JPH07203517A - Hand-over system - Google Patents

Abstract

PURPOSE:To prevent previously a call from being disconnected which can be generated because of the rapid deterioration of the intensity of the reception electric field of a radio base station in communication when a mobile equipment moves from indoor to outdoor and vice versa ui a mobile communication system. CONSTITUTION:This hand-over system is composed of an exchange station 3, an indoor radio base station 2a, outdoor radio stations 2b and 2c, and the mobile equipment 1 provided with a function identifying whether the radio base station in communication and an adjacent radio base station are for indoor or for outdoor and a function measuring the intensity of the reception electric field and the intensity variation quantity of the reception electric field per a unit time concerning the adjacent radio base station, so as to hand-over requirement when both intensity of the electric field and the intensity variation quantity per the unit time are over the respective threshold values in some radio base station among the adjacent radio base station without regard to the intensity of the reception electric field of the radio base station in communication.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a handover system and, more particularly, to a handover system in a mobile communication system capable of talking regardless of whether it is indoors or outdoors.

[0002]

2. Description of the Related Art In a conventional handover method in a mobile communication system, the received electric field strength of a radio base station currently used by a mobile station and the received electric field strength of a radio base station adjacent to the radio base station are measured and compared. Then, based on the result, the handover was performed to the radio base station having the maximum received electric field strength. (See Japanese Patent Publication No. 1-303817)

In the conventional handover method, the received electric field strength of the radio base station currently used by the mobile station and the received electric field strength of the radio base station adjacent to the radio base station are measured and compared. , As a result, even if the received electric field strength of the adjacent wireless base station is the strength at which the call can be made, if the received electric field strength of the wireless base station currently in use is stronger, the handover is not performed and the current use is continued. I was using a wireless base station.

In a mobile communication system capable of making a call regardless of whether it is indoors or outdoors, when the mobile unit moves from indoors to outdoors, the received electric field strength of the indoor radio base station which has been used until now due to an obstacle or the like is high. There is a possibility that the call will be disconnected before it is handed down due to sudden deterioration.

[0004]

According to the handover method of the present invention, a mobile unit identifies a wireless base station in communication and an adjacent wireless base station as an indoor wireless base station or an outdoor wireless base station. And a means for measuring the received electric field strength of the adjacent wireless base stations and the received electric field strength change amount per unit time, and the wireless base station with which the mobile device is communicating is an indoor wireless base station. In this case, when the received electric field strength of the adjacent outdoor radio base station and the amount of change in the received electric field strength per unit time both exceed respective threshold values set in advance in the mobile device, the indoor The mobile device has means for requesting the indoor radio base station to switch the channel from the indoor radio base station to the outdoor radio base station regardless of the received electric field strength of the radio base station for use, , Mobile When the receiving wireless base station is an outdoor wireless base station, the reception electric field strength of the adjacent indoor wireless base station and the reception per unit time exceeding the threshold of the received electric field strength change amount per unit time If the amount of change in electric field strength exceeds both thresholds preset in the mobile device, the mobile device is transmitted from the outdoor radio base station regardless of the received electric field strength of the outdoor radio base station. It has means for requesting the outdoor radio base station to switch the channel to the indoor radio base station.

[0005]

Embodiments of the present invention will be described with reference to the drawings. [Embodiment 1] FIG. 1 is a block diagram showing an embodiment of a mobile communication system in which the present invention is used.

In FIG. 1, 1 is a mobile unit, 2a is an indoor radio base station, 2b and 2c are outdoor radio base stations, 3 is a mobile switching center, and 4a to 4c are radio base stations 2a to 2c, respectively. Zone 5 indicates a house, and points a to c indicate the position of the mobile device 1. Point a indicates the position where the mobile device 1 makes a call indoors, point b indicates the boundary point between indoors and outdoors, and point c indicates the inside of the wireless zone 4b outdoors.

