JP2621783B2 - Handover method - 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 indoors and outdoors.

[0002]

2. Description of the Related Art In a conventional handover method in a mobile communication system, a mobile station measures and compares a received electric field strength of a radio base station currently used by a mobile station and a received electric field strength of a radio base station adjacent to the radio base station. However, based on the result, the handover to the wireless base station having the highest received electric field strength was performed. (See Japanese Patent Laid-Open Rights 1-303817)

[0003] In a mobile communication system capable of talking whether indoors or outdoors, when a mobile unit moves from indoors to outdoors, the reception electric field strength of the indoor radio base station used up to that point due to obstacles or the like is reduced. There is a possibility that the call will be disconnected before handover due to rapid deterioration.

[0004]

According to the present invention, there is provided a handover system in which a mobile station identifies whether a communicating radio base station and an adjacent radio base station are an indoor radio base station or an outdoor radio base station. And a means for measuring the reception electric field strength of the adjacent radio base station and the amount of change in the reception electric field strength per unit time, wherein the radio base station with which the mobile station is communicating is an indoor radio base station. In the case, when the reception electric field strength of the adjacent outdoor wireless base station and the reception electric field intensity change amount per unit time both exceed respective thresholds set in advance for the mobile device, the indoor environment is changed to the indoor state. Means for the mobile station to request the indoor radio base station to switch channels from the indoor radio base station to the outdoor radio base station regardless of the reception electric field strength of the radio base station; , Mobile If the transmitting wireless base station is an outdoor wireless base station, reception per unit time exceeds the threshold of the received electric field strength of the adjacent indoor wireless base station and the amount of change in the received electric field strength per unit time. When the amount of change in the electric field strength exceeds each of the threshold values preset for the mobile device, the mobile device is transmitted from the outdoor radio base station regardless of the reception electric field intensity of the outdoor radio base station. Means for requesting the outdoor wireless base station to switch channels to the indoor wireless 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 station, 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. Zone 5 indicates a house, and points a to c indicate positions of the mobile device 1. Point a indicates the position where the mobile device 1 originated the call indoors, point b indicates the boundary point between indoor and outdoor, and point c indicates the inside of the wireless zone 4b outdoors.

FIG. 2 is an example of a sequence diagram of the handover method when the mobile station sets each threshold value.
At this time, it is assumed that in FIG. 1, the mobile unit 1 is talking at the point a, and has moved from the point a to the points b and c thereafter.
The mobile device 1 identifies from the information on the control channel that the wireless base station on which it is talking is the indoor wireless base station 2a. The mobile station 1, which has identified that the wireless base station in communication is the indoor wireless base station 2a, measures the received field strength of the control channel of the adjacent wireless base station and the received field strength change per unit time. . Then, the reception electric field strength of the control channel of the outdoor radio base station 2b exceeds a 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 exceeds a predetermined threshold value, the amount of change in the received electric field strength per unit time regardless of the received electric field strength of the indoor radio base station 2a at that time The mobile device 1 requests the indoor wireless base station 2a to switch channels to the outdoor wireless base station 2b. Upon receiving the channel switching request, the indoor radio base station 2a issues a channel switching instruction to the mobile device 1, and then the mobile device 1 requests the outdoor radio base station 2b to establish a link channel. Thereafter, the handover is performed by performing the procedure shown in FIG. Also, in FIG. 1, when the mobile unit 1 that is talking at the point c moves from the point c to the points b and a, the handover is performed in the same manner as described above.

FIG. 3 shows a mobile station 1 communicating indoors (point a).
Is a diagram showing the timing at which the mobile device 1 performs a handover until the mobile device 1 moves outside (point c). The horizontal axis represents time t, and the vertical axis represents the reception electric field intensity E of the control channel of the radio base station.
The times ta, tb, and tc indicate the times when the mobile device 1 has reached the points a, b, and c in FIG. 1, respectively.
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 'and B2b "indicate the reception electric field strength of the control channel of the outdoor radio base station 2b, and the dashed line α indicates the movement. Is a threshold value of the reception electric field strength preset in the mobile device 1, β is a threshold value of the change amount of the reception electric field intensity 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 a call is disconnected if the received electric field strength is smaller than this. The quantities are ΔE / Δt, ΔE ′ / Δt,
Conventionally, the mobile station 1 is activated when a radio base station having a control channel reception electric field strength exceeding the control channel reception electric field strength of the communicating radio base station appears (point A). In the present invention, the reception electric field intensity B2 of the control channel of the outdoor radio base station 2b is used.
Even if b is lower than the reception electric field intensity B2a of the control channel of the indoor radio base station 2a, the reception electric field intensity B2b exceeds the threshold value α and the reception electric field intensity change amount ΔE / Δt per unit time becomes the threshold value β. , The mobile device 1 performs handover at that time (point B).

