Title of Invention

SYSTEM AND METHOD OF ESTIMATING EARLIEST ARRIVAL OF CDMA FORWARD LINK SIGNALS

Abstract

A system and method for estimating the earliest signal arrival in a wireless communication system, is presented herein. In accordance with an embodiment of the invention, the system includes a base station that transmits a plurality of pilot signals and a mobile station configured to receive a plurality of signals corresponding to one of the transmitted pilot signals. The mobile station includes a receiver containing a searcher correlating mechanism and at least one finger correlating mechanism. The mobile station receiver detects the arrival times and energy levels of the received signals and constructs a searcher histogram and a finger histogram representing an arrival ti~e distribution of samples corresponding to the received signals. The mobile station then generates a delay index for each of the estimated early signal arrivals and forwards the delay indices to the base station or a position determination entity to select the minimum delay index corresponding to the earliest signal arrival.

Full Text

StfSTM-M AND rt!3?H0X» OF ESTIMATING EARLIEST ARRIVAL OF CW& FORWASD LEAK SIGNALS BACKGROUND OF THE INVENTION 1, Field of the Invention [0001] The present invention relates in general to wireless communications systems, and, in particular* to system and method for accurately estimating The earliest arrival of CDMA radio signals, either in the forward or reverse links. % Description of Related Art and GeneralJBackgromid [0002] Efforts are underway to augment wireless communications systems by adding; the capability to locate the position of a particular mobile station (MS). The Federal Communications Commission (FCC) has promulgated a regulation directed to this capability (Docket No. 94-102, third report and order adopted September 15, 1999, released October 6, 1999). This regulation requires wireless carriers adopting hand-held position location solutions to locate the position of a mobile station making an emergency 911 call to within 50 meters for 67% of calls (and to within 150 meters for 95% of calls) by October 2001, [0003] In satisfying this requirement, one approach to deiermining the position of a MS may be to use the available, information at the base stations (BSs) and MSs of a wireless eo::am.unication system, operating under Code Division Multiple Access (CDMA) schemes. CDMA is a digital radio-frequency (RF) channelization technique that is defined in the Telecommunications Industry Association/Elecrroracs Industries Association interim S synchronization by conducting a search through all pilot signal code phases of the same code. [i]006] A.si is well laiown, signal transmissions traveling across air interface UM nay be. subject 1:0 multipath propagation. As such, MS 110 may first receive a direct (he., line-of-sight (LOS)) signal corresponding to the forward link signal transmitted by BS ±06, followed by time-delayed arid attenuated versions of the same signal due t:o multipath. There may be situations where the first LOS signal is not received and only th'3 multipath components are present. MS 110 may determine the time of arrival (IX)A) and energy of all received pilot signals to identify the earliest useable received pilot signal. [0007] To determine the TO A of the received pilot signals, MS 110 may count and store the number of chips (or fractions thereof) of PN code sequences (i.e., PN chips) that laps 5 from a reference while the signals were received. MS 110 may then identify the earliest received pilot signal by detecting which pilot signal was received jifter the smallest number of lapsed FN chips. The reference (or zero arrival time) may in general b« txi arbitrary mark: because of this, isolated TOA measurements cannot be used directly in position determination algorithms. There is the need of at least two TOA measurements corresponding to pilots coming from different geographical points to overcome this arbitrary error. For instance, by subtracting said two measurements, we get a measurement proportional to the difference between the radial distances of the mobile 10 the two origins: the common error induced by the ambiguity in tlis 2ero timing falls out in the subtraction. [0008] To compensate for the effects of multipath propagation, CDMA systems, isuch as system 100, employ ralce receivers, which process and combine the direct and. multipath versions of the forward link pilot signal to generate a better received signal. FIG. 2 (Prior Art) depicts a high-level functional block diagram of a MS 110 receiver 2007 including a rake receiver demodulator 225 for coherently dessiodulsiing the forward link sigmils received by MS 110. As indicated in FIG. 2, the radi">frequency/digj.tal converter modulo205 downconveits and digitizes the received signal from the antenna/producing digital samples. The digital samples axe supplied to a ralce receiver demodulator 225, which includes a searcher 215. [('009] Searcher 215 is configured to search for signals by sweeping across the samples that are likely to contain multipath signal peaks in steps of one or half-PN C'dp increments. Se^cher 215 then assigns finger correlators 21GA-C to the stronger mi\ltipath signals. Each fingar correlator 210A-C locks onto their assigned multipath