JP2001095031A - Mobile communication terminal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To always restart communication with optimal transmitting power, when communication with an original vase station is restarted after measurement of reception quality of the adjacent base station is completed, thus to prevent generation of interference and line disconnection as a result and to hold communication quality after the communication is restarted as well. SOLUTION: When communication with the original base station BSa is restated, after the measurement of reception quality of the adjacent base station BSb, the last transmission power value, received electric field intensity and time immediately before switching are stored and received electric field intensity and time immediately after recovery of switching are stored. Than the size relation between the received electric field intensity immediately before switching and one immediately after the recovery of switching is determined, time required for measurement is calculated from the time immediately before switching and the time immediately after the recovery of switching, omitted frequency of transmission power control during the measurement period is obtained, correction quantity of transmission power is calculated based on the missing control frequency of transmission power, a transmission power value decided based on the correction quantity and a determination result of the size relation and the communication is restarted.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mobile communication terminal device used in a cellular mobile communication system, and more particularly to a mobile communication terminal device having an inter-frequency handover function.

[0002]

2. Description of the Related Art For example, as a wireless access system, Code Division Multiple Access (CDMA) is used.
s) In a cellular mobile communication system adopting the system, a large number of base stations are dispersedly arranged in a service area to form a wireless area called a cell or a sector by these base stations, and the mobile station exists as the mobile station. Wireless communication is enabled by connecting to a base station of a cell or a sector via a wireless channel. When the mobile station moves to another cell or sector during communication, the communication can be continued by performing a handover.

A handover between the same frequency performed when a mobile station moves between cells or sectors to which the same radio frequency is assigned, and a handover between cells or sectors to which a mobile station is assigned a different radio frequency. And handover between different frequencies performed when the mobile terminal moves.

The handover between different frequencies is performed, for example, as follows. 6 and 7 are diagrams for explaining the operation. That is, now the mobile station MS
Is moving from the point P1 in the cell A to the point P3 in the cell B shown in FIG.
Suppose we reach 2. When the base station BSa forming the cell A detects a decrease in the received electric field strength in the mobile station MS, first, from the candidate table, a base station suitable as a handover destination, that is, an adjacent base station to which the same frequency as the cell A is allocated Search for suggestions. If an appropriate base station is found, handover control between the base station and the same frequency is executed.

[0005] On the other hand, if no suitable base station is found, the base station BSa first sends an instruction message to the mobile station MS in order to execute inter-frequency handover, and transmits a radio frequency signal that can be a candidate. Instruct search. Upon receiving the instruction message, the mobile station MS temporarily suspends communication with the base station BSa at time T2 as shown in FIG. 7, and starts searching for the adjacent base station BSb from F1 which is communicating the radio frequency. And the reception field strength of the pilot signal received at this radio frequency F2 is measured. When the measurement of the received electric field strength of the radio frequency F2 is completed, the measured value is notified to the base station BSb, and the radio frequency is changed to the original radio frequency F2.
In this state, when the communication condition with the base station BSa is satisfied, the communication is restarted.

[0006] Whether the communication condition is satisfied or not is determined, for example, in a downlink channel from the base station BSa to the mobile station MS in a period (24) corresponding to 12 frames.
This is performed depending on whether or not two good frames have been received within 0 msec).

Thus, the preparation for the inter-frequency handover is completed, and in this state, when a handover instruction from the base station BSa to the base station BSb arrives, the connection destination of the mobile station MS is switched from the base station BSa to the base station BSb. Inter-frequency handover control is performed.

[0008]

However, such a conventional handover control method has the following problems to be improved. That is, when switching the radio frequency from the radio frequency F1 of the communicating base station BSa to the radio frequency F2 of the adjacent base station BSb and measuring the received electric field strength, the mobile station MS immediately before switching the radio frequency from F1 to F2. The communication parameter of (T2) is stored. And
When the measurement is completed and the radio frequency is returned from F2 to F1, and communication with the original base station BSa is resumed at time T3,
The communication is restarted using the stored communication parameters as they are.

However, if, for example, the mobile station moves further or the radio transmission path environment changes during the measurement period, the actual communication parameters immediately after the restart of communication greatly change from the communication parameters stored immediately before the measurement. As a result, the communication quality immediately after the restart of communication may be significantly deteriorated. this is,
This is a particularly serious problem when considering transmission power, which is one element of communication parameters.

