FILE HISTORY
`
`US 5,659,891
`
`PATENT:
`
`5,659,891
`
`INVENTORS: Hays, William D.
`
`Cameron, Dennis
`
`Roehr, Walter
`
`TITLE:
`
`Multicarrier techniques in bandlimited
`channels
`
`APPLICATION
`NO:
`
`US1995480718A
`
`FILED:
`
`07 JUN 1995
`
`ISSUED:
`
`19 AUG 1997
`
`COMPILED:
`
`13 JUN 2013
`
`1
`
`APPLE-1002
`
`

`
` ISSUE
`CLASSIFICATION
`
`'°AT"“'”’”.'
`
`i
`
`i
`
`PATENT
`
`5559391
`
`
`
`
`IIIIIIIIIIIIIIIIIIIIIIIII
`
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`
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`sEnIAI. NUITABER
`
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`GROUP AEITIT UNIT
`
`
`‘
`-5659 91
`
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`
`Foreign priority claimed
`5 USC 119 conditions met
`Verified and Aeknowledged
`A
`‘..i".
`
`Ii
`
`ADDRESS
`
`
`_ 3
`
`PARTS OF APPLICATION
`F"-ED SEPARATELY
`
`y
`
`LEE
`‘ Assistant Examiner
`
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`n Iations Examiner
`LAI S ALLOWED
`
`Total Claims
`t
`S
`DRAWING 9
`9
`Sheets Drwg. Figs. Drwg.
`
`Print Claim
`I
`
`'
`
`.. " .
`
`‘
`
`BATCH
`NUMBER \
`
`WARNING: The information disclosed herein may be restricted. Unauthorized disclosure may be prohibited
`by the United States Code Title 35, Sections 122, 181 and 368. Possession outside the US.
`Patent & Trademark Office is restricted to authorized employees and contractors only.
`
`Form PTO-436A
`(Rev. 8/92)
`
`(FACE)
`
`U,
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`3ILin.
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`1%;
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`
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`
`

`
`5,659,891
`
`MULTICARRIER TECHNIQUES IN BANDLIMITED CHANNELS
`
`Transaction History
`
`Date
`
`Transaction Description
`
`7/21/1995 Notice MailedͲͲApplication IncompleteͲͲFiling Date Assigned
`
`8/9/1995 Request for Foreign Priority (Priority Papers May Be Included)
`
`9/6/1995 Preliminary Amendment
`
`10/3/1995
`
`Information Disclosure Statement (IDS) Filed
`
`10/3/1995
`
`Information Disclosure Statement (IDS) Filed
`
`11/9/1995 Miscellaneous Incoming Letter
`
`11/13/1995 Application Is Now Complete
`
`12/5/1995 Application Captured on Microfilm
`
`12/18/1995 Case Docketed to Examiner in GAU
`
`1/17/1996 Mail Miscellaneous Communication to Applicant
`
`1/17/1996 Miscellaneous Communication to Applicant Ͳ No Action Count
`
`2/5/1996 NonͲFinal Rejection
`
`2/9/1996 Mail NonͲFinal Rejection
`
`8/9/1996 Response after NonͲFinal Action
`
`8/9/1996 Request for Extension of Time Ͳ Granted
`
`8/21/1996 Date Forwarded to Examiner
`
`10/28/1996 Final Rejection
`
`10/29/1996 Mail Final Rejection (PTOL Ͳ 326)
`
`1/21/1997 Amendment after Final Rejection
`
`1/28/1997 Date Forwarded to Examiner
`
`2/4/1997 Mail Notice of Allowance
`
`2/4/1997 Notice of Allowance Data Verification Completed
`
`2/4/1997 Mail Examiner's Amendment
`
`2/4/1997 Examiner's Amendment Communication
`
`3/3/1997 Mailroom Date of Drawing(s)
`
`3/7/1997 Drawing(s) Matched to Application
`
`3/7/1997 Drawing(s) Received at Publications
`
`3/25/1997 Drawing(s) Processing Completed
`
`4/3/1997 Mailroom Date of Drawing(s)
`
`4/10/1997 Drawing(s) Matched to Application
`
`4/10/1997 Drawing(s) Received at Publications
`
`4/30/1997 Drawing(s) Processing Completed
`
`5/1/1997
`
`Issue Fee Payment Verified
`
`7/14/1997
`
`Issue Notification Mailed
`
`8/19/1997 Recordation of Patent Grant Mailed
`
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`Staple Issue Slip Here
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`POSITION
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`8
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`8
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`*~k-k-A-~A-~k-k-k**-A-***-k*:\-**-k~k**-k-A-*'k**a\-**
`FILE 'USPAT‘ ENTERED AT 12:46:04 ON 15 OCT 96
`*
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`*
`P A T E N T
`T E X T
`-k~k~k*~k~k**~k*~k*~k~k~k~k
`*
`*
`*
`*
`=> s multicarrier or multi-carrier
`
`*
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`*
`
`*
`
`H F [11
`*
`*
`*
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`EF
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`*
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`»+**
`
`110 MUETICARRIER
`188216 MULTI
`254738 CARRIER
`118 MUETI-CARRIER
`(MULTI(W)CARRIER)
`198 MUETICARRIER OR MULTI—CARRIER
`L1
`=> d 11 1-10
`
`5,563,909, Oct. 8, 1996, Radio communication system;
`1.