signal, coherently demodulates the signal, and continues to track the signal until the signal fides away or the finger correlator 210A-C is reassigned by searcher 215. The demodulated outputs of finger correlators 210A-C are then combined by combiner '.120 to form a stronger received signal. [0010] Gdven the ability to detect the TOA of forward link signals, CDMA systems may, ec least in theory, exploit these capabilities to extract MS 110 location information. As noted above, MS 110 is capable of determining the TOA of the . received niultipath components. [0011] As noted above, the promulgated'FCC regulation requires the location of a V;>S to witldn 50 meters for 67% of calls. A limitation of current CDMA systems is their inability to estimate TOAs with the necessary, resolution to comply with the location requirements. For example, counting lapsed PN sequences to within a tolerance of a PN chip to determine the earliest received pilot signal, is of no consequence in establisliing a communications link with the closest BS. However, given the tact 'that a PN chip corresponds to approximately SQOns,, which translates into a radial distance of 240 meters, such a tolerance clearly fails to comply with the location requirements, [0012] Furthermore, since the LOS signal may not be the strongest signal arriving at the receiver, isolating that first arriving signal will not be a trivial task. Note that using a multipath delayed signal for ranging information will have an inherent error due to the extra delay. [0013] Another limitation of current CDMA systems is the effect of time offset jittering on finger correlators of rake receivers. As noted above, the searcher in a MS rake receiver detects the strongest forward link receive signals and assigns a finger correlator to track and coherently demodulate one of the detected signals. However, clue to the resolution on the hardware, finger correlators may experience jitttir as they attempt to trade their assigned signal. The resolution of finger correlators a::; typically 1/8 of a PN chip, which translates to jittering jumps of approximately 24 rosters* Cumulatively, such effects may compromise the accuracy of the ranging information. i,"(!'()14] Accordingly, what is needed is a system and method capable of a-Muratttly estimating the earliest arrival of CDMA forward and reverse link signals. SUMMARY OF THE INVENTION 10015] 'Ihe present invention addresses the need identified above by providing a novel system and method capable of accurately estimating the earliest arrival of ■forward and reverse link CDMA signals. [0016] Although the description will be done for the forward link case where the receiver is fire mobile station and the transmitters ate the base stations, the method £.nd apparatus of the present invention apply the same in the reverse link case where the base station acts as receiver and the mobile station is the transmitter. [00171 System and methods consistent with the principles of the present invention a si embodied mid broadly described herein include a base station,, or group of base :;tatio:aii, that transmit a plurality of pilot signals and a mobile station configured to receive a plurality of signals corresponding to one of 'the transmitted pilot signals. The mobile station includes a receiver containing a searcher correlating mechanism and at least one finger correlating mechanism. For each different pilot signal, the mobile station receiver detects the arrival times and energy levels of the multipath signals corresponding to said pilot and constructs a searcher histogram and a finger histogram representing an arrival time distribution of samples. The mobile station rece:.ver -processes the: samples contained within searcher histogram and finger histogram to generate an estimate of the TOA for the first received multipath component of each pilot. At that point., the mobile station can choose to report all the results (or:.e per pilot) to another entity (base station , PDE ,...),or if it has xhe knowledge of which PN pilot sequences are transmitted from which base stations, further process 'the measurements, reporting only one measurement per base station, corresponding to the smallest TOA of the pilots belonging to that base station, BRIEF DESCRIPTION OF THE DRAWINGS [01)18] FIG. I (Prior Art) is a block diagram illustrating a conventional CDMA tireless, communication system. 10019] KG. 2 (Prior Art) is a block diagram depicting a conventional CDMA :r.ike receiver demodulator. [0-020] FIG. 3A is a flow-chart illustrating a process; for estimating the earliest iativaisi of CDMA signals, constructed and operative in accordance; with an embodiment of'."he present invention. [0021] HGs, 3B, 3C depict histograms generated by an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION [0022] The following detailed description refers to the accompanying drawings that illustrate embodiments of the present invention. Other embodiments are possible and modifications may be made to the embodiments without departing from the spirit and scope of the invention. Therefore, the following detailed description is not meant to limit the invention. Rather the scope of the invention is; defined by the appended claims. [002:5] It will be apparent to one of ordinary skill in the art that the embodiments