JP2004193851A - Mobile terminal and transmission power control method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a mobile terminal capable of quickly performing transmission power control to maintain prescribed communication quality and to provide a transmission power control method thereof. <P>SOLUTION: A memory section 17 stores an initial setting value for the transmission power control to obtain the prescribed communication quality at start of data communication together with a setting value in past data communication and base station information, and a corresponding initial value is set on the basis of the stored base station information in the case of next data communication. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a mobile terminal system, and more particularly to a mobile terminal capable of quickly setting a transmission power of a mobile terminal to a predetermined value and a transmission power control method thereof.
[0002]
[Prior art]
A mobile terminal (including a mobile phone) performs data communication with one of a plurality of base stations having a relatively small service area by wireless communication using a frequency of about 2 GHz. Therefore, the base station with which the user communicates changes depending on the position (place) where the user uses the portable terminal. The communication environment between the base station communicating with the mobile terminal changes variously depending on a physical distance, an obstacle, and the like. Further, the communication between the mobile terminal and the base station needs to be set so that the transmission power is controlled and the communication quality or the communication error occurrence rate is equal to or higher than a predetermined value. In other words, the mobile terminal needs to satisfy the communication quality according to the service being connected.
[0003]
The mobile terminal executes “Outer Loop transmission power control” to obtain the target quality. Here, “Outer Loop transmission power control” means that the mobile terminal itself has a target SIR (Signal-to-Interference Ratio) so that the communication quality (BER: Bit Error Rate and BLER: Block Error Rate) becomes a target value. ).
[0004]
Specifically, the mobile terminal measures the communication quality with a certain section length (several hundred mS to several S) and sets an appropriate Target SIR for obtaining the target quality. The mobile terminal executes “Inner Loop transmission power control” so as to satisfy the Target SIR value. Here, “Inner Loop transmission power control” is a method of controlling the power of the downlink communication channel (CH) of the base station by comparing the target SIR with the reception SIR. Specifically, the mobile terminal measures the SIR of the communication channel being received, and compares the measured SIR with the target SIR held inside the mobile terminal. If the target SIR has not been reached, an Up (increase in transmission power) command is transmitted as a TPC (Transmitter Power Control) bit if the target SIR is exceeded or higher. The base station receives and decodes the TPC bit. Based on the decoding result, the transmission power is changed by 1 dB, and as a result, the SIR of the received communication CH is set to a target value.
[0005]
As described above, in “Outer Loop transmission power control”, it is important to set an appropriate Target SIR in order to obtain the target quality of the received communication CH. The conventional “Initial TargetSIR value” is determined only in accordance with the target quality of the received communication CH. Here, the “initial target SIR value” indicates a maximum value, a minimum value of the SIR value, or a target SIR value set immediately after the received communication CH is opened. As the “initial target SIR value”, an average value that is satisfied in all environments is set.
[0006]
FIG. 3 is a flowchart illustrating a conventional transmission power control method for a mobile terminal. First, data communication is started (step A1), and an initial value is set by “Initial Target SIR” of “Outer Loop transmission power control” (step A2). The initial setting value is set to the maximum value or the minimum value of the SIR value, or an average value that is satisfied in all environments. Here, the average value is set. When an average value is set, it is a constant value stored for each service with which the mobile terminal communicates without being affected by the environment. “Outer Loop transmission power control” is executed with this Target SIR value as “Initial Target SIR”. The BLER is measured by the error count unit (step A3), and the power control determination unit compares and determines whether the BLER value satisfies the preset service quality, that is, the required quality (step A4).
[0007]
As a result of the comparison, if the required quality is satisfied (step A4: Yes), the target SIR is set to Target SIR Down, and a target SIR value smaller than the reception SIR value measured by the SIR measurement unit is set (step A5). The power control unit compares the Target SIR value with the received SIR value, and requests the TPC control unit to generate a TPC bit meaning lowering the power to the base station in order to perform “Inner Loop transmission power control”. Upon receiving this request, the TPC generation unit generates a TPC bit for lowering the power, and passes the TPC bit to the TPC mapping unit. In the TPC mapping, in order to transmit the generated TPC bits to the base station, the TPC bits are mapped to the physical CH, and the TPC bits are transmitted to the base station via the RF unit.
