JP6348756B2 - Band search apparatus and method, and wireless communication terminal - Google Patents

Description

  The present invention relates to a band search apparatus and method, and a radio communication terminal, and can be applied to, for example, a mobile station in an OFDM (Orthogonal Frequency Division Multiplexing) mobile communication system.

  The OFDM system is adopted in various standards such as LTE (Long Term Evolution) which is a standard of 3.9G wireless interface. In a mobile station in an OFDM mobile communication system, for example, when power is turned on or when the mobile station is out of service, a cell search for detecting a cell with a small path loss is performed, and a path is established with a base station related to the detected cell. To do. In such a cell search, first, a band search (frequency search) for detecting a frequency used in a downlink channel in a serving cell is performed, and a cell list having a frequency having a reception level equal to or higher than a threshold as a candidate. After that, the cell which actually performs communication is determined from the cell candidates related to the frequency in the cell list (see Patent Document 1).

  In the mobile station, band information that allows communication (UE Capability) is set in advance. For example, a mobile station that can handle band I (hereinafter referred to as band 1), band III (hereinafter referred to as band 3), and band X IX (hereinafter referred to as band 19) described in Non-Patent Document 1. For example, a band search is performed at a frequency switched by 0.1 MHz for these three bands. Here, band 1 is 2110 MHz to 2169.9 MHz, and switching frequency is 0.1 when switching by 0.1 MHz, band 3 is 1805 MHz to 1879.9 MHz, and switching frequency is 0.1 MHz, switching frequency is There are 750 bands, and the band 19 is 875 MHz to 889.9 MHz. When switching by 0.1 MHz, the switching frequency is 150.

  In the conventional band search method (first conventional method), band 1, band 3, and band 19 are switched in ascending order of band numbers, and within each band, a change unit defined (0.1 MHz described above). Switch frequencies in ascending order. Then, from a result of searching all the frequencies, a frequency equal to or higher than a predetermined threshold is detected as a candidate for the assigned frequency of the cell related to the neighboring base station.

  Instead of the simple switching of the frequency as described above, the frequency of the serving cell at the time of power-off or transition to the out-of-service state is searched first, and then the frequency other than this frequency is changed to the band and frequency as described above. A band search method (second conventional method) that switches in ascending order is proposed (see FIG. 6 of Patent Document 2).

WO2014 / 016870 JP2007-20049

3GPP TS36.101

  However, in the first and second conventional methods described above, after the band search is started and the frequency of the cell in which the mobile station is located (existing) is searched, the existing cell is visible (detectable). In such a case, there is a problem that it often cannot be detected by the current series of band searches, but can be finally detected by the next band search restarted after a certain time. In such a case, it takes a long time to detect the frequency of the cell in the area.

  FIG. 10 is an explanatory diagram of such a problem, and shows a case where the first conventional method is applied. Note that the tunnel TN in FIG. 10 is a tunnel in which a base station is not provided.

  When the mobile station MV goes out of service by entering the tunnel TN, a band search (first band search) BS1 is started after a predetermined time from the time t1 when the mobile station MV becomes out of service. It is assumed that the mobile station MV is in the tunnel TN at the start time t2, and the radio wave from the base station does not reach from the start time to the time t4 at which the mobile station MV exits the tunnel TN at a position P1 in the vicinity. In such a situation where radio waves from the base station do not reach (around time t3), a sufficient reception level can be obtained even if a search is made for a cell frequency (for example, 2140 MHz in band 1). Can not. Therefore, the second band search is started from the time t6 when a predetermined time has elapsed from the end point t5 of the first band search, and the search frequency is the frequency of the cell that is in the area (existing) (for example, 2140 MHz of band 1). When it becomes (around time t7), a sufficient reception level is obtained, and at the time t8 when the second band search is completed, the frequency of the cell in the area is detected.

  From the user's point of view, when you exit the tunnel TN, you want to be within range (I want the pictograph of the antenna to appear), but in the example of Fig. 2, it is not within range until the second band search is completed. The first band search that was in progress when exiting the tunnel was wasted.

