CA 02268485 2002-10-04
SECTOR CEIrI~ CONFIGURATION FOR IMPROVEL1
CARRIER-TO-INTERFERENCE RATIO
BACKGROUND GF THE iN'JENTION
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 of:cers cammunications services
such as a telephone service, an inf:~r~natian service, a graphic
service, and a multimedia service.
Description of the Re'ated Art
A conventional dominant cell struer_ure emplayed in the
Field of mobile communi~:ations such as that found in a radio
system is a sector cell con'igurar_=an, wherein a directional
antenna is used for a site formed from a plurality,; of sector
cells (often simply ref~'rred to as "se:~tars"). FIGS. 27 and
28 show an example of the sector :.s'~'_ ;.-.onfiguration. In FIG.
27, each svte is formed Lrom three sectors. Seven sites
comprising a tatal of 2 ~ sectors a r~. :candled as a unit, and
rrequencies are a~-located repeatedi'.; on a per-unit basis (such
c.on::iq~_:ratic-~ ~Nil1 i,:e:=.-~ina~ter to rarer:-ed t~: simply as a
~c~;~q,.l,~nCl_~De,'i~:.On:=,.:.-.J~th~aa-5,~-~''c:~S/S°V2n-:3lteS").
FIG.
J'hC'v~ls a."1 a:iaT;C'_e ::? S~l:w _;': tai'..': >;w~. _:i :uralGd L~vm jLX
seCtorS.
Je.,.e:': si-es ,~~m.o_is~i. .= _.'_~.~~-~ ___ ;:a::-~'~a~~as a 'r:=t, ar.~
CA 02268485 2002-10-04
frequencies are allocated repeatedly on a per-u«t basis (such
a configuration will be herei:~aftee referred to as a "frequency
repeti tion every six-sectors!seve,~.-sites"o _ In the drawings,
reference numerals 91 to 96 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 d8 emitted from fixed terminal statvlons disposed in the
service areas 97 of the sites 92 to 96. In FIG. 28, the site
98 receives an interference wave signal of 1Ø5 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 App~ication paid-Open No.
Hei-3-;93556 entitled "Radio System, " showing the relationship
between frequencies used among adacent sites ar..d the layout
of beams emanated from antennas. Iithe drawing, reference
numerals 105 to 107 designate sertTice areas of individual
antennas, and areas allccr_ed the same reference numeral are
assigned the same frequency. Reference numerals 108 and 109
designate sites; and 110 designates a ti;ted terminal station.
In a radio commur~icatiens system, radio communication is
established between a sire, such as a s~.~~s~.riber radio system,
aa.d a p'~u=ality o= fy:~ed ~ter.-r::.a,al :~r_at~:~n:~ ~i spc~;ed l.. .a cell
~v'T~?rW: b'- ..:":e jir~. .";,cue ~~;~. ~~'. ~a'a~. r~.::.~ _';-' t~alY 1
a;lO~.::t jn:'rJn
__ ~> a
CA 02268485 1999-04-08
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 p::urality 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 r.=ceiving 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
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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 d_Lrectional 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 hol:izontal directions;
the antennas assigned the same' frequency as that of the
site are arranged in the same sequE:nce;
a cell group comprises three cf~lls, 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 wic',th;
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,
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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 t:o 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 ho::izontal 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
CA 02268485 1999-04-08
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 ,end 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 a~ 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 directio n:.
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According to a fourth 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 each 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;
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 offset from one site to another site by an amount
approximately equal to the beam width;
the cells are arranged such tha~~ "L" (where "L" designates
0 or a positive integer greater than 1) cells having an antenna
assigned a different frequency is interposed between the
adjacent cells;
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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 fifth aspect of the present invention, the
radio communications system as defined in any one of the first
through fourth aspects is further characterized by that the
minimum unit areas are repeatedly arranged in the vertical
direction so as to become horizontally offset from one another.
According to a sixth aspect of the present invention, the
radio communications system as defined in any one of the first
through fourth aspects is further characaerized by that the
minimum unit areas are repeatedly arranged such r_hat a column
of minimum unit areas becomes ~rertically offset from another
column of minimum unit <areas.
Accordingly, in one aspect, the present invention provides
a radio communications system far establishing radio
communication between arbitrary sites and fixed terminal
stations, each of the fixed terminal stations being directional
and disposed in a cell centered on a respective one of the
arbitrary sites, whe.re:in each of. the sites is provided with
three antennas of ecrsal !°aorizantal beam width and whose
orientations are horizontally oFfset from one another; beams
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emanated from the three antennas ta~Cen toget=her cover all
horizontal directions; corresponding ones of the antennas
assigned the same frequency as that of the site are arranged in
the same sequence; the radio communications system further
comprising: a cell group comprising three cells centered on
three respective sites, in which the centers of beams emanated
from ones of the respective three antennas associated with each
of the three sites, which ores are assigned the same frequency
are offset from one site to another site by an amount
approximately equal r_o a beam width; wherein the three cells
are adjacent to one another; the cell group further comprises a
plurality of groups of different frequencies and constitutes a
minimum unit area to h~e repeated; and the minimum unit areas
are repeatedly arranged wn longitudinal and lateral directions.
