JP2001112039A - Mobile wireless terminal - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To provide a mobile radio terminal capable of performing an accurate handover and performing a stable call. SOLUTION: A reception field strength detection unit 16 detects a plurality of samples of RSSIs of a plurality of connectable PHS base stations, and a control unit 100 detects a PHS base station in which an RSSI detection value tends to increase from the detection result. That is, a process of adding the priority point to the RSSI detected from the PHS base station existing in the direction in which the PHS terminal device approaches is performed. Each unit is controlled so as to perform handover to the PHS base station having the largest RSSI among the processing results.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to, for example, PHS
(Personal Handyphone System) and PDC (PublicDigi
TAL Cellar) TDMA (Time D
ivision Multiple Access) system.

[0002]

2. Description of the Related Art As is well known, for example, in a PHS terminal device, when performing a handover, communication is temporarily interrupted to search for a connectable base station, and the above search is performed according to a sequence as shown in FIG. Handover is performed based on the result.

[0003] However, in the conventional PHS terminal device, when it is in a stationary state, it is possible to select and connect an effective base station accurately by the above-mentioned handover. In such a case, there is a problem in that even if the base station is in a direction away from the terminal, the connection is established, and it is necessary to perform the handover immediately after the handover, and the call is frequently interrupted.

[0004] Fig. 8 shows an example of this. When the PHS terminal device moves to the point A, the PHS terminal device receives the received electric field strength from the connected base station 1 despite the presence of the base station 3 in the traveling direction. Handover to the strongest base station 2 is performed. However, since base station 2 is a base station that has already gone away,
Handover to the base station 3 will be performed at the point.

In addition, when a handover is performed due to a decrease in signal strength received from a connected base station (switching base station), connection with a new base station (switching base station) suitable for communication is established. If not successful, as shown in FIG. 9, a switchback operation for reconnecting to the original base station (switching base station) is performed.

However, as shown in, for example, FIG. 10, when a wireless zone formed by a base station is moving in an area where the radio zone is depopulated, such as when passing through a tunnel, a new radio network suitable for communication is required. Not only was a simple base station not found, but also because it was moving away from the original base station, it could not be reconnected and the communication link was opened.

[0007]

In a conventional mobile radio terminal, a handover is performed to a base station in a direction away from the mobile station, and it is necessary to perform the handover immediately or when the handover is performed. In addition, there is a problem that not only a new base station suitable for communication cannot be found, but also the original base station cannot be reconnected and a communication link is opened.

[0008] The present invention has been made to solve the above problem, and has as its object to provide a mobile radio terminal capable of performing an accurate handover and performing a stable call.

[0009]

In order to achieve the above object, a first aspect of the present invention is directed to a mobile radio terminal which selectively connects to a plurality of base stations connectable to a network by a time division multiplex method. An electric field strength detecting means for detecting electric field strengths of radio signals received from a plurality of base stations; and a receiving apparatus in which the electric strengths are increasing based on the received electric field strengths of the plurality of base stations detected by the electric field strength detecting means. A base station detecting means for detecting a base station capable of obtaining an electric field strength; and a base station detecting means for detecting a base station in place of the connected base station when a communication condition with the connected base station is deteriorated below a preset condition. The base station detected by the means is provided with a handover control means for preferentially making a wireless connection.

[0010] In the mobile radio terminal having the above-described configuration, when a communication situation with the connected base station is degraded and a handover is performed, a base station that can obtain a receiving electric field strength that tends to increase is provided.
Handover is performed preferentially.

[0011] Therefore, according to the mobile radio terminal having the above configuration, even if the received electric field strength is large, the mobile station is preferentially connected to the approaching base station rather than the far away base station. It can be performed.

A second invention provides a mobile radio terminal which selectively connects to a plurality of base stations connectable to a network by a time-division multiplexing method, in a receiving radio field intensity of radio signals from the plurality of base stations. When the communication condition with the connected base station deteriorates below a preset condition, instead of the connected base station,
First handover control means for wirelessly connecting to another base station, and switchback connection control for wirelessly connecting to the base station that was connected when the first handover control means does not allow wireless connection to another base station. Means and the return connection control means, when it is not possible to wirelessly connect to the base station connected within a predetermined time, based on the received electric field strengths of the plurality of base stations detected by the electric field strength detecting means, suitable for communication. Second handover control means for wirelessly connecting to the base station is provided.

[0013] In the mobile radio terminal having the above configuration, when the handover performed due to the deterioration of the communication condition with the connected base station fails and the connection is switched back to the connected base station, a predetermined time is required. If reconnection is not possible even after
Based on the received electric field strength detected in advance, handover to an appropriate base station is performed by communication.

