Attorne Docket No.:
`
`CML01942M
`
`CML01942M
`
`A— T
`
`First Inventor:
`
`itle:
`
`k
`
`llllllllllllllll
`
`903080
`
`UTILITY
`PATENT APPLICATION
`TRANSMITTAL
`(Only for new nonprovisional applications under 37 CFR 1.53(b))
`
`METHOD AND APPARATUS FOR
`ACCESSING A WIRELESS
`COMMUNICATION SYSTEM
`——Exress Mail Label No.: EV580331299
`Commissioner for Patents
`p_ o_ Box 1450
`
`APPLICATION ELEMENTS
`see MPEP chater 600 concernin utlli
`atent a llcation contents
`
`1.
`
`Fee Transmittal Form (e.g., PTO/SB/17)
`(Submit an original and a duplicate for fee processing)
`2. :] Applicant claims small entity status
`See 37 CFR 1.27
`
`I
`
`3.
`
`25]
`
`[Total Pages
`Specification
`(preferred arrangement setforth below)
`-Descriptive title of the invention
`-Cross Reference to Related Applications
`-Statement Regarding Fed sponsored R & D
`-Reference to sequence listing, a table, or computer program
`listing appendix
`-Brief Summary of the Invention
`_}3riefDe5crjp1i0n of the Drawings Q-ffi1ed)
`-Detailed Description
`_C,al.m(S)
`-Abstract of the Disclosure
`
`ADDRESS TO:
`
`Alexandria. VA 22313-1:4 6
`7. E] CD-ROM or CD-R in duplicate, large
`5: V‘
`-table or Computer Program (Appendix) (/5 8
`8. El Nucleotide and/or Amino Acid Sequenced E
`C)S
`(if applicable, all necessary)
`co
`‘-
`a. [3 Computer Readable Form (CFR)
`1-
`
`b. :] Specification Sequence Listing on:
`
`i. B CD-ROM or CD-4 (2 copies); or
`
`ii. E Paper
`c. I: Statements verifying identity of above copies
`
`ACCOMPANYING APPLICATION PARTS
`9. E Assignment Papers (cover sheet & document(s))
`
`4.
`
`Drawing(s) (35 U.S.C. 113)
`
`[Total Sheets
`
`[Total Sheets
`5. Oath or Declaration
`a.
`Newly executed (original or copy)
`
`6
`
`3
`
`]
`
`]
`
`10. D 37 CFR 3.73(b) Statement E] Power ofAttomey
`(when there is an assignee)
`1 1. B English Translation Document (ifapplicable)
`
`b. |:] Copy from prior application (37 CFR l.63(d))
`(for continuation/divisional with Box 18 completed)
`
`i.
`
`DELETION OF INVENTOR(S)
`Signed statement attached deleting invcntor(s)
`name in the prior application, see 37 CFR
`l.63(d)(2) and l.33(b)
`
`6.
`
`Application Data Sheet. See 37 CFR 1.76
`
`. E] Information Disclosure 2 Copies of IDS
`Statement (IDS)/PT-1449
`Citations
`. D Preliminary Amendment
`.
`Return Receipt Postcard (MPEP 503)
`(Should be specifically itemized)
`I:-_] Certified Copy of Priority Document
`
`.
`
`16.
`
`Nonpublication Request under 35 U.S.C.
`
`El l22(b)(2)(B)(i). Applicant must attach form
`
`PTO/SB/35 or its equivalent.
`17. :1 Other:
`
`I8.
`
`IF A CONTINUING APPLICATl0N,check appropriate box and supply the requisite information below and in thefirst sentence ofthe
`specificationfollowing the title. or in an Application Data Sheet under 37 CFR 1.76:
`of prior application No.
`E] Continuation
`El Divisional
`D Continuation-in- Part (CIP)
`Art Unit:
`Prior application information:
`Examiner:
`For CONTINUATION OR DIVISIONAL APPS only: The entire disclosure of the prior application, from with an with or declaration is supplied under Bax Sb, is considered a pan of the disclosure of
`the accompanying continuation or divisional application and is hereby incorporated by reference. The incorporuio@_q_n1x be relied upon when a portion hlu been inadvertently omitted from the submitted
`application parts.
`
`E Customer Number
`James A. Lamb
`
`22917
`
`0|’
`
`El Corresondence address below
`
`19. CORRESPONDENCE ADDRESS
`
`847 576-3750
`Fax
`576-5054
`84
`James A. Lamb Jfifiigj 38.529
`S11.’
