USOO8265096B2
`
`(12) United States Patent
`Zheng et al.
`
`(10) Patent No.:
`(45) Date of Patent:
`
`US 8,265,096 B2
`Sep. 11, 2012
`
`(54) METHOD FOR CONSTRUCTING FRAME
`STRUCTURES
`
`(75) Inventors: Yan-Xiu Zheng, Shulin (TW); Ren-Jr
`Chen, Hsinchu (TW); Chang-Lung
`Hsiao, Hsinchu (TW); Pang-An Ting,
`Fongyuan (TW)
`
`(73) Assignee: Industrial Technology Research
`Institute, Hsinchu (TW)
`Subject to any disclaimer, the term of this
`patent is extended or adjusted under 35
`U.S.C. 154(b) by 385 days.
`
`(*) Notice:
`
`(21) Appl. No.: 12/168,855
`
`22) Filed:
`(22) File
`(65)
`
`L. 7, 2008
`l. f.
`Prior Publication Data
`US 2009/0016371 A1
`Jan. 15, 2009
`Related U.S. Application Data
`(60) Provisional application No. 60/929,798, filed on Jul.
`12, 2007, provisional application No. 60/973,157,
`filed on Sep. 17, 2007.
`(51) Int. Cl.
`(2006.01)
`H043/24
`(52) U.S. Cl. ......... 370/473; 370/474; 370/476; 455/448
`(58) Field of Classification Search .................. 370/329,
`370/478, 491, 349,469, 473, 474, 476, 338;
`375/148, 354
`See application file for complete search history.
`
`(56)
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`5,491,531 A * 2/1996 Adams et al. ................. 375,354
`6,904,550 B2
`6, 2005 Sibecas et al.
`
`9/2006 Lietal.
`7,110,350 B2
`7,586,887 B2 * 9/2009 Trachewsky .................. 370,338
`7,809,020 B2 * 10/2010 Douglas et al. ............... 370/474
`8,077,592 B2 12/2011 Webster et al.
`2002/0034172 A1
`3/2002 Ho ................................ 370,338
`2004/0223478 A1* 11/2004 Fischer et al. ................ 370,338
`2005, OO63345 A1
`3, 2005 Wu et al.
`2005/01 11529 A1* 5/2005 Bradley ........................ 375,148
`2005, 0180461 A1
`8, 2005 Kao et al.
`2006, OO18279 A1
`1, 2006 A al et al.
`2006/022.7778 A1 10, 2006 ity a
`2007/0097.946 A1* 5/2007 Mujtaba ................... 370,349
`2007/O155315 A1
`7/2007 Lee et al.
`2007/0189149 A1
`8/2007 Terabe .......................... 370,491
`2008/0095.195 A1 *
`4, 2008 Ahmadi et al.
`370/478
`2008/0285513 A1* 1 1/2008 Jung et al. ..................... 370,329
`2009/00 16371 A1
`1/2009 Zheng et al.
`2009/01 16435 A1* 5/2009 Koorapaty et al. ........... 370,329
`2011/02225.04 A1
`9, 2011 Ma et al.
`2012fO140730 A1* 6, 2012 Marks et al. .................. 370,330
`FOREIGN PATENT DOCUMENTS
`WO WO 2006/092852
`* 8, 2006
`* cited by examiner
`Primary Examiner — Jeffrey M. Rutkowski
`74). Att
`, Agent, or Firm — Alston & Bird LLP
`(74) Attorney, Agent, or Firm
`SO
`1.
`(57)
`ABSTRACT
`A method of constructing a frame structure for data transmis
`Sion, the method comprising generating a first Section com
`prising data configured in a first format compatible with a first
`communication system, generating a second section follow
`ing the first section, the second section comprising data con
`figured in a second format compatible with a second commu
`nication system, wherein the second format is different from
`the first format, generating at least one non-data section con
`taining information describing an aspect of data in at least one
`of the first section and the second section, and combining the
`first section, the second section and the at least one non-data
`section to form the frame structure.
