United States Patent rlel
`Hays et al.
`
`t54] MI.]IjTICARRIOR TECHNIQT]ES IN
`BÄ,NDLIMITED CBA.NNELS
`fl5| Inventors: YViIIiam D. Eays; Dennis Camemn.
`both of Jackson. Miss.; Walter Roehr'
`Reston. Va.
`
`fßl Assignee: Mobile Telecommunication
`Tecbnologies, Jackson' Miss.
`
`l2ll Appl. No.: 480118
`t22l Filed: Jun.7,1995
`Fi04ßu02
`t51l InL CL6
`lsn U.S. Cl.
`4551103;455145;3'10t339.:
`370t343
`I58l Field of Seareh
`..-...'. 4551L03, L04,
`455117,46, 59. 60. 61. 62, 49.1, 45; 37 5DÑ;
`3'10169.I.70, 38, 40, L2l; 340/825.M
`
`156I
`
`References Cited
`
`U.S. P¿TENT DOCUMENTS
`3383,445 1/19?0 Chang
`3,914554 10/19?5 Seidel
`
`.-.---.- 370169-1
`... 179115.55 R
`
`itililllllllllllil|llllllllllllllilllllllllllllllllllllllll¡¡lllllllllllill
`us0056598914
`tlll Patent Nrrmber:
`t45l Date of Patent:
`
`5,659,891
`Aag.19,1997
`
`4244,047 1/1981 Pe¡kins
`-.-.-...... 370169
`5,163,181 11t1992 Koonv.
`.......- 455ll03
`5343199 8/1994 Jasperetal.'.....'.....'...'......'.----- 375ß9
`5,3y2,452 2ll995"Daws
`..'...... 455/38.1
`OTHER PUBUCATIONS
`
`47 C.F.R. $ 22.106 (19%).
`
`aBSTRÄCT
`
`P r imary Emmine r-Fieipltard J. Eisenzopf
`A s si stant Emmine r-Leæ NguYen
`Attomey, Agent, or Fine-Finnegan, Henderson, Faraboq
`Garreü a¡rd Dunner
`ls7l
`A method of multicarrìer rnodulation using colocated trans-
`miüers to achieYe higher tansmission capacity for mobile
`paging and two.way digital cornmunication in a rì¡rnn€,r
`consistent with FCC emission mask limits. Co-location of
`the transmitters obviates the need for stringen! symmetrical
`subchaanel interference protection and provides for a wider
`range of operating parameters. including peak ftequency
`deviation, bit ¡ate, and carrier ftequencies, to obtain optirnal
`transmission perforrnance.
`
`5 Çl¡ims, 11 Drawing Sheets
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`EXHIBIT 7
`
`WT:
`
`DATE:
`Micheal A. Johnson, CSR' CRR
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`MTel., Exhibit 2010, Aruba v. MTel., Page 1, IPR2016-00768
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`MTel., Exhibit 2010, Aruba v. MTel., Page 3, IPR2016-00768
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`

`
`I
`MULTICARRIER TECUNIQUF,S IN
`BANDLIMITED CEÀNNELS
`
`5,659,891
`
`FIELD OFTITEII.IVENTION
`The present invention relates generally to multicarrier 5
`modulation techniques. and mo¡e particularly, to a method
`for operating more than one carrie¡ in a single rnask-defi¡ed'
`bandlimited channel assigned to mobile paging use.
`DISCUSSION OF RELAffED ARI
`The rising popularity of mobile paging services has
`resulted in increased competition for air time on the limited
`number ofradio-frequency channels allocated by the Federal
`Cornmunications Cornmission (FCC) for mobile paging use-
`As dernand begins to approach and even excsed theiapacity ls
`of assigned channels to handle transmission traffc, delays in
`service and deterioration of ta¡smission quality me becom-
`ing a major concern to mobile paging users and providers.
`The ability of mobile paging providers to successfully
`address the problem of transmission saturation is limiúed by
`the ûnite range of air space dedicated to mobile paging use.
`Channels assigned by the FCC to radio paging providers
`rypically have narrow band'øidths (e-g- 25 klfz) and are
`subject to stringent emission mask limit¿tioûs'
`One method that can be used to allow greater access to a
`particular channel is to increæe the number of messages
`tatrsmitted over the channel in a given period. This cal be
`achieved, for exarnple. by increasing the data rate of the
`tansmission or by reducing the length of fransmiüed mes-
`sages. U.S. Pat No- 5392,452 issued to Davis, for exarnple,
`describes a high data raæ transmission sçhsms fc|¡ hanrlling
`lengthy messages in a paging systern- Systems employing
`techniques to i¡crease tratsmission rates. however, âIe
`prone to higher enor rates. In addition. high data rates tend
`to getrerate greater tansmission interference.