[0007] FIG. 2 is an example of a sequence diagram of a handover method when the mobile station sets each threshold value.
At this time, in FIG. 1, it is assumed that the mobile device 1 is talking at the point a and is moving from the point a to the point b and then to the point c.
The mobile device 1 identifies from the information on the control channel that the wireless base station with which it is talking is the indoor wireless base station 2a. The mobile device 1 that identifies that the wireless base station in communication is the indoor wireless base station 2a measures the received electric field strength of the control channel of the adjacent wireless base station and the received electric field strength change amount per unit time. . Then, the reception electric field strength of the control channel of the outdoor radio base station 2b exceeds the preset threshold value of the reception electric field strength and the outdoor radio base station 2b.
If the amount of change in the received electric field strength per unit time of the control channel of the above exceeds the threshold value of the amount of change in the received electric field strength per unit time set in advance, that time is obtained regardless of the received electric field intensity of the indoor radio base station 2a. Then, the mobile device 1 requests the indoor radio base station 2a to switch the channel to the outdoor radio base station 2b. The indoor wireless base station 2a that has received the channel switching request issues a channel switching instruction to the mobile device 1, and then the mobile device 1 requests the outdoor wireless base station 2b to establish a link channel. After that, the handover is performed by performing the procedure shown in FIG. Also, when the mobile device 1 in the call at the point c in FIG. 1 moves from the point c to the point b and then to the point a, the same handover is performed.

FIG. 3 shows a mobile unit 1 communicating indoors (point a).
Is a diagram showing a timing at which the mobile device 1 performs a handover until the mobile device 1 moves outdoors (point c). The horizontal axis represents time t, and the vertical axis represents the received electric field strength E of the control channel of the wireless base station.
The times ta, tb, and tc respectively indicate the times when the mobile device 1 reaches the positions a, b, and c in FIG.
In the figure, the solid line B2a indicates the reception electric field strength of the control channel of the indoor radio base station 2a, the solid lines B2b, B2b ′, B2b ″ indicate the reception electric field strength of the control channel of the outdoor radio base station 2b, and the alternate long and short dash line α indicates movement. The threshold value of the received electric field strength preset in the mobile device 1, β is the threshold value of the received electric field strength change amount per unit time preset in the mobile device 1, Δ
t is a unit time, ΔE, ΔE ′, and ΔE ″ are received electric field strength change amounts, and a dotted line indicates a call limit level at which the call is disconnected when the received electric field strength is smaller than this. The amount is ΔE / Δt, ΔE ′ / Δt,
ΔE ″ / Δt. Conventionally, when the wireless base station having the reception electric field strength of the control channel exceeding the reception electric field strength of the control channel of the communicating radio base station appears (point A), the mobile device 1 In the present invention, the received electric field strength B2 of the control channel of the outdoor radio base station 2b is used.
Even if b is lower than the received electric field strength B2a of the control channel of the indoor radio base station 2a, the received electric field strength B2b exceeds the threshold value α and the received electric field strength change amount ΔE / Δt per unit time is the threshold value β. If it exceeds, the mobile unit 1 performs a handover at that time (point B).

When the received electric field strength of the control channel of the outdoor radio base station changes as shown by the solid line B2b ', time t'.
, The received electric field strength of the control channel of the outdoor radio base station exceeds the threshold value α, but the received electric field strength change amount ΔE ′ / Δt per unit time falls below the threshold value β. Is the outdoor radio base station 2b as in the conventional case.
A received electric field strength B2b of the control channel exceeds the received electric field strength B2a of the control channel of the indoor radio base station 2a.
Hand over at a point.

When the received electric field strength of the control channel of the outdoor radio base station changes as shown by the solid line B2b ", the time t'is exceeded.
Change in received electric field strength per unit time ΔE ″ /
Although Δt exceeds the threshold value β, the received electric field strength of the control channel of the outdoor wireless base station is lower than the threshold value α, so that the mobile device 1 has the outdoor wireless base station 2b as in the conventional case.
A received electric field strength B2b of the control channel exceeds the received electric field strength B2a of the control channel of the indoor radio base station 2a.
Hand over at a point.

FIG. 4 shows a mobile unit 1 communicating outdoors (point c).
Is a diagram showing a timing at which the mobile device 1 performs a handover until the mobile terminal 1 moves indoors (point a). The horizontal axis represents time t, and the vertical axis represents the received electric field strength E of the control channel of the wireless base station.
The times ta, tb, and tc respectively indicate the times when the mobile device 1 reaches the positions a, b, and c in FIG.
In the figure, solid lines B2a, B2a ', and B2a "indicate received field strength of the control channel of the indoor wireless base station 2a, solid line B2b indicates received field strength of the control channel of the outdoor wireless base station 2b, and a dashed line α indicates movement. The threshold value of the received electric field strength preliminarily set in the mobile device 1, β is the threshold value of the change amount of the received electric field strength per unit time preset in the mobile device 1, and Δ
t is the unit time, ΔE, ΔE ′, ΔE ″ are the received electric field strength change amounts, and the dotted line shows the call limit level at which the call is disconnected when the received electric field strength is smaller than this. The amount is ΔE / Δt, ΔE ′ / Δt,
ΔE ″ / Δt. Conventionally, when the wireless base station having the reception electric field strength of the control channel exceeding the reception electric field strength of the control channel of the communicating radio base station appears (point A), the mobile device 1 In the present invention, the received electric field strength B2 of the control channel of the indoor radio base station 2a is used.
Even if a is lower than the reception electric field strength B2b of the control channel of the outdoor radio base station 2b, if the reception electric field strength B2a exceeds the threshold value α and the reception electric field strength change amount ΔE / Δt exceeds the threshold value β, At the time point (point B), the mobile device 1 makes a handover.