[0008]
On the other hand, as a result of the comparison in step A4, if the BLER value measured in step A3 does not satisfy the required quality of service (step A4: No), a target SIR value larger than the reception SIR value is set, and “ As a result of “Inner Loop transmission power control”, a TPC bit meaning to increase downlink power is transmitted to the base station, that is, Target SIR Up is performed (step A6). The above-described operation is continuously performed until the required quality of the received service is satisfied.
[0009]
In a portable terminal or a portable telephone, a transmission power control apparatus and method for providing a threshold value determination unit and controlling transmission power based on a magnitude relationship between a measured value and a target value are disclosed in various conventional technologies (for example, See Patent Literature 1, Patent Literature 2, and Patent Literature 3.)
[0010]
[Patent Document 1]
JP 2001-244879 A (Page 4-5, FIG. 1)
[Patent Document 2]
JP-A-2002-152127 (page 3, FIG. 1)
[Patent Document 3]
JP-A-11-340908 (page 4, FIG. 1)
[0011]
[Problems to be solved by the invention]
However, in the related art, when the difference between the “initial Target SIR value” and the Target SIR value to be converged is large, it takes time to converge. In particular, in a stable environment (when the converging Target SIR value is sufficiently smaller than the initial Target SIR value), excessive downlink power is required for the base station until the convergence, and the line capacity is reduced. There was a problem that it became a factor to do.
[0012]
[Object of the invention]
The present invention has been made in view of the above-mentioned problems of the related art, and sets the “Initial Target SIR” used in “Outer Loop transmission power control” to a convergence value as much as possible instead of a fixed initial value as in the related art. It is an object of the present invention to provide a portable terminal and a transmission power control method thereof, which enable transmission power control to be completed in a short time by selecting a close value.
[0013]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, a portable terminal and a transmission power control method thereof according to the present invention employ the following characteristic configurations.
[0014]
(1) A portable terminal having transmission power control means for controlling transmission power for wirelessly performing data communication with a base station so as to obtain a predetermined SIR value according to a communication environment,
Storage means for storing and storing the convergence value of Target SIR and base station information used in Outer Loop transmission power control, wherein the Target SIR value stored in the storage means is stored in the Outer Loop transmission power control in accordance with the base station information; The mobile device to set as the initial value for.
[0015]
(2) The portable terminal according to (1), wherein the storage unit stores a plurality of combinations of Target SIR convergence values and base station information at the time of past data communication.
[0016]
(3) The portable terminal according to (1) or (2), wherein a predetermined initial set value is used when information on a base station with which data is communicated is not stored in the storage means.
[0017]
(4) The portable terminal according to (1), (2) or (3), wherein the location information obtained by GPS or the like is stored in the storage means together with or instead of the base station information.
[0018]
(5) A transmission power control method for a mobile terminal that appropriately selects one of a plurality of base stations installed at different locations and controls the transmission power of the mobile terminal that performs data communication wirelessly so as to have a predetermined communication quality. ,
A transmission power control method for a mobile terminal, wherein a convergence value of transmission power during data communication of the mobile terminal is stored and set as an initial setting value of transmission power at the start of next and subsequent data communication.
[0019]
(6) The transmission power control method for a portable terminal according to (5), wherein the initial setting value of the transmission power is selected and set from the stored convergence values based on a base station with which the data communication is started at the time of the data communication.
[0020]
(7) The transmission power control method for a portable terminal according to the above (5), wherein the initial setting value of the transmission power is selected based on a location of the portable terminal at the start of the data communication.
[0021]
(8) The transmission power control method for a mobile terminal according to the above (5), (6) or (7), wherein the convergence value of the transmission power is automatically saved at the end of the data communication by the mobile terminal.
[0022]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the configuration and operation of a preferred embodiment of a portable terminal and its transmission power control method according to the present invention will be described in detail with reference to the accompanying drawings.
