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TITLE OF THE INVENTION
RADIO COMMUNICATION DEVICE, RADIO COMMUNICATION METHOD AND
RADIO COMMUNICATION SYSTEM
Background of the invention
The present invention relates to radio communication technology, and more particularly to reducing the electric power requirement of a radio communication device when standing by for reception.
Radio communication systems, each having base stations and radio communication devices, include an active tag system. An active tag system is a system in which radio communication is accomplished between an active tag, which is a radio communication device, and a base station; the active tag has a power source; and the distance of communication is generally dozens of meters. An active tag system usually uses a different carrier frequency for each base station to prevent interference. The carrier frequency is called the channel. Among radio communication devices for mounting on a vehicle, there is known a type that switches over the channel for reception at prescribed intervals of detection time when standing by for reception to solve the problem of a higher cost that would arise if the device were equipped with the number of reception means matching the number of channels operated (Japanese Patent

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Application Laid-Open Publication No. 2000-307506) .
Brief Summary of the invention
For a radio communication device for mounting on a vehicle, which usually can receive power supply from the vehicle, consumption of power required when standing by for reception poses no problem. However, for a radio communication device to be carried by a person and whose power source is a battery or the like limited in capacity, such as an active tag, consumption of power required when standing by for reception poses a problem.
A radio communication device according to the present invention is provided with a first circuit that is actuated by a radio wave from outside and, when it receives a radio wave and is actuated, stores a record of actuation as log information, a power source, and a second circuit that is driven by power from the power source and reads out the log information.
A radio communication method according to the invention is a method of radio communication with base stations each of which sends out a radio wave on one carrier frequency out of a plurality of carrier candidates to perform radio communication, the method having a step of storing, when a circuit driven by a radio of any carrier frequency out of the candidates is actuated, the record of

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actuation as log information into a memory that is provided, and a step of referencing the memory and, in the presence of any record of actuation of the circuit, searching the base stations.
A radio communication system according to the invention has: a base station that sends out a radio wave on one carrier frequency out of a plurality of carrier frequency candidates; and a radio communication device having a memory, a first circuit that is driven by a radio wave driven by a radio wave of any carrier frequency out of the candidates and, when actuated by reception of a radio wave from the base station, stores the record of actuation as log information into the memory, and a second circuit that references the memory and, if a record or actuation is found therein, searches the base station.
The invention, as it utilizes log information recorded without depending on power from a particular power source such as a battery, enables power consumed for standing-by to be reduced.
Brief description of the drawings
Fig. 1 illustrates an example of configuration of a radio communication system according to the present invention;
Fig. 2 illustrates an example of configuration of a

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radio communication device according to the invention;
Fig. 3 illustrates an example of configuration of a first circuit in the radio communication device according to the invention;
Fig. 4 illustrates an example of operation of the first circuit in the radio communication device according to the invention;
Fig. 5 illustrates another example of configuration of the radio communication device according to the invention;
Fig. 6 illustrates an example of procedure of determining priorities of channel search in the radio communication device according to the invention;
Fig. 7 illustrates an example of communication log stored in a memory in the example of radio communication device according to the invention;
Fig. 8 illustrates another example of radio communication device according to the invention;
Fig. 9 illustrates an example of application of the device to control over entrance into and exit from rooms; and
Fig. 10 illustrates an example of application of the device to a position finding system.
Detailed description of the invention

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Embodiments of the present invention will be described in detail below with reference to the accompanying drawings. In all the drawings illustrating the embodiments, the same members will be assigned respectively the same reference signs as a rule, and repeated description thereof will be dispensed with. [First Embodiment]
Fig. 1 illustrates, as one example of embodiment of the invention, an active tag system 100, which is a radio communication system. The active tag system 100 has a plurality of base stations 101 and 102, which send out radio waves to perform radio communication with a radio communication device 103 or a radio communication device 104. In the example shown in Fig. 1, the radio communication device 103 receives transmitted data 105 carried over a radio wave sent out from the base station 101. Also, the other radio communication device 104 receives transmitted data 106 carried over a radio wave from the base station 102.
If in this case the base stations 101 and 102 are located close to each other, the radio communication device 103 will also receive, in addition to the data 105 transmitted from the base station 101, a radio wave sent out from the base station 102 as an interfering wave 107. As a consequence, the radio communication device 103 may be

