JPH11298942A - Redialing type channel changeover processing system in portable communication terminal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a redialing type channel changeover processing system in a portable communication terminal, in which interrupt of a speech due to hand-over or a call loss due to a call connection failure at a changeover destination base station is prevented. SOLUTION: When the received electric field level of a base station 1 is decreased (102) during communication with the base station 1 through a 1st time slot (100), retrieval processing of a switching destination base station is executed (104). Then an optimum base station 2 with a received electric field level higher than that of the base station 1 is selected for a channel switching destination base station (106), and after the setup processing of a control channel has been conducted (108), a communication channel is set up by using a 2nd time slot (110), so that the communication state is set (112). Then a speech which is made through the 1st time slot is switched to the 2nd time slot (114), and when the switching processing (handover) is finished, the communication with the base station 1 being made through the 1st time slot is stopped.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a portable communication terminal, and more particularly, to a channel switching system which is advantageously applied to a portable communication terminal which performs, for example, a re-calling type channel switching (handover) process.

[0002]

2. Description of the Related Art The radio channel control system of a portable communication terminal includes:
There are two types, a centralized control system and an autonomous distributed control system. The centralized control system is a system in which base stations and control stations control and control radio channels in a centralized manner. The autonomous distributed control system distributes control functions to the base station and mobile communication terminals to control autonomously. It is a method to do.

The autonomous decentralized system is a radio line control system applied to, for example, PHS, analog cordless, and the like.
When a mobile communication terminal of this type moves between cells while communicating, it performs a call re-establishment, sets a new radio channel with a new base station, and performs a channel switching (handover) process.

FIG. 3 is a process flow showing a channel switching process of a PHS terminal in the prior art. In the figure, the PHS terminal, when communicating with the base station 1 (300), receives a handover instruction from the base station 1 or detects that the reception electric field level with the base station 1 has decreased (3).
02), transmission and reception with the base station 1 are stopped (304).

[0005] Then, a switching destination base station search process is executed (306). Specifically, the control channel transmitted from the base station is monitored, and the base station having the highest received electric field level is selected as the base station 2 from among the control channels (30).
8). Next, the PHS terminal establishes a control channel with the base station 2 (310), establishes a communication channel (312), and transitions to a communication state (314).

In the PHS, the radius of the communication area is 100 to 2
Since it is as narrow as 00 m, handover is inevitably frequently performed, for example, even if a call is made while walking, and the switching process at the time of handover greatly affects the call quality. For this reason, for example, in Japanese Patent Application Laid-Open No. 8-154269, the handover timing is detected not by the control carrier but by the communication carrier so that a reliable handover can be performed.

[0007]

However, even in such a PHS terminal channel switching process in the prior art, the handover performs a recalling type switching process, so that it takes a long time to shift from the base station 1 to the base station 2. This causes a problem that a call is interrupted. Further, if the call connection in the base station 2 fails, a call loss may occur, and there is a problem that the call is completely disconnected.

[0008] Such a problem as a break in communication at the time of handover hardly occurs in a portable telephone, a car telephone, or the like using the above-mentioned centralized control system. In addition, in these portable telephones, car telephones and the like, call loss due to movement is very small as compared with PHS. For this reason, compared to mobile phones and car phones,
These problems at the time of handover are major issues in improving the PHS communication quality.

The present invention solves the above-mentioned problems of the prior art, and makes it possible to prevent a call interruption due to a handover or a call loss due to a call connection failure at a switching destination base station. It is an object to provide a channel switching processing method.

[0010]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a first base station which, when communicating with the first base station, receives a signal from the first base station, and receives a signal from the first base station. The control channel other than the above is monitored, and the process of selecting the second base station to be switched next is performed. Then, when a transition is made to a communication state with the second base station during communication with the first base station, channel switching processing is performed from the first base station to the second base station.

Further, according to the present invention, a portable communication terminal for performing a re-calling type channel switching process is connected to a public base station via a wireless link, and receives a control channel for performing a standby process from the public base station. And a first time slot to which signals transmitted / received to / from a base station connected by a wireless link by the first wireless unit and the second wireless unit are assigned. And the second
And a call control unit that controls the first radio unit, the second radio unit, and the communication path unit. The call control unit monitors the control channels of the base stations other than the first base station by the second radio unit when the reception electric field level of the first base station communicating with the first radio unit decreases. Start.

