9OZLLO
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`2960U.S.PTO60/759697 I
`dSNe702
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`Page 3 of 54
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`

`

`PATENT APPLICATION
`Attorney Docket No. CE15637R
`
`PREAMBLE SEQUENCING FOR RANDOM ACCESS CHANNEL
`IN A COMMUNICATION SYSTEM
`
`TECHNICAL FIELD OF THE INVENTION
`
`[001]
`
`This invention relates generally to communications and more
`
`particularly to use of a random access channel in a communication system.
`
`BACKGROUND OF THE INVENTION
`
`[002]
`
`Various communications protocols are known in the art. For example,
`
`the Third Generation Partnership Project (3GPP) has been working towards developing
`
`a numberofprotocols for use with a wireless communication path. The original scope
`
`of 3GPP wasto produceglobally applicable technical specifications and technical
`
`reports for a 3rd generation mobile system based on evolved Global System for Mobile
`
`communication (GSM)core networks andthe radio access technologies that they
`
`support, such as Evolved Universal Terrestrial Radio Access (EUTRA)including both
`
`Frequency Division Duplex (FDD)and TimeDivision Duplex (TDD) modes. 3GPP's
`
`scope was subsequently amendedto include the maintenance and development of GSM
`
`technical specifications and technical reports including evolved radio access
`
`technologies (e.g. General Packet Radio Service (GPRS) and EnhancedData rates for
`
`GSM Evolution (EDGE)).
`
`[003]
`
`Presently, EUTRA calls for a random access channel (RACH) protocol
`
`and in particular a physical random access procedure requiring reserved resources for
`
`RACH access. The RACH channelis used for initial access to the network as well as
`
`to transmit small to medium amountofcontrol information and data packets. This
`
`3GPP UMTSspecification permits an overall procedure that allows for various
`
`protocol/operational states to suit varying degrees of needed, anticipated, and/or desired
`
`operational activity for transmission of data packets. Unfortunately, for some desired
`
`applications using small of medium amounts of control information and data packets,
`
`the amountof data transmission activity appears to underutilize these reserved RACH
`
`resources, thereby wasting transmission resources.
`
`Page 4 of 54
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`

`

`PATENT APPLICATION
`Attorney Docket No. CE15637R
`
`[004]
`
`The RACH(random access channel)is essential for initial access to the
`
`network,for the transmission of control information and data packets. Theinitial
`
`access channelhas different names in different systems, such as RACHin the context
`
`of 3GPP,or ranging in the context of IEEE std. 802.16e. In this invention, we use
`
`RACHinits general sense to representthe initial access channel of communication
`
`systems.
`
`[005]
`
`It is desired that the RACHinclude a contention channel, fast acquisition
`
`of preamble, minimization ofinterference, minimum impact on other scheduled data
`
`transmission, and low data rate transmission for short data/control messages. Several
`
`optionsare available for multiplexing between the RACHand scheduled-based
`
`channels; Time Division Multiplexing (TDM), Frequency Division Multiplexing
`
`(FDM), and Code Division Multiplexing (CDM). However, in the 3GPP system
`
`problemsarise for multiplexing between RACHand scheduled-based channels using
`
`either TDM or FDM.In particular, TDM requires reservation of slots for RACH
`
`access, and FDM requires a frequency (subcarrier) reservation for RACHaccess. In
`
`either case, a resource reservationis allotted even if there are few RACH requests in the
`
`system, which withholds unused resources that adversely affect system capacity. CDM
`
`transmission, on the other hand, will generate interference to other uplink users.
`
`[006]
`
`To control interference generated by CDM transmission, a MC-CDMA
`
`(multi-carrier code division multiple access) technique can be applied for RACH design
`
`without reserving system resources. This invention uses this technique for non-
`
`reserved RACH access of EUTRA communication system.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`[007]
`
`The features of the present invention, which are believed to be novel, are
`
`set forth with particularity in the appended claims. The invention, together with further
`
`objects and advantages thereof, may best be understood by making reference to the
`
`following description, taken in conjunction with the accompanying drawings,in the
`
`several figures of which like reference numerals identify identical elements, wherein:
`
`Be
`
`Page 5 of 54
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`