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prevented from receiving the data 105 correctly due to the influence of the interfering wave 107.
In view of this problem, reception errors are prevented in this embodiment by using different channels as carrier frequencies (hereinafter referred to as channels) of the radio waves sent out by the base station 101 and the base station 102. Thus, a plurality of channel candidates are made available, and each base station uses one out of the plurality of channel candidates. In this embodiment, the frequency range for each channel is selected out of a 950 MHz band.
Therefore, the radio communication device 103 receives the data 105 by searching for the channel over which the base station 101 transmits out of a plurality of channels (e.g. six channels) (this action will be hereinafter referred to as "channel search") and selecting that channel. For instance, the radio communication device 103 actuates its receiver circuit to set a channel for reception. Then, the radio communication device 103 successively switches over the channel for reception to search for the data 105 transmitted by the base station 101. For instance, if there are six channels in total, from channel 1 through channel 6, the radio communication device 103 performs channel search by scanning them in the order of channel 1, channel 2, channel 3, channel 4, channel 5

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and channel 6.
Fig. 2 illustrates a radio communication device 200 as an example of configuration of the radio communication device 103. As shown in Fig. 2, the radio communication device 200 has a first circuit 201 that generates electric power from a radio wave from outside and carries out driving, a power source 202, and a second circuit 203 that is driven by the power source 2 02 and communicates with the first circuit 201.
The first circuit generates electric power and carries out driving in any frequency band of the channel candidates used by the base station 101. Thus, the first circuit carries out driving on any channel of the channel candidates used by the base station 101. Further, the first circuit 201 is provided with a memory. As the power source 202, a battery or a capacitor can be used, for instance. In this embodiment, a battery is used as the power source 202. Although Fig. 2 illustrates an instance in which the first circuit 201, the power source 202 and the second circuit 203 are housed in a case, it is also permissible to provide the power source 2 02 and the second circuit 203 in a case and the first circuit 201 in a medium, such as an IC card, fitted to that case, as will be described afterwards with reference to a fourth embodiment.
The circuit configuration of the first circuit 201 is

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illustrated in Fig. 3. As shown in Fig. 3, the first circuit 201 is provided with a rectifier circuit 301 for rectifying received signals, a power detector circuit 3 02 for detecting the power value of the rectifier circuit 301, a memory 3 03 for storing log information on the actuation of the first circuit 201, a logic circuit 304 for instructing each circuit to operate, a demodulator circuit 305 for demodulating signals from a passive reader/writer circuit 204 to be described afterwards, a transmitter circuit 3 06 for transmitting signals generated by the logic circuit 3 04 according to demodulated data, and an antenna 307. The antenna 307, which may be a dipole antenna for instance, can receive radio waves of the 950 MHz band sent out from base stations in this embodiment, and can also send out radio waves of the 950 MHz band. As the memory 303, a nonvolatile memory such as a flash memory or a phase change memory.
The second circuit 203 has the passive reader/writer (hereinafter abbreviated to passive R/W) circuit 204 that performs radio communication with the first circuit 201, an active tag circuit 205 that performs radio communication with base stations, which are external radio communication equipment, and a control circuit 2 06 that controls the passive R/W circuit 204 and the active tag circuit 205. The passive R/W circuit 204, the active tag circuit 205 and

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the control circuit 206 receive power supply from the power source 202. The power source 202 and the active tag circuit 205 constitute an active tag. Thus, the power source 202 and the active tag circuit 205 constitute an IC tag that can transmit and receive signals to and from base stations serving as reader/writers over a long distance of a few tens of meters. Further, the passive R/W circuit 2 04 sends out radio waves in the 950 MHz band to accomplish read and write actions. The use by the passive R/W circuit 2 04 of radio waves of the same frequency band as the base stations enables the first circuit 201 to receive power supply over a common circuit from either of the base stations or the second circuit 203. Therefore, the radio communication device 103 can be manufactured at reduced cost.
In the basic procedure of communication between the radio communication device 103 and the base station 101, the base station transmits the data 105, the first circuit 201 is actuated by the data 105, namely a radio wave from the base station 101, and the record of actuation is stored into the memory 303 of the first circuit 201 as log information. For instance, if one bit in the memory 3 03 is utilized to store "0" as an initial value before the actuation, the record of actuation is stored as "1" in the log information.