That is, the transmission power of the mobile station MS is set to a short period (for example, 800 per second) in accordance with the power control bit notified from the base station BSa in order to cope with the situation of the radio transmission path that changes every moment during communication. Times) is frequently controlled. However, this control of the transmission power is stopped during the reception electric field strength measurement period of the adjacent base station BSb. For this reason, if the transmission power value at the time of restarting communication is determined using the old transmission power value stored immediately before the start of measurement as it is, the transmission power value immediately after restarting communication is far different from the actual transmission power value. As a result, various problems occur.

[0011] For example, if the transmission power value immediately after resuming the communication is larger than necessary, it interferes with the communication of the surrounding mobile stations, which causes the communication quality to deteriorate. Conversely, if the transmission power value immediately after restarting communication is extremely insufficient, the uplink data may not reach the base station of the communication partner, and the communication may be disconnected, resulting in the line being disconnected.

The present invention has been made in view of the above circumstances, and has as its object to always optimize communication when resuming communication with the original base station after measuring the reception quality of the adjacent base station. It is an object of the present invention to provide a mobile communication terminal device capable of restarting communication according to a parameter, thereby preventing occurrence of interference or disconnection of a line and maintaining good communication quality after restarting communication.

[0013]

In order to achieve the above object, a mobile communication terminal according to the present invention changes a first radio frequency being communicated to a second radio frequency in a peripheral radio area with movement between radio areas. After performing a process of temporarily switching to the radio frequency and measuring the reception quality thereof and then switching to the original first radio frequency and resuming communication, when the process of switching from the first radio frequency to the second radio frequency is performed. Immediately before switching, the communication parameter is detected and stored as pre-switching information, and immediately after switching back from the second radio frequency to the first radio frequency, the communication parameter is detected and switched. Stored as post-information, and in the communication parameter correction means, compares the pre-switch information with the post-switch information,
Based on the comparison result, the communication parameters of the communication restarted after the return from the switching are corrected.

More specifically, the first detecting means detects the reception quality immediately before the switching of the first radio frequency and stores this as pre-switching information, and the second detecting means detects the first radio frequency. Detecting the reception quality immediately after the switching of the frequency, storing this as information after the switching, and comparing the reception quality immediately before the switching of the first radio frequency with the reception quality immediately after the switching by the communication parameter correction means, The transmission power of the communication restarted after the return from the switching is corrected based on the magnitude relation.

Further, when obtaining the correction amount of the transmission power, the first detection means detects the reception quality immediately before the switching of the first radio frequency and the time thereof and stores them as pre-switching information. At the same time, the second detection means detects the reception quality and the time immediately after the switching of the first radio frequency and stores them as post-switching information, and the communication parameter correction means detects the time immediately before the switching and the time immediately after the switching. And the processing time required for measuring the reception quality of the second radio frequency is calculated from the time and the number of transmission power controls lost during the processing time is predicted. The optimum correction amount of the transmission power is calculated according to the predicted number. Ask for.

Therefore, according to the present invention, based on the comparison result between the communication parameter stored immediately before switching and the communication parameter detected immediately after switching recovery, the communication parameter of communication restarted after switching recovery is corrected to an optimum value. You. For this reason,
Even if the communication parameters change during the reception quality measurement period of the adjacent wireless area, the communication can always be restarted with the optimum communication parameters.

For example, based on the magnitude relationship between the reception quality stored immediately before switching and the reception quality stored immediately after switching recovery,
It is determined whether the transmission power at the time of restarting the communication is corrected in the increasing direction, the correction is performed in the decreasing direction, or no correction is made. Further, the reception quality measurement time of the second wireless area is obtained from the difference between the time immediately before the switching and the time immediately after the return from the switching, and the transmission power is estimated based on the estimated number of transmission power control missing during this measurement time. Is obtained. By doing so, it is possible to accurately correct the transmission power immediately after the restart of communication.

