Telecommunications – Transmitter and receiver at same station – Radiotelephone equipment detail
Reexamination Certificate
2000-02-28
2001-10-02
Maung, Nay (Department: 2681)
Telecommunications
Transmitter and receiver at same station
Radiotelephone equipment detail
C455S067150, C455S502000
Reexamination Certificate
active
06298248
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a base station apparatus and frame synchronization acquisition method in a radio communication system in which frame synchronization is acquired between base station apparatuses.
2. Description of the Related Art
In radio communication systems, in order to cancel interference between base station apparatuses to increase the system capacity, as disclosed in Japanese Unexamined Patent Publication HEI5-308333, a method is sometimes adopted in which the frame synchronization is acquired between a plurality of base station apparatuses, and the timing of a transmission slot and that of a reception slot are made the same between the base station apparatuses.
FIG. 1
is a diagram illustrating a radio communication system including conventional base station apparatuses. It is assumed that base station apparatus
12
synchronizes the frame timing thereof with the frame timing of base station apparatus
11
which is currently a reference of the frame synchronization. It is further assumed that base station apparatus
11
performs communications with mobile station apparatuses
21
and
23
existing in communication area
31
of base station apparatus
11
, base station apparatus
12
performs communications with mobile station apparatus
22
existing in communication area
32
of base station apparatus
12
, and that base station apparatus
13
starts communicating.
Base station apparatus
13
acquires the frame timing of base station apparatus
11
which is the reference of the frame synchronization before starting ordinary communications. In this case, since base station apparatus
11
exists out of communication area
33
of base station apparatus
13
, base station apparatus
13
cannot receives a signal from base station apparatus
11
directly.
Therefore, base station apparatus
13
synchronizes the frame timing thereof with that of base station apparatus
12
to be indirectly in frame synchronization with base station apparatus
11
. Base station apparatus
13
starts communicating with mobile station apparatus
24
existing in communication area
33
thereof after acquiring the frame synchronization.
Thus, in the case where the conventional base station apparatus detects the frame timing of a neighboring base station apparatus to synchronize, the conventional base station apparatus detects the frame timing of the neighboring base station apparatus existing closest thereto, and performs communications in synchronization with the frame timing of such a neighboring base station apparatus.
FIG. 2
is a diagram illustrating the frame timing of each base station apparatus after the frame synchronization acquisition is completed.
As illustrated in
FIG. 2
, due to errors caused by that each base station apparatus receives a transmission signal from another base station apparatus to detect the timing, the transmission timings of frames to mobile station apparatuses from respective base station apparatuses are not completely synchronous, resulting in errors almost equivalent to a guard time.
Since the error of the transmission timing between base station apparatuses
11
and
12
is within a range of the guard time, and both base station apparatuses do not transmit a message at the guard time portion, interference does not occur between both base stations. Similarly, the interference does not occur between base station apparatuses
12
and
13
.
However, the error of the frame synchronization between the base station apparatuses are accumulated, and consequently some part of the transmission signal of base station apparatus
11
and that of base station apparatus
13
overlap in time each other, causing the case where the interference sometimes occurs between base station apparatuses
11
and
13
.
Such interference occurs at a portion with oblique lines in
FIG. 1
where the communication area of base station apparatus
11
and that of base station apparatus
13
overlap each other. Accordingly, as illustrated in
FIG. 2
, the interference occurs when base station apparatus
13
transmits a signal to mobile station apparatus
24
in some frame, and base station apparatus
11
transmits a signal to mobile station apparatus
11
in next frame.
Thus, in the conventional base station apparatuses, when a base station apparatus with the frame timing as a reference of the frame synchronization does not exist in the communication area of some apparatus, the apparatus does not acquire the frame synchronization directly, but acquires that indirectly, resulting in the problem that errors of frame timings between the base station apparatuses become large, and that the interference occurs.
SUMMARY OF THE INVENTION
An object of the present invention i s to provide a base station apparatus and frame synchronization method which do not cause interference between base station apparatuses in the case where a base station apparatus as a reference of frame synchronization does not exist in an ordinary communication area.
The base station apparatus of the present invention achieves the above object by controlling the directivity of an antenna to receive a transmission signal from the base station apparatus as the reference of frame synchronization directly with the antenna, detecting a transmission timing of the base station apparatus as the reference of synchronization, and controlling the transmission timing thereof in accordance with the detected transmission timing.
REFERENCES:
patent: 4231114 (1980-10-01), Dolikian
patent: 5613211 (1997-03-01), Matsuno
patent: 5722080 (1998-02-01), Kondo
patent: 5761198 (1998-06-01), Kojima
patent: 5774810 (1998-06-01), Sugi
patent: 5875402 (1999-02-01), Yamawaki
patent: 6081571 (2000-06-01), Jansson
patent: 6097709 (2000-08-01), Kuwabara
patent: 6112088 (2000-08-01), Haartsen
patent: 6119016 (1998-06-01), Matusevich
patent: 5308333 (1993-11-01), None
Hiramatsu Katsuhiko
Miyoshi Ken'ichi
Matsushita Electric - Industrial Co., Ltd.
Maung Nay
Stevens Davis Miller & Mosher LLP
Vuong Quochien B.
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