Abstract: The invention provides an adaptive turbo decision feedback equalizer for executing an adaptive turbo decision feedback equalization method in response to a reception a packet including samples transmitted to the adaptive turbo decision feedback equalizer via a channel. The adaptive turbo decision feedback equalizer generates a first set of soft estimates of bits based upon a computation of a first feed-forward filter and a first feedback filter as a function of an estimation of the channel. The adaptive turbo decision feedback equalizer subsequently generates additional sets of soft estimates of the bits and a set of hard estimates of the bits based upon a computation of additional feed-forward filters and additional feedback filters as a function of a plurality of additional soft symbol estimates.

Abstract: A reduced rank adaptive digital filtering method is described for a received signal consisting of a sequence of N×1 received vectors. Each received vector is formed from a group of N successive samples. D+1 basis vectors are generated where D is less than N and the dimension of a desired reduced rank subspace. Each successive basis vector is generated by multiplying an immediate preceding basis vector by the covariance matrix for the sequence of received sample vectors and the first basis vector is formed from a given or estimated steering vector. D filter coefficients are generated from correlations between pairs of basis vectors. The adaptive digital filter of the present invention achieves near optimal rank performance with substantially fewer training symbols than heretofore possible.

Abstract: The invention provides an adaptive turbo decision feedback equalizer for executing an adaptive turbo decision feedback equalization method in response to a reception a packet including samples transmitted to the adaptive turbo decision feedback equalizer via a channel. The adaptive turbo decision feedback equalizer generates a first set of soft estimates of bits based upon a computation of a first feed-forward filter and a first feedback filter as a function of an estimation of the channel. The adaptive turbo decision feedback equalizer subsequently generates additional sets of soft estimates of the bits and a set of hard estimates of the bits based upon a computation of additional feed-forward filters and additional feedback filters as a function of a plurality of additional soft symbol estimates.

Abstract: In a cellular network, a multiple-access methodology and concomitant circuitry in which TDMA is used inside each cell and CDMA signals, having pulse shapes with low cross-correlations, are assigned to adjacent cells. For example, these pulses could be Direct-Sequence Spread-Spectrum pulses. Such a hybrid system combines the high intra-cell capacity of TDMA with the inter-cell and multipath interference rejection capabilities of CDMA.

Abstract: Circuitry and concomitant methodology for demodulating Direct-Sequence, Spread-Spectrum Code-Division Multiple-Access (DS/SS CDMA) channel signal using multiple samples per transmitted symbol and a minimum mean squared error criterion to suppress interference. In one embodiment, a bank of cyclically shifted filters determined with reference to the conventional matched filter for CDMA is used to demodulate the channel signal. In another embodiment, a bank of sub-filters determined with reference to the conventional matched filter for CDMA is employed to demodulate the channel signal. In yet another embodiment, the output of a conventional matched filter is oversampled to demodulate the channel signal. Each embodiment utilizes a set of adaptive coefficients selected to minimize the mean square error between the transmitted symbol and detected symbol.

Abstract: A spread-time code division multiple access (ST-CDMA) technique is disclosed for bandlimited access to a channel. With ST-CDMA, pseudo-random (PN) sequences are assigned to each transmitter in the multi-transmitter system, and the Fourier transform of the transmitter pulse for a given transmitter is determined by modulating the phase of the desired transmitter spectrum by the PN sequence assigned to the transmitter. The data symbols produced by the transmitter are conveyed by delayed versions of the transmitter pulse. The transmitted data for a particular transmitter is recovered at a receiver synchronized to the transmitter by sampling the output of a filter matched to the corresponding transmitter pulse.

Abstract: A spread-time code division multiple access (ST-CDMA) technique is disclosed for bandlimited access to a channel. With ST-CDMA, pseudo-random (PN) sequences are assigned to each transmitter in the multi-transmitter system, and the Fourier transform of the transmitter pulse for a given transmitter is determined by modulating the phase of the desired transmitter spectrum by the PN Sequence assigned to the transmitter. The data symbols produced by the transmitter are conveyed by delayed versions of the transmitter pulse. The transmitted data for a particular transmitter is recovered at a receiver synchronized to the transmitter by sampling the output of a filter matched to the corresponding transmitter pulse.

Abstract: A spread-time code division multiple access (ST-CDMA) technique is disclosed for bandlimited access to a channel. With ST-CDMA, pseudo-random (PN) sequences are assigned to each transmitter in the multi-transmitter system, and the Fourier transform of the transmitter pulse for a given transmitter is determined by modulating the phase of the desired transmitter spectrum by the PN sequence assigned to the transmitter. The data symbols produced by the transmitter are conveyed by delayed versions of the transmitter pulse. The transmitted data for a particular transmitter is recovered at a receiver synchronized to the transmitter by sampling the output of a filter matched to the corresponding transmitter pulse.

Abstract: A spread-time code division multiple access (ST-CDMA) technique is disclosed for bandlimited access to a channel. With ST-CDMA, pseudo-random (PN) sequences are assigned to each transmitter in the multi-transmitter system, and the Fourier transform of the transmitter pulse for a given transmitter is determined by modulating the phase of the desired transmitter spectrum by the PN sequence assigned to the transmitter. The data symbols produced by the transmitter are conveyed by delayed versions of the transmitter pulse. The transmitted data for a particular transmitter is recovered at a receiver synchronized to the transmitter by sampling the output of a filter matched to the corresponding transmitter pulse.

Abstract: A digital decision feedback equalizer is disclosed in which compensation for the post-cursors of the impulse response of the transmission channel is divided up into two regions. A first region encompasses the initial rapidly changing unpredictable transient response, possibly oscillatory, of the transmission channel. A fast acting, close-tracking linear filter is used to compensate for this largely unpredictable initial transient. The second region of the impulse response is the slowly changing, easily predictable asymptotic tail of the impulse response. This second region can be compensated for by a relatively slow acting, simple pole-zero filter. Together, the two equalizer sections provide an overall equalizer design far less complicated and less expensive than an equalizer based on a single linear compensating filter.