MXPA06005810A - Method and apparatus for ds-cdma interference suppression using code-specific combining - Google Patents

Abstract

Interference, such as inter-symbol interference, from a symbol of interest in a RAKE receiver (200) is reduced. The RAKE receiver comprises a plurality of RAKE fingers (220), a processor (230), and a combiner (232). The plurality of RAKE fingers despread symbols received over multiple paths of a multi-path channel. The processor determines cross-correlations between symbol waveforms from different symbols and multiple paths. The combiner combines the despread symbols using the cross-correlations to reduce interference from the symbol of interest.

Description

METHOD AND APPARATUS FOR SUPPRESSION OF INTERFERENCE OF DS-CDMA USING SPECIFIC CODE COMBINATION BACKGROUND OF THE INVENTION The present invention relates generally to RAKE receptors and particularly to RAKE interference suppression receivers. The RAKE receivers represent a well-known procedure for the reception of multi-trajectory, particularly in wireless communication of Multiple Division Access by Direct Sequence Code (DS-CDMA). In a multi-path communication channel, a transmitted signal travels through multiple propagation paths to the receiver. In this way, the receiver receives multiple "echoes" of the transmitted signal, with each multi-path echo usually suffering from different path delay, phase and attenuation effects. RAKE receivers exploit multi-path propagation by assigning each of two or more RAKE "fingers" to one of the incoming multi-path echoes. Each finger is tuned to a particular multi-path echo. By estimating channel effects, for example, phase and attenuation, and by appropriately explaining the differences in path delays, the individual result of each RAKE finger can be combined with the outputs of the other fingers to provide a RAKE output signal. combined with a significantly improved signal-to-noise ratio (SNR). In DS-CDMA system, such as broadband CDMA and IS-2000, high transmission data rates are achieved by transmitting data in a low propagation factor and / or in more than one propagation code (multi-code) . When a low spread and / or multi-code factor is used, the performance is sensitive to the multi-path spread. With dispersion, there are multiple echoes of the transmitted signal with different relative delays. These echoes interfere with each other. Not only is orthogonality lost between successive symbols as one symbol overlaps with the next, but orthogonality is also lost between symbols sent in different orthogonal codes. As a result, performance is often limited by interference between the different symbols that are sent to a particular user. These symbols may correspond to the previous or next symbol, symbols sent in parallel in another code carrier, or both. In general, this interference is referred to as self-interference, where self-interference may include inter-symbol interference (ISI) or inter-code interference (ICI). A key aspect of ISI is that it varies from symbol to symbol. This variation is due to the propagation codes that are a combination of Walsh codes and a common scrambling code. The scrambling code has a much longer period than the symbol period, which effectively changes the general propagation code from symbol period to symbol period.

COMPENDIUM OF THE INVENTION The present application describes a method and apparatus for reducing interference, such as interference between symbols, from a symbol of interest in a RAKE receiver. The RAKE receiver comprises a plurality of RAKE fingers, a processor and a combiner. The plurality of RAKE fingers deproduces symbols received on multiple paths of a multi-path channel. The processor determines the cross-correlations between different symbols. The combiner combines the de-propagated symbols using cross-correlations to reduce interference from the symbol of interest.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 comprises a block diagram of a conventional generalized RAKE receptor (G-RAKE). Figure 2 comprises a block diagram of an exemplary multi-symbol RAKE receiver (M-RAKE) according to the present invention. Figure 3 comprises a block diagram of an exemplary M-RAKE receiver restricted in accordance with the present invention. Figure 4 illustrates an exemplary multi-channel linear cross-section filter for the restricted M-RAKE of Figure 3. Figure 5 illustrates an exemplary linear cross filter for the multi-channel linear cross-section filter of Figure 4. Figure 6 illustrates an exemplary linear equalizer in accordance with the present invention. Figure 7 illustrates an exemplary multi-code linear equalizer in accordance with the present invention. Figure 8 illustrates an exemplary multi-channel filter for the multi-channel linear equalizer of Figure 7. Figures 9A and 9B illustrate a mathematical technique for simplifying weighting calculations associated with RAKE receivers. Figure 10 illustrates an exemplary wireless communication system using the RAKE receivers of the present invention.

DETAILED DESCRIPTION OF THE INVENTION Figure 1 illustrates a conventional wireless communication receiver 100 using a generalized RAKE 112 (G-RAKE). The wireless communication receiver 100 comprises a receiver input terminal 110 and G-RAKE 112. The receiver 100 and / or G-RAKE 112 can be represented in a specific application integrated circuit (ASIC). Receiving terminal 110 of the receiver produces received signals r (t) to G-RAKE 112. These received signals r (t) comprise streams of sample values obtained from wireless signals received by one or more antennas associated with one or more terminals 110. input of the receiver. An exemplary input terminal 110 may include amplifiers, filters, mixers, digitizers and other electronics as needed to produce a sampled signal suitable for processing by the G-RAKE 112. The received signal r (t) produced to G-RAKE 112 typically comprises a composite signal that includes one plus multi-path echoes that arise from the multi-path propagation and that reach the receiver 100 from different directions and with different time delays. In addition, the received signal r (t) may include components transmitted from or received by different antennas (not shown). The task of G-RAKE 112 is to generate an estimate (m) of each transmitted symbol s (m) of the received signal r (t). G-RAKE 112 comprises a plurality of fingers 120 RAKE, processor 130 RAKE and combiner 132 RAKE. Each RAKE finger 120 processes different time shifts or multi-path echoes of the received signal r (t). Typically, each finger 120 RAKE comprises a delay element 122 and a correlator 124. The delay elements 122 delay the received signal r (t) to time-align the multi-path echoes processed by each finger 120 RAKE. The correlators 124 correlate the delayed signals with a propagation code to extract the assigned multi-path echoes from the received signal r (t). The depropagation values of the correlators 124 are combined in the combiner 132. The combiner 132 typically includes weighting elements 126 and the adder 134. The weighting elements 126 weight the multi-path echoes produced from the respective correlators 124. The weighted multi-trajectory echoes are added symbol by symbol by the adder 134 to form an estimate of a symbol of interest, (m), during each symbol period. While some of the figures refer to the estimated symbol of interest as (m), through this specification, the symbol of interest s (m) and the estimated symbol of interest (m) can be represented by s (0) and (0) ), respectively, where m = 0, without loss of generality. In addition, those skilled in the art will appreciate that the time shifts associated with the delay elements 122 correspond to the delays of the multi-path echoes, while combining the weights associated with the weighting elements 126 may correspond to the conjugates of multiplication coefficients of multi-path echoes (RAKE) or conjugates of the weights that depend on the coefficients and a noise correlation matrix (G-RAKE). In the conventional receiver 100 described in the foregoing, the symbol estimates (m) produced during each symbol period may be corrupted by interference, such as intersymbol interference (ISI), which may result in demodulation and decoding errors. The ISI may be due in part to the dispersive effects of the communication channel, and partly to the cross-correlations between the propagation codes used for different symbols. It should be noted that the propagation code is a combination of an assigned Walsh code and a scrambling code. The scrambling code period is typically larger than a symbol period, so that the net effect is a propagation code that varies with time. The present invention uses knowledge of the communication channel and cross-correlations between propagation codes for different symbols to determine the cross-correlations between symbols to reduce the interference. Figure 2 illustrates an exemplary multi-symbol RAKE 200 (M-RAKE) according to the present invention. As with the G-RAKE 112, M-RAKE 200 can be represented in an ASIC. M-RAKE 200 comprises a plurality of fingers 220 RAKE, a processor 230 RAKE and a combiner 232 RAKE. Unlike the 120 RAKE fingers of G-RAKE 112, 220 RAKE fingers can disprove symbols from different symbol periods. Typically, one or more 220 RAKE fingers will have a delay corresponding to a symbol of interest s (0). Other 220 RAKE fingers will have delays that correspond to interfering symbols (ie, symbols close to the symbol of interest that contribute to intersymbol interference). During each symbol period, weighting elements 226 weight the disproportionate symbols produced from the corresponding correlators 224 to form weighted results, which are then