`
`43 Claims, 6 Drawing Sheets
`
`
`
`70-1-N
`
`71-n D sligatoility are
`(Extended System)
`
`
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`U.S. Patent
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`Sep. 11, 2012
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`Sheet 1 of 6
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`US 8,265,096 B2
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`
`
`16-1
`17
`FIG 2 (Prior Art)
`
`18-1
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`19
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`U.S. Patent
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`Sep. 11, 2012
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`Sheet 2 of 6
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`US 8,265,096 B2
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`U.S. Patent
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`Sep. 11, 2012
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`Sheet 3 of 6
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`US 8,265,096 B2
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`U.S. Patent
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`Sep. 11, 2012
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`Sheet 4 of 6
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`US 8,265,096 B2
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`U.S. Patent
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`Sep. 11, 2012
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`Sheet 5 of 6
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`US 8,265,096 B2
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`5-166-1966-3 97.2
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`U.S. Patent
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`Sep. 11, 2012
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`Sheet 6 of 6
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`US 8,265,096 B2
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`
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`
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`70-1
`
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`(Extended System)
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`

`1.
`METHOD FOR CONSTRUCTING FRAME
`STRUCTURES
`
`US 8,265,096 B2
`
`CROSS-REFERENCE TO RELATED
`APPLICATION
`
`This application claims the benefit of U.S. Provisional
`Application No. 60/929,798, entitled “Frame Structure in
`Wireless Communication Systems.” filed Jul. 12, 2007, and
`60/973,157, entitled “Bandwidth Scalable OFDMA Frame
`Structure.” filed Sep. 17, 2007. These applications are hereby
`incorporated by reference in their entirety.
`
`10
`
`BACKGROUND
`
`15
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`25
`
`30
`
`35
`
`The present invention generally relates to orthogonal fre
`quency-division multiple access (OFDMA) systems, and
`more particularly, the present invention relates to methods for
`constructing frame structures in OFDMA systems.
`Orthogonal Frequency Division Multiple Access
`(OFDMA) is a multiple access scheme for transmitting data
`in different subcarriers in a channel, wherein the data may
`come from different users and may be transmitted in disjoint
`subsets of sub-channels in a transmission bandwidth. The
`orthogonality property among the Subcarriers may allow
`simultaneous transmission of data from different users with
`out interference from one other. The multiple access scheme
`of the OFDMA may generally be applied in various commu
`nication systems, such as those defined in IEEE standard
`802.16e (“legacy system' hereafter) and IEEE standard
`802.16m (“new system' hereafter). The new system defined
`in the IEEE standard 802.16m may be required to provide
`enhanced spectrum efficiency, higher speed tolerance and full
`backward compatibility with the legacy system defined in the
`IEEE Standard 802.16e.
`FIG. 1 is a diagram illustrating an OFDMA frame structure
`under the IEEE 802.16 standard. Referring to FIG. 1, the
`frame structure may include a downlink sub-frame (DL sub
`frame) 16 and an uplink sub-frame (UL sub-frame) 18. The
`UL sub-frame 18 may follow the DL sub-frame 16 in time
`domain with a transmit/receive transmission gap (TTG) 17
`from the DL sub-frame 16. Moreover, the frame structure
`may be separated from the next frame structure, led by a
`preamble 10-2, by a receive/transmit transmission gap (RTG)
`19.
`The DL sub-frame 16 may include a preamble 10-1, a
`frame control header (FCH) 11, a downlink map (DL-MAP)
`12, a downlink burst (DL burstii.1) 13 and a data region
`(DATA) 14-1. The UL sub-frame 18 may include a ranging
`sub-channel 15 and a data region (DATA) 14-2. Since the
`DL-MAP 12 may be used to identify the division or structure
`of the DATA 14-1 in the DL sub-frame 16, it may be desirable
`to integrate the OFDMA frame structure of an old OFDMA
`system with that of a new OFDMA system by using the
`DL-MAP 12 to define different Zones in the DATA 14-1 and
`55
`DATA 14-2 of the frame structure for data of the old OFDMA
`system and data of the new OFDMA system.
`FIG. 2 is a diagram illustrating a placement of guiding
`signals (or pilot symbols) 24-1 for time-domain and fre
`quency-domain OFDMA signals under the IEEE 802.16 stan
`dard. Referring to FIG. 2, upper and lower frequency bands
`may serve as guard bands 22-1 and 22-2, respectively, which
`may not be used to carry information. The placement of
`information may include a first part and a second part. For
`example, the first part of the placement includes a preamble
`10'-1 having a fixed length, and the second part of the place
`ment includes data and guard intervals between an upper row
`
`40
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`45
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`50
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`60
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`65
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`2
`and a lower row of the data interlaced with the pilot symbols
`24-1, represented by blocks marked with “X”. In some appli
`cations such placement of information may be inflexible to
`bandwidth scaling due to the fixed-length preambles 10'-1
`and/or 10'-2 and the often unusable guard bands 22-1 and
`22-2. Moreover, the placement may be susceptible to a Dop
`pler effect in a high mobility scenario because the placement
`may be usually designed with a relatively large symbol
`period, which in turn may induce relatively short carrier spac
`ing and less dense pilot symbol placement. Moreover, the
`limitation on pilot symbol placement may cause channel esti
`mation error at a receiving end because of insufficient infor
`mation provided for channel estimation.
`
`SUMMARY
`
`Examples of the present invention may provide a method
`for constructing a frame structure for data transmission, the
`method comprising generating a first section comprising data
`configured in a first format compatible with a first communi
`cation system, generating a second section following the first
`section comprising data configured in a second format com
`patible with a second communication system, wherein the
`second format is different from the first format, generating at
`least one non-data section containing information describing
`an aspect of data in at least one of the first section and the
`second section, and combining the first section, the second
`section and the at least one non-data section to form the frame
`Structure.
`Examples of the present invention may provide a method of
`generating a frame for transferring data in a communication
`system. The communication system may include a first sys
`temand a second system. The method may include generating
`a first sub-frame for downlink transmission, wherein the first
`Sub-frame comprises a first region comprising first mapping
`information, a second region comprising second mapping
`information, and a third region carrying data to be transferred
`in the downlink transmission, the third region comprising a
`first Sub-region and a second Sub-region, wherein the first
`Sub-region and second Sub-region are defined by the first
`mapping information, the first Sub-region being capable of
`carrying first data of the first system and the second Sub
`region being capable of carrying second data of the second
`system in the downlink transmission, and generating a second
`Sub-frame for uplink transmission, wherein the second Sub
`frame comprises a fourth region carrying data to be trans
`ferred in the uplink transmission, the fourth region compris
`ing a third Sub-region and a fourth Sub-region, wherein the
`third sub-region and the fourth sub-region are defined by the
`second mapping information, the third Sub-region being
`capable of carrying third data of the first system and the fourth
`Sub-region being capable of carrying fourth data of the second
`system in the uplink transmission.
`Examples of the present invention may also provide a
`method of generating a frame for transferring data in a com
`munication system. The communication system may include
`a first system and a second system. The method may include
`generating a first frame comprising a first Sub-frame for
`downlink transmission and a second Sub-frame for uplink
`transmission in a first band, generating a second frame com
`prising a third Sub-frame for downlink transmission and a
`fourth Sub-frame for uplink transmission in a second band,
`identifying a guard band between the first band and the sec
`ond band, and generating a third frame comprising a fifth
`Sub-frame for downlink transmission and a sixth Sub-frame
`for uplink transmission in the guard band.
`
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`3
`Examples of the present invention may provide a method
`for allocating information in a frame of a communication
`system. The communication system may include a first sys
`tem and a second system. The frame may be used for first data
`transmission of the first system and second data transmission
`of the second system. The method may include allocating
`data of the first system and the second system in first mapping
`information, dividing a data region of the frame to form a first
`Sub-region and a second Sub-region according to the first
`mapping information, performing the first data transmission
`of the first system by using the first Sub-region and perform
`ing the second data transmission of the second system by
`using the second Sub-region.
`Examples of the present invention may provide another
`method for allocating information in a frame of a communi
`cation system. The frame may include a first frame, a second
`frame and a band between the first frame and the second
`frame. The communication system may include a first system
`and a second system. The frame may be used for first data
`transmission of the first system and second data transmission
`of the second system. The method may include allocating
`data of the first system and the second system in first mapping
`information or second mapping information, dividing a data
`region of the first frame or the second frame to form a first
`Sub-region, a second Sub-region, a third Sub-region or a sec
`ond Sub-region in the data region of the first frame or the
`second frame according to the first mapping information or
`the second mapping information, performing the first data
`transmission of the first system by using the first Sub-region or
`the third Sub-region and performing the second data transmis
`sion of the second system by using the second Sub-region or
`the fourth sub-region.
`Additional features and advantages of the present inven
`tion will be set forth in part in the description which follows,
`and in part will be obvious from the description, or may be
`learned by practice of the invention. The features and advan
`tages of the invention will be realized and attained by means
`of the elements and combinations particularly pointed out in
`the appended claims.
`It is to be understood that both the foregoing general
`40
`description and the following detailed description are exem
`plary and explanatory only and are not restrictive of the inven
`tion, as claimed.
`
`5
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`US 8,265,096 B2
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`4
`FIG. 6A is a diagram illustrating an OFDMA frame struc
`ture Supporting high mobility and having a scalable band
`width according to an example of the present invention;
`FIG. 6B is a diagram illustrating an OFDMA frame struc
`ture Supporting high mobility and having a scalable band
`width according to another example of the present invention;
`and
`FIG. 7 is a diagram illustrating an exemplary placement of
`signals and pilots in time-domain and frequency-domain of
`an OFDMA system supporting high mobility and having a
`scalable bandwidth.
`
`DETAILED DESCRIPTION
`
`Reference will now be made in detail to various embodi
`ments of the invention, examples of which are illustrated in
`the accompanying drawings. Wherever possible, the same
`reference numbers will be used throughout the drawings to
`refer to the same or like parts.
`Examples of the present invention may allow data of an old
`orthogonal frequency-division multiple access (OFDMA)
`system (hereinafter a legacy system) and data of a new
`OFDMA system to co-existinian OFDMA frame by changing
`a frame structure of the OFDMA frame. The new OFDMA
`system may have a larger bandwidth and Support higher
`mobility, and may use an updated transmission technology. In
`order to be backward compatible with the old OFDMA sys
`tem, the new OFDMA system may be developed based on the
`old OFDMA system. Throughout the specification, a “new”
`or “extended system or standard may refer to an “updated.”
`"evolved” or “next-generation” system or standard, while a
`“legacy” system or standard may refer to an “old” or “cur
`rent system or standard. For example, a “new” standard may
`be a standard that is in use as of the date of the filing of this
`application, and a "legacy standard may be a standard that is
`in use prior to the date of the filing of this application and may
`be still in use for sometime after the filing of this application.
`FIG.3 is a diagram illustrating an OFDMA frame structure
`according to an example of the present invention. Referring to
`FIG. 3, the OFDMA frame structure may include a downlink
`sub-frame (DL sub-frame) 16 and an uplink sub-frame (UL
`sub-frame) 18. The DL sub-frame 16 may include a preamble
`10-1, an FCH 11, a DL-MAP 12, a DL burst #113 with an
`UP-MAP (not shown), and a data region including DATA
`30-1 (Zone 1) and DATA30-2 (zone 2). The UL sub-frame 18
`may include a ranging Sub-channel 15 and a data region
`including DATA 34-1 (Zone 1) and DATA 34-2 (Zone 2).
`Data of the new OFDMA system (the extended system)
`may be carried in extended Zones, that is, the DATA 30-2
`and/or the DATA 34-2, allocated to the DL sub-frame 16
`and/or the UL sub-frame 18, respectively. Furthermore, the
`extended system in the data region DATA 30-2 and/or the
`DATA 34-2 may have the same symbol period or the same
`placement of pilot symbols as the old system (the legacy
`system) in the data region DATA 30-1 and the DATA 34-1,
`respectively, in the OFDMA frame structure. In one example,
`the data region including the two Zones DATA 30-1 (Zone1)
`and DATA 30-2 (Zone 2), for the old system and the new
`system, respectively, may be placed according to the mapping
`information of the two Zones defined in the DL-MAP 11.
`Similarly, the data region of the UL sub-frame 18 including
`the two Zones DATA34-1 (Zone 1) and DATA34-2 (Zone 2),
`for the old OFDMA system and the new OFDMA system,
`respectively, may be placed according to the mapping infor
`mation of the two Zones defined in the UL-MAP in the DL
`burst #113.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`45
`
`The foregoing Summary, as well as the following detailed
`description of the invention, will be better understood when
`read in conjunction with the appended drawings. For the
`purpose of illustrating the invention, there are shown in the
`drawings examples which are presently preferred. It should
`be understood, however, that the invention is not limited to the
`precise arrangements and instrumentalities shown.
`In the drawings:
`FIG. 1 is a diagram illustrating an orthogonal frequency
`division multiple access (OFDMA) frame structure under the
`IEEE 802.16 standard;
`FIG. 2 is a diagram illustrating a placement of guiding
`signals for OFDMA signals under the IEEE 802.16 standard;
`FIG.3 is a diagram illustrating an OFDMA frame structure
`according to an example of the present invention;
`FIG. 4 is a diagram illustrating an OFDMA frame structure
`Supporting high mobility according to an example of the
`present invention;
`FIG. 5 is a diagram illustrating an OFDMA frame structure
`with a scalable bandwidth according to an example of the
`present invention;
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`5
`FIG. 4 is a diagram illustrating an OFDMA frame structure
`Supporting high mobility according to an example of the
`present invention. Referring to FIG. 4, the OFDMA frame
`structure may be similar to that described and illustrated with
`reference to FIG. 3 except that, for example, a DL sub-frame
`16-2 may further include a preamble 43, a sub-MAP 42-2 and
`a data region DATA 40-3 (Zone 3), and a UL sub-frame 18-2
`may further include a data region DATA 44-3 (Zone 3). To
`Support communication in a high-mobility environment, the
`Zones 3 for the new system (the extended system) under high
`mobility may be allocated to the data region of both the DL
`Sub-frame 16-2 and the UL Sub-frame 18-2. The DATA 40-3
`and/or 44-3 (Zones 3) may have a shorter symbol period or
`more pilot symbols placed therein than the DATA 40-1, 40-2,
`44-1 and 44-2 in order to enhance the performance of channel
`estimation. Generally, a shorter symbol period may be more
`robust to inter-symbol interference, while denser pilot sym
`bols may achieve better channel estimation accuracy. More
`over, the DATA 40-3 of the DL sub-frame 16-2 for the new
`system (extended system) under high mobility may be
`divided based on the mapping information defined in at least
`one of the DL-MAP11 and the Sub-MAP 42-2 of DATA 40-3,
`and the DATA 44-3 of the UL sub-frame 18-2 for the new
`system (extended system) under high mobility may be
`divided based on the mapping information defined in the
`UL-MAP (not shown) in the DL burstii1 13. Placements of
`pilot symbols, symbol periods of OFDM symbols and FFT
`sizes in the Zones 1 for the old (legacy) system and the Zones
`2 for the new (extended) system may be the same in the DL
`sub-frame 16-2 and the UL sub-frame 18-2. The preamble 43
`30
`placed in front of the Zone 3 of the DL sub-frame 16-2 for the
`new system (extended system) may be used to support high
`mobility. As compared to the Zones in the data region of the
`UL sub-frame 18-2 or the DL sub-frame 16-2 of the old/
`legacy system or the new/extended system, the placements of
`35
`the pilot symbols may be denser, the symbol periods of
`OFDM symbols may be shorter and the FFT sizes may be
`Smaller in the DATA 40-3 and/or DATA 44-3 of the DL
`sub-frame 16-2 or the UL sub-frame 18-2, respectively, for
`the extended system under high mobility.
`FIG. 5 is a diagram illustrating an OFDMA frame structure
`with a scalable bandwidth according to an example of the
`present invention. Referring to FIG. 5, the OFDMA frame
`structure may include a first frame structure 500, a second
`frame structure 502 and a third frame structure 504. The first
`frame structure 500 may include a first DL sub-frame 16-3a
`and a first UL sub-frame 18-3a, the second frame structure
`502 may include a second DL sub-frame 16-3b and a second
`UL sub-frame 18-3b, and the third frame structure 504 may
`includea third DL sub-frame 16-3c and a third UL sub-frame
`18-3c. The first frame structure 500, which may be allocated
`to a first band, may be similar to the frame structure described
`and illustrated with reference to FIG. 3. Specifically, the first
`DL sub-frame 16-3a of the first frame structure 500 may
`include a preamble 50-1, an FCH, a DL-MAP 54-1, a DL
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`burst #155-1 with an UL MAP (not shown), DATA 56-1
`(Zone 1) for the old OFDMA system (legacy system) and
`DATA 56-3a (Zone 2) for the new OFDMA system (extended
`system). The first UL sub-frame 18-3a of the first frame
`structure 500 may include a ranging sub-channel 58-1, DATA
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`59-2 (Zone 1) in the data region for the old OFDMA system
`(legacy system) and DATA 59-1a (Zone 2) in the data region
`for the new OFDMA system (extended system).
`The second frame structure 502, which may be allocated to
`a second band, may be similar to the frame structure
`described and illustrated with reference to FIG. 3. Similarly,
`the second DL sub-frame 16-3b of the second frame structure
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`502 may include a preamble 52-1, an FCH, a DL-MAP54-2,
`a DL burst #155-2 with an ULMAP (not shown), DATA 56-2
`(Zone 1) in a data region for the old OFDMA system (legacy
`system) and DATA 56-3b (Zone 2) in the data region for the
`new OFDMA system (extended system), and the second UL
`sub-frame 18-3b of the second frame structure 502 may
`include a ranging sub-channel 58-2, DATA 59-3 (Zone 1) in a
`data region for the old OFDMA system (legacy system) and
`DATA 59-4 (Zone 2) in the data region for the new OFDMA
`system (extended system).
`The third frame structure 504, which may be allocated to a
`third band, may be arranged between the first frame structure
`500 and the second frame structure 502. Specifically, a guard
`band between the first frame structure 500 and the second
`frame structure 502 may serve as the third frame structure 504
`to facilitate data transmission. Unlike the guard band 22-1 or
`22-2 in FIG. 2, data to be transmitted in the new (extended)
`system or a high-mobility system may be allocated to a guard
`band between the first frame structure 500 and the second
`frame structure 502. The third frame structure 504 may
`include a third DL sub-frame 16-3c and a third UL sub-frame
`18-3c. The DL sub-frame 16-3c may include a preamble 51-1,
`an FCH, a DL-MAP and a data region DATA 56-3c (Zone 3)
`for the new (extended) system. Furthermore, the UL sub
`frame 18-3c may include a data region DATA 59-1b for the
`new (extended) system.
`An OFDMA frame structure thus constructed may have a
`scalable bandwidth. For example, data of the old (legacy)
`OFDMA system in the Zones 1 of the first frame structure500
`and the second frame structure 502 may be transmitted in
`parallel using the first band and second band, respectively,
`and data of the new (extended) OFDMA system in the third
`frame structure504 and the Zones 2 of the first frame structure
`500 and the second frame structure 502 may be together
`transmitted using the first, second and third bands. In one
`example, the first, second and third bands may be contiguous
`with one another. Furthermore, upper and a lower guard
`bands (not shown) may be required to transmit the OFDMA
`frame structure via the first, second and third bands.
`The 'Zone 156-1 of the first frame structure 500 and the
`“Zone 1° 56-2 of the second frame structure 502 may be
`divided from the data region in the DL sub-frame 16-3a of the
`first frame structure 500 and the data region in the DL sub
`frame 16-3b of the second frame structure 502, respectively,
`according to the mapping information in the DL-MAP54-1
`and the DL-MAP 54-2, respectively. Similarly, the UL sub
`frame 18-3a of the first frame structure 500 and the UL
`sub-frame 18-3b of the second frame structure 502 may be
`divided based on the mapping information in the UL-MAP in
`the DL burst #155-1 of the first frame structure 500 and the
`UL-MAP in the DL burstii.155-2 of the second frame struc
`ture 502, respectively.
`The guard band 504, which is in a frequency spectrum not
`used in the old or legacy system, may be used to transfer data
`in the present example, and the data region of the guard band
`may be divided based on the mapping information in at least
`one of the DL-MAP54-1 or the DL-MAP54-2. The preamble
`part of the extended frame structure described and illustrated
`with reference to FIG. 5 may include the preamble 50-1 and
`the preamble 52-1. The preamble 51-1 may carry data, or may
`carry no information. Moreover, the DL-MAP and the FCH in
`the guard band 504 may be used to divide the data regions
`56-3c and 59-1b. In one example, a Sub-MAP (not shown)
`may be placed in the DATA 56-3c for further description of
`the extended system.
`FIG. 6A is a diagram illustrating an example of an
`OFDMA frame structure supporting high mobility and hav
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`ing a scalable bandwidth according to an example of the
`present invention. Referring to FIG. 6A, the frame structure
`may be similar to the frame structure in FIG.5 except that, for
`example, regions related to Zones 3 for a high-mobility envi
`ronment may be added. Specifically, in a DL sub-frame 16-4,
`a first region may include a preamble 68, a sub-MAP 67-2 and
`DATA 66-4, and in a UL sub-frame 18-4, a second region may
`include DATA 69-3 and 69-6 (Zones 3). DATA 66-4, 69-3 and
`69-6 may be allocated for the new OFDMA system (extended
`system) under high mobility. The DL sub-frame 16-4 may be
`divided according to the mapping information in DL-MAP1,
`DL-MAP 2 and DL-MAP 3, while the UL Sub-frame 18-4
`may be divided according to the map information in UL
`MAPs in DL burstii.165-1 and/or 65-2. A portion of the guard
`band that overlaps data Zones 69-1 and 69-2 in the UL sub
`frame 18-4 may be used to transmit data in the extended
`system. In one example, placements of pilot symbols, symbol
`periods of OFDM symbols and FFT sizes in the Zones 1 for
`the old (legacy) system and the Zones 2 for the new (extended)
`system may be the same in the DL sub-frame 16-4 and the UL
`Sub-frame 18-4. As compared to the Zones in the data region
`of the DL sub-frame 16-4 or the UL sub-frame 18-4 of the
`old/legacy system or the new/extended system, the place
`ments of the pilot symbols may be denser, the symbol periods
`of OFDM symbols may be shorter and the FFT sizes may be
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`smaller in the Zones 3 of the UL sub-frame 18-4 or the DL
`sub-frame 16-4 for the extended system under high mobility.
`FIG. 6B is a diagram illustrating an OFDMA frame struc
`ture Supporting high mobility and having a scalable band
`width according to another example of the present invention.
`Referring to FIG. 6B, the OFDMA frame structure may be
`similar to the OFDMA frame structure described or illus
`trated with reference to FIG. 6A except that, for example, the
`Zone 2 in a UL sub-frame 18-4" using the guard band may be
`transmitted after the Zone3 in the UL sub-frame 18-4', and the
`locations of Zones 1 for the legacy system and Zones 3 for the
`new (extended) system for high mobility are swapped.
`FIG. 7 is a diagram illustrating an exemplary placement of
`signals and pilots in time-domain and frequency-domain of
`an OFDMA system supporting high mobility and having a
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`scalable bandwidth. Referring to FIG. 7, an upper band and a
`lower band may be guard bands 73-1 and 73-3, respectively.
`In the prior art, guard bands do not carry any data or signals in
`a conventional OFDMA system. Consistent with some
`examples of the present invention, the guard bands 73-1 and
`73-3 may be used to carry data or signals. Moreover, to satisfy
`backward compatibility, preambles 70-1 and 72-1 may be
`similar to those in the conventional OFDMA system. Similar
`to those described and illustrated with reference to FIGS. 6A
`and 6B, signals, pilot symbols, both, or neither may be placed
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`in a preamble 71-1. The placement may define one or more
`regions, which may include, for example, regions 74-1, 74-2,
`76-1 and 76-2 for the old (legacy) OFDMA system, regions
`74-3 and 76-3 for the new (extended) OFDMA system sup
`porting lower mobility, and regions 74–4 and 76-4 for the new
`system supporting high mobility. The old OFDMA system
`and the new OFDMA system supporting lower mobility may
`use the same frequency intervals or the placement of pilot
`symbols. The new OFDMA system supporting high mobility
`may use larger frequency intervals or shorter OFDM symbol
`period to avoid frequency jitter. Therefore, the placement of
`the pilot symbols in a first region such as one of the regions
`74-1, 74-2, 76-1 and 76-2 of a frame structure divided for the
`old OFDMA system may be the same as that in the prior art,
`the placement of the pilot symbols in a second region Such as
`one of the regions 74-3 and 76-3 of the frame structure
`divided for the new OFDMA system supporting lower mobil
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`ity may be the same or denser than the that in the prior art, and
`the placement of the pilot symbols in a third region Such as
`one of the regions 74-4 and 76-4 of the frame structure
`divided for the new OFDMA system supporting high mobil
`ity may use more denser pilot placement with more pilot
`symbols for increasing accuracy of the channel estimation.
`It will be appreciated by those skilled in the art that changes
`could be made to the examples described above without
`departing from the broad inventive concept thereof. It is
`understood, therefore, that this invention is not l