  The second conventional method is a method in which the frequency of the cell that has been in the location is searched first, and the frequency of the cell that has been in the location of the cell at the position where the mobile station MV has exited the tunnel TN. When the frequency is the same, the same problem as described above occurs.

  Therefore, a band search device and method that can increase the possibility of detecting the frequency of a cell in the band search that was being performed when the terminal became capable of detecting a frequency, and a wireless communication terminal It is desired.

In order to solve this problem, the first aspect of the present invention provides a band search device that searches for a frequency used in a cell in which a wireless communication terminal equipped with the band search device is located. Based on the frequency-related information of the cell that was in the area immediately before the power-off or transition to the out-of-service state in a series of band searches after a predetermined time has elapsed since the transition to the out-of-service state, It is characterized by having scheduling means for determining a schedule in which the search order is set the latest, and (2) search frequency switching control means for changing the frequency in order according to the determined schedule.

According to a second aspect of the present invention, in the band search method for searching for a frequency used in a cell where a wireless communication terminal equipped with a band search device is located, (1) the scheduling means has shifted to a power-off or out-of-service state In a series of band searches after a lapse of a predetermined time from the point in time, based on the frequency-related information of the cell that was in the area immediately before the power-off or transition to the out-of-service state, the frequency search order related to that cell is the latest The set schedule is determined, and (2) the search frequency switching control means sequentially changes the frequency according to the determined schedule.

  The third aspect of the present invention is characterized in that the band search device of the first aspect of the present invention is applied as a band search device to a wireless communication terminal equipped with a band search device.

  ADVANTAGE OF THE INVENTION According to this invention, possibility that the frequency of the cell which exists can be detected by the band search currently performed when the terminal will be in the state which can detect a frequency can be made high.

It is a block diagram which shows the principal part structure of the mobile station (radio | wireless communication terminal) containing the band search apparatus of 1st Embodiment. It is a flowchart which shows the storing operation | movement of the previous cell area information in the mobile station of 1st Embodiment. 3 is a flowchart showing a band search operation in the mobile station of the first embodiment. It is explanatory drawing of the effect of the band search method by 1st Embodiment. It is a flowchart which shows the storing operation | movement of the immediately existing serving cell information in the mobile station of 2nd Embodiment. 6 is a flowchart showing a band search operation in the mobile station of the second embodiment. It is explanatory drawing of the effect of the band search method by 2nd Embodiment. It is a flowchart which shows the storing operation | movement of the immediately existing serving cell information in the mobile station of 3rd Embodiment. It is a flowchart which shows the storing operation | movement of the immediately existing serving cell information in the mobile station of 3rd Embodiment. It is explanatory drawing of the subject of the conventional band search method.

(A) First Embodiment Hereinafter, a band search apparatus and method and a first embodiment of a wireless communication terminal according to the present invention will be described in detail with reference to the drawings. The mobile station (wireless communication terminal) of the first embodiment is, for example, a mobile station in an OFDM mobile communication system according to LTE. This mobile station may be any of a mobile phone terminal, a smartphone, a tablet terminal, and the like.

(A-1) Configuration of First Embodiment FIG. 1 is a block diagram showing a main configuration of a mobile station (wireless communication terminal) including a band search device of the first embodiment. FIG. 1 shows the main parts viewed from the band search surface.

  In FIG. 1, a mobile station 1 according to the first embodiment includes an antenna 2, a receiving circuit selection switch 3, a band 1 receiving circuit 4, a band 3 receiving circuit 5, a band 19 receiving circuit 6, a band search order control unit 7, A storage unit 8 is provided.

  The antenna 2 captures a downlink channel signal (radio signal) having a carrier frequency belonging to band 1, band 3, and band 19 transmitted by a base station (not shown). Although FIG. 1 shows that the antenna 2 can handle all bands, a separate antenna may be provided for each of the band 1, the band 3, and the band 19. In this case, the receiving circuit selection switch 3 is not necessary. Further, an antenna may be provided so that one antenna corresponds to two bands and another one antenna corresponds to one band. In this case, the former antenna is connected to the receiving circuit selection switch.

