JPH11252611A - Communication system, communication method and radio terminal base station - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the communication system with a simple configuration where hand-over is realized with a simple processing procedure. SOLUTION: The communication system 10 is provided with plural base stations 14 that are communicated with an ISD network 18 via a digital service unit DSU 16 and PHS telephone sets 12 that make communication with any of the base stations 14. A CPU 70 of the base station 14 is provided with a call interrupt processing section 74 that replies a request of hand-over from a busy radio terminal to generate information denoting an interrupt request including information specifying the radio terminal and provides an output to the ISD network and with a call restart processing section 76 that generates information denoting a restart request including the information specifying the radio terminal in response to a communication setup request from the radio terminal during hand-over and provides an output of the information to the ISDN.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a PHS (Personal
Handy-phone System) and other communication systems, communication methods and wireless terminal base stations, more specifically, IS
The present invention relates to a communication system, a communication method, and a wireless terminal base station having a wireless telephone device connected to a DN network.

[0002]

2. Description of the Related Art In recent years, PHS (Personal Handy-phone Sy
stem) to the office (especially, SOHO (Small Office, Ho
me Office)) and extensions in two-family houses have been proposed, and have been put to practical use in not a few offices and homes.
However, due to the size and structure of offices and houses, a single base station may not be able to secure a communication area.

In such a case, a plurality of base stations are provided,
By realizing a handover in which a connected base station is changed during a call, even if the caller is walking in a facility such as an office, the communication can be practically continued without interruption. This handover is a PHS
In the above, when the voice quality is degraded during a call (for example, when the bit error rate is increased) or when the electric field reception level is lowered, the PHS executes a predetermined process, Of the base station and establish communication with the base station.

In order to perform handover with another base station, in a conventional communication system, as shown in FIG. 6, a public line network (for example, an ISDN network 18) and base stations 114-1 and 114-2 are used. For example, it is necessary to intervene a control device 110 having a PBX, a main device, and the like to manage the position information of the terminal and to instruct the suspension or resumption of the call. Accordingly, there is a problem that the cost for constructing the system increases due to the installation of the control device, and that a process is required between the control device and the base station for handover.

[0005] There is the following prior art which discloses a mobile communication system.

[0006] Japanese Patent Application Laid-Open No. 3-280633 dispenses with the need for a radio network controller for tracking and registering the position of a mobile body, and enables simple, low-cost bidirectional connection using only the ISDN public network. A mobile telephone system is disclosed. this is,
It states that the wired system and the wireless system are handled in a unified manner by devising a subscriber calling code of a mobile phone, but does not disclose a handover method. The two-way communication zone used for this is 1 km or more, which requires large power for transmission and reception, increases costs, and cannot be realized by PHS.

[0007] Japanese Patent Application Laid-Open No. 4-137831 discloses a low-cost mobile telephone system capable of two-way connection and eliminating the distinction between a home cordless telephone and an outdoor mobile telephone. This can be used for both wired and wireless without adding a special database by devising the ISDN address, but there is no description of handover.

Japanese Patent Application Laid-Open No. 9-205670 discloses a handover method capable of reducing the number of pseudo base stations conventionally required to two to one, but requires a control station.

[0009]

As described above, in the prior art, a control device must be installed, so that the cost for constructing the system increases, and the control device and the base station are required for handover. There was a problem that processing was required between the station and the station.

[0010] The present invention has been made to solve such a problem, and an object of the present invention is to provide a communication system capable of implementing handover with a simple configuration and a simple processing procedure.

[0011]

SUMMARY OF THE INVENTION An object of the present invention is to provide an ISD
A communication system comprising: a plurality of base stations connectable to an N network; and a wireless terminal capable of communicating with any of the base stations, wherein the base station responds to a request from a communicating wireless terminal. In response to a request for establishing a communication from the wireless terminal and a call suspension means for generating a suspension request including information for identifying the wireless terminal and outputting the suspension request to the ISDN network side, The present invention is attained by a communication system that includes a call resuming unit that generates a resuming request including information specifying a wireless terminal and outputs the resuming request to the ISDN network side.

[0012] According to the present invention, by using "interruption" and "resume" in ISDN, the base station of the switching source can
The request for “interruption” includes information (call identifier) for specifying the wireless terminal that is performing handover, and this is given to the ISDN network side. Also, the switching destination base station includes the information (call identifier) for specifying the wireless terminal for which the handover has been completed in the request for “resume”, and provides this to the ISDN network side. Here, the information for specifying the wireless terminal is the same if the wireless terminal is the same, so that the connection between the wireless terminal and the ISDN network can be restarted via the switching destination base station.

