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  Parameter estimate initialization using interpolationUSPTO Application #: 20060067383Title: Parameter estimate initialization using interpolation Abstract: A receiver is described herein that is capable of receiving and processing a radio signal and further capable of using interpolation to initialize receiver parameters when there is a change in at least one delay associated with the received radio signal or when there is at least one new correlator position. For instance, the receiver parameters that can be initialized include: (1) channel coefficients; (2) AFC parameters; (3) tracking parameters; (4) noise statistics (noise correlations); (5) signal statistics (channel coefficient correlations); (6) data statistics (despread values or chip samples); or (7) combining weights. (end of abstract) Agent: Ericsson Inc. - Plano, TX, US Inventors: Carmela Cozzo, Gregory Bottomley, Rajaram Ramesh USPTO Applicaton #: 20060067383 - Class: 375147000 (USPTO) Related Patent Categories: Pulse Or Digital Communications, Spread Spectrum, Direct Sequence, Receiver The Patent Description & Claims data below is from USPTO Patent Application 20060067383. Brief Patent Description - Full Patent Description - Patent Application Claims
BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] The present invention relates in general to the wireless telecommunications field and in one exemplary embodiment to a receiver that receives a signal and estimates signal delays associated with the received signal and when there is a new signal delay then the receiver uses interpolation to estimate an initial value of a parameter (e.g., channel coefficient, tracking parameter) associated with the new signal delay. [0003] 2. Description of Related Art [0004] In direct-sequence code-division multiple-access (DS-CDMA) systems, such as WCDMA and IS-2000, coherent RAKE receivers are commonly used. This type of receiver often estimates a channel response which consists of path delays and channel coefficients. The receiver also uses despread values to search for signal paths. Based on all of this information, the receiver positions its correlators or "fingers" at certain delays. As these delays change over time, the receiver needs to move the fingers to different positions. Every time a new finger position is used, the receiver needs to initialize a channel coefficient or some other parameter like channel tracking parameters, automatic frequency correction (AFC) quantities, noise correlations and fading correlations. The last two parameters are needed for advanced receivers like G-RAKE receivers or joint scaling receivers. [0005] A traditional approach that can be used by a receiver to initialize a channel coefficient after a finger is moved to a new position is one that uses prior knowledge of the channel in a nearby position. In this approach, the receiver considers the distance between the new finger position provided and the closest finger delay to the new position in a delay tracker. If the distance is less than 1/4-chip period, it is assumed that the finger has not moved much and the old channel coefficient is kept. For larger distances, the channel coefficient in the new position is set to zero, or its value is computed by scaling an initial, noisy measured value. This approach is described in U.S. Pat. No. 6,560,273 entitled "Delay Searcher and Delay Trackers Interaction for New Delays Assignment to RAKE Fingers". The contents of this patent are incorporated herein. [0006] Although this approach works well it does have a potential shortcoming in that the accuracy of the initial channel coefficient estimates may not be good enough to ensure a reliable channel estimate and/or provide a fast enough convergence. And, if the initial values of these initialized channel coefficient estimates (or other parameters) are not good enough, then there can be a transient loss in performance while the receiver develops better estimates of the initial channel coefficients. Accordingly, there is a need for a receiver that addresses the problem of initialization of a channel coefficient (or other parameters) when there is a new signal delay or when a finger is moved to a new position. This need and other needs are satisfied by the receiver of the present invention. SUMMARY OF THE INVENTION [0007] The present invention includes a receiver that is capable of receiving and processing a radio signal and further capable of using interpolation to initialize receiver parameters when there is a change in at least one delay associated with the received radio signal or when there is at least one new correlator position. For instance, the receiver parameters that can be initialized include: (1) channel coefficients; (2) AFC parameters; (3) tracking parameters; (4) noise statistics (noise correlations); (5) signal statistics (channel coefficient correlations); (6) data statistics (despread or received sample correlations); or (7) combining weights (for combining despread values or chip samples). BRIEF DESCRIPTION OF THE DRAWINGS [0008] A more complete understanding of the present invention may be had by reference to the following detailed description when taken in conjunction with the accompanying drawings wherein: [0009] FIG. 1 is a block diagram of a wireless communication system that includes a transmitter and a receiver which is configured in accordance with the present invention; [0010] FIG. 2 is a diagram that illustrates in greater detail the components within a baseband processor in the receiver shown in FIG. 1; [0011] FIG. 3 is a diagram that illustrates in greater detail the components within one embodiment of a weight formation unit in the baseband processor shown in FIG. 2; [0012] FIG. 4 (PRIOR ART) is a flowchart that shows the steps of a traditional method that can be used to initialize a channel coefficient within the weight formation unit shown in FIG. 3; [0013] FIG. 5 is a flow chart that shows the steps of a method that can be used within the weight formation unit shown in FIG. 3 to initialize a channel coefficient for a new finger position by using interpolated values from old or prior finger positions in accordance with one embodiment of the present invention; [0014] FIG. 6 is a diagram that illustrates an example used to help describe the different types of interpolation methods that can be used in the present invention; [0015] FIG. 7 is a diagram that illustrates in greater detail the components within one embodiment of a weight formation unit that can be used in the baseband processor of a G-RAKE receiver in accordance with the present invention; [0016] FIG. 8 is a diagram that illustrates in greater detail the components within one embodiment of a weight formation unit that can be used in the baseband processor of a joint scaling RAKE receiver in accordance with the present invention; [0017] FIG. 9 is a diagram that illustrates in greater detail the components within one embodiment of a finger placement unit that can be used within the baseband processor shown in FIG. 2; [0018] FIG. 10 is a flow chart that shows the steps of a method where initialization of channel coefficients is performed by using the most recent complex/delay profile (CDP) from a finger placement unit in accordance with another embodiment of the present invention; [0019] FIG. 11 is a diagram that illustrates the components of a finger placement unit that can be used within the baseband processor of a G-RAKE receiver to initialize noise statistics in accordance with another embodiment of the present invention; [0020] FIG. 12 is a flowchart that shows the steps of a method on how initialization of noise and channel statistics can be performed within a joint scaling RAKE receiver by using interpolation in accordance with yet another embodiment of the present invention; [0021] FIG. 13 is a diagram that illustrates the components within an initialization unit shown in FIG. 3 that can use multiple CDP measurements for channel tracking in accordance with another embodiment of the present invention; Continue reading... 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