`Another approach to addressing the saturation problem is
`to increase the transmission capacity of the channel itself.
`Tladitionally. mobile paging providers have operated only
`one transmission signal. or carrier, within au assigned chan-
`nel. While this mode ensures sirnplicity of operation and
`cor4pliance with FCC rnask requirements, it does not pro-
`vide the most efrcient use of the limited frequency band-
`width available. Successful multicarrier modulation,
`however, is diñcult to achieve without incurring unaccept-
`able levels of fuærference-
`The problem of interference is compounded when a
`receiver is attempting to acquire a signal from a dista¡t
`transmitter while in close proximity to a transmitter oPer-
`ating on an adjacent .channel In this environment. the
`receiver may experience diñculty in detecting the signal
`from the distant source due to interference from the signal
`tansmitted on the adjacent channel from the closer source.
`This is known as the "near-fa¡" problem. This problem can
`be avoided by co.locating the tansmitters at essentially the
`same geographic location.
`The FCC requires signals to be confined within emission
`Iimit masks in order to prevent interference caused by
`signals staying or spilling into adjacent channels. FCC
`masks typically require the porver spechal density of a
`sigoal to be attenuated at least 70 dB at the band edge.
`Despite these shingent constaints. some carrier overlap can
`be expected, even when the maximum carrier spacing con-
`sistent with the FCC rnask requirements is u-:ìized. Such
`overlap can result in unacceptable interference of the
`carriers. making it difficult for the receivers to acquire the
`proper carrier.
`
`10
`
`2
`Thus. a traditional multicarrier design would cornrnonly
`require the same stringent protection levels betweeD sub-
`channels. Specifically, when more than one carrier is oper-
`ating within a single channel, each carrier is traditionally
`confined to a submask deflning a subchannel internal to tt¡e
`cha¡nel. The carriers are symmetrically located within the
`channel such that they are evenly spaced relative to each
`other and to the band edges of the primary mask deñning the
`prfunary channel. Although such syrnmetry achieves rnaxi-
`mum inter-carrier spacing and reduces the oppornrnity for
`interference arnong adjacent ca¡riers, it often necessitates
`the need for sophisticated receiver and transmitter schemes.
`SIJMMÄRY OF TIIE INVENfiON
`It is an object ofthis invention to achieve higher capaciry
`over a bandlimited channel for p¡ging without the need for
`stringent subchannel interference protection. Additional
`objects. advantages. and features of the invention wíll be set
`forth in part in the description that follows, and in part will
`2q be obiious from the description, or may be learned by
`practice of the invention The advantages of fhe invention
`will be reelìzed and attained by meaûs of the instrumetrt¿li-
`ties and combinations particularly pofuted oùt in the written
`description and claims herein, as well as the appended
`25 drawings.
`To achieve these and otfier objects, advantages, and
`feah¡res in accordance wirù the purpose of the invention, as
`embodied and broadly described herein. the invention pro-
`vides a method of operating a phnality of paging carrias in
`30 â single mask-deûned, bandlimited channel comprising the
`step of tansmiti.ng the carrie.rs from the sarne location at
`center frequencies within the channel such that the fre-
`quency diffaence between the center frequency of the outer
`most cariqs and the band edge of the mask deûning said
`ss channel is more than h¿Ifthe frequency difference between
`the cetrær frequencies of each adjacent carier.
`In another aspect, the invention provides a method of
`operating at least two paging carriers each in a correspond-
`ing subchannel of a single mask-deûned. bandlimited chan-
`æ nel comprising the step of transmitting the carriers from the
`sarne location with each carrier cenûally locate{ in a cor-
`responding subchannel wherein the frequency difference
`between the center frequenqr of the outq most subchannels
`and the band edge ofthe rnask deûning said channel is more
`45 than half the frequency difference between the center fte-
`quencies of each adjacent carrier
`in another aspect, the invention provides a method of
`operating a phnality of carrien in a single rnaskleûned.
