Title of Invention

METHOD AND APPARATUS FOR CANCELLING PILOT INTERFERENCE IN A WIRELESS COMMUNICATION SYSTEM

Abstract

The present invention relats ta tecqes for canceling pilot intrferene in a wIreless (e.g:CMDA) communIcatIon systenf. In one method, a receIved sIgnal comprised of a number of signal in'Stances, each including a pilot, is initially processed to provide data samples. Each signal instance's pilot spreading may be estimated by dispreading the data samples with a data to provide pilot symbols, filtering the pilot symbols to estimate the channel response of the signal instance, and ~}~ multiplying the estimated channel response with the spreading sequence to provide the estimated pilot interference. The pilot interference estimates due to all interfering multi paths are combined to deri,ve the total pilot interference, which is subtracted from the data samples to provide pilot-canceled data samples. These samples are then Iprocessed to derive demodulated data for each of at least one (desired) signal instance if) the received signal.

Full Text

METHOD AND APPARATUS FOR CANCELLING PILOT INTERFERENCE IN A TIRELESS COMMUNICATION SYSTEM [0001] This application claims the benefit of provisional U.S. Application Seri.il No. 60/296,259. entitled "METHOD AND APPARATUS FOR CANCELLATION OF MULTIPLE PILOT SIGNALS," filed June 6, 2001, which is incorporated herein by reference in its entirety for all purposes. BACKGROUND Field [0002] The present invention relates generally ta data communication, and mo:re specifically to techniques for canceling interference due to pilots in a wireless (e.g., CDMA; communication system. BachgrouT'l [00fl3] Wireless communication systems an; widely deployed to provide various types of communication such as voice, packet data, and so on. These systems may be based on code division multiple access (CDMA)f time division multiple access (TDMA), or some other multiple access technique. CDMA systems may provide ccxtdn advantages over other types of systems, including increased system capacity. A CDMA system is typically designed to implement one or more standards, such as IS -95, cdma20CO, IS-856, W-CDMA, and TS-CDMA standards, all of which are known in the art. [0004] In some wireless (e.g., CDMA) communication systems, a pilot may be transmitted from a transmitter unit (e.g., a terminal) to a receiver unit (e.g., a base station) tc assist the receiver unit perform a number of functions. For example, the pilot may be used at the receiver unit for synchrotization with the timing and frequency of che transmitter unit, estimation of the channel response and the quality of the communication channel, coherent demodulation of data transmission, and so on. The pilot is typically generated based on a known data pattern (e.g., a sequence of ii\ zeros) end using a known signal processing scheme (e.g., channelized with a particular channelization code and spread with a known spreading sequence). [00-05] Or the reverse link in a cdmo2000 sys:em, the spreading sequence for each terminal is generated based on (I) a complex, pseudo-random noise (PN) sequence cammon to all terminals and (2) a scrambling sequence specific to the terminal, b this way, the pilots from different terminals may be identified by their different spreading sequences. On the forward link in cdma2000 and IS-95 systems, each base station is assigned a specific offset of the PN sequence. In this way, the pilots from different base stations may be identified by their different assigned PN offsets. [0006] At the receiver unit, a rake receiver is often used to recover the transmitted plot, signaling, and traffic data from all transmitter units thai have established, communication with the receiver unit. A signal transmiued from a pariicuiar transmitter unit may be received at the receiver unit via multiple signal paths, anc each received signal ins:ar.ce (or multipath) of sufficient strength may be individually demodulated by the rake receiver. Each such multipath is pressed in a xuanoer complementary to that performed at the transmitter unit to recover the data and pilot received via this multipath. The recovered pilot has an amplitude and phase detetninec! by, and indicative of, the channel response for the multipath. The pilot is typically used for coherent demodulation of various types of data transmitted along with the pilu:, which are similarly distorted by the channel response. For each transmitter unit, the pilots for a number of multipass for the transmitter unit are also used to combine demodulated symbols derived from these muldpaths to obtain combined symbols having improved quality. [OO07J On the reverse link, the pilot from each transmitting terminal acts as interference to the signals from all other terminals. For each terminal, the aggregate intetference cue to the pilots transmitted by all other terminals may be a large percentage or' the total interference experienced by this terminal. This pilot interference can degrade performance (e.g., a higher packet error rate) and further reduce the reverse link capacity. [OO'08] There is therefore a need for techniques to cancel interference due to pilots in a wireless (e.g., CDMA) communication system. SUMMARY [0089] Aspects of the present invention provide techniques for estimating and canceling pilot interference in a wireless (e.g., CDMA) communication system. A received signal typically includes a number of signal instances (i.e., multipaths). For each multipath to be demodulated (i.e., each desired multipath), the pilots in all muJtipath;; are interference to the data in the desired multipath. If the pilot is generated based on a known data pattern (e.g., a sequence of all zeros) and channelized "ith a known channelization code (e.g., a Walsh code of zero), then the pilot in a:i interfering multipath it ay be estimated as simply a spreading sequence with a phiie corresponding to the arrival time of that multipath at the receiver unit. The pilot interference from each interfering multipath nay be estimated based on the spreading sequence and an estimate of the channel response of that multipath (which may be estimated based on the pilot). The total pilot interference due to a number of interfering nviltipaths may be derved and subtracted from the, received signal to provide a pilot-canceled signal having the pilot interference removed. [0010] In one specific embodiment, a method for canceling pilot interference a: a receiver unit (e.g., a base station) in a wireless (e.g., cdma2000) communication system is provided. In accordance with the method, & received signal conprised of a numocr or: signal instances, each of which includes a pilot, is initially processed to provide data samples. The data samples are then processed to derive an estimate of the f ilot interference due to each of one or more (interfering) signal instances, and the pilot interface estimates are further combined to derive the total pilot interference. The total pile. interference is then subtracted from the data samples to provide pilot-cancsled data samples, which are further processed to derive demodulated data for each of at least one (desired) signal instance in the received signal. 10011] The pilot interference due to each interfering signal instance may be estimated by (1) despread the data samples with a spreading sequence for the signal instance, (2) channelizing the despread samples with a pilot channelization code to provide pilot symbols, (3) filtering ihe pilot symbols to provide an estimated channel response of the signal instance, and (4) multiplying the spreading sequence for the siguid instance with the estimated channel response to provide the estimated pilot interfeiernce:. The: data demodulation for each desired multipath may be performed by (1) despreadirg the pilot-canceled data samples with the spreading sequence for the sigri;il instance, (2) channelizing the despread samples with a data channelization code to provide data symbols, and (3) demodulating the data symbols to provide the demodulated data for the signal instance. For improved performance, the pilot estimation and cancellation may be performed at a sample rate that is higher than the PN chip nits [0012] Viirious aspects, embodiments, and features of the invention are described in Urther detail below. BRIEF DESCRIPTION OF THE DRAWINGS [0013] The features, nature:, and advantages of the present invention will become more apparent from the detailed description set forth below when taken in conj motion with the drawings in which like reference characters identify com:spon±ngly throughout and wherein; [0014] FIG. 1 is a diagram of a wireless communication system; [0015] FIG. 2 is a simplified block diagram of an embodiment of a base station and a terminal; [0016] FIG. 3 is a block diagram of an embodiment of a modulator for the reverse litis, ix cdma2000; [0017] FIG. 4 is a block diagram of an embodiment of a rake receiver; [0018] FIG. 5 is a block diagram of a specific embodiment of a finger processor within the rake receiver, which is capable of estimating and canceling pilot interference in addition to performing data demodulation; [001*] FIGS. 6A and 6B are diagrams that graphically illustrate the processing; of the data samples to derive estimates of pilot interference, in accordance with a specific, implementation of the invention; [0020] FIG. 7 is a flow diagram of an embodiment of a process to derive the total pilot interference fo: a number of multipaths; arid [0021] FIG. 8 is a flow diagram of an embodiment of a process to data demodula^ i\ number of multipaths with pilot interference cancellation. DETAILED DESCMPTIQW [00.22] FIG. 1 is a diagram of a wireless communication system 100 that supports a number of osers and wherein various aspects and embodiments of the invention may be implemented. System 100 provides communication fur a number of cells, with each cell being serviced by a corresponding base station 104, A base station is also commonly referred i.o as a base-station transceiver system (BTS), an acc&is point, or a Node B. Various terminals 106 ars dispersed throughout the system. Each terminal 106 may communicate with one or more base stations 104 on the farwaid and reverse links at any given moment, depending on whether or no: the terminal i> active and whether or not it is in soft handoff. The forward link (i.e., downlink) refers to transmission from the base station to the terminal, and the reverse link [i.e., up-Lnk) refers to transmission from the terminal to the base statioi. [0023] A signal transmitted from a terminai may reach a base station via ore or nultiph signal paths. These signa! paths may include a straight path (e.g., signal path 110a) and reflected paths (e.g., signal path 110b). A reflected path is created when the ircxftoiitted signal is reflected off a reflection source and arrives at the base static>n via a different path than the line-of-sight path. The reflecdon sources are typically artifacts in the environment in which the terminal is operating (e.g., builcings, tiees, or some other strucrures). The signal received by each antenna at the base staticn may thus comprise a number of signal instances (or multipaths) from one or mote terminals. [002*1] In system 100, a system controller 102 (which is also often referred to as a base staton controller (BSC)) couples to base stations 104, provides coordination and control fee the base stations coupled to it, and further controls the routing of calls to fcrminals 106 via the coupled base stations. System controller 102 may further couple to u public switched telephone network (PSTN) via a mobile switching center (MSC), arc to a packet data network via a packet data serving node (PDSN), which are not stov-u in FIG. 1. System 100 may be designed to support one or more CDMA staiciards such as edma2030, IS-95, IS-S56., W-CDMA, TS-CDMA, some other CDMA standards, or a combinalion thereof. These CDMA standards are knov/n in he iirt and incorporated herein by reference. [0025] Various aspects and embodiments of the invention may be applied for the forward atd reverse links in various wireless communication systems. For clarity, the pilot interference cancellation techniques are specifically described for the reverse link in u oJma2000 system. [0025] FIG. 2 is a simplified block "diagram of an embodiment of base station 104 and luminal 106. On the reverse link, at terminal 106, a transmit (TX) data processor 214 receives various types of ^"traffic" such as user-specific data from a data source 212, messages, and so cm. TX data processor 214 then formats and codes the cifferent types of traffic based on one or more coding schemes to provide coded data. Eaci ceding scheme may include any combination of cyclic redundancy check (CRC), ccMivolutional, Turbo, block, and other coding, or no coding at all. Interleaving is commonly applied when error correcting codes are used to combat fading. Other coding scheme may include automatic repeat request (ARQ), hybrid ARQ, anc r.tremental redundancy repeat. Typically, different types of traffic are codad using different coding schemes. A modulator (MOD) 216 then receives pilot data and the coded data from TX data processor 214, and further