JP2005210640A - Mobile communication system and mobile communication terminal therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To avoid collision between different frequency measurement and random access communication in advance, and improve the throughput of the random access communication in a system which performs random access communication of the mobile communication terminals, and also performs different frequency measurement (Fach Measurement Occasion), corresponding to a different frequency measurement enable frame (Occasion Frame)transmitted from the network. <P>SOLUTION: The mobile communication terminal calculates a disable access slot overlapping the different frequency measurement enable frame (Occasion Frame), and the random access communication is performed by the use of the access slots excluding the above disable access slots from the permitted access slots. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a mobile communication system such as a mobile phone and a mobile communication terminal such as a mobile phone, and more particularly to a mobile communication system having a function of measuring different frequencies during reception of a common channel and the mobile communication terminal.

In a next-generation mobile communication system, a technique for reducing random access communication delay caused by a collision or error in random access communication at a base station and reducing an interval between random access transmissions is disclosed in, for example, JP-T-2002-524990. It is disclosed in the publication.
JP 2002-524990 A

  However, in a mobile communication system that performs random access communication at a certain frequency between a certain base station and a large number of mobile communication terminals such as mobile phones, the communication of the other base station It is recommended to perform different frequency measurements. This different frequency measurement is called Fach Measurement Occasion, and is performed by changing the reception frequency in a different frequency measurable frame (Occasion Frame) periodically designated for the common channel.

  When there is a random access request, the mobile communication terminal performs random access communication with the base station. In this random access communication, the mobile communication terminal selects an arbitrary access slot from among the permitted access slots, performs preamble transmission to the base station using the permitted signature, and performs this preamble transmission. On the other hand, it is necessary to receive a communication permission called AICH from the base station.

  In a mobile communication system that performs this kind of different frequency measurement, this random access communication is performed with a fixed reception frequency with the base station. Only one of random access communication and different frequency measurement can be executed.

  If this random access communication and different frequency measurement collide, if priority is given to random access communication, the different frequency measurement cannot be performed and this different frequency cannot be tracked. Come. For example, there is a base station A transmitting at the frequency fa and a base station B transmitting at the frequency fb, and the mobile communication terminal is present in a communication cell formed by the base station A. If the mobile terminal moves toward the base station B during communication, the mobile terminal needs to switch from communication with the communication cell of the base station A to communication with the communication cell of the base station B, so-called cell reselection is required. However, if the different frequency cannot be measured and the base station B cannot be detected, the base station B cannot be switched to the cell.

  Conversely, if priority is given to different frequency measurement, random access communication cannot be performed, and throughput such as packet communication from the terminal is reduced.

  The present invention proposes an improved mobile communication system and its mobile communication terminal capable of performing such random access communication and different frequency measurement more efficiently.

  In the mobile communication system according to the present invention, a mobile communication terminal moving in a network including a plurality of base stations each constituting a communication cell is used for an uplink using a common channel for the base station corresponding to the existing communication cell. When the base station sends a permission signal in the downlink direction to the mobile communication terminal in response to this preamble transmission, the mobile communication terminal performs random access communication in the access slot permitted through the common channel. A mobile communication system that performs different frequency measurement in a different frequency measurable frame notified from a network for communication with another base station, wherein the mobile communication terminal measures the different frequency Calculate the impossible access slots that overlap with possible frames, and from the allowed access slots, Wherein the at the inaccessible slots excluded access slot performing the preamble communications.

  In addition, the mobile communication terminal according to the present invention can move in a network including a plurality of base stations each constituting a communication cell, and is connected to the base station corresponding to the communication cell in which the mobile communication terminal exists using a common channel. Preamble transmission is performed in the direction, random access communication is performed in the permitted access slot based on the permission signal sent from the base station in the downlink direction for this preamble transmission, and also for communication with other base stations A mobile communication terminal that performs different frequency measurement in a different frequency measurable frame notified from the network, comprising an access slot conversion unit that restricts an access slot of the random access communication, and the request for the random access communication is In some cases, the access slot conversion unit overlaps the different frequency measurable frame. Disabling access slot is calculated and the mobile communication terminal from said authorized access slots, characterized by performing the preamble transmission in an access slot that exclude this inaccessible slots.

