JPH11136738A - Base station selecting method at the time of waiting for moving body communication terminal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve call quality by predicting a base station from which optimum received electric field intensity is obtained among monitored base stations with the values of the latest received electric field intensity and the inclination of the received electric field intensity for respective base stations. SOLUTION: CPU 58 continuously monitors the base station twice at the prescribed interval of about four seconds, for example, and stores received electric field intensity in RAM 58b as time sequential data for respective base station identification numbers. The received electric field intensity of the respective base stations is calculated from time sequential data of the base stations, which are stored for the respective identification numbers. Time sequential data of the base stations, which are stored for the respective identification numbers, are referred to and the base station in an existing radio zone is selected by the latest received electric field intensity in the respective base stations and the change of the received electric field intensity in the respective base stations, which is calculated in a received electric field intensity calculation means. The change of the electric field intensity of the base station against the moving direction of the moving body communication terminal at the time of movement is predicted and the optimum base station is selected.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for selecting a base station for a mobile communication terminal, and more specifically, a mobile communication terminal for selecting a base station in a local radio zone in consideration of the mobile elements of the mobile communication terminal. And a method of selecting a base station at the time of standby.

[0002]

2. Description of the Related Art A so-called mobile communication system such as a portable telephone or a car telephone has a great feature that communication is possible even when a mobile communication terminal is moving, and has been rapidly spreading in recent years. . As is well known, in a mobile communication system, a base station capable of good communication is appropriately selected from public base stations arranged regularly in order to enable communication even while moving. Such a process of selecting a base station is very important for securing the line quality because in the case of wireless communication, the propagation of radio waves is affected by the surrounding conditions and the propagation state of the radio waves greatly affects the connection state. It is. Therefore, the mobile communication terminal periodically monitors the burst signals of the incoming control channels from some public base stations during standby, and performs a standby operation on the base station having the highest reception electric field strength among the burst signals. Is programmed to

Specifically, the mobile communication terminal monitors burst signals from a plurality of base stations, for example, about ten base stations in order during standby, and pairs the ID, which is the identification number of the base station, with the received electric field strength in a pair. Store each. Then, the mobile communication terminal extracts and selects the ID of the base station having the highest reception electric field strength from the stored reception electric field strengths. Thereafter, the base station having this ID is set as the base station on which the communication terminal waits, and all information reported from the base station is received and a standby process is performed. In this way, once the base station is selected, the base station that performs standby processing on the base station until the received electric field strength with the base station falls below a predetermined value or until the power is turned on again And

On the other hand, the zones of the base station are composed of a handover zone, a callable / receivable zone, and a zone with good call quality. The good call quality zone is a zone in which a stable call can be made, and it is preferable that a base station in this zone be selected when an actual call is made. On the other hand, the callable / receivable zone can perform the process of establishing the communication channel, but the communication quality is unstable. The handover zone is the zone having the worst communication conditions instead of being the widest, and when the mobile communication terminal enters this zone, only the control signal can be received. This handover zone substantially overlaps with the zone of another base station, so that even if the mobile communication terminal is in another zone, it is possible to receive control signals of the base station in this zone.

[0005]

As described above, in the mobile communication terminal, the base station selected in the standby state is used as the base station for performing actual communication. However, in the case of a mobile communication terminal, since the terminal often moves with the passage of time, the position in the standby state where the base station is selected is not necessarily the same as the position where the actual communication is performed. Therefore, there is a problem that there is no guarantee that the best base station is selected when performing actual communication.

That is, in the prior art, when monitoring the standby state, the electric field strength of the public base station is stored as one piece of information, and the change of the received electric field strength with the passage of time is not considered at all. For this reason, when used after moving, there are many cases where the telephone is already out of the good call quality zone and the received electric field strength is weak, and depending on the case, even if you try to make a call, it will not be cut off or stopped There was a problem that sometimes.

The present invention solves the above-mentioned problems of the prior art, and improves the communication quality during communication by selecting a base station during standby by predicting a change in received electric field strength over time. An object of the present invention is to provide a method of selecting a base station when a mobile communication terminal waits, which can be expected.

[0008]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a method of selecting a base station when a mobile communication terminal is on standby. A first step of storing the received electric field strength of the base station selected by the above as time-series data for each base station, and a reception of each monitored base station based on the time-series data of the received electric field strength stored in the first step. A second step of calculating the gradient of the electric field intensity, the latest value of the received electric field intensity for each base station in the time-series data stored in the first step, and the reception of each base station calculated in the second step. A third step of predicting, from the monitored base stations, a base station that can obtain the optimum reception electric field strength based on the gradient of the electric field strength.