processes the received data .o generate modulated data. [0027] FIG. 3 is a block diagram of an embodiment of a modulator 216a, which may be used for modulator 216 in FIG. 2. For the reverse link in cdma2000, the processing by modulator 216a includes covering the data for each of a number of cods channels (e.g., traffic, sync, paging, and pilot channels) with a respective Walsh cods, CCfo, by a multiplier 312 to channelize the user-specific data (packet data), messages fxntrol data), and pilot data onto their respective code channels. The channelized data for each code channel may be scaled with a respective gsrin, Gi$ by a unit 314 to control the relative transmit power of the code channels. The scaled data for all code channels for the inphase (I) path is then summed by a summer 316a to provide I-channel data, and the scaled data for all code channels for th * quadrature (Q) path is summed by a summer 316b to provide Q-channel data. 1007,81 FIG. 3 also shows an embodiment of a spreading sequen:e generator 320 for the reverse link in cdma2000. Within generator 320, a long code generator 322 receives a long code mask assigned to the terminal and generates a long pseudo-rancom ncrisi: (PN) sequence with a phase determined by the long code mask. The long PN sequence is then multiplied with an I-chanrel PN sequence by a multiplier 326a to generate an I spreading sequence. The long FN sequence is also delayed by a delay elemetii 324, multiplied with a Q-channel PN sequence by u multiplier 326b, decioaatec by a factor of two by element 328, and covered with a Walsh code (Cs - +-) and further spread witli the I spreading sequence by a multiplier 330 to generate a Q spreading sequence. The I-channel and Q-channel PN sequences form the complex short PN sequence used by all terminals. The I and Q spreading sequences form the complex spreading sequence, S*. that is specific to the terminal. [0029] Within modulator 216a, the I-channel data and the Q-channel data (Pet: +/E,:ii(£ ar* spread with the I and Q spreading sequences (Su + /Stq), via a complex multiply operation performed by a multiplier 340, to generate I spread data and Q spread data (D^i + jD^]. The complex despreading operation may be expressed as: [0030] (1) [0031] The I and Q spread data comprises the modulated data provided by mod llator 216a. [0032] The modulated data is then provided to a transmitter (TMTR) 2i8a and 3oadn*3ttttL Transmitter 218a is an embodiment of transmitter 218 in FIG. 2. The signa.. conditioning includes filtering the I and Q spread data with filters 352a and 352b, respectively, and upconvering the filtered I and Q data with cos(WcT) and sm(vct), respectively, by multipliers 354a and 354b. The I and Q components from multipliers 3-4a and 354b are then summed by a summer 356 and further amplified with a gain; G0, by a multiplier 358 to generate a reverse link modulated signal. 10033J Referring back to FIG. 2, the reverse link modulated sijjnal is then narimitted v:.a an antenna 220 and over a wireless communication link to one or mores base stations. [0034] At base station 104, the reverse link modulated signals from a number of ttnninuU aire received by each of one or more ar.tcnnas 250. Multiple antennas 250 may t>:s used to provide spatial diversity against deleterious path effect such as fading. As an example, for a base station that supports three sectors, two antennas may be used for each sector and the base station may then include six antennas. Any number of antennas may thus be err ployed at the base station. [0035] Each received signal is provided to a respective receiver (RCVR) 252, which conditions (e.g., filters, amplifies, downcor.vens) and digitizes the received sign;il to provide data samples for that received signal. Each receive signal may include one or more signal instances (i.e., multipaths) for each of a number of terminals. [0036] A demodulator (DEMOD) 254 then receives and processes the data samples for all received signals to provide recovered symbols. For cdraa2000, the procsssing by demodulator 254 to recover a data transmission from a particular terminal includes (I) despreading the data samples with the same spreading sequence used to spread the data, at the terminal, (2) channelizing the despread samples to isolate or chainelize the received data and pilot onto their respective code channels, and (3) coherently demodulating the channelized data with a recovered pilot to provide demodulated data. Demodulator 254 may implement a rake receiver that can process multiple signal instances lor each of a number of terminals, as described below. [0037] A receive (RX) data processor 256 then receives and decodes the dexnodula'£d data for each terminal to recover the user-specific data and messages transmitted by the terminal on the reverse link. The processing by demodulator 254 and l. [0038] FIG. 4 is a block diagram of an embodiment of 2 rake receiver 254a, which is capable of receiving and demodulating the reverse link modulated signals from a number of terminals 106. Rake receiver 25^a includes one or more (L) sample buffers 403, one or more (M) finger processors 410, a searcher 412, and a symbol combiner 420, The embodiment in FIG. 4 shows all finger processor 410 coupled to the same symbol combiner 420. [0039] Due to die multipart* environment, the reverse link modulated signal transmitter; from each terminal 106 may arrive at base station 104 via a number of signal paths (as shown in FIG. t), and the received signal for each base station antenna tjpically comprises a combination of different instances of the reverse link modilatcc signal from each of a number of terminals. Each signal instance (or multipart^ ir a received signal is typically associated with a particular magnitude, phas;, and arrival time (i.e., a time delay or time offset relative to CDMA system time). If :he diffidence between the arrival times of the raultipaths is more than one PN chip at the base station, then each received signal, yt(t), at the input to a respective receiver 252 may be expressed as: [0043] (2) [0041] where [0042] Xj(t) is the /-th reverse link modulated signal transmitted by the ;-th terminal; [0043] ttJl is the arrival time, at the Mh antenna, of the i-th multipart) relative to the time: rhej-tli reverse link modulated signal, xfe), is transmitted; [0044] PtjA*) represents the channel gain and. phase for the i-th multipart! for the;-th terminal at the I-th antenna, and is a function of the fading process; [0045] is the summation for all reverse link modulated signals in the /-th received s.&niJ; [0045] is ths summation for all multipass cf each reverse link modulated signd in the /-th received signal; and [0047] n(0 represents the real-valued channel noise at RF pus internal receiver noist: [0043] Each receiver 252 amplifies and frequency downconverts a respective received floral, y,(0» and further filters the signal with a received filter that is typically r.atched to the transmit filter (e.g., filter 352) ust:d at the terminal to provide a condition;d signal. Each receiver unit 252 then digitizes the conditioned signal to provide a respective stn;ara of data smnp!esy which is then provided to <. respective sample buffer> [0049] Each sample buffer 405 stores the received data samples and further prov.des the ?xoper dam samples to the appropriate processing units (e.g., finger proaissors 413 and/or searcher 412) at the appropriate time. In one design, each buffer 408 provides the data samples to a respective sst of finger processcrs assigned to prxess the multipaths in the received signal associated with the buffer. In another desijji, a number of buffers 408 provide data sample; (e.g., in a time division multiplexed manner) to a particular finger processor thai has the capability to process a number of multipaths in a time division multiplexed! manner. Sample buffers 408a through 4l)hl may also be implemented as a single buffer of the appropriate size and speed. . [0050] Searcher 412 is used to search for strong multipaths in the received signals asd to provide an indication of the strength and timing of each found mult path that meets a set of criteria. The search for multipaths of a particular terminal is typically performed by correlating the data samples for each received signal with ttis terminal's spreading sequence, locally generated at various chip or sub-chip offsets (or phases). Due to the pseudo-random nature of the spreading sequence, tin; correlation of the data samples with the spreading sequence should be low, excejv. when the phase of the locally-generated spreading sequence is time-aligned w» Ji :iat of a multipath, in which case the correlation results in a high value. [0051] For each reverse link modulated signal. JC;.(:)> searcher 412 may provide a sd of one or more time offsets, /(;i, for a set of one or more multipaths found for Ui&t reverse link modulated signal (possibly along with the signal strength of each fount multipath). The time offsets, tt Jf prcvided by searcher 412 are relative tc th;: baiie station timing or CDMA system time, and are related to the time offsets, f. f lf shown in equation (2) which are relative the time of signal transmission. [0052] Searcher 412 may be designed with ore or multiple searcher units, each of which rr.ay be designed to search for muldpaths over a respective search window. Each search window includes a range of spreading sequence phases to be searched. The searcher units may be operated in parallel to speed up the search operation. Additionally or alternati ve*y, searcher 412 may be operated at a high clock rate to speed up the search operation. Searcher and searcliing are described in further deta.1 in U.S. Patent Kos. 5,805,648, 5/781,543, 5,764,687, and 5,644,591, all of which are incorporated herein by reference. [0053] Each finger processor 410 nay then be assigned to process a respective te: of one or more multipaths of interest: (e.g., multipaths of sufficient strength, as diterrnined by controller 260 based on the signal strength information provided by searcher 412). Each finger processor 410 then receives, for each assif7)ed xnuitipath, the following: (1) the data samples for the received signal that includes ths assigned multipath, (2) either the time offset, titJJ, of die assigned multipath or a spreading sequence, StJJ, with a phase corresponding to the time offset, fu>, (which may be generated by a spreading sequence generator 414), and (3) the channulLzalion code (e.g., the Walsh code) for the code channel to be recovered. Each finger processor 410 then processes the received data samples and provides demodulated da& for each assigned multipath. The processing by finger processor 410 is described in further detail below. [0054] Symbol combiner 420 receives and combines the demodulated data (i.e., the demodulated symbols) lor each terminal. In particular, symbol combiner 420 receive; the demodulated symbols for all assigned muJtipaths for each terminal and, depending or. the design of the finger processors, may time-align (or tieskew) the symbols to account for differences in the time offsets for the assigned multipass. Symlwl combiner 420 then combines the time-aligned demodulated symbols for each terminal to provide recovered symbols for the terminal Multiple symbol combiners may be provided to concurrently combine symbols for multiple terminals- The recovered ?ytnbol.> for each termini axe then provided to RX data processor 256 and decoded [OOfii] The processing of tht inuJt:paths may oc performed based on various demcdulat:>r designs. In a first demodulator design, one finger processor is assigned to process *; -number of multipaths in a received signal. For this design, the data samples from the sample buffer may be processed in "segments" covering a particular time duration (i.e.. a particular number of PN chips) and starting at some defined time boundaries. In a second demodulator design, multiple fmger processors are assigned to process multiple multipaths in the received signd. Various aspects and erabcdime-irs of the invention are described for the first demodulator design. [00£(i] The pilot interference cancellation may also be performed based on various sctirmes. In a first pilot interference cancellation scheme that is based on the first iiemodulator design, the channel response of a particular multipath is estimated based on a segment of data samples. and the estimated chiinnel response is then used to derive ar. tstiin&te of the pilot interference due to this multipath for the same segmsnt This scheme may provide improved pilot interference cancellation. However, this scheme also introduces additional processing delays in the data demcdulatoo for the multipath since the segment of data samples is first processed to estimate and cancel the pCot interference before the data demodulation can proceed on the sam? segment [005^] In a second pilot interference cancellation scheme that is also based on the first demodulator design, the channel response of a particular multipath is estimated baaed on a segment of data samples, and the estimated channel response is then used to derive an estimate of he pilot interference due to this multipath for the next segment. This scheme may be used to reduce (or possibly eliminate) the addiional processing delays in the data demodulation resulting from the pilot interference ^stxmation and cancellation. However, since the link conditions may contnually change over time, the time delay between die current and next segments should be k-;:pt sufficiently short such that the channel response estimate for the current segment is still accurate in tie next segment. For clarity, the pilot interference estimation and cancellation are descrited below for the second scheme. [00:58] FIG. 5 is a block diagram of a specific embodiment of a finger processor 410x, which is capable of estimating and canceling pilot interference in addiion b: performing the data demodulation. Finger processor 4t0x may be used for each finger processor 410 in rake receiver 254a shown in FIG. 4. In the following description,, FIG. 5 shows the processing elements and FIGS. 6A and 6B graphically show the timing for the pilot interference estimation and cancellation. [0059] Finger processor 4I0x is assigned to demodulate one or more "de.