  In the mobile communication system and the mobile communication terminal according to the present invention, the mobile communication terminal calculates an inaccessible access slot that overlaps with the different frequency measurable frame and excludes the inaccessible access slot from the permitted access slot. Since the random access communication is performed in the slot, it is possible to automatically eliminate beforehand that the preamble transmission of the random access communication overlaps with the different frequency measurement.

  In addition, since the random access communication does not overlap with the different frequency measurable frame, for example, after the transmission of the random access communication preamble overlaps with the different frequency measurable frame, the random access communication preamble is retransmitted. Therefore, the throughput of random access communication can be improved.

  Several embodiments of the present invention will be described below with reference to the drawings.

Embodiment 1 FIG.
FIG. 1 shows a first embodiment of a mobile communication terminal used in a mobile communication system according to the present invention. The mobile terminal 1 according to the first embodiment is a W-CDMA mobile phone. The mobile communication terminal 1 performs mobile communication in a network including a plurality of base stations. A plurality of base stations each form a communication area called a communication cell, and the mobile communication terminal 1 performs random access communication RAC at a predetermined frequency with a base station corresponding to the communication cell in which it exists, In preparation for communication with another base station corresponding to the cell, the mobile station moves between the communication cells while performing the different frequency measurement of the other base station.

  The mobile communication terminal 1 includes an antenna 10, a high frequency unit (RF unit) 11, a demodulation unit 12, a modulation unit 13, a wireless communication control unit 14, a communication path encoding unit 15, a terminal I / F unit 16, a speaker 17, and a microphone. 18, an access slot conversion unit 20 and a random access unit 21 are provided along with the camera 19.

  The antenna 10 is connected to a high frequency unit 11, and a demodulation unit 12 and a modulation unit 13 are connected between the high frequency unit 11 and the communication path encoding unit 15. A received signal received by the antenna 10 is input to the demodulator 12 via the high frequency unit 11, demodulated by the demodulator 12, and the demodulated signal is input to the communication encoder 15, and the communication encoder 15 Is decoded by the terminal I / F unit 16 and supplied to the speaker 17.

  Transmission signals from the microphone 18 and the camera 19 are converted by the terminal I / F unit 16, encoded by the communication path encoding unit 15, and then high-frequency modulated by the modulation unit 13, via the high-frequency unit 11 and the antenna 10. Sent.

  The wireless communication control unit 14 controls the common channel, controls different frequencies, and controls random access communication, and is connected to the demodulation unit 12, the access slot conversion unit 20, and the random access unit 21. Specifically, the access slot conversion unit 20 is called an occasion frame / access slot conversion unit, and calculates the impossible access slot of the random access communication RAC based on the occasion frame FMO-FR of the different frequency measurable frame FMO. It is connected to the wireless communication control unit 14 and the random access unit 21. The random access unit 21 controls the modulation unit 13 based on a command or notification from the wireless communication control unit 14 or the access slot conversion unit 20, and controls the random access communication RAC.

  Now, the operation of the first embodiment will be described. First, when a request for random access communication RAC exists in the mobile communication terminal 1, the mobile communication terminal 1 uses the same common channel as many other mobile communication terminals with a base station corresponding to the communication cell in which the mobile communication terminal 1 exists. Use random access communication. This random access communication is performed in the following procedures (1), (2), and (3).

(1) Preamble transmission from the mobile communication terminal In response to the request for the random access communication RAC, the radio communication control unit 14 generates a random access channel request RACH, and sends a random access communication RAC start command to the random access unit 21. Notify access slots and signatures allowed from the network. Based on the start command and the notification, the random access unit 21 controls the modulation unit 13, and when the different frequency measurable frame FMO is not designated from the permitted access slot and the permitted signature. The random access communication preamble RAC-PRE is transmitted using an arbitrarily selected access slot and signature of the uplink UL.

(2) Reply from the base station The base station uses the synchronization detection display channel AICH (Acquisition Indicator Channel) to permit uplink access to the mobile communication terminal 1 that has transmitted the preamble RAC-PRE of random access communication. If so, an Ack signal is returned. When rejecting uplink access, a negative Ack (Negative Ack) signal is returned. At this time, the base station uses the access slot and signature of the downlink DL corresponding to the access slot of the uplink UL to which the preamble RAC-PRE for random access communication is transmitted.