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The action of each circuit in the basic procedure of communication will be described in detail below.
The action of the first circuit 201 is illustrated in Fig. 4. As shown in Fig. 4, the first circuit 201 rectifies a received signal with the rectifier circuit 301 to generate internally operating power (step SI). The output of the rectifier circuit 3 01 is transmitted to the power detector circuit 302 and the demodulator circuit 305. After that, the power detector circuit 3 02 detects the power value of the received signal. Also, the demodulator circuit 305 demodulates the received signal (step S2). Next, the logic circuit 3 04 judges whether or not the demodulated signal from the demodulator circuit 3 05 is a transmitted signal from the passive R/W circuit 204 (step S3) .
If the demodulated signal is a transmitted signal from the passive R/W circuit 204, processing corresponding to a transmitted signal from the passive R/W circuit 204 is done (step S4) . For instance, if it is a transmitted signal requesting log information recorded in the memory 303, the transmitter circuit 306 transmits the log information via the antenna 307.
If the demodulated signal is not a transmitted signal from the passive R/W circuit 204, "Start made" is stored into the memory 303 of the first circuit 201 as log

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information (step S6) . If log information is stored in one bit, the initial state of "0" is rewritten to "1". By providing step S5 here, it will be possible to perform processing of not storing "Start made" if the power value detected by the power detector circuit 3 02 is lower than a preset threshold. This enables the radio communication device 103 to be so set as to start radio communication in a radio wave state in which even greater electric power than what is sufficient to start the first circuit 201 is supplied, and makes possible, for instance, adjustment of the distance for communication to be made between a base station and the radio communication device 103. Further, if the threshold at step s5 is set to 0, for example, it will be sufficient to store log information of simply "Start made".
In the second circuit 203, the control circuit 206 gives an instruction to the passive R/W circuit 204 to intermittently (e.g. from every few seconds to every few minutes) read the log information stored in the memory 3 03 of the first circuit 201. The passive R/W circuit 204 so instructed reads the log information out of the first circuit 201. Incidentally, as the procedure for reading log information, a radio communication procedure conforming to the international standards of ISO/IEC18000-6C is used for instance.

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The passive R/W circuit 2 04 transmits to the control circuit 2 06 the log information read out of the first circuit 201. If the read log information is "1", which means that "a start was made," the control circuit 206 gives an instruction to the active tag circuit 2 05 to start radio communication with a base station. The active tag circuit 2 05 having received the instruction searches for a base station by actuating a receiver circuit included in the active tag circuit 205 to perform channel search.
If the channel search succeeds in identifying the channel used by the base station 101, the active tag circuit 205 selects the identified channel and receives the data 105. Also, under the control of the control circuit 2 06, the passive R/W circuit 2 04 resets the log information of the memory 303 of the first circuit 201. Namely, the bit of the memory 303 is returned to "0".
On the other hand, if the log information is "0" indicating the absence of record of actuation, the control circuit 206 will not instruct the active tag circuit 205 to start radio communication with any base station. Therefore, no channel search is done. In this way, when there is no base station with which communication is possible, the actions of the radio communication apparatus 103 are restricted to restrain its power consumption for standing-by.

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Through the steps described above, radio communication between the radio communication apparatus 103 and the base station 101 is ended.
As so far described, the radio communication apparatus 103 of this embodiment actuates the first circuit 201 by utilizing power generated from the radio wave sent out from the base station, and leaves the record of the actuation in the memory 3 03 as log information. And the second circuit 2 03 of the radio communication apparatus 103 reads out the log information. The radio communication apparatus 103 performs radio communication according to the log information that has been read out. Thus, if the read¬out information contains a record of actuation, the radio communication apparatus 103 actuates the receiver circuit included in the active tag circuit 205, finds the pertinent base station and receives data carried on the radio wave sent out by the base station.
The radio communication apparatus 103, without having to keep the receiver circuit of the active tag circuit 205 all the time, can confirm the presence of the base station from the log information of the first circuit 201 by intermittent operation, thereby making possible standing by for reception at reduced power consumption. Also, the radio communication apparatus 103 can limit actions by performing no channel search in the absence of a record of

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actuation in the log information if, for instance, the distance between the radio communication apparatus 103 and the base station 101 is beyond a supposed range, and thereby further restrain power consumption for standing-by. Therefore, power consumption by the radio communication apparatus 103, namely, exhaustion of the battery, which is the power source 2 02, can be restrained. [Second Embodiment]
Fig. 5 illustrates, as one example of configuration of the radio communication device 103 in a first embodiment, a radio communication device 501 having an additional memory 500. In the memory 500, the communication log of the active tag circuit 205 is recorded. More specifically, the data 105 received by the active tag circuit 205 from the base station 101 and information on the reception channel are stored into the memory 50 0 via the control circuit 206.
While the procedure of radio communication between the radio communication device 501 and the base station 101 according to the invention is basically the same as that between the radio communication device 103 and the base station 101 of the first embodiment, the difference consists in that the sequence of searching different channels in channel search is varied according to information on reception channels stored in the memory 500.