$ red" multipaths in a particular received signal. Sample buffer 408x stores data samples for :he received signal that includes the multipaths assigned to finger processor 41 Ox. Buffer 408x then provides the appropriate data samples (in segments) to "ht finger processor when and as they are needed. In the embodiment shown in FIG, 5, finger processor 410x includes a resarnpler 522, a pilot estimator 520 ^or channel estimator), a summer 542, a data demodulation unit 550, and a pilot interference estimator 530. [0069] For each desired multipath to be demodulated by finger processor 410*, the data in all other multipaths and the pilots in al! multipaths in the same received signal act as in:erference to this multipath. Since the pilot is generated based on a knov/i; data pattern (e.g., typically a sequence of all zeros) and processed in a knov™ manner, the pilots in the "interfering" multipaths may be estimated and removed from the desired multipath to improve the signal quality of the data comj)onent in the desired multipath. Finger processor 410x is capable of estimating and canceling the pilot interference due to a number of multipaths found in the received signal, including the pilot of the desired multipath, as described below. [0061] In an embodiment, the pilot interference estimation and cancellation and the ca'a demodulation are performed in "bursts". For each burst (i.e., each procsssin*; cycle;, a segment o: data samples for a particular number PN chips are processed to rotiraate the pilot interference due to a particular multipath. In a specific embodiment, each segment comprises data samples for one symbol period, which may be 64 PN chips for cdma2000. However, other segment sizes may also be used (e.g., for cla^i symbols of other durations), and this is within the scope of the invention. As described below, the data demodulation may be performed in parallel and in a p penned manner with the pilot interference estimation to increase processing throughput and possibly reduce the overall processing time. [0062] Tc derive an estimate of the pilot interference due to the m-th multipath {where m = w, j\ I) arid is the notation for the i-th multipath for the j-th tevo-se link nodulated signal fourd in the 2-th received signal), a segment of data samples is initially provided from buffer 408x to a resampler 522 within finger processor 410x. Resarnplcr 522 may then perform decimation, interpolation, or a combination thereof, to provide decimated data sample:; at the chip rate aid with the proper "tint-grain" timing phase. [0063] FIG. 6A graphically illustrates an embodiment of the resampling performed by resampkr 522. The received signal is typically oversampled at a sample rale that is multiple (e.g., 2,4, or 8) times the chip rate to provide higher time resolution The data samples are stored to sample burfer 408x, which thereafter prov.des a segment of (e.g., 512) data samples for each processing cycle. Resampler 522 Jiien '"resamples" the data samples received from buffer 408x to provide samples at the chip rate and with the proper timing phase. [0061] As shown in FIG. 6A, if the received signal is sufficiently oventampleii (e.g., at 8 times the chip rate), then the resampling for the m-multipath may be perforated by providing every, e.g., 8-th data sample received from the buffer, with the selected data samples being the ones most closely aligned to the timing of the peak cf ths m-th multipath. The m-th multipath is typically a multipath assigned for data demodulation, and the multipath's time offs3t, tm, may be determined and provided by searcher 412. However, pilot interference due to multipaths that are not asst;jned fcr iiate demodulation may also be estimated aid canceled, so long as the tircit offsc: of each such multipa:h is known. Each multipath's time offset, rw, may be ^iewei &> comprising an integer number of symbol periods and a fractional portion of a symbol period (i.e., tm =fMffli ■»*t/r((r or CDMA system time, where a symbol period is clelermincd by the length of the charmelizattcn cede (e.g., 64 PN chips for cdrna2(XX)). The fractional part of the time offset, tfrcn may ^ u;'ei*t0 select the particular segment of data samples to provide to re samp kr 522 and for decimation. In the example shown in FIG. 6A, the fractional part of the: time offset for the m-th multipath is tJnicm •= 5, data sample segment 622 is provided by buffer 408;;, and the decimated data samples provided by renampler 522 are iepres:nted by the shaded boxer.. [0065] For some other receiver design in whi:h the received signal is not sufficiently ovenampled. then interpolation may alternatively or additionally be performed along with decimation to derive new samples at the proper timing phase, as is known in the art. [0066] Within pilot estimator 520, a despreader 524 receives the decimated data samples md a (complex-conjugate) spreading sequence, Sm*(k), having a phase cormspondin =, to the time offset, tm, of the m-th multipath whose pilot interference is to b: estimated. The spreading sequence, Sm\k), may be provided by spreading sequence generator 414. For the reverse link in cdna2000, the spreading sequence, Sn*(k), may be generated as shown for spreading sequence generator 320 in FIG. 3. And as shown in FIG. 6A, a segment of the spreading sequence, Sm\k), of the same lengvh and with the same timing phase as the data sample segment is used for the despreading (i.e., the spreading sequence, Sm*{k) is time-aligned with the decimated data samples'). [0067] Despreader 524 (which may be implemenied as a complex multiplier such as multiplier 340 shown in FIG. 3) despreads the decimated data samples with die spreading sequence, Sm*(k)7 and provides despread samples. A pilot channelizer 526 :hen multiplies the despread samples with the channelization code, Cpiioi^, used for the p.i M at the terminal (s.g, a Walsh code of ::ero for cdma2000). The decovered pibt samples are then accumulated over a particular accumulation time interval to provide pilot symbols. The accumulation time interval is typically an integer multiple of the pilot channelization code length. If the pilot data is covered with a channelization cede of zero (as in cdrou2000), thtr the multiplication with the channclizaitcn code, Cp(7c,ffl, may be omitted and pilot channelizer 526 simply performs the accumulation of the despread samples from despreader 524. In a spec fie embodiment, one pilot symbol is provided for each segment, which has a size of one synbel period. [006SJ The pilot symbols from pilot channelizer 526 are then provided to a pilot filtei '525 and filtered based on a particular lowpass filter response to remove noise:. Pilo: Titer 528 may be implemented as a finite impulse response filter (FIR), an infinite impulse response (HR) filter, or some other filter structure. Pilot filter 528 provides pi.."o: estimates, Pm(k) , which are indicative of the channel respor.se (i.e., the gain and plia-e, am *eJOm) of the m-th oiultipadi. Each pilot estimate, Pm0'c), is thus a complex vahs. The piJot estimates are provided at sufficient rate such that non-insigaific£jit changes in the channel response of the raultipath are captured and reported. In a specific embodiment, one pilot estimate is provided for each segment, which has a sue of one symbol. [0 due to the m-tli maltipath for the next segment. To estimate the pilot interference, the pilot data arid the pilot channelization code, CpterW, for the m-th maltipath are provided to £ pilot channelizer 532, wliich channelizes the pilot data with the pilot channelization code to provide channelized pilot data. A. spreader 534 then receives and spreads the channelized pilot data with a spreading sequence, Sm(k + N), to generate spresid pilot data (i.eM processed pilot data). The spreading sequence, Sm(k -f N), has a phase corresponding to the time offset, tmJ of the m-th interfering multpath and is further advanced by N PN chips for the next segment, as shown in FIG. 6A. If the pilot data is a sequence of all zeros and the pilot channelization code is also a sequence of all zeros (a> in cdma2000)> then pilot channelizer 532 and spreader 534 may be omitted and the spread pilot, data is simply ths spreading sequence, ■!'„,(&+ N). [OO70J A maltiplier 536 then receives and multiplies the spread pilot data with the pilot estimates, Pm(k), from pilot filter 528 to prov:.de EJI estimate of the pilot interference, Ipilaltm (k + N), due to the m-th multipath for the next segment. Since the pilot estimsit;;*, PM(k), are derived from the current segment and used to derive the estimated pilot interference for the next segment, prediction techniques may be used to derive pilot predictions for the next segment based on the pilot estimates. These pilot predictions may then be used to derive the estimated pilot interference for the next segment. {0071] In an embodiment, multiplier 536 provides the estimated pilot interference due to the m-th multipath at the sample rate (e.g., Sx the chip rate) and with the lining phase of the m-th multipath. This allows the estimated pilot interferences for all multipaths (wliich have different time offsets that ere typically not «dl aliened to the PN chip timing boundaries) to be accumulated at a higher time resolution. The estimated pilot interference, /^^(fc + N), for the /n-di multipath, which induces the same number of interference samples as for the data sample segment, is t!ien provided to an interference accumulator 538. As shown in FIG. 6A, the interference samples for the /n-th multipath are stored (or accumulated with the interference samples already stored) at locations in the accumulator determined by the fractional part of the multipathfs time offset. [0072] Tc derivs the total pilot interference for all multipaths in a given received signal, the processing described above may bs iterated a number of times, one iterat.cn or processing cycle for each interfering multipath for which the pilot interference is to be estimated and canceled from a desired multipath. The pilot interference cancellation is typically performed for the multipaths received via the same antenna, not cross antennas, because the channel estimate from one antenna is typically net good for another antenna. If the same finger processor hardware is used for multiple iterations, then the processing may be performed in bursts, with each ban.