  The receiving circuit selection switch 3 connects the antenna 1 to any one of the band 1 receiving circuit 4, the band 3 receiving circuit 5, and the band 19 receiving circuit 6 under the control of the band search order control unit 7, and the antenna 1 captures the antenna 1 The received signal (downstream channel signal) obtained in this way is given to the connected receiving circuit.

  The band 1 reception circuit 4 receives and processes a reception signal having a carrier frequency belonging to band 1 (2110 MHz to 2169.9 MHz). At the time of band search, the band 1 receiving circuit 4 is instructed by the band search order control unit 7 about the carrier frequency of the received signal to be received (band searched), and the reception level at that time (for example, received field strength (RSSI)) ) To the band search order control unit 7.

  The band 1 receiving circuit 4 includes, for example, a bandpass filter that uses band 1 as a pass band, a local oscillator that can generate a local oscillation signal having a frequency belonging to band 1, and a reception signal and a local oscillation signal that have passed through the bandpass filter. A mixer for multiplication is provided, and the reception level in the output signal from the mixer is captured and output.

  The band 3 reception circuit 5 receives and processes a reception signal having a carrier frequency belonging to band 3 (1805 MHz to 1879.9 MHz). Although the band to be handled is different, the function and internal configuration of the band 3 receiving circuit 5 are almost the same as those of the band 1 receiving circuit 4, and the description thereof is omitted.

  The band 19 reception circuit 6 receives and processes a reception signal having a carrier frequency belonging to the band 19 (875 MHz to 889.9 MHz). Although the band to be handled is different, the function and internal configuration of the band 19 receiving circuit 6 are almost the same as those of the band 1 receiving circuit 4, and the description thereof is omitted.

  The band search order control unit 7 controls a band switching order, a frequency switching order, and the like during the band search. In order to perform the above-described control, the band search order control unit 7 relates to a cell that is in service (existing) at that time when the mobile station 1 is turned off or transitions to an out-of-service state. Information (immediately existing cell information) is stored in the storage unit 8. In the case of the first embodiment, the previous serving cell information is information on a band to which the frequency of the downlink channel signal from the cell currently serving belongs. The band search order control unit 7 determines a band change / frequency change schedule in the band search with reference to the immediately preceding serving cell information, and changes the band and frequency according to the determined schedule. The band search order control unit 7 controls the receiving circuit selection switch 3 according to the selected band, and controls the band 1 receiving circuit 4, the band 3 receiving circuit 5, or the band 19 receiving circuit 6 according to the selected frequency. To do.

  The band search order control unit 7 is configured mainly with, for example, a CPU and software executed by the CPU, and receives reception level information, for example, an analog provided in an input stage in the band search order control unit 7. The data is taken in via the digital / digital converter, and the selection control signal or the like is sent out via the digital / analog converter provided at the output stage in the band search order control unit 7.

  The storage unit 8 stores immediately preceding cell information, a cell list, and the like. Control may be performed by executing software according to the schedule described above, or may be performed by writing out the order. In the latter case, the storage unit 8 also stores schedule information.

(A-2) Operation of First Embodiment Next, an operation related to band search in the mobile station 1 according to the first embodiment will be described.

  First, the operation of storing immediately preceding cell information will be described with reference to the flowchart of FIG.

  The band search order control unit 7 starts the processing shown in FIG. 2 when the mobile station 1 transitions to an out-of-service state or when the mobile station 1 is turned off, and has been in the service area until then. The band number in the cell is written in the storage unit 8 as the immediately preceding cell information for band search (step S100), and then the series of processing shown in FIG. 2 is terminated.

  Next, the band search operation in which the immediately existing cell information is reflected will be described with reference to the flowchart of FIG.

  When the band search order control unit 7 transitions to the out-of-service state, the band search order control unit 7 performs time measurement by a timer (not shown) so as to start the band search operation when a predetermined time has elapsed from the time of the transition, 3 is started, a series of processes shown in FIG. 3 is started. The band search operation is included in one of various operations executed when the mobile station 1 is powered on. When the power is turned on, the band search order control unit 7 performs a series of processes shown in FIG. Start.

  When starting the series of processing shown in FIG. 3, the band search order control unit 7 first reads out the immediately preceding cell information from the storage unit 8 (step S200), and determines the band number in the immediately existing cell information (step S201). ).