`bandlimited channel to achieve higher tralsmission capacity
`50 over the channel in a mobile paging system having a
`pluratity of transmitters generating a plurality of modulated
`carriers over a single bandlimited channel and a plurality of
`mobile. independent receiving units- capable of receiving
`one of said plurality of c¿rrie6. The method comprises the
`5s steps of co-locating the plurality of transmitters such that the
`phnality of ca¡riers can be emanated from the same üans-
`mission sou¡ce, and transmitting the carriers over a plurality
`of subcha¡nels spaced asymmetrically within the rnask
`deûning the channel.
`60 It is to be understood that both the foregoing general
`description and the following detailed descriptioû are exem-
`ptary and explanatory only and are not restrictive of the
`invention, as claimed.
`BRIEF DESCRIPTION OF THE DRAWINGS
`65
`The accompanying drawings. which a¡e incorporated in
`and constitute a pâ¡t of this speciûcation. illustrate several
`
`MTel., Exhibit 2010, Aruba v. MTel., Page 13, IPR2016-00768
`
`

`
`3
`embodiments of the invention a¡d together wit.h the
`description. serve to explain the principles of the invr:ntion.
`In the drawings,
`FIG. L is a block diagram of a co-located multi:ar¡ier
`ûansmitter system in a linear amplifier conigurati)tr for 5
`using the present invention;
`FIG. 2 is a block diagram of a co-located multi:a¡¡ier
`transmitte¡ system in a cornposite transmitter configr.uation
`for using the present invention;
`FIG. 3A is a graph depicting trvo submasks deûnirrg two 10
`subchannels in a single. rnask-deûned bandlimited channel.
`FIG. 38 is a graph depicting the powø spectra (f two
`ca¡riers asyrnmetricaliy located within a single .mask-
`deñned. bandlimited ch¿nnel.
`FIG. 4 is a graph depicting an exemplary FCC emissions
`mask that requires the power specFal density to be aftenu-
`ated at least 70 dB within 10 kIIz from center Aequr:ncy.
`FIG. SAis a graph depicting the power spectra of a system
`with peak deviation of 2400 Hz and data rate of 6000 b its per æ
`second (bps);
`FIG. 5B is a graph depicting the perforrnance r¡f the
`system of FIG. 5A i¡ ær¡ns of bit €rror
`rate versus the signal
`noise ratio (SNR);
`FIG. 6A is a graph depicting the power spectra of a syrr"nr "
`with peak deviation of 1800 IIz and a data rate of 6401) bps;
`FIG. 68 is a graph depicting the perforrnance cf the
`system of FIG. 6A i¡ terms of bit error rate versus SNR;
`EIG. 7A is a graph depicting the power spectra of a q/stem 30
`with peak deviation of 2100 Hz and a data rate of 640i) bps;
`alrd
`FIG. ?3 is a graph depicting the perforrnance c,f the
`systern of FIG. 7A in ter¡ns of bit error rate versus S.NR.
`
`15
`
`35
`
`DE'TAITED DESCRIPI1ION OF TIIE
`PREFERRED EMBODMENTS
`Reference will trow be made in detail to the prerrently
`preferred embodime¡ts of the invention. exam¡rles of which oo
`are illustrated in the accorqpanying drawings. Wherever
`possible, the same reference trumbers will be used ltrough-
`out the drawings to refer to the same or like parts.
`Referring to FIG. 1. a co-located multicarrier transrnius
`system in a line¡¡ ampliûer configuration 10 coroprises a a5
`first and seco¡ddata source. lla and llå, afust and se.cond
`¡nodulator, l?¿ a¡d L2, a surnmation circuit 13. a line¡¡¡ RF
`ampliñe.r 14. and an anterìna 15. The f¡st and second data
`sotrces. 11¿ and |Lå, generate a respective first a¡d second
`digital bit stream which are provided to respective frst and 5s
`second modulators. 12¿ and,l2b. Each modulator coaverts
`the incoming digital inforrnation into a representative nrodu_
`Lated signal or carrier. The outputs of eìch modulator are
`then combined into a single ouÞut signal by surnrnation
`circuit 13, the ouþut of which is fed i¡to linear RF amplifer 55
`14. The combi¡ed output sipalis then appliedto antenna 1.5
`fo¡ transmissio¡ i¡ ¿ þ¿¡¡ilimiled channel.
