Radio communications system

Details Radio communications system Radio communications system

1999-04-08

2003-09-02

Bost, Dwayne (Department: 2681)

Telecommunications

Radiotelephone system

Zoned or cellular telephone system

C455S447000, C455S562100

Reexamination Certificate

active

06615047

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a radio communications system which establishes connection, through a radio channel, between a fixed terminal located at the home of an ordinary subscriber or at a business establishment and an exchange or a basic trunk cable, and which offers communications services such as a telephone service, an information service, a graphic service, and a multimedia service.
2. Description of the Related Art
A conventional dominant cell structure employed in the field of mobile communications such as that found in a radio system is a sector cell configuration, wherein a directional antenna is used for a site formed from a plurality of sector cells (often simply referred to as “sectors”).
FIGS. 27 and 28
show an example of the sector cell configuration. In
FIG. 27
, each site is formed from three sectors. Seven sites comprising a total of
21
sectors are handled as a unit, and frequencies are allocated repeatedly on a per-unit basis (such a configuration will hereinafter be referred to simply as a “frequency repetition every three-sectors/seven-sites”).
FIG. 28
shows an example in which each site is formed from six sectors. Seven sites comprising
42
sectors are handled as a unit, and frequencies are allocated repeatedly on a per-unit basis (such a configuration will be hereinafter referred to as a “frequency repetition every six-sectors/seven-sites”). In the drawings, reference numerals
91
to
97
and
98
to
103
designate sites; and
97
and
104
designate service areas, wherein areas allotted the same reference numerals are assigned the same frequency. In
FIG. 27
, the site
91
receives an interference wave signal of 7.7 dB emitted from fixed terminal stations disposed in the service areas
97
of the sites
92
to
96
. In
FIG. 28
, the site
98
receives an interference wave signal of 10.5 dB emitted from the fixed terminals disposed in the service areas
104
of the sites
99
to
103
.
FIG. 29
is a plan view similar to a plan view of sector zones provided in Japanese Patent Application Laid-Open No. Hei-8-193556 entitled “Radio System,” showing the relationship between frequencies used among adjacent sites and the layout of beams emanated from antennas. In the drawing, reference numerals
105
to
107
designate service areas of individual antennas, and areas allotted the same reference numeral are assigned the same frequency. Reference numerals
108
and
109
designate sites; and
110
designates a fixed terminal station. In a radio communications system, radio communication is established between a site, such as a subscriber radio system, and a plurality of fixed terminal stations disposed in a cell covered by the site. As can be seen from the cell layout shown in
FIG. 29
, in each of the plurality of adjacent sites frequencies are assigned to the cells in the same sequence. Further, the centers of the beams emanated at the same frequency from the antennas are offset from one site to another adjacent site by an amount approximately equal to the beam angle.
In a conventional radio communications system, a certain district is divided into a plurality of cells, and a site is disposed at the center of each cell. Radio communication is established between the site and a plurality of fixed terminals disposed in the cell where the site is located. The cells are assigned frequencies in the same sequence, and the centers of beams emanated from the antennas are offset from one site to another adjacent site by an amount approximately equal to the beam angle. As shown in
FIG. 29
, a fixed terminal
110
receives a radio wave signal from the site
109
, in addition to a radio wave signal from the site
108
, thus receiving interference wave signals of the same frequency. At this time, a receiving carrier-to-interference (C/I) ratio, which is a ratio of carrier wave signal power to interference wave signal power is 5.2 dB, thus inducing considerable radio interference.
SUMMARY OF THE INVENTION
The present invention has been made to solve the above problems with the prior art, and therefore an object of the present invention is to provide a radio communications system which diminishes the level of radio interference by ensuring a sufficient C/I ratio and required frequencies.
According to a first aspect of the present invention, there is provided a radio communications system which establishes radio communication between arbitrary sites and fixed terminal stations which are directional and disposed in a cell centered on the site, wherein
each of the sites is provided with three antennas of equal horizontal beam width and whose orientations are horizontally offset from one another;
at each site, the beams emanated from the individual antennas, as a whole, cover all horizontal directions;
the antennas assigned the same frequency as that of the site are arranged in the same sequence;
a cell group comprises three cells, in which the centers of beams emanated from the antennas assigned the same frequency are offset from one site to another site by an amount approximately equal to the beam width;
the cells are adjacent to one another;
the cell group comprises a plurality of groups of different frequencies and constitutes a minimum unit area to be repeated; and
the minimum unit areas are repeatedly arranged in longitudinal and lateral directions.
According to a second aspect of the present invention, there is provided a radio communications system which establishes radio communication between arbitrary sites and fixed terminal stations which are directional and disposed in a cell centered on the site, wherein
each of the sites is provided with “n” (where “n” represents a positive integer equal to or greater than 4) sector antennas which are equal in horizontal beam width and whose orientations are horizontally offset from one another;
at each site the beams emanated from the individual antennas, as a whole, cover all horizontal directions;
frequencies are arranged such that sectors within a cell are assigned the same frequency every “m” sectors (where “m” represents a positive integer of equal to or greater than 2, and m<n);
the antennas assigned the same frequency as that of the site are arranged in the same sequence;
a cell group comprises “m” cells, in which the centers of beams emanated from the antennas assigned the same frequency are horizontally offset from one site to another site by an amount approximately equal to the beam width;
the cells are adjacent to one another;
the cell group comprises a plurality of groups of different frequencies and constitutes a minimum unit area to be repeated; and
the minimum unit areas are repeatedly arranged in longitudinal and lateral directions.
According to a third aspect of the present invention, there is provided a radio communications system which establishes radio communication between arbitrary sites and fixed terminal stations which are directional and disposed in a cell centered on the site, wherein
each of the sites is provided with three antennas which are equal in horizontal beam width and whose orientations are horizontally offset from one another;
at each site, the beams emanated from the individual antennas, as a whole, cover all horizontal directions;
the antennas assigned the same frequency as that of the site are arranged in the same sequence;
a cell group comprises three cells, in which the centers of beams emanated from the antennas assigned the same frequency are offset from one site to another site by an amount approximately equal to the beam width;
the cells are arranged such that a cell having an antenna assigned different frequency is interposed between adjacent cells;
the cell group comprises a plurality of groups of cells assigned different frequencies and constitutes a minimum unit area to be repeated; and
the minimum unit areas are repeatedly arranged in longitudinal and Lateral directions.
According to a fourth aspect of the present invention, there is provided a radio communications system which establishes radio communic

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