Further, according to the present invention, a method of selecting a base station when a mobile communication terminal is on standby monitors a communicable base station at a predetermined interval, and receives the received electric field strength for each base station in time-series data. A first step of storing the received electric field strength stored in the first step, a second step of calculating a slope of the received electric field strength for each monitored base station from the time-series data of the received electric field strength stored in the first step, and a first step. Based on the latest received electric field strength value for each base station in the stored time-series data and the slope of the received electric field strength for each base station calculated in the second step, the optimum received electric field is selected from among the monitored base stations. A third step of estimating a base station from which a strength can be obtained and selecting a predetermined number of base stations; and monitoring the base station selected in the third step again to obtain a signal having the highest reception electric field strength. And a fourth step of selecting a have the base station.

Further, according to the present invention, a mobile communication terminal having a standby function of selecting a base station in a located wireless zone by monitoring a base station that can communicate in a standby state is provided by the base station. Monitoring means for continuously performing at least two times at predetermined intervals, and storing the received electric field strength obtained as time-series data for each identification number of the base station; and a base station stored for each identification number. Receiving electric field strength change calculating means for calculating a change in the received electric field strength of each base station from the time series data of the base station, and the latest received electric field at each base station by referring to the time series data of the base station stored for each identification number. A base station selecting means for selecting a base station in the in-range wireless zone based on the strength and a change in the received field strength at each base station calculated by the received field strength change calculating means.

[0011]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing an embodiment of a method for selecting a base station when a mobile communication terminal is on standby according to the present invention; FIG. 5 is a functional block diagram showing an embodiment of a mobile communication terminal to which the present invention is applied. The antenna 52 radiates or receives radio waves in order to exchange data with a public base station (not shown) corresponding to any of the handover zone, the callable / receivable zone, and the good call quality zone.
An RF unit 54 is connected to the antenna 52.

The RF section 54 amplifies and frequency-converts the signal received by the antenna 52 and outputs a demodulation signal to the baseband section 56;
And a transmission circuit for amplifying and frequency-converting the voice-modulated signal from the antenna 6 and outputting the result to the antenna 52.
The baseband unit 56 includes a CPU 58 and a codec 68
And demodulates the RF signal received from the antenna 52 including the voice signal and the caller number under the control of the CPU 58. The baseband unit 56 also notifies the CPU 58 of the ID, which is the identification number of the public base station, which has been received by the RF receiving circuit when the power supply is in the on state, and the received electric field strength thereof.

The codec 68 is a converter that converts a digital signal into an analog signal and converts an analog signal into a digital signal. That is, the codec 68 is
8, the digital audio signal input from the baseband unit 56 or the CPU 58 is converted into an analog signal and output to the speaker (SP) 66, and the microphone (MI)
C) The analog audio signal input from 64 is converted into a digital audio signal and output to the baseband unit 56. The codec 68 is also connected to the DTMF receiver 70, converts a digital signal input from the baseband unit 56 into an analog signal, and outputs the analog signal to the DTMF receiver 70. DT
When the signal input from the codec 68 is a DTMF signal, the MF receiver 70 outputs the content to the CPU 58.

The CPU 58 is a control unit for controlling the entire mobile communication terminal, and includes a ROM 58a, which is a non-volatile memory in which programs and the like are written, and various devices for selecting a base station at the time of standby. And a RAM 58b for temporarily storing information. CPU
Reference numeral 58 denotes a display unit 60 for displaying a telephone number and the like, and a key input unit 62 constituted by various keys such as an input key for inputting a telephone number and characters, a power key, and a calling key for performing a calling process. Is connected.

The CPU 58 also has a function of performing a monitoring process, a reception electric field strength change calculation process, and a base station selection process when waiting to select a base station. The monitoring process is a process of continuously performing the monitoring of the base station twice at a predetermined interval of, for example, about 4 seconds, and storing the obtained received electric field strength as time-series data in the RAM 58b for each base station identification number. It is. Further, the reception electric field intensity change calculation process is a process of calculating a change in the reception electric field intensity of each base station from the time-series data of the base station stored for each identification number by the monitoring process. Further, the base station selection processing is performed by referring to the time-series data of the base station stored for each identification number and the latest reception electric field strength at each base station and the reception electric field strength at each base station calculated in the reception electric field strength change calculation processing. This is a process of selecting a base station in the in-range wireless zone based on a change in the electric field strength.

