Case 2:22-cv-11408-TGB ECF No. 10-2, PageID.58 Filed 07/20/22 Page 1 of 15
`
`Exhibit 1
`
`

`

`USOO8467366B2
`
`(12) United States Patent
`Li et al.
`
`(10) Patent No.:
`(45) Date of Patent:
`
`US 8.467,366 B2
`*Jun. 18, 2013
`
`(54) METHODS AND APPARATUS FOR RANDOM
`ACCESS IN MULTI-CARRIER
`COMMUNICATION SYSTEMS
`
`(58) Field of Classification Search
`USPC .......................................................... 37O/342
`See application file for complete search history.
`
`(75) Inventors: Xiaodong Li, Kirkland, WA (US); Titus
`Lo, Bellevue, WA (US); Kemin Li,
`Bellevue, WA (US); Haiming Huang,
`Bellevue, WA (US)
`Assignee: Neocific, Inc., Bellevue, WA (US)
`Notice:
`Subject to any disclaimer, the term of this
`patent is extended or adjusted under 35
`U.S.C. 154(b) by 149 days.
`This patent is Subject to a terminal dis
`claimer.
`
`(73)
`(*)
`
`(21)
`(22)
`(65)
`
`(63)
`
`(60)
`
`(51)
`
`(52)
`
`Appl. No.:
`
`Filed:
`
`13/205,579
`Aug. 8, 2011
`
`Prior Publication Data
`US 2011 FO292881 A1
`Dec. 1, 2011
`
`Related U.S. Application Data
`Continuation of application No. 10/583,158, filed as
`application No. PCT/US2005/008169 on Mar. 9,
`2005, now Pat. No. 7,995,967.
`Provisional application No. 60/551,589, filed on Mar.
`9, 2004.
`
`Int. C.
`H04Q 7/216
`U.S. C.
`USPC ........................................... 370/342; 370/329
`
`(2006.01)
`
`(56)
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`4,977,593. A 12/1990 Ballance et al.
`5,991.308 A 11/1999 Fuhrmann et al.
`6,519,449 B1
`2/2003 Zhang et al.
`7,995,967 B2
`8, 2011 Li et al.
`2010/011 1017 A1* 5, 2010 Um et al. ...................... 370,329
`
`KR
`KR
`KR
`
`FOREIGN PATENT DOCUMENTS
`2005OO15119 A
`2, 2005
`100.585233 B1
`5, 2006
`20060055636 A
`5, 2006
`
`OTHER PUBLICATIONS
`International Search Report and Written Opinion; International
`Patent Application No. PCT/US05/08169: Filed Mar. 9, 2005; Appli
`cant: Waltical Solutions, Inc.; Mailed Jun. 9, 2005: 9 pages.
`
`* cited by examiner
`Primary Examiner — Ajibola Akinyemi
`(74) Attorney, Agent, or Firm — Perkins Coie LLP
`(57)
`ABSTRACT
`Methods and apparatus in a multi-carrier cellular wireless
`network with random access improve receiving reliability
`and reduce interference of uplink signals of a random access,
`while improving the detection performance of a base station
`receiver by employing specifically configured ranging sig
`nals.
`
`24 Claims, 8 Drawing Sheets
`
`
`
`3D
`
`Case 2:22-cv-11408-TGB ECF No. 10-2, PageID.59 Filed 07/20/22 Page 2 of 15
`
`
`
`3.
`Base
`Station
`
`302
`
`

`

`Case 2:22-cv-11408-TGB ECF No. 10-2, PageID.60 Filed 07/20/22 Page 3 of 15
`
`

`

`U.S. Patent
`
`US 8.467,366 B2
`
`QUIL #' —“—* —* ——
`
`S?OIS
`
`Z 'OICH
`
`
`
`S?OIS QUIL
`
`
`
`Case 2:22-cv-11408-TGB ECF No. 10-2, PageID.61 Filed 07/20/22 Page 4 of 15
`
`@ Z
`
`SeuueuoqnS
`
`

`

`U.S. Patent
`
`Jun. 18, 2013
`
`Sheet 3 of 8
`
`US 8.467,366 B2
`
`
`
`£ (91 H.
`
`Case 2:22-cv-11408-TGB ECF No. 10-2, PageID.62 Filed 07/20/22 Page 5 of 15
`
`