`375/224; 342/196; 375/347 [IMAGE AVAILABLE]
`
`Isao Nakazawa,
`
`5,561,686, Oct. 1, 1996, Radio information communication system using
`2.
`**multi**—**carrier** spread spectrum transmission system; Hiroshi
`Kobayashi, et al., 375/200 [IMAGE AVAILABLE]
`
`5,559,830, Sep. 24, 1996, Equalization system for AM compatible
`3.
`digital receiver; Mark J. Dapper, et al., 375/230, 232 [IMAGE AVAILABLE]
`
`5,557,612, Sep. 17, 1996, Method and apparatus for establishing
`4.
`communication in a mu1ti—tone data transmission system; John A. C.
`Bingham, 370/71, 124 [IMAGE AVAILABLE]
`
`5,555,257, Sep. 10, 1996, Cellular/satellite communications system
`5.
`with improved frequency re—use; Paul W. Dent, 370/95.1; 342/352; 379/58;
`455/13.3, 54.1, 63
`[IMAGE AVAILABLE]
`
`5,551,070, Aug. 27, 1996, Cartesian **multicarrier** feedback; Ulf
`6.
`Skarby, et al., 455/126; 330/149; 375/261; 455/103, 119 [IMAGE AVAILABLE]
`
`5,550,812, Aug. 27, 1996, System for broadcasting and receiving
`7.
`digital data,
`receiver and transmitter for use in such system; Norbert J.
`L. Philips, 370/19, 69.1; 375/362; 455/182.2 [IMAGE AVAILABLE]
`
`5,548,813, Aug. 20, 1996, Phased array cellular base station and
`8.
`associated methods for enhanced power efficiency; Philippe M. Charas, et
`al., 455/33.2; 343/890; 455/53.1 [IMAGE AVAILABJE]
`
`5,548,671, Aug. 20, 1996, Programmable, differential wavelength
`9.
`discriminator; Chi Wu, et al., 385/37, 45 [IMAGE AVAILABLE]
`
`5,548,582, Aug. 20, 1996, **Multicarrier** frequency hopping
`10.
`communications system; Americo Brajal, et al., 370/18, 20, 23; 375/202
`[IMAGE AVAILABLE]
`=>
`
`9
`
`

`
`1
`4,858,225 [IMAGE AVAILABLE]
`
`L3: 16 of 21
`
`US PAT NO:
`SUMMARY:
`
`BSUM(8)
`
`bandwidth B.sub.T while the remaining bandwidth
`.
`.
`According .
`B.sub.T —B.sub.x may be channelized into a multiplicity of narrow VBVCF
`channels suitable for **multicarrier** traffic with a varying number of
`different carriers.
`In its operation, each channel is subsequently routed
`to a defined downlink.
`
`DETDESC:
`
`DETD(lO)
`
`carrier, variable bit rate traffic in uplink plan 20 occupies
`.
`.
`A .
`a useful bandwidth B.sub.x 22 from f.sub.Tl to f.sub.x1 while
`**multicarrier** traffic occupies a bandwidth B.sub.T —B.sub X from
`f.sub.x2 to f sub.T2.
