JP3213475B2 - Digital mobile phone - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a recall function in a digital portable telephone capable of communicating with a destination via a destination base station.

[0002]

2. Description of the Related Art A digital portable telephone is also called a PDC (Personal Digital Cellular) system and is an efficient wireless telephone system employing a digital system. In other words, the digitization has improved the frequency use efficiency and communication quality, and further enhanced the confidentiality function and communication contents, etc., and further reduced the size of the terminal by converting the components to LSI. It is planned.

[0003] Further, because of the cellular system, the area where telephone service is provided is divided into small areas called cells (with a radius of about 2 to 5 km).
Each cell is provided with a base station serving as a wireless relay station of a terminal located in the cell. Then, the terminal moves between adjacent cells to change the base station (in this case, switching of a communication channel is performed), so that a wide range of mobile communication can be performed. Such a system is called a small zone system, and has an advantage that a radio wave output can be small and a limited frequency can be effectively used, and it has become a mainstream of mobile communication in the near future.

The specifications of the digital portable telephone are as follows. The operating frequency band is 800MHz band and 1.5G
Hz band is assigned. Terminals (mobile stations)
Has a maximum transmission output of 0.3 to 3 W, a modulation method of π / 4 shift QPSK, and a communication method of a TDMA method (time division multiple access method). In the time division multiple access system, a synchronization signal serving as a time reference is transmitted from one base station to each mobile station located in a cell, and each mobile station transmits the synchronization signal. To determine the time reference, and confirm the time positions in the downlink (circuit for receiving signals transmitted from the base station) and the uplink (circuit for transmitting signals to the base station) allocated to the own station. Then, each communication line is captured.

[0005] Specifically, the setting of a communication path between a mobile station and a base station is performed as follows. First, the base station transmits, via a broadcast channel (BCCH), broadcast information such as radio channel information and system information (where a synchronization signal is placed) to the mobile station. The mobile station that has received the broadcast information transmits a “communication channel allocation request” to the base station through an individual control channel (SCCH). Upon receiving this, the base station monitors the uplink communication channel, selects an available channel from the plurality of communication channels determined to be unused, and allocates the available channel to the mobile station. Note that such a channel assignment scheme is called a dynamic channel assignment scheme. Then, the mobile station starts transmission to the base station using the assigned communication channel.

[0006]

The mobile station measures the electric field strength of the received radio wave for each arriving burst. This is because the reception level of the radio wave is affected by the relative communication distance with the base station, the deterioration of the radio wave condition due to buildings existing on the radio wave propagation path, and other factors such as burst interference with other stations. For this reason, even if a dial key is input to perform a call and a calling process is performed, the reception level is low and the connection with the base station may not be successful. In such a case, a recall process is usually performed.

FIG. 3 is a flowchart showing dialing and recalling processing performed by a conventional portable telephone.
That is, when waiting, a process for waiting for an incoming call is performed (S31). Then, when the dial key is input (Yes in S32), a calling process is executed (S33). Here, when the call is successful (S34)
In the case of “Yes” in the above), the process subsequently proceeds to the call processing. If the call has failed due to a timeout (No in S34), the process returns to the standby state in step S31. If the call is to be made again,
The process shifts to the process of step S32, and the dial key of the same number is input again to make a call, or the input of the redial key is awaited (in the case of Yes in S35), and then the call is made again.

As described above, in a conventional mobile phone, when a call is to be made again, the telephone number of the other party must be remembered,
It is necessary to perform the key operation of inputting the same dial key or inputting the redial key again. Even if the call is re-issued by such a key operation, if the reception level is still low, the key operation of the re-call must be further performed, so that the key operation becomes troublesome and unless the reception level is improved to some extent. However, the calling success probability is also low.

The present invention has been made in view of such circumstances, and has as its object to provide a digital portable telephone having an automatic recall function with a high probability of success.

[0010]

According to one aspect of the present invention, there is provided a digital portable telephone capable of communicating with a destination via a destination base station, Storage means for storing the telephone number of the call destination, and the electric field strength of the received radio wave measured at the time of the call failure and thereafter, and the determination means for determining the stored electric field strength at the time of the call failure at several levels. And when the determination unit determines that the electric field strength at the time of the call failure is a low level at which communication is difficult, the first level based on the electric field strength measured and stored after the time of the call failure is used as a reference. The first detecting means for detecting whether or not the communication time has reached the predetermined time, and when the determining means determines that the electric field strength at the time of the call failure is at a low level at which communication failure occurs, a predetermined time period elapses. , After the point of failure Constant and the electric field strength stored in said first
A second detecting means for detecting whether or not a second level, which is a reference higher than the predetermined level, has been reached, and the predetermined time has elapsed based on the detection result of the first or second detecting means. And a re-calling means for re-calling the same destination.

