Abstract: A communication system includes a transmitter for transmitting messages to a plurality of receiving devices of the communication system, and a processing system. The processing system is adapted to convert a caller's voice message to a sequence of phonemes whereby the caller's voice message is intended for a receiving device. To accomplish the conversion, steps of Fourier transform, spectral subdivision, envelope filtering autocorrelation function determination of each subdivision, and voiceness determination for each subdivision are performed. The processing system is further adapted to generate a sequence of phoneme indexes and voice features corresponding to the sequence of phonemes, and to cause the transmitter to transmit the sequence of phoneme indexes to the receiving device for generating a voice signal representative of the caller's voice message. The voice features can include spectral features, average energy, duration, and pitch to improve the quality of the voice signal.

Abstract: A MBE synthesizer (2200) for generating speech from information received by a receiver (114) includes a voiced signal generator (2280) for generating voiced signal components in the time domain using an IDFT in a pitch wave generator (2210) and and a pitch wave resampler (2232) and an unvoiced signal generator (2290) for generating unvoiced signal components in the time domain. The MBE synthesizer also includes a voicing processor (2218) responsive to band voicing flags within the excitation information for controlling selection of a voiced spectral component or an unvoiced spectral component from a harmonic amplitude spectrum.

Abstract: An interactive method for composing an alphanumeric message by a caller using a telephone keypad includes storing (215) a lexical database (135) from which unigram probabilities, forward conditional probabilities, and backward conditional probabilities for a plurality of words can be recovered; storing a received sequence of key codes (405) representing a sequence in which keys on a telephone style keypad are keyed; generating a word trellis including candidate words (415) derived from the sequence and the lexical database; determining a most likely phrase (420) from the candidate words, the unigram probabilities, forward conditional probabilities, and backward conditional probabilities; generating a most likely message (425) from the most likely phrase and presenting the most likely message to the caller; and confirming that the most likely message is the alphanumeric message (430).

Abstract: 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.

Abstract: An interactive method for composing an alphanumeric message by a caller using a telephone keypad includes storing (215) a lexical database (135) from which unigram probabilities, forward conditional probabilities, and backward conditional probabilities for a plurality of words can be recovered; storing a received sequence of key codes (405) representing a sequence in which keys on a telephone style keypad are keyed; generating a word trellis including candidate words (415) derived from the sequence and the lexical database; determining a most likely phrase (420) from the candidate words, the unigram probabilities, forward conditional probabilities, and backward conditional probabilities; generating a most likely message (425) from the most likely phrase and presenting the most likely message to the caller; and confirming that the most likely message is the alphanumeric message (430).

Abstract: 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.

Abstract: An apparatus and method for processing a voice message to provide low bit rate speech transmission processes the voice message to generate speech parameters which are arranged into a two dimensional parameter matrix (502) including a sequence of parameter frames. The two dimensional parameter matrix (502) is transformed using a predetermined two dimensional matrix transformation function (414) to obtain a two dimensional transform matrix (506). Distance values representing distances between templates of a set of predetermined templates and the two dimensional transform matrix (506) are then derived. The distance values derived are identified by indexes identifying the templates of the set of predetermined templates. The distance values derived are compared, and an index corresponding to a template of the set of predetermined templates having a shortest distance is selected and then transmitted.

Abstract: A communication device (400) with a polarization diversity antenna configuration, having a first antenna (410) with a first plane of polarization and a second antenna (412) with a second plane of polarization. Signal strength of a demodulated signal when the antenna switch (420) is coupled to one of the antennas (410, 412) is measured by a signal strength measuring circuit (440) to generate a short-term average signal power (SA) representing signal strength over a first predetermined number of symbol periods, a medium-term average signal power (MA) representing signal strength over a second predetermined number of symbol periods, and a long-term average signal power (LA) representing signal strength over a third predetermined number of symbol periods, greater than the second predetermined number of symbol periods and first predetermined number of symbol periods. Switching between antennas (410, 412) is made in response to differences between SA, MA and LA.

Abstract: 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).

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: A voice packet, containing coded voice information for a communication talkgroup that is currently being monitored, is received and stored in a buffer (200-202) dedicated to the communication talkgroup. When a decoder (203-205) is available, the voice packet is decoded and the resulting decoded voice information is combined with other decoded voice information, pertaining to other monitored communication talkgroups, such that the combined decoded voice information can be rendered audible.

Abstract: A communication resource allocator of a trunking communication system may more efficiently handle service requests during extremely busy times in the following manner. While receiving service requests from communication units, the communication resource allocator determines whether it can process the service request within a predetermined period of time. If the communication resource allocator cannot process the service request within a predetermined period it generates a global system busy which indicates that the communication resource allocator cannot individually process or acknowledge additional service requests. Having generated the global system busy signal, the communication resource allocator transmits it to the plurality of communication units. The communication units process the global system busy signal such that they will not transmit nonpriority service requests during the duration of the global system busy signal.

Abstract: A random multiple-access communication system operates both a feedback-ignored (e.g. ETHERNET) and a feedback-utilized (e.g. STACK) protocol simultaneously. The system is useful for communicating two types of information such as voice and data wherein one of the information types (e.g. voice) is subject to delay constraints. The feedback-utilized protocol has the effect of taking priority over the feedback-ignored protocol in the communication system to provide a priority transmission system.

Abstract: A packet switched local communication system includes means for detecting collisions and resolving conflicts between transmitting terminals by a random splitting process. In transmitting mixed types of information comprising short packets and long packets, priority of transmission is given to short packets.