`In this example, **mu1ticarrier** traffic is
`assigned to two connectivity paths 23 and 24 each containing traffic
`destined to the same downlink beam.
`
`DE”DESC:
`
`DE”D(ll)
`
`. with the M—th channelization level of passband 32. Under
`.
`The .
`these circumstances,
`the adjacent channel
`interference (ACI) between
`single carrier and **multicarrier** traffic is suppressed more than 39
`dB. The center frequency of passband 32 is f sub.RC =(f.sub.R3
`+f.sub.R4)/2. It is referred.
`
`DE"DESC:
`
`DE"D(4l)
`
`according to the relationship f.sub.Xl ~(f.sub.LO
`.
`.
`If .
`+B'.sub.X)=f.sub.R2.
`In this way, all single carrier traffic remains
`within passband 31 while all **multicarrier** traffic is within passband
`32. Traffic within the bandwidth 32 emerges from port 47 of the
`paralleling circuit 46. Output.
`CLAIMS:
`
`CLMS(7)
`
`. variable bandwidth variable center—frequency satellite
`.
`.
`7.
`communications system as recited in claim 6 wherein the filter banks of
`adjacent subchannels have **asymmetric** transmission amplitude
`characteristics at the edges thereof.
`
`10
`
`10
`
`

`
`US PAT NO:
`
`4,757,495 [IMAGE AVAILABLE]
`
`L3: 17 of 21
`
`ABSTRACT:
`. quality, a requested data rate, or a value indicating the
`The .
`.
`relative user weighting of speech quality and data rate. A
`**multi**—**carrier** multi—mode modulation scheme is employed for data
`transmission, with this scheme having the ability to fully utilize the
`remaining bandwidth,.
`
`SUMMARY:
`
`BsUM(26)
`
`The first component is a **multi**—**carrier**, mu1ti—mode, ensemble
`modem as disclosed in U.S. patent application Ser. No. O6—736,200 filed
`May 20, 1985 entitled "Ensemble Modem Structure.
`DETDESC:
`
`DETD(6l)
`
`. Duplex protocol approach is that the full transmission
`The ._ .
`capacity of the link is available at all times to respond to
`**asymmetric** data transmission requirements.
`
`CLAIMS:
`
`CLMs(33)
`
`33.
`for data transmission, said evaluating means being operatively
`associated with the selecting means for said selecting of the data
`sub~band, and
`**multicarrier** data transmitting means for transmitting data in the
`data sub-band on a plurality of carriers.
`
`11
`
`

`
`US PAT NO:
`
`4,328,902 [IMAGE AVAILABLE]
`
`L3: 20 of 21
`
`SUMMARY:
`
`BSUM(4)
`
`The Muller and Masser patents are examples of prior art interlocking
`carriers which have **asymmetrical** interlocking arrangements that are
`both difficult to fabricate and time consuming to assemble. The Cornelius
`patent requires that the carriers.
`
`SUMMARY:
`
`BsUM(5)
`
`desirable and it is an object of this invention to provide
`.
`.
`.
`It
`carrier units which may be readily interlocked into a
`**multi**—**carrier** assembly.
`
`L3: 21 of 2l
`3,898,566 [IMAGE AVAILABLE]
`Method and apparatus for reducing distortion in
`**multicarrier** communication systems
`
`US PAT NO:
`TITLE:
`
`SUMMARY:
`
`BsUM(2),
`
`patent application using harmonically related coherent
`.
`.
`The .
`carriers for transmitting a plurality of multiplexed signals such as
`television programs in a **multicarrier** communications system were
`deemed to be sufficiently great to outweigh the possible disadvantage of
`a theoretically predicted increase in crossmodulation..
`SUMMARY:
`
`BSUM(9)
`
`The present invention thus provides a method of reducing distortion such
`as crossmodulation between modulated carriers in a **multicarrier**
`communication system by establishing a coherent harmonic frequency
`relationship between the carriers, combining the carriers to transmit a
`signal which.
`DETDESC:
`
`DETD(l1)
`
`.pi.
`lb are symmetrical about
`la and FIG.
`forms of both FIG.
`.
`.
`In .
`radians, no consideration has yet been given to **asymmetry** as must be
`done in more complex cases. However, it will be noted that in FIG.