as described below may be implemented in many different embodiments of software, firmware, and hardware in the entities illustrated in the figures. The actual software code or specialized control hardware u&ed to implement the present invention is not limiting of the present invention. Thus, the operation and behavior of the ^mbodirnentij will be; described without specific reference to the actual software coda or specialised hardware components. The absence of such specific; references is feasible because it is clearly understood that artisans of ordinary skill would be able to design software and control hardware to implement the embodiments of the present invention based on the description herein. [0024] Moreover, the processes associated with the presented embodiments may be stored in any storage device, such as, for example, non-volatile memory, an octical disk, magnetic tape, or magnetic disk. Furthermore* the processes, may be programmed when the system is manufactured or -via a computer-readable medium at a. later date. Snch a medium may include any of the forms listed above with respect to storage device and may further include, for example, a carrier wave modulated, or [0025] FIG- 3A is a high-level flow diagram illustrating process 300, constructed SJid operative in accordance with an embodiment of the present invention. M indicated in block B360, process 300 first establishes, at searcher 215 of MS rake receiver 200, threshold levels for the minimum energy of pilot signals (E^) to be proceed, the minimum number of samples occurring for any bin (Tmm) of a searcher histogram (to to* described below). Threshold levels E^, and Tmin will be used to discriminate, between pilot signals, reflected multipath signals, noise, etc. and axe» therefore, selected in a manner that ensures the processing of valid pilot signals. ■;;■■: [0026] In block B362, MS receiver 200 detects, for a particular BS (denoted BSj), the relative TOAi and energy level E; for each signal Pi received by searcher 213 of MS rak^ receiver 200. As noted above, each BSj may transmit up to 6 different pilot signals and for a given PN offset corresponding to a particular pilot signal, searcher 215 sweeps across samples corresponding to received signals in order to detect: signal p:&k3. For a given PN offset, searcher 215 may detect signal peaks that comprise a corresponding LOS pilot signal, reflected versions of the pilot signal, and noise. Upon detecting signal peaks, searcher 215 measures the peaks snd produces two values, oat indicating when the signal arrives (TOA), and one indicating the energy of thai: signal (E). As noted above, the calculation of TOA may be achieved by counting md storing the number of PN chips that lapse while each signal was received. [0027] In block £364, MS receiver 200 discards from further processing, any signal containing an energy level E that is less than threshold level Emia. By discarding signals with energy levels E less than E^, process 300 ensures that the TOA estimation is from a vaiid pilot signal. [0:)2S] Far each PN offset, MS receiver 200? in block B366, constructs a searcher histogram 390A for the undiscarded signals PM- Pn based on their corresponding TOAji/TOAn. As is well known, a histogram depicts the distribution (•:;' a collection of values over a predefined interval. In this case, searcher histogram li)0A is constructed by collecting samples of signals having signal strengths above ilireshold level E1Tlb over a starch period, corresponding to a particular PN offset For a 3Sj that transmits 3 pilot signals, MS receiver 200 may construct 3 separate searcher ;.istognuns 390A-390C. [O>029] An exemplary searcher histogram 390A for a particular PN offset is illustrated in FIG. 3B. The horizontal axis represents relative TO A** of an mdiscarded signal Pmi measured in bins (from earliest -38 to latesc 15.7), and the vertical axis represents the number of samples occurring at the relative TOAm. Generally, the stronger the signals, the higher the number of occurrences within the bins; weak signals will be discarded more often by the E^u threshold. Each bin is configured to represent a fraction of a PN chip, which depends on the resolution of the hardware. In gin exemplary implementation, a bin is equivalent to 1/8 of a PN chip. As indicated in HG. 3B, searcher histogram 390A contains three signal peaks A, B, C, as evidenced by three tans having the highest number of occurrences occurring at relative TOAs of -28, -16 ad -4. [0030] As noted above, for each PN offset, searcher 215 assigns a finger correlator 2"10A. to a signal to track and process the corresponding samples in order to demodulate the signal. After finger correlators 210A-210C have been assigned to the strongest signal peaks (e.g., peaks Av B, C) by searcher 215, MS receiver 2007 in block B36f>, coi:.stnxts a finger histogram 395A for all the assigned signals Pm-Pn. Much like searcher histogram 390, for a BSj transmitting thifce pilot signals, process 300 may conslnxr; three separate finger histograms 395A-395C [OOJ-1] An exemplary finger histogram 395A is shown in FIG. SC. Although fingsr histogram 395A is similarly constructed to searcher histogram 390A, it is to be noted that ar.ger histogram 395A depicts the distribution of the assigned signals Pm-Pn wiili a higher resolution