[0011]

According to the above arrangement, the storage means stores the telephone number of the called party, the time of the call failure, and the electric field strength of the received radio wave measured after that. Then, the level of the electric field strength at the time of the failure of the call is determined in several stages by the determining means. Here, if it is determined that the electric field strength at the time of the call failure is at a level at which communication is difficult, the first
The detection means detects whether or not the electric field strength measured and stored after the failure of the call has reached the first reference level.

If it is determined that the electric field strength at the time of the call failure is at a low level at which communication is poor, the second detecting means measures the time after the failure of the call until a predetermined time elapses. It is detected whether or not the electric field strength stored as described above has reached a second level which is a reference larger than the first level. Then, based on the detection result of the first or second detecting means or when the predetermined time has elapsed, the re-calling means makes a re-call to the same destination.

As a result, when communication is difficult or communication is poor, re-calling is automatically performed after the electric field strength of the received radio wave is improved, and the success probability of re-calling is determined. Is improved.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be specifically described below with reference to the drawings. FIG. 1 is a block diagram showing a circuit configuration of a digital mobile phone according to the present invention. The circuit configuration of this digital mobile phone will be described together with its operation. RF ・ I
In the F unit 1, the frequency conversion of the burst signal input / output from the antenna is performed. The modulation / demodulation unit 2 performs modulation / demodulation of π / 4 shift 4-phase QPSK. The digital signal processing circuit 3 performs digital signal processing such as TDMA processing. In the audio signal processing circuit 4, ADPCM /
PCM conversion and D / A and A / D conversion are performed.
Further, the microphone connected to the audio signal processing circuit 4 is used for inputting a transmitted voice, the ringer is used for outputting a ringing tone, and the speaker is used for outputting a received voice.

On the other hand, at the time of reception, various data for control is extracted by the digital signal processing circuit 3 and the control device 5
Is input to At the time of transmission, the control data output from the control device 5 is processed by the digital signal processing circuit 3 and is superimposed on the transmission radio wave. Then, based on the control data (message or the like), the control device 5 executes a protocol such as calling and receiving with the base station (and the base unit).

[0016] In addition, for each burst in which the electric field strength (RSSI) of the received radio wave arrives (the burst cycle is about several ms), R
It is measured by the F / IF unit 1 and input to the control device 5 as RSSI data. Further, the control device 5 is provided with a timer 50 for counting a predetermined time until a call is re-established. In addition to the display unit 6 and the key input unit 7, a memory 8 is connected.

The memory 8 stores the last dialed number as a redial number in order to redial the call, and also stores RSSI data (OLD RSD data) measured when the call failed.
SI), RSSI data measured thereafter (this is called NEW RSSI), and other telephone numbers and the like are stored in the respective storage areas. The display unit 6 is formed of an LCD, and the input R
The comparison result of the RSSI level determined by the control device 5 based on the SSI data is displayed as a pictogram as described below.

Strong electric field ──── → ‖ ‖ ３ (3 bars displayed) Medium electric field ──── → ‖ ‖ (2 bars displayed) Weak electric field ──── → ‖ (1 bar displayed) Super weak Electric field ──── → (no bar display) Out of service ──── → Out of service (character display) Here, the “strong electric field” is a reception level exhibiting an electric field strength of about 23 dBμ or more. Is 17 to 22 dBμ, “weak electric field” is 11 to 16 dBμ,
The “ultra-weak electric field” is a reception level that exhibits an electric field strength of 5 to 10 dBμ, and the “out of range” is an electric field strength of 4 dBμ or less. Note that the electric field strength when a voltage of 1 μV is induced in an antenna having an execution length of 1 m is 1 dBμ.

The case where the reception level is "strong electric field" is a state in which a normal telephone call is performed, and as the state changes from "medium to weak", the state of the telephone becomes more difficult. Also, in the case of "ultra-weak electric field", it is extremely difficult to talk, and in the case of "out of service", it is impossible to talk at all. In a digital mobile phone, when the reception level of a radio wave decreases, occurrence of a bit error in a digital signal processing circuit is unavoidable, and the influence of external noise and the like cannot be ignored, so that communication becomes difficult. In such a case, unless the mobile station moves to a position where the reception level is improved, communication with the base station cannot be performed. Therefore, by displaying the RSSI level as described above, the movement of the terminal is encouraged.