`lb the
`peak—to—peak excursion.
`
`DE_D;SC:
`
`D3"D(4l)
`and +9.73 for a peak—to—peak excursion of 21.63. The
`.
`.‘
`Again .
`reduction factor in this case is 21.63/50 = 0.432 and the **asymmetry**
`
`12
`
`12
`
`

`
`biasing is (11.9o—9.73)/2
`CLAIMS:
`
`II
`
`1.08.
`
`CLMS(l)
`
`What we claim is:
`
`1. The method of reducing distortion in a **multicarrier** CATV cable
`communication system comprising the steps of:
`a. establishing a harmonically related coherent frequency relationship
`between the carriers of.
`
`CoAIMS:
`
`C4MS(3)
`
`3. The method of reducing distortion in a **multi**—**carrier**
`communication system in which a plurality of said carriers is
`individually modulated and then combined to form a vector sum.
`
`CLAIMS:
`
`CLMs(4)
`
`4. The method of reducing distortion in a **multi**—**carrier**
`communication system in which a plurality of said carriers is
`individually modulated and then combined to form a vector sum.
`
`CLAIMS:
`
`CLMS(5)
`
`5. The method of reducing distortion in a **multi**—**carrier**
`communication system in which a plurality of said carriers is
`individually modulated and then combined to form a vector sum.
`
`CLAIMS:
`
`CLMS(6)
`
`In a **multi**—**carrier** communication system,
`6.
`comprising;
`a. means to estalish a harmonically related coherent frequency
`relationship between the carriers of said.
`
`the improvement
`
`CLAIMS:
`
`cLMs(7)
`
`In a **multi**-**carrier** CATV cable system,
`7.
`comprising:
`'
`a. means to establish a harmonically related coherent frequency
`relationship between the carriers of.
`
`the improvement
`
`CLAIMS:
`
`cLMs(8>
`
`13
`
`13
`
`

`
`In a **multi**—**carrier** CATV cable system,
`8.
`comprising:
`a. means to establish a harmonically related coherent frequency
`relationship between the carriers of.
`
`the improvement
`
`CLAIMS:
`
`CLMS(9)
`
`In a **mu1ti**—**carrier** CATV cable system,
`9.
`comprising:
`_
`a. means to establish a harmonically related coherent frequency
`relationship between the carriers of.
`
`the improvement
`
`CLAIMS:
`
`CLMS(28)
`
`the visual effect of triple beat and other second and third
`.
`.
`.
`28.
`order distortion in the transmitted multiplexed signal
`in a
`**multi**—**carrier** cable television system having the same channel
`frequency bandwidth for each channel, said method comprising the steps
`Of:
`'
`a. providing.
`=>
`
`14
`
`14
`
`

`
`=> d I3 1-21
`
`5,557,612, Sep. 17, 1996, Method and apparatus for establishing
`1.
`communication in a multi—tone data transmission system; John A. C.
`Bingham, 370/71, 124 [IMAGE AVAILABLE]
`
`5,550,812, Aug. 27, 1996, System for broadcasting and receiving
`2.
`digital data, receiver and transmitter for use in such system; Norbert J.
`L. Philips, 370/19, 69.1; 375/362; 455/182.2 [IMAGE AVAILABLE]
`
`5,519,731, May 21, 1996, ADSL compatible discrete multi—tone
`3.
`apparatus for mitigation of T1 noise; John M. Cioffi, 375/260; 348/388,
`436; 370/6, 70; 375/240, 285, 296, 340, 346; 379/93 [IMAGE AVAILABLE]
`
`5,506,141, Apr. 9, 1996, Apertured cell carrier; Arye Weinreb, et
`4.
`al., 435/309.1; 422/101; 435/288.4, 307.1, 308.1 [IMAGE AVAILABLE]
`
`5,479,447, Dec. 26, 1995, Method and apparatus for adaptive, variable
`5.
`bandwidth, high—speed data transmission of a **multicarrier** signal over
`digital subscriber lines; Peter S. Chow, et al., 375/260; 370/118;
`375/377 [IMAGE AVAILABLE]
`
`5,461,640, Oct. 24, 1995, Method and system for optimizing an
`6.
