Motorola Corporation

Xiaojun Li

Floyd D Simpson

Jian-Cheng Huang

Thomas V D'Amico

Zaffer S Merchant

Sunil Satyamurti

Keith A Chanroo

A pitch determiner (414) for use with a speech analyzer includes a pitch function generator (414) which generates a plurality of pitch components representing a pitch function for one or more sequential segments of speech. which are represented by a predetermined number of digitized speech samples. A pitch enhancer (1116) enhances the pitch function of a current segment of speech utilizing the pitch function of one or more sequential segments of speech to generate a plurality of enhanced pitch components. A pitch detector (1118) detects the pitch of the current segment of speech by determining the pitch of an enhanced pitch component having a largest amplitude of the plurality of enhanced pitch components.

Pitch determiner for a speech analyzer

A selective call communication system (10) transmits a frequency hopped spread spectrum signal as a Reed Solomon code word modulated as a four-level frequency shift keying (4FSK) signal. A base site transceiver (150) receives the signal on a plurality of narrow band channels and a DSP (152) performs an FFT on the signal. The DSP (152) has a comparator (342) that computes energy of an 4FSK symbol. The comparator (342) establishes a ratio of a maximum energy and a next largest energy to an eye-opening threshold to indicate a probability of error. A determinator (344) in response to the probability of error determines when there is a fade, an erasure marker (346) marks a position of a Reed Solomon symbol in the fade as an erasure and error correcting code (348) corrects errors in the Reed Solomon code word with the marked erasure.

Method for correcting errors from a fading signal in a frequency hopped

A MBE (Multi-Band Excitation) synthesizer (116) generates excitation components from information received by a receiver (2004). The information received includes spectral information representing a segment of speech. The MBE synthesizer (116) includes an excitation generator (2241) and a nonlinear voicing processor (2211). The excitation generator (2241) generates voiced excitation components and unvoiced excitation components. The nonlinear voicing processor (2211) is responsive to the spectral information and controls a selection of the excitation components from the voiced excitation components and the unvoiced excitation components.

MBE synthesizer utilizing a nonlinear voicing processor for very low bit

A selective call communication system (10) has a selective call device (100) for transmitting a frequency hopped spread spectrum signal (320) encoded as Reed Solomon code words and modulated as a four-level frequency shift keying (4FSK) signal. A base site transceiver (156) receives the signal on a plurality of narrow band channels. A digital signal processor (DSP)(152) performs a fast fourier transform on the signal to generate frequency samples. The DSP (152) has a comparator (342) that compares an 4FSK symbol to a predetermined threshold, a determinator (344), in response to the comparator (342), determines when there is an interference signal jamming the narrow band channel, an erasure marker (346) marks a position in the Reed Solomon symbol determined to be jammed as an erasure and an error correcting code (348) corrects errors in the Reed Solomon code words marked with erasures.

Method for correcting errors from a jamming signal in a frequency hopped

An MBE synthesizer (116) for generating a segment of speech from compressed speech data received by a receiver (2004). The compressed speech data includes one or more indexes (2240, 2242) and pitch data (2248). The MBE synthesizer (116) includes the following: an excitation generator (2222) utilizing a transform function for generating transformed excitation components responsive to the pitch data (2248). A memory (3006) for storing a table of predetermined spectral vectors (2205) and associated predetermined voicing vectors (2203). A harmonic amplitude estimator (2209) that is responsive to the one or more predetermined spectra/vectors identified by the indexes (2240, 2242) received, that generates harmonic amplitude control signals. The harmonic amplitude estimator (2209) which includes a peak detector (2503), a peak enhancer (2505), a valley detector (2507), a valley enhancer (2509). A multi-band voicing controller (2214), responsive to the predetermined voicing vectors which are associated with the one or more predetermined spectral vectors identified, for controlling a selection of the excitation components.

MBE synthesizer for very low bit rate voice messaging systems

A method and apparatus is provided for a low bit rate speech transmission. Speech spectral parameter vectors are generated from a voice message and stored in a sequence of speech spectral parameter vectors within a speech spectral parameter matrix. A first index identifying a first speech parameter template corresponding to a first speech spectral parameter vector of the sequence of speech spectral parameter vectors is transmitted. A subsequent speech spectral parameter vector of the sequence is selected and a subsequent speech parameter template is determined having a subsequent index. One or more intervening interpolated speech parameter templates are interpolated between the first speech parameter template and the subsequent speech parameter template. The one or more intervening speech spectral parameter vectors are compared to the corresponding one or more intervening interpolated speech parameter templates to derive a distance. The subsequent index is transmitted when the distance derived is less than or equal to a predetermined distance.

Very low bit rate voice messaging system using variable rate backward

An apparatus codes excitation parameters for very low bit rate voice messaging using a method that processes a voice message to generating speech parameters. The speech parameters are separated (316) to produce a first group of energy parameters and a second group of pitch and voicing parameters. Subsequently, the first group of energy parameters are encoded and compressed using a non-uniform root-mean-square scalar process (318) to create a first plurality of encoded data. Additionally, the second group of pitch and voicing parameters are compressed, encoded, and combined into a single parameter using a three slope vector encoding process (320) that creates a second plurality of encoded data. Finally, the first and second plurality of encoded data are multiplexed (322) to create a multiplexed signal for transmission, the multiplexed signal representing the voice message.

Apparatus and method for coding excitation parameters in a very low bit

Error detection and correction of a received message, such as a digitized voice message is achieved by generating (318) interpolated vectors for each error vector corresponding to a codebook index in a sequence of codebook indexes representing parameters of portions of the message. A plurality of error corrected candidate vectors for the vector corresponding to the codebook index in error, are generated (322,324,326) by flipping one bit in a sequence of bits representing the codebook index in error. The error corrected candidate vector which has a minimal difference from its corresponding interpolated vector is used (338) to replace the error vector. In the case of digital voice, the vectors are spectral vectors which represent spectral information for a time sample of a voice message. An ordering property of vector components is exploited to detect errors in a received codebook index without parity bits.

Method and apparatus for minimal redundancy error detection and

A method and apparatus for mitigating effects of multipath fading, interference, and noise in a single sideband (SSB) signal transmitted by a radio communication system and demodulated by a portable subscriber unit (122) utilizing a demodulator (304) compensated by a pilot signal power (406). The apparatus performs the mitigation process by calculating (708) a pilot fading threshold in addition to a muting threshold. When samples of the mean pilot signal power fall below the fading threshold, the compensation of the demodulated signal is adjusted (714). In addition, when the mean analog message signal power falls below the muting threshold, the samples included in the predetermined portion of the message are muted (718).

Method and apparatus in a radio communication system for mitigating

A selective call base station (100) for receiving a signal comprising a plurality of communication signals has an Analog-to-Digital (A/D) converter (220) for digitizing the signal. A memory (204) for storing the signal as a plurality of digitized bits (502-518), and a Digital Signal Processor (DSP) (218) for converting each of the plurality of digitized bits (502-518) into a frequency domain signal (FIG. 6) that has a plurality of frequency samples. The memory (204) stores the plurality of frequency samples corresponding to each of the plurality of digitized bits (502-518). A decoder (206, 218) decodes the plurality of communication signals from the plurality of frequency samples. The decoder (206, 218) further includes a generator (718) for generating a window (902) for measuring energy of at least one frequency sample of the plurality of digitized bits (502-518) in each of the plurality of communication signals. A determinator (728) determines the at least one frequency sample of each of the plurality of communication signals having a maximum energy.

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Boynton Beach, FL, United States of America

Xiaojun Li