summed in the adder 234 to form a symbol estimate (0). The RAKE processor 230 calculates the combination weights of the weighting elements 226 to cancel or reduce the intersymbol interference due to the effects of the communication channel and the cross correlations between the spread codes for different symbols. The combination weights or weighting factors for M-RAKE 200 can be determined from a maximum likelihood (ML) or a minimum root mean square error (MMSE) solution calculated by the 230 RAKE processor using knowledge of the different propagation sequences of symbols and channel coefficients. Typically, these combination weights are based on an analysis of the results of the correlator. With many of the mathematical details and definitions postponed later, the vector of correlator results can be represented as: where y (dJ r mj) corresponds to the result of the J element of delay and the correlator J, h0 s (0) + _h ¡s (i) represents the ¡? o components of the vector result associated with each transmitted symbol, and n represents a noise result vector (thermal noise, other interference). Generally speaking, hi comprises the composite channel impulse response associated with the symbol ith, s (i), which includes channel effects and depropagation (cross correlations of propagation sequence). The first term in Equation (1) represents the symbol of interest and the sum in Equation (1) represents the contribution of all the other symbols, or the ISI, in y. The symbol of interest, s (0), is estimated by using a linear combination of the results of the 220 RAKE fingers, which can be represented as (0) = wH y, where wH is the conjugate transposition of a solution vector w weighing. The linear combination is performed in the combiner 232 RAKE by the weighting elements 226 and the adder 234. The weighting solution vector, based on a maximum likelihood criterion for the estimation, can be calculated by: = Ru_1h0, (2) where Ru is the correlation matrix of all the unwanted components in Equation 1. The correlation matrix Ru can be calculated by taking the expectation with respect to the transmitted noise and random symbols (assuming, the random transmitted symbols are independent). The correlation matrix resulting from the unwanted components can be represented by: where Rp is the noise correlation matrix, which may be crossed correlation fingers after the depropagation process. The calculation of the noise correlation matrix Rn is shown in the following. Because the expectation is taken over the randomly transmitted symbols, instead of the known propagation codes, the combination weights applied by the weighting elements 226 will change each symbol period due to the nature that varies with time of the form propagation wave. The derivation of the correlator results defined in Equation 1 will now be described. The transmitted signal for a simple code channel can be defined as: x (t) = E? s (?) ai (t - iT), (4) where E is the symbol energy, and s (i) and a ± (t) are the ith symbol and its propagation waveform, respectively. The waveform of propagation to? (t) consists of a complex sequence of code chips convolved with a pulse shape. It is assumed that the propagation waveform is normalized so that if the multi-path channel is discrete and comprises L-rays, then g (t) =? g, d (t - tx) (5) / - / represents its impulse response where g and j are the complex gain coefficient and the ray delay lth, respectively. The signal received through this channel can be represented by: L a > r (t) = E? £ gls (í a¡ (t -iT- t,) + n (t), 1 = 1; _- *. (6) where n (t) is a complex noise process.The finger of a RAKE receiver incorporates a challenger, d, that precedes a correlator matched with the propagation waveform of the symbol mth, am (t) The result of the finger can be given as: y (d, m) = P r (+ d) am '( )gives = ^ £? S ^ (iH (a + ¿-r -r / (a) -a + »(í., Bi)) (7) where ñ (d, m) is the result of complex noise of the correlator. Assume that the symbol of interest is s (0), the Traditional RAKE can have m = 0 and the finger delays can be correlated with the delays of the resolvable rays of the multi-trajectory. However, for M-RAKE 200 of the present invention, the propagation waveform used for the correlation can be generalized to be any symbol propagation waveform. The Equation 7 can be rewritten as: y (d, m) = fr (+ d) a "(a) gives _o L 8 = ^ E £ SSS? S (i) a, (a + d -iT- t,) am (a) da + ñ (d, m) M '= - "_ ^ ?? = -_ or (0? / = 1sAm (- * Tr /) + / 7 (i, m) ? h. (d- iT, m) s (i) + n (d, m) (8) where ñ (t, m) = | ° n (a + t) am (a) gives (9) is the result of noise color of the correlator, and is the correlation of the propagation waveform of the ith symbol against the propagation waveform of the mth symbol, used by the finger correlator. Finally, the components associated with a particular symbol (a correlation between the symbol m and í) can be grouped together in a net channel impulse response for the ith symbol, where the propagation code and pulse shape information provides R?, m (t) and the channel estimate is used to get g \. Finally, the results of the RAKE finger can be vectorized for the detection of the symbol of interest as: y = [y (di, mi), y (d2, m2), ... r y (dj, ms)] t, (12) where there are J fingers 220 RAKE. In a case of the traditional correlated filter, J = L, the number of resolvable rays in the multi-path channel. J >fingers may also be used. L. The calculation of the noise covariance or the correlation matrix Rn referred to in Equation 3, is calculated in one of two ways. In the first form, the noise correlation matrix represents the white noise, n (t), which has been colored by the correlation process (filtering) of fingers 220 RAKE to produce ñ (d, m), where the Noise is a function of finger delay 220 RAKE and the particular propagation waveform of symbol m used by correlator 224. Defining finger noise result vector 220 RAKE as n = [ñ (d1, m1) ñ (d2, m2) ... ñ (d, ms)] t, (13) the noise correlation matrix can be represented by: The cross correlation of the ith finger and the jth finger can be given as: (] 5) Because the noise is white, E { n (t) n * (t + t)} = s2d (t + t), where s2 is the noise power, Equation 15 becomes: R "(z ~ 'j) = £ £ W - ß d (+ di-ß- dj) dadß. (16) The classification property of the function d (•) in the integration results in: R "\ J) = s2 £ a¡ (a) aQ (a + d, - d.}.) Da = 2Rmj ,,, (di -dJ). (17) In this way, the noise covariance can be constructed using the cross-correlation information of the propagation code and the noise power estimates (s2). The latter can be estimated by using known techniques. When the interference of other user signals is present (ie, not modeled as ISI or ICI), then the noise on the receiving antenna may not be white. A second way to calculate the noise covariance matrix is to estimate the noise correlations using de-propagated values. For example, the model in Equation 1 also applies to pilot symbols that are sent in the pilot channel. This model can be used to obtain vectors of the noise samples, n, by subtracting the pilot symbol contributions of the vector y. The external products of the noise sample vectors can be formed and smoothed in time to give an estimate of the noise covariance matrix. When this matrix is Hermitian symmetric, only the upper or lower triangle of the matrix needs to be estimated. Returning now to Figure 3, an alternative embodiment of the present invention, referred to herein as restricted M-RAKE 300, will now be discussed, restricted M-RAKE 300 comprises a plurality of RAKE fingers 320 and a multi-line linear filter 340. -channel (MC-LTF). In restricted M-RAKE 300, each RAKE finger 320 includes a delay element 322 and a correlator 324. In this embodiment, the delays associated with each RAKE finger 320 are selected such that the disproportioned symbols produced from each correlation 324 are aligned by time. The disproportionate symbols produced from the RAKE fingers 320 are input to the MC-LTF 340. As shown in Figure 4, the MC-LTF 340 comprises a plurality of parallel linear transverse filters 342 (LTFs), each associated with a finger. 320 RAKE corresponding, and an adder 344 that adds the filtered results of each LTF 342 to generate a symbol estimate (m). Those skilled in the art will appreciate that other modalities of the MC-LTF 340 are possible. In general, past finger results are stored, and the results of multiple fingers and multiple symbol periods are combined. Each LTF 342 combines the disproportionate symbols produced from a corresponding RAKE finger 320 during a plurality of successive symbol periods as shown in Figure 5. The combined undone symbols for each LTF 342 include a symbol of interest and nearby interfering symbols ( both precedent and successive the symbol of interest) that contributes to ISI. The function of the LTF 342 is to reduce the ISI in the symbol of interest as described in greater detail in the following. The filtered signals produced from each LTF 342, referred to herein as the filtered output signals, are aggregated by the multi-path adder 344 to generate the symbol estimates. The adder 344 performs a similar function as an adder in a conventional RAKE receiver to improve the signal to noise ratio of the final symbol estimates. Each LTF 342 comprises 2M + 1 weighting elements 346, 2M delay elements 348, and LTF summing 350, where M represents the length of the ISI in the symbol periods. Thus, when M equals 2, there will be four interfering symbols (two precedents and two successive ones) surrounding an interest symbol s (m). LTF 342 receives and delays the disproportionate symbols produced from a corresponding RAKE finger 320 in a derived delay line comprising a plurality of delay elements 348. Deprecated