`

`U.S. Patent
`
`Jun. 18, 2013
`
`Sheet 4 of 8
`
`US 8.467,366 B2
`
`
`
`Case 2:22-cv-11408-TGB ECF No. 10-2, PageID.63 Filed 07/20/22 Page 6 of 15
`
`

`

`Case 2:22-cv-11408-TGB ECF No. 10-2, PageID.64 Filed 07/20/22 Page 7 of 15
`
`

`

`U.S. Patent
`
`Jun. 18, 2013
`
`Sheet 6 of 8
`
`US 8.467,366 B2
`
`
`
`s
`
`Case 2:22-cv-11408-TGB ECF No. 10-2, PageID.65 Filed 07/20/22 Page 8 of 15
`
`

`

`U.S. Patent
`
`US 8.467,366 B2
`
`
`
`Case 2:22-cv-11408-TGB ECF No. 10-2, PageID.66 Filed 07/20/22 Page 9 of 15
`
`

`

`U.S. Patent
`
`Jun. 18, 2013
`
`Sheet 8 of 8
`
`US 8.467,366 B2
`
`
`
`Case 2:22-cv-11408-TGB ECF No. 10-2, PageID.67 Filed 07/20/22 Page 10 of 15
`
`8 "OICH
`
`

`

`US 8,467,366 B2
`
`1.
`METHODS AND APPARATUS FOR RANDOM
`ACCESS IN MULTI-CARRIER
`COMMUNICATION SYSTEMS
`
`CROSS-REFERENCE TO RELATED
`APPLICATION(S)
`
`This application is a continuation of U.S. patent applica
`tion Ser. No. 10/583,158, entitled “METHODS AND APPA
`10
`RATUS FOR RANDOMACCESS IN MULTI-CARRIER
`COMMUNICATION SYSTEMS, filed Aug. 27, 2008,
`which is a U.S. National Stage application of PCT/US05/
`08169, entitled “METHODSANDAPPARATUS FORRAN
`DOM ACCESS IN MULTI-CARRIER COMMUNICA
`15
`TION SYSTEMS, filed Mar. 9, 2005, which claims the
`benefit of U.S. Provisional Patent Application No. 60/551,
`589, entitled “METHODS AND APPARATUS FOR RAN
`DOM ACCESS IN MULTI-CARRIER COMMUNICA
`TION SYSTEMS, filed Mar. 9, 2004.
`
`BACKGROUND
`
`2
`FIG. 5 illustrates a case of time misalignment in a ranging
`signal, with a base station OFDM time frame, due to uncer
`tainty of a mobile station’s round trip delay at an initial stage
`of random access.
`FIG. 6 depicts a smeared spectrum of a subcarrier in a
`ranging subchannel when the ranging signal is received using
`a regular OFDM time frame.
`FIG. 7 illustrates a ranging sequence's corresponding
`time-domain signal that can be approximated with a binary
`Sequence.
`FIG. 8 shows a ranging Subchannel arrangement in which
`spacing between Subcarrier blocks in the frequency domain
`has no, or minimum, repetition.
`
`DETAILED DESCRIPTION
`
`In the following description, the invention is explained
`with respect to Some of its various embodiments, and pro
`vides specific details for a thorough understanding. However,
`one skilled in the art will understand that the invention may be
`practiced without such details. In other instances, well
`known structures and functions have not been shown or
`described in detail to avoid obscuring aspects of the embodi
`mentS.
`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 also include the plural or singular
`number respectively. Additionally, 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 of this application. When the
`claims use the word 'or' in reference to a list of two 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.
`The embodiments of this invention disclose methods and
`apparatus for random access in a multi-carrier system. In
`particular, ranging signals are designed to improve receiving
`reliability and to reduce interference with other uplink sig
`nals. Furthermore, methods and apparatus are described that
`improve the detection performance at the base station
`receiver.
`In a multi-carrier communication system Such as multi
`carrier code division multiple access (MC-CDMA) and
`orthogonal frequency division multiple access (OFDMA)
`systems, information data are multiplexed on Subcarriers that
`are mutually orthogonal in the frequency domain. In effect, a
`frequency selective channel is partitioned in frequency into a
`number of parallel, but Small, segments that can be treated as
`flat fading channels and can employ simple one-tap equaliz
`ers. The modulation/demodulation can be performed using
`the fast Fourier transform (FFT).
`In a multi-carrier communication system the physical
`media resource (e.g., radio or cable) 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. A basic structure of a multi-carrier signal in the frequency
`domain is made up of Subcarriers, and within a particular
`spectral band or channel there are a fixed number of subcar
`riers. There are three types of subcarriers:
`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
`
`In a wireless communication system, a mobile station first
`needs to perform a random access for establishing commu
`25
`nication with a base station. The random access typically
`includes two steps: (1) Ranging and (2) Resource Request and
`Allocation. During Ranging, the mobile station sends a signal
`to the base station, so that the base station can identify the
`mobile station and measure the power and time delay of the
`mobile station, and inform the mobile station for power
`adjustment and time advance. During Resource Request and
`Allocation, the uplink and downlink resources for communi
`cation are requested and allocated. Ranging is a critical part of
`multi-carrier wireless communication system, and there are
`several important issues related to ranging:
`1. The bandwidth efficiency of the ranging signals
`2. The interference of ranging signal with other uplink
`signals
`3. The detection performance and complexity at the base
`station receiver
`The ranging process typically involves an exchange of
`messages between the base station and the mobile station by
`which the mobile station aligns itself with the start of each
`time slot after compensating for propagation delay and other
`factors. One problem in a shared medium communication
`network involves the ranging of many mobile stations. When
`many mobile stations attempt to perform the ranging simul
`taneously, they are forced to contend for access to the shared
`channel and it becomes difficult for any of the mobile stations
`to complete the ranging process due to the large number of
`collisions. As a result, the time needed for all of the mobile
`stations to complete the ranging process is excessive, and
`much bandwidth on the shared channel is wasted.
`
`30
`
`40
`
`45
`
`50
`
`55
`
`Case 2:22-cv-11408-TGB ECF No. 10-2, PageID.68 Filed 07/20/22 Page 11 of 15
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`FIG. 1 depicts a basic structure of a multi-carrier signal in
`the frequency domain, made up of Subcarriers.
`FIG. 2 shows a radio resource divided into small units in
`both the frequency domain (subchannels) and the time
`domain (time slots).
`FIG.3 shows a cellular system with at least one cellandone
`base station.
`FIG. 4 depicts a ranging subchannel composed of at least
`one block of subcarriers.
`
`60
`
`65
`
`