Therefore, according to the mobile radio terminal having the above configuration, before the communication link is released due to the failure of the reconnection, the connection is attempted to another base station. Can make calls.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of a mobile radio terminal according to the present invention will be described below with reference to the drawings. Here, a PHS terminal device will be described as an example. FIG. 1 shows the configuration.

The PHS terminal shown in FIG. 1 includes a radio unit 10 having an antenna 11, a modem unit 20, a TDMA
Unit 30, speaker 43 and microphone 44 (M)
, A call notification unit 50, and a memory unit 6
0, the user interface unit 70, and the battery 80
, A battery monitoring unit 90, and a control unit 100.

A radio frequency signal transmitted from a PHS base station via a radio communication channel is received by an antenna 11 and then input to a receiving unit 13 via a high frequency switch (SW) 12 of a radio unit 10.

In the receiving section 13, the received radio frequency signal is mixed with a receiving local oscillation signal generated from the frequency synthesizer 14 and frequency-converted into a receiving intermediate frequency signal.

The local oscillation frequency generated by the frequency synthesizer 14 is instructed by the control unit 100 according to the radio channel frequency. Further, the radio unit 10 is provided with a reception field strength detection unit (RSSI) 16.

The reception field strength detection section 16 receives a radio field signal from a PHS base station (hereinafter, referred to as reception field strength).
RSSI) is detected, and the detected value is
00 is notified.

The received intermediate frequency signal output from the receiving section 13 is input to a demodulating section 21 of a modem section 20. The demodulation section 21 performs digital demodulation of the received intermediate frequency signal, thereby reproducing a digital communication signal.

TDMA decoding section 31 of TDMA section 30
Then, the digital communication signal is decomposed for each time slot according to the instruction of the control unit 100. Then, of the plurality of decomposed digital communication signals, the digital communication signal of the slot addressed to the own device is input to the communication unit 40.

The communication unit 40 comprises an adaptive difference PCM transcoder (ADPCM TRANS CODER) 41 and a PCM codec (PCM CODEC) 42, and the digital communication signal is generated by the adaptive difference PCM transcoder 41 and PC
The signal is sequentially decoded by the M codec 42 and reproduced into an analog call signal. The analog communication signal is amplified by a receiving amplifier (not shown) and then output from the speaker 43.

On the other hand, the transmission voice input to the microphone 44 is sequentially encoded by the PCM codec 42 and the adaptive difference PCM transcoder 41 to become a digital communication signal, which is input to the TDMA encoder 32.

In the TDMA encoder 32, the digital speech signal output from the adaptive difference transcoder 41 is inserted into a time slot specified by the controller 100 and input to the modulator 22. In the modulation unit 22,
The carrier signal is digitally modulated by the digital communication signal. The carrier signal thus modulated is
It is input to the transmission unit 15.

In the transmitting section 15, the modulated carrier signal is mixed with the transmitting local oscillation signal generated from the frequency synthesizer 14 to be frequency-converted to the radio channel frequency specified by the control section 100. It is amplified to a predetermined transmission power level. Then, the radio frequency signal whose frequency has been converted and amplified by the transmission unit 15 is transmitted from the antenna 11 via the high frequency switch 12 to the PH.
It is transmitted to the S base station.

The incoming call notifying section 50 notifies the user of an incoming call under the control of the control section 100 when there is an incoming call to the terminal device. , Light-emitting body 52 that gives notification by light emission
And a vibrating body 53 that generates vibrations by, for example, an eccentric motor or the like to perform notification.

The memory section 60 uses a semiconductor memory such as a ROM or a RAM as a storage medium. The storage medium includes a control program of the control section 100, ID data of the self-device required for authentication, and various control programs. Data, various setting data, dial data corresponding to abbreviated dialing and the like are stored.

The user interface unit 70 includes a display unit 71 and a key input unit 72. The display unit 71 is composed of, for example, an LCD (Liquid Crystal Display), and is used to visually indicate to the user the state of the own device (outgoing / incoming, remaining battery level, receiving strength) and dial data read from the memory unit 60. belongs to.

The key input section 72 includes keys for performing normal functions relating to outgoing / incoming calls such as a numeric keypad for inputting a dial number, and an incoming call notifying method (audible sound / light emission /
It is provided with a function setting key for performing various settings such as switching between vibrator and no notification).

The battery 80 is composed of a secondary battery such as a lithium ion battery or a nickel hydride battery, and is a driving power source for the terminal device. The battery monitoring unit 90 monitors the battery 80. In addition to the function of detecting the remaining amount of the battery and notifying the control unit 100, the battery monitoring unit 90 also
Is provided with charge detection means 91 for detecting whether or not the battery is being charged.

The control unit 100 includes, for example, a microcomputer as a main control unit. The control unit 100 controls each unit related to the communication as described above, and stores it in the memory unit 60 in response to a user's request through the key input unit 72. Various controls such as editing control of dial data to be performed are performed.

