Abstract: The spectral shape of a communication signal is preserved by filtering it into a selected number of frequency band signals representing a selected number of the frequency bands. A calculator generates a plurality of initial gain signals having initial gain values for altering the gain of the frequency band signals. Each initial gain signal corresponds to one of the frequency band signals. Each initial gain value is derived from a measurement of the power of at least a portion of one of the frequency band signals. The calculator also generates a plurality of modified gain signals having modified gain values. Each modified gain signal corresponds to at least one of the frequency band signals and each modified gain value is derived from one or more functions of at least two of the initial gain values. The frequency band signals are altered in response to the modified gain signals to generate weighted frequency band signals which are combined to generate an improved communication signal.

Abstract: A multiple carrier communication system includes a primary impulse shortening filter that receives an output signal of an analog to digital converter and accepts coefficients. A secondary impulse shortening filter receives the output signal of the analog to digital converter, outputs an output signal, and passes coefficients to the primary impulse shortening filter. A reference signal generator outputs a reference signal. A comparator compares the output signal and the reference signal and outputs a resulting error signal. An adaptive processor computes coefficients for the secondary impulse shortening filter based on the error signal.

Abstract: A method of managing a signal over a symbol period includes supplying samples of the signal at beginning and end portions of the symbol period. The method further includes suppressing the supply of samples of the signal at a middle portion of the symbol period.

Abstract: A multi-point communications system is set forth herein. The communications system includes a receiver and transmitter disposed at a primary site for communication with a plurality of remote service units disposed at respective secondary sites. The receiver of the primary site receives OFDM/DMT signals over a number of transmission bins. A transmitter at the remote service unit includes an improved transmitter architecture. The transmitter comprises a first circuit for converting a signal into a first serial digital data stream and a second circuit for generating a second serial digital data stream from the first serial digital data stream of the first means. The second serial digital data stream is a digital representation of an OFDM/DMT signal that is to be transmitted to the receiver of the primary site and is generated from the first serial digital data stream through a modulated direct digital synthesis thereof.

Abstract: A multi-point communications system is set forth herein. The communications system comprises a transmitter for transmitting OFDM/DMT symbols over a predetermined number of bins across a transmission medium. The OFDM/DMT symbols are generated using at least one timing signal. At least one of the predetermined number of bins includes a pilot tone sub-symbol having a frequency corresponding to the clock signal. The communications system also includes a receiver for receiving the OFDM/DMT symbols from the transmission medium. The receiver demodulates the received symbols using at least one timing signal. The receiver has a first pilot tone search mode of operation in which the receiver adjusts its timing signal to scan the frequency range of the predetermined number of bins looking for the pilot tone sub-symbol and identifies the bin including the pilot tone sub-symbol.

Abstract: A method and apparatus for interference suppression in wireless communication systems, especially Orthogonal Frequency Division Multiplexed (OFDM) systems. The array apparatus includes a two-tier adaptive array system which provides for both spatial diversity and beamforming at the uplink. The adaptive array is comprised of sub-arrays spaced at a distance sufficient to provide spatial diversity, ideally 5 to 15 wavelengths at the frequency of operation. Each sub-array is composed of at least two antenna elements spaced in proximity sufficient to provide effective beamforming or scanning, ideally less then one-half of one wavelength at the frequency of operation. The Direction of Arrival (DOA) of signals impinging upon the array can be calculated by comparing signals from sub-array elements.

Abstract: A multiple carrier communication system includes a primary impulse shortening filter that receives an output signal of an analog to digital converter and accepts coefficients. A secondary impulse shortening filter receives the output signal of the analog to digital converter, outputs an output signal, and passes coefficients to the primary impulse shortening filter. A reference signal generator outputs a reference signal. A comparator compares the output signal and the reference signal and outputs a resulting error signal. An adaptive processor computes coefficients for the secondary impulse shortening filter based on the error signal.

Abstract: A multi-point communications system is set forth herein. The communications system comprises a transmitter for transmitting OFDM/DMT symbols over a predetermined number of bins across a transmission medium. The OFDM/DMT symbols are generated using at least one timing signal. At least one of the predetermined number of bins includes a pilot tone sub-symbol having a frequency corresponding to the clock signal. The communications system also includes a receiver for receiving the OFDM/DMT symbols from the transmission medium. The receiver demodulates the received symbols using at least one timing signal. The receiver has a first pilot tone search mode of operation in which the receiver adjusts its timing signal to scan the frequency range of the predetermined number of bins looking for the pilot tone sub-symbol and identifies the bin including the pilot tone sub-symbol.

Abstract: In order to enhance the quality of a communication signal comprising speech signal components due to speech and noise signal components due to noise, a filter divides the communication signal into a plurality of frequency band signals representing the speech signal components and the noise signal components in a plurality of frequency bands. A calculator generates a plurality of weighting signals having weighting values corresponding to the frequency band signals. The weighting values represent at least approximations of the normalized powers of the noise signal components in the frequency band signals. The frequency band signals are altered in response to the weighting signals to generate weighted frequency band signals which are combined to generate a communication signal with enhanced quality.