`I
`equalizer in a data transmission system; Alan Gatherer, 375/231;
`364/724.2 [IMAGE AVAILABLE]
`
`J
`5,408,260, Apr. 18, 1995, Customer premises ADSL signal distribution
`7.
`arrangement; Epiraim Arnon, 348/6, 12; 455/5.1 [IMAGE AVAILABLE]
`
`5,400,322, Mar. 21, 1995, Updating of bit allocations in a
`8.
`**multicarrier** modulation transmission system; Ronald R. Hunt, et al.,
`370/19, 76, 121 [IMAGE AVAILABLE]
`
`5,329,249, Jul. 12, 1994, High efficiency RF power amplifier; Stepien
`9.
`C. Cripps, 330/302, 306 [IMAGE AVAILABLE]
`
`I
`5,321,542, Jun. 14, 1994, Control method and apparatus for wireless
`10.
`data link; Richard F. Freitas, et al., 359/172, 113, 152; 370/84 [IMAG3
`AVAILABLE]
`
`5,317,596, May 31, 1994, Method and apparatus for echo cancellation
`11.
`with discrete multitone modulation; Minnie Ho, et al., 375/232; 370/32.1;
`379/410, 411 [IMAGE AVAILABLE]
`
`5,310,674, May 10, 1994, Apertured cell carrier; Arye Weinreb, et
`12.
`al., 435/286.1; 422/101; 435/308.1, 309.1 [IMAGE AVAILABLE]
`
`5,272,081, Dec. 21, 1993, System and methods for cell selection;
`13.
`,Arye Weinreb, et al., 435/240.1, 240.2, 240.21, 243, 261, 948 [IMAGE
`AVAILABLE]
`
`5,119,042, Jun. 2, 1992, Solid state power amplifier with
`14.
`dynamically adjusted operating point; David L. Crampton, et al., 330/295,
`136, 284, 285; 455/116, 126, 127, 129 [IMAGE AVAILABLE]
`
`5,017,885, May 21, 1991, Optical amplifier with reduced
`15.
`nonlinearity; Adel A. M. Saleh, 359/337, 124, 181 [IMAGE AVAILABLE]
`
`15
`
`15
`
`

`
`*
`4,858,225, Aug. 15, 1989, Variable bandwidth variable
`16.
`center-frequency multibeam satellite—switched router; Pietro desantis,
`370/95.3, 104.1 [IMAGE AVAILABLE]
`
`4,757,495, Jul. 12, 1988, Speech and data multiplexer optimized for
`17.
`use over impaired and bandwidth restricted analog channels; Dwight W.
`Decker, et al., 370/76, 69.1 [IMAGE AVAILABLE]
`
`4,742,576, May 3, 1988, Optical communication system employing
`18.
`coherent detection and method; Donald H. McMahon, 359/126, 168, 182, 183,
`184, 190, 191 [IMAGE AVAILABLE}
`
`4,729,949, Mar. 8, 1988, System and methods for cell selection; Arye
`19.
`Weinreb, et al., 435/30; 209/38, 397; 210/222, 695; 356/38, 244; 422/101;
`435/34, 173.9, 288.4, 288.7, 308.1; 436/63, 177 [IMAGE AVAILABLE]
`
`4,328,902, May 11, 1982, Beverage carrier; Thomas M. North,
`20.
`220/23.4, 516 [IMAGE AVAILABLE]
`
`3,898,566, Aug. 5, 1975, Method and apparatus for reducing
`21.
`distortion in **multicarrier** communication systems; Israel Switzer,‘et
`al., 455/4.1; 370/69.1; 455/67.3 [IMAGE AVAILABLE]
`=>
`
`16
`
`16
`
`

`
`United States Patent
`
`[191
`
`Hays et al.
`
`[11] Patent Number:
`
`5,659,891
`
`[45] Date of Patent:
`
`Aug. 19, 1997
`
`USO05659891A
`
`........ 370/69
`
`1/1981 Perkins ......
`11/1992 Koontz ......
`8/1994 Jasperet al.
`2/l995"Davis
`OTHER PUBLICATIONS
`
`
`
`4,244,047
`5,163,181
`5,343,499
`5,392,452
`
`47 C.F.R. § 22.106 (1994).
