JP2005045316A - Diversity handover method of mobile communication terminal, and mobile communication terminal - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a diversity handover method of mobile terminals, capable of eliminating the wireless channel branches less contributing to the communication quality while maintaining the communication quality and to provide a mobile communication terminal. <P>SOLUTION: An individual pilot signal quality measurement section 21 measures the quality of an individual radio wave signal sent from a base station, and a branch elimination discrimination section 24 selects the wireless channel branches established with the base station for transmitting radio waves with a low quality and eliminates the selected branches. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a diversity handover method for a mobile communication terminal device and a mobile communication terminal device, and more particularly, to a process of selecting and deleting a radio channel branch that has little contribution to communication quality during diversity handover.
[0002]
[Prior art]
In a cellular mobile communication system, a mobile communication service area is divided into small areas called cells, and a base station is installed in each cell. When the mobile station is in a certain cell, the mobile station selects a base station installed in the cell as an active base station (Active Cell), establishes a radio line branch with the base station, and performs communication. To do.
[0003]
When moving from a certain cell to a cell adjacent to the cell, the mobile station performs a handover process. That is, the communication base station is switched from the base station installed in the cell where the mobile station was located before moving to the base station installed in the cell where the mobile station is located after moving to maintain communication quality. To do.
[0004]
In a code division multiple access (CDMA) system or the like, a mobile station receives a radio wave transmitted from a communicating base station and a radio wave transmitted from a base station (Neighboring Cells) adjacent to the base station. Then, the quality of each received radio wave is measured.
[0005]
Here, the quality of radio waves refers to the strength of the common pilot signal of the common pilot channel for broadcasting a signal common to all mobile stations, and the signal power to interference noise power ratio (Signal Interference Ratio. Hereinafter, SIR). Etc.) and the like. Note that a base station in communication and a base station adjacent to the base station in communication are collectively referred to as a monitored base station (Monitored Cells).
[0006]
When the mobile station receives a radio wave having a higher quality than the radio wave transmitted from the base station in communication, the mobile station sets the base station that has transmitted the high-quality radio wave as a new communication base station. Switch over. At the time of this switching, a diversity handover method is used in the CDMA method or the like. The diversity handover method is sometimes called a soft handover method.
[0007]
In the diversity handover method, when a mobile station receives a radio wave having a quality higher than the quality of the radio wave transmitted from the communicating base station, the mobile station establishes a radio line branch with the base station that has transmitted the high quality radio wave. Establish. Then, the base station is added to the communicating base station, and communication is performed in the same manner as the base station that has already communicated.
[0008]
That is, the mobile station transmits transmission information to a plurality of base stations in communication, and reception information is received from a plurality of base stations in communication. Then, by communicating with a plurality of base stations, loss of communication information at the time of handover is prevented. In order to avoid complications, the quality of radio waves transmitted to and received from a base station is referred to as the quality of a radio line branch established with the base station.
[0009]
By the way, when a mobile station holds a plurality of radio channel branches, that is, communicating with a plurality of base stations simultaneously, it means that the mobile station uses a lot of radio channel resources of the mobile communication system. It is not preferable that the mobile station uses a lot of resources from the viewpoint of the efficiency of the mobile communication system.
[0010]
Therefore, the number of radio circuit branches that the mobile station holds at a time is determined to be equal to or less than a predetermined maximum number of branches. That is, the number of base stations with which the mobile station communicates at the same time is not more than the maximum number of branches.
[0011]
Therefore, when the number of radio circuit branches to be held exceeds a predetermined maximum number of branches, the mobile station immediately deletes some of the radio circuit branches to be retained and sets the number of radio circuit branches to be retained. The number is equal to or less than a predetermined maximum number of branches. Furthermore, as long as communication quality can be ensured, the number of radio circuit branches to be held is minimized, i.e., close to one.
[0012]
Here, it is necessary to prevent a decrease in communication quality when deleting the held wireless line branch. For this reason, it is necessary to select and delete a radio line branch that does not contribute to communication quality. Therefore, the radio channel branch to be deleted is determined by comprehensively judging the quality of the radio channel branch in the upstream direction (from the mobile station to the base station) and the quality of the downstream channel (from the base station to the mobile station). Is known (see, for example, Patent Document 1).