  If the band number in the immediately preceding serving cell information is the number of band 1, the band search order control unit 7 sets band 3 as the first search band A, band 19 as the second search band B, band 19 and the third. Band 1 is set as band C to be searched (step S202). Further, if the band number in the previous serving cell information is the band 3 number, the band search order control unit 7 uses the band 19 as the band 1 to search first, the band 19 as the band B to search second, and the bands 19 and 3 as the band B to search second. Band 3 is set as the band C to be searched next (step S203). Further, if the band number in the previous serving cell information is the number of the band 19, the band search order control unit 7 uses the band 3 as the first search band A, the band 3 as the band B to search second, and the band 3 or 3 as the band B. The band 19 is set as the band C to be searched next (step S204).

  That is, in the first embodiment, the transition of the band is scheduled so that the band in the immediately preceding serving cell information is searched last.

  When the schedule for the band is determined as described above, the band search order control unit 7 changes in increments of 0.1 MHz between the minimum frequency and the maximum frequency of the band set as the band A to be searched first. While searching, the frequency related to the currently located cell is searched (step S205). Next, the frequency related to the cell currently located is searched while changing in increments of 0.1 MHz between the minimum frequency and the maximum frequency of the band set as the band B to be searched second (step S206). . Finally, the frequency related to the cell currently located is searched while changing in increments of 0.1 MHz between the minimum frequency and the maximum frequency of the band set as the band C to be searched third (step S207). .

  In the search in steps S205 to S207, the band search order control unit 7 takes in the reception level at that frequency, compares it with a threshold value, and stores the frequency of the reception level equal to or higher than the threshold value in the storage unit 8.

  When the search for all the frequencies is completed as described above, the band search order control unit 7 detects a frequency that is equal to or higher than a predetermined threshold as a candidate for an assigned frequency of the currently located cell (step S208). The series of processes shown in FIG.

  For example, it is assumed that the mobile station 1 transitions to an out-of-service state while being in a cell of band 1 having a frequency of 2140 MHz. By the process shown in FIG. 2 executed when the state is changed to the out-of-service state, “band 1” is stored in the storage unit 8 as the immediately existing cell information.

  After entering the out-of-service state in which “band 1” is stored as the previous serving cell information in the storage unit 8, the mobile station 1 periodically performs the band search operation shown in FIG. 3 until the frequency of the serving cell can be detected. to start. When the process shown in FIG. 3 is started, first, the immediately preceding cell information “band 1” stored in the storage unit 8 is read, and the band change is scheduled. Since the immediately preceding serving cell information is “band 1”, the band change is determined to be band 3 -band 19 -band 1 by this scheduling. When each band is to be processed, a search is made for a frequency related to the cell currently in the area while changing the band from the minimum frequency to the maximum frequency in ascending order in increments of 0.1 MHz. If the cell located at the time of the band search is the same as the cell in the out-of-service state, a reception level exceeding the threshold can be obtained when the frequency 2140 MHz in band 1 is set as the search target.

(A-3) Effect of First Embodiment According to the first embodiment, in the band search, the band of the cell when transitioning to the out-of-service state or the band of the cell when the power-off operation is performed is performed. Since the band to be searched most recently is used, on average, the detection rate in the early band search can be improved and the time for returning to the service area can be shortened.

  It will be described that the above-described effect can be obtained by taking as an example the change in the position of the same mobile station as the problem of the conventional method. FIG. 4 is an explanatory diagram of such an effect, and corresponds to FIG. 10 described above.

  When the mobile station MV enters the tunnel TN and becomes out of range, “band 1” is stored as the immediately preceding in-zone cell information immediately after the time t11 when the mobile station MV becomes out of range. The first band search BS1 is started after a predetermined time from the time t11 when the band is out of service. As an initial operation of the band search BS1, band change scheduling is executed, and band 3 -band 19 -band 1 are determined. At the start time t12 of the first band search BS1, the mobile station MV is in the tunnel TN. From the start time to the time t13 at which the mobile station MV exits the tunnel TN and is near the position P1, the radio wave from the base station Is not reached, and before the frequency 2140 MHz of the band 1 to be processed is finally searched, the radio wave from the base station arrives (around time t13). Therefore, when 2140 MHz of band 1 becomes the search frequency (time t14), a sufficient reception level can be obtained. Therefore, the area display can be executed at the time t15 when the first band search ends, and unlike the conventional method, the second band search is not executed.