When the received electric field strength of the control channel of the indoor radio base station changes as shown by the solid line B2a 'or the solid line B2a ", the handover is performed not at the point B but at the point A as in the conventional case for the same reason as in FIG. [Second Embodiment] In the above-mentioned first embodiment, the mobile station sets the threshold value in advance, but in the second embodiment, the wireless base station sets each threshold value to the mobile station. A handover method in the case of specifying the above will be described with reference to the drawings.

FIG. 5 is an example of a sequence diagram of a handover method when the radio base station specifies each threshold value to the mobile station. When the mobile device 1 is turned OFF / HOOK indoors, first, a radio base station having the maximum received electric field strength of the control channel is searched and a link channel establishment request is made to the radio base station. Here, the mobile device 1 is indoors (a in FIG. 1).
Since it is OFF / HOOK at the point), the indoor radio base station 2a is requested to establish a link channel. At this point, the mobile device 1 identifies that the partner to whom the request for link channel establishment is made is the indoor radio base station 2a based on the information on the control channel of the indoor radio base station 2a. The indoor radio base station 2a that has been requested to establish a link channel is the mobile device 1
Link channel allocation to. Next, the mobile device 1, which has identified that the other party who has made the link channel establishment request is the indoor radio base station 2a, requests definition information from the indoor radio base station 2a, and receives the definition information for indoor use. Radio base station 2a
Returns a definition information response to the mobile device 1. The definition information response includes information about the threshold value of the received electric field strength specified by the indoor radio base station 2a for the mobile device 1 and the threshold value of the received electric field strength change amount per unit time. . The mobile device 1 stores the threshold value of the received electric field intensity and the threshold value of the amount of change in the received electric field intensity per unit time specified here, and the mobile device 1 and the indoor radio base station 2a are connected to each other. After the call is connected, the mobile device 1 measures the received electric field strength of the control channel of the adjacent wireless base station and the received electric field strength change amount per unit time. The subsequent procedure is similar to that of the first embodiment. [Third Embodiment] The second embodiment is an example of the handover method in which the radio base station specifies each threshold value to the mobile station. In the third embodiment, the radio base station moves the channel switching. This is a handover method when instructing the machine.

The block diagram of the mobile communication system in which the third embodiment is used is similar to that of the first embodiment and is as shown in FIG.

FIG. 6 is an example of a handover system sequence map when the radio base station specifies channel switching to the mobile station.

At this time, in FIG. 1, it is assumed that the mobile unit 1 is talking at point a and is moving from point a to point b and then point c. The mobile device 1 identifies from the information on the control channel that the wireless base station with which it is talking is the indoor wireless base station 2a. The mobile device 1 that identifies that the wireless base station in communication is the indoor wireless base station 2a measures the received electric field strength of the control channel of the adjacent wireless base station and the received electric field strength change amount per unit time. . The mobile device 1 notifies the indoor radio base station 2a of the measurement result at regular intervals. In the indoor radio base station 2a, the mobile station 1 notifies the threshold value of the received electric field strength of the control channel and the threshold value of the received electric field strength change amount per unit time which are set in advance by the mobile station 1 at a constant cycle. Compare with the measurement result. As a result of the comparison, the received electric field strength of the control channel of the outdoor wireless base station 2b exceeds the preset threshold value of the received electric field strength and the received electric field strength change amount of the control channel of the outdoor wireless base station 2b is set. If the amount of change in the received electric field strength per unit time that has been set exceeds the threshold value, the indoor radio base station 2a at that time is outdoors with respect to the mobile device 1 regardless of the received electric field strength of the indoor radio base station 2a. The channel switching to the wireless base station 2b is instructed. Mobile unit 1 that received a channel switching instruction
Requests the outdoor radio base station 2b to establish a link channel. After that, the handover is performed by performing the procedure shown in FIG.

