CA2234625A1 - A method for frequency allocation and assignment in wireless communication systems - Google Patents
A method for frequency allocation and assignment in wireless communication systems Download PDFInfo
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- CA2234625A1 CA2234625A1 CA002234625A CA2234625A CA2234625A1 CA 2234625 A1 CA2234625 A1 CA 2234625A1 CA 002234625 A CA002234625 A CA 002234625A CA 2234625 A CA2234625 A CA 2234625A CA 2234625 A1 CA2234625 A1 CA 2234625A1
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W16/00—Network planning, e.g. coverage or traffic planning tools; Network deployment, e.g. resource partitioning or cells structures
- H04W16/02—Resource partitioning among network components, e.g. reuse partitioning
- H04W16/12—Fixed resource partitioning
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W16/00—Network planning, e.g. coverage or traffic planning tools; Network deployment, e.g. resource partitioning or cells structures
- H04W16/24—Cell structures
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W28/00—Network traffic management; Network resource management
- H04W28/16—Central resource management; Negotiation of resources or communication parameters, e.g. negotiating bandwidth or QoS [Quality of Service]
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W72/00—Local resource management
- H04W72/50—Allocation or scheduling criteria for wireless resources
- H04W72/54—Allocation or scheduling criteria for wireless resources based on quality criteria
- H04W72/541—Allocation or scheduling criteria for wireless resources based on quality criteria using the level of interference
Abstract
A single-cell wireless communication system is partitioned into n sectors, to which channels are allocated from two groups of non-adjacent channels. If the available channels are consecutively numbered from lowest to highest frequency, or vice versa, the groups are, respectively, the even-numbered channels and the odd-numbered channels. These two groups are each subdivided into n/2 sets, with the first set of each group including the lowest numbered channels of the group, the next set including the next lowest-numbered channels of the group, and so forth. The sets are then allocated to the sectors such that the first set of one of the groups is allocated to a first sector, the next set of the same group is allocated to a contiguous sector and so forth, with the last set of the second group allocated to the nth sector.
The dividing points between the sets are selected such that any sector has at most a single channel that may experience adjacent-channel interference from a channel that is allocated from a contiguous sector. Preferably, a channel is selected for assignment to the mobile units such that the selected channel is within a greatest gap between the channels of the same set that are then in use. If the selected channel is the one channel that may experience adjacent-channel interference, another channel may be selected from the set.
The dividing points between the sets are selected such that any sector has at most a single channel that may experience adjacent-channel interference from a channel that is allocated from a contiguous sector. Preferably, a channel is selected for assignment to the mobile units such that the selected channel is within a greatest gap between the channels of the same set that are then in use. If the selected channel is the one channel that may experience adjacent-channel interference, another channel may be selected from the set.
Description
W O 97/14259 PCT~US96tl6898 A METHOD FOR FREQUENCY ALLOCATION AND ASSIGNMENT IN WIl~Tt'T F..~S
COMMUNICATION SYSTEMS
FTTt'T,T) OF TT-Tl;', Tl~VTt'NTION
This invention relates generally to wireless radio frequency cn.,..... ,ication systems and in particular to a technique for stc~igning frequencies to mobile units.
RAcKGRouND OF TT~ INYF,l~TTON
The ever-increasing ~en stn.l for wireless co~ .ication services, such as cellular mobile telephone, digital cellular network, personal c~ .... -.. ications services and the like, requires the operators of such systems to attempt to make ........ i.x;.. effective use of available radio frequency bandwidth. A system op~.dlol is typically stlloc~te~ a geographic l.,l.ilol~, and a certain arnount of bandwidth that affords the ability to ~ ...;L and receive on a particular number of dirr~,.cnl channel frequencies (referred to h~ drl~. as "channels") within that le.lilul ~. In an effort to make the best use of the available frequency space, a large geographic territory is typically divided into a number of sub-areas called cells. Each cell includes an associated base station and an stnt~nnst that together handle col~ -ications with mobile units within the cell. Each area covered by an stntennzt and thus, each cell, is cc-n~iAered a single coverage area.
Once the geographic territory is divided into cells, the system u~c.dlol allocates the available ~~hsmnel~ among the cells, or coverage areas, so as to minimi7~ cPnt-charmel h.te.re.~.lce and, also, to ...i~.;...i~ co-channel hlL~.r~,.ci-ce. To do this, the ope.dlor typically allocates non-StcljStrent ~.hstnn~-le to a single coverage area. If, for example, the available ~.hst.~el.c are co-.~e~ ely numbered from lower frequencies to higher frequencies, or vice versa, a cell is stllocstt~d every other channel, i.e. the odd-.lulllb.,.cd or the even-numbered channels. Under this sch.~nne, a geographic territory serviced by a single cell is allocated a set of non-st(ljstrçnt channels, which is one-half of the spectral allocation. Accordingly, only one-half of the chstnnel~
available to the system OpcldlOI are made available to the mobile units.
-W O 97/14259 PCT~US96/16898 To further in-,l.,ase channel availability, the cell may be subdivided into a number of sectors, with each sector serviced by an aC.coci~t~cl directi~ n~l ~ntenn~ Each sector is thus con.ci~lPred a single service area, which means that each sector has allocated to it a subset of the available rh~nnPIc Accordingly, in a cell that has three sectors, the first sector may be allocated ,..",~lc 1, 4, 7 and so forth; a second sector allocated sl~ .FIc 2, 5, 8 and so forth; and a third sector allocated ch~nn~-lc 3, 6, 9 and so forth. Thus each sector is allocated a group of ~h~ lc modulo "n", where n is the number of sectors. This ensures that each sector is allocated a set of non~ r.ont rhsmnf~ic-A problem with ~ cent-channel hllc.r~lc,.-ce arises at the sector bolm~7~ries, hov~
Each ~ntPnn~ provides strong signals throughout the entire ~c50~ d sector, and thus, at the boundaries b~ ,-, for ~X~ ,1P7 the first and second sectors, co.. ~.. ;cations on ~ CPnt rhs~nn~l.c 1 and 2, 4 and 5 and so forth may h.Le.r~ imil~rly, at the boundary b~ .- the first and third sectors, c~,.. l.. ;cations on A.ljAr,.,L rh~nnPlc 4 and 3, 7 and 6, and so forth may iuL~,r~.c. This scheme results in a large portion of the cell being subject to strong s~ r,ent_ rhs~nn~l illL~,~r~G~lCeS.