`

`US 8,467,366 B2
`
`Case 2:22-cv-11408-TGB ECF No. 10-2, PageID.69 Filed 07/20/22 Page 12 of 15
`
`40
`
`45
`
`50
`
`55
`
`60
`
`65
`
`3
`are used for assisting system functions such as estima
`tion of system parameters; and
`3. Silent subcarriers, which have no energy and are used for
`guard-bands and DC carriers.
`The data Subcarriers can be arranged into groups called
`Subchannels to Support Scalability and multiple-access. The
`carriers forming one subchannel are not necessarily adjacent
`to each other. Each user may use part or all of the Subchannels.
`The concept is illustrated in FIG. 1 for the interleaved sub
`channels at the base station transmitter. Data Subcarriers can
`be grouped into subchannels in a particular way and the pilot
`subcarriers are also distributed over the entire channel in a
`particular way. The basic structure of a multi-carrier signal in
`the time domain is made up of time slots to Support multiple
`access. The resource division in both the frequency and time
`domains is depicted in FIG. 2.
`FIG. 3 illustrates a typical cellular structure. In this illus
`tration no distinction is made between a cell and a sector. If a
`cell is divided into sectors, from a system engineering point of
`view each sector can be considered a cell. In this context, the
`terms “cell' and “sector” are interchangeable. Both of them
`are generally called a cell. In the communication system of
`FIG. 3 Base Station 310 is communicating with Mobile Sta
`tions 301 and 302 in Sector A of its cell site while Base Station
`320 is communicating with Mobile Stations 303, 304, and
`305 in Sector B of its cell site.
`FIG. 4 illustrates two ranging subchannels, each of which
`is composed of multiple blocks of subcarriers. The subcarri
`ers in each block are contiguous in frequency. FIG. 4 sche
`matically shows that the signal power of the Subcarriers
`towards the boundary (the lower ends and the higher ends in
`frequency) of a block is lower than that of the subcarriers
`towards the center of the block. (In a special case, the power
`levels of the two subcarriers at both ends of a block are set to
`Zero.) Because different factors may cause possible overlap of
`two subcarrier blocks from to different transmitters, the
`attenuated boundary Subcarriers will minimize the resulting
`interference.
`In accordance with aspects of some embodiments, the
`ranging signal is carried over a ranging Subchannel that con
`tains multiple Subcarriers. Either binary or non-binary signals
`can be modulated on the Subcarriers of a ranging Subchannel.
`The sequence of modulating signals in a ranging subchan
`nel is called a ranging sequence. Multiple ranging sequences
`are permitted in a cell. A mobile station chooses a ranging
`sequence for random access and uses the sequence to identify
`itself in the initial communication with a base station. The
`period of a ranging signal is called a ranging slot. A ranging
`slot may last over one or multiple OFDM symbols. Multiple
`ranging slots can be provided to increase the random access
`opportunity and reduce the collision probability.
`In one embodiment, different cells may have different sub
`carrier configurations for their ranging Subchannels. Differ
`ent cells may also have different ranging sequence sets. These
`differences may be used to identify the association of a
`mobile station with a cell.
`FIG. 5 illustrates the timing of regular uplink data signals
`and ranging signals (with a Guard Period G.P.). In the begin
`ning of a random access attempt, the mobile station is
`unaware of its round-trip time to the base station. As a result,
`the arrival time of ranging signal at the base station may be
`misaligned with other signals which have been synchronized