`

`PATENT APPLICATION
`Attorney Docket No. CE15637R
`
`[008]
`
`(009)
`
`FIG. | illustrates a TDM/FDM RACHstructure;
`
`FIG. 2 is a table of RACH parametersforthe structure of FIG.1;
`
`[0010]
`
`FIG.3 is a graphical representation of a circular auto/cross correlation of
`
`a Chu-sequence with M=15, in accordance with the present invention;
`
`[0011]
`
`FIG.4 is a graphical representation of a correlation sequencein the
`
`presence of two RACHrequests with delays of 0 and 2, in accordance with the present
`
`invention;
`
`[0012]
`
`FIG.5 is a graphical representation of a detection error rate and false
`
`alarm performance of TDM-RACHover an AWGNchannel, in accordance with the
`
`present invention;
`
`[0013]
`
`FIG.6 is a graphical representation of a detection error rate and false
`
`alarm performance of TDM-RACHoveran TU channelat 3 kilometers/hour,in
`
`accordance with the present invention;
`
`[0014]
`
`FIG. 7 is a graph of an example of a RACH preamble,in accordance
`
`with the present invention;
`
`FIG.8 is a block diagram of RACHpreamble generation using time-
`[0015]
`domain modulation, in accordance with the present invention;
`
`FIG.9 is a block diagram of RACH preamble generation using
`[0016}
`frequency-domain modulation, in accordance with the present invention;
`
`[0017]
`
`FIG. 10 is a graphical representation of a circular auto/cross correlation
`
`of a Chu-sequence with M=300,in accordancewith the present invention;
`
`[0018]
`
`FIG. 11 is a graphical representation of RACHdetection error andfalse
`
`alarm performance over an AWGNchannel,in accordance with the present invention;
`
`3.
`
`Page 6 of 54
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`

`

`PATENT APPLICATION
`Attorney Docket No. CE15637R
`
`(0019)
`
`FIG. 12 is a graphical representation of RACHdetection error and false
`
`alarm performance over an TU channelat 3 kilometers/hour, in accordance with the
`
`present invention;
`
`[0020]
`
`FIG. 13 is a table showing a comparison of the TDM/FDM and
`
`hybrid/CDM embodiments ofthe present invention; and
`
`[0021]
`
`FIG. 14 comprises a flow diagram of a method, in accordance with the
`
`present invention; and
`
`[0022]
`
`FIG. 15 illustrates a block diagram of a communication system, in
`
`accordancewith the present invention.
`
`[0023]
`
`Skilled artisans will appreciate that commonbut well-understood
`
`elements that are useful or necessary in a commercially feasible embodimentare
`
`typically not depicted in orderto facilitate a less obstructed view of these various
`
`embodiments ofthe present invention.
`
`DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
`
`[0024]
`
`To minimize the performance impactto scheduled users, the present
`
`invention presents a hybrid approach to the RACH preamble in an EUTRA system.
`
`Specifically, the RACH preamble is transmitted in a CDM manner, while the message
`is either scheduled by the Node B in the same manneras weiltae transmission,
`contention based transmitted, or ACK based transmitted. With proper configuration of
`
`the preamble sequence, the amountof interference generated can be minimized.
`addition, the message portion is scheduled, whereby variable data rates can be |
`supported with no impactto other uplink users. Moreover, both TDM/FDM and
`
`In
`
`Hybrid/CDMtechniquescan be utilized as candidate RACH methods for EUTRA,as
`
`will be detailed below.
`
`[0025]
`
`A RACHpreamble can be sequenced using TDM/FDM.In this scheme
`
`a dedicated or special symbol is used for RACH. The RACH symbolcan be reserved
`
`every x frames(e.g. x = 1
`
`... 10) as shown in FIG. 1. The schemecanuseeither
`
`Page 7 of 54
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`