  As a result, when exiting the tunnel TN, it is possible to promptly display the area (pict display of the antenna).

(B) Second Embodiment Next, a band search apparatus and method according to the present invention and a second embodiment of a wireless communication terminal will be described in detail with reference to the drawings.

  The mobile station (wireless communication terminal) 1A including the band search device according to the second embodiment can also be represented in FIG. 1 as its main configuration by the configuration of the first embodiment. However, the control operation executed by the band search order control unit 7 is different from that of the first embodiment.

  An operation of storing immediately preceding cell information in the second embodiment will be described with reference to the flowchart of FIG.

  The band search order control unit 7 starts the processing shown in FIG. 5 when the mobile station 1A transitions to the out-of-service state or when the mobile station 1A is turned off, and has been in the service area so far. The band number and the frequency used in the cell are written in the storage unit 8 as the immediately preceding cell information for band search (step S300), and then the series of processing shown in FIG. 5 is terminated.

  Next, the band search operation of the second embodiment in which the immediately preceding serving cell information is reflected will be described with reference to the flowchart of FIG.

  When the series of processing shown in FIG. 6 is started, the band search order control unit 7 first reads the immediately preceding cell information from the storage unit 8 (step S400), and determines the band number in the immediately preceding cell information (step S401). ).

  If the band number in the immediately preceding serving cell information is the number of band 1, the band search order control unit 7 sets band 3 as the first search band A, band 19 as the second search band B, band 19 and the third. Band 1 is set as band C to be searched (step S402). Further, if the band number in the previous serving cell information is the band 3 number, the band search order control unit 7 uses the band 19 as the band 1 to search first, the band 19 as the band B to search second, and the bands 19 and 3 as the band B to search second. Band 3 is set as the band C to be searched next (step S403). Further, if the band number in the previous serving cell information is the number of the band 19, the band search order control unit 7 uses the band 3 as the first search band A, the band 3 as the band B to search second, and the band 3 or 3 as the band B. The band 19 is set as the band C to be searched next (step S404).

  That is, in the second embodiment, the band transition is scheduled so as to be the last band to search for the band in the previous serving cell information.

  When the schedule for the band is determined as described above, the band search order control unit 7 recognizes the frequency in the immediately preceding cell information, and after the search for all the bands A to C is completed, A setting for performing a frequency search is added to the schedule (step S405).

  When the schedule is completely determined as described above, the band search order control unit 7 increments between the minimum frequency and the maximum frequency of the band set as the band A to be searched first in ascending order in 0.1 MHz units. While changing the frequency, a search is made for a frequency relating to a cell that is currently located (step S406). Next, the frequency related to the cell currently located is searched while changing in increments of 0.1 MHz between the minimum frequency and the maximum frequency of the band set as the band B to be searched second (step S407). . Further, while changing the frequency from the minimum frequency to the maximum frequency of the band set as the band C to be searched third in ascending order in units of 0.1 MHz, the frequency related to the currently located cell is searched (step S408). Finally, the frequency in the previous serving cell information is searched (step S409).

  When the search for all the frequencies is completed as described above (for the frequency in the previous serving cell information, the search when the band to which it belongs is the object of processing and the search executed last are performed twice. ), The band search order control unit 7 detects a frequency equal to or higher than a predetermined threshold as a candidate for the assigned frequency of the currently located cell (step S410), and ends the series of processes shown in FIG.

  For example, it is assumed that the mobile station 1A transitions to an out-of-service state while being in a cell with a frequency of 2140 MHz in band 1. By the processing shown in FIG. 5 executed when the state is shifted to the out-of-service state, “band 1” and “frequency 2140 MHz” are stored in the storage unit 8 as the immediately existing cell information.