symbols can be corrupted by ISI. During each symbol period, the LTF 342 ponders and combines the disproportionate symbols produced during 2M + 1 symbol periods centered on the symbol of interest s (m) in the weighting elements 346 and the summing LTF 350. The weighting factor for each weighting element 346 is solved together in a simple step by the processor 330 based on the channel coefficients and the cross-correlation between the propagation codes, as further described in the following. Restricted M-RAKE 300 reduces the number of RAKE fingers 320 while providing the same RAKE finger results typically provided by a larger number of 220 RAKE fingers on the M-RAKE 200 shown in Figure 2. For example, assume, an M- RAKE 300 restricted comprises four fingers 320 RAKE, where each RAKE finger produced is fed into a multi-channel LTF 340 that spans _ + 1 symbols (M = 1) around the desired symbol. This model M-RAKE 300 is equivalent to the unrestricted M-RAKE 200 with the 12 fingers 220 RAKE. In this way the processing advantages can be achieved with restricted M-RAKE 300. Figure 6 shows a linear equalizer 400 (LEQ) constructed in accordance with the present invention. LEQ 400 comprises a generalized RAKE 410 (G-RAKE) and a linear transverse filter 442 to combine the successive results of the G-RAKE 410. Those skilled in the art will understand that the G-RAKE 410 can use a variety of combination methods. , which include the traditional RAKE combination. G-RAKE 410 comprises a plurality of fingers RAKE 420, a processor RAKE 430, and a combiner 432 RAKE. Each RAKE finger 420 comprises a delay element 422 and a correlator 424. Like the restricted M-RAKE 300 of Figure 3, the delays associated with each RAKE finger 420 are selected such that the disproportionate symbols produced from each correlator 424 are they line up for time. The results of the correlators 424 are weighted in the weighting elements 426 and summed by the adder 434 to form a RAKE result signal. The RAKE result signals from combiner 432 are input to LTF 442. As with the restricted M-RAKE 300 discussed in the foregoing, the delay length of LTF 442 is 2M + 1 symbols centered on the symbol of interest s (m). During each symbol period, LTF 442 combines 2M + 1 RAKE result signals to generate a symbol estimate. The RAKE result signals are combined using determined weighting factors based on the channel coefficients and the cross-relationships between the propagation codes to reduce ISI of the interest symbol s (m). The weighting factors for LTF 442 are determined according to essentially the same ML criteria form as with the M-RAKE 200, with some redefinition of the data vectors in question. When the results of the RAKE finger are stored in LTF 442, the vector of the RAKE finger results is redefined according to the time they were produced. That is, the results of the correlators 424, previously defined in Equation 1, can be rewritten as y (mT) = ¡? ImT + d ^ m) y (mT + d2, m) ... y (mT '+ d_ ,, m)] = h0 (mT) s (O) +? h, (mT) s (i) + n (mT \ (18) 0 where i (T) is the response of the symbol i ch seen in the vector result of finger RAKE mth, and where the symbol of interest is represented by s (0) The result of combiner 432 comprises the mth-combined result of the RAKE finger results and can be defined as: z (_nT) = gH? (mT), (19) where, for example, the weighting and combining process simply comprises the complex conjugate of coefficients of the channel derivations in the dispersed channel, (traditional RAKE) g = [gi g • • - i t- The contents of LTF 442 can be represented in vector form as: z = [z (-MT) z (- (M -?) T) ... z (MT)] t = h'-5 (0) +? h; í (+ n ', (20)? -0 Equation 20 has the same general form as Equation 1, with the components of the various symbols and noise separated.The estimate (m) of the symbol of interest can be represented as: (0) = vH z. (21) The weighting vector, v, in the LTF 242 can be calculated by: v = 'K (22) where the cross-correlation matrix Ru- of the unwanted portion of the signal can be given as: R ", =? H; .h; * + R", (23) ?? 0 The cross correlation matrix RU 'describes cross correlations between the effective propagation codes for different symbols. The details regarding the calculation of the noise correlation matrix Rp- are further discussed in the following. As with the M-RAKE 200 of Figure 2, the weighting factors calculated according to the ML criteria change each symbol period due to the change in the propagation waveform. Substituting Equation 18 in Equation 19 produces: z (mT) = * y = gHho (mT) s (0) +? g * h,? m_ zj + gHn (mT) .. (24), vo from which the vector z can be written as: From this, h 'can be defined as: h; - l) T) ... gHh,. (- F)] r, (26) and the noise vector, n ', as: n' = [gHn (MT) gHn ((M -l) T) ... g "u (-MT) (27) This noise vector n 'can be rewritten as: where this diagonal block matrix of the channel coefficients can be defined as: This allows the correlation matrix Ru > of the noise vector, n ', is written as: R, = E { n'n "H.}. = GHE { n" n "H j] G (30) = G? R ,,, G, Equation 30 shows that Rp "can be the element for the element calculated in the same way as Rn was calculated (for example, Equation 17 for the case of white noise) .The present invention can also be used in multi-receiver receivers. code.The results of multi-code transmission when multi-code channels are dedicated to a single downlink receiver to increase the capacity to carry data.This is analogous to several separate simultaneous transmissions that are received by a single receiver. the receiver is linked to demodulate each of these code channels, you can also use the results of the demodulation of one code channel to aid in the demodulation of another code channel, in addition, due to the multi-codes received by the receiver of multi-code, each demodulated symbol may, in addition to ISI, be susceptible to inter-code interference (ICI) caused by adjacent code symbols. For example, the M-RAKE 200 of Figure 2 can be adapted to process multi-code signals by assigning a subset of 220 RAKE fingers to each code channel. Although those skilled in the art understand that tuning to the propagation codes of other code channels does not necessarily demodulate the other code channels, they will also appreciate that this tuning process provides information about the other code channels, which can also help reduce the effects of cross-interference in the code channel of interest. In its most general form, the modified M-RAKE includes multiple subgroups of 220 RAKE fingers tuned to the propagation codes of different code channels. In addition, these 220 RAKE fingers can be tuned to different symbol intervals and delays. The restricted M-RAKE 300 of Figure 3 can also be extended to multi-code by adding additional 320 RAKE fingers tuned to different code channels, with the expansion of MC-LTF 340 according to the number of 320 RAKE fingers added. In this scenario, the joint solution of the weights within the MC-LTF 340 takes into account the propagation codes of all the code channels. Similarly, the LEQ 400 of Figure 6 can also be extended to multi-code by using a plurality of LEQ 400 tuned to different code channels and extending LTF 442 after each LEQ 400 to an MCO-LTF as shown in Figure 7 The linear multi-code equalizer 500 (MCO-LEQ) comprises three G-RAKE 510, each tuned to one of three code channels, a 530 RAKE processor, and a 540 multi-code linear cross filter. Each G-RAKE 510 comprises a plurality of fingers 520 RAKE and a combiner 532 RAKE. Each RAKE finger includes a delay element 522 and a correlator 524. The delays for the delay element 522 are selected such that the result of each finger 520 RAKE is aligned for time with the other fingers 520 RAKE. The 524 correlators deprogate the received symbols, which are then weighted in the weighting elements 526 and summed by the adder 534. The weights applied by the weighting elements 526 are calculated in a conventional RAKE or G-RAKE form as is well known in the art. The MCO-LTF 540 combines the RAKE result symbols of each G-RAKE 510 using determined weighting factors based on cross-correlations between symbols based on channel coefficients and cross-correlations between propagation codes as previously described. In the situation where all the code channels are assigned to a single user, the MC-LTF 540 produces a symbol estimate for each code channel (co-channel). Thus, if there are three code channels, the MCO-LTF 540 can produce three symbols per symbol period. In this case, the MCO-LTF 540 can reduce the interference between symbols that can be attributed to symbols transmitted in the same code channel, as well as inter-code interference due to symbols transmitted over different co-channels. The present invention, however, can also be used in the situation where each co-channel is assigned to a different user. Figure 8 illustrates an exemplary MCO-LTF 540 corresponding to MC-LEQ 500 of Figure 7. MCO-LTF 540 in one embodiment of the invention, may comprise a plurality of multi-channel linear transverse filters 340 (MC- LTF) as shown in Figure 4. Each MC-LTF 340 combines the RAKE result symbols of all the G-RAKE 510 using the weighting factors determined based on the channel coefficients and the cross-correlations between the symbols. Each MC-LTF 340 in the MCO-LTF 540 produces a simple symbol estimate corresponding to the selected co-channels for each symbol period. The weighting factors for each LTF 342 may differ. For example, the weighting factors for the MC-LTF 340 associated with co-channel 1 can be selected to reduce the interference of the symbols in co-channels 2 and 3. The same procedure can be used for the MC-LTF 340 for co-channels 2 and 3, which results in different weighting