`03/02/2005
`
`CMLO1942M
`
`1
`
`APPLE 1008
`
`

`
`CML01942M
`
`Effective on 12/03/2004
`
`Fees pursuant to the Consolidated Appropriations Act. 2005 (H.R. 4818)
`FEE TRANSMITTAL
`F°' FY 2°°5
`‘
`B Applicant claims small entity status. See 37 CFR 1.27
`
`(5) "°°-°°
`METHOD OF PAYMENT (check all that apply)
`
`A
`Com 0 Iete if Known
`A , , “cation Number —
`Filing Date
`First Named Inventor
`Examiner Name
`Grou Art Unit
`Attome Docket No.
`
`CML01942M
`
`V
`
`I:] Other (please identify):
`E] None
`E] Credit card C] Money Order
`D Check
`Deposit Account Deposit Account Number: 502117 Deposit Account Name: MOTOROLA, INC.
`For the above-identified deposit account, the Director is hereby authorized to: (check all that apply)
`XI Charge fee(s) indicated below
`.
`E] Charge fee(s) indicated below, except for the filing fee
`IX Charge any additional fee(s) or underpayments of fee(s)
`[Z Credit any overpayments
`under37 CFR1.16 and 1.17
`.
`lnforrnation on this form may become public. Credit card information should not be included on this form. Provide credit card
`WARNING:
`information and authorization on PTO-2038.
`
`A
`
`FEE CALCULATION
`
`'
`
`1. BASIC FILING, SEARCH, AND EXAMINATION FEES
`’
`FILING FEES
`SEARCH FEES
`
`EXAMINATION FEES
`
`— all Et
`
`65
`100 “ 130
`200
`Desi - n
`lim--E-T-—
`I EEIKEIT‘
`Provisional
`0
`0
`0
`0 —
`
`2. EXCESS CLAIM FEES
`Fee Description
`Each claim over 20 or. for Reissues. each claim over 20 and more than in the original patent
`Each independent claim over 3 or. for Reissues. each independent claim more than in the original patent
`Multiple dependent claims
`Fee Paid '-
`Fee 1
`Extra Claims
`_
`Total Claim
`-zoorwre Eix = in:
`HP=highest number of total claims pad for, if greater than 20
`
`-
`
`Fee(§)
`50
`200
`360
`Multiple Degendentclaims
`met my
`l
`
`Small Entity
`Fee ($1
`25
`100
`180
`
`lnde. Claims
`
`Extra Claims
`
`Fee ‘-
`
`Fee Paid
`
`HP=highest number of independent claims paid for, if greater than 3
`
`3. APPLICATION SIZE FEE:
`If the specification and drawings exceed 100 sheets of paper. the application size fee due is $250 ($125 for small entity) for each additional 50
`sheets or fraction thereof. See 35 U.S.C. 41(a)(1)(G) and 37 CFR 1.16(s).
`Total Sheets
`Extra Sheets
`umber of ea
`ad itional 50 o fractio
`ereof
`Fee
`Fee
`id
`' - 100 = E /50 =
`(round up to a whole number)
`x
`
`4. OTHER FEE(S)
`Non-English Specification, $130 fee (no small entity discount)
`Other:
`
`SUBMITTED 3}’
`
`'
`
`‘_
`1 Lamb
`
`_
`
`,
`
`Fee Paid (5)
`
`Complete (ii applicable)
`Registration No.
`38529
`(847) 576-
`4 :- 5054
`03/02/2005
`
`CMLO1942M
`
`2
`
`

`
`Attorne Docket No.:
`
`CML01942M
`
`CML01942M
`
`A— T
`
`First Inventor:
`
`itle:
`
`k
`
`llllllllllllllll
`
`903080
`
`UTILITY
`PATENT APPLICATION
`TRANSMITTAL
`(Only for new nonprovisional applications under 37 CFR 1.53(b))
`
`METHOD AND APPARATUS FOR
`ACCESSING A WIRELESS
`COMMUNICATION SYSTEM
`——Exress Mail Label No.: EV580331299
`Commissioner for Patents
`p_ o_ Box 1450
`
`APPLICATION ELEMENTS
`see MPEP chater 600 concernin utlli
`atent a llcation contents
`
`1.
`
`Fee Transmittal Form (e.g., PTO/SB/17)
`(Submit an original and a duplicate for fee processing)
`2. :] Applicant claims small entity status
`See 37 CFR 1.27
`
`I
`
`3.