Therefore, the transmission power value immediately after resuming communication can always be set to an appropriate value corresponding to the actual situation. As a result, interference with other mobile communication terminal devices due to excessive increase in transmission power and transmission can be prevented. It is possible to prevent communication interruption due to too low power and maintain stable and high-quality communication even after resuming communication.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a mobile communication terminal according to the present invention will be described below. FIG. 1 is a circuit block diagram showing a configuration of a CDMA mobile communication terminal device according to one embodiment of the present invention.

In FIG. 1, a radio frequency signal transmitted from a base station (not shown) is received by an antenna 1 and then received by a receiving circuit (RX) 3 via an antenna duplexer 2 (DUP).
Is input to In the receiving circuit 3, the radio frequency signal is mixed with the receiving local oscillation signal output from the frequency synthesizer (SYN) 4 and frequency-converted into an intermediate frequency or baseband receiving signal. Note that the frequency of the reception local oscillation signal generated from the frequency synthesizer 4 is specified by a control signal SYC output from the control unit 40.

The received signal is subjected to a quadrature demodulation process in a CDMA signal processing unit 6, and then subjected to a despreading process using a spreading code (PN code) assigned to a reception channel, and a predetermined signal corresponding to a data rate. Is converted to demodulated data of the format The converted demodulated data is input to the voice code processing unit 7, and data indicating the data rate among the received data is input to the control unit 40 as the reception data rate.

The voice code processing unit 7 performs an expansion process on the demodulated data output from the CDMA signal processing unit 6 according to the reception data rate notified from the control unit 40, and then uses Viterbi decoding or the like. The received digital data is reproduced by performing the decoding process and the error correction decoding process.

The PCM code processing section 8 performs different signal processing according to the type of digital voice signal communication output from the control section 40 (whether voice communication or data communication). That is, at the time of voice communication, the received digital data output from the voice code processor 7 is PCM decoded and an analog reception signal is output. This analog receiving signal is
After being amplified by the receiving amplifier 9, the amplified sound is output from the speaker 10. On the other hand, at the time of data communication, the received digital data output from the voice code
Output to 0. The control unit 40 outputs the received digital data from an external interface (not shown) to a personal computer (not shown) such as a personal digital assistant (PDA) or a notebook personal computer. The data transfer between the control unit 40 and the personal computer uses a personal computer communication interface including a modem or the like.

On the other hand, the input voice of the speaker at the time of voice communication is input as an analog transmission signal through the microphone 11, amplified to an appropriate signal level by the transmission amplifier 12, and then processed by the PCM code processor 8. Then, the data is supplied to the voice code processor 7 as transmission data. The data output from the personal computer is input to the control unit 40 via an external interface, and is output from the control unit 40 to the voice code processing unit 7 via the PCM code processing unit 8.

At the time of voice communication, the voice code processing unit 7
The energy amount of the input voice is detected from the transmission voice data output from the CM code processing unit 8, and the data rate is determined based on the detection result. Then, the transmission data is compressed into a burst signal having a format corresponding to the data rate, and further subjected to error correction coding processing.
Output to MA signal processing unit 6. At the time of data communication, the transmission data output from the PCM code processing section 8 is compressed into a burst signal having a format corresponding to a preset data rate, and further subjected to error correction coding processing to perform CDMA signal processing. Output to the unit 6. In addition, at the time of voice communication and data communication, both data rates are notified to the control unit 40 as transmission data rates.

The CDMA signal processing unit 6 performs a spreading process on the burst signal compressed by the voice code processing unit 7 using a PN code assigned to a transmission channel. A quadrature modulation process is performed on the spread-coded transmission signal, and the quadrature modulation signal is transmitted to a transmission circuit (TX)
Output to 5

The transmission circuit 5 combines the quadrature modulated signal with a transmission local oscillation signal generated from the frequency synthesizer 4 and converts the signal into a radio frequency signal. Then, the transmission circuit 5
Based on the transmission data rate notified by the control unit 40, only the effective portion of the radio frequency signal is subjected to high frequency amplification,
Output as a transmission radio frequency signal. The transmission radio frequency signal output from the transmission circuit 5 is supplied to the antenna 1 via the antenna duplexer 2, and is burst-transmitted from the antenna 1 to a base station (not shown).