factors. Note that LTF units that store the same RAKE results can share memory to reduce memory requirements. As discussed in the foregoing, the weighting factors for LTF 342 can be determined according to a ML solution. However, computational savings can be achieved if a ML solution is calculated as a minimum squared mean error solution (MMSE), and then converted to a ML solution through a scaling of the combination (or final result) weights, which can be calculated from the elements of the MMSE solution. It is normal to show that for a 200, 300, 400 RAKE single-user detection receiver, the weighting vector, w, the ML combination of the RAKE finger results is the same as the MMSE weighting vector solution, v , within a scaling factor, that is, = Ov (31) where a is a true coefficient. This coefficient a essentially refers to the reliability of symbol estimation. By first examining the case for a single user, the RAKE finger results can be written as: where h2 is the net response through the fingers of the ith symbol, s (i), through the propagation and despreading channel. The noise vector n represents the vectorized result of multiple fingers with white noise as the input. Without loss of generality, h0s (0) corresponds to the symbol of interest where _n = 0. For the MMSE solution, the data correlation matrix, Ry = I? (Y and j, can be used to solve the familiar expression v = R X > 03) where h0 results from l_ | ys * (0) j, with this expectation taken only on the symbols. For the ML solution, the perturbation correlation matrix, Ru, is used, which is the data correlation matrix minus the part related to the desired symbol, or R ^ R ^ -hoh ^, (34) to solve another similar expression, still familiar Equation 31 can be easily tested, starting with Equation 33 and using the data from Equation 34: v = R'h0 = R; 'R.R;, h0 Because h0 V is a scalar, w can be written as: = i-híV (37) resulting in a scaling factor of: a - 1 l-hfv (38) or This scaling factor, a, is written in terms of an MMSE solution, with the assumption that it is desirable to convert a MMSE solution to a ML solution. That is, the terms to calculate a may already have been calculated for the MMSE solution. Another expression for "£ 7" can be used without explaining the fact that the channel estimate can be an escalated version of the true channel coefficient, due to differences between the pilot and traffic channel power levels and the propagation factors. Specifically, the "£ 7" factor can be calculated as a = - (39) \ - Ah • "ov where A corresponds to the radius of energy in a traffic symbol to the energy in the pilot symbol For example, A can be expressed as A = rlr2, (40) where rl is The ratio of power assigned to the traffic channel to the power assigned to the pilot channel can be estimated or established at the same nominal value Estimation of this relationship is addressed in Bottomley et al., "Methods, communications apparatus and products of computer program using gain multipliers ", US Patent Application No. 09 / 968,443, filed October 1, 2001. The variable r2 represents the ratio of the propagation factor of the traffic channel to the propagation factor of the pilot channel (length of the pilot symbol used for channel estimation.) These quantities are known in the receiver, with respect to the multi-user / multi-code detection case, which can be used in the transmission of WCDMA multi-code, parallel data channels sent to a user are considered as multiple user signals. Separate banks of RAKE fingers, each tuned to a user propagation sequence, can produce a vector of RAKE finger results, z, and these can be combined together for a vector symbol estimation, where the vector elements are estimates of the individual user symbols. For the case of MMSE, this can be represented by GSB = VH z and for the case of ML, MLSE = V¡H z, where V and W are the weight matrices of MMSE and ML, respectively. The same escalated relationship between the multi-user weighting solution of MMSE and the multi-user weighting solution of ML is not as obvious as in the case of a single user. Now consider the case of multi-code / multi-user, where there are K codes in parallel. The result vector of the RAKE finger can be given by: where j / k is the net response of the ith symbol of the user kth, s (i, k). Again, n is the result of noise vector from the fingers. Solving together for a vector of user symbols a (i) = [s (i, l) s (i, 2) ... s (i, K)] t (42) produces: (43) where vk is the weighting vector to provide the MMSE estimate of the user kth symbol. This can be rewritten as a matrix V times the results of the RAKE finger MMSB (0) = VH z, (44) where V = [vx v2 ... v?] And MMSE (0) represents the symbol of interest. It is normal to show that the joint MMSE solution that minimizes || s (0) - (0) || 2 is the same as the solution that minimizes the quadratic error of the individual estimates of the user's symbols, as a result, the matrix of weighting for the joint MMSE solution, V, can be written as: = R :? 0 '(45) where the net responses of the K users become the K columns of the H0 matrix, the 0 subscript indicates that this is the answer for the desired 0th symbol vector. Continuing, the 0 can be discarded for clarity, understanding that the response vectors for the 0th symbol are being considered. All this vector and matrix manipulation provides a concise way to write a joint MMSE solution. Assuming that this equation is solvable using the matrix equation, the implication of Equation 45 is that only a simple matrix inversion needs to be calculated. For the ML solution, it is not obvious that this is the case. The vector ML solution can be written in much the same way as in the above ML. { 0) = WH z (46) where W = [wx 2 ... w?]. As a solution that gives us logarithmic probability relationships (LLR) for the bits we want from the individual users, the estimates are desired from the symbols that are ML individually. The weighting matrix, W, for the ML solution can therefore be represented by: W = | R3ih, R "._ b2 z i (47) where the perturbation correlation matrix for each ML weighting vector solution of the user may be different, as indicated in Ru, k for the user kth. Maintaining the assumption that the weights that use the matrix investment are being solved, it may seem that it is necessary to calculate K different investments to solve this system, as opposed to the simple investment matrix of the MMSE solution. However, it should be noted that as in the case of the simple user, the perturbation correlation matrix for the ML solution is the same as the MMSE data correlation matrix minus the desired symbol component, ie * ". * = *. - ** - (48) It is recognized that the investment of u, k can be written as an "update of a scale" investment so, The kth column of becomes: v_ + vA and the same conclusion for the case of a single user is achieved, although it is shown from a slightly different direction (using the update of a scale). Then Equation 47 becomes: W = [?, V, ¿2V2 - ¿A-VJ. ] (51) where and at the end where W = V? (53) where? is a diagonal matrix with Aj. as the diagonal element kth. Grouping these individual solutions into a matrix equation provides a concise expression in Equation 53, but also points out the important implementation points. Specifically, given a solution that involves matrix inversion, it emphasizes that only a simple investment matrix is calculated from a solution of MMSE as opposed to the investment matrices K for the ML solution, which can represent important processing savings. As discussed in the above and as shown in Equation 54, the shape of the MMSE solution is similar to the shape of the ML solution. vmSE = (Rz) a h'0 (54) However, the correlation matrix of the data, R2 is used, instead of the disturbance or noise correlation matrix, Ru. The z vector form of the RAKE results for the qth symbol can be represented by: zg = [z (q - M) z (q - (- 1)) ... z (q + M)] t, (55) where the symbol period, T, is discarded for convenience. This vector essentially represents the contents of LTF 442 corresponding to LEQ 400 discussed above. In another form, zg can be rewritten as: zg = [z (q - M) ag] t, (56) where most of the vector z is now represented by the sub-vector ag. Note that for the next symbol, q + 1, the data is changed through LTF 42, producing: zg + 1 = [ag z (q + M + l)] t, (57) where z (q + M + l) comprises the new combined RAKE result introduced in the filter. As discussed in the above, the correlation matrix for the solution for the qth symbol can be represented by: Rz (q) = E < l (58) where E { -} it is the operation of statistical expectation, which in this case is taken only on random noise. Substituting Equation 56 in Equation 58 results in: Repeating this with Equation 57 for q + 1 results in: As shown in Equations 59 and 60, a submatrix E ü j appears in the correlation matrix for the symbol g and q + 1, indicating that it can be reused. Essentially, for each of the sub-matrices E ñ j of successive symbols can be changed to partially form a new correlation matrix for the new symbol. Figures 9a and 9b illustrate the nature of this matrix change. As shown in Figure 9a, Rg 600 comprises row one 610, column one 620, and sub-matrix Em. & J630. Row one 610 and column one 620 limit the limits to the left and more upper of the sub-matrix Em 2L j 630. Also, Figure 9b illustrates that Rg +? 602 comprises the row M 612, column M 622, and submatrix i? Ja 630 < -g + l 602 can be generated from Rg 602 by changing the submatrix a to H 630 in the upper left corner of Rg + i 602. As a result, only row M 612 and column M 622 are calculated to complete Rg + X 602. Depending on the size of the R matrix, the computational savings can be substantial.

