Telecommunications – Radiotelephone system – Zoned or cellular telephone system
Reexamination Certificate
2001-01-23
2004-04-27
Appiah, Charles (Department: 2686)
Telecommunications
Radiotelephone system
Zoned or cellular telephone system
C455S456100, C370S336000
Reexamination Certificate
active
06728539
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to methods of registering the locations of mobile communication systems, and, more particularly, to a method of registering the location in a mobile communication system that registers the location of each mobile device. The present invention also relates to the mobile device.
2. Description of the Related Art
A mobile communication system comprises a plurality of base stations, and a mobile device connected to a mobile switching center via the base stations, thereby establishing a connection with another mobile device or a fixed device. To call a mobile device, the mobile switching center needs to grasp where the mobile device is located, i.e., near which base station the mobile device is located.
Conventionally, a location area (or a network fixed location registration area) LAi is allocated to each group of base stations, as shown in FIG.
1
. In this figure, each small circle represents the area of a base station, and each large circle represents a location area. In this case, only when a mobile device moves from one location area to another, the mobile device transmits a location registration signal to the mobile switching center, thereby performing a location registration operation. The mobile switching center manages the location of the mobile device in each location area LAi. When the mobile device receives a call, a simultaneous call operation is performed on all the base stations corresponding to the location area LAi in which the location of the mobile device is registered.
The information of each location area LAi is incorporated in notification information that is constantly sent from the base stations. The mobile device compares its location area LAi with the location area LAi defined by the notification information. If the location area LAi of the mobile device does not coincide with the location area LAi, the mobile device transmits a location registration signal so as to perform a location registration operation. The mobile switching center manages the information of each mobile device, including the current location (i.e., the location area LAi). The information is managed by a HLR (Home Location Register) or a VLR (Visitor Location Register). When the mobile device receives a call, the mobile switching center refers to the HLR or VLR, and reads out the location area LAi corresponding to the mobile device. All the base stations (BSj) corresponding to the location area LAi then simultaneously call the mobile device.
If each location area LAi is made smaller, the call signal traffic can be made smaller accordingly, but the location registration signal traffic is increased. If each location area LAi is made larger, the location registration signal traffic can be made smaller, but the call signal traffic is increased. Therefore, in a mobile communication network, the size of each location area LAi (or the number of base stations) is determined in such a manner as to optimize the balance between the location registration signal traffic and the call signal traffic.
To reduce the location registration signal traffic and the call signal traffic, various suggestions have been made. In a case where a mobile device moves in the vicinity of the boundary of a location area LAi, to prevent an increase in location registration signal traffic, the location area has a hierarchical structure. More specifically, a first-layer location area and a second-layer location area have different boundaries from each other. If the location of a mobile device changes in the first-layer location area LAi, the location is registered in the second-layer location area, thereby giving hysteresis to the location registration operation.
For a mobile device having a high motion frequency and a small call reception frequency, a location registration operation is performed with a location area LAi that extends in a wide area. On the other hand, for a mobile device having a low motion frequency and a high call reception frequency, a location registration operation is performed with a location area LAi that extends only in a narrow area, thereby reducing the location registration signal traffic and the call signal traffic. However, those location areas LAi are selected from predetermined ones on the network side, resulting in unnecessary call signal traffic.
Generally, a person's sphere of action is limited. For some people, a location registration operation is performed between their houses and workplaces. For others, a location registration operation is performed only in the vicinity of their houses. In this case, the location registration operation in the location registration area shown in
FIG. 1
results in unnecessarily large call signal traffic. In order to avoid such unnecessary call signal traffic, the following suggestions have been made.
Japanese Laid-Open Patent Application No. 8-84364 discloses a mobile switching center call system in a cellular phone network. As shown in
FIG. 2
, in a case where a mobile device frequently moves between two location registration areas MLA
1
and MLA
2
, it is necessary to restrict the location registration signal traffic that increases every time the location registration areas are changed. In the mobile switching center call system, the following operation is performed. A plurality of base stations near which the mobile device has a high probability of being located are determined in advance, in accordance with the tendency of call transmission and reception of the mobile device. The plurality of base stations are then registered as a virtual mobile location area VMLA that is inherent to the mobile device, thereby preventing a location registration operation even when the mobile device moves within the location registration areas MLA
1
or MLA
2
. The base stations in the virtual mobile location area VMLA are a first call group, the base stations in the rest of the location registration area MLA
1
are a second call group, and the base stations in the rest of the location registration area MLA
2
are a third call group. When the mobile device receives a call, the first call group, the second call group, and the third call group are called in this order.
Japanese Laid-Open Patent Application No. 9-116952 discloses a mobile communication system in which a location registration area is formed within each user's sphere of action, as shown in FIG.
3
. When the mobile device is located within the location registration area, a location registration operation is not performed, thereby reducing the location registration signal traffic. The mobile device counts the number of base stations near which the mobile device passes, and notifies the network of the result, if necessary. The mobile device notifies the mobile switching center of which base stations the mobile device frequently passes near and stays over a long period of time.
The mobile switching center stores the base stations notified from the mobile device. When the mobile device receives a call, the mobile switching center carries out a simultaneous call operation on all the registered base stations for the mobile device. Also, depending on the passing count number and the duration of stay, the base stations are grouped in the descending order of probability of having the mobile device staying therein. In
FIG. 3
, the staying probability of the mobile device is the highest at the base stations with black solid circles, the second highest at the base stations with double circles, and the lowest at the base stations with single circles. When the mobile device receives a call, the mobile switching center first calls the base stations with the black solid circles. If the mobile switching center cannot detect the mobile device, the mobile switching center calls the base stations with the double circles for the mobile device. If the mobile device cannot be found yet, the mobile switching center calls the group of base stations with the single circles. If the mobile device moves outside the shaded area,
Appiah Charles
Katten Muchin Zavis & Rosenman
Mehrpour Naghmeh
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