;n a further aspect, the present invention provides a
radio communi::ations sy~~tem for establishing radic
communication between arbitrary sites and fixed terminal
stations, each of r_he fixed germinal stations being directional
and disposed in a cel.':. ..enr_er.ec~ on a respective one of the
arbitrary sites, wherein each of the sues is provided with "n"
sector antennas wherein each of the "n" sector antennas has
equal horizontal beam width amd whereir: orientations associated
with the each are horizontally offset ~rcm one another, wherein
"n" represents a positive integer equal to or greater than 4;
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beams emanated from the "n" sector antennas taken together
cover all horizontal d~_rections; frequencies are arranged such
that ones of the "n" sectors within a cell are assigned the
same frequency every "m" sectors where "m" represents a
positive integer of eqwal to or greater than 2, and "m"<"n";
corresponding ones of ~.he antennas assigned the same frequency
as that of the site are arranged in the same sequence; a cell
group constituting a mi:zimum unit area to be repeated, the cell
group comprising "m" adjacent cells each assigned a group of
different frequencies, wherein ce:iters of beams emanated from
the corresponding ones of the "n" sector antennas assigned the
same frequency are horizontally offset from one site to another
site by an amount approximar~ely equal to one beam width; the
"m" adjacent cells associated with the cell group are further
arranged such that "~a" additional each assigned different
frequencies from any of the group o:P different frequencies are
interposed between the "m" adjacent r_e"~.ls, where "L" designates
0 or a positive integer greater than 1; wherein the minimum
unit area is repeatedly arranged in Longitudinal and lateral
directions.
In a still further aspect, the present invention provides
a radio communications :system for estab~~ishing radio
communication comprisin<~: on~> or more cell groups each having
at least three adjacent cells; wherein each of= the adjacent
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cells has at least "n" antennas with equal horizontal beam
width, the "n" antennas associated wir_h corresponding "n" cell
sectors, the "n" antennas directed approximately
(360/"n")degrees apart from each other in a horizontal p ane;
wherein each of three adjacent cells in the one or more cell
groups are assigned a pi.urality of frequencies; wherein
corresponding ones of the "n" antennas are assigned the same
frequency every "m" of the "n" corresponding cell sectors and
wherein the corresponding ones of the "n" antennas assigned the
same frequency in each of the three adjacent cells are further
arranged in the same :sequence; and wherein one or more cell
groups constitutes a minimum unit area tr be repeated over a
geographical area associated with the radio communications
system; and wherein a plurality of minimum unit areas are
repeatedly arranged in Longitudinal and la~:eral directions.
In a further aspect, the present invention provides a
method for establishing radio communication comprising:
arranging one or more cell groups each having at least three
adjacent cells; wherein each of the adjacent cells has at least
"n" antennas with equal. hori~ontai. t:~eam width, the "n" antennas
associated with corresponding "n" cell sectors, the "n"
antennas directed approximate:Ly (~6e~i"n°"jdegrees apart from
each other in a horizontal plane; assigning a plurality of
f requenc ies to each of three adj acent ce.l1 s in the one or more
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cell groups; and ass_Lgning correspcmdir~g ones of the "n"
antennas the same freqL.ency every "m" of the "n" corresponding
cell sectors, wherein. the corresponding ones of the "n"
antennas assigned the same frequency in each of the three
adjacent cells are further arranged in the same sequence;
wherein one or more cells groups constitutes a minimum unit
area to be repeated over a geographical. area associated with
the radio communications system; and wherein a plurality of
minimum unit areas are repeatedly arranged in longitudinal and
lateral directions.
BRIEF DESt~RIPTION OF THE DRAWINGS
FIG. 1 is a plan view st~zowing the minimum unit areas to be
repeated according to a 2:irst. embodiment of the present
invention;
FIG. 2 is a plan view showing a relationship among
antennas of sites in a radio communications system according to
the first embodiment;
FIG. 3 is a plan view showing frequencie~~ assigned to
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three antennas and service areas thereof according to the
present invention;
FIG. 4 is a plan view showing interference among radio
wave signals according to the first embodiment:
FIG. 5 is a plan view showing the minimum unit areas to
be repeated according to a second embodiment of the present
invention;
FIG. 6 is a plan view showing the minimum unit areas to
be repeated according to a third embodiment of the present
invention;
FIG. 7 is a plan view showing the minimum unit areas to
be repeated according to a fourth embodiment of the present
invention;
FIG. 8 is a plan view showing a relationship among
antennas of sites in a radio communications system according
to the fourth embodiment;
FIG. 9 is a plan view showing frequencies assigned to a
plurality of antennas of a site and service areas thereof
according to the present invention;
FIG. 10 is a plan view showing frequencies assigned to
a plurality of antennas of a site and service areas thereof
according to the present invention,;
FIG. 11 is a plan view showing interference among radio
wave signals according to the fourth embodiment:
FIG. 12 is a plan view showing the minimum unit areas to
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CA 02268485 1999-04-08
be repeated according to a fifth embodiment of the present
invention;
FIG. 13 is a plan view showing the minimum unit areas to
be repeated according to a sixth embodiment of the present
invention;
FIG. 14 is a plan view showing the minimum unit areas to
be repeated according to a seventh embodiment of the present
invention;
FIG. 15 is a plan view showing a relationship between
antenna beams and frequencies assigned to adjacent sites which
are situated while is interposed between them a cell having a
site whose antenna is assigned different frequency, in the radio
communications system according to the seventh embodiment;
FIG. 16 is a plan view showinc interference among radio
wave signals according to the seventh embodiment:
FIG. 17 is a plan view showing the minimum unit areas to
be repeated according to an eighth embodiment of the present
invention;
FIG. 18 is a plan view showing the minimum unit areas to
be repeated according to a ninth embodiment of the present
invention;
FIG. 19 is a plan view showing the minimum unit areas to
be repeated according to a tenth err.bodiment of the present
invention;
FIG. 20 is a plan view showing a relationship between
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antenna beams and frequencies assigned to adjacent sites which
are situated while is interposed between them a cell having a
site whose antenna is assigned different frequency, in the radio
communications system according to the tenth embodiment;
FIG. 21 is a plan view showing interference among radio
wave signals according to the tenth embodiment:
FIG. 22 is a plan view showing the minimum unit areas to
be repeated according to an eleventh embodiment of the present
invention;
FIG. 23 is a plan view showincl the minimum unit areas to
be repeated according to a twelfth embodiment of the present
invention;
FIG. 24 is a graph showing one example of a receiving
pattern (0.3mQ3) of an antenna of the fixed terminal station;
FIG. 25 is a graph showing a receiving C/I ratio in
frequency bands required by athree-sectors cell configuration;
FIG. 26 is a graph showing a receiving C/I ratio in
frequency bands required by a six-sectors cell configuration;
FIG. 27 is a plan view showing a frequency repetition
every three-sectors/seven sites which is a dominant cell
structure in the field of conventional radio communications
systems;
FIG. 28 is a plan view showing a frequency repetition
every six-sectors/seven sites which is a dominant cell
structure in the field of conventional radio communications
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systems; and
FIG. 29 is a plan view showing a relationship between
frequencies assigned to conventional adjacent sites and beams
emanated from antennas of the sites.