[0013]
[Patent Document 1]
Japanese Patent Laid-Open No. 2000-197092 (page 2-4, FIG. 4)
[0014]
[Problems to be solved by the invention]
However, the channel used to communicate information between the mobile station and the base station is not a common pilot channel, but an individual channel assigned exclusively for communication between the mobile station and the base station. The transmission power at which the base station transmits the common pilot channel is constant, but the transmission power at which the dedicated channel is transmitted is variable.
[0015]
Further, the transmission power at which the base station transmits the dedicated channel is increased or decreased based on an instruction from the mobile station. Since the transmission power increase / decrease instruction from the mobile station is simultaneously transmitted to all the communicating base stations, the transmission power for transmitting the dedicated channel is not always optimally controlled for each communicating base station. Absent.
[0016]
Therefore, there are cases where the quality of radio waves when measured using a common pilot channel signal does not match the quality when measured using individual channel signals.
[0017]
For this reason, there is a problem that it is impossible to accurately grasp the degree to which each wireless line branch contributes to communication quality using the measurement result of the signal of the common pilot channel.
[0018]
The present invention has been made in order to solve the above-mentioned problems, and a diversity handover method and mobile communication of a mobile communication terminal device capable of selecting and deleting a radio line branch having a low degree of contribution to communication quality An object is to provide a terminal device.
[0019]
[Means for Solving the Problems]
In order to achieve the above object, a diversity handover method for a mobile communication terminal apparatus according to the present invention receives radio waves transmitted from a plurality of communicating base stations and measures the quality of individual channel signals of the received radio waves. When the measured quality is lower than a predetermined value, the communication with the base station having the low quality is terminated.
[0020]
Further, the diversity handover method of the mobile communication terminal device of the present invention receives radio waves transmitted from a plurality of base stations in communication, measures the quality of individual channel signals of the received radio waves, and receives the received radio waves. Accumulating transmission power control information included in the individual channel of the radio wave, measuring the quality of the common pilot channel signal of the received radio wave, the quality of the measured individual channel signal being lower than a first predetermined value, and , When the accumulated transmission power control information indicates an increase in transmission power, and the quality of the measured common pilot channel signal is lower than a second predetermined value, communication with the base station is terminated. It is characterized by.
[0021]
According to the present invention, the quality of the individual channel signal of the radio wave transmitted from the base station is measured, and the base station that has transmitted the radio wave having the low measured quality is selected to terminate the communication, thereby contributing to the communication quality. It is possible to select and delete a radio line branch having a low level.
[0022]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of a mobile communication terminal apparatus diversity handover method and a mobile communication terminal apparatus according to the present invention will be described below with reference to the drawings.
[0023]
FIG. 1 is a block diagram showing a configuration of a mobile communication terminal apparatus (mobile station) according to an embodiment of the present invention. This apparatus includes a control unit 11 that controls the entire apparatus, an antenna 12a that transmits and receives radio waves to and from a base station (not shown), a communication unit 12b, a transmission / reception unit 13, a speaker 14a, and a microphone. 14 b, a call unit 14 c, an output unit 15, an input unit 16, and a signal quality determination unit 17.
[0024]
FIG. 2 is a block diagram illustrating a configuration of the signal quality determination unit 17. The signal quality determination unit 17 is connected to the dedicated pilot signal quality measurement unit 21 connected to the transmission / reception unit 13, the transmission power control signal addition unit 22 connected to the transmission / reception unit 13, the transmission / reception unit 13, and the control unit 11. The common pilot signal quality measurement unit 23 and the branch deletion determination unit 24 connected to the control unit 11.
[0025]
The operation of each part of the mobile communication terminal apparatus configured as described above according to the embodiment of the present invention will be described with reference to FIG.
[0026]
First, the communication unit 12b outputs the high-frequency signal received by the antenna 12a to the transmission / reception unit 13, and transmits the high-frequency signal output from the transmission / reception unit 13 from the antenna 12a.