FIG. 1 is a flowchart showing an embodiment of a method of selecting a base station when a mobile communication terminal waits according to the present invention. When the power is turned on to the mobile communication terminal shown in FIG. 5 (S102), the mobile communication terminal performs the following processing in order to select a base station in the located wireless zone.
The mobile communication terminal sequentially monitors about 10 communicable public base stations (S104), and obtains the ID of the monitored base station and its received electric field strength. The process in step S104 is performed until the base station search time expires (S1).
06), the base station ID obtained as a result of the monitoring and the received electric field strength are paired with the CPU 58, respectively.
Is stored in the RAM 58b (S108). If an abnormality is detected in step S106, the process returns to step S104 to perform monitoring again (S122).

When the monitored result is stored in the RAM 58b, the number of monitored base stations and the field strength are determined (S110). As a result of the determination, if there is no monitored base station or if the electric field strength or the like has not reached the threshold value, out-of-service processing (S124) is performed, and after the out-of-service timer time has expired (S126), step S1 is performed again.
Return to 04 and perform monitoring. On the other hand, step S11
If it is determined that there is a base station that could be monitored at 0, it is determined whether the number of base stations is appropriate (S112).

In this embodiment, about 10 base stations are monitored. This is because if the number of base stations to be monitored is large, the load of the prediction process of the optimum base station described later becomes very large. Therefore, when the number to be monitored exceeds 10, control data for selecting a base station is changed (S130). In this way, it is determined whether the monitoring of the public base station has been performed twice at intervals of 3 seconds to 4 seconds (S114). If the base station ID selected at the end of the second monitoring is the same as the base station ID stored in the previous monitoring result, the RAM is set so as to be paired with the corresponding base station ID as a time difference electric field strength.
58b. That is, in the present embodiment, by performing monitoring twice in succession, one base station has two sets of reception field strength data in time series.

Based on the received electric field intensity data for each base station ID obtained in this manner, a change in the electric field intensity of the base station with respect to the moving direction of the mobile communication terminal when moving is predicted, and the optimum base station is selected. (S116). This step S11
6, when the optimal base station is selected, the ID of this base station
Receives all the notified information and performs a standby operation. If there is an outgoing / incoming call (S1
18) The control channel is established by the base station selected at the time of standby, and a call is started (S12).
8).

When the received electric field strength of the base station becomes equal to or smaller than the threshold value (S120), the process returns to step S104, and the process of selecting a new base station for performing a standby process is performed again. At this time, the data is compared with previously stored data, and if the currently monitored base station also exists last time, it is used as a comparison target. If the currently monitored base station does not include the previously stored base station, the information of the previous base station is deleted.

When estimating the optimum base station from the base stations monitored by the mobile communication terminal, it is not always possible to make a judgment only by the received electric field strength. Judgment at two points on the time axis makes it possible to detect a better base station by an algorithm that also considers user mobility.
Even when the mobile communication terminal is not moving, the electric field intensity changes due to the influence of the lower field, for example, the position of the terminal, the passing of a car, or the influence of the shaking of a standing tree. Therefore, it is desirable to select a base station in consideration of a temporal environmental change. In the algorithm for predicting the optimal base station in the present embodiment, first, the gradient (θ) of the electric field intensity of each base station calculated from the received electric field intensity acquired in the two monitorings and the inclination (θ) acquired in the second monitoring An optimal base station is predicted based on the received electric field strength obtained.
Then, by using this algorithm, the candidates to be the optimum base stations are reduced to about three out of about ten base stations, and the base stations that have been further reduced to three are monitored again, and among them, the reception electric field strength having the highest reception electric field strength is obtained. Select a base station.

Next, the details of the process of step S116 for selecting such an optimal base station will be described with reference to FIGS. 2 and 3 are flowcharts showing the details of the processing in step S116. Step S shown in FIG.
By 104 to S114, the received field strength data is monitored twice in time series for each base station ID. In the monitoring performed twice, the slope of the received electric field strength with respect to the change with time (from the received electric field strength obtained at the first time and the detection time thereof and the value of the received electric field strength obtained at the second time and the detection time thereof) ( θ) is obtained for each base station ID and stored in the RAM 58b (S204). The calculation process of the gradient (θ) of the received electric field strength is performed for all the monitored base stations (S206).