  After entering the out-of-service state in which “Band 1” and “Frequency 2140 MHz” are stored in the storage unit 8 as the immediately existing cell information, the mobile station 1A periodically repeats FIG. 6 until the frequency of the cell being detected can be detected. Starts the indicated band search operation. When the process shown in FIG. 6 is started, the band information “band 1” in the immediately preceding serving cell information stored in the storage unit 8 is first read and band change scheduling is performed. Since the immediately preceding serving cell information is “band 1”, the band change is determined to be band 3 -band 19 -band 1 by this scheduling.

  Thereafter, the frequency information “frequency 2140 MHz” in the immediately preceding cell information stored in the storage unit 8 is recognized, and finally set as the frequency to be searched.

  As described above, when the schedule of band 3 -band 19 -band 1 -frequency 2140 MHz is determined, a search for each frequency is executed. First, the frequency related to the cell currently in service is searched while changing the band 3 from the minimum frequency to the maximum frequency in ascending order in units of 0.1 MHz. Next, the band 19 is searched between the minimum frequency and the maximum frequency. While changing the frequency in ascending order by 0.1 MHz unit, search for the frequency related to the cell currently in the area, and further, change the frequency from the lowest frequency of band 1 to the maximum frequency in ascending order by 0.1 MHz unit. A search is made for a frequency related to a cell in the range, and finally, a search is performed to determine whether the frequency 2140 MHz related to the immediately existing cell information is a frequency related to the cell currently in the range. For example, the band search order control unit 7 or the storage unit 8 describes the correspondence between the band number and the frequency range (minimum frequency to maximum frequency) of the band, and finally when searching for a frequency of 2140 MHz. The band to which this frequency belongs is recognized, and the receiving circuit 4 related to the recognized band is activated.

  If the cell located at the time of the band search is the same as the cell in the out-of-service state, at least the search when the frequency is set to 2140 MHz in the search related to band 1 and the search of the last frequency of 2140 MHz Thus, a reception level exceeding the threshold can be obtained.

  According to the second embodiment, the band and frequency of the cell at the time of the transition to the out-of-service state, or the band and frequency of the cell at the time of power-off operation are searched most recently in the band search. Therefore, on average, the detection rate in the early band search can be improved and the time for returning to the service area can be shortened. Such an effect can be expected more than in the first embodiment.

  Taking the change in the position of the same mobile station as the problem of the conventional method as an example, the second embodiment will explain that the above-described effect can be obtained more than the first embodiment. FIG. 7 is an explanatory diagram of such an effect and corresponds to FIG. 4 described above.

  Even if the cell at the time of exiting the tunnel is the same as the cell at the time of transition to the out-of-service state, the timing of the band search is early, and at the time of the search (time t21) belonging to “Band 1” related to the immediately preceding in-zone cell information Even if the frequency of the cell cannot be detected, the cell frequency may be detected at the time of searching for “frequency 2140 MHz” related to the last immediately existing cell information (time t22). However, the possibility of detecting the cell frequency by one band search is greater than that of the first embodiment.

(C) Third Embodiment Next, a band search apparatus and method and a third embodiment of the wireless communication terminal according to the present invention will be described in detail with reference to the drawings.

  The mobile station (wireless communication terminal) 1B including the band search device of the third embodiment can also be represented in FIG. 1 by using FIG. However, the control operation executed by the band search order control unit 7 is different from that of the first and second embodiments.

  The operation of storing the immediately preceding cell information in the third embodiment will be described with reference to the flowchart of FIG.

  The band search order control unit 7 starts the processing shown in FIG. 8 when the mobile station 1B transitions to the out-of-service state or when the mobile station 1A is turned off, and has been in the service area so far. The frequency used by the cell is written in the storage unit 8 as immediately preceding cell information for band search (step S500), and then the series of processing shown in FIG. 8 is terminated.

  Next, the band search operation of the third embodiment in which the immediately preceding cell information is reflected will be described with reference to the flowchart of FIG.

  When the series of processing shown in FIG. 9 is started, the band search order control unit 7 first reads the immediately preceding cell information from the storage unit 8 (step S600), and recognizes the frequency fn related to the immediately existing cell information (step S600). S601).