[0027]
The transmission / reception unit 13 amplifies, converts and demodulates the high frequency signal from the communication unit 12b. The transmission / reception unit 13 separates a high-frequency signal from a received radio wave for each propagation path through which the radio wave has passed, and a plurality of fingers receive the separated high-frequency signals. Then, a method of combining and outputting the signals extracted by the fingers is used. The transmission / reception unit 13 sends the digital audio signal obtained by the demodulation to the call unit 14 c and the control signal to the control unit 11.
[0028]
In addition, the transmission / reception unit 13 sends the individual pilot signal of the individual channel signal extracted by each finger to the individual pilot signal quality measurement unit 21, and also transmits a transmission power control signal (TPC, Transmit Power Control Command) of the individual channel signal. The signal is sent to the transmission power control signal adding unit 22, and the common pilot signal of the common pilot channel signal extracted by each finger is sent to the common pilot signal quality measuring unit 23.
[0029]
Further, the transmission / reception unit 13 modulates, frequency-converts and amplifies the digital audio signal output from the call unit 14c and the control signal output from the control unit 11, obtains a high-frequency signal, and sends it to the communication unit 12b. .
[0030]
At this time, if the transmission power control signal of the dedicated channel signal transmitted from all base stations in communication instructs to increase the transmission power, the communication unit 12b is instructed to increase the transmission power and transmit. Also, if the transmission power control signal of the dedicated channel signal transmitted from at least one base station in communication is instructing to reduce the transmission power, the communication unit 12b is instructed to reduce the transmission power and transmit. .
[0031]
Next, the calling unit 14c converts the digital audio signal output from the transmission / reception unit 13 into an analog audio signal, amplifies it, and sends the analog audio signal to the speaker 14a. The analog audio signal output from the microphone 14 b is amplified, converted into a digital audio signal, and transmitted to the transmission / reception unit 13.
[0032]
The output unit 15 is a display device of an LCD, for example, and starts a display operation when activated by the control unit 11. The same content is displayed on the output unit 15 until the control unit 11 is activated in response to an input operation from the input unit 16.
[0033]
The input unit 16 includes a plurality of keys. The input unit 16 starts operating when the control unit 11 is activated, and notifies the control unit 11 of a code for identifying the key in response to a key input input by the user. finish.
[0034]
Next, the operation of the signal quality determination unit 17 (see FIGS. 1 and 2) will be described. The dedicated pilot signal quality measurement unit 21 receives the dedicated pilot signal in the dedicated channel signal extracted by each finger output from the transmission / reception unit 13. Then, the SIR value of each received individual pilot signal is calculated.
[0035]
The dedicated pilot signal quality measurement unit 21 further calculates the sum of the SIR values of the individual pilot signals of the branch for each branch and sets it as the SIR value of the branch. Also, the sum of SIR values of all branches is calculated. The SIR value of a branch is an index representing the contribution to the communication quality of the branch. The sum of SIR values of all branches is an index representing the total contribution to the communication quality of all branches.
[0036]
Next, the transmission power control signal adding unit 22 receives the transmission power control signal in the dedicated channel signal output from the transmission / reception unit 13. Then, for each branch, the sum of the values of the transmission power control signals in the individual channel signals of that branch received between the present and the time that is a predetermined time before the present is calculated.
[0037]
Here, the transmission power control signal is an instruction to increase / decrease the transmission power performed by the base station to the mobile communication terminal apparatus, and this signal is either “increase” or “decrease”. Here, “increase” is an instruction to increase transmission power transmitted by the mobile communication terminal apparatus, and “decrease” is an instruction to decrease transmission power transmitted by the mobile communication terminal apparatus.
[0038]
An instruction to increase the transmission power control signal from a base station in communication means that the quality of the radio wave received from the mobile communication terminal apparatus received by the base station is low. In addition, transmission of an instruction “decrease” in the transmission power control signal from a base station in communication means that the quality of the radio wave received from the mobile communication terminal apparatus received by the base station is high.
[0039]
Therefore, by summing the values of the transmission power control signals received within the predetermined time width for each branch, the radio wave quality of the uplink method of each branch can be estimated without instantaneous quality fluctuations. In order to calculate the sum of the transmission power control signals, if the signal is “increase”, the signal is converted to “1”, and if it is “decrease”, the signal is converted to “−1”. The sum of the obtained values is calculated as the sum of the transmission power control signals.
