Telecommunications – Radiotelephone system – Zoned or cellular telephone system
Reexamination Certificate
1999-08-30
2002-10-22
Bost, Dwayne (Department: 2681)
Telecommunications
Radiotelephone system
Zoned or cellular telephone system
C455S552100, C455S439000
Reexamination Certificate
active
06470184
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a mobile communication system, and more particularly, to a mobile communication system in which traffics are equalized between switching apparatuses.
2. Description of the Related Art
Conventionally, various mobile telephone systems are known such as a PHS (personal handy phone system) in which a minimal cell method is adopted, an automobile telephone system in which a small cell method is used, and a PDS (portable digital phone system). Each of the mobile phone systems have a merit and a defect.
For example, in the PHS system, the area which a radio wave reaches has the radius about 100 m from a base station. Therefore, in order to form a wide service area, a lot of base stations are densely installed. As a result, there is a problem in that there is an area where the radio wave is difficult to be received, depending on the installed state of the base stations. On the other hand, there is an advantage in low communication charge in the PHS system, compared with the other mobile phone systems.
On the other hand, in the PDS system, because the small cell method is adopted such that the radio wave can reach to a relatively wide area, there is a low possibility of the above-mentioned problem that the radio wave is difficult to be received. However, there is a problem in a high communication charge in the PDS system, compared with the PHS system.
In order to eliminate such a conventional problem, a dual band portable phone is discussed in recent years to be possible to be applied to two mobile phone systems such as the PHS system and the PDS system. In the following description, an operation mode is referred to as a “PHS mode” when the dual band portable phone operates as a mobile station of the PHS system, and as a “PDS mode” when the dual band portable phone operates as the mobile station of the PDS system.
The switching of the operation mode in the dual band portable phone, i.e., the switching of the mobile communication system is conventionally carried out on the dual band portable phone. That is, a control unit of the dual band portable phone operates in the PHS mode when the dual band portable phone is in a service area of the PHS system and out of any service area of the PDS system. Oppositely, the operation mode of the dual band portable phone operates is automatically switched to the PDS mode when the dual band portable phone is out of any service area of the PHS system and in a service area of the PDS system. Also, the control unit of the dual band portable phone automatically switches the operation mode to be PHS mode with low communication charge, when the dual band portable phone is in an area which is covered by the PHS system and the PDS system.
Also, the dual band portable phone is possible to operate in either of the PHS mode or the PDS mode in response to the operation of a predetermined button by a user in addition to the automatic switching.
Conventionally, the mobile communication system to which the dual band portable phone belongs is selectively switched based on the control of the dual band portable phone itself, as mentioned above. In this case, the traffic of a base station of each mobile telephone system is not considered. Therefore, the dual band portable phone sometimes operates in the PHS mode with a large traffic quantity while the traffic of the PDS system is small. Or, the opposite situation occurs. As a result, there is a problem in degradation of communication quality due to traffic jam.
It should be noted that “a digital radio communication system and a digital radio communication apparatus” is disclosed in Japanese Laid Open Patent Application (JP-A-Heisei 10-65606) as the technique to improve the communication quality. In the reference, the communication system is composed of base stations A
1
to C
1
and terminal stations A
2
to C
2
. Radio communications between the base station and the terminal station and between the base stations are carried out. In such a digital radio communication system, the base station selects a combination of the frequency with a smallest transmission error to noise around the base station and a convolution code, and communicates using the frequency and the convolution code of the selected combination.
In this way, an error correcting code used for the communication is appropriately selected in accordance with the radio wave situation around the communication environment. As a result, the deterioration of the communication quality which is caused by the transmission path error can be restrained because the transmission path error becomes little. However, in this digital radio communication system, it is not possible to prevent the deterioration of the communication quality which is caused by the large traffic.
In conjunction with the above description, a mobile communication system is described in Japanese Laid Open Patent Application (JP-A-Heisei 4-70094). In this reference, a service area is composed of a plurality of zones, in which base stations are respectively provided. A mobile station communicates with one of the base stations. When the mobile station moves to an adjacent area during the communication, the base station is switched to another base station for the adjacent area. Each base station has notifying means for notifying a control channel frequency information. of the other base station for the adjacent area and a channel operation percentage of the base station. The mobile station has monitoring means and a selecting means. The monitoring means monitors the channel operation percentage notified from each base station and reception levels from each base station. The selecting means selects one of the base stations which has the reception level higher than a predetermined value and the channel operation percentage lower than a predetermined value as a switching destination base station.
Also, a traffic distributing system in a mobile communication system is described in Japanese Laid Open Patent Application (JP-A-Heisei 5-75530). In the reference, a traffic distribution start threshold value T
1
, a traffic distribution stop threshold value T
2
, and a channel selection re-execution instruction transmission period &tgr; are stored in a main control unit of a radio base station. When a communication channel usage percentage exceeds the traffic distribution start threshold value T
1
, the transmission of a channel selection re-execution instruction is started at the transmission period T&tgr;. When the communication channel usage percentage is decreased below the traffic distribution stop threshold value T
2
, the transmission of the channel selection re-execution instruction is stopped. Thus, a mobile terminal communicating with a radio base station which has no empty communication channel because of a high traffic quantity is made to communicate with another radio base station.
Also, a mobile communication system is described in Japanese Laid Open Patent Application (JP-A-Heisei 7-226973). In the reference, permission or inhibition of mode switching between one mode and another mode is set for each of zones which corresponds to at least one mode. An unnecessary mode switching is restrained in the mobile communication system in which communication is carried out using one selected from a plurality of modes.
Also, a communication channel switching system is described in Japanese Laid Open Patent Application (JP-A-Heisei 8-70479). In the reference, a control station (
5
) notifies a usable communication channel to a mobile station (
1
) via base station (
2
,
3
). The mobile station monitors the present communication condition. When the communication condition is degraded, the mobile station independently switches to a new channel by which good communication condition is attained. The mobile station notifies the new channel to the control station (
5
) via the base station (
2
,
3
).
Also, a communication restriction control system is described in Japanese Laid Open Patent Application (JP-A-Heisei 9-9340). In the
Bost Dwayne
Gelin Jean A.
McGinn & Gibb PLLC
NEC Corporation
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