`
`25]
`
`[Total Pages
`Specification
`(preferred arrangement setforth below)
`-Descriptive title of the invention
`-Cross Reference to Related Applications
`-Statement Regarding Fed sponsored R & D
`-Reference to sequence listing, a table, or computer program
`listing appendix
`-Brief Summary of the Invention
`_}3riefDe5crjp1i0n of the Drawings Q-ffi1ed)
`-Detailed Description
`_C,al.m(S)
`-Abstract of the Disclosure
`
`ADDRESS TO:
`
`Alexandria. VA 22313-1:4 6
`7. E] CD-ROM or CD-R in duplicate, large
`5: V‘
`-table or Computer Program (Appendix) (/5 8
`8. El Nucleotide and/or Amino Acid Sequenced E
`C)S
`(if applicable, all necessary)
`co
`‘-
`a. [3 Computer Readable Form (CFR)
`1-
`
`b. :] Specification Sequence Listing on:
`
`i. B CD-ROM or CD-4 (2 copies); or
`
`ii. E Paper
`c. I: Statements verifying identity of above copies
`
`ACCOMPANYING APPLICATION PARTS
`9. E Assignment Papers (cover sheet & document(s))
`
`4.
`
`Drawing(s) (35 U.S.C. 113)
`
`[Total Sheets
`
`[Total Sheets
`5. Oath or Declaration
`a.
`Newly executed (original or copy)
`
`6
`
`3
`
`]
`
`]
`
`10. D 37 CFR 3.73(b) Statement E] Power ofAttomey
`(when there is an assignee)
`1 1. B English Translation Document (ifapplicable)
`
`b. |:] Copy from prior application (37 CFR l.63(d))
`(for continuation/divisional with Box 18 completed)
`
`i.
`
`DELETION OF INVENTOR(S)
`Signed statement attached deleting invcntor(s)
`name in the prior application, see 37 CFR
`l.63(d)(2) and l.33(b)
`
`6.
`
`Application Data Sheet. See 37 CFR 1.76
`
`. E] Information Disclosure 2 Copies of IDS
`Statement (IDS)/PT-1449
`Citations
`. D Preliminary Amendment
`.
`Return Receipt Postcard (MPEP 503)
`(Should be specifically itemized)
`I:-_] Certified Copy of Priority Document
`
`.
`
`16.
`
`Nonpublication Request under 35 U.S.C.
`
`El l22(b)(2)(B)(i). Applicant must attach form
`
`PTO/SB/35 or its equivalent.
`17. :1 Other:
`
`I8.
`
`IF A CONTINUING APPLICATl0N,check appropriate box and supply the requisite information below and in thefirst sentence ofthe
`specificationfollowing the title. or in an Application Data Sheet under 37 CFR 1.76:
`of prior application No.
`E] Continuation
`El Divisional
`D Continuation-in- Part (CIP)
`Art Unit:
`Prior application information:
`Examiner:
`For CONTINUATION OR DIVISIONAL APPS only: The entire disclosure of the prior application, from with an with or declaration is supplied under Bax Sb, is considered a pan of the disclosure of
`the accompanying continuation or divisional application and is hereby incorporated by reference. The incorporuio@_q_n1x be relied upon when a portion hlu been inadvertently omitted from the submitted
`application parts.
`
`E Customer Number
`James A. Lamb
`
`22917
`
`0|’
`
`El Corresondence address below
`
`19. CORRESPONDENCE ADDRESS
`
`847 576-3750
`Fax
`576-5054
`84
`James A. Lamb Jfifiigj 38.529
`S11.’
`03/02/2005
`
`CMLO1942M
`
`3
`
`

`
`CML01942M
`
`Effective on 12/03/2004
`
`Fees pursuant to the Consolidated Appropriations Act. 2005 (H.R. 4818)
`FEE TRANSMITTAL
`F°' FY 2°°5
`‘
`B Applicant claims small entity status. See 37 CFR 1.27
`
`(5) "°°-°°
`METHOD OF PAYMENT (check all that apply)
`
`A
`Com 0 Iete if Known
`A , , “cation Number —
`Filing Date
`First Named Inventor
`Examiner Name
`Grou Art Unit
`Attome Docket No.
`
`CML01942M
`
`V
`
`I:] Other (please identify):
`E] None
`E] Credit card C] Money Order
`D Check
`Deposit Account Deposit Account Number: 502117 Deposit Account Name: MOTOROLA, INC.
`For the above-identified deposit account, the Director is hereby authorized to: (check all that apply)
`XI Charge fee(s) indicated below
`.
