Telecommunications – Carrier wave repeater or relay system – Portable or mobile repeater
Reexamination Certificate
2001-02-12
2004-03-30
Maung, Nay (Department: 2684)
Telecommunications
Carrier wave repeater or relay system
Portable or mobile repeater
C455S007000
Reexamination Certificate
active
06714762
ABSTRACT:
CROSS REFERENCE TO RELATED APPLICATION
This application claims benefit of priority under 35 U.S.C. § 119 to Japanese Patent Application No. 2000-35824, filed on Feb. 14, 2000, the entire contents of which are incorporated by reference herein.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a radio communication system in which a terminal communicates by radio through a repeater, and more particularly to a radio communication system allowing continuous communication under an environment where shielding objects move by selecting a terminal in an optimum receiving condition, a radio communication method and a recording medium for storing a program for selection of a repeater in the radio communication system.
2. Description of the Related Art
In a conventional radio communication for communicating with a moving terminal through a public communication network, if field intensity of electronic wave received by the moving terminal weakens, the moving terminal switches its base station so as to continue the communication.
Here, a radio communication system using the conventional public communication network will be described with reference to FIG.
1
. In the radio communication system shown in
FIG. 1
, field intensity of electronic wave received by a moving terminal
51
is detected.
If the field intensity of the received electronic wave weakens as this moving terminal
51
moves, the moving terminal
51
dispatches a communication channel switching request to a base station
52
on communication. This switching request is sent from the base station
52
to a control station
53
and then, this control station
53
notifies the moving terminal
51
of a base station
54
which has the highest receiving level of plural base stations from which the moving terminal
51
can receive electronic wave as a new base station. Consequently, the moving terminal
51
can switch communication to the base station
54
located in an area to which the moving terminal
51
moves, so that it can continue communication during moving.
In this radio communication system, when switching the base station, a communication channel between the moving terminal
51
and the base station
52
on communication is kept and if a new communication channel capable of communicating at a receiving level from the base station
54
located in an area to which the moving terminal
51
moves is found, communication with the base station
54
is started through the new communication channel.
This conventional radio communication system produces no problems under a communication system which assumes that field intensity drops gradually when the moving terminal
51
moves as seen in a wide area based on the public communication network and allows communication through a currently used communication channel in a while during the moving. However, the conventional radio communication system cannot be applied to such an environment in which the field intensity drops suddenly when the terminal or shielding object moves like in communication in a small area.
Particularly, the field intensity is proportional to 1/(distance)
2
and thus depends upon a distance between the moving terminal and base station. In case where the unit of distance is large like in communication system using the public communication network, even if the distance changes more or less, the field intensity never changes largely. However, if the unit of distance is small like in indoor radio communication system in vehicle compartment or factory, the field intensity changes largely due to a slight change of the distance.
Further, the indoor radio communication system employs a minute or small output power. Thus, if such a shielding object as wall, man, chair or equipment moves near communication path, electronic wave damps largely even if the distance is not changed, so that communication maybe sometimes disabled.
In indoor radio LAN system shown in
FIG. 2
, repeaters
62
a
,
62
b
,
62
c
connected to the wired LAN
61
are provided on ceiling and terminals
63
a
,
63
b
,
63
c
are communicating with a repeater located just vertically above. That is, the terminal
63
a
is communicating with the repeater
62
a
, the terminal
63
b
is communicating with the repeater
62
b
and the terminal
63
c
is communicating with the repeater
62
c
. Consequently, this radio communication system lowers a possibility that communication between the terminal and repeater is interrupted.
This radio LAN system can secure a sufficient space just vertically above the terminal and any shielding object never enters between the repeater and the terminal. Further, the above described problem can be solved under an environment in which the terminal and shielding object are semi-fixed, like office. However, there is a possibility that any shielding object may enter between the terminal and the repeater under such an environment in which no sufficient space can be secured as the vehicle compartment and factory, so that the above-described problem cannot be solved.
SUMMARY OF THE INVENTION
The present invention has been achieved in views of the above described problem and therefore an object of the present invention is to provide a radio communication system capable of securing continuous communication even under an environment in which no sufficient space can be secured and a terminal or shielding object moves, by selecting a repeater which secures an optimum communication state from plural repeaters, a radio communication method thereof and a recording medium for storing a program for selection of a repeater in radio communication system.
To achieve the above described object, according to an aspect of the invention, there is provided a radio communication system for a terminal to carry out radio communication through a repeater securing an optimum communication state selected from plural repeaters, wherein a reception condition of a repeater when each of plural repeaters receives a connection request sent from the terminal through broadcast is detected as a repeater reception condition and a reception condition of a terminal when the terminal receives a connection request echo sent from the plural repeaters after receiving the connection request is detected as a terminal reception condition so as to select a repeater securing an optimum communication state based on the terminal reception condition and the repeater reception condition.
According to the present invention, communication is carried out always by selecting a repeater securing an optimum communication with each terminal. Therefore, this communication method enables continuous communication to be carried out under such an environment in which no sufficient space can be secured and a terminal and a shielding object move, as vehicle compartment and factory.
Further, to achieve the above object, according to another aspect of the invention, there is provided a radio communication system for a terminal to carry out radio communication through a repeater securing an optimum communication state selected by a path management repeater from plural repeaters, the system comprising: a terminal for sending a connection request for starting radio communication through broadcast, receiving a connection request echo sent back by a repeater receiving the connection request so as to detect a reception condition at this time as a terminal reception condition and sending the terminal reception condition through broadcast; plural repeaters for receiving the connection request sent by the terminal so as to detect a reception condition at this time as a repeater reception condition, sending the connection request echo including the repeater reception condition to the terminal and the path management repeater and when receiving the terminal reception condition sent by the terminal, sending the terminal reception condition to the path management repeater; and a path management repeater for receiving the connection request sent by the terminal so as to detect a reception condition at this time as a repeat
Maung Nay
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Trinh Tan
Yazaki -Corporation
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