than searcher histogram 390A. As such, finger histogram 395 is more accurate than searcher histogram 390A and may indicate groups of signal peaks 2.1 the finger conelaicrs 210A-210C track pilot signals Pm-Pn. These group signal psaks are symptomatic of the jittering effects noted above. As illustrated in KG. 3C, finger histogram 395A contains a first significant group of peaks A\ proximately disposed at relative TOA -28, a second significant group of peaks B\ proximately disposed at relative TOA -17,5, and a third significant group of peaks C\ proximately disposed at relative TOA -2.9, [0032] I::t block B370, MS receiver 200 locates the first bin in each of the searcher histograms 39OA-390C having the number of occurrences greater than or tsqual to Ttubi- By locating the first bin with a significant number of samples, process 300 m?oumi:«:JS the chances of identifying the earliest arriving pilot signals !Pfc for each "!?N offset [•0033] In block B372, MS receiver 200 constructs a narrow window around the first bir. in each of the searcher histograms 390A-390C as well as constructs a narrow window around the samples in each of the finger histograms 395A-395C that correspond to the first bins of the searcher histograms 390A-390C. The searcher histogram 390A-390C and finger histogram 395A-395C windows compensate for the differences in ihe resolution between searcher 215 and finger correlators 210A-210C, which ma}1 -«:«'ult in the timing misalignment of die signal. Such xnisidignment is indicated in HGs. 3B and 3C, where searcher histogram 390A demonstrates signal peafc; A, 13, C at respective TO As of -28, -16 and -4 while finger histogram 395 A demonstrates .signal group peaks A', B\ C? centered at respective TOAs of -28, -17.5, and-2.9. [0034] FIGs. 3B and 3C also depict the constructed windows for a single searcher histogram 390A and finger histogram 39:5A set. The windows may be centred &t a specific bin and have bin offsets equivalent to + a fraction of a PN chip (e.g., + V5 PN chip). For example, if the bins of the searcher histograms 390A-39OC and finger histograms 395A-395C represent 1/8 of a PN chip, the windows would span 4 bins on either side of the respective bins for a window resolution of ± Vz PN chip. [0035] In block B374, MS receiver 200 processes the sample information contained within each set of searcher histogram 390A-390C and finger histogram 3f>5A-395C windows to provide a timing estimate for each of the earliest arriving pilot signals P](C. In particular, tor ttch set of searcher histogram 390A-390C and finger histogram 395A-395C windows, process 300 combines and averages ail the samples contained within the respective windows to obtain an average TOA value (TOA_.mean0 fa; each of the earliest pilot signals P&. If finger histograms 395A- 335C do not contain samples corresponding to the first bins of searcher histograms . 390A-390C, MS receiver 200 simply combines and averages the samples contained within l.he searcher histograms 390A-390C window to produce TOAjrueanv- 10036] In block B37 the estimated earliest arriving pilot signals P* transmitted by BSj. For each of the earliest arriving pilot signals P^, delay index Dk provides a metric that accurately quantifies fc.e delay incurred by each signal. Delay index D^ is produced by subtracting a cotresponding proportionate standard deviation quantity from each of the TOA^mean-* values calculated, in'block B374- As is well known, the standard deviat-on is a quantity that measures the distribution (i.e., spread) of a collection of samples. Subtracting the standard deviation from TOAjnean^ minimizes the error arising from reflections, noise, or interference, thereby providing a more accurate estimation of the timing for each of the earliest arriving pilot signals P^. MS receiver 200 nay then forward the delay index D* information to BSj to determine the first pilot signal (Pi [0037] In block 3378, process 300 determines PF by selecting the minimum of the forwarded delay indices Bk (Dk,min) produced for each of the earliest .arriving pilot signitls Pic By definition, Dk,mm corresponds to the minimal delay incurred by any of the earlier, arriving pilot signsis Pk corresponding a given base station BS,. Therefore, by selecting Dkjnfe, process 300 identifies, tne first pilot signal Ppfrom all the earlier: ardving pilot signals F*. [il)D38] Became MS 110 may not possess a priori knowledge of which BSj is transmitting which PN offset, the selection of D^mi* may be performed by BSj, or an to&ocia:ed PDE sesrver (noted above), which has that knowledge. [(1039] Filially, in block B380, process 300 increments a counter and returns to block B362 to point to a new BSj+i in order to determine the earliest arriving pilot iiEgnal originating therefrom. If the mobile does not have the knowledge of which pilot signals correspond to which base stations, the process starting at BS62 would ';.3op across all pilot signals (instead of across all base stations) and the final step B378 will need to be performed somewhere else. 1.0040] The foregoing description of the preferred embodiments is provided to enable any person skilled in the art to make or use the present invention. Various :,nodificatior (; to these embodiments are possible, and the generic principles presented herein may be applied to other