* being performed on a respective segment of data samples determined by the mult path's fractional tine offset. [0071] Prior to "he first iteration, accumulator 538 is cleared or reset. For each iteration, the estimated pilot interference, / W|W, das to the current multipath is accumulated with the accumulated pilot interference for all prior-processed mulLpaths. However, as shown in FIG. 6A, the estimated pilot interference, IpSgt^m, is accumilited with simples in a specific section of accumulator 538, which is deteimined by the current multipass time offset. After all interfering multipaths have been processed, the accumulated pilot interference in accumulator 538 comprises die total pilot interference, I iat, due to all processed multipaths. [0074] PIG. 6A also shows an embodiment of accumulator 538. While finger processor segment (using the total pilot interference, lpilot{k), cerived earlier and stored in one section of accumulator 538), the pilot interferenc2 due to the m-th multipath, /pitor^C* + N'l. for the next segment may be estimated find accumulated in another section of the accumulator. [0075] The pilot for the m-th multipath is interference to all multipaths in the received signal, includiog the m-th multipath itself. For a demodulator design in which the multiple finger processois are assigned to process a number of multipaths in a :;eceived signal for a given terminal, the estimated pilot interference, lpiiotm, due to tli2 m-di multipath may be provided to other finger processors assigned to process other multipaths in the same received signal. [007'5] For the demodulation to recover the data on the m-th multipath, the data sample:; for a segment are provided from buffer 408x to resampler 522. Resampler 522 then resamples the received data samples to provide decimated data samples at the chip rate and with the proper timing phase for this multipath. The decimated data .samples are processed as described above to provide the pilot estimates, Pm(k). [0077] Correspondingly, interference samples for the total pilot interference, / JUlt(k), lor the same segment are provided from accumulator 538 to a resampler 540. Resampler 540 similarly resanples the received interference samples to provide decimated uvierference samples at the chip rate and with the proper timing phase for the .72-th m:.;.tipath. Summer 512 then receives and subtracts the decimated interference s&mples from the decimated data samples to provide pilot-canceled data samples. [007;?] Within data demodulation unit 550, a despreader 544 receives and desp;"eads th:: pnot-canceIed data samples with a (complex-conjugate) spreading sequence, l:J(k)f to provide despread samples. The spreading sequence, Sm*(k), has a phase corresponding to the time offset, tm, of the m-th multipath. A data chanielizer 546 then multiplies the despread samples with the channelization code, Cc/lt/, used for the code channel being recovered by the finger processor. The channelized cita samples are then accumulated over the length of the channelization cod;. Cchn. to provide data symbols. [007)] A data demodulator 548 then receives and demodulates the data syctiols w:li the pilot estimates, Pm(k), to provide demodulated symbols (i.e., demodulated data) for the /w-th multipath, which are then provided to symbol combiner 420. The data demodulation and symbol combining may be achieved as described in tie aforementioned US Patent No. 5,764,637 patent The '687 patent describes 3?SK data demodulation for IS-95 by performing dot product between the desp;^ead cata and the filtered pilot. The demodulation of QPSK modulation, which is used in ccmiClOOO and W-CDMA: is a straight-forward extension of the techniques described in >he fc687 patent. That is, instead of dot product, both dot product and cross-prod u;r: arc used to recover the inphase and quadrature streams. [008*)] As noted above, the data demodulation for the m-th multipath may be performed La parallel and in a pipelined manner with the pilot interference estimation. While desoreader 544 and data channelizer 546 are processing the pilot-canceled data samples for the current segment (with the spreading sequence, Sm\k), and the channelization code, CfAtW) to provide the data s>7nbols for the w-tii rnultipath, desf reader 524 and pilot channelizer 526 may process the same data samples for the current segment (with the spreading sequence, 5„,*(/c), and the pilot channelization coa:, CpttMi„) to provide the pilot symbols for this rnultipath. The pilot symbols are filtered by pilot filter 528 to provide pilot estimates, Pm{k), for the muhipath. Pilot interference estimator 530 then derives the estimated pilot interference, Ipa* «(*"* W* due t0 ^ nwltiparh for the following segment, as described above. In this manner, while data demodidation is performed on the current segment using the lotal pilot interference, /^(A:), derived from a prior segment, pilot interference for the ne*;i augment is estimated aid stored to another section of the accumulator, to be used for th-s next segment. [0081] In an embodiment, the pilot for a particular rnultipath being demodulated is estimated based on the "raw" received data samples (from sample buffer 403x) as described above, and not based on the pilot-canceled data samples (from ace jjnuiator 538). In another embodiment, the pilot may be estimated based on the pilot-canceled data .samples if the total pi;ot interference includes some or all of the interfering pilots except for the pilot of the rnultipath being demodulated (i.e., the pilot of the rnultipath being demodulated is included in the pilot-canceled data samples). This alternative embodiment may provide an improved estimate of the channel response of the rnultipath being demodulated, and is especially advantageous for the itvKse link where the piZot estimation is typically the limitirg factor in dealing w/Ji i weak rnultipath. The same "other pilots canceled" data samples that is used for pilot estimation may also be processed to recover the data for the rnultipath, which is advantageous for a finger processor architecture that performs both pilot estimation and data demodulation in parallel on the same data sample stream. The same concep: may be used to estimate the channel response of a particular interfering rnultipath (:.e., the estimated channel response may be based on either the raw data samples or tte "other pilots canceled" data samples having interfering pilots except for the pilot of that particular rnultipath removed). [0082J FIGS. 6A and 6B an; diagrams that illustrate the processing of the data samples lo oerive estimates of pilot interference, in accordance with a specific implementation of tlie indention. In the example shown in FIGS. 6A and 6B, the rece ved tt-ignal include;; three mullipaths that are associated with time effsets of fp t2, iind ts. The received signal is digitized at a sample rate that is 8 tines the chip rate to provide data samples, which are stored to the sample buffer. These multipass may or may not be sampled at their peaks. [0083] In the example shown in FIGS. 6A and 6B, each segment included 512 data samples for a symbol period of 64 PN chips. The pilot interference is estimated for each of the three multipaths and for each symbol period. The symbol riming for each multipath is determined by the multipath'* fractional time offset. If the fractional lime offsets of the multipaths are not the same, which is generally true, then the t-ymbol tuning for these multipaths will be different and will be associated with different data sample segments. Ir. an embodiment, the multipaths are processed in an order fcascd on their fractional time offsets, with tte multipath having die smallest fractional tine offset being processed first and the multipath having the largest fractional time offset being processed last. This processing order ensures that the total pilo: interference is derived and available for each multipath when it is processed [0084] In FIG. 6A, for the .i-th symbol period for the m-th multipath with a fractional time offset of t^tm = 5, resampler 522 receives data sample:; 5 through 516 from the sample buffer and provides to despreader 524 data samples 5, 13, 20, and so on, and 509, which are represented by the shaded boxes. Correspondingly, despreader 524 receives the spreading sequence, Sm\k), with a phase corresponding to the same time offset of fm, and despreads the decimated data samples with the spreading sequence. A pilot estimate, Pm (k), is then derived based on die despread samples for tins segment, as described above. [QQ&5] To derive the estimated pilot interference due to the *t-th multipath, sprestder 534 receives the spreading sequence, Sm(k + N), corresponding to the next segment. Multiplier 536 then multiplies the spreading sequence, Sm (k + N), with the pilov estinats, Pct (k), derived from the cuireut segment to provide the estimated pilot interference, lpiitlt,m(k + N), for the next segment. The estimated pilot interference, Ip(lHm(k-~S)1 comprises interference samples 517 through 1028, which are accumulated with the samples a the same indices 517 through 1028 in the interference accumulator, as showr in FIG. 6. In this way, the fractional time offset of tie m-th nultipath is accounted tor in the derivation of the total pilot interference. [00S6] For the data demodulation of the m-th rnultipath for the n-th symbol period, the s.*me segment of interference samples 5 through 516 are provided from accumulator 538 to resampler 540. Resarapler 540 then provides to summer 542 interference samples 5, 13, 20, and so on, and 509 (which arc also shown by the shaded boxes), corresponding to the same-indexed data samples provided by rcsarapler 522. The data demodulation of die pilot-canceled data samples is then performed as described above. Each rnultipath may be processed in similar manner. However, since each rnultipath may be associated with a different lime offset, different cenmated date and interference samples may be operated on. [00S17] FIG. 6B shows the three data sample segments, the decimated data samples, aid the three spreading sequences used to derive the estimated pilot interferences due to the three multipatlis. [0083] In another demodulator design, the pilot interference estimation/car.celiation and the data demodulation may be performed in real-time (e.g„ as diita samples are received), if sufficient processing capabilities are provided. For example, M finger processor; may be assigned to concurrently process M mult.paths ir a received signal. For each symbol period, each finger processor can derive a pilot estimate for that symbol period, which is then used to derive the estimated pilot interference due to that finger processor's assigned rnultipath for the next symbol period. A summer then sums the estimated pilot interferences from all M finger processors' (taken into account their respective time offsets), and the total pilot interference for the next symbol period is stored in ±c interference accumulator. [00&9] The total pilot interference may then be subtracted from the data samples as t/isy are received for the next symbol period, and the same pilot-canceled data sample may be provided to all M finger processors for data demodulation. (These finder processors are also provided with the received data samples, without the oilot cancellation, which are used to derive the pilot estimates.) In this way, the data demodulation may be performed on pilot-canceled data samples in real time, and the sample buffer may possibly be eliminated. For the scheme in which the pilot estimate is used to derive the estimated pilot interference for the same segment (and not the n:xt segment), the data samples may be temporarily stored (e.g., for one symbol period) while the total pilot interference is derived. [0OS0] For the demodulator design In which the same data Samples arc processed multip'e times (e.g., if one finger processor is assigned to process a number of irultip&ths), the sample buffer may be designed and operated in a manner to ensure that the data samples are not inadvertently dropped. In an embodiment., the sample buffer is designed to receive incoming data samples while providing stored data samples to the finger processors). This may be achieved by implementing the sample bufter in a manner such that scored data samples may be read from one part of the buffer while new data samples are written into another part of the buffer. The sample bufter may be implemented as a double buffer or multiple buffers, a multi-port buffer, a circular buffer, or some other buffer design. The interference accumulator may be implemented in similar manner as the sample buffer (e.g., as a circular buffer). [0091] For the above demodulator design, to avoid overwriting samples that are still being processed, the capacity of the sample buffer may be selected to be at least twice ths time required to derive the total pilot interference for all M multipaths (wirli the relationship between time and buffer capacity being defined by the sample rate). If a different data sample segment may be used for each of the M multipaths, then the opacity of the sample buffer may be selected to be at least (2 • N" • NOT) for each received signal assigned to the sample buffer, where N is the duration of data samples u;>ed Co derive die estimated pilot interference for one multipath and Nm is the oversampling factor for the data samples (which is defined as the ratio of the sample rale ever the chip rate). For the above example in which a segment of one symbol period (e.g., N = 64 PN chips) is processed for each multipath, a buffer of two symbol periods would be able to provide a segment cf one symbol period of data samples far t:ach multipath regardless of its fractional time offset. And if the ove:n;araple J*ate is Nw=8, then the minimum size of the buffer is (2-N-N^ =2-64-8 = 1024) data samples. [0092] Similarly, the capacily of the interference accumulator may be selected to be at least '3• N• NM). The extra symbol period for the interference tccumulator (i.e., 3-N instead of 2 N) is to account for the fact that the estimated pilot interference if; derived for the next segment. [009.3] As noted above, the estimated pilot interference derived from one data sample segment may be cancelled from a later data sample segment. For a mobile terni.nal, *:he communication link and, consequently the channel response of the varicus m-itipath> are constantly changing. Therefore, it is desirable to reduce the delay between the data samples from which the pilot interference is estimated and the data samples from which that estimated pilot interference is canceled. This delay ma)' be as gseat as 2 • N chips. [0091] By selecting a sufficiently small value for N, the channel ::esponse of each multipath may be expected to remain relatively constant over the period of 2 • N chips. However, the value of N should be selected to be large enough to dlow for an accurate estimate of the channel response of each multipath to be processed. [009:5] FIG. 7 is a flow diagram of a process 700 to derive the total pilot interference for a number of multiparas, in accordance with an embodiment of the invention. Process 700 may be implemented by the finger processor shown in FIG. 5. [OOJHJ] Initially, the accumulator used to accumulate the estimated pilot interference:; is cleared, at step 712. An interfering multipath that has not been processed is; then selected, at step 714. Typically, the pilot interference is estimated for each multipath assigned for dam demodulation. However, pilot interference due to unassignsd multipaths may also be estimated. In general, any number of interfering; nxiJtipaths may be processed, and these multipaths are those fcr which the pilot interference is to be estimated and accumulated to derive the total pilot interference. [00!