[0013] In a preferred embodiment of the present invention, after the call suspension means outputs the suspension request, information indicating a restart request by another base station and / or ISDN.
A resumption detection means for detecting information indicating resumption confirmation from the network side, and when the resumption detection means does not detect information indicating a resumption request and / or resumption confirmation within a predetermined time, indicates a call disconnection. Call disconnection means for creating information and outputting the information to the ISDN network side.

Alternatively, the call disconnecting means may be configured to disconnect the call after resuming the communication state.

[0015] Alternatively, the DSU may be configured to disconnect the call if the DSU does not receive information indicating a restart request from another base station within a predetermined time after the suspension.

Alternatively, there may be provided a device which is connected to the ISDN network and disconnects the call when the confirmation of resumption to another base station is not detected within a predetermined time after the suspension request is output. .

In a further preferred embodiment of the present invention, the predetermined time is set to be equal to or longer than a time secured for performing handover at the wireless terminal.

Further, the object of the present invention is achieved by the above-mentioned base station and also by a communication method realized by the above-mentioned communication system.

[0019]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a block diagram schematically showing a wireless telephone system according to an embodiment of the present invention. As shown in FIG. 1, the wireless telephone system 10 includes a PHS telephone 12, a plurality of base stations 14-1 and 14-2, and a DSU (Digital Service Uniform).
t) 16. Each of the base stations 14-1 and 14-2 and the DSU 16 are connected by a wired line 20. The DSU 16 includes an ISDN (IntegratedS
ervices Digital Network) network 18 is connected. P
The HS telephone 12 transmits the DS via any of the base stations 14.
Information can be exchanged with the ISDN network via the U16, so that it is possible to communicate with and communicate with other telephones and the like via the ISDN network 18.

FIG. 2 is a block diagram showing the configuration of the PHS telephone 12. As shown in FIG.
The HS telephone device 12 includes an antenna 22 and an RF (Radio Frequency).
ency) amplifier 24, multiplier 26, frequency synthesizer 2
8, band pass filter (BPF) 30, second multiplier 32, local oscillator 34, demodulator 36, channel codec 38, audio codec 40, modulator 42, third multiplier 44, second BPF 46 and power An amplifier 48 is provided. Further, the PHS telephone device 12 includes a switch 50 for switching between transmission and reception, a control circuit 52 for controlling the entire device, a liquid crystal display (LCD) 54, and a key switch 56.
And a memory 58 for storing a program for operating the PHS telephone device 12 and data necessary during execution of the program.

In the PHS telephone device 12 described above,
Via an antenna 22, a certain base station (CS: Cell Stati
on) Upon receiving signals (radio waves) from 14-1 and 14-2, the signal received by the RF amplifier 24 is amplified, and then the output signal from the RF amplifier 24 is output by the multiplier 26 to the frequency synthesizer. 28 is converted to an intermediate frequency signal, which is converted to an intermediate frequency signal.
0 is given. The signal that has passed through the BPF 30 is provided to a second multiplier 32, where the signal is multiplied by the output of the local oscillator 34, and frequency-converted. The baseband signal obtained in this manner is supplied as received data to a channel codec 38 via a demodulator 36, and after error correction decoding, the audio data among them is transmitted to an audio codec 40. Via the speaker SP. The data (reception control data) corresponding to the control signal extracted by the channel codec 38 is transmitted to the control circuit 5.
2 given.

On the other hand, the voice given via the microphone is coded via the voice codec 40 and the channel codec 38 and then converted into an intermediate frequency signal by the modulator 42. Next, the output of the modulator 42 is multiplied by the local oscillation signal from the frequency synthesizer 38 by the third multiplier 44 and converted into a signal of a predetermined frequency. The frequency-converted signal is supplied to the antenna 22 via the BPF 46, the power amplifier 48, and the switch 50, and transmitted from the antenna 22. In this way,
The PHS telephone device 12 can receive a signal from any of the base stations 14 or transmit a signal to any of the base stations 14.

FIG. 3 shows a base station 14 according to the present embodiment.
Is a block diagram of FIG. As shown in FIG. 3, the base station receives an electric wave from the PHS telephone 12 or transmits an electric wave to the PHS telephone 12 through an antenna 60.
An RF circuit 62 for performing filtering, frequency conversion, and the like;
A demodulation circuit 64, a modulation circuit 66, a signal processing circuit 68 for creating a signal that can be transmitted to the ISDN network, or performing a predetermined process on a signal from the ISDN network, and a CPU 70 for controlling the operation of the base station 14. , And a memory 72.
The signal processing circuit 68 is connected to the DSU 16, so that communication with another telephone can be executed via the ISDN.