SUMMARY OF T~F, INVh',NTION
The invention is a single-cell wireless c~.. ;cation system that utilizes all of the spectr~l allocation available to the system o~e.dlol by ~iloc~ting ~ n~k to cell sectors from two subdivided groups of non-~ cçnt rh~nnel.c The l~ lU~ number of sectors is four.
More srecifirAlly, the çl.~.",~lc in the spectral ~lloç~tir,n are cor~ce.;~ ,ly numbered, from lower to higher freql~Pnriec, or vice versa, and divided into two groups of non-s~ rPnt namely, the odd-numbered ~ lc, So and the even-numbered rh~nnPIc SE. If there are four sectors, the So group of çh~nnPIc is further subdivided into 4/2, or two sets, SoL and SoH, which contain, ~ e.,~ ,ly, the lower half and the upper half of the odd-numbered chSmnPIc The SE group of r~l~nnPIc are similarly subdivided into two sets, SEL and SEH, which contain, e.;livc:ly, the lower half and the upper half of the even-numbered channels. The four subsets of ch~nnPIc are then allocated to the four sectors so as to ",;";,-,i,~ the ~ccignmPnt of ~ cPnt ch~nnPIc to contiguous sectors. For example, if the sectors are numbered clockwise from 1 to 4, and sector one is allocated the SEL set of ch~nnPIc, sector two is allocated the SEH set of CA 02234625 l998-04-l4 W O 97/14259 PCTrUS96/16898 channels, sector three is allocated the SoL set of channels and sector four is allocated the SoH
set of ch~nnele As ~iec~l~eed in more detail below, the dividing points between the sets are chosen such that there is at most one channel in any sector that may t;~..c.lce ~ r~onf-channe hll~,~r~.~,.lce at a sector boundary.
For a cell with more than four sectors, the two groups SE and So are each divided into n/2 sets of lowest to highest-numbered channels, where "n" is the nurnber of sectors. The sets are then allocated to the sectors by allocating to the first set of one of the groups to the first sector, the second set of the same group to the second sector, and so forth, with the last set of the second group allocated to the nth sector.
In a ~rer~ d embodiment of the invention, çh~nn~lc within a sector are ~eeignPd to mobile units in accold~ulce with a technique that I refer to as the "greatest gap" technique. Using this technique, the base station ~etPrrninec which of the allocated channels are ~ ,llly unused, or free. It then d~ e~ which of these free rh~nnPlc are inrln-lç~ in the largest group of "crntiguous," that is, contiguous within the set, ~h~nnRI~ In the SEL set, for Px~mrlP, if rhz~nnPIe 6, 8, 10, 16, 18 and 24 are cul~;nlly free, the largest group of contiguous unused channels col~isl:i of ch~nn~le 6, 8 and 10. This contiguous group may be thought of as a "gap"
b~ l rh~nnelc that are ~ ly in use. In the example, the greatest gap is b~lw~ l rh~
4 and 12. Other gaps in the set consist of rh~nnel~ 2 and 4, and channels 16 and 18. The base station then selects for ~eejf~nment to the mobile unit the channel that is in the middle of the greatest gap.
If the sçlecfP(l channel is one that could result in ~ cPnt-channel i~ .r~ ce at one of the sector boun~l~riPc, the base station may first det.. ;.. e if the ~ r--nt channel in the contiguous sector is in use. If that channel is in use, the base station then selects another channel to assign to the mobile unit. The base station may select this channel from the greatest gap or from another gap, as a~lu~l;ate.
~ ltPrn~tively, the base station may select another channel for ae-eignment to the mobile unit regardless of whether or not the ~ c ent channel is in use in the contiguous sector.
W O 97/14259 PCTrUS96/16898 RRT~,F nF,.SCR~PTION OF T~F,nR ~ WIN GS
The above and further advantages of the invention may be better lln~1Prst~lod by referring to the following description in conjunction with the accc,~ ulying drawings, in which:
Fig. 1 is a block ~ gr~m of a wireless co., ........ ~ ti- n system according to the invention;
Fig. 2 is a block diagram of a base station inclu-lP(l in the system of Fig. 1;
Fig. 3 is a sc1.~ ..,./;c diagram of the system of Fig. 1 that depicts the channel allocation scheme that is used in the system of Fig. l; and Fig. 4 is a flow chart of the operations of the base station of Fig. 2 when the system is op.,.dlmg in accol.ial.ce with the greatest gap techl~i4ue.
T~T'TATT,F,T) T)li ~CRTPTION OF ~7 ~,USTR~TIVh' h'MROT)TMT~ TS
Referring now to Fig. 1, a cellular co........ ~-ication system 10 coneiete of a single cell 12 that is partitioned into a .. ;.. ;... of n=4 sectors 14. Such an a~n~m~nt is suitable, for example, for a system that se, vices an island or other isolated area.
As ~lepict~ in the drawing, the cell 12 is partitioned into four ninety-degree sectors 14.
The cell 12 inchl~s a centrally-located base station 16 that has a plurality of directional A.~ e 18a-d, which are arranged such that each antenna 18 services an associated sector 14.
A mobile teleph-nto ~o~crh~n~ 20, which u~c-aLGs in a CO11V~ m~nn~r, provides co~ clions bG~ n the base station 16 and a public ,wilcl1ed telephone network (PSTN) 22.
The system thus allows mobile units 20 within the cell 12 to cc,lll,lul.icate with each other or with other devices that may be conn~ct~ d to the PSTN 22. To simplify the drawing col-n~ ne b~ - the mobile telephone exchange 20 and the PSTN 22 are not shown.
CA 02234625 l998-04-l4 W O ~7/14259 PCTrUS96/16898 Referring also to Fig. 2, the base station 16 is depicted in more detail. The four directional ~nt~nn~c 18a-d, which each, respectively, handle com~ munications between mobile units within their associated sectors 14, are connected to corresponding mllltich~nn~ scecivers 24a-d. The L~ scGivers 24a-d operate in a conventional manner in conjunction with a base station controller 26, to provide filt~rin~ modulation and ~ltom~ lllation fimrtionc that are ~lr~ecc;~y to couple radio signals received from the mobile units 20 to the PSTN 22, and conv~.sely, to rc.l w~u~d signals from the PSTN 22 to the mobile units 20.
