coverage area mode (M11) because the adjacent base station suspension flag is set ON (for example, Y in S72inFIG. 15). Therefore, it is also possible for the terminal200-2to execute a handover procedure, and service quality can be maintained as compared to a case that the terminal200-2becomes the outside coverage area mode (M11) when moving to the service area of the base station100-1placed in the suspension mode (M3).

Moreover, when the terminal200is in the station suspension mode (M14), transmission of the common channel from the terminal200becomes less frequent as compared to a case when the terminal200is continuously in the communication mode (M13), and therefore, interference to another terminal200can be avoided. Then, because the terminal in the station suspension mode (M14) refrains from common channel transmission in an insensitive zone existent in the service area of the base station100, it is also possible to avoid interference to another terminal outside the insensitive zone, for example.

Other Embodiments

Next, other embodiments will be described.

Each configuration example of the base station100and the terminal200is described in the second embodiment, with the examples ofFIG. 6andFIG. 7. Also, for example, by each configuration example illustrated inFIGS. 18A and 18B, the operation example described in the second embodiment can be performed.

As illustrated inFIG. 18A, the base station100further includes a CPU (Central Processing Unit)160, a DSP (Digital Signal Processing)161and a memory162. For example, the DSP161operates on the basis of a control signal output from the CPU160, and can record a flag etc. by appropriately accessing the memory162. By the operation of the DSP161, for example, it is possible to achieve each function of the RACH signal detection unit131, the incoming call information processing unit133, the suspension mode shift prohibition determination unit134, the suspension mode switching control unit136and the power control unit137in the second embodiment. From such a thing, the DSP161corresponds to the RACH signal detection unit131, the incoming call information processing unit133, the suspension mode shift prohibition determination unit134, the suspension mode switching control unit136and the power control unit137. Also, the memory162corresponds to the last communication time recording unit132and the suspension prohibition recording unit135.

Also, as illustrated inFIG. 18B, the terminal200further includes a CPU260, a DSP261and a memory262. The DSP261operates on the basis of a control signal from the CPU260, and can record a flag etc. by appropriately accessing the memory262. By the operation of the DSP261, for example, it is possible to achieve each function of the broadcast information detection unit221, the mode switching control unit222, the display control unit223, the RACH signal generation unit224and the measurement result processing unit226. From such a thing, the DSP261corresponds to the broadcast information detection unit221, the mode switching control unit222, the display control unit223, the RACH signal generation unit224and the measurement result processing unit226. Also, the memory262corresponds to the adjacent base station suspension recording unit225.