DETAILED DESCRIPTION OF THE (REFERRED EMBODIMENTS
Now, a description will be given in more detail of
preferred embodiments of the inven~~ion with reference to the
accompanying drawings.
(First Embodiment)
FIG. 1 shows the minimum area to be repeated in a cell
configuration shown in FIG. 2, wherein cell groups having
sixteen different frequencies are arranged in a repeating
pattern. In the drawings, reference numerals 1A to 1C, 2A to
2C, . . . ; and 16A to 16C designate cells, and reference numeral
1 designates the minimum unit area t_o be repeated. Reference
numerals 1A to 1C designate cells that constitute the cell group
shown in FIG. 2 and are assigned a set of frequencies. Reference
numerals 1A to 1C, 2A to 2C, . . . ; and 16A to 16C shown in FIG.
1 are arranged the same as the cells :>hown in FIG. 2. The cells
1A to 1C are assigned a set of frequ~=ncies; the cells 2A to 2C
are assigned another set of frequenc ~ es; . . . ; and the cells 16A
to 16C are also assigned still another set of frequencies. The
group of cells 1A to 1C, the group of cells 2A to 2C, . . . , and
the group of cells 16A to 16C differ from one another in frequency.
_ 1.o
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The cells 1A to 1C shown in FIG. 1 are the same in configuration
as the cells shown in FIG. 2 and are assigned a set of frequencies.
In these cells 1A to 1C, antennas are arranged in the same
sequence, and the orientations of the antennas provided at the
sites are horizontally offset from one site to another site by
120 degrees. The group of cells lA.to 1C, the group of cells
2A to 2C, ..., and the group of cells 16A to 16C differ in
frequency from one another. The cells constitute the minimum
unit area to be repeated in such a way as to diminish interference
among the frequencies by means of directionality of the antennas
disposed at the site or the fixed terminal stations.
FIG. 2 shows one of cell groups constituting the unit area
to be repeated shown in FIG. 1. The <:e11 group has three sites,
and each of the sites is equipped with three antennas of
different frequencies. The three cells are assigned one set
of frequencies and are adjacent to one another. Each of the
sites is assigned three frequencies in the same sequence, and
the centers of beams emanated from the antennas assigned the
same frequency are horizontally offset from one another by 120
degrees . In the drawing, reference numerals 2 to 7 designate
sites, and reference numerals 8 to 10 designate service areas
of the antennas having different frequencies.
FIG. 3 is a plan view showing one' of the cells constituting
the cell group shown in FIG. 2, wherein the site has three
antennas having different frequencies and corresponding
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SerVlCe dred5. -i2 the ~rawing, re~e,rence ~,vmeral 11 desi~gnateS
a Slte. SlnCe the trlr~'e dntennas are assigned dr=ferent
frequencies, there is no interferer.~e among antennas at the same
frequency within the same sate.
FIG. 4 is a schematic representation, wherein attention
is directed solely to a cell group i:vcluding the cells 1A to
1C within the minimum ar~aa r_o be repeated shown in FIG. I. FIG.
4 shows interference oetween the site w'~th.in the cells and fixed
terminals within the service areas. In the drawing, reference
numerals 12 to 15 desig;iate cells; 1~ to l designate service
areas assigned the same frequency; 2(.~ designates a site; 21
designates a fixed term.inai station disposed it the area 15
within the cell i2; 22 designates a f.:{ed termin~:I station
disposed in the area I8 within the cell 14; and 23 designates
a fixed terminal stati~.an disposed :ic; r_he area I9 within the cell
15. The areas 16, 17, 1t3 and 19 are assigned the same frequency.
The site 3 disposed in the cell i3 receives interference wave
signals frcm a fixed termina'w station 21 located in the cell
12, a fixed terminal station 22 located in the cell 1~, and a
fixed terminal station 1'3 ic~cated i:~: t'm cell 15. The C/I ratio
of the inter_erance wavy ~v gna.~. receitrecr rcm the f fixed terrni nal
sta tier. ?1 is censiuere:~ '~o ce sign:. i~~a.:.r_iy aimir.isied oymeans
Ot tale ~lreCtl.~.va~_~.t''i J~ t~',e iCltc'n:':a O': t''!.-'. 5i.tc .~.