The CPU 70 executes a process for registering the location of the PHS telephone 12 and a process for transmitting and receiving based on the program stored in the memory 72. Further, in the present embodiment, the CPU 70 includes a call interruption processing unit 74 and a call resumption processing unit 76, which operate in a predetermined case to realize a handover described later.

Now, in the PHS telephone apparatus operating in this manner, when a caller moves and approaches a periphery of a zone (for example, Z1) covered by a base station (for example, 14-1) with which communication is currently being performed. , The channel codec 38 detects that the bit error rate is higher than a predetermined threshold, or the RF amplifier 24 detects that the electric field reception level is lower than a predetermined level, 52. Control circuit 5
2 executes a handover process in response to the information being given. Also, in the base station 14-1 or the like, according to the information from the PHS telephone 12,
The CPU 70 executes a handover process. For example, as described in “Easy Personal Handy Phone” (edited by Keisuke Ogawa and Tadao Kobayashi: Telecommunications Association, Ohmsha), the handover process includes (1) recall type handover request and (2) recurring handover request. A predetermined procedure of call-type handover reception, (3) RT function request, (4) secret key setting, (5) MM function request, and (6) response notification is executed.

Meanwhile, in the ISDN network, standards are defined so that a call can be suspended (SUSPend) and resumed (RESume) (CCITT Q.931, JT-Q931: "ISDN").
User / Network Interface Layer 3 Specification JT-Q931 ", Telegraph and Telephone Technical Committee, 1996). Therefore, by transmitting information determined by the user side to the network side, the suspension / resumption of the call can be realized. For example, in the case of a call interruption, the user can be put on hold by sending a protocol identifier, a call number, a message type, and a call identifier from the user side to the network side. On the other hand, when the call is resumed, the communication can be resumed by transmitting the protocol identifier, the call number, the message type, and the call identifier from the user side to the network side. The call identification information element is used to identify the interrupted call. The call identification information element is assured by the network of unity of the user network interface to which the user belongs. The call identification is assigned at the beginning of the call suspension and can be reused after the restart procedure is completed.

FIG. 4 is a diagram showing a processing sequence between the PHS telephone apparatus, the base station and the DSU (ISDN network) according to the present embodiment. As shown in FIG.
The HS telephone (PS) 12 is connected to the base station (switching source CS) 14
-1 and is connected to the ISDN 18 via the base station 14-1 and the DSU 16 (see step 401 in FIG. 4).

If the bit error rate becomes larger than the threshold value or the electric field reception level becomes smaller than a predetermined level due to the movement of the talker, the TCH (traffic channel) is transmitted between the PHS telephone 12 and the base station 14-1. : Tr
(Affic channel) switching request and transmission / reception of a TCH switching instruction are performed (step 402), and then the base station 14 issues a request for temporary suspension to the ISDN network (step 4).
03). The PHS telephone 12 that has issued the TCH switching request
Since the ID number and extension number of the base station 14 are already known by the base station 14,
The call interruption processing unit 74 in the PU 70 performs the above-described CCITT Q.931 (J
Information specific to the PHS telephone 12, for example, information indicating the ID number or extension number of the PHS telephone 12, is provided to the ISDN as a call identifier included in the "interrupt" message according to T-Q931). . That is, the base station 14 suspends the call (S
USP), and at this time, predetermined information (call identifier) is transmitted to the network side so that the telephone having interrupted the call becomes the PHS telephone 12 to be handed over.

The ISDN responds to the request by the base station 1
The information indicating the interruption confirmation is output to 4-1 (step 40).
4). As a result, the base station 14-1 and the DSU 16 (IS
With the DN network 18) (step 40).
5).

When the caller moves, the PHS telephone 12
Enters the zone covered by the base station (switching destination CS) 14-2, the PHS telephone 12 and the base station 14-2 need to establish a link channel, establish a synchronization burst, and set up a call. The process is executed (Step 40)
6). This processing is the same as that of a normal handover, and is described in detail in the above-mentioned “Easy Personal Handy Phone”, and thus the description thereof is omitted here.

PHS telephone 12 and base station (CS to switch to)
When communication with the base station 14-2 is established, the base station 14-2
Of the PHS telephone 1 with which the communication has been established
Obtain the ID number or extension number for CCITT Q.
Information indicating the ID number or extension number of the PHS telephone 12 as a call identifier included in the “resume” message according to 931 (JT-Q931) is transmitted via the DSU 16 to the ISDN.
This is given to the network (step 407). That is, the base station 14
Requests the ISDN network to resume the call (RES) on the user side, and in this case, transmits predetermined information (call identifier) to the network so that the telephone that resumes the call is the handovered PHS telephone 12. To the side.