>7] The data samples for the received signal with the selected multipath is then processed to derive an estimate of the channel response of the selected multipath, ai s;ep 716. "["he channel response may be estimated based on the pilot in the selected multipath, as described above. For cdma2000, this processing entails (1) spreading the data s&uples with a spreading sequence for the multipath (i.e., with the proper phas3 coin* ponding to the time offset of the multipath)* (2) channelizing the despread dm. samples to provide pilot symbols (e.g., multiplying the despread samples v/ith the pilot channelization code and accumulating the channelized data samples over the pilot channelization code length), and (2) filtering the pilot symbols to derive pilot estimates that are indicative of the channel response of Ihe selected multipath. Estimation of the channel response based on some other techniques may also be used, smd this is within the scope of the invention. [00!)5] The pilot interference due to the selected multipath is then estimated, at stop 718 The pilot interference may be estimated by'generating processed pilot data and multiplying this data with the estimated channel response derived in step 716. The ppxessed pilot data is simply the spreading sequence for the selected multipath ii the pilot data is a sequence of all zeros and the pilot channelization code is also ali zeros. In general, the processed pilot data is the data after all signal processing it the transmitter unit but prior to the filtering and frequency upconversion (e.g.. the da:a at the output of modulator 216a in FIG. 3 for the reverse link in cdma200C). [00!W] The estimated pilot interference for the selected multipath is then accnnulated in the interference accumulator with the estimated pilot interferences for prici-procfssed multipaths, at step 720. As noted above, the timing phase of the mult.path is. observed in performing steps 716,718, and 720. [OOl'W] A determination is ±en made whether or not all interfering multipaths have been processed, at step 722. If the answer is no, then the process returns to step 714 and Jincther interfering multipath is selected for processing. Otherwise, the content of th:; accumulator represents the total pile: interference due to all processed multipart!, which may be provided n step 724. The process then terminates. [001 Dt] The pilot interference estimation in TCG. 7 may be performed for all multipart^: in a time-division mulliplexed manner using one or more finger processor*. Alternatively, the pilot interference estimation for multiple multipaLhs may be performed in parallel using a number of finger processors. In this case, if the hardware t;a* sufficient capabilities, then the pilot interference estimation and cancelation may be performed in real-time along with the data demodulation (e.g., as the data s&mpies are received, with minimal or no buffering, as described above). [00192] FIG. 8 is a flow diagram of a process 800 to data demodulate a number of raultipeJli5. with pilot interference cancellation, in accordance with an embodiment of the invention. Process 800 may also be implemented by the finger processor shown in FIG. 5. [00153] Initially, the total piiot interference due ro all multipaths of interest is derived, at stsp 812. Step 812 may be implemented using process 700 shown in FIG. 7. A particular multipart! is then selected for data demodulation, at step 814. In an embodiment and as described above, the total pilot interference is initially canceled from the selected multipath, at stq) 816. This may be achieved by subtracting the interference samples for the total pilot interference (which are scored in the accumulator) :frora the data samples for the received signal that includes the selected multipath. [001'M] Data demodulation is then performed on the pilot-canceled signal in the normal manner. For cdma2000, this entails (I) despreading the pilot-canceled data samples.. (2) channelizing the despread data to provide data symbols, and (3) demodulating the data symbols with the pilot estimates. The demodulated symbols (i.e., the demodulated data) for the selected multipath are then combined with the demodulated symbols for other multipaths for the same transmitter unit (e.g., terminal). The demodulated symbols for multipaths in multiple received signals (e.g., if receive diversity is employed) may also be combined. The symbol combining may be achieved by the symbol combiner shown in FIG. 4. [00105] A detennination is then made whether or not all assigned muldpaths have been fenodulated, at step 822. If the answer is nc, then the process returns to step 814 and another multipath is selected for data demodulation. Otherwise, the process tenninaies. [0010$] Aii noted above, the data demodulation for all assigned multipaths of a given trar.:>xitter unit may be performed in a time-division multiplexed manner using one or mors linger processors. Alternatively, the data demodulation for all assigned mulipaths may be performed in parallel using a number of finger processors. [00107] Referring back to FIGS. 4 and 5, searcher 412 may be designed and opeiated to search for new multipaths based on the pi lot-canceled data samples (instead of the raw received data samples from buffers 408). This may provided improved search performance since the pilot interference from some or all known muliipathi x.z.y have been removed as described above. [00108] The pilot interference cancellation techniques described herein may be able to provide noticeable improvement in performance. The pilot transmitted by each terminal on the reverse link contributes to the tola] channel interference, Io, in similar mirxei as background noise, NQ. The pilots from all terminals miy represent a substantial r-art of the total interference level seen by all terminals. This would then resut in a lower signal-to-total-noise-plus-interference ratio (SNR) for the individual terminal, b fact, it is estimated that in a cdma2000 system (which supports pilots on the levers r link) operating near capacity, approximately half of the interference seen at a bast; station may be due to the pilots from the transmitting terminals. Cancellation of die pilot interference may thus improve the SNR of each individual terminal, which then allows each terminal to transmit at a lower power level and increase tha reverse link capacity. [00109] The techniques described herein for estimating and canceling pilot interference nay be advantageously used in various wireless communication systems that transreit e. pilot along with data. For example, these techniques may be used for varkHis CDMA systems (e.g., cdma2000, IS-95, W-CDMA, TS-CDMA, and so on), Persona] Communication Services (PCS) systems (e.g., ANSI J-STD-008), and other wireless communication systems. The techniques described herein may be used to estimate ard caned pilot interference in cases where multiple instances of [00110] For clarity, various aspects and embodimsnts of the invention have been described for the reverse link in cdma2000. Tne pilot interference cancellation techniques described herein may also be used for the forward link from the base station to :he terminal. The processing by the demodulator is determined by the particular CDMA standard being supported and whether the inventive techniques are used ::or the forward or reverse link. For example, the "despreading" with a spreading sequence in IS-9S and cdma2OO0 is equivalent to the ^scrambling" with a scrambling sequence in W-CDMA, and the channelization with a Walsh code or a quasi-orthcgonal function (QOF) in IS-95 and cdma2000 is equivalent to the "despreadinfcf with an OVSF code in W-CDMA. In general, the processing performed by the demodulator at the receiver is complementary to that performed by the modulator at the transmitter unit. [00111] For the forward link, ±c techniques described herein may also be used to approximately cancel other pilots that may be transmitted in addiiion to, or possibly in p]ace of, a "common" pilot transmitted to all terminals in a cell. For example, cdma2000 supports a "transmit diversity"' pilot and an "auxiliary" pilot. These other pilots may utilize different Walsh codes (i.e., different channelization codes, which may be quasi-orthogonal functions). A different data pattern may also be used for the pi]oL To process any of these pilots, the despread samples are decovered with the same Walsh cods used to channelize the pilot at the toise station, and further correlated (i.e., multiplied and accumulated) with the same pilot data pattern used a the base station for the pilot. The transmit diversity pilot and/or auxiliary pilot may be estimated and canceled in addition to the common pilot. 100112] Similarly, W-CDMA supports a number of different pilot: channels. First, a commoa pilot channel (CPICH) may be transmitted on a primary base station antenna. Second, a diversity CPICH may be generated based qn non-zero pilot data and transmitted on a diversity antenna of the base station. Third, one or more secondary CPICHs may be transmitted in a restricted parr of the cell, and each secondary CFICH is generated using a non-zero channelization code. Fourth, the base: stadon may further transmit a dedicated pile, to a specific user using the same channelization cede as the user's data channel. Li this case, the pilot symbols are time mult.pkxed with the data symbols to thai user. Accordingly, it will be understood by those skilled in die art that the techniques described herein are applicable for processing all of the above different types of pilot channeLs, and other pdot channels that may also be transmitted in a wireless communication system. [001131 The demodulator and other processing units that may be used to implement various aspects and embodiments of the invention may be implemented in hardware, software, firmware, or a combination thereof. For a hardware design, the demodulaicr (including the data demodulation unit and the elements used for pilot interference estimation and cancellation such as the pilot estimator and the pilot interference estimator), and other processing units may be implemented within one or more applita:on specific integrated circuits (ASIC), digital signal processors (DSP), digitil signal processing devices (DSPDs), field programmable gate arrays (FPGA), processors, :coicroprocessors, con trailers, microcontrollers, programmable logic devices (PLD;, other electronic units, or any combination thereof. [00114] For a software implementation, the elements used for pilot interference estimation and cancellation and data demodulation may be implemented with modules (e.g., procedures, functions, and so on) that perform the functions described herein- Ths software codes may be stored in a memory unit (e.g., memory 262 in FIG. 2) ard executed by a processor (e.g., controller 260). The memory unit may be implemented within the processor or external to the processor, in which case it can be communicatively coupled to the processor via various means as it known in the art. [001 IS] The elements used to implement the pilot interference estimation and cancellation described herein may be incorporated in a receiver unit or a demodulator that may further be incorporated in a terminal (e.g., a handset, a handheld unit, a stanc-alone unit, and so on), a base station, or some other communication devices or units. The receiver unit or demodulator may be implemented with one or more integrated circuits. [0011.6] The previous description of the disclosed embodiments is provided to enable any person skilled in the a^ to make or use the present invention. Various modifications, to these embodiments will be readily apparent to those skilled in the art, and the: generic principles defir.ee herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present inversion :.s not intended to be limited to the embodiments shown herein but is to be accoided tbs widest scope consistent with the principles and novel features disclosed heieii. WE CLAIM : 1. A method for canceling pilot interference at a receiver unit in a wireless communication system, comprising: receiving a signal comprised of a plurality of signal instances, wherein each signal instance includes a pilot and data; estimating pilot interference due to each of the plurality of signal instances; accumulating estimated pilot interference due to the plurality of signal instances in a buffer to provide a total pilot interference; subtracting the total pilot interference from the received signal to derive a pilot-canceled signal; and processing the pilot-canceled signal to derive data for each signal instance in the received signal, wherein the pilot interference due to each of the one or more signal instances is estimated by processing the signal instance to derive an estimate of a channel response of the signal instance; and multiplying pilot data for the signal instance with the estimated channel response to provide the estimated pilot interference. 