The MMSE solution allows the special time variation structure of the data correlation matrix, R_. As seen in the above, the variation of the propagation waveform requires the calculation of a new weighting vector for each symbol period. This variation of the propagation waveform manifests itself in the change of h'0 and R? '1 - However, R2 does not change completely from symbol to symbol, and therefore, a substantial portion of R2 can reuse. As a result, only a portion of Rz needs to be calculated from erasing for each new symbol. Furthermore, in the multi-code scenario, the same MC-LEQ 500 with the same data contents can be used to solve all the K-code channels in a given symbol case. If the ML solution is used, the Ru matrix is encashed for each code channel because Ru varies from channel code to channel code. However, with the MMSE solution, a single common data correlation matrix, R_ can be calculated and used for all the K solutions. The RAKE receiver modes discussed herein can be arranged in any wireless communication device, such as a base station 700 or mobile terminal 710, as shown in Figure 10. As used herein, the term "mobile terminal" may include a cellular radiotelephone with or without a multi-line display; a Personal Communications System (PCS) terminal that can combine a cellular radiotelephone with data processing, fax and data communication capabilities; a personal data assistant (PDA) that can include a radiotelephone, search engine, Internet / intranet access, Web browser, organizer, calendar, and / or global positioning system (GPS) receiver; and a conventional laptop computer and / or a palmtop receiver or other apparatus that includes a radiotelephone transceiver. Mobile terminals can also be referred to as "dominant computing" devices. The base station 700 includes antenna 702 for transmitting symbols to the mobile terminal 710. Objects, such as the interference object 720 can cause multiple echoes of the transmitted symbols to reach the mobile terminal 710 at different times, as described above. The symbols received in the antenna 712 of the mobile terminal 710 are then processed in the receiver 714 RAKE. Receiver 714 RAKE represents any of the exemplary embodiments described in the foregoing. Similarly, the mobile terminal 710 can transmit symbols along multiple paths to the base station 700. The receiver 704 RAKE in the base station 700 can then process the received symbols according to any of the exemplary embodiments described in the foregoing. In discussing exemplary embodiments of the present invention, it should be understood that one or more embodiments of the present invention comprise signal processing methods that can be implemented in hardware using integrated or discrete circuits, in software as stored program instructions, or in some combination thereof. More generally, one or more embodiments of the present invention may be represented in hardware and / or software (including firmware, resident software, micro-code, etc.) including a specific application integrated circuit (ASIC). The present invention, of course, can be carried out in other forms than those specifically set forth herein without departing from the essential features of the invention. The present modalities will be considered in all respects as illustrative and not restrictive, and all changes that fall within the meaning and scope of equivalence of the appended claims are intended to be encompassed therein.

Claims (89)

1. CLAIMS 1. A RAKE receiver comprising: a plurality of RAKE fingers for despreading symbols received on multiple paths of a multi-path channel, wherein the first of the plurality of RAKE fingers comprises a delay corresponding to a symbol of interest and the second of the plurality of fingers RAKE comprises a delay corresponding to an interference symbol; a processor to determine a cross-correlation between the symbol of interest and the interference symbol; and a RAKE combiner to combine by RAKE the symbol of interest of the first of the plurality of fingers RAKE with the interference symbol of the second of the plurality of fingers RAKE using the cross-correlation to reduce the interference between symbols that can be attributed to the symbol of interference from the symbol of interest. The RAKE receiver of claim 1, wherein the processor estimates the channel coefficients for the multi-path channel trajectories and determines the cross-correlation between the symbol of interest and the interference symbol based on the estimated channel coefficients . 3. The RAKE receiver of claim 1, wherein the processor further calculates the cross-correlations of the propagation sequence and determines the cross-correlation between the symbol of interest and the interference symbol based on the cross-sectional correlations. 4. The RAKE receiver of claim 1, wherein two or more of the plurality of RAKE fingers disproportes the same symbol received on different multi-path channel paths. A method for reducing intersymbol interference from a symbol of interest comprising: deproducting received symbols on multiple paths of a multi-path channel, wherein the symbols include a symbol of interest and an interference symbol; determine a cross-correlation between the symbol of interest and the interference symbol; and combining by RAKE the symbol of interest with the interference symbol using determined weighting factors based on the cross-correlation to reduce the inter-symbol interference that can be attributed to the interference symbol from the symbol of interest. The method of claim 5, wherein determining the cross-correlation between the symbol of interest and the interference symbol comprises estimating the channel coefficients for multiple trajectories of the multi-path channel and determining the cross-correlation based on the coefficients of estimated channel. The method of claim 5, wherein determining the cross-correlation between the symbol of interest and the interference symbol comprises calculating cross-correlations of propagation sequence and determining the cross-correlation between the symbol of interest and the interference symbol based on in cross-sectional correlations. A RAKE receiver comprising: a plurality of RAKE fingers for despreading symbols received on multiple paths of a multi-path channel, wherein the symbols include a symbol of interest and at least one interference symbol; a processor for determining the cross-correlations between the symbol of interest and at least one interference symbol; and a multi-channel filter for reducing intersymbol interference that can be attributed to at least one interfering symbol from the symbol of interest by combining decayed symbols of different symbol periods produced by the plurality of RAKE fingers using factors of weighting determined based on the cross-correlations between the symbols, the multi-channel filter comprises: a plurality of linear transverse filters, each of which is associated with the corresponding one of the plurality of RAKE fingers, to weight and combine disproportionate symbols produced by the corresponding of the plurality of RAKE fingers over a plurality of symbol periods using weighting factors determined based on the cross-correlations between the symbols to generate a plurality of filtered result symbols; and an adder to combine the plurality of filtered result symbols to generate an estimate for the symbol of interest. The RAKE receiver of claim 8, wherein the processor further estimates the channel coefficients for multiple trajectories of the multi-path channel and determines the cross-correlations between the symbol of interest and at least one interference symbol based on the estimated channel coefficients. The RAKE receiver of claim 8, wherein the processor further calculates cross-correlations of propagation sequence and determines the cross-correlation between the symbol of interest and at least one interference symbol based on the cross-sectional correlations. The RAKE receiver of claim 8, wherein each of the linear transverse filter comprises: a derivative delay line comprising a series of delay elements for delaying the disproportionate symbols produced by the corresponding one of the plurality of RAKE fingers; a plurality of weighting elements for weighting the corresponding ones of the deproposed symbols delayed by the weighting factors determined based on the cross correlations to generate the weighted result symbols; and an adder to combine the weighted result symbols to generate the filtered result symbol. 12. A method for reducing intersymbol interference of a symbol of interest comprising: despreading multiple received symbols onto multiple trajectories of a multi-path channel; determine cross correlations between the symbol of interest and at least one interference symbol; combining the disproportionate symbols received on the same path during a plurality of symbol periods using weighting factors determined based on the cross-correlations between the symbols to generate a plurality of filtered result symbols; and combining the filtered result symbols to produce an estimate of the symbol of interest with reduced inter-symbol interference. The method of claim 12, wherein determining the cross-correlations between the symbols for the symbol of interest and at least one interference symbol comprises estimating the channel coefficients for the multiple trajectories of the multi-path channel and determining the cross-correlations between the symbols based on the estimated channel coefficients. The method of claim 12, wherein determining the cross-correlations between the symbol of interest and at least one interference symbol comprises calculating cross-correlations of propagation sequence and determining the cross-correlation between the symbol of interest and at least an interference symbol based on the cross-sectional correlations. The method of claim 12, wherein combining the disproportioned symbols received on the same path during a plurality of symbol periods using weighting factors determined based on the cross-correlations between the symbols to generate a plurality of filtered result symbols comprises : delaying the disproportioned symbols received on the same path in a derived delay line to generate a plurality of delayed symbols; weighting each of the plurality of delayed symbols using the weighting factors determined based on the cross-symbol correlations to generate a plurality of weighted symbols; and adding the weighted symbols to generate each of the plurality of filtered result symbols. 