`to the base station clock. As depicted in FIG. 5, the random
`access Ranging Signal does not coincide with the expected
`arrival time at the base station. As shown in FIG. 6, time
`misalignment of regular signals and ranging signals can cause
`spectrum of ranging signals to be Smeared when it is received
`
`5
`
`10
`
`15
`
`25
`
`30
`
`35
`
`4
`using the OFDM time window of regular signals. Therefore,
`misaligned Subcarriers within a ranging Subchannel will
`interfere with each other and with other data subchannels that
`are adjacent to them. In the following description, several
`methods are presented to address Such problems.
`In one embodiment, the ranging subchannel is composed
`of multiple blocks of subcarriers. The subcarriers in each
`block are contiguous in frequency. The signal power of the
`subcarriers towards the boundary (the lower ends and the
`higher ends in frequency) of a block is lower than that of the
`Subcarriers towards the center of the block. In a special case,
`the power levels of the two subcarriers at both ends of a block
`are Set to Zero.
`In yet another embodiment, each segment of a ranging
`sequence is a Hadamard sequence and a full ranging sequence
`is composed of multiple Hadamard sequences. Each segment
`corresponds to a block of contiguous Subcarriers. In Table 1,
`a typical example is shown for two ranging sequences. Each
`segment is a 4-bit Hadamard sequence and each ranging
`sequence is composed of 4 segments. The two ranging
`sequences are segment-wise orthogonal to each other.
`
`TABLE 1
`
`Example of ranging sequences
`
`Ranging +1-1+1-1
`Sequence
`1
`Ranging
`Sequence
`2
`
`+1+1+1+1
`
`+1+1+1+1
`
`+1+1-1-1 +1-1-1 +1
`
`+1-1-1 +1
`
`+1-1+1-1 +1+1-1-1
`
`In addition, other properties in signal processing can be
`exploited in sequence design. In one embodiment of the
`implementation, the ranging sequence is designed Such that
`its corresponding time-domain signal exhibits relatively low
`peak-to-average power ratio. This improves the power effi
`ciency of the mobile station transmission power amplifier.
`Furthermore, the ranging signal is designed such that the time
`signal can be approximated with a binary sequence (e.g., FIG.
`7), thereby reducing the complexity of the receiver correlator.
`While in theory, and even in practice, each modulating digit of
`a ranging sequence can represent a range of logic levels, a
`binary format is practically the simplest representation and
`requires the simplest receiver components for its processing.
`FIG. 7 illustrates a ranging sequence's corresponding time
`domain signal that can be approximated with a binary
`Sequence.
`In another embodiment, the blocks of a ranging Subchannel
`can be distributed or allocated in such a way that the autocor
`relation of a ranging sequence corresponding to the ranging
`Subchannel, in time-domain, exhibits a set of desired proper
`ties Such as a narrow main peak and low sidelobes. For
`example, the blocks can be distributed in the frequency band
`of interest Such that there is minimum redundancy in a co
`sampling function. In other words, spacing between the
`blocks of a ranging subchannel in the frequency domain has
`no or minimum repetition, as illustrated in FIG. 8, where the
`spacing consists of the set {d, 2d, 3d, 4d, 5d, 6d.
`FIG. 8 is merely an example of such possible arrange
`ments, where an autocorrelation process only produces one
`major peak, regardless of the ranging sequence carried by the
`ranging Subchannel blocks. During an autocorrelation pro
`cess, two copies of a ranging signal move in parallel with
`respect to each other, in a step-wise manner, and at each step
`the sum of the multiplication of their corresponding values is
`computed and recorded. Note that in an interval of a ranging
`
`