(3) Message transmission The mobile communication terminal 1 receives the AICH of the access slot of the downlink DL corresponding to the access slot of the uplink UL that has transmitted the preamble RAC-PRE of random access communication, and receives uplink access from the base station. Determine whether or not is allowed. When the Ack signal is received, it is determined that uplink access is permitted, and the message RAC-MSG of the random access communication RAC is transmitted. If a negative Ack signal is received, the random access communication RAC is stopped. If the reception of the Ack signal and the negative Ack signal cannot be confirmed and the determination of permission or rejection cannot be made, it is assumed that the preamble RAC-PRE of the random access communication RAC has not been received by the base station, and the uplink transmission power is increased. Then, the preamble RAC-PRE of the random access communication RAC (1) is transmitted again.

  The transmission of the message RAC-MSG of the random access communication RAC, the cancellation of the random access communication RAC, or the retransmission of the preamble RAC-PRE of the random access communication RAC is performed as a result of the radio communication control unit 14 determining the output of the demodulation unit 12, The wireless communication control unit 14 is executed by controlling the modulation unit 13 via the random access unit 21. The message RAC-MSG of the random access communication RAC is transmitted including uplink control data or user data.

  In the first embodiment, when the mobile communication terminal 1 exists in a communication cell of a predetermined base station, random access communication RAC is performed with the predetermined base station, and other adjacent base stations are connected. In the future communication, the adjacent base station is configured to periodically measure different frequencies. Specifically, the wireless communication control unit 14 performs SCCPCH reception control for receiving the common channel to the demodulation unit 12 during reception of the common channel, and can periodically measure different frequencies from the network in this SCCPCH. A frame FMO (Fach Measurement Occasion) is designated, and the mobile communication terminal 1 performs different frequency measurement in a different frequency measurable frame.

  Since the request for the random access communication RAC is generated at random timing, there is a possibility that the AICH reception slot for the random access communication RAC, specifically, the preamble transmission overlaps the frame FMO capable of measuring different frequencies. When the different frequency measurable frame FMO is specified by the network, the wireless communication control unit 14 sets the parameter FMO-PM for obtaining the different frequency measurable frame FMO and the frame offset between the synchronization detection display channels AICH and SCCPCH. The access slot conversion unit 20 is notified.

The access slot conversion unit 20 calculates the different frequency measurement execution frame FMO-FR based on the notified parameter FMO-PM, notifies the radio communication control unit 14 of the frame FMO-FR, and When preamble transmission to the base station is performed from the FR and the frame offset between the AICH and the SCCPCH, a disabled access slot DAS (disable access slot) in which the reception slot of the AICH collides with the frame FMO-FR is calculated. The random access unit 21 is notified of the impossible access slot DAS.
The impossible access slot is calculated as follows. An access slot used in random access communication has 15 access slot numbers and a period of 20 msec. The start timing of the downlink access slot coincides with the start timing of the even frame of AICH. The frame period of this AICH is 10 msec, and the mobile communication terminal 1 demodulates this AICH and obtains the AICH frame number when synchronizing with the base station. The offset between the common channel SCCPCH and the frame timing of the AICH is reported from the network. Therefore, the mobile communication terminal 1 can know “timing offset between the downlink access slot and the common channel”.
Since the different frequency measurable frame FMO is specified by the network at a predetermined period, based on “the frame number of the currently received common channel”, “the frame number in the common channel of the next different frequency measurable frame FMO”. Based on “the frame number in the common channel of the next different frequency measurable frame FMO” and “the timing offset between the downlink access slot and the common channel” and colliding with the next different frequency measurable frame FMO. The head access slot can be calculated, and the period during which the next different frequency measurable frame can collide can be calculated from the period of the common CH. Thus, the impossible access slot DAS can be calculated.

  The random access unit 21 designates to the modulation unit 13 possible access slots AAS that excludes the impossible access slot DAS from the permitted access slots notified from the wireless communication control unit 14. Therefore, when the mobile communication terminal 1 has a request for the random access communication RAC, the mobile communication terminal 1 starts the different frequency measurement execution frame FMO− from the preset possible access slot ASS, that is, the access slot permitted from the network. In the possible access slot AAS excluding the inaccessible access slot DAS that collides with the FR, the preamble RAC-PRE of the random access communication is transmitted, and the random access communication RAC overlaps with the different frequency measurable frame FMO in advance. The result will be avoided.