`E] Charge fee(s) indicated below, except for the filing fee
`IX Charge any additional fee(s) or underpayments of fee(s)
`[Z Credit any overpayments
`under37 CFR1.16 and 1.17
`.
`lnforrnation on this form may become public. Credit card information should not be included on this form. Provide credit card
`WARNING:
`information and authorization on PTO-2038.
`
`A
`
`FEE CALCULATION
`
`'
`
`1. BASIC FILING, SEARCH, AND EXAMINATION FEES
`’
`FILING FEES
`SEARCH FEES
`
`EXAMINATION FEES
`
`— all Et
`
`65
`100 “ 130
`200
`Desi - n
`lim--E-T-—
`I EEIKEIT‘
`Provisional
`0
`0
`0
`0 —
`
`2. EXCESS CLAIM FEES
`Fee Description
`Each claim over 20 or. for Reissues. each claim over 20 and more than in the original patent
`Each independent claim over 3 or. for Reissues. each independent claim more than in the original patent
`Multiple dependent claims
`Fee Paid '-
`Fee 1
`Extra Claims
`_
`Total Claim
`-zoorwre Eix = in:
`HP=highest number of total claims pad for, if greater than 20
`
`-
`
`Fee(§)
`50
`200
`360
`Multiple Degendentclaims
`met my
`l
`
`Small Entity
`Fee ($1
`25
`100
`180
`
`lnde. Claims
`
`Extra Claims
`
`Fee ‘-
`
`Fee Paid
`
`HP=highest number of independent claims paid for, if greater than 3
`
`3. APPLICATION SIZE FEE:
`If the specification and drawings exceed 100 sheets of paper. the application size fee due is $250 ($125 for small entity) for each additional 50
`sheets or fraction thereof. See 35 U.S.C. 41(a)(1)(G) and 37 CFR 1.16(s).
`Total Sheets
`Extra Sheets
`umber of ea
`ad itional 50 o fractio
`ereof
`Fee
`Fee
`id
`' - 100 = E /50 =
`(round up to a whole number)
`x
`
`4. OTHER FEE(S)
`Non-English Specification, $130 fee (no small entity discount)
`Other:
`
`SUBMITTED 3}’
`
`'
`
`‘_
`1 Lamb
`
`_
`
`,
`
`Fee Paid (5)
`
`Complete (ii applicable)
`Registration No.
`38529
`(847) 576-
`4 :- 5054
`03/02/2005
`
`CMLO1942M
`
`4
`
`

`
`CMLO l 942M
`
`METHOD AND APPARATUS FOR ACCESSING A WIRELESS COMMUNICATION
`
`SYSTEM
`
`Field of the Invention
`
`The present invention relates generally to communication systems, and
`
`in particular,
`
`to a method and apparatus for randomly accessing a wireless
`
`communication system by a subscriber station in order to obtain or maintain
`
`such parameters as uplink timing, power control, channel estimation, and
`
`frequency alignment of the subscriber station.
`
`Background of the Invention
`
`In a wireless communication system, it is critical to design a mechanism
`
`for allowing a remote subscriber station (SS) to access the network by sending
`
`an access signal to a Base Station (BS). The access signal fixlfills important
`
`functions such as requesting resource allocation from the BS, alerting the BS of
`
`the existence of the SS that is trying to enter the network, and initiating a
`
`process that allows the BS to measure some parameters of the SS (e.g., timing
`
`offset caused by propagation, transmit power, etc.) that must be maintained and
`
`adjusted constantly in order to ensure a non-interfering sharing of the uplink
`
`resource. Unlike ordinary data traffic that is sent using scheduled resources that
`
`are allocated by the BS to the SS, such an access signal is often transmitted in
`
`an unsolicited manner. Therefore, this process is often referred to as a random
`
`access. Sometimes the process is also referred to as “ranging”, as used in the
`
`Institute of Electrical and Electronic Engineers (IEEE) 802.16 standards,
`
`because the access signal can help the BS to measure the propagation distance
`
`from the SS (thus, its range). A parameter known as a timing advance offset is
`
`used by the SS to advance its transmission relative to the reference timing at the
`
`BS so that the signals from all the SS’s appear synchronized at the BS (i.e.,
`
`uplink timing synchronization). Once uplink timing synchronization is
`
`achieved,
`
`the SS orthogonality is ensured (i.e., each SS occupies its own
`
`allocated sub-carriers without interfering with other SS). In this specification,
`
`the
`
`terms
`
`“access”,
`
`“random access”,
`
`and
`
`“ranging” will
`
`be
`
`used
`
`5
`
`

`
`CMb0l942M
`
`interchangeably to describe these processes and also to describe the signal
`
`transmitted by the SS to initiate the access process.
