Abstract: Synchronization techniques for reducing the effects of time dispersive wireless communications channels are presented. A synchronization technique for communications over a time dispersive wireless channel includes receiving a signal having at least identical first and second symbols, and calculating a metric for each sampling time by correlating respective samples of the first symbol included in a first sampling window with respective samples of the second symbol included in a second sampling window. The technique further includes identifying one of the sampling times at which the metric attains a maximum value, and estimating an optimal time offset for synchronizing to the received signal based on the identified sampling time. Optionally, the technique further includes estimating a carrier frequency offset based on the difference of phase of the complex conjugate samples at the maximum absolute value of the metric.

Abstract: Methods and systems for detecting and synchronizing to frequency hopped packets are presented. A technique for detecting a transmitter frequency hopping pattern includes receiving a packet of preamble symbols respectively transmitted over multiple frequency sub-bands according to the transmitter frequency hopping pattern, and partitioning predetermined frequency hopping patterns into disjoint groups of patterns, each group of patterns having an associated periodicity of the received preamble symbols. A group of patterns is selected by comparing a correlation metric of two received preamble symbols for each of the associated periodicities in a first selected frequency sub-band, and a pattern from the selected group of patterns is selected based on a timing of a detected first peak of the correlation metric in a second selected frequency sub-band.

Abstract: A method and system eliminate spectral lines and shapes the power spectral density of an ultra bandwidth signal. First, a train of non-periodic pulses is generated. The non-periodic pulses are then modulated in time according to uncorrelated symbols. A polarity of the non-periodic pulses is inverted randomly before transmitting the non-periodic pulses as an ultra wide bandwidth signal to eliminate spectral lines and to shape a power spectral density of the ultra wide bandwidth signal.

Abstract: Synchronization techniques for reducing the effects of time dispersive wireless communications channels are presented. A synchronization technique for communications over a time dispersive wireless channel includes receiving a signal having at least identical first and second symbols, and calculating a metric for each sampling time by correlating respective samples of the first symbol included in a first sampling window with respective samples of the second symbol included in a second sampling window. The technique further includes identifying one of the sampling times at which the metric attains a maximum value, and estimating an optimal time offset for synchronizing to the received signal based on the identified sampling time. Optionally, the technique further includes estimating a carrier frequency offset based on the difference of phase of the complex conjugate samples at the maximum absolute value of the metric.

Abstract: Methods and systems for detecting and synchronizing to frequency hopped packets are presented. A technique for detecting a transmitter frequency hopping pattern includes receiving a packet of preamble symbols respectively transmitted over multiple frequency sub-bands according to the transmitter frequency hopping pattern, and partitioning predetermined frequency hopping patterns into disjoint groups of patterns, each group of patterns having an associated periodicity of the received preamble symbols. A group of patterns is selected by comparing a correlation metric of two received preamble symbols for each of the associated periodicities in a first selected frequency sub-band, and a pattern from the selected group of patterns is selected based on a timing of a detected first peak of the correlation metric in a second selected frequency sub-band.

Abstract: An OFDM transmitter generates FSK symbols in a communications network. Complex values representing OFDM tones are partitioned in groups. A distinct energy is assigned to each group of complex values. An OFDM modulator is applied to the complex values having the assigned distinct energies to generate FSK symbols corresponding to the groups, and the FSK symbols are transmitted serially.

Abstract: An OFDM receiver detects FSK symbols in a communications network. An FFT has an input connected to receive temporal samples of a received, frequency-hopped FSK signal. Outputs of the FFT represent the FSK signal in a frequency domain. The outputs are grouped according to predetermined frequencies assigned by a transmitter of the FSK signal. An energy for each group of outputs is determined, and the energies of each group are then compared to recover a data stream from the FSK signal.

Abstract: A method eliminates spectral lines in a time hopping ultra wide bandwidth signal. First, a train of pulses is generated from input symbols. The pulses are then modulated in time according to symbols. The modulation can use pulse position modulation and time hopping. A polarity of the pulses is inverted randomly before transmitting the pulses as an ultra wide bandwidth signal. By randomly inverting the polarity of the pulses spectral lines in the ultra wide bandwidth signal are eliminated.

Abstract: A speech encoding/decoding method using an encoder working at very low bit rates, comprises a learning step enabling the identification of the representatives of the speech signal; and an encoding step to segment the speech signal and determine the best representative associated with each recognized segment. The method also comprises at least one step for the encoding/decoding of at least one of the parameters of the prosody of the recognized segments, e.g., the energy, pitch, voicing, and/or length of the segments, by using a piece of information on prosody pertaining to the best representatives. The method can employ a bit rate of lower than 400 bits per second.

Abstract: A method eliminates spectral lines and shapes the power spectral density of an ultra bandwidth signal. First, a train of pulses is generated. The pulses are then modulated in time according to symbols. A polarity of the pulses is inverted randomly before transmitting the pulses as an ultra wide bandwidth signal.

Abstract: A method and system communicates ultra wide bandwidth signals using orthogonal frequency division multiplexing modulation. Tones are received over an ultra wide bandwidth channel. The tones were generated from a single frequency interleaved input symbol subjected to spreading and modulation. The received tones are de-spreaded, and frequency de-interleaving is applied to the de-spreaded tones to recover the single input symbol.

Abstract: A method and system communicates ultra wide bandwidth signals using orthogonal frequency division multiplexing modulation. QPSK input symbols are frequency interleaved. The frequency interleaved symbols are spread over a plurality of tones, and the tones are modulated for transmission over an ultra wide bandwidth channel. When the tones are received, the received tones can be de-spreaded to recover the input symbols.

Abstract: An OFDM receiver detects FSK symbols in a communications network. An FFT has an input connected to receive temporal samples of a received, frequency-hopped FSK signal. Outputs of the FFT represent the FSK signal in a frequency domain. The outputs are grouped according to predetermined frequencies assigned by a transmitter of the FSK signal. An energy for each group of outputs is determined, and the energies of each group are then compared to recover a data stream from the FSK signal.

Abstract: An OFDM transmitter generates FSK symbols in a communications network. Complex values representing OFDM tones are partitioned in groups. A distinct energy is assigned to each group of complex values. An OFDM modulator is applied to the complex values having the assigned distinct energies to generate FSK symbols corresponding to the groups, and the FSK symbols are transmitted serially.

Abstract: A method eliminates spectral lines in a time hopping ultra wide bandwidth signal. First, a train of pulses is generated. The pulses are then modulated in time according to symbols. A polarity of the pulses is inverted randomly before transmitting the pulses as an ultra wide bandwidth signal.

Abstract: A speech encoding/decoding method using an encoder working at very low bit rates, comprises a learning step enabling the identification of the “representatives” of the speech signal and an encoding step to segment the speech signal and determine the “best representative” associated with each recognized segment. The method comprises at least one step for the encoding/decoding of at least one of the parameters of the prosody of the recognized segments, such as the energy and/or pitch and/or voicing and/or length of the segments, by using a piece of information on prosody pertaining to the “best representatives”. Application to bit rates lower than 400 bits per second.