PrOVided
tf'!at an ~tte.~;llai.~0.~. '~I: '..ic-' .?'!t~~=~::'c"-'.~:.'"~ '.,I~Va j'
~.?~.~ ~C:al t~a
__..d'taL'~T.1:';_._ St... 1~:.. _~ .~cl~~::~~<'~ :J~,,~ _.. _...a ° ~
_y ~:".~.:_ '' O= tfla
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CA 02268485 1999-04-08
antenna of the site 3 is 25 dB, a transmission loss inversely
proportional to the square of a distance between the site 3 and
the fixed terminal station 22 is 4.8 dB. Therefore, the C/I
ratio of the interference wave signal received from the fixed
terminal station 22 is 29.8 dB (i.e., the sum of 25dB and 4.8
dB) . An attenuation in the interference wave signal from the
fixed terminal station 23 caused by the directionality of the
antenna of the site 3 is 0 dB, and a transmission loss inversely
proportional to the square of the distance between the site 3
and the fixed terminal station 23 is 20.3 dB. Therefore, the
C/I ratio of the interference wave signal received from the
fixed terminal station 23 is 20.3 dB (i.e., the sum of 0 dB and
20.3 dB) . The total C/I ratio of the interference wave signals
received by the site 3 is 19.8 dB. In contrast, the C/I ratio
of the interference wave signal received by the site from the
fixed terminal stations in the conventional cell configuration
shown in FIG. 29 assumes a value of 9.5 dB. The conventional
cell configurations shown in FIGs. 27 and 28 require frequencies
corresponding to the traffic of seven cells. As shown in FIG.
25, the conventional cell configurations can ensure only the
C/I ratios of 7.7 dB and 9.1 dB. In contrast, the frequencies
assigned to the cell configuration chown in FIG. 1 correspond
to traffic of eight cells of a conventional cell configuration.
Accordingly, as shown in FIG. 25, the radio system according
to the present invention prevents interference among the sites
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or fixed terminal stations, which would otherwise be caused by
an interference wave signal, while: using frequencies
substantially equal in number to those used in the conventional
radio system, thereby enabling effective utilization of
frequencies.
(Second Embodiment)
FIG. 5 is a plan view showing a cell configuration
according to a second embodiment of the present invention. In
the drawing, reference numerals 1A to 1C designate cells that
constitute the cell group shown in FIG. 2 and are assigned a
set of frequencies. Reference numeral 1 designates a minimum
unit area to be repeated. In the drawing, the cells 1A to 1C
are the same as the cells shown in FIG. 2 and are assigned a
set of frequencies. The group of cells 1A to 1C, the group of
cells 2A to 2C, ..., and the group of cells 16A to 16C differ from
one another in frequency. FIG. 5 is similar to FIG. 1, showing
the layout of minimum unit areas to be repeated. The difference
between the drawings is that in FIG. 5 the minimum unit areas
are repeatedly arranged in the vertical direction so as to
become horizontally offset from ones another.
(Third Embodiment)
FIG. 6 is a plan view showing a cell configuration
according to a third embodiment of the present invention. In
the drawing, the cells 1A to 1C are the same as the cells shown
in FIG. 2 and are assigned a set of frequencies. The group of
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cells 1A to 1C, the group of cells 2A to 2C, ..., and the group
of cells 16A to 16C differ from one another in frequency. FIG.
6 is similar to FIG. I, showing the layout of minimum unit areas
to be repeated. The difference between the drawings is that
in FIG. 6 the minimum unit areas are repeatedly arranged such
that a column of minimum unit areas becomes vertically offset
from another column of minimum unit areas.
(Fourth Embodiment)
FIG. 7 shows the minimum area to be repeated in a cell
configuration shown in FIG. 8, wherein cell groups having
sixteen different frequencies are arranged in a repeating
pattern. Reference numerals 1D to 1F designate cells that
constitute the cell group shown in FIG. 8 and are assigned a
set of frequencies. Reference numeral 24 designates a minimum
repeated area. In the drawings, each of the cells 1D to 1F shown
in FIG. 8 is equal in structure to the cell shown in FIG. 9 and
is assigned a set of frequencies. T;~e group of cells 1D to 1F,
the group of cells 2D to 2F, ..., and the group of cells 16D
to 16F differ from one another in frequency. In the drawings,
the cells 1D to 1F are equal in structure to the cells shown
in FIG. 8 and are assigned a set of frequencies. Each of the
cells is assigned a set of frequencies in the same sequence.
The beams emanated from antennas of t:he sites are horizontally
offset from one site to another site by 60 degrees. The group
of cells 1D to 1F, the group of cells 2D to 2F, ..., and the group
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of cells 16D to 16F differ from one another in frequency, thereby
constituting the minimum unit area to be repeated while
diminishing interference among the cells within the unit area.
FIG. 8 shows one of the cells constituting the cell group
shown in FIG. 7, wherein three cells, which are assigned a set
of frequencies and are identical to one another in terms of
antenna layout, are adjacent to one .another. Further, each of
the three sites is assigned the frequencies in the same sequence.
The centers of beams emanated from the antennas assigned the
same frequency are set so as to become offset from one another
by 60 degrees. In the drawing, reference numerals 25 to 30
designate sites; and 31 to 33 designate service areas of
individual antennas, wherein areas allotted the same frequency
numeral are assigned the same frequency.
FIGS. 9 and 10 are plan views each showing one example
of one of the cells that constitute the cell group shown in FIG.
