Abstract: A method and apparatus is provided for facilitating coherent communication reception. A received reference symbol coded spread spectrum communication signal is despread with a spreading code to derive a stream of reference samples and a stream of data samples. The channel response is estimated by utilizing the stream of reference samples. An offset frequency detector determines an offset to be applied to the received signal via a frequency locked loop, while a timing control compensates for slow timing drift and fast fading based on power estimates derived from the stream of reference samples and/or the stream of data samples. A rate estimator determines the rate at which the information was encoded, and the rate information is used to optimize the timing control, frequency offset detector and channel estimator. Thus an improved detection of estimated data symbols from the stream of received data samples is provided.

Abstract: A method and apparatus is provided for estimating signal power. This is accomplished by demodulating a received communication signal to derive a stream of samples. These samples may consist of either reference samples, data samples, or a combination thereof. An estimate of the power of the received communication signal is then generated as a function of the stream of samples. The signal power estimate may, for example, be used in a power control algorithm by setting a power control indicator in response to a comparison between the signal power estimate and a predetermined threshold. Subsequently, the power control indicator is transmitted over a communication channel to another communication unit. The communication unit detects a power control indicator within a signal received from over the communication channel and adjusts a particular signal transmission power of a signal transmitter in response to the detected power control indicator.

Abstract: A device and method utilize a linear feedback/feedforward configuration to estimate and cancel a listener echo wherein equalizer (202) and listener echo cancellation (204 and 208) units are jointly updated, allowing determination of an error signal (204 and 208), in place of the former method of separate error signal determination for each of an equalizer and a listener echo canceller. An improved phase-correction scheme is utilized to compensate the frequency offset in the listener echo. The relationship between the listener echo and talker far echo is utilized to facilitate the listener echo cancellation.

Abstract: A method and apparatus is provided for encoding and decoding to facilitate coherent communication. In encoding, reference symbols are inserted into a stream of input data symbols to form a reference coded stream of input data symbols. Subsequently, the reference coded stream of input data symbols are prepared for transmission over a communication channel by spreading the reference coded stream of input data symbols with a spreading code prior to transmission over the communication channel. In decoding, a received communication signal is despread with a spreading code to derive a stream of reference samples and a stream of data samples. The channel response is estimated by utilizing the stream of reference samples. Finally, an estimated data symbol is detected from the stream of data samples by utilizing the estimated channel response.

Abstract: A device and method utilize a linear feedback/feedforward configuration to estimate and cancel a listener echo wherein equalizer (202) and listener echo cancellation (204 and 208) units are jointly updated, allowing determination of an error signal once (204 and 208), in place of the former method of separate error signal determination for each of an equalizer and a listener echo canceller. An improved phase-correction scheme is utilized to compensate the frequency offset in the listener echo. The relationship between the listener echo and talker far echo is utilized to facilitate the listener echo cancellation.

Abstract: The power of a received signal is measured at a base station. This measured power is used to predict a future power level of the received signal and from that to determine the appropriate power adjustment command. The power adjustment command is then sent to the transceiver.

Abstract: A method and apparatus is provided for estimating signal power. The estimating is accomplished by correlating (206) an input data vector (204) with a set of mutually orthogonal codes to generate a set of output values. The input data vector (204) consists of data samples of a received orthogonal coded signal (202). Each output value corresponds to a measure of confidence that the input data vector is substantially similar to one of the orthogonal codes from within the set of mutually orthogonal codes. Finally, an estimate of the power of the received orthogonal coded signal is generated (208) as a nonlinear function of the set output values.

Abstract: The present invention relates to a method and apparatus for providing carrier frequency offset compensation in a time division multiple access (TDMA) communication system. In this effort a TDMA receiver is adapted to receive, via a transmission channel, a transmitted signal burst which includes a synchronization signal pattern, a message signal portion and at least one known portion, in a TDMA time slot. Initially, a phase error at that portion of the received signal which corresponds to the known portion of the transmitted signal is determined. Thereafter, various received signal parameters are adjusted in order to eliminate the phase error and thereby compensate for any carrier frequency offsets.