`

`US 8,467,366 B2
`
`5
`Subchannel where there are no Subcarriers, the ranging signal
`value is Zero. Therefore, employing the proposed arrange
`ments, at any step except for the step during which the two
`copies of the ranging signal are substantially aligned, most of
`the non-zero values of either copy will correspond to the Zero
`values of the other copy and the multiplication result of the
`corresponding values will be zero, which results in low side
`lobe values.
`With regard to controlling the power settings of a ranging
`signal, before a random access, a mobile station estimates the
`path loss from a base station, using the received downlink
`signal. It uses open-loop power control to set the power level
`of the ranging signal. In one embodiment, the mobile station
`adds a negative offset to the open-loop power setting and
`gradually ramps up the transmission power of the ranging
`signal as the number of random access failures and retrials
`increase.
`In one embodiment, the base station receiver detects the
`presence of each ranging signal, its time delay, and its power
`level through the use of a matched filter, a correlator, or other
`means in the time domain, the frequency domain, or both.
`In another embodiment, when the ranging Subchannel is
`composed of blocks of contiguous Subcarriers, the base sta
`tion performs hierarchical detection: first in frequency
`domain, then in time domain. The detection process is as
`follows:
`1. The FFT is applied to a selected window of the received
`time-domain signal, S(t).
`2. For a particular ranging subchannel, its received version,
`{r(k)}^, , is correlated in the frequency domain with
`the ranging sequences associated with the cell, in a seg
`ment-wise fashion, where K is the total number of
`blocks in a ranging subchannel. If the m” sequence
`associated with the cell is denoted by {b,(k)}^. , the
`correlation value, P, is computed by:
`
`5
`
`10
`
`15
`
`25
`
`30
`
`35
`
`Xs(t + t) : (i)
`C(t) =
`
`for t = 0, 1, ... , D
`
`where T denotes the length of the time-domain ranging
`sequence, D corresponds to the maximum time delay
`allowed by the system, and z*(t) represents the time
`domain signal of the detected ranging sequence. The
`maximum value of C(t) for t=0, 1,..., D is the estimate
`of the power of the ranging signal and the corresponding
`value of t indicates the time delay associated with the
`ranging signal.
`In the case of ranging sequences composed of Hadamard
`sequences, the dot-products of the received signal and the
`ranging sequence in a particular segment in Step 2 can be
`evaluated simultaneously using a single Fast Hadamard
`Transform (FHT), thereby simultaneously detecting multiple
`ranging sequences.
`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, are incorporated herein by reference. 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 embodiments 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.
`
`Case 2:22-cv-11408-TGB ECF No. 10-2, PageID.70 Filed 07/20/22 Page 13 of 15
`
`40
`
`45
`
`50
`
`55
`
`60
`
`65
`
`where the dot-product is computed by:
`
`W
`
`(r(k) b,(k) = Xxck, n) (c. (k, n)
`
`and where N denotes the number of subcarriers in a
`block, x(k,n) denotes the received version of the n”
`subcarrier of the k" block in the given ranging subchan
`nel, and c,(k,n) represents the value of then" subcarrier
`of the k" block in the given ranging subchannel for the
`m" sequence. It is noted that that both r(k) and b,(k)
`are vectors of the dimension same as the segment length.
`If P is greater than a given threshold, this indicates that
`a ranging signal corresponding to the m” sequence has
`been detected.
`3. For the ranging signal identified in Step 2, a time-domain
`correlation of the full sequence of the ranging signal is
`performed, in a sliding-window fashion, to find the time
`delay of that ranging signal, that is:
`
`