embodiments as well. For example, the invention may be implemented in part or in whole. a's a hardwired circuit, as a circuit configuration fabricated icao an application-specific integrated circaii:. or as a fiimware program ioadet: into non-volatile storage o.c a software program loaded from or into a data storage medium as machine-readable code, such code being instructions executable by an array of logic elements such as a microprocessor or other digital signal processing unit, [0041] As such, the present invention is not intended to be limited to the embodiments shown above but rather is to be accorded the widest scope consistent with :he principles and novel features disclosed in any fashion herein. WHAT IS CLAIMED 1. A method for estimating an earliest signal anival in a wireless communication .system comprising a base station and a mobile station, scad mobile station including a receiver containing a searcher correlating mechanism and at least one finger correlating mechanism, sad method comprising: detecting, in said mobile station receiver, arrival times tod energy levels of a oluralny of signals received by said mobile station, said plurality of received signals oorrespondmg to one of a plurality of pilot signals transmitted by said base -stations; constructing a seajcher histogram and a finger histogram associated with each of said pilot sisals based on samples corresponding to said received signals meeting z predetermined energy threshold level, each of said searcher histograms and finger idstograms representing an arrival time distribution of said signals; processing samples contained within each of said searcher histograms and said Snger histograns to generate a plurality of estimated early signal arrivals, each of said estimated ear!)' signal arrivals corresponding to one of said pilot signals; and determining the earliest signal anival per base station based on the earliest of said estimated early signal arrivals.. 2. Tfc method of Claim 1, further including identifying a first bin in each of said searcher histograms containing a number of samples greater than a predetermined threshold. ■ 3. 'TV, method of Claim 2=7 further including, constructing a searcher window around -said samples within each of said se:m:her histogram, first bins* and constructing a finger window around samples of each of said finger histograms corresponding to said samples contained within said searcher histogram first bins. 4-. Th.« rcethod of Claim 3, wherein said searcher windows and s^tid finger histogram windows are centered at a bin having an offset of ± a fraction of a PN clip. ;5. The method of Claim 4, wherein said processing samples includes, combining sad samples, contained within each of said searcher '^indovs unci saa-i finger windows, 6. The method of Claim 5, wherein said processing samples further includes, averaging said combined samples to generate an estimated early signal no-rival corresponding to one of said pilot signals. 7. The method of Claim 6, further including generating,a delay index for each ■rf said. estiwAtSul esrly signal arrivals. 8. The 'method of Claim 7, wherein each of said delay indexes is generated by subtracting a. corresponding proportionate standard deviation quantity from each of said estimated early signal arrivals, 9. The method o:: Claim 8, wherein said determining the earliest signal arrival per base station includes determining the minimum of said delay indices, which corresponds t:> the earliest signal arrival. 10. The method of Claim 9, wherein said mobile station forwards said delay indices to at. least one of said base station and a position determination entity to select said minirraux: delay index corresponding to the earliest signal arrival. 1L A system for estimating an earliest si glial arrival in a wireless communication system, comprising: a base station transmitting a plurality of pilot signals; and a mobile station configured to receive a plurality of signals corresponding, to one of said pilot signals, said mobile station including a receiver containing a searcher con-elating mechanism and at least one finger correlating mechanism, wherein said mobile station receiver detects arrival times and energy k vels of said received signals, constructs a searcher histogram and a finger histogram representing an arrival time distribution of samples corresponding to said received signals meeting a predetermined energy threshold level, processes said samples contained within each of said searcher histograms and said finger histograms to generate a. plurality of estimated early signal arrivals, and whersin the earliest signal arrival is deteiinined based on the earliest of said estimated early signal arrivals. 12, The system of Claim 11, wherein said mobile station receiver identifies a v:rst b:n in each of said searcher histograms containing a number of samples greater than a prederarained threshold. 13- The system of Claim 12, wherein said mobile station receiver constructs a searcher window around said sampJ.es within each of said searcher histogram first bins and constructs a finger window around samples of «ach of said finger histograms corresponding to said samples contained witliin said searcher histogram fiist bins. 14. The system of Claim 13, wherein said searcher windows and said finger histogram windows are centered at a bin having an offset of ± a fraction of a PN chip. 15. The system of Claim 14, wherein said mobile station receiver processes said samples by combining said samples contained within each of aaid searcher windows and said finger windows. 