`

`PATENT APPLICATION
`Attorney Docket No. CE15637R
`
`localized or distributed mode. In the localized mode the subcarriers are divided into
`
`Nprg resource blocks with each resource block using a fixed numberof contiguous sub-
`
`carriers. Next, for each of the Neg resource blocks, a numberofsignature sequence
`
`groups are pre-defined so that every group consists of Ns signature sequences and
`
`different groups can be assigned to different neighboring sectors. Each group also
`
`consists of several cyclically shifted versions of the signature sequences (Ns; ). As
`
`such, the total number of RACH opportunities per DFT-SOFDM symbolis given by
`
`Nre*Ns* Nsu.
`
`[0026]
`
`As an example for5SMHz bandwidth,all 300 subcarriers are divided into
`
`twenty resource blocks with Ngp =20. A RACHsignature sequence occupiesfifteen
`
`subcarriers corresponding to 225kHz bandwidth, thus the length of a signature
`
`sequenceis fifteen. For the scalable bandwidth structure, the length of a signature
`
`sequenceis fixed to fifteen. The number of RACH opportunities thus varies according
`
`to different bandwidth deployments. Detailed numerology is shown in FIG.2 for a set
`
`of scalable bandwidth.
`
`[0027]
`
`Dividing the RACH opportunities into resource blocks provides the
`
`opportunity to take advantage of channel frequency selective characteristics to further
`
`improve the performance. The user equipment (UE) choosesthebestavailable
`
`resource blocks for RACHpreamble transmission based on information of the current
`
`frequencyselective nature of the channel.
`
`[0028]
`
`In general, the signature sequences are obtained from a constant
`
`amplitude zero autocorreleation (CAZAC) sequence, which include different “classes”
`
`of generalized chirp like (GCL) or Chu-sequences which are complex valued and have
`
`unit amplitude. The GCL/Chu sequencehas low crosscorrelationat all time lags
`
`which improvesthe detection performance. Asused herein, the CAZAC, Chu and
`
`GCLsequences can be used interchangeably.
`
`[0029]
`
`The numbers of RACH groupsfor different bandwidths are summarized
`
`in FIG. 2. The total RACH overhead is dependent on the reserved RACHaccessrate.
`
`;
`
`Page 8 of 54
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`

`

`PATENT APPLICATION
`Attorney Docket No. CE15637R
`
`For example,if the RACHaccessis reserved every 1 millisecond, the RACH overhead
`
`is 1/14=7.1%.
`
`[0030)
`
`Specific RACH preamble sequencing can be defined. Since the
`
`sequence length equals to fifteen, a Chu-sequence can be selected whichis defined as
`inl
`-j——pn(n41
`oH cant)
`
`, n=01,...,M-1
`
`8n =
`
`where M=15, andpis relatively prime to M. In this case, p = {1,2,4,7,8,11,13,14,...}.
`
`For a fixed p, the Chu-sequence is orthogonalto its time-shift. For a different p, Chu-
`
`sequences are not orthogonal.
`
`The circular autocorrelation and cross-correlation
`
`properties of a Chu sequence is shown in FIG. 3. FIG.3 shows that Chu sequence has
`
`optimal autocorrelation property, while its cross-correlation has relatively small value
`
`for different delays.
`
`[0031]
`
`If the preamble is detected at the Node-B, the Node-B sends an
`
`ACKnowledge. Upon detection of the ACKat the UE, the UE sends the message part
`
`in the next slot using the same resource block (RB) location which wasused to send the
`
`preamble. Asan alternative, if the system is lightly loaded the message can be
`
`scheduled as outlined below.
`
`[0032]
`
`In accordance with the present invention, a hybrid/CDM approachis
`
`used for the RACH preamble configuration. To minimize uplink interference, the
`
`RACHpreamble is designed to use time-frequency spreading with a long spreading
`
`factor. With this approach, no reservation of symbols and sub-carriers are required and
`uplink interference generated is minimal(e.g. 27.8dB reduction with a spreading gain
`
`of 600). In addition, a simple receiver structure with frequency domain processing can
`
`be used to process the preamble. The RACH preamble structure is summarized as
`
`follows: a) the preamble length is 1 millisecond using two 0.5 millisecond sub-frames;
`
`a total of 4200 chips excluding Cyclic Prefix length, b) frequency spreading with
`
`spreading factor M using a Chu-sequence (complex quadratic sequence), where M is
`
`the occupied sub-carriers excluding DC (direct current) component, c) time spreading
`
`with a Walsh sequenceof length two, d) signature sequences with combined spreading
`
`Page 9 of 54
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`

