JP2002152791A - Phs (r) handing-over method and phs (r) terminal device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To shorten call interruption time attendant on handing-over. SOLUTION: When a PHS (R) terminal is to switch a radio zone, by selecting the radio base station of best conditions out of access timing synchronously secured by much more radio base stations, an environment in which a large number of other radio base stations securing synchronism exist is selected. Further, when the quality of communication with one radio base station is deteriorated in such a satisfactory environment, a communication line with the next radio base station is set while securing a communication line with this radio base station.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a PHS (Persona) which moves in a plurality of radio zones formed by a plurality of radio base stations.
l Handy Phone System) Used for zone switching of terminal devices (hereinafter abbreviated as PHS terminals). Although the present invention has been made for PHS, it can be widely used for other mobile communications.

[0002]

2. Description of the Related Art In a PHS, since a radio zone formed by one radio base station is as small as a radius of several hundred meters, switching of radio zones may occur frequently as a user moves. FIG. 5 shows a wireless base station, a wireless zone formed by the wireless base station, and a PHS terminal moving in the wireless zone. In FIG. 5, the radio base stations (CS) 3-1 and 3-2 form two radio zones 5-1 and 5-2, and the PHS terminal 4 moves from one radio zone 3-1 to the next radio zone 3 -2 when moving to both wireless zones 3
The switching of the wireless zone is performed in a portion where -1 and 3-2 overlap.

[0003] Such switching of the wireless zone is called handover. In the prior art, when the communication quality in the wireless zone where the user is currently located degrades to a predetermined value or less during the handover, the communication is performed. It is configured to close the line once, search for another wireless base station that can communicate with a communication quality equal to or higher than a predetermined value, and when such a wireless base station is found, set a communication line with the wireless base station again. ing. Therefore, the processing time is about 2
Takes seconds. During this time, user communication is interrupted. This conventional handover will be described with reference to FIG. FIG. 6 is a sequence diagram showing a procedure of a handover according to the related art.

[0004] If a handover condition such as deterioration of communication quality below a predetermined value is established during communication between the old radio base station (old CS) and the PHS terminal, communication with the old radio base station is cut off. As a result, the voice path with the old wireless base station is turned off
Becomes Here, the PHS terminal performs a search operation for a peripheral wireless base station (neighboring CS) (section 1). The time required for section 1 is about 300 ms.

The effective radio base station (effective C
S), when the PHS terminal finds a new radio base station (new C
A link channel establishment request is made to S) (section 2). The time required for section 2 is about 200 ms.

[0006] When receiving the link channel establishment request from the PHS terminal, the new radio base station allocates a link channel to the PHS terminal (section 3). The time required for section 3 is about 1 second.

Thereafter, between the PHS terminal and the new radio base station, call setting → call setting acceptance → authentication request → authentication response → response →
Voice path ON with the new wireless base station → response confirmation is performed (section 4), and the new wireless base station and the PHS terminal start communication. The time required for this section 4 is about 500 ms.
The total required time from section 1 to section 4 is about 2 seconds.

[0008]

The interruption of communication for about 2 seconds in such a conventional handover is not desirable. A break of about 2 seconds will hinder a smooth call.
In addition, the user may have a feeling of psychological anxiety. For example, there is anxiety that a communication fee is charged even though communication is not possible, or that the user may be worried that the communication that has been interrupted will be recovered. Therefore, the shorter the interruption time of the communication due to the handover, the better it is, and it is possible to reduce anxiety given to the user. When the communication is a data communication instead of a voice conversation, a data retransmission operation is performed, and the actual communication speed is reduced.

SUMMARY OF THE INVENTION The present invention has been made in such a background, and an object of the present invention is to provide a method and an apparatus capable of shortening a communication interruption time accompanying a handover.

[0010]

A plurality of radio base stations access one common channel at any one of a plurality of access timings at different times. By monitoring this common channel, the PHS terminal can search for a valid wireless base station in the vicinity.