16. A RAKE receiver comprising: a plurality of RAKE fingers for despreading symbols received on multiple paths of a multi-path channel; a processor to determine the cross-correlations between symbols for a symbol of interest and at least one interference symbol; a RAKE combiner to combine the disproportionate symbols received on different trajectories in the same symbol period to generate RAKE result symbols; and a second combiner for combining the successive RAKE result symbols produced over a plurality of successive symbol periods using weighting factors determined based on the cross-correlations between the symbols to reduce the inter-symbol interference that can be attributed to at least one symbol of interference from the symbol of interest. The RAKE receiver of claim 16, wherein the processor estimates the channel coefficients for the multiple paths of the multi-path channel and determines the cross-correlations between the symbol of interest and at least one interference symbol based on the estimated channel coefficients. 18. The RAKE receiver of claim 16, wherein the processor further calculates the cross-correlations of the propagation sequence and determines the cross-correlation between the symbol of interest and at least one interference symbol based on the cross-sectional correlations. 19. The RAKE receiver of claim 16, wherein the second combiner comprises: a derived delay line comprising a series of delay elements for delaying the successive of the RAKE result symbols to generate a series of delayed result symbols; a plurality of weighting elements to weight the corresponding ones of the delayed result symbols using the weighting factors determined based on the cross correlations between the symbols to generate weighted result symbols; and an adder to combine the weighted result symbols to generate an estimate for the symbol of interest. 20. The RAKE receiver of claim 16, wherein the RAKE combiner comprises a G-RAKE combiner. 21. A method for reducing intersymbol interference of a symbol of interest comprising: deproducting multiple symbols from different symbol periods received on multiple paths of a multi-path channel, the multiple symbols include a symbol of interest and at least an interference symbol; determine the cross-correlations between the symbol of interest and at least one interference symbol; combining by RAKE the disproportioned symbols received on different trajectories during the same symbol period to generate the RAKE result symbols; and combining the successive RAKE result symbols produced by a plurality of successive symbol periods using weighting factors determined based on the cross-correlations between the symbols to reduce the inter-symbol interference that can be attributed to at least one interfering symbol from of the symbol of interest. The method of claim 21, wherein determining the cross-correlations between the symbol of interest and at least one interference symbol comprises estimating the channel coefficients for the multiple trajectories of the multi-path channel and determining the cross-correlations between the symbols based on the estimated channel coefficients. The method of claim 21, wherein combining the successive RAKE result symbols produced over a plurality of successive symbol periods comprises: delaying successive RAKE result symbols in a derived delay line to generate a plurality of result symbols retarded; weighting each of the plurality of delayed result symbols using a given weighting factor based on the cross-correlations between the symbols to generate a plurality of weighted result symbols; and adding the plurality of weighted result symbols to generate an estimate for the symbol of interest. 24. A multi-code RAKE receiver comprising: a plurality of parallel RAKE receivers that provide RAKE result symbols for a plurality of code channels; a processor for determining the cross-correlations between the symbol propagation codes for a symbol of interest and at least one interference symbol; and a multi-channel filter for combining the RAKE result symbols to reduce the interference that can be attributed to at least one interfering symbol from the symbol of interest, the multi-channel filter comprising: a plurality of transverse filters linear, of which each is associated with the corresponding one of the plurality of parallel RAKE receivers, to weight and combine the RAKE result symbols produced by the corresponding RAKE receiver over a plurality of symbol periods using weighting factors determined based on the cross-correlations between the symbols to generate filtered result symbols; and an adder to combine the filtered result symbols to generate an estimate of a symbol of interest. 25. The multi-code RAKE receiver of claim 24, wherein the plurality of RAKE receivers comprises a plurality of G-RAKE receivers. 26. The multi-code RAKE receiver of claim 24, wherein the processor determines the cross-correlations between the symbols based on channel coefficients that correspond to the multiple paths of the multi-path channel. 27. The multi-code RAKE receiver of claim 24, wherein each linear transverse filter comprises: a derived delay line comprising a series of delay elements for delaying successive RAKE result symbols to generate delayed result symbols; a plurality of weighting elements to weight the corresponding ones of the result symbols delayed by the weighting factors determined based on the cross correlations between the symbols to generate weighted result symbols; and an adder to combine the weighted result symbols. 28. A method for reducing interference of a symbol of interest comprising: despreading and combining the received symbols on a plurality of code channels in a plurality of RAKE receivers to produce RAKE result symbols, wherein each code channel comprises multiple paths; determine the cross-correlations between different symbols; combining a plurality of RAKE result symbols produced from each RAKE receiver over a plurality of symbol periods using weighting factors determined based on the cross-correlations between the symbols to generate a filtered result symbol for each RAKE receiver; and combining the plurality of filtered result symbols to generate an estimate of the symbol of interest with reduced self-interference. The method of claim 28, wherein determining the cross-correlations between different symbols comprises estimating the channel coefficients for each path of each code channel and determining the cross-correlations between the symbols based on the estimated channel coefficients. The method of claim 28, wherein combining a plurality of RAKE result symbols produced from each RAKE receiver over the plurality of symbol periods using determined weighting factors based on the cross-correlations between the symbols to generate the plurality of symbols of filtered results, comprising: delaying the RAKE result symbols in a derived delay line to generate a plurality of delayed result symbols; weight the result symbols delayed by the weighting factors determined based on the cross-correlations between the symbols to generate a plurality of weighted symbols; and add the plurality of weighted symbols. The method of claim 28, wherein the depropagation and combination of symbols received on a plurality of code channels is performed on G-RAKE receivers. 32. A RAKE receiver for reducing interference of a symbol of interest comprising: a plurality of RAKE fingers for deproducting a plurality of symbols received on multiple paths of a multi-path channel; a processor to determine cross correlations between different symbols; and a combiner for combining the de-propagated symbols of different symbol periods using weighting factors determined based on the cross-correlations between different symbols to generate an estimate of the symbol of interest with reduced interference. 33. The RAKE receiver of claim 32, wherein the first of the plurality of fingers RAKE has a delay corresponding to the symbol of interest and the second of the plurality of fingers RAKE has a delay corresponding to an interference symbol. 34. The RAKE receiver of claim 33, wherein the processor determines a cross-correlation between a symbol propagation code for the symbol of interest and a symbol propagation code for the interference symbol. 35. The RAKE receiver of claim 34, wherein the combiner combines the symbol of interest with the interference symbol using the cross-correlation to reduce the interference that can be attributed to the interference symbol from the symbol of interest. 36. The RAKE receiver of claim 32, wherein the combiner comprises a multi-channel filter comprising: a plurality of linear transverse filters, each of which is associated with the corresponding one of the plurality of RAKE fingers, to weight and combining the disproportionate symbols produced by the corresponding RAKE fingers over a plurality of symbol periods using weighting factors determined based on the cross-correlations between the different symbols to generate a plurality of filtered result symbols; and a filter combiner to combine the filtered result symbols. 