Next, a process of selecting a second base station for performing channel switching is performed, and a transition is made to a communication state with the second base station during communication with the first base station. Perform the channel switching process for the base station.

[0013]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing a portable communication terminal according to an embodiment of the present invention; Referring to FIG.
FIG. 2 is a functional block diagram showing an embodiment in which a TDMA mobile communication terminal according to the present invention is applied to a PHS terminal. The PHS terminal 10 according to the present embodiment has 2
This is a TDMA mobile communication terminal capable of performing 64 kbit / s bearer transmission using one time slot.

That is, in the present embodiment, as described above,
By enabling control of one time slot, if the reception electric field level of the base station communicating using one time slot decreases, the communication channel is established using the other time slot while continuing this communication. Can be established. Therefore, even if the re-calling type channel switching process is performed, there is a feature that a call is hardly interrupted as compared with the related art. The applicant of the present application has already filed a Japanese Patent Application No. 8-316453 as a related technique of a PHS terminal capable of controlling two time slots.

In FIG. 2, an antenna 12 receives a radio wave transmitted from a base station and outputs the radio wave to radio units 14a and 14b, and radiates signals input from these radio units 14a and 14b into space. Each of the radio units 14a and 14b is a radio unit that processes a signal of one slot having a transmission speed of 32 kbit / s. That is, these radio units 14 amplify and frequency-convert the signal for one slot received from the antenna 12 and output it to the channel control unit 16, and also convert the voice modulated signal for one slot from the channel control unit 16. The signal is amplified and frequency-converted and output to the antenna 12.

The channel control unit 16 has two 32 kbits.
/ S time slot switching control, channel codec, voice processing, modulation / demodulation, and other functions.

Specifically, the channel control unit 16 demodulates and decodes the signal input from the radio unit 14 according to the time slot controlled by the call control unit 18, decodes the signal, amplifies the signal, and outputs the amplified signal to the speaker 20. Similarly, the signal input from the microphone 22 is amplified, encoded, modulated, and output to the radio unit 14.

The call control unit 18 is a control unit that controls the entire PHS terminal 10 including the processing of the protocol. The call control unit 18 includes a memory such as a ROM and a RAM therein, and operates according to a call processing program stored in the ROM. That is, the call control unit 18 detects the reception electric field level of the control channel received from the base station via the radio unit 14, and performs switching control of the base station that performs the standby process.

The call control unit 18 also includes, for example, the radio unit 14a
When communication with the base station is performed using one of the time slots via the base station (or may be performed by the base station), when the detection of a decrease in the reception electric field level or the channel switching instruction from the base station is received, the radio unit 14b is activated. Control is performed to select a base station having a high reception electric field level. And the radio unit 14
After performing control channel establishment processing and communication channel establishment processing using b and the other time slot, channel switching processing (handover) is performed.

An LCD display unit 24 and a key operation unit 26 are connected to the call control unit 18.

The LCD display section 24 is a display section for performing various displays such as a telephone number, a message or a received electric field level of a base station. The key operation unit 26 includes various keys for performing some action on the call control unit 18, such as a power key, an input key for inputting a telephone number and characters of a called terminal, and a call key for performing a call process. It is configured.

FIG. 1 is a processing flow showing the operation of the recalling type channel switching processing of the PHS terminal 10 shown in FIG.
Hereinafter, the operation of the present embodiment will be described with reference to FIGS. In the following description, an old slot performing communication with the base station 1 shown in FIG. 1 will be described as a first time slot, and a new slot performing communication with the base station 2 will be described as a second time slot. .

While the PHS terminal 10 is communicating with the base station 1 in the first time slot (100), for example, the reception electric field level of the base station 1 decreases due to movement or the base station 1
When a channel switching instruction is received from the PHS (102), the PHS
The terminal 10 executes a search process for the switching destination base station (10
4). Specifically, the call control unit 18 of the PHS terminal 10
For example, when the radio unit 14a communicates with the base station 1 using the first time slot and receives the detection of the decrease in the reception electric field level and a switching instruction, the radio unit 14b
Performs monitoring for selecting a base station. Then, the optimum base station 2 having a higher received electric field level than the base station 1 is selected as the base station for performing the channel switching (10
6).

