Telecommunications – Transmitter and receiver at separate stations – Distortion – noise – or other interference prevention,...
Reexamination Certificate
2000-12-20
2004-03-23
Maung, Nay (Department: 2684)
Telecommunications
Transmitter and receiver at separate stations
Distortion, noise, or other interference prevention,...
C455S025000, C455S562100, C455S277200
Reexamination Certificate
active
06711382
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a mobile communication system and a communication method performed in the mobile communication system in which a radiation pattern of a signal output from an antenna of a base station and a radiation pattern of a signal output from an antenna of a mobile station such as a portable telephone or a portable information terminal are controlled in a communication between the base station and the mobile station to improve a communication quality in both the base station and the mobile station.
2. Description of Related Art
FIG. 7
is an explanatory view showing a signal transmission from a mobile station to a base station in a conventional mobile communication system, for example, disclosed in Published Unexamined Japanese Patent Application H9-219615 (1997), and
FIG. 8
is an explanatory view showing the reception of a signal output from a base station in a mobile station in the conventional mobile communication system. In FIG.
7
and
FIG. 8
,
1
indicates an antenna of a base station. A directivity control of an adaptive antenna is performed for the antenna
1
of the base station in signal transmission and reception operations of the base station.
2
indicates an antenna of a mobile station such as a portable telephone or a portable information terminal.
3
indicates an interference wave source for reflecting a transmission wave output from the antenna
1
of the base station and a transmission wave output from the antenna
2
of the mobile station. R
1
denotes a space distribution indicating a radiation characteristic of the antenna
1
of the base station for a signal received in the antenna
1
of the base station. T
2
denotes a space distribution indicating a radiation characteristic of the antenna
1
of the base station for a signal transmitted from the antenna
1
of the base station. T
1
denotes a space distribution indicating a radiation characteristic of the antenna
2
of the mobile station for a signal transmitted from the antenna
2
of the mobile station. R
2
denotes a space distribution indicating a radiation characteristic of the antenna
2
of the mobile station for a signal received in the antenna
2
of the mobile station.
Next, an operation is described.
As shown in
FIG. 7
, in a signal transmission operation in which a desired signal is transmitted from the mobile station to the base station, a transmission directivity inherently held in the antenna
2
of the mobile station is used in the mobile station as it is. That is, a space distribution T
1
indicating a radiation characteristic of the antenna
2
is determined according to the transmission directivity. Therefore, a signal is transmitted from the antenna
2
of the mobile station according to the space distribution T
1
. In this case, because the space distribution T
1
is uniform in all directions, the signal is equally transmitted in all directions.
In contrast, as shown in
FIG. 7
, a directivity control of an adaptive antenna is performed for the antenna
1
of the base station to form a space distribution R
1
, which indicates a radiation characteristic of the antenna
1
for a signal received in the antenna
1
of the base station, as a reception directivity. In this space distribution R
1
denoting the reception directivity of the antenna
1
, a main beam of the antenna
1
is directed in a desired signal coming direction to receive a desired signal directly coming from the mobile station, and the reception directivity toward the interference wave source
3
is set to zero in cases where a reflected wave is transmitted from the interference wave source
3
. Therefore, even though a reflected wave output from the interference wave source
3
comes as an interference wave to the antenna
1
of the base station, the reception of the interference wave in the antenna
1
can be prevented according to the space distribution R
1
of the radiation characteristic of the antenna
1
, and a desired signal directly coming from the mobile station is received in the antenna
1
at a prescribed communication quality.
Also, as shown in
FIG. 8
, in a signal transmission operation in which a desired signal is transmitted from the base station to the mobile station, a directivity control of an adaptive antenna is performed for the antenna
1
of the base station to form a space distribution T
2
, which indicates a radiation characteristic of the antenna
1
for a signal transmitted from the antenna
1
of the base station, as a transmission directivity. The space distribution T
2
denoting the transmission directivity of the antenna
1
is determined by multiplying the space distribution R
1
, which indicates the reception directivity of the antenna
1
, by an assumed weighting factor. Therefore, in this space distribution T
2
of the radiation characteristic of the antenna
1
, a main beam of the antenna
1
is directed in a desired signal transmitting direction to directly transmit a desired signal to the mobile station, and the transmission directivity toward the interference wave source
3
is set to zero. Therefore, no signal is output from the antenna
1
of the base station to the interference wave source
3
according to the space distribution T
2
of the radiation characteristic of the antenna
1
, and no reflected wave is output from the interference wave source
3
.
In contrast, as shown in
FIG. 8
, in the antenna
2
of the mobile station, a reception directivity inherently held in the antenna
2
of the mobile station is used in the mobile station as it is, and a space distribution R
2
of a radiation characteristic of the antenna
2
is determined according to the reception directivity. Therefore, a desired signal directly transmitted from the antenna
1
of the base station is received in the antenna
2
of the mobile station according to the space distribution R
2
. In this case, because the space distribution R
2
is uniform in all directions, signals arriving from all directions are equally received in the antenna
2
of the mobile station.
As is described above, in the conventional mobile communication system shown in FIG.
7
and
FIG. 8
, the directivity control of the adaptive antenna is performed for the antenna
1
of the base station in the signal transmission and reception operations. Therefore, the reception of the interference wave, which is output from the interference wave source
3
, in the antenna
1
of the base station and the antenna
2
of the mobile station can be prevented, and a communication quality in the signal transmission and reception operations can be improved.
Next, a case that a problem occurs in the conventional mobile communication system is described.
FIG. 9A
is another explanatory view showing a signal transmission from a mobile station to a base station in the conventional mobile communication system shown in FIG.
7
and
FIG. 8
, and
FIG. 9B
is another explanatory view showing the reception of a signal output from a base station in a mobile station in the conventional mobile communication system shown in FIG.
7
and FIG.
8
. In FIG.
9
A and
FIG. 9B
,
4
indicates an interference wave source denoted by an antenna of a second mobile station such as a portable telephone or a portable information terminal.
As shown in
FIG. 9A
, in the signal transmission from the mobile station to the base station, the directivity control of the adaptive antenna is performed for the antenna
1
of the base station to form the space distribution R
1
, which indicates the radiation characteristic of the antenna
1
for a signal received in the antenna
1
, as the reception directivity. That is, in this space distribution R
1
, a main beam of the antenna
1
is directed in a desired signal coming direction, and the reception directivity toward the interference wave source
4
is set to zero in cases where a reflected wave is transmitted from the interference wave source
4
. Therefore, the reception of an interference wave, which comes from the interference wave source
4
, i
Chiba Isamu
Hara Yoshitaka
Urasaki Shuji
Lee John J
Maung Nay
Mitsubishi Denki & Kabushiki Kaisha
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