According to the present invention, when the PHS terminal switches the radio zone, the PHS terminal monitors the common channel and selects the radio base station with the best condition from among the access timings at which more radio base stations can ensure synchronization. Thus, the most important feature is to select an environment in which there are many other wireless base stations that can ensure synchronization.

Further, in such a favorable environment, when the communication quality with one radio base station is degraded, a communication line with the next radio base station is set while maintaining a communication line with this radio base station. Is performed.
By this means, when searching for other radio base stations during communication, there are many other radio base stations that can ensure synchronization, so a new radio base station is searched before the current communication quality is significantly degraded. The probability of being able to do so can be kept high.

Also, when searching for a new radio base station, a group having the largest number of radio base stations is selected from among the access timings at which the synchronization of the radio base stations can be ensured, and the most effective radio base station is selected. Perform handover processing for the base station. As a result, the handover processing time can be continuously reduced, and the next new wireless base station can be easily obtained because there are many wireless base stations in the vicinity of which synchronization can be ensured even in the next handover processing.

That is, a first aspect of the present invention is a PHS
A handover method characterized by the present invention is characterized in that a plurality of radio base stations set with a plurality of access timings different in time monitor a common channel commonly accessed, and the plurality of common channel access timings are monitored. Establishes synchronization with the access timing that can be received by the largest number of wireless base stations among the wireless base stations, and executes a step of selecting a wireless base station having the best reception condition among the wireless base stations and setting a communication line. There.

When a communication line with one radio base station is set and the communication quality is equal to or less than a predetermined value, each of the above steps is performed in a state where the communication line with the radio base station is set. To set a new communication line.

A second aspect of the present invention is a PHS terminal. A feature of the present invention is that a plurality of wireless base stations set to have a plurality of access timings having different times are commonly used. Means for monitoring a common channel to be accessed; means for establishing synchronization with the access timing that can be received by the most radio base stations among the access timings of the common channel according to the monitoring result of the monitoring means; Means for selecting a radio base station having the best reception condition among the radio base stations and setting a communication line.

A means for simultaneously accessing a plurality of radio base stations is provided. When a communication line with one radio base station is set by the access means and the communication quality falls below a predetermined value, Means for setting a new communication line by means of the monitoring means, the means for establishing the synchronization, and the means for setting the communication line via the means for accessing while the communication line with the wireless base station is set. It is desirable to provide.

The simplest method for setting a plurality of wireless base stations so that their access timings are different is to configure the plurality of wireless base stations so that the access timings are not synchronized. .

As a result, the communication interruption time due to the handover can be shortened, the communication becomes smooth, and the ratio of repeated transmission in the case of data communication is reduced. In addition, it is possible to prevent the user from feeling wasted communication charges or feeling uneasy due to communication interruption.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The configuration of a PHS terminal according to an embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a block diagram of a PHS terminal according to an embodiment of the present invention. FIG. 2 is a diagram for explaining group selection based on access timing according to the embodiment of the present invention.

According to the present invention, as shown in FIG. 2, a common channel including a plurality of access timings having different times and provided by a plurality of radio base stations (CS) to access in common is provided, and the PHS terminal 4 shown in FIG. The CPU 2 includes means for monitoring the common channel, and means for establishing synchronization with the access timing that can be received by the most radio base stations among the access timings of the common channel according to the monitoring result of the monitoring means. And means for selecting a radio base station having the best reception condition among the radio base stations and setting a communication line.

Further, there is provided a radio unit 6 having synthesizers 1-1 and 1-2 as means for simultaneously accessing a plurality of radio base stations, and the CPU 2 controls the radio unit 6 according to the frequency of the synthesizer 1-1. When a communication line with one wireless base station is set and the communication quality becomes equal to or lower than a predetermined value, the wireless communication is performed with the frequency of the synthesizer 1-2 while the communication line with the wireless base station is set. Means for establishing a new communication line by means of said monitoring means, means for establishing said synchronization, and means for setting said communication line via a unit 6;

Hereinafter, embodiments of the present invention will be described in more detail.