An optional omni-directional ~nt~nn~ 23 may be cO~ to a control-signal lCC~
28, to permit the tr~nemiccion and reception of control signals between the base station controller 26 and the mobile units 20 that are located allywh~lG within the cell 12. In n,;".ol1se to the receipt of control signals that request a channel ~cci~nm~nt the control-signal l~,C~ ,. 28 ~let~rmin~s in which sector 14 the l~.lueslillg mobile unit 20 is located, and assigns to the unit a channel that is allocated to that sector. The ~~,.,.,;~c. 28 then ~n~es for the a~ Jl;alG
l-~,sc~ er 24a-d and ~nf~nn~ 18a-d to handle further c.~ ..ic~tions with the mobile unit. In a ~ f~,.led embodiment, the control-signal l.,CC;~. assigns ~ n~.l.c to the mobile units in accu..l~ce with a ~ aLc~l gap" technique, as ~1icc~lc$ed below with reference to Fig. 4.
R~f~rring now to Fig 3, the charmel allocations to the sectors 14 are made so as to ..~;..;...;~ a~jacPnt-channel hlle.rtl~.lce. The ch~nnlolc in the spectral allocation available to the system are conse-;ulivcly numbered, from the lowest fi._~lu~,lcies to highest rl~quen~;ies or vice versa. The channels are then grouped into two groups of non-acij~ç~nt ch~nnf~lc, such as even-numbered ch~nn~1c SE, and odd-numbered ch~nnt?lc, So. Next, the two groups are subdivided into n/2 sets of higher and lower frequenri~c. Thus, for n=4, the group of SE ~ rl~ are subdivided into two sets of higher and lower rl~ uellcies, namely, SEH and SEL, and the group of So ~h~nnPI~ are also subdivided into two sets of higher and lower frequencies, namely, SOH
and SoL . As explained below, the dividing points of the groups into sets are chosen and the four sets of çl".."~cl.c are allocated to the sectors 14 such that contiguous sectors include at most one channel that may t;~.,.ic.rce at1j~r~ont-channel hll~.r~.~..ce.
If the sectors are nurnbered clockwise from 1 to 4, sector 1 is allocated the SEL set of çh~nntoi~, sector two is allocated the SEH set of channels, sector three is allocated the SOL set of channels and sector four is allocated the SOH set of channels. There are no ac~jac~nt channels in - =
W O 97/14259 PCTrUS96116898 sectors 1 and 2, or 3 and 4, and thus, there is no arlj~cçnt-channel hllGlr~ ce at the l~ ,ecLive boundaries between these sectors. rne dividing points between the SEL and SEH sets, and SoL
and SoH sets are ay~upliately chosen such that there is at most a potential for S~djS~c~?nt-rhannP
hl~,.r~,c..ce between co,.,~ c~tions ûver a single channel bGL~ sectors 1 and 4, or sectors 2 and 3. The sets are thus divided such that the highest-numbered channel in, for example, the SEL set is ~dj~cPnt to the lowest-numbered channel in the SoH set, or the lowest-numbered channel in SEH set is ~ cPnt to the highest-numbered channel in the SoL set. Acco.dil~ly, there is a .,~;";.. " amount of ~ nt-channel hlL~-rG-Gnce bGL.. _~,. the sectors.
If, for example, the odd-numbered ch~....rlc are divided such that channel 41 is the lowest-numbered channel in sector 4, the even numbered ~h~nnPIc should be divided such that SEL has ch~nnel 40 as its highest-numbered ch~nnel Otherwise, co...."~,..;r~ti~nc ûn the rhzlnnPlc of sector 1 may i-lL~,.r~.e with more than one charmel in sector 4. If the dividing point beL~._.,n the high and low sets of the even-nurnbered ~h~nnlolc was instead chosen such that the highest-nurnbered channel in SEL is channel 42, there could be hlt~.r~.~..ce b~Lv~ that ch:mn~l and two ~ .rlc in sector 4, narnely, channels 41 and 43.
If n is odd, that is, if the cell 12 is partitioned into an odd nurnber of sectors, the two groups of non-~ cent ch~nnelc So and SE, are divided such that one group has ~n/2~ sets, where ~~ .~lG~e.lLs an integer value. rhe other group is tnen divided into ~nt2~+1 sets. The first sets of each group include the lowest-nurnbered ch~nnPIc in the group, the next sets include the next lowest-nurnbered ch~nnPIc in the group and so forth, with the last sets of the groups including the highest-numbered rh~nnP!c The sets are then allocated to the sectors in clockwise order, with the first set of one of the groups allocated to sector 1, the next set of the sarne group allocated to sector 2 and so forth, and the last set of the second group allocated to sector n. In this cell, only the sectors that have been ~lloc~tPd the first or last sets of a group may G~.ie.lcc -r~ nn.sl illL~,.r~ ce at one of their sector bounrl~ri~s With an odd nurnber of sectors, dirr~,.Gnces in the number of rh~nnPlc that are allocated to the various sectors can be colllp~ ,aLed for by allocating fewer ~h~nnPIc to the sectors that cover areas with lower population dencitipc~ or by ch~nging the sizes of the sectors that have fewer r.h:lnn~lc allocated to them.