Abstract: A method and apparatus is provided for maintaining received signal power levels at an average level when a signal power estimate is on average similar to the average of actually received signal power levels. The maintaining of the received signal power levels is accomplished by generating an estimate of the power of a received signal. Subsequently, a difference signal is generated by subtracting the estimated received signal power from a predetermined reference signal power. Finally, a signal power control threshold is adjusted as a function of the difference signal.

Abstract: A method and apparatus is provided for encoding and decoding. In encoding, bits (202) are encoded (204) into symbols (206) such that maximum likelihood decoding is facilitated. Groups of symbols (206) are translated by either interleaving by group each group within a block (208) and subsequently deriving an orthogonal code from each group (212) or deriving an orthogonal code from each group and subsequently interleaving by code each code within a block. In decoding, groups of samples (228, 229) are transformed by either generating metrics and index symbols (242) for each group of samples (232, 234, 236, 238, 240) and subsequently deinterleaving by group each group of metrics within a block (244) or deinterleaving by group each group of samples within a block and subsequently generating metrics and index symbols for each deinterleaved group of samples. Each metric represents the confidence that a group of samples is a particular orthogonal code.

Abstract: A first and second digital rate converter device and method provides for synchronization between a first digital sample sequence and a second digital output sequence related to the first digital sample sequence for a rate converter pair (501, 511; 601, 611). The method typically utilizes at least one of: queue monitoring and zero-crossing with resetting to minimize sampling timing error.

Abstract: A method and apparatus is provided for encoding and decoding. In encoding, bits (202) are encoded (204) into symbols (206) such that maximum likelihood decoding is facilitated. Groups of symbols (206) are translated by either interleaving by group each group within a block (208) and subsequently deriving an orthogonal code from each group (212) or deriving an orthogonal code from each group and subsequently interleaving by code each code within a block.In decoding, groups of samples (228, 229) are transformed by either generating metrics and index symbols (242) for each group of samples (232, 234, 236, 238, 240) are subsequently deinterleaving by group each group of metrics within a block (244) or deinterleaving by group each group of samples within a block and subsequently generating metrics and index symbols for each deinterleaved group of samples. Each metric represents the confidence that a group of samples is a particular orthogonal code.

Abstract: A signal weighting system for associating a confidence level with portions of a communication signal transmitted upon a multipath channel and received by a receiver. A signal received by the receiver is equalized by an equalizer circuit, such as a maximum likelihood sequence estimator, and the equalized signal generated thereby is supplied to an adaptive filter which is synthesizes portions of the multipath channel. The signal received by the receiver is altered responsive to values of a filtered, equalized signal generated by the adaptive filter.

Abstract: A sample rate converter receives an input stream of samples representative of a time-varying signal and generates a corresponding output stream of samples which is also representative of the time-varying signal and in which each output stream sample appears at a desired time which may differ from the time when a sample appears in the input stream; filter circuitry receives the input stream and generates at least two intermediate samples which appear at different times, and interpolation circuitry combines selected intermediate samples to form a sample of the output stream at the desired time.

Abstract: An echo cancellation modem having a fast training echo canceller in which the echo cancellation coefficients are computed by taking correlations between a complex, periodic training signal sequence and a real component of the corresponding echo signal. The modem includes a receiver circuit for detecting a signal on a channel possibly including an echo; an echo canceller for estimating the real component of the echo signal; training circuitry for applying the complex training sequence to the channel and for taking correlations between the training sequence and the real component of the corresponding echo signal. The modem also includes a computational element for computing the period of the periodic sequence, generating the complex periodic train sequence in real time and for computing a phase roll frequency based upon the computed echo cancellation coefficients.

Abstract: Echo cancellation to remove, from a locally received data communication signal, an echo signal component having a changing phase difference relative to the phase of a locally transmitted data communication signal, said locally transmitted communication signal are generated by modulating a carrier based on sequences of complex data signal points, is accomplished by correcting the phase of an input sequence of complex samples of the modulated carrier based on the changing phase difference to generate complex phase corrected samples, and generating a real-valued simulation of the echo signal based on the complex, phase corrected samples.