[0040]
As a result, the larger the total transmission power control signal transmitted from a certain base station, the lower the quality of the radio wave received from the mobile communication terminal device received by that base station. It can be estimated that the quality of the radio wave received from the mobile communication terminal apparatus is high.
[0041]
The common pilot signal quality measurement unit 23 receives a common pilot signal in the common pilot channel signal extracted by each finger output from the transmission / reception unit 13. Then, for each branch, the correlation value of the common pilot signal of that branch is calculated and used as the common pilot channel correlation value of that branch. This correlation value represents the status of a plurality of paths through which the common pilot signal has been propagated, and is an index representing the stability of the propagation path.
[0042]
The transmission / reception unit 13 also receives radio waves transmitted from a base station for which a branch is not established, that is, a monitored base station that is not communicating. Therefore, the common pilot signal quality measurement unit 23 calculates the common pilot channel correlation value for each base station from the common pilot signal in the common pilot channel signal transmitted from the base station that is not communicating.
[0043]
Next, the operation of the branch deletion determination unit 24 will be described. The branch deletion determination unit 24 adds the SIR value of each branch output from the dedicated pilot signal quality measurement unit 21 and the SIR value of all branches, and the branch of the transmission power control signal output from the transmission power control signal addition unit 22. This is a device that determines a branch to be deleted based on the total for each branch and the common pilot channel correlation value for each branch output from the common pilot signal quality measurement unit 23. FIG. 3 shows a flowchart of the operation of the branch deletion determining unit 24.
[0044]
The branch deletion determining unit 24 is activated from the control unit 11 at predetermined time intervals and starts operating (step 24a). First, the number of branches to be held, that is, the number of communicating base stations is checked (step 24b). If the number of branches to be held is 1, there is no branch to be deleted (step 24c), and the process ends immediately (step 24b). Step 24d).
[0045]
If the number of branches to be held is two or more in step 24b, the branch deletion determination unit 24 deletes each branch to be held by the following process until the processing for all the branches to be held is completed (step 24e). Check the availability. That is, first, the sum of the SIR value of the branch being processed and the SIR value of all the branches output from the individual pilot signal quality measurement unit 21 is received, and the SIR value of the branch being processed is converted into the SIR value of all the branches. The quotient divided by the sum of is checked (step 24f).
[0046]
If the quotient is equal to or greater than a predetermined threshold, the branch deletion determination unit 24 determines that the branch is not suitable for deletion because the contribution to the downlink communication quality of the branch is high. Then, returning to step 24e, it is checked whether or not the processing for all branches has been completed. If it is incomplete (“incomplete” in step 24e), the processing for the unprocessed branch is repeated.
[0047]
If the quotient is less than the predetermined threshold value in step 24f, the branch deletion determining unit 24 determines that the branch is suitable for deletion. Subsequently, the total transmission power control signal of the branch being processed output from the transmission power control signal adding unit 22 is received and the total is examined (step 24g).
[0048]
If the sum is equal to or less than a predetermined threshold, the branch deletion determination unit 24 determines that the quality in the uplink direction of the branch is high, and therefore determines that the branch is not suitable for deletion. Then, returning to step 24e, it is checked whether or not the processing for all branches has been completed. If it is incomplete (“incomplete” in step 24e), the processing for the unprocessed branch is repeated.
[0049]
If the total exceeds the predetermined threshold value in step 24g, the branch deletion determining unit 24 determines that the branch is suitable for deletion. Subsequently, the common pilot channel correlation value of the branch being processed output from the common pilot signal quality measurement unit 23 is received, and the square of the common pilot channel correlation value of the branch is multiplied by the SIR value of the branch The product is examined (step 24h).
[0050]
If the product is equal to or greater than a predetermined threshold value, the branch deletion determining unit 24 determines that the downlink direction of the branch is not suitable for deletion because it has a stable high quality. Then, returning to step 24e, it is checked whether or not the processing for all branches has been completed. If it is incomplete (“incomplete” in step 24e), the processing for the unprocessed branch is repeated.