`

`PATENT APPLICATION
`Attorney Docket No. CE15637R
`
`factor 2xM out of whicha total of twenty are’used, and e) a repetition of seven is used
`
`to rate-match the preamble sequence length to one millisecond.
`
`[0033]
`
`given by
`
`The Chu-sequence (complex quadratic sequence) or GCL sequenceis
`
`(= apes
`zg, =ete M2 wath. eed
`
`and the delayed Chu-sequenceis given by
`
`Zan = &(n-10d)moam> 4 = 9%...9
`
`Note that the Chu-sequence is a special sequence of the GCL sequence class. Other
`GCL sequences can be applied as the signature sequence as well. For example, for
`even M,we candefine g, as
`
`iG-iGPan
`g,=e M2
`OM"
`
`| n=0.-+,M-1
`
`wherepis an integer relatively prime to M,andqis any integer.
`
`To provide temporal spreading, a Walsh sequence of length two is used; w=0, 1. The
`
`sequenceis given by
`
`w° = {+141}, w' = {+1-}
`
`To generate the twenty unique signature sequences, a sequence identifier s is first
`
`computed via s = 2 xd +k where d=0,...9 correspondsto the delay of the Chu-sequence.
`
`and k=0,/] is the index of the Walsh sequence. The resulting s-th RACH preamble
`
`signature sequence (with length 2M) is then given by
`
`P.=[wW Og, WSgnu]
`
`2 =0;.,M-1
`
`An example of the RACH preamble sequence is shown in FIG. 7.
`
`In this case, d=5,
`
`and k=1 with a resulting sequence index numberof eleven. The sequence P};, made up
`
`ofgs, and —gs,, (i.e. Walsh code {1,-1}) is then repeated seven timesin order to cover 1
`
`millisecond.
`
`,
`
`Page 10 of 54
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`

`

`PATENT APPLICATION
`Attorney Docket No. CE15637R
`
`[0034]
`
`To mitigate inter-cell interference of RACH channel, different Chu-
`
`sequences or GCL sequencescan beused fordifferent sectors/cells. A generalized
`
`Chu-sequenceis given by:
`
`g,=e “*?
`
`, n=1,...,M-1
`
`where p is chosen suchthat the greatest commondivisor ofp and M is 1. For example,
`
`when M = 300, and p represents the prime numbers {1,7,11,13,17,19,23,29,31,37,...}.
`
`Given a fixed p, the corresponding Chu-sequence is orthogonal whenit is shifted
`
`circularly. However, the sequences are not orthogonal for different p and behave as
`
`random sequences. Thus, by assigning different p to different sector/cell, inter-cell
`
`interference can be mitigated.
`
`[0035]
`
`RACHpreamble generation can be accomplished using either time-
`
`domain modulation (FIG.8) or frequency-domain generation (FIG. 9). In time-domain
`
`modulation, a message symbolis mixed with a frequency-spreading sequence as
`
`described herein in accordance with the present invention. The combinedsignal is then
`
`processed using time-spreading, followed by a Discrete Fourier Transform (DFT),
`
`mapping, Inverse Fast Fourier Transform (IFFT), and Cyclic Prefix (CP), as are known
`
`in the art. In frequency-domain modulationisfirst processed using time-spreading,
`
`whichis copied to multiple paths, as are knownin the art. These different paths are
`
`then mixed with frequency-spreading sequence as described herein in accordance with
`
`the present invention. The combined signals are then processed by an Inverse Fast
`
`Fourier Transform (IFFT), and Cyclic Prefix (CP), as are known in the art.
`
`[0036]
`
`Thecircular autocorrelation and crosscorrelation properties for M=300
`
`is shown in FIG. 10. This figure illustrates an optimal property ofcircular
`
`autocorrelation and goodcross correlation performance of Chu-sequence with length
`
`300. FIGs. 11 and 12 show the RACH preamble detection error rate and false alarm
`
`rate for AWGNandTU (typical urban) channel. The RACH preamble detection is
`
`outlined above. In this case, BW=5 MHz,corresponding to a Chu-sequenceof length
`
`300. Compared to the power requirement for data transmission,it is seen that the
`
`transmit power of the CDM RACHpreambleissignificantly less (20-30 dB lower) per
`
`Re
`
`Page 11 of 54
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`