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Regarding the first embodiment, as an example of channel search sequence, where there are six channels in total, a sequence of searching in the order of channel 1, channel 2, channel 3, channel 4, channel 5 and channel 6 is shown. In the radio communication device 501 of this embodiment, where the receiver circuit of the active tag circuit 205 references the reception channel of the previous round of communication stored in the memory 500 via the control circuit 206, the order of channel search is so set as to give priority to other channels over the reception channel of the previous round of communication. Where there are six channels in total from channels 1 through 6 and the reception channel of the previous round of communication is channel 2, channel 2 is placed last in the sequence of channel search where channel 3, channel 4, channel 5, channel 6 and channel 1 are searched in that order. When there is communication with the base station 101, the active tag circuit 205 stores the data 105 transmitted by the base station 101 and information on the reception channel into the memory 500 via the control circuit 206. This causes information on reception channels stored in the memory 500 to be updated every time communication is made.
As hitherto described, the radio communication device 501 of this embodiment, searching channels with the active

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tag circuit 205, references the reception channel of the immediately previous round of communication stored in the memory 500, and performs the channel search with priority given to other channels than the reception channel of the immediately previous round of communication. Therefore, when the radio communication device 501 is in a position where it can receive transmitted data from a plurality of base stations, it is possible to prevent the radio communication device 501 from consecutively receiving transmitted data from the same base station. [Third Embodiment]
While the first embodiment and a second embodiment were cases in which each of a plurality of base stations used a different channel from the others, there are cases in which different base stations use the same channel and transmit data so as not to suffer overlapping of transmitting periods between one another and the radio communication device 501 needs consecutive reception on the same channel of transmitted data from different base stations.
In view of this point, the radio communication device 501 in this embodiment determines by the procedure charted in Fig. 6 the priorities of channel search by the active tag circuit 205 by using not only the reception channels stored in the memory 500 but also the reception data.

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As charted in Fig. 6, the active tag circuit 2 05 reads out the communication log stored in the memory 500 via the control circuit 206 (step S61), and judges whether or not the reception channel of the immediately previous time is the same as that of the next immediately previous time (step S62) . Fig. 7 shows one example of communication log stored in the memory 500. As shown in Fig. 7, if the reception channel of the immediately previous time is the same as that of the next immediately previous time, it is judged whether or not the reception data of the immediately previous time are the same as those of the next immediately previous time (step S63) . And if the reception data of the immediately previous time are different from those of the next immediately previous time as in Fig. 7, channel search is performed with priority given to the reception channel of the immediately previous time (step S64). If the total number of channels is six in the case of Fig. 7, the reception channel of the immediately previous time is channel 2, and therefore channel search is performed with channel 2 coming first in the order of channel 2, channel 3, channel 4, channel 5, channel 6 and channel 1.
Further, if the judgment at step S62 reveals a difference between the reception channel of the immediately previous time and that of the next immediately previous time or the judgment at step S63 indicates that the

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reception data of the immediately previous time are the same as those of the next immediately previous time, channel search is performed with priority given to other channels than the reception channel of the immediately previous time (step S65).
As described above, the priorities in the channel search by the active tag circuit 2 05 are determined the basis of the communication log on reception channels and received data stored in the memory 500. Therefore, when different base stations are to transmit data over the same channel so as not to let their transmission periods overlap each other, the radio communication device 501 is enabled to consecutively receive transmitted data from different base stations using the same channel. [Fourth Embodiment]
In this embodiment, the power source 2 02 and the second circuit 2 03 are housed in a case, and the first circuit 201 is disposed in a medium, such as an IC card, fitted to that case. This form enables the radio communication device according to the invention to be realized at a lower cost by utilizing an existing case and a medium, such as an IC card.
Fig. 8 illustrates, as another example of the radio communication device 103, a radio communication device 802 whose first circuit 201 is disposed in an IC card 801