The ISDN responds to the request by the base station 1
The information indicating the restart confirmation is output to 4-2 (step 40).
8). Thereby, the base station 14-2 and the DSU 16 (IS
Communication with the DN network 18 is resumed (step 40).
9). Before or after this, the base station 14-2 transmits a predetermined response to the PHS telephone 12. Therefore, finally, the PHS telephone 12 is connected to the ISDN network, and can resume the call and the communication.

As described above, according to the present embodiment, at the time of interruption, a call identifier for specifying PHS telephone 12 is provided to ISDN network side (DSU 16) by the switching source base station. The call identifier that identifies the PHS telephone 12 is transmitted from the base station to the ISDN network side (DSU1).
6). Therefore, the handover is performed and the PHS
Even when the intervening base station for communication with the telephone 12 is different, the communication can be appropriately resumed.

It should be noted that a certain base station (switching CS) and ISD
The interruption with the N network (steps 402 to 404 in FIG. 4) is realized, and the state changes to “pending” (step 405).
Later, a case where communication is not established between another base station (switching destination CS) and the PHS telephone 12 may be considered. For this reason, in the base station that is the switching source CS, the call suspension processing unit 74 executes the processing shown in FIG.

A PHS telephone 12 that is talking to a certain base station (for example, 14-1) in a zone covered by itself
Therefore, if there is a TCH switching request (Yes in step 501), the call interruption processing unit 74 of the base station 14-1 returns to TCH
After outputting the CH switching instruction to the PHS telephone 12 (step 502), a call interruption process is executed (step 50).
3). The processes of steps 502 and 503 correspond to the processes of steps 402 and 403 in FIG. 4, respectively.

After the call is interrupted, the base station 14-1
Monitors whether information indicating "resume confirmation" has been output from the ISDN (DSU 16) (step 50).
4). This is because after communication between PHS phone 12 and another base station (eg, 14-2) has been established, DSU1
This is because information about the restart request and the restart confirmation is transmitted / received between the ISDN network and the other base station 14-2 via Step 6 (see Steps 407 and 408 in FIG. 4).

When the information indicating the confirmation of restart is detected (Yes in step 504), the processing is terminated.
This means that the handover has been performed normally as shown in FIG. On the other hand, if not detected, it is determined whether a predetermined time has elapsed (step 50).
5). In this embodiment, the predetermined time is set to 60 seconds, but is preferably longer than the time required for completing the handover. That is, the fact that the information indicating the restart confirmation cannot be detected within this time indicates that the PHS telephone 1
2 moves outside the zone covered by any base station and can be considered to have left the service area.

The above-mentioned time of 60 seconds is merely an example, and is generally (predetermined time)> (time required for handover). If (predetermined time)-(time required for handover) = α, it is systemically preferable that α is as short as possible, since time waste can be minimized. Further, there is an effect that the fee is reduced and the partner is not made to wait.

If no information indicating resumption confirmation is detected within the predetermined time (Yes in step 505)
In s)), the call suspension processing unit 74 instructs the ISDN network to disconnect the call (step 506). Thereby, the communication is disconnected.

As described above, according to the present embodiment, IS
By utilizing the transmission of information to the DN network, it is possible to appropriately implement handover without interposing a special device between the DSU and the base station.

Even if handover cannot be performed, the switching source CS performs disconnection processing. As a result, it is possible to minimize a state in which a call charge is taken in spite of a state in which a call cannot be made.

The present invention is not limited to the above-described embodiments, and various modifications can be made within the scope of the invention described in the appended claims, which are also included in the scope of the present invention. Needless to say, this is done.

For example, in the above-described embodiment, the interruption processing unit 74 of the base station disconnects the call when handover cannot be performed, but this may be executed on the ISDN network side. . That is, if the DSU 16 cannot receive the information indicating the restart request from the base station within a predetermined time, the call may be disconnected.

Further, in the above embodiment, the radio telephone system is provided with two base stations. However, the present invention is not limited to this, and it may be said that there may be three or more base stations. Not even.

Furthermore, in the present embodiment, the interruption processing unit 74 of the base station detects the information indicating the restart confirmation from the ISDN network side (DSU 16), but the present invention is not limited to this. Information indicating a restart request from any other base station may be detected.

In the above embodiment, a PHS telephone is used as a mobile station, but another mobile terminal (mobile terminal or mobile phone) may be used.