The control unit 40 has, for example, a microcomputer as a main control unit. Its control function is to establish a communication link with a base station (not shown) in response to outgoing / incoming calls to perform voice communication and data communication. In addition to a normal control function such as a communication control function for performing and a control function of recording / reproducing the voice of the other party using the storage unit 41, a handover control means 40a between different frequencies as a control function according to the present invention, And a transmission power correction processing function 40b.

Inter-frequency handover control means 40a
When the reception quality measurement instruction of the adjacent base station arrives from the base station, temporarily suspends communication with the communicating base station, switches the radio frequency to the radio frequency of the adjacent base station, and measures the reception quality. . Then, after notifying the measurement result to the base station, the base station is switched to the original radio frequency to re-establish synchronization with the base station, and then resumes communication.

In the process of the inter-frequency handover control, the transmission power correction processing function 40b changes the radio frequency from the frequency of the adjacent base station to the original radio frequency immediately before switching the radio frequency to the frequency of the adjacent base station. Immediately after switching to, the communication parameters with the base station at that time are saved. The communication parameters stored at this time include, for example, as shown in FIG.
In addition to system configuration information (basic parameters) such as channel information and channel information, the final transmission power value, the received electric field strength, the time immediately before switching (measurement start time), the received electric field strength immediately after switching recovery, and the Time (measurement end time)
And are included. Then, the transmission power correction processing means 40b
Immediately after the switching is restored, an optimum transmission power value to be set at the time of restarting communication is calculated using the stored communication parameters.

Reference numeral 31 denotes a power supply circuit, and the battery 3
Based on the output of 0, a predetermined operating power supply voltage Vcc is generated and supplied to each circuit unit. Reference numeral 42 denotes an input unit, which is provided with various keys such as a dial key, a transmission key, a power key, an end key, a volume control key, and a mode designation key. Reference numeral 43 denotes a display unit using an LCD or the like, which displays a telephone number of a communication partner terminal, an operation state of the apparatus, and the like.

Next, the operation of the inter-frequency handover of the CDMA mobile communication terminal device configured as described above will be described. FIG. 3 is a flowchart showing the control procedure and control contents.

As shown in FIG. 6, the mobile station MS moves from the point P1 in the cell A to the point P3 in the cell B through the vicinity P2 of the boundary between the cells A and B during communication. Will be described as an example.

In the cell A, the mobile station MS monitors whether or not the radio frequency needs to be switched in step 2b while controlling the communication with the base station BSa in step 2a. In this state, when an instruction message for instructing a search for a radio frequency arrives from the base station BSa, the mobile station MS stores the system configuration information relating to the current communication, that is, the basic parameters in step 2c, and also stores this information in step 2d. The final transmission power value at the time, the received electric field strength, and the time (measurement start time T2) are stored in the storage table (FIG. 5) in the storage unit 42.

When the storage of the communication parameters is completed, the mobile station MS switches the radio frequency to the radio frequency F2 of the adjacent base station BSb to be searched in step 2e as shown in FIG. The received field strength of a pilot signal arriving from the base station BSb via F2 is measured. Then, when the measurement of the received electric field strength is completed, the measured value is notified to the adjacent base station BSb, and then the original radio frequency F1 is switched in step 2g as shown in FIG.

When the mobile station MS switches back to the original radio frequency F1 and returns to the original radio frequency F1, the mobile station MS returns to the base station BSa of the communication partner.
Is resumed, at this time, the transmission power is corrected in step 2h. FIG. 3 is a flowchart showing the processing procedure and processing contents.

That is, the mobile station MS first performs step 3
In step a, the received electric field strength of the radio signal arriving via the radio frequency F1 immediately after the return from the switching is detected, and this detected value is stored in the storage table together with the current time (measurement end time T3) as shown in FIG. Then, in step 3b, the received electric field intensity immediately before switching stored in the storage table is compared with the received electric field intensity immediately after switching recovery.

As a result of this comparison, if (reception electric field intensity immediately before switching) <(reception electric field intensity immediately after switching recovery), it is determined that transmission power needs to be reduced from immediately before switching, and transmission power Find the correction amount.

