Abstract: Cancellation of interference in a communication system with application to S-CDMA. A relatively straight-forward implemented, and computationally efficient approach of selecting a predetermined number of unused codes is used to perform weighted linear combination selectively with each of the input spread signals in a multiple access communication system. If desired, the predetermined number of unused codes is always the same in each implementation. Alternatively, the predetermined number of unused codes are selected from within a reordered code matrix using knowledge that is shared between the two ends of a communication system, such as between the CMs and a CMTS. While the context of an S-CDMA communication system having CMs and a CMTS is used, the solution is generally applicable to any communication system that seeks to cancel narrowband interference. Several embodiments are also described that show the generic applicability of the solution across a wide variety of systems.

Abstract: Outer code covered synchronous code division multiple access for cable modem (CM) channels. Outer pseudo-noise (PN) code is employed, along with orthogonal codes (OCs), to spread CM signals thereby mitigating inter-code-interference (ICI) effects caused by residual multi-path propagation within CM communication systems. The added and implemented PN sequences have relatively good autocorrelation properties (when compared to the autocorrelation properties of the OCs) that mask the possible bad autocorrelation and/or cross-correlation properties of the OCs. This outer-code covered PN coding, along with the OC coding, enables much better performance in the presence of residual multi-path. The PN code's added complexity is very minimal as the PN may use the same chip rate of the orthogonal code while providing for better performance in the presence of residual multi-path components.

Abstract: Channel estimation and/or equalization using repeated adaptation. Repeated adaptation approach is performed within the system identification mode and/or the channel equalization mode. In one embodiment, the repeated adaptation generates a very accurate estimate of the communication channel, and then direct tap computation is performed to compute the optimal equalizer tap coefficients corresponding to the channel estimate. In another embodiment, the repeated adaptation is used to converge the equalizer tap coefficients directly without obtaining an estimate of the channel first. The repeated adaptation operates on the same training sequence for multiple cycles. The resulting conditions, in either the channel equalization mode or the channel estimation/system identification mode, may then be used as the initial condition for the next cycle.

Abstract: Optimal Decision Feedback Equalizer (DFE) coefficients are determined from a channel estimate h by casting the DFE coefficient problem as a standard recursive least squares (RLS) problem, e.g., the Kalman gain solution to the RLS problem. A fast recursive method, e.g., fast transversal filter (FTF) technique, for computing the Kalman gain is then directly used to compute Feed Forward Equalizer (FFE) coefficients gopt. The complexity of a conventional FTF algorithm is reduced to one third of its original complexity by choosing the length of a Feed Back Equalizer (FBE) coefficients bopt (of the DFE) to force the FTF algorithm to use a lower triangular matrix. The FBE coefficients bopt are then computed by convolving the FFE coefficients gopt with the channel impulse response h. In performing this operation, a convolution matrix that characterizes the channel impulse response h extended to a bigger circulant matrix.

Abstract: Multi-Input-Multi-Output (MIMO) Optimal Decision Feedback Equalizer (DFE) coefficients are determined from a channel estimate h by casting the MIMO DFE coefficient problem as a standard recursive least squares (RLS) problem and solving the RLS problem. In one embodiment, a fast recursive method, e.g., fast transversal filter (FTF) technique, then used to compute the Kalman gain of the RLS problem, which is then directly used to compute MIMO Feed Forward Equalizer (FFE) coefficients gopt. The complexity of a conventional FTF algorithm is reduced to one third of its original complexity by choosing the length of a MIMO Feed Back Equalizer (FBE) coefficients bopt (of the DFE) to force the FTF algorithm to use a lower triangular matrix. The MIMO FBE coefficients bop, are computed by convolving the MIMO FFE coefficients gopt with the channel impulse response h. In performing this operation, a convolution matrix that characterizes the channel impulse response h extended to a bigger circulant matrix.

Abstract: A method and apparatus that provides an accurate estimate of the time and amplitude of arrival of the first arriving overlapping multipath components (rays) in wireless locating finding systems. Overlapping fading multipath components for mobile-positioning are resolved by exploiting the fact that multipath components fade independently. Although fast channel fading is usually considered a challenge to the location finding process, it is used as an additional tool to detect and resolve overlapping multipath rays. A projection technique is also provided that exploits all possible a-priori channel information into a adaptive filtering algorithm, thus providing needed robustness to divergence of the adaptive algorithm that might result from possible severe data matrix ill-conditioning and high noise levels, which are common in wireless location applications.