37. The RAKE receiver of claim 36, wherein each linear transverse filter comprises: a derivative delay line comprising a series of delay elements for delaying the successive symbols produced by the corresponding RAKE fingers to generate a set of delayed symbols during each symbol period; a plurality of weighting elements for weighting the corresponding ones of the symbols delayed by the weighting factors determined based on the cross correlations to generate weighted result symbols; and an adder to combine the weighted result symbols to generate each of the plurality of filtered result symbols. 38. The RAKE receiver of claim 32, wherein the combiner comprises: a RAKE combiner for combining by RAKE disproportionate symbols received on different paths in the same symbol period to generate a combined RAKE result symbol for each path; and a linear transverse filter for combining successive RAKE result symbols produced over a plurality of successive symbol periods using weighting factors determined based on the cross-correlations between the different symbols to reduce the interference that can be attributed to the interference symbols from of the symbol of interest to generate the estimate of the symbol of interest. 39. The RAKE receiver of claim 38, wherein each linear transverse filter comprises: a derived delay line comprising a series of delay elements for delaying successive RAKE result symbols to generate a plurality of delayed RAKE result symbols during each period of symbol; a plurality of weighting elements to weight the RAKE result symbols delayed by the weighting factors determined based on the cross-correlations between the different symbols to generate weighted RAKE result symbols; and an adder to combine the weighted RAKE result symbols. 40. The RAKE receiver of claim 32, wherein the RAKE fingers are divided into two or more groups, and wherein each group of RAKE fingers deproduces symbols received on a different code channel. 41. The RAKE receiver of claim 40, wherein the combiner comprises: a RAKE combiner for each group of RAKE fingers to combine the result symbols of the RAKE finger within the corresponding group to generate the RAKE result symbols; and a multi-channel filter for combining the RAKE result symbols to reduce the interference that can be attributed to at least one interfering symbol from the symbol of interest, the multi-channel filter comprising: a plurality of transverse filters linear, of which each is associated with one of the code channels, to weight and combine the successive RAKE result symbols produced from a corresponding RAKE combiner over a plurality of symbol periods using weighting factors determined based on the cross-correlations between the different symbols to generate filtered result symbols; and an adder to combine the filtered result symbols. 42. The RAKE receiver of claim 41, wherein the RAKE combiners are G-RAKE combiners. 43. The RAKE receiver of claim 42, wherein each linear transverse filter comprises: a derived delay line comprising a series of delay elements for delaying the successive RAKE result symbols produced by the corresponding RAKE combiner to generate a plurality of delayed result symbols; a plurality of weighting elements for weighting the result symbols delayed by the weighting factors determined based on the cross correlations between the different symbols to generate the weighted result symbols; and an adder to combine the weighted result symbols. 44. The RAKE receiver of claim 32, wherein the cross-correlations between the different symbols form a correlation matrix used to determine the weighting factors. 45. The RAKE receiver of claim 44, wherein the correlation matrix of a first symbol period reuses a sub-matrix of the correlation matrix of a previous symbol period. 46. The RAKE receiver of claim 32, wherein the combiner further determines a scaling factor based on the channel estimate and multiplies the scattered symbols combined by the scaling factor to improve a reliability of the symbol of interest estimate. 47. The RAKE receiver of claim 46, wherein the scaling factor is based on the weighting factors. 48. The RAKE receiver of claim 46, wherein the RAKE receiver receives signals from the traffic and pilot channel and wherein the scaling factor is based on a ratio of a power allocated to the traffic channel signal with an assigned power to the pilot channel signal. 49. A method for reducing the interference of a symbol of interest comprising: deproducting received symbols on at least one multi-path channel; determine the cross-correlations between different symbols; and combining the de-propagated symbols of different symbol periods using weighting factors determined based on the cross-correlations between different symbols to generate an estimate of the symbol of interest with reduced interference. 50. The method of claim 49, wherein despreading the received symbols onto at least one multi-path channel comprises despreading the symbol of interest and at least one interfering symbol. 51. The method of claim 50, wherein determining the cross-correlations between the different symbols comprises determining a cross-correlation between a symbol propagation code for the symbol of interest and a symbol propagation code for at least one symbol of the symbol. interference. 52. The method of claim 51, wherein combining the de-propagated symbols of different symbol periods using weighting factors determined based on the cross-correlations between the symbol propagation codes comprises combining the symbol of interest with at least one symbol of the symbol. interference. 53. The method of claim 49, wherein combining the de-propagated symbols of different symbol periods using weighting factors determined based on the cross-correlations between the different symbols comprises filtering the de-propagated symbols in a multi-channel filter. 54. The method of claim 53, wherein filtering the de-propagated symbols in the multi-channel filter comprises: filtering each of the de-propagated symbols in a linear transverse filter to combine disproportionate symbols received over a plurality of symbol periods using factors of weights determined based on the cross correlations between the different symbols to generate a plurality of filtered result symbols; and adding the plurality of filtered result symbols. 55. The method of claim 54, wherein filtering each of the de-propagated symbols in a linear transverse filter comprises: delaying the received de-propagated symbol on the same path in a derived delay line to generate a plurality of delayed symbols; weighting each of the plurality of delayed symbols using a given weighting factor based on the cross-correlations between the different symbols to generate a plurality of weighted symbols; and adding the plurality of weighted symbols to generate each of the plurality of filtered result symbols. 56. The method of claim 49, wherein combining the disprobed symbols of different symbol periods using weighting factors determined based on the cross correlations between the different symbols comprises: combining by RAKE the disproportionate symbols received on different trajectories during the same period symbol to generate a combined RAKE result symbol during each symbol period; and combining successive RAKE result symbols produced over a plurality of successive symbol periods using weighting factors determined based on the cross correlations between the different symbols. 57. The method of claim 56, wherein combining the successive RAKE result symbols produced over a plurality of symbol periods comprises. delaying the RAKE result symbol in a derived delay line to generate a plurality of delayed result symbols during each symbol period; weight the delayed result symbols using weighting factors determined based on the cross correlations between the different symbols to generate a plurality of weighted result symbols; and adding the plurality of weighted result symbols. 58. The method of claim 49, wherein despreading symbols received on at least one multi-path channel comprises despreading symbols received on multiple paths of multiple code channels. 59. The method of claim 58, wherein combining the disprobed symbols of different symbol periods using weighting factors determined based on the cross-correlations between the different symbols comprises: combining RAKE disproportionate symbols received on each code channel to generate a combined RAKE result symbol for each code channel; and combine the RAKE result symbols in a multi-channel filter. 60. The method of claim 59, wherein combining the RAKE result symbols in the multi-channel filter comprises: filtering the RAKE result symbols for each code channel over a plurality of symbol periods in a linear transverse filter using weighting factors determined based on the cross-correlations between the different symbols to generate a filtered result symbol for each code channel during each symbol period; and combining the filtered result symbols to generate the estimate of the symbol of interest. 61. The method of claim 60, wherein filtering the combined RAKE result symbols for each code channel over the plurality of symbol periods in the linear transverse filter using the weighting factors determined based on the cross correlations between the different symbols to generate a filtered result symbol for each code channel during each symbol period comprises: delaying each of the RAKE result symbols in a derived delay line to generate a plurality of delayed result symbols during each symbol period; weight the result symbols delayed by the weighting factors determined based on the cross correlations between the different symbols to generate a plurality of weighted result symbols; and adding the plurality of weighted result symbols. 62. The method of claim 49, wherein combining the de-propagated symbols of different symbol periods using weighting factors determined based on the cross-correlations between different symbols comprises combining the disproportionate symbols from different symbol periods using weighting factors determined based on a correlation matrix formed of the cross correlations between different symbols. 