Abstract: A method and apparatus for receiving data over a dispersive media is disclosed. The received signal is composed of an unknown data segment preceded and followed by known data segments. A replica of each known data segment is generated by the communication apparatus. Channel characteristics existing at the time of transmission of the known data segments are estimated by comparing the known data segments with the replica. Using estimations of the channel characteristics, symbols of the unknown data segment can be determined. Decisions can be made on the various unknown symbols as they are analyzed. Channel characteristics can be re-estimated after determining each symbol, each pair of symbols or each group of symbols. Two solutions of the unknown symbols can be combined in various ways to arrive at a final determination of the unknown transmitted symbols.

Abstract: A method and apparatus for receiving data over a dispersive media is disclosed. The received signal is composed of an unknown data segment preceded and followed by known data segments. The communication apparatus generates a replica of the known data segments. Channel characteristics existing at the time of transmission of the known data segments are estimated by comparing the known data segments with the replica. The symbols of the unknown data segment are then determined via application of a QR factorization. Factorization can be accomplished via Householder transformation, Givens rotation or fast Givens rotation. Decisions can be made on the various unknown symbols as they are analyzed and then fed back via back substitution.

Abstract: An apparatus and method of detecting signals transmitted via frequency-shift keying techniques. An observation window encompassing a frequency band is defined and searched for received tones, the frequency spacing between received tones is calculated and compared to known FSK modulation techniques to determine whether at least part of a transmission is potentially present. The transmission may be an automatic link establishment signal. A histogram can store data on received tones. The observation window can be shifted to center a potential FSK transmission for parallel modem processing that will attempt to demodulate and decode it.

Abstract: A speech processor for processing speech signals in a manner that minimizes the peak to average ratio of a vocal tract response waveform of the speech signal with minimal loss of intelligibility of speech reproduced from the processed waveform. This is accomplished, in general terms, by providing a speech processor for providing an approximately constant peak level within periods of a vocal tract response waveform. The speech processor may include a feedback-controlled signal compressor multiplier and an input signal delay means. The attack, hang and decay parameters of the speech processor are determined in accordance with typical vocal tract response characteristics to optimize the balance between compression of the vocal tract response waveform and introduction of harmonics into the resulting signal.