[0017]

As described above, the handover method of the present invention is set in advance when a mobile unit that is communicating indoors is outdoors or when a mobile unit that is talking outdoors is indoors. If there is a radio base station having a received electric field strength exceeding the threshold value of the received electric field strength and a received electric field strength change amount exceeding a preset threshold value of the received electric field strength change amount, communication is performed. A radio having a received electric field strength exceeding the threshold value and a received electric field strength change amount from the communicating radio base station even if the received electric field strength of the communicating radio base station is not deteriorated yet and the call is strong enough. Since the handover to the base station is performed, the received electric field strength of the wireless base station, which has been used until then, is rapidly deteriorated due to obstacles etc. when the mobile unit in communication moves from indoor to outdoor or from outdoor to indoor. Hand over Call has prevent effects that would be cut.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of a mobile communication system in which a handover system of the present invention is used.

FIG. 2 is a sequence diagram in the first embodiment of the handover system of the present invention.

FIG. 3 is a diagram showing an example of a handover timing according to the present invention.

FIG. 4 is a diagram showing an example of timing of performing a handover according to the present invention.

FIG. 5 is a sequence diagram in the second embodiment of the handover system of the present invention.

FIG. 6 is a sequence diagram in the third embodiment of the handover system of the present invention.

[Explanation of symbols]

 1 mobile station 2a indoor radio base station 2b, 2c outdoor radio base station 3 mobile switching center 4a-4c radio zone a point-c point position of mobile station 1

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location 7605-5K H04B 7/26 109 H 7605-5K 109 C

Claims (3)

[Claims] 1. A switching center, one or more wireless base stations for controlling a radio link to a mobile station and for making a call connection with the switching center, and a service area formed by the wireless base stations. It is composed of the mobile device that can talk with a fixed network subscriber inside, and the radio base station has an indoor radio base station and an outdoor radio base station, and the mobile device can talk both indoors and outdoors. In the mobile communication system, the mobile device has a function of identifying whether the wireless base station in communication and the adjacent wireless base station are an indoor wireless base station or an outdoor wireless base station, and the adjacent wireless base station. And a function of measuring a received electric field strength change amount per unit time, and when the wireless base station with which the mobile device is communicating is an indoor wireless base station, an adjacent outdoor wireless Base station reception field strength and When the amount of change in the received electric field strength per unit time exceeds both of the threshold values set in advance in the mobile device, the mobile device is operated regardless of the received electric field intensity of the indoor radio base station. When the indoor radio base station is requested to switch the channel from the indoor radio base station to the outdoor radio base station, and the radio base station with which the mobile device is communicating is the outdoor radio base station. In the case where both the received electric field strength and the amount of change in the received electric field strength per unit time of adjacent indoor radio base stations exceed respective threshold values preset in the mobile unit, the outdoor radio base station Handover method characterized in that the mobile device requests the outdoor radio base station to switch the channel from the outdoor radio base station to the indoor radio base station regardless of the received electric field strength of the station. 2. A function of an exchange or a radio base station designating a threshold value of a received electric field strength and a threshold value of a received electric field strength change amount per unit time to a mobile device, and the mobile device, 7. A function of storing the threshold value of the electric field strength designated by the exchange or the radio base station and the threshold value of the received electric field strength change amount per unit time. The handover method described in 1. 3. A function of a mobile device for discriminating between a wireless base station in communication and an adjacent wireless base station as an indoor wireless base station or an outdoor wireless base station, and a received electric field strength of the adjacent wireless base station. And the amount of change in received electric field strength per unit time is measured, and the measurement result and the type of the wireless base station (indoor wireless base station or outdoor wireless base station) are notified to the wireless base station in communication at a constant cycle. The indoor radio base station having a function, the reception electric field strength and the reception electric field strength change amount per unit time which are preset in the indoor radio base station in the measurement result notified from the mobile device. If there is an outdoor radio base station that has a received electric field strength that exceeds both the thresholds and the amount of change in the received electric field strength per unit time, regardless of the received electric field strength of the local station, the outdoor radio base station is transmitted from the own station. To the base station A function of instructing the mobile device to switch the channel, and the outdoor radio base station has a reception electric field preset in the outdoor radio base station in the measurement result notified from the mobile device. If there is an indoor radio base station with a received field strength and a received field strength change per unit time that exceed both the threshold of the received field strength change per unit time and the received field strength change per unit time, 2. The handover method according to claim 1, further comprising a function of instructing the mobile device to switch the channel from its own station to the indoor radio base station regardless of strength.