CA 02234625 l998-04-l4 W O 97/14259 PCT~US96/16898 Referring now to Fig. 4 in conjunction with Figs 1 and 3, I discuss a p.GÇ_...,d technique for zlccigning ~h5~ 1c to the mobile units. When a mobile unit 20 requests a cc,l~c.,lion, the base station first r~ct~ ....;..PC which sector 14 the mobile unit is in (step 100). In this rYA~..ple, the mobile unit 20 is located in sector 1. Next, the base station 16 dçtP~minPs which of the rhsmnPlc zllloe~tPd to sector I are not in use, and further dçl~ ...in~s which of these ~,h~l~"~lc are inrhlded in the greatest "gap" between c~h~nnPIc that are then in use (step 102). If sector 1 has allocated to it çh~ -flc 2, 4, 6...40, and fll,.".~rlc 6, 8, 10, 16, 18 and 24 are ~ ly free, the largest group of unused rh;1l~l.rlc that are contiguous within the set c~n.cictC of rh~nnPlc 6, 8 and 10. These rh~nnPIc u~ ;L.~Iç the greatest gap l~ ,n ~h~nn~lc that are then in use. The base station may rl~l~ ~...;..P which çh~nnPlc are free by conclllting a table (not shown) or by sç~nning the rh~ rlc The base station then selects for ~cci~nmPnt to the mobile unit the rh~nnPI that is in the middle of the greatest gap (step 104). The base station thus selects ch~nnPI 8. If the select.od channel is the one r.h~nnPI that may result in ~ -r-~t-channel illlelr~.Gll~.e at a sector boundary, the base station clet.. ;.. ~s if the ~ r~-nt channel in the contiguous sector is in use (steps 106, 108). If the ~djs~cPnt channel is not in use, the base station assigns the selPctçd rh:~nn~ol, that is, rhzlnnPI 8, to the unit (step 110). Otherwise, the base station refrains from slccigning the selectPd channel to the unit and instead assigns to the unit another of the free rh~nnPI-C (steps 112, 114).
The base station may select this channel from the greatest gap, or from any other gap. In this way, the base station avoids a potential problem with ~-ljac~ont-channel iIllGlr~ ce.
, the base station may select another channel for ~csi~nmPnt to the mobile unit, without first ~içt~ ....;. ~;~ g if the ?~ çnt channel is in use.
The r~ ,goi.lg description has been limited to a specific embodiment of this invention. It will be ~a.Glll, however, that variations and modifications may be made to the invention, with the~ll.;.. lofsomeorallofits adv~ g~c Therefore,itistheobjectofthe~ppen~ dclaims to cover all such variations and mo-lifit~tionc as come within the true spirit and scope of the mventlon.
What is cl~imp(l is:
COMMUNICATION SYSTEMS
FTTt'T,T) OF TT-Tl;', Tl~VTt'NTION
This invention relates generally to wireless radio frequency cn.,..... ,ication systems and in particular to a technique for stc~igning frequencies to mobile units.
RAcKGRouND OF TT~ INYF,l~TTON
The ever-increasing ~en stn.l for wireless co~ .ication services, such as cellular mobile telephone, digital cellular network, personal c~ .... -.. ications services and the like, requires the operators of such systems to attempt to make ........ i.x;.. effective use of available radio frequency bandwidth. A system op~.dlol is typically stlloc~te~ a geographic l.,l.ilol~, and a certain arnount of bandwidth that affords the ability to ~ ...;L and receive on a particular number of dirr~,.cnl channel frequencies (referred to h~ drl~. as "channels") within that le.lilul ~. In an effort to make the best use of the available frequency space, a large geographic territory is typically divided into a number of sub-areas called cells. Each cell includes an associated base station and an stnt~nnst that together handle col~ -ications with mobile units within the cell. Each area covered by an stntennzt and thus, each cell, is cc-n~iAered a single coverage area.
Once the geographic territory is divided into cells, the system u~c.dlol allocates the available ~~hsmnel~ among the cells, or coverage areas, so as to minimi7~ cPnt-charmel h.te.re.~.lce and, also, to ...i~.;...i~ co-channel hlL~.r~,.ci-ce. To do this, the ope.dlor typically allocates non-StcljStrent ~.hstnn~-le to a single coverage area. If, for example, the available ~.hst.~el.c are co-.~e~ ely numbered from lower frequencies to higher frequencies, or vice versa, a cell is stllocstt~d every other channel, i.e. the odd-.lulllb.,.cd or the even-numbered channels. Under this sch.~nne, a geographic territory serviced by a single cell is allocated a set of non-st(ljstrçnt channels, which is one-half of the spectral allocation. Accordingly, only one-half of the chstnnel~
available to the system OpcldlOI are made available to the mobile units.
-W O 97/14259 PCT~US96/16898 To further in-,l.,ase channel availability, the cell may be subdivided into a number of sectors, with each sector serviced by an aC.coci~t~cl directi~ n~l ~ntenn~ Each sector is thus con.ci~lPred a single service area, which means that each sector has allocated to it a subset of the available rh~nnPIc Accordingly, in a cell that has three sectors, the first sector may be allocated ,..",~lc 1, 4, 7 and so forth; a second sector allocated sl~ .FIc 2, 5, 8 and so forth; and a third sector allocated ch~nn~-lc 3, 6, 9 and so forth. Thus each sector is allocated a group of ~h~ lc modulo "n", where n is the number of sectors. This ensures that each sector is allocated a set of non~ r.ont rhsmnf~ic-A problem with ~ cent-channel hllc.r~lc,.-ce arises at the sector bolm~7~ries, hov~
Each ~ntPnn~ provides strong signals throughout the entire ~c50~ d sector, and thus, at the boundaries b~ ,-, for ~X~ ,1P7 the first and second sectors, co.. ~.. ;cations on ~ CPnt rhs~nn~l.c 1 and 2, 4 and 5 and so forth may h.Le.r~ imil~rly, at the boundary b~ .- the first and third sectors, c~,.. l.. ;cations on A.ljAr,.,L rh~nnPlc 4 and 3, 7 and 6, and so forth may iuL~,r~.c. This scheme results in a large portion of the cell being subject to strong s~ r,ent_ rhs~nn~l illL~,~r~G~lCeS.
SUMMARY OF T~F, INVh',NTION
The invention is a single-cell wireless c~.. ;cation system that utilizes all of the spectr~l allocation available to the system o~e.dlol by ~iloc~ting ~ n~k to cell sectors from two subdivided groups of non-~ cçnt rh~nnel.c The l~ lU~ number of sectors is four.