`Alternatively. referring to FIG. 2. a co-located mulicar-
`¡ier bansmitter in a cornposite arnplifier conûguration 20
`comprises a fi¡st and second data source. 2la and?tb, a ûrst oo
`and second modulator. 22a and 22b, a ñ¡st and seconrl RF
`arnplifi€r. 2fu and 23å, a summation ctcuit A, an! an
`aûtenna 25. The fi¡st and second digital bit stre¡ms gr:ner_
`âted respectively by the first and seco¡d data sources. 21o
`a¡d Zlb, are provided to fust and second modulators. ?.?¿ 65
`and22b, respectively. Each moduiator converts the incom-
`ing digital information into a representative modulated sig-
`
`s.659
`
`,891
`
`4
`nal o¡ ca¡rie¡. The ouÞuts of the first and second modulators
`are fed into first and second RF arn¡rlifiers. 2.k and 2*,
`respectively. The outputs of the RF amplifrers are combined
`into a single output signal by surnmation circuit ?A. ttre
`ouþut of which is applied to antenDa 25 for tra¡smission i¡
`â banrilimited channel.
`Alternative embodiments of co-located transmitter sys-
`tems are also possible. For exarnple, the co-located trans-
`mitter conñgurations discussed above can be expanded to
`support more than two data sources atrd tansmit more than
`two cariers in the bandlimited cha¡¡el.
`Because traÈsmiü€r colocation does not give rise to the
`near-far problem to which the FCC mask requiremetrts are
`directed. carrier spacings far closer tha¡ would ordinarily be
`allowed (e.g.. 5 to 10 kIIz) are achievable. Mcreover, the
`carriers need not be symmetrically or evenly qpaced within
`the mask defining the channel. That is, the frequency spac-
`ings between adjacent carriers. while symmetric to èach
`other. can be smaller than the frequency spacings between
`the baad edges of the rnask and the nearest respective carrier.
`Indeed carrier spacings may be irregular such that the
`carriers are asymmetrically located within the mask without
`incurrìng undue interference.
`Referring to FIG. 34. fwo submasks defining two
`subchan¡els. 30¿ ¿nd 30b, arc asyrnmetically located
`within a single rnask-deñned. bandlimited channel 31,
`resulting in some subcha¡nel overlap. FIG. 38 depids fwo
`car¡iers. 32a and 32å, operating respectiveþ over two
`asyrnmetrically-located subchannels, resulring in some car-
`rier overlap. I¡ accordance with this asymmetry, the fre-
`quency diference between tl¡e center ftequency of each
`ca¡rier and the nearest band edge of the mask is greater than
`half the frequency difference between the center frequencies
`of the two c¿rriers.
`The practical implication of tra¡smitter co-locatioû is that
`a greater range of operating parameters, including the peak
`frequency, deviation bit rate. and car¡ier frequencies. are
`avaìlable so that multicarrier modulation in a srrndard
`bandli¡nited channel can be obtained without the need for
`sbingent subcha¡nel interference protection- In accordance
`with the ¡rresent invention. these and other parameters cal be
`adjusted so that the cariers getrerated and transmitted
`according to the present invention will remain within the
`FCC ernissio¡ limits while providing optimal transmission
`perforrnance.
`FIG. 4 shows a FCC emissions ¡nask ¡vhich requires the
`povier specral density to be attenuated at least 70 dB withi¡
`10 kHz from cenrer ûequency. Co-location of the tansmit-
`ters allows for signals with a greater range of deviation and
`baud rates to be carried in úe bandlimited channel than has
`been otherwise thought possible in view of FCC Z0 dB
`cutoff requirements. The present invention will be ñrthe¡
`cla¡ified by the following exam¡rles. which are intended to
`be purely exemplary of the i¡vention.
`FIG. 5A is a spectra graph of a two-carier system in
`which the foilowing pararneter values were selected: a peak
`frequency deviation of 2400 Hz. a bit rate of 6000 þs.
`premodulation fllter cutofffrequency of 3000 Hz. and car¡ier
`frequencies set to withi¡ 4590 Hz of the center frequency.
`Using this o¡rerative parameter combination. the ca¡rieis
`remained within the FCC mask while providing an accept-
`able er¡or-rate versus signal strength performance (FIG. 5B).
`Alternatively, FIG. 6A is a specba graph of a two-carrier
`system using a peakfrequency deviation of 1800 Hz. a bit
`rate of 6400 bps. a premodulation filter cutoff frequency of
`3200, and carrier frequencies set to within 5150 Hz of ttre
`
`MTel., Exhibit 2010, Aruba v. MTel., Page 14, IPR2016-00768
`
`

`
`5,659,891
`
`5
`
`10
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`15
`
`5
`frequency. As depicted fu FIG. 68. this combination
`cont€r
`of operative parameters exhibited a higher bit error rate than
`the system of FIG. 5.A'.