In preparation for a handover, the control unit 100 detects a plurality of connectable PHS base stations in advance based on the RSSI detected by the reception electric field strength detection unit 16, and if a handover becomes necessary, Among the plurality of detected PHS base stations, control is performed to preferentially handover to the PHS base station in which the RSSI is increasing.

Next, the operation of the PHS terminal having the above configuration will be described below. Note that the description of ordinary outgoing / incoming calls is omitted because the operations are the same as those in the related art. FIG. 2 is a flowchart for explaining this control.

First, in step 2a, as shown in FIG. 3, at the timing of a reception slot that is not used for communication, the RSSI detection values from a plurality of PHS base stations other than the currently connected one are sampled, for example, by three samples. And the process proceeds to step 2b. FIG. 4 shows an example of the detection data in this step.

In step 2b, based on the detection result in step 2a, the PHS in which the RSSI detection value is increasing
For example, “5 dB” is added as a priority point to the latest RSSI detection value of the base station, and the process proceeds to step 2c.

In step 2c, based on the result of adding the priority points in step 2b, the latest RSSI detection value of each PHS base station is compared, and
The PHS base station from which the SI detection value is obtained is selected, and the process proceeds to step 2d.

Then, in step 2d, step 2c
Perform handover to the PHS base station selected in, and end the process.

In this process, assuming that the RSSI detection value as shown in FIG. 4 is obtained from each PHS base station, as shown in FIG.
The base station 2 having the largest I detection value is selected.

However, in the PHS terminal device, RSS
The base station 3 is selected by adding the priority point to the RSSI detection value of the base station 3 whose I detection value is increasing in step 2b.

As described above, the PHS terminal having the above-described configuration detects a plurality of samples of the RSSIs of a plurality of connectable PHS base stations, and from this detection result, the PHS base station whose RSSI detection value tends to increase, that is, R detected from the PHS base station existing in the direction in which the PHS terminal device approaches
A process for adding a priority point to the SSI is performed. Then, P having the largest RSSI among the processing results
Handover to the HS base station is performed.

Therefore, according to the PHS terminal device having the above-described configuration, the handover is preferentially performed to the PHS base station existing in the direction in which the terminal is approaching, so that the handover to the PHS base station in the direction away from the terminal is possible. Therefore, it is possible to perform an accurate handover and to make a stable call.

The present invention is not limited to the above embodiment. For example, the control unit 100 attempts to reconnect to the original PHS base station without performing handover to a new PHS base station as a result of performing a handover when the RSSI detection value of the communication slot falls below a preset threshold. When the return connection processing occurs, after a predetermined time has elapsed, control is performed to connect to the PHS base station including the original PHS base station, the RSSI detection value of which exceeds the preset threshold value.

Hereinafter, a mobile radio terminal having such a configuration including the control unit 100 will be referred to as a second embodiment, and description of ordinary outgoing / incoming calls will be omitted because the operations are the same as those in the related art. In particular, a description will be given of handover control in a case where a connection to a new PHS base station is not made and a return connection is started.

FIG. 6 is a flowchart for explaining the operation. This processing is performed by the control unit 100 when the return connection is started. First, in step 6a, since the reconnection is started, the timer in the control unit 100 is started, and the process proceeds to step 6b.

In step 6b, it is re-connected to the PHS base station connected before the handover, and it is monitored whether or not the switching back is successful. Here, if the return is successful, the process is terminated. On the other hand, if the connection is not yet reconnected to the PHS base station and the return is not successful,
Move to step 6c.

In step 6c, it is determined whether the timer started in step 6a has counted a predetermined time or more. Here, if the timer has counted a predetermined time or more, the process proceeds to step 6d, while if the count value is less than the predetermined time, the process proceeds to step 6b.

In step 6d, the reception electric field strength detection section 1
The RSSI detected in step 6 is monitored to detect the PHS base station having the largest RSSI detection value, including the PHS base station connected before the handover, and the process proceeds to step 6e. In step 6e, handover control for connecting to the PHS base station having the largest RSSI detection value detected in step 6d is performed, and the process ends.

As described above, in the PHS terminal having the above-described configuration, before the switching back operation after the handover failure takes a predetermined time or more and the radio link is released,
During the switchback operation, a PHS base station with which communication is possible is searched for and connected.

Therefore, according to the PHS terminal having the above-mentioned configuration, even if the reverting operation is not completed immediately, the connection is made to the PHS base station that can be connected during the reverting operation, so that the wireless link is opened. Communication can be continued without being performed.

The present invention is not limited to the above embodiment. For example, also in the second embodiment,
To detect the RSSI of the radio signal from the base station, the first
Similarly to the embodiment, when the PHS terminal device is performing communication through a certain PHS base station, the PHS terminal device transmits the PHS terminal device at a timing of a reception slot other than the reception slot used for communication by the PHS terminal device. The RSSI of a radio signal from a base station other than the base station in communication may be detected. It goes without saying that various modifications can be made without departing from the spirit of the present invention.