8, as well as showing frequencies and service areas of a
plurality of antennas disposed in the site. In the drawings,
reference numerals 34 and 35 designate sites; and 36 and 37
designate service areasof individualantennas, whereinservice
areas allotted the same reference numeral are assigned the same
frequency. As shown in FIGS. 9 and 10, in the fourth embodiment,
one site is equipped with a plurality of antennas assigned the
same frequency. In the cell shown in FIG. 9, two antennas
assigned the frequency of the area 31, two antennas assigned
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CA 02268485 1999-04-08
the frequency of the area 32, and two antennas assigned the
frequency of the area 33 are arranged in a repeating pattern.
In the cell shown in FIG. 10, three antennas assigned the
frequency of the area 36 and three antennas assigned the
frequency of the area 37 are arranged alternately. More
specifically, antennas of twoadjacentfrequenciesare arranged
alternately, thereby diminishing interference between the
antennas assigned the same frequency within the same site.
FIG. 11 is a schematic represe;ztation, wherein attention
is directed solely to a cell group including the cells 1D to
1F within the minimum area to be repeated shown in FIG. 7. FIG.
11 shows interference between a site and fixed terminals within
the service areas. In the drawing, reference numerals 38 to
41 designate cells; 42 to 49 designate service areas assigned
the same frequency; 50 designates a ~~ite; 51 designates a fixed
terminal station disposed at the area 46 within the cell 40;
52 designates a fixed terminal station disposed in the area 47
within the cell 40; and 53 designates a fixed terminal station
disposed in the area 49 within the cell 41. The areas 46, 47,
and 49 are assigned the same frequency. The site 50 disposed
in the cell 42 receives interference wave signals from a fixed
terminal station 51 located in the cell 40, a fixed terminal
station 52 located in the cel l 40, and a fixed terminal station
53 located in the cell 41. FIG. 24 shows one example of an
antenna pattern of the fixed terminal station, and the C/I ratio
-19-
CA 02268485 1999-04-08
of each of the interference wave signals is considered to be
the same as that mentioned previously. Provided that an
attenuation in the interference wave signal from the fixed
terminal station 51 caused by the directionality of the antenna
of the site 50 is taken as 27 dB from FIG. 24, a transmission
loss inversely proportional to the' square of the distance
between the site 50 and the fixed terminal station 51 is 6.0
dB. Therefore, the C/I ratio of the interference wave signal
received from the fixed terminal station 51 is 33.0 dB (i.e.,
a sum of 27 dB and 6.0 dB). Similarly, the C/I ratio of the
interference wave signal from the fixed terminal station 52 is
29.8dB, and the C/I ratio of the interference wave signal from
the fixed terminal station 53 is 20.3 dB. An overall C/I ratio
of the interference wave signals received by the site 50 is 19. 6
dB. In contrast, the C/I ratio of the interference wave signal
received by the fixed terminal from the sites in the
conventional cell configuration shown in FIG. 29 assumes a value
of 9.5 dB. The conventional cell configurations shown in FIGs.
27 and 28 require frequencies corresponding to traffic of seven
cells. As shown in FIG. 26, the conventional cell
configurations can ensure only C/I ratios of 10.5 dB and 11.0
dB. In contrast, the frequencies assigned to the cell
configuration shown in FIG. 7 correspond to traffic of eight
cells of a conventional cell configuration. Accordingly, as
shown in FIG. 26, the radio system according to the present
-'?0-
CA 02268485 1999-04-08
invention prevents the site and fixed terminal station from
experiencing interference, which would otherwise be caused by
an interference wave signal, while using frequencies
substantially equal in number to those used in the conventional
radio system, thereby enabling effective utilization of
frequencies.
(Fifth Embodiment)
FIG. 12 is a plan view showing a cell configuration
according to a fifth embodiment of the present invention. In
the drawing, reference numerals 1D to 1F designate cells that
constitute the cell group shown in FIG. 8 and are assigned a
set of frequencies. Reference numeral 24 designates a minimum
unit area to be repeated. In the drawing, the cells 1D to IF
are the same as the cells shown in FIG. 8 and assigned a set
of frequencies. The group of cells 1D to 1F, the group of cells
2D to 2F, ..., and the group of cells 16D to 16F differ from one
another in frequency. FIG. 12 is similar to FIG. 7, showing
the layout of minimum unit areas to be repeated. The difference
between the drawings is that in FIG. 12 the minimum unit areas
are repeatedly arranged in the vertical direction so as to
become horizontally offset from one another.
(Sixth Embodiment)
FIG. 13 is a plan view showing a cell configuration
according to a sixth embodiment of the' present invention. FIG.
13 is similar to FIG. 7, showing the layout of minimum unit areas
_.01_
CA 02268485 1999-04-08
to be repeated. The difference between the drawings is that
in FIG. 13 the minimum unit areas are repeatedly arranged such
that a column of minimum unit areas becomes vertically offset
from another column of minimum unit areas.
(Seventh Embodiment)
FIG. 14 shows the minimum area to be repeated in a cell
configuration shown in FIG. 15, wherein cell groups having
sixteen different frequencies are arranged in a repeating
pattern. In the drawing, reference' numerals 1G to 1I, 2G to
2I, ..., and 16G to 16I designate cells; and 54 designates a minimum
unit area to be repeated. Reference numerals 1G to 1I designate
cells that constitute the cell group shown in FIG. 15 and are
assigned a set of frequencies. In t=he drawings, the group of
cells 1G to 1I, the group of cells 2(~ to 2I, . . . , and the group
of cells 16G to 16I are equal in structure to cells shown in
FIG. 15, and each of the cell groin?s is assigned a set of
frequencies. The group of cells 1G to 1I, the group of cells
2G to 2I, ..., and the group of cells 16G to 16I differ from
one another in frequency. In the drawings, the cells 1G to 1I
are equal in structure to cells shown in FIG. 15 and are assigned
a set of frequencies. Each of the cells is assigned frequencies
in the same sequence. The orientations of the beams emanated
from antennas of the sites are horizontally offset from one site
to another site by 120 degrees. The group of cells IG to 1I,
the group of cells 2G to 2I, ..., a:~d Lhe group of cells 16G
_»_
CA 02268485 1999-04-08
to 16I differ from one another in frequency, thereby
constituting the minimum unit area. to be repeated while
diminishing interference among the cells within the unit area
by means of directionality of the antennas disposed at the site
or fixed terminal station.