2. The method of claim 1, wherein the pilot data for each of the one or more signal instances is a spreading sequence for the signal instance. 3. The method of claim 2, wherein the spreading sequence for the signal instance has a phase corresponding to an arrival time of the signal instance. 4. The method of claim 1, wherein the estimated channel response for each of the one or more signal instances is derived by despreading data samples for the received signal with a spreading sequence for the signal instance, channelizing the despread samples with a pilot channelization code to provide pilot symbols, and filtering the pilot symbols to provide the estimated channel response. 5. The method of claim 1, wherein the estimated channel response of the signal instance is derived based on a current segment of data samples for the received signal and the estimated pilot interference is for a subsequent segment of data samples. 6. The method of claim 1, wherein the estimated channel response of the signal instance is derived based on a current segment of data samples for the received signal and the estimated pilot interference is for the same segment of data samples. 7. The method of claim 1, wherein the estimated channel response for each of the one or more signal instances is derived based on data samples for the received signal. 8. The method of claim 1, wherein the estimated channel response for each of the one or more signal instances is derived based on data samples having pilot from the signal instance unremoved but pilots from other interfering signal instances removed. 9. A method for canceling pilot interference at a receiver unit in a wireless communication system, the method comprising: receiving a signal comprised of a plurality of signal instances, each signal instance comprising a pilot and data; deriving total pilot interference due to one or more signal instances; subtracting the total pilot interference from the received signal to derive a pilot-canceled signal; and processing the pilot-canceled signal to derive demodulated data for each of at least one signal instance in the received signal, wherein the processing of the pilot-canceled signal for each of the at least one signal instance includes: despreading samples for the pilot-canceled signal with a spreading sequence for the signal instance; channelizing the despread samples with a data channelization code to provide data symbols; and demodulating the data symbols with pilot estimates to provide the demodulated data for the signal instance. 10. The method of claim 9, wherein the pilot estimates for each of the at least one signal instance are derived based on data samples for the received signal. 11. The method of claim 9, wherein the pilot estimates for each of the at least one signal instance are derived based on data samples having pilot from the signal instance unremoved but pilots from other interfering signal instances removed. 12. A method for canceling pilot interference at a receiver unit in a wireless communication system, the method comprising: receiving a signal comprised of a plurality of signal instances, each signal instance comprising a pilot and data; deriving total pilot interference due to one or more signal instances; subtracting the total pilot interference from the received signal to derive a pilot-canceled signal; and processing the pilot-canceled signal to derive data for each of at least one signal instance in the received signal, wherein the pilot interference due to the one or more signal instances is estimated in a time-division multiplexed manner. 13. A method for canceling pilot interference at a receiver unit in a wireless communication system, comprising: receiving a signal comprised of a plurality of signal instances, wherein each signal instance includes a pilot and data; estimating pilot interference due to each of the plurality of signal instances; accumulating estimated pilot interference due to the plurality of signal instances in a buffer to provide a total pilot interference; subtracting the total pilot interference from the received signal to derive a pilot-canceled signal; and processing the pilot-canceled signal to derive data for each signal instance in the received signal, wherein the subtracting includes subtracting samples for the total pilot interference from data samples for the received signal, and wherein the samples for the total pilot interference and data samples are both provided at a particular sample rate. 14. A method for canceling pilot interference at a receiver unit in a wireless communication system, comprising: receiving a signal comprised of a plurality of signal instances, wherein each signal instance includes a pilot and data; estimating pilot interference due to each of the plurality of signal instances; accumulating estimated pilot interference due to the plurality of signal instances in a buffer to provide a total pilot interference; subtracting the total pilot interference from the received signal to derive a pilot-canceled signal; and processing the pilot-canceled signal to derive data for each signal instance in the received signal, wherein the pilot interference due to a signal instance being processed to derive the data is excluded from the total pilot interference. 15. A method for canceling pilot interference at a receiver unit in a wireless communication system, the method comprising: receiving a signal comprised of a plurality of signal instances, each signal instance comprising a pilot and data; deriving total pilot interference due to one or more signal instances; subtracting the total pilot interference from the received signal to derive a pilot-canceled signal; processing the pilot-canceled signal to derive data for each of at least one signal instance in the received signal; and processing the pilot-canceled signal to search for new signal instances in the received signal. 16. The method of claim 13, wherein the sample rate is multiple times a chip rate. 17. The method of claim 1,wherein the deriving the total pilot interference is performed based on segments of data samples for the received signal. 18. The method of claim 17, wherein the each segment includes data samples for one symbol period. 19. The method of claim 1, wherein the processing to derive data is performed based on segments of pilot-canceled data samples for the pilot-canceled signal. 20. A method for canceling pilot interference at a receiver unit in a wireless communication system, comprising: receiving a signal comprised of a plurality of signal instances, wherein each signal instance includes a pilot and data; estimating pilot interference due to each of the plurality of signal instances; accumulating estimated pilot interference due to the plurality of signal instances in a buffer to provide a total pilot interference; subtracting the total pilot interference from the received signal to derive a pilot-canceled signal; and processing the pilot-canceled signal to derive data for each signal instance in the received signal, wherein the deriving the total pilot interference and the processing of the pilot-canceled signal are performed in parallel. 21. The method of claim 1„ wherein the deriving the total pilot interference and the processing of the pilot-canceled signal are performed in a pipelined manner. 22. The method of claim 1, wherein the wireless communication system is a CDMA system. 23. The method of claim 22, wherein the CDMA system supports cdma2000 standard. 24. The method of claim 22, wherein the CDMA system supports W-CDMA standard. 25. The method of claim 22, wherein the CDMA system supports IS-95 standard. 26. The method of claim 22, wherein the received signal comprises one or more reverse link modulated signals in the CDMA system. 27. The method of claim 22, wherein the received signal comprises one or more forward link modulated signals in the CDMA system. 28. A method for canceling pilot interference at a receiver unit in a wireless communication system, comprising: processing a received signal comprised of a plurality of signal instances to provide data samples, wherein each signal instance includes a pilot; processing the data samples to derive an estimate of pilot interference due to each of one or more signal instances; deriving total pilot interference due to the one or more signal instances based on the estimated pilot interference; subtracting the total pilot interference from the data samples to derive pilot-canceled data samples; and processing the pilot-canceled data samples to derive data for each of at least one signal instance in the received signal, wherein the processing the data samples to derive the estimated pilot interference due to each of the one or more signal instances includes despreading the data samples with a spreading sequence for the signal instance, channelizing the despread samples with a pilot channelization code to provide pilot symbols, filtering the pilot symbols to provide an estimate or a channel response of the signal instance, and multiplying the spreading sequence for the signal instance with the estimated channel response to provide the estimated pilot interference due to the signal instance. 29. A method for canceling pilot interference at a receiver unit in a wireless communication system, comprising: processing a received signal comprised of a plurality of signal instances to provide data samples, wherein each signal instance includes a pilot; processing the data samples to derive an estimate of pilot interference due to each of one or more signal instances; deriving total pilot interference due to the one or more signal instances based on the estimated pilot interference; subtracting the total pilot interference from the data samples to derive pilot-canceled data samples; and processing the pilot-canceled data samples to derive demodulated data for each of at least one signal instance in the received signal, wherein the processing the pilot-canceled data samples to derive the demodulated data for each of the at least one signal instance includes despreading the pilot-canceled data samples with a spreading sequence for the signal instance, channelizing the despread samples with a data channelization code to provide data symbols, and demodulating the data symbols to provide the demodulated data for the signal instance. 30. The method of claim 29, wherein the subtracting includes subtracting interference samples for the total pilot interference from the data samples for the received signal, wherein the interference samples and data samples are both provided at a particular sample rate that is multiple times a chip rate. 31. A receiver unit in a wireless communication system, the receiver unit comprising: a receiver configured to process a received signal comprised of a plurality of signal instances to provide data samples, wherein each signal instance includes a pilot and data; and a demodulator including: a pilot interference estimator configured to process the data samples to derive an estimate of pilot interference due to each of the plurality of signal instances; a buffer configured to accumulate estimated pilot interference due to the plurality of signal instances to provide a total pilot interference; a summer configured to subtract the total pilot interference from the data samples to derive pilot-canceled data samples; a data demodulation unit configured to process the pilot-canceled data samples to derive data for each signal instance in the received signal; and a channel estimator configured to provide an estimated channel response for each of the one or more signal instances. 32. The receiver unit of claim 31, wherein the pilot interference estimator is further configured to multiply pilot data for each of the one or more signal instances with the estimated channel response for the signal instance to provide the estimated pilot interference due to the signal instance. 33. A receiver unit in a wireless communication system, the receiver unit comprising: a receiver configured to process a received signal comprised of a plurality of signal instances to provide data samples, wherein each signal instance includes a pilot and data; and a demodulator including: a pilot interference estimator configured to process the data samples to derive an estimate of pilot interference due to each of one or more signal instances and to derive total pilot interference due to the one or more signal instances based on the estimated pilot interference, a summer configured to subtract the total pilot interference from the data samples to derive pilot-canceled data samples, and a data demodulation unit configured to process the pilot-canceled data samples to derive demodulated data for each of at least one signal instance in the received signal, wherein for each of the at least one signal instance the data demodulation unit is configured to despread the pilot-canceled data samples with a spreading sequence for the signal instance, channelize the despread samples with a data channelization code to provide data symbols, and demodulate the data symbols with pilot estimates for the signal instance to provide the demodulated data for the signal instance. 