`
`The random access or ranging process includes an initial/handover
`
`ranging function for synchronizing an SS with a BS during the initial network
`
`entry or re-entry and during cell handoff, a periodic ranging function for
`
`maintaining SS synchronization, and a bandwidth request function that allows
`
`each SS to request uplink bandwidth allocation. These uplink ranging functions
`
`fulfill very important tasks that can significantly influence the user experience.
`
`For example, the bandwidth request ranging performance directly impacts the
`
`access latency perceived by a user, especially during communication sessions
`
`(e.g., HTTP) that consist of sporadic packet traffic that requires fast response, in
`
`which case high detection and low collision probabilities of the access request
`
`are very desirable.
`
`In another example, robust detection of an initial ranging
`
`signal is essential in order to allow a user to quickly enter the network or to be
`
`handed over to a new serving sector. Reliable extraction of the accurate timing
`
`oifsets from the initial ranging signals is also critical for achieving uplink
`
`synchronization that ensures user orthogonality (i.e., to make sure that each SS
`
`occupies its own allocated sub-carriers without
`
`interfering with other SS).
`
`Other important information that the BS needs to extract from ranging includes
`
`power measurement, frequency synchronization, and channel impulse response
`
`estimation, etc. Therefore, there is a need for an efficient and flexible air
`
`interface mechanism that enables fast and reliable user access to the network.
`
`Brief Description of the Drawings
`
`FIG.
`
`1
`
`is a block diagram of a communication system,
`
`in
`
`accordance with some embodiments of the present invention.
`
`FIG. 2 is a time-domain diagram of a “basic” dedicated basic
`
`ranging interval,
`invention.
`
`in accordance with some embodiments of the present
`
`FIG. 3 is a time-domain diagram of an extended dedicated
`
`ranging interval,
`invention.
`
`in accordance with some embodiments of the present
`
`FIG. 4 is a frequency-domain diagram of a variation of the
`
`extended dedicated ranging interval, in accordance with some embodiments of
`
`the present invention.
`
`6
`
`

`
`CMLO 1 942M
`
`FIG. 5 is a time-domain diagram of an example design for an
`
`OFDM system such as the one defined by the IEEE 802.16 standard.
`
`FIG. 6 is
`
`a block diagram of the division of ranging
`
`opportunities in frequency, time, and code domains, in accordance with some
`
`embodiments of the present invention.
`
`FIGS. 7 and 8 are flow charts of methods of accessing a
`
`communication system, in accordance with some embodiments of the present
`invention.
`
`FIGS. 9 and 10 are methods used by a base station in a wireless
`
`communication system for facilitating an access of the communication system
`
`by a subscriber station, in accordance with some embodiments of the present
`invention.
`
`Detailed Description of the Invention
`
`Before describing in detail
`
`the particular communication system
`
`accessing technology in accordance with the present
`
`invention,
`
`it should be
`
`observed that the present invention resides primarily in combinations of method
`
`steps and apparatus components related to accessing a communication system
`
`by a subscriber station. Accordingly, the apparatus components and method
`
`steps have been represented where appropriate by conventional symbols in the
`
`drawings, showing only those specific details that are pertinent to understanding
`
`the present invention so as not to obscure the disclosure with details that will be
`
`readily apparent to those of ordinary skill in the art having the benefit of the
`
`description herein.
`
`Turning now to the drawings, wherein like numerals designate like
`
`components, FIG.
`
`1
`
`is a block diagram of communication system 100.
`
`Communication system 100 comprises a plurality of cells 106 and 107 (only
`
`two shown) each having a base station (BS) 104, 105. The service area of the
`
`BS 104 covers a plurality of subscriber stations (SS5) 101-103, each at a time
`
`may be performing some type of ranging function, which is also called herein a
`
`random access function. For example, SS 101 may move out of the service area
`
`of BS 104 and enter into the service area of BS 105, in which case a handover
`
`occurs that often involves a handover access. In other examples, SS 102 makes
`
`7
`
`

`
`CML0l942M
`
`a bandwidth request and/or SS 103 makes an initial entry access when it is first
`
`activated within the communication system. In one embodiment of the present
`
`invention, communication system 100 utilizes an Orthogonal Frequency
`
`Division Multiplexed (OFDIVI) modulation or other variants of OFDM such as
`
`multi-carrier CDMA (MC-CDMA), multi-carrier direct sequence CDMA (MC-
`
`DS-CDMA).