FIG. 15 shows a cell group comprising three cells which
are assigned a set of frequencies, and each of the cells is equal
in structure to that shown in FIG. 3. In each of the cells,
the site has three antennas assigr..ed different frequencies.
The three cells are arranged such that a cell having a site
equipped with antennas of different frequencies is interposed
between adjacent cells. Each of th~~ three sites of the cells
is assigned three frequencies in the ;game sequence. The centers
of beams emanated from the antennas assigned the same frequency
are set so as to become horizontally offset from one another
by 120 degrees. In the drawing, reference numerals 8 to 10
designate service areas of the antennas assigned different
frequencies, wherein areas allotted the same reference numeral
are assigned the same frequency. Further, reference numerals
55 to 57 designate sites.
FIG. 16 is a schematic representation, wherein attention
is directed solely to a cell group including the cells 1G to
II within the minimum area to be repeated shown in FIG. I4 . FIG.
16 shows interference between a site and fixed terminals within
the service areas. In the drawing, reference numerals 58 to
_.03_
CA 02268485 1999-04-08
61 designate cells; 62 to 65 designate service areas assigned
the same frequency; 66 and 67 desi~~nate sites; 68 designates
a fixed terminal station disposed in the area 62 within the cell
58; 69 designates a fixed terminal station disposed in the area
64 within the cell 60; and 70 designates a fixed terminal station
disposed in the area 65 within the cell 61. The areas 62, 63,
and 64 are assigned the same frequency. The site 66 disposed
in the cell 59 receives interference wave signals from the fixed
terminal station 68 located in the cell 58, the fixed terminal
station 69 located in the cell 60, and a fixed terminal station
70 located in the cell 61. The C/I ratio of the interference
wave signal received from the fixed terminal station 68 is
considered to be significantly diminished by means of the
directionality of the antenna of the site 66. Provided that
an attenuation in the interference wave signal from the fixed
terminal station 69 caused by the directionality of the antenna
of the site 66 is 25 dB from FIG. 27, a transmission loss
inversely proportional to the square of a distance between the
site 66 and the fixed terminal station. 69 is 10.8 dB. Therefore,
the C/I ratio of the interference wave signal received from the
fixed terminal station 69 is 35.8 dB (i.e., the sum of 25 dB
and 10.8 dB) . An attenuation in the interference wave signal
from the fixed terminal station 70 caused by the directionality
of the antenna of the site 66 is 0 dB, and a transmission loss
inversely proportional to the square of the distance between
CA 02268485 1999-04-08
the site 66 and the fixed terminal. station 70 is 20.3 dB.
Therefore, the C/I ratio of the ir..terference wave signal
received from the f fixed terminal station 70 is 20 . 3 dB ( i . a . ,
the sum of 0 dB and 20.3 dB). The overall C/I ratio of the
interference wave signals received by the site 66 is 20.2 dB.
In contrast, the C/I ratio of the interference wave signal
received by the site from the fixed terminal stations in the
conventional cell configuration shown in FIG. 29 assumes a value
of 10.5 dB. The conventional cell configurations shown in FIGs.
27 and 28 require frequencies corresponding to traffic of seven
cells. As shown in FIG. 25, the conventional cell
configurations can ensure only the C/I ratios of 7. 7dB and 9. ldB.
In contrast, the frequencies assigned to the cell configuration
shown in FIG. 14 correspond to traffic of eight cells of a
conventional cell configuration. Accordingly, as shown in FIG.
25, the radio system according to the present invention prevents
the site or fixed terminal station from experiencing
interference, which would otherwise be caused by an
interference wave signal, while using frequencies
substantially equal in number to those used in the conventional
radio system, thereby enabling effective utilization of
frequencies.
(Eighth Embodiment)
FIG. 17 is a plan view showing a cell configuration
according to an eighth embodiment of the present invention. In
_y_
CA 02268485 1999-04-08
the drawing, reference numerals 1G to 1I designate cells that
constitute the cell group shown in FIG. 15 and are assigned a
set of frequencies. Reference numeral 54 designates a minimum
unit area to be repeated. In the drawing, the cells 1G to 1I
are the same as the cells shown in FIG. 15 and are assigned a
set of frequencies. The group of cells 1G to 1I, the group of
cells 2G to 2I, ..., and the group of cells 16G to 16I differ from
one another in frequency. FIG. 17 is similar to FIG. 14, showing
the layout of minimum unit areas to be repeated. The difference
between the drawings is that in FIG. 17 minimum unit areas are
repeatedly arranged in the vertical direction so as to become
horizontally offset from one another.