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fitted to a case having the power source 2 02 and the second circuit 203 built into it. Description of its operation is dispensed with because it is no different from any of the first through third embodiments except in that the first circuit 201 is not built into, but is fitted to, the case.
To add, fitting of the medium to the case can be achieved by, for instance, pasting with a tacky adhesive. As the case, the case of a mobile phone can as well be used as shown in Fig. 8. Where the case of a mobile phone is to be used, a radio communication system utilizing the mobile phone's own radio communication function in addition to that of the active tag circuit 205 can be realized. [Fifth Embodiment]
In this embodiment, an example in which the radio communication system according to the invention is used for control over entrance into and exit from rooms is shown.
Fig. 9 illustrates an example of application to control over entrance into and exit from rooms. The base station 101 is installed in a room 901, and the base station 102, in a room 902. The walls of each room are supposed to intercept radio waves from the respective radio stations. Also, the base station 101 and the base station 102 are connected to a server not shown. In the server, information on the periods on the use of each room by the person carrying the radio communication device 103, for

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instance the beginning and ending times of a conference, is stored. The data 105 include information on the durations of use of the room 901.
The radio communication device 103 carried by a person 903 positioned near the entrance to the room 901 actuates the first circuit 201 by utilizing the transmission of the data 105 sent by the base station 101, and leaves the record of actuation in the memory 3 03 as log information. Then, the second circuit 203 of the radio communication device 103 reads out the log information. Afterwards, a receiver circuit contained in the active tag circuit 205 is actuated, and the data 105 are received. In this procedure, the radio communication device 103 acquires information on the periods of use of the room 901 from the data 105. If, for instance, the mobile phone referred to in connection with the fourth embodiment is used here, information on the periods of use can be shown on the display screen of the mobile phone, and it can be checked whether or not the person carrying the radio communication device 103 arrived at the place of conference as scheduled.
On the other hand, radio communication device 104 carried by a person 904 having left the room 901 cannot receive the data 105 because the walls of the room 901 intercept the transmission of the data 105 from the base station 101. The radio communication device 104 here is of

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the same type as the radio communication device 103, and differs from the radio communication device 103 in the identification number as an active tag stored in the active tag circuit 205. Therefore, in the radio communication device 104 carried by the person 904, the first circuit 201 is not actuated and the active tag circuit 205 is kept inactive to restrain power consumption for standing-by. Accordingly, consumption of power by the radio communication device 104, namely the exhaustion of the battery constituting the power source 2 02, can be prevented.
Further, when log information has been read out here, by setting the time interval until the next reading of log information to be 10 seconds, for instance, if there is no record of actuation of the first circuit 201, and setting the time interval until the next reading of log information longer, 60 seconds for example, if there is any record of actuation of the first circuit 201, the consumption of power by the radio communication device 103 when it is positioned in a communicable range from the base station can be further reduced where data not required frequently, such as information on the day and hours of a conference as in the case of this embodiment, are to be transmitted and received. [Sixth Embodiment]
This embodiment is a case in which the radio

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communication system according to the invention is used for position finding.
Fig. 10 illustrates a case of application to position finding. Base stations 1001, 1002 and 1003 are arranged, a server not shown is provided with a database, and the respective positions of the base stations 1001, 1002 and 1003 are stored. In this embodiment, the distance in which the base stations 1001, 1002 and 1003 can actuate the first circuit 201 of the radio communication device 103 is set to 5 m each. The data transmitted by each base station transmits contains information on that station.
In the radio communication device 103 carried by a person 1004 within a range of 5 m from the base station 1001, the first circuit 201 is actuated by a radio wave from the base station 1001, and the record of actuation is left in the memory 303. And the second circuit 203 of the radio communication device 103 reads out the log information. After that, the receiver circuit contained in the active tag circuit 205 is actuated, and the data 105 are received from the base station 1001. In this way, the radio communication device 103 obtains information that it is within 5 m from the base station 1001.
When the mobile phone referred to in connection with the fourth embodiment is used here, the information can be displayed on the display screen, and the person 1004 using

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the radio communication device 103 can confirm that he or she is positioned near the base station 1001. Further, the radio communication device 103 can acquire information on the positions of base stations through connection via the mobile phone line to the server in whose database positional information on the base stations 1001, 1002 and 1003 is stored, and find its current position in a resolution of about 5m. For more accurate position finding, it is possible to receive transmitted data from the base stations 1002 and 1003, in addition to those from the base station 1001, with the active tag circuit 205 and derive the position of the radio communication device 103 from positional information on, and the intensity of the radio wave from, each base station. Connection to the server via the mobile phone line would save the trouble of connection wiring between the base stations and the server, and enable a position finding system to be introduced at lower cost. Also by providing the base stations themselves with a function of connection to the mobile phone line, it is made possible to connect the active tag circuit 205 to the server by one or another of the base station and moreover to save the trouble of connection wiring between the base stations and the server, enabling a position finding system to be introduced at lower cost. The system of this embodiment is particularly suitable for position finding