`
`In other embodiments of the present invention, the multi-channel
`
`communication system 100 can use any arbitrary technology such as TDMA,
`
`FDMA, and CDMA.
`
`Definition of dedicated ranging zone
`
`Referring to FIG. 2, a time-domain diagram shows a “basic” dedicated
`
`basic ranging zone 201 defined for an OFDM example system (the term “zone”
`
`is interchangeable herein with the term “interval” used in the figure),
`
`in
`
`accordance» with some embodiments of the present invention. The duration of
`
`the dedicated basic ranging interval 201 consists of an interval of a special
`
`OFDM symbol 202 (denoted as “extended-CP” OFDM symbol) and a “dead
`
`interval” 204 that is a no-transmission interval equal to the maximum timing
`
`delay to be accommodated in the cell. The special OFDM symbol 202 has a
`
`duration equal to the sum of the duration of a special Fast Fourier Transfonri
`
`(FFT) window 209 and the duration of an extended cyclic prefix (CP) 203
`
`wherein the CP represents the repeat of a portion of the signal as commonly
`
`known in OFDM. Hence, the special OFDM symbol is also referred to as an
`
`“extended-CP” OFDM symbol in FIG.2. The special Fast Fourier Transform
`
`(FFT) window 209 may be chosen conveniently to be the same as a “regular”
`
`OFDM symbol period in an example deployment of an OFDM system, or other
`designed value (discussed later). The duratiori of the extended CP 203 equals to
`
`the sum of the duration of a “regular” CP 205 and the maximum timing delay
`
`206 to be accommodated. The maximum timing delay is chosen based on the
`
`possible timing differences among all possible subscriber locations. This value
`
`size.
`to the round-trip propagation delay and the cell
`directly relates
`Meanwhile, the duration of a “regular” CP 205 within the extended CP 203 is
`
`the same as the CP length defined for regular data transmissions if the invention
`
`is used for an OFDM system,. For other systems, the time duration of a regular
`
`CP is oflen chosen based on the excessive delay spread of the channels
`
`encountered in a deployment environment, which is also how the CP length is
`
`8
`
`

`
`CML0l942M
`
`determined for OFDM systems. Lastly, as described above,
`
`the appended
`
`“dead” interval is chosen according to the maximal timing delay,
`
`A ranging signal is allowed to be transmitted only in the defined ranging
`
`interval. The ranging waveform itself is constructed as an OFDM symbol, i.e.,
`
`by appending a CP of a certain length to a ranging signal. For convenience, we
`
`will use the tenn “waveform” to refer to, the CP-included signal and the tenn
`
`“signal” for the CP—excluded portion only. The ranging waveform transmission
`
`starts from what the SS detennines to be the right timing. For initial ranging
`
`users,
`
`that transmission point (i.e.,
`
`the transmission start time) will be the
`
`beginning of the dedicated ranging interval according to the base reference plus
`
`the one-way propagation delay. The initial ranging SS should send at that point
`
`a waveform whose CP portion is of the length of an extended CP. For other
`
`ranging SS’s that have already synchronized with the BS, the SS should have
`
`known the timing advance and transmit in advance to some reference point so
`
`that all the SS signals arrive at the BS at roughly the same time.
`
`In one
`
`embodiment, the non-initial ranging SS can either transmit a waveform with a
`
`regular CP at a timing point in advance to the start of 205 within 203 of FIG. 2,
`
`or transmit a waveform with an extended CP at a timing point in advance to the
`start of 203.
`
`With the above definition of ranging interval, all types of ranging signals
`
`will not interfere with any transmission that precedes and follows the ranging
`
`interval, such as OFDM symbols 207 and 208 in an OFDM-based example
`
`system. The maximum timing delay should be large enough to accommodate
`
`the maximum propagation delay for SSs that have not adjusted their timing (i.e.,
`
`initial ranging users). The maximum timing delay is a parameter determined
`
`based on the cell size. For the receiver processing at the BS, ‘since the BS
`
`predefines the maximum timing delay and thus the extended CP length, the BS
`
`should know how to adjust the sampling position accordingly in order to extract
`
`the special FFT window 209, The special FFT window can be any size in
`
`theory. A large special FFT window can reduce the proportion of the extended
`
`CF to the special FFT size (i.e., reducing the overhead) and provide more
`
`ranging opportunities to reduce collision.