16. The system of Claim 15, wherein said mobile, station receiver further processes said samples by averaging said combined samples to generate an estimated ecily signal amvs.1 corresponding to one of said pilot signals. 17. The system of Claim 16, wherein said mobile station receiver generates a dslay index for each of said estimated early signal arrivals* 18. The system of Claim 17, wherein each of said delay indexes is generated l;y subtracting a corresponding proportionate standard deviation quantity from each of s aid est imated early signal arrivals. 19. The system of Claim 18, wherein said determining the earliest signal jclival include;? determining the minimum of said delay indices, which corresponds to •.lie earliest aignaJ arrival. 20. The system of Claim 19, wherein said mobile station forwards said delay indices to at least one of said base station and a position determination entity to select said minimum delay index corresponding to the earlaes: signal arrival. 21. A machine-readable medium encoded with a plurality of processor- executable instruction sequences for estimating an earliest signal arrival in a wireless communication system comprising a base station and a mobile station, said mobile station including a receiver containing a searcher correlating mechanism and at least one finger conflating mechanism, said instruction sequences comprising: detecting arrival times and energy levels of a plurality of signals received by said mobile station, said plurality of received signals corresponding to one of a plurality of pilot signals transmitted by said base station; constructing a searcher histogram and a finger histogram associated with each of s aid pilot signals based on samples corresponding to said rec ei ved signals mee:ing a. predetermined energy threshold level, each of said searcher histograms and finger histograms representing an arrival time distribution of said samples; processing samples contained within each of said searcher histograms a:;d said, finger histograms to generate a plurality of estimated early signal, arrivals, e*ch of said estimated early signal arrivals corresponding xo one of said pilot signals; and determining the earliest signal arrival based on the earliest of said oriiima-ied eaily *:,gnal arrivals.' 22. The machine-readable medium of Claim 21, further including identifying ;3 first bin in each of said searcher histograms containing a number of samples greater :han a piedexeardned threshold. 23. The machine-readable medium of Claim 22, further including, constructing a searcher window around said samples within each of j;aid searcher histogram first bins, and constructing a finger window around samples of each of said finger histograms corresponding to said samples contained within said searcher histogram first bins. 24. The xnachine-xeadable medium of Claim 23, wherein said searcher windows and md finger histogram windows are centered at a bin having an offset of ± a fraction of a FN chip. 25. The machine-readable medium of Claim 24, wherein said processing samples includes, combining said samples contained within each of said searches winc'ows and said finger windows. 26. The machine-readable medium of Claim 25, wherein said processing sannles farther includes, averaging said combined samples to generate an estimated early signal arrival corresponding to one of said pilot signals. 27- The machine-readable medium of Claim 26, further including generating a dt.£ay index for each of said estimated early signal arrivals. 28. The machine-readable medium of Claim 27, wherein each of said delay indexes is geaerited by subtracting a corresponding proportionate standard deviation' quantity from ea:h of said estimated early signal arrivals., 29. The machine-readable medium of Claim 28, wherein said determining the earliest: signal arrival includes determining the minimum of said delay indices, which corresponds to the earliest signal arrival. 30. The machine-readable medium of Claim 29, wherein said mobile station forwards said delay indices to at. least one of said base station and a position determination entity to select said minimum delay index corresponding to the earliest signal arrival. 31. A method for estimating an earliest signal arrival in a wireless communication system substantially as herein described with reference to the accompanying drawings. 32. A system for estimating an earliest signal arrival in a wireless communication system substantially as herein described with reference to the accompanying drawings.

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0154-chenp-2004 abstract duplicate.pdf

0154-chenp-2004 claims duplicate.pdf

0154-chenp-2004 description(complete)duplicate.pdf

0154-chenp-2004 drawings duplicate.pdf

154-chenp-2004-claims.pdf

154-chenp-2004-correspondnece-others.pdf

154-chenp-2004-correspondnece-po.pdf

154-chenp-2004-description(complete).pdf

154-chenp-2004-drawings.pdf

154-chenp-2004-form 1.pdf

154-chenp-2004-form 13.pdf

154-chenp-2004-form 3.pdf

154-chenp-2004-form 5.pdf

154-chenp-2004-pct.pdf