  Then, the order of the recognized frequency fn (n is 1 to N) is excluded from the predetermined change order of the frequencies f1 to fN (step S602), and the order of the frequency fn is set last (step S602). S603).

  When the schedule is determined as described above, the band search order control unit 7 searches for a frequency related to the cell currently in the area while changing the search order from the first frequency f1 to the last frequency fn. (Step S604).

  When the search for all the frequencies is completed as described above, the band search order control unit 7 detects a frequency equal to or higher than a predetermined threshold as a candidate for an allocated frequency of the currently located cell (step S605). The series of processes shown in FIG.

  For example, it is assumed that the mobile station 1B transitions to an out-of-service state while being in a cell with a frequency of 2140 MHz in band 1. By the process shown in FIG. 8 executed when the state is changed to the out-of-service state, “frequency 2140 MHz” is stored in the storage unit 8 as the immediately existing cell information.

  After entering the out-of-service state in which “frequency 2140 MHz” is stored in the storage unit 8 as the immediately existing serving cell information, the mobile station 1B periodically performs the band search operation shown in FIG. 9 until the frequency of the serving cell can be detected. to start. Here, for simplification of explanation (different from the actual band allocation), the predetermined frequency change order is 2110 MHz-2120 MHz-2140 MHz-2160 MHz-1810 MHz-1830 MHz-1850 MHz-1870 MHz-870 MHz-880 MHz. Suppose there was.

  Since the read immediately preceding cell information is “frequency 2140 MHz”, the frequency 2140 MHz is excluded from the order of the frequency change, and this frequency 2140 MHz is connected to the end of the order. As a result, the order of frequency changes in the band search is changed to 2110 MHz-2120 MHz-2160 MHz-1810 MHz-1830 MHz-1850 MHz-1870 MHz-870 MHz-880 MHz-2140 MHz.

  The search for each frequency is executed in accordance with the frequency change order in the band search changed as described above. That is, finally, a search is performed to determine whether the frequency 2140 MHz related to the immediately preceding serving cell information is a frequency related to the currently located cell. Also in the third embodiment, for example, the band search order control unit 7 or the storage unit 8 describes the correspondence between the band number and the frequency range (minimum frequency to maximum frequency) of each band. When the search is performed, the band to which this frequency belongs is recognized, and the receiving circuit 4, 5 or 6 related to the recognized band is activated.

  If the cell located at the time of the band search is the same as the cell at the time of the out-of-service state, a reception level exceeding the threshold value can be obtained in the last search of frequency 2140 MHz.

  According to the third embodiment, the frequency of the cell at the time of transition to the out-of-service state or the frequency of the cell at the time of power-off operation is set as the frequency to be searched later in the band search. On average, the detection rate in the early band search can be improved, and the time for returning to the service area can be shortened.

(D) Other Embodiments In the description of each of the above embodiments, various modified embodiments have been mentioned, and further modified embodiments as exemplified below can be given.

  In each of the above embodiments, a mobile station that supports three bands is shown, but the number of bands that the mobile station can support is not limited to three bands. For example, one band may be supported. In this case, the technical idea described in the first and second embodiments cannot be applied, but the technical idea described in the third embodiment can be applied.

  In each of the above embodiments, the scheduling process is shown as the first process in the band search operation. However, the scheduling process may be separated from the band search operation. For example, the scheduling process may be executed immediately after storing the previous serving cell information. Here, the immediately preceding cell information may be deleted after the scheduling process is executed. In addition, the scheduling process may be performed as a process separated from the band search operation and the storage operation of the previous serving cell information. For example, even if the band search operation is repeatedly executed by setting the scheduling process as a single operation or immediately after storing the immediately preceding in-zone cell information, the scheduling can be performed only once. It will be over.

  In each of the embodiments described above, the information that affects scheduling is the previous cell information, but in addition to this, other information may also affect scheduling. For example, in the case where the mobile station manages neighboring cell information (band and frequency) in order to smoothly perform handover in addition to the information on the cell in which the mobile station is located, the neighboring cell information is also reflected in the scheduling. You may do it. For example, scheduling may be performed so that the search for the band or frequency related to the immediately preceding cell information is slowed down and the search for the band or frequency related to neighboring cell information is slowed down next.