(Ninth Embodiment)
FIG. 18 is a plan view showing a cell configuration
according to a ninth embodiment of t:he present invention. In
the drawing, reference numerals 1G t:o 1I designate cells that
constitute the cell group shown in fIG. 15 and are assigned a
set of frequencies. Reference numeral 54 designates a minimum
unit area to be repeated. In the drawing, the cells 1G to 1I
are the same as the cells shown in fIG. 15 and assigned a set
of frequencies. The group of cells 1G to 1I, the group of cells
2G to 2I, ..., and the group of cells 1.6G to 16I differ from one
another in frequency. FIG. 18 is similar to FIG. 14, showing
the layout of minimum unit areas to be repeated. The difference
between the drawings is that in FIG. 18 the minimum unit areas
-?6-
CA 02268485 1999-04-08
54 are repeatedly arranged such that a column of minimum unit
areas becomes vertically offset from another column of minimum
unit areas.
(Tenth Embodiment)
FIG. 19 shows the minimum area to be repeated in a cell
configuration shown in FIG. 20, wherein cell groups having
sixteen different frequencies are arranged in a repeating
pattern. Reference numerals 1J to 1L designate cells that
constitute the cell group shown in FIG. 20 and are assigned a
set of frequencies. Reference numel:al 71 designates a minimum
repeated area. In the drawings, the cells 1J to 1L are equal
in structure to cells shown in FIG. 20 and are assigned a set
of frequencies . The group of cells 7.J to 1L, the group of cells
2J to 2L, ..., and the group of cells 16J to 16L differ from
one another in frequency. In the drawings, the cells 1J to 1L
are equal in structure to cells shown in FIG. 20 and are assigned
a set of frequencies. Each of the cells is assigned a set of
frequencies in the same sequence. The orientations of the beams
emanated from antennas of the sites are horizontally offset from
one site to another site by 60 degrees. The group of cells 1J
to 1L, the group of cells 2J to 2L, . . . , and the group of cells
16J to 16L differ from one another in frequency, thereby
constituting the minimum unit area to be repeated while
diminishing interference among the cells within the unit area.
F IG. 20 shows a cell group comprising three cells which
-?~-
CA 02268485 1999-04-08
are assigned a set of frequencies, and each of the cells is equal
in structure to that shown in FIG. 9. In each of the cells the
site has three antennas assigned different frequencies. The
three cells are arranged such that a ~~ell having a site equipped
with antennas of different frequencies is interposed between
the adjacent cells. Each of the three sites of the cells is
assigned three frequencies in the same sequence. The centers
of beams emanated from the antennas assigned the same frequency
are set so as to become horizontally offset from one another
by 60 degrees. In the drawing, reference numerals 31 to 33
designate service areas of the antennas assigned different
frequencies, wherein areas allotted the same reference numeral
are assigned the same frequency. Further, reference numerals
72 to 74 designate sites.
FIG. 21 is a schematic represer..tation, wherein attention
is directed solely to a cell group .including the cells 1J to
1L within the minimum area to be repea~~ed shown in FIG. 19. FIG.
21 shows interference between a site and fixed terminals within
the service areas. In the drawing, reference numerals 75 to
78 designate cells; 79 designates a site; 80 to 87 designate
service areas assigned the same frequency; 88 designates a fixed
terminal station disposed in the area 84 within the cell 77;
89 designates a fixed terminal station disposed in the area 85
within the cell 77; and 90 designates a fixed terminal station
disposed in the area 86 within the cell 78. The areas 84, 85,
CA 02268485 1999-04-08
and 86 are assigned the same frequency. The site 79 disposed
in the cell 76 receives interference wave signals from the fixed
terminal stations 88 and 89 located in the cell 77 and the fixed
terminal station 90 located in the cell 78. The C/I ratio of
each of the interference wave signals is considered to be the
same as that mentioned previously. Provided that an
attenuation in the interference wave signal from the fixed
terminal station 88 caused by the directionality of the antenna
of the site 79 is taken as 27 dB from FIG. 27, a transmission
loss inversely proportional to the square of the distance
between the site 79 and the fixed terminal station 88 is 12.3
dB. Therefore, the C/I ratio of them interference wave signal
received from the fixed terminal station 88 is 39.3 dB (i.e.,
the sum of 27 dB and 12.3 dB) . Simi_arly, the C/I ratio of the
interference wave signal from the fixed terminal station 89 is
35.8 dB, and the C/I ratio of the interference wave signal from
the fixed terminal station 90 is 20.3 dB. An overall C/I ratio
of the interference wave signals received by the site 79 is 20.1
dB. In contrast, the C/I ratio of the interference wave signal
received by the fixed terminal from the sites in the
conventional cell configuration shown in FIG. 29 assumes a value
of 9.5 dB. The conventional cell configurations shown in FIGS.
27 and 28 require frequencies corresponding to traffic of seven
cells of a conventional cell configuration. As shown in FIG.
26, the conventional cell configurations can ensure only the
_y_
CA 02268485 1999-04-08
C/I ratios of 10.5 dB and 11.0 dB. In contrast, the frequencies
assigned to the cell configuration shown in FIG. 19 correspond
to traffic of eight cells of a conventional cell configuration.
Accordingly, as shown in FIG. 26, t:he radio system according
to the present invention prevents a site or a fixed terminal
station from experiencing interference, which would otherwise
be caused by an interference wave signal, while using
frequencies substantially equal in number to those used in the
conventional radio system, thereby enabling effective
utilization of frequencies.
(Eleventh Embodiment)
FIG. 22 is a plan view showing a cell configuration
according to an eleventh embodiment of the present invention.