More srecifirAlly, the çl.~.",~lc in the spectral ~lloç~tir,n are cor~ce.;~ ,ly numbered, from lower to higher freql~Pnriec, or vice versa, and divided into two groups of non-s~ rPnt namely, the odd-numbered ~ lc, So and the even-numbered rh~nnPIc SE. If there are four sectors, the So group of çh~nnPIc is further subdivided into 4/2, or two sets, SoL and SoH, which contain, ~ e.,~ ,ly, the lower half and the upper half of the odd-numbered chSmnPIc The SE group of r~l~nnPIc are similarly subdivided into two sets, SEL and SEH, which contain, e.;livc:ly, the lower half and the upper half of the even-numbered channels. The four subsets of ch~nnPIc are then allocated to the four sectors so as to ",;";,-,i,~ the ~ccignmPnt of ~ cPnt ch~nnPIc to contiguous sectors. For example, if the sectors are numbered clockwise from 1 to 4, and sector one is allocated the SEL set of ch~nnPIc, sector two is allocated the SEH set of CA 02234625 l998-04-l4 W O 97/14259 PCTrUS96/16898 channels, sector three is allocated the SoL set of channels and sector four is allocated the SoH
set of ch~nnele As ~iec~l~eed in more detail below, the dividing points between the sets are chosen such that there is at most one channel in any sector that may t;~..c.lce ~ r~onf-channe hll~,~r~.~,.lce at a sector boundary.
For a cell with more than four sectors, the two groups SE and So are each divided into n/2 sets of lowest to highest-numbered channels, where "n" is the nurnber of sectors. The sets are then allocated to the sectors by allocating to the first set of one of the groups to the first sector, the second set of the same group to the second sector, and so forth, with the last set of the second group allocated to the nth sector.
In a ~rer~ d embodiment of the invention, çh~nn~lc within a sector are ~eeignPd to mobile units in accold~ulce with a technique that I refer to as the "greatest gap" technique. Using this technique, the base station ~etPrrninec which of the allocated channels are ~ ,llly unused, or free. It then d~ e~ which of these free rh~nnPlc are inrln-lç~ in the largest group of "crntiguous," that is, contiguous within the set, ~h~nnRI~ In the SEL set, for Px~mrlP, if rhz~nnPIe 6, 8, 10, 16, 18 and 24 are cul~;nlly free, the largest group of contiguous unused channels col~isl:i of ch~nn~le 6, 8 and 10. This contiguous group may be thought of as a "gap"
b~ l rh~nnelc that are ~ ly in use. In the example, the greatest gap is b~lw~ l rh~
4 and 12. Other gaps in the set consist of rh~nnel~ 2 and 4, and channels 16 and 18. The base station then selects for ~eejf~nment to the mobile unit the channel that is in the middle of the greatest gap.
If the sçlecfP(l channel is one that could result in ~ cPnt-channel i~ .r~ ce at one of the sector boun~l~riPc, the base station may first det.. ;.. e if the ~ r--nt channel in the contiguous sector is in use. If that channel is in use, the base station then selects another channel to assign to the mobile unit. The base station may select this channel from the greatest gap or from another gap, as a~lu~l;ate.
~ ltPrn~tively, the base station may select another channel for ae-eignment to the mobile unit regardless of whether or not the ~ c ent channel is in use in the contiguous sector.
W O 97/14259 PCTrUS96/16898 RRT~,F nF,.SCR~PTION OF T~F,nR ~ WIN GS
The above and further advantages of the invention may be better lln~1Prst~lod by referring to the following description in conjunction with the accc,~ ulying drawings, in which:
Fig. 1 is a block ~ gr~m of a wireless co., ........ ~ ti- n system according to the invention;
Fig. 2 is a block diagram of a base station inclu-lP(l in the system of Fig. 1;
Fig. 3 is a sc1.~ ..,./;c diagram of the system of Fig. 1 that depicts the channel allocation scheme that is used in the system of Fig. l; and Fig. 4 is a flow chart of the operations of the base station of Fig. 2 when the system is op.,.dlmg in accol.ial.ce with the greatest gap techl~i4ue.
T~T'TATT,F,T) T)li ~CRTPTION OF ~7 ~,USTR~TIVh' h'MROT)TMT~ TS
Referring now to Fig. 1, a cellular co........ ~-ication system 10 coneiete of a single cell 12 that is partitioned into a .. ;.. ;... of n=4 sectors 14. Such an a~n~m~nt is suitable, for example, for a system that se, vices an island or other isolated area.
As ~lepict~ in the drawing, the cell 12 is partitioned into four ninety-degree sectors 14.
The cell 12 inchl~s a centrally-located base station 16 that has a plurality of directional A.~ e 18a-d, which are arranged such that each antenna 18 services an associated sector 14.
A mobile teleph-nto ~o~crh~n~ 20, which u~c-aLGs in a CO11V~ m~nn~r, provides co~ clions bG~ n the base station 16 and a public ,wilcl1ed telephone network (PSTN) 22.
The system thus allows mobile units 20 within the cell 12 to cc,lll,lul.icate with each other or with other devices that may be conn~ct~ d to the PSTN 22. To simplify the drawing col-n~ ne b~ - the mobile telephone exchange 20 and the PSTN 22 are not shown.
CA 02234625 l998-04-l4 W O ~7/14259 PCTrUS96/16898 Referring also to Fig. 2, the base station 16 is depicted in more detail. The four directional ~nt~nn~c 18a-d, which each, respectively, handle com~ munications between mobile units within their associated sectors 14, are connected to corresponding mllltich~nn~ scecivers 24a-d. The L~ scGivers 24a-d operate in a conventional manner in conjunction with a base station controller 26, to provide filt~rin~ modulation and ~ltom~ lllation fimrtionc that are ~lr~ecc;~y to couple radio signals received from the mobile units 20 to the PSTN 22, and conv~.sely, to rc.l w~u~d signals from the PSTN 22 to the mobile units 20.
An optional omni-directional ~nt~nn~ 23 may be cO~ to a control-signal lCC~
28, to permit the tr~nemiccion and reception of control signals between the base station controller 26 and the mobile units 20 that are located allywh~lG within the cell 12. In n,;".ol1se to the receipt of control signals that request a channel ~cci~nm~nt the control-signal l~,C~ ,. 28 ~let~rmin~s in which sector 14 the l~.lueslillg mobile unit 20 is located, and assigns to the unit a channel that is allocated to that sector. The ~~,.,.,;~c. 28 then ~n~es for the a~ Jl;alG
l-~,sc~ er 24a-d and ~nf~nn~ 18a-d to handle further c.~ ..ic~tions with the mobile unit. In a ~ f~,.led embodiment, the control-signal l.,CC;~. assigns ~ n~.l.c to the mobile units in accu..l~ce with a ~ aLc~l gap" technique, as ~1icc~lc$ed below with reference to Fig. 4.