  As described above, in the mobile communication terminal 1 of the first embodiment and the mobile communication system using the same, the mobile communication terminal 1 sets the possible access slot AAS excluding the impossible access slot DAS that overlaps the different frequency measurable frame FMO in advance. Since the random access communication RAC is performed in this possible access slot AAS, it is possible to automatically eliminate in advance that the random access communication RAC overlaps with the different frequency measurable frame FMO.

  In addition, in the mobile communication terminal 1 of the first embodiment and the mobile communication system using the same, the transmission of the preamble RAC-PRE of the random access communication does not overlap with the different frequency measurable frame FMO. After the RAC-PRE transmission overlaps the different frequency measurable frame FMO, the preamble RAC-PRE of the random access communication is not retransmitted, so that the throughput of the random access communication RAC can be improved.

  2 is a process flowchart of the wireless communication control unit 14 according to the first embodiment, FIG. 3 is a process flowchart of the random access unit 21, and FIG. 4 is a process flowchart of the access slot conversion unit 20.

  The wireless communication control unit 14 is configured to operate according to a processing flowchart including seven steps S11 to S17 illustrated in FIG. In the first step S11, it is determined whether or not a different frequency measurable frame FMO is specified. If the determination result is Yes, the process proceeds to the next step S12. If the determination result is No, the third step S13 is performed. Proceed to In step S12, the access slot conversion unit 20 is notified of the parameter FMO-PM for obtaining the different frequency measurement.

In step S13, it is determined whether or not to execute random access communication RAC. If the determination result is Yes, the process proceeds to the next step S14, where the radio communication control unit 14 generates a RACH request. If the determination result in step S13 is No, the process proceeds to step S15.
In step S15, it is determined whether the received frame is a different frequency measurement execution frame FMO-FR. If the determination result is Yes, the process proceeds to step S16, and the radio communication control unit 14 performs different frequency measurement. If the determination result of step S15 is No, it will progress to following step S17 and it will be determined whether the common channel is closed. If the determination result is Yes, the process ends. If the determination result is No, the process returns to step S11 again.

  The random access unit 21 is configured to operate according to a processing flowchart including six steps S21 to S26 shown in FIG. In the first step S21, it is determined whether there is a request for random access communication RAC. If the determination result is Yes, the process proceeds to the next step S22, and a possible access slot AAS excluding the inaccessible access slot DAS notified by the access slot conversion unit 20 is selected from the access slots permitted from the network. If the determination result in step S21 is No, the process ends.

  In step S23 following step S22, it is determined for confirmation whether or not the impossible access slot DAS from the access slot conversion unit 20 collides with the possible access slot AAS from step S22. If this determination result is Yes, the process returns to step S22 again to select the possible access slot ASS again. If the decision result in the step S23 is No, the process proceeds to the next step S24, and the transmission of the preamble RAC-PRE for random access communication is executed in the selected possible access slot ASS.

  Subsequent to step S24, in step S25, it is determined whether or not the synchronization detection display channel AICH is OK, that is, whether or not the Ack signal from the base station has been received. If the determination result in step S25 is Yes, the process proceeds to the next step S26, where the message part is transmitted, that is, the random-access communication message RAC-MSG is transmitted. If the determination result of step S25 is No, it will return to step S22 again.

  The access slot conversion unit 20 is configured to operate according to a processing flowchart including three steps S31 to S33 shown in FIG. In first step S31, it is determined whether there is a request for random access communication RAC. If this determination result is Yes, the process proceeds to step S32, and the impossible access slot DAS is calculated from the different frequency measurement execution frame FMO-FR and the frame offset between the preamble transmission and the corresponding AICH reception. The slot DAS is notified to the random access unit 21 and the processing is terminated. If the determination result in step S31 is No, the process proceeds to step S33. In this step S33, it is determined that there is no impossible access slot DAS, and the process ends.

  FIG. 5 is a timing chart showing the operation of the mobile communication terminal 1 when the impossible access slot DAS is set based on the different frequency measurable frame FMO. 5A shows an uplink access slot from the mobile communication terminal 1, FIG. 5B shows a downlink access slot to the mobile communication terminal 1, and FIG. 5C shows an SCCP channel. 5A, 5B, and 5C, the horizontal axis represents time, and shows the same time that is common to FIGS. 5A, 5B, and 5C. “F” in FIG. 5C is the period of the frame FMO capable of measuring different frequencies.