`
`Also,
`
`the time span of the
`
`transmission can also be extended so that there will be more signal power
`
`arriving at the BS for the same average transmit power. However, with a large
`
`special F FT window, the overall overhead of a ranging signal as a portion of the
`
`uplink sub-frame increases and the ranging signal also becomes more
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`9
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`CML01942M
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`susceptible to channel time variations (e.g. mobility) that results in inter-carrier
`
`interference caused by Doppler shift. The choice of the special FFT size should
`
`also consider practical
`
`implementation. For example,
`
`in an OFDM system,
`
`making it an integer multiple of the regular FFT size may simplify the BS
`
`processing.
`
`The total ranging overhead, which is the ratio of the duration of the
`
`dedicated basic ranging interval to the entire uplink sub-frame, depends only on
`
`the uplink sub-frame. The longer the uplink, the lower is the overhead.
`
`If the
`
`overhead due to the “dead interval” 204 delay becomes too excessive, the “dead
`
`interval” 204 can be omitted at the price of generating inevitable interference to
`
`the next symbol.
`
`Referring to FIG. 3, a time-domain diagram shows an “extended”
`
`dedicated ranging interval 303 that is built upon the “basic” dedicated ranging
`
`interval 201, in accordance with some embodiments of the present invention. If
`
`more ranging opportunities are needed than what a basic ranging interval can
`
`provide, an extended ranging interval 303 can be defined where one or more
`
`regular OFDM symbols 301 and 302 with only a regular CP length may be
`
`added in front of the extended-CP special symbol.
`
`Initial ranging transmission
`
`is
`
`allowed only during the
`
`extended-CP interval, but other
`
`ranging
`
`transmissions are allowed everywhere. This design is an alternative to the case
`
`in which the special FFT size is enlarged, as described with reference to FIG. 2.
`
`Referring to FIG. 4, a frequency-domain diagram of a variation of the
`
`extended dedicated ranging interval
`
`is shown,
`
`in accordance with some
`
`embodiments of the present invention. In these embodiments, the ranging signal
`
`is allowed to occupy only a portion of the system bandwidth instead of the
`
`entire bandwidth as before. For example, for the extended-CP symbol 401 (that
`
`is the same as extended CP symbol 202 in FIG.2), a portion of the bandwidth
`
`402 is dedicated to ranging, and the remaining bandwidth 403 is for data traffic.
`
`In fact, such a design in which the ranging and data traffic are multiplexed can
`
`be done using different data/ranging ratios for each symbol
`
`in the extended
`
`ranging interval such as that illustrated in FIG. 4, where the additional regular
`
`OFDM symbols 404 and 405 are used. The generic term “frequency-time
`
`ranging zone” is used for these cases.
`
`Referring to FIG. 5, a time-domain diagram shows an exemplary
`
`ranging interval for an OFDM system similar to OFDM systems described by
`
`drafts and the published version of the IEEE 802.16 standard The ranging
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`CMLOl942M
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`interval 501 is composed of one special OFDMA symbol with an extended CP
`
`that may be preceded by up to four regular OFDMA symbols each having a
`
`regular CP for providing more ranging opportunities if needed. The duration of
`
`the extended CP is signaled by the base in a control message sent from the BS
`
`(e.g., the UL-MAP message defined in draft and published versions of IEEE
`
`802.16 standards) as an integer multiple of the regular CP. Similarly, the special
`
`FFT size of the extended-CP symbol, which may also be an integer multiple of
`
`the regular FFT size, is signaled in the control message as well.
`
`Immediately
`
`alter the special OFDMA symbol, there is a “dead” interval that equals to the
`
`largest maximum timing difference. But it may be omitted to trade performance
`
`degradation for overhead reduction. The control message may indicate whether
`
`the dead interval is included. The duration of the dead interval is implicitly
`
`known to the SS and is equal to the difference between the extended-CP symbol
`
`duration and the regular CP duration.