For measuring the electric field strength of the received radio wave, a measuring instrument is connected to the input end of the intermediate amplifier circuit in the RF / IF unit 1 shown in FIG. 1 to measure the electric field strength of the received radio wave for each arriving burst. Although not shown, the configuration of the measuring device is usually composed of an amplifier, an envelope detector, and a low-pass filter. FIG.
3 is a flowchart showing dialing and recalling processing performed by the digital mobile phone shown in FIG. 1. At the time of standby, a process for waiting for an incoming call is performed (S
1). Then, in response to dial key input through the key input unit 7 (S2), a calling process is executed (S3). Here, when the call is successful (Yes in S4)
Then, the process proceeds to the call processing. If the call fails due to a timeout (No in S4), the RSSI data measured at that time is written to the OLD RSSI write area in the memory 8 (S4).
5). Then, the level of the OLD RSSI is determined (S
6) If the electric field is other than the ultra-low electric field and the weak electric field (that is, any of the strong electric field, the medium electric field, and the out-of-area), the respective states are displayed on the display unit 6 (S17). Return to the processing of. Otherwise (that is, either the weak electric field or the extremely weak electric field), the respective states are displayed on the display unit 6 (S7 and S14), and the following processing is performed according to the RSSI level of the determination result. [1] When OLD RSSI = ultra-weak electric field The reception level during movement is measured intermittently and R
The SSI data is written in the new RSSI write area in the memory 8 (S15). Then, the control device 5 determines whether the written RSSI data has reached the weak electric field level (S16). Therefore, when the RSSI data becomes the weak electric field level (Yes in S16), the calling start sound is transmitted from the speaker as a confirmation sound (S18), and is written in the redial number writing area of the memory 8. A re-call process is automatically executed using the redial number (S19). Then, when the call is successful (Yes in S20), the process proceeds to the call processing. Also, if the call fails (S
20), the process returns to step S5, and the RSSI data measured at that time is stored in the OL of the memory 8.
D Write to RSSI write area. [2] In the case of OLD RSSI = weak electric field The timer 50 is set to a predetermined time (S8), and when a timeout occurs (Yes in S9), a call start sound is transmitted from the speaker as a confirmation sound (S18). This process is executed when the probability of successful call origination is somewhat higher than that at the above-mentioned extremely weak electric field level, and automatic re-calling is performed even if the RSSI data does not reach the medium electric field level. It has become. Until the timeout occurs (in the case of No in S9), similarly to the case of [1], the reception level during the movement is intermittently measured, and the RSSI data is written in the NEW RSSI in the memory 8 each time. The data is written into the area (S10), and the control device 5 determines whether the written RSSI data has reached the middle electric field level (S1).
1). When the electric field level reaches the middle electric field level (Yes in S11), the process proceeds to step S18, and the call start sound is transmitted from the speaker as a confirmation sound.

Note that, as a result of the measurement of the RSSI data, when the mobile phone is in a standby state other than the out-of-service area, it is possible to perform a redialing process by inputting a redial key or the like. Alternatively, it is also possible to forcibly receive a redial key or the like.

[0022]

According to the present invention described above, even when the electric field strength of the received radio wave falls below the weak electric field level during the movement of the terminal and the call fails due to a timeout,
Since the re-call is automatically performed after the electric field strength increases, the success probability of the re-call increases.

Also, the user does not need to remember the telephone number of the other party, but can hear the call start tone to confirm the call to the other party. Since the key operation required for the recall of the input is omitted, the recall is quickly performed, and the usability is greatly improved.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a circuit configuration of a digital mobile phone according to the present invention.

FIG. 2 is a flowchart showing dialing and recalling processing performed by the digital mobile phone shown in FIG. 1;

FIG. 3 is a flowchart showing dialing and recalling processing performed by a conventional mobile phone.

[Explanation of symbols]

 Reference Signs List 1 RF / IF unit 2 Modulation / demodulation unit 3 Digital signal processing circuit 4 Audio signal processing circuit 5 Control unit 6 Display unit 7 Key input unit 8 Memory 50 Timer

Claims (1)

(57) [Claims] 1. A digital portable telephone capable of communicating with a destination via a destination base station, comprising: a telephone number of a calling destination; and a reception measured at the time of a call failure and thereafter. Storage means for storing the electric field strength of the radio wave; determining means for determining the stored electric field strength at the time of the call failure at several levels; and the determining means, wherein the electric field strength at the time of the call failure is a low level at which communication is difficult. If it is determined that there is, the first electric field strength measured and stored after the time of the failure of the call becomes a reference.
A first detecting means for detecting whether or not a predetermined level has been reached, and a predetermined time elapses when the determining means determines that the electric field strength at the time of the call failure is a low level at which communication is poor. Until then, second detection means for detecting whether or not the electric field strength measured and stored after the time of the failure of the call has reached a second level which is a reference higher than the first level; A recalling means for recalling the same destination based on the detection result of the first or second detection means or when the predetermined time has elapsed. .