`
`Primary Examiner—Reinhard J. Eisenzopf
`Assistant Examiner—-Lee Nguyen
`Attomey, Agent, or Firm—Finnegan, Henderson, Farabow,
`Garrett and Dunner
`
`[57]
`
`ABSTRACT
`
`A method of multicairier modulation using co-located trans-
`mitters to achieve higher transmission capacity for mobile
`paging and two-way digital communication in a manner
`consistent with FCC emission mask
`Co-location of
`the transmitters obviates the need for stringent, symmetrical
`subchannel interference protection and provides for a wider
`range of operating parameters. including peak frequency
`deviation. bit rate, and carrier frequencies. to obtain optimal
`transmission performance.
`
`5 Claims, 11 Drawing Sheets
`
`[54] MULTICARRIER TECHNIQUES IN
`BANDLlMI'I‘ED CHANNELS
`
`[75]
`
`Inventors: William D. Hays; Dennis Cameron.
`both of Jackson. Miss.; Walter Roehr,
`Reston, Va.
`
`[73] Assignee: Mobile Telecommunication
`Technologies, Jackson. Miss.
`
`[21] Appl. No.: 480,718
`
`[22] Filed:
`
`Jun. 7, 1995
`
`Int. Cl.6 ............................................... H04B 1/02
`[51]
`[52] U.S. Cl.
`.............. 455/103; 455/45; 370/339;
`370/343
`[58] Field of Search ..................................... 455/103. 104,
`455/17. 46, 59, 60, 61. 62. 49.1, 45; 375/260;
`370/69.1, 70, 38, 40, 121; 340/825.44
`
`[56]
`
`References Cited
`U.S. PATENT DOCUM.ENTS
`
`1/1970 Chang
`3,488,445
`3,914,554 10/1975 Seide]
`
`............ 370/69.1
`...... 179/15.55 R
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`U.S. Patent
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`Aug. 19, 1997
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`U.S. Patent
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`Aug. 19, 1997
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`
`U.S. Patent
`
`Aug. 19, 1997
`
`Sheet 4 of 11
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`5,659,891
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`U.S. Patent
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`Aug. 19, 1997
`
`Sheet 5 of 11
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`Aug. 19, 1997
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`Aug. 19, 1997
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`
`5,659,891
`
`1
`MULTICARRIER TECHNIQUES IN
`BANDLIMITED CHANNELS
`
`FIELD OF THE INVENTION
`
`The present invention relates generally to multicarrier
`modulation techniques, and more particularly. to a method
`for operating more than one carrier in a single mask—defined.
`bandlimited channel assigned to mobile paging use.
`DISCUSSION OF RELATED ART
`
`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
`Communications Cormnission (FCC) for mobile paging use.
`As demand begins to approach and even exceed the capacity
`of assigned channels to handle transmission traffic, delays in
`service and deterioration of transmission quality are 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 limited by
`the finite range of air space dedicated to mobile paging use.
`Channels assigned by tl1e FCC to radio paging providers
`typically have narrow bandwidths (e.g. 25 kHz) and are
`subject to stringent emission mask limitations.
`One method that can be used to allow greater access to a
`particular channel is to increase flre number of messages
`transmitted over the channel in a given period. This can be
`achieved. for example. by increasing the data rate of the
`transmission or by reducing the length of transmitted mes-
`sages. U.S. Pat. No. 5392,452 issued to Davis, for example,
`describes a high data rate transmission scheme for handling
`lengthy messages in a paging system. Systems employing
`techniques to increase transmission rates. however, are
`prone to higher error rates. In addition. high data rates tend
`to generate greater transmission interference.
`Another approach to addressing the saturation problem is
`to increase the transmission capacity of the channel itself.
`Traditionally. mobile paging providers have operated only
`one transmission signal, or carrier, within an assigned chan-
`nel. While this mode ensures simplicity of operation and
`compliance with FCC mask requirements, it does not pro-
`vide the most efficient use of the limited frequency band-
`width available. Successful multicarrier modulation,
`however. is difficult to achieve without incurring unaccept-
`able levels of interference.
`
`The problem of interference is compounded when a
`receiver is attempting to acquire a signal from a distant
`transmitter while in close proximity to a transmitter oper-
`ating on an adjacent
`.channeL In this enviromnent.