`

`We claim:
`1. In a multi-cell orthogonal frequency division multiple
`access (OFDMA) wireless communication system compris
`ing a plurality of base stations and mobile stations, a mobile
`station configured to communicate with a serving base station
`in a cell via a communication channel, the mobile station
`comprising:
`an apparatus configured to transmit a data signal to the
`serving base station in the cell over a data Subchannel,
`wherein the data subchannel comprises a plurality of
`adjacent or non-adjacent Subcarriers within the commu
`nication channel; and
`an apparatus configured to transmit a ranging signal to the
`serving base station in the cell over a ranging Subchannel
`for random access, wherein:
`the ranging signal is formed from a ranging sequence
`selected from a set of ranging sequences associated
`with the cell for identifying the mobile station;
`the ranging signal lasts over a period of one or multiple
`orthogonal frequency division multiplexing (OFDM)
`symbols and the ranging signal exhibits a low peak
`to-average power ratio in the time domain; and
`the ranging Subchannel comprises at least one block of
`Subcarriers within the communication channel and
`power levels of subcarriers at both ends of a block are
`Set to Zero.
`2. The mobile station of claim 1, wherein the subcarrier
`configuration of the ranging Subchannel for the cell is differ
`ent from Subcarrier configurations of ranging Subchannels for
`other cells.
`3. The mobile station of claim 1, wherein the set of ranging
`sequences for the cell is different from sets of ranging
`sequences for other cells.
`4. The mobile station of claim 1, wherein subcarriers in a
`block are contiguous in frequency.
`5. The mobile station of claim 1, further comprising an
`apparatus configured to control a transmission power of the
`ranging signal using an open-loop power control method by:
`estimating a path loss between the serving base station and
`the mobile station based on a received downlink signal;
`setting the transmission power of the ranging signal based
`on the path loss; and
`increasing the transmission power of the ranging signal for
`retransmission.
`6. The mobile station of claim 1, wherein a power level of
`45
`Subcarriers towards the high-end and low-end frequency
`boundaries of a block of subcarriers is lower than a power
`level of subcarriers towards the center of the block.
`7. The mobile station of claim 1, wherein boundary sub
`carriers of a block of Subcarriers in the ranging Subchannel are
`attenuated to reduce interference with other uplink signals
`when signal time misalignment occurs at the base station.
`8. The mobile station of claim 1, wherein the ranging
`sequence is a binary or non-binary sequence.
`9. In a multi-cell orthogonal frequency division multiple
`access (OFDMA) wireless communication system, a base
`station configured to communicate with mobile stations in a
`cell via a communication channel, the base station compris
`ing:
`an apparatus configured to receive a data signal from a first
`mobile station in the cell over a data subchannel,
`wherein the data subchannel comprises a plurality of
`adjacent or non-adjacent Subcarriers within the commu
`nication channel; and
`an apparatus configured to receive a ranging signal from a
`second mobile station in the cell over a ranging subchan
`nel for random access, wherein:
`
`55
`
`25
`
`30
`
`35
`
`40
`
`50
`
`60
`
`65
`
`US 8,467,366 B2
`
`7
`
`5
`
`10
`
`15
`
`8
`the ranging signal is formed from a ranging sequence
`selected from a set of ranging sequences associated
`with the cell for identifying a mobile station;
`the ranging signal lasts over a period of one or multiple
`orthogonal frequency division multiplexing (OFDM)
`symbols and the ranging signal exhibits a low peak
`to-average power ratio in the time domain; and
`the ranging Subchannel comprises at least one block of
`Subcarriers within the communication channel and
`power levels of subcarriers at both ends of a block are
`Set to Zero.
`10. The base station of claim 9, wherein the subcarrier
`configuration of the ranging Subchannel for the cell is differ
`ent from Subcarrier configurations of ranging subchannels for
`other cells.
`11. The base station of claim 9, wherein the set of ranging
`sequences for the cell is different from sets of ranging
`sequences for other cells.
`12. The base station of claim 9, further comprising an
`apparatus configured to detect the ranging sequence in the
`received ranging signal in the time domain, frequency
`domain, or both time and frequency domain.
`13. The base station of claim 12, wherein the apparatus
`applies matched filtering to the received ranging signal to
`detect the ranging sequence.
`14. The base station of claim 12, wherein the apparatus
`correlates the received ranging signal with a ranging
`sequence stored at the base station to detect the ranging
`Sequence.
`15. The base station of claim 9, further comprising an
`apparatus configured to detect a time delay of the received
`ranging signal and to inform the second mobile station to
`adjust transmission time based on the detected time delay.
`16. The base station of claim 9, further comprising an
`apparatus configured to detect a power level of the received
`ranging signal and to inform the second mobile station to
`adjust a transmission power based on the detected power
`level.
`17. In an orthogonal frequency division multiple access
`(OFDMA) wireless communication system, a method for
`signal transmission by a mobile station to a serving base
`station via a communication channel, the method comprising:
`transmitting a data signal over a data subchannel to the
`serving base station, wherein the data Subchannel com
`prises a plurality of adjacent or non-adjacent Subcarriers
`within the communication channel; and
`transmitting a ranging signal over a ranging Subchannel to
`the serving base station for random access, wherein:
`the ranging signal is formed from a ranging sequence
`selected from a set of ranging sequences for identify
`ing the mobile station;
`the ranging signal lasts over a period of one or multiple
`orthogonal frequency division multiplexing (OFDM)
`symbols and the ranging signal exhibits a low peak
`to-average power ratio in the time domain; and
`the ranging Subchannel comprises at least one block of
`Subcarriers within the communication channel and
`power levels of subcarriers at both ends of a block are
`Set to Zero.
`18. The method of claim 17, wherein a power level of
`Subcarriers towards the high-end and low-end frequency
`boundaries of a block of subcarriers is lower than a power
`level of subcarriers towards the center of the block.
`19. The method of claim 17, wherein boundary subcarriers
`of a block of subcarriers in the ranging subchannel are attenu
`ated to reduce interference with other uplink signals when
`signal time misalignment occurs at the base station.
`
`Case 2:22-cv-11408-TGB ECF No. 10-2, PageID.71 Filed 07/20/22 Page 14 of 15
`
`