[0052]

As described above, according to the first aspect of the present invention, when a communication situation with a connected base station is deteriorated and a handover is performed, a base station capable of obtaining a receiving electric field strength which tends to increase is provided. Handover is performed preferentially.

Therefore, according to the first aspect of the present invention, even if the received electric field strength is large, the base station is preferentially connected to the base station approaching rather than the base station moving away. It is possible to provide a mobile radio terminal capable of performing the operation.

According to the second aspect of the present invention, if the handover performed due to the deterioration of the communication condition with the connected base station fails and the connection is switched back to the connected base station for a predetermined time, If reconnection is not possible even after elapse, the handover to a suitable base station for communication is performed based on the received electric field strength detected in advance.

Therefore, according to the second aspect of the present invention, a connection is attempted to another base station before the communication link is released due to the failure of the switch-back connection. A mobile radio terminal capable of performing the following.

[Brief description of the drawings]

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

FIG. 2 is a flowchart for explaining handover control in the first embodiment of the mobile radio terminal shown in FIG. 1;

FIG. 3 is a diagram illustrating an example in which the mobile radio terminal according to the first embodiment uses RSS.
The figure for demonstrating the timing which performs I detection.

FIG. 4 is a diagram illustrating an example of a mobile radio terminal according to the first embodiment;
The figure which shows an example of SSI detection result.

FIG. 5 is an exemplary view for explaining a priority order of PHS base stations selected by the mobile radio terminal according to the first embodiment;

FIG. 6 is a flowchart for explaining handover control in a second embodiment of the mobile wireless terminal shown in FIG. 1;

FIG. 7 is a diagram showing a sequence flow performed between a PHS terminal device and a PHS base station at the time of handover.

FIG. 8 is a diagram for explaining a problem of a conventional mobile radio terminal.

FIG. 9 is a diagram showing a sequence flow for explaining a switching operation in which handover fails and the PHS terminal device reconnects to the original PHS base station.

FIG. 10 is a diagram illustrating a problem of a conventional mobile wireless terminal.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 ... Radio | wireless part 11 ... Antenna 13 ... Receiving part 14 ... Frequency synthesizer 15 ... Transmitting part 20 ... Modem part 21 ... Demodulation part 22 ... Modulation part 30 ... TDMA part 31 ... TDMA decoding part 32 ... TDMA encoding part 40 ... Communication part 41 … Adaptive difference PCM transcoder (ADPCM TRANS CO
DER) 42 PCM CODEC 43 Speaker 44 Microphone (M) 50 Incoming notification unit 51 Speaker 52 Light emitter 53 Vibrator 60 Memory unit 70 User interface unit 71 Display unit 72 ... key input unit 80 ... battery 90 ... battery monitoring unit 91 ... charge detection means 100 ... control unit

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Akihito Tsukamoto 3-Terminal, Asahigaoka, Hino-shi, Tokyo F-term in the Toshiba Hino Plant (reference) 5K067 AA26 AA33 BB04 CC04 EE02 EE10 EE24 GG11 HH22 JJ37

Claims (3)

[Claims] 1. A mobile radio terminal that selectively connects to a plurality of base stations connectable to a network by a time division multiplexing method, wherein a field strength for detecting a reception field strength of a radio signal from the plurality of base stations is provided. Detecting means, and base station detecting means for detecting, based on the received electric field strengths of the plurality of base stations detected by the electric field strength detecting means, a base station capable of obtaining a received electric field strength whose strength tends to increase, When the communication status with the base station deteriorates below a preset condition, handover control for giving priority to the base station detected by the base station detecting means in place of the currently connected base station and performing wireless connection is performed. And a mobile radio terminal. 2. A mobile radio terminal which selectively connects to a plurality of base stations connectable to a network by a time division multiplexing method, wherein an electric field intensity for detecting a reception electric field intensity of a radio signal from the plurality of base stations is provided. Detecting means; and first handover control means for wirelessly connecting to another base station in place of the connected base station when the communication condition with the connected base station is deteriorated below a preset condition. When the first handover control means does not enable wireless connection with another base station, a return connection control means for wirelessly connecting to the connected base station; If it is not possible to wirelessly connect to the base station that was connected to the base station, the wireless connection to a base station suitable for communication is performed based on the received electric field strengths of the plurality of base stations detected by the electric field strength detection means. Mobile radio terminal characterized by comprising a second handover control means for. 3. The wireless communication apparatus according to claim 1, wherein said electric field strength detecting means receives a radio signal from a base station other than the base station with which it is communicating in a receiving slot other than the receiving slot used for its own communication during its own communication. The mobile radio terminal according to claim 1 or 2, wherein the mobile radio terminal detects an electric field strength.