Then, after executing the control channel establishment process (108), the call control unit 18 performs the communication channel establishment process using the second time slot (11).
0), transition to the communication state using this second time slot (112). After the communication state is established using the second time slot in this way, the call performed by the first time slot is switched to the second time slot (114). When this switching process (handover) is completed, the communication with the base station 1 performed in the first time slot is stopped.

The embodiment has been described in detail above.
The present invention is not limited to the above embodiments, and variations or modifications that can be made by those skilled in the art without departing from the spirit of the present invention are included in the scope of the present invention. That is, in the present embodiment, the present invention is applied to a PHS to which the present invention is advantageously applied. However, the present invention is not particularly limited to the PHS, and can be applied to a communication system of another system.

[0026]

As described above, according to the re-calling type channel switching processing method in the portable communication terminal of the present invention, the communication path is switched after the new communication channel is established on the new base station side. Time base station side (including network side)
Only the time required to switch the communication channel is required. Therefore, it is possible to prevent a call loss due to a call interruption or a call connection failure at a switching destination base station as conventionally occurred.

[Brief description of the drawings]

FIG. 1 is a processing flow showing an embodiment of a re-calling type channel switching processing method in a portable communication terminal according to the present invention.

FIG. 2 shows a PDMA portable communication terminal according to the present invention as P
FIG. 3 is a functional block diagram showing an embodiment when applied to an HS terminal.

FIG. 3 is a processing flow showing an operation of a re-calling type channel switching processing method according to the related art.

[Explanation of symbols]

 Reference Signs List 10 PHS terminal 12 Antenna 14a, 14b Radio unit 16 Call path control unit 18 Call control unit 20 Speaker 22 Microphone 24 LCD display unit 26 Key operation unit

Claims (5)

[Claims] When a reception electric field level with the first base station decreases to a predetermined value during communication with a first base station, a control channel other than the first base station is monitored, and Performing a process of selecting a second base station for performing channel switching; and when transiting to a communication state with the second base station during communication with the first base station, the first base station switches from the second base station to the second base station. A re-calling type channel switching processing method in a portable communication terminal, wherein a channel switching processing is performed for a station. 2. The re-calling type channel switching processing method according to claim 1, wherein the portable communication terminal is capable of controlling two time slots of a first time slot and a second time slot, and Communicates with the first base station by the time slot of, establishes a communication channel with the second base station by the second time slot, and establishes a communication channel by the second time slot. A re-calling type channel switching processing method in a portable communication terminal, wherein a communication path is switched from a first time slot to the second time slot, and thereafter, communication with the first base station is stopped. . 3. The re-calling type channel switching processing method according to claim 1, wherein the timing of starting the selection processing of the second base station is performed when the mobile communication terminal detects a decrease in level or when the second base station detects a level drop. A re-calling type channel switching processing method in a portable communication terminal after receiving a handover instruction from one base station. 4. A portable communication terminal for performing a re-calling type channel switching process, comprising: a first radio unit connected to a public base station via a radio link, and receiving a control channel for performing a standby process from the public base station; A first time slot to which a signal transmitted / received to / from a base station connected by a wireless link by the first wireless unit and the second wireless unit is assigned; A call path unit that forms a call path of two time slots; a call control unit that controls the first wireless unit, the second wireless unit, and the call path unit; The unit controls the base station other than the first base station by the second wireless unit when the reception electric field level of the first base station communicating with the first wireless unit decreases to a predetermined value. Channel moni When a ring is started and a process of selecting a second base station to perform next channel switching is performed, and a transition is made to a communication state with the second base station during communication with the first base station, the first base station A mobile communication terminal of a TDMA system, wherein a channel switching process is performed from a station to the second base station, and then communication with the first base station is stopped. 5. The mobile communication terminal according to claim 4, wherein the call control unit detects a level drop or after receiving a handover instruction from the first base station. A mobile communication terminal of a TDMA system, which starts selection processing.