Abstract: A method for switching multi-rate communications is described. The method includes filling a first set of p timeslots with p sets of data from a first data collection of a first type, where the first data collection includes m sets of data and p is less than m. The method also includes loading at least one overflow timeslot with at least one overflow set of data from the first data collection, where the overflow set of data exceeds a size of the first set of p timeslots.

Abstract: A communications system includes a transmitter that generates symbols in a plurality of bins using a first timing signal and generates a reference signal by using the first timing signal. The transmitter transmits the symbols and the reference signal carried by a first signal, which is frequency multiplexed with a second signal from another transmission source. A demultiplexer frequency demultiplexes the first signal, which is downconverted in response to a control signal to generate a frequency downconverted signal, and a processing circuit is responsive to the frequency downconverted signal to identify the predetermined bin and to generate the control signal in response to the identification of the predetermined bin.

Abstract: In order to enhance the quality of a communication signal derived from speech and noise, the likelihood that the communication signals result from at least some speech is determined. A calculator calculates a first power signal representing the power of at least a portion of the communication signals estimated over a first time period and calculates a second power signal representing the power of at least a portion of the communication signals estimated over a second time period longer than the first time period. The calculator also generates a comparison signal having a value related to the likelihood that the portion of the communication signals result from at least some speech by comparing a first expression involving the first power signal with a second expression involving the second power signal.

Abstract: In order to enhance the quality of a communication signal derived from speech and noise, a filter divides the communication signal into a plurality of frequency band signals. A calculator generates a plurality of power band signals each having a power band value and corresponding to one of the frequency band signals. The power band values are based on estimating, over a time period, the power of one of the frequency band signals. The time period is different for different ones of the frequency band signals. The power band values are used to calculate weighting factors which are used to alter the frequency band signals that are combined to generate an improved communication signal.

Abstract: Input interfaces convert a predetermined data frame structure, such as a Sonet STS-1, into an internal format comprising a predetermined number of rows and columns, the rows being a multiple of a number evenly divisible into the bytes contained in the internal frame format. A time-space switch switches the frame format while storing a row of bytes in a data memory. Output interfaces convert the switched data to the same type of data frame format received at the input.

Abstract: A communication system (10) receives a communication signal comprising first and second data with different compression levels, such as highly compressed and weakly compressed levels. A mode detector (15) detects the level of compression. One or more signal decoders (20, 22) decode the highly compressed data. An analyzer (30) determines the type of enhancement required. One or more processors (48, 50, 80) enhance the data as required. An encoder (60) reencodes the enhanced decoded data. Metrics (90) may aid the operation of the analyzer (30).

Abstract: The spectral shape of a communication signal is preserved by filtering it into a selected number of frequency band signals representing a selected number of the frequency bands. A calculator generates a plurality of initial gain signals having initial gain values for altering the gain of the frequency band signals. Each initial gain signal corresponds to one of the frequency band signals. Each initial gain value is derived from a measurement of the power of at least a portion of one of the frequency band signals. The calculator also generates a plurality of modified gain signals having modified gain values. Each modified gain signal corresponds to at least one of the frequency band signals and each modified gain value is derived from one or more functions of at least two of the initial gain values. The frequency band signals are altered in response to the modified gain signals to generate weighted frequency band signals which are combined to generate an improved communication signal.

Abstract: A multiple carrier communication system includes a primary impulse shortening filter that receives an output signal of an analog to digital converter and accepts coefficients. A secondary impulse shortening filter receives the output signal of the analog to digital converter, outputs an output signal, and passes coefficients to the primary impulse shortening filter. A reference signal generator outputs a reference signal. A comparator compares the output signal and the reference signal and outputs a resulting error signal. An adaptive processor computes coefficients for the secondary impulse shortening filter based on the error signal.

Abstract: A processor (300) is arranged to divide a communication signal into a plurality of frequency band signals including speech and noise components due to speech and noise. The processor generates first and second power signals for the frequency band signals. Each first power signal is based on estimating over a first time period the power of one of the frequency band signals. Each second power signal is based on estimating over a second time period less than the first time period the power of one of the frequency band signals. The processor generates condition signals representing conditions of the frequency band signals, and adjusts the gain of the frequency band signals in response to the condition signals to generate adjusted frequency band signals. The processor then combines the adjusted frequency band signals to generate an adjusted communication signal.

Abstract: Methods and apparatus for processing at least one voice signal in which a centralized voice processing unit controls operation of a plurality of voice processing blocks. In a first embodiment, the centralized voice processing unit comprises a centralized voice activity detector that provides at least one voice activity indication to the plurality of voice processing blocks. In a second embodiment, the centralized voice processing unit comprises a centralized noise estimator that provides at least one noise estimate to the plurality of voice processing blocks. In a third embodiment, the centralized voice processing unit comprises a centralized signal characteristic estimator that provides at least one signal characteristic estimate to the plurality of voice processing blocks.

Abstract: Methods and apparatus for processing a received voice signal from a variable-delay network by a communications system that has at least one echo canceller. An echo canceller determines delay characteristics that are associated with the received voice signal and correspondingly modifies echo cancellation processing. In a variation of the embodiment of the invention, a first echo canceller sends silence descriptor information to a second echo canceller. The second echo canceller reconstructs a voice signal based upon the silence descriptor information and excitation vector information.