`the
`receiver may experience difficulty in detecting the signal
`from the distant source due to interference from the signal
`transmitted on the adjacent channel from the closer source.
`This is known as the “near-far” problem. This problem can
`be avoided by co-locating the transmitters at essentially the
`same geographic location.
`The FCC requires signals to be confined within emission
`limit masks in order to prevent interference caused by
`signals straying or spilling into adjacent channels. FCC
`masks typically require the power spectral density of a
`signal to be attenuated at least 70 dB at the band edge.
`Despite these stringent constraints, some carrier overlap can
`be expected. even when the maximum carrier spacing con-
`sistent with the FCC mask requirements is utilized. Such
`overlap can result in unacceptable interference of the
`carriers. making it difficult for the receivers to acquire the
`proper carrier.
`
`2
`Thus. a traditional multicarrier design would commonly
`require the same stringent protection levels between sub-
`channels. Specifically. when more than one carrier is oper-
`ating within a single channel, each carrier is traditionally
`confined to a submask defining a subchannel internal to the
`channel. 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 defining the
`primary channel. Although such symmetry achieves maxi-
`mum inter-carrier spacing and reduces the opportunity for
`interference among adjacent carriers. it often necessitates
`the need for sophisticated receiver and transmitter schemes.
`SUMMARY OF THE INVENTION
`
`It is an object of this invention to achieve higher capacity
`over a bandlimited channel for paging without the need for
`stringent subchannel
`interference protection. Additional
`objects. advantages, and features of the invention will be set
`forth in part in the description that follows, and in part will
`be obvious from the description, or may be learned by
`practice of the invention. The advantages of the invention
`will be realized and attained by means of the instrumentali-
`ties and combinations particularly pointed out in the written
`description and claims herein, as well as the appended
`drawings.
`To achieve these and other objects, advantages, and
`features in accordance with the purpose of the invention, as
`embodied and broadly described herein, the invention pro-
`vides a method of operating a plurality of paging carriers in
`a single mask—defined, bandlimited channel comprising the
`step of transmitting the carriers from the same location at
`center frequencies within the channel such that the fre-
`quency ditference between the center frequency of the outer
`most carriers and the band edge of the mask defining said
`channel is more than half the frequency difference between
`the center frequencies of each adjacent carrier.
`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-defined. bandlimited chan-
`nel comprising the step of transmitting the carriers from the
`same location with each carrier centrally located in a cor-
`responding subchannel wherein the frequency difference
`between the center frequency of the outer most subchannels
`and the band edge ofthe mask defining said channel is more
`than half the frequency difference between the center fre-
`quencies of each adjacent carrier.
`in another aspect, the invention provides a method of
`operating a plurality of carriers in a single mask-defined.
`bandlimited channel to achieve higher transmission capacity
`over the channel
`in a mobile paging system having a
`plurality 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 carriers. The method comprises the
`steps of co-locating the plurality of transmitters such that the
`plurality of carriers can be emanated from the same trans-
`mission source. and transmitting the carriers over a plurality
`of subchannels spaced asymmetrically within the mask
`defining the channel.
`It is to be understood that both the foregoing general
`description and the following detailed description are exem-
`plary and explanatory only and are not restrictive of the
`invention. as claimed.
`BRIEF DESCRJPTION OF THE DRAWINGS
`
`The accompanying drawings. which are incorporated in
`and constitute a part of this specification, illustrate several
`
`5
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`

`
`5,659,891
`
`3
`embodiments of the invention and together with the
`description. serve to explain the principles of the invention.
`In the drawings.
`FIG. 1 is a block diagram of a co—located multicariier
`transmitter system in a linear amplifier configuration for
`using the present invention;
`FIG. 2 is a block diagram of a co-located multicarrier
`transmitter system in a composite transmitter configuration
`for using the present invention;
`FIG. 3A is a graph depicting two submasks defining two
`subchannels in a single. mask—defined bandlimited channel.
`FIG. 3B is a graph depicting the power spectra of two
`carriers asymmetrically located within a single mask-
`defined. bandlimited channel.
`
`FIG. 4 is a graph depicting an exemplary FCC emissions
`mask that requires the power spectral density to be attenu-
`ated at least 70 dB within 10 kHz from center frequency.