`

`10
`the ranging signal is formed from a ranging sequence
`selected from a set of ranging sequences for identify
`ing the mobile station;
`the ranging signal lasts over a period of one or multiple
`orthogonal frequency division multiplexing (OFDM)
`symbols and the ranging signal exhibits a low peak
`to-average power ratio in the time domain; and
`the ranging Subchannel comprises at least one block of
`Subcarriers within the communication channel and
`power levels of subcarriers at both ends of a block are
`Set to Zero.
`23. The method of claim 22, further comprising detecting a
`time delay of the received ranging signal and informing the
`second mobile station to adjust transmission time based on
`the detected time delay.
`24. The method of claim 22, further comprising detecting a
`power level of the received ranging signal and informing the
`second mobile station to adjust a transmission power based on
`20 the detected power level.
`
`10
`
`15
`
`k
`
`k
`
`k
`
`k
`
`k
`
`US 8,467,366 B2
`
`9
`20. The method of claim 17, wherein subcarriers in a block
`are contiguous in frequency.
`21. The method of claim 17, further comprising controlling
`a transmission power of the ranging signal using an open-loop
`power control method by:
`estimating a path loss between the serving base station and
`the mobile station based on a received downlink signal;
`setting the transmission power of the ranging signal based
`on the path loss; and
`increasing the transmission power of the ranging signal for
`retransmission.
`22. In an orthogonal frequency division multiple access
`(OFDMA) wireless communication system, a method for
`receiving signals by a base station from a plurality of mobile
`stations via a communication channel, the method com