Pacific Communication Sciences, Inc.

Rockwell Semiconductor Systems, Inc.

Conexant Systems, Inc.

Silicon Wave, Inc.

Neal K Riedel

David A Wright

James E Petranovich

Rex L Baker

Terrance Raymond Bourk

Terrance R Bourk

The present invention is a novel method and apparatus for implementing a high-precision timer utilizing a non-optimal oscillator and a high-speed oscillator wherein only one oscillator is enabled at a given moment in time. The high-precision timer method and apparatus comprises a timer and an error-correction technique. In one embodiment, the timer of the present invention is constructed from a high-speed oscillator and a low-speed non-optimal oscillator. The timer operates from the high-speed oscillator during on-the-air modes of operation and from the low-speed non-optimal oscillator during sleep modes of operation. The present inventive method corrects errors that are introduced by the non-optimal oscillator and a swallow counter. The errors are corrected using an error-correction technique having two steps: an error-determination step and an error-correction step. In the preferred embodiment of the error-determination step, a total error for a time interval is determined by performing the following steps: (1) calculating an individual error that occurs at each pulse; (2) multiplying the individual error by the number of pulses occurring during the time interval; and (3) adjusting for a non-optimal counter. Once an error has been determined, the error-correction step adjusts a clock counter accordingly. Depending upon the error-correction technique used, the error-correction step can correct the total error at one of several locations within a timer counter chain that is used to practice the present invention. The implementation of the present invention allows a straightforward realization of multiple timers.

Method and apparatus for implementing a high-precision interval timer utilizing multiple oscillators including a non-optimal oscillator

Method and apparatus for reducing the perceptible impact to user traffic during a hand-off process in a full duplex wireless communications system having subscriber units and base stations, the subscriber unit being responsible for locating candidate base stations where the subscriber unit monitors the voice activity of the subscriber unit user and/or network user (connected to the base station) and uses the monitored activity to determine when it may miss one or more signal transmissions or receptions to search for a candidate base station without perceptibly impacting the voice traffic between the subscriber unit user and network user.

Method and apparatus for minimizing perceptible impact on an interrupted call prior to hand-off

The present invention provides methods for combining antenna diversity and gain control in a communications system using a single chain of receiver electronics. A number of input parameters related to various characteristics of a received signal are used to determine the quality of the received signal. The antenna diversity and gain control procedures are enabled or disabled based on the signal quality. The antenna diversity procedure estimates the signal level of the non-operational antenna using an infinite impulse response digital filter. The gain control procedure selects one of three gain paths based on the received signal strength.

Multiple antenna home base for digital cordless telephones

The present invention provides a system and methods for coding and decoding digital data to improve the subjective quality of a voice signal. According to the invention, a sampled voice waveform is compressed by an ADPCM algorithm resulting in a sequence of samples. The sequence of samples are formed into an array and coded into parity bits. Row and column checksums are preferably performed on the parity bits to form row and column vectors. The samples and row and column vectors are transmitted to a receiving unit preferably having a diversity capability. The receiver processes each diversity block by generating row and column vectors from the received samples and comparing the generated row and column vectors to the row and column vectors received. Then based on the comparison, the samples of the best diversity block are used to reconstruct the voice waveform on a sample-by-sample basis.

ADPCM coding and decoding techniques for personal communication systems

Methods and apparatus for improving the perceived quality of ADPCM encoded signals by magnitude limiting samples of the ADPCM encoded signals prior to the decoding of samples of the ADPCM encoded signals, preferably, a sample of the ADPCM encoded signal is magnitude limited only if a receive error is detected for the sample.

Adaptive error control for ADPCM speech coders

Methods and apparatus for digital cordless telephone systems are disclosed for detecting and correcting errors in received signals. Such methods and apparatus include providing a table of predetermined syndromes, wherein each of the predetermined syndromes has an associated error correction pattern. The table is formed by selecting from all possible syndromes that could be predetermined from the segment length of received digital data, those predetermined syndromes having error patterns for correcting a predetermined number of errors within the segment and arranging the predetermined syndromes in the table in accordance with a predetermined order, such as ascending or descending numerical order. Thereafter, a current syndrome is calculated for the received digital data and the predetermined syndrome contained in the table matching the current syndrome is located by using a predetermined search technique. Received digital data is corrected by retrieving the error correction pattern associated with the located predetermined syndrome and correcting the error in the received digital data in response to this error correction pattern.

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Encinitas, CA, United States of America

Neal K Riedel