R~f~rring now to Fig 3, the charmel allocations to the sectors 14 are made so as to ..~;..;...;~ a~jacPnt-channel hlle.rtl~.lce. The ch~nnlolc in the spectral allocation available to the system are conse-;ulivcly numbered, from the lowest fi._~lu~,lcies to highest rl~quen~;ies or vice versa. The channels are then grouped into two groups of non-acij~ç~nt ch~nnf~lc, such as even-numbered ch~nn~1c SE, and odd-numbered ch~nnt?lc, So. Next, the two groups are subdivided into n/2 sets of higher and lower frequenri~c. Thus, for n=4, the group of SE ~ rl~ are subdivided into two sets of higher and lower rl~ uellcies, namely, SEH and SEL, and the group of So ~h~nnPI~ are also subdivided into two sets of higher and lower frequencies, namely, SOH
and SoL . As explained below, the dividing points of the groups into sets are chosen and the four sets of çl".."~cl.c are allocated to the sectors 14 such that contiguous sectors include at most one channel that may t;~.,.ic.rce at1j~r~ont-channel hll~.r~.~..ce.
If the sectors are nurnbered clockwise from 1 to 4, sector 1 is allocated the SEL set of çh~nntoi~, sector two is allocated the SEH set of channels, sector three is allocated the SOL set of channels and sector four is allocated the SOH set of channels. There are no ac~jac~nt channels in - =
W O 97/14259 PCTrUS96116898 sectors 1 and 2, or 3 and 4, and thus, there is no arlj~cçnt-channel hllGlr~ ce at the l~ ,ecLive boundaries between these sectors. rne dividing points between the SEL and SEH sets, and SoL
and SoH sets are ay~upliately chosen such that there is at most a potential for S~djS~c~?nt-rhannP
hl~,.r~,c..ce between co,.,~ c~tions ûver a single channel bGL~ sectors 1 and 4, or sectors 2 and 3. The sets are thus divided such that the highest-numbered channel in, for example, the SEL set is ~dj~cPnt to the lowest-numbered channel in the SoH set, or the lowest-numbered channel in SEH set is ~ cPnt to the highest-numbered channel in the SoL set. Acco.dil~ly, there is a .,~;";.. " amount of ~ nt-channel hlL~-rG-Gnce bGL.. _~,. the sectors.
If, for example, the odd-numbered ch~....rlc are divided such that channel 41 is the lowest-numbered channel in sector 4, the even numbered ~h~nnPIc should be divided such that SEL has ch~nnel 40 as its highest-numbered ch~nnel Otherwise, co...."~,..;r~ti~nc ûn the rhzlnnPlc of sector 1 may i-lL~,.r~.e with more than one charmel in sector 4. If the dividing point beL~._.,n the high and low sets of the even-nurnbered ~h~nnlolc was instead chosen such that the highest-nurnbered channel in SEL is channel 42, there could be hlt~.r~.~..ce b~Lv~ that ch:mn~l and two ~ .rlc in sector 4, narnely, channels 41 and 43.
If n is odd, that is, if the cell 12 is partitioned into an odd nurnber of sectors, the two groups of non-~ cent ch~nnelc So and SE, are divided such that one group has ~n/2~ sets, where ~~ .~lG~e.lLs an integer value. rhe other group is tnen divided into ~nt2~+1 sets. The first sets of each group include the lowest-nurnbered ch~nnPIc in the group, the next sets include the next lowest-nurnbered ch~nnPIc in the group and so forth, with the last sets of the groups including the highest-numbered rh~nnP!c The sets are then allocated to the sectors in clockwise order, with the first set of one of the groups allocated to sector 1, the next set of the sarne group allocated to sector 2 and so forth, and the last set of the second group allocated to sector n. In this cell, only the sectors that have been ~lloc~tPd the first or last sets of a group may G~.ie.lcc -r~ nn.sl illL~,.r~ ce at one of their sector bounrl~ri~s With an odd nurnber of sectors, dirr~,.Gnces in the number of rh~nnPlc that are allocated to the various sectors can be colllp~ ,aLed for by allocating fewer ~h~nnPIc to the sectors that cover areas with lower population dencitipc~ or by ch~nging the sizes of the sectors that have fewer r.h:lnn~lc allocated to them.
CA 02234625 l998-04-l4 W O 97/14259 PCT~US96/16898 Referring now to Fig. 4 in conjunction with Figs 1 and 3, I discuss a p.GÇ_...,d technique for zlccigning ~h5~ 1c to the mobile units. When a mobile unit 20 requests a cc,l~c.,lion, the base station first r~ct~ ....;..PC which sector 14 the mobile unit is in (step 100). In this rYA~..ple, the mobile unit 20 is located in sector 1. Next, the base station 16 dçtP~minPs which of the rhsmnPlc zllloe~tPd to sector I are not in use, and further dçl~ ...in~s which of these ~,h~l~"~lc are inrhlded in the greatest "gap" between c~h~nnPIc that are then in use (step 102). If sector 1 has allocated to it çh~ -flc 2, 4, 6...40, and fll,.".~rlc 6, 8, 10, 16, 18 and 24 are ~ ly free, the largest group of unused rh;1l~l.rlc that are contiguous within the set c~n.cictC of rh~nnPlc 6, 8 and 10. These rh~nnPIc u~ ;L.~Iç the greatest gap l~ ,n ~h~nn~lc that are then in use. The base station may rl~l~ ~...;..P which çh~nnPlc are free by conclllting a table (not shown) or by sç~nning the rh~ rlc The base station then selects for ~cci~nmPnt to the mobile unit the rh~nnPI that is in the middle of the greatest gap (step 104). The base station thus selects ch~nnPI 8. If the select.od channel is the one r.h~nnPI that may result in ~ -r-~t-channel illlelr~.Gll~.e at a sector boundary, the base station clet.. ;.. ~s if the ~ r~-nt channel in the contiguous sector is in use (steps 106, 108). If the ~djs~cPnt channel is not in use, the base station assigns the selPctçd rh:~nn~ol, that is, rhzlnnPI 8, to the unit (step 110). Otherwise, the base station refrains from slccigning the selectPd channel to the unit and instead assigns to the unit another of the free rh~nnPI-C (steps 112, 114).