34. A terminal in a CDMA system, the terminal comprising: a receiver configured to process a received signal comprised of a plurality of signal instances to provide data samples, wherein each signal instance includes a pilot and data; and a demodulator including a pilot interference estimator configured to process the data samples to derive an estimate of pilot interference due to each of the plurality of signal instances; a buffer configured to accumulate estimated pilot interference due to the plurality of signal instances to provide a total pilot interference; a summer configured to subtract the total pilot interference from the data samples to derive pilot-canceled data samples; a data demodulation unit configured to process the pilot-canceled data samples to derive data for each signal instance in the received signal; and a channel estimator configured to provide an estimated channel response for each of the one or more signal instances. 35. The terminal of claim 34, wherein the pilot interference estimator is further configured to multiply pilot data for each of the one or more signal instances with the estimated channel response for the signal instance to provide the estimated pilot interference due to the signal instance. 36. A terminal in a CDMA system, the terminal comprising: a receiver configured to process a received signal comprised of a plurality of signal instances to provide data samples, wherein each signal instance includes a pilot and data; and a demodulator including a pilot interference estimator configured to process the data samples to derive an estimate of pilot interference due to each of one or more signal instances and to derive total pilot interference due to the one or more signal instances based on the estimated pilot interference; a summer configured to subtract the total pilot interference from the data samples to derive pilot-canceled data samples; and a data demodulation unit configured to process the pilot-canceled data samples to derive demodulated data for each of at least one signal instance in the received signal, wherein for each of the at least one signal instance the data demodulation unit is configured to despread the pilot-canceled data samples with a spreading sequence for the signal instance, channelize the despread samples with a data channelization code to provide data symbols, and demodulate the data symbols with pilot estimates for the signal instance to provide the demodulated data for the signal instance. 37. A base station in a CDMA system, the base station comprising: a receiver configured to process a received signal comprised of a plurality of signal instances to provide data samples, wherein each signal instance includes a pilot and data; and a demodulator including a pilot interference estimator configured to process the data samples to derive an estimate of pilot interference due to each of the plurality of signal instances; a buffer configured to accumulate estimated pilot interference due to the plurality of signal instances to provide a total pilot interference; a summer configured to subtract the total pilot interference from the data samples to derive pilot-canceled data samples; a data demodulation unit configured to process the pilot-canceled data samples to derive data for each signal instance in the received signal; and a channel estimator configured to provide an estimated channel response for each of the one or more signal instances. 38. The base station of claim 37, wherein the pilot interference estimator is further configured to multiply pilot data for each of the one or more signal instances with the estimated channel response for the signal instance to provide the estimated pilot interference due to the signal instance. 39. A base station in a CDMA system, the base station comprising: a receiver configured to process a received signal comprised of a plurality of signal instances to provide data samples, wherein each signal instance includes a pilot and data; and a demodulator including a pilot interference estimator configured to process the data samples to derive an estimate of pilot interference due to each of one or more signal instances and to derive total pilot interference due to the one or more signal instances based on the estimated pilot interference; a summer configured to subtract the total pilot interference from the data samples to derive pilot-canceled data samples; and a data demodulation unit configured to process the pilot-canceled data samples to derive demodulated data for each of at least one signal instance in the received signal, wherein for each of the at least one signal instance the data demodulation unit is configured to despread the pilot-canceled data samples with a spreading sequence for the signal instance, channelize the despread samples with a data channelization code to provide data symbols, and demodulate the data symbols with pilot estimates for the signal instance to provide the demodulated data for the signal instance. 40. The receiver unit of claim 31, further comprising: an interference accumulator unit configured to accumulate the total pilot interference for the one or more signal instances. 41. The interference accumulator unit of claim 40, further comprising: a plurality of sections defined by a time offset. 42. A receiver unit configured to receive a wireless signal comprising at least first and second signal instances, each signal instance comprising data and a pilot signal, the receiver unit comprising: a processor configured to: determine a first channel estimate for the first signal instance; use the first channel estimate and a spread pilot signal associated with the first signal instance to estimate a first pilot of the first signal instance; determine a second channel estimate for the second signal instance; and use the second channel estimate and a spread pilot signal associated with the second signal instance to estimate a second pilot of the second signal instance; and a buffer configured to accumulate the estimated first and second pilots, the processor being configured to subtract the accumulated, estimated first and second pilots from the received signal to estimate a pilot-canceled received signal, the processor being configured to use the estimated pilot-canceled received signal to demodulate data of the first signal instance. 43. The receiver unit of claim 42, wherein the wireless signal comprises a Code Division Multiple Access (CDMA) signal. 44. The receiver unit of claim 42, being configured to receive the first and second signal instances from first and second remote terminals, respectively. 45. The receiver unit of claim 42, wherein the first and second signal instances are multipath components of a signal from one remote terminal. 46. The receiver unit of claim 42, wherein the buffer is further configured to accumulate (a) the estimated first pilot according to a first estimated time offset of the first signal instance and (b) and the estimated second pilot according to a second estimated time offset of the second signal instance. 47. The receiver unit of claim 42, further comprising a sample buffer configured to store the wireless signal at a sample rate equal to a multiple of a chip rate of the wireless signal. 48. The receiver unit of claim 47, wherein the sample rate of the sample buffer is equal to a sample rate of the buffer accumulating the estimated pilots. 49. The receiver unit of claim 42, wherein each spread pilot signal comprises a pilot signal spread by a pseudo-random noise (PN) sequence. 50. The receiver unit of claim 42, wherein the first channel estimate, the spread pilot signal associated with the first signal instance, and the first estimated pilot correspond to a segment of the received signal, the segment comprising data samples for a time period of the received signal. 51. The receiver unit of claim 42, wherein the processor is further configured to: determine a first noise estimate of the first signal instance; derive a cancellation factor a based on the first channel estimate and the first noise estimate; multiply the first channel estimate by the cancellation factor to produce a weighted channel estimate; and use the weighted channel estimate and the spread pilot signal associated with the first signal instance to estimate the first pilot of the first signal instance. 52. The receiver unit of claim 51, wherein the cancellation factor a is derived from: where h is the first channel estimate, Nt is the first noise estimate, and N is a number of samples used to estimate h and Nt of the first signal instance. 53. The receiver unit of claim 51, wherein the cancellation factor ranges from 0 to 1.0. 54. The receiver unit of claim 51, wherein the cancellation factor ranges from 0 to a value greater than 1.0. 55. The receiver unit of claim 51, further comprising a look-up table with sets of channel estimates and noise estimates corresponding to cancellation factors. 56. The receiver unit of claim 42, wherein the processor is further configured to multiply the first channel estimate by a convolution of a transmit pulse and a receive filter function; and perform a convolution of (a) the spread pilot signal associated with the first signal instance and (b) a product of the first channel estimate and the convolution of the transmit pulse and the receive filter function to estimate the first pilot of the first signal instance. 57. The receiver unit of claim 56, wherein the transmit pulse is defined by a Code Division Multiple Access (CDMA) standard. 58. The receiver unit of claim 56, wherein the processor is configured to downsample a rate of at least one of (a) the convolution of the transmit pulse and the receive filter function, and (b) the convolution of (i) the spread pilot signal associated with the first signal instance and (ii) the product of the first channel estimate and the convolution of the transmit pulse and the receive filter function to match a rate of the buffer. 59. The receiver unit of claim 565 wherein the processor is contigurea xo upsampie a rate of at least one of (a) the convolution of the pre-determined transmit pulse and the receive filter function, and (b) the convolution of (i) the spread pilot signal associated with the first signal instance and (ii) the product of the first channel estimate and the convolution of the pre-determined transmit pulse and the receive filter function to match a rate of the buffer. 60. The receiver unit of claim 56, wherein the processor is configured to: --..... decimate samples of the convolution of the pre-determined transmit pulse and the receive filter function according to a phase associated with an estimated time offset of the first signal instance; multiply the first channel estimate by decimated samples of the convolution of the pre-determined transmit pulse and the receive filter function; and perform a convolution of the spread pilot signal associated with the first signal instance and the product of the first channel estimate and the decimated samples to estimate the first pilot of the first signal instance. 61. The receiver unit of claim 56, further comprising a polyphase finite impulse response filter (FIR) configured to: decimate samples of the convolution of the pre-determined transmit pulse and the receive filter function according to a phase associated with an estimated time offset of the first signal instance; multiply the first channel estimate by decimated samples of the convolution of the pre-determined transmit pulse and the receive filter function; and perform a convolution of the spread pilot signal associated with the first signal instance and the product of the first channel estimate and the decimated samples to estimate the first pilot of the first signal instance. 62. The receiver unit of claim 56, further comprising a filter table of predetermined filter coefficients that correspond to a plurality of different phases, the processor being configured to select a phase and corresponding filter coefficients based on an estimated time offset of the first signal instance. 63. The receiver unit of claim 42, wherein the processor is further configured to filter the estimated pilot-canceled received signal by a convolution of a predetermined transmit pulse and a receive filter function. 64. The receiver unit of claim 42, wherein the processor is configured to determine the first channel estimate and use the first channel estimate and spread pilot signal associated with the first signal instance to estimate the first pilot of the first signal instance substantially in parallel with determining the second channel estimate and using the second channel estimate and spread pilot signal associated with the second signal instance to estimate the second pilot of the second signal instance. 