In the drawing, reference numerals 1J' to 1L designate cells that
constitute the cell group shown'in E~IG. 20 and are assigned a
set of frequencies. Reference numeral 71 designates a minimum
unit area to be repeated. In the drawing, the cells 1J to 1L
are the same as the cells shown in fIG. 20 and are assigned a
set of frequencies. The group of cells 1J to 1L, the group of
cells 2J to 2L,..., and the group of cells 16J to 16L differ
from one another in frequency. FIG. 22 is similar to EIG. 19,
showing the layout of minimum unit areas to be repeated. The
difference between the drawings is that in FIG. 22 minimum unit
areas are repeatedly arranged in the vertical direction so as
to become horizontally offset from one another.
-30-
CA 02268485 1999-04-08
(Twelfth Embodiment)
FIG. 23 is a plan view showing a cell configuration
according to a twelfth embodiment of t:he present invention. FIG.
23 is similar to FIG. 19, showing t:he layout of minimum unit
areas to be repeated. The difference between the drawings is
that in FIG. 23 minimum unit areas are repeatedly arranged such
that a column of minimum unit areas becomes vertically offset
from another column of minimum unit areas.
In the previous embodiments, repetition of the number of
antennas and frequencies have been described with reference to
examples. Clearly, there may be employed a plurality of
combinations other than the examples mentioned previously.
However, in practice, there may arise some variations in the
shape of cells as well as in the positions of sites disposed
at the respective centers of the cells. Obviously, the present
invention can also be applied to such a case. Receipt of radio
signals by the site has been described in terms of explanation
of interference among radio wave s_Lgnals. The difference
between the case where the site recei~res radio wave signals from
fixed terminal stations and the case' where the fixed terminal
station receives radio wave signals from sites is that radio
wave signals are transmitted in opposite direction. Therefore,
there is no need to provide a specia_L explanation for the case
where the fixed terminal station receives radio wave signals
from sites.
-31-
CA 02268485 1999-04-08
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 equa:L 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 ooze 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.
A conventional sector cell configuration requires
frequencies corresponding to traffic of seven cells. In
contrast, the sector cell configuration according to the
present invention requires the frequencies corresponding to
traffic of eight cells of a conventional cell configuration.
Accordingly, the radio system accor~~ing to the present
invention prevents a site or a fixers terminal station from
-32-
CA 02268485 1999-04-08
experiencing interference, which would otherwise be caused by
an interference wave signal, while using frequencies
substantially equal in number to these used in the conventional
radio system, thereby enabling effective utilization of
frequencies.
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 clirectional 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 antermas 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 wi dth; the cells are adj acent to one another;
the cell group comprises a plurality of groups of different
CA 02268485 1999-04-08
frequencies and constitutes a minimum unit area to be repeated;
and the minimum unit areas are red?eatedly arranged in
longitudinal and lateral directions. A conventional sector
cell configuration requires frequencies corresponding to
traffic of seven cells. In contrast, the sector cell
configuration according to the pre~;ent invention requires the
frequencies corresponding to traffic intensity of eight cells
of a conventional configuration. Accordingly, the radio
system according to the present invention prevents the site or
fixed terminal station from experiencing interference, which
would otherwise be caused by an interference wave signal, while
using frequencies substantially eqL.al in number to those used
in the conventional radio system, thereby enabling effective
utilization of frequencies.
According to a third aspect of the present invention,
there is provided a radio communications system which
establishes radio communication bet=ween 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
CA 02268485 1999-04-08
cells, in which the centers of beams emanated from the antennas
assigned the same frequency are off:>et 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 o:E 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.
A conventional sector cell configuration requires
frequencies corresponding to traffic of seven cells. In
contrast, the sector cell configuration according to the
present invention requires the fre~~uencies corresponding to
traffic of eight cells of a conventional cell configuration.
Accordingly, the radio system acco:_ding to the present
invention prevents a site or a fixed terminal station from
experiencing interference, which would otherwise be caused by
an interference wave signal, while using frequencies
substantially equal in number to those used in the conventional
radio system, thereby enabling effective utilization of
frequencies.
According to a fourth 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
-3~-
CA 02268485 1999-04-08
a cell centered on each 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; 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 cent=ers 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 "L" (where "L"
designates 0 or a positive integer greater than 1) cells having
an antenna assigned a different frequency is interposed between
the adjacent cells; 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.
A conventional sector cell configuration requires
frequencies corresponding to traffic of seven cells. In
contrast, the sector cell configuration according to the
present invention requires the frequencies corresponding to
CA 02268485 1999-04-08
traffic intensity of eight cells of a conventional cell
configuration. Accordingly, the radio system according to the
present invention prevents a site or a fixed terminal station
from experiencing interference, which would otherwise be caused
by an interference wave signal, while using frequencies
substantially equal in number to those used in the conventional
radio system, thereby enabling effective utilization of
frequencies.
According to a fifth aspect of the present invention, the
minimum unit areas are repeatedly arranged in the vertical
direction so as to become horizontally offset from one another.
Accordingly, the radio system for offering communication
services to a plurality of fixed terminal stations according
to the present invention prevents << site or a fixed terminal
station from experiencing interference, which would otherwise
be caused by an interference wave signal, while using
frequencies substantially equal in number to those used in the
conventional radio system, thereby enabling effective
utilization of frequencies.
According to a sixth aspect of the present invention, the
minimum unit areas are repeatedly arranged such that a column
of minimum unit areas becomes vertically offset from another
column of minimum unit areas. Accordingly, the radio system
for offering communication services to a plurality of fixed
terminal stations according to the Fresent invention prevents
-3i-
CA 02268485 1999-04-08
the site or fixed terminal station from experiencing
interference, which would otherwise be caused by an
interference wave signal, while using frequencies
substantially equal in number to those used in the conventional
radio system, thereby enabling effective utilization of
frequencies.
-3S-