When the received electric field strength of the control channel of the outdoor radio base station changes as indicated by a 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 intensity change amount ΔE ′ / Δt per unit time is less than the threshold value β. Is the outdoor radio base station 2b as in the prior art.
A when the received electric field strength B2b of the control channel of the indoor radio base station 2a exceeds the received electric field strength B2a of the control channel of the indoor radio base station 2a.
Hand over at points.

When the received electric field strength of the control channel of the outdoor radio base station changes as indicated by a solid line B2b ", time t '
In the received electric field intensity change ΔE ″ / unit time /
Although Δt is greater than the threshold value β, but the received electric field strength of the control channel of the outdoor wireless base station is less than the threshold value α, the mobile station 1 is connected to the outdoor wireless base station 2b as in the prior art.
A when the received electric field strength B2b of the control channel of the indoor radio base station 2a exceeds the received electric field strength B2a of the control channel of the indoor radio base station 2a.
Hand over at points.

FIG. 4 shows a mobile station 1 communicating outdoors (point c).
Is a diagram showing the timing at which the mobile device 1 performs handover until the mobile device 1 moves indoors (point a). The horizontal axis represents time t, and the vertical axis represents the reception electric field strength E of the control channel of the radio base station.
The times ta, tb, and tc indicate the times when the mobile device 1 has reached the points a, b, and c in FIG. 1, respectively.
In the figure, solid lines B2a, B2a 'and B2a "indicate the received electric field strength of the control channel of the indoor wireless base station 2a, the solid line B2b indicates the received electric field strength of the control channel of the outdoor wireless base station 2b, and the dashed line α indicates the movement. Is the threshold value of the reception electric field strength preset for the mobile device 1, β is the threshold value of the change amount of the reception electric field intensity per unit time preset for 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 a call is disconnected if the received electric field strength is smaller than this. The quantities are ΔE / Δt, ΔE ′ / Δt,
Conventionally, the mobile station 1 is activated when a radio base station having a control channel reception electric field strength exceeding the control channel reception electric field strength of the communicating radio base station appears (point A). In the present invention, the reception 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 α and the reception electric field intensity change ΔE / Δt exceeds the threshold β, At time (point B), the mobile device 1 performs 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 at the point A instead of the point B for the same reason as in FIG. [Embodiment 2] Although Embodiment 1 described above is an embodiment in which the mobile station sets a threshold value in advance, the present embodiment 2 employs the radio base station to set each threshold value to the mobile station. Will be described with reference to the drawings.

FIG. 5 is an example of a sequence diagram of the handover method when the radio base station designates each threshold value to the mobile station. When the mobile device 1 is turned OFF and HOOK indoors, the mobile station 1 first searches for a wireless base station having the maximum received electric field strength of the control channel and requests the wireless base station to establish a link channel. Here, the mobile device 1 is located indoors (a in FIG. 1).
Since it is OFF / HOOK at the point (), it requests the indoor wireless base station 2a to establish a link channel. At this point, the mobile device 1 identifies from the information on the control channel of the indoor wireless base station 2a that the other party that has made the link channel establishment request is the indoor wireless base station 2a. The indoor radio base station 2a that has been requested to establish the link channel is the mobile station 1
Is assigned to the link channel. Next, the mobile device 1 that has identified that the other party that 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 indoor radio base station 2a. Wireless base station 2a
Returns a definition information response to the mobile device 1. The definition information response includes information on the threshold value of the reception electric field strength specified by the indoor radio base station 2a for the mobile device 1 and the threshold value of the change amount of the reception electric field strength per unit time. . The mobile device 1 stores the threshold value of the reception electric field strength designated here and the threshold value of the change amount of the reception electric field intensity per unit time, and stores the threshold value between the mobile device 1 and the indoor radio base station 2a. After the call is connected, the mobile station 1 measures the received field strength of the control channel of the adjacent radio base station and the received field strength change per unit time. Subsequent procedures are the same as in the first embodiment. [Embodiment 3] Embodiment 2 is an example of the handover method when the radio base station designates each threshold value to the mobile station. In Embodiment 3, the radio base station moves the channel switching. This is a handover method when instructing the device.

A configuration diagram of a mobile communication system in which the third embodiment is used is the same as that of the first embodiment and is as shown in FIG.

FIG. 6 shows an example of a handover type sequence map when the radio base station designates channel switching to a mobile station.