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indoors, where the use of GPS is difficult. Further, by-storing the measured position of the radio communication device 103 into the database of the server via the mobile phone line, the current position of the radio communication device 103 can be checked through connection to the server.
On the other hand, the radio communication device 104 carried by a person 1005 in a position more than 5 m away from any of the base stations 1001, 1002 and 1003 is not in an area where his or her current position can be found. The radio communication device 104 here is of the same type as the radio communication device 103, its identification number as an active tag stored in the active tag circuit 2 05 is supposed to be different from that of the radio communication device 103. In the radio communication device 104 carried by the person 1005 in this case, the first circuit 201 is not actuated, and the active tag circuit 2 05 is kept inactive to restrain power consumption for standing-by. Accordingly, consumption of power by the radio communication device 104, namely the exhaustion of the battery constituting the power source 2 02, can be prevented.
Although the invention made by the present inventor has been described in specific terms with reference to the modes of embodiment thereof, the invention is not limited to these modes of implementation, and obviously various

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modifications thereof can be made within the extent of not deviating from the essentials of the invention.

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What is claimed is:
1. A radio communication device comprising:
a first circuit that is driven by a radio wave from outside and, when actuated by the radio wave received from outside, stores a record of actuation as log information,
a power source, and
a second circuit that is driven by electric power from the power source and reads out the log information.
2. The radio communication device according to Claim
1,
wherein the radio communication device communicates with external radio communication equipment over a carrier frequency selected out of a plurality of carrier frequency candidates, and
the first circuit can be actuated by any radio wave out of the candidates.
3. The radio communication device according to Claim 1, which performs radio communication according to the log information.
4. The radio communication device according to Claim 1,

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wherein the radio communication device, if the log information is found to contain a record of actuation of the first circuit when the log information has been read out, searches carrier frequencies of a radio wave from outside.
5. The radio communication device according to Claim
1,
wherein the second circuit intermittently reads out the log information, and
if the log information is found to contain a record of actuation of the first circuit when the second circuit has read out the log information, the length of time until the next reading-out of the log information is made longer than in a case in which the log information is found to contain no record of actuation of the first circuit.
6. The radio communication device according to Claim
1,
wherein the second circuit is disposed in a case, and the first circuit is disposed on a medium to be fitted to the case.
7. The radio communication device according to Claim
6,

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wherein the case is a case of a mobile phone.
8. The radio communication device according to Claim
6,
wherein the medium is an IC card.
9. The radio communication device according to Claim
1,
wherein the power source is a battery.
10. A radio communication method by which radio
communication is performed by sending out a radio wave on
one carrier frequency out of a plurality of carrier
frequency candidates, comprising:
a step of storing, when a circuit driven by a radio wave of any carrier frequency out of the candidates is actuated, the record of actuation as log information into a memory that is provided, and
a step of referencing the memory and, in the presence of any record of actuation of the circuit, searching base stations.
11. The radio communication method according to Claim
10,
wherein the plurality of carrier frequencies are

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scanned at the step of searching.
12. The radio communication method according to Claim
10,
wherein the memory is a flash memory.
13. A radio communication system comprising:
a base station that sends out a radio wave on one carrier frequency out of a plurality of carrier frequency candidates; and
a radio communication device having a memory, a first circuit that is driven by a radio wave driven by a radio wave of any carrier frequency out of the candidates and, when actuated by reception of a radio wave from the base station, stores the record of actuation as log information into the memory, and a second circuit that references the memory and, if a record or actuation of the first circuit is found therein, searches the base station.
14. The radio communication system according to Claim
13,
wherein the base station is installed in a room, the base station is connected to a server storing information on reservation of the room, and
the base station transmits the information on

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reservation to the radio communication device.
15. The radio communication system according to Claim 13, further comprising:
a database for storing positional information on the base station,
wherein the position of the radio communication device is measured on the basis of the positional information.
16. A radio communication device, substantially as herein described with reference to accompanying drawings and examples.
17. A radio communication method, substantially as herein described with reference to accompanying drawings and examples.
18. A radio communication system, substantially as herein described with reference to accompanying drawings and examples.
Dated this 27"* day of June 2012
of Anand^& Anand Advocates Agents for the applicants