`

`user. Asaresult, interference generated by the RACH preamble is expected to be
`
`PATENT APPLICATION
`Attorney Docket No. CE15637R
`
`insignificantfor lightly loaded system.
`
`[0037]
`
`The RACHpreambledetectionis similar to the detection algorithm of
`
`TDM/FDM-based RACHat a Node-B. The block-by-block detection utilizes
`
`frequency-domaincorrelation, which is suitable for Frequency Domain Equalization
`(FDE). There is no time-domain correlation needed, which makescalculationsless
`
`complex. For example, assume an UE randomly selects a RACH preamble sequence
`
`with sequence identifier number s. The 2M length RACH sequenceis
`P.=[WOSan Wi OBanel = 0,.4M =
`
`where s = 2xd +k. At
`
`the receiver side of Node-B,
`
`the received signal can be
`
`represented as
`
`Yn =X_ Oh, + Zn
`
`where @indicates circular convolution, h,
`
`is channel
`
`impulse response, z,
`
`is the
`
`channel noise, and x, is either w*(0)g,,, or w‘(l)gy.»-
`
`[6038]
`
`At the receiver the circular (periodic) correlation of sequence g, and
`
`yn.is computed. This yields
`
`] M-|
`
`=
`
`Cm = VM x Yn8(n-m)modM
`
`The correlation can be performedeither in time or frequency domain. Through some
`
`simple manipulations, the following is obtained
`
`Cr
`
`_| VMhy-s0a+2Zm k= 0
`-VMhp_304+2Z_ k=!
`
`>
`
`where the term z,,’ is the equivalent channel noise. Usually the channel maximum
`
`delay is assumedto beless than the length of cyclic prefix. Here, it is assumedthat the
`
`maximum channel delay is less than thirty signal chips.
`
`For SMHz bandwidth
`
`Page 12 of 54
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`PATENT APPLICATION
`Attorney Docket No. CE15637R
`
`deployment, the length of thirty chips using current E-UTRA numerology equals to
`
`6.67 microseconds.
`
`[0039]
`
`Since there are two Walsh sequence for k=0 and k=1, one can combine
`
`the nearby two blocks for both Walsh sequences. There are a total of fourteen blocks
`
`of which one 2M RACHsequenceuses two blocks. Two neighbor c,, are added to
`
`yield seven correlation sequences for k=0. For k=/, two neighborc,, are subtracted
`
`accordingly to yield another seven correlation sequences for k=/. In the next step, we
`detect the delay index d, so that the RACH sequenceidentifier numbers (s = 2d +k)
`
`can be obtained.
`
`[0040]
`
`From the correlation sequence c,,, when a RACH request with delay
`
`indexdis present, the channel impulse responsewill appear in the frame {30d,
`
`30d+30}, as illustrated in FIG. 4. The figure shows two RACH requests with sequence
`
`delay 0 and sequence delay 2. The correlation sequence c,, indicates corresponding
`
`channel impulse response at {0-30} and {60-90} regions. By detecting powerin
`
`different regions, one can thus detect the RACH preamble at the Node-B.
`
`[0041]
`
`It is possible to have a ML (maximum likelihood) optimal detection of
`
`the RACHrequestif the channel impulse response is known. However, usually such
`
`channel informationis not available to the receiver at the Node-B. A simple detection
`
`algorithm is the maximum powerdetection. When the maximum powerin a certain
`
`region is greater than a power threshold, a RACH request correspondingto that region
`
`is assumed.
`
`[0042]
`
`The detection algorithm hasthree steps. First, calculate average power
`
`of correlation sequence. This yields
`
`Thefinal step is to check whether the maximum poweris greater than a pre-defined
`
`powerthreshold ;,,,. Thus,
`
`-10-
`
`Page 13 of 54
`Page 13 of 54
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`