[0023]
First, FIG. 1 shows a system configuration diagram of a preferred embodiment of a portable terminal according to the present invention. The mobile terminal 10 according to the present invention includes an RF (radio frequency) unit 11, a signal processing unit 12, a control unit 13, an error counting unit 14, an SIR measurement unit 15, a power control determination unit 16, a memory unit (storage means) 17, a TPC. It comprises a generating unit 18 and a TPC mapping unit 19. The transmitting / receiving antenna 20 is connected to the RF unit 11.
[0024]
Next, main functions and the like of each of the components 11 to 19 constituting the mobile terminal 10 of the present invention will be described. The RF unit 11 down-converts the frequency received by the antenna 20, A / D (analog / digital) converts the data, D / A (digital / analog) converts the data to be transmitted, and converts the data to a frequency to be transmitted from the antenna 20. Upconvert. The signal processing unit 12 despreads the data received from the RF unit 11 and performs a decoding (decoding) process. The control unit 13 controls the decoded data from the signal processing unit 12 and the operation of the mobile terminal 10.
[0025]
The error counting unit 14 counts the number of CRC errors from the decoding result from the signal processing unit 12 and calculates BLER. The SIR measuring unit 15 calculates the SIR of the received channel (CH) based on the data obtained from the signal processing unit 12. The power control determining unit 16 performs “Outer Loop transmission power control” from the BLER value obtained by the error counting unit 14 and the measured SIR value measured by the SIR measuring unit 15. The memory unit 17 stores an “initial Target SIR value” used in power control, a Target SIR value that converged last time, and a service. TPC generation section 18 calculates a TPC bit based on the result determined by power control determination section 16. TPC mapping section 19 maps the generated TPC bits to a physical CH.
[0026]
Next, the operation of the mobile terminal 10 shown in FIG. 1 will be described with reference to the flowchart in FIG. The user of the portable terminal 10 uses the portable terminal 10 at various places or while moving as described above. However, the location where the mobile terminal 10 is used is not always different (every service), and most of the services are frequently used in relatively limited places such as homes, offices, specific business trip destinations, friend's homes, and the like. Based on the fact that the mobile terminal 10 is often used, an appropriate transmission power set value is selected for each base station with which the user's mobile terminal 10 communicates.
[0027]
In the mobile terminal 10 according to the present invention, when starting data communication (step B1) and setting the “initial Target SIR value” of “Outer Loop transmission power control”, it is possible to select a target SIR that has converged in the past. It is characterized by. That is, after starting the data communication in step B1, it is determined whether or not there is a convergence value stored in the memory unit 17 (step B2).
[0028]
When communication is performed for the first time, that is, when there is no convergence value (step B2: No), “normal initial Target SIR value” is set (step B4). After that, the conventional “Outer Loop transmission power control” is performed. After the communication is completed (step B10), the converged Target SIR value is determined by the power control determining unit 16, and the target SIR value and the base station information at the time of converging with the service being communicated are stored in the memory unit 17. (Step B11) and end (Step B12).
[0029]
Next time, when the same service is executed (Step B2: Yes), the base station information stored in the memory unit 17 is referred to, and when communication is performed with the same base station, the previous service is converged. The target SIR value that has been set is selected as an “initial target SIR value” and set as an initial value (step B3). In particular, when performing communication in an environment where the mobile terminal 10 is stopped, it is conceivable that the mobile terminal 10 connects to and communicates with the same base station as in the previous communication. The convergence value of the Target SIR value in this communication is likely to be the same as the previous time. (Steps B5 to B9 to be described later are substantially the same as those described with reference to the flowchart of FIG. 3).
[0030]
Therefore, based on the base station information stored in the memory unit 17, the initial Target SIR value is set to the Target SIR value that has converged with the previous time (step B3). As a result, when communication is performed in the same environment as the previous time, the received SIR value can be brought closer to the Target SIR value earlier than when a normal initial value is selected. That is, by simultaneously storing the base station information and the Target SIR value in the memory unit 17 (step B11), it is possible to set a highly accurate initial Target SIR value. Here, when the initial value is the previous Target SIR value, the current communication environment may be degraded (improved) compared to the past environment, but in the present invention, the measured BLER value is the required quality. If it has deteriorated (improved), a normal initial Target SIR value can be set (step B8).