`FIG. SA is a graph depicting the power spectra of a system
`with peak deviation of 2400 Hz and data rate of 6000 hits per
`second (bps);
`FIG. 5B is a graph depicting the performance of the
`system of FIG. 5Ain terms of bit error rate versus the signal
`noise ratio (SNR);
`FIG. 6A is a graph depicting the power spectra of a system
`with peak deviation of 1800 Hz and a data rate of 6400 bps;
`FIG. 6B is a graph depicting the performance of the
`system of FIG. 6A in terms of bit error rate versus SNR;
`FIG. 7A is a graph depicting the power spectra of a system
`with peak deviation of 2100 Hz and a data rate of 6400 bps;
`and
`
`FIG. 7B is a graph depicting the performance of the
`system of FIG. 7A in terms of bit error rate versus SNR.
`
`DETAILED DF£CRIF'I'ION OF THE
`PREFERRED EIVIBODIJVIWTS
`
`Reference will now be made in detail to the presently
`preferred embodiments of the invention. examples of which
`are illustrated in the accompanying drawings. Wherever
`possible. the same reference numbers will be used through-
`out the drawings to refer to the same or like parts.
`Referring to FIG. 1. a co-located multicarrier transmitter
`system in a linear amplifier configuration 10 comprises a
`first and second data source. 11a and 11b, a first and second
`modulator. 12a and 12b, a summation circuit 13. a linear RF
`amplifier 14. and an antenna 15. The first and second data
`sources. 11a and 11b, generate a respective first and second
`digital bit stream which are provided to respective first and
`second modulators. 12a and 121:. Each modulator converts
`the incoming digital information into a representative modu-
`lated signal or carrier. The outputs of each modulator are
`then combined into a single output signal by summation
`circuit 13. the output of which is fed into linear RF amplifier
`14. The combined output signal is then applied to antenna 15
`for transmission in a bandlimited channel.
`Alternatively. referring to FIG. 2. a co—l0cated multicar-
`rier transmitter in a composite amplifier configuration 20
`comprises a first and second data source. 21a and 21b, a first
`and second modulator. 22a and 22b, a first and second RF
`amplifier. 23a and 2312, a summation circuit 24, and an
`antenna 25. The first and second digital bit streams gener-
`ated respectively by the first and second data sources. 21a
`and 21b, are provided to first and second modulators. 22a
`and 22b, respectively. Each modulator converts the incom-
`ing digital information into a representative modulated sig-
`
`4
`nal or carrier. The outputs of the first and second modulators
`are fed into first and second RF amplifiers. 23a and 23b,
`respectively. The outputs of the RF amplifiers are combined
`into a single output signal by summation circuit 24. the
`output of which is applied to antenna 25 for transmission in
`a bandlimited channel.
`
`Alternative embodiments of co-located transmitter sys-
`tems are also possible. For example. the co-located trans-
`mitter configurations discussed above can be expanded to
`support more than two data sources and transmit more than
`two carriers in the bandlimited channel.
`
`Because transmitter eo—location does not give rise to the
`near-far problem to which the FCC mask requirements are
`directed. carrier spacings far closer than would ordinarily be
`allowed (e.g.. 5 to 10 kHz) are achievable. Moreover. the
`carriers need not be symmetrically or evenly spaced within
`the mask defining the channel. That is. the frequency spac-
`ings between adjacent carriers. whfle symmetric to each
`other. can be smaller than the frequency spacings between
`the band edges of the mask and the nearest respective carrier.
`Indeed, carrier spacings may be irregular such that
`the
`carriers are asymmetrically located within the mask without
`incurring undue interference.
`Referring to FIG. 3A.
`two submasks defining two
`subchannels. 30a and 30b, are asymmetrically located
`within a single mask—defined. bandlimited channel 31.
`resulting in some subchannel overlap. FIG. 3B depicts two
`carriers. 32a and 32b, operating respectively over two
`asymmetrically-located subchannels, resulting in some car-
`rier overlap. In accordance with this asymmetry, the fre-
`quency ditference between the center frequency of each
`carrier and the nearest band edge of the mask is greater than
`half the frequency difference between the center frequencies
`of the two carriers.
`The p