63. The method of claim 62, further comprising reusing a sub-matrix of the correlation matrix of a first symbol period to form the correlation matrix of a second symbol period. 64. The method of claim 49, further comprising determining a scaling factor based on a channel estimate of at least one multi-path channel and multiplying the scattered symbols combined by the scaling factor to improve reliability of the estimate of the symbol of interest. 65. The method of claim 64, further comprising determining the scaling factor based on the weighting factors. 66. The method of claim 64, wherein the RAKE receiver receives traffic and pilot channel signals, the method further comprising determining the scaling factor based on a ratio of a power allocated to a traffic channel signal with a power assigned to a pilot channel signal. 67. A wireless communication device comprising: at least one antenna for receiving symbols on at least one multi-path channel; and a RAKE receiver for reducing the interference that can be attributed to the interference symbols from a symbol of interest, the RAKE receiver comprises: a plurality of RAKE fingers for despreading symbols received on at least one multi-path channel; a processor to determine the cross-correlations between different symbols; and a combiner for combining the de-propagated symbols from different symbol periods using weighting factors determined based on the cross-correlations between the different symbols to generate an estimate of a symbol of interest with reduced interference. 68. The wireless communication device of claim 67, wherein the combiner comprises a RAKE combiner for combining RAKE symbols received over a plurality of symbol periods. 69. The wireless communication device of claim 67, wherein the combiner comprises a multi-channel filter comprising: a plurality of linear transverse filters, each of which is associated with the corresponding one of the plurality of RAKE fingers, for weighting and combining non-propagated symbols produced by the corresponding RAKE finger over a plurality of symbol periods using the weighting factors determined based on the cross-correlations between the different symbols to generate a plurality of filtered result symbols; and a filter combiner to combine the filtered result symbols. 70. The wireless communication device of claim 67, wherein the combiner comprises: a RAKE combiner to combine by RAKE disproportionate symbols received on different trajectories in the same symbol period to generate a result symbol RAKE combined for each trajectory in each symbol period; and a linear transverse filter for combining the successive RAKE result symbols produced over a plurality of successive symbol periods using weighting factors determined based on the cross correlations between the different symbols to generate the estimate of the symbol of interest. 71. The wireless communication device of claim 67, wherein the RAKE fingers are divided into two or more groups, and wherein each group of RAKE fingers deproduces symbols received on a different code channel. 72. The wireless communication device of claim 71, wherein the combiner comprises: a RAKE combiner for each group of RAKE fingers that combines the RAKE finger result symbols within the corresponding group to generate RAKE result symbols; and a multi-channel combiner for combining the RAKE result symbols to reduce the interference that can be attributed to at least one interfering symbol from the symbol of interest, the multi-channel filter comprising: a plurality of transverse filters linear, of which each is associated with one of the code channels, to weight and combine the successive RAKE result symbols produced from a corresponding RAKE combiner over a plurality of symbol periods using weighting factors determined based on the cross-correlations between the different symbols to generate filtered result symbols; and an adder to combine the filtered result symbols. 73. The wireless communication device of claim 72, wherein the RAKE combiner for each code channel comprises a G-RAKE combiner. The wireless communication device of claim 67, wherein the processor determines the cross-correlations between different symbols by determining the cross-correlations between a symbol propagation code for the symbol of interest and a symbol propagation code for minus an interference symbol. 75. The wireless communication device of claim 67, wherein the wireless communication device comprises a mobile terminal. 76. The wireless communication device of claim 67, wherein the wireless communication device comprises a base station. 77. A computer-readable medium stored in a wireless communication device for storing a set of instructions for reducing interference that can be attributed to at least one interfering symbol from a symbol of interest, the set of instructions comprises: instructions for despreading symbols received on at least one multi-path channel; instructions to determine the cross-correlations between different symbols; and instructions for combining the de-propagated symbols of different symbol periods using weighting factors determined based on the cross-correlations between the different symbols to generate an estimate of a symbol of interest with reduced interference. 78. The computer readable medium of claim 77, wherein the instructions for determining cross-correlations between different symbols comprise instructions for determining cross-correlations between a symbol propagation code for the symbol of interest and a propagation code of symbols for at least one interference symbol. 79. The computer readable medium of claim 78, wherein the instructions for combining the disprobed symbols of different symbol periods using weighting factors determined based on the cross correlations between the different symbols comprise instructions for combining the symbol of interest with at least one interference symbol. 80. The computer-readable medium of claim 77, wherein the instructions for combining the disprobed symbols of different symbol periods using weighting factors determined based on the cross-correlations between the different symbols comprises filtering the disprogated symbols in a multi-channel filter. 81. The computer readable medium of claim 77, wherein the instructions for combining the disprobed symbols of different symbol periods using weighting factors determined based on the cross-correlations between the different symbols comprise: instructions for combining by RAKE the disproportionate symbols received on different trajectories during the same symbol period to generate a combined RAKE result symbol during each symbol period; and instructions to combine result symbols Successive RAKEs produced over a plurality of successive symbol periods using weighting factors determined based on the cross correlations between the different symbols. 82. The computer readable medium of claim 77, wherein the instructions for combining the disprobed symbols of different symbol periods using weighting factors determined based on the cross correlations between the different symbols comprise: instructions for combining by RAKE disproportionate symbols received on each code channel to generate a combined RAKE result symbol for each code channel; and instructions to combine the RAKE result symbols in a multi-channel filter. 83. A circuit for implementing a process for reducing interference that can be attributed to at least one interfering symbol from a symbol of interest, the circuit comprising: a receiver circuit for: dispropering symbols received on at least one channel of multi-trajectory; determine cross correlations between different symbols; and combining the de-propagated symbols of different symbol periods using weighting factors determined based on the cross-correlations between the different symbols to generate an estimate of a symbol of interest with reduced interference. 84. The circuit of claim 83, wherein the receiver circuit determines the cross-correlations between different symbols by determining the cross-correlations between a symbol propagation code for the symbol of interest and a symbol propagation code for at least one interference symbol. 85. The circuit of claim 84, wherein the receiver circuit combines the disprobed symbols of different symbol periods using weighting factors determined based on the cross-correlations between the different symbols by combining the symbol of interest with at least one symbol of interference. 86. The circuit of claim 83, wherein the receiver circuit combines the disprobed symbols of the different symbol periods using weighting factors determined based on the cross-correlations between the different symbols when filtering the disprogated symbols in a multi-channel filter. 87. The circuit of claim 83, wherein the receiver circuit combines the disproportionate symbols of different symbol periods using weighting factors determined based on the cross-correlations between the different symbols by: combining by RAKE the disproportionate symbols received on different paths during the same symbol period to generate a combined RAKE result symbol during each symbol period; and combining successive RAKE result symbols produced over a plurality of successive symbol periods using weighting factors determined based on the cross correlations between the different symbols. 88. The circuit of claim 83, wherein the receiver circuit combines the disproportionate symbols of different symbol periods using weighting factors determined based on the cross-correlations between the different symbols by: combining by RAKE the disproportionate symbols received on each channel of code to generate a combined RAKE result symbol for each code channel; and combine the RAKE result symbols in a multi-channel filter. 89. The circuit of claim 83, wherein the circuit comprises an integrated circuit of specific application.