[0031]
By providing a means for selecting the “initial Target SIR value”, the present invention does not degrade the convergence speed of “Outer Loop transmission power control” even in an environment where the communication state is poor (or good). It is possible to increase the convergence speed of the Target SIR value under the same environment as described above.
[0032]
Next, a modified example or another embodiment of the present invention will be described. First, a plurality of combinations of the base station and the Target SIR value can be stored in the memory unit 17, and the initial value of the Target SIR can be selected from the stored plurality of base station information. Secondly, in the preferred embodiment described above, the method of storing the “initial Target SIR value” and the base station information (scrambling code) in the memory unit 17 has been described. However, fading information, moving speed information, GPS (Global Positioning), etc. It is also possible to store the location information by System and use it as a reference for selecting and setting the “Initial Target SIR value”.
[0033]
The configuration and operation of the preferred embodiment of the portable terminal and its transmission power control method according to the present invention have been described above in detail. However, it should be noted that such embodiments are merely examples of the present invention and do not limit the present invention in any way. It will be readily apparent to those skilled in the art that various modifications and changes can be made in accordance with the particular application without departing from the spirit of the invention.
[0034]
[Explanation of effects]
As is clear from the above description, according to the portable terminal and the transmission power control method of the present invention, the following various remarkable practical effects can be obtained. First, the convergence of “Outer Loop transmission power control” can be accelerated. The reason is that it is possible to store the target SIR value that converged last time and apply the target SIR value that converged at the next connection.
[0035]
Second, convergence of Outer Loop can be accelerated according to the environment. The reason is that the Target SIR value according to the environment can be stored.
[0036]
Third, it is possible not to request excessively the downlink power of the base station. The reason is that the convergence of the outer loop can be accelerated, so that it is possible to prevent the base station from excessively requesting the downlink power.
[0037]
Fourth, an improvement in line capacity can be expected. The reason is that it becomes possible not to request the downlink power of the base station excessively.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a configuration of a preferred embodiment of a portable terminal according to the present invention.
FIG. 2 is a flowchart illustrating a transmission power control operation of the mobile terminal illustrated in FIG. 1;
FIG. 3 is a flowchart illustrating a transmission power control operation of a conventional mobile terminal.
[Explanation of symbols]
Reference Signs List 10 mobile terminal 11 RF unit 12 signal processing unit 13 control unit 14 error counting unit 15 SIR measurement unit 16 power control determination unit 17 memory unit (storage means)
18 TPC generation unit 19 TPC mapping unit

Claims (8)

In a portable terminal having transmission power control means for controlling transmission power for wirelessly performing data communication with a base station so as to obtain a predetermined SIR value according to a communication environment,
Storage means for storing and storing the convergence value of Target SIR and base station information used in Outer Loop transmission power control, wherein the Target SIR value stored in the storage means is stored in the Outer Loop transmission power control in accordance with the base station information; A mobile terminal, which is set as an initial value. The mobile terminal according to claim 1, wherein the storage unit stores a plurality of combinations of Target SIR convergence values and base station information at the time of past data communication. 3. The portable terminal according to claim 1, wherein a predetermined initial setting value is used when information on a base station with which data communication is performed is not stored in the storage unit. The portable terminal according to claim 1, 2 or 3, wherein location information acquired by GPS or the like together with or instead of the base station information is stored in the storage unit. A transmission power control method for a mobile terminal, which appropriately selects one of a plurality of base stations installed at different locations and controls the transmission power of the mobile terminal performing wireless data communication so as to achieve a predetermined communication quality.
A transmission power control method for a mobile terminal, wherein a convergence value of transmission power at the time of data communication of the mobile terminal is stored and set as an initial setting value of transmission power at the start of next and subsequent data communication. 6. The transmission power control method for a mobile terminal according to claim 5, wherein the initial setting value of the transmission power is selected and set from the stored convergence values based on a base station that communicates at the time of starting the data communication. The transmission power control method for a mobile terminal according to claim 5, wherein the initial setting value of the transmission power is selected based on a location of the mobile terminal when the data communication is started. The transmission power control method for a mobile terminal according to claim 5, 6, or 7, wherein the convergence value of the transmission power is automatically saved when data communication by the mobile terminal ends.

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