The base station may select this channel from the greatest gap, or from any other gap. In this way, the base station avoids a potential problem with ~-ljac~ont-channel iIllGlr~ ce.
, the base station may select another channel for ~csi~nmPnt to the mobile unit, without first ~içt~ ....;. ~;~ g if the ?~ çnt channel is in use.
The r~ ,goi.lg description has been limited to a specific embodiment of this invention. It will be ~a.Glll, however, that variations and modifications may be made to the invention, with the~ll.;.. lofsomeorallofits adv~ g~c Therefore,itistheobjectofthe~ppen~ dclaims to cover all such variations and mo-lifit~tionc as come within the true spirit and scope of the mventlon.
What is cl~imp(l is:
Claims (8)
1. A method for allocating channels to sectors of a cell of a wireless communication system, the method including the steps of:
A. partitioning the cell into n sectors;
B. consecutively numbering the channels, from lowest to highest frequency, and grouping the numbered channels into a first group and a second group of non-adjacent channels, C. subdividing each of the first and second groups into n/2 sets of channels, with a first set of each group containing the lowest-numbered channels of the associated group, the second set containing the next lowest-numbered channels of the associated group, and so forth;
D. assigning the first set of the first group of channels to a first sector of the cell;
E. assigning to a contiguous sector of the cell the second set of the first group;
F. assigning to a next contiguous sector of the cell the next set of the first group;
G. repeating step F until all of the sets of the first group are assigned to sectors;
H. assigning the first set of the second group to a next contiguous sector; and I. repeating step F for the sets of the second group.
A. partitioning the cell into n sectors;
B. consecutively numbering the channels, from lowest to highest frequency, and grouping the numbered channels into a first group and a second group of non-adjacent channels, C. subdividing each of the first and second groups into n/2 sets of channels, with a first set of each group containing the lowest-numbered channels of the associated group, the second set containing the next lowest-numbered channels of the associated group, and so forth;
D. assigning the first set of the first group of channels to a first sector of the cell;
E. assigning to a contiguous sector of the cell the second set of the first group;
F. assigning to a next contiguous sector of the cell the next set of the first group;
G. repeating step F until all of the sets of the first group are assigned to sectors;
H. assigning the first set of the second group to a next contiguous sector; and I. repeating step F for the sets of the second group.
2. The method of claim 1, where the cell is partitioned into four cells, the channels are grouped into groups of even-numbered and odd-numbered channels, and the groups are subdivided into sets of even-numbered high and low channels and odd-numbered high and low channels.
3. A method for assigning to a mobile unit channels that are allocated to sectors of a cell in a wireless communication system, the method including the steps of:
A. determining the sector in which a mobile unit that is requesting a channel assignment is located;
B. determining unused channels that are allocated to the sector in which the mobile unit is located;
C. determining which of the unused channels are associated with a greatest gap between channels that are in use;
D. selecting the channel that is in the middle of the greatest gap and assigning the selected channel to the mobile unit.
A. determining the sector in which a mobile unit that is requesting a channel assignment is located;
B. determining unused channels that are allocated to the sector in which the mobile unit is located;
C. determining which of the unused channels are associated with a greatest gap between channels that are in use;
D. selecting the channel that is in the middle of the greatest gap and assigning the selected channel to the mobile unit.
4. The method of claim 3 further including the steps of:
i. determining if the selected channel is adjacent to a channel that is allocated to a contiguous sector;
ii. assigning to the mobile unit another channel that is not adjacent to a channel in the contiguous sector; or iii. if the selected channel is not adjacent to a channel that is allocated to a contiguous sector assigning the selected channel to the mobile unit.
i. determining if the selected channel is adjacent to a channel that is allocated to a contiguous sector;
ii. assigning to the mobile unit another channel that is not adjacent to a channel in the contiguous sector; or iii. if the selected channel is not adjacent to a channel that is allocated to a contiguous sector assigning the selected channel to the mobile unit.
5. The method of claim 4 wherein the step of assigning another channel to the mobile unit includes assigning to the unit another channel from the greatest gap.
6. The method of claim 3 further including the steps of:
i. determining if the selected channel is adjacent to a channel that is allocated to a contiguous sector;
ii. determining if the adjacent channel is in use in the contiguous sector;
iii. if the adjacent channel is in use, selecting another channel and assigning the channel to the mobile unit; and iv. if the adjacent channel is not in use, assigning the selected channel to the mobile unit.
i. determining if the selected channel is adjacent to a channel that is allocated to a contiguous sector;
ii. determining if the adjacent channel is in use in the contiguous sector;
iii. if the adjacent channel is in use, selecting another channel and assigning the channel to the mobile unit; and iv. if the adjacent channel is not in use, assigning the selected channel to the mobile unit.
7. The method of claim 6 wherein the step of selecting another channel includes selecting another channel from the greatest gap.