`PATENT APPLICATION
`Attorney Docket No. CE15637R
`
`Ya 2¥rq RACH request with delay d is present
`Ya <¥ry
`RACH request with delay d is absent ‘
`
`[0043]
`
`With the detected d, and its corresponding Walsh codeindexk,the
`
`RACHsequenceidentifier number s, can be obtained through s = 2d +k.
`
`[0044]
`
`The above technique detects the received powerbased oncorrelation of
`
`the received sequenceto all the possible sequences. The correlation can be carried out
`
`either in time or frequency domain. Once the detected poweris greater than a pre-
`
`defined powerthreshold, a RACH preamble is detected. Naturally, the choice of
`
`threshold determines detection performance. FIGs.5 and6 illustrate detection
`
`performance of the TDM/FDM RACHpreamble under AWGNand TU (typical urban)
`
`propagation channels, respectively. The following definitions were used in the
`
`performanceevaluation: a) false alarm refers to a scenario where a particular code was
`detected when nothing or a different code was transmitted, and b) detection error refers
`
`to when a particular code wastransmitted but not detected.
`
`[0045]
`
`To maximize capacity utilization in the uplink, there are three
`
`approaches for RACH message transmission. At first, RACH message transmission
`
`can be scheduled by the Node B ona time-frequency region reserved specifically for
`
`RACH messagetransmissions. These regions are fixed and known beforehandso as to
`
`minimize control message overhead. The frequency, size, and number of these RACH
`
`messagesregions will depend on system design and deploymentscenarios. Naturally,
`
`whenthere is no RACH messagetransmission, the Node B can schedule otherusers in
`
`these time-frequency regions. At the Node B, once the RACHpreamble is successfully
`
`received, a four-bit acknowledgement corresponding to the sequence numberis
`
`transmitted to the UE. This is done even when the UE maynotbe scheduled for some
`
`time to prevent the UE from transmitting the RACH preamble again. Subsequent to
`
`receiving an acknowledgement, the UE monitors the downlink control channel for a
`
`period of time for scheduling information in order to transmit the RACH message. Due
`
`to the use of micro-sleep mode, power consumption from monitoring the downlink
`
`control channel is not expected to be an issue. In addition, the UE may already need to
`
`monitor the downlink control channel for possible downlink data transmission.
`
`Pts
`
`Page 14 of 54
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`

`

`PATENT APPLICATION
`Attorney Docket No. CE15637R
`
`[0046]
`
`The second RACH messagetransmission approach can be contention
`
`based. Once UE receives ACK from Node-B for RACHaccess, UE sends the RACH
`
`messagein the predefined channel. Then UE can further monitor downlink control
`
`channel for further ACK information for the transmitted RACH message.
`
`[0047]
`
`The third RACH messagetransmission approach is ACK based. With
`
`this approach, a resource block for message transmission is reserved by Node-B once
`
`needed. The RACH ACKinformation indicates the readiness of the reserved channel.
`
`OnceUEreceives this ACK information, the RACH messageis sent in the reserved
`
`channel.
`
`[0048]
`
`FIG. 13 compares the RACH features between the TDM/FDMtechnique
`
`and the Hybrid/CDM embodimentsofthe present invention.
`
`[0049}
`
`Referring to FIG. 14, the present invention also provides a method for
`
`random channel access between a user equipment (UE) and a Node-B of a EUTRA
`
`communication system, as shown in FIG. 15, wherein the UE 1500 reserves and
`
`transmits information on the RACH channel 1516, and the Node-B1502 receives the
`
`information on the RACH channel. Howeverit should be recognized that the present
`
`invention is applicable to other systems including 3GPP, 3GPP2, and 802.16
`
`communication systems, and that the terms ‘user equipment’ can be used
`
`interchangeably with ‘mobile station’, and that ‘base station’, ‘BTS’ and ‘node-B’ can
`
`be used interchangeably, as are known in the art. The UE 1500 includesa transmitter
`
`1504, receiver 1506, and processor 1508 coupled thereto. The node-B 1502 also
`
`includesa transmitter 1510, receiver 1512, and processor 1514 coupled thereto.
`
`[0050]
`
`In a first step, the UE 1500 defines 1400 a plurality of spread sequences
`
`derived from a plurality of constant amplitude zero autocorrelation (CAZAC)
`
`sequences. Specifically, the sequences can be Chu-sequences or GCL sequences. In
`
`addition, the sequence may be delayed. The UE then combines 1402 the spread
`
`sequenceswith an orthogonalcode (e.g. Walsh code) to form extended spread
`
`sequences(signature sequences). In a next step, the UE selects 1404 one ofthe
`
`signature sequences, whichis used 1406 in a preamble fora RACH. Preferably, the
`
`-|2-
`
`Page 15 of 54
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`