65. The receiver unit of claim 42, wherein the processor is configured to estimate pilots for a plurality of signal instances in a time division multiplexed manner. 66. A communication system comprising: a base station configured to receive a wireless signal comprising at least first and second signal instances, each signal instance comprising data and a pilot signal, the base station comprising: a processor configured to: - determine a first channel estimate for the first signal instance; - use the first channel estimate and a spread pilot signal associated with the first signal instance to estimate a first pilot of the first signal instance; - determine a second channel estimate for the second signal instance; and - use the second channel estimate and a spread pilot signal associated with the second signal instance to estimate a second pilot of the second signal instance; and a memory configured to accumulate the estimated first and second pilots, the processor being configured to subtract the accumulated, estimated first and second pilots from the received signal to estimate a pilot-canceled received signal, the processor being configured to use the estimated pilot-canceled received signal to demodulate data of the first signal instance. 67. The communication system of claim 66, wherein the processor is further configured to: multiply the first channel estimate by a convolution of a pre-determined transmit pulse and a receive filter function; and perform a convolution of (a) a spread pilot signal associated with the first signal instance and (b) a product of the first channel estimate and the convolution of the pre-determined transmit pulse and the receive filter function to estimate the first pilot of the first signal instance. 68. The communication system of claim 66, wherein the base station comprises a plurality of antennas and a plurality of buffers in the memory, each buffer being configured to accumulate the estimated pilots of signal instances received by one of the antennas. 69. The communication system of claim 66, wherein the base station comprises a plurality of antennas, the memory having a single buffer configured to accumulate the estimated pilots of signal instances received by the plurality of the antennas. 70. The communication system of claim 66, wherein the base station comprises X number of antennas and Y number of buffers in the memory, X being greater than Y, wherein at least one buffer is configured to accumulate estimated pilots of signal instances received by two or more antennas. 71. A receiver unit comprising: a means for receiving a wireless signal comprising at least first and second signal instances, each signal instance comprising data and a pilot signal; a means for determining a first channel estimate for the first signal instance; means for deriving a product of the first channel estimate and a convolution of a pre-determined transmit pulse and a receive filter function; a means for using the product of the first channel estimate and the convolution to estimate a first pilot of the first signal instance; a means for determining a second channel estimate for the second signal instance; a means for deriving a product of the second channel estimate and the convolution 6f the pre-determined transmit pulse and the receive filter function; a means for using the product of the second channel estimate and the convolution to estimate a second pilot of the second signal instance; a means for accumulating the estimated first and second pilots; and a means for subtracting the accumulated, estimated first and second pilots from the received signal to derive an estimated pilot-canceled received signal. 72. A method comprising: receiving a wireless signal comprising at least first and second signal instances, each signal instance comprising data and a pilot signal; determining a first channel estimate for the first signal instance; deriving a product of the first channel estimate and a convolution of a pre-determined transmit pulse and a receive filter function; using the product of the first channel estimate and the convolution to estimate a first pilot of the first signal instance; determining a second channel estimate for the second signal instance; deriving a product of the second channel estimate and the convolution of the pre-determined transmit pulse and the receive filter function; using the product of the second channel estimate and the convolution to estimate a second pilot of the second signal instance; accumulating the estimated first and second pilots; and subtracting the accumulated, estimated first and second pilots from the received signal to derive an estimated pilot-canceled received signal. 73. The method of claim 72, wherein receiving the wireless signal comprises receiving the first and second signal instances from first and second terminals. 74. The method of claim 72, wherein each signal instance has an estimated time offset due to a transmission path of the signal instance. 75. The method of claim 72, wherein the wireless signal comprises a Code Division Multiple Access (CDMA) signal. 76. The method of claim 72, wherein the wireless signal is transmitted from a terminal to a base station. 77. The method of claim 72, wherein the wireless signal is transmitted from a base station to a terminal. 78. The method of claim 72, further comprising buffering the received wireless signal at a sample rate equal to a multiple of a chip rate. 79. The method of claim 72, wherein determining the first channel estimate for the first signal instance comprises: despreading samples of the received signal with a spreading sequence associated with the first signal instance to provide despread samples; de-channelizing the despread samples with a pilot channelization code to provide pilot symbols; and filtering the pilot symbols to provide the first channel estimate. 80. The method of claim 72, wherein determining the first channel estimate for the first signal instance uses a first segment of data samples from the received signal, the first estimated pilot corresponding to the first segment of data samples. 81. The method of claim 80, wherein the first segment comprises data samples for a time period of the received signal. 82. The method of claim 72 further comprising: determining a noise estimate'of the first signal instance; deriving a cancellation factor based on the first channel estimate and the noise estimate of the first signal instance; and multiplying the first channel estimate by the cancellation factor to produce a weighted channel estimate; using the weighted channel estimate and a spread pilot signal associated with the first signal instance to estimate the first pilot of the first signal instance. 83. The method of claim 82, wherein deriving the cancellation factor a uses: where h is the first channel estimate, Nt is the noise estimate, and N is a number of samples used to estimate h and Nt for the first signal instance. 84. The method of claim 72, further comprising: decimating samples of the convolution of the pre-determined transmit pulse and the receive filter function according to a phase associated with an estimated time offset of the first signal instance; multiplying the first channel estimate by decimated samples of the convolution of the pre-determined transmit pulse and the receive filter function; and performing a convolution of a spread pilot signal and the product of the first channel estimate and the decimated samples to estimate the first pilot of the first signal instance. 85. The method of claim 72, further comprising: selecting a phase based on an estimated time offset of the first signal instance; using the selected phase to retrieve pre-determined filter coefficients, the pre-determined filter coefficients corresponding to the convolution of the predetermined transmit pulse and the receive filter function; and multiplying the first channel estimate by the retrieved filter coefficients. 86. The method of claim 72, wherein using the product of the first channel estimate and the convolution to estimate the first pilot of the first signal instance comprises performing a convolution of (a) the product of the channel estimate and the convolution and (b) a spread pilot signal associated with the first signal instance. 87. The method of claim 86, wherein the first channel estimate, the spread pilot signal associated with the first signal instance, and the first estimated pilot correspond to a first segment of the received signal, the first segment comprising data samples for a time period of the received signal. 88. The method of claim 86, wherein the spread pilot signal associated with the first signal instance has a phase corresponding to an arrival time of the first signal instance. 89. The method of claim 72, further comprising using the estimated pilot-canceled received signal to demodulate data of the first signal instance, 90. The method of claim 89, wherein using the estimated pilot-canceled received signal to demodulate data of the first signal instance comprises: despreading samples of the estimated pilot-canceled received signal with a spreading sequence for the first signal instance to provide despread samples; de-channelizing the despread samples with a data channelization code to provide data symbols; and demodulating the data symbols with the first channel estimate for the first signal instance to provide demodulated data for the first signal instance. 91. The method of claim 72 wherein determining the first channel estimate, deriving the product of the first channel estimate and the convolution, and using the product to estimate the first pilot of the first signal instance occurs substantially in parallel with determining the second channel estimate, deriving the product of the second channel estimate and the convolution, and using the product to estimate the second pilot of the second signal instance. 92. The method of claim 72, wherein said determining the first channel estimate, deriving the product of the first channel estimate and the convolution, and using the product to estimate the first pilot of the first signal instance occurs in a time division multiplexed manner with determining the second channel estimate, deriving the product of the second channel estimate and the convolution, and using the product to estimate the second pilot of the second signal instance. 93. The method of claim 72, wherein accumulating the estimated first and second pilots comprises accumulating (a) the estimated first pilot according to a first estimated time offset of the first signal instance and (b) and the estimated second pilot according to a second estimated time offset of the second signal instance. 94. The method of claim 72, wherein accumulating the estimated first and second pilots occurs at a pre-determined sample rate, which is equal to a sample rate of the received signal. 95. The method of claim 94, wherein the sample rate is a multiple of a chip rate. 96. A method comprising: receiving a wireless signal comprising at least first and second signal instances, each signal instance comprising data and a pilot signal; determining a first channel estimate for the first signal instance; using the first channel estimate to estimate a first pilot of the first signal instance; determining a second channel estimate for the second signal instance; using the second channel estimate to estimate a second pilot of the second signal instance; accumulating the estimated first and second pilots; filtering the accumulated estimated, first and second pilots with a convolution of a pre-determined transmit pulse and a receive filter function; and subtracting the filtered, accumulated, estimated first and second pilots from the received signal to derive an estimated pilot-canceled received signal. 97. A method comprising: receiving a wireless signal comprising at least first and second signal instances, each signal instance comprising data and a pilot signal; process (a) a convolution of a pre-determined transmit pulse and a receive filter function and (b) a spread pilot signal associated with the first signal-' instance to generate reconstructed pilot samples of the first signal instance; determining a first channel estimate for the first signal instance; multiply the reconstructed pilot samples by the first channel estimate to derive a first pilot estimate of the first signal instance; processing (a) a convolution of the pre-determined transmit pulse and a receive filter function and (b) a spread pilot signal associated with the second signal instance to generate reconstructed pilot samples of the second signal instance; determining a second channel estimate for the second signal instance; multiply the reconstructed pilot samples of the second signal instance by the second channel estimate to derive a second pilot estimate of the second signal instance; accumulating the first and second pilot estimates; and subtracting the accumulated, first and second pilot estimates from the received signal to derive an estimated pilot-canceled received signal.

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