[0051]
If the product is less than the predetermined threshold value in step 24h, the branch deletion determination unit 24 determines that the branch is suitable for deletion, and sets the branch to be deleted (step 24i). Then, returning to step 24e, it is checked whether or not the processing for all branches has been completed. If it is incomplete (“incomplete” in step 24e), the processing for the unprocessed branch is repeated.
[0052]
When the processing for all branches is completed in step 24e ("complete" in step 24e), the branch deletion determining unit 24 next determines whether the number of branches to be deleted is equal to the number of branches held. That is, it is checked whether or not all the branches to be held are the branches to be deleted (step 24j).
[0053]
If they are equal, a branch having a high quality is selected from the branches to be deleted, the branch is changed not to be deleted (step 24k), and the process ends (step 24d). A branch having a high quality is a branch having a large SIR value output from the dedicated pilot signal quality measurement unit 21, but is not limited thereto.
[0054]
If it is determined in step 24j that the number of branches to be deleted is not equal to the number of branches held, step 24k is skipped and the process ends (step 24d).
[0055]
If there are more branches to be deleted than the branches to be deleted, that is, if the value obtained by subtracting the predetermined maximum number of branches from the number of branches to be stored is larger than the number of branches to be deleted obtained in step 24j. More branches need to be deleted.
[0056]
In that case, select as many branches as necessary and delete them as low as necessary. A branch with low quality is a branch with a small SIR value, but is not limited thereto.
[0057]
In the above description, each branch is deleted when it is determined that all three determination criteria described in steps 24f to 24h are suitable for deletion, but the present invention is not limited to this. For example, when one of the above three criteria, or two, or any one of the above three criteria, or two, indicate that it is suitable for deletion It may be deleted.
[0058]
In addition, although the above-mentioned three determination criteria determine whether deletion is appropriate or not, it is not limited to this. For example, the degree suitable for deletion may be evaluated as a real value or an integer value. In that case, the three evaluated real values or integer values are calculated, and whether or not each branch can be deleted is determined based on the calculation result.
[0059]
Next, a description will be given of the control operations for establishing and deleting branches of the control unit 11 in the mobile communication terminal apparatus according to the embodiment of the present invention configured as described above, that is, adding and reducing base stations for communication.
[0060]
FIG. 4 shows a flowchart of the control operation of the control unit 11 when establishing and deleting a branch. The branch establishment and deletion control operations start at predetermined time intervals (step 11a). Subsequently, the radio wave transmitted from the base station being monitored is received and its quality is measured (step 11b).
[0061]
Here, the quality of the received radio wave is measured by the common pilot channel correlation value output from the common pilot signal quality measurement unit 23, but is not limited thereto. The SIR value of the common pilot signal of the common pilot channel may be calculated and measured using the SIR value.
[0062]
Next, the control unit 11 checks whether or not a radio wave having higher quality than the radio wave transmitted from the communicating base station has been received (step 11c). If the radio wave having the high quality is received, the base station that has transmitted the radio wave is added to the communicating base station, that is, a new branch is established (step 11d). Subsequently, the branch deletion determining unit 24 is activated to determine a branch to be deleted among the established branches (step 11e).
[0063]
The control unit 11 checks whether there is a branch to be deleted determined by the branch deletion determination unit 24 (step 11f), and if there is a branch to be deleted, deletes the branch (step 11g) and ends (step 11h).
[0064]
In the above description, the control unit 11 deletes the branch determined by the branch deletion determination unit 24 after the number of branches held exceeds the predetermined maximum number of branches, and sets the number of branches to be stored as the predetermined maximum number of branches. It was decided as follows. However, before establishing additional branches, make sure that the number of branches to be retained does not exceed the predetermined maximum number of branches even if a branch is established, and if so, reduce the number of branches to be retained. A branch may be established after doing so.
[0065]
In this embodiment, the mobile communication terminal apparatus determines the branch to be deleted. However, the mobile communication terminal apparatus only measures the quality of the radio wave transmitted from the base station being monitored, and the other processes are mobile. An apparatus other than the communication terminal apparatus may be used. The present invention is not limited to the above configuration, and various modifications are possible.