That is, first, in step 3d, the time (T3-T2) required for measuring the reception electric field strength of the radio frequency F2 is obtained from the measurement start time T2 and the measurement end time T3 stored in the storage table. The time required for measurement (T3-T2) is based on the time required to switch the radio frequency from F1 to F2, the time required to measure the received electric field strength, and the time required to switch the radio frequency from F2 to F1. Be composed. Then, in step 3e, the number of transmission power controls for the radio frequency F1 missing during the measurement required time (T3-T2) is obtained. The number of missing transmission power controls is calculated by (measurement time (T3-T2)) / (transmission power control cycle). The control cycle of the transmission power is set to, for example, 800 times per second.

Next, in step 3f, the mobile station MS determines (the number of missing transmission power controls) × (one time of the missing transmission power control) based on the calculated number of missing transmission power controls and one power control amount S. The power control amount S) is calculated to determine the correction amount of the transmission power, and further, based on this correction amount and the final transmission power value immediately before switching stored in the storage table, (final transmission power value immediately before switching) − ( The transmission power value (transmission power 1) to be set at the time of retransmission is obtained.

On the other hand, if the result of the comparison in step 3b is that (reception electric field strength immediately before switching) ≧ (reception electric field strength immediately after switching recovery), the mobile station MS needs to correct the transmission power value. It is determined that there is not, and the process proceeds to step 3c. And
Here, the transmission power value is set to the final transmission power value immediately before switching stored in the storage table. That is, the transmission power value after the communication restart (transmission power 2) = (final transmission power value immediately before switching).

When the transmission power value at the time of resuming communication is set, the mobile station MS sets the determined transmission power value in the transmission circuit 5, and the frame synchronization with the base station BSa is established again. Thereafter, the communication with the base station BSa is restarted.
With this restarted communication, the measurement result of the received electric field strength of the adjacent base station BSb obtained by the previous adjacent base station search is reported to the base station BSa (step 2i).

As described in detail above, in this embodiment, the communication with the base station BSa is interrupted, the radio frequency is temporarily switched to the radio frequency F2 of the adjacent base station BSb, and the reception quality is measured. When switching to the original radio frequency F1 and restarting communication with the base station BSa after the measurement is completed, the final transmission power value, the received electric field strength, and the time immediately before switching from the radio frequency F1 to F2 are saved and saved. Then, the received electric field intensity and the time immediately after switching from the radio frequency F2 to F1 are stored. Then, the received electric field strength immediately before switching and the received electric field strength immediately after switching are compared to determine the magnitude relationship, and the time required for measurement is obtained from the time immediately before switching and the time immediately after returning from switching. The number of transmission power controls missing during the transmission power control is calculated, a correction amount of the transmission power is calculated based on the number of transmission power controls that are missing, and the transmission power value is calculated based on the correction amount and the determination result of the magnitude relationship. The decision is made to resume communication.

Therefore, according to this embodiment, even if the mobile station MS moves or the radio environment changes during the reception quality measurement period of the adjacent radio area B, the transmission power value immediately after the communication restart is always changed to the actual status. Can be set to an appropriate value corresponding to the above, and as a result, interference with other mobile communication terminal devices due to excessive increase in transmission power, preventing communication interruption due to excessive decrease in transmission power, even after resuming communication Stable and high quality communication can be maintained.

The present invention is not limited to the above embodiment. For example, in the above embodiment, the transmission power value is corrected by calculating the correction amount only when (reception electric field intensity immediately before switching) <(reception electric field intensity immediately after switching recovery). Also in the case of (reception field strength)> (reception field strength immediately after switching recovery), the correction amount may be calculated to correct the transmission power value.

In addition, not only is the magnitude relationship between the received electric field strength immediately before switching and the received electric field strength immediately after switching restored, but also the difference determined, and the transmission power value is determined only when this difference exceeds a predetermined amount. Correction may be performed. In this case, when the difference between the received electric field strengths is small and the correction is not substantially required, the correction processing is omitted, and thus the time required until the communication is restarted can be reduced.

Further, in the above-described embodiment, the reception electric field strength is detected and is used as the reception quality as it is.
The data error rate may be detected together with the reception electric field strength, and the reception quality may be determined based on the data error rate.

In addition, the type and configuration of the terminal device, the procedure and contents of the transmission power correction processing, and the like can be variously modified without departing from the gist of the present invention.