When all the processes for calculating the gradient of the received electric field strength are completed, two base stations are arbitrarily selected from among them (S
208). Here, the two selected base stations are referred to as base station 1 and base station 2 for convenience. The latest difference ΔRSSI of the latest received electric field strength monitored for the second time by the selected base station 1 and base station 2 is obtained by the following equation (1) (S210). ΔRSSI = RSSI_1−RSSI_2. . . (1) where RSSI_1 is the received electric field strength of the base station 1 RSSI_2 is the received electric field strength of the base station 2 In the case of an intensity gradient,
The processing shown in FIG. That is, for example, FIG.
If the slope of the electric field intensity so that the inclination is the inclination of the base station 2 in the negative positive electric field strength of the base station 1 as shown in (A) are different, the received field strength at the time a ₁ base station 1 RSSI_1
One of the base stations is selected according to the processing flow of FIG. 3A, based on the received electric field strength RSSI_2 and the angle θ2 of the base station 2 at time a ₂ and the angle θ1.

First, RSSI_1-R which is ΔRSSI
SSI_2 is larger than 8 dB or 3 dB or more and 8 dB
It is determined whether it is below or less than 3 dB (S226). RSS
If I_1-RSSI_2 is larger than 8 dB, the base station 1 is selected regardless of the inclination of the angle θ1 of the base station 1 and the inclination of the angle θ2 of the base station 2. Also, RSSI_1-RSSI_2
Is between 3 dB and 8 dB, if | θ1 | ≦ | θ2 |, base station 1 is selected (S228, S232), and | θ
If 1 | ≦ | θ2 |, the base station 2 is selected (S22
8, S230). Further, RSSI_1-RSSI_2
Is less than 3 dB, the base station 2 is selected (S23).
0).

Returning to FIG. 2, the inclinations of the two base stations, base station 1 and base station 2, are compared (S212). If the inclinations of the electric field strength are the same as shown in FIG. Is selected (S214). Therefore, in FIG. 4B, the base station 1 is selected. Such comparison selection processing is performed for all monitored base stations (S21
8) Narrow down the base station candidates to be selected to three (S22)
0). Then, as shown in FIG. 3B, monitoring is again performed on the three candidate base stations (S236),
The base station having the highest received electric field strength is selected as the best base station to perform the standby processing from among them (S238, S2).
40). The third monitoring performed in step S236 is performed, for example, one to two seconds after the second monitoring is performed.

Although the embodiments of the present invention have been described in detail, the present invention is not particularly limited to the embodiments shown here. That is, in step S116 of performing the optimal base station prediction processing and selection in FIG. 1, the base station that changes with the slope at which the received electric field strength is increased is extracted, and the base station with the latest received electric field strength is extracted from among them. It is also possible to use a prediction algorithm that selects one of the three base stations, monitors these three base stations again, and selects a base station having the highest received electric field strength from the three base stations as a base station during standby.

Also, in the present embodiment, the received electric field strength of the base station is measured twice, the difference is processed, and prediction is performed by linear approximation. Instead, another processing method, such as a prediction method based on quadratic curve approximation, may be used.

Furthermore, in the present embodiment, a mobile communication terminal connected to a public base station has been described as an example, but the present invention is not particularly limited to a public network. That is, if the communication system is a communication system that wirelessly communicates by arranging a plurality of fixed base stations regularly, including, for example, self-managed systems such as private telephones and cordless telephones for home use, without being limited to mobile terminals. The present invention is widely applicable to communication systems that exchange information wirelessly.

Further, specific numerical values and the like shown in the prediction algorithm for base station selection described in the present embodiment are merely shown as embodiments, and are not particularly limited thereto.

[0030]

As described above, according to the method of the present invention, it is possible to predict in advance which base station will be the next best, and to wait for the predicted base station. Therefore, the best base station can be predicted and selected even when the mobile communication terminal is moving or when the received electric field strength during movement is fluctuated due to the influence of surrounding buildings and the like. . Therefore, outgoing and incoming calls can be reliably performed, and the call quality during a call can be ensured in a better state than before.

[Brief description of the drawings]

FIG. 1 is a flowchart showing an embodiment of a method of selecting a base station when a mobile communication terminal waits according to the present invention.

FIG. 2 is a flowchart showing an example of an optimal base station prediction process and selection in the process flow shown in FIG. 1;

FIG. 3 is a processing flow (A) illustrating an example of base station selection processing when two base stations have different inclinations, and a processing flow of selecting an optimal base station from base stations selected as candidates ( The flowchart which showed B).

FIG. 4 is an explanatory diagram showing an example of a case where the slopes of the received electric field strengths of two base stations are different (A) and an example of the same case (B).

FIG. 5 is a block diagram showing an embodiment of a mobile communication terminal to which the present invention is applied.