[0066]
【The invention's effect】
As described above, according to the present invention, it is possible to select and delete a radio line branch having a low degree of contribution to communication quality at the time of diversity handover. For this reason, it is possible to prevent a decrease in communication quality at the time of diversity handover.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a configuration of a mobile communication terminal apparatus according to an embodiment of the present invention.
FIG. 2 is a block diagram showing a configuration of a signal quality determination unit according to the embodiment of the present invention.
FIG. 3 is a flowchart showing an operation of a branch deletion determination unit according to the embodiment of the present invention.
FIG. 4 is a flowchart showing branch establishment and deletion control operations of the control unit according to the embodiment of the present invention;
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 11 Control part 13 Transmission / reception part 17 Signal quality determination part 21 Individual pilot signal quality measurement part 22 Transmission power control signal addition part 23 Common pilot signal quality measurement part 24 Branch deletion determination part

Claims (9)

Receive radio waves transmitted from multiple communicating base stations,
Measure the quality of the individual channel signal of the received radio waves,
A diversity handover method for a mobile communication terminal apparatus, wherein communication with a base station having the low quality is terminated when the measured quality is lower than a predetermined value. The quality of the dedicated channel signal of each base station is a value obtained by dividing the signal power to interference noise power ratio of the dedicated channel signal by the sum of the signal power to interference noise power ratios of the dedicated channel signals of the plurality of base stations. The diversity handover method for a mobile communication terminal apparatus according to claim 1, wherein: Accumulating transmission power control information included in the individual channel of the received radio wave,
The mobile terminal according to claim 1, wherein when the measured quality is low and the accumulated transmission power control information indicates an increase in transmission power, communication with the base station is terminated. A diversity handover method for a communication terminal apparatus. The transmission power control information is an instruction of either increase or decrease, and the accumulated transmission power control information includes the number of times of increase instruction and the number of instructions of decrease performed within a predetermined time. The diversity handover method for a mobile communication terminal apparatus according to claim 3, wherein: Receive radio waves transmitted from multiple communicating base stations,
Measure the quality of the individual channel signal of the received radio waves,
Accumulate the transmission power control information included in the individual channel of the received radio wave,
Measure the quality of the common pilot channel signal of the received radio waves,
The measured quality of the dedicated channel signal is lower than a first predetermined value, the accumulated transmission power control information indicates an increase in transmission power, and the quality of the measured common pilot channel signal is A diversity handover method for a mobile communication terminal device, wherein communication with the base station is terminated when lower than a second predetermined value. A receiving device having a plurality of fingers receives radio waves transmitted from a plurality of base stations in communication,
6. The diversity handover method for a mobile communication terminal apparatus according to claim 5, wherein the quality of the common pilot channel signal is obtained from a correlation value of the common pilot channel signal extracted by the plurality of fingers. The quality of the common pilot channel signal is a product obtained by multiplying a square value of a correlation value of the common pilot channel signal by a signal power to interference noise power ratio of an individual channel signal of the received radio wave. Item 7. A diversity handover method for a mobile communication terminal device according to Item 6. Means for receiving radio waves transmitted from a plurality of base stations in communication;
Means for measuring the quality of individual channel signals of radio waves received by the receiving means;
Means for accumulating transmission power control information included in an individual channel of radio waves received by the receiving means;
When the quality of the dedicated channel signal measured by the measuring means is lower than a predetermined value and the transmission power control information accumulated by the accumulating means indicates an increase in transmission power, the communication with the base station is terminated. A mobile communication terminal apparatus comprising: Means for receiving radio waves transmitted from a plurality of base stations in communication;
First measuring means for measuring the quality of the individual channel signal of the radio wave received by the receiving means;
Means for accumulating transmission power control information included in an individual channel of radio waves received by the receiving means;
Second measuring means for measuring the quality of a common pilot channel signal of radio waves received by the receiving means;
The quality of the dedicated channel signal measured by the first measuring means is lower than a first predetermined value, the transmission power control information accumulated by the accumulating means indicates an increase in transmission power, and the first A mobile communication terminal apparatus comprising: handover control means for terminating communication with the base station when the quality of the common pilot channel signal measured by the second measurement means is lower than a second predetermined value.

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