`FIG. 7A is a spectra graph of a two-carrier system using
`a peak frequency deviation of 2100 Hz. a bit rate of 6400
`þs. a premodulation ûlter cutofi frequency of 3200, and
`carrier ñequencies set to within 4750 Hz of the center
`Aequency. As depicted in FIG. 78. this combiration gives
`signifrcantly better perforrnance than the system of FIG. 6A
`but perforrns sligþtly worse than the system of EIG. 54.
`Thus, according to the present invention, increased trans-
`mission capacity is achieved by operating more tha¡ one
`ca¡¡ier in a stand¿rd bandli¡nited chan¡el assigned for
`mobile paging use. such as in the Nanowband Personal
`Communications Service o¡ the Part 22 Service, In the
`modulation technique of the present iavention, cariers oper-
`ating at diffoent ftequencies are ñt within a single band-
`width allocation in a man¡er consistent with FCC rnask
`requirements. This is achieved tlrough the use of colocated
`trammiüers and the selection of aa optimal combination of
`operating parameters, including peak frequency deviation,
`bit rate, and carrier separation frequencies. Through the
`multicarrier modulation technique of the present invention,
`the norrnal tansmission capacity ofa standard channel can
`be increased without the need for shingent subcha[nel
`protection levels and complicated receiver and tansrniüe¡
`schemes.
`The moth¡Iation technique of the present invention has
`particular application in metropolitan areas where the vol-
`ume and concentation of tansmission trafic is high and
`whe¡e the need for increased tansmission capacity is acute.
`In addition, the modulation technique of the present inven-
`tion rnay also be suited for use in ateas where the incidence
`of unacceptable interference is high, such as international ,,
`border regions. In that type of environ¡nent. tansmissiotrs
`from the respective bordering countries can be assigned to
`one of the carriers operating within the channel to reduce the
`risk of interference.
`It will be apparcnt to those skilled in the a¡t that various 4q
`modifrcation and va¡iations can be made to present invention
`without departing from the spirit or scope of the invention.
`Other embodiments of the invention will be apparent to
`those skilled in the art from considsation ofthe specif.ca-
`tion and practice of the invention disclosed herein. Thus, it
`is intended that the speciûcation and exarnples be considered
`
`20
`
`)<
`
`30
`
`6
`as exemplary only. with a true scope and spirit of ûe
`invention being irdicated by the following claims.
`What is clairned is:
`1. A method of operating a plurality of paging carriers in
`a single mask-defined, bandlimited channel cornprising the
`step of transrnitting said carriers from the same location with
`said carriers having center frequencies within said ch¿nnel
`such that the ftequency difference between the center fre-
`quency of the outer most of said carriers and the band edge
`of the rnask def,ning said channel is more than half the
`frequency difference between the center frequencies of each
`adjacent carrier.
`2. The method of claim I wherein adjacent ca¡riers
`overlap with each other.
`3. A method of operating at least two paging carriers each
`in a correçonding subchannel of a single rnask-deñled-
`bandlimitedch¡nnel comprising the step of transmiüing said
`carriers frorn the same location with each carrier centrally
`located in said corresponding subchanuel whe¡ein the fre-
`quency diference between the center frequency of the outer
`most of said corresponding subchannels and the band edge
`of the m¡sk defining said channel is more than half the
`frequency difference befween the center frequencies of each
`adjacent carrier.
`4. The rnethod of claim 3 wherein adjacent subchannels
`overlap with each other.
`5. In a paging system having a plurality of tansmitters
`transmiüing a plurality of modulated ca¡riers over a single
`mask-deñned, bandlimited channel and a plurality of mobile
`receiving units independently receiving one of said plurality
`of carriers, a method ofoperating said plurality of ca¡riers in
`ru¡¿ çþ¡nnel to achieve higher transmission capacity com-
`prising the steps of:
`coJocating said plurality of tansmifiers such that said
`plurality of ca¡riers can be e¡nanated from the same
`transmission source: a¡d
`transmitting said plurality of ca¡riers over a plurality of
`subcha¡ûels spaced v¡ithin the rnask deñning said chan-
`nel wherei¡ the frequency difference betrveen the cen-
`ter frequency of tl¡e outer most carriers and the band
`edge of said mask is greater than half the frequency
`' difference between the center ùequencies of each adja-
`cent carri€r.
`
`+*t**
`
`MTel., Exhibit 2010, Aruba v. MTel., Page 15, IPR2016-00768