`
`Division of ranging opportunities in frequency, time, and code domains
`
`Referring to FIG. 6, a block diagram shows the division of ranging
`
`opportunities in frequency, time, and code domains, in accordance with some
`
`embodiments of the present invention. Each random access signal is generated
`
`based on a ranging sequence (interchangeable with “access sequence” and
`
`“ranging code” and “access code”) that is randomly chosen from a code group
`
`601 allocated to the sector (the code group size is denoted herein as Ne, an
`
`integer). The access sequences used in a code group and the allocation of code
`
`groups to different sectors are specified later. The ranging sequence may be
`
`used to generate an access signal by directly modulating the contiguous sub-
`
`carriers in a frequency block (sub-band) that is randomly chosen among Nb,
`
`sub-bands 602, wherein Nb. is an integer including the value “1” known to both
`
`BS and SS. Nb; may be determined based on the system bandwidth and be made
`
`known to the BS and the SS. The time-domain access signal is generated by
`
`perfomiing an IFFT on the ranging sequence afier modulating the chosen sub-
`
`band. Before a CP is inserted in front of the access signal to form a complete
`
`access wavefomi, the access signal may be cyclically (circularly) shified in time
`
`domain, where the shifi is chosen randomly among N5}, allowed values 603 that
`
`are known to the BS and SS, wherein N5}, is an integer. Lastly, a CP is added to
`
`form the final ranging waveform where the length of the Cl’ is that of the
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`CML01942M
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`extended CP for initial ranging and for other ranging, either the extended CP or
`
`the regular CP depending on the transmission point (discussed above). The
`
`duration of the waveform corresponds to the duration of one OFDM symbol in
`
`in embodiments such as those described with
`the extended ranging interval,
`reference to FIG. 3 and FIG. 5 In embodiments such as those described with
`
`reference to FIG. 5, the ranging sequence may be used to generate an access
`
`wavefonn by appending data symbols to the ranging sequence and directly
`
`modulating the contiguous sub-carriers in the frequency block (sub-band) that is
`
`randomly chosen, using terms of the appended ranging sequence.
`
`More detail on the division of ranging opportunities in frequency, time,
`
`and code domains is as follows. Firstly,
`
`in the frequency domain, an entire
`
`frequency band is divided into Nb, frequency blocks 602 (Nb. sub-bands with K
`
`sub-carriers in each sub-band). A ranging signal may occupy only one sub-
`
`band. The reason for dividing the bandwidth into orthogonal blocks is for better
`
`flexibility. First, the number of ranging opportunities can be made adjustable to
`
`the bandwidth: larger bandwidth systems need to provide more opportunities
`
`than narrower bandwidth systems
`
`for a similar collision rate. Second,
`
`transmitting on a narrow sub-band allows power boost on that band to achieve a
`
`decent uplink SNR, even though narrowband transmission has lower timing
`
`resolution than wider bandwidth transmission (Nb. channel taps will collapse
`
`into one channel tap when only 1/Nb. of the bandwidth is excited). On the other
`
`_ hand, the number of sub-carriers in each sub-band, which equals to the length of
`
`the ranging sequence code, affects the cross-correlation characteristics. For
`
`example, halving the number of sub-carriers in a sub-band allows a 3dB
`
`transmit power boost on that band, but the potential interference from other co-
`
`channel ranging codes also increases by 3dB. So the number of sub-carriers in
`a sub-band involves a tradeoff between SNR boost and interference sacrifice. In
`
`summary, the parameter Nb; is specified by the BS based on the bandwidth (FFT
`
`size), uplink SNR requirement,
`
`timing precision requirement, suppression
`
`capability to potential co-channel
`
`interferences, and the number of ranging
`
`opportunities that needs to be provided.
`
`It should also be specified jointly with
`
`the other two parameters.Nc and Nah described in more detail below.
`
`Secondly,
`
`in each sub-band, a number of ranging codes 601 (i.e., N.
`
`sequences) may be allowed. Since these ranging codes occupy the same band,
`
`they may interfere with each other even without any code collision. Sequences
`
`with good cross-correlation are much desired for better code detection and
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`12
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`CMDOI 942M
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`In addition, a low PAPR of the time-domain ranging
`channel estimation.
`wavefomi is also much desirable in order to be able to boost the transmission
`
`power to improve the uplink SNR. The details of the sequences that have these
`
`desirable properties will be discussed in the next section. Additionally, for
`
`cellular deployment, a number of sequence groups (each having NC access
`
`sequences) are also required for allocating to different neighboring sectors. So
`
`when those codes are generated and grouped, any pair of codes from distinct
`
`groups needs to have good cross correlation, just like any pair of codes in the
`
`same group.
`
`In summary, the parameter NC is determined by the BS based on
`
`the access needs and the maximally tolerable interference level at which the
`
`successful detection rate is still good.
`
`Thirdly, for each ranging code, N51, cyclic time shifts 603 of the time-
`
`domain ranging signal (phase rotation in frequency domain) can be used to
`
`further increase the number of ranging opportunities. Mathematically,
`
`the
`
`frequency domain sequence, after thefh shifi is
`S,»(k) = s (k)e'””’*"""’”‘",
`
`(1)
`
`where s(k) is the original (or 0"‘ shift) sequence, L is the CP length (regular or
`
`extended CP, depending on the type of ranging) and Npn is the F