In the present invention, as shown in FIG. 2, grouping is performed for each common channel access timing,
From the access timing group where the largest number of wireless base stations are installed, the wireless base station waits for the wireless base station with the best condition (actually, the strongest electric field) and establishes a communication channel connection by calling and receiving. As a result, it is possible to secure an environment in which there are many other radio base stations that are synchronized with the radio base station around the standby radio base station.

As shown in FIG. 1, the PHS terminal 4 according to the embodiment of the present invention includes two synthesizers 1-1 in one radio unit 6.
And 1-2 are mounted. When a condition for operating the handover process occurs, one synthesizer 1
Using -1, the wireless base station search is performed using the other synthesizer 1-2 while the currently used communication channel is connected. At this time, it is necessary to search for the wireless base station while securing the access timing during the current communication so that the deterioration of the voice currently being communicated does not occur. It is effective that there are many other radio base stations that can ensure synchronization.

The search results are also grouped for each access timing of the common channel as shown in FIG. 2, and the group of the access timing in which the largest number of radio base stations are installed has the best condition (the electric field is higher). strong)
Using the synthesizer 1-2 searched for the radio base station, synchronization is established with the radio base station common channel of the radio base station.

Next, a request for a new communication channel assignment is transmitted to the new radio base station to the radio base station that has established synchronization. If a communication channel is allocated from the wireless base station, check that there is no interference, and if there is no interference, close the communication channel that has been communicating so far and open a new communication channel using the synthesizer that has continued communication. . After that, information of the wireless base station is obtained in the same manner as in the existing handover processing, and the communication returns to the previous step.

[0028] Thus, the process from the search for the wireless base station, which is the existing process, to the allocation of the new communication channel can be performed in the communication state, so that the time required for the handover process can be reduced. Also, a new communication channel is connected to the wireless base station at the access timing at which the wireless base station is arranged most, while the communication channel is connected at the access timing at which the wireless base station is arranged most. Therefore, the possibility that high-speed handover can be performed when the next handover process is performed is expanded.
That is, the communication quality can be improved by using the high-speed handover more frequently.

Next, the operation of the embodiment of the present invention will be described with reference to FIGS. FIG. 3 is a diagram showing a sequence of a handover process according to the embodiment of the present invention. FIG. 4 is a flowchart showing a handover processing flow according to the embodiment of the present invention.

As already described with reference to FIG. 6, in the prior art, a search for a peripheral wireless base station is performed after the communication is once interrupted. On the other hand, the sequence of the handover according to the embodiment of the present invention is different in that the process from the search for the peripheral radio base station (CS) to the assignment of a new communication channel is performed while the communication is continued.

As shown in FIG. 3, the result of searching for a radio base station for standby is divided into groups for each access timing, and the most common channels (CC
H) The radio base station with the best condition (strong electric field) from the group of the access timing where the base station is installed (old CS)
By acquiring synchronization in the common channel, securing synchronization, and transitioning to a standby state, it is possible to secure a situation in which there are many other wireless base stations that can secure synchronization with the wireless base station. When an incoming or outgoing call occurs,
The communication channel (TCH) is connected to the old radio base station to maintain the communication state. The high-speed handover operation must be performed so that the current communication voice is not degraded during the search.Therefore, by performing communication in an environment where many wireless base stations that can secure synchronization with the old wireless base station are arranged. Further, more radio base stations than the prior art can be selected.

When a condition (high-speed handover condition) where communication continuation becomes severe due to level deterioration and quality deterioration occurs, a search for another radio base station is executed while communication is continued. The search results are grouped for each access timing, and the access timing group in which the most common radio base station common channels are installed is sent to the radio base station (new electric field) with the best condition (strong electric field). Acquisition of synchronization is performed on the common channel (section 1). The time required for this section 1 is about 300 ms.

When the synchronization has been acquired, a request for allocating a channel that can communicate (new communication channel) is transmitted to the new radio base station (section 2). The time required for this section 2 is about 20
0 ms.

[0034] The new radio base station allocates a new communication channel to the PHS terminal (section 3). The time required for this section 3 is about 1 second.