At this time, in FIG. 1, it is assumed that the mobile unit 1 is talking at the point a, and has moved from the point a to the points b and c thereafter. The mobile device 1 identifies from the information on the control channel that the wireless base station on which it is talking is the indoor wireless base station 2a. The mobile station 1, which has identified that the wireless base station in communication is the indoor wireless base station 2a, measures the received field strength of the control channel of the adjacent wireless base station and the received field strength change per unit time. . The mobile device 1 notifies the indoor radio base station 2a of the measurement result at a fixed period. The indoor radio base station 2a is notified of the threshold value of the reception electric field strength of the control channel and the threshold value of the change amount of the reception electric field strength per unit time, which are set in advance by the own station, from the mobile station 1 at regular intervals. And compare it with the measurement result. As a result of the comparison, 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 change amount of the reception electric field strength of the control channel of the outdoor radio base station 2b is set. If the received electric field strength change per unit time exceeds the threshold value, the indoor radio base station 2a will be in contact with the mobile device 1 at the time regardless of the received electric field strength of the indoor radio base station 2a. To switch the channel to the wireless base station 2b. Mobile station 1 that has received a channel switching instruction
Requests the outdoor wireless base station 2b to establish a link channel. Thereafter, 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 communicating indoors moves outdoors or when a mobile unit talking outdoors has moved indoors. If there is a wireless base station having a received electric field strength exceeding the threshold value of the received electric field strength and having a received electric field strength change amount exceeding a preset threshold value of the received electric field change amount, communication is performed. Even if the receiving electric field strength of the middle radio base station is not deteriorated yet and the communication strength is high, the radio having the receiving electric field strength exceeding the threshold value and the receiving electric field strength change amount from the communicating radio base station. Since the handover to the base station is performed, when the communicating mobile unit moves from indoors to outdoors or from outdoors to indoors, the reception electric field strength of the wireless base station used up to that point suddenly deteriorates due to obstacles or the like. Hand over Call has prevent effects that would be cut.

[Brief description of the drawings]

FIG. 1 is a diagram showing one embodiment of a mobile communication system using a handover method of the present invention.

FIG. 2 is a sequence diagram in the first embodiment of the handover method 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 a handover timing according to the present invention.

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

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

[Explanation of symbols]

 Reference Signs List 1 mobile station 2a indoor radio base station 2b, 2c outdoor radio base station 3 mobile switching center 4a-4c wireless zone point a-c point location of mobile station 1

Claims (3)

(57) [Claims] 1. An exchange, at least one radio base station for performing radio channel control for a mobile station and for making a call connection with the exchange, and a service area formed by the radio base station The mobile base station comprises a mobile station capable of talking with a fixed network subscriber, and the wireless base station includes an indoor base station and an outdoor base station, and the mobile station can talk both indoors and outdoors. A mobile communication system, wherein the mobile station has a function of identifying whether a communicating radio base station and an adjacent radio base station are an indoor radio base station or an outdoor radio base station, and the adjacent radio base station And a function of measuring the amount of change in the received electric field strength per unit time and the received electric field strength per unit time. When the wireless base station with which the mobile device is communicating is an indoor wireless base station, an adjacent outdoor wireless base station is used. The received electric field strength of the base station and If the amount of change in the received electric field strength per unit time exceeds both thresholds set in advance for the mobile device, the mobile device is controlled by the mobile device regardless of the received electric field intensity of the indoor radio base station. Requesting the indoor radio base station to switch channels from the indoor radio base station to the outdoor radio base station, and if the radio base station with which the mobile station is communicating is the outdoor radio base station If the received electric field intensity of the adjacent indoor radio base station and the amount of change in the received electric field intensity per unit time exceed both thresholds preset for the mobile station, the outdoor radio base station A handover method wherein the mobile station requests the outdoor radio base station to switch channels from the outdoor radio base station to the indoor radio base station regardless of the reception electric field strength of the station. 2. A function in which an exchange or a radio base station designates a threshold value of a reception field strength and a threshold value of a change amount of a reception field strength per unit time for a mobile station, A function of storing a threshold value of the electric field strength designated by the exchange or the radio base station and a threshold value of a change amount of the received electric field strength per unit time. 1. The handover method according to 1. 3. A function in which a mobile station identifies whether a communicating radio base station and an adjacent radio base station are an indoor radio base station or an outdoor radio base station, and a reception electric field strength of the adjacent radio base station. And the amount of change in the received electric field strength per unit time, 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 fixed cycle. Having a function, the indoor radio base station, the reception electric field intensity and the reception electric field intensity change amount per unit time previously set in the indoor radio base station in the measurement result notified from the mobile device. If there is an outdoor wireless base station having a received electric field strength exceeding the threshold value and a received electric field strength change amount per unit time, the outdoor radio base station is irrespective of the received electric field strength of the own station. Access to base station A function of instructing the mobile station to perform a tunnel switching, wherein the outdoor radio base station is configured to receive a reception electric field previously set in the outdoor radio base station in the measurement result notified from the mobile station. If there is an indoor wireless base station that has both a received electric field strength exceeding the threshold value and the received electric field strength change per unit time, The handover method according to claim 1, further comprising a function of instructing the mobile device to switch a channel from the own station to the indoor radio base station regardless of the strength.