Abstract:
A digital signal processor is provided having an instruction set with a logarithm function that uses a reduced look-up table. The disclosed digital signal processor evaluates a logarithm function for an input value, x, by decomposing the input value, x, to a first part, N, a second part, q, and a remaining part, r, wherein the first part, N, is identified by a position of a most significant bit of the input value, x, and the second part, q, is comprised of a number of bits following the most significant bit, wherein the number is small relative to a number of bits in the input value, x; obtaining a value Log 2 ( 1 + 1 2 q ) from a first look-up table based on the second part, q; computing an epsilon term, ε, using the expression 2 - N 1 + 1 2 q r ; evaluating an expression Log2 (1+ε) using a polynomial approximation, such as a cubic approximation; and determining the logarithm function for the input value, x, by summing the values of N, Log Z ( 1 + 1 2 q ) and Log2(1+ε).
Abstract:
Multi-dimensional finite impulse response filters ale disclosed in hybrid and transpose forms. Multi-dimensional signals can be expressed in a vector (ox matrix) form to allow multi-dimensional signals to be processed collectively. Known hybrid and transpose FIR filters are extended to the multi-dimensional case to allow multi-dimensional signals to be processed with reduced redundancies. The input signals are vectors with multidimensional components. The disclosed FIR filters include multipliers that perform matrix multiplications with multiple coefficients, and adders for performing vector additions with multiple inputs and outputs. The z-transforms are provided for the disclosed hybrid and transpose multi-dimensional FIR filters.
Abstract:
A method and apparatus are disclosed for performing joint equalization and decoding of multidimensional codes transmitted over multiple symbol durations. An RSSE scheme is disclosed that cancels the intrasymbol interference caused by other symbol components within the same multidimensional code symbol. The disclosed RSSE technique for multidimensional codes applies where the number of trellis code dimensions exceeds the number of channels. The disclosed RSSE decoder computes the intersymbol interference caused by previously decoded multidimensional code symbols and subtracts the intersymbol interference from the received signal. In addition, a branch metrics unit compensates for the intrasymbol interference caused by other symbol components within the same multidimensional code symbol.
Abstract:
A search sphere-based linear block decoder is provided. A received vector, v, is decoded by computing a syndrome vector, S, corresponding to the received vector, v; (S=vH); obtaining a set of all possible error vectors, e, corresponding to the computed syndrome vector, S, wherein the set of all possible error vectors, e, is obtained from a pre-computed error table and has a specified maximum number of bit errors; calculating a set of all possible received vectors, x, based on the received vector, v, and the set of all possible error vectors, e; determining a k-bit code-vector x that is closest to the received vector, v; and determining an n-bit data-vector, d, associated with the k-bit code-vector x. The pre-computed error table can be generated by multiplying all possible error vectors by a Syndrome Matrix, to obtain all possible syndrome vectors associated with all possible error vectors.
Abstract:
A method and apparatus are disclosed for canceling cross-talk in a frequency-division multiplexed communication system. The disclosed frequency-division multiplexed communication system employs multiple carriers having overlapping channels and provides an improved cross-talk cancellation mechanism to address the resulting interference. Bandwidth compression is achieved using n level amplitude modulation in each frequency band. An FDM receiver is also disclosed that decomposes the received broadband signal into each of its respective frequency bands and returns the signal to baseband in the analog domain. Analog requirements are relaxed by removing cross-talk from adjacent RF channels, from image bands, and minimizing the performance degradation caused by In-phase and Quadrature-phase (I/Q) phase and gain mismatches in modulators and demodulators. The disclosed transmitter or receiver (or both) can be fabricated on a single integrated circuit.
Abstract:
A method and apparatus are disclosed for performing joint equalization and decoding of multidimensional codes transmitted over multiple symbol durations. An RSSE scheme is disclosed that cancels the intrasymbol interference caused by other symbol components within the same multidimensional code symbol. The disclosed RSSE technique for multidimensional codes applies where the number of trellis code dimensions exceeds the number of channels. The disclosed RSSE decoder computes the intersymbol interference caused by previously decoded multidimensional code symbols. In addition, a branch metrics unit compensates for the intrasymbol interference caused by other symbol components within the same multidimensional code symbol. In addition, the disclosed RSSE decoder compensates for the intrasymbol interference caused by other symbol components within the same multidimensional code symbol.
Abstract:
Methods and apparatus are provided for wireless channel estimation using interpolation elimination in the Eigen domain. Channel components at known OFDM symbol locations are interpolated to other OFDM symbol locations. Methods and apparatus are provided for interpolating in the Eigen domain between reference signals (i.e., training signals) to estimate the equalizer coefficients with a reduced complexity. In particular, one aspect of the present invention performs the required interpolation before a required matrix inversion in the Eigen domain.
Abstract:
In one embodiment, a receiver is provided for use in a multiple-input system that includes a receiving antenna receiving a time-domain signal corresponding to a plurality of signals transmitted from a plurality of transmitting antennas. The receiver includes: (a) a transform unit adapted to transform the time-domain signal into a frequency-domain signal; (b) a channel estimation unit adapted to estimate, based on the frequency-domain signal and a frequency-domain pilot signal, a combined transfer function corresponding to a plurality of transfer functions of respective channels between the plurality of transmitting antennas and the receiving antenna; and (c) a channel separation unit including a plurality of frequency-domain convolution units that separate the combined transfer function into a plurality of estimated channel transfer functions.
Abstract:
Methods and apparatus are provided for a digital signal processor having an instruction set with one or more non-linear complex functions. A method is provided for a processor. One or more non-linear complex software instructions are obtained from a program. The non-linear complex software instructions have at least one complex number as an input. One or more non-linear complex functions are applied from a predefined instruction set to the at least one complex number. An output is generated comprised of one complex number or two real numbers. A functional unit can implement the one or more non-linear complex functions. In one embodiment, a vector-based digital signal processor is disclosed that processes a complex vector comprised of a plurality of complex numbers. The processor can process the plurality of complex numbers in parallel.
Abstract:
A method and apparatus are disclosed for reducing cross-talk in an unbalanced channel with a reduced number of redundancies. A cross-talk canceller is disclosed that uses a multi-dimensional finite impulse response (FIR) filter to process a received signal. Redundancies are reduced or even removed entirely by processing the signals received on each twisted pair in a vector form, using multi-dimensional finite impulse response filters. The signals received by a transceiver on each twisted pair are represented in a vector form so that the signals received on each twisted pair, and the cross-talk effect that each signal has on one another, can be performed collectively. A multi-dimensional cross-talk canceller processes a vector representation of the corresponding signals transmitted by the transceiver on each twisted pair. An adder sums the equalized vector representation of the signals received by the transceiver and the processed vector representation of the signals transmitted by the transceiver to generate an estimate of the received signal on each twisted pair.