Abstract: A method and apparatus in a communications system (100) for providing communications units (134) access to the communications system (100). The communications system (100) includes a cable distribution network (106) with a base communications unit (102) and a number of downstream communications units (134) all connected to the cable distribution network (106). A plurality of channels are used to transmit data between the base communications unit (102) and the downstream communications units (134). A first set of channels are used primarily for access to the communications system (100) and a second set of channels are used for transmitting data within the communications system (100) after access to the communications system (100) has been gained. The base communications unit (102) sends a first type of data transmission including an identification of access channels used for requesting access to the communications system (100).

Abstract: The process of the present invention computes the update to the least mean square channel estimator taps. The update coefficient for each tap is computed independently based on the power of each tap relative to the main tap power.

Abstract: In a receiver (101) that receives a signal (103) subsequent to transmission thereof by a transmitter on a communication channel, an apparatus and method for determining a point in time for detecting the signal, sampled at multiple points in time, to produce a detected signal (112). The communication channel is modeled, at the multiple points in time, responsive to the sampled signal (110) to produce signal and noise channel models (209) and (204), respectively. Signal and noise values (210) and (205) indicative of the quantity of signal and noise in the signal and noise channel models, respectively, are generated. A sampling point selector (203) selects, from among the multiple points in time, a point in time (111), corresponding to a determined minimum noise value (206) or a determined maximum signal to noise ratio value (213), for detecting the sampled signal (110) to produce the detected signal (112).

Abstract: In a communication unit (200) that coherently demodulates differentially-encoded modulated signals (201) to produce soft symbols (210) including first and second soft symbols, a method and associated apparatus, for use by the communication unit (200), converts the soft symbols (210) into soft bits (212). A quality measure (305) is determined for at least the first soft symbol (210) indicating when the quality for the first soft symbol (210) is favorable and when the quality for the first soft symbol (210) is unfavorable. The first and second soft symbols (210) are processed in a forward direction in time (208) to produce the soft bits (212) when the quality measure (305) for the first soft symbol (210) is favorable. The first and second soft symbols (210) are processed in a reverse direction in time (209) to produce the soft bits (212) when the quality measure (305) for the first soft symbol (210) is unfavorable.

Abstract: A system and method for correcting for Rayleigh interference of a signal transmitted upon a multi-path channel. The system adaptively calculates values of channel gain and noise variance of the channel upon which the signal is transmitted, and generates signals indicative of such calculations which are supplied to a decoder. The system may be utilized to form a portion of a coherent, or noncoherent receiver which receives encoded and differentially-encoded signals.

Abstract: In a communications device, two coherent detection algorithms (102 and 103), one of which has a decision feedback equalizer (103), and a detector selection algorithm (104) are used to dynamically select a detector depending on whether delay spread distortion is present. First the correlation of the detector without the equalizer (102) is measured. If this correlation is greater than a predetermined threshold, the data from that detector (102) is used by the communications device. If the correlation is less than the threshold, the correlation of the detector with the equalizer (103) is measured. If this is less than the correlation of the detector without the equalizer (102), the data from the detector without the equalizer (102) is used, otherwise the data is taken from the equalizer (103). In any case, if the detector without the equalizer is used, the detector with the equalizer is turned off.

Abstract: A Viterbi equalizer for decoding a .pi./4 DQPSK modulated signal. Because symbol values of adjacent symbols of a .pi./4 DQPSK signal are offset in phase relative to one another, allowable values of succeeding states of a .pi./4 DQPSK signal are four in number. The signal paths of the Viterbi equalizer are thereby limited in number to four allowable next-states, and the Viterbi equalizer is operative to select certain ones of the paths connecting the states at the adjacent time intervals as survivor paths to form maximum likelihood paths thereby.

Abstract: The process of the present invention generates an optimum automatic frequency control signal in an apparatus that has a plurality of adaptive algorithms, each adaptive algorithm having a reference signal with an associated frequency dither. The process starts by comparing the performance of each of the plurality of adaptive algorithms. This difference is input to a comparator where it is compared to zero. This delta signal then modifies the numerically controlled oscillator frequency. After several iterations, the frequency offset is reduced to substantially zero.

Abstract: A system and method for correcting for Rayleigh interference of a signal transmitted upon a multi-path channel. The system adaptively calculates values of channel gain and noise variance of the channel upon which the signal is transmitted, and generates signals indicative of such calculations which are supplied to a decoder. The system may be utilized to form a portion of a coherent, or noncoherent receiver which receives encoded and differentially-encoded signals.

Abstract: In a communications device, two coherent detection algorithms (102 and 103), one of which has a decision feedback equalizer (103), and a detector selection algorithm (104) are used to dynamically select a detector depending on whether delay spread distortion is present. First the correlation of the detector without the equalizer (102) is measured. If this correlation is greater than a predetermined threshold, the data from that detector (102) is used by the communications device. If the correlation is less than the threshold, the correlation of the detector with the equalizer (103) is measured. If this is less than the correlation of the detector without the equalizer (102), the data from the detector without the equalizer (102) is used, otherwise the data is taken from the equalizer (103).

Abstract: System and method for determining an absolute phase value of a differentially-encoded, DQPSK signal. A stored set of sequences of an ID sequence is compared with a received ID-sequence of a differentially-encoded, DQPSK signal transmitted to the receiver. The stored and the received ID sequences are correlated, and the stored values of the ID sequence are adjusted by the value of the calculated correlation.