  Based on the different frequency measurable frame FMO of FIG. 5C, the impossible access slot DAS of FIG. 5A is set, and the possible access slot AAS excluding this impossible access slot DAS is set. This possible access slot AAS Is used to perform random access communication RAC.

Embodiment 2. FIG.
FIG. 6 shows a second embodiment of a mobile communication terminal according to the present invention and a mobile communication system thereby. The mobile communication terminal 1A according to the second embodiment includes a radio communication control unit 14A and a different frequency measurement unit 22 separated therefrom, and is different from the access slot conversion unit 20 of the mobile communication terminal 1 of FIG. Part 20A is included. Other configurations are the same as those of the mobile terminal 1 according to the first embodiment shown in FIG.

  The mobile communication terminal 1A according to the second embodiment moves in which the different frequency measurement request FMO is specified with a shorter period f than the different frequency measurement period Fm that can sufficiently secure the reselection performance of the communication cell. This is effective in the communication system, and the inaccessible slot DAS is calculated in a necessary different frequency measurable frame from the different frequency measurable frame from the network. In other words, in the mobile communication terminal 1A of the second embodiment, the different frequency measurement unit 22 actually performs different frequency measurement corresponding to a specific different frequency measurable frame in the plurality of different frequency measurable frames FMO. Configured to run.

  In the second embodiment, the wireless communication control unit 14A is configured by separating the different frequency measurement unit 22, and when performing different frequency measurement, the different frequency measurement execution command FMO- A is given, and the control of the demodulator 12 in the different frequency measurement execution frame FMO-FR is transferred to the different frequency measurement unit 22 by this different frequency measurement execution command FMO-A. When the different frequency measurement unit 22 receives the different frequency measurement execution command FMO-A from the wireless communication control unit 14A, the different frequency measurement unit 22 issues a request to disable transmission of the preamble RAC-PRE to the access slot conversion unit 20A. The access slot conversion unit 20A calculates the impossible access slot DAS and notifies the random access unit 21 only when the preamble RAC-PRE transmission disable request is received.

  When the different frequency measurement unit 22 does not receive the preamble RAC-PRE transmission disable request, the different frequency measurement unit 22 does not perform the different frequency measurement even if the network specifies the different frequency measurable frame FMO. If the random access unit 21 does not receive a preamble RAC-PRE transmission disable request, the random access unit 21 does not designate an impossible access slot DAS even if the network issues a different frequency measurable frame FMO. All access slots that are present can be selected to perform random access communication, which can further improve the throughput of the random access communication RAC.

  Specifically, for example, a different frequency measurement execution command FMO-A is issued in correspondence with every other different frequency measurable frame FMO among a plurality of different frequency measurable frames FMO which are sequentially generated at the period f. In the remaining different frequency measurement requests, the different frequency measurement is not executed and the inaccessible access slot DAS is not set. As a result, for example, one different frequency measurement is performed for two different frequency measurable frames FMO, and the impossible access slot DAS is not set for the remaining different frequency measurable frames FMO, and random access communication is performed. Since RAC is enabled, the throughput of random access communication RAC can be further improved.

  FIG. 7 is a process flowchart of the access slot conversion unit 21A according to the second embodiment, and FIG. 8 is a process flowchart of the different frequency measurement unit 22.

  The access slot conversion unit 21A is configured to operate according to a processing flowchart including the four steps S31 to S34 shown in FIG. Steps S31, S32, and S33 are the same as the steps shown in FIG. Step S34 determines whether or not there is a request to disable transmission of the preamble RAC-PRE from the different frequency measurement unit 22 when the determination result of Step S31 is Yes, that is, when there is a request for random access communication RAC.

  Step S32 calculates the impossible access slot DAS when both the determination results of steps S31 and S34 are Yes, and notifies the random access unit 21 of this. If the determination result in step S34 is No, in the same manner as in the case where the determination result in step S31 is No, it is determined that there is no disabled access slot DAS in step S33.

  The different frequency measurement unit 22 is configured to operate according to a process flowchart including five steps S41 to S45 shown in FIG. In step S41, it is determined whether there is a different frequency measurement execution command FMO-A from the wireless communication control unit 14A. If the determination result is Yes, the process proceeds to step S42 to generate a preamble RAC-PRE transmission disable request. If the decision result in the step S41 is No, the process proceeds to a step S43, where there is no impossible access slot, and the process ends.