[Explanation of symbols]

 54 RF unit 56 Baseband unit 58 CPU 58a ROM 58b RAM

Claims (9)

[Claims] 1. A method for selecting a base station when a mobile communication terminal is on standby, comprising the steps of monitoring a communicable base station at predetermined intervals, and measuring a received electric field strength of the base station selected by the monitoring for each base station. A first step of storing the received electric field strength as time series data, a second step of calculating a gradient of the received electric field strength for each of the monitored base stations from time series data of the received electric field strength stored in the first step, The monitoring was performed by the latest value of the received field strength for each base station in the time-series data stored in the first step and the slope of the received field strength for each base station calculated in the second step. A third step of predicting a base station that can obtain an optimum reception electric field strength from among the base stations. Base station selection method. 2. A method for selecting a base station when a mobile communication terminal is on standby, wherein a communicable base station is monitored at predetermined intervals, and the received electric field strength is stored as time-series data for each base station. A step of calculating a gradient of the received electric field strength for each monitored base station from time-series data of the received electric field strength stored in the first step; and Optimum reception among the monitored base stations by the latest value of the received field strength for each base station in the sequence data and the slope of the received field strength for each base station calculated in the second step. A third step of predicting a base station from which electric field strength can be obtained and selecting a predetermined number of base stations; and monitoring the base station selected in the third step again, and Base station selecting method during standby of a mobile communication terminal; and a fourth step of selecting the most received electric field intensity higher base station. 3. The base station selection method according to claim 1, wherein the second step stores the reception electric field strength of the base station selected at the time of monitoring in association with a base station ID. A first monitoring step to be performed, monitoring is performed again after monitoring in the first monitoring step, and the base station selected at this time is associated with the base station ID stored in the first monitoring step. A second monitoring step of storing the received electric field strength; and a change of the received electric field strength for each base station ID obtained in the first monitoring step and the second monitoring step, wherein the change of the received electric field strength for each of the selected base stations is performed. Calculating a gradient of the received electric field strength, the mobile communication terminal comprising: Local station selection method. 4. The base station selection method according to claim 3, wherein the number of base stations selected in the first monitoring step and the second monitoring step is out of a predetermined range. A method for selecting a base station in a standby state of a mobile communication terminal, wherein the monitoring is performed again by changing a threshold value of a received electric field strength, which is control data for selecting the number of the mobile communication terminals. 5. The base station selection method according to claim 1, wherein the third step is performed by selecting a latest one of the two base stations selected from the plurality of base stations stored in the first step. A base station at the time of standby of a mobile communication terminal, wherein a base station that obtains an optimum reception field strength is narrowed down by comparing and selecting a reception field strength and an inclination according to a predetermined algorithm, and repeating the procedure sequentially. Selection method. 6. The base station selection method according to claim 5, wherein the predetermined algorithm is that the inclinations of the first base station and the second base station, which are the two selected base stations, are in the same direction. The latest received electric field strength is selected, the inclination of the first base station is a negative inclination in which the received electric field strength decreases, and the inclination of the second base station is the received electric field strength. In the case of a positive slope that is an increasing direction, when a value obtained by subtracting the latest reception field strength of the second base station from the latest reception field strength of the first base station is larger than the first value, Selecting the first base station, wherein the value obtained by subtracting the latest received electric field strength of the second base station from the latest received electric field strength of the first base station is equal to or greater than a second value, and If the value falls within the range, the absolute value of the negative slope is smaller than the absolute value of the positive slope. In this case, the first base station is selected. If the absolute value of the negative slope is larger than the absolute value of the positive slope, the second base station is selected. Mobile communication characterized by selecting the second base station when a value obtained by subtracting the latest received electric field strength of the second base station from the latest received electric field strength is smaller than the second value. A method of selecting a base station when the terminal is on standby. 7. The base station selection method according to claim 6, wherein the first value is 8 dB and the second value is 3 dB. Selection method. 8. The base station selecting method according to claim 1, wherein the third step extracts a base station that changes with a slope at which the received electric field intensity increases, and from among the extracted base stations, A method for selecting a base station when a mobile communication terminal waits, wherein a base station having a high electric field strength is selected. 9. A mobile communication terminal having a standby function of selecting a base station in a located wireless zone by monitoring a base station capable of communication in a standby state, wherein the monitoring of the base station is performed by a predetermined number. At least 2 in intervals
Monitoring means for successively performing the operation and storing the resulting received electric field strength as time-series data for each base station identification number; and for each base station from the base station time-series data stored for each identification number. Receiving electric field intensity change calculating means for calculating a change in the received electric field intensity, the latest received electric field intensity at each base station with reference to the time-series data of the base station stored for each identification number, and the received electric field intensity A mobile communication terminal comprising: a base station selecting unit that selects a base station in the in-area wireless zone based on a change in the received electric field strength at each base station calculated by a change calculating unit.