  In each of the above-described embodiments, the band search associated with the power-off and the band search associated with the transition to the out-of-service state are distinguished from each other. The band search method may be changed between the band search accompanying the transition to the out-of-service state. For example, a conventional band search method is applied to a band search accompanying power-off, and any of the band search methods of the first to third embodiments is applied to a band search accompanying a transition to an out-of-service state. good.

  In addition, the band search method may be switched according to the change time from the time when the event (power-off or transition to the out-of-service state) that causes the band search occurs. For example, in a band search performed before a predetermined time has elapsed from the time when an event occurred, any of the band search methods of the first to third embodiments is applied, and after a predetermined time has elapsed from the time when the event occurred A conventional band search method may be applied to the band search performed.

  In each of the above-described embodiments, the frequency search after the schedule processing has been shown to search all frequencies even if there is a frequency with a reception level equal to or higher than the threshold. However, the frequency search scheduled in the same manner as in each of the above-described embodiments. When there is a frequency with a reception level equal to or higher than the threshold value and information can be determined in the cell in which the frequency is located, even if other frequencies set in the schedule remain, search at other frequencies is stopped. Anyway. In the band search in such a case, in addition to delaying the search at the frequency related to the immediately preceding cell information, the search may be performed at an early timing of the band search.

  In the first and second embodiments, the case where the change of the frequency belonging to the same band is performed in ascending order has been described, but it is needless to say that the frequency change may be performed in descending order.

  Here, as a modified example of the second embodiment, the one in which the search at the frequency related to the immediately preceding in-zone cell information is delayed in ascending order or descending order may be employed. For example, it is possible to determine whether the ascending order becomes slower or the descending order becomes slower by comparing the center frequency of the band with the frequency related to the immediately preceding in-zone cell information.

  In the second embodiment, the frequency in the previous serving cell information has been shown to be searched twice, that is, the search when the band to which it belongs is the target of processing, and the search executed last. The search may not be executed.

  In the third embodiment, the order in which the frequency in the immediately previous serving cell information is determined in advance is excluded and the search for the frequency is performed last. You may make it perform two searches, the search in the fixed order, and the search performed last.

  DESCRIPTION OF SYMBOLS 1, 1A, 1B ... Mobile station (wireless communication terminal), 2 ... Antenna, 3 ... Reception circuit selection switch, 4 ... Band 1 reception circuit, 5 ... Band 3 reception circuit, 6 ... Band 19 reception circuit, 7 ... Band search Order control unit, 8... Storage unit.

Claims (5)

In a band search device for searching for a frequency used in a cell where a wireless communication terminal equipped with the band search device is located,
Based on the frequency-related information of the cell that was in the area immediately before the power-off or transition to the out-of-service state in a series of band searches after a predetermined time has elapsed since the power-off or transition to the out-of-service state , Scheduling means for determining a schedule in which the frequency search order is set the latest;
And a search frequency switching control means for sequentially changing the frequency according to the determined schedule. The wireless communication terminal is compatible with a plurality of bands,
The scheduling means applies a band to which the frequency of the cell that has been located belongs as the frequency-related information, and determines a schedule so that a search for a frequency belonging to the band is slower than a search for a frequency belonging to another band. The band search device according to claim 1, wherein:   The scheduling means applies a frequency of a cell that has been in the area as the frequency-related information, and determines a schedule so as to search for the frequency of the cell that has been in the area last. Or the band search apparatus of 2. In a band search method for searching for a frequency used in a cell in which a wireless communication terminal equipped with a band search device is located,
Based on the frequency-related information of the cells that were in the area immediately before transitioning to the power-off or out-of-service state in a series of band searches after a predetermined time has elapsed since the time when the scheduling means transitioned to the power-off or out-of-service state. , Determine the schedule with the slowest frequency search order for the cell,
A band search method, wherein the search frequency switching control means changes the frequency in order according to the determined schedule. In a wireless communication terminal equipped with a band search device,
A wireless communication terminal, wherein the band search device according to claim 1 is applied as the band search device.

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