`PATENT APPLICATION
`Attorney Docket No. CE15637R
`
`selection is randomly selected. However, the select sequence could be predefined or
`
`selected to reduce the possibility of interference.
`
`[0051]
`
`The UEthen determines an available RACHaccessslot and other
`
`transmission parameters. In a next step, the UE sets 1408 a transmission power. Ina
`
`next step, the UE transmits 1410 the RACH preamble usingthe selected slot, signature
`
`sequence, and power, and then monitors 1412 for a positive acquisition indicator
`
`(ACKnowledgement) from the node-B 1502. If no positive acquisition indicatoris
`
`detected, in a next step, the UE may wait 1414 for a period of time or the UE changes
`
`1416 transmission power with a new accessslot and a new randomlyselected signature
`
`until the maximum numberoftransmissions or maximum poweris reached.Ifpositive
`
`acquisition indicator is detected, in a next step, the UE sends 1418 RACH messageto
`
`Node-B. FIG. 16 illustrates the procedure of preamble detection in Node-B 1502.
`
`Node-B detects 1420 preamble until the preamble is detected 1422. Then the RACH
`
`ACKis sent 1424 to UE. The nextstep will be the RACH messagetransmission.
`
`[0052]
`
`There are three approaches for RACH message transmission. The
`
`details of message transmitting 1418 in UE and message receiving 1426 in Node-B will
`
`be illustrated in FIG. 17, 18, and 19.
`
`[0053]
`
`FIG. 17 is the method of schedule-based RACH messagetransmission.
`
`UE monitors 1430 the downlink control channelfor a fixed amountoftime to obtain
`
`1432 scheduling information for the RACH message. The Node-B can besignaled for
`
`RACH messagetransmission, and the RACH messagecan then be sent 1434 as
`
`scheduled. Node-B schedules 1436 RACH message transmission after the RACH ACK
`
`is sent. Node-B will receive 1438 RACH messageatits scheduled time and frequency.
`
`[0054]
`
`FIG. 18 is the method of contention-based RACH message transmission.
`
`UE sends 1440 the RACH message upon RACH ACKisreceived.
`
`In the next step, UE
`
`listens 1442 the downlink control channel for RACH message ACKto determine 1444
`
`whether the message is received by Node-B. Node-B will receive 1446 RACH
`
`messageafter the RACH ACKis sent. When the messageis received 1448, a RACH
`
`message ACK should be sent 1450.
`
`43:
`
`Page 16 of 54
`Page 16 of 54
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`

`PATENT APPLICATION
`Attorney Docket No. CE15637R
`
`[0055]
`
`FIG. 19 is ACK-based RACH message transmission approach. A
`
`RACH message channelis reserved. UE will wait 1452 for RACH MSG (message)
`
`ACKfrom Node-B for clear of RACH message channel. Once the channelis available,
`
`the RACH messageis sent 1454. Node-B monitors the availability of the RACH
`
`message channel. It will send 1456 MSG ACKand receive 1458 RACH messagein
`
`the nextstep.
`
`[0056]
`
`Advantageously, the present invention provides a CDM type of RACH
`
`with a MC-CDMAapproach in the EUTRA system. Thereis no reservation of time
`
`slots or sub-carriers involved, which results in zero RACH overhead. The present
`
`invention has the capability of working at very low transmitting power (L=600
`
`spreading gain), and any interference introduced in minimal(spreading gain L=600
`
`results in 27.8dB reduction). In addition, a simple receiver configuration can be used
`
`with frequency domain processing.
`
`[0057]
`
`The present invention provides the advantage of enhancing capacity of
`
`the E-UTRA system pursuantto the above embodiments. In particular, providing the
`
`RACHpreamble sequencing without the need for reserved RACH access resources
`
`enhancesthe peak rate of data transmission and can reducelatency issues for data
`
`transmissions. One can also expect to achieve higher sector and user packetcall
`
`throughput. Notwithstanding these benefits, these embodiments can be realized with
`
`only minimal changesto the relevant 3GPP, 3GPP, and 802.16 standards.
`
`[0058]
`
`It will be appreciated that the above description for clarity has described
`
`emb