Further, in this specification, means does not necessarily mean physical means, but also includes a case where the function of each means is realized by software.
Further, the function of one unit may be realized by two or more physical units, or the function of two or more units may be realized by one physical unit.

[0048]

According to the present invention, with a simple configuration,
With a simple processing procedure, it is possible to provide a communication system, a communication method, and a wireless terminal base station capable of realizing handover.

[Brief description of the drawings]

FIG. 1 is a block diagram schematically showing a wireless telephone system according to an embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration of a PHS telephone.

FIG. 3 is a block diagram showing a configuration of a base station according to the present embodiment.

FIG. 4 is a PHS telephone device according to the embodiment;
FIG. 3 is a diagram showing a processing sequence between a base station and a DSU (ISDN network).

FIG. 5 is a flowchart illustrating a process executed by a call suspension processing unit of the base station according to the present embodiment.

FIG. 6 is a block diagram schematically showing a conventional wireless telephone system.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Radio telephone system 12 PHS telephone 14-1 and 14-2 Base station 16 DSU 18 ISDN network 20 Wired line 70 CPU 74 Call interruption processing part 76 Call resumption processing part

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Kazuhiko Seki 2-12-7 Hatchobori, Chuo-ku, Tokyo Inside Uniden Corporation

Claims (11)

[Claims] 1. A communication system comprising: a plurality of base stations connectable to an ISDN network; and a wireless terminal capable of communicating with any of the base stations, wherein the base station communicates with the wireless terminal. In response to the request from the wireless terminal, a call interrupting unit that generates an interrupt request including information for identifying the wireless terminal, and outputs the interrupt request to the ISDN network side; and a request for establishing communication from the wireless terminal. A communication system, comprising: a call resumption unit that responds to the request by generating a resumption request including information specifying the wireless terminal and outputting the resumption request to the ISDN network side. 2. The system according to claim 1, wherein said call suspension means outputs a suspension request after said suspension request is detected, and a restart detection means detects a restart confirmation from the ISDN network side. If not detected, a call disconnection request is sent to I
The communication system according to claim 1, further comprising: a call disconnecting unit that outputs the call to the SDN network. 3. The resuming detecting means for detecting the resuming request by another base station after the call suspending means outputs the suspending request, and the resuming request by the resuming detecting means within a predetermined time. Is not detected, the call disconnection request
The communication system according to claim 1, further comprising: a call disconnecting unit that outputs the call to the SDN network. 4. The communication system according to claim 2, wherein the call disconnecting means disconnects the call after resuming the communication state. 5. An apparatus which is connected to an ISDN network and disconnects a call when a restart confirmation to another base station is not detected within a predetermined time after a suspension request is output. The communication system according to claim 1, wherein: 6. An apparatus which is connected to an ISDN network and disconnects a call when a restart request by another base station is not detected within a predetermined time after a suspension request is output. The communication system according to claim 1, wherein: 7. The communication system according to claim 2, wherein the predetermined time is determined based on a time required for performing a handover in the wireless terminal. 8. A wireless communication system comprising: a plurality of base stations connectable to an ISDN network; and a wireless terminal capable of communicating with any one of the base stations, wherein the wireless terminal and the ISD are connected via the base station.
A communication method for communicating with an N network, wherein the wireless terminal requests a handover to at least one of the base stations, and the base station performs a handover from the wireless terminal. In response to the request, creating a suspend request including information identifying the wireless terminal, outputting the suspend request to the ISDN network side, and establishing a communication from the wireless terminal with another base station. Creating a restart request including information identifying the wireless terminal in response to the request, and outputting the restart request to the ISDN network side. 9. The method according to claim 1, wherein the base station outputs a suspend request, and then detects a resume request by another base station. If the resume request is not detected within a predetermined time,
9. The communication method according to claim 8, further comprising the step of: generating a call disconnection request and outputting the request to the ISDN network side. 10. The method according to claim 1, wherein the base station outputs a suspend request, and then detects a restart confirmation from the ISDN network side. If the restart confirmation is not detected within a predetermined time,
9. The communication method according to claim 8, further comprising the step of: generating a call disconnection request and outputting the request to the ISDN network side. 11. A wireless terminal base station that is connectable to an ISDN network via a DSU and is capable of communicating with a wireless terminal located in its own zone. In response, a call interruption unit that creates a suspension request including information specifying the wireless terminal, and outputs the suspension request to the ISDN network side; and in response to a request for establishment of communication from the wireless terminal, A wireless terminal base station, comprising: a call restart unit that creates a restart request including information specifying the wireless terminal and outputs the restart request to the ISDN network side.