8. The method of claim 6 wherein the step of selecting another channel includes determining other gaps in the used channels and selecting another channel from a gap other than the greatest gap.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US08/542,720 | 1995-10-13 | ||
| US08/542,720 US5835859A (en) | 1995-10-13 | 1995-10-13 | Method for frequency allocation and assignment in wireless communication systems |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2234625A1 true CA2234625A1 (en) | 1997-04-17 |
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ID=24165002
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
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| CA002234625A Abandoned CA2234625A1 (en) | 1995-10-13 | 1996-10-15 | A method for frequency allocation and assignment in wireless communication systems |
Country Status (5)
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| US (1) | US5835859A (en) |
| EP (1) | EP0855126A1 (en) |
| AU (1) | AU7465196A (en) |
| CA (1) | CA2234625A1 (en) |
| WO (1) | WO1997014259A1 (en) |
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| CN1108033C (en) * | 1995-01-20 | 2003-05-07 | 西门子公司 | Process for signal transmission between movable and fixed radio receiving and transmitting apparatuses in wireless communication system and device for carrying same out |
| GB9525942D0 (en) * | 1995-12-19 | 1996-02-21 | Nokia Telecommunications Oy | Channel allocation in a radio telephone system |
| US6138024A (en) * | 1997-10-23 | 2000-10-24 | Allen Telecom Inc. | Dynamic channel selection in a cellular communication system |
| US6078815A (en) * | 1997-10-23 | 2000-06-20 | Nortel Networks Corporation | Method and apparatus for allocating radio channels |
| US6311068B1 (en) * | 1998-10-19 | 2001-10-30 | At&T Corp. | Method and apparatus for a high-capacity cellular network by improved sectorization and interleaved channel assignment |
| US6424836B1 (en) | 1999-02-09 | 2002-07-23 | Innowave Eci Wireless Systems Ltd. | Method for allocating frequency channels for sectors of a cell in cellular systems |
| US6418327B1 (en) | 1999-04-06 | 2002-07-09 | Spike Broadband Systems, Inc. | Methods and determining an optimum sector distribution within a coverage area of a wireless communication system |
| KR100340032B1 (en) * | 1999-10-19 | 2002-06-12 | 이계철 | Base station transmitter and subscriber receiver using circular polarization and method for designing and extending cell using the same |
| US6728544B1 (en) * | 1999-12-15 | 2004-04-27 | Verizon Laboratories Inc. | Methods and techniques in channel assignment in a cellular network |
| US6871073B1 (en) * | 1999-12-15 | 2005-03-22 | Verizon Laboratories Inc. | Methods and techniques in channel assignment in a cellular network |
| US7142523B1 (en) * | 2000-07-31 | 2006-11-28 | Lucent Technologies Inc. | Methods and apparatus for design, adjustment or operation of wireless networks using pre-frequency-assignment optimization |
| US7248877B2 (en) * | 2002-11-21 | 2007-07-24 | Bandspeed, Inc. | Multiple access wireless communications architecture |
| US7512404B2 (en) * | 2002-11-21 | 2009-03-31 | Bandspeed, Inc. | Method and apparatus for sector channelization and polarization for reduced interference in wireless networks |
| US7136655B2 (en) * | 2002-11-21 | 2006-11-14 | Bandspeed, Inc. | Method and apparatus for coverage and throughput enhancement in a wireless communication system |
| US7130586B2 (en) * | 2003-05-30 | 2006-10-31 | Microsoft Corporation | Using directional antennas to mitigate the effects of interference in wireless networks |
| US7295806B2 (en) * | 2003-05-30 | 2007-11-13 | Microsoft Corporation | Using directional antennas to enhance wireless mesh networks |
| US7302278B2 (en) * | 2003-07-03 | 2007-11-27 | Rotani, Inc. | Method and apparatus for high throughput multiple radio sectorized wireless cell |
| EP1708419A3 (en) * | 2003-08-01 | 2007-01-24 | Bandspeed, Inc. | Method and apparatus for coverage and throughput enhancement in a wireless communication system |
| IL160832A (en) * | 2004-03-11 | 2009-02-11 | Alvarion Ltd | Spectrum sharing between wireless systems |
| KR100663557B1 (en) | 2004-11-08 | 2007-01-02 | 삼성전자주식회사 | An interference canceling method for distributed wireless communication system |
| US7489282B2 (en) * | 2005-01-21 | 2009-02-10 | Rotani, Inc. | Method and apparatus for an antenna module |
| JP2006339909A (en) * | 2005-05-31 | 2006-12-14 | Toshiba Corp | Communication apparatus and communication control method |
| BRPI0520591B1 (en) * | 2005-09-27 | 2019-01-29 | Telecom Italia Spa | method including estimating territorial distribution of traffic, data processing system and computer readable storage |
| EP2475106A1 (en) | 2006-02-28 | 2012-07-11 | Rotani Inc. | Methods and apparatus for overlapping mimo antenna physical sectors |
| US8917673B2 (en) * | 2006-07-14 | 2014-12-23 | Qualcomm Incorporation | Configurable downlink and uplink channels for improving transmission of data by switching duplex nominal frequency spacing according to conditions |
| US11611405B2 (en) | 2020-08-11 | 2023-03-21 | Microsoft Technology Licensing, Llc | Efficient spectrum allocation in a multi-node optical network |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4144496A (en) * | 1976-03-17 | 1979-03-13 | Harris Corporation | Mobile communication system and method employing frequency reuse within a geographical service area |
| US4485486A (en) * | 1982-08-03 | 1984-11-27 | Motorola, Inc. | Method and apparatus for assigning duplex radio channels and scanning duplex radio channels assigned to mobile and portable radio telephones in a cellular radiotelephone communications system |
| US4726050A (en) * | 1986-02-18 | 1988-02-16 | Motorola, Inc. | Scanning receiver allocation method and apparatus for cellular radiotelephone systems |
| US5073971A (en) * | 1989-09-05 | 1991-12-17 | Motorola, Inc. | Cellular radiotelephone communications system |
| US5257398A (en) * | 1990-02-27 | 1993-10-26 | Motorola, Inc. | Hopped-carrier dynamic frequency reuse |
| US5319796A (en) * | 1990-12-14 | 1994-06-07 | Motorola, Inc. | Communication system that avoids co-channel interference |
| US5212830A (en) * | 1991-05-31 | 1993-05-18 | International Mobile Machines Corporation | Radio frequency communications system |
| JPH0744725B2 (en) * | 1993-03-17 | 1995-05-15 | 日本電気株式会社 | Channel allocation method for wireless communication system |
| US5483667A (en) * | 1993-07-08 | 1996-01-09 | Northern Telecom Limited | Frequency plan for a cellular network |
-
1995
- 1995-10-13 US US08/542,720 patent/US5835859A/en not_active Expired - Lifetime
-
1996
- 1996-10-15 CA CA002234625A patent/CA2234625A1/en not_active Abandoned
- 1996-10-15 WO PCT/US1996/016898 patent/WO1997014259A1/en not_active Application Discontinuation
- 1996-10-15 AU AU74651/96A patent/AU7465196A/en not_active Abandoned
- 1996-10-15 EP EP96936821A patent/EP0855126A1/en not_active Withdrawn
Also Published As
| Publication number | Publication date |
|---|---|
| EP0855126A1 (en) | 1998-07-29 |
| AU7465196A (en) | 1997-04-30 |
| WO1997014259A1 (en) | 1997-04-17 |
| US5835859A (en) | 1998-11-10 |
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