  When a request to disable transmission of the preamble RAC-PRE is generated in step S42, the process proceeds to the next step S44, and it is determined whether or not the received frame has generated a different frequency measurement frame FMO-FR. If the determination result is Yes, the process proceeds to the next step S45, and the different frequency measurement is executed. If the determination result in step S44 is No, the process ends.

  FIG. 9 is a timing chart showing the operation of the mobile terminal 1A according to the second embodiment. FIG. 9 shows an operation at the same timing as FIG. 5, FIG. 9 (a) shows an uplink access slot, FIG. 9 (b) shows a downlink access slot, and FIG. 9 (c) shows an SCCP channel. Show.

  In FIG. 9C, two different frequency measurable frames FMO1 and FMO2 are shown. In the rear different frequency measurable frame FMO2, the inaccessible access slot DAS is not set, and there is a request for random access communication RAC. Accordingly, the random access communication RAC is executed. The impossible access slot DAS is set for the front different frequency measurable frame FMO1, and the random access communication RAC similar to that of the first embodiment is executed in the possible access slot AAS excluding the impossible access slot DAS.

  The mobile communication system according to the present invention is used as a communication system for a mobile phone, for example, and the mobile communication terminal according to the present invention is used as a mobile phone, for example.

1 is a block diagram showing a first embodiment of a mobile communication terminal according to the present invention and a mobile communication system using the same. 4 is a process flowchart of a wireless communication control unit according to the first embodiment. 4 is a processing flowchart of a random access unit according to the first embodiment. 4 is a processing flowchart of an access slot conversion unit according to the first embodiment. 4 is a timing chart of the mobile communication terminal according to the first embodiment. The block diagram which shows Embodiment 2 of the mobile communication terminal by this invention, and a mobile communication system using the same. 10 is a process flowchart of an access slot conversion unit according to the second embodiment. 9 is a process flowchart of a different frequency measurement unit according to the second embodiment. 4 is a timing chart of the mobile communication terminal according to the second embodiment.

Explanation of symbols

1, 1A: mobile communication terminal, 14, 14A: wireless communication control unit,
20, 20A: access slot conversion unit, 21: random access unit,
22: Different frequency measurement unit, FMO: Frame capable of different frequency measurement,
DAS: Impossible access slot.

Claims (4)

  A mobile communication terminal moving in a network including a plurality of base stations each constituting a communication cell transmits a preamble in the uplink direction to the base station corresponding to the existing communication cell using a common channel. When a base station sends a permission signal to the mobile communication terminal in the downlink direction for transmission, the mobile communication terminal performs random access communication in an access slot permitted through the common channel, together with another base station. A mobile communication system for performing different frequency measurement in a different frequency measurable frame notified from a network for communication with the mobile communication terminal, wherein the mobile communication terminal overlaps with the different frequency measurable frame. And excluded this impossible access slot from the allowed access slots. Mobile communication system and performing the preamble communication access slot.   The mobile communication system according to claim 1, wherein when performing different frequency measurement, the mobile communication terminal generates a request for disabling preamble transmission of the random access communication, and calculates the disabling access slot based on the disabling request. The mobile communication system is characterized in that the random access communication is performed in an access slot excluding the impossible access slot from the permitted access slot.   Each is movable in a network including a plurality of base stations constituting a communication cell, and performs preamble transmission in the uplink direction using a common channel with a base station corresponding to the communication cell in which the communication cell exists. Based on the permission signal sent from the base station in the downstream direction, random access communication is performed in the permitted access slot, and different frequencies measured from the network can be measured for communication with other base stations. A mobile communication terminal that performs different frequency measurement in a frame, comprising an access slot conversion unit that limits an access slot of the random access communication, and when there is a request for the random access communication, the access slot conversion unit Calculate the impossible access slot that overlaps with the different frequency measurable frame, and Mobile communication terminal to the authorized access slots, characterized by performing the preamble communication access slot excluding the inaccessible slots.   4. The mobile communication terminal according to claim 3, further comprising a radio communication control unit that generates a request to disable transmission of the preamble of the random access communication when performing different frequency measurement, wherein the access slot conversion unit includes the preamble. The mobile communication terminal characterized in that the impossible access slot is calculated when a transmission impossible request is generated.

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