[0049]

As described above in detail, according to the present invention, the first radio frequency during communication is temporarily switched to the second radio frequency in the peripheral radio area, and the reception quality is changed. Is measured, and then the processing for switching to the original first radio frequency and resuming communication is performed.
Immediately before switching from the second radio frequency to the second radio frequency, the communication parameter is detected and stored as pre-switch information, and immediately after switching from the second radio frequency to the first radio frequency is restored. The communication parameters are detected and stored as post-switching information, and the communication parameter correction means compares the pre-switching information with the post-switching information, and resumes after the switching return based on the comparison result. The communication parameters of the communication are corrected.

Therefore, according to the present invention, when the communication with the original base station is resumed after the reception quality measurement of the adjacent base station is completed, the communication can always be resumed in accordance with the optimal communication parameters, thereby preventing interference or interference. It is possible to provide a mobile communication terminal device capable of preventing occurrence of line disconnection and maintaining good communication quality after communication restart.

[Brief description of the drawings]

FIG. 1 is a circuit block diagram showing a configuration of a CDMA mobile communication terminal device according to an embodiment of the present invention.

FIG. 2 is a flowchart showing a control procedure and control contents of a handover between different frequencies by the apparatus shown in FIG. 1;

FIG. 3 is a flowchart showing the procedure and contents of a transmission power correction process during control shown in FIG. 2;

FIG. 4 is a view for explaining an operation of inter-frequency handover by the device shown in FIG. 1;

FIG. 5 is a diagram showing an example of parameters stored in a storage table for correcting transmission power.

FIG. 6 is a diagram for explaining an operation when a mobile station moves between cells having different radio frequencies.

FIG. 7 is a diagram for explaining a conventional inter-frequency handover operation.

[Explanation of symbols]

 A, B: Cell BSa, BSb: Base station MS: Mobile station F1, F2: Radio frequency 1: Antenna 2: Antenna duplexer (DUP) 3: Receiving circuit (RX) 4: Frequency synthesizer 5: Transmitting circuit (TX) Reference Signs List 6 CDMA signal processing unit 7 Voice code processing unit 8 PCM code processing unit 9 Receive amplifier 10 Speaker 11 Microphone 12 Transmit amplifier 20 External interface 30 Battery 31 Power supply circuit 40 Control unit 40a Inter-frequency handover control means 40b transmission power correction processing means 41 storage section 42 input section 43 display section

Claims (3)

[Claims] 1. A first radio frequency assigned to a first radio frequency
When moving from the wireless area to the second wireless area to which the second wireless frequency is assigned, the first wireless frequency during communication is temporarily switched to the second wireless frequency in the second wireless area. In a mobile communication terminal device having a function of switching to the original first radio frequency and restarting communication after measuring the reception quality, immediately before switching from the first radio frequency to the second radio frequency, First detecting means for detecting the communication parameter at this time and storing it as pre-switching information; and detecting the communication parameter at this time immediately after the return from the switching from the second radio frequency to the first radio frequency. A second detecting means for storing the information as post-switching information; and comparing the pre-switching information detected by the first detecting means with the post-switching information detected by the second detecting means. Comparison results Mobile communication terminal apparatus characterized by comprising a communication parameter correcting means for correcting the communication parameters resume communication after the switching back to and. 2. The radio communication apparatus according to claim 1, wherein the first detection unit detects reception quality immediately before switching of the first radio frequency and stores the reception quality as pre-switching information. The communication parameter correction means compares the reception quality immediately before the switching of the first radio frequency with the reception quality immediately after the switching, and stores the reception quality immediately after the switching. 2. The mobile communication terminal device according to claim 1, wherein the transmission power of the communication restarted after the return from the switching is corrected based on the relationship. 3. The first detecting means detects the reception quality immediately before the switching of the first radio frequency and its time, and stores the same as pre-switching information. Detecting the reception quality and the time immediately after the switching of the radio frequency and storing the same as the post-switching information, wherein the communication parameter correction unit determines the second radio frequency from the time immediately before the switching and the time immediately after the switching. 3. The method according to claim 2, further comprising: calculating a processing time required for measuring the reception quality, predicting the number of transmission power controls missing during the processing time, and calculating an optimum correction amount of the transmission power according to the predicted number.
The mobile communication terminal device according to claim 1.