Freewave Technologies, Inc.

At&t Wireless Services, Inc.

Cingular Wireless Ii, LLC

Steven E McMeekin

Timothy G Mester

Michael Hirano

Gregory J Veintimilla

Jari Heinonen

David B Gibbons

Elliott Hoole

Hongliang Zhang

Siavash Alamouti

David J Ryan

Yan Zhang

Mary Jesse

James Timothy Golden

Robert Lee Maxwell

David J Nix

Jeffrey A Battin

Reijo Savola

William H Warner

Jeffrey Battin

A method for operating a receiver in a wireless communication system to synchronize the receiver to a received signal. The received signal is preamble correlated to identify a preamble portion of the signal. Portions of the received signal near the identified preamble portion are processed to determine signal-distorting channel characteristics, such as multipath channel delay spread, of the channel over which the received signal propagated. A digital filter is configured based on the determined channel characteristics to compensate for the signal-distorting channel characteristics, and the received signal is filtered with the configured digital filter. The filtered received signal is second preamble correlated with a second preamble that is different than the first preamble to produce a second preamble correlation. The second preamble correlation is processed to identify delay in the filtered received signal. Portions of the filtered received signal are identified and processed based on the identified delay.

Techniques for transmitting/receiving portions of received signal to identify preamble portion and to determine signal-distorting characteristics

A method for operating at least a first of a plurality of co-located, non-time synchronous radios at a first location communicating data by frames with one or more other remote radios at a second and optionally additional locations in a wireless communication system, to synchronize first or uplink and/or second or downlink frame portions of the frames to mitigate interference between the co-located radios. A frame table of attributes of uplink and/or downlink frame portions associated with frames of the first radio is stored. The spectral content of transmissions from at least a second of the co-located radios is monitored. Based on the monitored spectral content, characteristics for uplink and/or downlink frame portions of the first co-located radio to mitigate interference with the at least second co-located radio are determined. Attributes in the frame table to enable interference-optimized uplink and/or downlink portions of frames of the first co-located radio are updated.

Synchronization of co-located radios in a dynamic time division duplex system for interference mitigation

A method for operating a downlink transmitter radio to automatically determine transmission parameters includes monitoring the spectral content of a range of frequencies, and identifying, based on the monitored spectral content, spectral characteristics associated with noise or interference. The downlink transmission channel carrier frequency and channel frequency bandwidth are determined based on the spectral characteristics of the interference together with operating requirements of the wireless transmission system.

Dynamic and flexible channel selection in a wireless communication system

A broadband transceiver includes an input to receive an RF signal, an output to output an RF transmit signal, a receiver section coupled to the input, and a transmitter section coupled to the output. A processor coupled to the receiver section and the transmitter section determines and generates an inverse waveform that will result in attenuation of undesired portions of a received RF signal when summed with the received signal, including optionally at one or more of an RF stage and an IF stage. A summing junction coupled between the processor and receiver section sums the inverse waveform with the received signal.

Pre-distortion of receive signal for interference mitigation in broadband transceivers

A broadband superheterodyne receiver. Embodiments include an input for receiving an RF signal including an RF data signal at a carrier frequency. An RF mixer coupled to the input shifts the RF data signal from the carrier frequency to an IF frequency. An IF band pass filter coupled to the mixer has a pass band, and band pass filters the signal near the IF frequency. A spectrum analyzer provides information representative of the spectral characteristics of the received RF signal around the RF data signal at the carrier frequency. An IF controller is coupled to the RF mixer and to the spectrum analyzer. The IF controller: (1) determines an interference-mitigating IF frequency within the pass band of the band pass filter that will result in attenuation of undesired portions of the RF signal, and (2) controls the RF mixer to shift the RF data signal to the interference-mitigating IF frequency.

Broadband superhetrodyne receiver with agile intermediate frequency for interference mitigation

A fixed wireless system (FWS) utilizing Orthogonal Frequency Division Multiplexing (OFDM) communication techniques is spectrally efficient and responsive to communications involving both voice and high speed data, such as Internet data. The FWS includes a wireless base unit; a plurality of fixed wireless remote units; a plurality of wireless data traffic channels available between the wireless base unit and the plurality of fixed wireless remote units; and a plurality of wireless voice traffic channels available between the wireless base unit and the plurality of fixed wireless remote units. Each wireless traffic channel is identifiable by a unique combination of frequency and time slots. Each wireless data traffic channel is used for carrying high speed data in addressed data packets to and from the plurality of fixed wireless remote units. On the other hand, each wireless voice traffic channel can be assigned and dedicated to a particular voice communication call involving one of the plurality of fixed wireless remote units for carrying voice data of the call.

Methods and apparatus for use in communicating voice and high speed data in a wireless communication system

An orthogonal frequency division multiplexing (OFDM) communication system includes base units which simultaneously transmit pilot tones in a predetermined pilot tone pattern during one or more time slots of a message slot. OFDM signals are received within a time slot; an OFDM signal level is determined at each frequency of a plurality of pilot tone frequencies; the signal levels and the predetermined pilot tone pattern are correlated; and a pattern detection value based on performing the correlation is generated and stored. This process is repeated for each time slot of a plurality of time slots. This process may be repeated for a plurality of message frame durations to produce a plurality of averaged pattern detection values, following which the plurality of averaged pattern detection values and a predetermined message frame pattern may be correlated. Then, a boundary of a message slot may be detected based on the correlation.

Methods and apparatus for use in obtaining frame synchronization in an OFDM communication system

A frequency correction process involves the steps of generating a plurality of tone values for a plurality of tone bins, where the plurality of tone bins includes a first set of tone bins assigned to a first frequency range and a second set of tone bins assigned to a second frequency range; performing complex conjugate multiplication between the tone values of the first and the second sets of tone bins; identifying a maximum value from results of the complex conjugate multiplication; and shifting receiver frequency based on a location of the maximum value relative to a predetermined pilot tone location. In this method, the first frequency range corresponds to a lower edge portion of a frequency band of interest, an upper edge portion of a lower adjacent frequency band, and a lower guard band in between the lower and the upper edge portions; and the second frequency range corresponds to an upper edge portion of the frequency band of interest, a lower edge portion of an upper adjacent frequency band, and an upper guard band in between the upper and lower edge portions.

Methods and apparatus for use in obtaining frequency synchronization in an OFDM communication system

An iterative method involves performing a coarse frequency correction process which adjusts receiver frequency so that a pilot tone signal is within a predetermined frequency range and, after performing the coarse frequency correction process, performing a fine frequency correction process which adjusts receiver frequency so that the pilot tone signal is substantially aligned with a pilot tone reference within the predetermined frequency range. By performing these processes, the receiver frequency may be adjusted so that the alias pilot tone signal is substantially aligned with the pilot tone reference and the pilot tone signal is undesirably shifted outside the predetermined frequency range. To eliminate this condition, the method further involves performing the coarse frequency correction process again and, after performing the coarse frequency correction process again, performing the fine frequency correction process again. By performing the coarse frequency correction process again, receiver frequency is adjusted so that the pilot tone signal is within both the predetermined frequency range and the Nyquist sampling frequency range. By performing the fine frequency correction process again, receiver frequency is adjusted so that the pilot tone signal is substantially aligned with the pilot tone reference.

An RF communications technique pre-distorts the signal in the baseband prior to its being applied to the RF transmitter, to avoid producing harmonics when the resultant signal is processed by the RF transmitter. Pilot tones are used to test the channels between the base station and a remote station. The technique provides an improved way to minimize the harmonic distortion imposed by RF transmitters.

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Evergreen, CO, United States of America

Steven E McMeekin