According to the present invention, the communication with the old radio base station is continued even though the communication is deteriorated up to this point. When the link channel assignment with the new radio base station is completed, the old communication channel is closed (communication cutoff).
At this time, if access to the new radio base station fails for some reason, the above operation is performed for the next valid radio base station. When there is no next wireless base station, the wireless base station is searched again. In addition, even when the radio condition of the old communication channel worsens during the handover process of the present invention, the process can be configured so that the priority is given to the fact that the communication is not interrupted.

The subsequent steps are the same as in the prior art. Between the PHS terminal and the new radio base station, call setting → call setting reception → authentication request → authentication response → response → voice path to the new radio base station →
Response confirmation is performed (section 4), and the new radio base station and PHS
Communication with the terminal starts. Therefore, the time required for this section 4 is about 500 ms.

When this is compared with the prior art, the time until standby can be reduced to about 500 ms. Conventionally, the time required from section 1 to section 4 was about 2 seconds, but the time required for handover can be reduced by about 75% to 1/4 (25%).

Further, according to the handover procedure of the present invention, it is possible to search for another radio base station and acquire information on the radio base station during communication, so that the time required to return to standby after communication can be reduced.

[0039]

As described above, according to the present invention,
It is possible to shorten the communication cutoff time due to the handover. As a result, the communication by handover is facilitated, and in the case of data communication, the substantial communication speed is improved. Further, it is possible to prevent the user from feeling wasted communication charges or feeling uneasy due to communication interruption.

[Brief description of the drawings]

FIG. 1 is a block diagram of a PHS terminal according to an embodiment of the present invention.

FIG. 2 is a diagram for explaining group selection based on access timing according to the embodiment of the present invention.

FIG. 3 is a sequence diagram showing a handover process according to the embodiment of the present invention.

FIG. 4 is a flowchart showing a handover process according to the embodiment of the present invention.

FIG. 5 is a diagram showing a wireless base station, a wireless zone formed by the wireless base station, and a PHS terminal moving in the wireless zone.

FIG. 6 is a sequence diagram showing a conventional handover process.

[Explanation of symbols]

 1-1, 1-2 Synthesizer 2 CPU 3-1, 3-2 Wireless base station 4 PHS terminal 5-1, 5-2 Wireless zone 6 Radio section

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Satoshi Maga 2-1-1-1, Nagatacho, Chiyoda-ku, Tokyo F-term in NTT DoCoMo, Inc. (reference) 5K067 AA23 BB04 CC06 DD44 EE02 EE10 EE71 FF16 JJ35 JJ39

Claims (4)

[Claims] 1. A step of monitoring a common channel commonly accessed by a plurality of wireless base stations to which a plurality of access timings each having a different time are set, and the most wireless base station among the access timings of the common channel PHS handover, comprising the steps of: establishing a synchronization with an access timing that can be received by a user, and selecting a radio base station having the best reception condition among the radio base stations and setting a communication line. Method. 2. When a communication line with one radio base station is set and the communication quality thereof is equal to or less than a predetermined value, the communication line with the radio base station is set and remains. 2. The PHS handover method according to claim 1, wherein each step is performed to set a new communication line. 3. A means for monitoring a common channel commonly accessed by a plurality of radio base stations set so as to have a plurality of access timings each having a different time, and a common channel according to a monitoring result of the monitoring means. Means for establishing synchronization with the access timing that can be received by the most wireless base stations among the access timings of the above, and selecting a wireless base station with the best reception condition among the wireless base stations to establish a communication line. A PHS terminal device comprising: a setting unit. 4. A means for simultaneously accessing a plurality of wireless base stations is provided, and when a communication line with one wireless base station is set by the accessing means, the communication quality of the plurality of wireless base stations falls below a predetermined value. In some cases, a new communication line is set by the monitoring means, the synchronization establishing means, and the communication line setting means via the accessing means while the communication line with the radio base station is set. 4. The PHS terminal device according to claim 3, further comprising: