ERIC-1001
`Ericsson v IV
`Page 1 of 20
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`US 7,787,431 B2
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`U.S. PATENT DOCUMENTS
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`OTHER PUBLICATIONS
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`................... .. 375/260
`5/2008 Miyoshi
`7,372,909 B2 *
`................. .. 455/436
`5/2008 Kim etal.
`7,376,424 132*
`2/2002 Vanderaar et al.
`......... .. 375/259
`2002/0018527 A1*
`2002/0142777 A1* 10/2002 McGovern et al.
`........ .. 455/450
`2004/0224691 A1
`11/2004 Hadad
`2005/0180314 A1
`8/2005 Webster et al
`2005/0201476 A1
`9/2005 Kim et al.
`
`International Search Report and Written Opinion; PCT Application
`No. PCT/US2005/014828; Applicant Waltical Solutions, Inc.; Date
`0fMa111I1g¢ D60 27a 2005a 5 Pages
`Chlnese 000°‘? A°“°“ 0” APP“°a“°“ N°~ CN 20058001299299
`Applicant: Neocific, Inc.; Date ofNotification: Jan. 29, 2010; 4 pages
`[99nS199°n attached’ 4 pages}
`* cited by examiner
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`U.S. Patent
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`Au .31 2010
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`Sheet 1 of 10
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`US 7,787,431 B2
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`U.S. Patent
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`Aug. 31, 2010
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`Aug. 31, 2010
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`ERIC-1001 I Page 12 of 20
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`US 7,787,431 B2
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`1
`METHODS AND APPARATUS FOR
`MULTI-CARRIER COMMUNICATIONS WITH
`VARIABLE CHANNEL BANDWIDTH
`
`2
`feasible solution for multi-carrier communication with vari-
`able channel bandwidth is desirable.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`CROSS-REFERENCE TO RELATED
`
`APPLICATION(S)
`
`This application is a National Stage Application and claims
`the benefit of PCT Application No. PCT/US05/ 14828, filed
`Apr. 29, 2005 (the ’828 application). This application, as well
`as the ’ 828 application, claims the benefit of U.S. Provisional
`Patent Application No. 60/567,233, filed on May 1, 2004.
`This application also relates to PCT Application No. PCT/
`US2005/001939 filed Jan. 20, 2005, which claims the benefit
`ofU.S. Provisional Application No. 60/540,032 filed Jan. 29,
`2004; PCT Application No. PCT/US2005/004601 filed Feb.
`14, 2005, which claims the benefit of U.S. Provisional Appli-
`cation No. 60/544,521 filed Feb. 13, 2004; PCT Application
`No. PCT/US2005/003889 filed Feb. 7, 2005, which claims
`the benefit of U.S. Provisional Application No. 60/542,317
`filed Feb. 7, 2004; and PCT Application No. PCT/US2005/
`008169 filed Mar. 9, 2005, which claims the benefit of U.S.
`Provisional Application No. 60/551,589 filed Mar. 9, 2004.
`The above-listed applications are hereby incorporated by ref-
`erence.
`
`BACKGROUND
`
`While it is ideal for a broadband wireless communication
`
`device to be able to roam from one part of the world to
`another, wireless communication spectra are heavily regu-
`lated and controlled by individual countries or regional
`authorities. It also seems inevitable that each country or
`region will have its own different spectral band for broadband
`wireless communications. Furthermore, even within a coun-
`try or region, a wireless operator may own and operate on a
`broadband spectrum that is different in frequency and band-
`width from other operators. The existing and future band-
`width variety presents a unique challenge in designing a
`broadband wireless communication system and demands
`flexibility and adaptability.
`Multi-carrier communication systems are designed with a
`certain degree offlexibility. In a multi-carrier communication
`system such as multi-carrier code division multiple access
`(MC-CDMA) and orthogonal frequency division multiple
`access (OFDMA), information is multiplexed on subcarriers
`that are mutually orthogonal in the frequency domain. Design
`flexibility is a result of the ability to manipulate parameters
`such as the number of subcarriers and the sampling fre-
`quency. For example, by using a different sampling fre-
`quency, a DVB-T (Digital Video Broadcasting-Terrestrial)
`device is capable of receiving signals broadcasted from a
`DVB-T station that is operating on a 6-, 7-, or 8-MHZ band-
`width.
`
`However, the change in the time-domain structure brings
`about a series of system problems. A varying sampling rate
`alters the symbol length, frame structure, guard time, prefix,
`and other time-domain properties, which adversely affects
`the system behavior and performance. For example, the MAC
`layer and even the layers above have to keep track of all the
`time-domain parameters in order to perform other network
`functions such as handoff, and thereby the complexity of the
`system will exponentially increase. In addition, the change in
`symbol length causes control and signaling problems and the
`change in the frame structure may cause unacceptable jitters
`in some applications such as voice over IP. A practical and
`
`FIG. 1 is a schematic presentation of a radio resource
`divided into small units in both the frequency and time
`domains: subcharmels and time slots.
`
`FIG. 2 illustrates a relationship between sampling fre-
`quency, channel bandwidth, and usable subcarriers.
`FIG. 3 shows a basic structure of a multi-carrier signal in
`the frequency domain, made up of subcarriers.
`FIG. 4 shows a basic structure of a multi-carrier signal in
`the time domain, generally made up of time frames, time
`slots, and OFDM symbols.
`FIG. 5 shows a cellular wireless network comprised of a
`plurality of cells, wherein in each of the cells coverage is
`provided by a base station (BS).
`FIG. 6 illustrates a variable channel bandwidth being real-
`ized by adjusting a number of usable subcarriers, whose
`spacing is set constant.
`FIG. 7 depicts a time-domain windowing function applied
`to OFDM symbols to shape the OFDM spectrum to conform
`to a given spectral mask.
`FIG. 8 depicts a preamble designed to occupy either an
`entire operating bandwidth or a core-band.
`FIG. 9 shows an entire range (e.g., from 5 Mhz to 40 MHZ)
`of bandwidth variation being divided into smaller groups or
`trunks (e.g., 5-10 MHZ, 10-20 MHZ, 20-40 MHZ, in siZes),
`wherein each trunk is handled in one particular range.
`FIG. 10 illustrates a multi-cell, multi-user cellular system
`comprising multiple base stations and mobile stations.
`
`DETAILED DESCRIPTION
`
`The multi-carrier system mentioned here can be of any
`format such as OFDM, or Multi-Carrier Code Division Mul-
`tiple Access (MC-CDMA). The presented methods can also
`be applied to downlink, uplink, or both, where the duplexing
`technique is either Time Division Duplexing (TDD) or Fre-
`quency Division Duplexing (FDD).
`The following description provides specific details for a
`thorough understanding of the various embodiments and for
`the enablement of one skilled in the art. However, one skilled
`in the art will understand that the invention may be practiced
`without such details. In some instances, well-known struc-
`tures and functions have not been shown or described in detail
`
`to avoid unnecessarily obscuring the description of the
`embodiments.
`
`The terminology used in the description presented below is
`intended to be interpreted in its broadest reasonable manner,
`even though it is being used in conjunction with a detailed
`description of certain specific embodiments of the invention.
`Certain terms may even be emphasiZed below; however, any
`terminology intended to be interpreted in any restricted man-
`ner will be overtly and specifically defined as such in this
`Detailed Description section.
`Unless the context clearly requires otherwise, throughout
`the description and the claims, the words “comprise,” “com-
`prising,” and the like are to be construed in an inclusive sense
`as opposed to an exclusive or exhaustive sense; that is to say,
`in the sense of “including, but not limited to.” Words using the
`singular or plural number in this Detailed Description section
`also include the plural or singular number respectively. Addi-
`tionally, the words “herein,” “above,” “below” and words of
`similar import, when used in this application, shall refer to
`this application as a whole and not to any particular portions
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`3
`of this application. When the claims use the word “or” in
`reference to a list oftwo or more items, that word covers all of
`the following interpretations of the word: any of the items in
`the list, all of the items in the list and any combination of the
`items in the list.
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`4
`
`areas called cells. In each cell the coverage is provided by a
`base station. This type of structure is normally referred to as
`the cellular structure. FIG. 5 depicts a cellular wireless net-
`work comprised of a plurality of cells. In each of these cells
`the coverage is provided by a base station (BS).
`A base station is connected to the backbone of the network
`
`via a dedicated link and also provides radio links to the mobile
`stations within its coverage. Within each coverage area, there
`are located mobile stations to be used as an interface between
`the users and the network. A base station also serves as a focal
`
`point to distribute information to and collect information
`from its mobile stations by radio signals. If a cell is divided
`into sectors, from system engineering point of view each
`sector can be considered as a cell. In this context, the terms
`“cell” and “sector” are interchangeable.
`Variable Bandwidth OFDMA
`
`In accordance with aspects of certain embodiments of the
`invention, a variable bandwidth system is provided, while the
`time-domain signal structure (such as the OFDM symbol
`length and frame duration) is fixed regardless of the band-
`widths. This is achieved by keeping the ratio constant
`between the sampling frequency and the length of FFT/IFFT.
`Equivalently, the spacing between adjacent subcarriers is
`fixed.
`In some embodiments, the variable charmel bandwidth is
`realized by adjusting the number of usable subcarriers. In the
`frequency domain, the entire charmel is aggregated by sub-
`channels. (The structure of a subcharmel is designed in a
`certain way to meet the requirements of FEC (Forward Error
`Correction) coding and,
`therefore, should be maintained
`unchanged.) However, the number of subcharmels can be
`adjusted to scale the channel in accordance with the given
`bandwidth. In such realization, a specific number of subchan-
`nels, and hence the number ofusable subcarriers, constitute a
`channel of certain bandwidth.
`
`For example, FIG. 6 illustrates the signal structure in the
`frequency domain for a communication system with param-
`eters specified in Table 1 below. The numbers of usable sub-
`carriers are determined based on the assumption that the
`effective bandwidth Befis 90% ofthe charmel bandwidth Bch.
`The variable charmel bandwidth is realized by adjusting the
`number of usable subcarriers, whose spacing is set constant.
`The width of a core-band is less than the smallest channel
`
`bandwidth in which the system is to operate.
`
`TABLE 1
`
`Sample System Parameters
`
`Sampling freq.
`FFT size
`Subcarrier spacing
`Channel bandwidth
`# ofusable subcarriers
`
`11.52 MHz
`1024 points
`11.25 kHz
`8 MHz
`6 MHz
`640
`480
`
`5 MHz
`400
`
`10 MHz
`800
`
`In this realization, using the invariant OFDM symbol struc-
`ture allows the use of same design parameters for signal
`manipulation in the time-domain for a variable bandwidth.
`For example, in an embodiment depicted in FIG. 7, a particu-
`lar windowing design shapes the spectrum to conform to a
`given spectral mask and is independent ofthe operating band-
`width.
`
`Radio Operation Via Core-Band
`To facilitate the user terminals to operate in a variable
`bandwidth (VB) environment, specific signaling and control
`methods are required. Radio control and operation signaling
`is realized through the use of a core-band (CB). A core-band,
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`Multi-Carrier Communication System
`The physical media resource (e.g., radio or cable) in a
`multi-carrier communication system can be divided in both
`the frequency and time domains. This canonical division pro-
`vides a high flexibility and fine granularity for resource shar-
`ing. FIG. 1 presents a radio resource divided into small units
`in both the frequency and time domains—subchannels and
`time slots. The subchannels are formed by subcarriers.
`The basic structure of a multi-carrier signal in the fre-
`quency domain is made up of subcarriers. For a given band-
`width ofa spectral band or channel (Bch) the number ofusable
`subcarriers is finite and limited, whose value depends on a
`size of an FFT (Fast Fourier Transform) employed, a sam-
`pling frequency (fs), and an effective bandwidth (B FIG. 2
`illustrates a schematic relationship between the sampling fre-
`quency, the channel bandwidth, and the usable subcarriers . As
`shown, the Befis a percentage of Bch.
`A basic structure of a multi-carrier signal in the frequency
`domain is made up of subcarriers and, illustrated in FIG. 3,
`which shows three types of subcarriers as follow:
`1. Data subcarriers, which carry information data;
`2. Pilot subcarriers, whose phases and amplitudes are pre-
`determined and made known to all receivers, and which
`are used for assisting system functions such as estima-
`tion of system parameters; and
`3. Silent subcarriers, which have no energy and are used as
`guard bands and DC carriers.
`The data subcarriers can be arranged into groups called
`subchannels to support scalability and multiple-access. Each
`subchannel may be set at a different power level. The subcar-
`riers forming one subchannel may or may not be adjacent to
`each other. Each user may use some or all ofthe subchannels.
`A subchannel formed by the contiguous subcarriers is called
`a congregated or clustered subchannel. A congregated sub-
`channel may have a different power level from others.
`FIG. 4 illustrates the basic structure of a multi-carrier sig-
`nal in the time domain which is generally made up of time
`frames, time slots, and OFDM symbols. A frame consists of a
`number oftime slots, whereas each time slot is comprised of 45
`one or more OFDM symbols. The OFDM time domain wave-
`form is generated by applying the inverse-fast-Fourier-trans-
`form (IFFT) to the OFDM signals in the frequency domain. A
`copy of the last portion of the time waveform, known as the
`cyclic prefix (CP), is inserted at the beginning of the wave-
`form itself to form an OFDM symbol.
`The downlink transmission in each frame begins with a
`downlink preamble, which can be the first or more of the
`OFDM symbols in the first downlink (DL) slot. The DL
`preamble is used at a base station to broadcast radio network
`information such as synchronization and cell identification.
`Similarly, uplink transmission can begin with an uplink
`preamble, which can be the first or more of the OFDM sym-
`bols in the first uplink (UL) slot. The UL preamble is used by
`mobile stations to carry out the functions such as initial rang-
`ing during power up and handoff, periodic ranging and band-
`width request, charmel sounding to assist downlink schedul-
`ing or advanced antenna technologies, and other radio
`functions.
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`Cellular Wireless Networks
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`In a cellular wireless network, the geographical region to
`be serviced by the network is normally divided into smaller
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`US 7,787,431 B2
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`5
`substantially centered at the operating center frequency, is
`defined as a frequency segment that is not greater than the
`smallest operating channel bandwidth among all the possible
`spectral bands that the receiver is designed to operate with.
`For example, for a system that is intended to work at 5-, 6-, 8-,
`and 10-MhZ, the width of the CB can be 4 MHZ, as shown in
`FIG. 6. The rest of the bandwidth is called sideband (SB).
`In one embodiment relevant or essential radio control sig-
`nals such as preambles, ranging signals, bandwidth request,
`and/or bandwidth allocation are transmitted within the CB. In
`addition to the essential control channels, a set of data chan-
`nels and their related dedicated control channels are placed
`within the CB to maintain basic radio operation. Such a basic
`operation, for example, constitutes the primary state of opera-
`tion. When entering into the network, a mobile station starts
`with the primary state and transits to the normal full-band-
`width operation to include the sidebands for additional data
`and radio control channels.
`
`In another embodiment, a preamble, called an essential, or
`primary preamble (EP), is designed to only occupy the CB, as
`depicted in FIG. 8. The EP alone is sufficient for the basic
`radio operation. The EP can be either a direct sequence in the
`time domain with its frequency response confined within the
`CB, or an OFDM symbol corresponding to a particular pat-
`tern in the frequency domain within the CB. In either case, an
`EP sequence may possess so1ne or all of the following prop-
`erties:
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`1.
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`2.
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`Its autocorrelation exhibits a relatively large ratio
`between the correlation peak and sidelobe levels.
`Its cross-correlation coefiicient with another EP
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`sequence is significantly small with respect to the power
`of the EP sequences.
`3. Its peak-to-average ratio is relatively small.
`4. The number of EP sequences that exhibit the above three
`properties is relatively large.
`In yet another embodiment, a preamble, called an auxiliary
`preamble (AP), which occupies the SB, is combined with the
`EP to form a full-bandwidth preamble (FP) (e.g., appended in
`the frequency domain or superimposed in the time domain).
`An FP sequence may possess some or all of the following
`properties:
`1.
`Its autocorrelation exhibits a relatively large ratio
`between the correlation peak and sidelobe levels.
`Its cross-correlation coefiicient with another FP
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`2.
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`sequences is significantly small with respect to the
`power of the FP sequences.
`3. Its peak-to-average ratio is relatively small.
`4. The number of FP sequences that exhibits the above
`three properties is relatively large.
`In still another embodiment, the formation of an FP by
`adding an AP allows a base station to broadcast the FP, and a
`mobile station to use its corresponding EP, to access this base
`station. An FP sequence may also possess some or all of the
`following properties:
`1. Its correlation with its own EP exhibits a relatively large
`ratio between the correlation peak and sidelobe levels.
`2. Its cross-correlation coefficient with any EP sequence
`other than its own is significantly small with respect to
`its power.
`3. The number of FP sequences that exhibit the above two
`properties is relatively large.
`
`Automatic Bandwidth Recognition
`The VB-OFDMA receiver is capable of automatically rec-
`ognizing the operating bandwidth when it enters in an oper-
`ating environment or service area of a particular frequency
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`and charmel bandwidth. The bandwidth information can be
`
`disseminated in a variety of forms to enableAutomatic Band-
`width Recognition (ABR).
`In one embodiment, a mobile station, when entering in an
`environment or an area that supports the VB operation or
`services, will scan the spectral bands of different center fre-
`quencies. If it detects the presence of a signal in a spectral
`band ofa particular center frequency by using envelope detec-
`tion, received signal strength indicator (RSSI), or by other
`detection methods, it can determine the operating channel
`bandwidth by bandwidth-center frequency association such
`as table lookup. For example, a table such as Table 2 is stored
`in the receiver. Based on the center frequency that it has
`detected, the mobile station looks up the value of the channel
`bandwidth from the table.
`
`TABLE 2
`
`Sample Center Frequency and Corresponding Bandwidth
`
`Center frequency
`2.31 GHZ
`2.56 GHZ
`2.9 G
`
`Channel Bandwidth
`10 MHZ
`6 MHZ
`8 MHZ
`
`In another embodiment, the system provides the bandwidth
`information via downlink signaling, such as using a broad-
`casting channel or a preamble. When entering into a VB
`network, the mobile stations will scan the spectral bands of
`different center frequencies in which the receiver is designed
`to operate and decode the bandwidth information contained
`in the broadcasting channel or preamble.
`
`Multi-Mode (Multi-Range) VB-OFDMA
`In accordance with the principles of this invention, multi-
`modes are devised for a VB-OFDMA system to handle an
`exceptionally wide range of variation in channel bandwidth.
`The entire range of bandwidth variation is divided into
`smaller parts—not necessarily in equal siZe—each of which
`will be dealt with as a separate mode or range.
`FIG. 9 illustrates the entire range (e.g., from 5 MHZ to 40
`MHZ) ofbandwidth variation being divided into smaller parts
`(e.g., 5-10 MHZ, 10-20 MHZ, 20-40 MHZ, in siZes). Each part
`is handled in one particular mode. The mode for the lowest
`range of bandwidth is labeled as “fundamental mode” and
`other modes are called “higher modes” (Mode 1, Mode 2,
`etc.).
`The sampling frequency of a higher mode is higher than the
`sampling frequency ofthe fundamental mode. In one embodi-
`ment the sampling frequency of a higher mode is a multiple of
`the sampling frequency of the fundamental mode. In this
`embodiment, in the higher modes, the FFT siZe can be mul-
`tiplied in accordance with the sampling frequency, thereby
`maintaining the time duration ofthe OFDM symbol structure.
`For example, the parameters for the case of a multi-mode
`design are given in Table 3. Alternatively, a higher mode can
`be realiZed by maintaining the FFT siZe and shortening the
`OFDM symbol duration accordingly. For example, for Mode
`1 in Table 3, the FFT siZe can be maintained at 1024, whereas
`the sampling frequency is doubled and the symbol length is a
`half of that for the fundamental range. Yet another higher-
`mode realiZation is to both increase the FFT siZe and shorten
`
`the symbol duration accordingly. For example, for Mode 2
`(20 MHZ to 40 MHZ in bandwidth), both the FFT siZe and the
`sampling frequency canbe doubled as those ofthe fundamen-
`tal range, whereas the symbol length is halved as that of the
`fundamental range. The width of the CB in a multi-mode
`
`ERIC-1001 I Page 15 of 20
`
`ERIC-1001 / Page 15 of 20
`
`

`
`7
`VB-OFDMA system may not be greater than the smallest
`bandwidth in the fundamental mode.
`
`8
`The above detailed description of the embodiments of the
`invention is not intended to be exhaustive or to limit the
`
`US 7,787,431 B2
`
`TABLE 3
`
`Sample System Parameters
`Mode 1
`
`Fundamental-Mode
`
`Sampling freq.
`FFT siZe
`Subcarrier spacing
`Channel bandwidth (MHZ)
`# ofusable subcarriers
`
`23.04 MHZ
`2048 points
`
`20
`1600
`
`18
`1440
`
`15
`1200
`
`11.25 kHZ
`12
`10
`960
`800
`
`11.52 MHZ
`1024 points
`
`8
`680
`
`480
`
`15
`
`5
`400
`
`FIG. 10 illustrates a multi-cell, multi-user cellular system
`comprising multiple base stations and mobile stations. The
`system of FIG. 10 is an example of an environment in which
`the attributes of the invention can be utiliZed.
`
`While specific circuitry may be employed to implement the
`above embodiments, aspects of the invention can be imple-
`mented in a suitable computing environment. Although not
`required, aspects of the invention may be implemented as
`computer-executable instructions, such as routines executed
`by a general-purpose computer, e.g., a server computer, wire-
`less device orpersonal computer. Those skilled in the relevant
`art will appreciate that aspects of the invention can be prac-
`ticed with other communications, data processing, or com-
`puter system configurations, including: Internet appliances,
`hand-held devices (including personal digital assistants
`(PDAs)), wearable computers, all manner of cellular or
`mobile phones, multi-processor systems, microprocessor-
`based or programmable consumer electronics, set-top boxes,
`network PCs, mini-computers, mainframe computers, and
`the like. Indeed, the term “computer” refers to any of the
`above devices and systems, as well as any data processor.
`Aspects of the invention can be embodied in a special
`purpose computer or data processor that is specifically pro-
`grammed, configured, or constructed to perform one or more
`of the processes explained in detail herein. Aspects of the
`invention can also be practiced in distributed computing envi-
`ronments where tasks or modules are performed by remote
`processing devices, which are linked through a communica-
`tions network, such as a Local Area Network (LAN), Wide
`Area Network (WAN), or the Internet. In a distributed com-
`puting environment, program modules may be located in both
`local and remote memory storage devices.
`Aspects of the invention may be stored or distributed on
`computer-readable media, including magnetically or opti-
`cally readable computer discs, hard-wired or preprogrammed
`chips (e.g., EEPROM semiconductor chips), nanotechnology
`memory, biological memory, or other data storage media.
`Indeed, computer implemented instructions, data structures,
`screen displays, and other data under aspects of the invention
`may be distributed over the Internet or over other networks
`(including wireless networks), on a propagated signal on a
`propagation medium (e.g., an electromagnetic wave(s), a
`sound wave, etc.) over a period of time, or they may be
`provided on any analog or digital network (packet switched,
`circuit switched, or other scheme). Those skilled in the rel-
`evant art will recogmZe that portions of the invention reside
`on a server computer, while corresponding portions reside on
`a client computer such as a mobile or portable device, and
`thus, while certain hardware platforms are described herein,
`aspects of the invention are equally applicable to nodes on a
`network.
`
`20
`
`25
`
`30
`
`35
`
`40
`
`45
`
`50
`
`55
`
`60
`
`65
`
`invention to the precise form disclosed above. While specific
`embodiments of, and examples for,
`the invention are
`described above for illustrative purposes, various equivalent
`modifications are possible within the scope of the invention,
`as those skilled in the relevant art will recogniZe. For
`example, while processes are presented in a given order,
`alternative embodiments may perform routines having steps
`in a different order, and some processes may be deleted,
`moved, added, subdivided, combined, and/or modified. Each
`of these processes may be implemented in a variety of differ-
`ent ways.
`The teachings provided herein can be applied to other
`systems, not necessarily the system described herein. The
`elements and acts of the various embodiments described
`
`above can be combined to provide further embodiments. All
`of the above patents and applications and other references,
`including any that may be listed in accompanying filing
`papers, are incorporated herein by reference. Aspects of the
`invention can be modified, if necessary, to employ the sys-
`tems, functions, and concepts of the various references
`described above to provide yet further embodiments of the
`invention.
`
`Particular terminology used when describing certain fea-
`tures or aspects of the invention should not be taken to imply
`that the terminology is being redefined herein to be restricted
`to any specific characteristics, features, or aspects of the
`invention with which that terminology is associated. In gen-
`eral, the terms used in the following claims should not be
`construed to limit the invention to the specific embodiments
`disclosed in the specification, unless the above Detailed
`Description section explicitly defines such terms. Accord-
`ingly, the actual scope of the invention encompasses not only
`the disclosed embodiments, but also all equivalent ways of
`practicing or implementing the invention.
`The above detailed description of the embodiments of the
`invention is not intended to be exhaustive or to limit the
`
`invention to the precise form disclosed above or to the par-
`ticular field of usage mentioned in this disclosure. While
`specific embodiments of, and examples for, the invention are
`described above for illustrative purposes, various equivalent
`modifications are possible within the scope of the invention,
`as those skilled in the relevant art will recogniZe. Also, the
`teachings of the invention provided herein can be applied to
`other systems, not necessarily the system described above.
`The elements and acts of the various embodiments described
`
`above can be combined to provide further embodiments.
`All of the above patents and applications and other refer-
`ences, including any that may be listed in accompanying
`filing papers, and the PCT Application entitled “Methods and
`Apparatus for Communication with Time-Division Duplex-
`ing,” filed Apr. 29, 2005, assigned to Waltical Solutions, (Ser.
`No. 11/568,385) are incorporated herein by reference.
`
`ERIC-1001 I Page 16 of 20
`
`ERIC-1001 / Page 16 of 20
`
`

`
`US 7,787,431 B2
`
`9
`Aspects of the invention can be modified, if necessary, to
`employ the systems, functions, and concepts of the various
`references described above to provide yet further embodi-
`ments of the invention.
`
`Changes can be made to the invention in light of the above
`“Detailed Description.” While the above description details
`certain embodiments of the invention and describes the best
`
`mode contemplated, no matter how detailed the above
`appears in text, the invention can be practiced in many ways.
`Therefore, implementation details may vary considerably
`while still being encompassed by the invention disclosed
`herein. As noted above, particular terminology used when
`describing certain features or aspects of the invention should
`not be taken to imply that the terminology is being redefined
`herein to be restricted to any specific characteristics, features,
`or aspects of the invention with which that terminology is
`associated.
`
`In general, the terms used in the following claims should
`not be construed to limit the invention to the specific embodi-
`ments disclosed in the specification, unless the above
`Detailed Description section explicitly defines such terms.
`Accordingly, the actual scope of the invention encompasses
`not only the disclosed embodiments, but also all equivalent
`ways of practicing or implementing the invention under the
`claims.
`
`While certain aspects of the invention are presented below
`in certain claim forms, the inventors contemplate the various
`aspects of the invention in any number of claim forms.
`Accordingly, the inventors reserve the right to add additional
`claims after filing the application to pursue such additional
`claim forms for other aspects of the invention.
`We claim:
`
`1. In a variable bandwidth wireless communication system
`communicating under multiple different communication
`schemes that each have a different bandwidth, a process per-
`formed by a base station ofgenerating an information bearing
`signal for wireless transmission, the process comprising:
`utilizing by the base station a number of subcarriers to
`construct a variable bandwidth wireless channel;
`